ALBERT R. MANN 
 LIBRARY 
 
 AT 
 
 CORNELL UNIVERSITY 
 
3 1924 054 698 885 
 
Cornell University 
 Library 
 
 The original of tiiis book is in 
 tine Cornell University Library. 
 
 There are no known copyright restrictions in 
 the United States on the use of the text. 
 
 http://www.archive.org/details/cu31924054698885 
 
THE 
 
 PHYSIOLOGICAL ANATOIT 
 
 PHYSIOLOGY OP MAN. 
 
THE 
 
 PHYSIOLOGICAL ANATP^¥=^^, 
 
 ^^..., 
 
 4i— ■ 
 
 ■-^ 
 
 PHYSIOLOGY OF MAN. 
 
 BY 
 
 ROBERT BENTLEY TODD, M.D., F.R.S., 
 
 FELLOW OF THE COLLEfJE OF FHTSICIAN8, AND PHYSICIAN TO KING'S COLLEGE HOSPITAL ; 
 
 WILLIAM BOWMAN, F.R.S., 
 
 FELLOW OF THE COLLEGE OF BURGEONS, SURGEON TO KING'S COLLEGE HOSPITAL AND THB 
 EOTAL LONDON OPHTHALMIC HOSPITAL ; 
 
 LATE PKOFESSOBS OF PHYSIOLOGY AND GENERAL AND MOKBID ANATOMY IN 
 king's college, LONDON. 
 
 COMPLETE IN ONE VOLUME. 
 
 WITH TWO HUNDRED AND NINETY-EIGHT ILLUSTRATIONS. 
 
 n 
 s 
 
 
 )^? 
 
 PHILADELPHIA: 
 BLANCHAED AND LEA. 
 
 1857. 
 
PHltADELPHIA: 
 T. K. AND P. Q. COLlIirs, PRINTEBS. 
 
TO 
 
 SIE BENJAMIN COLLINS BRODIE, BART., 
 
 D.C.L, F.K. S., ETC. ETC., 
 
 COKBESPOMDING MEMBEK OP THE IHSTIT0TE OP FRANCE, 
 SEEGEANT SUEGEOH TO THE QUEEN, 
 
 WHOSE MIND, 
 
 EARLY TRAINED IN PHYSIOLOGICAL RESEARCHES 
 
 HAS BEEN DEVOTED 
 
 THROUGH A LONG LIFE OF EMINENT USEFULNESS 
 
 TO THE PRACTICE AND IMPROVEMENT 
 
 OF THE HEALING ART, 
 
 ]U Maxk u ^iVmUli 
 
 THE AUTHORS. 
 
PEEFACE 
 
 The work, which is now brought to a conclusion, was commenced 
 in the year 1843, having been designed as a text-book for the lec- 
 tures on General Anatomy and Physiology, given in King's College, 
 London. 
 
 In its title, we adopted the term Physiological Anatomy, in pre- 
 ference to the older one of Creneral, or the later one of Histological, 
 as being more comprehensive than either, and as denoting precisely 
 that kind of anatomy, a knowledge of which is especially required 
 for the investigation of those subjects which ought to come under 
 consideration in a Physiological course. 
 
 We proposed to ourselves to give such a view of the main facts 
 and doctrines of Anatomy and Physiology, particularly of those 
 bearing on practical Medicine and Surgery, as might suffice for the 
 wants of the student and practitioner. Following that great master, 
 Haller, we were desirous of giving to Anatomy a greater degree of 
 prominence than had been usual in Physiological works, under the 
 conviction that a thorough training in its several branches, descrip- 
 tive, physiological, and comparative, is necessary to the formation of 
 those habits of mind which best fit their possessor for the successful 
 investigation and the correct appreciation of physiological science. 
 And we aimed at resting our anatomical descriptions, at least as 
 regards the more important points, upon our own investigations, and 
 
Vlll PREFACE. 
 
 at repeating former experiments, or devising new ones, -whenever 
 questions of sufficient interest presented themselves. 
 
 "While we must humbly confess how small have been the advances 
 attributable to our own labours, the immense extension given to the 
 sciences of Anatomy and Physiology during the last fifteen years, 
 may be admitted as some explanation of the delay that has occurred 
 in the publication of our work, a delay that has been a constant 
 source of regret to us, since we began to discover how impossible it 
 would be for us to complete it within the term originally contem- 
 plated. That, in spite of repeated procrastination, it should have 
 been so favourably received, both at home and abroad, has been the 
 greatest encouragement to us, and demands our most thankful 
 acknowledgments. If, indeed, our pursuits had tended to no other 
 end than the cultivation of science, this book might have been 
 finished long ago; but the increasing interruptions incident to a 
 professional life, and the large demand made on us by studies of a 
 practical kind, began at an early period to impede our progress. 
 These hindrances did not diminish as time wore on, nor were they 
 lessened by the fact of the authorship being in the hands of two 
 persons, however cordially united by common views and the ties of 
 friendship, or by the necessity for frequent and prolonged confer- 
 ences which that double authorship entailed. 
 
 Such is the apology we have to offer for the tardy completion of 
 our work. It will, we doubt not, be fully appreciated by candid 
 men who know by experience how multifarious are the calls made 
 upon those who not only are candidates for professional employment 
 in London, but hold also the responsible position of public teachers 
 in a large School and Hospital. 
 
 Were it not, indeed, for the kind and valuable co-operation of Dr. 
 Beale, who is n6w the sole occupant of the physiological chair in 
 King's College, we should not even yet have 1?een released from our 
 
PREFACE. IX 
 
 difficulties. Dr. Beale, knowing all our views, and having worked 
 with us on many points, has given us very important assistance in 
 drawing up the concluding chapters of the work. Our warmest 
 thanks are due to our friend and colleague for the patient industry 
 and admirable judgment, with which, stepping out of his proper 
 path of independent investigation, he has carried out our intentions, 
 and enabled us, although at the eleventh hour, to fulfil our engage- 
 ment to our pupils and to the public. 
 
 To our friend Dr. H. Hyde Salter we are indebted for several 
 excellent drawings, as well as for other valuable assistance. 
 
 We desire also to express our thanks to Mr. Vasey for the skill 
 and ability with which he has executed his portion of the task, that 
 of engraving the drawings on wood. 
 
 W. B. R. B. T. 
 
 London, December 1, 1856. 
 
CONTENTS 
 
 INTRODUCTION. 
 
 Kemarks on the method of study, 25. 
 Organized and unorganized bodies, 27. 
 Aotiye and dormant life, 27-8. 
 Chemical constitution of unorganized 
 
 bodies, 28, 
 Ditto of organized bodies, 29. 
 Their essential and incidental elements, 
 
 29. 
 Proximate principles, 29. 
 Secondary organic compounds, 30. 
 Complex structure of organized bodies, 
 
 32. 
 Primary organic cell, 32. 
 Form, duration, and mode of origin of 
 
 organized bodies, 32. 
 Spontaneous generation, 33. 
 Beproduction, 33. 
 Assimilation, 34. 
 Excretion, 34. 
 Decomposition, 34. 
 Life, 35. 
 Vital stimuli, 36. 
 
 Vital properties, 36. 
 
 Death, 36. 
 
 Theories of life, of Aristotle, of Harvey, 
 and of Hunter, 37. 
 
 Of Muller, of Dr. Prout, 38. 
 
 Functions of Animals and Plants, 42. 
 
 Organic, 42. 
 
 Animal, 45. 
 
 Volition, 45. 
 
 Sensation, 45. 
 
 The Mind, 46. 
 
 Instinct, 46. 
 
 Importance of Physiology to Medicine, 
 47. 
 
 Mode of conducting Physiological inqui- 
 ries, 49. 
 
 Value of Anatomy, human and compa- 
 rative, 49 ; of Experiment on living 
 animals, 49 ; of Pathology, 50 ; of the 
 Microscope, 50 ; of organic Chemis- 
 try, 51. 
 
 CHAPTER I. 
 
 OF THE CONSTITUENTS OP ANIMAL BODIES. — THE TISSUES AND THEIR 
 
 PROPERTIES. 
 
 Fluid and Solid constituents of animal 
 bodies, 51. 
 
 Table of proximate principles, and of 
 secondary organic compounds, 52. 
 
 Proximate principles, 53. 
 
 Albumen, 53. 
 
 Fibrine, 54. 
 
 Caseine, 55. 
 
 Prot^ine, 56. 
 
 Vegetable albumen, fibrine, and case- 
 ine, 56. 
 
 Gelatine, 57. 
 
 Chondrine, 58. 
 
 Fatty principles, 59. 
 
 Importance of a mixed diet, 59. 
 
 Secondary organic compounds, 60. 
 
 Classification and properties of the tis- 
 sues, 61. 
 
 Development of the tissues from cells, 
 63. 
 
 The ovum a nucleated cell, 63. 
 
 The nucleus and cell-wall, probably 
 both share in development, 63. 
 
 Properties of the tissues, 65. 
 
 Physical, 65. 
 
 Elasticity, extensibility, porosity, 66. 
 
 Endosmose, 67. 
 
 Vital, 68. 
 
 Contractility, 68. 
 
 Nervous force, 68. 
 
 Common sensation, 69. ' 
 
 Special sensation, 69. 
 
 These properties dependent on nutri- 
 tion, 69. 
 
XU CONTENTS. 
 
 CHAPTEE II. 
 
 01' THE MINUTE MOVEMENTS OCOURRINQ IN THE BODY. 
 
 Molecular motion of Robert Brown, 71. 
 Organic molecular motion, 71. 
 Molecular changes in nerve and mus- 
 cle, 72. 
 Ciliary motion, 73. 
 Structure of the cilia, 73. 
 
 Circumstances affecting their motion, 
 
 74. 
 Surfaces on which they exist in man, 
 
 75. 
 Cause of ciliary motion, 77. 
 Motions of Spermatozoa, 77. 
 
 CHAPTEE III. 
 
 OF LOCOMOTION. — ITS PASSIVE ORGANS. 
 
 Locomotion peculiar to animals, 78. 
 
 Movements included in the term, 78. 
 
 Passive and active organs, 78. 
 
 Of the Fibrous tissue, 78. 
 
 White fibrous tissue, 79 ; its forms and 
 structure, 79 ; physical and vital pro- 
 perties, 80; chemical constitution, 
 80. 
 
 Ligaments and their varieties, 80. 
 
 Tendons, 81. 
 
 Fascise, 81. 
 
 Reparation of white fibrous tissue, 82. 
 Yellow fibrous tissue, its forms and 
 structure, 82 ; chemical constitution, 
 83. 
 
 Areolar tissue, 83. 
 
 White and yellow fibrous elements, 84 ; 
 
 development, 85 ; distribution in the 
 body, 86; modifications of its ele- 
 ments, 87 ; physical properties, 88. 
 
 Of the Adipose tissue, 88. 
 
 Fat-vesicles, 89; their bloodvessels, 90. 
 
 Otfat, 90. 
 
 Proximal constitution, 91. 
 
 Spontaneous separation of the marga- 
 rine and elaine within the vesicles, 
 91. 
 
 Ultimate analysis, 91. 
 
 Distribution of the adipose tissue in 
 the animal kingdom, 91 ; in the hu- 
 man body, 92. 
 
 Development, 93. 
 
 Source of fat, Liebig's views, 94. 
 
 Uses of fat, 94. 
 
 CHAPTEE IV. 
 
 PASSIVE ORGANS OP LOCOMOTION, CONTINUED. 
 
 Of Caktilage, temporary and perma- 
 nent, 95, 
 Physical characters, 96. 
 Simple cellular cartilage, 96. 
 Temporary, 96. 
 Articular, 97. 
 Costal, 97. 
 Memhraniforrn, 98. 
 Perichondrium, 98. 
 Vessels of cartilage, 99, 
 
 Articular cartilage not penetrated by 
 vessels, 99. 
 
 Mr. Toynbee's observations, 99. 
 
 FiBRO-CARTiLAGE, articular and non-ar- 
 ticular, 400. 
 
 Its properties, vessels, chemical com- 
 position, and varieties, 100. 
 
 Intervertebral discs, and menisci, 101. 
 
 Reparation, 102. 
 
 CHAPTEE V. 
 
 PASSIVE ORGANS OP LOCOMOTION, CONTINUED. 
 
 External and internal skeletons, 102. 
 
 Bone, 102. 
 
 Physical properties, 103. 
 
 Animal and earthy constituents, 103. 
 
 Researches of Dr. John Davy and Dr. 
 G. 0. Rees on their relative propor- 
 tions in different bones, 104. 
 
 Rickets, mollities, 104-5. 
 
 Bone resists decomposition, 105. 
 
 Analysis of the animal and earthy parts, 
 105. 
 
 Compact and cancellated forms of osse- 
 ous tissue, 106. 
 
 Periosteum, medullary membrane, me- 
 dulla, medullary canal, 107. 
 
 Long bones, 107. 
 
CONTENTS. 
 
 xm 
 
 Flat bones, 108. 
 
 Irregular bones, 109. 
 
 Eminences and depressions of bones, 
 109. 
 
 Vessels, 109. 
 
 Haversian canals, 110. 
 
 Veins of bones, llO. 
 
 Mr. Tomes' observations on the ulti- 
 mate structure of the osseous tissue, 
 111. 
 
 Lacunce and canaliculi, or pores, of the 
 osseous tissue, 112. 
 
 Their varieties, 113 ; usual shape and 
 size, 114. 
 
 Laminated texture of bone, 114. 
 
 Outer, inner, and Haversian surfaces 
 
 of a long bone, 114. 
 Periosteal, medullary, and Haversian 
 
 layers, or systems of lamellw, 114. 
 Arrangement of the lacunae and pores 
 
 with regard to the vascular surface 
 
 of bone, 116. 
 Lamellae, 116. 
 Development of bone, 118. 
 Centres of ossification, 118. 
 Process of ossification traced through 
 
 its stages, 119. 
 Growth of bone, 122. 
 Experiments vrith madder, 123. 
 Reparation of bone, 125. 
 
 CHAPTER VI. 
 
 PASSIVE ORGANS OF LOCOMOTION, CONTINUED. 
 
 Synovial membranes of joints, 126. 
 
 Bursse, 127. 
 
 Synovial sheaths, 127. ^ 
 
 Synovia, 128. 
 
 Serous membranes, 128. 
 
 Minute structure of synovial and serous 
 
 membranes, 129. 
 Physical and vital properties, 130. 
 Of the Joints, 130. 
 Accessory structure, 131. 
 Influence of atmospheric pressure on the 
 
 joints, 131. 
 Of the forms and classification of joints, 
 
 131. 
 Synarthrosis, Suture, 132. 
 
 Schindylesis, Gomphosis, Amphiar- 
 
 throsis, 133; 
 Diathrosis, 133. 
 
 Various motions of joints, 134. 
 Arthrodia, Bnarthrosis, 134-5. 
 Ginglymus, Diarthrosis rotatorius, 135- 
 
 136. 
 Mechanism of the Skeleton, 136. 
 Cranium, 136. 
 Spine, 137. 
 Pelvis, 139. 
 Thorax, 140. 
 
 Pelvis and thorax compared, 140. 
 Lower extremities, 141. 
 Upper extremities, 143. 
 The hand, 145. 
 
 CHAPTEE VII. 
 
 ACTIVE ORGANS OF LOCOMOTION. 
 
 Of Muscle in general, 146. . 
 
 Of the striped fibres, 146. 
 
 Size and shape, 147. 
 
 Internal structure, 147. 
 
 Saroous elements, 148. 
 
 Sarcolemma, 150. 
 
 Attachment of tendon, 152. 
 
 Development, 152. 
 
 Growth, 153. 
 
 Of the unsiriped fibres, 153. 
 
 Size, shape, and structure, 154. 
 
 Distribution of the striped and unsiriped 
 fibres in the body, 155. 
 
 Dartos, 155. 
 
 Distribution in,the animal series, 156. 
 
 Arrangement of fibres in voluntary mus- 
 cles, 157. 
 
 Arrangement of tendon in muscles, 157. 
 
 Origin and insertion, 158. 
 
 Arrangement of fibres in ike hollow 
 muscles, 158. 
 
 Areolar tissue of muscles, 159. 
 
 Bloodvessels, 159. 
 
 Nerves, 160. 
 
 Antagonism of muscles, 162. 
 
 Arrangement of muscles on the Skeleton, 
 162. 
 
 Contractility, elasticity, and tenacity 
 of muscle, 163. » 
 
 Passive contraction, 164. 
 
 Tonicity, 164. 
 
 Active contraction, muscular fatigue, 
 164. 
 
 Stimuli of muscle, nervous and physi- 
 cal, 165. 
 
 Contraction caused by a physical stimu- 
 lus applied to the isolated sarcous 
 tissue, 166. 
 
XIV 
 
 CONTENTS. 
 
 Contractility a property of the sarcous 
 tissue, 166. 
 
 A muscle not smaller during contrac- 
 tion, but shorter and thicker, 167. 
 
 The same true of the sarcous tissue, 168. 
 
 Minute movements in passive and aotiye 
 contraction, 170 ; as exhibited in te- 
 tanic muscle, 173. 
 
 Muscular sound, 173. 
 
 Seat developed during contraction, 174. 
 
 Varieties of contraction, 175. 
 
 Zigzags explained, 175. 
 
 Schwann's experiment, 176. 
 
 Character of contractility varies with 
 nutrition, 177. 
 
 Analogy to fibrine of blood, 178. 
 
 Rigor mortis, 179. 
 
 Muscular sense, 179. 
 
 Action of the sphincters, 180. 
 
 Peristaltic contraction, 180. 
 
 Rhythmical contractions, 182. 
 
 Association of movements, 182. 
 
 The attitudes of man, 183. 
 
 Power of volition and emotion over the 
 
 muscles, 185. 
 Reflex movements, 186. 
 Instinctive movements, 186. 
 Mechanical or habitual movements, 188. 
 
 CHAPTER VIII. 
 
 INNERVATION. 
 
 Examples of Nervous actions, 187. 
 
 Connection of nervous actions with the 
 mind, 188. 
 
 Physical nervous actions, 190. 
 
 Nervous matter, 191. 
 
 ■Elements of the nervous system, 192. 
 
 Properties of nervous matter, 192. 
 
 Tubular fibre, 193 ; tubular membrane, 
 white substance, and axis-cylinder, 
 194 ; varicosities, size, 196. 
 
 Gelatinous fibre, 196. 
 
 Vesicular nervous matter, 197. 
 
 Ganglion-globules, 197. 
 
 Caudate vesicles, 198. 
 
 Connection of the fibrous with the vesicu- 
 lar matter, 199. 
 
 Nerves, 200. 
 Cerebrospinal, 200. 
 Neurilemma, bloodvessels, 200. 
 Origin, branching, 200-1. 
 Anastomosis, 201. 
 Plexuses, 203. 
 Termination of nerves, 204. 
 Oanglionic nerves, 205 ; their anion 
 
 with the spinal, 205. 
 Nervous centres, 207. 
 Coverings, 207. 
 Minute structure, 207. 
 Nerves and nervous centres of inverte- 
 
 brata, 209. 
 Development of nerve-fibres, 209. 
 Regeneration of nervous matter, 211. 
 
 CHAPTER IX. 
 
 INNERVATION, CONTINUED. 
 
 PotABITT OP NEKVES, 212. 
 
 Endowments of nerve-fibres, motor, sen- 
 sitive, and exciter, 212-13. 
 Common and special sensation, 214. 
 Subjective TohenomsTia,, 214. 
 Stimuli of nerves, mental and physical, 
 
 Nerves not passive conductors, 216. 
 
 The nervous force, 217. 
 
 Nervous and electrical forces compared, 
 
 218. 
 The nervous force not electricity, 223. 
 Animal electricity and ' 
 
 224. 
 
 CHAPTER X. 
 
 INNERVATION, CONTINTJED. 
 
 Nervous system in vertebrata, 225 ; in 
 invertebrata, 226. 
 
 MENrNGES ; Dura mater, its processes, 
 227 ; arterie's and sinuses, 229. 
 
 The arachnoid, and sub-arachnoid ca- 
 vity, 230. 
 
 Cerebro-spinal fluid, 231. 
 
 Pia mater, 232. 
 Ligamentum dentatum, 232. 
 Pacchionian glands, 233. 
 Atiatomy of the Spinal cord, 233. 
 Arrangement of gray and white matter, 
 
 235. 
 Minute anatomy of the cord, 236. 
 
CONTENTS. 
 
 XV 
 
 Four classes of fibres, 237. 
 
 Of the Encephalon, 237. 
 
 Subdiyisions, 287. 
 
 Weight of the brain in animals and man, 
 237-8. 
 
 Connection of the mind with the brain, 
 238. 
 
 Medulla oblongata, 239. 
 
 Anterior pyramids, 240. 
 
 Arciform fibres, 241. 
 
 Decussation of the anterior pyramids, 
 241. ^ 
 
 Restiform bodies, 242. 
 
 Posterior pyramids, 242. 
 
 Olivary bodies, 242. 
 
 Stilling and Wallach's researches on 
 the med. oblong., 244. 
 
 Cerebellum, 245. 
 
 Hemispheres, median lobe, and vermi- 
 form processes, 245. 
 
 Crura cerebelli, 246. 
 
 Intimate structure, 247. 
 
 Fourth ventricle, 248. 
 
 Mesocephale, 248. 
 
 Pons Varolii, 249. 
 
 Quadrigeminal bodies, 249. 
 
 Processus cerebelli ad o«rebrum, 250. 
 
 Cerebrum, 250. 
 
 Optic thalamus and corpus striatum, 
 
 250. 
 Pineal gland, 252. 
 
 Middle and posterior commissures, 252. 
 Cerebral hemispheres, 253. 
 Convolutions, 253. 
 Regular convolutions, observations of 
 
 Leuret, 254. 
 Varieties of the convolutions, 255 ; their 
 
 structure, 256. 
 Commissures of the cerebrum, trans- 
 verse and longitudinal, 257. 
 Septum luoidum and fifth ventricle, 
 
 260. 
 Pituitary body, 261. 
 Third and lateral ventricles, 261. 
 Lining membrane of the ventricles, 262. 
 General view of the course of nervous 
 
 power in the brain, 262. 
 Circulation in the brain, arteries, 263. 
 Consequence of obstruction, 265. 
 Conservative provisions, 266. 
 Capillaries, 266. 
 Veins, 266. 
 Brain subject to atmospheric pressure, 
 
 267. 
 Brain compressible, 268. 
 Practical inferences, 269. 
 
 CHAPTER XI. 
 
 INNEEVATION, CONTINUED. 
 
 Of the Ceeebro-spinal nerves in gene- 
 ral, 269. 
 Spinal nerves, their double root, 270. 
 Mode of connection, with the cord, 270. 
 Mr. Grainger's researches, 271. 
 Encephalic nerves, 271. 
 How to determine the function of a nerve, 
 
 272. 
 Anatomy, experiment, 272-3. 
 Clinical observation, 274. • 
 Functions of the roots of spinal nerves, 
 
 274. 
 Discovery of Sir C. Bell, 274. 
 Functions of the Spinal cord, 275. 
 Mental and physical nervous actions of 
 
 the cord, 275. 
 Spread of irritation in the cord, 280. 
 Tetanus, epilepsy, 280. 
 Efiects of strychnine, &c., 281. 
 Polarity of cord attending peripheral 
 
 excitement, 281. 
 Efi"eots of cold, 282. 
 Functions of the columns of the cord, 
 
 282. 
 Mechanism of the action of the cord, 287. 
 (a) Dr. Hall's hypothesis of excito-mo- 
 
 tory nerves, and a true spinal cord, 
 
 288. 
 
 Emotional fibres of Dr. Carpenter, 289. 
 
 Mr. Newport's researches on the nerv- 
 ous system of myriapoda, 290. 
 
 (6) The cord considered as a continua- 
 tion of the spinal nerves to the brain, 
 292. 
 
 (c) Hypothesis advocated by the au- 
 thors, 293-302. 
 
 Antagonism of voluntary and reflex ac- 
 tions, 296. 
 
 Many actions need a double stimulus, 
 297. 
 
 Peripheral disposition of nerves for re- 
 flex actions, 298. 
 
 Irritation propagated in the centres by the 
 gray matter, 299. 
 
 Action of the sphincter ani, 299. 
 
 Physical nervous actions of the cord in 
 locomotion and the attitudes, 301 ; in 
 regard to the generative organs, 302 ; 
 in regard to nutrition, 302. 
 
 In what sense the cord aids in main- 
 taining muscular tone. Dr. John 
 Reid'e observation, 302-3. 
 
 The cord not the source of muscular irri- 
 tability, 303. 
 
 Functions of the Medulla oblongata, 
 303 ; shares in voluntary motion, 305 ; 
 
XVI 
 
 CONTENTS. 
 
 in sensation, 305 ; in respiration and 
 deglutition, 306 ; in emotion, 307 ; is 
 affected in hysteria, chorea, hydro- 
 phobia, 307. 
 
 Functions of the Cokpoba striata, 308 ; 
 their action on motor nerves indirect, 
 309. 
 
 Functions of the Optic thalami, 309. 
 
 They are the principal foci of sensi- 
 bility, 310. _ 
 
 The corpora striata and thalami not 
 connected respectively with the low- 
 er and upper extremities, 311. 
 
 Functions of the Quadkigeminal bodies, 
 312. 
 
 Ganglia of the special senses, 313. 
 
 Centre connected loith emotion, 314. 
 
 Emotion occasions certain diseases, 316 ; 
 affects nutrition, 317. 
 
 Functions of the Oebebellum, 317. 
 
 Experiments of Flourens and others, 
 317 ; their conclusions confirmed, 
 318. 
 
 Gall's hypothesis controverted, 320. 
 
 Functions of the Cerebral convolu- 
 tions, 321. 
 
 Results of anatomy, 321 ; of experi- 
 ment, 322 ; of disease, 323. 
 
 Phrenology, 324. 
 
 Attention and memory, 324^5. 
 
 Power of speech, 325. 
 
 Cerebral sensations, 325. 
 
 Vertigo, 326. 
 
 Sleep, 327. 
 
 Somnambulism, 328. 
 
 Mesmerism, 328. 
 
 Functions of the Commissures, 329. 
 
 Some general inferences, 330. 
 
 0::;/="Appendix to the IIth Chapter contains an account of Professor Miit- 
 teucci's Electro-physiological researches, 330-39. 
 
 CHAPTER XII. 
 
 INNEEVATIO^, CONTINtTED. 
 
 Examples of Sympathetic phenomena, 
 
 339. 
 Sympathetic sensations, 340. 
 Sympathetic movements, 340. 
 
 Three classes of sympathies, 342. 
 Rationale of sympathetic phenomena, 
 343. 
 
 CHAPTER XIII. 
 
 INNERVATION, CONTINUED. 
 
 Of the Pacinian corpuscles of the nerves, 345 ; their structure, 347 ; their func- 
 tion, 350. 
 
 CHAPTER XIV. 
 
 INNERVATION, CONTINUED. 
 
 General remarks on sensation, 351. 
 
 Common or general sensibility, 352. 
 
 Special sensations, 352. 
 
 Sensation is attended by the idea of 
 locality, 352. 
 
 Of Touch, 352. 
 
 Nerves of touch, 353. 
 
 Anatomy of the shin. Elements of the 
 mucous system, 353. 
 
 Surfaces of the skin, 353-4. 
 
 Intimate structure of the Cutis, 354. 
 
 Contractility of the skin, 355. 
 
 Tactile papillce, their arrangement and 
 varieties, 356 ; internal structure, 
 359 ; their nerves, 359. 
 
 Of the Cuticle, 360. 
 
 Changes in its particles as they ad- 
 vance to the surface, 361. 
 
 The reie Malpighii not a distinct struc- 
 ture, 362. 
 
 Cuticle of coloured races, 362. 
 
 The nails, 363. 
 
 Hairs, 364. 
 
 Follicle, cortex, and fibrous part, 364. 
 
 Chemical and hygrometric characters, 
 367 ; varieties, 367. 
 
 Lymphatics of the skin, 367. 
 
 Sweat-glands, 368 ; arrangement and 
 structure, 368. 
 
 The ducts have a proper tunic in tra- 
 versing the cuticle, 369. 
 
 Sebaceous glands, 370. 
 
 Entozoa of these glands, 371. 
 
 Ceruminous glands, 371. 
 
 Functions of the skin, 371. 
 
 Absorption and secretion, 372. 
 
COOTENTS. 
 
 XVll 
 
 The skin as the organ of touch, 373 ; 
 
 aided by the muscular sense, 373. 
 Examples of the local concentration of 
 
 the seDse amoog the lower animals, 
 
 373. 
 
 Experiments of Weber on its relative 
 
 acuteness in different parts, 374. 
 Power of estimating weight, 376. 
 Heat and cold, 376. 
 
 Duration of impressions of touch, 377. 
 Sulyective sensations of touch, 377. 
 
 CHAPTER XV. 
 
 INNERVATION, CONTINUED. 
 
 Of Taste, 378. 
 
 Structure of the mucous membrane of the 
 
 tongue, 378. 
 Chorion, papillae, and epithelium of the 
 
 tongue, 379. 
 Simple and compound papUlce, 380. 
 Circumvallate papillae, 381. 
 Fungiform papillae, 382. 
 Conical ov filiform papillae, 382. 
 Nerves of the papillae, 383. 
 Functions of the papillm, 384, 
 
 Gradations of papillary structures, 385. 
 
 Precise seat of taste, 385. 
 
 Nerves of taste, 386. 
 
 Conditions of taste, 388. 
 
 Do taste and touch coexist in any of 
 
 the papillae? 389. 
 Are the varieties of taste referable to 
 
 the varieties of the papillae 1 389. 
 After-tastes, 390. 
 Subjective phenomena of taste, 390. 
 
 CHAPTER XVI. 
 
 INNERVATION, CONTINUED. 
 
 Of Smell. — Cavities of the nose, 391. 
 Structure of the nasal mucous mem- 
 brane, 392. 
 The olfactory region, 394. 
 
 Nerves of the nose, 396. 
 Conditions of smell, 399. 
 Subjective phenomena, 401. 
 
 CHAPTER XVII. 
 
 INNERVATION, CONTINUED. 
 
 Of Vision, 401. 
 
 Anatomy of the eyeball, 402. 
 
 Sclerotic coat, 403. 
 
 Cornea, 404. 
 
 Its five layers, 404. 
 
 Choroid, 407. 
 
 Choroidal epithelium, 409. 
 
 Ciliary processes of the choroid, 410. 
 
 Iris, 410. 
 
 Ciliary ligament and muscle, 412. 
 
 Retina, 413. 
 
 Its layers, 413. 
 
 Yellow spot, 415. 
 
 Vitreous body, 416. 
 
 Crystalline lens, 417. 
 
 Aqueous humour, 420. 
 
 Optic and other nerves, 421. 
 
 Muscles of the eye, 423. 
 
 Eyelids, 424. 
 
 Lachrymal apparatus, 426. 
 
 Phenomena of vision, 427. 
 
 2 
 
 Formation of an image on theretihaj 428; 
 
 Visual angle, 428. 
 
 Distinct and perfect vision, 429. 
 
 Adaptation to distance, 429i 
 
 Short and long sight, 430-. 
 
 Spherical and chromatic aberration cor- 
 rected, 481. 
 
 Reflection from the bottom of the eye, 
 432. 
 
 Excitability of the retina, 483. 
 
 Duration of impressions, ocular spectra, 
 434. 
 
 Blind spot, 435. 
 
 Action of the retina in vision, 437. 
 
 Correct vision with an inverted image : 
 visual idea of direction, 437 ; of 
 shape and size, 438 ; of motion in ob- 
 jects, 439. 
 
 Doubleness of the organ, 439 , 
 
 Single vision, 440.. 
 
 Mr. Wheatstono's researches, 441. 
 
xvm 
 
 CONTENTS. 
 
 CHAPTER XVIII. 
 
 INNERVATION, CONTINUED. 
 
 Of Hearing, 442. 
 
 Tlie organ in man and animals, 442. 
 
 External ear, 444. 
 
 Middle ear, 446. 
 
 Internal ear, 449. 
 
 Osseous labyrinth, 449. 
 
 Spiral lamina and its zones, 453. 
 
 Cochlearis muscle, 455. 
 
 Cochlear nerves, 457. 
 
 Membranous labyrinth, 458. 
 
 Vestibular nerves, 459. 
 
 The auditory and accessory nerves, 461. 
 
 Function of the external ear, Savart's 
 
 experiments, 463-4. 
 Of the tympanum, 465. 
 Of the labyrinth, 469. 
 
 CHAPTER XIX. 
 
 innervation; continued. 
 
 Of the Encephalic Nerves exclusivelt 
 
 MOTOR in function, 473. 
 Third pair, 473. 
 Fourth pair, 476. 
 
 Sixth pair, .476. 
 Facial nerves, 477. 
 Ninth.pair, 480. 
 
 CHAPTER XX. 
 
 innervation, continued. 
 
 Of the CoMPocND Encephalic Nerves, 
 
 481. 
 Fifth pair, 481. 
 Eighth pair, glosso-pharyngeal, 485. 
 
 Pneumogastric, 488. 
 Branches of the vagus, 488-9. 
 Spinal accessory, 495. 
 
 CHAPTER XXI. 
 
 iniJervation, continued. 
 
 Of the Sympathetic Nerve, ■ 
 Cephalic portion, 500. 
 Cervical portion, 501. 
 
 Thoracic portion, 503. 
 
 Lumbar and sacral portions, 504. 
 
 Function of the sympathetic nerve, 506. 
 
 CHAPTER XXII. 
 
 digestion. 
 
 Subordinate processes of Digestion, 
 
 512. 
 Modifications in animals, 513. 
 Classification of food, 514. 
 
 Diet, 517. 
 
 Quantity of food necessary for health, 
 
 518. 
 Hunger and thirst, 521. 
 
 CHAPTER XXIII. 
 
 DIGESTION, continued. 
 
 PREPARATORT PROCESSES, 522. 
 
 Prehension, 523. 
 
 Mastication, 524. 
 
 The tongue, 525. 
 
 The teeth, 525. 
 
 Internal structure of the teeth, 527. 
 
 Development of the teeth, 532. 
 
 First and second dentitions, 536. 
 
 Of the jaw bones at diflferent ages, 538. 
 
 Movements of mastication, 538. 
 
 Insalivation, 539. 
 
 The saliva, 540. 
 
 Deglutition ; the pharynx, 541. 
 
 CEsophagus, 544. 
 
CONTENTS. 
 CHAPTER XXIV. 
 
 XIX 
 
 DIGESTION, CONTINUED. 
 
 The Stomach, 545. 
 Its mucous coat, 546. 
 Stomach cells, 547. 
 Stomach tubes, 548. 
 Pyloric tubes, 549. 
 Movements of the stomach, 550. 
 Changes in the mucous membrane dur- 
 ing digestion, 551. 
 
 Of the solution of the stomach after 
 
 death, 553. 
 The gastric juice, 554. 
 The acid of the gastric juice, 567. 
 Nature of the digesting power of the 
 
 gastric juice, 559. 
 The chyme, 561. 
 Rate of stomach digestion, 561. 
 Eructation and vomiting, 563. 
 
 CHAPTER XXV. 
 
 DIGESTION, CONTINUED. 
 
 Anatomy of the Intestinal Canal, 
 567. 
 
 The intestinal canal in vertebrata, 568. 
 
 The tunics of the intestinal canal, 572. 
 
 Of the valvulae conniventes, folds and 
 villi, 574. 
 
 Of the glands of the intestine, 579. 
 
 Brunner's glands, 579. 
 
 Peyer's glands, 581. 
 
 Movements of the intestines, 583. 
 
 Changes in the mucous membrane dur- 
 ing intestinal digestion, 585. 
 
 Of the chyle, 587. 
 
 Changes of the food in the small in- 
 testine, 587. 
 
 Function of the Pancreas in digestion, 
 592. 
 
 The function of the Liver, 596. 
 
 Quantity, and the physical and chemi- 
 cal properties of the bile, 597-8. 
 
 Use of the bile, 600. 
 
 Digestion in the large intestine, 608. 
 
 Defecation, 608. 
 
 CHAPTER XXVI. 
 
 ABSORPTION. 
 
 Nature of Absorption, 611. 
 The absorbent vessels, 612. 
 Contractility of the absorbent vessels, 
 
 615. 
 Origin of the lymphatics, 616. 
 Do the lacteal and lymphatic vessels 
 
 absorb ? 618. 
 Contents of the absorbents, 619. 
 Ljjmph, 620. 
 
 Chyle, 620. 
 
 Quantity of chyle and lymph, 622. 
 
 Absorption as influenced by the quali- 
 ties of the fluids, 623. 
 
 Absorption as influenced by pressure, 
 625. 
 
 Absorption as influenced by the motion 
 of the fluid within the vessels, 626. 
 
 Function of the absorbents, 627. 
 
 CHAPTER XXVII. 
 
 THE BLOOD. 
 
 General characters of the Blood, 628. 
 
 The constitution of the blood, 629. 
 
 The quantity of blood in the body, 630. 
 
 The phenomenon of the coagulation,630. 
 
 BufSng and cupping, 632. 
 
 Physical analysis of the blood, 633. 
 
 The fibrine, 634. 
 
 The red corpuscles, 634. 
 
 The colourless corpuscles, 637. 
 
 Function of the red corpuscles, 640. 
 Office of the colourless corpuscles, 641. 
 Of the development and decay of the 
 
 blood corpuscles, 642. 
 The Chemical analysis of the blood, 643. 
 Composition of the red particles and of 
 
 the haematine, 644. 
 Influence oivenesection and disease upon 
 
 the blood, 645. 
 
XX 
 
 CONTENTS. 
 
 CHAPTER XXVIII. 
 
 THE CIECULATION OF THE BLOOD. 
 
 Of the Bloodvessels, 649. 
 
 The middle or fibrous coat of the artery, 
 
 650. 
 Muscular fibres, 652. 
 Epithelial layer, 653. 
 Anastomoses of arteries, 656. 
 The structure of veins, 658. 
 Of the capillaries, 659. 
 Of the heart, 662. 
 
 Cavities and valves of the heart, 664. 
 Pericardium and endocardium, 666. 
 Of the structure of the valves of the 
 
 heart, 667. 
 Mechanism of the valves, 669. 
 Of the muscular tissue of the heart, 
 
 669. 
 Nutrition of the heart, 671. 
 Nerves of the heart, 671. 
 Of the action of the heart, 672. 
 Rhythm of the heart, 674. 
 
 The course of the circulation, 676. 
 
 Of the portal circulation, 676. 
 
 Of the fcetal circulation, 677. 
 
 Of the forces which circulate the blood, 
 678. 
 
 Of the circulation in arteries, 679. 
 
 The pulse, 681. 
 
 Contractility of arteries, 682. 
 
 The force of the heart, 684. 
 
 Influence of respiration upon the cir- 
 culation, 689. 
 
 Of the velocity of the blood in arteries, 
 690. 
 
 Of the circulation in the capillaries, 
 693. 
 
 Of the forces which maintain the capil- 
 lary circulation, 694. 
 
 Circulation in the veins, 700. 
 
 Suction-power of the auricle, 702. 
 
 Rapid effect of poisons, 705. 
 
 CHAPTER XXIX. 
 
 RESPIRATION. 
 
 General description of Respibatory 
 
 Organs, 706. 
 Comparative anatomy, 706. 
 Organs of respiration in man; the 
 
 trachea, 707. 
 Coats of the bronchi, 709. 
 Infundibula, 712. 
 Pulmonary artery, 712. 
 Minute anatomy of the lungs, 713. 
 Movements of respiration, 716. 
 Action of therespiratory muscles, 718. 
 Power of the respiratory muscles, 720. 
 Use of the trachealis muscle, 721. 
 Excitation of respiratory movements, 
 
 721. 
 
 Ratio of respirations to the pulse, 722. 
 Amount of air breathed, 722. 
 Changes in the respired air, 723. 
 Influence, of exercise, temperature of 
 
 the surrounding medium, age, sex, 
 
 etc., upon the exhalation of carbonic 
 
 acid, 725-6. 
 Amount of Oxygen inhaled, 727. 
 Exhalation of nitrogen, 728. 
 Changes in the blood resulting from 
 
 respiration, 728. 
 Quantity of carbon removed from the 
 
 body, 730. 
 Theory of respiration, 731. 
 
 CHAPTER XXX. 
 
 ANIMAL HEAT. 
 
 Of the Development of Heat in the 
 body, 733. 
 
 Development of heat in plants and ani- 
 mals, 733-4. 
 
 Temperature of the human body, 735. 
 
 Influence of age, sleep, exercise, climate, 
 and seasons, etc., upon the temperature 
 of the hp^y, 735-6. 
 
 Loss of heat by evaporation, 737. 
 Influence ot food, 738. 
 Influence of disease, 739. 
 Hibernation, 739. 
 Theory of animal heat, 740, 
 Influence of the nervous system, 742. 
 
CONTENTS. 
 CHAPTBE XXXL 
 
 XX. 
 
 VOICE. 
 
 The Larynx, the Organ of the Voice, 
 
 744. 
 The cartilages oftlie larynx, 745. 
 Vocal chords, 747. 
 Action of laryngeal muscles, 749. 
 Nerves, 750. 
 
 Action of larynx and theory of vocaliza- 
 tion, 750. 
 Production of vocal sounds, 752. 
 Chest voice, and falsetto, 753-4. 
 Singing, 754. , 
 
 Influence of nerves on voice, 755. 
 Speech, 756. 
 
 CHAPTER XXXII. 
 
 SECRETION. 
 
 Of Secretions and Excretions, 757-8. 
 Secretions, not excrementitious, which 
 
 serve ulterior offices, 759. 
 Vicarious secretion, 760. 
 Ingesta and egesta, 761. 
 
 Anatomy of secreting organs generally, 
 
 Of the gland cell, 764. 
 
 Of the ducts of glands, 764. 
 
 CHAPTER XXXIII. 
 
 SECRETING GLANDS. 
 
 Of the Pancreas, 766. 
 Of the Liver, 767. 
 Chemical composition, 768. 
 Lobules of the liver, 771. 
 Portal canals, 772. 
 Portal vein, 773. 
 Hepatic artery, 774. 
 Duct, 775. 
 Parietal sacculi, 775. 
 
 Gall-bladder, 111. 
 
 Hepatic vein, 778. 
 
 Of the liver cells, 119. 
 
 Of the smallest branches of the hepatic 
 
 duct, 781. 
 Of the passage of the bile into the 
 
 ducts, 784. 
 Quantity and uses of the bile, 784. 
 
 CHAPTER XXXIV. 
 
 SECRETING GLANDS, CONTINUED. 
 
 Of the Kidney, 785. 
 
 Surface of the kidney, 787. 
 
 Matrix of the kidney, 788. 
 
 Uriniferous tubes, 789. 
 
 Malpighian bodies, 789. 
 
 Convoluted portion of the uriniferous 
 
 tube, 791. 
 Straight portion of the tube, 792. 
 Vessels of the kidney, 793. 
 
 Malpighian tufts, 794. 
 
 Of the secretion of urine, 796. 
 
 Of the Urine, 797. 
 
 Composition of healthy urine, 799. 
 
 Uric acid, 800. 
 
 Extractive matters, 801. 
 
 Pelvis of the kidney, 803. 
 
 Bladder, 804. 
 
 Epithelium of bladder, 805. 
 
 CHAPTER XXXV. 
 
 DUCTLESS GLANDS. 
 
 Of the Spleen, 806. 
 
 Trabecular tissue of the spleen, 807. 
 
 Spleen pulp, 808. 
 
 Splenic artery, 810. 
 
 Malpighian corpuscles, 811. 
 
 Uses of the spleen, 813, 
 Of the Thyroid, 815. 
 Of the Thymus, 816. 
 Mr. Simon's researches, 818. 
 
xxu 
 
 CONTENTS. 
 
 CHAPTER XXXVI. 
 
 GENERATION. 
 
 Fissiparous Generation, 819. 
 Multiplication by Gemmation, 820. 
 Metamorphosis and metagenesis, 821-2. 
 
 Sexual organs in invertebrata, 825. 
 Sexual organs in vertebrata, 827. 
 
 CHAPTER XXXVII. 
 
 GENERATION, CONTINUED. 
 
 Male Organs of Generation, 829. 
 
 Testicle, 829. 
 
 Vesiculm seminales, 831. 
 
 Prostate gland, 831. 
 
 Penis, 832. 
 
 Ureilra, 833. 
 
 Seminal tubules, 835. 
 
 Spermatozoa, 836. 
 
 Development of spermatozoa, 836. 
 
 Movements of the spermatozoon, 837. 
 
 CHAPTER XXXVIII. 
 
 GENERATION, CONTINUED. 
 
 Female Organs or Generation, 839. 
 Ovaries, 839. 
 Chraafian follicles, 840. 
 Ovum, 841. 
 Fallopian tube, 842. 
 
 Uterus, 842. 
 
 Nerves of the uterus, 844. 
 
 Vagina and accessory female organs, 
 
 845. 
 Urethra, 846. 
 
 CHAPTER XXXIX. 
 
 GENERATION, CONTINUED. 
 
 Of Pdbertt, 846. 
 
 Menstruation, 847. 
 
 Maturation and discharge of ova, 848. 
 
 Heat and Rut in animals, 849. 
 Formation of corpora lutea, 850. 
 True and false corpora lutea, 852. 
 
 CHAPTER XL. 
 
 GENERATION, CONTINUED. 
 
 Of the Impregnation of the Ovum, 
 853. 
 
 Micropyle, 853. 
 
 Changes in the ovum immediately suc- 
 ceeding impregnation, 854. 
 
 Rotation of the yolk, 855. 
 
 Cleavage of the yolk, 855. 
 
 Formation of blastodermic vesicle or 
 
 germinal membrane, 857. 
 Formation of decidua, 859. 
 Structure and nature of membrana 
 
 decidua, 860. 
 Decidua reflexa, 861. 
 
 CHAPTER XLI. 
 
 DEVELOPMENT. 
 
 Of the Development of the Embryo, 
 
 863. 
 Investing membrane and membrana 
 
 intermedia of Reichert, 864. 
 First trace of the embryo, 865. 
 Primitive streak, 866. 
 
 Formation of dorsal and ventral lamina;, 
 
 867. 
 Formation of amnion, 869. 
 Branchial fissures and arches, 870. 
 Development of the human embryo, 871. 
 
CONTENTS. 
 
 CHAPTEE XLII. 
 
 XXlll 
 
 DEVELOPMENT, CONTINUED. 
 
 Of the De7Elopment of the Different 
 
 Organs, 875. 
 Spinal column, 875. 
 Of the face and visceral arches, 877. 
 Of the nervous system, 878. 
 Of the organs of vision and hearine, 
 
 879. 
 Of the heart, 880. 
 Of the aortic arches, 882. 
 
 Of the anterior venous trunks, 8 
 Of the lungs, 883. 
 Thyroid glands, 883. 
 Of the alimentary canal, 883. 
 Of the Liver and Pancreas, 884. 
 Of the Spleen, 885. 
 Wolffian bodies, 886. 
 Supra-renal capsules, 887. 
 Organs of generation, 887. 
 
 CHAPTEK XLIII. 
 
 DEVELOPMENT, CONTINUED. 
 
 Of the Membranes of the Fcetcs, 1 
 Tormation of the placenta, 888. 
 Amnion, 892. 
 Liquor amnii, 892. 
 Umbilical vesicle, 893. 
 
 Development of the allantois, 894. 
 Allantoic fluid, 896. 
 Umbilical cord, 897. 
 Birth, 897. 
 
 CHAPTER XLIV. 
 
 LACTATION. 
 
 Of the Lacteal Glands, 898. 
 Follicles of the lacteal glands, 899. 
 
 I Bloodvessels and absorbents, 900. 
 I mm, 901. 
 
LIST OF ILLUSTRATIONS. 
 
 FIG. . PAGE 
 
 1 . Primary organic cell ..... Authors 32 
 
 2. Examples of cilia ....... 73 
 
 a. Portion of a bar of the gill of the sea-mussel — from Dr. Shar- 
 
 pey's art. Cilia, in Cyel. Anat. and Phys. 
 g. Leucophrys patula — after Bhrenberg. 
 The rest from the art. Mucous Membrane in Cycl. Anat. 
 
 3. Cilia of the uriniferous tube . . . Phil. Trans. 1842 76 
 
 4. White fibrous tissue ..... Authors 79 
 
 82 
 84 
 After Schwann 84 
 Authors 85 
 
 89 
 90 
 
 5. Yellow fibrous tissue .... 
 
 6. The two elements of the areolar tissue 
 
 7. Development of the areolar tissue 
 
 8. Meshes of the areolar tissue when dried 
 
 9. Polyhedral form of fat vesicles 
 
 10. Bloodvessels of fat . 
 
 11. Margarine and elaine of human fat, separated within ) ,, q| 
 
 the vesicle ..... j 
 
 12. Development of the adipose tissue . . . After Schwann 93 
 
 13. Cartilage-cells from the chorda dorsalis of the Lamprey Authors 96 
 
 14. Section of articular cartilage from the head of the humerus " 97 
 
 15. Section of the cartilage of the ribs ... " 98 
 
 16. Section of the thyroid cartilage ... " 98 
 
 17. Elementary structures from an intervertebral disc . " 101 
 
 18. Vertical section of the upper end of thefemur After Bourgery 106 
 
 19. Longitudinal section of bone . . . Authors 110 
 
 20. Venous canals in the diploe of the cranium . . " 111 
 
 21. Ultimate granules of bone . From a preparation of Mr. Tomes 112 
 
 22. Lacunae and pores of osseous tissue ... " 112 
 
 23. Transverse section of bone surrounding an Haver-) „ ■,-.„ 
 
 sian canal . . . . . . ) 
 
 24. Forms of the lacunae and pores of osseous tissue . From Mr. Tomes 113 
 
 25. Systems of lamellae in the compact tissue of a long bone Authors 115 
 
 26. Badiation from the Haversian canals . . From Mr. Tomes 116 
 
 27. Haversian systems of lamellae ... " 116 
 
 28. Vertical section of the knee-joint of an infant . Authors 118 
 
 29. Scapula of a foetus, exhibiting the progress of ossification " 119 
 
 30. Vertical section of cartilage near the ossifying surface " 119 
 
 31. Horizontal section near the ossifying surface . From Mr. Tomes 120 
 
 32. Vertical section of newly formed bone, showing the 1 . ,, ,„, 
 
 second stage of ossification . . ,J -a-utnors i^l 
 
 33. Another section ..... " 121 
 
 34. Epithelium of serous membrane ... " 129 
 
 35. Yellow fibrous element of the areolar tissue of serous \ „ ,on 
 
 membrane . . . . . . ] 
 
 36. Transverse sections of injected striped muscles f Cycl. Anat., art. 1 -iaj 
 
 from the Frog and from the Dog . . ( Muscle | 
 
 37. Fragments of elementary fibres, showing a f Altered from Cycl. 1 -.^j, 
 
 cleavage into discs and fibrillae . . \ Anat., art. Muscle J 
 
XXVI LIST OF ILLUSTBATIONS. 
 
 FIG. PAGE 
 
 38. Transverse section of striped muscle, showing the f From the Phil. | ^^g 
 
 sarcous elements . . . . \ Trans. 1840 J 
 
 39. Lateral union of the sarcous elements , . . " 150 
 
 40. Sarcolemma stretching between two fragments of a striped fibre " 151 
 
 41. Hernial protrusion of the sarcous tissue through the 1 „ jgj^ 
 
 sarcolemma . . . . .J 
 
 42. Attachment of tendon to muscle . From the Phil. Trans. 1840 151 
 
 43. " " " . " " 152 
 
 44. Stages of the development of striped muscle, partly from Schwann 
 
 [a. Schwann ; b.f. Authors; the rest from Phil. Trans. 1840) 152 
 
 45. Development of striped fibre in the Insect . Phil. Trans. 1840 153 
 
 46. Fibres of unstriped muscle and their cytoblasts Cycl. Anat., art. Muscle 154 
 
 47. Capillaries of muscle ..... Authors 160 
 
 48. Termination of the nerves in muscle . . After Burdach 161 
 
 49. Contraction of striped muscle . From the Phil. Trans. 1840 170 
 
 50. " " " . . " " 171 
 61. " " " . . " " 172 
 
 52. Tubular and gelatinous fibres of nerves . . Authors 194 
 
 53. Nerve-tubes of the Eel, in water and ether ... " 195 
 
 54. Nerve-vesicles from the Gasserian ganglion . " 197 
 
 55. Caudate nerve-vesicles from the cerebellum and cord " 197 
 
 56. Caudate nerve-vesicle, and axis-cylinder of a tubular 1 „ igg 
 
 fibre, from the cord J 
 
 57. Two views of the vesicular and fibrous matter of the cerebellum 199 
 
 58. Vesicular and fibrous matter in the Gasserian ganglion " 199 
 
 59. Decussation of fibres within a nerve . . . After Valentin 202 
 
 60. Terminal loops of nerve in the pulp of a tooth . " 204 
 
 61. Origin of a spinal nerve and union with the sympathetic Authors 205 
 
 62. Ganglion of the Greenfinch .... After Valentin 207 
 
 63. Otio ganglion of the Sheep .... " 208 
 
 64. Nervous fibres of Insects .... Authors 209 
 
 65. Stages of the development of nerve . . . After Schwann 210 
 
 66. Six transverse sections of the spinal cord . . Authors 235 
 
 67. Transverse section of the cord . After Stilling and Wallach 236 
 
 68. Front view of the Medulla oblongata . . Authors 240 
 
 69. Posterior view of the Medulla oblongata . . " ■ 242 
 
 70. Transverse section ofthe Medulla oblongata After Stilling and Wallach 244 , 
 
 71. Diagram of the encephalon .... After Mayo 246 
 
 72. Capillaries of the gray substance of the convolutions Authors 266 
 
 73. Portions of the cord in Spirostreptus . , After Newport 291 
 
 74. A. B. c. D. Pacinian corpuscles . . . Authors 1 o^e 
 " E. " " rare form After Henle and KoUiker j 
 
 75. Pacinian corpuscle — general structure . . Authors 347 
 
 76. Pacinian corpuscles — arrangement of nerve-tube . " 349 
 
 77. Elastic element of the cutis of the axilla . . " 355 
 
 78. Tactile ridges of the skin of the palm, with the 1 ,, ,-., 
 
 orifices of the sweat-ducts J 
 
 79. Deep surface of the cuticle of the palm, with the cuti- I ,, „.- 
 
 cular lining of the sweat-ducts | 
 
 80. Under-surfaoe of the cuticle of the leg, contrasted . ■ " 358 
 
 81. Papillae of the palm, cuticle detached . . " 359 
 
 82. Bloodvessels of the papillw of the heel . . " 359 
 
 83. General section of the integument of the sole . " 360 
 
 84. Skin of the heel, treated with weak and strong solution of potass " 361 
 
 85. Cuticle of the scrotum of a negro ... " 302 
 
 86. Section of the nail and its matrix ... " 363 
 
 87. Hair and hair-follicle seen in section . . " 364 
 
 88. Surface, longitudinal and transverse sections, of hair " 365 
 
 89. Layer of sweat-glands of the axilla ... " 368 
 
 90. Sweat-gland and its bloodvessels ... " 368 
 
 91. Cuticular portion of a sweatrduot of the heel . " 309 
 
LIST OF ILLUSTRATIONS. 
 
 XXVH 
 
 via. 
 
 92. 
 
 93. 
 
 94. 
 
 95. 
 
 96. 
 
 97. 
 
 98. 
 
 99. 
 100 
 
 101. 
 102. 
 103- 
 104. 
 105. 
 106. 
 107. 
 108. 
 109. 
 110. 
 111. 
 112. 
 113. 
 114. 
 115. 
 116. 
 117. 
 118. 
 119. 
 120. 
 121. 
 122. 
 123. 
 124. 
 125. 
 126. 
 127. 
 128. 
 129. 
 130. 
 131. 
 ]32. 
 133. 
 134. 
 135. 
 136. 
 137. 
 138. 
 139. 
 140. 
 141. 
 142. 
 143. 
 144. 
 145. 
 146. 
 147. 
 148. 
 149. 
 150. 
 151. 
 
 PAGE 
 
 Three views of sebaceous glands and hair-follicles . Authors 370 
 
 Entozoa of the sebaceous follicles . . . " 371 
 
 Dorsal surface of the tongue . . . After Soemmering 379 
 
 Simple papillae near the base of the tongue 
 Vertical section of a circumvallate papilla . 
 Compound and simple papillae of the foramen caecum 
 Fungiform papilla, with its simple papillae and vessels 
 Forms of the conical or filiform papillae 
 
 A. Section of filiform and fungiform papillse 1 
 
 B. Structure of filiform papillfe J 
 Nerves of the papillae of the tongue 
 Cartilages of the nose ' . 
 Ciliated epithelium of the nose 
 Olfactory region of the nose, vertical section 
 Capillaries of the olfactory region . 
 Nerves of the outer wall of the nose . . 
 Olfactory filaments of the dog 
 Nerves of the septum of the nose . 
 Vertical section of sclerotica and cornea . 
 Tubes of the cornea proper 
 Vertical section of the cornea 
 Choroid and iris .... 
 Vessels of the choroid and iris 
 Choroidal epithelium, and pigment of the choroid 
 Border of posterior elastic lamina of cornea 
 Diagram of ciliary muscle . 
 Vertical section of the retina 
 Membrane of Jacob 
 Yellow spot of retina 
 Position of lens in vitreous humour 
 Lens at dififerent ages 
 Cells and fibres of the lens . 
 Lens, to show its lamella 
 Arrangement of fibres in the lens . 
 Plan of the optic tracts and nerves 
 Course of fibres in the chiasma . 
 Tubules of the optic nerve . . 
 Conjunctival surface of eyelids 
 Meibomian gland of a foetus 
 Lachrymal apparatus 
 General section of the ear . 
 Diagram of the inner wall of the tympanum 
 Ossicles of the ear .... 
 Osseous labyrinth of the left side . . 
 Interior of the osseous labyrinth 
 Cochlea of a new-born Infant 
 Section of the cochlear canal 
 Denticulate lamina of the cochlea . 
 Lamina spiralis of the cat . . 
 Cochlearis muscle of the sheep 
 Plexiform arrangement of cochlear nerves 
 Membranous labyrinth of left side . 
 Nerves of membranous labyrinth . 
 Termination of nerve in ampulla 
 
 Authors 380 
 381 
 381 
 
 Authors 382 
 
 382 
 
 " 383 
 
 " _ 384 
 
 After Soemmering 392 
 
 Authors 393 
 
 394 
 
 " _ 395 
 
 After Soemmering 396 
 
 Authors 
 After Arnold 
 Authors 
 
 After Zinn 
 
 After Arnold 
 
 Authors 
 
 397 
 399 
 405 
 405 
 408 
 408 
 408 
 409 
 411 
 412 
 414 
 415 
 416 
 417 
 
 After Jacob 
 After Soemmering 
 
 After Arnold 
 
 After Scemmering 417 
 
 Authors 418 
 
 After Arnold 
 
 Authors 
 
 1 Diagrams illustrative of Savart's researches on 
 I hearing 
 
 Vertical section of human incisor . 
 Sections of enamel and dentine 
 Sections of tubules of dentine 
 
 419 
 
 419 
 
 421 
 
 422 
 
 423 
 
 After Soemmering 425 
 
 From a preparation of Dr. Goodfellow 426 
 
 After Soemmering 426 
 
 After Scarpa 444 
 
 Authors 447 
 
 After Arnold 448 
 
 After Soemmering 450 
 
 451 
 
 After Arnold 453 
 
 Authors 454 
 
 455 
 
 " 455 
 
 " 456 
 
 457 
 
 After Breschet 458 
 
 After Steifensand 460 
 
 After Wagner 460 
 
 ' 465 
 
 466 
 
 466 
 
 [467 
 
 Authors 528 
 
 529 
 
 530 
 
 I After Savart | 
 
XXVlll 
 
 LIST OF ILLUSTRATIONS. 
 
 pia. 
 
 152. Views of the enamel fibres . . - . 
 
 153. Enamel pulp and matrix .... 
 
 154. Stomach cells and epithelium 
 
 155. Horizontal section of stomach cell and tubes 
 
 156. Vertical sections of mucous membrane of stomach 
 
 157. Section of mucous membrane of the small intestine "I 
 
 in the dog . . . . . .J 
 
 158. Transverse section of Lieberklihn's tubes or follicles 
 
 159. Villi of duodenum of dog .... 
 
 160. " " the columnar epithelium 
 stripped off . . 
 
 161. Capillary plexus of the villi of the human small 
 
 intestine ...... 
 
 162. Vertical section of the coats of the small intestine 
 
 of a dog ' . 
 
 163. Epithelium from the cavity of the duodenum of a 
 
 dog 2J hours after food .... 
 
 164. Vertical section of the mucous membrane of the 
 
 duodenum in the horse, showing Brunner's glands 
 
 165. A solitary gland from the small intestine of the 
 
 human subject ..... 
 
 166. A patch of Peyer's glands of the adult human sub- 
 
 ject ....... 
 
 167. Vertical section through a patch of Peyer's glands 
 
 in the dog ...... 
 
 168. Diagram to illustrate the formation of a backward 
 
 axial current ..... 
 
 169. Longitudinal wavy fibres from the thoracic duct of 
 
 the horse, with nucleated particles lining the 
 vessels ...... 
 
 170. One of the inguinal lymphatic glands injected with 
 
 mercury ; and superficial lymphatic trunks 
 
 171. Bamification of a lymphatic of the under part of 
 
 the tail of a tadpole 
 
 172. Fluid from the mesenteric gland of a rabbit, when \ 
 
 white chyle was present in the lacteals 
 
 173. Red corpuscles from human blood . 
 
 174. Red corpuscles of the ox 
 
 175. Red corpuscles of pigeon's blood 
 
 176. Blood corpuscles of the common frog 
 
 177. Red corpuscles of fishes 
 
 178. Blood corpuscles of the crab 
 
 179. Phases of the human blood corpuscle 
 
 180. Corpuscles from the vena cava nepatica of the em 
 
 bryo chick, on the twentieth day of incubation 
 
 181. Granules, granule-cells and red. blood corpuscles 1 
 
 from the embryo chick . . . .J 
 
 182. Granules, granule-cells, and red corpuscles . 
 
 183. Nucleated cells, red corpuscles, and granules 
 
 184. Finely fibrous layer of the longitudinal fibrous tunic 
 
 of the aorta of the horse .... 
 
 185. Coarsely fibrous layer of the longitudinal fibrous 
 
 tunic of the aorta of the horse 
 
 186. A portion of the circular fibrous tunic of the aorta 
 
 of the horse .... 
 
 187. Section of the aorta of the ox . . 
 
 188. Section of the whole thickness of the artery 
 
 189. Circular fibrous coat, showing penniform fibres 
 
 190. A single bar or penniform fibre from the circular ] 
 
 fibrous tunic of the aorta of the ox . . | 
 
 After 
 
 After Retzius 
 Authors 
 
 (( 
 
 PAGE 
 
 531 
 533 
 547 
 548 
 548 
 
 Authors 
 
 573 
 
 Dr. Salter 
 
 574 
 576 
 
 tt 
 
 577 
 
 tt 
 
 577 
 
 Authors 
 
 578 
 
 Dr. Salter 
 
 579 
 
 (( 
 
 579 
 
 After Boehm 
 
 580 
 
 It 
 
 580 
 
 Authors 
 
 581 
 
 Dr. Brinton 585 
 
 Dr. Salter 
 
 5l4 
 
 After Mascagni 
 
 614 
 
 After Kblliker 
 
 617 
 
 Dr. Salter 
 
 620 
 
 635 
 635 
 636 
 636 
 Wharton Jones 636 
 636 
 " 638 
 
 Dr. Salter. 
 
 638 
 
 ' (< 
 
 639 
 
 (( 
 
 639 
 639 
 
 ti 
 
 651 
 
 ft 
 
 651 
 
 It 
 
 651 
 
 tt 
 11 
 
 652 
 652 
 653 
 
 tt 
 
 653 
 
LIST OP ILLUSTRATIONS. 
 
 XXIX 
 
 Authors 
 Dr. Salter 
 
 ':! 
 
 653 
 654 
 654 
 
 660 
 
 661 
 
 667 
 667 
 667 
 668 
 
 668 
 
 691 
 
 709 
 
 Dr. Salter 710 
 
 From Rossignol 712 
 712 
 
 Authors 714 
 
 PIG. 
 
 191. Unstriped muscular fibres from the aorta of the 1 
 
 horse . . . . . .J 
 
 192. Epithelial particles from the aorta of an ox 
 
 193. Particles of epithelium and nuclei from the aortal 
 
 of a horse . . . . ' . 
 
 194. Arrangement of the capillaries on the mucous I 
 
 membrane of the large intestine of the human 
 subject . . . _ . 
 
 195. A capillary vessel from the vesicular matter of the 1 
 
 human brain . . . . . j 
 
 196. Epithelium from the left auricle of the horse 
 
 197. Epithelium from the left ventricle of the horse 
 
 198. A portion of the aortic semilunar valve in the dog 
 
 199. Diagram of the semilunar valves of the aorta . After Morgagni 
 
 200. Fibrous tissue of a semilunar valve, beneath the 1 j, goUg, 
 
 endocardium . . . . . J ' 
 
 201. Poiseuille's hsemadynamometer, modified by Volk- 1 a ftgr Volkmann 6R7 
 
 mann ...... J " 
 
 202. Hsemadromometer of Volkmann 
 
 203. Small bronchial tube from a man, age 50 . 
 
 204. Small bronchial tube laid open, showing the ar- 1 
 
 rangement of the cartilaginous flakes 
 
 205. Thin slice from the pleural surface of a cat's lung . 
 
 206. Bronchial termination in the lung of the dog 
 
 207. Thin section of a oat's lung, injected with gelatine 1 
 
 through the pulmonary artery . . .J 
 
 208. Section of the lung of a fowl . . . . From Mr. Rain ey 715. 
 
 209. Diagrams to show the movements in ordinary and f From Dr. 1 
 
 forced respiration . . . . . | Hutchinson j 
 
 210. Cartilages of the larynx and epiglottis, and upper f ^rom a prepa- 1 
 
 ringsl-fthetraeheJ .'' . . '' .[ 1%IZ^\ 
 
 211. Thyroid, cricoid, and arytenoid cartilages . 
 
 212. View of the larynx from above 
 
 213. Internal parts of larynx of the right side 
 
 214. Diagram to show parts in vocalization 
 
 215. Caeoal biliary tube of the cray fish . 
 
 216. 'Transverse section of a small portal canal and its 1 
 
 vessels . . . . , .J 
 
 217. Human liver, showing arrangement of vessels 
 
 218. Portion of the fibrous capsule of a lobule of pig's 1 
 * liver . . . . . . . I 
 
 219. Lobules of a cat's liver injected through the portal 1 
 
 vein, and also through the hepatic vein . . j 
 
 220. Longitudinal section of a small portal vein and canal 
 
 221. A lobule of pig's liver, showing branches of portal ) 
 
 vein . . . . . . .J 
 
 222. Part of arterial ring from a lobule of pig's liver 
 
 223. A small lobule of the pig's liver, showing the mode | 
 
 of branching of the duct . . . . j 
 
 224. Portion of a large duct of the pig's liver, showing f 
 
 parietal sacculi . . . . . ) 
 
 225. Longitudinal section of a hepatic vein 
 
 226. Section of horse's liver, showing radiating lines of 
 
 cells ...... 
 
 227. Portions of tubular network of the lobule . 
 
 228. Terminal portion of interlobular duct to illustrate \ 
 
 Dr. Handfield Jones' view . . . .J 
 
 229. Small branch of interlobular duct, pig 
 
 230. Narrowest portion of the duct and its junction with 1 
 
 the cell-containing network . . .J 
 
 717 
 
 745 
 
 '■] 
 
 After Willis 
 
 a 
 
 After Leidy 
 
 746 
 748 
 749 
 753 
 763 
 
 After Kiernan 769 
 
 Dr. Beale 
 
 770 
 
 it 
 
 771 
 
 Mr. Bowman 
 
 771 
 
 After Kiernan 772 
 
 Dr. Beale 
 
 773 
 
 tt 
 
 774 
 
 (t 
 
 775 
 
 tt 
 
 776 
 
 After Kiernan 
 
 778 
 
 Dr. Beale 
 
 779 
 
 it 
 
 780 
 
 
 782 
 
 Dr. Beale 
 
 783 
 
 il 
 
 783 
 
XXX 
 
 LIST OF ILLUSTKATIONS. 
 
 no. 
 231. 
 232. 
 233. 
 
 234. 
 235. 
 
 236. 
 237. 
 238. 
 239. 
 
 240. 
 241. 
 242. 
 
 243. 
 244. 
 245. 
 
 246. 
 247. 
 248. 
 
 249. 
 
 250. 
 251. 
 
 252. 
 253. 
 254. 
 255. 
 256. 
 257. 
 258. 
 259. 
 260. 
 261. 
 262. 
 
 263. 
 264. 
 265. 
 
 266. 
 
 267. 
 
 Malpighian arteries, bodies, and uriniferoua tubes . 
 
 Malpighian tuft from the proteus anguineus 
 
 Small portion of loop of capillary vessels of tiie tuft ) 
 
 Mr. Bowman 
 Dr. Beale 
 
 I 
 
 of kidney of the large water newt 
 Entire urihiferous tube from the large black newt 
 Transverse section of a pyramid of the human kid- 1 
 
 ney, about a quarter of an inch from the papilla . J 
 Malpighian tuft of the horse. 
 Malpighian tuft injected, showing efferent vein 
 Malpighian tuft from the parrot 
 Plan of the arrangement of the elements of a lobe ) 
 
 of the kidney of the boa constrictor . . J 
 
 Part of Fig. 239, shaded and more highly Inagnified 
 Plan of r^nal circulation in man and mammalia 
 Various forms of lithic acid crystals, lithate of] 
 
 soda, oxalate of lime, etc. . . . .J 
 
 Casts of uriniferous tubes . . . Partly after Dr. Johnson 798 
 
 PAGE 
 
 789 
 790 
 
 791 
 
 792 
 
 793 
 
 793 
 794 
 794 
 
 795 
 
 796 
 796 
 
 Dr. Beale 798 
 
 Mr. Bowman 
 
 Mr. Bowman 
 
 Crystals of triple phosphate and cystine 
 
 Cells from the trabecular tissue of the spleen of 1 
 
 human foetus . . . . .J 
 
 Muscular fibre-cells from the spleen of the sheep 
 Pulp of the spleen ..... 
 Transverse section of the human spleen, showing 1 
 
 the mode of the distribution of the arteries . J 
 
 Splenic corpuscle, and its connection with the I 
 
 neighbouring vessels . . . . | 
 
 Dr. Beale 
 
 Mr. Gray 
 
 After Mr. Simon 
 
 799 
 
 807 
 
 808 
 809 
 
 810 
 
 811 
 
 817 
 
 '818 
 
 After Ehrenberg 819 
 
 MuUer 820 
 
 821 
 
 821 
 
 830 
 
 830 
 
 .After E.H.Weber 83 1 
 
 . After Kolliker 833 
 
 Dr. Beale 835 
 
 836 
 
 :}. 
 
 After Meyen 
 Dr. Beale 
 
 After EoIIiker 
 After Coste 
 
 268. 
 
 269. 
 270. 
 
 271. 
 
 272. 
 
 Development of the thymus . 
 
 Binary and quaternary divisions of the simple fol 
 licles of the thymus 
 
 Multiplication of vorticella microstoma 
 
 Multiplication of nais proboscidea . 
 
 Gemmation of hydra and vorticella . 
 
 Conjugation of conferva bipunctata . 
 
 Origin and branching of the seminal tubes . 
 
 Transverse section of the vas deferens 
 
 Vesicula seminalis .... 
 
 A small artery of the corpora cavernosa 
 
 Portion of seminal tubules of man . 
 
 Spermatozoa of the river cray-fish . 
 
 Development of the spermatic filaments of the rab- 
 bit . . , . . . ■ . 
 
 Ovary of the human subject . 
 
 Mammalian ova ..... 
 
 Ova in various stages of development from the 
 toad's ovary. ..... 
 
 Muscular fibre-cells, from a gravid uterus, in va- 
 rious stages of development 
 
 Muscular fibre-cells from the uterus three weeks 
 after parturition ..... 
 
 Corpora lutea of the human female at different 
 periods ...... 
 
 Cleavage of the yolk in asoaris nigrovenosa, and 
 acuminata ...... 
 
 Multiplication of cells in the yolk of ascaris dentata 
 and cucuUanus elegans .... 
 
 Ova of the guinea-pig in various stages of develo^' 
 ment ••.... 
 
 Section of human uterus at commencing pregnancy After Weber 
 
 837 
 
 840 
 841 
 
 Dr. Beale 841 
 After Kolliker 843 
 
 After Kalliker 844 
 
 Altered from ] 
 Montgomery, I 
 Kolliker, and f ^ol 
 
 Dalton I 
 
 AfterKoUikeri 
 
 and Bagge j 
 
 After Kolliker 
 
 856 
 
 AfterBisohoff-^ 
 
 857 
 
 857' 
 858 
 859 
 860 
 
LIST OF ILLUSTRATIONS. 
 
 XXXI 
 
 Fie. 
 
 273. Uterine glands of the biteh . . ._ . 
 
 274. Thin section of human decidua soon after impreg- 
 
 nation ....•• 
 
 275. Portion of germinal membrane about the sixteenth 
 
 hour of incubation ..... 
 
 276. Portion of the germinal membrane of the bitch's 
 
 ovum ...... 
 
 277. Plan, showing the development of the dorsal and 
 
 ventral laminsB ..... 
 
 278. Germinal membrane with rudiments of the embryo 
 
 of the dog . 
 
 279. f Plan showing the manner of formation of the 
 
 280. 1 amnion, allantois, and umbilical vesicle 
 
 281. visceral, or branchial arches of an embryo dog 
 
 282. A human ovum about fifteen days after conception 
 
 283. Human foetus between the twenty-fifth and twenty- 
 
 eighth days . 
 
 284. Heart of chick at forty-fifth, sixty-fifth, and eighty- 
 
 fifth hours of incubation .... 
 
 285. Development of respiratory organs . 
 
 286. Embryo dog, showing junction of umbilical vesicle, 
 
 with intestinal canal .... 
 
 287. Extremity of a villus of the placenta 
 
 288. Relation between foetal and maternal vessels in pla- 
 
 centa ...... 
 
 289. Uterine sinuses and foetal tufts 
 
 290. Villi of the foetal portion of a placenta 
 
 291. Folds of vitellary membrane and vasa lutea 
 
 292. Diagrams to show the arrangement of the allantois 
 
 and placenta in different classes of animals 
 
 293. Diagram of uterus with a fully-formed but very 
 
 young ovum ..... 
 
 294. Preparation with six milk-tubes injected 
 
 295. One of the smallest lobules of a lacteal gland 
 
 296. Terminal follicles of lacteal gland . 
 
 297. Lacteal gland of a newly-born child 
 
 298. Colostrum corpuscles and milk globules 
 
 PAGE 
 
 After Dr. Sharpey 861 
 I " 861 
 
 1 865 
 
 I After Bischoff 867 
 
 f Partly after 1 ggg 
 [ MuUer J 
 
 I After Bischoff 868 
 
 Dr. Beale 869 
 After Bischoff 870 
 
 872 
 
 873 
 
 After Dr. A. 1 
 Thomson j 
 
 After Coste 
 
 \ Dr. A. Thomson 881 
 
 Rathke 883 
 
 I After Bischoff 884 
 
 E. H. Weber 889 
 
 I Dr. J. Reid 890 
 
 890 
 
 E. H. Weber 891 
 
 Mr. Dalrymple 893 
 
 I Dr. Beale 895 
 
 I After Wagner 896 
 
 Sir Astley Cooper 899 
 
 After Langer 900 
 
 Dr. Beale 901 
 
 Langer 901 
 
 Dr. Beale 902 
 
THE 
 
 PHYSIOLOGICAL ANATOMY 
 
 AND 
 
 PHYSIOLOGY OF MAN. 
 
 INTRODUCTION. 
 
 TiiE aim of all natural knowledge is to ascertain the laws, which 
 control and regulate the phenomena of the universe. So nume- 
 rous, and so diversified are these phenomena, that a division of 
 labour has been found, not merely convenient, but absolutely neces- 
 sary, for the study of them. The position and movements of the 
 planetary system, the crust of the earth, and its various component 
 strata, the treasures hidden in its womb, the abundant vegetation 
 that grows upon its surface, or beneath its waters, and the number- 
 less hosts of animals that dwell upon the land, or in the rivers, lakes 
 and seas, form separate branches of scientific investigation, between 
 which a sufficiently distinct line of demarkation is established by the 
 nature of the objects of inquiry peciiliaf to each. But, in all depart- 
 ments of science, the same general rules, for conducting the investi-, 
 gation, prevail, and it is only by a close adherence to these, that we 
 can arrive at safe and satisfactory conclusions. 
 
 In any scientific inquiry, the first step must be, to form a general 
 notion of the characters and properties of the objects of investigaticJiii 
 In the next place, it is necessary to observe carefully the phenomena 
 which they naturally present ; and, if they be within our reach, to 
 produce such variation in them by artificial means (by experiments), 
 as may serve to throw light upon them. If the phenomena, under 
 observation, be complex, we must analyze them, with a view to 
 ascertain the simpler ones, of which they are composed. By this 
 analysis, and by the elimination of such as are merely collateral, we 
 arrive at a phenomenon, uncomplicated, incapable of further sub- 
 division, and fundamental ; and this we are contented to receive as 
 an ultimate /ad, the result of a law in constant and universal opera- 
 tion. The accumulation of observations and experiments affords u* 
 Experience ; points out the ordinary succession of phenomena, and 
 teaches us the ways of Nature. If these phenomena are found tO' 
 present a certain uniformity, we are authorized to refer them to the 
 3 
 
26 ULTIMATE FACTS— THEORIES— HYPOTHESES. 
 
 operation of one common Cause, and we are thus led to the expres- 
 sion of the Law which reguhtes their occurrence. Proceeding in 
 this way, we are enabled to explain the whole .train of phenomena 
 ■which have been investigated,— that is, to devise a Theory which 
 develops the rationale of their occurrence. 
 
 But sometimes our experiments and observations throw an imper- 
 fect li^ht upon the phenomena which are the subjects of investiga- 
 tion ; or the latter are so remote, or so little under our control, as to 
 render both observation and experiment extremely difficult, and, in 
 some cases, impossible. The " instances" which we are enabled to 
 collect, are consequently dubious and obscure, and point darkly, or 
 not at all, to ultimate facts ; they present little or no general resem- 
 blance, and cannot be properly associated together. Here is no 
 foundation on which to build a theory: but great advantage may be 
 gained, if, with the little light we derive from these particular obser- 
 vations, aided by previous knowledge of general laws, we can frame 
 an hypothesis, offering some explanation of the phenomena. The 
 adoption of such an hypothesis, even for a temporary purpose, will 
 " afford us motives for searching into analogies," may suggest new 
 njodes of observation and experiment, and " may serve as a scaffold 
 for the erection of general laws." 
 
 Previously to the time of Lavoisier, chemists were perfectly fami- 
 liar with the occurrence of combustion under various circumstances; 
 but the opinions (hypotheses) which prevailed as to the real nature of 
 this process, afforded a very unsatisfactory explanation of it. Sub- 
 sequently, however, by the labours of Lavoisier, Davy, and others, 
 this complex" phenomenon has been observed in all its phases ; it has 
 been carefully analyzed, and has been proved to occur in all cases, 
 where substances possessed of strong chemical attractions, or different 
 ■electrical relations, are brought within mutual influence. The ulti- 
 mate fact, thus arrived at, is, that intense chemical combitiation al- 
 ways gives rise to the evolution of heat, and, in many instances, to 
 that of light also. 
 
 Again, a great number of observations have shown that bodies 
 combine tpgether^only in certain quantities, or in multiples of them; 
 that each body has its proper combining quantity, and that it never 
 enters into combination except in that quantity, or some multiple of 
 it. This is an uUimate^act, ascertained by numerous experiments, 
 and indicates the law, which is so important in chemistry, that 
 bodies unite with each other in their combining proportions only, , 
 or in. multiples of them, and in no intermediate proportions. And 
 this, again, has led to the beautiful generalization of Dalton, that the 
 ultimate atoms of bodies are their respective combining quantitifes, 
 and bef^r to each other the same proportion as their combining equi- 
 valents do,| 
 
 Or, to take an example from the science which is to form the 
 subject of the, following pages. The function of respiration in ani- 
 mals is: a very compleJ? process, respecting the nature of which many 
 unsatisfactory hypotheses had been, formed, owing to the obscurity in 
 •which many of the phenomena, immediately or remotely connected 
 
ORGANIZED AND UNORGANIZED BODIES. 27 , 
 
 with it, -were involved. Until the law of the diffusion of gases, and 
 of the permeability of membranes by them, had been developed, 
 and until it had been shown that carbonic acid is held in solution in 
 venous blood, no theory of respiration could be framed adequate to 
 explain all the phenomena. It is now proved that, in this process, a 
 true interchange of gases takes place through the coats of the pulmo- 
 nary blood-vessels, the oxygen of the air abstracting and occupying 
 the place of the carbonic acid of the blood. An admirable example 
 is thus afforded of a most important vital process taking place , iri 
 Obedience to a purely physical law. 
 
 lAvmg objects are those which properly belong to the science of 
 Physiology. These are strongly contrasted with the inanimate bodies 
 (which have never lived), to which other branches of natural science' 
 refer. At the same time, there are many points of resemblance be- 
 tween them; and as both owe their origin to the same Creative man- 
 date, and are reducible (as will be seen by-and-by) to the same 
 elementary constituents, so they are subject in a great degree to the 
 same physical laws, and are to be investigated according to the same 
 principle's of philosophical inquiry. 
 
 We propose, in the first place, to compare living, or organized 
 bodies, with inanimate, mineral, or unorganized bodies, and to explain' 
 what is meant by the term Life. Secondly, to review briefly, and' 
 with reference to th^r leading distinctions, the phenomena of the 
 vegetable and animal kingdoms. Thirdly, to point out the val,tie of 
 a knowledge of Physiology, especially that of Man, in relation to» 
 medicine, and to explain the best mode of pursuing it. 
 
 I. Every living Being is organized, — that is, composed of different* 
 parts or organs, each of which has its definite structure, by- which it 
 differs from other parts, and is capable of fulfilling a certain end. 
 The complex matter, which enters into the composition of an organ-| 
 ized being, or organism, is termed organic matter, and is obtained 
 by its proximate analysis. The ultimate analysis of this matter re- 
 solves it into elementary principles, such as constitute other objects' 
 of the universe.. 
 
 , The various bodies that compose the mineral kingdom, do not ex- 
 hibit the same distinctness, and variety of structure in their component 
 parts, nor is there any adaptation of their parts to separate functions ; 
 they are therefore called unorganized or inorgUnic, and chemical ana- 
 lysis .resolves them into those simple elements which admit of no fur- 
 ther subdivision. 
 
 Organized bodies are found in two states or conditions. The one, 
 that of life, is a state of action, or of capacity for aption. The other,' 
 that of death,' is one in which all vital action has ceased, and to which 
 the disintegration of the organized body succeeds as a natural conse- 
 quence. 
 
 An organized body in a state of active life exhibits certain pro- 
 cesses, by which its growth and nutrition are providbd for, and which, 
 enable it to resist the destructive influence of sifri-ounding agents — 
 processies,' the object of ■v^liich is to promote th^ development, and ta 
 
28 ORGANIZED AND UNORGANIZED BODIES. 
 
 preserve the integrity of the body itself. The simplest animal, or 
 vegetable, is an illustration of this remark. 
 
 But there are orgajiized bodies in which life may be said to be 
 dormant. In these, no actions or processes can be observed, nor any 
 phange taking place : yet, if placed under certain favourable condii 
 tions, vital activity will soon become manifest. Of this, we have 
 familiar examples in a seed, and in an egg. It is well known, that 
 seeds will retain their form, size, and other properties for a very 
 considerable period ; and afterwards, if suitably circumstanced, will 
 exhibit the process of germination as completely as if they had been 
 only recently separated from the parent plant. Eggs, also, may be 
 preserved for a long time without injury to the power of development, 
 or to the nutrition, of the embryo contained within them. 
 
 It is worthy of observation, that those processes, which denote 
 vital activity, may be sometimes temporarily suspended, even in fully 
 formed animals and vegetables; and, in such instances, life may be 
 said to become dormant. The privation of moisture is the ordinary 
 cause of this interruption to the phenomena of life. In dry weather, 
 mosses often become completely desiccated and appear quite dead, 
 but will speedily revive on the application of moisture. And the 
 common wheel animalcule, although apparently killed by the drying 
 up of the fluid in which it had been immersed, will speedily resume 
 its active movements on being supplied anew with water. 
 
 Inorganic bodies may be resolved by ultimate ahalysis into Oxy- 
 gen, Hydrogen, Nitrogen, Carbon, and about fifty other substances, 
 which Chemists regard as simple, because they appear to consist of 
 one kind of matter only ; that is to say, they have hitherto resisted 
 further decomposition. These elements unite in certain definite pro- 
 portions to form the compound inprganic substances. And this 
 union may consist either of two simple elements — as oxygen and 
 hydrogen, to form water; oxygen and the metal sodium, to form 
 soda ; chlorine and sodium, to form common salt ; or, of one binary 
 compound with another similar one, as of sulphuric acid (sulphur + 
 oxygen) with soda (sodium + oxygen), to form sulphate of soda ; 
 or, again, of two such salts as the last with one another, as alum, 
 which consists of sulphate of alumina united with sulphate of potassa. 
 
 As regards the mode of combination in the first of the examples 
 enumerated in the preceding paragraph, where single equivalents of 
 the elementary bodies unite, there can be but one opinion. In the 
 formation of water, one equivalent of hydrogen combines directly 
 -with one equivalent of oxygen. But when One equivalent of one 
 element is united with two or more of the other, to form the com- 
 pound substance, the mode of combination is not so evident. Per- 
 oxide of hydrogen, for example, may either result from the direct 
 combination of one equivalent of hydrogen with two of oxygen, or it 
 may be a compound of one equivalent of water with one of oxygen. 
 
 In the second example, in which two binary compounds unite to 
 form a salt, two modes of constitution have been suggested. The 
 'first supposes a direct union of a basic oxide with an acid oxide, as 
 ■of soda (sodium -f- oxygen) with sulphuric acid (sulphur + oxygen) 
 
CHEMICAL CONSTITUTION OF ORGANIZED BODIES. 29 
 
 in sulphate of soda ; and that each constituent preserves its proper 
 nature in the compound. According to the second view, one pf the 
 constituents of the salt is supposed to undergo decomposition, yielding 
 up to the other an element, which, joined to it, forms a corhpound 
 radicle, to which the remaining element is united; as hydrogen 
 would be to a simple, or compound radicle (chlorine or cyanogen), 
 to form a hydro-iacid. Thus, in the salt commonly called sulphate 
 of soda, this view supposes that the soda* yields its oxygen to the 
 sulphuric acid, and that a compound is formed of sulphuric acid, 
 plus an additional equivalent of dxygen, which may be represented 
 by SOj, and has been called by Professor Daniell oxysulphiop. The 
 compound radicle thus formed unites With the metal sodium, and 
 the resultant salt should be called oxysulphlon of sodium; This 
 view, then, it is evident, would lead us to regard Glauber's salts as a 
 binary compound, instead of a ternary one under the first theory; just 
 as chloride of sodium is a binary compound, the compound radicle, 
 oxysulphion, and the simple one, chlorine, standing in the same rela- 
 tion to the metal sodium. 
 
 This latter theory, of the binary constitution of salts hitherto re- 
 garded as oxygen salts, is of great interest in reference to the com- 
 position of organic substances, as will appear in a future paragraph. 
 It has been supported by Professor Graham, and subsequently by 
 Professor Daniell, whose opinion has been grounded on the phenomena 
 of electrical decompositions. 
 
 Organized bodies are capable of being resolved, by chemical ana- 
 lysis, into the inorganic simple elements ; but the list of simple sub- 
 stances which may be obtained from this source comprises only about 
 seventeen. 
 
 Of the four widely-spread elements, oxygen, hydrogen, nitrogen, 
 and carbon, two, at least, will be found in every organic compound; 
 hence, as Dr. Prout has suggested, these four maybe conveuiiently 
 distinguished as the essential elements of organic matter. The 
 other simple substances are found in smaller quantities, and are less 
 extensively diffused ; these maybe termed \Ks incidental elements. 
 They are sulphur, phosphorus, chlorine, sodium, potassium, calcium, 
 magnesium, silicon, aluminum, iron, manganese, iodine and bromine; 
 the last two are obtained almost exclusively from marine plants and 
 animals. 
 
 Between these elementary substances, and the organized anintal' 
 or vegetable texture, there intervenes a cldss of compounds, called 
 proximate principles, or organic compounds, or organizahle substances,! 
 These may be obtairied iii the first stage of the chemical analysis 
 of various animal or vegetable tissues. From the organized struc- 
 ture, called muscle, for example, we obtain hy analysis, first, _/?6m, 
 a proximate principle, which is its chief constituent ; and, subse- 
 quently, by the analysis of fibrin, we get the simple elements, 
 oxygen, hydrogen, carbon, nitrogen and sulphur, in certain propor- 
 tions. On the other hand, by synthesis, the combination of certaiii 
 inorganic elements (which hitherto has been effected only in the 
 living body) will produce the organic compound, fibrin ; from which, 
 
30 CHEMICAL CONSTITUTION OF ORGANIZED BODIES. 
 
 again, the organized structure muscle, is formed. And so in other 
 cases. 
 
 In the organized body the constituent particles are, as it were, art- 
 fully arranged, so as to form peculiar textures, destined to serve spe- 
 cial purposes in the living mechanism of the animal or plant to which 
 they belong. The organic compounds which may be obtained from 
 these are devoid of this mechanical arrangement of particles, and it 
 is a beautiful feature of the organized body, that every part has its 
 special office, that there is nothing superfluous, nothing wanting. As 
 each organized body has a certain end to serve in the economy of 
 the living world, so each organ has its proper use in the animal or 
 plant. In this adaptation of parts to the performance of certain 
 functions, we see the strongest evidence of Design ; and, amidst 
 much apparent difference of form and obvious diversity of purpose, 
 the anatomist recognizes a remarkable unity of plan — affording in- 
 contestable proof that the whole was devised by One Mind, infinite, 
 in wisdom, unlimited in resource. ; 
 
 The true proximate principles are those substances which are the 
 first obtained by the analysis of the organized textures ; such are 
 gluten, starch, lignine, from the vegetable textures, or albumen, 
 Ji^rin, casein, from the animal ones. From these again a great vari- 
 ety of compounds has been obtained by various processes, owing 
 to the tendency which their elements have to form new combinati(f)ns. 
 By boiling starch in dilute acids, it becomes converted into a kind of 
 gum, and starch-sugar. By placing yeast in contact with sugar, the 
 latter is converted into alcohol and carbonic acid, without the yeast 
 affording it any of its chemical constituents ; and, in the germination 
 of barley, or of the potatoe, a peculiar substance is formed, the con- 
 tact of which with the starch of the barley or potatoe converts it into 
 sugar. Innumerable examples might be quoted from various vege- 
 table compounds, showing that the affinity, which holds together the 
 elements of organic substances, is so feeble, that it affords but slight 
 resistance to their entrance into new combinations. In this way a 
 large class of organic matters is formed, which it seems proper to 
 distinguish from the true proximate principles, under the name of 
 secondary organic compounds. 
 
 In analyzing the true proximate principles of organic substances, 
 it is found that they consist for the most part of three or four of the 
 essential simple elements, and that, as many of them contain a large 
 number of atoms, their combining proportion is represented by a 
 very high number. Respecting the mode of combination of these 
 elements much uncertainty prevails. Some chemists consider them 
 united equally with each other, and regard the organic principles 
 themselves as ternary or quaternary compounds of them. But others 
 have suggested a mode of combination more analogous to that of 
 inorganic substances (see pages 28, 29) ; namely, that two or three of 
 the elements form a compound radicle, with which the remaining one 
 unites to form a binary compound. In a body, for example, consist- 
 ing of three elements, two would form the compound radicle, or, in 
 one composed of four elements, three would constitute it. This mode 
 
CHEMICAL CONSTITUTION OF ORGANIZED BODIES. 3l 
 
 fflf composition has been rendered more probable in the secondary 
 organic products, than in the true proximate principles; and it may 
 be illustrated by an example takeii from the former class. Ether is 
 composed of four atoms of carbon, five atoms of hydrogen, and one 
 atom of oxygen ; the carbon and hydrogen constitute a hypothetical 
 compound radicle, called ethyl, which is united with one atom of 
 oxygen : so that ether is an oxide of ethyl, and its formula may be 
 expressed d Hs + 0. .. 
 
 Among the secondary organic products of the vegetable class wfe 
 meet a few instances of binary compounds of simple elements; but 
 the great majority of proximate organic elements, whether primary or 
 secondjiry, are composed, of three or four essential elements. 
 
 In contrasting, then, the chemical composition of organic with that 
 of inorganic substances, we perceive that, applying the binarjr theory 
 to both classes of substances, their mode of combination is strictly 
 analogous ; there being, however, this distinction, that, among organic 
 substsftices combination with a compound radicle is the prevailing 
 mode, and that the union of two simple substances is rare. If, on 
 the other hand, we adopt the theory of oxy-acid salts for inorganic 
 compounds, and view the organic principles as ternary or quaternary 
 compounds of simple elements, each to each, then it is evident that 
 the most marked difference must exist between the two classes of 
 compounds, the latter being formed on principles entirely dissimilar 
 .from those which regulate the composition of the former. 
 
 It is probable, however, that the progress of Chemistry will show 
 that the biliary theory is applicable to both classes of substances, and 
 that the same mode of chemical composition prevails through both 
 kingdoms of Nature. 
 
 If so much uncertainty exists in reference to the manner of combi- 
 nation of the simpler elements to form organic compounds, it is no 
 wonder that the attempts of chemists to produce them by artificial 
 processes should have met with so little success. No one has suc- 
 ceeded in the synthesis of any of the true proximate principles ; and, 
 indeed, it is very questionable whether any of those products of a 
 vital chemistry will ever be produced elsewhere than in the living 
 organism. The formation of urea, a secondary organic compound^, 
 has been effected by Wohler from the cyanate of ammonia, by de- 
 priving it of a little ammonia through the action of heat. And it 
 must be admitted, as no unimportant step in the synthesis of organic 
 compounds, that nitrogen gas has been found to unite with charcoal, 
 under the influence of carbonate of potassa at a red heat. The 
 cyanide of potassium, which is thus fprmed, yields ammonia, when 
 decomposed by water ; so that cyanogen, and, through cyanogen, 
 ammonia, can be primarily derived from their respective elements 
 contained in the inorganic world. {Graham's CAewiisirj, p. 709, [Am. 
 Ed. p. 671].) Allantoin, an analogous compound to urea, and formic 
 acid, have likewise been artificially produced. 
 
 We proceed from this review af the chemical constitution of or- 
 ganic and inorganic substances, to compare them together in other 
 respects. 
 
32 ORGANIZED BODIES. 
 
 In examining an organic substance which is orgamzed, i. e., so 
 constructed as to form part of a living organism, w6 find it to pos- 
 sess very distinctive characters. It generally contains water in con- 
 siderable proportion ; its form is more or less rounded and free from 
 angularity, and it is never crystallized. When considerable hardness 
 or density is required, the quantity of water is small, and an inorganic 
 material is combined with the organic matter ; as, in bones, phosphate 
 of lime with the gelatine of the bone, or, in plants, silex with their 
 epidermic tissues. 
 
 An organized body is composed of parts, distinct from each other 
 in structure and function, and it may be subdivided into a series of 
 textures, each differing from the others in physical and vital proper- 
 ties. The existence of ^ great variety of textures, 
 Fig- !• in an animal, is an indication of a high degree 
 
 of organization. Among the low«st organized 
 creatures thete is much uniformity of structure, 
 although variety of parts^or organs. Still these 
 creatures by their: actions show* that materials of 
 different properties must exist throughout their 
 bodies. 
 
 The simplest and most elementary organic 
 
 Primary organic cell, fo"""!' ^ith which wc are acquainted, is that of 
 Bhpwing the ceii-raem- a Cell, Containing another within it (nviclmis), 
 
 brane, the nucleus, and i-i • .■ iii/i'i^ 
 
 the nucleolus. which again contams a granular body {nucleoms). 
 
 , (Fig- !•) 
 This appears, from the interesting researches of Schleiden and 
 
 Schwann, to be the primary form which organic matter takes when 
 
 it passes from the condition of a proximafte principle to that of an 
 
 organized structure. 
 
 The bodies of some animals and of some plants, are composed 
 almost entirely of cells of this kind ; and in the early development of 
 the embryo, all the tissues, however dissimilar from each other, con- 
 sist at first of nucleated cells, which are afterwards metamorphosed 
 into the proper elements of the adult texture. 
 
 An organized body possesses a definite form and disposition, not 
 only as regards its component parts, but. likewise when viewed as a 
 whole. Each organized body has its appropriate and specific shape; 
 and to each a certain size is assigned. To observe and classify the 
 wonderful diversity of form exhibited by plants and animals, has 
 given employment to Naturalists in all ages ; and the sciences of 
 Zoology and systematic Botany have been founded upon the results 
 of their labours. 
 
 Every organized body is limited in its duration ; it has " its time 
 to.be born and its time to die," and at death it passes by decompo- 
 sition into simpler and more stable combinations of the inorganic 
 elements. 
 
 In their origin, organized bodies are generally, if not always, de- 
 rived from similar ones. Some have supposed that out of decaying 
 vegetable or animal matter minute animals or plants of other kindt 
 may be formed : but it seems most probable that in those cases in 
 
REPRODUCTION. ' 33 
 
 which they had been suppbsed to be formed, the seeds or eggs, 6r 
 even the parents themselvejS, had been concealed in the decayiwg 
 matter, or floated in the surrounding atmosphere. ReCeilt experi- 
 ments thro^' considerable doUbt upon. this doctrine of the spontaneous 
 'generittion of organized bodifes; by showing that neither vegetation 
 nor the development of animalculas will go On in fliiids which have 
 been subjected to such ijJ'Ocesses as miist Irievitably kill whatever 
 germs may' hdve been diffil^eflarouhd or throughout therii^ 'In the 
 present state of 6ur knoWrledge it mat be said,' that the H^rveiiah 
 maxim, "Omnfe yivum ex dvo," is the rule ; and that if there beany 
 other mode in which' the development bf living bein'gs takes 'platje, 
 it is the exception. The prbgress of Anatomical knowledge i^ S^rV 
 day revealing to us the organs, and the mode of generatioh in the 
 .minutest and' the least cOrtsplcaous forms of vegetable' atnd animal 
 life; and thus the doctrijie; wfeh supipbs'es that living ribjects may 
 arise by a sort of conjunctiop of the elements of decomposing oj^anic 
 matter, becomes more and mote iriiprbbable. 
 
 How beautiful is the provision which this pow4r, possessed by 
 organized bodies, of generating bther^,' affords, for preserving a per- 
 petual successioh of living Ibeittgs over the globe! The cbinm^nd, 
 "Increase and multiply," has n'eter ceased'to be flilfilled from the 
 moment it was tittered. Every hour, nay, every minufej brings into 
 being doatitless myriads of plants and animals, to siipply in lavish 
 profusion the havoc Which death is' continually making'; and itls 
 impossible to suppose that the earth can cease to be in this way 
 replenished, until:the same Almighty" PbMreTjihai: gave the command, 
 shall see fit to oppose some obStaele/tD'itsftilfilltnent; ' ' 
 
 Jn addition to this power of propagation, organized bodies enjoy 
 one of conservation and reprodUCtiolr. Solutions of continuity^ the 
 loss of particulai" 'textuTeS, whether resulting from injury or from 
 disease, can' be repaired." Parts^, that haVe been removed, may Ijfe 
 restored by, a process of growth in the plant o|" animal, and in some 
 animals the reprodqctive power is so enfefrge'ttc^Mliat if aii indiTidUal 
 be divided, each segment will become a perfect being. This power 
 of reproduction is greater; the more Simple the structure of the orgari- 
 ized body ; the more similar to each (Aher ate the constituent pairts, 
 the more easy will 'reprodu'ctiori be;' Numerous examples of this 
 '][)ower maybe adduced, -^the healing of wounds, 'the adhesion of 
 divided parts are familiar to every one. New individuals are deve- 
 loped from the cutting of plants: the division of the hydra into two, 
 gives rise to tbe production of tWo' new ' individuals. If a Planaria 
 be cut into eight or ten pktts; accbrdii^g tb Duges, each patt tcill 
 assume an independent existence. ' ' ' ''"'" 
 
 The power of reproducing single parts bnly, is possessed by animals 
 higher' in the scale. In snails, part of the head; with the antennae-, i 
 may be reproduced, prbvided the section', hiave been 'niade so as not I 
 to injure the cerebral ganglion. ptafbS'arid Ibb^terS can regenerate ' 
 their claws, wheil the separation has taken. place at an artieulation ; 
 and spiders etijoy'thfe same powi^r. In liiiards, the tail, of a limb, 
 
34 ASSIMILATION.— EXCBETION.-^DECOMPOSITION. 
 
 cau be restored, and in salamanders th^ same phenoinenon has been 
 frequently -witnessed. ^ . ■. . ' 
 
 Organized bodies ean appropriate and .assimilate to their own tex- 
 tures other substances, whether inorganic or organic. This process 
 is that, which is most characteri'Stic of liying creatures: ii\ virtue of it, 
 animsJs and plants are continually adding to their textures new 
 matter, by which they, are no,urJ5ihed. Plants .appfopria,te their nutri- 
 mentsfrom^the inorganic kingdom, as well as from decaying organic 
 matter;, animals, chiefly from organic matters, Ayhether animal or 
 vegetable. Both possess the wonderfuj. power, of re-arranging the 
 constit^ieuts of these substances into forrns identical with those of the 
 elpjiiepts of theii; various tissues — and of ,thu^ making them part and 
 parcel of themsplvps. 
 
 Together with a process of supply, there is one of waste con- 
 tinually in, operation, Animal^ and plants are ever throwing off 
 ^ffete particles from their organisms, /these, under the name of 
 excretions, HTppeav in various fprms — eitlier, as inorganic compounds, 
 or as secondary organic products. Thus, carbonic acid is given off 
 ii^.large quantities ftom animals ; water, likewise, forms a considerable 
 portion of their excreted matter, and serves to hold in solution salts, 
 and Jsecondary organic compounds, which result from the waste of the 
 tissues. In this way, ajso, urea, Uthic acid, and biliary matters are 
 excreted. In plants, water is exci;eted ^rom the, leaves, a pheno- 
 menon which has been compared to the perspiration of animals; and 
 various lOther excretions, which, are sometimes made to serve an addi- 
 tional purpose in the economy of the vegetable,, besides that of get- 
 ting rid of superfluous matter, are doubtless formed by the secondary 
 fipt^iiialions of the effete particles of their textures. 
 
 .Tixese two processes,, eEcref;ion, or the expulsion of effete particles, 
 an4 assimilation oi substances from without, are necessarily mutually 
 dependent. As long as new ina,tter is, being appropriated, ojd par- 
 ticles must be thrown off, otherwise growth would be unlimited — 
 and were excretion, alone to go on, the destruction of the organism 
 mi^s!; speedily, ensue, by the gradual waste of the tissues, to which 
 no,new ?upply was afforded. In both processes new combinations 
 are taking, place, as it were, in opposite directions ; in the one from 
 t;he simple to the complex to forni prganized part?, in the other, from 
 the, complex constituents of the textures to the simple organic, or 
 inorganic compounds. , 
 
 As, each texture of the organism has this tendency to change during 
 life, soj the .whole organism .^encls, tp decomposition, wjien death puts 
 a stop to all further absorption of nutritive matters. , JDead organized 
 matter is speedily dissipated under cprtai'J.conditiqna, ,, Tjhese are the 
 presence of air, moisture, and a certain temperature, or contact with 
 at) prgajiic substance which is itself undergoing decomposition. The 
 affinity, whiph held together the elements of the organic substances is 
 destrpy^d by the cause which occasioned thefr death, and they are 
 Sft free to, obey new affinities and fprm new comppunds. 
 
 When we consider the; large number of equivalents which enter 
 into the formation of each molecule bf organic compounds, it need 
 
DECOMPOSITION.— LIFE. 35 
 
 not excite surprise that a great variety of products results from the 
 decomposition of atiimal and vegetable matter. This' decomposition 
 is of two kirtds, which are distinguished by the names, fermentation 
 and putrefaction. Liebig proposes to limit the former term to the 
 decomposition of substances devoid of nitrogen, and the latter to that 
 of azotized matters. The- products of vegetable' matter in fermenta- 
 tion, by the action of yeaSt, are carbonic acid and alcohol ; those of 
 azotized matters, whether animal or vegetable, are carbonic acid,' 
 hydrogen, phosphuretted and carburetted hydrogen, hydrosulphuric' 
 acid, cyanogen, hydrocyanic acid, ammonia, and lactic acid. ' 
 
 Let us compare the characters of organized bodies, as described in 
 the preceding paragraphs, with those of inorganic substances. 
 
 In form, in size, in duration, the Contrast is most striking. The 
 inorganic matters are aeriform, liquid, or solid: they are prone to- 
 assume the crystalline form, and 'to exhibit surfaces bounded by' right 
 lines, and uniting to form angles. No distinction of parts, or organs, 
 is to be found in the mineral substance; its minutest fragment is in 
 every respect of the same nature with the largest mass. A portion 
 of chalk, not weighing a drachm, contains particles of~ the same 
 form and size as those of the largest cliff ;on the sea-coast. Inorganic' 
 substances, as compared with "organic, are unlimited in size ani dura- 
 tion: they will continue for ages without augHientation or waste,' 
 provided no mechanical violence, nor chemical agent be brought to' 
 act upon them. 
 
 None of those internal actions or processes, which we described in 
 the organized body, occur in the unorganized one ; there is no power 
 of reproducing lost or injured ^'arts, no growth, no excretion, no 
 generation. From age to age the mineral remains unchanged, with* 
 out motion, obedient to the common laws of matter, and unable to 
 resist them by any inherent power. ■ < - ' 
 
 Within the. living organisms of the organic kingdom, on the-'con- 
 traryjare ceaseless motion and change. The absorption of the new 
 material, and the ejection 'of the old, comprise a continual succession 
 of actions^ in whifch -the' organized beingis ever organiisMg and 
 disorganizing. This constant round of actions, which is the 'more 
 diversified as the organism 'is more complex, we call Life; There 
 is an apparent spontaneousness in these actiohSj which distinguishes 
 the mechanism of an animal or plant frrtm the machines of human 
 construction. Yet the living organism is not the less dependent for 
 the continuance, nay, for the very existence of those actions upoii 'the 
 ordinary agencies of- nature.' Light, be'at, the atmosphere, chemical 
 affinity} each has its Share in promoting the ifunctions in the play of 
 which Life consists ; all are more or less necessary tO the integrity of 
 these actions; and it is contrary to experience to suppose that Life' 
 can be manifested without their co-operation. Yet we cannot say*^ 
 that Life is produced by, or is the- result of, these agencies. It iS' 
 equally contrary to experience to find the manifestation of Life in 
 other than organized' bodies. Nevertheless, it cannot be affirmed that 
 organization is the cause of Life, for 'Withoutthe other agents no vital 
 action occurs, and it has already been shown that the organization of 
 
36 LIFE.— yiTAL STIMULI.— DEATH. 
 
 new matter is effected:only by living bodies. The mutual co-operation 
 (?f organized matter with the forces at work in the inorganic world, 
 is necessary, to. the development of vital phenomena. • 
 
 The term Life, then, inay be regarded as denoting an ultimate feet 
 ijn science, whiph may be thus expressed; that certain compounds of 
 matter— which, as being artfully arranged in a paitjculai form for a 
 fecial end, and associated together by a certain mechanism, are 
 called o»-g;«»iz«rf— do,, by theirs coioperatien with physical and; chemi- 
 cal forces, manifest a traiq of phenomena, which are of the same; or' 
 of an analogous kind, for aU organized beiijgs; , that is to say^ they, 
 ipanifest the; phenomena of Life. AH organized substances, capable 
 of thus co-operatingTWith the other natural agencies, are called, fejjng; 
 apd; although they m^ not be ^wativeJy in taction, thfey aire yet aUre, 
 as being ready to apt: wheii thia c6mpleaiBntary conditions- to vital 
 siction shalli be suppUed to tb^tn. Thus the seed is :alive,< although 
 not in action; but, imjoaediately it is brought into contact with mois- 
 ture and heat, life, ig ; manifested. Hence these agents, moistures- 
 heat, light, &c., are said, to stct as mini stirrmli. The organic matter^ 
 in becoming part of, a living machine,; acquires certain properties,, 
 very different from what it possessed befoire ; these are called vitui 
 jeeaperUesa they continue as liong as the organisation remains un- 
 changed, , For example, a certain proximate element is organized to 
 form muispl!e; it then acquireSith^ property of contr&otility^ Which <it 
 retains during life. 
 
 Accordiijg to our experience, organic matter derives "vit^al pro- 
 perties in ty ffir the jswjprity of instances^ and^probably in all, from 
 a previously existing organism.. The egg, while within the body of 
 the mother, aaquires^vij^l j>i!Qpertiias; and it manifests an independent 
 life when iti is ]aidj if the rfiquisi,te conditions (vitalnstiot'uli) are then 
 supplied. Thus is life transmitted from one living being to another ;■ 
 and the life of a pr^ent generation) of > animals and. plants has 'its 
 source in that of a previous generation j , If we trace a race upwards^ 
 through generations innumerable, to that which first flourished on the 
 earth, we find the true source of vital action tO' be in Him, " in wi»oIn^ 
 we live, 'an4 move, an<l. have our being." , 
 
 , Tblis, thenj Qttt ofithe same elements of which the^norganic king- 
 dom consists, God haSfPrfeateda^^iies of material substances, which 
 Vy their lactipn and reaction • with, other physical agencies, exhibit, 
 apparently in a spontaneous manner, the phenomena of Life, and 
 manifest a series of peculiar fprces cap^able of opposing and controlling 
 tjje other forces of nature. While titl^se subatancea retain a perfect 
 prganizatioin,,and are supplied v?ith. their, proper stihiuli, vital actions 
 go on without I interruption,, and nq.changes take: place in the matter 
 of the organism, excepting suc^asresult from its proper affinities. 
 But no sooner is thp integrity of its structure destroyed, or the influ- 
 ence*, of thp vital stimvili withdrawoj than action ceases, the organism- 
 dim, and the organic matter yields up its. elements to form new com- 
 pounds, a large proportion of which are inorganic. 
 
 j Many are not content , with this simple. expression of facts, and seek 
 ^ theory to explain theiphenomena of organized bodiiea, and to account 
 
THKOaiES OF LIFE. 37 
 
 for the mysterious actions, of Life. , The ingenuity of philosophers has 
 been not a little taxed for this purpose ; and the history of the rise 
 and fall of many an hypothesis, which has been framed upon this 
 subject, affords a salutary warning to those who may be tempted to 
 wander itto the regions of speculation and fancy, deserting the safe 
 and beaten path of inductive reasoning. 
 
 It does not fall within the scope of this work to examine the various 
 theories of Life. One or two^ however, we deem it right to notice, 
 with the hope of at once exposing their inadequacy, and elucidating 
 more fully the statement above given respecting Life. 
 
 From a very early period in the history of natural science, there 
 kas been a tendency to ascribe these effects to a certain principle, or 
 Entity, possessing powers and. properties which (however men may 
 try to impress themselves with tfie contrary notion) entitle it to rank 
 as an intelligent agenti It is true, that, according to most of the ad- 
 vocates of this doctrine, this power is supposed to be superintended 
 and controlled by the Deity himself, and, by this supposition, they 
 have screened themselves against the accusation of attributing to a 
 creature the powers of the Creator. 
 
 A little examination of this doctrine will show^ that is has no pre- 
 tensions to the title of a theory. 
 
 Aristotle attributed the organization of animals and vegetables, 
 and the vital actions exhibited by them, to a series of animating 
 principles, (^«it<»'j) differing according to the nature of the organized 
 bodies constructed by them, and acting under the direction of the 
 Supreme animating principle (^van). He supposes that each pat^ 
 ticular kind of organized body had its proper animating principle, 
 or ■^zVi ^^^ that the variety of the former really depended upon 
 certain original differences in the nature of the latter, so that every 
 distinct species of animating principle would necessarily have its ap- 
 propriate species of body. 
 
 Harvey, likewise, assumes the existence of an animating principle^ 
 by which every organism is moulded into shape, out of materials fur-' 
 nished by the parent^ and which, pervading the substance, regulates 
 the various functions of its corporeal residence. But, at a subsequent 
 stage of his inquiries, in assigning the blood as the special seat of this 
 principle, he advances another supposition totally at variance with 
 his previous hypothesis ; namely,: that as, during the development of 
 the ehick in ovo, the blood is formed and is moved, before any 
 vessel, or any organ of motion exists^ so in it and from' it originate, 
 not only motion and pulsation but animal temperature, the vital ^irit, 
 and even the principle of life itself. So completely biased were the 
 views of this illustrious man, by ibis exaggerated notions respecting 
 the nature and properties of the blood ! 
 
 The celebrated Joha, Hunter, who does not appear to have been 
 acquainted with the views expressed by Harvey, revived; a somewhat 
 similar ibypothesis ; and it is curious that the same fact should have 
 so attracted the attention of both as to have given the first impulse to 
 thfeir speculations^ This fact was, that a prolific egg will remain sweet 
 in a warm atmosphere, while an unfecundated one will putrefy. The 
 
38 THEORIES OF LIFE. 
 
 views of Hunter have been received with very general favour by 
 English physiologists. 
 
 Hunter ascribes the phenomena of life to a materia vita, diffused 
 throughout the solids and the fluids of the body. This materia vita 
 he considers to be " similar to the materials of the brain :" he distin- 
 guishes it from the brain by the title " materia vita d^usa," while 
 he calls that organ" mafem vita coacervata," and supposes that it 
 communicates with the former through the nerves, the chorda inter- 
 nuncia. And Mr. Abernethy, in commenting upon these views, 
 explains Mr. Huntei-'s materia vita to be a subtile substance, of a 
 quickly and powerfully mobile nature, which is superadded to organi- 
 zation and pervades organized bodies ; and this he regards as, at 
 least, of a nature similar to electricity. 
 
 Miiller advocates the presence of an " organic force," resident in 
 the whole organism, on which the existence of each part depends, 
 and which has the property of generating from organic matters the 
 individual organs necessary to the whole. " This rational creative 
 force is exerted in every animal strictly in accordance with what the 
 nature of each requires ; it exists already in the germ, and creates in 
 it the essential parts of the future animal." 
 
 An hypothesis, not dissimilar to that last mentioned, is maintained 
 by Dr. Proutj and, as appears to us, it has been pushed by him to 
 the utmost limits which the most fanciful speculation would admittof. 
 He supposes that a certain organic agent (or agents) exists, the inti- 
 mate nature of which is unknown, but to which very extraordinary 
 powers are ascribed. It is superior to thbse agents whose operatibns 
 we witness in the inorganic world:' it possesses the power of con- 
 trolling and directing the operations of those inferior agents. " If," 
 says Dr. Prout, " the existence of one such organic agent be admitted, 
 the admission of the existence of others can scarcely be withheld ; 
 Jbr the eMstence of one only is quite inadequate to explain the infinite 
 diversity among plants and atiimals.'" " In all cases it inust be con- 
 sidered an ultimate principle, endowed by the Creator with a faculty 
 little short of intelligence, by means of which it is enabled to con- 
 struct such a mechanism from natural elements, and by the aid of 
 natural agencies, as to render it capable of taking further advantage 
 of their properties, and of making them subservient to its use." 
 
 The hypotheses of Aristotle, Miiller, and Prout, and the earlier of 
 those proposed by Harvey, seem all alike; they assume that organi- 
 zation and life are directed and controlled by an Entity^ or Power, 
 "endowed with a faculty little short of intelligence," the ^^^^ of 
 Aristotle, the animating principle of Harvey, the organic force of 
 Miiller, and the organic agent of Proiit. What the mechanism may 
 be by which this entity acts, they do not. determine ; but it is evi- 
 dently such as bears no analogy to any kniblvn natural agency. Its 
 existence is independent of the oj-ganism, for it. has directed both the 
 organizing process and the living actions of the being. Whence then 
 is it derived.' According to Miiller, from the parent, for it exists in 
 the germ, — it derives its powers from the same source, and its pedi- 
 gree may, therefore, be traced to the first created individual of each 
 
THEORIES OF LIFE. 39 
 
 species of animal or plant. Are we to conclude,,' then, Uia): organic 
 agents generate organic agents, an4 transmit ^l^eir powers to their 
 offspring? Or must we assume, that, for ieack newly geperat^cl' ani- 
 mal, or pl9nt, a special organic agent, is deputed " to control and 
 direct" its organization, development, and growth? 
 
 The modern ad,vocates of this doctrine have been driven to its 
 adoption, from the di^iculty (or, as they conceive, the impossibility) 
 ,of explaining the' phenomena of organization and life on principles 
 analogous, to those on which the changes of inorganic, matter may 
 be accounted for: this difficulty consisting in the supposed existence 
 of certain differences in the mode of comhinEition of the elementary 
 coi^stituents of orgajiic and inorganic compounds, seconded by the 
 fact, of the synthesis of organic compound^ haying hitherto baffled the 
 chemislj's art. It has puzzled tl^em tp think that out of the same 
 elementary and proximate principles, so infinite a variety of animals 
 and plants could be formed; and, Dr, Prout has been especially 
 staggered by the fact,, that carbon and water, which contribute so 
 largely to the formation of various organisms, have never, although 
 aided by heat, light, and electricity, when out of an organized body, 
 and left entirely to^ themselves, been able to unite, either in yirtue of 
 their own properties or frpm accident, so as to form any plant or ani- 
 mal, however insignificant. 
 
 In the first place, let it be observed, that many of the phenomena 
 of life maybe accounted for on, physical or cheniical principles. 
 The changes effected in tlje air and in the blood by respiration, the 
 phenomena of absorption, and, in some degree, those of secretion, are 
 the results of purely phy.sical processes. It is in the highest degree 
 .probable that many of the actions of the nervous system are due to 
 physical changes in the two kinds of nervous matter, substances of 
 complex constitution and high equivalent number, and therefore 
 prone to change. Stomach-digestion is now known to be a chemical 
 solution ; the generation of heat is due to the same chemical phe- 
 nomenon as will give rise to it in the inorganic world; and electricity 
 is also similarly developed within the body. How entirely dependent 
 on physical changes are the senses of vision .and hearing, and how 
 completely are their organs adapted to the laws of light and sound! 
 And, doubtless, a further insight into the nature of the various organic 
 processes will reveal to us a closer analogy between the laws by which 
 the two great kingdoms of nature are gove.rned. 
 
 Nor is there so great a chasm between matters organic and 'in- 
 organic, as, to chemical composition, as some would have us believe. 
 It has already been shown that modern chemical research tends to 
 prove a siinilarity as regards the mode of. combination of the ele- 
 ments in both ; and the labours of chemises, have been crowned with 
 success in forming some organic products by artificial means. — 
 (See p. .31.) 
 
 And let it not be forgotten that the living lE^boratDry of the animal 
 and plant is one well stored with means for analysis and synthesis : 
 the continual introduction of new material gives full scope to the play 
 of chemical affinity, and at every point the constant attendants of 
 
40 THEORIES OP LIFE. 
 
 chemical action, heat and electricity, are developed. May it not 
 reasonably be inferred that these agencies, which thei themist can so 
 readily tarn to account in bis artificial processes, are not idle in the 
 "work of combination and decomposition in the living body .'' A great 
 difference as to sensible qualities, in the various organic products, by- 
 no means implies great difference of chemical constitution, for it is 
 well known that the addition or removal of a single, atom oi one of 
 the ingredients of any compound is sufficient to produce a substance 
 with totally new properties ; and such is the complex nature of orgatiic 
 molecules, that the attraction between their component elements yields 
 readily to disturbing causes. ' 
 
 But how shall we explain the strange process of organization, in 
 the production of that infinite diversity of forms, that " insatiabk 
 variety of Nature," which is so conspicuous in the vegetaible and 
 animal kingdoms ? Must we imagine this creation, in corresponding 
 number and Variety, of a duplicate order of bfeirtgs, '(vhoge duty it 
 shall be to preside over the development of each species, and to 
 impress eac^ with its peculiar characters.' Or doe^ it not seem 
 more consistent with that grand simplicity, which the phenomena of 
 nature everywhere present, to suppose that the organization of ani- 
 mals and plants, in such 'gfreat variety, is the result of the prima'ry 
 endowment of organic matter, at the creation of the first parents of 
 each species, by the Alniighty.' The animal or vegetable matter of 
 each species was created to propagate after a certain fashion, and 
 after that only ; the organic cells, of Which these organisms consist in 
 the early stages of development, have the power of evolving the 
 adult tissues of animals and plants of their own species only: the 
 simple volvox develops, from its interior^ organic cells whith become 
 volvoces; and the cell, which forms the ovUm of the elephant or the 
 mouse, is able, by an inherent power of multiplication, to evolve the 
 skeletons and organs of each of those animus respectively. 
 
 The peculiar endowments of the organic matter^ composing the 
 various tribes of animals and plants, are fran'smittea ' from parent to 
 offspring. But they admit of certain modifications under the influ:- 
 ence of circumstances affecting the parents, as is proved both in the 
 animal an^ vegetable kingdoms in the proddfetion of hybrids. 
 " Two distinct species of the same genus of plants'," says Dr. Lindley, 
 " will often together produce an offspring intermediate in charactet 
 between themselves, and capable of performing all its vital functions 
 as perfectly as either parent, with the exception of its being unequal 
 to perpetuating itself permanently by iseed ; should it not be abso- 
 lutely sterile, it will become so after a few generations. It may, 
 ho>yever, be rendered fertile by the application of the pollen of either 
 of its parents; in which case itsi offspring assumes the character of 
 the parent by which the pollen was supplied." The same thing 
 precisely occurs among animals, and . the mixed offspring, or mule, 
 produced by the union of diSerent species is incapable of breeding 
 with another mule; but not so with an animal of the same species as 
 either of its parents. How entirely inadequate is the theory of 
 organic agents to explain these occurrences ; it cannot, surely, ht 
 
THEORIES OF LIFE. 41 
 
 maintained that a rnixied organic agent is produced from the con- 
 junction of the organic ageats of the dissimilar species to direct the 
 formation of this mixed organism! ♦ 
 
 The remarkable fact, that the various tribes of the human race, 
 dissimilar as they are, were derived from the first created pair, may 
 be adduced as a striking illdstration of the influence' of physical 
 agency in modifying organic development. The most potent cause 
 of these changes has been climate ; but particular customs and usages, 
 connected with the uncivilized state, have not been without their 
 influence. Climate also produces considerable modifications in the 
 size and other characters of the lower animals. Sturm affirms that 
 icattle transported from the. temperate zones of Europe (Holland or 
 England) to the East Indies, become considerably smaller in their 
 succeeding generations. - 
 
 The theory of organic agents affords no more satisfactory explana- 
 tion of disease, or of death. In both cases the organic agent must 
 be at fault; for as it is the sole guide and controller of the organizing 
 process, so it is not to be supposed that anything can go astray, 
 'except under its guidance: And yet it seems impossible to imagine 
 that the ordinary causes of disease could affect such an entity. On 
 the other hand, any physical or mental cause, -general or local, affect- 
 ing the substance of which the body is composed, may so alter and 
 modify the affinities of its particles as to occasion a material dis- 
 turbance in their actions; and it is not difficult to conceive that this 
 disturbance may be of such a kind as to put a stop to vital action 
 immediately or remotely. '- 
 
 So much for the dependence of Life and Organization on a con- 
 trolling and directing Entity. The sagacity of John Hunter led him 
 to reject this doctrine entifely; but, as he completely passed over the 
 influence of the natural agencies of inorg'anic nature upon organized 
 beings, he was forced to assume the presence of a peculiar material 
 substance, pervading and giving vital properties to solids and fluids : 
 yet such a constituent of 'the body ought to be demonstrable by 
 chemical or other means. It is clear that this materia vitce cannot 
 be, as Mr. Abernethy suggested, electricity, or anything akin to it. 
 Electricity requires for its development the reciprocal action of dif- 
 ferent kinds of matter, and it is abundantly evolved in various 
 animal- processes, as a necessary result of chemical laws. If, there- 
 fore, organization and vital actions depended upon electricity, this 
 ■agent would, at once, be formed by, and direct the formation of each 
 organism. 
 
 Mere composition of matter does not give life, says Hunter; if he 
 had added, that organized bodies actedon by, and co-operating with, 
 certain vital stimuli, developed vital actions, there would have been 
 no need for the assumption of a materia vitSB. The resistance which 
 living animals introduced into the stomach are capable of affording 
 to its solvent powers, and the digestion of the walls of the stomach 
 ■by its own fluid after sudden and violent death, seemed to denote 
 that the dead animal, or dead stomach, had lost a something which 
 previously protected them against the influence of tlie gastric '< fluid. 
 
42 FUNCTIONS OF ANIMALS AND PLANTS. 
 
 But this is no more than a case familiar to chemists, vizi, the influ- 
 ence of a stronger affinity controlling a weaker. When iodide of 
 potassium is mixed with a solution of starch, no change ensues ; but, 
 if a minute quantity of chlorine be added, a blue iodide of starch is 
 instantly formed ; the superior affinity of the iodine for- the potas- 
 sium hindered the union of the former with the starch ; but, as soon 
 as the iodine was set free by the stronger attraction between the 
 potassium and the chlorine, it speedily united with the stkrcb. So, 
 in the living animal, the affinity of its component particles for each 
 other is greater than their affinity for the gastric fluid; but in the 
 dead animal the former affinity is destroyed, the latter* comes into 
 play. Whether is it more philosophical to assume the removal of a 
 particular agent, for which removal no cause can be assigned; or, to 
 state the simple fact of the physical difference between dead and 
 living organic matter ? 
 
 II. It is very difficult to define a precise boundary between the 
 vegetable and animal kingdoms. The lowest animals exhibit so much 
 of the plant-nature, that naturalists are as yet undecided as to thp 
 true location of some species. The common sponge, for instance, is 
 claimed for each kingdom. 
 
 ' The various processes by which are effected the ceaseless motion 
 and change, so characteristic of living beings, are called, in physio- 
 logical language, Functions. 
 
 The functions, which are common to all organized beings, have a 
 twofold object ; the preservation of the individual, and the propa- 
 gation of the species. Those destined for the former purpose are the 
 JVutritive Functions : those for the latter are comprehended under the 
 general title Generation. 
 
 The first step in the nutritive functions of both plants and animals, 
 is to form a fluid, which contains all th^. elements necessary to nour- 
 ish the various textures, and to supply materials for the secretions. 
 This fluid is, in plants, the sap ; in animals, the Mood. 
 
 In both classes of beings a process o{ absorption precedes the full 
 development of the nutritive fluid : it is by this means that material 
 is obtained for its formation. Within the plant or animal it becomes 
 more completely elaborated. 
 
 In plants, the absorption takes place by the spongioles of the roots. 
 A fluid, already prepared in the soil, — water, holding in solution 
 carbonic acid and various mineral substances, — passes through them 
 into the vegetable organism, without undergoing any reduction or 
 preparation during its transit. In animals, however, the food expe- 
 riences much change, and a more or less elaborate process of digestion 
 takes place, before a fluid is formed, capable, when absorbed, of 
 furnishing the materials of the blood. 
 
 Plants, fixed by their, roots in the soil, imbibe from it their nutri- 
 ment. Animals, obtaining food from various sources, introduce it 
 into a digestive cavity, where it is prepared for absorption. 
 
 The presence of a digestive organ, or stomach, is characteristic of 
 animals. The only instances in which a similar organ may he sup^ 
 posed to exist in the vegetable kingdom are to be found in those 
 
FOOD OF ANIMALS AND PLANTS. 43 
 
 remarkable modifications of kaves, called pitchers {ascidia) in JVe- 
 peniJtes, Sarracenia, and Dischidia, In the last two plants, these 
 organs certainly serve to retain and dissolve the bodies of insects in 
 the fluid which partially fills them : in Sarracenia, according to Mr. 
 Burnett, the fluid contained in the pitchers is very attractive to in- 
 sects, whicli, having reached its surface, are prevented from return- 
 ing by the direction of the long bristles that line the cavity. The 
 dissolved food is then absorbed into the plant. 
 
 On the other hand, the animal kingdom affords some exceptions to 
 the presence of a sto&acJi. In such animals, the absorption of nu- 
 trient fluid takes place by a general surface. The Volvox globator 
 has no inlet to its interior but through the pores in its walls. A 
 parasite of the human body, the Jlcephalocyst, also derives its nutri- 
 ment by imbibition through 'its walls. A familiar example is the 
 Acephalocystis endbgena, or pill-box hydatid of Hunter. It consists 
 of a globular bag, closed at all points, containing a limpidi fluid, 
 capable of grbwlh, and of reproduction by the development of 
 gemmUles from the inner su'rface of the sac. The Eckinococcas is 
 also nourished by direct absorption intoi the walls of the globular sac 
 of which it consists. 
 
 . Somie diflerehce may be noticed as regards the nature of the food 
 in animals and pl&nt's. The former derive their nutriment entirely 
 frpm the organized world, unless, indeed, we suppose that the nitro- 
 gen absotbed in respiration contributes to their sustenaiice. Plants 
 appropriate .inorganic elementary matters for food, as carbon, car- 
 bonic acid, ammonia, &c. " Inorganic matter," says Liebig, " affords 
 food to plants; and they, on the other hand, yield the' means of sub- 
 sistence to animals. The conditions necessary for animal and vege-i 
 table liutritibn are essentially diffferent. An animal requires for its 
 di^velopment, gnd for the sustenance of its vital functions, a certain 
 class of rsubstances which can only be. generated by organic beings 
 possessed of life. Although' many animals are entirely carnivorous, 
 yet their primary nutriment must be derived, from plants; for the 
 animals upon which thefy subsist receive their nourishment from 
 vegetable matter. But plants find new nutritive material only in 
 inorganic substances. Hence one great end of vegetable life is to 
 generate matter adapted for the nutrition of animals out of inorganic 
 substances which are not fitted for this purpose." 
 
 ' The nutrient fluid, however formed, is distributed throughout the 
 textures of the plant, or animal, by vital or physical foi-ces, or by the 
 junction of both; and the function, by which this is effected, is called 
 Circulation. In plants, this function is very simple, and is performed 
 without the agency of a propelliiig organ ; butj in the greatest number 
 of animals, such an organ, a heart, is the main instrument in the dis- 
 tribution of the blood. In animals, then, there is a true circulation ; 
 the fluid setting out from, and returning to, the same place. But, in 
 plants, the fluid is found to circulate, or rotate, within the interior 
 of cells, as in Chara and Vallisneria, the fluid of one cell not com- 
 municating with that of the adjacent ones, or to pass up from the 
 
44 RESPIRATION.— SECRETION.— GENERATION. 
 
 spoQgioles in an ascending current, and to descend in another set of 
 vessels. 
 
 But in many simple animals, some entozoa, for example, and poly- 
 gastrica, there is no good evidence of the existence of any circulation 
 at all ; their textures imbibing the fluid in which they live. 
 
 The presence of atmospheric air is necessary to the ejjistence of all 
 organized beings. The air both passes by endosmose into their 
 nutrient fluids, and receives from them certain deleterious gases de» 
 veloped in their interior. The function, by which the fluids are thus 
 aerated, is called Respiration. In plants, the introduction of atmo- 
 spheric air conveys nutriment to the organism; carbonic acid and 
 ammonia are thus introduced; the former is decomposed, its carbon 
 is assimilated, and its oxygen is exchanged for a fresh supply of 
 atmospheric air. As the agent 'in the decomposition of the carboni© 
 acid is light, it is evident that the generation and the evolution of 
 oxygen can take place only in the day-time. Consequently, during 
 the night, the carbonic acid, with which the fluids of the plant 
 abound, ceases to be decomposed, and is exhaled by its leaves. 
 Hence, plants exhale oxygen in the day-time, and carbonic acid at 
 night. 
 
 In animals, carbonic acid accumulates in the blood during its cir- 
 culation ; and, when the atmosphere is brought to bear upon the 
 capillary vessels containing the blood charged with this gas, a mix> 
 ture takes place through the delicate walls of the vessels, the atmo- 
 spheric air passing in, and carbonic acid, with nitrogen and oxygen, 
 in certain proportions, escaping. Thus the evolution of carbonic 
 acid, and the absorption of oxygen and nitrogen, are the character- 
 istic features of respiration in animals. 
 
 It is highly interesting to notice, how plants are thus subservient to 
 the well-being of animals, in the respiratory function, as well as in 
 preparing nutriment for them. By their respiration they serve to 
 purify the air for animals; for, in absorbing the carbonic acid from 
 the atmosphere, they are continually depriving it of an element 
 which, if suffered to accumulate beyond certain bounds, would 
 prove destructive to animal life. 
 
 From the fluids of animals and plants, certain materials are sepa- 
 rated by a singular process, nearly allied in its mechanism to nutri- 
 tion, and called the function of Secretion. The secreted matters are 
 various, and have very different ends: in some cases being destined 
 for some ulterior purpose in the economy; in others, forming an 
 excrement, the continuance of which in the organism would be pre- 
 judicial to it. 
 
 The function, which has for its object the propagation of the spe- 
 cies. Generation, presents many points of resemblance in plants and 
 animals. In the former it is cryptogamic, or phanerogamic ; in the 
 latter, non-sexual, or sexual. In the phanerogamic and sexual, the 
 junction of two kinds of matter furnished by the parents is necessary! 
 to the development of fertile ova. In the cryptogamic and non- 
 sexual generation, the new individual is developed by a separation of 
 particles from the body of the parent, by which the new formation is 
 
TOLTTION.-™SENSATION. 45 
 
 nourished until it has been so far niatured as to be capable of an 
 independent existence, i' . , 
 
 ■The functions, hitherto enumerated, may be called organic, as 
 being common to all organized beings;' but there are others which, 
 as being peculiar to, and characteristic of, animals, may be appro- 
 priately designated i«w»i»ia/ functions. 
 
 The prominent characteristic of animals is the enjoyment of Voli- 
 tion or Willi which implies necessarily the possession of Consciousness. 
 Our knowledge of the share which consciousness and the will have 
 iu the production of certaiti phenomena of animal life, is derived 
 from the experience which each person has of his own movements, 
 and a comparison of them with the actions of inferior animals. We 
 are conscious that,, by a certain effort of the mind, we can excite 
 our muscles to action ; and when we see precisely similar acts per- 
 formed by the lower creatures, with all the marks of a purpose^ it is 
 fair to infer that the same process takes place in them as in ourselves. 
 Moreover, we learn by experience^ that injury or disease of the 
 nerves, which are distributed to our muscles, destroys the power of 
 accomplishing a certain act, but does not affect the desire or the 
 wish to perform it: and experiments tell us that the division of the 
 nerves of a limb in a lower animal destroys its power over that 
 member ; ' while its ineffectual struggles to move the limb obviously 
 indicate that the will itself is not affected by the bodily injury, though 
 its powers are limited by it. 
 
 Again, certain external agents are capable of affecting the mind, 
 through certain organs, thus giving rise to Sensations. Light, sound, 
 odour, the sapid qualities of bodies, their various mechanical pro- 
 perties, hardness, softness, &c., are respectively capable of producing 
 corresponding, affections of the mind, which experience leads us to 
 associate with their exciting causes, and which maybe agreeable, and 
 produce pleasure, or the leverse, and give rise to pain. 
 
 In a similar way to that by which we learn that the will stimulates 
 our muscles through the nerves, we can ascertain that the nerves are 
 the channels through which our sensations also are excited. " Certain 
 states of our bodily organs are directly followed by certain states 
 or affections of our mind ; certain states or affections of our mind are 
 directly followed by certain states of our bodily organs. The nerve 
 of slight, for example, is affected in a certain manner ; vision, which 
 is an affection, or state of the mind, is its consequence. I will to 
 move my hand ; the hand obeys my will so rapidly, that the motion, 
 though traly subsequent, seems almost to accompany my volition, 
 rather than to follow it." (Dr. Brown. Philosophy of the Human 
 Mind, p. 106.) ' 
 
 And in all the inferiar animills, possessed of like organs, there can 
 be no doubt that sensations may be produced similar to those which 
 arise in the human mind. In many of ;thera, indeed, the sense of sight, 
 hearing, or smell seems much more acute than in man, and affords 
 examples of a beautiful and providential provision for the peculiar 
 sphere which the creatures are destined to occupy. The unerring 
 precision of the 'beast or bird of prey, in pouncing upon its victim — 
 
46 MIND.— SOUL.— INSTINCT. 
 
 the accuracy with which the hound tracks by its scent the object 
 of its pursuit — or, the quickness with which, most of our domestic 
 animals detect sounds and judge of their direction, are familiar 
 illustrations of the superiority of these senses in animals whose gene- 
 ral organization is inferior to that of man. 
 
 There are few animals, however small and insignificant, in which 
 we cannot recognize evidence of a controlling and directing will. 
 But even in those few, in which voluntary movements are fiot dis- 
 tinctly to be discerned, the presence of a special system of organs, 
 with which in the higher animals vdlition and sensation are associ- 
 ated, namely, a nervous system, serves as a characteristic distinction 
 from plants. 
 
 Apovver of perception^ and a power of volition, together constitute 
 our simplest idea of Mind; the one excited through certain corporeal 
 organs, the other acting on the body. Throughout the greatest part 
 of the animal creation mental power exists, ranging from this its 
 lowest degree — a state of the blindest instinct, prompting the animal 
 to search for food — to the docility, sagacity, and memory of the brute ; 
 and to its highest state, the reasoning powers of man. 
 
 The phenomena of Mind, even in their simplest degree of deve- 
 lopment, are so distinct from anything which observation teaches 
 us to be produced by material agency, that we are bound to refer 
 them to a cause different from that to which we refer the phenomena 
 of living bodies. Although associated with the body by some un- 
 known connecting link, the mind works quite independently of it ; 
 and, on the other handj a large proportion of the bodily acts are 
 independent of the mind. The immortal Soul of man, divines parti- 
 cula auree, is the seat of those thoughts and reasonings, hopes and 
 fears, joys and sorrows, which, whether as springs of action, or mo- 
 tions , excited by passing events, must ever accompany him through 
 the checkered scene in which he is destined to play his part during 
 his earthly career. 
 
 Although the animals, inferior to man, exhibit many mental acts 
 in common with him, they are devoid of all power of abstract rea- 
 soning. " Why is it," says Dr. Alison, " that the monkeys, who 
 have been observed to assemble about the fires which savages have 
 made in the forests, and been gratified by the warmth, have never 
 been seen to gather sticks and rekindle them when expiring > Not, 
 certainly, because they are incapable of understanding that the fire- 
 which warmed them formerly will do so again, but because they are 
 incapable of abstracting and reflecting on that quality of wood, and 
 that relation of wood to fires already existing, which must be com- 
 prehended, in order that the action of renewing the fire may be sug- • 
 gested by what is properly called an effort of reason." 
 
 Yet animals are guided by Instinct to the performance of certain 
 acts which have reference to a determinate end : they construct 
 various mechanical contrivances, and adopt measures of prudent 
 foresight to provide for a season of want and difficulty. None of 
 these acts could be effected by man without antecedent reasoning, 
 experience, or instruction. But animals do them without previous 
 
MOTIONS OF PLANTS.— IMPORTANCK OP PHYSIOLOGY. 47 
 
 assistance; and the young and inexperienced are as expert as those 
 which have frequently repeated them. "An animal separated im- 
 mediately after its birth from all communication with its kind, will 
 yet perform every a!ct peculiar to its species, in the same manner, and 
 with the same precision, as if it had regularly copied their example, 
 and been instructed by their society. , The animal is guided and 
 governed by this principle alone ; by this all its powers are limited, 
 and to this all its actions are to be ultimately; refelred. An animal 
 can discover nothing new; it can lose nothing oldl The beaver 
 constructs its habitation, the sparrow its nest, the bee its comb, 
 neither betternor woi-se than they'did five thousand years ago." 
 
 In plants there is no nervous system ; there are no mental pheno- 
 mena. The motions of plants correspond in some degree with those 
 movements of animals in which neither consciousness nor nervous 
 influence participates. Such movements are strictly organic,' and 
 result from physical 'changes produced direcytly in the part moved. 
 Amongst the most interesting examples of these movements are those 
 of the Mimosa' pudica, the' Dioniea muscipula, and the Berheris. ■ 
 ■ III. It is "the province of Physiology to investigate the ways in 
 which the functionsof living beings are effected; and this investiga- 
 tion naturally involves the examination of their mechanism, of the 
 chemical constitution, and of the properties of their component tex- 
 tures. The study, of Anatomy must always accompany that of Phy- 
 siology, on the principle that we must understand the construction of 
 a machine before we can comprehend the way in which it works. 
 The history of physiology shows that it made no advance until the 
 progress of anatomical knowledge had unfolded the structure of the 
 body. ■ There is so much of obvious mechanical design in the -inti- 
 mate structure of the various textures and organs, that the discovery 
 of that structure opens the most direct road to the determination of 
 their uses. That kind of anatomy which investigates structure with 
 a special view to function may be properly designated Physiotoeical 
 Anatomy. ■ • 
 
 • A correct physiology must ever bel the' foundation of rational medi- 
 cine. He who is ignorant of the jproper construction of a watch, 
 and of the nature of thfe materials of which it is made, could not 
 find out in what part'its actions were faulty, and would therefore be 
 very urifit to hi entrusted with repairing it. In medicine, the first 
 step towards the cure of disease is' to find out what the disease is and 
 where it is situate {diagnosis). Without a knowledge of the oflSces 
 which various parts fulfil in the animal economy, our search to 
 determine what organ or function is deranged must be most vague 
 and indefinite. :P<ttAo/og-y is the physiology of disease; and it is 
 obviousj that no pathological doctrines can command' confidence, 
 which are hot founded upon accurate views of the natural functions. 
 It is also certain- that improvements in- pathology must follow in the' 
 wake of an advancing physiology. 
 
 The practice of niedicine and surgery abounds with examples, 
 illustrating the immense benefits which physiology has conferred 
 upon the healing art. The great advance which has been made 
 
48 MOTIONS OP PLANTS.— IMPORTANCE OF PHYSIOLOGY. 
 
 of late years in the pathology of nervous diseases, is mainly owing 
 to the discoveries of Bell, and many others, in the functions of vari- 
 ous nerves, and the general doctrines of nervous actions. We may 
 instance the case of the facial nerve — the portio dura of the seventh pair. 
 It was supposed formerly that this nerve was the seat of that painful 
 disease, called tic douloureux, arwl section of it has been perfornied 
 for the relief of the patient. It is now known that this nerve could 
 not be the seat of a very painful disease, for it is itself, in a very 
 great degree, devoid of sensibility. It need hardly be added, that 
 the operation is discarded. 
 
 The dangerous disease, to which many children have fallen vic- 
 tims, laryngismus stridulus or crowing inspiration, although admira- 
 bly described by practical physicians, was never properly understood' 
 until the functions of the laryngeal nerves were clearly ascertained, 
 and until it had been shown tkat spasmodic actions! ™*y be excited 
 by irritation of a remote part, or through a stimulus reflected from 
 the nervous centre. It is now known, that this disease has not its. 
 seat in the larynx, where those spasms occur which excite so much, 
 alarm for the fate of the little patient ; but that it is an irritation of a 
 distant part, which derives its nerves from the same region of the 
 cerebro-spinal centres with the larynx,— that the afferent nerves of 
 that part convey the irritation to the centre, whence it is reflected by 
 certain efferent nerves to the muscles of the larynx. 
 
 The accurate diagnosis of diseases of the heart rests entirely upon 
 a correct knowledge of the physiology of that organ. This improve- 
 ment in medicine may be said to date frOm the time of Harvey, for 
 he was the first who clearly expounded the mechanism of the central 
 organ of the circulation. But the application of auscultation to the 
 exploration of the sounds developed in its action, and the correct 
 interpretation of those sounds in health by the experiments and 
 observations of the last few years, have almost completely removed 
 whatever difficulties stood in the way of the detection of cardiac 
 maladies. 
 
 We are not less indebted to the illustrious Englishriian,^ who dis- 
 covered the circulation of the blood, for having paved the way to a 
 rational treatment of aneurismal and wounded arteries by the modern 
 operation of placing a ligature between the heart and the seat of the 
 disease or injury. " The active mind of John Hunter," says Mr. 
 Hodgson, " guided by a deep insight into the powers of the animal 
 economy, substituted for a dangerous and unscientific operation, an 
 improvement founded upon a knowledge of those laws which influ- 
 ence the circulating fluids and absorbent system ; and few of his 
 brilliant discoveries have contributed more essentially to the benefit 
 of mankind." 
 
 In investigating the functions of the human body, the physiologist 
 cannot do better than follow the instructions laid d.dwn by Halter in 
 the preface to his invaluable work, "Elementa PhysioldgiaB Corporis, 
 Humani." 
 
 The first and most important step towards the attainment of pbysir 
 ological knowledge, is the study of the fabric of the human body^ 
 
IMPORTANCE OF COMPARATIVE ANATOMY. 49 
 
 " Et primum," says Haller, " cognoscenda est fabrica corporis hu- 
 mani, cujus pehe infinite partes sunt. Qui physiologiam ab anatome 
 avellere studuerunt, ii certe mihi videntur, cum inathematicis posse 
 comparari qui machinse alicujus vires et functiones calculo expriraere 
 suscipiunt, cujus neque rotas cognitas habent, neque tympana, neque 
 mensuras, neque materium." 
 
 A knowledge of human anatomy alone is, however, not sufficient 
 to enable us to form accurate views of the functions of the various 
 organs. Before an exact judgment can be formed of the functions of 
 most parts of living bodies, Haller says, that the construction of the 
 same part must be examined and compared in man, in various quad- 
 rupeds, in birds, in fishes, and even in insects. And, in proof of 
 the value which attaches to this knowledge of comparative anatomy, 
 he shows how, from that science, "it may be determined that the liver 
 is the organ which secretes bile ; and that the bile found in the 
 gall-bladder is not secreted by, but conveyed to, that organ : for 
 no animal has a gall-bladder without a liver, although many have 
 a liver without a gall-bladder; and, in every case where a gall-blad- 
 der is present, it has such a communication with the liver, that the 
 bile secreted by the latter may be easily transferred to the former. 
 " Vides adeo," he adds, " bilem hepate egere, in quo paretur, vesi- 
 cula non egere, non ergo in vesicula nasci, ex hepate vero in vesicu- 
 lum transire." 
 
 And Cuvier has happily compared the examination of the compara- 
 tive anatomy of an organ, in its gradation from its most complex to 
 its simplest state, to an experiment which consists in removing suc- 
 cessive portions of the organ, with a view to determine its most 
 essential and important part. In the animal series we see this 
 experiment performed by the hand of nature, without those dis- 
 turbances which mechanical violence must inevitably produce. We 
 thus learn, from comparative anatomy, that the vestibule is the funda- 
 mental part of the organ of hearing ; and that the other portions, the 
 semicircular canals, the cochlea, the tympanum and its contents, are 
 so many additions made successively to it, according as the increas- 
 ing perceptive powers of the animals render a more delicate acoustic 
 organ necessary. In a similar manner we learn, that one portion 
 of the nervous system, in those animals in which it- has a definite 
 arrangement, is pre-eminently associated with the mental principle, 
 and is connected with, and presides over, the other parts. This 
 organ, the brain, is always situate at the anterior or cephalic ex- 
 tremity of the animal, and with it are immediately connected the 
 organs of the senses, the inlets to perception. We soon find that 
 the brain exhibits a subdivision into distinct parts ; and of the rela- 
 tive importance of these parts, and their connection with the organs 
 of sense, and with the intellectual functions, we derive the most 
 important information from the study of comparative anatomy. 
 
 Haller further assigns the examination of the living animal as a 
 
 valuable aid in physiological research. Doubtless, many obscure 
 
 points have been elucidated by experiments on living animals, and 
 
 discoveries have been made which have greatly contributed to the 
 
 4 
 
50 THE MICROSCOPE. 
 
 progress of physiology; but the best physiologists are ever reluctant 
 to interrogate nature in this way, knowing that replies elicited by 
 torture are rarely to be depended upon. Very useful.knowledge may 
 be derived from observing the play of certain functions in living 
 animals, or in Man himself, — contrasting them in various individuals, 
 and noting the effects of age, sex, and temperament, and ascertaining 
 the influence which other conditions, natural or artificial, may exert 
 upon them. 
 
 The investigation of disease, both during life and after death, is of 
 great value to enable us to appreciate the action of an organ in 
 health. If, for example, as Haller remarks, a particular function be 
 ascribed tp a certain part, how can there be a more favourable oppor- 
 tunity of testing the accuracy of such a doctrine than by the exami- 
 nation of a body in which that part was affected with a disease, of 
 which the previous history was known ? If the function in question 
 had been vitiated, or destroyed, it may be fairly presumed to have 
 had its seat in the diseased organ. Nothing has contributed, more 
 largely to determine the functions of particular nerves, than exact 
 histories of the symptoms during life, in cases in which they had 
 been found, after death, in a diseased condition. 
 
 For exploring the minute structure of various textures, the ana- 
 tomical elements of the body, Haller advises the use of the Micro- 
 scope. The great improvements which modern opticians have ac- 
 complished, not only in the dioptric but also in the mechanical 
 adjustments of this instrument, render it an invaluable adjuvant in 
 physiological research. We shall have frequent occasion in the fol- 
 lowing pages to refer to anatomical analyses, effected by the micro- 
 scope, of the utmost value to the knowledge of function. It may, 
 however, be remarked, that, as the sour(?es of fallacy are numerous 
 even with the best instruments, more depends upon the observer 
 himself, in this kind of investigation, than in almost any other. 
 
 The great impediment to deriving correct inferences from micro- 
 scopical observations has arisen from the discordance, too apparent, 
 in the narrations of different observers. This discordance has been 
 the result of a twofold cause ; namely, imperfection of the instru- 
 ments, and the very unequal qualifications of different observers. 
 The former cause is now almost completely removed ; the latter must 
 remain, while men imperfectly appreciate their own abilities for par- 
 ticular pursuits. 
 
 To make microscopical observation really beneficial to physiologi- 
 cal science, it should be done by those who possess two requisites: 
 an eye, which practice has rendered familiar with genuine appearances 
 as contrasted with those produced by the various aberrations to w^hich 
 the rays of light are liable in their passage through highly refracting 
 media, and which can quickly distinguish the fallacious frpm the real 
 form ; and a mind, capable of detecting sources of fallacy, and of 
 understanding the changes which manipulation, chemical reagents, and 
 Other disturbing causes may produce in the arrangement of the ele- 
 mentajy parts of various textures. 
 
 To these we will add another requisite, not more important for 
 
, ANATOMICAL AND CHEMICAL ANALYSIS. 51 
 
 microscopical than for other inquiries ; namely, a freedom from pre- 
 conceived views or notions of particular forms of structure, and an 
 absence of bias in favour of certain theories, or strained analogies. 
 The history of science affords but too many instances of the baneful 
 influence of the idola speeds upon the ablest minds ; and it seems 
 reasonable to expect that such creatures of the fancy would be espe- 
 cially prone to pervert both the bodily and the mental vision, in a 
 kind of observation which is subject to so many causes of error, as 
 that conducted by the aid of the microscope. 
 
 Finally, the sagacious Haller perceived how necessary to the 
 furtherance of physiology is a knowledge of Organic Chemistry; and 
 ■we could adduce many instances to prove, that the attention, which 
 has of late years been paid to this subject, has not been without its 
 fruit, in giving us an insight into the nature of many functions, which, 
 ■without it, we could not have obtained. 
 
 In the living body the most delicate chemical processes are un- 
 ceasingly going on, for the formation of new compounds and the 
 destruction or alteration of old ones. It is evident that no progress 
 can be made in the investigation of these invisible processes, unless 
 we can arrive at an exact knowledge of the chemical composition 
 of the various substances which are employed in them. 
 
 Henceforward, in physiological research, anatomical and chemical 
 analysis must go hand in hand : the former to ascertain the minute 
 mechanism of the various processes ; the latter, to determine the 
 nature of the affinities by which the syntheses and analyses of the 
 living laboratory are effected. 
 
 In the composition of the preceding chapter we have to acknowledge valuable 
 aid derived from the following works: — Haller, Elementa Physiologias Corporis 
 Humani ; Barclay on Life and Organization ; Roberton on Life, and Mind; Prichard 
 on the Doctrine of a Vital Principle; Dr. Carpenter's article Life, and Dr. Alison's 
 article Instinct, in the Cyclopsedia of Anatomy and Physiology; Remarks on Skep- 
 ticism, by the Rev. Thomas Rennell ; Daniell's Chemistry ; Graham's Chemistry. 
 
 CHAPT?ER I. 
 
 SOLID AND FLUID CONSTITUENTS OF ANIMAL BODIES. PROXIMATE PRIN- 
 CIPLES. — SECONDARY ORGANIC COMPOUNDS. CLASSIFICATION OF THE 
 
 Tissues. — DEVELOPMENT OF THE TISSUES FROM CELLS. PROPERTIES 
 
 OF THE TISSUES. 
 
 Animal bodies are composed of solids and fluids. The former 
 constitute the various textures and viscera ; the latter, the blood, 
 lymph, chyle, and the liquid secretions of glands, contained either in 
 their excretory ducts or in special reservoirs. 
 
 The solid textures contain only about one-fourth of solid matter, 
 the rest is water. The great shrinking which they experience, when 
 dried, shows how much of their bulk they owe to this combination ; 
 
52 SOLID AND FLUID CONSTITUENTS OF ANIMAL BODIES. 
 
 and parts thus shrunken swell out again, and assume their natural 
 condition on the addition of water. The mumray of a large man is 
 of a very trifling weight. Blumenbach possessed the entire perfectly 
 dry mumray of a Guanche or aboriginal inhabitant of Tenerifie, pre- 
 sented to him by Sir Joseph Banks, which, with all its muscles and 
 viscera, weighed only seven pounds and a half. 
 
 Water is one of the most important constituents of animal bodies. 
 It forms four-fifths of their nutrient fluid, the blood ; and it gives more 
 or less of flexibility and softness to the various solid textyres. The 
 loss of it in great quantity speedily puts a stop to vital action, as may 
 be easily shown in the lower animals ; and some animalcules, in which 
 all appearance of life may have ceased on being deprived of it, will 
 revive on its being supplied to them again. It is a solvent of many 
 organic matters; some also are suspended in it: it is, therefore, a 
 valuable medium for conveying these substances to the several tex- 
 tures and organs. It plays a most important part in the various 
 chemical operations of the body ; and its addition to, or subtraction 
 from a particular compound is capable of converting it into a substance 
 of very different properties. 
 
 By anatomico-physiological analysis we separate the solids and fluids 
 of the body into their various kinds, and classify and arrange them 
 according to their characters and properties. 
 
 By chemical means we obtain from them a class of substances, 
 called proximate principles, substances but one step removed from the 
 organized tissue, some of which are held in solution in the blood. 
 These, in combination with sulphur, phosphorus, and other simple 
 substances (incidental elements), and salts, form the material out of 
 which the organized tissues are framed. 
 
 The general chemical constitution of these proximate principles 
 has already beeri discussed in the Introduction ; and they have been 
 distinguished from another class of organic substances, the secondary 
 organic compounds, among which we must particularize those which 
 are formed by chemical action in the living organism, from materials 
 furnished by it. These are found in various secreted fluids, and are 
 easily obtained from them, either by spontaneous separation, or by 
 simple chemical means ; and they must not be confounded with a vast 
 variety of compounds, which the chemist can create at will both from 
 them and from the proximate principles, through the affinities of vari- 
 ous chemical substances for them. 
 
 The following table contains a list of substances which, in the 
 present state of our knowledge, may be properly assigned to the two 
 classes of organic compounds, to which allusion has been made : 
 
 PBOXIMATE PIII2TCIII,ES. SECONDABT OHSASIC COMPOUKDS. 
 
 Albumen.T Urea; 7 . , ... 
 
 Fibrine, ^ Compounds of Proteine. ' Uric or Lithic acid ; 5 '" ^ ^'''°*' 
 
 ' Caseine, J Cholesterine; in the Bile. 
 
 Gelatine. Biliary matters. 
 
 Chondrine. Pepsine; in the Gastric Juice. 
 
 Elaine. Sugar of milk. 
 
 Stearine. Lactic acid. 
 Margarine. 
 Hasmatosine, 
 Globuline. 
 
PROXfMATE PRINCIPLES.— ALBUMEN. 53 
 
 Of the Proximate Principles. — 1. Albumen. — This substance is so 
 called from the white colour it possesses in the solid state. It is very 
 readily obtained from the white, of .egg, ovalbumen. In tl;ie human 
 body it exists in two states: fluid, being dissolved in the serum of 
 the blood, and in some of the secretions: and solid, forming certain 
 of the tissues, which are thence called albuminous tissues. These 
 are, the brain, spinal cord- and nerves, and the mucous membranes; 
 it also enters into the composition of the muscles, and of the aqueous 
 and vitreous humours of the eye, It is also contained in the effusions 
 of serum or pus, which are the products of disease. 
 
 Albumen may be readily made to pass from the fluid to the solid 
 state, or to coagulate, by the influence of certain reagents; but it has 
 no spontaneous tendency to assume the solid form, except by the loss 
 of the water which is combined with it. By evaporating white of 
 eggs, at a temperature not exceeding J20'', its water is driven off, 
 and solid albumen, in the form of a yellowish transparent brittle 
 mass, is obtained with all its properties unimpaired. If a solution 
 of albumen, as serum of the blood, be exposed to a heat between 
 140° and 150°, it coagulates, and then it becomes insoluble in water. 
 
 The mineral acids have the property of coagulating albumen. Of 
 these, that which is most used in medical practice is the nitric, a drop 
 or two of which will readily detect a small quantity of albumen dis- 
 solved in a clear fluid, by rendering it more or less opaque. Alcohol 
 also has this property; and hence any albuminous textures submitted 
 to its influence become hardened and condensed. Bichloride of 
 mercury exercises a similar influence, and is a delicate test for albu- 
 men. It was Offila who first employed this proximate principle as an 
 antidote to the poisonous effects of the bichloride, which combines 
 with the albumen arid is by it partially converted into calomel. Ac- 
 cording to Peschier, the white of one egg is sufficient to render four 
 grains of the poison innocuous. 
 
 Another delicate test for albumen is the ferro-cyanide of potassium, 
 which will precipitate it from solution, provided a little acetic acid 
 have been previously added, in order to neutralize the soda in com- 
 bination with it. Albumen is also precipitated from solution by 
 tannin. 
 
 Albumen coagulates at the negative pole of the galvanic battery, 
 or at both poles, when a strong battery is employed. 
 
 Many other reagents will coagulate this principle, but enough have 
 been mentioned for all practical purposes. 
 
 It often happens that albumen is carried off from the system in large 
 quantities by the urine. By any of the means above-mentioned, its 
 presence in that fluid may be detected. . When heat is used, it will 
 always be advisable to ascertain previously whether the urine be acid 
 or alkaline; for the presence of alkali prevents the coagulation of 
 albumen by heat. Hence it is a good rule, in testing for this sub- 
 stance, to employ both heat and nitric acid. 
 
 Albumen is soluble in caustic alkalies. 
 
 The existence of sulphur as a constituent of albumen, is shown 
 by the blackening of silver that has remained long it contact with it. 
 
54 FIBRINE. 
 
 According to Mulder, this principle yields the following elements 
 
 in one hundred parts : 
 
 Nitrogen 15'R3 
 
 Carbon 54-84 
 
 Hydrogen 7-09 
 
 Oxygen 21-23 
 
 Phosphorus 0-33 
 
 Sulphur 0-68 
 
 100-00 
 
 2. Fibrine. — This proximate principle forms the basis of the mus- 
 cles ; and is, therefore, the chief constituent of the flesh of animals, 
 in -which it is found in the solid form. It exists in a state of solution, 
 in the serum of the blood, forming, with that fluid, the liquor san- 
 guinis of Dr Babington, in the lymph, and in the chyle. It is a con- 
 stituent of the exudation (coagulable lymph) which forms on certain 
 surfaces, as the result of the inflammatory process, and it sometimes 
 occurs in dropsical fluids. 
 
 Fibrine is distinguished from the other proximate principles, by its 
 remarkable property of spontaneous coagulation. When blood is drawn 
 from a vein, and allowed to rest, it speedily separates into a solid por- 
 tion, the crassamentum or clot, and a fluid portion, the serum. The 
 former consists of fibrine, with the red particles entangled in it during 
 its coagulation. It sometimes happens, that, owing to an unusual 
 aggregation of the red particles together, and to their more speedy 
 precipitation, a portion of fibrine on the surface coagulates without 
 enclosing the colouring matter. A yellowish-white layer forms the 
 upper stratum of the crassamentum, and this is called the buffy coat 
 or inflammatory crust. It is an example of nearly colourless fibrine, 
 but contains also peculiar globules. 
 
 We may obtain fibrine in a state of considerable purity, by cutting 
 the crassamentum into slices, and washing them in clean water so as to 
 dissolve out the colouring matter ; or by briskly stirring, with a bundle 
 of twigs, blood as it flows from a vein: the fibrine coagulates upon the 
 twigs in small portions, which, being washed, afford good specimens 
 of colourless fibrine ; by digesting afterwards in alcohol and ether, the 
 adhering impurities are got rid of. Another mode of obtaining this 
 substance is that suggested by Miiller, namely, to filter frogs' blood, 
 the red particles of wh^ch being too l^rge to permeate the pores of 
 the filter, the liquor sanguinis passes through in a colourless state, and 
 its fibrine coagulates free from colouring matter. Sometimes we obtain 
 masses of fibrine, great part of which is colourless, from the cavities 
 of the heart, and from the large arteries, after death. It is also accu- 
 mulated, and disposed in a peculiar lamellar form, in the sacs of old 
 aneurisms. 
 
 Pure fibrine is white, tasteless, and inodorous; it tears into thin 
 laminae, which are transparent, and it is remarkably elastic; by dry- 
 ing, it becomes yellow, hard, and brittle, and loses three-fourths of 
 its weight, but imbibes water again when moistened: it is insoluble 
 in both hot and cold water, in alcohol, and in ether. By long-con- 
 tinued boiling in water, its composition is changed, and it becomes 
 
CASEINE. 55 
 
 soluble. Strong acetic acid converts it into a jelly-like mass, which 
 is sparingly soluble in water. All the alkalies dissolve fibrine. Any 
 of these solvents of fibrine will prevent the coagulation' of blood, 
 which has been allowed to drop into it as it flows fronri the blood- 
 vessels. 
 
 Fibrine is dissolved by cold concentrated muriatic acid, and, if 
 kept at a cool temperature for twenty- four hours, the solution acquires 
 an indigo-blue colour. Albumen, similarly treated^ assumes a violet 
 colour. 
 
 Caustic potash, common salt, carbonate of potash, and many neu- 
 tral salts, when mixed in certain quantities with the blood, have the 
 property of preventing the coagulation of its fibrine.* 
 
 We subjoin the ultimate analysis of fibrine, as given by Mulder. In 
 one hundred parts, he found 
 
 Nitrogea l.'j-Ta 
 
 Carbon ...... 54-56 
 
 Hydrogen 6-90 
 
 Oxygen 22-13 
 
 Phosphorus • . . . . OSS 
 Sulphur 0-36 
 
 100-00 
 
 3. Caseine. — This principle has many properties in common with 
 albumen and fibrine. It is found abundantly in milk; its occurrence 
 in other fluids has not been positively determined. The curd, which 
 is formed by heating milk in which a free acid existed, consists of a 
 combination of caseine with the acid. Heat alone will not effect the 
 precipitation of the curd ; but the addition of a little acid of any kind 
 will occasion it. 
 
 When dilute sulphuric acid is added to skimmed milk, a -precipi- 
 tate occurs, which is sulphate of caseine. By digesting the clot, thus 
 formed, with water and carbonate of lime, the acid combines with the 
 lime, and the caseine, set free, dissolves in the water, and may be 
 obtained by evaporation. 
 
 Caseine is coagulated very perfectly by the action of rennet (the 
 fourth or true digesting stomach of the calf) aided by heat. This 
 pow^er of coagulating caseine is not to be attributed to the acid of the 
 calf's stomach, but to the organic principles (pepsine) resident in it ; 
 for the power remains after all evidence of acid reaction has been 
 removed. This is one of the most powerful agents'in causing the 
 coagulation of caseine, and it has been employed in domestic economy 
 for the manufacture of cheese, which consists of the curd mixed with 
 bntter, compressed and dried. So perfect is the coagulating power 
 of rennet, that not a. particle of caseine in milk submitted to its action 
 will remain uncoagulated. 
 
 Caseine comports itself with reagents in ^ manner very similar to 
 albumen. In the coagulated state it is insoluble in water, but soluble 
 in liquor potassse. It is not precipitated by heat alone, in which 
 respects it differs from albumen. Acetic acid, which will not precipi- 
 
 * See further observations on the results of the examination of fibrin by the micro- 
 scope, in the chapter on the Blood. 
 
56 PROTEINE. 
 
 tate albumen, causes the coagulation of caseins, and an excess of aci^ 
 again dissolves it. 
 
 Caseine contains sulphur, but no phosphorus. 
 
 Mulder's ultimate analysis is as follows : 
 
 Nilrogea lS-95 
 
 Carbon 55-10 
 
 Hydrogen 6-97 
 
 Oxygen 21-63 
 
 Sulphur 0-36 
 
 100-00 
 
 If albumen, or fibrine, or caseine be dissolved in a moderately strong 
 solution of caustic potash, and exposed for some time to a high tem- 
 perature, it becomes decomposed ; and if acetic acid be now added, 
 a precipitate takes place of a gelatinous translucent matter. This 
 substance was discovered by Mulder, and named by him Protdne 
 (from the Greek verb n§attva,I am first), as being the radicle of these 
 proximate principles ; or, in the language of Liebig, the commence- 
 ment and starting-point of all the tissues; so that it appears that each 
 of these principles is composed of this substance, with the addition 
 of certain proportions of phosphorus, sulphur, or of both. In the 
 process by which it is obtained, the object is to remove the sulphur 
 and phosphorus and any salts which may be mixed with it, and to set 
 the proteine free. » 
 
 Proteine, when dried, forms a hard, brownish-yellow substance, 
 without taste, and insoluble in water and alcohol. It attracts moisture 
 from the air, and swells out again into a gelatinous mass when moist- 
 ened. It is soluble in all acids, when diluted ; and forms combina- 
 tions with them, which are with difficulty, or not at all, soluble in 
 excess of acid. It is also dissolved in dilute alkalies, or in solutions 
 of alkaline earths. 
 
 The ultimate analyses of proteine, according to Mulder, from one 
 hundred parts.gives as follows: 
 
 Nitrogen . . . . • 16-01 
 
 Carbon 55'29 
 
 Hydrogen 7'00 
 
 Oxygen 21-70 
 
 100-00 
 
 The following table exhibits the relations which albumen, fibrine, 
 and caseine bear respectively to proteine : 
 
 Albumen of serum = 10 eqts. Proteine -)- 1 eqt. Phosph. -(- 2 eqts. Sulph. 
 Albumen of Egg := 10 eqts. Proteine -f- > eq'- Phosph. -f 1 eqt. Sulph. 
 Fibrine := 10 eqts. Proteine -(- 1 eqt. Phosph. -f- 1 eqt. Sulph. 
 
 Caseine = 10 eqts. Proteine -j- 1 eqt. Sulph. 
 
 Beside.s the essential elements of these proximate principles, which 
 are obtained by their ultimate analysis, we find certain salts mixed 
 ■with them. In albumen, phosphates and sulphates of earths and 
 alkalies and chloride of sodium ; in fibrine, phospate of lime; and in 
 caseine, the same salt, in the proportion of 6-24 per cent. As the 
 phosphate of lime is the same as bone-earth, the existence of it in 
 
GELATINE,- 57 
 
 union with the proximate principle, which forms the chief constituent 
 of milk, seems to have reference to the process of ossification during, 
 the growth of the infant. 
 
 Proteine, in every respect the same as that which forms the basis of 
 the proximate principles just described, may be obtained from similar 
 elements in the vegetable kingdom. Gluten, which exists abundantly 
 in the seeds of the Cerealia, yields a principle which is called vege- 
 table Jibrine ; the same substance coagulates spontaneously in the newly 
 expressed juice of vegetables. From the. clarified juices of cauli- 
 flower, asparagus, mangel-wurzel, or turnips, when made to boil, a 
 coagulum is formed, which cannot be distinguished from the coagu- 
 lated albumen of serum or the egg. This is vegetable albumen. And 
 in peas, beans, lentils, and similar leguminous seeds, we find a sub- 
 stance similar to caseine. It is vegetable caseine, which, like the ani- 
 mal principle of the same name, does not coagulate by heat alone, but 
 yields a coagulum on the addition of an acid, as in milk. "The 
 chemical analysis of these three substances," says Liebig, " has led 
 to the very interesting result, that they contain the same organic ele- 
 ments, united in the same proportions by weight; and, what is still 
 more remarkable, that they are identical in composition with the chief 
 constituents of blood, animal fibrine, and albumen. They all three 
 dissolve in concentrated muriatic acid with the same deep purple 
 colour ; and, even in their physical characters, animal fibrine and albu- 
 men are in no respect different from vegetable fibrine and albujnen. 
 It is especially to be noticed, that by the phrase identity of composi- 
 tion, we do not here imply mere similarity ; but that, even in regard 
 to the presence and relative amount of sulphur, phosphorus and phos- 
 phate of lime, no difference can be observed." 
 
 4. Gelatine. — This substance exists in a peculiar combination with 
 the tissues of which it forms a constituent, and can only be obtained 
 by artificial means. If the cutis or true skin, tendon, or bone, be 
 subjected to continued boiling, this substance is obtained in solution 
 in the hot water, and upon cooling assumes the form of a solid jelly, 
 which is the more solid as the quantity of water contained in it is less. 
 The textures which yield gelatine are, the white fibrous tissue, areo- 
 lar tissue, skin, serous membranes, bone. Glue prepared from hides, 
 &c.; size from parchment, skin, &c.; and isinglass from the swim- 
 ming bladder of the sturgeon, are various forms of gelatine used in 
 commerce. 
 
 Gelatine, obtained by boiling, is in combination with a considerable 
 quantity of water: by a slow and gentle heat this. may be driven off, 
 and the gelatine obtained in a dry state. Dry gelatine is hard, trans- 
 parent, colourless, without smell or taste, of neutral reaction ; in cold 
 water it softens and swells up, and dissolves in warm water. It is 
 insoluble in alcohol and ether, but very soluble in the dilute acids 
 and alkalies. When tannin, or the tincture or infusion of galls, is 
 added to its solution in water, a brownish precipitate is thrown down 
 — the tanno-gelatine, which may be precipitated from a solution of 
 gelatine in 5000 times its weight of wate-r. 
 
 The process of tanning leather results from the affinity of gelatine 
 
58 CHONDRINE. 
 
 for tannin. The skins of the animals having been first freed from 
 cuticle and hairs by soaking in lime-water, are tanned by submitting 
 them to the action of infusion of oak-bark, the strength of -which is 
 gradually increased until a complete combination has taken place. 
 An insoluble compound is thus formed, capable of resisting putre- 
 faction. 
 
 According to Mulder, gelatine contains in one hundred parts, 
 
 Nitrogen 18-350 
 
 Carbon 50-048 
 
 Hydrogen 6-477 
 
 Oxygen 25-125 
 
 I 100000 
 
 to which may be added some inorganic material, chiefly phosphate 
 of lime. 
 
 Dr. Prout remarks, the gelatine in animals may be said to be the 
 counterpart of the saccharine principles of plants ; it being distin- 
 guished from all other animal substances by its ready convertibility 
 into a sort of sugar, by a process similar to that by which starch may 
 be so converted. If a solution of gelatine in concentrated sulphuric 
 acid be diluted with water and boiled for some time, gelatine-sugar may 
 be obtained from it, on saturating with chalk. Again, by boiling 
 gelatine in a concentrated solution of caustic alkali, it is separated into 
 leiicine and gelatine sugar, or glycicoll. The latter product crystalizes 
 in pretty large rhoraboidal prisms ; is colourless, inodorous, and very 
 sweet. {Graham's Chemistry, p. 1039. [Am. Ed., p. 700.]) It 
 differs from sugar, however, in the important particular, that it con- 
 tains nitrogen ; and Mulder assigns to it the following formula, C^ H, 
 Na O, + 2 HO. 
 
 Proteine cannot be obtained from gelatine ; but it seems reasonable 
 to infer, that it or its compounds must have contributed to the forma- 
 tion of the latter substance, for, in the egg, the gelatine of the chick 
 cannot be derived from any other material than a compound of pro- 
 tfeine. Scherer has shown that gelatine contains the elements of two 
 equivalents of proteine, with three of ammonia, and seven of water. 
 
 5. Chondrine is a substance in many respects similar to gelatine. It 
 is obtained in a State of solution, by boiling water, from the perma- 
 nent cartilages and from the cornea ; also from the temporary carti- 
 lage prior to ossification ; it gelatinizes on cooling, and when dry 
 assumes the appearance of glue. It differs from gelatine, in not being 
 precipitated by tannin, and in yielding precipitates to acetic acid, alum, 
 acetate of lead, and the protosulphate of iron, "which do not disturb a 
 solution of gelatine. It resembles the proteine compounds in containing 
 a minute quantity of sulphur. 
 
 M!ulder's analysis of one hundred parts is. 
 
 Nitrogen 14-44 
 
 Carbon 49-96 
 
 Hydrogen 6-63 
 
 Oxygen 28-59 
 
 Sulphur 0-38 
 
 100-00 
 
IMPORTANCE OF A MIXED DIET. 59 
 
 Respecting the remaining substances included in the list of true 
 proximate principles, very few words are necessary, as they will be 
 more fully treated of in subsequent chapters. 
 
 Elaine, Stearine, and Margarine are proximate principles of fat, and 
 are found also in the brain and nerves. Stearine exists but sparingly, 
 or not at all, in human fat. 
 
 Hcematosine and Globuline are the constituents of the particles, or 
 corpuscles, to which the blood owes its colour. They are both 
 nearly allied to albumen, and the latter is regarded as a compound of 
 proteine. 
 
 The proximate principles which have been described in the pre- 
 ceding paragraphs are constituents of the animal food, upon which 
 the human race, and the inferior creatures, to a great extent, subsist; 
 and the discovery that similar principles exist in the vegetable king- 
 dom, also adapted for food, is of the highest interest, as proving that 
 both kingdoms of organized nature are capable of aflbrdirig the mate- 
 rials which are suited to supply the waste in the animal tissues which 
 is the necessary result of their vital actions. The blood is the imme- 
 diate pabulum of the tissues ; its composition is nearly or entirely 
 identical with them ; it is, indeed, as Bordeu long ago expressed it, 
 liquid flesh ; it contains the elements of the solids in a state of solution 
 — le sang est de la chair coulante. The proteine compounds more 
 immediately. contribute to the formation of the blood, and, as we, have 
 seen, may be obtained directly from that fluid ; and the process of 
 nutrition consists in the attraction of certain of these principles from 
 the blood, and the appropriation of them by the textures and organs, 
 in a form assimilated to that. of their elementary parts. 
 
 It is necessary to the support of nutrition, that these proximate 
 principles should be,supplied in proper quantity to the blood, from 
 time to time, together with a due proportion of water; and, as the 
 human body is composed of a variety of textures, differing in their 
 chemical composition, so a variety of food is required for its perfect 
 nourishment. This statement, which appears most reasonable prior 
 to experience, is fully borne out by the results of the various experi- 
 ments on the nutritive power of different substances, from the tjme of 
 Papin to the present day. No one proximate principle is of itself 
 adequate to support life: if any such substance be administered 
 alone to animals, they will perish sooner or later, with signs of waste 
 and destruction in various textures. This had been long ago ascerr 
 tained respecting gelatine ; but a commission appointed by the French 
 Academy have lately reported that it applies equally to albumen, 
 caseine, or fibrine, if employed alone ; and that neither animals nor 
 man should be restricted to any course of diet, which does not contain 
 all the proximate elements of their frame. 
 
 These facts should be made known to, and impressed upon all, 
 whose position in society leads them to superintend the administration 
 of food to a number of human beings congregated in prisons, work- 
 houses, or other public institutions. A complex machine, made up 
 of many different kinds of substances, requires for its repair a corre- 
 sponding variety of materials. The fabric of man's body is a piece 
 
60 SECONDARY ORGANIC COMPOUNDS. 
 
 of mechanism compounded of divers parts, derived from albumen, 
 fibrine, gelatine, &c.; and the material, which is to supply the wear and 
 tear that continually go on in it, ought to contain these substances. It 
 is even more important for sufficient nourishment that attention should 
 be paid to the quality than to the quantity of the food administered. 
 
 By the function of digestion, a fluid (the chyle) is prepared, which 
 contains those constituents of the food that are adapted to nourish the 
 ■body, and the first step of the nutrient process consists in the addition 
 of this new supply of nutritious material to the blood. A further stage 
 of this process is that whereby the several proximate principles are 
 separa'ted in order to be applied to the support of tHeir appropriate 
 textures; as albumen, to the albuminous tissues ; fibrine, to the fibrin- 
 ous. These two principles have already appeared in the chyle, and 
 pass with it into the blood-vessels, in which all the changes neces- 
 sary to nutrition take place. It is probable that gelatine is formed in 
 the blood, but is attracted from it by its proper tissues immediately 
 upon its formation, so that it does not accumulate in it; and this 
 accounts for our not being able to find it in the blood. The fatty 
 elements also separate in the blood, and are destined to nourish the 
 adipose tissue, and the nerves. It may be fairly conjectured that the 
 development and separation of these principles take place in the 
 capillary blood-vessels, because those vessels penetrate and play 
 freely among the elementary parts of the tissues ; and also because 
 the blood does not manifest a decided change in its characters until 
 it has passed through that part of the sanguiferous system. 
 
 The blood is likewise the seat of other changes, not less important 
 to the well-being of the animal economy. As certain particles of the 
 various tissues become effete and useless, they are removed either by a 
 direct absorbing power of the blood-vessels, or by that of certain vessels, 
 called lymphatics, and thus they again find their way into the current 
 of the circulation. Here the elements of the tissues, by some un- 
 known chemical agency, undergo certain transformations, and the 
 secondary compounds are formed, to be excreted from the system by 
 means of particular organs. Urea and uric acid, thus formed in the 
 blood, are excreted by the kidneys ; lactic acid, by the kidneys and 
 the skin ; the elements of the bile, by the liver, &c., &c. But whilst 
 it is highly probable that the effete particles furnish materials for these 
 compounds, there seems good reason to believe, that, at least with 
 respect to some of them, the food likewise contributes immediately 
 to their formation. That this is the case with respect to the bile, is 
 rendered very likely by several circumstances which cannot be dwelt 
 upon at present. 
 
 In the present state of our knowledge it is impossible to assign the 
 particular tissues whose metamorphoses give rise to the formation of 
 certain secondary compounds. Dr. Prout has expressed the opinion 
 that urea is derived from the gelatinous, and uric acid from the 
 albuminous tissues. And it may be conjectured that the fatty tissues 
 afford material for the formation of some of the constituents of the 
 bile. 
 
 As each of these secondary organic compounds forms a component 
 
THE TISSUES. 61 
 
 part of some special secretion, it would be premature to do more at 
 present than allude to them ; we, therefore, postpone the further 
 investigation of them to those parts of the work where the respective 
 secretions will be treated of. 
 
 Classification and properties of the tissues. — From the proximate 
 principles, the various textures are produced by the development of 
 particular organic forms. It has already been stated, that the simplest 
 form which animar matter assumes in its organization is that of a 
 nucleated cell. Such cells exist in vast numbers, free and isolated, 
 floating in the blood, but having occasionally a remarkable tendency 
 to cohere. These are the red particles of the blood, which perform 
 some very important ofSce in reference to that fluid and the different 
 tissues, as appears from the serious results consequent upon a great 
 deficiency of them. They may be considered to be among the sim- 
 plest products of organization. 
 
 In the embryonic state all the tissues are composed of cells, analo- 
 gous in structure to the corpuscles of the blood. These are united 
 together by a more or less abundant intercellular substance, which is 
 either homogeneous (hyaline), minutely granular, or indistinctly fibrous. 
 Some tissues retain, as their permanent character, this cellular struc- 
 ture ; whilst in others the cells undergo certain metamorphoses by 
 which they are converted into other forms, which constitute the ana- 
 tomical elements of the adult textures. 
 
 It seems impossible to devise a satisfactory arrangement of the 
 tissues, which shall be based on one principle of classification. The 
 following table has been constructed chiefly with the object of pre- 
 senting to the reader a general view of the various tissues, the anato- 
 mical characters of which will be discussed in subsequent pages. 
 
 TABULAn VIEW OF TBE TISSUES OF THE HUMAN BODY. 
 
 1. Simple membrane, homogeneous, or nearly Examples. — Posterior layer of the 
 
 so, employed alone, or in the formation of Cornea Capsule of the lens. — 
 
 compound membranes. Sarcolerama of muscle, &c. 
 
 3. Filampntous tissues, the elements of which White and yellow fibrous tissues, 
 are real or apparent filaments. — Areolar tissue. 
 
 3. Compound membranes,composed of simple Mucous membrane. — Skin. — True 
 
 membrane, and a layer of cells, of various orsecretingglands. — Serous and 
 
 forms (epithelium or epidermis), or of synovial membranes, 
 areolar tissue and epithelium. 
 
 4. Tissues which retain the primitive cellular Adipose tissue. — Cartilage.^Gray 
 
 structure as their permanent character. nervous matter. 
 
 5. Sclerous or hard tissue. Bone. — Teeth. 
 
 6. Compound tissues. 
 
 a. Composed of tubes of homogeneous Muscle. — Nerve, 
 membrane, containing a peculiar sub- 
 stance. 
 
 b. Composed of white fi,brous tissues and Fibro-cartilage. 
 cartilage. 
 
 The firsttexture enumerated in this table is an example of the 
 simplest form of membrane. Its principal character is extension; 
 but as to the arrangement of its ultimate particles nothing is known, 
 •for under the highest powers in the microscope it appears homoge- 
 neous, that is, without visible limits to its particles, or, at most, irregu- 
 larly and very indistinctly granular. The capsule of the lens, the 
 
62 THE TISSUES. 
 
 posterior layer of the cornea, and the walls of the primary organic 
 cells, are composed of it ; and it is employed in forming muscle, 
 nerve, and the adipose and tegumentary tissues. 
 
 The filamentous tissues are extensively used for connecting different 
 parts, or for associating the elements of other tissues. The ligaments 
 of joints, for instance, are composed of the white or yellow fibrous 
 tissues; and areolar tissue surrounds and connects the elementary 
 parts of nerves and muscles, accompanies and supports the blood- 
 vessels, and unites the tegumentary tissues to their subjacent parts or 
 organs. 
 
 Under the title compound membranes we include those expansions, 
 which form the external integument of the body, and are continued 
 into the various internal passages, which, by their involutions, con- 
 tribute to form the various secreting organs or glands. These are 
 composed of the simple homogeneous membrane covered by epi- 
 dermis or epithelium, and resting upon a layer of vessels, nerves, and 
 areolar tissue in great variety ; and they constitute the skin and mucous 
 membranes, with the various glandular organs which open upon their 
 surface. Hairs and nails, being hardened cuticle, are justly regarded 
 as appendages to the former. 
 
 To these we may add those remarkable membranes, composed of 
 areolar tissue and a thin indusium of epithelium, which are employed 
 as mechanical aids to motion. These are the serous membranes w];^ch 
 line the great cavities of the body, and the synovial membranes, which 
 are interposed between the articular extremities of the bones in cer- 
 tain joints, or are connected with and facilitate the motions of tendons. 
 
 The tissues which compose the fourth class have no common cha- 
 racter, except their adherence, in the adult state, to the primitive 
 cellular structure, and their analogy in that particular with the vege- 
 table tissue. Although a certain agreement, in morphological charac- 
 ters, allows these textures to be grouped together, none can be more 
 dissimilar as regards their vital endowments. They differ materially 
 as to the degree of cohesion between their cells: in cartilage there is 
 generally a firm and resisting intercellular substance; in adipose 
 tissue, the interval between the cells is occupied by areolar tissue 
 and blood-vessels, which are foreign to the true adipose cells ; and, 
 in the gray nervous matter, vessels and nerve tubes exist between 
 the cells. 
 
 The sclerous tissue (axTujgoj, hard), contains a large proportion of 
 inorganic material, to which it owes its hardness ; it differs very 
 materially from all the other tissues, excepting cartilage and fibro-car- 
 tilage, which, as regards hardness, might be classed with it. 
 
 The compound tissues are those, the elementary parts of which are 
 made up of two distinct tissues. Thus both muscle and nerve are 
 composed of parallel fibres or threads, each fibre being compound ; 
 in muscle, it is composed of homogeneous membrane, disposed like 
 a tube, containing a fleshy {sarcous) substance, arranged in a particu- 
 lar manner, which is the seat of the vital properties of the tissue ; 
 and, in nerve, the fibres are composed of similar-tubes of homoge- 
 neous membrane containing an oleo-albuminous substance, murine. 
 
DEVELOPMENT OF THE TISSUES FROM CELLS. 63 
 
 Fibro-cartilage is also properly a compound texture, being made up 
 of white fibrous tissue and cartilage; it is employed almost exclu- 
 sively in the mechanism of the joints of the skeleton, in which it is 
 associated with bone, cartilage, and ligaments. 
 
 Of the development of the tissues from cells. — At the earliest period 
 of embryonic life, the process of organization has advanced to so 
 slight an extent, that the variety of textures above described has not 
 yet appeared. 
 
 The prevailing mode, in which the development of animals takes 
 place, is by the formation, within the parent, of a body containing the 
 rudiments of the future being, as well as a store of nutrient material 
 sufficient to nourish the embryo for a longer or shorter period. This 
 body is called the ovum or egg. It is of that form which, in a former 
 page (p. 32, fig. 1), has been described and delineated as the simplest 
 which organization produces. It consists of a vesicular body filled 
 by a fluid, and enclosing another, within which is a third, consisting 
 of one or more minute, but clear and distinct granules. The first, or 
 the vitelline membrane of the ovum, is the wall of a cell; it is com- 
 posed of homogeneous membrane : the second, or the germinal vesicle 
 of the egg, is the nucleus of the first: and the third, which is called 
 by embryologists the germinal spot, is a nucleolus to the second. It 
 appears, from the researches of Wagner and Barry, that the nucleus 
 pr germinal vesicle precedes the formation of the vitelline membrane, 
 but the precise relation as to the period of its formation ot the nucle- 
 olus or germinal spot to the nucleus has not yet been satisfactorily 
 made out. The germinal vesicle and spot become the seat of a series 
 of changes, which give rise to the development of new cells, for the 
 formation of the embryo. 
 
 At this period the embryo consists of an aggregate of cells, and 
 its further growth takes place by the development of new ones. This 
 may be accomplished in two ways : first, by the development of new 
 cells within the old, through the subdivision of the nucleus into two 
 or more segments, and the formation of a cell around each, which 
 then becomes the nucleus of a new cell, and may in its turn be the 
 parent of other nuclei ; and, secondly, by the formation of a granular 
 deposit between the cells, in which the development of the new cells 
 takes place. The granules cohere to each other in separate groups 
 here and there, to form nuclei, and around each of these a delicate 
 membrane is formed, which is the cell-membrane. The nuclei have 
 been named cytoblasts, because they appear to form the cells {xvtos, 
 cell; ^-Kaaita, to produce) ; and the granular deposit in which these 
 changes take place is called the cytoblastema. 
 
 In every part of the embryo the formation of nuclei and of cells 
 goes on in one or both of the ways above-mentioned ; and, by and by, 
 ulterior changes take place, for the production of the elementary parts 
 of the tissues. The precise share which the cells take in this process 
 cannot be made intelligible in the present stage of our inquiry, even 
 if observers were agreed in their accounts of the phenomena. It must 
 suffice for us now to explain, as far as we are able, the general changes 
 
64 DEVELOPMENT OF THE TISSUES FEOM CELLS. 
 
 that occur, and the probable office which each part of the cell per- 
 forms in them. 
 
 The changes which the cells undergo in the formation of the tissues, 
 may be described under two heads ; first, those affecting the cell- 
 membrane; and,, secondly, those in which the nucleus is concerned. 
 In those tissues, whose ultimate elements are fibrous, that is, consist- 
 ing of real or apparent fibres, as areolar and fibrous tissues, the cell- 
 merabranes become elongated, and so folded or divided as to give the 
 appearance of a subdivision into minute threads or fibres. In the 
 tissues, which are composed of tubes of homogeneous membrane 
 containing a peculiar substance within them, as muscle and nerve, the 
 cells are joined end to end, and, the partitions at each extremity being 
 removed, their cavities communicate, so that they together form a 
 tube, or sheath, in which the deposit of the proper muscular or ner- 
 vous substance takes place. The smallest or capillary blood-vessels 
 also are formed by the coalescence of the walls of the cells, not at 
 one or two, but at several points, owing to their elongation, here and 
 there, into pointed processes, which unite and form the ramifications 
 of the vessels. 
 
 In these examples,, the nucleus of the cell appears to take no part 
 in the formation of the tissue. What becomes of it? does it become 
 absorbed, or does it waste away, its office having ceased ? There is 
 abundant evidence to show that the nuclei are still persistent in the 
 fully-formed tissues, for they have been seen in all those emimerated 
 in the last paragraph. They are generally altered in form, being 
 fattened and elongated. Henle believes that, while they retain their 
 peculiar characters, they are prolonged at either pole into peculiar 
 fibres, distinct, in anatomical and chemical characters, from the pro- 
 per fibres of the tissue ; he designates the latter Zellenfasern, cell- 
 fibres ; and the former Kernfasern, nucleus fibres. For instance, the 
 two elements of areolar tissue, which will be described at a future 
 page, are derived, according to him, the white fibrous element, from the 
 cell; the yellow, from the nucleus. The formation of the homoge- 
 neous simple membrane which forms the basement of the skin and 
 mucous membrane, maybe ascribed to the flattening and fusion of the 
 cell-walls into one another. The free surface of these membranes, 
 wherever they may be found, whether as integuments to the body, or 
 folded into glands, is the seat of a continual development of new cells, 
 which may have primarily sprung from the nuclei of the formative 
 cells of the basement membrane. 
 
 In other tissues the walls of the cells become thickened by a depo- 
 sition around and between them, with which they become united and 
 incorporated, and thus an intercellular substance is formed. This 
 substance becomes the seat of a further deposition, or new arrange- 
 ment of particles,, which, as far as we know at present, is not preceded 
 by the development of cells. In cartilage, which in its simplest state 
 is only an aggregate of cells, this substance assumes a fibrous form. 
 In most textures, it is not improbable that the nuclei are persistent ; 
 in cartilage, they remain in the cell-cavities, and possibly contribute 
 to the growth and nutrition of the cartilage ; in bone, they form the 
 
PROPERTIES OF THE TISSUES. 65 
 
 lacunje from which minute canals are prolonged into neighbouring 
 ones, or into the vascular channels; and, in teeth, they are probably 
 converted into the dental tubuli. 
 
 From the preceding brief and necessarily imperfect sketch, it seems 
 evident that, in the various metamorphoses of the fcetal into the per- 
 fect tissues, both the elements of the cells take a part. In no instance 
 does there appear to be an actual conversion of either cell-wall or 
 nucleus into the ultimate elements of the tissues. The cell- walls may 
 be changed into a part, accessory to the complete texture, as the sar- 
 colemma or sheath of the muscular fibre ; but the further organizing 
 process takes place on its outer or inner surface. And the nuclei, 
 likewise, may be changed into parts, which contribute to the nutrition 
 of the tissue ; but not into its essential elements. These, it must be 
 remarked, are always tRe product of an ulterior organizing process, 
 connected chiefly with the cell-wall. 
 
 There seems reason to believe, that during the organizing process 
 which occurs simultaneously with the changes of the cell, a chemical 
 alteration takes place; for the cells of cartilage sometimes contain 
 fat, and the cartilage of bone prior to ossification contains chondrine, 
 but, after the ossific process, gellatine is found : and, it is also stated, 
 that the element which may be obtained from the young cells of 
 areolar tissue is pyine ; whereas gelatine is yielded by the fully-formed 
 tissue. 
 
 The formation of cells does not cease with the infancy of the 
 organism. These minute organic elements are most important agents 
 in various functions of the body at every period of its .existence. By 
 them the secretions are separated ; and it is not improbable that they 
 contribute largely to those changes in which nutrition immediately 
 consists. They are found floating in immense numbers in the blood, 
 as wey as in the chyle and lymph ; and, even in diseased secretions, 
 as pus, they exist in great quantity. In the inflammatory process, they 
 9re formed in great abundance ; and in the malignant growths, which 
 infest the body, so as to manifest themselves at different parts of it, 
 such as the various forms of cancer, the same organic forms are to be 
 found. 
 
 In short, Schleiden and Schwann have proved that the nucleated 
 cell is the agent of most of the organic, processes, whether in the 
 plant or animal, from the separation of the embryo from its parent, 
 to the development, growth, and nutrition of the adult individual. 
 
 Properties of the Tissues. — The fully-grown tissues manifest dif- 
 ferences among themselves, not merely by their anatomical characters, 
 but by their properties. These may be conveniently subdivided into 
 physical and vital. Strictly speaking, this is a distinction without a 
 difference, for doubtless all the properties of animal tissues may be 
 ascribed to the peculiar arrangement of their particles, and are, there- 
 fore, physical. I Our reasons for adopting the division will appear in 
 explaining the nature of these properties. 
 
 The physical properties of the tissues are those which are dependent 
 simply on the peculiar arrangement or mode of cohesion of their con- 
 stituent pafticles, as well as upon their chemical constitution, and will 
 
66 ELASTICITY.— EXTENSIBILITY.— POROSITY. 
 
 manifest themselves in the dead, as distinctly as in the living, texture. 
 The elasticity of yellow ligament, for instance, is as evident in a spe- 
 cimen which has been preserved in spirits for years, as in one taken 
 fresh from the body. The vital properties are those which exist only 
 during life, and which cease immediately when molecular life has 
 ceased. A musde will contract only so long as it is alive ; when 
 dead, it refuses to respond to those stimuli, which so easily excited 
 it while living. 
 
 The most striking physical property which certain tissues manifest, 
 is that of elasticity, in virtue of which the tissue reacts, after a stretch- 
 ing or a compressing force has been withdrawn. The yellow ligament^ 
 which constitutes the ligamenta subflava of the vertebral laminae, is 
 as elastic as India-rubber; the middle coat of arteries manifests quite 
 as much elasticity. Cartilage is flexible ah^ elastic ; and is exten- 
 sively employed, in consequence of this property, to encrust the 
 articular extremities of the bones, for their protection in the move- 
 ments of the joints. . 
 
 The existence of elasticity implies that of extensibility. All elastic 
 tissues must admit of being stretched before they can manifest their 
 elastic reaction. But some textures are extensible without being 
 elastic. Such tissues yield only to along-continued extending force; 
 and, in the healthy state, they are capable of resisting such a force of 
 tension for a considerable period. The resistance which a fibrous 
 membrane offers to the enlargement of an organ or tumour, which it 
 covers, illustrates this statement : the pain felt in hernia huraoralis 
 or inflammatory enlargement of the testicle, is doubtless due to the 
 resistance of its fibrous coat to the swelling, of the soft substance of 
 the gland. 
 
 The various animal tissues exhibit a property oi porosity, or evince 
 a power of attraction for aqueous fluids. If a piece of areolar* tissue 
 from the axilla be soaked in water, it will imbibe it as freely as a sponge. 
 Serous membranes, being chiefly composed of areolar tissue, have the 
 same property, but to a less degree ; and the coats of blood-vessels, 
 and hollow membranous viscera,^are also porous. The occurrence 
 of transudations, through living and dead tissues, is explained by this 
 property. When the blood is loaded with water, or its passage 
 through the blood-vessels is impeded, or when the vital changes in 
 the blood-vessels go on feebly and imperfectly, their walls exert a 
 morbid attraction upon the water of the contained blood, which trans- 
 udes into the surrounding areolar tissue, and gives rise to that drop- 
 sical effusion, which is commonly called Anasarca. In the minute 
 capillary vessels, this property is always present in a state of health, 
 and the nutrition of the surrounding tissues is effected by the exercise 
 of it. After death, the influence of porosity is favoured by the total 
 absence of motion in the fluids, and of vital change in the walls of 
 the vessels ; and, therefore, in the dead body we find the areolar tissue 
 more or less loaded with water in all those places in which gravita- 
 tion favoured its accumulation. The progress of decomposition, by 
 disintegrating the tissues, also favours the occurrence of transudation. 
 
 It is probable that certain vital processes consist solely in transuda- 
 
ENDOSMOSE.— EXOSMOSE. 67 
 
 tion. In this way the watery part of the secretions doubtless escapes 
 from the blood-vessels, into the canals of the secreting organs ; and 
 this is especially likely as regards the mechanism of the kidney, 
 where the blood-vessels of the Malpighian bodies, reduced to their 
 minutest size, naked, and unassociated with any other tissue, are most 
 favourably placed for the occurrence of this phenomenon ; and the 
 absorption of fluids brought in contact with certain surfaces is expli- 
 cable on the same principle. 
 
 The process, which was first described by Datrochet, under the 
 name Endosmose and Exosmose, is intimately connected with the 
 porosity of animal tissues. It is a process, " in which the mutual 
 attraction of two liquids is called into action, one of which is more 
 capable than the other of freely wetting a porous solid which forms 
 part of the combination." (DanieWs Chemistry.) 
 
 If an animal bladder, the caecum of a fowl, partially filled with 
 syrup, and tied tightly at its open end with a string, be suspended in 
 a vessel of water, it will soon be found distended almost to bursting, 
 in consequence of a considerable quantity of the water having passed 
 through the walls into the cavity of the bladder (Endosmose). If the 
 exterior fluid be examined, a portion of the syrup will be found to 
 have passed out of the bladder {Exosmose). Or the phenomenon may 
 be illustrated by the following experiment : — Take a funnel, and tie 
 over its broad end (of three or four inches diameter) a piece of blad- 
 der, invert it, and fill it with spirits of wine, and fit to its small end a 
 glass tube, three or four feet in length, and then place it in a vessel 
 of water. In a short time the water will be observed to rise in the 
 tube, and it will ultimately reach the top and flow over. " The first 
 moving power here," says Professor Daniell, "is the force of adhe; 
 sion between the water and the bladder ; the former penetrates the 
 por^s of the latter, and comes in contact, upon its upper surface, with 
 the spirit, by the attraction of which, it is removed from the bladder 
 and mixes with its mass. The height of the column is in some 
 degree the measure of the force thus called into action." The purely 
 physical nature of this process is shown by the fact that it will equally, 
 take place through poroqs inorganic substances, as through organic 
 membranes. It would be impossible to do more here than give ^ 
 brief explanation of this remarkable phenomenon. It is important 
 to add, that the observations of Dutrochet clearly show that the 
 nature of the septum exerts an important influence upon the direction 
 of the predominant current. If the attraction of the septum for the 
 exterior fluid be the greater, the endosmotic current will prevail, and 
 vice versa. 
 
 Endosmose is a more important agent in the vital phenomena of 
 plants than in those of animals. It is supposed, by some physio- 
 logists,, to be brought into play in the processes of secretion and 
 absorption. 
 
 The animal membranes exercise the property of porosity in refer- 
 ence to gases, as well as to liquids; and the tendency of dissimilaf 
 gases to become diffused among each other manifests itself even 
 through compound textures. As in the case of liquids, there is a 
 
68 VITAL PROPERTIES. 
 
 double current, when two dissimilar gases are separated by a porous 
 septum, and the predominant current is that which has the strongest 
 attraction for the septum. The following experiments illustrate this 
 phenomenon : — Confine some common air in a jar, by tying tightly 
 over it a piece of sheet-caoutchouc, and then place the jar under a 
 large bell-glass filled with hydrogen gas; the hydrogen will gradually 
 penetrate the partition, distend the caoutchouc, and ultimately burst it. 
 Or, suspend a membranous bag, the stomach of a rabbit,' filled with 
 common air, in an atmosphere of carbonic acid ; the latter will pene- 
 trate to the former and burst the bag. In both instances there is an 
 exosmose greatly inferior in the quantity of gas to the endosmose. In 
 respiration, this phenomenoq occurs at every inspiration through the 
 walls of the pulmonary air-cells and the plexus of capillary vessels 
 distributed upon them. [DanielVs Chemistry.) 
 
 Although in the manifestation of these phenomena there is no direct 
 exercise of vital force, the tissues are not the less dependent on healthy 
 vital action for the preservation of their peculiar properties in a state 
 of integrity. Whoever will corlipare the compact figure of a vigorous 
 healthy man, accustomed to field-sports and active exercises, with the 
 relaxed, feeble, half-dislocated limbs of an ill-nourished, hysterical 
 woman, will readily perceive how great an influence healthy nutrition 
 must exert in preserving and improving the physical properties of the 
 tissues. 
 
 The vital properties manifest themselves by a change which occurs 
 in the molecules of certain tissues, as the result of a stimulus applied. 
 The change, thus produced, may be evident from a visible alteration 
 in the tissue stimulated ; or it may show itself through a secondary 
 influence exerted upon some other texture or organ, with which the 
 stimulated tissue may be in connection. ' 
 
 These properties exist in two tissues, namely, in muscle ana in 
 nerve. A muscle, when stimulated, shortens itself; and, therefore, 
 it is said to possess the property of contractility. This power of con- 
 tracting, in obedience to a stimulus, is characteristic of muscle, and 
 probably occurs in no other kind of animal texture. The stimulus 
 may be direct irritation by mechanical means, or by galvanism, or by 
 some chemical substance ; but the natural one, during life, is propa- 
 gated by the nerves. 
 
 In nerve, the vital changes are unaccompanied by any alteration in 
 the tissue itself, which is appreciable by our senses. The excitation 
 or irritation of the nerve may be manifested in three ways: first, by 
 its inducing the contraction of the muscle which it supplies ; secondly, 
 by its exciting contraction, in muscles which it does not supply, through 
 a change wrought in the nervous centre ; thirdly, by its exciting a 
 sensation. The same stimuli, which we have mentioned as capable 
 of exciting muscular contraction, will produce these eflfects in nerves ; 
 and the will, and other emotions of the mind, are capable of stimu- 
 lating nerves which are connected with the brain, and exciting action 
 in the muscles to which they are distributed. 
 
 That a nerve, when irritated, may excite a sensation, it is neces- 
 sary that it shall be in connection with the brain. The bodily feelings 
 
NERVES OF COMMON AND OF PROPER SENSATION. 69 
 
 of pain or pleasure are thus produced, through the medium of what 
 are called sensitive nerves, or nerves of common sensation; and we 
 say that the sensibility of any tissue is great or small, according as it 
 is supplied with such nerves in more or less quantity. Tendon, in 
 which probably few nerves exist, is a tissue of low sensibility ; whilst 
 the skin, which is largely supplied with nerves, is highly sensitive. 
 
 Light, sound, and' the sapid and odoriferous qualities of bodies, are 
 capable of stimulating certain nerves, and exciting appropriate sen- 
 sations in the mind. The nerves which respond to such stimuli, are 
 called nerves of proper or special sensation; and this name seems 
 appropriate, because these nerves, when otherwise stimulated, excite 
 only their peculiar sensations. If the optic nerve be mechanically 
 irritated, a flash of light is produced ; as sometimes occurs if the 
 retina be touched by the needle in the operation for cataract. If the 
 auditory nerves be stimulated by a galvanic shock, a sound is pro- 
 duced. Volta, who tried the experiment on his own person, perceived 
 a hissing and pulsatory sound, which he compared to that of a viscid 
 substatice boiling: and Ritter relates, that, upon closing the circle 
 when both his ears were included in it, he was sensible of the sound 
 of G treble; if but one ear was in the circuit, and the positive pole 
 applied to it, the sound was lower than G ; if the negative pole was 
 applied to the ear, the sound was higher. (Muller's Physiology, 
 translated by Baly.) These peculiarities of the nerves of proper 
 sensation are due to the fact, that at their periphery they are so organ- 
 ized as to be admirably adapted for receiving the impressions of their 
 special stimuli, and at their centres they are connected with those 
 parts of the brain which take cognizance of these special agents. 
 Thus the optic nerve is admirably disposed in the eye for the recep- 
 tion of luminous impressions, and the auditory nerve is beautifully 
 adapted to receive the pulsations of sound, whilst each is connected 
 with a different part of the brain ; and what are called subjective 
 phenomena of vision or hearing are often the result of local congesr 
 tions of blood affecting the respective nerves of these senses, and 
 producing mechanical irritation of them. 
 
 In the manifestation of the vital properties, under the influence of 
 appropriate stimuli, it cannot be doubted that an organic molecular 
 change is produced in nerve as well as in muscle. This may be 
 considered as a polar state, in which the ultimate particles of the tissue 
 assume a polarized condition, which may be fairly compared to that 
 which friction or other means can produce in various substances, by 
 which they may be rendered mutually attractive or repulsive. In 
 muscle, it becomes at once evident by the powerful attraction which 
 is exerted between its particles, by which the shortening is effected. 
 In nerve, it is shown by the rapidity with which the change excited 
 by the stimulus at one part of the nerve is conveyed throughout its 
 course to the muscle, or to the brain or other nervous centre, with 
 which it may be connected, producing in them the same or an analo- 
 gous state. 
 
 As these phenomena occur in tissues, whose chemical composition 
 is more complex than that of any others in the body, and which are 
 
70 FUNCTIONS.— ANIMAL MOTIONS. 
 
 the seat of continual changes, they are subject to many disturbing 
 causes, and are easily afTected by slight modifications in the general 
 state of the system. Many substances quickly exert an influence upon 
 them, as opium, strychnine, and various sedatives, narcotics, or stimu- 
 lants. Those properties are therefore entirely dependent on the nutri- 
 tion of their respective tissues ; they quickly vary with the state of 
 that function, and when it ceases, in death, they vanish with it. 
 
 For information upon the subjects treated of in this chapter we refer to the fol- 
 lowing sources: — Henle, Algemeine Anatomie; Berzelius, Chimie Organique, Fr. 
 edit., 1833; Prout on Siomaoh and Urinary Diseases; Liebig's Animal Chemistry, by 
 Gregory; Graham's Chemistry; Daniell's Chemistry; Schwann, Mikroskopische 
 Untersuchungen uber die Uebereinstimmung in der Struktur und dem Wachslhum 
 der Thiere und Pflanzen ; Dulrochet, article Endosmose, in the CyclopEedia of Ana- 
 tomy and Physiology. 
 
 CHAPTER 11. 
 
 FTJNCTIONS. — ANIMAL MOTIONS. — MOLECULAR MOTION. ORGANIC MOLE- 
 CULAR MOTION. — MUSCULAR MOTION. — CILIARY MOTION. — MOTIONS OF 
 SPERMATOZOA. 
 
 The subdivision of the functions of the human organism into the 
 animal and the organic, as already stated, maybe adopted as the least 
 objectionable basis for their arrangement. Under the former title we 
 include those functions, which are peculiar to and characteristic of 
 the animal part of the living creation, and to which there is nothing 
 similar or analogous in the vegetable kingdom. These are locomo- 
 tion and innervation. The organic functions are present in both king- 
 doms, with certain modifications. They are digestion, absorption, 
 circulation, respiration, secretion, and generation. 
 
 In examining these various processes, we propose to follow the 
 order in which they have been enumerated. We find it convenient to 
 take the locomotive function first, because so large a proportion of the 
 mechanical arrangements, or of the anatomy of the body, is connected 
 with it. The transition from locomotion to innervation is easy and 
 obvious; for the nervous system has a special connection with the 
 locomotive organs, in order that the influence of the will may be 
 conveyed to them. It may be here stated, that in the animal functions 
 the interference of volition is more frequent than in the organic ones; 
 and that, in all, the nervous system exerts a certain control, and may 
 influence to a great degree the performance of the functions, although 
 some of them are essentially independent of it. 
 
 Of the minute movements occurring in the interior of the body. — Of 
 these we may distinguish three kinds : 1. Those in which particles are 
 moved passively by forces independent of themselves. 2. Those 
 accompanying the incessant changes of the organic elements of the 
 tissues. 3. Those which occur in certain entire tissues on the appli- 
 
MOLECULAR MOTION. 71 
 
 cation of an appropriate stimulus. All these movements may be 
 called molecular on account of the minuteness of the particles con- 
 cerned in them. 
 
 1. The term molecular motion was used many years ago by Mr. 
 Robert Brown, to denote a phenomenon which he had witnessed in 
 the particles of various organic and inorganic substances in a state of 
 extremely minute subdivision. When these particles were suspended 
 in water, they exhibited, under the microscope, motions, which con- 
 sisted in more or less rapid oscillations and rotations of the particles 
 themselves. He found them in the pollen of plants, in many mineral 
 and metallic substances, in various animal matters, reduced to a subtle 
 powder, consistipg of particles that ranged in diameter between the 
 T'sio ''nd s^iinr of ^n inch. The movements are clearly not peculiar 
 to living or organic parts, for they occur in inanirhate ones : they 
 never occur excepting when the particles are suspended in water, or 
 some liquid ; and they are attributable to currents produced in the 
 fluid by evaporation at its surface or edges, for they may be arrested 
 by covering the fluid with oil, or using other means to prevent such 
 evappratipn. They are not, therefore, inherent in the particles them- 
 selves, which only obey the impulse communicated to them by the 
 currents created in the fluid which holds them in suspension. 
 
 Certain particles, naturally very minute, which are met with in the 
 bodyj exhibit motions when examined under the microscope floating 
 in fluid. These motions are entirely due to the same cause as would 
 excite them in inorganic particles, namely, to currents in the fluid 
 created by its evaporation. The minute granules, or particles of the 
 chyle, have been found to exhibit molecular motion ; and it has been 
 ingeniously supposed, that "these motions indicate the first obvious 
 impress of vitality which the new material has received from its 
 association with living matter." But, before this supposition can be 
 admitted, we require evidence to show that these motions are inherent, 
 and do not result from currents. The minute rod-like bodies, which 
 form the outer coat of the retina, or Jacob's membrane, also some- 
 times exhibit a molecular motion, when separated and examined in 
 water, and there seepis no reason to doubt that this is due to the 
 evaporation of the fluid in which they float. 
 
 2. Orgq/nic molecular motion. ^Some of the motions, which take 
 place within the living body, maybe compared to those described by 
 Mr. Brown, inasmuclj^ as they are generally, if not always, due to an 
 extraneous force acting upon the particles moved; but they differ in 
 this respect, viz., that the producing force is developed by the pro- 
 cesses inseparable from life. Such motions are notin general visible, yet 
 some have been seen, which clearly indicate that forces are developed, 
 during life, capable of producing them. The movements of particles 
 within cells afford an example: such motions are, either of a uniform 
 rhythmical kind, or they are apparently irregular and oscillating. 
 Those of the former kind are familiarly known in the vegetable king-' 
 dom by the Cyclosis which takes place in the oblong cells of Chara; 
 the granules, which may be seen in motion, are quite passive and are 
 carried along by currents within the cell. Motions of the latter kind 
 
72 MOLECULAR MOTION. 
 
 have been seen by Schwann aniong the granules contained in the cells 
 of the germinal membrane of the hen's egg, as if occasioned by an 
 endosmotic current through the wall of the cell. This membrane is 
 the seat of active change, the development and growth of new cells, 
 destined for the evolution of the textures of the embryo ; and they 
 derive their nutriment from the yelk, on the surface of which they 
 lie. Here the contained particles are passive, and the motion in them 
 is only the index of the currents which give rise to it. A molecular 
 motion of the same kind may be seen in the very minute granules, 
 which occupy the cells of the membrane of black pigment on the 
 choroid coat of the eye. Whether this go on during life, it is of 
 course impossible to say, but the conditions for its production are 
 undoubtedly present. In the blood may be seen another example of 
 the kind of motion under consideration. The circulation of this 
 fluid may be readily followed in transparent parts ; and certain par- 
 ticles, the blood-discs, which float in it in great numbers, exhibit 
 movements which can scarcely be attributed solely to the current of 
 the circulating fluid. It is probable that secondary currents may be 
 established in the blood, or that attractions and repulsions may exist 
 between the particles themselves, or between them and the walls of 
 the blood-vessels giving rise to these motions. According to some 
 observers, the blood-discs undergo actual changes of shape, becom- 
 ing now swollen, and now flattened ; and this might be attributed to 
 the alternate predominance of endosmose or exosmose. But the state- 
 ment, that they possess an inherent power of contraction of their own, 
 stands greatly in need of confirmation. 
 
 Organic molecular motion occurs in nearly all the internal processes. 
 The introduction of new matter from without into the blood ; the re- 
 moval of effete particles by a process of absorption ; the transfer of 
 nutrient matter from the blood to supply the place of the particles 
 thus removed ; the separation of organic compounds in glands, can- 
 not take place without a movement of molecules in the textures con- 
 cerned in these processes. We are as much at liberty to infer, that 
 these motions are produced by certain affinities of the particles of the 
 tissues, as that chemical action is the result of affinities between cer- 
 tain forms of matter. These motions of the organic and inorganic 
 elements are incessant during the ceaseless round of organizing and 
 disorganizing actions of which every tissue is the seat, as long as it 
 continues living. The currents alluded to in th% preceding paragraph 
 are visible indications of the presence of these organic movements. 
 
 3. The molecular movements of nerve and muscle under stimula- 
 tion have been already mentioned in the preceding chapter. The 
 capacity of exhibiting these movements exists only while the nutri- 
 tive process continues to be carried on in the respective tissues — it 
 ceases with life. It would appear that the precise chemical constitu- 
 tion, which is essential to its existence, is of so unstable a nature as 
 to be constantly prone to change, and to require' incessant renewal ; 
 or, it may be, that this capacity is one which is only developed during 
 the active operation of certain chemical forces, as if it depended ne- 
 
CILIARY MOTION. 
 
 73 
 
 cessarily on. certain peculiarities of the organic elements when in a 
 nascent or changing state. 
 
 In muscular movement there is a visible approximation of the ulti- 
 mate particles of the tissue in a determinate direction, as will be fur- 
 ther explained in the proper place ; and in this consists the whole 
 value of muscular tissue as a part of the mechanism of the body. All 
 those motions in the living body which are visible to the naked eye, 
 and many of those which cannot be seen without the aid of lenses, 
 are effected by muscular action. By it canals or tubes adapt them- 
 selves to their contents ; the heart propels the vital fluid ; the digest- 
 ive canal transmits the ingesta from one part to another : the excretory 
 reservoirs, or ducts, expel their contents ; and lastly, by it the attitudes 
 are maintained, and the locomotive function is performed. 
 
 Ciliary motion. — In the same category with the molecular motions 
 of the living body we would place that singular phenomenon now 
 well ascertained by multiplied observations, which is called Ciliary 
 motion. 
 
 Certain surfaces, which are, in their natural and healthy state, 
 lubricated by fluid, are covered with a multitude of hair-like pro- 
 cesses, of extreme delicacy of structure and minuteness of size. 
 These are called cilia, from cilium, an eyelash. They are generally 
 conical in shape, being attached by their bases to the epithelium 
 that covers the surface on which they play, and tapering gradually 
 to a point; or, as Purkinje and Valentin state, they are more or less 
 flattened processes, of which the free extremities are rounded ; and 
 this latter form prevails in the human subject. They vary in length 
 from the toW to the titoo' of an inch. They are disposed in rows, 
 and are adapted in their arrangement to the shape and extent of the 
 surface to which they belong ; they adhere to the edges, or to a por- 
 tion of the surface, of the 
 
 particles of the epithelium, F'g- ^^ 
 
 preferring the columnar va- 
 riety of them. 
 
 During life, and for a cer- 
 tain period after death, these 
 iil-aments exhibit a remark- 
 able movement, of a fanning 
 or a lashing kind, so that 
 each cilium bends rapidly in 
 one direction, and returns 
 again to the quiescent state. 
 The motion, when viewed 
 under a high magnifying 
 power, is singularly beauti- 
 ful, presenting an appearance 
 somewhat resembling that of 
 a field of corn agitated by a 
 steady breeze. Any minute 
 objects coming in contact 
 with the free extremities of the cilia are hurried rapidly along in the 
 5 
 
 Examplesof Cilia:— 1. Portion of a bar of the gill of 
 the Sea-mussel, Mytilus edulis^ showing cilia at rest 
 and in motion. 2. Ciliated epithelium particles from 
 the frog's mouth. 3. Ciliated epithelium particle from 
 inner surface of human raembrana tympaili. 4. Ditto, 
 ditto: from the human bronchial mucous membrana. 
 5. Leucophrys patula, a polygastric infusory animal- 
 cule : to show its surface covered with cilia, and the 
 mouth surrounded by them. 
 
74 CILIARY MOTION. 
 
 direction of the predominant movement ; one or more blood-discs, 
 accidentally present, will sometimes pass rapidly across the field, pro- 
 pelled in this way, and very minute particles of powdered charcoal 
 may be conveniently used to exhibit this phenomenon, and to indi- 
 cate the direction of the movement. The action of the cilia produces 
 a current in the surrounding fluid, the direction of which is shown 
 by the course which the propelled particles take. 
 
 An easy way to observe this phenomenon is to detach by scraping 
 with, a knife a few scales of epithelium from the back of the throat 
 of a living frog. These, moistened with water, or serum, will con- 
 tinue to exhibit the movement of their adherent cilia for a very con- 
 siderable time, provided the piece be kept duly moistened. On one 
 occasion we observed a piece prepared in this way exhibit motion 
 for seventeen hours; and it would probably have continued doing 
 so for a longer time, had not the moisture around it evaporated. 
 However, Purkinje and Valentin have observed it to last for a much 
 longer time than this in connection with the body of the animal. In 
 the turtle, after death by decapitation, they found it lasted, in the 
 mouth, nine days; in the trachea and the lungs, thirteen days; and, 
 in the oesophagus, nineteen days. In frogs, from which the brain 
 had been removed, it lasted from four to five days. The longest time 
 they observed it to continue in man and mammalia was two days ; 
 but in general it did not last nearly so long. What appears to be 
 immediately necessary to the continuation of the movement, is the 
 integrity of the epithelial cells to which the cilia adhere ; for as soon 
 as these shrink up for want of moisture, or become physically altered 
 by chemical reagents or by the progress of putrefaction, the cilia im- 
 mediately cease to play. 
 
 From these facts we learn two important points in connection with 
 this phenomenon. The first is, the truly molecular character of the 
 movement. Whatever be the immediate cause of the action of the 
 cilia, it is evidently intimately connected with the minute epithelial 
 particles to which they are attached ; for cilia never exist in man and 
 the higher animals without epithelial particles, and these particles 
 have no organic connection with the subjacent textures, excepting 
 such as may arise from simple adhesion. And, secondly, we per- 
 ceive, that this movement is independent of both the vascular and 
 the nervous systems, for it will continue to manifest itself for many 
 hours in a single particle isolated from the rest of the system. After 
 death it remains longer than the contractility of muscle ; a circum- 
 stance which, together with the facts just mentioned, indicates that 
 the cilia cannot be moved by little muscles inserted into their bases, 
 as some have supposed. And experiment also shows this independ- 
 ence. If the abdominal aorta be tied, the muscles of the lower 
 extremities will be paralyzed in consequence of their being deprived 
 of their blood; and on removing the ligature, and allowing the blood 
 to flow, the muscles will recover themselves. But a ciliated surface 
 is not affected at all in its movements, though the supply of blood to 
 the subjacent tissues be completely cut off. Again, hydrocyanic acid, 
 opium, strychnine, belladonna, substances which exert a powerful effect 
 
CILIARY MOTION. 75 
 
 on the nervous system, produce no influence upon ciliary motion. In 
 the bodies of animals killed by these poisons, the phenomenon is still 
 conspicuous; and even the local application of them does not hinder 
 it, provided the solutions do not injure the epithelial texture. Shocks 
 of electricity passed through the ciliated parts, do not affect the 
 movement. Lastly, the removal of the brain and spinal cord in 
 frogs, by which all muscular movements are destroyed, does not stop 
 the action of the cilia. This striking fact may likewise be adduced 
 to disprove the supposition, that these movements result from the 
 action of minute muscles ; for, although muscles may be excited to 
 contract without nerves, we have no instances in the higher animals 
 in which they habitually act without the interference of the nervous 
 system ; nor is it likely that a movement existing over so extended a 
 surface, as that by the cilia, would, if effected by muscles, be inde- 
 pendent of nervous influence. 
 
 Alterations of temperature affect the ciliary motion, owing, doubt- 
 less, to the physical change they induce in the epithelial' particles. 
 In warm-blooded animals it ceases on a reduction of the temperature 
 below 43° F. In cold-blooded animals, however, it continues even 
 at 32°. In all, a very high temperature effectually puts a stop to it. 
 It is interesting to notice, that all observers agree in stating, that blood 
 is the best preservative of the ciliary motion, but the blood of verte- 
 brata destroys it in the invertebrata. Bile puts a stop to it, very 
 probably by reason of its thick and viscid nature, and not from any 
 chemical influence. 
 
 This phenomenon exists most extensively in the animal kingdom. • 
 It has been found in all the vertebrate classes ; and in the inverte- 
 brata likewise, with the exception of the Crustacea, arachnida, and 
 insects. It is the agent by which the remarkable rotation of the 
 embryo in the ova of mollusca is effected ; and it occurs on the sur- 
 face of the ova of polypes and sponges. The bodies of some of 
 the infusoria are covered with cilia, which are apparently employed 
 by them as organs of locomotion, and for the prehension of food 
 (5, fig. 2.) 
 
 In man, the ciliary motion has been ascertained to exist on several 
 surfaces: — 1. On the surface of the ventricles of the brain and on 
 the choroid plexuses. So delicate are the cells of epithelium here, 
 that the slightest mechanical injury destroys them ; it is, therefore, 
 very difficult to see the movement. Valentin states that its duration 
 is considerable in these parts, so that it may be seen in subjects used 
 for dissection. 2. On the mucous membrane of the nasal cavities, 
 extending along the roof of the pharynx to its posterior wall, on a 
 level with the atlas, on the upper and posterior part of the soft palate, 
 and, in the immediate neighbourhood of the Eustachian tube, extend- 
 ing through the tube itself to the cavity of the tympanum. 3. On 
 the membrane lining the sinuses of the frontal bone, the sphenoid, 
 and the superior maxillary. 4. On the inner surface of the lachrymal 
 sac and lachrymal canal. 5. On the membrane of the larynx, trachea, 
 and bronchial tubes. 6. On the lining membrane of the female 
 organs of generation. \ It does not exist in the vagina; but it may be 
 
76 
 
 MOTIONS OF SPERMATOZOA. 
 
 Fig. 3. 
 
 traced from the lips of the os uteri, through its cavity, and through 
 the Fallopian tubes to their fimbriated margins. 
 
 In nearly all these instances there appears to be a mechanical use 
 for the ciliary movement, namely, to promote the expulsion of the 
 
 fluid secreted by the surfaces on 
 ■which the cilia exist. Wherever 
 the direction of the motion has 
 been ascertained, it is that which 
 ■would be favourable to such a 
 purpose. In the bronchial tubes 
 and trachea, the direction of the 
 motion is towards the larynx, 
 so that the cilia may be regard- 
 ed as agents of expectoration. 
 In the nose of the rabbit. Dr. 
 Sharpey observed the impulse 
 to be directed forwards, and in 
 the maxillary sinus it appeared 
 to pass towards the back part 
 of the cavity, where its opening 
 is situated. In the Fallopian 
 tube, the direction is stated by 
 Purkinje and Valentin to be 
 from the fimbriated extremity 
 towards the vagina. It seems 
 very probable that ciliary mo- 
 tion exists in the kidney, at the 
 narrow neck of each uriniferous 
 tube, as it passes off from the 
 capsule of the Malpighian body. 
 This has not been actually ob- 
 served in the human subject. 
 It was discovered, and has been 
 frequently seen in the frog, 
 {Bowman, Phil. Trans., 1842,) 
 and is shown in the annexed 
 drawing, (fig. 3.) The move- 
 ment is here directed towards 
 the uriniferous tube, and it 
 doubtless is destined to favour 
 the flow of the aqueous portion of (he secretion from the capsule to 
 the tube. 
 
 In the inferior animals the cilia seem to answer a similar end to 
 that in man. They exist extensively on respiratory surfaces, and in 
 connection with the generative organs ; and also, but to a less de- 
 gree, with the organs of digestion. But in some situations, both in 
 man and in the inferior creatures, it is difl!icult to determine what 
 functions the ciliary motion can perform. Such are, in man, the 
 ventricles of the brain ; and, in the frog, the closed cavities of the 
 
 Uriniferous tube of Frog's kidney, arising from 
 capsule of Malpighian body : — a. Cavity of the 
 tube, 6, Epitlrelium. e. Basement membrane. 
 6'. ciliated epithelium at the neck of the tube, b" , 
 Detached ciliated particle, c'. Malpighian cap- 
 sule, m. Malpighian tuft. 
 
MOTIONS OF SPERMATOZOA. 77 
 
 pericardium and peritoneum. Here there are no excretory orifices, 
 toward which the current might set. 
 
 What is thfe cause of ciliary motion } We have shown it to be 
 independent of the blood and of the nerves, and to resist those de- 
 pressing causes which usually put a stop to the action of contractile 
 tissue. It requires for its continuance three conditions : a perfect 
 epithelium cell; moisture, not of too great density; and a temperature 
 within certain limits. From Schwann's observations it appears that 
 cells exhibit a power of endosmose ; that a chemical change occurs 
 in the fluids in contact with them ; and that a movement of their in- 
 ternal granules may be seen under certain circumstances. If ciliated 
 epithelium cells exert an attraction of end-osmose upon the surround- 
 ing fluid, may not this physical phenomenon afford a clue to determine 
 the cause of the movement ? 
 
 A very remarkable movement is manifested by certain particles 
 found in the secretion of the testicle, which prevails most extensively 
 throughout the animal series, and is even found among plants. From 
 the regularity of these movements and their resemblance to those of 
 minute animals, a place had been assigned by naturalists to the par- 
 ticles in question, in their zoological classifications, under the name 
 '■'■ Cercarim seminis," Spermatozoa, or Spermatic animalcules, and 
 Ehrenberg refers them to the Haustellate Entozoa. These particles 
 consist chiefly of a long filament or tail, which is sometimes swollen 
 at one extremity, to form the body of the supposed animalcule. The 
 motions consist in a sculling action of the tail, or a slight lateral 
 vibra.tion of it. In many of its conditions it closely resembles ciliary 
 motion ; and its duration after death, or after the separation of the 
 fluid, is pretty much the same as that of the ciliary movements. The 
 particles are extremely minute, even measured in their length ; but 
 especially so in thickness. They are, therefore, well adapted to obey 
 those impulses which we have shown to be capable of giving rise to 
 molecular motions. We shall return to this curious subject again in 
 discussing the function of generation. 
 
 On the subjeols treated of in this chapter reference is made to the following sources 
 of information: — Rob. Brown, A brief Account of Microscopical Observations on the 
 particles contained in the pollen of plants, and on the general existence of active 
 mojecules in organic and inorganic substances; Purkinje and Valentin, Commentatio 
 Physiologica de phenomeno molus vibraiorii continui; article Cilia, by Dr. Sharpey, 
 in the Cyclopaedia of Anatomy and Physiology; Valentin's articleFilmraer-bewegung 
 in Vl'agner's Handworterbuch der Physiologic. 
 
78 ORGANS OF LOCOMOTION. 
 
 CHAPTER III. 
 
 LOCOMOTION. — PASSIVE AND ACTIVE ORGANS OF LOCOMOTION. FIBROUS 
 
 TISSUE, WHITE AND YELLOW. — AREOLAR TISSUE. — ADIPOSE TISSUE 
 AND FAT. 
 
 Locomotion is that function by which an animal is able to trans- 
 port itself from place to place. It is enjoyed exclusively by animals; 
 there being nothing analogous to it in the vegetable kingdom. 
 
 But even, among animals, there are exceptions to the existence of 
 this function. Many of them are fixed in their places throughout 
 their lives ; others enjoy the power of locomotion for a short period, 
 but subsequently become fixed ; others, again, begin life fixed to one 
 place, and are at length set free. 
 
 The power of maintaining the body in certain positions, must be 
 included in the faculty of locomotion, for the organs that are used for 
 one, are also employed for the other ; and the more difficult it be to 
 accomplish the former, the more complicated will be the mechanism 
 of the locomotive acts. In a large quadruped, — the horse, for exam- 
 ple,-^-standing is effected with a trifling expenditure of muscular force, 
 because the animal's body is maintained on four pillars of support, 
 which resist the attraction of gravity acting upon it. Man has to , 
 maintain the erect attitude, and to counteract by muscular action the 
 tendency of his body to gravitate forwards. The mechanical adjust- 
 ments of his frame are less favourable to preserve the standing pos- 
 ture than in the four-footed animals. Hence, in man, the mechanism 
 of locomotion is more complicated, both as regards the power of 
 preserving certain attitudes, and that of moving from one place to 
 another. 
 
 The organs employed in locomotion are of two kinds, the passive, 
 and the active. The former consist of all those textures which form 
 the skeleton, and by which its segments are united. The latter are 
 the muscles, to which the nerves convey the mandates of the will. 
 It will be necessary to examine in detail the following textures among 
 the passive organs of locomotion: — 1. Fibrous tissue, sis binding 
 together the various segments of the skeleton, and connecting the 
 muscles to the bones ; 2. Areolar tissue, which is so extensively dif- 
 fused throughout the body, at once separating and uniting neighbour- 
 ing parts ; 3. Cartilage, fibro-cartilage, and bone, which enter imme- 
 diately into the construction of the skeleton; and, lastly, synovial 
 and serous membranes, being peculiar arrangements of tissue admi- 
 rably suited to facilitate motion. 
 
 riBROUS TISSUE. 
 
 Under this head anatomists range two kinds of texture, resembling 
 each other only in the fact that they present to the naked eye a fibrous 
 
FIBROUS TISSUE. 79 
 
 aspect, as if they were compounded of a series of bundles of threads 
 or fibres. They differ, however, very materially in colour, in physical 
 properties, in ultimate structure : the general purposes which they 
 serve in the animal economy are pretty much the same ; for both are 
 used in connection with the skeleton, and are concerned in the me- 
 chanism of animal motion and locomotion. They are distinguished 
 as, 1. White Fibrous Tissue ; 2. Yellow Fibrous Tissue. 
 
 1. White Fibrous Tissue. — When a texture of great strength and 
 flexibility, and of an unyielding nature, is required, either to bind 
 parts of the skeleton together, to cover and protect organs of delicate 
 texture, to unite muscles to bone, or other parts, to compress the mus- 
 cles of a limb, or strengthen the walls of a cavity, we find white 
 fibrous tissue called into requisition for these purposes. Hence we 
 observe it to assume a great variety of forms, according to the various 
 uses to which it is applied. It occurs, 1, as ligaments, connected 
 with joints; 2, as tendons, connecting muscles to bones; 3, in a 
 membranous form, covering and protecting certain organs, as the 
 dura mater of the head and spine, the tunica albugineaof the testicle, 
 the sclerotic coat of the eye, the fibrous pericardium, the covering of 
 the corpora cavernosa penis, the fibrous sheaths' of tendons, the 
 periosteum of bone, the perichondrium of cartilage, the aponeuroses 
 of the limbs, as the fascia lata, &c. 
 
 When we examine a portion of fibrous tissue taken from any of 
 these sources, we find connected with it a greater or less quantity of 
 areolar tissue, which adheres to its outer surface like a sheath. This 
 is the case in all fibrous structures, except 
 those which have a serous membrane con- ^'S- *• 
 
 nected with them, or those adherent to bone — i 
 
 or cartilage. The areolar tissue sinks into I 1 
 
 the fibrous material, and mingles with its i I 
 
 fibres ; and, doubtless, it not only serves the 1 ' i I ' 
 
 purpose of a nidus for conducting vessels to 
 
 its surface, but it accompanies them spar- ^'ff A \ j 
 
 in^ly into its substance. 1 < I i 
 
 When the areolar tissue has been dis- )j \ \ ^ 
 
 \ 
 
 ingly into its substance 
 
 issue has been dis- \\ i 
 
 sected off, the surface of the fibrous tissue \ ^ 
 
 exhibits a beautiful silvery-white aspect, ^ 1 i I M 
 
 and seems composed of bundles of fibres, , '! I 
 
 which in some are arranged parallel to each | ^ , 
 
 other ; in others are disposed on different I \ 
 
 planes, and interlace, or cross in different / l ' / " 
 
 directions. On placing a very thin piece u,n,u, nip. ym 
 
 01 the iibrous tissue under a high power ot '31- 
 
 the microscope, we observe what may be 
 
 ■ 1 J Al- T_ i * i" p i. r iL" White fibrouB tissue: — 2. 
 
 considered the characteristic feature ot this straight appearance of thetis- 
 
 fpvtnrp ^^® when stretched. 1. 3. 4. 5. 
 
 LcJkLUlc. ^ Various wavy appearances 
 
 The piece under examination seems to be ^'>'<^'' <i'« «'=s"e exhibits when 
 
 f , . , , _ - !• 1 1 I- not stretched.— Magnified 320 
 
 composed or a leash ot exceedingly delicate diameters. 
 
 fibrillse, running parallel to one another, 
 
 and, if not stretched, disposed to take a wavy course, like a skein of 
 
80 ORGANS OF LOCOMOTION. 
 
 silk. But, on more accurate inspection, it is found impossible to 
 distinguish threads of a determinate size ; they seem, indeed, to be 
 of various sizes, according to the degree of splitting to which the 
 ■whole has been submitted, and many are to be seeii so very minute, 
 as at first almost to elude the eye. In other parts the mass splits up 
 into membranous rather than filiform fragments ; so that it would ap- 
 pear incorrect to describe this tissue as a bundle of threads. It is rather 
 a mass, with longitudinal parallel streaks, (many of which are creas- 
 ings,) and which has a tendency to slit up almost ad infinitum in the 
 longitudinal direction. The correctness of this view is further shown 
 by the action of acid, which obliterates, for the most part, all appear- 
 ance of fibrillae, and swells it up as an entire mass. 
 
 Physical and vital properties. — White fibrous tissue isinelastic, and, 
 under ordinary circumstances, inextensihle ; though it does admit of 
 being somewhat stretched by the influence of a long-continued and 
 slowly acting force, as is seen occasionally when an effusion of fluid 
 has taken place into an articular cavity, or when a tumour has slowly 
 grown under a fascia. Its force of cohesion is the most valuable and 
 characteristic quality pf the white fibrous tissue, and to this its vari- 
 ous important uses are chiefly due. Mascagni calculates the force 
 requisite to rupture the tendo-Achillis as equalto 1,000 pounds' weight 
 Instances are constantly seen where muscles are torn, or bones frac- 
 tured, while the tendons or ligaments, through which the forCe 
 has acted, have escaped. Thus, the malleoli are often dragged off by 
 twists of the foot acting on those processes of bone through the late- 
 ral ligaments of the joint. It is entirely devoid of contractility or 
 irritability ; and its sensibility is very low, so much so that tendons 
 hanging out of a wound have been cut without the patient being aware 
 of it. 
 
 Vessels and Mrves. — White fibrous tissue contains few vessels ; 
 they are small, and follow for the most part the course of the bundles 
 of the tissue; they appear more numerous in the dura mater, and in 
 periosteum, than in other parts. The presence of nerves, and their 
 mode of subdivision, have not as yet been satisfactorily demonstrated 
 anatomically ; we infer their existence from the tissue manifesting 
 sensibility in some forms of disease. 
 
 Chemical composition. — The flexibility of fibrous tissue is owing to 
 its containing a small proportion of water. A tendon, ligament or 
 fibrous membrane, will dry readily; it then becomes hard and rigid; 
 it resists the putrefactive process when not kept moist, and even then 
 putrefies less readily than the softer textures. Acetic acid causes it 
 to swell up, instantly removes its peculiar appearance of wavy fibre?, 
 and displays some broken elongated corpuscles, which are proba- 
 bly the remains of the nuclei of the development-cells. Gelatine 
 may be extracted in considerable quantity from white fibrous tissue 
 by boiling, and it would appear to constitute its chief proximate prin- 
 ciple. 
 
 Of the different forms of white fibrous tissue.— A. Ligaments.— 
 Ligaments are connected with joints. They pass in determinate 
 directions from one bone to another, and serve to limit certain move- 
 
FIBROUS TISSUE. 81 
 
 ments of the joint, while they permit others. They, therefore, con- 
 stitute an extremely important part of the articular mechanism in pre- 
 serving the integrity of the joint in its various movements. There 
 are three principal kinds of articular ligaments : — 1. Funicular, 
 rounded cords of white fibrous tissue, of which we may give as 
 examples the external lateral ligament of the knee-joint, the perpen- 
 dicular ligament of the ankle-joint, &c.: 2. Fascicular, flattened bands, 
 more or less expanded ; ex. internal lateral ligament of the knee-joint, 
 lateral ligaments of the elbow-joint, anterior and posterior ligaments 
 of the wrist-joint, and, indeed, the great majority of ligaments in the 
 body : 3. Capsular; these are barrel-shaped expansions, attached by 
 their extremities around the margin of the articular surfaces compos- 
 ing the joint, and forming a complete but a loose investment to it, 
 so that its movements are not particularly restricted in one direction 
 more than another. They constitute one of the anatomical characters 
 of an enarthrodial or ball-and-socket joint, and are found in the only 
 two perfect examples of that form of articulation, namely, the shoulder 
 and hip joints. 
 
 B. Tendons. — Tendons serve to attach muscle to bone, or some 
 other part of the sclerous system. We may enumerate three varieties 
 of tendon, as regards form : 1. Funicular, e. g., long tendon of the 
 biceps cubiti ; 2. Fascicular, short tendon of the same muscle, and 
 most of the tendons of the body; 3. Aponeurotic, tendinous expan- 
 sions, sometimes of considerable extent, and very useful in protecting 
 the walls of cavities. The tendons of the abdominal muscles afford 
 good examples of this variety. 
 
 The tendons are for the most part implanted by separate fascicles 
 into distinct depressions in the bones, and are also closely incorpo- 
 rated with the periosteum ; so that in maceration, when the latter is 
 separated, it becomes easy to remove the tendons. In some birds, 
 whose tendons are black, the periosteum is black also ; and in the 
 human subject we may often see the tendinous fibres continued on 
 the surface of the periosteum, as a shining silvery layer, following 
 the primitive direction of the tendinous fibres, from which they were 
 derived ; a marked example of this may be seen on the sternum, in 
 front of which the tendinous fibres of the opposite pectoral muscles 
 meet and decussate, and thus form the superficial layer of the perios- 
 teum covering that bone. The length of the tendons is beautifully 
 adapted to the quantity of contractile fibre required to perform a cer- 
 tain movement ; thus, in the biceps cubiti, were the whole length 
 between the scapula and radius occupied by muscularfibre, there would 
 be a great waste of that contractile tissue, as there would be much 
 more than is wanted to produce the required motion; tendon is, there- 
 fore, made to take the place of the superfluous muscle : in this way 
 we may explain the differences in length of the tendons even in the 
 same limb. 
 
 C. Membranous. — In the form of an expanded membrane white 
 fibrous tissue is used to cover, protect, and support various parts. 
 Under such circumstances we often find that it not only forms an ex- 
 ternal covering to them, but that it sends in processes or septa, which 
 
82 
 
 ORGANS OF LOCOMOTION. 
 
 Fig. 5. 
 
 separate certain subdivisions or smaller parts. Thus, the fascia lata 
 of the thigh not only invests the muscles of the thigh, but sends in 
 processes which pass down to the periosteum, and separate the several 
 muscles from each other ; and the dura mater of the cranium sends in 
 processes by which certain portions of the encephalon are separated 
 from one another. 
 
 Reparation and Reproduction. — When a solution of continuity takes 
 place in white fibrous tissue, it readily heals by the interposition of 
 a new substance, every way similar to the original tissue, excepting 
 that it wants its peculiar glistening aspect, and is more bulky and 
 transparent.* 
 
 2. Yellow Fibrous Tissue. — In colour, and in the possession of elas- 
 ticity to a remarkable extent, this tissue differs manifestly from that 
 last described. 
 
 It is yellow: disposed in bundles of fibres, and covered by a thin 
 sheath of areolar tissue, which likewise sinks in among its fibres. 
 In man it exists in the fascicular, funicular, and membranous forms. 
 Under the microscope we observe it to consist of 
 fibres, round in some, flattened in other specimens. 
 These fibres are very variable in diameter, usually 
 from s/jj to Tsi^s of an inch in diameter. They 
 bifurcate, or even divide into three ; and the sum 
 of the diameters of the branches considerably ex- 
 ceeds the diameter of the trunk. They anastomose 
 freely with each other. They are prone to break 
 under manipulation, and the broken extremities 
 are abrupt and disposed to curl up : when many of 
 these broken ends exist together in the same piece, 
 they give it a very peculiar and characteristic ap- 
 pearance. 
 
 In the human subject we find this tissue employ- 
 ed in the spine, as the ligamenta subflava, extended 
 between the laminae of the vertebrae ; in the larynx, 
 forming the thyro-hyoid and crico-thyroid mem- 
 branes, and the chordae vocales ; and in the trachea, 
 forming the longitudinal or elastic bands of that 
 tube, and of its branches. The internal lateral liga- 
 ment of the lower jaw, the stylo-hyoid ligament, 
 and the transversalis fascia of the abdomen, are 
 also, in a great measure, composed of it. Among 
 the lower animals it is very extensively used for 
 mechanical purposes, of which there is a familiar 
 instance in the ligamentum nuchse of quadrupeds. 
 Its great elasticity fits it for restoring parts after they have been moved 
 by muscular action. Hence it is generally employed to supply an 
 antagonist force to the muscular. 
 
 A peculiar modification of the yellow fibrous tissue composes the 
 proper coat of the arteries, and it will be described with the blood- 
 vessels. 
 
 • We have ascertained this in the case of a divided tendo-Achillis. 
 
 Yellow fibrous tis- 
 sue, showingthe curly 
 and branched dispo- 
 sition of its fibrillae, 
 their definite outline, 
 and abrupt mode of 
 fracture. At 1, the 
 structure is not dis- 
 turbed, as in the rest 
 of the specimen. — 
 Magnified 320 diame- 
 ters. 
 
AREOLAR TISSUE. 83 
 
 In chemical constitution, this tissue differs remarkably from the 
 white fibrous tissue. It is unaffected by the weaker acids, or by 
 boiling, and will resist putrefaction, and preserve, its elasticity dur- 
 ing a very long period. Very long boiling appears to extract from 
 it a minute quantity of a substance allied to gelatine ; but this is 
 perhaps derived from the areolar tissue and vessels, which always 
 penetrate sparingly among its fibres, and cannot be separated by dis- 
 section. 
 
 There appear to be no vestiges of the nuclei of cells in this tissue ; 
 at least we have failed to detect them. 
 
 We have hitherto spoken of the two forms of fibrous tissue as they 
 occur in isolated masses ; but their distribution through the body is 
 far more extensive than this description would imply. In a diffused 
 form, blended with one another in very varying proportions, and each 
 one of them presenting a variety of modifications, they compose the 
 areolar tissue, which may now be conveniently considered under a 
 separate head. 
 
 OF THE AREOLAR TISSUE. 
 
 {Cellular or Filamentous Tissue.) 
 
 This is very widely dispersed among the other tissues of the 
 body, and of itself constitutes a principal portion of some organs. 
 It serves the most important purposes in the construction of the 
 body, by binding together, and yet allowing movement between, its 
 elementary parts : and it contributes largely to the formation of 
 membranes conferring protection by their toughness, resistance, and 
 elasticity. 
 
 Microscopic characters. — When a fragment of the areolar tissue 
 from a favourable situation is examined, it presents an inextricable 
 interlacement of tortuous and wavy threads intersecting one another 
 in every' possible direction. They are of two kinds. The first are 
 chiefly in the form of bands of very unequal thickness, and inelastic. 
 Numerous streaks are visible in them, not usually parallel with the 
 border, though taking a general longitudinal direction. These streaks, 
 like the bands themselves, have a wavy character, but they are ren- 
 dered straight by being stretched. The streaks seem more the marks 
 of a longitudinal creasing, than a true separation into threads : for it 
 is impossible by any art to tear up the band into filaments of a deter- 
 minate size, although it manifests a decided tendency to tear length- 
 wise. The larger of these bands are often as wide as 7J5 of an inch ; 
 they branch, or unite with others, here and there. The smaller ones 
 are often too minute to be visible, except with a good instrument. 
 These are the white fibrous element. 
 
 The others are long, single, elastic, branched filaments, with a dark, 
 decided border, and disposed to curl when not put on the stretch. 
 These interlace with the others, but appear to have no continuity df 
 
84 
 
 ORGANS OF LOCOMOTION. 
 
 substance with them. They are for the most part about the ^^%s of 
 an inch in thicljness; but we often see, in the same specimen, others 
 
 Fig. 6. 
 
 Fig. 7. 
 
 The two elements of Areolar tissue, in their natural rela- 
 tbns to one another;—!. The w^hite fibrous element, with 
 ceil-nuclei, 9, sparingly visible in it. S. The yellow fibrous 
 element, showing the branching or anastomosing character 
 of itsfibrillas. 3. Fibriilce of the yellow element, far finer 
 than the rest, but having a similar curly character. 8. Nu- 
 cleolated rell-nuclei, often seen apparently loose. — From 
 the areolar tissue under the pectoral muscle, magnified 320 
 diameters. 
 
 Development of the Areolar tissue 
 (while fibrous element) :— 4. Nucle- 
 ated cells, of a rounded form. 5. 6- 7, 
 The same, elongated in different de- 
 grees, and branching. At 7, the 
 elongated extremities have joined 
 others, and are already assuming a 
 distinctly fibrops character.— After 
 Schwann. 
 
 of much grpater density. These form the yellow fibrous element^ 
 
 (fig- 6-) 
 
 These two tissues maybe most easily discriminated by the addition 
 of a drop of dilute acetic acid, which at once swells-up the former, 
 and renders it transparent, while it produces no change in the latter. 
 The wavy bands of the white fibrous part, on being touched by the 
 acid, may be seen to expand en masse, and not as though they con- 
 sisted of a mere bundle of smaller filaments ; yet there often remains 
 in them an appearance of more or less wavy transverse lines at pretty 
 equal distances, remotely resembling those on the fibre of striped mus- 
 cle. These we are unable to explain. The acid also brings into 
 view corpuscles of an oval shape, often broken into fragiuents, and 
 stretching for some distance along the interior of the band. These 
 seem to be the nuclei of the cells from which the bands have been 
 originally produced. ^ 
 
 In the earliest period at which the areolar tissue can be examined, 
 Schwann has described it as consisting of nucleated particles, sending 
 
AREOLAR TISSUE. 
 
 85 
 
 offsets on the opposite sides, and connecting themselves with others 
 in the vicinity. The threads thus formed are at first homogeneous ; 
 the longitudinal streaks and the wavy character appear subsequently 
 (fig. 7). His description is draw^'from the white fibrous element ; 
 but it may be extended to the yellow also. 
 
 We have observed frequently among the threads of areolar tissue 
 taken from adult subjects a number of corpuscles (8, fig. 6), either 
 isolated, or having very delicate prolongations among the neighbouring 
 threads. These seem xyith great probability to be either advancing 
 or receding stages of the tissue. 
 
 It is not known whether the ultimate elements of the areolar tis- 
 sue have any immediate attachment or union with the other tissues, 
 among which they lie, or whether they merely enclose them by the 
 complexity of their web. 
 
 By the endless crossing and twining of these microscopic fila- 
 ments, and of fasciculi of them, among one another, a web of amaz- 
 ing intricacy results, of which the interstices are most irregular in 
 size and shape, and all necessarily communicate with one another. 
 
 This is well seen by forcibly filling the tissue with air or water in 
 any region. In the living body this is very obvious in anasarca, and 
 in traumatic emphysema, as in the remarkable case related by Dr. 
 W. Hunter in his celebrated paper {Med. Obs. and Inquir., vol. ii. p. 
 17), where the whole body was blown up so tensely as to resemble a 
 drum. 
 
 The interstices are not cavities possessed of definite limits, because 
 they are open on all sides, and ulti- 
 mately constituted out of a mass of 
 tangled threads. The application of 
 the term, cell, to them, is therefore 
 inappropriate ; and it cannot be won- 
 dered at, that it should have led to 
 much confusion. In certain situa- 
 tions, however, where this tissue is 
 in great abundance, and where it first 
 attracted attention at the time when 
 elementary tissues began to be sepa- 
 rately studied, the meshes thus form- 
 ed are disposed so as to' constitute 
 secondary cavities, having a some- 
 what determinate shape and size, and 
 which are visible to the naked eye. 
 These generally contain fat, and may 
 be admirably studied in most parts of 
 the subcutaneous tissue. They are 
 better deserving the name of cells 
 than the interstices formed by the 
 first interlacement of the elementary 
 filaments. But they communicate freely, as the smaller interstices do, 
 their walls being everywhere cribriform, and capable of giving passage 
 to air or fluids. 
 
 Fig. 8. 
 
 Portion of Areolar tissue, inflated and 
 dried, showing the general cliaracter of its 
 largermeslies. Each lamina and filament 
 here represented contains numerous small- 
 er ones mati'ed together by the mode of pre- 
 paration. — Magnified twenty diameters. 
 
86 ORGANS OF LOCOMOTION. 
 
 The areolar tissue is one of the most extensively diffused of all the 
 elements of organization, and its chief purpose seems to be that of 
 connecting together other tissues in such a way as to permit a greater 
 or less freedom of motion between them. To do this, it is placed in 
 their interstices, and is more or less lax, more or less abundant, 
 according to the particular exigency of the part. It is by means of 
 this tissue, as well as by the complexity of its own web, that almost 
 every part of the vascular system is fixed in its position, and allowed 
 to undergo the movements impressed upon it by the circulati ve powers. 
 Even the capillaries supplying this system itself are for the most part 
 brought to it, and enveloped, by this tissue. 
 
 So true and comprehensive is this description of the association 
 of the areolar tissue with the vascular, that it would be difficult to 
 point out a single instance in which one office of the former is not 
 to envelop and protect the latter. But the statements that have 
 been made of its universal presence have no good evidence in their 
 favour. In the compacter parts of bone, in teeth, and in cartilage, 
 it is certainly not present ; and, indeed, it could serve no purpose 
 in those structures. In the substance of the brain, also, it does not 
 exist, excepting around the vessels two or three removes from the 
 capillaries. 
 
 In the muscles it connects the elementary fibres to one another, 
 and preserves them from undue separation during contraction ;' but 
 even here it is bound within the same limits as the capillaries, not 
 penetrating the sarcolemma to touch the contractile element within. 
 It enters the muscles abundantly along with their vessels and nerves. 
 It is remarkable, however, that the central organ of the circulation, 
 like the central organ of the nervous system, contains this tissue in 
 very small proportion ; one reason of which seems to be, that its fibres 
 differ from the parallel fibres of other muscles, by twining among one 
 another, and thus are enabled to dispense with an extraneous bond 
 of connection. 
 
 Besides penetrating between the fibres of the muscles, whose mi- 
 nute parts are in continual movement upon one another during con- 
 traction, it generally invests their exterior, in a profusion proportioned 
 to the extent to which these organs move as a whole upon neigh- 
 bouring parts, of which the best examples may be seen between the 
 great muscles of the extremities ; between these and their enveloping 
 fasciee (not their fascise of origin); under the occipito-frontalis muscle 
 and its tendon ; and in the upper eyelids. 
 
 The areolar tissue is also present in immense quantities under the 
 skin of most parts of the body, and especially where great mobility of 
 the integument is required, either as a protection to deeper organs 
 against external violence, or to facilitate the various movements of 
 the frame. Such are the regions of the abdomen, and of several of 
 the articulations, and the eyelids. 
 
 Around internal organs which change their form, size, or position 
 in the routine of their functions, and which are wholly or partially 
 without a free surface, as the pharynx, oesophagus, lumbar colon, blad- 
 der, &c,, this tissue is abundant, and its filaments so long, tortuous, 
 
AREOLAR TISSUE. 87 
 
 and laxly interwoven, as to admit of a ready and extensive motion 
 on the neighbouring viscera. 
 
 This tissue likewise forms a layer lying under the mucous and 
 the serous membranes in almost every situation, though presenting 
 great variations of quantity and denseness : it renders the move- 
 ments of such parts easy. It also closely invests the exterior of 
 every gland and parenchymatous organ, and enters more or less 
 abundantly into its inner recesses, along with its vessels, nerves, and 
 absorbents : but there is no doubt that it has been supposed to have 
 a much greater share in the formation of this numerous class of or- 
 gans than an ultimate anatomical analysis of them, conducted with 
 careful precision, will at all warrant. In all these cases it is a more 
 or less copious attendant on the vessels ; but wherever, either from 
 the intricacy of the interlacement of the capillaries with the other 
 essential elements of the particular organ, or the greater strength of 
 these elements themselves, the firm contexture of the whole is pro- 
 vided for, while little or no motion is required between its parts, this 
 interstitial filamentary tissue will be found to be confined to the larger 
 blood-vessels, and to the surface of the natural subdivisions of the 
 organ. 
 
 For the present, it may be sufficient to illustrate this remark by 
 contrasting two important glands, in reference to this point. The 
 liver is well screened from injury by its position ; it is liable to no 
 change of bulk; it consists throughout of a continuous and close net- 
 work of capillaries, the interstices of which are filled by the nucleated 
 secretion-particles. The lobules resulting from the distribution of 
 the vessels and ducts blend together at numerous points, and have 
 no motion on one another. Here the areolar tissue is in very small 
 quantity, and is limited to the ramifications of the vessels and ducts. 
 The mamma, on the other hand, is, by its situation, peculiarly ob- 
 noxious to external injury. It is broken up into numerous subdi- 
 visions, which move with the utmost freedom on one another, and it is 
 moreover liable to temporary augmentations of bulk. In this import- 
 ant gland not only is there a common investment of peculiar density, 
 but an extraordinary abundance of areolar tissue disseminated through- 
 out its interior. 
 
 Thus, this tissue, so widely spread throughout the body, whether 
 it serve the purpose of an investment to large segments or masses, 
 under the form of a membrane, strengthening and protecting them, 
 and escorting their vessels and other components into and from their 
 substance (atmospheric), or as a web of union between the simplest 
 elements of their organization (parenchymal), is to be regarded as 
 rather taking a subordinate or ministering. share in the constitution of 
 the frame, than as being of primary importance in itself. 
 
 It is a cement that allows of separation between xwhat it binds to- 
 gether ; and it accomplishes this double purpose in a manner suited 
 to the necessities of diverse parts, by a variety so simple in the num- 
 ber, intricacy, and closeness of its threads, as to be worthy of the 
 highest admiration, while it is wholly inimitable by art. 
 
 Where great elasticity is required, the yellow element preponde- 
 
88 ADIPOSE TISSUE. 
 
 rates ; while the white fibrous element abounds in parts demanding 
 tenacity and power of resistance. In all cases the openness of the 
 network is proportioned to the extent of mobility required. Where 
 the meshes are small, the threads composing them branch and 
 anastomose with one another with much greater frequency. The 
 texture of the cutis affords the most characteristic example of, this 
 condition. 
 
 Physical properties. — These have only been studied hitherto in 
 those situations where the tissue exists in great abundance, as in the 
 subcutaneous fascia, the sheaths of muscles, &c. It has here a whit- 
 ish hue, especially when steeped in water. It is extensible in all 
 directions, and is very elastic, returning to its original disposition 
 after stretching. It possesses no contractility beyond that attribu- 
 table to the vessels which are everywhere found in connection with 
 it, and in such situations in great profusion. Its sensibility is 
 usually stated to be low ; but it may be doubted whether the nerves 
 can in any case be said to be distributed to this tissue, which has 
 been already shown to be an appendage and protector to these and 
 other organs. Its asserted powers of absorption and secretion apper- 
 tain to the capillary blood-vessels, rather than to the threads of the 
 areolar tissue. 
 
 This tissue, like all other soft solids, contains a large quanti|y of 
 water. This keeps the filaments moist, without being so abundant 
 as to be free in their interstices. A morbid increase of this tluid in 
 the subcutaneous areolar tissue occasions the condition called ana- 
 sarca, and which may be known by the skin pitting under the pressure 
 of the finger. 
 
 When dried, out of the body, areolar tissue becomes hard and 
 transparent, but resumes its former state if moistened. It undergoes 
 the putrefactive process slowly. It is one of that class of tissues 
 which yields gelatine by boiling, the gelatine being derived from the 
 white fibrous element only. 
 
 The great value of areolar tissue, in facilitating the motion of 
 parts between which it is situate, is shown by the effects of inflam- 
 mation, or other diseases which injure its physical properties. It is 
 well known, that, when the subcutaneous tissue is the seat of phleg- 
 monous inflammation, the movements of the part affected are stiff 
 and painful, or altogether impeded, because the subjacent muscles 
 cannot move freely, by reason of the loss of elasticity in the areolar 
 tissue. When this tissue becomes indurated by an effusion of coagu- 
 lable material, the movements of the diseased limb are similarly 
 impaired. 
 
 OF THE ADIPOSE TISSUE, AND OF FAT. 
 
 This tissue has no alliance either of structure or function with the 
 areolar tissue ; it is, however, usually deposited in connection with 
 that tissue, and therefore we find it convenient to notice it here. 
 Malpighi, W. Hunter, Monro, and, more recently, other distinguished 
 
ADIPOSE TISSUE. 89 
 
 anatomists, pointed out the distinctness of these two tissues ; but such 
 has been the influence of the, term cellular, applied to both, that they 
 are still usually classed together. Now, however, that microscopes, 
 on which reliance can be placed, declare their totally distinct nature, 
 it is full time that they be treated of as altogether distinct and inde- 
 pendent tissues. 
 
 A common use of the adipose tissue being to occupy spaces of 
 various dimensions left in the interstices between organs, and thus 
 to facilitate motion and contribute to symmetry, it is very commonly 
 closely associated with the areolar tissue ; but the connection is not 
 an essential one. In the cancelli of bones there is a large deposit of 
 fat, but none of this filamentary tissue ; and in numerous situations, 
 as the eyelids, beneath the epicranial aponeurosis, between the rec- 
 tum and bladder, under the mucous membranes, and in the whole 
 of the cutis, the areolar tissue exists without being ever accompanied 
 by fat. Nevertheless, their apparent admixture in many situations 
 has given rise to the term " adipose cellular tissue" applied to the 
 two combined, as distinguished from that areolar tissue which contains 
 no fat. This term should be discarded as leading to much miscon- 
 ception. 
 
 A. distinction is to be dra.wn between fat and the adipose tissue. 
 The tissue is a membrane of extreme tenuity, in the form of closed 
 cells or vesicles ; the_/a< is the material contained within them. 
 
 The membrane of the adipose vesicle does not exceed the ^5^55 of 
 an inch in thickness, and is quite transparent. It is moistened by 
 watery fluid, for which, as Mr. Paget has suggested, it has a greater 
 attraction than for the fat it contains. It is perfectly homogeneous, 
 having no appearance of compound structure, and consequently be- 
 longs to the class of simple or elementary membranes. Each vesicle 
 is a perfect organ in itself; is from the ^l-^ to the 555 of an inch in 
 diameter, when fully developed ; and is 
 supplied on its exterior with capillary Fig- ^• 
 
 blood-vessels, having a special disposi- 
 tion. 
 
 The fat vesicles are usually deposited 
 in great numbers together, and they then 
 become flattened on their contiguous as- 
 pects, and assume a polyhedral figure more 
 or less regular (fig. 9). But, if isolated, 
 their form is rounded, as may be seen in 
 eminent beauty in the double series of them 
 which frequently accompanies the minute 
 vessels traversing membranous expansions 
 of the areolar tissue, and other lamellar Fat vesicles, ass„ming the poiy- 
 structures, as the mesentery of small ani- iie<ir»' fo™ f™'" pi-esfure agamst 
 
 , ,_, , ,, .* ,j 1 1 1 one another. 1 he capillary vessels 
 
 mals. The vessels are thus attended by are not lepresemed.-From the 
 p , . 1 /•„ .1 „ \p i. „^ „f omentum; magnified about 300 
 
 fat vesicles, lor the manifest purpose ot diameters. 
 
 protection from the pressure to which they 
 
 would be exposed in their open course, and they throw around each 
 
 vesicle a capillary loop. 
 
90 
 
 ORGANS OF LOCOMOTION. 
 
 Where the fat is in considerable quantity, it is comndonly sub- 
 divided into a number of small fragments or lobules, fitted accurately 
 to one another and invested with areolar tissue, for the purpose, 
 chiefly, of permitting motion between the parts of the mass, but, also, 
 for the convenience of the distribution of its blood-vessels. 
 
 Fig. 10. 
 
 Blood-vessels of Fat :— 1. Minute flattened fat-lobule, in which the vessels only are represented. 3. 
 The terminal artery. 4. The primitive vein. 5. The fat vesicles of one border of the lobule, sepa- 
 rately represented. Hagniiied 100 diameters.— 2. Flan of the arrangement of the capillaries on the 
 exterior of the vesicles : more highly magnified. 
 
 The blood-vessels enter the chinks between the lobules (fig. 10, 
 1, 2), and soon distribute themselves through their interior, under the 
 form of a solid capillary network, whose vessels occupy the angles 
 formed by the contiguous sides of the vesicles, and anastomose with 
 one another at the points where these angles meet. This is one of 
 those situations where the capillary vessels can be most unequivocally 
 proved to possess distinct membranous parietes. 
 
 Fat. — Fat is a white or yellow unctuous substance, unorganized, 
 and secreted into the interior of the adipose vesicles.' Chemists 
 have di.stinguished in it two solid proximate principles, stearine and 
 margarine, combined with a fluid one, or- oil, elaine; on the relative 
 proportions of which the principal of the numerous modifications of 
 its external qualities would seem to depend. These principles may 
 be obtained by diflTerent means. Boiling alcohol dissolves both, but 
 on cooling deposits the stearine in snow-white flakes ; and the elaine 
 may be set free by the addition of water, for which the alcohol has 
 a superior affinity. Or, the elaine may be separated by pressure. 
 Stearine preserves its solidity at a temperature of 167° Fahr., and 
 elaine remains fluid at 63° or 65° F. Margarine exists along with 
 stearine in most fats, and may be separated from it by ether, which 
 dissolves margarine, but not stearine ; it is said to exist alone in 
 human fat, which is therefore destitute of stearine. These proximate 
 
ADIPOSE TISSUE AND FAT. 91 
 
 elements of fat are regarded by modern chemists as natural com- 
 pounds of certain -organic acids with an organic base, to which the 
 name of glycerine has been given, from its sweet taste. The acids 
 are, the, stearic, margaric, and elaic ; and the proximate principles 
 are, respectively, a stearate, a margarate, and an elaate of glycerine. 
 By boiling oil or fat with a solution of caustic alkali, the acids unite 
 with the potash, forming soap, and the glycerine remains dissolved 
 in the liquid. By evaporating this liquid (in which any excess of 
 alkali had been previously neutralized by tartaric acid) to a thick 
 syrup, the glycerine may be obtained from it in solution by strong 
 alcohol. 
 
 We may often dqtect a spontaneous separation of these two proxi- 
 mate principles within the fat vesicle of the human subject. The 
 solid portion collects in a spot on the inner surface of the cell-mem- 
 brane, and looks like a small star (fig. 11, 
 2, 2, 2). The elaine occupies the remainder Fig. 11. 
 
 of the vesicle, except when the quantity of 
 fat in the cell is smaller than usual ; in which ^^k\ 
 
 case we may often discern a little aqueous -('^^S^^^ ^ 
 
 fluid between the elaine and the cell-mem- /*~X^^K'^% ^ 
 
 brane on the side farthest from the star (fig. ^j^^^^^SI 
 
 11, 1, 1,): a condition, by the way, which * ^^^J^^^ 
 is very favourable for the observation of this , ^9^^~ a 
 membrane itself. 
 
 mi /!,i'i/»/.i 1 -.1 Fat vesicles from an emactat- 
 
 Ihe sorter kinds of fat were denominated ed suhject:— i. i. The oeii- 
 by the older anatomists pn^wecfo, lard ; and ^ottr"o"ect6^'■a■^'tar!like 
 
 the more solid, SeJwm or SeVUm, suet, tal- mass, with the elamemconnec- 
 , ^^ ,'. . . I p ' . .' tion with It, but not fiUing the 
 
 low. Hunter distinguishes four varieties as ceii. 
 to fluidity ; oil, lard, tallow, and spermaceti. 
 
 The elaine of human fat retains its fluidity at 40° F. Lard melts at 
 86° ¥.; tallow at 104° F. Spermaceti is fluid in a heat above 115° 
 F.^ and solid at 112°. Oil is elaine with little qr no stearine, as the 
 neat's foot oil, obtained from the bones of the ox. In lard the stearine 
 is in abundance, but the elaine slightly predominates. In tallow and 
 spermaceti there is a predominance of stearine. 
 
 Ultimate analysis of Fat. — Human fat, according to Chevreul, con- 
 sists of 
 
 Hydrogen 11 '4 16 
 Carbon 79000 
 Oxygen 9'584 
 
 100-000 
 
 Distribution. — The adipose tissue is found very extensively in the 
 animal kingdom. It is found in larvee as well as in the perfect 
 insect : also in the mollusca. It prevails in all the tribes of the 
 vertebrata. In fish it occurs throughout the body ; but in some, 
 as the cod, whiting, haddock,' and' all of the ray kind, according 
 to Hunter, it is only met with in the liver. In reptiles it exists 
 chiefly in the abdomen. In the frog, toad, &c., it is found in the 
 form of long appendages, like the appendices epiploic©, situated on 
 
92 ORGANS OF LOCOMOTION. 
 
 each side of the spine. In birds it exists chiefly between the peri- 
 toneum and abdominal muscles ; but there is also a considerable 
 deposit in the bones of the legs, feet, last bones of the wings, and 
 of the tail, especially of the swimming tribes, the oily principle being 
 more abundant than in mammals. In mammalia it is very generally 
 diffused. This class, as a whole, has the greatest quantity under 
 the skin, and about certain of the abdominal viscera; but the hare 
 forms a remarkable exception, it being sometimes difficult to find a 
 particle in its whole body. It usually abounds most in the beginning 
 of winter ; and this is especially the case with the hog, and with hy- 
 bernating animals, which, during their dormant state, absorb it into 
 the system. 
 
 It is ordinarily accumulated in large masses about the kidneys, more 
 particularly in ruminants, where it furnishes the best example of that 
 variety of it termed suet. 
 
 Among mankind many remarkable varieties exist in regard to this 
 tissue. Thus, in general, women are fatter than men. The healthy 
 human fcetus, after the middle of the period of gestation, accumulates 
 fat in considerable quantities : towards middle age, there is a similar 
 disposition, which has not escaped ordinary observation, " Fat, fair, 
 and forty:" in old age and decrepitude, the adipose deposit greatly 
 diminishes. 
 
 Differences are also constantly seen in individuals, which can be 
 referred only to an onginal constitutional bent. Thus young children 
 are occasionally so overloaded with this tissue as to be unaole to fol- 
 low their sports; and it is not uncommon for a similar tendency to 
 manifest itself towards the adult period, particularly in girls. In 
 elderly persons, fat is especially prone to be accumulated over the 
 abdomen, and between the layers of the epiploon and mesentery. 
 Instances where it attains the thickness of three or four inches under 
 the skin of the belly are not unfrequent in corpulent persons. A 
 similar abundance occasions the " double chin." 
 
 It is perhaps possible for the body to grow so egregiously fat as to 
 become lighter than water ; but whether implicit faith is to be placed 
 in the story of the Italian priest Paolo Moccia, who weighed thirty 
 pounds less than his bulk of water, and therefore could not sink in 
 that fluid, we do not pretend to decide. The excessive deposit of 
 this substance constitutes a disease, which has been not very correctly ' 
 called polysarcia. John Bull is celebrated for his proneness to accu- 
 mulate fat: M. Blainville remarks, with naivete, " We have seen many 
 individuals of the English nation whom embonpoint had rendered al- 
 most monstrous ; and I remember, among others, a man exhibited at 
 the Palais Royal who weighed five hundred pounds. He was literally 
 as broad as he was long." 
 
 Among the Hottentot women, the fat is apt to gather in the but- 
 tocks, and is considered a prominent mark of beauty ; but this does 
 not usually occur till after the first pregnancy. A somewhat analo- 
 gous formation exists in a variety of sheep, {Ovis steatopyga; fat- 
 buttocked sheep, Pallas,) reared by the pastoral tribes of Asia, in 
 ■which a large mass of fat covers the buttocks and takes the place of 
 
ADIPOSE TISSUE AND FAT. 93 
 
 the tail, appearing when viewed from behind as a double hemi- 
 sphere, in the notch of which the coccyx is buried, but is just percep- 
 tible to the touch. These protuberances, when very large, fluctuate: 
 from side to side, and sometimes attain the weight of thirty or forty 
 pounds. 
 
 The quantity of fat'in a moderately fat man is estimated by Beclard 
 at about the twentieth of the weight of the body. 
 
 Fat is found in the following situations in the human body : in the 
 orbits, in the cheeks, the palms of the hands and soles of the feet, 
 at the flexures of the joints, and between the folds of the synovial 
 membranes of joints, around the kidneys, in the mesenterj' and omen- 
 tum, in the appendices epiploicae, on the heart, in the subcutaneous 
 layer of areolar tissue, but especially that of the abdomen, and of the 
 mammary region, and in the cancelli and canals of the bones, form- 
 ing the medulla. It never occurs in the areolar tissue of the scrotum 
 and penis, or of the nymphae, nor in that between the rectum and 
 bladder, nor along the median line beneath the skin, nor in sundry 
 other situations. 
 
 Fat is found in the liver, and in the brain and nerves, and occa- 
 sionally in other organs. In these organs it is not enclosed in vesi- 
 cles of adipose membrane, but in the elementary parts of the tissues 
 themselves, as in the epithelium cells of the liver, and in the tubes 
 and globules of the nervous substance. 
 
 Development of adipose tissue. — The vesicles of 
 the adipose tissue are originally furnished with 
 nuclei, with a central granule or nucleolus. The 
 nucleus is situated on the inner surface^ of the cell- 
 membrane, or, if this be thick, in its substance. 
 The nucleus is speedily absorbed, and never after- 
 wards appears. Thus it is probable that the origi- 
 nal development-cell assumes a permanent form in 
 the adipose vesicle. 
 
 Formation of fat. — Many facts prove that the a fat-ceii, to show 
 elements of fat are derived from the blood. All Schwann;— c. The 
 the most recent analyses of that fluid assign to it a L'^'^TUe nudeuT.'"^"^" 
 certain proportion of both the crystalizable and the 
 oily portion of the fat ; according to Lecanu, about four parts in a 
 thousand. In some instances, the fatty matter accumulates in the 
 blood ; cases of which have been recorded by Morgagni, Hewson, 
 Marcet, Traill, and Babington. In such cases the serum is opaque 
 and nearly as white as milk, and, on stariding a short time, a film 
 forms on the surface like cream. On the addition of ether, the creamy 
 pellicle is dissolved, and the serum loses its opacity. M. Blainville 
 relates that, in dissecting the last elephant which died at the Jardin 
 des Plantes, he happened to wound the jugular vein, and the next 
 morning he found that the stream of .blood, which flowed from the 
 vein, had deposited on each side a considerable quantity of a fine fatty 
 matter, which on analysis he found to have exactly the composition 
 of ordinary fat. 
 
 From what source is this fatty material furnished to the blood } 
 
94 ORGANS OF LOCOMOTION. 
 
 From fatty matters introduced into the system in the food whether 
 in animal or vegetable substances ; probably, also, from those parts 
 of the food, which, in composition, resemble fat most nearly, such as 
 the non-nitrogenized articles of diet, starch, gum, sugar, alcohol, beer, 
 &c. Liebig states, that, by the separation of a small proportion of 
 oxygen, any of these substances will present a composition similar to 
 that of fat, and that an equivalent of starch may be changed into one 
 of fat, by giving up one equivalent of carbonic acid, and seven equi- 
 valents of oxygen. 
 
 If, then, the system be imperfectly supplied with oxygen, while 
 organic compounds containing carbon are furnished to it in con- 
 siderable qi!kntity, the most favourable conditions will exist for the 
 development of fat. The oxygen required will be abstracted from 
 the carbonized food, which, by that diminution of oxygen, will be 
 changed into a fat. On the other hand, exercise and labour, which 
 increase the supply of oxygen, diminish or prevent the formation of 
 fat. " The production of fat," says Liebig, " is always a consequence 
 of a deficient supply of oxygen, for oxygen is absolutely indispen- 
 sable for the dissipation of the excess of carbon in the food. This 
 excess of carbon, deposited in the form of fat, is never seen in the 
 Bedouin or in the Arab of the Desert, who exhibits with pride to the 
 traveler his lean, muscular, sinewy limbs altogether free from fat ; 
 but in prisons and gaols it appears as a puffiness in the inmates„fed, 
 as they are, on a poor and scanty diet; it appears in the sedentary 
 females of oriental countries; and, finally, it is produced under the 
 well-known conditions of the fattening of domestic animals." (Lie- 
 big's Organic Chemistry of Physiology.) 
 
 A good illustration of those views is afforded by the carnivorous 
 animals. In the wild state, living entirely on azotized food, and 
 enjoying abundance of air and exercise, they are lean ; but, when 
 domesticated, living on a mixed diet, devouring a highly carbona- 
 ceous food, taking little exercise, and being imperfectly supplied with 
 oxygen, they grow fat. 
 
 In animals that hybernate, fat is deposited in enormous quantity 
 just prior to the hybernating period, and during that time it gradually 
 disappears, supplying nutriment to the system, and carbon fojvthe re- 
 spiratory procesSt These facts were clearly ascertained, in hedgehogs, 
 by the celebrated Dr. Jenner. 
 
 Liebig supposes that the formation of fat is attended with the de- 
 velopment of heat, for the oxygen disengaged in this process unites 
 with carbon derived from the same or a different source, and an 
 amount of heat is generated proportionate to the quantity of carbonic 
 acid thus formed. But it may be fairly questioned, whether the 
 temperature of the body is thereby elevated, since the separation of 
 the oxygen would be doubtless attended by a degree of cooling suf- 
 ficient to neutralize the heat developed in the formation of carbonic 
 acid. 
 
 Lastly, fat, being a bad conducfbr of heat, is useful for retaining it 
 in the bodies of animals. Hence those animals that have little hair 
 on their skins, have the greatest quantity of subcutaneous fat. This 
 
CARTILAGE. 95 
 
 is remarkably the case in the seal tribe, which has a large quantity 
 of fat between the skin and its muscle, and is almost devoid of 
 cutaneous covering ; and, in man, the subcutaneous fat, which is so 
 generally met with, even in apparently lean subjects, is doubtless a 
 protection against cold. 
 
 The following works may be consulted on the subjects discussed in this chapter: 
 — The treatises on General Anatomy by Bichat, Beclard, Craigie, and Henle ; Hilde- 
 brandt's Anatoraie, by Weber; Blainville, Iie9ons de Physiologie; Liebig's Organic 
 Chemistry; Hunter's remarks on Fat, in the Catalogue of the Hunterian Museum, vol. 
 iii. p. 2. 
 
 CHAPTER IV. 
 
 PASSIVE ORGANS OF LOCOMOTION, CONTINUED. — OF CARTILAGE AND 
 FIBRO-CARTILAGE, 
 
 Cartilage is extensively used in the animal frame, and is one of 
 the simplest of the textures. Like the adipose tissue, it approaches 
 very closely in its iijtimate structure to the cellular tissue of vege- 
 tables. 
 
 In the development of the embryo, it is one of the first tissues to 
 appear as a distinct structure, and it constitutes the internal skeleton 
 in its earliest condition in the animal scale. The rudimentary skele- 
 ton of the cephalopoda consists of it ; and in one class of fishes (hence 
 termed cartilaginous, as the shark, ray, lamprey) the skeleton is en- 
 tirely composed of it. 
 
 In man, and the higher animals, cartilage is employed temporarily, 
 as a nidus^for bone, in the early stages of life, and is then called 
 temporary cartilage. This, at a certain period, begins to ossify, and 
 finally disappears by being converted into bone. At one time, the 
 greatest part, if not the whole, of the skeleton is cartilaginous ; and 
 for a considerable period after birth the extremities of the long bones 
 are chiefly composed of cartilage, and the larger processes are con- 
 nected to the shaft of the bone by this substance. 
 
 For other purposes, however, a cartilage is employed which is not 
 prone to nss\^Y, viz., permanent cartilage, and this is used either in 
 joints [articular cartilage), or in the walls of cavities {memhrani- 
 form cartilage). The articular variety is either disposed as a thin 
 layer between two articular surfaces, and equally adherent to both, 
 as in the synarthrodia! joints (the cranial sutures, the sacro-iliac 
 symphyses, &c.) ; or it forms an encrustation upon the articular 
 ends of the bones entering into the composition of diarthrodial 
 joints; thus, the extremities of the femur, tibi^ the arm-bones, &c., 
 are all coated with a layer of cartilage, moulded to the shape of the 
 articular surfaces. The membraniform cartilages are not employed 
 in connection with the locomotive mechanism, but serve to guard 
 
96 ORGANS OF LOCOMOTION. 
 
 the orifices of canals or passages, or to form tubes, th-at require to 
 be kept permanently open ; the elasticity of the material affecting 
 this -without the expenditure of any vital force. Thus we fijjji this 
 variety of cartilage in the external ear, in the Eustachian tube, in 
 the nostrils and eyelids, and in the larynx, trachea, and bronchial 
 ramifications. 
 
 Physical characters, — Cartilage, in colour, varies from an azure, 
 or pearly white, to a whitish yellow. The .temporary and articular 
 varieties present the former colour ; the membraniform, for the most 
 part, the latter. 
 
 Elasticity, flexibility, and considerable cohesive power are the chief 
 physical properties of this texture ; and in these qualities, and espe- 
 cially in the first, consists its great value, both in contributing to the 
 perfection of the locomotive apparatus, and in its adaptation to other 
 purposes. Cartilage is not brittle : a thin piece may be broken 
 across by being suddenly bent at a very acute angle ; but, in general, 
 cartilage will bend easily without the occurrence of fracture, and 
 will speedily resume its former direction on the bending force being 
 removed. 
 
 Structure. — The simplest kind of cartilage consists merely of nu- 
 cleated cells, and exceedingly resembles the cellular tissue of plants. 
 The cells are very large, roundish or ovoidal, and more or less flat- 
 tened by their mutual contact. Each has a diminutive transpgrent 
 nucleus attached to the inner surface of the cell-membrane, and con- 
 taining within it a minute granule, or nucleolus. We have also' met 
 with other transparent globules, of variable size and extreme delicacy, 
 within the cells. Some white fibrous tissue usually encloses the mass 
 of cells, and penetrates to a certain distance among the more super- 
 ficial of them, which are smaller and more densely packed than the 
 rest. 
 
 This kind of cartilage is found in the. chorda dorsalis, or rudimen- 
 tary spinal column of the early embryo : it also 
 Fig- 13- exists in the permanent chorda dorsalis of the 
 
 cartilaginous fishes, and may be well seen in 
 a thin piece of that structure from the lamprey 
 (fig. 13). 
 
 But, in other kinds of cartilage, the cells 
 are imbedded in an intercellular substance, or 
 matrix, more or less abundant in the differ- 
 ent kinds, and presenting certain varieties of 
 appearance. In all, it is possible to see that 
 the cells have a proper, membrane of their 
 own, and are not mere excavations iii the in- 
 Four nucleated cells from tcrcellular substancc ; this may often be deter- 
 L™p'L7ti''Nude„s°'whh mined at a broken edge, the cell-membrane 
 "n profire'; ^' ^"'"''"' "™ projecting : but it is not easy to extract 
 a cell entire, apparently on account of the 
 delicacy of its texture, and the density of the surrounding mass. 
 
 In temporary cartilage the cells are very numerous, and' situated at 
 nearly equal distances apart in the intercellular substance which is 
 
CARTILAGE. 
 
 97 
 
 Fig. 14. 
 
 not abundant. The cells vary in shape and size, but most are round 
 or oval. Their nuclei are for the most part minutely granular ; the 
 granules being, in some specimens, at a distance from one another. 
 When ossification begins, the cells, which hitherto were scattered 
 without definite arrangement, ^become disposed in clusters or rows, 
 the ends of which are directed towards the ossifying part. These 
 and other changes will be described in the chapter on bone. 
 , In articular cartilage the cells are oval or roundish, often disposed 
 in small sets of 2, 3, or 4 irregularly disseminated through a nearly 
 homogeneous matrix, which is more abundant than in the last-n^med 
 variety ; fig. 14, 1. The cells measure from j^sn to jjj of an inch. 
 The nuclei are for the most part small. In the interior part of the 
 cartilages of encrustation we usually find the 
 cells assuming more or less of a linear direc- 
 tion, and pointing towards the surface ; fig. 14, 
 3. This arrangement is probably connected 
 with a corresponding peculiarity of texture of 
 the intercellular substance, but which it is 
 more difficult to distinguish,; for these speci- 
 mens have a disposition to fracture in a regular 
 manner along planes vertical to the surface, 
 and the broken surface is striated in the same 
 direction. 
 
 Near its deep or attached surface, articular 
 cartilage blends gradually with the bone it in- 
 vests. The cells in the neighbourhood, as 
 well as their nuclei, are surrounded with a 
 sprinkling of fine o'paque granules, which seem 
 to be a rudimentary deposit of bone. The 
 true bone dips unevenly into the substance of 
 the cartilage. 
 
 A pavement of nucleated epithelial parti- 
 cles has been described by Henle to exist on 
 the free surface of articular cartilage. In the 
 foetus this may be readily seen ; but in the 
 adult we have often failed to detect it, even 
 in perfectly fresh specimens, and notwithstanding great care. An 
 irregularity of surface, like that represented in fig. 14, 2, often exists, 
 and seems to show that this covering ceases when the part becomes 
 subject to friction and pressure. - Cells, too, are often seen close to 
 this surface, and even partly projecting from it ; appearances indica- 
 tive of attrition. 
 
 In the cartilages of the ribs, which occupy an intermediate place 
 between the articular and membraniform varieties, the cells are larger 
 than in any other cartilage in the body, being from ^ j^ to j^-^ of an 
 inch in diameter. Many of them contain two or more nuclei, which 
 are clear and transparent ; and some seem to contain a few oil-glob- 
 ules, a condition occasionally met with in other varieties. The 
 cells often affect a linear arrangement. The rows of them are turned 
 in all directions, and have the appearance of having been formed by 
 6 
 
 Articular canilage, from the 
 head of the Huhierus; — VerticA 
 sections: 1. Section close to the 
 surface, 2. 3. Section far in the 
 interior.— Magnified 320 diame- 
 ters. 
 
98 
 
 ORGANS OF LOCOMOTION. 
 
 Fig. 15. 
 
 
 - jf *■* "-t '/<=' f» i^ 
 
 
 
 the division of one cell, and the separation of its parts from each 
 other. It is probable that the splitting of the nucleus may be the 
 
 first step in this process, as, for ex- 
 ample, in fig. .15, a. 
 
 The intercellular substance is very- 
 abundant in these cartilages; and 
 though it usually presents, on a sec- 
 tion, a very finely mottled aspect, 
 such as is very correctly portrayed 
 in the figure, yet we may often dis- 
 cern in it a most distinctly fibrous 
 structure, in vsfhich the fibres are 
 parallel, and which is most evident 
 in the aged. Perhaps it would be 
 most correct to say that these fibres 
 are only formed by an artificial dis- 
 integration, for they are aggregated 
 into a solid mass in the unmutilated 
 structure. They have very little 
 resemblance to the white fibrous 
 tissue. It is not known whether 
 they take any constant direction. , 
 In the true membraniform cartilages, the cells are very numerous 
 in proportion to the surrounding substance, which is consequently in 
 
 small quantity. This intercellular matrix 
 is very distinctly fibrous towards the ex- 
 terior of these cartilages, and often in 
 their interior, but with considerable va- 
 riety. The thyroid and cricoid cartilages, 
 and the rings of the trachea, seem chiefly 
 composed of clearly defined and roundish 
 nucleated cells, huddled together, as it 
 were, in a promiscuous manner, fig. 16. 
 In specimens from persons of adult age, 
 the cells have frequently a fine granular 
 opaque matter sprinkled on their exterior; and these, in older sub- 
 jects, are seen to have become minute centres of a spurious ossifi- 
 cation. 
 
 In the cartilage of the ear the cells are small, and very close to 
 each other; in shape they are very uniform, and vary in size from 
 TsV^ *" nitr of an inch. A piece of this cartilage, when examined 
 by a high power, has very much the appearance of a sieve; the 
 holes of which are occupied by nuclei and their nucleoli. The in- 
 tercellular substance is not exactly white fibrous tissue ; but so nearly 
 resembles it, especially towards the surface, as to make this form of 
 cartilage approach fibro-cartilage more nearly than does any other. 
 
 The membraniform cartilages are invested by a layer of white 
 fibrous tissue containing blood-vessels, and called the perichondrium. 
 Its fibres are densely interwoven in all directions, and adhere inti- 
 mately to the intercellular substance of the cartilage. This investr 
 
 Canilage of ihe Ribs. Section showing 
 the cell?, their nuclei and nucleoli. The 
 transparent spaces result from ihe removal 
 of the cells hy the knife, their cavities re- 
 maining —Magnified 320 diameters. 
 
 Fig. 16. 
 
 ThyroM rnriilna-e : — Thin section. 
 —Magnified 320 diameters. 
 
CARTILAGE. 99 
 
 ment corresponds with the periosteum of bone, and in the temporary 
 cartilages is indeed the very same structure. It is a nidus for the 
 nutrient vessels of cartilage, and often serves to give attachment to 
 muscles. It is best examined on the cartilages of the ribs. Its 
 great toughness is sometimes well displayed in fractures of these 
 cartilages, where the perichondrium remains untorn between the 
 fragments. 
 
 The articular cartilages, which have no perichondrium, are sup- 
 ported and supplied with blood by the bone to which they are 
 adapted, and by the synovial membrane, which always passes for at 
 least some little distance over their free surface. 
 
 Vessels of cartilage. — Speaking in general terms, cartilage may be 
 styled a non-vascular substance, for considerable masses of all its 
 varieties exist, unpenetrated by a single vessel. The term non- 
 vascular, however, it is important to observe, is to be understood in 
 a relative sense. All tissues deriving their nutriment from blood- 
 vessels, are, in fact, if traced up to their microscopic elements, on 
 the outside of the channels through which the blood flows. If the 
 quantity of vessels be large in proportion to the tissue, or if the two 
 are mingled in an intimate manner, we term the part very vascular. 
 If, on the other hand, there be a considerable mass of tissue, among 
 the elementary parts of which no vessels penetrate, it is styled non- 
 vascular. This word is not used in an absolute sense ; for, if so 
 used, it would apply equally to all tissues, except the lining mem- 
 brane of the vascular system itself, which is probably nourished by 
 the blood immediately in contact with it. 
 
 Returning from this digression, we -remark, that temporary car- 
 tilage, when in small mass, is not permeated by vessels; but that, 
 when more than about an eighth of an inch thick, it contains canals 
 in its interior, for the transmission of vessels. ' These canals are 
 somewhat tortuous, and contain a delicate extension of the peri- 
 chondrium. They tnay be regarded as so many involutions of the 
 outer surface of the cartilage. 
 
 The same description will apply to the various membraniform 
 cartilages, with this difference, that their blood-vessels are less 
 numerous. In those which are thin, no vascular canals are to be 
 found; but where there is much substance, as in the costal carti- 
 lages, they are easily detected. 
 
 Nothing is more certain than that articular cartilage, in man, is 
 not penetrated by blood-vessels. Coloured fluids injected into the 
 vessels cannot be made to enter it, but are seen to turn back, on 
 reaching it, into the tissue which conveyed them to it. But we 
 possess a more certain test than this, in the examination of thin 
 slice,s of the tissue under a high power. This brings no vessels into 
 view: on the contrary, it proves their non-existence, beyond dispute. 
 In some diseased states, however, the presence of a few vessels 
 seems to have been established. 
 
 Mr. Toynbee {Phil. Trans., 1841) has pointed out, that the vessels 
 of bone, at the part on which cartilage rests, are separated from the 
 cartilage by a bony lamella, in which no apertures exist. The 
 
100 ORGANS OF LOCOMOTION. 
 
 minute vessels, on approaching this lamella, seem to dilate, and 
 then, forming arches, they run back into the cancelli of the bone. 
 Such an arrangement must, of course, be attended with a retardation 
 of the blood near the "articular lamella." The vessels of the syno- 
 vial membrane advance with it a little way upon the articular surface 
 of the cartilage, but only over those parts which are not subject to 
 pressure during the natural movements of the joint. These likewise 
 terminate in loops. In diseased states they often advance far upon 
 the cartilage, as they do naturally, according to Mr. Toynbee's ob- 
 servations, during the middle period of foetal life. 
 
 OF FIBRO-CARTILAGE. 
 
 This texture is a compound of white fibrous tissue and cartilage 
 in varying proportions. 
 
 It is principally employed in the construction of joints, and con- 
 tributes to their perfection at once by its strength and its elasticity; 
 but as it is also, to a limited extent, used for other purposes, it may 
 be conveniently described as, 1, Articular; 2, Non-articular. 
 
 Fibro-cartilage, examined by the naked eye, has much of the 
 colour and general appearance of the thyroid cartilage, or of other 
 examples of the membraniform variety, which Bichat, indeed, classed 
 among fibro-cartilages. Its colour is white, with a slight tinge of 
 yellow; it is interspersed by the shining fibres of white fibrous tissue, 
 and its appearance differs with the quantity of that texture that is 
 mingled with it. Its consistence also varies, for the same reason; 
 in some instances* being extremely dense, 'in others soft, yielding, 
 and almost pulpy. 
 
 When examined microscopically, fibro-cartilage is found to consist 
 of bundles of wavy fibres, with the cells or corpuscles of cartilage 
 occupying the spaces formed by the interlacement of the fibrous 
 tissue. This interlacement is often very intricate, and calculated to 
 increase the strength of the structure in those directions in which the 
 greatest toughness is required. 
 
 Physical and vital properties. — To the strength and density of 
 fibrous tissue, fibro-cartilage adds the elasticity of cartilage ; it is 
 more variously flexible than the latter tissue, so that it will not crack 
 when bent too much. Its sensibility is low, and it is devoid of vital 
 contractility. 
 
 Vessels and nerves. — Its vessels are few, and are derived from the 
 textures (synovial membrane or periosteum) with which it is in im- 
 mediate connection. Nothing is known respecting its nerves, if 
 indeed it possesses them. 
 
 Chemical composition. — Fibro-cartilage contains water; when de- 
 prived of it by drying, it shrivels up, and becomes hard and yellow. 
 It yields gelatine in abundance on boiling. 
 
 Forms of fibro-cartilage. — The articular fibro-cartilage is that 
 •which is found most extensively, and it exists in three forms, a. As 
 discs, interposed between osseous surfaces, and equally adherent to 
 
PIBRO-CARTILAGE. 
 
 101 
 
 both, of which the intervertebral discs and the inter-pubic fibro-carli- 
 lage are instances, b. As laminae, free on both surfaces, placed in 
 the cavity of diarthrodial joints between the articular surfaces of the 
 bones. These are the menisci of authors; they exist in the temporo- 
 maxillary, the sterno-clavicular, and the knee-joints, and between 
 the scaphoid and lunar, and lunar and cuneiform bones, c. As tri- 
 angular edges to the glenoid and cotyloid cavities of the shoulder 
 and hip joints. These are styled circufnferential. 
 
 In examining these different forms of fibro-cartilage, some varie- 
 ties are met with deserving of a brief notice. 
 
 The intervertebral discs consist of concentric layers of white fibrous 
 tissue, placed vertically between the 
 surfaces of the vertebrae: although 
 the layers are vertical, the fibres of 
 which each layer is composed, are 
 directed obliquely from above down- 
 wards, and the direction of the fibres 
 of one layer is such as to decussate 
 with those of the layer immediately 
 behind it. Each pair of layers of 
 fibrous tissue is separated by a la- 
 mina of cartilage. This arrangement 
 belongs to rather more than the 
 outer third of the disc ; the central 
 portion is occupied by a soft, yield- 
 
 Fig- 17. 
 
 ing, pulpy matter, which, when a 
 
 Eleraentary structures from an interver- 
 tebral >dJBc;~l, Two cartilage-cells lying 
 amongst the while fibrous tissue. The re- 
 maining objects are from the central pulfiy 
 substance, and exhibit various forms of 
 cell. In several of these there is an ap- 
 pearance of maltiplication by subdivision 
 of the nucleus, and some seem attached by 
 a fibrous tissue. The full meaning of this 
 does not yet appear. 
 
 disc is cut horizontally, rises up 
 considerably above the surrounding 
 level. This soft mass consists of a 
 few bundles of white fibrous tissue, 
 (wavy fibres,) with numerous nucle- 
 ated cells, very variable in shape 
 and size, loosely interspersed. It 
 is girt by the surrounding vertical 
 fibrous layers and their interposed 
 cartilaginous lamellae, and also com- 
 pressed by the vertebrae between 
 ■which it is placed; the pulpy matter 
 
 being separated from immediate contact -with the surfaces of the ver- 
 tebrae by the interposition of thin layers of cartilage. 
 
 In the menisci the white fibrous tissue predominates considerably 
 at their circumferences, while the cartilage chiefly abounds in the 
 centre. These of the knee-joint and teraporo-maxillary joint are the 
 densest: that of the sterno-clavicular is softer and more cartilaginous. 
 The circumferential fibro-cartilages contain a considerable predo- 
 minance of fibrous tissue. 
 
 .The non-articular form of fibro-cartilage is found deposited on the 
 surfaces of the grooves in bones, which lodge tendons ; as, for ex- 
 ample, the groove for the lodgment of the tibialis posticus.^ In 
 intimate structure it resembles the articular forms. 
 
102 ORGANS OF LOCOMOTION. 
 
 Reparation and reproduction. — Fibro-cartilage heals by a new sub- 
 stance of similar texture. Sometimes the union of bone is effected 
 by a material of this kind, in cases where osseous union cannot be 
 obtained. 
 
 In addition to the works on General Anatomy mentioned at the end of the last 
 chapter, we refer to Miiller's Physiology, by Baly, p. 390; the articles Cartilage and 
 Fibro-Caftilage, in the Cyclopsedia of Anatomy; and Mr. Toynbee's paper on Non- 
 vascular Tissues, in Phil. Trans. 1841. 
 
 CHAPTER V. 
 
 PASSIVE ORGANS OF LOCOMOTION, CONTINUED. — OF BONE. 
 
 The distinction of animal textures into hard and soft prevails very 
 extensively throughout the animal series. The former are charac- 
 terized by containing a proportion of inorganic material, in combi- 
 nation with animal matter, sufficient to give them that degree of 
 hardness which is their principal physical property. 
 
 Among the invertebrated classes there are hard parts, although 
 very differently constituted from those of the higher animals. They 
 serve an analogous purpose, — being a basis of support for the soft 
 parts, and in many instances a protection to them, and affording a sur- 
 face of attachment for the muscles of the animal ; thus playing an 
 important part in its locomotion, or in its ordinary movements. To 
 this category we may refer the earthy support to the soft fleshy mass, 
 whether as an internal stem or axis, or as an external covering, which 
 is to be found among the polypifera, performing a function similar to 
 the skeleton of the higher animals, and composed of carbonate of 
 lime, with a little phosphate, in combination with a small quantity of 
 animal matter. 
 
 The calcareous plates of the star-fish and sea-urchin, (asterias and 
 echinus,) the hard coriaceous covering of insects, the hard external 
 integuments of Crustacea, and the infinitely various shells of the gas- 
 teropoda and conchifera, must all be regarded in the light of hard 
 parts performing the offices above referred to. 
 
 The skeleton of the higher animals is internal; it is clothed by 
 the muscles and other soft parts. The first example of this arrange- 
 ment is met with in the cephalopodous moUusks, in which certain 
 cartilaginous plates are enclosed in the body of the animal, protect- 
 ing certain parts of the nervous system. The skeleton of the lowest 
 organized fishes, although much more extensive, and of a more com- 
 plicated arrangement, is yet placed but little above that of those 
 animals. It is composed of a kind of cartilage, which in its greater 
 density, and in its having a certain quantity of calcareous deposit 
 around it, approaches the nature of the skeleton of the higher classes. 
 
 Bone is the substance employed to form the internal skeleton of 
 the osseous fishes, of reptiles, birds, and mammalia. It forms organs 
 
BONE. 103 
 
 of support, or levers for mption, or it encloses cavities affording pro- 
 tection to soft and vital organs. 
 
 To a superficial examination bone presents the following proper- 
 ties: hardness, density, a whitish colour, opacity. An examination 
 of its physical constitution will explain these characters. 
 
 Bone contains less water than any other organ in the body; and 
 exposure to air, even for a short time, removes the fluid by evapora- 
 tion: to this, in part, may be attributed its hardness. Bone consists 
 of an inorganic and an organic material, which may be obtained 
 separately by very simple processes. Steep a bone in dilute mineral 
 acid, muriatic or nitric; the earthy matter is dissolved out by the 
 acid, and the organic substance remains, retaining the original shape 
 and size of the bone. In fact, we obtain, by this process, the carti- 
 laginous nidus of the bone, upon which its form depends. The 
 vessels of the bone ramify throughout this mass; for if they have 
 been injected, previously to the action of the acid, they will be dis- 
 tinctly seen ramifying through the semi-transparent animal substance. 
 A preparation of this kind dried, and afterwards preserved in spirits 
 of turpentine, serves beautifully to exhibit the disposition of the ves- 
 sels in bone. 
 
 By subjecting a bone to a strong heat in a crucible, the animal 
 part will be burnt out, and the earthy part will remain. Still the 
 bone retains its form, but the cohesion between the earthy particles 
 is extremely slight, so that the least touch will destroy its continuity ; 
 a fact which obviously points to the animal matter as afTording to 
 bone its strength of cohesion. 
 
 Bone may be deprived of its animal matter by long-continued 
 boiling, under strong pressure, in a Papin's digester. The animal 
 matter is extracted, in combination with water, in the form of gela- 
 tine ; and the weight of the quantity which may thus be* obtained 
 will, owing to this union with water, exceed by three or four times 
 that of the bone itself. 
 
 A certain proportion between these two constituents of bone is 
 necessary to the due maintenance of its physical properties. To the 
 earthy part it owes its hardness, its density, its little flexibility: but 
 it is equally^necessary for these properties that the animal portion 
 shall be healthy, and in proper quantity; for the cohesion of the par- 
 ticles of the former is secured entirely by it. A due proportion of 
 the animal part gives bone a certain degree of elasticity; and, were 
 it not for the earthy matter, bones would be exceedingly flexible, as 
 may be shown in a bone deprived of its calcareous matter by acid. 
 Hence old bones, in which the animal matter is less abundant, as 
 well as perhaps defective in quality, are more brittle than young 
 ones, and old persons are more liable to fractures. But in the young, 
 in whom the organic processes are active, and whose animal matter 
 is fully adequate in quantity and quality to the wants of the system, 
 the bones possess their due degree of flexibility, and hence in them 
 fractures are less frequent; the cohesive force of the bones being 
 sometimes so considerable, that they will bend to a great degree 
 before yielding. 
 
104 ORGANS OF LOCOMOTION. 
 
 The following table from Schreger illustrates the relative propor- 
 tions of the two constituents, at three periods of life, in 100 parts of 
 bone: 
 
 Child. Adult. Old. 
 
 Animal matter 47-20 20-18 12-2 
 
 Earthy matter 48-48 74-84 84-1 
 
 Or it may be stated in general terms, that in the child the earthy 
 matter forms nearly one-half the weight of the bone, in the adult it 
 is equal to four-fifths, and in the old subject to seven-eighths; a con- 
 clusion agreeing in the main with that drawn from the analyses of 
 Davy, Bostock, Hatchett, and others. 
 
 It had long been known that certain bones of the body contained 
 these constituents in other proportions than those named ; for ex- 
 ample, the petrous portion of the temporal bone had been shown by 
 Davy to owe its stony hardness to a large proportion of earthy matter* 
 But Dr. G. 0. Rees has lately pointed out some interesting particulars 
 as to the relative proportions of these elements in the composition of 
 different bones. 
 
 The long bones of the extremities have, according to Dr. Rees's 
 analysis, more earthy matter than the bones of the trunk. The 
 bones of the upper extremity have a larger proportion of the same 
 material than those of the corresponding bones in the lower; the 
 humerus has more than the radius and ulna; the femur more than 
 the tibia and fibula; while the bones of the fore-arm, as well as 
 those of the leg, are respectively alike in constitution. The verte- 
 brae, ribs, and clavicles are similarly constituted. The ilium has 
 more earthy matter than the scapula or sternum; the bones of the 
 head have more of this material than those of the trunk. 
 
 In the fcEtus the same law prevails as regards the relative quantity 
 of the earthy matter, excepting that the long bones, and the cranial 
 bones, do not contain the excess of earthy matter which characterizes 
 them in the adult. 
 
 The diseased state, called Rickets, so common in the children of 
 scrofulous parents, and in the ill-nourished ones of the lower orders, 
 consists in a deficient deposit of earthy matter; the animal matter 
 being probably of an unhealthy quality. In this disease the bones 
 are so flexible, that they bend under the weight that they may be 
 called on to support, or under the action of the muscles. The 
 lower extremities exhibit deformity first, and to the greatest degree, 
 and the direction in which they become bent is evidently influenced 
 by the superimposed weight; the bend almost always appears as an 
 aggravation or the natural curves of the bones. The rickety femur 
 has always its convexity directed forwards: the tibia is convex for- 
 wards and outwards, and the fibula follows the same direction. When 
 the nutritive powers of the system are fully restored, the deposition 
 of earth goes on in its healthy proportion, the animal matter becomes 
 healthy, and the bones acquire their due degree of strength and hard- 
 ness. In the tibia of a rickety child. Dr. Davy found, in 100 parts, 
 74 parts animal matter, and 26 earthy; and Dr. Bostock found in the 
 vertebra of a similar subject 79-75 animal, and 20-25 earthy. 
 
BONE. 105 
 
 The brittleness of the bones in old age is due to an opposite cause^ 
 namely, the defective deposit of animal matter, so as to give to the 
 earthy matter the undue preponderance already specified. But this 
 state cannot be looked upon as morbid ; it is the natural result of the 
 feeble condition of the powers of nutrition, -which ensues in the ad* 
 vance of years ; and it will vary^ in different individuals, according 
 to the original strength of constitution of each, and according to the 
 freedom from exposure to debilitating influences. 
 
 That state of bone which accompanies malignant disease (cancer, 
 or- fungoid disease) in adults or old persons, and which some patho- 
 logists have designated mollities ossium, results from the dissemination 
 of cancerous matter through the system. In this disease the whole 
 nutritive process of bones seems tainted ; the animal part is not so 
 much deficient in quantity, as bad in quality; the physical, as well as 
 the vital properties of the bone are completely deranged ; the osseous 
 texture has lost its cohesive power. Hence these bones often break 
 on the application of the slightest force, or on the feeblest exercise 
 of the muscles. They are soft, too, in the recent state ; the knife will 
 sometimes penetrate them ; and they are often pervaded by a con- 
 siderable quantity of oil. 
 
 Bones possess a remarkable power of resisting decomposition. 
 Even the animal part seems to acquire this power through its combi- 
 nation with the earthy. This is manifest from analyzing bones which 
 have been long kept, or fossil bones. Cuvier states that the latter 
 bones exhibit a considerable cartilaginous portion ; and Bichat found 
 that clavicles, which had been exposed for ten years to the wind and 
 rain at the cemetery of Clamart, presented, under the action of acid, 
 an abundant cartilaginous parenchyma. In an old Roman frontal 
 bone, dug up from Pompeii, Dr. Davy found 35'5 animal parts, and 
 64-5 earthy ; and in a tooth of the mammoth, 30-5 animal, and 69'5 
 earthy. 
 
 The animal part of bone consists of cartilage, with vessels, medul- 
 lary membrane, and fat. The cartilage, is readily convertible into 
 gelatine, according to Berzelius, after three hours' boiling ; and, when 
 this has been removed, there remain only four grains out of 100, 
 which may be considered to have been composed of blood-vessels. 
 
 The earthy part of bone consists of phosphate and carbonate of 
 lime, with a small quantity of phosphate and carbonate of magnesia. 
 The phosphate of lime forms the principal portion of the earthy 
 part; in 100 parts of bone Berzelius found 51-04 of this salt. It 
 was discovered by Gahn, and the discovery announced by Scheele, 
 •"that bone-earth consisted of " phosphoric acid and lime." Accord- 
 ing to Berzelius, the phosphate consists of eight atoms of lime and 
 three atoms of phosphoric acid ; but Mitscherlich regards it as com- 
 posed of three atoms of lime with one of phosphoric acid (a tribasic 
 salt). It may be formed artificially by dropping chloride of calcium 
 into a solution of phosphate of soda. It appears as a gelatinous 
 precipitate, which does not crystalize, and is readily soluble in acids. 
 
 The existence of fluoride of calcium in bone was announced many 
 years ago by Berzelius ; but the observations of our friend, Dr. G. 
 
106 
 
 ORGANS OF LOCOMOTION. 
 
 0. Rees, throw considerable doubt upon this assertion. Dr. Rees 
 attributes the action of the supposed fluoric acid upon glass to phos- 
 phoric acid in combination with water, which, if heated on glass of 
 inferior quality until it volatilizes, will act upon it with considerable 
 energy. The proportion of carbonate of lime to the phosphate is 
 small. According to Berzelius, there are 11-30 parts in 100 of bone. 
 We subjoin the following process, by which the qualitative analysis 
 of bone may be readily effected : 
 
 In order to insulate the animal matter, digest the bone for some 
 days in muriatic acid diluted with about thrice its bulk of water ; 
 the earthy constituents will thus be gradually removed, leaving a 
 semi-transparent cartilaginous tissue behind. 
 
 The earthy matters are best examined by treating a portion of 
 burnt bone with nitric acid, diluted with from four to six times its 
 bulk of water; brisk effervescence ensues, proving the presence of 
 carbonic acid. Filter the acid liquid afte* diluting it with water, and 
 add solution of caustic ammonia as long as the precipitate at first 
 formed continues to be redissolved by agitation ; then add solution 
 of acetate of lead till it no longer occasions any precipitate. The 
 dense white precipitate thus produced consists of phosphate of lead, 
 which melts before the blow-pipe, and on cooling assumes its charac- 
 teristic crystaline structure. 
 
 Through the solution, filtered from the phosphate of lead, pass a 
 stream of sulphuretted hydrogen to remove the excess of lead ; warm 
 the liquid, to drive off the superfluous gas, and filter: then neutralize 
 
 by ammonia, and add oxalate 
 ^'g- 18. of ammonia as long as any 
 
 precipitate occurs; abundance 
 of oxalate of lime will fall as 
 a white powder. 
 
 Evaporate the filtered liquid 
 to dryness; ignite the residue, 
 and wash with hot water ; the 
 magnesia will be left behind 
 in a pure form. 
 
 In examining a section of 
 almost any bone, we observe 
 two varieties of osseous sub- 
 stance : the one dense, firm, 
 compact, always situated on 
 the exterio'r of the bone, 
 either as a thin layer, or as a' 
 dgnse thick structure pos- 
 sessed of great strength ; the 
 other loose, reticular, spongy, 
 enclosing spaces or cells, 
 which communicate freely 
 with each other, and which, 
 being called cancelli, give to 
 cancellated. These cells are 
 
 Vertical section of Ihe upper end of Ihe Femur, show- 
 ing tlie cancellated and compact tissues. 
 
 this kind of osseous tissue the name 
 
BONE. 107 
 
 formed by an interlacement of ' numerous bony fibres and laminse, 
 ■which although to a superficial observation exhibiting an indefinite 
 arrangement, have nevertheless, in those bones which have to support 
 weight, a more or less perpendicular direction. The cancellated 
 structure of bone is always situated in its interior, enclosed and pro- 
 tected by the compact tissue. 
 
 The relative situation of these varieties may be well seen in a 
 vertical section of one of the long bones (fig. 18). At the extremities, 
 the cancellated texture is accumulated, invested by a thin lamella of 
 compact tissue, giving expansion and lightness to those parts of the 
 bone. In the intermediate portion, or shaft, the compact tissue is 
 highly developed, affording great strength in the situation where that 
 quality is the most needed. 
 
 The compact external surface of bone (except on its articular as- 
 pects) is covered by a firm tough membrane, termed the periosteum, 
 which, like the perichondrium investing cartilage, consists of white 
 fibrous tissue, densely interwoven in all directions. The cancelli are 
 filled with fat, or medulla, the marrow of bone. They are lined by a 
 delicate membrane, called the medullary membrane, which serves 
 to support the fat. In the shaft of the long bones the medulla 
 is contained not in ordinary cells, but in one great canal, which 
 occupies the centre of the shaft, the medullary canal. Here the 
 medullary membrane lines the compact tissue that forms the wall of 
 the cavity. 
 
 Both the periosteum and the medullary membrane adhere intir 
 mately to the bone. Both are abundantly supplied with blood- 
 vessels, which, after ramifying upon them, send numerous branches 
 into the bone. These membranes are of great importance to the 
 nutrition of the bone, inasmuch as they support its nutrient vessels ; 
 and, if either of them be destroyed to ahy great extent, the part in 
 contact with them necessarily perishes : and they not only cover 
 the outer and inner surfaces of the bone, but also send processes, 
 along with the vessels, into minute canals traversing the compact 
 tissue, and are, through the medium of these, rendered continuous 
 with one another. 
 
 The great variety of uses to which the bones are applied in the 
 construction of the skeleton, occasions much difference of shape as 
 well as of size. The following arrangement comprehends all these 
 varieties, and is that commonly adopted. We classify them as, 1, 
 Long bones ; 2, Short ; 3, Flat ; 4, Irregular. 
 
 The long bones form the principal levers of the body ; their 
 length greatly exceeds their breadth and thickness. In descriptive 
 anatomy, a long bone is divided into a shaft, or central part, and 
 two extremities. The shaft is never perfectly straight, it is more or 
 less curved, as in the femur ; and has always an appearance as if, 
 while yet in a soft and flexible condition, it had received a twist, 
 and its extremities had been turned in opposite directions. This is 
 very manifest in the femur and humerus ; more especially in the lat- 
 ter, where the groove, in which the radial nerve runs, is just what 
 
108 ORGANS OF LOCOMOTION. 
 
 one mi^t fancifully suppose to have resulted from such a cause as 
 that above named. 
 
 The shaft is never perfectly cylindrical ; although in some bones 
 it approaches that form, in others it is prismatic. It is hollow, as 
 already mentioned, and contains medulla. This arrangement has the 
 advantage of making the bone very much lighter than it would have 
 been if solid ; while it is attended with no sacrifice of strength, since 
 the central osseous substance is that -which contributes least to its 
 power of resistance. 
 
 The strength of the shaft is amply provided for by its being com- 
 posed of compact tissue, of thickness proportionate to the length of 
 the bone, and the bore of the medullary canal. In the curved bones, 
 additional strength is obtained in the position ^vhere the bone would 
 be most likely to yield, by increased thickness and density along its 
 concavity. Of this provision a good example will be found in the 
 spine of the femur, — a ridge of extremely dense bone, placed along 
 its posterior concave surface. In the bent bones of rickety subjects 
 which have become fully ossified, the compact tissue on the concavity 
 of the bend acquires an enormous development. 
 
 At the extremities of the long bones the medullary canal ceases ; 
 the osseous tissue expands ; and the cancellated texture takes the 
 place of the compact substance of the shaft, and forms the whole 
 thickness of these portions of the bone, the medulla penetrating i(ito 
 its cells. Here great strength is not required, but surface is needed_ 
 for the articulation of the bones together, and for affording attachment 
 toligaments and tendons. The cancellated tissue is admirably adapted 
 to attain this object ; for, while by the looseness of its texture it readily 
 affords an extent of surface, its lightness is such, that even a consider- 
 able bulk of it does not materially affect the weight of the bone. 
 The surface of this texture is covered with a thin cortex of compact 
 tissue, which is perforated by innumerable orifices for the transmission 
 of vessels. 
 
 The long bones are the great levers of the extremities; as the bones 
 of the thigh and leg, arm and fore-arm. Among the bones of the 
 hand and foot are certain ones which have all the anatomical charac- 
 ters of the long bones, except that of length ; they, may, therefore, be 
 grouped together in a class under the name of short bones. These 
 are, the metacarpal and metatarsal bones, and the phalanges of the 
 fingers and toes. 
 
 The flat bones are remarkable for their slight thickness ; they are 
 composed of two thin layers of compact tissue, enclosing a layer of 
 cancellated texture of variable thickness. Examples of this class 
 of bone, may be found in most of those enclosing the great cavities 
 of the body ; as the bones of the cranium, the ribs, the scapula, the 
 OS innominatum, all of which will be found to possess the same essen- 
 tial characters. 
 
 The cranial bones present one or two peculiarities which demand 
 a special notice. The layers of compact tissue in them are fami- 
 liarly known as the tables of the skull : the outer one is stouter and 
 tougher ; the inner one denser and much thinner, and therefore more 
 
BONE. 109 
 
 brittle. The Intervening structure is called the diploe ; in some places 
 it is absent, leaving a vacant space produced by the separation of the 
 tables, and which communicates with the external air, as in the frontal 
 sinuses : the diploe is generally a very fine cancellated texture ; but, 
 in the mastoid process of the temporal bone, it is of a much looser 
 kind ; its cancelli are larger, and instead of being occupied by medulla, 
 as elsewhere, they communicate with the cavity of the tympanum, 
 and are therefore always filled with air. The diploe of the cranial 
 bones in birds is everywhere devoid of medulla, and occupied by air, 
 which gains access to it from the tympanum. 
 
 A fourth group of bones consists of those, which seem to combine 
 many of the offices and forms of the three preceding ones with cer- 
 tain characters proper to themselves. They exhibit much irregularity 
 of shape and size; and, on this account, are called irregular bones. 
 The vertebrae, the tarsal and carpal bones, certain bones of the head 
 and face, belong to this group. Lightness, vyith extent of surface, is 
 their principal character. They are composed mainly of cancellated 
 texture, covered by a layer of compact, and here and there a portion 
 of compact tissue, for the purpose of affording a firm bond of connec- 
 tion of some process to the main part of the bone; as the pedicles, 
 uniting the laminae to the bodies of the vertebree. 
 
 In examining the surfaces of these different groups of bones, we 
 are struck with the variety of projections or eminences, and of de- 
 pressions, which are found upon thern. These are of two kinds ; 
 articular, and non-articular. The former are destined for the forma- 
 tion of joints : as the head of the thigh-bone, an articular eminence ; 
 and the acetabulum, an articular depression. 
 
 The non-articular eminences chiefly serve as points of insertion for 
 ligaments and tendons, and exhibit a great diversity of shapes, so that 
 anatomists designate them as tuberosities, tubercles, spines, cristee, 
 &c. The non-articular depressions serve a similar purpose, and are 
 equally various in form, being described as fossae, cells, furrows, 
 grooves, fissures, pulleys, &c. 
 
 With reference to these eminences and depressions, it may be 
 observed that they are well marked in proportion to the muscularity 
 of the subject. In the female, for instance, they are less distinct 
 than in the male ; in the powerfully muscular man they are at the 
 maximum of development. As Sir Charles Bell has remarked, a 
 person of feeble texture and indolent habits has the bone smooth, 
 thin, and light ; while with the powerful muscular frame is combined 
 a dense and perfect texture of bone, where every spine and tubercle 
 are well developed. And thus the inert and mechanical provisions 
 of the bone always bear relation to the muscular power of the limb ; 
 and exercise is as necessary to the perfect constitution of a hone, 
 as it is to the perfection of muscle. It is an interesting fact, that if 
 a limb be disused, from paralysis, the bones waste as well as the 
 muscles. 
 
 Of the Vessels of Bone. — We now prpceed to inquire into the 
 manner in which the nutrition of bone is provided for. A texture 
 containing so much animal matter, and needing a constant supply of 
 
110 
 
 ORGANS OF LOCOMOTION. 
 
 inorganic material likewise, must necessarily be largely supplied with 
 blood, the common source of the materials of all the tissues. 
 
 The blood-vessels of bone are very numerous, as may be satis- 
 factorily seen on examining a weil-injected specimen. The arteries 
 are in great part continued from those of the periosteum : those which 
 penetrate the cancellated texture of the extremities of the long bones 
 are very large, and ramify freely among the cancelli. 
 
 The membrane of the medulla which is contained in the shaft, 
 receives its blood from a special artery that pierces the compact tissue 
 through a distinct canal, known as that for the nutritious artery. 
 This vessel divides into two immediately on entering the medullary 
 canal; of these, one ascends, the other descends, and both break up 
 into a capillary network, anastomosing with the plexuses in the ex- 
 tremities of the bone, derived from the arteries that penetrate there. 
 From the copious vascular network thus formed within the bone, the 
 innermost part of the compact substance of the shaft receives its 
 blood-vessels. 
 
 In the compact tissue the arteries pass into very narrow capillary 
 canals, most of which are invisible to the naked eye. In carefully 
 raising the periosteum from a bone that has been subjected to a little 
 maceration, the vessels may be seen in great numbers passing from 
 that membrane into the osseous texture, and many of the larger ones 
 seem to be surrounded by a sheath derived from the periosteum. 
 Similar sheaths may be seen surrounding the vessels of the cancel- 
 lated texture. 
 
 The vascular canals of the compact tissue are styled Haversian, after 
 their discoverer, Clopton Havers. They are 
 disseminated pretty uniformly through the tis- 
 sue, and inosculate everywhere with one ano- 
 ther. In the long and short bones they follow 
 the same general direction as the axis of the 
 bone, and are joined at intervals by cross 
 branches. The meshes thus formed are more 
 or less oblong (fig. 19). The deeper ones 
 open into the contiguous cancelli, with the 
 cavities of which they ar.e continuous. 
 
 The arteries and veins of bone usually 
 occupy distinct Haversian canals. Of these 
 the venous are the larger, and commonly pre- 
 sent, at irregular intervals, and especially 
 where two or more branches meet, pouch- 
 like dilatations, calculated to serve as reser- 
 voirs for the blood, and to delay its escape 
 from the tissue. In many of the large bones, 
 particularly in the fat and irregular ones, the 
 veins are exceedingly capacious, and occupy 
 a series of tortuous canals of remarkable size 
 and very characteristic appearance. These 
 are well described by Bresehet in his elabo- 
 rate work on the venous system ; from which 
 
 Haversian canals, seen on a 
 longitudinal seclion of Ihe com- 
 pact tissue of llie sliaft of one of 
 the long lioiiep :— 1. Arterial canal. 
 2. Venoijp ciinal. 3. Dilatation of 
 Huothcr venous canal. 
 
VESSELS OF BONE. Ill 
 
 the accompanying figure (fig. 20) is taken. ^ These canals run, for the 
 most part, in the cancellated structure of the bones, and are lined by 
 a more or less complete layer 
 
 of compact tissue, which itself ^'S- ^*'' 
 
 often contains minute Haver- 
 sian canals. The veins they 
 contain discharge themselves 
 separately on the surface. 
 
 The Haversian canals vary 
 in diameter from ^jVo to the 
 ,2-Jo of and inch, or more, the 
 average being about -g^. 
 Their ordinary distance from 
 one another is about -rio- of sn 
 inch. They may be regarded 
 as involutions of the surface 
 of the bone for the purpose of 
 allowing vessels to come into 
 
 .mntnni- ■.„;*U U ;„ „„»««„_ Venous canals in the dipIoB of the cranium.— Afler 
 
 contact with it in greater sreschet. 
 abundance. It is evident that 
 
 the cancelli, and even the great medullary canal itself, are likewise 
 in volutions, of the osseous surface, though for a partly different end. 
 These larger and more irregular cavities in bone may be considered 
 as a dilated form of Haversian canals. They contain vessels not only 
 for the nutrition of the thin osseous material forming their walls, but 
 also for the supply of the fat enclosed within them. 
 
 Thus the true osseous substance may be described as lying in the 
 interstices of a vascular membrane, or of a network of blood-vessels. 
 The most interesting points in the minute anatomy of bone relate to 
 the mode in which nutrition is provided for in those parts not in im- 
 mediate contact with the blood-vessels. We have already seen that 
 considerable masses of cartilage derive their nutriment from vessels 
 placed on their exterior only, apparently by a kind of imbibition, per- 
 haps aided by the presence of the nucleated cells, and by a more or 
 less fibrous texture : but bone, which is of a far harder and denser 
 nature, is unable to imbibe its nourishment so easily. Hence its 
 surface is greatly augmented by the arrangements already detailed ; 
 and, in addition to this, the osseous tissue itself is provided with a 
 special system of microscopic cavities and canaliculi, or pores, by 
 which its recesses may be irrigated, to a degree of minuteness greatly 
 exceeding what could have been effected by blood-vessels alone, 
 consistently with the compactness and density required in the tissue. 
 The study of this delicate apparatus will now demand attention, but 
 a few words must be premised on the ultimate structure of the osseous 
 
 It appears from the researches of Mr. Tomes, about to be published 
 in the Cyclopaedia of Anatomy, that the ultimate structure of the 
 osseous tissue is granular. The granules of bone are often very dis- 
 tinctly visible, without any artificial preparation, in the substance of 
 the delicate spiculs of the cancelli, viewed with a high power, and 
 
112 
 
 ORGANS OF LOCOMOTION. 
 
 in various sections of all forms of bone. They may be generally 
 obtained in calcined bone, either by bruising a fragment of it, or by 
 steeping it in dilute muriatic acid ; they may also be 
 made very evident by prolonged boiling in a Papin's 
 digester. Those represented in fig. 21 were obtained 
 in the latter mode. The granules vary in size from 
 6^Vo- to TT^erir of an inch. In shape they are oval or 
 oblong, and often angular. They cohere irmly toge- 
 ther, possibly by the medium of some second sub- 
 boM''Tsoi1itld''a"d''i°f stance. In some few instances, Mr. Tomes has met 
 small masses, from the with a verv minute nctwork, which seems adapted 
 
 Femur.— (From a pre- . . ,? • •, • . ..• i_ x iu ■ i_ -j 
 
 parationofMr.Tomes.) to receivc thcm in its intcrstices ; but this he considers 
 Magnified 320 diame- ^^ ^^^^j^g Confirmation. A frequent appearance of 
 the granular texture is well represented in fig. 22. 
 
 Where bone exists 
 I'ig- 22. naturally in an exceed- 
 
 ingly attenuated formj 
 it may consist of a mere 
 aggregation of these 
 granules, unpenetrated 
 by any perceptible 
 pores. This constitutes 
 the simplest form under 
 which the tissue can 
 present itself. 
 
 But all the osseous 
 tissue with which the 
 human anatomist is con- 
 cerned is of such bulk 
 as to contain the series 
 of pores and cavities 
 already alluded to for 
 the conveyance of fluid from and to its 
 vascular surface. These pores always 
 advance into the bone from open orifices 
 on its surface. They soon arrange them- 
 selves in sets, each of which, after anas- 
 tomosing with neighbouring ones, dis- 
 charges itself into a small cavity or lacuna, 
 in which its individual pores coalesce. 
 From the sides of this lacuna other pores 
 pass off to similar cavities in the vicinity^ 
 and others proceed from its opposite sur- 
 face to penetrate still deeper into the 
 tissue. These pour themselves into ano- 
 ther lacuna, or divide themselves between 
 two or three, which are connected in lik'e 
 manner by lateral channels. From these 
 again pass others, which pursue an onward 
 course from the surface ; and so on, until 
 
 Two lacunre of osseous tissue, seen on their surfaeee. showing 
 the disposition of their pores. The granular aspect of the tissue 
 both oil their walls and around them is well represeined.— Mag- 
 nified 1200 diameters. Drawn from a preparation of the caneelli 
 of the Femur made by Mr. Tomes. 
 
 Fiff. 23. 
 
 Transverse section of a part of the 
 bone surrounding an Haversian canal, 
 showing the pores commencing at the 
 surface, a, anastomosing and passing 
 from cavity to cavity — Magnified 
 about 300 diameters. From a prepa- 
 ration made by Mr. Tomes^ 
 
LACUNA OF BONE. 
 
 113 
 
 the whole substance of the bone is perforated by them. The pores 
 from the further side of the extreme lacunaa either open on the surface 
 of the bone which they may now have reached, or else take a re- 
 curved direction back into the tissue. 
 
 When this beautiful system of microscopic pores and cavities was 
 first seen, it was not recognized as such. The lacunae were imagined 
 to be solid corpuscles (a name still commonly applied to them), and 
 the lines radiating from them to be branching threads of the earthy 
 constituent of bone. They may be proved in many ways, however, 
 to be real excavations in the tissue. With a sufficiently high power 
 their opposite walls can be distinctly seen, as well as their hollow 
 interior; but the most conclusive evidence lies in our being able to 
 fill them with fluid. If a dry section of bone, in which they are very 
 apparent, be moistened with oil of turpentine while in the field of the 
 microscope, the course of this penetrating material can be witnessed, 
 as it advances into the tissue. It is seen to run quickly along the 
 pores from the Haversian canals, and from the surface of the speci- 
 men., where they have been cut across. Having entered a lacuna, it 
 suddenly extends along the pores radiating from it, and, through 
 these, reaches other lacunEe ; rendering the tissue transparent by fill- 
 ing up its vacuities. In parts where air has previously occupied 
 the vacant spaces, and the turpentine cannot displace it, the charac- 
 teristic appearance of minute bubbles is often present. 
 
 The lacuna of osseous tissue, if examined extensively in the ver- 
 tebrate class, are found of very various shapes : sometimes scarcely 
 to be distinguished from the pores, of which they are simple fusiform 
 dilatations ; at other times large and bulky, and forming the point of 
 junction of a great multitude of pores. Mr. Tomes has allowed us 
 
 Fig. 24. 
 
 
 
 •m \ ^ 
 
 S^j,^^^*^ 
 
 Form of various Lacunse, and their pores: — a. Simple irregular cavities, Tvithout pores; from an 
 ossification of ihe pleura; 6, from healthy bone of the human subject, h' . One of the o.uter lacunas of 
 an Haversian system, with the pores all betiding down towards the H. canal, c. Other forms from 
 human bone, showing the laieral connecting pores. 
 
 d. From the Boa. External lacunEe of an H. system, with unusually large pores dipping towards " 
 the vascular surface, d' . Cavity intermediate between a lacuna and a pore, e, Another variety from 
 the same reptile.— From Mr. Tomes. 
 
1 14 ORGANS OF LOCOMOTION. 
 
 to represent the principal varieties which he has met with in the 
 human subject; and some remarkable ones from the lower animals 
 are shown (fig. 24) from the same source. In the true dental sub- 
 stance, which is a kind of bone, the lacunee are almost entirely defi- 
 cient, and. the pores attain a very singular development, which will 
 be described in a subsequent chapter. 
 
 But though varieties are occasionally met with, yet, in the true 
 bone of man and the mammalia, the lacunae possess a very constant 
 form ; being somewhat oval, and more or less flattened on their 
 opposite surfaces. The two surfaces look respectively to and from 
 the nearest surface of the tissue, and meet in a thin edge. As pores 
 pass off equally from all parts of the lacunae, it follows that by far 
 the greater number pass to or from the surface of the bone ; an 
 arrangement admirably adapted for the transmission of the nutritious 
 fluids. The pores passing from the edge principally serve to connect 
 together those lacunae that lie at nearly the same distance from the 
 surface. In fig. 22, the lacunae are seen on their surface ; in fig. 23, 
 on their upper edge. 
 
 The lacunae have an average length of TaVo- of ^n inch, and they 
 are usually about half as wide, and one-third as thick. The diameter 
 of the pores is from job^ott to T^hvs of an inch. 
 
 The osseous tissue, thus studded by thousands of flattened lacunae, 
 which lie for the most part in planes parallel to the surface, has a 
 decided disposition to split up into laminis, following the same direc- 
 tion. This is more evident in the bones of old persons, and may be 
 generally promoted by maceration in dilute acid. It is most apparent 
 where the mass of material between two vascular surfaces is great, 
 and the series of lacunae numerous. It is probable that this lamellated 
 structure depends in part on the mode of development and growth of 
 this tissue, and it perhaps contributes to the perfection of the nutritive 
 process within it. 
 
 It will now be easy to comprehend the apparently complex arrange- 
 ment of the osseous tissue in the interior of bones. Let us take, for 
 example, one of the long bones. The entire vascular surface con- 
 sists of, 1, the outer surface, covered by the periosteum ; 2, the inner 
 surface, lined by the membrane of the medullary cavity, and of the 
 cancelli ; 3, the Haversian surface, or that forming the canals of the 
 compact tissue, and having in contact with it the vascular network 
 that occupies them, and which has been already described. These 
 involutions of the surface are so arranged that no part of the osseous 
 tissue is in general at a greater distance than -j-ls- of an inch from the 
 vessels that ramify upon them. 
 
 There is a layer of tissue on the exterior of the bone deriving its 
 nourishment from the periosteum, and which may be called \\ie peri- 
 osteal layer. The lacunae of this layer all face that surface, and the 
 pores of the superficial ones open upon it. There is another layer, 
 forming the immediate wall of the medullary cavity, and termed the 
 medullary layer. Its lacunae, in like manner, face this cavity ; and 
 the pores of the inner ones open upon it. This layer becomes 
 variously folded to form the plates and fibres of the cancelli ; and all 
 
LACUNA OF BONE. 115 
 
 the lacunae of these face these irregular cavities, and their pores open 
 into them. The Haversian surface, too, being an involution of the 
 outer and inner surfaces, and serving to connect them, is, in fact, 
 formed b,y an involution of the periosteal and medullary layers, and 
 unites these with one another. Where a vessel enters the compact 
 tissue from the exterior, it carries with it a sheath of bone from the 
 periosteal layer. The lacunae of this osseous sheath, instead of being 
 turned outwards, like those of the periosteal layer, preserve their 
 relation to the vascular surface to which they pertain, and face inwards 
 towards the vessel. Wherever the vessel penetrates, whatever direc- 
 tion it takes', and however it branches, it is everywhere accompanied 
 by this sheath from the periosteal layer;, or by offsets from it ; and, 
 when it enters the medullary canal, its sheath expands into the medul- 
 lary layer. 
 
 Tlie vessels of the compact tissue are so close together that the 
 osseous sheaths respectively surrounding them come into contact and 
 unite ; and thus all the space between the outer and the inner surface 
 of the compact tissue is filled up: thus, in a word, the compact tissue 
 is constructed. 
 
 As the vessels of the compact tissue take a longitudinal direction, 
 a transverse section of the bone (fig. 25) will 
 appear pierced by numerous holes which are the Fig- 25. 
 
 Haversian canals cut across. Each hole appears 
 
 as the centre of a roundish area, which is the ./—-~ " 
 
 section of an involuted periosteal layer now | 
 become a vertical rod, containing a vessel in its * ' 
 
 axis. The Haversian canals vary considerably 
 in size, and do not maintain a very close relation i 
 
 to the thickness of their respective osseous walls. ■■* .'J 
 
 They are frequently eccentric, owing to their wall ^ 
 
 bulging more in one direction than another, to fit ' ^^ ~^ , I 
 
 in between others in the vicinity : for though the f^ ' V' 
 
 rods of bone, containing the vessels, affect the ' ' / y 
 
 cylindrical form, they often present an oval, or ' ' /^ » 
 even a very irregular, figure, on a section ; their ^ \_ 
 
 close package having modified their form. The 
 
 ' 1 ° 1 I 11 1 1 11 Transverse section of the 
 
 periosteal and medullary layers are also well compact tissue of a long 
 seen on the same section, the latter curving in- ^S^lThlSui: 
 
 wards to constitute the walls of the Cancelli. lary)ayer,andtlieinteriHe- 
 , • 1 1 • 1 dia's IrJaversian systems of 
 
 Ihese two layers are or very irregular thick- lameiias.each perforated by 
 ness, as the Haversian rods encroach on them about le'diameters."^"' ^ 
 unequally (fig. 25). 
 
 On a further examination of such a section, with a sufficient mag- 
 nifying power, we observe the lacunae of the periosteal and medul- 
 lary layers facing those surfaces, and their pores opening upon them ; 
 while the lacunae of each Haversian layer all face the corresponding 
 canal, and their pores radiate from it (fig. 26, and the previous fig. 23, 
 more highly magnified). The lacunae facing the Haversian surface 
 are generally curved concentrically with it. They are more numerous, 
 and their pores more abundant, on the side where there is most osse- 
 
116 
 
 ORGANS OF LOCOMOTION. 
 
 Fig. 26. 
 
 left J^-?<- 
 
 
 ous substance, and where it consequently extends furthest from the 
 source of nutriment, the Haversian vessel. The reason of the want of 
 
 proportion between the width of the 
 canals, and the thickness of their re- 
 spective osseous walls, appears to be 
 this, that the larger canals transmit 
 vessels to other parts, besides con- 
 taining those which nourish their own 
 layer ; while some of them are, no 
 doubt, in a great measure channels 
 for veins. 
 
 The outer lacunae belonging to an 
 Haversian canal sometimes send out 
 pores to anastomose with those of 
 the neighbouring rods ; but "this 
 seems to happen chiefly where the 
 contiguous rods have just sprung 
 from a common stock. Occasionally, 
 also, lacunae of irregular shape (as 
 at s, fig. 26) ^ie in the interval of two 
 or more rods, add communicate with 
 lacunae of all of them; but, in general, 
 the outermost pores of the extreme 
 lacunae droop back on all sides (fig, 
 24, b', d), and re-enter the penulti- 
 mate series of their own rod. 
 Owing to this arrangement, there always appears a transparent 
 interval between contiguous rods; the pores and lacunae not existing 
 there to intercept the passage of the light (fig. 26). This is a re- 
 markable circumstance, and will be illustrated when we come to 
 speak of the development of bone. 
 
 The lamellated character of bone can be frequently distinguished 
 
 in the periosteal, medullary, 
 Fig- 27. and Haversian layers ; and, 
 
 in general, wherever several 
 successive series of lacunae 
 exist. The Haversian rods, 
 however, are remarkably 
 prone to exhibit this appear- 
 ance, especially under the con- 
 ditions previously mentioned 
 (p. 114). Their lamellae, how- 
 ever, are not concentric, as 
 commonly described. The 
 fissures which disclose them 
 are indeed concentric, but 
 they are always incomplete, 
 never extending completely 
 round the canal; so that the 
 lamellae run into one another at various points. This results from 
 
 \«?- 
 
 Part of the preparoiion represented in the 
 last figure, more highly mngnified : showing 
 the package of the Haversian systems, and 
 also the light spaces between neighhouriiig 
 ones. The system, a, appears to fill up an 
 interval between the others. The lacunEE are 
 seen facing the Haversian canals, and their 
 pores taking ageneral radiatin^direction. At 
 5, an irregular lacuna communtcates wUh the 
 pores of three contiguous systems. 
 
 Transverse section of the compact tissue of a tibia 
 from an aged subject, treated with acid; showing the 
 appearance of lamellEe surrounding the Haversian ca- 
 nals. Portions of several systems of lamellce are seen. 
 The appearance of the lacuniE, when theic pores are 
 filled with fluid, is also seen, as well a.-i the radiation 
 from the canals which then remains.— From Mr. Tomes. 
 
LAMELLA OF BONE. Il7 
 
 the fact, that the lacuns are not arranged in sets equidistant from the 
 centre, but are scattered, as it were, independently of one another, at 
 every possible variety of distance from the canal (figs. 23 and 27). 
 The larger concentric cracks, •which generally run through the lacunae, 
 seem to occur where two or three of these happen to lie nearly in the 
 same curve. Bone is very apt to crack in the interval between the 
 rods ; and each of these rods is really so distinct from those near it, 
 that it may be designated conveniently, for the purposes of descrip- 
 tion, as an Haversian system of lamella. 
 
 In a longitudinal section of the compact tissue of a long bone 
 (fig. 19, p. 110) the appearance of lamellation is generally less evi- 
 dent, except where a longitudinal canal happens to lie exactly in the 
 plane of section. When the Haversian canal is a little below the cut 
 surface, it is of course covered by some of its lamellae, the lacunse 
 of which directly over it are seen in face, while the lamellee dipping 
 in on either side, in their course round the canal, present the thin 
 edges of their lacunee to the observer. In the former part those pores 
 alone are seen that proceed from the edge of the lacunae ; while in the 
 latter those from both surfaces are seen, and of course appear much 
 more numerous. 
 
 The description now given of the intimate texture of the compact 
 tissue of long and short bones will apply, in all essential respects, to 
 every other example of the, compact tissue ; the chief difference con- 
 sisting in the direction taken by the Haversian canals, which is 
 irregular where the tissue follows an irregular course. In general, 
 however, the canals, with the Haversian rods forming their sheaths, 
 run in the direction in which the tissue needs the greatest strength. 
 Thus, in the long bones it is vertical ; and in those flat bones, which 
 have to support weight, it is also more or less vertical ; while in those 
 designed to sustain the action of forces of other kinds it is liable to 
 corresponding variety. 
 
 So beautifully mechanical is this disposition of the Haversian sys- 
 tems in the compact tissue, that we need not smile at the descriptions 
 of Gagliardi, who, with imperfect means of observation, appears to 
 have been at least faithful in his attempts to delineate nature. The 
 periosteal and medullary layers are true plates of bone, and the Ha- 
 versian systems are true fibres or pins, all connected with one another 
 by direct continuity of tissue, and most artfully arranged for the me- 
 chanical ends in view ; and we cannot sufficiently admire the skill 
 which has caused the means, employed for these ends, to conspire 
 with those which were indispensable for the due n'utrition of the 
 tissue. 
 
 In the ordinary cancellated texture, each cancellus must be re- 
 garded as a little medullary cavity, containing, as it does, medulla 
 and highly vascular medullary membrane. The plates of bone which 
 form its walls consist of lamella?, among which lacunee, with their 
 pores, are scattered ; and they sometimes, when thick, contain Haver- 
 sian canals. Usually, however, the pores of these laminae com- 
 municate directly with the cavity of the cancellus to which they 
 belong. 
 
118 
 
 ORGANS OF LOCOMOTION. 
 
 JYerves of Bone. — The skill of anatomists has hitherto failed to 
 demonstrate the presence of nerves in the interior of bones. Some 
 nerves pass through bones, but no supply strictly to the osseous mat- 
 ter has yet been proved. Yet there is little doubt that the vascular 
 surface of bones is furnished with nerves : the painfulness of many 
 affections of the periosteum, and of the medullary membrane seems 
 to place this beyond dispute. 
 
 Development. — In the earliest period at which the skeleton can be 
 detected among the other tissues of the embryo, it is found to consist 
 only of a congeries of cells, constituting the simplest form of car- 
 tilage. These increase in number and in density, and become sur- 
 rounded and held together by an intercellular substance in small 
 quantity ; thus forming the temporary cartilage, which subsequently 
 becomes converted into bone. The temporary cartilages have the 
 same general shape before as after their ossification ; and as this 
 process is slow, and not finally completed until adult age, they share 
 during a considerable period in the functions of the bony skeleton. 
 
 Until the completion of the process of ossification, the temporary 
 cartilages increase in bulk by an interstitial development of new 
 cells. A few vessels, also, shoot into them at an early period, 
 occupying small tortuous canals, which subsequently become obli- 
 terated. 
 
 Ossification commences in the interior of the cartilage at deter- 
 minate points, hence called points or centres of ossificalion. From 
 
 these the process advances into the 
 surrounding substance. The period 
 at which these points appear varies 
 much in the different bones, and in 
 different parts of them. The first is 
 the clavicle, in which the primitive 
 point appears during the fourth week ; 
 next is the lower jaw ; the ribs, too, 
 appear very early, and are completed 
 early ; next the femur, humerus, tibia, 
 and upper*jaw. The vertebrse and 
 pelvic bones are late, as well as those 
 of the tarsus and metatarsus. Some 
 bones do not begin to ossify till after 
 birth, as the patella. 
 
 In most bones ossification begins 
 at more than one point. Thus, in 
 the long bones (fig. 28) there is a 
 middle point, to form the future shaft ; 
 and one at each extremity, to form 
 the articular surface and eminences. 
 That in the shaft is the first to appear, 
 and the others succeed it at a variable 
 interval. The central part is termed 
 the diaphysis, and for a long period 
 after birth there remains a layer of 
 
 Fig. 28. 
 
 Vertical Bection of the knee-joint of an in- 
 fant; showing the points of OBSification in the 
 shaft and epiphysis of the femur and tibia, 
 ahd in the patella. A few vascular canals 
 are also seen in the cartilage. Natural size. 
 —From the Museum of King's College. 
 
DEVELOPMENT OF BONE. 
 
 119 
 
 ^^ 
 
 unosslfied cartilage between this and the epiphyses, as the extremities 
 
 are then styled. Processes of bone have usually their own centres of 
 
 ossification, and are termed epiphyses 
 
 until they are finally joined to the main Fig. 29. 
 
 part, after which they receive the name 
 
 of apophyses. 
 
 Ossification generally extends in the 
 direction that the future laminae and 
 Haversian rods are to assume, and 
 which corresponds in a great measure 
 to that in which it is designed that the 
 chief strength of the structure may lie. 
 Thus, in the bones composing the 
 
 vault of the cranium, there is always Soapula of a fetus at the seventh month; 
 
 d. 1 1 !• J* r- ji J showinglheprogressof ossification. Natu- 
 
 eClded radiation from the most ralslze. The light pans are epiphyses as 
 
 prominent part of the convexity of MngTcowfg™Lo7d™?'" ''' ''""™ "' 
 each. In the scapula this direction is 
 indicated by the lines of sha- 
 ding represented in figure Fig. 30. 
 29. The_ outline marks the 
 limits of the temporary car- 
 tilage, in which no other 
 points of bone have yet ap- 
 peared. 
 
 The minute history of the 
 process by which temporary 
 cartilage is converted into 
 bone, is of extreme interest. 
 Very good descriptions of it 
 have been given bySharpey, 
 Miescher, and others ; from 
 which, however, it will be 
 seen by the following ac- 
 count that we differ in some 
 important particulars. 
 
 The nucleated cells of 
 temporarycartilage are small, 
 and pretty uriiformly scat- 
 tered through a sparing, ho- 
 mogeneous intercellular sub- 
 
 Fig. 30. "Vertical section of cartilage 
 near the surface of ossification:— 1. Ordi- 
 nary appearance- of the temporary carti- 
 lage. 1'. Portion of the same more highly 
 rnagnified, 2. The cells heginning lo as- 
 sume the linear direction. 2'. Portion 
 more magnified. Opposite 3, the ossifica- 
 tion is extending in the intercellular 
 spaces, and the rows of cells are seeji 
 reeling in the cavities so formed ; the 
 nuclei being more separated than above. 
 3'. Portion of the same more highly mag- 
 nified.— From a new-born rabbit which had 
 been preserved in spirit. 
 
 
 
120 
 
 ORGANS OF LOCOMOTION. 
 
 Fig. 31. 
 
 stance. The nuclei are granular, and large compared with the cells, 
 which are distinguished from the surrounding substance principally 
 by their transparency around each nucleus (fig. 30, 1.1')- 
 
 In the vicinity of the point of ossification, (for example, in one of 
 the long bones,) a singular change is observed. The cells are seen 
 to be gradually arranging themselves in linear series, which run down, 
 as it were, towards the ossifying surface. The appearance they pre- 
 sent on a vertical section is represented in fig. .30. At first their 
 aggregation is irregiilar, and the series small (2. 2') ; but, nearer to 
 the surface of ossification, they form rows of twenty or thirty. These 
 rows are slightly undulated, and are separated from one another by 
 the intercellular substance. The cells composing them are closely 
 applied to one another, and compressed, so that even their nuclei 
 seem in many instances to touch : the nuclei themselves are also 
 flattened, and expanded laterally. 
 
 The lowest rows dip into, and rest in deep narrow cups of bone, 
 formed by the osseous transformation of the in- 
 tercellular substance between the rows. These 
 cups are seen by a vertical section in fig. 30, 3. 
 3', and by a transverse section on the level of 
 the ossifying surface in fig. 31. As ossification 
 advances between the rows, these cups are of 
 course converted into closed areolae of bon«, the 
 walls of which are laraelJiform, and at first ex- 
 tremely thin. 
 
 Immediately upon the ossifying .surface, the 
 nuclei, which were before closely compressed, 
 separate -considerably from one another by the 
 increase of material within the cells. The nuclei 
 likewise often enlarge and become more trans- 
 parent; a condition first pointed out to us by 
 Mr. Tomes, but not present in fig. 31, which 
 was taken from a preparation that had been im- 
 mersed in spirit. The changes now enumerated 
 may be conveniently consitlered to constitute the 
 first stage of the process, which extends only to 
 the ossification of the intercellular substance. In this stage there are 
 no blood-vessels directly concerned. 
 
 The areolae or minute cancelli, when first formed, contain only the 
 rows of cells which they have enclosed. It is remarkable, that, when 
 the cartilage is torn from the bone, it usually carries with'it one or 
 two layers of these cancelli, or a little more than is represented in 
 fig. 30. If the specimen be examined deeper in the bone, even at a 
 depth of xVor ^ of an inch, other appearances are met with. The 
 lamellae of bone enclosing the cancelli are no longer simply homoge- 
 neous or finely granular in texture, but have acquired more the aspect 
 of perfect bone. They are also thicker,' and include in their sub- 
 stance elongated oval spaces, which, excepting that they are of a 
 roughly ^granular nature, exactly resemble the lacuna of bone already 
 described. They are evidently the nuclei of the cells of the tempo- 
 
 Horizontal section at the 
 
 ossifying surface of a fcetal 
 bone ; showing the cups of 
 bone cut across, with the 
 granular nuclei of the in- 
 cluded cells, a New bone. 
 &. Nucleus. — From the rab- 
 bit. Taken from a drawing 
 of JMr. Tomes. 
 
OSSIFICATION. 
 
 121 
 
 rary cartiljge. they are scattered at pretty uniform distances apart, 
 and they all follow the direction of the lamella to which they belone; 
 {fig. 32, d.g). Thecur- 
 
 their 
 can 
 dis- 
 
 Fig. 33. 
 
 -Vertical section from the same specimen as df;. 30, but 
 deeper in th,e boqe ; showing the cancelli' with blastema and a 
 few eartilage-cells, and also tlie osseous laminEe containing 
 lacunae, similar to the nuclei of the cells:— d. Seen by a low 
 power, d!. portion of d more highly magnified. /. Blastema 
 around the cartilage-cells, e. Garttlage-cell apposed to the 
 wall, and its nitcleus ready to become similar to the other 
 lacunae, as g. 
 
 vilinear outline of 
 now ossified cells 
 often be partially 
 cerned (fig. 32, e). 
 
 Within the cancelli, 
 only a few cells can be 
 detected, these cavities 
 being chiefly occupied by 
 a quantity of new sub- 
 stance, consisting of gra- 
 nules, and resembling a 
 formative blastema or 
 basis, like that out of 
 which all the tissues are 
 evolved (fig. 32, /, and 
 fig. 33, i). The cells 
 that are met with are in apposition with the wall ; and sometimes (as 
 in fig. 32, e) one of them seems half ossified, and its nucleus about to 
 become a lacuna. The nuclei of these cells 
 have now always the same direction as the Fig- 33. 
 
 neighbouring lacunse. 
 
 In fig. 33, tiaken from a little deeper in the 
 bone, we have portions of three cancelli, i. i, i., 
 together with the osseous material, now of 
 considerable thickness, that intervenes be- 
 tween them. In the centre of this last is seen 
 a lamella, I, of a peculiar kind, containing no 
 lacunee, and quite distinct from the layers, h. 
 h., between which it lies. These consist of 
 nucleated cells, corresponding in size with 
 those of the temporary cartilage, and having 
 their nuclei disposed vertically, and of the 
 same shape and dimensions as the lacunae of 
 bone. They are still granular, however, and 
 no pores can be seen emerging from them. 
 The cells are united together, and the lines of 
 their junction have for the most part disap- 
 peared. The curvilinear border of each can 
 be still seen, however, at its union with the 
 central lamina, /. In the cancelli, i. i. i., the 
 granular blastema exists in great abundance. 
 
 It hence appears, that, after the ossification 
 of the intercellular substance, the rows of car- 
 tilage cells arrange themselves on the inner 
 surface of the newly formed cancelli, and 
 become ossified, with the exception of their 
 nuclei, which remain granular, and subse- 
 7 
 
 Another porlion from the 
 same specimen:— i i.i. Portion 
 of three cancelli, containing 
 blastema, and having between 
 ihem the wall of bone. The 
 interior of this wall,/, is finely 
 granular, and coniaing no lacu- 
 nre, being the lamina first forrp- 
 ed between the rows of cells in 
 the cartilage. Coating this on 
 both sides is a layer of bone in 
 which the form of the cartilage- 
 cells is still visible,'as well as 
 their nuclei formingthe lacunee. 
 On the wall of the cancelluR on 
 the right are seen two nuclei, 
 w^hich appear to be forming 
 there. This last is an appear- 
 ance often seen. 
 
122 ORGANS OF LOCOMOTION. 
 
 quently form the lacunae of bone ; and that a new substance, or 
 blastema, appears within the cancelli, from which, probably, vessels 
 are developed, and the future steps in the growth of the bone pro- 
 ceed. 
 
 The cancelli when first formed are closed cavities. At a subse- 
 quent period they appear to communicate, and thus to form the 
 cancelli and Haversian canals of perfect bone ; a complete net- 
 work of blood-vessels becoming developed within them at the same 
 time. 
 
 The subsequent progress of ossification seems to consist essentially 
 of a slow repetition, on the entire vascular surface of the bone, of 
 that process which has been now briefly described. It is probable 
 that new cartilage-cells are developed on that surface, and become 
 ossified in successive layers, their nuclei remaining to form the lacunee, 
 the uniform dispersion of which through bone is thus explained. The 
 cause of the lamination of bone parallel to its vascular surface, is also 
 thus illustrated. 
 
 The first appearance of pores is in the form of irregularities in the 
 margin of the lacunae. These increase with the consolidation of the 
 tissue, and are converted into branching tubules which communicate 
 with those adjacent. These pores must consequently be formed in 
 the ossified substance of the cartilage-cells. In our account of the 
 lacunae of perfect bone it was mentioned, that, for the most part, 
 those of contiguous Haversian systems do not communicate across 
 the narrow interval that separates the Haversian rods ; this interval 
 having in fact no pores. It results from what has just been said pf 
 the mode of deposition of new layers, that the primary osseous net- 
 work, formed in the intercellular substance of the temporary carti- 
 lage, must come to constitute the substance intervening between the 
 Haversian rods, the non-porosity of which is thus satisfactorily ac- 
 counted for, as well as the facility with which the rods themselves 
 may be made to separate from one another. As for the lacunae, their 
 originally granular interior seems to be gradually removed, so that 
 they become vacuities adapted for the conveyance of the nutritious 
 fluids through the compact material of the perfect bone. 
 
 Growth of Bone. — But it must not be imagined, that, when bone 
 is once deposited in a certain form, it thenceforward permanently 
 maintains its size and shape. Though a lamella be completely ossi- 
 fied, its particles are in constant course of change, during which the 
 most important and extensive alterations of size and figure take place 
 in a slow and gradual manner. Thus the layers first deposited on 
 the inner surface of the early cancelli are pushed out by the succeed- 
 ing ones, and also acquire a concomitant augmentation of mass ; and 
 as, in general terms, the number of lacunae in bone is proportioned 
 to its amount, the early layers most likely increase by a growth and 
 ossification of cells in their own substance, even for long after they 
 have been pushed away from the vascular surface, and supplanted by 
 the more recent ones. Thus, though bone grows chiefly by layers 
 formed in succession on its vascular surface, yet it also grows in an 
 interstitial manner after being originally deposited. It is in this way 
 
GROWTH OF BONE. 123' 
 
 only that we can explain the great expansion which the primary inter- 
 cellular osseous network must undergo, to form that which intervenes 
 between the Haversian systems. 
 
 Bone, when first formed, then, is disposed as an expanded surface, 
 variously and complexly involuted, and which soon becomes covered 
 with vessels. This is the foundation for its subsequent vascularity, 
 and is the source also of that active power" of internal growth, which • 
 has been long a theme of admiration with physiologists. 
 
 But the expansion of bone once deposited is limited. We before 
 observed that no part of the osseous tissue was at more than a certain 
 minute distance from the vascular surface ; and that, if it were so, 
 its nutrition could not be suitably carried on. Now, if more than a 
 certain number of laminae of new bone were laid doWn, the earlier 
 ones would be pushed too far from the supply of blood ; and hence 
 the limitation we have spoken of. But it is necessary for bone to 
 grow much more between the commencement of ossification and the ■ 
 adult age than this limitation appears to allow of; and here we come 
 upon an admirable provision to meet this apparent difficulty. 
 
 In the first place, a most important process of growth is continu- 
 ally going on in the cartilage, especially near the ossifying surface, 
 by the multiplication of the cells; and, in the latter situation, by the 
 increase in their dimensions, occasioning that separation of their 
 nuclei, already described (p. 119, and fig. 30, 3), In the long bones 
 this takes place chiefly in the longitudinal direction, which is that in ' 
 which growth is most active; and it continues till adult age. This 
 fact has been long ascertained, though its real purpose appears to 
 have been overlooked. Hales and Hunter both inserted metallic sub- 
 stances along the shaft of a growing bone, in a young animal, at a 
 certain distance apart ; and found after an interval of time, that the 
 distance between them remained the same, or nearly so, while the 
 extremities of the bone were much further apart : thus proving that 
 the principal growth had taken place near the extremities. 
 
 Secondly, bones increase in dimensions by an accession of new 
 osseous substance on their exterior ; this new substance consisting not 
 merely of new laminae, but of new systems of laminse, and of new 
 involutions of the vascular surface to form new Haversian canals, so 
 that the earlier systems of laminae are covered over by the more 
 recent ones. This has been best proved by the experiments with 
 madder. 
 
 It was ascertained accidentally by Belchier that the rubia tinc- 
 torum, or madder, mixed with the food of pigs, imparted its red ■ 
 colour to their bones ; and this circumstance has been ingeniously 
 taken advantage of .by several physiologists in the prosecution of 
 researches on the growth of bone.* Duhamel, Hunter, and many 
 
 * The colouring of bone by madder Results from an affinity of the colouring: prin- 
 ciple for the phosphate of lime. This opinion was distinctly broached by Haller 
 (El. Phys. t. viii. p. 329), and it was subsequently proved by Rutherford, who showed 
 it experimenlaliy. To an infusion of madder in distilled water add muriate of lime: 
 no change takes place. Then add phosphate of soda in solution. By double elec- 
 tive affinity, phosphate of lime and muriate of soda are formed. The phosphate is 
 insoluble, and subsides in union with the colouring matter as a crimson lake. When 
 
124 ORGANS OF LOCOMOTION. 
 
 others, have performed multiplied experiments of this kind. In the 
 Museum of King's College are some good preparations of bones so 
 acted upon. 
 
 It is found that, in very young animals, a single day suffices to 
 colour the entire skeleton, apparently in an uniform manner ; in these 
 there is no osseous material far from the vascular surface. But, if we 
 make a transverse section of one of the long bones so treated, we 
 observe the deepest, or even the only colour, to be really on the vascular 
 surface ; the Haversian canals are each encircled by a crimson ring. 
 This beautiful illustration is due, as far as we know, to Mr. Tomes, 
 who has long possessed some very elegant specimens prepared in this 
 way. 
 
 In full-grown animals the bones are very slowly tinged, because 
 the great mass of the bone is not in contact with blood-vessels ; each 
 Haversian system, for example, has only its small innermost lamella 
 in contact with them ; and, besides, the osseous matter is altogether 
 more consolidated and less permeable by fluids than at a very early 
 period of life. In the bones of half-grown animals a part of the bone 
 is nearly in the perfect condition, while a part is new and easily 
 coloured. Hence, it is easy in them to distinguish the new from the 
 old by means of madder. 
 
 Now, madder given to half-grown animals colours the long bones 
 most deeply in the interval between the shaft and extremities, and 
 on the surface of the shaft. When madder is given at intervals, the 
 tints in the bone are interrupted ; the layers in course of formation 
 during its administration are coloured, while those formed during the 
 intervening periods are colourless. The long period during which 
 bones retain the madder tinge, shows that the colouring matter is not 
 readily resumed by the blood, from its combination with the phosphate 
 of lime ; and it seems also to indicate a sluggishness of the nutrient 
 process in bone. 
 
 Perhaps few questions have more divided the minds of physiolo- 
 gists than that regarding the share taken by the periosteum in the 
 growth and regeneration of bone ; for these last are essentially the 
 same process. We now see that bone does not grow on its exterior 
 because the periosteum is there ; and that the only part this membrane 
 takes in the deposit of new bone is by the vascular network mingled 
 with its fibrous tissue, and which does not differ from that on other 
 portions of the osseous surface. 
 
 The limited expansibility of the bone already formed is the remote 
 cause to which the growth by new deposit on the exterior is to be 
 referred ; and, in this respect, the superficial growth is strictly analo- 
 gous to the exogenous mode of growth in vegetable structures. 
 
 A third mode in which increase of size is provided for, appears 
 to be by the dilatation of the primary cancelli and Haversian canals 
 in the central parts of the bone. In early life the cancelli are small, 
 
 madder is given as food, its colouring principle is absorbed, and circulates with the 
 blood; and it colours first that part of the bone which is in course of formation 
 from that fluid, or which has been last formed, i. e. which is nearest the vascular 
 surface. 
 
REPARATION OF BONE, 125 
 
 and there is no medullary cavity. Gradually the cancelli enlarge, 
 and those within the shaft blend more and more with one another, by 
 the removal to a greater or less extent of the intervening osseous 
 walls, until at length a medullary canal is formed, around which the 
 cancelli are very open, large and irregular. This augmentation of 
 the vascular cavities of bone is attended with a development of adi- 
 pose vesicles,^d their capillaries in the new space, while the proper 
 vessels of theosseous tissue remain pretty much as before. The fat 
 contained in the medullary canal gradually accumulates so much, that 
 a special artery becomes enlarged to supply it, assuming the very 
 inappropriate title of " the nutrient artery of the bone." Duhamel 
 placed a ring of silver round a bone of a young pigeon, without in- 
 juring the periosteum. After some time, during which the bone had 
 increased in diameter, he found the ring in the medullary canal, which 
 had acquired a capacity equal to the previous diameter of the whole 
 shaft. 
 
 This enlargement of the diameter of a long borte by the dilatation 
 of its'interior, is attended by two consequences, equally important. 
 The shell of compact tissue is thus adapted to offer greater resistance 
 to injurious mechanical forces, while the disadvantage of a corre- 
 sponding increase of weight is obviated. 
 
 Reparation of Bone. — The great importance of this subject to the 
 surgeon has led to many very interesting researches from the time of 
 Duhamel to the. present day, and by these the several steps of the 
 process by which new bone is deposited have been ably elucidated in 
 all that relates to their more obvious characters. When a fracture 
 occurs, blood is, of course, effused into the wound, both from the 
 ruptured vessels of the bone itself, and from those of the surrounding 
 structures participating in the injury. At a short period subsequently, 
 a semi-transparent lymph is found mingled with the coagulum, and 
 covering the surfaces of the hard and soft parts exposed. This 
 lymph in ail probability is the same as that by which the adhesive 
 process in other wounds is effected. In the second and third weeks 
 a gradual condensation of this takes place, accompanied with an in- 
 terstitial change, converting it into a substance resembling temporary 
 cartilage. 
 
 Ossification takes place throughout this in a nearly uniform manner, 
 until towards the fourth or sixth week, the whole is transformed into 
 a spongy, but firm osseous mass, investing the exterior of the broken 
 extremities, and extending between them in the form of a case, by 
 which they are firmly held together. If the medullary canal has been 
 broken across, and the broken ends evenly adjusted, there will be 
 likewise an interior stem of new bone connecting the medullary canal 
 of the fragments in the axis of the hone ; the opposed surfaces of the 
 compact tissue being as yet ununited. The callus, or new bone, thus 
 formed, was termed by Dupuytren jorowiono^, as it is gradually ab- 
 sorbed during the succeeding months, while the permanent callus is 
 being slowly deposited between the contiguous surfaces of the com- 
 pact tissue. It would appear that new bone is formed more exube- 
 rantly in the situations of the provisional callus because of their greater 
 
126 ORGANS OF LOCOMOTION. 
 
 vascularity ; just as we may suppose the function of ordinary nutrition 
 to be more active in those parts, than in the compact tissue of the 
 bone. The permanent callus has all the characters of true bone. 
 
 When the reparative process in bone is interfered with, either by 
 mal-apposition of the fragments, or by constitutional fault, a spurious 
 union may occur by the medium of a ligamentous substance, or even 
 a diarthrodial joint may be formed at the seat of fractflre. The ends 
 of the bones become altered in form, and adapted to one another ; a 
 kind of false capsular ligament is developed, and sometimes even 
 an imperfect cartilage, and a lining membrane furnishing a lubricating 
 fluid. 
 
 The following works may be consulted on Bone : — The systems of General Ana- 
 tomy already quoted (p. 95); Meckel, Anat. G^n^rale Descript. et Patholog., torn. i. ; 
 Dr. Bostock's Physiology, where will be found an excellent and learned summary of 
 the observations of preceding physiologists on the structure and growth of bone; Mr. 
 Faget's paper on the influence of Madder on the Bones of growing Animals, Lond. 
 Med. Gazette, vol. xxr ; Deutsch, de penitiori OsSium structure observationes ; 1834: 
 lyiiescher.de inflammatione Ossium eorumque anatome generali ; 1836 : Miiller's Phy- 
 siology by Baly, vol. i. M. Flourens has lately published a handsome volume on the 
 growth of bone, illustrated with figures. 
 
 CHAPTER VI. 
 
 SYNOVIAL MEMBRANES. — SEROUS MEMBRANES. — VARIETIES OF JOINTS. — 
 MECHANISM OF THE SKELETON. 
 
 The different forms of bones, when united according to various 
 mechanical contrivances, constitute the skeleton. The framework 
 of the body, being thus formed of several pieces jointed together, is 
 admirably arranged for extended, or for minute and nicely adjusted 
 motions, and for distributing concussions over a large surface. The 
 interposition of discs, or laminae, of elastic cartilage, or fibro-carti- 
 lage, between some bones, contributes to the latter object, by inter- 
 rupting the medium through which the shock would be conducted, 
 as well ashy the elasticity of the intervening substances; and, at 
 the same time, these discs, by their intimate adhesion to the opposed 
 osseous surfaces, serve as powerful bonds of union between them. 
 Joints of this kind (synarthrodial) enjoy a very limited degree of 
 motion, which is entirely due to the yielding and elastic nature of 
 the interposed material. When a greater range of motion is re- 
 quired than can be obtained in this way, the surfaces of the osseous 
 segments are constructed so as to glide the one upon the other in 
 certain directions, which are determined by the form of the articular 
 surfaces, and by the positions at which the connecting ligaments are 
 placed. Here the bond of union consists of the ligaments and the 
 surrounding muscles ; the osseous segments are not, as in the former 
 instance, continuous with each other through the interposed texture, 
 
SYNOVIAL MEMBRANES.— BURS^. 127 
 
 but are separated by a space which is called the cavity of the joint. 
 Each osseous surface is encrusted by a layer of articular cartilage 
 adapted to its form, and the cavity of the joint is lined by a delicate 
 membrane which, secretes a peculiar viscid matter, synovia, admi- 
 rably suited to lubricate the surface. This membrane is termed 
 synovial, and is constantly present in the diarthrodial piais. 
 
 The articular synovial membrane forms a closed bag, placed be- 
 tween the articular surfs^ces of the bones. Its free surface is smooth 
 and moist ; its attached surface adheres by very fine areolar tissue to 
 the ligaments of the joint, and to the cartilages encrusting the ex- 
 tremities of the bones. From the ligaments it may be readily detached, 
 and traced to the edge of the cartilage ; to this it is very intimately 
 adherent for some little distance, beyond which it cannot be followed 
 where the cartilage has been exposed to pressure during the motions 
 of the joint. In the foetus it is continued over the whole cartilage 
 (p. 97). 
 
 In some of the more complex joints the synovial membrane forms 
 folds, which project more or less into the articular cavities, and contain 
 fat, which Clopton Havers and other anatomists erroneously imagined 
 to perform a glandular office, and to secrete the synovia. The knee 
 affords some remarkable examples of these folds, in what are known 
 as the alar ligaments. 
 
 A great number of blood-vessels are distributed in the areolar 
 tissue upon the attached surface of the synovial membrane. In in- 
 flammation, the membrane acquires a red hue by the repletion of 
 these vessels, and in a minute injection also it becomes coloured. 
 Excepting in very rare cases, the vessels cannot be traced beyond 
 the edge of the cartilage, where they form a series of loops. (See 
 p. 99—100). 
 
 Bursa. — A very simple form of synovial membrane is employed 
 to facilitate the gliding of a tendon, or of the integumerit, over an 
 osseous projection. It consists of a bag, generally closed at every 
 point, connected by areolar tissue with the neighbouring parts, and 
 secreting into its interior a fluid, which lubricates its free surface. 
 Sometimes, when one of these bursae exists in the neighbourhood of 
 a large joint, it communicates freely with the cavity of its synovial 
 membrane, as in the bursa behind the rectus femoris above the knee- 
 joint, and that near the hip-joint behind the tendon of the psoas and 
 iliacus muscles. These synovial sacs are found in great numbers 
 throughout the body: some are superficial,- or subcutaneous, swch. as 
 that between the skin and the patella, or that over the great trochan- 
 ter of the femur, or that over the olecranon ; ihe deep-seated bursas, 
 however, constitute the largest proportion of them ; these are almost 
 always connected with tendons, and interposed between them and the 
 bones over which they play. On opening a bursa, we often find its 
 cavity traversed by bands which are either congenital and approaching 
 to the cellular or areolar disposition, or, as seems not unlikely, of the 
 nature of adhesions, and consequently a morbid production tending 
 to the obliteration of its cavity. 
 
 Synovial sheaths, — These are synovial bags prolonged into the 
 
128 ORGANS OF LOCOMOTION. 
 
 form of sheaths, and surrounding long tendons, such as those of the 
 flexor or extensor muscles of the fingers and toes, as they lie in their 
 osseo-fibrous sheaths in the hand or foot. One layer of the synovial 
 sheath adheres to the wall of the osseo-fibrous canal ; the other, to the 
 contained tendon ; and,- the free surface being lubricated by synovia, 
 the tendon plays freely within the canal. In deep-seated whitlow, 
 •when the inflammation extends to one of these synovial sheaths, and 
 gives rise to the formation of adhesions within its cavity, the motion 
 of the tendon within is completely destroyed, and a stiff finger is the 
 result. Similar sheaths on a larger scale envelop the tendons which 
 pass beneath the annular ligaments of the wrist and ankle. 
 
 Synovia. — The synovial membranes, in health, contain only suffi- 
 cient fluid to keep their free surfaces moist. It is, therefore, diffi- 
 cult to collect the synovia in sufficient quantity for examinationj 
 It is a transparent, yellowish-white fluid, viscid like the white of an 
 egg, whence its name (bw, cum ; wo*, ovum). Lassaigne and Boissel, 
 who have published an analysis of human synovia, state that it does 
 not coagulate spontaneously; that it is an alkaline fluid, containing 
 albumen and salts, such as are found in the serum of the blood : and 
 M. L'Heritier has lately analyzed two specimens of this fluid, and 
 completely confirmed the statement of those chemists.* 
 
 It is plain, from the description above given, that synovial mem- 
 branes contribute to the locomotive function by lubricating the artiiJU- 
 lar surfaces, so that they may glide smoothly on one another with the 
 least possible friction, and also by facilitating the play of some tendons 
 over prominent surfaces, and of others within sheaths. 
 
 Serous membranes. — The movements of the viscera within the 
 great cavities of the trunk are provided for by an arrangement similar 
 to that described in the joints. Between the wall of the cavity and 
 the surface of the contained viscus (the thorax and the lungs, for 
 example,) a closed sac is placed, one layer of which is parietal, and 
 the other visceral. These are respectively attached to the wall of the 
 cavity and to the surface of the viscus by fine areolar tissue ; and their 
 continuity is shown at certain reflections, where the one passes into 
 the other. The free surface, as in the synovial membranes, is con- 
 tinually moistened by the proper secretion, which, containing a larger 
 proportion of water than synovia does, resembles serum of blood. 
 The serous membranes are, the arachnoid, in the head and spine; the 
 pleura and pericardium, in the thorax; the pericardium, in the abdo- 
 men; and the tunica vaginalisjtestis, in the scrotum. These are all 
 closed at every point ; so that their secretion, if morbidly increased, 
 is retained within the cavity, and can only be removed by absorption, 
 or by an opening through the membrane. In the healthy state, the 
 surfaces are only moistened ; and, when more fluid exists, it is the 
 product of disease, or of post-mortem change. If the surfaces be 
 dry, or a viscid adherent matter be effused upon them, the move- 
 ments of the contained organ become impeded, and are accompanied 
 by a peculiar sound of friction, and a vibration sensible to the hand ; 
 
 * Berzelins, Chemie Organ, t. vii. 
 
SEROUS MEMBRANES. 
 
 129 
 
 both of which are well known to physicians in the pericardium, 
 pleura, and peritoneum, and may frequently be noticed by the patients 
 themselves. 
 
 The peritoneum of the female affords a remarkable exception to 
 the closed character of serous sacs. At two points this membrane is 
 open, where it communicates with the canal of each Fallopian tube 
 at its dilated extremity. 
 
 * The blood-vessels of serous membranes are distributed in con- 
 siderable numbers in the areolar tissue which is connected with their 
 attached surface. We infer that nerves exist freely in the same 
 tissue, from the intense pain which accompanies inflammation of these 
 membranes. There is good reason to believe that lymphatics also are 
 freely distributed in their areolar tissue. 
 
 The serous membranes connect the viscera contained in the cavities 
 to which they respectively belong, by the folds they form as they pass 
 from each viscus to the wall of the cavity. As the viscera in the 
 abdomen are so many, and the folds proportionately numerous, the 
 peritoneum is more complicated in its disposition than any other 
 serous membrane ; and it is part of the study of the descriptive ana- 
 tomist to show, that the remarkable complication of folds which this 
 membrane exhibits is not inconsistent with its adherence to the chief 
 morphological character of serous membranes. 
 
 Microscopic characters of synovial and serous membranes. — These 
 membranes appear to be essentially alike in their minute structure. 
 On their free surface is a single layer of 
 epithelium, the particles of which are poly- 
 gonal in shape, and of transparent texture. 
 A siriall fragment of this pavement, from 
 the peritoneum of the rabbit, is represented- 
 in fig. 34. This was discovered by Henle. 
 We have found this epithelium to rest 
 immediately on a continuous transparent 
 basement membrane of excessive tenuity, 
 apparently identical with that which sup- 
 ports the epithelium of mucous membranes. 
 Beneath this is a lamina, of areolar tissue, 
 which constitutes the chief thickness of the 
 membrane, and confers on it its strength 
 and elasticity. This areolar tissue is tra- 
 versed by a network of capillary vessels, 
 the meshes of which are large and of 
 rather unequal size, and by lymphatics 
 and nervous filaments in varying number. 
 It is of close texture, and continuous with 
 that laxer variety by which the membrane is attached to the parts it 
 lines. 
 
 The most favourable position for examining the areolar tissue of 
 serous membrane, is the transparent part of the mesentery, or of any 
 of the duplicatures of the peritoneum in small animals. 
 
 Here we observe the yellow fibrous element assuming a very beau- 
 
 Fig. 34. 
 
 Epithelium of serous membrane ; — 
 At a, an accidental fold is represented, 
 tlie Iwo dar]£ edges of wKich' exhibit 
 the thickness of the particles, and of 
 their nuclei. 6. One of the oval nuclei, 
 c. Line of junction between two parti- 
 cles.— Magnified 300 diameters. 
 
130 ORGANS OF LOCOMOTION. 
 
 tiful arrangement (fig. 35). Its filaments interlace and inosculate 
 chiefly in a plane beneath the basement membrane, in such a manner 
 as to confer equal elasticity in every direction. The intermediate 
 
 space is occupied by the white 
 .Fig. 35. fibrous element, disposed in 
 
 wavy bands, variously intersect- 
 ing, and which become straight 
 only when the elastic threads are 
 stretched. 
 
 Physical and vital properties, 
 — These are precisely those of 
 areolar tissue : the elasticity of 
 the serous membranes is very 
 considerable, owing to the ad- 
 mixture of the yellow fibrous 
 element in the layer which forms 
 the chief substance of the mem- 
 brane. These tissues are en- 
 tirely devoid of vital contract- 
 ility and their sensibility is low, 
 
 Yellow fibrous element of the areolar tissue of se- eXCCpt in a State of aCUte iu- 
 rous membrane. From the mesentery of the Rabbit, iXr^mmr^i'ti^n 
 ueated with acetic acid.— Magnified 300 diameters. uammauon. 
 
 These membranes exhibit, in 
 their inflamed state, a remarkable tendency to throw out lymph on 
 their interior, so as to cause adhesion of their opposed surfaces. 
 Hence a frequent result of inflammation of a serous membrane is the 
 obliteration, to a greater or less extent, of its cavity. Synovial mem- 
 branes are not so prone to the adhesive inflammation as the serous 
 are, which seems more to be accounted for by the nature of their 
 secretion, than by any difierence of their structure. The proneness of 
 these membranes to the effusion of coagulable lymph seems to be due 
 to the extreme tenuity of the layer of epithelium which separates the 
 nutrient blood-vessels from the cavity of the serous membrane. The 
 lymph eflTused becomes gradually converted into areolar tissue and 
 vessels usually constituting what are termed adhesions, but some- 
 times forming merely a thickened condition of the membrane. 
 
 Of the joints. — A joint, or articulation, may be defined to be the 
 union of any two segments of an animal body, through the interven- 
 tion of a structure or structures different from both. 
 
 The most perfect and elaborate forms of the articulations are those 
 which are seen in animals that possess a fully developed internal 
 skeleton, and in none may they be studied with more advantage than 
 in man. In the human subject, and in the vertebrated animals gene- 
 rally, we have indeed, particular occasion to admire the articulations 
 as"mirabiles commissuras, et ad stabilitatem aptas et ad artus fini- 
 endos accommodatas, et ad motum, et ad omnem corporis actionem.*' 
 
 The textures which form the joints, are bone, cartilage, fibro-carti- 
 lage, ligaments, synovial membrane. Bone constitutes the funda- 
 mental part of all joints; ligament variously modified is employed in 
 
THE JOINTS. 131 
 
 all as a bond of union ; but the three remaining textures are present 
 chiefly in th^se joints which enjoy a free gliding motion. 
 
 In addition to the structures already named as entering intrin- 
 sically into the formation of joints, we find that the tendons and mus- 
 cles, which lie in the immediate vicinity of or which surround the 
 joints, contribute much to their strength and security. In joints of 
 the hinge kind we generally see the anterior and posterior parts pro- 
 tected more or less by the tendons of muscles, and even by muscles 
 themselves passing from one segment of a limb to another; and here 
 it frequently happens that the tendon is bound down on the bones 
 which form the member, by a fibrous expansion of great strength, 
 lined by a synovial membrane of the same characters as the articular, 
 but adapted in its form to the osseo-fibrous canal in which the tendon 
 is placed, e. g., the tendons of the fingers. The protection and 
 strength afforded by muscles is particularly evinced in the case of the 
 shoulder-joint, where the capsular ligament is closely embraced by 
 four muscles, whose tendons become identified with the fibrous cap- 
 sule as they go to be inserted into the bone. A muscular capsule is 
 thus provided for the joint, by which the bones are maintained much 
 more firmly and powerfully in apposition than they would be if kept 
 together by an uncontractile ligamentous capsule alone ; hence the 
 elongation of the arm that occurs as a consequence of paralysis, and 
 hence also the greater liability to luxation which exists in a debili- 
 tated state of the system. Articular or capsular muscles, thus placed, 
 have also the effect, as it is said, of presenting the pinching of the 
 capsule or synovial membrane between the articular extremities of 
 the bones in the different motions of the joint. 
 
 Atmospheric pressure, exerting as it does a force of nearly fifteen 
 pounds on the square inch, is a powerful agent in maintaining the 
 contact of articular surfaces. This is well illustrated by the diffi- 
 culty of separating the surfaces composing the hip and shoulder 
 joints, when the surrounding ligaments are air-tight; while, on the 
 other hand, these surfaces may be separated by the mere weight of 
 either bone, if one of these joints be suspended in the exhausted 
 receiver of an air-pump. In exhibiting this experiment, we find 
 the shoulder joint shows the effects of atmospheric pressure more 
 strikingly than the hip, for its capsule being loose, and the osseous 
 cavity for the reception of the head of the humerus small, the pres- 
 sure of "the atmosphere pushes in the capsule so that it fits closely 
 to the head of the bone. When this pressure has been removed by 
 exhausting the receiver, the head of the humerus falls rapidly from 
 the socket, and the ligament becomes stretched by the weight of the 
 bone. 
 
 The joints are supplied copi^jusly with blood, and are remark- 
 able for the arterial anastomoses which take place about them. The 
 best examples of these inosculations are met with around the large 
 joints of the extremities. The parts supplied with blood are the 
 synovial membranes, the ligaments, the fat, and the extremities of 
 the bones ; but the cartilages certainly do not contain blood-vessels. 
 
 Of the forms and classification of the joints. — It is not difficult. 
 
132 ORGANS OF LOCOMOTION. 
 
 by passing in review the various motions which take place between 
 any two segments of a limb, to form an idea, a priori, as to the 
 kinds and shapes of the articulations by which the segments will 
 be united ; it is only necessary not, to lose sight of the fact, that in 
 the construction of a joint regard is had not to its mobility alone, 
 but to its security, its durability, and the safety of the neighbouring 
 parts. We may expect to find joints varying in the degree of motion, 
 from the slightest perceptible, to the freest that is coujpatible with 
 the maintenance of the segments in their proper relation with each 
 other ; and also in extent of motion, from that which is so slight as 
 to admit of almost no appreciable change in the position of the parts, 
 to that which allows of the most ample variety of movement between 
 the segments, consistent with the integrity of the articulation. 
 
 It will appear, then, that, the most simple kind of articulation is 
 that by which two parts are so united as that only the slightest ap- 
 preciable degree of motion shall exist between them. This consti- 
 tutes the first great division of, joints — the Synarthrosis, where the 
 parts are continuous, i. e., not separated from each other by an inter- 
 vening synovial cavity. Some anatomists consider all synarthrodia! 
 joints to be immovable ; which, although not far from the truth, cannot 
 be said to be strictly accurate. Had immobility been the object to 
 be attained, that might have been more effectually accomplished 
 by the fusion of the extremities of the segments together, as in anchy- 
 losis. 
 
 In the second class of joints, motion is enjoyed freely and fully: 
 this class is designated by the tevm Diarthrosis : the segments are 
 interrupted completely in their continuity : the extremities of the bones 
 can only be said to be contiguous. 
 
 Synarthrosis. — The general characters of the articulations belong- 
 ing to this class are, 1, that they are very limited. in their motion, 
 insomuch as to be considered by some as immovable; 2, that their 
 surfaces are continuous, i. e., without the intervention of a synovial 
 cavity, but with that of some structure different from bone. The 
 following varieties may be noticed among synarthrodia! articulations. 
 
 a. Suture. — When the margins of two bones exhibit a series of 
 processes and indentations ; (dovetailing) which are received and 
 receive reciprocally, with a very thin cartilaginous lamina interposed, 
 this is the ordinary kind of suture, sutura vera, of which three \inds 
 are distinguished : sutura dentata, where the processes are long and 
 dentiform, as in the interparietal suture of the human skull ; sutura 
 serrata, when the indentations and processes are small and fine like 
 the teeth of a saw, as in the suture between the two portions of the 
 frontal bone ; sutura limbosa, when there is along with the dentated 
 margins a degree of beveling of one, so that one bone rests on the 
 other, as in the occipito-parietal suture. 
 
 When the two bones are in juxtaposition by plane but rough 
 surfaces, the articulation is likewise said to be by suture, and this is 
 the false suture, sutura notha, of which there are two kinds ; sutura 
 squamosa, where the beveled edge of one bone overlaps and rests 
 upon the other, as in the temporo-parietal suture, and harmonia 
 
THE JOINTS. 133 
 
 (ago, adapto), where there is simple apposition : this last kind of 
 articulation is met with, as Bichat observes, wherever the mecha- 
 nism of the parts is alone sufficient to maintain them in their proper 
 situation, as may be seen in the union of most of the bones of the 
 face. 
 
 The sutures have a considerable tendency to become obliterated by 
 age, the intervening cartilage becoming ossified ; it rarely happens 
 that the sutures are all manifest in a human skuUjpast fifty years of 
 age, and sometimes the obliteration takes place at a much earlier 
 period. The frontal suture is by no means permanent ; it is not often 
 found at puberty. In birds and fishes this tendency to the obliteration 
 of the sutures is particularly manifest. 
 
 b. Schindylesis [exi.vSv'h.riaii, Jissio ; a;i;tfw, diffindo). — This form of 
 articulation is where a thin plate of bone is received into a space or 
 cleft formed by the' separation of two laminae of another, as is seen 
 in the insertion of the azygos process of the sphenoid bone into the 
 fissure on the superior margin of the vomer ; and in the articulation 
 of the lachrymal bone with the ascending process of the superior 
 maxillary. 
 
 c. Gomphosis (yoju^of, clavus. Clavatio, conclavatio). When a 
 bone is inserted into a cavity in another, as a nail is driven into a 
 board, or as a tree is inserted into the earth by its roots, the articula- 
 tion is by gomphosis. The only example we have of it in the human 
 subject or in quadrupeds is in the insertion of the teeth into the 
 alveoli. 
 
 d. Amphiarthrosis. — This is a form of articulation where two plane, 
 or mutually adapted surfaces are held together by a cartilaginous or 
 fibro-cartilaginous lamina of considerable thickness, as well as by 
 external ligaments. In virtue of the elasticity of the interposed car- 
 tilaginous or fibro-cartilaginous lamina, the amphiarthrosis possesses 
 a manifest, although certainly a very limited degree of motion, and 
 hence most systematic writers class it with the diarthrodial articu- 
 lations. But it appears much more consistent to- place it among the 
 synarthrodial joints, for, 1, its anatomical characters agree precisely 
 with those of synarthrosis ; 2, the surfaces in amphiarthrosis being 
 continuous, it would make an exception in diarthrosis were we to 
 place it there ; and, 3, its degree of motion is greater than that of 
 suture, only because of the greater development of the interosseous 
 substance. 
 
 The examples of this form of joint in the human body are the 
 articulation between the bodies of the vertebrse, that between the two 
 ossa pubis at what is called the symphysis, and that between the ilium 
 and sacrum. Like the sutures, the amphiarthroses are liable to be- 
 come obliterated in old age, by the ossification of the interosseous 
 lamina. This is not uncommon in the interpubic, and occurs now 
 and then in the intervertebral and sacro-iliac joints. 
 
 Diarthrosis. — Mobility is the distinguishing characteristic of this 
 class of joints; the articular surfaces are contiguous, each covered by 
 a lamina of cartilage {diarthrodial cartilage), having a synovial sac 
 interposed, and in some cases two, separated by a meniscus. Th'e 
 
134 ORGANS OF LOCOMOTION. 
 
 integrity of the articulation is maintained by ligaments which pass 
 from one bone to the other. Their mechanism is much more com- 
 plicated than that of synarthrodial joints, being intended not only for 
 security, but also to give a certain direction to the motions of which 
 they are the centre. 
 
 Before proceeding to the enumeration of the varieties of joints that 
 come under this head, it will not be amiss to describe briefly the 
 various motions which may take place between any two segments of 
 a limb, and which it is the object of these joints to admit of. It is 
 obvious that the most simple kind of motion which can exist between 
 two plane or contiguous surfaces, is that of gliding : one surface glides 
 over the other, limited by the ligaments which extend between the 
 bones. This motion, however, is not confined to plane surfaces; it 
 may exist evidently between contiguous surfaces, whatever their form. 
 When two segments of a limb, placed in a direct line, or nearly so, 
 can be brought to form an angle with each other, the motion is that 
 of flexion, the restoration to the direct line is extension. These two 
 motions belong to what Bichat calls limited opposition; the flexion and 
 extension of the fore-arm on the arm illustrate it. Sometimes a 
 motion of this kind takes place in four directions, indicated by two 
 lines which cut at right angles. This is best understood by a refer- 
 ence to the motions which take place at the hip-joint: there it will be 
 seen that the thigh-bone may be brought forward so as to form an 
 angle with the trnnk, flexion— ot it may be restored, extension; it may 
 be separated from the middle line of the body so as to form an angle 
 with the lateral surface of the trunk, abduction — or it may be restored 
 and made to approximate the middle line, adduction. It is evident 
 that a joint, which is susceptible of these four motions, may also 
 move in the intermediate directions. When these motions are per- 
 formed rapidly, one after the other, one continuous motion appears 
 in which the distal extremity of the bone describes a circle indi- 
 cating the base of a cone whose apex is the articular extremity 
 moving in the joint; this motion is called circumduction. 
 
 Rotation is simply the revolving of a bone around its axis. It is 
 important to bear this definition in mind : through losing sight of it 
 many anatomists have attributed rotation to a joint which really does 
 not possess it. 
 
 The varieties of the diarthrodial joint are as follows : 
 
 a. Arthrodia. — In this species the surfaces are plane, or one is 
 slightly concave, and the other slightly convex : the motion is that 
 of gliding, limited in extent and direction only by the ligaments of 
 the joint, or by some process or processes connected with the bones. 
 The examples in men are, the articular processes of the vertebrae, 
 the radio-carpal, carpal, carpo-metacarpal, inferior radio-ulnar, supe- 
 rior tibio-fibular, tarsal and tarso-metatarsal, temporo-maxillary, acro- 
 mio-clavicular, and sterno-clavicular joints. This last articulation and 
 the wrist-joint possess a greater latitude of motion than the others; 
 the former, in consequence of the shape of its articular surfaces ; each 
 surface is convex in one diameter and concave in the other, so that the 
 gliding that takes place in this joint is in the direction of the long and 
 
THE JOINTS. 135 
 
 short diameters, which intersect each other at right angles. It is 
 capable, therefore, of vague opposition in those lines, but certainly 
 not in the intermediate directions, the nature of the surfaces being 
 calculated to prevent this. The wrist owes its mobility to the la-xity 
 of its ligaments, which permit it to move as well in its transverse as 
 in its antero-posterior diameters, as also in the intermediate direc- 
 tions; it consequently admits of vague Opposition and circumduction. 
 The articulation of the metacarpal bone of the thumb with the trape- 
 zium is also an arthrodia very similar to the sterno-clavicular, but with 
 a greater degree of motion. Arthrodial joints are generally provided 
 with ligaments, placed at the extremities of the lines in the direction 
 of which the gliding motion takes place. 
 
 6. Enarthrosis. — This is a highly developed arthrodia. The convex 
 surface assumes a globular shape, and the' concavity is so much deep- 
 ened as to be cup-like ; hence the appellation ball and socket. The 
 ball is kept in apposition with the socket by means of a capsular liga- 
 ment, which is sometimes strengthened by accessory fibres at certain 
 parts that are likely to be much pressed upon. The best example of 
 enarthrosis is the hip-joint, and next to it the shoulder : in the latter 
 the cavity is but imperfectly developed. All the quadrupeds have 
 their shoulder and hip joints on this construction, and the same com- 
 mon plan is observed in the vertebrata generally whose extremities 
 are developed. In birds and reptiles the bodies of the vertebrae are 
 articulated by enarthrosis. 
 
 This species of joint is capable of motion of all kinds, opposition and 
 circumduction being the most perfect, but rotation limited. Indeed, 
 what is called rotation at the hip-joint, is effected by a gliding of the 
 head of the femur from before backwards, and vice versa, in the 
 acetabulum ; it is not a rotation of the head and neck, but of the shaft, 
 of the femur. 
 
 c. Ginglymus (yiyy>.i)^of, cardo). — The articular surfaces in the 
 hinge-joint are marked with elevations and depressions which exactly 
 fit into each other, so as to restrict motion in all but one direction. 
 They are always provided with strong lateral ligaments, which are the 
 chief bonds of union of the articular surfaces. 
 
 The elbow and ankle joints in man are perfect gihglymi ; the knee 
 also belongs to this class, but is by no means a perfect specimen, 
 for, in a certain position of the bones of this joint, the ligaments are 
 so relaxed as to allow a slight rotation to take place. The phalangeal 
 articulations, both of the fingers and toes, are ginglymi. This form 
 of joint is most extensively employed among the lower animals. In 
 quadrupeds, most of the joints of the extremities come under this 
 head. In amphibia and reptiles, too, there are many examples of the 
 hinge-joint. The bivalve shells of conchiferous mollusca are united 
 by a very perfect hinge, and a great number of the joints of Crustacea 
 and insects are of this form. 
 
 The true ginglymus is only susceptible of limited opposition : hence 
 the knee-joint cannot be regarded as a perfect example ; in fact, in 
 the perfect ginglymus there is every possible provision against lateral 
 motion. 
 
136 ORGANS OF LOCOMOTION. 
 
 d. Biarthrosis rotatorius. — A pivot and a ring constitute the me- 
 chanism of this form of joint. The ring is generally formed partly 
 of hone and partly of ligament, and sometimes moves on the pivot, 
 sometimes the pivot moves in it. The motion is evidently confined 
 to rotation, the axis of -which is the axis of the pivot. 
 
 In the human subject the best example of this articulation is that 
 between the atlas and odontoid process of the axis or vertebra den- 
 tata. The ring is formed by a portion of the anterior arch of the 
 atlas, completed behind by a transverse ligament. Here the atlas 
 rotates round the odontoid process, which is the axis of motion. 
 Another example is the superior radio-ulnar articulation : here one- 
 fourth of the ring is formed by bone, namely, the lesser sigmoid cavity 
 of the ulna, and the remaining three-fourths by the round ligament 
 called the coronary ligament of the radius. In this case there is rota- 
 tion as perfect as in that just mentioned; but the head of the radius 
 rolls in the ring, and the axis of motion is the axis of the head and 
 neck of the bone. Some anatomists consider this joint a species of 
 ginglymus, which they designate lateral. 
 
 The terms Symphysis, Synchondrosis, Synneurosis, Syssarcosis, 
 Meningosis, have been employed by anatomists to designate certain 
 kinds of articulation, chiefly in reference to the nature of the con- 
 necting media. Symphysis, although originally employed with great 
 extent of meaning, seems to have been in later days applied exclu- 
 sively to denote the articulations of the pelvis, which we have classed 
 under Amphiarthrosis. We pass over the other terras because they 
 ought to be discarded from use, as only tending to encumber a voca- 
 bulary already too much crowded with difficult and unnecessary 
 terms. 
 
 Mechanism of the skeleton. — We shall conclude this chapter with 
 some remarks upon the mechanical disposition of the various parts 
 of the skeleton, and their adaptation to the purposes they were des- 
 tined to fulfil. 
 
 The skeleton consists of the head, trunk, and extremities. 
 
 The head is composed of a cavity, surrounded by osseous walls 
 (cranium), destined to contain and protect the brain ; and of an ex- 
 panded portion {the face), with which some of the organs of the 
 senses are connected, and upon which the features are formed. The 
 size of the cranium affords a good clue to determine the absolute size 
 of the brain ; and the proportion of the face to it, offers a not inexact 
 index of the relation which the intellectual faculties and the animal 
 propensities bear to each other.* 
 
 The spheroidal form of the cranium admirably adapts it for pro- 
 tecting the organ which it contains against external violence. The 
 arched form is that which possesses most strength, and offers the 
 greatest resistance. When, says Dr. Arnott, we reflect on the strength 
 displayed by the arched film of an egg-shell, we need not wonder at 
 the severity of the blows which the cranium can withstand. And he 
 adds, in reference to the former, " what hard blows of the spoon or 
 
 * See a good account of the comparative mensuration of the skull in Mr. Ward's 
 Outlines of Human Osteology. 
 
THE CRAKIUM.— THE SPINE. 137 
 
 knife are often required to penetrate this wonderful defence of a dor- 
 mant life !" And this form, which gives so much strength to the 
 skull, favors the transmission of vibrations along its walls, and thus 
 saves ■the delicate viscus enclosed by them. Thus blows inflicted 
 upon the cranium become diflfused; and sometimes the violence ap- 
 plied directly to the vertex is spent upon the base of the skull, and 
 causes a fracture there. 
 
 The compound structure of the cranial bones is an important ele- 
 ment in the architecture of the skull as a protecting case to the brain. 
 Most of these bones are formed of two tables : the outer one is 
 tough, strong, and fibrous; the internal table is dense and brittle, and 
 hence caWed tabula vitrea ; and there is interposed between them a 
 spongy texture, the diploe, in which blood- vessels. are freely distributed 
 (fig. 20, p. 111). The varying density of these three layers evidently 
 diminishes their power of conducting vibrations to the parts within, 
 whilst it does not oppose the propagation of those vibrations in the 
 direction of the layers themselves. 
 
 The manner in which the bones of the skull are united together 
 has an evident reference to the physical properties of their inner and 
 outer tables. The sutures are formed by the dovetailing of the outer 
 table ; the inner being cut straight, and simply placed in apposition (a 
 layer of cartilage intervening), forming a sort of harmonia. The 
 inner table, which is the brittle one, is not dovetailed, because its 
 teeth would break readily ; but the toughness and elasticity of the. 
 outer table fit it well for such a mechanism. On the same principle, 
 Sir C. Bell remarks, a carpenter joins wood, which is tough and 
 elastic, by tenon and mortise or by dovetailing; but, if pieces of glass 
 or marble are to be joined, cement is employed for that purpose. 
 
 The principal part of the vault «f the cranium is formed by the 
 parietal bones, which rest upon the wings of the sphenoid, and upon 
 the temporal bones: these overlap the lower borders of the parietal 
 bones in such a way as to prevent them from starting outwards. 
 They act on the principle of the tiebeam in the roofs of houses. 
 
 At certain exposed situations the bones experience a thickening of 
 their structure, causing tuberosities, which are familiar to descriptive 
 anatomists. These contribute to the strength of the roof of the skull: 
 in front, in the frontal bone on each side of the middle line; laterally, 
 in the parietal bones , and, behind, in the centre of the occipital bone. 
 At this last situation two ribs, analogous to grdnings in architecture, 
 intersect each other: one extends from the centre of the frontal bone to 
 the most projecting part of the occipital foramen ; the other passes hori- 
 zontally across the occipital bone, and terminates immediately behind 
 the wedge-like processes which are formed by the petrous portions of 
 the temporal bones. The occipital protuberance, which is the point 
 of intersection of these groinings, is the " thickest and strongest part 
 of the skull ; and it is the most exposed, since it is the part of the 
 head which would strike upon the ground when a man falls back- 
 wards." (Sir C. Bell.) 
 
 Of the Spine. — The spinal column, in man, is a vertical, elastic 
 
138 ORGANS OF LOCOMOTION. 
 
 pillar, expanded inferiorly where it rests upon the sacrum. It is 
 composed of a series of light and spongy bones, between each pair 
 of which (except the first) a compressible and elastic disc of fibro- 
 cartilage is placed. It has a three-fold office in the human subject: 
 first, it is the great bond of connection between all the parts of the 
 skeleton ; secondly, it forms a canal for the lodgment and protection 
 of the spinal cord; and thirdly, it is a column of support for the head.; 
 For these purposes the spinal column requires considerable strength, 
 as the central pillar of the trunk : it needs mobility, to adapt itself to 
 the various attitudes and movements of the body, and elasticity, to 
 guard the tender organ contained within it, as well as the brain, from 
 concussion. 
 
 The strength of the spinal column is abundantly provided for in 
 the powerful ligament which binds the bodies of the vertebrae toge- 
 ther in front (anterior common ligament), and in the strong and elastic 
 intervertebral discs, which at once connect and separate them. The 
 degree of motion which may take place between any two vertebrae 
 is regulated partly by the thickness of the intervertebral disc, and 
 partly by the disposition of the joints of the articular processes. 
 When the latter are vertical in their direction, the vertebrae are so 
 locked in, that their movements are very much impeded ; but when 
 they approach the horizontal direction, as in the neck, the range of 
 motion is greater. The mobility of the spine may be compared' to 
 that of a chain ; between any two links of which there is but little 
 motion, while the whole chain is abundantly pliant. This restriction 
 of motion between each pair of vertebrae enhances the strength of the 
 column, and affords complete protection to the spinal cord, which 
 ■would speedily suffer, did any vertebra pass beyond its prescribed 
 limits. 
 
 In the flexuous form of the spinal column, and in the connection of 
 the vertebral laminae by broad bands of yellow elastic ligament, we 
 see further provision for its elasticity, in addition to that afforded by 
 the discs of fibro-cartilage which lie between the bodies of the ver- 
 tebrae. The concavity in the region of the back is doubtless intended 
 to give full scope to the play of the important organs within the tho- 
 rax; and the cervical and lumbar curves necessarily result from this, 
 in order that the relation of the whole column to the line of gravita- 
 tion of the body may be duly preserved. The triple curvature of the 
 spine enables it to yield with less jerk than if it were a straight 
 spring, or one that could bend only in a single direction. " It yields 
 in the direction of its curves, and recoils, and so forms the most per- 
 fect spring, admirably calculated to carry the head without jar or in- 
 jury of any kind." 
 
 The pliancy of the spinal column favours its flexion in various 
 directions, in obedience to the action of the numerous muscles which 
 are inserted into the vertebral processes. Nothing is more common 
 than to see a misshapen and crooked spine produced by the predomi- 
 nance of action given to certain sets of muscles, through the habitual 
 assumption of awkward attitudes : most of the curved spines which 
 
THE PELVIS. 139 
 
 occur in weakly females may be traced to uncorrected bad habits as 
 their origin.* 
 
 The spine, gradually expanding at its Ipwer part, rests upon the 
 base of the sacrum ; and the last lumbar vertebra is separated from 
 that bone by a fibro-cartilaginous disc. The sacrum forms a wedgp 
 separating the pelvic bones, and is admirably adapted to transmit the 
 weight of the spine to them. 
 
 Of the pelvis. — " The spinal column," to use the words of Mr. 
 Mayo, " rests on an elastic hoop, in the extreme circumference of 
 which on either side the deep cups are wrought which receive the 
 heads of either thigh-bone. But this elastic hoop is not disposed 
 vertically, but slants in such a manner, that, when we alight upon 
 our feet, the force of the arrested motion tells in great measure on 
 the extensor muscles of the hip." 
 
 In the articulation of the sacrum with the ossa innominata we see 
 remarkable provision against its displacement backwards, by a force 
 acting from above downward, the direction in which the superin- 
 cumbent weight bears, or even by one acting from before back- 
 wards. This security is obtained not only by the strong ilio-sacral 
 ligaments, which tie the bones together behind, and the cartilage, 
 which intervenes between the ilium and sacrum, and adheres firmly 
 to both, but also by the double wedge-like shape of the sacrum itself: 
 for this bone is wider above than below, so that it can thereby resist 
 the downward pressure ; and it has a greater width before than be- 
 hind, which enables it to oppose the pressure in front. And Mr. 
 Ward has shown that the sacrum is also well secured against dis- 
 placement forwards, not only by the general compactness which the 
 ssicro-iliac joints derive from their ligaments and cartilages, but also 
 by the cuneiform character which the bone assumes about the middle 
 of the articular surface, where the base of the wedge is turned in the 
 opposite direction to that which it occupies either at the upper or the 
 lower part of the articular surface, f 
 
 These provisions for the strength and security of the sacrum are of 
 great importance to the general mechanism of the pelvis, whether we 
 regard it as a bony girdle constructed for the transmission of the 
 weight of the trunk to the thigh-bones, or as an osseous cavity de- 
 stined to contain and protect certain important viscera. 
 
 Viewing the pelvis in the former light, we must notice the thick- 
 ening of the iliac bones along either side of its upper outlet. The 
 groinings, thus formed, terminate opposite the acetabula, and trans- 
 mit the superincumbent weight, which they share with the sacram, 
 to each of those cavities, whence it is again transferred to the heads 
 of the thigh-bones; they are formed of dense compact substance, 
 which contrasts strikingly with the thin lamellated structure of the 
 surrounding osseous tissue. 
 
 The obliquity of the pelvis has a twofold object ; first, with refer- 
 ence to the weight from above ; and, secondly, with respect to con- 
 
 • Dr. Aniott's remarks bearing upon this subject deserve a careful perusal.— See 
 his Elements of Physics, 
 f We refer for further details on this subject to Mr. Ward's excellent work, p. 256. 
 
140 ORGANS OF LOCOMOTION. 
 
 cussions transmitted upwards by the lower limbs, in leaps, or other 
 rapid movements. In both instances, the shock is distributed over 
 a greater extent of surfacp, and is participated in by a greater number 
 of joints, than if the pelvis were placed directly beneath the spine ; 
 for it is obvious, that, were the axis of the pelvis vertical, and the 
 femora placed perpendicularly under it, the weight from above would 
 bear its chief force upon the sacrum, and the concussion from below 
 would be felt in the hip-joints alone. 
 
 In progression, the whole pelvis receives the concussions, when 
 they proceed from above or from below. Hence the ossa pubis are 
 unked by an intervening elastic fibro-cartilage ; and any disturbance 
 of this joint during pregnancy, or in the act of parturition, occasions 
 great diiEculty to the patient in walking, or even in maintaining the 
 erect posturp. 
 
 Of the Thorax. — The thorax is a conoidal cavity, slightly flattened 
 on its anterior aspect. It is constructed with obvious reference to 
 lightness, elasticity, and mobility ; all these qualities being requisite 
 for its adaptation to the ever-varying movements of the organs it 
 contains. 
 
 The walls of the chest are formed behind by the dorsal vertebrae, to 
 which twelve ribs are articulated on each side : seven of these, the true 
 ribs, are connected to either margin of the sternum by pieces of cartilage, 
 which are of the same shape and breadth as the ribs themselves. ''I'he 
 ribs are articulated by their heads and tubercles with the bodies, as well 
 as with the transverse processes of the vertebrae, and enjoy at these 
 points a limited gliding motion in the upward or downward direction. 
 The direction of the true ribs is forwards, sloping downwards ; the 
 obliquity being greatest in the lowest ribs, least in the first rib. The 
 mobility which each rib enjoys at its vertebral articulation, permits 
 this direction to be altered by muscular action ; and the ribs, under 
 the influence of their elevator muscles, pass from the sloping to the 
 horizontal position. By this change the dimensions of the chest are 
 enlarged in the transverse as well as in the antero-posterior direction, 
 for the middle curved portions of the ribs are carried outwards, and 
 therefore brought further apart from each other ; and their sternal ex- 
 tremities are moved forwards, accompanied by the sternum, the dis- 
 tance of which from the dorsal vertebrae is thereby increased. The 
 forces, which depress the ribs, restore their planes of position to theif 
 previous oblique direction, and the two diameters of the chest to their 
 former dimensions. It is scarcely needful to add that the elevation 
 of the ribs accompanies inspiration, and their depression expiration. 
 
 The following happy comparison between the thorax and the pelvis 
 is from the pen of Mr. Mayo. 
 
 " When we compare together the several regions of the trunk, we 
 observe that it is laid out in corresponding organs, or pairs of organs, 
 on either side of a centre, which is formed by the five lumbar verte- 
 brae. Above the lumbar vertebrae are the dorsal ; above these, the 
 cervical : below the lumbar vertebrae are the sacral bones ; below 
 these, the coccygeal. To the dorsal vertebrae and to the sacrum, 
 bones are articulated, which have the double ofiice of forming a vis- 
 
THE EXTREMITIES. 141 
 
 ceral cavity, and of throwing to a convenient distance from the me- 
 sial plane the bones of the extremities. The ribs and sternum, the 
 clavicles and scapulae, form, with the dorsal vertebrse, an organ strictly 
 analogous to that formed by the ossa innominata and the sacrum. 
 But the chest for the function of respiration requires to be continually 
 altering its dimensions, and the upper extremity is characterized by 
 the extent and velocity of its movements, rather than by strength : 
 to suit both these objects, the chest and shoulder are formed of many 
 bones, that are movable in various senses ; the ribs are capable both 
 of rotating upon their sternal and vertebral joints, and of being raised 
 or depressed upon their vertebral joints, carrying with them the ster- 
 num : the clavicle again rolls upon the sternum, and the scapula rolls 
 upon the convexity of the ribs. On the other hand, the pelvis, as 
 regards the viscera, is intended merely for their support; and if, 
 during labor, a temporary enlargement of its lower aperture is re- 
 quisite, the flexibility of the joints of the os coccygis in the female 
 skeleton, with the temporary yielding of the ligaments, affords a suf- 
 ficient provision, for this object: the inferior extremities again require 
 to be articulated to a solid, unyielding platform, upon which they 
 may poise the incumbent weight of the trunk and head. The bones 
 of the pelvis are for these reasons few, weighty, massive, and knit 
 together immovably. Thus accurately do the points, in which a 
 resemblance is wanting between the chest and pelvis, preserve the 
 analogy between these parts." 
 
 Of the Extremities. — In no part of the skeleton is the adaptation of 
 anatomical disposition and structure to function more strikingly ob- 
 vious than in the bones of the extremities. 
 
 The lower extremities form powerful pillars of support for the trunk 
 in the erect posture. The great strength of the femur and tibia, 
 which form the principal portion of each pillar, fit them admirably 
 for this office ; and it is interesting to notice that dense osseous tissue 
 in each of these bones is most abundant in those situations where the 
 greatest strain of the pressure from above is felt. This may be seen 
 in a transverse section of either, when a dense spine of bone is found 
 corresponding to the concave surface of each ; this is most distinct 
 in the femur, where the dense bone alluded to constitutes the linea 
 aspera. 
 
 The femur is curved forward, and this incurvation gives elasticity 
 to the bone, and aids in distributing the force of concussions. Its 
 shaft is inclined downwards and inwards, so that the opposite femora 
 approach each other inferiorly at the knee-joints, while they are sepa- 
 rated by a considerable interval above. And this interval is increased 
 by the head and neck of each femur being united to the shaft at an 
 obtuse angle ; this angle is one of about 135 degrees in the male ; it 
 is somewhat smaller in the female. 
 
 It is evident that the femur must suffer in point of strength from 
 this mode of junction of its neck and shaft, for a bone without any 
 bend in its axis must necessarily be more capable of resisting down- 
 ward compression, than one consisting of two pieces united at an 
 angle. But we observe here, as in other parts of the mechanism of j 
 
142 ORGANS OF LOCOMOTION. 
 
 the human body, that the disadvantage in one respect is more than 
 counterbalanced by certain advantages which this peculiar arrange- 
 ment offers, and which could be attained in no other way ; for the 
 junction of the neck with the shaft throws the thigh-bone outwards to 
 a certain distance, and leaves abundant room for the play of the ad- 
 ductor muscles : this could only be attained otherwise by greatly 
 enlarging the pelvis in the transverse direction. And again, in the 
 movements of the femur, much is gained ; for rotation can be per- 
 formed with little muscular effort by reason of the favourable leverage 
 afforded by the neck of the bone and the trochanter major. The 
 increased power thus given to the rotator muscles has considerable 
 effect in walking, which is on that account performed more lightly, 
 and without any circumduction of the limb. 
 
 , It is owing to this disposition of the neck of the thigh-bone, that, 
 when its lower extremity advances in the vertical plane, its head and 
 neck turn on a horizontal axis ; in other words, that the angular 
 motion of its shaft is converted into a rotatory movement at the hip- 
 joint. And from such an arrangement this great advantage results, 
 that in the various motions or states of the joints, as extreme or par- 
 tial flexion, extension, &c., the same, or very nearly the same, extent 
 of the articulating surfaces is exposed to pressure : for, as Mr. Ward 
 expresses it, the rotation of a hemispherical head within a socket of 
 the same form invalves no diminution of the extent of the contiguous 
 articulating surfaces; but the angular motion of a joint of this kind 
 throws part of the ball out of the socket, and leaves part of the socket 
 without bearings to rest upon, so that the weight, instead of being 
 distributed equally over the whole surface of the head, is concentrated 
 upon that portion which remains within the cavity. (Ward, loc. cit.) 
 Moreover, the joint gains as regards the extent of flexion by this 
 conversion of angular into rotatory motion, for an angular motion in 
 the acetabulum would be readily checked by the edge of the cavity 
 coming in contact with the neck of the bone; " whereas rotation 
 meets no such check in the conformation of the joint itself, but may 
 be continued. indefinitely, until opposed by the tension of ligaments, 
 or some other adventitious obstacle." 
 
 In the structure of the extremities of the femur, we find evidence 
 of much beautiful mechanical contrivance, in the disposition of the 
 compact tissue, and of the rods or fibres of the cancellous texture, 
 having an obvious reference to the direction of the weight to be sus- 
 tained as well as to the dispersion of concussions. The neck of the 
 thigh-bone, having to bear considerable superincumbent weight, is 
 strengthened on its inferior surface by an arch of compact tissue, 
 gradually increasing in thickness as it proceeds from above down- 
 wards, and well suited by its rigidity to oppose bending ; but on its 
 upper surface the compact tissue is thin, and the reticular texture 
 consists of somewhat arched fibres freely interwoven, running parallel 
 to bat surface, and disposed so as to present a surface to resist the ' 
 direct influence of pressure (fig. 18, p. 106). The direction of the 
 fibres of the < reticular texture of the inferior part of the neck is 
 chiefly downwards to the trochanter minor, and it seems to establish 
 
THE UPPER EXTREMITY. 143 
 
 a communication between the osseous tissue of the head of the bone, 
 and the dense structure which forms the lower part of the neck. 
 
 The lower extremity of the femur is almost entirely composed of 
 cancellated texture, and affords a broad surface, for articulation with 
 the head of the tibia to form the knee-joint. As the tibia is placed 
 vertically under it, it not only transfers the weight from above to that 
 bone, but it is particularly exposed to suffer from concussions con- 
 veyed upwards by the tibia. Its structure seems disposed so as to 
 facilitate the dispersion of such concussions, the sides of the condyles 
 projecting considerably beyond the surface of the shaft of the bone, 
 and there being but little continuity of tissue between it and the 
 lower end of the bone. 
 
 Of the bones of the leg, the tibia, from its strength and size, is 
 evidently that which is destined to support the thigh ; the fibula must 
 be regarded as entirely accessory in its office, affording attachment to 
 the interosseous ligament, and forming a greater extent of surface for 
 the origin of muscles. By its lower extremity it supports the ankle- 
 joint on the outside. 
 
 The tibia rests upon the astragalus, and through that bone trans- 
 mits the weight to the foot. The length of this organ, its breadth, 
 and its arched form, adapt it as a basis of support for the body in 
 the erect posture, and as an instrument of locomotion. It obtains 
 elasticity, and a certain amount of mobility, from its being composed 
 of several small and light bones articulated together. These bones, 
 although almost entirely composed of reticular texture, possess con- 
 siderable power of resistance to direct pressure in those directions in 
 which the strain would chiefly bear in the movements of the ^organ, 
 and this is to be attributed to the direction of the fibres of their 
 cancellous tissue. The principal elasticity of the foot is longitudinal, 
 by reason of its arch being in that direction, resting upon the heel 
 behind, and on the toes in front ; but it also yields somewhat in the 
 transverse direction, or that of the arch formed by the cuneiform bones. 
 The extension of the os calcis backwards not only adds to the length 
 of the longitudinal arch, but it also affords a considerable leverage to 
 the muscles of the calf of the leg. 
 
 Upper Extremity. — ^^The disposition and structure of the bones of 
 the upper extremity afford a marked contrast to those of the lower. 
 The latter are organs of support, and therefore are solid, firm, strong, 
 and, withal, elastic. Tbe former are destined to perform extended 
 motions, as well as minute and nicely adjusted ones ; and, therefore, 
 while they possess all the requisite strength, they are light, present 
 little expanse of surface, and are articulated by numerous very mov- 
 able articulations. 
 
 The scapula and clavicle are the media through which the bones 
 of the arm are united to the trunk. The former bone is remarkably 
 thin and light, and seems little more than a surface of attachment for 
 various muscles, on whose actions the extensive movements of the 
 arm depend. By the clavicle it is connected to the sternum, through 
 the sterno-clavicular articulation, the movements of which, although 
 occurring only in two planes, intersecting each other at right angles,, 
 
144 ORGANS OF LOCOMOTION. 
 
 are such as to favour a wide range of motion in the shoulder. So 
 necessary is this joint to the general movements of the shoulder, that 
 any injury or disease of it, or of the bone itself, shows itself speedily 
 in the impediment offered to those movements. And the law of the 
 development of this bone in the lower animals is clearly connected 
 with a necessity for a wide range of motion in the anterior extremity. 
 In those animals that employ the anterior extremity only as an instru- 
 ment of progressive motion, there is no clavicle ; hence this bone is 
 absent from the skeletons of Pachydermata, Ruminantia, Solipeda, 
 and the motions of the shoulder are only such as may be required for 
 the flexion and extension of the limb. In the Carnivora, where there 
 is a slight increase in the range of motion of the anterior extremities, 
 a rudimentary clavicle exists; and in this class we observe that the 
 size of the bone bears a direct relation to the extent of motion enjoyed 
 by the limb. Thus it is smallest in the dogs, and largest in the cats: 
 in these animals it has no attachment to either the sternum or the 
 scapula, but is enclosed in the flesh, and does not occupy much more 
 than half the space between the two bones last named. " But how- 
 ever imperfect," says Sir C. Bell, "it marks a correspondence in the 
 bones of the shoulder to those of the arm and paw, and the extent 
 of the motion enjoyed. When the bear stands up, we perceive, by 
 his ungainly attitude, and the motion of his paws, that there must be 
 a wide difference in the bones of his upper extremity from thoge of 
 the ruminant or soliped ; he can take the keeper's hat from his head, 
 and hold it ; he can hug an animal to death. The ant-bear, especially, 
 as he is deficient in teeth, possesses extraordinary power of hugging 
 with his great paws; and, although harmless in disposition, he can 
 squeeze his enemy, the jaguar, to death. These actions, and the 
 powers of climbing, result from the structure of the shoulder, or from 
 possessing a collar bone, however imperfect." (Bridgewater Treatise, 
 p. 48.) 
 
 In those Mammalia that dig and burrow in the ground, or whose 
 anterior extremities are so modified as to aid them in flight, or which 
 are skillful in seizing upon and holding objects with their paws, the 
 clavicle is fully developed, and extends the whole way from the sca- 
 pula to the sternum. Thus in the Rodentia this bone is very perfect, 
 as, for example, the squirrel, the beaver, the rabbit, the rat, &c. The 
 bat affords an example of a very strong and long clavicle, as also do 
 the mole and the hedgehog among the Insectivora. 
 
 Among the Edentata those tribes possess a clavicle whose habits 
 are fossorial, as the ant-eater, the armadillo, and even the gigantic 
 extinct megatherium. In the Quadrumana the clavicles are strong, 
 and curved, as in the human subject. 
 
 The clavicle possesses considerable elasticity by reason of its curves ; 
 a property obviously of the greatest importance to it, because, as the 
 bond of connection of the shoulder to the trunk, it is liable to partici- 
 pate in the many concussions to which the upper extremity is exposed. 
 This point has been put to the test of direct experiment by Mr. Ward. 
 He employed the clavicle of a well-developed male subject, of the 
 middle age : this was placed upon a smooth surface, with its shaft 
 
THE UPPER EXTREMITY. 145 
 
 perpendicular to the plane of a wall, against which its inner extremity 
 rested ; a smart blow was then struck with a hammer on the outer 
 extremity of the bone in the direction of its long axis; the hammer 
 rebounded from the end of the bone, which sprang to a distance of 
 nearly two feet from the wall. 
 
 The humerus is the principal lever of the upper extremity : in man 
 it is light, and its articular extremities are constructed to contribute 
 to the formation of very movable joints. The bones of the fore-arm 
 are also remarkable for their lightness and elasticity ; and they move 
 freely, not only on the humerus, but on each other. The movements 
 of pronation and supination, which are necessary to the free and full 
 use of the hand, are performed by the rotation of the radius round an 
 axis passing through its head and neck ; the slight curve in the shaft 
 of the radius causes its carpal extremity to pass through a considera- 
 ble space during the rotation of the forearm. 
 
 The contrast between the solidity and elastic firmness of the foot, 
 and the lightness, flexibility and mobility of the hand, is most striking. 
 The analogy between the anatomical elements of both organs is com- 
 plete : but they are modified to suit the office for which each is de- 
 stined ; the foot as a basis of support, the hand as a prehensile organ. 
 The hand is modified remarkably from the form of the foot by the 
 divergence of the outer metacarpal bone, to form the thumb: this 
 bone at its articulation with the carpus enjoys a considerable degree 
 of mobility, in virtue of which exists the opposable faculty of the 
 thumb ; a power which, in a state of perfection, is peculiar to the 
 human hand. 
 
 While the hand is so remarkably mobile, it is well protected 
 against the effects of compression, or concussion, by the number of 
 its joints, and the interposed cartilages and fibro-cartilages, and the 
 soft covering of fat which lies beneath the skin of the palm ; and its 
 strength is abundantly provided for in the strong ligaments which 
 connect the bones to each other, and the fibrous expansions which 
 cover them. 
 
 One of the most wonderful circumstances in the construction of the 
 hand, is its adaptability to an infinite number of offices. A powerful 
 organ of prehension, it is yet capable of adjusting the finest pieces of 
 mechanism, or of exposing to view the minutest wonders of nature : 
 an admirable and most delicate instrument of touch, it may neverthe- 
 less be employed as a fearful and deadly weapon of offence : at one 
 time it may be used to lift great weights, to pull at the cable, or to 
 turn the windlass; and, again, it will execute the most varied and 
 rapid movements, in the performance -of works or artifices which 
 human talent has invented. 
 
 The hand is the obedient minister of man's volition and of his 
 genius, and, too often, the blind slare of his emotions and his pas- 
 sions. 
 
 The following references are subjoined: — The various treatises on General Ana- 
 tomy; thearticle Articulation, in the Cyclopsediaof Anatomy and Physiology; Mayo's 
 Physiology, chap. xi. ; Bell's Animal Mechanics ; Arnoti's Elements of Physics, vol. 
 i. p. 218; Anatomie Descriptive, par Bichat, t. i. ; Oatlines of Human Osteology, by 
 8 
 
146 ORGANS OF LOCOMOTION. 
 
 F. O. Ward, a work to te strongly recommended, as well for its exact and clear de- 
 scriptions, as for the excellent and original views on the mechanism of the skeleton, 
 with which it abounds. We shall be glad to see it published in aform more suitable 
 to its great merit. 
 
 CHAPTER VII. 
 
 ACTIVE ORGANS OF LOCOMOTION. — OF MUSCLE. — MUSCLE WITH STRIPED 
 
 FIBRES MUSCLE WITH UNSTRIPED FIBRES. MUSCULAR ACTION. — 
 
 ATTITUDES AND MOVEMENTS OF THE FRAME. 
 
 The principal movements of the body, and all those by which 
 locomotion is efTected, are performed by means of a tissue termed 
 muscle, endowed with the power of contracting, and consisting, 
 ■chemically, of fibrine. This substance is arranged in the foriii of 
 unbranched fibres of definite size and structure, and which, when 
 examined under a high magnifying power, are found to be of two 
 kinds, distinguishable from one another by the presence or absence 
 of very close and minute transverse bars or stripes. The fibres of the 
 voluntary muscles, (or those whose movements can be either excited 
 or controlled by volition,) as well as the fibres of the heart, and some 
 of those of the oesophagus, are striped ; while all other muscles, in- 
 cluding those of the alimentary canal, the uterus, and bladder, all of 
 which are involuntary, are unstriped. 
 
 The elementary fibres of the voluntary muscles are connected to 
 one another by areolar tissue, and arranged in sets parallel to one 
 another. They are supplied with vessels and nerves, which lie in 
 the intervals between them ; and are attached, by their extremities, 
 through the medium of tendon, aponeurosis, or somfe form of the 
 fibrous tissue, to the parts which they are destined to move. They 
 form organs, for the most part solid and elongated, but which are 
 sometimes expanded into a membranous shape. 
 
 The sets of fibres of the involuntary muscles, on the other hand, 
 usually cross each other at various angles, and interlace, and they are 
 always arranged as membranous organs enclosing a cavity, which 
 their contraction serves to constrict. The heart, besides being inde- 
 pendent of the will, agrees in both these anatomical characters with 
 the involuntary muscles, and is only allied to the voluntary by the 
 presence in its fibres of the transverse stripes. 
 
 We shall commence with a description of the two forms of fibre. 
 Of the striped fibres. — The length of these is usually about that of 
 ■ the muscle to which they belong, but occasionally they are interrupted 
 by tendinous intersections, as in the rectus abdominis and semiten- 
 dinosus ; and it is very common for them to fall short of the length of 
 the whole organ, in consequence of an oblique disposition, as seen in 
 penniform muscles. In the sartorius they often exceed two feet in 
 length, while in the stapedius they are not two lines. They vary in 
 
STRIPED MUSCLE. 
 
 147 
 
 diameter from A to 
 
 _i 
 
 5 
 
 of an inch, be 
 
 Fig. 36. 
 
 Transverse sections of striped 
 muscle that hsul been injected 
 and dried, magnified 70 diame- 
 ters ; — A. From tlie Frog. B. From 
 the Dog. b. b. Section of elemen- 
 tary fibres, sliowing their angular 
 form and various size, a, a. Sec- 
 tions of the injected capillaries, 
 showiiigthc position they occupy 
 among'the libres. a' .Transverse 
 branch between two longitudinal 
 capillaries. These figures show 
 the greater vascularity of the 
 muscle, with the narrower ele- ' 
 mentary fibres. 
 
 largest in Crustacea, fish and reptiles, where 
 their irritability is enduring; and smallest in 
 birds, where it is most evanescent. The in- 
 dividual fibres, however, vary considerably 
 in thickness in the members of the several 
 tribes, and even in the same animal and 
 muscle. Their average width in man is 
 about 4-g^ of an inch. They are not cylin- 
 drical, but flattened more or less, by being 
 closely packed together. This may be ascer- 
 tained in the recent state, or still better by 
 a transverse section of a dried muscle. Small 
 interspaces are left, however, for the passage 
 of the capillary blood-vessels along the angles 
 of junction, and sometitaps between the con- 
 tiguous sides. (Fig. 36.) 
 
 Internal structure. — The beautiful cross- 
 markings on the voluntary fibre have been 
 known from the early days of microscopical 
 research, and have given occasion to a 
 variety of hypothetical and generally me- 
 chanical solutions of the problem of contraction ; which, by warping 
 the minds of observers, have had the effect of greatly complicating 
 an already difficult subject, that of the internal anatomy of the fibre, 
 which can only be determined by pure observation. Fontana alone 
 among the older anatomists abstained from vague speculation ; and he 
 arrived nearest to the truth. He found that the fibre was apt to split 
 up into fine fibrillae, each of which was a series of particles ; and he 
 imagined that the transverse lines were; caused by the regular apposi- 
 tion side by side of the particles of the contiguous fibrillse. It was 
 customary both before and since his time, as at the present day, to 
 regard the fibre as a bundle of smaller ones, whence the term primi- 
 tive fasciculus, first given to it by him and,, adopted by Miiller: but 
 this view of the subject is imperfect. The fibre always presents, upon 
 and within it, longitudinal dark lines, along which it will generally 
 split up into fibrillae ; but it is by a fracture alone that such fibrillae 
 are obtained. They do not exist as such in the fibre. And, further, 
 it occasionally happens that no disposition whatever is shown to this 
 longitudinal cleavage ; but that, on the contrary, violence causes a 
 separation along the transverse dark lines, which always intersect the 
 fibre in a plane perpendicular to its axis. By such a cleavage, discs, 
 and not fibrillae, are obtained ; and this cleavage is just as natural, 
 though less frequent than the former. Hence it is as proper to say 
 that the fibre is a pile of discs, as that it is a bundle of fibrillije : but, 
 in fact, it is neither the one nor the other, but a mass in whose struc- 
 ture there is an -intimation of the existence of both, and a tendency 
 to cleave in the two directions. If there were a general disintegration 
 along all the lines in both directions, there would result a series of 
 particles, which may be termed primitive particles or sarcous elements, 
 
148 
 
 ORGANS OF LOCOMOTION. 
 
 the union of •which constitutes the mass of the fibre. These element- 
 ary particles are arranged and united together in the two directions. 
 
 Fig. 37. 
 
 Fraj^ents of striped elementary fibres, showing a cleavage in opposite directions; magnified 
 300 diameters:— 1. Longitudinal cleavage. The longitudinal and transverse lines are botii seen. 
 Some longitudinal lines are darker and wider than the rest, and are not continuous from end to end : 
 this results from partial separation of the fibrillEE. 6. FibrillBe, separated from one another by violence 
 at the broken end of the fibre, and marked by transverse lines equal in width to those on the fibre. 
 7, 8, represent two appearances commonly presented by the separated single fibrillae. (More highly 
 magnified.) At 7, the borders and transverse lines are all perfectly rectilinear, and the included 
 spaces perfectly rectangular. At 8, the borders are scalloped, the spaces bead-like. When most 
 distinct and deiinite, the fibrilla presents the former of these appearances. — 2. Transverse cleavage. 
 The longitudinal lines are scarcely visible. 3. Incomplete fracture following the opposite surface of 
 a disc, which stretches across the interval and retains the two fragments in connection. The Vdges 
 and surface of this disc are seen to be minutely granular, the ^anules corresponding in size to the 
 thickness of the disc, and to the distance between the faint longitudinal lines. 4. Another disc nearly 
 detached. 5. Detached disc more highly magnified, showing the sarcous elements 
 
 All the resulting discs as well as fibriliee are equal to one another in size, 
 and contain an equal number of particles. The. same particles compose 
 both. To detach an entire fibrilla is to abstract a particle of every disc, 
 and vice versa. The width of the fibre is therefore uniform, and is 
 equal to the diameter of any one of the discs. Its length is thei length 
 of any one of its fibrilise, and is liable to the greatest variety. 
 
 Muiler, Schwann, Lauth, and others, consider, with us, that the 
 cross stripes of the fibre are formed by the apposition side by side of 
 the dark points seen on the separated fibrillse; but some believe these 
 stripes to be present only on the surface of the fibre, and to be formed 
 by the spiral windings of a filament. Considerable diversity of opin- 
 ion also exists as to the nature of the alternate light and dark points 
 seen on the individual fibrillse ; some conceiving them to indicate a 
 single spiral, others a double spiral arrangement ; some imagining 
 them to be minute zigzag bendings, others indentations, and others 
 still that they depend on the alteration of two kinds of substance. 
 On this account we shall explain in a few words our reason for 
 adopting the view above summarily given. A sofl mass made up of 
 an immense congeries of highly refracting particles cannot but exhibit 
 many deceptive appearances when viewed by transmitted light, and 
 through glasses of bad defining power. The slightest disturbance of 
 its interior structure will affect the refractions, which will thus be rea- 
 dily made to disguise and modify the true form and arrangement of its 
 integrant parts ; on which account great care and circumspection, and 
 
STRIPED MUSCLE. 149 
 
 a total freedom from bias, are requisite for an observer who would 
 not be misled to mistake appearances for realities. 
 
 That the stripes are not caused by a structure distinct from the 
 fibrillffi, and present only on the surface of the fibre, is evident from 
 the following facts : 
 
 1 . That a transverse section of a fibre "'S- 38. 
 shows it to be solid, and not hollow; 
 and that the ends of fibrillae, as seen 
 on the section, exist throughout its inte- 
 rior just as on its surface (fig. 38). 
 
 2. That fibriUaj taken from any part 
 of a fibre are marked -with light and 
 dark points, corresponding in distance 
 and force with the transverse stripes of 
 
 the fibre. Transvexsesectionofthreeelementary 
 
 r\ rrii i *ii T ■ 1- T ■ fibres of the dried pectoral muscle of the 
 
 6. inat With a nign magnilying leoHQuerquedula crecca),tiea.tadvrith 
 
 .^« ««„li„^ +,^- o tUirtlr flU*.n -.-..ri weak citric acid ; -showinff the round re- 
 
 power, applied to a thick hbre, we fractingparticles separated from one an- 
 
 mav bring all parts of its interior into other. The cut edge of the tubular sheath 
 
 'J . o ^ . 1 . of each fibre isalso seen, as well as the 
 
 focus in succession, and perceive capillary vessel s, a, in the intervals. 
 
 throughout the same kind of stripes. 
 
 The occasional appearance, therefore, of these stripes being con- 
 fined to the surface is deceptive. They are sometimes more strongly 
 marked there, partly because there is a greater condensation of the 
 tissue there, and partly from the circumstance of the fibre being usu- 
 ally immersed, when examined, in a fluid of less density than itself. 
 This appearance is always greatly diminished by placing the fibre in 
 syrup. But the point of greatest interest is as to the nature of the 
 markings on the individual fibrillse or discs. It is unsafe to come to 
 a conclusion on this question from any appearances seen on the entire 
 fibre ; for it is clear that the relative position of the particles may be 
 very easily deranged, ahd their regularity broken, by the slightest 
 injury to the mass. 
 
 Two appearances commonly present themselves in examining the 
 striped fibres : in some parts the cross stripes are perfectly rectilinear, 
 or, if curvilinear, parallel in their course ; in other parts, these stripes 
 do not extend across the fibre, but are more or less interrupted, 
 forming zigzags and enclosing spaces of a great variety of shape and 
 size, in concert with the longitudinal stripes. In such specimens we 
 see the semblance of spirals in almost infinite number and variety. 
 The former of these appearances is most seen in large fibres, and 
 where great care has been used not to drag the tissue ; the latter 
 under the reverse circumstances. The former seems on 21 prima facie 
 view an unrautilated, the latter a deranged condition ; and they may 
 be proved to be so by a further examination. 
 
 For this purpose we should make choice of a fresh fibre which is 
 prone to separate into its individual fibrillee, and which exhibits their 
 outline in the greatest distinctness and beauty.* If fibrillse entirely 
 
 * The fibres of fishes will generally provre better than those of mammalia, because 
 they usually cleave into fibrillas having very sharp and clear outlines; and those of 
 the salmon, for example, will seldom fail to do su. 
 
150 
 
 ORGANS OF LOCOMOTION. 
 
 Fig. 39. 
 
 isolated be now inspected, they will be found to present alternate 
 light and dark points, when the part is a little out of focus. The 
 light points are the centres of highly refracting particles, acting as 
 lenses; the dark points, the intervals between them (fig. 37, 8). If 
 now the focus be carefully adjusted, and the achromatic condenser 
 be employed for the purpose of defining the outline with the utmost 
 precision, each dark interspace between the refracting points will be 
 found to be reduced to two very slender straight lines, crossing the 
 fibrilla in a perfectly transverse direction, and giving the light spaces, 
 as now seen, a rectangular figure (fig. 37, 7). Now, it is absolutely 
 certain that no spiral arrangement could produce, or even co-exist 
 with, these unequivocal appearances; but itis^not difficult to compre- 
 hend how a derangement of the lateral parallelism of 
 these refracting particles should produce an appear- 
 ance of spirals in the fibre, or how two fibrillae running 
 together, but with their particles slightly deranged, 
 should wear the same very deceptive aspect. 
 
 In fig. 39 is represented the border of some fibres, 
 from which several of the sarcous elements have been 
 removed accidentally by maceration in weak spirit. 
 The remaining ones project in lateral series, evincing 
 their adhesion to one another in that direction, and 
 the non-existence of any spiral arrangement. • 
 
 The size of the particles composing the fibre may 
 be measured in one direction by the transverse stripes 
 formed by their union. 
 
 The following average, deduced from numerous 
 observations, shows great uniformity in this respect. 
 
 Eiig. In. No. of Observations, 
 
 In the Human subject j Jj^ 27 
 
 " Mammalia generally T^itrff 13 
 
 "Birds • .„iij5 
 
 "Reptiles „^5j. . . .,. . . . 
 
 Fish 
 
 rh 
 
 " Insects 5^155 
 
 7 
 
 7 
 
 20 
 
 In the opposite direction, or that marked by the distance between 
 the longitudinal dark lines of the fibre, their diameter is less, often by 
 one half. It is important to remark, that these measurements are 
 taken from uncontracted specimens, since during contraction the 
 relative diameters of the particles are changed. 
 
 Of the sarcolemma. — The striped fibre is enclosed in a tubular 
 sheath or sarcolemma, adapted to its surface, and adhering to it. 
 This consists of a transparent, very delicate, but tough and elastic 
 meinbrane, which isolates the fibre from all other tissues. In gene- 
 ral, it has no appearance of any kind of structure; but in the case of 
 bulky fibres, where it is strong in proportion, faint indications may 
 be detected of a complex interweaving of filaments far too minute to 
 be individually recognized. It occasionally has small corpuscles, 
 the remains of cell-nuclei, in contact with it. 
 
THE SARCOLEMMA. 
 
 151 
 
 This membrane may be sometimes seen forming a transparent 
 border to the fibre beyond, the limit of the cross stripes; or it may 
 be seen stretching between the separated fragments of a fibre which 
 has been brokien within it, for its toughness will often resist a force 
 
 Fig. 40. 
 
 Fig. 41. 
 
 
 Fragments of an elementary fibre of the 
 Skate, held together by the untorn but tvrist- 
 ed sarcolemma. 
 
 ^ 
 
 Part of an elementary fibre Yrom the "Skate, 
 treated -with liq.potassse; showing a protrusion 
 through the sarcolemma: — Corpuscles are seen 
 scattered througliout the mass, and soine de- 
 tached ones are represented ; their average di- 
 ameter is one-thousandth of an English inch. 
 
 before which its brittle contents give way. If the fibre be immersed 
 in acid, it swells, often so suddenly as to burst the sheath at nume- 
 rous places, and protrude in the form of small hernias. These her- 
 niee are very peculiar and illustrate the account already given of the 
 internal composition of the fibre ; for the particles of the protruded 
 mass are necessarily deranged, and their lateral parallelism destroyed. 
 Now, the result of this is the production of the most beautiful and 
 varied curves, intersecting one another, very similar to those already 
 spoken of on the injured fibre, and wearing a very plausible aspect 
 of spirals (fig. 41). Again, the sarcolemma may be seen raised in 
 the form of vesicles from the surface of the fibre, in certain states of 
 contraction in water, which will be reverted to. By one or more of 
 these modes of demonstration, we know that this isolator of the 
 sarcous tissue invests the striped elementary fibre of voluntary muscle 
 in all animals. Its existence is as yet doubtful in the heart. 
 
 Every fibre is attached by its extremities to fibrous tissue, or to 
 some tissue analogous to it ; but an accurate examination of this 
 difficult subject lends no countenance to the ordinarily received 
 opinion, that this tissue is prolonged over the whole fibre from end to 
 
 Fig. 42. 
 
 Elementary fibre from the leg of the large Meat-fly {Musca vomitoria) : a. a. Line of termination 
 of the fibre, along which the tendon, *, is attached to it. m. Central series of corpuscles.— Along the 
 margin, the sarcolemma is elevated t)y water, (which has been absorbed,) and is thereby shown to 
 be atlherent to the margin of the discs. 
 
152 
 
 ORGANS OF LOCOMOTION. 
 
 Fig. 43. 
 
 end, as its cellular sheath; nor is this view reconcilable with the 
 physical requirements of the case. It is extremely difficult to iso- 
 late a muscular fibre, with the tendinous fibrillae pertaining to it, 
 either in mammalia or birds ; but this may be occasionally accom- 
 plished in fishes, and in certain muscles of insects. In these exam- 
 ples, the minute detachment of the 
 fibrous tissue may be seen to pass, 
 and to become attached to the 
 truncated extremity of the fibre. 
 The fibre ends by a perfect disc, 
 and with the wht)le surface of 
 this disc the tendon is connected 
 and continuous. The sarcolemma 
 ceases abruptly at the circumfer- 
 ence of the tertninal disc, and here 
 some small' part of the tendinous 
 material appears to be joined to it. 
 In other cases, where the muscle 
 is fixed obliquely to a membranous 
 surface, each fibre is obliquely 
 truncated at its extremity, at an 
 angle determined by the inclination of its axis ; instances of which 
 may be seen among the Crustacea, and elsewhere. , 
 
 The researches of Valentin and Schwann have shown that a muscle 
 consists, in the earliest stage, of a mass of nucleated cells, which first 
 arrange themselves in a linear series, with more or less regularity, and 
 then unite to constitute the elementary fibres. As this process of the 
 
 Fig. 44. 
 
 Attachment of tendon to an elementary fibre 
 from the Skate :— On bringing deeper and 
 deeper portions of the specimen into focus, 
 along the line of union, a.- a., fresh tendinous 
 ■wavy filaments and striated muscular parts 
 came into view together. /. Tendon, m. 
 Muscle. 
 
 Stages of the development of striped muscular fibre. 
 
 1. Arrangement of the primitive cells in alinear series.— Ai^er Schwann. 
 
 2. The cells united. The nuclei separated, and some broken up ; longitudinal lines becoming ap- 
 parent,— Prom a fcetal calf three inches lone. 
 
 3. 4. Transverse stripes apparent. In 3, the nuclei are internal, and bulge the fibre. In 4, Ihey 
 are prominent on the surface.— From a fojtal calf of two months old. 
 
 . ?■ Transverse stripes, fully formed and dark j nuclei disappearing from view.— From the human 
 infant at birth. 
 
 6. Eleraentajy fibre from the adult, treated with acid ; 
 300 diam. ' 
 
 showing the nuclei.— Magnified about 
 
 union of the cells is going forward, a deposit of contractile material 
 gradually takes place within them, commencing on the inner surface, 
 and advancing towards the centre, till the whole is solidified. The 
 
UNSTRIPED MUSCLE. 153 
 
 deposition occurs in granules, which, as they come into view, are 
 seen to be disposed in the utmost order, according to the two direc- 
 tions already specified. These granules, or sarcous elements, being 
 of the same size as in the perfect muscle, the transverse stripes 
 resulting from their opposition are of the same Width as in thte adult; 
 but, as they are very few in number, the fibres which they compose 
 are of corresponding tenuity. From the very first moment of their 
 formation, these granules are parts of a mass, and not independent of 
 one another ; for, as soon as solid matter is deposited in the cells, faint 
 indications of a regular arrangement in granules are usually to be met 
 with. It is common for the longitudinal lines to become well-defined 
 before the transverse ones. When both are become strongly marked, 
 as is always the case at birth, the nuclei of the cells, which were be- 
 fore visible, disappear from view, being shrouded by the dark shadows 
 caused by the multitudinous refractions of the light transmitted through 
 the mass of granules : but they can still be shown to exist in the per- 
 fect fibre, in all animals, and at all periods of life, by immersion in a 
 weak acid : which, while it swells the fibrous material of the granules, 
 and obliterates their intervening lines, has no action on the nuclei. 
 
 These nuclei in insects are arranged, in the early con- 
 dition of the fibre, as a single or double series along the ^'S- ^5. 
 axis (fig. 45) ; and, in the adult state, they retain the 
 same position (fig. 42). In vertebrate animals they are 
 scattered more irregularly, but at pretty equal distances 
 throughout the mass in both fcetal and adult conditions. 
 In the fully formed fibre, if it be large, they lie at various 
 depths within it,; but, if small, they are at or near the sur- 
 face. They are oval and flat, and of so little substance, 
 that though many times larger than the sarcous elements, 
 and lying amongst them, they do not interfere with their 
 mutual apposition and union. These corpuscles are fre- 
 quently the cause of irregular longitudinal dark streaks, g^e^ftomthe 
 seen in the fibre by transmitted light. They usually con- i^F^.^f "j" 
 tain some central granules or nucleoli. It is doubtful aneariys'tage 
 whether the identical corpuscles, originally present, remain mem'i'^lhowl 
 through life, or whether successive crops advance and j^i, "io^*^^"} 
 decay during the progress of growth and nutrition : but it S?'"P"?S'|^3^ 
 is certain, that as development proceeds, fresh corpuscles diam. 
 are deposited, since. their absolute number is far greater in 
 the adult than in the fcetus, while their number relatively to the bulk 
 of the fibre, at these two epochs, remains nearly the same. 
 
 Muscles grow by an increase, not of the number, but of the bulk 
 of their elementary fibres: there is reason to believe that the number 
 of fibres remains through life as it was, in the fcetus, and that the 
 spare or muscular build of the individual is determined by the mould 
 in which his body was originally cast. 
 
 Of the unstriped fibres. — This variety possesses less interest than 
 the othef, in consequence of the apparent simplicity of its structure. 
 The fibres consist of flattened bands, generally of a pale colour, 
 bulged at frequent intervals by elongated corpuscles, similar to those 
 
154 
 
 ORGANS OF LOCOMOTION. 
 
 Fibres of unstriped muscle:— c. In 
 their natural state, a. Treated with 
 acetic acid, sho'wina: the corpuscles. 6.' 
 Corpuscles, or nuclei, detached^ sl^ovr- 
 ing their various appearances. 
 
 Fig. 46. of striped muscle and capable of being 
 
 displayed by the same process.* The 
 texture of these fibres seems to be ho- 
 mogeneous. By transmitted light, they 
 have usually a soft, very finely mottled 
 aspect, and -without a darkly-shaded 
 border. Sometimes the mottling is so 
 
 i\ If Hi lilllll decided as to appear granular, and oc- 
 9 H M i« ;'iflll 1 casionally these granules are arranged 
 in a linear series for some distance. 
 This condition is probably an approach 
 towards the structure of the striped fibre, 
 for these granules are about the size of 
 the sarcous elements already described. 
 It is generally to be seen more or less 
 distinctly in the gizzards of birds ; and 
 may be now and then met with in the 
 fresh muscle of the stomach, intestinal 
 canal, urinary bladder, and uterus of 
 mammalia. The ordinary diameter of 
 the unstriped fibre is from ^bVs to js'n 
 of an inch. 
 
 It might be expected, from this §ic- 
 count of the appearance of these fibres, that their discrimination from 
 other tissues would be often diflacult. The peculiar texture, however, 
 the size, the soft margin, and, above all, the presence of numerous 
 elongated oval corpuscles with two or three granules near their centre, 
 are characters which, when united, will seldom be mistaken.. As a 
 number of fibres commonly take a parallel course together, the bulg- 
 ings occasioned by the corpuscles give rise to partial longitudinal 
 shadows, extending for some way beyond the corpuscles in the inter- 
 vals of the fibres. As these irregular longitudinal shadows occur 
 pretty uniformly throughout a bundle of fibres, and as some of them 
 are necessarily out of focus, while others are in focus, the whole 
 mass commonly presents a confused reticulated appearance, which 
 has given rise to an almost universal notion that the fibres interlace 
 one with another. This idea, however, is, in most cases erroneous. 
 It is doubtful whether these fibres are invested by a sarcolemma: none 
 has hitherto been detected in an unequivocal manner. It is also still 
 a matter of speculation how they terminate, or whether they in all 
 instances have a termination. In the case of the transverse fibres of 
 the intestine, for example, it is uncertain whether each fibre sur- 
 rounds the canal once, returning into itself as a ring, or more than 
 once, as a spiral ; or whether it passes only partially round it, the 
 circle being completed by others. Whether the areolar tissue (the 
 representative of the fibrous), that is found in connection with these 
 fibres, serves to give them an attachment, by union with their extre- 
 mities, or by involving them in its meshes, is also altogether unknown. 
 
 • In some specimens, however, of both varieties of fibre, they may be discerned 
 without the addition of an acid. 
 
DISTRIBUTION OF MUSCLE. 155 
 
 In the gizzard of the bird, the ends of the fibres are united to white 
 fibrous tissue, thus making an approximation to the striped fibre, as 
 they do in colour. But we ^ave not been able, after diligent search, 
 to detect the true transverse stripes, which Ficinus descpbes to exist 
 in this organ. . , 
 
 Of the distribution of the two varieties of fibre in the body. — The 
 striped fibre is met with in all muscles of the body whose action can 
 be directly influenced by the will, and also in those of the pharynx, 
 the oesophagus, and the heart. In the oesophagus it seems to be min- 
 gled with the other variety to a somewhat uncertain extent. In some 
 specimens from the human subject we have failed in detecting any 
 in the lower half of that tube, either in the circular or longitudinal 
 layer ; but in another example we have found them to within an inch 
 of the stomach.* It is still unknown in what manner the two kinds 
 of fibre are arranged at their point of junction: some supposing them 
 to be intermingled ; others, that they pass into one another by imper- 
 ceptible gradations of structure. The former of these views is the more 
 accordant with our own observations ; and Mr. Mayo mentions a fact, 
 which seems to corroborate it: "When the nervi vagi are pinched, one 
 sudden action of the fibres of the oesophagus ensues, and, presently 
 after, a second, of a slower character, may be observed to take place." 
 {Physiology, 3d ed. p. 41.) The characters of these movements 
 would appear to indicate the existence of both varieties of fibre. 
 
 The cross stripes on the fibres of the heart are not usually so 
 regular, or distinct, as in those, of the voluntary muscles. They are 
 often, interrupted, or even not visible at all. In some of the lower 
 animals their sarcous elements never form transverse stripes. These 
 fibres are usually smaller than the average diamfeter of those of the 
 voluntary muscles of the same subject by two-thirds, as stated by 
 Mr. Skey; and in most parts of the parietes of this viscus they are 
 not aggregated in parallel sets, but twine and change their relative 
 position. This may be seen in a well-boiled heart. Striped fibres 
 have been found in the iris, in the small muscles of the ear, and in 
 those muscular fasciculi that surround the urethra immediately in 
 front of the prostate. They are also found in the sphincters of the 
 anus and vagina. 
 
 The unstriped fibre is met with in the alimentary canal, and con- 
 stitutes the double layer investing that tube. It also forms the mus- 
 cular coat of the bladder, and that of the uterus. The dartos owes 
 its contractility to the presence of fibres of this variety ; which, in 
 consequence of their admixture with a great abundance of areolar 
 tissue, have been often overlooked. But they may be detected by 
 the addition of acetic acid, which, by bringing into view the peculiar 
 corpuscles they contain, distinguishes them from both the white and 
 yellow fibrous] elements of the areolar tissue. A very distinct peri- 
 staltic contraction may be often discerned in the dartos, extending 
 across the raph6 of the scrotum, and too similar to the contraction of 
 unstriped muscle to be mistaken. 
 
 * Among the lower animals, Mr. Gulliver has pointed out similar varieties. (Pro- 
 ceed, of Zool. Soc, No. 81.) (See also Lancet, Aug. 1842.) 
 
156 ORGANS OF LOCOMOTION. 
 
 The fibres which have been described as peculiar to the dartos 
 seem to be nothing more than a certain modification of the areolar 
 tissue in that region. The erection of the penis may be, in part, 
 owing to the compression exerted on the superficial veins of the 
 organ by a continuation of a structure analogous to the dartos, which 
 is continued over the base of the penis under the skin. The erection 
 of the nipple also occurs, on any mechanical irritation, with a motion 
 so very like muscular contraction, that a layer of these might per- 
 haps be found under the skin of that region. And it may be matter 
 of question how far the general contractility of the skin may be de- 
 pendent on a diffusion of this tissue, in small quantities, throughout its 
 areolar structure. The excretory ducts of all the larger glands seem 
 to possess a covering of fibres pertaining to this variety : such is the 
 case with the ductus choledochus in birds, and probably in mammalia, 
 and with the ureters and vasa deferentia. The bronchial tubes may 
 be here alluded to in their capacity of an excretory apparatus, as 
 furnishing the best marked example of this arrangement. The 
 trachealis muscle consists evidently of the unstriped fibres, and the 
 same may be traced down the bronchial ramifications as far as the 
 air-cells themselves, though not into them. The distinctive charac- 
 ters of this form of muscle may here be unequivocally discerned ; and, 
 if anatomists had been better acquainted with them, there would not 
 have been room for those disputes regarding the muscularity of ^e 
 bronchial tubes which have so long attracted the interest of practical 
 physicians. Recently, indeed, there haS been added to the satisfac- 
 tory evidence of anatomy the fact, that these fibres may be excited to 
 contraction by the galvanic stimulus. {Dr. C. J. Williams, on Dis- 
 eases of the Chest. Last edit. Appendix.) In the case of other 
 glands, it is still unknown how far the muscular coat invests the 
 ramifications of the duct: it is most likely that it gradually ceases a 
 short way within the organ, and at least it seems clear that no portion 
 of the secreting membrane itself is ever invested by it. 
 
 Distribution of the two kinds of fibre in the animal scale. 
 
 The striped fibres have been found in all vertebraled animals, and in iiisects, 
 Crustacea, cirropods, and arachnida; and future researches will probably show 
 them to be even more extensively diffused. But in the lower animals we find 
 that the distinctive characters of the two varieties begin to naerge together and be 
 lost; especially where the fibres are of diminutive size. The transverse stripes 
 grow irregular, not parallel, interrupted: a fibre will,, perhaps, possess them only 
 near its centre, where its development is most advanced, and its contractile 
 energy greatest. Even the peculiarities of the unstriped fibre are sometimes no 
 longer to be met with in parts which are undoubtedly muscular, as the alimentary 
 canal of small insects. It is evident that fibres of the usual bulk would be greatly 
 too large for the recjuirements of the case ; and they consequently seem to be 
 reduced within limits which deprive them of those anatomical characters by 
 which alone we can elsewhere positively aver their existence. It is possible that 
 a tissue identical in nature and properties with that of striped muscle, may be the 
 effective agent to which are due those wonderfully vivacious movements witnessed 
 in the bodies of many of the minutest infusoria, where the best microscope can 
 hardly diEcern even the organs put in motion. 
 
TENDONS. 157 
 
 Each one of the elementary fibres now described may be properly 
 regarded' as a distinct and perfect organ. In some of the smaller 
 forms of animal life^ we have examples of a striped muscle consisting 
 of a singlefibre; and not only so, but this fibie reduced to a single 
 series of sarcous elements, or afibrilla. But in all the larger animals, 
 and in the human body, with which we are specially concerned, soli- 
 tary fibres never occur: they are always aggregated in parallel series 
 of greater or smaller size, and associated with other tissues, which 
 minister to their nutrition, or to their mechanical connection either to 
 one another or to neighbouring parts. Thus the compound organs 
 termed muscles are formed. 
 
 In these, the angular figure of the fibres results from their contact. 
 The sets in which they are packed usually contain ten, twenty, thirty, 
 or more; these again being united into larger sets, and so on, so as to 
 form the variously sized Jasdculi and lacerti of Prochaska and others, 
 until the whole muscle is formed, consisting, it may be, of very many 
 thousands. Though the fibres of a small set are always parallel, and 
 the primary sets usually so, it often happens that the larger sets are 
 placed obliquely to one another, and therefore do not act ii» the same 
 direction ; and, even when all are parallel to one another, they are often 
 oblique to the cord or tendon their force acts upon. Such muscles 
 are styled doubly or singly penniform, from their resemblance to the 
 plume on a writing-quill. All such arrangements, infinitely varied, 
 are mechanical contrivances by which symmetry of form, or extent of 
 motion, is obtained at the expense of power. 
 
 White fibrous tissue reaching from the end of a muscular fibre to 
 some structure which i» to serve as a fixed attachment for it, or which 
 it is intended to move, is called a tendon. The fibrous tissue thus 
 running from many contiguous fibres (as those of a whole muscle) is 
 usually united into a single tendon. This may be laraellated, cordi- 
 form, &c., according to the arrangement of the muscular fibres them- 
 selves (see p. 81). 
 
 Tendinous fibres are much less bulky than the muscular fibres of 
 which they are the prolongation ; and from this result many conse- 
 quences. Tendons are employed for symmetry, and where muscular 
 structure would be useless, from the mechanical impossibility of more 
 than a certain amount of motion in a part. Moreover, where a muscle 
 consisting of a large number of fibres has to be attached to a large sur- 
 face, the tendinous fibres are diffused ; but, if the same muscular sub- 
 stance has to be fixed to. a small point of bone, the tendon must be 
 collected into a cord. Now, it would be impossible for all these 
 muscular fibres to be attached to the tendinous ones on the same 
 level, on account of the great difference in bulk between the two 
 structures. Hence, in such cases, we find the muscular fibres to end 
 in tendon in regular progression one after the other, and the tendon 
 at its muscular extremity to be expanded, some of its fibres being 
 long, others short. And yet the inconvenience which would ensue 
 from the muscular fibres being of unequal length in the same organ, 
 is counteracted by the tendon at their other extremity having its fibres 
 precisely reversed ; as in the rectus of the thigh, and numerous other 
 
158 ORGANS OF LOCOMOTION. 
 
 instances. Where muscular fibres are really of different lengths in a 
 muscle, it is because, from the direction in which they act, they have 
 to shorten to different degrees. Thus, in the square pronator of the 
 fore-arm, the deeper and shorter fibres are attached to a part of the 
 radius, which in pronation passes through a much smaller space than 
 that to which the superficial and longer fibres are fixed ; and under the 
 innumerable modifications of muscular form in man and animals, how- 
 ever force is sacrificed to mechanical exigencies, or other causes, it 
 is invariably accomplished with the utmost economy of power con- 
 sistently with the end in view ; there is never any waste, never any 
 force provided which is not wanted. 
 
 Where a great mass of fibrous tissue runs into a muscle, the num- 
 ber and obliquity of the muscular fibres are very much increased, 
 while the length of each is diminished ; and, as a general result, the 
 power of such a muscle is great, the extent of its contractions com- 
 paratively limited. 
 
 A given mass of contractile material may be arranged as a few long 
 fibres (as in the sartorius), or as many short ones (as in the masseter) : 
 its contractions would, in the former case, be characterized by their 
 extent ; in the latter, by their power : for, ceteris paribus, the extent 
 is as the length, the power as the thickness. 
 
 The terms origin and insertion are employed with great convenience 
 in ordinary language to denote the more fixed and the more movable 
 attachments of muscles. In human anatomy general consent has 
 sanctioned their ,use, and even with few exceptions their particular 
 application to each muscle in the body; although this assignment. is 
 in many cases arbitrary, in consequence of its toeing impossible to de- 
 termine which attachment is the more frequently the fixed one. 
 
 The arrangement of the fibres in the heart is very peculiar. With- 
 out attempting a particular account of their course, we may state that 
 they do not preserve the same parallelism, nor extend straight be- 
 tween two points, as in the voluntary muscles, but twine round one 
 another, and around the organ, in a very intricate and more or less 
 spiral figure. Most of them come from the tendinous cord encircling 
 the orifices of the ventricles, and, after winding through their walls, 
 return either to some part of the same circle of tendon, or end as one 
 sort of columnae carneee in the ventricles by union with the chordae 
 tendinese. 
 
 In the muscular coat of the alimentary canal, of the bladder and 
 uterus, the unstriped fibres are disposed, as in the heart, so as to 
 enclose a cavity, but without having, as in that organ, any point at 
 which they can be said to commence or terminate. In the alimentary 
 tube they are arranged in two laminse, the respective fibres of which 
 take a course at right angles to each other. In the bladder the ar- 
 rangement is reticulate. The elementary fibres form sets of variable 
 thickness, which at numerous points send off detachments to join 
 neighbouring bundles, whence has sprung the notion that the fibres 
 are branched. It is manifestly, however, the sets of them only that 
 are branched ; the unstriped, like the striped fibres, being invariably 
 simple from end to end. In the uterus the disposition of the fibres is 
 
AREOLAR TISSUE AND BLOOD-VESSELS OF MUSCLES. 159 
 
 essentially similar, calculated to allow of great variety in the capacity 
 of the cavity they encircle. 
 
 Of the areolar tissue of muscles. — This tissue is much more abun- 
 dant in the voluntary than in the involuntary muscles. To the 
 former it gives an external investment, which sends septa into the 
 intervals between the larger and smaller packets of fibres, and thus 
 enables them to move in some degree independently of one another. 
 The density of these general and partial sheaths is proportioned to 
 the amount of pressure to which the organ may be subject, as is ex- 
 emplified in the superficial muscles of the back, and in those super- 
 ficial muscles generally where a fibrous aponeurosis does not exist. 
 The areolar tissue does not usually clothe every individual fibre from 
 end to end, giving it a cellular sheath, except in cases where the 
 elementary fibres are of large dimensions. The areolar tissue, besides 
 affording protection to the muscular fibres, admits of motions between 
 them; and, by forming a connecting bond between neighbouring 
 bundles, it must also serve the important office of limiting undue 
 motions of one part of a muscle on another part. But a principal use 
 of it appears to be that of furnishing a resisting nidus in which the 
 delicate vessels and nerves can traverse the interstices of the fibres, 
 and by which they can be protected from hurtful dragging during the 
 unequal and oscillating movements of the fibres of a voluntary muscle 
 in its state of activity. This idea is supported by the fact that scarcely 
 any areolar tissue exists in the heart, or in the unstriped muscles 
 generally. In the heart, though the contraction is powerful, it is 
 instantaneous, or nearly so, and therefore probably more uniformly. dif- 
 fused, so that neighbouring fibres must be less moved on one another 
 than in the more sustained contraction of a voluntary muscle. More- 
 over, the mutual intertwining of even the elementary fibres in this 
 organ is in many parts of it so intricate, as to contribute much to their 
 mutual support; and, in the other involuntary muscles, the Contrac- 
 tions are slowly and evenly progressive along the fibres of the same 
 set. • 
 
 Of the blood-vessels of muscles. — The arteries and veins of muscles 
 commonly run together; and most of the arterial branches, to within 
 two removes from the capillaries, are accompanied , by two ven{B 
 comites. They invariably pass more or less across the direction of 
 the fibres, divide and subdivide, first in the intervals between the 
 larger sets, then between the smaller sets, till the ultimate twigs in- 
 sinuate themselves between the fibres composing the smallest bundles, 
 and break up into their capillary terminations. In this course the 
 vessels supply the areolar tissue, their own coats, and the attendant 
 nerves. The capillary plexus of the areolar membrane consists of 
 irregular but pretty equal-sized meshes, and contrasts strongly with 
 that of the muscular tissue itself. 
 
 The proper capillaries of muscle are quite characteristic in their 
 arrangement, so that a person, who has once seen them, can never 
 afterwards mistake them. They consist of longitudinal and transverse 
 vessels: the longitudinal always following the course of the element- 
 ary fibres, and lying in the intervals between them ; the transverse 
 
160 
 
 ORGANS OF LOCOMOTION. 
 
 Fig. 47. 
 
 being short communications placed at nearly equal distances between 
 the longitudinal ones, and crossing nearly, or quite, transversely over 
 or under the fibres. The manner in which the longitudinal vessels 
 are placed in relation to the. fibres, is seen in fig. 36, represented 
 as they are seen on a transverse section. They usually occupy the 
 interstice between three or more fibres, but sometimes also the space 
 between the contiguous surfaces of two fibres. The length of the longi- 
 tudinal vessels does not usually exceed the twentieth of an inch ; in 
 other words, the terminal tvyigs of the artery and vein pertaining to 
 the same capillary are seldom further than that apart. The length of 
 the transverse anastomosing capillaries necessarily varies with the 
 thickness of the fibres over which they pass (fig. 36, b, a). 
 
 The diameter of the capillaries of muscle varies, like that of others, 
 with the size of the blood-particles of the animal. It is, however, 
 only just sufficient to allow of the particles to pass. If a fragment of 
 a frog's muscle, perfectly fresh, be examined, 
 series of blood-particles will be seen in the 
 longitudinal capillaries. These particles are 
 compressed and elongated, sometimes to a 
 great extent, evidently by the narrowness of 
 the canal which contains them. It may seem 
 at first sight not doubtful that in the living 
 creature these elastic blood-discs are simyarly 
 elongated in their passage through the vessels 
 of muscle, but the admirable researches of 
 Poiseuille will perhaps serve to explain this 
 appearance without our being driven to sup- 
 pose the presence of so formidablean obsta- 
 cle to the capillary circulation through these 
 organs. It is more probable that the con- 
 traction of the vessels, and the compression 
 of the blood-discs, occur op the escape of 
 some of their contents bfcing permitted by 
 the cutting oflf of the fragment for microsco- 
 pic examination. The coats of the capillaries 
 of muscle consist of a simple diaphanous 
 membrane, in which a few irregular-shaped 
 cytoblasts occur at infrequent intervals. 
 
 It results from this description of the capil- 
 laries of muscle, that their number must cor- 
 respond nearly to that of the elementary fibres,; 
 consequently, that the same amount of mus- 
 cular tissue, arranged as a large number of 
 small fibres, would be supplied with a larger 
 absolute number of capillaries than if ar- 
 ranged as a small number of large fibres. 
 This difference of vascular supply is exceed- 
 ingly remarkable, and will be reverted to in 
 considering the contractility of muscle. 
 Of the nerves of muscle. — Nerves being the appropriate channel 
 
 Capillaries of a small fascicu- 
 lus of muscular fibres from the 
 ixeck of the Dog :— a. Terminal 
 twig of the artery, v. Terminal 
 twigr of the vein. p. Plexus of 
 capillaries «. Elementary fibre, 
 to show the relative size and 
 direction of those to which the 
 capillaries, here represented, 
 are distributed. 
 
NERVES OF MUSCLES. 
 
 161 
 
 through which muscles are excited to contraction, we have now to 
 inquire into the manner in which the two tissues communicate 
 together. As far as is at present known, all muscles in the larger 
 animals have nerves distributed to them ; and, if we extend the in- 
 quiry to those extremely simple and minute muscles which have been 
 already alluded to as existing in the smallest of living creatures, 
 though we can no longer trace nerves, yet our inability to do so pro- 
 bably depends more on a corresponding simplicity of the nervous sub- 
 stance itself, so that it ceases to be anatomically recognizable, than 
 on its entire absence. So general is the connection of the two tissues, 
 and so apparently indispensable for the subjection of the muscles to 
 the purposes of the organism of which they constitute a part, that we 
 may regard it as constant and necessary. 
 
 The distribution of the nerves through muscular structures has 
 always been a subject of great interest to those who looked to this 
 line of inquiry for some clue to the explanation, either of that won- 
 derful active connection subsisting between them, or of the nature of 
 the contractile act itself. But though the anatomical results accruing 
 from this inquiry are of a highly satisfactory kind, considered in them- 
 selves alone, yet they cannot be said to have hitherto contributed in 
 any great degree to the elucidation of these mysterious questions. 
 The best mode of inspecting the arrangement of the ultimate nervous 
 twigs is, to select a very thin muscle, as one of the abdominal mus- 
 cles of any small animal, or one of the muscles of the eye of a small 
 bird, to steep it in weak acetic acid, 
 and then to thin it out under the 
 compressorium. The primitive tu- 
 bules of the nerve may then be 
 readily distinguished with a mode- 
 rately high power. They separate 
 from one another at first in sets, 
 afterwards in twos, threes, or fours ; 
 and, if these be followed, they will 
 be found ultimately separating from 
 one another, forming arches, and 
 returning either to the same bundle 
 from which they set out, or to some 
 neighbouring one (fig. 48). 
 
 In this looprlike course they ac- 
 company to some extent the minute 
 blood-vessels, but do not accurately 
 follow them in their last windings, 
 since their distribution is in a differ- 
 ent figure. They pass among the 
 fibres of the muscle, and touch the 
 sarcolemma as they pass; but, as far 
 as present researches have informed 
 us, they are entirely precluded by 
 this structure from all contact with the contractile material, and from 
 all immediate intercourse with it. How then shall we explain the 
 
 Fig. 48. 
 
 Loop-like,^ termination of the nerves in vo- 
 luntary mnsole.— After Burdach. 
 
162 ORGANS OF LOCOMOTION. 
 
 transmission of the nervous influence to a material thus enclosed ? If 
 it were wise or safe to go a single step in advance of pure observa- 
 tion on so abstruse a question, we might suggest, resting on the 
 seemingly sure ground of exact anatomy, that this influence must be 
 of a nature capable of emanating beyond the limits of the organ which 
 furnishes it. But further than this, as to how, or to what extent this 
 influence may so emanate, or as to what may be its nature, it would, 
 perhaps, in the present state of knowledge, be hardly warrantable 
 even to speculate. 
 
 The number of fibres in a muscle is always exactly proportioned to 
 the power demanded, and their length to the amount of shortening 
 required of them; but, these circumstances being secured, muscular 
 parts are subject to great variety of form, being short, thick, or 
 rounded, long, slender, or flat,, according to their position relatively 
 to particular bones, joints, other muscles, or the like. Thus, all are 
 compactly knit and adapted to work in concert, without any mechani- 
 cal interference with one another ; and perfect symmetry, both of shape 
 and action, is provided for. 
 
 We notice that the muscles are arranged on the skeleton in a great 
 measure in sets, having opposite actions; as, for example, the flexors 
 and extensors, pronators and supinators of the fore-arm. It is evident 
 that the action of every muscle depends solely on its mechanical at- 
 tachments, and that a tendon running round to a different side ^of a 
 limb might quite reverse a given action. But we find that in general 
 the muscles of the same set are designed to act together, not only by 
 their attachment on the same side of a joint, but by a supply of nerves 
 from the same source (congeneres). Yet even this can confer no 
 special action of extension or flexion, but only an association of ac- 
 tion which may be both at once ; for example, the flexors of the toes 
 extend the ankle, and the extensors of the toes bend it. Even a 
 single muscle, the rectus femoris, flexes the thigh, and by the same 
 action extends the leg. Muscles opposed in action are termed an- 
 tagonists. This antagonism is in most cases required by the neces- 
 sity there is for an active moving power in opposite directions ; but 
 it serves the important accessory purpose of elongating muscles when 
 they cease to be contracted, as we see illustrated by the presence of 
 elastic or some other force for the same purpose, when there is no 
 antagonist muscle. When antagonists act together, the part is fixed. 
 
 The locomotive framework may be regarded as a series of levers, 
 of which the fulcrum is for the most part in a joint, i. e. at one ex- 
 tremity, the resistance at the further end, and the power (or the 
 muscle) in the intermediate portion. In most cases the muscles are 
 attached very near the fulcrum, as in the familiar instance of the 
 biceps, inserted into the tubercle of the radius. By this disposition, 
 a contraction of a single inch in the muscle moves the hand in the 
 same time through the extent of a foot, but then the hand moves 
 through every inch with only the twelfth part of the power exerted in 
 the muscle ; i. e. a resistance at the hand equal to one-twelfth of the 
 force of the muscle would stop its motion. Thus, force is converted 
 into extent and velocity of movement, at the same time that the great 
 
FUNCTIONS OF MUSCLES. 163 
 
 inconvenience is avoided of having the muscles extended like bow- 
 strings between the distant ends of jointed continuous levers. By 
 the junction of two or more levers in one direction, as in the dif- 
 ferent segments of the extremities, the extent and velocity of their 
 united actions are given to the extreme one. A blow of the fist may 
 be made to include the force of all the muscles engaged in extending 
 the shoulder, elbow, and wrist. 
 
 In the conspicuous example of the tendo-Achillis, inserted into 
 the OS calcis, the resistance (or the weight of the body) rests on the 
 astragalus, intermediate between the power and the fulcrum, which 
 is here the ground, pressed by the ball of the foot. The extent and 
 velocity of motion are here converted into power. If the tendo 
 Achillis draws on the heel when the foot is ofi' the ground, the front 
 part of the foot is extended on the lower end of the tibia as a ful- 
 crum, and exhibits an instance of the other of the three varieties of 
 lever. 
 
 Of the function of muscles. — The great property of muscular tissue 
 is that of shortening in a particular direction, and this property is 
 called contractility. It is not thaf mechanical power which elastic 
 substances possess of shortening themselves on the removal of some 
 force which has stretched them, but it is an endowment, responsive 
 to appropriate stimuli, and dirainishingor disappearing with the healthy 
 st^te of the tissue (p. 69-70). 
 
 The distinction between the contractility, the elasticity, and the 
 physical tenacity of a muscle may be illustrated by the following imag- 
 inary experiment: Suppose the leg of an animal so severed from 
 the trunk as to hang by a single muscle, which, after retaining its' 
 contractility for some time, were gradually to lose it. The limb 
 would at first be borne up by the contractile power: but, as that 
 ceased, the muscle would elongate under the weight, and the limb 
 would remain suspended simply by the tenacity of the part, if, now, 
 the muscle were stretched between the hands, we should find it to 
 possess some slight elasticity. The elasticity and much of the tena- 
 city of muscles are attributable to the sarcolemma, and to the ca- 
 pillary and areolar tissues. It does not appear that elasticity is in 
 any degree a property of the sarcQus elements, and their tenacity mu^t 
 be comparatively slight: but it is the sarcous tissue. alone that pos- 
 sesses contractility. 
 
 Although it is universally allowed that the muscular tissue is the 
 contractile substance, yet the strange question has been raised, and is 
 still warmly debated, whether it possesses this power in itself, and in- 
 dependently of all other tissues : some contending that nerve is neces- 
 sary to confer contractility on muscle, — to charge it, as it were, with 
 this property ; others, that nerve is only necessary to call it into action; 
 and others, that the property is the essential attribute of the tissue, 
 and totally independent of all nerves. The time is past when the 
 intricacies of this keen contest can be threaded with any benefit to 
 the student, and we therefore refrain from attempting to follow them. 
 We shall prefer oflf'ering him a view of the facts of the subject, as at 
 present known, drawing our conclusions as they arise. 
 
164 ORGANS OF LOCOMOTION. 
 
 The contractility of muscle is exhibited in two varieties of contrac- 
 tion, passive and active. 
 
 Passive contraction is that which every muscle is continually prone 
 to undergo, by the mere quality of its tissue, as long as it remains in 
 its natural situation in the body. The muscles are ever kept on the 
 stretch by the nature of their position and attachments, and cannot 
 have their ends so approximated, by attitude or otherwise, that 
 their tendency to shorten themselves shall cease. If, for example, 
 the rectus muscle of the thigh have its extremities brought as near 
 together as can be effected artificially by posture, they would yet be 
 found to approach still nearer on being freed from their attachment to 
 the bones. The stimulus to this contraction may be therefore con- 
 sidered to be that of extension. In fractures and dislocations attended 
 with shortening of the limb, the muscles adapt themselves permanently 
 to their shortened state by virtue of this property. This tendency to 
 contract has been distinguished by the term retractility, from its being 
 manifested by the retraction that occurs when the belly of a muscle is 
 cut across. But, in this instance, the retraction would appear to be 
 in part caused by an active contraction excited by the stimulus of the 
 injury. It has been also styled <omc%. It is well exemplified in all 
 those contracted states of muscles which follow paralysis of their 
 antagonists, as when the features are drawn towards the healthy side 
 in hemiplegia. The passive contraction of muscles is continually»op- 
 posed to their elongation by the active or passive contraction of antago- 
 nists, and restores them when that subsides. By it they are accom- 
 modated to an attitude artificially given, when no muscular effort is 
 required to maintain it. When no active contraction is present in a 
 limb, the passive contraction remains ; and being brought to a state 
 of equilibrium in all the muscles, by their mutual antagonism, the 
 limb is said to be at rest. This is the general condition during sleep, 
 in which the posture assumed by the limbs is determined by the re- 
 lative power of antagonist muscles: the flexors overcome the exten- 
 sors, and hence the limbs are bent. 
 
 Active contraction is attended with those striking manifestations of 
 powerthat specially characterize muscle. It is always excited by a local 
 or partial stimulus, and is always exerted in opposition to another force 
 ■within the body, which it is able more or less completely to master. 
 The opposing force is generally the passive contraction of antagonist 
 muscles, as well as the weight or resistance of some part upon which 
 the muscle acts directly ; but it may be the elasticity of parts, or, in 
 the case of hollow muscles, the resistance of their own contents. 
 Active contractions are also frequently opposed to one another in the 
 maintenance of a fixed posture. Active conttaction is partial and in- 
 terrupted, both in extent and duration. It requires intervals of rest, 
 being attended with exhaustion of the power which produces it ; which 
 exhaustion, in the voluntary muscles, is attended with the sensation 
 called muscular fatigue. 
 
 The contractility of muscles, therefore, is being ever exerted, in 
 obedience to the equable stimulus of tension, without fatigue, in the 
 production of what we have termed passive contraction ; when it is 
 
STIMULI TO MUSCULAR CONTRACTION. 165 
 
 affected by a powerful, partially-applied stimulus, active contraction 
 results, inducing the necessity for subsequent rest. But there seerns 
 no good ground for supposing the contractile force to differ in its 
 nature, ■when exhibited under these different modes of action. 
 
 Stimuli to muscular contraction. — Whatever is capable of inducing 
 contraction in the muscles, when either naturally or unnaturally ap- 
 plied to, them, is termed a stimulus. In the living body, the muscu- 
 lar fibres are in most instances made to contract by the immediate 
 influence of the nervous tubules distributed among them; and this 
 influence, however called into play, should be styled the nervous 
 stimulus, or the vis nervosa. This nervous stimulus, then, is simply thp 
 effect of such a condition of the motor nerves as enables them to induce 
 contraction in muscular fibres which are in the due relation to their 
 terminal loops. Of the nature of this condition, and of the mode of its 
 production, we are as completely ignorant as we are of the nature of all 
 those other conditions of the nervous system on which the manifestation 
 of its various phenomena depends ; but we know sorrie little of the 
 agents by which the nerves are thrown into this state. The chief of 
 them are volition, emotion and impressions carried by the afferent 
 nerves to the nervous centres, and there affecting the efferent, or motor 
 nerves,,independently of volition or consciousness; but to these are to 
 be added various impressions from diseases and injuries of the motor 
 nerves, either at their origin or in their course, together with pressure, 
 heat, chemical substances, electricity, &c., applied to their texture. 
 The former are the natural excitants of the nervous stimulus in the living 
 body; the latter may be proved to possess this property by observation, 
 and byexperiments on nerves distributed to muscles. Cither in the body, 
 or soon after their removal from it. The power of inducing contraction 
 in the muscles is an endowment of those nerves onjy which have a 
 certain organic connection with the muscles ; and these nerves are, 
 therefore, distinguished as motor. 
 
 There are other stimuli of muscle besides the vis nervosa, which 
 occasion contraction in the living body ; but, in general, these affect 
 only the hollow muscles. Experiment has, indeed, shown these mus- 
 cles to be under the influence of motor nerves derived from the spinal 
 marrow ; but it seems probable that some of them, at least, are nor- 
 mally excited to contract by the stimulus of stretching or distension, 
 to which they are peculiarly liable from their arrangement as invest- 
 ments to hollow viscera. Muscles have not the capacity of elongating 
 themselves that has sometimes been ascribed to them : when once 
 contracted, they remain shortened, notwithstanding the contractile 
 force have subsided, unless their ends be drawn apart by some ex- 
 traneous force. This force is that which has been already specified 
 as being always exerted in opposition 'to active contraction in the 
 living body. In the case of the voluntary muscles, this force always 
 continues to act after the active contraction has ceased ; but in the 
 case of the hollow muscles, where it consists of the resistance of their 
 contents, it sometimes happens that these, wberi remored, are not at 
 once replaced ; and hence an enduring contraction, though the active, 
 contractile force is no longer exerted. Thus an empty intestine is 
 
166 ORGANS OF LOCOMOTION. 
 
 reduced to the size of a tobacco-pipe, and the sphincters of the anus 
 and bladder are kept contracted, without any tetanic spasm, or per- 
 manent expenditure of contractile force, as has been sometimes sup- 
 posed. 
 
 Now, the stimulus of distension is, in the first instance, nothing 
 more than the elongating force which calls into play the contractility 
 of a muscle under its passive form : and there is this peculiar to it, 
 that it afTects equally every point of the substance of each fibre, which 
 no other stimulus can do : and hence would result the uniformity 
 which will presently be shown to characterize passive contraction, 
 for contraction is an answer to a stimulus. This consideration tends 
 strongly to confirm the view which we have taken of the identity of 
 the forces displayed in passive and active contraction, of tonicity and 
 contractility. 
 
 Other stimuli maybe mentioned as capable of causing muscular 
 contraction by their direct agency on the tissue ; but it is important 
 to observe that these take ho share in the production of natural 
 contraction in the healthy body. It was long supposed impossible to 
 observe the effect of stimuli on the muscular tissue when isolated 
 from the nervous ; and the fact, that the artificial stimuli which in- 
 duced contraction when applied to a muscle itself, were the same 
 ■with those which induced it when applied to the motor nerves, was 
 considered sufficient proof that in the former case the effect was pro- 
 duced through the medium of nervous tissue still mingled with the 
 muscular. 
 
 But this question has been brought to an issue by the positive ob- 
 servation that fragments of the fibre of voluntary muscle, entirely 
 isolated from every extraneous tissue, whether nerve or vessel, may 
 be made to contract in obedience to a stimulus topically applied to 
 them. When such fragments are examined, they are found to con- 
 tract first of all where they have sustained mechanical injury, viz. 
 at their broken extremities; and, if water be brought into contact 
 ■with them, it is absorbed, and thereby excites them to contractions, 
 ■which commence at their surface.* The same thing is frequently 
 to be observed under a different form. A particle of foreign matter, 
 as a hair or a piece of dust, may be included by design or accident 
 in the field of the microscope, so as to touch the side of a fibre at a 
 single point. When this happens, the fibre will often exhibit a con- 
 traction, so plainly limited to the point touched, as to give unequivo- 
 cal proof of its being the result of the irritation of the pressure. Che- 
 mical substances may be seen to act similarly, if they be not so 
 powerful as to destroy the texture of the part : and it is probable that 
 electricity has a like agency. These interesting phenomena may be 
 
 * Water has long been known as a rapid exhauster of the contractility of mus- 
 cles. " Rigidity is produced almost instantaneously if warm water be injected into 
 the arteries of a muscle. The flesh, under these circumstances, becomes pale, in- 
 creased in bulk, and suddenly hardens. The operation of crimping fish consists 
 in dividing the muscular fibre before it has become rigid, and immersing it in 
 spring water. A small part treated in this manner contracts and hardens within 
 five minutes." — Mayo, Physiol., p. 38. It exhausts contractility by inducing vio- 
 lent contraction, by which the fibre is often disorganized. 
 
STIMULI TO MUSCULAR CONTRACTION. 167 
 
 observed more or less satisfactorily in all animals whose fibres retain 
 their contractility for a sufficient length of time after removal from the 
 body; and the crab and lobster will be found very favourably adapted 
 for the purpose. In many reptiles, and fish also, the steps occur 
 slowly enough to be adequately scrutinized. 
 
 The facts in question can admit only of one explanation, if it be 
 conceded that the muscular tissue has been here separated from the 
 nervous : and certainly that separation has been efiected, unless the 
 nervous tubules send oS' from their terminal loops a set of fibrils 
 which penetrate the sarcolemma, and diffuse themselves through the 
 contractile material within; a supposition for which there exists, at 
 present, no foundation in the observations of the most diligent investi- 
 gators of this subject. They will, therefore, probably, be .regarded 
 as conclusive proof that contractility is a property inherent in the very 
 structure of muscle, and capable of being excited to action independ- 
 ently of the instrumentality of nerves. 
 
 An interesting phenomenon has been pointed out by Dr. Stokes, 
 which, when illustrated by the foregoing observations, we may safely 
 consider as an example of contraction in the living body in answer to 
 a physical stimulus. In various cases of phthisis, and, indeed, in 
 all cases attended with emaciation, a sharp tap with the fingers on 
 any muscular part is instantly followed by a contraction, and by 
 the rise of a defined firm swelling, at the point struck, enduring 
 several seconds before it gradually subsides. This is often so pro- 
 minent as to throw a shadow along the skin, and for the moment it 
 might almost be rhistaken for a solid tumour. That it is limited to 
 the point struck is full proof of its being a direct effect of the irrita- 
 tion, and not produced through the medium of nerves; for a contrac- 
 tion excited in the latter mode would be diffused over the parts to 
 ^which the nervous twigs irritated were supplied, and would therefore 
 frequently occur in parts at some distance. 
 
 Having premised these words respecting the stimuli of muscle, we 
 proceed to consider what is known of the phenomena which attend 
 the act of contraction. It is evident that the subject we are now 
 approaching is one of primary importance, because on the positive 
 information regarding it must chiefly depend our means of judging of 
 the conflicting hypotheses of the nature and laws of action of the con- 
 tractile force. 
 
 A muscle, when contracted, is firmer than before ; but this rigidity 
 is proportioned rather to the intensity of the contractile force exerted, 
 than to the amount of shortening occasioned by it. The circumstance, 
 however, has led to the belief, that the act is accompanied with a 
 compression of the substance of the muscle into a smaller compass; 
 but it is, on the contrary, well ascertained that it gains in thickness 
 what it has lost in length. The experiments by which this fact is 
 attested have been often repeated, and their general results accord 
 well together. If a muscular mass be made to contract by means of 
 galvanism in a vessel of water furnished with a very delicate tube, 
 the slightest diminution of bulk would be at once indicated by the 
 fall of the water within the tube ; but the water, under these circum- 
 
168 ORGANS OF LOCOMOTION. 
 
 stances, is found to retain its level. Mr. Mayo varied this experi- 
 ment by selecting the heart of a dog, {Jinat. and Phys. Comment, vol. 
 i. p. 12,) -which, continuing to beat during some time, was in this 
 way distinctly seen to undergo no change of size. 
 
 The familiar practice of accelerating the flow from the vein at the 
 elbow by desiring the patient to contract the muscles of the fore-arm, 
 does not, as is sometimes imagined, show any diminution of their 
 bulk, but only a forcible increase of their lateral dimensions, by which 
 the deep veins are compressed within the inelastic sheath of fascia, 
 and the blood diverted into the superficial channels. In those mus- 
 cles which have a bulging centre or belly, as the biceps of the arm, 
 the fibres are arranged in a curved form, and during contraction must 
 tend towards a straight line in the direction of the axis of the muscle. 
 In such instances the blood-vessels that traverse their interstices must 
 be in some degree compressed. 
 
 If we examine under the microscope the contracted state of a mor- 
 sel of the sarcous tissue, we find it to present essentially the same 
 characters as that of the entire organ, a shortening in length, with a 
 corresponding increase in thickness ; and this is true, however minute 
 the fragment may happen to be. This is all that can be said in gene- 
 ral of the visible features of this remarkable phenomenon. Late 
 investigations, instead of explaining the manner in which contraction 
 is effected, by showing its dependence on forces previously under- 
 stood, have only served to display the inadequacy of the coarse and 
 mechanical hypothesis, that physiologists have been. so prone to con- 
 fide in, and to make it more than probable that they must ever be 
 content to repose upon the fact above stated, as the simplest which 
 the most refined microscopical analysis will ever disclose. 
 
 All muscle retains its contractility for a longer or shorter period 
 after its separation from the body, or after death. During this perio^ 
 contractions may be excited by the nervous, and all other stimuli, 
 ■which we can apply to it ; and it is certain that these contractions are 
 the same in their nature with those occurring in the living body under 
 natural influences. Being also easy of inspection, they are admirably 
 suited to the display of the minute changes occurring in muscle during 
 its active state. 
 
 The muscle with striped fibres is peculiarly adapted for the display 
 of these changes; for, its texture not being homogeneous, but marked 
 throughout with perfect regularity into spaces or particles so minute 
 as to require to be very highly magnified before they can be even 
 seen at all, the anatomist is provided with the means of detecting 
 movements, which, without this circumstance, must have remained 
 concealed. 
 
 When a piece, retaining its contractility, is torn up into its ele- 
 mentary fibres, the fragments of these, when placed in water, are seen 
 to undergo a slow movement at certain points, especially where they 
 have suffered violence, as at their broken extremities. This move- 
 ment consists of a shortening and thickening of the material com- 
 posing the fibre, as is shown by the general outline of the part, but 
 especially by the appearances visible in its interior. The transverse 
 
MUSCULAR ACTION. 169 
 
 stripes, both light and dark, become longer and thinner: in other 
 "words, the discs expand in circumference, flatten, and approximate 
 to one another ; or, to use another form of expression, the fibrillse 
 become shorter and thicker, both in the particles composing them and 
 the material connecting those particles (fig. 49). 
 
 These changes are always local, or partial ; and it is most evident, 
 from the characters they, constantly present, that they are not limited 
 to any determinate regions, points, or segments, but occur indifferently 
 ■wherever the exciting cause may chance to be exerted. Neither discs 
 nor fibrillae appear to have the smallest share, as aggregations of par- 
 ticles bearing those particular forms, in producing the phenomena of 
 contraction. A contraction is never bounded to a particular number 
 of discs or fibrillse, and is never accurately limited by the interval 
 between two discs. It constantly happens, that at the edge of the 
 contracted part, several discs are only partially engaged in it. A 
 contraction generally, when commencing at the broken end of a fibre, 
 occupies its whole width there ; but, when it commences at the border 
 of the fibre, it may be confined to a portion of many discs: and, fur- 
 ther, the contractile force is never exerted along the whole length 
 of a fibre or fibrilla at once. A contraction excited in an elementary 
 fibre by the contact of a hair extends into the mass equally in all 
 directions, as we might suppose it would do, if the mass were homo- 
 geneous. 
 
 An attentive study of these interesting phenomena will lead to the 
 conviction, that, in the bare fact of contraction, the huild of the fibre 
 is an item of no importance whatever : the exquisite symmetry dis- 
 played in the apposition of its component particles is, as it were, dis- 
 regarded and overlooked; while the whole process is to be referred 
 to the material itself, the ultimate tissue, whose property is contract- 
 ility. This property appears to reside both in the particles and the 
 substance connecting them. 
 
 The ultimate movements, therefore, on which contraction depends, 
 whatever they may consist in, are molecular, and far beyond the reach 
 of sense. 
 
 It will be perceived that this view of the subject is the only one 
 which can harmonize the fact of contraction in voluntary muscle with 
 the same phenomenon in structures which have no complicated internal 
 arrangement of particles, as, for example, in the unstriped fibre; and 
 the contractility manifested by fibrine, immediately after coagulation, 
 is a property too nearly allied to the contractility of muscle (a form of 
 fibrine) not to give it additional credibility. 
 
 In regarding contractility, therefore, as a property of the living 
 muscular fibre in general, it is meant that it resides in it as a property 
 without which it would not be muscle ; and in such a manner, that no 
 particle, however microscopic, can be detached from muscle which 
 does not of itself, and independently of the rest, possess this property 
 as long as it possesses vitality. 
 9 
 
170 ORGANS OF LOCOMOTION. 
 
 Of the differences between the minute movements of Muscle in passive 
 and active contraction. 
 
 In passive contraction. — It is perhaps impossible in the higher ani- 
 mals to observe the nature of the microscopic movements occurring 
 in muscle in its ordinary state or during its passive shortening ; but, 
 in the lower and smaller forms of life, this may sometimes be accom- 
 plished. It may always appear doubtful, however, whether any con- 
 traction that may be here witnessed be entirely of the passive kind, 
 and consequently the movements here noticed are not worthy of im- 
 plicit reliance. But it is more easy, and quite as satisfactory, to bring 
 a muscle under inspection, which is still in situ and in equilibrium with 
 its antagonists: in such, contractile force is being still exerted, though 
 its full effects are prevented from taking place. This may be done in 
 various small animals : perhaps the tail of small fish, or of the tadpole 
 of the common frog, is the best adapted for the purpose. In the latter, 
 deprived of its integument, we have obtained such a view, and have 
 found the contraction to be quite uniform throughout, the transverse 
 stripes being stationary and equidistant. This is nothing more than 
 might have been expected on a priori grounds. The contraction, 
 being the effect of the passive exercise of the property shared equally 
 by all parts of the tissue, would be equal in equal masses ; and, as 
 the elementary fibres are of precisely equal width and substance from 
 end to end, no part of them could predominate in action as long as 
 only the equable stimulus coincident with their natural state of tension 
 were applied. It may be concluded, therefore, that passive contrac- 
 tion is attended by a movement absolutely uniform throughout the 
 whole mass of an elementary fibre, or of a muscle. 
 
 In active contraction, the case is far otherwise, as may now be con- 
 sidered proved by a considerable body of evidence. 
 
 It might be argued, prior to direct proof, that active contraction 
 must be partial, at least at its commencement ; because the stimuli 
 which occasion it cannot, iri their very nature, be applied to every 
 particle of the fibre at one and the same instant of time. 
 
 Certain features of the phenomena witnessed under the microscope 
 in fragments removed from the body, and contracting in water, have 
 
 a close bearing on the present 
 
 ^'g'*^' question. It has been already 
 
 said, that such contractions are 
 uniformly partial ; but they pre- 
 sent two further varieties, either 
 I jf I'ji »---- remaining in the part where they 
 -^^•..^^ y ' ^ i first occur, or leaving it as they 
 
 J ^= J • advance to others in the neigh- 
 
 Frswmentofan elementary ftbre (from iho Eel) bourhood. The accidental cir- 
 
 Fraffmentof an elementary nbre (from Ihc Eel) uijuiiiuuu. xiic auuiuciiiaj. i^ii- 
 
 partially contracted in water. Magnified 300 dia- riimstancps iindpr wViifVi thp fraff. 
 
 meteis.-a. Uncontractcd part. 6. Contracted '-"'"'•^'•nLtf. unuer wnicnme irag 
 
 part, alone the border of which the Rarcolemma mentS are placed, CXplain thcSC 
 18 raised from the surface by the water that has • , • K ,^ ,. ' 
 
 been absorbed, that has thereby caused the con- Varieties. In the former CaSC, 
 
 SclKas'sl''''''''''''^'^^'''"''""'"*''™"- the ends of the fragments happen 
 
MUSCULAR ACTION. 
 
 171 
 
 to be freely movable, and are drawn towards each other, according to 
 the amount of contraction occurring in particular spots; and, as the 
 contractile force leaves these spots and engages others, the ends con- 
 tinue to approximate, the parts once contracted remaining so, because 
 there is no force to extend them. Hence the contraction appears per- 
 manent. , 
 
 In the latter case, certain parts of the fibre (as its broken extre- 
 mities) are fixed more or less firmly, so as to offer a resistance to the 
 contraction that takes place ; this resistance enabling the contractile 
 force advancing to new parts to obliterate the traces of contraction in 
 the parts in which it is subsiding, by stretching them. The ends 
 usually become fixed in consequenceof their being the first to thicken 
 from contraction, and from their thus receiving the pressure of the 
 lamina of mica or glass with which it is requisite to cover the object; 
 and they are the first to contract, because irritated by' being broken, 
 and by the water, which is absorbed soonest where the sheath is de- 
 ficient. . This fixing of-- the ends brings the fibres in question nearly 
 into the condition under which they exist in the living body, where 
 it has already been explained that there is always a resistance to be 
 overcome in active contraction. This particular variety of the phe- 
 nomenon, therefore, deserves special study. Those animals whose 
 muscles are most tenacious of their contractility are the best suited 
 for examination ; and, among these, the young' crab or lobster may 
 be most easily obtained. 
 
 In an elementary fibre from the claw, laid out on glass, and then 
 covered with a wet lamina of mica, the following phenomena are 
 always to be observed. The ends become first contracted and fixed. 
 Then contractions commence at isolated spots along the margin of the 
 fibre, which they cause to bulge. At first they only 'engage a very 
 limited amount of the mass, spreading into its interior equally in all 
 directions, and being marked by a close approximation of the trans- 
 verse stripes. These contractions pull upon the remainder of the fibre 
 only in the direction of its length, so that along its edge the transverse 
 stripes in the intervals are very much widened and distorted. These 
 contractions are never stationary, but oscillate from end to end, relin- 
 quishing' on the one hand what they gain on the other. When they 
 are numerous along the same margin, they interfere most irregularly 
 with one another, dragging one another as though striving for the 
 mastery, the larger ones , con- 
 
 tinually overcoming the smaller; 
 then subsiding as though spent, 
 stretched again by new spots of 
 contraction ; and again, after a 
 short period of repose, engaged 
 in their turn by some advancing 
 wave : this is the first stage of 
 the phenomenon (fig. 50). At 
 a subsequent stage, the ends of 
 the fibre commonly cease to be 
 fixed, in consequence of the in- 
 
 Fig. 50. 
 
 Border of an elementary flbie of a young Crab, 
 showingja spot of contraction, and the sarcolemma 
 elevated in the form of buUse by the expressed 
 water.— Magnified 300 diameters. 
 
172 
 
 ORGANS OF LOCOMOTION. 
 
 terraediate portions, by their contraction receiving some of the pres- 
 sure of the glass. The contractions, therefore, increasing in number 
 and extent, gradually engage the whole substance of the fibre, which 
 then is reduced to at least one-third of its original length. 
 
 The muscular tissue in these animals is comparatively tough; but 
 where it is more fragile, as in the frog, it may give way in the inter- 
 vals between spots of contraction, and be- 
 come ruptured and disorganized in various 
 degrees. {Phil. Trans., 1840, p. 490, pi. 
 xix. fig. 75.) In fishes we have seen a 
 succession of phenomena similar to what 
 has been described in the crab ; waves of 
 contraction advancing and receding, but 
 gradually augmenting in bulk, till the 
 whole fibre was finally contracted (fig. 51). 
 In all these examples, as long as the 
 ends of the fragment are fixed, and will 
 not yield to the convellent force, that force 
 is seen to be exerted in a momentary man- 
 ner in successive portions of the mass. 
 In proportion as they yield to it, the re- 
 sistance which enabled the contraction of 
 new parts to stretch those from which it 
 was receding is removed, and the appear- 
 ances of contraction remain. A distinc- 
 tion is required between the contractile 
 force and the contraction resulting from 
 its exercise. The latter will be perma- 
 nent, if no force from without be exerted 
 to obliterate it by stretching ; for a contracted muscle has no power 
 of extending itself; there is no repellent force between its molecules. 
 From these phenomena, therefore, it is possible to eliminate the 
 appearances resulting from a subsided force and to judge of the mode 
 and duration of action of the force itself. Thus sifted, they prove 
 that, even when directly stimulated by water after removal from the 
 body, a muscle contracts in successive portions, never in its totality 
 at once ; and that no particle of it is capable of exhibiting an active 
 contraction for more than an instant of time. 
 
 The appearances presented by muscle that has been ruptured by 
 its own inordinate contraction in fatal tetanus, in the human subject, 
 will supply the link wanting to connect the foregoing phenomena with 
 those occurring in healthy contraction during life: for tetanic spasm 
 differs from sustained voluntary contraction, only in its amount and 
 protracted duration, and in its being independent of the will; none of 
 which circumstances are of essential importance in regard to the nature 
 of the act of contraction itself. 
 
 The muscles are so arranged in the body, that no amount of con- 
 traction which the mechanism of the bony and ligamentous frame- 
 work will permit one of them to undergo, can by possibility occasion 
 the rupture of an antagonist, provided it remain relaxed: to be rup- 
 
 Slages of contraction seen on one 
 occasjon in an elementary fibre of 
 the Skate. The uppermost stale is 
 that i)revious to the commencement 
 of active contraction. 
 
 a. a. a. Successive "waves" of 
 contraction seen moving along one 
 margin of the fibre, marked by a bulg- 
 ingof the margin, by an approxima- 
 tion of the transverse stripes, and by 
 a consequent darkening of the spots. 
 
 b. b. b. Similar "waves" still mov- 
 ing alon^ the fibre, but engaging its 
 whole thickness. 
 
MUSCULAR SOUND. l73 
 
 tured, the antagonist must be itself contracted. But a muscle, if 
 contracted beyond its natural amount, may be so resisted by mechani- 
 cal powers, in or out of the body, as to rupture itself. Hence, the 
 contraction of a muscle is a necessary condition, and generally the 
 essential cause of its own rupture: the other condition being a force 
 greater than the tenacity of the ruptured part, holding its ends 
 asunder; ■which latter may be either the active or passive contraction 
 of antagonists, or mere mechanical resistance: but it is evident, that, 
 for a muscle to be ruptured by its own contraction, that contraction 
 must be partial, as is shown in the case of the frog's muscle, already 
 mentioned. 
 
 An examination of muscle ruptured in tetanus is found to bear out 
 these observations in the fullest manner. {Phil. Trans., 1841, p. 69.) 
 The elementary fibres present numerous bulges of a fusiform shape, 
 in which the transverse stripes are very close together. These swell- 
 ings, or contracted parts, are separated from one another by intervals 
 of various lengths, in which the fibre has either entirely given >vay, 
 or is more or less stretched and disorganized. These appearances 
 are met with after all contractility has departed ; they are the vestiges 
 of the spasm during life. Yet in other muscles, which have been 
 likewise convulsed, but not ruptured, they are not found. Their 
 presence is, therefore, the result of the rupture. They admit only of 
 the following explanation : the contractile force has operated at the 
 points found contracted, and, by its excess, the intermediate portions 
 have been stretched to laceration. Having once given way, the con- 
 tracted parts have become isolated, and can no longer have been 
 extended after the subsidence of contractile force ; they consequently 
 retain the form and appearances they possessed, when surprised, as 
 it were, by the rupture they have themselves produced of the inter- 
 vening parts. 
 
 Supposing, for a moment, that active contraction were an univer- 
 sal and equable act, and that, by the superior power of an antagonist, 
 a weak muscle had been ruptured, the appearances resulting would 
 manifestly be entirely different from those now detailed. The fibres 
 beyond the ruptured point would have their transverse stripes uniformly 
 approximated. 
 
 It may be concluded from the preceding facts, — 1st. That active 
 contraction never occurs in the entire mass of a muscle at once, nor 
 in the whole of any one elementary fibre, but is always partial at any 
 one instant of time : — 2d. That no active contraction of a muscle, 
 however apparently prolonged, is more than instantaneous in any 
 one of its parts or particles : — and therefore, 3d. That the sustained 
 active contraction of a muscle is an act compounded of an infinite 
 number of partial and momentary contractions, incessantly changing 
 their place, and engaging new parts in succession ; for every portion 
 of the tissue must take its due share in the act. 
 
 Two phenomena yet remain to be mentioned, which, by admitting 
 of a satisfactory explanation on this view of the subject, give strong 
 testimony to its correctness. 
 
 The first is the muscular sound, heard on applying the ear to a 
 
174 ORGANS OF LOCOMOTION. 
 
 muscle in action. It resembles, according to the apt simile of Dr. 
 Wollaston, (PW. Trans., 1811,) the distant rttmbiing of carriage- 
 wheels ; or rather, perhaps, an exceedingly rapid and faint tremulous 
 vibration, -which, when well marked, has a metallic tone. It is the 
 sound of friction, and appears to be occasioned by those movements 
 of the neighbouring fibres upon one another, with which the partial 
 contractions must be attended in their incessant oscillations. 
 
 The other phenomenon is one whose existence has been recently 
 ascertained by MM. Becquerel and Breschet, {Recherches sur la 
 Chaleur Jlnimale. Archiv. du Museum, torn. i. p. 402,) viz., that a 
 muscle, during contraction, augments in temperature. They have found 
 this increase to be usually more than 1° Fahr.; but sometimes, when 
 the exertion has been continued for five minutes, (as the biceps of 
 the arm, in sawing a piece of wood,) it has been double that amount. 
 This development of heat may be in a great measure attributable to, 
 and even a necessary consequence of, the friction just alluded to. 
 
 Thus it would appear, that in active contraction there is a disturb- 
 ance of the state of equilibrium, or rest, by the application of a special 
 stimulus to certain portions only of each fibre ; by which first these 
 portions, then others in succession, are made to contract strongly, and 
 to pull on the extremities of the fibre through the medium of the parts 
 not so contracted. The contractions undulate along the fibre frgra 
 the point stimulated, and there is always a considerable part of each 
 fibre uncontracted. This will account for the remarkable fact, that 
 detached fragments of the voluntary fibre will contract by two-thirds 
 of their length ; though an entire muscle, in its natural situation, can- 
 not shorten by more than one-third. This great capacity of contrac- 
 tion in the tissue would be without a purpose, if it -vfrere not that it 
 only admits of momentary exertion, and therefore requires that in the 
 organ successive parts should take up the act, and by so doing, 
 render it, as a whole, continuous. In an active fibre the contracting 
 parts are continually dragging on those in which the contractile force 
 has just subsided, and which intervene between them and the extre- 
 mities of the fibre. These are thereby instantly stretched, and come 
 to serve the temporary purpose of a tendon ; but one which resists 
 extension more by its passive contractility than by its mere tenacity. 
 It is these parts which in tetanic spasm suffer laceration ; which hap- 
 pens in consequence of the contraction excited by the vis nervosa 
 being then too powerful to be resisted by the passive contractility. 
 
 The preceding account of the minute changes occurring during 
 contraction rests on data furnished by the striped form of muscular 
 fibre; but there is nothing contained in it which seems at variance 
 with the little that is positively known regarding the contractions of 
 the other form. The differences between the contractions of the two 
 varieties are almost certainly confined to the manner of exercise, and 
 do not extend to the essential nature of the act. Though the un- 
 striped fibre has not been studied by the microscope, during its active 
 state, with the same success as the other, yet the sirpilarity of the 
 gross changes observed in it by the naked eye, to those seen in volun- 
 
VARIETIES OF CONTRACTION. 175 
 
 tary muscle, forbids us to doubt the identity of the phenomenon in all 
 that is essential to it as an act of contraction. 
 
 From the knowledge we possess, we are perhaps entitled to hazard 
 some further conjecture? respecting the differences in the mode of 
 exercise of the contractile power in different cases. In whatever 
 that mysterious power may consist, it would appear that the structu- 
 ral modifications of the two kinds of fibres are intimately connected 
 with the manner in which it is capable of being exerted. Wherever 
 the striated structure occurs, we witness an aptitude for quick, 
 energetic, and rapidly repeated movements ; while, where it is defi- 
 cient, they are sluggish, progressive, and more sustained. 
 
 The varieties in the character of contractions performed by striated 
 muscles are very striking, especially that of the heart, as compared 
 with the prolonged action of the voluntary muscles. In both, there 
 is an alternate momentary action and repose of every contractile 
 particle : but in the heart the contraction is universal at one instant, 
 and the repose equally universal at the next; while, in the prolonged 
 action of the voluntary muscles, contractions of certain parts of each 
 fibre always co-exist with repose of other parts.* 
 
 The contractions of voluntary muscles differ greatly from one another 
 in duration, energy, and extent. Dr. WoUaston {Philos. Trans., 1811), 
 was of opinion, that the phenomenon of the muscular sound affords a 
 proof that the duration of a muscle's contraction depends on the appli- 
 cation to it of a succession of distinct impulses; and this idea, accord- 
 ing very nearly, as it does, with the later evidence of observation, 
 appears, on the whole, the most satisfactory that has been advanced 
 on this abstruse subject. He also thought that the intensity of a con- 
 traction corresponds with the rapidity with which these impulses, are 
 transmitted to it ; and this likewise may be, in part, true. But there 
 is, in addition to this, in all probability, a difference in the intensity 
 of the stimulus itself in different cases, producing a difference in the 
 size of each wave, a difference in the amount of contractile energy 
 exerted in each, and a difference in the rapidity with which the waves 
 oscillate along the fibre. The extent of the contraction (the duration 
 and intensity being the same) will manifestly depend on the amount 
 of the length of the fibre which is contracted at once ; but we are 
 ignorant whether this variation in amount is effected by a variety in 
 the number of waves, or in the extent of the fibre engaged by each 
 of them. 
 
 In describing the white fibrous tissue, we remarked the facility 
 with which its fibres are thrown into a wavy or zigzag course when 
 their ends are brought near together. The same thing occurs in the 
 nerves, and may be observed in almost any flexible non-elastic cord. 
 The muscular fibre easily assumes this zigzag course, when its eiids 
 are approximated by any other force than its own contractility. It 
 may thus be at any time thrown into zigzag, long after it is quite 
 dead, and has lost all its contractility : and, in general, such zigzags 
 
 * By the expression "universal at one instant," we do not mean absolutely so» 
 for observation, and ihe presence of the muscular sound, both declare that the contrac- 
 tion, even of the heart, though so apparently momentary, is progressive. 
 
176 ORGANS OF LOCOMOTION. 
 
 occur at pretty regular intervals, determined by the force employed 
 and the flexibility of the tissue; and, when several fibres are lying in 
 contact, their zigzags usually correspond. 
 
 Now, such zigzags have been frequently observed in -the living 
 fibre, of course accompanied with an approximation of its extremi- 
 ties; and some physiologists, mistaking the effect for the cause, have 
 concluded the zigzags to have occasioned the shortening. Dr. Hales, 
 and, long after him, Prevost and Dumas, examined this appearance 
 in the flat abdominal muscle of a frog, laid on glass, and made to 
 contract by a galvanic shock ; and, noticing that the angles of the 
 zigzags corresponded in many places with the transit of nerves across 
 the fibres, they concluded that an electrical current, passing from one 
 to the other, occasioned the flexion of the fibres at the points of 
 contact. 
 
 This hypothesis, when first proposed, attracted great regard, from 
 its appearance of simplicity, and from its falling in with the then 
 favorite notion of-flie identity of the nervous influence with some 
 form of electricity ; and without sufficient caution it was very generally 
 adopted. The facts previously stated, however, completely over- 
 throw it, and render an explanation of the causes of the error scarcely 
 more than historically interesting. It would appear that the galvanic 
 shock, when passed through a mass of fibres, affects them unequally, 
 some only being contracted by it : but these, by their cellular and 
 vascular union with others, draw towards each other the ends of the 
 uncontracted ones, and, of course, throw them into zigzag; and it is 
 most natural that the passage of nerves or vessels across them should 
 determine the flexures to take place at this or that particular point. 
 When some fibres are straight and others zigzag, and yet the ends of 
 all equidistant, it is clear that the straight ones are the short or con- 
 tracted ; the zigzag, the long or relaxed. So, also, when a living 
 muscle is laid bare in situ, the air excites tremors and a zigzag appear- 
 ance on its surface, by the different fibres taking on non-simultaneous 
 contractions. 
 
 Schwann (Muller^s Physiology, by Baly, p. 905), contrived an 
 apparatus by which he could estimate the varying force of contraction 
 which a muscle could evince under the same stimulus, (an electric 
 shock of a given power applied to the nerve,) when its length was 
 varied, by its passive contractility being balanced by different weights. 
 He sought to discover whether the contractile force was increased as 
 the contracting parts approached each other more nearly. If he had 
 found it so augmented, there would have been some reason for con- 
 necting contractility with the other forces of attraction with which we 
 are acquainted, the power of which increases with the nearness of the 
 points attracted, in the ratio of the square of the distance. But the 
 results of several ingenious experiments were quite opposed to this 
 notion ; proving that, within certain limits, the power of a muscle to 
 contract under a stimulus is greater in proportion as it is less con- 
 tracted, and that it diminishes as the amount of contraction in- 
 creases. 
 
 Considering, as we are perhaps entitled to do, that an equal mass 
 
CONTRACTILITY OF MUSCLE. 177 
 
 of each fibre, say one-third, -was in contraction at any one instant by 
 each application of the stimulus, we may reduce the result of these 
 experiments to an estimate of the passive contractile power under 
 different amounts of stretching ; for then the -varying amount of aggre- 
 gate shortening under the same stimulus would indicate the varying 
 amount of resistance to elongation afforded by the intermediate two- 
 thirds to the same amount of active contractile force in the one-third. 
 
 It is clear, from that which precedes, that contractility is a property 
 residing in the sarcous tissue by virtue of its chemical constitution, 
 and that it is capable of being called into action by other stimuli be- 
 sides the nervous. That it departs with life, is a proof that those 
 actions of waste and nutrition, concomitant with the ilux of life, are 
 essential for its integrity. We know that contractility is exhausted 
 both by disuse of a muscle, and by over-use consequent on over- 
 stimulation ; and in no other way can these opposite causes act than 
 by their both interfering with healthy nutrition. That they do thus 
 act, is rendered probable by other proofs. It has long been known 
 that cutting off the supply of blood from a muscle destroys its con- 
 tractility ; that unnatural temperature has the same effect ; and, in 
 general, that all causes affecting nutrition affect also contractility in 
 the same degree. 
 
 The contractility of a muscle has also invariably a certain com- 
 plexion or character connected, we might almost say, with the vigor, 
 but at least, with the character, of the nutrient process in the particu- 
 lar muscle. This fact has been ably illustrated by Dr. Marshall Hail, 
 (see article "Irritability," Cyclop, of Jlnat. and Phys.,) who never- 
 theless is opposed to the great conclusion which we consider to flow 
 from it, that contractility is proportioned to the activity and perfection 
 of the nutrient function. 
 
 If we suddenly check the supply of nutrient material to the mus- 
 cles of various animals, in the same state as regards previous stimu- 
 lation, and in such a manner as not to stimulate the muscles in so 
 doing, we shall find thatt their contractility, as evidenced by their 
 contracting under a given stimulus, endures through very unequal 
 periods of time. Thus, in the bird it is very evanescent; in the 
 insect, also, it is very evanescent ; in the mammal less so ; in the 
 reptile it lingers longer; while in the fish and crustacean it is in gene- 
 ral very enduring. 
 
 The degree in which oxygen is admitted to the tissues in these ani- 
 mals, corresponds in the main with the scale thus designated by the 
 relative endurance of the contractility of their muscles. Nothing is 
 more probable than that the amount of oxygen admitted to the tis- 
 sues may be taken as a fair estimate of the activity in them of the 
 processes of waste and assimilation. Now, we know that the vitality 
 of the tissues does not cease immediately on their supply of nutriment 
 being cut off; that death of the whole animal, as an individual, is not 
 necessarily attended with simultaneous death of every part ; that so- 
 matic death generally follows systemic death from the functions being 
 no longer concatenated in mutual dependence ; and it is entirely 
 consonant with facts to suppose that the endurance of the vital func- 
 tions in the tissues after systemic death is proportionate to the slow- 
 
178 ORGANS OF LOCOMOTION. 
 
 ness with which they are ordinarily performed. The close, corre- 
 spondence, therefore, between the duration of contractility and the 
 slowness of the nutrient function in various animals, is a strong evi- 
 dence of the dependence of the one on the other. 
 
 And it is extremely interesting to observe, that not only does a less 
 arterial character of the blood co-exist with a more enduring contrac- 
 tility, but also that there is less of it supplied to the muscles, for the 
 above scale corresponds also with that in which animals are ranged 
 in regard to the size of the elementary fibres ; and we have already 
 seen that the vascularity of a muscle is inversely as the thickness of 
 its fibres. 
 
 Thus we have animals ranged in the same series, whether we esti- 
 mate it by the duration of contractility, the degree of the oxygena- 
 tion of the blood and tissues, or the quantity of blood sent to the 
 muscles, viz., birds, insects, mammalia, reptiles, fish, and Crustacea. 
 The meaning of this correspondence may be further illustrated by the 
 phenomena of hybernation, in which all the functions are held en- 
 chained, and we are certain that nutrition proceeds with extreme lan- 
 guor. In the hybernating animal, contractility is very enduring, as 
 compared with that property in the very same organs when in a. state 
 of greater vital activity. 
 
 Nor must the evident relation subsisting between fibrine and the 
 sarcous tissue, in respect of their vital properties, be passed over in 
 silence. In chemical constitution they may be said to be identical; 
 and there seems no doubt that muscle is formed by the direct deposi- 
 tion in a solid form of the fluid fibrine of the blood, under the elective 
 attraction of the previously existing tissue. Now, in birds, the blood, 
 i. e., its fibrine, coagulates, or assumes the solid form, very quickly 
 when it is withdrawn from the vessels, in mammalia less so, and in 
 reptiles and fishes very tardily, if in these several cases it be placed 
 in similar circumstances. A fatal stroke of lightning, which instanta- 
 neously destroys contractility in the muscles, prevents also the coagu- 
 lation of the blood. In the same person, under health and disease, 
 the blood may vary much in the speed with which it coagulates, 
 according to its chemical constitution, the amount of oxygen accu- 
 mulated in it, and the activity of the vital processes : and, after death, 
 the coagulability of the blood, and the contractility of the muscles, 
 have a general correspondence, which has been even made the basis 
 of an hypothesis, ascribing the rigor mortis, or the dying act of contrac- 
 tion, to coagulation of the blood.* It will be subsequently explained 
 (see chapter on the Blood), that the fibrine of the blood, on becoming 
 solid, acquires for a brief period the property of contractility; and 
 this in very different degrees, according to varieties in the same 
 causes which affect the speed of its coagulation. No one will pre- 
 tend that this is not as much a property of living fibrine when solid, 
 as that of coagulating is of the same substance when fluid ; and the 
 correspondence between the coagulated living fibrine of the blood and 
 the living sarcous tissues in chemical constitution, in the possession 
 
 * Orfila, B^olard, and Treviranns hold this view, which Miiller seems to regard as 
 not untenable. 
 
VARIETIES OF MUSCULAR MOVEMENT. 179 
 
 of contractility, and in the modes in which that vital property in both 
 is affected by similar causes, adds strong confirmation to the opinion 
 we have expressed, that contractility is a property of the living mus- 
 cular substance as such. 
 
 But contractility does not vary in its durability alone; it also pre- 
 sents great differences in regard to its aptness to excitation by stimuli: 
 and it would appear that these characters are always, cmteris paribus, 
 in an inverse relation to one another. In birds and insects, which 
 have for the most part to sustain themselves by very energetic^and 
 rapid muscular movements ir\ the air, the excitability is extreme ; 
 and certainly the motions performed by these creatures far exceed in 
 precision, regularity, and frequency those of any other animals. 
 
 The rigor mortis, or stiffening of the bpdy after death, is due to a 
 contraction of the muscles. If the contractility of a muscle be endur- 
 ing, the rigor comes on late and lasts long ; but if it be evanescent 
 and its character excitable, the rigor begins very soon and quickly 
 terminates. This is true in different individuals and classes of animals, 
 and corresponds entirely with what we have already said of the varie- 
 ties of this property. Its cause is obscure, and may be complex; but 
 its resemblance to the contraction of fibrine after recent coagulation 
 is too obvious to be overlooked. Its nature is shown by the preceding 
 observations (p. 170). 
 
 We have the power, at will, under certain limitations, of produc- 
 ing, checking, and regulating the amount of contraction in the volun- 
 tary muscles ; and, as a necessary part of this power, we are able to 
 appreciate, by certain sensations originating in the muscles, what pre- 
 cise degree of contraction is present in each. This latter is only that 
 modification of common sensibility which belongs to muscle. It has 
 been termed the muscular sense. In it we possess a most important 
 aid to the sense of touch, being able accurately to vary the posi- 
 tion and amount of pressure on external objects in voluntary accord- 
 ance with the impressions these communicate to the serisorium through 
 the tactile nerves ; and by it we are able to estimate with nicety the 
 amount of muscular power required to balance various resistances, as 
 weight, &c. In general, these resistances must be brought into rela- 
 tion with the muscular sense through the organ of touch, which is 
 adapted to this purpose by its superficial position on the body. But 
 the powers of the muscular sense, isolated from tact, are exhibited, 
 in its enabling one to estimate the weight of a tumour developed in 
 the interior of the limb, and in general the resistance afforded by the 
 weight of one part of the body, or the action of one muscle or set of 
 muscles to that of another. Hence a principal source of the marvel- 
 lous power which all animals possess of associating the various parts 
 of their bodies in numberless combinations of harmonious movement. 
 Of some varieties of muscular movement. — Having described the 
 differences between the movements of active and passive contrac- 
 tion, we shall now be more able to refer to their proper causes those 
 varieties o£ movement by which certain muscles or classes of mus- 
 cles are distinguished. In briefly adverting to these, we shall have 
 to glance at some collateral considerations regarding the mode of their 
 
180 ORGANS OF LOCOMOTION. 
 
 connection with the nervous system, which cannot be fully under- 
 stood without reference to what will be afterwards said under that 
 head. 
 
 The action of the sphincters of the anus and bladder seems, at first, 
 peculiar. They are constantly contracted, except during the passage 
 of the contents ; and yet no fatigue attends this persistent action. The 
 explanation is very simple. They remain contracted unless the con- 
 tained matters are forced within them by a superior power. Now, 
 their mass, and therefore their contractility, is superior to that of the 
 wall of the cavity above ; consequently their passive contraction en- 
 dures while that of the parts above is being gradually mastered by 
 the accumulation of the feces or urine. But, when these excretions 
 at length excite active contraction in the walls of the cavity contain- 
 ing them, this overcomes the passive contraction of the sphincters, 
 and the evacuation occurs. The sphincters have striped fibres and 
 voluntary nerves, by means of which we can for a time add active to 
 passive contraction, and thus retard the expulsion ; but, as the accu- 
 mulation proceeds, this power is diminished or lost, and the sphinc- 
 ters yield. The levator and sphincter ani frequently aid the accumu- 
 lation of the feces by temporary active contractions, by which the 
 feces tending to dilate the sphincter are pushed backwards for a while. 
 The rectum is thus preserved empty until the period immediately pre- 
 ceding defecation. . 
 
 In paralysis of the lower part of the body from disease or injury 
 of the spine, the voluntary power of the sphincters is lost, and the 
 feces and urine pass involuntarily. But thi? is no proof, as is com- 
 monly imagined, • that the ordinary contraction of the sphincter is 
 an active one, performed in obedience to a continuous nervous stimu- 
 lus. The difference is, that it can now induce no active contrac- 
 tion through the nerves, to counteract temporarily, and in obedience 
 to the will, the active contractions of the parts above, which are not 
 under the influence of volition, and are not paralyzed. Hence, when- 
 ever the feces are driven against it, it gives way, against the patient's 
 will, and (if the sensitive nerves are also paralyzed), without his 
 knowledge. 
 
 Contractions are called peristaltic or vermicular, which advance 
 through a muscle in a slow atid progressive manner. When analyzed 
 closely, we shall find that they are only a variety of the active con- 
 traction already described. If a number of striped fibres are ahanged 
 in a long series, and are contracted in succession (as in caterpillars), 
 the resulting movement is vermicular ; but in the higher animals it 
 is only in the hollow unstriped muscles that this varietyof contraction 
 occurs ; and the best example of it is in the alimentary canal. On 
 laying bare the intestines of an animal just killed, we observe suc- 
 cessive waves of contraction advancing down the tube, and urging 
 its contents along. They appear to be rendered more active by the 
 contact of the cold air ; but may be re-excited, when they have almost 
 subsided, by irritation of the sympathetic ganglia, from which the 
 muscles are supplied with nerves. If a single point of the intestine 
 be touched, a contraction presently occurs there, which moves on- 
 
VARIETIES OF MUSCULAK MOVEMENT. 181 
 
 ■wards to a considerable distaiice, and is often succeeded by others 
 spontaneously arising. 
 
 It is impossible not to remark the close similitude between these 
 contractions and those visible by the microscope in the striped ele- 
 mentary fibre. We have here on a large scale the wave-like charac- 
 ter there exhibited. A contracting voluntary muscle exposed to view 
 exhibits a tremulous motion, and it may be a question how far this 
 may depend on numerous contractions strictly vermicular, affecting 
 successive sets of fibres, but prevented, by their irregularity and 
 want of coincidence through the whole muscle, from appearing so to 
 the eye. When the pectoral muscle is struck, a knot-like contraction 
 often moves off in a slow manner in the direction of the fibres. Peri- 
 staltic contraction is coincident in a large number of contiguous 
 fibres ; and its progressive character is more easily perceived in con- 
 sequence of the arrangement of the fibres around a compressible cftv- 
 ity. The contraction appears more sluggish than other forms ; but, 
 as we are ignorant of the length of each unstriped fibre, we cannot 
 say whether this slowness is in advance along each one, or merely 
 from one to another. 
 
 The contraction exhibited by the muscles in question is always of 
 the perist^tic character, by whatever stimulus excited ,' and its type 
 is therefore probably derived from some peculiarity in the fibres them- 
 selves, as in their arrangement. But it is remarkable that the stimuli 
 which usually exicite it, are applied in succession to different parts, 
 and are thus entirely suited to the production of the peristaltic con- 
 traction. We have a striking example of this in the oesophagus, 
 which is simply a tube of transmission, and not intended to delay the 
 food. The pellet, when thrust into it by the muscles of the pharynx, 
 distends its fibres, which, then contracting upon it, propel it into a 
 fresh portion ready to receive it. This in its turn contracts, and urges 
 it along; and so on, until it is conducted to the stomach. 
 
 In this instance, it is evident that the propelled substance is itself 
 the stimulus to the successive contractions. This it may be, either 
 by distending the fibres, and so acting locally upon them ; or else by 
 impressing the nerves of the membrane touched, in such a way as to 
 excite a nervous stimulus to the muscular coat at each particular part, 
 at the proper moment. As the food is not propelled if the nerves 
 are divided, there can be little doubt that the latter is the true expla- 
 nation. 
 
 The contraction of the bladder occurs after a gradual distension, 
 and, though very temporary, is probably of the true peristaltic kind. 
 The more protracted action of the uterus is undeniably so. In preg-, 
 nant animals this may be as distinctly perceived as in the intestines, 
 and it probably occurs during the gradual development of the muscu- 
 lar structure as pregnancy advances ; but at length a very powerful 
 impulse occasions the expulsion of the young, and the uterus subse- 
 quently remains contracted, because no force distends its fibres. The 
 after-pains mark the final efforts of active contraction. Atrophy of 
 the tissue then occurs, as its development had done, in accordance 
 with other laws. 
 
182 ORGANS OF LOCOMOTION. 
 
 Rhythmical contractions are those which succeed one another after 
 regular intervals of repose. The muscles of respiration and the heart 
 exhibit them through life, which would cease if they were intermitted 
 even for a brief period ; for the oxygenation of the blood, and the 
 dispersion of that fluid through the substance of the various organs, 
 must incessantly proceed. Hence neither is an act of the will re- 
 quired for their production, nor could it under any circumstances pre- 
 vent them. The heart beats independently of our consciousness or 
 control; but the respiratory actions may be hastened, or retarded, at 
 will, though not stopped. This voluntary power is given because 
 these muscles are required in various movements of the body, either 
 alone, or in aid of others ; they minister to other functions besides 
 that of respiration. The voluntary, or irregular action, however, is 
 entirely subordinate to the involuntary and rhythmical. 
 
 The rhythmical character of the respiratory act is to be explained by 
 reference to the stimulus by which it is ordinarily excited. This is an 
 impression made on the internal surface of the lungs by the deterio- 
 rated air, and recurs periodically from the change induced in the 
 inspired air by its contact with the blood in the air-cells. 
 
 Though the heart is in no respect under voluntary influence, yet 
 emotional and instinctive impulses easily affect it : its action is throb- 
 bing, tumultuous, or feeble. These impulses act through the cardiac 
 nerves, which, if stimulated mechanically, will excite contractidfts in 
 a heart removed from the body, and which has almost ceased to beat: 
 but, under all circumstances, the action of the heart is rhythmical. 
 The cause of the rhythm it is exceedingly difficult to resolve. This 
 variety of contraction is coincident with periodic distension of the 
 cavities, and impressions on their lining membrane. But it continues 
 long after the heart is empty, and its nerves cut. Hence, whatever 
 share these circumstances may have in givingthe rhythmical character 
 in the natural condition of the parts, they are certainly not essential 
 to each individual pulse. It is singular that a mechanical stimulus 
 applied once to the heart will often excite a series of contractions 
 after they had ceased, or modify the rhythm of those previously exist- 
 ing; its effects being thus prolonged through many beats. 
 
 In reviewing the actions of the voluntary muscles we may remark 
 the following interesting circumstances : 
 
 1. As to association of movements. — By the mechanical arrange- 
 ments of the muscles on the bony framework, and by the peculiarity 
 of their several nervous connections, they are rendered capable of 
 conspiring in those combined actions which produce the various atti- 
 tudes and general movements of the body. There are few muscular 
 actions, indeed, of an entirely solitary kind. In the animation of the 
 features under the passions, in articulation, in deglutition, in respira- 
 tion, and in numberless other cas^s, we have examples of this asso- 
 ciation of many actions to the production of one effect. Even the 
 consent of the fibres of a single muscle in contraction is an instance 
 of this fact. Among innumerable other proofs of harmonious design 
 in the construction of the animal body, this might be singled out as 
 a most convincing one, that not only are the hard levers, and their 
 
ASSOCIATION OF MOVEMENTS. 183 
 
 joints and motive engines,, so built up as to be entirely proportioned 
 and adapted to one another in shape, strength, and position, and a 
 system of nervous communications established, by which the motor 
 power can be at once excited, prolonged, or controlled in any particu- 
 lar muscle ; but that the mere will, an emotion, an excitement of sense, 
 or even one unconsciously received, is able, by the correspondence 
 existing between the different parts of the nervous system, to pro- 
 duce associated actions in precisely those parts mechanically adapted 
 to move in concert, and this 'with exquisite exactitude as well as va- 
 riety. 
 
 Such is the nature of the nervous communications between certain 
 muscles, that, in numerous instances, one cannot be stimulated to 
 contraction without others contracting of necessity at the same time. 
 This depends very generally on the mechanical disposition of mus- 
 cles, obliging certain of them to fix a point from which others pnay 
 act. Thus the scapula is continually being fixed by the muscks 
 connecting it with the trunk, in order that the arm may be wielded 
 upon it. Thus, also, the brow cannot be elevated by the . frontalis 
 without the occipitalis fixing the intel-mediate tendon. But, in other 
 instances, this necessary consent is dependent on the symmetrical 
 arrangement of similar parts on the two sides of the body. Some 
 persons cannot close one eye, keeping the other open ; or dilate one 
 nostril without the other : we cannot look up with one eye, and down 
 with the other ; nor compress the abdominal cavity by the muscles of 
 one side without those of the other. There is, indeed, a general tend- 
 ency to symmetrical movement, which it is the part of education 
 and habit to overcome within certain limits. The movements of the 
 hands — those wonderfully versatile instruments of man's intellect — 
 are, in his state of infancy, generally symmetrical. , The unsymme- 
 trical actions of walking are a slow acquisition. Most motions that 
 are symmetrical are also harmonious ; but there is one example in 
 which symmetry gives way to harmony of movement, viz., in the 
 lateral motions of the eyes, where symmetry would produce a squint, 
 and derange the consent of the images on the two retinae. Here, 
 therefore, by the distribution of the nerves, non-symmetrical muscles 
 are made to produce a harmonious movement. 
 
 The various attitudes of man may here be briefly explained. Mus^ 
 cular actions associated to produce an attitude are styled co-ordinate. 
 They conspire in obedience to the particular organization of the nerv- 
 ous and muscular systems ; and the resulting postures are natural, 
 and perfectly accordant with the wants and habits of the species. 
 Most attitudes, if perfectly natural, are graceful, just as external fig- 
 ure is graceful ; unnatural attitudes are more or less constrained, or 
 awkward. The co-ordinate, like other movements of the voluntary 
 muscles, are liable to be influenced by passions and affections of the 
 mind. Hence the internal comnaotions of the soul betray themselves 
 in the attitudes of the body as surely as in the lineaments of the coun- 
 tenance. 
 
 In considering the different attitudes, it is to be remembered that 
 the human body is not withdrawn, either by its organization or vital 
 
184 ORGANS OF LOCOMOTION. 
 
 endowments, from the operation of the general laws of matter ; and, 
 accordingly, that the muscular actions occurring with in it are all adapt- 
 ed to act upon its several parts, as upon masses of certain shapes, 
 sizes and weights. In all attitudes the centre of gravity must be 
 maintained within the base of support. 
 
 In standing, the base of support is the space included between the 
 extreme points of the feet. The feet are separated, and the toes 
 turned outwards to increase it. If the body be pushed aside, the foot 
 is instantly carried under it, or it falls ; and if motion be unexpectedly 
 given to the feet, while the body remains at rest by its inertia, (as 
 when a boat in which we are standing is suddenly shoved off from the 
 shore,) the body falls. In standing upright, both legs are kept ex- 
 tended, and the spine and head erect: if the muscles that effect this 
 be suddenly paralyzed, as when a man is shot dead, the head droops 
 on the chest, the curves of the spine are increased by the pressure 
 of the superincumbent weight, and the whole trunk approaches the 
 ground by bending the joints that were before extended. 
 
 The muscular action required to maintain the erect posture of the 
 body is very great. This is shown by the fatigue that ensues on an 
 attempt to remain perfectly still in the erect posture, even for a very 
 short time.' In fact, though we can stand long at a time, it is only 
 by frequently relieving one set of muscles, and bringing anothgr into 
 play, as every one may convince himself by attention to his own ease. 
 We throw the weight of the body first on one leg, then on the other; 
 we change the position of the feet, and of the ankle, knee, and hip 
 joints, as well as of the rest of the body. 
 
 Under all these movements, the centre of gravity has to be kept 
 within the basis of support; and, to effect this object, the different 
 muscular actions on which the erect posture depends must be ex- 
 quisitely balanced against one another, and, when one is altered, the 
 rest must be re-adjusted in harmony with it. In the practised tum- 
 bler, balancing himself on a point, or the opera-dancer, poised on a 
 single toe, we have the most beautiful examples of the precision of 
 this adjusting power. Where the basis of support is ampler, it is less 
 apparent, but not less real. 
 
 The various parts of the body are weights, and, in the muscular 
 adjustments, are treated as such. By their symmetrical develop- 
 ment on the two sides, they are naturally balanced, and thereby car- 
 ried with less muscular effort. When two equal artificial weights 
 are fixed on opposite sides of the body, equidistant from the centre of 
 gravity, (as when buckets are suspended from a bar passing across 
 the shoulders,) the mere weight is all that the muscles have to sup- 
 port: but, if one be removed, a corresponding inclination of the body 
 must instantly be made towards that side to counterpoise the other ; 
 and for this a sustained muscular effort must be made in addition to 
 that required for the support of the remaining weight. Now, a part 
 of the body on one side (say, an arm), by being carried from the cen- 
 tre of gravity, may disturb the equilibrium of weight, just as moving 
 the weight on a scale-beam disturbs it : that side of the body becomes 
 relatively heavier, and an inclination towards the opposite is rendered 
 
MOVEMENTS OF PROGRESSION. 185 
 
 necessary. In all the changes of attitudes, similar adjustments are 
 being constantly made; and, in general, the more accurately they are 
 effected, and the more economically in regard to the outlay of mus- 
 cular power, the more graceful and pleasing are the movements and 
 postures themselves. 
 
 In the associated movements of progression, or locomotion, the same 
 circumstances are observed : walking, running, and leaping are but 
 different modes in which the body is repeatedly inclined by muscular 
 effort beyond the basis of support ; and this basis brought again and 
 again, by muscular effort, under the centre of gravity; 
 
 The movements of ordinary walldng may be readily analyzed. 
 Suppose we commence by advancing the left leg. We first slightly 
 raise the left heel, arid bend the left knee, to disengage the limb from 
 the ground ; throwing the weight of the body on the right limb, and, 
 therefore, inclining the body towards the right side. The body is 
 now raised by an extension of the right ankle-joint, effected chiefly 
 by the calf; the ball of the foot resting on the ground, which serves 
 as a fulcrum. At the same time the body is thrown in advance of 
 this fulcrum, and would fall, were it not that the left leg is now 
 brought under it, and receives its weight, by which- the body is in 
 turn inclined to the left. The right leg, which ha(| been extended, 
 is then bent, raised from the ground, and swung forwards, ready 
 again to sustain and project the body, when the left leg has gone 
 through a similar movement. In running, the muscular actions are 
 performed in a similar succession, but more rapidly and more vigor- 
 ously. The body is more bent forwards, and its weight made more 
 effectually to aid progression. In leaping, the body is projected by a 
 .sudden extension of both the lower limbs, and raised, for a brief 
 time, entirely from the ground, the feet being advanced again in time 
 to receive its weight as it descends. 
 
 2. ^^to the manner in which movements of the voluntary muscles are 
 excited. — These muscles are subject, through the motor nerves, to 
 the influence of several remote stimuli, already enumerated, and the 
 chief of which, volition, gives its name to the class. These stimuli, 
 in the healthy body, impress the motor nerve in the nervous centre, 
 and the effect is a contraction of the muscle. By an exertion of the 
 will we can contract more or fewer muscles at once, and to any de- 
 gree, within certain limits : we can contract antagonist muscles toge- 
 ther, or alternately, and through a longer or shorter period. , 
 
 But every voluntary muscle is subject to other influences more 
 certain and more powerful in their operation than the will, and to 
 which the will has often to yield. The wonderful and characteristic 
 movements of the body, and especially of the features under the 
 impulses of passions and emotions, are all involuntary, of which the 
 best proof is to be found in the very partial power the will has of 
 restraining them. To imitate the movements of passion is a task of 
 extreme difficulty ; and those actors succeed the best who lose them- 
 selves the most in their characters, that is, who the most completely 
 assume for the time the passion they design to portray. Without 
 this quality the most elaborate imitation is' cold, and fails to touch our 
 
186 ORGANS OF LOCOMOTION. 
 
 sympathies. The genius of th^ histrionic artist consists chiefly in this 
 power. 
 
 Many movements ensue involuntarily when certain impressions are 
 made on the surface of the body, or in any part of its interior, either 
 by external or internal causes. Such impressions are usually attended 
 with consciousness, but sometimes not ; so that there is no reason to 
 believe that perception of the impression is in any way essential to 
 the production of the movement. All such movements are termed 
 reflex. The contraction of the esophagus in swallowing is an exam- 
 ple of them without consciousness. The sudden inspiration that fol- 
 lows a dash of cold water on the skin, and the writhings produced 
 by tickling, are instances attended with consciousness. All muscular 
 actions consequent on pain, and which are not the immediate act of 
 the will, are similar in kind, though the stimulus producirig them is 
 unnatural. 
 
 Reflected movements are sometimes called instinctive; but this term 
 is better limited to actions resulting from a propensity in the mind, of 
 the meaning of which we are ignorant, but which we follow blindly 
 without reference to consequences. Such propensities are developed in 
 animals much more than in man; and in man more during his infancy 
 than in his mature state, when reason asserts her domination over in- 
 stinct. Instinct exhibits foresight ; but it is the foresight of the Creator, 
 and not of the creature. It is the reason of God working with the mate- 
 rial instruments of the creature's reason, independently of the crea- 
 ture's will. Hence the movements consequent on its impulses have 
 all the concatenation and character of movements impelled by reason 
 through the will ; while they are altogether independent of the will. 
 Instinctive movements approach the most nearly to voluntary ones. 
 
 Thus passion, emotion, reflected stimulation, and instinctive im- 
 pulses will all excite involuntary movements of the voluntary mus- 
 cles ; but, in the natural state of the body, all these causes are found 
 acting in harmony with one another, often conspiring to produce the 
 same movement. The power of the will to control them is but slight, 
 and in some cases null. It differs with the original strength of that 
 faculty, with the temperament of the individual, and especially with 
 the degree in which it has been affected by habit. The power of this 
 law is in nothing more conspicuous than in its influence over the 
 human will. A frequent and energetic repetition of voluntary acts 
 of control over the involuntary movements of passion, emotion, an;l 
 instinct, is invariably followed by an increased power of control, and 
 vice versa. This also extends (but in a less degree) to those move- 
 ments of voluntary muscles, consequent on reflex stimulation, which 
 are not essential to life. 
 
 When movements, which haye been at first voluntary, come to b,e 
 performed more or less unconsciously, they are styled mechanical, A 
 thousand instances of them might be given ; all voluntary ones becom- 
 ing more or less so by habit. The nervous paths through which the 
 mandates of the will pass to the muscles grow more accessible and 
 open by use ; and less and less effort of volition becomes necessary 
 to thread them, every time that effort is made. In the early periods 
 
INNERVATION. 187 
 
 of life the will is exercised in tutoring its corporeal instruments to 
 give prompt and ready obedience to its commands; every day new 
 lessons are acquired, and old ones confirmed ; and, having at length 
 a practised body at its beck, it is able to execute numerous and com- 
 plicated movements with as much precision as those of the most deli- 
 cate and subtile kind, and all, or any of them, without being itself 
 distracted with the business of their immediate supervision. Like 
 the general of a disciplined array, the will issues mandates of action 
 or control ; but is not cognizant, without a special effort of attention, 
 of anything beyond the general result of the various movements that 
 its orders produce. And the body, that executes them, is constantly 
 performing other movements, of a routine nature, connected with its 
 safety, comforts, or ordinary functions ; which, though at first they had 
 demanded the general's attention, and might again attract it, yet hav- 
 ing been learnt by drilling, are now executed without his anxiety or 
 even co-operation. They are the working of a practised organiza- 
 tion. Thus many particular movements are included in general ones, 
 without the will having the smallest iraniediate share in their produc- 
 tion. The countenance takes its expression from the prevailing action 
 of its muscles, often in spite of our efforts to the contrary; and, in 
 general, the attitude and bearing wear a corresponding character. And 
 thus several general movements, which naturally (or by an act of the 
 untutored will) are impossible because incompatible, are rendered 
 capable of being simultaneously performed. 
 
 The following works may be consulted in reference to Muscle and Musctilar Ac- 
 tion : — Prochaska, de carne musculari; 1778: Fontana, sur le venin de lavipere; 
 1781: John Hunter's Croonian Lectures, works by Palmer, vol. iv.; Blane, on Mus- 
 cular Motion, in his select dissertations ; the various works on General Atiatomy 
 quoted in former cha4)ters ; Barclay on Muscular Motion ; Mayo's Physiology ; Miil- 
 ler's Physiology, by Baly; the Articles Muscle and Muscular Action, in th& Cyclop. 
 Anat. and Phys. For greater details on the Motions and Attitudes uf the body than 
 would be consistent with the plan of this work, we refer to the Article Motion in the 
 Cyclop. Anat. and Phys.; and to Weber's Mechanik der Menschlichen Gehewerk- 
 zeuge. 
 
 I CHAPTER VIII. 
 
 INNERVATION. — EXAMPLES OF NERVOUS ACTIONS. — NERVOUS MATTER, ITS 
 
 CHEMICAL AND ANATOMICAL ANALYSIS, THE FIBROUS AND VESICULAR 
 
 NfiRVOUS MATTER. — THE NERVOUS SYSTEM. — THE NERVES, CEREBRO- 
 SPINAL AND SYMPATHETIC. — THE NERVOUS CENTRES. — NERVES AND 
 NERVOUS CENTRES IN IN VERTEBRA TA. — DEVELOPMENT AND REPRO- 
 DUCTION OF NERVES. 
 
 The function of innervation is effected through the medium of the 
 nerVous system, which, ramified throughout the body, and connected 
 with and passing between its various organs, serves them as a bond 
 of union with each other, as well as with the sentient principle of the 
 
188 INNERVATION. 
 
 animal. The mind of man influences his corporeal organs through 
 the instrumentality of this system, as when volition or emotion excites 
 them to action ; and, on the other hand, certain changes in the organs 
 or textures of the body may affect the mind through the same channel, 
 as when impressions made upon them excite mental perceptions. In 
 this way the nervous system becomes the main agent of what has been 
 called the life of relation ; for without some channel for the trans- 
 mission of the naandates of the will to the organs of jnotion, or some 
 provision for the reception of those impressions which external ob- 
 jects are capable of exciting, the mind, thus completely isolated, could 
 hold no communion with the external world. 
 
 The nervous system, however, can act independently of mental 
 influence. A material or physical change in the nervous substance, 
 unconnected with any affection of the mind, is capable of exciting the 
 action of nerves, and consequently of those organs which are sub- 
 ject to their influence. Some kind of molecular change in the nerv- 
 ous matter is all that is at any time required for the development of 
 its peculiar power ; and it is as easy to conceive that this alteration 
 may result from some organic cause, as from mental influence. Of 
 this kind, no doubt, are all those nervous actions with whi»h are 
 associated the functions of the life of the individuals, or, in the lan- 
 guage of Bichat, of organic life ; an essential character of which is, 
 that they are completely removed from the influence of the will, 
 
 In every ordinary voluntary action, the first step is a mental change,, 
 in which consists the act of volition. The mind is perfectly able to 
 induce this change in itself, without any reference to the body: but 
 if it direct its influence upon certain muscles, the contraction of those 
 muscles immediately ensues, in a combined and regular manner, so 
 as to produce the predetermined voluntary action. .B4tthe influence 
 of the mind cannot be brought to bear upon the muscles, save through 
 the intervention of the nerves, as is amply proved by the destruction 
 of certain voluntary movements, which is consequent upon the de- 
 struction of certain nerves. 
 
 Again, in all cases of common or of special sensation, that state 
 of the mind, in which the sensation consists, is induced by an impres- 
 sion made upon certain bodily organs, and conveyed to the mind 
 through the instrumentality of the nerves. For there is abundant 
 evidence to prove, that, while the mind is of itself capable of enter- 
 ing that state, it cannot do so in obedience to bodily change, if cer- 
 tain nerves be destroyed or impaired ; that, in short, the nerves are 
 the only corporeal channel through which sensations can be excited. 
 If the skin be forcibly irritated or compressed, instantly pain is felt; 
 but, were the nerves of the skin destroyed, no degree of irritation or 
 pressure would make the mind cognizant of the injury. Light is 
 admitted to the eye, and forthwith a corresponding afTection of the 
 mind ensues ; but, for the production of this, the integrity of the optic 
 nerve is a necessary condition. 
 
 In these examples of nervous action, it will be observed that, in 
 the former instance, mental change produces .bodily action ; and, in 
 the latter, an impression upon some part of the body precedes and 
 
CONNECTION OF NERVOUS ACTIONS WITH THE MIND. 189 
 
 gives rise to an affection of the mind. In both cases nervous power 
 is called forth : in the one, it acts in the direction from mind to body ; 
 in the other, from body to mind. In both cases, destruction of the 
 nervous matter ^ji-opld prevent the developnient of the force. The 
 muscles may be sound, and the will may be vigorous; but without 
 perfect nerves the latter cannot impart its mandates to the former. Or 
 the eye may be perfect in all its optical adjustiiients, and the mental 
 sensibilities keen and quick; and yet, if the optic nerve be diseased, 
 the light which falls upon the retina produces no impression upon the 
 mind. ' ~ 
 
 " Of the nature of the connection of this great sensorial organ," 
 (the nervous system,) says Dr. Brown, " with the sentient mind, we 
 nev€r shall be able to understand more than is involved in the sim- 
 ple fact, that a certain affection of the nervous system precedes im- 
 mediately a certain affection of the mind. But though we are ac- 
 customed to regard' this species of succession Of bodily and mental 
 changes as peculiarly inexplicable, from Ihe/very different nature of 
 the substances which are reciprocally affected, it is truly not more 
 so than any other case of succession of events, where the phenomena 
 occur in substances that are not different in their properties, but ana- 
 logous, or even absolutely similar ; since, in no one instance of this 
 kind, can we perceive more than the uniform order of the succession 
 itself; and of changes, the successions of which are all absolutely 
 inexplicable, none can be said to be more or less so than another. 
 That a peculiar state of the mere particles of the brain should be fol- 
 lowed by a change of state of the sentient mind, is truly wonderful ; 
 but, if we consider it strictly, we shall find it to be by no means 
 more wonderful than that the arrival of the moon at a certain point of 
 the heavens should render the state of a body on the surface of our 
 earth different from what it otherwise would naturally be ; or that the 
 state of every particle of our globe, in its relative tendencies of gra- 
 vitation, should be instantly changed, as it unquestionably would be, 
 by the destruction of the most distant satellite of the most distant 
 planet of our system, or, probably too, by the destruction even of one 
 of those remotest of stars which are illuminating their own systems of 
 planets, so far in the depth of infinity that their light — to borrow a 
 well-known illustration of sidereal distance^may never yet have 
 reached our earth since the moment at which they darted forth their 
 first beams on the creation of the universe. We believe, indeed, 
 with as much confidence, that one event will uniformly have for its 
 consequent another event, which we have observed to follow it, as 
 we believe the simple fact, that it has preceded it in the particular 
 case observed. But the knowledge of the present sequence, as a 
 mere fact to be remembered, and the expectation of future similar 
 sequences, as the result of an original law of our belief, are precisely 
 of the same kind, whether the sequence of changes be in mind or in 
 matter, singly, or reciprocally in both." {Philosophy of the Human 
 Mind. Lect. xix.) 
 
 It is not merely through voluntary effort that the mind can excite 
 the action of nerves. The involuntary, and often uncoritrollable, in- 
 
190 INNERVATION. 
 
 fluence of emotion is likewise able to give rise to certain movements, 
 and even to produce certain sensations, through the nerves. How 
 quickly the expression of the countenance changes under the varying 
 phases of mental emotion ; and how faithfully does it naturally por- 
 tray the working of the mind within ! And fear, joy, disgust, horror, 
 are each accompanied with sensations so peculiar, as to -leave an iri'^ 
 delible impression on the minds of those who have once experienced 
 them. 
 
 There are many actions of the living frame, however, in which the 
 play of the nervous system is unconnected with mental chahge, which 
 are therefore wholly physical, in origin, as well as in nature. The 
 movement of the oesophagus in propelling food onwards to the sto- 
 mach is dependent mainly, if not solely, upon the physical stimulus of 
 the food acting upon the nerves of the organ, which in their turn 
 provoke its muscular fibres to contract. The slightest touch, even of 
 a feather, to the mucous membrane of the fauces causes the muscles 
 of deglutition to contract forcibly, as in the act of swallowing ; nor 
 can the will control or prevent their action. When the edge of the 
 eyelid is touched, the orbicular muscle contracts forcibly, and in im- 
 mediate response to the stimulus applied. When light is suddenly 
 admitted to the eye, the pupil may be observed to contract to a de- 
 gree proportionate to the intensity of the stimulus. Of this action of 
 the iris the individual is quite unconscious, although perfectly sensi- 
 ble of the admission of light to the eye ; nor can he, by any direct 
 influence of volition, modify or oppose it. 
 
 We remark, in reference to these actions, that the rnind has no 
 share in their production. In some of them, indeed, it is conscious 
 of the application of the stimulus, as well as of the muscular act 
 ■which follows. But no effort of the will, however great, could in- 
 terrupt the uniform and natural sequence of the phenomena. And it 
 is well known to medical men that actions of this kind may take 
 place in coma, when all mental manifestations are completely in abey- 
 ance. ' 
 
 These facts afford abundant evidence of a class of nervous actions, 
 ■which, in respect of their exciting cause, as well as in their intrinsic 
 nature, are independent of mental influence, and which ought on this 
 account to be distinguished from those of volition, sensation and 
 emotion. Their mechanism is more complex than that of the mental 
 nervous actions ; for, while in the latter the change in the nerves is 
 propagated in only one direction, in the former it passes first to some 
 central part of the nervous system, and thence it travels in an oppo* 
 site course to the motor organs. Hence two nerves are necessary for 
 such actions ; the one as an excitor, the other as a motor nerve; and, 
 on this account, Dr. Marshall Hall has distinguished these actions by 
 the name o{ excito-motory. 
 
 That a physical change may excite nervous action quite independ- 
 ently of mental influence, is further proved by instances of convuls- 
 ive movements, more or less violent, which are produced by a morbid 
 irritation of the brain or spinal cord. 
 
 The peculiar animal matter, through the agency of which all these 
 
NERVOUS MATTER. 191 
 
 phenomena take place, the nervous matter, is found in two forms, the 
 vesicular and the fibrous. Thevesicularnervous matter is gray orcine- 
 ritious in colour, and granular in texture ; it contains nucleated nerve- 
 vesicles, and is largely supplied with blood ; it is more immediately 
 associated with the mind, and is the seat in which originates the force 
 manifested in nervous actions. The fibrous nervous matter, on the 
 other hand, is in most situations white, and composed of tubular fibres, 
 though in some parts it is gray, and consists of solid fibres : it is less 
 vascular than the other, and is simply the propagator of impressions 
 made upon it. 
 
 When these two kinds of nervous matter are united together in a 
 mass of variable shape or size, the body so formed is called a nervous 
 Centre, and the threads of fibrous matter which pass to or from it are 
 Called nerves. The latter are internuncial in their oflice ; they estab- 
 lish a communication between the nervous centres and the various 
 parts of the body, and vice versa ; they conduct the impulses of the 
 centres to the periphery, and communicate the impressions made upon 
 the peripheral nervous ramifications to the centres. The centres are the 
 great sources of nervous power, the laboratories in which the nervous 
 force is generated : the mind is more immediately connected with one 
 of them, the brain, which, on that account, possesses greater physical 
 development and acquires pre-eminence over the others. The smaller 
 nervous centres are called ganglions ; the larger ones are the hrain 
 and spinal cord. All of these are found in the human subject, and in 
 the vertebrate animals. In the invertebrate classes, the centres are 
 ganglia variously disposed, according to the shape and actions of the 
 animals. 
 
 The brain and spinal cord, and the system of nerves connected with 
 them, constitute the cerebrospinal portion of the nervous system, 
 which Bichait distinguished as the nervous system of animal life. 
 The nerves of the senses, and those of volition and common sensation, 
 are connected with it, as well as those which are concerned in many 
 of those purely physical nervous actions with which the mind has no 
 connection. There are very numerous ganglions connected with this 
 system which are conveniently comprehended under the same title. 
 These are, the ganglions on the posterior roots of the spinal nerves, 
 the ganglion of the fifth pair, those of the glosso-pharyngeal and of the 
 vagus. 
 
 The remainder of the nervous system is made up entirely of gan- 
 glions, with their connecting cords and nerves, which ramify in a 
 plexiform manner among various internal viscera, and upon the coats 
 of blood-vessels. In the higher vertebrate animals, it is disposed as 
 a chain of ganglia on each side of the vertebral column, and at the 
 base of the skull near the foramina through which the spinal and en- 
 cephalic nerves pass out ; and at all these situations it forms a very 
 intimate connection with the brain and spinal cord. This portion of 
 the nervous system possesses many peculiarities, both in its compo- 
 sition, in its arrangement, and in its connection with the organs among 
 which its nerves ramify, which, at least, entitle it to be considered 
 apart from the cerebro-spinal system. How far it can be regarded 
 
192 INNERVATION. 
 
 as independent of that system, is a question which must be reserved 
 for future examination. This is the sympathetic or ganglionic system, 
 formerly known and described as the great intercostal nerve, and by 
 Bichat as <Ae nervous system of organic life: it has also been called 
 the visceral nerve. All these titles are liable to objection, inasmuch 
 as each involves to ar greater or less extent some theory of the uses 
 or actions of these nerves ; but the two first-mentioned are preferable, 
 as those which are best known, and most confirmed by use. 
 
 The nervous system, then, in man and the vertebrate serieSj con- 
 sists of the brain, spinal cord, and the nerves associated therewith, 
 the cerebrospinal system; and that double chain of ganglia, with their 
 nerves, situate along the spinal column, the sympathetic or ganglionic 
 system. Among the invertebrata, although the arrangement of the 
 nervous system differs very materially from that in the vertebrata, an 
 analogous subdivision of it may be made in a large proportion of those 
 classes, the anatomy of which has been satisfactorily made out. 
 
 Physical and Chemical properties of the JVervous Matter. — ^^The nerv- 
 ous matter of both kinds is a soft, unctuous substance, easily dis- 
 turbed by slight mechanical force. Were it not associated with other 
 tissues, and supported, to a certain extent, by the blood-vessels 
 which ramify among its elements, its physical tenacity would be very 
 feeble. 
 
 Its great softness is due, in part, to the admixture of a large quan- 
 tity of water with it, which constitutes three-fourths, or four-fifths, 
 and, in many instances, seven-eighths, of its weight. According to 
 Vauquelin, whose analysis was made in 1812, the brain is an emul- 
 sive mixture of albumen, fatty matter, and water ; the last holding in 
 solution certain saline and other ingredients common to the brain 
 with other parts of the body. By solution in boiling alcohol, Vau- 
 quelin was enabled to resolve the fatty matter into elaine and stear- 
 ine (margarine ?) The following table gives the result of his analysis: 
 
 Albumen . . . . 7-00 
 
 Cerebral fat . { f^^ l%] 5-23 
 
 Phosphorus .... 1-50 
 
 Osmazome . . . . . 1-12 
 
 Acids, Salts, Sulphur . . . 5-15 
 
 Water 80-00 
 
 100-00 
 
 Vauquelin remarked that the medulla o-blongata, and medulla spinalis, 
 have the same composition as the brain, but contain a much larger 
 proportion of cerebral fat, with less albumen, osmazome, and water. 
 
 These results are confirmed, in the main, by the analysis of Fremy, 
 which was published in the Annales de Chimie for 1841. M. Fremy 
 states, that the three principal constituents previously detected by 
 Vauquelin, exist in the following proportions in one hundred parts: 
 seven parts of albumen, five parts of fatty matter, and eight parts of 
 ■water. 
 
 From the fatty matter of the brain M. Fremy extracts various 
 secondary organic compounds; namely, 1. Cerebric acid; a white 
 
NERVOUS MATTER. 193 
 
 substance in the form of crystaline grains, abounding in carbon, and 
 containing a minute proportion of phosphorus. 2. Cholesterine, the 
 same as that which is obtained from bile. In preparations of the 
 brain preserved in spirits, a substance of crystaline character resem- 
 bling cholesterine is apt to form round the piece. ,3. Oleophosphoric 
 acid ; a peculiar fatty acid, containing from 1-9 to 2 per cent, of phosr 
 phorus in the condition of phosphoric acid. Fremy regards it as 
 analogous to the compound of sulphuric acid and elaine, or sulph- 
 oleic acid. 4. Traces of elaine, margarine, and fatty acids. These 
 principles dp not always exist in an isolated state ; for the cerebric 
 acid is often combihed with soda, or phosphate of lime, and the oleo- 
 phosphoric acid is commonly found in union with soda. 
 
 The quantity of phosphorus which may be found in the nervous 
 matter varies considerably at different periods of life, and lis very 
 small in idiotcy. According to L'Heriti6's analyses, the minimum 
 of this element is found in infancy, in old age, and in idiotcy ; and 
 the maximum of water exists in the infant. The following is a table 
 of his comparative analyses: 
 
 
 Infants. 
 
 Youth. 
 
 Adults. 
 
 Old Men. 
 
 Idiots. 
 
 Albumen 
 
 7-00 
 
 10-20 
 
 9-40 
 
 8.65 
 
 . 8-40 
 
 Cerebral fat . 
 
 3-45 
 
 . 5-30 
 
 6-10 
 
 4-32 
 
 . 5-00 
 
 PhoBphoras . 
 
 0-80 
 
 , 1-65 
 
 1-80 
 
 1-00 
 
 . 0-85 
 
 Osmazome and Salts 
 
 5-96 
 
 . 8-59 
 
 . 10-19 
 
 12-18 
 
 . 14-82 
 
 Water . . . 
 
 82-79 
 
 . 74-26 
 
 . 72-51 
 
 73-85 
 
 . 70-93 
 
 
 10000 
 
 100-00 
 
 100-00 
 
 100-00 
 
 10t)-00 
 
 A careful comparative analysis of the vesicular and fibrous matter 
 is as yet a desideratum. We are ignorant of the nature of the color- 
 ing material of the former. John states that the vesicular substance 
 is deficient in white fatty matter, and that its albumen is less tena- 
 cious than that of the fibrous substance. 
 
 Of the fibrous nervous matter. — Of the two kinds of nervous mat- 
 ter, the fibrous is that which is most extensively diffused throughout 
 the body. It not only forms a large portion of the nervous centres, 
 either alone or mixed with vesicular matter, but it is the principal 
 constituent of the infinite multitude of nerves which connect them 
 with the various tissues and organs. 
 
 The structure of the fibrous matter should be examined in a piece 
 of nerve, and in a thin section from the white part of a nervous 
 centre, as the brain or spinal cord. These should be torn with nee- 
 dles, so as to separate and isolate as much as possible the elementary 
 parts, and to remove, as far as may be practicablcj extraneous, tissues. 
 
 The fibrous nervous matter, wherever it is found, consists of fibres 
 which have a definit-e arrangement. Two kinds of primitive fibre 
 are present in the nervous system, and these we shall distinguish 
 as the tubular fibre, or the nerve-tube, and the gelatinous fibre. The 
 former are infinitely the more numerous ; the latter , being found 
 chiefly in the sympathetic system. 
 
 1, Of the tubular fibre. — When a nerve-tube is perfectly recent, 
 and unaffected by regents, it presents, if viewed by reflected light, 
 a beautiful pearly lustre, and appears to be quite homogeneous. B\it 
 10 
 
194 
 
 INNKRVATION. 
 
 if viewed by transmitted light, and with a sufficient magnifying 
 power, a more complicated structure becomes visible in all the largest 
 and best marked specimens (fig 52, a, b, and fig. 53, a). Most ex- 
 ternally is the tubular membrane (a, d d), an homogeneous and proba- 
 bly elastic tissue of extreme delicacy, analogous to the sarcolemma 
 of striped muscle (p. 150), and according to our observation, not 
 presenting any such distinct, longitudinal, or oblique fibres in its com- 
 position as have been described by some writers. Within the edge 
 
 of the tubular membrane, on 
 each side, are seen two thicker 
 and darker lines (a, c, c, b), 
 which appear to mark the outer 
 and inner limits of an inner 
 layer of different composition 
 and refracting power, and which 
 is generally known as the white 
 substance of Schwann. This 
 forms a tube within the tubular 
 membrane. Within the white 
 substance of Schwann is a trans- 
 parent material, occupying the 
 axis of the nerve-tube (a, a). 
 This has been called by Ramak 
 the flattened band ; but a better 
 name for it is that of axis cylin- 
 der, employed by Rosenthal and 
 Purkinje. 
 
 It is evident, that the whole 
 of the matter contained in the 
 tubular membrane is extremely 
 soft, for it is found to yield un- 
 der very slight pressure, and may 
 be readily made to pass frbm 
 one part of the tube to another. 
 When pressed out (b. h to /), it 
 is apt to assume more or less the 
 appearance and form of globules, 
 which retain the same characters 
 of outline which they possessed 
 in the nerve-tube ; that is, they 
 have a transparent interior, 
 bounded by a layer of the white 
 substance of Schwann, marked 
 by its double contour. It would 
 appear that the latter structure 
 is particularly apt to form a coating or film over the central material, 
 and thus to isolate it from surrounding tissues. This tendency may 
 be understood by a reference to fig. 52, h to I. 
 
 When the nerve-tube is placed in ether, the white substance is in 
 part immediately dissolved, and a number of oil-like globules appear 
 
 fibre of 
 6. Inner border of 
 
 spinal 
 
 A. Diagram of tubular 
 nerve ; — a. Axis cylinder, 
 ■white substance, c c. Oliler border of "white sub- 
 stance, d^ d. Tubular membrane. E. -Tubular 
 fibres ; e, in a natural stale, showing the parts as 
 in A.'/. The ■white substance and axis cylinder 
 interrupted by pressure, -while the tubular mem- 
 brane remains, g. The same, -with varicosities. 
 h. Various appearances of the white substance 
 and axis cylinder forced out of the tubular mem- 
 brane by pressure, i. Broken end- of a tubular 
 fibre, with the white substance closed over it. k. 
 Lateral bulging of white substance and axis cy- 
 linder from pressure. I, The same more complete. 
 g'. Varicose fibres of various sizes, from the cere- 
 bellum, c. Gelatinous fibres from the solar plex- 
 us, treated with acetic acid to exhibit their cell- 
 nuclei. B and G magnified 320 diameters. 
 
TUBULAR FIBRE. 
 
 195 
 
 both -within and without the tubular membrane (fig. 53, b). Proba- 
 bly its margarine is dissolved, and the elaine set free in the form of 
 oil-globules. The interior of the tube is 
 also rendered decidedly granular. In water 
 the white substance of Schwann remains 
 undissolved, while the interior of the fibre 
 is frequently, though not always, rendered 
 granular. 
 
 The tubular membrane presents the same 
 general characters wherever it is met with. 
 But the white substance of Schwann exhibits 
 much variety as regards its thickness in dif- 
 ferent parts of the nervous system. In the 
 nerves it is more developed than in the cen- 
 tres ; but even in the former it differs a good 
 deal as to thickness. We find it most de- 
 veloped in the ordinary spinal nerves ; in 
 those of pure sense it exists in small quan- 
 tity. Both these elements of the tubular 
 fibre evidently afford mechanical protection 
 to the substance which forms its axis ; but 
 doubtless one or both of them may have a 
 further physiological office, insulating the 
 axis, and keeping it distinct from any in- 
 terference with constituents of neighboring 
 fibres. The chemical composition of the 
 white , substance, being obviously different 
 from that of the axis, sufficiently denotes a 
 difference of function in these two portions of the nerve-tube. The 
 axis cylinder of the nerve-tube, though in general soft and pulpy, is 
 in some instances of firm texture, and when broken projects beyond 
 the white substance (fig. 56, c). It then occasionally exhibits a well- 
 marked fibrous character, and may even split into filaments. 
 
 When the tubes are quite fresh, and have been but little disturbed 
 by manipulation, their form is that of a perfect cylinder. Pressure, 
 or separation, is apt to alter their shape by disturbing the position pf 
 the contained pulp, pushing more than is natural into some parts of 
 the tube, and consequently diminishing the bulk of the contents in the 
 adjacent parts ; so that the latter collapse, whilst the former become 
 distended, enlarged, and even varicose (fig. 52, b). Nerve-tubes, 
 that have been thus affected, sometimes present merely a slight wavi- 
 ness of one or both margins, but more frequently a series of distinct 
 swellings or varicosities separated by constricted portions. These 
 swellings are found at v.ery irregular distances from each other, and 
 vary extremely in shape and size. They are much more apt to form 
 upon some nerve-tubes than upon others ; and this is apparently 
 owing to a feebleness of the tubular membrane, and perhaps, also, to 
 a less degree of consistence of the contained nervous pulp. In the 
 nerves of special sensation the tubes are very delicate in structure, 
 and very apt to exhibit this change ; and in the fibres of the brain 
 
 , Nerve-tubes of the common 
 eel; — a. In water. The delicate 
 line on its exterior indicates the 
 tubular membrane. The dark^ 
 double-e.dffed inner one is the 
 white substance of ' Schwann, 
 slightly wrinkled.^ b. The same 
 in ether. Several oil-globules 
 have coalesced in the interior, 
 and others have accitmulated 
 around the exterior of the tube. 
 The white substance has in part 
 disappeared'.— Magnified 300 di- 
 ameters. 
 
196 INNERVATION. 
 
 and spinal cord the same tendency is observable. It was formerly 
 supposed by Ehrenberg, that these varicosities were natural, and 
 existed during life ; and that they afforded a valuable morphological 
 character of the nerves of pure sense, and of the cerebro-spinal cen- 
 tre. Many circumstances, however, oppose this view : thus, the irre- 
 gularities in the shape, size, and number of the varicosities appear 
 very unlike a natural disposition : in a piece of the brain or spinal 
 cord which has not been much pressed or torn, the nerve-tubes often 
 exhibit a cylindrical figure, and even in the manipulated specimen 
 the varicose tubes form only a portion. In some nerves, such as 
 those of muscles, the tubes, although not prone to become varicose, 
 may be made so by firm pressure and violence in manipulation ; and 
 in the nerve-tubes of young animals, the tissues of which are more 
 tender, and contain more abundant water, this chaflge is particularly 
 apt to take place. 
 
 The nerve-tubes, for the most part, lie parallel to each other, al- 
 ways without branching, and if we except their terminal looping in 
 other textures, without any inosculation. This very interesting and im- 
 portant feature in the anatomy of the nerve-tubes was recognized long 
 ago by Fontana, and has been confirmed by nearly every subsequent 
 observer. It may be seen in the nervous centres, as well as in the 
 nerves themselves. In the latter it may be well demonstrated by 
 examining a piece of nerve on a dark ground as an opaque object. 
 The primitive fibres, viewed in this way, appear as so many trans- 
 parent tubes, containing an exquisitely delicate, soft, pearly-white 
 material. The tubular fibres vary in diameter, from -j^Vo to even 
 Tsios of an inch ; but their average width is from ^3 oVo to ^Vo of 
 an inch. 
 
 2. Of the gelatinous nerve-fibre. — This term is applied by Henle 
 to certain fibres found principally in the sympathetic nerve. They 
 are flattened, soft, and homogeneous in appearance ; containing nu- 
 merous cell-nuclei, some of which are round, others oval ; some 
 situated in the centre of the fibre, others adhering to either edge ; 
 their lon.gest diameter being generally parallel to the longitudinal axis 
 of the nerve. These nuclei are arranged at nearly equal distances, 
 and frequently exhibit distinct nucleoli (fig. 52, c). Sometimes these 
 fibres show a disposition to split into very delicate fibrillffi. Acetic 
 acid dissolves the fibre, leaving the nuclei unchanged. These fibres, 
 containing nothing analogous to the white substance of Schwann, are 
 devoid of that whiteness which characterizes the tubular fibre ; and it 
 would seem that the gray color of certain nerves depends chiefly upon 
 the presence of a large proportion of the gelatinous fibres. Hence 
 they are sometimes called gray fibres. 
 
 The mode or connection of the gelatinous fibres with the elements 
 of the nervous centres, is, as yet, quite unknown. They are found, 
 in considerable numbers, in what are called the roots of the sympa- 
 thetic, or the communications of that nerve with the spinal nerves : 
 it has been supposed by Valentin that they are continuous with cer- 
 tain elements of the vesicular nervous matter. 
 
 These fibres are smaller, in general, than the tubular fibres ; their 
 
GELATINOUS FIBKE. 
 
 197 
 
 Nerve-vesicles from the Gasserian ganglion of 
 the human subject -.—a A globular one with de- 
 fined border ; 6. its nucleus ;c. its nucleolus, d. 
 Caudate vesicle, e. Elongated- vesicle, with two 
 groups of pignxent particles. /. Vesicle surround- 
 ed .by its sheath, or capsule, of nucleated parti- 
 cles, g. The same, the sheath only being in fo- 
 cus.— Magnified 300 diameters. 
 
 diameter ranges between the ^ oVo a"<l the 4 ^Vt of an inch. They 
 resemble very much the fibres of unstriped muscle. 
 
 Of the vesicular nervous matter. — This is distinguished by its dark 
 reddish gray color, and soft consistence : it is found in the nervous 
 centres, but never in nerves, probably so called, and it is always 
 supplied by a considerable plexus of blood-vessels., 
 
 The essential elements of the 
 gray nervous matter are vesicles 
 or cells, containing nuclei, E^nd 
 nucleoli. They have been also 
 called nerve or ganglion globules. 
 The wall of each vesicle consists 
 of an exceedingly delicate mem- 
 brane, containing a soft but te- 
 nacious finely granular mass. 
 The nucleus oi the cell is gene- 
 rally eccentric, much smaller than 
 the containing vesicle, and adhe- 
 rent to some part of its interior. 
 Its structure is apparently the 
 same as that of the outer vesicle. 
 The nucleolus is a minute, re- 
 markably clear and brilliant 
 body, also vesicular, inclosed 
 within the nucleus. It forms a 
 most characteristic and 
 often conspicuous part of 
 the nervervesicle. 
 
 The ordinary or pre- 
 vailing form of these ele- 
 ments is that of a globu- 
 lar vesicle. So soft and 
 compressible are they, 
 however, that a good 
 deal of diversity of shape 
 is manifest in them, by 
 reason of the compres- 
 sion they suflTer as they 
 lie -packed together in 
 situ. Hence some are 
 spherical, others ovoidal, 
 or ellipsoidal. In some 
 vesicles we find, external 
 to the nucleus, particles 
 of a coarser kind, which 
 are accumulated in a 
 mass, frequently of a 
 semilunar form. These 
 pigment granules ; 
 
 are 
 
 their 
 
 dark 
 
 presence gives a 
 color to a portion 
 
 Ganglion globules, with their processes, nuclei, and nucle- 
 oli :— a. a. From the deeper part of the gray matter of the con- 
 volutions of tlte cerebellum. The larger processes are directed 
 towards the surface of the organ, i. Another from the cerebel- 
 lum, c.d Others from the post.horn of graymatterof the dor- 
 sal region of the cord. These contain pigment, which sur- 
 rounds the nucleus in s. In all these specimens the processes 
 are more or less broken.— Magnified 200 diameters. 
 
198 
 
 INNEBVATION. 
 
 of the vesicle. Sometimes we find two groups of pigment granules 
 in one vesicle. They are usually of a reddish, or yellowish-brown 
 color. 
 
 Another form of nerve-vesicle is characterized by one or more tail- 
 like processes extended from it, and to such nerve-vesicles we may 
 apply the term caudate. They possess the nucleus and nucleolus, as 
 in the more simple form ; and contain one or more masses of pigment, 
 which are often of very considerable size. Both the vesicles and 
 their caudate processes vary greatly in size and shape. The largest 
 nerve-vesicles are found among those of this kind. Sometimes there 
 is but a single process from this vesicle ; or there may be two, pro- 
 ceeding from opposite sides ; or there' may be several, extending in 
 various directions. There is great dilTerence in the shape of these 
 caudate vesicles, as may be observed in figs. 55 and 56, where 
 different varieties of them are represented. In point of structure, 
 the caudate processes are exceedingly delicate, and finely granular, 
 like the interior of the vesicle, with which they distinctly seem to be 
 continuous. Such is the delicacy of these processes, that they readily 
 break off; in general, very close to the vesicle. Sometimes^ how- 
 ever, one or more of them may be traced to a considerable distance, 
 and will be found to divide into two or into three branches, which 
 undergo a further subdivision, and give off some extremely fine trans- 
 parent fibres (fig. 56, b), the connection of which with the other'tle- 
 ments of the nervous tissue has yet to be ascertained. It is most 
 probable, however, that they either serve to connect distant vesicles, 
 or else that they become continuous with the axis cylinders of the 
 tubular fibres. In the cerebro-spinal centre, we have found the tis- 
 sue in the vicinity of the caudate vesicles freely traversed in all direc- 
 
 a. A large caudate nerve-vesicle, with diverging and branching processes, some of which, 6, are 
 seen to pass off into extremely minute filaments. These seem to bear a very close resemblance to 
 the central part of a tabular fibre, c, which is prolonged some way beyond the broken edge of its 
 tubular membrane and while substance, d. At «, are some small nerve-vesicles, stellate in form, 
 doubtless from numerous processes given off from them ;/, several extremely sittall nerve-tubes, 
 some of which are varicose. This figure exhibits the great variety of size of the vesicles and tubes. 
 o. is froin the posterior horn of the gray matter 6f the spinal marrow, and is magnified only 120 diame- 
 ters, while the vesicles and tubes at e, from the gray matter of the lower eiid of the cord, are mag- 
 nified 300 diameters, d. is also from the spinal marrow, and is magnified 200 diameters. 
 
NERVES. 
 
 199 
 
 tions by numerous very delicate filaments, -which seem to be the rami- 
 fications of the caudate processes. These often exhibit considerable 
 tenacity and elasticity. The situations from which we may obtain 
 such caudate vesicles as are best suited for examination are the locus 
 niger in the crus cerebri, and the gray matter of the cerebellum and 
 spinal cord. •< 
 
 The nervS-vesicles do not lie in immediate contact with each other. 
 They are either imbedded in a soft, granular matrix, as in the brain, 
 or enveloped in a capsule of 
 
 nucleated cells, as in the gan- 
 glia (fig. 54,/, g). The inti- 
 mate connection of this granular 
 sheath to the vesicle, and to its 
 processes when they exist, in- 
 creases greatly the difficulty of 
 examining them. It is not easy 
 to detach them from this invest- 
 ment. This is generally effected 
 by accident more than by skill 
 in manipulation, and it is along 
 the broken margin of the piece 
 under- examination that we shall 
 succeed in detecting the most 
 perfect vesicles. 
 
 In most situations where 
 vesicular matter is found in the 
 nervous centres, tubular fibres 
 of small though variable size 
 mingle with its elements in 
 greater or less number, and in 
 some places both varieties of 
 fibre, are found (figs. 57 & 58). 
 To determine the precise con- 
 nection which these respective 
 elementary parts form with each 
 other is a problem.of the deep- 
 est interest. No more, how- 
 ever, can be said respecting it 
 at present, than that the relation 
 of nerve-fibres'to nerve- vesicles 
 in the centres is most intimate, 
 and that the latter are rarely 
 met with without one or more of 
 the former in immediate connec- 
 tion with them. 
 
 Having premised this general 
 account of the anatomical ele- 
 ments of the two kinds of nerv- 
 ous matter, we may now con- 
 sider separately the two leading 
 
 Fig. 57. 
 
 
 ft ^^\ 
 
 A. Blending of the vesicular and fibrous nervous 
 matter in the dentate body of the cerebellum ;—o. 
 Ganglion glohulej with its nucleus and nucleolus. 
 6. iVerve'-tubej slightly varicose, in close contact 
 ■with the ganglion globule. 6'. Smaller nerve-tubes. 
 These parts all lie in a finely granular matrix in- 
 terspersed with nuclei, c. b. vesicular and fibrous 
 matter of the laminse of the cerebellum, a. Gan- 
 glion globule. 6. "Very minute nerve-tubes tra- 
 vei-singa finely granular matrix, in which are nu- 
 nierous rounded nuclei, c. 
 
 Fig. 58. 
 
 Frbm the Gaaserian ganglion of an adult :~~a. a. 
 Ganglion globules with their nucleus, nucleated 
 capsule, and pigment, t. Tubular fibres, running 
 among; the globules in contact with their capsule. 
 g. Gelatinous fibres also in contact with the gan- 
 glion globulfcs-— Magnified 320 diameters. 
 
200 INNERVATION. 
 
 subdivisions of the nervous system ; namely, the nerves and the cen- 
 tres. 
 
 Of nerves. — A bundle of nerve-fibres, surrounded and connecte'd 
 by areolar tissue, constitutes a nerve. 
 
 The nerves of the cerebro-spinal system differ in several important 
 particulars from those of the sympathetic, and they should, therefore, 
 be examined separately. 
 
 Of the cerebrospinal nerves. — The areolar tissue which invests 
 the nerve-fibres is called the neurilemma. It is analogous to the 
 sheath of the same membrane which surrounds the elementary fibre 
 of striped muscle. From its deep surface the layers of areolar tissue 
 pass, forming^so many partitions between the smaller bundles, or the 
 individual fibres, of which the nervous trunk is composed. The office 
 of this structure is evidently to give protection to the delicate nerve- 
 tubes, and to support the plexus of minute capillary vessels frtom 
 which they derive their nutriment. 
 
 The neurilemma is composed of fibres of white fibrous tissue, and 
 presents to the naked eye the silvery aspect of that texture. Some 
 persistent cell-nuclpi are scattered throughout it. That portion of it 
 which forms the partition between the fibres contains a little yellow 
 fibrous tissue of the finest description. 
 
 The blood-vessels are distributed upon the external investing sheath, 
 and upon the septa. They are disposed similarly to those of mus- 
 cles, and run parallel to the fibres of the nerve. The capillaries are 
 among the smallest in the body : they form oblong meshes of consi- 
 derable length, completed at long intervals by vessels which cross the 
 fibres of the nerve more or less transversely. These blood-vessels 
 are generally derived from neighboring arterial branches; sometimes 
 a special vessel accompanies a nervous trunk, and even perforates 
 it, passing along its axis, as in the great sciatic and the optic nerves. 
 
 The composition of a cerebro-spinal nerve may be shown by re- 
 moving the neurilemma, and separating the fibres by needles. These 
 fibres are chiefly of the tubular kind. In diameter they vary con- 
 siderably, but do not exceed the t^Vt of an inch in man and the 
 mammalia. They lie within the sheath in simple juxtaposition, and 
 parallel to each other ; excepting where a branch is about to separate, 
 when a bundle of nerve-tubes gradually deviates from its previous 
 course, and forms a very acute angle with the trunk, still, however, 
 preserving the parallelism of its constituent fibres. 
 
 Nerves are said to arise or have their origin in the nervous centre 
 to which they are on the one hand attached, and to terminate or be 
 distributed among the elements of the various textures on the other 
 hand. It is best to continue the use of so definite and simple a mean- 
 ing to these terras. Attempts to alter their signification in accordance 
 with opinions of the functions of the constituent fibres can at present 
 do little but confuse descriptions. We call a nerve cerebral or ence- 
 phalic, if it be connected at its origin with some part of the nervous 
 mass within the cranium ; and spinal, if its apparent origin be from 
 the spinal cord. 
 
 Origin. — The fibres of nerves may be traced into the nervous cen- 
 
ORISJN OF NERYES. ' 201 
 
 tres, the white or ftbrous part of which they contribute to form. As 
 they enter the centre, the fibres diverge slightly either singly or in 
 separate bundles, and pass on to form a connection with vesicular 
 matter, in the immediate vicinity of the point of immergence or at a 
 more remote situation. How the fibres comport themselves with re- 
 spect to the elements of the vesicular matter is not exactly known. It 
 is certain^ however, that nervcrtuhes frequently adhere to the sheaths 
 of nerve-vesicles, and that many of them pass between the nerve- 
 vesicles, probably to form a connection with more distant ones. This 
 may be well seen in the vesicular matter of tiny of the centres. It 
 is very distinct in the ganglions, and also sufiiciently manifest in the 
 spinal cord or brain. In the last-named centres some of the tubes 
 which are found in the vesicular matter are reduced to an extremely 
 minute size (figs. 56,_/; 57, A, b' and B, b), and exhibit sn^all vari- 
 cosities, sometimes at very regular distances from each other. 
 
 Valentin describes a looped and plexiform arrangement of the fibres 
 in the vesicular matter of the centres. Hitherto, such an arrange- 
 ment has eluded our observation so completely, that, but for the 
 high authority on which this statement rests, we should not have 
 deemed it necessary to allude to it. The only confirmation of this 
 view with which we have met is derived from an highly interesting 
 dissection, by Mr. Lonsdale of Edinburgh, of a monstrosity, in which 
 the spinal cord, medulla oblongata^ and cerebellum werp absent, but 
 the hemispheres of the brain were present. Several of the encepha- 
 lic and spinal nerves hung "as loose threads" in the cavity of the 
 cranium or spine. On examining the free or central extremities of 
 these nerves, their constituent fibres were found to form distinct loops, 
 convex towards the cranial or spinal cavity. These loops were im- 
 bedded in granular matter, supposed to be vesicular matter in an 
 early stage of formation. Similar loops were observed by the same 
 anatomist in the cranial nerves of an anencephalous foetus which had 
 been preserved in spirits.* 
 
 Branching. — As a nerve passes from centre to periphery, it breaks 
 up into a number of small bundles, which form so many branches 
 destined for the organs or tissues among which they are placed. 
 These branches generally separate from the pajrent trunk at an acute 
 angle, and soon plunge into the muscles or other parts to which they 
 tend, dividing and subdividing among them. Some exceptions to 
 this rule, however, are occasionally met with, in which the branch 
 forms a right or an obtuse angle with the trunk. 
 
 Before a branch separates, the parent nerve seems wider for some 
 distance above the point of visiljle separation. This is owing to a 
 divergence of the fibres within the trunk before they actually leave it, 
 and not to any increase in the number of the nervous elements. A 
 good example may be seen in the auricular nerve of the neck, as it 
 winds upwards over the sterno-mastoid muscle. 
 
 Anastomosis. — In their branchings nerves subdivide, not only to 
 pass immediately to their distribution in muscles or other parts, but 
 
 • Dr. Lonsdale's case oi Monstrosity. Ed. Med. and Surg. Journ., J^o. 157. 
 
202 
 
 INNERVATION. 
 
 Fig. 59. 
 
 also to form a connection, by some of their filaments, with other 
 nerves, and to follow the course of the latter, whether to the periphery, 
 or back again to the centre, instead of passing to the destination of 
 the primary . trunk. By these means nervous filaments connected 
 with very different parts of the brain and spinal cord become bound 
 together in the same neurilemma, and a nerve is formed compound- 
 ed' of nerve-tubes possessing different functions. The anastomosis 
 of nerves thus formed differs from the more correctly named anasto- 
 mosis of blood-vessels ; for in the latter case the canals, of the anasto- 
 mosing vessels communicate, and their contents are mingled ; but in 
 the former the nerve-tubes simply lie in juxtaposition, without any 
 coalescence of their walls, or any admixture of the material contained 
 within them. 
 
 The simplest kind of anastomosis is that which occurs in almost 
 every spinal nerve. The anterior and the posterior roots of these 
 nerves, emerging from different parts of the spinal 
 cord, and possessing, as is now proved, very dif- 
 ferent endowments, are united after passing through 
 the dura mater, and are bound together as one 
 nerve ; the respective tubules being so completely 
 intermixed that the ramifications, which pass off 
 in the subsequent course of the nerve, for the most 
 part contain tubules from both roots, and therefore 
 possess the functions of both. 
 
 And even in a nervous trunk, thus formed, there 
 is an interchange of place between the component 
 filaments,' so that those which were at first on the 
 surface of the nerve pass into its centre, and are 
 replaced by others which had been deep-seated; a 
 decussation of the fibres occurring as they change 
 •places (fig. 59). Hence it is often difficult to fol- 
 low a bundle for any distance in a nervous trunk. 
 , According to Kronenberg, this kind of interchange 
 
 Diagram to show the . , /> ^ ■ ,i • xl 
 
 decussation of the fibres IS more f rcquont in some nerves than m others ; 
 i1^lV(After vakmin-V 3"^ i* i? Stated by this author that in the external 
 cutaneous nerve of the arm he found some bundles, 
 which passed through a distance of six inches without uniting with 
 neighbouring ones. 
 
 By another form of anastomosis nervous loops or arches are formed, 
 the convexities of which are directed towards the periphery, and give 
 off filaments to the neighbouring parts. The well-known anastomo- 
 sis between the ninth or hypoglossal nerve, and the cervical plexus, 
 in front of the carotid artery, may be quoted as a good example. 
 Certain fibres, which come from the medulla oblongata as part of 
 the ninth nerve, leave that nerve as it crosses over the carotid artery, 
 pass down in front of the artery, and apply themselves to a descend- 
 ing branch of the cervical plexus, forming in front of the carotid artery 
 and jugular vein an arch with the concavity directed upwards, several 
 nerves passing from the convexity to neighbouring muscles. Some 
 of the filaments which are given off from this arch, are derived from 
 
PLEXUSES OF NERVES. 203 
 
 the ninth nerve, and others from the cervical plexus ; whilst others 
 seem to form a co.raplete arch, and to be equally connected with both 
 nerves ; and, if we trace these latter fibres from the ninth nerve, 
 we find them passing upwards and backwards into the descending 
 branch of the cervical plexus, 'and so returning to the spinal cord. 
 The nervous loop, thus formed, must evidently establish a communis 
 cation between the cervical region of the spinal cord and that portion 
 of the medulla oblongata whence the ninth nerve appears to derive 
 its origin. - • 
 
 Similar nervous loops, leaving the nervous centre as a constituent 
 of one nerve, and returning to it at some distance in company with 
 a. different nerve, are found in various parts of the nervous system. 
 The commissural fibres of the optic tracts may be quoted as an ex- 
 ample. These fibres leave the centre by one tract, and return to it 
 by the other. It is probably owing to an anastomosis of this kind, 
 between the posterior and anterior roots of the spinal nerves, that the 
 latter enjoy a slight degree of sensibility. Other instances of a similar 
 kind have been described by Volkmann. In the calf he found an 
 anastomosis between, the fourth pair of nerves and the first branch of 
 the fifth pair, forming an arch, frbm the convexity of which several 
 branches passed off in the peripheral direction. By fat the greater 
 part of these, on microscopic examination, appeared to receive their 
 fibres from the fourth ; while those fibres of the fifth, which contri- 
 buted to the formation of the arch, passed centripetally to the brain, 
 bound up in the sheath of the fourth nerve. There is a similar nerv- 
 ous arch formed between the second or third cervical nerve and the 
 accessory nerve. Certain fibres, when traced from the former, ap- 
 pear to pass back to the centre in the sheath of the latter. This anas- 
 tomosis Volkmann found in the human subject, and in several of the 
 lower animals.* 
 
 According to Gerber, similar loops are found in the sheaths of 
 spinal nerves. Certain fibres emerge from and return to the nervous 
 centre, forming a loop with the convexity directed towards the peri- 
 phery, without connecting themselves with any peripheral organ or 
 texture, or going beyond the nerve-sheath. To these loops this ana- 
 tomist has given the fanciful title, ngrvi nervorum.. 
 
 Plexuses, — When several neighbouring' nerves freely interchange 
 their fires, a complicated form of anastomosis is produced,, which 
 is called a plexus. Four or five nerves, for example, proceed from 
 the spinal cord, for a certain distance without any communication 
 with each other. A division of each then takes place, and from the 
 conjunction of their neighbouring branches new nerves result, which 
 again subdivide and interchange fibres, and by the free communica- 
 tion which is thus established, a network is sometimes formed, (as 
 in the cervical plexus,) in the meshes of which areolar tissue, and 
 sometimes fat, are deposited* Finally, certain nerves emerge from 
 the plexus thus formed, which are composed of fibres derived from 
 several, of the original trunks. Examples of this kind of anastomo- 
 
 * Mailer's Archiv., 1840. 
 
204 
 
 INNERVATION. 
 
 Fig. 60. 
 
 sis are found iii connection with the anterior branches of the spinal 
 nerves in the neck, the axilla, the loins, and the sacral region ; and 
 there are also plexuses formed in the course of the fifth nerve, the 
 portio dura of the seventh, the glosso-ph^ryngeal, and the par vagum. 
 The fibres, ■which pass through a plexus, notwithstanding the ap- 
 parent intricacy of their communication, preserve their individualily. 
 This may be proved by irritating a single nerve before it has broken 
 up in the plexus. Such irritation will produce contraction of certain 
 muscles only; of tho'Se, namely, to which the fibres of that nerve are 
 distributed. It is probable that, owing to tbe frequent change of 
 place which the fibres undergo within the plexus, they are brought 
 into communication with a greater number of muscles than if no such 
 subdivision had taken place. Kronenberg's experiments showed that 
 the irritation of certain nerves of the plexus before their subdivision 
 caused the contraction of those muscles only which received filaments 
 from them.* 
 
 Termmation of Jferves. — The connection which the terminal fila- 
 ments of nerves form with the proximate constituents of the striped 
 muscle has been already described (p. 161). From that description 
 it will appear that the nervous fibres do not come into immediate 
 communication with the sarcous substance, unless we have recourse 
 
 to the supposition that some minute 
 elements proceed from those fibwes, 
 and penetrate the sarcolemma. Such 
 a supposition has no foundation in 
 anatomy, so far as our present know- 
 ledge extends. It is a curious sub- 
 ject of investigation to' determine 
 what becomes of the nerve-tubes, 
 which, after the formation of the 
 loops which cross the muscular fibres, 
 take a retrograde course towards the 
 nervous centre. Do they, for in- 
 stance, return to the spinal cord? 
 and can it be their oflice to form a 
 second connection with the vesicu- 
 lar matter of the cerebro-spinal cen- 
 tre, the descending fibre coming from 
 the brain, and the returningone being 
 implanted in the gray matter of the 
 cord ? 
 
 In the skin the arrangement is 
 plexiform ; but this is reducible to 
 loopings, as will be explained in the 
 chapter on Touch. 
 
 The arrangement of the primitive 
 fibres in loops has been also seen by 
 Henle on some parts of mucous membrane ; in the merabrana nic- 
 
 Tenninal nerves on the sac of the second 
 molar tooth of the lower jaw in the sheep, 
 showing the arrangement in loops.— (After 
 Valentin.) 
 
 Plexuum nervorum strnctura et virlutes. Bero!. 1836. 
 
SYMPATHETIC NERVES. 
 
 205 
 
 titans of the frog,' for example, and in the raucous membrane of 
 the throat in the same animal. A similar disposition has been de- 
 scribed and delineated by Valentin in the pulps of the teeth (fig. 60), 
 and we have seen it in the papillae of the tongue. 
 
 The so-called nerves of pure sense, the olfactory, optic, and audi- 
 tory nerves, may more properly be regarded as portions of the brain 
 itself than as mere nerves, for they possess most of the anatomical 
 characters of nervous centres. The intra-eranial portion of the first 
 is as distinctly compounded of vesicular and fibrous matter as a con- 
 volution of the brain. In the peripheral expansion of the optic nerve, 
 the retina, it will be hereafter shown that the vesicular elements of a 
 nervous centre are as unequivocally present as in the olfactory bulb. 
 As regards the auditory nerve, there are also some grounds for the 
 statement that the vesicles of gray matter are deposited at its peri- 
 pheral expansion, in the internal ear.* 
 
 Of the Ganglionic or Sympathetic JVerves. — The composition of 
 these nerves is essentially si- 
 milar to that of the cerebro- Fig. 61. 
 spinal nerves. They consist 
 of a series of nerve-fibres 
 bound together by areolar 
 tissue, which fornis their neu* 
 rilemma. This sheath is, 
 however, denser than in the 
 cerebro-spinal nerves, so that 
 the nerve-fibres are more 
 difficult of separation, and 
 the fasciculated Character is 
 not so obvious. It consists al- 
 most entirely of white fibrous 
 tissue longitudinally dispos- 
 ed, which are crossed by some 
 fine circular fibres of yellow 
 tissue, surrounding the nerves 
 at various distances from each 
 other. When a nerve is torn 
 tip by needles, and treated by 
 acetic acid, numerous small 
 ovar cell-nuclei are seen ly- 
 ing in and among the fibres, 
 with their long axes parallel 
 to the latter. 
 
 The sympathetic nerves 
 contain the fibres of both 
 kinds, the tubular and the 
 gelatinous, in very variable 
 quantity in different nerves. 
 Thus, the former are numerous in the ramifications of the solar plexus 
 
 Roots of a dorsal spinal nerve, and its union with 
 sympathetic : — c, c. Anterior fissure of tlie spinal cord. 
 a: Anterior root. p. Posterior root, -witli its ganglion. 
 a'. Anterior branch. ^'. Posterior branch, s. Sympa- 
 thetic, e. Its double junction with the anterior branch 
 of the spinal nerve by a white and a gray filament. 
 
 See further on these points the chapters on Smel], Vision, and Hearing. 
 
206 INNERVATION. 
 
 and in the cardiac nerves ; and the latter almost exclusively compose 
 one of the fascicles by which the sympathetic communicates with the 
 spinal nerves (fig. 61, e): they are so numerous, while the tubular 
 fibres are few, in the sympathetic cord in the neck. In some nerves, 
 the tubular fibres are quite on the surface ; and in others, they are 
 enclosed in the axis of the nervous trunk. It is probable that the 
 same change of place between the fibres occurs in these nerves as 
 that which we have noticed in ^the cerebro-spinal nerves ; so that 
 those fibres which at one part of the nerve were superficial, would at 
 another be deep-seated, and vice versa. 
 
 The mode of branching of these, nerves is essentially the same as 
 that of the cerebro-spinal. But the frequent formation of ganglia in 
 the course of the trunks, and of their ramifications, constitutes a re- 
 markable feature. The branches attach themselves to the exterior of 
 arteries, forming very intricate plexuses, which entwine around them, 
 "hederee ad modum" (Scarpa). Along these vessels the nerves are 
 conveyed to the tissues; but of the mode in which their filaments, 
 connect themselves immediately with those textures we are at present 
 entirely ignorant. The ramifications of the sympathetic seem to be 
 limited to the trunk and head : it has probably no connection, or at 
 most a very limited one, with the extremities. ' 
 
 The connection of the sympathetic system with the brain and spinal 
 cord appears to take place through the cerebro-spinal nerves. CJer- 
 tain filaments connect each spinal nerve to some portion of the gan- 
 glionic chain which lies on each side of the spinal column. And a 
 similar connection takes place between ganglia of the cephalic portion 
 of the sympathetic and the encephalic nerves, of which the following 
 may be cited as well-known instances : — The third nerve is con- 
 nected with the ophthalmic ganglion ; the sixth with the superior 
 cervical ganglion ; the fifth nerve with the spheno-palatine and otic 
 ganglia. These connecting filaments have been called the roots of 
 the sympathetic ; and thus this nerve has been represented as taking 
 an extended origin from numerous points of the cerebro-spinal cen- 
 tre. This is true : but, in dissecting the connection between the 
 sympathetic and the spinal nerves, we find that, for the most part, 
 two distinct fascicles connect them, one of which is white, being 
 composed of tubular fibres ; the other is gray, and consists of ^ela-, 
 tinous fibres. The former seem evidently cerebro-spinal fibres, 
 which pass to or from the periphery conjoined with the other ele- 
 ments of the sympathetic : but, in the present state of our knowledge, 
 it is difficult to form a correct idea as to the precise object of the 
 latter bundles, or as to the central connection which they form, whe- 
 ther with the ganglion on the posterior root of each spinal nerve, or 
 with the spinal cord. That the sympathetic has intimate and exten-, 
 sive connections with the brain and spinal cord, is abundantly proved, 
 not only by the anatomical statements above detailed, but by the cir- 
 cumstance of which every one is conscious, that pain may be excited 
 in parts supplied from this system of nerves alone, as in the intestines ; 
 as well as by the fact that irritation of the spinal cord may produce 
 contraction of muscles which derive their nerves from this source, and 
 
THE NERVOUS CENTRES. 207 
 
 that destructive disease of that organ may occasion paralysis of those 
 muscles. 
 
 Of the nervous centres. — The nervous centres exhibit to us the 
 union of the vesicular arid the fibrous nervous matter. Indeed, the 
 association of these two forms of nervous substance in a mass of vari- 
 able shape or size is the main anatomical condition for the formation 
 of a nervous centre. The former is never met with in nerves pro- 
 perly so called, and when a true nerve has a grayish appearance, we 
 iind that it is owing to a paucity of the tubular, and an excess of the 
 gelatinous fibres. , 
 
 All nervous centres are provided with a proper covering which 
 serves to isolate them from adjacent textures,, and to protect them, as 
 well as to support their nutrient blood-vessels. In the ganglia this 
 covering is continuous and identical with the neurilemma of the nerves 
 •which are connected with the,m, and it is in every respect of the same 
 structure as the latter membrane. 
 
 In the larger centres, the brain and spinal cord, the coverings are 
 of a more complicated kind: They are called meninges, membranes. 
 Three of them are enumerated : The dura mater, which is external ; 
 the /)ia Tnafer, which is in immediate connection with the nervous 
 matter of the centre; and .the arachnoid membrane, a serous sac inter- 
 mediate to the two tunics just mentioned, which is evidently destined 
 to facilitate the movements of these organs within their proper cavi- 
 ties. These will be more particularly described 
 further on. ' Fig. 62. 
 
 In examining the ganglia, we obtain a good 
 idea of the minute structure of nervous centres 
 in general. A thin slice of one of the larger gan- 
 glia, torn up by needles, or a small ganglion from 
 some small animal, serves to show the disposition 
 of the vesicular and fibrous matter in these bodies. 
 
 A ganglion may be compared to a plexus, with 
 nerve-vesicles deposited in its meshes (figs. 62, 
 63). In tracing a nerve into a ganglion, its com- 
 ponent fibres appear to separate, and to pass 
 through the ganglion in different directions ; some 
 maintaining their original course, others diverg- 
 ing from it for a short- way and afterwards return- j, ^ ,^ 
 ine to it, and others taking altogether a new direc- ' . ,\ ■ , 
 
 . o 1 • n y !• • 1 ■ ■ '- Second abdominal 
 
 tion and passmg out ot the ganglion in combination ganglion of the green- 
 
 with other fibreS)- to form an emerging nerve. A ed.° Vhf course™ofThe 
 
 certain degree of interlacement of the fibres thus ^?e7emM^ rllntering 
 
 takes place within the ganglion, and in its inter- flbi:es. ,*. Emerging a- 
 
 ^ , , , ,, f ° . ; , , , bres. I. Outline of in- 
 
 stices are lodged the nerve-vesicles enveloped by vesting tunic, beneath 
 their proper sheaths. A great number of nerve- uSvaiemin'r^'''"" 
 fibres may be traced through the ganglion, so that 
 the emerging nerves may be regarded as resulting from a new com- 
 bination of the fibres that compose the nerves which entered the 
 ganglion. These, however, are possibly not the only constituent fibres 
 of the emerging nerves, for it has yet to be ascertained whether some 
 
208 INNERVATION. 
 
 fibres may not take their rise from the vesicular matter of the ganr 
 
 glion, and it is a not less interesting 
 Fig. 63. object of inquiry whether some of the 
 
 entering fibres may not terminate in it. 
 That the nerve-tubes have an intimate 
 connection with the elements of the ve? 
 sicular matter is apparent from the fact 
 that they lie in close apposition with 
 them, and appear to indent their sheaths 
 of nucleated corpuscles (fig. 57). Some- 
 times the sheath seems to taper off from 
 the nerve-vesicles, and to become con? 
 tinuous with the nerve-tubes. It is a 
 conjecture by no means devoid of pro? 
 bability, that the processes of the cau- 
 A small piece of the otic ganglion of date vesicle may, after passing some way, 
 
 the sheep, slightly compressed ; show- , . i i t_ Ii_ x i_ i 
 
 ing the interfacement of the internal bCCOme invested Dy the tUDUlar fflem- 
 
 fervkSftii^''''''"^""''"""^'^''' brane and by the white substance of 
 
 Schwann, and we have seen some ap- 
 pearances to warrant this view (see fig. 56, c, d). Yet it should 
 be stated, as opposed to this view, that in the gray matter of the 
 cerebellum the caudate vesicles are so placed that their processes pass 
 toward the free surface of the cortical layer, and not into the viite 
 matter. 
 
 Besides the tubular fibres, the ganglia contain likewise gelatbous 
 ones, which, however, are more abundant in the sympathetic than in 
 the cerebro-spinal ganglia (fig. 58, g). These fibres are, doubtlessi, 
 continuous with those of the same kind which may exist in the enr 
 tering or emerging nerves. We may also add, that the vesicular 
 matter does not appear to be confined to the interstices between the 
 fibres, but is likewise found at the surface of the ganglia, lying in 
 immediate contact with their investing tunic. 
 
 In the brain and spinal cord, there is a greater separation of the 
 vesicular and fibrous matter than in the ganglia. The former very 
 complicated organ, indeed, consists of various masses which are in 
 all essential points very similar to the ganglia in structure, and doubt- 
 less also in function : but its hemispheres are larger masses, of which 
 the interior substance is composed exclusively of fibrous matter, sur- 
 rounded by a layer of vesicular, which forms a rind or cortex to it. 
 The fibres of the former, however, are prolonged into this cortical 
 layer, and the intermixture of the two forms of nervous substance is 
 thereby effected (fig. 57). 
 
 The spinal cord is composed of certain columns of fibrous sub- 
 stance, in which a large number of the fibres take a longitudinal 
 direction. These, in a great degree, enclose a distinct arrangement 
 of vesicular matter, into which, however, as in the cortical layer of 
 the cerebral hemispheres, some, at least, of the fibres of the external 
 white matter are continued, intermingling with its elements. It may, 
 therefore, be stated generally that in the brain the vesicular matter 
 is external and cortical, and in the spinal cord it is internal and aU 
 
DEVELOPMENT OF NERVOUS MATTER. 
 
 209 
 
 most completely surrounded by the white fibrous matter. This dif- 
 ference of arrangement is probably to be ascribed to the fact, that 
 throughout the whole course of the spinal cord nerves are being given 
 off, whilst from the encephalon they come only from certain regions. 
 In these regions the white matter is superficial ; but in the hemispheres, 
 from which no nerves proceed, it is deep-seated. We shall describe 
 more minutfely the disposition of the two kjnds of nervous matte rin 
 the cerebro-spinai centre at a future page. 
 
 Of the Nerves and Nervous Centres in Invertebrate Animals. 
 
 The description above given applies to the human subject, and to the verte- 
 brate classes generally. In aU essential points, so far as the present state of our 
 knowledge enables us to judge, the structural arrangement of the nerves and 
 nervous centres of the invertebrate classes accords with this. Some differences, 
 however, exist which require to be noticed here. In the lobster, the nerve- 
 tubes are large; the tubular metnbrane has 
 
 the same transparent, homogeneous ap- Fig. 64. 
 
 pearanoe, which we have noticed in the 
 vertebrata. But it enclose^^ many delicate 
 nuclei a,t various intervals. Within the tu- 
 bular membrane there is a very thin layer 
 of the white substance of Schwann. The 
 nerve-tubes are very transparent, and are 
 much larger than the average size in verte- 
 brata. Respecting the existence or structure 
 of the gelatinous fibres, we can offer no re- 
 mark. In insects and myjiapoda, the nerve- 
 tubes vary coisisiderably in size; they are 
 collected into bundles, and are surrounded 
 by a trarisparent sheath ^ of homogeneous 
 membrane, which accompanies the larger 
 ramifications of the nerve-trunks. The white 
 substance of Schwann is not so obvious nor 
 so constant in these nerves as in those of the 
 lobster, and the existence of nuclei (fig. 64) 
 makes them resemble closely the gelatinous 
 fibres of the vertebrata. The anatomical 
 characters of the vesicular nervous matter of 
 invertebrata do not essentially differ from 
 those of the same substance in the vertebrate 
 classes, so far as our observation enables us 
 to judge. The nerve-vesicles with nuclei and nucleoli are equally apparent 
 in both, though in the former they are more transparent, and contain less pigment. 
 
 Of the development of nene-fibres. — We can add nothing to the 
 account given by Schwann of the development of nerve.. The fol- 
 lowing is quoted from Dr. Willis's translation of Wagner's Physio- 
 logy :— 
 
 " The nerves appear to be formed after the same manner as the 
 musclels, viz., by the fusion of a number of primary cells arranged 
 in rows into a secondary cell. The primary nervous cell, however, 
 has not yet been seen with perfect precision, by reason of the diffi- 
 culty of distinguishing nervous cells whilst yet in their primary state, 
 from the indifferent cells out of which entire organs are evolved. 
 
 Nervous fibres of insects : — a. Trans- 
 parent sheath. 6. Nerve-filnreSj-withovaJ 
 nuclei, c. Sliows the bifurcation of the 
 sheath. 
 
210 
 
 INNERVATION. 
 
 When first a nerve can be distinguished as such, it presents itself as 
 
 a pale cord with a longitu- 
 Fig. 65. dinal fibrillation, and in this 
 
 cord a multitude of nuclei are 
 apparent (fig. 65, a). It is 
 easy to detach individual fila- 
 ments from a cord of this kind, 
 as the figure just referred to 
 shows, in the interior of which 
 many nuclei are included, si- 
 milar to those of the primitive 
 muscular fasciculus, but at a 
 greater distance from one ano- 
 ther. The filaments are pale, 
 
 Various stages of the development of nerve :— a. granulated, and (aS appears 
 Earliest stage. 6. Detached fibre, c. Nucleated fibre Kv tVipir fartbpr Hpvplrinmpnn 
 
 in the iowe?pari of which, <i, the white substance of oy ^eir idrcuer ueveiopmeni; 
 
 Schwann has-begun to be deposited, e. Nucleus in a holloW. At thlS period, aS in 
 more fully-formed fibre between the white substance , j , j *j 
 
 and tubular membrane. /. Displays the tubular mem- mUSCle, a Secondary / .fflepOSlt 
 
 schw'aL^"""''^"'^'^"'"'^™^^"'"''^^'""^^'" takes place upon the inner as- 
 ~ pect of the cell-membrane of 
 
 the secondary nervous cell. This secondary deposit is a fatty white- 
 coloured substance, and it is through this that the nerve acquires 
 its opacity. This is seen in fig. 65 ; superiorly, at c, the fibril is 
 still pale ; inferiorly, at d, the deposition of the white substance has 
 occurred, and its eflfect in rendering the fibril dark is obvious. With 
 the advance of the secondary deposit, the fibrils become so thick, that 
 the double outline of their parietes comes into view, and they acquire 
 a tubular appearance. On the occurrence of this secondary deposit 
 the nuclei of the cells are generally absorbed ; yet a few may still be 
 found to remain for some time longer, when they are observed lying 
 outwardly between the deposited substance and the cell-membrane, 
 as in the muscles (e). The remaining cavity appears to be filled by 
 a pretty consistent substance, the band of Remak, and discovered by 
 him. In the adult a nerve, consequently, consists, 1st, of an outer 
 pale thin cell-membrane, — the membrane of the original constituent 
 cells, which becomes visible, when the white substance is destroyed, 
 by degrees; 2d, of a white fatty substance deposited on the inner as- 
 pect of the cell membrane, and of greater or less thickness ; 3d, of a 
 substance, which is frequently firm or consistent, included within the 
 cells, the band of Remak." 
 
 The fully-formed vesicular matter exhibits the persistent state of 
 the cells of primitive development. According to Schwann, the only 
 change which the full-grown cell exhibits consists in an increase of 
 size, and in the development of the pigmentary granules within. 
 According to Valentin's description, the following is the process of 
 development of the nerve-vesicles. In the very young embryos of 
 mammalia, as the sheep or calf, the cerebral mass in the course of 
 formation contains, in the midst of a liquid and transparent blastema, 
 transparent cells of great delicacy with a reddish-yellow nucleus. 
 Around these primitive cells, which we find likewise formed after the 
 
REGENERATIO^f OF NERVOUS MATTER. 211 
 
 same type in the spinal cord, a finely granular mass becomes depo- 
 sited, which probably is not at first surrounded by an enveloping cell- 
 membrane. At this early period of formation the primitive cell still 
 preserves its first delicacy to such a degree, that the action of water 
 causes it to burst immediately. In proportion as the granular mass 
 contracts itself within certain limits, a cell-membrane probably is 
 developed around it, so that the vesicle gradually acquires the exact 
 form and size, and its contents the proper characters, which belong 
 to the fully-formed nervous corpuscle. 
 
 Of the regeneration of nervous matter. — Our chief knowledge on 
 this subject is with respect to the regeneration of the tubular fibres. 
 Many years ago our countryman, Dr. Haighton, in making expe- 
 riments to determine the functions of the vagus nerve, showed that 
 when a nerve is simply divided, without removing any portion of it, 
 union would take place, and the nerve resume its proper office. If 
 a considerable piece were excised, so as to leave much interval 
 between the cut ends, there would be union after the lapse of some 
 time, but not by true nervous fibres, nor in such a way as to restore 
 the action of the nerve. It appears, however, from recent observa- 
 tions, of which those of Schwann, Steinruch, and Nasse are the most 
 interesting, that true nerve-fibres may be developed in this uniting 
 substance, but apparently in smaller numbers than in the nerve itself. 
 The proof of th e regeneration of the true nerve-fibres depends upon the 
 restoration of the nerve's function, and the demonstration of the pre- 
 sence of proper nerve-tubes by microscopical examination. Perfect 
 restoration of the action of the nerve does not generally take, place, 
 owing, most probably, to the fact that the central and peripheral por- 
 tions of the same fibres do not always meet again. The central portion 
 of a motor fibre might unite with the peripheral segment of a sensitive 
 one, and thus the action of each would be neutralized. 
 
 Nothing satisfactory is known respecting the regeneration of the 
 nervous matter of the brain or spinal cord after a loss of substance 
 from injury or disease. When a portion of the brain is removed in 
 animals, its place is supplied by new matter; but, whether this be- 
 comes true cerebral substance, future research with good microscopes 
 must determine. 
 
 We refer on the subjects of this chapter to the various works on General Anatomy 
 quoted in former chapters, especially to that of Henle ; to Miiller's, and Wagner's 
 Physiology; to the articles Nerve, and Nervous Centres, in the Cyclop. Anat. and 
 Phys.; to the fourth vol. of Soemmering's Anat. by Valentin (German and French) ; 
 to Valentin, iiber den Verlauf und die letzten Enden der Nerven ; and to Bidder and 
 Volkmann,Die Selbstandigkeit des sympathetischen Nervensys,tem. Leipzig, 1842. 
 The researches of Bidder and Volkmann on the sympathetic systein are of great in- 
 terest, if further observation shall confirm them. These authors describe the pecu- 
 liar fibres of the sympathetic as originating independently of the spinal cord or brain. 
 Their description of these fibres does not exactly accord with what we have seen of 
 the gelatinous fibres, nor are we at present prepared .to express any decided opinion 
 respecting the accuracy of their observations, which are very favourable to the theory 
 of the independence of the sympathetic systein. 
 
212 
 
 CHAPTER IX. 
 
 VITAL PROPERTIES OF NERVES AND NERVOUS CENTRES. — CLASSIFICATION 
 OF NERVES ACCORDING TO THE VITAL ENDOWMENTS OF THEIR FIBRES. 
 STIMULI OF NERVOUS ACTION, MENTAL AND PHYSICAL. — VIS NER- 
 VOSA — ITS nature; is it electrical.' 
 
 Of the vital properties of nerves and nervous centres. — There are 
 no textures which exhibit such proneness to molecular change, under 
 the influence of their proper stimuli, as nerve and muscle. It has 
 already been stated in the first chapter (p. 69), that each of these tis- 
 sues manifests its vital action in a different, although a very analogous 
 way. Muscles, while they are capable of responding to other stimuli, 
 almost invariably act in obedience to that of nerve ; and the changes 
 which muscular contraction produces are obvious to our unaided 
 senses in the shortening of the muscle, and in its greater thickness 
 and hardness. Even the alterations in the condition of its sarcous 
 elements may be discerned by the microscope, and have been de- 
 scribed at page 170. 
 
 The changes, however, which take place in nerve, when in action^ 
 are known to us only by the effects which they produce on the sentienti 
 mind or on muscular parts. There is no alteration in the physical 
 appearance of the nerve or its fibres, which can be detected by our 
 aided or unaided vision. Yet, from the rapidity with which stimuli 
 applied to nerves produce their effects on distant muscular pairtSy 
 from the instantaneous cessation of these effects on the removal of 
 the stimulus, and the speedy renewal of them on its reapplicaitioh,we 
 can refer the phenomena to nothing so well as to a moleeular change, 
 rapidly propagated along the course of the nerve from the point of 
 application to the stimulus. And in the instantaneousness of its pro- 
 duction, and the velocity of its propagation, we may compare it to 
 that remarkable change in the particles of a piece of soft iron, in 
 virtue of which it acquires the properties of a magnet so long as it is 
 maintained in a certain relation to a galvanic current ; these pro- 
 perties being instantaneously communicated when the circuit is com- 
 pleted, and as instantaneously removed when it is broken. A state 
 of polarity is induced in the particles of the nerve by the action of the 
 stimulus, which is capable of exciting an analogous change in other 
 particles, whether muscular or nervous ; whence results the peculiar 
 effect of the nerve's influence. 
 
 Thus, if a nerve be distributed among muscular fibres in the man- 
 ner described at a former page, it will be capable of exciting muscu- 
 lar contraction, and is properly a muscular or motor nerve; and it is 
 so connected, at its origin, with the nervous centre, that a change 
 there, whether induced by mental or by physical influence, may be 
 readily communicated to it. When a nerve is distributed upon an 
 expanded surface, as upon the skin or mucous membrane, or is other- 
 
ENDOWMENTS OF NERVE-FIBRES. 213 
 
 wise favourably disposed for the reception of any physical stimulus 
 from without, it will propagate the change induced by such stimulus 
 to the nervous centre ; and this change in the centre may produce 
 an impression upon the mind, giving rise to a sensation ; or it may 
 affect a motor nerve connected with the excited one or arising from 
 the nervous centre adjacent to it, and thus may indirectly excite mus- 
 cular movement. When a nerve is capable of acting in the former 
 way, it is called a nerve of sensation, or sensitive; when in the latter, it 
 is an excitor of a motor nerve. 
 
 It is not necessary to suppose any intrinsic difference of structure 
 in the nerves which are thus capable of producing effects so mani- 
 festly different. The action of a nerve depends upon the nature of 
 its central and peripheral connections. It cannot be motor, unless it 
 be intimately connected with muscles ; nor sentient, if its relation to 
 the nervous centre be not such as will enable it to affect the senso- 
 rium commune. The terms efferent and efferent are only so far ap- 
 plicable to certain nerves, as they refer to the direction in which 
 such nerves appear to propagate the change produced in them, or to 
 the position at which the effects of the stimulation become manifest, 
 that direction having reference to the point at which the stimulus is 
 destined to act. In a motor nerve, the ordinary stimulus acts from 
 the, nervous centre; but a mechanical or electrical stimulus affecting 
 such a nerve at any part of its course will cause contraction of the 
 muscles supplied by it below the point of irritation. In the sensitive 
 or excitor nerves, the usual situation from which the stimulus acts 
 is at their peripheral distribution; but at whatever point a sentient 
 nerve be stimulated, a sensation will be produced, which will be re- 
 ferred to those parts, and to those only, to which the fibres irritated 
 are distributed ; and, wherever the stimulus be applied to an excitor 
 nerve, it will, with equal effect, rouse its corresponding motor nerve 
 to action. There are no good grounds for supposing that the mole- 
 cular change consequent upon the stimulation of a nerve is limited to 
 that part of the nerve which is included between the point stimulated 
 and the centre, or the muscles, where the effect of the stimulation ap- 
 pears : on the contrary, it is not improbable, that', at whatev'er point 
 the stimulus be applied, the whole length of the nerve-fibre partici- 
 pates in the change. This is not unlikely in the case of motor nerves. 
 For a continued or violent irritation of a motor nerve in some part of 
 its course, causing spasm or convulsive movement of the muscles it 
 supplies, may be propagated along its whole length to the centre, and 
 may there give rise to irritation of neighbouring fibres, whether motor 
 or sensitive, exciting more convulsion and pain. The phenomena of 
 many cases of epilepsy, in which the fit begins with irritation of a few 
 muscles, may be referred to in illustration of this position. And it 
 is equally probable as regards sensitive nerves. If the ulnar nerve be 
 irritated where it passes behind the internal condyle, a sensation of 
 tingling is excited, which is referred to the sentient surface of the 
 ring and little fingers; and if the irritation be kept up, the skin of 
 those fingers becomes tender to the touch, its sensibility being very 
 much exalted. This fact cannot be explained unless upon the sup- 
 
214 INNERVATION. 
 
 position that the molecular change in the nerve-fibres, produced by 
 the irritation, extends peripherad as well as centrad, exalting the ex- 
 citability of their distal extremities. _ _ - 
 
 At whatever part of their course sensitive fibres be irritated, the 
 same sensation will be produced, whether the seat of irritation be 
 the centre, the periphery, or the middle of their course, provided only 
 the same fibres are irritated in the same degree. Nothing is more 
 certain than that an affection of the central extremity of the nerve- 
 fibres is sufficient to excite sensations precisely similar to those which 
 the excitation of the peripheral portion of the same fibres would pro- 
 duce. Hence it is that a morbid irritation at the centre is frequently 
 referred to the periphery ; and that the sensation of tingling or formi- 
 cation, in the hand or foot, leg or arm, becomes an indication of 
 cerebral or spinal disease. The remarkable fact, that persons who 
 have suffered amputation will continue to feel a consciousness of the 
 presence of the amputated limb long after its removal, derives some 
 explanation from this> doctrine. Two cases have lately come before 
 us, in one of which the arm, in the other the leg, was amputated, so 
 long before as forty years ; yet each person had the sensation of his 
 fingers or toes as distinctly as immediately after the operation. And 
 not only is there, in such cases, the consciousness above referred to, 
 but likewise, when the principal nerve of the limb is irritated, the pa- 
 tient complains of pains or tingling, which he refers to the amputated 
 fingers or toes. 
 
 It may be stated, in confirmation of the view above taken, that 
 in many cases of complete paralysis of a limb from cerebral disease, 
 the patient is not conscious of its presence, and really feels as if it 
 did not exist. We have known instances in which this unconscious- 
 ness has been so great, that when the paralyzed part came in con- 
 tact with some sensitive portion of his body, the patient for a time 
 believed it to belong to another person, or imagined it some entirely 
 foreign substance. In such cases the affection of brain necessary to 
 create the feeling cannot be produced in consequence of the morbid 
 state of that organ. 
 
 The ' distinction which has been made between nerves of common 
 and of special sensation, is indicated by the fact, that while a stimu- 
 lus to the former causes pain, that to the latter gives rise to a pecu- 
 liar or special sensation, as of light, sound, or taste. These nerves 
 are so organized at their periphery as to be peculiarly adapted to re- 
 ceive impressions from the agents to which they specially respond: 
 and in this, as well as in their connection with some special part of 
 the great centre of sensibility, consist their main anatomical peculi- 
 arities (see p. 69). 
 
 The same law of nervous action applies to these nerves as to those 
 of common sensation. Thus, their ordinary mode of action is to pro- 
 pagate to the centre impressions made at the periphery ; but irritation 
 at any part of them may give rise to their peculiar sensation ; and if 
 the brain be stimulated at the part whence these nerves arise, similar 
 sensations are produced. Such phenomena of vision and hearing, to 
 which the term subjective has been applied, are familiarly known to 
 
THE NERVOUS FORCE. 215 
 
 practitioners, as not unfrequent forerunners of more serious symptoms 
 of cerebral disease. Muscee volitantes, ocular spectra, tinnitus aurium, 
 are instances of these phenomena, which, although of every-day oc- 
 currence, ought always to excite the attention of the medical man, as 
 indicating some departure from the normal state of the optic or audi- 
 tory nervous apparatus. Pressure on the eyeball, a galvanic current 
 passed through it,* rotation of the body, are capable of giving rise to 
 similar phenomena, by exciting the retina, or the central connec- 
 tions of the optic nerve. A sense of giddiness, similar to that pro- 
 duced by the means last named, is also a very common symptom of 
 cerebral affection arising from a disturbed circulation, or from the 
 blood being defective in one or more of its staminal principles, or 
 vitiated by some morbid element. 
 
 The nervous trunks as they exist in different regions are usually 
 compound ; that is, they contain fibres of difTerent endowments. In 
 some situations, it is true, the fibres of one kind predominate so much 
 as to give the trunk the physiological character which belongs to 
 them; but it likewise enjoys in a proportionate degree the functions 
 of those fibres, which are few in number. For example, the facial 
 nerve, or poriio dura of the seventh pair, is called -motor because it 
 is almost wholly composed of motor fibres ; but it contains, besides, 
 in very much smaller number, some sensitive filaments, which it 
 probably derives from anastomoses with neighbouring nerves. The 
 third, fourth, and sixth pairs of nerves may be quoted as of similar 
 constitution to the facial. In the ramifications of the fifth nerve, on 
 the other liand, the filaments of sensation are predominant ; those of 
 motion being much fewer, and confined to the branches of its inferior 
 maxillary division. 
 
 It is at the points of emergence of the roots of the nerves from 
 the nervous centres that we find the most complete isolation of func- 
 tion. This is well exemplified in the spinal nerves and in the fifth 
 pair. These nerves emerge from their respective centres by two 
 bundles of fibres, of which one is sensitive, the other motor ; the for- 
 mer having almost always the distinctive features of greater size than 
 the latter, and of having a ganglion formed upon it. But, even in 
 these instances, it has lately been made a matter of question whether 
 the smaller root, which experiment has satisfactorily shown to be 
 motor in its function, does not also contain a very slight proportion 
 of sensitive filaments. 
 
 The stimuli by which the action of nerves is ordinarily provoked 
 are of two kinds, mental ^nd physical. In all voluntary actions, an act 
 of the mind is the excitant of the nerve. Sensations are caused by 
 the influence of physicaLagents upon nerves, which communicate with 
 the sensorium commune. -The change in the nerve, by reason of this 
 communication, gives rise to a corresponding affection of the mind. 
 It is wonderful how quickly such changes are propagated, and with 
 what precision they are perceived by the mind, although the physical 
 
 * A strong sensation of a flash of light' may be produced by passing a galvanic 
 current in the close vicinity of the eyeball. 
 
216 INNERVATION. 
 
 excitant may itself be a fine point invisible to the naked eye, applied 
 with the slightest force, and coming in contact with a spot equally 
 difficult of appreciation. If the communication between the nerve 
 and the centre be cut oflf, the will can exert no influence upon the 
 muscles supplied by the nerve below the section ; nor will the mind 
 iperceive any stimulus applied to parts which derive their nerves from 
 (it below the separation. And the reason is obvious ; the solution of 
 continuity of the nerve interrupts the propagation of the change which 
 the mental or physical stimulus excites in it. In the case of the vo- 
 luntary nerve, the mental stimulus is propagated no further peripher 
 rad than liie point of section : and in that of the sensitive nerve, the 
 change travels no further centrad than the same point. That the in- 
 terruption is caused solely by the solution of continuity, and not by 
 any alteration in the properties of the nerve, is proved by the fact that 
 the lower segment of the motor nerve will still continue to respoodto 
 a physical stimulus. Mechanical or chemical irritation, or the pas- 
 sage of an electric current across it, will cause its muscles to contract. 
 Such a degree of injury to a nerve as will destroy the continuity of 
 the nervous matter within the tubular fibres is likewise sufiicient to 
 destroy its power as a propagator of nervous change. This effect 
 will be produced by tying a ligature very tightly round a nerve, or 
 by pressing it very forcibly between the blades of a forceps. The 
 paralysis which results from the compression of a nerve by a tumor, 
 or in any other way, is no doubt due to a similar solution of conti- 
 nuity in the nervous matter. 
 
 From these facts we draw the important inference that, in propa- 
 gating the influence of a stimulus, either from periphery to centre, 
 or vice versa, nerves are not mere passive conductors. The whole 
 extent of the fibre between the point stimulated and its peripheral 
 or central connection is the seat of change. How necessary, then, 
 to the normal action of nerves must it be to preserve their physical 
 condition in a healthy state ! A morbid fluid impregnating a nerve 
 -at any point may irritate it, or may suspend or destroy its inherent 
 property by modifying its nutrition. It is thus, likewise, that nerves 
 may be paralyzed by soaking them in a solution of opium, or of bel- 
 ladonna, aconite, tobacco, or other powerfully sedative or narcotic 
 substances, or that they may be unduly excited by applying a solu- 
 tion of strychnia. The contact of a solid body with a nerve may irri- 
 tate and keep up a continual state of excitement, if it do not destroy 
 its properties. A spicula of bone in contact with nervous fibres is 
 often the cause of the severest forms of neuralgia. That alteration 
 of nutrition which we call inflammation may produce like effects. 
 Various physical agents are followed by similar consequences. The 
 benumbing influence of cold is explained in this way. Exposure to 
 a continuous draught of cold air is a frequent cause of facial paralyi- 
 sis. How instantaneously will the giving way of a carious tooth 
 occasion toothache by exposing the nerves of its pulp to the irritating 
 action of the air, or of the fluids of the mouth ! And heat is equally 
 injurious to the physical constitution, and consequently to the action, 
 of nerves. 
 
THE NERVOUS FORCE. 217 
 
 The organic change, whatever be its intrinsic nature, which stimuli, 
 whether mental or physical, produce in a nerve, develops that won- 
 derful power long' known to physiologists by the nanje vis nervosa, 
 t1ae nervous force. This force is more or less engaged in the. play of 
 alVthe vital functions, whether organic or animal. In thp, former its 
 office is to regulate, control, a'nd fiarmonizp, as will behereafter ex- 
 plained ; in the latter, it is 1;h,e main-spriijg of action, without which 
 none of the phenomena can take place. It is the natural excitant of 
 muscular motion, and the display of that worrdrous power depends 
 upon its energy. Unless tliere were vigour in the development and 
 application of the nervous force, a well-formed muscular system would 
 be of little avail, for it would quickly suffer in its nutrition if deprived 
 of that exercise which is so necessary to it. 
 
 Although jhe workings of the mind are doubtless independent of 
 the body, experience convinces us that in those combinations of 
 thought which take place in the exercise of the intellept, the nervous 
 force is called into play in many a devious track ,throughout the in- 
 tricate structure of the brain. How else can we explain the bodily 
 exhaustion which mental labour induces? The brain often gives way, 
 lits an overwrought machine, under the loi)g-sustained exercise of a 
 vigorous intellectual effort ; a^d many a master-mind of the present 
 or a former age has, from this,cause, ended his days " a driveller and 
 a show." A frequent indication of commencing disease in the brain 
 is the difficulty which the individual feels in "collecting his thoughtSj" 
 the loss of the power of combining his ideas, or impairment of me- 
 mory. How many might have been saved from an early grave or 
 the madhouse, had they taken in good time the warning of impend- 
 ing danger which such symptoms afford! The delicate mechanism 
 of the brain cannot bear up long against the incessant wear and tear 
 to which men of great intellectual powers expose it, without frequent 
 and prolonged periods of repose. The precocious exercise of the 
 intellect in childhood is frequently prejudicial to its acquiring vigour 
 in manhood, for the too early employment of the brain impairs its 
 organization and favours the development ^of, disease. Emotion, 
 when suddenly or strongly excited or unduly prolonged, is most de- 
 structive to the proper texture of the brain, and to the operations of 
 the mind. Our lunatic hospitals affijrd many examples of men, the 
 working of whose minds has been wholly or partially destroyed by 
 the shock which a sudden reverse of fortune, or the loss of some near 
 and dear relative, may have occasioned. Constant or frequent ex- 
 cesses in th^ use of ardent spirits may probably be thus injurious in 
 two ways; first, by the direct influence of the alcohol on the cerebral 
 fibre itself, producing a chemical alteration in the nervous substance; 
 and secondly, by the frequent mental excitement which the use of such 
 a stimulus induces. 
 
 Can we form any conception of the nature of this wonderful power, 
 which is so intimately connected with the functions of our bodies 
 and with the working of our minds? That it presents many points 
 of resemblance to electricity, a comparison of the laws of these two 
 forces leaves no room to doubt; although there are abundant reasons 
 11 
 
218 INNERVATION. 
 
 for questioning their identity. The comparison niay be best iiisti- 
 tutetl between the nervous power and the force of voltaic electricity, 
 or current affinity, as it has lately been called, which is developed in 
 the galvanic battery. For the production of this force the ordinary 
 requisites are two dissimilar metals, and an interposed compound 
 liquid. When the metals are brought into contact with each other, 
 a chemical action immediately commences, and an electric current 
 sets in a definite direction, namely, from the metal which exerts the 
 greatest affinity for one of the elements of the interposed liquid to* 
 wards the other metal. Thus if zinc, platinum, and dilute sulphuric 
 acid be used, the fluid is decomposed ; its oxygen is attracted to the 
 zinc, which being oxidized and uniting with sulphuric acid, sulphate 
 of zinc is rapidly formed, and dissolved as quickly as formed, in the 
 liquid; its hydrogen is evolved at the platinum. So long as there is 
 fluid for decomposition, and so long as contact between the metals is 
 maintained, these phenomena will continue. During the continuance 
 of these chemical actions, the metals as well as the interposed fluid 
 are supposed to be in a peculiar molecular coiidition, upon which the 
 development of force in a current form depends. Commencing from 
 the immersed portion of the zinc, each particle, whether of metal or 
 fluid, communicates its peculiar state tp that which succeeds it, until 
 the whole circuit, from the zinc through the fluid to the platinum, 
 and back again to the zinc, is in th^e same state, one, namely,* of 
 polarity or electrical tension. A similar state may be induced in 
 glass, sealing-wax, &c., by friction; or in two dissimilar metals in 
 intimate contact, by heating them at the place of junction; or in one 
 metal, as a coil of platinum wire, by heating it unequally (thermo- 
 electricity). The simple contact, indeed, of two plates of difierent 
 metals with perfectly clean surfaces is sufficient to excite a state of 
 polarity in each. ^ 
 
 In the development of the galvanic current in the battery, one plate 
 or metal may be regarded in the light of the generator of force, the 
 other as its propagator or conductor. The former has therefore been 
 called the positive, the latter the negative pole. The absolute contact 
 of the metallic plates themselves is not necessary. It will suffice if 
 they be connected by any material which is itself capable of serving 
 as a conductor. A piece of platinum wire, for instance, extended 
 between the two plates, although it actually connects only a very 
 small portion of the- surface of each, will answer the purjiose. From 
 such an arrangement it may be concluded that, during the develop- 
 ment of the galvanic current, the conducting metal is in a state similar 
 to that of the generating plate, for the temperature of the conducting 
 Avire is raised considerably; and, when there is much energy of action, 
 the wire is melted. 
 
 The existence of a galvanic current is readily detected, even when 
 of feeble intensity, by certain phenomena, which are now familiar to 
 those who conduct such investigations. If the poles of a battery be 
 connected by conducting wires with a delicate galvanometer (elec- 
 tro-dynamic multiplier), the needle is obviously deflected during the 
 passage of the current, and returns to its previous position when- 
 
NERVOUS AND ELECTRICAL FORCES COMPARED. 219 
 
 ever the current is- interrupted. By making and breaking the con- 
 nection, in rapid succession, theneedk moves to' and fro with corre- 
 sponding rapidity and energy. So delicate is this test of galvanic 
 action, that it -will detect even the very feeble current which results 
 from the heating of two dissimilar metals, or from the partial heatirig 
 of a coil' of platinum wire. As this is the most delicate test, so is it 
 also the most constant, and it has the additional advantage of ena- 
 bling the observer to judge of the direction of the current from the 
 position which the needle assumes under the electric influence. 
 
 When a galvanic cfurrent is made to pass through certain liquids, 
 as dilute sulphuric acid, solution of iodide of potassium, of sulphate 
 of copper, &c., it induces such an amount of disturbance of the at- 
 tractions existing. in them as to cause their decomposition, and give 
 rise to chemical actions of a similar kind to those which take place 
 in the genetation of the current (electrolysis). This, therefore, be- 
 comes a test of the presence of galvanic action. The decomposition 
 of iodide of potassium will detect the existence of a current deve- 
 loped by a single pair of plates, and iodine will be set free at the 
 positive pole. 
 
 Further tests of the preseince of galvanic action are found in the 
 magnetization of a steel needle placed within a coil of wire through 
 which the current is made to pass; and in the evolution of heat and 
 light^' which takes place when the circuit is completed or broken. 
 This latter effect, however, does not occur from currents of very fee- 
 ble intensity. 
 
 Let us inquire how far the phenomena of the nervous force corre- 
 spond with those of this current electricity, and whether it will respond 
 to any of the tests just described. 
 
 It has already been remarked that the instantaneousness with which 
 nervous power is developed,' when a mental or physical stimulus is 
 applied to a nerve, resembles remarkably the rapid evolution of the 
 galvanic force throughout the whole circuit, the instant the necessary 
 contacts are completed. And both cease with equal rapidity when 
 the conditions for their production are destroyed. 
 
 Some analogy is apparent in the conditions which are requisite 
 for the development of both forces. The dissimilar metals and the 
 interposed fluid, which we have seen to be necessary for the produc- 
 tion of the galvanic force, may have as analogues for the develop- 
 ment of the polarity of nerves, the two kinds of nervous matter (the 
 vesicular and fibrous), and the blood. Nervous power is never 
 developed from a centre without the conjoint action of these two 
 kinds of nervous matter. The analogy fails, however, when we com- 
 pare the relation of the metals in the battery with that of the gray 
 and white matter in the nervous centre. The former need not have 
 any connection but such as a conducting wire of ever so minute di- 
 mensions passing from one to the other is capable of effecting ; that 
 is to say, union of a few points of one metal with as many of the 
 other, is sufficient for the generation and transmission of the polar 
 state. In the nervous centres, however, the poirits of contact are pro- 
 bably most numerous. The vesicles of the gray matter certainly are 
 
220 INNERVATION. 
 
 brought most extensively into connection with the nerve-fibres; and 
 there is much to justify and confirm the opinion that each fibre is 
 connected with a vesicle, and that each vesicle, at least of the cau- 
 date kind, may be regarded as the point of departure of one Or more 
 fibres. If such an arrangement exist,, we may regard each nerve- 
 vesicles, and the fibres emerging from it, with the blood-vessels, which 
 play around it, as a distinct apparatus for the development of nervous 
 polarity. 
 
 There appears to be a provision for the insulation of the central 
 axis of each nerve-fibre in the white substance of Schwann ; but there 
 is no such arrangement for insulating the vesicles. In like manner, 
 we can insulate the galvanic current by covering the conducting wire 
 with silk, or some other non-conductor, and thus cause it to pass 
 through an indefinite length of wire disposed in coils, or through any 
 number of separate wires disposed parallel to each other, which m^y 
 be brought into connection with the metals. 
 
 These remarks are clearly most applicable to those nervous actions 
 which emanate_/rom a centre. But in those in which the nervous 
 force is propagated to a centre, as when pain is excited by touching 
 a nerve, or in the excitation of the motor nerve of an amputated 
 limb by artificial stimuli, the analogy of the mode of its development 
 with that of the galvanic force is not so obvious. Still, when we 
 remember how easily thermo-electric currentsrnay be excited by the 
 disturbance of the equilibrium of heat in a wire of even a single 
 metal, it seems not unreasonable to refer this excitability of nerve 
 to some similar proneness to change in it. 
 
 Nothing is more certain than that a very slight mechanical or che- 
 mical stimulus to a nerve, whatever be its proper vital endowment, 
 is capable of producing in it that state of polarity on which we sup- 
 pose the manifestation of nervous force to depend; and it seems not 
 incorrect to imagine that, in the battery, the point of departure of the 
 galvanic action may either be at the poles or at the battery itself, 
 according to the place at which the completion of the circuit takes 
 place; thus affording a more marked analogy to the two kinds of 
 nervous actions above referred to. Thus the conducting wires may 
 be. in contact with each other, and with their respective metals; but, 
 if there be no fluid interposed, there is no action. The instant the 
 fluid is added, the current begins; and in this case its point of depar- 
 ture may be regarded to be from the battery — in analogy with those 
 nervous actions which proceed from the centre. On the other hand, 
 the arrangements of the battery itself may be perfect, but action will 
 not begin until the circuit is completed by bringing the conducting 
 wires into contact. In this case, the polar change may be said to 
 commence at this point of contact, and to travel to the battery, in a 
 manner analogous to that in which nervous action is propagated from 
 the periphery to the centre. In both cases, moreover, so long as gal- 
 vanic action continues, the whole apparatus is in the polar state : and 
 so long as nervous action continues, the particular nervous apparatus 
 involved (vesicular matter and nerve-fibre) must be considered to be 
 in a state of polarity through its whole extent. 
 
NERVOUS AND ELECTRICAL FORCES COMPARED. 221 
 
 * 
 
 Thus far we remark unquestionable analogy in the mode of deve- 
 lopment' and of propagation of the electrical and nervous forces. 
 We must not, however, omit to notice the following points in which 
 the analogy does not hold good. In the development of nervous 
 power, there is nothing, so far as our present anatomical know- 
 ledgC' enables us to decide, resembling that corapfetion of the circuit 
 which is the necessary prelude to galvanic acticin, or the interruption 
 of it which is followed by the cessation of that action. The mental 
 or physical stiinulus, which must be regarded as a necessary element 
 in every nervous action, stands in lieu of the former ; but how it 
 could accomplish the completion of a nervous circuit is a question at 
 present irivolved in the greatest obscurity. It is, indeed, a favorite 
 notion with some, that the looped arrangement of the peripheral 
 nerve-fibres, in muscles and on some sentient surfaces, forms part of 
 a nervous arc, which is completed at the centre ; nor is it impossible 
 to conceive a mechanism by which the completion or interruption 
 necessary for the development or the stoppage of the nervous power 
 might be accomplished. But it would be hazardous to speculate on 
 such a subject until anatomical research has revealed to us more 
 information respecting the exact disposition of the elements of the 
 vesicular matter. 
 
 The gelatinous fibres appear to want the provision which we have 
 noticed in those of the tubular kind for insulating the nervous power. 
 They supply the unstriped muscular fibres, which probably require a 
 stimulus less definite, as well as of less intensity, than that necessary 
 to excite and regulate the action of the striped fibres. This difference 
 of character in the conducting fibres is worthy of note in making com- 
 parison between the respective modes of action of the nervous and 
 electric forces. 
 
 We come now to inquire whether, by means of the ordina!ry tests 
 for electricity mentioned in a former page, we can obtain any evidence 
 of the identity of the nervous and electrical forces. The results bf 
 experiment certainly afford no support to the advocates of the elec- 
 trical theory ; and indeed it will be seen that there are difficulties in 
 the way of- obtaining the necessary conditions for a satisfactory re- 
 sult, which of themselves invalidate the experiments which have been 
 reported to prove favourable to that theory. • 
 
 Attempts have been made to affect the galvanometer by bringing 
 the nerves of living animals into connection with it. This is done 
 by inserting wires into the exposed nerve, and attaching their oppo- 
 site extremities to the galvanometer. When the nervous power is 
 excited so as to cause muscular contraction, the needle, it is said, is 
 deflected.* The experiment, however, has failed in the hands of 
 Prevost and Dumas, who are advocates of the electrical theory, as 
 well as in those of Person, of Miiller, and of Matteucci; and on seve- 
 ral trials we have been unable to observe the slightest movement 
 of the needle. , Person connected the wires of a galvanometer with 
 the surfaces of the spinal cord in kittens and rabbits, in which spas- 
 
 • David, quoted by Muller, p. 685. 
 
222 INNERVATION. 
 
 modic action of the muscles had been excited by the influence ofnux 
 vomica, and could not discover any evidence of electrical action. It 
 has been also affirmed that needles introduced into the nerves of a liv- 
 ing animal become magnetic, so as to attract iron filings. No such 
 result, however, could be obtained by Miiller, or by Matteucci, from 
 their repetition of these experiments. The latter philosopher took the 
 precaution of employing astatic needles for the purpbse, but could 
 discover no trace of magnetization. He also introduced the prepared 
 limbs of a frog into the interior of a spiral covered on its inside with 
 .varnish: the extremities of this spiral were united to those of another 
 smaller spiral, into which he introduced a wire of soft iron. The 
 nerves of the frog were irritated to excite muscular action, and at the 
 same time Matteucci sought to ascertain if an induced current would 
 traverse the spirals, and magnetize the wire. But, he adds, all his 
 endeavours were useless. 
 
 No one has tried to obtain a spark from a nerve during its action, 
 as a test of the electrical nature of the nervous power. Nor have any 
 experiments been devised with a view to ascertain whether decom- 
 positions similar to those which occur in electrolysis may be effected 
 by it. The separation of certain elements from the blood, in the vari- 
 ous secretions, has, indeed, been attributed to a kind of electrolytic 
 influence of the nerves upon the secerning organs. But it has been 
 proved that the secretions may go on to a considerable extent inde- 
 pendently of nervous influence, and it seems highly probable that the 
 nervous system can affect the act of secretion only through its influ- 
 ence upon the blood-vessels of the secreting organ. 
 
 But even were it certain that an electrical current passes along the 
 nerve-fibres during nervous action, it does not seem likely that the 
 required evidence of such a current could be obtained from any of 
 the experiments above detailed. For if the nerve-tubes are to be re- 
 garded as insulated conductors, of which the central axis is the active 
 portion, and the white substance of Schwann merely the insulator, 
 sinking a needle between these fibres will not obtain that contact 
 with the true conducting material which is necessary to affect the 
 galvanometer. Let it be remembered that these nerve-fibres are of 
 microscopic size ; and that, when a needle is sunk into a bundle of 
 them, it does not pierce the nerve-tubes, but passes in between them, 
 and is separated from their central axes by the insulating structure. 
 And were the electric current, passing through such minute conduct- 
 ors as nerve-fibres, of sufficient intensity to magnetize a needle, it is 
 scarcely possible to conceive that it would be completely or perfectly 
 insulated by the delicate membranes which invest the central axis. 
 Yet, without some provision for very complete insulation of the seve- 
 ral conductors in such a bundle as a nervous trunk, it is obvious 
 that disturbances must continually arise from the secondary currents 
 induced in neighboring fibres by the electricity passing through those 
 in action. 
 
 The proofs, therefore, of the passage of an electric current through 
 fhe nerve-fibres during nervous action must be held to be altogether 
 defective. Not only is experimental evidence wanting to support the 
 
ANIMAL ELECTRICITY AND LUMINOUSNESS, 223 
 
 electrical theory, but certain facts are admitted ■which greatly inva- 
 lidate it. Of these,, a very important one has been adduced in the 
 preceding paragraph. The following may be added, some of which 
 have already been adduced by Muller. 
 
 1. The firm application of a ligature to a nerve stops the propaga- 
 tion of the nervous power below the points of application, but not of 
 electricity. The nervous trunk is as good a conductor of electricity 
 after the application of the ligature as before it. 
 
 2. If a small piece of a nervous trunk be cut out, and be replaced 
 by an electric conductor, electricity will still pass along the nerve, 
 but no nervous force, excited by stimulus above the section, will be 
 propagated through the conductor to the parts below. 
 
 3. Nervous fibre is not a better conductor of electricity than other 
 tissues. Matteucci assigns to muscle a conducting power four times 
 greater than that of nerve or cerebral matter ; and Weber states that 
 no substance in the human body is so good a conductor as the metals. 
 From our own observations on this subject, made with the mos< deli- 
 cate instruments, we are led to state that both nerve and muscle are 
 infinitely worse conductors than copper, and that we have failed in 
 detecting any appreciable difference in the conducting power of these 
 two animal substances. In fact, their power of conduction does not 
 rank above that of water holding in solution a small quantity of saline 
 matter. 
 
 From the preceding, review of the arguments for and against the 
 theory of the identity of the nervous force and electricity, we are led 
 rather to reject than to adopt it. The same reasons induce us to re- 
 gard the nervous force as a power developed in the nervous structure 
 under the influence of appropriate stimuli; as muscular force is deve- 
 loped in muscle under similar influence. Both tissues are charac- 
 terized by their tendeijcy to assume a polar state, different in each, 
 although analogous, in obedience to certain excitants. That this 
 polarity bears a remarkable analogy to that which may be produced 
 in inorganic inatter is evident. Further observation and research 
 conducted with a full knowledge of the details of anatomy, as well 
 as of the laws of the polar forces, as displayed in inorganic sub- 
 stances, will doubtless throw great light on this intricate subject ; 
 for, as Faraday remarks, if there be reasons for supposing that mag- 
 netism is a higher relation of force than electricity, so it may well 
 be imagined that the nervous power may be of a still more exalted 
 character, and yet within the reach of experiment. {Phil. Trans., 
 1839.) 
 
 Of the electrical fishes. — The fact that some fishes possess a pecu- 
 liar electrical apparatus, which they are enabled to discharge under 
 voluntary influence, is supposed by the adherents of the electrical 
 theory to favour their views. The torpedo, the gymnotus electricus, 
 or electrical eel, and the silurus electricus, are the best known of the 
 electrical fishes. From the two former, the most unequivocal evi- 
 dence has been obtained by Walshe, Davy, Linari, Matteucci, and 
 recently by Faraday, that electricity is discharged. Conductors or 
 
224 INNERVATION. 
 
 non-conductors are afi'ected by the electrical apparatus of these fishes 
 just as by ordinary electricity: a chain of several persons, of -whom 
 those at the extremities touch the fish, feel the shock as they would 
 that of a Leyden jar. The sensation produced by the shock from 
 the fish is exactly that which is caused by accumulated electricity as 
 developed by the ordinary machine. A spark has been obtained 
 during the discharge: chemical decomposition or electrolysis has been 
 effected by it. The galvanometer is also readily disturbed, and indi- 
 cates that the current passes from the anterior to the posterior part 
 of the animal. And a needle has been made a magnet when placed 
 in a helix through which the current passes. These effects have been 
 obtained from the torpedo and the gymnotus. 
 
 It is further shown that the electricity cannot be developed in 
 these animals if the organ be removed, or if its communication with 
 the brain be cut off. If the nerves of the organ of one side be cut, 
 it will cease to develop electricity ; but the opposite organ will con- 
 tinue to act perfectly. When the organ is partially cut away, the 
 remaining portion continues to discharge ; or, if some of its nerves 
 be cut, that portion of which the nerves are entire will continue to 
 develop electricity. The nerves excite some change in the otgan 
 which causes the development or discharge of electricity, but no traces 
 of an electrical current can be detected in the nerves themselves. If 
 the nerves of an electrical organ be cut, irritation of those segmgnts 
 of them which adhere to the organ will excite discharges, just as the 
 irritation of muscular nerves under similar circumstances will cause 
 contractions ; or direct irritation of portions of the organ itself will 
 produce discharges (Matteucci). Any general excitation of the nerv- 
 ous system will cause discharges; thus strychnine, while it throws 
 the muscular system into spasms, provokes frequent and violent dis- 
 charges of the electrical organs. 
 
 From these observations it seems impossible to adopt any other 
 conclusion than that the electrical organ is the generator of the elec- 
 tricity ; or, at least, that it may collect and accumulate the electri- 
 city generated all over the body in the ordinary nutritive processes. 
 This latter opinion, however, is rendered unlikely from the imperfect 
 conducting power of animalsubstances, unless further research should 
 develop some channels by which electricity generated at a distance 
 might be conveyed to the electrical organ. Whatever view of the 
 case be adopted, it is difficult to discover in the facts above stated 
 respecting the electrical fishes any support to the electrical theory of 
 nervous power. On the contrary, the very existence of a peculiar 
 organ for the specific purpose of generating electricity would appear 
 adverse to such a doctrine. Were the nervous centres the source of 
 electricity, surely an arrangement, of a less complex character, and 
 deviating to a less extent from the natural structure of other fishes 
 of the same genus, would have sufficed for the manifestation of the 
 peculiar power of the electrical fishes. 
 
 Some insects (the glow-worm for instance), and other creatures, 
 possess the faculty of generating light. The power resides in a par- 
 ticular organ, and is regulated by the nervous system. It is strik- 
 
THE NERVOUS SYSTEM IN VERTEBRATA. 225 
 
 ingly analogous to that by v?hich electricity is developed. Yet no 
 one would assign the nervous system as the source of the luminous 
 emission. Nor are we justified in affirming from the one instance 
 that the nervous power is electricity, any more than we should, 
 from the other, be authorized in asserting that the nervous power is 
 light. 
 
 Oa the subjects discussed in this chapter, reference is made to Miiller's Physiology 
 by Baly; Daniell's Chemistry; the articles "Animal Electricity" and "Animal Lu- 
 minousness," in the Cyclop. Anat. et Physiol.; Malteucci, Trait6 des Phenomenes 
 Electrophysiologiques des Animaux. 
 
 CHAPTER X. 
 
 ARRANGEMENT OF THE NERVOUS SYSTEM IN VERTEBRATA. — IN INVERTE- 
 BRATA. — NERVOUS CENTRES IN MAN. — THEIR COVERINGS OR MENIN- 
 GES.^THEIR VENOUS SINUSES.— THE SPINAL CORD. — THE ENCEPHA- 
 LON. THE CIRCULATION WITHIN THE CRANIUM. 
 
 The leading subdivision of the animal kingdom into Vertebrate and 
 Invertebrate animals is so obviously sanctioned by the disposition 
 of the nervous system peculiar to each, that no naturalist hesitates 
 to adopt it. In the vertebrate animals, an osseous or cartilaginous 
 column, composed of separate pieces united by amphiarthrosis, forms 
 the principal support and bond of connection for the other parts of 
 the trunk. This column encloses a canal, within which is placed 
 that portion of the nervous centres called the spinal cord, or marrow, 
 with some of its nerves. At its anterior or upper extremity, the com- 
 ponent pieces of the column are so modified as to form a dilated 
 cavity, the cranium, in which another portion of the central nervous 
 system, the brain, or encephalon, with part of the nerves connected 
 with it, is contained. In the invertebrate animals generally there is 
 no internal skeleton, if we except the slight traces which exist in the 
 cephalopodous mollusks ; but in many of them a modification of the 
 external integument aflfords the requisite- amount of protection and 
 support to the soft tissues and organs. The nervous system, the 
 central part of which is disposed either in detached masses, or in a 
 series along the abdominal surface of the animal, receives no special 
 protection from this external skeleton. 
 
 The brain and spinal cord, in the vertebrate classes, form a central 
 axis with which all other parts of the nervous system are con ne ctd. 
 The former is evidently an aggregate of gangliform swellings, 
 each possessing the characters of a nervous centre, but so con- 
 nected with the others, that their functions are in no small degree 
 mutually dependent. The latter has throughout its entire length all 
 the characters of one uniform nervous centre, of cylindrical shape ; 
 but experiment has shown that, if divided into segments, in animals 
 
226 INNERVATION. 
 
 tenacious of vitality, each portion may exert an independent influ- 
 ence on that segment of the body whose nerves are connected with 
 it. From this fact we may properly regard the cord also in the light 
 of a ganglion compounded of smaller ones, which have been, as it 
 were, fused together. And certain anatomical indications in the 
 lower animals, as well as in man, favour this view; thus, in the 
 common gurnard {trigla lyra), there is a series of gangliform swell- 
 ings situate on the posterior surface of the cervical portion of the 
 cord at its upper part, from which large nerves pass off to the feelers; 
 and in all animals the cord exhibits a distinct enlargement, at each 
 segment with which large nerves are connected, or a contraction, if 
 the nerves be of small size and of comparatively little physiological 
 importance. 
 
 The cerebro-spinal axis, with the nerves pertaining to it, consti- 
 tutes the greatest portion of the nervous system of the human sub- 
 ject and of the vertebrate animals. The sympathetic system, how- 
 ever, is connected with a large number of those parts on which the 
 principal organic functions depend. This portion of the nervous 
 system always bears a direct relation in point of development to that 
 of the cerebro-spinal portion, with every part of which it is very in- 
 timately associated. If we except the olfactory, optic, and auditory 
 nerves, there is no nerve with the origin of which it does not form a 
 connection. Its segments remain separate, as distinct ganglia, ocn- 
 nected, however, by intercommunicating cords passing from one to 
 the other, by which the continuity of the chain on either side of the 
 vertebral column is maintained. In mammals and birds the sympa- 
 thetic is fully developed ; but in some reptiles and fishes it is partly 
 deficient, and its anterior part which is wanting, is supplied by the 
 vagus nerve. In the cyclostomatous fishes, as the lamprey, it is want- 
 ing altogether, and the vagus seems to supply its place. In no animal 
 is it so fully developed as in man. 
 
 Arrangement of the Nervous System in Inveiiebrata. 
 
 It is foreign to the purpose of this work, to enter into details of comparative ana- 
 tomy. The following paragraphs are merely intended to call the reader's atten- 
 tion to the general plan of the nervous system in the Irivertebrata. The arrange- 
 ment adopted is that suggested by Professor Owen. 
 
 The Invertebrate animals' may be classed in three groups, according to the pre. 
 vailing type of arrangement of the nervous system. 1. The first, or Nematoneuifose, 
 exhibits no other trace of nervous system man is to be found in simple threads 
 or filaments. In the asterias, one thread surrounds the mouth, and others pass 
 from it to the rays ; and in the strongylus gigas, a slender nervous ring su> 
 rounds the upper part of the gullet, and irom it a single thread is continued along 
 the ventral surface to the opposite extremity, where another nervous loop is found 
 surrounding the anus. No distinct evidence of the existence of ganglia in animals 
 included in this group has been obtained. It would be premature, however, to 
 suppose that the absence of gangliform swellings implies that of vesicular nervous 
 matter. 
 
 2. The second group of animals is designated Heterogangliate, from the unsym- 
 metrical disposition of the nervous system. The principal portion of it consists 
 in a ring surrounding the gullet, on which one or more ganglia are placed. In 
 the ascidia mamillata there is but a solitary ganglion, which regulates the orifices 
 
THE DURA MATER. 227 
 
 of ingestion and egestion by nerves -which it sends to their respective sphincter 
 muscles. And ijx all the-other classes of mollusks the nervous system is the more 
 complex, as the kind and number of the vital actions demand a higher degree of 
 orgaiiization. In conchifera^ for instance, ingestion of the food, respiration, and 
 locomotion have distinct organs assigned to them, and accordingly the nervous 
 system is sq disposed that there is a nervous centre or ganglion in immediate 
 relatiomto the principal organs connected with each of these functions. Thus, in 
 the more perfect animals of this class we find, 1, two (Esophageal ganglia situate 
 near the mouth, connected to each other by nervous filaments, which form a ring 
 round the gullet. These ganglia are connected with all the rest, and probably 
 exercise an influence upon them, as the principal centre of the nervous system or 
 the brain. 2. There is a irancfeiaZ- ganglion, which presides over the function of 
 respiration. When there is but one respiratory organ, this ganglion is single ;, but 
 it is double when there are two branchice. From this source are supplied not only 
 the organs of respiration themselves, but also the muscles upon which the respira- 
 tory movements depend. The postetior adductor muscle, the mantle, and intes- 
 tine, derive nerves from it. 3. We fiad a, pedal ganglion, which is immediately 
 connected with the locomotive function. Tljis ganglion exists only in those genera 
 in which a muscular organ called the foot is developed, and its size is always in 
 direct proportion to the muscular power of that organ : it is situated at its base, and 
 imbedded in it. We find it, therefore, in the mussel (mytilus) , but not in the oyster. 
 The development of organs of sensB in the higher animals of this group demands 
 an increased development of the cerebral ganglion, as is the case in the gasteropod 
 and cephalopod nioUusks. And the great powers of locomotion enjoyed by the 
 latter aninials require a high development of the pedal ganglion, and a multiplica- 
 tion of smaller ganglia in connection with the muscular apparatus of their arms or 
 tentacles. These organs are supplied with nerves from the subcesophageal gan- 
 ghon ; and, where suckers exist upon the arms, an ,additional series of ganglia is 
 provided, which seem to exert an especial influence in the exercise and the main- 
 tenance of their siiotion power. 
 
 3. The third, or Homogangliate group, is distinguished by the symmetrical ar- 
 rangement of the nervous system. The articulate classes furnish examples of this 
 type. A bilobed ganglion is situated above the ossophagus, and is connected with 
 the organs of sense when they are present. From this there proceeds on each 
 side of the ossophagus a nervous cord to a pair of ganglia beneath that canal, 
 and therefore on the ventral surface. To these succeed, in most of the articu- 
 lata, and likewise on the ventral surface, a pair of ganglia for each segment, from 
 which are supplied the nerves to that segment. The ganglia are connected 
 throughout, however, by cords of communication from the cephalic to the caudal 
 segment. The number of pairs of ganglia is always in accordance with the num- 
 ber of segments of the animal; and, if some of these segments be fused together, 
 a similar coalescence of the ganglia takes place. This is observed in insects in 
 the change from the larva to the perfect state ; and, in some genera of Crustacea, 
 the permanent form of the nervous system has obvious relation to peculiarity in 
 the shape pf the body. The annular arrangement of the ganglia in the body of 
 the common crab (^cancer), and of the king-crab {limuhs), is evidently explained 
 by reference to the compressed form of the body, and the articulation of the legs 
 arouiid it. 
 
 Some additional ganglia are met with in a few animals of the homogangliate 
 group, which seem to represent rudimentary conditions of the sympathetic sys- 
 tem. These have been best observed in insects, and they are described under the 
 name of stornatogastric ganglia. They are two or more in number, connected by 
 delicate filaments with the cephalic ganglia; and they give off' long nerves, which 
 supply the digestive organs and the dorsal vessel, or heart, and which, in some 
 instances, unite with small ganglia in the abdomen to be distributed on the viscera 
 .of that cavity. 
 
 Of the Spinal cord and Brain. — The cerebro-spinal centre is en- 
 closed in certain membranes or meninges, which are three in number ; 
 the dura mater, the arachnoid, and the pia mater. 
 
 The dura mater consists of white fibrous tissue. It is thick, very 
 
228 INNERVATION. 
 
 strong and flexible, without being elastic. Its fibres are disposed 
 on different planes, but freely intermingle. At certain situations it 
 separates into two layers to form the venous canals, which are called 
 sinuses. The inner surface of the cranial cavity is covered by dura 
 mater, which adheres closely to the bones, and serves as an internal 
 periosteum to them ; and certain processes of the dura mater pass into 
 the interior of the cranial cavity, dividing it into compartments, which 
 contain certain segments of the encephalon. These processes are, 1. 
 The Jhlx cerebri, which extends from the crista' galli to the occiput 
 along the line of the sagittal suture, and forms, a vertical septum.be- 
 tween the hemispheres of the brain. 2. The tentorium cerebelli, which 
 is attached to the occipital bone along the groove for the lateral sinus, 
 and to the posterior superior edge of the petrous bone. This process 
 forms a vaulted roof to the compartment which contains the cerebel- 
 lum, and extends between the upper surface of that organ and the 
 inferior surface of the posterior cerebral lobes. In some animals, the 
 cat, for instance, it is partially replaced by bone. 3. The falx cere- 
 belli, a small nearly vertical process which descends from the internal 
 occipital protuberance, and occupies the notch between the hemi- 
 spheres of the cerebellum. 
 
 In the spinal canal, the dura mater does not adhere to the inner 
 surface of the spinal bones as a periosteum. On the contrary, it ,js 
 separated from it by a soft unctuous fat mixed with very numerous 
 veins. It adheres pretty closely to the anterior common ligament 
 which intervenes between it and the bodies of the vertebra, and 
 seems to be continued from the cranial dura mater at the foramen 
 magnum as a funnel-shaped process of that membrane adapted to the 
 shape of the spinal canal. It ends in a blunted extremity in the 
 sacral canal, and is tied down in that situation by certain filiform 
 processes, of which the central one is attached to the coccyx. The 
 spinal dura mater is evidently much more capacious than is necessary 
 merely to contain the spinal cord, and therefore it generally has a 
 loose and flaccid appearance. During life it is kept tense by the fluid 
 which surrounds the cord. The dimensions of the canal of the dura 
 mater vary with those of the spinal canal. It is wider, therefore, in 
 the neck and loins, and narrow in the back. In the lumbar and 
 sacral region it forms a wide sac around the leash of nerves called 
 Cauda equina. 
 
 The dura mater, in both cranium and spine, exhibits numerous 
 perforations for the transit of nerves from the contained centre to the 
 peripheral parts. In the spinal region each of these perforations is 
 subdivided, by a vertical slip of the membrane, into two foramina, 
 which correspond to the anterior and posterior roots of the spinal 
 nerves, and extend on each side down to the lower part of the sacral 
 region. 
 
 The blood-vessels of the dura mater are very numerous. Those 
 of the cranial membrane communicate freely with those of the bones. 
 Hence, when separated from the cranium, the external surface of the 
 dura mater has a rough appearance from the number of blood-ves- 
 sels which have been torn. This membrane derives its supply of 
 
SINUSES OP THE DURA MATER. 229 
 
 anterior blood from the ophthalmic and ethmoidal arteries in front; 
 in the middle, from the internal maxillary artery by the middle 
 meningeal, which enters the cranium by the foramen spinosum, 
 and by small branches from the internal carotid, called the inferior 
 meningeal arteries. Posteriorly the vertebral, the occipital, and the 
 ascending pharyngeal supply branches which go by the name of pos- 
 terior meningeal arteries. The arteries of the spinal dura mater 
 come from the deep cervical, the occipital, and the vertebral, in the 
 cervical region, from the intercostals in the back, and from the lum- 
 bar arteries in the loins. These vessels pass in at the vertebral fora- 
 mina, and send branches to the bones as well as to the spinal mem- 
 branes. 
 
 The veins of the dura mater in the cranium constitute a remark- 
 able portion of the vascular system of that cavity. The venous 
 radicles collect the blood from the dura mater, and from the bones of 
 the skull ; large veins are formed on the former membrane, and dis- 
 Jinct canals in the osseous diploe, figured at pages 110 and 111. These 
 all tend to certain venous channels, rigid canals, formed by the sepa- 
 ration of two layers of the dura mater, which are lined by processes 
 of the inner membrane of the venous system, and are so placed as to 
 collect the blood from all parts of the cranium. These canals, sinuses 
 of the dura mater, receive likewise the venous blood of the brain. 
 The largest sinuses are the superior longitudinal and the lateral 
 sinuses. The former extends alpng the convex edge of the falx cere- 
 bri, commencing very small by receiving veins from the ethmoid and 
 frontal bones, and terminates in a reservoir common to it and other 
 sinuses at the internal occipital protuberance {torcular Herophili). It 
 thus serves to, collect blood from the superior and lateral parts of 
 the dura mater, from the vault of the cranium, and from the hemi- 
 spheres of the brain; the veins of the latter entering it obliquely for- 
 wards. The lateral sinuses are lodged in tortuous furrows, which 
 mark the occipital, the parietal, and the temporal bones. They are 
 two in nuiiiber, and extend on each side from the torcular Herophili to 
 the jugular foramen, where they are continued into the internal jugular 
 veins. These sinuses serve not only to carry into the jugular veins 
 all the blood which is poured into the torcular, but likewise to receive 
 blood from the lateral and posterior parts of the dura mater and cra- 
 nium, from the inferior surface of the posterior lobes of the brain, and 
 from the cerebellum. A short sinus, also of considerable width, is 
 lodged in the tentorium cerebelli. This is the straight sinus; it passes 
 from before backwards, occupying about the middle of the vault of 
 the tentorium, and opening behind into the torcular. It receives blood 
 froin the interior of the brain by two large veins, the vence magnce 
 Geleni. The cavernous sinuses, two in number, lie one on each side 
 of the sella Turcica,' from which the internal carotid arteries separate 
 them. Their irregular shape is rather that of reservoirs than of 
 canals. They receive the ophthalmic veins from the orbit, as well as 
 numerous small veins from the cranial bones, the dura mater, and the 
 anterior and middle lobes of the brain. 
 12 
 
230 INNERVATION. 
 
 Other small sinuses are met with which serve chiefly to establish 
 a communication between those above mentioned, while at the same 
 time they receive some blood from the neighbouring textures. The 
 petrosal sinuses, two on each side, superior and inferior, pass between 
 the cavernous and lateral sinuses: the transverse sinus runs between 
 the petrosal and cavernous sinuses of opposite sides; and the circu- 
 lar or coronary sinus, while it receives blood from the pituitary body 
 and from the sphenoid bone, connects together the cavernous sinuses 
 in front, and thus completes the venous circle around the sella Tur- 
 cica. 
 
 We see, in this arrangement of venous canals, a beautiful provision 
 against the effects of undue venous congestion within the cranium, 
 insured not merely by the inextensible nature of the principal venous 
 canals, but also by the free anastomosis that exists between them, arid 
 by the numerous points- at which they communicate with the veins 
 of the cranium, and through these with the superficial veins of the 
 scalp. 
 
 The spinal veins are extremely numerous and complicated. A very 
 intricate venous plexus surrounds the dura mater on its lateral and 
 posterior surfaces, imbedded among the lobules of soft fat by which 
 the exterior of that membrane is invested. This plexus, less intri- 
 cate in the dorsal than in the cervical and lumbar regions, commu- 
 nicates very freely with a plexus of veins which surrounds the ck- 
 terior of the vertebral laminae and processes (the dorsi-spinal veins 
 of Dupuytren). In front of the dura mater, and situate between the 
 outer edge of the posterior common vertebral ligament and the pedi- 
 cles of the vertebrae, we find two remarkable venous sinuses which 
 extend the whole length of the vertebral column from the occipital 
 foramen to the sacrum. They are the longitudinal spinal sinuses of 
 Willis. In calibre they present many inequalities, being dilated at 
 one part and constricted at another, according to the number and size 
 of the vessels which communicate immediately with them. The 
 sinuses of opposite sides are parallel to each other, and communicate 
 by transverse branches, which pass beneath the posterior common 
 ligament. These transverse branches are of variable calibre, like 
 the sinuses themselves, and are dilated at their middle ; at which 
 point they receive veins which emerge from the spongy texture of 
 the bodies of the vertebra {basi-vertebral veins of Breschet).* At 
 the highest part of the vertebral canal, the spinal sinuses communi- 
 cate with the internal jugular veins; in the neck, they communicate 
 with the deep and superficial vertebral veins ; with the intercostal 
 veins in the dorsal region, and with the lumbar ones in the loins. 
 
 The arachnoid is the serous membrane of the cranio-spinal cavity. 
 By its parietal layer it adheres to the dura mater, both of the cra- 
 nium and spine, and by its visceral layer to the brain and spinal 
 cord, with the intervention of the pia mater. The space between 
 these two layers is the arachnoid cavity. In most regions an inter- 
 val exists between the visceral layer of the arachnoid and the pia 
 
 • See his very beautiful illustrations of the venous system. 
 
THE CEREBRO-SPINAL FLUID. 231 
 
 mater, which is called the sub-arachnoid cavity. This space rnay he 
 demonstrated by driving air or coloured liquid beneath the visceral 
 layer of the arachnoid. In the spine the connection of the arachnoid 
 and pia mater is very loose, being effected by some' long- filaments 
 of fibrous tissue, which interlace slightly, and are most abundant in 
 the cervical region. Along the posterior surface of the spinal cord, 
 in the middle line, the sub-arachnoid space is divided by means of a 
 septum, which is probably only a modified portion of the tissue of the 
 pia mater. This septum is most perfect in, the dorsal region, but in 
 the lumbar and cervical regions it is cribriform, and in some parts is 
 very difficult of demonstration. Dr. Sharpey regards it as the reflec- 
 tion along the median line of a serous membrane, which he supposes 
 to line the sub-arachnoid cavity. Did such a membrane exist, we 
 should find an epithelium, which, however, we have sought for in 
 vain. 
 
 The connection of the arachnoid to the subjacent pia mater is not 
 so loose in the head as in the spine. On the superior and lateral sur- 
 faces of the brain, where the convolutions are most prominent, the 
 adhesion is very close, but opposite the sulci between the convolu- 
 tions the pia mater recedes from the arachnoid and sinks to the bot- 
 tom of each fissure, leaving large areolee in which fluid may accumu- 
 late. Along the fissure of Sylvius, at the base of the brain between 
 the cerebellum and the posterior surface of the medulla oblongata, 
 and between the posterior edge of the corpus callosura and the supe- 
 rior surface of the cerebellum, the arachnoid and pia mater are very 
 loosely connected, so that at these situations spaces are found which 
 are favourable for the accumulation of fluid. 
 
 The cerebrospinal fluid. — This fluid, which fills the sub-arachnoid 
 space during life, keeps the opposed surfaces of the arachnoid mem- 
 brane in intimate contact. Its quantity, which varies between two 
 and ten ounces, is in the inverse ratio of the bulk of the brain and 
 spinal cord. Thus it is most abundant in old persons in whom these 
 organs have shrunk, and it accumulates in cases of deficiency of any 
 portion of them from malformation or disease. Its presence seems 
 necessary to the healthy action of the nervous centres, for the removal 
 of it in dogs by Majendie caused considerable disturbance of their 
 functions, probably by favouring distension of the blood-vessels. It 
 is, however, capable of being regenerated as quickly as the aqueous 
 humour of the eye, and its reproduction restores the nervous centres 
 to their natural State. When removed from the body a few moments 
 after death, this fluid is, according to Majendie, remarkably limpid ; 
 it has a sickly odour antl a saltish taste, and is alkaline, restoririg the 
 colour of reddened litmus. 
 
 The cerebro-spinal fluid is most probably secreted by the pia 
 mater, since it is found wherever that membrane and sufficient space 
 exist. The ventricles of the brain contain a secretion of very similar, 
 if not identical characters, which Majendie describes as communicat- 
 ing with that of the sub-arachnoid space through an orifice at the 
 inferior extremity of the fourth ventricle. This, however, is extremely 
 
232 INNERVATION. 
 
 doubtful, as the fluid of the ventricles is enclosed by a proper mem- 
 brane which lipes their cavity. 
 
 The cerebro-spinal fluid obviously affords mechanical protection to 
 the nervous centres which it surrounds. The interposition of a fluid 
 medium between them and the walls of the cavities is well adapted 
 to guard the former against shocks communicated from without. Its 
 accumulation at the base of the brain is highly favourable for the pro- 
 tection of the large vessels and nerves situate there. 
 
 The pia mater is the, immediate investing membrane of the brain 
 and spinal cord. It is composed of white fibrous tissue and blood- 
 vessels. The former is most abundant in the pia mater of the cord, 
 the latter are most numerous in that of the brain. The principal 
 distinction, therefore, between the spinal and cerebral pia, mater is as 
 regards strength and thickness ; the spinal being dense and strong, 
 the cerebral being vefy delicate, almost wholly composed of minute 
 blood-vessels, which are accompanied by white fibrous tissue in small 
 quantity. The spinal membrane forms a complete sheath to the cord, 
 and sends in processes which dip into its anterior and posterior me- 
 dian fissures. It is continuous with the neurilemma of the roots of the 
 nerves on each side. At the inferior extremity of the cord it tapers and 
 terminates in a thread-like process [filum terminale) which is inserted 
 into the inferior extremity of the dura mater. Superiorly it gradually 
 diminishes in density as it passes over the medulla oblongata to the 
 cerebral and cerebellar hemispheres. To the surface of these it ad- 
 heres closely, and innumerable minute blood-vessels pass from it into 
 the nervous substance. It sinks into all the sulci and fissures, and 
 passes into the lateral, the third and fourth ventricles. In the lateral 
 and fourth ventricles it forms projecting processes or folds, somewhat 
 fringed, highly vascular, and invested by epithelium derived from the 
 membrane which lines the ventricles. These processes are called 
 the choroid plexuses. Into the third ventricle it sends a lamellar fold 
 of triangular shape {velum interpositum), which forms a roof to that 
 cavity and supports the fornix. 
 
 Attention has lately been directed to some minute sandy particles, 
 globular in shape, which are frequently connected with the minute vas- 
 cular ramifications of the internal pia mater. They are found chiefly 
 in the choroid plexuses, and in that portion of the velum which invests 
 the pineal gland. This sabulous matter is composed of phosphate of 
 lime, with a small proportion of phosphate of magnesia, a trace of 
 carbonate of lime, and a little animal matter. ( Van Ghert de pelxubus 
 choroideis.) 
 
 Of the ligamentum dentatum. — This remarkable structure, found in 
 the sub-arachnoid space, requires a brief notice. It seems to be a 
 process of the pia mater, which exhibits more of the glistening ap- 
 pearance of white fibrous tissue than the rest of that membrane. It 
 extends from the occipital foramen to the filiform termination of the 
 pia mater, adhering by its inner straight border to that membrane, and 
 attached on the other hand to the dura mater by a series of dentated 
 processes which penetrate the visceral and parietal-layers of arachnoid, 
 
THE SPINAL CORD. 233 
 
 pinning them, as it were, down to the fibrous membrane. They form 
 a vertical septum between the anterior and posterior roots of the 
 spinal nerves. The dentated processes vary in number from eig^hteen 
 to twenty-two. The first is attached to the diira mater which covers 
 the occipital foramen just behind the vertebral artery; the rest are 
 inserted between the orifices for the exit of the spinal nerves, and 
 the last is on a level with the first or second lumbar vertebra. A 
 considerable quantity of yellow fibrous tissue exists in this structure, 
 especially in its dentated processes. 
 
 The Pacchionian glands or bodies are whitish granules, composed 
 of an albuminous material, which are found among the vessels of the 
 pia mater, on the edges of the cerebral hemispheres, which push the 
 arachnoid before them, and even project into the longitudinal sinus. 
 They do not occur in the earliest periods of life, and are frequently 
 absent even at the more advanced ages, but they are so often met 
 with in the brains of adult and old persons that many anatomists 
 regard them as normal structures. 
 
 Of the Spinal Cord. — The spinal cord is somewhat cylindrical in 
 shape, slightly flattened on the anterior and posterior surfaces. Its 
 anatomical limits are, the occipital plane above, and a point ranging 
 in different subjects between the last dorsal and second lumbar ver- 
 tebra below. It tapers to its inferior extremity, which lies concealed 
 among the leash of nerves which comes off from its lumbar region, 
 the Cauda equina. Superiorly the spinal cord is separated from the 
 medulla objongata by the decussating fibres of the anterior pyramids. 
 
 In the cervical and lumbar regions the cord exhibits di-stinct swell- 
 ings, of which the cervical is the larger. The cervical swelling ex- 
 tends from the third cervical to the third dorsal vertebra, the lumbar 
 one commencing about the ninth or tenth dorsal vertebra, and not 
 extending beyond the space corresponding to two vertebrae. These 
 enlargements correspond to the situations at "which the large nerves 
 to the extremities emerge, in conformity with a law that the phy- 
 sical development of any portion of the cord is in the direct ratio 
 of the sensitive and motor power of the parts which it supplies with 
 nerves. 
 
 The spinal cord is divided alojrtg the median plane by an anterior 
 and posterior fissure into two equal and symmetrical portions, of which 
 one may be called the right, the other the left spinal cord. A trans- 
 verse bilaminate partition, extending throughout the entire length of 
 the cord, separates these fissures, and serves to unite its lateral por- 
 tions. This partition is composed of a vesicular or gray and a white 
 or fibrous lamina or commissure, the gray being situate posteriorly. 
 When examined in a transverse section, the anterior fissure appears 
 evidently wider but of less depth than the posterior- ; it is penetrated 
 by a distinct fold of pia mater ; its floor is formed by the white com- 
 missure, which has a cribriform appearance, from being perforated by 
 numerous blood-vessels. The posterior fissure is much more delicate 
 than the anterior, and about the middle of the cord its existence may 
 be doubted; its depth, in the upper part of its course, is equal to fully 
 
234 INNERVATION. 
 
 one half of the thickness of the cord. A single, very delicate layer 
 of pia mater enters it and penetrates to its floor, which is formed by 
 the gray commissure. 
 
 On further examination of a transverse section of the cord, we ob- 
 serve that the interior of each half of it is occupied by vesicular mat- 
 ter, disposed somewhat in a crescentic form. The concavity of this 
 crescent is directed outwards: its anterior extremity, ov horn, is thick, 
 but its margin has a dentated or stellate appearance, which is very 
 distinct in some situations. The gray matter is prolonged backwards 
 in the form of a narrow horn, which reaches quite the surface of the 
 cord, near which it experiences a slight enlargement. This enlarge- 
 ment appears to consist of a gray matter, paler and softer than that of 
 the remainder of the crescent, which has been distinguished by Ro- 
 lando as substantia cinerea gelatinosa, surrounded by a layer of red- 
 dish-brown substance (see fig, 66, d., where the central part of the 
 posterior horn is pale). An exact symmetry exists between the gray 
 crescents of opposite sides, so that the description of one is applicable 
 to the other. 
 
 The prolongation of the posterior horn of each gray crescent to the 
 surface divides each half of the cord into two portions. All that is 
 anterior to the posterior horn is called the antero-lateral column : and 
 this comprehends the white matter forming the sides and front of tjiat 
 half of the cord, limited in front by the anterior fissure, and posteri- 
 orly by the posterior horn. The posterior column is situated behind 
 the posterior horn of gray matter, and is separated from its fellow of 
 the opposite side by the posterior fissure. The antero-lateral columns 
 are united across the middle line by the anterior or white commissure ; 
 the gray crescents, by the posterior or gray commissure ; while the 
 posterior columns are not connected, except where the posterior fis- 
 sure is imperfect or deficient. 
 
 In the different regions of the cord great variety exists as regards 
 the quantity of gray and white matter, and the disposition of the 
 lateral portions of the former. There seems to be a much greater 
 proportion of gray matter to white in the lumbar, than in the cervical 
 or dorsal region of the cord. In the cervical region the crescentic 
 portions are small, and the white matter is abundant. That portion 
 of the white substance which is placed between the posterior gray 
 horns, is augmented by the existence of two small colunms (posterior 
 pyramids), which extend from the medulla oblongata into this region. 
 In the dorsal region the gray matter is at its minimum of development, 
 and the white matter is likewise small in quantity. The diminution 
 in the qiaantity of the latter appears more striking as affects the antero 
 lateral, than the posterior columns. In the lumbar region both the 
 horns of the gray matter are manifestly thicker, and the stellate cha- 
 racter of the anterior horn is well marked. Towards the inferior ex- 
 tremity of the cord the white matter appears gradually to cease, leaving 
 the gray to form the principal constituent, until in the commencement 
 of the filiform process it is found alone (fig. 66). 
 
 The roots of the spinal nerves emerge from the cord on each side 
 
THE SPINAL CORD. 
 
 235 
 
 along two lines which are separated by the ]igaraentun:i dentatum. 
 The posterior line corresponds to the margin of the posterior horn of 
 gray matter, the anterior one is placed about mid- 
 way between it and the anterior fissure. When Fig. 66. 
 the roots of the nerves have been carefully re- 
 moved, their points of emergence are indicated 
 by two series of foramina in linear sequence on 
 each side, but there is no appearance of fissures 
 in those situations. The roots of the nerves pe- 
 netrate the substance of the cord, and are chiefly, 
 if not entirely, connected with the antero-lateral 
 columns. 
 
 The fibrous matter of the cord consists of some 
 fibres which pass in a longitudinal direction, 
 which are chiefjy superficial or contained in the 
 posterior columns, and of others which are oblique 
 or transverse, and' are found in the antero-lateral 
 columns, or in the white commissure, which is 
 wholly composed of such fibres. Am'ong the 
 elements of the gray matter fibres are found in 
 great numbers, the direction of which is pro- 
 bably for the most part oblique or transverse, as 
 considerable portions of them may be seen so 
 running, when a piece of gray matter, cut 
 transversely, is examined under the microscope. 
 The gray matter of the cord is disposed in two 
 longitudinal columns, the shape of which in the 
 several regions of the cord is represented in the 
 above transverse sections (fig. 66). These co- 
 lumns extend from the lower part of the medulla 
 oblongata, with the gray matter of which they 
 are continuous. The aspect of their surfaces is 
 outwards and inwards. That which looks in- 
 wards is convex, and is united to the corre- 
 sponding surface of the opposite side by the gray 
 commissure, which is a vertical plane, with sur- 
 faces looking directly forwards and backwards. 
 At the inferior extremity of the cord these columns 
 gradually taper to a point, and coalesce as the 
 white matter diminishes. 
 
 Caudate and spherical vesicles, imbedded in 
 their usual granular matrix, exist in the gray 
 matter of the cord at all situations, in the horns 
 as well as in the commissure. The caudate 
 vesicles are most numerous and distinct in the anterior horn, and at 
 the root of the posterior one. The rest of the posterior horn and 
 the gelatinous substance resemble very closely in structure the gray 
 matter of the convolutions of the brain. When very thin transverse 
 sections are examined with low powers, a good general view of the 
 relative disposition of the gray and white columns is obtained, but 
 
 E 
 
 Transverse sections ,of 
 the spinal cord: — a. Im- 
 mediately b_elow the de- 
 cussation of the pyramids. 
 B. At middle of cervical 
 bulb. c. Midway be- 
 tween cervical and lum- 
 bar bulbs. D. Lumbar 
 bulb. E. A-ninch loiyer. 
 F. Very near the lower 
 end. a. Anterior surface. 
 p. Posterior surface. The 
 points of emerg:ence of 
 the anteripr and posterior 
 roots of the nerves are al- 
 so seen. 
 
236 
 
 INNERVATION. 
 
 Fig. 67. 
 
 ■we gain no satisfactory inforination as regards the relation of the 
 elements of these columns (fig. 67). Stilling and Wallach's plates 
 
 accord generally with the re- 
 sults of our own examina- 
 tions, but we cannot admit 
 the accuracy of their interpre- 
 tation of some of the appear- 
 ances which they have wit- 
 nessed and delineated. 
 
 In such a section as that 
 just described, the distinc- 
 tion of gray and white mat- 
 ter is very obvious. From 
 the surface of each horn of 
 the former several lines, of 
 the same colour and general 
 appearance as the central 
 mass, pass, in a radiating 
 manner, towards the surface 
 of the cord and to the sur- 
 face of the fissures (fig. 67). 
 These lines, according, to 
 Stilling and Wallach, are 
 continuous with the roots of 
 the nerves, and are nerve- 
 tubes proceeding from the gray matter to form these roots. Their 
 existence, however, in sections made in situations intermediate to the 
 points of emergence of the nerves, shows that this explanation can- 
 not be the true one. Moreover, they radiate over a surface much 
 more extensive than that from which the roots take their rise, and' 
 several pass to that part of the surface of the cord which bounds the 
 fissures, and from which it is impossible that they could reach the point 
 of emergence of either root to contribute to its formation. It is not 
 improbable, however, that they may be processes of the gray matter 
 prolonged toward the surface, to which blood-vessels may pass from 
 the pia mater.* 
 
 We observe in the gray matter numerous nerve-tubes of various 
 size passing among its elements in different directions. Besides these, 
 the branching processes from the caudate vesicles are found here : 
 these processes differ from the nerve- tubes in the absence of the white 
 substance of Schwann, in their grayish colour, in their branching, and 
 in a certain minutely granular texture. Numerous extremely minute 
 fibres, perfectly transparent in texture, may be traced to be continu- 
 ous with the finer subdivisions of these processes (fig. 56, p. 198). 
 Fibres of the same appearance are occasionally found among the tubes 
 of the white substance of the spinal cord; their connection with those 
 of the gray matter is unknown. 
 
 Transverse section of hunxa-n spinal cord, close to 
 the third and fourth cervical' nerves ; magnified ten 
 diameters, (from Stilling;)— /. Posterior columns, ii. 
 Gelatinous substance of the posterior horn. k. Pos- 
 terior root: I. Supposed anterior roots, a. Anterior 
 fissure, c. Posterior fissure, b. Gray commissure, in 
 which a canal is contained, which, according to these 
 writers, extends through the length of the cord. g. 
 Anterior horn of gray matter containing caudate Vesi- 
 cles, e. Antero-lateral column (from & toa). 
 
 • Mr. Smee has lately exhibited to us some well-injected preparations, in which 
 these lines are shown to contain vessels. 
 
WEIGHT OF THE BRAIN. 237 
 
 Capillary blood-vessels are met with in great numbers ramifying 
 in the. gray matter. They are much more numerous in this than in 
 the white matter, and the observer should be careful not to confound 
 the most minute of them with some of the fibrous elements above de- 
 scribed. 
 
 So far as our present knowledge of the minute anatomy of the 
 spinal cord extends, it is favourable to the supposition that the spinal 
 nerves derive their origin, at least partly, from the gray matter. The 
 longitudinal fibres of the cord may consist in part of fibres continuous 
 with those of the brain or cerebellum, and in part of commissural 
 fibres, serving to unite various segments of the cord with each 
 other, or to connect some part or parts of the encephalpn with them. 
 Those fibres which may be regarded as strictly spinal are probably 
 oblique in their course, forming their connection with gray matter at 
 a point higher up in the cord than that at which they emerge from 
 its surface, and may be readily confounded with the longitudinal 
 fibres when their course is long. Other oblique or transverse fibres 
 probably do not emerge from the cord, but connect the segments 
 of oppcsite sides, forming a transverse commissure. So that four 
 classes of fibres, each different in function, may be considered to ex- 
 ist in the cord. 1. Spinal fibres, oblique or transverse, which pro- 
 pagate nervous power to or from the segments of the cord itself. 
 2. Encephalic fibres, longitudinal, the paths of volition and sensation, 
 which connect the spinal cord with the various segments of the en- 
 cephalon. 3. Longitudinal commissural fibres. 4. TVansverse com- 
 missural fibres. 
 
 Of the encephalon. — The brain or encephalon is that mass which 
 is contained within the cranial cavity. The plane of the occipital 
 foramen separates it from the spinal cord, inasmuch as that plane 
 would about pass through the inferior extremity of the medulla ob- 
 longata. 
 
 Four segments are obviously distinguished in the encephalon. 1. 
 1h& medulla oblongata. 2. "Yh^ cerebrum. 3. The cereWiwrn. Some 
 fibres of the medulla oblongata extend to the cerebrum, and some to 
 the cerebellum. The fourth segment, which is called the mesocephdle, 
 contains fibres passing between all the rest, as well as some connect- 
 ing opposite sides. This constitutes a sort of conflux to the segments 
 above named, and may be compared to a railway terminus, at which 
 several lines meet and pass each other. 
 
 The brain of the adult man weighs about 50 oz., or a little more 
 than 3 lbs. avoirdupois.* This great weight depends mainly upon the 
 cerebrum and cerebullum, the medulla oblongata and mesocephale 
 forming not more than one-tenth of the whole weight. These parts 
 exist in their highest state of development in man. Their size does 
 not appear to be regulated by the physical development of the body, 
 either in man or in the lower animals. Thus the horse, although 
 greatly exceeding the human subject in the size of his body, has a 
 
 * See Keid's Tables. Lond. and Edinb. Monthly Journal of Med. Science. April, 
 1813. 
 
238 INNKRVATION. 
 
 brain considerably inferior. Tiie largest brain of a horse weighs, 
 according to Soemmering, 1 lb. 7 oz., but the smallest adult human 
 brain may be estimated at 2 lbs. 5|- oz. Many other instances might 
 be cited, of animals of great bulk, with brains weighing considerably 
 less than that of man. The brains of the elephant and the whale, 
 however, .although inferior to it in general organization, are absolutely 
 heavier than that of man. That of an elephant, dissected by Sir Astley 
 Cooper, had a weight of 8 lbs. 1 oz. ; and Rudolphi found the brain 
 of a whale, 75 feet long, {Balcmamydicetus,) to weigh 5 lbs. 10|^ oz. 
 Yet how inferior must be the development of the brain in these stu- 
 pendous animals relatively to the whole body, if, with their enormous 
 superiority of bulk, their brains exhibit so little excess of weight over 
 that of man! 
 
 Even among men there does not appear to be any fixed relation 
 between the bulk of the body and that of the brain. A large man 
 has by no means necessarily a large brain, and it often happens that 
 persons of small stature have the brain above the average size. In 
 women the brain is generally lighter than in men. Dr. John Reid 
 assigns an average difference of 5 oz. 11 dr. in favour of the male 
 brain. Yet this difference is scarcely proportionate to the general 
 inferiority of organization and of size of the female to the male. 
 
 It is impossible to explain the great superiority of the human br^in, 
 both in organization and in the absolute quantity of nervous matter 
 which it contains, without admitting its connection with the mind, 
 and the influence exerted upon its nutrition and growth by that 
 immaterial principle. The men of greatest intellectual power are 
 those who possess the largest brains. Cuvier's brain, as stated by 
 Tiedemann, weighed 4 lbs. 11 oz. 4 dr. 30 grs. troy; and that of Du- 
 puytren 1 oz. 4 dr. 30 grs. less. On the other hand, the brain of an 
 idiot weighs scarcely more than that of the horse mentioned above. 
 Tiedemann found the brain of an idiot, fifty years old, to weigh 1 
 lb. 8 oz. 4drs. ; and that of another, forty years old, lib. 11 oz. 4 
 drs. In advanced age, when the mental faculties have declined, 
 the brain generally experiences a decrease of size ; there are many, 
 however, who preserve their intellectual vigor to a very advanced 
 period of life, and in such persons, doubtless, the brain does not ex- 
 hibit any evidence of shrinking. It is during the period of greatest 
 mental activity and power that the brain acquires and maintains its 
 highest point of development, that is, between the- ages of twenty and 
 sixty. 
 
 Whilst there is an evident connection between a large quantity of 
 cerebral matter, and a highly developed intellect, the quality of the 
 mind and that of the brain substance may also be supposed to have a 
 close relation to each other. For great power of action a large mus- 
 cle is needed, but for vigorous and well-adjusted muscular movement 
 a certain quality of fibre is also necessary to give full scope to the 
 nervous power (see pp. l«75-7-79). It is impossible to determine 
 what this peculiarity in quality is, but some idea of the great influence 
 which it may possess in the exercise of the two great vital forces, the 
 muscular and nervous, may be gained from comparing the energy and 
 
THE MEDULLA OBLONGATA. 239 
 
 action of a well-bred horse with those of one which, in the language 
 of the turf, shows little or no breeding. The actual amount of mus- 
 cular or nervous fibre may be the same in both, or it may be less in 
 the horse of good breeding than in the other, yet the former does his 
 work and endures fatigue better. 
 
 The nature of the connection between the mind and nervous matter 
 has ever been, and must continue to be, the deepest mystery in phy- 
 siology; and they who study the laws of Nature, as ordinances of 
 God, will regard it as one of those secrets of his counsels " which 
 Angels desire to look into."* The individual experience of every 
 thoughtful person, in addition to the inferences deducible from re- 
 vealed Truth, affords convincing evidence that the mind can work 
 apart from matter, and we have many proofs to show that the neglect 
 of mental cultivation may lead to an impaired state of cerebral nutri- 
 tion ; or, on the other hand, that diseased action of the brain may in- 
 jure or destroy the powers of the mind. These are fundamental truths 
 of vast importance to the student of mental pathology as well as of 
 physiology. It may be readily understood that mental and physical 
 development should go hand in hand together, and mutually assist 
 each other; but we are not, therefore, authorized to conclude that 
 mental action results from the physical working of the brain. The 
 strings of the harp, set in motion by a skillful performer, will produce 
 harmonious music if they have been previously duly attuned. But if 
 the instrument be out of order, although the player strike the same 
 notes, and evince equal skill in the movements of his fingers, no- 
 thing but the harshest discord will ensue. As, then, sweet melody 
 results from skillful playing on a well tuned instrument of good con- 
 struction, so a sound mind, and a brain of good development and 
 quality, are the necessary conditions of healthy and vigorous mental 
 action. 
 
 Medulla oblongata. — Of the segments of the encephalon above 
 enumerated, the medulla oblongata is that which is more immedi- 
 ately connected with the spinal cord, and through which the brain 
 is brought into conimunicalion with the other vital organs and with 
 most of the peripheral parts. It is, therefore, truly "the link which 
 binds us to life." In form and general anatomical characters, it 
 very much resembles the spinal cord, with which it is continuous, 
 standing in the same relation to it as the capital to the shaft of a 
 column. 
 
 In the sense in which we here speak of it, the medulla oblongata 
 is limited above by the mesocephale; but its constituent fibres ex- 
 tend beyond that segment, and form important connections with the 
 rest of the brain. It is completely contained within the cranial cavity, 
 its lowest part being just above the level of the plane of the occipital 
 foramen. 
 
 The size of the medulla oblongata is in the direct ratio of that of 
 the nerves which proceed from it. Hence it is very much larger, both 
 
 * The admirable chapter in Bp. Butler's Analogy "Of a Future Life," cannot be 
 too attentively studied in reference to this subject. 
 
240 
 
 INNERVATION. 
 
 absolutely and relatively, in some of the lower animals than in man : 
 in many of them it forms the largest of all the segments of the ence- 
 phalon, while in man it is much the smallest. 
 
 In the medulla oblongata there is the same symmetry of arrange- 
 ment which we have noticed in the cord. An anterior and posterior 
 fissure divide it into two equal and symmetrical portions. The pos- 
 terior fissure is deep and narrow, and is continuous with that of the 
 cord. The anterior fissure is wider and less deep, and is. separated 
 from the same fissure of the cord by certain fibres which cross obliquely 
 from each side in its kwer third, decussating each other. These fibres 
 are called the decussating fibres of the anterior joyrami&, and form, 
 very fitly, an anatomical demarkation between the medulla oblongata 
 and the spinal cord. 
 
 The floor of the anterior fissure is formed by a layer of fibrous 
 matter which is rendered cribriform by the orifices of the numerous 
 bloodvessels which penetrate it. This consti,tutes a commissure of 
 transverse fibres, similar to that described in the spinal cord. The 
 posterior fissure extends to the posterior surface of this commissure, 
 there being no such transverse lamina of vesicular matter in the me- 
 dulla as in the cord. 
 
 When the pia mater has been carefully removed from the surface 
 of the medulla oblongata, certain grooves are seen which indicate a 
 subdivision of the organ, which is convenient for the purpoSfesof 
 description. In front are the anterior pyramids {corpora pyramidalia 
 antica) separated from each other along the middle line by the ante- 
 rior fissure. External to each anterior pyramid there is an oval pro- 
 minence surrounded by a superficial groove, which in some instances 
 is partially interrupted by some arciform fibres which cross it at its 
 lower part. These projections are the oli- 
 vary bodies. External to these, and forming 
 the lateral and a great part of the posterior 
 region of the medulla oblongata, are the res- 
 tiform bodies', two thick columns of fibrous 
 matter, which are -separated from each other 
 along the middle line by two slender columns, 
 the posterior pyramids. These last bound the 
 posterior fissure. 
 
 The anterior pyramids are bundles of 
 fibrous matter which extend between the 
 antero-lateral columns of the cord and the 
 cerebral hemispheres. Below the mesoce- 
 phale the fibres are compactly applied to each 
 other so as to form on each side of the me- 
 dian line a column of white matter, the trans- 
 verse section of which has more or less of a 
 triangular outline. Traced upwards, the 
 pyramids are found to pass into the meso- 
 cephale above its inferior layer of transverse 
 fibres, the pons Varolii. At its entrance 
 into this part of the brain each pyramid 
 
 Fig. 68. 
 
 Front view of the medulla ob- 
 longata :— y, p. Pyramidal bo- 
 (lieB, decussating , at d. o, o. 
 Olivary' bodies, r, r, Reetiform 
 bodies, a. a, Arcifprm fibres, 
 f. Lower fibres of the Pons Va- 
 rolii. 
 
THE MEDULLA OBLONGATA. 241 
 
 experiences a slight but well-marked constriction, but immediately 
 expands again ; and its fibres in their further course upwards gra- 
 dually diverge, and contribute to form the inferior lamina of the crus 
 cerebri. 
 
 In their ascent through the mesocephale the fibres of the pyramids 
 are crossed at right angles by some deep transverse fibres on differ- 
 ent planes which belong to the same system as those which constitute 
 the pons. With 'these fibres those of the pyramids interlace. Ve- 
 sicular matter is deposited in the intervals between the more deeply 
 seated fibres, from which probably some fibres take their origin, and 
 join the pyramids at their emergence from the pons, to form the in- 
 ferior layer of the crus cerebri. 
 
 Traced downwards, the fibres of each anterior pyramid pass in 
 greater part backiaards.as well as downwards, sinking into the ante- 
 ro-lateral column of the cord of the opposite side (fig. 68, d), whilst 
 a small portion of them, those, namely, which constitute the outer 
 margin of each pyramid, pass to the column of the same side. Other 
 fibres of these bodies do not pass down into the spinal cord at all, but 
 taking a curved course around the inferior extremity of each olivary 
 body they ascend towards the cerebellum, forming the arciform fibres. 
 Or, if the description be pursued in an opposite direction, each pyra- 
 mid may be stated to be composed of some fibres from the antero- 
 lateral spinal column of its own side, and of others which greatly 
 exceed the latter in number, from the antero-lateral column of the 
 opposite side, and it is connected with the restiform body of the same 
 side by the arciform fibres. 
 
 The decussation takes place by from three to five bundles of fibres 
 from each pyramidal body. In separating the margins of the anterior 
 fissure, these fibres are found to interrupt its continuity with the an- 
 terior -fissure of the medulla oblongata, and, therefore, may be con- 
 veniently referred to as a boundary between the medulla oblongata 
 and the spinal cord. ' 
 
 This decussation has great interest in reference to the explanation 
 of the phenomena of diseased brain. It. is well known that lesion of 
 one hemisphere of the brain when sufficiently extensive to cause pa- 
 ralysis, will induce that paralysis on the opposite side of the body. 
 And, although a very few exceptions have been recordedj this is so 
 constant that it must be regarded as a law, that the influence of each 
 hemisphere is rather upon the opposite half of the body than on that 
 of its own side. It is not, however, meant that the hemisphere has 
 no influence on the same side of the body. On the contrary, it is 
 most probable that it does exert some influence from the partial con- 
 nection of each anterior pyramid with the antero-lateral column of the 
 spinal cord on the same side. Now the decussation, above described, 
 obviously suggests an explanationof this phenomenon, which is among 
 the most interesting that anatomy can offer. In confirmation of this 
 statement it may be remarked, that lesion of one side of the cord, 6e- 
 low the decussation, affects the same side of the body, and that alone ; 
 whilst disease of a paralyzing influence, wherever it occurs above the 
 decussation, affects the opposite half of the body. The exceptions 
 
242 
 
 INNERVATION. 
 
 Fig. 69. 
 
 to this rule are too anomalous and few to invalidate the explanation 
 so long adopted. 
 
 The restiform bodies form the lateral and posterior part of the me- 
 dulla oblongata. They ,are cylin- 
 drical in form. Bel6w they are 
 distinctly continuous with the an- 
 tero-lateral and posterior columns 
 of the cord. As they ascend, they 
 diverge and leave a considerable 
 space between them, which is the 
 fourth ventricle. Each restiform 
 body passes into the corresporrding 
 hemisphere of the cerebellum, form- 
 ing a considerable portion of the 
 crus, the stalk of fibrous matter 
 around which the hemisphere is 
 formed. These bodies are, there- 
 fore, the borid of connection be- 
 tween the cerebellum and the 
 spinal cord, for which reason they 
 have been appropriately designated 
 processus cerebelli ad medullam ob- 
 longatam. 
 
 The posterior median fissure is 
 bounded on each side by a small 
 column, not exceeding one-eighth 
 of an inch in breadth. These co- 
 lumns are called \he posterior pyra- 
 midal bodies, Their outer limit and 
 line of demarkation;from the rest- 
 iform bodies is indicated by a superficial groove, along ■which a 
 separation of the two structures readily takes place, in a preparation 
 previously hardened in spirit. 
 
 The olivary bodies are oVal projections on each side of the anterior 
 pyramids. When the latter have been carefully removed, it may be 
 demdnstrated that these bodies are continuous with the central part of 
 the medulla oblongata. They are coated on the outside with fibrous 
 matter, within which is a folded lamella or capsule of ■ vesicular sub- 
 stance, enclosing a white nucleus. By slicing off a layer of this body 
 even with the surface of the medulla, the capsule may be seen dis- 
 posed as a wavy line, surrounding an oval space of white matter. If 
 examined in transverse section,. this wavy line of vesicular matter is 
 still apparent, but it is incomplete behind and within; and the same 
 may be observed on a vertical section of the olivary body. This 
 lamina is called the corpus dentatum. 
 
 When the pyramids are very largely developed these oval projec- 
 tions on the surface of the medulla oblongata do not appear. Hence 
 the olivary eminences are peculiar to the human subject, and some of 
 the monkeys. 
 
 On tracing the olivary bodies downwards, they are found to ap- 
 
 Postenor view of the medulla oblongata: 
 —pp. Posterior pyramids, separated by the 
 posterior fissure, rr, Restiform bodies, com- 
 
 fiosed of cc, posterior columns, and dd, 
 ateral part of the antero-lateral columns of 
 the cord. aa. Olivary columns, as seen on 
 the floor of the foUTth ventricle, 'separated 
 by s, the median fissure, and c,rossed by 
 some fibres of origin of nil, the seventh pair 
 of nerves. 
 
THE MEDULLA OBLONGATA. 243 
 
 proximate towards each other, the anterior pyramids which separate 
 thern gradually diminishing in breadth, and they apparently terminate 
 by becoming continuous with the antero-lateral columns of the spinal 
 cord. 
 
 The olivary bodies, though separated from the margin of the pons 
 Varolii by a distinct depression, may be traced upwards through the 
 mesocephale along with the central substance of the medulla ob- 
 longata {fasciculi innominati of Cruveilhier), forming a considerable 
 portion of the superior layer of each cms cerebri, and apparently 
 becoming continuous with the optic thalamus and quadrigeminal 
 bodies. , . 
 
 The olivary bodies and the central spbstance of the medulla oblon- 
 gata may be described as connecting the spinal cord with the quadri- 
 geminal bodies and the optic thalami. 
 
 It seems highly probable that the olivary bodies constitute the es- 
 sential portion or nucleus of the medulla oblongata; that on whichits 
 power as an independent centre depends. Strong support to this view 
 is derived from the important fact, that these bodies-and the central 
 portion of the medulla oblongata, with which they are directly con- 
 tinuous, contain that intermixture of vesicular and fibrous matter 
 which constitujtes the main character of a nervous centre. 
 
 If this be correct, the anterior and posterior pyramids, and the rest- 
 iform bodies, must be regarded as consisting chiefly of fibres which 
 pass from the spinal cord to the cerebrum, or cerebellum, and not 
 essentially concerned in the formation of the medulla oblongata. 
 The fibres of these bodies are in fact mainly commissural; the an- 
 terior pyramids serving to connect the cerebral hemispheres to the 
 spinal cord, the restiform bodies connecting the cerebellum to it, 
 and the posterior pyr-amids being the means of connection posteriorly 
 between the medulla oblongata and the cervical and dorsal regions 
 of the spinal cord. But the olivary bodies and the central matter of 
 the medulla are directly continuous with certain principal gangliform 
 masses of the brain, the optic thalami and quadrigeminal bodies, and 
 by their prolongation upwards form a large portion of the crura of the 
 brain. 
 
 From the description of the minute structure of the medulla ob- 
 longata by Stilling, founded upon investigations conducted in the 
 same way as those on the spinal cord, it would appear that nume- 
 rous transverse fibres pass into the central and posterior part of the 
 medulla. It is not unlikely that many of these so called fibres may 
 be bundles of nerve tubes, but it is also highly probable that many 
 of them are blood-vessels, which pass in great numbers into the cen- 
 tral substance of the medulla. The same mode of cbnnection which 
 exists between the roots of the nerves and the spinal cord, whatever 
 that may be, will no doubt be found to prevail in the medulla ; and 
 as several important nerves emerge from' this portion of the ence- 
 phalon, it seems very likely that their fibres should penetrate to its 
 central part to form a connection with its gray matter. This ques- 
 tion^ however, is not to be decided by the use of low powers of 
 the microscope, such as Stilling employs; nor have our trials with 
 
244 
 
 INNERVATION. 
 
 higher ones as yet led to any information sufficiently specific to ena- 
 ble us to make a positive statement respecting the points in question. 
 There is nothing in the results of Stilling's researches which does not 
 confirm that which previous dissections, by coarser meains of obser- 
 vation, had pointed Out^namely, that the restiform and pyramidal 
 
 Fig. 70. 
 
 
 Transverse sjection of the ineduUa oblongata through the lower third of the olivary bodies. (From 
 Stilling.) Magnified 4 diameters. ■ ' 
 
 a. Anterior fissure, h. Fissure of the calamus scriptorius. c. Raphfi. d. Anterior columns. 
 e. Lateral columns. /. Posterior columns, g. Nucleus of the hypoglossa;! nerve, containing large 
 vesicles. A. Nucleus of the vagus nerve, i, i. (relatinous substance, h^h. Roots of the vagus 
 nerve. I.. Roots of the hypoglossal, or ninth nerve, m. A thick bundle of white longitudinal fibres 
 connejDted with the root of the vagus, n. Soft column (Zctftstrang-, Stilling), o. .Wedge-like column 
 (ifeefoirang", Stilling), y. Transverse and arciform fibres, g. Nucleus of the olivary bodies, r. The 
 large nucleus of the pyramid. 5, s,s. The small nuclei of the pyramid, w. A mass of gray substance 
 near the nufeleus of the olives [OHven-Nebenkern). w, g, r, are traversed by numerous fibres pass- 
 ing in a transverse semicircular direction, v, w. Arciform fibres. ». Gray fibres. 
 
 bodies are composed in great part of fibres, taking a longitudinal 
 course, -while the central portion contains both the vesicular and 
 fibrous nervous elements. The fibres of the latter, according to Stil- 
 ling, taking chiefly, if not exclusively, a transverse direction. 
 
 There is no evidence of any interchange of fibres between the rest- 
 iform bodies, nor between the posterior pyramids of the right and 
 left sides, such as has been noticed between the anterior pyramids 
 in the description of their decussating fibres. The central or olivary 
 columns of the medulla oblongata, however, have a very intimate con- 
 nection with each other, along the mesial plane, apparently by fibres 
 passing from one to the other. 
 
THE CEREBELLUM. 245 
 
 When the medulla oblongata is.divided vertically along the median 
 plane, a series of fibres, is seen to form a septum between- its right and 
 left half. These fibres take a direction from before backwards, and 
 appear to connect themselves with the posterior olivary columns. 
 They are limited inferiorly by the decussating fibres. Cruveilhier 
 proposes for them the name antero-posterior fibres ; they appear to be- 
 long to the same sjstem as the arciform fibrest 
 
 Of the cerebellum. This segment of the encephalon is situated 
 above and behind the medulla oblongata in a distinct compartment of 
 the cranium, which has for its roof the tentorium cerebelli. It bears 
 to the cerebrum in point of weight about the proportion 1 : 8, and to 
 the entire encephalon, 1: 10. 
 
 The cerebellum consists of a central and of two lateral portions. 
 The former, also called the median lobe, is the primary part; it is the 
 only part of the organ which exists in fishes and reptiles ; the lateral 
 portions or hemispheres are additions to this, and denote an advance 
 in development.. It is in bii'ds that these are first found ; they are 
 most highly developed, in mammals, and attain their maximum in 
 man. 
 
 Upon removing the pia mater from the surface of the cerebellum, 
 we observe its arrangement in numerous thin lamellse, which are at- 
 tached to a central column of fibrous matter. A vertical section of 
 either hemisphere serves well to display their structure. A series of 
 planes of fibrous matter become detached from the central white 
 column, each plane separating from it at a different angle. These 
 planes are in number about ten, counting those on the upper as well 
 as the under surface. Those situated in front are detached at a right 
 angle, the posterior ones at an acute angle. Each plane forms the 
 centre of a lobule, and as it proceeds outwards secondary planes^re 
 detached from it, and from these again others separate. These se- 
 condary and tertiary planes are clothed by a layer of vesicular matter, 
 which also invests the primary planes at the angles of separation from 
 the principal central column. 
 
 We have described each primary plane as forming the central por- 
 tion, or stem of a lobule. Each lobule is circumscribed and separated 
 from those in immediate relation to it, by a fissure which extends to 
 the principal column. The lobules are composed of laminae which 
 derive their fibrous matter from the central stem. 
 
 Thus the substance of each hemisphere of the cerebellum is pene- 
 trated by a number of fissures, easily traced by following ~ the pia 
 mater, which lines them. These fissures are divisible into two classes, 
 primary and secondary. The primary penetrate to the principal cen- 
 tral column, and isolate the lobules ; the secondary separate the 
 lamellae of which each lobule is composed. The deepest and most 
 remarkable of the former corresponds to the posterior margin of each 
 hemisphere, passing in the horizontal plane forwards and separating 
 the posterior laminae into a superior and inferior set. 
 
 The structure of the median lobe is essentially the same as that of 
 the hemispheres. A stem of fibrous matter, continuous with the pro- 
 cessus cerebelli ad testes, constitutes the central column, and planes 
 
246 
 
 INNERVATION. 
 
 radiate from it in the same manner as in the hemispheres. Lobules 
 are formed around these planes, and the aggregate of those on the 
 superior surface of the median lobe constitutes what is called the 
 superior vermiform process ; and that of the inferior ones, the inferior 
 vermiform process. The lobules of the median lobe have a distinct 
 continuity of substance with those of the hemispheres on each side, 
 and thus the entire lobe becomes a medium of connection, or a com- 
 missure between the hemispheres ; nevertheless, the similarity of its 
 structure to that of the hemispheres, and its existence in the animal 
 series without the lateral portions, denote that it exercises an inde- 
 pendent function. 
 
 Within the central stem of each hemisphere of the cerebellum, tiie 
 fibrous matter is partially interrupted by a peculiar arrangement of 
 
 Analytical diagram of the encephalon — in a vertical section. (After Mayo.) 
 s. Spinal cord. r. Reetiform bodies passing to, c, the cerebellum, d. Corpus dentatum of the 
 cerebellum, o. Olivary body. /. Columns conti^iuous with the. plivary bodiea and central part of 
 the medulla oblongata, and ascending to the tubercular quadrigemina and optic thalami. p. An- 
 terior pyramids, u. Pons Varolii, n, 6. Tubercula quaxlrigemina.' g-. Geniculate body of the optic 
 thalamus. «. Processus oerebelli ad testes, a. Anterior lobe of the brain, j. Posterior lobe of the 
 brain. 
 
THE CEREBELLUM. 247 
 
 the vesicular substance, called by Vicq d'Azyr corpus dentatum (fig. 
 71, d). This is only found in the inner half of the stem, at about a 
 quarter of an inch from the origin of the crus. It may be demon- 
 strated by making a vertical section through the cerebellar hemisphere, 
 leaving two-thirds of its substance to the outside of the section. The 
 surface of the section presents at the situation above described a re- 
 markable layer or capsule of gray matter, surrounding ^in great part 
 an oval space; the gray layer has an undulating disposition, and is 
 convex towards the surface, but open towards the crus. The precise 
 object of this remarkable structure is not known; but the microscopic 
 investigation of it shows that in it there is a mingling of the elements 
 of the vesicular and fibrous substances. 
 
 The central stem, or criis, around which each hemisphere of the 
 cerebellum is developed, is formed by three bundles of fibres, each 
 on a different plane. These are called its peduncles. Through them 
 the cerebellum forms a connection with other parts of the epcephalon. 
 The superior layer or peduncle is a bundle of fibres which extends 
 to the corpora' quadrigemina, processMS cerebelli ad testes; the middle 
 layer passes to the medulla oblongata, the restiform bodies; and the 
 inferior peduncle consists of transverse fibres {Pons Varolii), which 
 pass to the opposite side, and also form a considerable portion of the 
 mesocephale. 
 
 Lesions of the cerebellum, when so deep seated as to affect the 
 primary planes of fibrous matter or the central stem, have the same 
 crossed effect as those of the cerebellum. This- is not so obviously 
 explicable as the similar instance of the cerebrum, for the cerebellar 
 fibres of the medulla oblongata (restiform bodies) do not' appear to 
 decussate. Yet it seems scarcely necessary, in order to explain the 
 phenomenon, to have recourse to the supposition that they do decus- 
 sate. The close connection between the restiform bodies and the 
 pyramids, by means of the arciform fibres, renders the latter exceed- 
 ingly liable to sympathise with the condition of the former, and, there- 
 fore, prone to propagate the morbid influence to the opposite half of 
 the spinal cord, and through that to the opposite half of the body. It 
 must be borne in mind that some of the fibres of the anterior pyra- 
 mids very -probably derive their origin from the central gray matter of 
 the medulla oblongata, as well as of the mesocephale, and that some, 
 at least, of those which affect the right half of the cord, probably de- 
 rive their origin from the left side of either or both of those segments 
 of the encephalon. That lesion of one hemisphere of the cerebellum 
 may influence the corresponding half of the medulla oblongata, is 
 likely, from the connection which the restiform fibres establish between 
 them. The connection of the cerebellum with the mesocephale is 
 most clearly established by means of the transverse fibres which con- 
 stitute the pons Varolii. 
 
 Respecting the intimate structure of the cerebellum, little is known 
 of a very exact nature. The white stems and plates are fibrous, and 
 consist of multitudes of n&rve-tubes of all sizes, which follow the 
 general direction of each stem or plate. These fibres doiibtless tend 
 principally to propagate the peculiar influence of the cerebellum, to the 
 
248 INNERVATION. 
 
 spinal cord and the raesocephale. Some probably are commissural, 
 as the processus cerebelli ad testes (or cerebro-cerebellar commis- 
 sures), the fibres of the pons, and some of those of the median lobe. 
 Mr. Mayo supposes that others pass between the laminae, but their 
 existence is extremely doubtful. 
 
 The vesicular matter which covers the plates contains the ordi- 
 nary elements, of which, however, the caudate vesicles constitute a 
 principal portion (p. 198). These are so disposed that their processes 
 pass off chiefly towards the circumference, their obtuse extremities 
 being directed towards the laminae. Besides these, there is in each 
 layer of vesicular matter a thin lamina composed of round clear nu- 
 cleus-like particles, which cohere to each other without the interven- 
 tion of any matrix or other connecting substance. Fine nerve-tubes 
 and blood-vessels pass through it. This lamina is intermediate to 
 two which contain nerve-vesicles, one of which is in immediate con- 
 nection with the fibrous matter of the cerebellum, the other with the 
 pia mater. 
 
 Of the fourth ventricle. — The divergence of the restiform bodies 
 in their ascent to the hemispheres of the cerebellum leaves a con- 
 siderable space, which is of a lozenge shape, having its superior 
 angle towards the brain, its lateral angles towards the cerebellar 
 hemispheres, and its inferior angle at the point of separation ^ of 
 the restiform bodies. Along its floor are seen the central or olivary 
 columns of the medulla oblongata, extending upwards to the optic 
 thalami. A fissure, continuous with the posterior median fissure, 
 separates these columns. Some bundles of white fibres, which may 
 be traced to the soft portion of the seventh pair of nerves, cross these 
 bundles nearly at right angles to them and to the fissure (p. 242), 
 and form with the latter the calamus scriptorius, the white fibres con- 
 stituting the barbs of the pen. The roof of this ventricle is formed 
 in front by the anterior laminae of the superior vermiform process, 
 which constitute the valve of Vieussens ; and behind by the inferior 
 vermiform process. A process of pia mater enters it at its inferior 
 angle, just as the choroid plexus penetrates the inferior cornu of the' 
 lateral ventricles of the brain. The reflexion of the lining membrane 
 on the process of pia mater seems to close up the ventricle below, 
 and cut off its direct communication with the subarachnoid space. A 
 canal, which passes through the mesocephale, establishes the com- 
 munication of this with the third venit\c\e, iter a tertio ad quartum 
 ventriculum. 
 
 The fourth ventricle properly belongs to the medulla oblongata. It 
 is, therefore, present in all the vertebrate classes, and is, in point of 
 size, directly proportionate to the medulla itself. 
 
 Of the mesocephale. — -This term, suggested by Chaussier, denotes 
 that this portion of encephalon is the bond of union to the rest, the 
 cerebrum above the medulla oblongata below, and the cerebellum 
 behind. 
 
 The inferior surface of the mesocephale, the pons Varolii, consists 
 of a series of curved fibres, which pass from one crus cerebelli to the 
 other. When the brain lies with its base uppermost, these fibres ap- 
 
THE MESOCEPHALE. 249 
 
 pear to cross over the upward continuations of the anterior pyramids, 
 as a bridge over a stream. Hence the4erm pons was applied to them 
 by Varolius.* The fibres form a series of curves, convex forwards, 
 concave towards the medulla oblongata, the posterior being much 
 less curved than the anterior. At either side they become more 
 closely packed, taper, and form the inferior layer of each crus cere- 
 belli. Along the middle line a groove traverses the surface of the 
 pons from its posterior to its anterior margin, in which the basilar 
 artery usually lies. 
 
 The fibres of the pons are always developed in the direct ratio of 
 the hemispheres of the cerebellum. In animals which have only the 
 median lobe, there is no pons; and when the hemispheres are small, 
 the pons is small likewise. Hence these fibres must be regarded as 
 especially belonging to the cerebellum, and as serving, whatever 
 other office they may perform, to connect the hemispheres of oppo- 
 site sides. They constitute, therefore, the great transverse commis- 
 sure of the cerebellum, and are to the hemispheres of that organ what 
 the corpus callbs'um is to -those of 4he brain. - 
 
 These transverse fibres do not for^i merely a superficial plane, 
 which covers the pyrainids in their upward passage : on the contrary, 
 they fxtend to more than one-half of the depth of the mesocephale, 
 as is appareiit on a transverse section of it. The more superficial 
 fibres simply cross from one side to the other; the deeper-seated ones 
 interlace with those of the pyramids. The fibres are irregularly dis- 
 posed in planes, and vesicular matter is interposed between the more 
 deeply-seated ones. From this gray piatter it is not improbable that 
 some of the fibres of the pyramids may take origin. 
 
 On the superior surface of the mesocephale are the quadrigeminal 
 bodies, {nates and testes,) and beneath these the olivary columns. A 
 slight longitudinal groove separates the quadrigeminal bodies iiito a 
 right and left pair, and a transverse groove indicates their division 
 into an anterior and posterior pair. They are gangliform bodies, of 
 a grayish white colour, containing fibrous and vesicular matter. 
 The anterior {nates) are somewhat elliptical in shape ; they are the 
 larger in man. The posterior (fesfes) are hemispherical, and some- 
 what lighter in colour. These bodies are much more ideveloped in 
 the lower animals than in man. In mammalia only do they exist as 
 four. In birds, reptiles, and fishes, they are only two in number, 
 and are called optic lobes, from their connection with the optic nerves. 
 They are hollow in these classes, but in mammalia they are solid. 
 
 Between each testis and the corresponding hemisphere of the 
 cerebellum, a band of fibrous matter ^extends — processus cerebelli ad 
 te^stern. Each band may be traced into the crus cerebelli of the same 
 side, of which it forms the superior layer, so that its fibres are doubt- 
 less continuous with some, of those which form the white plates of 
 the median and lateral lobes. ,The connection of these processes 
 ■with the testes is more apparent than real. They seem rather to pass 
 beneath them to the optic thalami ; andj therefore, it has been justly 
 
 * The terms dnnular protuberance, isthmus, mcephali, nodus eneephali, are also fre- 
 quently used. 
 
250 INNERVATION. 
 
 remarked, they might be more appropriately named processus cerehelli 
 ad cerebrum. The valve of Vieussens occupies the interval between 
 these processes. This layer evidently results from the spreading out 
 of some of the anterior lamellae of the superior vermiform process. 
 
 From the preceding description, it will appear, as before stated, 
 that the stem of fibrous matter which forms the crus cerebelli derives 
 its fibres from, or is continuous with, three planes of fibrous matter ; 
 the highest, or most superficial, being the processus cerebelli ad tes- 
 tem; the second, or middle, the restiform body ; and the inferior the 
 fibres of the pons. By the first, the cerebellum and cerebrum are 
 connected ; by the' second the cerebellum is connected with the- me- 
 dulla oblongata ; and by the third, each hemisphere is brought into 
 union with its fellow, and with the mesocephale. Foville assigns 
 other fibres as constituents of the crura cerebelli, which he describes 
 as expansions connected with the fifth and auditory nerves. 
 
 The crura cerebelli seem to emerge from the posterior angles of 
 the mesocephale. From its anterior part there proceed upwards, 
 with a slight divergence, two similar processes, of considerable 
 thickness, which enter each hemisphere of the brain, and upon which 
 each of those masses rests, as a- mushroom upon its stalk. 
 
 A sej)tum,of a similar kind to that described in the medulla oblon- 
 gata is found in the mesocephale. The fibres derived from the super- 
 ficial layer of the pons pass backwards from the median groove to 
 the posterior and superior part of the mesocephale. 
 
 Of the cerebrum. — The constitution of each crus cerebri may be 
 best understood by examining a transverse section made a little be- 
 yond its emergence from the mesocephale. Upon the surface of such 
 a section three planes of nervous matter may be distinctly observed. 
 The inferior one is composed of fibrous matter, continuous below 
 with that of the mesocephale, and the anterior pyramids, and which 
 passes upwards to the corpus striatum. Immediately above it is a 
 remark'cfcle mass of a peculiarly dark, almost black, matter, which 
 constitutes the well-known locus niger of the crus cerebri. It con- 
 tains large caudate vesicles, abounding in pigment, with nerve fibres 
 passing among them, or originating from them. This black layer 
 does not extend beyond the crus. It forms a partition between the 
 inferior or fibrous layer, and a superior one, which composes the 
 principal portion of the crus. This consists of a grayish matter, 
 continuous with the central portion of the medulla oblongata, or the 
 olivary columns, and passes into the optic thalami. 
 
 The optic thalamus and corpus striatum are large ganglia formed 
 upon the anterior and upper extremity of each crus, and with which 
 the nervous matter of its upper and lower planes appears to be inti- 
 mately connected. The optic thalamus is manifestly continuous with 
 the superior plane, or olivary columns : its colour and texture are 
 quite of the same nature with those of that plane; and when a longi- 
 tudinal section of it is carried down through the mesocephale and 
 medulla oblongata, no distinction is apparent between the ganglioh 
 and the olivary column, so complete is the continuity of texture. 
 The colour of these bodies has been not inaccurately compared to that 
 
OPTIC THALAMUS AND CORPUS STRIATUM. 251 
 
 of coffee largely diluted with milk {cafe, au lait). This arises from 
 the intermixture^of vesicular matter \C-ith a very close interlacement 
 of fibres. . . 
 
 The corpus striatum has a much darker colour than the optic 
 thalamus. When a section of it is made in an, oblique direction, 
 upwards and outwards, it exhibits the striated appearance whence 
 its name is derived. This arises from the passage of the fibres of the 
 inferior layer of the crus into the vesicular matter of the ganglion. 
 The fibres do not at first blend with the vesicular matter, as in the 
 thalamus, but are collected into bundles, which are large; at their en- 
 trance from the crus, but subdivide into much smaller ones, diverg- 
 ing from each other, and radiating through the ganglion in yarious 
 directions, upwards, forwards, outwards, and backwards. 
 , When thin sections of the corpus striatum are examined by trans- 
 mitted Ijght, the smallest bundles of fibres observable in them appear 
 to consist of tubules reduced to their minutest dimensions, and closely 
 united to each other. So compactly applied are they, that very little 
 light passes through or between them. Hence they appear to be dafk 
 masses lying in the substance of the ganglion, and, from their opa- 
 city, it is very difficult to determine their exact relation to the ele- 
 ments of the vesicular matter. Many of the bundles, however, 
 appear to us to attach themselves, at different p^arts of the ganglion, 
 as if around a large vesicle of which, with its nucleus, we have 
 sometimes seen indications at ane extremity, of the dark mass of 
 aggregated fibres. Other bundles of fibres appear to emerge from 
 the corpus striatum, and to contribute to form the fibrous matter of 
 the hemisphere. 
 
 If this view of the structure of the corpus striatum be correct, it 
 would appear, that while a large proportion o^f the fibres which con- 
 stitute the inferior layer of the crus penetrateJhat ganglion, many of 
 them do not pass beyorid it. They may be describe.d as terminating 
 in it — or, more properly, if traced from above, as taking their origin 
 or point of departure from it., Many of the fibres which seem to 
 pass from the corpus striatum into the white matter of the hemisphere 
 are doubtless similarly related to the former body, i. e., take their 
 rise from the vesicular matter, pr, to speak more exactly, pass be- 
 tween the vesicular matter of the hemisphere and that of the corpus 
 striatum. It is also highly probable that some fibres pass completely 
 through the corpus striatum. 
 
 Thus, three sets pf fibres may be described as existing in the cor- 
 pus striatum; 1st, those which below enter into the formation pf the 
 crus, and' above are connected with that ganglion ; 2d]y, those which, 
 are connected .inferiorly with the corpus striatum, 'and above with 
 the cerebral convolutions; and lastly, those which pass fpra the 
 white substance of the hemispheres through the corpus striatum to 
 the crus cerebri. And of these three sets of. fibres, the first serves 
 to connect the corpora striata with the mesocephale and medulla ob- 
 longata; the second to connect the cerebral convolutions with the 
 corpora striata; and the third''to connect the convoliitions with the 
 mesocephale and medulla oblongata. It.tnust be confessed, however, 
 
252 INNERVATION. 
 
 that the evidence upon which the existenceof the third class of fibres 
 rests is less satisfactory than that for the first and second, although 
 most of those anatomists who are contented with coarse dissection 
 seem to recognize only the third class. 
 
 The fibres of the optic thalamus are doubtless; ^Iso, continuous 
 with some of those which form the white matter of the hemispheres ; 
 and from the intimate manner in which this body is embraced, by the 
 corpus striatum, and the close connection which exists between 
 them, there can be but little doubt that fibres pass from the one to 
 the other. 
 
 Projecting from the external and posterior part of each optic thala- 
 mus, there are two small gangliform masses, similar in colour and in 
 structure to that body. These are the corpora geniculata, externum 
 and internum (fig. 71, g). Some fibres of the optic tracts appear to 
 form a connection with them. By a transverse section throug'h either 
 geniculate body into the substance of the thalamus, the distinctness 
 of the former may be demonstrated. 
 
 A fissure which exists between the optic thalami is called the third 
 ventricle. It? roof is formed by the velum interpositum, one of the 
 principal internal processes of the pia mater. It contains a bridge 
 of soft grayish matter, extending from one optic thalamus to the 
 other. This is called the rtdddle or soft commissure. 
 
 The free and continuous surface of the optic thalamus and corpus 
 Striatum, which projects into the anterior and middle part of each 
 lateral ventricle, is covered by a delicate epithelium, which is con- 
 tinuous with, and of the same nature as, that which lines the whole 
 interior of the ventricle. This epithelium is, probably, ciliated. 
 Beneath it we find a layer of nucleus-like particles, which also extend 
 over the whole internal surface of the ventricles. 
 
 The pineal body, ov gland as it has been miscalled, is placed im- 
 mediately behind the posterior extremity of the third ventricle. It 
 is a cone-shaped body, of a dark gray colour, intimately connected 
 with the deep surface of the velum interpositum, a process of which 
 encloses it and adheres closely to it. It rests in a groove between 
 the nates: its base is turned forwards towards the third ventricle, 
 and its apex is directed downwards and backwards. No part of its 
 base is contained in the third ventricle ; but it is connected to the 
 inner surfaces of the thalami by some fibres which pass forwards 
 from each angle of its base. , These are called the peduncles or ha- 
 6en<e, of the pineal gland. A cord of transverse fibres, some of 
 which appear to be continuous with the peduncles, is situated beneath 
 the base of theb^ody; most of these fibres are connected with the pos- 
 terior extremity of each thalamus, and constitute what is called the 
 posterior commissure. 
 
 The pineal body consists principally of large nucleated, vesicles, 
 and contains some tubular fibres. In a cavity which is formed to- 
 wards its base, is contained a mass of sabulous matter, which is com- 
 posed of phosphate and carbonate of lime. To this Soemmering 
 gave the name acervulus.. It is found only in subjects after seven 
 years of age, and is in a great degree peculiar to the human subject. 
 
THE CEREBRAL HEMISPHERES. 253 
 
 The structure of the pineal body is very imperfectly known ; and 
 although its office has been a theme for some of the wildest specu- 
 lators in physiological theories, we are still utterly in the dark respect- 
 ing it. 
 
 Of the Cerebral Hemispheres. — The hemispheres of the brain are 
 ovoid masses, which in man constitute by far the largest portion of 
 the encephalon. All that mass of nervous matter which is external 
 and superficial to the optic thalami and corpora striata constitutes the 
 hemispheres properly so called. A vertical fissure separates the right 
 and left hemispheres, which, although not pei'fectly symmetrical, very 
 closely resemble each other. This fissure contains the great falciform 
 process of the dura mater, which thus forms a septum between the 
 cerebral hemispheres. 
 
 When a horizontal section is made through either hemisphere, an 
 oval surface is exposed (centrum ovale of Vieussens), which consists 
 of an area of white or fibrous matter, bounded by a waving margin 
 of gray. The latter is about an eighth of an inch in thickness: it is 
 covered on its exterior by pia mater, from which innumerable minute 
 vessels penetrate it; and within it adheres intimately to the White 
 matter, the fibres of which extend into it, and mingle with its ele- 
 ments. 
 
 In examining the surface of a hemisphere from which the pia mater 
 has been stripped, the peculiar folded arrangement of it is manifest. 
 These folds, commonly known as the convolutions of the brain, re- 
 semble the rugae which are produced in the mucous membrane of the 
 stomach when its muscular coat is very much contracted. They are 
 evidently destined to pack into a small compass a large surface of 
 vesicular matter. A sulcus separates each convolution from the 
 neighbouring one. The gray matter is found at the bottom of the 
 sulci, as well as upon the prominences of the folds, and its union 
 with the fibrous matter takes place equally in the one as in the other 
 situation. A sulcus, therefore, contains the gray (vesicular) and 
 white (fibrous) elements as distinctly as a fold or convolution. It is 
 evident, that if the surface of the gray did not exceed that of the 
 white matter, folds or convolutions would not be necessary, but a 
 simple expanse of the former would suffice to cover the surface of the 
 latter. The convoluted arrangement increases the vesicular surface 
 to an immense extent, without occupying much additional space; 
 and, by the prolongation of the fibres, which correspond to the con- 
 cavities of the convolutions, some distance beyond those which pene- 
 trate the gray matter of the sulci, the fibrous matter is adapted to it. 
 
 The existence of convolutions on the surface of the hemispheres 
 affords evidence of a large relative amount of the dynamic or vesicu- 
 lar nervous matter in those segments of the brain, anxl their number 
 and complexity are a measure of the extent to which the vesicular 
 surface is increased. Of two brains, equal as regards bulk, and occu- 
 pying the same space, that which has the more numerous convolutions 
 on its surface has the greater quantity of vesicular matter, and must 
 be regarded as physiologically the more potential, 
 
 A remarkable gradation is observable as regards the number of the 
 13 
 
254 INNERVATION. 
 
 cerebral convolutions from the lowest mammalia up to man. Some 
 of the Rodentia, Cheiroptera, and Insectivpra, occupy the lowest 
 place; and monkeys, the elephant, and the whale, rank next to Man, 
 in whom the convolutions reach their highest point of development. 
 In the rat, mole, &c., the surface of the brain is perfectly smooth; 
 and the only tendency to complication which it exhibits, is to be 
 found in the convolution of the gray matter at the fissure of Sj'lvius. 
 The brains of these animals resemble, in this respect, to a striking 
 degree, those of birds, which are equally destitute of all semblance 
 of a convolution. But in the rabbit, guinea-pig, beaver, &c., the 
 occurrence of certain fissures on the surface of the hemispheres, and 
 the greater depth of the fissure of Sylvius, denote the first steps in 
 the development of convolutions. 
 
 A further stage of development is indicated by the existence of 
 certain rounded folds which generally take a direct course parallel to 
 the long axis of the hemispheres. These folds are but few in number, 
 and quite simple, but may be readily distinguished from the rest of 
 the cerebral surface, by the fissures which bound them. 
 
 However complicated and numerous the convolutions of the most 
 highly developed brains may be, it cannot be supposed that their ar- 
 rangement is accidental, or has reference merely to the space within 
 which the brain is enclosed. On the contrary, there seems no doubt 
 that the position, size, and connection of certain primary folds influ- 
 ence mainly the number and variety of those which occupy the inter- 
 vening spaces. This interesting point has been strongly insisted 
 upon by M. Leuret, who shows, by comparison of the most completely 
 convoluted brain with those in which the folds are few and simple, 
 that the convolutions of the latter, which are, as it were, the original 
 landmarks in this intricate arrangement of the cerebral surface, may 
 be demonstrated in each successive group of brains which form a 
 stage in the ascending series. 
 
 Taking the brain of the fox as the standard of comparison, M. 
 Leuret* describes in it six obvious convolutions, prominently marked 
 on the surface of its hemispheres. Four of these are external, the 
 uppermost of which occupies also the principal portion of the supe- 
 rior surface ; one is internal, and situate immediately above and 
 parallel to the corpus callosum ; while the sixth is on the inferior 
 surface of the anterior lobe, and rests upon the orbit, whence it is 
 named supra- orbitar. Of the four external, the inferior one bounds 
 the fissure of Sylvius above, in front, and behind : and its relation to 
 that fissure enables the observer to distinguish it very readily. The 
 three remaining ones, curved similarly and parallel to the first, and 
 to each other, occupy the remainder of the external, and, in part, the 
 superior surface of the hemisphere. 
 
 M. Leuret distinctly traces these convolutions in other groups of 
 animals in which the general organization of the brain has manifest- 
 ly acquired a considerable increase. Some of them, however, are 
 
 * Professor Owen has pursued the same subject extensively, and has given his 
 results in his lectures at the Royal College of Surgeons ; but we believe these have 
 not yet been published. 
 
CONVOLUTIONS OF THE BRAIN. 255 
 
 fissured, or exhibit a tortuous appearance; or one or more small 
 folds unite neighbouring convolutions at one or more points ; or a 
 fissure may be of such depth as to divide a convolution at one ex- 
 tremity into two, either or both of which may form a junction with 
 others. Thus, from a few primary or fundamental convolutions, a 
 highly complicated surface of the brain may be formed, by their 
 subdivision, by their tortuosity, and by their junction at various 
 points, through the intervention of straight or tortuous secondary 
 folds. 
 
 In some animals, however, the primary convolutions may even be 
 less numerous than those above mentioned ; and yet the surface of 
 the brain may appear more complex, owing to the tortuosity of those 
 which do exist, and their subdivision into, or junction with, numerous 
 secondary folds. This is the case in that group of which the sheep 
 forms the type. There are but two primary convolutions on the ex- 
 ternal surface, one of which corresponds to that of the fissure of 
 Sylvius in the fox, the other to the one immediately above it ; and 
 there are the internal convolution and the supra-orbitar one, making 
 in all only four primary convolutions. Yet the surface of the sheep's 
 brain exhibits a much greater number of folds than that of the fox. 
 
 On the other hand, when the brain has acquired an enormous 
 increase of size, as in the elephant and in man, new convolutions 
 seem to be added to the prinjary ones met with ,in inferior groups, and 
 the secondary folds are greatly increased in number. The additional 
 convolutions are found chiefly at the superior and anterior part of the 
 hemisphere. 
 
 In the human brain the following convolutions are constantly pre- 
 sent, and resemble the primitive ones, which have been already 
 referred to in the brains of the inferior animals. The internal one is 
 always, well marked ; it lies parallel to the corpus callosum, overlap- 
 ping it slightly on either side. In front it winds round the anterior 
 margin of the corpus callosum, and is connected with the convolu- 
 tions of the anterior lobe ; posteriorly it divides, appears to be con- 
 tinuous with some posterior convolutions, and passes into the middle 
 lobe forming the hippocampus major. Numerous small folds pafes 
 from its upper edge to the superior convolutions. The supra-orbitar 
 convolution is well developed, and bears a constant relation to the 
 fissure for the olfactory process. The fissure of Sylvius is bounded 
 by a tortuous external convolution, which forms numerous connections 
 with others on the external surface of the brain. In this fissure is 
 found constantly a group of shallow convolutions, which form what 
 has been called by Reil the island, insula, from their isolated position, 
 having only deep-seated connections in the vicinity of the corpus 
 striatum. Some longitudinal convolutions are found on the supet^ior 
 and on the inner surfaces of the hemispheres, uniting with neigh- 
 bouring ones by means of numerous transverse folds. 
 
 According to Leuret, that only can be properly called a convolu- 
 tion which is primary ; and these, for the most part, take a direction 
 in the length of the brain. Those which form angles with the pri- 
 mary convolutions are, in his estimation, mere folds derived from 
 
256 INNERVATION. 
 
 them, and connecting them to others. When the convolutions are 
 very, highly developed, as in man and the elephant, their numerous 
 undulations obscure in a great degree their real direction. Hence 
 many of the primary convolutions in the human brain seem to take 
 a vertical direction. 
 
 There are, however, other differences in the convolutions, whether 
 of the brains of the same or of different groups, besides those depend- 
 ent on form and degree of undulation. These are referable to their 
 depth and their thickness. Animals, even of the same group, or of 
 the same species, exhibit much variety with respect to these points. 
 The wolf has precisely the same convolutions as the fox ; but those 
 of the former are deeper, and thicker, as well as more undulating 
 than those of the latter. Much difference is also observable. in these 
 respects in the human brain. The convolutions of the female brain^ 
 are not so deep nor so thick as those of the male. Age, too, causes 
 a marked difference. The convolutions of the child just born, 
 besides being much more simple, and having fewer undulations, are 
 less deep and less thick than those of the adult ; and in old age, when 
 the brain has shrunk, the mental faculties being less vigorous and 
 active, the convolutions have become much smaller in every dimen- 
 sion, and water is apt to accumulate in the intergyral spaces. 
 
 In man, the convolutions of the right and left hemispheres do not 
 present a perfect symmetry. It is important, however, to notice, that 
 careful examination will invariably display the same essential con- 
 volutions on each side, although they present such striking differences 
 in detail that it is at times difficult to recognize the likeness ; and it 
 is not a little remarkable, that, in general, the lower the development 
 of a brain, the more exact will be the symmetry of its convolutions. 
 Thus the brains of all the inferior mammalia, even of those which 
 make the nearest approach to man, are exactly symmetrical. The 
 imperfectly developed brain of the child exhibits a similar symmetry j 
 and that of the inferior races of mankind, in whom the neglect of 
 mental culture, and habits approaching those of the brute, are opposed 
 to the growth of the brain, also presents a symmetrical disposition of 
 the convolutions. 
 
 A convolution consists of a fold of the gray, or vesicular matter, 
 enclosing a process of the fibrous. The gray matter of neighbouring 
 convolutions is obviously continuous throughout at the bottoms of the 
 sulci, so that it forms one unbroken although undulating sheet over 
 the whole convoluted surface of the brain. That portion of the gray- 
 layer which is in contact with the pia mater is purely vesicular, i. e., 
 unmixed with nerve-tubes, with the exception of a few stray ones on 
 the surface; but blood-vessels penetrate it in very great numbers. 
 The more deeply seated portion, however, contains very numerous 
 tubular fibres, which become larger as they approach the white matter. 
 It is very plain, that a large proportion of the constituent fibres of the 
 white matter of the convolutions penetrate the gray matter: these 
 appear to enter it more or less at right angles to that portion of the 
 gray surface with which they are more immediately in relation ; and, 
 on the other hand, they converge inwards towards the central parts of 
 
COMMISSURES OF THE BRAIN. 25? 
 
 the brain, the corpora striata and optic thalami. A large proportion, 
 therefore, of the white substance pf the hemispheres, the centrum 
 ovale, consists of fibres which establish a communication between the 
 gray undulating surface and these central gangliform bodies. 
 
 We are unable, however, to state' that all the fibres of the con- 
 volutions take this inward direction. Some of them, it has been 
 asserted, pass from convolution to convolution, uniting those imme- 
 diately adjacent, as well as the more remote. Such fibres, did they 
 exist, would pass at right angles to those above described, and parallel 
 to the gray surface. They would constitute intergyral commissures. 
 But the existence of such a series of fibres rests on a foundation too 
 uncertain to warrant us in speaking confidently respecting it. When 
 a brain which has been hardened by long immersion in alcohol is 
 torn along the surface of the convolutions, the torn surfaces take on 
 a fibrous appearance. But nothing of the kind can be shown in the 
 fresh brain, in which the direction of the fibres which converge to 
 the corpora striata may be as easily demonstrated as upon the hardened 
 one. 
 
 The gray matter of the convolutions does not exhibit a uniform 
 colour throughout its entire thickness. Much depends, as regards 
 the depth of colour of the whole layer, upon the quantity of blood 
 in its vessels. Compare the gray matter of an anaemic brain with 
 that of a healthy one, or, still more, of a congested one, and the 
 difference cannot fail to strike the most superficial observer. The 
 external portion has the darkest colour, and the internal in general 
 the lightest. In some convolutions, however, the intermediate layer 
 is white, and appears on the section like a white line separating the 
 inner from the outer layers. This is very obvious in the convolutions 
 forming the exterior of the descending horn of the lateral ventricles. 
 This white layer contains fine nucleus-like particles, similar to those 
 which form the intermediate layer of the gray matter of the cerebellum ; 
 a coincidence of structure between certain convolutions of the brain, 
 and the gray matter of the cerebellum, which, doubtless, is not with- 
 out some physiological significance. 
 
 Certain systems of fibres exist in the cerebrum, which seem very 
 evidently to unite portions of the same, or of opposite hemispheres. 
 The most obvious of these commissures are, the corpus callosum, the 
 anterior comntissure, the posterior commissure, the soft commissure, the 
 superior longitudinal commissure, and the fornix. All, except the 
 two last, are transverse, and unite parts of the hemispheres of opposite 
 sides. 
 
 The corpus callosum is a thick stratum Of transverse fibres, bent at 
 its anterior and posterior extremities,, situate between the hemispheres, 
 and forming a floor to a portion of the great median fissure which 
 separates them. Its fibrous structure is very apparent to the naked 
 eye, the fibres being collected in coarse bundles. On each side it 
 penetrates into the hemisphere, under cover of the internal convolu- 
 tion already mentioned, which overhangs it in its entire length. It 
 thus connects the anterior, middle, and part of the posterior lobes of 
 each hemisphere; at least, its fibres penetrate the hemispheres at these 
 
258 INNERVATION. 
 
 parts. Foville describes the fibres of this commissure as being de- 
 rived partly from the posterior columns of the medulla oblongata, 
 from the optic thalami, from the corpora striata, and, lastly, from the 
 fibrous matter of the hemispheres ; and although the demonstration of 
 these numerous sources of origin of these fibres is attended with 
 much difficulty, it nevertheless seems highly probable that the nume- 
 rous fibres,, of which so extensive a stratum is formed, would derive 
 their origin from several sources. 
 
 The corpus callosum is crossed from before backwards along the 
 median line by two stripes of longitudinal fibres, which, although 
 easily separable, generally lie in close apposition with each other and 
 form a kind of raphe, dividing the upper surface of the corpus callo- 
 sum into two equal and symmetrical portions. These fibres seem to 
 be commissural in their office. 
 
 The anterior commissure is a remarkable bundle of transverse fibres ; 
 which passes from one hemisphere to the other. It is iii its centre 
 a cylinder of fibrous matter, a little thicker than a crowquill, but 
 becoming very much flattened and expanded at its extremities. Its 
 central part is seen at the anterior extremity of the third ventricle, in 
 front of the anterior pillars of the fornix, crossing from side to side, 
 quite free, and unconnected with nervous matter. It plunges on 
 either side into the anterior extremity of the corpus striatum, and, 
 passing through it, its fibres diverge and spread out into the whfte 
 matter at the floor of the Sylvian fissure, and near the anterior per- 
 forated space. 
 
 The posterior commissure crosses the posterior extremity of the 
 third ventricle, and passes transversely between the optic thalami. 
 It is a slender cylinder of fibrous matter, which lies immediately 
 above the anterior orifice of the aqueduct of Sylvius. On each side 
 it seems to sink into the posterior part of the optic thalamus. The 
 base of the pineal body rests upon it, and is connected with it by 
 fibrous matter, which is continuous with the peduncles. 
 
 The soft commissure is a soft pale-gray layer consisting of vesicular 
 matter with nerve tubes, which stretches from one optic thalamus to the 
 other, having no other connection, and being free on its upper as well 
 as its under surface. This layer, thus extended horizontally between 
 the thalami, divides the third ventricle into a superior and an inferior 
 portion. As it comprises vesicular matter, it is not a commissure in 
 the same sense as the others, which contain none. 
 
 The superior longitudinal commissure is enclosed in the internal 
 convolution overhanging the corpus callosum. Posteriorly it passes 
 over the posterior border of the corpus callosum, to the under part of 
 the middle lobe, where it is chiefly connected with the hippocampus 
 major. Anteriorly it winds over the front border of the corpus callo- 
 sum to join the lower convolutions of the anterior lobe in front of the 
 fissure of Sylvius. Thus it takes a course similar to that of the fornix, 
 though more extensive and superficial. 
 
 The fornix or vault is the most extensive, and in every way the 
 most remarkable of the cerebral commissures. It is placed imme- 
 diately beneath the corpus callosum, with the posterior half of which 
 
COMMISSURES OP THE BRAIN. 259 
 
 it is intimately connected, and from which it is with difficulty sepa- 
 rated. A principal portion of the fornix consists of a horizontal 
 lamella of fibrous matter, parallel to the corpus callosum, of a trian- 
 gular shape, with the apex forwards {corpus fornicis). The base is 
 enclosed by the posterior reflection of the corpus callosum, the termi- 
 nal transverse fibres of which are seen on its inferior surface, forming 
 the appearance which has been designated lyra. 
 
 The fornix may be divided along the middle line into two equal 
 and Symmetrical portions, one belonging to each hemisphere. Suf- 
 ficient indication of its double form is evinced by the prolongation 
 from its apex of two cylindrical cords, which curve forwards and 
 downwards, then backwards, with their convexities touching the 
 posterior border of the anterior commissure. These are the anterior 
 pillars of the fornix. In their descent they diverge slightly from 
 each other, leaving an interval between them, thifough which the 
 anterior commissure appears. These pillars form the anterior boundary 
 of ihe foramen commune anterius, through which the lateral ventricles 
 communicate with the third, and with each other. 
 
 Each anterior pillar of the fornix in its descent penetrates the an- 
 terior and inner part of the optic thalamus. Here it is surrounded 
 by vesicular matter, which may be readily scraped away from it. 
 Numerous striae of fibrous matter join the pillar as it passes through 
 the vesicular matter ; their constituent fibres, doubtless, being derived 
 from the thalamus. Finally, each pillar terminates in a small spheri- 
 cal body at the base of the brain. These bodies called corpora 
 mamillaria!, are white outside, but when cut into, exhibit a reddish* 
 gray colour, like that of the optic thalami. They contain nerve-tubes 
 and vesicular matter in considerable quantity, and therefore resemble 
 ganglia in structure. A considerable fasciculus of fibres connects 
 each mamillary body with the optic thalamus. 
 
 From each angle of the base of the fornix a broad band of fibrou^ 
 matter passes outwards, and spreads partly into the posterior horn of 
 the lateral ventricle, and partly into, its descending horn. These 
 bands constitute the posterior pillars of the fornix. They connect 
 themselves with certain convolutions which project into the posterior 
 and inferior cornua of the lateral ventricles ; in the latter with the 
 hippocampus minor, and in the former with the hippocampus major. 
 
 The fornix consists of longitudinal fibres, unmixed with vesicular 
 matter, save in the optic thalami and corpora mamillaria. The supe- 
 rior surface of the body of the fornix is connected to the inferior 
 surface of the corpus callosum, at its base apparently by the direct 
 adhesion of the fibres of the two planes, but towards its apex by 
 the septum lucidum, which extends vertically from the middle line of 
 the inferior surface of the corpus callosum to that of the superior 
 surface of the fornix. ' 
 
 From the great extent of the fornix, and the numerous connections 
 which its pillars form, it is plain that it must serve as a commissure 
 to many and distant parts. Each half of it is a longitudinal or antero- 
 posterior commissure for the hemisphere of its own side. It is not 
 improbable that some of the convolutions contain antero-posterior 
 
260 INNERVATION. 
 
 commissures for the superficial part of the hemisphere ; such is cer- 
 tainly the case with the longitudinal convolution above the corpus 
 callosum. The fornix, however, connects deep-seated parts, for it 
 passes between the optic thalamus and the deep convolutions of the 
 posterior and middle lobes. 
 
 The septum lucidum consists of two-layers of fibrous matter, which 
 enclose a space or cavity called i\\e fifth ventricle. The fibresxif this 
 layer radiate upwards and forwards, and connect the anterior pillars 
 of the fornix with the corpus callosum. Each fibrous layer is covered 
 on its outside by a layer of nuclear particles, which again is covered 
 by the membrane of the lateral ventricle. 
 
 A band of fibrous matter, which belongs to the same system of 
 commissural fibres as the fornix, is found, on each side, in the groove 
 between the corpus striatum and optic thalamus. This is called tcenia 
 semidrcularis. It may be described as connected with the corpus 
 mamillare, in much the same way as the anterior pillar of the fornix. 
 Traced from this point, it is found to penetrate the optic thalamus, 
 following the general course of the anterior pillar of the fornix, but 
 slightly diverging from it, and to emerge from the thalamus in the 
 anterior part of the groove between it and the corpus striatum, whence 
 it passes backwards, outwards, and downwards into the inferior cornu 
 of the lateral ventricle. 
 
 Other structures exist in the brain, which seem likewise to act as 
 commissures to the parts between which they are placed. Thus, 
 between the crura cerebri a layer of fibrous matter, mingled with a 
 few vesicles, is placed, which fills up the angle formed at their diverg- 
 ence; this layer is remarkable for being perforated by numerous 
 foramina, which give passage to the blood-vessels of the locus niger. 
 It is called the pons Tarini ; it probably connects the gray matter of 
 the crura. 
 
 The innermost fibres of the optic tracts are evidently commissural. 
 These fibres form an arch, which crosses the tuber cinereum. In 
 the mole, they are the only fibres of the optic tracts existing: those 
 which form the optic nerves are not present. These fibres connect 
 the quadrigerainal tubercles and the geniculate bodies of opposite 
 sides. 
 
 The tuber cinereum is a remarkable layer of vesicular matter, with 
 which nerve-tubes freely intermingle, which extends from the ma- 
 millary bodies forwards to the posterior reflection of the corpus 
 callosum, and has intimate connections with the anterior pillars of 
 the fornix, the optic tracts, the septum lucidum, and, at the floor of 
 the third ventricle, with the optic thalami. An infundibuliforra tube 
 passes from it down towards the pituitary gland, which is situate in 
 the sella Turcica. 
 
 It is curious how few are the fibres which seem to connect the 
 cerebrum and cerebellum. The only ones to which this office can be 
 assigned are those which form the processus cerebelli ad testes. 
 Hence these structures may more fitly be denominated cerebro-cere- 
 bellar commissures. They extend between the cerebellum on the one 
 hand, and the optic tubercles and thalami on the other. 
 
PITUITARY BODY.— VENTRICLES OP THE BRAIN. 261 
 
 Of the manner in which the commissures connect tlje various parts 
 between which they are placed, it is difficult to form an exact opinion. 
 Are the commissural fibres directly continuous with those of the seg- 
 ments which they unite? or do they intermingle or interlace with 
 them in some intricate way, so that tiiey may come into intiraatie or 
 frequent contact? Or, do they, like other fibres, blend with the gray 
 matter, and thus connect the really dynamic portion of the segments? 
 This latter view seems to be the most probable. , 
 
 The pituitan/ body or hypophysis is a glandiform mass lodged in the 
 sella Turcica, and surrounded by the coronary sinus. It is connected 
 with the brain by the infundibular process, the small extremity of 
 which is attached to its superior concave surface. 
 
 This body consists of two lobes, of which the anterior is much the 
 larger; and which also differ in point of colour, the anterior being 
 of a yellowish gray, the posterior more similar to the gray matter of 
 the brain. The former is considerably denser and firmer than the 
 latter, which does not differ in consistence from the cerebral gray 
 matter. The infundibulum is chiefly connected with the posterior 
 lobe. 
 
 In point of Structure this body resembles somewhat the vesicular 
 matter of the brain. We find in it large vesicles with distinct nuclei 
 and nucleoli lodged in a granular matrix, and between them numerous 
 bundles of white fibrous tissue. These are most numerous in the 
 anterior lobe. Its use is quite unknown. 
 
 Of the Ventricles of the Brain.^-By the apposition of the two 
 hemispheres of the brain along the median plane, a fissure-like space 
 is enclosed beneath the corpus callosum and fornix, limited in front 
 by the anterior pillars of the latter, and behind by the posterior com- 
 missure; this is the middle ov- third ventricle. This fissure is closed 
 inferiorly by the pons Tarini, mamillary tubercles, and tuber cinereum ; 
 its roof is formed by the velum imterpogitum, a process of pia mater, 
 which separates it from the body "of the fornix. It communicates 
 posteriorly with the fourth ventricle through the aqueduct of Sylvius 
 (iter a tertio ad quartum ventriculurp,) , and immediately behind the 
 anterior pillars of the fornix it freely opens into each lateral ventricle. 
 At the same situation the velum interpositum and the choroid plexuses 
 communicate with each other. The optic thalami form the lateral 
 boundaries of the third ventricle, and its cavUy is crossed by the soft 
 commissure. 
 
 The lateral ventricles result from the folding of the convoluted 
 surface inwards and downwards. By their extension inwards, and 
 their junction along the median line by the corpus callosum, the 
 horizontal portion of each ventricle is enclosed; and by the folding 
 inwards of the inferior convolutions, posterior to the fissure of Sylvius, 
 the inferior horn is formed. The horizontal portion extends into the 
 anterior lobe (anterior or frontal horn), and into the posterior lobe 
 (posterior or occipital horn). The central part of the horizontal por- 
 tion is separated from the third ventricle by the body of the fornix. 
 In this portion of the ventricle are seen the upper surfaces of the corpus 
 striatum and optic thalamus, with the teenia semicircularis between 
 
262 INNERVATION. 
 
 them, covered by the lamina cornea. The thalamus is partly con- 
 cealed by the choroid plexus. The descending or inferior horn 
 (sphenoidal horn) communicates ■with the body of the ventricle just 
 behind the corpus striatum, and from that point passes downwards 
 and outwards, and then forwards and inwards. It contains a re- 
 markable convolution, the hippocampus major, which projects into it, 
 and is a continuation of that enclosing the superior longitudinal com- 
 missure ; this is covered by an expansion of fibrous matter continuous 
 "with the posterior pillars of the fornix. The posterior horn contains 
 a similar but smaller convolution, called hippocampus minor. 
 ■ The inferior horn of the lateral ventricle contains a considerable 
 portion of the choroid plexus. This enters at its inferior extremity 
 between the hippocampus major and the crus cerebri, and passes 
 upwards into the horizontal portion of the ventricle. 
 
 Thejburth and the Jifth ventricles have been already described. 
 
 AH the ventricles are lined by a very delicate membrane, similar 
 in structure to serous membrane; It is covered by a fine epithelium 
 consisting of polygonal scales, and provided with cilia, which were 
 first observed by Purkinje and Valentin. This epithelium is found 
 covering the surface not only of the wall of the ventricle, but also of 
 the pia mater within it, the choroid plexuses, and the deep surface of 
 the velum interpositum. It is by means of the reflection of this 
 membrane upon the intraventricular processes of pia mater that the 
 ventricles are closed at those points where nervous matter does not 
 exist, such as the inferior cornua of the lateral ventricles, and the 
 inferior extremity of the fourth ventricle. There is, therefore, no 
 direct communication of these cavities at these points with the sub- 
 arachnoid space; and, if fluid pass from one to the other, it must be 
 by filtration through the delicate ventricular membrane. 
 
 In a state of health there is little or no fluid in the lateral or other 
 ventricles of the brain. Their inner surfaces are doubtless in contact, 
 but lubricated with a moisture, as all serous surfaces are. When 
 fluid is found in them, it results either from changes which take place 
 after death, or from some morbid process during life. A state of 
 anaemia, or an impoverished condition of the blood, in which its 
 colouring matter and its fibrine are found in small quantity, is very 
 favourable to the effusion of fluid into the ventricles. 
 
 It may serve, in some degree, to convey a clearer general idea of 
 the anatomy of the brain, if, in conclusion, we explain the course 
 which the nervous force might, and probably does follow, when 
 developed in any particular segment of this complex organ. 
 
 If we suppose the source of power to be the convolutions on either 
 side, the nervous force would be propagated by the fibres of the 
 hemisphere to the vesicular matter of the corpus striatum ; from which 
 it would pass along the fibres of the inferior layer of the crus cerebri, 
 through the mesocephale, to the anterior pyramids of the medulla 
 oblongata ; along which it would be conveyed to the opposite half of 
 the spinal cord, exciting the nerves which spring from that segment. 
 Supposing this to be the route in which the impulse of volition is 
 propagated to the muscles, it becomes very easy to understand why a 
 
THE CIRCULATION IN THE BRAIN. 263 
 
 state of paralysis must ensue, when an apoplectic clot, or other morbid 
 deposit in any part of the course above described, compresses or 
 ruptures the fibres, or when a state of softening destroys their vital 
 powers, or causes a solutipn of their continuity. If the seat of disease 
 be in the white matter, the channels along which the nervous power 
 travels will be interrupted ; if it b^ in the gray matter, the sources of 
 nervous power are impaired. In all cases the extent of the paralysis 
 will be proportioned to that of the lesion, and for the most obvious 
 reasons. 
 
 If the cerebellum be the source of power,. the nervous force will 
 travel from either hemisphere along the fibres of the crus, and by those 
 of the restiform body to the spinal cord, and from the continuity of 
 the former with the posterior column of the latter it is probable that 
 this column would be more immediately excited. 
 
 So little is'known of the precise channels through which impressions 
 created at the periphery are propagated in the central organ, that we 
 can hardly dp more than speculate on the subject. We may, how- 
 ever, fairly conclude, that those segments with which nerves admitted 
 to be sensitive are in close connection, must be instrumental in the 
 propagation of the nervous power, when excited by sensitive impres- 
 sions ; and hence we are led to assign to the olivary columns of the 
 medulla oblongata, and their continuations in the mesocephale, with 
 the optic tubercles and the thalami, a considerable share in this office, 
 inasmuch as the auditory, the fifth, and the optic nerves, are intimately 
 connected with them. And admitting, for the present, that the hemi- 
 spheres are the common centre of sensitive impressions, it ds easy to 
 understand how nervous power, excited by the impulse of sound upon 
 the ear, for example, may be propagated along the auditory nerves to 
 the olivary columns in the fourth ventricle, and thence to the optic 
 thalami, in which are found many fibres which are continuous with 
 those of the hemispheres, and capable of propagating the nervous 
 force to the convolutions. 
 
 To this it may, however, be objected, that perfect sensation is fre- 
 quently co-existent with a cerebral lesion, sufficient to produce very 
 complete paralysis of motion, and that an enduring paralysis of sensa- 
 tion is a rare accompaniment of cerebral disease. But such facts do 
 not so much militate against these views, as they serve to denote that 
 the channels of sensation are more numerous than those of motion ; 
 and that, if one route be interrupted, another is easily opened. It 
 may be, that the commissures are valuable instruments for this pur- 
 pose; and it is highly worthy of notice, that no segment of the cere- 
 brum has so many commissures either with the opposite or its own 
 side, as the optic thalamus. 
 
 It should be borne in mind that the foregoing remarks are partly 
 conjectural, and that they are introduced rather as a convenient 
 form of illustration, than as implying more than a probability of their 
 general correctness and accordance with the best established views. 
 
 Of the Circulation in the Brain. — An organ of such great size, of 
 such high vital endowments, so active, and which exerts so consider- 
 able an influence upon all other parts of the body, must necessarily 
 
264 INNERVATION. 
 
 require a large supply of the vital fluid. Hence we find that the 
 blood-vessels of the brain are numerous and capacious. Four large 
 arteries carry blood to it; namely, the two internal carotids, and the 
 two vertebrals. Each carotid penetrates the cranium at the foyamen 
 on the side of the sella Turcica, and almost immediately divides into 
 three branches, the anterior and the middle cerebral arteries, and the 
 posterior communicating artery. 
 
 The anterior cerebral arteries supply the inner sides of the anterior 
 lobes of the brain : they ascend through the great longitudinal fissure, 
 and pass along the upper surface of the corpus callosum, giving 
 off branches to the inner convolutions of both hemispheres of the 
 brain. These arteries anastomose with each other just beneath the 
 anterior margin of the corpus callpsum by a transverse branch, called 
 the anterior communicating artery. The middle cerebral arteries, the 
 largest branches of the carotids, pass outwards in the fissures of 
 Sylvius, and supply the outer convolutions of the anterior lobes, and 
 the principal portion of the middle lobes. At the inner extremity of 
 each fissure of Sylvius numerous small branches of these arteries 
 penetrate, to be distributed to the corpus striatum. The choroid 
 arteries which supply the choroid plexus sometimes arise from these 
 arteries, but also occasionally come from the carotid itself. The 
 posterior communicating artery is an anastomotic vessel, which passes 
 backwards along the inner margin of the middle lobe on the base of 
 the brain, and communicates with the posterior cerebral artery, a 
 branch of the basilar. 
 
 The vertebral arteries, having passed through the canals in the 
 transverse processes of the cervical vertebrae, enter the cranium through 
 the occipital foramen towards its anterior part. In their ascent they 
 incline towards each other in front of the medulla oblongata, and at 
 the posterior margin of the pons they coalesce to form a siflgle vessel, 
 the basilar, which extends the whole length of the pons. 
 
 The vertebral arteries furnish the anterior and posterior spinal arte- 
 ries, and the inferior cerebellar arteries. These last vessels arise from 
 the vertebrals very near their coalescence, and pass round the medulla 
 oblongata to reach the inferior surface of the cerebellum, to which 
 they are principally distributed. 
 
 The basilar artery sends numerous small vessels to penetrate the 
 pons, and at its anterior extremity divides into four arteries two on 
 each side : these are, the two superior cerebellar, and the two posterior 
 cerebral arteries. 
 
 The superior cerebellar arteries pass backwards round the crus 
 cerebri, parallel to the fourth nerve, and divide into numerous 
 branches on the upper surface of the cerebellum, some of which 
 anastomose with branches of the inferior cerebellar artery over the 
 posterior margin of the cerebellum. Some branches of these arteries 
 are distributed to the velum interposituin. 
 
 The posterior cerebral arteries are the largest branches of the 
 basilar. They diverge and pass upwards and backwards round the 
 crus cerebri, and reach the inferior surface of the posterior lobe, 
 anastomosing in the median fissure with ramifications of the anterior 
 
THE CIRCULATION IN THE BRAIN. 265' 
 
 cerebral, and on the outside with branches of the middle cerebral 
 arteries. Njamerous small vessels pass from this artery at its origin, 
 and penetrate the interpeduncular space, and one or two are distri- 
 buted to the velum. Shortly after its origin the artery receives the 
 posterior communicating branch from the carotid. 
 
 A remarkable, freedom of anastomosis exists between the arteries 
 of the brain. This takes place not only between the smaller rami- 
 fications, but likewise between the primary trunks. The former is 
 evident all over the surface of the cerebrum and cerebellum. The 
 latter constitutes the well-known circle of Willis. This anastomosis 
 encloses a space, somewhat of an oval figure, within which are found 
 the optic nerves, the tuber einereum, the infundibulum, the corpora 
 mamillaria, and the interpeduncular space. The anterior communicat- 
 ing artery, between the anterior cerebral arteries, completes the circle 
 in front. The lateral portion of the circle is formed by the posterior 
 communicating artery, and it is completed behind by the bifurcation 
 of the basilar into the two posterior cerebral arteries. Thus, a stop- 
 page in either carotid, or in either vertebral, would speedily be 
 remedied. The coalescence of the vertebrals to form the basilar, 
 aflfords considerable security to the brain against an impediment in 
 one vertebral; and, should the basilar be the seat of obstacle, the 
 anastomoses of the inferior cerebellar arteries with the superior ones 
 would insure a sufficient supply of blood to that organ. If either or 
 both carotids be stopped up, the posterior communicating arteries 
 will supply a considerable quantity of blood to the intracranial por- 
 tions of them ; or, if one carotid be interrupted, the anterior commu- 
 nicating branch will be called into requisition to supply blood from 
 the opposite side. 
 
 Obstruction to the circulation in both carotids and both vertebrals 
 is productive of a complete cessation of cerebral action, and death 
 immediately ensues, unless the circulation can be quickly restored. 
 This was proved clearly by Sir A. Cooper's experiments on rabbits. 
 The circulation may, however, be interrupted in both carotids, or in 
 both vertebrals, without permanent bad effect; or in one carotid or 
 one vertebral, provided the condition of the remaining vessels be 
 such as not to impede the circulation in them. In cases where the 
 neighbouring anastomotic branches are not sufficient to restore the 
 circulation to a part from which it has been cut off' by the obliteration 
 of its proper vessel, the cerebral substance of that region is apt to 
 experience a peculiar form of softening or wasting, which is distin- 
 guished by the absence of any discoloration by the effusion of blood, 
 and of any new matter. 
 
 The four great channels of sanguineous supply to the brain are 
 continued up straight from the aorta itself, or from an early stage of 
 the subclavian. The contained columns are propelled very directly 
 towards the base of the brain, through wide, canals. Were such 
 columns to strike directly upon the base of the brain, there can be 
 no doubt it would suffer materially. Considerable protection, how- 
 ever, is afforded to the brain ; first, by the blood ascending against, 
 gravity, during at least a great portion of life ; secondly, by a tortuous 
 
266 
 
 INNERVATION. 
 
 Fig. 72. 
 
 arrangement of both carotids and vertebrals before they enter the 
 cranial cavity, the carotid being curved like the letter S in and above 
 the carotid canal, and the vertebral being slightly bent between the atlas 
 and axis, then taking a horizontal sweep above the atlas, and after it 
 has pierced the occipito-atlantal ligament, inclining obliquely upwards 
 and inwards; thirdly, by the breaking up of the carotids into three 
 branches, by the inclined position of the vertebrals, and by their junc- 
 tion into a single vessel, which takes a course obliquely upwards, and 
 afterwards subdivides into smaller branches. Such arrangements 
 most effectually break the force of the two columns, and, as it were, 
 scatter it in different directions. 
 
 A further conservative provision is found in the manner in which the 
 blood-vessels penetrate th'e brain. The larger arterial branches run 
 in sulci between convolutions, or at the base of the organ; smaller 
 branches come off from them, and ramify on the pia mater, breaking 
 up into extremely fine terminal arteries, which penetrate the brain ; or 
 these latter vessels spring directly from the larger 
 branches, and enter the cerebral substance. As 
 a general rule, no vessel penetrates the Cortical 
 layer of the brain, which, in point of size, is more 
 than two removes from the capillaries ; and, when- 
 ever any vessel of greater size does pierce the 
 cerebral substance, it is at a situation where' the 
 fibrous matter is external, and the part perforated 
 by foramina for the transmission of the vessels. 
 Such places are the locus perforatus, the inter- 
 peduncular space, &c. The accompanying figure 
 shows the manner in which the terrtiinal arterial 
 twigs dip vertically into the cerebral substance, 
 and break up into a solid plexus of capillaries in 
 the stratum of vesicular matter. The capillary 
 plexus of the fibrous or white matter has similar 
 characters, only its meshes are much wider (fig. 
 72). The capillaries of the cerebral substance 
 are easily seen to possess an independent dia- 
 phanous wall, with cell-nuclei disposed at in- 
 tervals. The smaller arteries and veins can also 
 be admirably studied in the pia mater of the brain. 
 The venous blood is collected into small veins, 
 which are formed in the pia mater at various 
 parts of the surface, and in the interior of the 
 brain. The superficial veins open by short 
 trunks into veins of the dura mater, or into the 
 neighbouring sinuses'; the superior longitudinal, 
 the lateral, and the strait sinuses receiving the 
 greatest number. Those from the interior form 
 two trunks, venee magna Galeni, which pass out from the ventricles 
 between the layers of the velum interpositum. The cerebral veins 
 are devoid of valves. 
 
 We remark here, that the venous blood of the brain is returned to 
 
 Two terminal arteries 
 leaving a branch on the 
 surface of a convolution 
 of the cerebrum, dipping 
 vertically inwards, and ex- 
 hibiting the mode of origin 
 and distribution of the ca- 
 
 fiillaries in the gray cortical 
 ayer. From an_ injected 
 specimen, 
 ters. 
 
 Mag, 30 diame. 
 
THE CIRCULATION IN THK BRAIN. 267 
 
 the centre of the circulation through the same channels as that of 
 the dura mater, of the cranial bones, and of the eyeball : the deep 
 jugular veins are the outlets by which the venous blood of the 
 cranium is discharged. An obstacle, therefore, in both or either of 
 these trunks must affect the entire venous system of the brain, or at 
 least that of the corresponding hemisphere. A ligature tied tightly 
 round the neck impedes the circulation, and may cause congestion 
 of the brain. The bodies of criminals who have died by hanging 
 exhibit great venous congestion, both of the- walls and the contents of 
 the craniam, in consequence of the strong compression to which the 
 veins have been submitted. 
 
 We have seen, that, when the blood of one carotid artery is cut off, 
 the parts usually supplied by it are apt to become exsangueous and 
 softened ; and this is more especially the case if the vertebral be also 
 impaicted, or the circulation in it impeded. And it has been remarked, 
 that these effects will follow the application of a ligature to either 
 common carotid artery. 
 
 Notwithstanding these facts, a doctrine has received very general 
 assent, and the support of men of high reputation, which affirms that 
 the absolute quantity of blood in the brain cannot vary^ because that 
 organ is incompressible, and is enclosed in a spheroidal case of bone, 
 by which it is completely exempted from the pressure of the atmo- 
 sphere. 
 
 The cranium, however, although spheroidal, is not a perfectly solid 
 case, but is- perforated by very numerous foramina, both external and 
 internal, by which large venous canals in the diploe of the bones 
 communicate with the circulation of the integuments of the head as 
 well as with that of the brain; so that the one cannot be materially 
 affected without the other suffering likewise. And as the circulation 
 in the integuments is not removed from atmospheric pressure, neither 
 can that which is so closely connected and continuous with it, be said 
 to be free from the same influence. Still it must be admitted, that the 
 deep position of the central vessels, and the complicated series of 
 channels through which they communicate with the superficial ones, 
 protect them in some degree from the pressure of the air, and render 
 them less amenable to its influence than the vascular system of the 
 surface. 
 
 If it were essential to the integrity of the brain that the fluid in its 
 blood-vessels should be protected from atmospheric pressure (as the 
 advocates of this doctrine would have us to believe), a breach in the 
 cranial wall would necessarily lead to the most injurious consequences; 
 yet, how frequently has the surgeon removed a large piece of the cra- 
 nium by the trephine without any untoward result! We have watched 
 for several weeks a case in which nearly the whole of the upper part 
 of the cranium had been removed by a process of necrosis, exposing a 
 very large surface to the immediate pressure of the atmosphere; yet in 
 this case no disturbance of the cerebral circulation existed. In the 
 large and open fontanelles of infants we have a state analogous to that 
 which art or disease produces in the adult: yet the vast majority of 
 infants are free from cerebral disease for the whole period during 
 
268 INNERVATION. 
 
 which their crania remain incomplete ; and in infinitely the greatest 
 number of cases in which children suffer under cerebral disease, the 
 primary source of irritation is in some distant organ, and not in the 
 brain itself. 
 
 Neither can it be said that the brain is incompressible. ^ That only 
 is incompressible, the particles of which will not admit of being more 
 closely packed together under the influence of pressure. That the 
 brain is not a substance of this kind, is proved by the fact that, while 
 it is always undergoing a certain degree of pressure, as essential to 
 the integrity of its functions, a slight increase of pressure is sufficient 
 to produce such an amount of physical change in it as at once to 
 interfere with its healthy action. Too much blood distributed among 
 its elements, and too much serum efTused upon its surface, are equally 
 capable of producing such an effect. 
 
 Magendie's experiments, alluded to at p. 231-2, show that the brain 
 and spinal cord are surrounded by fluid, the pressure of which, pro- 
 bably, antagonises that which must be exerted through the blood- 
 vessels. The removal of this fluid disturbs the functions of these 
 centres apparently by allowing the vessels to become too full. The 
 pressure exerted by the former we shall call the fluid-pressure from 
 without the brain ; that by the blood, the pressure from within. As 
 long as these two are balanced, the brain enjoys a healthy state of 
 function, supposing its texture to be normal. If either prevail, 
 more or less of disturbance will ensue. Their relative quantities, 
 if not in just proportion, will bear an inverse ratio to each other. If 
 there be much blood, the surrounding fluid will be totally, or in a 
 great measure, deficient; if the brain be ansemic, the quantity of sur- 
 rounding fluid will be large. 
 
 The existence of these two antagonizing forces may-be taken as a 
 proof that either of them may prevail ; and therefore, from the exist- 
 ence of the cerebro-spinal fluid we may infer that the actual quantity 
 of blood circulating in the brain is liable to variation. 
 
 This fluid is a valuable regulator of vascular fullness within the 
 cranium, and a protector of the brain against too much pressure from 
 within. So long as it exists in normal quantity, it resists the entrance 
 of more than a certain proportion of blood into the vessels. Under 
 the influence of an unusual force of the heart, an undue quantity of 
 blood may be forced into the brain ; the eflfects of which will be, first, 
 the displacement of a p^rt, or of the whole surrounding fluid, and, 
 secondly, the compression of the brain. 
 
 On the other hand, the brain may receive too little blood. In such 
 a case, if the surrounding fluid do not increase too rapidly, the 
 requisite degree of pressure will be maintained, and the healthy action 
 of the brain preserved. But, if the brain be deprived of its due pro- 
 portion of blood by some sudden depression of the heart's power,vthere 
 is no time nor source for the pouring out of new fluid, and a state of 
 syncope, or of delirium, will ensue. Such seems to be the explana- 
 tion of those cases of delirium which ensue upon hemorrhages, large 
 bleedings, or the sudden supervention of inflammation of the peri- 
 cardium or endocardium. In many of these cases, however, it is 
 important to notice, that the blood is more or less damaged in quality, 
 
ROOTS OF THE SPINAL NERVES. 269 
 
 deficient in some of its stamina] principles, or charged with some mor- 
 bid matter; and this vitiated state of the vital fluid has, no doubt, a 
 considerable share in the production of the morbid phenomena. 
 
 The following infereneies, which are of practical application, will 
 form a suitable conclusion to these remarks on the circulation within 
 the cranium. 
 
 1. That the brain, although not so amenable to the influence of 
 atmospheric pressure as more superficial parts, is sufiicienlly so to 
 admit of variations in the quantity of its circulating, fluid. 
 
 2. That, consequently, general or local bleeding will exert the 
 same kind of influence upon the circulation in the brain, as in other 
 organs, so far as relates to diminishing the quantity of blood in it. 
 
 3. But that the brain is liable to suffer from the loss of blood in a 
 different way from other viscera, inasmuch as copious bleeding may 
 occasion serious disturbance in the functions of the brain by lessen- 
 ing, the force of the heart's action, and thereby depriving the brain 
 of that amount of pressure on its vascular surface which seems essen- 
 tialjo its healthy action. 
 
 4. That the depression of the heart's force from any other cause, 
 is capable of producing similar cerebral disturbance for the same 
 reasons. 
 
 The following works may be consulted upon the subjects treated of in this chapter: 
 
 Cruvei|hier's Anat. Descr. t. iv. — Meckel, Anal. G6n. Descr. et Pathol, t. ii. — Reil's 
 
 Essays, translated in Mayo's Anat. and Phys. Commentaries. — The article Nervous 
 
 Centres in the Cyclopaedia of Anatomy Mayo's Plates of the Brain. — Stilling uud 
 
 ■^allach, Untersuchungenviberdie Textur des Riickenmarks. Leipz. 1S42. — Still- 
 ing, iiber die Textur und Function der Medulla oblongata. Erlang. 1843. — Foville, 
 Anat du Syst. Nerveux. Par. 1844. — Leuret, Anat. Compar^e du Syst. Nerveux. 
 Par. 1839. 
 
 The subject of the circulation in the brain has been treated with great acuteness 
 and learning by Dr. George Burrows, in the Lumleian Lectures for 1843, Lond. Med. 
 Gazette, vol. xxxii. 
 
 CHAPTER XL 
 
 OF THE SPINAL NERVES. OF THE ENCEPHALIC NERVES. — METHOD OF 
 
 DETERMINING THE FUNCTIONS OF NERVES. — OF THE FUNCTIONS OF 
 THE SPINAL CORD AND ENCEPHALON. 
 
 Before we can satisfactorily investigate the functions of the cere- 
 bro-spinal centre, or of its various segments, it will be necessary to 
 give some account of the nerves which are connected with them. 
 
 These nerves are described in two classes, the spinal and the ence- 
 phalic. The former class consists of all those which arise from the 
 spinal cord, and emerge from the spinal canal through orifices in its 
 wall. The latter consists of those which are connected with the 
 encephalon. 
 
 Ojf the spinal nerves. — There is a pair of spinal nerves for each 
 
270 INNERVATION. 
 
 pair of intervertebral foramina on the same level, and for those be- 
 tween the atlas and occiput. We can thus enumerate in all thirty-one 
 pair of nerves having their origin from the spinal cord, exclusive of 
 the spinal accessory nerve, which is connected with the upper part of 
 the cervical region. 
 
 The spinal nerves have the following very constant characters. 
 Each has its origin by two roots, of which the anterior is distinctly 
 inferior in size to the posterior (fig. 61, p, a, p. 205). The ligamen- 
 tum denticulatum is placed between these roots. Each root passes 
 out by a distinct opening in the dura mater. Immediately after its 
 emergence a gariglion is formed on the posterior root, and the ante- 
 rior root lies imbedded in the anterior surface of the ganglion, and 
 inclosed in the same sheath, but without mingling its fibres with those 
 of the ganglion. Beyond it, the nervous fibres of both roots inter- 
 mingle, and a compound spinal nerve results. The trunk thus formed 
 passes immediately through the intervertebral canal, and divided into 
 an anterior and posterior branch (fig. 61, a',p'). The former is in 
 general considerably the larger. The latter passes backwards,«iand 
 sinks in among the muscles of the posterior regions of the trunk. The 
 anterior branches in the cervical, lumbar, and sacral regions form 
 large and intricate plexuses, (cervical, axillary, lumbar, and sacral,) 
 from which nerves are furnished to the extremities and the anterior 
 part of the trunk. 
 
 The first spinal nerve, called by Winslow the suboccipital, oflTers an 
 exception to this arrangement. Generally it arises by two roots, of 
 which, however, the anterior is the larger. Sometimes it has only 
 one root, corresponding to the anterior. 
 
 The spinal nerves are arranged naturally in classes, according to 
 the regions of the spine in which they take their rise. We number 
 eight in the cervical region, the suboccipital included; twelve in the 
 dorsal region; five in the lumbar, and six in the sacral regions. All 
 the nerves after the second pass obliquely outwards and downwards, 
 from their emergence from the spinal cord to their exit from the verte- 
 bral canal ; and this obliquity gradually increases from the higher to 
 the lower nerves, so that the inferior ones are nearly perpendicular, 
 and, as their intraspinal course is of some length, they are collected 
 into a leash, which constitutes the cauda equina. 
 
 All the spinal nerves arise from the cord by separate fasciculi of 
 filaments, which, as they approach the dura mater, converge to each 
 other, and are united together to constitute the anterior or the posterior 
 roots. The posterior roots arise at a pretty uniform distance from the 
 posterior median fissure in all regions of the cord, indicating but a 
 very trifling change in the thickness of the posterior columns through- 
 out their entire course. Not so the anterior ones : they are farthest 
 from the anterior median fissure in the neck, but very near it in the 
 dorsal region ; this difference being due to the variation in the thick- 
 ness of the i antero-lateral columns in the difTerent regions. The 
 ganglia on the posterior roots are always proportionate in size to the 
 roots themselves. 
 
 In tracing the mode of connection of the roots of the spinal nerves 
 
ENCEPHALIC NERVES. 271 
 
 with the cord, great care is required, from the sudden changef of. con- 
 sistence which their fascicles experience on penetrating the substance 
 of the cord. They lose the sheath of pia mater which gave firmness 
 to that part which is external to the cord, and soon break up into their 
 Component fibrillee. For this reason, the specimen employed for the 
 dissection should be quite recent, and slightly hardened by previous 
 immersion in spirit. 
 
 The anterior roots penetrate the lateral part of the antero-lateral 
 columns. Their fibres soon radiate, some passing upwards and in- 
 wards, others horizontally inwards towards the centre of the cord, 
 mingling, no doubt, with the elements of the vesicular matter com- 
 posing the anterior horn. It is a matter of uncertainty whether the 
 fibres which take an upward course pass into the gray matter, o;f simply 
 merge into the longitudinal fibres of the cord and pass upwards to the 
 brain. Mr. Grainger's researches lead him to suppose that each root 
 consists of a double set of fibres, — one which penetrates, and has its 
 origin from, the gray matter, and the other which is continuous with 
 the longitudinal fibres. This view is considered to derive proba- 
 bility from the hypothesis which ascribes the voluntary an^ involun- 
 tary actions of the cord to two distinct series of fibres, of which one 
 is under cerebral influence, and the other merely excito-motory, and 
 it might be acknowledged to do so, if the necessity of distinct fibres 
 for the two kinds of action were first proved. It is possible, how- 
 ever, that «W the fibres penetrate and arise from the gray matter. 
 But we have seen nothing to justify Stilling and Wallach's assertion, 
 that the anterior and posterior roots coalesce in the gray matter, form- 
 ing loops, the convexities of which are directed to the centre of the 
 cord ; and we have already stated our reasons (p. 236) for doubting 
 the fibrous nature of the lines which these writers represent as radiat- 
 ing between the gray matter and the surface of the cord. 
 
 The posterior roots adhere to the posterior part of the antero- 
 lateral column, and ^re doubtless closely connected with the posterior 
 horns of gray matter. In separating the columns of the cord along the 
 line of sequence of the fascicles of the posterior roots, we have always 
 found these rooljs to remain with the antero-lateral columns, and to 
 have little- or no connection with the posterior ones. We would 
 therefore refer the origin of these nerves to the posterior horns of gray 
 matter, and to the posterior part of the antero-lateral columns. 
 
 Of the encephalic nerves. — The arrangement of these nerves, ori- 
 ginally proposed by Willis, although open to many objections, has 
 nevertheless been so long adopted in this country and on the Con- 
 tinent, and is so constantly used by scientific as well as practical 
 writers, that to abandon it would be productive of great inconveni- 
 ence, and would be of no advantage, unless some other arrangement 
 of unexceptionable kind could be substituted for it. In the absence of 
 any such new mode of arrangement, we propose to adhere to that of 
 Willis; at the same time remarking, that much of the imperfection of 
 it is obviated by naming each pair of nerves from some prominent 
 feature either of its function or its anatomical connections. 
 
 Twelve pairs of nerves are found connected with the base of the 
 
in2 INNERVATION. 
 
 encephalon. Five pairs have been so classed by Willis as to form 
 two in his arrangement; three pairs being allotted to his eighth pair 
 of nerves, and two to his seventh. Willis' arrangement, therefore, 
 comprises the following nine pairs of nerves, which he enumerates 
 in passing from the anterior to the posterior part of the base ; the first 
 pair, or olfactory nerves; the second pair, or optic; the third pair, 
 motores oculorum; the fourth pair, pathetici ; the fifth pair; the sixth 
 pair, abducentes oculum ; the seventh pair, including the portio mollis 
 or auditory nerve, and the portio dura ov'fadal nerve ; the eighth pair, 
 including the glosso-pkaryngeal, the pneumo- gastric, and the spinal 
 accessory ; the ninth pair, or hypoglossal. Willis included among his 
 encephalic nerves the first cervical nerve or sub-occipital, which he 
 therefore numbered as the tenth pair. 
 
 As the cranium may be shown to be composed of the elements of 
 three vertebrse, it has been attempted to prove that among these nerves 
 some may be classed with the vertebral or spinal nerves. The fifth 
 is obviously of this kind, from its anatomical characters, namely, two 
 roots ; one small, ganglionless, the other large, ganglionic ; and with 
 the formed, the analogue of the anterior spinal root, the third, fourth, 
 and sixth nerves may be conjoined from their similarity in structure 
 and distribution. Thus one cranio-vertebral nerve is formed, the 
 anterior or motor root of which consists of the smaller portion of the 
 fifth, the third, fourth, and sixth nerves, and the posterior or sensitive 
 root of the larger portion of the fifth. A second cranio-vertebral nerve 
 consists of the eighth pair, to which might be added the facial, con- 
 tributing to its motor portion. A third is formed by the hypoglossal,* 
 but the analogy, in the latter case, is certainly far from obvious. 
 
 How to determine the Junction of a nerve ? — It has been stated in a 
 former chapter that nerves evince special properties, depending on 
 the connections which they form at the periphery, or at the centre ; 
 that they may be divided into motor, sensitive, and, according to one 
 view, excito-motor, according to the manner in which Ihey respond 
 to particular stimuli ; and that fibres possessing each of these endow- 
 ments may be bound together in a common sheath as one nerve. To 
 determine with precision the office which each nerve performs is a 
 problem of great importance, not only from its bearing upon the phy- 
 siology of the nervous centres, but from its great practical value in 
 the diagnosis and treatment of disease. — (Introd., p. 47.) 
 
 The following are the means on which we should rely, in order to 
 determine the function of a nerve. 
 
 First, its anatomy in man. — The origin by a double root denotes a 
 double function. Its peripheral distribution, however, gives more 
 valuable assistance. If distributed to muscles only, it clearly must 
 be motor; if to sentient surfaces only, sensitive and perhaps excitor; 
 if to both, motor, and sentient, or excito-motor. 
 
 Secondly, its anatomy in animals. — The comparison of the origin 
 and distribution in the lower animals with those in man often throws 
 light on the function, by confirming the result of anatomical investi- 
 
 • Miiller's Physiology by Baly, vol. i. p. 841. 
 
FUNCTIONS OF NERVES, HOW DETERMINED. 273 
 
 gation in the human subject,- or by displaying either a peculiar deve- 
 lopment of the nerve, in reference to some special function proper to 
 particular animals ; or, on the other hand, the non-development of a 
 nerve, or of a part of one, where some function may be deficient. 
 The enormous development of a branch of the fifth nerve in animals 
 with proboscides, or highly tactile snouts, — of a branch of the facial, 
 ■where such an organ is very movable, — the small size of the latter 
 .nerve where the muscles of the face are few, are instances quite in 
 ■ J)olnt. 
 
 Thirdly, experiment on animals just>dead, or on those living. — The 
 irritation of a motor nerve in an animal recently dead causes contrac- 
 tion of the muscles to which it is distributed. The section of one in 
 a living animal paralyses its muscles ; but irritation of the portion 
 below the section causes contraction of those muscles which that seg- 
 ment of the nerve supplies. The simplest way of applying a stimulus 
 for experimental purposes is by passing a galvanic current from a small 
 battery. If the current be directed through a nerve so that it shall 
 pass along the smallest portion of it, by placing one pole on one side 
 of it, and the other on the opposite, but a little lower down or higher 
 up, we may gain a strong indication of the motor power of the nerve, 
 if contractions are thereby excited. This indication becomes certain 
 if the same effect be produced by galvanizing the nerve ih this way, 
 after it has been separated from all connection with the spinal cord or 
 brain. Such an experiment on a sensitive nerve would produce no 
 motor effect. Matteucci has shown that to produce the motor effect 
 in a motor nerve, the current must pass along some portion of the 
 nerve-fibre, howgver small; and that a current directed precisely at 
 right angles to the fibres will not excite nervous power.* 
 
 MM. Longet and Matteucci affirm that a motor nerve may be dis- 
 tinguished from a compound one by the different effect of opening or 
 closing an electric current on each under certain circumstances. It 
 had already been ascertained by Lebot, Bellingeri, Nobili, and Mari- 
 anini, that compound nerves, the sciatic, for instance, are at first ex- 
 cited equally on closing and on opening the electric circuit, whether 
 the current be direct (i. e. from the brain or cord to the nerves), or 
 inverse (from the nerves to the brain or cord); but after a time they 
 are excitable, as shown by the contraction of the muscles below the 
 point of the nerve stimulated, only on closing the direct current or 
 opening the inverse. With a purely motor nerve, however, such as 
 the anterior root of a spinal nerve, a different result is obtained ; in- 
 asmuch as the contractions of the muscles can only be excited on 
 opening the direct current or closing the inverse, j 
 
 Sometimes we find thatj if the trunk of a nerve be divided at some 
 distance from its origin, irritation of the central segment will excite 
 contractions, whilst that of the peripheral one will fail to do so. Such 
 a nerve haS been called an excitor ; for it causes muscular movement, 
 
 • See an account of Malteucci's observations on the different effects of electricity 
 on nerves, in ihe appendix to this chapter. ,, 
 
 •j- Maiieucci et Longet, sur la relation qui^xiste entre le sens du conrant <51ectrique 
 et les contractions musculaires dues a ce courant. Paris, 1844. 
 
274 INNERVATION. 
 
 not by its direct influence upon muscles, but by exciting the centre, 
 which in its turn stimulates mator nerves arising from it. We judge 
 a nerve to be sensitive, if, when irritated in man or the lower animals 
 during life, a peculiar sensation or pain be excited ; or if section of it 
 destroys the sensibility of the parts to which it is distributed. 
 
 Fourthly. Clinical observation furnishes most valuable opportuni- 
 ties of testing the true function of nerves. We observe a particular 
 form of paralysis, and we inquire what nerve is diseased ; we find 
 pain felt in particular regions, and we ascertain that this is in conse- 
 quence of a morbid state of particular nerves ; certain functions are 
 impaired or suspended, if certain nerves be affected with disease. A 
 woman, lately in King's College Hospital, had a singular train of 
 symptoms, which were at first referred to hysteria. However, in a 
 little time they became so confirmed, that no doubt could be enter- 
 tained of organic lesion. There were ptosis of the upper lids, — 
 paralysis of the muscles of the eyeball supplied by the third nerve, 
 — paralysis of the pharynx, so that the power of deglutition was de- 
 stroyed, — paralysis of the trapezii muscles, and of those on the back 
 of the neck, — great feebleness of voice. She died like one asphyx- 
 iated. After death, the following nerves were found involved in a 
 thickened neurilemma, with altered nerve-tubes, — the third pair, the 
 fourth pair on the left side, the glossopharyngeal, the vagus, the 
 spinal accessory ; each of which contributed more or less to sijpply 
 with nerves the parts paralyzed. 
 
 Functions oy the roots of spinal nerves. — The application of ana- 
 tomical investigation, and of experiment, to determine the functions 
 of the anterior and posterior roots of spinal nerves respectively, was 
 the first important step towards a right understanding in the physiology 
 of the nervous system. This was undoubtedly taken by Sir C. Bell; 
 and, although there were other labourers in the same field not un- 
 worthy claimants of some share in the merit of this important inves- 
 tigation, it cannot be denied that the endowments of the roots were 
 discovered by Bell. 
 
 The original experiments of Bell, in which he was assisted by the 
 late Mr. John Shaw, consisted in laying open the spinal canal in rab- 
 bits, and irritating or dividing the roots of the spinal nerves. Bell 
 distinctly affirmed that irritation of the anterior roots caused muscular 
 movement, and that the posterior roots might be irritated without 
 giving rise to any muscular action. Destruction of the posterior roots 
 did not impair the voluntary power over the muscles. Hence it was 
 inferred that the anterior roots were motor, and the posterior roots not 
 motor; but, from the violence of the operation, and the pain produced 
 in performing it, the experiments having been tried on rabbits, it was 
 impossible to determine what degree of sensibility remained in parts 
 supplied from the divided roots. 
 
 Numerous subsequent experimenters arrived at similar results to 
 those of Bell; but no one obtained such satisfactory conclusions as 
 Miiller, who adopted the expedient of experimenting on frogs instead 
 of mammalia, with which latter the experiments involved the neces- 
 sity of a tedious and painful operation, and much bloodshed. In 
 
FUNCTIONS OF THE SPINAL CORD. , 275 
 
 frogs, on the contrary, from the great width of the lower part of the 
 spinal canal, the roots of the nerves can be exposed with facility, and 
 their excitability lasts sufficiently long to yield every result. These 
 experiments we have repeated frequently, with results precisely similar 
 to those which Miiller obtained. 
 
 In the experiments on frogs, irritation, mechanical or galvanic, of 
 the anterior root always provokes muscular contraction. No such 
 effect follows irritation of the posterior root. Section of the anterior 
 root causes paralysis of motion ; that of the posterior, paralysis of 
 sensation. This latter effect is evinced by the utter insensibility to 
 pain shown on pinching a toe, whilst in the limb in which the poste- 
 rior root is entire such an irritation is evidently acutely felt. If the 
 anterior roots of the nerves to the lower extremity be cut on one side, 
 and the posterior roots on the other, voluntary power without sensation 
 will remain in the latter, and sensation without voluntary power in the 
 former. - 
 
 Valentin, Seubert, Panizza, and Longet have performed similar 
 experiments upon mammiferous animals with precisely the same ef- 
 fects. 
 
 The conclusion to be derived from these experiments is as follows: 
 that the anterior root of each spinal nerve is motor, and the posterior 
 sensitive. 
 
 Comparative anatomy confirms this conclusion, by showing that a 
 similar arrangement of the spinal roots prevails among all classes of 
 vertebrate animals, and that if, in any particular class of animals, either 
 the motor or sensitive power predominate, there is in correspondence 
 with it a marked development of the anterior or posterior roots ; and 
 the frequent occurrence of paralysis of sensation and motion, as a 
 consequence of disease within the spinal canal, also tends to the same 
 inference. 
 
 Magendie affirms that the anterior root is slightly sensitive, owing, 
 as Kronenberg has shown, to an anastomotic filament which it derives 
 from the posterior root. 
 
 Functions of the spinal cord. — Since nerves of sensation and mo- 
 tion have their origin from the cord, it cannot be doubted that this 
 organ is the medium for the reception and propagation, first, of sensi- 
 tive impressions made upon those surfaces on which its nerves are 
 distributed, and secondly, of those impulses which are the ordinary 
 excitants of muscular movements. 
 
 Experiment and clinical observation, however, show that sensa- 
 tion Bind voluntary motion are not connected with, or dependent on, 
 the spinal cord alone. If the connections of this organ with the en- 
 cephalon be perfect, and uninterrupted by any solution of continuity, 
 morbid deposit in it, or morbid growth causing compression, then the 
 essential condition for the full play of the nervous force, whether for 
 sensation or voluntary motion, is fulfilled. But if the cord be severed 
 just below the plane of the occipital foramen, as when an animal is 
 pithed, all voluntary power over the parts supplied by spinal nerves 
 ceases, and all sensation in those parts disappears at the same time. 
 
276 , INNERVATION. 
 
 Here the cord itself is uninjured; but its continuity with the ence- 
 phalon is destroyed. 
 
 In cases of injury to the vertebral column, causing fracture and 
 displacement of the vertebrae, and destruction of the cord, the parts 
 supplied from that portion of the cord which is below the seat of 
 injury are paralyzed as regards voluntary motion and sensation. The 
 higher the seat of injury, the more extensive will be the paralysis. 
 A man who has received extensive injury of the spinal cord in the 
 neck, is like a living head and a dead trunk, — dead to its own sensa- 
 tions, and to all voluntary control over its movements. 
 
 Similar remarks may be made respecting those cases in which dis- 
 ease, or compression of the cord by some intra-spinal growth, has 
 interrupted its continuity in some region. The extent of the para- 
 lyzed parts always affords a correct indication of thse seat of the 
 solution of continuity. 
 
 If the spinal cord be divided partially in the transverse direction, 
 there will be paralysis of parts on the same side with the injury in- 
 flicted. A longitudinal section of the cord along the median line 
 does not cause any paralysis; a temporary disturbance of its functions, 
 however, ensues, which soon subsides. 
 
 So long, then, as the spinal cord and encephalon are continuous, 
 and in their normal state, the former organ must be regarded as spe- 
 cially adapted to receive and propagate sensitive impressions from the 
 trunk and extremities, or to convey the stimulus of volition to their 
 muscular nerves. 
 
 There is nothing, however, in these facts to denote that the spinal 
 cord does not share, in some degree in the function of sensation and 
 voluntary motion. All that we are justified in inferring from them is, 
 that the union of the encephalon with the spinal cord is necessary for 
 voluntary motion and for sensation. 
 
 Indeed, the recent discovery of the amphioxus lancenlatus, a small 
 fish found in the Archipelago, makes it probable that voluntary mo- 
 tion and sensation may exist where there is a well-developed spinal 
 cord, the anterior extremity of which tapers to a fine point, and is far 
 from exhibiting the ordinary characteristics even of a brain so inferior 
 in organization as that of fishes.* 
 
 In most instances where the spinal cord has been divided, whether 
 by design or accident, it has been found that, although the will can- 
 not move the paralyzed parts, movements do occur in them of which 
 the individual is unconscious, and which he is wholly unable to pre- 
 vent. These take place sometimes as if spontaneously, at other times 
 as the effect of the application of a stimulus to some surface supplied 
 by spinal nerves. The apparently spontaneous movements frequently 
 resemble voluntary actions so closely, that it is almost impossible to 
 distinguish them. 
 
 These phenomena occur in all classes of animals, warm-blooded as 
 well as cold-blooded. In the latter, however, they are much more 
 marked ; the nervous force endures much longer in these animals than 
 
 • Goodsir, in Ed. Philos. Transactions, and Cyclop, of Anat., vol. iii., p. 615. 
 
FUNCTIONS OF THE CORD. 277 
 
 in the higher classes of mammalia and birds, just as we have already 
 seen that^he muscular' po^er does, although we have no reason, to 
 suppose that either force is more energetic, because it is'more enduring. 
 On this account cold-blooded animals must be selected for exhibiting, 
 the phenomena; and accordingly hosts of frogs, salamanders, snakes, 
 turtles, and fishes have falletl a prey to the experimental researches 
 of the n-umerous physiologists who have devoted themselves to these 
 -investigations. 
 
 The following experiments serve to illastrate these actions: 
 
 If a frog be pithed by dividing the spinal cord between the occi- 
 pital hole and the first vertebrae, an universal convulsion takes place 
 while the kiiife is .passing through the nervous centre. ■ Thig, how- 
 ever, quickly subsides; and, if the animal be placed on a table, he 
 will assume his ordinarypdsition of rest. Trt some exceptional cases; 
 however, frequent combined movements of the lower extremities will 
 take place for a longer or shorter time after the operation. When all 
 such disturbance has ceased, the animal remains perfectly quiet, and 
 as if in repose, nor does there appear to be the slightest expression 
 of paiiT or suffering. He is quite unable to move' by any voluntary 
 eflJbrt. However one may try to fri!ghten him, he remains in the same 
 place and posture. If now a toe be pinched, instantly the limb is 
 drawn up, orhe seems to push awaj the irritating agent, and then 
 draws up the leg again into its old position. Sometimes a stimulus 
 of this kind causes both limbS to be violently moved backwards. A" 
 similar movement follows stimulation of the anus. If the skin be 
 pinched at any part, some neighbouring muscle or muscles will be 
 thrown into action. Irritation of the anterior extremities will occa- 
 sion movements in them ; but it is worthy of note, that these move- 
 ments are seldom so energetic as those of the lower extremities. 
 
 It is not out of place to .state here, that phenomena of this ki ild 
 are not confined to the trunk and extremities which are supplied by 
 spinal nerves only. The head and face with which the ehcepha on 
 remains in connection exhibit similar actions. The slightest touch to 
 the margin of either eyelid, or to the surface of the conjunctiva, causes 
 instantaneous winking; the attempt to depress the lower jaw, for the 
 purpose of opening the mouth, is resisted; and the act of deglutition 
 is provoked by applying a mechanical i^timulus to the back of "the 
 throat. 
 
 The stimuli which excite these movements are those ordinary ones 
 which are capable of calling nervous power into play, such as mecha* 
 hical irritation, heat, cold, galvanism, chemical irritants. 
 
 There can be no grounds for supposing that the will has anything 
 to do with these movenients. An animal pithed, which is to all in- 
 tents and purposes in thersame condition as one decapitated, shows 
 iio sign of voluntary action, excepting perhaps for a short time alter 
 the operation, whil^ the irritation caused by the division of the cord 
 remain^. He maintains one and the same position, without evincing 
 any sign of sense or motion, unless a stimulus be applied to some 
 part of the surface; and, after the movement which such a stimulus 
 excited has ceased, he resumes the same state of inactivity. 
 14 
 
278 INNERVATION. 
 
 Coteparing this state of a pithed or decapitated, gnitnal with the' 
 phenomena which we know to take place in the human subject in 
 effect of-particular forms of accident pr disease, it is impossible to 
 regard these actions in any other light than as involuntary ones. To 
 refer dnce more to such a case as that cited in a former paragraph, 
 when, from-the.destructionof the cervical part of the cord, the trunk 
 appears as if dead, while the head liveS, we find in many instances, 
 if the stunning effect have not been too great, that similar motions to 
 those described in the frog may be produced by the application of 
 mechanical or other stimali to the surface.; Tickling th& soles of the 
 feet causes movements of theJower extremities: the introduction of 
 a catheter into , the urethra, which is not felt by the patient, excites 
 the penis to erection. Over these acts not only have the patients no 
 control, but they are absolutely unconscious of their occurrence, as 
 well as of the application of the stimuli by which they were provoked. 
 It is plain, then, that these movements take place, without the con- 
 currence or even the cognizance of the wiinti, whether as the recipient 
 of stimuli, or as the source of voluntary impulses. 
 
 In hemiplegia, the result of diseased brain, when the paralysis is 
 complete, the influence of the will over the paralyzed side is altogether 
 cut off. In such cases, movements may be excited . in the palsied 
 leg--Very rarely in the arm — by stimuli applied to the sole of the 
 foot, or elsewhere; and we often astonish the patient himself, wht) 
 'expresses his utter inability, by any effort of his will, to move his 
 leg, by exciting active movement of it on touching the sole of the 
 foot very lightly with a feather. It is proper to add, that there is 
 much variety as regard? the extent to which, these actions take place 
 in hemiplegic cases, owing to causes, which are not yet fully under- 
 stood. Still, they do occur in a larg€ proportion of instances, and in 
 the most marked way. In most of the cases of hemiplegia the sur- 
 face retains its sensibility; but in most of those of paraplegia sensi- 
 bility is much diminished or completely destroyed. 
 
 In the anencephalic foetus, in which all the ehcephalon but part of 
 the medulla oblongata is wanting by congenital defect, actions take 
 place in obedience to stimuli propagated to the cord from some sur- 
 face, or applied directly to it; but no ihovements are seen which, can 
 be supposedto, originate in an effort of the will, nor is there any proof 
 of the existence of sensibility. 
 
 Other fatts may' be adduced in evidence of the involnntaTy nature 
 of these movements. 
 
 It is remarkable that actions of this kind will continue to be mani- 
 fested after decapitation, not only in the trunk, but also in segments 
 of it with which a portion of the spinal cord remains in connection. 
 If the body of a snake or an eel be divided into several segments, 
 each one will exhibit movements for some time, upon the, application 
 of a stimulus. The same thing may be observed in frogs, salaman- 
 ders, turtles, and other coid-bloed^d creatures. In birds and mam- 
 malia, however, they are less conspicuous, because in them the nervous 
 power is 80 soon extinct. 
 
 These facts suggest an obvious comparison between^the spinal cord 
 
FUNCTIONS OF THE GORD. 279 
 
 of vertebrate animals and the abdominal ganglionic chain of articulate 
 invertebrata. In the latter, each segment of the body has its proper 
 ganglionic centres, and is, therefore, to a certain extent, independent 
 Qf the rest. Eyery schoolboy has witaessed the. writhings of an 
 earthworvm, which his mischievous propensity has prompted him to 
 divide. into several pieces. Movements will continue in each pieqe 
 so long as the irritation produced by the subdivision, remains; and, 
 after that has ceased, movements may be excited in any segment by 
 stimulating it^ surface.. These movements seem precisely analogous 
 to those which may be excited in the subdivisions of the trunk of a 
 vertebpate animal. The spinal cord, tl^en, may be viewed' as one 
 continuous centre, made up of a number of segments fused together 
 at their e;xtremities. In the articulate ganglionic chain the centres of 
 the segments remain distinct, although connectedby fibres which pass 
 from one to the other. 
 
 When the spiiiai cord is divided about its middle, a remarkable 
 difference may be noticed in the eifect.s. of irritation on the anterior 
 and the posterior segment, as shown in some of Flourens' experiments. 
 When the anterior segmetif (that which still retains its connection 
 with the brain) is irritated, not only are movements of the anterior 
 extremities produced, but the animal evinces unequivocal signs of 
 pain ; but, when the pjosterior segment is irritated, the animal seems 
 not onl^ insensible to pain,, but unconscious even of the movements 
 that have been excited in the posterior extreiniKes. 
 
 Nothing can be more conclusive than such an experimerit, in illus- 
 tration of the fact that connection with the encephalon is necessary to, 
 sensation ; and that movements, not only without volition, but even 
 without consciousness, may be excited by stimulating the posterior 
 segments. > 
 
 Direct irritation of the spinal cord is capable of exciting these mo ve- 
 ments as much as when the stimulus is applied to the skin. 
 
 When the spinal cord is removed, all these motions cease ^ no 
 movement of any kind, voluntary or involuntary, cati then be excited, 
 except by direfctly stimulating the muscles, or the motor nerves by 
 which the muscles are supplied. Division of all the roots of the 
 nerves at their emergence from the cord produces precisely the same 
 effect. Under such circumstances no motion can, be excited by stim-, 
 ulation of the surfacej^nor by stimulation, of the cord itself; and 
 this fact may be regarded as an unequivocal proof that the nerves, in 
 ordinary actions, are propagators of the change produced by im- 
 pressions to or from the centres ; and that in the physical nervous 
 actions the stimulus acts not froin one nerve to another directly, but 
 through the afferent nerve upon the centre, by which the motor nerve 
 is excited. 
 
 From these details we may draw the following conclusions: — 1, 
 that the spinal cord, (we use the term in its simple aijatomical sense, 
 — the intra-spinal nervous ma5S,)iw unionwith the brain, is the instru- 
 ment of sensation and voluntary motion to the trunk and extremities; 
 3, that the spinal cord maybe the medium for the excitation of move- 
 ments, independently of volition or sensation, either by direct irritation 
 
280 INNERVATION. 
 
 of its substance, or by the influence of astitnulus conveyed to it from 
 some surface of the trunk or extremities by its nerves distributed upon 
 that surface. 
 
 This latier qfEce of the 'cord, although recognized by Whytt, 
 Prochaska, Blane, and Flourens, had not attracted all the notice 
 ■which its great importance merits, until the researches of Dr. Mar- 
 shall Hall and Professor Miiller drew attention to them ; and to these 
 physiologists, but especially to the former, much praise is due for the. 
 zealous and efficient manner in which they have investigated the sub- 
 ject. ^ ' ^ 
 
 The class of actions which take place in virtue of this power of 
 the cord are so, independent of all mental influence, and so purely 
 physical in their cause, &s well as in their nature, being provoked by 
 a physical stimulus, and consistijig essentially in a physical change 
 in the centre, as well as in its afferent and efferent nerves, that 
 they may be distinguished from those of volition- and sensation, in 
 which the mind has a necessary share, by being designated " phy- 
 sical." It has been already stated that Dr. Marshall Hall uses the 
 not unobjectioliable title of " excito-motory" in reference to these 
 actions. 
 
 In general, when a stimulus is applied to the spinal cord, the ac- 
 tions which are excited by it are confined to a part W^hich derives its 
 nerves from that segmgnt of the cord on which the stimulus fafls. In 
 some instances, however, parts supplied from other and even distant 
 segments are thrown into action. Thus irritation of one leg will 
 cause movements of orie or both of the upper extremities ; the intro- 
 duction of a catheter into the urethra will sometime cause forcible 
 contractions of the muscles of all the limbs. No doubt these effects 
 are due to the extension of the irritation in the cord beyond the point 
 first stimulat€d ; and they may be regarded as proofs that that peculiar 
 state of physical change which nervous irritation can excite in a 
 centre may be propagated in the spinal Cord, upwards, downwards, 
 or side^vays from the seat of the primary stimulation. 
 
 Disease affords some striking instances in' confirmation of (his re- 
 mark. 
 
 A wound in the sole of the foot, or the ball of the thumb, or in 
 some other situation favourable to the maintenance of prolonged 
 irritation, is capable of exciting a particular region of the cord, from 
 which the state of excitement spreads so as to involve not only the 
 whole cord, but part of the medulla oblongata also ; and in this state 
 a large proportion of the motor nerves participate, so as to induce 
 tonic contraction of the muscles they supply. This is the rationale 
 of the development of that fearful malady called tetanus. It consists 
 not in an inflammatory affection of^the cord, or of its membranes, nor 
 in congestion of them, but simply in a state of prolonged physical 
 excitement, the natural polar force of the centre being greatly exalted, 
 and kept so by the constant irritation propagated to it by the nerves 
 of the wounded part. 
 
 In cases of paraplegia from disease of the spinal cord, even when 
 the paralysis of sensation and of motion is complete, patients are 
 
POLAR STATE OF THE CORD. 281 
 
 lormented with involuntary movements of the lower extremities at 
 night, which not otily prevent sleep, but occasion considerable pain 
 and distress. Thus, parts which in their quiescent state are insensible, 
 become painful in;the state of excitement. The cause of thi's;is no 
 doubt to be foundi in a periodical exacerbation of the primary disease 
 of the cord, aijd the extension of the state of excitement from the 
 seat of the lesion to the wholei cord ; to that portion which is in con- 
 nection with the brain, as well as to that which is below 'the legion. 
 
 The rigid and contracted state of the muscle? of paralyzed limbs, 
 which frequently accopipanies red softening of the brain, arises from 
 the propagation of the excited state of the diseased part of the brain 
 to that portion of the spinal cord which is connected with it, and from 
 which the nerves of the paralyzed parts arise. These nerves likewise 
 participate in the irritation of the cord, and thus keep the muscles in 
 a continual state of active contractiop. There is no organic lesion of 
 the cord in these Cases ; its state of excitement is dependent on the 
 cerebral irritation. 
 
 The convulsions of epilepsy arise from a similar cause, namely, 
 irritation of the brain, involving the whole or a part of the spinal cord, 
 and the nerves arising from it. In many instances the convulsions are 
 limited to one-half of the body : in such cases there is generally lesion 
 of the brain on one side, and the Cerebral excitement is propagated 
 only to one-ihalf (the opposite) of the cord. . . 
 
 Some substances exert a peculiar influence upon the spinal cord, 
 and throw it into a state of considerable polar excitement. Strychnine 
 is the most energetic substance of this class. If a certain quantity of 
 this drug be injected into the blood, or taken into the stomach of 
 an animal, a state of general tetanus will quickly ensue, sensibility 
 remaining unimpaired. The slightest touch ' upon any part of the 
 surface^ even a breath of wind blown upon it, will cause a general 
 or partial convulsive movement. The whole .extent of the cord is 
 thrown into this polar state, and even the medulla oblongata is in- 
 volved in it ; wlience the closed jaws, the spasmodic state of the facial 
 muscles, the difficult deglutition. In this remiarkable state Of excite- 
 ment it is curious to observe that the spinal cord is perfectly natural 
 in point of structure, as far as our means of observation- enable us to 
 judge.' We have examined sO me spinal cords, of animals which 
 haVe died exhausted by the effects of the strychnine, but have always 
 found the nerve-tubes and other elements of the cord exhibiting their 
 natural appearance. 
 
 Opium is capable of creating a similar slate of polarity in the .cord. 
 This is most oonspicuous in cold-blooded animals; but no doubt it 
 produces, in a much less degree, a similar effect in the warm-blooded 
 classes. Hence there xs an objection to the use of. opium in large 
 doses in cases of tetanus ; and experience has shown its utter inefficacy 
 when administered to a l^rge amount. 
 
 This polar state of the cord, at least of a part of it, is sometimes 
 developed naturally.. The most remarkable example of this with 
 which we are acquainted is in the case of the male frog, in the spring 
 of the year, the season of copulation; the thumb on each hand be- 
 
282 INNERVATION. 
 
 coming at this season considerably enlarged, as is well known to 
 naturalists. This enlargement is caused principally by a considerable 
 development of the papillary structure of the skin which covers it, 
 so that large papillae are formed all over it. A male frog at this season 
 has an irresistible propensity to cling to apy object by seizing it be- 
 tween his anterior extremities. It is in this way he seizes upon and 
 clings to the female, fixing his thumbs to each side of her abdomen, 
 and remaining there for weeks, until the ova have been completely 
 expelled. An effort of the will alone could not keep up such a grasp 
 uninterruptedly for so long a time ; yet so firm is the hold that it can 
 with difficulty be relaxed. Whatever is brought in the way of the 
 thumbs will be caught by the forcible contraction of the anterior 
 limbs; and hence we often, find frogs clinging blindly to a piec^ of 
 wood, or a dead fish,' or some other substance which they may chance 
 to meet with. If the finger be placed between the anterior extremi- 
 ties, they will grasp it firmly; npr will they relax their graspuntil they 
 are separated by force. If the animal be decapitated whilst the finger 
 is within ^rasp of its anterior extremities, they still continue to hold 
 on firmly. The posterior half of the body may be cut away, and yet 
 the anterior extremities will still cling to the finger; but immediately 
 that segment of the cord from which the anterior extremities derive 
 their nerves has been removed all their motion ceases. This curious 
 instinct, then, of the male frog, which naturalists have long noticed, 
 is evidently connected with an exalted polarity of the cord, which is 
 most manifest in the anterior extremities by reason of the enlargement 
 of the thumb. It only exists during the period of sexual excitement, 
 for at other periods the excitability of the anterior extremities is con- 
 siderably less than that of the posterior. 
 
 Nothing seems to control this polar state of the cord so effectually 
 as cold. Ice applied along the spine, or the cold douche, may be 
 frequiently employed with great advantage in cases of muscular dis- 
 turbance dependent on this polar state of the cord. We know of no 
 substance which, when introduced into the blood, efiectually calms 
 this excited state. Conium and belladonna have been, in our hands, 
 very useful in relieving the cramps and startings in paraplegic cases. 
 We have seen no marked benefit from hydrocyanic acid, although 
 we have administered it freely: on the contrary, we fear that both it 
 and the two former substances might, if given in large doses, have 
 the contrary effect, and increase the polarity of the cord. Certain it 
 is, that animals poisoned by large doses of these drugs always die in 
 a state of general convulsion, and that in the instances where they 
 have acted as poisons on the human subject, general convulsions 
 have come on a longer or shorter time before death. 
 
 Functions of the columns of the cord. — Having so far determined 
 the functions of the entire cord, the next question which demands 
 our attention is, whether its columns have special functions, in ac- 
 cordance with those of the separate roots of the nerves. Could it be 
 proved that the anterior or motor roots were exclusively connected 
 with the antero-lateral columns, and that the posterior or sensitive 
 ones arose exclusively from the posterior columns, then there would 
 
OFFICE OF THE COLUMNS OF THE CORD. 283 
 
 bp good anatomical grounds for the doctrine so long erroneously pre- 
 valent, that the functions of these columns coincided with those of 
 the 'roots, that the posterior columns were sensitive aiid the anterior 
 motor: but nothing is more certain than that both roots are connected 
 with the antero-lateral columns; aind it is a matter of some doubt 
 whether the'posterior roots have any connection at allwifli the poste- 
 rior coliimhs. Hence, all that anatomy warrants us in stating is, that 
 the antero-lateral columns are probably compound in function, both 
 motor and sensitive. Respecting the office" of the posterior columns 
 little can be said. Are they sensitive.-' Were they so, it might be 
 expected that they would exhibit aii obvious enlargement at the 
 situations which correspond to the origins of the largest sensitive 
 nerves; but it is remarkable that the posterior columns exhibit little 
 variation of size .throughout the entire length of the cord. And it is 
 not likely they can be motor, inasmuch as the apparent Origin of the 
 motor roots is so distinctly remote from them. 
 
 Comparative anatomy throws no light on this question. New and' 
 careful researches are much needed to determine the development 
 of the posterior columns, and the exact relation which the posterior 
 roots bear tO theni in different classes of animals. 
 
 Nor do we derive much positiv-e knowledge from the researches of 
 the morbid anatomist. Cases, indeed, are on record, which show that 
 disease" of the posterior columns does not necessarily destroy sensi- 
 bility; that perfect .sensibility is "compatible with total destruction of 
 the posterior columns in some particular region, the posterior roots 
 remaining intact ; and others have occurred in which sensibility has 
 been impaired or destroyed, while the posterior columns remained 
 perfectly healthy. In a remarkable case, related by Dr. Webster, 
 there was complete paralysis of motion in the lower extremities, but 
 sensibility remained ;* yet there was complete destruction of the 
 posterior columns in the" lower part of the cervical region. Similar 
 cases have been put on record by Mr. Stanley and by Dr. W. Budd. 
 Dr. Nasse, of Bonn, refers to several cases of the same kind, observed 
 by himself or others. f We have ourselves seen two cases in which 
 the prominent symptom was great impairment of the motor power 
 without injury to the sensitive; yet the seat of organic lesion in both 
 was in the posterior columns of the cord. Such a case as^ thiit of Dr. 
 Webster's appears to us to be conclusive, so far as the following pro- 
 position extends, nariiely, that serisation may be enjoyed in the inferior 
 extremities independently of th posterior columns ; and that, even if 
 those columns be sensitive, there must be some other channel for the 
 transmission of sensitive impressions besides them. 
 
 We are not aware of any well observed case in which the motor 
 power persisted after extensive lesion of the antero-lateyal columns; 
 on the contrary. We believe it may be laid down as the general rule, 
 that lesion of those columns always' impairs both the motor and the 
 sensitive functions to an extent proportionate to the amount of morbid 
 structure. 
 
 * Med. Chir. Trans., vol. xxvi. 
 
 f Untersuohungen zur Physiologic und Pathologie. Bonn, 1835-36. 
 
284 INNER VATIOir. 
 
 Pathological observations, then, appear to warrant the conclusioir 
 that the antero-lateral cohimn^ are compound in function, both sensi- 
 tive and motor, but they do not justify us in attributing sensitive 
 power to the posterior columns. 
 
 Direct experiipents on the anterior and posterior columns of the 
 cord are surrounded by difficulties, which embarrass the experimenter, 
 and weaken the force of his inferences. The depth at which the 
 cord is situate in most vertebrate animals, its exti'eme excitability, the 
 intimate connection of its various columns with each other, so that 
 one can scarcely be irritated without the participation of the others, 
 the proximity of the roots of its nerves to each other, and the difE- 
 culty- of irritating any portion of the cord itself without affecting either 
 the anterior or the posterior roots, are great impediments to accurate 
 experiments, and sufficiently explain the discrepancies which are ap- 
 parent in the results of the various experiments which, have been 
 published. Moreover, the resultant phenomena, after experiments of 
 this kind, are extremely difficult of interpretation, especially with 
 reference J to sensation. ''The gradations of sensibility," remarks 
 Dr. Nasse, " are almost imperceptible ; the stiades are so delicately 
 and so intimately blended, that every attempt to determine the lipe 
 of transition proves inadequate. There is a great deal of truth in an 
 expression of Calmeil, that it is much easier to appreciate a hemi- 
 paralysis of motion than a hemiparalysi? of sensation. If the anterior 
 fasciculi of the cord possess sensibility, but only in a slight degree, 
 the mere opening of the vertebral canal and laying bare the cord must 
 cause such a degree of pain as would weaken or destroy the manifest- 
 ations of sensibility in the anterior fasciculi. This has not been 
 sufficiently attended to by experimenters. Again the practice of first 
 irritating the posterior fasciculi, and afterwards the anterior, must 
 have had considerable effect in producing the same alteration. It is 
 plain that, in this way, the relations which the aiiterior fasciculi bear 
 to sensation must b€ greatly obscured; y^t with the exception of some 
 few experiments, this has been the order of proceeding generally 
 ^^dopted.''* 
 
 All those who liave made experiments with the view of ascertaining 
 the functions of the columns of the cord, agree in stating tha^ irritation 
 of the anterior columns was attended with more or less movement. 
 The results of stimulation of the posterior columns, however, have 
 been differently stated by various observers: many found that it was 
 attended with the excitation of motion; and others, that the least irrita- 
 tion of the posterior columns excited pain. M. Longet, who is among 
 the latest experimenters on this subject, observes, that motions result 
 from irritation of the posterior columns only when the experiment has 
 been made immediately after the transverse division of the cord, and 
 he refers such motions to the excitability of the cord itself. After a 
 little time, however, this subsides; and then M- Longet has been able 
 to pass the galvanic current through each or both of the posterior 
 columns, without exciting any motions when the lower segment of the 
 
 • Loc. oit.; quoted from an abstract in the Brit, and For. Med. KevieWi vol. iv. 
 
OFFICE OF THE POSTERIOR, COLUMNS. 285- 
 
 cord was acted upon, but causing pain, as evinced by loud cries and 
 writhing of the body, when the upper segment was tried. Dr. Baly's 
 experiments on tortoises showed that movements might be excited 
 whether the anterior or posterior Columns were irritated,* much 
 stronger motions being excited by the posterior than by the anterior 
 columns. , _ 
 
 It is clear, then, that we must not draw any other conclusion from 
 experiment than that the antero-lateral columns appear to be motor 
 in their function. Respecting their sensitive power we gain no inform- 
 ation from this source : and it must be confessed that our knowledge 
 is no more advanced by it as regards the posterior columns. 
 
 We are much disposed to think that the antero-lateral columns are 
 the centres of the main actions of the c&rd, whether mental or physical. 
 Both roots of the nerves are ^connected with these columns, and there- 
 fore fibres of sensation and of motion must be found in them. These 
 columns are always proporticinate to the nerves which arise from them: 
 they enlarge when thenerves.are large, and contract when the nerves 
 diminish in size. The posterior oolunins, on the other hand, are of 
 uniform dimensioti throughout nearly the entire length of the cord, 
 although the posterior, roots, of. thf^ nerves exhibit, considerable dif- 
 ference in point of size, in different regions. . 
 
 We v^inlure to suggest that the posterior col ut^ns inay have a func- 
 tion different from any hitherto assigned to thexu. They may be in 
 part commissural between the various segments of the cord, and in 
 part subservient to, the function of the cerebellum in regulating and 
 co-ordinating the moveraenls necessary for perfect locomotion, 
 
 The analogy of the brain, in which the various segments are. con- 
 nected by longitudinal commissures, suggests the probable existence, 
 of fibres similar in office for the spinal cord. ,lf we admit such fibres 
 to be necessary to ensure harmony of action, between the several seg- 
 ments of the encephalon, there ,are, as good grounds for supposing 
 their existence in the cord, which in reality may be regarded as con- 
 sisting' of a number of ganglia, each a, centre of innervation to its 
 proper segment of the body, and therefore requiring some special 
 connecting fibres to secure, consentaneous action with the rest. 
 
 The attribute of locomotive power rests upon the connection of the 
 posterior columns with the, cerebellum, and the probable influence of 
 that organ over locomotion. ,If the cerebellum be the regulator of 
 Ibcomotive actions, it seems reasonable to suppose that those coiumns 
 of the cord which mainly pass into it, should enjoy a similar function ; 
 that, as they are the principal medium through which the cerebellurn 
 is brought into connection with the cord, it must be through their 
 constituent fib,res that the cerebellum exerts its influence on the. nerves 
 of the lower extreinities, and of other parts concerned in the locomo- 
 tive function. 
 
 The nearly uniform size of the, posterior columns in the different 
 regions of the cord has been , already remarked as unfavourable to 
 their being channels of sensation. But this anatomical fact maybe 
 adduced as a good argument in support of the hypothesis which we 
 
 • See his translation of Miiller's Pivysiology, Second Edit., p. 796. 
 
286 INNERVATION. 
 
 are now discussing. It is worthy of notice that these columns ex- 
 perience no marked diminution in size until the large sacral nerves, 
 ■which furnish the principal nerves of the lower extremities, begin to 
 come off. 
 
 In examining a transV'erse section of the lumbar region of the cord, 
 we observe a great predominance of its central gtay matter; the pos- 
 terior columns appear large, arid ihe antero-lateral columns inadequate 
 in proportion to the large roots of nerves which emerge from it. 
 Now, an analysis of the locomotive actions renders it highly proba- 
 ble that they are partly of a volitional character and partly dependent 
 on the inherent power of that segment of the cord from which the 
 lower extremities derive their nerves. In progression there are two 
 objects to be attained, — to support the centre of gravity of the body, 
 and to propel it onward; the former object requiring, first, that the 
 muscles of the lower extremities, the pillars of support to the trunk, 
 should be well contracted, in a degree proportionate to the weight 
 they have to sustain. Those actions by which the trunk is balanced 
 upon the limbs, and by which the movements of progression are 
 effected, are subsequently called into play through mental influence- 
 The contraction of the muscles of the limbs seems well provided for 
 in an arrangement for the development of nervous power by a stimulus 
 propagated to the centre. This stimulus is afforded by th^pplication 
 of the sofes of the feet to the ground ; it is therefore proportionate to 
 the weight which presses them downwards. It is well known that 
 physical nervous actions are more developed in the lower than in the 
 upper extremities, and the surface of the sole of the foot is well adapted 
 for the reception of sensitive impressions. No object can be assigned 
 for this peculiarity, unless it have reference to the locomotive actions; 
 and the great development of the vesicular mqtter in this region be- 
 tokens the frequent and energetic evolution of the nervous force. All 
 the structural arrangements necessary for this purpose are found in the 
 antero-lateral columns. The posterior columns come into play in 
 balancing the truhk, and in harmonizing its movements with those of 
 the lower extremities. 
 
 Experiment, while it fails to elucidate the function of the posterior 
 columns, exhibits nothing in opposition to the views we have ex- 
 pressed.^ It is not to be expected that commissural and co-ordinat- 
 ing fibres should react with stimuli similarly to fibres of voluntary 
 motilJh. 
 
 We think that the phenomena of disease may be referred to in 
 support of our view. In many cases where the principal symptom 
 has been a gradually increasing difficulty of walking, the posterior 
 columns have been the seat of disease. We may notice two kinds 
 of paralysis of motion, distinguished respectively by impairment or 
 loss of voluntary motion, and of the power of co-ordinating move- 
 ments. In the latter form, while the voluntary powers are consider- 
 able, the patient walks with great difficulty, and a gait so tottering 
 that his centre of gravity is easily displaced. , These cases are gene- 
 rally of the most chronic kind, and many of them go on from day to 
 day without any increase of the disease or improvement in, their con- 
 
MECHANISM OF THE ACTIONS OF THE CORD. 287 
 
 dition. In two examples of this variety we ventured to predict disease 
 of.the posterior columns of the cord: and this was found to exist on a. 
 post-mortem inspection. All cases on record, which we have had 
 the opportunity of examining, in which the posterior columns were 
 the seat of disease, began by evincing rhore or less disturbance of the 
 locomotive powjers; and it seems to us that the degree to which sensi- 
 bility may become affected will greatly depend upon the extent to 
 which the posterior roots of the nerves are involved in the disease. 
 
 The hypothesis, then, which vre are most disposed to adopt, is the 
 following: — That the afitero-lateral columns of the spinal cord with the 
 gray matter are, in conneption with the brain, the recipients of sensi- 
 tive impressions and volitional impulses, and thatthey.are the centres 
 of the independent or physical nervous actions of the cord ; and that 
 the ppsterior, columns propagate the influence of that part of the ence- 
 phalori which combines with the nerves of volition to regulate the 
 locomotive powers, and serve as commissures in harmonizing the 
 actions of the several segments of the cord. 
 
 What is the mecAanjsm of these actions of the spinal, cord — mental, 
 physical, locomotive ? This is a problem of the highest interest, bear- 
 ing upon the mechanism by which nervous power developed in any 
 nervous centre j as well as in the cord, is capable of affecting peripheral 
 parts ; and it is on that account weli deserving the most patient in- 
 vestigation*. 
 
 We assume, as necessary postulates, preliminary to the. discussion 
 of this question, the two following, propositions : — 1. That the brain, 
 or some part of it, is the sensorium commune; or in other'words, that 
 mental nervous actions (acts of volition and sensation) cannot take 
 place without the brain. 2. That the vesicular is the truly dynamic 
 nervous matter, the source of all nervous power.* 
 . ,Th« following hypotheses have been proposed in explanation of 
 these actions. 
 
 * The first of these postulates will be considered farther on in this chapter. The 
 second appears to us to have a sufficiently firm foundation to warrant ns in assuming 
 its-oorrectness, for the-sake of arguing the important question referred to in the text. 
 We shall state briefly here the proofs that the association ofihe vesicular and fibrous 
 matter is necessary to the development of nervous force. 
 
 1. Nerves, when separated for a time from the nervous centre, lose all power of 
 stimulating their muscles to contraction. No irritation, mechanical or electrical, i? 
 sufficient to excite them. If a nerve be divided some distance from the centre, the 
 peripheral portion, will, after a time, waste, and lose all power of developing nervous 
 force; but ihetentral portion, which remains in connection with ihe centre, retains 
 its nutrition and its vital properties unimpaired. 
 
 8. All nervous centres contain vesicular matter, with which nervous fibres freely 
 intermix. 
 
 3. The power of a nervoiis centre appears to be proportionate to the quantity of its 
 vesicular matter. This is well exemplified in the cereljral convolutions, the vesicular 
 surface of which is always in the direct proportion of the. development of mental 
 power; or, in general terms, ihe gray matter increases in ihe exact ratio of the nervous 
 energy. (Grainger.) 
 
 4. AH nerves appear to arise from vesicular matter. Stilling represents special 
 accumulations of vesicular matter at the origins of the nerves of the medulla 
 oblongata. ... 
 
 5. Nerves, whose power is exalted for some special purpose, have an increased 
 quantity of gray matter at their origin, of which the electric lobe in the torpedo; 
 connected with the origins of the fifth and eighth pairs of nerves, is an extraordinary 
 instance. — See Mr. Grainger's excellent work on the Spinal Gord, pp. 18-21. 
 
288 INNERVATION. 
 
 1. The various muscles and sentient surfaces of the body are con- 
 nected with the brain by nerve-fibres, which pass from the one to the 
 other. Those fibres destined for, or proceeding from, the trunk to 
 the brain pass along the spinal cord, so that that organ is in great 
 part no more than a bundle of nerve-fibres going to and from the 
 brain. These fibres are specially for sensation and voluntary motion. 
 
 But, in addition to these, there is another class of fibres proper to 
 the spinal cord and to its intra-cranial continuation, which form a 
 connection with the gray matter of the core!. Of these fibres, some 
 are afferent or incident, others efferent or reflex, and these two kinds 
 have an immediate but unknown relation tct each other, so that each 
 afferent nerve has its proper efferent onC, the former being eixcifor, 
 the latter motor. The aggregate of these fibres together with the gray 
 matter constitutes the true spinal cord of Dr. Marshall Hall, which is 
 not limited to the spinal canal, but passes up into the cranium as far 
 as the crura cerebri. -These fibres are quite ihdependent of those of 
 sensation and volition, and of the sensoriura commune. Although 
 bound up with sensitive and motor fibres, they are not affected by 
 them, and they maintain their separate course in the nerves as well 
 as in the centres. Such is the hypothesis of an exdto-ntotory- system 
 of nerves, and of a true spinal cord, the centre of all physical nervous 
 actions, which has been proposed and most ably advocated by Dr. 
 Marshall Hall. ' . ' ' ' 
 
 2. The fibres of sensation and volition proceed to and from some 
 part or parts of- the intra-cranial mass. Those which are distributed 
 to the trunk pass along the spinal cord, separating from it with the 
 various roots of the nerves, and in their course within the spine they 
 mingle more or less with the gray matter. There are no other fibres 
 but.these (save the commissural), and they are sufficient to manifest the 
 physical as well as the mental acts. Nerves of sensation are capable 
 of exciting nerves of motion which are in their vicinity; and'they 
 may produce this effect even when the spinal cord has, been severed 
 from the'brain, for their relation to the gray matter of the eord is such 
 that their state of excitement is readily conveyed to it. This explana- 
 tion tallies with the views of Whytt, Prochaskay and- the other phy- 
 siologists who had recognized the existence of a class of actions 
 produced by the influence of sensitive upon motor nerves. 
 
 3. According to a third hypothesis, it is assumed that all the spinal 
 and encephalic nerves, of whatever function, are implanted in the 
 gray matter of the segments of the cerebro-spinal centre with which 
 they are severally connected, and do not pass beyond them* The 
 segments are connected with each other through the continuity, of the 
 gray matter from one to another, and through the mediuni of com- 
 missural fibres 'which pass between them. . Through these means, 
 motor or sensitive impulses are propagated from segment to segment; 
 and a stimulus conveyed tp any segment, from the periphery may 
 either simultaneously affect the brain and cause a sensation, or be 
 reflected upon the motor nerves of that segment and stimulate their 
 muscles to contract. . 
 
DR. HALL'S HYPOTHESIS. 289 
 
 The first hypothesis, which assumes the existence of a distinct 
 series of incident and reflex nerves for the physical nervous actions, 
 offers a very beautiful explanation of those cases in ■which, while 
 sensation is entirely destroyed, movements may yet be excited with- 
 out the consciousness of the individual. In such cases it is supposed 
 that the fibres of sensation and volition are alone paralyzed, but that 
 those of the true spinal cord remain free from injdry or disease, and 
 therefore competent to perform their functions. Sometimes, however, 
 these fibres participate in the' general shock which the spinal cord or 
 brain experiences at the onset of disease or accident^ and therefore 
 reflex movements are not to be excited in all cases-in which the in- 
 fluence of the brain has been cut off by disease of that organ, or of 
 the cord itself. 
 
 This hypothesis has very much to commend it ; and not the least 
 . argument in its favour is that drawn from the compound nature of 
 spiqal nerves, as proved by Bell, in which filaments of very different 
 endowments are bpund together in the sarrie sheath. If it be proved 
 that filaments of sensation and of motion may be thus tied together, 
 it is not going too far to conjecture the existence df another series of 
 fibres of distinct function. 
 
 The movements of decapitated animals, of parts in connection with 
 small segments of the spinal cord, of limbs paralyzed to sensation 
 and voluntary motion from diseased brain or spinal cord, are satisfac- 
 torily explained by this hypothesis.. But there are two phenomena 
 familiar to those who observe disease -with a knowledge of the many 
 interesting discussions now going on upon the nervous system, which 
 ar^ not explained by it : these are, the movements which may be ex- 
 cited by mental emotion in limbs paralyzed to the infl^ience of the 
 will, and the tptal paralysis of the sphincter ani, which frequently 
 accompanies diseased brain, whilst, at the same time, the limbs are 
 only affected to a partial degree. 
 
 Gases occur sometimes in which hemiplegia arises from an apo- 
 ;^lectic clot or other destructive lesion in one hemisphere of the brain. 
 The arm and leg, or either of them, are completely removed from the 
 influence of the will; yet, ocdasionally, under the influence of some 
 sudden emotion, fear, joy, surprise, the palsied limb is raised invo- 
 luntarily with considerable force.* Mental emotions probably affect 
 some part of the brain : if the only communication between the brain 
 and the limbs be by the fibres of sensation and volition, it is impossi-. 
 ble to understand how, in such a case, tbe emotional influence could 
 be conveyed through a channel which has long been stopped. If we 
 are tb adopt Dr. Hall's theory, it will be necessary to suppose, with 
 Dr. Carpenter, the existence *of Certain emotional fibres to explain 
 the phenomena of this particular case. But it is difficult ta adrnit 
 the existence of three orders of fibres in each muscle, which, to be 
 effective, must have the same relation to the component elements of 
 the la-usele. It is impossible to imagine how each order of fibre 
 
 ' Even so slight a cause as yawniDg, which is an action of emotional character, 
 ■*U1 excjte a palsied limb. , In the case of a patient now in King's College Hospital 
 With very feompiete hemiplegia, the arm is raised involuntarily every time be yawns. 
 
290 INNERVATION. 
 
 should comport itself with reference to the other two, so that their 
 actions maj not interfere. Nor can any one fail to perceive that the 
 emotional fibres must be infinitely less frequently employed than the 
 others, and in some individuals,- so little called into action, as to ex- 
 pose the fibres greatly to the risk of atrophy for want of use. 
 
 Paralysis of the sphincter ani is most frequently produced by dis- 
 ease of the spinal cord ; but it is by no means a rare accompaniment 
 of diseased brain, and generally indicates a lesion of grave import. 
 Now, such a lesion is always accompanied with paralysis, chiefly of 
 the hemiplegic kind, but not necessarily complete ; on the contrary, in 
 several such cases we have seen distinct reflex movements, indicating, 
 that although the brain's influence was withheld. from the limbs, that of 
 the cord was not. If then the cord be sufilciently free from morbid 
 depression to allow of reflex movements taking place in the inferior 
 limbs, why is the sphincter so completely paralyzed that it offers not 
 the slightest resistance to the introduction of the finger into the anits? 
 It is admitted that the sphincter is under the influence of the will; 
 according' to Dr. Hall's theory, this must be through special, fibres of 
 volition distributed to it : . but it "is also under the influence of the 
 spinal cord, as the limbs are ; yet, if the cerebral, fibres be diseased, 
 there seems no reason why the influence of the cord upon it should 
 be at the same time destroyed. A cerebral lesion ought not to affect, 
 the sphincter further than to destroy the control of the will upon it, 
 unless its depressing influence extend to the whole cord, and in such 
 a case there ought to be complete paralysis of the limbs likewise. 
 
 These are not unimportant pathological objections to this theory:, 
 to them we must add the fact, that this view wants the support of 
 anatomy. However disposed we may be to admit the existence o^ 
 fibres implanted solely in the gray matter of the cord, it must be con- 
 fessed that it is as yet far from being proved that either such fibres, 
 or those which are continued up into the brain, exist in the cord of 
 yertebrata, or in its analogue of theinvertebrata. Dr. Carpenter and 
 Mr. Newport, it is true, affirm that they; have demonstrated the two 
 sets of fibres in insects^ — the sensori-volitional, and the excito-motory. 
 The former author describes the nerves of articulata as consisting of 
 fibres derived, from two sources — namely, the anterior or cerebral 
 ganglion, and the ganglion of that segment of the body to which they 
 belong. Those fibres which are connected vrith the brain, he states, 
 pass down alojjg the dorsal surface of the ganglionic chain, and are 
 fibres of sensation and voluntary motion ; those which are immediately 
 irjiplanted in the ganglia are excito-motory, Mr. Newport, in his 
 recent able and elaborate description of the nervous system of Myria? 
 poda, thinks that he shows a somewhat simikr arrangement in those 
 animals. The ganglionic chain has on its dorSfil surface a pair of 
 columns, superior longitudinal fibres,- which pass over the ganglia, 
 sending a few fibres to mingle with them, or with an inferior pair of 
 longitudinal columns, These latter, the inferior longitudindl fibres, 
 are placed along the abdominal surface of the ganglionic chai'n^ and 
 are intimately connected with the ganglia. In the intervals between 
 tlje ganglia these two columns lie in close juxtaposition, separated 
 
MR. NEWPORT'S RESEARCHES. 
 
 291 
 
 only bj some transverse fibres. The inferior colurhns appear, as Mr, 
 Newport states, to receive fibres from the superior columns, and pro- 
 bably to send sonie to them, "thus decussating eacli other in the 
 middle substance of the cord, where these two longitudinal series are 
 in close apposition; since it is almost- impossible, even in the lar^e 
 nervous cord of; Scolopendra," to separate these two tracts from each 
 other, although their distinctness is evinced in their relative size and 
 longitudinal lines of separation."* The ganglia, then, are placed 
 between these two columns, the inferior pair being intimately con- 
 nected with them. Almost the whole of the fibres of the' inferior 
 longitudinal series are traceable, says Mr. Newport, in the lulidae, 
 directly through each enlargement of the cord which' they mainly 
 assist to form. Two other sets 
 
 of fibres are distinguished by Fig. 73. 
 
 this anatomist in these animals, 
 which do not. take a longitu- 
 dinal course. These are, fii-st, 
 the comthissural fibres, which 
 pass transversely between cor- 
 responding nerves of opposite 
 side's of the body ; and second- 
 ly, the fibres of reinforcement 
 of the cord, which communi- 
 cate between nqrves of the 
 same side of the body, passing 
 from a nerve which arises from 
 a superior ganglioii to one that 
 comes from an inferior one. 
 These nerves do not appear to 
 penetrate the cord: judging 
 from Mr. Newport's descrip- 
 tion, they merely pass from 
 lierve to nerve, forming loops 
 which are convex towards the 
 cord, and constitute the lateral 
 portion of the cord in the in- 
 tervals between the points of 
 emergence of the nerves with 
 which they are connected. 
 The two sets of transverse arid 
 lateral fibres agree in the fact 
 that they do not pass upwards to the brain ; but of their connection 
 with the cord nothing is known. Indeed it is by no means apparent 
 that the lateral fibres form any junction with the vesicular matter of 
 the cord or with any other than peripheral portions of the nervous 
 system; Mr. Newport's researches show only that they are in juxta- 
 position with the margins of the cord, but we cannot infer from them 
 that they mingle with its elements. Moreover it is far from being 
 proved that the longitudinal fibres pass up to the brain. The brain, 
 
 • Phil. Trans., 1844. 
 
 . Upper and under surfaces of a portion of the cord 
 in SpiroStreptus.— After Newport. 
 
 A. Under surface. , b. Upper surface. 
 
 o. Inferior longitudinal Abres. c. Superior longitu- 
 dinal fibres. /;. Fibres of rein&rcemeiit, also seen at 
 h and c. g. Cotnnxissural fibr^p,, also seen at d, h. 
 
292 INNKRVATION. 
 
 indeed, is not necessarily the largest of the ganglia, and it must be 
 admitted to bear a most inadequate proportion to the number of longi- 
 tudinal fibres. Let any one compare the size of the cerebral ganglia 
 of the scorpion (as figured by Mr. Newport) with the size of. the 
 animal and that of its cord, and it will be evident to him Jiow dis- 
 proportionately small such a centre is. to the number of sensori- voli- 
 tional fibres which must be distributed over so large a surface, and to 
 so many muscles. When too- it is stated that the observations of these 
 physiologists were made with low powers of the micrqscope, it must 
 be confessed that there is as much obscurity. ias to the origin of the 
 nerves in invertebrata as in vertebrata; and that we are not yet 
 entitled to conclude that the existenc;e of two orders of fibres has 
 been actually demonstrated in the former dass. Anatomy offers no 
 objection to the hypothesis that the roots of the nerves are implanted 
 in the ganglia, and that the longitudinal fitaes act as commissures 
 between different segments (both adjacent and remote). of the cord. 
 
 And we may add here, that Mr. Newport's experiments on the 
 myriapods and other articulata throw no light on the question of the 
 existence of two orders of fibres ; nor do they add anything to our 
 knowledge beyond the important fact, that actions take place „ in in- 
 vertebrata after decapitation which are of t)h.6 same nature With those 
 which occur in vertebrata after a similar mutilation. The mechanism 
 of these actions has not been at all elucidated by these experiments. 
 
 Respecting the second hypothesis, we must remark, that it is just 
 as competent to explain the phenomena pf decapitated animalsj and 
 paralyzed limbs, as that of Dr. Hall, and that it receives some support 
 from the almost universal concurrence of sensation with those normal 
 actions which T>t. Hall would attribute to excito-motory fibres. If it 
 be supposed thatthese.fibres have a certain relation to the gray matter 
 of the spiqal cord, there can be no good reason against the further 
 supposition, that they may continue to b.e affeqted by it after the brain 
 has been separated from the cord. .This hypothesis, however, is 
 liable to the same objections as that of excito-motory fibres : it is 
 inadequate to explain the influence of emotion on paralyzed limbs^ 
 and the paralysis of the sphincters; and, moreover, it cannot be con- 
 sidered to be proved that fibres are continued up directly from the 
 spinal nerves to the brain. The fibres of the anterior pyrainids, no 
 doubt, are true cerebro-spinal fibres; but they may be merely com- 
 missural. We have no evidence that fibres of the lumbar region of 
 the cord pass into the brain. The longitudinal course of fibres in the 
 spinal cord affords no proof that those fibres pass into the brain, for. it 
 is well known that most of the nerves take a very oblique course from 
 their point of separation from the cord to their emergence from the 
 spinal canal ; and it is probable that the fibres continue their obliquity 
 in the cord itself, so that their real origin would be higher up than 
 their apparent one. This great length of oblique course gives to the 
 fibrei the appearance of being strictly longitudinal, whereas it may be 
 implanted in the gray matter of the cord. 
 
 The third hypothesis appears to us to admit of fewer, objections 
 than either of the others, and to be more Consonant with what seems 
 
MECHANISM OF A VOLUNTARY ACTION. 293 
 
 to be the correct anatomy of the cord, It supposes that the mechan- 
 ism" of a mental and that of a physical nervous action are essentially 
 the same, differing only in the nature and the mo^e of application of the 
 stimulus. The same aff^erenf and efferent {ihres are exejted in the one 
 case as in the other; the former acting as sensitive or £^citor, or both; 
 the latter as channels for lioluntary, emotional or strictly ^A^sica/ im- 
 pulses to motion. 
 
 This hypothesis is content to assume that fibres of sensation and 
 voluntary motion do not pass beyond that particular segment of the 
 cord with which -they are connected ; and that each segment of the 
 cord communicates readily with the brain through the horns of gray 
 matter, or through commissural fibres which pass. between the seg- 
 ments of the cord, and from the upper segment of tbc latter to the 
 brain. The anatomy of the cord, so far as our present knowledge 
 extends, is favourable to this hypothesis, for it is much more probable 
 that all the roots of the spinal nerves are implanted, in their proper 
 segments of the cord, than that some pass up to the brain, and others 
 remain in the cord,. The varying dimensions of the cord, at different 
 regions, disincline us to admit the existence of fibres which are con- 
 tinued up into the brain from the spinal nerves'.. It is impossible to 
 uHderstarid, the great superiority of size of the lumbar portion over the 
 dorsal segment of the cord, if we admit that this latter segment con- 
 tains, in addition to its own fibres, (sensori- volitional and excito- 
 motory,) the sensori-volitional fibres of the lumbar swelling also. 
 The fibres of sensation and volition, which pass to the great Lumbar 
 and sacral nerves, could, in that case, be only extremely few in pro- 
 portion to the excito-motory ones; nor would they seem adequate to 
 the motor and sensitive endowments of the lower extremities; where 
 it must be admitted volition and sensation enjoy an extensive sway. 
 Moreover, it may be stated that the great size of the lumbar swelling 
 depends mainly on the .large quantity of vesicular matter which exists 
 in it ; and the total amount of fibrous matter is hardly so jnuch as 
 might be expected to exist if the lower extremities and the pelvis 
 were supplied with both sensori-volitional and excito-motory fibres. 
 
 It is very generally admitted that the only channel by which the 
 will caii influence the spinal cord is through the fibres of the anterior 
 pyramids, the greater number of Which decussate each other along 
 the median line, as already explainedin page 241. The ,most frequent 
 pathological phenomena favour this view. Now it is in therhighest 
 degree improTaable that these fibres, occupying so small a space as ' 
 they do, should form the aggregate of the volitional fibres (still less 
 of the sensori-volitional fibres) of the trunk and extremities. It seems 
 to us much more reasonable to regard the fibres of the, pyramids in 
 the light of cominissures, connecting the gray matter of the cord with 
 that of the brain, and serving to associate these two great divisions 
 of the cerebro-spinal centre in the voluntary, if not in all the mental 
 nervous actions. 
 
 The mechanism of a voluntary action, in parts, supplied with spinal 
 nerves, would be, according to this hypothesis^ as follows : The im- 
 pulse of volition, primarily excited in the brain, acts at the same time 
 
294 INNERVATION. 
 
 upon the gray matter of the cord (its anterior horn), -whicli in virtue 
 of its association with the former, by means of the fibres of the ante- 
 rior pyramids, becomes part and'parcel of the organ of the will, and 
 therefore as distinctly amenable to acts of the mind as that portion 
 which is contained within the cranium. If we destroy the commissural 
 connection through the pyramidal fibres^ the spinal cord ceases to take 
 part in mental actions ; or, if that connection be only partially de- 
 stroyed, that portion of the cord which the injured fibres had associated 
 veith the brain, is no longer influenced, by the mind. Again, if the 
 seat of volition in the brain be diseased, the cord, or part of it, par- 
 ticipates in the effects of tjie disease, as far as regards voluntary 
 actions. That it is not, too much to ascribe such power to the pyfa- 
 midal fibres, appears reasonable, if we considerhow the fibres of the 
 corpus callosum, and perhaps other transverse commissures, so con- 
 nect the hemispheres and other parts of the brain that the separate 
 divisions of a double organ act harmoniously in connection with the 
 operations of a single mind; or that, conversely, two impressions from 
 one and the same source on a double sentient organ are perceived as 
 single by the mind. 
 
 An objection to this exjplanation will readily be raised, that the 
 excitation of the anterior horn of the gray matter, in the way stated, 
 does not explain the remarkable power which the will has of limitiitg 
 its action to one or two, or a particular class of muscles. We reply 
 to this, however, that there can be no reason for dehyinig to the mind 
 the faculty of concentrating its action upon a particular series of the 
 elementary parts of the vesicular matter, or even upon one or more 
 vesicles, if we admit that it can direct its influence to one or more 
 individual fibres, as the advocates of the first and second hypotheses 
 do. If, indeed, we admit the btle, we must admit the other ; for 
 whether the primary excitation of a fibre take place in the eneephalon 
 or in the spinal cbrd, the part first affected must probably be (accord- 
 ing to our second postulate) one or more vesicles of the gray sub- 
 stance. 
 
 The series of change? which Avould develop a sensation, admits 
 of the following explanation : A stitnulus applied to some pairt of the 
 trunk or extremities is propagated by the sensitive- nerves to the 
 posterior horn of the gray matter' of the spinal cord, and from the 
 junction of this part with the brain either through the direct continuity 
 ,of the vesicular matter of the cord with that of the centre of sensa- 
 tions, or through longitudinal commissural fibres, analogous to, or 
 even perhaps forming part of, the anterior pyramids, this organ is 
 simultaneously affected. To this likewise it will be objected, that 
 the limitation of sensations is not sufficiently explained. But the 
 reply is obvious: the intensity and land of sensation depend upon the 
 nature of the primary stimulus at the surface ; the extent upon the 
 number of fibres there stimulated. Wherever these fibres form their 
 proper organic connection with the vesicular matter, that matter will 
 participate in their change to an extent proportionate to the number of 
 fibres stimulated, and with an intensity commensurate with the forpe 
 of the primary stimulus. It is not necessary to the development of- 
 
THEQRy. OF NERVOUS ACTION. 295 
 
 sensation that the fibre stimulated should be implanted directly in the 
 brain; if it be connected with this centre through the medium of 
 vesicular matter of the same character as that which is found in it or 
 through commissural fibres, all conditions necessary for the develop- 
 ment and propagation of nervous force would appear to be fulfilled. 
 It must not be supposed^ however, that: in making this statement we 
 mean to assign the spinal cord to be the seat of sensation ; all we 
 assert is, that the posterior horns of its gray matter, as being the part 
 in which the sensitive roots are implanted, participate largely in the 
 mechanism of sensatioii ; and that by their union with the brain they 
 become, pro tanto, a part of the centre of sensation, so long as that 
 union is unimpaired. 
 
 This hypothesis oifers an explanation of the hitherto unexplained, 
 phenomenon of impaired sensation on that side of the body which is 
 opposite to the seat of cerebi'al lesion. If we regaVd the anterior 
 pyramids as commissujes between the sensitive, as well asbetween 
 the motor portions of the cerebro-spinal centre, it will be obvious 
 that the posterior horns of the spinal gray matter on the right-side 
 will be associated with the left centre of sensation in the brain, and 
 vice v^ersa. 
 
 And we gain, moreover, an explanation of the almost universal 
 association of sensation with reflex or physical actions. The excitor 
 nerves of these actions being the same as the sensitive nerves, the 
 impression conveyed by th^m is calculated at once to excite motion 
 and sensation. Were it not for the controlling influence of the will, 
 all sensitive impressions made through the spinal cord would likewise 
 be accompanied by corresponding movements. When the spinal 
 cord has been excited by strychnine, the physical power, prevails 
 over the mental, and the will ceases to be able to control the move- 
 ments excited by impressions through, sensitive nerves. 
 
 A highly important argument in favour of this view is derived from 
 the marked difference of structure of the anterior and posterior horns 
 of the spinal vesicular matter. The anterior and posterior roots of 
 the nerves exhibit no difference of structure ; no anatomist could 
 distinguish in a compound nerve the sensitive from the motor fila- 
 ments. The vesicular matter, however, in the anterior horn,, contains 
 large caudate vesicles of a remarkable, and peculiar kind (fig. 56, p. 
 198) ; whilst that in the posterior hori^ resembles very much the 
 vesicular matter of the cerebral convolutions, and of other parts of 
 the cerebrum, and does not contain caudate vesicles, except near the 
 base. Here, then,, we find associated with the well-attested differ- 
 ence in the functions of the anterior and posterior roots, a striking 
 diflference in the structure of the anterior and posterior horns of gray 
 matter. 
 
 This hypothesis is adequate to the explanation of the influence of 
 emotion or limbs paralyzed as to voluntary movement, without the 
 necessity of assuming the existence of a totally distinct series of fibres 
 for this class of actions. The change in the brain, excited by emotion, 
 is propagated to the spinal gray matter, in a manner analogous to that 
 in which the influence of the will is brought to bear on it. It thqs 
 
296 INNERVATION. 
 
 affects the ordinary motor fibres; and, therefore, the movements which 
 are produced by emotion resemble very closely those excited by the 
 ■will. 
 
 This hypothesis suggests a very obvious explanation of the kind 
 ■of antagonism which appears to exist between voluntary and reflex 
 actions. It is well known that in health the will can in a great (de- 
 gree control and prevent the development of reflex actions in the 
 lower extremities. If one be paralyzed, as in hemiplegia, from dis- 
 ease of the brain, whilst the other remains sound',. a very striking 
 contrast is sometimes to be observed between the two limbs. On 
 stimulating the sole of the foot in the diseased limb, reflex actions are 
 readily produced ; but, on applying the same stimulus to the same 
 part of the sound limb, ho such movements occur, the patient being 
 conscious of the application of the stimulus, but resisting the tendency 
 to action which it produces. The will has lost its control over the 
 diseased limb ; but, as the motor nerves and the spinal gray matter 
 are sound^ actions may still be excited through a stimulus from the 
 periphery; and, the more complete has been the separation of the 
 brain's influence from the cord, the more perfect will be the reflex 
 actions. Hence we frequently find these movements more perfect 
 in cases where sensation as well as voluntary power is destroyed in a 
 lirnb, than where the latter only has ceased. 
 
 It may be here remarked, that movements which at Ohe time are 
 voluntary, may at -another time be physical. If the influence of the 
 will be suspended for a brief period, stimulation of the surface will 
 produce the same movements which previously were excited by volun- 
 tary impulse. Thus, tickling the soles of the feet, in a person asleep, 
 excites movements which doubtless are of the reflex kind ; but; the 
 same stimulation, in a person awake, will give rise to precisely the 
 same movements, which he is conscious are, at least in a great degree, 
 voluntary. 
 
 Some reflex actions are imperfectly controllable by the will ; of 
 which the contraction of the pupil, and the movement of deglutition 
 at the isthmus faucium, are examples. It is remarkable, however, 
 that the will may give rise to these actions by associating pthers with 
 them : the pupil n\ay be contracted at will, by directing the eye in- 
 wards ; and the fauces may be contracted by bringing some saliva in 
 contact with them. In the latter case the stimulus of volition alone 
 is not suflScient to excite the movement ; the addition of a physical 
 stimulus is likewise necessary : and, in the former, the excitability of 
 the fibres of the third nerve by a mental stimulus may be materially 
 modified by their re-association with vesicular matter in the ophthalmic 
 ganglion. 
 
 There is nothing in this hypothesis repugnant to the idea, that cer- 
 tain nerves may be connected in the centres with masses of vesicular 
 matter over which the will usually exercises little or no control, and 
 which, perhaps, have but a slight connection with the brain through 
 eotaraissural fibres. Facts like those instanced in the preceding para- 
 graphs may be accounted for on such a supposition as this. This 
 supposition may be required to explain some of the actions of nerves 
 
MANY ACTIONS NEED A DOUBXE STIMULUS. 297 
 
 connected with .the medulla oblongata, the, vagus for instance, but 
 certainly not of spinal nerves. 
 
 It is probable that in many actions the doublfr stimulus, mental 
 and physical, is necessary to their perfect development. The former 
 is excited- by the mind acting, on the«vesicular rbatter ; the latter is 
 propagated at the same time, by sensitive nerves, to the same region 
 of vesicular matter ; and both simultaneously influence the same motor 
 fibres. Inlocomotion, it seems probable' that this is the case: the 
 degree of contraction of the muscles necessary to maintain the super- 
 incumbent weight is obtained by the physical stimulus of pressure 
 against the soles of the feet ; but the movements of the limbs, andi 
 the harmonizing association of the muscular actions, is efTected by 
 mental influence. The pressure against the. soles is felt, however; 
 and the same nervQ-fibres which excite the sensation; stimulate the 
 vesicular matter in which the motor nerves are itnplanted. In many 
 actions of familiar occurrence, the voluntary effort is greatly enhanced 
 by the- simultaneous application of a physical stimulus to a part of 
 the surface which is supplied with nerves from the same region of the 
 cord. The horseman feels more secure when his legs are in close 
 contact with the horse's flank. We gain a much firmer hold of an 
 object which adapts itself well to the palmar surface of the hand, 
 than of one which, although of no greater bulk, is yet so irregular 
 in surface as not to allow of such intimate contact with the palm. 
 Closure of the. eyelids in. winking is an action of similar kind, result- 
 ing from a physical stimulus, \vhich in the perfect state of the cerebro- 
 spinal centre produces sensation, and excites-motion which is at once 
 the result of the physical impression, and of the exercise of volition 
 provoked by the sensation.. Every one must be conscious that he 
 exercises considerable control over the movements of his eyelids, and 
 that it requires a great effort to prevent winking for a certain period. 
 At length,- however, the physical impression, arising from the contact 
 of. air with the conjunctiva, and the diminution of temperature from 
 evaporation on the surface of that membrane, which at first caused 
 but'a slight sensation, produces pain ; the physical stimulus overcomes 
 the mental resistance, and causes contraction of the orbjcular muscle. 
 And it may be remarked further, that the closure of the lids by voluri- 
 tary effort is much more powerful if a stinjulus'be applied at the same 
 time to the conjunctival surfaccj than if left solely to the exercise of 
 the will. 
 
 In the action just referred to, as well as in all other instances of 
 reflex actions which -the will can prevent, no satisfactory explanation 
 of this controlling power of the, mind can be given by Dr. Hall's 
 hypothesis — Do the volitional fibres exceed in number the excito- 
 motory? If this were adm'itted, then we could understand that an 
 excito-motory act might be prevented by substituting a voluntary act 
 for it; but, ini the cases in question, the mind prevents action alto- 
 gether, notwithstanding the exciting influence of the impression. The 
 triie explanation seems to be, that the mind can. exert upon the vesi-N 
 cular matter a power which can prevent the exercise of that ichange, 
 
298 INNERVATION. 
 
 or neutralize the change, ■without which the motor fibres will not be 
 affected by a physical stimulus. 
 
 Reflex actions are more manifest in some situations than others: 
 thus, in cases of hemiplegia from diseased brain, they are generally 
 very obvious in the lower extremity, but totally absent in the upper. 
 This, the advocates of the excito-motory theory ascribe to a paucity 
 of excito-motory fibres in the latter limb, and to a larger amount of 
 them in the former. Or, it has been attributed to the greater and 
 more enduring influence of shock upon thatsegmeiit of the cord from 
 which the nerves of the upper extremities arise, as nearer the seat of 
 lesion, than upon the lumbar segment. But another explanation ap- 
 pears to us equally satisfactory, and more accordant with other phe- 
 nomena. A certain disposition oj^ the nerves upon the tegimientq,ry 
 surface is as necessary for the development of reflex actions as of sen- 
 sations; and these movements will be more or less easily manifested, 
 according as this organizatioil of the nerves on the surface is more or 
 less perfect. 
 
 That disposition of the cutaneous nerves which renders the surface ; 
 easily excitable by titillation seems most fiivourable to the develop- 
 ment of these actions. Hence, there is no place where they are more 
 readily excited than in the lower extremities by stimulating the soles 
 of the feet or the intervals between the toes, both of which situations 
 are highly susceptible of titillation. At the isthmus faucium the 
 slightest touch on the surface excites a movement of deglutition ; and 
 this touch, at the same time, produces 'a very peculiar sensation of 
 tickling, quite distinct from that which may be excited at other parts 
 of the pharynx, or mouth. When this part of the mucous membrane 
 is in a state of irritation as an effect of coryza, this tickling sensation 
 is present, and repeated acts of swallowing are provoked. 
 
 Two facts may be stated here, which illustrate the pos'ition we have 
 laid down respecting the necessity of a- certain disposition of the 
 nerves on the tegumerital surface, for the development of reflex actions. 
 The first is one which has been noticed by Volkmann, and which we 
 had ourselves repeatedly observed, namely, that in frogs, and other 
 animals, reflex actions are readily excited by stimulating the feet; but 
 irritating the posterior roots of the spinal nerves, which supply th^se 
 parts, is not sufficient for this purpose. In experiments repeatedly 
 made upon the posterior roots of the nerves we have very rarely seen 
 movements excited whilst they have been subjected to irritation, and 
 the recorded statements of all modern experimenters agree in the 
 main with this statement. The second fact is this : in the male frog 
 the development of a papillary structure on the skin of the thumb 
 seems to have reference to the excitation of the physical power of the 
 cord, to enable the animal to grasp the female without the necessity 
 of a prolonged exercise of volition. Stimulating the fingers will 
 scarcely produce reflex actions, but the slightest touch to the enlarged 
 thumb will cause the animal to assume the attitude of grasping. If 
 the papillae be shaved off the thumb, its power of exciting these ac- 
 tions is instantly lost. 
 
 When the polarity of the cord is greatly excited by strychnine or 
 
DISPOSITION OF NERVES FOR«(lEFLEX ACTION. 299 
 
 other substances, or whetf tetanus exists, all parts of the surface are 
 equally capable of exciting reflex actions. The least touch will cause 
 them, 'not only in the limb touched, but in all that side of the trunk, 
 or eyen throughout the whole bod'y. So general is the excitayipn, 
 that the least impression made on the peripheral extremity of a sensi- 
 tive nerve in any part of the body is instantly converted into muscular 
 spasm, more or less general. ' A slight curjent of aip, in tetanus, 
 is suiScient to excite general spasm. Miiller remarts, that, in such 
 states of the cord, the reflex actions excited by stimulating the nerves 
 themselves are much less than those produced by excitation of the , 
 surface. 
 
 The readiness with which a physical change, induced in one pgrt 
 of the centre,;is propagated to others, whether above or below it, is 
 due no doubt to the vesicular matter. An experiment made by Yan 
 Deen illustrates, this statement. If, in an animal poisoned by strych- 
 nine, the cord be divided in its entire length along the median line, 
 leaving only a slight bridge ,6f gray matter, stimuli applied to any 
 part of the surface will, exhibit as extensive reactions as if the cord 
 were entire. It is evident that the only medium of communication 
 between the opposite halves, must be the small portion of vesicular 
 matter left undivided. 
 
 Impressions conveyed to the cord by the posterior roots of any of 
 its nerves, may be reflected to the corresponding motor nerves and 
 cause movement, or, may extend irregularly along the posterior horns 
 of gray matter, and stimulate the nerves implanted in them, and thus 
 give rise to new sensations, which may ^e referred to other and even 
 distant parts of the body. 
 
 The hypothesis, under consideration, affords us an explanation, 
 more satisfactory, than any other, of the paralytic state of the sphinc- 
 ter ani in brain, disease, already referred to, as well as in that of the 
 spinalcord. This muscle is certainly chiefly under the influence of 
 the will. In ordinary cases of diseased brain where the lesion is con- 
 fined to one side, the centre of volition is not, sufficiently impaired to 
 affect its influence upon the sphincter. In graver lesions, however, 
 although the will may still continue to exert its control upon one side 
 of the body, it loses its power over the sphincter, which is not ex- 
 citable by any stimulus.; In -disease of the spinal cord, there js parar 
 lysis of the sphincters if the lesion involve a sufficient portion of the 
 cord's substance, in whatever region of the cord it may exist. Even 
 when the lesion is situate high up inthe neck, or in the dorsal region, 
 leaving the lumbar portion perfectly whole, the sphincter will never- 
 theless be paralyzed. In the fojmer instances, the centre of volition 
 in the cranium is diseased; in the latter, the defect consists in , the 
 destruction of the communication of the brain with that portion of the 
 cord in which the nerves of the sphincter muscle are implanted. 
 
 An examination of the action of the sphincter will show that the 
 anus is kept closed ordinarily by the passive contraction of the muscle 
 itself (seep* 180); but that its active contractions are mainly excited 
 by voluntary influence, allowance being made for some slight action 
 which may be produced by the stimulus of sudden distension, as in 
 
300 ftjNERVATION. 
 
 Other circular muscles. Now, as a stimulus to sentient nerves con- 
 stitutes no necessary part of any of these actions, it is probable that 
 the motor nerves of the sphincter have little or no connection with 
 the (sentient ones ; dnd, consequently, that muscle is not excitable to 
 contraction by a stimulus applied to a sentient surface. Hence, 
 whenever the influence of the will upon the lumbar portion of the 
 cord is susplnded, this muscle ceases to act, whether a mental or a 
 physical stimulus be exerted. 
 
 Dr. Hall indeed cites two experiments which imply that the action 
 of the sphincter is dependent on the cord. In both, however, (one 
 ' on a horse, the other on a turtle,) the observations were made imme- 
 diately after division of the cord. By the division, the whole organ 
 was thrown into an excited, state, both above and below the section, 
 and therefore manifested phenomena similar. to thoSe excited by voli- 
 tion. Indeed, we have seen the sphincter repeatedly contracting 
 after division of the cord without the application of any new stimulus 
 to it; and the dog continuing to raise and depress, his tail as long as 
 the irritation of the cord produced by the section hais continued. 
 
 On the same principle, animals will exhibit movements of volun- 
 tary character for some time after decapitation. A bird thus treated 
 will fly for some distance, and with considerable energy, and will flap 
 its wrings if the cut surface of the cord be irritated. A fly decapitated 
 flies for some way immediately after the removal of the head ;* and 
 Walckenaer observed a singular fact Respecting the Ceroeris ornata, 
 a wasp which attacks a bee that inhabits holes: " at the moment that 
 the insect was forcing its way into the hole of the bee; Walckenaer 
 decapitated it ; notwithstanding which, it continued its motions, and, 
 when turned round, endeavoured to resume its position, and enter the 
 hole."* The change in the vesicular matter of the ganglia necessary 
 for the movements of the wasp in pursuit of its prey, had already 
 been excited by a powerful stimulus of volition, which continued 
 even after the removal of the centre from which it had emanated. 
 
 So similar is the change which a physical stimulus can excite in 
 the gray matter to that produced by the influence of the will, that, as 
 has been oftten remarked, the actions excited in decapitated animals 
 present a striking resemblance to the ordinary voluntary movements. 
 When a certain portion of the skin is "irritated, the animal pushes 
 agaiiist the offending substance, as if trying to remove or displace it. 
 If the anus be irritated, both legs are excited to action. It may 
 also be observed, thst the same motions follow the same irritations of 
 the skin. If, in a frog, the sfeat of irritation be on the right side, the 
 corresponding hind-foot will be raised, as if to remove the irritating 
 cause. The exact resemblance of these to voluntary movements 
 seems to admit of being explained only on th^. supposition that the 
 same fibres are employed in the execution of both. 
 
 It must be borne in mind, that, whilfe this hypothesis rejects the 
 class of sensori-volitional fibres which pass with the spinal nerves 
 along the cord into the brain, it admits the existence of only three 
 
 • Quoted in Muller's Physiology, by Baly, vol. i. p. 787, 3d ed. 
 
PHYSICAL ACTIONS OF THE CORD. 301 
 
 orders of fibres implanted in the various segments flf the cord, viz., 
 those at &nce sensitive and exciter; those at once for voluntary and 
 involuntary motion ; and commissural fibres. Moreover, it .i? not 
 intended by this hypothesis to assume that the intervention ofhema- 
 iion {i. e. the perception of an impression by the minid) is necessary 
 for the production of those muscular actions which are excited by 
 stimulation of the surface. No more is affirmed than that the same 
 stimulus to the sensitive nerve which can and does excite a sensation, 
 may sir/iultaneousty, but independently, cause -a changein tjie vesicular 
 matter which shall stimulate the motor nerves; and that this change 
 is of the same kind as that which the will may excite, and affects the 
 same motor nerves. 
 
 Lastly, -this hypothesis involves the enunciation of a highly im- 
 portant proposition with reference tonervous centres^ It is this : that 
 all the centres which are connected to the bra;n by commissural 
 fibres, are therehy submitted to,' and brought into connection with, 
 the mind, to an extent proportionate to the number of connecting 
 fibres, so that voluntary iinpulses act upon them as part and parcel of 
 the centre of volition ; and sensitive impressions, in affecting them, 
 affect the sensoriumcomiivune simultaneously. 
 
 In voluntary actioiis, then, it may, be stated, that, while the brain 
 is the part primarily affected, the mental impulse is at the same time 
 directed to that portion of the cord upon which the required action 
 depends. 
 
 In the development of sensation the stimulus affects, the posterior 
 horns of the gray matter of the cord, which, from its commissural 
 connection with the brain, is in reality a part of the Sensorium. 
 When the power of mental interference is removed, or kept under 
 control, physical actions develop themselves ; being effected through 
 the same nerves as those which volition influences, or which sensi- 
 tive impressions affect. The lalter are, in suqh instances, the excitors 
 of the former, no doubt through the vesicular matter in which they 
 are implanted. These actions become most manifest when the con- 
 nection of the brain with the spinal cord has been severed ; and they 
 occur in the most marked way in those situations where the cutaneous 
 nerves are so organized as readily to respond to the application of a 
 stimulus applied to the surface, or they become universal wh^en the 
 cord is in a state of general excitement. 
 
 The movements in locomotion and the maintenance of the various 
 attitudes, are effected through the ordinary channels of the physical 
 and volitional actions ; and the posterior colurpns of the cord, by their 
 influence on the vesicular matter of the segments in which the nerves 
 are implanted, co-ordinate and harmonize the complicated muscular 
 actions of the limbs and the trunk under the control of that portion 
 of the encephalon which probably is devoted to that purpose. This 
 power of co-ordination is probably mental, and intimately conriected 
 with the muscular sense. 
 
 To conclude the discussion of the functions of the cord, we shall 
 here enumerate the physical nervous actions of which it is the centre, 
 remarking, at the same time, that we contihue to use the term spinal 
 15 
 
302 INNERVATION. 
 
 cord in its ordinary sense, and that we reject the hypothesis of a true 
 spinal corrf, anatomically distinct from that which has to do with 
 mental nerTOus actions.' 
 
 Weliave already stated, that probably part of the muscular, adjust- 
 ments in locomotion are excited by the pressure against th« soles of 
 the feet. All involuntary movements of the mnscles of the trunk or 
 eitremities, when excited by external stimuli, have their centre in 
 the spinal cord. The sudden application of.coldto the surface of 
 the trunk or extremities frequently excites respiratory movements. 
 This jnay be attributed to cutaneous nerves affecting the gray matter 
 of the cord, and through ttis the intercostal and phrenic nerves ira- 
 plaated in it. 
 
 Certain conditions of the generative organs are dependent on the 
 spinal cord ; but they are developed only in a polar state of that 
 organ, usiially present under sexual excitement. Erection of the 
 penis is evidefitly dependent on the cdrd in this way. In a state 
 of irritation of the cord, such as may be -caused by traumatic injury, 
 erection or semi-ereclion is frequently present. , In paraplegia, there 
 is frequently an absence of the power. , The excited state of the 
 Fallopian tubes in the female is attributable to the same cause. The 
 action of the uterus in parturition, of the bladder and rectum when 
 distended, is partly due to the stimulus of distension on the muscular 
 coats, and partly to the physical, power of the cord excited by the 
 sensitive nerves of those organs. 
 
 The nervous actions whidh accompany the nutritive functions are 
 of the physical kind, although not altogether removed from the in- 
 fluence of volition and emotion, and have their centre in the spinal 
 cord. Thus, the heart is very liable to be influenced by the spinal 
 cord, and, no doujit, the blood-vessels are similarly related to it; and, 
 through their infl'wince upon the distribution of blood to the various 
 textures, it is plain that th& state of the spinal cord, or of parts of it, 
 may readily affect the molecular changes in which nutrition and secre- 
 tion intrinsically consist. This subject will be further discussed when 
 •we corne to consider the functions in question. 
 
 It has been supposed, that the tone of the muscular system is 
 maintained by the spinal cord. If by tone be meant what we have 
 described as passive contraction, we can only remark, that the phe- 
 nomena which characterize that state are just as obvious in muscles 
 taken from animals recently deprived of the spinal cOrd as in others; 
 and that the analogous state, rigor mortis, comes on as distinctly 
 when the spinal cord and brain have been removed, as if they were 
 untouched. Healthy nutrition, in our opinion, supplies all the con- 
 ditions necessary for the maintenance of the tone or the passive 
 contraction ; nor is the spinal cord (although itself healthy) able tp 
 preserve the tense condition of the muscles, if they are not well 
 nourished. The removal of the spinal cord, indeed, immediately 
 produces a flaccid state of the, muscles of the limbs ; but this is owing 
 to the immediate cessation of the slight degree of active contraction 
 necessary to maintain a certain posture, A decapitated frog will 
 continue in the sitting posture through the influence of the spinal 
 
FUNCTIONS OF THE ENCEPHALON. 303 
 
 cord ^ but, immediately this organ is removed^ the limbs fall' apart, 
 from the loss of the controlling and co-ordinating influence of the 
 ner^rous centres. But careful examination will show, that in these 
 limbs the moleculair phenomeria which characterize passive contrac- 
 tion continue. Itmust be remarked, however, that musples separated 
 from their proper nervous connection soon suffer in their nutrition, 
 from the want of that araoiint of exercise which is necessary for, it. 
 For this important observation We are indebted to Professor John 
 Reid, who likewise called attention to the confirmatory fact, that, in 
 those palsies with which there isxombined more or less irritation of 
 the nervous centre, the muscles do not suffer in their nutritioti, jn 
 consed|u&nce of the exercise th^ey undergo in the startings so frequently 
 excited in them by the central, irritation. 
 
 After these remark^, it is scarcely necessary to add, that we must 
 enter our protest against the doctrine which assigns the spinal cord as 
 the source of muscular irritability. This doctrine, indeed, has but 
 slender support either in reason or experience. It is contrary to all 
 analogy to assign to one tissue the power of conferring vital properties 
 on another. If bone, tendon, and Cartilage have thejr distinctive pro- 
 perties, they possess them in virtue of some peculiarity inherent in 
 their mode of nulrition, and d-o not derive them from any other texture. 
 And, -surely, it is too much to suppose that a tissue, like muscle, so 
 complex in its chemical constitution, and so exquisitely organized for 
 the development of its proper force, should be dependent on the 
 nervous system, oi- a pprtion of it, for- its contractile power! Our 
 own experience is quite opposed to the statement of Dr. Hall, that^ 
 in cases, of palsy dependent on cerebral lesion, the muscles of the 
 affected limbs acquire an increased irritability, from the cord, which 
 he supposes to be the source of irritability, remaining intact, while 
 the influence of the exhauster of irritability (the Main) is removed. 
 In all our experiments, which have been numerous, we have found 
 the palsied muscles less excitable by'the galvanic stimulus than those 
 of the sound side, and the difference has been more manifest the 
 longer the period since the paralytic seizure. Exceptions to this 
 statement, however, are found in those cases in which the paralysis 
 has been accompanied with cerebral irritation!' sufficient to keep up a 
 state of more or less active contraction of the affected muscles.* 
 
 Functions of the medulla oblorigata, mesocephale, corpora striata, 
 and optic thalami. — Although the anatomist may find it convenient 
 to describe these parts each by itself, it is impossible, in the consi- 
 deration of their functions, to separate them completely, they are so 
 closely connected with each other, and the functions of one part are 
 So readily affected by any change in those of the other. Thus, the 
 olivary columns, which form the central- and most essential part of 
 the medulla oblongata, extend upwards through the mesocephale to 
 the optic thalami ; and the anterior pyramids form an intimate con- 
 nection not only with the vesicular matter of the mesocephale, but^ 
 
 * See also Dr. Pereira's experiments, Hat. Med,, vol. ii. p. 1301. 
 
304 INNERVATION. 
 
 to a great extent, with that of the corpora striata. All these parts 
 taken together, withjthe quadrigeminal tvibercles, will be found. to be 
 the centre of the principal mental nervous actions, and of certain 
 physical actions which are very essential . to the integrity of the 
 economy. 
 
 The office of the, nerves which arise from the segment of the ence- 
 phalon throws light upon its function. These nerves are partly d€- 
 stined for respiration, partly for deglutition, and partly also for acts of 
 volition and sensation. - 
 
 Destrubtion of the medulla oblongata is followed by the immediate 
 cessation of the <pheriomena of respiration ; and this takes place 
 whether it be simply divided, or completely removed. When an 
 animal is pithed, he falls down apparently senseless, and exhibiting 
 only such convulsive movements as may be due to the irritation of 
 the' medulla by the section, or siich reflex actions as may be excited 
 by the application of a stimulus to some part of the trunk. 
 
 If, in an animal which breathes without a diaphragm, as in a, bird 
 or reptile, the spinal cord be gradually removed in successive por- 
 tions, proceeding frombelow, up to within a short distance of the 
 medulla' oblongata, loss of motor and sensitive power takes place 
 successively in the segments of the body- with which the removed 
 portions of the cord were connected. But the animal still retains 
 its power of perceiving impressions made on those parts of the body 
 which preserve, their nervous Connection with the medulla oblongata, 
 and continues to exercise voluntary control over the movements of 
 those parts. The movements of respiration go on, and deglutition is 
 performed. The higher senses are unimpaired. (Flourens, p. 179.) 
 
 These phenomena are Sometimes observed in man— in such cases 
 as that alluded to in a former page ; where, from injury to the spinal 
 cord in the neck, below the origin of the phrenic nerve, the patient 
 appears as a living head with a dead trilnk. The sensibility and 
 motor power of the head are perfect ; respiration goes on partially, 
 and deglutition can be readily performed. The senses and the intel- 
 lectual faculties remain for a time unimpaired. < 
 
 Irritation of any part of the rnedulla oblongata excites convulsive 
 movements in muscular parts which receive nerves from it, and, 
 through the spinal cord, in the muscles of the trunk. Spasm of the 
 glottis, difficulty of deglutition, irregular acts of breathing, result from 
 irritation of the medulla oblongata ; and, if the excitement be pro- 
 pagated to the cord, convulsions will become more or less general. 
 
 If a lesion affect one-half of the medulla oblongata, does it pro- 
 duce convulsions or paralysis on the opposite side of the body ? This 
 question may be certainly answered in the affirmative, vp'hen the seat 
 of the lesion is in the continuations of the cblumns of the medulla 
 oblongata above the posterior margin of the pons. It is not so easily^ 
 solved, however, when the disease is situate below the pons. The 
 results of experiment on this subject are contradictory, owing probably 
 to the extreme difficulty of limiting the injury inflicted to a portion of 
 the medulla on one side ; and those of Flourens are of no^ value for 
 
FUNCTIONS OF THE ENCEPHALON. 305 
 
 the decision of this question, as it appears that he injured chiefly 
 the restiform bodies.. Anatomy suggests, that a lesion limited to 
 either anterior pyramid would affect, the opposite, side of the trunk, .for 
 it is known that such an effect follows disease of the continuation of 
 it in the mesocephale or Crus cerebri; and that lesion limited to the 
 posterior half of the medulla on either side wouldaffect the same side 
 of the body, no decussation existing, between the fibres of opposite 
 restiform or posterior pyramidal bodies. Theiirritating or depressing 
 influence of the lesion would.probably be extended to the spinal gray 
 matter of the same side. 
 
 That the medulla oblongata is the chartnel through which the 
 operations of the brain are associated in voluntary actions with the 
 spinal cord, is shown by the fact that paralysis of all the muscles of 
 the, trunk follows the separation of the latter organ from the formier. 
 It seems not improbable that the centre of volition is connected with 
 one or both of the gangliform bodies (corpora striata and optic tha- 
 lami) in which the columns of the medulla oblongata terminate above. 
 When the cerebral heifiispheres have been removed, as in Flourens' 
 and in Magendie's experiments, the bird is thrown into a deep sleep, 
 a state of stupefaction, and insensibility to surrounding objects. But 
 he can maintain his attitude^ — ^stands-walk, when first propelled — fly, 
 if thrown into the air. This continuance of the locomotive power 
 implies some- degree at least of mental or volitional effort. All the 
 animal's movements have much of the appearance of the exercise of 
 will, although, doubtless, many of them are in a great degree excited 
 by physical stimuli. Hence there seems reason to believe th^t the 
 will exerts a primary influence upon either or both of these gangliform 
 bodies, more vigorous when aided and guided by the power of the 
 cerebral hemispheres. The frequent paralysis of motion apart from 
 sensation when the upward continuations of the pyramidal fibres in 
 the corpora striata are diseased, renders it extremely probabk that 
 these fibres are the media of connection between the brain and cord 
 in voluntary actions. 
 
 The medulla oblongata is not less the medium fpr the transmission 
 of sensitive impressions from all the regions of the head, trunk, and ex- 
 tremities ; and from it;s olivary columns at their upper and posterior part 
 being, as it were, the concourse of all the nerves of pure sense, it 
 seems fair to assign these parts as the prime seat of those central 
 impressions which are necessary for sensation. The reception of 
 these impressions by the cerebral hemispheres is the stage immediately 
 associated with mental perception. True sensation, therefore^ cailnot 
 take place without cerebral hemispheres. In a sensation excited in 
 parts supplied by spinal nerves, the first central change is probably 
 in the posterior horn of the vesicular matter of the cord; and the 
 olivary column of the medulla oblongata is simultaneously affected, 
 from its connection with the cord. The change in this latter part is 
 then propagated to the cerebral hemispheres. 
 
 Thus much is suggested by anatomy, as regards the mechanism of 
 sensitive impressions. Experiment affords us no aid in this intricate 
 
306 INNERVATION. 
 
 and difficult subject; neither does pathological anatomy : for the parts 
 are so closely associated with each other, that any morbid state of one 
 readily involves the others, so that it is almost impossible to find a 
 morbid state of the parts devoted to sensation, apart from an affection 
 of those more immediately concerned in motion. 
 
 The function of the restiform bodies is probably associated with 
 that of the hemispheres of the cerebellum, and of the posterior col- 
 umns of the spinal cord. 
 
 The experiments of Le Gallois and Flourens render it certain that 
 the medulla oblongata is the centre of respiratory movements. The 
 latter physiologist assigns as the "primum raovens" of these acts all 
 that portion of the medulla which extends from the filaments of 
 origin of the vagus nerve to the tubercula quadrigemina, the former 
 only inclusive. Destruction of this portion, in whole or in part, 
 invariably impairs or destroys the respiratdryJhctions, and a morbid 
 state of it gives rise to irregular or excited movements of respiration. 
 Sighing, yawning, coughing, are probably connected with excitation 
 of this centre, either directj or propagated to it from some sentient 
 surface. 
 
 This portion of the encephalon is also the centre of action in tlie 
 movements of deglutition, through fibres of the glosso-pharyngeal 
 and vagi nerves. A morbid state of it occasions difficulty, or even 
 paralysis, of deglutition. Animals deprived of the cerebral hemi- 
 spheres and cerebellum will preserve the power of swallowing food 
 introduced within the grasp of the fauces, so long as the medulla 
 oblongata continues unjnjured. In foetuses born without cerebral 
 hemispheres, those actions are present which tlepend on the spi-nal 
 cord and medulla oblongata ; all the movements of respiration and 
 deglutition are performed as well as in the perfect fctetus. Mr. Grain- 
 ger's experiments show that puppies deprived of the hemispheres of 
 the brain can perform the movements of suction with considerable 
 vigour, when the finger is introduced into' the mouth, {loc. cit., 
 pp. 80-1,) and the remarkable fact of the adhesion of the foetus of 
 the kangaroo to the nipple within the pouch, no- less than its respira- 
 tory movements, must, as this author remarks, be regarded as a most 
 interesting display of the physical power of the medulla oblongata, 
 while the rest of the brain is as yet undeveloped. 
 
 The actions of respiration and deglutition are, to a great extent, of 
 the physical kind, being excited by impressions propagated from the 
 periphery. In those of respiration, the ordinary exciting cause is 
 probably, as Dr. Hall supposes, due to the chemical changes in the 
 respired air which are effected in the lungs. These movements may 
 be, to a certain extent, controlled by the will ; but every one is con- 
 scious, from his own sensations, that after a time the physical stimulus 
 is capable of conquering the restraining influence of the mind ; a 
 striking example of a mental stimulus giving way to a physical one ; 
 and illustrative, as we think, of the doctrine that the same fibres are 
 affected by both stimuli. The excitation of the medulla oblongata in 
 respiration does not, however, depend solely upon the pulmonary 
 
FUNCTIONS OF THE ENCEPHALON. 307 
 
 nerves. Those of the skin are capable of exciting it, either directly 
 as the fifth pair, or through the spinal cord, as is proved by the in- 
 spirations which are instantly excited by suddenly dashing cold water 
 on the face or trunk. 
 
 In deglutition, the exciting cause is the stimulus of contact applied 
 to the mucous membi'ane of the fauces. , So highly sensitive is the 
 mucous membrane in this situation, that the slightest touch of it with 
 a feather is sufficient to produce contraction of the muscles of deglu- 
 tition, which the will is scarcely able to control. Without this stimu- 
 lus, it is doubtful whether these muscles would obey the will alone ; 
 and it seems probable that this part of the act of deglutition must be 
 regarded as one of those actions referred to at a former page,, which 
 require a double stimulus, both mental and physical, for their full 
 performance. (See p. 296.) 
 
 The medull^ oblon^ta and its Continuations in the mesocephale 
 appear to be the centre of. those actions which are influenced by 
 emotion. The comrnon excitement of movements of deglutition or 
 respiration, or of sensations referred to the throat, nnder the influence 
 of emotion, evidently points to this part of the cerebro-spinal centre 
 as being very prone to obey such impulses ; and as the nerves of pure 
 sense, especially the optic and auditory, are very commonly the 
 channels of sensitive impressio'ns well calculated to arouse the feel- 
 ings, it seems highly probable that the centre of such actions should 
 be contiguous to the origin of these nerves, We would assign this 
 office to that region of the mesocephale which is in the vicinity oflhe 
 quadrigeminal tubercles. It is not a little remarkable that the nerves 
 which arise from this and the neighbouring parts are very readily 
 influenced by emotions. Thus, the third and fourth pairs of nerves 
 regulate the principal movements of the eyeballs, those especially 
 which most quickly betray emotional excitement; and the portio dura 
 of the seventh pair, the motor nerve of the face, is the medium 
 through which changes of the countenance are effected. It may be 
 added, that the centre of emotional actions ought to be so situated 
 that it could readily communicate with the centres of all. the volun- 
 tary actions of the body, and with the immediate seat of the in- 
 tellectual operations, as well as with the nerves ot pure sense ; and 
 no part possesses these relations so completely as that to which we 
 refer. 
 
 In those diseases which mental emotion is apt to give rise to, many 
 of the symptoms are referable to affection of the medulla oblongata. 
 In hysteria, the globus, or peculiar sense of suffocation or constriction 
 about the fauces ; in chorea, the difficulty of deglutition, the peculiar 
 movement of the tongue, the excited state of the countenance, the 
 difficulty of articulation, may be attributed to the exalted polarity of 
 the centre of emotional actions. In. hydrophobia this part is probably 
 always affected, and frequently so in tetanus. 
 
 Certain ganglifprm bodies are connected with the upward con- 
 tinuations of the medulla oblongata, both in the brain and in the 
 mesocephale, which doubtless have proper functions. These are the 
 corpora striata, optic thalami, and quadrigeminal bodies. 
 
308 INNERVATION. 
 
 Corpora striata. — The' anatomy ^f the corpora striata and optic 
 thalami, while jt denotes a very intimate union between them, also 
 shows so manifest a diflference in their structural characters, that it 
 cannot be doubted that they perform essentially 'different functions. 
 In the corpora striata the fibrous matter is arranged ia distinct fascicles 
 of very difTerent size, many, if not all of which, form ,a , special con^ 
 nection with its vesicular matter. In the optic thalami, on the other 
 hand, the fibrous matter forms a very intricate interlacement, which is 
 equally complicated at every part. , Innumerable fibres pass from one 
 to the other, and both are connected to the hemispheres by extensive 
 radiations of fibrous matter. The corpora striata, however, are con- 
 nected chiefly, if not solely, with the inferior fibrous layer of each 
 crus cerebri ;, whilst the optic thalami are continuous with the superior 
 part of each crus, which is situate above the locus niger. 
 
 It will be observed, then, that while these bodies possess, as a 
 principal character in common, their extensive connection with the 
 cerebral hembpheres, or, in other words, with the convoluted surface 
 of the brain, they are, in the most marked way, connected inferiorly 
 with separate and distinct portions of the medulla oblongata; the 
 corpora striata with the inferior fibrous planes of the crura cerebri 
 and their continuations; the anterior pyramids; and the optic thalami 
 with the olivary column^, the central and probably fundamental por- 
 tions of the medulla oblongata. And this anatomical fact must be 
 taken as an additional proof of their possessiiig separate functions. 
 
 Now, it may be inferred, from their connections with nerves chiefly 
 of a sensitive kind, that the olivary columns, and the optic thalami, 
 which are continuous with them, are chiefly concerned in the recep- 
 tion of sensitive impressions, which may principally have reference 
 merely to informing the mind (so to speak), or partly to the excitation 
 of motion, as in deglutition, respiration, &c. The posterior horns of 
 the gray matter of the cord, either by their direct continuity with the 
 olivary columns, or their union with them through commissural fibres, 
 becoine part and parcel of a great centre of sensation, whether for 
 mental or physical actions. 
 
 The pyramidal bodies evidently connect the gray matter of the 
 cord (its anterior horns?) with the corpora striata; and not only these, 
 but also the intervening masses of vesicular matter, such as the locus 
 niger, and the vesicular matter of the pons, and of the olivary col- 
 umns; and, supposing the corpora striata to be centres of volition 
 in intimate connection with the convoluted surface of the brain by 
 their numerous radiations, all these several parts are linked together 
 for the common purposes of volition,' and constitute a great centre 
 of voluntary actions, amenable to the influence of the will at every 
 point. 
 
 It has been pretty generally admitted by anatomists, that both the 
 corpora striata and the anterior pyramids are concerned in voluntary 
 movements. The motor tracts of Bell were regarded by that phy- 
 siologist as passing upwards from the anterior columns of the cord to 
 the corpora striata, and, after traversing those bodies, as diverging 
 into the fibrous matter of the hemispheres; and the fact of the origin 
 
FUNCTIONS OF CORPORA STRIATA AND OPTIC THALAMI. 309 
 
 of certain motor nerves, in connection with those fibres, was con- 
 sidered to be very favourable to this view. The decussation of the 
 pyramids, likewise, so illustrative of the cross influence of the brain 
 in lesions sufficient to produce paralysis, has been looked upon as an 
 additional indication of the motor influence of these parts. 
 
 The invariable occurrence of paralysis as the result of lesion, even 
 of, slight amount, in the corpora striata, must be regarded as a fact 
 of strong import in reference to the motor functions of these bodies. 
 
 Nor is this fact at all incompatible with the statements made by all 
 experimenters, that simple section of the corpus striatum does not 
 occasion either marked paralysis or convulsion ; and that in cutting 
 away the different segments of the brain, beginning with the hemi- 
 spheres, convulsions are not excited until the region of the mesoce- 
 phale is involved. The influence of the corpora striata is not upon 
 the nerves directly, but upon the segments of the medulla oblongata 
 or of the spinal cord, and, through them, upon the nerves which arise 
 from them. Were the nerve-fibres continued up into the corpora 
 striata, according to an opinion which has been long prevalent, there 
 would be no good reason for supposing that they should lose in the 
 brain that excitability to physical stimuli which they are known to 
 possess in the spinal cord, and at their peripheral distribution. 
 
 The latest experiments, which are those of Longet and Lafargue, 
 agree in the following result, which is not at variance with that 
 obtained by Flourens. The animals remain immovable after the 
 removal of the corpora striata, whether those bodies have been re- 
 moved alone or in conjunction with the hemispheres; nor do they 
 show any disposition to move, unless strongly excited by some exter- 
 nal stimulus. None of these observers had noticed the irresistible 
 tendency to rapid propulsion, which was described by Magendie. 
 Removal of the corpus striatum of one side caused weakness of 
 the opposite side. 
 
 In order to form a due estimate of these experiments, it must be 
 borne in mind, that the effect of simple excision of either corpus 
 striatum would be very different from those of diseases of it. The 
 depressing effects of the latter would be absent, at least, until some 
 alteration in the process of nutrition had been set up in the mutilated 
 parts. Simple excision of the centre of volition, and inflammatory 
 diseases of its substance, or an apoplectic clot, must produce essen- 
 tially different effects; — the one simply cuts off" the influence of 
 the will, the other affects the vital action, and, consequently, the 
 vital power of the centre, and of the commissural fibres connected 
 with it. 
 
 Judging from structure only, it might be conjectured that the locus 
 niger, that remarkable mass of vesicular matter which separates the 
 anterior and posterior planes of each crus cerebri, exerts a motor in- 
 fluence. It resembles in structure the anterior horns of the gray matter 
 of the cord, and contains numerous large caudate vesicles with very 
 abundant pigment. 
 
 Optic thalami. — The same line of argument which leads us to 
 view the corpora striata as the more essential parts of the nervous 
 16 
 
310 INNERVATION. 
 
 apparatus which control direct voluntary movements, suggests that 
 the optic thalami may be viewed as the principal foci of sensibility, 
 without which the mind could not perceive the physical change re- 
 sulting from a sensitive impression. 
 
 The principal anatomical fact which favours this conclusion, is the 
 connection of all the nerves of pure sense, more or less directly, with 
 the optic thalami or with the olivary columns. The olfactory pro- 
 cesses, which apparently have no connection with them, form, no 
 doubt, through the fornix, such a union with them, as readily to bring 
 them within the influence of the olfactory nerves. 
 
 According to this sense of its office, we must regard the optic 
 thalami as the upper and chief portions of an extended centre, of 
 •which the lower part is formed by the olivary columns, which we 
 have already referred to as taking part in the mechanism of sensation. 
 The continuity of the olivary columns with the optic thalami justifies 
 this view: nor is it invalidated by the fact, that some of the nerves 
 ■which arise from the medulla oblongata are motor in function ; for 
 Stilling's researches render it probable that these fibres have their 
 origin in special accumulations of vesicular matter, which contain 
 caudate vesicles of the same kind as those found in the anterior horns 
 of the gray matter of the cord. (See fig. 70.) 
 
 The results which experiments have yielded, add little that is posi- 
 tive to our knowledge of the functions of these bodies. Floureris 
 found that neither pricking nor cutting away the optic thalami by suc- 
 cessive slices, occasioned any muscular agitation, nor did it even in- 
 duce contraction of the pupils. Longet found that removal of one 
 -optic thalamus in the rabbit was followed by paralysis on the oppo- 
 site side of the body. ' It appears, however, that this was done after 
 the removal of the hemisphere and corpus striatum, whereby the 
 experiment was so complicated as to invalidate any conclusion that 
 might be drawn from it respecting the function of the thalamus. In- 
 deed, vivisections upon so complex an organ as the brain are ill cal- 
 culated to lead to useful or satisfactory results ; but we do not hesi- 
 tate to quote such as have been made, from the imperfect negative 
 information which they afford. 
 
 Nothing definitive respecting the proper office of the thalami can 
 be obtained from pathological anatomy. Extensive disease of these 
 bodies is attended with the same phenomena during life, as lesion of 
 similar kind in the corpora striata. Hemiplegic paralysis accompa- 
 nies both ; nor does it appear that sensation is impaired when the 
 thalamus is diseased, (pore than when the corpus striatum is affected. 
 
 We see nothing in the phenomena which attend morbid states of 
 the thalami, to oppose the conclusion which their anatomical rela- 
 tions indicate, namely, that they form a principal part of the centre 
 of sensation. The intimate connection between the striated bodies 
 and the thalami, sufficiently explains the paralysis of motion which 
 follows disease of the latter ; whilst, as the thalami do not constitute 
 the whole centre of sensation, but only a part, it cannot be expected 
 that lesion of this part would destroy sensation, so long as the re- 
 mainder of the centre on the same side, as well as that of the oppo- 
 
FUNCTIONS OF THE ENCEPHALON. 311 
 
 site side, retain their integrity. Complete paralysis of sensation on 
 one side is very rare in diseased brain : a slight impairment of it fre- 
 quently exists in the early periods of cerebral lesion, apparently as 
 an effect of shock ; for it quickly subsides, although the motor power 
 may never return. 
 
 According to the views above expressed, the corpora striata and 
 optic thalami bear to each other a relation analogous to that of the 
 anterior to the posterior horn of the spinal gray matter. The corpora 
 striata and anterior horns are centres of motion ; the optic thalami 
 and posterior horns centres of sensation. The anterior pyramids con- 
 nect the former ; the olivary columns, and perhaps some fibres of the 
 anterior pyramids, the latter. The olivary columns, however, are in 
 great part continuations of the thalami on the one hand, and of the 
 gray matter of the cord on the other: and contain abundance of ve- 
 sicular matter, in which nerves are implanted. 
 
 And it must be admitted that the intimate connection of sensation 
 and motion, whereby sensation becomes a frequent excitor of motion, 
 — and voluntary motion is always, in a state of health, attended with 
 sensation, — would a priori lead us to look for the respective centres 
 of these two great faculties, not only in juxtaposition, but in union 
 at least as intimate as that which exists between the corpus striatum 
 and optic thalamus, or between the anterior and the posterior horns of 
 the spinal gray matter. 
 
 Saucerotte, Foville, Pinal Grandchamps, and others, advanced the 
 opinion that the corpora striata and the fibrous substance of the an- 
 terior lobes of the brain had a special influence upon the motions of 
 the lower extremities, and that the optic thalami and the fibrous sub- 
 stance of the middle and posterior part of the brain presided over the 
 movements of the upper extremities. We find, however, but little 
 to favour this theory either in the results of experiments, in patho- 
 logical observation, or the anatomy of the parts. Longet states, that, 
 ia his experiments upon the optic thalami, the paralysis affected 
 equally the anterior and the posterior extremities. Andral analyzed 
 seventy-five cases of cerebral lesion limited to the corpus striatum or 
 optic th'alamus. In twenty-three of these cases, the paralysis was 
 confined to the upper extremity : of these, eleven were affected with 
 lesion of the corpus striatum or of the anterior lobe ; ten with lesion 
 of the posterior lobe, or of the optic thalamus; and two with lesion 
 of the middle lobe.* Hence it is plain that a diseased state of the 
 corpus striatum is as apt to induce paralysis of the upper extremity, 
 as lesion of the thalamus ; and we are forced to conclude, that patho- 
 logical anatomy is not competent to decide the question. Lastly, the 
 anatomy of these two bodies renders it highly improbable that they 
 perform a function so similar, as that of directing the movements of 
 particular limbs. The great size of the optic thalamus, its multitude 
 of fibrous radiations, its extensive connections both in the medulla - 
 oblongata and in the hemispheres by means of commissural fibres, 
 
 Clin. Med. t. v. 
 
312 INNERVATION. 
 
 the marked difference of its structure from that of the corpus striatum, 
 its connection more with the posterior horns of the spinal gray matter 
 than with the anterior ones, and its intimate relation to nerves of 
 sensation, are, in our judgment, sufficient anatomical facts to warrant 
 the opinion that the thalami must perform a function which, although 
 it may be subservient to, or associated with, that of the striated bo- 
 dies, is yet entirely dissimilar in kind. 
 
 It has been supposed that the corpora striata are special centres or 
 ganglia to the olfactory nerves, and to the sense of smell. But such 
 a supposition is altogether superfluous, inasmuch as a very distinct 
 and obvious centre to these nerves exists in the olfactory process or 
 lobe, miscalled nerve by descriptive anatomists. The small olfactory 
 nerves are implanted in the anterior extremity or bulb of this pro- 
 cess, which is provided with all the structural characters of a nervous 
 centre, and contains a ventricle. This lobe, moreover, is always 
 developed in the direct ratio of the. size and number of the olfactory 
 nerves, and of the development of the sense of smell ; and in the 
 Cetacea, a class in which the olfactory nerves and process either do 
 not exist at all, or are so imperfectly developed as to have escaped 
 the notice of some of the ablest anatomists, the corpora striata are 
 of good size proportionally to that of the entire brain. 
 
 Corpora quadrigemina. — The marked connection of these gangli- 
 form bodies with the optic nerves plainly indicates that they bear 
 some special relation to those nerves, and to the sense of vision ; and 
 this indication becomes more certain when we learn, from compara- 
 tive anatomy, that in all vertebrate tribes in which the encephalon is 
 developed, special lobes exist, bearing a similar relation to the optic 
 nerves (pp. 249-50). When the optic nerves are large, these lobes are 
 large; and in the pleuronecta, in which the eyes are of unequal size, 
 Gottsche states that the optic lobes are unequal. Stfll, as Serres has 
 remarked, the quadrigeminal tubercles probably perform some other 
 office besides that which refers to vision ; inasmuch as the absence, 
 or extremely diminutive size, of the optic nerves in some animals 
 (the mole, for instance), does not materially affect that of tl\ese bo- 
 dies. (Cyclop. Jinat., art. Optic nerves.) 
 
 Flourens found that destruction of either of these tubercles on one 
 side was followed by loss of sight of the opposite side, and conse- 
 quently that the removal of both deprived the animal altogether of 
 the power of vision, but did not affect its locomotive or intellectual 
 powers, nor its sensibility, except to light. In these experiments the 
 action of the iris was not impaired if the tubercles were only par- 
 tially removed ; as long as any portion of the roots of the optic 
 nerves remained uninjured, the iris continued to respond to the stimu- 
 lus of light, but the total removal of the tubercles paralyzed the irides. 
 If the lobes of the brain and cerebellum were removed, leaving the 
 tubercles untouched, the irides would continue to contract. These 
 experiments leave no room to doubt that the optic tubercles are the 
 encephalic recipients of the impressions necessary to vision, which 
 doubtless are simultaneously felt by means of the optic thalami ; and 
 
FUNCTIONS OF THE CORPORA QUADRIGEMINA. 313 
 
 that they are the centres of those movements of the iris which con- 
 tribute largely not only to protect the retina, but likewise to increase 
 the perfection of vision. The optic nerve is at once the nerve of 
 vision, and the excitor of motor impulses which are conveyed to the 
 iris by the third nerve, which takes its origin very near to the optic 
 tubercles. It is interesting to add, that irritation of an optic tubercle 
 on one side causes contraction of bothirides: — this is quite in accord- 
 ance with the well-established fact, that, if light be admitted to one 
 eye so as to cause contraction of its pupil, the other pupil will con- 
 tract at the same time. So simultaneous is the action of the two 
 centres ; so rapid must be the transmission of the stimulus from one 
 side to the other. 
 
 When the injuries inflicted on these tubercles were deep, more or 
 less general convulsive movements were produced ; if one tubercle 
 ■were injured, the opposite side only was so affected. These con- 
 vulsions were due to the lesion of the central parts of the medulla 
 oblongata, with which the optic tubercles are intimately connected. 
 A remarkable vertiginous movement was likewise caused, the animal 
 turning to the side from which the tubercle had been removed. It 
 does not appear that this rotation could be attributed to any special 
 influence of the inedulla oblongata, but rather to a state of vertigo 
 induced by the partial destruction of vision ; for Flourens found that 
 the same effects could be produced in pigeons by blindfolding one 
 eye. The movements, however, were not so rapid, nor did they 
 continue so long. And Longet saw the same movements in pigeons 
 in which he had evacuated the humours of one eye.* 
 
 It may be remarked, that deep injuries to the quadrigeminal tuber- 
 cles are very likely to affect the only commissural connection between 
 the cerebrum and cerebellum [processus cerebelli ad testes), the in- 
 tegrity of which must doubtless be essentially necessary to ensure 
 harmony of action between these two great nervous centres. 
 
 There are many instances on record in which blindness was coin- 
 cident with pathological alteration of structure in one or both quadri- 
 geminal tubercles. In some of the cases where the lesion extended 
 to parts seated beneath the tubercles, disturbed movements were ob- 
 served, as in the experiments above related. 
 
 We are ignorant of the object of the extensive connections of the 
 optic tracts with the tuber cinereum, the crura cerebri, and the cor- 
 pora geniculata; but these points are highly worthy of future inquiry, 
 especially with reference to the. office of these last-named bodies, 
 which is at present involved in much obscurity. Many of the fibres 
 of the optic tracts are undoubtedly commissural between the corre- 
 sponding points of opposite sides, and exist when those which form 
 the optic nerves are deficient. 
 
 We see, then, in the quadrigeminal tubercles, centres, which, 
 whatever other functions they may perform, have a sufficiently ob- 
 vious relation to the optic nerves, the eye, and the sense of vision. 
 
 * Flourens' experiments have been amply confirmed by those of Hertwig and 
 Longet. 
 
314 INNERVATION. 
 
 This is clearly indicated by anatomical facts, by the results of experi- 
 ment, and by the phenomena of disease. These bodies may, there- 
 fore, be justly reckoned as special ganglia of vision; and we are led 
 to seek for similar centres in connection with the other senses. The 
 olfactory processes seem very probably to perform a similar office in 
 reference to the sense of smell. Their structure, their relation to the 
 olfactory nerves, and their direct proportion of bulk to that of these 
 nerves, and to the development of the olfactory apparatus, place 
 this question beyond all doubt. It is not so easy to determine the 
 special ganglia of hearing; but the olivary bodies, or the small 
 lobules connected with the crura cerebelli, called by Reil the flocks, 
 may be referred to as bearing a sufficient close anatomical relation to 
 the auditory nerve to justify our regarding either of them as well cal- 
 culated to perform this function. And, with respect to touch, the 
 ganglia on the posterior roots of the spinal and the fifth nerves may 
 perhaps be considered in the same light ; for this sense being diffused 
 so universally, in various degrees, over the whole surface of the 
 body, and being seated in a great number of different nerves, would 
 need ganglia in connection with all those nerves which are adapted 
 to the reception of tactile impressions. The analogous sense of taste 
 has its ganglia in those of the glosso-pharyngeal and the fifth.* 
 
 The upper and posterior part of the mesocephale has already been 
 referred to, as being most probably that part of the brain which fs 
 most directly influenced by emotional excitement. Dr. Carpenter 
 appears to localize the seat of emotional influence more specially in 
 the corpora quadrigemina, and refers to certain fibres, which he con- 
 siders terminate in those bodies, as channels of emotional impulses. 
 Although we cannot agree with this able writer in this limitation of 
 the centre of emotion (so to speak), nor in the existence of a distinct 
 series of fibres for emotional acts, we think the arguments, he ad- 
 vances are most applicable to that view which refers the influence of 
 emotion to the gray matter of this entire region, which is brought 
 into connection with the spinal cord by the fibres of the anterior 
 pyramids, as well as probably through the continuity of the olivary 
 columns and the posterior horns of the spinal gray matter. , 
 
 Every one has experienced in his own person how the emotions of 
 the mind, whether excited by a passing thought, or through the ex- 
 ternal senses, may occasion not only involuntary movements, but 
 subjective sensations. The thrill which is felt throughout the entire 
 frame when a feeling of horror or of joy is excited, or the involun- 
 tary shudder which the idea of imminent danger or of some serious 
 hazard gives rise to, are phenomena of sensation and motion excited 
 by emotion. The nerves which take their origin from the medulla 
 
 • II may beurged against this conjecture respecting the functions of the ganglia 
 of the spinal nerves anj the fifth, that the analogy between these bodies and the 
 quadrigeminal tubercles is incomplete, inasmuch as the optic nerves are probably 
 implanted in the latter, but the-nerves of touch merely pass through the former. But, 
 in truth, we know so little of the positive relation of the nerves in question to the 
 ganglia, that no argument, either for or against the above view, can rest upon such 
 imperfect information. 
 
FUNCTIONS OF THE ENCEPHALON. 315 
 
 oblongata, mesocephale, or crura cerebri, are especially apt to be 
 affected by emotions. The choking sensation which accompanies 
 grief is entirely referable to the pharyngeal branches of the glosso- 
 pharyngeal and vagi nerves, which come from the olivary columns. 
 The flow of tears which the sudden occurrence of joy or_ sorrow is 
 apt to induce may be attributed to the influence of the fifth nerve, 
 which is also implanted in the olivary columns, upon the lachrymal 
 gland ; or of the fourth nerve, which anastomoses with the lachrymal 
 branch of the fifth. The more violent expressions of grief, sobbing, 
 crying, denote an excited state of the whole centre of emotion, in- 
 volving all the nerves which have connection with it, the portio dura, 
 the fifth, the vagus, and glosso-pharyngeal; and even the respiratory 
 nerves, which take their origin from the spinal cord, as the phrenic, 
 spinal accessory, &c. And laughter, "holding both his sides," 
 causes an analogous excitation of the same parts of the central organ 
 and of the same nerves. The very different effect produced by the 
 excitement of the same parts must be attributed to the different- 
 nature of the mental stimulus. 
 
 As the passing thought — the change wrought during the exercise 
 of the intellect — may excite the centre of emotion, so this latter 
 may exert its influence upon the general tenor of the mind, and give 
 to all our thoughts the tinge of mirth or sadness, of hope or despond- 
 ency, as one or the other may prevail. We say of one man, that 
 he is constitutionally morose ; of a second, that he is naturally gay 
 and mirthful ; and of a third, that he is a nervous man, and that he 
 is not likely to be otherwise. One man allows his feelings to hurry 
 him on to actions which his intellect condemns ; whilst another has 
 no difficulty in keeping all his feelings in entire subjection to his 
 judgment. " Of two individuals with differently constituted minds," 
 remarks Dr. Carpenter, "one shall judge of everything through the 
 medium of a gloomy morose temper, which, like a darkened glass, 
 represents to his judgment the whole world in league to injure him ; 
 and all his determinations, being based upon this erroneous view, 
 exhibit the indications of it in his actions, which are themselves, 
 nevertheless, of an entirely voluntary character. On the other hand, 
 a person of a cheerful, benevolent disposition, looks at»the world 
 around as through a Claude-Lorraine glass, seeing everything in its 
 brightest and sunniest aspect, and, with intellectual faculties pre-, 
 cisely similar to those of the former individual, he will come to oppo- 
 site conclusions; because the materials which form the basis of his 
 judgment are submitted to it in a very different form." Such ex- 
 amples abundantly, illustrate the important share which the emotions 
 take in the formation and development of character, and how all 
 things presented to the mind through the senses may take their hue 
 from the prevailing state of the feelings. If a certain part of the 
 brain be associated with emotion, it is plain that that part must be in 
 intimate connection with the seat of change in the operations of the 
 intellect, in order that each may affect the other ; that the former 
 may prompt the latter, or the latter excite or hold in check the 
 former. And this association of the emotions with a certain portion 
 
316 INNERVATION. 
 
 of the brain explains the influence of natural temperament, and of 
 varying states of the physical health, upon the moral and intellectual 
 condition of individuals. We may gather from it how necessary it 
 is to a well-regulated mind that we should attend not to mental cul- 
 ture only, but to the vigour and health of the body also; that to 
 ensure the full development of the mens sana we must secure the 
 possession of the corpus samim. 
 
 Certain diseases are evidently associated .with disturbed or excited 
 states of emotion. I/i such cases, the nerves most affected are those 
 connected with the mesocephale and medulla oblongata, denoting an 
 excited state of those portions of the encephalon. Of these diseases 
 the most remarkable are hysteria and chorea; both of which may be 
 induced either by a cause acting primarily upon the mind, or by 
 functional disturbance of the body, as deranged assimilation, in per- 
 sons of a certain character of constitution. In hysteria, the globus, 
 the tendency to cry or laugh, the disturbed breathing, the variously 
 deranged state of the respiratory acts, all denote affection of most, if 
 not all, the nerves coming from those segments. In chorea the 
 frequent movements of the face and eyes, the peculiar and very 
 characteristic mode of protruding the tongue, the impaired power of 
 articulation, are dependent on an altered state of that part in which 
 the portio dura of the seventh pair, the third, fourth, and sixth, and 
 the ninth nerves are implanted. In both diseases the principal 
 central disturbance is in the mesocephale; and that may be caused 
 either by the direct influence of the mind upon it, or by the propaga- 
 tion of a state of irritation to it from some part of the periphery. 
 Chorea, even of the most violent and general kind, is very com- 
 monly produced by sudden fright; and it is well known how fre- 
 quently mental anxiety or excitement develops the paroxysm of 
 hysteria. 
 
 There is no part of the cerebro-spinal centre which appears to 
 exercise such extensive sway over the movements and sensations of 
 the body as this portion, the mesocephale, which we regard as the 
 centre of emotional actions. Its influence extends upwards to the 
 cerebral convolutions — backwards to the cerebellum — downwards to 
 all the nerves of sensation and motion. Through its connection with 
 the posterior horns of the spinal gray matter, it can excite the sensi- 
 tive as well as the motor nerves of the trunk. Hence it is not to be 
 wondered at that a highly disturbed state of this centre is capable of 
 deranging all the sensitive as well as motor phenomena of the body, 
 and even the intellect. Hence we may explain the extraordinary 
 movements in hydrophobia and general chorea,. in both of which 
 diseases this part of the nervous centre is doubtless affected. It has 
 often been remarked how much more powerful are the voluntary 
 actions when prompted by some strong emotion, than when excited 
 only by an effort of the will. Rage, or despair, is able to magnify 
 the power of the muscles to an incalculable degree. This may be 
 due to the increased .stimulus derived from the influence of the centre 
 of emotion being conjoined with that of the centre of voli'ion. 
 
 The intimate connection of the olivary columns with the gray 
 
FUNCTIONS OF THE CEREBELLUM. 317 
 
 I 
 
 matter of the cord, and through that with all the roots of the spinal 
 nerves, illustrates the power of emotional changes upon the organic 
 processes. HOw often does the state of the feelings influence the 
 quantity and quality of the secretions, no doubt through the power 
 of the nerves over the capillary circulation! Blushing is produced 
 through an affection of the mind, acting primarily on the centre of 
 emotion, and through it on the nerves, which are distributed to the 
 capillary vessels of the skin of the face. 
 
 The sexual passion must be ranked among the mental emotions. 
 Lilce them, it may be excited and ministered to by a certain line of 
 thought, or by particular physical states of the sexual organs. It 
 seems, therefore, more correct to refer this emotion to the common 
 centre of all, than to a special organ — according to Gall's theory; 
 and it may be remarked, that great development of this part of the 
 brain is just as likely to produce great width of cranium in the occi- 
 pital region as a large cerebellum. 
 
 Of the functions of the cerebellum. — All anatomists are agreed in 
 admitting, in the whole vertebrate series, (the amphioxus excepted,) 
 the existence of a portion of the encephalon which is analogous to 
 the cerebellum. This extensive existence of such an organ indicates 
 its great physiological importance, as a special element of the ence- 
 phalon. The cerebellum exhibits much difference both as regards 
 size and complexity of structure in the different classes; and al- 
 though, upon the whole, it increases in its development in the same 
 ratio as the hemispheric lobes, it exhibits no constant relation of size 
 to those parts. 
 
 The large size and complicated structure of this organ in the 
 higher vertebrate animals, and its distinctness from the other parts of 
 the brain, — for its commissural connections are not extensive, — have 
 excited the interest and curiosity of speculative physiologists; and, 
 accordingly, we find no part respecting which a greater variety of 
 hypotheses have been suggested, most of them being entirely devoid 
 of foundation. The experiments of Flourens have, however, thrown 
 more light on this subject than any previous observations ; and his 
 hypothesis appears to us nearer the truth than any which has been 
 proposed. We shall content ourselves with examining this theory, 
 as well as that of Gall, which assigns the cerebellum as the organ of 
 the sexual instinct. 
 
 The facility with which the cerebellum may be removed or in- 
 jured, especially in birds, without involving the other segments of 
 the brain, renders it a much more favourable object for direct expe- 
 riment than them. A skilful operator may remove the greater part 
 or the whole of the cerebellum without inflicting any injury on the 
 hemispheres or other parts. 
 
 Flourens removed the cerebellum from pigeons by successive slices. 
 During the removal of the superficial layers there appeared only a 
 slight feebleness and want of harmony in the movements, without 
 any expression of pain. On reaching the middle layers an almost 
 universal agitation was manifested, without any sign of convulsion: 
 the animal performed rapid and ill- regulated movements; it could 
 
318 INNERVATION. 
 
 hear and see. After the removal of the deepest layers, the animal 
 lost completely the power of standing, walking, leaping, or flying. 
 The power had been injured by the previous mutilations, but now it 
 was completely gone. When placed upon his back, he was unable 
 to rise. He did not, however, remain quiet and motionless, as 
 pigeons deprived of the cerebral hemispheres do ; but evinced an 
 incessant restlessness, and an inability to accomplish any regular or 
 definite movement. He could see the instrument raised to threaten 
 him with a blow, and would make a thousand contortions to avoid it, 
 but did not escape. Volition and sensation remained ; the power.of 
 executing movements remained ; but that of co-ordinating these move- 
 ments into regular and combined actions was lost. 
 
 Animals deprived of the cerebellum are in a condition very similar 
 to that of a drunken man, so far as relates to their power of locomo- 
 tion. They are unable to produce that combination of action in 
 different sets of muscles which is necessary to enable them to assume 
 or maintain any attitudes. They cannot stand still for a moment; 
 and, in attempting to walk, their gait is unsteady, they totter from 
 side to side, and their progress is interrupted by frequent falls. The 
 fruitless attempts which they make to stand or walk is sufficient proof 
 that a certain degree of intelligence remains, and that voluntary 
 power continues to be enjoyed. 
 
 Rolando had, previously to Flourens, observed effects of a similar 
 nature consequent upon mutilation of the cerebellum. In none of 
 his experiments was sensibility affected. The animal could see, but 
 was unable to execute any of the movements necessary for loco- 
 motion. * 
 
 Flourens' experiments have been confirmed by those of Hertwig 
 in every particular, and they have been lately repeated with similar 
 results by Budge and by Longet. The removal of part of the cere- 
 bellum appears capable of producing the same vertiginous affection 
 which has been already noticed in the case of deep injuries to the 
 mesocephale. After the well-known experiments of Magendie, of 
 dividing either crus cerebelli, the animal was seen to roll over on its 
 long axis towards the side on which the injury was inflicted. 
 
 The effects of injuries to the cerebellum, according to the reports of 
 the experimenters above referred to, contrast in a very striking man- 
 ner with those of the much more severe operation of removing the 
 cerebral hemispheres. " Take two pigeons," says M. Longet ; " from 
 one remove completely the cerebral lobes, and from the other only 
 half the cerebellum; the next day, the first will be firm upon his 
 feet, the second will exhibit the unsteady and uncertain gait of drunk- 
 enness." 
 
 Experiment, then, appears strikingly to favour the conclusion 
 which Flourens has drawn, namely, that the cerebellum possesses 
 the power of co-ordinating the voluntary movements which originate 
 in other parts of the cerebro-spinal centre, whether these movements 
 have reference to locomotion or to other objects. 
 
 That this power is mental, i. e., dependent on a mental operation 
 for its excitation and exercise, is rendered probable from the expe- 
 
FUNCTIONS OP THE CEREBELLUM. 319 
 
 rience of our own sensations, and from the fact that the perfection of 
 it requires practice. The voluntary movements of a new-born infant, 
 although perfectly controllable by the will, are far from being co-ordi- 
 nate: they are, on the contrary, remarkable for their vagueness and 
 want of definition. Yet all the parts of the cerebro-spinal centre are 
 well developed, except the cerebellum and the convolutions of the 
 cerebrum. Now, the power of co-ordination improves earlier and 
 more rapidly than the intellectual faculties; and we find, in accord- 
 ance with Flourens' theory, that the cerebellum reaches its perfect 
 development of form and structure at a much earlier period than the 
 hemispheres of the cerebrum. 
 
 It may be stated as favourable to this view of the mental nature 
 of the power by which voluntary movements are co-ordinated, that, 
 in the first moments of life, provision is made for the perfect per- 
 formance of all those acts which are of the physical kind. Thus, 
 respiration and deglutition are as perfect in the new-born infant as 
 in the full-grown man; and the excitability of the nervous centres to 
 physical impressions is much greater at the early age, partly perhaps 
 in consequence of the little interference which is received at that 
 period from the will. 
 
 That the cerebellum is an organ favourably disposed for regulating 
 and co-ordinating all the voluntary movements of the frame, is very 
 apparent from anatomical facts. No other part of the encephalon 
 has such extensive connections with the cerebro-spinal axis. It is 
 connected slightly indeed with the hemispheres of the brain, but 
 most extensively with the mesocephale, the medulla oblongata, and 
 the spinal cord. Now it is not unworthy of notice that its connection 
 with the brain proper is more immediately with that part which we 
 regard as the centre of sensation ; namely, with the optic thalami, 
 through the processus cerebelli ad testes. And it cannot be doubted 
 that the muscular sense materially assists in the co-ordination of 
 movements. 
 
 The cerebellum is connected with the medulla oblongata and 
 spinal Cord by the restiforra bodies, and the posterior columns of 
 the cord, and with the mesocephale by the fibres of the pons. Thus 
 this organ is brought into union with each segment of the great nerv- 
 ous centre, upon which all the movements and sensations of the 
 body depend. It would be difficult to conceive any other function 
 for which so elaborate a provision would be necessary, excepting 
 that of regulating and co-ordinating the infinitely complex move- 
 ments which the muscular system is capable of effecting; more espe- 
 cially when it is plain that the antero-lateral columns of the cord and 
 the anterior pyramids and olivary columns supply all the anatomical 
 conditions which may be necessary for the development of acts of 
 sensation and volition. 
 
 So far, then, we derive from experiment and from anatomy argu- 
 ments highly favourable to Flourens' theory of the use of the cere- 
 bellum. The results of pathological inquiry afford no satisfactory 
 information on this point; for so closely connected are the transverse 
 fibres of the pons with the anterior pyramids in the mesocephale, that 
 
320 INNERVATION. 
 
 the morbid influence of any deep-seated lesion of either hemisphere 
 of the cerebellum is very readily transferred to that segment, and 
 produces symptoms precisely resembling those of lesion of either 
 cerebral hemisphere. The signs referable to cerebellar lesion are 
 therefore obscured by those which result from the affection of the 
 pyramidal bodies. A few cases, however, have been put on record 
 in which a tottering gait, like that of a drunken man, and a defective 
 power of co-ordination existed in connection with a diseased state of 
 cerebellum. {Andral, Clin. Med., t. v. p. 428.) 
 
 It remains for us to notice the celebrated theory of Gall, that the 
 instinct of propagation has its seat in the cerebellum ; which, indeed, 
 according to the author of the theory, and the majority of his followers 
 of the phrenological school, is exclusively devoted to that function. 
 We conceive that this view is far from admissible, on several grounds, 
 of which the following deserve particular mention. 
 
 1. It is extremely questionable how far the sexual instinct admits 
 of being separated from the emotions — from those especially which 
 are clearly instinctive in their nature ; and, even if it were separable 
 from them, it seems scarcely of such importance, when compared 
 with the other instincts, as to need a separate organ of .great magni- 
 tude and of complex structure. If we compare it, for example, with 
 the instinct of self-preservation, as manifested in providing eithe^r for 
 the wants of the body, or for defence against assault, it certainly can- 
 not be admitted to have a superior influence in the animal economy 
 to this the most pressing of all. Yet it is not pretended to assign a 
 separate seat even to this. 
 
 2. The nature of the generative instinct is scarcely such as to re- 
 quire in its central organ connections so extensive as those possessed 
 by the cerebellum. It is not likely that this organ would be con- 
 nected with any other part of the spinal cord than that from which 
 nerves are derived to the organs of generation; nor is it conceivable 
 that an instinct like this should require for its exercise fibrous matter 
 in such large quantity as exists in the cerebellum, taking its rise from 
 so great a surface of vesicular matter. 
 
 3. The generative instinct is not so pre-eminently developed in 
 man as to account for the great superiority in size, as well as struc- 
 ture, of the human cerebellum over that of the lower animals, even 
 of the mammiferous class. On the contrary, it may be safely asserted 
 that this instinct is much more powerful in the monkeys, and also in 
 the frogs; in the latter of which the cerebellum is absolutely very 
 small, and especially so, relatively to the spinal cord and the cerebral 
 lobes. 
 
 4. If the cerebellum be the seat of the generative instinct, it ought 
 to exhibit marked indications of wasting, in cases where the genital 
 organs have been mutilated ; or where they have decayed in the 
 natural progress of age. Yet the recorded cases of this nature are 
 by no means conclusive ; on the contrary, M. Leuret's remarkable 
 observations show, that, in the gelding, the cerebellum is actually 
 heavier than in either the stallion or th« mare. 
 
 5. It does not appear, from pathological research, that the cerebel- 
 
FUNCTIONS OF THE CEREBRAL CONVOLUTIONS. 321 
 
 lum has any peculiar influence, upon the genital organs. Injury or 
 disease of that org3n ¥ery rarely produces any effect upon the penis.; 
 but lesion of the medulla oblongata or of the spiijal cord is very apt 
 to occasion a semi-erection of that organ. 
 
 Of the Convolutions of the brain. — These, with the fibrous matter 
 ■which connects them with the optic thalami and corpora striata, form 
 by far the largest portion of the encephalon ; and this fact alone 
 ought to stanap them with great physiological importance. The com- 
 plexity of the convolutions in the animal scale is in the direct ratio 
 of the advance of intelligence. It must, be remarked, however, that 
 the weight of the brain, whether absolute, or in relation to the body, 
 affords no criterion, or at best an imperfect one, of the extent of 
 the convoluted surface. Highly complicated convolutions may exist 
 along with a brain both absolutely and relatively, small. Thus Leuret 
 asserts, that the ferret, which has several well-marked convolutions 
 on each hemisphere, has a brain no larger than that of the squirrel, 
 which has no convolutions at all, ancT which wants even the few 
 fissures which mark their first development in the rabbit, the beaver, 
 the agouti, &c. And the last-named animals have the brain both 
 absolutely and relatively larger than that of the cat, the pole-cat, the 
 roussette, the unau, the sloth, and the pangolin, all of which- possess 
 convolutions. We hence learn the physiological distinctness of these 
 organs from the more deeply-seated gangliform bodies of the brain, 
 to which we have already seen that separate functions may be 
 assigned. 
 
 At the early periods of human Iife,Jn infancy and childhood, the 
 convolutions of the brain are very imperfectly developed, and their 
 increase of size goes on simultaneously with the advance of mental 
 power. If the former be arrested, or if some congenital fault prevent 
 the further growth of the convolutions, the mental powers are of the 
 lowest and feeblest kind, but little above those of the brute with 
 imperfect convolutions. In all idiots the brain is not only small, but 
 its convoluted surface is extremely limited. 
 
 We remark here that the convoluted form must be regarded no 
 otherwise/ than as a convenient mode of packing, which affords an 
 indication of a greater or less superficial extent of vesicular matter, 
 for in cases where a slow and gradual accumulation of water takes 
 place within the ventricles of the brain, when accompanied with cor- 
 responding enlargement of the cranium, the convolutions become 
 unfolded; and yet the intellect may remain unimpaired, at least so 
 far as the obvious damage to the quality of the nervous matter in 
 such cases will allow. 
 
 In examining the brains in the animal series, we observe a pro- 
 gressive increase in the complication of the convolutions, and there- 
 fore in the extent of the convoluted Surface, as we pass from the 
 inferior to the higher classes, — from those endowed with but feeble 
 intelligence to those which enjoy sagacity, docility, and memory. 
 Instances have been already referred to of animals of the same group, 
 although of different species, having brains very differently developed 
 as regards the convoluted surface. In the animal with greater mental 
 17 
 
322 INNERVATION. 
 
 power, the convolutions are always deeper or more complex (vid. p. 
 256). 
 
 If a similar comparison were instituted between the brains of dif- 
 ferent men, whose intellectual powers had been known, there can be 
 no doubt that a similar result would be obtained. A series of outline 
 views of the convolutions of the brain in various known individuals 
 ■would be of great interest and advantage in reference to the question 
 of their function. 
 
 Thus anatomy leads to the conclusion that the operations of the 
 mind are associated with the convolutions. Perception, memory, 
 the power of abstraction, imagination, all possess, as instruments of 
 corporeal action, these folds of vesicular and fibrous matter. These 
 parts, in the language of Cuvier, are the sole receptacle in which the 
 various sensations may be as it were consummated, and become per- 
 ceptible to the animal. It is in these that all sensations take a distinct 
 form, and leave lasting traces of their impression ; they serve as a 
 seat to memory, a property by means of whibh the animal is furnished 
 with materials for his judgments.* 
 
 It is quite established as the result of all the experiments upon the 
 cerebral convolutions and the white matter of the centrum ovale, that 
 mechanical injury to them occasions no pain, nor disturbance of 
 motion. The endowments of the nerve-fibres which form the fibrous 
 substance of the cerebral convolutions appear to be quite distinct 
 from those of sensitive or motor nerves. They are internuncial 
 between parts which are beyond the immediate influence of the 
 ordinary physical agents, and which have no direct connections with 
 muscular organs. And if, under the influence of morbid irritation, 
 they da excite pain or convulsion, which is frequently the case in 
 disease of the cerebral meninges, this is effected through a change 
 produced in the corpora striata or optic thalami propagated to the 
 origins of motor and sensitive nerves. 
 
 The recorded experiments upon the removal of the hemispheres of 
 the brain do not lead to any satisfactory conclusion, as in all of them 
 the corpora striata and thalami have been removed at the same time. 
 But it may be here stated, that the effect of the removal of the hepoi- 
 spheres in Fiourens' experiments was to throw the animal into a state 
 of deep sleep, retaining its full muscular power, yet apparently in- 
 capable of a single mental nervous action, whether voluntary or 
 sensitive. 
 
 When the membranes of the brain are in a state of inflammation, 
 disturbance of the mental faculties is an invariable accompaniment 
 to an extent proportional to the degree of cerebral irritation, and 
 more especially so when the inflammation is seated in the pia mater 
 of the convolutions. This disturbance of mind is frequently indicated 
 by the manifestation of delirium of a more or less violent kind. It is 
 plain that in such a case the delirium arises from the altered state of 
 the circulation in the gray matter of the convolutions, the blood-ves- 
 sels of which are immediately derived from those of the pia mater, so 
 that the one cannot be affected without the other likewise suffering. 
 
 • Cuvier, Rapport sur le mfimoire de Fiourens sur le systdnle nerveux. 
 
FUNCTIONS OF THE CEREBRAL CONVOLUTIONS. 323 
 
 And it may be stated, as a fact no less interesting in a physiological 
 th^n important in a practical point of view, that in many,' if not in 
 most, instances of violent delirium, such, for example, as delirium 
 tremens, the vesicular matter of the cbnvolqtions is found after death 
 to be bloodless, as if its wonted supply of blood had been com- 
 pletely cut off from it. Thus it happens in the delirium after great 
 operations — in that of rheumatic fever — and perhaps also of gout— 
 and in that which occurs in the more advanced stages- of continued 
 fever. ,. 
 
 We learn from the most trustworthy reports of the dissections of 
 the brains of lunatics, that there is invariably .found more or less 
 disease of the vesicular surface, and of the pia mater and arachnoid 
 in connection with it, denoted by opacity or thickening of the latter, 
 with altered colour or consistence of the former. 
 
 From these premises it may be laid down as a just conclusion, that 
 the convolutions of the brain are the centre of intellectual action, or, 
 more strictly, that this centre consists in that vast sheet of vesicular 
 matter which crowns the convoluted surface of the hemispheres. 
 This surface is connected with the centres of volition and sensation 
 (corpora striata and optic thalami), and is capable at once of being 
 excited by, or of exciting them. Every idea of the mind is associated 
 with a corresponding change -in some part or parts of this vesicular 
 surface; and, as Joc^l- changes of nutrition in the expansions of the 
 nerves of pure sense may give rise to subjective sensations of vision 
 or hearing, so derangements of nutrition in the vesicular matter of 
 this surface may occasion analogous phenomena of thought, the rapid 
 development of ideas, which, being ill-regulated or not at all directed 
 by the will, assume the form of delirious raving. 
 
 The actions of the convoluted surface of the brain, and of the 
 fibres connected with it, are altogether of the mental kind. The 
 physical changes in these parts give rise to a corresponding mani- 
 festation of ideas; nor is it likely that any thought, however simple, 
 is unaccompanied by change in this centre. The ^hock of concus- 
 sion so far, checks the organic changes of the vesicular surface, and 
 perhaps also of the fibrous matter, as to interrupt, for a time those 
 conjoint actions of the mind and the brain which are necessary for 
 perfect consciousness. The condensation of the substance of the 
 hemispheres which is produced by an apoplectic clot, or by the effu- 
 sion of some other foreign matter, prevents a similar consent of action, 
 and thus gives rise to the phenomena of coma, in which all mental 
 nervous actions are destroyed or suspended. Those parts of the 
 cerebro-spinal centre on which the physical actions depend, being 
 more completely protected from compression, do not suffer in their 
 functions, and consequently actions of this kind remain unimpaired. 
 
 This view of the function of the convolutions of the brain has been 
 held by nearly all the great anatomists who have directed their 
 investigations to this wonderful organ. Our countryman, Willis, 
 distinctly advanced this opinion in the seventeenth century, and' 
 conjectured that the various, gyrations were intended for retaining the 
 animal spirits "for the various acts of imagination and memory" 
 
324 INNER\rATION. 
 
 ■within certain limits. The distinguished Gall, however, proposed 
 to assign certain convolutions as the seat of certain faculties of the 
 mind — moral feelings, or instinctive propensities — and upon this 
 basis raised the celebrated theory of Phrenology, -which has been 
 pursued since his time with all the zeal and interest naturally attach- 
 ing to a science which professes from external signs to detect the 
 natural tendencies of'the spirit within. 
 
 We do not propose to discuss the validity of this theory, which 
 seems to have been taken up with more apparent zeal for victory, 
 than love of truth. But- we shall remark, thatj in considering the 
 truth or falsehood of Phrenology, it is absolutely necessary to separate 
 the metaphysical question^as to the existence of certain faculties of 
 the mind — from what has been admitted as a physiological fact before 
 the foundation of the phrenological school, that the vesicular surface 
 of the brain is the prime physical agent in the working of the intel- 
 lect. A physiologist may hold the validity of this latter doctrine, 
 and yet think as we do, that many of the so-called faculties of the 
 phrenologists are but phases of other and larger powers of the ruind ; 
 and that the psychologist must determine what are, and what are not, 
 fundamental faculties of the mind, before the physiologist can venture 
 to assign to each its local habitation. The empirical method, by which 
 Gall first fixed upon certain parts of the brain as the seat of certain 
 faculties, is exposed to this serious fallacy, that a part on the surface 
 of the brain may appear largely developed, by reason of the large size 
 of some subjacent or neighbouring part. We have already shown 
 how this may be the case with reference to the cerebellum, and that 
 a thick neck and large occipital region may, and probably do, indi- 
 cate a large mesocephale more frequently than a large cerebellum. 
 At the same time we think that all observation, both in man and in 
 the lower animals, proves that the energy of any nervous centre 
 always bears a direct proportion to its bulk, whether absolute or 
 relative ; and that the phrenologists do not err in attaching great and 
 primary importance to the size of those parts with which they asso- 
 ciate certain faculties ; while the attention which recent writers of 
 that school have paid to the temperaments of the individuals under 
 examinatioh, is a proof of their admission that the quality of the 
 nervous matter constitutes a highly important element in the develop- 
 ment of nervous power.* 
 
 We have seen that the convoluted vesicular surface, and the fibres 
 of the centrum ovale, are the seat of those physical changes which 
 accompany, and are necessary to, intellectual action. A large num- 
 ber of these fibres is commissural, but the greatest proportion of them 
 serves to establish a communication between the centre of intellectual 
 action, and the centres of volition and sensation. Through the con- 
 nection with the former the intellect may prompt or excite the will ; 
 and the will, on the «ther hand, may control, direct, or apply the 
 powers of the intellect. The faculty of Attention, and, therefore, in 
 
 . • Cams has lately propounded a new Cranioscopy, founded upon the tripartite 
 rcompositionpf the cranium, which bids fair to rival the system of Gall. See a Lec- 
 ture iu Loud. Med. Gazette, vol. xzxir., translated by Dr, Freund. 
 
PHRENOLOGY. 325 
 
 a certain d^ree, the power of Memory, are dependent on the influ- 
 ence of the centre of volition upon the centre of intfellectual action. 
 Every one is sensible of a power which he possesses of fixing his 
 attention on any given subject, as distinct as that by which he can 
 contract any particular muscle. Again, the association of the intel- 
 lectual ceijtre with that of sensation is necessary to ensure the full 
 perception of sensitive impressions. The experiejice of each indi- 
 vidual can supply him with numberless instances in which, while 
 the mind was employed upon some other object of interest, an im- 
 pression was made upon some one of the organs of sense, and indis- 
 tinctly ye^<, but not fully perceived. When the mind has become 
 disengaged, the fact that an impression had been made is remembered, 
 without any ability to recollect its precise nature. And in many 
 lunatics the centre of intellectual action is so impaired as to destroy 
 or greatly reduce, the power of perception, whilst there is abundant 
 evidence to show that the' affections of the organs of sense still make 
 a sufficient impression on the centre of sensation. In, some cases, 
 however, this centre likewise, participates in the^general hebetude. 
 
 Perfect power of speech, that is, of expressing our thoughts in 
 suitable language,, depends upon the due relation between the centre 
 of volition and that of intellectual action. The latter centre may have 
 full power to frame the thought ; but, unless it can prompt the will 
 to a certain mode of sustained action, the organs of speech cannot be 
 brought into play. A loss of the power of speech is frequently a 
 precursor of more extensive derangement of sensation and motion. 
 In some cases, the intellect seems clear, but the patient is utterly 
 unable to express his- thoughts ; and in others there is more or less of 
 mental confusioq. The want' of consent between the centre of intel- 
 lectual action and of volition, is equally apparent in cases of this 
 description, from the inability of the patients to commit their thoughts 
 to writing. , 
 
 The hemispheres of the brain, as has been already stated, are 
 insensible to pain frorn mechanical division or irritation ; in wounds 
 of the cranium in the human subject, pieces of the brain which had 
 protruded have been removed without the knowledge of the patient. 
 Nevertheless, pain is felt in certain lesions of the brain, even when 
 seated in the substance of the hemispheres, or in the, optic thalami or 
 corpora striata. This results from the morbid state affecting other 
 parts with which nerves are connected, as the medulla oblongata; or 
 in which nerves are distributed, as the membranes. The nearer a 
 cerebral lesion is to the membranes or to the medulla oblongata, the 
 more likely is it to excite pain. Headaches, of whatever nature, must 
 be referred to irritation. either at their centres or at their periphery, of 
 those nerves which are distributed in the dura mater, or in the scalp. 
 The branches of the fifth pair, of the occipital nerve, and the auricu- 
 lar branch of the cervical plexus, are those most frequently affected. 
 
 Certain sensations are referred to the head which may occur from 
 a morbid state, or may be produced by changes of position in the 
 body. Such are, vertigo, a sense of fullness, or of a weight in the 
 head, a feeling of a tight cord round the head. These are, no dpubtj 
 
326 INNERVATION. 
 
 truly subjective, arising from alterations in the distribution or in the 
 quality of the blood sent to the brain. A sensation of a rushing of 
 blood to the head is often consequent upon excessive hemorrhage, or 
 accompanies a state of extreme debility from any cause. This is 
 owing in great part to the feeble tone of the arteries, resisting imper- 
 fectly the flow of blood to the head, and allowing it to impress the 
 nervous matter too much. It is well known, that, by turning round 
 quickly on one's own axis, the sense of vertigo may be produced, — a 
 confused fueling in the head, and an inability to maintain perfectly 
 the balance of the body, accompanied by an appearance as if external 
 objects were revolving. If the eyes be kept shut, theuneasy feeling 
 of the head will take place, but no true vertigo. To obtain this feel- 
 ing perfectly, the eyes must be open, and objects presented to them. 
 And Purkinje has shown that the direction in which external objects 
 appear to revolve is influenced by the position of the body and of the 
 bead while turning round, and by the position of it afterwards^ when 
 the experimenter has ceased to rflove round. If the experimenter 
 have kept his head in the vertical position while moving round, and 
 afterwards when standing still, the objects appear to revolve in the 
 horizontal direction. If the head be held with the occiput upwards 
 ■while turning round, and then erect when standing still, the objects 
 seem to rotate in a vertical plane, like a wheel placed vertically 
 revolving round its axis. {Muller^s Physiology, by Baly, vol. i., p. 
 848.) It is highly probable that these sensations, as well as those 
 which arise spontaneously, are due to some irregular distribution of 
 blood to various parts of the brain. A sense of giddiness frequently 
 precedes fainting, and is attributable to the temporary deficiency in 
 the stipply of blood to the head. If the horizontal position be imme- 
 diately adopted, or the body be laid with the head inclined down- 
 wards, the faint may be prevented; The sense of giddiness which 
 is experienced upon rising from the horizontal position after illness, 
 is doubtless of the same kind. Anemic patients experience this feel- 
 ing of giddiness even in the horizontal posture ; — and both it and the 
 headache and delirium, which accompany this state of bloodlessness, 
 maybe somewhat relieved by placing the patient on an inclined 
 plane with the head downwards. 
 
 The mind possesses a remarkable power of exciting and of exalting 
 painful sensations in various parts of the body. If the attention be 
 directed very strongly, and for some time, to any part, that part may 
 become the seat of pain, for which the most effective remedy is to 
 engage the thoughts as much as possible on some other object. In 
 many instances, where pain has been excited by a physical cause, 
 there can be no doubt it has been continued long after the cessation 
 of its exciting cause, by the attention of the patient having been 
 directed to it. It is probable, that in such cases the perceiving parts 
 of the brain (so to speak) become habituated to a certain condition of 
 the centre of sensation, produced by the original exciting cause of 
 the pain. 
 
 Nerves are implanted only in those parts of the encephalon which 
 are capable of physical nervous actions : the convolutions of the 
 
SLEEP.— COMA. 327 
 
 train, the corpus striatum, the optic thalamus, and the cerebellum, 
 are capable only of mental- nervous actions. In every change of 
 these latter, the mind is either the excitor or excited; the conditions 
 of the nerves involve them only through the influence of the centres 
 in which the nerves are implanted; and they affect the nerves only 
 through the same medium. Matteucci's experiments as to the effects 
 of electricity On the different parts of the brain, showed that, as long 
 as the current was coniined to those parts which are capable only of 
 mental actions, no apparent effect was produced. But when (he 
 poles of the battery had penetrated to the base of the brain so that 
 th« current might pass through the deeper seated parts, th'en the animal 
 cried out with pain, and strong convulsions were produced. 
 
 Those parts in which physical nervous actions take place, (although 
 capable of partaking in the mental actions,) require tbe excitation of 
 physical stimuli in order to develop their peculiar phenomena, and 
 thus have frequent remissions in the active performatice of their func- 
 tions in the frequent absence- of the ordinary stimuli. But the ever- 
 active mind keeps up a constant and proportionally rapid train of 
 changes in those parts which are more especially connected with 
 mental actions: hence these parts, requiring repose, fall at certain 
 periods into that peculiar and inscrutable state called slee'p.; in which, 
 whatever be the condition of the mind itself,' the brain either refuses, 
 or is slow to respond to its stimulation, or to convey impressions to 
 it. In deep sleep we are completely unconscious, and may remain 
 for a considerable time motionless. But, as the accustomed period 
 of repose approaches to its termination, the sleep becomes lighter, a 
 degree of consciousness returns, and mental changes take place, 
 which, whether incoherent or qonnected-, constitute what are fami- 
 liarly known as dreams. In lighter sleep, it .cannot be said that 
 there is complete want of consciousness; nor is the mind, although 
 comparatively quiescent, in complete repose. The readiness with 
 which, at times, some persons, during sleep, i?eply when addressed, 
 and resume the waking state, — the power which many unquestionably 
 have of limiting the duration of sleep to a predetermined period, as 
 contrasted with the deep unconsciousness and slowness to awake of 
 others, — strongly favour this idea. j 
 
 This state, with which the revolution of each diurnal period makes 
 us familiar as one of repose to the great centres of mental nervous 
 actions — "tired Nature's sweet restorer" — occurs, with modifications, 
 as the result of certain morbid processes, as the effect of certain phy- 
 sical agents, or even as the consequence of peculiar states of mind. 
 Thus, under the influence of pressure, from a clot of blood compress- 
 ing the braia, or from lymph or fluid at its base, a state vai'ying from 
 that of drowsiness up to the profoundest sleep, or coma, may be in- 
 duced. Whatever be the nature of the compressing substance, or 
 wherever situate, if the hemispheres experience general pressure, this 
 result will ensue. Again, a class of drugs, of the sedative or narcotic 
 kind, exerts a similar influence; and, if given in too large a dose, 
 will paralyze (he brain. We have daily evidence of this in the effects 
 of opium, which paralyzes at first the centres of mental actions, and 
 
328 INNERVATION. 
 
 ultimately those of physical actions. Lastly, particular states of the 
 system, induced, perhaps, by deranged assimilation, or by great pre- 
 vious disturbance of mind, dispose persons to fall into that state -which 
 is called somnambulism. The somnambulist is one who dreams, and 
 acts in his dream as if he were awake, and as if all the phenomena 
 presented to him were real. He appears to the bystanders in a deep 
 sleep, but acts with wonderful precision, 'walks with steady gait, and 
 avoids obstacles. Yet frequently accidents, injurious or even fatal, 
 occur; which show that on such occasions he is asleep, and has not 
 the full command of his senses. Persons in this state will answer 
 qaestions rationally and with readiness, and do not appear to be at all 
 disturbed by being questioned. The hypochondriacal or hysterical 
 diathesis disposes greatly to the development of somnambulism both 
 in male and female. 
 
 A state remarkably analogous to this of somnambulism may be 
 induced in persons of nervous temperament, which has been called 
 the Mesmeric steep, or trance. It requires for its production the 
 apparent influence of another individual, who watches the person 
 experimented on with an intent look, and makes certain movements 
 before him, which are called passes. All persons are not susceptible 
 of passing into this state, any more than they are of exhibiting the 
 phenomena of somnambulism. The same state of constitution which 
 disposes to the latter is favourable to the former. Remarkable stdtte- 
 ments have been made, and confirmed by the testimony of a large 
 number of observers, tending to imply that in these cases the faculties 
 become exalted in an extraordinary manner; and that the. individual 
 acquires powers of a hovel description, and even of a superhuman 
 kind. It behoves all sober-minded persons to be slow to accept 
 such statements as true, and, without impugning the veracity of the 
 reporters, to inquire whether they do not rest more upon a misinter- 
 pretation than upon a misrepresentation of facts. The polar force of 
 the mental nervous centres may, in this peculiar state, be so aflfected 
 as to favour the development of subjective phenomena, which it is 
 evident may assume particular forms under the influence of impres- 
 sions made from time to time upon the senses. The ravings of a 
 delirious or of a lunatic patient often take a particular direction under 
 the influence of a question or remark let fall by some bystander ; it 
 is not unlikely that persons, with a mental bias for the marvellous, 
 might discover in such patients quite as much evidence of superhu- 
 man power, as has been adduced by the Mesmerists. 
 
 We cannot avoid remarking how much it is to be lamented that 
 inquiries of so delicate a nature, affecting the very confines between 
 mind and matter, should have usually fallen into the hands of per- 
 sons ill qualified for such pursuits, either by mental constitution or 
 by previous experience in the study of subjects involving both phy- 
 sical and metaphysical knowledge. Little is to be expected in such 
 difficult researches from dilettanti ai t\\hev sex; much less from those 
 whose excessive zeal for novelty and notoriety must necessarily cast 
 suspicion on their statements. Nor can we hope that truth can be 
 elicited from experiments and observations which are made before 
 
FUNCTIONS OF THE COMMISSURES. ^ 329 
 
 the public gaze, -with more of the characters of a theatrical exhibition 
 than of a sober philosophical investigation. 
 
 Functions of the Commissures. — The commissures of the brain have 
 long -been regarded as provisions to ensure the harmonious co-opera- 
 tion of certain parts of the nervous centres, whether on the same or 
 on opposite sides. This opinion rests mainly:upon their anatomical 
 connections ; for but little that is satisfactory can be concluded from 
 either the comparative anatomy or pathological cbnditions of them. 
 It is evident that the principal commissures bear a direct ratio in 
 point of development to that of certain parts; and th?it, when those 
 parts are imperfect or absent, the commissures are deficient or wholly 
 wanting. Thus the corpus callosum and the hemispheres are deve- 
 loped together; the fornix and the hippocampi^ the pons Varolii and 
 the cerebellar hemispheres. 
 
 The anatomy of the corpus callosum favours the hypothesis that 
 it is the bond of union to the convoluted surface of.the hemispheres, 
 and that it is the medium by which the double organic change is 
 made to correspond with the working of a single mind. There is 
 nothing in the recorded observations of morbid dhange or congenital 
 defect of this- part to militate against this idea ; but it must be re- 
 marked that all these cases are accompanied with lesion or defect of 
 other parts, which weaken the inferences to be drawn respecting the 
 corpus callosum. Direct experiments upon this commissure yield 
 only negative resujts. Longet and others found that irritation of it 
 did not cause convulsions: and Longet states, that injury to the 
 Corpus callosum in young rabbits and dogs did not appear to disturb 
 voluntary movements ; and that, whenhe incised this body in its 
 whole length in rabbits standing, they have continued to maintain 
 that position ; or, when urged on, ran ; and that no convulsive 
 movement whatever, nor any sign of pain was manifested. Such 
 statements are certainly favourable to the supposition that these fibres 
 are destined to connect centres whose appropriate stimulus is mental. 
 
 The fibres' of the fornix manifest the same insensibility to mechani- 
 cal irritants ; and their obvious anatomical connection with particular 
 convolutions warrants but one conclusion, that they associate the 
 actions of those parts. Lallemand relates a case in which the symp- 
 toms were altogether limited to mental disturbance, without any 
 affection of the sensitive or motor powers, and the fornix and corpus 
 callosum were found in a state of complete softening without dis- 
 coloration. 
 
 The fibres of the pons Varolii bring the cerebellar hemispheres 
 into connection with each other, and, with the vesicular matter of the 
 mesocephale. Direct experiments on these fibres can yield no satis- 
 factory Jesuit, because they are so intimately associated with the 
 deeper seated parts of the mesocephale, and with the nerves of the 
 fifth paii" and others, that it is impossible to irritate them in the living 
 animal "without likewise irritating these other parts. And it is suffi- 
 ciently evident that these fibres have no necessary connection with 
 sensation and volition, from their non-existence in birds; nor even 
 with the cerebellum when that organ is single. It will be borne in 
 
330 INNERVATION. 
 
 mind, that at a previous page we have referred to the connection of 
 these fibres with the mesocephale as explaining the crossed influence 
 of lesion of one hemisphere 'of the cerebellunj. 
 
 , We conclude this chapter with the following inferences, which, 
 we think, the present state of knowledge justifies: 
 
 1. The spinal cord contains within itself all the physical condi- 
 tions necessary for the raental and physical action's of the trunk and 
 exlrenaiti^s, so long as its connection with the encephalon is perfect 
 through the anterior pyramids. 
 
 2. There is no sufficient evidence to prove the exisfepce of a class 
 of sensori- volitional fibres distinct from those which are the instru- 
 ments of physical actions. 
 
 3. Each segment of the cerebro-spinal centre, whether in the 
 cranium or in the spinal canal, gives origin to its own proper nerves, 
 and has no connection with the neighbouring segments, otherwise 
 than by Commissural fibres or vesicular matter. 
 
 4. The antero-later^il columns of the cord, with the anterior and 
 posterior horns of the gray matter, are the effective centres of motion 
 and sensatiori of the trunk and extremities. The positerior columns 
 are longitudinal commissures by which the influence of the cerebellum 
 is brought to bear on the various segments of the cord. 
 
 5. When the pyramids are in a state of integrity, the corpus 
 striatum, certain accumulations of gray matter connected with the 
 nerves of the medulla oblongata, the locus niger- and the anterior 
 horns of the spinal gray majter are the centres of voluntary motion to 
 the whole body; while the optic thalami, olivary columns, and pos- 
 terior horns of gray matter are the centres of sensation. 
 
 6. The medulla oblongata, when connected to the corpora striata 
 by the pyramidal fibres, is a centre of volutitary actions to those parts 
 whose nerves are derived from it; and, in addition, it is the principal 
 centre of the actions of respiration and deglutition. 
 
 7. The corpora quad):igemina are primary centres of visual im- 
 pressions, and, with a large portion of the gray matter in the meso- 
 cephale, are centres of emotional actions. 
 
 8. The cerebellum is the eo-ordirmtor of voluntary and locomotive 
 actions. 
 
 9. The convolutions of the brain are the centres of intellectual 
 actions, and are intimately associated with the mental phenomena of 
 attention, association, and memory. 
 
 On the subjects discussed in this chapter we refer to the more recent treatises on 
 Physioloey, by Miilier, Wagner, and Carpenter;— to Dr. Marshall Hall's writings on 
 the Nervous System; the most imporiant of which wril be found in an octavo vol- 
 ume "On the Diseases and Derangements of the Nervous System," 1841 ; and in a 
 quarto volume "On the Nervous System," 184.3; — to Henle's General Anatomy; — 
 Whytt on vital motions; — Prochaska, Annol. Academica;; — Le Gallois, Olluvres; — 
 Flourens sur le syt^ieme nerveux; — DesmoulinseiMagendie surle sysiSme nerveux; 
 — Longet, Anat. el Physipl. du systeme nerveux; — Volkmann, in Miiller's Archiv. ; — 
 Van Deen, sur la Physiol, de la Mofille Epiijiere, and the works referred to at the 
 conclusion of the last chapter. 
 
 Appendix in the Eleventh Chapter. — Whilst the preceding pages were passing 
 through the press, we were favoured, through the kindness of Prof. Malteucci of Pisa, 
 
MATTEUCCI'S ELECTRO-PHYSIOLOGICAL RESEARCHES. 331 
 
 ■with several opportunities of witnessing his highly important electro-physiological 
 experiments. As these experiments tend very much to confirm and substantiate the 
 views expressed in Chap. IX., we subjoin here) a succinct account of them 
 
 The facts which- M. Matteucci's researches have developed are the following: — 1. 
 That muscle is a better conductor of electricity than nerve, and that nerve conducts 
 betterthan brain. 2. That in the muscles of living animals, as well as of those re- 
 cently killed, an electric current exists, which is directed from the iflterior of each 
 inuscle to its surface. 3. That in frogs, a current exists peculiar to the Batrachian 
 reptiles, which proceeds from the feet to the head, and is distinct from the muscular 
 current. 4. In continuation of Marianini's and Noblli's researches, Matteucci illus- 
 trates the effects of the inverse and direct currents in nerves of different function, and 
 shows very strikingly the difference in the influence of the electrical stimulus upoa 
 nerves, from that of other stimuli upon these organs. 
 
 For these researches Matteucci employed the galvanometer of Rumkorff (Paris), 
 which is the same as thatof Nobili with the addition of a small apparatus, by means 
 of which the ne,edles may be rendered more or less astatic, and thus the sensibility 
 of the galvanometer may bef more or less increased. But he also takes the' pre- 
 caution, to guard against the deyelopirient of currents^, by unequal chemical action 
 upon the pole? of the galvanometer, to have them made of plates of platina, which is 
 not acted upon by water or saline solutions. He takes two plates of platina, about a 
 quai-ter of an inch in breadth, and fixes each in a handle of wood. The plates are 
 then soldered to the wires of, the galvanometer, and both, the handles and the plates 
 are covered with a layer of sealing wax-varnish, leaving only a space of about a 
 quarter of an inch uncovered at the extremity of each jilatinum plate. 
 
 The frog's leg, prepared in a certain way, is most susceptible of electric influence, 
 and therefore may be used as a galvanometer of extreme delicacy. The skin is strip- 
 ped off one lower extremity of a lively frog, and the wholelengih of the sciatic nerve is 
 dissected out from among the muscles of the -posterior part of the thigh ; after which, 
 the thigh is cut across just above the knee, the nerve remiaining attached to the knee 
 and leg. The leg is now placed in a glass tube, in such a position that the' nerve 
 hangs loosely from the end of the tube. To use this galvanoscope, the operator holds 
 the glass tube at the opposite extremity to that in which the leg is placed, and causes 
 the nerve, which hangs loosely from the tube, to touch at two po.ints the electromotor 
 element under examination. If the nerve be traversed by a current, the leg instantly 
 contracts. This apparatus, called by Matteucci grenouit/e galvfmoscopigue, is the 
 most dglicate we possess, if it be renewed from time to lime. And it is capable, not 
 only of indicating the existence of an electric current, hut also of showing", with a 
 great degree of probability, the direction of that current. When (he frog has become 
 a little weakened, it almost constantly happens that the contraction takes place on 
 closing' t]ie circuit, if the current pass from the nerve to the leg; but if it pass from 
 the leg to the nerve, contraction will take place on opening the circuit,' 
 
 1. Matteucci's experimetits upon the relative conducting power of animal sub- 
 stances, were founded upon a law of derived currents. When a liquid, or any other 
 body, is traversed by an electric current, and the plates of the galvanometer are 
 pliinged into it, there are immediate indications of a (/eraerfcurrent,|So directed in the 
 galvanometer, that the. point at which it enters the coil of the galvanometer, corre- 
 sponds to the positive pole of the current which traverses the liquid. The derived 
 current is always greater, as the plates of the galvanometer, plunged in the liquid, 
 are more distant from each other. If a current be made to traverse different sub- 
 stances, which correspond as nearly as possible as regards shape, bulk, etc., the de- 
 rived current from each will be exactly in the inverse ratio of the conducting power 
 of the substance traversed. . 
 
 Pieces of nerve, brain, and muscle, froin a rabbit just killed, were selected for the 
 comparative experiments; these were cut so as to correspond as nearly as possible 
 in pointof size and shape, and disposed as achain oii aii insulating plane. Platinuih 
 wires, fixed by sealing-wax to two pieces of cork, which were held apart at a certain 
 distance by a rod of glass which transfixed each of them, were soldered to the wires 
 of the galvanometer, the platinum wires having been previously varnished to within 
 a very short distance of their extremities. A current from twelve cells of a constant 
 battery, was now passed through the chain of animal substances. The platinum 
 wires, held always at the same distance from each other, were successively brought 
 
 * Those who propose to employ the galvanometer in physiological experiments, should 
 carefully observe the precautions assigned by Matteucci, in the third chapter of his-book, 
 to guard against erroneous inferences. 
 
332 INNERVATION. 
 
 into contact with brain, nerve and muscle, and the deviation of the needle resulting 
 fi'om the derived current in each case was carefully noted. The derived current 
 from nervous matter was always greater than that from ihuscle; that from braiii 
 greater than that from nerve, denoting a less conducting power in nervous matter 
 than in muscle — in brain than in nerve. By increasing the distance between the 
 platinum wires, a derived current may be obtained from muscle equal to that ob- 
 tained from brain ; and Matteucci, frpm this latter experiment, infers that the^on- 
 ducting po*er Of muscle may be taken as four times greater than that of brain or 
 nerve. 
 
 Another interesting experiment confirmed the results obtained froni those just de- 
 tailed. The current was niade to traverse the whole trunk of i rabbit just killed and 
 flayed, and the platinum wires.held at a constant distance, were applied succesjsively 
 to different parts, muscles, nerves, etc.; the current was found to traverse all parts, 
 with s^chdifference as was due to the different power of conduction of the different 
 substances ; that is, so as to yield a derived current of less iiitensity from muscle than 
 from nerve, or from nerve than from brain. 
 
 2. To demonstrate the existence of an electric current in the muscles of animals 
 recently killed or living, the following experiments have been adopted by Matteucci. 
 
 If a jjeep wound be made in a muscle of any living animal, and ihf nerve of the 
 galvanoscopic frog be introduced into it, so that the nerve shall touch the cut surface 
 at one point, and the outer surface of the muscle at the other, contractions iastanlly 
 take place on completing the circuit. It is evident that this effect is due to an electric 
 current developed by the muscle, because it is necessary that'the nerve should touch 
 the muscle at two points; and because, if the nerve be brought into similar contact 
 with two points of any other body, no such effect will fbllow. To guard against the 
 fallacy that might arise from contact with the blood, Matteucci shows, that if a nerve 
 be brought into contact with a layer of blood at two different points, no evidence of 
 an electric current will appear. In this, and all experiments with the galvanoscopic 
 frog, it is to be remembered that the frog's leg must be held in the glass tube to in- 
 sure perfect insulation. The experiment is always followed by the same resufes, 
 whatever be the muscle or the animal tquched, or even if muscles separated from 
 the animal be operated on. The indications of the electric current remain longest in 
 those animals in -which the muscular contractility lasts longest; in cold-blooded 
 animals, such as fish and reptiles, Matteucci has seen the phenomena last for many 
 hours. The current is sufficient to excite the nerve of a warm-blooded animal. 
 The thighs of a rabbit having been removed, a long portion of the crural nerve was 
 dissected out, and the muscles exposed. With a glass tube the nerve was raised and 
 brought to touch the muscles at two points, when the whole limb was thrown into 
 contraction. 
 
 So far, distinct evidence was afforded .by the animal galvanometer, (so to speak,) 
 of the existence of a niuscular current. 'When the frog's leg becomes a little *eak, 
 it indicates the direction of the current to be from the interior to the surface of the 
 muscle. 
 
 In order to demonstrate the influence of this current on the galvanometer, a parti- 
 cular arrangement is necessary.. 
 
 Several small cup-like cavities are scooped out in a piece of wood, twelve inches 
 square, and an inch and a half thick. The wood and its little cavities are coaled 
 over with a layer of varnish, or small capsules sunk into the wogd may be employed'. 
 Five or six frogS are prepared, by flaying the posterior extremities, and the legs are 
 separated by disarticulating them at the knee; which must be dohe with care, iri 
 order not to wound the mass of crural muscles. Next, each thigh is divided at its 
 middle, and thus a certain number of conical masses (the lower halves of the thighs) 
 are obtained. These must be arranged on the board in a chain. One half-thigh is 
 placed at the edge of one of the cavities, with its apex to the cavity, and the cut, sur- 
 face outwards; and the chain is completed by arranging the others in a semicircle, 
 so that the apex of one freely touches the cut surface of the other, and the piece 
 which forms ihe opposite extreme of the series ought to touch the edge of another of 
 the cavities by its cut surface. Thus, a pile is formed, of which one of the extremi- 
 ties is the interior of the muscle, and the other its external surface. The board, 
 with Ihe muscular pile arranged upon it in this way, is now brought to the galvano- 
 meter, the platinum poles of which, if it be a very sensible one, have been some 
 time placed in distilled water; or, if not very sensible, in a saline solution. The 
 next step of the experiment is wiih a pipette, to pour into the cavities with which the 
 extremea of the pile are connected, either water or some of the saline solution, ac- 
 cording as the plates of the galvanometer have been immersed in either of those 
 fluids. 
 
MATTEUCCI'S ELECTRO-PHYSIOLOGICAL RESEARCHES. 333 
 
 The platinum poles of the galvanometer are now withdrawn from the fluid, in 
 which they had been immersed, and introduced into the fluid of either of the cavities;, 
 if no deviation of the needle follow this, they are at the same time plunged into the 
 two extreme cavities of the pile, so as to close the circuit. A deviation of the needle 
 takes place immediately, which varies in amount according to (he number of seg- 
 ments which constitute the pile. Matleucci has obtained a deviation of 15°, ^°t30°, 
 40°, 60°, etc., accordiiig to the number of half-thighs, supposing the frogs employed 
 to be equally lively i he obtained 3° or 4° ;with two elements, 6° or 8° with four ele' 
 mehts, 10° or 13° with six, and so on. These numbers are obtained, using distilled 
 water in the cavities; but the deviation may be increased considerably if a few drops 
 of sulphuric acid be added to ir, .so that a pile of eight half-thighs, which gave a de- 
 viation of 15° with distilled water, will cause 50° with the acid, liquid. "When the 
 fluid was slightly saline or alkaline, the same number Of elements caused a deviation 
 of 35°. In all the trials the current had the same direciion — that is, from the internal 
 part of the muscle to its surface. 
 
 The muscular current may be demonstrated with the muscles of otlier cold-blooded 
 and of warm-biqoded animals. In all cases it is necessary so to arraiige the elements 
 of the pile, that the inner surface of oiie segment shall be in contact with^he outer 
 surface oflhe next, and that the inner surface of a piece of muscle .shall form one 
 pole, and the outer surface of another piece the opposite pole. a 
 
 The duration of the muscular current corresponds with that of contractility. In 
 cold-blooded animals, therefore, it is greatest. In mammalia and birds it is very 
 brief. Temperature has a considerable influence upon the intensity of the current. 
 If frogs ai;e placed for some time in a very cold medium, piles made from their mus- 
 cles yield no evidence of electricity; but, if the frogs are placed in a warm mediura 
 for a short time after they have been taken from a Cold one, the current of electricity 
 obtained from their muscles will be stronger than that from a similar pile which had 
 not been subjected to any change of temperature. 
 
 Any circumstances which enfeeble frogs, and derange their general nutrition, will 
 diminish the power of the muscles lo generate eleclricity,;as they also impair the 
 contractile force. Thus, Malteucci found the great heat of summer Jo impair mate- 
 rially-lhe development of electricity. We have found the same result in frogs which, 
 having been kept crowded together in a small compass during the month of Decem- 
 ber, became ill-nourished, with soft, flabby muscles, full o,f ^ moisture. The redder 
 and more consistent the, muscles are, as Matteucci remarks, the more distinct will be 
 the signs of electricity. 
 
 The muscular current appears to be quite independent of the nervous system. Th e 
 segments of which the piles are formed, are obviously beyond the influence of the 
 nervous centres ; and Matteucci has taken great pains to remove from such segments 
 all'the larger nervous trunks and filaments <listributed among the muscles without 
 affecting the electripal current. And in frogs, in which the lower part, of the: spinal 
 cord had been destroyed by burning, there wasflo evidence of impairinent of the 
 electric current in the muscles of the lower extremities. 
 
 Matteucci found that narcotic poisons, in moderate doses, had little or no influence 
 upon the muscular current. On one occasion, he found it slightly increased in a frog 
 to which a very small dose of opium had been given. In very strong doses, such a.s 
 to kill the animal, the muscular current is destroyed. The influence of the narcotic 
 gases upon the current is of no importance, with the. exception of sulphuretted jjy- 
 drogen, which has the eflect of materially weakening its intensity. 
 
 On one occasion, we endeavored to obtain a current from a pile composed of 
 pieces of human muscle from a leg that had just been amputated; but the muscles 
 were in so atrophied a condition, that the experiment failed with the galvanoscopio 
 frog, as well as with the galvanometer. We have since learned from Professor Mat- 
 teucci, that he has obtained evidence of the current in human muscle under similar 
 circumstances. 
 
 It is plain, from, the statements above given, that the essential condition for the full 
 development of the muscular current, is a healthy and vigorous slate of the muscles 
 themselves, and that the nervous system contributes to the electrical phenomena only 
 so far as it contributes to the healthy nutrition of the muscles by promoting their 
 natural actions. The muscular current is one of the phenomena which attend the 
 passive contraction of muscles;, it disappears from dead muscle, and from living 
 muscles which have so suffered in their nutrition as to lose their characteristic pro- 
 perty. All external influences which materially affect the nutrition, and therefore 
 the passive contraction of muscles, exert a corresponding effect upon the mviscular 
 current. The duration of the current after systemic death, continues in the different 
 animals just so long as the phenomena of contractility are present. 
 
334 INNERVATION. 
 
 3. In the latter part of the last century, Galvani announced his celebrated experi- 
 ment, of causing contraction of the frog's leg by bringing its muscles in contact with 
 the lumbar nerves. The following are the steps of this experiment: The integuments 
 are stripped off the lower extremities, which are separated from the tntnk at the 
 middle of the back; a small portidSii of the lumbar region of thfe spine, from which 
 the lumbar nerves emerge, is left with these nerves in connection with the lower 
 limbs, the pelvis having been cut away. If, now, the limbs be suspended by the seg- 
 ment of the spine, and one leg be carefully bent up, so as to bring the foot into con- 
 tact with the lumbar nerve, the whole limb is convulsed at the moment of contact. 
 The foot may be made to touch the muscles at various parts of the limb without any 
 such effect. The contraction is general, and evidently of the same nature as that 
 ■which the passage of an electric current through the lumbar nerves would produce. 
 When the experiment is carefully tried, it is impossible that the nerve can experience 
 any mechanical dragging, such as would produce an effect like that described. Gal- 
 vani pointed out, that, in order to succeed perfectly in the experiment, it is necessary 
 to wait until the frog has recovered from the tetanic state which is likely to ensue 
 upon the necessary mode of preparation. He also stated, that the experiment is 
 more likely to be successful if the frog have been previously moistened by a solution 
 of salt; and that the contraction of the muscles may be produced if the nerve and 
 foot are connected by a piece of muscle, and not directly. The accuracy of Gal- 
 vani's observations has been, fully established by Humboldt, ?alli, and many mod- 
 ern experimenters. We have frequently repeated the experiment with the same re- 
 sult. 
 
 Fifty years after Galvani, Npbili* took up the same line of inquiry. Having pre- 
 pared the legs of a frog according to Galvani's method as above described, he plunged 
 the lumbar nerves into one capsule and the feet into another, thecapsules being filled 
 with water. When the poles of a galvanometer were introduced into the fluid of the 
 capsules, a deviation of the needle followed to the extent of 5°, 10°, or 15° or more. 
 The deviation could be increased by making a chain of frogs' legs prepared in the 
 saime way. The legs were placed on an insulating plane, so that the nerves of tine 
 touched the feet of the next, and so on. It is necessary that the extremities of this 
 pile should be plunged into capsules filled with water. Or, a pile may be made with 
 a series of capsules containing water, connected together by frogs' legs; the nerves 
 being placed in one, and the feet in the next. With such piles, a deviation of the 
 needle to the extent of 60° may be obtained ; or to a much greater extent, if, instead 
 of distilled water, a weak solution of salt be employed to fill the capsules; or still 
 more, if the fluid of the capsules be slightly acid. 
 
 In aH these experiments the direction of the electric curi^ent was found to be con- 
 stant, from the feet to the head. At the same time that the needle was made to deviate, 
 the frogs' legs, whatever be thenumb'Jr constituting the pile, are thrown into con- 
 traction. It is not necessary for the production of the phenomena that the several 
 legs should touch one ar^other; it will sufl5ce if they be connected by a conducting 
 material, such as a skein of cotton moistened, wire, wet paper, or even water. 
 
 Nobili found that these signs of an electric current continued for many hours after 
 the preparation of the animal. He distinguished the current by the title of fe courant 
 de la grenouille, ou courant propre I and he attributed it to a thermo-electric current 
 caused by the unequal cooling of the nerve and mijscle produced by evaporation. 
 
 {t is evident that the experiment of Nobili is essentially the same as the original 
 one of Galvani. In the latter the electric current w^s brought to act upon the nerves 
 of the limb; in the former, upon the galvanometer. 
 
 The galvanoscopic frog maybe used as a test of the electric current when Nobili's 
 arrangement is preserved. If the extremes of the pile be connected by the nerve of 
 the galvanoscopic limb, the instant the circuit is completed, its muscles will contract; 
 and, as in other experiments with the galvanoscopic frog, we may determine the di- 
 rection of the current when the frog becomes a little weakened. 
 
 Matteucoi gives the name " contraction propre" to the contraction of the muscles 
 ■which takes place in the frogs' legs, whether used singly or as a pile, at the same 
 time that the deviation of the needle occurs. In order to obtain this phenomenon, 
 the lumbar nerves must not be plunged completely in the water; otherwise the pro- 
 per current circulates without passing through the nerves, and consequently the con- 
 tractions do not take place, or are extremely feeble. These contractions continue, 
 generally, only for ten or fifteen minutes, but rarely for half an hour after preparation. 
 
 Nobili has stated, that in arranging the frogs, .so that the nerves of one touched 
 those of the other, or the muscles came in contact with muscles, no contractions 
 
 * Bibliothftque Universelle, 1827. 
 
MATTEUCCI'S ELECTRO-PHYSIOLOGICAL RESEARCHES. 335 
 
 ensued, because, as he explained, the eleclromotor elements were opposed. In Mat- 
 teueci's hands, however, such a result was not obtained. If care be taken not to 
 oppose to each other the nerves or muscles of symmetrical parts, contraction will 
 always ensue. 
 
 The following is Matteucci's mode of showing this remarkable experiment. The 
 limbs, of a frog are prepared in the ordinary W'ay ; but, in addition, the heads of the 
 thigh-bones and the ilium are completely removed, so as to leave the legs connected 
 to each other only by the nerves, through the portion of the cord which is contained 
 in the segment of the spine which remains. The parts are placed on an insulating 
 plane. If the muscles of one leg are made to touch the other ikigh, contractions' 
 ensue ; buj not so if the leg of one side touch the kg of Ih'e other. Or the same 
 effect may be produced by'bringing the different parts of the limbs into connection 
 by moist pap^r or cotton; or, if the galvanometer be employed.signs of a current 
 ai-e afforded, by touching a thigh with one pole, and the opposite leg with the oiher. 
 
 In these experiments, when the frog is lively, contractions are produced, in touching 
 the muscles of the thigh with those of the leg, as well on opening, as on closing the 
 cirtuit. But when it has become weak* cfcntraciigns take place-in oae limb on clos- 
 ing the.circuit, and in the other on opening it. 
 
 Mafleucci explains the failure in producing contractions by touching correspond- 
 ing parts, on the supposition that, under such circumstances, the currents of the two 
 linabs circulate with equal -intensity, and in a contrary direction. This he proves by 
 the following experiment: If the frogs' legs, prepared as aljove described, are severed 
 from each other, and the nerve of one leg and the foot of the other are placed in one 
 capsule filled with water, while another-capsule receives the other nerve and foot; the 
 moment the circuit is completed, strong c6ntra<^tions in both limbs are produced. 
 But to the galvanometer no sign of an electric current is afforded when its poles are 
 plunged into the capsules. "In this case,?' says Matteuoci, "the currents of the two 
 limbs circulate together, passing equally through the lim"bs; and if even the parts of 
 the current weie to take the course of the galvanometer, it is easy to see thai they 
 would circulate in it in opposite directions, and therefore would.produce no deviation. 
 If, on the contrary, the disposition of the two limbs.be such that the nerves are placed 
 in one vessel, and the feet in the other, it is easy to see that the two portlonjS of the 
 current which do not circulate through the animal arc, enter the extremities of the 
 galvanometer, and circulate in it in the same direction. It is the sum of these two 
 portions which constitutes the proper current of the frog, which sum is measured by 
 the galvanotheier. 
 
 If several frogs' legs be arranged with opposed nerves and feet in the two capsules, 
 the effect upon the galvanometer is not increased. 
 
 Comparative experiments as to the difference of the currents in piles formed of 
 both the lower esstremities of frogs, as akeaidy described, ^nd in piles formed of an 
 equal number of single extremities, showed no greater effect upon the galvanometer 
 in the one case thaii the other. > 
 
 From these and numerous other experiments, varied with great ingenuity and skill, 
 Matteucci draws these conclusions: — 1, that the complete electromotor element in 
 the current of the frog is formed by one of its limbs — that is, of one leg, the thigh, its 
 spinal nerve, and a piece of its spine; — 2, that the current of one limb circulates 
 by the other every time that, leaving the frog intact, a communication is established, 
 in any way, between the two legs of the same frog; — 3, that in the experiment Jsy 
 which we detect the current of the frog by the galvanometer, thpreis never in the 
 wire of the instrument any other current save that which results from the sum of the 
 two portions of the currents of the two limbs which are not discharged from limb to 
 limb. , 
 
 It is important to notice, that there is no necessary connection between nerves and 
 muscles in the production of the proper current of the frog. Matteucci shows by 
 several ingenious experiments, that, although in Galyani's and Nobili's observations, 
 the nerve and muscle were brought in contact, or were made to form conspicuous 
 parts of the arrangerJient employed in the development of the phenomena, the"signs 
 of the electric current are just as distinct when the circuit is completed by the con- 
 tact of other pai'ts; or if the continuity be m?iintained by muscles, the main nervous 
 trunks having been removed. Thus, if a frog be flayed, and the bones and muscles 
 of the pelvis be cut away, so as to leave the lower extremities attached to the thorax 
 by the lumbar nerves, contractions will be produced by bending up the leg so as to 
 bring it in contact with the eyes, the muscles of the head, or the back. And if this- 
 frog be placed with its head in one capsule and its legs in another, the current may 
 be detected by the galvanometer in the ordinary way. Or, if the spinal nerves and 
 the piece of the spinal cord be removed from the lower limbs prepared in the ordinary 
 
336 INNERVATION. 
 
 ■way, the signs of the current may be obtained by the usual methods. Piles made of 
 legs prepared in this way develop a current equally intense with that produced 
 from piles with an equal number of elements composed of limbs with the nerves re- 
 maining. It thus appears that the electromotor element of the current is reduced to 
 the muscles of the leg and thigh in organic union. 
 
 So far, indeed, is the nerve from contributing to the production of the electrical 
 phenomena, that Matteucei found that a more feeble current was developed in piles 
 formed of the. legs of frog's in which a very long portion of the nerve forpied an ele- 
 ment. He prepared the legs, leaving attached to them the lumbar and crural parts 
 of the nerve, and formed the pile by placing the nerve on the adjacent leg, so that the 
 communication between the segments was maintained only by the nerves. And it 
 may be shown further, that the nerve in these experiments' acts only as a bad con- 
 ductor of the electricity developed by the muscles ; for, if the nerves be cut awa}', and 
 the segments of the limbs connected by pieces of moist cotton instead, the phenomena 
 of the pile continue unchanged. 
 
 Nothing analogous to the proper current has been found in any other reptiles but 
 the Batrachian — nor in any other class of animals. It is not improbable, therefore, 
 that the proper current of the frog may he due to some undiscovered peculiarity of 
 structure in that animal. 
 
 How can we explain' these remarkable electrical phenomena in the muscular cur- 
 rent directed from the interior to the exterior of all muscles in all animals ; and t,he 
 proper current of the frog, directed from the feet to the. head, and peculiar to the Ba- 
 trachian reptiles ? - 
 
 It is not difBcult to discover an pxplanation of the rhuscular current. The essen- 
 tial conditions necessary to develop the signs 0:f this current are simply, that, by 
 means of a conducting material, the interior of the musculat mass should be brought 
 into communication with the. exterior of the muscle, which is mflre or less tendinous, 
 and covered with areolar tissue, and therefore different from the interior in structure 
 and function. And as the signs of this current are apparent only whilst the muscle 
 isliving — that is, while it continues to display its contractile power, we may infer 
 that the same organic conditions which are necessary to the development of contrac- 
 tion, are requisite for the development of electricity. Now all that is necessary for 
 the development of the contractility of mpscle is (as has been shown in Chap, vii.) 
 a healthy nutrition, a due supply of arterial blood, and sufficient exercise of the organ. 
 And it would be impossible, as Malteucci remarks, not to admit that the chemical 
 action which must be going on throughout muscle, in the constant supply and waste 
 of which it is the seat, can be unattended with the development'of electricity. 
 
 In short, the organic actions of muscle, by which ihe electrical current is developed, 
 may be compared to the inorganic phenomena attending its produclion from the de- 
 composition of metals. When a plate of metal,* immersed in an acidulated fluid, is 
 oxidized by the oxygen of the water, and then dissolved in Ihe acid, we admit that 
 an enormous quantity of electricity is developed during this action ; we add, like- 
 wise, that, just as the two electrical states are disengaged, a synthesis lakes place, 
 and the effects of the previous decomposition are neutralized. It is only by means 
 of certain arrangements, that we can obtain the free electricity which is developed 
 during chemical action. We unite to the metallic plate, another which is not attacked 
 by the water, and plunge tMs second plate also in the water. The circuit is thus 
 established, and the electric current circulates in the liquid from the metal acted on 
 to the other, and from this latter back again to the first through the metallic arc of 
 union. 
 
 The metal acted upon in the artifical arrangement is represented, in the phenome- 
 non of the muscular current, by the muscular fibre; the acidulajed fluid is the arte- 
 rial blood. The surface of the muscle, or any other conducting body not muscular 
 fibre, biJt which is in contact with the muscle, represents the second plate of metal, 
 which does not suffer chemical action, and which serves only to form the circuit. The 
 direction of the muscular current is precisely such as it should be,. supposing the 
 current to be, as we have represented it, due to a chemical action taking place in the 
 interior of the muscle. 
 
 The nervous system may act in two ways in connection with this phenomenon; 1, 
 as an imperfect conductor, which makes part of a circuit, but is not the source of 
 electricity ; it represents the electrical state of the muscular mass, interior or sur- 
 face, with which it is in connection : and S, it acts in the conservation of the cause 
 which disengages electricity, namely, nutrition. It is fully proved, that the integrity 
 of the nervous system, and the nutrition of the muscles, are closely leagued together ; 
 
 * Matteucei, loc. cit., p. 124. 
 
MATTE0CCPS ELECTRO-PHYSIOLOGICAL RESEARCHES. 337 
 
 but as it cannot be admitted that the chemical action which takes place in nutrition is 
 immediately arrested or suspended by the cutting off nervous influence, so we must 
 allow that the muscular current may continue after the nerve has ceased to exert any 
 control over the muscle. 
 
 The proper current of the frog dots not admit of being explained upon these prin- 
 ciples. It has been supposed, as already stated, that this current is a thermo-electric 
 one, due to the unequal Cooling of nerve and muscle, depending on the difference of 
 evaporation in these two parts of the animal. But it has been shown that this cur- 
 rent persists even after the removal of the nerve ; and, moreover, as Malleucci re- 
 marks, a current which is sensible to a galvanometer with a long coil, which traverses 
 thick layers of liquid, which may be obtained by bringing muscle in contact with, 
 muscle, and which may be produced by holding animal parts in water, cannot, cer- 
 tainly, be of thermo-electric origin. It has also been supposed that this current is 
 due to an electro-chemical action ; that the leg of the frog is charged with alkali or 
 salts, whilst the thigh or the lumbar nerve contains acid. But chemical analysis 
 of these parts affords no countenance whatever to this hypothesis. There are 
 remarkable points of analogy between this current and the muscular current. Mat- 
 teucct's experiments have |Shown that the former has some marked connection with 
 muscles, and with those of the leg more especially; and he has found that the same 
 circumstances which increase or diminish the muscular current, exert a similar in- 
 fluence upon the proper current. But they differ remarkably in point of duration; 
 as the latter continues long after all traces of a muscular current has ceased to be 
 discoverable. It is highly probable, as before stated, that the true source of this cur- 
 rent will be found in some anatomical peculiarity of the frog. 
 
 As in the ordinary phenomena of the nutrition of muscles, by which their stale of 
 passive contraction or tone is maintained, electricity is developed, it is most reasona- 
 ble to expect that during active contraction there should be a development of elec- 
 tricity, as th^re is of heat likewise, according to Becquerel and Breschet's observa- 
 tions. This is shown by Matteucci in a very beautiful experiment which we have 
 frequently repeated with the same results. Place a prepared frog upon an insulating 
 plane; then prepare the leg of another frog with the crural nerve dissected out and left 
 attached to the leg, the thigh being removed. Place the nerve of this leg upon one 
 or both thighs of the 'other frog, and every time that those legs are excited to contract 
 by a galvanic or a mechanical stiniulus, contractions will be produced in the second 
 leg, which is connected with the iirst only by the contact of its nerve with the sur- 
 face of their muscles. The same effect will be produced, if the nerve of the frog's 
 leg be placed on the muscles of a warm-blooded animal, — a rabbit, for instance, — 
 care being taken to remove any thick aponeurosis which may cover the latter. 
 
 If an insiilating substance be placed between the muscles of the thjgh and the nerve 
 of the leg, no action will take place. The same effect is observed when gold-leaf is 
 interposed ; but- if the gold-leaf be torn, to however slight a- degree, the leg will be 
 thrown into contraction. 
 
 The electricity developed during the contraction of the muscles, stimulates the 
 nerve which is laid upon them; the interposition of a non-conducting substance 
 prevents the electric discharge from reaching the nerve ; and gold-leaf, being a better 
 conductor than nerve, carries the electricity along it, passing by the nerve. 
 
 4. The study of the effects of electricity applied in various ways upon nerves has 
 led to some highly interesting and curious results. 
 
 Nobili ascertained that, in passing an electric current through the lumbar nerves 
 of a frog, contractions occurred under different circumstances, according to the state 
 of vitality of the nerves. He divided the vitality of the nerve into five periods, 
 during each of which different phenomena were produced by the passage of the cur- 
 rent. In the first period, the A>ec< current, or that directed from the brain to the 
 nerves, caused contractions in the muscles on closing the circuit; iheinverse current, 
 or that from the nerves to the brain, on opening it. In the second period, the direct 
 current causes contractions on closing the circuit, and slight ones on opening it; the 
 iraaerse current causes contractions only on opening the circuit. In the third period, 
 contractions occur only on closing the direct current and opening the inverse. In the 
 fourth period, contractions occur only on closing the AVeci! current; and in the fifth, 
 the nerve ceases to be influenced by the electrical stimulus. Marianini, who subse- 
 quently studied this subject, affirms that contractions lake place only under two cir- 
 cumstances, namely, from the closure of the direct current, or from opening the im- 
 verse ,■ and that a sensation is caused by the direct current on opening, but by the 
 inverse on closing. 
 
 Matteucci repealed these observations on the sciatic nerves of the rabbit, devoting 
 one nerve to the direct, the other to the inverse, current. On closing the direct 
 
338 INNERVATION. 
 
 current, contractions were produced in the muscles of the limbs and back, with 
 marked signs of pain; the same phenomena result frotli closing the inverse current, 
 and from opehing both. The signs of pain were greatest at the closure of the inverse 
 current, and the contractions were most at the closure of the direct current. The 
 commencement and the interruption of an electric current of a certain intensity, 
 acting upon a certain portion of the nervous system, are followed by the same phe- 
 nomena, whatever be the direction of this current in the nerve. After some time, 
 which is shorter as the current is more intense, the phenomena take place in a differ- 
 ent manner. Upon interrupting the direct current, the conlractioris pf the muscles 
 of the limbs are feeble, but there are signs of pain, and the muscles of the back are 
 contracted; but, when the direct current is closed, the effects are limited to contrac- 
 tions of the posterior limbs. When the inverse current is used, contractions of the 
 muscles of the' back and signs of pain occur on closing it, while the contractions of 
 the limbs are slight; but, on the interruptionof it, contractions of the limbs alpnetake 
 place. 
 
 The following tAular view will exhibit these latter results more olearlyJ 
 
 
 , . 5 contractions in muscles of posterior 
 
 " ' limbs. 
 
 Direct current . . . ^ ? marked signs of pain, and contraction 
 
 (opening . . . ^ of muscles of the back. 
 
 ( feeble contractions of posterior limbs. 
 
 , . r sighs of pain, contractions of muscles 
 
 T„,„...» „.,„.„, (Closing • • • \ ofback.and feeble ones of the pos- 
 
 Inverse current . . . < < . ■ v u 
 
 ) • ) tenor limbs. 
 
 ' P S • • • ^ contractions of the posterior limbs. 
 
 So that, after the lapse of a little time, the phenomena produced by closing the 
 inverse current, become precisely the same as those on opening the direct, and vice 
 versa. 
 
 The contractions of the muscles of the back, which are supplied from nerves which 
 come off above the point of excitation, are due to the irritation of the nervous cenire, 
 affected through sensitive nerves; for these contractions cannot be produced if the 
 portion of the cord from which the nerves arise have been removed. 
 
 After the nerve has been exhadsted, so as to yield the phenomena of the second 
 period, as shown in the table, it may be excited to act as at first, either by increasing 
 the intensity of the current, or by exciting points of the nerve nearer its peripheral 
 extremities. 
 
 A simple experiment illustrates the different effects of the direct and inverse cur- 
 rent in a very striking manner. The limbs of a frog are prepared according to the 
 ordinary method of Galvani. If a current be passed from one side to the other 
 through the lumbar nerves, it is plain that it will be direct in the nerves of one side, 
 and inverse in those of the other side. During the first period, there are contractions 
 bolh on completing and interrupting the circuit;' but in the second period, one limb 
 contracts on opening, the other on closing, so ihat the limbs are made to kick alter- 
 nately, that which is traversed by the direct current on closing, and that by the inverse 
 current on opening. 
 
 It is impossible to observe these curious- phenomena, whether of the muscular 
 current, or of the effects of electricity on nerves, without perceiving how utterly in- 
 explicable they are by the electrical' iheory of nervous power, or, indeed, how much 
 opposed Ihey are to such a view. They serve, in the most remarkable manner, to 
 confirm ihe views which we have advocated in a former chapter, which regard the 
 nervous power as a polar force developed by molecular changes in nerves excited 
 by various stimuli, of which, next to the mental, that of electricity is the most power- 
 ful. 
 
 We have already (p. 223) given the general results of Professor Matteuoci's very 
 interesting series of experiments on the torpedo. We shall content ourselves, now, 
 with remarking thai he has succeeded in illustrating very strikingly the marked ana- 
 logy between the actions of the electrical organ and those of muscle, and the relation 
 which each bears to the nervous system. Both are organized to act in a particular 
 way: Ihe one to develop electricity without any visible change in itself; the other 
 to coniract, with a demonstrable evolution of bolh heat and electricity. Both will 
 manifest their peculiar phenomena by direct irritation, or by indirect irritation through 
 the nerves. Both are brought under the control of the will by the nerves ; the section 
 of which paralyzes the influence of the will over both, but does not destroy the pe- 
 culiar power uf either. In the electrical fish, irritation of the electrical lobe of the 
 
SYMPATHY AND SYMPATHE;nC SENSATIONS AND MOTIONS. 339 
 
 brain is capable of exciting a discharge of the organ ; jnst as irritation of a segment 
 of the spinal cord causes contraction of the muscles sapplied by it. Acurrentof 
 electricity transmitted through the electrical organ or its nerves,, causes discharge; 
 and a similar current sent through a muscle or its nejyes, causes it to contract. All 
 the circumstances which modify the nutrition of muscle, will similarly affect that of 
 the electricaj organ.* 
 
 CHAPTER XII. 
 
 ON SYMPATHY AND SYMraiTHETIC SENSATIONS ANli^RIOTIONS. 
 
 It is popularly known that the act of yawning, performed by one 
 individual in a company, is apt to induce in many of the others an 
 irresistible tendency to the same act. In a similar manner, the ex- 
 citement of certain emotions (mirth or sadness, laughter or tears) is 
 apt to spread through an assen),blage of persons with extraordinary 
 rapidity. The power of eloquence, of music, or of spectacle, to pro- 
 duce such effects, is witnessed every day in places of public resort, 
 ■whether for devotion, business, or amusement. 
 
 Many instances are known in which convtalsions have been ex- 
 cited in persons not previously subject to them, by the sight of a 
 patient in an epileptic fit. And peculiar nervous disorders, of a con- 
 vulsive kind, have been found to affect nearly all the members of a 
 community, without the slightest evidence of. their being contagious 
 or infectious. An impression upon' an organ of sense may pfoduce 
 effects very different in their nature to anything which could be anti- 
 cipated ; afld these may be purely of a physical kind, or they may 
 act primarily upon the mind. Thus certain odours will induce syn- 
 cope in some people; and the smell of a savoury dish to a hungry 
 person, or even the mention or the thought of a meal, will excite, a 
 flow of saliva. The emotion of pity excited by the sight of some 
 object of compassion, or by a narrative of a mournful kind, will pro- 
 duce a copious flow of tears. 
 
 All such phenomena are said to result from Sympathy. When 
 one yawns, immediately in consequence of another's yawning, the 
 fortner evidently and truly sympathises with the latter ; and the 
 convulsions which are induced by the sight of another in a fit, are 
 not less sympathetic. The individual in whom the convulsions are 
 induced sympathizes with the other. Such obvious instances of 
 sympathy between different individuals -led to the supposition of 
 some such similar consent between different or even distant parts in 
 the same person. 
 
 Motions or sensations caused in certain parts in consequence of a 
 primary irritation of other and distant parts are of the sympathetic 
 kind. These motions or sensations are produced in, as it were, an 
 
 * Traits des ph^nomfenes electro-physiologiques des animaux, par C. Matteucci ; suivi 
 d'etades anatomiques sur le eystfeme nerv«ux et sur J'organe electrique dela TorpiUe, par 
 Faul Savi. Far. 1844. 
 
340 INNERVATION. 
 
 indirect or circuitous manner, or one different from that in which 
 they are ordinarily excited. 
 
 Thus a stimulus to the olfactory membrane causes a peculiar 
 affection of the sense of smell, and thus occasions that depression of 
 the heart's action from which results a state of syncope. Or, another 
 affection of the same sense causes a suddenly increased action of the 
 salivary glands. 
 
 If we analyze any one of these examples of sympathetic actions, it 
 will appear that three circumstances are to be noticed in the produc- 
 tion of the phenomena: 1st, the primary exciting cause, which may 
 be an object presented to the mind through one of the organs of 
 sense, or causing an impression upon ai^ sensitive nerve, and there- 
 fore upon some' part of the centre of sensation ; 2dly, the part affected 
 directly by this primary stimulus; and, 3dly, the action or sensation 
 resulting from the affection of this part. 
 
 Many other sensations or motions may be enumerated besides 
 those above referred to, whether Occurring. in health or in disease ; 
 and we shall give examples of these before we discuss this subject 
 further. 
 
 The examples of sympathetic sensations which may be adduced 
 are chiefly of the morbid kind. Pain is felt at a certain part, in 
 consequence of an irritation in another part distant from it, and ap- 
 parently altogether unconnected with it. One of -the most farailiap of 
 these is pain in the knee from disease of the hip-joint. So marked 
 in some instances is the pain in the knee, and so much has it absorbed 
 the patient's attention, that the real seat of the disease has been 
 overlooked, and the remedies been applied exclusively to the knee. 
 Pain in the right shoulder from disease of the liver is a sympathetic 
 sensation of similar kind ; and sometimes the hepatic irritation causes 
 pain over a more extensive surface. Whytt mentions, that, in two 
 cases of suppuration of the liver, he had seen the patients " affected 
 with a numbness and debility of the right arm, thigh, and leg." 
 The peculiar sensations felt in the teeth from a noise which grates 
 upon the ears, is sympathetic of the irritation of the auditory nervfe. 
 Practitioners are well aware how many morbid sensations in parts 
 remote from the intestinal canal may be cured by the removal of 
 scybala or other accumulations from it. Painful affections of the 
 nerves of the face, and of other parts, are often due to a cause of 
 this kind. The irritation of a stone in the bladder gives rise to, pains 
 in the thighs, or to itching at the end of the penis ; arid uterine irri- 
 tation, whether frpta disease or frOm the enlargement of that organ in 
 connection with the early stage of pregnancy, causes similar pains in 
 the nerves of the thighs. 
 
 Headache and defective vision are frequently produced by disor- 
 dered stomach. A draught of very cold water, or ice, taken quickly 
 into the stomach, may occasion acute pain in the course of either 
 frontal nerve. This same nerve on one side is frequetitly the seat of 
 pain after the imprudent use of acid wine or Other fermented liquors. 
 
 Movements^ excited by the operation of a stimulus applied at a 
 distance, form a large proportion of the instances of sympathetic 
 
SYMPATHETIC MOTIONS. 341 
 
 phenomena. All the ordinary physical nervous actions in which 
 motions are excited by stimulating a sentient surface, may be re- 
 garded as examples of sympathetic actions.* The contraction of 
 the iris upon the ap{)licatibn of the stimulus of light to the' retina, or 
 of the pharyngeal muscles by stimulating the mucous membrane of 
 the fauces,, are instances/in point, where the stimulus acts indirectly 
 upon the contracting fibre. Nothing .is more sure than that in these 
 instances the change wrought by the stimulus in certain sentient 
 nerves travels by a circuitous route through a nervous centre to the 
 muscles which are called into action. Akin to these actions are the 
 fdrcible respiratory movements which may be excited by irritation of 
 the tracheal membrane, as coilghihg; or sneezing, by, stimulating the 
 nasal membrane; or vomiting, by irritating the' fauces. Spasmodic 
 affections are often instances of morbid actions in sympathy with 
 intestinal irritation, or the irritation of teething in children. Partial 
 or general convulsions are very frequently due to either or both these 
 causes. We have known the most violent opisthotonos co-existing 
 for a considerable time ^with the presence of lurabrici in the intestine; 
 but ceasing immediately on the removal of the worms. Vomiting is 
 commonly sympathetic of diseased kidney, or of the passage of a 
 calculus along the ureter ; or it may be inducedby the introduction 
 of a catheter into the urethra. Irritation of the intestines, as in 
 cholera, causes cramps of the most violent kind in the lower extremi- 
 ties and abdominal muscles. The contractions of the abdominal 
 miiscles'in parturition, although materially aided by the will, are in 
 consent with the expulsive efforts of the uterus. 
 
 The consentaneous action of symmetrical parts is no doubt due to 
 a similar cause to that by which most of the syrapalhetic actions are 
 excited, and more especially in those parts where symmetry of action 
 is constant, although liable to be interrupted by the influence of the 
 will. 
 
 A distinct class of sympathetic actions consists of those in which 
 certain parts enlarge or become developed simultaneously with, and 
 to a certain extent in effect of, the increase of others. The penis, 
 the beard, the vocal" organs, experience a marked increase of de- 
 velopment at the adult period of life simultaneously with the enlarge- 
 ment of the testes ; and, it may be added, in effect of their increase, 
 because the early removal of these organs prevents the growth of the 
 others. And so likewise as the ovaria are developed, the uterus, the 
 , vulva, the mammae, increase in size ; the ovarian and uterine irrita- 
 tion which accompanies the menstrual flux causes enlargement of the 
 ■breasts, which subsides as soon as that period has gone by. 
 
 The various examples enumerated in the preceding paragraphs 
 maybe classed under three heads: first, sympathies between different 
 individuals; secondly, those which affect the mind, and, through it, 
 
 • It has been remarked, that the term, " sympathetic actions" involves a contradic- 
 tion. But it may be observed, that the contraction of the muscles, on which the 
 action depends, is only the natural mode in which that class oT vital organs can 
 manifest their consent with certain states of nervous centres, or of sensitive nerves. 
 • The action is the result of the state which the muscle assumes in sympathy with the 
 stimulated nerve. The oontradictiou is therefore apparent, not real. 
 
342 INNERVATION. 
 
 the body; and, thirdly, those which are strictly organic, and there- 
 fore physical. 
 
 Of the first class of sy^npathies we can offer no physical explana- 
 tion. Whether the nervous system of one individual can directly 
 affect that of another, or whether the effect is produced on the ima- 
 gination, and afterwards on the nervous system, are questions still 
 subjudice. The serpent fascinates his prey, a.pparently by the power 
 of his eyes, and it is well known that, one man can exert a marked 
 control over another by a mere look; and in the same way man can 
 control other animals, even the fiercest carnivora, by a firm and de- 
 cided glance of the eyes. It is no explanation of sympathetic pheno- 
 mena of this kind to ascribe them to the effect of a tendency to imita- 
 tion. Imitation is voluntary; these actions are involuntary, or take 
 place even in despite of the will. [Bostack's Physiology, vol. iii., 
 p. 227.) 
 
 In the second class of sympathetic phenomena, an affection of the 
 mind is a ne.cessary link. But why that affection of the mind should 
 produce its peculiar effect is a question of difficult solution. Why 
 should the perception of certain odours produce in one case increased 
 action of the salivary glands, and in the other case cause syncope.' 
 The only reply which can be made to this question is, that in these 
 instances the impression on the sensorium causes a change there 
 analogous to that which an original affection of the mind of simJiar 
 kind would produce, and therefore gives rise to effects of the same 
 nature as thqse resulting from that mental change. Thus the smell 
 of savoury foot! excites iri the mind the idea of food, which in a 
 hungry man would, if it occurred spontaneously, occasion a flow of 
 saliva. And the odour which occasions syncope, creates in the mind 
 an emotion of disgust, which, if it arose independently of the physi- 
 cal impression, would affect the heart through the centJ-e of emotion. 
 It is plain, however, that that portion of the nervous centre which 
 is affected in such cases, must have a direct influence upon the parts 
 in which the sympathetic phenomena appear; and this through com- 
 missural fibres, or the continuity of its gray matter with that of the 
 centre from which its nerves immediately spring ; thus, in the in- 
 stances referred to, the centre of sensation, which is first affected, is, 
 through the medulla oblongata, connected with the salivary glands 
 by the fifth nerve, and with the heart by the vagus. 
 
 We derive an explanation of the third class of sympathetic phe- 
 nomena from the known laws of sensitive and motor nerves. It is 
 known that stimulation of a sensitive nerve at its origin, or in any 
 part of its course, will give rise to a sensation which will be referred 
 to the peripheral extremity of the stimulated fibres; and that a stirau- 
 liis applied to a motor nerve causes a change in it which spreads 
 peripherad from the point stimulated, and therefore affects the muscu- 
 lar parts with which it is connected. It is known, also, that a sentient 
 nerve may excite a motor or sensitive nerve which is implanted near 
 to it in the nervous centre — doubtless through the change which it 
 produces in that centre; nor can it be doubted that a sensitive nerve 
 may receive such a powerful stimulus as to exalt the polar force of 
 
SYMPATHETIC SENSATIONS AND MOTIONS. 343 
 
 a large portion of the nervous centre in the neighbourhoocj of its 
 insertion, and thus to excite a similar change in all the nerves, 
 whether motor or sensitive, which are connected with it. Thus, 
 according to the intensity of the original stimulus, there will be a 
 radiation of nervous force from the centre, either in one or two 
 motor or sensitive nerves, or in several such; and th6 number and 
 variety of the sympathetic phenomena will thus depend o'n the in- 
 tensity and extent of the change in the nervous centre excited by the 
 primary stimulus. 
 
 To explain then the phenomena of sensation and motion under 
 consideration, we must determine the individual nerves affected in 
 each instance, and ascertain what connections they have with each 
 other. We learn from anatomical, investigation, that, although nerves 
 anastomose with each other in their distribution, this anastomosis is 
 by no means of that kind which would justify the supposition that 
 an irritation could be communicated from one to the other in their 
 course. The nerve-fibres only lie in juxtaposition, but do not com- 
 municate: and there is an evident provision in the tubular membrane 
 and white substance of Schwann for the insulation of the central 
 axis, which is probably the effective substance in the nervous action. 
 We must seek, therefore, in the nervous centres for such a communi- 
 cation between these nerves as may explain the excitability of one by 
 the other. In the present state of our knowledge we can do no more 
 than state it as in the highest degree probable that nerves implanted 
 in the centre immediately contiguous to each other can exert an influ- 
 ence upon the vesicular matter of the centre, and upon each other. • 
 
 But there are certain facts which demonstrate beyond all doubt, 
 that, in such actions as we refer to, the integrity of the centre forms 
 a necessary condition. First, in many of the instances, it is plain that 
 there can be no connection between th€ affected nerves elsewhere 
 than in the centre, for they are so distinct from each other that there 
 is not even that apparent connection which results from the anasto- 
 mosis of a fasciculus of fibres of the one with a portion of the other. 
 Secondly, the removal of the portion of the nervous centre with 
 which any one of the nerves concerned in the sympathetic action is 
 connected, will prevent the development of .the phenomenon, al- 
 though the nerves themselves remain uninjured in their peripheral 
 distribution, or in their connection with each other. Thirdly, if there 
 were any peripheral communication between nerves, it would be 
 most likely to. take place in the plexuses. Experiments, however, 
 upon the nerves which lead to these show that each nerve-tube^ in its 
 passage through them, retains its isolation as distinctly as in any other 
 part of its course. The three nerves which supply the, lower ex- 
 tremity in the frog, says MiJller, form a plexus from which two nervous 
 trunks issue : if one of these latter be divided and isolated from all 
 its connections with muscles, and the portion of it connected with the 
 plexus irritated, the impression will be transmitted in the centripetal 
 direction by the sensitive fibres of the nerve ; but the motor fibres of 
 the other nerve arising from the plexus are not affected, and excite 
 
344 INNERVATION. 
 
 no contractions in the muscles to ■which they are distributed. {Balyh 
 Muller, vol. i. p. 756.) . 
 
 In applying these principles to the explanation of the instances 
 which we have quoted, we shall find it difficult to determine the 
 central connection in some, although in others such a connection is 
 highly probable. It remains, therefore, for future anatomical research 
 to ascertain what that connection is which enables one nerve to sym- 
 pathize with another. In the instance of pain in the shoulder in 
 sympathy with irritation of the liver, the hepatic irritation excites a 
 change in some sensitive nerves, which is propagated to the centre, 
 and there affects some of the sentient fibres distributed in the region 
 of the shoulder. The phrenic and the external thoracic nerves are 
 both or either of them, but more especially the former, favourably 
 situated to constitute the excitant of such a sympathetic sensation. 
 The phrenic nerve of the right side is largely distributed upon the 
 peritoneal surface of the diaphragm, and upon the inferior vena cava, 
 and forms many connections with the hepatic plexus in the substance 
 of the liver. It may therefore readily participate in any irritation of 
 that organ. Now the phrenic nerve is implanted in the spinal cord 
 on a level with the third or fourth cervical nerves; and the nerves of 
 the shoulder form their connection with this central organ about the 
 same level. The origins of these nerves are sufficiently contiguous 
 to each other to warrant the belief that an irritated state of one may 
 be propagated to the other through the vesicular matter of the centre. 
 But it may be inquired why the irritation is limited to sensitive nerves 
 of the shoulder; and why movements are not excited by the stimula- 
 tion of the motor fibres of the phrenic itself, or of other nerves ? 
 The limitation of the irritation to one or two nerves depends on the 
 degree of the stimulus, and the absence "of niovements is due to 
 the disposition of the phrenic on the surface being unfavourable for 
 the excitation of motions by irritation of its peripheral branches (see 
 page 298). And the experiment cited from Miiller, in the last para- 
 graph, shows that simple irritation of the trunk of a compound nerve 
 in connection with the centre is not sufficient to produce motion ; 
 which requires probably either a more prolonged and violent irrita- 
 tion of the nerve, or a polar state of the centre in which it is im- 
 planted. 
 
 Some of the instances of sympathetic sensations, referred to above, 
 do not admit of an explanation so obvious. The pain over the brow, 
 from ice or cold \yater in the stomach, may be referred to irritation 
 of the gastric branches of the A'agus, communicated in the medulla 
 oblongata to the fifth ; but why the irritation should be limited to the 
 Ophthalmic division of the fifth, cannot be accounted for in the pre- 
 sent state of our knowledge. 
 
 In those sympathetic movements which are of ordinary and nor- 
 mal occurrence, two provisions seem to be secured, namely, a certain 
 peripheral organization of the excitor nerve, and a certain central 
 relation between it and the motor nerve. But in those which are of 
 a morbid kind, it is necessary to suppose the existence of a more or 
 less exalted polarity of the centre, in order to explain the phenomena 
 
PACINIAN CORPUSCLES OF THE NERVES. 345 
 
 fully. This polar state will continue, in many instances, even after 
 the primary peripheral irritation has been removed, as in tetanus, or 
 in the convulsions from intestinal irritation ; and we learn from this 
 fact the importance in practice of attending to the state of the nerv- 
 ous centre, as well as to the removal of the irritating cause. 
 
 There are other sympathetic phenomena, of the physical kind, in 
 which, however, the nervous system does not appear to take a pro- 
 minent part. Such are the changes which occur in different and 
 distant organs in connection with a particular period of life, or the 
 development of a particular function. Among these, are the pheno- 
 mena of puberty in both sexes; the enlargement of the mammae in 
 pregnancy. Whatever part the nervous system may take in such 
 changes, it is impossible to account for them by reference to that sys- 
 tem only ; they must rather be regarded as phenomena of nutrition 
 occurring in harmony with the laws of growth, and therefore .affect- 
 ing the vital fluid more particularly than any part of the system of 
 solid parts. 
 
 Continuity of texture disposes, as is well known, to the extension 
 of a diseased state originating at some one point. So also does con- 
 tiguity. Phlegmonous inflaramatiofi of the areolar tissue, and ery- 
 sipelas in the skin, spread with great rapidity. Inflammation arising 
 in one of the opposed surfaces of a serous membrane, readily attacks 
 the other. These effects have been vaguely assigned to sympathy, 
 (the continuous and contiguous sympathy of Hunter.) But it cannot 
 be supposed, that the nervous system takes part in the production of 
 such phenomena, which ought rather to be ascribed, in the one case, 
 to the continuity of blood-vessels, — and, in the other, to contamina- 
 tion either by effused fluids or by morbid blood. 
 
 On the subjects referred to in this chapter, consult Whytt on the Sympathy of the 
 Nerves, an admirable exposition of the phenomena, obscured, however, by his erro- 
 neous views respecting the all-pervading influence of the mind upon vital pheno- 
 mena; — Hunter on the Blood, &c. ; — Alison on the Physiological Principle of Sym- 
 pathy, Edin. Med. Chir. Trans., vol. ii. ; — Miiller's Physiology. 
 
 CHAPTER Xni. 
 
 OF THE PACINIAN CORPUSCLES OF THE NERVES. 
 
 We propose to give in this chapter an account of certain very 
 remarkable structures, appended to the nerves, to which attention 
 has only very recently been drawn in this country.* These are the 
 Pacinian corpuscles, so named by Henle and Kollikerf from their 
 
 • Brit, and For. Med. Rev., Jan. 1845. 
 
 t Ueber die Pacinischen Korperchen an den Nerven des Menschen undder Siuge- 
 thiere. Zurich, 1844. ; ;<■: 
 
 18 
 
346 
 
 INKERVATION. 
 
 discoverer, Pacini.* In the human subject they are found in great 
 numbers, in connection with the nerves of the hand and foot, the 
 nerves, as it may be presumed, of touch ; but they also exist spar- 
 ingly on other spinal nerves, and on the plexuses of the sympathe- 
 tic, though never on the nerves of motion. In the mesentery of most 
 cats they are very readily seen by the naked eye, (usually in consider- 
 able nuiiibers,) as pellucid, oval grains, rather smallef than hemp- 
 seeds, and they are here very favourably situated for examination. 
 
 A. Nerve from the finger, natural size; showing the Pacinian corpuscles. 
 b' Ditto, magnified 2 diam ; showing their different size and shape. 
 
 c. Unusual form, Irom the mesentery of the cat; showing two included in a common envelop: 
 ■— o. b. are the two nerve-tubes belonging to them. 
 
 D. Another, from the same : showing an olfset from tlie central cavity, containing a branch of the 
 pale nerve 
 
 E. Rare form, from the mesentery of the cat (reduced from Henle and Kolliker) ; showing two cor- 
 puscles placed in succession on a single stalk, and furnished witii the same nerve-tube, which re- 
 suthes its white substance in the interval between them. 
 
 -Fig. 74, A, B, ■will give a correct idea of their relation to the nerves 
 in the palm and sole. They are especially numerous on the smaller 
 twigs, to which they are generally placed parallel, though frequently 
 at an acute, and sometimes at an obtuse angle. They are more or 
 less oval, often elongated and bent ; sufficiently tough to resist mode- 
 rate pressure, and nearly transparent, with a whitish line traversing 
 their axis. They lie imbedded in the areolar tissue, and adhere to it 
 by their outer surface. They always present a proximal end, attached 
 to the nerve by a stalk of fibrous tissue, prolonged from the neuri- 
 lemma, and occasionally tV of 3i inch long ; and a distal end, lying 
 free in the areolar tissue. The corpuscles in the human subject have 
 an average length of from aV to tV of an inch. 
 
 ♦ Pacini first noticed them in 1830, and subsequently in 1835 ; and in 1840 gaVe ah 
 account of them (Nuovi organi scoperti del corpo umano dal Don Fillippo Pacini. 
 •Pistojai 1840), which has been rendered much more accurate and complete in its de- 
 tails by Henle and Kolliker. Coming to the investigation of these corpuscles with 
 the knowledge of what these eminent analomists had accomplished, we have con- 
 firmed their results by numerous observations, from which the account about to be 
 given has been principally taken. A. G. Andral, Camus, and Lacroix had announced 
 their existence at a amcoura in Paris in 1833, but do not appear to have apprehended 
 their real nature. 
 
PACINIAN BODIES. 
 
 347 
 
 Tig. 75. 
 
 A minute examination of these singular bodies discloses an internal 
 structure of a highly interesting kind. They consist, first, of a series 
 of membranous capsules, from thirty to sixty or more in number, en- 
 closed one within the other; and, secondly, of a single nervous fibre, 
 of the tubular kind enclosed in the stalk, and advancing to the central 
 capsule, which it traverses from end to end. 
 
 ^By reference to the accompanying figure (75), which exhibits the 
 general structure, the ten or fifteen innermost capsules may be ob- 
 served to be in contact with one another, while the rest are separated 
 by a clear space containing fluid. This is almost constantly observed, 
 unless the specimen has been allowed to imbibe water sufficient to 
 detach the inner capsules from each other ; and hence these have 
 been distinguished from the rest as 
 the system,^ internal capsules. The 
 intercapsular spaces between' the 
 others vary in width, especially 
 under pressure, and sometimes we 
 have seen someof the outer capsules 
 in close contact. The capsules are 
 here and there united by connecting 
 bands of similar structure, passing 
 transversely or obliquely across the 
 spaces; the spaces do not commu- 
 nicate : if some of the outer capsules 
 are punctured, their fluid escapes; 
 but those within remain distended. 
 A single puncture down to the 
 inner series of capsules causes all 
 the fluid to escape, and the whole 
 to collapse; and again, the capsules 
 may he often peeled off in succes- 
 sion, showing their union to be but 
 slight. In fact, except by the few 
 bands already mentioned, they are 
 united only along the stalk, and for 
 a. variable extent at the opposite 
 end. The stalk seems to be inserted 
 into a kind of conical tube, which 
 penetrates all the capsules in suc- 
 cession, but has its proper wall, so 
 as not to communicate with the 
 intercapsular spaces. This wall 
 connects the capsules, and the 
 fibrous tissue of the stalk is gradu- 
 ally united with its inner surface 
 as far as the central capsule, where 
 it terminates. There is generally a. 
 strong union between a variable number of the capsules, as we trace 
 them from the opposite end, of the central capsule towards the surface 
 (fig. 76, B, o) ; this was called by Pacini the intercapsular ligament. 
 
 Pacinian corpuscle, from tlie mesentery of a 
 cat ; intended to show the general constrnction 
 of these bodies. The stalk and body, the outer 
 and the inner system of capsules, with the cen- 
 tral cavity^ are seen. a. Arterial twig:, ending 
 in capillaries, which form loops in some of the 
 intercapsular spaces, and one penetrates to the 
 central capsule. 6. The fibrous tissue of the 
 stalk prolonged from the neurilemma, n. 
 Nerve-tube advancing to the central capsule, 
 there losing its white substance, and stretching 
 along the axis to the opposite end, where it is 
 fixed by a tubercular enlargement. 
 
348 INNKRVATION. 
 
 We do not, with Henle and Kolliker, deny its existence, but have 
 seldom seen it reach the surface of the corpuscle. 
 
 The wall of the capsules of the external system often appears to 
 consist of two laminae. The inner of these contains, at intervals, 
 flattish, oval nuclei projecting inwards (fig. 76, a, d). The outer is 
 sometimes seen, as if in section, by a series of dots, representing 
 transverse or circular fibres. The capsules always exhibit a decided 
 transverse fibrillation, which in a great measure disappears on the 
 addition of acetic acid, showing the almost complete absence of the 
 yellow fibrous tissue. The outermost capsule of all, however, is 
 invested with the network of this, as well as of the white ^brous ele- 
 ment of the areolar tissue. The internal capsules do not show the 
 double wall, but they contain nuclei. 
 
 The capsules seem to be over-distended by their fluid, so as to be 
 naturally kept tense. If allowed to dry, they do not fill again on 
 being moistened. 
 
 ' The fluid of the intercapsular spaces is so abundant as to constitute 
 far the largest portion of the bulk of the entire corpuscle, and by its 
 clearness imparts the peculiar pellucid lustre so characteristic of these 
 bodies. It is supposed to resemble the serum of the blood. 
 
 There are generally a few capillary blood-vessels ranging over the 
 surface of the capsules; but the corpuscles are chiefly supplied by a 
 minute artery that enters in the fibrous tissue of the stalk, sends off 
 a few capillaries which perforate the tubular canal, and form each a 
 short loop in the intercapsular spaces (fig. 75): one capillary vessel 
 usually reaches the central capsule (fig. 76, a), and sometimes, though 
 rarely, may be traced some way along its wall. In the larger cor- 
 puscles of the palm and sole, the capillaries penetrate to the distal 
 part of some of the intercapsular spaces, and may there form a kind 
 of bunch before returning. If a quite recent specimen be examined, 
 under a high magnifying power, the blood-globules are often visible 
 in the capillaries, and, by their swelling on the addition of water, 
 may be sometimes hurried into a sort of circulation. When this 
 happens, the course of the blood in the corpuscles is displayed with 
 singular beauty. 
 
 We have said that the stalk of every corpuscle contains a single 
 nerve-tube. When two corpuscles are seated on a common stalk, 
 two nerve-tubes are included, one of which belongs to each (fig. 
 
 ■^4,0). _ . '. . 
 
 The nerve-tube is proportioned in size to that of the corpuscle, 
 that is, to the number of capsules composing it. Even when smallest, 
 it is conspicuous enough, if the specimen be recent; for it is invaria- 
 bly furnished with the white substance of Schwann, and displays the 
 double contour. When largest, it equals any found in the body. It 
 is very liable to present varicosities, and its course in the stalk is 
 more or less undulating. 
 
 On entering the innermost capsi.rle, the nerve-tube suddenly loses 
 its envelop of white substance and becomes pale; the axis-cylinder 
 alone remaining, perhaps still invested by the tubular membrane (see 
 p, 194), Thus reduced in size and rendered pale, the nerve stretches. 
 
PACINIAN BODIES. 
 
 349 
 
 like an arrow along the very centre of the capsular cavity to the 
 opposite end, where it swells into a knob, or button, which fixes 
 itself to the inner surface of the capsule. In this swelling nothing 
 can be detected beyond the pale, faintly fibrous character of the axis- 
 cylinder. No nucleus, like 
 
 that of the caudate nerve- ^'S- ''B. 
 
 vesicles, can be seen. — 
 Sometimes the axis-cylin- 
 der divides near its termi- 
 nation into two or even into 
 three branches, each of 
 which terminates by an ad- 
 herent "swollen extremity. 
 Sometimes this division oc- 
 curs near the proximal end 
 of the central capsule, and 
 one of the branches passes 
 in a retrograde course into 
 a subordinate offset from the 
 central cavity, and there 
 terminates (fig." 74, d). In 
 the midst of these varieties 
 one thing is constant, viz., 
 the remarkable accuracy 
 with which the pale nerve 
 pursues its path in the axis 
 of the cavity, everywhere 
 equidistant from the walls. 
 This is most apparent when 
 the cavity is bent upon itself, 
 
 Qnfl «-K*in if- mirrlit V»p imair- A. Termination of the Btalk, and commencement of the 
 anU wnen it migni ne iraag- ^^^j^, „^^ny „. Nerve-iul.e advancing to the central 
 ined that the nerve would capsule, and tliere suddemly losing iw white substance 
 ,. - . and becoming: pale. a. Artery ending in capillaries; 
 
 ■incline trom ttie centre to- 6ne af which enters' an intercapsular space, the other 
 i-lc +liQ rtrtri/ioTrifir r,f tVi a advances with the nerve into the inner capsuie. &. Coni- 
 WarOS me concavity or tne ^al tube which receives the stalk: theiflbroiis tissue of 
 Konrl . V»iif it- b-opnc n ppntral the stalk is not represented, c. Wall of this tube, con- 
 ueiiu, uuu II K.eejj» d i,eiuirti ijnuous with the successive capsules. Here seen in se.ctioii. 
 course there as well as else- ^- corpuscle of the capsular wall. e. More spherical 
 
 granular corpuscle, of which a few only exist. 
 
 fi. Distal end of the .cfentr&l cavity, n. Pale nerve ad- 
 vancilig along the axis, to be fixed by a ^swollen part at 
 the farther end. c. Wall of the central cavity, receiving 
 the insertion of some of the neighbouring capsules, here 
 a little separated from each other by water, o. Intercap- 
 Cavitv, immediately envel- sular ligament of Pacini, coi>tinued, a Uttle way towards 
 
 •^ , , '^ ^.T the surface. 
 
 oping the pale nerve. JNear c. Two varieties ofblfid extremity of nerve, attached to 
 the wall of the cavity an the distal extremity of the, central cavity.- ah magmfied 
 
 appearance of soft, delicate, 
 
 longitudinal fibres, with elongated nuclei, is often visible (fig. 76, a) ; 
 and although the space immediately surrounding the nerve is quite 
 transparent, we are disposed to consider the substance occupying it 
 sufficiently solid to keep the nerve in its place. It does not seem to 
 be mere fluid, like that distending the iritercapsular spaces. 
 
 Henle and Kolliker have remarked^ that, where two corpuscles are 
 seated in succession on a single stalk (fig. 74, e), the pale axis-cylin- 
 
 where. This, perhaps, may 
 depend on the nature of 
 the contents of the central 
 
350 INNERVATION. 
 
 der regains its envelop of white substance from its point of leaving 
 the central cavity of the first, to its entering that of the second ; and 
 that in some cases, where the central cavity is bent suddenly upon 
 itself, so that it cannot be fairly surrounded by capsules at the bend, 
 it is there provided for a little way with white substance. A very 
 delicate layer of the same substance, just thick enough to give a dark 
 edge, occurs occasionally along the course of the pale fibre. 
 
 We have gone thus minutely into the structure of the Pacinian 
 corpuscles, because of the novel aspect in which they present the 
 constituent parts of the nerve-tube, placed in the heart of a system 
 of concentric membranous capsules with intervening fluid, and di- 
 vested of that layer which we regard as an isolator and protector of 
 the more potential central axis within. The object of this arrange- 
 ment is quite unknown, and in the present uncertain state of our 
 knowledge respecting the nature of the nervous force, it seems almost 
 idle to hazard guesses on the subject. The apparatus of lamellae 
 may either effect some change in the enclosed nerve, by which the 
 nervous centres in connection with it may be influenced as to their 
 polarity ; or, on the other hand, this apparatus may be the special 
 instrument of some peculiar vital agency, which the nervous filament 
 is designed simply to bring into communication with the nervous 
 system. The latter view, to which we incline, would bring these 
 organs under the same category with muscles, and the organs which 
 develop light or electricity in certain of the lower animals. Pacini 
 has already drawn a comparison, in point of structure, between them 
 and the electrical organs of the torpedo ; and Henle and Kolliker 
 favour this idea. The well-known prisms of the electrical organs, 
 according to Savi,* consist of a congeries of very delicate transverse 
 lamellae, on' which the nerve-tubes are distributed in a plexiform 
 manner; and, if we may judge from his figure, this plexus is not 
 resolvable into loops, but consi.sts of true inosculations of the ultimate 
 lubes, which also retain the white substance of Schwann: but further 
 researches are greatly needed on this point. Wagner, with more 
 probability, describes the nerves to terminate on the lamelise in the 
 same looplike manner as in striped muscle. f These lamellse are 
 separated by fluid, and only adhere through the medium of the wall 
 of the prism. If this be the true history of this structure, it appears 
 to establish some general analogy between the electrical organs and 
 the corpuscles ; but how far this can be shown to hold in essential 
 characters, especially in the mode of termination of the nerves, and 
 their arrangement with regard to the membranes and fluid, is still a 
 matter of doubt. Meanwhile we deem it most prudent to forbear 
 from speculating concerning the office of the Pacinian corpuscles. 
 
 Having thus far completed the physiological anatomy and phy- 
 siology of nerves in general and nervous centres, we proceed next 
 
 • Paul Savi, in Matteucci, loc. cit. 
 
 f Cuinparative Anat., Iranslaled by Talk. 
 
GENERAL REMARKS ON SENSATION. 351 
 
 to the consideration of particular nerves; and we shall state here the. 
 order in which we find it convenient to examine them. The Ence- 
 phalo-spinal nerves very conveniently arrange themselves into the 
 three following classes : — I. The nerves of pure sense. H. The 
 nerves of motion. III. The compound nerves. The first class in- 
 cludes some nerves, namely, the nerves of touch and taste, which, 
 are mixed up with those of the third class ; but, as the consideration 
 of these senses could not without great inconvenience be separated 
 from the others, we prefer to consider these particular fibres along 
 with the other nerves of pure sense, namely, the olfactory, the optic, 
 and the auditory. As the peculiar function of these nerves depends 
 upon their peripheral organization, as well as on their central con- 
 nection, their physiological anatomy involves necessarily that of the 
 organs of sense. We shall commence with the most simple, namely, 
 Touch and Taste, and afterwards proceed to Smell, Vision, and 
 Hearing. 
 
 The second class of nerves contains the third, fourth, sixth, portio 
 dura-of the seventh, and the ninth pairs of nerves according to Willis's 
 arrangement, all of which are motor in function. 
 
 In the third class we place the fifth and eighth pairs of nerves, and 
 the spinal nerves. 
 
 Lastly, we shall examine the Sympathetic nerve. 
 
 CHAPTER XIV. 
 
 GENERAL REMARKS ON SENSATION. — OF THE SPECIAL SENSES. OE*' THE 
 
 SENSE OF TOUCH. — ANATOMY OF THE SKIN, AND ITS APPENDAGES. 
 
 Sensation is an affection of the mind occasioned by an impression 
 made on certain parts of the nervous system, hence called sensitive. 
 A state of the sensitive organs, and a corresponding perception by 
 the mind, must concur to produce sensation: either condition may 
 exist alone, but then the phenomenon is not a true sensation, in the 
 acceptation here given to the word. Thus, light falling on the eye 
 in sleep excites the whole visual sensitive apparatus, while the organ 
 of perception is inactive: on the other hand, in dreams, vivid pictures 
 of objects float before the mind, and are referred by it to the external 
 organ, w^hich may be all the while entirely quiescent. 
 
 The organs of sensation are those parts of the nervous system, 
 and their dependencies, which, when stimulated, occasion in the 
 mind a perception of the impression. Hence certain parts of the 
 cerebro-spinal centre, as well as certain nerves and their peripheral 
 expansions, are comprehended under this term. It is remarkable that 
 the organ of the mind itself does not appear capable of thus under- 
 going sensory excitement. Little is known of the central parts of 
 the organs of sensatioji, in consequence of their deep seat, and of, 
 
352 INNERVATION. 
 
 their ill-defined limits. The peripheral parts are more conspicuously 
 placed, and on several accounts are commonly styled, par excellence^ 
 the organs of sensation : they are specially adapted to receive in the 
 most advantageous manner the impressions to which their excitability 
 is adapted to respond. The intervening nerves are, more properly 
 speaking, media of transmission. 
 
 Sensations excited by a stimulus originating in the body itself, 
 especially if it act rather on the intermediate or central part of the 
 sensitive apparatus than on the peripheral, are termed subjective: on 
 the other hand, they are styled objective if the stimulus be derived 
 from without. 
 
 Under the name of common or general sensibility may be included 
 a variety of internal sensations, ministering for the most part to the 
 organic functions and to the conservation of the body. Most parts 
 of the frame have their several feelings of comfort and pleasure, of 
 discomfort and pain. In many of the more deeply seated organs no 
 strong sensation is ever excited, except in the form of pain, as a 
 warning of an unnatural condition. The internal sensations of warmth 
 and chillness, of hunger, thirst, and their opposites, of nausea, of 
 repletion of the alimentary and genito-urinary organs, and of the relief 
 succeeding their evacuation, of the privation of air, &c., with the 
 bodily feelings attending strongly excited passions and emotions, may 
 be mentioned among the principal varieties of common sensation. 
 
 The special sensations are referable to five leading forms, and are 
 distinguished not less by their several modes or characters, than by 
 the more special and elaborate construction of the peripheral parts of 
 their respective organs, whereby these are adapted to receive the 
 impressions of their appropriate stimuli. The special sensations ex- 
 cited through the instrumentality of the peripheral organs of touch, 
 taste, smell, vision, and hearing, are primarily designed to inform the 
 mind of the conditions of the external world ; and it is for the most 
 part only in a secondary manner, or through the mind, that they ope- 
 rate on the organic functions, or for the construction of the body. 
 
 Almost all sensation is attended with the idea of locality, the mind 
 referring the cause of the change it experiences to the peripheral part 
 of the sensitive apparatus excited. Thus the ideas of distance, ex- 
 tent, and relative position originate in the very construction of our 
 bodies, and soon become applied to the material objects around us by 
 the comparison of the impressions on our diflferent organs, and their 
 several parts, with one another. The abstract idea of space is a 
 further conception of the mind. 
 
 OF TOUCH. 
 
 This is the simplest and most rudimentary of all the special senses, 
 and maybe considered as an exalted form of common sensation, from 
 which it rises, by imperceptible gradations, to its state of highest 
 development in some particular parts. It has its seat in the whole of 
 the skin, and in certain mucous membranes, as that of the mouth, 
 
OF TOUCH— THE SKIN. 35'3 
 
 and is therefore the sense most generally diffused over the body. It 
 is also that which exists most extensively in the animal kmgdom ; 
 being, probably, never absent in any species. It is, besides, the 
 earliest called into operation, and the least complicated in its im- 
 pressions and mechanism. On these accounts it will be the first 
 treated of. 
 
 The nerves of touch are the same, or at least are derived from the 
 same part of the cerebro-spinal centre as those of common sensation. 
 They are the posterior roots of the spinal nerves, and some fibres of 
 the eighth and fifth encephalic nerves. The peripheral organ of touch 
 to which they are distributed is a tissue everywhere diffused over the 
 sentient surface, but which in most situations is elevated into papillae 
 more or less distinct from one another, and closely set, according to 
 the tactile power. The nerves of touch are remarkable for the 
 ganglia which are formed upon them on their emergence from the 
 vertebral canal, and for the subsequent admixture with most of them 
 of nerves of motion. In these respects they differ from those of the 
 other special senses, except taste, which ranks next to touch in the 
 ascending scale. 
 
 In accordance with our general plan, we shall commence with an 
 anatomical description of the skin, which is the principal seat of 
 touch ; and it will be convenient to include with it an account of the 
 various glands and appendages found in connection with this organ, 
 whether they have any relation to the sense in question or not. We 
 must premise, however, that this external integument is a part only 
 of a great physiological system, which comprehends also the mucous 
 membranes, and the true or secreting glands; all of which, taken 
 together, and reduced to their most simple expression, are a continuous 
 membrane, more or less involuted, more or less modified in the 
 elementary tissue which compose it or are in connection with it, and 
 within which all the rest of the animal is contained. This expanse 
 consists of two elements ; a hasement tissue composed of simple mem- 
 brane, uninterrupted, homogeneous, and transparent, covered by an 
 epithelium, or pavement, of nucleated particles. Underneath the 
 basement membrane vessels, nerves, and areolar tissue are placed 
 
 (P- 62). . / . 
 
 The sense of touch exists only in those regioris of this great sys- 
 tem which are exposed to the contact of foreign bodies, and where 
 it is essential to the comfort or preservation of the animal that the 
 presence and qualities of external objects , should be perceived. 
 These regions, however, demand a greater protection, for the same 
 reason ; and hence it happens that the development of this sense 
 is found to be generally accompanied with the most remarkable in- 
 crease and transformation of the epithelial element, and of the areolar 
 tissue lying under the basement membrane. In the skin the thick 
 and hard epithelium is termed cuticle or epidermis, and the dense and 
 altered areolar tissue constitutes by far the largest proportion of the 
 cutis derma, or cutis vera. 
 
 The external surface of the skin, formed by the cuticle, (which 
 everywhere adapts itself to the form of the surface on which it restsj) 
 
354 INNERVATION. 
 
 is marked by furrows of various kinds. Some of these (furrows of 
 motion) occupy the neighbourhood of joints, especially on the side of 
 flexion, and are generally transverse, facilitating the formation and 
 determining the position of the folds that result from the movements of 
 one segment of a limb or another. Others correspond to the insertion 
 of cutaneous muscles ; for example, many of those which give force 
 and character to the features; and these are much modified by the 
 quantity of subjacent fat. The elevator muscle of the lower lip thus 
 causes the " double chin," Furrows of another kind are seen in 
 aged and emaqiated persons, and after the subsidence of any great 
 distension of the integument, such as that occasioned by anasarca or 
 pregnancy. But, besides these coarser lines, almost every part of 
 the skin is grooved by numberless very minute furrows, which, in the 
 more highly developed regions, run in nearly parallel curved lines, 
 and elsewhere assume a stellated arrangement, or from a close inter- 
 lacement of no regular figure. Those lines are important, as they 
 depend upon peculiarities in the texture of the skin, having particular 
 relation to the sense of touch : they may be best studied on the palmar 
 aspect of the hand and fingers, and on the sole of the foot. The 
 outer surface of the skin likewise presents innumerable pores, the 
 orifices of the sebaceous follicles and sudoriferous ducts; and the 
 various modifications of the epidermis, termed " appendages of the 
 skin," as hairs, nails, &c., all project on the same aspect. 
 
 The deep sy,rface of the skin is formed by the cutis, or cutis vera, 
 and is attached to the parts which it invests by an extension of the 
 areolar tissue, of which it is itself principally composed, as well as 
 by vessels, nerves, and sometimes muscular fibres, passing into its 
 substance from the subjacent region. It is on this surface that the 
 sweat-glands rest; they are imbedded in it more or less deeply, ac- 
 cording to their size, and the length of their excreting ducts ; and 
 together with the fatty pellets, so abundant in most parts of the siib^ 
 cutaneous fascia, occasion that areolar or cribriform appearance which 
 is seen on this aspect of a cleanly dissected portion of integument. 
 In preparing such a specimen, it is at once made evident, however 
 great the diflTerence may seem to be between the dense and closely 
 woven texture of the cutis and the lax fascia to which it owes its 
 mobility on subjacent organs, that these tissues blend insensibly to ■ 
 gether, and are not separated from one another by any abrupt limit. 
 Their ultimate texture is, indeed, essentially the same. Hence the 
 boundary we assign to the skin in this direction is in some measure 
 artificial. Its precise nature will be seen by considering the 
 
 Intimate structure of the Cutis. — The white and yellow fibrous 
 elements of the areolar tissue are both much modified, to constitute 
 the framework of this layer; and in different parts of the skin, as 
 might be expected, they exist in different proportions, and in some 
 variety of arrangement. These varieties are not yet made out in 
 all their particulars ; but we believe we may state in general, that, 
 where great extensibility, with elasticity, is required, the elastic ele- 
 ment predomipates (as in the skin of the axilla) ; and that where, 
 on the contrary, resistance is demanded, the cutis is chiefly compose^ 
 
THE CUTIS. 355 
 
 of a dense interweaving of the inelastic white element (as in the sold 
 of the foot). But in all situations the meshes are very close, and the 
 quantity of the mixed fibrous tissues very great, as compared with 
 almost any other part of the body (pp. 86 — 8). 
 
 The fibres of the yellow element take a generally horizontal course, 
 and lie in multiplied series over one another, branching at very fre- 
 quent intervals, to join those above, below, and on either side. The 
 resulting meshes are open on all sides, but are most flattened in a 
 direction parallel with the general surface. They are more or less 
 lozenge-shaped, and vary in size not only with the region of the skin 
 in which they are examined, but according to their immediate relation! 
 W'ith the sudorific ducts, and of other cutaneous appendages which 
 traverse them. This element of the cutis can be easily studied on 
 thin vertical slices, moistened with acetic acid, which acts on other 
 parts, leaving it entire, and, as it were, isolated. (Fig. 77.) 
 
 The thick and abundant fibres of 
 the white element twine in great pro- Fig- 77. 
 
 fusion among the interstices just 
 described, but what their precise 
 attachments are it is difficult to de- 
 termine. They accompany all the 
 larger vessels and nerves, and invest 
 the several small glands with a loose 
 capsule. 
 
 The gelatine, which may be ob- 
 tained in considerable quantity from 
 the skin> is derived from this latter 
 part of the cutis, and it is probably 
 
 *i: 1 . „i j_i* I, ■ _ ' •_ n Yellow fibrous element of the cutis of iho 
 
 this element also which is principally a3cilla.-Magnified 320 diameters. 
 
 concerned in the changes the skin 
 
 undergoes during the process of tanning. The varieties in the quali- 
 ties of diflerent skins for this purpose might be explained by a 
 Reference to those two varying elements of their fibrous framework. 
 In the museum of King's College is a specimen of excellent leather 
 tanned from the skin of Bishop, one of the murderers of the Italian 
 boy, who fell a victim to the infamous system of "Burking" many 
 years since. 
 
 Some anatomists have thought that the contractility of the skin, 
 manifested under the influence of cold, and even under certain emo- 
 tions, is due to the existence of peculiar fibres; and Gerber has very 
 recently figured what he considers to be such fibres. He describes 
 them as begirting the hair-bulbs. 
 
 There is a good reason for believing that these fibres, if they exist, 
 do not essentially differ from those of unstripied muscle; for in thd 
 dartos we have found the latter interminglfed with an abundant and 
 lax areolar tissue ; and the close resemblance between the contrac* 
 tion of the scrotal membrane and that of the skin has been generally 
 recognized. In fact, the dartos seems to be nothing more than a 
 modification of the dermoid and subdermoid tissue, of which the 
 principal peculiarities are the excess of this form of muscle, the la^jty 
 
356 INNERVATION. 
 
 of the meshes, and the absence of fat. It is probable, also, that the 
 phenomenon of "erection" of the nipple is due to the contraction of 
 similar fibres. [Cyclop, of Jinat. and Phys., vol. iii. p. 518.) 
 
 The thickness and strength of the cutis, or areolar framework of 
 the skin, differ greatly in different parts according to the amount of 
 resistance required against internal or external pressure. On the 
 hinder surface of the body it is denser than in front, and on the outer 
 than on the inner surfaces of the limbs. It is usually thin over the 
 flexures of the joints. It is particularly delicate on the eyelids, and 
 proportionately so in some other situations, where great mobility is 
 demanded. ' In regions which are most subject to external pressure, 
 as the soles of the feet, it is firmly united by very dense laminee, to 
 the subcutaneous fascia ; and the intervals between these are provided 
 ■with pellets of fat, forming a cushion, as an additional means of pro- 
 tection to the delicate organs it encloses and covers. 
 
 Among the lower animals we may notice numberless examples of 
 an analogous kind. One of the most striking is that of the great 
 whales, which, being liable to enormous pressure on the surface of 
 their bodies, from the medium in which they live, are provided with 
 a cutis of extraordinary toughness and density, as well as with a 
 growth of subcutaneous fat, called blubber, of prodigious thickness. 
 
 Fat occurs very generally in the subcutaneous areolar tissue, serving 
 as a soft bed on which the skin may rest, and giving roundness and 
 symmetry to the outline of the body. 
 
 It is on the exterior surface of the cutis that the tactile papillcB 
 are developed; and it is here to be remarked that there is no neces- 
 sary relation between the degree of their development, and of that 
 either of the dermoid framework which supports, or the cuticle which 
 covers them. It is true that in the palm and sole all these attain a 
 large size, but, in the back, the tactile organ is well-nigh absent, 
 though the cutis is dense; and in the tongue, on the contrary, this 
 organ is highly developed, while the areolar framework is nothing 
 more than a very thin expansion ; and the investment of cuticle is so 
 thin that the papilias form separate projections from the surface. On 
 the buccal surface of the lips and cheeks, too, the cuticle is compara- 
 tively thin. 
 
 In all parts of the cutaneous surface, as well as in some portions 
 of the internal mucous tracts, common sensation exists, attended with 
 a feeble discriminating power, which must be regarded as the lowest 
 condition of the sense oi touch ; but the organ peculiarly fitted for 
 receiving tactile impressions is concentrated in a very remarkable 
 manner in certain portions of the integument, which in other respects, 
 ■whether from the precise and varied movements they can perform, 
 or from their peculiar position, are the best adapted to be inlets of 
 this kind of sensation. The palmar surface of the hand and fingers, 
 or the sole of the foot, may be selected for description, as presenting 
 the most highly developed form of the organ of touch. 
 
 The integument in these regions is finely and regularly furrowed 
 by grooves^ separated from one another hy corresponding ridges. 
 
TACTILE PAPILLJE. 
 
 357 
 
 The direction of these grooves and ridges is various; they run in 
 sweeping curves, frequently branch to adapt themselves to the ine- 
 qualities of the general surface, and differ 
 somewhat in width and distinctness. 
 These lines indicate the arrangement and 
 development of the tactile organ below. 
 Each ridge is produced by a single or 
 double row of elongated conical processes, 
 termed papillse, projecting from the sur- 
 face of the cutis into the epidermis. The 
 grooves are occasioned by the epidermis 
 sinking in to occupy the intervals between 
 the rows of papillae. The papillae in each 
 row are usually arranged in pairs, the 
 intervals between which are indicated on 
 the outer surface by corresponding minute 
 and very shallow grooves, crossing the 
 tops of the ridges more or less at right 
 angles. Each pair of papillse thus occu- 
 pies a little division of the ridge. In the 
 centre of each cross line, between the 
 pairs of papillae, is observed the orifice 
 of a sweat-duct (shortly to be noticed), 
 which often is so large as to destroy the 
 linear character of the cross groove. In a square inch of the palm 
 
 Fig. 79. 
 
 Surface of the skin of the palm, 
 showing the ridees, furrows, cross 
 
 frooves, and orifices of the sweat- 
 ucls. The scaly texture of the cuti- 
 cle is indicated by the irregular lines 
 on the surface.— Magnified 20 diam. 
 
 Under surface of the'cnlicle. detached by maceration from tlie palm ; showing the dontle roufrS of 
 depressions in which ihe papilte have been lodged, with the hard epithejmm lin(ng the sudoriferous 
 doois in their course through the cutis Some of these are contorted at the end, whete they have 
 entered the sweat-gland.— Magnified 30 diamelBTB. 
 
358 INNERVATION. 
 
 xve may generally count rather more than forty rows of papilla, and 
 in each row rather more than sixty paii-s of them. 
 
 In the natural state the papilla are intimately united at all points of 
 their surface to the epidermis which invests thetii. By a slight mace- 
 ration this union may be so loosened that the two structures may be 
 readily separated from one another. In gradually tearing off the epi- 
 dermis, the foregoing account of the arrangement of the papillae may 
 be fully verified with the aid of a pocket lens. They are seen to 
 form a close pile on the surface of the chorion, each one being lodged 
 in a separate cavity in the deep surface of the cuticle. The papilla 
 are not equal in size, but frequently a small one is joined with a large 
 one : and the clefts left between them, by the removal of the epidermis, 
 are unequal likewise ; those between the rows being deepest, and 
 those between the individuals of a pair being commonly shallower 
 than those between the pairs. This subordination corresponds (though 
 not accurately in degree) with that of the grooves on the outer surface 
 of the cuticle, where the shallow intervals between the individuals 
 
 of a pair are not even visible 
 Pig- 80. at all, being lost by the thick- 
 
 ^ -v« -3 ness of the superimposed sub" 
 
 .*^ • ^ ■*'^%^''*?* f* stance. Such is the exactness 
 
 ■-.*• •^ 1*^!^^^ * of ^^^ impression or mould of 
 
 i i w. '' 1 ^^^ papillary structure which 
 
 * V *'] the under surface of the epi- 
 
 * i»* ^ - dermis presents, that it fur 
 
 ^ ilk « nishes an excellent test of the 
 
 
 A ■» M^ , ^ amount and complication of 
 yg * t* ^ jt'T) the former structure in dif- 
 
 ^ * '^^ jj^ ferent regions of the skin. 
 
 ^ ing figs. 79 and 80 ; the latter 
 
 Under-Burtaoe of the cuticle, from the leg:— o. of which, taken frOm the CU- 
 Small creases or furrows. 6. Shallow depressions for , . . /• ^Z \ 1 ti- 
 the papillary structure, c. Epithelium of sudoriferous ticle ot the leg, represents the 
 duc«, corresponding to those in fig. 79.-Magn. 30 ghaHo^ depressions intO which 
 
 the few dwarf papillary eleva- 
 tions of the cutis in that part have been received. The gradations 
 of size in the papillary structure can be everywhere admirably traced 
 in this way ; and will be found to correspond accurately with the ac- 
 count of the relative acuteness of the sense of touch in different 
 parts, deduced from experiments, which will be subsequently given. 
 The papilla are of an average length, in man, of tttt of an inch ; 
 at their base, where they spring from the cutis, they measure about 
 aj7 of an inch in diameter, and they taper off to a slightly rounded 
 •point. They are semi-transparent and flexible ; but suflficiently firm 
 in texture to resist maceration long, and not readily to admit of being 
 detached from the cutis. Viewed, when fresh, with a high microscopic 
 power, their outline is definite and sharp, and there is good t-eason to 
 suppose it formed of an unbroken expansion of the homogeneous 
 basement membrane already spoken of. Within this it is difficult to 
 distinguish any special tissue, except by artificial modes of prepara- 
 
TACTILE PAPILLAE. 
 
 359 
 
 Papillee of the palm, the cuticle 
 being detached.— Magnified 35 
 diameters. 
 
 Fig. 83. 
 
 tion. A fibrpus structure, however, is ap- ^'S- 81. 
 
 parent, having a more or less vertical ar- 
 rangement: and with the help of solution of 
 potass, filaments of extreme delicacy, which 
 seem to be of the elastic kind, are generally 
 discoverable in it. Injection of the blood- 
 vessels demonstrates the existence of a small 
 arterial twig derived from the arterial plexus 
 of the cutis, entering at the base, advancing 
 up the interior of the papilla, and subdi- 
 viding into two or more capillary vessels, according to the size of the 
 particular prgan. These, after forming small loops, reunite either at 
 the base of the papilla, or in the subjacent texture, into small veins, 
 which empty their blood into the venous plexus of the cutis. The 
 capillaries of the smaller papillee frequently join with those of the fat- 
 vesicles that lie beneath. The vascularity of the papillse is such, that 
 their presence and relative size may be 
 determined simply by the depth of the 
 colour imparted to a portion of skin by a 
 good injection of its vessels. The vascu- 
 larity of the integument is therefore, in 
 general terms, proportioned to its perfection 
 as an organ of touch. 
 
 Since the discovery of the papillae as 
 the sentient organs, the existence of nerves 
 within them has been usually taken for 
 granted, or they have been loosely styled 
 expansions of the nerves; and to the gene- 
 ral truth of such statements we may readily 
 assent. But we have reason to doubt the 
 accuracy of some recent writers, who have professed to give minute 
 details of the mode of termination of thp nervous tubules in the 
 papillee. The subject is difficult of investigation. According to 
 Ernst Burdach (jBeitrag zur Mikroskop. Anat. der JiTerven: Konigsb. 
 1837), and others, the nerves are arranged in a plexiforra manner 
 under the skin of the frog, and loops are formed by the union of 
 tubules from neighbouring branches. On examination we find this 
 description correct as far as it goes, but that it does not carry us to the 
 papillary structure. The plexus in question is situated underneath 
 an expansion of fibres crossing each other at right angles, which is 
 itself placed beneath the true skin, and separable from it ; and we 
 have observed single tubules from the plexus penetrating this expan- 
 sion in their course to the skin. They have then been lost to view. 
 We have hardly been more fortunate in discovering the true termina- 
 tion of the nerves in the nictitating membrane of the eye in the same 
 animal, or in the papillary tissue so largely developed on the thumb 
 at a certain season. 
 
 In our attempts to follow the nerves for any distance under the 
 papillary structure in the higher animals, the fibrous tissue (and espe^ 
 cially the elastic variety), forcning the cutis, has been found so much 
 
 Vessels.of papillEB, from the heel : 
 — a. Terminal aiterial twig. «. Com- 
 mencing vein.— Magnified SO dia- 
 meters. 
 
360 
 
 INNERVATION. 
 
 Fig. 83. 
 
 to impede the view, that no satisfactory conclusion has been arrived 
 at. In regard to their presence in the papiiias themselves, we can 
 affirm that we have distinctly traced solitary tubules ascending among 
 the other tissues of the papillae about half-way to their summits, but 
 then becoming lost to sight, either by simply 
 ending, or else by losing the white substance 
 of Schwann, which alone enables us to dis- 
 tinguish them in such situations from other 
 textures. Thin vertical sections of perfectly 
 fresh specimens are essential for this investi- 
 gation, and the observer should try upon 
 them the several effects of acetic acid and 
 solution of potass. In thus describing the 
 nerves of the papillae from our own observa- 
 tions, we do not deny the existence of true 
 loop-like terminations as figured by so re- 
 spectable an authority as Gerber, {General 
 Anatomy, translated by Gulliver,) but nei- ' 
 ther do we feel entitled to assent to it. We 
 have in numerous instances failed to detect 
 any nerves at all within the papillae, when 
 such were plainly visible at their base, and 
 when, consequently, the chemical agfint 
 employed could scarcely have destroyed 
 their characteristic structure, had they been 
 present. We incline to the belief that the 
 tubules either entirely or in a great measure 
 lose the white substance when within the 
 papillae. We would, however, refer the 
 reader to what will be found respecting the 
 nerves of the papillae of the tongue in the 
 chapter on taste. 
 
 The essential tissue of the papillae pro- 
 bably exists even where no projections large 
 enough to be called papillae are present. 
 These portions of the skin are more scantily 
 supplied with nerves ; and it is probable 
 from this circumstance, as well as from ex- 
 periments afterwards to be detailed, that the 
 individual nervous tubules are wider asun- 
 der, and occupy each a more extensive 
 surface than in parts thickly set with pa- 
 pillae. 
 
 The cuticle, or epidermis, (fig. 83, a,) like 
 the cutis, varies greatly in its thickness. 
 As its chief use is that of affording protection, it attains most density 
 on parts most exposed to pressure and friction, as the soles of the 
 feet and the palms of the hands. In the same parts, too, it varies 
 with the amount of pressure to which it is subjected at different times; 
 whence the hard hands of the artizan, compared with those of persons 
 
 Vertical section of the sole :— a. 
 Culiele f the deep layers (rete mu- 
 eosum) more coloured than the up- 
 per, and their particles rounded; 
 the superficial :layers more and 
 more scaly. 6. Papillary structure. 
 c. Cutis, d. Sweat-gland, lying in 
 a eavity on the deep surface of the 
 skin, and imbedded in globilles of 
 fm. Its duct is seen passing to the- 
 gurfa^e. — JVlagnitied 4U diameters. 
 
STRUCTURE OF THE CUTICLE. 
 
 361 
 
 Fig. 84. 
 
 •who have spent their time in gentler occupations. This increase in 
 thickness probably results frOm the mechanical stimulus applied to 
 the capillaries of the part. But, in ■whatever manner it may admit 
 of explanation, there is scarcely a more striking instance of that in- 
 herent power which the body possesses of adapting itself to varied 
 external circumstances, than this one presented by the human cuticle. 
 
 This investment is not permeated by either vessels or nerves, but 
 consists solely of a congeries of nucleated particles, arranged in 
 numerous superimposed laminae, and united together by an interven- 
 ing substance in very small quantity. Those particles that lie deep- 
 est, and rest immediately on the cutis, are little more than small 
 granules, scattered in a homogeneous matrix, which serves to unite 
 them together. Those of the next layers are rounded cells, consist- 
 ing of a transparent membrane, in which similar granules, but some- 
 what larger in size, are visible. In the succeeding layers these cells 
 are more and more compressed as 
 they are nearer to the surface ; and 
 on the surface they are so flatten- 
 ed, that their opposite surfaces are 
 in contact, and adhere, forming 
 mere scales, in which the nucleus 
 remains. The diameter of the 
 deep particles is about a^oW inch, 
 and of the superficial ones j-^ 
 inch. 
 
 We know that the superficial 
 scales are being continually shed 
 in small lamelliform masses, and 
 it is evident that their loss is 
 supplied from below ; hence new 
 particles must be constantly pro- 
 duced in the deepest layers, and 
 must be in uninterrupted advance, 
 through a series of changes, till 
 they are cast off from the surface.* 
 These changes are not confined to 
 their figure ; the laminae they first 
 form are moist, and coraparativelj 
 soft, and rest like a cushion on the 
 highly sensitive surface to which 
 they are adapted, and whose ves- 
 sels supply the materials for their 
 development. The more external 
 ones are hard, horny, and much 
 drier. Schwann has also pointed out that their chemical properties be- 
 
 • The cuticle of reptiles and amphibia is periodically cast off in a more or less 
 entire state, a new one being previously formed beneath it. In amphibia the epider- 
 mis is tesselated ; the scales adhering; to one another by their edges, and being usually 
 pentagonal. A similar ecdysis, or shedding, occurs in the larva state of insects, aad 
 in the arachnidans. ' 
 
 A. Section of the slcin of Ihe heel, treated wllh 
 weak solution of poiass ; — a. Basement mem- ' 
 brane of papilla, b. Layer of nucleated cells 
 resting on. the basement membrane, c. Several 
 succeeding layers, partially dissolved and Iheii 
 nuclei gone. d. Higher layers, not affected l)y 
 the menstruum. «. Elastic fibrous tissue of tho 
 papilla. V. Its capillary vessel. 
 
 B. A similar specimen, treated with strong 
 solution of potass :— o, e, and «, as in A. The 
 layer b is wanting, having been displayed, r. 
 Converted into a gelatinous mass with strise. d. 
 Unaffected. 
 
 The more external layers of the epidermic 
 scales are not represented in these ^gures. — 
 Magn. 150 diam. 
 
362 INNERVATION. 
 
 came modified ; that at first they are soluble, but afterwards insoluble, 
 in acetic acid ; and this circumstance of a chemical change occurring in 
 the stages of their development seems to us so important that we shall 
 illustrate it by two views, fig. 84, a and b. In the former the action 
 of weak solution of potass is shown : the layer of cells immediately 
 resting on the basement membrane, together with the more super- 
 ficial scales, is but slightly or not at all dissolved ; while several inter- 
 mediate layers are swollen and rendered very transparent, having lost 
 their nuclei. The abruptness of the change is remarkable, and con- 
 tinues after the whole specimen is saturated. In the latter figure a 
 stronger solution has been employed ; the deep layer is dissolved, but 
 the superficial scales are still unaffected, while the intermediate part is 
 reduced to a semi-fluid mass, in which scarcely any vestige of struc- 
 ture remains. It is very possible that other agents might disclose 
 further varieties of chemical constitution in smaller subdivisions of 
 the cuticular lamellse. 
 
 These facts will go far to explain why it happens that the union 
 between the particles composing the same layer is in general more 
 intimate than that between different layers, so that it is not difficult 
 to divide the cuticle into two, three, or more laminae ; and, in parti- 
 cular, why it is easy, at a certain stage of maceration, to separate the 
 harder from the softer layers, and thus to isolate the structure termed 
 " rete Malpighii." This is nothing more than the deepest, or most 
 recently formed, part of the cuticle. When isolated, it presents de- 
 pressions, or sometimes complete apertures, which have been occupied 
 by the projecting papillae; and hence the term rete. When apertures 
 exist, the cuticle on the top of the papillae has been detached with the 
 outer hard layer, and that in contact with and encircling their bases 
 remains by itself. 
 
 In the coloured races of mankind, there is, at first sight, some 
 ground for supposing the rete Malpighii to be a structure distinct 
 from the other layers of the cuticle, the colouring matter being found 
 to reside chiefly in this part. However various in quantity and hue, 
 the colouring matter always consists of oblong or oval grains of ex- 
 treme minuteness, (-joioTr of an inch in their long diameter,) and 
 'occupying the interior of some of the epidermic particles. In the 
 
 negro it is accumulated in enormous quan- 
 F'g-SS. tity, and completely envelops the nuclei, 
 
 immediately resting on the cutis. On ex- 
 amining a vertical section of the whole 
 cuticle, we find the colouring matter gra- 
 dually diminishing as we approach the 
 surface ; and it is most clear that there is. 
 Vertical section of tiie cuticle, "o truc line of demarkation between the 
 dTp «iil"oad™d°wr.h";^em: two portions. We may observe the colour 
 s. Cells at a higiier level, paler and of the rctc mucosum deeper at poluts : and 
 
 more flattened, c Cells at the sur- ^ • , i i /. i • 
 
 face, scaly and colourless ax in the a greater proportionate depth 01 colour is 
 white races-Magnified 300 diame. traceable over such points, through all the 
 
 layers, as far as the surface: we may even 
 discern a sort of stream of coloured grains advancing towards the 
 surface. Hence there can be little doubt that the decrease of colour 
 
NAILS AND HAIRS. 363 
 
 In the superficial laminffl is due to that chemical change which has 
 just been described as gradually taking place in the interior of the 
 epidermic particles. As it is not always easy in this country to obtain 
 specimens of the negro's skin, the above facts may be verified in the 
 skin of coloured domestic animals, or, less satisfactorily, in that of 
 some portions of the skin of the white race, as that of the scrotum, 
 of the hippie during pregnancy; or of accidental moles, or freckles.* 
 The bronzing of parts exposed to the sun is effected by a similar 
 deposit of colouring matter in the deeper laminae of the cuticle. 
 
 The subject here referred to has been invested with additional 
 interest by its supposed bearing on the warmly debated question of 
 the specific difference of the negro from the white man. We need 
 not inquire how far the existence of a distinct cuticular lamina might 
 avail the advocates of such a difference, for we may freely state our 
 conviction that no such peculiar layer exists. The sole variety is in 
 the presence of pigment — which may occur, partially, under many 
 circumstances in the white races, and may be wanting in the true 
 negro. {See Dr. Prichard, JVatural History of Man.) The reader of 
 the preceding paragraphs will understand how little such processes as 
 maceration, and even the most delicate dissection by the naked eye, 
 and with ordinary instruments, are to be depended on for the deter- 
 mination simply of the anatomical fact. 
 
 The nails and hairs are peculiar modifications of the epidermis, and 
 consist essentially of nucleated particles. 
 
 The nails are flattened, elastic, horny, Fig. 86. 
 
 protective coverings, placed on the dorsal, 
 surface of the terminal phalanges of the 
 hands and feet, and projecting beyond the 
 flesh. Hoofs, claws, &c., are varieties 
 of them. The nail has a root, or part 
 concealed within a fold of the cutis ; a 
 body, or exposed part attached to the sur- 
 face of the cutis ; and a free or projecting 
 vdge. The cutis underneath the root and 
 body is termed the matrix, from its being 
 the producing organ of the nail. This is section of the sWn on the end of 
 
 ,, . 1 1 1 • I 1 1 J 'i 1 the finerer: — ^The cuticle and nail n. 
 
 thick and highly vascular, and its colour detached from the cutis and matrix,™. 
 
 is seen through the transparent tissue. 
 
 Near the root it is white, and occasions the appearance termed lunula. 
 The nail has a firm adhesion to the matrix, and is moulded upon it, 
 like the epidermis in other situations. The true epidermis (as dis- 
 tinguished from the nail), is continuous with the nail at the whole 
 circumference of its body ; the root dips into the fold of cutis, within 
 the epidermis, and the free edge projects beyond it. In the advanced 
 foetus we find the edge of the nail to be directly continuous with the 
 epidermis of the end of the finger, and only to become free by a 
 rupture of this connection after birth. Thus the nail covers that 
 portion of cutis which is without cuticle. It has been frequently 
 discussed whether the cuticle is continued over and under the nail ; 
 
 • Dr. Simon of Berlin has ably investigaled this part of the subject.— Muller's 
 Arohiv. 1840. 
 
364 
 
 INNERVATION. 
 
 but this is a question of words only, the nail being the same essential 
 structure as the cuticle. The border of the root of the nail is jagged, 
 thin, and soft, and consists of newly formed substances ; the deep 
 surface of the body is also soft, and marked by longitudinal grooves, 
 corresponding to the papillary ridges on the surface of the matrix. 
 These vsoft under-parts consist of nucleated particles, similar to those 
 of the deep layers of the epidermis. The m^re superficial lamince of 
 the nail are more and more dense and fibrous; but when treated with 
 acetic acid, some imperfect traces of nuclei may still be detected in 
 them. The nail grows both at the root and on the deep surface of 
 the body; as the substance furnished by the root advances towards 
 the free edge, it receives accessions from the surface of the matrix. 
 
 Hairs are found on all parts of the surface, except the palms of the 
 hands and the soles of the feet, and differ much in length, thickness, 
 shape, and colour, according to situation, age, sex, family, or race. 
 We may select one of average size for a description of their structure 
 
 and mode of growth. The shaft of the 
 hair is that part which is fully formed, and 
 which projects beyond the surface. Trac- 
 ing this into the skin, we find it lodged in 
 a follicular involution of the basement mem- 
 brane (fig. 87, a), which usually passes 
 through the cutis into the subcutaneous 
 areolar tissue. This hair-follicle is bulbous 
 at its deepest part, like the hair which it 
 contains. Its sides have a cuticular lining, 
 
 b, continuous with the epidermis, and re- 
 sembling the cuticle in the rounded form 
 of its deep cells, and the scaly character 
 of the more superficial ones, which are 
 here in contact with the outside of the hair, 
 
 c. The hair grows from the bottom of the 
 follicle, and the cells of the deepest stra- 
 tum there resting on the basement mem- 
 brane are very similar to those which in 
 other parts are transformed into scales of 
 cuticle. A gradual enlargement occurs in 
 these cells as they mount in the soft bulb 
 of the hair, which, indeed, owes its size to 
 this circumstance. If the hair is to be 
 coloured, the pigment grains are also here 
 developed — for the most part in scattered 
 cells, which may send out radiating pro- 
 cesses — at other times, in a diffused man- 
 ner around the nuclei of the cells generally. 
 
 andtiie' wb MnseguemiVtWckefl It frequently happens that the cells in the 
 lJ;r„Von&'K"or'i:AlS a^ls of the bulk become loaded with pig- 
 »n;'^; ■It'PV* * they assume a do- ment at One period, and not at another ; so 
 
 cidedly nbrouB character, and be- , ^ * ' i • ji i /v 
 
 coHte condeined. «. A maesof oeiin that, as they pass upwards in the shait, a 
 wilhpigmlnl""' "'''' '""' """"^ dark central tract is produced of greater or 
 
 Bulb of a small blauk Tiair, from 
 the scrotum, seen in section, a. 
 Basement merabTane of the follicle. 
 fc. Layer of epidermic cells resting 
 upon it, and becoming more scaty 
 as they approach c, a layer of im- 
 bricated cells, forming the outer 
 lamina, or cortex, of the hair. These 
 imbricated cettB are seen more flat- 
 tened and compressed, the higher 
 they are traced on 'he bulb. Within 
 the cortex is the proper substance 
 of the hair, consisting at the base, 
 where it rests on the basement 
 membrane, of small angular cells 
 «carcely larger than their nucle' 
 
STRUCTURE OF HAIR. 
 
 365 
 
 Fig. 88. 
 
 less length, often only in irregular patches, and the hair appears here 
 and there to be tubular, e. The shaft is much narrower than the bulb, 
 and is produced by the rather abrupt condensation and elongation into 
 hard fibres of the cells, both of those which contain pigment and 
 those which do not. These fibres may be demonstrated by simply 
 crushing small fragments of hair, but they become more conspicuous 
 when the tissue is softened by a strong acid. The granules of pigment 
 assume a linear arrangement between the fibres, which are firmly 
 united into a solid rod by a material similar, it may be supposed, to 
 that which cements the scales of the cuticle. 
 
 The central series of cells just mentioned, when filled with pigment, 
 seems less disposed to become fibrous than those around ; and some 
 authors have described it as a medulla, 
 in distinction from the fibrous part of 
 the shaft, which they then term cortex. 
 But the tubular character, however 
 constant in the hair of many animals, 
 is very variable in human hair, both in 
 diflferent situations, and in the same 
 hair at different points of its length, 
 as may be seen very well by means of 
 transverse sections (fig. 88, a, 6).* 
 
 The human hair has a proper bark, 
 or cortex, formed in the following way. 
 A single layer of the cells immediately 
 surrounding those about to form the 
 fibrous tissue of the shaft are seen near 
 the bottom of the follicle to assume an 
 imbricated arrangement (fig. 87. c), 
 and gradually to mount on the hair, 
 becoming more compressed against it 
 in their ascent, until they form upon 
 its surface a thin transparent colour- 
 less film, in which the overlapping of fibrois tissue wuh its soanered pigment, 
 , ' . 1 T • 1 u ^ ^ central space filled with pigment. 
 
 the delicate cells is still exhibited by l. a. similar seotiori of a; hair, at a point 
 
 elegant and exceedingly fine sinuous 
 cross lines (fig. 88, d, d'). The fibrous 
 interior and this peculiar cortex to- 
 gether compose the shaft of the hair. 
 By the continual emergence of fresh 
 portions of the shaft from the follicle, 
 fragments of the cuticular lining of the latter are apt to be drawn up 
 
 I 
 
 a. Transverse , section of a hair of the 
 head, shovring tHe exterior cortex, the 
 
 where no aggregation of pigment in the 
 axis exists, c. Longitudinal section, with- 
 out a central cavity, showing the imbrica- 
 tion of the cortex, and the arrangement of 
 the pigment in the fibrous part. d. Sur- 
 face, snowing the sinuous transverse lines 
 formed by the edges of the cortical scales. 
 d' . A portion of the margin, showing their 
 imbrication. Magh. 150 diam. 
 
 » Transverse sections of extreme thinness may be made by fixing a lock of hair 
 between two pieces of card or wood in a vice, and then shaving it with a razor. In 
 many animals, as the horse and dog. the hairs are tubular. In others they present a 
 central series of ceils, round or compressed, with or without pigment,'as in the cat 
 and mouse. In others, again, their external surface is regularly marked by annular, 
 and sometimes toothed projections, as in the Indian bat: and numerous other varieties 
 might be enumerated. The quills of the porcupine, and the feathers of birds, are 
 modifications of the epidermic tissue, and, in their essential characters, are closely 
 allied to hairs. See Busk, in Microsc. Journal ^ 
 
366 INNERVATION. 
 
 upon the hair, aided, probably, in this, by the imbrication of its sur- 
 face, and are often found clinging around it for some way ; but they 
 are not to be regarded as any part of the hair itself. 
 
 In the larger hairs there is usually a double series of these imbri- 
 cated cortical scales; the outer having its teeth interlocked ■with those 
 of the inner, but apparently but loosely adherent to them. This 
 outer series seems to be intermediate between the true cortex and the 
 cuticle of the follicle, and to belong rather to the latter, since it does 
 not appear upon the extended portion of the hair. The cortex is 
 much denser than even the fibrous part of the hair, and is less acted 
 upon by strong solution of potass. 
 
 From the preceding description it will be evident that the fibrous 
 pj^rt of the hair is a peculiar development of the cuticular cells 
 resting on the bottom of the follicle, that the imbricated cortex is 
 formed by a single series differently developed at the circumference 
 of these, and that beyond this series comes the cuticular lining of the 
 follicle ; so that the hair is neither covered nor underlaid by cuticle, 
 but it is in fact the modified cuticle of the bottom of the follicle. A 
 thin layer of papillary tissue probably coats the bottom of the follicle 
 in most cases ; and where the hairs are large, and especially where 
 they serve principally as tactile organs, there may be a projection of 
 a true papilla, furnished with nerves and capillaries, into the bulb of 
 the hair, as is very conspicuous in the whiskers of some animals and 
 in the quills of the porcupine An approach to this papillary pro- 
 jection may be frequently seen in the hairs of man; but its real size 
 appears to have been much overrated, from the basement membrane 
 having been overlooked. Where a papilla exists, the basement mem- 
 brane is of course continued over it, and separates it from the true 
 hair, which is never penetrated by either vessels or nerves. 
 
 The sebaceous glands of the skin very generally open into the hair 
 follicles at a short distance from the surface. 
 
 The hair follicle is fixed more or less firmly in its place, according 
 to the size and stiffness of the hair, by the dermoid and subderraoid 
 tissues uniting intimately with it on its deep or convex surface, where 
 also are spread out the capillary vessels which furnish the materials 
 of growth. These latter are adapted in number to the dimensions 
 of the follicle. 
 
 Thus the hairs, like the cuticle, are beautifully organized, and 
 maintain a vital, though not a vascular, connection with the body. 
 Some evidence of their retaining a degree of vitality is found in thei 
 fact, first pointed out by Mandl, and verified in some instances by 
 ourselves, that hairs have a tendency to become pointed after having 
 been cut short off. The process is very slow, and seems to consist 
 in a further condensation and elongation of the elementary cells at 
 the new extremity. 
 
 Well-authenticated instances have occurred, in which the hair has 
 grown white in a single night, from the sudden influence of some 
 depressing passion ; and some have held this circumstance a proof 
 that fluids circulate through thera. It seems most probable that this 
 phenomenon results from the secretion, at the bulb, of some fluid-r- 
 
LYMPHATICS OF THE SKIN. 367 
 
 perhaps an acid, as Vauquelin supposes — which percolates the tissue 
 of the hair, and chemically destroys the colouring matter. The 
 ordinary gray hairs of age resemble other hairs in every respect but 
 colour, and the process of change from dark to gray seems to take 
 place rapidly ih each individual hair. 
 
 According to Vauquelin, the colour of hair depends on the pre- 
 sence of a peculiar oil, which is of a sepia tint in dark hair, blood- 
 red in red hair, and yellowish in fair hair. When extracted, as it 
 may be by alcohol or aether, the hair is left of a grayish yellow. The 
 colour is destroyed by chlorine, and probably otherwise resembles 
 closely that of the cuticle in the dark races. The substance of hairs 
 is similar in chemical composition to that of horn. After being 
 softened by maceration in cold nitric acid, it is , soluble in boiling 
 water, and the solution after evaporation becomes a gelatinous mass 
 on cooling. The horny matter is said to be distinguishable from 
 coagulated albumen or fibrine by its being readily soluble in caustic 
 fixed alkalies, but not in caustic ammonia. The ashes of hair amount, 
 according to Vauquelin, to one and a half per cent, of its weight ; 
 and contain oxide of iron, a trace of oxide of manganese, of sulphate, 
 phosphate, and carbonate of lime, and of silica. Black hair contains 
 most iron, and light hair least. {Baly^s Muller, p. 424-5, quoted 
 from Berzelius.) 
 
 Hairs, when dry and warm, are easily rendered electrical. They 
 readily attract moisture from the atmosphere, and no doubt from the 
 body also, yielding it again by evaporation, if the air be dry. When 
 moist, they elongate considerably ; a property which Sau'ssure took 
 advantage of in the construction of his hygrometer, in which a human 
 hair, by its elongation and shortening in moisture and dryness, is made 
 to turn a delicate index. 
 
 The shape of the hairs in different situations offers some variety. 
 In general they taper towards their free end. Those of the head are 
 often not cylindrical, but compressed on one or both sides, so that 
 their transverse section is reniform or oval. The eyebrows and eye- 
 lashes taper towards both extremities. Hairs also vary in being lank 
 or woolly, permanent or deciduous. The frizzled hair of the negro 
 is one of his most remarka;ble characteristics, but has all the essential 
 structural characters of the hairs of the other races. 
 
 The diseased condition called plica Polonica is a matting together 
 of the hairs from the effusion of a glutinous mattel- probably from the 
 cutaneous glands. It is said that hairs so affected bleed, if cut close to 
 the skin. This, if true, may result from a morbid elongation of the 
 vascular papillae at their roots. In the whiskers of large animals 
 these papillae are so long that they are cut and bleed if the whiskers 
 are shaved off. 
 
 In some regions of the skin it appears certain that a lymphatic net- 
 work exists immediately under the surface of the cutis, probably 
 under its basement membrane. Mercury injected into this network 
 through a puncture in the cuticle passes readily into the neigbour- 
 ing lymphatic trunks, and removal of the cuticle does not injure its 
 meshes. These circumstances may be observed in the penis, scro- 
 
368 
 
 INNERVATION. 
 
 Fig. 89. 
 
 turn, and nipple ; but it is probable that the network sometimes ex- 
 hibited by this procedure in other parts of the skin, is a fallacious 
 appearance due to the mercury having insinuated itself between the 
 cutis and cuticle, in the furrows at the base of the papillary structure ; 
 for it does not find its way into the lymphatic trunks, aud is deranged 
 by a complete separation of the cuticle. [Cycl. of Anat, and Phys.; 
 art. Lacteal and Lymphatic System: by Mr. Lane.) 
 
 The sweat-glands exist under almost every part of the cutaneous 
 surface. They lie in small pits (fig. 83, d) on the deep aspect of 
 the cutis ; or, if large, entirely in the subcutaneous fascia. As before 
 mentioned, their orifices are discernible in the middle of the cross 
 grooves that intersect the ridges of papillae on the hands and feet. 
 Here their arrangement is necessarily regular, 
 and their size is about that of a pin's head. 
 But in other parts they are irregularly scat- 
 tered, though in general in pretty equal num- 
 bers over areas of the same dimensions. In 
 certain situations, however, they are very 
 'large; and, as might be expected, we find 
 their size and number in different districts of 
 the skin to correspond with the amount of 
 perspiration afforded by each. Thus, they 
 are nowhere so remarkakle, or so easily ex- 
 amined, as in the axilla, over a space pre- 
 cisely defined by the growth of the hair in the adult. They here 
 form a layer, which towards the middle, is often an eighth of an inch 
 
 thick, but thinner towards the edge. 
 It is of a reddish colour, and mam- 
 millated by the individual glands 
 which compose it. Some of these 
 are as large as the labial glands, 
 but most of them are somewhat 
 smaller. They are soft, and more 
 or less flattened by lateral apposi- 
 tion with one another. They lie in 
 an atmosphere of delicate areolar 
 tissue, and are covered and per- 
 meated with a network of capillary 
 blood-vessels. 
 
 The sweat-glands can be shown, 
 wherever they exist, by dissecting 
 a piece of fresh integument on its 
 deep surface. They are distin- 
 guishable from the pellets of fat, 
 with which they have doubtless 
 been repeatedly confounded, by 
 their pink colour semi-transparent 
 texture. Where the areolar frame- 
 work of the cutis is densely inter 
 woven, they are less readily discerned, but injection of the blood- 
 
 Vertical sectiou of the skin 
 and sweat-glands of the axilla; 
 — a. Layer of glands with their 
 ducts traversing b, the cutis and 
 cuticle, c. Small hair, df d. 
 Portions of larger hairs. — 
 Magn. one and a half diam. 
 
 Fig. 90. 
 
 
 Sweat-gland and the commencement of its 
 duct :— a. Venous radicles on the wall of the 
 cell in which the gland rests. This vein anas- 
 tomoses with others in the vicinity. 6. Capilla- 
 ries of the gland separately represented, ariBing 
 from their arteries, which also anastomose. 
 The blood-yeasela are all situated on the outside 
 or deep surface of the tube, in contact with the 
 baaement<ineinbrane.— Magi). 35 diam, 
 
THE SWEAT GLANDS. 
 
 369 
 
 vessels makes their detection easy. On detaching one of these glands, 
 and highly, magnifying it, it is seen to consist of a solitary tube intri- 
 cately ravelled, one end of which is closed, and usually buried within 
 the gland ; the other emerges 
 
 from the gland, and opens on the .^'S- si- 
 
 skin. Sometimes this tube is 
 branched, but its diameter ,is 
 usually very uniform from end 
 to end. When very long, the 
 open end fpnning the duct is a 
 little wider than the rest. The 
 wall is comparatively thick, so 
 that the calibre is not more than 
 a third of the whole diameter. 
 It consists, like the correspond- 
 ing part of most other glands, of 
 two layers : an outer or basement 
 membrane, with which the ves- 
 sels are in contact; and &n epi- 
 thelium, lining the interior. The 
 basement membrane is extremely 
 thin, and is continuous with the 
 outer surface of the papillae. The 
 epithelium is much thicker, and 
 is an involution of the epidermis 
 that rests on th{e papillae and 
 dips in between them. Hence 
 the tube, traced outwards from 
 the gland, loses the basement 
 membrane at the surface of the 
 papillae ; arid the remainder of 
 its course is pursued upwards 
 through the successive laminae 
 of cuticular scales. 
 
 The preparation exhibited in 
 fig. 91 shows the continuity of 
 the epithelium lining the ex- 
 creting part of the duct -with the 
 cuticle, and also discloses its 
 hardness and cuticular character, 
 quite different from that of the 
 secreting epithelium within the 
 gland, which is soft and easily 
 decomposed. We have remarked 
 that the duct, in traversing the layers of the cuticle, is lined by epi- 
 dermic particles having a different arrangement from those of the 
 cuticle itself; being flattened in the vertical instead of the horizontal 
 direction, and especially distinct in the deeper and softer stratum of 
 the cuticle. This special cuticular tunic of the duct is best exhibited 
 by treatment of recent specimens with solutioH of potass. 
 19 
 
 a Vertical section of tlie cuticle from the heel, 
 detached by maceration as in fig. 79. The epithe- 
 lium of the sweat-duct, continuous with the cuticle, 
 has been drawn out of the tube of basement mem- 
 brane, as far as the gland, where it begins .to he 
 contorted. The cavity of the duct is seen dilating 
 as it enters the cuticle, and then stretching up to 
 the surface through the epidermic laminae. The 
 deep surface of the duct is continuous with the 
 surface of the cavities in which the papillse are 
 loctod.— Magn. 35 diam. 
 
 oDacl at Its entrance into the cuticle.— More 
 highly ihagni&ed. 
 
370 
 
 INNERVATION. 
 
 The duct, on leaving the gland, follows a meandering, and often 
 rather spiral direction, through the areolae of the cutis, to the interval 
 between the papillae, where it becomes straight; and it again assumes 
 a spiral course in perforating the cuticle (fig. 88). In the cutis its 
 curves are unequal, elongated, and wide; but, in the cuticle, they 
 are commonly as close and regular as those of a common screw, the 
 form of which may be taken as a fair model of the duct in this part. 
 It is not easy to explain the mode in which the spiral form is given 
 to the cuticular part of the duct. It has been imagined to result 
 from the condensation and flattening of the laminae of epidermis as 
 they approach the surface ; but the fact, that the spirals are not closer 
 near the orifice, is opposed to this notion. Their use, also, is obscure ; 
 for we cannot admit the validity of the ingenious idea that the orifice 
 of a spiral tube must be valvular, and, therefore, that they mecha- 
 nically resist the entrance of foreign, substances. If they do offer 
 this opposition, it is only by the tortuosity resulting from the spiral 
 arrangement. The proper tunic of the duct in the substance of the 
 cuticle seems designed to keep it pervious, and may be that which 
 gives it its peculiar spiral form. The average diameter of the cavity 
 of the duct is ttW inch ; but, as it enters the cuticle, it usually be- 
 comes wider. 
 
 The last two figures, as well as some of the preceding ones, illus- 
 trate the anatomy of the sweat-glands. * 
 The sebaceous glands are found in most parts of the skin, but are 
 
 absent from the 
 Fi3- 92. palms and soles. 
 
 They are most 
 abundant on the 
 scalp and face (es- 
 pecially about the 
 nose), and about 
 the anus and scro- 
 tum. The glandula 
 odoriferee of the 
 genital organs are 
 a variety of them, 
 only remarkable 
 by their secretion. 
 The orifices open 
 either on the gene- 
 reil surface, or into 
 the hair-follicles, 
 and they lie either 
 in the cutis or sub- 
 dermoid tissue, ac- 
 cording to their 
 size. They are usually associated with the hairs, in the manner re- 
 presented in fig. 92. They consist of a more or less capacious duct, 
 generally biainched, and terminating in blind, pouch-like extremities. 
 The basement membrane of these glands is thicker than that of the 
 
 Sebaceous glands, showing their size and relation to the haii-folU- 
 'Oles :— Aand b from the nose ; c'from the be&rd. In the latter the cutis 
 sends Apvffi an investment of the hair-foUic)e.— Magn. 18 diam. 
 
ENTOZOA OF THE SEBACEOUS GLANDS. 
 
 371 
 
 sweat-glands, and is lined by an epithelium, in the particles of which 
 are included granules of sebaceous matter. The terminal vesicles and 
 the ducts are filled with an accumulation of this epithelium, which, 
 having been detached from the walls, constitutes the secretion. On 
 the deep or parenchymal surface of the basement membrane a web of 
 capillary vessels is spread out. 
 
 While speaking of the sebaceous glands, we must say a few words 
 of a parasite so generally found in their ducts in many parts of the 
 body, that it may almost be regarded as a denizen. This was recently 
 discovered by Dr. Simon, of Berlin, {Muller''s Jirchiv., June, l842,) 
 and has been further described by Mr. Wilson, {Phil. Transact., 
 1844,) who speaks of two principal varieties of the adult animal, 
 chiefly distinguished by their length ; the one measuring from tw to 
 iVj the other from too to r^j of an inch. . He details several interest- 
 ing particulars concerning their structure and development, for which 
 we must refer to the origi- 
 nal memoir. These singular ^'S- ^3. 
 animals " are found in al- 
 most every individual, and 
 especially in those possess- 
 ing a torpid skin, and they 
 multiply in sickness. In 
 living and healthy persons 
 from one to three or four 
 may be found in each folli- 
 cle." We have represented 
 them as we have found them 
 in a sebaceous follicle of the 
 scalp (fig. 93). 
 
 The ceruminous glands of 
 the ear resemble in their 
 structure those just de- 
 scribed. They exist in great 
 abundance in the skin of 
 the cartilaginous part of the 
 
 external meatus, and provide an adhesive secretion calculated to 
 entangle particles of dust and small insects, and to prevent their access 
 to the delicate membrane of the tympanum.* 
 
 Of the functions of the Skin. — Having now considered the several 
 constituents of that very complicated organ, the skin, it remains for 
 us~to take a brief general view of its functions before proceeding to 
 a particular account of that one which brought us to this structure, 
 viz., the sense of touch. All these functions have reference to its 
 external anatomical position with respect to the other structures of 
 the body. Regarded as a protective covering, the skin possesses the 
 united advantages of toughness, resistance, flexibility, and elasticity. 
 The areolar framework of the cutis is the part chiefly conferring these 
 
 * In the sharks an4 rays there is a remarkable system of mucous tubes opening 
 on the skin. These tubes are nearly as large as crow-quills, and of great length. 
 They end by a blind extremity, to which a small nerve of the fifth pair is attached. * 
 
 Fntozoa from the sebaceous follicles ;— o. Two seen in 
 their ordinary position in the orifice of one of the seha- 
 ceous follicles of the scalp. 6. Short variety, c. Ijong 
 variety. 
 
372 INNERVATION. 
 
 properties^ which, are due, also in some measure to the epidermis. 
 Both these ■structures aie developed in a degree proportioned to the 
 force and frequency of external contact to which different regions of 
 the body are liable. They are thickest on the palms and soles, on the 
 back of the trunk, and the outer surface of the limbs: thinner on the 
 front of the body, and on the inside of the limbs. 
 
 •These two elements also afford protection and support to the other 
 more delicate ones with which they are associated. The areolae of 
 the cutis sustain the intricate networks of blood-vessels, lymphatics, 
 and'herves, which traverse it. The sweat-glands are imbedded in 
 cavities accurately fitted to receive them ; and their ducts, with the 
 sebaceous follicles, and hairs, are all lodged in channels or spaces 
 adapted to their respective sizes. The epidermis is a defensive in- 
 vestment to the tactile organ, and, while it shields it from the inju- 
 rious effects of pressure, is the medium through which impressions of 
 contact are conveyed to it with admirable nicety and truth. The 
 epidermis furnishes also special organs, such as nails and hairs ; which 
 are developed in particular situations, for the purposes of defence, 
 the preservation of warmth, or as aids to the sense of touch. The 
 infinite variety of modifications which the epidermis presents among 
 the lower animals, joined 'with others of nearly equal diversity in the 
 neighbouring textures, adapt it to very numerous and even opposite 
 uses in the animal kingdom. 
 
 The skin Combines the opposite functions of absorption and secre- 
 tion. Its lymphatic network, and the capillaries, are both concerned 
 in the former, which, under certain conditions, is very actively per- 
 formed. 
 
 Secretion may be said to be carried on at every point of the surface 
 of the cutis, since the cuticle is a deciduous product, constantly in 
 course of separation from it. But the principal seat of this function 
 are those glandular offsets from the skin that lie scattered in num- 
 berless multitudes beneath it. It may be safely said, that the secreting 
 membrane they comprise far exceeds, in extent, the surface of the 
 whole body. By the involutions of the sweat-glands, the surface is 
 multiplied, for the sole purpose of secretion, and the quantity of 
 material capable of being thus eliminated is enormous. There is one 
 peculiarity connected with this great glandular surface, which results 
 from its not being made up into a solid organ, but disseminated in 
 detached points under the integument, viz., that it is more than all 
 others subject to the influence of external temperature, acting upon 
 the cutaneous blood-vessels; but an apparatus for adjusting the irre- 
 gularities hence resulting is provided in the kidneys, as will be here- 
 after explained. 
 
 The sebaceous glands are another great system, chiefly subservient 
 to the protection and health of the skin itself, but resembling th'e 
 sweat-glands in their disseminated arrangement. They are extremely 
 numerous, and yield an oily material for the lubrication of the surface 
 of the cuticle. On most parts of the body they are as abundant as 
 the hairs themselves. They are an important accessory organ for the 
 elimination of hydro-carbonous matters from the system. Thus the 
 
FUNCTIONS OF THE SKIN. 373 
 
 skin is a superficial emunctory oJ^ great extent and importance, and 
 will demand subsequent consideration in that character. 
 
 We may now consider the function of the skin as the organ of touch. 
 One of the distinguishing characteristics of this sense is its universal 
 diffusion over the exterior of th€ body, by which its sphere of action 
 as a recipient of impressions, and as a criterion of locality; is rendered 
 more extensive than that of any other. The contact of foreign bodies 
 is perceived as occurring at the point at which they actually strike the 
 organ of touch, whether that point be within the sphere of operation 
 of any other sense or not. The precision with which this is effected 
 depends very much on the degree of development of the papillary 
 tissue in the several regions of the body. 
 
 We have already seen that the papillas present great varieties in 
 different parts. These varieties will be found to correspond very 
 much with differences in the mobility of such parts. In general, 
 touch is most acute in regions best suited, by their structure, for easy 
 and diversified contact with external substances ; for the power of 
 nicely determining the position, direction, and amount of pressure 
 upon the organ of touch, is essential to the perfection of the sense. 
 The will can not only excite and check the contractions of the mus- 
 cles, but is able to regulate their force and duration with wonderful 
 precision ; for, by the muscular sense, as stated in a previous chapter, 
 the mind is able to appreciate the state of contraction of a muscle by 
 impressions originating in the nerves supplied to its fibres. This 
 power, both of recognizing and governing the muscular movements, 
 is from our earliest infancy brought into association with the irppres- 
 sions derived from the tactile organ, and made accessory to its func- 
 tion ; and the perfection to which habit, in numerous instances, brings 
 the sense of touch, is chiefly due to an improved capacity it confers, 
 of appreciating the impressions made on the organ, in connection with 
 niceties of muscular movement. 
 
 In animals, as in man, we may notice the local concentration of the sense in 
 general obedience to this relation of mobility. In monkeys the fingers are highly 
 endowed with it, and the papillae there developed closely resemble those on the human 
 hand. The prehensile tails of certain tribes possess great mobility, can readily he 
 applied all round an object, and are largely supplied with nerves and papillse. In 
 addition to this, there is an absehce of hair from that surface adapted for contact wiih 
 bodies. In some ant-eaters the tail is highly tactile, and likewise in the chameleon. 
 
 In the canine and feline races the sense of touch resides in the paws, which pre- 
 sent a large papillary structure; in the lips, where the whiskers are developed; and 
 in the tongue. In ruminants and solipeds it has its special seat in the lips, which are 
 long, very movable, and largely supplied with sensitive and motor nerves. The 
 upper lip of the rhinoceros is an excellent example of these condi'ions; and, still 
 more so, the snout of the tapir and the trunk of the elephant, where the inleguments 
 about the orifice of the nostrils are endowed with exquisite powers both of sense and 
 motion. 
 
 Bui nowhere, perhaps, is the sense of touch more acute than in the membranous 
 expansions of the wings of bats, whereby they are enabled to traverse dark and tor- 
 tuous passages, in rapid flight, withoutinjnry. Spallanzani blinded them with a view 
 of determining whether sight conferred any part of this singular power, but found 
 that this mutilation interfered in no respect with the faculty. They were still able to 
 fly in the space between suspended threads without touching ihem. He could not 
 conceive it possible that so wonderful an endowment could depend on any exaltation 
 of mere touch, and he resorted to the supposition of the existence of a sixth sense, 
 possessed of some unknown mode of action. But Cuvier, with more sagacity, has 
 
374 INNERVATION. 
 
 referred it to an eminent sensibility of the nerves, which are profusely expanded over 
 the jweb of the wings. This membrane seems admirably calculated to receive, exact 
 impressions from the vibrations of the air, and so to be a means whereby the animal 
 may be informed of the disiance and figure of the neighbouring objects, which reflect 
 or otherwise modify the undulations of the surrounding medium. It is very probable 
 that hearing also may be concerned in this power. 
 
 In man, as compared with animals, the sense of touch is extensively 
 diffused; but very interesting differences in its intensity are observable 
 in different parts of the surface, which have been especially illustrated 
 by the experiments of Weber. 
 
 These consisted in placing the two points of a pair of compasses, 
 blunted with sealing-wax, at different distances asunder, and in 
 various directions, upon different parts of the skin or an individual, 
 who was not permitted to see the bodies in contact with him. It 
 was then found, that the smallest distance at which the contact 
 can be distinguished to be double, varies in different parts between 
 the thirty-sixth of an inch and three inches; and this seems a happy 
 criterion of the acuteness of the sense. We recognize a double im- 
 pression on very sensible parts of the skin, though the points are 
 very near each other ; while, in parts of obtuse sensibility, the im- 
 pression is of a single point, although they may be, in reality, far 
 asunder. 
 
 In many parts we perceive the distance and situation of two points 
 more distinctly when placed transversely than when placed longitu- 
 dinally, and vice versd. For example, in the middle of the arm or 
 forearm, points are separately felt at a distance of two inches, if 
 placed crosswise ; but scarcely so at a distance of three, if directed 
 lengthwise to the limb. 
 
 Two points at a fixed distance apart feel as if more widely separated 
 when placed on a very sensitive part, than when touching a surface 
 of blunter sensibility. This may be easily shown by drawing them 
 over regions differently endowed ; they will seem to open as they ap- 
 proach parts acutely sensible, and vice versa. 
 
 If contact be more forcibly made by one of the points than by the 
 other, the feebler ceases to be distinguished ; the stronger impression 
 having a tendency to obscure the weaker, in proportion to its excess 
 of intensity. 
 
 Two points at a fixed distance are distinguished more clearly 
 when brought into contact with surfaces varying in structure and 
 use, than when applied to the same surface, as, for example, on the 
 internal and external surface of the lips, or the front and back of the 
 finger. 
 
 Of the extremities, the least sensitive parts are the middle regions 
 of the chief segments, the arm, fore-arm, thigh, and leg. The con- 
 vexities of the joints are more sensible than the concavities. 
 
 The hand and foot greatly excel the arm and leg, and the hand the 
 foot. The palms and soles respectively excel the opposite surface, 
 which are even surpassed by the lower parts of the forearm and leg. 
 Qn the palmar aspect of the hand the acuteness of the sense corre- 
 sponds very accurately with the development of the rows of papillae ; 
 
NICETIES OF TOUCH. 375 
 
 and where these papillae are almost wanting, as opposite the flexions 
 of the joints, it is feeble. 
 
 The scalp has a blunter sensibility than any other part of the head, 
 and the neck does not even equal the scalp. The skin of the face 
 is more and more sensible as we approach the middle line; and the 
 tip of the nose and red part^of the lips are acutely so, and only inferior 
 to the tip of the tongue. This last, in a space of a few square lines, 
 exceeds the most sensitive parts of the fingers ; and points of contact 
 with it may be generally perceived distinctly from one another, when 
 only one-third of a line intervenes between them. As we recede from 
 the tip along the back or sides of the tongue, we find the sense of 
 touch much duller. 
 
 The sensibility of the surface of the trunk is inferior to that of the 
 extremities or head. The flanks and nipples, which are so sensitive 
 to tickling, are comparatively blunt in regard to the appreciation of 
 the distance between points of contact. Points placed on opposite 
 sides of the middle line, either before or behind, are better distin- 
 guished than when both are on the same side. 
 
 The above are the results obtained by making the several parts 
 mere passive and motionless recipient? of impressions. They evince 
 the precision of the sense in so far only as it depends on the organi- 
 zation of the tactile surface. The augmented power derived from 
 change of position of the object with regard to the surface, is well 
 illustrated by keeping the hand passive, while the object is made to 
 move rapidly over it. In this case the contact of the two points is 
 separately perceived, when so close that they would, if stationary, 
 seem as one. If, still further, the fingers be made to freely traverse 
 the surface of an object, under the guidance of the mind, the appre-, 
 ciation of contact will be far more exquisite, in proportion to the 
 variety of the movements, and the attention given to them. We are 
 then said to feel, or to examine by the sense of touch. 
 
 How great is the aid thus capable of being afforded, is manifest in 
 the following experiment. With shut eyes, and the hand still, let 
 another apply to the finger various articles, such as books, paper, 
 glass, metals, wood, cork, &c.; they will be very imperfectly dis- 
 tinguished. That our power of varying the force of contact adds 
 much to the delicacy of touch, is evident from this: that a plane sur- 
 face may be made to seem concave, by drawing it over the passive 
 tip of the finger of a person whose eyes are covered, provided it be 
 pressed at first strongly, then lightly, then strongly again ; or it may 
 be made to seem convex by reversing these gradations of pressure. 
 But, if the individual himself is the regulator of the pressure, the 
 deception vanishes. We may obtain some knowledge of the irregu- 
 larities of surfaces, and the shape of objects^ by simply bringing the 
 tactile organ into contact with them ; but much more by moving it 
 over them with attention. Thus, too, the infinite diversities of tex- 
 ture may be made distinguishable by the education of tact combined 
 with that of the muscular sense. It is related, of Saunderson, the 
 blind professor of mathematics at Cambridge, that he could distinguish 
 a spurious from a genuine medal, when the deception had imposed 
 
376 INNERVATION. 
 
 upon connoisseurs; and the case of the blind man, referred to by 
 Rudolphi, who was able to distinguish between woollen cloths of 
 different colours, of course by some slight variety in their texture, is 
 rendered credible by many well-attested examples of a parallel kind- 
 
 Our power of appreciating the weight of bodies, as well as resist- 
 ances in general, depends on those of estimating, separately and in 
 concert, both pressure on the tactile organ and the amount of con- 
 tractile energy acting, in the muscles. Weber performed experiments 
 to ascertain how far we are capable of judging of weight by the mere 
 sense of contact. He found that when two equal weights, every way 
 similar, are placed on corresponding parts of the skin, we may add 
 to or subtract from one of them a certain quantity without the person 
 being able to appreciate the change ; and that when the parts bearing 
 the weights, as the hands, are inactively resting upon a table, a much 
 greater alteration may be made in the relative amount of the weights 
 without his perceiving it, than when the same parts are allowed free 
 motion. For example, 32 ounces may thus be altered by from 8 to 
 12, when the hand is motionless and supported ; but only by from 1^ 
 to 4, when the muscles are in action : and this difference is in spite 
 of the greater surface affected (by the counter pressure against the 
 support) in the former than in the latter case. Weber infers that the 
 measure of weight by the mere touch of the skin is more than doubled 
 by the play of the muscles. We believe this estimate to be rather 
 under than over the mark. 
 
 The relative power of different parts to estimate weight corre- 
 sponds very nearly with their relative capacities of touch. Weber 
 discovered that the lips are better estimators of weight than any 
 other part, as we might have anticipated from their delicate sense of 
 touch and their extreme mobility. The fingers and toes are also very 
 delicate instruments of this description. The palms and soles possess 
 this power in a very considerable degree, especially over the heads 
 of the metacarpal and metatarsal bones ; while the back, occiput, 
 thorax, abdomen, shoulders, arms, and legs, have very little capacity 
 of estimating weight. 
 
 Heat and cold are peculiar sensations excited by alterations of tem- 
 perature on the surface of the body. They are, beyond all other sen- 
 sations, of a relative rather than of an absolute kind, and are always 
 most marked in contrast. Thus, in the familiar experiment of dipping 
 one hand into hot, and the other into cold water, and then plunging 
 them both into water of an intermediate temperature, the new medium 
 will seem cold to the former and hot to the latter ; and natives of the 
 polar and tropical regions of the globe will respectively complain of 
 the warmth or chilliness of our temperate climate when they visit our 
 shores. But it is observable that the sensations of heat and cold, 
 when exalted in degree, resemble each other very nearly. The sus- 
 ceptibility to both is greatest within moderate limits; and impressions 
 of either, when acute and powerful, amount to pain, and soon cease 
 to be distinguishable from one another. 
 
 Temperature appears higher in degree when it is applied to a larger 
 surface : thus, water feels hotter when we put our whole hand into it, 
 
DURATION OP IMPRESSIONS OF TOUCH. 377 
 
 than when we only dip a finger; the extent of the sensation augment- 
 ing the intensity with which it is appreciated, perhaps by more forcibly 
 attracting the attention. 
 
 Sensations of temperaturp have been usually, and we believe pro- 
 perly, attributed to the nerves of common sensation. These sensa- 
 tions are certainly quite different from touch, both in their peculiar 
 characters and in the source of excitement; but no less may be said 
 of various other inodifications of common sensation, to which it is 
 impossible to assign nerves of special endowment. The existence of 
 fibres fitted to be acted on by heat and cold, but by no other stimulus, 
 may be fairly doubted so long as they are undistinguishable from those 
 of touch, both at their origin from the nervous centre and in their 
 peripheral distribution. Still, however, it may be noted that in certain 
 states of paralysis, the sensibility to heat and cold may be destroyed, 
 while common sensation and touch remain.* 
 
 The sensation of tickling, tingling, itching, and many others allied 
 to them, are also referrible to the nerves of touch. Respecting tickling, 
 it has been well observed by Weber, that it is most apt to be excited 
 in parts of feeble tactile power. 
 
 Impressions made on the organ of touch, as on the other organs of 
 sense, continue perceptible for a period more or less prolonged after 
 the stimulus has ceased to be applied. The sting of a smart blow 
 does not soon subside ; and even the simple contact of any object, as 
 a ring or an article of clothing, with a part of the skin, if long con- 
 tinued enough, leaves, after its removal, an impression of its presence, 
 which is apt to deceive the individual for a considerable time. The 
 influence of habit on sensation in general, may be well illustrated in 
 the case of the nerves of common sensation and of touch. Impres- 
 sions sufficiently strong in the first instance to arouse the attention, 
 soon become feeble, and in time wholly disregarded, if continued 
 uniformly or frequently repeated; although the mind can still, at any 
 moment, take cognizance of them by a voluntary effort. The sen- 
 sations of heat and cold may, by long habit, in like manner come to 
 be unnoticed, or lightly heeded, within certain bounds. This is a 
 matter of common experience, and may be exemplified in the case of 
 the lower classes of society, among whom the privation of the com- 
 forts of warm clothing and lodging, and the absence of the mistaken 
 luxury of over-heated rooms, are compensated for by the possession 
 of that diminished susceptibility to cold, under slight exposures, 
 which is so remarkable in those subject, in a moderate degree, to the 
 inclemencies of the seasons. 
 
 Little needs be said of the subjective sensations pertaining to the 
 nerves now under consideration. They are among the best known, 
 and most familiar in the body. The peculiar tingling of a limb 
 " asleep," which commonly depends on pressure on its trunk, may 
 result from morbid changes in the centre; as may likewise sensations 
 of formication, or the creeping of insects, and those of itching, of heat, 
 of chilliness, &c., and lastly of pain of various kinds. 
 
 * See an instructive case by Dr. W, Budd, in the Med. Chir. Trans., vol. xxii. 
 
378 INNERVATION. 
 
 Besides the references in thefoot-notes and the various ireatises on Physiology and 
 general Anatomy already cited, we may refer on the su6ject of the preceding chapter 
 to Budolphi, Grundriss der Physiologie, band ii.;^-Weber, de pulsa, resorptione, 
 audita, et tactu; Lips., 1834; — Breschet et Roussel de Vauzeme, Ann. d. Sciences 
 Nat., 1834, torn, i.;— Schwann, Mikroskpp. Untersuchungen j — Eble, die Lehre von 
 den Haaren ; — Gurlt, Muller's Archiv., 1836 ; — Van Laer, de structure capillorum 
 bamanoram ; Traj. ad Rhen., 1841. 
 
 CHAPTER XV. 
 
 OF TASTE. OF THE MUCOUS MEMBRANE OF THE TONGUE, AND OF ITS 
 
 SIMPLE AND COMPOUND PAPILLA. — NERVES OF TASTE. NERVES OF 
 
 TOUCH IN THE TONGUE. — SEAT AND PHENOMENA OF TASTE. 
 
 The sense of taste is subservient to the nutritive function by guid- 
 ing us in the discrimination of the qualities of our food, and is there- 
 fore appropriately situated in the mouth, the antechamber to the 
 digestive canal. The food being .delayed more or less in this cavity^ 
 is brought, by the movements to which it is exposed, jnto intimate 
 and varied contact with the surface; and, its properties being ascef- 
 tained while it is still under voluntary control, we are able to reject 
 it or to propel it onwards, according to the impressidi^ produced on 
 the nerves of taste. 
 
 The mucous membrane of the tongue, as the principal .seat of the 
 sense, ■will now demand description. The muscular apparatus of this 
 organ, though increasing its powers of taste^ relates chiefly to its 
 employment in the processes of mastication and deglutition, and will 
 therefore.be considered at a Mture page. 
 
 In the mucous membrane of the tongue we find a chorion, a papil- 
 lary structure, and an epidermis or epithelium ; all corresponding, in 
 essential characters, with the same constituents of the skin. 
 
 The chorion, or cutis, is tough, but thinner and less dense than in 
 most parts of the skin: it receives the insertion of all the intrinsic 
 muscles of the tongue, which send up their fibres to it in small separate 
 bundles, so that the surface of the totigue is exceedingly mobile, even 
 in its minute portions, and its powers as an organ of touch are thereby 
 much exalted. The termination of the muscular fibres in the fibrous 
 •tissue of the chorion can be well seen in thin vertical sections. The 
 chorion contains the ramifications of the vessels and nerves from 
 which the papillary structure is supplied. Both the arteries and 
 veins form plane plexuses, open on all sides, like those of the skin, 
 and respectively connected with the vessels of the papillae above 
 them. 
 
 The papillary structure has, in general, this peculiarity, that it is 
 not concealed urlder the epithelium, but stands out freely from the 
 surface, like the villi of the intestinal tube, occasioning the familiar 
 
MUCOUS MEMBRANE OF THE TONGUE. 
 
 379 
 
 roughness of the tongue. This, however, is to he taken with the 
 limitations hereafter iio be detailed. 
 
 The epithelium of the tongue is of the scaly variety, and in this 
 respect resembles the cuticle. Like the cuticle also, it undergoes 
 certain modifications in its mode of aggregation indifferent localities. 
 In general it is much thinner than in the skin, so that the intervals 
 between the large papillae are not filled up by it, but each has a 
 separate investment, from root to summit. The continuity of the 
 epidermis over the whole organ admits of easy demonstration by 
 maceration, or boiling; by which it it detached entire, bearing the 
 print of the surface below, on which it has been moulded.' The 
 deeper epithelial particles may sometimes be detached as a separate 
 sheet, corresponding to the so-called rete mucosum; but these par- 
 ticles never contain colouring matter. In animals which have the 
 epithelium of the tongue much thicker than in man, it admits of being 
 separated with care into a great many layers, at the will of the ana- 
 tomist. The density of the epithelium is evidently a provision to 
 defend the invested structures from the bad effects of the pressure and 
 friction to which they are exposed during mastication, and hence it 
 is greatest about the middle of the 
 upper silrface of the organ. It is Figr. 94. 
 
 here that the" fur" usuallyaccu- 
 mulates most in disease, being, 
 in fact, no other than a depraved 
 and over-abundant formation of 
 the epithelium. 
 
 Three principal varieties of 
 papilla are visible with the naked 
 eye on the dorsal aspect of the 
 tongue. These are, 1 , the circum- 
 vallate or calyciform, eight to ten 
 in number, situated in a V-shaped 
 line at the base of the organ 
 (fig. 94, a); the j^n^g^orjw, scat- 
 tered over the surface, especially 
 in front of the circumvallate, and 
 about the sides and apex, h; and 
 the conical ov filiform, much the 
 most numerous, studding most 
 of the surface, though most large- 
 ly developed in the central part, 
 d. These three varieties will 
 require a separate description ; 
 they are very distinct from one 
 another if well-marked speci- 
 mens are selected ; but, as might 
 be expected, there are many in- _ 
 
 ',.,.' : ... •^, Tongue, Been on Its upper surface :— a. One of 
 
 termediate forms by WlllCh they the circumvallate papilise. t. One of the fungi- 
 
 seem to run imperceptibly into ^™6ln''J^?„,'i!rr;L''i.,;^.'e.""rSlotre 
 one another. We may premise, l!embire*-?fc- sSmSg. """' °' '""'"'"'' 
 
 
 •^. 
 
380 
 
 INNERVATION. 
 
 however, with regard to them all, that although they appear to have 
 been hitherto regarded as simple papillae, analogous to, though larger 
 than, those of the skin, yet we have found them to be compound 
 organs, clothed with secondary, simple, and much more minute pa- 
 pilias, concealed under the epithelial investment, and scarcely or not 
 at all visible until this covering is removed. 
 
 In their compound nature they present much resemblance to the 
 intestinal villi of the rhinoceros and other large animals. We have 
 further ascertained the existence of similar minute papillae, inter- 
 spersed very unequally among the compound forms, as well as occu- 
 pying much of the surface behind the circumvallate variety, where 
 the compound forms do not exist. These minute papillae seem to 
 have hitherto escaped detection, in consequence of their being com- 
 pletely buried and concealed under the common sheet of epithelium. 
 If we examine the mucous membrane immediately in front of the 
 epiglottis, we find it perfectly smooth, almost transparent, and supplied 
 by capillary vessels spread uniformly under the surface, and connected 
 with simple plane submucous plexuses of arteries and veins : here 
 the papillary tissue is undeveloped. Further forwards, however, 
 where the membrane still seems smooth, the plexus of arteries be- 
 neath it sends upwards, at pretty regular intervals, a series of twigs, 
 each of which terminates in one or two capillary loops, sometimes 
 dilated in the bend, from which a small vein returns the blood to the 
 submucous venous plexus. These loops ,correspond to those of the 
 
 simple papillae of the 
 skin, p. 359; they sup- 
 ply simple papillae, bu- 
 ried under a common 
 investment of scaly epi- 
 thelium, that differs 
 from the cuticle only 
 in its greater tenuity 
 and moistness. On the 
 removal of this delicate 
 epithelium by macera- 
 tion, the papillae stand 
 out free from the mem- 
 brane, and are seen to 
 consist of an envelop 
 of basement membrane 
 (p. 353), enclosing a 
 parenchyma obscurely 
 granular, with the ca- 
 pillary loop already 
 mentioned. Aftermuch 
 care, we have not been 
 able to see nervous 
 tubules within them; 
 but they must exist under some important modification, which most 
 
 Fig. 95. 
 
 Simple papUlse near the base of the tongue :— a. a. concealed 
 under the epithelium ; 6. uncovered by it,— Magnified 10 diame- 
 ters. B.4, Arterialtwig,supplyingtheircapillary Joops. «. Vein. 
 The vessels are all contained within the line &, 6. of baseme'nt 
 membrane, e, c. Deeper epithelial panicles resting on the base- 
 ment membrane, d. Scaly epithelium on the surface. The 
 (granular interior of the papillse is represented at «. c. Papillee 
 in ^hich the basement mernhrane is not visible; and the deep 
 layer of epithelium seems to rest on the capillary loop.— Magni- 
 fied 800 diam. 
 
COMPOUND PAPILLiE OP THE TONGUE. 
 
 381 
 
 probably consists in the absence of their characteristic white substance 
 of Schwann. These simple papillae are represented in fig. 95. 
 
 The circumvaJlate papillee (fig. 94, a, and fig. 96) consist of a cen- 
 tral flattened projection of the raucous membrane, of a circular figure, 
 and from ^V to ^V of an inch wide, surrounded by a tumid ring of 
 about the same elevation, but less 
 
 diameter, from which it is sepa- ^'S- ^^• 
 
 rated by a narrow circular fissure, 
 with, it is said, a few mucous ducts 
 opening at the bottom. In the 
 smaller examples this fissure exists 
 only on one side. The surface of 
 both centre and border is smooth, 
 and invested by scaly epithelium, 
 concealing a multitude of simple 
 papillae, in all respects similar to 
 those just described. 
 
 About the point where the two lines of circumvallate papillae meet, 
 there is usually one with the fissure so large and deep as to have 
 received the name of foramen ccecum. The central part is frequently 
 small, or elongated and thrown on one side of the foramen. In the 
 specimen next represented (fig. 97), this is shown covered with 
 
 Fig. 97. 
 
 Vertical seclion of one of the circumvallate 
 papillee : — a. Central part. 6, 6. Border, c, c. 
 Fissure between centre and Border. The se- 
 condary papillae are seen covered bythe epi- 
 thelium. Simitar papillas are seen, d, dy on the 
 membrane beyond.— Magn. 8 diam. 
 
 A. Compound papillae on the side of the foramen caecum, injected;— a, a. Arterial twigs, r, ti. 
 Viens. The capillary loops indicate the simple papillae ; in one of which. &, the injected matter has* 
 been exlravasated within the basement membrane of the papilla, the outline of which is thus dis- 
 tinguished, c. Capillary plexus, where no papillee exist, fi, e. External surface of the epithelium of 
 the papilla.— Ma^n. 15 diam. 
 
 B One of the simple papillae of A.: — ra, «, v. Arterial and venous sides of the capillary loops. 6, 6. 
 Basement membrane, d. Deeper epithelial particles resting on the basement membrane, s. Scaly 
 epithelium on the surface.— Magnified 300 diameters. 
 
 secondary papillae, having all the characters of those above men- 
 tioned. In its interior we failed to detect any nerves provided with 
 white substance. In this region of the tongue fissures and papillae of 
 irregular size and shape are often met with, and mucous glands are 
 disseminated beneath the surface. 
 
382 
 
 INNERVATION. 
 
 The fungiform papillee (iig. 94, 6, and fig. 98) are scattered singly 
 among the filiform papillae, chiefly on the sides and tip of the tongue, 
 and very sparingly in the middle of the dorsal region. They are 
 suually narrower at their base than summit, where they are from ^'j to 
 ■ss of an inch in diameter. Like those last described, they are clothed 
 
 Fig. 98. 
 
 A. Fungiform papilla, showing the secondary papillEB on its surface, and at a its epithelium cover- 
 ing them over.— Magnified 35 diameters. 
 
 B. Another, 'with the capillary loops of its simple papillse injected, a. Artery, v. Vein. The 
 groove around the base of some of the funffiform papillEe is here represented, as well as the capil. 
 fary loops, c, c, of some neighbouring simple papillse.— Magnified 16 diameters. 
 
 with simple papillae; and their investing epithelium is so thin, that 
 the blood, seen through it, gives them a red colour, usually suflScient 
 to distinguish them, from the filiform ones among which they lie. 
 They contain nerve-tubes, having a loop-like arrangement. 
 
 The compound papillae of the third variety (fig. 94, d, and figs. 99 
 and 100) are of the average length of ^V of an inch, and, as their 
 name implies, are more or less conical or filiform, in shape. They 
 
 are distinguished, more- 
 Tig. 99. ~ over, by their whitish 
 
 tint, derived from the 
 thickness and density of 
 their epithelium. This, 
 indeed, frequently com- 
 poses two-thirds of their 
 length, being sent off 
 from the sides and sum- 
 mits of their secondary 
 papillae in long pointed 
 processes, whicih are 
 immersed in the mucus 
 of the mouth, and may 
 be moved in any direc- 
 tion, though they are generally inclined backwards. These epithelial 
 processes are more stiff, according as the particles of which they con- 
 sist approach more nearly to the dense texture of hair; and a few 
 among them actually enclose minute hairs, pointed at the end, and 
 provided in some oases with an extremely fine central canal. One of 
 the largest of these we found tV of an inch long, and from ^jVir to 
 
 Various forms of the conical compound papillffi. deprived of 
 their epithelium :— a, b, and especially c, are the best marked, 
 4nd were provided with the siilTest and longest epithelium; 
 their simple papillfs are more acumiitated. d^ approaches the 
 fungiform variety : e,/, come near the simple papillEE.— Magni- 
 fied 20 diameters. 
 
STRUCTURE OF THE SECONDARY PAPILLA. 
 
 383 
 
 ^xnriT of an inch thick (fig. 100, 2). The others have an imbricated 
 arrangement of the particles in various degrees, which will be under- 
 stood without detailed description on reference to figure 100, 3, 4, 5. 
 Many of them may be regarded as soft or uncondensed hairs, and 
 preserve the same thickness for a considerable length. 
 
 Fig. 100. 
 
 A. Vertical section near the middle of the dorsal surface of the tongrue :— a, a, Fun^form papilla?. 
 h. Filifonn papillse, -with their hair-like processes, c. Similar ones deprived of their epithelium. — 
 Magnified a diameters. 
 
 B. Filiform compound papillae:— a. Artery. i». Vein. c. Capillary loops of the secondary papillce. 
 b. Line of basement membrane, d. Secondary papill 33, deprived of e, «, the epithelium. /.Hair-like 
 processes of epithelium capping the simple papillse.— Magnified 25 diameters, g. Separated nucleated 
 particles of epithelium, magnified 300 diameters. 
 
 1,2. Hairs found on the surface of the tongue. 3, 4, 5. Endsof hair-like epithelial processes, show- 
 ing varieties in the imbricated arrangement of the particles, but in all a coalescenc&of the particles 
 towards the point. 5, encloses a soft hair.— Magnified 160 diameters. 
 
 The structure of the secondary papillae, from which these hair-like 
 processes pass off, differs somewhat from that of the simple papillae 
 in the situations previously described. This difference consists in 
 their larger size and more pointed form, as well as in their greater 
 stiffness and elasticity; the latter quality depending on the abundant 
 yellow fibrous tissue they contain, and which, with a wavy, almost 
 spiral character, has a general longitudinal direction (fig. 101 j c,c, c). 
 They are commonly found to contain tubular; nerve-fibres, which we 
 have on several occasions, but not always, seen to terminate in loops 
 (fig. 101, A, B, c). We have usually found it easiest to distinguish 
 the tubular fibres in the papillse at the front of the tongue. 
 
384 INNERVATION. 
 
 The reader will at once recognize the broad and obvious distinc- 
 tion between the papillae last described and all the other varieties, and 
 
 Fig. 101. 
 
 A Secondary papilla of the conical class, treated with acetic acid : — a. Its basemenl membrane. 
 h. Its nerve-tube forming a loop. c. Its curly elastic tissue. The epithelium in this instance is not 
 abundant ; but the vertical arranpfement of its particles over the apex of the papilla is well seen, d, 
 and illustrates the mode of formation of the hair-like processes described iu the text.— Mag. 160 diam. 
 
 B. A similar papilla, deprived of its epithelium :—o. Basement membrane. 6. Tubular fibre, pro- 
 bablsr forming a loop, but its arch hot clearly seen, c, c. Elastic fibrous tissue at its base and in its 
 interior. — JVlagnified 320 diameters. 
 
 c. Nerves of a compound papilla near the point of the tongue,|n which their loop-like arrangement 
 is distinctly seen.— Magnified 160 diameters. 
 
 will probably surmise, on structural grounds, that they can scarcely 
 share in the reception of impressions which depend on the contact of 
 the sapid material with the papillary tissue. The comparative thick- 
 ness of their protective covering, the stiffness and brush-like arrange- 
 ment of their filamentary productions, their greater development in 
 that portion of the dorsum of the tongue which is chiefly employed 
 in the movements of mastication, all evince the subservience of these 
 papillge to the latter function rather than to that of taste ; and it is 
 evident that their isolation and partial mobility on one another must 
 render the delicate touch with which they are endowed more available 
 in directing the muscular actions of the organ. The almost manual 
 dexterity of the organ in dealing with minute particles of food is pro- 
 bably provided for, as far as sensibility conduces to it, in the struc- 
 ture and arrangement of these papillae. 
 
 The simple papillae on the base of the tongue, and those clothing 
 the circumvallate and fungiform papillae, do not appear to differ from 
 one another in any important structural condition, notwithstanding 
 their variety of outward form and arrangement in the compound organs : 
 
PRECISE SEAT OP TASTE. 385 
 
 their epithelium, though of the scaly kind, is very thin, and would 
 easily permit the transudation of sapid substances dissolved in the 
 mucus of the mouth. The softer and perhaps cellulated interior of 
 these. papillae may have a further influence on the act of sensation. 
 With regard to the use of the singular configuration of the circum- 
 vallate and fungiform papillse, it may be conjectured that the fissures 
 and recesses about their base are designed to arrest on their passage 
 small portions of the fluids in which the sapid materials are dissolved, 
 and thus to detain them in contact with the most sepsitive parts of 
 the gustatory membrane. 
 
 We may here allude to a certain gradation that is apparent from 
 the papillae of touch, through those of taste, to the absorbing villi of 
 the small intestines. Touch shades into taste, and at a lower point 
 sensibility is lost. In the tactile papillae, the excitant of the nerves 
 merely comes into contact with the exterior of a thick epidermic 
 covering: in those of taste, the epithelium is permeated by the special 
 excitant of the nerves ; while the intestinal villi are still more elabo- 
 rately and exclusively organized for absorption. Another class of 
 papillae might be here spoken of in conjunction with those of taste, 
 as will be seen at a future page. 
 
 On the precise seat of Taste. — Authors differ considerably on this 
 subject: some limit it to the hinder part of the tongue, about the root 
 and sides ; some extend it more or less over the whole dorsal aspect 
 and to the tip ; others describe it as existing also on the soft palate ; 
 while Magendie is of opinion that the pharynx, gums, and teeth are 
 likewise possessed of it. This contrariety, while it shows the diSi- 
 culty of the subject, may be in some measure explained by the inde- 
 finiteness of tastes when faintly perceived by small portions of the 
 surface, by the influence on taste of the commonly associated senses 
 of touch and smell, by some diversities really existing in different 
 individuals, and by the anibiguity necessarily attending experiments 
 on special sensation among thfe lower animals. As the subject is 
 interesting in its bearing on the question of the nerves of taste, we 
 shall here briefly consider it. 
 
 Touch, as it exists in the tongue and other highly endowed parts, 
 discovers to us not merely the presence and physical properties of 
 bodies, but their actual position : we recognize the situation of the 
 impression in reference to the whole organ, by virtue of a power 
 common in a greater or less degree to all sensitive nerves (p. 352). 
 Every one who has attended to the effect of sapid substances applied 
 to small separate parts of the tongue must feel that a sitnilar capacity 
 of assigning the position of flavours accompanies the sensation of 
 taste; and on this power in the nerves of taste, aided, as is usually 
 the case, by the nerves of touch, we greatly rely for the determination 
 of the question before us. 
 
 In the first place, all allow that acute taste resides at the base of 
 the tongue, over a region, of which the circumvallate papillae may be 
 taken as the centre, and also on the sides near the base. These 
 parts are supplied solely by the glossal twigs of the glosso-pharyngeal 
 nerves. 
 
386 INNERVATION. 
 
 Secondly, some writers, among whom are Valentin and Wagner, 
 believe the middle and anterior partf; of the dorsum of the tongue to 
 be usually incapable of appreciating flavours; while numerous others 
 hold the contrary opinion, with which our own careful and repeated 
 experiments, on other persons as well, as ourselves, quite accord. 
 Sour, sweet, and bitter substances applied to the sides, and especially 
 to the tip, of the protruded tongue, we find to be at once distin- 
 guished; though, when placed on the middle of the dorsal region, 
 they make little or no impression till pressed against, the roof of the 
 mouth. In the latter case, however, the taste of sugar is sufficiently 
 distinct, and referred definitely to the. spot on which it islait} ; so that 
 its being tasted does not depend on its diffusion or removal from the 
 central to the circumferential patts, as some imagine. The region 
 now spoken of is supplied almost solely by the lingual branch of the 
 fifth nerve, though Valentin has described, a twig of the glosso- 
 pharyngeal running on the under surface towards the tip. 
 
 We conclude generalFy, with regard to the tongue, that the whole 
 dorsal surface possesses taste, but especially the circumferential parts, 
 viz., the base, sides, and apex. These latter regions are fiiost favour- 
 ably situated for testing the sapid qualities of food: while they are 
 much less exposed than the central part, to the pressure and friction 
 occasioned by the muscles of the tongue during mastication. The 
 central region, as a whole, is more strongly protected by its dense 
 epithelium, and is rougher, to aid in the comminution and dispersion 
 of the food. 
 
 Thirdly, the soft palate and its arches, with the surface of the ton- 
 sils, appear to be endowed with taste in various degrees in different 
 individuals. Admirault and Guyat afi^rm that the sense is acute in 
 a spot about the centre, above the uvula; and in some individuals it 
 has so appeared to us. We have also found evidence of the existence 
 of taste on the sides and arches of the soft palate in some individuals, 
 but not on the pharynx, gums, or elsewhere. The soft palate and 
 its arches are supplied by the posterior palatine branches of Meckel's 
 ganglion, and sparingly by the glosso-pharyngeal nerves. 
 
 Of the Jferves of Taste. — Taste having been shown to exist inde- 
 pendently in parts supplied, on the one hand solely by the glosso- 
 pharyngeal nerves, on the other solely by the lingual branches of the 
 fifth pair, it follows, as a direct consequence, that these nerves must 
 respectively participate in the sense ; and there is, besides, reason to 
 attribute a share to the palatal branches of the fifth. Amid many 
 conflicting, and some quite irreconcilable statements on this. disputed 
 point, with which it would be needless to distract the reader's atten- 
 tion, the weight of evidence derived from other sources seems to be 
 much in favour of the above conclusion. 
 
 The origin and connections of the glosso-pharyngeal nerves, which 
 will be described at a future page, may be referred to in connection 
 with this question. Rapp found no lingual branch of the fifth in the 
 tongue of the swan or parrot, both of which have acute taste. The 
 glosso-pharyngeal and par vagum supplied the organ. 
 
 Evidence from Experiments. — From observations on the effects of 
 
NERVES OP TASTE. 887 
 
 section of the glosso-pharyngeal nerves in (logs, Panizza, and, subse- 
 quently, Valentin and Wagner, concluded that taste was completely 
 lost after their division, artd, consequently, that these are the sole 
 nerves of the sense. But in such an inquiry negative results have far 
 less value than positive ones; and we therefore consider the experi- 
 ments of Miiller, Gurlt, and Kornfeld, and those of Alcock and Reid, 
 who all agree that decided indications of taste remained after these 
 nerves had been cut, as proving that the lingual branches of the fifth 
 share in the sense. Mailer, Gurlt, and Kornfeld, however, failing to 
 find signs of taste after the lingual branches of the fifth were divided, 
 concluded too hastily that these are the sole, or by far the principal 
 nerves of the sense, in opposition to the experiments of Panizza and 
 his followers, the positive evidence of which in this regard carries 
 greater weight. The experiments of Dr. Alcock directly tend to re- 
 concile these inconsistencies. He found that though taste remained 
 after dividing the lingual branches of the fifth, yet it seemed com- 
 pletely lost in the anterior part of the tongue. Besides, it Is not impos- 
 sible that the rude injury inflicted in these contradictory experiments 
 on either the glosso-pharyngeal or the lingual branch of the fifth might 
 temporarily deaden the sense of taste in the other, in a way somewhat 
 similar to that, whatever it be, in which loss of smell impairs taste. 
 Valentin admits that one of the dogs in which he had cut the glosso- 
 pharyngeal nerves was able to taste 'a fortnight afterwards; a period 
 quite too short to have allowed reunion and restoration of function 
 to the nerves, and making it likely that the sense had been only ap- 
 parently, and not really lost. 
 
 Evidence from Disease. — In some cases loss of common sensation 
 consequent on disease of the fifth nerve has been reported as being 
 attended with loss of taste (Bishop, Med. Gaz., 1833; Romberg, 
 Muller^s Archiv., 1838, heft iii.); in others, taste appears to have 
 been preserved (Noble, Med. Gaz., vol. xv. p. 120; Vogt, Muller''s 
 Archiv., 1840, p. 72) : on the other hand, taste has been sometimes 
 lost while common sensation in the tongue remained (Noble, Med. 
 Goz., vol. xvi.). We would interpret the apparently contradictory 
 evidence of these cases by one which we have ourselves lately wit- 
 nessed, and which will be found to accord remarkably with the 
 foregoing views. A middle-aged man suffered for eight years from 
 complete loss of sensation in all parts supplied by the fifth nerve on 
 the left side, with the exception of the forehead. The left eye was 
 lost by destructive inflammation: the tongue was quite without feel- 
 ing on the left side. On experimenting on his sense of taste, it was 
 found to be clearly absent in the anterior and middle part of the 
 affected side; but to be present behind, in the region supplied by the 
 glosso-pharyngeal. He tasted acutely enough on the other side in 
 front. 
 
 Blumenbach and others relate cases of congenital deficiency of the 
 tongue, in which taste existed. These would show that taste resides 
 in other parts of the mouth besides the tongue, if it were not very 
 probable that a portion of the base of the organ with its gustatory 
 papillae, supplied by the glosso-pharyngeal nerves, existed in these 
 
388 INNERVATION. 
 
 individuals. Without accurate dissections of the parts, such instances 
 throw littk light on the question. 
 
 The tongue, as an organ of mastication, is provided with the sense 
 oi touch ; the anterior portion, and especially the sides and tip, 
 possessing this sense in an eminent degree. Division of the lingual 
 branches of the fifth nerves in animals is attended with evidence of 
 severe pain, and is immediately followed by loss of sensation in the 
 front part of the organ ; while cases of disease of the fifth nerve in 
 the human subject are marked by loss of sensation in the tongue, in 
 common with the other parts which the nerve supplies. The experi- 
 ments of Alcock and Reid further show, that mechanical irritation of 
 the glosso-pharyngeal nerve in animals is accompanied with manifest 
 pain. Hence there can be no doubt that the lingual branches of the 
 fifth pair are the chief nerves of touch to the tongue, while the glosso- 
 pharyngeal nerves furnish the feeble common sensation existing in its 
 hinder part. 
 
 Conditions of Taste. — Taste may be produced by a mechanical or 
 chemical excitation of its nerves. Dr. Baly has observed that a smart 
 tap with the fingers on the tip of the tongue causes a taste sometimes 
 acid, sometimes saline, which lasts several seconds; and galvanism 
 acts in a similar way. Any tasteless substance pressed upon the base 
 of the tongue occasions a bitter sensation, and, if prolonged, a feeling 
 of nausea. These phenomena sKow that the sensation of taste follows 
 excitation of its nerves, however produced: and analogous ones have 
 been observed in connection with the other sensitive nerves. But 
 sapid substances cause taste only when dissolved and made to per- 
 meate the tissue of the papillae, soas to come into contact with their 
 nerves. This is proved by the fact that no insoluble substance admits 
 of being tasted, and constitutes a broad distinction between taste and 
 touch ; which in some respects approach each other very nearly, par- 
 ticularly in regard to the effects of strong chemical agents on their 
 respective nerves, producing a harsh, pungent, burning taste ov feel. 
 Taste, like touch, is much influenced by the extent of surface acted 
 on: and it is also heightened by the motion and moderate pressure of 
 the substance upon the gustatory membrane. By the latter move- 
 ments, the mucus and outer layers of the epithelium are removed, 
 and the sapid material is brought into closer contact with the papillae. 
 The act of swallowing seems further necessary to the perfect appre- 
 ciation of flavours. This is partly explained by considering how 
 much the concurrent exercise of smell exalts the sense of taste. Most 
 sapid substances, though in different degrees, affect the nose through 
 the throat on being swallowed; and we are thus led to attribute to 
 taste much of what is in reality due to smell. The nurse's device of 
 holding the nose of the child in giving it disagreeable medicine, 
 though commonly said to deaden taste, seems rather serviceable by 
 excluding smell. Thus tested, taste is a less acute and definite 
 sensation than most persons imagine. Nevertheless the diflSculty of 
 discriminating between the two senses indicates a real, though obscure, 
 alliance between them, rendered closer by habit and association. 
 ' The impression of cold air deadens the sense of taste, and has, we 
 
CONDITIONS OF TASTE. 389 
 
 believe, been the source of some of the discordance in the recorded 
 results of experiments. Cold acts similarly on touch. 
 
 Do taste and touch co-exist in any of the papillce'? — A papillary 
 structure is, essentially, an arrangement for increasing the surface by 
 which a membrane may have contact with external substances; and, 
 while the analogy with the skin leaves no doubt that this structure in 
 the tongue is concerned in the exquisite touch enjoyed by the organ, 
 it is almost as certain that it is also concerned in taste. The question 
 then arises whether touch and taste reside in the same papillae or in 
 distinct ones. 
 
 Now it is possible, as far as we know, that nerve-fibres of difTerent 
 endowments may be associated in the same papillse, and therefore 
 that one and the same papilla may possess both capacities. Taste, 
 however, it is evident, demands a more delicate external apparatus 
 in connection with its nerves than touch ; so that touch might be ex- 
 ercised with an apparatus adapted to taste, though not in all cases 
 the reverse. As far, therefore, as regards the simple papillae at the 
 base of the tongue, and those covering the circumvallate and fungi- 
 form varieties, it seems impossible, in our ignorance of any anatomical 
 distinction between the nerve-fibres of the two endowments, to decide 
 whether the two senses are or are not resident together in the same 
 papillae. But there are good grounds for supposing that the conical 
 or filiform papilla are not designed for taste. They are most largely 
 developed in a part of the tongue where taste is feeblest, and are 
 there intermixed with a number of fungiform papillae sufficient to 
 account for the little that exists. Their structure and position, as 
 already remarked, lead to the same conclusion. It may be added, 
 that, in the lion, where these papillae are capped with spines, so thick 
 and rigid as totally to incapacitate them for taste, they are furnished 
 at the base with an additional tuft of soft secondary papillae, that seem 
 specially adapted for the latter function. It is possible that certain 
 soft papillae, which we have frequently seen springing up about the 
 base of the less developed filiform ones in the human tongue, may 
 contribute, in a similar manner, to the sense of taste. 
 
 ^re the varieties of taste referable to the varieties of the papilla ? — 
 It has been imagined that the differences of form met with in the 
 papillae might be in some special relation to the leading varieties of 
 tastes, as the bitter, sweet, sour, &c.; but the careful experiments of 
 Horn on this interesting point can scarcely be considered as tending 
 to establish such a correspondence. The difficulties, however, of 
 experimenting are so great, that neither can they be said to disprove 
 it: for a considerable extent of impression is necessary to ensure a 
 perception sufficiently definite to be relied on ; and the different papillae 
 are for the most part too much intermingled to admit of several of a 
 similar kind being tested apart from others. The most that can be 
 deduced from Horn's observations is, that more than three-fourths of 
 the substances he applied to the circumvallate papillae, including, we 
 suppose, the simple papillae we have described on the neighbouring 
 surface excited a bitter taste, or one in which the bitter was asso- 
 ciated with some other, especially an alkaline or saline flavour ; and 
 
390 INNERVATION. 
 
 that on the region where the filiform papillae abound- the majority of 
 substances tasted acid, or acid with a mixture of bitter or sweet. 
 In regard to the fungiform variety no decided results were obtained. 
 These facts will perhaps help to explain the effect of the act of swal- 
 lowing in modifying and heightening flavours, since the food is much 
 more completely brought into contact with the papillae on the hase of 
 the tongue during that act. 
 
 Jifter-tastes. — Impressions of taste remain longer than those of the 
 other senses, because the fluids exciting them must of necessity con- 
 tinue for some time in contact with the nerves after having saturated 
 the intervening papillary investment. For the same reason it is diflS- 
 cult to say how much of the taste that lingers after the substance has 
 apparently left the mouth is due to the excitation of the nerves by 
 particles still remaining in the papillae, and how much to that slate 
 of the nerves, which, in all the senses, prolongs the perception, after 
 the mere excitation has ceased. The taste left in the mouth by 
 many substances is, however, very different from that which they 
 produce in the first instance. Horn has remarked that this after- 
 taste is usually bitter ; while, with one of the most bitter substances 
 known, viz., tannin, it is sweet. This circumstance appears to show 
 something in taste corresponding to the complementary colours in 
 vision, and seems dependent on a state of the nerves which, for want 
 of a better word, may be termed one of exhaustion, consequent on 
 their previous stimulation. It will illustrate the cause of many fami- 
 liar phenomena of taste; such as the effect some flavours have in ex- 
 alting, modifying, or destroying our appreciation of others. Repeated 
 over-stimulation of the nerves by the same substance exhausts their 
 excitability by that or similar substances for some time afterwards. 
 
 There also appear to be relations between certain varieties of 
 taste, which, though not. classified or described by philosophers, are 
 instinctively perceived, and constitute the foundation of the art of 
 cookery. Attention and study given to the perceptions of this sense 
 greatly enhance their delicacy. 
 
 Little is known of the subjective phenomena of taste, or those 
 dependent on excitation of the nervous apparatus of the sense by 
 internal causes. The various tastes which are experienced in disease 
 are probably occasioned by depraved secretions in the mouth acting 
 as foreign substances on the papillae. The epithelium of the tongue, 
 it is well known, is very prone to accumulate in the form of sordes, 
 loaded with unnatural materials ; on the removal of which, the natural 
 taste is, in a great measure, restored. Magendie observed that dogSj 
 after the injection of milk into their veins, licked their lips, and gave 
 other signs of tasting. Such phenomena, if uniformly present, might 
 be occasioned by the transudation of the fluid from the vessels to the 
 nerves of the papillae. 
 
 On the subject of taste we refer to the general treatises already cited ; to Magendie's 
 Physiology; Rudolphi's Physiology; Horn.ilber den Geschmackssinn des Menscben, 
 Heidelberg, 1825; Panizza, Richerche Sperimenlali sopro i Nervi, 1834, given by Dr. 
 G. Burrowes in Med. Gaz., vol. xvi.; Dr. Alcook, Med. Gaz., Nov. 1836; Dr. Jno. Reid, 
 Brit, and For. Med. Rev., vol. v. p. 309 ; Valentin, de funct. nerv., p. 116. 
 
OF SMELL. 391 
 
 CHAPTER XVI. 
 
 OF SMELL. — CAVITIES OF THE NOSE. — STRUCTURE OF THE NASAL MUCOUS 
 MEMBRANE. — OLFACTORY REGION. — NERVES OF THE NOSE. — CONDI- 
 TIONS OF SMELL. 
 
 This sense, designed to acquaint us with the odorous qualities of 
 particles suspended or dissolved in the atmosphere, is seated in a 
 portion of the nasal mucous membrane to which the air has access 
 during ordinary breathing, and it may fairly be regarded as appended 
 to the respiratory organ, much as the sense of taste has been seen to 
 pertain to the digestive apparatus. But though it may serve to pro- 
 tect the lungs from the inhalation of deleterious gases, its principal 
 use appears to be that of seconding the impressions of taste in con- 
 veying intelligence of the properties of food ; for it almost ipvariably 
 happens, that food possessing a decided flavour has likewise a not 
 less characteristic smell. 
 
 Unlike the organs of touch and taste, that in which smell resides 
 has no capacity of movement in relation to its ordinary stimuli ; a 
 deficiency quite supplied by the expansion of the chest in breathing, 
 which carries the stream of odorous particles over the sentient sur- 
 face. 
 
 The nose consists, 1, of two chief cavities or nasal fossm separated 
 from one another by a vertical, bony, and cartilaginous septum, and 
 each partially subdivided, by the spongy or turbinated bones, pro- 
 jecting from the outer wall, into three passages or meatuses: and, 2, 
 of subordinate chambers, cells, or sinuses, pi irregular size, hollowed 
 principally in the ethmoid, sphenoid, frontal, and superior maxillary 
 bones, and communicating by narrow apertures with one or other 
 meatus. 
 
 The nasal fossce are lofty and of considerable depth, but much nar- 
 rowed in lateral extent by the projection of the spongy bones towards 
 the septum, which they almost touch. They open in front- by the 
 nostrils, which, by their horizontal position, direct the air, as it enters, 
 towards the upper region, where the sense of smell is developed ; 
 behind, they lead, through a vertical slit on each side, the posterior 
 nares or nostrils, into the upper compartment of the pharynx, above 
 the soft palate, into which the food never penetrates, which is strictly 
 a part of the respiratory tract, and which communicates through the 
 Eustachian tubes with the middle ear. The nostrils, as parts of the 
 countenance, and placed as safeguards at the commencement of the 
 air-passages, are more elaborately organized than the posterior nares, 
 -which indeed are simple communications, without anything remark- 
 able in their construction, except the shelving of the floor of the nose 
 into the upper surface of the soft palate, favouring the gravitation of 
 mucus from the nose into the pharynx. The nostrils have a carti- 
 laginous framework, which keeps them open, unless forcibly com- 
 
392 
 
 INNERVATION. 
 
 Fig. 102. 
 
 Front view of the cartilages 
 of the nose. Above is seen the 
 outline of the nasal bones — a. 
 Front edge of the septal car- 
 tilage. &. 6. Lateral cartilages, 
 e, e. Alar cartilages, with their 
 appendages. — After Scemmer- 
 ling. 
 
 pressed. This framework consists of five principal pieces: one in the 
 middle, the septal cartilage, a, completing the septum in front; and 
 two on each side, the lateral and alar carti- 
 lages, b, c, forming respectively the side of 
 the nose below the na.sal bones, and the wing* 
 of the nose. The former of these is triangu- 
 lar, and rests against the front edge of the 
 septal cartilage; the latter is thinner and more 
 flexible, and curved upon itself to form the 
 dilatable chamber just within the nostril. 
 Several loose nodules or flakes of cartilage 
 frequently exist in connection with the alar 
 cartilages. The nostrils are further supplied 
 with three pairs of muscles; viz., that called 
 by Albinus compressor naris, but which is 
 rather a lateraLdilator, the levator and depres- 
 sor altB nasi. By these the orifices are dilated 
 when we snifT the air in smelling, as well as 
 under the influence of certain passions. The 
 integuments of the nose are studded with the 
 orifices of sebaceous follicles, which are among 
 the largest in the body, and so numerous as 
 to form a thick continuous layer under <he 
 cutis; and immediately within the nostrils is 
 a growth of strong hairs, or vibrissee, designed 
 to obstruct the entrance of injurious substances. 
 
 With regard to the interior of the nose, its cavities are formed of 
 bone, generally thin, compact, and laminated, everywhere invested 
 with periosteum. This latter is lined with mucous membrane, the 
 Schneiderian or pituitary membrane, continuous with the skin of the 
 face at the nostrils, with the raucous covering of the eye through the 
 lachrymal passages, and with that of the pharynx and middle ear 
 through the posterior nares. 
 
 Thff mucous membrane of the nose varies in its structure in dif- 
 ferent regions. In many situations, especially in the sinuses, it is so 
 intimately connected with the periosteum that that fibrous membrane 
 is in fact a submucous areolar tissue; and the entire lining of the 
 bone has been sometimes called a fibro-mucous membrane, which, 
 as a whole, is delicate in the extreme. On the septum and spongy 
 bones, bounding the direct passage from the nostrils to the throat, 
 the lining membrane is much more thick, partly in consequence of a 
 multitude of glands being disseminated beneath it, and opening upon 
 it, but chiefly perhaps from the presence of ample and capacious sub- 
 mucous plexuses of both arteries and veins, of which the latter are 
 by far the more large and tortuous. These plexuses, lying, as they 
 do, in a region exposed more than any other to external cooling in- 
 fluences, appear to be designed to promote the warmth of the part, 
 and to elevate the temperature of the air on its passage to the lungs. 
 They also serve to explain the tendency to hemorrhage from the nose 
 in cases of general or local plethora. 
 
THE SCHNEIDERIAN MEMBRANE. 393 
 
 Tn the vicinity of the nostrils the mucous membrane exhibits pa- 
 pillae, and a'scaly epithelium, like the corresponding parts of the skin. 
 In the sinuses and in all the lower region, of the nose, the epithelium 
 is of extreme delicacy, being of the columnar variety, ^nd clothed 
 with cilia. This being the first occasion on which we have had to 
 speak of this kind of epithelium, vie shaU briefly describe its structure 
 and mode of growth. 
 
 The nucleated particles of which it consists are found in a double 
 series : of which the first, resting on the subjacent basement tissue, 
 is as yet imperfect ; and the second, rising to and forming the free 
 external surface of the membrane, is completely developed, and 
 furnished with cilia. The deeper series is the more adherent, and 
 if recent will be found to remain more or less attached, when the 
 superficial and perfect layer has been removed by a .gentle stream of 
 water. It will then have the appearance represented at &, fig. 103. 
 The nuclei, which are arranged nearly on the same level, are ovoid, 
 and contain usually two nucleoli, even more pellucid than themselves. 
 The surrounding substance is in relatively small quantity, and is seen 
 either as a mere film abound the nucleus, or vertically elongated in 
 various degrees. In the superficial series, o, the nuclei, though 
 lying on the same general level, are placed some higher and some 
 lower, as if for convenience of package, since the particles bulge 
 where the nuclei are situated. The nuclei are scarcely different in 
 
 View of the ciliated epithelium of the noae, seen in section:— o. Superficial series, clothed with 
 cilia. 6. Deeper series, becoming elongated vertically, c. Various shapes of the perfect ciliated 
 particles.— Magnified ISO diameters, 
 
 size or shape from those below. The surrounding granular sub,stance 
 of the particle is, however, much longer than before; below, -where 
 it is implanted between the parades of the deep series, it is pointed, 
 though sometimes blunt, and often club-shaped, while the upper end 
 enlarges, and terminates by a flat surface, from which the cilia pro- 
 ject, c. It must be observed, that the cell-membrane, so apparent in 
 the scaly epithelium heretofore described, is not to be found in this 
 variety. It is either early absorbed, or else so delicate and so united 
 to the contained substance, as not to be distinguishable as a separate 
 object. 
 
 It appears clear that this double series' of particles constitutes two 
 stages of growth of the same structure. Instances are not wanting of 
 particles intermediate between the two, in which the futiir? surface 
 of the membrane is marked by a horizontal line, above which the 
 granular substance exhibit?? rertioally. fibrous structure, indicative 
 20 
 
394 
 
 INNERVATION. 
 
 of Ihe coming cilia. Moreorer, xve have met with examples in 
 which a surface perfectly ciliated was still covered with a layer of 
 other ciliated particles, that, from their half-dissolved appearance, 
 had evidently passed their prime, and were in process of decay. 
 This progressive developmen.t of the particles as they recede from 
 the vascular source of their nutriment, and especially the evolution 
 at last of those delicate evidences of life, the ciliary appendages, is a 
 glaring example of the essential independence of the vitality of the 
 tissues on the blood-vessels, and makes it more easy to conceive the 
 really subordinate or ministerial office of those channels. 
 
 We now come to the proper seat of the sense of smell, a com- 
 paratively limited district of the nasal organ, to which we shall apply 
 the term olfactory region. As this olfactory region has not hitherto 
 been distinguished, nor its character understood, we shall describe 
 it somewhat minutely. This, as well as other parts, can be best 
 examined in animals, because they can be procured fresh, and in a 
 state of health. The mucous membrane so soon loses many of its 
 most interesting features, especially where death has followed on 
 chronic disease, that the human subject is not the most favourable 
 for the investigation of its physiological anatomy, and can only be 
 advantageously inspected after the lower animals have furnished 
 the general clue. This remark is well illustrated by the present 
 instance. 
 
 The olfactory region is situated at the top of the nose, immediately 
 
 below the cribriform plate of the 
 ethmoid bone, through which the 
 olfactory nerves reach the membrane ; 
 and it extends about one-third, or 
 one-fourth, downwards on the sep- 
 tum, and over the superior and part 
 of the middle spongy bones of the 
 ethmoid. Its limits are distinctly 
 marked by a more or less rich sienna- 
 brown tint of the epithelium, and by 
 a remarkable increase in the thickness 
 of this structure, compared with the 
 ciliated region below ; so much so, 
 that'it forms an opaque soft pulp upon 
 the surface of the membrane, very 
 different from the delicate, very 
 transparent film of the sinuses and 
 ,J;'i'sTlr.rrb'bl?r-°f IffiJITthf lower spongy bones. The epithelium 
 epithelium, J. Layer coloured by pigrajni. indeed here Quite alters its character, 
 
 c. Line of basement membrane, d Nu- , • . ' -t j i i i 
 
 rieated tissue seen beiow. e. Olfnoorv being, JIO longer Ciliated, DUt COm- 
 nervous filament branching. -Magn. 250 ^^g^j ^f 3^, aggregation of SUpCr- 
 
 posed nuclijated particles, of pretty 
 uniform appearance throughout^; except that, in many instances, a 
 layer of those lying deepest, or almost deepest, is of a darker colour 
 than the rest, from the brown pigment con^ajnecl in the cells, (iig. 
 104, S). Thfise epithelial. particles, tli,efli, are nol.cJUated,; and, tbey 
 
 Fig. 104. 
 
THE OtPACTORY REGION. 395 
 
 form a thick, soft, and pulpy stratum,-r6stirig on the basement mem- 
 brane. The deepest layer often adheres after the others are washed 
 away. On looking on the under surface lof. this epithelium, wheni it 
 has been detached, we observe projecting' tubular fragments, similar 
 to' the cuticularllning drawnout of the sweat-fducts of thei skin, when 
 the cuticle is removed after maceration (figs. TOandSO). In fact, 
 glan'ds apparently identical' with the sweat-^glands exist in; this region 
 in great-numbers. They dip down in the; recesses of the submucous 
 tissue,' among the ramifications- of the olfactory nerves ; and their 
 orifices are very easUy seen, after the general brown coat of epithe- 
 lium has been detached, lying more or less in vertical rows, the 
 arrangement of which is probably determined by the course of those 
 nerves beneath. They become more and • more sparing- towards the 
 limits of the olfactory region. The epithelium of .these iglands is 
 bulky, and like that of the sweat-glands, contains some pigment. As 
 the duct approaches the ieipithehum of the general surface, its wall 
 becomes thinner and more transparent;. and, in its subsequent course 
 upwards, it is difficult to be traced, for it does not appear to be spiral, 
 or its ■ particles to differ from those which they traverse. We have 
 sometimes seen rods of epithelium, apparently hollow, left projecting 
 from the basement membrane, aifter the brown epithelium has been 
 washed away; and these are perhaps portions of the excretory ducts 
 of these glands. 
 
 A good injection of the nasal organ in the foetus, both of man and 
 animals, will display a multitude of minute capillary loops upon the 
 surface of the olfactory region, bearing a close jesemblance to those 
 of rudimentary papillae. These loops we,re first pointed out to us two 
 years ago by Mr. Quekett in the foetal pig, and also in the human 
 foetus at its full term; and so clearly did they seem to indicate the 
 presence of true psipillae in this region, that we 
 made repeated and close examinations of the 
 recent organ, in order to expose their structure, 
 supposing them^to be concerned in the sense 
 of smell. These researches, pursued on adult 
 specimens, have been hitherto fruitless; at 
 least, we have ' found no other evidence of 
 papillae than delicate hollow epithelial pro- 
 cesses remaining, after a gentle current of 
 
 , , , °, »i • • 1 1- Dilated loopmg3 of the ca- 
 
 water had washed^ away the principal portion piiiMie* of the-'oifactory re- 
 of the brown epithelial investment— an ap- tii'"ctedlndma^fier'"' 
 pearance too ambiguous to be spbken of with 
 confidence. In the human foetuses we have injected, the loops are 
 such as are represented above (fig. 105). The convexity of the loops 
 presents a decided dilatation, being from ^TyVs-to ^jVir of an inch 
 wide, while the diameter of the capillary on either side is only 
 about jjTTB- inch. We have hitherto failed in seeing any loop-like or 
 projecting capillaries in injebtions of adult specimens. Care must be 
 taken not to confound these loops in the olfactory region of the fcetus 
 with the loops of the undoubted true papillae, situated jijst within tfag 
 nostrils, and which belong to touch. 
 
396 
 
 INNERVATION. 
 
 Of the JVerves of the JVose. — These are the first pair, and branches 
 of the fifth pair, besides motor filaments from the facial nerve to the 
 external muscles. The first pair has long been considered as the 
 proper nerve of smell, though not without dispute. That it has been 
 rightly so regarded, however, is evident for many reasons. Its limi- 
 tation to the upper and middle spongy bones, to the roof of the nasal 
 fossae, and to the upper half of the septum, where the mucous mem- 
 brane exhibits peculiar characters, and smell is, principally, if not 
 exclusively, exercised ; its development in the vertebrate class, pro- 
 portionate, cateris paribus, to the acuteness of smell, being largest in 
 animals of keenest scent; the loss of smell, without other effect, 
 consequent on its division ; together with the perversion or loss of 
 smell found in many authentic cases in connection with disease of 
 these nerves or their associated cerebral region: all these facts point 
 irresistibly to this conclnsion. 
 
 Of the First Pair. — Under this head are to be described the 
 olfactory process or lobe, and the olfactory filaments distributed to 
 the nose. 
 
 The olfactory process, or lobe {a, b, fig. 106), is a slender prisni 
 
 Fig. 106. 
 
 Outer wal of the nasal fossa, with the three spongy bones and meatus; the nerves being shown 
 as Ihey would appear through the membrane if it were transparent— o. Olfactory process J. Ol- 
 factory bulb (represented ralTirfr too Short) resting on the cribriform plate. BBlow is seen the plsxi- 
 form arrangement of the olfactory filaments on the upper and middle spongy bones, c. Fflh nerve 
 within the c/""'"'? with lis Gnsserian ganglion, d. Its superior maxillary division, sending 
 branches to Meckel's ganglion, and through that to the three spongy bones, where they anastomose 
 wilh ihe olfactory filaments, and wilh s, branches of the nasal division of Ihe ophthalmic nerve, 
 o. Posterior palatine iwigsfroin Meckel's ganglion, supplying Ihe soft and hard palate. I Orifice 
 of the h-usiachian lube ou the side of the pharynx, behind the lower spongy bone.— From Sffirnmer- 
 ing, two-thirds diameter. , ° 
 
 of fibrous and vesicular nervous matter, terminating in front iff a 
 bulb; and it is sunk in the fissure which bounds the supra-orbitar 
 convolutions fin the under surface of the anterior lobe of the cerebrum 
 (p. 255). It is connected with the inferior surface of the brain by 
 jui external and internal root. • The former is the Ibnger^ and nJay 
 
THE OLFAGTOBY NEKVE. 397 
 
 te traced in the nervous matter forming the floor of the fissure of 
 Sylvius, and among the arteries of the locus perforatus, towards the 
 lower and outer part of the corpus striatum, hear the anterior com- 
 missure of the cerebrum. In the dog and cat, where this process is 
 much larger, the anterior commissure seems to have a more intimate 
 relation to the olfactory processes. In the same animals the white 
 matter of the process is continuous also with that of the largely 
 developed hippocampus major. The internal root winds inwards, 
 and is lost in the gray matter in front of the optic, commissure, near 
 the anterior extremity of the corpus callosum. In front of the point 
 ■where the roots join, there is a process of gray matter constituting a 
 third or gray root, and which is continued forwards as a portion of 
 the olfactory process, as far as the bulb, where it expands. 
 
 The bulb of the olfactory- process (frg. 106, b) is an elongated oval 
 mass of nervous matter, which lies upon the cribriform plate. The 
 ■white portions of the olfactory process terminate, in its posterior ex- 
 tremity. It contains a small ventricle, wliich, in some of the lower 
 animals, is prolonged backwards as for. as the cerebral ventricles. 
 This ventricle is lined with a delicate white layer, but with this ex- 
 ception, the whole olfactory lobe consists of gray matter. In particular 
 it is to be observed, that the under portion, which reposes on the 
 cribriform plate, and sends down the olfactory filaments, contains no 
 tubular fibres. 
 
 The olfactory ^filaments (figs. 106, 7, 8) are from fifteen to twenty- 
 five in number, and, passing through the apertures of the cribriform 
 plate, may be seen, invested with fibrous sheaths derived from the 
 dura mater, upon the deep or attached surface of the mucous mem- 
 brane of the olfactory region. They here branch, and sparingly re- 
 unite in a plexiform manner, as they descend. They form a con- 
 siderable part- of the entire thickness of the membrane, and differ 
 widely from the ordinary cerebral nerves in structure.- They contain 
 no white substance of Schwann, are 
 notdivisible into elementary fibrilla?, 
 are nucleated, and finely granular in 
 
 t-exture, and are invested with a nflj ft 1 ^ 
 
 sheath of homogeneous membrane, j ' . 
 
 much resembling the sarcolemma, il ' f I il 
 
 or, more strictly, that neurilemma ' jt I ' 
 
 which we figured from the nerves of t ) / \ 'i I 
 
 insects in fig. 64, p. 209. These facts r ' J ; 1 I J| M 
 
 we have repeatedly ascertained, and \ j i / Hi** I 
 
 they appear to be of great importance |* | T I il' i 
 
 tto the general question of the func- J | ^ I ' / I J ' i 
 
 tlon of the several ultimate elements f't^ I *! I 
 
 of the- nervous structure, especially / ] i 1 | 
 
 when viewed in connection with "w"*"'^ ^ 
 
 what will be said pn the anatomy oifactoiy fliamems of the Dog-.—aU 
 
 of the retina. We are aware that wa.er. 4. i„ acetic acid-Magnified 200 dm- 
 
 some anatomists deny the existence 
 
 of the white substance of Schwann as a natural element of the nerve- 
 
 fl-o n 
 
 Fig. 107. 
 1 
 
 4f . 
 
 n 
 
 \ \ 
 
 J 
 
 
 
 w\ 
 
 n 
 
 fell^ 1 J 
 
 ' 1 
 
 f fll i 
 
 ? f,y 
 
398 INNERVATION. 
 
 fibre in any case, pretending that it is formed by artificial modes of' 
 preparation ; we hold it to be a true structure ; but, howet'^er that may 
 be, these nerves never exhibit it, however prepared. They rather 
 correspond with the gelatinous fibres. Now there is no kind of 
 doubt that they are a direct continuation from the vesicular matter 
 of the olfactory bulb. The arrangement of the capillaries in well- 
 injected specimens is a convincing proof of this, as these vessels 
 gradually become elongated on the nerve assuming a fibrous character 
 as it quits the surface of the bulb ; and further, no tubular fibres can 
 ever be discovered in the pulp often left upon the orifices of the crib- 
 riform plate after detachment of the bulb. It must be remembered, 
 that a few tubular fibres from the nasal nerve of the fifth here and 
 there accompany the true olfactory filaments, but these only serve to 
 make the difference more evident by contrast. 
 
 Although these nucleated olfactory filaments lie in great abundance 
 under the mucous membrane of the olfactory region, we have been 
 quite foiled in our attempts to trace their .ultimate distribution in the 
 membrane, and the difficulty is attributable to their want of the cha^ 
 racterislic white substance. Their elongated nuclei render the larger 
 branches unmistakeable; but if these become resolved at last into 
 fibrous elements, the nuclei cease to be distinct from those of the 
 numerous n-ucleated tissues which they traverse. In this respect they 
 correspond, in all probability, with the nerves of some of the papillae 
 of the tongue (see pp. 379-380) ; and, considering the similarity 
 between the two senses, an argument may be hence deduced for the 
 limitation of the sense of taste to those elementary nerve-fibres going 
 to the tongue which are without the white substance of Schwann. If 
 this be so, the looped tubular fibres are confined to the impressions of 
 touch in that organ. 
 
 We are averse from speculating prematurely on the meaning of 
 anatomical facts, but as some hypothesis will intrude itself, we would 
 venture to hint that this amalgamation of the elements of the peripheral 
 part of the olfaetory nervous apparatus in the larger branches, and 
 probably in the most remote distribution, as well as the nucleated 
 character indicative of an esisetitial continuity of tissue with the vesi- 
 cular matter of the lobe, are in accordance with the oneness of the 
 sensation resulting from simultaneous impressions on different parts 
 of this organ of sense, and Seem to show that it would be most correct 
 to speak of the first pair of nerves, as a portion of the nervous centre 
 put forward beyond the cranium, in order that it may there receive, 
 as at first hand, the impressions of which the mind is to become cog- 
 nizant. No true itubular fibres belong to the olfactory nervous appa- 
 ratus, except those commissural ones passing between the bulb and 
 certain portions of the cerebrum. 
 
 The branches of the fifth pair given to the nose (figs. 106 and 108), 
 are derived from its ophthalmic and superior maxillary divisions. 
 The nasal twig of the former, crossing the orbit, passes over the crib- 
 riform plate of the ethmoid bone into the nose, in close contact with 
 a portion of the olfactory nerve, and most probably forms some anas- 
 tomoses with It. Its subseq^uent coursa is dx)wjj.w,ardsj. subdividing, 
 
CONDITIONS OF SMELL. 
 
 to supply the mucous membrane and skin in the neighbourhood of the 
 anterior orifices. The pungent sensation preceding sneezing seems 
 to be an affection of this twig, 
 and the flow of tears that accom- 
 panies' that act is accounted for 
 by the common source of this 
 and of the lachrymal nerve. The 
 nasal branches of Meckel's gan- 
 glion enter the nose through the 
 spheno-palatine foramen, or by 
 pores between this and the pos- 
 terior palatine canal, and thfn 
 spread over the three turbint^ted 
 bones and the septum nasi, anas- 
 tomosing at several points with 
 the olfactory filaments, and with 
 the nasal branch of the ophthal- 
 mic (ags. 106 and 108). When 
 
 the fiflh nerve is diseased, so that Nervesof Uie scptumof.the Nose-.— «. Olfac- 
 
 o^oncotlnn In l^cf r.»»n_nll.. ;„ iU torv liulb restiiijoii iftn cfibriform plate, below 
 
 sensation is lost generally m the which Hs branches may be traced on the sepmm 
 
 narl-Q <stinn]ipr1 hv it- a hrncVimc»t? about half way down.. Behind, the naso-palatiiuj 
 
 pares SUppiiea Oy it, a Orusn may „^^^^ ^.^^^ MickePs ganglion is seen deseeiiding 
 
 be introduced into the nostril, and ^ 'he nafo-pal^tme canal. in rronl. the nasal 
 
 1,1 , p - 11 twig of the ophthalmic nerve descends towards 
 
 rUt)De<l over the surfaces usually the up of the uose. dividing Imo two principal 
 
 ^^ ^..t»/^r»n1., r,»»«:i:..» :*u« *. branches, jj. Roof of the mouth, c. Orificeof the 
 
 SO extremely sensitive, without Eustachian tube.- From Amold.one-halfdiatn. 
 
 the slightest discomfort to the 
 
 patient. Similar efTects follow division of the nerve. Hence it may 
 be concluded that the fifth gives common sensibility to the nose, in 
 common with most of the other parts- which it supplies. 
 
 Conditions of smell. — In adiiition to the essential conditions of 
 integrity of the nervous apparatus, and the presence of the requisite 
 stimulus, a healthy condition of the epithelial investment of the papillae 
 seems necessary for perfect smell. If the mucous surface is dry, or 
 if it is in the raw irritable state, attended with watery discharge, 
 induced by cold, smell is impaired or lost. This is explained by 
 considerirrg the manner in which the nerves are ordinarily brought 
 under the influence of the stimulus. As in ta,ste, a solution of the 
 stimulus in the surface of the membrane is requisite in order that the 
 odorous substance may actually reach the nerve. Insoluble sub- 
 stances cannot be smelt. Hence, whether the membrane be too dry, 
 or an inordinate excretion of fluid be going on from its surface, the 
 necessary penetration of the stimulus to the nerves is alike interfered 
 with. In the latter case, the effect 'may partly depend also on a 
 change produced by the inflammatory action, in the excitability of the 
 nerves themselves. 
 
 Since odorous substances must undergo solution before they can 
 affect the olfactory nenves, why, it may be asked, cannot such sub- 
 stances, if dissolved in water and injected into the nose, be recog- 
 nized by their smell .i" In answer to this it may be stated, that there 
 is no reason to deny the possibility of their being so recognized, as 
 far as Jthe .excitability of the nerves is concerned. But the ciliated, 
 
400 INNERVATION. 
 
 epithelium of the nose, and the nerves of common sensation supply- 
 ing the lining membrane, instantly resent the contact of all other fluids 
 than the film which moistens the surface, and which is naturally fur- 
 nished by it in due proportion to the exigencies of the part; and 
 when the membrane is thus irritated, and its texture altered by the 
 water, it need not excite surprise that its special sensibility should be 
 altered or disguised. The organ of smell in fishes resembles that of 
 air-breathing animals in every essential point of structure, and dtders 
 mainly in the habitual poptact of its sentient surface with the sur- 
 rounding water. It may therefore be concluded, that sensations of 
 smell are excited in it by substances brought to it through the water, 
 corresponding in kind with/throse brought in the other case through 
 t-he air, but eventually dissolved in the moisture of the membrane. 
 The nature of the sensation will depend on the special sensibility 
 of the nerve, which in both cases can be excited only by the stimu- 
 lating substance in .solution ; and whether air or water brings the 
 stimulus to the surface of the membrane, is made important only by 
 the special adaptation of that -surface to the contact of one or the other 
 medium. 
 
 We may here notice two important reasons for the situatian of th& 
 organ of smell, so high up in the nose, in addition to the obvious one 
 of the protection from mechanical injury thus afforded to so delicate 
 a part. These are, that it is thereby screened from the contact of air 
 either too colcL or too dry. The interposition between the outer 
 orifice and the organ of smell of projecting and folded menabrartes of 
 active secreting powers, and containing large reservoirs of blood (in 
 the plexuses already described), seems designed to answer both these 
 purposes. These parts break the force of the current, warm it, and 
 iCnpart that degree of moisture which is best calculated to aid the 
 solution of the odoriferous particles on the sentient surface to wbicb 
 they are afterwards applied. The remarkable complexity of the 
 lower turbinated bones in animals with acute scent, without any 
 ascertained distribution of the olfactory nerves upon thetti, has given 
 countenance to the supposition that the fifth nerve may possess some 
 olfactory endowment, and seems not to have been explained by those 
 who rejected that idea. If considered as accessory to the perfection 
 of the sense in the way above alluded to, this striking arrangement 
 will be found consistent with the view which limits the power of 
 smell to the first pair of nerves. 
 
 We have already remarked that the exercise of the sense of smell 
 is not attended with more than a general idea of locality. The sen- 
 sation is even more simple in this respect than that of taste. Unless 
 the experiment be made, we know not that we are constantly exerting 
 the sense on two sides, for the double sensation is perceived as a 
 single one. Our observations on the anatomy of -the olfactory nervous 
 apparatus may assist in the explanation of this fact. 
 
 The sense of smell may be voluntarily heightened by short and 
 quick inspirations, which drive the air smartly against the upper region 
 of the nose, and tbus lead to the more effectual detention of its odori- 
 ferous pacticles. by th.e ra.en[),brane,, while tlxe att^eatioo, iA-g^lveo. to. iite 
 
OF VISION, 40JL 
 
 sensations. On the other hand, by closing the nostrils, and breathing 
 through the mouth, all access to the organ of smell is prevented, 
 except that gradually effected by admixture through the pharynx 
 and posterior nares. It is through this latter channel that the 
 odorous particles of food, rising from the throat to the nose during 
 expiration, blend the sensation of smell with that of taste so strongly 
 and habitually, that it becomes difEcult to discriminate between 
 them. 
 
 Analogy would lead to the belief that the nervous apparatus of 
 smell, if irritated by an internal cause, would be the seat of olfactory 
 sensations. Such subjective phenomena have been known to exist 
 in certain cases of disease, in which the nerve, or the anterior lobe 
 of the brain, has been afterwards found disorganized. Occasionally, 
 too, odours are perceived without the actual presence of the object 
 usually giving rise to them. These also must be regarded as sub- 
 jective. 
 
 The quality of the sense, also, seems to vary not a little in different 
 persons; some being strongly affected, even to faiiitn?ss, by a scent 
 ■which is almost imperceptiljle to others. The odours of flowers, for 
 example, are very variously appreciated, as every one must have more 
 or less observed. There are corresponding idiosyncrasies in the other 
 senses. 
 
 On the subjects of this chapter, in addition to the elementary works before quoted, 
 the following may be consulted:— 'Sehneiderius, de osse cribriformi et sensu ac 
 brgano odoratus; iScarpa, de organo olfactus; also, de audita el olfactu; Scemmering, 
 Icones brgani humani ojiactus, 1809 ; H.Cloquet, Osphr^siulogie, ou trait^ des odeurs. 
 Paris, 1821. 
 
 CHAPTER XVII. 
 
 OF VISION. OF THE ANATOMY OF THE EYEBALL, OPTIC NERVES, AND 
 
 APPENDAGES. — OF THE PHENOMENA OF VISION. 
 
 It would appear that an animal may be sensible to light without 
 possessing an organ of vision. Thus, that beautiful little; polyp, the 
 hydra, shows a decided predilection for the light side of the vessel 
 in which it is kept. Most animals, too, require the presence of light 
 for the full performance of their functions ; and this is not the case 
 with animals alone, but with plants likewise: both, in the great ma- 
 jority of instances, pine away in the dark, or fail to arrive at complete 
 development. 
 
 But the presence of an organ of vision implies something more than 
 the mere power of distinguishing between light arid darktiess. It 
 must enable the anirhal to discern something of the colour, or at least 
 of the form, of surrounding objects; and this in a degree proportioned 
 to the perfection and complexity of its organisation. 
 
402 INNERVATION. 
 
 The principle on which the organ is constructed seems to be in 
 all cases the same, viz., that of the camera obscura — a dark chamber 
 ■with a small aperture for the admission of light, a quantity of black 
 matter for the absorption of superabundant rays, and a nervous expan- 
 sion on that -wall which receives the rays of light. 
 
 Among the lower invertebrata, the eyes, or ocelli, consist only of a 
 nervous point, shielded with a minute quantity of colouring matter. 
 The chief additions which increase the complexity of these organs in 
 the higher animals consist of transparent media and lenses for the 
 refraction of the light, and the production of a more precise image; of 
 an apparatus for the regulation of the quantity of light admitted to the 
 retina; and of other appendages for protection and movement. 
 
 The position of the human eye at the upper part of the face and 
 directed forwards, while it gives to the countenance its most important 
 element of beauty, adds greatly to the utility of the organ, by increas- 
 ing the visual range. For protection in this exposed situation, it is 
 sunk deeply in a cushion of fat, within a bony cavity, the orbit, the 
 prominent borders of which are well adapted to receive the force of 
 blows directed towards that region. It is furnished with muscles 
 capable of moving it towards any side, and of protruding or sinking 
 it. It is likewise provided with movable lids to guard its exposed 
 surface from mechanical injury, and its nerve from the effects of ex- 
 cessive light ; and with a lachrymal apparatus, by which the front of 
 it is continually irrigated with a bland fluid. 
 
 In the globe of the eye itself we Recognize, as the most essential 
 constituents, the expansion of the optic nerve, called the retina; and, 
 in front of this, the transparent refracting media which, as a whole, 
 transmit the light so as to bring its rays to a focus upon the nervous 
 sheet. The curved form of the retina, and the rounded figure of the 
 eye thence derived, are perfectly adapted to the curvatures of the 
 refracting media: so that, if the nervous lamina had assumed any 
 other shape, it would have been more or less out of focus, and vision 
 consequently have been indistinct. 
 
 To maintain the figure of the retina, and to protect a part of so 
 much delicacy, in which the slightest change of form would be attended 
 with injury to the function, the whole is encased in a dense tunic of 
 great strength, termed the sclerotica (axAijgo;, durus), which is opaque, 
 except in front, where it is modified in structure, becomes perfectly 
 transparent to allow the light to enter, and is knoWn as the cornea. 
 Between the sclerotica and the retina is interposed a layer of dark 
 pigment, contained in a delicate membrane termed the choroid. In 
 front of the retina are the transparent media. One of these (the 
 vitreous body or humor) is contained immediately within the cup 
 which the retina forms, and appears specially constructed to give it. 
 that necessary support inside which the sclerotica furnishes on the 
 outside. The vitreous body occupies four-fifths of the whole globe. 
 Imbedded in its anterior part is a double convex lens (the crystalline 
 lens or Body), which comes nearly up to the cornea; leaving, however, 
 a small cavity containing a watery fluid, the aqueous humor, between 
 itself and that transparent part of the external case. Across this 
 
THE. EYJE. 4Q3 
 
 cavity, and dividing it into an. qnienV and posterior chamber, hangs 
 a vertical curtain-like process of the choroid, cajled the iris, perforated 
 in the centre by an aperture, th^ pupil, for the adinissipn of light to 
 the interior, and contractile under the influence of light on the retina, 
 in order that it njay regulate the; amount of liglit entering the organ. 
 The perfect fluidity of the aqueous humor is a provision to allow of 
 the expansion and contraction of the pupil, and of the movements of 
 lihe lens itself. towards or from the cornea. 
 
 The human eye would be nearly globular were it not that the, 
 anterior portion, forined by the cornea, is a part of a smaller sphere, 
 than the rest, and is therefore slightly protuberant. Hence the an- 
 tero-posterior axis qf the, eye is Ipnger thap the transverse, in the' 
 proportion of twerity to nineteen. 
 
 In terrestrial quadrupeds its shape is for the most part nearly similar. In animals 
 that inhabit the water, as Cetacea and fishes, the eye is considerably flattened in 
 front; so thatrin spoje fisl^es, it, is almost a half-sphere. In birds, o;d the cpnirary, 
 e.specially those which flj high, the cornea is very prominent compared with the rest 
 of the eye, which is of a more' dV'less flattened (0™!.*^ These differences have an 
 evident reference to the density or rareness of the medium' through which the light 
 passes to the org^tf, 
 
 A more detailed- description of the several structures composing 
 the ball of the eye will now be giy;en, in which we sjiali follow the 
 order most natural to a dissector^ viz,, that from without, inwards. 
 
 The sclerotic coat, consists, of white fibrous, tisstje, in which, how- 
 ever, the iiltimate filamenis are more distinct, and less wavy than in 
 ordinary specitnens!' These fprm numerous layers, crossing one an- 
 other chiefly at right angles, and thus constitute a membrane capable 
 of resisting distension, aijd of retaining its figure under pressure. 
 It has a white glist^iiing aspect, especially in front, wher^ it receives 
 the insertion of the tendons of the four straight miiscles, and, being; 
 Visible, is familiarly krio\yn as the " white of the eye." The 
 sclerotic is thickest behind, and l^ecoines gradually thinner in front, 
 till nearly in contact vi'xi]^ the cornea, where it increases in strength a 
 little;' ' •■■ — .-' - ■■• ^ — • . • ■■ ^■■;, 
 
 In the animal series, the sclerotic "becomes of greater relative thickness behind, in 
 proportion to the .flattening X)f ibe'organ in front, a,n,d the pressure which it will have 
 to sustain from the surroiindi,ng, medium, In aqufitic .msfl^njalia this is^ffecied 
 simply by an acciimplation of itie fiWoiis ti.ssue in that situation, 'aS in the whale, 
 where it is often an inch in thickness, a wonderful provision against the tnbrmous 
 pressure to which that anirpal is exposed, at. great depths. In reptiles and fishes 
 there is a thjclf can(ilaginoijf! lamin,a incjjudeid,in thf fihroiis tissue; and in, soiree this, 
 cartilage ossifies, as in tile sea-brean/i, mentioned hy t)r, Japoh. In birds, too,' where 
 the sclerotica 'is flattened from before ba'ckwards, a'thin cartilaginous piale'exists in 
 it, which confers a peculiar elasticity and firmness, and is at the same time light and 
 sJender. Its anterior part is further fortified by fpurteen or. fifteen osseous plates, 
 .disposed in a regular series round the margin of the cornea. Similar plates occur 
 in various reptiles, arid are especially remarkable in those gigantic specimens of this 
 class, the Ichthyosauri and Plesiosauri, which are only known to us By their fossil 
 remains. 
 
 The optic nerve comes through the sclerotic behind, at a distance 
 of about its own breadth, or nearly one-eighth of an inch, on the 
 inner side of the axis of the eye, by which is meant the axis of the 
 
404 INNERVATION. 
 
 dioptric media. This nerve contains a considerable quantity of fibrous 
 tissue separating and supporting its fasciculi, and as it traverses the 
 sclerotic this tissue becomes continuous with the borders of the aper- 
 ture, sb that the aperture itself may be said to be cribriform; the nerve 
 passing through a number of distinct canals of fibrous tiissue, before 
 it reaches the inner surface of the sclerotic. It is indifferent whether 
 this cribriform tissue be called neurilemma or sclerotic. One thing, 
 however, may be always observed. The nerve, as it pierces the 
 sclerotic, contracts, and lies in a smaller compass, so that the entire 
 aperture is somewhat funnel-shaped, and wider behind than in front; 
 and, though the nerve is movable on its entrance into the sclerotic 
 aperture, it is always fixed firmly at the inner surface of that aperture, 
 where the retina commences. 
 
 The aperture in the sclerotic in front, for the cornea, is circular, 
 and usually about rV^^^ ^^ ^" 'n<^h in transverse diameter, and rather 
 less vertically, though in some individuals altogether smaller. Be- 
 tween the point of entrance of the optic nerve, and the attachments 
 of the recti muscles, there are several minute apertures for the trans- 
 mission of vessels and nerves to the interior. The nutrition of this 
 tunic itself is provided for by small vessels ramifying on its surface, 
 and sparingly continued into its substance. Its own proper vascularity, 
 does not seem to be greater than that of other fibrous structures. 
 
 Of the Cornea. — The size and shape of this transparent part of tbe' 
 outer case of the eye have been already indicated. It is spherical 
 rather than spheroidal, aiid its posterior surface is of parallel curvature 
 with the anterior; so that it does not appear to be a meniscus lens, 
 thicker in the middle, as some authors have described : this at least 
 is the result of our careful examination. The cornea, when its con- 
 cavity is filled up with the aqueous humor, is of course a powerful 
 converger of the rays of light towards the iris, and through the pupil 
 to the lens. Viewed from within, its circumference is exactly cir- 
 cular; but on the outside it generally appears wider transversely, from 
 the sclerotic, which overlaps it on all sides, encroaching upon it rather 
 more above and below. The cornea and sclerotic are firmly con- 
 nected by continuity of texture, and cannot be disunited even by 
 maceration. The cornea is possessed of great toughness, and will 
 even resist a force capable of rupturing the sclerotic. 
 
 The cornea, though a beautifully transparent substance, and ap- 
 pearing at first sight as homogeneous as glass, is nevertheless full of 
 elaborate structure. It is, in fact, composed of five coats or layers, 
 clearly distinguishable from one another. These are, from before 
 backwards, the conjunctival layer of epithelium, the anterior elastic 
 lamina, the cornea proper, the posterior elastic lamina, and the epithe- 
 lium of the aqueous humor, or posterior epithelium. The cornea, when • 
 uninflamed, contains no blood-vessels; those of the surrounding parts 
 running back in lo,)ps, as they arrive at its border. 
 
 On the cornea proper, or lamellated cornea, the thickness and 
 strength of the cornea mainly depend. It is a peculiar modification 
 of the white fibrous tissue, continuous with that of the sclerotic. At 
 their line of junction (fig. 109), the fibres, which in the sclerotic have 
 
OF THE CORNEA. 
 
 405 
 
 been densely interfaced in various directions, and mingled with 
 elastic fibrous tissue, flatten out into a membranous form, so as to 
 
 Fig. 109. 
 
 Venlcal section of the Sclerotic and Cornea, showings Ihe feontlnuity of their tissue between the 
 dotted lines :-ra. Cornea, b. ^.clerotic. In the cornea lhe,-.tubular spaces are seen cat through, 
 and in the sclerotic the irregular areolee. Cell-nuclei, as at c, are seen scattered throughout, ren- 
 dered more plain by acetic acid. Magniiied 320 diameters. 
 
 follow in the main the curvatures of the surfaces of the cornea, and 
 to constitute a series of more than sixty lamelloe, intimately united to 
 one another by very numerous processes of similar structure, passing 
 from one to the other, and making it impossible to trace any one 
 lamella over even a small portion of the cornea. The resulting 
 areolae, which in the sclerotic are irregular, and on all sides open, are 
 converted in the cornea into tubular spaces, which have a very sin- 
 gular arrangement, hitherto undescribed. They lie in superposed 
 planes, the contiguous ones of the same plane being for the most part 
 parallel, but crossing those of the neighbouring planes at an angle, 
 and seldom communicating with them (fig. 110). The arrangement 
 
 Tig. no. 
 
 Tubes of the Cornea Proper, as shown in the eye of the Ox by mercurial injection. Slightly 
 magnified. 
 
 and size of these tubes can be shown by driving mercury, or coloured 
 size, or air, into a small puncture made in the cornea. They may 
 also be shown under a high power by moistening a thin section of a 
 dried cornea, and opening it out by needles. The tissue forming the 
 parietes of these tubes is membranous rather than fibrous, though with 
 the best glasses a fibrous strlation maybe frequently seen, both in the 
 laminae separating the different series of tubes, and in that dividing 
 those of the same layer from each other. By acetic acid, also, the 
 
406 
 
 INNERVATION. 
 
 Fig. 111. 
 
 A - :^^S 
 
 sfrueture swells, and displays corpuscles resembling those a{)parent 
 in the white fibrous tissue. Such is the lamellar structure of the 
 cornea, which makes it so much easier to thrust an instrument hori- 
 zontally than vertically into its substance. The tubes or elongated 
 spaces of which we have spoken, are not distended with any fluid, 
 but are merely moistened in the same way as the areolae of ordinary 
 areolar tissue. A perfectly fresh and transparent cornea is rendered 
 opaque by pressure, but it regains its brilliance on the removal of the 
 compressing force. Some have supposed this to result from the ex- 
 pulsion of fluid frombetweep itslaminee; but that the opacity is owing 
 simply to a derangement of the elementary parts of its structure is 
 
 plain from the fact, that the same pheno- 
 mena are exhibited by a section, however 
 thin, immersed in water, and deranged by 
 stretching. 
 
 Of the anterior elastic lamina. — This is 
 a transparent, homogeneous lamina, co- 
 extensive with the front of the cornea, and 
 forming the anterior boundary of the cornea 
 proper. It is a peculiar tissue, the office 
 of which seems to be that of maintaining 
 the exact curvature of the front of the 
 cornea ; for there pass from all parts of its 
 posterior surface, and in particular from' its 
 edge, into the substance of the cornea 
 proper and sclerotic, a multitude of fila- 
 mentous cords, which take hold, in a very 
 beautiful artificial manner, of the fibres and 
 membranes of those parts, and serve to 
 brace them and hold tfaem in their right 
 configuration (fig. 111,6). These cords, 
 like the elastic lamina of which they are 
 productions, appear to be allied to the 
 yellow element of the areolar tissue. They 
 are unaffected by the acids. The anterior 
 elastic lamina sustains the conjunctival 
 epithelium which covers the cornea, and 
 is very probably the representative of the 
 basement membrane of the mucous system, 
 as it occupies the corresponding position 
 in regard to the epithelium. Its thickness 
 is about -joW of ^" inch. 
 
 The conjunctival epithelium of the cornea 
 may always be obtained from a fresh eye, 
 by gently scraping its surface. It consists 
 of three or four layers of superposed par- 
 ticles, inclinirig. to the columnar form, 
 where they rest on the anterior elastic 
 lamina, and becoming imbricated scales 
 on the surface (fig. Ul, a). In matiy of 
 
 n nni-, f, r^ n ^ Q j-i r- 
 
 A. Vertical aection of the Human 
 CoTnea. a. Conjunctival epithelium. 
 b. Anterior elaBiic lamina, from 
 which there pass off a nunYber of 
 fibres into c, the layer* of the cor- 
 nea proper, among which the nu- 
 clei are apparent, d. Posterior 
 elastic lamina e. Posterior epithe- 
 lium. - Magnified 80 diameters. 
 
 B. The posterior epiihelium, o, 
 seen in pection} p, seen in face.— 
 
CHOROIfi COAT OF THE EYE. 40t 
 
 the larger animals this epithelium consists of a much deeper series of 
 nucleated particles, and its transparency then becomes a rernarkable 
 character. 
 
 It is in this epithelium that particles driven with force against the 
 eye generally lodge, and it is easily detached by the instrument used 
 to extract them. Vessels shooting into the cornea in disease lie under 
 it, and small ulcers are formed by its destruction. In animals which 
 cast their skin this lamina is shed with the cuticle of the body. 
 
 The posterior elastic lamina of the cornea (fig. Ill, d) is a very 
 thin membrane in which no structure can be detected. It has all the 
 transparency of glass, and does not become opaque by maceration, 
 boiling, or the action of acids. It adheres but slightly to the cornea 
 proper, and, when peeled off, it has such a tendency to curl with its 
 anterior surface inwards, that it is difficult to retain a piece of it in an 
 extended form. If floated in water, it exhibits a peculiar glistening 
 lustre resulting from its density. It readily tears,'yet is so hard that 
 it is bitten through with difficulty. Its elasticity is great, and has 
 been supposed to contribute to the exact mainlenanc-e of the curvature 
 of thecorneaj so necessary for correct vision. This lamina extendi 
 only to the circumference of the cornea, where it becomes thinner; 
 and it ceases at the border of the iris, in a manner Jiereafter to be 
 described. ^ 
 
 Of the epithelium of the aqueous hiimor,~^The elastic lamina is itself 
 lined -by an exceedingly delicate epithelium, which exactly resembles 
 that existing on serous membtanes, (%. Ill, e,6,p; see also p. 129.) 
 Thrs-epitheliura is probably concerned iathe secretion of the aqueous 
 humor, but it does not extend over the'whole surface with which that 
 fluid is in ^lontact. It is probably limited to the cornea. 
 
 Of the Choroid.'— On turning aside the sclerotic and cornea (fig. 
 112), the choroid, with its process the iris, is exposed. The choroid 
 is of course perforated behind by the optic nerve. Around this it 
 adheres pretty firmly to the sclerotic, but in the rest of its extent very 
 slightly, and only by the medium of a slender web (lamina fusca), 
 and of those vessels and nerves which pass from the one coat to the 
 other. The rupture of these adhesions occasions a flocculent ap- 
 pearance of the choroid, and sets free some of the brown colouring 
 matter with which its structure is loaded. There is no serous cavity 
 between the sclerotic and choroid, as some have imagined, for a true 
 epithelium is wanting, though the lamina fusca contains nuclei. 
 
 The choroid, oh coming up to the cornea, gives off' its process the 
 iris, and it there adheres intimately to the sclerotic by a very narrow 
 ring of white tissue — the ciliary ligament. For an eighth of an inch 
 behind thi,s, however, it is coated by a semi-transparent band, which 
 we shall distinguish as the ciliary musclij, and the fibres of which 
 radiate from the cornea. 
 
 The chofoid contains some fibrous tissue, resembling that of the 
 sclerotic ; but it is composed principally of blood-vessels and pigment- 
 cells. It has been usual to describe it as having two layers, an arte- 
 rial and a venous; an incorrect view. It is in fact essentially a thin 
 lamina of capillaries, disposed in a close network, the meshes of 
 
408 
 
 INNERVATION. 
 
 ■which are rather smaller behind than in front. This plexus forms 
 the inner surface of the choroid, and has been kno\yn as the tunica 
 Ruyschiana. The arteries suppljiing it, and the vems carrying off its 
 blood, come to it and leave it at very numerous points, but on its 
 outer surface only, where they are so thickly arranged, side by side, 
 as to appear to form the whole of that surface. The veins in par- 
 ticular are large and numerous, and disposed in beautiful curves, 
 converging to four or five trunks, before quitting the choroid, and 
 styled the vasa vorticosa (fig. 112, e, e). The arteries run between 
 these, but less regularly. 
 
 Fig. 11-2. 
 
 Fig. 113. 
 
 Choroid and Iris, exposed by turning aside the sclero- 
 tica; — c, e. Ciliary, nervesbranchin^ in ihe ir-is. d. Small&r 
 ciliary nerve, e, e. Vasa voriicosa. h. Ciliary filament 
 and muscle. ■ ie. Converging fibres of the -greater circle .of 
 the iris. I. Looped and knotted form of these near the 
 pupil, with the converging fibres of the lesser circle of the 
 iris within Ihem. o. The optic nerve.— From Zinn. 
 
 Vessels of the choroid Ciliary 
 processes and Iris, inner surface. 
 — a. Portion of ihe capillary 
 network or tunica Ruyschiatia. 
 b. Ciliary proe-esaes. c. Portion of 
 the iris.— Prom an Infant. Mag- 
 nified 14 diam. AAer Arnold. 
 
 The capillary network of the inner surface is so close that there is 
 no room for pigment-cells in its interstices; but between it and the 
 arteries and veins, as well as among the veins theraselres, there is a 
 great abundance of colouring matter, which deeply tinges the whole 
 thickness of the membrane. 
 
 The pigment-cells in the substance of the choroid (fig. 114, b) are 
 extremely irregular in shape, and lie in various directions amongst 
 the other elementary tissues. Similar ones are found in the iris, an4 
 sparingly in the anterior part of the sclerotic. They are so loaded 
 with pigment that their nuclei are often obscured by it. 
 
 The pigmentary matter within these cells is of, a sepia colour, and 
 occurs in the form of oblong or oval grains, less than ■jsis-^ of an inch 
 
THE CHOHOIDAL EPITHELIUM. 
 
 4091. 
 
 A. ChoTOfdal Epilhelium, with the cells filled 
 with pigment, except at o, where the nuclei are 
 visible. The irrejulkrity of the pigment-cells is 
 seen. 6. Grains of pigment. 
 
 B. Pigment-cells from the, substance of the 
 Chorpid. A detached nucleus is' seen. — MagnS- 
 jied-32U diameters.i 
 
 long (fig. 114, 6). These grains exhibit molecular raotion when re^ 
 moved from the cells, and sorpetimes even within the cells (p. 72). 
 They are insoluble in hot or cold 
 water, in the dilute mineral ^cids, 
 and in strong acetic acid, in oil, 
 alcohol, and ether ; but are dis- 
 solved, after long digestion, by 
 diluted liquor potassse. The ash 
 consists of common salt, lime, 
 phosphate of lime, and oxide of 
 iron {Gmelin and Berzelius). 
 
 In albinos the colouring matter 
 is deficient, not only in the eyes, 
 but in other organs in which it 
 usually exists. The eyes have 
 consequently a pink appearance, 
 derived chiefly from the blood in 
 the choroid and iris. 
 
 Of the Choroidal Epitheliun^. — 
 On the inner surface of the choroid, within the capillary network, 
 and adhering slightly -to it, is an epithelium, consisting of a single 
 layer of nucleated particles, of a pentagonal or hexagonal shape, filled 
 with pigment. This was first particularly described by Mr. Wharton 
 Jones, who termed it the membrane of the black pigment. In using 
 this name, it must be remembered that the colouring matter is not 
 peculiar to this epithelium; and that this epithelium exists without 
 pigment in front of the tapetum lucidum of animals; and also that it 
 is present, without pigment, in albinos, as was firsts poifited out by 
 Mr. Jones. Hence the presence of pigment in its cells is a secondary 
 character. The nuclei of the cells project on the inner surface of 
 the membrane. They are concealed by the pigment if it is very 
 abundant, but in general they are visible. Both conditions are seen 
 in fig. 114, A. 
 
 In many quadrupeds and fi.shes the inner suVface of Ihe choroid, in its posterior 
 part, has a brilliknt lustre, owing to the presence of' a thick layer of wavy fibrous 
 tissue; peculiarly arranged, outsitie the choroidal epithelium (here colourless). This 
 tapetum lucidum must act as a concave reflector, causing the rays of light to traverse 
 the retina a second time, and thus, probably, increasing the visual power, particularly 
 when the quantity of light admitted into the eye is small. 
 
 In the osseous fishes there is a singular vascular organ of a horse-shoe shape ap- 
 pended to the outer surface of the choroid, and covered by a silvery membrane, lis 
 structure is imperfectly made out, and its ofBce is quite unknown. It is called the 
 choroid gland. 
 
 In birds there is a remarkable plicated, comb-like process of the choroid, projeeted 
 into the vitreous humor, and termed the peeten. It is a vascular membrane, and 
 covered with pigment; its base commenpiiig at the entrance of the optic nerve, and 
 its apex reaching more or less nearly to the crystalline lens. The retina does not 
 extend over it. No Satisfactory use has yet been assigned to it. Its size and shape 
 are subject to considerable variety. 
 
 The description of the ehoraid now given refers only to that por- 
 tion of it which corresponds to the retina, and tliis latter membrane 
 ceases at a line [ora serrata) about aa eighth of an iuch behind tti^ 
 
410 INNERVATION. 
 
 margin of the cornea. In front of this line, and as far as the iris, the 
 choroid is known as the ciliary body, being modified to form the 
 ciliary processes ; and it is covered on its outer surface by a serai- 
 transparent tissue, the ciliary musch, at the anterior edge of which is 
 a more opaque white ring, the ciliary ligament. 
 
 The ciliary processes of the choroid project as folds, or plaitings, 
 into the vitreous humor, and are there lodged in corresponding folds, 
 the ciliary processes of the vitreous body. They are seen from within 
 to commence at the anterior border of the retina, or ora serrata, as 
 mere streaks, converging towards the lens; and it is only when ad- 
 vanced more than half way to that body that they become projected 
 into about sixty or seventy plaits, with subordinate ones between. 
 These terminate by Sinall free extremities, which slightly overlap in 
 front the border of the lens, without touching it, being united to it 
 through the medium of a delicate layer of the hyaloid membrane of 
 the vitreous humor. These folds take firm hold of the vitreous humor 
 in its front part, all round the lens. Their texture is_very vascular 
 (fig. 113, b) and filled with irregular pigment-cells, (which in the 
 human eye are least numerous on the most prominent parts,) and on 
 their inner surface is a tough colourless lamina, composed of ill-defined 
 nucleated cells, (continuous with the border of tine retina, but clearly 
 not composed of nervous matter,) by means of which they are imme- 
 diately conhected with the hyaloid membrane. The strength of th?s 
 connection is evinced in attempts to sever it in the recent eye. After 
 a certain amount of decomposition has taken place, the separation is 
 much more easy. The ciliary processes by their anterior surface, 
 near their apex, contribute to form the posterior wall and side of the 
 posterior chamber, and are continuous with the back of the iris. 
 They are there free, and washed by the aqueous humor. The ciliary 
 processes are covered, and therefore concealed, on the outside by the 
 ciliary muscle. 
 
 The iris may rightly be regarded as a process of the choroid; it is 
 continuous with it,' although of a modified structure. It forms a 
 vertical curtain stretched in the aqueous humor before the lens, and 
 perforate,d for th-e transmission of light. It is attached all round at 
 the junction of the sclerotic and the cornea, so near, indeed, to the 
 latter that its anterior surface becomes continuous in the following 
 manner with the posterior elastic lamina. This lamina near its border 
 begins to send off from its anterior surface, or that towards the lami- 
 nated cornea, a network of elastic fibres, which stretch towards the 
 border, becoming thicker as they advance, until at length the entire 
 thickness of the lamina is expended by being converted into them. 
 These fibres then bend backwards from the whole circumference of 
 the cornea, to the circumference of the front of the iris, and are there 
 implanted, passing in this course across the rim of the anterior cham- 
 ber, and through the aqueous humor. They are seen more easily in 
 some animals than in others, forming a regular series of pillars around 
 the anterior chamber. Behind these there is a more diffused union 
 of the tissue of the iris with the sclerotic, by means of the- ciliary 
 ligaraenL The iris is continuous behind, near its border, with the 
 
STRUCTURE OP THE:IRIS. 
 
 411 
 
 Fig. 115. 
 
 ciliary processes, and \s only free in the inner half of its extent, near, 
 the pupil, where it is covered, with a dense layer of pigment, and 
 marked by converging striae. This posterior surface is termed uvea. 
 In consequence of the extreme proximity of the iris to the lens, the 
 posterior chamber is much less capacious than the anterior, as it is, 
 likewise of smaller diameter. 
 
 The anterior surface of the iris has a brilliant lustre, and is marked 
 by lines accurately described by Dr. Jacob, 
 taking a more or less direct course towards the 
 pupil. These lines are important as being in- 
 dicative of a fibrous structure. Slender, and 
 very numerous in, the outer three-fourths of the 
 membrane (the pupil being contracted), and 
 often crossed near the border by wave-like 
 differently coloured lines, they unite at about 
 T2 of an inch from the pupil into a circular 
 series of knotted and much thicker elevations, 
 from which finally proceed a multitude of mi- 
 nute branching and anastomosing filaments, 
 to the extreme verge of the pupil. When the 
 pupil is contracted, these converging fibres are 
 stretched; when it is dilated, they are thrown 
 more or less into zigzags. The pupil is nearly 
 circular, and is situated rather to the inner side 
 of the centre of the iris. By the movements 
 of the iris it is dilated or contracted, so as to 
 admit more or less light to the interior ; and its 
 diameter under these circumstances may vary 
 from about ^V to ^ of an inch. 
 
 The varieties of colour in the eyes of dif- 
 ferent animals and individuals depend almost 
 solely on the colour of the front of the iris, 
 which itself resides chiefly in pigment-cells, 
 situa'ted in its substance rather than as a layer 
 on its anterior surface. These cells are most irregular in shape aad 
 size, and lie in the interstices of the more essential tissues, which 
 they much obscure. The iris is consequently best examined in albino 
 specimens. 
 
 The iris is undoubtedly contractile, and the anatomical characters 
 of its principal tissue so nearly resemble those of unstriped muscle, 
 that it may be considered as. a variety of that tissue. Its fibres are 
 loaded with nuclei which are rather rounded than those of unstriped 
 muscle, and more loosely attached to the contractile material. The 
 principal direction taken by the fibres is towards the pupil, although 
 they are more or less meandering and interlacing in this course. 
 Arrived near the pupil, they appear to join, and fornj indistinct arches. 
 In many instances it is easy to detect a set of circular fibres, either 
 gathered into a principal bundle near the pupil or more diffused, but 
 always lying in front of the others. These seem to answer to the 
 circular fibres of the bird's irisj which are of the striped variety, and 
 
 Network of yellow fibrous 
 lispue at the border of the 
 elastic lamina of the cornea: 
 —a. Outer border, where the 
 fibres approach the iris. At 
 their inner end, 6, they are 
 lost on the elastic lamina, — 
 Magnlfied-70 diameters. 
 
412 
 
 INNERVATION. 
 
 occupy the front of the membrane. There may also be usually dis- 
 tinguished in the very thin margin of the pupil an arrangement of 
 fibres more circular than radiating. 
 
 The iris is so vascular that some anatomists have considered it 
 erectile, and have erroneously ascribed its movements to this pro- 
 perty. But its vessels are slender and delicate, and resemble those of 
 the unstriped muscle. They are derived chiefly from the two long 
 ciliary arteries, which on approaching it bifurcate, and form a circle 
 around it, whence pass inwards a great number of minute branches, 
 which form loops near the pupillary tnargin. 
 
 On the anterior surface near the pupil a vascular circle marks the 
 line from which in the fcetus the memhrana pupillaris stretched across 
 in front of the piipil. This membrane at that early period divides the 
 anterior from the posterior chamber, and receives from several parts 
 of the circular vessel last mentioned, small branches which approach 
 the centre, and then return in arches, after inosculating sparingly 
 across the central point. The memhrana pupillaris is almost absorbed 
 at birth. 
 
 The grayish structure coating the choroid for about an eighth of an 
 inch behind the cornea, presents at its anterior edge a more white 
 and opaque circle, the ciliary ligament, which seems to be chiefly of 
 a fibrous character, and to connect the border of the iris firmly to the 
 sclerotic. The plexiform tissue of the posterior elastic lamina of the 
 cornea already noticed, adjoins this ligament, and partially blends 
 with it. 
 
 The ciliary muscle is that grayish, semi-transpareni: structure behind 
 the ciliary ligament, and covering the out- 
 side of the ciliary body. It- has been tie- 
 scribed as muscular by many of the older 
 anatomists, especially by Porterfield, while 
 others have assigned to it a different cha- 
 racter. Lately it has been so regarded by 
 Wagner and Dr. Wallace of New York, 
 and we believe correctly. It belongs to the 
 unstriped variety of muscle, and its fibres 
 appear to radiate backwards from the junc- 
 tion of the sclerotic and cornea, and to lose 
 themselves on the outer surface of the ciliary 
 body. The more superficial fibres are in 
 contact with, but scarcely adhere to, the 
 sclerotic, and are inserted into the posterior 
 part of the ciliary body; while the deeper 
 ones seem to dip behind the iris to the more 
 prominent parts of the ciliary processes which 
 approach the lens. The ciliary muscle must 
 have the effect of advancing the ciliary pro- 
 cesses, and with them the lens, towards the 
 cornea. The ciliary nerves pierce this muscle on their way to the 
 iris, distributing to it many filaments which may be seen for the most 
 part to cross the fibres. 
 
 Fig. 116. 
 
 Diagram to show the po9Llion 
 and actionof the Ciliaiy Muscle ; 
 — a. Sclerolic, 6. Cornea, c. Cho- 
 roid, separated a little from the 
 sclerotic. £2. Siiuaiujuof the ci- 
 llftTy ligament, and point from 
 which the ciliary musele radi- 
 ates. f.Iris. n Lens, connected 
 with the ciliary processes by the 
 anterior wail of the canal of 
 Petit, the situation of which is 
 inariced by Iho •.—Magnified 3 
 rfliamelerB. 
 
STRUCTURE OF THE RETINA. 41 
 
 The muscular nature of ihjs structure is confirmed by its anatomy in birds, where 
 it is largely,developed, as noticed by Sir P. Crampton. We iind its fibres to be of 
 the striped variety, like the circular fibres of the iris in the same class, and to be sup- 
 plied by ciliary nerves traversing the mnsclein a circular direction. 'J'hey likewise 
 all radiate from the cornea, at the circumference of which they are attached to the 
 • deeper layers of the cornea proper, the elastic lamina being here exceedingly thin. 
 
 Within the choroid is the retina, which we shall describe as a 
 structure distinct from the optic nerve, though continuous with it ; 
 reserving our account df that nerve, and of the others pertaining to 
 the eye, till the anatcimy of the globe is concluded. 
 
 The retina is the sheet of nervous matter which receives the 
 images of external objects thrown upon it by the transparent media, 
 and it is accordingly placed iranpediately behind the vitreous humor, 
 the deepest of those media. It may be said to commence at the 
 forainen in the selero,tic and choroid by which the optic nerve enters 
 the eye, and, to terminate by a finely jagged border (the ora serraia) 
 at the hinder bjnrder of the striated part of the ciliary body. It is 
 thicker behind, in the deepest part of the globe, and gradually thinner 
 forwards. Of a pinkish-gray tint, and semi-transparent when fresh, 
 the images formed upon it may be seen through it from behind, if 
 the sclerotic and choroid coats be first carefully retnoved. When 
 thrown into accidental folds, it resembles in appearance the vascular 
 gray substance of the cerebral convolutions. The exquisite function 
 performed by this nervous membrane, its expanded form and sepa- 
 rability from other structures, have always made it an object of pecu- 
 liar interest with physiologists, who have not unreasonably expected 
 that important secrets of nervous function might be disclosed by an 
 accurate insight into its structure. Whatever the conclusions to be 
 drawn, it is certain that this structure is elaborate and complex, and 
 worthy of an attentive study. 
 
 The first part of the retina to be described is the Jfibi-ous gray layer, 
 which forms the immediate continuation of the optic nerve, and which' 
 is seated on its inner surface. This is a layeri of fibrous character, 
 radiating from the end of the optic nerve, and apparently consisting 
 of the tubular fibres of that nerve deprived of their white substance; 
 that is, being no longer tubular and white, but solid and gray, and 
 united together more or less into a membrane. This at least seems 
 to us to be certain, that the white substance of Schwann does not 
 exist in the nervous substance of the retina, but ceases as the nerve 
 perforates the sclerotic. . It has been particularly described as existing 
 in the retina of the rabbit ; but the fact seems to be, that in this aniinal 
 the nerve does not end in the retina till some way within the globe, 
 for, after bifurcating and spreading out as a white streak within the 
 choroid, the bundles of nerve-tubes suddenly lose their white lustre, 
 and assume the appearance pf the gray fibres of the layer now under 
 consideration. These bundles, both in animals and man, may be 
 seen to anastomose in a close plexiform manner, especially near the 
 optic nerve, and finally constitute a thin sheet, which becomes thinner 
 and less fibrous as we trace it forwards, tintil at length it can be no 
 longer discerned. This i^brous gray layer of the retitia is tinited.to 
 the hyaloid membrane, containing the vitreous humor, by a layer of 
 
414 IJfNERVATION. 
 
 nucleated cells almost perfectly transparent, and sometimes very 
 difficult of discovery on that account. It is to be remarked, that the 
 fibrous gray layer is the only nervous element of the retina existing 
 over the extremity of the optic nerve where it enters the globe — a 
 spot incapable of vision. Immediately around this spot, the other 
 
 Fig. 117. 
 
 Vertical section of the Human Retina and Hyaloid "Membrane, h. TTyalo'ia'meinbVane. A'. Nnclei 
 on its' Innei' feiirfabe. c. liayter of trtSnteparem oellsj obnhecllng the iyaloidand retina, c'. Sepa- 
 rate cell «n)arged by Lmbibitio,n of water, n. Gray nervous layer, with its capillaries. 1. Its fibrodb 
 lamina. 3. tts vesicular laiUtna. 1'. Shred of 'fibrous 'fantitra detached. S'. Vesicle and nucleus 
 -detached, g-. Granular- iayer. 3. liight lamina frequently seen. £*'. Detached nucleated particle 
 ■of the granular layer, m. Jacob's membrane, m'. Af^earan'ces of its particles, 'when detached. 
 m"': Iti outer surface. Magnilied S30 diameters. 
 
 layers commence which have now to be described, and the first of 
 these is the vesicular gray layer. This layer is on the outer surface 
 of the fibrous layer, and so intimately blended with' it, that it might 
 almost seem as if the fibres successively terminated in it. The vesi- 
 cular layer is thicker behind, and gradually thinner forwards. It very 
 accurately corresponds with the vesicular ma:tter of the convolutions 
 of the cerebrum, consisting of a finely granular matrix with inter- 
 spersed very delicate vesicles, furnished with pellucid globular nuclei 
 of characteristic appearance. 
 
 The blood-vessels of the retina, ^)?hich are thickly distributed, be- 
 long solely to the fibroug and vesicular layers now mentioned. The 
 central artery of the retina, after entering the globe in the axis of the 
 optic nerve, sends four or five radiating branches, which almost imme- 
 diately perforate the fibrous layer and spread out in a beautifully 
 arborescent manner, as a capillary network in the substance of the 
 vesicular stratum. After slight maceration, it is easy to wash the 
 nervous material out of the meshes of the vessels ; and they tjien form 
 a vascular layer, but which it is hardly correct to describe as a dis- 
 tinct lamina of the retina. They are merely the nutrient vessels of 
 the part, and are the representative of the close network of the gray 
 substance of the cerebral convolutions. Their wall is a diaphanous 
 membrane with nuclei projecting at intervals, and the meshes average 
 f^^ of an inch diameter. 
 
 Behind the vesicular gray layer is the granular layer, a term we 
 shall apply to it, because it seems to consist of a close aggr^'gation 
 
STRUCTURE OF THE RETINA. 415 
 
 of small granules, which refract the light mpre po\!Ferfully than the 
 neighbouring parts, and have scarcely any appearance of intervening 
 matrix; they might he regarded perhaps as analogous to the nuclei of 
 cells, and much resemble a layer of granules in the substance of some 
 of the cerebral convolutions, and of the laminse of the cerebellum. 
 They are made more evident by acetic acid.. This layer is divided 
 into two, of which the inner is much the narrower, by di. pale stratum, 
 which can only be seen by very, careful manipulation, 
 
 On the outside of the granular layer is that remarkable lamina, 
 known by the name of its discoverer, 
 the membraria Jacobi. It consists of Fig. 118. 
 
 club-shaped rods, placed uprightly, 
 the thin end invvards, the thick out- 
 wards ; and it is very easily detached 
 from the rest of the retina, wh^n the 
 choroid is removed, so as to float as 
 delicate shreds, visible to the naked 
 eye, in the water in which the eye is 
 immersed. The rods have a tendency 
 to separate from one another when 
 placed in water, and the club-shaped 
 extremities are then often seen to be 
 formed by a sudden bending back of Outer surface of the Retina, showing 
 
 , •',., , ,.° , the membrane of Jacob, partially deiach- 
 
 the stem like a crook, which may be ed. After Ja,coh. 
 more or less opened out. Interspersed 
 
 among the rods are seen on the outer surface a number of -clear spaces, 
 as though transparent cells were disseminated aijaong them. This 
 layer forms the connecting medium between the retina and the cho- 
 roidal epithelium. 
 
 It has been before stated that the optic nerve pierces the sclerotic 
 and joins the retina about an eighth of an inch on the inner side of the 
 axis of the eye. Precisely in this axis, the retina is of a decidedly 
 yellow colour in a roundish spot of about ^j of an inch diameter, 
 called, after its discoverer, the yellow spot of Scemmerring. This 
 spot exists only in man and the monkey among mammalia, but an 
 analogous part has been found by Dr. Knox in reptiles. It has been 
 described by some as a fold, by others as a foramen in the retina, anfl 
 after several examinations we should speak of it as a small mound, 
 or projection of the retina towards the vitreous humor, with a minute 
 aperture in the summit. On removing the sclerotic and.choroid with 
 the utmost care, the interior of the globe can be seen from the out- 
 side, through this hole; and yet the membrane of Jacob appears to be 
 continued over it. On examining the structure of the retina about 
 the yellow spot, fronj within, the fibrous expansion of the optic nerve 
 (though stretching in every other direction to a much greater dis- 
 tance) cannot be traced quite up to the spot itself. Nucleated cells 
 occupy the elongated meshes of the, fibrous plexus already describefj, 
 until at length the fibres disappear, and the closely set cells seem to 
 cover the whole, surface of the spot. The gradual subsidence of the 
 §br.e^ in the .interstices of the cells we have distinctly seen. As for 
 
416 INNERVATION. 
 
 the colouring matter, it is not in grains of pigment, but stains the 
 several tissues, and soon disappears in water. The use of the yellow 
 spot is unknown. It is interesting to observe, in 
 Fig. 119. connection with the perfection of vision over the 
 
 spot, that the principal branches of the artery 
 and vein of the retina, above and below, curve 
 round it at a distance, going, as it were, out of 
 their course to avoid it, so that only capillary 
 vessels are found in its immediate vicinity. 
 
 It now remains /to describe the transparent 
 
 The yellow spot of the media which occupy the interior of the ball of 
 
 Retina occupying tjie axis fUp pyp 
 
 of the eye I and the en' Tni • 7 i i • • i • r 
 
 trance of the optic nerve, The vitreous ooov, lying in the concavity 01 
 
 retinsB on the inner side of -the ■Tctina, and filling all but about the anterior 
 ring"""''""®'^'"'™'" fifth of the globe, has, when entire, the consist- 
 ence of soft jelly. It consists of an exceedingly 
 fine and close, but perfectly transparent web of fibrous tissue, the 
 meshes of which are exceedingly small, and contain an aqueous fluid. 
 If the tissue be cut into, the water will slowly drain off", showing the 
 continuity of the cells with one another; and the manner in which 
 they are constructed by interlacing fibres may be very plainly seen 
 with a high power near the ciliary processes, in the vicinity of which 
 these fibres are particularly strong. The whole vitreous body is 
 bounded by or contained in an envelop of extremely thin homoge- 
 neous membrane, having corpuscles or cell-nuclei on its inner surface, 
 where the fibrous tissue is attached (fig. 117, h, h'). It would perhaps 
 be convenient to restrict the term hyaloid membrane to this envelop. 
 Where the retina extends, that is, as far as the ciliary body, the 
 hyaloid membrane is in contact with its inner surface, and united 
 to it by an extremely transparent layer of cells, whicb often remain 
 invisible until swollen by the imbibition of water (fig. 117, c, c'). 
 These cells serve merely as a bond of connection between the hyaloid 
 membrane and the fibrous lamina of the retina. Between the ante- 
 rior border of the retina and the border of the lens, the vitreous body 
 is accurately adapted to the ciliary striee and processes of the chol-oid, 
 and presents a series of plaitings precisely similar to those of the pro- 
 cesses themselves, and termed the ciliary processes of the vitreous body. 
 Collectively they form a circle called zonula ciliaris, or, zone of Zinn. 
 The two structures are in a manner dovetailed into one another; and 
 so intimate is their union, that, when the processes of the choroid are 
 drawn away from the vitreous body, some of their pigment is gene- 
 rally left adhering to the processes of the latter. 
 
 In the centre of its anterior surface, in a space nearly corresponding 
 to the area between the points of the ciliary processes, the vitreous 
 body is hollowed out to receive the crystalline lens. This latter is 
 contained in, or bounded by, a perfectly closed capsule, composed of 
 a tissue exactly resembling the elastic lamina of the cornea already 
 described. To the whole posterior surface of this capsule, and to a 
 very narrow circumferential portion of its anterior surface, the fibrous 
 structure of the vitreous body is firmly attached ; the hyaloid mem- 
 
VITREOUS BODY.— CRYSTALLINE LENS. 
 
 417 
 
 Fig. 120. 
 
 brane itself not passing behind the lens, but adhering to the capsule 
 all round a little in front of its rim, after crossing the interval sepa- 
 rating the tips of the ciliary processes of the choroid from the lens. 
 Thus the rira of the lens is not exactly at the surface of the vitreous 
 body, but buried slightly within it, and over- 
 lapped a little by it. All round the rira of the 
 lens, there is a cavity in the vitreous body, ex- 
 tending under the circle of the ciliary processes 
 of the latter, and termed the canal of Petit (fig. 
 120, and fig. 116*). The hyaloid membrane 
 constituting these ciliary processes forms the 
 anterior wall of this canal, which, by its adhe- 
 sion to the ciliary processes of the choroid, is 
 subject to be drawn forwards by the contraction 
 of the ciliary muscle already described (p. 412). 
 When this occurs, the lens also is advanced, in 
 consequence of the union of this anterior wall 
 of the hyaloid to its anterior surface near the 
 rim. Were the canal of Petit wanting^ the 
 
 ciliary muscle would act rather on the vitreous body around the lens, 
 than on the lens itself. Its existence may be easily shown by filling 
 it with mercury or air, through an artificial orifice in its anterior wall. 
 The injected fluid fills out the plaitings of the ciliary processes. 
 
 The refracting index of the vitreous body is about 1'339, that of 
 water being r336, so that the difference between them is very trifling, 
 and may be referred in part to the transparent fibrous tissue. Its 
 chemical constitution, according to Berzelius, is as follows: 
 
 Posiiion of the Lens in the 
 vitreous humor, shown by an 
 imaginary section. Thedarlc 
 triangular space oh each 
 side ottlie lens is intended to 
 indicate the position of the 
 canal of Petit.— After Ar- 
 nold. 
 
 Water .... 
 Chloride of Sodium, with extractive mailer 
 Albumen 
 
 98-40 
 1-42 
 
 •18 
 
 100 00 
 
 i 
 
 In early life the vitreous body gives passage by a canal to a branch 
 of the central artery of the retina to the back of the lens; and in large 
 animals, though not in man, this appears to supply some branches to 
 the vitreous body itself even in the adult state. 
 
 The crystalline, as already mentioned, is a double convex lens; 
 but its surfaces are of unequal curvature, the posterior being the more 
 convex. In the adult the difTer- 
 ence is nearly as 4 to 3, but it is Fig. lai. 
 
 liable to some variety in difTerent 
 subjects. Chossat has observed 
 that the curvatures of the lens in 
 the ox are ellipsoids of revolu- 
 tion round the lesser axis, but 
 whether they are so in man is not 
 determined: the subject is one 
 very difficult of investigation. 
 The lens alters its shape with age ; being in the fcgtus more spherical, 
 more flattened in childhood, and still more so in advanced life. In 
 21 
 
 Human Lens 
 old. c Adult. 
 
 tially separated inlQ segments.- 
 ring. 
 
 At birth. 6. At six years 
 Hardened in spirit, and par- 
 _ _■_..__ , After Sccminer- 
 
418 
 
 INNERVATION. 
 
 Fig. 122 
 
 infancy it projects into the aqueous humor so as to touch the iris; but 
 in old age there is a space intervening. The lens also varies in con- 
 sistence with age ; being very soft at an early period, very firm in 
 declining years. At no epoch of life, however, is it of uniform con- 
 sistence throughout; being always denser and firmer from without 
 inwards. In the adult its diameter is from 5 to # of an inch, and its 
 antero-posterior axis about i to ^ of an inch. It weighs from three 
 to four grains. 
 
 The lens is divided into capsule and body. The manner in which 
 it is encased and fixed by the capsule in the vitreous body, has been 
 already described. It only remains to add, that the anterior wall of 
 the capsule is nearly four times thicker than the posterior ; greater 
 strength being required in front, where the surface is free in the 
 aqueous humor, than behind, where it is adherent to the tissue of the 
 vitreous body. The diminution in thickness does not occur abruptly 
 at the rim of the lens, but commences gradually on the anterior 
 surface near the rim, at a line corresponding to the attachment of 
 the anterior wall of the canal of Petit. The capsule is perfectly 
 closed, and cannot allow of the passage of either vessel or nerve to 
 its interior. . 
 
 The body, of the lens is constructed in a manner calculated to excite 
 
 admiration. Its super- 
 ficies, by which it co'mes 
 into contact with the cap- 
 sule, consists of a layer 
 of extremely transparent 
 nucleated cells repre- 
 sented in fig. 122, a. 
 These cells form an or- 
 ganized connecting me- 
 dium between the body 
 and capsule of the lens, 
 and there is no interspace 
 not occupied by them. 
 After death they very 
 soon become loaded with 
 water (absorbed most 
 probably by the capsule 
 from the aqueous humor), which is the aqua Morgagni, that some 
 have supposed to exist naturally between the capsule and body of the 
 lens near its border. 
 
 The body of the lens is composed of fibres superimposed on one 
 another, and united side to side in laminae, of which many hundreds 
 must exist. The mode of arrangement of the fibres is, however, more 
 artificial than this. In the mammalia in general there are visible on 
 the front surface, when the lens has slightly lost its transparency, 
 three lines, extending from the centre two-thirds to the border, and 
 dividing it into three equal parts: and on the opposite surface three 
 similar lines exist, having an intermediate position. From and to 
 these lines the fibres pass from surface to surface. Thus, a fibre pro- 
 
 a. Cells'connecting the bodyof the lens tails capsule (hu- 
 inan). 6. Fibres of the lens, with slightly sinuous edges 
 (human), c. Ditto from the Ox. with Irnely serrated edges* 
 d. Ditto from the Cod; the teeth much coarser.— JMagnified 
 320 diameters. 
 
STRUCTURE OF THE LENS. 
 
 419 
 
 ceeds from the centre in front, advances midway between two of the 
 lines over the border, and comes on the opposite surface to the ex- 
 tremity of one of the lines. Others pass from the extremities of the 
 lines in front, and are lost in the centre behind. And the rest of the 
 superficial plane are intermediate to these, and as nearly parallel as 
 their curved course will allow. If we now consider that these lines 
 on the surface are but the edges of planes which dip to the centre, 
 and afford points of divergence and concourse for all the fibres deep 
 as well as superficial, we shall readily comprehend what may at first 
 sight seem an intricate structure. This arrangement was known to 
 
 Fig. 123. 
 
 Fig. 124. 
 
 Lens, hardened in spirit and 
 partially divided along the three 
 interior planes, as well ' as into 
 laraellEe.— Magnified 3? diameters. 
 After Arnold. 
 
 Triple line on 'the surfaca 
 of the Lens of the Sheep, 
 with the radiation of the fi- 
 bres indicated. The inter- 
 space between the radiating 
 lines at the circumferences 
 of this figure would each in- 
 clude about a hundred fibres. 
 ~J\lagnified 3 diameters. 
 
 Leeuwenhoeck, and has been shown by Sir D. Brewster to present 
 varieties in different classes of animals. In the human lens we find 
 the tripartite division is seen imperfectly, and only in the centre ; for 
 the three primary diverging lines bifurcate again and again, and with 
 considerable irregularity, so that the ultimate sub4ivision is into from 
 twelve to sixteen parts in the adult, but only from four to six in the 
 foetus. 
 
 To the account now given may be added, that as the fibres are 
 shorter in proportion as they are more internal, so do they appear 
 narrower, more cylindrical, solid, and intimately united to each 
 other, as we trace the structure inwards. The superficial fibres are 
 flattened according to the surface they answer to ; and of all it may 
 be said, that they are narrower towards their extremities, as their 
 arrangement renders necessary. The edges of the fibres in fishes are 
 most beautifully toothed, and dovetailed together, as Sir D. Brewster 
 pointed out (fig. 122, d) ; and .something similar may be detected in 
 the more superficial fibres of the lens of the larger mammalia, and in 
 man. But the deepest fibres present scarcely any trace of this eler 
 gant structure. Near the tripartite division of the lens the fibres are 
 rapre united than elsewhere, and appear more or less consolidated 
 together. The average thickness of the fibres in man is about j ^V^ of 
 an inch. 
 
 The increasing density of the lens towards its centre is attended 
 with an increase of the refracting power, designed to augment the 
 
420 INNERVATION. 
 
 convergence of the central rays of the transmitted pencils in their 
 course through the lens, and thus to bring them to the same focus with 
 the circumferential rays. Sir D. Brewster states the refracting power 
 of the lens at its surface to be 1"3767, and at the centre 1'3990. 
 
 The lens, during its development, has a very copious distribution 
 of blood to the outer surface of its capsule, from two sources. The 
 central artery of the retina sends a vessel through the vitreous humor 
 to the centre of its posterior surface, which branches into a radiating 
 series of capillaries investing it as far as the border, where they 
 anastomose with vessels derived from the ciliary processes, which 
 proceed some way over the front of the capsule, and return in loops. 
 None of these vessels continue after the lens has attained to maturity. 
 
 The lens consists chiefly of albumen, and becomes hard and opaque 
 by boiling. The central parts evidently contain a smaller proportion 
 of water than the outer layers, which merely become flocculent by the 
 action of heat. The fibrous and lamellar structure is more easily seen 
 when thus rendered opaque, and it then separates more easily along 
 the triple or multiple planes already indicated. Berzelius states the 
 precise chemical constitution of the lens to be as follows: 
 
 Water 
 
 Albumen 
 
 Alcoholic extract, with salts 
 
 Watery extract 
 
 Membrane 
 
 58- 
 
 35-9 
 24 
 1-3 
 2-4 
 
 100-0 
 
 The aqueous humor, as its name imports, is very nearly pure water, 
 containing, according to Berzelius, less than a fiftieth of its weight of 
 other matters, of which more than half is chloride of sodium, and the 
 rest extractive, soluble either in water or alcohol. 
 
 It fills up the space between the cornea and lens — a space divided 
 into two cavities by the membrana pupillaris in the foetus, and still 
 partially divided by the iris into an anterior and posterior chamber, 
 continuous through the pupil. The anterior, though small, is much 
 larger than the posterior, and is bounded by the cornea in front, the 
 iris behind, aijd a portion of the ciliary ligament at its circumference. 
 The posterior is bounded by the iris in front, the lens and a narrow 
 circle of hyaloid membrane behind, as well as by the ciliary processes 
 which slope towards the iris, and thus limit the lateral dimensions of 
 the chamber. It is very easy to imagine the existence of a lining 
 membrane to this cavity of the aqueous humor, such as would form 
 a closed sac, and answer to the serous structures; and a membrane of 
 the aqueous humor has accordingly been described by several anato- 
 mists. But the most careful observation fails to detect any such 
 serous sac, though the posterior epithelium of the cornea (p. 407) 
 closely resembles that of serous surfaces. No epithelium exists in 
 front of the iris, and certainly none is present on the anterior surface 
 of the lens: this we can aver from repeated examination. On the 
 posterior surface of the iris, however, there seems to be a pigmentary 
 membrane. 
 
 Of the Optic JVerves, and their central connections. — The second 
 
THE OPTIC NERVES. 421 
 
 pair of nerves is devoted to the sense of sight, and on that account 
 has received the name of Optic Nerves. 
 
 The marked manner in which these nerves terminate in the retinae, 
 the constant relation in size between them and the organ of vision, 
 the atrophy which they suffer when the visual apparatus has been 
 destroyed, the impairment or loss of vision which follows a morbid 
 state of them, place it beyond all question that they are the proper 
 conductors of visual impressions to the sensorium. 
 
 The optic nerves form a most extensive connection with the brain 
 through the optic tracts. The optic tracts are 
 two flattened bands of nervous matter, which ^'g- 135. 
 
 proceed from the posterior and superior surface 
 of the mesocephale (the region of the quadrige- 
 minal tubercles) forwards along the inferior sur- 
 face of each crus cerebri, and after passing in a 
 curved course (concave inwards) along the base 
 of the brain, unite in front of the tuber cinereura 
 and mamillary bodies, and form a very intimate yi^''~'\^ 
 
 junction, which is called the chiasma or com- /T, \\ 
 
 missure of the optic nerves. \n // 
 
 From this chiasma the optic nerves spring. Plan ofiheopiio nerves on 
 
 di- _. .1 r I • 1. i.i_ L • T a small scale, sliowiner Iheir 
 
 diverge as they pass forwards into the orbits divergence from the cw as- 
 through the optic foramina. This point may rgiob"e,on'aeT„rr^il^ 
 be looked upon, therefore, as their origin. To ofthe axis of the humors. 
 understand, however, more exactly their relation 
 to the brain, it will be necessary to trace the connections of the optic 
 tracts, and to inquire into the structure of the chiasma. 
 
 In tracing each optic tract back from the chiasma, we find that it 
 first forms a pretty close connection with the locus perforatus on the 
 outside, and with the tuber cinereum on the inside. Whether any of 
 its fibres spring from the tuber cinereum is matter of great uncer- 
 tainty. Further back the optic tract adheres by its outer margin to 
 the crus cerebri, and is concealed by the middle lobe of the brain. 
 In this course it expands con^derably, and at the posterior edge of 
 the crus cerebri it forms intimate connections with certain gangUforra 
 masses of the brain. First, we observe its connection with the ex- 
 ternal geniculate body, a small prominent tubercle of darker colour 
 than the surrounding parts, and situate at the posterior margin of the 
 crus; it seems to involve the outermost fibres of the tract, as a gan- 
 glion, and from it a band of fibres is continued back to the posterior of 
 the quadrigeminal bodies. Beneath the posterior extremity of the 
 optic thalamus the innermost fibres. of the tract form a connection with 
 another similar body, the internal geniculate body, from which fibres 
 are continued backwards to the anterior of the corpora quadrigemina. 
 The tracts, thus, appear to divide, each into two bands: of which th^ 
 outer one, after passing through the external geniculate body, reaches 
 the testes; and the inner one, similarly related to the internal geni- 
 culate body, reaches the nates. 
 
 The optic tracts are connected with the optic. thalami chiefly through, 
 the geniculate bodies. Each tract adheres to the outer side cf its cor- 
 
422 
 
 INNKRVATION. 
 
 responding thalamus for some distance, but whether any fibres sink 
 into it is not determined. In the horse, dog, sheep, and monkey, 
 this arrangement is very conspicuous, as the greater portion of tiie 
 fibres of the tract expands over the internal geniculate body, which 
 is incorporated with the posterior extremity of the thalamus. The 
 diameter of the tubules of the optic tracts we have found to vary 
 
 from 
 
 to ToTTTT of an inch. 
 
 and inferior to, the tuber cinereum. 
 Fig. 126. 
 
 Course of fibres in Ihe chlasma, as exhibited by 
 tearing olf the superficial bundles from a spee.men 
 hardened in spirit, a. Anterior fibres. coTnmissural 
 between the two retinae, p Posterior fibres, com- 
 missural between the tUaiami. a\p'. Diagram of 
 the preceeding. 
 
 The chiasma results from the junction of the optic tracts in front of. 
 
 The fibres which form the inner 
 margin of each tract, jOj are con- 
 tinued across from one side of 
 the brain to the other, and form 
 no connection with the optic 
 nerves, and exist where those 
 nerves do not exist, as in the 
 mole. These fibres may be re- 
 garded, as commissural between 
 the thalami of opposite sides. 
 The remaining fibres of the 
 tracts go to form the optic 
 nerves ; the central ones pass 
 into the nerve of the opposite 
 side, decussating the similar 
 fibres of the other tract ; and the outermost fibres, much fewer in 
 number than the central ones, pass to the optic nerve of the same 
 side. 
 
 This disposition of the fibres of the chiasma may be demonstrated 
 on a specimen which has been sufficiently hardened in spirit, by tearing 
 the fibres in iheir proper direction after the removal of the neurilemma. 
 By such a procedure it may be shown that each optic nerve derives 
 its principal fibres from the tract of the opposite side, and only a few 
 fibres from those of its own side. 
 
 The existence of such a decussation of fibres in the chiasma is, 
 moreover, rendered highly. probable by the strong indications of most 
 extensive decussation, resembling that of the anterior pyramids, in 
 some of the large carnivorous birds, and also in the crossing of the 
 entire optic nerves in some of the osseous fishes, the cod for example. 
 In the common domestic quadrupeds the decussation of the fibres 
 is not to be made out so plainly, probably from its being more com- 
 plicated. The chiasma somewhat resembles a knotted union of the 
 two tracts, which is dense and firm in structure. 
 
 The optic nerves appear also to be connected by fibres, forming the 
 anterior border of the chiasma, and which may be regarded as com- 
 missural between the two retinje (a, fig. 126). 
 
 From the quadrigeminal tubercles to the chiasma, nerve-tubes, 
 mostly of large size, are visible by the microscope in the tracts. In 
 the chiasma and the optic nerves, the fibres, although very variable 
 in size, are so closely connected together that it is exceedingly diffi- 
 cult to separate them. They seem to be collected into numerous 
 small bundles, having an intricate plexiform interlacement within the 
 
THE OPTIC NERVES. 423 
 
 common sheath. Each bundle is surrounded by a firm but dense 
 neurilemma, and thus it is impossible by the ordinary means of mani- 
 pulation to separate a portion of the nerve of sufficient delicacy to 
 examine any considerable length of its fibres. 
 The size and character of the fibres may be Fig^i27. 
 
 estimated by examining portions of them 
 which project from the margin of the piece. 
 The optic nerve is abundantly supplied 
 with capillaries, which form a network wTth 
 elongated meshes in its substance. A little 
 behind the globe, it receives from the oph- 
 thalmic artery a branch, before alluded to, 
 the arteria centralis retinae, which penetrates 
 to its axis, along which it runs to the interior rl^f^'SS^.'l^: Zf^S^Vr 
 of the eye, in a canal of fibrous tissue. This various sizes, and varicose. At 
 
 , 11 I'j. 11 • o the central axis projects be- 
 
 brancn then radiates to supply the retina, yond the white substance at a 
 and in the fcetus sends forwards a twig to the Si^!° ex.remity.-Mag«. 320 
 lens. It is accompanied everywhere by cor- 
 responding veins. 
 
 Other nerves are distributed to the eye, which are connected with 
 the nutrient and other actions of the eyeball. These are derived«from 
 the ophthalmic division of the fifth, from the third pair, and from the 
 sympathetic. It is remarkable, however, that all these nerves, with 
 two exceptions, between their origin, and their distribution in the 
 globe of the eye, meet in a small ganglion situated on the outer side 
 of the optic nerve, called the ophthalmic or lenticular ganglion. This 
 body is usually considered a portion of the cephalic division of the 
 sympathetic; it is connected with the superior cervical ganglion by a 
 long branch which ascends from the carotid plexus along the carotid 
 artery, and enters the orbit. A long nerve from the nasal branch of 
 the ophthalmic division of the fifth also joins this ganglion at its supe- 
 rior and posterior angle, and a short thick branch from the third nerve 
 joins the ganglion at its inferior posterior angle. From the anterior 
 angles of the ganglion thus formed, proceed two bundles of delicate 
 nerves, from twelve to sixteen in number (ci/iarynerees), which, after 
 having pierced the sclerotic at its posterior third, pass between that 
 tunic and the choroid, and are distributed chiefly to the ciliary muscle 
 and iris, but also to the cornea. 
 
 From the nasal branch of the ophthalmic there proceed two long 
 nerves, called long ciliary nerves, which do not form any connection 
 with the ophthalmic ganglion. These nerves pass off in company, 
 but soon separate from each other, one going to the inner, the other 
 to the outer side of the eyeball; they penetrate the sclerotic, and- 
 accompany the other ciliary nerves in their distribution to the ciliary 
 muscle and iris. 
 
 The eye is moved by six muscles, four straight and two oblique. 
 The former arise from the margin of the optic foramen, at the apex, 
 of the orbit, and are inserted into the sclerotic near the cornea, above, 
 below, and on each side. The superior oblique arises with the recti, 
 but has its direction changed by a pulley of fillrous tissue at the upper 
 
424 INNERVATION. 
 
 and inner part of the margin of the orbit; whence it passes back- 
 wards, outwards, and downwards, under the superior rectus muscle 
 to the sclerotic behind the transverse median plane of the globe, be- 
 tween the superior and external recti. The inferior oblique arises 
 from the lower part of the margin of the orbit, about its inner third, 
 and passing backwards, outwards, and upwards, under the inferior 
 rectus, is inserted into the sclerotic, near, but beneath the superior 
 oblique. The action of the recti muscles is obvious: when used in 
 concert, they fix the eyeball ; when singly, they turn it towards their 
 respective sides. The globe, besides being imbedded in fat, is sus- 
 pended or slung in a capsule of fibrous tissue, with which it is in 
 immediate contact. This is attached in front to the tarsal cartilages, 
 and is prolonged backwards over the globe and optic nerve, after 
 being perforated by the muscles. Mr. O'Ferrall, who has lately 
 directed attention to this fibrous structure, has termed it the tunica 
 vaginalis oculi. It is important, as furnishing support to the eyeball 
 under muscular movements. The recti muscles are supplied by the 
 third pair of nerves, except the external, which receives the sixth. 
 The oblique muscles antagonize the recti, and must in addition, if 
 acting together, draw the globe inwards, and converge the axes of 
 the eyes. The superior oblique, if alone, would most probably direct 
 the front of the eye downwards and outwards, and the inferior oblique 
 upwards and inwards; but on these points much difference of opinion 
 still prevails. The former is supplied by the fourth pair, the latter 
 by the branch of the third that gives the motor fibres to the ophthal- 
 mic or lenticular ganglion, from which the ciliary muscle and iris 
 receive their nerves. And, in connection with the latter arrangement, 
 it is interesting to remark that the pupil contracts when the eyes are 
 directed inwards and upwards, and generally also in the adjustment 
 for near vision, which is attended with a convergence of the optic 
 axes. During sleep the eyes are usually turned inwards and upwards, 
 and the pupil is contracted — actions produced through the medium 
 of the inferior division of the third pair supplying the inferior oblique 
 and iris. The iris is evidently involuntary in its movements; it 
 contracts only in obedience to this stimulus of light upon the retina, 
 or when the eye is turned upwards and inwards. 
 
 The eyelids are exquisitely adapted to shield the eye from too strong 
 light, and to protect its anterior surface from the contact of hurtful 
 substances. In the upper lid, which is much larger and more move- 
 able than the lower, there is a thin sheet of cartilage, curved to fit 
 the front of the eye, and to facilitate its gliding motion over the globe. 
 To the posterior convex border of this tarsal cartilage the levator 
 palpebrse muscle is attached, which thus serves to elevate the whole 
 lid. The lower lid possesses a very narrow slip of cartilage, which 
 meets the upper at each side through the medium of fibrous tissue, 
 which, at the outer angle of the eye is attached loosely to the malar 
 bone, and at the inner angle forms a tendinous cord, the tendo oculi, 
 about a quarter of an inch long, which passes horizontally to be fixed 
 to the nasal process of the superior maxillary bone. This latter is 
 the principal attachment of the eyelids. The eyelids enclose the 
 
THE EYELIDS. 425 
 
 orbicularis muscle between the skin and their cartilages. Its fibres 
 run in curves from the lower border of the tendo-oculi and neigh- 
 bouring part of the border of the orbit, encircling the eye and form- 
 ing a thin layer under the skin, both of the lids, cheek, and brow, 
 and returning to the upper border of the tendo-oculi. They are sup- 
 plied by the portio dura, and perhaps by some fibres of the fifth nerve, 
 and act generally in answer to the stimulus of air or foreign particles 
 on the fifth nerve in the conjunctiva, as well as of a too strong light 
 upon the retina. The will exerts a limited power over the orbicula- 
 ris, but is quite unable to restrain its action when sufficiently excited 
 by the before-named stimuli. The entire muscle consists of striped 
 fibres. The lids are further armed along their free margin by the 
 delicate curved hairs, called the lashes. These intercept the entry of 
 foreign particles directed against the eye, and assist in defending the 
 organ from excess of light. 
 
 At the border of the eyelids, the skin becomes continuous with their 
 mucous lining, termed the conjunctiva. This membrane lies upon 
 the tarsal cartilages, and is then reflected over the front of the globe, 
 ■where it has been already in part described with the cornea. Be- 
 tween the cartilages and the conjunctiva, and partially imbedded in 
 the former, are the Meibo- 
 mian glands, which may be F'g- 1^8. 
 
 seen through the conjunctiva ,,„ 
 
 (figure 128). Each gland * 
 
 consists of a series of folli- 
 cles, arranged upon an elon- 
 gated common duct, which 
 empties itself on the border 
 of the lid. They consist of 
 a basement membrane and 
 an epithelium (fig. 129); 
 the latter contains sebaceous 
 matter in its cells, and is in 
 continual course of forma- 
 tion. Its particles, when 
 
 fully developed, are thrust view ofthe conjunctival surface of the Eyelids. The 
 
 frtrwrnrA alrtTirr fVio flnnf arirl Meibomian fflands are Seen running towards the edffes 
 
 lorwarU aiOng tne aucr, ana „f ^^^ Me-.-l. The lachrymal glana removed wilh The 
 
 constitute the secretion. The ^^^^- d. Orifices of its seven ducts on the conjunctiva. 
 
 c L TIT ■! • 11 At the inuer extremity of the borders of the lids ihe ori- 
 
 USe Ot the Meibomian glands fices ofthe canalloull (puncta lachrymalla) are seen. c. 
 
 is obviously to prevent ad- J:^Orbicularis muscle beyond the lids.-FromScammer- 
 
 hesion ofthe lids; and their 
 
 arrangement side by side, so as to form an even layer, adapts them to 
 the surface of the globe, over which they are being constantly moved. 
 They are a variety of the cutaneous sebaceous glands, which they 
 resemble in every particular except shape. At the inner canthus is 
 a large-sized sebaceous gland, covered with mucous membrane, and 
 usually termed the caruncle (fig. 130). 
 
 The conjunctiva of the lids presents on its free surface a minute 
 papillary structure, probably connected with the exquisite sensibility 
 which renders .this membrafie so valuable a covering to tlje eve, In 
 
426 
 
 INNERVATION. 
 
 the disease termed granular lids, these papillae are hypertrophied. 
 To the sclerotic coat the conjunctiva is loosely attached by lax areolar 
 tissue in which numerous tortuous vessels lie. 
 
 The front of the eye is irrigated by the lachrymal fluid secreted by 
 the gland of that name. This gland is placed within the orbit, under 
 cover of the external angular process of the frontal bone, and is about 
 the size represented in fig. 128, /. In appearance and structure it has 
 much similarity to the salivary glands ; its ultimate parts being vesi- 
 cular. Its ducts, about seven in number, open on the conjunctiva, 
 at its upper and outer part near its reflexion on to the globe, and are 
 arranged in a row, so as to disperse their secretion over the mem- 
 brane (fig. 128, d). The constant motion of the upper lid facilitates 
 the distribution of the fluid, which thus streams continually over the 
 
 Fig. 129. 
 
 rig. 130. 
 
 One of the Meibomian glands of 
 aFcetusoffive and ahalf montiis : 
 — a. Basement membrane of l^e 
 follicles, b Epiihelium conslitut- 
 Uig the secretion, c. Orifice of 
 the common duct.— From a speci- 
 men prepared by Dr. Goodfeilow. 
 Magn. 30 diameters. 
 
 Anterior view of the Lachrymal' Apparatns — 7. 
 The lachrymal gland in outline. At the inner can- 
 thus are the puneta, 1. and canaliculi, S. with the 
 caruncula between them The lachrymal sac forms 
 the upper third of the vertical tube, 5, 6. and the 
 nasal diict the remainder. Thejje parts are sepa- 
 rated within by a fold of the lining membrane. 
 
 front of the eye, and carries ofT any extraneous particles that may 
 have found their way into it. The fluid is then conducted into the 
 nostril through a singular system of channels, lined by raucous mem- 
 brane, continuous between that of the eye and nose. Near the inner 
 end of the border of each tarsus there is an orifice, a little prominent, 
 and projecting slightly backwards, so as not to be obstructed when 
 the lids are closed. These are the puneta lachrymalia (figs. 128 and 
 130). They lead by two ducts {canaUcidi], into the lachrymal mCy a 
 
PHENOMENA OF VISION. 427 
 
 cavity formed by the lachrymal and superior maxillary bones, com- 
 pleted by fibrous membrane. This is continued, under the name of 
 nasal duct, into the inferior meatus of the nose, where it opens under 
 cover of the lower spongy bone. A fold of mucous membrane usually 
 guards its orifice. 
 
 Of the phenomena of Vision.* — The consideration of the changes 
 
 • The following laws affecting the passage of rays of light through transparent 
 media of various density ought to be kept steadily in view by the student of the phy- 
 siology of vision. 
 
 1. A ray of light, in its passage from a rare into a dense medium, is bent, or, in 
 optical language, refracted, towards the perpendicular to the point of incidence, if it 
 fall obliquely upon the surface of the latter medium. The direction of the ray, there- 
 fore, is altered in the dense medium. The degree of this refraction depends partly 
 Upon the density of the medium, and partly upon the angle at which the ray falls 
 upon it (the angle of incidence). If the ray of light fall upon the transparent surface 
 at right angles to it, it will pass through it without undergoing any change in its di- 
 rection. 
 
 2. If the ray pass from a dense to a rare medium, it will be refracted_/5-om the per- 
 pendicular to the point of incidence. 
 
 3. It is obvious, from what. has been stated, that the incident and refracted ray will 
 be always on different sides of the perpendicular. 
 
 4. In all casts where rays of light pass from one transparent medium to another, a 
 certain portion of them is reflected at the surl'ace of each new medium. If, therefore, 
 light pass through many different media in succession, much of it will be completely 
 diverted from its original direction by reflexion. 
 
 5. In general, the greater the specific gravity of a body, the greater is its refracting 
 power. 
 
 6. If a pencil of rays diverging from a luminous point fall directly upon the surface 
 of a convex lens, they will not all be equally refracted. The central ray will pass 
 through unchanged in its course. Those nearest the centre will be least refracted; 
 those most distant from it (which consequently fall with the greatest obliquity upon. 
 the surface of the refracting medium) will be most refracted. 
 
 7. On the emergence of the rays of light from a bi-convex lens into air, or any 
 other medium less dense than the lens itself, each ray will be bent away from the 
 perpendicular to the point of emergence. The effect of this is to cause a converg- 
 ence of all the emerging rays towards the central ray; at this point of convergence, 
 or focus, an image of the luminous point from which the rays originally passed is 
 formed. 
 
 8. This point of convergence, or focus, varies as to its distance from the surface of 
 emergence, according to the refracting power of the lens, the amount of curvature of 
 its surfaces, and the distance of the luminous body. Its distance constitutes the focal 
 length or distance of a lens. 
 
 9. In consequence of the unequal refraction of rays passing through a convex 
 lens, the focus of convergence of the central rays is more distant from the surface of 
 the lens than that of the peripheral rays. Hence the image formed at the focus of 
 the lens is in some degree indistinct at its edges. The imperfection is due to what 
 is technically called spherical aberration ,• and it can be ccunleractefl only by inter- 
 cepting the passage of the circumferential rays, or by employing such a combination 
 of lenses as will establish a just proportion between the refraction of the central and 
 peripheral rays. This aberration is liable to occur in all forms of lenses, whether 
 convex or concave. 
 
 10. White light is compound, and may be analyzed by passing a beam of sunlight 
 through a prism. The solar spectrum thus formed on a surface opposite the prism is 
 composed of bands of different colours insensibly passing into each other, which are, 
 beginning from above, violet, indigo, blue, green, yellow, orange, and red. Of these 
 different coloured rays, that which is moat bent from the original direction of the solar 
 beam is the violet, and the red is the least refracted. It is owing, therefore, to this 
 unequal refrangibility of the different kinds of simple light that we are enabled to 
 decompose white light by its transmission through a prism. 
 
 11. If the different coloured rays which have emerged from the prism be allowed 
 to traverse a second similar prism, held in a reversed position, they will on their 
 emergence unite to &rm white light again. 
 
428 INNERVATION. 
 
 produced in the rays of light passing through a double convex lens 
 explains, to a great degree, the phenomena resulting from the passage 
 of the rays through the dioptric media of the eye. 
 
 A ray, falling on the surface of such a lens, is bent towards the 
 perpendicular to the point of incidence, and continues in that direc- 
 tion to the opposite surface of the lens. It then emerges from the 
 lens, and, in thus passing from a dense to a rare medium, it is bent 
 from the perpendicular to the point of emergence. It can thus be 
 shown that the component rays of a pencil diverging from a point, 
 will be bent towards the central ray of the pencil, or that which falls 
 perpendicular to the convex surface, and be brought to a focus in the 
 line of the central ray. And the several pencils of rays, proceeding 
 from different points of an object, cross one another in traversing the 
 lens, so that the foci to which they are respectively brought beyond 
 the lens are in positions the reverse of those from which they set out, 
 and the entire image is a reverse of the object. 
 
 To apply this to the eye. — If a luminous object, as the flame of a 
 candle, be placed eight or ten inches in front of the organ, some rays 
 fall on the sclerotic and are reflected; the more central ones fall on 
 the cornea: some are reflected, and others pass through it, are slightly 
 converged by it, and enter the aqueous humour, which, being proba- 
 bly of the same refracting power, does not alter their course. Pass- 
 ing onwards, some meet the iris and are absorbed or reflected by it, 
 whilst others advance through the pupil. Thus rays, falling on a 
 large extent of the cornea, are converged so as to fall on the lens. 
 By the convexity of the surface of the lens, as well as by the greater 
 density of that body towards its centre, this convergence is much in- 
 creased. Lastly, by their passage into the rarer medium of the vitre- 
 ous humour, the rays are further converged by the refraction of each 
 ray from the perpendicular to the point of incidence, and the several 
 pencils which they form are brought to as many foci in the retina. And 
 still further, the rays from the opposite points of the luminous object, 
 by reason of the change of direction which they undergo through these 
 successive refractions, cross one another, (the angle of crossing being 
 called the visual angle,) and thus the image of the flame on the retina 
 iappears inverted. 
 
 This inversion of the image may be exhibited by a model, repre- 
 senting the transparent media of the eye, with a retina of ground 
 glass ; or it may be shown on a recent eye by simply removing the 
 opaque coats behind the retina, or in the eye of a white rabbit, after 
 removing the muscles and areolar tissue around it. 
 
 "When the retina corresponds, or nearly so, to the points of con- 
 vergence of the several pencils of light, distinct vision of the object 
 is obtained ; and the distance for distinct vision is ordinarily about 
 
 12. The different refrarifribility of the rays of simple light is another source of iiito- 
 tinctness in images formed by the transmission of light through lenses with curved 
 surfaces. The images are fringed by prismatic colours. It is called technically 
 chromatic aberration ; and may be corrected by means analogous to those adopted for 
 correcting spherical aberration.. It is obviously of great importance in all optical in- 
 struments for aiding or increasing the powers of visioa that Ihey should as much as 
 possible be free from these sources of imperfeelioa.. 
 
ADAPTATION TO DISTANCES. 429 
 
 ten inches. If that distance be increased or diminished (no change 
 being produced in the eye), vision is indistinct; for when the object 
 is removed to a greater distance from the eye, it is obvious that the 
 focus will be moved forwards, or will fall short of the retina ; and 
 when the object is approximated, the focus will be moved backwards 
 or beyond the retina : in both which cases the same point of the re- 
 tina will receive rays from several points of the object. Hence it is, 
 that when the eye is adapted to distinct vision at a distance of ten 
 inches, we cannot distinctly see objects at a greaj;er or less distance. 
 From the cause of this, which has been just alluded to, however, it 
 is evident that, provided the rays unite very nearly on the retina, 
 vision, especially of large objects, may prove sufficiently distinct, al- 
 though not perfectly clear. Hence the distinction of Jurin between 
 distinct and perfect vision is worthy of being borne in mind. Dis- 
 tinctness of vision will depend on the size of objects, as well as on 
 their distance from the eye ; perfection of vision, on their distance 
 alone. 
 
 This leads to the consideration of one of the most admirable pro- 
 visions for the extended utility of the organ ; viz., its capacity of 
 adaptation, under the influence of the will, to distinct vision at every 
 distance beyond that of a few inches. We have the power of pro- 
 ducing some change in the eye by which its focal length is modified 
 to suit the varying angle at which rays from surrounding objects fall 
 upon it. Many different explanations have been -attempted of the 
 mode in -which this adaptation is effected, of which may be mentioned 
 that of Jurin, Ramsden, and Home, that the cornea undergoes a change 
 in its curvature, becoming more convex for near objects: and that of 
 Des Cartes, Albinus, Hunter, and Dr. Young, who considered the 
 lens muscular, and to possess within itself the power of changing its 
 curvature. 
 
 Others, again, ascribe this power of adaptation to the iris, the mo- 
 tions of which might, as Knox supposed, alter the curvature of the 
 lens ; or, according to Sir David Brewster, cause the lens to change 
 its place, and come forward during contraction of the pupil. A change 
 in the position of the lens has also been supposed to occur from con- 
 tractions in the ciliary processes or zonula, and many have contended 
 that the entire eyeball may alter its relative dimensions by the action 
 of its muscles. 
 
 It is, conceivable that any of these changes, could they be proved 
 actually to take place, might be sufficient to account for the effect; 
 but, in estimating their relative value, the greatest importance is to be 
 attached to the anatomical evidence by which they may be supported. 
 In the eye of the bird, the ciliary muscle, from its position and at- 
 tachments, must necessarily approximate the lens to the cornea ; and 
 the reasons for considering the same part muscular in mammalia, and 
 if so, for ascribing to it the same function as in birds, have been al- 
 ready mentioned,, and appear to us conclusive. We, therefore, on 
 anatomical grounds alone, adopt this view, ably advocated by Por- 
 terfield,* conceiving that, when the eye is intent on near objects, the 
 
 * Treatise on the Eye. Vol. i. p. 448. 
 
430 INNERVATION. 
 
 ciliary muscle is contracted, the lens advanced towards the cornea, 
 and the latter membrane, perhaps, rendered more convex by the 
 traction of the muscle on its border by means of the cordage of the 
 posterior elastic lamina ; while in vision of remote objects the lens is 
 carried back towards the retina by the elasticity of the neighbouring 
 parts. It is interesting to notice that this adjusting faculty of the eye 
 is greatly impaired or altogether lost by extraction of the lens, or by 
 paralyzing the ciliary and iridial muscles by belladonna. 'Dr. Clay 
 Wallace considers that the ciliary muscle advances the lens by com- 
 pressing the veins, and thus causing an erection or lengthening, of 
 the ciliary processes. 
 
 It has long been observed that the pupil is very prone to contract 
 during near vision, and to dilate when the organ is adapted to view 
 remote objects ; and it has been imagined that this change is the ne- 
 cessary condition of adaptation, and may aflfect the lens through the 
 ciliary body. In some persons, however, not at all deficient in the 
 adjusting power, the iris continues to oscillate for sometime after the 
 eye is adjusted, without disturbing vision; and we have occasionally 
 found the pupil to remain dilated, though a near object is being gazed 
 at and the illumination remains the same. Moreover, the action of 
 light on the pupil has no effect on the adjustment of the eye, since 
 we can continue to see an object distinctly, whether it be viewed by 
 a strong or by a feeble light. 
 
 These facts are sufficient to prove that the movements in the iris, 
 usually coincident with the act of adjustment, are not the cause of that 
 act. They seem rather to be of the nature of associate movements, 
 produced by the close connection of the iris with the ciliary muscle, 
 and by the community of source from which both these derive their 
 motor nerves, viz., from the third pair, through the ophthalmic gan- 
 glion. And it is an important circumstance, that certain consensual 
 movements of the eyeballs, performed through the medium of the third 
 pair, are likewise associated with the act of adjustment. The move- 
 ments of the iris chiefly minister to another function, the regulation 
 of the quantity of admitted light. 
 
 The contraction of the pupil during near vision, by obstructing 
 more of the circumferential rays, answers the important purpose of 
 correcting the excessive aberration of sphericity which results from 
 the greater divergence of the rays entering the eye from near objects. 
 
 Some persons have the power of adjusting the eye to distinct vision 
 at different distances, either to a very limited extent or not at all; 
 and we observe two states of vision connected with this defect, which 
 are generally dependent on certain physical conditions of the lenses of 
 the eye: these are shortsightedness, or myopia ; and longsightedness, 
 or presbyopia. 
 
 Myopia. — Thus, we meet with many persons who cannot distinctly 
 see a yard before them, — who fail to recognize the features of their 
 acquaintances in the street. In reading, they are obliged to bring 
 the book close to their eyes: in looking at an object at all distant, 
 they exhibit a characteristic winking {/iva, connivo). Myopia occurs 
 in adolescence, and is accompanied with a too great refracting power 
 
OFFICE OF THE IRIS. 431 
 
 of the media, SO that the image is formed anterior to the retina. In 
 order, therefore, to throw bacii the image on the retina, the object is 
 brought very close to the eye ; or the convergence of the rays of light 
 may be diminished by the use of a concave lens. 
 
 It seems probable that the state of myopia may be acquired by the 
 habit of looking intently at small and near objects, and that the com- 
 mon practice of remedying the inconvenience by the use of concave 
 glasses tends to increase the defect. Frequent exercise of the eyes on 
 remote objects has, no doubt, the effect of making them far-sighted. 
 It is a common error to say that myopia disappears naturally in ad- 
 vanced life. 
 
 Presbyopia. — Others again imperfectly distinguish near objects, 
 whilst they see distant ones very plainly, and the distance at which 
 they can see distinctly is sometimes very great. Persons thus affected 
 cannot read small print with the eyes unassisted, and they prefer 
 holding the book at a distance. This condition of vision is connected 
 with a too flat cornea, a deficient aqueous humour, or a flattening of 
 the lens : and it is in a great degree accounted for by the diminution 
 in the refracting power thence resulting, so that the focus is behind 
 •the retina. It belongs to the advanced- periods of life. It may be 
 corrected by convex glasses, which increase the convergence of the 
 rays of light. 
 
 It is manifest that neither of these defects is dependent on the mus- 
 cular apparatus of adjustment, but rather on the curves of the refract- 
 ing media, which throw the organ in one direction or the other beyond 
 the range of the adjusting power with which it is provided. When 
 the refracting media are optically corrected, as by the use of glasses, 
 the adjusting faculty can be exercised. 
 
 In the eye, considered as an optical instrument, there are other 
 powers besides those already named, which serve to make it more 
 perfect, and to place it in favourable contrast with the most success- 
 ful creations of human ingenuity. 
 
 One important office of the iris is to prevent the passage of rays 
 through the circumferential part of the lens, and thus to obviate that 
 indistinctness of vision which would arise from spherical aberration, 
 or that unequal rtefraction which results from the difference in the 
 angle of incidence of the several rays on a curved surface. In this 
 respect it resembles the diaphragms used in optical instruments. By 
 its position, close to the surface of the principal lens, — and behind or 
 within the first one by which the light is converged, viz., the concavo- 
 convex one formed by the cornea and aqueous humour, — it is adapted 
 to admit the greatest quantity of light to the lens, consistently with 
 the correction of the spherical aberration. 
 
 The aberration of sphericity is further obviated by the increased 
 density of the lens from its surface towards its centre, so that the 
 rays falling on its middle region are made more convergent as they 
 traverse it, than those passing near its border. 
 
 Chromatic aberration, or that which occasions a coloured image by 
 the inequality of the refraction of the elementary colours of white 
 
432 INNERVATION. 
 
 light by the same medium, is in some way prevented in the human 
 eye, when adjusted to distinct vision. 
 
 The image formed by a convex lens is slightly coloured at its mar- 
 gin. This colouring is corrected in practice by a compound arrange- 
 ment of lenses differing in shape and density, of which the second, 
 while it continues the convergence of the rays from their original 
 course, re-associates the dispersed colours and recomposes the white 
 light. 
 
 The achrotaatism of the eye may be in part due to the diversity of 
 shape and density of the refractive media, which seem to bear some 
 analogy to the system forming the achromatic object-glass of Her- 
 schel. This is formed of a double convex lens of crown-glass, with 
 surfaces of unequal curvature, the more convex being turned towards 
 the object; and of a concavo-convex of flint-glass, the concave side 
 of which receives the lens of crown-glass, while its convex side is 
 towards the eye.. The cornea and aqueous humour form a concavo- 
 convex lens which differs in density from the crystalline. 
 
 It is possible that the greater density of the inner fibres of the lens 
 may likewise share in producing the effect. But this entire subject 
 is involved in much obscurity, and it is right to add that some very 
 high authorities, including Sir D. Brewster, deny that the chromatic 
 aberration receives any correction in the eye ; that, in fact, it exists 
 in all cases, and is imperceptible only in consequence of its being*so 
 slight. It may be observed that when the eye is not adjusted to dis- 
 tinct vision, a coloured fringe is seen around objects. If the eye be 
 fatigued and incapable of adjustment, or if belladonna be used, then 
 colours are seen. 
 
 The rays of light which have now been traced to the retina, al- 
 though they come to a focus in that membrane, yet can scarcely, 
 from its extremely thin and transparent nature, be said to form an 
 image upon it. The image, however, which becomes visible in the 
 experiment on a dead eye, though partly due to the opacity the re- 
 tina acquires soon after death, is yet an evidence that this membrane 
 does not give passage to the light, like transparent glass, or the hu- 
 mours, but rather like ground glass, dispersing and reflecting some 
 portion, as indeed its peculiar texture must dispone it to do. The 
 pink colour of the pupil in albinos shows the reflection that occurs in 
 those cases from the vascular choroid and retina ; and Mr. Curaraing 
 has recently pointed out that in the eyes of all persons, where the 
 pupil is tolerably large, a very decided reflection from the bottom of 
 (he eye may be observed under favourable circumstances. To make 
 it apparent he places the individual at a distance of ten feet from a 
 single gas-light or lamp, and directing him to look a little on one side, 
 a strong glare becomes visible to any one standing almost directly be- 
 tween him and the light. In some persons this glare is exceedingly 
 brilliant, like that from burnished brass; in others it is fainter. This 
 reflection can hardly be regarded as important in a physiological point 
 of view. It probably proceeds from the hyaloid membrane, the retina, 
 and from the choroid also, but from the latter more or less according 
 to the amount of pigment present in the particular instance. It is 
 
EXCITABILITY OF THE RETINA. 433 
 
 remarkable that these reflections do not interfere Avith the perfection 
 of the sense, do not derange the integrity of the impression resulting 
 from the first passage of the rays. Corresponding but more vivid re- 
 flections from the tapetum lucidum in certain animals serve a useful 
 purpose, by giving an additional stimulus to the retina, where but a 
 feeble light is admitted to the organ. 
 
 Excitability of the retina, and of the allied nervous parts. — When 
 the retina is stimulated, we have the sensation of light, whatever 
 may be the nature of the stimulus applied. Pressure, for instance, 
 made on the side of the eye in the dark, gives rise to the sensation 
 of a spot of light, the situation and size of which will be determined 
 by those of the point of the retina touched. The same is true of the 
 optic nerve, and of certain parts of the encephalon with which the 
 nerve is connected. The sensation of light, then, consists in a recog- 
 nition by the mind of a certain condition or affection of these nervous 
 parts, and this condition may be induced by the application of any of 
 the ordinary stimuli of nerves. The retina, however, is capable of 
 being affected in this way by the luminous rays; and perhaps this 
 capacity is dependent on the peculiar manner in whicrh the nervous 
 matter is spread out in this part. However that may be, the light 
 incident on the retina is the only stimulus which can naturally afi'ect 
 it; and the other parts, endowed with the same kind of excitability^ 
 can, in the natural state, be stimulated only in a secondary manner, 
 as though by induction through the retina. It is certain that the 
 integrity of these other parts is essential to vision, and it may there- 
 fore be concluded that during vision they are all, immediately or 
 mediately, in a state of excitation. 
 
 The retina is not, affected sufficiently for the purposes of vision by 
 a very faint light; and, on the other hand, a very strong light, espe- 
 cially if long applied, will produce effects analogous to those resulting 
 from an inordinate stimulus to other organs: the blood-vessels of the 
 retina will become unduly injected, its nutrition disordered, and even 
 its texture destroyed. But the retina exhibits a considerable power 
 of accommodation to different amounts of light, and thereby the utility 
 of the organ is much enhanced, as well as its safety provided for. 
 After a short stay in the dark, objects disclose themselves, which at 
 first were imperceptible; and, on the other hand, a light which was 
 at first too bright, becomes agreeable by use. This adaptability is 
 quite independent of the iris, and has its analogue in the case of 
 every nerve of sense. 
 
 The iris, however, by its contractile power, is a most important 
 agent in protecting the retina from the effects of sudden transitions 
 from dark to light; and in thus co-operating for the maintenance of 
 its most essential quality, excitability, the iris is seconded by the eye- 
 lids and brows. The iris contracts under a strong light, by virtue of 
 the stimulus imparted to the retina; for if this or the optic nerve be 
 destroyed or paralyzed, as in amaurosis, the iris no longer contracts. 
 It is interesting, however, to notice that the iris of the unsound eye 
 will often contract in company with its fellow, when the opposite 
 sound retina is stimulated. The motion is therefore evidently caused. 
 
434 INNERVATION. 
 
 by a reflexion of the stimulus from the optie nerve, through the nerv- 
 ous centre along the inferior branch of the third pair to the iris, and 
 the consensual action of the two sides is effected in the nervous 
 centre. Mechanical irritation of the ciliary nerves, or third pair, 
 occasions contraction of the pupil on the same side. The orbicularis 
 palpebrarum and corrugator supercilii likewise contract under a pow- 
 erful glare, in obedience to a stimulus reflected through the optic 
 nerve, and quite independently of the will. This is well exemplified 
 in children affected with strumous ophthalmia, in whom the excita- 
 bility of the retina is highly exalted. 
 
 The pigmentum nigrum is a permanent shield to the retina, absorb- 
 ing the light which falls upon it, and remaining the same under all 
 degrees of illumination. The excitability of the retina in creatures 
 usually exposed to the full light of day, requires this additional protec- 
 tion ; and where it is deficient, as in albinos, an ordinary light becomes 
 painful, and the movable protecting parts are habitually brought into 
 increased use. In animals of nocturnal habits, furnished with a tape- 
 tum lucidum, the excitability of the retina is probably somewhat 
 modified, and the iris also is generally larger, and capable of an 
 ampler range of motion. 
 
 Duration of impressions on the retina. — We continue to see an 
 object after the rays of light emerging from it have ceased to fall upon 
 the retina, and this for a period proportioned to the intensity and 
 duration of the impression they have left. The familiar experiment 
 of twirling a lighted stick, so as to see a luminous circle, shows that 
 the impression made by it, when at any one point of space, remains 
 on the retina until it reaches that point again. By ascertaining the 
 speed necessary for completing a luminous circle of a certain size we 
 can estimate the duration of the impression ; and by augmenting or 
 diminishing the brilliancy of the ignited point its duration is found 
 to be affected. A momentary impression of moderate intensity con- 
 tinues for a fraction (according to D'Arcy, about an eighth part) of a 
 second. But if the impression be made for a considerable time on 
 any one point of the retina, it endures for a longer period after the 
 object is removed. It is owing to this retentive power of the retina, 
 that the rapid and involuntary act of winking does not interfere with 
 continuous vision of surrounding objects. 
 
 Appearances of objects remaining after the removal of the objects 
 themselves from the field of vision, come under the head of ocular 
 spectra. In figure they correspond to the image the object has thrown 
 on the retina, but they are of the complementary colour to that of the 
 object. Thus, the spectrum left by a red spot is green ; by a violet 
 spot, yellow; by a blue spot, orange; and these colours of the spectra 
 are particularly obvious when the eye is directed towards a white 
 ground. It is further rpmarkable, that after long gazing on a very 
 bright light, as the sun's disc, the remaining spectrum, if viewed on 
 a white surface, assumes the different colours in succession, from 
 black, through blue, green, and yellow, to white: if viewed on a 
 black surface, the order of the succession is reversed. These several 
 phenomena can only be referred to particular states or modes of exci- 
 
OCULAR SPECTRA.— LUMINOUS IMPRESSIONS. 435 
 
 tation of the retina, by means of which alone it is that the differences 
 of the component colours of white light are made evident to our per- 
 ceptiviB pow^ers. 
 
 It appears by a simple experiment, for the principle of which we 
 are indebted to Mariotte, that the small portion of the retina corre- 
 sponding to the entrance of the optic nerve, is incapable of exciting 
 visual sensation though it receive the image of an object. Place the 
 thumbs together at arm's length, shut the left eye and fix the right 
 eye steadily on the left thumb ; then the right thumb, if moved gradu- 
 ally outwards (so that its image on the retina of course traverses 
 inwards), ceases to be visible in a particular spot, but is again seen 
 beyond it. It will be remembered that the fibrous lamina of the gray 
 nervous layer of the retina is here evolving itself from the nerve, and 
 is not yet invested with the vesicular or other lamina; a circumstance 
 of great interest in regard to the modus operandi of the constituents 
 of the retina in vision. 
 
 It has indeed been denied by an eminent physiologist, that the 
 retina is insensible to light at this point, on the ground that, if such 
 were the case, we should see a dark spot in our field of view when- 
 ever we use only one eye. To produce the physical sensation of 
 darkness, however, the retina seems as necessary as the nerves of 
 ordinary feeling are to the production of the physical sensation of 
 cold. Both sensations are occasioned by the absence of the respective 
 stimulus, but the specially endowed nerve is as essential to acquai'nt 
 us with the absence as with the presence of the stimulus. What 
 Mariotte's experiment proves is simply that over that spot no nervous 
 matter, having the peculiar power of excitability by light, exists; and 
 as far as the faculty of seeing with that spot is concerned, it is as 
 though the piece of retina had been punched out. We no more see 
 a dark spot corresponding to it, when we look with one eye, than 
 we see everything dark behind us — where there is no nervous expan- 
 sion visually, endowed. For, in strict language, a distinction must 
 be drawn between the sensation of darkness and the absence of the 
 sensation of light. 
 
 This incapacity of vision at the entrance of the optic nerve, seems 
 to be essential to the mode of junction of the retina with the nerve, 
 since it appears to have been the chief reason why the nerve was not 
 made to enter in the axis of the eye. If the blind spot had been 
 situated in the axis, a blank space would have always existed in the 
 centre of the field of vision, since the axes of the eyes, in vision, are 
 made to correspond. But, as it is, the blind spots do not correspond 
 when the eyes are directed to the same object; and hence the blank, 
 which one eye would present, is filled up by the opposite one. 
 
 Though no other part of the retina is insusceptible of luminous 
 impressions, yet there is good reason to suppose that the hinder part 
 of it is much more capable of appreciating them than the anterior. 
 When using one eye only, we naturally direct it towards the object 
 we wish to inspect, and in that way throw the image to the bottom 
 of the globe. When the eye is thus fixed, objects near the boundary 
 of the field of vision are less distinctly seen than those at its centre. 
 
436 INNERVATION. 
 
 The posterior part of the retina, too, is the best adapted to receive 
 correct images through the dioptric media, and we find its gray nerv- 
 ous layer becoming thinner and thinner towards its anterior border. 
 
 It is probable that the most anterior part of the retina is never used 
 in vision, since it can scarcely receive rays directly from the lens. 
 Dr. Young, by fixing the eye in the most natural direction, viz., for- 
 wards and a little downwards, and by then moving before it a luminous 
 object, in various directions until it passed beyond the range of vision, 
 ascertained the range upwards to be 50°; downwards, 70°; inwards, 
 60°; and outwards, 90°: the extent in each direction being limited 
 by the contiguous parts of the face. An object, therefore, occupying 
 only an angle of 120°, both in the vertical and horizontal direction, 
 and suitably placed, would about fill the iield of vision of a single 
 eye, when the organ was fixed as above described. Now, it may be 
 proved that no part of the image of such an object would fall on the 
 anterior part of the retina. 
 
 Perhaps it is only in, or very near, the axis of vision, that sight 
 can be said to be perfect. The existence of the yellow spot of Soem- 
 merring at that point continues a riddle which the most attentive 
 examination of its anatomy has not yet solved. And from the absence 
 of this spot in almost all the lower animals, we are led to doubt its 
 importance to perfect vision. 
 
 To the perfect exercise of vision, as of all the other senses, 'an 
 effort of attention is necessary ; and this effort is naturally accompanied 
 with a motion of the eyeball towards the object, so that the image 
 may be thrown upon the central part of the retina. The range of 
 motion of the eyeball Dr. Young calculated at 55° in every direction ; 
 so that, the Tiead being fixed, a single eye may have perfect vision of 
 any point within a range of 110°. This field is further widened by 
 the use of the opposite organ, but beyond this an increased range is 
 only to be acquired by movements of the entire head. 
 
 The internal, or gray nervous layer of the retina seems to be the 
 essential part on which the power of the retina in the process of vision 
 depends. That layer is an unbroken sheet, continuous by its fibrous 
 internal surface with the axes of the tubules of the optic nerve, and 
 having its external surface formed by a structure similar to that of the 
 cineritious substance of the cerebral hemispheres. Its permeation by 
 a close network of capillaries assimilates it still further to the gray 
 nervous matter; for which reasons it may be considered as a portion 
 of the cerebrum advanced towards the surface of the body into a 
 suitable relation to a dioptric apparatus for the reception of rays of 
 light from external objects. The optic nerve may be regarded as a 
 commissure between the gray nervous sheet within the sclerotic, and 
 the gray nervous matter of certain parts of the cerebrum. We have 
 no more reason to deny the immediate connection of the sensorium 
 with the retina, than its immediate connection with any small portion 
 of the cerebral convolutions, duly united with the rest. The nature 
 of the connections between the retina and the brain, and the phe- 
 nomena to which their disruption gives rise, have been the occasion 
 of many interesting speculations regarding the mode in which the 
 
CORRECT VISION WITH AN INVERTED IMAGE. 437 
 
 mind is reached, or, in other words, as to how an impression on the 
 retina becomes a sensation to the mind. But we shall probably be 
 disappointed if we imagine that any facts which have been or may 
 be hereafter ascertained, are capable of leading to the solution of a 
 problem too inscrutable for our limited powers. 
 
 It is a matter of considerable interest, as regards the mode of action 
 of the retina in vision, to determine how distant the images of two 
 points on the retina must be, to be seen distinctly as two; in other 
 words, how small a portion of the retina is capable of independent 
 sensation. As the result of many experiments and calculations by 
 Smith, Harris, and others, this may be stated as probably about joW 
 of an inch, so that the objects must subtend an angle of at least 40". 
 Two points within an angle of that size would appear as one. It is 
 a question somewhat different, what is the smallest portion of the 
 retina capable of sensation ; and undoubtedly an object whose sides 
 subtend an angle very much -smaller than the preceding may be 
 visible, if sufficiently bright. But this circumstance of quantity of 
 light introduces a difficulty into the inquiry, since even a mathemati- 
 cal point, if sufficiently brilliant and out of focus, might become 
 visible by its circle of aberration on the retina; although, if its rays 
 met in the retina, it would be invisible. But, in carrying our specu- 
 lations thus far, we must cease to regard the retina as a mathematical 
 plane, and remember that it has a certain thickness, in traversing 
 ■which the rays would necessarily cover more than a point, either in 
 front of or behind the exact focus. It is obvious that a linear object 
 would be more perceptible than a point, and a moving object more 
 so than a stationary one, in consequence of wider and more distant 
 portions of the retina being affected in both cases. 
 
 The apparent truthfulness of a view, recently put forward on high 
 authority in Germany, and copied into several works in this country, 
 makes it necessary to explain here that the rod-like particles of Jacob's 
 membrane, though corresponding nearly in size with the points of the 
 retina capable of independent sensation, yet being on the choroidal 
 surface, and separated from the gray nervous layer by the intervening 
 granules, can scarcely have a share in determining the size of the 
 independent visual points. The unfortunate error which placed these 
 rods as papillae on the hyaloid surface of the retina, was too tempting 
 a ground of theory not to be readily admitted as true, without scru- 
 pulous examination; and the price to be paid will probably be some 
 degree of discredit thrown on minute anatomical research. 
 
 Correct Vision with an inverted Image. — Visual idea of Direction. — 
 The image on the retina being the reverse of the picture of external 
 objects seen by the mind, it is manifest that in some way or other the 
 inversion is counteracted ere the impression becomes a sensation. It 
 is conceivable that this correction may lake place in the optic nerve 
 or brain, but it is far more probable that it occurs in the retina. It 
 is certain that we do not see the image as it exists on the retina, or 
 its inversion would not have remained so long unknown ; we rather 
 see out of or from the retina. The simple experiment of pressing 
 with the finger on the retina through the ocular tunics, and thus 
 
438 INNERVATION. 
 
 eliciting a luminous appearance on the opposite side, seems to prdve 
 that the apparent projection of a luminosity in a direction perpen- 
 dicular to the point stimulated, is a necessary part of the excitability 
 of the retina. If this be granted as an ultimate -fact, it will explain 
 why an inverted image, formed on a concave retina, shows objects 
 in the same position as they are shown by the other senses which 
 receive direct impressions from them, particularly touch. 
 
 It has been supposed by Miiller and Volkmann, that objects do 
 really appear inverted ; but they argue that, as long as all do so, even 
 visible parts of our own bodies, there is no need of a correction. But 
 this will not explain the perfect harmony existing between impres- 
 sions conveyed through the senses of hearing and touch, with those 
 derived from sight. Sounds are appreciated, and tactile impressions 
 are felt, as proceeding from a particular direction as regards the body 
 — our several organs are conceived as existing in a particular relative 
 position, altogether independently of vision — and vision accords 
 entirely, and at once, with these senses in the determination of 
 locality, without the necessity of an education of the sense, such as 
 a reversed impression on the mind through the eye would require. 
 
 Were the eye and the whole body fixed, we should still have a 
 knowledge of the relative position of visible objects, and of course of 
 the direction in which each point of their surface was placed, as re- 
 gards the organ of sense ; and as rays coming from objects in the same 
 direction as regards the body, would then always fall- on the same 
 part of the retina, we might conclude that each part of that membrane 
 had the power of conveying the notion of position in one direction 
 only as regards the body. But the eye being a very movable organ, 
 ■we are enabled to make the image of a stationary object travel suc- 
 cessively over a large tract of the retina without the object appearing 
 to move ; since we are conscious, through the muscular sense, of the 
 motion in our own eye. The visual idea of direction in regard to the 
 body, therefore, does not depend on the image falling on a particular 
 point of the retina, but in a great measure on the muscular sense, in 
 conjunction with that quality of the excitability of the retina already 
 spoken of. 
 
 It is proper also to mention that the limits of the field of vision, 
 formed'by certain parts of the face, are a standard to which the mind 
 refers in estimating the position of visible objects. The outline of the 
 field remains the same, through all movements of the eye. The 
 motions of the head or body can alone bring new objects into the 
 field; and the muscular sense thus still further contributes to enhance 
 the usefulness of the sense of vision. 
 
 Visual Perception of Shape and Size. — If an object form a large 
 image on the retina, and of a square figure, we conceive it at once 
 to be large and square; and of this no other explanation can be given 
 than that the visual points making up the surface of the ?etina have, 
 as regards space, a relation to one another, of which the mind is in- 
 tuitively cognizant in framing its ideas from visual impressions. But 
 the size of an image, relatively to the whole retina, will vary with 
 the distance of the object; and the conception of its real dimensions 
 
■ DOUBLENESS OF THE ORGAN OF VISION. 439 
 
 ■would be erroneous, were it not that the impression were corrected 
 by the muscular sense engaged in the adjustment of the eye to dis- 
 tance, and by the leSsons of experience. When a person, blind by 
 cataract from infancy, is couched, he concludes that the diversified 
 details of the scene presented to him are at an uniform distance, as 
 in a picture; and a species of education can alone undeceive him. 
 He learns, through touch, that all objects are not equally near to him, 
 and gradually familiarizes himself with the changes in their apparent 
 size, distinctness and colours, produced by the movements of his 
 whole body with regard to them. The adjusting faculty is an addi- 
 tional source of correct knowledge. 
 
 Visual Perception of Motion in Objects. — When an object moves 
 in a direct line, to or from the eye, its motion is inferred chiefly by 
 the change effected in the size of its image on the retina, as when a 
 locomotive engine, at full speed, approaches the observer. When 
 the object moves in an arc, of which the eye is the centre, its mo- 
 tion is known, if the eye be fixed, simply by the movement of its 
 image across the retina. But most motions, occurring around us are 
 known in both these ways. When, too, the attention is excited to 
 the moving object, the eye is naturally moved in concert with it, 
 in order to keep its image near the axis of the organ where vision 
 is most perfect. Our appreciation of the direction and velocity of 
 the motion is thus heightened by the exercise of the muscular sense. 
 
 Doubleness of the Organ of Vision. — The preceding account has 
 been almost confined to the phenomena of vision with a single eye ; 
 it remains to be explained how the doubleness of the organ affects the 
 sense. 
 
 In some animals the eyes are so placed as to look in different di- 
 rections, and in these the images formed are, doubtless, independ- 
 ently recognized by the animal, just as are those thrown on different 
 parts of the retina of a single eye in ourselves. But where the eyes 
 are both directed the same way, it is manifest that a doubhe image of 
 each object must be received, and that the singleness of the result- 
 ing sensation must depend either on our noticing only one of these 
 images, or else on our forming a single conception from both conjoint- 
 ly. It is easy to prove that the latter is generally the case, although 
 we sometimes derive our information from the affection of only one 
 eye. 
 
 The eyes are moved in concert by the muscles attached to them, 
 so that their axes always converge towards the object to which they 
 are adjusted. The consequence of this is, that the corresponding 
 points of the two images are made to occupy corresponding points of 
 the two retinse, or very nearly so, and single vision is produced. If 
 the two images are unsymmetrically placed on the retina, as where 
 the optic axes do not converge to the object, a double sensation is 
 excited. Thus, in squinting, two impressions are excited, unless, by 
 long habit, one eye ceases to be adjusted and employed, and gradually 
 loses its excitability: but when two- similar objects are presented to 
 •the eyes of a squinting person, one carefully in the axis of each, their 
 images coincide and they are seen as one. The double vision of 
 
440 INNERVATION. 
 
 drunkenness, and of certain cerebral affections, is explicable partly on 
 the same ground, but in such cases considerable allowance must be 
 made for the disordered state of the sensorium. Again, if correspond- 
 ing points of the two retinae are pressed by the finger, a single lumi- 
 nosity, is perceived ; but a double one, if the points touched are non- 
 symmetrical. Something similar to this blending of two impressions 
 in one sensation exists in the sense of hearing, and, perhaps, also in 
 taste and smell. 
 
 The corresponding points of the two retinae are such as would be 
 in contact, if the two retinse were adapted to one another: the upper 
 and lower parts correspond with the upper and lower, and the inner 
 side of one with the outer side of the other. 
 
 As we are entirely ignorant of the mode in which the mind takes 
 cognizance of a single impression on an organ of sense, we cannot 
 hope to understand how a single sensation can result from a double 
 impression. But it is most interesting to remark a structural pecu- 
 liarity in the course of the optic nerves, which certainly allies itself 
 with this wonderful part of their function. Their partial decussation 
 in the chiasma, or commissure, connects each retina with both optic 
 tracts, and with the corresponding portions of the cerebrum ; and it 
 is not improbable, as Dr. Wollaston conceived, and Mr. Mayo has 
 described, that the right side of both retinae is continuous with the 
 right optic tract, and the left side of both with the left. This wotild 
 place each side of the central apparatus in connection with its own 
 side of both the symmetrical images, and might be supposed to favor 
 their conception as one. Dr. Wollaston relates, that on different oc- 
 casions he lost the power of seeing one half of an object to which he 
 directed both eyes ; and others have experienced similar temporary 
 attacks. Thus, Abernethy would humorously affirm that he could 
 sometimes see only his »ie and thy, having lost the other members of 
 his name. Such phenomena are readily explained by supposing the 
 anatomical arrangement of the sides of the retinse, with regard to the 
 optic tracts, to be such as above described, since any derangement of 
 one optic tract would then affect the same part of both optic images. 
 Indeed, in Dr. Wollaston's own case, a tumour was found involving 
 one of the optic tracts, as had himself inferred from the phenomenon 
 above mentioned. 
 
 What we have before advanced, however, regarding the unbroken 
 sheet of gray nervous matter in the retina, leads us to attach even 
 more importance to the commissural fibres which appear to connect 
 the two retinae together, through the medium of the chiasma, and 
 independently of parts behind it. We conceive that these commis- 
 sural fibres may connect corresponding parts of the retina, much in 
 the same way as corresponding parts of the cerebral convolutions of 
 the opposite hemispheres are linked together by the corpus callosum 
 or other commissures; and that the unity of action of the double 
 organ may depend, as to its physical cause, on the same principle in 
 both._ 
 
 This capacity of forming a single conception from a double impres- 
 sion may appear, at first sight, to be given simply to obviate con- 
 
SINGLE VISION WITH A DOUBLE ORGAN. 441 
 
 fusion ; but Mr. Wheatstone has most ingeniously shown that it con- 
 fers a new power on the sense, viz., that of appreciating forms pro- 
 jected in relief. 
 
 Such objects, if sufficiently near the eyes for the optic axes to 
 converge in viewing them, are seen from two different directions: 
 they are represented on each retina by a different perspective pro- 
 jection; and the more so, the nearer the object to the observer. 
 
 Mr. Wheatstone has shown that the single sensation excited by 
 these two images is that of a third image different from them both, 
 but excitable only by both of them at once, and attended with the 
 notion of solidity, or projection in relief. He has illustrated this by 
 an instrument which he terms the stereoscope. Some object of three 
 dimensions (as a cube) is represented in two drawings as it would be 
 seen at a small distance by each of the two eyes. These drawings 
 are then placed symmetrically in the right and left compartments of a 
 small box, so as to be reflected by sloping mirrors to the eyes of the 
 observer, each view to its corresponding eye. When he looks at 
 each separately, it seems a mere drawing on a flat surface; but when 
 he regards both views at once, they appear to coalesce, and a solid 
 prominent figure seems to occupy their place. Mr. Wheatstone has 
 also shown that the same effect occurs, although there may exist 
 some disparity between the size of the two images; and that the 
 resultant idea is that of a figure of intermediate size. Now, unless 
 an object is placed directly in front of the eyes, its image is larger in 
 one eye than the other, because it is nearer one eye than the other; 
 and this faculty of striking a mean between the two impressions is, 
 therefore, constantly made use of. 
 
 The above facts abundantly prove the non-existence of absolutely 
 corresponding points on the two retinee, such as were formerly held 
 to exist. But they do not invalidate what has before been advanced 
 respecting the general correspondence of certain tracts of the two 
 retinae, and the absolute non-correspondence of others. 
 
 Mr. Wheatstone further observes, that if two dissimilar images are 
 represented at once to the corresponding parts of the two retinae, 
 they are not blended, but seen alternately, according to their dis- 
 tinctness and degree of illumination. This is a very singular cir- 
 cumstance, and agrees closely with what takes place when dissimilar 
 colours are viewed in the same way. 
 
 On the subjects treated of in this chapter, reference is made to the following works : 
 Zinn, Descriptio Anatomica Oculi Humani; Haller, Elementa PhysiologisE, torn, v.; 
 Porlerfield on the Eye and Vision (an admirable work) ; Dr. Jacob's paper on the Phil. 
 Trans. 1819,-and in the 12th vol. Med. Chir. Trans., and the article "Eye" in the 
 Cyclop. Anat. and Phys., by the same author; Mr. Dalrymple's Anatomy of the Eye, 
 London, 1834; the introduction to Mr. Lawrence's Treatise on Diseases of the Eye, 
 2d Edit., 1841 ; Mr. Wharton Jones' Essay prefixed to MacKenzie on Diseases of the 
 Eye; Arnold, iiber das Auge des Menschen; Scemmerring's Plates of the Eye; Miil- 
 ler's and Wagner's Physiology; Mackenzie on Vision; Bowman (W.) Illustrations 
 of the Anatomy of the Eye in health and disease, now in course of publication. 
 22 
 
442 INNERVATION. 
 
 CHAPTER XVIII. 
 
 OF HEARING. THE ORGAN OF HEARING. — ITS DEVELOPMENT IN THE 
 
 ANIMAL SERIES. THE EXTERNAL EAR. THE TYMPANUM. THE 
 
 LABYRINTH. THE FUNCTIONS OF THESE PARTS. 
 
 It is by the sense of hearing that the mind takes cognizance of 
 those oscillations of elastic matter which give rise to the phenomena 
 of sound. 
 
 The communication of these oscillations to the ear may take place 
 through the air, or through the intervention of some solid conductor, 
 brought into immediate connection with the organ of hearing. 
 
 The essential part of the organ of hearing is a sac, containing fluid, 
 upon which the nerve of hearing is freely distributed: this sac being 
 in connection with the cranial parietes. This is represented in the 
 human subject by that small cavity which is excavated in the petrous 
 portion of the temporal bone, called the vestibule. This, and three 
 semi-circular canals, with a spirally disposed canal, divided by a par- 
 tition, constituting the cochlea, form the labyrinth. External to this, 
 and situate between the squamous and petrous portions of the tempo- 
 ral bones is a cavity, the tympanum, which in front further communi- 
 cates very freely with the cavity of the throat through an open 
 channel, the Eustachian tube, whereby air has a free access into the 
 tympanum. This cavity is closed on the outside by a membrane 
 [membrana tympani) which extends over its external orifice as over 
 a drum. A communication is established between the membrane 
 and the inner wall of the tympanum, by a chain of small bones which 
 extends from the one to the other. These are the ossicles of the ear. 
 The outer bone of the chain is intimately attached to the membrana 
 tympani, and the inner one to a membrane which closes the vestibule 
 on the outside. The three bones which compose the chain are 
 articulated by moveable joints, and are moved by small muscles, 
 •which are thus enabled to regulate the tension of the membrana tym- 
 pani, as well as of the membrane of the vestibule. Externally is an 
 apparatus for collecting sounds, and conducting them to the tym- 
 panum. 
 
 Development of the Organ of Hearivg in the Animal Serien. — There is no organ in 
 the body in wtiich we find a more remarkable gradation of development in the, various 
 classes of animals, ihan in ihe ear. We see it existing as a simple sac in the cepha- 
 lopod and gastercipod mollusks, and in Crustacea. In the cullle-fish, it consists of a 
 small sac filled with fluid, lodged in a chamber excavated in the cranial cartilage. 
 The chamber is closed everywhere except at the entrance of the auditory nerve, 
 ■which passes in to expand upon the sac. From its inner surface there project 
 several obtuse processes, of a soft, elastic nature, which support the sac. The sac 
 contains a calcareous body or otolithe. Even at this early stage of development the 
 organ is double, and the two cavities are separated from each other by a very thin 
 septum. It is obvious that these cavities are strictly analogous to the vestibule in 
 the hiaher classes. 
 
 In Gasteropoda, the organ consists of a sac, to which the nerve is distributed, and 
 
( f 
 
 ORGAN OF HEARING IN THE ANIMAL SERIES. 443 
 
 which contains fluid and several small otolithes, which, according to Siebold, exhibit 
 Remarkable movemenls. 
 
 In Crustacea, the organ still exists as a simple sac. This, as Dr. Arthur Farre has 
 shown, is situate, in the lobster, in the base or first joint of the lesser antenna. Its 
 place is indicated by a tough membrane which covers an oval aperture in the upper 
 surface of this joint; the membrane being a continuation of the same structure which 
 forms the shell, but in which the earthy matter is wanting. Towards the inner and 
 anterior margin of this membrane, there is a small round aperture, through which a 
 bristle may be passed. "On removing this oval membrane, together with a portion 
 of the surrounding shell, the internal organ is brought into view,completely imbedded 
 in the soft integument and muscular structure of the antenna." It consists of a sac, 
 in shape like an auricle, and of a horny structure, like soft quill, suspended in the 
 centre of the joint, free on all sides, and having only a single attachment near the 
 aperture in the oval membrane already described; it nearly fills the cavity of the 
 joint. The sac contains particles of siliceous sand, which find their way into it 
 through the aperture already described, and probably fulfil the office of the otolithes 
 which exist in other classes of animals. Numerous very remarkable ciliated pro- 
 cesses are attached to the lower surface of the vestibular sac: they are arranged in a 
 semicircular line. In the neighbourhood of this line the auditory nerve attaches 
 itself to the sac, and forms a plexus, which covers the whole under surface of the 
 sac, extending also towards its upper surface. The nerve is derived from the lesser 
 and greater anlennal nerves. 
 
 Dr. A. Farre has shown that the cavity situate at the base of the greater antenna 
 is not, as has been hitherto supposed, suited to act as an organ of hearing. It is a 
 conical papilla, abruptly truncated, and having stretched over it a membrane, which 
 is pierced in its centre by an aperture capable of admitting a small bristle. On 
 making a section of this part, nothing more is seen than' a narrow canal in the 
 fleshy substance leading perpendicularly from the external orifices, and terminating 
 abruptly at the depth of two lines. A nerve is sent off to this organ from the supra- 
 CBSophageal ganglion. Such an organ is very ill-adapted for hearing. Dr. Farre 
 has ascertained that this is the most sensitive part of the body of the lobster; 
 "since, while the mechanical irritation of any other parts excited only a slight 
 movement in the limbs of the animal, when out of water, and somewhat feeble, the 
 touching of this part was immediately followed by a violent and almost spasmodic 
 flapping of the tail." {Farre on the Organ of Hearing in Crustacea. Phil. Tr. for 
 1843, p. 233.) 
 
 In Fishes the organ of hearing acquires a considerable increase in the complexitj' 
 of its organization. It consists of a vestibular sac, with the accession of, in general, 
 three semicircular canals. In the myxine, however, a fish of very low organization, 
 there is only one of these canals. In the lamprey there are only two. The vestibular 
 sac consists of a large sac {utriculus oi Breschet),into which the semicircular canals 
 open, and with the walls of which they are continuous, and of a small ofl^set from 
 this larger one (the naccuhis of Breschet). This apparatus is composed of a thin, 
 transparent, elastic membrane. It is filled with fluid, and contains in each sac, either 
 porcelainous bodies (pioUthes), of beautiful structure and great diversity, as in the 
 osseous fishes, or masses of pulverulent deposit, like powdered chalk (pto/eonia), as 
 in the cartilaginous fishes. These, whether hard or soft, consist of carbonate of lime, 
 and therefore may be quickly decomposed by a mineral acid. The whole of this 
 auditory apparatus is deposited in an excavation of the cranial wall, which commu- 
 nicates with ihe>cavity of the cranium itself, excepting in the rays and sharks, in which 
 it is enclosed by the cranial cartilages. It is suspended in fluid (part, probably, of 
 the cerebro-spinal fluid), which constitutes the analogue of the perilymph in the 
 higher animals. In some fishes, according to Breschet, an additional offset from the 
 larger sac exists, to which he gives the name cystieuk. All these parts ere analogous 
 to the membranous labyrinth of the higher animals, there being nothing to represent 
 the tympanum or the cochlea. In many of the osseous fishes the auditory apparatus 
 has no communication whatever with the exterior. In rays and sharks, however, a 
 prolongation of the labyrinth extends through an opening in the occipital portion of 
 the skull to the surface just beneath the skin. In many fishes, according to Weber, 
 there is an intimate connection between the auditory apparatus and the swimming 
 bladder, although their cavities have no communication with each other. 
 
 In Amphibia, the auditory apparatus is closed off from the cranial cavity, and is 
 contained. in the cranial bones. It consists of a vestibule with three semicircular 
 canals. In some, there is placed external to this labyrinth a tympanic cavity, 
 
444 
 
 INNERVATION. 
 
 closed on ihe exterior by a membrane, which is intimately united with, or a porlioii 
 of, the integument, or a thin layer of cartilage. An osseous pillar (the columella), 
 or a chain of two or three ossicles, extends from the wall of the vestibule to this 
 tympanic membrane, analogous to the tympanic bones in the human subject. In 
 the Reptiles, there is a short canal connected with the vestibule, analogous to the 
 cochlea. The existence of this canal establishes that of a second external opening 
 belonging to the labyrinth, or fenestra cochleae, in addition to the fenestra vestibuli. 
 Some of the Reptiles, as the serpents, are devoid of a distinct tympanic cavity; but 
 the existence of a columella beneath the skin indicates a rudimentary state of it. In 
 others, as the tortoises, crocodiles, and lizards, such a cavity exists, with its usual 
 canal of communication with the fauces, the Eustachian tube, and with a columella. 
 The fluid of the labyrinth contains crystalline particles in place of otolithes. 
 
 In Birds, the organ of hearing has the same parts as in the higher reptiles. Its 
 labyrinth has the cochlea and semicircular canals, and the two fenestras, and there 
 is a tympanic cavity with a columella. The cochlea is a very slightly bent canal, 
 divided by a membranous septum into two passages, scala vestibuli, and scala 
 tympani. 
 
 In Mammalia, the general characters and structure of the organ of hearing closely 
 resemble those of man. 
 
 In examining the anatomy of the human ear, we shall first describe 
 the external ear, next, the middle ear, or tympanum, and lastly, the 
 labyrinth. 
 
 Fig. 131. 
 
 General view of the external, middle, and internal ear, as seen in a prepared section through a, 
 the auditory canal, b. The tympanum or middle ear. c. Eustachian tulie, leading to the pharynx. 
 d. Cochlea; and c. Semicircular canals and vestibule, seen on their exterior, as brought into view 
 by dissecting away the surrounding petrous bone. The styloid process projects below; and ihe 
 inner surface of the carotid canal is seen above the Eustachian lube. From Scarpa. 
 
 The External Ear comprises the free, expanded part, auricle or 
 pinna, and the auditory canal or external meatus. 
 
 The auricle presents an outer surface, which is on the whole con- 
 cave, and slightly inclined forwards. On this surface are several 
 eminences and depressions, resulting from the folded, or rather 
 crumpled, form of its cartilaginous basis, and which are seen reversed 
 on the free portion of the opposite surface. These are : — a prominent 
 rim or helix, and within it another curved prominence, the anthelix, 
 
THE EXTERNAL EAR. 445 
 
 ■which bifurcates above, so as to enclose a space, the scaphoid fossa, 
 and describes a circuit round a deep, capacious, central cup, the 
 concha. At the end of the helix, in front of the concha, is a small 
 detached eminence, the tragus, so named from its bearing a tuft of 
 hair resembling a goat's beard. Opposite this, behind and below 
 the concha, is the antitragus. Below is the pendulous loie, com- 
 posed of dense areolar and adipose tissues. The concha is imper- 
 fectly divided into an upper and a lower part by the anterior curved 
 extremity of the helix. The groove of the helix is continued into the 
 upper division, and the auditory canal leads from the front and 
 deepest part of the lower division where it is overhung by the tragus 
 and its protective tuft of hairs. The cartilage of the pinna consists 
 of one principal piece, from which that of the tragus and antitragus 
 is separated by a fissure filled up by fibrous membrane. It is very 
 flexible, and elastic, has a yellowish colour, and belongs to the same 
 category as the cartilages of the alae nasi, &c. Ligamentous fibres 
 bind the concha behind and above, and the tragus in front to the 
 bone and fascia in the neighbourhood. A few muscular fibres passing 
 between different parts of the auricle, serve to impress upon them 
 movements, but so slight as to be hardly worthy of note. These 
 fibres are found externally on the tragus, the antitragus, the upper 
 end of the helix, and behind on the concha. The whole of the car- 
 tilaginous part of the ear is rendered movable by three muscles, the 
 superior and anterior auris, arising from the epicranial aponeurosis, 
 and converging to the concha and helix, and the posterior auris, 
 passing between the mastoid process and concha. 
 
 The auditory canal passes from the concha inwards for about an 
 inch, or rather more. It inclines a little forwards, and is slightly 
 bowed, so as to be higher near the middle than at either end. Its 
 width does not equal its height, and it is altogether narrower in the 
 middle. The membrana tympani, which terminates it, is placed 
 obliquely, in consequence of the lower side of the meatus being longer 
 than the upper. The canal consists of two parts, a cartilaginous 
 and fibrous one, and an osseous. To form the first, the cartilage of 
 the concha and tragus is prolonged inwards as far as the auditory 
 process of the temporal bone, and constitutes a tube imperfect at 
 the upper and back part, where its deficiency is supplied by fibrous 
 membrane. This cartilage is rendered still further movable by 
 partial slits in a vertical direction {incisures Santorini). Muscular 
 fibres are described by some to exist in the meatus, which, accord- 
 ing to Haller, become shortened by their contraction. The osseous 
 part of the auditory canal consists in the foetus of a ring of bone, to 
 which the membrana tympani is attached (tympanic ring of the tem- 
 poral bone). In the adult, it is nearly three-quarters of an inch 
 long, and gives the meatus the form and direction already described. 
 
 The skin of the external ear is delicate, and well supplied with 
 vessels and nerves. The orifice of the meatus, besides being con- 
 cealed behind the tragus, is defended by hairs, and a close arrange- 
 ment of ceruminous glands, which furnish an abundant secretion, 
 calculated to entangle particles of dust, or small insects, and to pre- 
 
446 INNERVATION. 
 
 vent their entrance into the organ. These glands are principally 
 seated in the subcutaneous tissue, where the cartilage is deficient, 
 and do not extend into the osseous portion of the canal. The 
 cerumen is an oily, very bitter substance, of a yellow colour, and 
 contains, in addition to fat, albumen, and colouring matter, a bitter 
 principle analogous to that of the bile. If not removed from time 
 to time, it is liable to form hard pellets, which either impact the 
 passage, or come into contact with the membrana tympani, and in 
 either case seriously interfere with the transmission of sound to the 
 internal parts. These concretions are partially soluble in ether and 
 turpentine. 
 
 The Middle Ear, or tympanic cavity, is a space filled with air, 
 communicating with the pharynx by the Eustachian tube, and inter- 
 posed between the external meatus and the labyrinth. It opens 
 behind into the mastoid cells, which are also filled with air, and it 
 is traversed by a chain of moveable bones, connecting the membrana 
 tyrapani with the vestibule, or common central cavity of the laby- 
 rinth. The tympanum is of irregular shape, compressed laterally, 
 and lined by a very delicate ciliated epithelium, prolonged from the 
 pharynx. 
 
 Tlie external wall of the tympanum is formed by the membrana 
 tympani, and a small extent of the surrounding bone. The meni- 
 brane is nearly oval, but wider above than below, and as already 
 stated, placed in a slanting direction, so as to form an obtuse angle 
 with the upper wall, and an acute one of about 45° with the floor 
 of the auditory canal. It consists of three laminae, an external, mid- 
 dle, and internal. The external is derived from the cuticular lining 
 of the canal, and easily detaches itself with that structure after mace- 
 ration. The middle is strong and fibrous, perhaps analogous to the 
 dermal part of the integurnent, and attached through the medium of 
 a dense fibrous rim to the bone,- which presents a distinct groove for 
 its reception, except above. The handle of the malleus is firmly 
 united to this layer of the membrane, in a vertical direction as far 
 down as the centre, and draws the membrane inwards along that 
 line, so that its outer surface is concave, its inner convex. The 
 abundant small vessels supplying this part run along the handle of 
 the malleus, and thence radiate more or less directly towards the 
 border. The fibrous tissue is in part similarly disposed, and thus 
 Sfems to have led Sir E. Home to describe a radiating muscle in the 
 membrane, which does not appear to exist. Seen from within, a 
 concentric arrangement of the fibres is more obvious. The inner 
 layer is the ciliated epithelial lining of the cavity, which is easily 
 scraped off for examination in the fresh state (see p. 73). 
 
 The internal wall of the tympanum (fig. 132) has two orifices of 
 communication with the internal ear; the fenestra ovalis, a, leading 
 to the vestibule, and the fenestra rotunda, b, opening into the cochlea. 
 Both these are closed by membrane which prevents the escape of the 
 fluid contained in these inner chambers, and communicates vibrations 
 to it. The fenestra ovalis is likewise occupied by the base of the 
 stapes, one of the chain of ossicles connecting it with the membrana 
 
THE INNER WALL OF THE TYMPANUM. 
 
 447 
 
 tympani. Between the fenestrse is the promontory, c, corresponding 
 to the first turn of the cochlea, and furrowed by two or three canals 
 for the nerves which form the anastomosis of Jacobson, n. Behind 
 the fenestra ovalis is a conical eminence, the pyramid, d, hollowed, 
 and presenting a small orifice at its summit, which is on a level with 
 the middle of the vestibular fenestra. The pyramid contains the 
 stapedius muscle, the tendon of which emerges at its summit, and 
 
 Fig. 132. 
 
 Diagram of the inner wall of the tympanum after maceration, the outer wall and ossicles being 
 removed, a. Fenestra ovalis. 6. Fenestra rotunda, c. Promontory, d. Pryramid, with the orifice 
 at its apex. e. Projection of the aqueductus Faljopii. f. Some of the mastoid cells communicating 
 ■with the tympanum; g. Processus cochleariformis, bounding i, the canal for the tensor tympani 
 muscle : the anterior pyramid is broken off, if it existed, h. Commencement of the Eustachian tube. 
 j. Jugular 'fossa, immediately below the tympanum, fc, Je. Carotid canal, with the artery in outline, 
 to show its course in relation to the tympanum and Eustachian tube. I. Portio dura of the seventh 
 pair of nerves, as it vi^ould be seen in the terminal pan of the aqueduct of Fallopius, m. Chorda 
 tympani, leaving the portio dura, and entering a short canal, which opens in the tympanum, at the 
 base of the pyramid, n. Grooves for the tympanic plexus. 
 
 runs to the neck of the stapes. This muscle is supplied by a twig 
 from the portio dura of the seventh pair. At the base of the pyramid 
 is an aperture through which the chorda tympani, m, enters the 
 tympanum. Thence this nerve passes forwards, between the handle 
 of the malleus and the long arm of the incus, and emerges through a 
 canal close to the Glaserian fissure. Above the pyramid an arched 
 prominence, e, indicates the course of the aqueductus Fallopii, close 
 to the tympanum ; and behind this is the free communication with 
 the mastoid cells, y. 
 
 The anterior part of the tympanum presents above the canal for 
 the tensor tympani muscle, and below the orifice of the Eustachian 
 tube. The former, i, is chiefly formed by a curled plate of bone, the 
 processus cochleariformis, g, ending in a kind of perforated summit, 
 that some have termed, anterior pyramid. This is a little above the 
 fenestra ovalis, and gives passage to the tendon of the tensor tym- 
 pani, which becomes attached to the short process of the malleus. 
 
448 
 
 INNERVATION. 
 
 Fig. 133. 
 
 The Eustachian tube, about one inch and a half in length, leads from 
 the tympanum downwards, forwards, and inwards, to its orifice in 
 the pharynx, which is seen as a slit with an elevated edge close be- 
 hind the inferior turbinated bone of the nose (see fig. 106, t, p. 396). 
 By its straight, but inclined course, the passage of mucus from the 
 tympanum is facilitated. Its upper extremity for more than half an 
 inch is bony, while in the rest of its extent it is cartilaginous. It 
 dilates at each end, especially the lower, where the cartilage is thick- 
 ened and everted. It forms a passage for the air in and out of the 
 tympanum. It exists in all animals in which a tympanum is found, 
 but in many, the tubes of opposite sides have a common outlet on the 
 pharynx. External to the opening for the Eustachian tube is the 
 opening for the anterior muscle of the malleus (Glaserian fissur.e) and 
 that for the escape of the chorda tympani. 
 
 The ossicles of the tympanum are three, the malleus, the incus, and 
 
 the stapes (fig. 133). The maZZews (ham- 
 mer) has a large extremity above, termed 
 the head, m, bounded by a constriction 
 or neck, from which the handle (manu- 
 brium), h, passes down, imbedded in the 
 membrana tympani, as already described. 
 Its concavity directed outwards explains 
 the similar inequality of that membrane. 
 The short process is a slight conical pro- 
 jection from the neck, which receives 
 the insertion of the tensor tympani mus- 
 cle: the slender process (p. gracilis),^, 
 also passes from the neck, but forwards 
 and outwards, to enter the Glaserian fis- 
 sure. On the back of the head and neck 
 an articulation is formed with the incus. 
 The incus (anvil), is shaped not unlike 
 a molar tooth. It articulates with the 
 malleus by the anterior surface or summit 
 of its body, and has two processes, a short 
 and a long crus: the former, sc, has a 
 backward direction, and projects into 
 the mastoid cells, the latter, Ic, descends to a level with the fenestra 
 ovalis, bends inwards, and is tipped with a lenticular process, to 
 which the head of the stapes is attached, a. The stapes, or stirrup 
 bone, s, is almost sufficiently described by its name. Its construction 
 is truly elegant. It has a head, neck, two branches, and a base. The 
 last fits into the fenestra ovalis, to the margin of which it is attached, 
 by membrane, so as to enjoy some freedom of motion. Its neck re- 
 ceives the insertion of the stapedius muscle. The chain of ossicles, 
 now described, stretches across the tympanum by no means in a 
 straight line, and its parts are permitted to enjoy some degree of 
 motion, not merely by the double joint existing between them, but 
 by the mode of thfeir attachment at either end. 
 
 These bones are moved by small muscles, two of which are not 
 
 Ospicles of the left ear articuJated, 
 and seen from the outside and below. 
 m. Head of the malleus, below which 
 is the constriction, or neck. g. Pro- 
 cessus gracilis, or long process, at the 
 root of which is the short process, h. 
 Manubrium, or handle, sc. Short crus ; 
 and Ic, long crus of the incus. The 
 body of this bone is seen articulating 
 with the malleus, and its long crus, 
 through the medium of the orbicular 
 process, here partly concealed, a, with 
 the stapes, s. Base of the slapes. Mag- 
 nified three diameters. From Arnold. 
 
THE IN-TERNAL EAR, 449 
 
 disputed. These are the internal muscle of the malleus, and the sta- 
 pedius muscle. Each of these muscles consists of striped fibres. 
 
 The internal muscle of the malleus, or tensor tympani, occupies the 
 canal above the osseous portion of the Eustachian tujje. It is at- 
 tached in front to the under surface of the petrous bone, and to the 
 cartilage of the Eustachian tube ; it proceeds backwards, and ends 
 in a tendon which turns abruptly outwards from the osseous canal in 
 which the muscle is lodged, and is inserted into the short process of 
 the malleus. It draws this part inwards, and thus heightens the ten- 
 sion of the membrana tympani. An anterior muscle of the malleus, 
 or laxator tympani muscle, is described by many anatomists as passing 
 from the Glaserian fissure to the processus gracilis. The stapedius 
 muscle occupies the conical interior of the pyramid ; its surface is 
 aponeurotic, its interior fleshy, and it terminates in a small tendon 
 which emerges at the apex of the pyramid, and then passes to be 
 inserted into the neck of the stapes. In contraction it would fix the 
 stapes by pulling its neck backwards. It probably compresses the 
 contents of the vestibule. 
 
 Of the -Internal Ear, or Labyrinth. This is the potential part of 
 the organ of hearing, and includes the ultimate distribution of the 
 nerve. It consists of three parts, the vestibule, the semicircular 
 canals, and the cochlea, all of which, from their delicacy and minute- 
 ness of structure, demand careful examination. They are a series of 
 cavities hidden in the hardest part of the petrous bone, communicating 
 on the outside with the tympanum, by the fenestras ovalis and rotunda 
 already described, and on the inside with the internal auditory canal, 
 which conveys the nerve to them. The very compact bone imme- 
 diately bounding these cavities, considered apart from the less dense 
 bone which surrounds it, is termed the osseous labyrinth, in distinction 
 from a membranous labyrinth within. 
 
 Of the Osseous Labyrinth. — The singularly complex shape of this 
 part of the organ makes it difficult to describe. 1. The vestibule, or 
 common central cavity, placed immediately to the inner side of the 
 tympanum, is flattened from side to side, and about a fifth of^n inch 
 in height, as well as from before backwards. The semicircular canals 
 open into it by five orifices behind, the cochlea by a single one in 
 front ; on its outer wall is the fenestra ovalis, on its inner several 
 minute holes, including the macula cribrosa for the entrance of a por- 
 tion of the auditory nerve from the internal auditory meatus. At the 
 hinder part of the inner wall is the orifice of the aqueductus vestibuli, 
 a fine canal penetrating the vestibule from the posterior surface of the 
 petrous bone, and containing, as some describe,,a tubular prolongation 
 of the lining membrane of the vestibule, ending in a minute pouch 
 between two layers of the dura mater, within the cranial cavity. 
 'Breschet considers this to be an evidence of a continuity once exist- 
 ing between the lining membrane of the cranium, and that of the 
 vestibule, and it is certain that in most fishes the vestibule is a pro- 
 cess of the cranial cavity, or separated from it only by a membrani- 
 form septum. Whatever other use the aqueduct of the vestibule may 
 
450 INNERVATION. 
 
 serve, it seems, certainly, to convey small vessels to the internal ear. 
 The lower part of the inner wall presents a hemispherical depression 
 {fovea kemisplierica), and immediately above it, and on the upper 
 wall, another, transversely oval and larger {fovea semi-elliptica). 
 These are separated by a small pyramidal eminence. 
 
 Fig. 134. 
 
 Osseous labyrinth of tlie left side. o. Fenestra ovalis, leading into the cavity of the vestibule. 
 From this a bristle, t, is passed into v v, the vestibular scala of the cochlea, which is laid open in 
 part by the removal of the outer wall. t. Fenestra rotunda, seen almost in profile. Through this a 
 bristle, t, is passed into the tympanic scala of the cochlea, t (, exposed by the removal of part of the 
 membranous portion of the lamina spiralis. The three semicircular canals are seen, witli their 
 extremities entering the vestibule, and one end of each dilated into an ampulla. Magnified 3i di- 
 ameters. Partly from Scemmerring. 
 
 2. The semicircular canals are three in number, all opening at 
 both ends into the vestibule, so that there would be six orifices, were 
 not one of the orifices common to two of the canals. The canals are 
 of unequal length, but all describe more than half a circle, and their 
 cavity is not cylindrical, but slightly compressed on the sides, and 
 about a twentieth of an inch in diameter. Each is dilated at one 
 end into an ampulla, of more than twice the diameter of the tube, and 
 at the oppo.site end it opens out slightly on entering the vestibule. 
 Each canal lies in a different plane, the direction of which being 
 constant, should be carefully noticed in relation to their function. 
 The superior vertical canal is also anterior, and lies across the petrous 
 bone. It forms about two-thirds of a circle, and its extremities are 
 more divergent than those of the others. In the foetus the concavity 
 of this canal is free, owing to a deficiency in the substance of the 
 petrous bone, and its arch forms a projection within the cranium, 
 even in the adult. The ampulla is on its outer extremity. The in- 
 ferior vertical canal is also posterior, and runs parallel to the posterior 
 surface of the petrous bone, and therefore at right angles to the for- 
 mer. The ampulla is at its lower extremity, and its upper end joins 
 
THE COCHLEA. 
 
 451 
 
 the inner end of the former canal, to constitute a common canal an 
 eighth of an inch long, rather wider than those which join to form it, 
 and opening behind and below. The horizontal canal is also inferior, 
 and shorter than either of the others ; its arch is directed outwards 
 and backwards ; its ampullar extremity is close to that of the superior 
 vertical canal. 
 
 Kg. 135. 
 
 Interiorof the osseous labyrinth. V. Vestibule, a u. Aqueduct of the vestibule, o. Fovea semi- 
 elliptica. r. Fovea hemispherica. S. Semicircular canals. S.Superior. 37. Posterior, i. Inferior. 
 00 a. The ampullar extremity of each. C. Cochlea, ac. Aqueduct of the cochlea, sv. Osseous 
 zone of the lamina spiralis, above which is the scala vestibuli, communicating with the vestibule. 
 St. Scala tyrapani below the spiral lamina. From Soemmerring. 
 
 3. The cochleais,m .shape, very like a common snail-shell. It lies 
 almost horizontally, its apex forwards and outwards, its base marked 
 near the bottom of the internal meatus, by a depression exhibiting a 
 spiral arrangement of pores for the reception of the cochlear division 
 of the auditory nerve. From base to apex extends the irregularly 
 conical axis, modiolus, or columella, which is perforated by numerous 
 branching channels, ascending from the pores just mentioned, and 
 distributing the nervous filaments in regular succession within the 
 spiral cochlear canal which winds around the axis. This spiral canal 
 is about an inch and a half in length, if measured along its outer 
 wall, and diminishes gradually in size from the base to the summit 
 of the cochlea, where it ends in a cul-de-sac. At its commencement 
 it is about one-tenth of an inch in diameter, but at its termination 
 scarcely half that size. At its base it diverges somewhat from the 
 modiolus, towards the tympanum and vestibule, and presents three 
 openings. Of these, one, free and oval, enters the vestibule; another 
 is the fenestra rotunda, communicating with the tympanum in the 
 dry bone, but filled up in the recent state by a proper membrane, the 
 memhrana tympani secundaria; the third is the minute orifice of the 
 aqueductus cochlece, a funnel-shaped canal leading to the jugular fossa, 
 
452 INNERVATION. 
 
 and supposed to transmit a snaall vein. The spiral canal describes 
 about two turns and a half, of which the first, passing round the large 
 base of the modiolus, takes much the widest -sweep, so as to encircle 
 most of the second turn. The inner wall of this coiled canal, as has 
 been shown by Ilg, forms the outer wall of the modiolus. 
 
 The spiral canal of the cochlea is subdivided into two passages by 
 an osseo-membranous lamina, extended between its modiolar and 
 peripheral wall, and of course taking the same spiral direction as the 
 canal itself. This is the lamina spiralis, the fundamental element of 
 the cochlea, on which the nervous tubules are spread out. More 
 than half its breadth on the side of the modiolus is formed by a very 
 brittle osseous process from the modiolus, called the osseous zone, 
 enclosing minute channels continuous with those of that part, and 
 transmitting the nerves; its opposite or outer portion is membranous 
 and muscular, and connects the outer thin edge of the osseous zone 
 to the outer wall. The osseous zone commences gradually within 
 the vestibule, and enters the spiral canal between the vestibular and 
 tympanic openings of the cochlea, forming, with the help of the 
 membranous extension, a complete septum between them. The 
 passages, or scales, into which the spiral lamina divides the canal, 
 correspond, therefore, respectively to those chambers; the upper, 
 towards the apex of the cochlea, scala vestibuli, the lower, towards 
 its base, scala tympani. These scalae are, on the whole, pretty equal 
 in size; the vestibular scala is, however, the smaller at the base, the 
 tympanic, near the apex, of the coil ; and the latter ceases ere it 
 reaches the summit. At the apex of the cochlea the parts have an 
 arrangement difficult to describe, though easily understood when 
 seen. The axis, no longer hollow, and containing nerves, is reduced 
 to a delicate lamella at about half a turn from the dome-like summit, 
 or cupola, formed by the last part of the spiral canal. This lamella, 
 which is the real apex of the modiolus, immediately expands, stretches 
 upwards, and becomes more twisted on itself, so as to include part, 
 or all of the last half turn of the cochlear canal, being termed from its 
 appearance as viewed from below, the infundibulum, or funnel. The 
 wide part of this imperfect funnel is directed towards the cupola, 
 with which it blends. It is not open above, but on the side, and it 
 is, in fact, the outside of the last half turn of the canal, projecting 
 into the turn below. 
 
 The osseous zone of the spiral lamina ceases with the hollow mo- 
 diolus at the slender lamella already mentioned, terminating by a 
 small projecting hook (hamulus), the concave border of which is 
 free, and directed towards the lamella, so as to leave an opening or 
 deficiency, the helicotrema of Breschet, by which the scalee tympani 
 and vestibuli communicate. The membranous zone connects the 
 convex border of the hook to the outer wall, and is also continued 
 upwards beyond the point of the hook, presenting, however, towards 
 the infundibulum, like the hook itself, a free concave border, con- 
 tributing to form the orifice of communication. 
 
 Such being the form of the osseous labyrinth, we may now pro- 
 ceed to consider the more delicate parts of the organ, and the imme- 
 
SPINAL LAMINA OF THE COCHLEA. 
 
 453 
 
 diate distribution of the auditory nerves. We must premise that the 
 cavity of the osseous labyrinth is occupied by a limpid fluid, the 
 perilymph, so called by De Blainville, from its surrounding, though 
 in the vestibule and semicircular canals only, a hollow membranous 
 apparatus, the membranous labyrinth, which latter itself contains a 
 similar fluid, the endolymph. 
 
 Fig. 136. 
 
 Cochlea of a new-born infant, opened on the side towards the apex of the petrous hone. It shows 
 the general arrangement of the two seals, the lamina spiralis, and the distribution of the cochlear 
 nerve. At the apex is seen the modiolus expanding into the cupola, where the spiral canal termi- 
 nates in a cul-de-sac. The helicolrema is not visible in this view. From Arnold. 
 
 Of the Structure of the Spiral Lamina of the Cochlea. — We shall 
 term the two surfaces of this lamina tympanic and vestibular, as they 
 regard respectively the tympanic or vestibular scala. The osseous 
 portion of the spiral lamina extends more than half way from the 
 modiolus towards the outer wall, and is perforated, as already de- 
 scribed, by a series of plexiform canals for the transmission of the 
 cochlear nerves; these canals, taken as a whole, lie close to the 
 lower or tympanic surface, and open at or near the margin of this 
 zone. The vestibular surface of the osseous zone presents in about 
 the outer fifth of its extent, a remarkable covering, more resembling 
 the texture of cartilage than anything else, but having a peculiar 
 arrangement quite unlike any other with which we are acquainted. 
 Being uncertain respecting the office of this structure, we shall term 
 it the denticulate lamina (figs. 137, and 138), from a beautiful series 
 of teeth, forming its outer margin, which project free into the ves- 
 tibular scala, and, in the first coil, terminate almost on a level with 
 the margin of the osseous zone, but more within this margin towards 
 the apex of the cochlea. They thus constitute a kind of second 
 margin to the osseous zone, on the vestibular side of the true margin, 
 and having a groove beneath them, which runs along the whole 
 lamina spiralis, in the vestibular scala, immediately above the true 
 margin of the osseous zone. The intervals between the teeth are to 
 be seen on their upper surface, on their free edge, and also within 
 this groove, so that the teeth are wedge-shaped, and their upper 
 and under surfaces, traced from the free edge, recede. The free 
 projecting part, or teeth of the denticulate lamina form less than a 
 fourth of its entire breadth, and in the remainder of its extent it ap- 
 
454 
 
 INNERVATION. 
 
 pears to rest on the osseous zone; seen from above, after the osseous 
 zone has been rendered more transparent by weak hydrochloric acid 
 (fig. 138), rows of clear lines may be traced from the teeth at the 
 
 convex edge, towards the op- 
 Fig. 137 posite or concave edge of the 
 lamina. These lines appear 
 to be a structure resembling 
 that of the teeth themselves, 
 and they are separated from 
 one another by rows of clear, 
 highly refracting granules, 
 which render the intervals very 
 distinct. These intervals, as 
 seen in the figure, are more or 
 less sinuous and irregularly 
 branched. 
 
 The denticulate lamina, thus 
 placed on the vestibular sur- 
 face of the osseous zone, is 
 above, and at some distance 
 from the plexus of the cochlear 
 nerves, which lie near its tym- 
 panic surface. The vestibufar 
 surface of the osseous zone, 
 including the denticulate la- 
 mina, is convex, rising from 
 the free series of teeth towards 
 the modiolus. 
 
 In the groove already men- 
 tioned there is a series of elon- 
 gated bodies, not unlike columnar epithelium, in which the nuclei 
 are very faint. These bodies are thick and cubical at one end, and 
 taper much towards the other. They are united in a row ; and it is 
 possible they may have some analogy to the club-shaped bodies of 
 Jacob's membrane. We can assign them no use. 
 
 Continuous with the thin margin of the osseous zone is the mem- 
 branous zone. This is a transparent glassy lamina, having some 
 resemblance to the elastic laminae of the cornea, and the capsule of 
 the lens. A narrow belt of it next the osseous zone is smooth, and 
 exhibits no internal structure, while in the rest of its width it is 
 marked by a number of very minute straight lines, radiating outwards 
 from the side of the modiolus. These lines are very delicate at their 
 commencement, become more strongly marked in the middle, and 
 are again fainter ere they cease, which they do at a curved line on 
 the opposite side. Beyond this the membranous zone is again clear, 
 and homogenous, and receives the insertion of the cochlearis muscle. 
 The inner clear belt of the membranous zone is little affected by acids. 
 It seems hard and brittle. The middle or pectinate portion is more 
 flexible, and tears in the direction of the lines. The outer clear belt 
 is swollen, and partially destroyed by the action of acetic acid. Along 
 
 A. Section of the cochlRar canal, where the scalse 
 are equal. 51;. Scala vestibuli. st. Scala tympani. 
 o. Osseous zone of lamina spiralis, d. Denticulate 
 lamina, vn. Membranous zone. c. Cochlearis mus- 
 cle, r. Osseous rim of the groove of the cochlearis. 
 
 B. Margin of osseous zone, more magnified, sv, 
 Scala vestibuli. st Scala tympani. g-. Groove, be- 
 tween d, denticulate lamina, and m, membranous 
 zone springing from edge of the osseous zone, n. 
 Cochlear nerves and capillaries, distributed on the 
 tympanic surface of the osseous zone. 
 
THE COCHLEARIS MUSCLE. 
 i 
 
 455 
 
 the inner clear belt, and on its tympanic surface, runs a single some- 
 times branched vessel, which would be most correctly called a capa- 
 cious capillary, as it resembles the capillaries in the texture of its 
 wall, but exceeds them in size. It is the only vessel supplied to the 
 membranous zone, and seems to be thus regularly placed, that it may 
 not mar the perfection of the part as a recipient and propagator of 
 sonorous vibrations. 
 
 Fig. 138. 
 
 Fig. 139. 
 
 Denticulate lamina of the os- 
 seous zone of the lamina spira- 
 lis, seen on the vestibular sur- 
 face, a. Free edge of the teeth, 
 which are separated by fissures 
 as far as the line 6. The clear 
 tracts, with intervening rows of 
 globules, are seen at ^. e. Mar- 
 gin towards the axis of the 
 cochlea. From the sheep. — 
 Magnified 100 diameters. 
 
 Tympanic surface of a portion of the lamina spiralis of the 
 cat^ a. Termination of the cochlear nerves at the border of the 
 osseous zone, with capillaries ramifying over them. b. Inner 
 clear belt of the membranous zone. c. IVIarginal capillary oa 
 the tympanic surface, d. Pectinate portion of the membranous 
 zone. The half-detached fragment on the opposite edge shows 
 its mode of tearing, e. Outer clear belt of membranous zone, 
 torn from the cochlearis muscle. Magnified 300 diameters. 
 
 Of the Cochlearis Muscle. — At its outer or convex margin, the 
 membranous zone is connected to the outer wall by a semi-transparent 
 structure. This gelatinous looking tissue was observed by Breschet, 
 and is indeed very obvious on opening the cochlea; but .we are not 
 aware of any one having hinted at what we regard to be its real 
 nature. The outer wall of the cochlear canal presents a groove, 
 ascending the entire coil, opposite the osseous zone of the lamina 
 spiralis, and formed principally by a rim of bone, which, in section, 
 looks like a spur (fig. 137, r), projecting from the tympanic margin 
 of the groove, the opposite margin being very slightly «r not at all 
 marked. This groove diminishes in size towards the apex of the 
 cochlea. It gives attachment to the structure in question, by means 
 
456 
 
 INNERVATION. 
 
 Inner view of cochlearis muscle of the 
 sheep, a. Line ofattachmentof membra- 
 nous zone of lamina spiralis, of wliicii a 
 portion, 6, remains attached. The surface 
 below tiiis line is in the scala tympaiii, the 
 surface above, in the scala veslibuli. c. 
 Projecting columns, with intervening re- 
 cesses, in the vestibular part of the coch- 
 learis muscle. 
 
 of a firm dense film of tissue, having a fibrous character, and the fibres 
 of which run lengthwise in the groove, and are intimately united to it, 
 especially along the projecting rim. From this cochlear ligameht, the 
 
 cochlearis muscle passes to the mar- 
 k's- 140. gin of the membranous zone, filling 
 I * the groove, and projecting into the 
 1 canal, so as to assist in dividing the 
 tympanic and vestibular scalae from 
 one another, and thus forming in fact 
 the most external, or the muscular zone 
 of the spiral lamina. Thus the coch- 
 lear muscle is broad at its origin from 
 the groove of bone, and slopes above 
 and below to the thin margin in which 
 it terminates, so that its section is tri- 
 angular, and it presents three surfaces, 
 one towards the groove of bone, and 
 one to each of the scalfe. The sur- 
 face towards the vestibular scala is 
 much wider than that towards the 
 tympanic scala, and presents, in a 
 band running parallel to, and at»a 
 short distance from the margin of the 
 membranous zone, a series of arched vertical pillars, with intervening 
 recesses, much resembling the arrangement of the musculi pectinati 
 of the heart (fig. 140, c). These lead to and terminate in the outer 
 clear belt of the membranous zone, which forms a kind of tendon to 
 the muscle. This entire arrangement is almost sufficient of itself to 
 determine the muscular nature of the structure. If its fibres were 
 of the striped variety, no doubt would remain ; but its mass, evidently 
 fibrous, is loaded with nuclei, and filled with capillaries, following 
 the direction of the fibres, and in almost all respects it has the closest 
 similarity to the ciliary muscle of the eye.' The nuclei diminish in 
 number as the fibres end in the tendinous part; and they are made 
 much more evident by the addition of acetic acid. The action of the 
 muscle must be that of making tense the membranous portion of the 
 lamina spiralis, and so perhaps of adjusting it to the modifications of 
 sound. As the ciliary muscle, though of the unstriped variety, ad- 
 justs the transparent media of the eye to distinct vision at different 
 distances under the guidance of the will, so it is not impossible that 
 the cochlear muscle may have a voluntary adjusting power, though 
 its precise mode of action as a part of an acoustic apparatus may still 
 remain obscure. On the whole, however, we are more disposed to 
 regard this very interesting structure as having a preservative office, 
 as being placed there to defend the cochlear nerves from undue 
 vibrations of sound, in a way analogous to that in which the iris 
 protects the retina from excessive light. These nerves are acted on 
 principally by vibrations brought through the osseous part of the 
 cochlea, and it is probable that the arrangement of the scalfe is one 
 designed to allow of protective movements of the lamina spiralis by 
 
THE COCHLEAR NERVES. 
 
 457 
 
 Fig. 141. 
 
 muscular action, under a stimulus reflected from impressions on the 
 auditory nerve. 
 
 The capillaries of the ciliary muscle are derived from vessels 
 meandering over the walls of the scalse before entering it, and 
 those from above and below do not anastomose across the line of 
 attachment of the membranous zone, thus indicating that the con- 
 tinuation of this zone enters as a plane of tendon into the interior of 
 the muscle, dividing it into two parts, and receiving the fibres in 
 succession. 
 
 The scalae of the cochlea are lined with a nucleated membrane, or 
 epithelium, which is very delicate and easily detached, usually more 
 easily seen in the vestibular than in the tympanic scala, and in many 
 animals containing scattered pigment. 
 
 Of the Cochlear Jferves. — These enter from the internal auditory 
 meatus through the spirally-arranged orifices at 
 the base of the modiolus, and turn over in suc- 
 cession into the canals hollowed in the osseous 
 zone of the spiral lamina, close to its tympanic 
 surface. In this distribution the nervous bundles 
 subdivide and reunite again and again, forming 
 a plexus with elongated meshes, the general 
 radiating arrangement of which can be readily 
 seen through the substance of the bone when it has 
 been steeped in diluted hydrochloric acid (fig. 
 141). Towards {he border of the osseous zone the 
 bundles of the plexus are smaller and more closely 
 set, so as at length almost to form a thin uniform 
 layer of nervous tubules. Beyond the border, 
 and partially on or in the inner transparent belt 
 of the membranous zone, these tubules arrange 
 themselves more or less evidently into small sets, 
 which advance a short distance and then termi- 
 nate much on the same level. These terminal 
 sets of tubules are cone-shaped, coming to a kind 
 of point ere they cease. The white substance of 
 Schwann exists in them throughout, but is thrown 
 into varicosities and broken with extreme facili- 
 ty, and they are interspersed with nuclei, so that 
 it is very difficult to discover the precise dispo- 
 sition of the individual tubules (fig. 139, a). 
 They seem to cease one after another, thus 
 causing the set to taper; and at least it appears 
 certain that evidence of loopings, such as have 
 been described by some, is wanting. In the cochlea of the bird, 
 however, we have seen at one end a plexiform arrangement of nucle- 
 ated fibres ending in loops; but this is a peculiar structure. 
 
 The capillaries of the osseous zone are most abundant on the 
 tympanic scala in connection with the nerves now mentioned, and 
 form loops near the margin, with here and there an inosculation with 
 the large marginal capillary already mentioned. 
 
 Plexiform arrangement 
 of the cochlear nerves 
 seen in the basal coil of 
 the lamina spiralis, treated 
 with hydrocliloric acid. 
 There are no ganglion 
 globules in this plexus, 
 which consists of tubular 
 libres. a. Twigofcochlear 
 nerve in the modiolus, its 
 fibres diverging and re- 
 uniting in 4, a band in the 
 plexus taking a direction 
 parallel to the zones. 
 From this other twigs ra- 
 diate, and again and again 
 branch and unite as far as 
 the margin of the osseous 
 zone c, where they termi- 
 nate. From the sheep. 
 Magnified 30 diam. 
 
458 
 
 INNERVATION. 
 
 .^rrt\ 
 
 Of the Membranous Labyrinth (fig. 142). — This has the same gene- 
 ral shape as the bony cavities in which it lies, but is considerably 
 
 smaller, so that the perilymph in- 
 Fig. 142. tervenes in some quantity, except 
 
 vphere the nerves passing to it con- 
 fine it in close contact with the 
 osseous wall. Its vestibular por- 
 tion consists of two sacs, viz. : a 
 principal one of transversely oval 
 figure and corapresse*! laterally, 
 called the utriculus, or common 
 sinus, occupying the upper and 
 back part of the cavity, in contact 
 with the fovea semi-elliptica, and 
 beneath this a smaller and more 
 globular one, the sacculus, lying in 
 the fovea heraispherica, near the 
 orifice of the vestibular scala of the 
 cochlea, and probably communi- 
 cating with the utriculus. 
 
 The membranous semicircular 
 canals have the same names, shape, 
 and arrangement as the osseous 
 canals which enclose them, but are 
 only a third of the diameter of the 
 latter. As the osseous canals open 
 into the vestibule, so the mem- 
 branous ones open at both ends 
 into the utriculus — there being, 
 however, a constricted neck be- 
 tween this sac and the ampuUated 
 extremity of each canal. The auditory nerve sends branches to the 
 utriculus, to the sacculus, and to the ampulla of each membranous 
 canal. These nerves enter the vestibule by the minute apertures 
 before described, and tie down, as it were, both the utriculus and 
 sacculus to the osseous wall at those points, the membrane being 
 much thicker and more rigid where the nerves join it. The branches 
 to tha ampullae of the superior vertical and the horizontal semicircular 
 canals enter the vestibule with the utricular nerve, and then cross to 
 their destinations, while that to the ampulla of the posterior vertical 
 canal traverses the posterior wall of the cavity, and opens directly 
 into the ampulla. 
 
 The wall of the membranous labyrinth is translucent, flexible, and 
 tough. When withdrawn from its bed and examined, it appears to 
 present three coats, an outer, middle, and internal. The outer is 
 loose, easily detached, somewhat flocculent, and contains more or 
 less colouring matter disposed in irregular cells, exactly resembling 
 those figured at page 409, from the outer surface of the choroid coat 
 of the eye. We have not found a true epithelium on this surface. 
 The middle is the proper coat, and seems more allied to cartilage 
 
 MerabTanous labyrinth of the left side, with 
 its nerves and otoliths: — su. Superior semi- 
 circular canal, -with the ampulla and its nerve 
 at one end, and the other end joined by p, the 
 posterior canal, to form the tubulus communis, 
 i. Inferior, or horizontal canal, with the am- 
 pulla and its nerve at one end, and the other 
 entering the utriculus separately, c. Powdery 
 otolith seen thrdiigh the translucent wall of the 
 common sinus, or utriculus, with the nerves 
 distributed to it. s. Powdery otolithof the sac- 
 culus seen with its nerve, in a similar way. 
 n. Cochlear division of the auditory nerve cut 
 off where it enters the cochlea, d. Portio dura 
 of the seventh pair leaving the auditory nerve, 
 or portio mollis^ to enter the aqueduct of Fallo- 
 pius. Magnified. From Breschet. 
 
MEMBRANOUS LABYRINTH.— VESTIBULAR NERVES. 459 
 
 than to any other tissue; its limits are well marked, it is transparent, 
 and exhibits in parts a longitudinal fibrillation: treated with acetic 
 acid, it presents numerous corpuscles or cell-nuclei. Where it is 
 thinnest it has a near resemblance to the hyaloid membrane of the 
 eye. The internal coat is composed of nucleated particles closely 
 apposed and but slightly adherent; the nuclei are often saucer-shaped, 
 and when seen edgeways, have the uncommon appearance of a cres- 
 cent. They easily become detached, and fall into the endolymph. 
 Minute arteries and veins, derived chiefly from a branch of the 
 basilar accompanying the auditory nerve, enter the vestibule from the 
 internal meatus, and ramify on the exterior of the membranous laby- 
 rinth, apparently bathed in the perilymph. A beautiful network of 
 capillaries, forcibly reminding the observer of that belonging to the 
 retina, is spread out on the outer surface and in the substance of the 
 proper coat. These vessels have the simple homogeneous wall, 
 interspersed here and there with cell-nuclei, that characterizes the 
 capillary channels in many other situations. There is an abundant 
 network of capillaries in the interior of the utriculus and sacculus 
 about the terminal distribution of the nerves, which evinces the 
 activity of the function of these parts. 
 
 The membranous labyrinth, or its simple representative the audi- 
 tory sac, contains, in all animals, either solid or pulverulent calca- 
 reous matter, in connection with the termination of the vestibular 
 nerves. This has been called by Breschet otolith, or ear-stone, when 
 solid, as in the osseous fishes, and otoconia, or ear-powder, when in 
 the form of minute crystalline grains, as in mammalia, birds, and 
 reptiles, but the former term may be conveniently employed to 
 designate both varieties. In the mammalia, including man, it is 
 found accumulated in small masses about the termination of the 
 nerves, both in the utriculus and sacculus, and we have found it 
 also sparingly scattered in the cells lining the ampullae and semicir- 
 cular canals. In the vestibular sacs, it appears to be entangled in a 
 mesh of very delicate branched fibrous tissue, in connection with the 
 wall, and it is most probably held in place by cells within which, 
 according to Krieger, (De Otolithis, Berpl., 1840,) its particles are 
 deposited. It has a regular arrangement, and is not free to change 
 its place in the endolymph. Otoliths consist always of carbonate of 
 lime. 
 
 Of the Vestibular Jferves. — In consequence of the thickness of the 
 wall of the membranous labyrinth where the nerves enter, and the 
 presence there of the calcareous and fibrous matter, it is not easy to 
 ascertain with certainty the precise manner in which the nerves ter- 
 minate. In the utricle and saccule, they appear to spread out from 
 one another as they enter, and then to pass, some to mingle with the 
 calcareous powder, others to radiate for a small extent on the inner 
 surface of the wall of the cavity, where they come into connection 
 with a layer of dark and closely-set nucleated cells, and presently 
 lose their white substance. We have seen a fibrous film on the inner 
 surface of these parts, which we are disposed to consider as formed, 
 like the inner surface of the retina, by the union of the axis-cylin- 
 
460 
 
 INNERVATION. 
 
 ders of the nerve-tubes, but confirmatory observations are required. 
 Those that traverse the calcareous clusters have appeared to us, in 
 the most lucid views we have succeeded in obtaining, to terminate 
 
 by free, pointed extremities. 
 Fig. 143. without losing their white sub- 
 
 stance. In the frog this has 
 been evident enough. 
 
 The nervous twigs belonging 
 to the semicircular canals do 
 not seem to advance beyond the 
 ampuUcB, in which they have a 
 remarkable distribution, enter- 
 ing them, as Steifensand has 
 well shown, by a transverse or 
 forked groove on their concave 
 side, and which reaches about a 
 third round. Within this, the 
 nerve projects so as to form a 
 sort of transverse bulge within 
 the ampulla. Their precise ter- 
 mination can be best seen in the 
 osseous fishes, and has been described by Wagner to be loop-like, ^s 
 ■will be apparent from the adjoined figure. We believe we have seen 
 
 Fig. 144. 
 
 View of the nerves going to the membranous la- 
 byrinth:— a. Branch to the ampulla of one of the 
 semicircular canals. It is seen perforating the wall 
 and expanding transversely within. 6. Semicir- 
 cular canal cut across. From Steifensand. 
 
 '■' ■'.'• ■ 'I 
 
 
 Termination of the nerve in the ampulla of a Ray, highly magnified. {From Wagner.) 
 
 this mode of termination, though certainly never so plainly as the 
 figure given by this excellent author would indicate ; and we may 
 add that we have found free extremities to the nerve-tubes, as well 
 as loopings, in the ampulla of the cod. The difficulty in these cases 
 of ascertaining the exact truth, arises from the curves formed by the 
 nerve-tubes in proceeding to their destination, and which are liable 
 to be mistaken for terminal loopings. 
 
AUDITORY NERVE. 461 
 
 .Of the Auditory JYerve. — The jaor/io mollis of the seventh pair has 
 its origin from the medulla oblongata by two roots. One penetrates 
 to the central part of the medulla oblongata in the same way, and fol- 
 lowing the same direction, as the portio dura, but passing to a much 
 greater depth into its substance. The other winds round the corpus 
 restiforme, not penetrating it, but simply adhering to its surface, until 
 it reaches the floor of the fourth ventricle, where it connects itself 
 with the olivary columns, and in many instances is evidently con- 
 tinuous with the white striae on either side of the calamus scriptorius, 
 which for that reason have been very generally regarded as fascicles 
 of origin of the portio mollis. 
 
 The portio mollis, when contrasted with the other nerves of the 
 medulla oblongata, is remarkable for its delicacy of structure, a 
 character which had attracted the attention of the older anatomists, 
 and by reason of which they had given the nerve the appellation 
 " mollis." It has but a very delicate neurilemma, and its fascicles 
 are loosely held together ; it seems strictly a direct prolongation of 
 the white matter of the brain. 
 
 The portio mollis enters the internal auditory foramen, and there 
 forms a connection with the portio dura, by means of a few fascicles 
 of fibres which constitute the " portio intermedia" of Wrisberg. It 
 is difficult to say whether this consists of fibres proceeding from the 
 auditory to the facial nerve, or from the latter to the former.^ It is 
 most reasonable to suppose that the muscular nerve (the facial) sends 
 some filaments into the labyrinth to the blood-vessels, and to the 
 muscular structure of that portion of the ear. 
 
 At the bottom of the meatus, the portio mollis divides into two 
 branches, one to the vestibule and semicircular canals, the other to 
 the cochlea. 
 
 The vestibular nerve divides into three branches: — the Jargest is 
 uppermost, and penetrates the depression which is immediately be- 
 hind the orifice of the aqueduct of Fallopius to be distributed to the 
 utriculus, and to the ampullae of the superior vertical and the hori- 
 zontal semicircular canal. The second branch of the vestibular nerve 
 is distributed to the sacculus, and the third to the posterior vertical 
 semicircular canal. 
 
 The cochlear nerve penetrates the funnel-shaped depression at the 
 bottom of the auditory canal, and proceeds from it through the tiu- 
 merous foramina, by which its wall is pierced, in a spiral manner, to 
 the lamina spiralis of the cochlea. 
 
 The mode of distribution of these nerves has been already de- 
 scribed. 
 
 The labyrinth receives nerves from no other source than the portio 
 mollis, unless we suppose the portio intermedia to consist of filaments 
 from the facial which accompany the ramifications of that nerve into 
 that part of the ear. 
 
 That the portio mollis is the nerve of hearing is abundantly proved 
 by the following arguments: — 1. The distribution of the nerve to 
 the internal ear, to which no other nerve of any importance is dis- 
 tributed. 2. Its softness of texture and cerebriform character dis- 
 
462 INNERVATION. 
 
 tinguish it from ordinary nerves of sensation or motion. 3. Diseased 
 states of it, or of parts immediately near to its origin, affect the sense 
 of hearing, whilst a paralytic state of the portio dura or of the fifth 
 does not affect the sense. 
 
 Of the JVervous Apparatus accessory to the Organ of Hearing. — 
 Besides the auditory nerve there are others which influence the audi- 
 tory apparatus. These are branches of the portio dura, branches of 
 the nerve of Jacobson, from the glosso-pharyngeal, and from the otic 
 ganglion. 
 
 These nerves present a striking analogy with those which are dis- 
 tributed to the eye; 
 
 The tympanum receives branches from the facial, and glosso-pha- 
 ryngeal, and probably from the sympathetic. 
 
 The facial, in its passage through the aqueduct of Fallopius, gives 
 bff the chorda tyrripani, which, however, seems to have no physiolo- 
 gical connection with the tympanum or its contents. The stapedius 
 muscle receives a branch from the facial nerve. The anastomosis of 
 Jacobson results from the subdivision of the tympanic branch of the 
 glosso-pharyngeal nerve, which enters the cavity of i the tympanum 
 below, and passing over the promontory, gives off branches to the 
 membranes of the fenestras, and Eustachian tube, and to the otic 
 ganglion. 
 
 A branch is described by Arnold as proceeding from< the ofic 
 ganglion to the tensor tympani muscle. 
 
 The external ear is supplied by the facial nerve as regards its 
 muscular apparatus, and by the fifth pair as regards its sentient sur- 
 faces. 
 
 The influence of the facial nerve upon the muscular apparatus of 
 the organ of hearing, whether tympanic or labyrinthic, is similar to 
 that of the third nerve upon the muscles of the eyeball, or upon the 
 iris and ciliary muscle. And it seems probable that while volition 
 can exercise a certain influence upon the muscular apparatus of 
 hearing, that apparatus may likewise be excited to action through 
 the physical stimulus of sound affecting the auditory nerve, which 
 reacting upon the portio dura excites its fibres to a degree propor- 
 tionate to the intensity of the sound ; as the stimulus of light affacting 
 the optic nerve reacts upon the iris. 
 
 We shall now proceed to inquire into the oflSce of each part of the 
 complex organ of hearing.* 
 
 • The following points respecting the laws of sound should be borne in mind in 
 considering the offices of the various parts of that complex acoustic apparatus, the 
 human ear. 
 
 1. Any irregular impulse communicated to the air will produce a noise,- a succes- 
 sion of impulses occurring at exactly equal intervals of time, and exactly similar in 
 duration and intensity, constitutes a musical sound. 
 
 2. The frequency of repetition necessary for the production of a continued sound 
 from single impulses is, probably, generally not less than sixteen times in a second, 
 but Savart thinks that some ears may distinguish a sound resulting from only ten or 
 eight vibrations in a second. On the other hand, sounds are audible which consist 
 of 24,000 vibrations in a second. 
 
 3. Sound may be propagated or conduoled by air, gases, liquids and solids, with 
 various degrees of rapidity. 
 
THE EXTERNAL EAR. 463 
 
 It is necessary for the reader to bear in mind that the organ of 
 hearing may be affected in two ways: first, through the external ear, 
 and secondly, through the bones of the head. Every person must 
 have noticed the difi'erence in the sound of the ticking of a watch if 
 it be held near the ear but not in contact with it, and if it be held 
 between the teeth. The waning note of the vibrating tuning-fork 
 seems revived when the stem of the fork is brought in contact with 
 the teeth or with any part of the head. These differences are due 
 to the difference of the medium through which the sonorous undula- 
 tions are made to affect the auditory nerve. In the former instance, 
 hearing is excited through the external ear, when the watch is held 
 near that part, and through the bones of the head, when the watch 
 is brought into contact with the teeth. And in the example of the 
 tuning-fork, the sound appears to revive when it is made to affect 
 the nerve through a medium (the bones of the head) which more 
 readily vibrates in unison with the most delicate oscillations of the 
 sounding body. 
 
 1. Of the External Ear. — The external ear consists of two parts, 
 the auricle, and the meatus auditorius externus. The complete de- 
 velopment of the former is found only in mammalia, in which class 
 it exists pretty generally; with, however, considerable diversity of 
 form, varying from what appears to be little more than a mere carti- 
 laginous lamella with a few irregularities upon its surface, enjoying 
 scarcely any motion, to an elongated funnel-shaped ear-trurapet, very 
 moveable, and completely under the control of numerous large mus- 
 
 4. Sound (ravels through air at the temperature of 62° Fahr., at the rate of 1125 
 feet in a second. 
 
 5. Sound is incapable of transmission through a vacuum. 
 
 6. The propagation ,of sound is the more efifectively performed as the medium of 
 transmission is more dense. Rarefied air, gases of low density, and soft solids, are 
 less perfect conductors of sound than much denser materials of the same kind. 
 
 7. We distinguish in sounds, \ , ihe pitch ; 2, the intensity or loudness; 3, the quality 
 or timbre. 
 
 The pitch of the sound depends on the rapidity with which the vibrations succeed 
 each other, and any two sounds produced by the same number of vibrations or im- 
 pulses in the same time, are said to be in unison. 
 
 The loudness or intensity depends upon the violence and extent of the primitive 
 impulse. 
 
 The quality is supposed by Herschel to depend on the greater or less abruptness 
 of the impulses; or generally on the law which regulates the excursions of the mole- 
 cules originally set in motion. 
 
 8. The velocity with which sound travels is, however, quite independent of its 
 intensity or of its tone; sounds of every pitch, and of every qualily, travel with the 
 same speed through the same medium, as is proved by the fact, that distance does 
 not destroy the harmony of a rapid piece of music played by a band. 
 
 9. Water propagates sound with much greater velocity than air does. Colladon 
 coticludes, from numerous observations, that the velocity of sound in water, at 40° 
 Fahr., was at the rate of 470S feet in a second. 
 
 10. According to Biot, cast-iron propagates sound at the rate of 11,090 feet in a 
 second. 
 
 11. Sonorous undulations, in passing from one medium to another, always ex- 
 perience a partial reflection, and when they encounter a fixed obstacle, they are 
 almost wholly reflected. The reflection of sound occurs according to the same law 
 which regulates the reflection of light, — namely, the angle of reflection is equal to the 
 angle of incidence. 
 
 12. The phenomena of echoes result from the reflection of sound from any promi- 
 nent object. 
 
464 INNERVATION. 
 
 cles. Man and the quadrumana are at one extremity of this scale; 
 the solipeds, the ruminants, and the bats at the other. 
 
 That the auricle performs the office of an acoustic instrument to 
 collect and reinforce the sounds which fall upon it, cannot be doubted 
 in those cases in which it is large and fully developed, as in the 
 horse, ass, &c. These animals employ it as we might expect such 
 an instrument would be used ; the open part is directed towards the 
 quarter whence the sound comes, and continues so directed as long 
 as the animal appears to listen. 
 
 Savart's experiments illustrate the manner in which an instrument 
 like the external ear may contribute to the propagation of sound to 
 the internal ear. When a thin membrane is stretched in a horizontal 
 direction over the mouth of a glass or other hollow vessel, it may be 
 made to vibrate by holding near it a glass thrown into vibration by 
 passing a violin bow across it. The vibrations of the paper are 
 easily demonstrated by the movements of particles of fine sand, or 
 lycopodium powder strewed upon it. The sand arranges itself into 
 certain very definite figures, the shape of which is determined by the 
 position of the lines of repose, or nodal lines, over which the sand 
 accumulates. These phenomena may be shown in the raembrana 
 tympani itself, by scattering a little sand upon it, the osseous meatus 
 having been previously cut away. When the vibrating glass is 
 brought near to it, the movement of the particles of sand affords suffi- 
 cient evidence of the vibration excited in the tympanic membrane, 
 but owing to the slight extent of the membrane it is impossible to 
 determine the existence of any nodal line. 
 
 Savart imitated the tympanic membrane, and the external auditory 
 apparatus by a hollow cone of paste-board ; across the narrow ex- 
 tremity some thin paper was stretched. When .the vibrating glass 
 was brought near to the narrow end, movements of a slight kind 
 were excited in the paper, but when the glass was brought to the 
 ■wide extremity of the cone, much more extensive movements were 
 excited in the paper; although now the glass was much more distant 
 from the paper than previously. 
 
 This result might have been due chiefly to one of two causes, 
 namely, either to the concentration of the sonorous undulations by 
 the walls of the cone, or to the excitation of vibrations in the walls 
 of the tube, which would be propagated directly to the paper; and 
 Savart showed by the following simple experiment that the latter 
 cause was obviously the most effective. He prepared a second conical 
 tube open at both ends, and having placed the narrow end of this 
 tube very near the paper on the former one, but not in contact with it, 
 he found that vibrations were excited on the paper by bringing the 
 vibrating glass near to the wide end of the second tube, but that 
 these vibrations were not nearly so extensive as when the glass was 
 brought near to the \\'ide extremity of the tube with which the paper 
 was connected. 
 
 Hence Savart inferred that the external ear and meatus were parts 
 adapted to enter into vibrations in unison with those of the air, or of 
 any liquid or solid vibrating medium which might be brought in con- 
 
OFFICE OF THE TYMPANUM. 465 
 
 tact with the auricle ; and he suggested that the latter part, in the 
 human subject, by the variety of direction and inclination of its sur- 
 faces, could always present to the air a certain number of parts whose 
 direction is at right angles with that of the molecular movement of 
 that fluid, and therefore in the most favourable circumstances for en- 
 tering into vibration with it. 
 
 We get a general notion of the value of the external part of the 
 auditory apparatus in collecting and directing the sonorous undula- 
 tions, from the assistance often derived in hearing by placing the 
 hand behind the external ear, so as to increase its concavity; and by 
 the dulness of hearing, which it is said follows the loss of the auricle^ 
 Kerner states that the loss of the auricle is followed by the greatest 
 dulness of hearing in those animals in which the osseous meatus is 
 wanting. In a cat from which the right ear was cut away close to 
 the skull, after the wound had healed without any stoppage of the 
 meatus, there was a remarkable disposition always to keep the head 
 turned so as to be ready to receive sounds with the left ear, and this 
 continued even after the left tympanic membrane was perforated, the 
 right remaining whole; and when the left ear was stopped, (although 
 the right tympanic membrane was sound, and the only injury on that 
 side was the removal of the auricle,) a total deafness was manifested 
 except to the loudest and clearest sounds. 
 
 The Tympanum and its Contents. — We have already stated that 
 Savart had demonstrated experimentally upon the membrana tympani 
 itself, that that membrane can be thrown into vibrations by undula- 
 tions of the air excited by a sonorous body. In a second experiment, 
 the cavity of the tympanum was opened, so as to expose the ossicles 
 of the ear and their muscles; and it was observed that when the in- 
 ternus mallei muscle acted and rendered the membrane tense, it was 
 much more difficult to produce manifest movements in the grains of 
 sand ; thus affording much reason to suppose that the tensor tympani 
 muscle is analogous in its use to the iris, and destined to protect the 
 organ from too strong impressions. These experiments can be best 
 tried on the membrana tympani of the calf. 
 
 In imitation of the mechanism by which the tension of the mem- 
 brana tympani is effected, and with a view to 
 determine more decisively the effects produced ^ig- 145. 
 
 by variation of the tension of that membrane, Sa- 
 vart constructed a conical tube (fig. 145), with 
 its apex truncated and covered by a layer of very 
 thin paper, m, which was glued to the edge of 
 the opening. A little wooden lever, I, I, intro- 
 duced through an opening in the side of the tube, 
 and resting on the lower margin of this opening, 
 c, as a fulcrum, was used to vary the tension of the 
 membrane, one of its extremities being applied 
 to the under surface of the membrane. By depressing the extremity 
 of the lever external to the tube, the inner one is raised, and thus the 
 membrane stretched to a greater or less degree, according to the 
 force used; on the other hand, by elevating the outer extremity, the 
 30 
 
466 INNERVATION. 
 
 inner one is separated from the membrane, which is accordingly re- 
 stored to its original tension. This little lever is an imitation of the 
 handle of the malleus, which, under the influence of its muscles, 
 causes the variation in the tension of the membrana tympani. The 
 artificial tympanic membrane having been then covered with a layer 
 of sand, it was found, that, under the influence of a vibrating glass, 
 used as in the former experiments, a manifest difference was pro- 
 duced in the movements of the grains of sand, by increasing the ten- 
 sion of the paper; the greater the tension, the less the height to 
 which the grains of sand were raised'; and these movements were 
 most extensive when the lever was withdrawn from contact, and the 
 membrane left to itself. 
 
 From these experiments Savart concludes that the membrana tym- 
 pani may be considered as a body thrown into vibration by the air, 
 and always executing vibrations equal in number to those of the 
 sonorous body which excites the oscillations of the air. But what 
 is the condition of the ossicles of the tympanum whilst the membrane 
 is thus in vibration.? The result of the following experiment affords 
 a clue to the answer to this question. To a membrane stretched over 
 a vessel, as in fig. 146, a piece of wood, a, b, uniform in thickness, 
 
 Fig. 146. Fig. 147. 
 
 is attached, so that the adherent part shall extend from the circum- 
 ference to the centre of the membrane, while the free portion may 
 project beyond the circumference. When a vibrating glass is brought 
 near this membrane, very regular figures are produced, modified, 
 however, by the adhesion of the piece of wood, and the vibrations of 
 the membrane are communicated to the wood, on which likewise 
 regular figures may be produced. The more extensive the membrane, 
 the longer and thicker may be the piece of wood in which it can 
 excite oscillations, and Savart states that, with membranes of a con- 
 siderable diameter, he has produced regular vibrations in rods of 
 glass of large dimensions. The oscillations of the piece of wood are 
 much more distinct when the adherent portion is thinned down, as 
 in c, d, fig. 147, by which it becomes more completely identified with 
 the membrane; the oscillations of this latter are communicated di- 
 rectly to the thinned portion of the wood, and thence propagated to 
 the thick portion, a: sand spread upon a will exhibit active move- 
 ments, and will indicate very distinct nodal lines. Hence it may be 
 inferred that the malleus participates in the oscillations of the tym- 
 panic membrane; and these vibrations must be propagated to the 
 incus and stapes, and thus to the membrane of the fenestra ovalis. 
 The chain of ossicles then evidently performs the office of a conductor 
 
SAVART'S EXPERIMENTS. 467 
 
 of oscillations from the tnembrana tympani to the membrane of the 
 fenestra ovalis ; but the malleus likewise has the important function 
 under the influence of its muscles of regulating the tension of the 
 tympanic membrane ; and to allow of the changes in the position of 
 this bone necessary for that purpose, we find it articulated with the 
 incus by a distinct diarthrodial joint, and between this latter bone 
 again and the stapes there exists another and a similar joint. This 
 mobility then of the chain of bones, and the muscular apparatus of 
 the malleus and stapes have obvious reference to the regulation of 
 the tension of the membrane of the tympanum as well as of that of 
 the fenestra ovalis. 
 
 We have already seen how the muscle of the malleus regulates the 
 membrana tympani, increases its tension, and thu^ limits the extent 
 of the excursions of its vibrations. The contraction of the stapedius 
 muscle causes the base of the stapes to compress the membrane of the 
 fenestra ovalis to a greater or less extent, so that the degree of ten- 
 sion of that membrane depends on the condition of this muscle. 
 Compression exerted upon the membrane of the fenestra ovalis ex- 
 tends to the perilymph, and through it is propagated to the membrane 
 of the fenestra rotunda, and rn this way the same apparatus which 
 regulates the tension of the membrane of the fenestra ovalis performs 
 that office for that of the fenestra rotunda, and Savart has devised an 
 apparatus which very prettily illustrates the manner in which this 
 may take place. In a disc of wood (a, 
 b, fig. 148) of sufficient thickness, he Fig- 148- 
 
 hollows out two cavities, o and r, which ^---' ~^~,^_^ 
 
 communicate at their bottoms with each /^ "' n, 
 
 other by a narrow canal (c) hollowed in [ ^T^-::::;™™;./*^ J'^ \ 
 
 the wood, but not open on its surface; K " " , ^^irr:=fi'^ J 
 
 a thin membrane is extended over each v>--^_ _^<X 
 
 of the cavities. Thus, the air contained ^ ...'^ 
 
 in these cavities may pass easily from 
 
 one to the other, and may always maintain the same degree of elastic 
 tension in both. If a vibrating glass be brought near the membrane 
 r, covered with a layer of sand, it will be found to enter freely into 
 vibration, as evinced by the active movements of the grains of sand. 
 If, now, pressure be made on o with the finger, r will become convex 
 in proportion as o is rendered concave by the pressure, and when in 
 this convex state, the movements of the sand upon it will be much 
 less considerable than before, presenting an effect precisely similar to 
 that produced on the tympanic membrane by an increase of tension. 
 Thus, the extent of the excursions of the vibrations of the membrane 
 r, is limited by the pressure exerted upon o, and as the membranes 
 of the two fenestras are related to each other in an analogous manner, 
 we may argue that pressure upon the membrane of the fenestra ovalis 
 will occasion tension of that of the fenestra rotunda, thereby limiting 
 the extent of the excursions of its vibrations.* 
 
 • All these experiments have been frequently repeated and exhibited by us, with 
 the same results as those stated in the text. 
 
468 INNERVATION, 
 
 Moreover it appears, upon reference to the anatomy of these parts, 
 that the only muscles which have been satisfactorily demonstrated 
 are tensors of the tympanum ; and that at whichever extremity of the 
 chain of ossicles muscular effort be first exerted, a corresponding 
 effect will be produced at the other; that when the stapedius muscle 
 acts; the malleus is thrown into a position favourable to the tension 
 of the membrana tympani, and, on the other hand, the contraction of 
 the internus mallei depresses the stapes, and consequently increases 
 the tension of the membranes of the two fenestree. The cessation of 
 muscular action restores all three membranes to their original laxity, 
 nor does it appear that they admit of any further degree of relaxation 
 through the influence of any vital process. The incus forms a bond 
 of union between the two other bones, and its motions depend en- 
 tirely upon theirs in consequence of its articulation with both, while 
 from the fixedness of its connection with the mastoid cells, as well as 
 from its intermediate position and want of muscular attachment, its 
 motions must obviously be much more limited than those of the other 
 bones. Its use seems to be to complete the chain in such a manner, 
 that by reason of its double articulation with the malleus on the one 
 hand and the stapes on the other, the tension of the tympanic mem- 
 branes may be regulated without any sudden or violent motion, which 
 could scarcely be avoided were the conductor between the membranes 
 of the tympanum and fenestra ovalis but one piece of bone. 
 
 The mobility of the tympanic bones has, however, a further use, as 
 Miiller suggests; namely, to favour the oscillations of the membrana 
 tympani, by allowing the approximation of the two extremities of the 
 chain of bones. And this opinion is strengthened by the facts of 
 comparative anatomy, for the ossicles have moveable articulations in 
 the frog, as in man, although they have no muscles attached to them. 
 
 The addition of a cavity filled with air outside the labyrinth has a 
 twofold use. First, to preserve uniformity of temperature in the air 
 immediately in contact with the fenestral membranes. Were these 
 membranes situate on the exterior of the head, and exposed to the 
 surrounding atmosphere, they would be constantly undergoing changes 
 in their elastic state, under the influence of atmospheric vicissitudes. 
 The air which accumulates in the tympanum and mastoid cells, finds 
 its way into them only through the Eustachian tubes, and as it does 
 not readily change its position, it is well placed for maintaining a 
 temperature equal to that of the body. Secondly, the action of the 
 chain of ossicles as conductors is materially enhanced by their being 
 completely surrounded by air. The insulation of a solid body by a 
 difl;'erent medium renders it a better propagator of sound ; for the sur- 
 rounding medium will obviate the dispersion of sound, and will 
 favour its retention in the solid conductor. 
 
 It results from Savart's experiments, that tension of the membrana 
 tympani is unfavourable generally to the propagation of sounds, es- 
 pecially of those of a low pitch. By rendering the membrana tympani 
 tense in one's own person, the correctness of this statement may be 
 readily ascertained. In blowing the nose forcibly, air is forced into 
 the tympanum, and its membrane is rendered convex and tense, and 
 
USE OF THE TYMPANUM. 469 
 
 every one must have experienced the temporary deafness which re- 
 mains after such an eflTort. The tympanic membrane may also be 
 rendered tense by forced inspiration, the nose and mouth being kept 
 shut. Under these circumstances the tympanic cavity is exhausted, 
 and the membrane rendered tense by the pressure of the external air. 
 
 In descending in the diving bell, the membrane of the tympanum 
 is rendered painfully tense by the increased pressure of the air, and 
 the want of counter pressure from within. This tension may be so 
 great as even to cause rupture of the tympanic membrane in some 
 cases, but it may be obviated by acts of swallowing, during which 
 the external air is driven into the tympana along the Eustachian tubes. 
 During the tense state of the membrane, hearing is impaired ; M. 
 Colladon found that the voices of his companions and of himself were 
 not so distinctly heard. 
 
 Dr. Wollaston performed many experiments upon the effects of 
 tension of the membrana tympani, and he found that deafness to 
 grave notes was always induced, which, as most ordinary sounds 
 are of a low pitch, is tantamount to a general deafness. Shrill 
 sounds, however, are best heard when the tympanic membrane is 
 tense. Miiller remarks, and we have frequently made the same ob- 
 servation, that the dull rumbling sound of carriages passing over a 
 bridge, or of the firing of cannon, or of the beating of drums at a 
 distance, ceases to be heard immediately on the membrana tympani 
 becoming tense; while the treading of horses upon stone pavement, 
 the more shrill creaking of carriages, and the rattling of paper, may 
 be distinctly heard. 
 
 The object of the Eustachian tube is chiefly to allow the free in- 
 gress of air into the tympanic cavity, in order to provide for the due 
 vibration of the membrana tympani and of the chain of bones. It 
 also, by permitting a free egress of air, renders the tympanum a non- 
 reciprocating cavity, and therefore obviates the production of echoes 
 in it, which would materially intetfere with perfect hearing. The 
 importance of the Eustachian tube to the integrity of hearing is well 
 known to all practical men, by the deafness which always accompa- 
 nies chronic or acute disease of the tonsils, or occlusion of the canal 
 of that tube from any other cause. 
 
 The idea of Boerhaave, and of Bressa, that sounds from without 
 which enter the mouth, or the sounds of one's own voice, were con- 
 ducted by the Eustachian tube to the labyrinth, is disproved by the 
 simple experiment of holding a sounding tuning-fork or a watch in 
 the open mouth, when it will be always found, if due care be taken to 
 avoid contact, that the sounds proceeding from them are not so well 
 heard as those from without, and the nearer they are brought to the 
 Eustachian tube the less distinctly are they heard. Indeed it may be 
 always noticed that persons deaf from obstruction of the Eustachian 
 tube hear the sounds of their own voices well. 
 
 Of the Labyrinth. — The essential part of the organ of hearing is 
 the vestibule. This is sufficiently proved by the constancy of this 
 part in the animal series, and by its central position in the most com- 
 
470 INNERVATION. 
 
 plex ears, so that it is in close relation not only with the other parts 
 of the labyrinth, but also with the tympanum. 
 
 Sound is conveyed to the labyrinth in a threefold manner: first, by 
 the chain of bones; secondly, by the air in the tympanic cavity; in 
 both these instances the external air is engaged in the conduction ; 
 and thirdly, through the bones of the head. 
 
 Miiiler has shown, by a very interesting experiment, that, whilst 
 the air in the tympanum conducts sound to the cochlea through the 
 fenestra rotunda, the chain of bones forms a much better conductor 
 of it to the vestibule through the fenestra ovalis. He imitated the 
 structure of the tympanum by means of a glass cylinder, two inches 
 and one-third in diameter, and six inches long; to the neck of this 
 he fixed a wooden tube, the diameter of whose bore was eight lines. 
 The upper end of this tube was adapted to the mouth of the metal 
 flute-pipe of an organ, one foot in length; its lower extremity was 
 covered with a tense membrane of pig's bladder, which represented 
 the membrana tympani, the tube itself corresponding to the meatus 
 externus, and the cavity of the glass cylinder to the tympanum. The 
 lower opening of the glass cylinder was closed by a thick piece of 
 cork, in which two holes were cut equidistant from the walls of the 
 cylinder. In these holes, which represented the fenestrse, two wooden 
 tubes were fitted, whose outer openings were covered with membrane. 
 From the membrane of the upper tube to one of these membranes, a 
 rod was extended to imitate the chain of tympanic bones extending 
 between the membrane. 
 
 The lower extremity of this apparatus (that, namely, which was 
 fitted with cork) was now introduced into water, to imitate the con- 
 nection between the tympanum and the labyrinth in which sound is 
 conducted from air to liquid. Miiiler, having plugged his ears, could 
 by means of a sounding-rod applied in succession to the membrane 
 of each of the artificial fenestrae, ascertain the relative intensity of the 
 sonorous vibrations coramunicated to the water through the two open- 
 ings, while another person sounded the pipe. He states that the 
 difference was very striking. The sound transmitted by the wooden 
 rod to the opening which represented the fenestra ovalis, was in a 
 remarkable degree louder than that propagated through the air of the 
 cavity to the membrane of the other opening. 
 
 The results of this experiment lead to the conclusion (which other 
 circumstances confirm), that the vestibule is adapted to receive sounds 
 from the tympanic membrane and external ear, while the cochlea is 
 not easily affected in this manner, but rather, as its structure and 
 connections point out, that it is fitted to receive vibrations through 
 the bones of the head. 
 
 The direct continuity of the walls and the septum {lamina spi7-alis) 
 of the cochlear canal, with the petrous bone, and the minute subdi- 
 vision of the nerve in distinct canals in the osseous substance, render 
 that pQrtion of the labyrinth most readily affected by the vibrations 
 excited in the cranial bones. The cochlea may therefore be properly 
 considered as that part of the labyrinth which is more immediately 
 affected by sounds communicated through the bones of the head, as 
 
OP THE LABYRINTH.— THE OTOLITHS. 471 
 
 the vestibule is the part primarily affected by the sounds communi- 
 cated through the external ear. 
 
 It may be easily shown by some experiments with the tuning-fork, 
 not only that the cranial bones do conduct, but also that sounds 
 inaudible, or imperfectly audible, through the meatus externus, may 
 be distinctly heard when the sounding body is brought into contact 
 with a bone of the cranium or face. When the tuning-fork is thrown 
 into vibration by striking it against any solid body, if held near the 
 external ear its vibrations are distinctly heard, but let the stem be 
 applied to the teeth, or to the upper jaw, or to the parietal bone, 
 and the sound appears much louder; or if the fork be held near the 
 ear until the sound has almost died away, and then its stem be ap- 
 plied to the superior maxilla, or to the teeth, the sound seems to 
 revive, and continues for a considerable period while the stem is 
 kept in contact with the bone. 
 
 The form of the cochlea probably has reference to the convenient 
 package within the smallest compass of the great number of nerve 
 fibres which proceed to it. 
 
 The remarkable subdivision which the cochlear nerve undergoes, 
 admirably adapts it for the reception of vibrations communicated 
 through the cranial bones. "The spiral lamina of the cochlea," says 
 Muller, "must be regarded as a surface upon which all the fibres of 
 the cochlear nerve are spread out, so as to be nearly simultaneously 
 exposed to the impulse of the sonorous undulation, and simultaneously 
 thrown into the maximum state of condensation, and again into the 
 maximum state of rarefaction." "This spreading out of the nerve 
 fibres upon the lamina spiralis, insures a more complete participation 
 of the fibres in the impulses communicated by the solid parts of the 
 cochlea." Moreover, " the intensity with which sonorous undula- 
 tions are communicated to a body, is proportionate to the extent of 
 surface over which they can act on it. Thus, when a sound is ex- 
 cited in water, and is conducted to the stopped ear by means of a 
 rod, the intensiity of the sound heard increases with the depth to 
 which the rod is immersed in the water, or with the extent in which 
 it is in contact with the surface of the water."* 
 
 The fluid in the scalae of the cochlea, with the helicotrema or orifice 
 of communication, must facilitate the vibrations of the lamina spiralis, 
 and we have already assigned to the cochlearis muscle a protective 
 use to the cochlear nerves. 
 
 The Otoliths. — The earthy particles, which, either as pulverulent 
 masses, or as hard porcelainous stones, are connected with the nerves 
 of the membranous labyrinth, must reinforce the sonorous undula- 
 tions, and communicate to the membranous labyrinth and its nerves 
 vibratory impulses of greater intensity than the perilymph alone could 
 impart. In illustration of this, Miiller mentions that sonorous undu- 
 lations in water are not perceived by the hand itself immersed in the 
 water, but are felt distinctly through the medium of a rod held in the 
 
 * Mailer's Physiology, by Baly, vol. ii. p. 1294. Dr. Young regarded the cochlea . 
 as a micrometer of sound. 
 
472 INNERVATION. 
 
 hand. The experiment of Camper is also illustrative. Fill a bladder 
 with water and place a stone or some other hard body in it. The 
 slightest impulse communicated to the bladder disturbs the stone, 
 which consequently produces a greater impression on the hand by 
 which the bladder is supported. 
 
 The Semicircular Canals. — There is nothing known of the function 
 of the semicircular canals. Yet their almost constant existence, and 
 nearly constant number evince their physiological importance. In 
 most cases of congenital deafness they are found defective. 
 
 Their constancy in the higher animals of number, and of position, 
 which is such that they correspond to the three dimensions of a cube, 
 its length, breadth, and depth, suggested to Autenrieth and Kerner 
 the opinion that they are the parts concerned in conveying a know- 
 ledge of the direction of sounds, a view which is also advocated by 
 Wheatstone. The latter philosopher conceives that we distinguish 
 best the direction of those sounds which are sufficiently intense to 
 affect the bones of the head, and that it is from the vibrations which 
 are transmitted through these bones that our perception of the direc- 
 tion is obtained. The three canals being situate in planes at right 
 angles with each other are affected by the sounds transmitted through 
 the bones of the head with different degrees of intensity, according 
 to the direction in which the sound is transmitted ; for instance, ijf 
 the sound be transmitted in the plane of any one canal, the nervous 
 matter in that canal will be more strongly acted on than that in either 
 of the other two; or if it be transmitted in the plane intermediate 
 between the planes of this canal and the adjacent one, the relative 
 intensity with which those two canals will be affected will depend 
 upon the direction of the intermediate plane. The direction suggested 
 to the mind will correspond with the position of the canal upon which 
 the strongest impression has been made. 
 
 There are remarkable differences in the range of the sense of bear- 
 ing in different individuals, analogous to the differences in the power 
 of vision with regard to colours. Some persons ajre insensible to 
 certain sounds, which are familiar to other ears, as some are unable 
 to see particular colours. The limits of audition in different indivi- 
 duals may partly depend on the condition of the auditory nerve, and 
 partly upon the size of the membrana tympani. It is probable that 
 animals with very large membranae tympani can hear much graver 
 sounds than man. The artificial tension of the membrana tympani, 
 alluded to at a former page, is capable of inducing insensibility to 
 sounds of a grave character, as Dr. Wollaston has shown. The 
 ordinary range of human hearing comprised between the lowest notes 
 of the organ, and the highest known cry of insects, includes, according 
 to Wollaston, more than nine octaves, the whole of which are dis- 
 tinctly perceptible by most ears. Dr. Wollaston has, however, related 
 some cases in which the range was much less, and limited as regards 
 the perception of high notes; in one individual, the sense of hearing 
 terminated at a note four octaves above the middle e of the piano- 
 forte; this note he appeared to hear rather imperfectly, but the f 
 above it was inaudible, although his hearing in other respects was as 
 
THIRD PAIR OF NERVES. 473 
 
 perfect as that of ordinary ears; another case was that of a lady who 
 could never hear the chirping of the field cricket; and in a third 
 case the limit was such that the chirping of the common house- 
 sparrow could not be heard. Dr. Wollaston supposes that inability 
 to hear the piercing squeak of a bat is not very rare, as he met with 
 several instances of persons not aware of such a sound. 
 
 Every one must be conscious that the sensation of sound frequently 
 lasts longer than the exciting cause of it, as the sensation of light 
 does. This has been demonstrated experimentally by Savart, who 
 found in his experiments upon toothed wheels that the removal of 
 one tooth did not produce any interruption of the sound. Othei 
 proof of this is obtained from the noise which remains in the ears 
 after long travelling in a coach, or in a train upon a railroad. The 
 subjective phenomena of hearing generally result from some affec- 
 tion of the brain, or of that part of it in which the auditory nerve is 
 implanted. The most common of them are tinnitus aurium, and the 
 buzzing or rushing noise in the ears, which is generally indicative of 
 a deficiency rather than a redundancy of blood in the brain; or it 
 may be caused by some disturbance of local nutrition of the brain 
 giving rise to an irregular development of nervous power. 
 
 Upon the subjects discussed in this chapter, the reader may consult the works of 
 Scarpa and Soemmering; the excellent article on the organ of Hearing by Mr. Whar- 
 ton Jones in the Cyclop, of Anat. ; Muller's elaborate chapter on Hearing in his Phy- 
 siology; Dr. Wollaston's paper on Sounds inaudible by certain ears, Phil. Trans., 
 1820; the article Hearing, Cyclop. Anat. ; Dr. Elliotson's Physiology, where the in- 
 genious views of Mr. Wheatstone are briefly stated ; and a paper by the latter phi- 
 losopher in the Journal of the Royal Institution, for July, 1837. 
 
 CHAPTER XIX. 
 
 ENCEPHALIC NERVES EXCLUSIVELY MOTOR IN FUNCTION. — THE THIRD 
 
 PAIR OF NERVES. THE FOURTH PAIR. THE SIXTH PAIR. THE 
 
 PORTIO DURA OF THE SEVENTH PAIR. — THE NINTH PAIR. 
 
 The nerves which we shall consider in this chapter are purely 
 motor in their function; and, on this account, are conveniently 
 classed together. We shall see, however, that from their occasional 
 anastomosis with sensitive nerves, they contain sentient filaments 
 which serve to inform the*tnind of the state, of the muscles to which 
 their motor filaments are distributed. 
 
 The Third Pair of Jferves, or Motores Oculorwn. — These nerves 
 are connected with the crura cerebri. Each nerve emerges from the 
 corresponding crus, on the side of the locus perforatus posticus, or 
 pons Tarini. 
 
 When traced into the substance of the crus, the component fas- 
 ciculi of each nerve are seen t& diverge from each other, and to sink 
 
474 INNERVATION. 
 
 into the dark vesicular matter constituting the locus niger. Here, no 
 doubt, the filaments connect themselves with the vesicles of this 
 mass of gray matter. 
 
 Each nerve proceeds forwards and outwards, and passes through 
 a canal in that portion of the dura mater which forms the outer wall 
 of the cavernous sinus into the orbit through the spheno-orbital fora- 
 men, and just as it has reached this foramen it divides into a superior 
 and an inferior branch, the distribution of which is shown in the fol- 
 lowing table : 
 
 . „ J- • • n. J. To the levator palpebrse superioris. 
 
 A. Superior division. | ^ j ^^ ^^^ superior rectus oculi. 
 
 rl. b. To the internal rectus. 
 2. b. To the inferior rectus. 
 
 B. Inferior division. ^ 3. b. To the inferior oblique. 
 
 I 4. b. To the ophthalmic ganglion, also called the short root 
 I, of that ganglion. 
 
 The anastomoses of the third nerve take place entirely in that 
 stage of its course in which it lies in the outer wall of the cavernous 
 sinus. They are with the ophthalmic division of the fifth nerve, and 
 with the carotid branch from the inferior cervical ganglion of the 
 sympathetic; and, as has been asserted by a few anatomists, with the 
 sixth nerve. 
 
 Function of the Third Jferve. — Proceeding according to the method 
 indicated at page 303, vol. i., we deduce the function of this nerve 
 from its anatomy in man, from its anatomy in animals, from experi- 
 ments, and from pathological observation. 
 
 From its anatomy in man we judge this nerve to be a motor 
 nerve, for it is distributed entirely to muscles. These muscles are, 
 in addition to the elevator of the upper eyelid, those upon which the 
 principal movements of the eyeball depend ; indeed, all the muscles 
 of that organ, except the superior oblique and the external rectus. 
 In addition to these there can be no doubt that the third nerve sends 
 filaments to the muscular apparatus within the eye by the short root 
 of the ophthalmic ganglion, which, after passing through that gan- 
 glion, escapes from it under the form of ciliary nerves, which may 
 be traced to the ciliary muscle and to the iris. It is, therefore, the 
 principal motor nerve of the eyeball, regulating all the movements of 
 that organ, excepting those which depend on the external rectus and 
 superior oblique muscles; and it also probably excites the movements 
 of the' iris and of the other muscular fibres within the eye. Upon 
 this latter point, however, anatomy speaks less positively, from the 
 fact that other nerves are distributed to the iris besides those derived 
 from the third. 
 
 The distribution of the third nerve, in the inferior animals, leads 
 to the same conclusion respecting its function, as that which we have 
 deduced from human anatomy. In all the mammalia it is distributed 
 to the same muscles of the eyeball as in man, and to the iris. In 
 birds a similar arrangement exists, and in some species of this class 
 we observe a remarkable development of that branch which is dis- 
 tributed to the iris in direct relation with the muscular activity of 
 
FUNCTION OF THE THIRD NERVE. 475 
 
 that structure. In the falcons and eagles, according to Desmoulins, 
 the third nerve is absolutely as large as in man, and this great size 
 is due to the development of the branch which is distributed to the 
 iris and ciliary muscle. 
 
 Experiments on this nerve are difficult of execution, and their 
 results are therefore not free from complication ; but such as have 
 been obtained entirely confirm the view of its function which ana- 
 tomy suggests. These results, as derived from the experiments of 
 Rumbold and Fowler, of Mayo, Valentin and others, may be sum- 
 med up as follows : 
 
 The application of the galvanic current to the nerve causes a con- 
 vulsive contraction of the principal muscles of the globe and of the 
 iris. The same effect is produced by mechanical irritation of the 
 trunk of the nerve. 
 
 Section of the trunk of the third nerve in rabbits or dogs, gives 
 rise to external strabismus with paralysis of the upper eyelid (ptosis), 
 and dilatation and immobility of the pupil. The eyeball is given up 
 to the influence of the external rectus and of the superior oblique 
 muscles, the former of which, being the more powerful, determines 
 its permanent position. 
 
 The paralysis of the iris, after section of this nerve, is so complete 
 that the most powerful light, directed into the eye, is incapable of 
 exciting the least contraction of the pupil. And Mayo's experiments 
 demonstrate that the fifth nerve, which is the only other, except, per- 
 haps, the sympathetic, connected with the iris, does not exert any 
 motor influence upon that membrane. 
 
 When the optic nerve is irritated, the third remaining intact, and 
 retaining its connection with the brain, the pupil contracts. This 
 action does not take place if the third nerve have been previously 
 cut. The motor action of the third nerve may, therefore, be excited 
 through the optic nerve. There can be no doubt, indeed, that this 
 is the ordinary method by which contraction of the pupil is produced 
 during life ; the stimulus of light falling upon the retina excites the 
 optic nerve, and, through it, that portion of the brain in which the 
 third nerve is implanted. 
 
 The eflfects produced by pathological changes affecting the third 
 nerve, or that part of the brain with which it is connected, are in 
 exact accordance with the results derived from experiment. 
 
 Paralysis of the levator palpebrse superioris muscle, permanent 
 squinting of the eyeball in the outward direction, and a dilated, mo- 
 tionless pupil are the unerring signs of a paralytic lesion affecting 
 the third nerve either at its central extremity or in some part of its 
 course. 
 
 The third nerve may, therefore, be stated to be the nerve of mo- 
 tion to the elevator muscle of the upper lid, and a principal nerve of 
 motion to the eyeball, and to the muscular apparatus within the eye. 
 It is a nerve of great importance to vision, not only from its influ- 
 ence over the eyeball itself, but also from its connection with the 
 muscular structures in the interior, on which the power of adjustment 
 probably depends. 
 
476 INNERVATION. 
 
 Of the Fourth Pair of JVerves. — These, which were called by 
 Willis ^^nervi pathetid,^' are the smallest of the encephalic nerves. 
 They are also remarkable for the very long course which they take 
 from their origin to their point of exit from the cranium. 
 
 The origin of the fourth nerve may be referred to the mesocephale, 
 from the superior surface of which it emerges, in close connection 
 with the testes, or immediately behind them. Its true origin is 
 doubtless from the olivary columns as they extend upwards beneath 
 the quadrigeminal tubercles. 
 
 The fourth nerve emerges from the cranium through a canal in the 
 dura mater, situate near the posterior clinoid process of the sphenoid 
 bone, external to that in which the third nerve is lodged. It passes 
 along the outer wall of the cavernous sinus beneath the third nerve, 
 and in entering the orbit it rises above that nerve, and lies immedi- 
 ately beneath the periosteum, attaching itself to the orbital surface 
 of the superior oblique muscle, into the posterior third of which it 
 penetrates. 
 
 This is the only muscle which the fourth nerve supplies, and the 
 nerve appears to be wholly lost in it. But as it passes through its 
 canal in the dura mater, it gives off a branch, which, taking a retro- 
 grade course, passes into the tentorium cerebelli as far as the lateral 
 sinus, where it subdivides into two or three filaments. 
 
 In its course it forms but few connections, and those apparently 
 not constant. As it crosses the cavernous sinus it anastomoses with 
 the sympathetic, and, as it enters the orbit, with the lachrymal. 
 
 That this nerve is the motor nerve to the superior oblique muscle 
 anatomy does not allow us to doubt, for the muscle receives no 
 other. 
 
 Experiments and pathological observation have thrown no satis- 
 factory light upon its function. 
 
 In animals of great power of expression, as in apes, according to 
 Sir C. Bell, this nerve, as well as the superior oblique muscle, is 
 large. 
 
 Of the Sixth Pair of JYerves. — ^These nerves emerge from between 
 the fibres of the anterior pyramids immediately behind the posterior 
 margin of the Pons Varolii. It is not improbable that the true origin 
 of each nerve is from the central part of the medulla oblongata, the 
 olivary columns, and that the nerves pass between the fibres of the 
 pyramids without forming any real connection with them. 
 
 The sixth nerve has a straight, but very short intracranial course; 
 it penetrates the dura mater, and passes over the outside of the 
 carotid artery, between it and the lining membrane of the cavernous 
 sinus, entering the orbit between the two origins of the rectus ex- 
 ternus muscle, to the ocular surface of which it is entirely distributed. 
 
 As the sixth nerve is passing along the outer side of the internal 
 carotid artery, it forms a very celebrated anastomosis with the sym- 
 pathetic, by means of two large and distinct branches, and it some- 
 times anastomoses with the nasal branch of the fifth. 
 
 Anatomy points to the function of this nerve as distinctly as it 
 does to that of the fourth. The sixth nerve can have no other office 
 
THE FACIAL NERVE. 477 
 
 than that of regulating the movements of the abductor muscle of the 
 eye. Experiment fully confirms this conclusion, and a few cases 
 have been observed in which internal strabismus was fou/nd to ac- 
 company compression of the nerve by a tumor. 
 
 Of the Facial Jferve. — {Portio dura of the seventh pair.) — This is 
 one of the most interesting and remarkable of the motor nerves. Its 
 close proximity to the auditory nerve led Willis to class it along with 
 that nerve. The former nerve is soft in its structure, and its bundles 
 loosely coherent; the latter is more compact, and surrounded by a 
 neurilemma of sufficient density to give to it a power of resistance 
 very superior to that of its neighbour. 
 
 These two nerves lie in a fossa situate on either side of the medulla 
 oblongata, and behind the posterior edge of the pons, bounded on 
 the outside by a small lobule of the cerebellum, called the flock by 
 Reil, or the lobule of the vagus or of the auditory nerve; the floor 
 of this fossa is formed by the restiform column. The portio dura 
 nerve, which lies inside the portio mollis, penetrates the restiform 
 column, and through it may be traced to the central part of the me- 
 dulla oblongata, the olivary columns, where it connects itself with 
 the vesicular matter.. 
 
 In examining the distribution of the facial nerve, it will be found 
 convenient to divide it into three stages, and to enumerate its 
 branches in each stage. 
 
 The first stage is intracranial, from its origin to its exit at the 
 internal auditory meatus. In this stage it forms a connection with 
 the auditory nerve by the portio intermedia of Wrisberg, an oblique 
 branch of communication, which seems like a fasciculus of fibres 
 passing off from the portio dura, and accompanying the auditory 
 nerve into the labyrinth. This branch was described by Arnold and 
 Gcedechens as a second root of the facial nerve, but inasmuch as it 
 does not form a connection with the centre, distinct from that which 
 the principal fibres of the nerve have with it, this view is not tenable. 
 Regarding the facial as a motor nerve, this branch may possibly be 
 viewed, as cohveying motor influence to the muscular apparatus of 
 the cochlea, which we have discovered. 
 
 The second stage is contained in the aqueductus Fallopii. In its 
 passage through this canal a gangliform swelling is formed on the 
 nerve where it is joined by the Vidian which comes through the 
 hiatus Fallopii, intumescentia genuform,is. A question arises as to 
 the nature of this swelling; is it a ganglion, or, is it merely the result 
 of the separation of the fibres of the nerve at this situation.' We 
 have failed to satisfy ourselves by microscopic examination of the 
 existence of vesicular matter in it, but we have found a large num- 
 ber of gelatinous fibres in it, as well as of tubular fibres.* 
 
 At this swelling the facial forms a communication by means of the 
 greater superficial petrosal nerve with Meckel's ganglion, and by the 
 lesser superficial petrosal nerve, with the otic ganglion; a third branch 
 
 * Morgae;ni has lately published an elaborate paper, in which he maintains the 
 ganglionic character of this swelling. — Annali Univ. di Medicina, 1845. 
 
478 INNERVATION. 
 
 less constant than these two, is distributed to vessels and dura mater 
 on the surface of the petrous bone. As it lies in the aqueduct of 
 Fallopius, the facial nerve gives off the following branches. 1. A 
 branch to the membrane of the fenestra ovalis. 2. A twig to the 
 stapedius muscle. 3. The chorda tympani. 4. An anastomotic 
 twig with the auricular branch of the vagus nerve. 
 
 The third stage commences at the stylomastoid foramen ; here the 
 nerve passes obliquely through the parotid gland, in the substance of 
 which it divides into its terminal branches. Immediately on its 
 emergence from the stylomastoid foramen, it gives off: 1. The pos- 
 terior auricular, or auriculo-occipital, distributed to the small muscles 
 of the ear, and the occipital muscle. 2. The stylohyoid branch to the 
 stylohyoid muscle. 3. The submastoid branch to the digastric mus- 
 cle. And lastly, it divides into two branches, the cervico-facial, dis- 
 tributed to the platysma, and to the muscles of the lower lip and 
 chin, and the temporo-facial, which is distributed to the orbicular 
 muscle of the eyelids, the corrugator supercilii, and the muscles of 
 the nose and upper lip. The plexiform distribution of these nerves 
 on the face forms the well-known pes anserinus. The facial nerve 
 anastomoses freely with the superficial temporal, .frontal, infra-orbital, 
 buccal and mental branches of the fifth pair, and with branches of 
 the cervical plexus. 
 
 Function of the. Facial JVerve. — Referring to the anatomy of this 
 nerve, we find it distributed by the vast majority of its fibres to 
 muscles, and those minute branches, respecting the ultimate destina- 
 tion of which some doubt exists, may be, and probably are, distri- 
 buted to muscular fibres. The muscles which are supplied by the 
 facial nerve are chiefly those upon which the aspect of the counte- 
 nance and the balance of the features depend. The power of closing 
 the eyelids depends on this nerve, as it alone supplies the orbicularis 
 palpebrarum ; and likewise that of frowning, from its influence upon 
 the corrugator supercilii. Anatomy indicates, therefore, that this 
 nerve is the motor nerve of the superficial muscles of the face and 
 ear, and of the deep-seated muscular fibres within the ear. 
 
 This conclusion is abundantly confirmed by comparative anatomy. 
 For wherever the superficial muscles of the face are well developed, 
 and the play of the features is active, this nerve is large. In mon- 
 keys it is especially so. That extremely mobile instrument, the 
 elephant's trunk, is provided with a large branch of the facial as its 
 motor nerve. In birds, on the other hand, it is very small, being 
 limited to the stylohyoid branch. 
 
 Section of the nerve, at its emergence from the stylomastoid fora- 
 men, has been followed by paralysis of the muscles of the face, and 
 of the orbicularis palpebrarum, in the hands of all experimenters. 
 Formerly when this nerve was supposed to preside over the sensi- 
 bility of the face, it was thought to be the seat of tic douloureux, 
 and was upon several occasions cut. But this operation yielded no 
 relief to the sufferings of the patient, and only served to illustrate the 
 function of the nerve, since it was always succeeded by paralysis of 
 
THE FACIAL \ERVE. 479 
 
 the face on that side, total loss of control over the features, of the 
 power of frowning, and of closing the eyelids. 
 
 The diseased states of the facial nerve illustrate its physiology in 
 the most interesting manner. It may be paralyzed from the influence 
 of cold, benumbing its superficial fibres, or from the compression of 
 a tumour at the angle of the jaw, or from a carious state of the petrous 
 portion of the temporal bone. From whatever cause the paralytic 
 state arises, the effect is invariably the same; the patient is unable to 
 close his eyelids, and in some rare cases he has not the power even 
 of approximating them to each other in the least degree. He cannot 
 move the ala nasi or either lip on the affected side, and if told to 
 purse up the mouth, as in whistling, he is unable to do it. When 
 he laughs, the movement is all on one side, and the angle of the 
 mouth on the sound side is drawn upwards towards the ear, whilst 
 that on the paralyzed side hangs below its ordinary level. With so 
 much paralysis of the superficial muscles, the deeper seated ones 
 which direct the masticatory movements of the lower jaw, and are 
 supplied by the fifth nerve, remain unaffected, and the sensibility of 
 the face is unimpaired. 
 
 When the paralytic affection of this nerve has been of long stand- 
 ing, there is great wasting of the muscles on that side of the face, 
 and even the buccinator, which is supplied by the fifth nerve also, 
 suffers to such an extent that it becomes reduced to a mere inert 
 membrane, and flaps to and fro as the patient speaks, interfering to a 
 great degree with the clearness of his articulation. 
 
 That the facial nerve in some degree influences the movements of 
 the soft palate, has been suggested by the record of gases in which . 
 palsy of the muscles on one side of the face has been accompanied 
 by paralysis of the corresponding half of the velum. That this 
 symptom sometimes accompanies the other signs of this form of 
 palsy, cannot be doubted; but the frequency of its absence is suflfi- 
 cient to denote the trifling influence of the nerve upon the palatine 
 muscles. Valentin irritated the greater superficial petrosal nerve, 
 which is the probable source of any nervous filaments from the facial 
 to the muscles of the palate, but failed to excite any movement of 
 those muscles in fifteen experiments. 
 
 Much uncertainty exists likewise as regards the function of the 
 chorda tympani. Regarding it, as we do, as a branch of the portio 
 dura, we think it must exercise a motor influence upon the parts to 
 which it is distributed, of which the principal is the duct of the sub- 
 maxillary gland. But the curious relation which it bears to the mal- 
 leus and incus denotes that it may have something to do with the 
 mechanism of the organ of hearing. 
 
 It has been made a question, how far the facial nerve possesses 
 any sensibility, and from whence it derives sensitive fibres. That 
 irritation of it causes pain, has been sufficiently proved by various 
 experimenters, and it appears that the sensibility is more marked 
 after the nerve has passed through the parotid gland. The sources 
 of the sensitive fibres appear to be clearly indicated by the various 
 anastomoses which the facial nerve forms in its several stages — in 
 
480 INNERVATION. 
 
 the Fallopian aqueduct with the vagus nerve, in the face with the 
 fifth nerve, and in the neck with spinal nerves ; the communications 
 with the fifth nerve being very numerous. There are, therefore, suf- 
 ficient means of communication with sensitive nerves to explain the 
 sensibility of the facial without its being necessary to have recourse 
 to the theory of Arnold, and to rank it with the double-rooted nerves. 
 
 Of the JVinth or Hypoglossal JVerve. — The origin of this nerve is 
 from the side of the medulla oblongata along the anterior margin of 
 the olivary body. Ten or twelve fasciculi of fibres emerge here from 
 the central part of the medulla oblongata, and unite into two bundles, 
 which coalesce and emerge as one nerve through the anterior con- 
 dyloid foramen. 
 
 The ninth nerve, on escaping from the anterior condyloid foramen, 
 passes outwards, and winds forwards around the pharynx, to the deep 
 surface of the tongue, being closely related to the internal carotid 
 artery, and the jugular vein, and winding round the external carotid, 
 in its course to the upper and anterior part of the neck. 
 
 Immediately after its emergence it forms anastomoses with the 
 vagus nerve, the superior cervical ganglion, and with the cervical 
 plexus, and then it gives off, 1. The descending branch, which 
 forms remarkable anastomotic arches with branches of the second 
 and third cervical nerves, either within or in front of the sheath, of 
 the common carotid artery and jugular vein. From the convexity of 
 this arch or these arches, there pass branches to the sterno-hyoid, and 
 sterno-thyroid muscles, and to the anterior belly of the omo-hyoid. 
 2. It gives nerves to the thyro-hyoid, genio-hyoid, hyoglossus, and 
 styloglossus muscles. 3. On the inferior surface of the tongue it 
 breaks up into its terminal or glossal branches which pass into the 
 muscular structure of the tongue. 
 
 As the hypoglossal nerve crosses the hyoglossus muscle it forms 
 an anastomosis with the lingual branch of the fifth pair. 
 
 Function of the JVinth JVerve. — As this nerve has no other con- 
 nection than with muscles we cannot regard it in any other light than 
 as a motor nerve. The muscles to which it is distributed are those 
 of the tongue, and as this is the principal nerve to these muscles, we 
 may justly regard it as the motor nerve of the tongue. The other 
 nerves of the tongue, the lingual branch of the fifth and the .glosso- 
 pharyngeal, are obviously traceable to the mucous membrane. 
 
 In the lower mammalia the ninth nerve is distributed precisely as 
 in man, and it is proportional in size to the muscular activity of the 
 tongue. 
 
 Numerous experiments have been made on this nerve. Section 
 of it on one side paralyzes the motor power of the tongue on that 
 side. And galvanic irritation of it throws the muscles on the same 
 side into convulsive action. 
 
 Several instances have been observed of tumours compressing this 
 nerve, and causing paralysis of the muscles of the tongue on the 
 same sid e. The tongue participates in the hemiplegia paralysis 
 which re suits from an apoplectic clot in the brain, or other extensive 
 disease of that organ, along with all those parts whose nerves are 
 
COMPOUND ENCEPHALIC NERVES. 481 
 
 I. 
 
 implanted in some part of the extended centre of volition, and are 
 ordinarily excited by a mental stimulus. In such cases the loss of 
 power in the tongue is usually indicated by its deviation to the 
 paralyzed side in its protrusion, though occasionally the tip is turned 
 towards the sound side. 
 
 We may then conclude from human and comparative anatomy, 
 from experiment and pathological states, that the ninth nerve is the 
 motor nerve of the tongue. Its anastomoses with the vagus, and 
 with the fifth, make it probable that it contains some sensitive fila- 
 ments, and this is confirmed by experiments which show that some 
 sensibility is possessed by the nerve, and that this is greatest the 
 nearer we approach the tongue. But that it has no influence upon 
 taste or upon the common sensibility of the organ, is proved by the 
 unimpaired state of both those powers, after complete section of the 
 nerve. 
 
 In addition to the principal systematic works on physiology, reference may be 
 made to Valentin, de Functionibus Nerv. Cerebr. ; the Papers of Sir C. Bell, col- 
 lected in an octavo volume, 1844; Mayo's papers in his Anat. and Physiol. Com- 
 mentaries, and his Physiology; Longet sur le Systeme Nerveux. 
 
 CHAPTER XX. 
 
 OF THE COMPOUND ENCEPHALIC NERVES. THE FIFTH PAIR. THE EIGHTH 
 
 PAIR. 
 
 It is proposed to devote this chapter to the examination of the 
 physiological history of those encephalic nerves which, from their 
 compound nature, combine the functions of sensitive and motor 
 nerves. These are the fifth pair and the eighth pair. 
 
 The fifth pair of nerves is one of the most interesting and exten- 
 sively connected nerves in the body. It presents a remarkable re- 
 semblance to spinal nerves in its mode of origin, a fact which bears 
 strongly on the determination of its functions. The first point of 
 resemblance is that its origin is by two roots, one large, and the 
 other small; and secondly, its larger root is involved in a ganglion, 
 the two roots being quite distinct until after the formation of the gan- 
 glion, when the lesser one coalesces with one of the nerves which 
 springs from the ganglion, to form the inferior maxillary nerve. 
 
 The two roots are implanted in the same column of the medulla 
 oblongata. They remain, however, quite distinct in the substance of 
 the medulla. Penetrating the latter at the crus cerebelli, between 
 the transverse fibres of the pons, ^ach root may be traced through a 
 separate but nearly parallel course downwards to the olivary column, 
 where each forms its separate connection with the vesicular matter. 
 The ganglion (ganglion Gasserii) which is formed upon the larger 
 
482 INNERVATION. 
 
 root of the fifth nerve Is situate in the raiddle fossa of the cranium 
 upon the upper surface of the petrous bone, and the middle lacerated 
 foramen, and behind the great ala of the sphenoid. It is of a trian- 
 gular form, its base curvilinear and directed forwards and outwards. 
 From this base there proceed three nerves, the ophthalmic on the 
 inside, the superior maxillary in the middle, and the inferior maxil- 
 lary on the outside. Of these the first two consist exclusively of 
 fibres derived from the larger root and ganglion ; the third, the infe- 
 rior maxillary, is composed of fibres derived from both roots. This, 
 therefore, is the only portion of the fifth nerve which is strictly com- 
 pound, and it constitutes the largest portion of the nerve. 
 
 The distribution of the nerve may be understood by reference to 
 the subjoined tabular arrangement of the distribution of each of its 
 three divisions. 
 
 tabulah view or the histribution of the fieth kebte. 
 
 I. Ophthalmic — (anastomoses with sympathetic). 
 
 il. b. To lachrymal gland. 
 2. b. To unite with temporo-malar branch of supra-maxillary 
 nerve. 
 3. b. To external canthns, eyelids, &c. 
 ri. Supra-trochleator b, to integuments of internal canthus, con- 
 6. Frontal . < juncliva, lids, &c. 
 
 (ji. Continued frontal nerve, or supra-orbital. 
 
 !1. Lenticular 6, to the ophthalmic ganglion. 
 2. Ciliary nerves, — two in number. 
 3. Nasal b, to the mucous membrane and skin of the anterior 
 part of the nostril. 
 4. Infra-trochleator, to the inner canthus and side of the nose. 
 
 II. SopEBion Maxillabt — (three stages, cranial, spheno-maxillary, orbital). 
 
 a. Temporo-malar b. — Anastomoses with the lachrymal, and is distributed to the 
 
 integument of the temporal and malar region. 
 
 b. Spheno-palatine b. — Two or three in number, which pass to the spheno- 
 
 palatine ganglion. 
 
 c. Post, superior dental b. — Two or three in number, going to the posterior teeth 
 
 of the upper jaw; one branch passing along the interior 
 of the antrum, and anastomosing with the anterior supe- 
 rior dental. 
 
 d. Ant. superior dental A.— Supplies the anterior teeth of the upper jaw. 
 
 e. Facial . . Vi Latal"^'?S"P.f'y'"g ">^ integuments ef those re- 
 
 6- Nasal S ^'°'''- 
 
 III. iNFEniOR Maxillabt. 
 
 a. Masseteric b. — To the masseter muscle. 
 
 b. Deep temporal b. — Two in number, to the temporal muscle. 
 
 c. Buccal b. — Anastomoses with branches of the facial, and goes to the external 
 
 pterygoid and buccinator muscles, and to the mucous membrane 
 of the mouth. 
 
 d. Pterygoid b. — To the circumflexus palati and internal pterygoid muscle. 
 
 e. Superficial temporal 4 — Anastomoses with the facial, and is distributed to the 
 
 skin of the temporal region and external ear. 
 
 'By its mylohyoid branch to the mylohyoid and digastric 
 muscles. 
 /. Inferior dental b.< To the teeth, alveoli and gums of the lower jaw ; 
 
 and by the mental branch to the integuments and mucous 
 
 membrane of the lower lip. 
 'Is joined by the chorda tympani. 
 
 Connecting filaments to the submaxillary ganglion or 
 g. Lingual b. . J, plexus. 
 
 Anastomotic branches to the ninth nerve. 
 _ Branches to mucous membrane of the tongue. 
 
THE FIFTH NERVE. 483 
 
 Function of the fifth nerpje. — The determination of the functions 
 of the roots of spinal nerves has afforded the clue to that of the func- 
 tions of the roots of the fifth nerve. The analogy of the smaller root 
 of the fifth with the anterior spinal root, and of the larger one with 
 the posterior spinal root has long been admitted by anatomists. — 
 Hence an analogy of function must be admitted, and the former must 
 be viewed as consisting of motor fibres, the latter of sensitive ones ; 
 and by tracing each of the three great divisions of the nerve, we may 
 determine its function by its constitution, according as it derives its 
 fibres from either root or from both. The ophthalmic and superior 
 maxillary are composed of fibres derived exclusively from the larger 
 root ; they are, therefore, sensitive nerves. The inferior maxillary 
 consists of fibres derived from both roots, and consequently is both 
 motor and sensitive. Sir C. Bell, in his original exposition of the 
 functions of this nerve, fell into error from having neglected to avail 
 himself of this method of analyzing the constitution of each of its 
 three divisions from which he would have seen that it is the inferior 
 maxillary alone which derives its fibres from both roots, and which 
 perfectly resembles a spinal nerve in constitution. 
 
 The distribution of the three divisions of the fifth nerve confirms 
 most amply the view of its physiology suggested by the anatomy of 
 its origin. The ophthalmic and superior maxillary are distributed 
 entirely to sentient surfaces, or anastomose with motor nerves (the 
 facial). They supply the skin of the forehead, of the eyelids, the 
 conjunctiva, the eyeball, the mucous membrane of the nostrils, the 
 integuments of the face, the upper lip, the- nose, the beard on the 
 upper lip, the integument of the ear, the temple, and the whiskers ; 
 they are the sensitive nerves to these regions. The inferior maxil- 
 lary has two distinct sets of branches, the one by which the muscles 
 of mastication are supplied — the other, which go to the integuments 
 of the lower lip and chin, and the beard, and the mucous membrane 
 of the mouth and tongue. This nerve is, therefore, the nerve of mas- 
 tication, and of sensation to the surfaces above named. 
 
 Repeated experiments in the hands of various physiologists, none 
 of which, however, were more conclusive than those of Mayo, indi- 
 cate the same views of function. Division of the ophthalmic or of 
 the superior maxillary induced loss of sensibility without muscular 
 paralysis, leaving only such an impairment of the motor power as 
 destruction of the sensitive nerves invariably produces, by impairing 
 the power of exact adjustment, for which a high degree of sensibility 
 is necessary. But when the inferior maxillary nerve was cut, then 
 both the power of mastication was destroyed on the same side, and 
 the sensibility of the lower part of the face and tongue was lost. If 
 the nerve were divided in the cranium, the whole side of the face 
 and forehead, with the eyeball and nose, became insensible, and the 
 muscles of mastication were paralyzed. Irritants might then be ap- 
 plied to the eyeball, without exciting winking, or causing pain, and 
 strong stimulants might be introduced into the nostrils without creating . 
 the least irritation. When the trunk of the nerve within the cranium 
 of an ass was irritated, the jaws closed with a snap from the excita- 
 
484 INNERVATION. 
 
 tion of the motor fibres, which are distributed to the muscles of mas- 
 tication. 
 
 The conclusions which we draw from anatomy and from experi- 
 ment are confirmed by the histories of cases in which the fifth nerve 
 had been diseased. In such instances we may observe the most 
 marked separation of the motor and sensitive power, when the larger 
 portion only or the two superior divisions of the nerve are affected, 
 and we find both motion and sensation destroyed when the whole 
 trunk of the nerve is involved in the disease. It is not uncommon 
 in such cases to find the eyeball totally insensible to every kind of 
 stimulus, the nose quite unexcitable by the fumes of ammonia, or the 
 most pungent vapors, and the mucous membrane of the mouth so 
 insensible to the contact of foreign matters that a morsel of food will 
 sometimes remain between the gum and the cheek until it has become 
 decomposed. The insensibility of the eyeball exposes it to the per- 
 manent contact of irritating particles of dust, &c., which excite de- 
 structive inflammation of its textures. The whiskers may be pulled 
 forcibly without sensation. The muscles of mastication become 
 wasted and inert, as shown by the distinct depression in the regions 
 of the masseter and temporal muscles, but the superficial muscles, 
 on which the play of the features depends, preserve their natural 
 condition. 
 
 The fifth nerve may, therefore, be regarded as the motor nerve in 
 mastication, and the sensitive nerve to that great surface, both inter- 
 nal and external, which belongs to the face and anterior part of the 
 cranium. From its great size, and the large portion of the medulla 
 oblongata with which it is connected, it may excite other nerves 
 which are iiiaplanted in that centre near to it. Thus it may be an 
 excitorto the portio dura, as in winking — or to the respiratory nerves, 
 as in dashing cold water in the face, or in sneezing. Its lingual por- 
 tion distributed to the mucous membrane of the tongue is at once a 
 nerve of taste, touch, and common sensibility, and its connection with 
 the papillary structure of the red parts of the lips constitutes it a pre- 
 eminently sensitive nerve of touch in those regions. 
 
 The study of the pathological conditions of this nerve illustrates 
 its physiology in a highly interesting manner. In the dentition of 
 children, whether primary or secondary, it is always aflfected, more 
 or less : and in excitable states of the nervous centres, the irritation 
 of it consequent upon the pressure of the teeth often gives rise to 
 convulsions, the brain and spinal cord being irritated ; and we can 
 often trace to such irritation, whether in infancy or in childhood, 
 the foundation of epileptic seizures in subsequent years. Painful 
 affections of the face (neuralgia) have their seat in this nerve ; tic- 
 douloureux, for example. Many of the instances of painful aff'ection 
 of this nerve or of branches of it, which come under our observation, 
 are well marked examples of reflected sensation, the primary irrita- 
 tion being conveyed to the centre by the vagus or the sympathetic 
 from the stomach or intestinal canal. No one of these is so common 
 as the pain over the brow, which so often follows derangement of 
 stomach digestion ; and which may frequently be instantaneously 
 
EIGHTH PAIR OF NERVES.— GLOSSOPHARYNGEAL. 485 
 
 removed by taking away the source of irritation, as by neutralizing 
 free acid in the stomach. Frequently also the branches of this 
 nerve, in greater or less number, on one or both sides, may, accord- 
 ing to the humoral view, form a focus of attraction for a morbific 
 matter generated in the blood, in persons exposed to the paludal 
 poison, or in persons of rheumatic or gouty constitution ; in these 
 cases, as in most others of similar pathology, the neuralgia occurs in 
 paroxysms of greater or less severity, each paroxysm being followed 
 by a period of convalescence, which lasts, it may be supposed, until 
 the morbid matter has been again accumulated in quantity sufficient 
 to induce a high degree of irritation of the nerves. 
 
 Of the Eighth Pair of JVerves. — We must examine separately the 
 anatomy and physiology of each of the three nerves, which, taken 
 together, constitute the eighth pair ; and, first, 
 
 Of the Glossopharyngeal. — This nerve consists of several small 
 fascicles of fibres, which lie close together, and are implanted in the 
 upper part of the medulla oblongata behind the olivary body. The 
 fibres penetrate to the centre of the medulla (the olivary columns), 
 where they connect themselves with a special accumulation of vesi- 
 cular matter. 
 
 The glossopharyngeal nerve escapes through a small foramen in the 
 dura mater, at the anterior part of the foramen lacerum posterius. 
 Immediately after it has passed this foramen, a small ganglion, which 
 invoh'es only some of the fibres of the nerve, is formed upon it. This 
 is the ganglion jugulare, discovered by Ehrenritter. Beyond this, 
 and lodged in a fossa in the side of the jugular foramen, is another 
 ganglion which involves all the fibres of the nerve ; this is the gan- 
 glion petrosum, origmaWy described by Andersch. After its escape 
 through the jugular foramen, the glossopharyngeal descends by the side 
 of the pharynx, between the styloglossus and stylopharyngeus mus- 
 cles, and in the region of the tonsil breaks up into its terminal 
 branches. 
 
 From the ganglion of Andersch, a nerve passes off, and enters the 
 cavity of the tympanum, occupying a groove upon the surface of the 
 promontory beneath the lining membrane of the tympanum. This 
 branch, lately called the branch of Jacobson, although described by 
 Andersch and Winslow, divides into six filaments, which form the 
 tympanic plexus or anastomosis. These filaments are as follows : — 
 
 1. To the membrane of the fenestra ovalis. 2. To that of the fenes- 
 tra rotunda. 3. To the carotid plexus in the carotid canal. 4. To 
 the mucous membrane of the Eustachian tube. 5. An anastomotic 
 branch, which, passing through the upper wall of the tympanum, unites 
 with the greater superficial petrosal nerve. 6. An anastomotic branch 
 to the otic ganglion called by Arnold the lesser superficial petrosal 
 nerve. 
 
 Near the petrosal ganglion the glossopharyngeal nerve forms anas- 
 tomoses with the facial and the par vagum. 
 
 The following are the terminal branches of the glossopharyngeal 
 nerve. 1. A branch to the digastric and stylopharyngeal muscles. ■ 
 
 2. Three or four carotid filaments which descend along the internal 
 
 24 
 
486 INNERVATION. 
 
 carotid artery, and may be traced as far as the bifurcation of the com- 
 mon carotid. These nerves anastomose with others from the superior 
 cervical ganglion, and form a plexus round the carotid artery. 3. 
 Tonsillitic branches, which are numerous, and along with nerves from 
 the vagus and from the superior cervical ganglion of the sympathetic, 
 form a plexus beneath the raucous membrane in the vicinity of the 
 tonsil, which is called ihe pharyngeal or tonsillitic plexus. Some of 
 the branches of this plexus are distinctly connected with the mucous 
 membrane, others with the muscular fibres of the pharynx. 4. Pha- 
 ryngeal branches, which are distributed to the mucous membrane of the 
 wall of the pharynx. 5. Lingual branches; these are given to the 
 mucous membrane at the base and side of the tongue, and one may 
 usually be traced into the soft palate. 
 
 From the preceding statement it appears that the distribution of 
 the glossopharyngeal nerve is chiefly, if not exclusively, to sentient 
 surfaces. Even its tympanic branch is connected with the lining 
 membrane of that cavity and of the Eustachian tube. But its princi- 
 pal branches are those on the pharynx and tongue, which latter region, 
 however, it must not be forgotten, has another nerve distributed to its 
 raucous membrane. Its digastric branch seems to be anastomotic with 
 a similar one from the facial. 
 
 The mode of origin of this nerve affords but a feeble clue to the djs- 
 .covery of its physiological import. Miiller and others attach some 
 value to the existence of the ganglion, involving only some of its fibres 
 shortly after their origin, and from the analogy with spinal nerves and 
 with the fifth, they infer that the glossopharyngeal must.be a compound 
 nerve of double origin, containing both motor and sensitive fibres. 
 There is not, however, sufficiently certain evidence of the existence 
 of two roots to this nerve to justify us in founding upon it an argu- 
 ment respecting its function. 
 
 The most extensive series of experiments on this subject are those 
 of Dr. John Raid, and they have very satisfactorily developed the 
 proper functions of the nerve. 
 
 Section of the nerve, or irritation of it, always caused pain, and 
 hence it may be said to contain fibres of common sensation. 
 
 When the trunk of the nerve was irritated before giving off its 
 pharyngeal branches, extensive muscular movements of the throat 
 and lower part of the face were produced. It was found that these 
 movements were equally produced, and to as great an extent, if the 
 ■ nerve had been cut a short way below its exit from the cranium, and 
 the cranial end of it irritated. Hence it was evident that the move- 
 ments were caused, not by the direct influence of the branches of the 
 iglossopharyngeal upon the muscles, but by that of the cranial end of 
 the nerve upon the medulla oblongata, whence the change was pro- 
 pagated to the muscles through the fibres of the vagus nerve and 
 through those of the facial, which emanate from the same part of the 
 nervous centre. 
 
 This view of the mode in which the glossopharyngeal causes mus- 
 cular action is confirmed by the result of experiments on it in animals 
 ,|ust dead. When the nerve was irritated under those circumstances, 
 
THE GLOSSOPHARYNGEAL NERVE. 487 
 
 no movements could be excited, provided it was sufficiently insulated 
 from the pharyngeal branches of the vagus. Now, were the fibres 
 of the glossopharyngeal motor, there is no doubt that mechanical 
 irritation of them would have caused muscular contraction. 
 
 Hence, the glossopharyngeal is one of those sensitive nerves which 
 is capable of exciting motion through its influence upon motor fibres 
 implanted immediately contiguous to it in the nervous centre. 
 
 It appeared, however, that other fibres were capable of exciting the 
 movements of the pharynx, for when the trunk of the nerve was cut 
 on both sides, the movements of deglutition continued. 
 
 Dr. Reid's experiments showed that section of the lingual branches 
 of this nerve did not destroy the power of taste, and therefore that the 
 glossopharyngeal cannot be regarded, according to the views of Pa- 
 nizza, as the sole nerve of that sense. And this accords so complete- 
 ly with anatomy, which shows that a part of the tongue, enjoying the 
 gustatory power, is supplied by the fifth nerve and that only, and that 
 another part, also enjoying the same power, is supplied only by the 
 glossopharyngeal, that no doubt can be entertained of the correctness 
 of the view which assigns gustatory power to this nerve as well as to 
 certain filaments of the fifth pair. At a former page we have referred 
 to a case of paralysis of the fifth nerve in which, while taste was 
 altogether lost in the anterior part of the tongue, it continued at its 
 posterior part; the fifth nerve which supplies the tongue in the former 
 situation being paralyzed, whilst the glossopharyngeal, distributed in 
 the latter region, was free from disease. Two very interesting cases 
 confirmatory of the same view have since been published by Mr. 
 Dixon, in the Med. Chir. Trans., vol. xxviii. 
 
 Disease, limited to this nerve, is of extremely rare occurrence. In 
 one instance that we have met with, in which its neurilemma was 
 considerably thickened, there was not only total inability to swallow, 
 but likewise the mucous membrane of the pharynx was quite insen- 
 sible to stimuli, and that surface of the fauces which, in health, may 
 be excited by the slightest touch of a feather, admitted even of fric- 
 tion without any uneasiness to the patient, or the least muscular 
 contraction. 
 
 The functions of the glossopharyngeal nerve are highly worthy of 
 an attentive study, in reference to the very important question dis- 
 cussed at a former page, as to the existence of distinct spinal and 
 cerebral fibres. We have in it an example of a nerve at once excitor 
 and sensitive ; it is a most marked instance of a nerve, not motor in 
 itself, but capable of exciting motion by its influence on others. Yet 
 no part of the surface to which it is distributed can be touched without 
 sensation being excited, and with it motion. The stimulation even of 
 that portion of the tongue which receives filaments from it, is capable 
 of exciting the pharyngeal muscles to contract, although the action 
 is not so energetic as when the stimulus is applied to the isthmus 
 faucium. In examining the fauces of patients, the practitioner has 
 frequent opportuiiity of observing the extraordinary sensibility of the 
 mucous membrane, where the glossopharyngeal nerve ramifies, and 
 
488 INNERVATION. 
 
 the remarkable rapidity with which the pharyngeal muscles respond 
 to the slightest stimulus applied to it. 
 
 The following conclusions may be adopted respecting the glosso- 
 pharyngeal nerve. 
 
 1. It is the sensitive nerve of the mucous membrane of the fauces 
 and of the root of the tongue, and in the latter situation it ministers 
 to taste and touch as well as to common sensibility ; and being the 
 sensitive nerve of the fauces, it is probably concerned in the feeling 
 of nausea which may be so readily excited by stimulating the mucous 
 membrane of this region. 
 
 2. Such are its peripheral organization and central connections, 
 that stimulation of any part of the mucous membrane in which it 
 ramifies, excites instantly to contraction all the faucial muscles sup- 
 plied by the vagus and the facial nerves, and the permanent irrita- 
 tion of its peripheral ramifications, as in cases of sore throat, will 
 affect other muscles supplied by the facial nerve likewise. It is, 
 therefore, an excitor of the movements necessary to pharyngeal de- 
 glutition. 
 
 Of the Vagus JYerve. — The par vagum or pneumogastric nerve is of 
 all the encephalic nerves the most extensively connected. 
 
 This nerve emerges from the medulla oblongata immediately be- 
 low the glossopharyngeal, by from eight to ten fasciculi of filires 
 which pass outwards to an opening in the dura mater, through which 
 it escapes in company with the spinal accessory. The line along 
 which its fascicles emerge from the medulla is placed a little behind 
 the posterior edge of the olivary body. These fascicles penetrate the 
 olivary columns, and are there implanted in especial accumulation of 
 vesicular matter. 
 
 A ganglion is formed upon the vagus nerve immediately it enters 
 the canal of the dura mater. From this ganglion some small nerves 
 come off. Shortly after the emergence of the vagus nerve from the 
 base of the skull, another gangliform enlargement is formed upon it, 
 which Arnold c^Ws plexus gangliformis. It is at the situation of this 
 enlargement that the union between this nerve and the internal branch 
 of the spinal accessory takes place. 
 
 At its upper part the vagus forms numerous anastomoses, at first 
 by nerves given off from the ganglion. These are, a, with the gan- 
 glion petrosum of the glossopharyngeal, b, with the carotid branch of 
 the superior cervical ganglion, c, with the facial nerve, through the 
 branch called by Arnold the auricular, which is situate in the jugular 
 fossa outside the vein, and is seen through its coats when that vessel 
 is laid open. It anastomoses likewise with the ninth nerve, with the 
 cervical plexus, and with the superior cervical ganglion, in a manner 
 sometimes very intimate. 
 
 The following branches are given off by the vagus nerve. 
 
 1. The Pharyngeal Branch. — This is believed by some anatomists 
 to be derived altogether from the spinal accessory nerve, through its 
 anastomosis with the vagus. It forms, along with the glossopharyn- 
 geal, some cervical nerves and sympathetic filaments, the pharyngeal 
 plexus, and its branches seem to be distributed to the muscles of the 
 
THE VAGUS NERVE. 489 
 
 pharynx. Sometimes there are two pharyngeal branches, a superior 
 and inferior. 
 
 2. The Superior Laryngeal JYerve, which gives 08' the external 
 laryngeal nerve to the crico-thyroid muscle, and is itself distributed to 
 the mucous membrane of the larynx, and sends an anastomotic branch 
 to the inferior laryngeal nerve. 
 
 3. Cervical Cardiac Branches. — These are at least two in number 
 on each side, and they pass down in front of the innominata on the right 
 
 ' and of the aortic arch on the left, and contribute to form the small 
 plexus between the aorta and pulmonary artery. 
 
 4. The Inferior Laryngeal JVerve. — This important nerve is distri- 
 buted to all the intrinsic muscles of the larynx, except the crico-thyroid. 
 The peculiarity of its course has given it the name recurrent. It has 
 interesting relations difTering on the right and left side. Arising on 
 the left side just in front of the arch of the aorta, it winds round the 
 concavity of that vessel, and ascends between the oesophagus and the 
 trachea to the lower edge of the inferior constrictor of the pharynx. 
 The nerve of the right side separates from the trunk just above the 
 subclavian artery, and winds round it, ascending in the neck to a 
 similar destination. 
 
 Both recurrent nerves before their ultimate distribution give off 
 filaments to the heart, to the trachea, to the oesophagus, and to the 
 inferior constrictor of the pharynx. 
 
 5. Inferior or Thoracic Cardiac Branches, distributed to the peri- 
 cardium, and the cardiac plexus. 
 
 6. Anterior Pulmonary Branches, passing in front of the bronchial 
 tube at the root of the lung, and penetrating the pulmonary substance, 
 along with the ramifications of the bronchus, and of the pulmonary 
 artery. 
 
 7. QJlsophageal Branches, which are very numerous, and distributed 
 to the oesophagus, throughout its entire length. 
 
 8. Tracheal Branches, to the mucous membrane and muscular fibres 
 of the trachea. 
 
 9. Posterior Pulmonary Branches ; these go to form the posterior 
 pulmonary jilexus, of which there are a right and a left plexus, 
 which anastomose freely with each other, situate behind the bifurca- 
 tion of the trachea. The ramifications of this plexus follow chiefly 
 the course of the bronchial tubes, being distributed to their mucous 
 membrane and muscular fibres. 
 
 After giving off the pulmonary branches, the vagi nerves pass 
 down along the oesophagus, giving off branches, to it, and passing 
 through the oesophageal opening of the diaphragm, are distributed to 
 the stomach. The Ze/if nerve passes in front of the cardiac orifice, 
 sends some filaments over the splenic cul-de-sac, and follows the 
 course of the lesser curvature ; some of its branches passing in the 
 lesser omentum to the liver, whilst the rest are distributed to the 
 coats of the stomach. The right nerve passes behind the cardiac 
 orifice, and after giving several branches to the stomach, sinks into 
 the solar plexus. 
 
 This outline of the anatomical distribution of this extensively con- 
 
490 INNERVATION. 
 
 nected nerve is sufficient to show that it is devoted to muscular 
 fibres as well as to sentient surfaces, and that it must be regarded as 
 a compound nerve, sensitive as well as motor. The existence of the 
 ganglion, which involves all the fibres of the vagus nerve, in the 
 canal of the dura mater, has led to the opinion that all its proper 
 fibres are sensitive, while those branches which go to muscles are 
 derived from its large anastomosis with the spinal accessory. Whe- 
 ther this view be correct or not, it is certain that a free communication 
 exists just below^ the basis cranii between the vagus and the spinal 
 accessory nerves. 
 
 The branches of this nerve, which anatomy shows to be purely 
 motor, are the pharyngeal and the inferior laryngeal, whilst the 
 cardiac, oesophageal, pulmonary, and gastric branches are doubtless 
 of a mixed character, and the superior laryngeal is purely sensitive, 
 with the exception of those of its fibres which form the external 
 laryngeal nerve. 
 
 The distribution of the vagus nerve in the inferior mammalia cor- 
 responds very closely with that in man, and so far confirms the views 
 of function suggested by human anatomy. Its connection with the 
 sympathetic in some of the mammalia (the dog and cat, for instance), 
 is more intimate than in man, for the upper part of the cervical portion 
 of the sympathetic is closely connected with it, so that they appear to 
 form but one nervous trunk. The general disposition of the nerve 
 in birds and reptiles does not materially differ from that in man, and 
 it has an analogous arrangement in fishes. 
 
 The results of the numerous experiments of which this nerve has 
 been made the subject, accord in a striking manner with the con- 
 clusions deducible from anatomy. Thus, mechanical and galvanic 
 irritation of the pharyngeal branches has always produced contrac- 
 tions of the pharynx: irritation of the superior laryngeal nerve 
 causes contraction of the crico-thyroid muscle only, whilst that of 
 the inferior laryngeal causes forcible contraction of the laryngeal 
 muscles as well as of the inferior constrictor of the pharynx. In a 
 living animal the slightest touch to the mucous membrane of the 
 glottis will cause the instant closure of that fissure, if the superior 
 laryngeal nerve be uninjured, but if that nerve be divided on both 
 sides, the glottis may be irritated with impunity. It is plain, then, 
 that the inferior laryngeal is the principal motor nerve of the larynx, 
 and that the superior laryngeal is at once the sensitive nerve, and 
 the excitor of the motor action of the inferior laryngeal through the 
 medulla oblongata. 
 
 It is scarcely necessary to remark how untenable is the opinion ad- 
 vocated by Majendie, that an antagonism exsits between the superior 
 and inferior laryngeal nerves, the one acting upon the constrictors, 
 the other upon the dilators of the larynx. The superior laryngeal 
 nerve supplies, as we have seen, only one muscle, and the inferior, 
 to which he assigns the office of opening the glottis, supplies those 
 muscles which are the principal agents in closing it. 
 
 Impairment or destruction of vocal power is a constant accom- 
 paniment to injury or complete section of the recurrent nerve. 
 
THE VAGUS NERVE. 491 
 
 An interesting experiment of Dr. J. Reid illustrates the power of 
 each laryngeal nerve respectively. When the inferior laryngeals were 
 cut, the superior remaining intact, a probe introduced into the glottis 
 occasioned signs of pain and efforts to cough, without any contraction 
 of the glottis. But when the superior laryngeal nerves were cut, the 
 recurrents being unimpaired, the probe could be introduced without 
 exciting any irritation or effort whatever. 
 
 This experiment demonstrates unequivocally, that the spasmodic 
 action induced in the larynx by the application of a stimulus to its 
 mucous membrane, must be referred to the class of physical nervous, 
 actions, and results from the influence of the superior laryngeal upon 
 the inferior, through the connection of their respective points of im- 
 plantation in the nervous centre. 
 
 There can be no doubt that the motions of the oesophagus are re- 
 gulated by the various oesophageal fibres given off from this nerve, in 
 its course through the thorax. Irritation of its trunk has always pro- 
 duced contractions of the oesophagus, as testified by many experi- 
 menters. These contractions, Dr. Reid states, extended throughout 
 the whole tube to the cardia, where they became slow and vermi- 
 cular ; the oesophagus being shortened and diminished in calibre at 
 each application of the irritant. 
 
 Distinct palsy of the oesophagus may be produced by section of the 
 vagus in the neck. The following effects followed this experiment 
 by Dr. Reid on a rabbit, which had been kept fasting for sixteen hours 
 previous to the experiment. The animal ate a quantity of parsley, 
 amid considerable dyspnoea and cough, with many efforts to vomit. 
 It died in five hours. The oesophagus was found full of parsley 
 throughout its entire extent down to the stomach, which was also filled, 
 although not distended ; and a good deal of the parsley had passed 
 into the trachea and bronchial tubes, and even into the minute air-cells 
 of the lungs. 
 
 The appearances in this experiment indicated complete paralysis 
 of the oesophagus. This lube was filled by the propulsive power of 
 the pharynx, which sent on morsel after morsel, until the whole 
 stomach and gullet were filled, the latter being perfectly passive ; 
 and after these parts were occupied, and thus resisted the further 
 passage of the parsley, it found its way more readily into the larynx 
 and trachea. 
 
 It may be inferred from this and similar experiments that some- 
 thing more than an irritable condition of the muscular coat of the 
 oesophagus is requisite in order to insure its contraction when dis- 
 tended by food. 
 
 The muscular fibres were quite uninjured, and, therefore, ought 
 to have acted, if the stimulus of distension were alone sufficient to 
 excite their contraction. The true cause of their inaction was the 
 destruction of the nervous circle through which the sensitive nerves 
 of the oesophagus could excite its motor nerves. This portion of 
 the act of deglutition, therefore, is like that in the pharynx, a physical 
 action, brought about by the impression of the food upon the sentient 
 nerves of the oesophagus, which propagate their change to the centre 
 
492 INNERVATION. 
 
 where the motor fibres become excited. It cannot be said, how- 
 ever, that the mind is unconscious of this part of the act of degluti- 
 tion, although it may be reasonably admitted that it has no necessary 
 share in it. 
 
 The results of section of the cardiac nerves show that these 
 nerves exert only a partial influence upon the heart : the destruction 
 of them affects the actions of that organ only to a limited degree, 
 inasmuch as the heart receives nerves from the sympathetic as well 
 as from the vagus. 
 
 . Numerous experiments demonstrate most unequivocally that this 
 nerve is of vast importance to the function of respiration. Section 
 of one nerve produces no effect upon the respiratory organs, either 
 structural or functional. Dr. Reid made careful examinations to 
 ascertain if, after cutting out a large portion of one nerve, the lung of 
 that side suffered any alteration in its texture, but he could not detect 
 any. But when both nerves have been divided above the giving ofT 
 of the pulmonary branches, the most severe dyspnoea comes on, the 
 respirations are generally much diminished in number, the animal 
 breathes just like an asthmatic; after a short time the lungs become 
 congested and cedematous, and the bronchial tubes filled with a 
 frothy serous fluid. When a piece has been cut out of each nerve, 
 or the cut ends of the nerves are kept apart, the animals never 
 survive beyond three days, and during the whole of that period they 
 suffer severe dyspncea. If the cut ends of the nerves be kept in con- 
 tact, the animals will live ten or twelve days. 
 
 It may be inferred from Dr. Reid's experiments, that section of 
 the vagi nerves does not destroy that peculiar feeling of distress 
 {hesoin de respirer), which is occasioned by the want of fresh air in 
 the lungs. He proved that animals, in which the vagi nerves had 
 been cut, struggled violently, and seemed to suffer greatly, when the 
 access of air to the lungs was cut off by compressing the trachea. 
 
 In such cases as tlyit just described, the only channel through which 
 sensitive impressions could be conveyed from the lungs to the brain, 
 is the sympathetic system, and it is to the afferent power of the sym- 
 pathetic nerves, and possibly to the same power in the cutaneous 
 ramifications- of the fifth and of the spinal nerves, that we must attri- 
 bute the imperfect excitation of the respiratory act, which, under 
 these circumstances, takes place. 
 
 The phenomena which follow section of both vagi are doubtless 
 to be explained by the imperfect manner in which the centre of 
 respiration is excited, after the destruction of the influence of these 
 nerves consequent on their section. The movements, after the sec- 
 tion, are partly of the voluntary kind, produced by the sense of dis- 
 tress occasioned by the imperfect supply. The asthmatic state which 
 also follows the section, may perhaps be in part caused by the irrita- 
 tion of the central portion of the nerve, exciting the medulla oblongata 
 and the extremities of the motor nerves of respiration. 
 
 Lastly, the office of the gastric branches of the vagi nerves, ap- 
 pears from Reid's experiments to be chiefly to control the move- 
 
THE VAGUS NERVE. 493 
 
 ments of the muscular coat of the stomach. Mechanical irritation 
 of these nerves causes slow and vermicular contractions of this tunic. 
 Section of them may cause, in the first instance, vomiting and loath- 
 ing of food, and it may retard the digestive process, but it does not 
 put an end to it. For not only do animals, with the vagi cut, eat 
 food from day to day, but, if killed at a sufficient period after diges- 
 tion, their lacteals are found filled with chyle ; affording unequivocal 
 evidence of the persistence of the digestive process. 
 
 Nor does the section of these nerves destroy the secretion of the 
 gastric fluid, for the matter vomited affords evidence of its having 
 been mingled with acid, and the fact of the formation of chyle proves" 
 that stomach digestion must have taken place. Miiller and Dickhoff, 
 in their experiments upon section of the vagi in geese, found the fluid 
 secreted by the stomach distinctly acid. In Dr. Reid's experiments, 
 the ordinary mucous secretion of the stomach was found in its usual 
 quantity, and when arsenic was administered to the animals, the 
 mucous secretion was quite as abundant as in others in which the vagi 
 nerves were not cut. 
 
 The few pathological facts which can be collected of diseased 
 states of the vagi nerves are confirmatory of the conclusions deduci- 
 ble from anatomy and experiment. Several instances are recorded 
 of loss of voice and dyspnoea, symptoms resembling those of chronic 
 laryngitis, caused by the compression of the recurrent by an aneu- 
 rismal or other tumour. The violent convulsive cough, which accom- 
 panies enlarged bronchial glands, is probably due to the irritation of 
 the pulmonary branches of the vagi nerves. Hooping-cough is 
 probably an affection of the vagi nerves by a peculiar poison. Dr. 
 Lay attributed the phenomena of laryngismus stridulus to the irri- 
 tation of enlarged cervical glands, affecting the recurrent nerves, 
 and there seems no doubt that, although the symptoms of this disease 
 occur more frequently as part of a peculiar exhausted state of system, 
 they may be, and are, produced sometimes by the local irritation of 
 such gland. 
 
 The diseases in which this nerve is involved are chiefly those 
 ■which affect its gastric and pulmonary branches. The sympathy 
 which all practitioners admit to exist between the digestive and respi- 
 ratory organs is explained by the anatomical relations of this nerve. 
 Asthma is essentially an irritation of the centre of respiration and of 
 this nerve ; this disease almost invariably begins by some deranged 
 state of digestion, or by the introduction of some poisonous material 
 from without; some very subtle material suspended in the air, and 
 brought by inhalation into contact with the respiratory surface, for ex- 
 ample, the minute particles which pass off" from powdered ipecacuanha, 
 or from hay. Asthma and intermittent fever often go together, be- 
 cause the marsh poison which gives rise to the one, may likewise 
 excite the other. Asthma, which has occurred once, is easily repro- 
 duced by irregularities of diet, and consequent disturbance of diges- 
 tion ; and the frequent recurrence of the asthmatic paroxysm causes 
 the dilated state of the air-passages and air-cells of the lungs, the 
 dilatation of the eight ca.vities. of the heart, and the genenal displace- 
 
494 INNERVATION. 
 
 naent of that organ, which are invariably present in persons who have 
 long been subject to this disease. Vomiting may be excited by irri- 
 tation of the central or the peripheral extremity of this nerve. In 
 disease at the base of the brain, vomiting is frequently an early symp- 
 tom, being caused by irritation of the central extremity of the vagus. 
 In sea-sickness the cerebral extremity of the nerve is irritated by the 
 disturbance of the circulation in the cranium. By introducing emetic 
 substances into the stomach, the vomiting is produced by the irrita- 
 tion of the peripheral extremity. 
 
 Many of the actions in which the vagus nerve is concerned are of 
 the physical kind. Of these, CBSopliageal deglutition is the most 
 marked. The closure of the glottis upon the application of any 
 stimulus to its mucous membrane, is another example of the same 
 nature. But in both these instances, and in all the movements with 
 which this nerve has to do, sensation accompanies the act. In oeso- 
 phageal deglutition, there is less sensation than in the other move- 
 ments, but it is, nevertheless, present, particularly in case of any 
 impediment being offered to the passage of the food. With reference 
 to the movements of the glottis, it is interesting to remark, that whilst 
 the will exercises a minuteness of control over them which is only 
 surpassed by the power which it has over those of the fingers, it is 
 only closure of the glottis which is caused by a physical stimulus. The 
 obvious explanation of this is derived from the great preponderance 
 of the constrictor over the dilator muscles of the glottis. 
 
 On what grounds Dr. M. Hall asserts that " the vagus nerve is 
 certainly the least sentient of any in the class vertebrata,"* we are at 
 a loss to discover. We do not hesitate to affirm that every act of an 
 excitorkind, in which it is concerned, is accompanied by sensation, 
 which in some is exquisite, in others feeble. Nor can we derive, either 
 from the anatomy or physiology of this nerve, any confirmation to his 
 hypothesis of a special series of excitor and motor nerves. It is well 
 known that continued stimulation of the pharyngeal portion of the 
 glosso-pharyngeal nerve upon the fauces will produce the feeling of 
 nausea, and even vomiting. Nausea is a feeling, accompanied by a 
 particular condition of the muscular coat of the oesophagus and sto- 
 mach, preparatory to vomiting, and may be produced by a certain 
 degree or kind of stimulation of any part of the mucous membrane 
 from the fauces to the stomach. The vagus as well as the glosso- 
 pharyngeal, is the instrument of this sensation; for the latter nerve 
 has not sufficiently extensive connections to justify the supposition that 
 it is the sole agent. And this may be cited as a most striking instance 
 of the sensitive endowment of the vagus. 
 
 The following conclusions may be adopted respecting this nerve 
 and its branches. 
 
 1. That the vagus nerve contains filaments both of sensation and 
 motion. 
 
 2. That its pharyngeal branches are- motor. 
 
 » The whole passage is, "This nerve (the vagus) is certainly the least sentient, and 
 the m»s/ purely excitor, of any in the class vertebrata."— iVeio ilfemotV on the Nenmu» 
 System, Adv. f. 9. 
 
THE SPINAL ACCESSORY NERVE. 495 
 
 3. That its superior laryngeal branch is the sensitive nerve of the 
 larynx, containing a few motor filaments to the crico-thyroid. 
 
 4. That the inferior laryngeal is the principal motor nerve of the 
 larynx. 
 
 5. That the cardiac branches exert a slight influence on the move- 
 ments of the heart. 
 
 6. That its pulmonary branches contain both motor and sensitive 
 filaments, and exercise an important influence upon the respiratory 
 acts, for they cannot be destroyed without retarding materially the 
 respirations, impeding the passage of the blood through the lungs, 
 and causing oedema of these organs. 
 
 7. That its oesophageal branches are the channel through which 
 the muscles of that tube are excited, through the medulla oblongata, 
 to contract. 
 
 8. That the gastric branches influence the movements of the 
 stomach, and probably in some degree the secretions and the sensi- 
 bility of its mucous membrane ; but that their integrity is by no 
 means essential to the continuance of the secretion, or to complete 
 chymification. 
 
 Of the Spinal Accessory Merve. — The term spinal is applied to this 
 nerve because of its extensive connection with the upper part of the 
 spinal cord. It escapes from the cranium along with the vagus 
 through a common opening in the dura mater ; but its roots are im- 
 planted in the side of the medulla oblongata, and of the cervical 
 region of the cord as low as to the level of the fifth or sixth cervical 
 nerve. On examining the side of the upper part of the spinal cord, 
 the fascicles of origin of this nerve are seen emerging from it, in the 
 interval between the ligamentura denticulatum and posterior roots of 
 the spinal nerves. The lowest fascicles are those nearest to the pos- 
 terior roots of the lower cervical nerves. By the union of all the 
 fascicles the nerve is formed, and it enters the cranial cavity from that 
 of the spine through the foramen magnum. 
 
 Sometimes some of the upper roots of the spinal accessory nerve 
 coalesce with the posterior roots of the suboccipital and the second 
 and third cervical nerves. This appears to be nothing more than a 
 junction of the fibres of two nerves which emerge from the nervous 
 centre in close proximity to each other. 
 
 Very shortly after the escape of the spinal accessory nerve from the 
 foramen lacerum, it divides into an internal and an external branch. 
 The former coalesces with the vagus, where its second ganglion is 
 formed, and, according to some physiologists, supplies the motor 
 branches of that nerve; the latter passes outwards and downwards, 
 through the deeper fibres of the sterno-mastoid muscle, to which it 
 gives some branches, and anastomoses with branches of the second 
 and third cervical nerves ; and having crossed the triangular space in 
 the neck between the sterno-mastoid and trapezius, it penetrates the 
 latter muscle at its deep surface, and is distributed in it, anastomosing 
 with other branches of the cervical plexus. 
 
 We learn from the anatomy of this nerve that it supplies two great 
 muscles, which play an important pgrt in ejecting certain movements 
 
496 INNERVATION. 
 
 of the head and shoulder, and, in a secondary manner, contribute to 
 the actions of respiration, especially to those of a forced or extraordi- 
 nary kind ; and likewise that it forms a junction with the vagus nerve 
 by a branch which consists of a considerable number of fibres. 
 
 There can be no doubt, from anatomy, that those fibres of the nerve 
 ■which pass to the trapezius and sterno-mastoid muscles, are princi- 
 pally motor, for their main distribution is to these muscles ; and all 
 experimenters agree in stating that, whenever stimulated, they excite 
 these muscles to contract. Anatomy, however, equally indicates 
 that these muscles derive motor power from branches of the cervical 
 plexus likewise. 
 
 The office of the internal branch, which incorporates itself with the 
 vagus nerve, is not so easily determined. Scarpa, Arnold, Bischoff, 
 Bendz, and others, viewed it as contributing the motor fibres to that 
 nerve, bearing to it the same relation as the anterior to the posterior 
 root of a spinal nerve. 
 
 An objection to this view, although not an insuperable one, is sug- 
 gested by the origin of the nerve, which seems more in accordance 
 with that of the posterior roots of the spinal nerves than with their 
 anterior roots, and this is especially the case with the lower fascicles 
 of origin which emerge from the cord quite close to the posterior roots 
 of the cervical nerves. The reply to this objection is, that the ex- 
 ternal branch of the nerve is nevertheless distinctly motor, and that 
 therefore the internal may be so likewise. Morganti and Bernard 
 affirm that the lower roots form the external branch ; if so, then the 
 superior fascicles may be those which contribute to form the internal 
 branch, and, therefore, its function probably differs from that of the 
 external branch. We have already alluded to the fact that a coali- 
 tion is sometimes observed between the posterior roots of the first or 
 second cervical nerves, and the upper roots of the spinal accessory. 
 The function of the former being confessedly sensitive, it is highly 
 probable that the latter nerves, which are apt to coalesce with them, 
 should perform a similar office. 
 
 To determine this question by experiment is extremely difficult 
 by reason of the small size of the internal branch and the great depth 
 at which it is situate, which render it almost impossible to expose 
 the nerve without injuring the vagus itself. Accordingly, we find the 
 recorded statements of physiologists regarding the results of such ex- 
 periments, quite contradictory. The greatest number of observers, 
 and the most recent ones, give their evidence against the motor func- 
 tion of the internal branch, at least against the doctrine of its yielding 
 the motor fibres of the vagus nerve. Most of them, however, agree 
 in stating that a degree of hoarseness and feebleness of voice always 
 followed the section of the internal branch, as if some of the motor 
 fibres of the laryngeal nerves were derived from it. From Miiller's 
 and Dr. John Reid's experiments, by irritation of the spinal acces- 
 sory nerve within the cranium, no conclusive results were obtained 
 favourable to the view which assigns motor power to the internal 
 branch ; on the contrary, these experiments rather tend to prove that 
 the vagus contains within itself the motor fibres sufficient for the parts 
 it supplies. These experimenters found that. irritation aftke trunk of 
 
THE SPINAL ACCESSORY NERVE. 497 
 
 the vagus, hefore its junction with the spinal accessory, caused con- 
 tractions of the pharyngeal and laryngeal muscles, as well as of the 
 fibres of the (esophagus. 
 
 Respecting the external branch of the spinal accessory nerve, it 
 has been already stated that experiment confirms the results dediicible 
 from anatomy. We know that the trapezius and sterno-mastoid mus- 
 cles receive nerves from the cervical plexus as well as from the spinal 
 accessory. If the latter be cut, these muscles are not paralyzed, 
 although weakened, and continue to act in respiratory as well as in 
 voluntary movements, contrary to the views of Sir C. Bell, who 
 regarded the spinal accessory nerves as special nerves of respira- 
 tion, whilst those of the cervical plexus were nerves of volition. 
 There are, indeed, no good grounds for coming to any other conclu- 
 sion than that which Dr. John Reid arrives at; namely, that the 
 external branch of the spinal accessory exactly resembles, in its func- 
 tions, the branches of the cervical plexus with which it so freely 
 anastomoses. 
 
 It may be fairly asked, however, why do the trapezii and sterno- 
 mastoid muscles receive their nerves from a double source? The 
 most reasonable reply to this is, that while the branches of the cer- 
 vical plexus Serve to connect these muscles with the centres of voli- 
 tion and sensation in the ordinary way, the external branch of the 
 spinal accessory connects it in a more direct manner with the centre 
 of respiration. Nevertheless, this branch, although especially im- 
 planted in that centre, is capable of obeying voluntary impulses, so 
 long as the medulla oblongata maintains its normal relation to the 
 centre of volition. 
 
 Thus, on the whole, we assign motor power to the external branch 
 of the spinal accessory, but we see no good reason to subscribe to 
 the opinion that its internal branch must be regarded as the motor 
 root of the vagus. Indeed, we are much more disposed, for ana- 
 tomical reasons, to regard the office of this branch as totally different. 
 None of the views hitherto put forward respecting this nerve explain 
 the object of its peculiar and most extensive connection with the nerv- 
 ous centre ; a connection which, in the larger quadrupeds, is still 
 more extensive than in man. Our view is as follows : the internal 
 branch of the spinal accessory consists of afferent fibres, which, 
 connected with the sensitive surface of the respiratory organs, pass 
 towards the centre in the trunk of the vagus, but separate from 
 that nerve to be implanted in a large extent of the respiratory cen- 
 tre. This mode of implantation of the spinal accessory nerve serves 
 to bring the sentient surface of the lungs and air passages into im- 
 mediate relations with the roots of all those nerves which animate 
 the great muscles of respiration, the phrenic, the external thoracic, 
 the cervical plexus, and the motor fibres of the spinal accessory and 
 vagus nerves. ^ 
 
 Respecting the subjects discussed in this chapter, the systematic works on 
 descriptive Anatomy and Physiology may be consulted ; also Sir C. Bell's and 
 Mayo's works, and Dr. Reid's Essays in the Edinb. Med. and Sur^. Journal ; Dr. 
 Marshall Hall's writings ; the Article " Par Vagum," in the Cyclopsedia of Anatomy 
 and Physiology. 
 
498 INNERVATION. 
 
 CHAPTER XXI. 
 
 THE SYMPATHETIC NERVE. ITS ANATOMY AND FUNCTIONS. 
 
 Under the title of Sympathetic nerve is comprehended a great sub- 
 division of the nervous system, which presents certain peculiarities 
 of structure and of distribution, whereby it is strikingly contrasted 
 with the strictly cerebro-spinal nerves. 
 
 It consists of an uninterrupted chain of ganglia, extending on each 
 side of the vertebral column, from the first cervical vertebra down to 
 the coccyx, and moreover extending upwards beside the cranial 
 vertebrae, and occupying spaces between the bones of the cranium 
 and those of the face. 
 
 The ganglia are on the whole rather less numerous than the verte- 
 brae : in the dorsal region there is generally a ganglion for each ver- 
 tebra. The continuity of the chain is preserved by cords of com- 
 munication which pass from one to the other : sometimes two ganglia 
 are, as it were, fused together ; the chains of opposite sides com- 
 municate with each other at various parts in the plexuses of nerves 
 which originate from them, and, in front of the coccyx, through a 
 single ganglion (ganglion impar), which is situate in front of that 
 bone ; whether they communicate at the cephalic extremity, or not, 
 is uncertain. Ribes has described a ganglion impar upon the ante- 
 rior communicating artery of the circle of Willis, similar to that on 
 the coccyx, and other anatomists regard the pituitary body in the 
 sella Turcica as a ganglion of this description, a common point 
 of union for the right and left sympathetic chains at their cranial 
 extremities. 
 
 The sympathetic nerve has very much the same general arrangement in mamma- 
 lia and birds as in man. In ihe former the cervical portion is closely associated with 
 the vagus nerve by a sheath of areolar tissue, but without interchange of fibres, ex- 
 cepting at its upper portion. In birds the cervical portion exists only in the canal 
 formed by the foramina of ibe transverse processes of the vertebrae. In the batra- 
 chian reptiles the sympathetic is disposed as in mammalia. In the chelonian reptiles 
 its ganglia are few and the lateral cords small. In serpents it appears to want the 
 distinct ganglia which exist in other animals; it is, however, continued down the 
 spine on each side, having frequent communications with the vagus. Numerous 
 plexuses occur in its course. In the larger osseous fishes the sympalhetic is sufficient- 
 ly distinct, as in the cod ; it is also present in ihe ray ; in both, but especially the 
 latter, it is the abdominal portion which is chiefly developed.* In the cyclostomalous 
 fishes the sympalhetic is said to be wholly deficient. 
 
 For the sake of description, the sympathetic in the human body 
 may be divided into the following portions : 1. The Cephalic. 2. The 
 Cervical. 3, The Dorsal. 4. The Lumbar. 5. The Sacral. 
 
 In comparing these several portions, we find that they have cer- 
 tain characters in common. Each portion consists of its proper num- 
 ber of ganglia, which seems in some degree influenced by the num- 
 
 • See Mr. Swan's beautiful Plates of the Comp. Anat. of the Nervous System. 
 
THE SYMPATHETIC NERVE. 499 
 
 ber of vertebroe in that region of the spine to which it belongs. The 
 ganglia are connected by cords of communication, which are not 
 mere nerves, but are true extensions of the ganglia in a cord-like 
 form ; so that each lateral chain might be described as a continuous 
 ganglion, with swellings at certain intervals. From each portion 
 certain sets of nerves may be pretty constantly traced : these are, 
 omitting the cords of communication between the ganglia, 1. Visceral 
 nerves, which generally accompany branches of neighbouring arteries 
 to the viscera. 2. Arterial nerves, apparently devoted to arteries 
 in the vicinity of the ganglia. 3. Nerves of communication with the 
 cerebral or spinal nerves, which emerge from the cranium or spine 
 near to the ganglia. 
 
 The visceral and arterial branches have a remarkable tendency to 
 form plexuses, generally very intricate, which entwine around the 
 blood-vessels, and, in the former case, are conducted by them to the 
 tissue of the viscera. 
 
 The branches of communication with cerebral or spinal nerves, 
 are among the most remarkable connected with this portion of the 
 nervous system. We have already (p. 205) described certain of 
 them as consisting very distinctly of two portions or bundles, one 
 composed of tubular fibres, the other almost exclusively of gelati- 
 nous fibres. These bundles have been very commonly described as 
 constituting the roots of origin of this nerve.* 
 
 On tracing back the gray bundle, connected with one of the spinal 
 nerves, it is found that most of its fibres go to the ganglion of the 
 posterior root of the nerve, some passing into the anterior root. A 
 few of these fibres maybe found in each root; they are not, however, 
 traceable into the spinal cord, but seem to connect themselves only 
 with the blood-vessels of that organ. Such is probably the anatomical 
 history of the so called gray root of the sympathetic connected with 
 every spinal nerve. It may, therefore, be more justly regarded as a 
 nerve originating from the sympathetic ganglion, which by some of 
 its fibres connects that ganglion to the ganglion on the posterior 
 spinal root, and by others is distributed to the vessels of the cord. 
 This is the conclusion which Mr. Beck's recent researches have led 
 him to adopt, and the careful examination of his very able dissections 
 induces us to believe this to be the correct view. 
 
 The white root, or the bundle of tubular fibres, when traced to the 
 spinal nerve, appears like a branch of it, i. e. a series of fibres, sepa- 
 rating from it, and passing to the sympathetic. It derives fibres in 
 nearly equal numbers from the anterior and the posterior root. In 
 every instance it may be seen, spreading out upon the adjacent sym- 
 pathetic ganglion, passing through its vesicular matter, and following 
 the course of the trunk of the sympathetic for a longer or shorter 
 way, and then proceeding from it in connection with its gelatinous 
 fibres chiefly to viscera. , Mr. Beck informs us that he can, under the 
 microscope, distinctly trace the continuity of these fibres through the 
 
 * A good figure of these roots is given in Wutzer's work, "De Corporis humani 
 gangllornm ikbrica atque usu." Wutzer does not, however, distinguish them as 
 wjiile and gray. Berlin, 1817. 
 
500 INNERVATION. 
 
 ganglion, and he is of opinion that they do not form any organic con- 
 nection (as some fibres in ganglia and other nervous centres undoubt- 
 edly do) with the vesicles of the ganglion, beyond that which might 
 result from passing between them. These fibres, then, according to 
 this statement, must be regarded as a branch of the spinal nerve, 
 distributed, in connection with gelatinous fibres derived from the sym- 
 pathetic ganglion, to viscera and other parts. 
 
 If this view of the anatomical relation between the sympathetic 
 ganglia and the cerebro-spinal nerves be correct, it seems evident 
 that the proper sympathetic fibres must be viewed as a separate por- 
 tion of the nervous system, consisting entirely of gelatinous or nucle- 
 ated fibres which originate in the vesicular matter of the sympathetic 
 ganglia. These fibres, however, are accompanied in their course by 
 tubular fibres, derived from the cerebro-spinal nerves, which pass 
 over or through the sympathetic ganglia without forming any intimate 
 connection with them, and which are distributed along with the gela- 
 tinous fibres to viscera and other parts. 
 
 1. Of the Cephalic -portion of the Sympathetic. — This portion of the 
 sympathetic consists of ganglia, which occupy different parts of the 
 head, and are connected with each other, and with the superior cervi- 
 cal ganglion. They are four in number : — 
 
 1. The ophthalmic ganglion. 2. The spheno-palatine, or Meckel's 
 ganglion. 3. The otic ganglion, discovered by Arnold. 4. The 
 submaxillary ganglion. ' 
 
 The ophthalmic, or lenticular, or ciliary ganglion is found in the 
 orbit, situate on the outer side of the optic nerve, a little way before 
 its entrance into the eye, enveloped in soft fat. It is a small quad- 
 rangular ganglion, of a reddish colour, not unlike a pellet of fat, for 
 which it may be very readily mistaken by an inexperienced dissector. 
 
 Numerous nerves proceed from the anterior angles of this ganglion 
 to the eyeball. These are the ciliary nerves, which have been 
 already described, p. 423. 
 
 The ophthalmic ganglion is connected with the third nerve, and 
 with the nasal branch of the ophthalmic division of the fifth. The 
 branch of communication with the third nerve is a short thick nerve 
 which comes from the inferior branch of that nerve: it is called by 
 descriptive anatomists, the short root of the ganglion. From the nasal 
 nerve proceeds the long root, a long and very delicate nerve, which 
 attaches itself to the superior posterior angle of the ganglion. 
 
 We have not examined by the microscope the constitution of these 
 branches of connection with the third and nasal; but it is not unin- 
 teresting to notice that several anatomists have remarked, in reference 
 to them, that the place of each is occasionally supplied by two, which 
 rnay answer to the two connecting nerves already noticed, in the 
 dorsal portion of the sympathetic. 
 
 By means of a third filament called by some the middle root, this 
 ganglion is brought into connection with the cavernous or carotid 
 plexus from the superior cervical ganglion. 
 
 The sphenopalatine ganglion is situate in the pterygo-maxillary 
 fossa; it is a small, somewhat triangular, ganglion connected with 
 
CERVICAL PORTION OF SYMPATHETIC. 501 
 
 the infra-orjiital nerve, at its crossing over the spheno-palatine fissure, 
 to pass along the floor of the orbit. This connection is effected by 
 two or three short nerves called commonly the spheno-palatine 
 branches of the infra-orbital nerve. 
 
 From this ganglion proceed, first, palatine nerves, which are three 
 in number (anterior, middle, and posterior), which pass through the 
 posterior palatine canal, to be distributed to the raucous membrane 
 of the hard and soft palate, and also to the nasal mucous membrane. 
 Secondly, nasal branches, described by Scarpa, which enter the nose 
 through the spheno-palatine foramen, and distribute branches to the 
 spongy bones, and to the septum. One of these, the naso-palatine 
 nerve, passes obliquely downwards and forwards, along the septum, 
 and enters a canal in front of the foramen incisivum, through which 
 it passes to subdivide in the mucous membrane of the hard palate. 
 Thirdly, the vidian nerve, which, coming off from the posterior part of 
 the ganglion, passes through the vidian canal, and divides into two 
 branches, the superior, or the great superficial petrosal nerve, which 
 enters the cranium, and under cover of the dura mater, passes through' 
 the hiatus Fallopii, to unite itself with the geniculate swelling of the 
 portio dura;* and the inferior, or carotid branch, which enters the 
 plexus around the carotid artery, and thus forms the bond of union 
 between the spheno-palatine and the superior cervical ganglion ; this 
 latter branch is much the larger. Arnold states that this ganglion is con- 
 nected with the optic nerve, and also with the ophthalmic ganglion. 
 
 The Otic Ganglion. — This ganglion, discovered and described by 
 Arnold, lies at the inner and inferior part of the inferior maxillary 
 division of the fifth nerve, just at its exit from the foramen ovale. It 
 is connected with this nerve by two filaments, which Arnold consi- 
 ders to be derived from the fibres of the lesser portion of the fifth nerve. 
 Besides branches to the internal pterygoid, and the tensor palati 
 muscles, it sends a filament into the cranium which passes through 
 the hiatus Fallopii into the cavity of the tympanum, and there anas- 
 tomoses with the tympanic branch of the glosso-pharyngeal. This is 
 the lesser superfidal petrosal nerve, which Arnold regards as an ema- 
 nation from the glosso-pharyngeal, and as a root for the ganglion, 
 analogous to the long root of the ophthalmic ganglion. The precise 
 connection of this ganglion with the sympathetic has not been clearly 
 made out. It contains numerous gelatinous as well as tubular fibres, 
 and its vesicles are large and distinct. 
 
 The Submaxillary Ganglion. — This ganglion is occasionally re- 
 placed by a plexus of nerves. One or two fibres from the gustatory 
 nerve constitute its roots, and its principal ramifications are distributed 
 to the submaxillary gland. It is connected with the superior cervical 
 ganglion through the cavernous plexus. 
 
 2. Of the Cervical portion of the Sympathetic. — This consists of 
 three ganglia on each side, the middle of which is by no means con- 
 stant. The superior is the largest, and extends from within an inch 
 
 • It is probably from this source that this swelling receives the many gelatinous 
 fibres already described. 
 
502 INNERVATION. 
 
 of the inferior orifice of the carotid canal, to the third cervical ver- 
 tebra, and sometimes as low as the fourth or fifth. It is connected 
 by large branches with the first, second, and third cervical nerves ; 
 from its upper extremity there passes upwards into the carotid canal 
 a branch which divides into two that accompany the carotid artery, 
 dividing and subdividing as they ascend, so as to form a plexus 
 around that artery, the cavernous or carotid plexus. With this plexus 
 numerous communications take place : there is one with Meckel's 
 ganglion, another with the tympanic plexus; a branch to the ophthal- 
 mic ganglion, and one or two large ones to the sixth nerve, which 
 formerly were regarded as roots of the sympathetic from that nerve ; 
 also one or two filaments to the third pair, and small branches attach- 
 ing themselves to the ramifications of the carotid artery within the 
 cranium. Communications exist between the superior cervical gan- 
 glion, and the several portions of the eighth pair, and the ninth pair 
 at their exit from the cranium. 
 
 Inferiorly the superior cervical ganglion is continued into a cord 
 of communication with the middle, or, when that is wanting, with 
 the inferior cervical ganglion. 
 
 The arterial and visceral branches of the superior cervical ganglion, 
 are, 1. The delicate gray nerves to the internal carotid artery, {nervi 
 molles of Scarpa,) which, with branches from the glosso-pharyngeal 
 and vagus, form a plexus round the internal, external and common 
 carotid arteries. 2. Pharyngeal branches, which, with filaments from 
 the vagus and glosso-pharyngeal, form the pharyngeal plexus 3. La- 
 ryngeal branches accompanying the superior laryngeal branch of the 
 vagus. 4. A cardiac nerve, not always present, and very variable 
 In size, (the superior cardiac nerve of Scarpa,) which, either united 
 with a similar nerve from the middle, or inferior cervical ganglion, 
 or alone, passes along the carotid artery into the chest, to contribute 
 to form the plexus of nerves belonging to the heart. 
 
 The middle cervical ganglion is very inconstant ; it is placed oppo- 
 site the fifth or sixth cervical vertebra, and besides the branches of 
 continuation with the third, fourth, and fifth cervical nerves, it gives 
 off one visceral branch, namely, the middle cardiac nerve, [nervus 
 cardiacus magnus of Scarpa,) which is the largest of the three, and 
 in default of the ganglion, comes off from the intercommunicating 
 cord. This nerve has a similar course to the inferior one ; it is 
 often absent, and its place is then supplied by filaments, which take 
 a similar course, but are derived from the superior nerve, or from 
 the vagus. 
 
 The inferior cervical ganglion. — This ganglion is situate very low 
 down in the neck, and is very deep seated ; it corresponds to the 
 transverse process of the last cervical vertebra, to the head of the 
 first rib, and is closely connected with the origin of the vertebral 
 artery. It is frequently fused with the first thoracic ganglion, and is 
 connected above with the middle, or, in its absence, with the supe- 
 rior cervical ganglion. It is connected with the fifth, sixth, and seventh 
 cervical nerves, and sometimes with the first dorsal. 
 
 The arterial and visceral branches of this ganglion are, 1. A nerve 
 
THORACIC PORTION OF SYMPATHETIC. 503 
 
 which accompanies the vertebral artery into the canal formed by the 
 transverse processes of the cervical vertebrae. This nerve forms a 
 plexus round the vertebral artery, and communicates with branches 
 of the five lowest cervical nerves. There is no satisfactory evi- 
 dence that this nerve passes up to the arteries of the brain. It seems 
 chiefly a nerve to the vertebral artery, but doubtless also contains 
 fibres from the cervical spinal nerves, which probably have a differ- 
 ent destination. 2. The sepond branch of this ganglion is the third 
 or inferior cardiac nerve which passes down, frequently in company 
 ■with the middle cardiac nerve, to the plexus on the heart. 3. 
 Branches which encircle the subclavian attery, in the first part of 
 its course. 
 
 It is worthy of note that the most important visceral branches of 
 the cervical portion of the sympathetic, are destined to an organ, the 
 heart, which is situated in the thorax at a considerable distance from 
 their source. 
 
 3. The Thoracic portion of the Sympathetic consists of a series of 
 ganglia, corresponding, or nearly so, in number to that of the ver- 
 tebrae ; the ganglia lie upon the heads of the ribs, and are mostly 
 small in size, and triangular in form. The first thoracic ganglion is 
 often fused with the last cervical. 
 
 Besides the branches of communication with the spinal nerves, 
 there are arterial branches which pass to the aorta, and there are also 
 branches which pass into the pulmonary plexus. 
 
 But the most remarkable nerves which proceed from these ganglia, 
 are the greater and the lesser splanchnic nerves. 
 
 The great splanchnic nerve arises by separate roots, probably from 
 all the thoracic ganglia, more obviously from the fifth, sixth, seventh, 
 eighth, and ninth; these roots unite to form a round cord, as large, 
 if not larger, than the trunk of the sympathetic. This nerve passes 
 alongside of the bodies of the vertebrae obliquely downwards and 
 forwards, enters the abdomen by piercing the diaphragm, and ends 
 in a large and complex ganglion placed by the side, and in front of 
 the aorta, close to the origin of the cceliac artery ; this is the great 
 semilunar ganglion* 
 
 The lesser splanchnic nerve takes its rise by two roots from the 
 eleventh and twelfth, or from the tenth and eleventh ganglia; it 
 passes down in a similar course to the larger nerve, parallel to, and 
 behind it, pierces the diaphragm, and unites with the renal plexus of 
 nerves, and with the aortic plexus. 
 
 • The composition of this nerve deserves particular attention as illustrating the 
 compound nature of the ramifications of the sympathetic. It may be regarded as 
 the aggregate of a series of visceral nerves proceeding from the intercostal nerves, 
 each of which, as it passes over the sympathetic ganglion immediately adjacent to the 
 nerve from which it arises, becomes associated with some gelatinous fibres. Thus, 
 while each intercostal nerve contributes certain tubular fibres, each thoracic ganglioa 
 contributes gelatinous fibres. Sometimes these two sets of fibres are kept distinct, 
 and the splanchnic nerve consists obviously of a white and a gray portion. The gela- 
 tinous fibres are considerably more numerous at the lower than at the upper part of 
 the splanchnic nerve, as pointed out by Mr. Beck, who very justly cites the fact as 
 strongly confirmatory of the statement that these fibres arise from the ganglia. — PhiL 
 Trans., 1846, p. 324 
 
504 INNERVATION. 
 
 The striking analogy between these nerves and the cardiac nerves 
 cannot fail to attract the attention even of the most superficial ob- 
 server. The latter nerves, distributed to an important organ in the 
 thorax, have their rise in the neck; and the splanchnic nerves, de- 
 riving their origin from nearly all the thoracic ganglia, are devoted 
 to important viscera of the abdomen. 
 
 Of the. Lumbar and Sacral portions of the Sympathetic. — The chain 
 may be followed down to the coccyx; the lumbar ganglia are small 
 and irregular in number. The continuity of the chain between the 
 lumbar and dorsal segments, is maintained sometimes by a small in- 
 tercommunicating cord, between the last dorsal and first lumbar gan- 
 glion, which pierces the diaphragm, sometimes by a branch of the 
 greater or lesser splanchnic, which of course establishes the conti- 
 nuity indirectly. The branches of communication of these nerves 
 with the lumbar spinal nerves, are suflSciently distinct, and some of 
 them are of great length. The gray branches are, according to Beck, 
 larger than the corresponding ones in the thorax. 
 
 The nerves which come from the lumbar portion of the sympa- 
 thetic are destined to the aorta, and to the lumbar arteries; the 
 greater part of them form a plexus around the aorta, between the 
 mesenteric arteries, from which proceed fibres to form the inferior 
 mesenteric plexus, which follows the inferior mesenteric artery ; below 
 this artery the aorta is still embraced by a plexus [inferior aorttc 
 plexus) which divides into the hypogastric plexuses, one on the right 
 and the other on the left, which supply the rectum and bladder, the 
 organs of generation, and the accessory parts. At the base of the 
 coccyx, the sympathetic of the right side anastomoses with that of 
 the left by means of a branch passing on each side from, the last sacral 
 ganglion to a ganglion in front of the Qoccyx, which is called the 
 ganglion impar. 
 
 Of the Thoracic and Abdominal Plexuses. — So large a portion of the 
 sympathetic is distributed to viscera in the thorax and abdomen, 
 that it may not improperly be designated as the visceral nerve ; for 
 those organs, upon which the great processes which contribute to the 
 nutrition of the body so much depend, derive their nerves mainly 
 from this source, and whatever cerebro-spinal fibres they receive, are 
 distributed to them in intimate association with the proper filaments 
 of the sympathetic. 
 
 The plexuses in the thorax which derive nerves from the sympa- 
 thetic are the pulmonary plexus, and the cardiac plexus. 
 
 The ptilmonary plexus is chiefly formed by branches of the vagus, 
 interlacing with each other from opposite sides along the median 
 plane. It occupies two planes, one anterior to the bronchi constitut- 
 ing the anterior pulmonary plexus, the oiher posterior, which is much 
 the more considerable, and lies behind the bronchi. To these, but 
 especially to the latter, nerves pass off from the higher thoracic 
 ganglia. 
 
 The cardiac plexus is almost wholly derived from the sympathetic, 
 only a few of its fibres coming from the cardiac branches of the vagi. 
 It is very remarkable that all the nerves which the sympathetic con- 
 
PLEXUSES OF THE SYMPATHETIC. 505 
 
 tributes to this plexus, are derived from the cervical, and not from 
 the thoracic ganglia. The plexus resulting from the anastomoses of 
 these nerves, occupies an anterior and a posterior plane ; the former 
 passing in front of the great arteries, and following the course of the 
 anterior coronary artery, in the anterior groove of the heart. The 
 plexus entwines around this artery and its ramifications, and its fibres 
 are doubtless conducted by them to the muscular fibres of the heart. 
 The posterior plexus follows the course of the right coronary artery, 
 and of its branches, which lies in the posterior fissure of the heart. 
 A plexus of fibres, occupying a position intermediate to these plex- 
 uses, lies behind the arch of the aorta, above the right pulmonary, and 
 sends a considerable plexus of nerves to the auricles. This plexus 
 was described by Haller, as the great cardiac plexus. 
 
 Several small ganglia, or gangliola, are found in connection with 
 the nerves of the heart. Wrisberg described one just above the 
 arch of the aorta, at the junction of anastomosing fibres from the 
 superior cardiac nerves. A ganglion is also sometimes found in the 
 plexus in front of the auricles, and Remak describes and figures 
 several small ganglia upon the subdivisions of the anterior and pos- 
 terior cardiac plexuses, and in the muscular substance of the heart. 
 MiiUerh Archiv., 1844. 
 
 The nervous plexuses in the abdomen are extremely complicated 
 and numerous. They are principally derived from two great gan- 
 glia, situate on each side of the CEeliac axis, in front of the aorta. 
 These ganglia are semilunar in shape, convex downwards and out- 
 wards ; they unite below the cseliac axis ; and chiefly from their 
 convex border, a vast radiation of plexiform nerves takes place, which 
 follow the course of, and entwine around the branches of the CEeliac 
 axis, and of other branches of the aorta. To this great radiation 
 anatomists have given the name of solar plexus, and the conjoint semi- 
 lunar ganglia must be looked upon as the great centre, — the sun of 
 the abdominal sympathetic system. 
 
 Plexuses radiate from this source around the principal branches 
 of the aorta, and they are named after the arteries which they accom- 
 pany. They are the diaphragmatic or phrenic; the supra-renal; the 
 cceliac; which divides into the hepatic, gastric and splenic; the supe- 
 rior mesenteric, from which proceed nerves, which, with others from 
 the lumbar portion of the sympathetic, form the inferior mesenteric 
 plexus; and the renal plexuses, from which chiefly are derived the 
 spermatic plexuses, destined to the ovaries in the female, and the 
 testicles in the male. Of these plexuses the following are deserving 
 a more particular notice: 
 
 The gastric plexus accompanies the coronary artery of the stomach, 
 and passes along the lesser curvature of that organ. With the gastric 
 branches of the vagus it forms the principal nervous supply to the 
 stomach, which is completed by an ofl'-shoot surrounding the right 
 gastro-epiploic artery from the hepatic plexus, and by other nerves 
 from the same plexus distributed chiefly to the pylorus, and by 
 branches from the splenic plexus. 
 
 The hepatic plexus follows the hepatic artery and the vena portae 
 
506 INNERVATION. 
 
 into the substance of the liver; it is joined by a branch of the vagus ; 
 and it gives off nerves to the stomach, and to the pancreas. 
 
 The splenic plexus surrounds the splenic artery, supplies the pan- 
 creas, and the left extremity of the stomach, by entwining round the 
 the left gastro-epiploic artery, and by direct branches to the great cul- 
 de-sac of the stomach. These nerves then follow the branches of 
 the splenic artery into the spleen. 
 
 The superior mesenteric plexus supplies the greatest portion of the 
 intestinal canal, entwining around the superior mesenteric artery and 
 its ramifications. Connected with it are some ganglia of variable 
 size, called caliac or mesenteric ganglia. From these ganglia, and 
 from the upper part of the plexus, nerves are derived to the pancreas, 
 and to the duodenum. 
 
 The branches of this plexus which pass between the laminae of 
 the mesentery do not accompany the smaller branches of the arteries 
 so closely as elsewhere. They anastomose by arches, from which 
 small branches pass to the intestine. The precise mode of termi- 
 nation of these nerves in the tunics of the intestines has not been 
 ascertained. 
 
 In the pelvis we find a remarkably complicated plexiforra arrange- 
 ment of nerves distributed to the viscera of that cavity. These 
 nerves are derived from the hypogastric and from the inferior me- 
 senteric (p. 504), and receive many fibres from the sacral nerves, 
 which latter fibres are principally distributed to the pelvic plexus, a 
 name given by Mr. Beck to an intricate anastomosis of nerves and 
 small ganglia distributed to the rectum, bladder, and vagina. This 
 plexus derives its nerves from the lower part of the hypogastric 
 plexus, and from the branches of the sacral plexus. 
 
 A very important peculiarity of all the plexuses, wherever found, 
 of the sympathetic nerve, consists in the presence of a quantity of 
 vesicular matter in them, deposited in ganglia of very variable size, 
 sometimes extremely minute, very rarely of great size, which are 
 found scattered amongst them. These ganglia appear to give origin 
 to gelatinous fibres. The plexuses, therefore, have the double oflSce 
 of intermingling fibres from different sources, and of affording points 
 of origin for new nerve fibres. 
 
 Function of the Sympathetic JVerve. — In considering the function 
 of this portion of the nervous system, it is of the utmost importance 
 to pay close attention to the facts which the anatomical analysis of it 
 discloses. 
 
 These facts are, that it contains a vast number of centres to and 
 from which nerves proceed, and in which, it may be stated almost 
 •with certainty, gelatinous fibres originate: that in nearly every part 
 of it two kinds of fibres exist, the gelatinous and the tubular; that 
 the tubular are derived from the cerebro-spinal centre, the gelatinous 
 from the sympathetic ganglia. 
 
 Two questions are to be solved in reference to the sympathetic. . 
 
 1. Is the sympathetic a distinct and independent portion of the 
 nervous system ? or is it merely an off-shoot from the brain and spinal 
 cord, exhibiting certain peculiarities of arrangement.-' 
 
FUNCTION OF THE SYMPATHETIC. 507 
 
 2. Do its fibres exhibit the same powers as those of cerebro-spinal 
 nerves? that is, are they sensitive and motor? 
 
 1. No physiological question has been more amply discussed of 
 late years than that of the relation of the sympathetic to the cerebro- 
 spinal centres. 
 
 The view, which we regard as the correct one, rests entirely upon 
 the facts of anatomy already stated. These facts lead us to consider 
 the sympathetic nerve a compound nerve, consisting of gelatinous 
 fibres, which are derived from the vesicular matter of the ganglia, 
 and of tubular fibres, proceeding from the spinal cord. These fibres 
 ai-e bound together in the same sheath, and whatever be the proper 
 function of each, they bear to each other a similar relation to that 
 ■which the anterior and posterior roots of spinal nerves do in the 
 compound nerve. Originating from diflferent sources, and possess- 
 ing probably different endowments, they travel in company to their 
 several destinations. 
 
 We are aware that some physiologists of high and deserved re- 
 pute altogether deny that the gelatinous fibres, which we have de- 
 scribed as entering so largely into the constitution of the sympathetic, 
 are nervous. They regard them as an early stage of fibrous or 
 areolar tissue. The following reasons appear to us quite decisive of 
 the nei'vous nature of these fibres. 1. They may be distinctly traced 
 to the vesicular matter of ganglia ; it is immaterial to the question 
 whether they form their connection with the sheaths or with the 
 vesicles themselves, for we are as much at liberty to regard the 
 nucleated envelope of the vesicles as a structure essentially nervous 
 as the vesicles themselves. Parts of the encephalon appear to consist 
 of little else than nuclei. 
 
 2. Throughout the sympathetic system these fibres and the tubular 
 fibres exist in the several nerves in different but determinate numbers. 
 Sometimes the two kinds are equal, sometimes one predominates over 
 the other; sometimes the nerves consist solely of igelatinous fibres. 
 Now if these latter performed the ofl5ce of a sheath or support to the 
 others, they would always be in due proportion to each other. More- 
 over, the gelatinous fibres would be always outside, enveloping the 
 tubular, which is not at all uniformly the case. 
 
 3. Nucleated fibres, very similar to the gelatinous fibres of the 
 sympathetic, exist in parts where their nervous character isindubitable, 
 as in the olfactory filaments (p. 397), and the nerve in the axis of the 
 Pacinian corpuscle exhibits very much the same appearance, save 
 that it is devoid of nuclei. 
 
 Adopting this view of the compound nature of the sympathetic, 
 it is obviously impossible to regard it either as independent of the 
 cerebro-spinal centres, or wholly depending on them. It seems pro- 
 bable that it is independent of them as regards its gelatinous fibres, 
 but dependent on them as regards its tubular fibres. 
 
 And it may be stated that the views of anatomy which we hold 
 to be correct, justify us in affirming that the sympathetic exhibits 
 marked indications if not of independence, yet of great peculiarity, 
 in its mode of distribution. Clinging to the coats of arteries, it 
 
508 INNERVATION. 
 
 follows them for the most part in their ramifications, and attaches 
 itself to them somewhat as ivy does to a tree. Yet of the mode of 
 termination of the gelatinous fibres of the sympathetic, and of the 
 nature of their relations with the elements of the tissues among which 
 they lie, nothing certain is known ; a fact attributable in a great 
 degree to their want of such obviously distinctive characters as the 
 tubular fibres possess. These latter, after leaving the blood-vessels, 
 are probably distributed either to sentient surfaces or to muscles in 
 the ordinary way.. 
 
 The proper mode, then, of stating the reply to this question seems 
 to us to be : that the sympathetic, taken as a whole, is not in itself a 
 special and independent nervous system, but a portion of the nervous 
 system peculiar in its composition, having, as regards some of its 
 constituent fibres, a special relation to blood-vessels, particularly 
 arteries, (and these are the fibres which are independent of the 
 cerebro-spinal centres, having distinct centres of their own,) but being 
 by others of its fibres connected, as all other nerves are, with the 
 cerebro-spinal centres. 
 
 II. The second question affects the endowments of the consti- 
 tuent fibres of the sympathetic. 
 
 If we interrogate anatomy, we learn that the ramifications of this 
 nerve are distributed to muscles as well as to sentient surfaces. The 
 heart, for instance, derives its principal supply of nerves from this 
 source. The intestinal canal between the stomach and the lowest 
 part of the colon receives no nerves direct from the cerebro-spinal 
 system, and is therefore dependent solely on the sympathetic, for 
 whatever of sensibility it enjoys, or for such motor power as may be 
 usually called into action by nervous influence. We, therefore, must 
 infer from anatomy that the sympathetic contains both sensitive and 
 motor fibres. 
 
 Many experiments lead to a similar conclusion. Stimulation of 
 the cervical ganglia excites the heart to increased action ; and irri- 
 tation of the splanchnic nerves causes increased vermicular motion 
 in the stomach and intestinal canal. Miiller proved a similar result 
 to ensue upon irritation of the CBsliac ganglion. He exposed the 
 intestines, and likewise the cseliac ganglion in a rabbit; he waited 
 until the increase of peristaltic action, which exposure to the air 
 always produces, had subsided, and then he applied potassa fusa to 
 the ganglion, when immediately the peristaltic movements became 
 very vigorous. There is less agreement in the statements of the 
 results obtained by different experimenters as to the sensibility of 
 these nerves, as indeed is very commonly the case, when the ques- 
 tion is respecting sensation ; but the well known occurrence of pain 
 in parts supplied only by the sympathetic, is alone more conclusive 
 as to the existence of sensitive fibres in that nerve, than the results 
 of any experiment on a brute animal. How exquisite are the suf- 
 ferings of patients labouring under colic, or the passage of a gall- 
 stone, or of a renal calculus! 
 
 It is plain, then, that the sympathetic nerve contains both motor 
 and sensitive fibres. An appeal to common experience shows us, 
 
FUNCTIOKS OP THE SYMPATHETIC. 509 
 
 that the latter cannot be very numerous, as parts supplied by the 
 sympathetic nerve are not, in the healthy state, highly sensitive, and 
 pain is felt in them only under the influence of great irritation. And 
 with regard to the motor fibres, it shows that they are not at all, or at 
 most to a very trifling extent, under the influence of the will. It is 
 true that the will may be brought to bear upon muscles supplied by 
 the sympathetic, by directing it simultaneously upon other distinctly 
 voluntary muscles. This is well illustrated in the case of the iris; 
 no effort, however great, if directed solely upon the iris, will cause 
 that muscle to contract, but if the voluntary influence cause a simul- 
 taneous contraction of the internal rectus muscle of the eye, con- 
 traction of the pupil will take place upon each adduction of the eye- 
 ball. 
 
 It is highly probable that the increase in force and in frequency 
 which takes place in the heart's action, during active exercise, is to 
 be explained on the same principle; and that a strong effort of the 
 will directed to the abdominal muscles, may excite an increased 
 peristaltic action of the intestines. 
 
 Muscles supplied by the. sympathetic nerve, although under ordi- 
 nary circumstances referable to the category of involuntary muscles, 
 must not then be considered as absolutely and entirely removed from 
 the influence of the will. 
 
 A very striking peculiarity, dependent in part probably upon the ana- 
 tomical arrangements of the sympathetic, consists in the rhythmical 
 nature of the movements of parts which derive their supply of nerves 
 from this source, of which the movements of the heart and the intesti- 
 nal canal afford good examples. And it is an important feature of 
 these actions that they take place even when the parts are discon- 
 nected from the main portion of the sympathetic system. It is well 
 known that the. heart's action will go on for a considerable time after 
 it has been removed from the body ; and that the peristaltic move- 
 ments of the intestines will continue under similar circumstances. 
 
 This peculiarity seems to be referable to a double cause; first, the 
 disposition of the muscular fibres themselves, which is such that a 
 contraction cannot take place at one part without affecting the adjacent 
 fibres, so that the contraction of one set of fibres appears to stimulate 
 those in their immediate vicinity. This progressive contraetion is 
 well seen in the intestines. Secondly, the frequent occurrence of 
 small ganglia,, not only among the plexuses of the sympathetic, but 
 also, as in the heart, upon or among, the muscular fibres themselves. 
 These ganglia, it is reasonable tO' suppose, are so many little Biaga- 
 zines of nervous force, which,, by their intimate connection with the 
 muscular fibres themselves, render them capable of repeating their 
 action at intervals, after their disconnection from the main trunk of the 
 sympathetic system. 
 
 Much, however, in the peristaltic actions, is perhaps, due to the 
 peculiar constitution of the unstriped muscular fibre itself; a consti- 
 tution which gives it a slow and enduring, rather than a quick, ener- 
 getic, and fleeting contraction. The actions of the heart are inter- 
 mediate to those of the intestine and of voluntary muscle, and so a^e 
 25 
 
510 INNERVATION. 
 
 its muscular fibres, which, while they exhibit the striped appearance 
 of voluntary muscle, are nevertheless devoid of the sarcolemma, and 
 interlace in a peculiar manner with each other. The gelatinous nerve- 
 fibres exhibit the same apparent inferiority of organization as the 
 unstriped muscular fibre. It is a remarkable confirmation of these 
 views, that in the tench {Cyprinus tinea), according to Ed. Weber, in 
 which the muscular fibres of the alimentary canal are of the striped 
 kind, there is no peristaltic action of the intestines, and that the 
 application of a rapid succession of electrical shocks from a magneto- 
 electric rotation instrument causes that sudden and quick contraction 
 which characterizes the striped muscular fibre.* 
 
 An observation made by Pourfour du Petit,f many years ago, sug- 
 gested an office of the sympathetic, distinct from sensation or ordinary 
 motion, but apparently not less important than either. He JFound that 
 the division of the trunk of the sympathetic in dogs, opposite the 
 third or fourth cervical vertebrae, was followed, with remarkable 
 rapidity, by a disturbance of the circulation in the eyeball ; giving 
 rise to a swollen and apparently inflamed state of the conjunctiva, a 
 contracted state of the pupil, a flattening of the cornea, and a re- 
 traction of the eyeball, with protrusion of the fold of the conjunctiva, 
 known by the name of the haw, and a flow of tears. Dupuy found 
 similar effects resulting from the extirpation of the superior cervical 
 ganglion in horses; and when the ganglia on both sides were removed, 
 there were superadded to these more local effects, a general emacia- 
 tion along with an anasarcous state of the limbs, and an eruption over 
 the whole cutaneous surface. 
 
 Dr. J. Raid confirms these results of section of one sympathetic 
 in the neck, as far as regards the eye, and he agrees with the other 
 observers in stating that the injected state of the conjunctiva fol- 
 lowed immediately after the section. In one case, he states that 
 the redness of the conjunctiva took place a few minutes after the 
 operation. 
 
 It has been already stated, that section of the branches of the fifth 
 nerve, which supply the eye, is followed by ulceration and other signs 
 of impaired nutrition in the eyeball. But these changes do not take 
 place for some time after the section of the nerve ; generally many 
 days elapse : and they are attributable to the presence of irritating 
 particles, which, owing to the insensible state of the conjunctiva, are 
 suffered to remain in contact with the surface of the eye, giving rise 
 to inflammation and ulceration of its textures. The effects of section 
 of the sympathetic are immediate; and are probably due to a change 
 produced in the blood-vessels, in consequence of the withdrawal of 
 their accustomed nervous influence. 
 
 The sympathetic thus appears to exercise a threefold office: first, 
 
 • By experiments with the magneto-electric instrument, E. Weber has given 
 additional illustration of the fact that the peristaltic contraction is characteristic of 
 the unstriped fibre, and that the sudden and quick contraction is peculiar to the 
 striped fibre. See his elaborate article "Muskelbewegung" in Wagner's HandwSr- 
 terbuch, 1S46, and our remarks at pp. 146, 149, ISO. 
 
 f Histoire de I'Acad. Royal des Sciences, an 1727, &c. Lettres concernant des 
 reflexions sur les d^couvertes faites sur les yeux, 173S. 
 
FUNCTIONS OF THE SYMPATHETIC. 511 
 
 that of a sensitive nerve to the parts to which it is distributed; 
 secondly, that of a motor nerve for certain muscular parts ; and, 
 thirdly, that of a nerve to the blood-vessels. It is almost certain 
 that blood-vessels enjoy in their coats a power of contractility; 
 and it seems highly probable that these nerve-fibres exercise an 
 influence upon that contractility. Such an influence, it is evident, 
 would materially affect the nutrition of parts the blood-vessels of 
 which are subject to it; and, as secretion is mainly dependent on 
 the normal nutrition of glands, it is reasonable to suppose that that 
 function likewise would be to a certain extent controlled by these 
 nerves. 
 
 It remains to inquire the sources whence these various classes of 
 fibres in the sympathetic respectively derive their powers. 
 
 Looking to the anatomy of the nerve, there can be no doubt that 
 some fibres are derived from the spinal cord or medulla oblongata, 
 and that others proceed from the sympathetic ganglia. The motor 
 and sensitive fibres, and some of those going to the other muscular 
 parts, belong, no doubt, to the former class; the vascular, with the 
 highest probability, to the Tatter. 
 
 Valentin's experiments indicate that the roots of the encephalic 
 and spinal nerves exert considerable influence upon the movements 
 of parts supplied by the sympathetic. For instance, irritation of the 
 roots of the first three or four cervical nerves, excites increased action 
 of the heart; and that of the dorsal and lumbar spinal nerves stimu- 
 lates the peristaltic action of the intestines through the splanchnic 
 nerves, and the abdominal plexuses. 
 
 The effects of diseased states of the spinal cord also afford a sup- 
 port, which is more to be relied upon than the previous experiments, 
 to the opinion that the motor and sensitive fibres of the sympathetic 
 are implanted in the spinal cord. When there has been extensive 
 lesion of the cord, from injury or disease, the intestinal canal is always 
 affected to a degree proportional to the extent of the lesion ; and this 
 affection shows itself in the torpor of the intestines, and the readiness 
 with which they become distended by flatus, giving rise to the tym- 
 panitic condition of abdomen, which so generally attends disease or 
 injury of the spinal cord. 
 
 It had long been thought that the sympathetic nerve plays an im- 
 portant part in the sympathies of the body. Our improved knowledge 
 of the anatomical distribution of the nerves, and of their physiological 
 anatomy, and of their endowments, clearly shows that the phenomenal 
 of sympathy are explicable by the known laws of action of the great 
 nervous centres, and that the sympathetic nerve can take no more 
 prominent part in it than any other nerve ; the extent to which it 
 or any other nerve may be engaged in the play of such sympathies 
 beino' proportioned directly to the extent of its central as well as its 
 peripheral connectiQns. 
 
 It would be more consistent, therefore, with a scientific nomen- 
 clature to discard the term Sympathetic as applied to this nerve; the 
 old name Intercostal would, in some respects, be preferable. There 
 is, however, great difficulty in finding a name which would adequately 
 
512 DIGESTION. 
 
 express its constitution and offices, which may he summed up as 
 follows. 
 
 1. In its constitution it is compound, consisting of tubular fibres 
 and of gelatinous fibres. 
 
 2. In its ofiices, it is a motor nerve to many of the internal viscera 
 of the body, the heart and the intestinal canal especially ; it is also 
 a sensitive nerve to these parts; and it presides over the actions of 
 the blood'Vessels of these as well as of other parts where it is dis- 
 tributed, as of the head and neck, and likewise of all the principal 
 glands of the body. 
 
 On the Sympathetic nerve, consult Cm veilhier, Anat. Descr. ; Valentin, in Soemnier- 
 ring, Anat.; Longet, Syst. Nerveux ; Lobstein, de nervi sympalh. fabrici, &c. ; Val- 
 entin de function, nerv. cerebr. et sympath.; Mr. Beck, paper in the Phil. Trans, for 
 1846; Miilier's Physiology; Bidder und Volkmann, die Selbstandlgkeit des symija- 
 thischen Nenrensystems, Leipzig, 1842 ; KoUiker, die Selbstandigkeit und Abhiingig- 
 keit des sympathischen Nervensystems, Zurich, 1844; Purkinje, in Muller's Archiv. 
 for 1845, and translated in thcLond.Med. Gazette, vol. xxxvi., has described nervous 
 ramifications which he considers to belong to the sympathetic, in the pia mater, 
 ■dura mater, serous membranes, and other parts. Mr, Rainey also describes (Mei, 
 Chir. Trans, vol. xxix.) the arachnoid and subarachnoid tissue as consisting almost 
 entirely of such nerves, a view which it is impossible for us to adopt. Much yet 
 remains to be cleared up as regards the anatomical history of the sympathetic nerve 
 in particular parts. Monographs upon the nerves of (he heart, of the stomach, the 
 intestines, &e., are great desiderata, founded on careful and minute dissections, by 
 experienced anatomists, with the aid of the microscope. Further researches are like- 
 wise required on its distribution to the extremities. 
 
 CHAPTER XXII, 
 
 GENERAL VIEW OF THE FUNCTION OF DIGESTION. — OF THE MINOR FUNC- 
 TIONS WHICH CONTRIBUTE TO IT.t^OF FOOD. — ITS QUALITY.^-ITS 
 <lUANTITy. 
 
 Having discusesd the great animal functions of Locomotion and 
 Innervation, we now commence the consideration of those organic 
 functions which are more directly concerned in maintaining the nu- 
 trition, and, consequently, the life of the individual. 
 
 Of the nutritive processes., the function of Digestion is clearly the 
 most prominent and most important, inasmuch as it is that through 
 which the animal is enabled to receive the aliment, and to prepare it 
 for being assimilated to, and appropriated by, the various textures and 
 organs of the body. 
 
 Under the general expression, "function of Digestion," must be 
 comprehended several minor processes, all tending to the same object, 
 namely, the reduction of the food for the nourishment of the body. 
 The number of these subordingite proqesses varies with the degree of 
 complication of the digestive funeUon, which is obviously influenced 
 
FUNCTION OF DIGESTION. 513 
 
 by the complicated nature of the animal's body, and by the part which 
 it has to play in the economy of the world. 
 
 Taking the digestive process, in its highest degree of complexity 
 in man and the mammalia, we find that there is provision, first, for 
 the prehension of th6 food; secondly, for its mechanical division and 
 comminution {mastication), and for its admixture with a peculiar fluid 
 {insalivation) ; thirdly, for the conveyance of the food into that por- 
 tion of the alimentary canal in which its principal chemical changes 
 are to take place {deglutition) ; fourthly, for the solution and reduction 
 of the food preparatory to its being brought into a condition favour- 
 able to absorption {ehymification) ; fifthly, for the separation of a ma- 
 terial which shall contain in a condensed form the chief nutritive 
 principles of the food, and which is easily absorbed into the blood 
 {chylification) ; and lastly, for the removal of such portions of the 
 food as have not been absorbed into the system during its passage' 
 along the alimentary canal {defeecation). 
 
 In examining the digestive process in the inferior classes of animals, various mo- 
 difications are found to take place in it, according to peculiarities in the habits of 
 the animals, or in the nature of their food; and also according to the complexity of 
 organization exhibited by them. 
 
 In Mammalia, modiiications occur in the masticatory process ;, the vegetable feeder 
 requiring a more complicated dental apparatus ; the carnivora being provided with 
 teeth of a simpler construction, but more fitted for seizing and lacerating the prey. 
 In others, again, the teeth are adapted to feed on insects, the Insectivora; in others, 
 the Rodentia, certain teeth are constructed for gnawing dry and resisting substances ; 
 whilst in some of the whales, there are no teeth at all, strictly speaking, but only an 
 apparatus which will allow of retaining the finer kinds of food in their passage into 
 the mouth of the animal. The other sub-processes of digestion are carried on very 
 much upon the same plan as in the human subject, with only such variations as the 
 habits of life of the animals may render necessary. Thus, in a large tribe of Mam- 
 mals, the Rummaniia, the food is macerated in a complex stomach, prior to, as well 
 as after, it has been subjected to a more complete mastication than is employed in 
 any other animals. In these, as well as in all vegetable feeders, the intestinal canal 
 is very long and capacious, and the ccscum of great size. In the Carnivora the 
 stomach is simple, and the intestines short and narrow. 
 
 In Birds there are no teeth; and mastication, properly so called, is effected in the 
 stomach, a portion of which (the gizzard) acquires a great increase of muscular 
 power, and is lined by a dense cuticle, and thus becomes a powerful organ for 
 triturating the food, the bird swallowing pieces of flint or other hard substances to 
 aid the mechanical reduction. ■ Insalivation is but slightly developed, excepting in the 
 woodpecker, where very large salivary glands pour out a considerable quantity of 
 saliva to aid the bird in picking the dry bark and wood of trees. In some birds, how- 
 ever, a dilated portion of the 03sophagus'(the crop) gives lodgment to the food for a 
 time, and pours out from its maeous membrane a fluid which probably performs an 
 office similar to that of the saliva, and which at least must serve to moisten the food 
 before it passes further along the digestive tube. Chymification and chylification 
 are essentially the same as in Mammals ; and there are likewise similar differences 
 as regards the length and development of the intestinal tube in carnivorous and 
 herbivorous birds. In Reptiles the digestive process is, on the whole, simpler than in 
 the preceding classes; but there are the same sub-processes, the alimentary canal 
 being of a simple construction. The dental apparatus varies according to the mode 
 of life of the reptile, (the fangs of serpents having evident reference to the predatory 
 habits of that class of reptiles,) excepting so far as the beak may be regarded as a 
 substitute; and in some, as the chelonia, it is entirely absent. In Fishes there are well 
 developed teeth of various forms, and often very numerous, with a simple stomach 
 and intestine, but no salivary apparatus. 
 
 In the higher Invertebrata the digestive process is carried on upon the same plan as 
 in the vertebrata. In the Cephalopods, there are powerful instruments of prehension 
 in the arms or tentacles which surround the animal's mouth and head. These 
 
514 DIGESTION. 
 
 animals enjoy a certain power of mastication by teeth, and some of ihem have a 
 gizzard. All the Mollusca have a large liver; but other glandular organs connected 
 with the intestinal canal, and more or less subservient to digestion, namely, ihe 
 pancreas and spleen, are absent. The stomach and intestinal tube are very much 
 I as in the vertebrata. The articulata have also a digestive system like that in the 
 
 vertebrate classes, but the liver is small, and developed in the rudimentary form of 
 coecal tubes opening into Ihe intestine. 
 
 In the lower Invertebrala digestion becomes very simple. The intestine and 
 stomach become much reduced in size ; and in some the digestive apparatus con- 
 sists only of a simple bag, as in the fresh water polyps, having the same orifice of 
 entrance and exit; or, of a series of sacs or bags, with certain tubular appendages, 
 as in the Asterias, and in the Actinia; in these latter animals one orifice answers 
 equally for the introduction of the food, and for the discharge of the superfluous 
 matters. In MedusEe, the oral aperture leads to a capacious cavity or stomach, 
 from which certain canals carry the nutritious material into the different parts of the 
 body ; these canals being probably analogous to the circulating systems of the higher 
 animals. In some polyps, the Sryozoa, as shown by Dr. Arthur Farre, a portion 
 of the stomach exhibits great muscular power, and seems to perform the function 
 of a gizzard. 
 
 We shall find it convenient to examine the function of digestion by 
 tracing it through the various stages, as above enumerated, describing 
 the mechanism of each of the subordinate processes, and the change 
 ■which each of them is capable of effecting in the food. 
 
 Before we enter upon these points, vre must make some remarks 
 upon the nature and quantity of the food suitable for the nourishment 
 of man. 
 
 It has been already remarked ki a former page (p. 59), thai no 
 food is suitable for the support of the human frame in a healthy state, 
 but that which contains the great staminal principles, which are the 
 chief constituents of the body. And the same remark applies with 
 equal force to the carnivorous, and probably to the herbivorous classes 
 of animals. 
 
 The food of the lower animals varies to a remarkable extent. But 
 nearly, if not entirely, throughout the series, organized matter, either 
 vegetable or animal, forms the proper nutrient material. It is pro- 
 bable that some of the lowest creatures enjoy the power of assimi- 
 lating inorganic matter, and thus become the instruments of making 
 the inorganic substances indirectly subservient to the nutrition of the 
 higher animals. 
 
 The elements of nutrition for man, and the higher classes of ani- 
 mals, exist in the vegetable as well as in the animal kingdom. But 
 some animals are so constituted, that, in a state of nature, they sub- 
 sist only on the flesh of other animals; while others live only upon 
 vegetable food. Some carnivorous animals, however, may, in a state 
 of domestication, be brought to eat vegetable food; but it rarely, if 
 A^ *,(>•■ ever, happens that the herbivora can be taught to eat animal food. 
 "^ Man is, by nature, a truly omnivorous animal; and a certain admix- 
 
 ture of animal and vegetable food is known, by experience, to be 
 that which is most conducive to his healthy nourishment. 
 
 The classification of food which Dr. Prout has adopted, appears 
 to us to be eminently practical — and on that account we recommend 
 it to the attention of our readers. As water enters so largely into 
 the constitution of the body, being essential to the integrity and to 
 the vital action of the solids, and as it forms the principal part of the 
 
CLASSIFICATION OF FOOD. 515 
 
 blood, it is necessary that all animals should be supplied with liquid 
 food in some shape. Accordingly, water, either alone or holding 
 important nutrient elements in suspension or solution, forms part of 
 the food of all animals — the aqueous group of alimentary materials 
 of Prout. 
 
 A large number of substances derived from the vegetable kingdom, 
 constitute the saccharine group of Dr. Prout. These are character- 
 ized by being composed of carbon, united to hydrogen and oxygen, 
 in the proportions in which these latter elements form water ; the pro- 
 portion of the carbon varying from 30 to 50 per cent. (See Proufs 
 papers in the Phil. Trans.) This group comprehends sugars, starch, 
 gums, vinegar. These substances are contained in vegetables of 
 various kinds, sometimes forming their principal constituent, and at 
 other times combined with other nutrient principles. 
 
 The oily or oleaginous group of alimentary substances comprehends 
 all those substances whose composition consists of defiant gas and 
 water. It includes the various fats and oils, as well as alcohol. It 
 resembles in ultimate constitution the saccharine group ; the propor- 
 tion of carbon in the various substances contained in it varying from 
 60 to 80 per cent. 
 
 A fourth group, the albuminous, is made up of all those substances 
 which contain nitrogen — such as fibrine, gelatine, albumen, caseine, 
 Vegetable gluten. All the materials which make up this group are 
 derivet^ generally from the animal kingdom, with the exception of the 
 last, which is contained in great abundance in wheat ; similar, if not 
 identical, principles exist in vegetables. Wheat, indeed, consists of 
 two substances — one referable to the saccharine group, the other to 
 the albuminous, the former consisting of starch, the latter of gluten. 
 This fact was recognized more than a century ago (an. 1742) by Bec- 
 caria, who assigned the glutinous portion to the nourishment of the 
 nitrogenous tissues of the body. (Dr. Thomson, Med. Chir. Trans,, 
 1846.) 
 
 In milk we find a natural combination of all the various substances 
 employed for nutrition — and it is a fact of the highest interest that 
 this product of animal secretion, elaborated for the nourishment of the 
 young, should contain one or more substances for each of the above- 
 named groups of alimentary materials. 
 
 Thus, milk consists of water, sugar, oily matters (butter), caseine ; 
 and wheat, a substance of almost universal application for food, ex- 
 hibits an analogous union of starch, the representative of the saccha- 
 rine group — and of gluten, representing the albuminous. 
 
 It must be borne in mind that the albuminous aliments are distin- 
 guished from those of other groups by their containing nitrogen. Food 
 of this kind is especially fitted to be directly assimilated to muscle, 
 nerve, and the other animal tissues, into the composition of which 
 nitrogen enters largely. These aliments contribute directly to the 
 formation of the blood, from which the tissues attract the principles 
 most proper for their nourishment. 
 
 The non-nitrogenous aliments are obviously fitted to nourish those 
 textures which do not contain nitrogen, as the fat ; or to supply those 
 
516 DIGESTION. 
 
 secretions in which carbon abounds, as the bile. Moreover, they 
 furnish those large supplies of carbon which, we are warranted in 
 supposing, the animal economy stands greatly in need of, not only 
 from the great amount of that element which is to be found in all the 
 tissues, but also from the large excretion of carbonic acid w'hich is 
 constantly taking place from the respiratory and other surfaces of the 
 animal body. The formation of carbonic acid in the economy by the 
 union of carbon and oxygen is, no doubt, the immediate cause of the 
 generation of animal heat, and thus the supply of carbon in the food 
 becomes of great importance to the maintenance of the proper tem- 
 perature of animals. 
 
 From the natural subdivision of the food of man into two classes 
 — one, consisting of the nitrogenized matters, well adapted by their 
 constitution for the formation of blood, and the other, the non-nitro- 
 genized substances, serving to supply a large amount of carbon — 
 Liebig proposes to name the former the plastic elements of nutrition, 
 and the latter elements of respiration. 
 
 To the first term we see no objection — but the use of any term 
 which would imply that respiration must be, as it were, fed directly 
 through the digestive process, appears to us scarcely consistent with 
 the real facts of the case. The respiratory process is partly a process 
 of supply, and partly one of depuration. It supplies oxygen, and it 
 assists in the removal of effete matters in the shape of carbonic acid. 
 The effete particles of the tissues would probably supply sufficient 
 carbonic acid to effect the attraction of the required amount of oxygen 
 — but as the supply of oxygen has the ulterior object of generating a 
 due amount of heat, there will be required for this purpose a larger 
 quantity of carbon than can be obtained merely from the destructive 
 assimilation of the tissues (to use Dr. Prout's expression). Hence, 
 for this purpose, a special supply of carbonaceous material must be 
 furnished to the blood — and this is derived from the non-azotized 
 alimentary substances. We prefer, then, the terms lately proposed 
 by Dr. R. D. Thomson, namely, calorifadent for the non-nitrogenized 
 substances, ntitritive for the azotized matters. 
 
 It is proper to notice that azotized matters may be calorifacient, 
 rnasrauch as they contain a large quantity of carbon ; and it is known 
 that large tribes of men live on animal food alone. A large number 
 of North American Indians, according to Cattlin, live almost exclu- 
 sively on the flesh of the buffalo, the only non-azotized food which 
 they obtain being the fat belonging to it. 
 
 In determining the nature of the diet to be furnished, in order to 
 preserve man in a healthy state, care must be taken to provide for 
 the calorific as well as the nutrient function; and hence the admixture 
 of a certain quantity of non-azotized food is needed for the former 
 function. In the cold northern climates the natives instinctively feed 
 on fat and oily food, which contains a large per centage of carbon ; 
 while the natives of the warm south feed on fruits, which, as Liebig 
 says, contain no more than twelve per cent, of carbon. Milk, the 
 food of the young, in whom the production of heat ought to be most 
 active, contains, according to Dr. Thomson, two parts of calorifa- 
 
DIET. 517 
 
 cient for one of nutritive matter. Eggs also contain nutritive matter 
 in a concentrated form, consisting chiefly of pure albumen, to which 
 a considerable quantity of calorifacient matter is added in the oleagi- 
 nous yolk. The accumulation of these substances, as a natural 
 provision for the nourishment of the young, whilst yet under the sole 
 guidance of the purest instinct, or, as in the egg, where the nutrient 
 matter is directly absorbed by the tissues of the embryo, affords the 
 surest indication that a compound food, consisting of such elements, 
 is necessary for perfect nutrition at this period of life. As age ad- 
 vances, or the generation of animal heat becomes less active, the 
 quantity of calorifacient food required is less, and that of the purely 
 nutrient food more. 
 
 . Experience justifies the conclusion to which our reasoning on 
 these points leads, namely, that in the temperate climates the proper 
 nutrient materials for infancy and childhood are milk, saccharine and 
 amylaceous substances, the latter being combined with gluten ; and 
 that to these must be added a certain amount of gelatine, albumen, 
 and fibrine, when the growth of the child and the more active play 
 of its nervous and muscular, systems call for a further supply of 
 nitrogenized food. In adult life, azotized substances are needed, as 
 a principal portion of the diet, to supply the waste which mental and 
 bodily exertion gives rise to. 
 
 It must be confessed, however, that the views which theory sug- 
 gests upon this subject are not such as would enable us with benefit, 
 or even with safety, to determine the suitable diet for man. We 
 learn much from instinct and more from experience, which we could 
 never have gathered from a priori reasoning. Thus the importance 
 of the admixture of vegetable w^th animal food could never have 
 been determined without the aid of the experience afforded by the 
 melancholy instances of disease generated by the privation of the 
 former kind of aliment. Scurvy, as it is now well known, is fre- 
 quently due to the want of a proper supply of fresh vegetable food ; 
 and it may be quickly and effectually cured by supplying this want. 
 Again, it cannot be the deficiency of any of the staminal principles 
 which givel rise to scurvy, because these exist in abundance in the 
 animal food ; and scurvy, it must be remembered, will occur in the 
 midst of plenty of this kind of food. The disease is due to the 
 deficiency of some unknown material necessary to health, which the 
 vegetable kingdom alone can supply ; and which, apparently, is most 
 readily obtained from citric acid, lemon or lime-juice, or vegetables 
 containing citric acid in good quantity, as the potatoe. 
 
 Nevertheless, the results of investigations as to the influence of 
 particular kinds of diet in modifying nutrition, are strongly confirma- 
 tory of the views expressed above. Diet may be insufficient, either 
 from its being given in too small quantity, or from its being defective 
 in some principle, essential or incidental, necessary to the health of 
 the blood — that fluid, upon the healthy condition of which the proper 
 nourishment of the body depends. The effects of a diet scanty in 
 quantity, although not objectionable in quality, are visible in the 
 general emaciation, the wasting of all the tissues, and the consequent 
 
518 DIGESTION. 
 
 debility. If dissolution be slow, the great non-nitrogenlzed material 
 of the body, fat, is employed to supply the animal heat, as is strik- 
 ingly seen in hyi)ernating animals. Specific effects follow the absence 
 of certain elements of the food, even although the absolute quantity 
 of it be abundant. If nitrogen be deficient in quantity, or alto- 
 gether absent, the imperfect nutrition shows itself in the form of 
 ulcerations of particular textures. Those tissues suffer most in which 
 there is but little inherent activity of nutrition, or which are exposed 
 to the contact of vitiated secretions. In Magendie's well-known ex- 
 periments of feeding dogs upon sugar and water, the cornea of the 
 eye ulcerated, and destruction of the organ ensued upon the conse- 
 quent evacuation of the humors. Similar cases now and then occur 
 in the human subject from the supplies of nourishment being inade- 
 quate. Ulcers are very apt to show themselves on the mucous mem- 
 brane of the alimentary canal ; they will form in the mouth or in the 
 intestine. These signs may be accompanied with a more or less 
 •scorbutic state, as shown in spongy gums, subcutaneous ecchyraoses, 
 &c., according to the extent to which the blood has suffered ; they 
 may occur, too, where there is abundance of fat, although wasting of 
 muscles. If the supply of non-nitrogenous food be large, fat will be 
 formed. When Magendie fed dogs exclusively on fat, there were 
 ulceration of the cornea and wasting of muscle, but the tissues were 
 infiltrated with fat. The case of the ill-fated Dr. Stark illustrated the 
 effects of the long continuance of a diet deficient in nitrogen. This 
 physician, with ill-directed zeal, dieted himself for four months chiefly 
 on non-azotized food, water, butter, oil, sugar, taking only bread in 
 small quantity, and meat or fish occasionally as azotized food. In a 
 short time, well-marked scorbutic symptoms showed themselves without 
 any diminution in the fat of his body ; but subsequently diarrhoea, 
 the result of ulceration of the intestinal mucous membrane, came on, 
 and terminated his career. 
 
 Of the Quantify of Food necessary for Health. — The proper quantity 
 of food necessary for the support of general nutrition in a healthy 
 state can only be determined by the results of observation and ex- 
 periment ; and the best mode of gaining information on this point is 
 to cohsult the diet tables of various public institutions, in which due 
 attention is paid to the health of the inmates, or to ascertain the 
 allowances which are found sufficient for the army and navy. Each 
 seaman in the British naval service, is allowed from 31 to 35J ounces 
 of dry nutritious food daily, of which 26 ounces are vegetable and 
 the rest animal, the latter consisting of nine ounces of salt meat or 
 4^ of fresh. Sugar and cocoa are also given. The soldier is allowed 
 a pound of bread and three quarters of a pound of meat. In most 
 of. the London hospitals, full diet, which is given to convalescent 
 patients who need a liberal diet, consists generally of half a pound 
 of meat, with from 12 to 14 ounces of bread, half a pound of pota- 
 toes, a pint of milk, and sometimes beer or porter, a pint of the former 
 or half a pint of the latter. The former dietary is destined for men 
 who must be in readiness for the most active athletic exercises, re- 
 quiring not only great muscular strength, but also considerable power 
 
DIET. 519 
 
 of enduring fatigue. The latter is intended to recruit the powers of 
 those who have been suffering from disease. If, now, we compare 
 with these a dietary which has been found sufficient for the support 
 of health in a state of more or less confinement, with a moderate 
 amount of daily labour, we may fairly infer that the proper allowance 
 for persons not engaged in actual manual labour lies between these 
 extremes. In the union workhouses of England, able-bodied men 
 obtain about 25 ounces of solid food daily, of which the quantity of 
 meat does not exceed 5 or 6 ounces. In prisons it has been found 
 necessary to give a certain amount of animal food to prisoners who 
 are subject to hard labour. Each of such prisoners, if confined for a 
 term exceeding three months, and kept at hard labour, has a daily 
 allowance of about 36 ounces of food, of which meat constitutes only 
 a very small portion, namely, about 16 ounces in the week, four ounces 
 on each of four days in the week. The prisoner has obviously the 
 advantage of the poor man, whose only crime is poverty. But there 
 is doubtless sufficient justification for this, in the fact that the labour of 
 the prison, and the mental depression which long-continued restraint 
 and confinement induce, render a greater amount of nutriment neces- 
 sary than the indigent would require who seek in the workhouse a 
 shelter from absolute want. 
 
 It is plain, then, that a daily amount of food, varying in quantity 
 between 35 and 25 ounces, is sufficient to maintain health; but of 
 this a fourth or a fifth ought to be animal food, especially when bodily 
 exertion is being used. An amount greater than this is prejudicial, 
 as affording material for' the formation of new compounds, which 
 serve only as materies morhi that may contaminate various tissues or 
 organs, and impair their physical and vital properties. A lesser 
 quantity, on the other hand, makes a poor blood, weakens the co- 
 hesive power of its elements as well as the attractive force of the tis- 
 sues; and thus, in this latter case, materies morhi may be generated 
 from the decomposition or the imperfect composition of the elements 
 of the blood, and the tissues will suffer partly from not appropriating 
 a sufficient quantity of the nutritious elements contained in the blood, 
 and partly from the inferior quality of those elements themselves, 
 which are probably also contaminated by some new compound. 
 
 In proportion as our knowledge of pathology, or the intimate nature 
 of disease, extends, we become better able to treat disease with ad- 
 vantage on physiological principles ; and it must be evident to all, 
 who fairly consider the subject, that nothing is more important than 
 to determine the proper diet suitable to particular maladies. We 
 must not content ourselves merely with starving or feeding a diseased 
 person ; but we must give him that kind of food (whether in large or 
 small quantity) which his digestive organs can most readily assimilate, 
 and which will not serve as pabulum to the morbid matter which is 
 apt to be generated in hii system. It is in diseases of the kidneys 
 and liver that the most manifest good is derived from a well directed 
 dietetic system. In diabetes it has long been determined that a diet 
 of animal food, with abstinence from sugar, and substances, such as 
 starch, capable of being converted into sugar, is productive of excel- 
 
520 DIGESTION. 
 
 lent results. In diseases of the liver, more is to be gained by close 
 attention to the quantity of the food than to the quality; at the same 
 time that it must be borne in mind that a nitrogenized diet is more 
 suitable than one abounding in carbon, which would throw upon that 
 organ a work of elimination greater than it may be able to bear. In 
 the rheumatic and gouty diatheses attention to diet is the main re- 
 source to counteract the tendency to generate the morbid agents which 
 severally produce those states of constitution. 
 
 When there is a tendency to the accumulation of fat, a nitrogenized 
 diet in regulated quantity is the most suitable to obviate it. When 
 more carbon enters the system than is required for the calorifacient 
 and respiratory functions, or for the nourishment of tissues, it will ac- 
 cumulate as fat : and it is only to be removed by the free admission 
 of oxygen to consume it, care being taken at the same time not to 
 favour further accumulation by the supply of too much food, especially 
 of the non-azotized kind. The practice of trainers furnishes a useful 
 commentary on this point, and may be imitated by many who suffer 
 from dyspepsia. The following account of the system pursued in 
 training was communicated to Sir John Sinclair by Mr. Jackson : — 
 
 " The diet is simple — animal food alone ; and it is recommended 
 to take very little salt and some vinegar with the food, which prevents 
 thirst, and is good to promote leanness. Vegetables are never given, 
 as turnips, carrots, and potatoes ; but bread is allowed, only it must 
 be stale. They breakfast upon meat about eight o'clock, and dine at 
 two. Suppers are not recommended, but they may take a biscuit and 
 a little cold meat about eight o'clock, two hours before they go to 
 bed. It is reckoned much against a man's wind to go to bed with a 
 full stomach, and they in general take a walk after supper. Some 
 people will have tea ; but it is not recommended, nor is it strengthen- 
 ing, and no liquor is given warm. Full and substantial meals are 
 given at breakfast and dinner ; beef and mutton are best. It is con- 
 tended that there is more nourishment in the lean of meat than the 
 fat, which is fully proved by experiment, fat, being of a greasy nature, 
 causes bile, and palls tlie stomach: the lean of fat meat is best. Veal 
 and lamb are never given, nor is pork. The legs of fowls, being 
 sinewy, are much approved of. The yolk of a raw egg is reckoned 
 the best thing in a morning, and is supposed to prevent bilious com- 
 plaints. Beefsteaks are reckoned very good, and rather underdone 
 than otherwise, as all meat in general is; and it is better to have the 
 meat broiled than roasted or boiled, by which nutriment is lost. No 
 fish whatever is allowed, because it is reckoned watery, and not to 
 be compared with meat in point of nutriment. The fat of meat is 
 never given, but the lean of the best meat. No butter nor cheese on 
 any account ; cheese is indigestible. Meat must be dressed as plain 
 as possible without seasoning of any kind. Men will live longer on 
 beef, without change, than on any other kind of animal food, but 
 mutton is reckoned most easily digested. The meat must always be 
 fresh, and never salted. No quantity of meat is fixed; it depends 
 upon the constitution and appetite. Little men will eat as much as 
 large men, and very frequently more. Pies and puddings are never 
 
HUNGER. i 521 
 
 given, nor any kind of pastry ; as to hard dumplings, people may as 
 ■well take earthenware into their stomachs." 
 
 This system, it must be remembered, is combined with one of 
 active and even severe exercise. 
 
 The periods for taking food, and the quantity to be taken, are 
 under the natural guidance of certain sensations, which we call Hun- 
 ger, Thirst, and Satiety. 
 
 Hunger, — The immediate cause of hunger cannot be explained^ 
 It is probably a sensation dependent on a peculiar condition of the 
 mucous membrane of the stomach, which certain states of disease 
 may blunt or may increase to an inconvenient extent, as in diabetes. 
 The nerve which is instrumental in this sensation is probably the 
 vagus nerve by its gastric branches, but there is no reason for deny- 
 ing to the sympathetic nerves, distributed to the stomach, some share 
 in this phenomenon. The experiments of Brachet and Dr. John 
 Reid, relative to the influence of the nerves on hunger, lead to no 
 satisfactory conclusion, because of the difiiculty of interpreting the 
 sensations of dumb animals, and the probability that appetite would 
 be destroyed or impaired after any serious operation^, even although 
 the injured nerve had nothing to do with the stomach. The sensa- 
 tions caused by extreme hunger would indicate that some further 
 change was taking place in the wall of the stomach. A peculiar 
 sense of sinking referable to the gastric region, general faintness, 
 secretion of gas into the stomach, and sometimes actual pain, accom- 
 pany this state. 
 
 When these sensations are not relieved by their appropriate stimu- 
 lus, food, the effects of fasting begin to show themselves. The body 
 now feeds upon itself — in other words, the process of destructive 
 assimilation is the only source from whence the blood derives its 
 materials of supply. All the tissues show the effects of impaired 
 nutrition in the deficient manifestation of their vital powers — the 
 animal loses weight, and, according to Chossat, this loss is most 
 rapid the few days immediately preceding death. The tissue which 
 wastes most is fat, and those which lose least are the osseous tissue 
 and the nervous. There is also great loss of heat; Chossat states 
 that the daily fall was half a degree of Fahrenheit ; but on the last 
 day it fell much more rapidly,*reducing the temperature to 77°. The 
 stomach is much contracted, and its mucous membrane thrown into 
 thick folds or rugae. The gall bladder is generally full to distentionj 
 the intestines are contracted like the stomach ; according to Collard 
 de Martigny, the lymphatics become full in the first ten days of fast- 
 ing, but afterwards their contents decrease considerably. The respi- 
 ratory movements become slow, and the pulse falls considerably in 
 frequency. The urine becomes scanty, and all the parenchymatous 
 organs are remarkable for their paleness. Furious delirium frequently 
 manifests itself, when the loss of strength becomes considerable. A 
 similar delirium sometimes ensues where too rigid an abstinence has 
 been observed in the treatment of disease. 
 
 The period at which death occurs from protracted abstinence 
 varies greatly ; young animals die sooner than old ones. Dogs live 
 
522 DIGESTION. 
 
 from twenty-five to thirty-six days. In man, total privation is not 
 borne above a week. By the aid of a little drink, given now and 
 then, life may be prolonged considerably, and instances are recorded 
 where it continued for eighteen or nineteen days, or even for thirty 
 days. Dr. Wilian saw a gentleman who voluntarily abstained from 
 everything but water, flavored with orange-juice, for sixty days, and 
 then died. Medical men, however, should exercise much circum- 
 spection in cases of professed abstinence, numerous impostures hav- 
 ing been practised on this subject. 
 
 Thirst results from a peculiar state of the mucous membrane of the 
 digestive tube, but more especially of the mucous membrane of the 
 mouth and fauces, caused by the imperfect supply of liquid. A sense 
 of clamminess in the mouth, pharynx, and even down the oesopha- 
 gus, accompanies extreme thirst. The thirst in fevers is probably 
 due to the state of the blood and the consequent change in the secre- 
 tions. Injecting thin fluids, as water, into the blood, relieves the 
 thirst of poisoned animals, as found by Dupuytren and Orfila. In- 
 jecting liquids into the stomach relieves thirst, as was found in a 
 case where the oesophagus had been wounded. 
 
 On the subjects of this chapter the reader may be referred to Dr. Front's papers 
 and works — Dr. Paris on Diet — Dr. Pereira's work on the same subject — Dr. Stark's 
 ■works — Dr. Latham's account of the disease prevalent at the Penitentiary, 1825 — 
 Dr. Budd's lectures on diseases produced by insufficient nourishment, Med. Gazette 
 — Sir John Sinclair's Code of Health, in which many interesting tracts relating to 
 diet and regimen have been preserved — Tiedemann,Physiologie, Band. iii. — Liebig's 
 AnimaJ Chemistry — Dr. K. D. Thomson on Food. 
 
 CHAPTER XXIII. 
 
 OF DIGESTION. PREPARATORY PROCESSES ; VIZ. PREHENSION, MASTICA' 
 
 TION, INSALIVATION, DEGLUTITIOl 
 CONCERNED IN THESE PROCESSES. 
 
 TION, INSALIVATION, DEGLUTITION ; THE ANATOMY OF THE ORGANS 
 
 « 
 
 In the present chapter we shall consider the preliminary stages in 
 the function of digestion, under which head may be included all those 
 which precede the entrance of the food into the stomach. 
 
 • In entering on a consideration of the alimentary processes, a few words may be 
 conveniently introduced regarding the general anatomy of the mucous system, a term 
 under which we include the skin, mucous membranes, and true glands, all of which 
 are continuous with one another, and composed essentially of similar parts. The 
 skin and the glands pertaining to it, as well as several parts of the mucous mem- 
 branes, have been already minutely described in treating of the organs of sense. It 
 only remains, therefore, to speak of the great internal mucous tracts, with their asso- 
 ciated glands. 
 
 The alimentary mucous membrane commences at the lips, and lines the passages 
 traversed by the food from the mouth to the anus. The principal glands whose ducts 
 open upon it, are the mucous and salivary glands, the pancreas, and the liver. Be- 
 sides these, its thickness is made up, in the stomach and small intestines, of an inii- 
 
OF PREHENSION.— THE LIPS. 523 
 
 Of Prehension, or the taking of food into the mouth, little needs be 
 said. It is performed chiefly by the hand, that wonderful instrument 
 of man's lower instincts as well as of his higher attributes. The lips 
 and cheeks, as well as the anterior teeth, and the tongue, are also 
 concerned in this function. 
 
 The lips are endowed with great sensibility, derived from the su- 
 perior and inferior maxillary divisions of the fifth pair of nerves, and 
 are covered with largely developed papillse of touch, which receive 
 
 nite series of tubular offsets, vertically arranged, pouring their contents on its free 
 surface, and forming an involuted or compound membrane, or a diffused or membranous 
 gland. The respiratory mucous membrane begins at the nostrils, sends processes to 
 the olfactory, the optic, and the auditory organs, and lines the air-passages to their 
 terminations; numerous mucous glands occur in this tract, has^ly, the genilo-urii- 
 nary mucous membrane commences at the genito-urinary orifices, lines the excretory 
 passages pertaining to both functions, and is the essential constituent of the glands 
 of both. In the female, however, there is an exception in the case of the ovaries, as 
 will be explained in a subsequent page. 
 
 Penetrating into all the recesses of the mucous system, and forming its chief bulk, 
 ■we find nucleated particles, arranged as a layer, and developed in succession, in such 
 a manner that the old ones disappear, while others advance from below. An epithcT. 
 Hum, is not peculiar to the mucous system, butis met with also on serous membranes, 
 and on the walls of the blood and lymphatic vessels, as well as elsewhere ; but it is 
 distinguished here by its external position as regards other textures, so as to be ca- 
 pable of passing from the body, or to be exposed to the contact of foreign substances. 
 The particles of this epithelium are very different in different parts, and may be di- 
 vided into scaly, columnar, glandular, and ciliated. The scaly variety is seen on the 
 skin, and in the alimentary tract as low as the stomach, as well as in the excretory 
 parts of the genito-urinary tract. (See vol. i. pp. 404, 412, 437, &c.) The columnar 
 variety consists of rod-like particles, placed endwise, generally bulged near the cen- 
 tre by the nucleus, and narrowest at the point of attachment. They are met with in 
 the air-passages, on the intestinal villi, in the bile-ducts, and elsewhere. The glandtt- 
 lar variety is bulky, its particles rather globular than flat or long, and found in all the 
 glands, the several secretions being essentially the contents or substance of the par- 
 ticles set free. The ciliated particles are columnar or sub-globular in shape, but 
 clothed on their free margin with cilia, as in the examples formerly figured, (vol. i. 
 p. 62, and ante, p. 4.) They are found chiefly in the respiratory tract, and in parts of 
 the genital tract of the female. The true scaly and glandular varieties of epithelium 
 are never ciliated. See Cyclop. Anat.,'art. Mucous Membrane. 
 
 The epithelium rests for the most part on a layer of membrane, hence termed base- 
 ment membrane, which, in the best-marked examples, is distinctly homogeneous and 
 transparent, but in some situations is finely fibrous, and not easily separable from 
 the areolar and other tissues which lie below it. These two, the epithelium and the 
 basement membrane, may be regarded as the constituents of a simple mucous mem- 
 brane, although the latter cannot be everywhere traced, for example, in the interior of 
 the hepatic lobules. The office of the basement membrane seems to be in all cases 
 to sustain the epithelium, and to shut in or cover over those tissues which may be 
 regarded as internal to the elements of the simple mucous membrane. Professor 
 Goodsir considers that the basement membrane is covered with points, which he 
 terms centres of nutrition, from which the development of the particles of epithelium 
 proceeds; but we cannot accede to this view; first, because the best examples of 
 basement membrane display no such points ; and, secondly, because such a suppo- 
 sition does nothing to explain the successive growth of the particles. 
 
 The tissues which lie under the simple mucous membrane, as now sketched out, 
 are areolar tissue, blood, and lymphatic vessels, and nerves, and in some situations a 
 peculiar papillary tissue. These, in iheir several forms and proportions, greatly 
 modify the characters of the membrane, as it is presented to the naked eye, and con- 
 tribute largely to our common notions of the structure of the skin, mucous mem- 
 branes, and glands. The areolar tissue forms the cutis vera of the skin, (vol. i. p. 
 406,) and the corresponding part of the great mucous tracts ; while in glands it is 
 generally in much smaller quantity. The blood-vessels and other textures are modi- 
 fied in various ways, as will be hereafter noticed in detail. 
 
524 DIGESTION. 
 
 an abundant supply of blood from the coronary arteries. Along their 
 margin the skin becomes continuous with the mucous membrane of 
 the digestive apparatus, ■which, within these parts, as well as over 
 the rest of the mouth, the pharynx and cesophagus, as far as the sto- 
 mach, has an epithelium of the scaly variety ; this variety forming 
 the most essential character of that subdivision of the digestive appa- 
 ratus considered in this chapter. The lips are moved by about twenty 
 muscles, and are capable of grasping and retaining the food placed 
 within them, and of aiding in the subsequent motions which it is 
 made to undergo in the mouth. Their employment in articulation 
 will be spoken of in another place. 
 
 The lips and the tongue undergo a variety of modifications in the animal series, 
 with reference to the function of prehension ; among these may be enumerated the 
 enlarged, pendulous, and very movable lips of the. ruminants and solipeds, and of 
 some montceys. Man uses his lips in suction, as do the young of all mammalia, at 
 the breast. Among fishes, the cyclostomatous group (as the lamprey) have a suc- 
 tion power of a similar kind, their circular mouth being surrounded and supported 
 by a ring of cartilage, and furnished with appropriate muscles for producing adhe- 
 sion to surfaces to which it is applied. In birds, the lips are modified so as to form 
 the bill, which is always the prehensile organ in that class. 
 
 The tongue is used by man and animals in suction, somewhat as a 
 piston, being drawn within the mouth so as to exhaust the anterior 
 part of that cavity, and allow fluids to enter by the atmospheric pres- 
 sure. The canine and feline races employ the tongue to lap fluids^ 
 the giraffe twines this organ around the leaves and branches of trees, 
 and detaches them with force. The ant-eaters have a remarkably 
 long tongue, covered with a* slimy secretion ; this they protrude, and 
 upon it entrap their victims. The caraeleon among reptiles, and the 
 woodpecker among birds, have each a tongue enormously developed 
 for the purposes of prehension : to these many other striking exam- 
 ples might be added. 
 
 The cavity of the mouth, in which' mastication is conducted, is 
 bounded, first, by the palate or roof of the mouth, a fixed and hard 
 surface formed by parts of the upper maxillary and palate bones, 
 supporting a dense fibrous structure, lined with closely adherent mu- 
 cous membrane, and fitted to act as a resisting surface against which 
 the tongue may press the food ; and, secondly, by the cheeks, lips, 
 and tongue, which, in reference to the present function, may be 
 classed together as tactile and muscular organs, designed to handle 
 the food while subjected within the mouth to the action of the teeth, 
 and then to forward it into the pharynx. Projecting into the mouth, 
 above and below, is an arched series of teeth, or grinding organs, 
 firmly fixed by roots into the alveoli of the upper and lower maxillary 
 bones. , Those of the upper jaw are immovable, or only movable 
 with the entire head ; but those of the lower jaw are capable of up- 
 ward, downward, backward, forward, and lateral motions, by means 
 of the muscles of mastication acting on the bone in which they are 
 implanted. By these motions of the lower teeth upon the upper, the 
 food is comminuted. A more detailed description of some of the 
 organs of mastication may now be given. 
 
 The cheeks form the outer wall of that part of the mouth which 
 
THE TONCFTTE.— THE TEETH. 525 
 
 lies outside the teeth. Like the lips with which they are continuous, 
 they consist of a muscular stratum interposed between the skin and 
 the mucous membrane of the mouth. They admit of distention and 
 compression, and form pouches which receive portions of food escap- 
 ing outside the teeth during mastication, and from which it is continu- 
 ally returned towards the inner cavity, to be submitted to the grinding 
 action. This use of the cheek is well exemplified in cases of paralysis 
 of the buccinator muscle, in which the food collects in the flaccid bag 
 to which this part is then reduced. 
 
 The tongue is an important agent of mastication, and has been al- 
 ready spoken of as the seat of taste and of an exquisite sense of touch. 
 By virtue of the latter it receives accurate impressions of the tangible 
 qualities of the food, and of its situation in the mouth ; and by its 
 great mobility it is constituted the main instrument by which the food 
 is moved within the mouth, so as to be effectually brought within the 
 range of the masticating organs. The tongue rests upon the hyoid 
 arch, to which, and to the concavity of the lower jaw, it is fixed by 
 the muscles. It lies within the curve of the teeth, and is covered on 
 its free surface with mucous membrane, which has been before de- 
 scribed. The muscular fibres which compose this organ intersect one 
 another in an intricate manner in its interior, but they all appear to 
 arrive ultimately at its dorsal surface, and to be there implanted, in 
 small sets or bundles, into the submucous stratum of dense areolar 
 tissue, a good deal of fat being disseminated throughout, but espe- 
 cially in the intervals between the muscular bundles at their insertion. 
 We refer to works on descriptive anatomy for the anatomy of these 
 muscles. By their action the upper surface of the tongue may be 
 made convex or hollow, or may be pressed forcibly against the roof 
 of the mouth ; the tip of the organ may be protruded or moved in 
 any direction, and to any recess within the cavity where food might 
 lodge, and the whole organ may be lowered or drawn back. These 
 several actions are so performed as to exemplify, in the most perfect 
 manner, the concert which has been already mentioned to occur be- 
 tween many muscular and sensitive parts. 
 
 Of tJie Teeth.' — These, in the widest acceptation of the term, and 
 in reference to the whole animal scale, are hard organs situated on 
 the inner surface of the digestive tube, fitted for comminuting the 
 food previous to its being acted on by the gastric juice. In the higher 
 classes they are of an osseous nature and fixed to bone, though not 
 originally. Among the invertebrata, the echini are remarkable for 
 their calcareous oral teeth, five in number. The mouth of the leech 
 is armed with three serrated teeth, worked by muscles, which saw 
 their way into the skin. In some insects the gizzard is armed with 
 a very complicated system of horny teeth. In the stomach of the 
 Crustacea is a cartilaginous framework, with projecting teeth, moved 
 by muscles, and capable of very powerful masticatory actions. Among 
 the gasteropods, the bullae have three stomach teeth ; and others, as 
 the Apiysia, a great multitude, of large size and of different forms. 
 
 True osseous teeth are found only in three classes of vertebrata, 
 viz., mammalia, reptiles, and fishes. Some of these, however, are 
 
526 DIGESTION. 
 
 •without them, as, among mammalia, the American ant-eater, the 
 manis, the echidna, the proper whales; among reptiles, the tortoises; 
 and the sturgeon among fishes. The teeth of fishes are fixed not 
 merely to the maxillary bones, but also to the palate and other bones, 
 bounding the mouth and throat, and they are often extremely nume- 
 rous. The bills of tortoises and birds perform some of the functions of 
 teeth ; but in those of the latter class which live on hard vegetable 
 substances, the muscular gizzard, with its hard cuticle, and by the 
 help of small angular stones which the instinct of the animals teaches 
 them to swallow with the food, performs the functions of a masticatory 
 apparatus. Among the mammalia, the teeth are few in number, and 
 limited to a single row in each jaw. 
 
 Teeth may be classed according to their shape and the function 
 they have to perform. Thus, the following varieties may be briefly 
 enumerated : — The cutting or gnawing teeth of the rabbit or beaver, 
 — the front teeth of man. The conical teeth of fishes for seizing and 
 retaining prey — the canine teeth of the lion and dog. The hinder 
 teeth of the carnivora, with several sharp elevations for tearing. The 
 more complex crushing teeth of the insectivora, and of the frugivor- 
 ous monkeys. Lastly, the true grinding teeth of granivorous and 
 graminivorous animals. 
 
 Of the Human Teeth. — The teeth in the adult human subject are 
 thirty-two in number, of which four are incisors, two canines, four 
 bicuspids, and six large molars, in each jaw. Those of the upper 
 jaw form the larger arch, so as to overlap those of the lower jaw in 
 front, and to overhang them somewhat at the sides, when the mouth 
 is closed. Each tooth has a crown or body, projecting above the gum, 
 and a roof, buried in the alveolus or'socket; and the division between 
 these is marked on the surface by a somewhat constricted line, termed 
 the neck. Each tooth has also an internal cavity; containing a vascular 
 and nervous pulp, and which is open only towards the root. Lastly, 
 each tooth consists mainly of a peculiar modification of osseous struc- 
 ture, termed dentine, or ivory, which is coated over with calcareous 
 enamel on the crown, and with a thin layer of true bone on the root. 
 The position and shape of the several varieties of the human teeth 
 are as follows : — 
 
 1. The incisors, or cutting teeth, are situated in front, (those of the 
 upper jaw being the larger,) and present a single conical root of large 
 size, and a vertical crown, bevelled behind so as to terminate in a 
 sharp horizontal edge. These teeth are fitted for cutting the food. 
 In herbivorous animals they crop the herbage, in rodents they are 
 capable of gnawing even very hard substances. 
 
 2. The canine teeth come next to, and are larger than, the incisors, 
 especially the root, which sinks deeply into the jaw, and renders the 
 alveolar arch prominent by its size. This root is conical, and the 
 crown more conical and less wedge-shaped than that of the incisors, 
 being usually surmounted with a small pointed tubercle or cusp, 
 whence they are termed cuspidate. In consequence of the small size 
 of the lower incisors, the lower canines are nearer together than the 
 upper, and fall within them when the mouth is closed. These teeth 
 
THE TEETH. 52T 
 
 in the canine, feline, and other carnivorous tribes, are largely deve- 
 loped, and more decidedly formed for lacerating and tearing the flesh 
 of prey. 
 
 3. The bicuspids, or false molars, are not so large as the canines, 
 which they succeed, but their crown presents two pyramidal emi- 
 nences, as their name implies, and there is a tendency in their root 
 to be double; this part being marked by a vertical groove, and its 
 apex, sometimes bifid, being perforated by two apertures leading to 
 the interior. 
 
 4. The true molars, or mulHcuspidate teeth, are placed most pos- 
 teriorly, and are distinguished by their great size, the square form 
 of their crown, surmounted by three, four, or five cusps, a distinct 
 neck, and by their shorter, but more divided root, which presents 
 from two to five branches, the inner the more divergent, and each 
 perforated at its apex. The hindermost of these are the wisdom 
 teeth. The false, and especially the true, molars are admirably 
 adapted for grinding and pounding the food, under the influence of 
 those powerful muscles by which the lower jaw is moved in a lateral 
 direction while being forced against the upper. Though the least 
 simple of the human teeth, these grinders are greatly surpassed in 
 complexity of form and structure by the corresponding teeth of herbi- 
 vorous animals, such as the ox, the horse, and the elephant. 
 
 The interrial structure of the teeth, like that of bone, has been 
 much illustrated by those modern microscopic investigations, which 
 have introduced a new era in the sciences of anatomy and physir 
 ology. The researches on this subject, opened by Purkinje, Fraenkel, 
 and Retzius, and subsequently pursued with more or less originality 
 and extent by Miiller, Schwann, Tomes, Nasmyth, and especially by 
 Professor Owen, have confirmed the almost forgotten discoveries of 
 Leeuwenhoek, and brought the whole subject of dental structure and 
 development into clear and consistent light. We shall now give a 
 short summary of the facts as they have appeared to our own minds, 
 and refer, once for all, to the works quoted at the end of the present 
 chapter, for information, as to the share each inquirer has had in the 
 general and very satisfactory result. 
 
 The three constituent substances, dentine or ivory, enamel, and 
 tooth-bone or crusta petrosa, are found in all the higher and more 
 perfect forms of teeth ; and their several conditions in the range of 
 animals have been greatly instrumental in leading to our present 
 knowledge of them in the human teeth: our design, however, will 
 allow us to speak of their character in the latter only, except in the 
 way of illustration. 
 
 Taking a simple tooth as an example, (fig. 149,) we find the great 
 bulk to consist of dentine, a term used by Mr. Owen to distinguish 
 this substance from the rest, in preference to that of ivory or tooth- 
 substance. The dentine gives the general form, size, and hardness 
 to the tooth, both root and crown, and in its central part is the cavity 
 containing the papillary substance or pulp, supplying the vessels and 
 nerves of the organ. 
 
 Dentine is manifestly a modification of the osseous tissue. Like 
 
528 
 
 DIGESTION. 
 
 Fig. 149. 
 
 bone, it may be seen in favorable specimens to present a finely 
 granulated ultimate texture, and, like bone, it is perforated by a 
 series of minute channels, opening on the one hand on a vascular 
 surface, (that of the pulp-cavity, which corresponds with the Haver- 
 sian surface of bone: p. 110,) and on the other sparingly branch- 
 ing, so as to permeate every portion of the tissue. The peculiarity 
 of dentine consists chiefly in these internal channels of nutrition; 
 and, as we have before shown the Haversian canals and systems 
 of lamellae in bone to be arranged in constant subservience to me- 
 chanical ends, so the corresponding parts in dentine, and especially 
 those parts which answer to the lacunae and 
 canaliculi of bone, appear to derive their 
 peculiar characters from the mechanical exi- 
 gences of the case. The tooth having to 
 sustain rude pressure on its crown, chiefly 
 in a vertical direction, great density and 
 compactness are reqiuisite in its main con- 
 stituent, and its internal vascular surface, 
 which is small in proportion to the mass of 
 dentine, is centrally placed, and receives its 
 vessels and nerves at the deepest point, most 
 remote from injury. As the vascular sur- 
 face is small, and therefore at a great dis- 
 tance from a large proportion of the tissue, 
 the interstitial channels of the dentine are 
 capacious, especially towards the vascular 
 surface, and comparatively direct in their 
 course from it ; and, instead of commencing 
 minute as the canaliculi of bone do, and 
 dilating at intervals, after a tortuous and 
 irregular route, into hollow chambers, like 
 the lacunffi of that texture, they are widest 
 at their commencement in the pulp- cavity, 
 retain throughoat the simple tubular cha- 
 racter, and are provided, for the most part, 
 with proper walls, so that each tubule may 
 be regarded as a hollow rod, the stem of 
 which is of a harder and corapacter nature than the intertubular 
 Substance through which it funs. 
 
 The direction taken by the tubes is further interesting ; for not only 
 do they radiate on all sides from the vascular surface, as being the 
 conduits of nutrition to the dentine, but they thus confer on every part 
 of the tooth a greater power of resistance in an inward direction from 
 the surface towards the centre, a power increased by the cylindrical 
 shape of the pulp-cavity, and its tendency to an arched figure towards 
 the crown. But it would appear that the beauty of the mechanical 
 contrivance does not stop even here, for it has been observed that 
 the tubes in many parts are doubly waved, like the Italicy, and that 
 within these primary curves are comprised very numerous secondary 
 meandexings ; from which, as those of contiguous tubes have a lateral 
 
 Vertical section of human In- 
 ciisor, showing the general ar- 
 rangement of its constituent 
 parts. The dentine and pulp- 
 cavity, the enamel on the crown, 
 and the bone on the fang, are 
 seen. a. Neck of the tooth. 
 Hae;ni£ed 3 diameters. 
 
DENTINE, 
 
 529 
 
 correspondence, a certain elasticity, and a greater capacity of resisting 
 €xternal force, must accrue. The tubuli of the den<tiae now described, 
 branch a few times dichotomously, and the branches retain for some 
 distance the diameter of the trunk, this multiplication of their num- 
 ber enabling them to occupy the spaces which would be left by the 
 radiation of unbranched tubes from a common centre. The tubuli are 
 in some parts about their own width asunder, in others they run in 
 
 •>^b>^^='^^ 
 
 Sections of a human incisor, showing : — 
 
 A. Junction of dentine and enamel near the neck of the tooth. ^. Tubes of the dentine, dividing 
 and ending; on 6 &, the cupped surface on which the enamel rods vertically rest. c. Free surface 
 of the enamel. The enamel rods are crossed by transverse lines and ai«o by obliQUe dark lines. 
 
 B. Bifurcation of the tubuli of the dentine, soon after their commencement ojid'^ the surface of the 
 -pulp-cavity. 
 
 c. Branching of the tubuli of the fang, and their termination in t)ie small irregular lacunae of the 
 "granular layer." 
 In these longitudinal views of the tubuli, their cavities, only, ^nd n,ot. their w£^Us, are visible. 
 Magnified .300 diameters. 
 
 mutual contact; and their compact proper wall is about as thick as 
 their cavity is wide. Except near the pulp-cayity, they are, as it 
 were, hairy with filamentary canalicnli, which diverge on all sides, 
 and form innumerable junctions with one another; so that the tubuli, 
 throughout most of the dentine, may be said to communicate with 
 each other independently of the pulp-cavity, into which they all open. 
 Towards the outer surface of the dentine, where it is incrusted on the 
 crown with enamel and on the root with bone, the tubuli gradually 
 taper, and finally terminate in diminutive canals, which open, some into 
 small, irregular lacunse (forming a layer on the root, termed by Mr. 
 Tomes the granular layer), some into the lacunse of the osseous in- 
 vestment of the fang, and others upon the surface on which the ena- 
 mel rests. Occasionally the tubuli are dilated into true lacunae, or 
 form free arches of communication. 
 
 The following facts illustrate the foregoing account of the structure 
 of dentine. The granularity of the ultimate tissue may be best seen 
 
530 
 
 DIGESTION. 
 
 in specimens in course of development. On the surface of the pulp- 
 cavity the orifices of the tubuli can be seen ; and in transverse sec- 
 tions of the tubuli,* (fig. 151,) their proper 
 walls, the width of their walls and calibre, 
 and their distance apart, are all discernible. 
 In broken fragments, especially if torn after 
 the tooth has been softened in acid, the tu- 
 bili may be observed to stand out from the 
 surface,being broken off at different lengths, 
 as if their structure was distinct from the 
 intertubular tissue. Their hollowness is 
 proved by the chasing of bubbles along 
 them, visible under the microscope when 
 turpentine is added to a dry section, and 
 also by the gas which may be seen to be 
 disengaged in bubbles, chiefly from their 
 interior, when a section is similarly treated 
 with acid. The latter experiment seems 
 also to show that the parietes of the tubuli 
 contain a denser deposit of earthy matter, 
 and are consequently harder and more re- 
 sisting than the intertubular tissue. 'VVe 
 do not regard the tubuli as filled up by 
 solid contents, but as possessing a truly 
 hollow bore, designed to give passage to 
 fluids. 
 
 The enamel, investing the crown of the tooth, and forming that part 
 which is exposed in the mouth to the contact of external substances, 
 is harder and compacter than the dentine, and of peculiar structure, 
 although formed, as will be afterwards shown, on the same general 
 plan as the other portions of organized bodies. As its earthy con- 
 stituents are in much larger proportion than in the dentine, (for they 
 make up 98 instead of 72 out of 100 parts, according to Berzelius,) 
 the enamel requires much less nutrient change, and its interstitial 
 passages are very minute. 
 
 The enamel (fig. 150, a, and fig. 152) consists of a congeries of 
 hexagonal rods, placed endwise side by side, so as to form a layer, 
 , of which the surfaces are formed by the ends of the rods, and the 
 thickness is determined by their length. The deep surface rests on 
 the dentine, which presents a number of minute depres^sions for the 
 reception of the deep ends of the vertical rods, a number of which 
 rest in each ; and the superficial surface, though said to be at first 
 coated with a thin film of osseous tissue, is afterwards rendered bare 
 by the earliest movements of attrition in masticating the food, and 
 then becomes the free surface-of the crown of the tooth. The rodi? 
 of enamel are about jj'jj^th of an inch in diameter, and they pursue 
 a more or less meandering course, which must augment their power 
 
 • Mr. Topping, of York Place, New Road, mounts these and other objects very 
 skilfully. 
 
 Transverse sections of tubnles 
 of dentine, showing their caviiies, 
 walls, and the intertubular tissue. 
 
 a. Ordinary distance apart. 
 
 b. More crowded. 
 
 c. Another view. 
 
 Human molar.— Magn. 400 diam. 
 
THE ALVEOLI. 
 
 531 
 
 A. Vertical Eection of the enamel, showing the 
 fibres, with their cross lines. 
 
 B. Fibres of the enamel, seen endwise. 
 Magnified 350 diameters. From Retzins. 
 
 of resisting external force. It is evident that their vertical position 
 admirably adapts them to sustain pressure, and withstand the effects 
 of force directed upon the surface of the tooth ; while, at the same 
 time, the interstices or chinks intervening between them, principally 
 at their angles of juxtaposition, are arranged in the most suitable 
 manner for permeation by the fluids derived from the subjacent den- 
 tinal tubuli. These tubuli, 
 Fig. 152. indeed, may be seen to com- 
 
 municate directly with the in- 
 terstitial passages of the ena- 
 mel. The enamel rods are 
 further marked, at pretty close 
 and regular intervals, by cross 
 lines, which, however, are far 
 from constant, and of doubtful 
 nature : some suppose them 
 explained by the process of 
 development. The enamel 
 rods are connected together by 
 some remnant of the original 
 organic matrix in which their 
 earthy portion was at first de- 
 posited, and which is repre- 
 sented by the dark lines or chinks which appear to bound and isolate 
 the rods. As the rods are placed vertically on the surface of the 
 dentine, which is not an even one, they are not everywhere parallel, 
 or of equal length, but are truncated where they 6but against each 
 other over a hollow, and in such parts are most liable to decay. In 
 many parts, however, near the dentine their vertical position seems 
 disordered ; they are curiously contorted, and neighboring series of 
 them are variously inclined, so as to lean against one another, while 
 the same rods nearer the surface assume an upright and parallel 
 course. The enamel on a vertical section further shows dark mark- 
 ings running obliquely across the fibres (fig. 150, a), and not well 
 understood, and also larger cracks or fissures (fig. 149), often branched, 
 running through a part or the whole of its thickness. As Mr. Owen 
 has pointed out, the enamel is the least constant of the dental tissues, 
 being absent in many fishes, in existing ophidian reptiles, and in the 
 edentate and many cetacean mammalia. 
 
 The tooth-bone or cement is disposed as a permanent thin layer of 
 osseous tissue on the roots of the teeth, and it also invests the enamel 
 with a delicate film on the first emergence of the tooth from the gum. 
 On the root it is thickest towards the apex, and often lines the pulp- 
 cavity of the dentine for a little way in. It contains sparingly the 
 lacuna and canaliculi which characterize bone ; and, when thick 
 enough, it presents also the lamella of that structure. In general it 
 is in too small a quantity to require special Haversian canals ; but 
 Mr. Tomes has shown, that, between the roots of the larger human 
 teeth, the tooth-bone is often in sufficient mass to be penetrated by a 
 true canal of that nature ; and, in the teeth of many animals, the ce- 
 
532 DIGESTION. 
 
 ment is as vascular as ordinary bone. The canaliculi of the tooth- 
 bone are, for the most part, directed from the lacunae towards the sur- 
 face, where the vessels are spread out, but a few communicate with 
 the peripheral branches of the tubuli of the dentine. It is through 
 this osseous investment of the roots that the teeth adhere so firmly to 
 the sockets in which they are implanted. 
 
 The cavity of the teeth, containing the pulp, is in the fully formed 
 tooth the analogue of the Haversian canal of bone, by which the or- 
 gans of nutrition and sensation find access to the internal surface. 
 The blood-vessels of the pulp are branches of the internal maxillary, 
 and the nerves of the fifth. pair, and they are both extremely abundant, 
 in proportion to the extent of surface with which they are in relation. 
 The capacious capillaries form numerous arches, and the nerves like- 
 wise end in loops,, (p. 204,) which are best seen in the young tooth. 
 The white substance of the nerve-fibres has seemed to us to be often 
 diminished or lost towards the convexity of the loops. 
 
 The alveoli, or sockets in which the teeth are set, are cavities in 
 the border of the jaws, corresponding in shape and direction to the 
 roots of the teeth, formed on the outer and the inner side by a firm, 
 compact plate of bone, which bounds the alveolar arch in front and 
 behind, and separated from one another by septa of less compact ma- 
 terial. The surface of these cavities is spongy, being perforated by 
 minute vessels, which pass across to the surface of the roots of the 
 teeth, and which there form a plexus in the substance of a firm elastic 
 tissue, which is the connecting medium between the socket and the 
 root, and is usually regarded as a periosteum. Thus the surface of 
 the root is supplied with blood, and the tooth is united to the jaw in 
 a way which allows it to yield very slightly under pressure. 
 
 The alveolar arch is covered on the outside by the gums, a dense, 
 elastic, peculiar tissue, adapted to sustain without injury the forcible 
 contact of the hard portions of food, to which its vicinity to the grind- 
 ing organs must expose it> 
 
 The dwelopment of the teeth may be described under two heads ; 
 first, that of the elementary tissues of the tooth, the dentine, the ena- 
 mel, and the true bone ; secondly, that of the dental series, which 
 will include the order of appearance of the teeth of the temporary and 
 permanent sets. 
 
 According to the most recent investigations of Arnold and Good- 
 sir, the teeth are developments from the mucous membrane covering 
 the dental arches, and not from the maxillary bones. They, there- 
 fore, would seem to correspond with the tegumentary appendages of 
 animals, such as horns, nails, feathers, and not to be a portion of the 
 true osseous system, or endo-skeleton of the vertebrata. The bills of 
 birds are an obvious intermediate condition of the integument of the 
 jaws. 
 
 The teeth may be regarded as formed in the following manner. 
 The first indication observed (according to the excellent observations 
 of Mr. Goodsir, which we have, in most particulars, had an oppor- 
 tundtljr of verifying) is a groove at the border of the palate in the 
 situation of the future teeth, whicK he terms the primitive dental 
 
DEVELOPMENT OP THE TEETH. 
 
 533 
 
 groove, and which is apparent in the foetus of six weeks old. At the 
 bottom of this groove there appear certain fine papillae, which in- 
 crease in size, and gradually assume the shape of the crowns of the 
 future teeth, having the edge "and cusps whicih are evelitually to dis- 
 tinguish them. As the papillae grow, the groove is converted into 
 follicles for their reception, by the growth of septa between its bor- 
 ders, that is, between the outer and inner alveolar processes, which 
 soon begin to be ossified within the walls of the groove; ' Thus the 
 follicles become alveoli lined by the periosteum of the jaw, such as it 
 is at this early period, and lodging a process of the mucous mem- 
 brane of the gum, from the bottom of which springs up the papilla 
 or germ of the future tooth. The summit of the papilla is at first 
 visible in the mouth of the follicle ; but ere it has assumed the figure 
 of the tooth, the margins of the orifice enlarge and lap over, and 
 finally meet and unite, so as to form a lid or operculum to the now 
 closed cavity. Thus the epithelium of the lining membrane of the 
 mouth may be shown to form the lining of the follicle, and to be re- 
 flected thence over the surface of the papilla. 
 
 Now, the tooth papilla must be regarded as homologous with, or 
 answering to, the tactile and hair papillae of the skin, already described 
 at a former page ; arid it would, therefore, be expected that its main 
 part would consist of a peculiar sub-mucous tissue, covered by a ho- 
 mogeneous basement membrane, and surmounted by a tissue answer- 
 ing to the epithelium ; and this seems actually the case^ The sub- 
 stance of the papilla is at first a congeries 
 of granular nuclei, dispersed irregularly 
 through a firm homogeneous sub-granu- 
 lar matrix, or blastema, in which ves- 
 sels and nerves are by, degrees deve- 
 loped. This is bounded by a definite 
 transparent raeinbrane, on which rests a 
 reflection of the epithelium lining the 
 sac, modified in structure, so as to pre- 
 sent a series of columnar-nucleated par- 
 ticles, the matrix of the fiiture enamel. 
 It would appear that the lining and re- 
 flected layers of the epithelium become 
 blended together, and constitute but 
 one, which is more adherent to the sac c^o°oo^tP° 
 
 Fig. 153. 
 
 OqQoo . • 
 
 than to the papilla, so that on opening 
 the sac its wall generally seems to be 
 unattached to the surface of the papilla, 
 and the latter to be limited by what we 
 ,have regarded as the basement mem- 
 brane. Or, it may be that the epithelium 
 reflected over the papilla disappears, 
 leaving only that which lines the sac. 
 
 Between the columnar epithelium 
 thus lining the sac, and the surface of 
 
 the alveolar cavity, that is, apparently in the wall of the sac itself, is 
 25 
 
 A. Vertical section of the enamel- 
 pulp, with, the columnar epithe.lium, 
 which is 'to become the enamel, a. 
 Pulp, b Posjtion -of, basement mem- 
 brane, c. Columnar epithelium, some 
 panicles being detached; 
 
 B. Columnar epithelium seen end- 
 ■wise. 
 
 From a huipan fcetus of about five 
 months. Magnified 2ti0 diam. 
 
534 DIGESTION. 
 
 now found a thick, serai-transparent, pulpy tissue, which has been 
 termed the enamel-pulp. It presents towards) the pulp of the tooth 
 (dentinal pulp) a series of elevations and depressions, precisely the 
 reverse of those of the dentinal pulp on which they rest, and answer- 
 ing mutually to these, with only the columnar epithelium intervening. 
 The structure of this thick pulpy tissue is very beautiful and pecu- 
 liar, as is seen in the annexed woodcut (fig. 153, a, a). It consists 
 of a mesh of short fibres, meeting in numberless points, and at each 
 point of junction a transparent clear nucleus is visible. 
 
 It is elastic, spongy, loaded with fluid albumen, but destitute of 
 vessels, and it seems perfectly distinct from that columnar structure 
 which appears to be afterwards converted into the enamel. 
 
 In a vertical section of these parts, the enamel-pulp is seen covered 
 with columnar epithelium, the enawieZ-jnairia; (fig, 153, a, c, b), on 
 the surface towards the dentinal or tooth-polp ; while, on the oppo- 
 site surface, the blood-vessels of the membrane lining the alveolus 
 are seen coming up to, and forming loops immediately under, the 
 enamel-pulp, without penetrating it. It is further remarkable, that 
 short tubes, filled with glandular epithelium, descend among these 
 vessels from the enamel-pulp, and end by blind extremities. How 
 these tubes, which are evidently glandular, can discharge their con- 
 tents, it is difficult to understand, seeing they appear to open into the 
 substance of the enamel-pulp : but their presence and precise situa- 
 tion we have ascertained to be as we have described them in the 
 molar teeth of the nine months, human foetus. 
 
 It is not impossible that the enamel-pulp may perform the mechani- 
 cal office of protecting the soft and growing tooth from pressure di- 
 rected on the gum, and of providing a space in which development 
 may advance without restraint. 
 
 The next stage is that of ossification, and the earthy matter is first 
 deposited in the homogeneous membrane forming the surface of the 
 dentinal pulp. The most prominent portions of the crown are the 
 first to harden ; and the ossification proceeds inwards by the gradual 
 conversion of the pulp into the dentine, or ivory. The nucleated 
 particles of the pulp nearest the ossifying surface are found arranging 
 themselves in series vertical to that surface ; and it appears, that, in 
 order to form these vertical series, they multiply by transverse divi- 
 sion, much as those of bone cartilage are found to do. The earthy 
 matters are then deposited in the indistinct cells surrounding the 
 nuclei, so as to form the hard and dense walls of the dentinal tubes, 
 as well as in the intercellular substance, so as to form the intertubular 
 tissue of the perfect tooth. The ceils unite endwise, and their nuclei 
 elongate and coalesce in a manner to constitute the cavities of the 
 tubes, and so as often to retain indications of this mode of origin in 
 their permanent form. In all these processes a striking similarity to 
 those noticed in the ossification of ordinary bone is to be traced. In 
 proportion as the ossification proceeds inwards, so as to occupy the 
 substance of the dentinal pulp, the vessels and nerves which had 
 been developed in that structure recede, and finally come to occupy 
 the cavity which remains in the interior of the tooth after its develop- 
 
DEVELOPMENT OF THE TEETH. 535 
 
 ment has been completed. The chief vascularity of the pulp is uni- 
 formly found near the ossifying surface, whence it is evid,ent that the 
 earthy materials are supplied from that source. In the teeth of some 
 animals, in which. the dentine is penetrated by many subordinate off- 
 sets from the central cavity, containing blood-vessels, these passages 
 are left in the progress of development, just as has been above de- 
 scribed. 
 
 It has .been already said that the reflexion of the original mucous 
 membrane of the follicle on to the papilla takes place at a line corre- 
 sponding nearly to the nec/c of the future tooth, and that the original 
 papilla answers to the crown or body of the tooth, and not to the root. 
 This latter is a subsequent formation, and is laid down gradually after 
 a certain amount of ossification has already taken place in the crown, 
 and after the enamel has been calcified. It is formed and ossified by 
 a process precisely similar to that of the dentine, of the crown, only 
 a more protracted one, and during which the tooth is raised out of 
 its sac, and bursts the containing gum. The letigtheiiing of the fang 
 preceding its ossification resembles closely that occurring at the junc- 
 tion of the shaft with the epiphyses of the long bones during their 
 development (p. 123), 
 
 The calcification of the enamel commences on the surface of the 
 dentine, in contact with that primary osseous sheet formed frdm the 
 basem«nt membrane of the dentinal pulp. On this primary layer are 
 minute shallow cups, closely aggregated, answering to the ends of 
 the enamel. columns, and- receiving them in a firmly cemented union, 
 as the consolidation of the elementary cells proceeds. The enamel 
 columns at a very early stage seem to consist only of a single series 
 of nucleated particles, intervening between the dentine and the ena- 
 mel-pulp; but subsequently others are added on the surface towards 
 the enamel-pulp.. Those of the new row arrange themselves endwise 
 on the others, which they resemble in all respects, so that the enamel 
 attains its proper thickness rather by the superposition of particle on 
 particle successively deposited, and by the subsequent calcification 
 of each in its turn, than by the development of its parts by an inter- 
 'stitial increase; and thus it appears to differ from the dentinal pulp, 
 and to resemble the epithelium, to which it is allied.. 
 
 It is from that surface of the enamel-pulp which looks towards the 
 tooth, that this successive development of new enamel columns pro- 
 ceeds ; as they form, this tissue wastes; but it is not probable that 
 the- pulp is converted into the columns, as the dentinal pulp is con- 
 verted into dentine, because the anatomical characters of the piilp 
 are so dissimilar from those of the columns. When first calcified, the 
 enamel rods are loosely aggregated, and easily separate frOm one an- 
 other under pressure ; but they gradually become so firmly consoli- 
 dated by the advance of the calcifying process in their interstices, as 
 to make the finished enamel the most hard and indestructible of all 
 the products of organization. 
 
 The development of the layer containing the ordinary lacunae of 
 bone, and which, in the human teeth, covers the fang, and iscontinued 
 a little wajr withip the cavity of the root, does not seem to have been 
 
536 DIGESTION. 
 
 SO accurately studied as that of the dentine and enamel. But this is 
 the less important, as it is in all probability essentially similar to that 
 of bone, which is now pretty well understood. There can be little 
 doubt that a membranous matrix, probably like that of the cranial 
 bones, is laid down as the fang is developed, in which the usual steps 
 of ossification proceed, the lacunae and their canaliculi being,. in our 
 opinion, formed from the corpuscles of the temporary matrix. Mr. 
 Nasmyth has described a prolongation of this layer over the entire 
 crown of the tooth, outside the enamel. To understand the formation 
 of such a layer, we must suppose it laid down in a matrix continuous 
 with that which invests the fang, passing over the crown between the 
 enamel-pulp and the wall of the sac inclusive of the lids. The crusta 
 petrosa in the fissures between the enamel of the compound grinders 
 of herbivorous animals must certainly be formed in this way. 
 
 When the ossification of the dentine is so far advanped that the 
 tooth can sustain with impunity the pressure to which it is destined, 
 and when the enamel is densely calcified, the eruptive stage occui;Sy 
 in which the tooth makes its way through the gum. This is due to 
 the same laws of development which govern the form and position 
 of other organs. The gum over the sac is absorbed, and the crown 
 of the tooth is forced upwards against it, chiefly by the increasing 
 size of the fang below. , 
 
 It may be stated, once for all, that, as the development of tke teeth 
 proceeds, so does that of the alveoli, or the bony sockets in which 
 they are lodged ; and that, by the time the teeth break through the 
 gums, their walls are sufficiently strong, and embrace the necks of 
 the teeth with firmness enough to furnish a solid basis of support. 
 Their vascular canals are developed, and especially those which con- 
 vey to each tooth its interior supply of vessels and nerves. The 
 gums and alveoli are likewise provided with vessels which play their 
 part in the development and subsequent nutrition of the organs. The 
 nerves of the teeth are derived from the second and third divisions 
 of the fifth pair. 
 
 Of the First and Second Dentitions. — As teeth are required before 
 the jaw-bones have attained their full- growth, and yet are organs in- 
 capable of enlarging pari passu with those bones, the young child is 
 provided with a temporary set, commonly known as the milk-teeth, 
 adapted to the size and form of its alveolar arches, and to the nature 
 of the food consumed in early life. This set consists of twenty teeth 
 — -four incisors, two canines, and four molars in each jaw. They are 
 formed in the manner already described : the papillae of the anterior 
 molars appearing first — between the sixth and seventh week of foetal 
 existence, according to Mr. Goodsir — ^.followed by those of the canines, 
 incisors, and posteripr molars, about the eighth, ninth, and tenth 
 weeks respectively. About the fourth rnpnth all these are in their 
 saccular stage, the mouth of the follicles having closed ; and there 
 then appear behind the opercula, or lids of the follicles, small cres- 
 centic depressions of the mucous membrane, soon becoming closed 
 cavities, called by the last-named author "cavities of reserve, to fur- 
 nish delicate raucous membrane for the future formation of the pulps 
 
FIRST AND SECOND CENTITION. 537 
 
 and sacs of the ten anterior permanent teeth" in each jaw. For two 
 or three weeks longer the primitive dental groove behind the posterior 
 milk molar is furnishing the papilla of the first permanent true molar; 
 and, as this becomes gradually in its turn enclosed in a sac, a cavity 
 of mucous membrane is said ^ by Mr. Goodsir, to be Jeft unobliterated 
 between its sac and the surface of the gum, which is the " cavity of 
 reserve" from which the development, fi/st of the second true molar, 
 and, secondly, of the third or wisdom tooth, is afterwards to proceed. 
 
 The temporary teeth usually make their way through the gum as 
 follows, those Of the'low6r jaw taking precedence: the four central 
 incisors about the seventh month after birth ; the four lateiral incisors 
 from the seventh to the tenth ; the anterior molars from the twelfth to 
 the fourteenth ; the canines from the fourteenth to the twentieth ; and 
 the posterior molars from the eighteenth to the thirty-sixth month. 
 This whole period is called that of the first dentition, and is of 
 great importance to the child, from the various Sympathetic morbid 
 States which universal experience attributes to the process of "cutting 
 the teeth ;" but it would be, beside our purpose to dilate in this place 
 on so interesting and prolific a theme. It may suffice to say, that, in 
 our opinion, the practice of lancing the gum over an advancing tooth 
 is often unnecessarily and prematurely resorted to, when there is no 
 evidence, from its tense or inflamed state, that it is offering any un- 
 due obstacle to the progress of the organ beneath. 
 
 The ossification of the permanent teeth commences alittle before 
 birth with that of the anterior molars, and in the course of the first, 
 second, and third' years it proceeds gf'adually in the incisors, the ca- 
 nines, and bicuspids. Their position in the jaw, meanwhile, has been 
 undergbing change. The cavities of reserve, from which the devel- 
 opment of the ten anterior permanent molars proceeds, are, at first, 
 placed between the milk sacs and the gum; but as the papillae are form- 
 ed, as already explained, they recede behind, or to the inner side, and 
 also pass deeper in the jaw, and ultimately get beneath them, acquir- 
 ing by degrees their alveolar cavities, and being closely and some- 
 what irregularly packed. As the anterior molar is developed, it soon 
 comes to occupy the tuberosity of the maxilla, and the base of the 
 coronoid process in the respective jaws, and, afterwards, by the 
 lengthening of the alveolar arch, descends into place on a level with 
 those before it. As this occurs, the cavity of reserve, situated over 
 it, furnishes the papilla and sac for the second molar, which soon 
 occupies the tuberosity or coronoid process, and then descends to 
 behind the anterior one, a portion of the cavity of reserve being still 
 left to furnish the hindmost molar or wisdom tooth in the same man- 
 ner. As these severklteeth descend to the alveolar arch, the jaw is 
 proportionally lengthened by a Suitable addition from behind ; so that 
 (he circular arch, of which the alveoli at first consisted, is altered into 
 an elliptical one. 
 
 As the permanent teeth are being prepared to penetrate the gum, 
 the bony partitions, which separate their sacs from those of the tem- 
 porary teeth, are absorbed ; the fangs of the temporary teeth are re- 
 moved by a very singular natural process; and the permanent teeth 
 
538 DIGESTION. 
 
 come to be placed directly under the now loose crowns of the tempo- 
 rary ones, which finally detach themselves and allow the permanent 
 teeth to take their places in the mouth. While it is impossible not to 
 admire the evidence of design furnished by this exquisite process, it 
 seems sufficient to assign it physiologically to that general law which 
 determines the form and size of the several parts of organized beings. 
 It has been supposed that elongated productions of- the cavities of 
 reserve, which have been carried down from the surface with the 
 permanent tooth sacs, serve to re-direct them to their proper places 
 as they rise through the gum. But it may be asked what served 
 previously to carry down the pulps aright, and to form these guber- 
 nacula .' It is manifest that we must ascfend to a higher secondary 
 law, to which to refer these wonderful phenomena of life. 
 
 The periods of eruption of the permanent teeth, though liable, like 
 those of the milk teeth, to some variety, are, according to Mr. Bell, 
 usually as follow: — the anterior true molars at 6^ years of age, the 
 central incisors at 7, the lateral ones at 8, the anterior and posterior 
 bicuspids at 9 and 10, the canines from 11 to 12, the second true 
 molars from 12 to 13, and the wisdom teeth from 17 to 19. 
 
 Of the Jaw-hones at different Jlges. — The bones undergo some inte- 
 resting changes of form in connection with the growth and decay of 
 the teeth, which have been, well explained by Hunter. The alveolar 
 processes in both jaws appear with the teeth, and disappatr when no 
 longer needed to support and eijclose them. In the foetus, before 
 the eruption of the teeth, the upper gum is about on a line with the 
 articulationof the jaw, the lower, consequently, is nearly on the same 
 line, and the angle of the jaw very obtuse. But as the teeth pro- 
 trude, and increase in number, the lower jaw is separated from the 
 upper by the depth of the alveoli and crowns of the teeth of both 
 jaws, the body and ascending ramus are both lengthened, and the 
 angle approaches nearly to a right angle. When the teeth are sub- 
 sequently shed, the alveoli disappear, and the lower jaw has to be 
 much more elevated in order to touch the upper. But as its body and 
 ramus cannot return to their former dimensions, its anterior part is 
 thrown a good deal beyond the upper in this action, and it is only 
 the hinder portions in the situation previously occupied by the molar 
 teeth which come into contact. 
 
 Of the Articulation of the lower Jaw, and the Movements of Mastica- 
 tion. — A constant relation subsists in animals between the nature of 
 the food, the shape and structure of the teeth, and the articulations of 
 the jaw ; so that, as Cuvier demonstrated, one of these elements being 
 known, the others may be more or less accurately inferred. Thus, 
 the purely carnivorous animals have teeth fitted to seize and lacerate 
 their food, and the jaw is capable only of the simplest hinge motion. 
 In the herbivorous families, on the contrary, teeth of a complex kind 
 are provided for pounding and bruising the food, and the joints are 
 so constructed as to allow of extensive sliding motions ; while in all 
 there is an inter-articular fibro-cartilage for protection under the ex- 
 treme pressure exerted. The form of the articulation in man, not 
 less than the dental series, denotes an intermediate condition, and 
 
THE SALIVA. 539 
 
 forms a strong physiological argument for the mixed diet, which gene- 
 ral custom and taste have decided to be natural to our species. As 
 there are cutting, tearing, and grinding teeth, all in moderate propor- 
 tions, of similar height, and in an uninterrupted row, so the articula- 
 tion of the jaw is intermediate between those of the animal and vege- 
 table feeder. The transverse condyle is received into the glenoid 
 cavity, and in the slighter movements of mastication and articulation 
 does not leave it; but when the grinding teeth ace used, or the 
 mouth is opened wide, the condyle leaves the cavity, and' slides for- 
 wards for nearly an inch on the prominent root of the zygoma. In 
 the latter action the axis of motion is not in the condyles, but a little 
 above the angle of the jaw, and the joint is arthrodial. A similar 
 advance of the condyles may occur with the mouth nearly closed, 
 the lower incisors being then carried to a level with, or even beyond 
 the upper ones. By the advance of one condyle a partial rotation is 
 effected, the centre of, motion being in the other condyle ; and when 
 this is performed alternately by both sides, together with an elevation 
 of the jaw, the lower molars are moved laterally over the upper, so 
 as to powerfully grind any intervening substance. The temporal, 
 masseteric, and internal pterygoid muscles more or less directly close 
 the jaw. The hinder fibres of the temporal and masseter carry it 
 also backwards, while the main part of the masseter, and especially 
 the internal pterygoid, advance it. Both pterygoids carry it to the 
 opposite side, chiefly by advancing its ramus, the centre of motion 
 being then in the opposite joint. The external pterygoid neither 
 raises nor depresses it. The depression of the jaw in mastication 
 seems to be performed solely by the. digastric ; and it may be conjec- 
 tured that even this muscle acts chiefly in its anterior belly, which, 
 unlike the posterior, is supplied by the inferior maxillary nerve, the 
 same which is.distributed lo the other muscles of mastication. 
 
 Of Insalivation. — The salivary organs consist of glands opening 
 into the mouth and pharynx, and furnishing a peculiar fluid which is 
 there mixed with the food and carried down with it to the stomach. 
 The principal are the parotid, submaxillary, and sublingual ; and to 
 these may be added a multitude of small detached glands of similar 
 structure, and probably yielding a similar fluid, scattered under the 
 mucous membi-ane of the lips, cheeks, soft palate, and parts of the 
 pharynx. The duodenal glands, comprising the pancreas and the 
 glands of Brunner, which have much in common with the salivary 
 glands, will be described at a subsequent page. 
 
 The salivary glands need not here be severally described. The 
 parotid is remarkable for its proximity to the temporo-maxiilary ar- 
 ticulation, and some have attributed its greater activity during mas- 
 tication'to the pressure to which it is supposed to be then subjected ; 
 but besides that the fact of pressure may be doubted^ so mechani- 
 cal an hypothesis seems quite superfluous, since the nervous sympa- 
 thies which po evidently stimulate or control other secretions, as the 
 tears, are quite sufficient to explain this. The parotids pour their 
 secretions into that compartment of the mouth which is outside the 
 
540 DIGESTION. 
 
 teeth, while the ducts of the submaxillary and sublingual glands open 
 under the tip of the tongue within the alveolar arches. 
 
 The salivary glands consist of a single excretory duct, continuous 
 with the mucous membrane, branching again and again towards the 
 gland, so as to subdivide it into a multitude of lobes and lobules in- 
 vested with subdivisions of a common areolar or fibrous capsule, and 
 reducible ultimately to follicles of a highly delicate basement mem- 
 brane, lined by glandular epithelium, and provided on their exterior 
 with a network of anastomosing capillaries. Some anatomists con- 
 sider that the ultimate follicles of these glands, in which the secretion 
 is elaborated, are at first closed sacs, in which the epithelium grows 
 4nd is multiplied, and which discharge themselves at stated intervals 
 into the extremities of the duct. Knowing how difficult it is to deter- 
 mine the positive truth on this question, we shall merely say that we 
 are disposed to regard the secreting follicles as permanently open to 
 the duct, and their secretory epithelium as a continuation of that which 
 lines the duct. 
 
 Salivary glands exist in all the vertebrata except fishes. 
 
 The mere sight, or even the idea, of food to a hungry man, excites 
 the salivary secretion — " makes the mouth water ;" and during mas- 
 tication it is poured very abundantly into the mouth, especially at the 
 commencement of a meal, or if the food taken is of a savoury quality. 
 Ordinarily, between meals and at night, these glands hardly pour but 
 any secretion ; but there can be little doubt that in these intervals of 
 comparative repose of their blood-vessels, the epithelium of the folli- 
 cles is undergoing those processes of growth and change Which pre- 
 cede the actual formation of the salivary fluid ; and the same may be 
 said of many other glands which have an apparently intermittent ac- 
 tion. The quantity of saliva furnished in a given time in a state of 
 health has been variously computed. Mitscherlich collected between 
 two and three ounces from the parotid duct in the course of twenty- 
 four hours, and nearly fourteen from the whole of the salivary organs ; 
 and his estimate appears worthy of being relied on. 
 
 The saliva is a slightly viscid transparent fluid, depositing a little 
 flocculent sediment on standing, which consists principally of the 
 scaly epithelium of the mouth, and of other smaller nucleated cells, 
 which seem to come from the salivary glands or ducts. Its viscidity 
 is increased by mixture with the mucus of the mouth. According to 
 Dr. Wright, its specific gravity is, on an average, about 1007-9. It 
 is usually alkaline, especially during a meal, but often neutral, and 
 sometimes slightly acid. Less than two parts in a hundred are organic 
 or saline matters, the rest is water. The organic matters are (besides 
 the nucleated cells) ptyalin or salivin, fat, (often visible as oil-globules 
 in the microscope,) and extractive matter, with a trace of albumen; 
 the inorganic constituents are alkaline lactates, chlorides of sodium 
 and potassium, phosphate of lime, some free soda, with sulpho-cyanide 
 of potassium, and perhaps others. The last named product gives a 
 red tinge with a persalt of iron, and seems peculiar to the saliva. 
 With regard to the nature and properties of what has been termed 
 ptyalin, chen^ists appear to be by no means agreed, or even whether 
 
DEGLUTITION. 541 
 
 it be at all peculiar to this secretion. Dr. Wright, who has paid a 
 great deal of attention to thesaliva, describes it as a yellowish- white, 
 adhesive, and nearly solid raatterj having alone, the characteristic 
 odour of saliva, soluble in ether, alcohol, and essential oils, but more 
 sparingly so in water; as unaffected by most of the agents which coa- 
 gulate albumen, but as abundantly precipitated by subacetate of lead 
 and nitrate of silver. Dr. Franz Simon, on the contr#y, describes 
 ptyalin as insoluble in alcohol and ether; and he adds, ''Our know- 
 ledge of this substance is by no means accurate ; and there is no 
 doubt that all the animal fluids yield an extract to water, which 
 strongly resembles, if it be not altogether identical, with ptyalin." 
 Mnimal Chemistry, translated by Geo.E. Day, (London, 1845,) p. 24. 
 Dr. Miller has published a recent analysis of the saliva. .Cyclop. 
 Ancii., art. Organic Analysis, p. 812. 
 
 An obvious use of the saliva is to aid in reducing the food to a 
 pultaceous form, in which it is more easily swallowed,. During the 
 movements of mastication, it is intimately mingled with the whole 
 mass, and may thus very probably mechanically enable the gastric 
 juice to penetrate more quickly to every part on jts arrival in the 
 stomach. But general experience attributes the ill-effects of rapid 
 eating or bolting of the food, tjo the saliva being swallowed in insuf- 
 ficient quantity, as well as to imperfect mastication ; and it is a ques- 
 tion of some interest, to ascertain whether this fluid has any digestive 
 powers-, at all allied to those of the gastric juice. The experiments 
 of Leuchs have proved that it has the power of converting starch into 
 sugar, a change similar to that which occurs in the stomach; and 
 Spallanzani observed that aliments enclosed in perforated tubes, and 
 introduced into the stomachs of living animals, were earlier digested, 
 when previously mixed with saliva, than with water. 
 
 Dr. Wright injected saliva into the blood-vessels of dogs, and 
 found the animals dying in a few days or weeks, with symptoms 
 much resembling those of hydrophobia. In other instances, where 
 he employed white^of egg, isinglass, and mucus, no such effects en- 
 sued. Lancet, 1844. Br. and For. Med. Rev., Jan. 1847. 
 
 Of Deglutition. — The parts concerned in this act are the mouth, 
 the pharjftt^, and the oesophagus, the two latter of which remain 
 to be considered. 
 
 The pharynx, as usually described, consists of all that cavity lined 
 with mucous membrane which is situated in front of the cervical 
 vertebrae, behind the nose, mouth and larynx, below the base of the 
 skull, and above the oesophagus. This cavity, however, as we shall 
 show, comprises two parts entirely distinct from one another : an 
 upper, with its walls never in contact, lined with ciliated epithelium 
 and containing air, which we shall term the respiratory compartment, 
 being in fact strictly a portion of the air-passages ; and a lower, dilat- 
 able and contractile, lined with scaly epithelium, and giving passage 
 to the food from the mouth to the oesophagus, which we shall terra 
 tbe alimentary compartment, as it is a portion of the alimentary tube. 
 The air-passages are interrupted between the upper compartment and 
 
542 DIGESTION. 
 
 the glottis, and in this interval the air has to traverse the lower or 
 alimentary compartment in its course from the nose to the lungs. 
 The alimentary and respiratory tubes may thus be said to intersect 
 each other in this common cavity, a fact of leading importance to the 
 understanding of the anatomical arrangement of these parts. Not 
 to speak of the laws of development to which this free communica- 
 tion of the ^-o great tracts ministering to the nutrient function may 
 be referrible, (a communication still freer previous to the fusion of 
 the sides of the palate at an early stage of foetal existence,) it may 
 be sufficient to allude to the great end answered by it, viz. the bring- 
 ing the whole apparatus of the mouth into connection with the lungs 
 for articulation and speech, and to the subordinate object of much 
 heightening the sense of taste during mastication, by allowing the 
 odour of the food to ascend from the mouth and pharynx to the ol- 
 factory region through the posterior nares. (See p. 388.) 
 
 From the hinder border of the hard palate passes the soft palate, 
 a fold of raucous membrane enclosing mucous glands, a fibrous sub- 
 stratum, and several muscles by which it is capable of various motions. 
 This terminates below by a free border, with the uvula in the centre; 
 and from this border on each side descend the two pillars of the soft 
 palate: the posterior downwards and backwards, enclosing and mark- 
 ing the course of the palato-pharyngeal muscle, and dividing the 
 alimentary compartment before alluded to from the respiratory olrie 
 above; the awfenor downwards and forwards, containing the much- 
 smaller palato-glossus muscle, and dividing the same compartment 
 from the mouth. Thus, this alimentary tract of the pharynx may be 
 said to have its upper part included within the diverging pillars of the 
 soft palate, with the tonsils projecting into it, and to have its summit 
 formed by the lower edge with the uvula, the posterior or upper sur- 
 face of the soft palate pertaining to the respiratory tract, and the an- 
 terior or lower to the mouth. The raucous membrane of the pharynx 
 seen between the soft palate and tongue on opening the mouth lies 
 above the posterior pillars, and consequently belongs to the respira- 
 tory compartment ; and we have on several occasions had interesting 
 proof of this in those cases of chronic syphilis attended with a dry 
 state of the pharyngeal membrane, and in which this part has remain- 
 ed dry after the patient has been made to swallow water. 
 
 The alimentary compartment of the pharynx has four orifices, all 
 capable of closure ; one towards the mouth, bounded by the lower 
 edge and anterior pillars of the palate, by the base of the tongue and 
 OS hyoides; another towards the oesophagus, at the lower border of 
 the cricoid cartilage: these two are alimentary. The third opening 
 is towards the upper compartment, and is bounded by the lower border 
 of the palate with the uvula, and by the posterior pillars with a por- 
 tion of the posterior wall ; the fourih is towards the lungs, and formed 
 by the upper part of the larynx defended by the epiglottis ; these 
 two are respiratory. The shape of the alimentary compartment is 
 very irregular, and capa'ble of great alteration by the movements 
 partly of the os hyoides and tongue with the larynx, and partly of 
 
DEGLUTITION. 543 
 
 the constrictor muscles forming its back and sides. Much lax areolar 
 tissue, containing no fat, surrounds it^ and allows of these movements 
 on the contiguous parts. As it is impossible in the compass of this 
 work to include a special description of the muscles and other con- 
 stituents of the, phajj^nx, we must suppose the reader to have already 
 made himself acquamted with them from the ordinary sources. 
 
 The soft palate contains a thick layer of glands under its mucous 
 membrane, in front of its muscles; and great numbers are situated 
 about the upper orifice of the larynx and on the general surface of 
 the pharynx. The tonsils are large and somewhat peculiar glands 
 projecting between the arches of the palate. They open by several 
 distinct orifices, which lead into cells, around which the secretory 
 structure, is arranged. They are very vascular organs, and evidently 
 placed where they are to lubricate the food in its passage from the 
 mouth. It is not, however, known with accuracy what is the nature 
 or composition of the secretion they furnish ; but it is, probably, 
 little besides simple mucus. That it is not identical with the saliva may 
 be inferred from the difference in striy?ture of the glands, and from 
 the tonsils being liable to inflammation and suppuration, as well as to 
 strumous enlargement, while the salivary glands are seldom or never 
 affected in the same way. 
 
 The food when sufficiently comminuted and mingled with saliva 
 in the mouth, and collected in the hollow of the tongue, is thrown 
 into the alimentary pharynx by the tongue being pressed upwards 
 against the roof of the mouth— this movement beginning at the tip, 
 and ending near the base. The division of the pharynx which is to 
 receive it is dilated as the food enters, by the advance and elevation 
 of the larynx, and by the yielding of its sides and posterior wall, 
 while the communication with the respiratory compartment above is 
 effectually closed by the coming together of the posterior pillars of 
 the fauces, by the contraction of the palato-pharyngeal and upper 
 constrictor muscles. The base of the tongue is now forced backwards 
 and upwards, so that the pellet is pressed between it and the soft 
 palate with its posterior pillars now in contact, anrt is thereby carried 
 downwards and backwards into that portion of the cavity which lies 
 behind the larynx. It crosses over the glottis without entering it, 
 because while the larynx is advanced the base of, the tongue presses 
 back the epiglottis, and so covers the orifice; this movement of the 
 epiglottis being assisted by the small aryteno-epiglottidean muscular 
 fibres, and by the very course of the food itself; but it is abundantly 
 proved, that even without an epiglottis the glottis would for the most 
 part be so closed by sudden spasm of its constrictors, as to prevent 
 any alimentary matters from falling into the larynx. In the act of 
 vomiting, where the matters pass in the contrary direction, it is proba- 
 ble that the glottis is partly protected by the backward position of the 
 tongue and epiglottis and partly by this conservative contraction of the 
 arytenoid muscles in answer to the mechanical stimulus of the food on 
 the mucous membrane in the vicinity. The pelkt of food having arrived 
 near the cesophagus, is projected into it by the contraction of the 
 
544 DIGESTION. 
 
 middle and inferior constrictors, the upper portion of that canal being 
 dilated by its entrance. 
 
 It might be imagined that a process which may thus be artificially 
 divided into consecutive stages, and which combine so many elabo- 
 rate and harmonized actions, would occupy something more than a 
 single second in its performance. It is, however, quite momentary. 
 The movements cannot be performed separately by any voluntary 
 control ; the food once willingly thrown by the tongue beyond the 
 isthmus of the fauces cannot be recalled, but is necessarily carried 
 forward to the stomach — a beneficent provision, in which the physical 
 supersede in a great degree the mental nervous actions, to ensure the 
 integrity of the vital function of respiration. On the action of the 
 nerves, however, we need add nothing to what has been already 
 stated (see 296, 306, 307, 487 and 488). 
 
 The msophagus is a tube continuous with the pharynx, fitted to 
 convey the food past the organs of respiration and circulation in the 
 thorax to the stomach below the diaphragm. It first lies upon the 
 vertebrae and inclines slightly to the left, bat afterwards, in its course 
 through the posterior mediastinum, it advances in front of the de- 
 scending aorta, and occupies the median line. It is surrounded in 
 its whole length by a lax areolar tissue, which permits its dilatation 
 and contraction during the passage of the food. It has a strong 
 muscular coat composed of two layers, an outer, of longitudinal 
 fibres, which commence from the cricoid cartilage; and an inner, of 
 circular fibres: both these spread out upon the stomach, and become 
 much thinner on that organ. The fibres of both layers are of the 
 striped kind in the upper part and for a variable way down, some 
 being often traceable as low as the diaphragm. In the middle region, 
 nnstriped fibres are mingled with the others ; and in the lower part 
 they are either the chief or only constituent. It has also a mucous 
 lining, continuous with that of the pharynx and stomach, but different 
 from both, being covered with a thicker and more opaque epithelium, 
 resembling cuticle, and thrown, when empty, into longitudinal folds 
 by the help of an abundant areolar tissue between the coats. Among 
 the creases, chiefly in the lower third, are scattered mucous glands, 
 which open on the surface, and serve to lubricate the canal daring 
 the passage of food. The cuticular lining of the oesophagus is changed 
 abruptly at the cardiac orifice of the stomach into the glandular lining 
 of the latter organ. Thus the oesophagus is organized as a simple 
 conduif. It has considerable muscular power, and a comparatively 
 thick and insensible lining membrane. 
 
 On receiving the morsel forced into its upper orifice by the last act 
 of pharyngeal deglutition, the oesophagus is mechanically dilated, 
 and its lining membrane stimulated by the contact. The result is a 
 contraction of its muscular coat upon the "pellet, which is thereby 
 carried forwards into the succeeding portions, in which the like ac- 
 tions are induced, until it has traversed the entire canaK This series 
 of actions is rapid and quite involuntary, but an obscure sensation 
 attends it, which is capable of being heightened to uneasiness or 
 pain if anv obstruction be met with, or if the descending morsel be 
 
THE STOMACH. 545 
 
 too hot. It has been already stated that the contractions are due to 
 a central stimulus on' the muscular nerves, derived from the pressure 
 of the food on those of the lining membrane (see p. 490). It has, 
 been pointed out by Miiller that rapid and slight peristaltic descend- 
 ing contractions occur in the oesophagus independent of the passage 
 of food. These are probably such as occur in the intestines and 
 uterus, without the accustomed stimulus and as a mere consequence 
 of their contractility. la vomiting, the oesophagus has an inverted 
 action, the muscular coat forcing up the food thrown into it from 
 below. In ruminating animals, this inverted peristaltic motion is 
 capable Of being accomplished by the will, and a similar power exists 
 in some individuals among mankind, of which we have witnessed 
 more than one striking example. 
 
 On passing a rapid series of electrical shocks down the oesophagus 
 of a dog just killed, the upper three-fourths of the tube are thrown 
 rnto continued or tetanic contraction, while the lower fourth takes on 
 a peristaltic or vermicular contraction ; thus demonstrating the situa- 
 tion of the change from the striped to the unstriped fibres of the 
 muscular coat, according to the recent test of Weber. 
 
 On the subject of the teeth the student may conveniently refer to the works of 
 Leeuwephoek, John Hunter, Thomas Bell; Tomes, Med. Gaz. 1839-46; Owen, 
 Odontography; Nasmyth on the Teeth; Miiller's Physiology, by Baly; Goodsir, Ed. 
 Med. and Sqrg. Journal, vol.51. On insalivation,he may consult Dr. Wright's works, 
 which are of "great interest and value, On deglutition, Dzondi's observations, iti 
 Muller, by Baly; a paper by Mr. Fergusson, in Med. Chir. Trans., vol. xxviii. p. 380; 
 and the Cyclop. Anat., arc. CEsuphagus, by Dr. Johnson. 
 
 CHAPTER XXIV. 
 
 DIGESTION CONTINUED. THE STOMACH. — ITS COATS, PARTICULARLY THE 
 
 MUCOUS COAT. STOMACH CELlrS AND TUBES. PYLORIC TUBES. r 
 
 MOVEMENTS OF THE STOMACH. THE GASTRIC JUICE, ITS NATURE AND 
 
 PROPERTIES. — PEPSINE. — STOMACH DIGESTION. 
 
 The alimentary canal below the diaphragm is naturally divided 
 into the stomach, the small intestine, and the large intestine, all of 
 which are lined by mucous membrane, have like the oesophagus, a 
 double muscular coat, and are, besides, invested with a serous mem- 
 brane, the peritoneum, which facilitates the motions by which the 
 contained matters are propelled from end to end. 
 
 The stomach, of which we have first to speak, is an elongated 
 curved pouch, very dilatable and contractile, fitted to receive the 
 food from the oesophagus, to retain it while acted on by the gastric 
 fluid secreted from the lining membrane, and then to transmit it to 
 the duodenum or first part of the small intestine. It is expanded 
 into an ample cul-de-sac at its left extremity, and becomes gradually 
 narrower towards the pylorus, where it joins the duodenum. A cir- 
 27 
 
546 DIGESTION. 
 
 cular constriction is often apparent three or four inches from the 
 pylorus, partially dividing thfe pyloric region from the rest of the 
 cavity. It has an anterior and posterior surface, which become re- 
 spectively rather upper and lower during repletion of the organ (owing 
 to its change of bulk, and its being fixed at its two orifices), and an 
 upper and lower curvature, called also lesser and greater, which un- 
 dergo a coi'responding alteration, becoming rather posterior and an- 
 terior. The peritoneum invests both surfaces, and passes from them 
 to the liver (forming the gastro-hepatic omentum), to the spleen 
 (forming the gastro- splenic omentum), and to the transverse colon 
 (forming first the anterior and then the posterior layers of the great 
 omentum). This peculiar arrangement of the serous membrane is 
 probably intended to allow of the extreme changes of bulk to which 
 this organ is liable. The muscular fibres of the stomach are continu- 
 ous with those of the oesophagus ; but, in consequence of its irregu- 
 lar shape and its bulging from the cardia towards the left hypochon- 
 drium and the umbilical region, these fibres are not regularly longitu- 
 dinal and circular as in the oesophagus, and as in the intestines. The 
 outer or longitudinal set may be best traced along the lesser curvature 
 and near the pylorus; and those beneath cross them either at right 
 angles or obliquely, according to their situation. Towards the lesser 
 extremity the fibres of both layers are much thicker, and particulary 
 so at the pylorus itself, where they form a circular constriction pro- 
 jecting the lining membrane, and capable of acting as a sphincter 
 muscle. They are of the unstriped variety. 
 
 The mucous membrane of the stomach is thick and soft, and thrown 
 into numerous irregular folds by the contraction of the muscular coat, 
 except in the distended state of the organ. To be capable of this 
 folding, it is separated from the muscular wall by a very lax areolar 
 tissue, containing no fat, but filled with the *essels belonging to the 
 raucous membrane, and also containing nerves. This is the coat 
 wrongly styled nervous by the older writers. 
 
 The stomach is freely supplied with blood by the three divisions 
 of the coeliac axis, the coronary, hepatic, and splenic. The branches 
 of the arteries reach it along its borders, soon pierce its muscular 
 tunic, and form plexuses in the sub-mucous areol&r tissue, where they 
 break up into numberless finer ramifications, which penetrate the 
 raucous coat. The veins accompany the arteries in their distribution 
 and discharge themselves into {he vena portae. Both orders of vessels 
 are very tortuous, and their contiguous branches everywhere anasto- 
 mose freely, so as to distribute the sanguineous supplies equally 
 during the changing volume of the organ. The nerves of the stomach 
 are derived from the pneumogastrics and from the coeliac plexus. 
 They advance from the lesser curvature over both surfaces, and after 
 supplying the muscular walls, enter the areolar layer under the secre- 
 ting lining membrane. 
 
 The mucous membrane of the stomach demands and will well re- 
 pay an attentive study. It is of that variety which has been termed 
 compound mucous membrane, i. e. its thickness is made up of an in- 
 finite mullJtude of tubular involutions of the simple membrane, with 
 
THE STOMACH. 
 
 547 
 
 intermediate vascular, and other tissues sent up into it from below. 
 The simple membrane consists of basement membrane and epithe- 
 lium, both of which are found throughout. The vessels are uniformly 
 on the deep surface of the basement membrane, and the epithelium 
 on its opposite surface. The compound mucous membrane of the 
 stomach is thinnest near the oesophagus, and is usually of a pinker 
 colour in the middle region, and paler towards the pylorus. 
 
 Over the whole surface of the membrane as seen on laying open 
 the organ, and stretching it so as to obliterate the larger folds, there 
 are visible, even with the naked eye, but still better with a lens, a 
 multitude of cavities of very irregular shape, and about ijj^th of an 
 inch in diameter, more or less (fig. 154, a). These cells are not the 
 result of creasings of the membrane, and they do not disappear when 
 it is stretched. They are usually filled with 
 mucus, which requires to be removed. Over 
 the greater part of the stomach they extend 
 in depth only about -g-th or Jth of the thick- 
 ness of the membrane, but they are larger 
 and deeper near the pylorus. In the ridges 
 between them runs a plexus of vessels larger 
 than ordinary capillaries (fig. 155 a, d), and 
 which often retains its blood after death, so 
 as to map out the cells in a beautiful manner. 
 This plexus is supplied by vessels sent up 
 from below, and may be very easily injected 
 artificially. 
 
 The epithelium which lines these stomach 
 cells and covers the ridges between them is 
 of the columnar variety (fig. 154 b) ; the 
 particles are shorter than in some other parts : 
 one end is free while the other is directed to- 
 wards the basement membrane ; and they 
 contain each a clear pellucid nucleus near 
 their deeper end. They seem to lie in a 
 double series, the deeper being in course of 
 development while the more superficial is in 
 course of decay. It has appeared to us that 
 each particle when arrived at maturity has, 
 besides the nucleus, granular contents enclos- 
 ed, and that at a subsequent period the gran- 
 ular contents escape at the free extremity by 
 a dehiscence or opening of the wall at that 
 part, leaving the transparent husk with its 
 nucleus subsisting for some time longer. 
 The clear structureless mucus which is al- 
 most always? found occupying the cells anci 
 covering the surface of the membrane seems 
 to be the altered contents, of these particles 
 after their escape, fo.r the unifonm. existence 
 of a minute cavity ia the- eenire of it, where it fills the cells, show 
 
 A. Inner surface oP the- sto- 
 mach, showiiigthe cells after the 
 mucus hafe been washed out. 
 Magnified 25 diameters, 
 
 B. Columnar epithelium of the 
 inner surface and cells- of the 
 Btojnach : — a Free ends of the 
 epithelial particles, ' seen on 
 looking down upon the memr 
 Vfane. 6. Nuclei visible at a 
 deeper level, c. The free ends 
 seen obliquely, d. Deep or at- 
 tached ends of the same. The 
 oval nuclei are seen near- the 
 deeper ends. 
 
 From the dog, MagniliedJSOO 
 diameters. 
 
648 
 
 DIGESTION. 
 
 that it has opz^d out from every part of their wall, so as gradually 
 to fill them up (see fig. 155, a). 
 
 Fig. 155. 
 
 Fig. 156. 
 
 V_ 
 
 Vertical section of a stomach eel], -with its tubes : 
 A in the middle regioti; b in the pyloric region', a a, 
 Orifices of the cells on t^ie inner surface of the sta- 
 mach. bb. Different depths at which the columnar epi- 
 thelium is exchanged for gla-ndulai, c. Pyloric tube, 
 or prolonged stomach cell. d. Pyloric tubes, termi- 
 nating variously, and lined to their extremities with 
 sub-columnar epithelium. 
 
 From the dog-, afier twelve hours' fasting. Magni- 
 fied 2(H) diameters. 
 
 A. Horizontal section of a stomach 
 cell, a little way within its orifice', 
 a. Basement membrane, b. Colum- 
 nar epithelium All but the centre 
 of the cavity of the cell is occupied 
 by transparent mucus, vrhich seems 
 to have oozed from the open extrem- 
 jiies of the epiihelial particles e. 
 Fibrous matrix surrounding and 
 supporting ihe basement membrane. 
 d. Small blood-vessel. 
 
 B. Horizontal section of a set of 
 stomach tubes proceeding from a 
 single cell. The letters refer to cor- 
 responding parts. The epithelium is 
 glandular; the nuclei very delicate ; 
 the cavity of the tubes very small, 
 and in some cases not visible. 
 
 From the dog. after twelve houra^i 
 fasting. Magnified SOO diameters. 
 
 It has been said that the cells are so shallow as to dip into the 
 compound membrane only about Jth of its thickness. The rest of 
 its thickness, except near the pylorus, is made up of minute tubular 
 offsets from the bottom of the cells, which may be termed the stomach 
 tubes, (fig. 155, b; and fig. 156,) and which pass vertically, two-, 
 three, or four from each cell, afterwards subdividing again and again, 
 and becoming more or less tortuous, till they terminate by blind ex- 
 tremities on a dense tough layer of areolar tissue continuous with 
 that laxer stratum which separates the mucous from the muscular 
 coat. 
 
 The stomach tubes have a basement membrane, and contain an 
 epithelium altogether different from that which has been just described. 
 Its particles are of the glandular variety, are rounded in shape, with- 
 out obvious walls ; their contents are darkly granular, often mixed 
 with oil globules, and their nucleus is less distinct. The tubes are 
 
THE STOMACH. 549 
 
 SO narrow that the particles seem to fill them, and obliterate their 
 cavity, except near their orifices, where they empty themselves into 
 the cells. Towards their blind extremities they often seem to be 
 simply a series or pile of epithelial particles; and this has led some 
 anatomists to deny that they are tubes. The existence, however, of 
 a basement membrane convinces us that they are to be regarded truly 
 as tubes, permanently laid down in the tissue of the stomach, for the 
 origination and discharge of the materials of their peculiar epithelial 
 particles on its inner surface. The tubes proceed in sets, correspond- 
 ing to the cells into which they open ; those of each set being en- 
 closed in a common envelope of nucleated tissue, lilce the matrix of 
 the kidney an,d some other glands. This firm investing structure is 
 attached on the one hand to the dense layer on which the compound 
 membrane rests, and on the other to the ridges between the cells; 
 and it sends delicate processes between the individual tubules of each 
 set, and between their branchings, so as to sustain every portion iil'^ 
 its proper place. Between the sets of tubules the larger vessels run 
 Tip to the ridges between the cells, and every tubule is invested with 
 capillaries, which take for the most part an upward direction, and are 
 cut across with the tubules in a transverse section of the latter, (fig. 
 155, B, d.) We have met with no tubular nerve fibres in the mucous 
 membrane of the stomach ; but it is highly probable that nucleated 
 nerve fibres run among) the tubes, though their want of characteristic 
 features renders it difficult to positively assert their presence. 
 
 The description now given will hold good for the whole lining of 
 the stomach, except near the pylorus. Here, in many of the lower 
 animals which we have examii;^ed, — for example, in the dog, and, it 
 may with probability be inferred, in man also, — a change occurs in 
 a very gradual manner, but evidently of an important kind. The 
 membrane is of a paler tint, and its cells seem not to terminate at 
 once in the true stomach tubes already described, but are prolonged 
 into much wider cylindrical tubes, lined with the same columnar epi- 
 thelium, and descending nearly or altogether to the deeper surface of 
 the compound membrane. For the most part, these prolongations of 
 the cells — pr, as we shall term them pyloric tubes — end at length in 
 very short and diminutive true stomach tubes (fig. 156, b); but we 
 have likewise found them terminating in either flask-shaped or un- 
 dilated extremities, lined throughout with the sub-columnar variety 
 of epithelium, (fig. ]56, d.) Thus in these animals a marked distinc- 
 tion exists between the mucous membrane of the pyloric compartment 
 and that of the rest of the organ, a distinction which must undoubt- 
 edly have an important physiological meaning ; and we have suspected 
 that the digestive power of the two parts must diflTer; that the office 
 of the pyloric tubes resembles that of the stomach cells generally, 
 and is different from that of the true stomach tubes; that perhaps the 
 acid product of the stomach may be furnished by one rather than by 
 the. other. We confess, however, that we have been unable, on the 
 one hand, to obtain human stomachs sufficiently fresh and healthy to 
 test the fact of the anatomical distinctness of the two regions in man, 
 or, on the other, to ascertain the value of the conjectures just alluded 
 
550 DIGESTION. 
 
 to as applied to animals in which the twofold structure is sufficiently 
 certain. 
 
 It is necessary to examine the changes that occur in the stomach 
 upon the introduction of food in it. These changes are threefold : — 
 1st, as regards its muscular coat; 2dj as regards its mucous mem- 
 brane; and, 3d, with respect to the nature and properties of the se- 
 cretion which is derived from that membrane. 
 
 1. Movements of the Stomach. — On exposing the stomach of a 
 living animal, or of one recently killed while digestion is going on, 
 we find that it firmly embraces its contents, and that both orifices are 
 closed, so as to prevent the escape of the food. This is particularly 
 the case as regards the pyloric orifice in the first period of digestion. 
 The contraction of the circular muscle which surrounds the pylorus 
 is so strong, that, even after the stomach has been separated from the 
 intestines, its contents do not escape for some time. 
 
 This contraction is due to the stimulus of the food ; and, when 
 the aliment is diificult of digestion, the muscular coat is proportion- 
 ably stimulated. 
 
 The movements of the stomach are very different in its cardiac and 
 in its pyloric portions. In the cardiac, two-thirds the movements are 
 very slow and scarcely perceptible, and seem to consist in little more 
 than a firm and steady contraction upon the contents, the muscular 
 coat thus slowly pushing on the food towards the pyloric portion, and 
 adapting itself to the diminished size of the organ. In the pyloric 
 portion they resemble closely the peristaltic movements of the intesti- 
 nal canal, which indeed appear, as it were, to start from the junction 
 of this portion of the stomach with i\^ cardiac portion. Under the 
 influence of the magneto-electric apparatus this mode of contraction 
 of the pyloric fibres may be well shown in dogs or cats just dead, 
 and the contrast with the action of the cardiac fibres may be strikingly 
 displayed. 
 
 We had lately an opportunity of observing the peristaltic character 
 of the movement of the pyloric portion of the stomach during life, 
 in a woman in whom that organ was so enormously enlarged as to 
 occupy nearly the entire abdominal cavity, the intestines being pushed 
 into the pelvis, and the arch of the colon lying behind the stomach. 
 The patient was so emaciated, and the abdominal parietes so attenu- 
 ated, that the action of the viscus could be distinctly seen through 
 them ; and it appeared to resemble precisely the vermicular action of 
 the intestines, for which, indeed, it was taken, as the nature of the case 
 could not be distinctly recognized during life. 
 
 When the action of the stomach is energetic, a constriction is pro- 
 duced, by which the pyloric third is separated from the cardiac por- 
 tion, thus giving rise to the hour-glass contraction, which continues 
 for some time after death if the animals have been killed at the mo- 
 ment of its occurrence. The same condition may be produced by 
 the magneto-electric apparatus. This constriction has been noticed 
 by all observers in dogs and cats, and may be now and then seen in 
 the human stomach. In some animals such a division between the 
 
CHANGES IN THE GASTRIC MUCOUS MEMBRANE. 551 
 
 two portions of the stomach exist in the natural conformation of the 
 organ. 
 
 The muscular action of the stomach in man anrl the mammalia seems 
 merely to push on the food into the intestine, and not to subject it to 
 any trituration or mechanical reduction, according to the views of 
 the physiologists of the early part of the last century. Reaumur, and 
 after him Spallanzani, introduced into the stomachs of dogs and cats 
 perforated tubes, made some of brittle and others of flexible materials- 
 These were found quite unaltered by the action of the stomach, al- 
 though the portions of food contained in them were softened and 
 digested. 
 
 2. Changes in the mucous membrane of the Stomach. — The gastric 
 mucous membrane of the stomach of an animal killed during stomach 
 digestion exhibits a faintish red and swollen appearance, due evidently 
 to an increased afflux of blood, excited by the stimulus of the food. 
 In the dog this redness is limited in a very marked manner to the 
 splenic two-thirds, the pyloric third presenting a white colour and a 
 wrinkled appearance, from the existence of numerous minute folds 
 upon it, which stretching does not obliterate. At the same time the 
 whole surface of the membrane is covered by a layer of mucus, which 
 varies in its thickness and in its viscidity. 
 
 It may be inferred from Beaumont's observations, that similar phe- 
 nomena are met with in the human stomach. Beaumont found that, 
 immediately on the introduction of food into the stomach, the vessels 
 of the mucous membrane became more injected, much, no doubt, as 
 those of the conjunctiva of the eye would become filled on the ap- 
 plication of a foreign body; and that its colour became deeper, being 
 changed from a pale pink to a deep red. A pure, colourless, and 
 slightly viscid fluid, with distinct acid reaction, was then observed to 
 distil from the surface of the membrane, and to collect in drops at 
 various points of it, trickling down the wall of the stomach until it 
 mingled with the food. The exudation of this fluid was always ex- 
 cited by the contact of any foreign substance ; even so smooth a sub- 
 stance as the bulb of a thermometer invariably excited it on its intro- 
 duction, and even when it had been previously ascertained that the 
 stomach was empty, and exhibited no reaction. 
 
 During fasting Mr. Beaumont observed no evidence of the exist- 
 ence of such a fluid as this, the sole contents of the stomach being 
 then only a little viscid mucus, occasionally slightly acidulated. 
 Beaumont describes this fluid as being clear, transparent, inodorous,, 
 saltish, and resembling in taste thin mucilaginous water slightly acid- 
 ulated with muriatic acid. It is, he states, readily diffusible in water, 
 wine, or spirits, and effervesces slightly with alkaline carbonates. It 
 coagulates albumen, and is powerfully antiseptic, checking putrefac- 
 tion in meat. When pure it will keep for many months; but if 
 diluted with- saliva, it becomes foetid in a few days. According to 
 the analysis of Professor Dunglison it contained free muriatic and 
 acetic acids, phosphates and muriates of potass, soda, magnesia, and 
 lime. 
 
 Beaumont's observations were made during a period extending be- 
 
552 DIGESTION. 
 
 tween May, 1825, and March, 1833. Various observations and ex- 
 periments, commencing from a date long antecedent to this, had led 
 to a very generally received opinion among physiologists that the 
 mucous membrane of the stomach was the seat of a special secretion, 
 which had a great share in affecting the changes which the food un- 
 dergoes in the stomach. 
 
 Reaumur was the first to offer satisfactory proof of the secretion 
 of a solvent fluid for the purposes of digestion by the walls of the 
 stomach. He obtained some of this fluid by making animals swal- 
 low sponges, which he could draw out of their stomachs by a string 
 attached ; and thus he was enabled to institute experiments on arti- 
 ficial-digestion, so as to show that alimentary substances out of the 
 body could be altered by this fluid in the same manner as they are 
 changed in the stomach. He likewise introduced food into the 
 stomachs of animals in perforated tubes, whereby they were defended 
 from the pressure of the walls of the stomach, but could imbibe its 
 fluids. His experiments disproved the favourite theory of the day, 
 which ascribed all changes of the food in stomach digestion to the 
 influence of trituration upon it by the action'of the muscular coat of 
 the stomach : they showed that the trituration in the gizzard of birds 
 was no more than mastication by teeth in other animals, and that 
 digestion was accomplished in birds of prey, dogs, &c., and probably 
 in man, by the action of a fluid which exerted a solvent influence 
 upon the food. Mem. de VAcad. des Sciences, an. 1752, pp. 705^ 
 752. 
 
 Spallanzani likewise illustrated this subject by numerous experi- 
 ments upon vertebrate animals of all classes, and even upon himself. 
 Following the plan of Reaumur, he obtained the gastric juice by 
 means of sponges, and he introduced food into the stomachs of ani- 
 mals enclosed in perforated tubes and balls. His essay on the sub- 
 ject of digestion is one of the most interesting dissertations in the 
 literature of physiology, and is full of f^cts proving the secretion of 
 a fluid capable of reducing and dissolving alimentary substances. 
 
 Stevens availed himself of a rare opportunity of investigating the 
 effects produced on food in the human stomach. A hussar had ac- 
 customed himself at the early age of seven to swallow stones and 
 other hard bodies; and, having continued the practice during twenty 
 years, what had originated in idle amusement was now resorted to 
 as a regular profession, to supply the necessaries of life. When Dr. 
 Stevens first saw him, his stomach was so distended, apparently by 
 the considerable weight to which it was repeatedly exposed, that he 
 could swallow several stones at once, which were not only felt in the 
 stomach, but might be heard by the bystanders moving against each 
 other when the hypogastric region was struck. 
 
 Dr. Stevens made this man swallow perforated silver balls, con- 
 taining sometimes raw animal food, sometimes vegetable substances ; 
 in general, raw animal substances suffered less than those which were 
 roasted or boiled ; roasted or boiled animal substances which had 
 been mechanically divided were most completely acted on ; the sub- 
 
SOLUTION OF THE STOMACH AFTER DEATH. 553 
 
 stances contained in balls with large holes were more completely 
 acted on than those contained in balls with minute holes ; and, 
 lastly, the various vegetable grains, as wheat, rye, barley, oats, and 
 peas, were least of all altered, having only become moistened and 
 swollen, while bone underwent no change. 
 
 Dr. Stevens also introduced leeches and earthworms in his per- 
 forated spheres, and found that even these animals, though intro- 
 duced living, were dissolved as inanimate matters** 
 
 John Hunter made some observations which furnished an inter- 
 esting proof of the existence of a solvent gastric fluid. He was 
 struck with the condition of the stomach in two cases of sudden and 
 violent death. A man had his skull fractured by a single blow of 
 a poker ; just before the accident he was in perfect health, and had 
 taken a hearty supper. Upon opening the abdomen, he found that 
 the stomach, though it still contained a good deal, was dissolved at 
 itf great end, and a considerable part of its contents lay loose in 
 the general cavity of the belly ; a circumstance, he adds, which 
 puzzled him very much. The second instance was in a man who 
 died at St. George's Hospital a few hours after receiving a blow on 
 his head which fractured his skull. In both these cases the solution 
 was at the splenic end of the stomach ; the edges of the opening 
 and the mucous membrane for some distance within were half dis- 
 solved, "very much," says Hunter, "like that kind of digestion 
 which fleshy parts undergo when ha^f digested in a living sto- 
 mach, or when acted upon by a caustic alkali,' viz., pulpy, tender, 
 ragged." 
 
 " In these cases," Mr. Hunter adds, " the contents of the stomach 
 are generally found loose in the cavity of the abdomen about the 
 spleen and diaphragm ; and in many subjects the influence of this 
 digestive power extends much farther than through the stomach. I 
 have often found, that, after the stomach had been dissolved at the 
 usual place, its contents, let loose, had come into contact with the 
 spleen and diaphragm, had dissolved the diaphragm quite through, 
 and had partly afi'ected the adjacent side of the spleen ; so that 
 what had been contained in the stomach was found in the cavity of 
 the thorax, and had even affected the lungs to a small degree." 
 
 " There are very few dead bodies in which the stomach at its 
 great end is not in some degree digested ; and one who is acquainted 
 with dissection can easily trace these gradations. To be sensible of 
 this effect, nothing more is necessary than to compare the inner 
 surface of the great end of the stomach with any other part of its 
 inner surface : the sound portions will appear soft, spongy, and 
 granulated, and without distinct bloodvessels, opaque and thick ; 
 while the others will appear smooth, thin, and more transparent, 
 and the vessels will be seen ramifying in its substance ; and upon 
 squeezing the blood which they contain from the larger branches to 
 
 * De Alimcntorum Concootione, Edinb. 1777 (in Smellie'e Thes. Med.). 
 36 
 
554 DIGESTION. 
 
 the smaller, it will be found to pass out at the digested ends of the 
 vessels, and to appear like drops on the inner surface."* 
 
 Hunter remarked that solution of the stomach is very commonly 
 found in fishes, which almost always die a violent death, and fre- 
 quently during digestion. f 
 
 Dr. Carswell investigated this subject, and obtained results con- 
 firmatory of the views of John Hunter. He killed rabbits and dogs 
 during the digestive process, allowing them to lie for various periods 
 after death. If examined four hours after death, he found that the 
 solution had affected the mucous, submucous, and muscular tunics ; 
 when six hours had elapsed, the peritoneal coat was found softened, 
 in addition to the others; the stomach was consequently perforated, 
 and the food passed through the opening and came in contact with 
 the liver, spleen, diaphragm, and intestines, one or all of which ex- 
 hibited the same kind of softening as that found in the stomach, at 
 those places where the digested food touched the parts. In another 
 series of experiments, where the animals were suffered to lie for a 
 still longer period after being killed, perforation of the diaphragm 
 or oesophagus had taken place, and the liquid part of the food had 
 flowed into the cavity of the chest, causing digestion and softening 
 of the pleura and of the lungs. J 
 
 3. The Gastric Juice. — From these various sources we derive the 
 most ample evidence of the existence of a fluid secreted by the wAlls 
 of the stomach during digestion, capable of exerting a reducing or 
 solvent influence upon food. This fluid is the gastric juice — the 
 succus gastricus. 
 
 It is of great importance to a correct theory of digestion to de-, 
 termine the precise composition of this fluid. Dr. Prout, in this 
 cpuntry, in 1823, two years prior to the commencement of Beau- 
 mont's experiments, had determined the existence of an acid fluid 
 secreted during digestion, and had analyzed it in the rabbit, hare, 
 horse, calf, and dog. And he announced, as the result of his ana- 
 lyses, "that free or at least unsaturated muriatic acid, in no small 
 quantity, exists in the stomach of those animals during the digestive 
 process." And in later publications, Dr. Prout has reasserted this 
 statement. 
 
 The weight which is so deservedly attached to the opinion of this 
 eminent philosopher has, no doubt, had great influence in determin- 
 ing the prevalent opinion in this country in favour of the view which 
 attributes the acidity of the gastric fluid to the existence of free 
 muriatic acid in it. The source of the acid, it is generally believed, 
 is the chloride of sodium of the blood, which at the mucous mem- 
 brane of the stomach contributes muriatic or hydrochloric acid to 
 the gastric juice, leaving free soda to be carried to the liver by the 
 veins of the stomach. 
 
 * Hunter's Animal Economy, Owen's edition, p. 119. 
 
 ■}• Spall'anzani confirmed Hunter's statements. 
 
 J Ed. Med. and Surg. Journal, toI. xxxiv. p. 262. See also an excellent delinea- 
 tion of this post-mortem condition, by Dr. Carswell, in his " Illustrations of the Ele- 
 mentary Forma of Disease," art. Softening. 
 
THE GASTRIC JUICE. 555 
 
 Experiment, however, shows that muriatic acid has little or no 
 solvent power on the food, and that the reducing action of the gas- 
 tric fluid cannot be attributed to it alone. Albumen or meat sub- 
 jected to the action of water acidulated with muriatic acid, and kept 
 for some hours at a temperature of 100°, undergoes no change 
 of any importance : neither substance exhibits any softening or 
 tendency to putrefaction or decomposition of any kind. Similar 
 experiments with acetic acid or with phosphoric acid lead to like 
 results. 
 
 It is plain, then, that the solvent powers of the gastric fluid are 
 not due simply to the acid which it contains, whatever that may be, 
 and that we must look for some other ingredient in it,'which, either 
 alone or in combination with acid, can exercise these powers. The 
 clue to this was given by Eberle, who adopted the expedient of 
 adding to water acidulated with mui'iatic acid a small piece of the 
 mucous membrane of the stomach. By this means he succeeded in 
 obtaining a digestive fluid which reduced animal substances as per- 
 fectly as the gastric juice itself. • 
 
 This discovery was of the last importance to the formation of a 
 correct theory of stomach digestion, and to exact views of the nature 
 of the gastric juice. It was soon followed up by numerous experi- 
 ments in Germany, by Schwann and MUller, and by Purkinje and 
 Pappenheim. The general result of these experiments was, that 
 the addition of a portion of gastric mucous membrane from the 
 true secreting stomach to an acidulated water produced a perfect 
 digestive fluid; but that no other mucous membrane would answer 
 this purpose. The following changes take place on macerating meat 
 and albumen in a digestive fluid : The meat is broken down to a 
 complete pulp; and if the digestion have been continued sufiiciently 
 long, it is dissolved. The albumen is likewise equally softened. 
 The early changes which take place in a cubic piece of solid white 
 of egg, macerated in the digestive fluid, are very characteristic. 
 Its edges become of a pearly hue, semi-transparent, almost fluid', 
 breaking down under the slightest touch of the finger ; and, after 
 longer digestion, the solid matters are completely dissolved. 
 
 The solvent power of a digestive fluid made with the mucous 
 membrane of the stomach is strikingly displayed if the results of 
 the digestion of meat and albumen with it be compared with those 
 obtained by digesting pieces of the same substances either with 
 simply acidulated water — muriatic, acetic, or phosphoric acid 
 being used — or with an infusion of mucous membrane without acid. 
 Simple acidulated fluids produce little or no change in meat and 
 albumen in the course of twelve or twenty-four hours ; and such 
 change as is produced presents a marked contrast to that caused by 
 the infusion of mucous membrane with acid. No acid, however, 
 appears to cause more change than the phosphoric. When the 
 .infusion of mucous membrane is used without acid, rapid putrescence 
 is produced. A similar effect results, alth^ough with less intensity, 
 from the use of too little acid ; and, if alkali be added, the putre- 
 faction becomes still more rapid and intense. 
 
556 DIGESTION. 
 
 In these experiments, it is of great importance to pay close atten- 
 tion to the temperature. It should be within the range of from 90° 
 to 110°, the higher temperature increasing the energy of the diges- 
 tive action. If it reach the point at which albumen is coagulated, 
 all solvent change ceases, and the meat or albumen becomes hard- 
 ened. In a low temperature, likewise, there is no change ; the 
 digestive fluid under such circumstances serving merely to prevent 
 decomposition. 
 
 The antiseptic power of an acid infusion of gastric mucous mem- 
 brane is one of its most remarkable properties ; and in this respect 
 it resembles the gastric fluid itself, which, according to all observers, 
 is remarkably antiseptic, being capable of, checking the further pro- 
 gress of putrefaction in meat in which that process had already 
 begun. This power seems principally due to the acid, the neu- 
 tralization of which destroys it; and if an infusion of mucous mem- 
 brane to which enough acid had not been added become putrescent, 
 its further decomposition may be checked by the addition of more 
 acid. We have kept the artificial digestive fluid for many months 
 in a bottle with a common cork without its undergoing any change. 
 
 The gastric fluid possesses the property of causing the coagulation 
 of the caseine of milk ; an artificial digestive fluid made from the 
 mucous membrane of the true stomach of ruminants possesses the 
 same power, even if its acid be neutralized by potass. This fatt 
 has been long known to the makers of cheese ; and the dried mucous 
 membrane of the fourth stomach of the calf has been used, under 
 the name of rennet, for the purpose of coagulating that principle in 
 milk. That it possesses this power independently of any acid which 
 it may contain, was first pointed out by Berzelius. Some have 
 affirmed that this power belongs only to the mucous membrane of 
 the stomach of sucking animals. 
 
 A fluid of such digestive power as that above described cannot be 
 made from any mucous membrane but that of the stomach. The 
 mucous membrane of the bladder, of the greatest portion of the 
 intestinal canal, is quite insufficient for this purpose ; but that of the 
 duodenum appears to exert some solvent influence. 
 
 The Organic Principle of the G-astric Juice. — All these facts show 
 that the gastric mucous membrane contains some material, which, 
 when dissolved or diffused in acidulated water, exercises a power 
 not to be distinguished from that of the gastric juice itself. Can 
 this material be isolated ? There is no doubt that we can obtain 
 from the mucous membrane of the digestive stomach of animals, an 
 organic substance, which exhibits reactions in close analogy with 
 those of albumen, and which exercises a solvent or catalytic influ- 
 ence upon various azotized substances ; to this substance Schwann 
 and Miiller gave the name pepsine.* 
 
 Valentin very justly remarks that the organic combinations upon 
 iifhich the solvent power of the gastric fluid depends, share the same 
 fate with other contact substances, namely, that they cannot be ob- 
 
 * Also called gasteraae, by French writers. 
 
THE GASTRIC JUICE. 557 
 
 tained in perfect purity, nor can their precise relative proportions 
 be determined with exactness. Pepsine, therefore, He adds, can 
 only be regarded as an hypothetical or conventional name for an un- 
 known mass which may be separated by alcohol, or by lead and al- 
 cohol in combination with other bodies. Nor do the reagents indi- 
 cate any definite character — they only aiford conjectural information. 
 To view it as a kind of diastase, whilst it does not remove our diffi- 
 culty, nevertheless denotes the power of the unknown substance in 
 a more precise and definite manner. 
 
 An artificial digestive fluid may be made in the following manner. 
 Let a piece of the mucous membrane of the stomach of a pig be 
 macerated in distilled water for twelve hours at the temperature -of 
 98° or 100° ; afterwards, add dilute muriatic acid to the fluid until 
 it redissolves the precipitate which is at first thrown down ; the fluid 
 thus formed will be found to possess full digestive powers, and all 
 the properties of the gastric fluid. It is, in fact, an acidulated so- 
 lution of pepsine in water. The pepsine may be precipitated from 
 this solution by some of the reagents which coagulate albumen. 
 Bichloride of mercury will do this, and render the fluid inert. Al- 
 cohol and water at the. boiling temperature produce the same effect; 
 the precipitate, however, thrown down by alcohol, is capable of being 
 redissolved in water, and then, with acid, will produce a digestive 
 fluid. Tannin also precipitates it. It is evident, therefore, that the 
 digestive fluid contains a principle capable of aff'ording distinct re- 
 actions. The solvents of this principle are water and dilute muria- 
 tic or acetic acids. 
 
 The power which the digestive fluid has of coagulating caseine, 
 indefendently of its acid, denotes that it holds in solution some 
 special agent derived from the mucous membrane of the stomach. 
 
 Alcohol added to a fresh infusion of mucous membrane throws 
 down a white flocculent precipitate, which may be collected on a 
 filter, and when dried will produce a gray compact mass. This, 
 when redissolved in water, will exhibit digestive powers, and these 
 powers are greatest when it is united with acetic and muriatic acids. 
 We obtain in this way the nearest approach to the isolation of pep- 
 sine. 
 
 The Acid of the Grastric Juice,. — Of the existence 'of an organic 
 principle, a secondary organic compound, the product of the secre- 
 tory action of the mucous membrane of the stomach, no doubt can 
 be entertained ; but we can speak with less certainty of the nature 
 of the acid which exists along with it in the gastric fluid of the 
 stomach, inasmuch as recent observers have thrown a doubt upon 
 the correctness of Prout's opinion. The following are the most re- 
 cent opinions put forward on this subject. 
 
 Blondlot affirms that the acidity of the gastric juice is due not to 
 the presence of a free acid, but to, the existence of biphosphate of 
 lime as one of its ingredients. To this, however, Melsens and 
 Dumas raise the objection that carbonate of lime, or Iceland spar, 
 placed in gastric juice for some hours, becomes corroded and su3"ers a 
 very notable diminution of weight, which can arise solely from the pres- 
 
558 DIGESTION. 
 
 ience of a free acid. MM. Bernard and Barreswil likewise state 
 some strong objections to the views of M. Blondlot in a paper pub- 
 lished in 1844. They show that M. Blondlot failed to obtain eflFer- 
 vescence by adding carbonate of lime to gastric juice, because he 
 employed a too much diluted fluid ; on concentrating the gastric 
 juice a little, the effect was readily produced. Admitting that a 
 free acid is present, they deny that it is hydrochloric acid, because 
 that acid exists in the gastric fluid only in the state of chloride. If 
 a minute quantity of oxalic acid be added to the gastric juice, a pre- 
 cipitation is occasioned by the formation of insoluble oxalate of lime, 
 whilst an equal quantity of the same reagent, added to distilled 
 water containing a two-thousandth part of hydrochloric acid; to 
 which chloride of lime had been added, produced no such effect. 
 The lime of the gastric juice unites with the oxalic acid ; but that 
 acid will not displace lime from its connection with hydrochloric acid. 
 Nor is the acid of the gastric juice free acetic acid ; the most deli- 
 cate tests failed to detect it. MM. Bernard and Barreswil infer 
 that there is in the gastric fluid a minute proportion of phosphoric acid, 
 which, however, is not the only free acid. The lactic acid, accord- 
 ing to these observers, is the principal acid of the gastric juice, be- 
 cause the behaviour of a fluid acidulated with that acid corresponds 
 very exactly under chemical examination with that of the gastric 
 juice. Thus the distillation of water acidulated with lactic, acid 
 exhibits exactly the same stages as that of the gastric fluid — first, 
 there passes over only pure water, in the next stage an acid liquid, 
 in which salts of silver do not throw down a precipitate, and there 
 remains a strongly acid fluid effervescing with carbonates ; in this, 
 remaining liquid hydrochloric acid may be detected, if a minute 
 quantity of chloride of sodium had been added to the fluid previous 
 to distillation. 
 
 The acid of the gastric juice produces salts of zinc, lime, baryta, 
 and copper, similar to those formed by lactic acid ; and MM. Ber- 
 nard and Ba,rreswil afiirm that it readily decomposes the chlorides 
 in concentrated solutions. Hence it is that hydrochloric acid 
 passes over in the last products of the distillation of the gastric 
 juice. 
 
 These authors also state that the nature of the food appears to ex- 
 ercise no influence upon the nature of the acid, and that they have 
 always found free lactic acid, whether after an exclusive vegetable 
 or animal regimen continued for many days, or after a prolonged 
 very sparing diet. 
 
 Dr. R. D, Thompson, of Glasgow, in a paper published in 1845, 
 also disproves the opinion of Blondlot by experiment, and comes 
 to the conclusion that the free acid of the stomach, in the digestion 
 of vegetable matter at least, of all the known acids corresponds only 
 with the lactic. 
 
 Lehmann attributes the acidity of the gastric fluid to both free 
 iiydrochloric and lactic acids. He obtained the former from the 
 stomach of a diabetic patient, to whom he had administered an 
 ipecacuanha emetic ; and the latter from the stomach of a cat, 
 
THE GASTRIC jblCE. 5^9 
 
 from which he was Etble to procure distinct crystals of lactate of zinc. 
 In subsequent researches, Lehmann confirmed this conclusion respect- 
 ing the nature of the acid of the gastric fluid. , 
 
 Liebig lends his sanction to this doctrine, and especially to the 
 view put forward by Bernard and Barreswil, that both lactic and 
 phosphoric acids exist in this fluid free, while there is no reason to 
 deny the existence of an acid phosphate likewise. The opinion 
 that free lactic acid exists in the gastric fluid is not new. It was 
 put forward by Chevreul many years ago, and afterwards by Leuret 
 and Lassaigne. In 1823 our distinguished friend. Dr. Graves, of 
 Dublin, published analyses of th^ fluid oi the stomach from two pa- 
 tients, in which he found free lactic acid in abundance. Notwith- 
 standing what has been done on this subject, it must be confessed 
 that the full truth has scarcely yet been arrived at. We have yet 
 to learn whether the constitution x)f the gastric juice is constant — 
 whether the same acids or acidifying agents are present in all ani- 
 mals, and under all conditions of feeding and food ; and we have 
 also to ascertain whether any and what changes may be produced 
 by disease in the chemical characters of the gastric fluid. The in- 
 quiry taken up on a large scale among the lower animals, and ex- 
 tended to man, in health and disease, would, no doubt, yield most 
 valuable and interesting results. 
 
 The digestive principle does not seem to be secreted in equal 
 quantity or of equal power at all parts of the stomach. Meat and 
 albumen, digested with mucous membrane from the cardia, is by no 
 means so much acted upon as if digested with mucous membrane 
 from the pylorus or from the central part of the stomach. In the pig, 
 there is a large patch of the membrane of a reddish hue, and of 
 considerable thickness, forming that portion of the mucous membrane 
 which corresponds to the middle of the great curvature of the sto- 
 mach ; this, we find, exercises a more energetic action upon, meat or 
 albumen than any other part. 
 
 It is highly interesting to notice that the mucus which accumu- 
 lates upon the surface of the mucous membrane of the stomach has 
 a digesting power corresponding to that of the portion of mucous 
 membrane from which it has been taken. This we have determined 
 by our own experiments. 
 
 Nature of the Digesting Power of the G-astric Juice. — Having 
 stated the leading facts which observation and experiment have de- 
 veloped respecting the act of digestion in the stomach, it remains 
 to inquire what is the real nature of the digesting power of the 
 gastric fluid. 
 
 Two questions present themselves for consideration : is the digest- 
 ing power of the stomach a true solvent power, producing simply 
 a solution of .the matters submitted to its action, without eff'ecting' 
 any change in their chemical constitution? or does the digestive fluid 
 exercise a catalytic action on the substances submitted to it, where- 
 by' it efi"ects a chemical decomposition of them, similar to that pro- 
 duced in barley by diastase, whereby the starch of the grain is 
 
560 DIGESTION. 
 
 Converted into sugar, or like the action of yeast upon sugar, whereby 
 the latter is decomposed into carbonic acid and alcohol ? 
 
 To decide these questions, it is necessary to examine the exact 
 nature of the changes produced in the food by stomach digestion. 
 
 Milk. — If milk be introduced into the stomach, its caseine is first 
 coagulated and afterwards apparently dissolved. The solidified 
 caseine seems gradually to melt down and becomes absorbed. In 
 overfed infants, milk-curd appears in the stools in considerable 
 quantity, the child having received so much milk that its stomach 
 is unable to digest the caseine precipitated from it. When, how- 
 ever, the quantity of milk is in Just proportion to the digestive 
 power of the stomach, all the cur* is digested, and therefore none 
 is found in the stools. 
 
 Albumen. — White of egg (ovalbumen), if swallowed raw, is imme- 
 diately coagulated by the gastric juice and then dissolved. Tiede- 
 mann and Gmelin found that, after three hours' sojourn in the sto- 
 mach of a dog, albumen was dissolved, forming " a yellowish mucous 
 liquor," which coagulated readily by heat. 
 
 Coagulated albumen becomes softened down and dissolved in the 
 fluids of the stomach, from which it may again be precipitated by 
 heat or nitric acid. 
 
 In experiments with the artificial digestive fluid, we find that if 
 the fluid in which albumen had been digested be carefully filtered 
 and subjected to heat and nitric acid, a copious precipitate of albu- 
 men will take place. 
 
 Meat is softened, gelatinized, and dissolved, and albumen may be 
 precipitated by heat, nitric acid, or ferrocyanate of potass from the 
 liquids obtained from the stomach. 
 
 Vegetable Substances. — In all the experiments upon animals of the 
 carnivorous kind (cats, dogs), bread, potatoes, and other vegetable 
 substances underwent change much more slowly than animal matters, 
 and they became softened by admixture with the fluids of the sto- 
 mach and appeared partially dissolved. 
 
 Boiled starch, in Tiedemann and Gmelin's experiments, underwent 
 solution, and then did not exhibit its characteristic blue colour with 
 iodine. In a dog, killed flve hours after a meal of boiled starch, the 
 contents of the stomach underwent no change of colour with iodine, 
 but appeared charged with sugij,r and with a kind of gum of starch 
 (dextrine). In another dog, similarly fed, and killed three hours 
 afterwards, the starch which was dissolved did not react in the usual 
 manner with iodine, but some portions not yet dissolved did exhibit 
 the characteristic reactions. It would seem that immediately the 
 starch becomes dissolved by the gastric fluid it loses its characteristic 
 property of forming the blue iodide of starch.* 
 
 In the artificial digestion of starch, with the mucous membrane of 
 the human stomach, we have not succeeded in producing any change 
 in the starch: it still evinced its usual reaction with the iodine test. 
 
 * Tiedemaim and Gmelin, Recherches sur la Digestion, par Jourdain, t. i. p. 840. , 
 
RATE OF STOMACH DIGESTION. 561 
 
 We have, however, found that starch digested for some time in this 
 way evolved a peculiar sour smell like that of cheese. 
 
 Bouchardat and Sandras report, respecting the influence of 
 stomach digestion upon starch, and upon amylaceous elements, differ- 
 ently from Tiedemann and Gmelin. They state that they have been 
 unable to obtain any evidence of the conversion of starch into sugar ; 
 that neither by fermentation, nor by the polarizing apparatus of M. 
 Biot, have they succeeded in procuring any indication of the exist- 
 ence of sugar in the digested substances; and they were equally . 
 unsuccessful in detecting the formation of dextrine. Lactic acid, 
 however, appeared to them to be formed in much larger quantity 
 after a meal of starch than after*one of fibrine or of gluten. These 
 observers likewise state as the result of their experiments, that in 
 the human subject, and in the carnivora, feculent substances are 
 digested with extreme slowness, and not at all unless the integument 
 of the starch-grain have been ruptured by boiling. 
 
 Fatty or oily substances, as suet, fat, oil, butter, or wax, undergo 
 
 i;io change in the stomach, according to Bouchardat and Sandras, 
 
 after the lapse of some hours, and may be found in that organ un- 
 
 • changed, in the midst of other matters upon which the stomach 
 
 exercises a solvent action. 
 
 This we have observed in our own experiments ; and on perusing 
 the MS. notes of the results of various experiments made thirty 
 years ago by Sir B. C. Brodie, and with great kindness placed at 
 our disposal by him, we find the following statement: "When dogs 
 were fed on lard, the lard passed into the small intestine unchanged." 
 
 It would seem to be the most reasonable conclusion which we can 
 deduce from the preceding statements, that, in man and the car- 
 nivora, the fluid secreted by the stomach during digestion simply 
 dissolves animal and vegetable substances of the azotized kind, with- 
 out altering their chemical constitution, leaving amylaceous, oily, 
 saccharine, and the allied substances but little or not at all acted 
 upon. 
 
 The Chyme. — The mass that is contained in the stomach after 
 digestion has been going on for four or five hours, and which is com- 
 monly known by the name of chyme, consists of aliments dissolved, 
 or softened and prepared for solution or other change by the gastric 
 juice. As they are mostly of the same kind, this mass presents a 
 homogeneous appearance, except when substances are present which 
 either require a longer sojourn in the stomach or are only digestible 
 by some lower portion of the intestinal tube. 
 
 Rate of Stomach Digestion. — The process of stomach digestion is 
 a slow one. In the artificial digestions above referred to, it took 
 from eight to twelve hours to produce any marked effect upon the 
 pieces of meat and albumen submitted to the action "of the digestive 
 fluid. This, however, is much longer than the natural process. Ac- 
 cording to Dr. Beaumont's researches upon Alexis St. Martin, it 
 took three or four hours before the stomach became empty after a 
 meal, consisting chiefly of azotized food — and his tables show that 
 the mean time required for the digestion of the principal animal 
 
562 DIGESTION. 
 
 substances in common use, such as butcher's meat, fowl, game, was 
 from two hours and three-quarters to four hours. 
 
 In experiments on dogs, it has been found by most experimenters 
 that no great advance in the solution of the contents of the stomach 
 is made under from two to four hours. Gosse, who possessed the 
 power of disgorging the contents of his stomach by previously swal- 
 lowing a quantity of air, found that no change had taken place in 
 the food after it had remained half an hour in the stomach: after the 
 lapse of an hour he found the food much softened — but not reduced 
 in weight : while, after two hours, it was not only much softened but 
 considerably reduced in quantity, so that he could not return from 
 his stomach more than half what he had taken.* 
 
 Purkinje and Pappenheim found, in their experiments upon arti- 
 ficial digestion, that, by gently shaking the tubes in which the pro- 
 cess of digestion was going on, it became accelerated. This accords 
 with what daily experience points out to us, namely, that agreeable 
 and lively conversation during a meal, or gentle exercise after one, 
 invariably promotes the primary stages of digestion. 
 
 Violent exercise after meals retards digestion, most probably by 
 preventing the constant action of the gastric fluid upon the pieces of 
 food in it — the movements of the body causing frequent change of 
 place in the morsels of food. 
 
 The use of alcoholic stimulants also retards digestion, by coagu- 
 lating the pepsine, and thereby interfering with its action. Were 
 it not that wine and spirits aye rapidly absorbed, the introduction of 
 them into the stomach in any quantity would be a complete bar to 
 the solution of the food, as the pepsine would be precipitated from 
 solution as quickly as it was secreted by the stomach. 
 
 Absorption hy the Stomach. — An important question, to which as 
 yet we can give no certain reply, is as to what becomes of the food 
 after it has been duly dissolved by the fluids of the stomach. When 
 we find how completely albuminous and fibrinous substances are dis- 
 solved by digestion in the natural or artificial gastric fluid, it cannot 
 be doubted that they are in a state fit for absorption while yet in the 
 stomach, nor can there be any good reason to deny that a consider- 
 able quantity must be absorbed without passing further on in the 
 alimentary canal. The great rapidity with which liquids of a simple 
 and limpid kind, or the aqueous solutions of certain salts, as iodide 
 of potassium, the alkaline carbonates, &c., find their way into the 
 blood, denotes that this must take place very quickly after they have 
 been swallowed, and that the bloodvessels of the stomach must be 
 the principal channel through which they efi"ect their entrance into 
 the circulating system, and it scarcely admits of doubt that the dis- 
 solved aliments, are removed through the same channels, f 
 
 The venous blood of the stomach passes to the vena portae. 
 Hence, matters absorbed by the sanguiferous system of the stomach 
 
 * (EuTres de Spallanzani, par Senebier, t. ii. 
 
 I We have detected iodine in tlie saliva and urine in twenty minutes after a solution 
 of a few grains of iodide of potassium in a large quantity of water had been swallowed. 
 
VOMITING. 563 
 
 pass by a very direct route to the liver, and probably excite that 
 gland to increased secretion for the purpose of digestion in the 
 small intestine. 
 
 The gastric fluid dissolves perfectly only the fibrinous and albumi- 
 nous animal substances, and probably also the glutinous or azotized 
 portion of vegetable food ; we must suppose, thei'efore, that it is only 
 these portions of the solid aliments which are absorbed by the sto- 
 mach. Drinks, as water and various other liquids, fermented. or not, 
 are, doubtless, likewise in great part absorbed in the same way. 
 All other kinds of food, and such remaining portions of the azotized 
 or liquid aliments as have' escaped absorption by the stomach, after 
 having undergone to a certain extent maceration in it, are pushed 
 onwards into other parts of the digestive tube, there to undergo fur- 
 ther changes to fit them for being absorbed. 
 
 Eructation and Vomiting. — As there can be no doubt that the 
 movements of the stomach are capable of pushing on the food to- 
 wards the intestinal canal, it appears prima facie extremely proba- 
 ble that the same muscular force may cause it to evacuate its contents 
 through the oesophagus, if there be any obstacle to their downward 
 passage, too strong to be overcome.* The muscular coat of the 
 stomach, pressing by its passive contraction upon its contents, will 
 cause them to pass in that direction which offers the least resistance. 
 Now, in a state of health, the food, in order to return by the oeso- 
 phagus, must not only overcome the passive contraction of the mus- 
 cular coat of that tube, but it must also ascend against gravity. 
 Moreover, the action of the fibres of the splenic extremity of the 
 stomach favours the passage' of the food toward the pylorus. Hence, 
 not only is there least resistance at the pylorus, but there is likewise 
 a vis a tergo, which favours the propulsion of the food in that direc- 
 tion. 
 
 When, however, air accumulates at the cardia in such quantity as 
 to distend that portion of the stomach, it opens the oesophagus by 
 its expansile force, and from its lightness rushes up the oesophagus, 
 carrying with it sometimes liquid or solid food. When air is gene- 
 rated in large quantity and with great rapidity, it is wonderful how 
 much may escape in this way, and large quantities of food may be 
 discharged from the stomach at the same time, solely by the con- 
 vective force of the large bubbles of air ascending from it. This is 
 eructation — it seems due solely to the presence of a large quantity 
 of air in the stomach. 
 
 Vomiting is an act of a more complex character than eructation ; 
 by it solids and liquids may be expelled from the stomach through 
 the oesophagus, even contrary to gravity. We must assume that a 
 necessary condition for. the production of the act of vomiting is the 
 existence ofobstruction at or near the pyloric portion of the stomach, 
 which prevents or opposes the passage of the gastric contents in that 
 
 * The old and Btill prevalent notion of an inversion in the action of the stomach is 
 most probably erroneous. The inversion is only apparent, not real. See an able paper 
 by Dr. Brinton on this subject. — Land. Med. Gazette, 1849. 
 
564 DIGESTION. 
 
 direction. Probably the whole of the pyloric third of the stomach 
 is strongly contracted under the circumstances which ordinarily give 
 rise to vomiting; and the contents of the viscus having been accumu- 
 lated in its cardiac two-thirds, are thus brought into more immediate 
 and direct communication with the oesophagus. The pylorus being 
 closed against them, the stomach contents are forced through the 
 oesophagus, not only by the muscular contraction of the stomach 
 itself, but also by that of the abdominal muscles and the diaphragm.* 
 
 It is probable that where a very complete obstruction exists at or 
 near the pylorus, as in cases of hernia and other mechanical obstacles, 
 the act of vomiting partakes much of the nature of an overflow, and 
 requires no more than the action of the muscular coat of the stomach 
 itself. The slight effort which accompanies the discharge of the 
 stomach's contents in cases of this description, denotes this. But 
 when vomiting is caused by an emetic, or is the result of sea-sick- 
 ness, or of nervous irritation, as in stimulation of the fauces, or in 
 brain disease, an active and almost convulsive contraction of the 
 diaphragm and abdominal muscles accompanies it, and, no doubt, 
 constitutes the principal expelling force. These muscles, by their 
 simultaneous forcible contraction, form two plane surfaces, one pass- 
 ing downwards and backwards, the other nearly vertically down- 
 wards, which are approximated very closely to each other, and com- 
 pressing the stomach between them, cause the forcible ejection of !ts 
 contents in that direction, which offers least or no resistance, namely, 
 through the oesophagus. 
 
 The act of vomiting is ushered in by a deep inspiration, during 
 which the diaphragm is firmly contracted. Just at this moment the 
 abdominal muscles contract forcibly and almost convulsively. Thus 
 an effort at expiration, in which, doubtless, other muscles take part, 
 besides those of the abdominal walls, quickly succeeds the act of in- 
 spiration. But the diaphragm does not become relaxed as in ordi- 
 nary expiratory efforts, because the air is only very partially and 
 slowly expelled. For, at the same time that the abdominal muscles 
 and the diaphragm are thrdwn into contraction, those of the glottis 
 are exerted to a like convulsive action, and maintain a partially closed 
 state of the glottis which resists the expulsion of air from the lungs 
 and keeps them in a certain state of distension until the effort of 
 vomiting is over, when the diaphragm relaxes and complete expira- 
 tion takes place. That there cannot be complete closure of the 
 glottis in the effort of vomiting, is shown by the fact that that act is 
 very frequently accompanied by a loud explosive noise, which must 
 be formed in an open, although a resisting glottis. 
 
 Dr. Anderson has shown by direct experiment that when dogs 
 vomit under the influence of tartar emetic, the diaphragm is forcibly 
 contracted. He introduced his finger into the abdomen, and found 
 that during each effort of vomiting the diaphragm became tense 
 
 i 
 
 * The power of returning portions of the food at TTill (rumination), which some men 
 have acquired, is effected by a strong voluntary contraction of the pyloric muscle, and 
 by expulsive efforts operating directly on the cardia portion of the stomach, which can 
 thus expel its contents only in the upward direction. 
 
VOMITING. 565 
 
 and rigid, and descended towards the abdomen. And this he found 
 took place even when the trachea had been previously opened; whence 
 we may infer that the force of the expiratory muscles is spent 
 chiefly upon the stomach.* , 
 
 A warm controversy took place in the last century, and was re- 
 vived in the present, with reference to the share which the stomach 
 itself takes in the act of vomiting. Many high names in physiology 
 took 'part in this discussion, some maintaining, among whom was 
 John Hunter, and subsequently, Magendie, that the stomach was 
 perfectly passive, and that the abdominal muscles and the diaphragm 
 were the sole agents of expulsion ; while others, as Haller, Rudolphi, 
 &c., allowed that the contractions of these muscles only assist the 
 expulsive efforts of the stomach, which, in some instances, may act 
 independently of the surrounding muscles. Maingault affirmed that 
 he had seen vomiting occur after the division of the diaphragm and 
 the abdominal muscles, and Rudolphi made the same assertion. And 
 the Committee of the French Academy appointed to investigate the 
 question, admitted that it needed only a very slight external pres- 
 sure to produce vomiting, and that distinct contractions of the mus- 
 cular coat of the stomach were seen during the act in the neighbour- 
 hood of the pylorus. The question is one which cannot be decided 
 by cruel experiments, unless it can be shown in several instances 
 that vomiting can take place under conditions which render the ab- 
 dominal muscles and diaphragm incapable of acting ; such evidence 
 would unequivocally demonstrate the activity of the stomach. f But 
 the opposite experiments, such as the non-occurrence of vomiting 
 when the abdominal muscles and diaphragm have been paralyzed, 
 or its occurrence when an inert bag, as a pig's bladder, has been 
 substituted for the stomach, the external muscles being intact (as in 
 Magendie's noted but most cruel experiment), lead to no conclusion, 
 for, in the one case, the violence done so impairs the conditions 
 necessary for the act (both nervous and muscular) that it cannot be 
 expected to take place ; and in the other, the substitution of the inert 
 bag, and the section of the oesophagus, are favourable to the escape 
 of fluids from the former and through the latter, under the slightest 
 pressure. 
 
 The nervous changes which take place in the act of vomiting are 
 of the most interesting kind. It must be borne in mind that this 
 act may take place — 1, from the introduction of certain substances 
 into the stomach, some of which, as bile, mustard, common salt, not 
 becoming absorbed, must act simply by the impression they make on 
 the mucous membrane ; 2, by the introduction of emetics, as tartar 
 emetic, into the blood, or by the presence of certain morbid poisons 
 
 * See Anderson, Lond. and Edin. Monthly Journal, 1844. In this paper, Dt. Ander- 
 son has given a complete refutation of Dr. Marshall Hall's supposition that the dia- 
 phragm is inactive in vomiting. 
 
 f M. L'Epione records^ in the Bulletin de I'Acad^mie de M^deciue, a case in point. 
 A man's abdomen was torn open by a horn, and the stomach wholly protruded. For 
 half an hour it was seen repeatedly and forcibly contracting itself, till, by its own 
 efforts, it expelled all its contents except the gases. — See Paget's Report for 1846. 
 
566 DIGESTION. 
 
 in that fluid ; 3, by mental emotion, as that excited by the sight of 
 a disgusting object ; 4, by irritation at the base of the brain. Vomit- 
 ing may be caused, therefore, either by the direct application of a 
 stimulus to the gastric surface, or by the disturbance of some part of 
 the brain through the presence of particular substances in the blood, 
 that is, by causes operating from periphery to centre, or by causes 
 acting directly on the centre itself. Either the disturbing cause, 
 as tartar emetic in the blood, affects the medulla oblongata, in which 
 are implanted the vagi nerves ; or some of the fibres of these nerves 
 propagate to the centre the effects of the peripheral irritation at the 
 gastric mucous membrane. When the medulla oblongata is thrown 
 into' excitement by any of the causes above mentioned, certain motor 
 nerves implanted in it are stimulated to action, and the abdominal 
 muscles, the diaphragm, and the muscles of the larynx as well as 
 the muscular fibres of the stomach and oesophagus, are thrown into 
 that combined action which is essential to the production of active 
 vomiting. 
 
 When vomiting is the result of a peripheral stimulation, it affords 
 a remarkable example of a reflex or physical nervous action of the 
 most complex kind, in which, from the excitation of a few sentient 
 nerves, the nervous force is made to radiate upon several muscles 
 and to excite to simultaneous and combined action some which usu- 
 ally antagonize each other, and are, therefore, never, excepting, in 
 this act, in the same condition at the same time. We allude to the 
 abdominal muscles and the diaphragm ; the former as muscles of 
 expiration being the habitual antagonists of the latter, which is the 
 great muscle of inspiration. In short, the excitation of the nervous 
 centre, which is sufficient to cause vomiting, gives rise to a forcible 
 act of respiration, in which the act of expiration is so powerfully 
 opposed by the contracted state of the constrictors of the larynx, 
 the diaphragm also remaining in strong contraction, that the main 
 force of the expiratory muscles is directed to compress the stomach 
 against the latter muscle. 
 
 On the subjects of this chapter, see the various works on Anatomy, and the principal 
 systems of Physiology previously referred to : CBuvres de Spallanzani ; Tiedemann et 
 Gmeliu sur la Digestion ; Himter's Animal (Economy, by Owen ; Eberle, Physiologie 
 der Verdauung, 1834 ; Simon's Chemistry, by Day ; Dumas, Traite de Chimie, torn. 
 viii. (1846); Beaumont on Digestion ; Blondlot sur la Digestion; Dr. Kirkes's excel- 
 lent Manual of Physiology; Bouchardat and Sandras, Comptes Rendus for 1844; 
 Bernard and Barreswil, Comptes Rendus, 1844 ; Dr. R. D. Thompson, Lond. Med. Gaz. 
 1845. 
 
THE INTESTINAL CANAL. 567 
 
 CHAPTER XXV. 
 
 OP INTESTINAL DIGESTION. — ANATOMY OF THE INTESTINAL CANAL IN 
 MAN AND VERTEBRATA. — THE MUCOUS MEMBRANE OF THE INTES- 
 TINE. — ITS FOLDS AND VILLI. — ITS GLANDS. — DIGESTION IN THE 
 SMALL INTESTINE. — FLUIDS POURED INTO THE SMALL INTESTINE. — 
 THE PANCREATIC FLUID. — THE BILE. — THEIR INFLUENCE. — DIGES- 
 TION IN THE LARGE INTESTINE. — DEFECATION. 
 
 Anatomy of the Intestinal, Canal. — The intestinal canal com- 
 mences at the pylorus and terminates at the anus. It exhibits a 
 very obvious subdivision, into two portions : a narrower and much 
 longer portion, disposed in numerous coils or convolutions, which is 
 called the small intestine (intestinum tenue) ; and a much wider but 
 shorter portion, the large intestine (intestinum crassum). The length 
 of the whole intestinal canal in the adult is between thirty and forty 
 feet, or about six times that of the body : the small intestine forms 
 five-sixths of this. 
 
 There is a very distinct natural demarcation between these two 
 portions of the intestinal canal ; the large intestine commences by 
 a dilated cul-de-sac, which communicates on its inner side with the 
 small intestine. This portion, which is the widest part of the large 
 intestine, is lodged in the right iliac fossa ; it constitutes the com- 
 mencement or the head of the colon, and as it forms a blind extrem- 
 ity or cul-de-sac beyond the junction of the small intestine with 
 it, it is named caput caecum coli, or commonly csecum. Connected 
 with it is a remarkable appendix, which proceeds from its inner and 
 posterior part, and hangs down into the pelvis in a slightly curved 
 form, which gives it the appearance of a worm (lumbricus), and re-- 
 ceiving support from a small fold of peritoneum. This is called the 
 appendix caeci vermiformis. It is a small process from the csecum, 
 hollow, cylindrical, in size rather larger than a goose-quill, about 
 three inches long, and ending in a blind extremity which lies free in 
 the pelvis, but having a free communication with the csecum where 
 it is attached to that intestine. The large intestine commencing at 
 this part ascends from the right iliac fossa, through the right lumbar 
 region, as high as the concave surface of the liver ; this forms the 
 right or ascending colon; at the liver it turns to the left and passes, 
 in an arched form, across the abdomen from the right to the left 
 hypochondrium, thus forming the transverse colon, or the arch of the 
 colon ; it then turns downward, passes through the left lumbar re- 
 gion to the left iliac fossa ; this portion, which is straight, or nearly 
 so, is the left or descending colon. In the left iliac fossa the intes- 
 tine becomes somewhat curved, and is rather loosely attached to the 
 wall of the pelvis ; its curve resembles the letter S ; this portion, 
 terminates in the pelvis, and is named the sigmoid flexure of the 
 
568 DIGESTION. 
 
 colon ; lastly, this becomes continuous with the pelvic or terminal 
 portion of the intestine, which, although far from being straight, is 
 designated intestinum rectum, or commonly the rectum. This opens 
 externally at the anus, its mucous membrane becoming continuous 
 with the skin at that orifice. 
 
 The small intestine is arranged in many convolutions, and, with 
 the exception of its upper portion, the duodenum, it is quite loose in 
 the cavity of the abdomen, and even in that of the pelvis, occupying 
 the central part of those cavities. The large intestine or colon 
 embraces it on the right, above, and on the left. Three portions of 
 the small intestine have always been recognized by anatomists, 
 which, although not distinguished by any well-marked external 
 boundaries, exhibit in their mucous membrane features (to be pointed 
 out hereafter) which form their most appropriate means of distinc- 
 tion. The upper portion is sufficiently distinct from the rest by its 
 dilated form, its horseshoe curve, and by being closely fixed to the 
 spine, in the greatest part of its extent, by peritoneum. This is the 
 duodenum : it forms about the first twelve inches of the small intes- 
 tine. 
 
 The middle portion of the small intestine is the Jejunum, and the 
 terminal portion is the ileum. These have no external mark to dis- 
 tinguish the one from the other. The jejunum is wider than the 
 ileum, and its coats are thicker ; the intestine tapers as it approacbtes 
 the caecum. 
 
 The whole intestinal tube is more or less completely covered by 
 the serous membrane of the abdomen, the peritoneum. The duode- 
 num above and the rectum below are least covered by it ; the rest is 
 almost entirely enveloped, a small portion being left uncovered where 
 the bloodvessels enter the intestine, and where the peritoneum passes 
 to the abdominal wall. Each portion of intestine is attached to the 
 abdominal wall by a process of peritoneum, the duodenum and the 
 rectum very closely, the rest more or less loosely. The process of 
 peritoneum which connects the small intestine to the spine is the 
 mesentery, and each portion of the large intestine is connected to 
 the corresponding region of the abdominal wall by a process of peri- 
 toneum, which is designated by prefixing the word meso (ixiaos me- 
 dius) to the name of the particular portion of intestine : thus meso- 
 csecum is the process which connects the caecum to. the iliac fossa ; 
 mesocolon, right, transverse, left, is that which belongs respectively 
 to the three portions of the colon ; and the mesorectum connects the 
 rectum to the concavity of the sacrum. 
 
 Attached to the colon are small processes of peritoneum, contain- 
 ing fat, and called appendices epiploicse, from their resemblance to 
 the epiploon, or great omentum, which descends from the great curva- 
 ture of the stomach and from the transverse colon, like a curtain, in 
 fron(; of the small intestine. 
 
 The Intestinal Canal in Vertebrata. — Tho intestinal canal is disposed in the four 
 vertebrate classes much on the same plan as in tho human subject: — 
 
 In Mshet, the intestinal canal exliibits for the most part a very simple conformation. 
 In many fishes it passes quite straight, or very nearly so, through the body : when it 
 
THE INTESTINAL CANAL IN VERTEBRATA. 569 
 
 does exhibit convolutions they are few and short, and rarely to any great extent. A 
 pyloric valve is generally present, separating the intestine from the stomach ; imme- 
 diately succeeding to this valve, the intestine generally experiences a dilatation, whence 
 it gradually contracts to its terminal portion, which again becomes dilated. This 
 portion corresponds to the large intestine, and commonly a valvular fold of the mucous 
 membrane is present at its union with the preceding portion ; it terminates in a cloaca 
 common to it with the genital and 'urinary organs. In some fishes, however, no dila- 
 tation is found, nor any external distinction between the stomach and intestine, and 
 the canal from the oesophagus to the anus is of uniform ' caliber. Immediately below 
 the pylons we very commonly find a series of tubular prolongations from the intestine, 
 terminating in blind extremities. These constitute the appendices pyloricce, or pyloric 
 follicles, which most comparative anatomists consider to supply the place of a paren- 
 chymatous pancreas. These appendices vary considerably in both number and size. 
 In pleuronectes flesus there are only two very short ones, placed opposite each other at 
 different sides of the intestine ;* in ammodytes tobicmus there is only one ; in Blennius and 
 Gasterosteus there are only two, so small that Wagner compares them to the follicles 
 of the proventriculus of birds ; there are from ten to thirty in many species of Clupea 
 and Salmo, and in the genera Oadus and Scomber (the common mackerel, for example), 
 there are as many as two hundred, f On the other hand, they are entirely absent 
 in many fishes. Again, in some they are simple, in others they become subdivided or 
 branched at their blind extremities, and in others stUl these branches undergo subdi- 
 vision, and the resemblance to the glandular formation is enhanced by the fact that 
 these branchings are connected by means of cellular membrane and bloodvessels. 
 
 In R^tiles, the intestinal canal differs from that in fishes chiefly in having tmder- 
 gone a slight increase of development. The division into large and smaU intestine is 
 distinct throughout the class, and often an Ueo-csecal valve is present. In Ophidia, 
 the small intestine presents numerous short convolutions at acute angles ; the large 
 intestine ends in a cloaca. The intestinal canal is longe.st in the Chelonia, and next 
 to them in the Crocodiles. In the Chelonia, the line of distinction between the 
 large and small intestine is not so distinct as in the rest, and the muscular coat is 
 remarkable for its great thickness. The tortoises have a short, wide, and cylindrical 
 csecum, which is continuous 'without interruption with the large intestine : they have 
 also a circular ileo-csecal valve. J The great thickness of the muscular coat, and the 
 almost total obliteration of the canal during its contracted state, constitute one of the 
 most striking peculiarities of the intestine in Chelonian reptiles. In Batrachia, the 
 difference between large and small intestine is very distinct, being chiefly indicated by 
 difference of caliber, and in frogs a circular ileo-csecal valve ; in the toad, however, 
 there is a small csecum, without an ileo-csecal valve. In most of the Saurian reptiles there 
 is a csecum, according to Meckel, and generally an ileo-csecal valve : in the Crocodile 
 the valve is present but the csecum absent. 
 
 In Birds, the intestinal canal, although longer than either in fishes or reptiles, yet 
 retains considerable simplicity of form. It presents much variety in length and in the 
 number of its convolutions, according to the food and habits of the bird. The duode- 
 num, which immediately follows the gizzard, has always the form of a long fold, which 
 contains the pancreas in it. The small intestine, more or less folded in different orders, 
 terminates in a short and somewhat wide large intestine, at the commencement of 
 which are two cseca, one on each side of the intestine. These cseca vary considerably 
 in length from almost simple papiUseform offsets, as in the Soland goose, J to processes 
 three feet in length, as in the grouse. It sometimes occurs that there is only one 
 caecum. The large intestine is short and straight, and is continued from the termina- 
 tion of the small intestine, without fold, to the cloaca. There is connected with the 
 small intestine an appendage, the remains of the duct of communication between the 
 yolk-bag and intestine in the chick. In some birds this appendage, which is said to 
 be devoid of a muscular tunic, is ae large or larger than the cseca. 
 
 So much diversity exists in the form, length, and arrangement of the intestinal canal 
 in the different orders of Mammalia, that it will be necessary briefly to state its pecu- 
 liarities in each order. 
 
 In Camivora, we find examples in which the intestinal canal is remarkably short in 
 relation to the length of the body. The small intestine has but few and simple con- 
 volutions; it opens into a short oseoum (convoluted, however, in the dogs), which 
 scarcely differs in width from the rest of the large intestine. The proportion in the 
 length of the intestinal canal to that of the body varies from, according to Meckel, five 
 
 * Figured in Carus>s Anat. Comp. pi. ix. Fig. 20. 
 
 t R. Wagner, Vergleicliend. Anatom. 
 
 t Meckel. ^ Sir E. Home's Comp. Anat. pi. civ. 
 
 37 
 
 I 
 
570 DIGESTION. 
 
 to one, as in tlie oats and dogs ; to eight to one, and nine to one, as in the hyena and 
 bear ; or to fifteen to one, as ascertained by Meckel, in Phoca vitalina. The large in- 
 testine is shorter and wider than the small ; it is cylindrical in form, not sacculated, as 
 in man and many others. 
 
 In Insectivora, the intestinal canal is short, and ■without caecum, the diameter being 
 pretty uniform throughout. In Sorex, according to Meckel, its length is to that of the 
 body as three to one, in the hedgehog as six to one ;-in a mole examined by ourselves, 
 which measured from snout to tail seven inches, the intestinal canal, from pylorus to 
 anus, measured four feet three inches. 
 
 In the Cheiroptera, a very marked distinction exists in the form of the intestinal canal 
 between the frugivorous and insectivorous genera. In the former, as in Pteropm, it 
 presents nuinerous coils, and is in length seven times that of the body — the osecum is 
 absent. In the latter, the canal is extremely short, bearing to the length of the body 
 the proportion of two or three to one as in VespertUio noctula. Much variety exists 
 as regards both the form and length of the intestinal canal in the Edentata. The dis- 
 tinction between large and small iotestine is not evident in many of the genera. In the 
 Mania and Bradypua there is no trace of a osecum ; on the other hand, the two-toed 
 ant-eater {Myrmecophaga didaoiyla) has, according to Daubenton and Meckel, two small 
 and narrow csecal appendages resembling those of birds, situated at the confines of 
 the two portions of the intestine ; the orifices of these cseca are so small that the fecal 
 matter oahnot find its way into them. Mr. Owen has preserved, in the Hunterian col- 
 lection, u. specimen from the weazel-headed armadillo {Dasypus mustelirms), of two 
 similar caeca between which the ileum terminates. The terminal aperture of this in- 
 testine is of a slit-like form, and from its position between the caeca it admits of being 
 effectually closed by the lateral pressure of the contents of the cseca.* 
 
 Great length and wide caliber are the characteristics of the intestinal canal in Ru- 
 minants, Solipeds, and Pachydermata. In the sheep, which belongs to the ruminant 
 order, the intestine is in length thirty times that of the body, and in the horse, accord- 
 ing to a measurement made by us, the intestinal canal was eighty-seven and a half 
 ^ 'f eet in length. There are numerous convolutions of the small intestines in each of these 
 orders, and a large capacious caecum, from which the wide and convoluted colon is 
 continued. In Ruminants, neither the caecum nor the colon is sacculated by longitud- 
 inal bands, whilst both the Solipeds and Pachydermata exhibit the sacculated character in 
 a very marked degree, and the bands of longitudinal muscular fibres are very highly 
 developed, extending from the blind extremity of the caecum to the rectum. There 
 is no ileo-caecal valve, properly so called, in these orders, but the passage from the 
 ileum to the caecum (a foot and a half long in the horse) is very much contracted, and 
 its inner membrane thrown into six or eight thick longitudinal folds, which are closely 
 applied to each other and keep the canal closed. The caecum in each of the orders 
 is very capacious ; in the Ruminants, the capacity of this portion of intestine some- 
 what exceeds that of the fourth stomach, according to Meckel. In the Solipeds, the 
 caecum is still more capacious. Meckel asserts that it is capable of containing 
 more than three times as much liquid as the stomach. In Pachydermata, the caecum 
 is shorter and wider than in the other orders ; it is, according to Meckel, less capacious 
 thi^n the stomach, "j* 
 
 The Rodentia have, in general, a very long and convoluted intestinal canal. The 
 small intestine has a mesentery of considerable length ; its caliber is small aqd pretty 
 uniform throughout, being however largest superiorly. In most of the Rodent genera 
 the caecum is of very gi-eat size, and in some it occupies a large portion of the abdo- 
 minal cavity ; in the omnivorous rodents, however, as the rat, the caecum is of small 
 dimensions. The whole large intestine is ceUulated, the cells being formed by longi- 
 tudinal fibres and circular constricting ones. 
 
 In the genus Myoxua (dormouse), the caecum is entirely absent, the only exception, 
 according to Meckel, to the presence of this cavity in the rodent order. 
 
 In the Marsupiate animals, the distinction between large and small intestine is clearly 
 marked by the presence of a caecum. The small intestine is long, and in some very 
 wtde; the caecum is of moderate length and width, its capacity being much below that 
 of the stomach. 
 
 The chief peculiarity of the intestinal canal, in the Monotremata, is to be found at its 
 inferior extremity, where a cloaca exists common to the rectum with the urino-genital 
 organs. A small caecum separates the long and small intestine. 
 
 * Catalogue ofthe Hunterian Museum, vol. i. pp. 219, 729, A. 
 
 t See Sir E. Home's plates of the cteca of several mammiferous animals, plates cxiii. et 
 leq. vol. ii. 
 
THE INTESTINAL CANAL IN VERTEBRATA. 571 
 
 The Cetaceous mammalia have an intestmal canal of consideraWe length. The length 
 of the canal in the zoophagous cetacea is to that of the body as eleven or twelve to 
 one. (Meckel.) According to Cuvier, the proper whales have no division between large 
 and small intestine, and consequently no caecum. This is the case in the porpoise. In 
 the Balcena Rostrata, however, according to Hunter, and in all the BalwncB, according 
 to Cuvier, a. small caecum, not unlike that of carnivora, exists. In the herbivorous 
 cetacea, the intestinal canal is of p'roportionally greater length than in the zoophagous 
 cetacea. In the dugong, according to Meckel, its length exceeds forty times, and in 
 the lamantin of Kamtschatka, twenty times that of the body. 
 
 The Quadrumana. The length of the intestinal canal in tiiis large order of Mammi- 
 fers .presents very remarkable variety, which is the more curious as the nature of the 
 food is, with few exceptions, similar in the various genera. The proportion of the 
 length of the intestinal canal to that of the body is in some as eight to one, whilst in 
 others it is only as three to one.* The division into two portions is effected in the 
 same manner as in the human subject, and the general arrangement of both small and 
 large intestine is very similar to those of man. A caecum exists in aU the genera, but 
 presents considerable variety as to length ; an increased length of this portion of intes- 
 tine along with a larger development of the splenic extremity of the stomach being 
 employed in some cases to compensate for a deficiency in the length of the intestinal 
 canal. The orangs and gibbons have the peculiarity, which they alone possess in com- 
 mon with man, of a process from the caecum, some inches in length, denominated the 
 vermiform appendix. 
 
 From the preceding brief review of the anatomical characters of the intestinal canal 
 in the vertebrate classes, we gather, that this portion of the digestive tube diminishes 
 in complexity as we descend from mammalia to fishes ; that a short and simple intestinal 
 canal is generally coexistent with a diet of animal food ; and, on the other hand, that 
 a diet of vegetable food, or a conjoint animal and vegetable diet requires greater length 
 and greater complexity in the form and structure of the intestines. In estimating the 
 length of the intestinal canal we must not confine our examination to a mere extei-nal 
 measurement, as we should thereby be led to a very ei-roneous conclusion. Deficiency 
 in length, as measured on the exterior of the intestine, may be supplied by increased 
 width — by a more highly-developed state of the villi of the mucous membrane — by 
 numerous folds of that membrane ; and the energy of the action of the mucous mem- 
 brane on the contents of the intestine, may be augmented by the greater number and 
 size of the glands which pour out their secretions on its surface. It may further be 
 observed, that as the several portions, whether of small or large intestine, have very 
 definite characters as regards the mucous membrane, we can readily determine the 
 relative length and development of each portion, and thus deduce its proper degree of 
 importance in intestinal digestion. But upon these^points it is much to be regretted 
 that we are greatly in want of precise information ; we are persuaded that nothing 
 would tend more to the correct determination of the ofBce performed by each portion 
 of the intestinal canal than a series of careful observations with special reference to 
 anatomical characters on the intestines of a great number of animals. 
 
 Much importance is attached by Physiologists, and apparently with good reason, to 
 the size and form of the caecum. It is difiicult, however, and in the present state of 
 our knowledge impossible to determine the law which influences its development. 
 Nevertheless, it may be stated that there appears to be a direct relation between this 
 development of the intestine and the hardness of digestion of the food : in some in- 
 stances we find that a large caecum compensates for a less capacious stomach, as in the 
 Solipeds, and in these cases there exists even a striking similarity in the forms of those 
 two organs. A large caecum, then, belongs to the herbivorous classes, as a large sto- 
 mach does, and a small caecum would, on the other hand, indicate a diet of animal food. 
 Anatomy would seem to point to the conclusion that the function of the caecum is not 
 dissimilar to that of the stomach, and that in it substances hard of digestion are sub- 
 jected a second time to a reducing action resembling that of the stomach. Perhaps 
 the anomaly which we have noticed in the dormouse, in the absence of a caecum, may 
 be explained on the supposition that this accessory digestive cavity was rendered un- 
 necessary in consequence of the existence of the glandular pouch at the cardiac orifice 
 of the stomach in that animal. 
 
 The subdivision of the intestinal canal, in man, into the small and 
 large intestine, by the difference in caliber of those two portions of." 
 
 * Vide a table in Meckel's Anat. Comp. (French ed.) tom. viii. p. 778. 
 
572 DIGESTION. 
 
 that tube, as well as by the existence of an ileo-caecal valve, has 
 already been described. There are other characteristics, however, 
 of anatomical constitution which likewise sufficiently distinguish 
 them. The whole of the intestinal tube is composed, of certain 
 tunics, which, enumerated from within outwards, are as follows: 1, 
 the mucous membrane; 2, the submucous tissue; 3, the muscular 
 coat; 4, the serous coat, which is connected to the tunic last named 
 by a thin layer of very delicate areolar tissue. Of these tunics, the 
 mucous membrane, the muscular coat, and the serous coat, exhibit, 
 on the whole, very distinctive characters in the two divisions of the 
 intestine. 
 
 The mucous membrane continuous with that of the stomach ex- 
 hibits very characteristic features in the different portions of the 
 intestine. We shall reserve the description of it until we have 
 spoken of the other tunics. 
 
 The submucous tunic is a layer of very fine areolar tissue, which 
 connects the mucous to the muscular coat ; it is entirely devoid of 
 fat, and presents the same characters throughout the whole intes- 
 tinal canal. Placed immediately underneath the mucous membrane, 
 it constitutes the medium, through which the various sanguiferous 
 and other vessels and the nerves pass to that membrane. 
 
 The muscular coat of the small intestine consists of two layers or 
 planes, which differ from each other as regards the direction «of 
 their fibres. The external plane is composed of longitudinal fibres, 
 continuous superiorly with the longitudinal fibres of the stoTnaach ; 
 they form a continuous tunic surrounding the intestine, and extend- 
 ing from the pylorus to the caecum. 0. B. Albinus* states that 
 they exist only as a band a finger-breadth broad, and corresponding 
 to the concave border of the intestine, along which the mesentery is 
 attached, and to this he attributes the concavity which the inflated 
 intestine presents towards the mesentery. We have no doubt, how- 
 ever, that the longitudinal fibres form a continuous tunic around the 
 intestine, though they are strongest along the line of attachment of 
 the mesentery, and are very apparent in that situation, at times 
 when they are indistinct elsewhere. The circular fibres are much 
 more distinct than the longitudinal ; the direction of which they cut 
 at right angles. They surround the intestine in a circular manner, 
 not spirally, as some anatomists have asserted. 
 
 The muscular tunic of the large intestine is likewise disposed in 
 two layers of fibres. The external, however, does not, as in the 
 small intestine, form a uniform layer round the intestine, but is 
 developed chiefly in three bands, about half an inch wide, with a 
 few intervening longitudinal fibres. These bands commence at the 
 root of the vermiform appendix of the caecum, and extend in this 
 form to the rectum, where they become expanded, and form a con- 
 tinuous tunic over the whole intestine. The longitudinal bands are 
 shorter than the intestine ; the effect of this is, to produce a puck- 
 
 * Specimen Anatomioum exhibons novam tenuium Hominis Intestinorum Desorip- 
 tioncm. Lugd. Bat. 1724. 
 
THE INTESTINAL MUCO0S MEMBRANE. 
 
 573 
 
 ering of all its coats at certain intervals throughout the whole 
 length of the colon. At these points the colon appears to be con- 
 stricted, as by a shorter bundle of circular fibres, and its mucous 
 membrane projects into the interior, forming large folds. These 
 folds separate sacculated portions of the intestine, -which are the 
 cells of the colon, and the convex bulgings sfeen on the exterior of 
 the inflated large intestine are the walls of these cells. The circu- 
 lar fibres are arranged in the same manner as in the small intestine, 
 being spread uniformly over the surface of the intestine. 
 
 Of the Mucous Membrane of the Intestinal Canal. — The intesti- 
 nal mucous membrane so far resembles that of the stomach, that it 
 is of the compound variety (see ante, p. 546) ; and its thickness is 
 caused by the involution of multitudes of tubes, which terminate in 
 blind closed extremities, and rest vertically upon the submucous tis- 
 sue. Most of the tubes remain undivided from their open to their 
 closed extremities, some are bifurcated towards the blind extremity. 
 Each tube has a separate orifice on the free surface of the mucous 
 membrane, except in the upper part of the duodenum, and in the 
 caecum, where they open by sets of three or more on the floors of 
 shallow cells, as in the stomach. These tubes are commonly called 
 Lieberkiihn's follicles ; but they were first described by Brunn, or 
 Brunner, who has given a good delineation of them ; and their real 
 nature was not known to Lieberkiihn, who regarded them as muscles. 
 In examining thin vertical sections of the mucous membrane from 
 any part of the intestine, we see 
 these tubes closely set parallel 
 to each other ; they are straight, 
 and, excepting that here and 
 there one is bifurcated, they ex- 
 hibit no irregularity or bulging 
 of their walls, and are pretty 
 uniform in diameter throughout 
 their length (Fig. 157). All th-e 
 elements of the mucous mem- 
 brane contribute to their forma- 
 tion ; the basement-membrane, 
 the epithelium, and .the submu- 
 cous tissue, which is sparingly 
 interposed between them. 
 
 The epithelium is columnar or 
 subcolumnar ; the cells are dis- 
 posed in a single layer, with one 
 end adherent to the basement- 
 membrane. The cast-ofi" parti- 
 cles often fill each tube as mu- 
 cus, which escapes at the orifice, on the free surface of the mucous 
 membrane. These tubes are shorter in the large than in the small 
 intestine ; and as the thickness of the mucous membrane is de- 
 pendent on their length, we 'ind it less thick in the former than in 
 
 Fig. 157. 
 
 Section of the mucous memlirane of the small 
 intestiue in the dog. showing Lieberkiihu's follicles 
 and villi. 
 
 a. Villi. &. Lieberktihn's foUicleB, c. Other 
 coats of the intestine. 
 
5Y4 
 
 DIGESTION. 
 
 the latter intestine. The mucous membrane is thickest where the 
 tubes are most developed, namely, in the jejunum. 
 
 Lieberkuhn's follicles are doubtless secreting agents, resembling 
 in that respect the tubes of the stomach. 
 Fig. 158. ■ Pi-obably their office, in reference to the 
 
 intestinal contents, is the same through- 
 out the whole intestinal tube, as they 
 present everywhere so much uniformity 
 of arrangement and structure, and as 
 each portion of the intestine possesses 
 other and peculiar glands. As yet, how- 
 ever, nothing is kn.own respecting the 
 nature of the mucus which is secreted by 
 them. 
 
 By the infinite multitude of minute 
 and microscopic involutions which form 
 Lieberkijhn's follicles, the extent of sur- 
 face of the mucous membrane is enor- 
 mously increased. It is still further en- 
 larged by the existence of various folds 
 and processes, which project into the 
 cavity of the intestine ; these we shall 
 now proceed to describe. * 
 
 Of the Valvuloe Conniventes, Folds, 
 and Villi. — The mucous membrane of 
 the small intestine exhibits numerous 
 folds, which, small, irregular, and resem- 
 bling the rugae of the stomach in' the 
 superior third of the duodenum, assume 
 a much more definite form, and are much more highly developed in 
 the remaining portions of the small intestine, but especially in the 
 jejunum. 
 
 The irregular foldings of the upper portion of the duodenum 
 very soon exhibit the tendency to assume a transverse direction 
 with reference to the axis of the intestine. In the middle and 
 inferior portions of the duodenum we find numerous transverse 
 plaitings or folds, from one-eighth to a quarter of an inch in depth. 
 These are simple folds of the compound mucous membrane, including 
 a process of the submucous areolar tissue : they are called valvulce 
 conniventes, from their valvular form, and from their movements 
 under water resembling the flapping of valves, or the winking 
 motion of the eyelids. Each fold passes round the intestine for 
 about three-fourths or five-sixths of its circumference, gradually 
 diminishing in depth towards each extremity, but sometimes bifur- 
 cating and coalescing by one or both subdivisions, with the fold 
 above and below. In the lowest part of the duodenum, and in the 
 jejunum, the valvulse conniventes acquire their highest development. 
 Here they lie very close together, and many of them pass nearly 
 round the intestine ; they are deeper, also, here than elsewhere, 
 
 A. Transverpe aection of Lieberkuhn's 
 tubefl or follicles, showing the basement- 
 membrane and subcolumnar epithelium 
 of their walls, with the areolar tissue 
 which connects the tubes, a. Basement- 
 membrane and epithelium, constituting 
 the wall of the tube. 6. Cavity or 
 lumen of the tube. Magnified 200 dia- 
 meters. 
 
 E. A single Lieberktihn's tube, highly 
 magnified. A happy accidental section 
 in the oblique direction has served to 
 display very distinctly the form and 
 mode of packing of the epithelial parti- 
 cles, the cavity of the tube, and the 
 mosaic pavement of its exterior, a, 
 Basement-membranQ. c. Internal sur- 
 face of the wall of the tube. Magnified 
 2(^0 diameters. 
 
THE INTESTINAL MUCOUS MEMBRANE. 575 
 
 being sometimes half or three-fourths of an inch in depth. In the 
 ileum they gradually diminish in length and iii depth, frequently 
 not passing round more than one-half the circumference of the 
 intestine, and measuring not more than one-fourth or one-eighth of 
 an inch in depth ; and in the lowest part of the ileum they almost 
 entirely disappear. 
 
 It is remarkable that these folds are peculiar to the human sub- 
 ject. No other animal, so far as we know, exhibits any arrange- 
 ment of transverse folds of the intestinal mucous membrane resem- 
 bling them. 
 
 The folds of mucous membrane in the large intestine are the 
 partitions between the cells of the colon ; they exhibit much uni- 
 formity of shape, although they vary very much in size ; they are 
 least d.eveloped in the sigmoid flexure. 
 
 At the junction of the ileum with the caecum, there are two folds 
 which bound the slit-like aperture of communication between the 
 small and the large -intestine. These are the segments of the ileo- 
 csecal valve. The aperture is a simple slit, which passes nearly hori- 
 zontally from before backwards, and is bounded on all sides by 
 mucous membrane. Its lower border is formed by the free edge of 
 a deep semilunar fold of mucous membrane, inclosing submucous 
 tissue, and a few circular muscular fibres ; and another fold, of 
 much less depth, but of similar shape and constitution, form its 
 upper lip. This latter fold has a more horizontal direction than the 
 former, which is nearly vertical. The folds coalesce in front of and 
 behind the aperture, and form small bands, called frsena, and which 
 follow for a short distance the course and direction of the segments 
 of the valve. The free margins of these two segments come in ap- 
 position in the distended state of the caecum, and close the aperture, 
 or at least diminish and constrict it so much as, in general, to pre- 
 vent the reflux of any but liquid or much-subdivided matters into the 
 small intestine. 
 
 In the rectum, there are folds of various sizes and directions, 
 which are most numerous in the empty state of the. gut, and are 
 effaced by its distension. The late Mr. Houston, of Dublin, has 
 described certain permanent folds, or valves, of semilunar shape, 
 which he demonstrated by moderately distending the , rectum with 
 alcohol, which, at the same time, hardens its tunics, and thus dis- 
 plays their condition in the state of repletion. Three is the average 
 number ; but sometimes a fourth is found, and at other times only 
 two are present. The largest and most constant valve iS situated 
 opposite the base of the bladder, about three inches from the anus. 
 The fold next in frequency is placed at the upper end of the rectum ; 
 and the third occupies a position midway between these. When a 
 fourth is present, it is situated about one inch above the anus. In 
 the empty state of the intestine, these folds overlap each other, 
 as Mr. Houston remarks, so effectually as to require considerable 
 manoeuvring to conduct a bougie or the finger along the cavity of 
 . the intestine. Their use seems to be " to support the weight of 
 
576 
 
 DIGESTION. 
 
 fecal matter, and prevent its urging towards the anus, where its 
 presence always excites a sensation demanding its discharge."* 
 
 Of the Yilli. — Villi are minute processes of the. mucous mem- 
 brane of the small intestine, to which they are^ exclusively confined 
 (Fig. 159). They project'from the free surface of the mucous mem- 
 brane into the cavity of the intestines, and seem admirably adapted 
 to become implanted, like so many little rpots, in any semifluid or 
 fluid material which may fill the bowel. Villi are first found in the 
 duodenum, where they appear to develop themselves as elongations 
 of the partitions between the cells into which Lieberkiihn's tubes 
 open. In the lower half of the duodenum, and the rest of the small 
 intestines, they are very numerous, and give to the surface of the 
 mucous membrane an appearance like that produced by the pile of 
 velvet. They are continued down to the ileo-csecal aperture, and 
 cease abruptly at its margin, covering the surface of the valve- 
 segments next the ileum, but being wanting on the caecal surface. 
 
 A good view of the shape, arrangement, and number of the villi 
 may be obtained by examining a piece of villous mucous membrane 
 fixed under water. In man, the villi are conical in shape, somewhat 
 flattened, and measure in length from apex to base from the l-60th 
 to the l-46th of an inch. They vary much in shape and size in the 
 lower animals : in the dog, cat, and lion they are long and almost 
 
 filiform; in the she«p 
 and rabbit they are 
 small, flattened, and co- 
 nical ; in the turkey 
 they are large and lamel- 
 liform. Most fishes and 
 reptiles are devoid' of 
 villi. 
 
 In structure, a villus 
 resembles an everted 
 Lieberkiihn's follicle ; — 
 the same elements exist 
 in both ; basement-mem- 
 brane, epithelium, sub- 
 basement tissue, which 
 occupies, along with ves- 
 sels and perhaps ijerves, 
 the interior of the villus. 
 The diiference between 
 the two structures is, 
 that the epithelium is in 
 the interior of the fol- 
 licle and on the exterior 
 of the villus. 
 
 A single layer of the 
 columnar epithelium co- 
 
 A. B. 
 
 A. Villi of duodenum of dog, two hours after death, showing 
 the substance of the villus retracted from the epithelial in- 
 Testmcnt, like a finger from a gloye. The process of digestion 
 was not going on at the time of the dog's death, as there was 
 no food in the stomach nor chyle in the lacteals. Magnified 80 
 diameters, 
 
 B. From the same part, and same dog, showing the epithe- 
 lium corrugated, being attached and free at Intervals. Magni- 
 fied 80 diameters. 
 
 * Dub. Hosp. Rep. toI. v. p. 168. 
 
THE VILLI. 
 
 577 
 
 vers each villus (Fig 159). The particles adhere by their sharp ex- 
 tremities to the basement-membrane, and their bases, packed to- 
 gether, present on the surface an appearance of a pavement. 
 
 The basement-membrane is readily seen -when the epithelial layer 
 falls off, which it is apt 
 to do during the diges- 
 tive process (Fig. 160). 
 It is a single layer of 
 homogeneous membrane, 
 beneath which, or in the 
 cavity of the villus, are 
 seen, in well - injected 
 specimens, the bloodves- 
 sels of the villus. 
 
 Each villus is provided 
 with a plexus of capilla- 
 ries. A single artery en- 
 ters its base, and 
 ing up its 
 
 with breaks up into a 
 capillary -plexus, which 
 is seen at all points of 
 the surface of the villus, 
 immediately beneath the 
 basement - membrane. — 
 From this arise at vari- 
 ous points small veins, which pass out of the villus in one or more 
 trunks (Fig. 162). 
 
 The cavity of the villus also contains one or more small lacteals, 
 in which originates the proper lacteal plexus of the intestine. The 
 villi are seen white with chyle, during the absorption of that fluid, 
 and the chyle may be fixed in them by coagulation, if the membrane 
 
 Fig. 161. 
 
 centre, forth- 
 
 A. B. 
 
 A. From the same part of another dog, fed 2}^ hours before 
 death, showing the columnar epithelium stripped off, and the 
 cellular substance of the villus coTered merely by basement- 
 membrane. Magnified 200 diameters, a. basement-membrane, 
 slightly raised. 6. Cellular substance of the villus, disposed 
 somewhat in columns. 
 
 B. From the same part and same dog, showing villus de- 
 nuded of epithelium, and the basement^membrane raised in a 
 bulla by the endosmosis of water, in which it was immersed. 
 Magnified 200 diameters, a. Basement-membrane. &. Cellu- 
 lar substance of the villus. 
 
 Capillary plexus of the villi of the human small intestine, as seen on the sur&ce, after a successful 
 injection, magnified 50 diam. 
 
578 
 
 DIGESTION. 
 
 is promptly immersed in alcohol. Respecting the manner in which 
 these vessels are disposed in the villus, however, nothing certain is 
 known. Some have described a network of these vessels extending 
 to the extremity of the villus. The investigation is one of the most 
 difficult in minute anatomy, and is highly important as bearing upon 
 the mechanism of the absorption of chyle. 
 
 Nothing whatever is known of the relation of the nerves to the 
 villi. The tissue which occupies the cavity of the villus, and which 
 supports the capillary plexus, and whatever other vessels may exist 
 in it, is a soft, imperfectly formed areolar tissue, containing nuclei 
 and granules, and resembling somewhat the tissue contained in the 
 gustatory papillae of the tongue. That portion of it which corre- 
 sponds to the free extremity of the villus dilFers from the rest ; it 
 exhibits a vesicular structure, and resembles very minute fat vesi- 
 cles, filled by some transparent fluid. The tissue which occupies 
 the remainder of the villus seems to consist chiefly of nuclei or 
 granules, some of which present an indistinct arrangement in 
 columns, which are parallel to the axis of the villus. During the 
 process of chylification it appears to be the seat of some very re- 
 markable changes connected with the absorption of chyle. 
 
 The function of the villi appears evidently to be connected with 
 absorption, and specially with the absorption of chyle. This view 
 
 rests upon the followifig 
 grounds : First, that the villi 
 exist only in the small intes- 
 tine, .where the most active ab- 
 sorption of digested matters 
 evidently goes on ; and that 
 they are most highly developed 
 and most numerous in that part 
 of the small intestine where 
 chyle is first formed. Secondly, 
 that during the process of chy- 
 lification the villi are turgid 
 with blood, and obviously pre- 
 sent all the appearance of being 
 the seat of some active vital 
 process ; they are enlarged and 
 opaque, apparently from a 
 change in the intravillous tis- 
 sue, and probably also from the 
 introduction of some new mat- 
 ter into them. In animals that 
 have been kept fasting for some 
 time prior to death, the villi 
 look small, and as if shrunken within their epithelial sheaths, which, 
 in some instances, adapt themselves to the diminished size of the 
 inclosed villi, by becoming thrown into folds (Fig. 162). But 
 during the digestive process the villi are large and full ; the nuclei 
 of their proper tissue are very distinct ; the basement-membrane is 
 
 Vertical section of the coats of tlie small intestine 
 of a dog, showing only the commencing portions of 
 the portal vein and the capillaries. The injection baa 
 Tbeen thrown into the portal vein, hut hoB not pene- 
 trated to the arteries, a. Vessels of the TiUi. 6. Those 
 of LieberltUlin's tubes, c. Those of the muscular coat. 
 
THE INTESTINAL GLANDS. 
 
 579 
 
 Fig. 163. 
 
 A. 
 
 B. 
 
 A. Epithelium detached, and free in the cavity of 
 the duodenum, taken, immediately after death, from 
 a dog fed 2i^ hours before. . Each cell ia filled with ap- 
 parently fatty matter, partly granular and partly in 
 globules. Magnified 600 diameters. 
 
 B. The some, suffered to stay an hour or two under 
 the microscope, showing the fa.tty material aggregated 
 into larger globules, the rest of the cell-structure hav- 
 ing become indistinct. 
 
 here and there bulged by them on the'surface, especially towards 
 the free extremities, and the peculiar vesicular structure at the 
 apices of the villi is compressed, 
 or otherwise concealed from 
 view or altered in character 
 (Fig. 160). Lastly, the epithe- 
 lium seems to adhere much less 
 closely to the villi during chyji- 
 fication than during fasting ; 
 and the epithelial particles 
 themselves appear to undergo 
 some change during this pro- 
 cess. This latter change is re- 
 presented in the annexed cut 
 (Fig. 163) ; the epithelial par- 
 ticles appear larger, their con- 
 tents more distinct, and con- 
 sisting of minute fatty grains 
 as well as of some small globules. 
 
 Of the Glands of the Intestine. — These are, in addition to the 
 Lieberkiihn's tubes or follicles' already described, and which are 
 themselves secreting organs : 1. Brunner's, or the duodenal glands; 
 2. The solitary glands ; 3. Peyer's glands, or glandulse aggregate. 
 
 Brunner's glands belong properly to the duodenum. They were 
 discovered and described by 
 
 J. C. Brunn in 1686. ' We find Fig. 164. 
 
 them in the submucous areolar 
 tissue, disposed as a more or 
 less thick layer of whitish 
 grains, immediately beneath 
 the mucous membrane. They 
 may be compared to '^he ele- 
 mentary grains of a salivary 
 gland spread out on an ex- 
 panded surface instead of being 
 collected into a mass. Near 
 the pylorus they are most 
 numerous, and most closely 
 
 set and largest ; towards the termination of the duodeiium they 
 become much fewer, smaller, and scattered ; and nothing resembling 
 tl;iem is found in any other portion of the intestine. They are much 
 more developed in the Herbivora than the Carnivora ; in man, they 
 are large and numerous, generally speaking, but exhibit a good deal 
 of variety in different subjects, and, in the very old, they appear to 
 have wasted and shrunk. 
 
 In point of structure, Brunner's glands resemble precisely the 
 pancreas. Their ultimate elements are bunches of vesicles which 
 contain globular epithelium, and from which ducts arise which 
 coalesce and form larger duets, through which the secretion is 
 
 Vertical section of the mucous membrane of the 
 duodenum in the horse, slightly magnified, showing 
 w, villi, b, c, mucous membrane and submucous tis.suc. 
 g. Brunner's glands cut vertically, and a little spresd 
 out, showing their lobulated structure. 
 
580 
 
 DIGESTION. 
 
 Fig. 165. 
 
 poured into the duodenum. The exact relation of these ducts to 
 the tubes of Lieberkuhn is not known. 
 
 Brunner's glands, no doubt, secrete a fluid similar, perhaps, in 
 nature, to the pancreatic fluid, which exercises an influence on that 
 portion of the digestive process which takes place in the duodenum. 
 Their restriction to the upper portion of the intestine, and their 
 mode of arrangement in an expanded form beneath the mucous 
 membrane, establish for them an analogy with the buccal glands, 
 which are similarly disposed beneath the mucous membrane of the 
 mouth, and which bear to the salivary glands the same relation as 
 the duodenal glands do to the pancreas. 
 
 These glands, restricted as they are to the 
 upper portion of the intestine, give a character 
 to it of a physiological kind, and therefore 
 more definite than any external boundary. 
 Accordingly, while the duodenum may properly 
 give its name to these glands, so the presence 
 and extent of them should denote that portion 
 of intestine which may be called duodenum, 
 and define its limits. 
 
 The solitary glands are found in all parts of 
 the intestine, but are most numerous in the 
 jejunum, in the caecum, in the vermiform 
 appendix, and in the rest of the large intestine. 
 When filled with their secretion they are like small grains, about 
 
 as large as those of mustard-seed, 
 placed beneath the mucous mem- 
 brane in ihe submucous tissue, 
 which cannot in those situations 
 be inflated ; they may be readily 
 seen by holding up the intestine 
 against the light. When empty 
 and collapsed, they are not easily 
 discovered, and therefore are fre- 
 quently overlooked. 
 
 One of these glands is a simple 
 vesicle, or sacculus, of membrane, 
 shaped like an India-rubber bottle, 
 with a narrow extremity corre- 
 sponding to the surface of the 
 mucous membrane, and a rounded 
 obtuse- base, imbedded in the 
 submucous tissue. Its precise 
 relation to the elements of the 
 mucous membrane cannot be ex- 
 actly determined ; its wall seems 
 to be formed of a structure dis- 
 tinct from the basement layer of 
 that membrane. It projects among 
 LieberkUhn's tubes, and, in the 
 
 A solitary gland from the 
 small intestine of the human 
 subject, magniiied. — After 
 Boehm. 
 
 Fig. 166. 
 
 A patch of Peyer's gland^ of the adult human 
 subject, from the lowest part of the iloum.— After 
 Boohm. 
 
THE INTESTINAL GLANDS. 
 
 581 
 
 small intestine, is concealed and covered by the villi of the mucous 
 membrane. Within it is contained a variable quantity of nuclei 
 and granular particles, which, in the present state of our knowledge, 
 must be viewed as a secretion. How this secretion is discharged is 
 a matter of uncertainty, as no orifice has as yet been clearly demon- 
 strated ; hence some anatomists regard these glands as closed vesicles, 
 which burst when distended to a certain point. 
 
 
 ^^A. 
 
 — ■t-'i^yp'*-^ ■*J 
 
 ' «« t , ^T ^ « 
 
 Vertical section through a patch of Peyer'a glands in the dog. a. Villi. fe.'Tubes of LieberkUIm "with the 
 apices of Peyer*s glands, c. Suhmucoufl tissue with the glands of Peyer imbedded in it. d. Muscular 
 and peritoneal coats, e. Apex of one of Peyer's glands projecting among the tubes of LieberkOhn. The 
 glands are seen laid open by the section. Magnified about 20 diameters. 
 
 Pey£r's Grlands.* — These may be regarded as aggregations of 
 solitary glands, forming circular or oval patches situated on the free 
 border of the intestine (Fig. 167). They belong particularly to the 
 ileum, and ought to be regarded as forming a special anatomico- 
 physjological feature of that portion of the intestine, and as indica- 
 tive of its proper limits. We find in man as many as from seven- 
 teen to twenty-two patches, but with great variety both as to number 
 and size. The patches are smallest towards the jejunum, and increase 
 considerably in size towards the csecum, so that some quite near 
 the latter intestine measure from two to four inches in their long 
 diameter. 
 
 Each of the small glands, the aggregate of which constitutes the 
 patch of Peyer, is placed in a depression and surrounded by a groove 
 resembling that which surrounds the papillae vallataj of the tongue ; 
 
 * The glands, so long known by this title, may be called " Grew's glands," with as 
 much justice. They were discovered in several animals by our countryman, Dr. Ne- 
 hemiah Grew, who also delineated them with great accuracy, and described them in 
 his lectures to the Royal Society, in the year 1676, before Peyer's book was published 
 (1677). Dr. Grew's descriptions and delineations maybe found in an essay appended 
 to his catalogue of the museum of the Royal Society, of which he was Curator, entitled 
 " The Compaijative Anatomy of the gtomach and Guts begun." See the advertisement 
 prefixed to this work. 
 
582 DIGESTION. 
 
 some being inclosed by a circle of the orifices of large tubes of Lle- 
 berkiahn. It seems to be in every respect similar, as regards its 
 intimate structure, to the solitary glands, and probably discharges 
 its secretion by a similar mechanism. The arrapgement and struc- 
 ture of these glands are well seen in a vertical section, as represent- 
 ed by Fig. 167. 
 
 Peyer's glands are well developed in the Carnivora, more so than 
 in Herbivora, and they commence very high up in the intestine, 
 whence it would appear that the shortness of the small intestine 
 which distinguishes the former animals is due to the imperfect deve- 
 lopment of the duodenum and of the jejunum. 
 
 The office of these glands is involved in great obscurity ; most 
 probably it is connected with the further reduction of the alimentary 
 matters as they pass through the intestine. But we are unable to 
 form any conjecture as to the causes which determine the peculiar 
 shape or position of th6 glands, or as to the nature of their secretion. 
 They are larger and more developed during the digestive process 
 than during fasting, a fact which denotes that the former is the 
 period of their greatest activity of function. It is not impossible 
 that the peculiar odour of the feces, which is in a great measure 
 characteristic in particular classes of animals, may be due to a secre- 
 tion by these glands. 
 
 In typhus or typhoid fever, these and the solitary glands are prane 
 to become inflamed and to ulcerate. The poisonous matter which 
 generates the fever is apt to fix on these glands ; or they may be 
 the special channel for its elimination, and in the process they suffer 
 irritation. In phthisis, these same glands are very liable to become 
 the seat of the tubercular deposit, and also of an ulcerative process, 
 whence results the diarrhoea which proves so troublesome an accom- 
 paniment of that disease.* 
 
 In Asiatic cholera, all these glands become greatly enlarged from 
 the accumulation of a large quantity of granular matter in the 
 vesicles. 
 
 Brunner's glands exhibit a remarkable immunity from disease, 
 and in this, as in other respects, they resemble the pancreas. 
 
 In concluding the account of the anatomy of the intestinal tube, 
 the following summary of the special characters of each portion of 
 it will serve to indicate more clearly what we have alluded to 
 above — that the physiological anatomy of the mucous membrane 
 affords the best basis for its subdivision into portions, each of which, 
 no doubt, exercises its special function in the digestive process : — 
 
 In the duodenum, the mucous membrane exhibits: 1, cells and 
 tubes like pyloric cells, gradually passing into straight Lieberkiihn's 
 tubes, which exist throughout the regt of the gut ; 2, villi commenc- 
 ing in the upper part by the elongation of the septa between the cells, 
 
 * Some excellent remarks on the etruoture of tlie solitary and Peyer's glands may 
 be found in a paper by Dr. Handfield Jones, "On tbe Intestinal Mucous Membrane." 
 — Land. Med. Oazeiie, 1848. 
 
INTESTINAL DIGESTION. 583 
 
 the villi becoming extremely numerous and crowded together in the 
 inferior two-thirds ; 3, in the lowest third a few solitary glands ; 4, 
 Brunner's glands, very numerous in the upper part, gradually dimin- 
 ishing in size and number below ; 5, valvulae conniventes, well de- 
 veloped in the inferior half. 
 
 The orifice by which the biliary and pancreatic ducts open into 
 the intestine, is placed where Brunner's glands have either become 
 very few or have ceased. In most of the Carnivora which we have 
 examined, these ducts open below the region of Brunner's glands ; 
 the point at which they pour their contents into the bowels has there- 
 fore no constant relation to the duodenum, if, as it is convenient to 
 do, we may make the presence of these glands the characteristic 
 mark of that portion of the intestine. 
 
 In the jejunum, the mucous membrane is characterized by, 1, 
 Lieberkiihn's follicles and villi well developed ; 2, valvulse conni- 
 ventes, larger and more complete than elsewhere ; 3, solitary 
 glands. 
 
 The ileum exhibits : 1, Lieberkiihn's follicles and villi well deve- 
 loped down to the ileo-csecal valve ; 2, valvulse conniventes, which 
 gradually diminish towards the termination of the ileum, and disap- 
 pear ; 3, solitary glands ; 4, aggregate glands, or Beyer's patches, 
 which are small at the upper part of the ileum, but greatly increase 
 in size at its lowest portion. 
 
 The mucous membrane of the csecum and of the .whole large in- 
 testine is distinguished by the complete absence of villi ; by the 
 presence of Lieberkiihn's follicles and of solitary glands of large 
 size, which are numerous in the vermiform appendix, as well as in 
 the csecum itself ; and by the folds which form the partitions be- 
 tween the cells of the colon, as well as by the valvular folds of the 
 rectum. 
 
 Movements of the Intestines. — The substances which enter the 
 intestinal canal from the stomach are moved onwards by means of 
 what is called the peristaltic, or the vermicular action of its muscu- 
 lar coat. 
 
 This action of the intestines is very conspicuous in animals opened 
 immediately after death ; under these circumstances it is probably 
 in an exaggerated state, owing to ' the stimulus created by the en- 
 trance of cold air into the abdomen. It may be displayed in a 
 highly active state by subjecting the intestinal canal of an animal 
 just dead to the influence of the magneto-electric machine, by the 
 successive shocks of which this action becomes greatly increased in 
 intensity and rapidity, though not altered in character. 
 
 In dogs and cats, in which we have most frequently observed the 
 peristaltic action, it seems to commence at the pyloric third of the 
 stomach, whence successive waves of contraction and relaxation (the 
 former being instantly succeeded by the latter) are propagated 
 throughout the entire length of the small and large intestines. The 
 advance of the waves is always downwards. In examining a por- 
 tion of intestine at the moment of its contraction, we perceive a di- 
 
584 DIGESTION. 
 
 latation above it as well as below it ; the latter being produced by 
 the protrusion into it of the cointents of the now contracted portion 
 of intestine ; the former, by the relaxation of a previously contract- 
 ed portion. The rapid succession of these contractions and relax- 
 ations give to the movements of the intestines the appearance of 
 the writhings of a worm, whence they are distinguished by the ap- 
 pellation vermicular. Sometimes we have opportunities of observ- 
 ing these movements during life in man, in cases of extreme attenu- 
 ation of the abdominal parietes ; or in cases where, from some 
 great obstruction in the course of the alimentary canal, the peri- 
 staltic action is very much increased in intensity above the seat of 
 the obstruction; or in wounds of the abdomen ; or during surgical 
 operations. 
 
 There are certain facts which justify the supposition that this ver- 
 micular action has a proper rate of speed in each individual, and 
 that substances introduced into the highest part of the intestinal 
 canal take a certain time, varying in each particular case, to traverse 
 it. For example, the act of defecation will, if allowed or encour- 
 aged, take place with the utmost regularity every twelve or twenty- 
 four hours, and the quantity discharged will exhibit but little va- 
 riation, the quantity and quality of the food remaining the same ; 
 and indigestible substances taken with the food, seeds, husks, skins, 
 &c., will at certain intervals appear in the feces, having traversed 
 the whole canal. There is no act of the animal economy more strik- 
 ingly under the influence of habit, i. e., under the control of physi- 
 cal causes, without mental interference, than this of defecation ; 
 nor, on the other hand, is there any act which may be more com- 
 pletely deranged by its being baulked, through the resistance which 
 the will can oppose to it. The intestinal movements are partly due 
 to the influence of the stimulus of distension upon the muscular 
 tunic, and partly to the reflex action of the ganglia of the intestinal 
 portion of the sympathetic, stimulated by the contact of the intes- 
 tinal contents with the mucous membrane. Direct irritation of the 
 solar plexus, or of the semilunar ganglia, produces a marked increase 
 in the movements of the intestines {Vide p. 508). 
 
 When obstruction exists at a certain point of the bowels they 
 become dilated above that point, and when the dilatation has at- 
 tained a certain amount their contents are found to flow back into 
 the stomach, and are ejected by vomiting. This is commonly sup- 
 posed to be due to an inverted direction of the action of the muscu- 
 lar tunic of the intestines (antiperistaltic action). But Dr. Brinton 
 has very ably shown that there is no antiperistalsis of the bowels 
 under these circumstances, any more than of the stomach in vomit- 
 ing, and that the altered course of the fluids is due simply to their re- 
 flux' along the axis of the intestine from the seat of obstruction. The 
 muscular coat of the bowels acting in the downward direction,- and 
 with force proportionate to the obstacle, propels the fluids to a point 
 where they encounter insuperable resistance, and whence they must 
 take the course which aiFords least or no obstacle. Thus, a back- 
 ward current is established in that part of the fluid least influenced 
 
INTESTINAL DIGESTION. 
 
 585 
 
 Fig. 168. 
 
 by the -walls of the intestine, that, namely, which occupies its axis, 
 or, in Dr. Brinton's words, "aw axial reversed current is developed, 
 ■which returns matters from the neighbourhood of the strangulation to 
 some higher point in the canal." When fluid returns along the sides 
 of a syringe with a piston not water-tight, we have a somewhat ana- 
 logous phenomenon, and we may imitate the reversed movement of 
 the intestinal fluids by trying to push water through an obstructed 
 syringe, the piston of which is perforated in the cen- 
 tre, as illustrated by the annexed wood-cut (Fig. 168).* 
 
 The content's of the intestine are moved on, portion 
 by portion, much as in oesophageal deglutition. And, 
 in their progress, they are mingled with fluids poured 
 out from the intestinal mucous membrane. 
 
 Changes in the Mucous Membrane during Intestinal 
 Digestion. — During intestinal digestioUj^ the mucous 
 membrane exhibits an increased nutrient activity, as 
 evinced by a greater afllux of blood, and by free secre- 
 tion, as well as absorption ; in connection with which 
 last function it exhibits peculiar changes, which must 
 be specially noticed. It is red, moist, and covered with 
 a more or less abundant mucus, &c. 
 
 The most remarkable change which takes place -in 
 the mucous membrane of the intestinal canal is ob- 
 served in that portion of it which is covered by villi ; 
 that is, throughout the small intestine, especially beloW 
 the point of entrance of the hepatic and pancreatic 
 ducts. The villi are the agents of a peculiar process 
 of absorption ; and the changes which take place in thetn 
 at this period appear to have immediate reference to 
 the part which they perform in this function. They 
 become enlarged and turgid, partly owing to an in- 
 creased afflux of blood to them, and partly in conse- 
 quence of a change which takes place in the intra- 
 Villous tissue, whereby the component nuclei and 
 granules acquire an increase of size, and some of them 
 arrange themselves in lines passing from the free ex- 
 tremity to the base of each villus (Fig. 160,_ a). These 
 lines appear to proceed from an accumulation of small 
 cells formed at the free extremity of the villus within 
 its cavity (Fig. 160, B h) : they are quite opaque, and 
 their structure is, therefore, impenetrable to high 
 powers in the microscope ; they coalesce at the base of each villus, 
 beyorid which we have not succeeded in tracing them.f 
 
 At this period an abundant quantity of loose epithelium is in 
 contact with the mucous membrane, and surrounds the villi; and the 
 
 Diagram to illus- 
 trate the forma- 
 tion of a back- 
 ward axial cui> 
 rent la pushing 
 water through 
 an obstructed sy- 
 ringe with a pis- 
 ton perforated in 
 the centre. 
 
 * Contributions to the Physiology of the Intestinal Canal, Idc. cit., a highly ingeni-^ 
 ous and interesting paper. 
 
 f The phenomena here described were observed in dogs and cats fed in the ordi- 
 nary way upon meat, milk, &c. 
 38 
 
586 DIGESTION. 
 
 sheaths of the latter seem to adhere very loosely to thtfm, and may 
 be much more readily detached than when the digestive process is 
 not going on. 
 
 Mingled with the abundant mucus of the, intestine, we find at this 
 period very numerous white flocouli of a soft, lbose,i curdy material, 
 the whiteness of which is conspicuous in the midst of other matters, 
 which are more or less coloured from intermixture with bile. And,' 
 at the same time, the plexus of lacteal vessels, which is formed 
 beneath the mucous membrane, and from which the larger lacteal 
 vessels proceed through the mesentery to the mesenteric glands, is 
 filled with a white fluid of the exact colour and appearance of milk, 
 commonly called the chyle. 
 
 The display of the lacteal vessels filled with white chyle, at this 
 period, is one of the most interesting sights among the many wonder- 
 ful objects which engage the observation and the attention of the 
 anatomist. 
 
 The white flocculent matter is most abundant in the duodenum 
 and jfejunum, and there the villi are most numerous; thence, likewise, 
 proceed the greatest number of lacteal vessels. Lower down in the 
 small intestine the flocculi gradually become less and less numerous, 
 and ultimately disappear, the contents of the intestine consisting of 
 a more or less fljiid mass, apparently homogeneous, and coloured by 
 bile. At the same time the villi become fewer and smaller, the 
 number of lacteal vessels diminishes, and the glandular apparatus 
 of the intestinal muco"us membrane is more developed and distinct. 
 
 The occurrence of the flocculent matter, in that part of the in- 
 tesfine where the absorbing organs and the chyliferous Vessels are 
 most numerous, denotes that it must be regarded as constituting 
 the nascent condition of that fluid which at this period fills the lacteal 
 vessels and gives them their white colour — the chyle. It appears 
 like a precipitate from the general mass of the intestinal contents, 
 and many distinguished physiologists have regarded it in that light, 
 and have attributed its precipitation to the addition of the biliary 
 and pancreatic fluids to the chymous mass which -has been pushed 
 on from the stomach into the intestines. 
 
 This flocculent matter consists of a multitude of minute molecules 
 apparently of a fatty nature (as they disappear under the action of 
 ether), mingled with larger oil-globules, and also of numbers of parti- 
 cles of columnar epithelium, containing within them several fatty 
 molecules of large size, readily distinguished by their highly refrac- 
 tive power. The contrast between the epithelial particles obtained 
 from this flocculent matter, and those of the intestine of an animal 
 that had fasted for some time before death, is very striking, and in- 
 dicates that they, undergo a change during chylification, either con- 
 nected with the absorbing process or with the transformation of the 
 alimentary substances. (Fig. 163.) 
 
 Of the peculiar mechanism by which this nascent chyle is intro- 
 duced into the lacteal vessels, and of the nature of the changes which 
 it'ufider^be&i'n'w^te to form perfect chyle, we can form no adequate 
 idea in the present state of our knowledge. We do know, however. 
 
CHANGES OF FOOD IN THE SMALL INTESTINE. 587 
 
 that the material before its entrance into the vessels is very different 
 from what it becomes after its introduction; and /that in its advance 
 towards the centre of the absorbent system it undergoes further 
 changes, all of which tend to assimilate it more nearly to the blood 
 itself. 
 
 Of the Chyle. — If, as seems most correct, we apply ,the term chyle 
 to the fluid contained in the lacteal vessels during and shortly after 
 digestion, we must make the distinction between white chyle and 
 transparent chyle. The .white chyle is a milk-like fluid, homogene- 
 ous in appearance, which, on being withdrawn from the lacteals and 
 allowed to stand, separates, as blood would do, into serum and a clot. 
 This clot consists of fibrine, Avhich entangles, by its coagulation, cer- 
 tain particles proper to the chyle. These are chyle-corpuscles or 
 globules, in every respect similar to lymph-corpuscles, and an infinite 
 multitude of particles of extreme minuteness, to which Mr. Gulliver 
 has given the name of molecular base of the chyle. These particles 
 consist of fatty matter in a state of extreme subdivision. 
 
 During fasting, and also during the digestion of food wholly devoid of 
 fat, the fluid contained in the lacteals is perfectly transparent and 
 colourless, and not to be distinguished from the lymph of the lym- 
 phatics. In this fluid there is no molecular base, while all the other 
 elements of the chyle are present. Hence there ^can be no doubt 
 that the white colour of the chyle is due to the presence of the mo- 
 lecular base. 
 
 The chyle may exhibit various degrees of milkiness, according to 
 the quantity of the molecular base. The white chyle, therefore, is 
 chyle with molecular base in greater or less quantity; the transparent 
 chyle is devoid of molecular base. Both kinds of chyle consist of a 
 liquor chyli, essentially the same as the liquor sanguinis, holding 
 suspended in it chyle-globules in the transparent chyle, and in the 
 white chyle-globules, fat-globules, and molecular base.* 
 , It would seem to follow, from observing the changes which the 
 food undergoes in the small intestine, that the immediate office of 
 that portion of the intestinal canal is to form this chyle; and it ap- 
 pears probable that the secretions poured into the small intestine 
 from the glands, especially the liver, pancreas, and the glands of 
 Brunner, which communicate with it, exercise a chemical influence 
 upon the alimentary matters whereby this material is formed. We 
 shall see further on that this view receives strong support from the 
 results of experiments and observations respecting the functions of 
 the pancreas and liver. 
 
 Changes of the Food in the Small Intestine. — It remains now to in- 
 quire whether all the digestible food which passes from the stomach, 
 undergoes the change into chyle, or whether certain parts of it only 
 are simply dissolved and pass by absorption directly into the portal 
 blood, as in the stomach, whilst other parts are converted into chyle, 
 and enter a different part of the circulation through the lacteal* 
 vessels. In other words, is it necessary that all food, prior to its- 
 
 * See the Chaptei: on Absokptios. 
 
588 DIGESTION. 
 
 appropriation by the blood as nutriment, should pass through the 
 condition of chyle? 
 
 As it has been shown that the stomach can absorb certain fluids 
 and dissolved solids, through the absorbing power of its bloodvessels, 
 there can be no good reason for denying the same power to the in- 
 testines, which have a vascular system precisely of the same kind 
 as that of the stomach. Now the substances which the stomach 
 completely dissolves and absorbs, are the azotized aliments : it seems 
 not unreasonable to conclude that such portions of these aliments as 
 have escaped absorption by the stomach, may undergo a similar so- 
 lution in the intestines, and be absorbed by their bloodvessels 
 without passing through the state of chyle. 
 
 But to answer this question accurately we must determine pre- 
 cisely the changes which each kind of food undergoes in the intestine. 
 
 Bouchardat and Sandras have obtained from their experiments 
 results which indicate that fibrine does not undergo the change into 
 white chyle. They fed animals with fibrine, coloured with saffron or 
 cochineal, and were unable to detect any trace of the colouring mat- 
 ter in the chyle. They found, likewise, that the contents of the lac- 
 teal vessels of animals kept fasting differed in no respect from that of 
 animals fed on fibrine. These experiments, therefore, render it highly 
 improbable that ljj)rine contributes to the formation of white chyle, 
 and Tiedemann and Gmelin had long since found that the quantiUJr 
 of fibrine contained in the lymph and chyle, after a long fast, is 
 not less than that which is found there after digestion. Bouchar- 
 dat and Sandras obtained the same results in their experiments on 
 animals fed on albumen, caseine, or gluten, as on animals fed with 
 fibrine ; these substances, therefore, must likewise be excluded from 
 the list of those which are capable of forming chyle. Hence the 
 whole class of neutral azotized substances, admitting of solution by 
 pepsin, may be absorbed without passing into the state of chyle. 
 
 Neither does it appear to be necessary for the appropriation of 
 amylaceous aliments that they should pass into the condition of 
 chyle. These substances are but little digested in the stomach, 
 and undergo their principal changes in the small intestines. Here 
 the pancreatic fluid exercises a similar influence upon them to that 
 which the neutral azotized matters experience from the gastric juice. 
 Bouchardat and Sandras found that a few drops of pancreatic fluid, 
 added to some boiled starch, and kept at the temperature of from 
 95° to 101°, dissolved it in a short time, the liquid became trans- 
 parent, and all trace of starch disappeared. The same effect is pro- 
 duced if a piece of the pancreas be used instead of the pancreatic 
 fluid.* 
 
 * Dextrine is a substiuice haying some of the properties of gum, and obtained from 
 starch by the action of heat, diastase, or dilute acids. It is soluble in water, and ex- 
 ists in almost every part of plants. When starch is boiled in water for some time, an 
 abundance of dextrine is produced. If the action of diastase or of the acids be con- 
 tinued too long, or if the quantity of either be too large, grape-sugar is produced. 
 Hence dextrine maybe regarded as the first stage in the transformation of starch 
 into sugcr. The formula for dextrine is C, H'"; 0'°. — Sec Mulder's Chemistry/ of 
 Animal and Vegetable Physiology, by Johnston, p, 224. 
 
INTESTINAL DIGESTION. 589 
 
 The starch in these experiments is converted into dextrine, or 
 into sugar, in which state it is soluble, and thus admits of direct 
 absorption into the bloodvessels, or the sugar undergoes a further 
 change into lactic acid, and in this condition passes into the circu- 
 lation. It appears that the presence of a free alkali is as neces- 
 sary for these changes, as that of acid is needed for the solution of 
 the neutral azotized substances. If the pancreatic fluid be acidu- 
 lated, it ceases to act on starch, but, according to Bernard and 
 Barreswil, acquires the- power of dissolving albumen, fibrine, &c. 
 We do not, however, find that alkalized pepsin is capable of dis- 
 solving amylaceous matters. 
 
 Bouchardat and Sandras have examined the changes which 
 starchy substances undergo in the stomach and intestines in dogs. 
 Man and carnivora are unable to digest raw starch in the stomach 
 or intestines. Raw potato-starch introdjaced in a muslin bag into 
 the stomach through a fistulous opening in the walls of the stomach, 
 and withdrawn after a sojourn of twenty-four hours in that viscus, 
 showed no sign of any change ; nor did the gastric juice out of the 
 body, the mixture having been kept at a high temperature for the 
 same time, exert any influence upon the starch grains. When dogs 
 were made to swallow raw starch, the grains were afterwards found 
 intact in every part of the intestinal canal. liabbits and gran- 
 ivorous birds, however, were found to possess the power of digesting 
 raw starch, although more slowly than that which had been cooked. 
 But this power was found to reside mainly in the upper part of the 
 small intestine, and as the grains of starch became gradually fewer 
 as the food descended in the intestinal canal, it seems reasonable to 
 believe that each succeeding portion exercises a certain digestive 
 power over them. In birds, the digestive power of the small intestine 
 was greater than in rabbits, the lower part of the intestine in the 
 former exhibiting no traces of the starch grains. In the upper part of 
 the small intestine sugar and dextrine were found, and the lower 
 the contents had passed down, the more did all traces of starch dis- 
 appear. 
 
 Boiled starch is more readily digested by all animals than raw ; 
 to the carnivora and to man, cooking is essential to its perfect di- 
 gestion. The same -changes take place in it as in the raw starch, 
 i. e., it seems to undergo conversion into sugar, dextrine, and 
 lactic acid. This change, however, is very slow and gradual, and 
 although it occurs chiefly in the upper portion of the intestine, it is 
 found taking place throughout the whole canal. The rapid forma- 
 tion of sugar in the intestinal canal leads to a proportionally rapid 
 absorption of it, and to the elimination of it by the kidneys. It is 
 apparently to guard against this, to protect the kidneys against the 
 irritating influence of this substance, that the change of the starch 
 into sugar and dextHne goes on with great slowness throughout the 
 whole intestinal canal. 
 
 Our own experiments have yielded results similar to those of 
 Bouchardat and Sandras, and confirm their conclusion, that neither 
 azotized matters nor amylaceous substances contribute to form the 
 
590 DIGESTION. 
 
 true white chyle. At least it may he affirmed that when animals 
 are fed on such food, carefully freed from all oily or fatty matters, 
 the fluid which is found in the lacteal vessels is perfectly trans- 
 parent, and in all respects identical with that which is found in 
 them after a long fast. We select the following experiments in 
 illustration of this statement: — 
 
 Hxp. 1. — A cat was fed on horse-flesh, carefully freed from fat, 
 on the 7th of July, 1848. On the two subsequent days it was fed 
 on the whites of eggs, freed from yelk : and on the 10th, it was fed 
 on the whites of five eggs, at nine o'clock A. M. At half-past one 
 P. M., on the same day, it was killed. The thoracic duct was 
 filled by a perfectly limpid chyle, which exhibited no molecular 
 base, a few chyle-corpuscles, and a few blood-corpuscles. The 
 lacteals were with difficulty visible in consequence of the transpa- 
 rency of the fluid by which they were filled. The stomach and 
 duodenum contained pieces of softened albumen, as well as a con- 
 siderable quantity of a soft homogeneous jelly-like mass. In the 
 latter intestine the villi were covered with epithelium, and did not 
 exhibit any appearance to indicate that they were the sea); of an 
 active process of absorption. 
 
 Exp. 2. — A small healthy terrier was fed at nine A. M. with half 
 a pound of wheaten bread, having previously fasted twenty-four 
 hours; it was killed at one o'clock on the same day. The thoracic 
 duct was filled with a clear fluid, which, when collected on a slip 
 of glass, exhibited a faintly reddish hue. Under the microscope it 
 was found to exhibit numerous red blood-corpuscles, with a much 
 small number of white corpuscles, but more than the usual pro- 
 portion for blood. No molecules were perceptible. The fluid, 
 when collected in a watch-glass, coagulated in two minutes into 
 ,a firm clot. A small quantity of softened bread was found in 
 the stomach, and a still smaller quantity of the same bread very 
 much softened, liquid, diffused, and coloured by bile, was found in 
 the duodenum. In both, the contents were acid. The villi were 
 covered with epithelium, which adhered firmly to them, without any 
 great opacity of their interior, or other indication of activity of 
 function. On chemical examination, by our friend Mr. Lionel 
 Beale, junior, a highly competent analyst, the contents of the 
 stomach were found to consist of a small quantity of sugar, with a 
 good deal of starch; while in the duodenum, sugar existed in great 
 abundance, and the starch only in very minute quantity, 
 
 Mxp. 3. — A similar dog to the preceding was fed at the same 
 time with two ounces and a ha,lf of horse-flesh, and the same quan- 
 tity of beef suet ; it was killed four hours and a half after having 
 been fed. The whole lacteal system was distended with a white 
 milky chyle, which, under the microscope, showed a large quantity 
 of molecular matter, as well as red and white blood-corpuscles. 
 The contents of the intestine were more or less acid throughout, 
 and abundantly coloured by bile. There were very numerous white 
 flocculi, most conspicuous in the duodenum, and becoming gradually 
 less numerous to within an inch or two of the cascum, where they 
 
INTESTINAL DIGESTION. 591 
 
 ceased. These flocculi consisted of an abundance of granular matter 
 with columnar epithelium, having the free ends of the particles 
 filled with minute oil-globules, while the neighbouring epithelium 
 contained no oily matter. The villi were mostly stripped of their 
 epithelial sheaths, or held them very loosely ; the intra- villous 
 structure was opaque, and the vesicular structure beneath the base- 
 ment-membrane at their free extremities was very distinct. 
 
 It was evident in these experiments that the marked contrast 
 between the state of the contents of the lacteals, and the condition 
 of the villi, was connected with the presence or absence of fat in the 
 food, and that so long as the food was purely albuminous or fibrin- 
 ous, or mainly amylaceous, the chyle was transparent, and the villi 
 apparently inactive ; but that the addition of fat to the food called 
 the villi into activity, and filled the lacteals with an abundant milky 
 chyle. 
 
 Are we to infer then that the lacteals absorb fatty matters only, 
 and that the villi are altogether inactive, save when fatty or oily 
 substances are to be absorbed ? We apprehend that such an infer- 
 ence is not justifiable ; it may, however, be concluded that the villi 
 and the lacteals are capable of absorbing all substances which the 
 bloodvessels absorb, and by a simple process ; but that the absorp- 
 tion of fatty matters devolves upon them only, and is a more com- 
 plex process, involving considerable changes in their tissue. 
 
 And upon similar grounds we may conclude that while albuminous 
 and fibrinous aliments contribute to the formation of chj^le, they do 
 not necessarily undergo the change into chyle in order to be ab- 
 sorbed. But fatty matters appear to admit of absorption in no other 
 way, except by a reduction to the state of molecular base of the 
 white chyle. 
 
 These observations and experiments denote sufiiciently clearly 
 that two channels exist for the transmission of the nutritious mat- 
 ters from the intestines to the blood ; one through the lacteals, by 
 the villi ', the other directly through the walls of the bloodvessels 
 themselves. Matters taking the latter route must pass through the 
 liver, and would be subjected to the influence of, that gland before 
 they reach the inferior vena cava and the right auricle, while those 
 passing through the former channel must permeate a totally distinct 
 system of vessels, namely, the lacteal system, to be conveyed to the 
 superior vena cava and to the right auricle, where, having mingled 
 with the blood coming from the liver, both are transmitted by the 
 right ventricle to the lungs. 
 
 And it would seem that the object of the two modes of absorption 
 at the intestine, and of the two paths of transmission from the in- 
 testine to the centre of the circulation, is to keep separate, up to a 
 certain point, two kinds of material resulting from the digestion of 
 the food. And probably the reason why one kind of product is re- 
 served to pass through the intricate capillary plexuses of the vascu- 
 lar system of the liver, to the exclusion of the other, is because it 
 contains material out of which the liver may elaborate bile ; whilst 
 
592 DIGESTION. 
 
 the other material is transmitted through a less complicated series 
 of channels more directly to the lungs. 
 
 Of the Offices of the Pancreas and Liver in Digestion. — The pre- 
 sence of two such great glands as the pancreas and the liver exist- 
 ing in a large portion of the animal kingdom at the upper part of 
 the intestinal canal, and pouring their secreted fluid into it, obviously 
 denotes a connection between the fluids secreted by these glands, 
 and the changes which the food undergoes in this part of the in- 
 testine. 
 
 As the function of the pancreas has been determined with greater 
 accuracy than that of the liver, it will be more convenient to con- 
 sider it first. 
 
 Function of the Pancreas in Digestion. — The presence of the 
 pancreas is constant, at least, in the vertebrate classes. 
 
 It is present in all the mammalia — it is, perhaps, better developed 
 in carnivora than herbivora ; in all it is in intimate relation with the 
 upper part of the small intestine into which it pours its secretion by 
 one or two ducts. In some, as in man, the pancreatic duct and the 
 common choledoch duct open into the duodenum at the same place ; 
 in others they open at some distance from each other (as much as 
 sixteen or seventeen inches in the rabbit) but in all they open into 
 the same portion of the intestinal canal ; and the pancreatic duiet, 
 always below the biliary duct, when they do not open together. 
 Some doubt exists as regards its presence in fishes. In rays and 
 sharks, a solid gland exists, corresponding to the pancreas; and in 
 osseous fishes a similar gland has recently been discovered by Stan- 
 nius, which appears to be its analogue.* i 
 
 The secretion of the pancreas has some resemblance to saliva. It 
 has been lately studied with great care by M. Bernard, from whose 
 clear and admirable memoir the following account of it is derived. 
 
 The pancreiitic fluid maybe procured most readily and in greatest 
 qjjantity at the commencement of the digestive process. Bernard 
 obtained it from the dog in the following manner : the animal having 
 been well fed, after a fast of some hours, an incision was made into 
 the abdomen below the margin of the ribs sufiSciently large to enable 
 the operator to draw out the duodenum, and with it a portion of 
 the pancreas. The larger of the two pancreatic ducts was now 
 rapidly isolated, and opened with fine scissors, and into this opening 
 a silver tube was introduced and fixed in the duct by a ligature. 
 The intestine and pancreas were replaced, and the wound in the ab- 
 domen closed by suture, the free extremity of the tube being allowed 
 to project through it. To the silver tube was now attached a small 
 caoutchouc bag, perfectly exhausted of air, and to the opposite end 
 of this another similar tube was fixed. The pancreatic fluid flowed 
 freely through the first tube into the caoutchouc bag, and accumu- 
 lated there ; and as much as two drachms and a quarter were col- 
 
 * MuUer's Arohiv., 1849. 
 
FUNCTION OF THE PANCREAS. 593 
 
 lected In five hours and a half. The fluid flowed from the tube freely 
 drop by drop. 
 
 When this operation was performed at the commencement of di- 
 gestion, Bernard obtained, between half-past seven A. M. and five 
 P. M., four drachms and one third of the fluid, making an average of 
 nearly half a drachm an hour. 
 
 On the following day^ when signs of inflammation had shown 
 themselves in the wound, more than four drachms of the fluid were 
 obtained in one hour and a quarter. The quantity of the secretion 
 was considerably increased, but its quality was altered — its consist- 
 ence being much diminished, and its physiological properties mate- 
 rially changed. 
 
 When the experiment was performed on an animal in which the 
 digestive process was fully established, the quantity of fluid obtained 
 was much less than at the earlier period, but its quality much the 
 same. During abstinence, only a very small quantity of the pancrea- 
 tic juice could be obtained .at the time of the operation; but the fol- 
 lowing day, when the wound became inflamed, a fluid much altered 
 in quality flowed out very freely. , 
 
 If the operation were slowly performed, so as to expose the intestine 
 long to the action of the air, and to irritate it and the gland, the 
 quantity and quality of the secretion were much altered. 
 
 As the characters of the pancreatic fluid vary so readily with the 
 circumstances attending the operation of obtaining it, Bernard de- 
 scribes fwo kinds of fluid, the first being the normal, or that ob- 
 tained under the best conditions, the second, the morbid, or that 
 obtained after inflammation has commenced in the wound and in.the 
 pancreas. 
 
 The normal pancreatic fluid is a colourless, limpid fluid, viscid 
 and gluey, flowing slowly by large pearly or syrupy drops, and be- 
 coming frothy on agitation. It has no characteristic odour — it has 
 a slightly saltish taste resembling that of the serum of the blood. 
 Bernard has always found it alkaline in reaction — never either acid 
 or neutral. It coagulates by heat as completely as white of egg, 
 becoming completely solid, and not leaving a drop of fluid. The 
 mineral acids, likewise, cause it to coagulate, as also the metallic 
 salts, akohol, and pyroxylic spirit, It is not coagulated by dilute 
 acetic, lactic, or hydrochloric acids. Alkalies cause no precipitate 
 in it, but redissolve that thrown down by heat, acids, or alcohol. 
 
 This constituent of the pancreatic fluid, which- is coagulable by 
 heat, &c., although apparently identical with albumen, is not so : 
 it diff'ers from albumen in the following point. When the coagulum 
 obtained from the pancreatic fluid by alcohol is dried, it can be re- 
 dissolved completely and readily in water, and it gives to the water 
 the peculiar viscidity of the pancreatic juice, and likewise its physio- 
 logical properties, whilst albumen treated in the same way, undergoes 
 scarcely any appreciable solution in water. 
 
 At a high temperature the pancreatic juice rapidly -changes, is 
 decomposed, and loses its property of coagulating by heat. At a 
 low temperature it may be preserved for many days — when its vis- 
 
594 DIGESTION. 
 
 cidity increases and it becomes of the consistence of a weak jelly. 
 Bernard has examined the pancreatic juice in rabbits, horses, and 
 birds, and has found it in all to exhibit the same essential character 
 as in dogs. 
 
 We have already stated that the pancreatic fluid, or a piece of the 
 pancreas itself, is capable of promoting the transformation of starch 
 into sugar, and therefore of promoting the digestion of amylaceous 
 matters. But that this power does not belong exclusively to the 
 pancreatic fluid is evident from the fact that other fluids or animal 
 substances are capable of producing similar transformations. Ber- 
 nard has shown by direct experiment that the pancreatic fluid pos- 
 sesses the peculiar property, which is not enjoyed by any other 
 animal fluid, of modifying in a special manner or digesting all the 
 neutral fsitty matters which are met with in food. 
 
 Thus by mixing fresh pancreatic juice, possessing the normal 
 characters above described of viscidity and alkalinity, with olive oil, 
 and shaking the fluids well together, a perfect emulsion is formed, 
 and a liquid similar to milk or chyle is the result. A similar effect 
 is produced by the admixture of pancreatic, juice and fresh butter, 
 or of mutton suet, or hog's lard, care being taken to expose the 
 mixture in a sand-bath to a temperature of from 95° to 100° Fahr., 
 so as to melt the butter and suet, and afterwards to shake the mix- 
 ture well.. 
 
 So perfect is the emulsion formed by means of the action of the 
 normal pancreatic fluid upon fatty matters, that the mixture, if left 
 from fifteen to eighteen hours at a temperature of from 95° to 100°, 
 continues to exhibit the same colour and appearance, nor does any 
 separation take place between the fatty matter and the pancreatic 
 fluid. It appears, nevertheless, that the fat is not simply divided, 
 and made into an emulsion, but that it has undergone a chemical 
 change into glycerine, and a fatty acid; the fluid, which immediately 
 after the admixture was distinctly alkaline, becomes, after remaining 
 five or six hours, as distinctly acid. In the tube in which butter 
 had been submitted to the action of the pancreatic juice, butyric 
 acid was easily recognized at a distance by its characteristic odour. 
 
 We find that on rubbing up a piece of quite recent pancreas taken 
 from an animal killed during the digestive process, with fat or 
 lard, and a little water at a temperature of 95° or 100°, a very per- 
 fect white emulsion is quickly formed. 
 
 Bernard instituted experiments to ascertain whether other animal 
 fluids possessed this power over oily or fatty matter. The fluids tried 
 were bile, saliva, gastric juice, serum of blood, and cerebro-spinal 
 fluid, but none of them were found to cause any permanent change, 
 either mechanical or chemical, in the substances submitted to their 
 influence. 
 
 It also appears, from Bernard's experiments, and this is a point 
 which may throw some light on certain forms of dyspepsia, that in 
 order that the pancreatic fluid should exercise its perfect action, it 
 must be strictly normal. Bernard found that what he calls the 
 abnormal fluid, namely, that which exhibits no viscidity, which is 
 
FUNCTION OF THE PANCREAS. 595 
 
 watery and does not coagulate by heat, has no effectupon fatty sub- 
 stances. 
 
 To complete the proof of the special action of the pancreatic 
 fluid^n the digestion of fatty matters, Bernard states that he has tied 
 in the dog the two pancreatic ducts, of which the smaller opens quite 
 close to the choledoch duct, and the larger about three quarters of 
 an inch lower down. Under such circumstances fat passes through 
 the small intestine unaltered, and the lacteals are filled with limpid 
 chyle totally devoid of the white colour. 
 
 The influence of the pancreatic fluid in the formation of the white 
 chyle, by its action upon fatty food, is beautifully illustrated by 
 Bernard, in a very simple experiment upon the rabbit, which we have 
 repeated with results precisely corresponding with those obtained by 
 him. The rabbit is selected for this observation, because, while the 
 choledoch duct opens into the duodenum just below the pylorus, 
 the pancreatic duct opens as much as sixteen or seventeen inches 
 lower down, so that all tl^at length of intestine receives bile only. 
 A small quantity of melted hog's lard was injectedjnto the stomach 
 (the animal having been kept without food for twenty-four hours 
 previously), after which it was left to eat freely of parsley and carrots. 
 After five or six hours it was killed. Between the openings of the 
 two ducts the lacteals contained a clear limpid fluid ; but below the 
 pancreatic duct the lacteals were turgid with a rich white creamy 
 chyle. 
 
 In confirmation of these results of experiments, it may be stated 
 that patients labouring under disease of the pancreas invariably suf- 
 fer from extreme emaciation, and in any cases are recorded in which 
 fat appeared unaltered in the stools — apparently in consequence of 
 malignant disease of the pancreas. Cases of this kind are recorded 
 by Elliotson, Bright, and others. 
 
 From the preceding facts, so well collected by the industry and 
 acuteness of Bernard, it seems to us that we must conclude that the 
 principal function of the pancreatic fluid is to digest fatty matters, 
 that is, to reduce them to ' a state which will admit of their ready 
 absorption by the lacteals. This power is mainly due to the organic 
 principle resembling albumen which is held in solution in the pan- 
 creatic fluid. 
 
 An objection to this view arises from the fact that some animals 
 have no fat, or oily matter, in their food, as, for example, many vege- 
 table feeders. This objection, however, may be thus met, that 
 nearly all vegetable substances contain a certain proportion of oily 
 matter, however small — and, moreover, the pancreatic fluid might 
 serve to digest the fatty matters of the bile which, by absorption into 
 the lacteals, are readily carried to the lungs for combustion. 
 
 But that the digestion of fat food is not the only ofiice of the pan- 
 creas in digestion, is sufficiently proved by the experiments of Bou- 
 chardat and Sandras, already referred to, which point out the import- 
 ant share it takes in the digestion of amylaceous matters. 
 
 We may therefore conclude that the pancreas secretes a fluid of ' 
 which the office is — first, and specially, to digest fatty and oily ele- 
 
596 DIGESTION. 
 
 ments; and, secondly, to convert starch into sugar, and thus to pro- 
 mote the digestion and absorption of amylaceous food. 
 
 The Function of the Liver. — The liver is the largest gland In the 
 body. It is remarkable not only for its complex structure, which 
 will be described in the chapter on Secretion, but also for its pecu- 
 liar double circulation. It is supplied with blood from two sources, . 
 namely, from the hepatic artery, which carries red blood to it, and 
 is distributed mainly to the coats of the ducts — and from the vena 
 portse, a vein in structure, but an artery in its mode of branching, 
 which conveys a large quantity of dark blood, derived from the 
 veins of the stomach, the intestines, the pancreas, and the spleen, 
 and which ramifies throughout every part of the liver, passipg into 
 a dense capillary plexus, whence it is taken up by the hepatic veins, 
 and carried to the right side of the heart. By this arrangement all 
 matters absorbed into the bloodfrom the gastro-intestinal surface must 
 pass through the liver, a point of anatomy which indicates' that the 
 material added to the blood by absorption from the stomach and in- 
 testines, in some way contributes to support the function of this 
 gland. 
 
 We may justly assume that the bilo is secreted from the blood of 
 the vena portse, because of the great size of that vessel and the vast 
 extent of the capillary plexus, which it supplies, more especially as 
 the small size of the hepatic artery compared with the great bulk 
 of the gland, and the trifling degree to which it can contribute to 
 the formation of the capillary plexus of the organ, clearly disqualify 
 it for contributing to the secreting process. 
 
 The bile, as a separated product, first shows itself in the minute 
 canals or ducts which originate in the substance of the liver, and 
 which, by frequent successive junctions, form two large ducts, each 
 somewhat larger than a crow-quill, which emerge at the transverse 
 fissure of the liver, the one from its right, the other from its left 
 lobe. These two ducts pass for a short distance downwards and in- 
 wards, enveloped by Glisson's capsule, along with the trunks of the 
 hepatic artery and portal vein, and with the hepatic plexus of nerves 
 and several large lymphatics, with some lymphatic glands. About 
 an inch below their emergence they unite at an acute angle, and 
 form a single duct a little larger than either ; this is the hepatic duct, 
 which soon unites with a short duct proceeding from the gall-blad- 
 der, the cystic duct. The union of these two ducts forms the ductus 
 communis choledochus, between two and three inches in length, 
 which passes behind the two upper thirds of the duodenum, and 
 opens, along with the pancreatic duct, into that intestine, in or close 
 to the angle of junction of its middle and inferior third. 
 
 The gall-bladder is a pyriform bag, placed in a depression on the 
 inferior surface of the right lobe of the liver, and serving as a reser- 
 voir for the accumulation of the bile when its flow into the intestine 
 is interrupted or retarded. "We infer, at least, that this is its prin- 
 cipal use, because it is always found full after a long fast, and empty 
 when digestion is going on. Blondlot tied the common bile-duct of 
 
THE BILE. 597 
 
 a dog, and establiislied a fistulous communication between the gall- 
 bladder and the external integument; thus the bile, which ought to 
 descend into the intestine, would flow out at this opening. He states 
 that while the animal was fasting sometimes not a drop of bile would 
 escape at the orifice, even for some hours ; but in about ten minutes 
 after the introduction of food into the stomach, the bile would begin 
 to flow freely, and continue to do so as long as digestion was going 
 on.* The process of digestion in the duodenum appears to favour 
 the flow of the bile into the intestine, either by the stimulus of the 
 food in contact with the mucous membrane, acting by reflection 
 upon the muscular coat of the gall-bladder, and causing it to contract 
 and expel its contents, or, by altering its position, so as to favour 
 the descent of the bile, or by changing the condition of the orifice 
 of the duct, which in the empty state of the bowel would be closed 
 by the contraction of the intestinal circular fibres. Indeed, it is 
 probable that all these causes would be brought into operation by 
 the duodenum becoming filled with food, and the digestive process 
 being set up in it. 
 
 That the gall-bladder is not an essential part of the excretory 
 apparatus of the liver is shown by the fact that it is not universally 
 present even in the highest classes of animals. This reservoir is 
 found in the animal series first in fishes ; but it is absent from many 
 ■genera of that class. It exists pretty constantly in reptiles and 
 birds, being occasionally wanting in the latter, and in mammalia it 
 is absent from many of the genera. We do not know the precise 
 law which regulates its presence or absence, but it seems that the 
 length of time for which animals are accustomed to fast has prob- 
 ably a good deal of influence. Thus, in the herbivora, which eat 
 often, and^at short intervals, and, whose digestion is slow, the gall- 
 bladder is frequently absent ; and in the carnivora, which eat at long 
 intervals, it is almost constantly present. But there are many of 
 the herbivora in which it is present, as in the ox, the sheep, the 
 goat, &c. In the first giraff'e examined in this country by Professor 
 Owen there was no gall-bladder; in the second two were found. f 
 
 Quantity of Bile secreted. — Various attempts have been made to 
 estimate the quantity of bile secreted by the liver in a given time ; 
 but, in truth, we have no satisfactory knowledge on this point. 
 Blondlot, by the experiment upon a dog detailed above, was able to 
 collect the bile that flowed out at the external oriflce, which must 
 have been all that was secreted. The quantity thus obtained from 
 one of his dogs amounted in twenty-four hours, on the average, to 
 twelve drachms and a half. Assuming, then, with Haller, that the 
 liver of a man secretes four or five times as much bile as that of a 
 dog, we may conclude that the average quantity poured into the 
 human intestine in twenty-four hours, is from six to eight ounces. 
 Haller, himself, however, had formed a much larger estimate than 
 this, namely, seventeen to twenty-four ounces. 
 
 * Essai sur les fonotions du Foie, p. 62. 
 I Art. "Liver," Cyclop. Anat. and Phys. 
 
598 DIGESTION. 
 
 The Physical and Ohemieal Properties of Bile. — The bile is a 
 thick, ropy fluid, of a greenish-yellow colour, a bitter taste, and a 
 peculiar nauseous smell, with a specific gravity of 1026 to 1030. 
 It has an antiseptic power, and not only itself resists putrefaction 
 for a considerable period, but prevents substances with which it 
 mixes from putrefying. The excessive fetor of the feces in some 
 cases of jaundice from complete obstruction, and, perhaps, also in 
 cholera, is probably due to the absence of the antiseptic influence 
 of the bile. The reaction of the bile, according to Gorup-Besanez is, 
 when first secreted, neutral ; but subsequently it becomes slightly 
 acid, and ultimately alkaline. The well-known cleansing properties 
 of ox-gall are due to the presence of alkali in it, in considerable 
 quantity. 
 
 According to the analysis of Berzelius, which seems to be the 
 most trustworthy, and with which that recently made by Mulder* 
 accords very closely, bile consists of water holding mucus in suspen- 
 sion, and in solution certain salts, with a peculiar complex substance 
 called by Berzelius Bilin ; also fat, and a special coloujring matter. 
 The following is Berzelius's table of the analysis of ox-gall. 
 
 Water 904.4 
 
 Bilin (with fat and colouring matter) 80.0 
 
 INIucus 03.0 
 
 Salts 12.6 
 
 a 
 
 1000.0 
 
 According to Berzelius's view of the composition of bile, its essen- 
 tial and most important constituent is the Bilin, a substance which 
 has a remarkable tendency, under certain circumstances, to be 
 metamorphosed into taurine, hydrochlorate of ammonia, and into 
 two resinous acids, which he has named fellinic acid and cholinic 
 acid. 
 
 Bilin is inodorou?, and has a peculiar sweetish-bitter taste, most 
 perceptible at the base of the tongue and fauces. This sweetness is 
 attributed by Berzelius to the admixture of some glycerine, which 
 may be derived from the fatty matters of the bile. It dissolves 
 readily in water and in alcohol, but not in ether. It is neutral, and 
 forms soluble combinations with acids and bases. 
 
 The substances above named may be obtained from bilin by 
 digesting it in dilute hydrochloric acid. The fellinic and cholinic 
 acids are insoluble, the others are soluble in water. 
 
 Taurine is a crystalline substance, consisting of colourless six- 
 sided prisms. It dissolves in about sixteen times its weight of water 
 at 60°, and is more soluble at a higher temperature. It contains 
 sulphur, according to Redtenbacher.f Its composition is repre- 
 sented by the formula C^N^H^OgSj. The fellinic and cholinic acids 
 resemble each other very much in their external properties. They 
 are little or not at all soluble in water, but are readily dissolved by 
 alcohol ; the fellinic acid is readily dissolved by ether, the qholinic 
 
 * Untersuohungen fiber die Qalle, &o. Frankfort, 1847. 
 
 f Annalcn der Chemie 'ind Pharmacie von Liobig und Woliler, Feb., 1846. 
 
THE BILE. 599 
 
 only sliglitly. They form nearly similar compounds 'with the alka- 
 lies, earthy and metallic oxides ; but their salts of baryta differ ; 
 the fellinate of baryta being soluble in alcohol, the cholinate of 
 baryta insoluble. The product called by Berzelius dyslysin, is 
 obtained by boiling these acids for a long time in hydrochloric acid. 
 It is dissolved with diflBculty in boiling alcohol, and on cooling pre- 
 cipitates an earthy powder. Fellinia and eholinic acids have the 
 property of combining and forming acid compounds with undecom- 
 posed bilin ; these have been named by Berzelius, Mli-fellinic and 
 hili-cholinie acids. 
 
 According to Berzelius and Mulder, bilin begins to undergo these 
 changes in the gall-bladder of the living animal ; and it is, probably, 
 this proneness to change on the part of its principal constituent 
 which makes the analysis of bile so difficult, and gives rise to so much 
 diversity of opinion among chemists. 
 
 The fat of bile exists fiartly in combination with soda, as oleate 
 and margarate of soda, and principally as a peculiar substance found 
 only in bile and in the nervous matter, namely, cholesterine. This 
 is separable from the other constituents of the bile by agitation in 
 ether, which dissolves it ; from this solution it crystallizes in plates'. 
 It exhibits, when pure, the white crystalline lamellated structure of 
 spermaceti, from which it differs, however, in requiring a much 
 higher temperature for its fusion, namely 278°, and in not forming 
 a soap with potash. Its formula is Cj^Hj^O. Cholesterine is the 
 principal constituent of the gall-stones most commonly met with in 
 the biliary passages. 
 
 The colouring-matter of bile {cJiolepyrrJiin, Berzelius) is one of 
 its most interesting constituents. It varies in different animals, and 
 perhaps in the same, animal at different times, according to tbe 
 state of health. Like bilin it decomposes very readily, and there- 
 fore cannot be obtained pure ; but it has been procured for analysis 
 from the gall-bladder, where it is sometimes deposited as a yellow 
 substance mixed with mucus. It is very sparingly soluble in most 
 fluids ; scarcely at all in water, and very little in alcohol. Its best 
 solvent is a solution of soda or potass. Such a solution, containing 
 the colouring matter of bile, becomes green on exposure to the air, 
 and on the addition of an acid precipitates green flocculi, which 
 possess all the properties of chlorophyll, the green colouring-matter 
 of plants. To this precipitate Berzelius has given the name hiliver- 
 din. The most remarkable property of the colouring-matter of 
 bile is the play of colours which it is capable of producing under 
 the influence of a mineral acid, especially nitric acid. A little of 
 this acid, added to bile, or to a fluid in which its colouring-matter is 
 dissolved, as it often is, in urine, will change the colour into blue, 
 green, violet, red, and ultimately brown, in a few seconds. It is 
 highly probable, as some chemists afiBrm, that there exists a great 
 analogy between the colouring-matter of the bile and that of the 
 blood: as there is also, most likely, between these colouring princi- 
 ples and those of nervous substance, skin, and hajr. 
 
 In addition to these constituents bile contains mucus in consider- 
 
600 DIGESTION. 
 
 able quantity, to which probably is due its peculiar viscidity. It is 
 derived chiefly from the numerous mucous follicles in the bile-ducts, 
 and from the mucous membrane of the gall-bladder, and perhaps 
 also from the debris of the hepatic cells after they have burst and 
 yielded up their contents. According to Berzelius, the mucus may 
 be separated by filtering the bile, when a considerable portion of it 
 remains on the filter, and if the bile which has passed through be 
 subsequently subjected to the action of alcohol, the remaining mucus 
 will separate; or it may be precipitated by the addition of acetic 
 acid. It is to the presence of this mucus in bile that Berze- 
 lius attributes the metamorphic tendency of bilin; and he afiirms 
 that if fresh bile be deprived of its mucus, the bijin will continue un- 
 changed for a considerable time. 
 
 Among the saline constituents of the bile Berzelius enumerates 
 the following: oleate, margarate, and stearate of soda, with chlo- 
 ride of sodium, sulphate, phosphate, and lactate of soda, and phos- 
 phate of lime. 
 
 Such is the view of the constitution of bile put forward by the 
 celebrated Berzelius, and sanctioned by Mulder. Berzelius re- 
 marks that the views which regard bile as a solution of soap, are so 
 far correct, as it contains a small quantity of soap dissolved in it. 
 
 The most recent analysis of bile is that by Strecker, made under 
 the direction of Liebig, who denies the accuracy of Berzelius's view, 
 adopting rather that of Demar^ay, Dumas, Liebig, and others, that 
 bile is a solution of a salt of soda with an organic substance of an 
 acid nature, which is not a single acid, but a mixture of a nitroge- 
 nous acid free from sulphur {cholie acid), with a second acid, con- 
 taining both sulphur and nitrogen {choleic acid). 
 
 Use of the Bile, and Function of the Liver. — From the anatomy 
 of the biliary organs, as well as from the chemistry of the bile, we 
 learn that, before the venous blood of the intestinal canal and the 
 spleen is allowed to reach the right side of the heart, a fluid very 
 rich in carbon is eliminated from it, and poured into the duodenum. 
 The following questions suggest themselves respecting the uses of 
 this fluid ; viz. : is the bile simply an excrement, like the urine ? or 
 is it an excrement which also serves some ulterior purpose, such as 
 aiding the solution or digestion of the food in the bowels ? ■ 
 
 The doctrine that the secretion of bile by the liver, is merely a 
 mode of eliminating carbon from the system, is strongly opposed by 
 the fact that in all the vertebrate classes the bile, instead of being 
 carried out of the system by the most direct channel, as the urine 
 is, is- made to pass through nearly the whole intestinal canal, and to 
 mingle freely with its contents. Moreover, the point at which it 
 enters the bowel always bears a pretty definite relation to that at 
 which the pancreatic fluid is poured into it. Either these fluids 
 enter the bowel together through a common opening, as in man, or 
 the bile is poured in above, never below, the point of opening of the 
 pancreatic duct. 
 
 These are capital facts, which must be accounted for by an ade- 
 quate theory of the uses of the bile. They indicate that the bile 
 
USE OF THE BTLE. 601 
 
 has some use in promoting the changes of the food in the intestines, 
 or in contributing to the general process of nutrition in some other 
 way. It is 'well known that an obstacle to the free admission of the 
 bile into the intestinal canal is always followed by a greater or less 
 derangement of digestion, and by more or less emaciation. But, as 
 these consequences might arise not so much from the want of a due 
 admixture of bile with the food which is undergoing digestion, as 
 from the accumulation of the elements of the bile in the blood, 
 which must derange all the functions more or less, Professor 
 Schwann, of Louvain, tried some experiments which had for their 
 jobject to stop the flow of bile into the bowel, and at the same 
 time to provide for its excretion. He tied the common bile-duct in 
 dogs, having first established an orifice of communication between 
 the gall-bladder and the skin, through which the bile flowed out of 
 the body as soon as it was secreted, instead of passing into the 
 bowel. It is plain that if the bile were merely excretory, such an 
 operation should produce no injurious effect upon the animal, as still 
 excretion was amply provided for.* 
 
 Schwann found that of eighteen dogs operated upon in this way 
 two only survived, and in these the divided bile-duct was found re- 
 established, and the bile had resumed its usual channel. Of the 
 remaining sixteen, ten died of the immediate effects of the operation, 
 and the remaining six lingered on for some time, and ultimately 
 died, without, exhibiting any other cause for the fatal termination 
 excepting the absence of bile in the intestinal canal. These six 
 died at periods varying from seven days (in a young dog) to two 
 months and a half, the average being two or three weeks after the 
 operation. During this time they exhibited indications of a very 
 enfeebled nutrition, emaciation, muscular weakness, unsteadiness of 
 gait, falling off of the hairs ; symptoms which became more deve- 
 loped the longer the dog survived the operation. The emaciation, 
 indicated by a deficiency of weight, began generally on the third 
 day from the operation. When the dogs licked the bile as it flowed 
 out of the fistulous opening, and thus introduced it into the stomach, 
 the digestion in that viscus was not impeded, nor were the results 
 of the operation otherwise embarrassed, showing that it was capable 
 of being digested by the stomach. 
 
 Blondlot makes an objection to Schwann's experiments, that, 
 from his mode of operating, the external opening is apt to close, 
 and thus the excretion of the bile is impeded and the nature of the 
 secretion altered. He adopted a different operation, and provided 
 for the free discharge of bile by inserting a canula in the wound. 
 A dog, treated in this way, lived three months ; at first he became 
 very thin, and lost strength ; but he recovered his strength, but did 
 not completely gain his condition. It appears, from a private com- 
 munication made by Schwann to Frerich,| that that distinguished 
 
 * Experiences pour constater si la BUe joue dans I'Economie Animale nn Rolq 
 essentiel pom- la Vie. — Mdm. de I' Acad. Roy. de Bruxelles, an.. 1844. 
 
 t Art. Verdauung, Wagner's Handworterbuch. This author states that Nasse 
 operated on a dog in a similar way, and that the animal lived nearly six months. 
 39 
 
602 DIGESTION. 
 
 Professor was induced, by these objections of Blondlot, to repeat 
 his experiments, which he did to the number of thirty, and he took 
 the precaution of keeping a canula in -the wound. The animals 
 died as before, but one lived a year, another four months ; immedi- 
 ately after the operation they lost weight, but after a time the ema- 
 ciation ceased, and the dogs recovered, but never reached their 
 weight previous to the operation. 
 
 The results of these experiments denote that the bile cannot be 
 exclusively an excretion, and, taken along with the facts already 
 referred to, make strongly against this doctrine. But as the excre- 
 ments of all or nearly all animals, and also the meconium, or the 
 feculent matter found in the bowels of the foetus in utero, contain 
 in certain proportion the elements of the bile, we are bound to infer 
 that a portion of the bile is thrown out of the system, along with 
 the refuse or undigested parts of the food. And that only a portion 
 of it, and that a small one, is thus excreted seems evident, because 
 the quantity of bile contained in the feces bears a very trifling pro- 
 portion to the amount secreted. Thus, Berzelius found only 9 parts 
 bile in 1000 parts of fresh human feces ; if we take the average 
 quantity of the feces expelled in the day to be five ounces, this 
 would yield about twenty-one grains of dried bile, equivalent to 210 
 grains of fresh bile ; but the lowest estimate of the quantity daily 
 secreted by the liver is between six and eight ounce,s, which exceeds 
 that of the feces discharged. 
 
 If, then, it be admitted that only a certain portion of the bile is 
 excrementitious, it remains to inquire what becomes of the remain- 
 der, and what purpose it may serve ? 
 
 Liebig suggests that it is absorbed from the intestine, and carried 
 into the circulation, where, by chemical union with the oxygen in- 
 troduced in respiration, it forms carbonic acid, and generates heat. 
 The liver, according to this view, secretes from the venous blood a 
 material, which, on reabsorption, serves as food for the calorifacient 
 process. It is not likely that this absorption takes place by the 
 veins, for if so, we should find the secreted material carried back 
 again through the very same vascular channels from which but a 
 short time previously it had been secreted ; an arrangement which 
 has no parallel in the animal economy. It is more probable, assum- 
 ing this view to be correct, that the portion of the bile absorbed is 
 taken up by the lacteals ; and if so, we should have an additional 
 indication that only a part of the bile re-enters the circulation, for 
 if the colouring matter were absorbed by the lacteals it would be 
 readily detected in the chyle. 
 
 There are some striking facts which denote a connection between 
 the office of the liver and the calorifacient and respiratory function. 
 Thus, in the boa, although the liver is large, and no doubt secretes bile 
 freely, the excrements contain no trace of bile. In this case, there- 
 fore, it must undergo complete decomposition in the intestine, or be 
 entirely absorbed. In carnivorous animals, whose respiratory func- 
 tion is very active, little or no bile is found in the excrements ; while 
 in those of the herbivora, which lead less active lives, and whose 
 
USE OF THE BILE. 603 
 
 food is more combustible in its nature, the elements of the bile are 
 present in considerable quantity. 
 
 According to this view, the bile would be in part excrementitious 
 and carried oiF in the feces ; and in part recrementitious, inasmuch 
 as by its absoption into the blood it serves to feed a process highly 
 important to general nutrition, namely, that of animal heat. Still, 
 there seem strong grounds for supposing that it must serve yet 
 another purpose ; felse why should the intestinal blood charged with 
 some of the combustible materials derived by absorption from the 
 digested food be subjected to the action of the liver in order to 
 yield a complex fluid, which is poured into the intestinal canal. In 
 truth, we can find no explanation of this remarkable course of the 
 intestinal venous blood, nor of the situation at which the secreted 
 fluid, the bile, is discharged from the liver, but in the hypothesis 
 that the bile has some function to perform in the intestinal canal. 
 
 This leads us to inquire whether the bile has any power of reducing 
 certain elements of food which have been only partially or not at 
 all dissolved in the stomach. 
 
 We have as yet no satisfactory observations which lead to any 
 positive conclusion upon this point. A series of careful experiments 
 as to the influence of bile upon alimentary matters is much needed. 
 Hunefeld's experiments* on this subject tend to establish the gene- 
 ral fact that fibrinous and albuminous matters do seem to be dis- 
 solved under its influence at a temperature equal, or nearly so, to 
 that of the blood. 
 
 The connection of a gall-bladder with the liver in most animals 
 in which the bile accumulates until intestinal digestion begins, evi- 
 dently associates the use of the bile with that process. 
 
 Sir Benjamin Brodie advocated the doctrine that the bile preci- 
 pitated the white chyle from the chyme, and was necessary to the 
 formation of the former. He tied the common choledoch duct in 
 young cats so as to prevent the passage of bile into the intestine ; 
 and he found that under these circumstances white chyle was not 
 formed, the lacteals being filled with a material apparently identical 
 with lymph.f Tiedemann and Gmelin experimented on dogs, and, 
 although they affirm that chyle was formed in the intestine (the 
 accuracy of which statement must not be completely relied upon 
 in default of microscopical examination), yet they admit that the 
 contents of the lacteals in the dog operated on consisted of " a 
 transparent liquid, not white," while in the dog not operated on it 
 was white. 
 
 By our own experiments we have ascertained that the formation 
 of white chyle took place, notwithstanding the closure of the com- 
 mon bile-duct, provided the animal took a sufficient quantity oi fatty 
 matter in its food. When this was not attended to, white chyle was 
 not obviously formed. But the most remarkable effects of the liga- 
 ture of the common duct were the emaciation, loss or capriciousness 
 
 * Quoted in Valentin, Physiologie, b. i. p. 349. 
 I Quarterly Journal of Science and the Arta, 1823. 
 
604 DIGESTION. 
 
 of appetite, and the general debility vrhich immediately ensued upon 
 it. Hence, although we do not subscribe to the doctrine that the 
 presence of bile in the small intestines is essential to the formation 
 of white chyle, we readily believe that its exclusion from the bowels 
 retards and impairs digestion. 
 
 When the biliary duct is obstructed, and the bile does not pass 
 through its ordinary channels, the organs which suffer most disturb- 
 ance in their functions are the kidneys ; as if, when the liver fails in 
 its action, these organs took on the work of eliminating a certain 
 portion of the bile. They secrete urine loaded with the colouring- 
 matter of the bile; and, at the same time, lithic acid, or lithate of 
 ammonia, or purpurate of ammonia (muroxid), is formed in consider- 
 able quantity. In cases of jaundice from obstruction, so long as 
 plenty of bile, or its colouring principle, appears in the urine, and, 
 a normal quantity of urine is secreted, no very serious symptoms 
 arise ; but as soon as the kidneys fail, then indications of poisoning 
 either by bile or urea, or both, arise, and the patients die in a coma- 
 tose state. 
 
 It is worthy of remark that the hepatic cells contain more or less 
 of oily fat: and that under some circumstances this fat accumulates 
 in them to a great extent, so as to occasion enormous enlargement 
 of that organ. And in some fishes the liver is naturally, at certain 
 periods, loaded with it. It is a point of great interest to determine, 
 whether this fat simply accumulates in the hepatic cells, as it does in 
 other tissues, or whether it may not be regarded as a part of the 
 secretion of the liver ; in other words, can it be a part of the office 
 of the liver to recombine certain elements of the absorbed food, and 
 to form fat, which, on being discharged into the intestinal canal, is 
 absorbed by the villi ?* 
 
 In connection with this subject we may refer here to a remark- 
 able fact lately brought to light by Bernard, which denotes that 
 chemical changes take place in the blood while it is passing through 
 the liver, whereby a material is generated in it which had not been 
 introduced in the food. 
 
 Bernard has found that sugar is developed in the hepatic capil- 
 laries, even when it is not present in the intestines, or in any of the 
 tributary veins of the vena portae. A dog, which had been fed some 
 hours previously on substances destitute of starch and sugar, was 
 quickly killed, the abdominal cavity was immediately opened, and 
 ligatures were placed on the mesenteric, splenic, and pancreatic 
 veins, and on the trunk of the vena portse. Blood collected from 
 each of these sources, on the distal side of the ligature, proved on 
 examination destitute of sugar in all, except the vena portae, in 
 which it was readily detected. Sugar was also found in the tissue 
 of the liver itself. If, then, sugar exists in the vena portse, but not 
 in its tributary veins, how does it get to the former ? As it exists 
 
 * It is true that the fatty matter of the bile is not free ; but it may be supposed to 
 form its combinations after it has been discharged from the hepatic cells, and while it 
 is passing through the ducts of the liver. 
 
USE OF THE BILE. 605 
 
 in tlie tissue of the liver, it is evident that it passes to the vena 
 portse by the reflux which, in the absence of valves in the portal 
 system, may take place after death. Hence it is reasonable to infer 
 that sugar is formed in the hepatic capillaries, and carried by the 
 hepatic veins to the right side of the heart, in the blood of which 
 Bernard states that sugar is constantly present, whatever food the 
 animal may have been fed on, and even after a long fast. 
 
 The evidence of the presence of sugar in the liver is obtained in 
 the following manner : a portion of the liver is beaten in a mortar, 
 and then boiled in a small quantity of water, and filtered. The 
 filtered liquid possesses all the properties of a saccharine fiuid ; it 
 becomes darker on being boiled with liquor potassse, and the addition 
 of the tartrate of potass and copper causes a precipitation of the 
 brown oxide of copper. Yeast added to it at a certain temperature 
 causes fermentation ; and alcohol may be obtained from the fermented 
 fluid by distillation. 
 
 There can be no doubt, then, that sugar is formed in the capil- 
 laries of the liver independently of the food ; it is equally certain 
 that fat is separated at the same point, for it appears in the hepatic 
 cells ; this, too, is doubtless the result of chemical changes in the 
 hepatic circulation, independent of the food, because we find good 
 grounds for concluding that the fat of the food, emulsified by the 
 pancreatic fiuid, is absorbed by the villi, and does not reach the 
 liver. 
 
 Thus are formed in--the laboratory of the liver these two products 
 — fat and sugar, very nearly allied in chemical constitution. The 
 former is carried into the intestine with the bile, and there absorbed, 
 with the fat of the food, by the villi. The latter is carried by the 
 hepatic veins to the right side of the heart, and thence to the lungs ; 
 and both appear to be formed by the liver, whether they have ex- 
 isted in the food or not. 
 
 What, then, it may be asked, can be the object of the formation 
 of these products by the liver? If it be to feed the calorifacient 
 process, then the additional question arises, why should each pass to 
 the right side of the heart by a difierent route ? 
 
 It seems to us that there is in these arrangements distinct indica- 
 tion of a provision for the slow and gradual transmission to the lungs 
 of these carbonaceous elements ; in order to guard against the- blood 
 in these organs becoming surcharged by them so as to interfere with 
 the due introduction of oxygen. 
 
 It seems necessary for health that the blood should be supplied, 
 on the one hand, duly, but gradually, with carbonaceous matters, 
 such as sugar and fat, and, on the other hand, with oxygen ; when 
 the former elements are deficient, fever is the result, the elements 
 of the tissues are consumed by the devouring element, oxygen ; and 
 hence it is that we often see such striking results from the gradual 
 introduction of alcohol, or other carbonaceous matters, into the 
 system ; but when the latter element is deficient, the great vital 
 changes of the blood are delayed, or suspended, and death rapidly 
 ensues. And in the various diseased states of the body there are 
 
606 DIGESTION. 
 
 infinite shades of difference, as regards the supply or the defect of 
 these great elements ; either too much carbon or too much oxygen ; 
 or the one is normal in amount, while the other is deficient. A com- 
 mon result of the too ready assimilation of carbonaceous matters, 
 or the too rapid formation of them, is the deposition of fat in various 
 parts of the body, sometimes to the augmentation of its bulk by an 
 increased development of the adipose tissue, at others, to the pro- 
 duction of various abnormal deposits, containing more or less fat, as 
 atheroma. 
 
 In conclusion, the following propositions will serve to exhibit at 
 a glance all that we may, in the present state of our knowledge, 
 a£Brm respecting the function of the liver: — 
 
 1. That it secretes a highly complex fluid, which is poured into 
 the intestinal canal, and there undergoes decomposition. Its colour- 
 ing-matter (cholepyrrhin, or biliverdin) is carried off in the excre- 
 ments, and may possibly assist in stimulating the action of the 
 intestine. Its fat is in great part, at least, absorbed by the villi. 
 So much of its fat as is not thus acted upon contributes to form 
 the feces. Its salts, also, are probably carried off in the feces. 
 Other of its elements contribute to the digestive process, by pro- 
 moting the solution in the bowels of some kinds of food which have 
 escaped the solvent action of the gastric fluid. What these elements 
 are, and what binds of food they serve to dissolve, we have yet*ac- 
 curately to determine ; it seems certain, however, that it exercises 
 no solvent power over fatty or oily matters, and probable, that it 
 acts upon azotized matters. 
 
 2. The liver forms sugar and fat by chemical processes in its 
 circulation, independently of any direct or immediate supplies of 
 these substances in the aliments. 
 
 3. The liver is a great emunctory ; it eliminates carbonaceous 
 matters, some directly, as the colouring-matter of the bile, which is 
 at once thrown out in the feces ; others indirectly, as fat and sugar, 
 which, passing to other parts of the circulation, are more or less 
 acted on by oxygen and eliminated as carbonic g.cid and water. 
 
 4. The liver contributes largely to the maintenance of general 
 nutrition ; flrst, by aiding in the solution of certain aliments in the 
 intestinal canal, and secondly, by furnishing food to the calorifacient 
 process. 
 
 Before we leave this subject, we must refer to the remarkable 
 observations of Weber, confirmed by Kolliker, respecting the ex- 
 tensive generation of blood-corpuscles in the liver of the embryo, 
 which have led the former physiologist to form the opinion that " not 
 only is the liver an organ for secreting bile, but that in it a material 
 is separated and accumulated from the blood, out of which blood- 
 corpuscles are formed, which are taken off by the bloodvessels, while 
 from the residuum the bile is formed, which is conveyed away by the 
 biliary ducts." ^ 
 
 During the latter days of incubation of the hen's egg, the liver 
 assumes a completely yellow colour, instead of the reddish-brown 
 which it had previously. This is connected with the rapid absorp- 
 
USE OP THE BILE. 607 
 
 tion of the yelk, probably by the bloodvessels of the yelk-sac, which 
 carry it to the liver, where it finds its way from the bloodvessels into 
 the fine gall-ducts, which at this time are full of particles exactly 
 the same as the yelk-globules. These particles are not carried into 
 the intestine along the biliary passages, but undergo a change by 
 which, on the one hand, blood-corpuscles are formed and pass into 
 the bloodvessels, and, on the other hand, bile is generated and carried 
 off by the ducts. 
 
 Weber states that he has observed a similar phenomenon in the 
 liver of the frog in the spring of the year, when the sexual organs 
 are highly developed, and when the lymphatic system is in a highly 
 active state. The liver undergoes a change of colour from reddish- 
 brown to greenish-yellow. It is covered with dark pigment-cells, 
 and contains numerous opaque masses, which probably consist of the 
 colouring-matter of the bile, which may have accumulated during 
 the winter, but which now undergo gradual solution and pass off in 
 the bile. The peculiar colour which characterizes the liver at this 
 time, in the frog, is resident, as with the chick, neither in the blood- 
 vessels nor in the hepatic cells, but in the minute ramifications^ of 
 the gall-ducts, which are filled with numerous small globules con- 
 taining fatty particles. These undergo the same metamorphoses as 
 those of the chick into blood-corpuscles. 
 
 This highly interesting subject requires further investigation — to 
 ascertain whether similar phenomena may be noticed in other 
 animals, as in intra-uterine life in Mammalia — or in hybernating 
 animals — or whether, indeed, they may not be constantly occurring 
 in adult animals, although with less activity than in the young. 
 
 The question occurs to us, may the liver be a source of supply of 
 blood-corpuscles, or may it contribute to the production of hsematine 
 in adult life ? It has often struck us that this question might be 
 answered in the afiirmative, while observing cases in which the pro- 
 cess of the formation of blood seemed greatly perverted, where no 
 organic disease could be detected beyond some degree of enlarge- 
 ment of the liver. Patients suffering in this way are pale, as if 
 from loss of blood, although no such loss had been experienced; 
 their nutrition is enfeebled, digestion impaired, and there is slight 
 yellowness of the complexion, as in cases of hepatic disease, and 
 after death no lesion is discoverable, but slight enlargement of the 
 liver.* 
 
 We have already remarked that the venous blood of the spleen 
 passes along with that from the stomach and intestines through the 
 liver. Recent researches of Kblliker and Ecker offer some expla- 
 nation of this fact, and at the same time of the relation between 
 hsematine and the colouring matter of bile, as well as between the 
 office of the liver and the generation of the red particles of the blood. 
 It would appear from these researches, which will be detailed when 
 we come to treat of the spleen, that the red blood-corpuscles 
 undergo decay in the red substance of the spleen, giving up their 
 
 * KoUiker iiber die Blutkorperbhen der Mensohliclieii Embryo und die Entwick- 
 elung der Blutkorperohen der Saugetliieren. 
 
608 DIGESTION. 
 
 hsematine in an altered form to the portal blood, from which it may 
 not improbably, as Kolliker conjectures, pass into the bile-cells to 
 form, and to be eliminated as the biliary colouring matter ; and, 
 perhaps, also to contribute to supply haematine to new blood-cells 
 developed in the liver.* 
 
 Of Digestion in the Large Intestine. — The contents of the large 
 intestine,' which constitute the feces, properly so called, differ much 
 from those of the small intestine. Generally, and in the normal 
 state, they are more solid, more homogeneous, exhibiting a certain 
 form, which is determined by the size and shape of the cells of the 
 colon. These characters are more marked the further the feces 
 have advanced in the colon. 
 
 The changes, upon which depends the difference of character of 
 the contents of the large and small intestine, commence in the 
 caecum. Many facts lead to the opinion that the intestinal contents 
 undergo some further digestion in the csecum, analogous to that of 
 the stomach. Schulz affirms that an acid fluid is secreted by the 
 mucous membrane of the csecum, which is more distinct in herbivora 
 than in carnivora ; Bernard and Blondlot state that the acidity of 
 this fluid is due to the presence of lactic acid, f In dogs, we have 
 found that litmus applied to the surface of the csecal mucous mem- 
 brane became reddened in some, but not in others ; a difference 
 probably depending upon some peculiarity in the food or the time'' of 
 digestion. The remarkable development of the caecum in some 
 animals as compared with others, denotes that it must exercise some 
 special function. In herbivora, its size is especially large ; in carni- 
 vora, it is small. Moreover, the mucous membrane of the caecum 
 resembles in structure that of the stomach, and is supplied with 
 glands like the solitary glands, which pour out an abundant secretion. 
 
 No material change takes place in the feces as they pass through 
 the large intestine, excepting such as is produced by the absorption 
 of fluid from them by the mucous membrane. Thus the feces 
 become drier the longer they remain in the bowels. 
 
 Defecation. — The contents of the large intestine are pushed 
 onwards by a vermicular action, essentially the same as that of the 
 small intestine. Propelled thus in successive portions, they accumu- 
 late in the rectum, whence they are prevented from escaping by the 
 contraction of the sphincter. The act of expulsion of the feces 
 from the rectum, the act of defecatioi)^^ is effected partly by the 
 contraction of the muscular fibres of the rectum, excited by the 
 stimulus of distension, and partly by the contraction of the abdomi- 
 nal muscles and of the diaphragm, which, by reducing the size of the 
 abdominal cavity, and compressing the intestinal canal at all points, 
 greatly assists the detrusive efforts of the rectum itself. 
 
 Within certain limits the act of defecation is favoured by the 
 bulk of the intestinal contents. When the rectum is moderately 
 distended, and its inner surface sufficiently lubricated by mucus, 
 defecation is effected with but little aid from the abdominal muscles, 
 and mainly by the expulsive force of the rectum, which is sufficiently 
 
 * Cycl. Anat. and Phys. ; art. Spleen. f Gazette Mid. de Paris, 1844. 
 
THE FECES. 609 
 
 strong to overcome tlie passive contraction of the sphincter. If the 
 contents of the fectum be too bulky, they occasion over-distension 
 of the gut, and diminish its contractility. Under such circumstances 
 immense accumulations may take place ; and, as small portions may 
 continue from time to time to be expelled, under the influence of the 
 abdominal fnuscles, the practitioner may thus be deceived as to the 
 real nature of the case. On the other hand, when the fecSs do not 
 accumulate in the rectum in sufficient quantity to distend the rec- 
 tum, the act of defecation is rendered difficult by the imperfect ) 
 actions of the rectum itself, and great efforts are required on the 
 part of the abdominal muscles, which often cause the protrusion of 
 portions of the mucous membrane near the anus. Under these 
 circumstances it is that enemata act so favourably, by giving the 
 gut its natural stimulus, that of distension. The action of the ab- 
 dominal muscles in defecation is chiefly voluntary, but partly reflex. 
 If the rectum be the seat of irritation, as in dysentery, the reflex 
 action is much increased, and the repeated strainings which occur 
 during the act of defecation in this disease are, in a great measure, 
 thus caused. 
 
 The ordinary expulsive actions of the rectum are due simply to 
 the stimulus of distension acting upon, the circular muscular fibres. 
 When the mucous membrane is irritated, as under the influence of a 
 purgative, or in diseased states, the action of the rectum takes on 
 the character of a reflex act, excited by the contact of the feces 
 with the irritable mucous membrane. 
 
 The quantity of the feces is determined partly by the quantity 
 and quality of the food, partly by the quantity of the secretions 
 poured into the canal. If the food exceed much what the aliment- 
 ary canal can reduce and absorb, the quantity of feces will be con- 
 siderable. Vegetable food produces a greater amount of feces than 
 animal, because the former is eaten in greater quantity than the 
 latter, and because it contains much that is incapable of reduction 
 in the, stomach or bowels. The feces of carnivora are always abso- 
 lutely and relatively smaller in quantity than those of herbivora. 
 And those tribes of mankind who feed chiefly on vegetable food 
 make large quantities of fece^. 
 
 The ordinary quantity of feces passed daily by men in health, is 
 about five or six ounges ; so that, if we assume thirty-five ounces as 
 about the average quantity of food taken in twenty-four hours, it 
 may be inferred that at least thirty ounces are appropriated to the 
 various purposes of the economy. 
 
 Berzelius's analysis of feces gives the following result: — 
 
 IC 
 
 Water 
 
 Matters soluble in water : Bile . 
 
 Albumen 
 
 Extractive 
 
 Salts . 
 Insoluble residue of the food 
 
 Insoluble matters derived from the intestinal canal, as mucus, 
 biliary resin, fat, and a peculiar animal matter . . 14.0 
 
 100.0 
 
 0.9] 
 
 0.9 i K „ 
 2.7 \ ^■' 
 1.2 J 
 
 7.0 
 
610 DIGESTION. / 
 
 The ashes of human feces yield, according to Berzelius and Ender- 
 lin, chloride of sodium, sulphate of soda, tribasic phosphate of soda, 
 phosphate and sulphate of lime, phosphate of magnesia, phosphate 
 of iron, and silica. The nature and quantity of these salts, how- 
 ever, vary with the quality of the food. 
 
 A remarkable property of the feces is their peculiar odour. Upon 
 what thia depends has not yet been satisfactorily ascertained. It 
 seems very doubtful that it can depend on any decomposition of the 
 bile ; for under certain circumstances, when bile is deficient or ab- 
 sent, the fetid odor of the discharges from the bowels becomes 
 greatly increased, as in jaundice from obstruction, and Asiatic 
 cholera. It is not improbable that some of the intestinal glands 
 may secrete a peculiar odoriferous- principle, which may be modified 
 by the bile. Peyer's glands may perform this office ; and this idea 
 derives support from the fact that in certain cases where these 
 glands are diseased, as in fever and phthisis, the fetor of the feces 
 is increased considerably. 
 
 Certain gases are generated in the course of the intestinal canal. 
 These are partly set free during the changes which the alimentary 
 matters undergo in the intestine ; and partly they are products of 
 secretion from the mucous membrane. They consist of carbonic 
 acid, hydrogen, carburetted and sometimes sulphuretted hydrogen, 
 and nitrogen. ^ certain quantity of these gases seems, by its 'dis- 
 tending action, to favour the vermicular movement of the bowels, 
 and so to promote the passage of their contents. Within certain 
 limits, therefore, the formation of gases in the bowels may be pre- 
 sumed to favour health ; but it is well known that under the in- 
 fluence of emotion, or of irritation, or of certain kinds of food, gases 
 are generated in the stomach, as well as in the intestines, to an 
 enormous extent. Tympanites shows itself in hysteria under the 
 influence of strong emotion ; and sometimes a few minutes will suf- 
 fice to generate a quantity of gas sufficient to distend the whole 
 canal. Also, in fever, the formation of gases in the intestines is a 
 prominent symptom, giving rise to that state of meteorism which is 
 known to be an unfavourable sign in that disease. 
 
 On the 6ubjeot3 discussed in this chapter, the reader is referred to the list of 
 writers at the end of the last chapter, and to those quoted in the foot-notes ; also to 
 the following : Berzelius, art. Galle, in Wagner's Handworterhuch ; Bernard, du Sue 
 Pancreatique, &o., Arch. G^n. de Med. 1849 ; Bernard, de I'origine du Sucre dans 
 Veconoraie animale, Arch. G6n. de Mid. 1848, and translated in Banking's Abstract 
 for 1849. French's art. Verdaxmng, in Wagner's Handworterbuch, a most able essay, 
 which did not reach us until this chapter had been some time in type ; Bouchardat 
 and Sandras, Comptes Bendus, 1845 ; Dr. All*n Thompson's paper on the Intestinal 
 Glands, in Goodsir's Annals of Anatomy and Physiology. Part i. 1850, 
 
ABSORPTION. 611 
 
 CHAPTEK XXVI. 
 
 OF ABSORPTION. — EXAMPLES. — ANATOMY AND DISTRIBUTION OE THE 
 ABSORBENT VESSELS AND GLANDS. — ORIGIN OF THE ABSORBENTS. — 
 PROOFS OF ABSORPTION. — CONTENTS OF THE ABSORBENTS. — ANALYSIS 
 OE CHYLE AND LYMPH. — THEIR QUANTITY. — MECHANISM OF THE 
 ABSORBENT PROCESS. — THE INFLUENCE OF THE QUALITIES OF THE 
 FLUIDS. — OF THE POROUS SOLIDS. — OF PRESSURE. — OF MOTION OP 
 THE FLUID WITHIN THE VESSELS.— rCONCLUDING OBSERVATIONS ON 
 THE FUNCTION OF THE ABSORBENTS. 
 
 The function of absorption is universal in organized bodies, as 
 they all live and grow by absorbing suitable material from without 
 and making it a part of themselves. All the tissues are more or 
 less porous, and capable of absorbing fluids brought into contact 
 with them. The cuticle of the hands soaked in water become soft 
 and swollen from the imbibition of that fluid, and if a soluble salt 
 be added to the water, this salt may, ere long, be detected in dis- 
 tant parts of the body by its appropriate tests ; showing that the 
 foreign substance has penetrated within the cuticle so as to reach 
 vessels capable of diifusing it throughout the frame.* In the same 
 way soluble substances taken into the mouth, and brought into contact 
 with the alimentary mucous membrane, are rapidly absorbed, either 
 immediately, or after having been first changed and adapted for ab- 
 sorption by the processes described in the preceding chapters. In a 
 similar way gases or fluids effused orinjected into the cavities or inter- 
 stices of the body may be gradually taken up and removed, as we see in 
 cases of emphysema, of ecchymosis, of dropsy, of inflammatory pro- 
 ducts, &c. An absorption of the tissues themselves is also constantly 
 going on, as a necessary part of their nutrition — the old materials 
 being taken away when no longer suited for the purposes of life. 
 When the effete matters of the tissues are thrown off from the sur- 
 face of the body, or from glands which are, in fact, a portion of 
 that surface, they are said to be secreted ; when they re-enter the 
 circulation for a time they may be rightly said to be absorbed. In 
 certain cases, entire organs waste Avhen the term of their usefulness 
 has expired, e. g., the mammary and spermatic glands, and all the 
 
 * Mr. Erichsen took advantage of a case of extroversion of the bladder to expe- 
 riment on the rapidity of absorption under different circumstances, as indicated by 
 the presence in the urine of the absorbed substances. The following are some of his 
 results. Prussiate of potass taken into the stomach, after a fast of eleven hours, may 
 be apparent in the urine in. one minute ; but if immediately after a meal, not till 
 thirty-nine minutes. Vegetable infusions required more time for passage through the 
 system. Galls, nva ursi, madder, rhubarb, logwood, &c., passed in from sixteen to 
 thirty- six minutes, according to the time after a meal. Citrates and tartrates of 
 potass and soda rendered the urine alkaline in from thirty-six to forty-eight minutes. 
 When the feet were immeiraed in a pail of water containing three ounces of acetate of 
 potass in solution, the urine became alkaline in sixty-seven minutes ; but no effect, 
 seemed to be produced when a solution of citrate, tartrate, or prussiate of potass was 
 employed (see Med. Oazeite, June, 1845). 
 
612 ABSORPTION. 
 
 organs, even the bones, tend to atrophy in advancing life. Again, 
 periodical absorption of the materials of certain organs occurs, as 
 in the testes of birds and other animals after the annual season of 
 impregnation, but perhaps the most remarkable example of absorp- 
 tion belonging to this he9,d, is that of the fat ■which is stored up in 
 large quantities in the bodies of hybernating animals, and gradually 
 disappears during the winter torpor, probably to furnish material3 
 for the generation of warmth. 
 
 These general observations wijl sufiSce to show the importance 
 of the subject of absorption. We are led to it, at the present stage, 
 by having to consider the mode in which the materials introduced 
 into the alimentary cavities are conveyed thence to mingle with 
 and form part of the common mass of the circulating fluid". But 
 we may conveniently treat of the process in general in the present 
 chapter. 
 
 The coats of the intestine are found to contain two sets of vessels, 
 one through which blood circulates, from arteries to veins through 
 the capillary network, the other containing a milky or transparent 
 fluid, chyle or lymph, which finally reaches the blood. Both of 
 these kinds of vessels are the agents of absorption, and both proba- 
 bly share in receiving the alimentary matters through the mucous 
 lining of the canal, but in the present chapter the structure of the 
 latter will be chiefly considered, and that of the bloodvessels 'de- 
 ferred. Together with the lacteals, the lymphatics will be also de- 
 scribed. 
 
 The lacteals and lymphatics together form one system of vessels, 
 which takes its rise in the midst of various organs of the body, 
 and conveys a fluid into the veins near their termination in the 
 heart. The lacteals constitute *that portion of this great system 
 which originates in the digestive mucous membrane, and they are 
 undoubtedly concerned in the absorption of a part at least of the 
 nutrient matters of the food^their contents [chyle) after a meal 
 being of a milky appearance — whence their name, vasa lactea, 
 given to them in 1622 by their discoverer, Asellius. The lymphatics 
 (and the lacteals during fasting) contain a pellucid fluid-^the lymph. 
 
 The lacteals originate in the mucous membrane of the intestines, 
 especially in the villi, and form a network with close meshes in the 
 submucous areolar tissue. There are also more superficial ones be- 
 tween the peritoneum and muscular coat, which take a more longi- 
 tudinal course, and join the others on the mesentery. They then 
 pass in great numbers between the layers of the mesentery towards 
 its root, anastomosing with one another and traversing glandular 
 organs, the mesenteric glands, in their way to the right side of the 
 aorta, where they all finally discharge themselves into an elongated 
 pouch common to them and to the lymphatics of the parts below — 
 termed the receptaculum chyli. From this the thoracic duct leads 
 upwards to the left subclavian vein. 
 
 The receptaculum is usually from an inch to an inch and a half 
 in length, and from a quarter to three-eighths of an inch in diameter. 
 The thoracic duct, which is continued upwards from it, lies in the 
 
THE ABSORBENT VESSELS. 613 
 
 chest between the aarta and vena azygos, then inclines behind the 
 arch of the aorta to the left side, and empties itself into the upper 
 and back part of the left subclavian vein close to the internal jugular 
 vein, its orifice being defended by two valves. The thoracic duct 
 is about an eighth of an inch or more wide, becomes more narrow 
 up to the sixth dorsal vertebra, and again dilates opposite the third. 
 It frequently divides into branches which reunite — and sometimes 
 opens into the subclavian Vein by two or even three separate trunks. 
 
 The lymphatic vessels of the upper and lower extremities form 
 two sets, a deep one accompanying the deep bloodvessels, and a 
 superficial one running in the deeper layer of the superficial fascia. 
 These sets anastomose and pass in common to the trunk by the groin 
 and axilla, where numerous glands occur upon them. (1) Those of 
 the lower extremities, after passing under Poupart's ligament, follow 
 the great bloodvessels, are joined by others from the pelvis, loins, 
 and abdominal walls and viscera, and open into the receptaculum 
 chyli by from four to six large trunks. Very numerous glands suc- 
 ceed each other in their course, forming an irregular chain. The 
 thoracic duct is joined by lymphatics from the left side of the walls 
 of the chest, and from the heart and left lung, on all of which 
 many glands ocQur ; and as it empties, itself into the great vein, 
 the lymphatics of the left upper extremity, and left side of the 
 head and neck come to meet it. (2) The lymphatics of the right 
 side of the chest, of the right arm, and of the right side of the neck 
 and head, crowd towards the junction of the right subclavian and 
 jugular veins, and open into the former, usually by a large but 
 short trunk. The number of lymphatic glands in the whole body 
 may be estimated at from two to three hundred, or even more. 
 
 In general, but especially in the Ijjmbs, the lymphatic vessels form 
 many trunks of equal diameter, taking the same direction, and join- 
 ing, and again dividing irregularly, without altering their size. In 
 all this they differ Remarkably from the ordinary arrangement of the 
 sanguiferous vessels. 
 
 The absorbent vessels differ from the bloodvessels in the delicacy 
 and semitransparency of their coats, which allow the nature of the 
 contents to be seen through them ; the white colour of the chyle in 
 the lacteals or mercury artificially thrown in, is at once visible from 
 the outside. When the vessels are filled we observe many constric- 
 tions, depending on the existence of valves in the interior, so placed 
 as to prevent a retrograde flow of the chyle or lymph. These valves 
 are closer together in some parts than in others. In general, they 
 are further apart in the narrower vessels, but in the thoracic "duct, 
 the largest of all, they are unfrequent. They are usually closest 
 set in vessels of medium size, i. e., in those of from Jjj to -Jg of 
 an inch diameter, but they are not so near to one another in the 
 lymphatics of the upper extremities, and the head and neck, as in 
 those of the lower limbs. Besides occurriiig in succession in the 
 course of the vessels, they are almost always found at the origin or 
 termination of branches, and also where the lymphatics empty them- 
 selves into the veins. 
 
614 
 
 ABSORPTION. 
 
 A. Longitudinal wavy fibres on the inner surface of 
 the contractile tranSTerse fibres of the thoracic duct of 
 the horse. — Magnified 80 diameters. 
 
 B. Stratum of nucleated epithelial cells lining the 
 lymphatic vessels. — From a largo lymphatic on the 
 trachea of a horse. — Magnified 320 diameters. 
 
 170. 
 
 The absorbent vessels have a proper coat, an outer investment of 
 areolar tissue, and an inner lining of epithelium. (1) The proper 
 coat is formed chiefly of circular fibres, relatively most abundant in 
 
 the smaller vessels, analogous 
 Fig- 169. to the contractile tissue of the 
 
 B A bloodvessels, and a modifica- 
 
 tion of the unstriped muscle, 
 containing elongated nuclei. 
 On the inner side of the cir-r 
 cular fibres are longitudinal 
 fibres, more resembling white 
 fibrous tissue (Fig. 169, A). 
 (2) The fibres of the areolar 
 coat have an irregular course, 
 and blend with the neighbour- 
 ing tissues. This coat allows 
 of slight movements of the 
 vessel, and contains the blood- 
 vessels which ramify in con- 
 siderable abundance on the 
 proper coat. (3) The epithe- 
 lial lining consists of a single 
 layer of extremely delicate 
 nucleated particles, first no- 
 ticed by Henle. They are 
 usually spindle-shaped, and 
 fitted sideways to each other 
 (Fig. 169, B). 
 
 The valves (Fig. 170, C) are 
 formed by a process of fibrous 
 membrane standing ofi" into 
 the vessel, probably with a 
 covering of the epithelium. 
 They are mostly in pairs, of a 
 crescentic shape, the convex 
 edge attached, the concave 
 free, and when in action con- 
 stitute a perfect barrier, the 
 wall of the vessels immediate- 
 ly above them being bulged 
 into a sinus, so as to give the 
 canal a beaded appearance 
 when distended. Mr. Lane 
 
 A. One of the inguinal lymphatic glands injeoted haS obsefved that SOme of the 
 with mercury, a. AfToront lymphatic vessel flrom the , . , i • i 
 lower extremity, b. Efferent vessel. Others are also ValvCS are Single and Circular, 
 
 B. One of the superficial lymphatio trunks of the With a Central perforation, 
 
 S One of the femoral lymphatio trunks laid open ^"^ therefore incomplete — 
 
 longitudinaUy to display the valves within it. o. Sinus while others are IlTifirinal in 
 
 between the valve and the wall of the vessel, d. Sar- ".""" uiueis aio Ulieijuai m 
 
 face of one valve, directed towards the opposite. «. SIZO. 
 Semicircular attached margin of the valve.— Aftor 
 Mascagni. 
 
STRUCTURE OP THE ABSORBENTS. 615 
 
 Contractility of the Absorbent Vessels. — This depends on the con- 
 tractile tissue of their proper coat. The property may be demon- 
 strated by mechanically irritating a large vessel, such as the tho- 
 racic duct, in an animal just killed — it undergoes slow contraction. 
 The absorbent vessels continue to propel their contents, even when 
 the current from the primary networks is arrested by pressure, and 
 this they seem to do by their vital contractility. As the contents 
 advance the vessels diminish in diameter. It is usual to find the 
 lymphatics empty and collapse some time after death. 
 
 The lymphatic glands are, for the most part, flattish oval bodies, 
 of firm consistence and light colour, situated in the course of the 
 lymphatic and lacteal vessels, these vessels being styled afi"erent as 
 they enter the gland, and efferent as they leave it. The glands 
 vary from the size of a millet-seed to that of an almond. They 
 usually lie loosely in the areolar texture, well protected from injury 
 by their mobility, and if near the surface of the body, by the dispo- 
 sition of the neighbouring bones or muscles. They have a firm but 
 delicate proper capsule, which is continuous with the outer coat of 
 the vessels, and which sends processes inwards upon the bloodvessels 
 and lymphatics which penetrate the glands. 
 
 The general structure of these glands has long been known, being 
 well displayed by mercuriail injections (Fig. 170, A). This metal, 
 when thrown into an afferent vessel, shows that this divides into 
 minute branches, most of which spread out over the gland before 
 entering it, and that the efferent vessels have a similar arrangement 
 on the opposite side. The mercury readily fills the entire gland, 
 and escapes by the efferent vessels. The surface of the gland, when 
 occupied by mercury, exhibits either a very close plexus of tortuous 
 minute vessels, or else a congeries of apparent cells ; and while there 
 has been no doubt of the continuity of the internal tracts of the 
 gland with both the afferent and efferent vessels, the question has 
 been discussed, whether these tracts are simply convolutions of 
 tubes, or cellular lateral offsets from channels traversing the gland 
 in a more direct course. Both of these views may possibly be true 
 in different cases, or probably the convoluted vessels of the gland 
 may be themselves dilated at intervals into cells which, from their 
 mode of package, may simulate detached cavities, as in the well- 
 known arrangement of the vesiculse seminales. In confirmation of . 
 this last view it may be observed, that the tracts of the gland are 
 usually more capacious than the ramifications of the afferent and 
 efferent vessels which immediately communicate with them. 
 
 A more important question concerns the changes in the tissues 
 forming the walls of the afferent vessels on their entrance into the 
 gland, and this has been ably illustrated by Professor Goodsir. He 
 describes the outer areolar coat as passing to form the capsule of the 
 gland, and the proper coat to become extremely thin, especially in 
 the deeper parts of the gland. The epithelium, however, becomes 
 thicker and more opaque, so as often no longer to transmit the light 
 under the microscope, and by the action of acetic acid very nume- 
 rous nuclei are disclosed in it. He describes the elongated nuclei 
 
616 ABSORPTION. 
 
 in the substance of the (proper) membrane on which this modified 
 glandular epithelium rests, and appears to consider that the epithe- 
 lium is in constant decay and renovation, being shed as a secretion 
 into the cavity of the ducts, to -mingle with and modify the passing 
 lymph.* 
 
 From the examinations we have made of the recent glands of the 
 lower mammalia, we are disposed to agree in most particulars with 
 this description. The very delicate simple layer of transparent 
 nucleated- cells lining the lymphatic vessel ere it enters the gland, 
 becomes in the gland a very thick and rather opaque granular mass 
 loaded with nuclei, in the debris of which are apparent a great 
 abundance of nucleated cells of different sizes, many of them pre- 
 cisely resembling the white or colourless lymph-corpuscles presently 
 to be described. We lean strongly to the opinion that these cor- 
 puscles are set free to a large amount, though, perhaps, not exclu- 
 sively, from the surface of the intra-glandular passages. The 
 structure of the lymphatic glands offers many diiSculties to the ana- 
 tomist, and there can be little doubt that further research would 
 discover peculiarities as yet undetected. 
 
 The lymphatic glands are well supplied with blood. The arteries 
 and veins derived from neighbouring sources subdivide together on 
 the surface, and penetrate between the ducts, carrying in with them 
 for some distance a sheath derived from the capsule. The capil- 
 lary'network is probably spread out on the exterior of the ducts, 
 i. e. in the interstices of the plexus which these form in the gland ; 
 but it cannot be said that the exact relation of the bloodvessels to 
 the abundant granular matter of the ducts has been as yet unequi- 
 vocally demonstrated. The capillaries are very fine, their meshes 
 large, and they anastomose throughout. 
 
 In injections of the ducts of the glands, the mercury is found to 
 find its way very readily into the veins, but not ■ into the arteries ; 
 and it has been concluded by Fohmann, that this indicates a natu- 
 ral communication between these sets of vessels in the glands. This 
 view is certainly -rendered plausible by the proved termination of 
 the lymphatics in the veins of the neck, and by the fact which 
 appears to be established by the observations of Fohmann, Lauth, 
 and Panizza, that in birds, as well as in reptiles and fishes, there 
 are communications with the small veins at many points of the 
 pelvis and abdomen. Nevertheless, the evidence for such a com- 
 munication in the lymphatic glands is very unsatisfactory. The 
 more probable explanation of the fact above noticed seems to be, 
 that the brittle texture of the interior of the glands readily gives 
 way before mercury, and that then the minute veins, which are 
 more numerous than the arteries and less resisting, are the first to 
 receive the extravasated metal. 
 
 Origin of the Lymphatics. — We have before spoken of the origin of 
 the lacteals in the villi of the small intestines. The lymphatics in 
 other regions have been usually considered to arise in the substance 
 
 * Anatomical and Pathological Observations. 
 
ORIGIN OP THE LYMPHATICS. 
 
 617 
 
 of the skin and mucous membranes, and on the surface of the 
 viscera by a plexus of somewhat variable character. In the skin 
 and elsewhere the meshes are very close and small, while on the 
 lungs they are much more open and the vessels larger. The surface 
 of the liver and spleen is overrun with a network of lymphatics of 
 remarkable luxuriance. So far as mercurial injection can inform us, 
 these plexuses are the commencement of the lymphatic system ; but 
 we have been recently made acquainted with a system of lymphatic 
 vessels discovered by Kolliker in the tail of the larvae of batrachian 
 
 Fig. 171. 
 
 Part of a ramification of a lymphatic of the under part of the tail of a tadpole, a. Simple membrane, 
 forming the wall of the vesBel. b. Prolongation or process of this membrane, c, d. Patty granules 
 attached to the inner surface of the membrane, and surrounding the nuclei, e. A closed extremity of 
 the vessel. /. Branched o«ll, just united to a corresponding extremity, g. Branched cell, on the point 
 of coalescing with a capillary lymphaticvessel already formed. — Magnified 400 diameters. After Eolliker. 
 
 reptiles, which renders it probable that a still finer series exists in 
 the higher animals and in man, than those comparatively large ones 
 which compose the plexuses just mentioned. Kolliker observed these 
 vessels during life, and satisfied himself of their continuity with the 
 neighbouring lymphatic trunks. He found them about the same 
 size but less numerous than the blood-capillaries, and composed of a 
 simple, very delicate membranous wall, projecting into small pointed 
 processes, here and there, and containing a few flattened nuclei. 
 The pointed processes may belong only to their rudimentary and 
 not to their cojnpletely developed condition. He states that they 
 ramify in an arborescent manner, without anastomosing, and end by 
 free closed extremities. They have no valves, and remain of the 
 same width during life, but after death exhibit the sam'e contrac- 
 tility, though not of so active a kind, as the capillaries, by lessening 
 uniformly, .in diameter during a certain time. He was able to 
 detect the movement of their transparent contents by that of the 
 granules and lymp^-corpuscles, which, in rare instances, they were 
 observed to contain, and found it to be continuous, and very slow, 
 almost twelve times as slow as that of the blood in the capillaries. 
 He found the mode of development of these primary lymphatics to 
 40 
 
618 ABSORPTION. 
 
 resemble closely that of the capillaries, i. e., it takes place by the 
 outgrowth and subsequent coalescence and tubulation of processes 
 from contiguous nucleated cells. 
 
 Kblliker's observations on the relations of these minute lymphat- 
 ics with the capillaries are interesting. He found that when the 
 current of blood was regular, there was no appearance of communi- • 
 cation between the two orders of vessels, but that when the circula- 
 tion was excited and tumultuous, owing to the confinement of the 
 tadpole under glass, during the observation under a high magnifying 
 power, red blood-corpuscles escaped more or less readily from the 
 bloodvessels intq the contiguous lymphatics ; and in several instances 
 he was able to detect actual communications between lymphatics of 
 the finest kind and the network of capillary bloodvessels. After 
 careful inquiry, however, he concludes that these junctions are due 
 to rupture, or, perhaps, in some cases, to a primitive abnormal form- 
 ation. He further noticed a reflux of blood into the lymphatics 
 through the orifices by which their trunks open into the larger veins. 
 This retrograde current was almost always observed when the respi- 
 ration was impeded by want of water, and the veins were consequently 
 gorged, or when a ligature was placed round the head. In the latter 
 case, the whole lymphatic tree was often fully and beautifully in- 
 jected with blood. 
 
 • ♦ 
 
 A lymphatic system exists in all the Tertebrata, but the glands are wanting in 
 fishes and reptiles, and are very few in birds, being found only in the neck. In fishes 
 and reptiles, however, there occur large and intricate lymphatic plexuses, chiefly 
 without valves, accompanying and sometimes completely surrounding the bloodvessels 
 in a luxuriance quite superior to anything found in the higher classes. Moreover, 
 there exists in the course of the lymphatic trunks in these animals and in birds, 
 pouches furnished with valves and muscular walls, which contract rhythmically and 
 urge on the lymph towards the veins. These lymphatic hearts are, in birds at least, 
 formed of the striped fibre, according to the observation of Stannius ; and we owe to 
 Volkmann the interesting fact that, in frogs, their contraction may be excited by the 
 direct influence of portions of the spinal marrow.* 
 
 Bo the Lacteal and Lymphatic Vessels absorb ? — From the 
 account now given, it is clear that the structure and arrangement of 
 the lymphatic vessels fit them only for the conveyance of fluid in 
 one direction, viz., from the various tissues in which they originate 
 to the great veins, and thence to the heart. Hence there can be 
 no doubt, that, whatever other function they may subserve, they 
 are deaigned to carry fluid into the blood either from the exterior 
 of the body, as in the case of the digestive mucous membrane and 
 the skin, or from the interstices of the various textures, where it 
 may hava been derived either directly from the circulating mass, or 
 indirectly from the waste of the textures themselves. It was till 
 lately assumed too exclusively that this system of vessels was the 
 sole agent in such absorption, and hence the name of absorbent 
 system, as applied to it, and the view which allowed the bloodves- 
 sels no share in the absorbent function. 
 
 To prove that the lacteals a^bsorb chyle, it is only necessary to 
 
 * Paget's Report, 1844-5, p. 27. 
 
PROOFS OF LYMPHATIC ABSORPTION. 619 
 
 examine them in a fasting and in a recently fed animal. In the 
 former their contents are transparent, in the latter they are milky, 
 and the opaque fluid can be shown, by simple means, to move on in 
 the course indicated by the valves. That the lymphatics absorb 
 is perhaps best shown by the phenomena of disease. The syphilitic 
 poison is frequently carried from the primary sore along the lymph- 
 atics, and exciting inflammation in this route may occasion de- 
 posits of lymph or pus either on the penis or in the groin, and 
 the matter of abscesses so formed is capable of .imparting the disease 
 to other .individuals, thus proving the multiplication, and probably 
 also the real transport of the virus along these channels. The in- 
 flammation of the lymphatic trunks and glands, so often observed to 
 ensue upon accidental wounds, either poisoned or not, especially in 
 debilitated subjects, seems due to an actual propagation of morbid 
 materials in the current of the lymph, exciting inflammation in suc- 
 cessive parts as it comes into contact wifh them ; and the severe 
 constitutional disturbance usually attendant on this state of lymphatic 
 inflammation is attributable, with a high degree of probability, to a 
 discharge of some such morbid fluid contaminating the lymph into 
 the bloodvessels, so as to mingle with the general circulating ma,ss 
 of blood. Wagner mentions that the axillary glands of a subject 
 brought for dissection were found of an intense red colour from the 
 deposition 6i cinnabar in their texture, while on the arm was a red 
 tattooed figure of old date, which had evidently furnished the mate- 
 rial.* 
 
 That the bloodvessels also absorb, however, is rendered certain, 
 not merely by considering that their structure and physical con- 
 ditions furnish every element requisite for this function, but by 
 experiments of a conclusive nature. Panizza poisoned a horse, by 
 confining hydrocyanic acid in a loop of intestine, which was sepa- 
 rated from the body excepting by one artery and vein which, main- 
 tained the circulation in it. As long as the vein was compressed 
 the animal escaped, but when the pressure was remitted the poison 
 took efi'ect ; and, in blood drawn from the vein, the acid was detected. 
 
 Contents of the Absorbents. — The lymphatics (and the lacteals when 
 digestion is not going on) contain a nearly colourless and transparent 
 fluid, termed lymph, in which are included a number of colourless 
 nucleated cells of globular shape {lymph-corpuscles, colourless cor- 
 puscles), analogous to, and even identical with, the colourless cor- 
 puscles of the blood. The lacteals, during the digestion of fatty 
 matters, always contain another element, which gives a milky hue to 
 the chyle, viz. a finely granular matter, termed, by Mr. (Julliver, the 
 molecular base. 
 
 Lymph and chyle, when withdrawn from their vessels, sponta- 
 neously coagulate into a slightly coherent jelly in the course of a 
 few minutes. This property depends on the presence of fibrine in 
 a fluid form, as in the blood, and varies with the point from which 
 the lymph is drawn, as well as with the activity of the nutritive 
 
 * Physiology, by Willis, p. 440. 
 
620 
 
 ABSORPTION. 
 
 Fig. 172. 
 
 vigour in the animal at the time. The clot at first entangles the 
 floating particles, and if the fibrine have sufiicient energy, it under- 
 goes some degree of subsequent contraction, by which a loose mesh 
 is separated from the fluid part, as the crassamentum from the serum 
 of the blood. Most of the corpuscles usually remain in the clot, 
 though some escape and remain with the fluid element. The coagu- 
 lability of the lymph appears to bear a close relation to that of the 
 blood in the same animal. 
 
 Lymph. — The liquid portion, liquor lymphae, is supposed by some 
 to be simply albuminous in the primary network, and to acquire its 
 fibrine on its passage onwards through the vessels and glands towards 
 1;he veins. The fibrine is found in increasing quantity towards the 
 main trunks, though never in so large a proportion as in the liquor 
 sanguinis. The same kind of saline matters are also met with in 
 the liquor lymphae as in the liquor sanguinis, together with a trace 
 of fatty substance and ^me iron. 
 
 The lymph-corpuseles are very scanty in the primary network and 
 
 branches (as already noticed in the 
 observations of KoUiker), and they 
 increase in number, and perhaps in 
 size, towards the trunks, especially 
 as they pass the glands. They pre- 
 sent themselves under some vari^ies ; 
 in one, and this is the most usual, the 
 nucleus is concealed by a granular 
 matter ; in another this granular mat- 
 ter appears in process of removal or 
 deliquescence, so that the nucleus is 
 visible; or, again, the interval be- 
 tween the nucleus and the cell-wall 
 may be quite clear, and the granular 
 matter wanting. These corpusclels 
 are (Jailed, by Mr. W. Joues, respect- 
 ively the granule cell amd the nucle- 
 ated eeU in the unooloured stage, and 
 'he further points out that there are 
 in the lymph other nucleated cells 
 approximating in colour to the red- 
 corpuscles of the blood, and which 
 he regards as in progress to become 
 red blood-corpuscles, by losing their 
 cell-wall, and becoming reduced to 
 a simple nucleus.* 
 
 Besides ihese true corpuscles of the 
 lymph, it is very common to find in it red blood-corpuaoles; These, 
 it is probable, have been accidenially introduced into the lymphatic 
 vessel during the dissection employed to lay it open. 
 
 Chyle.— Ihe liquor chyli contains more albumen and more fat 
 
 ¥]uid from a mesenteric gland of a rabbit, 
 when white cbyle was present in tbe lacteals. 
 a. Molecular base. &, c, <2, &c. Various or. 
 ganlc corpuscles, h. Appearance of tbe 'ma- 
 jority of corpuscles. The contained granliles 
 are most numerous and coarse iu the largest 
 .ones, but almost entirely disappear ui^der the 
 action of acetic acid, which thereby discloees 
 an appearance of one or two nuclei.. The 
 majority of tbe corpuscles are either large or 
 small, and but few of intermediate siz^. . d. 
 Exhibits tbe effect of actitic'acid in'reniierln^ 
 the corpuscles more clear and' their nuclei 
 more distinct. «. Large , lymph-corpuscle, 
 showing well the granulated border. /. l^rge 
 corpuscle, apparently inclosing three smaller 
 ones, each of which has tbe granulated cba-' 
 racter. This appearance of inclosed cells is 
 not comipon. — Magnified 300 diameters. 
 
 * Philosophical Transactions, 1846, p. 82, and the next chapter, on the Blood. 
 
CONTENTS OF THE ABSORBENTS. 621 
 
 than the liquor lymphse. It has been noticed that the lacteals near 
 the intestine contain little or no fibrine ; their contents do not ac- 
 quire the power of spontaneously coagulating till we approach the 
 main trunks. Even in -the receptaculum chyli and the thoracic duct, 
 where the chyle- is commingled with the lymph from distant parts,, 
 the clot formed is still much softer than that' of blood. 
 
 The corpuscles of the chyle are the same as those of lymph. In 
 ad-ditiop, however, we have in most instances the m,olecular base. 
 This varies with the amount of fatty matter in the food. It gives 
 the chyle that milky colour which was shown by Tiedemann and 
 Gmelin to have a close correspondence with the fat of the food. It 
 has been noticed to be generally 'absent or very deficient in birds; it 
 is less abundant in herbivorous animals than in carnivorous. If a 
 dog be fed on food from which fat is carefully excluded, the chyle 
 is not milky, but whey-like or transparent. 
 
 Sir Benjamin Brodie, in 1816, fed a cat on jelly, ^and a dog on 
 isinglass jelly : the animals were killed after two hours. The 
 stomachs were found nearly empty, the duodena filled with a mix- 
 ture apparently of chyle and jelly ; the lacteals and thoracic ducts 
 contained transparent chyli, which coagulated spontaneously. He 
 likewise fed a dog on lard, after a fast of thirty-six hours, and in 
 three hours killed the animal. Some lard was found in the stomach, 
 some fluid of albuminous character in the duodenum, the same tinged 
 with bile in the ileum, and in the thoracic duct perfect milky 
 
 * 
 
 chyh 
 
 The molecular base is present in the lacteals from the very com- 
 mencement, even from the villi of the intestines. It seems to con- 
 sist of almost infinitely small particles (Fig. 172, a) of oleaginous or 
 fatty matter, thrown into this form by contact with the pancreatic 
 secretion, as so well proved by Bernard. The particles do not look 
 like oil under the microscope — their outline is not definite or sharp, 
 and from this circumstance, as well as from their extreme minute- 
 ness, it is not easy to assign them an exact size. In fact, they vary 
 somewhat. Mr. Gulliver makes their diameter -j^Jjjtj of an inch. 
 Thus the white colour of the chyle does not depend on precisely the 
 same cause as that of the milk, foi^ the latter exhibits under the 
 microscope myriads of true oil-globules of difiierent sizes. - A few 
 oil-globules are commonly found in the chyle, but they are probably 
 extraneous. 
 
 Dr. G. 0. Rees gives the following analysis of the contents of 
 the thoracic duct. of a criminal, who had taken two ounces of bread 
 and four ounces of meat on the preceding evening, and two cups of 
 tea and a piece of toast an hour before he was executed, and whose 
 body was examined one hour and a quarter after death. Nearly 
 six drachms were obtained, of a milky hue, with a slight tinge of 
 buflf.f 
 
 * "Selections from Notes of Physiological Experiments," by Sir B. C. Brodie Bart., 
 MS. pp. 39, 40, 41. 
 t Phil. Trans. 1842, p. 82. 
 
622 
 
 ABSORPTION. 
 
 Water ..... 
 
 Albumen, with traces of fibrine 
 Aqueous extractive .... 
 Alcoholic extractive, or osmazome . 
 Alkaline chloride, carbonate, and sulphate, 
 of alkaline phosphate, and oxide of iron . 
 Fatty matters 
 
 with traces "I 
 
 90.48 
 7.08 
 0.56 
 0.52 
 
 0.44 
 
 0.92 
 
 100.00 
 The following is his analysis of the lymph and chyle of the 
 
 assr 
 
 
 Lymph. 
 
 Cbyle. 
 
 Water . 
 
 . 96.536 
 
 90.237 
 
 Albumen 
 
 . 1.200 
 
 3.516 
 
 Fibrine 
 
 . 0.120 
 
 0.370 
 
 Extractive 
 
 . 1.559 
 
 1.565 
 
 Fatty matter . 
 
 . a trace 
 
 3.601 
 
 Salts . 
 
 . 0.585 
 
 0.711 
 
 
 100.000 
 
 100.000 
 
 These latter may probably be taken as fair samples of the con- 
 stitution of the lymph and chyle. Much variety, however, will of 
 course exist in specimens, derived from diiFerent animals, and at 
 different periods of digestion. The chief distinctions between lymph 
 and blood, are : 1st, the absence of the red particles in the former, 
 and, 2d, the smaller proportion of albumen and fibrine. Cljyle 
 differs from blood in the same points, and, moreover, in its large 
 proportion of fat, which may rise, according to Nasse, as high as 
 15 in 1000. Chyle differs from lymph in containing more albumen, 
 and much more fat. 
 
 Quantity of Chyle and Lymph. — That the chyle enters the blood 
 very rapidly along the lacteals during digestion is obvious on open- 
 ing the body of an animal. It is easy to collect from the thoracic 
 duct of a small dog, in the course of a few minutes, as much as will 
 fill a watch-glass. If absorption is actively going on at the moment, 
 a ligature on the duct will often be followed by a rupture of some 
 vessel below by the onward pressure of the current. So the lymph, 
 in some instances, has been collected in considerable quantity in a 
 short space of time. Geiger, from an open lymphatic on the foot of 
 a horse, collected from three to five pounds of lymph daily. Bidder 
 has performed some experiments on cats, from which he estimates 
 that a quantity of lymph and chyle, together equal to one-sixth the 
 weight of the body, or the whole weight of the blood, enters the 
 circulation every twenty-four hours. But it must be borne in mind 
 that this does not all form new supply, the lymph' being, probably, 
 in large measure derived from that liquor sanguinis which has escaped 
 from the capillaries into the interstices of the tissues, and which 
 cannot re-enter the capillaries in a direct manner. 
 
 Mechanism of Absorption. — In considering this part of the sub- 
 ject, the^ following points should be remembered: — 
 
 li The process of absorption in living bodies implies imbibition by their tissues and 
 Bubseque|it transmission of the imbibed fluid by the vascular channels to distant purts. 
 
 * Med. Gazette, Jan. 1841. 
 
MECHANISM OF ABSORPTION. 623 
 
 2. As regards imbibition, it is a phenomenon of a purely pliysico-cbemical nature, 
 and occurs in inorganic as well as organic bodies, and in organic bodies both when 
 dead and living. It depends mainly on the force of adhesion between a fluid and a 
 porous solid, by which the fluid is drawn into the interstitial passages of the solid. 
 
 3. The fluid chiefly concerned in this process in aU animal and vegetable bodies is 
 water, which, as already stated, has a close affinity for their tissues, and forms an 
 essential ingredient of them, without which they for the most paVt lose their vital 
 and physical properties. 
 
 4. The various other substances which are imbibed in living bodies are taken up in 
 a state of aqueous solution, such as gases, albumen, flbrine, salts, &c. 
 
 5. Where the fluid is rendered complex by holding in solution various substances 
 which have diiferent degrees of the force of heterogeneous adhesion for each other, 
 for the water they are dissolved in and for the porous solid, the phenomena of their 
 transmission are also complex : various preferences, if we may so express it, exist ; 
 one ingredient penetrates rather than another, and the results depend very much on 
 the chemical qualities of the elements concerned. 
 
 6. The laws relating to the mixtui-e of different fluids also exert an important in- 
 fluence on the phenomenon. 
 
 Referring to a former page (p. 67) for a brief notice of the phe- 
 nomena of endosmose and exosmose, as observed by Dutrochet, we 
 may conveniently proceed with the consideration of the n^echanism 
 of absorption in the living body under the following heads :— 
 
 Absorption as influenced hy the Qualities of the Fluids. — It was 
 shown by Chevreul, that an animal tissue imbibed very diiferent 
 amounts of different fluids with which it was brought into contact 
 after it had been dried. Thus the cornea took up water, brine, and 
 oil, in the proportions of 461, 370, and 9; and Liebig, in experi- 
 ments with the dried bladder of the ox and pig, has found that " of 
 all liquids, pure water is taken up in the largest quailtity ; that the 
 absorptive power for solution of salt diminishes in a certain -ratio as 
 the proportion of salt increases; and that a mixture of alcohol and 
 water is taken up more abundantly the less alcohol it contains."* 
 
 The mixture of two dissimilar fluids through a membrane is much 
 influenced by their respective attractions for the membrane. Thus, 
 as water has a stronger affinity for the membrane than brine or 
 alcohol, it permeates it more readily and arrives in greater quantity 
 in a given time on the opposite surface than either of those fluids. 
 ; Hence more water comes through to mix with the alcohol, than 
 alcohol to mix with the water, and an accumulation of the mixed 
 fluids consequently takes place on the side of the alcohol ; for the 
 alcohol, or the water, having once traversed the thickness of the 
 membrane, comes into contact with the opposite fluid, and becomes 
 diffused through it in obedience to known laws. The same is true 
 in regard to various substances miscible with water or dissolved in it. 
 
 Within the bloodvessels and the lymphatics is a fluid considerably 
 denser than water, and having less affinity for the walls than water. 
 Hence, if water be applied to the surface of the body or taken into 
 the stomach, it readily enters the circulation, particularly in the lat- 
 ter case, where it is brought into much closer contact with the blood- 
 vessels. If a quart of warm water be injected into a torpid colon, 
 half an hour will almost suffice to convey it into the bloodvessels, 
 
 * Researches on the Motion of the Juices in the Animal Body. Translated by 
 Wm. Gregory, M. D. London: 1848. P. 9. 
 
624 ABSORPTION. 
 
 and thence through the kidneys into the bladder. If, however, the 
 injected water hold a considerable quantity of common salt in solu- 
 tion, it will be absorbed more slowly ; while, if the solution be a con- 
 centrated one, the fluid portion of the blood will pass out of the 
 vessels to mix with the saline solution. The action of many 
 medicines taken by the mouth, particularly of saline purgatives, is 
 in some measure explained by these laws. 
 
 It is interesting to notice that albumen passes less readily through 
 an animal membrane than gelatine, gum, or sugar. Thus alcohol, 
 ether, oil, albumen, gum, and sugar would disappear from the 
 stomach in very different intervals of time. 
 
 Absorption as influenced ly the Porous Solid. — An extensive 
 and accurate series of experiments has been recently performed by 
 MM. Matteucci and Cima, in which they investigated the influence 
 of difi"erent kinds of animal membranes, and of various arrangements 
 of them, on the transmission of various fluids. They employed — 
 1. The skin of the frog, the torpedo, and the eel ; 2. The mucous 
 lining of the stomach of the lamb, cat, and dog, and of the gizzard 
 of the fowl ; and, 3. The mucous lining of the bladder of the ox 
 and pig. The following are the general conclusions derived from 
 these experiments, in the words of their translator : — 
 
 " 1st. The membrane interposed between the two liquids is very 
 actively concerned, according to its nature, in the intensity and 
 direction of the endosmotic current. 
 
 "2ndly. There is, in general, for each membrane, a certain 
 position in which endosmose is most intense ; and the cases are very 
 rare in which, with fresh membrane, endosmose takes place equally, 
 whatever be the relative position of the membrane to the two 
 liquids. ' 
 
 ",3rdly. The direction which is most favourable to endosmose 
 through skins, is usually from the internal to the external ^I'face, 
 with the exception of the skin of the frog, in which • endosmose, in 
 the single case of water and alcohol, is promoted from the external 
 to the internal surface. 
 
 " 4thly. The direction favourable to endosmose through stomachs 
 and urinary bladders varies with diff'erent liquids much more than 
 through skins. 
 
 " 5thly. The phenomenon of endosmose is intimately connected 
 with the physiological (natural or healthy) condition of the mem- 
 branes. 
 
 " 6thly. With membranes, dried or altered by putrefaction, either 
 we do not observe the usual diff'erence arising from the position of 
 their surfaces, or endosmose no longer takes place."* 
 
 With the mucous lining of the stomach of the lamb (whether the 
 pauncn or the true digestive stomach is not mentioned) these trust- 
 worthy experimenters found that water passed through towards a 
 solution of sugar in greater quantity when the water was at first 
 
 * Leotures on the Physical Phenomena of I^iving Beings. By Carlo Matteuoci. 
 Translated under the superintendence of Dr. Pereira. Am. Ed, p. 71. 
 
MECHANISM OP ABSORPTION. 625 
 
 placed on that side of the membrane 'vrhich is naturally turned to- 
 wards the interior of the cavity of the stomach, than when it was 
 placed on the opposite side; the proportions being about as six to 
 five. On the contrary, when solutipn of white of egg was used, 
 water passed more readily, when placed in contact with the attached 
 or submucous surface than when in contact with the free or epithe- 
 lial surface. It passed also towards the albumen in only half the 
 quantity that 'it did to the sugar. Again, with a, solution of gum, 
 the endosmose was very feeble, whichever way the membrane was 
 turned — and seemed to follow no rule. 
 
 These facts show the influence exerted by the structure or chemi-. 
 cal properties of the membrane in this process, but we are still very 
 much in the dark as to the intimate cause of the infl^uence thus 
 operating. 
 
 They are sufficient, however, to indicate the extremely important 
 principle in physiology, that the chemical and structural properties 
 of the tissues exert a great influence on all those processes in which 
 the molecular motion of fluids is concerned. 
 
 The thickness or thinness of the membrane also much afi'ects the 
 result, and that for an obvious mechanical reason. If the transmis- 
 sion of fluids is so rapidly carried on out of the body, through the 
 entire thickness of compound and dense membranes, how much more 
 expeditious must it be in the living tissues, where the external fluid 
 has in general but one or two very attenuated films of membrane to 
 traverse in order to arrive within the capillary bloodvessels. 
 
 Absorption as influenced hy Pi'es^ure. — The influence of pressure 
 on the passage of fluids through membranes is illustrated by a 
 common filter, or by tying a membrane over one end of a vessel 
 containing fluid, to which a syringe capable of applying various de- 
 grees of pressure is adapted. In the latter case, the rapidity of 
 transtoission will be found, cseteris paribus, to depend on the degree 
 of pressure employed, and after a certain time the transmission 
 will be accelerated by the enlargement of the pores of the membrane. 
 In this way pressure may be used as a test of the relative transmis- 
 sibility of diff'erent fluids through membranes of various thickness 
 and quality; and Li^big has found that "through ox-bladder, j^^ 
 of an inch thick, water flows under a pressure of twelve inches of 
 mercury ; that a saturated solution of sea salt requires from eighteen 
 to twenty inches; and that marrow oil only flows out under a pres- 
 sure of thirty-four inches of mercury. 
 
 " When the membrane used is the peritoneum of the ox, j^^ 
 of an inch in thickness, water is forced through it by eight to ten 
 inches, brine by twelve to sixteen inches, oil by twenty-two to twenty- 
 four inches, and alcohol by thirty-six to forty inches of mercury;" 
 and hence it appears, as this eminent writer remarks, that " the 
 power of a liquid to filter through an animal membrane bears no 
 relation to the mobility of its particles ; for under a pressure which 
 causes water, brine, or oil to pass through, the far more mobile al- 
 cohol does not pass." 
 
 As pressure promotes the transmission of fluid through a mem- 
 
626 ABSORPTION. 
 
 brane in one direction, so it tends to interrupt the passage of the 
 other fluid in the opposite direction — or, to apply this to the blood- 
 vessels of the living body, if they are distended by an over-great 
 quantity of blood, so that this fluid reacts upon their inner surface, - 
 as in the case of plethora, fluids enter them with diflSculty from 
 ■without — whereas, if their bulk is diminished by venesection, 
 absorption is comparatively rapid. This conclusion was established 
 by Magendie on good grounds, and it has some illustrations and 
 valuable applications in practice. 
 
 Absorption as influenced hy motion of the Fluid within the Vessels. 
 — Fluid may be raised out of a reservoir against gravity, by direct- 
 ing a stream along a membranous canal, which lies immersed in the 
 stagnant fluid. The outer fluid enters the canal by endosmose, and 
 is carried away with a speed proportioned to the velocity of the cur- 
 rent. If the fluid in motion is so compressed as to exert much 
 lateral pressure on the wall of the tube, it will rather itself pass out- 
 wards, so as to mingle with the fluid at rest, than receive and carry 
 off" the latter. If the fluid in motion is also the more dense, or 
 otherwise, that towards which the external fluid would flow if both 
 were stagnant, then its motion accelerates the endosmose by con- 
 stantly bringing on fresh fluid of the original density, so that the 
 first rate of transmission is maintained.* 
 
 It will be scarcely necessary to state in detail the particular bear- 
 ing which the preceding considerations have on the question of the 
 mechanism of the absorbent process in the living body. It is, how- 
 ever, very evident that they leave us with little more than some 
 general indications of the lines in which further investigation may be 
 pursued with advantage. 
 
 Applying them to the mechanical arrangements provided in the 
 living animal for this function, it is plain that they have a nearer 
 reference to the capillary bloodvessels than to the lymphatics. In 
 both we have a simple membrane of extreme thinness, through 
 which the absorbed fluid has to pass, and in doing so it must neces- 
 sarily obey those laws which form the proper subject of experimental 
 physico-chemical inquiry. But in the bloodvessels, the fluid on the 
 side towards which absorption tends, is alrea,dy in motion by a 
 mechanical force, the heart's action, and the absorption is accompa- 
 nied with a contrary current of exosmose ; whereas in the lympha- 
 tics, the internal fluid appears to have no motion but what is derived 
 from the same force on which the endosmose depends, and we have 
 no evidence of any outgoing current. In these respects the absorb- 
 
 * In a valuable paper by our friend, Dr. Robinson, of Newcastle {Med. Gazette, 
 1S44), many experiments and arguments are given to show that absorption goes on 
 rather on the venous side of the capillary network, and in the small veins, than on 
 the arterial side. He considers the motion of the blood to be an influential cause of 
 absorption, by diminishing its pressui-e outwards on the vascular walls, and thus 
 allowing the external pressure (that of the atmosphere and of the surrounding tissues) 
 to predominate. There can hardly be a doubt that the rapidity of absorption would 
 be influenced by the rate of movement of the blood as well as by other mechanical 
 conditions. 
 
FUNCTION OF THE ABSORBENTS. 627 
 
 ents resemble, more nearly than the capillaries, the spongioles and 
 absorbent vessels of plants. 
 
 Function of the Absorbents. — A few words may be added on the 
 use of the absorbents in the economy. The ehyliferous vessels 
 probably have the same office for the intestinal tissues as the lympha- 
 tics in other parts ; but besides this, they are largely developed, 
 and specially adapted by their mode of origin on the mucous surface, 
 to take up a portion, at least, of the food, after it has been rendered 
 capable of absorption by the action of the pancreatic secretion. This 
 portion appears to be pre-eminently the fatty or oily, which, as far 
 as experiments and observation have yet determined, is almost ex- 
 clusively absorbed by the lacteals. It is chiefly in containing so 
 much more fat that chyle differs from lymph. 
 
 The lymphatics cannot yet be said to have their office at all defini- 
 tively ascertained, yet it is hot difficult to assign them a part with 
 some degree of probability. It appears that they form an interlace- 
 ment among the capillaries in the interstices of most of the organs 
 and tissues of the body, .and contain a fluid not disimilar in kind 
 from the liquor sanguinis, though more dilute. They cannot be en- 
 gaged in distributing new material to the organism, because their 
 structure adapts them only for removing fluid from the tissues, and 
 pouring it into the bloodvessels, and because the current within them 
 is unequivocally in that one direction. Thus the fluid -they contain 
 must enter them from the interstices of the tissues, having been ulti- 
 mately derived either directly from the capillaries, or indirectly from 
 them through the tissues. It seems not improbable that the liquor 
 sanguinis efiused through the capillary walls for the nutrition of the 
 tissues, may have its superfluous parts removed through the lympha- 
 tics, as it would, perhaps, be more readily received into these new 
 channels than into the same from which it had just been poured. It 
 is a question quite undetermined, whether the effete materials of the 
 tissues are returned to the circmation in any large measure through 
 the lymphatics, or whether they are principally restored to it by 
 directly entering the capillaries, in exchange, for that outgoing cur- 
 rent of renovating plasma which serves to 'supply the waste in nutri- 
 tion. The carbonic acid at least, if indeed that product be formed 
 among the tissues, outside the capillaries, and not in the blood, 
 seems to enter the capillaries in a direct manner through their wall, 
 since it is found in greater quantity in venous than in arterial 
 blood. 
 
 The absorbent system, with its glands, may be regarded in yet 
 another light, viz., as a great internal glandular or secreting system, 
 the ducts of which open not on the surface of the body, but into the 
 vascular system. ,It is conceived that the inner surface of the 
 lymphatics, and especially of the lymphatic glands,- serves to elabo- 
 rate and separate from the lilood contained in the vessels distributed 
 on their walls a secretion which is set free into their interior, and is 
 transmitted ultimately to the current of circulating blood through 
 the efferent vessels of the glands, which may be thus looked upon 
 as excretory ducts. Some physiologists attach much importance 
 
628 THE BLOOD. 
 
 to the alleged increase in the quantity of fibrine contained in the 
 lymph as it traverses the absorbent system, and conclude that this 
 is due to the elaborating agency of the epithelial element of the 
 absorbent tracts on the albumen of the lymph. We owe to Dr. 
 Carpenter a very interesting hypothesis on the influence, in this 
 ■ respect, of the colourless corpuscles, which he imagines to exert this 
 catalytic action on the albumen in which they float. This idea will 
 be best considered in the Chapter on the Blood. 
 
 On the subjects of the foregoing chapter, in addition to the systematic Trorks on 
 Physiology before referred to, the student may consult Mr. Lane's article "Lym- 
 phatic System," in the Cyoloptedia of Anatomy and Physiology; Matteucci's 
 "Lectures on the Physical Phenomena of Living Beings," translated by Pereira ; and 
 the valuable "Reports" by M. Paget, in the British and Foreign Medical Review. 
 We would also refer to a recent work by Liebig, on the motion of the juices of the 
 anjmal body, ably translated by Dr. Gregory, from which we have derived much as- 
 sistance. 
 
 CHAPTER XXVII. 
 
 THE BLOOD. — ITS QUALITIES. — ITS PHYSICAL ANAItSIS. — THE LIQUOR 
 
 SANGUINIS. — THE BLOOD-PARTICLES. THE QUANTITY OF BLOOD IN 
 
 THE BODY. — THE PHENOMENON OF COAGULATION. — THE CONSTITU- 
 ENTS OP THE BLOOD. — ANATOMY OF THE BLOOD-CORPUSCLES. — THEIR 
 MODE OF ORIGIN. — THEIR FUNCTION. — THE CHEMICAL ANALYSIS OF 
 , THE BLOOD. — CHANGES PRODUCED IN THE BLOOD BY VENESECTION 
 — AND BY DISEASE. 
 
 The blood is a fluid, which is always circulating in numberless 
 canals among the various tissues an& organs of the body ; it is the 
 source whence those tissues and organs draw their nutriment, and 
 from which the glands derive the materials for their several secre- 
 tions. The lymph and the chyle are poured into it as tributary 
 streams ; the former conveying to it, in solution, materials yielded 
 ijp by the wear and tear of the tissues, and also derived from 
 •yrithout ; the latter bringing to it new njatter formed by the digestive 
 process. 
 
 The blood is a thick fluid, apparently homogeneous, of high 
 specific gravity (1041 — 1082, Simon), and of a red colour, in all 
 the vertebrate and most of the invertebrate classes, but exhibiting 
 differences of colour, according to circumstances to be noticed here- 
 after. — A saltish taste, and a peculiar heavy odour, must also be 
 reckoned among its characters. If allowed to rest in a cup, or 
 Other vessel, it exhibits a remarkable spontaneous analysis. In 
 the course of from ten minutes to a half an hour it separates into a 
 solid portion (the crassamentum) and a fluid portion (the serum). 
 The latter, if carefully decanted ofi', will be found to be a clear 
 straw-coloured fluid, the menstruum of that great variety of mate- 
 
THE CONSTITUTION OF THE BLOOD. 629 
 
 rials which ia held in solution or suspension in the blood. Albumen 
 in large quantity, salts, and various organic matters, are ' dissolved 
 in it ; oily matters are suspended in it ; and prior to coagulation 
 fibrine is held in solution, and coloured and other particles are dif- 
 fused in infinite multitudes throughout it. 
 
 An artificial physical analysis of the Mood, first suggested by 
 Miiller, shows satisfactorily the true relation of its various con- 
 stituents. If the blood of an animal whose coloured particles are 
 of large size, as the common frog, be passed through filtering 
 paper, its liquid portion passes throtigli, leaving the coloured parti- 
 cles upon the filter ; thus analyzing the blood into two parts — tTie 
 liquor sanguinis and the blood particles. The former, by the spon- 
 taneous coagulatio'n of the fibrine, quickly separates into serum and 
 fibrine, which in this instance is colourless, but in the ordinary 
 coagulation it is more or less coloured by the red pa;rticl€S, which 
 become entaingled by the coagulating fibrine. Another mode of 
 eifecting a similar analysis is that suggested by Dr. A. Buchanan of 
 Glasgow ; it consists in mixing fresh-drawn blood with six or eight 
 times its bulk of serum, and filtering through blotting-paper: coagu- 
 lation is retarded by the admixture with serum, and a great part of 
 the diluted liquor sanguinis passes through the filter, and subse- 
 quently coagulates. By microscopical analysis of the blood, we find 
 that, besides the red particles, it contains others which are devoid 
 of colouring matter — namely, the colourless corpuscles. 
 
 The constitution of the blood is expressed by the following table : — 
 
 f corpuscl'eS ; red and colouifless. 
 
 The Wood consists of ■< ,. . . -^ »f fibrine. 
 
 iiiv. uiu^,u >-u o = u 1 jjq^joj, ganguijug^ consisilng oi-j 
 
 That the blood has the same essential characters in both the ver- 
 tebrate and invertebrate classes, has been shown by Mr. Wharton 
 Jones's researches, who finds the coloured and colourless corpuscleB 
 in the blood of all animals, presenting, however, sufficiently distinct- 
 ive features. 
 
 In man and the mammalia there are two kinds of blood, distin- 
 guished by diiOFerence of hue, the scarlet, arterial blood, obtained 
 from the left side of the heart, and from the arteries ; and the black, 
 or dark red, venous blood, obtained from the right side of the heart, 
 and from the systemic veins. We shall consider, further on, the 
 special characters of each kind, and the cause of their differences. 
 
 The temperature of the blood ranges between 100° and 105°. 
 Its reaction is slightly alkaline, so that a drachm of blood will satu- 
 rate rather more than a drop of vinegar. 
 
 The consideration of the natural history of the human blood 
 involves the determination of the following points : — 
 
 First, the^quantity of blood in the body. 
 
 Secondly, the phenomenon of coagulation, and the circumstamces 
 which promote or retard it. 
 
 Thirdly, the physical analysis of the blood, and the characters of 
 its constituents. 
 
 Fourthly, the chemical analysis of the blood. 
 
630 THE BLOOD. 
 
 I. Of the Quantity of Blood in the Body. — It is almost impossible 
 to obtain sufficiently accurate data upon -which to found a calculation 
 of the total quantity of the blood which circulates in the vascular 
 system. The various estimates which have been formed have been 
 guesses, based on trials by bleeding animals to death, and compar- 
 ing the weight of the blood drawn with that of the animal's body : 
 also, on ascertaining, in various cases of hemorrhage, or of venesec- 
 tion, the quantity of blood which had been lost in a brief period, 
 without destruction to life. 
 
 Harvey estimated the weight of the blood as one-twentieth of 
 that of the body, and Haller at one-fifth. According to the former 
 estimate, a man of one hundred and fifty pounds' weight would have 
 only about seven and a half pounds of blood, whilst the latter would 
 assign him thirty pounds. 
 
 Valentin devised an ingenious method of estimating the quantity 
 of the blood. He first ascertains the amount of solid constituents 
 in a certain quantity of blood, withdrawn by venesection ; this is 
 replaced by a certain quantity of distilled water, and then he ascer- 
 tains the amount of solid constituents in a quantity of the now 
 diluted blood equal to that which had been first withdrawn. From 
 the data thus obtained he calculates the whole quantity of the fluid, 
 which admits of such a change in its specific gravity, by the sub- 
 stitution of a certain quantity of distilled water for the quantity of 
 the fluid itself previously withdrawn. The problem is, to determine 
 the quantity of fluid of specific gravity B, which, on removing from 
 it say six ounces, and replacing those six ounces by a certain quan- 
 tity of distilled water, becomes reduced to the specific gravity |3. 
 Having by this method determined the quantity of the blood in dogs, 
 he deduces the quantity of blood in the human body by comparing 
 the weight of men with that of dogs. And thus he assigns about 
 thirty-two pounds for a man between thirty and forty years of age, 
 and twenty-eight pounds for the female.* 
 
 On the whole, we have no right to infer that the quantity of blood 
 in the human body exceeds thirty pounds ; and, for practical pur- 
 poses, we shall do well to form a much lower estimate of it, and to 
 learn from thence how important it is to avoid being prodigal in the 
 removal of a fiuid, so essential to the phenomena of life — and to 
 beware of subjecting patients to those excessive losses of blood, 
 which, experience' teaches us, too often infiict upon the general nu- 
 trition of the body a shock so severe, that it is more or less seriously 
 affected by it ever after. 
 
 II. The Phenomena of Coagulation. — We have already described 
 the separation of the blood into serum and crassamentum. In this 
 consists the phenomenon of coagulation. In a few minutes after 
 blood, has been allowed to rest in a vessel, its surface assumes the 
 appearance of a jelly, on which, after a little more time, drops of 
 serum appear to ooze out here and there ; these drops multiply and 
 coalesce, so as to cover the jelly-like surface with a layer of serum, 
 
 * Valentin, Physiol. 
 
COAGULATION OF THE BLOOD. 631 
 
 ■which increases so much in quantity, as coagulation advances, that 
 the clot is at last found covered and more or less completely sur- 
 rounded by serum. 
 
 The crassamentum, or clot, is a solid mass, varying much in con- 
 sistence : sometimes soft and tremulous, like jelly ; at other times 
 firm and tough almost as leather. If a section of it be made, it 
 will be found in most instances coloured throughout, but always 
 most deeply so at its lower half or third, the heavy red particles 
 gravitating to the lowest part ; that portion which is exposed to the 
 air having always a scarlet tint. The surface of the clot is always 
 slightly concave ; sometimes it is remarkably so, and exhibits the 
 appearance of a hollow cup, and on these occasions the upper layers 
 of the clot generally consist of fibrine only, which is of a whitish 
 yellow or buff colour, with an intermixture of colourless corpus^cles 
 entangled in its meshes. Hence blood which presents these appear- 
 ances is said to be "cupped and buffed." The phenomenon is due 
 to the more complete subsidence of the blood-particles as the clot is 
 being formed, so that its upper layers are left quite free from colour- 
 ing-matter. The clot, when this state is present, is generally small, 
 tough, and well contracted, and it floats in a large quantity of serum. 
 
 The period required for the completion of coagulation varies very 
 much : it commences in about two minutes after the blood has been 
 collected in a vessel, and is rarely completed for half an hour after- 
 wards, but more frequently the clot is not perfectly formed in less 
 than one or two hours. After it has been formed, it will continue to 
 contract for many hours, and to press out the serum, which will thus 
 increase in quantity while the bulk of the clot undergoes diminution. 
 
 Coagulation appears to take place more rapidly under the influ- 
 ence of a high temperature, 114° to 120°, according to Hewson ; it 
 is also favoured by spreading out the blood on a flat surface; and, ' 
 within certain limits, by an increase in the fluid parts of the blood. 
 
 On the other hand coagulation is retarded by the addition of alka- 
 lies, and some of their salts, as sulphate of soda, nitrate of soda,' car- 
 bonate of soda, chloride of sodium, also carbonate of potass, nitrate 
 of potass, and nitrate of lime. A strong solution of any of these 
 salts, added to fresh-drawn blood, will delay or stop its coagulation 
 according to the strength and quantity of the solution. 
 
 Authors affirm that the blood will not coagulate in the bodies of 
 animals killed by blows on the epigastrium, or after having been long 
 hunted, or by electricity or lightning. It will not coagulate after 
 asphyxia by carbonic acid, as in the following cases, recorded by 
 Mr. Gulliver: A man, setat. thirty-five, and three children, were 
 suffocated in a burning house, their bodies being untouched by the 
 fire ; in all of them the blood was fluid, forty-eight hours after death, 
 in the heart and great vessels, and did not coagulate after its remo- 
 val out of the body. 
 
 The coagulation of the blood appears to be retarded by its contact 
 with living surfaces. Thackrah's experiments showed that blood conr 
 fined between two ligatures in living vessels, remained fluid for a 
 considerable time, from five to sixty minutes ; F, Simon affirms 
 
632 THE BLOOD. 
 
 that it will retain its fluidity for three hours ; and experiments of 
 the same kind by Hewson, lead to the conclusion that the coagulation 
 is retarded under similar Gircumstq,nces. Fluids withdrawn from 
 serous cavities, as in ascites or hydrocele, often exhibit a coagulum 
 of considerable size, which does not form till some minutes after their 
 removal, showing that the fibrine must have been prevented from 
 coagulating so long as it remained in the living cavity. 
 
 The addition of bile retards or prevents coagulation, probably by 
 the mechanical obstacle which it affords to the cohesion of the par- 
 ticles of fibrine. According to John Hunter, the addition of a solu-: 
 tion of opium to the blood retards its coagulation. 
 
 It is needless to waste time in inquiring into the cause of coagu- 
 lation. That the phenomenon belongs only to one of the constituents 
 of the blood is proved, unequivocally, by the fact that if that ma- 
 terial, the fibrine, be removed by whipping blood with a bunch of 
 twigs, as it flows from a vein, coagulation will nob take place in the 
 fluid which remains. The fibrine has accumulated in a coagulated 
 state round the twigs, and the fluid received into the vessel consists 
 only of serum and red particles. The coagulation of the fibrine of 
 the blood is one of those ultimate facts in physiology which we must 
 be content to observe and to describe, but of the cause of which we 
 are likely to remain ignorant. 
 
 The huffing and cupping of the blood has long attracted the notice 
 of observers, and is regsirded by many practical men as an indication 
 of a state of inflammation in some part of the body at the time of 
 the abstraction of the blood. The immediate cause of this pheno- 
 menon is explained with the highest probability, as follows, by Dr. 
 Babington: — 
 
 " The blood, consisting of liquor sanguinis and insoluble red 
 particles, preserves its fluidity long enough to permit the red par- 
 ticles, which are of greater specific gravity, to subside through it. 
 At length, the liquor sanguinis separates by a general coagula- 
 tion into two parts, and this phenomenon takes place uniformly 
 throughout the liquor. That part of it through which the red par- 
 ticles had time to fall, furnishes a pure fibrine or buffed crust, while 
 that portion into which the red particles had descended furnishes 
 the coloured clot." The following ebcperiment, made by the same 
 ingenious observer, illustrates the truth of the explanation given by 
 him. " Take two similar tall jars or phials, each capable of holding 
 about four or five ounces, and let one of them be half-filled with 
 olive oil; draw the blood of a healthy subject into each. That 
 which flows through the oil will be found to have a layer of liquor 
 sanguinis on its surface, which will form a buffed crust, while there 
 will be none upon that which is received in equal quantity, and 
 in other respects under the same circumstances, into the empty 
 jar."* 
 
 According to the observations of Nasse, and of Mr. Wharton 
 Jones, the red particles of blood which is disposed to become buffed 
 
 * Med.-Chir. Trans., and Cyclop. Anat., art Blood 
 
THE PHYSICAL ANALYSIS OF THE BLOOD. 633 
 
 and cupped, exhibit a remarkable tendency to cohere in the form of 
 rolls, like piles of coin, and this probably facilitates their precipita- 
 tion to the lowest part of the coagulating mass. 
 
 The circumstances ■which favour the formation of the huffy coat 
 may be any or all of the following : 1. Slowness of coagulation ; 
 2. Increased weight of red corpuscles ; 3. Diminished specific grav- 
 ity of serum, which obviously would have a corresponding effect 
 to the preceding ; 4. A great diminution in the proportionate quan- 
 tity of the red corpuscles, or an increase in that of fibrine, and of 
 colourless corpuscles. The occurrence of the cupped and buffed 
 blood, after gi'eat hemorrhage, or in cases of anasmia, is very pro- 
 bably in a great degree due to the disproportion between the red 
 particles and the fibrine. 
 
 Although the phenomenon of cupping and buflSng frequently 
 occurs in that state which is called inflammatory, it is not so exclu- 
 sively confined to it as to justify practitioners in regarding it, as is 
 too often done, as a proof of the existence of inflammation, suffi- 
 cient of itself to warrant or call for further depletory measures. 
 
 III. The Physical Analysis of the Blood. — By physical analysis 
 we find in the blood the following parts ; viz. the serum ; the fibrine 
 held in solution in the serum prior to coagulation ; the red cor- 
 puscles and the colourless corpuscles, both of which float in the 
 liquor sanguinis. 
 
 The serum is a straw-coloured fluid, of sp. gr. 1025 to 1030. — 
 When heated to 165° it becomes nearly solid, proving that it holds 
 in solution a very large quantity of albumen, as much as seven or 
 eight parts per cent. In twelve ounces of serum there wouH, there- 
 fore, be nearly one ounce of albumen, equal to the white of one egg. 
 But this is not the only ingredient which we find dissolved in the 
 serum. It is an alkaline fluid, and its alkalinity is chiefly due to 
 the presence of free soda, and of carbonate of soda. Besides these 
 it contains chloride of sodium, phosphate of lime and of magnesia, 
 and probably lactate of soda. 
 
 The serum also contains a small quantity of fatty matter in which 
 can be detected the crystallizable as well as the oily portion. In 
 health, the proportion of this does not exceed half a part in 1000 
 parts, so that a pint of serum will contain about five grains of fatty 
 matter ; but in some cases it exists in so large a proportion as to 
 render the serum milky. This occurs not only in certain forms of 
 disease, but likewise, according to Drs. Buchanan and R. D. Thom- 
 son,* very shortly after the ingestion of food of an oily or amylace- 
 ous nature. 
 
 Whatever other elements may exist in the blood, as serving to 
 furnish materials for the various secretions, are held in suspension 
 or solution by the water of the serum. Thus, urea is sometimes 
 found in it, and the recent observation of Bernard, referred to at p. 
 604, shows that it constantly contains sugar ; when the liver acts 
 imperfectly, some of the elements of bile are found in it. 
 
 * Med. Gaz. vol. xxxvi. p. a72. 
 41 
 
634 THE BLOOD. 
 
 It is as yet uncertain whether the existence of even minute quanti- 
 ties of some of these substances in the blood, such as urea and the 
 biliary matters, is consistent with health. It is not improbable that 
 they may be constantly being developed by the chemical changes 
 which are unceasingly going on in that fluid, but that they become 
 attracted from it as quickly as they are formed in it, and do not 
 accumulate in it in any quantity which admits of being easily de- 
 tected. According to Dr. Thomson, sugar may be always easily 
 detected in the blood, shortly after a meal containing starch.* 
 
 The Fihrine. — We have . already explained the manner in which 
 fibrine may be obtained from the blood. One thousand parts of 
 healthy blood contain two or three of fibrine. A pint of blood will 
 therefore yield about twenty-nine grains of fibrine, adopting the 
 highest estimate. 
 
 Pure fibrine, or, to speak more exactly, fibrine separated from the 
 red corpuscles, for it cannot be completely separated from the 
 colourless corpuscles, has a remarkable tendency to assume the 
 fibrous form. A drop of the colourless liquor sanguinis, which is 
 found on the surface of blood, about to form a bufly coat, exhibits, 
 when coagulated, an intricate interlacement of minute fibres. — 
 Here and there a colorless cell is entangled in it, appearing as a 
 centre, whence pass numerous radiations of minute fibres. Dr. W. 
 Addison, who believes that the fibrine is contained within the colour- 
 less corpuscles, considers the bursting of a large number of these, 
 and the consequent liberation of their inclosed fibrine, as the first 
 step in the process of coagulation, which explains the entanglement 
 of them in the fibrillating fibrine. The process may be best seen, 
 as this excellent observer recommends, by examining a drop of the 
 colourless liquor sanguinis from blood, about to form a buffy coat, 
 and allowed to coagulate upon a slip of glass.f 
 
 The Red Corpuscles. — It is to the multitude of coloured particles 
 which float in the liquor sanguinis, under the name of "the red 
 corpuscles," that the blood owes its colour. To examine these, it 
 is only necessary to place a drop of blood in the field of the micro- 
 scope, taking care to dilute it with a fluid, similar or nearly so in 
 specific gravity to the serum ; a solution of sugar or of salt in 
 water, answers this purpose completely. So numerous and so crowd- 
 ed together are the corpuscles in a drop of blood, that it would be 
 diflBcult to obtain a complete view of any one of them without this 
 precaution. 
 
 In the human blood, the coloured corpuscle is a circular double 
 concave lens; from being concave on each surface, its margin is 
 thick and rounded, and its thickness is less' in its centre than at 
 any other part (Fig. 173). Its size varies considerably ; in the 
 same drop of blood there are corpuscles of ^11 sizes within a range 
 of from 7^ij,^ to jg'jg of an inch in diameter, the average being 
 from the ^^'g, to ^j'^g. With a good microscope, and a magnifying 
 power of 200 diameters, the characters of the blood-corpuscles may 
 be most clearly seen, and when the instrument is perfectly adjusted, 
 
 * Loc. cU. f Dr. W. Addison's second series of Exp. Eesearohes, 1843. 
 
THE BLOOD-CORPUSCLES. 635 
 
 the double concave surface may be unequivocally demonstrated. If 
 the corpuscles are floated in water, they become biconvex ; if in- a 
 fluid denser than serum, as in a strong saline or saccharine solution, 
 they shrink, put on a shrivelled aspect, and become granulated on 
 
 Fig. 174. 
 B A 
 
 Red corpuscleB from human blood, a. Viewed Red corpuscles of the ox, magnified 400 diame- 
 
 on the Bur&ce. c. Viewed in profile. &. An ters. A. In their natural state, a. Profile Tiew. 
 
 aggregation of the corpuscles in a roll. — Magni- b. Viewed on the surface, c. A corpuscle altered 
 
 fied 400 diameters. in shape. B. Corpuscles altered by a menstruum of 
 
 high density. 
 
 their surface (Fig. 174, b) ; this shrivelled appearance may again be 
 got rid of by diluting the menstruum and reducing its specific 
 gravity to the lowest point. 
 
 It has been aflSrmed, by Mulder and others, that the blood-cor- 
 puscles of venous blood are biconvex — those of arterial being bicon- 
 cave — and they attribute the difference of colour of these two kinds 
 of blood to the difi"erent mode in which the light is reflected from 
 the concave and the convex surfaces of their respective corpuscles. 
 With reference to this doctrine, we have, only to state that we have 
 carefully examined two portions of the same blood after they had 
 been agitated in oxygen and carbonic acid gas, and thus been ren- 
 dered respectively scarlet and purple, but that we have failed to 
 detect any well-marked diff'erence in shape between the blood- 
 corpuscles of the two specimens. 
 
 The blood-particles have a remarkable tendency to aggregate in 
 rolls like pieces of coin (Fig. 173, h): this tendency, as has been 
 already remarked, is said by some to be greatly increased in blood 
 which forms a buffy coat in its coagulation. 
 
 The red blood-corpuscle of Mammals resembles in shape and structure that of 
 man (Pig. 174) : there is much dirersity of size in the various orders ; it is smallest 
 in the ruminants, and the smallest known is that of the Napu musk-deer, which is 
 reported by Mr. Gulliver not to exceed 1-12,000 of an inch in diameter. The corpuscles 
 of the goat are very small, 1-6300 — 1-7045 of an inch in diameter. The largest cor- 
 puscles in Mammalia are found in the elephant ; they measure, according to Gulliver, 
 1-2745 of an inch in diameter. The Camelidse offer a remarkable exception to the 
 circular form of the blood-corpuscle of Mammalia. In these animals it is oval, as 
 first pointed out. by Mr. Gulliver, with a long diameter of from 1-3100 to 1-3650 of 
 an inch, and a short diameter of 1-5800 to 1-6444 ; in all other respects, however, these 
 corpuscles agree with those of other mammals. 
 
 In Birds, the corpuscles are oval in shape ; they have a very distinct nucleus, 
 which is much smaller than the corpuscle itself. The long diameter of the blood-cor- 
 puscle of Birds ranges between 1-1500 and 1-2000 of an inch, and the short diameter 
 from 1-8000 to 1-4000 of an inch. (Figs. 175, 181, 183.) 
 
 In Reptiles, the red corpuscles are of an oval shape, with a distinct and large 
 nucleus (Fig. 176). The long diameter of the corpuscle has a range of from 1-420 to 
 
636 
 
 THE BLOOD. 
 
 1-1400 of an inch, the short diameter ranging between 1-760 to 1-2600 of an inch. — 
 Among these are to be found the largest kuoTra blood-corpuscles, as those of the pro- 
 teus and of the syren.' 
 
 Fig. 175. 
 
 Fig. 176. 
 
 •S) 
 
 (D 
 
 Red corpuscles of pigeon's blood, magnified 
 400 diameters, a. Red particles unaltered, 
 ■with two or tliree CQlourless particles, b. 
 Treated with acetic acid, which develops the 
 cell-wall and nucleus more clearly. 
 
 Blood-corp'uacles of the common frog. Magnified 
 400 diameters, a. In serum, a. Fully developed 
 corpuscle, b. Nucleus with pale cell-wall and 
 clear contents, c. Colourless corpuscle. B. Treat- 
 ed with acetic acid. 
 
 In Fishes, the red corpuscle is oval in most of the genera, and possesses a distinct 
 micleTis (Fig. 177, b). In the lowest cartilaginous fishes, as the lamprey and the 
 myxine, however, it returns to the circular and biconcave form of the Mammalian red 
 corpuscle (Fig. 177, a). This remarkable fact was first pointed out by Professor R. 
 Wagner. Mr. Wharton Jones has shown that it contains a nucleus, which cannot be 
 detected in the red corpuscles of Mammalia. 
 
 Fig. 177. 
 
 Fig. 178. 
 
 
 Red corpuscle of fishes, a. Lamprey. 
 6. Skate. — After Wharton Jones. 
 
 A 
 
 Blood-corpuscles of the crab. A. Granule cells. 
 Nucleated cells. — After Wharton Jones. 
 
 In the Invertebrate classes, corpuscles exist which are in close analogy with those 
 of the Vertebrata, but differ from them in several particulars (Fig. 178). They are 
 nucleated cells, some of which eoutaiu within them numerous granules which conceal 
 the nucleus ; some of these corpuscles, according to Mr. Wharton Jones, are, upon 
 their first removal from the body, of an elongated oval form, and others spindle- 
 shaped. Their size does not exceed 1-2000 of an inch in their long diameter, nor 
 1-3000, in the short. In most of the classes the particles do not exhibit any indica- 
 tions of colour, although they contain some of the ingredients of hematine; in a 
 few, however, slight traces of colour are present.* 
 
 Of the Structure of the Red Corpuscle. — The structure of the 
 red corpuscle of most of the Vertebrata may be readily demon- 
 strated in the blood of Reptilia^-that of the frog, for instance. — 
 It is distinctly a nucleated cell — consisting of a delicate cell mem- 
 brane, within which is a granular nucleus, which ma,j\ be rendered 
 more distinctly granular by acetic acid (Fig. 176, b). The nucleus 
 is globular and much smaller than the cell, and. the interval between 
 
 * Mr. Wharton Jones's papers in the Phil. Trans, for 1846, " On the blood-cor- 
 puscle considered in its diffei-ent phases of development in the animal series," con- 
 tain an account of a careful examination of these particles, and may be refei-red to 
 with advantage by all who are engaged in the study of this most interesting subject. 
 
THE COLOURLESS CORPUSCLES. 637 
 
 the inner surface of the latter and the outer surface of the former 
 is filled by fluid which holds the colouring matter in solution. Cor- 
 puscles of this kind floated in pure water become distended by the 
 endosmosis of it, burst, and give exit to their nuclei, while the 
 shreds of the cell-membrane are scattered in the fluid. 
 
 It cannot be shown satisfactorily that the biconcave circular cor- 
 puscle of human blood and of that of mammalia is of the same 
 structure as this, because it cannot be demonstrated to consist of 
 cell and. nucleus. If it be as the blood-corpuscles of birds, reptiles, 
 and fishes undoubtedly are, a nucleated cell, the obscurity of its 
 nucleus is probably due to one of two causes ; either it is so large 
 as accurately to fill the cell, leaving no space between the outer 
 surface of the one and the inner surface of the other, or it is so ex- 
 tremely minute as completely to elude our means of observation. 
 
 Mr. Wharton Jones supposes that the mammalian red corpuscle 
 is a nucleus, the cell of which had existed only in the earlier stages 
 of development. Kolliker, on the other hand, affirms that the nu- 
 cleus disappears while the cell-wall is persistent. All that micro- 
 scopic examination with the highest powers and the best instruments 
 shows respecting the structure of this corpuscle is that it consists of 
 a delicate membrane, inclosing a semifluid material, impregnated 
 with the proper colouring matter of the blood ; and that this struc- 
 ture may truly be assigned to it is amply proved by the change of 
 form which it undergoes by the endosmosis of pure water, which 
 will cause it to burst and evacuate its contents, consisting of 
 nothing more than some minute granules, none of which can be 
 compared to a nucleus. So far as microscopic analysis would 
 enable us to decide this question, we should be disposed to declare 
 in favor of Mr. Jones's view ; but it seems greatly opposed by two 
 facts ; first, that in the corpuscle of the lower vertebrata, the 
 colouring matter is contained between the nucleus and the cell-wall, 
 whereas in the mammalian corpuscle it would be contained in the 
 nucleus ; and, secondly, that this peculiarity of structure is limited 
 to one class of vertebrate animals. It receives support, however, 
 from observing the several steps of the development, for the cor- 
 puscle exhibits a stage in which a nucleus is visible (the stage of 
 coloured nucleated cell,) (Fig. 179, d,) and this nucleus, in the very 
 large corpuscle of the elephant, and likewise in the very small cor- 
 puscle of the goat, exhibits a strict correspondence in size with the 
 perfectly formed blood-corpuscle. But here, again, we notice the 
 difficulty, above referred to, that in this stage of nucleated cell, the 
 colour is found between the cell and the nucleus. It seems to us 
 that further research is required, in order to determine the exact 
 homology of the mammalian red corpuscle. 
 
 The Colourless Corpuscles.-^— These particles are found in all 
 kinds of blood. They are spherical bodies, destitute of colour ; 
 their structure is that of nucleated cells, the cell-membrane being 
 extremely delicate; both the cell-membrane , and the nucleus and 
 nucleolus are rendered distinct by the action of dilute acetic acid, 
 which dissolves some granules which are contained in the cell. — 
 These granules are external to the nucleus. When they are 
 
638 
 
 THE BLOOD. 
 
 Fig. 179. 
 
 numerous and large the nucleus is concealed by them. Corpuscles! 
 of this kind, denominated granule-cells by Mr. W. Jones (Fig. 179, 
 
 a, b), are viewed by him as constituting 
 an earlier stage than those in which the 
 nucleus and nucleolus are distinct, which 
 he calls nucleated cells (Fig. 179, c, d). 
 In size, the colourless corpuscles slightly 
 surpass the red corpuscles in mammalia, 
 but not in the other vertebrata. They 
 are essentially the same as the nucleated 
 particles found in lymph and in chyle. — 
 In examining the capillary circulation in 
 the transparent parts of some animals, 
 as the web of the frog's foot, they may 
 be seen sparingly at the margin of the 
 current of red corpuscles, either station- 
 ary and adherent to the wall of the blood- 
 vessels, or slowly moving forward in the 
 layer of liquor sanguinis which is in con- 
 tact with the wall, and which is thus shown to be comparatively 
 motionless. 
 
 The colourless corpuscles are much fewer in number than the 
 coloured ; it is said that they exist in the proportion of one colour- 
 less to fifty coloured, but that in inflammatory states of the blood, 
 the former are much more numerous, being as one in twelve. After 
 great loss of blood, the proportion of the colourless corpuscles is 
 considerably increased. 
 
 Phases of the human Wood-cor^ 
 puscle (after Wharton Jones), a and 
 o. Oranule-cells in the coarsely and 
 finely granular state, c and d. Nu- 
 cleated cells, c without colour, d with 
 colour, e. Free cellseform nucleus or 
 perfect red corpuscle. 
 
 Fig. 180. 
 
 
 A. 
 
 A very important inquiry is to determine — 1. The histological 
 
 relation of these particles to 
 each other; and, 2. The part 
 which they take respectively 
 in the vital phenomena of the 
 blood. 
 
 With regard to the first 
 point, physiologists are divid- 
 ed in opinion as to whether 
 they may be regarded as dis- 
 tinct and independent par- 
 ticles, performing each their 
 special functions, or whether 
 the one, namely, the colour- 
 less, corpuscle, may be viewed' 
 as an early or embryo condi- 
 tion of the red corpuscle. 
 
 The weight of argument 
 seems to favour the conclu- 
 sion that the colourless cor- 
 puscles are to be regarded as 
 an early stage of the coloured 
 
 Corpuscles from the bloodTena of the cava hepatlca 
 of the embryo chick on the twentieth day of incubation. 
 A. Red blood-corpuscles altered by water. D. Blood-cor- 
 puscles coherent and modified in shape by cohesion. 
 
 . Large spherical cells containing highly refracting 
 granules (fatty), b. The same represented only in out- 
 line, to show their shape, c. Tnlly formed rod corpus- 
 
THE COLOURLESS CORPUSCLES. 
 
 639 
 
 Fig. 181. 
 A 
 
 /K 
 
 
 eorpuscles, which are in the adult or perfect state. In the earliest 
 periods of foetal life, the blood-corpuscles, as is shown by the re- 
 searches of Vogt, Kblliker, and Cramer, originate, in the same way 
 as the elements of the tissues, from nucleated cells, which are the 
 same in point of constitution as the colourless corpuscles ; with this 
 exception, that they contain between the nucleus and the cell a con- 
 siderable number of granules, which are largest at the earliest 
 periods of embryonic life. At later periods similar nucleated cells 
 are generated in the liver, as first 
 pointed out by Weber, and in the 
 mesenteric and lymphatic glands, 
 and from these • sources supplied to 
 the blood. In this fluid they un- 
 dergo a transformation into the com- 
 pletely formed blood-corpuscles, by 
 the removal of the granules, the in- 
 creased development of the nucleus, 
 and the generation of colouring 
 matter, excepting in the mammifer- 
 ous corpuscle, whofee ultimate 
 change seems to consist in the com- 
 plete absorption of the nucleus, ac- 
 cording to Kblliker, or the removal of the wall of the cell, accord- 
 ing to Wharton Jones. 
 
 Now, as there can be no doubt that, in the adult, the lymphatic 
 and chyliferous systems afford a source for the constant develop- 
 ment of particles identical with the colourless corpuscles, and as 
 such corpuscles are always found in considerable proportion in the 
 blood (being more numerous under circumstances unfavourable to 
 normal changes,, as in inflammations), it seems very reasonable to 
 infer that similar transformations of colourless into coloured par- 
 
 
 Granules, granule-cells, and red blood-cor- 
 puscles from the embryo chick et the twen- 
 tieth day of incubation, a a. Granules, 
 some being enveloped by a'faint cell-wall, and 
 gran\ile-cellR with coarse granules, b b. Red. 
 blood-corpuscles. — Magnified 200 diameters. 
 
 Fig. 182. 
 
 Fig. 183. 
 
 \%^ 
 
 t. 
 
 a. Granules of which the cell- 
 wall is not visible. &. Granule- 
 cells and red corpuscles. — Mag- 
 nified 200 diameters. 
 
 Nucleated cell (a), red corpuscles (b), and 
 granules from the chick on the 20th day of 
 incubation. — Magnified 200 diameters. 
 
 tides are going on in the adult as in the embryo, and that the lym- 
 phatic and lacteal systems must be at least one, and that a fertile 
 source, from T^^hich red corpuscles are being continually supplied to 
 the blood. 
 
640 THE BLOOD. 
 
 If, however, we reject this view of the relation of the colourless 
 to the coloured corpuscles, then we must regard them as independ- 
 ent particles, each having its special function ; and it devolves upon 
 the advocates of this view to suggest the office, g-nd to explain the 
 mode of origin and decay of each. 
 
 Function of the Red Corpuscles. — It is clear that the red cor- 
 puscles must perform some very important office in the life of the 
 blood, because of their grteat numbers, their constancy, and the 
 serious consequences to the general nutrition and the vital actions 
 of the body, which ensue upon any considerable diminution in the 
 quantity of them. But we have no definite knowledge on this sub- 
 ject, and all that can be suggested is, as yet, of a speculative and 
 hypothetical nature. 
 
 Liebig adopted the highly ingenious notion, that the red cor- 
 puscles are carriers of oxygen, and that by their colouring matter 
 they are peculiarly adapted for attracting that principle. The 
 property of attracting oxygen is due to the iron, which forms six 
 per cent, of the hematine contained in the red corpuscle. In venous 
 blood, according to Liebig, the iron is in the state of carbonate of 
 the protoxide of iron ; this, as the blood jfasses through the ca- 
 pillaries of the lungs, or becomes otherwise exposed to the action of 
 the air, is by the absorption of oxygen converted into the hydrated 
 peroxide of iron, the state in which that metal exists in arterial 
 blood. And at the same time it gives off " for every volume of 
 oxygen necessary for the change from protoxide to peroxide, four 
 volumes of carbonic acid." As the arterial blood passes through 
 the capillaries of the system, the peroxide of iron yields oxygen to 
 certain constituents of the body, which is employed in producing 
 the change of matter, and in oxidizing newly-formed substances in 
 the blood, while in their return towards the heart, the red particles 
 which had lost their oxygen " combine with carbonic acid, producing 
 venous blood ; and when they reach the lungs an exchange takes 
 place between this carbonic acid and the oxygen of the atmosphere." 
 
 This doctrine of Liebig assigns the use of the colouring matter, 
 or of the contents of the blood-corpuscle, rather than of the cor- 
 puscle itself; it is, indeed, highly reasonable to suppose that the 
 hematine has an important connection with the attraction of 
 oxygen into the system, or to speak more generally, with the 
 changes which take place in the blood in respiration. The differ- 
 ence of colour, being the prominent feature of distinction between 
 arterial and venous blood, is strongly indicative of this ; and also the 
 fact now demonstrated by Mr. Wharton Jones, that the blood of 
 the invertebrata contains a certain degree of colour, or at any rate, 
 even where no colour can be distinguished, according to Professor 
 Graham's analysis, " a sensible quantity of iron, perhaps as much 
 as red corpuscles." 
 
 Liebig, however, does not explain why the hematine is invariably 
 contained in a multitude of nucleated cells. The consideration of 
 this point seems to us to afford the clue to determine the real func- 
 tion of the red particles. 
 
DR. CARPENTER'S HYPOTHESIS. 641 
 
 The true office of the red blood-corpuscles would, probably, be 
 most correctly described as that of forming or secreting the hema- 
 tine, which in. the greatest part of the animal kingdom is coloured, 
 but which even, though colourless, appears to contain iron. These 
 particles are floating gland-cells, as Henle suggested some years 
 ago ; they are in all essential points of structure like the secreting 
 cells of true glands, and there is no reason why, free and floating 
 in a liquid like the liquor sanguinis, they may not exercise upon 
 materials dissolved in that fluid an influence analogous to that ex- 
 ercised by the elementary particles of the liver, or the kidney, or 
 the pancreas upon the blood. The matter secreted by the blood- 
 cells is the hematine, which term we would here use to signify not 
 merely the colouring matter, but the entire contents of the blood- 
 corpuscle, of which iron is an important if not an essential ingredi- 
 ent, and which is coloured in the vertebrata and in some of the 
 invertebrata. It is this hematine which plays an important part in 
 the attraction of oxygen, and which by its colouring matter also 
 exercises some important influence on the whole economy ; for there 
 seems no other source from whence can be derived all that pigment 
 which is diffused throughout various textures, such as muscle, the 
 nervous centres, the skin and its appendages, the eye, &c., but that 
 which is formed in such great quantity in the blood. 
 
 Office of the Colourless Corpuscles. — If these particles do not 
 constitute an early stage of development of the coloured corpuscles, 
 it is clear that they must be viewed as performing some special 
 function in the blood, independently of the latter. R. Wagner 
 viewed them as identical with chyle and lymph corpuscles, and 
 assuming that in the invertebrata no coloured particles existed, 
 he regarded the blood in such animals as identical with chyle or 
 lymph ; as,- in fact, the latter fluid not yet elaborated into blood. — ■ 
 In the blood ofv vertebrata, therefore, he would view these particles 
 as chyle or lymph globules not yet transformed into blood particles. 
 
 But Dr. Carpenter has put forward a more elaborate hypothesis 
 respecting the office of the white corpuscles. This able physiolo- 
 gist regards these particles as the agents in the development of 
 fibrine in the blood, or in the conversion of albumen or other ma- 
 terials of that fluid into that "plastic" compound. This substance 
 certainly first appears in the chyle and lymph, where these particles 
 are found in great numbers floating in an albuminous fluid. Nor 
 does it appear in the chyle until after that fluid has passed through 
 the mesenteric glands, which furnish these particles in large num- 
 bers. 
 
 Dr. Carpenter regards the appearance of these colourless cor- 
 puscles or cells in the blood as a phenomenon in close analogy with 
 the development of cells in the albumen of the seed in the vegetable 
 kingdom, and in the yolk of the eggs of oviparous animals; and he 
 supposes that the office of these cells is to convert crude alimentary 
 materials into proximate principles; which again, through the agency 
 • of cells, may be converted into, or may afford the materials for the 
 
642 THE BLOOD. 
 
 peculiar compounds which form the characteristic ingredients of the 
 secretions, or may pass into organized tissue.* 
 
 Of the Development and Decay of the Blood- Corpuscles. — It 
 seems to us that the view which Mr. Wharton Jones takes respect- 
 ing the development of the blood-corpuscles, already described at 
 pp. 637, 638, aifords the most simple and correct explanation of the 
 origin and development of these particles. According to it, the 
 lacteal and lymphatic systems may be regarded as the source 
 whence fresh supplies of blood-corpuscles are being continually fur- 
 nished to the blood at all periods of life. In the early embryo, as 
 well as in the adult, the process of the formation of the blood-cor- 
 puscle would be the same ; that is, the development of a nucleated 
 cell, which undergoes transformation into the coloured particle ; the 
 steps of the process being successively granule cell, nucleated cell, 
 and coloured particle (Fig. 179). This view would lead us to regard 
 the system of lymphatic and mesenteric glands as the seat of an 
 unceasing generation of new particles, which undergo their later 
 stages of transformation in the blood. And it is well worthy the 
 attention of pathologists, as affording an explanation of the great 
 influence which (as we learn from experience) this extensive system 
 of glandular bodies exercises upon general nutrition. 
 
 Prior to the formation of this glandular system and the develop- 
 ment of the lymph and chyle corpuscles, the blood-particles "are 
 derived as nucleated cells from the cells of the germinal membrane, 
 but they undergo essentially the same changes as in the more ad- 
 vanced periods of life. In mammalian embryos they are described 
 *' as of large size, spherical or oval, pellucid and colourless, nu- 
 cleated, and full of minute granules." Mr. Paget, whose description 
 we follow, confirms the observation made by Kblliker, Fahrner, and 
 others, of the occasional occurrence of " a process of multiplication 
 by bi-partition of the nucleus, each of which, either, by appropriat- 
 ing half the cell, or by developing a cell around itself, becomes the 
 central nucleus of a new cell, differing from the parent cell from 
 which it escapes in little except in being smaller and more gener- 
 ally circular, "t 
 
 Of the manner in which the blood-corpuscles decay we really 
 know nothing — no more than of the mode of decay of the elements 
 of the tissues. The notion held for a time, by some physiologists, 
 that the existing particles gave birth to new ones by a gemmiparous 
 or fissiparous generation, has no foundation in careful observation. 
 Audit is most probable that, as Mr. Paget remarks, " new corpuscles 
 never appear to be produced from the germs of old ones ; when a 
 corpuscle is past its perfection, it degenerates and probably liquefies." 
 "The changes of such degeneration," adds this excellent observer, 
 " have not been clearly seen in mammalian corpuscles ; but they are 
 
 * Dr. Carpenter's remarks on this subject deserve the attentive perusal and con- 
 sideration of physiologists — See Princyplea of Human Physiology, 22 153-159, fourth 
 Am. Ed. 
 
 f Kirkes's Handbook of Physiology, Am. Ed. p. 63, Fig, 12. 
 
THE CHEMICAL ANALYSIS OP THE BLOOD. 643 
 
 probably nearly similar to wliat occur in those of fish and reptiles; 
 in which the old and degenerate corpuscles 'appear perfectly white 
 and pellucid (not shaded or granular, like the lymph-corpuscles), 
 smaller than they were, and in some instances cracked, or as if 
 eroded. The nuclei appear to degenerate with the cells, but be- 
 cause of their darker and harder outlines, remain longer distinct, 
 and often look like free nuclei, unless the dim cell-wall round them 
 be carefully searched for. But in this process, no germ for a new 
 corpuscle issues from the transient cell. Every new corpuscle forms 
 itself in and from the materials of the lymph and chyle, and is 
 perfected in the blood, and the blood is maintained by constant 
 repetitions of this process."* 
 
 Kblliker has lately put forward the remarkable opinion that the 
 spleen is the seat of a process of destruction or dissolution of the 
 blood-corpuscles. We shall examine this view farther on, when we 
 come to describe the structure of the spleen.f 
 
 IV. The Chemical Analysis of the Blood. — The blood is a fluid 
 of the greatest complexity, as must be expected, if we regard it 
 as containing the material for the nutrition of all the tissues, as well 
 as for all the secretions. Thus, in addition to ,the water which forins 
 four-fifths of it, and without which no transfer of materials could 
 take place from it to other parts, it contains albumen for the al- 
 buminous tissues ; fibrine for the fibrinous ; salts which are found in 
 the various secretions ; colouring matter, which, more or less modi- 
 fied, is found in the nervous matter, the skin, the eye, the bile, the 
 urine, the cerumen ; and fatty matters identical with those which 
 are found in fat. 
 
 The researches of the last few years, in which Lecanu, Andral 
 and Gavarret, Rees, Becquerel and Rodier, Christison, Miller, and 
 others have taken a conspicuous part, have determined, with a very 
 near agreement, the relative proportions in which the various stami- 
 nal principles exist in healthy blood. 
 
 The following method may be adopted for this kind of quantita- 
 tive analysis. f Let the blood flow at four diff'erent periods and in 
 equal quantities into two vessels ; the first and third into the first 
 vessel ; the second and fourth into the second ; the weight of each~ 
 should be taken. 
 
 From one portion the fibrine may be separated by whipping, or 
 by shaking up the blood in a bottle containing small pieces of lead ; 
 the residue will consist of the serum and red particles. The weight 
 of this, deducted from that of the whole portion of blood, will give 
 the weight of the fibrine. 
 
 The second portion may be set aside to coagulate spontaneously ; 
 when this process is completed, the crassamentum must be taken out, 
 and, after the serum has completely drained away from it, it should 
 be weighed. The weight of the fibrine, as obtained by the first ex- 
 periment, being deducted from that of the entire clot, will give that 
 
 * Loe. cit. p. 67. t ^^- ^^^^, Cyclop. Anat. and Phys. 
 
 J For a more elaborate and exact method of analysis, see Mr. J. E. Bowman's 
 " Handbook of Medical Chemistry," Am. Ed. p. 160. 
 
644 
 
 THE BLOOD. 
 
 of the coloured corpuscles. The amount of albumen may be obtained 
 by precipitating it from the serum, and weighing it after filtration. 
 
 The general results of this method of analysis may be thus stated 
 roughly. In one hundred parts of blood, about seventy-eight parts 
 are fluid and twenty-two parts solid material ; and of the last, 
 the albumen constitutes rather less than seven parts, the fibrine 
 one-fourth of a part, and the red particles rather more than four- 
 teen parts. 
 
 The following table gives a summary of the analysis of the blood 
 of healthy individuals of both sexes, by Becquerel and Rodier, who 
 are among the most recent analysts. 
 
 Composition of one thousand parts of blood in men, derived from 
 eleven analyses. 
 
 Water 
 
 Red particles 
 
 Albumen 
 
 Fibrine 
 
 Extractive matters and free salts 
 
 Fatty matters 
 
 Mean, 
 
 779 
 
 141.1 
 
 69.4 
 
 2.2 
 
 6.8 
 
 1.6 
 
 Maximum. 
 
 760 
 
 152 
 
 73 
 
 3.5 
 
 8 
 
 3.255 
 
 Minimum. 
 
 800 
 
 131 
 
 62 
 
 1.5 
 
 Composition of one thousand parts of blood in women, derived 
 from eight analyses. 
 
 Water 
 
 Red particles 
 
 Albumen . . , 
 
 Fibrine 
 
 Extractive matters and free salts 
 
 Fatty matters 
 
 Mean. 
 
 791.1 
 
 127.2 
 
 70.5 
 
 2.2 
 
 7.4 
 
 1.62 
 
 773 
 
 137.5 
 
 75.5 
 
 2.5 
 
 8.5 
 
 2.86 
 
 Minimum. 
 813 - 
 113 
 65 
 1.8 
 6.2 
 1 
 
 Composition of the Red Particles, and of the Hematine. — The 
 large proportion which the coloured particles form of the solids of the 
 blood, entitles them to the most attentive consideration of physiolo- 
 gists ; they are ynore than fifty times the quantity of the fibrine, and 
 nearly double as much as the albumen. 
 
 The red corpuscles consist, according to most chemists, of two 
 elementary substances, globuline and hematine ; the former is nearly 
 allied to if not identical with albumen, and forms the solid part of 
 the blood-corpuscle, its cell-wall, and nucleus, when i't exists ; the 
 latter is the colouring material, or blood-pigment. 
 
 The following process is recommended by Figuier for the separa- 
 tion of the hematine from the globuline. 
 
 Defibrinated blood should be mixed with at least four times its 
 bulk of a saturated solution of sulphate of soda ; the mixture must 
 then be thrown on afilter; the fluid and some corpuscles pass through, 
 leaving the mass of coloured particles on the fllter. This must 
 next be boiled in alcohol, slightly acidulated with sulphuric acid ; 
 the hematine will be thus dissolved, the colourless globuline, in 
 combination with some of the sulphuric acid, remaining undissolved. 
 
 The next step in this process is, to add to the hot solution of 
 hematine enough carbonate of ammonia to remove the sulphuric 
 acid ; the fluid must then be filtered, to remove the sulphate of 
 ammonia thus formed, and the liquor must be exposed for evapora* 
 
MORBID BLOOD. 645 
 
 tion ; -when, by this means, it is reduced one-twelfth of its bulk, it 
 ■ffill be found to deposit hematine as a dark or black powder. 
 
 This hematine is insoluble in water, alcohol, or ether, unless 
 mixed with some alkali, which renders it readily soluble ; when 
 burned, it yields a considerable quantity of iron. 
 
 Mulder's ultimate analysis gives the following as its composi- 
 tion : — 
 
 Carbon 
 
 65.84 
 
 Hydrogen 
 
 5.37 
 
 Nitrogen 
 
 10.40 
 
 Oxygen 
 
 11.75 
 
 Iron 
 
 66.5 
 
 Much difference of opinion exists among chemists as to the state 
 in which iron exists in the blood. We have already referred to the 
 opinion of Liebig, who affirms that in venous blood it is in the 
 state of protoxide, while in arterial blood it is in that of peroxide; 
 and that the change of colour, from the dark red of the former to 
 the bright scarlet of the latter, is due to the conversion of the pro- 
 toxide of iron into peroxide by the absorption of fresh oxygen at 
 the lungs. Mulder supposes that it exists in the metallic state as 
 a simple ingredient, as essential to the colour as its oxygen, its 
 hydrogen, its carbon, or its nitrogen. Scherer's experience, how- 
 ever, would go to sbow that iron is not essential to the colour of 
 the blood. He treated the red particles with sulphuric acid, so as to 
 reniove their iron, and found that their colour still remained. — 
 Hence he infe,rs that iron is not essential to the colour. 
 
 The value of the administration of iron in the treatment of cases 
 of anemia after loss of blood, is well known and highly appreciated 
 by practitioners ; it remains to be "determined in what way it con- 
 tributes so powerfully, as it unquestionably does, to the restoration 
 of the blood to its normal state. The fact that it does exercise a 
 powerful influence evidently indicates its importance as an ingre- 
 dient in the hematine. And it may be remarked that iron, even 
 if not essential to its colour, may nevertheless be an essential in- 
 gredient of a normal hematine. 
 
 Difference of Arterial and Venous Blood. — The prominent differ- 
 ence between blood drawn from the arteries and that from the 
 veins, is to be found in the bright scarlet colour of the former, and 
 the dark red, almost black, of the latter. To which may be added 
 some difference of temperature, that of arterial being one or two 
 degrees higher than venous; perhaps also some difference as to den- 
 sity, but upon this point observers are very far from being agreed ; 
 and also as to the proportions of solid constituents; but on this sub- 
 ject, likewise, the reports of analyists are contradictory and highly 
 unsatisfactory. 
 
 The blood of the vena porta is said by F. Simon to coagulate 
 more slowly and less perfectly than ordinary venous blood ; it con- 
 tains less fibrine and much more fat. 
 
 Influence of Venesection and of Disease upon the Blood. — The 
 influence of venesection and of some morbid states upon the rela- 
 
646 THE BLOOD. 
 
 live quantities of these constituents of the blood deserves to be well 
 impressed upon practitioners. 
 
 Venesection, or the loss of blood by any mfeans, reduces the 
 amount of the red particles chiefly, and the more so in proportion to 
 its frequency ; the serum is diminished in density, and the quantity 
 of the albumen and the fat is slightly reduced ; that of fibrine is 
 not affected, nor are the extractive salts. 
 
 The following cases from Dr. Christison illustrate the influence of 
 venesection upon the blood. 
 
 The first is that of a middle-aged woman, who had been previ- 
 ously repeatedly bled for palpitations of the heart. The analysis of 
 her blood gave the following result : — 
 
 Fibrine ... 2 
 
 Solids of serum ... 76 
 
 Red particles ... 57 
 
 Water ... 863 
 
 In the second case there had been frequent bleedings after rheu- 
 matism : — 
 
 Fibrine ... 4 
 
 Solids of serum ... 93 
 
 Bed particles ... 57 
 
 Water ... 844 
 
 This latter case shows how impotent is venesection, even when 
 carried to a great extent, over the reduction of fibrine, the material 
 that forms those new deposits of organizable matter or plastic 
 lymph, which in inflammations of internal organs, such as the lungs 
 and heart, so much interfere with their normal action. 
 
 The following experiment, also, illustrates the effect of venesec- 
 tion upon the blood, first, when the animal was well fed at the time 
 when the bleedings were being practised ; and, secondly, when it 
 was starved between the operations. 
 
 A large dog was fed upon two pounds of meat, and a quart of 
 milk a day, and six ounces of blood were drawn on each of four 
 successive days from his jugular vein. The blood was analyzed by 
 our friend, Mr. Lionel Beale, Jun., who obtained the results shown 
 in the following table : — 
 
 No. OP Bmedinos. 
 
 Firat. 
 
 Second. 
 
 Third. 
 
 Pourtli. 
 
 Water 
 
 783.79 
 
 810.89 
 
 816.18 
 
 813.04 
 
 Fibrine 
 
 2.42 
 
 4.72 
 
 4.84 
 
 3.99 
 
 Solids of serum 
 
 70.94 
 
 70.85 
 
 69.92 
 
 76.01 
 
 Blood-corpuscles 
 
 142.85 
 
 113.54 
 
 110.58 
 
 106.95 
 
 
 1000.00 
 
 1000.00 
 
 1000.02 
 
 1000.00 
 
 Density of serum 
 
 1025.8 
 
 1024.8 
 
 1023.5 
 
 1023.6 
 
 Here, notwithstanding the liberal allowance of food, the red par- 
 ticles suffered a considerable diminution. 
 
 The dog was now allowed to recover, and was well fed for three 
 weeks, and at the end of that time his blood was analyzed ; he was 
 then starved for four days, being allowed nothing but water, and on 
 each of these four days was bled. The following table gives the 
 result of these analyses. 
 
DRBID 
 
 BLOOD. 
 
 
 
 Second. 
 
 Third. 
 
 Fourth. 
 
 Fifth. 
 
 804.40 
 
 805.44 
 
 838.30 
 
 849.84 
 
 1.91 
 
 3.95 
 
 .5.26 
 
 5.13 
 
 72.61 
 
 71.46 
 
 68.46 
 
 71.62 
 
 121.08 
 
 119.15 
 
 87.98 
 
 74.21 
 
 647 
 
 No. OF Binmraos. First. 
 
 Water . . 802.71 
 Fibriue . . 2.28 
 Solids of serum 74.13 
 Blood-corpuscles 120.88 
 
 Dog fed. Dog starred. 
 
 In the latter experiments we notice a diminution of the red par- 
 ticles to an extent even more marked than in the former ; and it 
 may also be observed that even after a lapse of three weeks, with 
 good feeding, the red particles had not recovered their original 
 amount. 
 
 With reference to the estimate of the quantity of fibrine, it is 
 right to observe, that, both in these and all other analyses, it is 
 liable to an important source of fallacy, which arises from the im- 
 possibility of forming a separate estimate of the quantity of the 
 colourless corpuscles which adhere to the fibrine, and must necessarily 
 increase its apparent quantity. 
 
 The modifications which disease produces in the relative quanti- 
 ties of the blood-constituents, are chiefly referable to an incrfeaSe 
 (real or apparent) in the quantity of fibrine, or a diminution of that 
 element, or of the blood-corpuscles ; or, lastly, to such an alteration 
 in ,the quality of the fibrine (its quantity being unaltered) that its 
 coagulating power is materially interfered with. 
 
 In diseases of an inflammatory type, in which there is active 
 fever of a sthenic character, with proneness to effusion of plastic 
 lymph, or to the formation of thick laudable pus, fibrine is said to 
 be increased in quantity to as much as five or six parts in one thou- 
 sand of blood ; it is also said that there is an increase in the colour- 
 less corpuscles, and at first a slight increase in the coloured corpuscles, 
 though these latter afterwards undergo a diminution, which is themore 
 marked in proportion to the extent of depletory measures employed. 
 In no diseases are these changes in the blood more conspicuous than 
 in rheumatic fever, pneumonia, and pleurisy. The cupping and 
 buffing of the blood is very marked, and the most exquisite examples 
 of that interesting phenomenon may be obtained from patients 
 labouring under these maladies. Sufficient allowance, however, does 
 not seem to have been made by observers generally for the ex- 
 tent to which the apparent increase of fibrine may be explained by 
 the increase of the colourless corpuscles.* 
 
 * Zimmerman, and more recently Mr. John Simon, in his valuable lectures on 
 Pathology (Lancet, 1850, and since republished in 8to.), have advocated the doctrine, 
 noTol indeed, but most worthy of attention, that the fibrine of the blood must be re- 
 garded not as an ingredient prepared for the nourishment of certain tissues, and 
 ready to be appropriated by them, but as " among those elements which have arisen in 
 the blood from its own decay, or have reverted to it from the waste of the tissues." 
 Mr. Simon has been led to adopt this opinion chiefly frdm observing the unaltered 
 or even increased quantity of the fibrine under bleeding, starvation, anaemia, and 
 other states of exhaustion and increased waste, and also from the fact that in these 
 respects the fibrine is in direct contrast with the red particles which are rapidly 
 reduced by these means. This view is also favoured by the fact noticed by Andral and 
 Gavarret, that an improvement in the breed of an animal tended always (cseteris pari- 
 bus) to increase the proportion of the red particles, but to diminish that of the fibrine. 
 The small quantity of fibrine in foetal blood, the absence of fibrine from the egg, the 
 chyme, and the smaller quantity of it in the blood of carnivora (which feed on it) 
 
648 THE BLOOD. 
 
 Diminution of the quantity of fibrine, accompanied with a de- 
 crease in the red particles, occurs chiefly in fevers arising from the 
 presence of a poison in the system. None show these changes 
 more than those fevers which are caused by the paludal poison — 
 namely, intermittent fevers. In rheumatic fever, and in acute gen- 
 eral gout, there is a remarkable tendency to the diminution of the 
 coloring matter of the blood, even when these diseases have been 
 treated in the mildest manner. It would seem as if the materies 
 morbi acted as a blight upon the red corpuscles, and prevented their 
 development in the normal proportions. 
 
 In some cases — especially those connected with enlarged liver and 
 spleen — the diminution in the coloured particles is accompanied by 
 a remarkable increase in the number of the colourless particles. — 
 Some cases of this condition of blood have lately been collected by 
 Professor J. H. Bennett, who proposes for it the name Leucocythemia 
 (xtnisof, white; xvtos, a cell; atfia, blooct).* 
 
 The fatty matters of the blood are sometimes increased in 
 quaptity apparently from non-elimination. Under these circum- 
 stances the eerum becomes quite milky, an appearance which is 
 quite characteristic of this state of blood, and may be removed by 
 ether. "We have already alluded (p. 633) to the milkiness which 
 follows the ingestion of fatty food, but which cannot be regarded' as 
 abnormal. « 
 
 There is a condition of blood to which F. Simon has given the 
 name spansemia (srtaKJs, poor), and whieh is popularly called poor 
 blood. This is characterized by changes in the quality rather than 
 in the quantity of the blood-constituents, and especially, perhaps, 
 in the quality of the fibrine. When the blood is in this state, 
 hemorrhages are of frequent occurrence, owing probably to the im- 
 perfect manner in which' the coats of the bloodvessels are nourished. 
 Purpura and scurvy are well-known diseases, of which the prominent 
 feature consists in this poorness of blood. In the former malady, 
 we have found thfe blood-corpuscles shrivelled, and even disintegrat- 
 ed ;t but it is difficult to determine whether this was due to a defect 
 in their mode of generation and development, or to a diminished 
 specific gravity of the serum favourable to its endosmose by them. 
 
 On the subject of the blood, reference is made to the works on Physiology already 
 quoted ; Hewson'a works, by Gulliver (Sydm. Soc.) ; J. Hunter on the Blood, &c.; 
 Mr. Gulliver's numerous and valuable observations in the Appendix to the English 
 edition of Gerber's Anatomy, and in his notes to Hewson's works ; Simon's Animal 
 Chemistry, by Day (Sydem. Soc.) ; Wharton Jones, On the Blood-corpuscle consider- 
 ed in its different Phases of Development in the Animal Series, Phil Trans. 1846 ; 
 Kolliker, iiberdie Blut-Korperchen eines menschlichen Embryo und die Entwickelung 
 dcr Blut-Kiirperchen bei Saugethieren ; Nasse, iiber das Blut ; Sharpey and Quain's 
 Anatomy; Dr. Miller's article on Organic^ Analysis in the Cyclop, of Anat. ; Andral, 
 Essai d'lrKraatologie Pathologique ; Becquerel and Rodier, Reoherches sur la Composi- 
 tion du Sang, &o., 1844 ; Dr. Owen Rees on the Blood and Urine; Mr. J. E. Bowman's 
 Practical Handbook of Medical Chemistry ; Mr. John Simon's Lectures on General 
 Pathology, 1850. 
 
 than in that of the herbivora, are additional facts adduced by Mr. Simon in support 
 of this view. 
 
 * Monthly Journal of Mod. Science, Edinb. Jan. 1851. f See a case. 
 
OF THE BLOODVESSELS. 649 
 
 CHAPTER XXVIII. 
 
 THE CIRCULATION OF THE BLOOD. — THE SANGUIFEROUS SYSTEM, — 
 
 ARTERIES. VEINS. CAPILLARIES. — THE HEART, IN THE LOWER 
 
 ANIMALS,- IN MAN. PHENOMENA OF ITS ACTION. — COURSE OF THE 
 
 CIRCULATION IN MAN. — FORCES BY WHICH THE CIRCULATION IS 
 CARRIED ON IN THE ARTERIES, CAPILLARIES, AND VEINS. 
 
 It is difficult to comprehend how it escaped detection for so long 
 a time that the complex fluid, the properties of which were consid- 
 ered in the last chapter, is perpetually in motion. Physiologists 
 were not insensible of the importance of the blood to the general 
 nutrition of the body; but of its relation to the elements of the va- 
 rious tissues, they seem to have formed no adequate idea. 
 
 The discovery of the circulation of the blood by our immortal 
 Harvey, and first taught by him in 1619, was, perhaps, the most 
 perfect physiological induction from well-ascertained anatomical 
 facts ever made. A careful study of the anatomy of the veins and 
 of their valves, and also of the heart and its valves, and the com- 
 pai-ison of the possible relation which these mechanical contrivances 
 in the^one, might bear to those in the other, led to the inevitable 
 inference that the fluid contained in these vessels and in the heart, 
 not only moved, but also moved in a certain and uniform direction. 
 
 The agents of the circulation of the blood, are the heart and the 
 bloodvessels; the latter being a series of tubes of various sizes and 
 structure, and of various vital endowments'; the former a sort of 
 living forcing-pump in free communication with this system of tubes, 
 which, by its unceasing action, keeps the blood in continual motion. 
 
 We shall first' examine th-e structure and vital endowments of each 
 of these agents of the circulation, and then inquire into the part 
 which, each plays in maintaining the circulation of the blood. 
 
 Of the Bloddvesseh. — The bloodvessels are of three kinds, Arte- 
 ries, Veins, and Capillaries. 
 
 The arteries are the vessels which convey the blood from the 
 heart.' The etymology of the term (ai^p, triptio), shows that it was 
 adopted at a period wiien nothing was known as to the real nature 
 of the contents of these tubes during life. The fact that so large 
 a proportion of the arterial- system is empty after death, led to the 
 opinion, which prevailed to the time of Herophilus, that it contained 
 vital Spirits, or air [spiritus, or nvtv/io), during life, and the arteries 
 
 ^Were called rtxsiiftariia dyytii;* 
 
 Arteries are cylindrical tubes, whose walls are formed mainly by 
 a high elastic material, whereby the cylindrical form is preserved 
 
 ' ' "' ' ' ' " ■ ' ' " ' * c- 
 
 * This'idea respecting the office of tlie arteries is thus expressed by Cicero. " Spiri- 
 tus ex pulmone in cor recipitur et per arterias distribuitnr, sanguis per venas." — De 
 Nat. Dear. L. ii. 
 
 42 
 
650 THE CIRCULATION OF THE BLOOD. 
 
 and the collapse of the tube is prevented. For the same reason 
 when an artery is cut across, its mouth is patulous, and remains so. 
 
 The walls of arteries consist of three different textures : first, 
 the external tunic, composed of areolar tissue, and commonly called 
 the cellular coat ; secondly, the middle coat, or fibrous tunic ; and 
 thirdly, the epithelial tunic. 
 
 The external tunic is that through the medium of which/the artery 
 is corinected with neighbouring structures, and it also forms a nidus 
 for the support of the nutrient bloodvessels of the arterial wall. 
 These minute vessels, named vasa vasorum, are derived from neigh- 
 bouring arteries; they ramify freely in the external tunic, and send 
 minute branches to a certain depth in the wall of the artery. In a 
 well-injected subject, they may be seen filled with injection on all 
 the larger arteries, and when great vascular congestion has accom- 
 panied or preceded death, these vessels participate in the general 
 plethora, and may be seen distended with blood on the aorta and its 
 larger branches. 
 
 In some of the large arteries, a few pellets of fat may be found 
 in the outer layers of the external tunic, which consist of very loose 
 areolar tissue ; the inner layers of this tunic are, however, very con- 
 densed, and adapt themselves closely to the middle coat of the ar- 
 tery to which they adhere intimately, probably by i-eason of the 
 continuity of some of their fibres with those of the middle tunic. 
 The same elements are found in the external coat of arteries, as in 
 areolar tissue elsewhere, namely, the white and yellow fibrous tissue, 
 but the former predominates in quantity so much that in some situ- 
 ations it seems to be the sole constituent of the tunic. 
 
 The extensibility, toughness, and power of resistance which this 
 tunic enjoys, by reason. of the large quantity of white fibrous tissue 
 which it contains, adapt it admirably as the external investment of 
 the arterial tube. It serves to give mechanical support to the other 
 tunics, and being the medium in which the nutrient bloodvessels are 
 distributed, it contributes to a certain extent to their nutrition. 
 Hence there is no other tunic, the loss of which an artery suffers 
 from so much ; in diseased or injured states of the other coats, it 
 preserves the integrity of the tube, and prevents any serious inter- 
 ruptions to the circulation ; the wall of many aneurisms consists in 
 great part of this tunic ; and, on the application of a ligature, while 
 the inner and middle coats give way under the pressure, this tunic 
 resists and preserves its continuity for a time. 
 
 Of the Middle, or Fibrous Coat. — This tunic constitutes the prin- 
 cipal portion of the arterial wall. It is in greatest part composed 
 of yellow elastic fibrous tissue ; but it likewise contains some white 
 fibrous tissue, and also some of the unstriped muscular fibre. 
 
 When a large artery, as the human aorta, or the aorta of a horse 
 or ox, is cut either longitudinally or transversely, two very distinct 
 portions may be observed on examining the surface of the section 
 with the naked eye. These are, an internal portion, quite yellow 
 in colour, and constituting not more than a tenth or a twelfth of the 
 
THE MIDDLE COAT OF ARTERIES. 
 
 651 
 
 Finely fibrous layer of the longitudinal fibrous tunic of 
 the aorta of the horse. — Magnified 200 diameters. 
 
 Fig. 185. 
 
 thickness of the whole tunic ; and an external portion of a grayish- 
 yellow colour. 
 
 The internal portion, which we shall call the longitudinal fibrous 
 tunic is composed of longitudinal fibres of yellow fibrous tissue, 
 disposed in two planes, form- 
 ing an internal and an exter- Fig. 184. 
 nal layer. The internal 
 layer is in intimate contact 
 with the epithelium, and 
 consists of fine, pale, some- 
 what flat, not branching 
 fibres, imbedded in a hyaline 
 membrane, which peels off 
 readily in the length of the 
 vessel, and when separated 
 from connection with the adjacent layer assumes a coiled form, as 
 shown in Fig. 184. These fibres are not altered in any degree by 
 the action of acetic acid. The external layer is composed of fibres 
 of elastic tissue, which also take a longitudinal direction, but are 
 much coarser, and branch freely, form- 
 ing a very intricate interlacement (Fig. 
 185). 
 
 The external grayish-yellow portion 
 of thfe fibrous coat of arteries forms 
 nine-tenths or eleven-twelfths of the 
 thickness of the wall of the artery, and 
 may be distinguished from the internal 
 portion by the name of the circular 
 fibrous tunic. It consists entirely of 
 
 transverse fibres,* which surround the artery at right angles to its 
 long axis. These fibres separate readily when pulled in the trans- 
 verse direction. They form a series 
 of concentric layers, in number pro- 
 portioned to the thickness of the 
 artery, composed of coarse yellow 
 fibres which branch and interlace 
 freely. 
 
 Upon fine transverse sections of 
 the middle coat of one of the large 
 arteries of man, or of the ox, we 
 may observe the peculiar arrange- 
 ment of these branching fibres 
 which gives rise to the tendency of 
 this coat to split into lamellae. Cer- 
 tain large fibres or rods of yellow 
 elastic tissue are disposed in succes- 
 sive conjcentric circles which pass transversely, and sometimes ob- 
 liquely round the artery. (Figs, 187, 189, 190.) These branch in 
 a penniform manner (hence we propose to call them the penniform 
 fibres), and interlace with those on the same plane as well as with 
 
 Coarsely fibrous layer of the longitudi- 
 nal fibrous tunic of the aorta of the horse. 
 — Magnified 200 diameters. 
 
 Fig. 186. 
 
 A portion of the circular fibrous tunic of the 
 aorta of the horse, ttf show the reticulation 
 formed by the interlacement of its fibres. — 
 Magnified 200 diameters. 
 
6B% 
 
 THE CIRCULATION OF THE BLOOD. 
 
 those on an inner and outer plane. The branches again subdivide, 
 and form by their frequent anastomoses that intricate 
 Fig.- 188. interlacement which is represented in Fig. 187. 
 
 Fig. 187. 
 
 Section of the aorta nf the ox, showing the arrangement of the two layers of the 
 longitudinal fihrous tunic and of the circular fibrous tunic. — Magnified 250 dia- 
 meters, a. The epithelial tunic, b. The internal layer of the longitudinal fibrous 
 tunic, c. The external coarse layer of the same. d. A small portion of the circu- 
 lar fibrous tunic. Most of the fibres are cut across, but a few, which take an ob- 
 lique course, are seen in their whole length, and their pcnniform branoliing is 
 slightly indicated. 
 
 * 
 
 This disposition of the fibres may be particularly 
 well seen on thin sections made from the dried aorta 
 of the ox, and afterwards moistened with acetic acid. 
 It is also sufiiciently obvious in tlie aorta of the human 
 subject, but the fibres are all very much smaller, 
 nearly one-half the size of those of the ox, and the 
 penniform subdivision is not so distinct. 
 
 Muscular Fibres. — Interposed between the layers 
 of penniform fibres we find some of the wavy white 
 fibrous tissue also arranged in a circular form, and 
 intermingled with this are some transverse fibres of 
 unstriped muscle, with oval nuclei, whose long axes 
 are at right angles to the arterial canal (Fig. 191). 
 These do not seem to form any single uniform layer, 
 but are disposed probably on different planes (some- 
 what like the fibres of the dartos in the areolar tissue 
 of the scrotum) among the fibres of the circular fibrous 
 
 A section of the whole thickness of the artery, to show the relative extent of the portions of its walls 
 shown in the preceding figure. — Magnified 40 diameters. 
 
 a. The coarsely fibrous portion of the longitudinal fibrous tunic, b. The longitudinal fibrous tunic and 
 a portion of the circular fibrous tunic, c. The entire thickness of the artery. 
 
EPITHELIAL LAYER. 
 
 653 
 
 coat, and follow the same direction. They are best developed in 
 arteries of the middle and smaller size, and may be most easily 
 
 Fig. 189. 
 
 A portion of the circujar fibrous coat, showing the penniform branching of the largo rods of elastic 
 fibrous tissue, each large rod giving origin to multitudes of small interlacing fibres. — Magnified 200 
 diameters. x 
 
 • separated from the fibrous tissue in arteries •which have undergone 
 slight decomposition. They are then seen to consist of long fusi- 
 form fibres of much delicacy, with a minute nucleus in most of them. 
 I» the mass, they have the appearance represented in Fig. 191. 
 
 Fig. 190. 
 
 A single bar or penniform fibre from the circular fibrous tunic of the aorta of the oi, the small fibres 
 having been broken off. — Magnified 400 diameters. 
 
 The external layers of the circular fibrous coat become gradually 
 more and more like the ordinary yellow elastic tissue, the penniform 
 and the muscular fibres cease, and the true yellow elastic branching 
 fibre becomes continuous with that which is found 
 in sparing quantity in the externsil coat. 
 
 Epithelial Layer. — The interior of the arteries is 
 covered by a single layer of delicate oval epithelial 
 particles, which separate very soon after death, and 
 must, therefore, -be sought for in quite recent sub- 
 jects. They may be best seen by scraping the inner 
 surface of the artery. The long axis of each of 
 these particles is parallel to that of the vessel. 
 They are pointed, or, as it were, drawn out at their 
 extremities; and, according to Henle, they are some- 
 times elongated into fusiform fibres. They are re- 
 markable for the large size and the distinctness of 
 their nuclei which are often visible when the cell- 
 wall cannot be detected. The particles seem to rest 
 immediately upon the innermost layer of the longi- unstriped muscu- 
 
 ,.,„,"' '^ , . 1 . 1 1. S 1 .. P lar fibres from the 
 
 tudinal fibrous tunic, which bears the relation oi a aorta of the horse.— 
 basement-membrane to them ; in this, when detached, Zt^"" '°° '''™'" 
 
654 THE CIRC0LATION OP THE BLOOD. 
 
 minute apertures appear constituting the fenestrated membrane of 
 Henle. It is possible, as suggested by Henle, that this membrane 
 arises from the transformation of the epithelium, ■which is ever draw- 
 ing the materials of its formation and nutrition from the blood con- 
 tained in the artery. Thus, it is not improbable that the innermost 
 layers of the arterial wall, at least, are nourished from the blood 
 flowing through the artery, and not from the blood of the vasa vaso- 
 rum, which do not seem to penetrate to them. And this view is 
 supported by observing that these innermost layers of the artery, 
 i. e. the longitudinal fibrous tunic, are the seat of the atheromatous 
 deposits which are so common in peculiar diatheses, or at an ad- 
 vanced period of life ; these deposits being doubtless derived from 
 the blood which traverses the artery. 
 
 Fig. 192. Fig. 193. 
 
 Epitbelial particles from the Particles of epithelium and nuclei from the 
 
 aorta of an ox. — Mi^nified 400 aorta of a horse ; some of the former exhibit 
 
 diameters. the elongated character, — Mag, 200 diameters. 
 
 From the preceding description, it would appear that the following 
 tunics may be enumerated as constituting the wall of an artery pro- 
 ceeding from without inwards. 
 
 First, the external coat, consisting of areolar tissue. 
 
 Secon'd, the circular fibrous coat, consisting of a series of lamellae, 
 composed of yellow elastic fibrous tissue, the most external of which 
 are intermingled with white fibrous tissue and with circular muscular 
 fibres. 
 
 Third, the longitudinal fibrous layer, which consists of two layers, 
 a finely fibrous, and a coarsely fibrous. 
 
 And lastly, a layer of epithelium. 
 
 The internal layer of longitudinal fibres — which is the same as 
 that described by Henle under the name oi fenestrated membrane — 
 constitutes, along with the epithelium, the internal tunic so long 
 recognized by anatomists. 
 
 The elastic reaction of arteries is evidently resident in the middle 
 fibrous coat, and in the same tunic the contractile power of the 
 artery resides. The existence of these two forces in the arterial 
 
COATS OF ARTERIES. 655 
 
 •wall, the one of .simple elastic reaction, the other of a slow muscular 
 contraction, is shown by the well-known experiments of John 
 Hunter. A piece taken from each of the large arteries of a horse, 
 bled to death, was laid open and extended on a flat surface without 
 stretching ; it was then measured, and afterwards subjected to strong 
 tension; it was then measured again ; on the removal of the stretch- 
 ing force, it failed to recover itself to its first dimensions' by a notable 
 difference. Wljen an animal has been bled to death, the arteries 
 are in their greatest state of contraction, the quantity of blood cir- 
 culating in them being reduced to a minimum. This state of con- 
 traction, Hunter assumed to be the result of muscular force, and 
 with good reason, as, nfter stretching, the artery did not contract 
 to its previous dimensions. The stretching destroyed the muscular 
 force, leaving whatever contraction would take place on the removal 
 of the stretching, to be effected by the elastic force. Thus a piece 
 of the aorta of a horse, when slit up and opened on a plane surface, 
 measured five inches and a half; on being stretched, it lengthened 
 to ten inches and a half; the stretching power being removed, it 
 contracted again six inches, " which," says Hunter, " we must sup- 
 pose to be the middle state of the vessel."* These powers inherent 
 in the arterial wall, of yielding under a distending force, and react- 
 ing upon its contents with a force equal to that of the primitive dis- 
 turbing one, and also that of muscular contraction, exercise an im- 
 portant influence in promoting or directing the circulation of the 
 blood through the arterial system. 
 
 The elastic element of the arterial tunic is always developed in 
 the direct ratio of the size of the artery ; and the muscular element, 
 although perhaps not bearing an inverse proportion to the size of 
 the artery, yet becomes more prominent and distinct as the elastic 
 tissue diminishes in coarseness and in strength. Thus it is in the 
 smaller arteries that we notice the most perfect arrangement of 
 muscular fibres, and in these the fibrous tissue is reduced to its in- 
 ternal longitudinal fibrous layer, the external circular fibres having 
 disappeared. 
 
 Bloodvessels and nerves are freely distributed to the arterial 
 tunics. To the former, allusion has already been made in describ- 
 ing their external tunic. We have no evidence that these blood- 
 vessels penetrate further thao to a slight depth into the fibrous 
 tunic. It is probable, therefore, that they are destined to nourish 
 the external tunic, and a portion (chiefly the muscular element) of 
 the fibrous tunic, leaving the remainder of the arterial wall to 
 imbibe its nutrition directly from the blood itself. The general 
 arrangement of the nerves on the outer coat of arteries has been 
 already described (vol. i. p. 223, and vol. ii. chap. xx.). The 
 plexuses formed are chiefly conducted by the arteries to parts be- 
 yond ; but they also furnish filaments penetrating to the muscular 
 fibres, and bringing these into relation with the nervous system. 
 
 The arterial system may be described as taking its starting-point 
 from the heart, by the attachment to that organ of each of the two 
 
 * Hunter on the Blood, Inflammation, &c., 4to. ed. p. 124, et uq. 
 
656 THE CIRCULATION OF THE BLOOD. 
 
 great vessels (the aorta and the pulmonary artery) which form the 
 main trunks of their respective systems. The middle coat of each 
 of these vessels is inserted into or adherent to the concavity of three 
 festoons composed of rounded cords of white fibrous tissue. To the 
 central portion of the convexity of each of these the muscular fibre 
 of the heart adheres closely in the case of the pulmonary artery ; 
 but in that of the aorta, one festoon and the half of another gives 
 attachment to muscular fibre, whilst the other half of this festoon, 
 and a third are attached to a part of the fibrous'zone, which forms 
 the base of the inner lip of the mitral valve. Along the line of these' 
 festoons the lining membrane of the heart, becoming continuous with 
 that of the arteries, forms three semilunar curtains, which are 
 strengthened by processes of fibrous tissue continuous with the 
 festoons. These folds constitute the valves of these vessels, the 
 only ones of the arterial system. We shall recur to these by and 
 by. ^ . ' 
 
 Arteries convey the blood to the various parts of the body by the 
 subdivision of their trunks and the giving ofi'of branch-vessels at vari- 
 ous points. The branches for the most part come off at an acute angle 
 with the continued trunk, so that the new stream of blood does not 
 experience any great diversion from the direction of its parent 
 stream. In a few instances, however, this arrangement is not ob- 
 served, as in some of the intercostal and lumbar arteries, which 
 form nearly a right angle with the aorta from which they originate. 
 
 Anastomoses of Arteries. — The manner in which difierent arterial 
 trunks communicate with each other indirectly, is one of the most 
 interesting points in the anatomy of the arterial system. This 
 anastomosis of arteries often affords the means of supplying the 
 nutrient fluid to a limb after its principal artery has been obliterated, 
 small collateral channels enlarging more or less for the reception of 
 a greater supply of blood than they were wont to convey. Hence 
 the study of the intercommunicating vessels has had great influence 
 upon the surgical treatment of aneurisms and wounds of arteries. 
 
 One of the most simple of these anastomoses is found in the union 
 of two arteries, originating from different trunks, to form one — as 
 the vertebral arteries unite to form the basilar ; another kind is, when 
 two vessels from the same or diff'erent trunks form by their union an 
 arch from the convexity of which others come off, which form similar 
 reunions and arches, giving off smaller branches which take a similar 
 course, and the arrangement continues tp be repeated until the 
 resulting branches are reduced to a very small size, when they pass 
 into the capillary system. This mode of frequent subdivision and 
 anastomosis is seen in the arteries which convey blood to the intestine 
 — the mesenteric arteries. A third form is where two neighbouring 
 arteries communicate by a distinct vessel, which passes from one to 
 the other. By such vessels the remarkable anastomosis at the base 
 of the brain, the circle of Willis, is formed. The anterior cerebral 
 Hrtcries passing upwards and forwards are united by a cross branch, 
 the anterior communicating artery, and the carotid artery on each 
 side is united to the posterior cerebral artery by a branch which 
 
ANASTOMOSES OF ARTERIES. 657 
 
 passes from before backwards — namely, the posterior communicating 
 artery. By this free communication of the arteries in front with 
 those behind, and of those on the right with those on the left, the 
 brain is protected. against loss of blood, if any of the main channels 
 of its supply should be stopped. 
 
 The most common form of anastomosis is found in the limbs. Twa 
 principal channels convey blood to a limb, as in the forearm, the 
 radial and ulnar arteries. The branches of these arteries communi- 
 cate at various points, especially in the vicinity of the joints, and thus, 
 if any impediment occurs in either, the other enlarges, conveys an 
 increased quantity of blood, and even the obstructed trunk beyond 
 the point of obstruction receives a supply by the anastomosing 
 branches. Or the single main artery of a limb, the femoral, or the 
 brachial, by its branches communicates with arteries which, originat- 
 ing from different sources, pass into- another portion of the limb. 
 Thus, in the thigh, the circumflex branches of the profunda anasto- 
 mose with branches which descend from the gluteal, sciatic, and ob- 
 turator arteries, which are branches of the internal iliac. Hence 
 an obstruction in the femoral, high up, or even in the external iliac, 
 will not deprive the limb of its due supply of blood, for the arteries 
 just named will convey blood to the branches of the femoral, which 
 arise' below. This anastomosis may compensate for an obstruction 
 in the internal iliac near its origin, and by a reflux of blood from the 
 femoral through the profunda arteries supply the lower part of that 
 artery. In the treatment of wounded arteries, the surgeon must 
 always make allowance for the anastomoses in the neighbourhood of 
 the wound. It rarely happens that a single' ligature on the cardiac 
 side of the wound ia sufficient to guard against secondary hemor- 
 rhage ; the anastomotic branches which arise from the main artery 
 above the wound supplying the vessel or its subdivisions below, so 
 that the blood finds its way by a reflex course to the distal part of 
 the trunk of the artery, and to the wound. This is very apt to 
 occur in wounds of the brachial artery at the bend of the elbow. 
 The only and the obvious method of guarding against such an effect 
 of arterial anastomosis, is to apply. a ligature to two points of the 
 artery, viz., below the wound, as well as above it. 
 
 The supply of blood to various segments of the body through dif- 
 
 ' ferent channels, and the free communication of these channels with 
 each other, must be regarded as one of the most beautiful of- the 
 various mechanical contrivances in the human body. By such an 
 arrangement a considerable security is obtained' against the failure 
 of the nutrition of the limb by the stoppage of one of its channels; 
 
 • And modern surgery is largely indebted to it for one of its most 
 brilliant triumphs. 
 
 The passage of the blood into a limb or organ through various 
 channels serves to distribute it more equally, and to relieve the ele- 
 mentary constituents of the limb or organ from the impetus which 
 the entrance into it of a single large column of blood would occa- 
 sion. This provision is especially secured for the brain by the sub- 
 division of the four great streams of blood which enter the cranium 
 
658 THE CIRCULATION OF THE BLOOD. 
 
 into several minor ones at the base of that organ, whieh again un- 
 dergo extreme subdivision before they penetrate the nervous matter. 
 In animals that hold their heads low, the subdivision of the carotid 
 and of the vertebral arteries is very remarkable, and gives rise to 
 the formation of the different kinds of rete mirabile. The most re- 
 markable instance of the subdivision of arteries, prior to the pene- 
 tration of the tissue they are destined to nourish, is that described 
 by Sir A. Carlisle, in the Sloth, which seems to be connected with 
 the extraordinairy power enjoyed by those animals of sustaining 
 muscular action for a lengthened period. 
 
 The anastomosis of the smaller arterial ramifications are also of 
 great importance in many of the organs and tissues, especially under 
 the skin and mucous membranes. Here a membranous expansion 
 is supplied by a great number of distinct twigs which form a plexus 
 everywhere continuous, and which again gives rise to other smaller 
 plexuses before the ultimate capillaries are given off. To this form 
 of anastomosis of the smaller arteries may perhaps be ascribed the 
 tendency of some inflammations of membranous parts to be propa- 
 gated rapidly along' an extensive surface, as in erysipelas. In 
 some organs, as the kidney, the arterial twigs have no anastomosis 
 whatever. 
 
 Of the Veins. — The veins carry the blood back to the heart from 
 the various tissues and organs. As the arteries divide and subdi- 
 vide, the veins follow a contrary course. They commence from the 
 capillary plexuses of the tissues and organs by minute radicle ves- 
 sels, which by their junction form larger ones, and these again unite 
 to form still larger ones ; and so by the fusion of the smaller veins 
 larger trunks are produced, until at length the venous blood, from 
 all parts of the body, is returned to the heart by two great venous 
 trunks, the superior and the inferior venas cavse. 
 
 Veins are much more numerous, and for the most part more 
 capacious than, arteries. In the extremities and the trunk they are 
 arranged upon two planes, a superficial plane and a deep-seated 
 one ; the latter accompanying the deep-seated arteries, the former 
 being immediately subjacent to the skin. The superficial veins are 
 more numerous and present greater variety, both as to number and 
 arrrangement, than the deep veins. Their smaller radicles anas- 
 tomose in the same manner as has been just described in the arteries. 
 
 A distended vein has a cylindrical form, which, however, in some 
 is interrupted here and there by a knotted appearance, caused by 
 its enlargement at the situation of its various sets of valves. The 
 coats of veins are essentially the same as those of arteries, but are 
 less developed. Proceeding from without inwards, we find, first, an 
 external tunic, composed of a thin layer of areolar ,tissue, answering 
 in structure, position, and function to the external coat of arteries. 
 Secondly, we find a fibrous tunic of which the outer portion consists 
 of circular fibres ; the inner portion of longitudinal fibres both coarse 
 and fine. The circular fibres' are but slightly developed ; they are 
 of the same nature as those in arteries and in th-e largtir veins, and 
 exhibit somewhat of the penniform disposition, which we have der 
 
CAPILLARY VESSELS. 659 
 
 scribed in the fibres of the arterial circular tunic. With them are 
 mingled unstriped muscular fibres in less quantity but of precisely 
 the same form and character as those in arteries. In the veins near 
 the heart, these circular fibres are replaced by similarly disposed 
 muscular fibres of the striped kin,d, continuous with and resembling 
 those of the auricles.* 
 
 The longitudinal fibres are well developed, consisting of the outer 
 coarse layer, which, in the large veins, as the cava ascendens, 
 are arranged in the form of large bundles, parallel to the long axis 
 of the vessel, and the internal layer or fenestrated membrane, which 
 in every respect corresponds to the internal longitudinal fibrous layer 
 of arteries. Upon this is placed the epithelium, which is precisely 
 the same as that of arteries. 
 
 The imperfect development in veins of a tunic possessing much 
 elastic power, like the circular fibrous coat of arteries, explains the 
 readiness with which these vessels collapse, and the general thin- 
 ness of the fibrous and areolar tunics accounts for the diaphanous 
 character of the venous wall. 
 
 In a large portion of the venous system peculiar processes, called 
 valves, are found projecting into the interior of the vessel at various 
 points. These processes are semilunar, attached by their convex 
 border to the wall of the vein, and free at their concave border, which 
 is a little thickened. They are disposed in pairs in immediate juxta- 
 position — sometimes there are three placed together. They are 
 most numerous in the superficial or subcutaneous veins ; and are 
 more so in the veins of the lower half of the body than in those of 
 the upper. The smallest veins are destitute of valves; as also are 
 the largest, as the cavse. The pulmonary veins, those of the liver, 
 and all the veins which contribute to the hepatic portal system, the 
 splenic and mesenteric veins, want valves. The renal veins are also 
 devoid of them. 
 
 The tissue of which these valves are composed is the same as the 
 longitudinal fibrous coat of the vein, covered by a layer of epithe- 
 lium ; the valves cannot be properly described as reduplications of 
 the inner membrane of the veins, they are processes of it.f 
 
 Of the Capillaries. — The system of vessels which is intermediate 
 to the veins and arteries, is called by the name capillary, from the 
 minuteness of their size. The finest arteries, and the finest veins 
 likewise, receive this appellation. But the true capillary system is 
 distinguished by a speciality of arrangement and an uniformity of 
 size, proper to each tissue or organ. 
 
 The capillary vessels may be examined in injected specimens, or 
 in recent transparent tissues, as in the pia mater, or in living trans- 
 parent tissues, as the web of the frog's foot, the mesentery or dis- 
 
 * Eauschel states that these fibres can be traced in the superior cava, as far as the 
 clavicle, and in the inferior as far as the diaphragm, and in the pulmonary veins as 
 far as the first subdivision of each. 
 
 f We have great pleasure in referring to an excellent article on the anatomy of veins, 
 in the 42d part of the Oyolopasdia of Anatomy and Physiology, by Dr. S. J. Salter, 
 
660 THE CIRCULATION OF THE BLOOD. 
 
 tended urinary bladder of the frog, the tail of the newt, the gill of 
 the tadpole, the tail or fins of fishes. 
 
 The diameter of the capillaries varies in different textures from 
 the y^'00 of an inch, to f^%js, according to the measurements' of 
 Weber. 
 
 The finest capillaries are found in the brain (Fig. 195, a) and in 
 the retina ; those of muscles, especially the cross branches which in- 
 tersect the fibres, are likewise very fine. Among the largest are 
 those of the lung and liver. 
 
 The capillaries form a network in each tissue or organ, which 
 derives its nourishment directly from them. 
 Fig. 194. and they exhibit an arrangement adapted to 
 
 ^^^^ the disposition of its proximate elements. In 
 
 ^P-^rvH.c'i^' the tissues which assume a fibrous form, as 
 ^^T^Iv^E^^lJ^ niiscle, nerve, fibrous tissue, the capillaries 
 P^)^^ r^^A?rVVr^ are disposed in lines parallel to the fibres, and 
 ™ ^ these parallel vessels are united at variable 
 
 intervals by cross branches, which pass at 
 right angles to the fibres. (See Figs. 47, 
 95, 161, 162, and 194.) In compound or in- 
 voluted mucous membranes, the capillaries 
 Arrangement of the capii- form a plcxus with morc or Icss circular 
 
 laries on the mucous mem- .< i.i I'f. l*^ 
 
 brane of the inrse intestine in mcshcs, which corrospond m lorm and size to 
 Ms^d^ameS""'"*''"''"" the arrangement of the membrane— good ex- 
 amples of this are found in the mucous mem- 
 brane of the stomach and of the intestines (Fig. 194). When the 
 elements of the mucous membrane are prolonged into processes, 
 forming villi or papillse, each villus or papilla is found to possess its 
 plexus or system of minute capillary vessels (Figs. 161 and 162). 
 In the simple raucous membranes, and in serous membranes,- the 
 plexus of capillaries placed in the submucous or subserous areolar 
 tissue exhibits large and irregular meshes. 
 
 In the compound tissues the capillaries have no direct relation 
 to the ultimate anatomical elements — that is to say, these minute 
 vessels do not ramify among the ultimate particles of the tissues. 
 
 It is with their proximate elements they connect themselves. 
 Thus in muscle the vessels lie between the fibres, and are separated 
 from the sarcous particles by the sarcolemma ; in nerve, in the same 
 way, they are separated from the nervous matter by the tubular 
 membrane ; and in the vesicular matter they play around the vesicles 
 and do not penetrate them. In most of the mucous membranes, the 
 basement-membrane is placed between them and the epithelium, 
 their nidus being the sub-basement tissue. So, also, with the serous 
 membranes. In bone, the finest vessels are very remote from a large 
 portion of the constituent osseous particles ; ramifying through 
 Haversian canals, they come in contact only with the osseous parti- 
 cles of those layers which immediately invest each canal ; or with 
 the periosteal or medullary layers. Vessels do not penetrate arti- 
 cular cartilage at all, which miist therefore draw its nourishment 
 from the vessels of neighbouring tissues. 
 
CAPILLARY VESSELS. 
 
 661 
 
 The finest capillaries, such as may be most easily examined in 
 connection with the pia mater of the brain, appear to consist of a 
 
 Fig. 195. 
 
 A. A capillary vessel from the vesicular matter of the human hrain. a. Homogeneous wall. 6. Nn- 
 cleusofthcwall. c. Red blood-corpuscle. 
 
 B, C. Different appearances of small arteries and veins of the human pia mater, a, a. Homogeneous mem- 
 brane. 6, b. Circular fibres, c, c. Oval nuclei of the internal epithelium, here about to cease, d, d. Trans- 
 verse indications of the circular fibres. 
 
 i>. Capillary artery from the mesentery of a rabbit. — Magnified 200 diameters. 
 
 homogeneous tissue, interrupted at short intervals by nuclei which 
 adhere to, or are imbedded in the wall of the vessel. (Fig- 195, a.) 
 These nuclei are mostly oval—sometimes nearly circular; most of 
 them have their long axes directed parallel to the course of the 
 vessel, but some are placed transversely. In some of these fine 
 capillaries, very faint indications of a circular striation may be 
 seen. 
 
 In some larger vessels, which perhaps may with more propriety 
 be regarded as capillary arteries, rather than as true capillaries, a 
 distinct arrangement of circular fibres may be seen. These fibres 
 are flat, uniform in diameter, devoid of nuclei, and in all respects, 
 but this, resemble the unstriped muscular fibres. 
 
 It had long been a question among physiologists, whether the 
 capillaries, had proper walls distinct from the tissues to which they 
 supplied blood. The microscope has settled this question in the 
 affirmative, for most of the tissues and organs of the body ; but it 
 may still be doubted whether the finest capillaries of the liver have 
 walls distinct from those cubical masses of epithelium which they 
 permeate. 
 
 Although it is the rule that an intermediate system of vessels 
 exists between, the arteries and veins, we find two remarkable excep- 
 tions to it. One is in the erectile tissue of the penis ; the other in 
 
662 THE CIRCULATION OF THE BLOOD. 
 
 the uterine circulation. In both these instances, the arteries com- 
 municate directly with the veins. In the penis, the ramifications of 
 the arteries pour their blood into the cells of the corpora cavernosa ; 
 in the uterus the small curling arteries of Hunter open directly into 
 large venous sinuses, ■which in the gravid uterus form an intimate 
 relation of contact with the villous processes of the placenta. These 
 points will be fully described in the chapter on Generation. 
 
 It is not improbable that further research may detect a direct 
 communication between arteries and veins, even in tissues, the 
 greatest part of which is furnished with a true capillary plexus. 
 In the cancellated structure of bone, and the diploe of the cranial 
 bones, it seems highly probable that the arteries communicate im- 
 mediately with the veins at many points. Mr. Paget* describes a 
 direct communication between the arteries and veins of the wing of 
 the bat, without any intermediate capillary plexus. f 
 
 Of the Heart. — This hollow muscular organ, which, like a forcing- 
 pump, drives the blood throughout the vascular system, varies in its 
 constitution, according to the complexity of the circulation, from a 
 simple muscular tube, such as the dorsal vessel of insects, to the 
 complex double heart of man, with its four cavities and its beautiful 
 apparatus of valves. 
 
 The dorsal vessel of insects is the most simple condition of the heart. It consists 
 of a muscular tube provided with certain valves, disposed like those of veins ; these, 
 hy affording an obstacle to the flow of the blood in one direction, determine tlie course in 
 which it is propelled by the contraction of the muscular wall, namely, towards the head. 
 It is situated along the middle of the back, whence its name. At the points which 
 correspond to the situation of the internal valves, it exhibits distinct constrictions, 
 which in some insects are so marked, that the vessel appears to consist of "a series 
 of slightly conical segments, partially sheathed one upon the other." (Owen.) The 
 
 * Lectures on Inflammation. 
 
 f The communication between arteries and veins by capillaries was not known 
 to Harvey. In his time, and for a long period afterwards, anatomists supposed the 
 blood to pass into the parenchyma of the tissues, whence it was received or withdrawn 
 by the veins. Malpighi (about 1687), by microscopic examination, first demonstrated 
 the intermediate capillary system in the lungs and urinary bladder of the frog. 
 Leuwenhoek afterwards (1729) pursued this investigation, and has given some good 
 illustrations of the capillaries examined in transparent parts during life. 
 
 Dr. Hales, in this country, many years later (1769), gave a very accurate descrip- 
 tion of these vessels, and denied altogether the idea of the intervention of a paren- 
 chyma, or, in his own words, of "glandular cavities." See his Hmmastalicks, p. 146; 
 § 9, vol. ii. W. Cowper, the distinguished myotomist, also made observations on the 
 capillaries of the transparent parts of warm-blooded animals, as the mesentery of a 
 dog, and the omentum of a cat. Haller threw great light upon the subject, and by 
 his facts and arguments, settled the question as to the direct continuity of arteries 
 and veins. Subsequently (1745), Lieberkiihn advanced our knowledge of the capil- 
 laries by his numerous injections, most of which are still extant at Vienna. In more 
 recent times, the distinguished Prochaska seems to have been the first to form a just 
 appreciation of the extent of the capillaries, and of their exact relations to the elements 
 of the tissues. His description of the disposition of these vessels, based upon the ex- 
 amination of Lieberkilhn's and his own injections, can scarcely be surpassed in the 
 present day. See the 9th chapter (devasis saguin, capillar.) of his Disquisitio Anat.- 
 Phys. Organismi Corporis Hum. ejusque Processus Vitalis. Vienna, 1812. Biohat, 
 indeed (1801), had erected these vessels into a system intermediate to that of the 
 arteries and of the veins, but no anatomist who compares the descriptions of the two 
 writers will hesitate to give to the former the merit of a more intimate practical know- 
 edge of the anatomy of these vessels. 
 
THE HUMAN HEART. 663 
 
 blood is propelled to the head through a tubular prolongation of the dorsal vessel, 
 ■which corresponds to the aorta ; this divides into numerous branches, which soon lose 
 themselves in the areolse, or diffused sinuses, which occupy the spaces between the 
 tissues of the insect ; from these sinuses, as from veins, the blood is returned to the 
 heart, and enters that tube at sevei-al points, at its posterior or caudal extremity, as 
 well as at several apertures which are found on each side of the dorsal vessel, near the 
 points of attachment of the valves. 
 
 In Crustacea, the heart is likewise of a very simple form. In some of the lower 
 Crustacea it is simply a muscular vessel, as in insects ; in the higher animals of this 
 class, as in crabs and lobsters, it forms a distinct muscular cavity, or ventricle, giving 
 origin to arteries, and pierced by several venous orifices through which the blood is 
 poured from the lai-ge venous sinuses which receive it on its return from the body. 
 It is situated, as in insects, beneath the enlargement of the back. 
 
 In the Molluscous classes the heart still retains great simplicity of structure. In the 
 lowest of these, as Tunicata, it is still a muscular vessel, propelling the blood through 
 arteries which ramify on the respiratory organ, whence it is taken up by veins, and 
 returned to the heart. In the compound Ascidians, we meet with the remarkable 
 phenomenon of the oscillation of the currents of the circulation, under the influence of 
 a change in the direction of the peristaltic contractions of the heart. 
 
 In the Acephalous moUusks, we first observe the subdivision of the heart into two 
 compartments, or cavities ; an auricle which receives the blood from the veins and 
 transmits it to a fusiform ventricle which drives it to the various parts of the body. In 
 one of the most highly organized of the Acephalous moUusks, Venus chione. Professor 
 Owen describes two auricles, which receive the blood from the veins of the gills, and 
 transmit it to the single fusiform ventricle, which is perforated by the rectum ; and in 
 the genus Area, the ventricle is divided into two cavities, having the rectum in the inter- 
 space. An artery is continued from each extremity of the ventricle, which distributes 
 the oxygenated blood over the viscera, the muscular system, and the mantle. The 
 heart of the Gasteropoda, likewise, consists of a single ventricle, which propels the blood 
 to the viscera and the muscular system of the body, and receives it from the branchiae 
 by one, and sometimes by two, auricles. , 
 
 In the Cephalopoda, the most highly organized mollusks, the general plan of the 
 heart is the same as in the Gasteropoda. The venous blood is received from all parts 
 of the body by great venous sinuses, which also take up the blood from the gills-» these 
 veins communicate with the heart, which consists of a single cavity, whence arise the 
 two' main arteries of the body, called the superior and infmor aorta. 
 
 In Fishes, the heart consists of two cavities ; one, large, loose, and thin-walled, 
 which receives the venous blood — the auricle; the second, thick and fleshy — the ven- 
 tricle, whence an artery springs, the first portion of which, dilated and surrounded by 
 thick muscular fibres, constitutes what is called the aortic bulb. 
 
 In the Batrachian reptiles there are two auricles, one which receives the blood from 
 the veins of the body — the systemic auricle ; the other, which receives it from the lungs 
 the pulmonic auricle. Both auricles communicate with a single ventricle, whence the 
 blood is propelled throughout the body, as well as to the lungs. In Serpents, the 
 heart presents a similar structure ; but in the Python the ventricle is divided by an 
 imperfect septum into two chambers, one of which communicates with the aorta, 
 the other with the pulmonary artery. In the Saurian reptiles, likewise, there 
 are two auricles, and a ventricle, which latter is subdivided into two or more cavities, 
 communicating with each other, and with certain arteries which spring from them — 
 excepting in the American alligator ( Crocodilus lucius), in which the existence of a 
 perfect septum creates two distinct ventricles. 
 
 In Birds and Mammals, the heart exhibits its highest development, consisting, as it 
 does, of two auricles and two ventricles, separated by a complete septum ; each auricle 
 communicating with its proper ventricle, and each ventricle giving rise to an arterial 
 trunk. 
 
 The human heart, in the adult subject, occupies an oblique posi- 
 tion in the thorax. Its apex is directed downwards, forwards, and 
 to the left side, and in the quiescent state corresponds to the inter- 
 yal between the fifth and sixth ribs. Its base corresponds to the 
 interval between the third or fourth, and the eighth«dorsal vertebrse, 
 from which it is separated by the parts contained in the posterior 
 
664 THE CIRCULATION OF THE BLOOD, 
 
 mediastinum. The base of the heart corresponds in front to the 
 sternum, at about the level of -the cartilage of the third rib. 
 
 The weight of the human heart -in the adult is about 11 ounces 
 for the male, and 9 ounces for the female (John Reid). 
 
 The two great arteries, the aorta and pulmonary arteries, spring 
 from the base of the heart in front. Posteriorly, the base is formed 
 by the auricles. 
 
 Both the anterior and the posterior surfaces of the heart are divided 
 into two, by means of a groove which corresponds to the anterior 
 and posterior margins of the septum of the ventricles, and which 
 passes from base to apex. The anterior groove contains the left 
 coronary a;rtery and vein ; the posterior, the right coronary artery 
 and vein. These are accompanied by nerves. A transverse groove 
 of considerable depth separates the auricles from the ventricles ; it 
 contains the coronary vein. All the grooves contain a greater or 
 less quantity of fat, which envelops the vessels and nerves lodged 
 in them. 
 
 Of the four cavities of the human heart, a ventricle and auricle 
 are on each side of the median groove. The ventricles are cone- 
 shaped cavities, their apices being directed towards the apex of the 
 heart, their bases corresponding to the auricles. The left ventricle 
 forms the apex of the heart. When the right ventricle is dilated, 
 its wall extends to, and contributes to form, the apex. Each ven- 
 tricle, when laid open, exhibits two distinct parts ; one, which com- 
 municates with the auricle by a large and free aperture, called the 
 auri^ulo-ventricular orifice, through which the blood passes from the 
 auricle into the ventricle; the other, called the infundibulum, a 
 funnel-shaped channel, which leads to the artery, and through which 
 the blood is propelled into it from the cavity of the ventricle. 
 
 The Valves of the Heart. — The auriculo-ventricular orifice on 
 each side is guarded by certain valves which, when not in action, 
 lie in the ventricle. The valve of the left side consists of two trian- 
 gular curtains, from the free margin and part of the ventricular 
 surface of which tendinous chords {chordae tendinese) pass to various 
 points of the wall of the ventricle. The bases of these curtains are 
 attached along a fibrous zone, which separates the auricle from the 
 ventricle. This valve is known by the name of the mitral valve, 
 and the orifice is called the mitral orifice; the larger curtain is that 
 which separates the infundibulum from the body of the ventricle. 
 The valve at the right auriculo-ventricular orifice, consists of three 
 portions, each having a pointed free extremity extending into the 
 ventricle, and connected to its wall by tendinous cords. Hence this 
 is called the tricuspid valve. The base of each segment corresponds 
 to the fibrous zone which intervenes between the auricle and ven- 
 tricle. Of the three curtains, of which the tricuspid valve consists, 
 the largest is anterior, and the next in size corresponds to the in- 
 fundibulum of the ventricle. 
 
 At each of the arterial orifices of the ventricles there are three 
 valves of semilunar form '(Fig. 199), which effectually close the 
 mouth of the artery against the regurgitation of blood into the ven- 
 
CAVITIES AND VALVES OF THE HEART. 665 
 
 tricle. Eacli of these valves has a convex border attached along 
 the fibrous zone, which connects the artery to the infundibulum of 
 the ventricle ; and a free concave border divided by a small round 
 body of fibrous tissue {corpus Arantii) into two equal portions. As 
 the blood flows from the ventricle, these valves lie up against the 
 wall of the artery ; but immediately the blood regurgitates towards 
 the ventricle, they are pushed by it in towards the mouth of the 
 artery; and their free margins, as well as a considerable portion of 
 their ventricular surfaces coming into close apposition, an effectual 
 barrier is formed against the return of the blood- The semilunar 
 valves of the aorta are essentially the same in all points of form 
 and structure as those of the pulmonary artery ; but those of the 
 aorta are the stronger. 
 
 The inner surface of the wall of the central cavity of each ven- 
 tricle is marked by very numerous fleshy columns (carnese columnse) 
 which project from it in relief. There are three orders .of them ; 
 first, the simple column in relief, which adheres throughout its whole 
 length to the wall of the ventricle ; secondly, the column, attached 
 at each extremity, but free in the interval, so that a probe or other 
 instrument may be passed beneath its middle part ; and thirdly, the 
 column attached at one extremity to the wall of the ventricle, and 
 projecting into its cavity by the other; these last are distinguished 
 from the others by the name of mnsculi papillares ; the chordse 
 tendinese spring from their free extremities, and are inserted into 
 the mitral and tricuspid valves, and one or two into the wall of the 
 ventricle. The infundibular portion of the ventricle is perfectly 
 smooth on its inner surface, and quite free from columnae carnese. 
 
 The auricles are thin-walled muscular bags, of irregular somewhat 
 cuboidal shape. Each communicates by a wide orifice, with its cor- 
 responding ventricle, and is separated from its fellow by a thin fleshy 
 septum, which, at its middle, is so thin as to be translucent. At 
 this situation an orifice existed during intra-uterine life, through 
 which a communication took place between ihe auricles {foramen 
 ovale, or Botalli). Each auricle has two distinct portions ; the sinus 
 venosus, which forms by far the greater portion of the bag, and the 
 proper auricle, or auricular appendage, which appears like an off- 
 shoot from the former, somewhat in the shape of a dog's ear, pro- 
 jecting forwards on each side of the aorta and pulmonary artery. 
 The veins pour their blood into the sinus venosus ; the auricular 
 appendage receives no bloodvessels, but its cavity communicates with 
 that of the sinus venosus. The right auricle receives the two great 
 veins of the system, and the great venous trunk of the heart, the 
 coronary vein. The superior vena cava opens into the upper angle 
 of the right auricle, passing downwards and forwards ; the inferior 
 cava opens into its lower angle, passing upwards, backwards, and 
 inwards. The coronary vein opens between the mouth of the infe- 
 rior cava and the auriculo-ventricular orifice. 
 
 On laying open the right auricle, by an incision extending between 
 the twp venae cavse, an intricate arrangement of muscular bundles, 
 called musculi pectinati, may be seen on its outer wall. These fleshy 
 43 
 
666 THE CIRCULATION OF THE BLOOD. 
 
 columns interlace freely with each other. On the septum a depres- , 
 sion exists about its middle, called the fossa ovalis, nearly surrounded 
 by a thick fleshy ring called the annulus ovalis. This marks the 
 situation of the orifice already alluded to, which existed during 
 intra-uterine life — i\e foramen ovale. 
 
 To the left of the orifice of the inferior vena cava, there is a val- 
 vular process which is another remnant of a mechanism adapted to 
 the circulation through the heart in intra-uterine life. This is the 
 Eustachian valve. It is a process of the inner membrane of the 
 auricle, of semilunar shape, which projects between the vena cava 
 and the auriculo-ventricular orifice, and in the foetus served to direct 
 the ascending current of blood through the foramen ovale into the 
 left auricle. The orifice of the coronary vein is guarded by a small 
 valve called the valve of Thebesius. Several small orifices are seen 
 scattered over the inner surface of the right auricle, called /oramma 
 Thebesii; some of these are the openings of small veins from the 
 wall of the auricle ; others merely lead into depressions between 
 the muscular fibres of the auricular wall. 
 
 Four veins pour their blood into the left auricle ; these are the 
 right and left pulmonary veins, two on each side. The left veins 
 open quite close to each other. The left auricle is placed in the 
 concavity of the aorta, and has lying in front of it the roots of both 
 the aorta and the pulmonary artery. 
 
 The inner surface of the left auricle is perfectly smooth, covered 
 with an opaque lining membrane, which appears somewhat thicker 
 than that of the right side. There is no appearance of musculi 
 pectinati in the left sinus venosus ; a few, however, exist on the inner 
 wall of the auricular appendage. Here and there some orifices are 
 seen, leading to depressions in the wall of the sinus venosus.. On 
 the left side of the septum, between the auricles, we observe traces 
 of the valve-like portions of the septum, which formed the immediate , 
 boundary of the foramen ovale during foetal life. 
 
 Of the Pericardium and Endocardium. — The heart is inclosed 
 in a fibrous bag, the fibrous pericardium, which is closely adherent 
 below, to the central tendon of the diaphragm, and above, becomes 
 continuous with the external tunic of areolar tissue, which invests 
 each of the large arterial and venous trunks that connect themselves 
 with the heart. This bag serves to fix the position of the heart, 
 and to prevent any sudden or extensive displacement, which might 
 interfere with its proper action. It consists almost exclusively of 
 white fibrous tissue. 
 
 Within this fibrous bag is a serous membrane, the serous pericar- 
 dium, which resembles in all points of arrangement and structure 
 the other membranes of its class. One portion of it invests the 
 internal surface of the fibrous pericardium, while the other covers 
 the heart, the line of reflection passing over the great vessels at the 
 base of the heart. 
 
 The cavities of the heart are lined by the endocardium, a mem- 
 brane continuous with and closely similar to the lining membrane of 
 arteries and veins. It .consists of a layer of epithelium placed on a 
 
STRUCTURE OF THE VALVES OF THE HEART. 667 
 
 stratum of fine fibres which exhibit minute wavings. The epithe- 
 lium appears to be extremely delicate, but the same in all its cha- 
 racters as that of the bloodvessels. It is so delicate, that to be 
 seen satisfactorily it must be examined in animals just killed. We 
 
 Fig. 196. Fig. 197. 
 
 H 
 
 JhM^i 
 
 Epithelium from the left auricle of the horse Kplthelium from the left 
 
 (ma{;nified 200 dia-ms.), showing the two forms ventricle of the horse, 
 
 of particles, the round and the pointed. — ^Magnified 200 diaxns. 
 
 observe two forms of epithelial particles, one soft, rounded, and 
 globular, the other somewhat compressed, and drawn out at opposite 
 poles into pointed or fibre-like processes (Fig. 196). It is difficult 
 to determine the precise relative position of these two forms of epi- 
 thelium, but it seems probable that the pointed processes are the more 
 deeply seated, and are- in immediate contact with the subjacent fibrous 
 layer, which here corresponds to the basement-membrane beneath 
 the epithelium of serous and mucous membranes. 
 
 The endocardium of the left auricle, and of the septum and auri- 
 cular appendage of the right auricle, is thicker and denser than that 
 in other parts of the heart. This is due to an increased development 
 of the fibrous layer beneath the epithelium, especially of its yellow 
 element. The precise meaning of the greater thickness of endo- 
 cardium in these parts of the heart is far from obvious. 
 
 Of the Structure of the Valves of the Heart. — The valves of the 
 heart are formed by processes of fibrous tissue covered by epithelium. 
 Between the aiiricle and ventricle, as well as at the mouths of the 
 aorta and the pulmonary artery, there are remarkable developments 
 of fibrous tissue. Interposed between each auricle and ventricle 
 there is a fibrous zone, or ring, to which the muscular fibres of the 
 auricle adhere on the one hand, 
 
 and those of the ventricle on ^ig- 1^8. 
 
 the other. The fibrous tissue is 
 prolonged inwards towards the 
 cavity of each ventricle, so as to 
 
 form three curtains on the right a portion of the aortic semilunar valve in the 
 
 . 1 /. ■ ■ -I T \ _ 1 J. dog. U. Surface of the valve. &. Nuclei of the 
 
 Side (tricuspid valve), and two on epithelium seen on its margin. 
 
 the left (the mitral valve). These 
 
 curtains are continuous with the chordae tendinse, which appear to be 
 inserted into them at their margins, and at various distances from 
 them on the surface next to the ventricle, but not at all on that 
 which corresponds to the auricle. They are covered on both surfaces 
 
668 
 
 THE CIRCULATION OF THE BLOOD. 
 
 Diagram of the semilunar valves of the aorta (after Mop- 
 gagni). a. Corpus Arantii on the free border, b. Attached 
 border, c. Orifices of the coronary arteries. 
 
 by epithelium, which, likewise extends over each of the chordae ten- 
 dinese. The fibrous tissue at the orifice of the pulmonary artery, 
 
 as well as at that of the 
 Fig. 199- aorta, consists of fibrous 
 
 cords arranged as three 
 festoons continuous with 
 one another, the convexity 
 of each being directed 
 towards the muscular tis- 
 sue of the infundibulum 
 of the ventricle, and its 
 concavity to the artery. 
 'On the right side, the 
 muscular fibres of the in- 
 fundibulum adhere to a 
 small portion of the centre of the convexity of each of these fes- 
 toons, and the circular fibrous coat of the artery seems closely 
 attached to the whole extent of the concavity. On the left side, the 
 fibrous festoons are connected partly with the muscular fibres of the 
 ventricle, and partly with the base of the inner curtain of the mitral 
 valve. The process of fibrous tissue extends from each festoon 
 towards the mouth of the artery, forming a loose semilunar curtain, 
 which is the basis of the valve. Each of these curtains presents a 
 convex attached border, and a concave free border, interrupted at 
 its middle, or bisected so as to form two concave borders, by a slight 
 thickening of the fibrous tissue, which forms a small spherical body 
 called the corpus Arantii ; it also has a convex surface directed 
 
 ■ towards the ventricle, and a con- 
 
 Fig. 200. 
 
 Fibrous tissue of a semilunar valve beneath the 
 Endocardium. 
 
 cave surface directed towards the 
 artery. The bundles of fibres 
 which constitute this fibrous basis 
 of each valve are disposed in fes- 
 toons, some parallel to the fibrous 
 festoon of the attached border ; 
 others, and the greatest number, 
 parallel to the smaller concave 
 borders on each side of the corpus Arantii. The fibres nearest the 
 attached border of the valve are considerably more developed than 
 those near its free margin. Indeed, for a space of about three or 
 four lines from the edge of the valve, the fibrous tissue is extremely 
 thin, and almost transparent. It is at this part of their ventricular 
 surface that the valves come in contact when they close the arterial 
 orifices, forming a mutual support to each other, and leaving the 
 main stress of the backward pressure of the column of blood in the 
 artery, to be borne by that portion of each valve which intervenes 
 between this and its attached border. Hence the greater thickness 
 of the fibrous basis in this situation. It is worthy of notice, that 
 the tissue of the endocardium is nearly, if not completely, identical 
 with the inner longitudinal fibrous tunic of arteries ; a fact which 
 
MUSCLE OF THE HEART. 669 
 
 explains the close similarity between the diseased states of the arte- 
 rial tissue, and those of the endocardiiim and the heart's valves. 
 
 Mechanism of the VaUes. — The valves are closed by the mere 
 hydraulic pressure of the blood. When the blood accumulates in 
 the ventricles, it pushes up the auriculo-ventricular valves towards 
 the auricle until their several portions come in contact with each 
 other, and close the orifice. But the simple contact of the curtains 
 of these valves with each other, would not prevent regurgitation ; 
 for the same hydraulic pressure which brings them in contact would 
 push them into the auricle, were it not that their margins are con- 
 nected with the walls of the ventricle and the musculi papillares, by 
 means of the chordae tendinese. When the ventricle contracts, it 
 draws firmly by means of the chordae tendinese upon the valves, and 
 not only keeps them closed, but causes them to exercise a considera- 
 ble pressure on the blood, which promotes its onward flow into the 
 artery. 
 
 Thus, by the attachment of the chordse tendinese to the several 
 curtains of the valves, not only is regurgitation of the blood op- 
 posed, but every part of the surface of each curtain is made to 
 press upon the blood, with a force equal to that of the contraction 
 of the ventricle, and to aid in propelling it through the artery. 
 Should, however, any imperfection of the valve exist, as by the im- 
 perfect apposition of its several portions, a chink remains between 
 their margins, and regurgitation takes place to a degree proportionate 
 to the size of the chink. 
 
 The semilunar or arterial valves are closed in their turn by the 
 pressure of the blood from the artery, backwards, towards the heart. 
 The blood forcibly driven back by the elastic reaction of the arterial 
 walls, slips between the wall of the artery and the valves, at the 
 sinuses of Valsalva, and throws the latter inwards, causing them to 
 meet and close the arterial aperture, thereby preventing regurgita- 
 tion into the ventricle. Thus the force by which the arterial valves 
 are closed, being the elastic reaction of the arterial walls, excited 
 by the expulsive force of the ventricle, bears a constant ratio to the 
 contractile power of the wall of the heart, and, therefore, the degree 
 of tension of the semilunar valves, and the sound which it develops 
 (the second sound of, the heart), enables us to form an estimate of 
 the expulsive force of the ventricle, which is often of great value 
 in practice. 
 
 Of the Muscidar Tissue of the Heart. — The heart is composed 
 of muscular fibres of very various sizes. In all essential points of 
 structure, these fibres resemble very closely the striped fibres of 
 the external muscles, differing from them, however, in the extreme 
 tenuity of the sarcolemma. They interlace with each other in an 
 intricate manner, and assume opposite directions on different planes, 
 thus forming a complicated interlacement of fibres, which adds 
 greatly to the power of resistance possessed by the organ. By this 
 interlacement the fibres of the heart adhere to each other, for be- 
 tween them there is little or none of that areolar tissue which exists 
 in considerable quantity in the external muscles, and unites their 
 
670 THE CIRCULATION OF THE BLOOD. 
 
 fibres and fascicles together. This interlacement takes place irre- 
 spective of any subdivision of the fibres. Nevertheless, it has re- 
 cently been noticed by KoUiker and other good observers, that a true 
 anastomosis does take place between adjacent fibres by the branching 
 of each fibre, and the fusion of neighbouring branches. A somewhat 
 similar branching and anastomosis of the ultimate muscular fibre 
 has-been observed at the surface of the tongue, an organ of which 
 the muscular structure is not unlike that of the heart. 
 
 The complicated disposition of the fibres of the heart on difi"erent 
 planes has, no doubt, the object of strengthening the walls of its 
 cavities, and insuring a uniformity and synchronousness in the con- 
 traction of all its fibres. This arrangement belongs particularly to 
 the ventricles, where such a mode of action is most needed. It may 
 be best demonstrated on hearts which have been subjected to long 
 boiling. By this process the fibre is hardened, and may be readily 
 torn in the direction of its course, and thus, by a little careful 
 manipulation, the connection of the fibres and bundles of fibres may 
 be unravelled. 
 
 The ventricles are covered by a thin layer of fibres common to 
 both. These may be traced, apparently emerging from the apex, 
 and spreading out over the anterior as well as the posterior surface 
 of the heart. At the apex, these fibres pass in to form a connection 
 with the fibres which form the innermost layer of the wall of each 
 ventricle ; from the same point these superficial fibres pass obliquely, 
 those of the posterior surface from right to left ; those of the ante- 
 rior surface rather in the direction from left to right. At the trans- 
 verse fissure, they sink in to attach themselves to the fibrous zone, 
 which separates auricles from ventricles. According to some anato- 
 mists (Reid and others), many of the superficial fibres do not pass 
 beyond the anterior longitudinal fissure, but sink into and become 
 incorporated with those of the septum. 
 
 If the fibres of the apex be traced inwards, they are found to 
 penetrate so as to form the innermost layers of the walls of the 
 ventricle, contributing likewise to form the carnese columnae, and 
 becoming attached to the fibrous structures of the ventricle, both to 
 the chordse tendinese, and the auriculo-ventricular zone. Some of 
 these fibres serve to connect opposite walls of the heart : thus, the 
 deep layer of fibres of the posterior wall of the heart receives fibres 
 from the superficial layer of the anterior wall, and reciprocally the 
 superficial layer of the posteribr wall contributes to the deep layer 
 of the anterior. But others of the superficial fibres are continuous 
 with the deep fibres of the same wall. These are the fibres which, 
 in passing from the superficial to the deep portion of the wall, make 
 a remarkable turn in figure of 8, of which the lower portion is very 
 small, as described and figured long ago by Lower. 
 
 Between the superficial and the deep or reflected portion of the 
 ventricular fibres, are some which have been described as the proper 
 fibres of the ventricles ; these pass round each ventricle in a circu- 
 lar direction, some obliquely, some at right angles to its axis ; they 
 form a sort of Lollow cylinder for each ventricle, which is attached 
 
NERVES OF THE HEART. 671 
 
 above to the fibrous zone of the auricles, and is open below towards 
 the apex. On the right side, a smaller number of circular fibres 
 embrace the infundibular portion of the ventricle, attaching them- 
 selves to the fibrous festoons of the pulmonary artery. 
 
 Of the Muscular Fibres of the Auricles. — In the auricles, we 
 find a common and a proper set of fibres. The former may be 
 traced along the anterior surface of both auricles, embracing them 
 like a belt, but not extending round to the posterior surface. The 
 latter are arranged in several circular or spiral bands, some of which 
 spring from the auriculo-ventricular zone, and return to it again, 
 and envelop the auricle before and behind, passing sometimes at 
 right angles to it, sometimes obliquely; others pass round the auricle 
 in a horizontal direction, and parallel to the auriculo-ventricular 
 zone. Each of the venous orifices of the auricles is surrounded by 
 a series of circular fibres (sphincterrlike) which are continued, as 
 already referred to, to a considerable distance along the trunks o^ 
 the veins, retaining in this latter situation just the same character 
 as at the auricle itself. This is a good situation for seeing the 
 branching and anastomosis of the fibres. 
 
 Nutrition of the Heart. — The heart is nourished by blood derived 
 from the aorta. Its arteries, the right and left coronary arteries, 
 are the first branches which spring from the aorta. They leave that 
 vessel just beyond the margins of the semilunar valves. The right 
 passes along the circular groove between the auricles and ventricles, 
 and sends a branch down the posterior median groove to the apex ; 
 the left passes along the anterior median groove, anastomosing at 
 the apex with the latter branches. Corresponding with the small 
 size and the oblique direction of the heart's fibres, are an extreme 
 closeness and an everywhere oblique sloping of the capillary network. 
 From this, venous radicles are formed at various points, and unite 
 into large veins, which are found in the grooves of the heart accom- 
 panying the arteries ; these veins terminate in the coronary vein, 
 which is lodged in the right portion of the circular groove, and 
 opens into the right auricle, close to the orifice of the inferior vena 
 cava. 
 
 Nerves. — The nerves of the heart are derived from the cardiac 
 branches of the pneumogastric nerve, and from the sympathetic. 
 These nerves form by their frequent anastomosis a plexus called the 
 cardiac plexus. It is situated upon the aorta and pulmonary artery, 
 just as they have issued from their respective ventricles, and is com- 
 monly described as consisting of two portions — the superficial cardiac 
 plexus, which corresponds to the concavity of the arch of the aorta, 
 and lies in front of the right branch of the pulmonary artery; and 
 the deep cardiac plexus, which is much the larger portion, and lies 
 behind the arch of the aorta, between it and the bifurcation of the 
 trachea. To the formation of these plexuses, branches derived from 
 the vagus and the sympathetic on both sides contribute. 
 
 The greatest part of the nerves which emanate from these plexuses 
 entwine round and accompany the right and left coronary arteries, 
 forming the anterior and posterior coronary plexuses. From these, 
 
672 THE CIRCULATION OF THE BLOOD. 
 
 nerves pass to the auricles and ventricles, but chiefly to the latter. 
 A ganglion, described first by Wrisberg, and called after him gan- 
 glion cardiacum Wrishergii, is generally found in front of the left 
 auricle, and behind the aorta. Scarpa has also described gaiigliform 
 enlargements of the nerves on the anterior surface of the ventricles, 
 to one of which, situated on the anterior surface of the horse's heart, 
 half-way down the anterior groove, he refers under the name of 
 " cardiaci sinistri ganglion insigne."* It is probable, however, 
 that none of these latter enlargements are truly ganglionic in their 
 nature. 
 
 Remak describes numerous microscopic ganglia on the nerves of 
 the heart of the calf. We have seen some of these small ganglia 
 upon the surface of the auricles in the calf's heart, although we have 
 not succeeded in detecting them on the surface of the ventricles, nor 
 in the substance of the septum, as delineated by Remak. We can 
 vouch for the truly ganglionic nature of those which we have seen 
 from the unequivocal existence of vesicular matter in them.f 
 
 Some elaborate dissections of the nerves of the heart have lately 
 been made by Dr. Robert Lee, J from which it appears that the heart 
 is more largely supplied with nerves than had been hitherto sup- 
 posed, and that a larger number go directly to the muscular struc- 
 ture of the heart, independently of the arteries, than had been 
 admitted by previous anatomists. Upon these nerves numerous 
 gangliform enlargements may be seen, which Dr. Lee figures as of 
 great size upon the nerves of the posterior surface of the heifer's 
 heart. 
 
 Our own dissections! enable us to confirm the general accuracy 
 of Dr. Lee's delineations, although we have not discovered so many 
 nor such large nerves as he depicts. We have likewise seen nume- 
 rous swellings on these nerves, which again we have failed to find, 
 either in such numbers, or of the same size as those represented in 
 Dr. Lee's plates. 
 
 The nerves are composed altogether of gelatinous fibres, and the 
 swellings do not contain vesicular matter ; and, therefore, do not 
 partake of the nature of ganglia. As filaments invariably pass 
 from these swellings into the muscular structure of the heart, we 
 woul(J regard them as resulting from that loosening of the consti- 
 tuent fibres of nerve trunks, which invariably takes place just before 
 branches are given oiF from them. 
 
 Of the Action of the Heart. — The action of the heart is remark- 
 able for its rhythmical character. Each of its cavities exhibits a 
 succession of contractions and dilatations, following each other with 
 the most perfect rhythm. Cavities of the same kind contract or 
 dijate simultaneously; but the ventricles are in contraction or systole 
 when the auricles are in dilatation or diastole, and vice versa. Fol- 
 
 * Scarpa, Tabulsc Anatomicss. Ticin. 1794, Tab. vii. iig. 1. 
 f Remak, Neurologischen Erlauterungen. MuUer's Arohiv. 1844. Tafel xii. 
 t Phil. Tran8. 1849. 
 
 I yie take this opportunity of acknowledging the valuable assistance of our friend 
 and pupil Mr. Samuel Martyn in these dissections. 
 
MOTIONS AND SOUNDS OF THE HEART. 673 
 
 lowing the course of the circulation through the heart, the auricles 
 having been filled from the veins which open into them, contract and 
 expel their blood into the ventricles, which, in their turn, contract 
 to drive the blood into the arteries. When the ventricles contract, 
 the heart experiences a peculiar tilting movement, by which its apex 
 is raised from the level of the sixth rib to the space between the fifth 
 and sixth, and at the same time it is rubbed more or less forcibly 
 against the wall of the chest. The wall of the ventricles is firmly 
 contracted at every point, and rendered hard and tense ; and, there- 
 fore, in its movement it communicates a considerable vibration to the 
 wall of the chest, giving rise to what is called the impulse. This 
 impulse is caused altogether by the systole of the ventricles, and 
 the consequent movement of the heart ; it is always directly pro- 
 portionate to the size of the ventricles, or to the extent of their 
 surface in contact with the wall of the thorax, and to the vigour of 
 their contractions. According to Valentin's experiments, the tilting 
 movement of the heart will take place even when thd apex has been 
 cut off, denoting that that phenomenon cannot be due to any recoil 
 consequent upon the resistance to the passage of the blood through 
 the great vessels, and that its true cause is the contraction of the 
 fibres of the ventricle. 
 
 Certain sounds accompany the heart's action, the accurate inter- 
 pretation of which has shed a flood of light upon the diagnosis of 
 diseases of that organ. On placing the ear over the region of the 
 heart in a healthy individual, the following phenomena may be per- 
 ceived ; first, a heavy, somewhat prolonged sound, which is synchron- 
 ous with the impulse, and is best heard over the heart's apex ; this 
 is the systolic or first sound; secondly, a short clicking sound imttie- 
 diately succeeding this ; it is synchronous with (but not caused by) 
 the diastole of the ventricles, and is called the diastolic, or second 
 sound ; it is best heard over the base of the heart near the root of 
 the aorta. After this the heart seems to pause, as it were to take 
 rest, and then follows the first sound again, followed instantly by 
 the second sound, and then the pause. The duration of the first 
 sound is about double that of the second, while that of the second 
 is equal to the pause. Thus, if the whole period of the heart's 
 action be divided into four parts, the first two would be occupied by 
 the first sound, the third by the second sound, and the fourth by the 
 pause. 
 
 Numerous experiments and observations have been made with 
 reference to the question of the signification of these sounds. We 
 must here content ourselves with stating the conclusions which we 
 think may be safely drawn from them. The first sound is composed 
 mainly of the muscular sound, generated by the contraction of the 
 ventricles, strengthened by that due to th6 sudden tension of the 
 auriculo-ventricular valves over the blood contained in the ventricles, 
 this tension being effected by thd contraction of the carnese columnse, 
 which is synchronous with that of the rest of the ventricular wall. 
 To these causes of sound may be added the impulse of the heart 
 
674 THE CIRCULATION OF THE BLOOD. 
 
 against the wall of the chest, and, perhaps, also the collision of the 
 blood against the orifices of the great vessels. 
 
 The second sound is due to the sudden tension of the semilunar 
 valves of the two great vessels, by the recoil of the columns of blood 
 injected into them by their respective ventricles. An experiment, 
 originally suggested by the late Dr. Hope, and repeated by seyeral 
 observers, proves this unequivocally. If in an animal whose respi- 
 ration is maintained by artificial insufflation, the heart's action being 
 thereby prolonged, a hook be introduced into the aorta so as to hold 
 back one of its valves, and leave a passage for the regurgitation of 
 a portion of the blood after each systole of the ventricle, a bellows 
 sound becomes generated, which usurps the place of the clicking 
 second sound. But the moment the valve is allowed to resume its 
 play, the natural click returns. 
 
 That this is the correct interpretation of the sounds of the heart, 
 is farther proved by the observation of the influence of various mor- 
 bid states of th'at organ upon them. Thus the first sound is modified 
 by whatever increases or weakens the intensity of the ventricular 
 systole, of the impulse, and of the tension of the auriculo-ventriculat 
 valves ; and when the latter takes place imperfectly, by reason of 
 the insufficiency of the valves to close the orifices, the first sound is 
 accompanied (not replaced) by a bellows-sound due to the regurgita- 
 tion of blood from ventricle to auricle. Again, should one or uipre 
 of the semilunar valves be so injured or altered as to prevent the 
 complete closure of the arterial orifice, at the time of the diastole, 
 the second sound is replaced by a bellows- sound, just as in the 
 experiment above detailed. 
 
 The regular succession of the two sounds and the pause, bearing 
 to each other the relative duration already mentioned, constitutes 
 the rhythm of the heart.* Sometimes the pause lasts for a much 
 longer period than a fourth of the whole, for as long or longer than 
 would suffice for the development of the other two sounds. Under 
 these circumstances the heart is said to intermit, and its rhythm is 
 interrupted. 
 
 At every systole of the heart an. impulse is felt in all the large 
 arteries of the body, which is synchronous with the contraction of 
 the ventricles, or so nearly that the difference is inappreciable, ex- 
 cept in very distant arteries, as those of the tarsus. This impulse 
 in the arteries constitutes the pulse — which will be fully described 
 by and by, and which, from its general accordance with the heart's 
 action, affords the readiest means of judging of the heart's rhythm, 
 and counting the frequency of its action. 
 
 When the rhythm of the heart is regular, this succession of first 
 and second sound (systole and diastole) and pause may be. heard a 
 certain number of times in a minute in each individual, and by a series 
 of observations, the scale may be formed showing the average fre- 
 quency of the heart's action at different periods of life in man. This is 
 shown in the following table, which is that formed by our able friend 
 
 * Some observers admit the existence of a short pause after the first soimd. 
 
ACTION OF THE HEART. 675 
 
 and colleague, Dr. Guy, from a comparison of numerous observa- 
 tions.* 
 
 TABLE OF THE AVERAGE FEEOUENOT OP THE HEAKT's ACTION, AND OF THE PULSE 
 AT DIFFERENT AGES. 
 
 At birth 140 
 
 iBfancy 120 
 
 Childhood 100 
 
 Youth 90 
 
 Adult age 75 
 
 Old age 70 
 
 Decrepitude 75-80 
 
 In general, the frequency of the heart's action and of the pulse 
 in the female exceeds that of the male, after the seventh year ; if 
 the average pulse of the adult male be stated at 70, that of the adult 
 female may be put down at 80. 
 
 The heart's action is seldom less frequent than 45 or 50 in health; 
 Heberden has counted it as low as 42, 30, and even 26, in healthy 
 males ; and Fordyce counted it in one case 26 in an old man, and 
 in another 20. In cases of chronic disease of the brain it falls very 
 low. We have ourselves counted it as low as 16 in one of these 
 cases for months together. 
 
 According to the researches of Drs. Knox and Guy, the frequency 
 of the heart's action (and the consequent frequency of the pulse) 
 varies at different periods of the day. It is most frequent in the 
 morning, and becomes gradually slower as the day advances. The 
 diminution is most marked at night. f 
 
 Posture exercises a remarkable influence on the frequency of the 
 heart's action. The law is, that the frequency is the greatest in the 
 erect position, next to that in the sitting, and least in the horizontal 
 posture. The following table has been framed by Dr. Guy from the 
 results of sixty-six observations in the male, and twenty-seven in the 
 female. 
 
 TABLE OF THE FREQUENCY OF THE HEART'S ACTION IN DIFFERENT POSTURES. 
 
 
 Standing. 
 
 Sitting. 
 
 Lying. 
 
 Differences. 
 
 Males 
 
 81 
 
 71 . 
 
 66 
 
 10, 5, 15 
 
 Females 
 
 91 
 
 84 
 
 80 
 
 7, 4, 11 
 
 These observations denote the curious fact that posture influences 
 the frequency of the pulse less in the female than in the male ; and 
 from another series of more numerous observations, Dr. Guy deduces 
 that the effect of change of posture on the frequency of the heart's 
 action in the male is more than twice as great as in the female. 
 
 The cause of this difference in the frequency of the pulse in dif- 
 ferent postures resides probably in the effort employed to maintain 
 the muscular contractions necessary to support the erect or sitting 
 postures. But careful experiments are still wanting to ascertain 
 whether a simple difference of posture, without muscular exertion, 
 
 * Art. Pulse, Cycl. Anat. and Phys. 
 
 f See Graves's Dub. Hosp. Rep. vol. vi., and Dr. Guy's art. Pulse, Cyolo. Anat. 
 and Phys. 
 
676 THE CIRCULATION OF THE BLOOD. 
 
 would develop a change in the frequency of the pulse. Those as yet 
 done by the revolving board, seem to have had reference only to the 
 exertion of muscular force in the production of the change of posture, 
 and not to that required for the continued effort to maintain the 
 attitude. 
 
 The Course of the Circulation in the Adult. — Taking the left 
 ventricle as the starting-poin,t for the circulation, we may describe 
 the blood as pursuing the following course. By the left ventricle 
 it is driven through the aorta into every artery of the body save the 
 pulmonary ; and having passed through the capillary system it enters 
 the venous radicles, and from them it passes to the venous trunks ; 
 it is at length returned by two great trunks, the superior and inferior 
 venee eavse, to the right auricle of the heart. This portion of the 
 circulation, from its traversing the whole system, except the lungs, 
 and from its occupying by far the largest part of the body, is called 
 the systemic or greater circulation. The venous blood, brought by 
 the great venous trunks to the right auricle, is expelled by that 
 cavity into the right ventricle, which drives it by the pulmonary 
 artery through the lungs to the pulmonary veins, through which it 
 passes to the left auricle, and so on to the left ventricle. .This portion 
 of the circulation, traversing only the lungs, and connecting the 
 right ventricle and left auricle, forms the lesser or pulmonic circula- 
 tion. 
 
 Of the Portal Circulation. — In general, the arterial blood passes 
 through a single system of capillaries and veins before it is returned 
 to the auricle. But there are two remarkable exceptions to this — one 
 in the portal circulation of the liver, the other in the kidneys. In 
 both these cases, the blood passes through two subsystems of capil- 
 laries after it leaves the arteries. Thus, as regards the hepatic cir- 
 culation, the blood conveyed to the intestines by the arteries, passes 
 through the intestinal capillaries into the intestinal veins, whence it 
 passes to the trunk of the vena portse, which again transmits it to 
 the hepatic capillaries, and thence to the hepatic veins, through 
 which it reaches the heart. A portion of the circulation, of which 
 the chief vessel is formed like a vein, and distributes its blood like 
 an artery, is called a portal circulation. A similar circulation is 
 found in the kidneys. The afferent arteries end in the Malpighian 
 tufts, whence the blood is taken up by the efferent veins, which 
 quickly break up like arteries into another capillary plexus surround- 
 ing the uriniferous tubes, and this plexus gives origin to the radicles 
 of the renal or emulgent veins. 
 
 The hepatic portal circulation, however, has several points of com- 
 munication with the systemic veins, or the inferior vena cava ; and 
 thus it happens, when from disease of the liver a considerable portion 
 of the portal system of that organ is obstructed or obliterated, that 
 a part of the blood from the intestinal canal finds its way into tribu- 
 tary veins of the cava, and returns by' that route to the right side 
 of the heart. The points of communication are between the veins 
 of the cava (left renal) and of the intestines, especially the colon 
 and the duodenum, and between the inferior mesenteric and the 
 
FETAL CIRCULATION. 677 
 
 hemorrhoidal veins, a fact which explains the freq,uent occurrence of 
 hemorrhoids in obstructions of the liver ; also between superficial 
 branches of the portal veins of the liver, and the phrenic veins, as 
 pointed out by Kiernan. 
 
 Bernard states that immediately after the portal vein has entered 
 the liver, and sometimes before, a certain number of branches are 
 given off from it, which, entering the liver, some superficially, others 
 more deeply, form communications with the vena cava. 
 
 Of the Foetal Circulation. — In the foetus in utero, the course of 
 the circulation is greatly modified, by reason of the inaction of the 
 lungs as aerating organs, and the consequent imperfect attraction of 
 the blood to them. During intra-uterine life, the aeration of the 
 foetal blood is effected by the placenta, a highly vascular organ, in 
 which the foetal blood is brought into a v6ry close relation to the 
 maternal blood as it circulates through the wall of the uterus. The 
 placenta, therefore, is in effect the lung of the foetus, and bears a 
 corresponding relation to its circulation. 
 
 A large portion of the^ foetal blood is carried to the placenta 
 through the umbilical arteries, which are continuations of the trunks 
 of the internal iliac arteries escaping from the body of the foetus 
 through the umbilicus. From the placenta the blood is returned to 
 the foetus by the umbilical vein, which is bound up with the umbilical 
 arteries in the umbilical cord, and enters the body of the foetus at 
 the navel. From this point the umbilical vein passes upwards and 
 to the right side under the liver, in its longitudinal fissure, and at 
 its transverse fissure it joins the sinus of the vena porta, through 
 which most of its blood is distributed to the liver. One large branch, 
 however, follows the course of the original trunk in the posterior 
 part of the longitudinal fissure, and opens into the inferior vena cava 
 just before that vessel communicates with the heart. This vessel is 
 the ductus venosus — a continuation of the trunk of the umbilical 
 vein — through which some of the blood returning from the placenta, 
 passes directly to the inferior vena cava, and to the right auricle of 
 the heart, without traversing the liver. 
 
 The blood thus received from the inferior vena cava (being that 
 from the body below the diaphragm), and also from the placenta, 
 does not pass into the right ventricle. A very interesting piece of 
 mechanism obstructs its passage in that direction, and favours its 
 flow across the right auricle through the foramen ovale, now freely 
 open in the septum, into the left auricle. This is the Eustachian 
 valve, which is situated between the inferior vena cava and the right 
 auriculo-ventrieular opening, and being connected with the anterior 
 and inferior part of the annulus ovalis, it brings the foramen ovale 
 into very close connection with the inferior vena cava, and forms an 
 imperfect septum towards the auriculo-ventrieular opening, quite 
 sufficient, however, to impede the flow of blood in the downward 
 direction. 
 
 Arrived in the left auricle, the blood is transmitted thence to the 
 left ventricle, and from this latter cavity through the arch of the 
 aorta to the head, neck, and upper extremities, whence it is returned 
 
678 THE CIRCULATION OF THE BLOOD. 
 
 by the venae innominatEe and by the superior vena cava to the right 
 auricle, which transmits it to the right ventricle. This latter ven- 
 tricle propels it into the trunk of the pulmonary artery, 'which, in 
 the foetus, divides into three vessels, not into two, as in the adult. 
 These are the two pulmonary arteries which separate from the trunk 
 at right angles, one for each lung ; and between them, following the 
 direction of the parent trunk, a large vessel, nearly as large as the 
 pulmonary artery itself, which forms a direct anastomosis with the 
 aorta, just below its arch. This is the ductus arteriosus, through 
 which the blood is transmitted directly from the right ventricle to 
 the commencement of the abdominal aorta. 
 
 Of the Forces by which the Blood is circulated. — The principal 
 force by which the blood is moved throughout the vascular system, 
 and returned to the heart, is that which is generated by the contrac- 
 tion of the left ventricle, or what is commonly called the vis a tergo 
 of the heart. 
 
 The force with which the heart propels the blood into the arterial 
 system has been variously estimated. Valentin considers that the 
 left ventricle exerts a force equal to one-fiftieth of the weight of the 
 body ; and, taking the muscular power of the right ventricle to be 
 half that of the left, he would estimate the power of the latter at 
 one-hundredth part of the weight of the body. This would give a 
 force of upwards of three pounds for the left ventricle for a man 
 weighing eleven stone, and half of that for the right. 
 
 Now Hales had long ago (1769) shown that, under the pressure of 
 a column of water nine feet and a half in height, fluid might be 
 made to pass from the carotid artery to the jugular vein through the 
 capillary system. And it is well known, to anatomists that, when 
 the vessels are free from coagulated blood or other mechanical ob- 
 struction, thin fluids may be transmitted by a very slight force from 
 the arteries to the veins. 
 
 Dr. Sharpey's experiments* indicate the exact amount of force 
 necessary for this purpose. A syringe with a hsemadynamometer, 
 to show the amount of pressure used, was adapted to the thoracic 
 aorta of a dog just killed, the abdominal aorta having been previously 
 tied immediately above the renal arteries, and the inferior vena cava 
 opened just as it passes through the diaphragm. Fresh defibrinated 
 bullock's blood was injected with a pressure of three and a half 
 inches of mercury, and passed through the double capillary system 
 of the intestines and the liver out of the veins with a full stream. 
 When the pressure was increased to five inches, the blood spirted 
 from the vein in a full jet. When the aorta was not tied above the 
 renal arteries, the same pressure sufficed to drive the blood through 
 the vessels of the lower extremities, and it was made to traverse 
 the capillary^ system of the .lungs, by a pressure of from one and a 
 half to two inches of mercury, so as to flow freely through the pul- 
 monary veins. Allowing one pound for every two inches of mercury, 
 
 * See Williams's Elements of Medicine, 3d Am. Ed. p. 154. 
 
THE CIRCULATION IN THE ARTERIES. 679 
 
 it would thus appear ttat a pressure of two pounds wa9 sufficient to 
 complete the circulation through the two abdominal capillary systems 
 — and of one pound for the pulmonary circulation. 
 
 Unless, then, we assume that there are obstacles to the flow of 
 blood through the vascular system, which, during life, are much 
 greater than those after death, it must be granted that the heart's 
 force,* which in man does not probably exceed three pounds, is sufii- 
 cient to drive the blood throughout the three systems of bloodvessels, 
 and to maintain the current of the circulation ; and that this force 
 alone is capable of producing all the grand phenomena of the circu- 
 lation. 
 
 It remains, then, to inquire whether the vis a tergo of the heart 
 is the sole force by which the circulation is maintained, or whether 
 we must not seek for the operation of other forces in order to ex- 
 plain its phenomena. To determine these points we must investigate 
 the phenomena of the circulation in each of the systems of blood- 
 vessels, and first in the arteries. 
 
 Phenomena of the Circulation in the Arteries. — By each contrac- 
 tion of the left ventricle a certain quantity of blood is pumped into 
 the arterial system, which is already full. Were the arteries and 
 other bloodvessels a series of rigid and inelastic tubes, there would 
 necessarily ensue upon this a discharge of blood, corresponding in 
 quantity and rapidity, from the opposite extremity of the system. 
 It is plain, however, from the slow rate of the venous circulation, 
 and the less capacity, of the auricles as compared with the ventricles, 
 that this does not take place in the vascular system ; nor, considering 
 the great extent of surface which the blood has to travel over in the 
 capillaries, and the consequent friction it has to encounter, can it be 
 expected that a quantity of blood should be discharged into the 
 capillaries equal to that which the heart injects into the arteries. 
 
 Room is obtained for each fresh quantity of blood (beyond that 
 which can be simultaneously expelled from the opposite extremity of 
 the vascular system), by the dilatation of the arteries under the 
 force of the heart. The eminently extensible and elastic character 
 of the arterial walls thus gives a peculiar .feature to the arterial cir- 
 culation, and is turned to good account in maintaining the flow in 
 that system of bloodvessels. In yielding under the force of the 
 heart the arteries become dilated at each systole, to the extent, ac- 
 cording to the experiment of Poiseuille upon the carotid of a horse, 
 of one twenty-third of its diameter, or of one twenty-second, in a 
 similar trial by Valentin on the carotid of a dog ; but which must 
 vary in difi"erent arteries and at difi"erent times with the force of the 
 heart, and the extensibility of the arterial wall. Poiseuille's ob- 
 servation, however, pointed out unequivocally the fact (previously 
 doubted), that the arteries are dilated at each systole of the heart.* 
 
 This dilatation of the arteries calls into play a force which in some 
 degree replaces the heart's force. The elastic arterial wall, stretched 
 
 * See the account of PoiBeuille's experiment, and a figure of his instrument in 
 Magendie's Journal, torn, ix., and also in Valentin's Phyaiologle, Bd. i. p. 449. 
 
680 THE CIRCULATION OF THE BLOOD. 
 
 by the contraction of the heart, reacts with a power which approxi- 
 mates more closely to that by which it was dilated according as the 
 arterial tissue is more or less elastic. The arteries are thus made 
 to contract upon their contained blood, and to drive it onwards or 
 from the heart, and backwards or to the heart. Its course, in the 
 latter direction, is speedily checked by the sudden and forcible 
 closure of the aortic valves under the pressure of the regurgitating 
 current. Therefore, the great mass of the blood rushes onwards 
 towards the capillary system — propelled first by the heart's impulse, 
 and, secondly, by the elastic reaction of the arterial walls. 
 
 This elastic reaction of the parietes of the arteries does not come 
 into play until the heart has ceased to contract and begun to dilate. 
 It is, therefore, synchronous with the diastole of the heart, and cor- 
 responds with it in duration ; so that, while the ventricle is inactive, 
 the blood in the arteries is still being pressed upon by the reacting 
 arterial walls. Thus the blood is ever moving onwards throughout 
 the arterial system, during the diastole, as well as during the systole 
 of the heart ; and the jerking impulses communicated to it by the 
 successive contractions of the ventricle, are gradually converted into 
 that continuous uniform forward movement, which is observed under 
 ordinary circumstances in the ultimate arterial ramifications, the 
 capillaries, and the veins. 
 
 An analogous application of the reacting force of an elastic agent 
 to convert a jerking movement into a continuous stream is found in 
 the mechanism of the fire-engine, and of the organ. In the one, 
 water, in the other, air, is forced into a chamber in which air already 
 exists. This air undergoes compression by the sudden introduction 
 of a new quantity of water or air. Its elasticity causes it to react, 
 and thus to supply an expulsive force during the subsidence of the 
 action of the piston in the one case, and of the bellows in the other.* 
 
 The heart, by its propulsion of blood into the arterial system, not 
 only dilates the arteries, but elongates them likewise. This is gene- 
 rally better seen than their dilatation, but it is most apparent in 
 arteries which are curved. Under the influence of the heart's systole 
 the curves are distinctly altered, so as to form segments of larger 
 
 * This explanation of the influence of the elastic reaction of the arterial wall in 
 promoting a continuous stream, and converting the jerking current of the blood in 
 the large arteries into a uniform one in the small ones, is very commonly attributed 
 by modern writers, to Weber. English physiologists ought not to have overlooked 
 John Hunter's remarks (on the Blood, &e. 4to ed. p. 129), nor Sir C. Bell's observa- 
 tions in his Animal Mechanics, p. 44. But the following passage from Hales will 
 show that that able observer held much the same views long prior to either of those 
 last named. * * * " The blood in the arteries," he says, "being forcibly propelled 
 foiTvard, with an accelerated impetus, thereby dilates the canal of the arteries, which 
 begin again to contract at the instant the systole ceases ; by which curious artifice of 
 nature, the blood is carred on in the finer capillaries, with an almost even tenor of 
 velocity, in the same manner as the spouting water of some fire-engines is contrived 
 to flow with a more even velocity, notwithstanding the alternate systoles and diastoles 
 of the rising and falling embolus, or force ; and this, by the means of a large inverted 
 globe, wherein the compressed air alternately' dilating or contracting, in conformity to 
 the workings to and fro of the embolus, and thereby impelling the water more equally 
 than the embolus alone would do, pushes it out in a more nearly equal spout." — ITama- 
 staticks, p. 22, § 26. 
 
THE CIRCULATION IN THE ARTERIES. 681 
 
 circles, a motion is communicated to the artery, and a change of 
 place results ; and straight arteries, which are more or less confined 
 by the superjacent parts, become slightly curved under the same 
 force. Thus, in the course of time, the arteries, especially those of 
 parts to which by reason of a more active nutrition in them there is 
 a considerable aflBux of blood, assume a tortuous form, as may be 
 seen in the temporal and radial arteries of old persons, and in the 
 spermatic artery of the bull. 
 
 The Pulse. — When the finger is applied to an artery during life, 
 it is felt to beat or pulsate in correspondence with the systolic 
 actions of the heart, so that the number of pulsations in the artery 
 corresponds exactly with the number of beats of the heart, and, 
 if an occasional interruption in the heart's action takes place, or 
 what is called an intermission, there will be at the same time a 
 failure in the beats in the artery. 
 
 This phenomenon is called the pulse. From their contiguity to 
 the heart, it is always present in arteries ; but it may occur in veins 
 under circumstances to be explained hereafter. It is due to the same 
 cause which occasions the blood to fiow per saltum, or by successive 
 jets, from a divided artery. That cause arises out of the manner in 
 which blood is pumped into the arterial system by successive jerks. 
 Each jet of blood creates a wave which moves along the whole arte- 
 rial system. The same phenomenon may be observed, if water be 
 injected by successive jerks into a narrow channel already full or 
 nearly full, and open on the surface. Each fresh jet will create on 
 the surface of the water in the channel a wave, which may be followed 
 to its most distant extremity. This wave, even in a rigid tube, if 
 sufiSciently forcible, would communicate to the wall of the tube a thrill 
 or vibration indicating the course which the wave takes. But in an 
 elastic tube which yields under the injecting force, the phenomenon 
 is more distinctly perceived as the tube dilates under the pressure 
 of the advancing wave. 
 
 It is important to notice that the phenomenon of the pulse in arte- 
 ries is due solely to the wave excited by each successive injection of 
 blood into the arterial system from the heart. The walls of the ar- 
 teries have nothing to do with the causation of the pulse, but may 
 render it more or less distinct according as they are more or less 
 yielding. 
 
 The character or quality of the pulse will depend primarily and 
 essentially upon the force of the heart — secondly, upon the integrity 
 of the mechanism by which that force is directed so as to drive the 
 blood into the arteries — thirdly, upon the quantity of blood in the 
 vascular system — and, fourthly, upon the condition of the arterial 
 wall, according as it is apt to oppose or to yield before the wave 
 caused by the heart's action. By reference to these points, we may 
 explain the various conditions of the pulse observed in practice. 
 Thus a weak heart, or a contracted arterial aperture, or a small sup- 
 ply of blood, will each equally produce a small pulse; while a cer- 
 tain power of heart, and an open unimpeded state of the arterial 
 aperture, with a full supply of blood, are quite necessary to the 
 44 
 
682 THE CIRCULATION OF THE BLOOD. 
 
 formation of a large round pulse. But the qualities of softness or 
 fulness, of hardness or wiryness, of compressibility, of incompressi- 
 bility, all which are familiar to the tactus expertus of the practical 
 man, are determined by the yielding or the resisting condition of the 
 arterial wall. 
 
 Contractility of Arteries. — Arteries possess a power of contraction 
 in virtue of the large quantity of elastic material which enters into 
 the constitution of their wall; but this is a contraction which may 
 occur in a dead as well as in a living artery, and which simply serves 
 to restore to its medium dimensions an artery previously distended 
 or stretched. They have, however, also a power of active contractil- 
 ity, which ceases with life, which is capable of being called into play 
 not only by distension, but by other appropriate stimuli, and which 
 can diminish the size of the vessels far beyond what their mere elas- 
 ticity could effect, and even against the influence of the elastic force.' 
 This contractile power is due to the presence of unstriped muscular 
 fibres in the arterial wall. The demonstration of these fibres in the 
 walls of arteries by the microscope leaves no more doubt of the exist- 
 ence of a muscular contractile force in them than of its existence in 
 the oesophagus or the intestine. Experiment anticipated anatomical 
 research in pointing out that arteries contract as tubes do whose 
 walls contain muscle, and it also indicated the peculiar manner in 
 which the muscular fibres of arteries act. Under the influence cf a 
 stimulus even of so slight a nature as exposure to the air, an artery 
 may be observed to contract very gradually, and to become very 
 much diminished in size. Thus, in one of Hunter's experiments, the 
 posterior tibial artery of a dog was laid bare ; it was observed, in a 
 short time, to be so much contracted, " as almost to prevent the 
 blood from passing through it, and when divided the blood only 
 oozed out from the orifice."* 
 
 Mechanical stimulation, applied to a living artery, such as gentle 
 friction with the point of a scalpel or needle, excites in its wall a, 
 slow and gradual contraction at the poinit stimulp,ted, so that it 
 appears constricted at that point. We have, by stimulating an 
 artery in this way, at several points at some distance from each 
 other, produced quite a moniliform appearance of it, causing a series 
 of constrictions separated by portions in which the size of the 
 artery was little altered. Verschuir was among the first to observe 
 the effects, of mechanical stimulation . upon arteries, and he has 
 recorded the results of his observations in his Inaugural Dissertation 
 De Arteriarum et Vena rum vi irritabili, published in 1766 ; and 
 numerous experiments of a similar kind were performed in this 
 country by our friend. Dr., now Sir Charles Hastings, which are 
 detailed in his treatise on Inflammation of the Mucoiis Membrane 
 of the Lungs, published in 1820. 
 
 The galvanic stimulus is also capable of producing cohtractions 
 in arteries, but it requires to be repeatedly renewed before the effect 
 is manifest. The most striking results from the application of this 
 
 * Hunter on the Blood, &c. 4to. ed. p. 114. 
 
THE CONTRACTILITY OF ARTERIES. 683 
 
 kind of stimulus, were obtained by the Webers, in their experiments 
 ■with the rotatory magneto-electric instrument. The shocks were 
 applied to the small mesenteric arteries of frogs, and a diminution 
 of their diameter to one-third was produced, in from four to ten 
 seconds ; and the contraction inereased under the continuance of the 
 stimulus, until the caliber of the vessel became from three to six 
 times smaller than at first, so that only a single row of blood-cor- 
 puscles could pass through it ; at length the vessel became completely 
 closed, and the circulation through it stopped. 
 
 From the combined evidence of anatomy and experiments, then, 
 it can no longer be doubted that arteries possess an inherent con- 
 tractility, in virtue of the presence of unstriped muscular fibres in 
 their tunics. It remains to inquire, in what manner this power 
 influences the circulation in the arterial system. Does it help to 
 propel the blood? This question may be answered in the negative. 
 The manner in which arterial trunks taper towards their distal 
 extremities, renders it mechanically impossible that the contraction 
 of circular muscular fibres around them would drive the blood on- 
 wards unless some valvular apparatus checked its passage backwards 
 or towards the heart. It is by reason of the existence of such an 
 apparatus at the mouth of the aorta that the elastic coat of the 
 arteries by its reaction propels the blood. But the muscular coat 
 would not contract simultaneously at all points as the elastic coat 
 does. It would, as in the oesophagus and intestines, act in successive 
 portions — and the artery would, as in those tubes, be almost or al- 
 together obliterated at the point of contraction. It is easy, however, 
 to show that no such vermicular action . takes place in the arteries, 
 nor can it occur in tubes which, like them, are always and at all 
 points filled. 
 
 It seems most probable that the contractile power of the arteries 
 exercises a regulating influence upon the flow of blood through them. 
 Its influence in this respect has long been recognized by practical 
 men, under the name of tone or tonic power. It restrains within 
 due bounds the distension of the arteries, limits the quantity of blood 
 in each artery, adapts the size of the artery to the volume of its 
 contents, and offers a certain amount of opposition or antagonism to 
 the force of the heart. 
 
 It is owing to the resistance afforded by this contractile power 
 of arteries to the passage of fluid into them, that the anatomist will 
 fail to inject a tissue completely, if he attempt it too soon after 
 death. The well known experiment of John Hunter, on the pla- 
 centa, shows how long the contractile power will remain in the 
 arteries of a part after its separation from the system, or after 
 death. In a woman delivered on Thursday, the navel-string was 
 separated from the foetus in the usual way, by tying the cord in 
 two places, and dividing it between them-^thus the blood was re- 
 tained . in the vessels of the cord and placenta. On the Friday 
 morning, a ligature was placed an inch below the lowest of those 
 ligatures, and that inch was cut off. The blood immediately gushed 
 out, and, on watching the cut ends of the vessels, Hunter observed 
 
684 THE CIRCULATION OF THE BLOOD. 
 
 the arteries contracting with the whole of their elastic power, which 
 took place immediately. The next morning (Saturday), on examin- 
 ing the mouths of these arteries, they were found quite closed up, so 
 that in twenty-fotr hours the muscular coat had contracted to such 
 a degree as to close up the area of th« artery. On Saturday morning 
 the experiment of Friday was repeated, with another inch of the 
 cord, with precisely the same results, but after its repetition on the 
 Sunday, it was found on the Monday that the mouths of the arteries 
 remained open, their muscular coat having by that time lost its con- 
 tractility.* 
 
 The difference in the results obtained by Hales, as regards the 
 velocity with which certain fluids passed through the bloodvessels, 
 is referable to the contractile power of the arteries. Thus, while 
 warm water, injected into the bloodvessel of a dog's bowels, passed 
 in fifty-two seconds, the same quantity of common brandy took sixty- 
 eight seconds; cold water (fourteen degrees above freezing) was 
 eighty seconds longer in passing than the same quantity of warm 
 water just before. A strong decoction of bark took much longer to 
 pass through the vessels than the same quantity of warm water. 
 Sixteen pots, of equally warm decoction of bark, were successively 
 poured in, the first of which passed in seventy-two seconds ; the 
 sixteenth, "as the vessels grew more and more contracted by the 
 styptic quality qf the decoction," was 224 seconds in passing.f * 
 
 This contractile power in the walls of arteries (their tone or pas- 
 sive contraction) is capable of modifying considerably the character 
 of the pulse. When it is feeble, the artery offers but slight resist- 
 ance to the entrance of the blood, and it therefore yields more com- 
 pletely under the force of the heart. Hence, fulness of pulse and 
 feebleness of muscular power of tone in the wall of the artery, are 
 apt to go together. On the other hand, an exalted muscular 
 power or tone in the wall of the artery, by contracting the arterial 
 tube, and resisting the flow of blood, would cause a small, hard, 
 and even a wiry pulse ; or a similar effect might be produced by 
 an irritating fluid, as a diseased blood, passing through the artery. 
 Again, failure of the tonic property of the arterial wall causes a 
 compressible pulse ; an excited or well-developed tonic power, will 
 case an incompressible pulse. 
 
 Of tlie Force of the Heart. — The blood encounters considerable 
 obstacles to its passage through the vascular system, which tend to 
 bring it to a state of rest. The friction against the inner sur&ce of 
 the vessels, and the resistance of the elastic and muscular elements 
 of their walls to distension, must be overcome by any force capable 
 of keeping up a continual renewal of the supply of blood to the several 
 organs. Moreover, a certain rate of movement must be maintained 
 in the blood's current. The attainment of these objects is clearly 
 
 * Hunter, loc. cit, p. 116. The muscular fibres of the arteries of a part recently 
 dead pass into the state of rigor mortis, like that of other muscles, which will last a 
 certain time; the proper period for anatomical injections is either before the rigor 
 mortis has come on, or after it has ceased. 
 
 j- HsemastaticUe, p. I'M, et aeg. 
 
THE FORCE OP THE HEART. 685 
 
 provided for, in the main, by the action of the heart, and that living 
 pump is doubtless endowed with energies sufficient to drive into 
 the bloodvessels renewed supplies of blood, 'with a force and a velo- 
 city exactly adapted to overcome such natural obstacles as the action 
 of the vascular system must naturally create. 
 
 To estimate the force of the. heart, we must ascertain the pressure 
 which the blood exercises on the walls of the bloodvessels during 
 life, and we must measure the rate at which it flows through them. 
 
 A fluid flowing through a tube exerts a double force, one in the 
 direction of the long axis of the tube, the force of the stream, of 
 which the velocity gives a measure, and another, which is the pres- 
 sure of the fluid against the wall of the containing tube or the lateral 
 pressure. This latter force is always proportionate to the resistances 
 which the fluid has to encounter to its flow. The longer the tube, 
 through which the fluid passes, the rougher its walls, the narrower 
 the opening through which it escapes ; and the more glutinous the 
 fluid, the greater the lateral pressure.* 
 
 A tube fixed into the walls of the tube through which the fluid 
 flows, and at right angles to it, aff'ords a simple means of measuring 
 the lateral pressure, by the height to which the fluid will rise in it. 
 By equally simple means we may measure both forces, if the measuring 
 tube be prolonged into the other tube with its orifice opposite to the 
 stream. The height which the column of fluid will attain in a tube 
 so arranged, will indicate the altitude from which it must have 
 fallen, to acquire the velocity and force with which it streams 
 through the main tube. 
 
 Pitot, a distinguished ^French engineer, who lived about the 
 middle of the last century, employed a tube of this kind for mea- 
 suring the velocity of the stream in rivers. The tube was bent at 
 a right angle, into two unequal branches, and the smaller or hori- 
 zontal branch was immersed in the stream with its mouth opposed 
 to it. The height of the column sustained in the tube afforded a 
 measure of the force and velocity of the stream, that height being 
 such as the water must have fallen from, in order to have acquired 
 the same velocity. 
 
 Hales adopted a similar method to measure the pressure of the 
 blood in the arteries. He inserted into the left crural artery of a 
 mare, a brass pipe, whose bore was one-sixth of an inch in diameter; 
 and to that, by means of another brass pipe, he fixed a glass tube 
 of nearly the same diameter, which was nine feet in length. When 
 the blood was allowed to flow into this tube it rose in it to a height 
 eight feet three inches above the level of the left ventricle of the 
 heart. After considerable loss of bloodj however, the power of 
 maintaining a column of this height ceased, and the blood rose, after 
 the successive bleedings to seven, six, five, four, and at length, to two 
 feet four inches. 
 
 In a second experiment, exactly the same, excepting that it was 
 made on a horse of more vigour than the subject of the previous one, 
 
 * See Volkmann, die Hoemodynamik naoli Versuchen. Cap. i. Leipzig, 1850. 
 
686 THE CIRCULATION OF THE BLOOD. 
 
 the blood rose to nine feet eight inches, and fell subsequently, after 
 successive bleedings, in the same manner as in the first experiment. 
 A third experiment made upon a mare, consisted in fixing the brass 
 pipe into the carotid artery towards the heart, and to that the wind- 
 pipe of a goose, on account of its pliancy, and to the other end of 
 that a glass tube, twelve feet nine inches long. The blood rose in 
 the tube to nine feet six inches, and behaved, in all respects, much 
 in the same way as in the former experiments. And afterwards. 
 Hales experimented in the same way on the sheep, the deer, the dog, 
 with results essentially similar, but varying with the size and general 
 power of the animal. • 
 
 Hales estimated the force of the left ventricle of the heart at the 
 moment of its systole, by multiplying the area of its inner surface 
 into the height of the column of blood in the tube which it was capa- 
 ble of sustaining, calculating also the absolute weight of the quantity 
 of blood which formed that column. Prom these data he concluded 
 that the contraction of the left ventricle of the horse's heart was 
 capable of sustaining a weight of 113 lbs., that of the sheep 36.56 
 lbs., that of the dog 33.61 lbs., when the animal weighed 52 lbs., 
 and 19.8 and 11.1 lbs. in dogs weighing respectively twenty-four and 
 eighteen pounds. 
 
 Poiseuille improved upon the method of Hales's experiments, and 
 obviated some objections to them. He employed an instrument 
 which he called the hsemadynamometer. (Fig. 201.) This consisted 
 of a glass tube bent so as to form a horizontal (B") and two perpen- 
 dicular (BB') portions. The horizontal portion is capable of being 
 adapted by means of brass tubes of various size to arteries or veins, 
 however different in caliber. The tube is -attached to a board ( AA'), 
 on which a scale is marked. To use it, mercury is poured into the 
 perpendicular branches of the tube, and will, of course, stand at 
 the same height in each when the instrument is kept in the per- 
 pendicular. 
 
 In order to prevent the coagulation of the blood, which, by caus- 
 ing it to adhere to the sides of the tube, would complicate the experi- 
 ment (a point not provided against in Hales's experiments), a quantity 
 of a strong solution of carbonate of soda is poured into the horizontal 
 branch, and will therefore rest upon the column of mercury in the 
 nearest vertical branch. 
 
 The instrument is now adapted by means of a pipe provided with 
 a stopcock (F) to the artery in which the blood is to be measured. 
 On opening the stopcock the blood rushes into the horizontal tube, 
 mingles with the alkaline solution, and pushes down the mercury, in 
 the vertical tube B', that in the tube B rising to the same extent as 
 the first is depressed. The rise and fall of the mercury in each ver- 
 tical branch can be measured on scales placed behind them, and -as 
 the rise and fall are equal, the double of either will give the height 
 of a column of mercury which the force of the stream of blood is 
 able to maintain. By causing the blood to press upon a column of 
 mercury, Poiseuille got rid of the necessity of having a very long 
 tube as used by Hales. 
 
THE FORCE OF THE HEART. 
 
 687 
 
 Hales inferred, from his observations on the lower animals, and a 
 comparison of the measurements of their arteries with those of man, 
 
 Fig. 201. 
 
 PohefuHMs hcsmadynamfymeter as slightly modified hy VoVcmann : AA' the board to which the bent glass 
 tube (BB'B'O is attached. CCC" a tin tube which is fixed through a cork (D) air-tight to the horizontal 
 branch of the glass tube. E an opening with a stopcock in this tube. F a conical tube which may be 
 introduced into an artery or vein. This is provided with a stopcock which serves to regulate the admi^ 
 sion of the blood into the tube of the hSBmadynamometer. G H G' an arm of wood connected with the 
 board which serves to support the tin tube, and so protect the horizontal branch of the glass tube. 
 
 that the force of the heart in the human subject is capable of sus- 
 taining in a tube fixed in the carotid artery a column of blood 7|- 
 feet high, and calculating the surface of the left ventricle at 15 
 square inches, he concludes that, when it first begins to contract, the 
 ventricle supports a pressure of 51.5 lbs. of blood. And Poiseuille 
 assigns 4 lbs. 4 oz. as indicating the force which the left ventricle 
 exerts at the moment of its contraction in propelling the blood into 
 the aorta. 
 
 Volkmann combats the grounds upon which Poiseuille's calculation 
 was formed; and assigns the heart's power as equivalent to the force 
 which sets the stream of blood in motion, and gives it its proper ve- 
 locity, and also to that which enables it to overcome the obstacles it 
 has to encounter. This latter power is determined by the pressure 
 in the artery, which is found in the mean, in the carotid artery of 
 mammals, to be capable of supporting a column of mercury of 200 
 millimetres, or about 7 inches ; or a column of blood of 2700 milli- 
 
688 THE CIRCULATION OF THE BLOOD. 
 
 metres (mercury being 13.5 times heavier than blood) ; whilst the 
 former force, taking the actual velocity of the blood in the com- 
 mencement of the aorta at 400, and in the carotid at 300, would be 
 represented by a column of blood a little more than 8 millimetres in 
 height. Thus it would appear that the force of the heart may be 
 expressed by the following formula: — 
 
 H== 8.2 + 2700 millim. 
 
 or that it is capable of supporting a column of blood nearly 9 feet 
 in height, which is equivalent to a column of mercury of about 8 
 inches.* 
 
 That the heart's force is extended to the whole arterial system, 
 and must therefore be highly instrumental in maintaining the circu- 
 lation through it, is shown by the fact that a considerable pressure is 
 exerted in the various arteries, which can be measured by the hsema- 
 dynamometer, or by other instruments. Poiseuille had affirmed that 
 the pressure in all the arteries was the same, a column of mercury 
 of the same height being supported by the blood's pressure in all.f 
 This doctrine, however, is at variance with every obvious hydrody- 
 namic fact, as also with the results of other observations, of which 
 those of Volkmann seem the most trustworthy. Volkmann shows 
 that a fluid flowing through a system of tubes has to encounter at 
 the point of its entrance into it the sum of the resistances wh^ch 
 oppose it throughout the entire area, and these resistances determine 
 the amount of pressure needed for its propulsion. Applying this to 
 the arteries, it is plain that in them the blood has to encounter the 
 resistances in the capillaries, in the small arteries, in the middle- 
 sized arteries, and in the arterial trunks — a fact, which, by assigning 
 to the resistance in each of these regions the symbols x, y, z, w, x 
 representing that in the arterial trunks, and the other letters that 
 in each of the remaining segments of the system, may be thus ex- 
 pressed, P (being the pressure in the commencement of the arterial 
 tree) = x4-y + z + i^, whence it is plain that the amount of pres- 
 sure cannot be the same in all parts of the arterial system, but dimi- 
 nishes steadily as the artery is more distant from the heart. 
 
 Spengler's experiments so far disprove the accuracy of Poiseuille's 
 statement as to show that the pressure of the blood difl"ers consider- 
 ably in different arteries ; but in the greater number of his observa- 
 tions the pressure appeared to be greater in the arteries more distant 
 from the heart, some showing a difference of 36 millimetres in favour 
 of the more distant artery; but in one of the instances quoted by 
 Volkmann from Spengler, there was a difference of 16.6 millimetres 
 in favour of the carotid artery as compared with the maxillary. 
 
 * See the remarks on this subject in the late Dr. Young's Croonian Lecture on the 
 Functions of the Heart and Arteries. Phil. Transl. 1809, and republished in his 
 Introduction to Med. Literature, 1823, p. 607, et seq. 
 
 ■)■ As an example, the pressure in the carotid of a dog, distant 208 millim. from the 
 heart, and that in the humeral artery 803 millim. distant, support a column of mer- 
 cury of 179.04 millimetres. Whence Poiseuille infers that a particle of blood in the 
 carotid, distant from the heart 208 millim., moves with the same force as a particle 
 in the humeral artery, which has a distance of 303 millim. 
 
INFLUENCE OF RESPIRATION. 689 
 
 ButVolkmann's very numerous observations, made with more per- 
 fect instruments than those used by Spengkr, show a marked differ- 
 ence of pressure in the near and in the distant arteries. Thus, eight 
 observations on the carotid, and a branch of the femoral artery of a 
 large dog, gave a mean of 7.2 millimetres (0.27 inch) in favour of 
 the carotid. And ten observations on the carotid and metatarsal 
 arteries of a calf yielded a mean of 27 millimetres (1.05 inch) in 
 favour of the carotid; and twelve observations on the same arteries 
 of another calf gave a mean of 19.5 millimetres also in favour of 
 the carotid. Volkmann has also shown that, in the same artery, a 
 notably greater pressure exists in the part near the heart, than in 
 that more remote from it, which is, of course, the more conspicuous, 
 as the distance between the two points measured is greater. 
 
 Influence of Systole and Diastole. — Hales had observed, in his 
 experiments with a simple glass tube, that a rise and fall took place 
 in the column of blood to a variable extent at and after each pulse. 
 This observation has been confirmed by Ludwig, and also by Volk- 
 mann. The rise corresponds to the heart's systole, the fall to the 
 diastole. This affords, in the greatest part of the arterial system, 
 the clearest proof of the extension of the heart's influence through- 
 out it. And Poiseuille showed that the pulsations of the heart could 
 be counted by noticing the advance of the blood in pulses along the 
 capillaries, and, under certain circumstances, even along the small 
 veins. 
 
 Influence of Respiration. — That respiration exercises an influence 
 upon the circulation has been likewise noticed by several observers. 
 Hales had referred to this ; he had noticed how the straining efforts 
 of the animals which were made the subjects of his experiments, 
 were followed by a rise of the column of blood in the tube, and how 
 the same effect followed deep sighing. And Poiseuille found that 
 during expiration the height of the column of mercury was much 
 increased, but that it fell in inspiration. In forced and deep inspi- 
 rations the force of' the heart becomes so much diminished in some 
 cases that no pulse, or at most a very feeble one, can be felt at the 
 wrist: on the other hand, in forcible expirations the pressure of the 
 blood in the arteries becomes double its normal amount. This has 
 been farther confirmed by Ludwig and Volkmann.- The fact is of 
 practical interest, and affords good reasons why the practitioner 
 should caution those whose arteries are weakened by a diseased state 
 of their tunics, against strong efforts, or against any action likely to 
 disturb the quiet and freedom of the breathing. 
 
 The heart's force is materially weakened, as Blake's experiments 
 show, by the introduction into the circulation of poisonous agents 
 of a sedative nature. And there is every reason to believe that the 
 existence of particular animal poisons in the blood, as the typhus 
 poison, that of scarlet fever, of erysipelas, &c., is capable of depress- 
 ing the heart and weakening the circulation. 
 
 Thus, then, as far as regards the powers by which the blood is 
 moved in the arteries, it may be stated that the circulation is main^ 
 tained in them by the force of the heart; replaced and propagated 
 
690 THE CIRCULATION OP THE BLOOD. 
 
 throughout the system by the elastic reaction of the arterial tunics, 
 and to a certain extent restrained or modified by the muscular con- 
 traction of the same tunic, which likewise serves very accurately to 
 adapt the size of the arteries to the quantity of blood contained in 
 them. 
 
 On the Velocity with which the Blood moves in the Arteries. — 
 The calculations of Hales and others on this subject, led to ideas 
 respecting the velocity of the blood, which appear to be extravagant. 
 Thus Hales inferred the velocity of the blood at the commencement 
 of the aorta in man, to be at the rate of 735 feet in a second ! The 
 data upon which these calculations were founded are uncertain and 
 unsatisfactory, such as the measurement of the area of the aorta at 
 its origin, and the capacity of the ventricle and the quantity of blood 
 expelled by each systole. 
 
 Volkmann has lately devised an instrument for the direct admea- 
 surement of the rate of the blood's movement in the arteries. He 
 calls it the haemodromometer. It consists of a glass tube, contain- 
 ing water, 52 inches long, bent into the form of a hair-pin, which is 
 substituted for a segment of the bloodvessel, in which it is required 
 to measure the velocity of the blood's stream. The column of 
 blood which comes from the heart pushes the column of water before 
 it, without any great mixture of the two fluids taking place, 
 and in passing through a determined space it takes a measutable 
 time, whence it may be calculated how far the blood moves in a 
 second. 
 
 The following description will explain the instrument and the 
 mode of using it. At A (Fig. 202) is a metal tube, an inch and a 
 half in length ; the ends of this (a, a') are conical, and fit into two 
 corresponding conical tubes {Jc, ¥), made like the pipes of an inject- 
 ing syringe, so that they, can be readily fitted into an artery. A 
 stopcock (5') commands the channel of this tube, not only at a' but 
 also, by two cogged wheels, at a. The mechan^m of this arrange- 
 ment may be readily understood, by reference to the adjoining sec- 
 tions of this portion of the instrument and B and C, and the view of 
 its other surface at D (r^ r' D). At 'h, h' are two short tubes, also 
 of metal, which are fitted into the horizontal tube below the stopcock, 
 and so that their channels (as shown at C) may communicate with, 
 and be exactly equal to, that of the horizontal tube. The stopcock 
 {b') commands this communication likewise. These short tubes [h, A') 
 fit exactly upon the bent glass tube {p,p), and complete the communi- 
 cation between its channel, and that of the horizontal tube at its ex- 
 tremities. When the stopcock is turned so as to open the channel 
 of the horizontal tube throughout, as at B, all communication with 
 the glass tube is cut off; on the other hand, when the communication 
 with the glass tube is opened, as at C, the channel of the horizontal 
 tube is stopped, and fluid entering at a', would have to pass through 
 h', and to traverse both limbs of the glass tube {p, p) emerging at a. 
 For the protection of the instrument in using it, the glass'tUbe is 
 attached to a board, to which is fixed a scale marked in metal. 
 
 la order, then, to use the instrument, a large artery is freely ex- 
 
THE H^MODROMOMETER. 
 
 691 
 
 posed for not less than three inches, and, after due precaution has 
 been taken to counteract hemorrhage, it is divided by cutting out a 
 piece ; the conical pipes {k, k') are then fixed into the open ends 
 
 Fig. 202. 
 
 Ill 
 
 A' 
 
 p jy 
 
 of the artery, one being directed towards the heart, the other to- 
 wards the capillaries. They must be fixed far enough apart to 
 admit of the introduction of the horizontal tube (A) between them, 
 without altering the usjial direction, of the arterial stream. When this 
 tube is fitted to the conical pipes, then the bent glass tube, pre- 
 viously filled with water, must be fixed to it by means of the short 
 tubes (A, A', C), the stopcock being so turned as to shut ofi" all com- 
 munication with the glass tube. As soon as the instrument has been 
 properly fixed in the artery, the blood is allowed to flow into the 
 glass tube. It may be now seen to traverse the glass tube with a 
 velocity very nearly the same as it has in the artery, and in doing 
 so it pushes the water before it into the peripheral bloodvessels, with 
 
692 THE CIRCULATION OF THE BLOOD. 
 
 (according to Volkmannn) only a very slight admixture between the 
 two fluids. 
 
 By trials made with his hsemodromometer, Volkmann found, in 
 the case of seven dogs, that the blood flowed in their carotids 
 with a velocity ranging between 205 and 357 millimetres in a 
 second ; in that of horses, 306 to 234 ; in the metatarsal artery 
 of the horse, 56, and in the maxillary artery of the same animal 
 99; in the carotid of a calf, 431. The average velocity in the 
 carotids of mammals is stated by Volkmann to be 300* millimetres 
 in a second. 
 
 It results, likewise, from these observations, that the velocity of 
 the blood in the large arteries, and also in the large veins, is con- 
 siderably greater than in the capillaries ; that the velocity in arteries 
 is not uniform, but is suddenly increased at each systole of the heart, 
 and that the blood moves most quickly in the arteries nearest the 
 heart. It appears, also, that the blood's velocity is materially les- 
 sened by loss of blood, and that increased rate of pulse, which always 
 follows considerable losses of blood, is no indication of a more rapid 
 blood-current, but, on the contrary, often accompanies a retardation 
 of it. The velocity of the blood-current is influenced not so much 
 by the rate of action of the heart, as by the intensity of its systole, 
 and the quantity of blood which it expels at each contraction. 
 
 Much was formerly said respecting the disposition of the arterial 
 tree, being such that the combined areas of the branches of an 
 artery exceeded that of the trunk, and that with each succeeding 
 series of subdivisions, the blood flows into an increased area. Haller 
 (tom. i. p. 77) ascribes the first observation of this kind to an 
 Englishman named Cole.f It is repeated by Keill, Hales, and many 
 others, among them John Hunter and Sir C. Bell. The general 
 effect of such an arrangement would obviously be to diminish the 
 rate of movement of the blood as it flows from trunks to branches. 
 But the careful measurements of Mr. Fernaby and of Mr. Paget, 
 render it necessary to modify the general proposition to some extent. 
 
 Mr. FernabyJ compared the areas of trunks and branches in the 
 only sound way, namely, according to the geometrical law, that the 
 areas of circles are as the squares of their diameters. Estimated 
 thus, he found that the excess of the combined areas of the branches 
 over those of the trunks was very trifling, and, in some instances, 
 scarcely appreciable ; and Mr. Paget, while confirming the general 
 statement of Mr. Fernaby, discovered a remarkable exception in the 
 case of the common iliac arteries, whose combined areas were dis- 
 tinctly less than that of the aorta above the^ point of bifurcation — 
 and the combined areas of the external and internal iliacs were less 
 than that of the common; but those of the branches of the external 
 iliac exceeded notably the area of their parent trunk. § 
 
 Volkmann states that, in general, the arterial capacity is increased 
 
 • Tolerably close approximations to the value of these measurements in English 
 inches, may be obtained by dividing each number by 25. 
 f De Seoretione animali. Oxon. 1674. 
 X Lond. Med, Gaz. 1839. g Lond. Med. Gaz. 1842. 
 
THE CIRCULATION IN THE CAPILLARIES. 693' 
 
 in area by tte division into branches. But he instances a remark- 
 able exception in the case of the external and internal carotids of 
 the horse, whose combined areas are smaller than that of the trunk. 
 He remarks, likewise, that the first divisions of the larger arterial 
 trunks (aorta and pulmonary artery) experienced very little inc;:ease 
 of area; but that, as subdivision goes on^the increase becomes mubh 
 more marked. And it is especially so near the capillaries, where the 
 combined areas of some small branches nearly double that of their 
 parent. This is particularly interesting, as denoting the coincidence 
 of physical conformation with the result of direct observation, on the 
 velocity of the blood, which show that it is near the capillaries that the 
 most decided diminution takes place in the rate of the blood's motion. 
 
 Of the Oirculation in the Capillaries. — The manner in which the 
 blood flows through the capillaries is easily made the subject of direct 
 observation by examining the transparent parts of certain animals, 
 as the wings of bats, the mesenteries of small animals as the mouse, 
 the web of the frog's foot, the lung of the frog, or of the newt, &c. 
 
 In watching the circulation in the web of the frog's foot under the 
 microscope, with a magnifying power of about 200 diameters, the 
 following points will attract observation ; first, it will be seen that 
 the stream is continuous, that is, it rushes with a considerable velo- 
 city, which is uniform when not afi^ected by any extraneous influence ; 
 the course and rate of the stream are indicated by blood-particles 
 which are carried along in it, and which seem to chase each other 
 through the various channels and among the little islands of the solid 
 particles of the tissue which the blood is destined to nourish. These 
 particles most frequently pass in a single row, with a variable inter- 
 val between th&m; sometimes, however, thej'^ seem to rush in pairs, 
 or in threes, according to the size of the capillary channels through 
 which they flow. Secondly, it will be noticed that the greatest velo- 
 city of the stream is in its centre, a fact which comports with what 
 is observed in rivers and other channels through whieh water flows, 
 while towards the circumference the stream becomes much slower, 
 so that the layer of fluid which is in immediate contact with the ca- 
 pillary wall is almost or completely still. The particles are carried 
 along in the centre or rapid part of -the stream, and but occasionally 
 a solitary particle seems attracted towards the circumference. This 
 is most frequently a colourless corpuscle, so that sometimes several 
 colourless corpuscles are seen at intervals in contact with the wall of 
 the capillary, as if drawn to it by some special attractive force, or 
 moving much more slowly around the central mass of red particles. 
 The sudden change from a rapid to a slow movement, or to perfect 
 stillness, when one of these particles is thus drawn from the centre 
 to the circumference of the stream, serves to display, in a very satisr 
 factory manner, the peculiar feature of this portion of the contents 
 of the capillary, which, from its apparent stillness and from the pau- 
 city of blood-particles in it, has been called the-Btill layer of the liquor 
 , sanguinis. The existence of this still layer is doubtless a purely phy- 
 sical phenomenon, identical with that which is known to take place 
 
694 THE CIRCULATION OF THE BLOOD. 
 
 when fluids pass througli inorganic capillary tubes, in which the cir- 
 cumferential layer seems to adhere or to be attracted to the wall of 
 the tube, and it would clearly favour the transmission of nutrient 
 or other material dissolved in the liquor sanguinis, through the wall 
 of the vessel, in obedience to a force of attraction between the blood 
 and the tissue. This still layer forms but a small portion of the whole 
 capillary stream — perhaps about one-eighth or one-tenth its breadth ; 
 it is greater when the circulation is slower ; it is also broader, and 
 therefore more visible, when a vessel makes a bend. The application 
 of cold to the capillaries increases the breadth of this layer, whilst 
 heat produces an opposite change. 
 
 The capillary vessels dilate or contract, under particular circum- 
 stances. Their dilatation is passive, and due either to an increased 
 pressure of the blood into them, or to their distension under the same 
 pressure in consequence of diminished tone of their wall. Their 
 contraction is caused either by an inherent contractile power in 
 them, or by the diminution of their contents in consequence of the 
 contraction of the capillary arteries, in which latter case diminished 
 pressure permits them to contract, in virtue of the elasticity of their 
 walls. This latter would be the more probable view, in default of 
 any proved existence of a muscular structure in the walls of the true 
 capillaries, but there is no good reason why the nuclei' observed in 
 them should not be regarded as belonging to muscular tissue here, in 
 a membranous rather than a fibrous form. 
 
 The rate at which the blood moves in the capillary circulation 
 has been made the subject of direct observation by various phy- 
 siologists. It is slower than in the smallest veins, and still more 
 so than in the smallest arteries. Hales had stated the rate of the 
 circulation in the capillaries of the muscles of a frog to be an inch 
 in a minute and a/ half, and in the pulmonary capillaries five times 
 that velocity. Subsequent observers, Weber, Valentin, and Volk- 
 mann, give a somewhat greater velocity; Weber and Valentin make 
 it about an inch and three quarters in a minute, and Volkmann found 
 it about the same in cold-blooded animals, but twice as much in the 
 capillaries of the mesentery of a young dog. These estimates are 
 probably rather below the real rate of motion of the blood in the 
 capillaries, if we allow for the degree of pressure and constraint to 
 which they must be subjected in making the observations. 
 
 Of the Forces which maintain the Oapillary Circulation. — The 
 principal force by which the 'circulation is supported in the capillary 
 system, is the vis a tergo of the heart. We have already adduced 
 sufficient evidence to prove that that force is capable of driving the 
 blood throughout the whole circulating system. The following facts 
 may be stated in proof of this doctrine. 
 
 1. The pressure of the blood may be measured in the veins, in 
 the same way as in the arteries, and this varies with the force of the 
 heart. If, then, the heart's force extends to the veins it must do so 
 through the capillaries. 
 
 2, The capillary and venous circulation in any segment of the 
 body, is greatly influenced by the circulation in the main artery of 
 
THE CAPILLARY CIRCULATION. 695 
 
 that segment. Thus, Magendie found the circulation much retarded 
 in the femoral vein by stoppage of that in the corresponding artery; 
 and by the hsemadynamometer it may be shown that the force of the 
 blood in the veins diminishes or increases with that in the correspond- 
 ing artery under certain circumstances. 
 
 3. In Fishes, the whole blood ejected from the heart passes, from, 
 the bulbus aortse, through the branchial capillaries, before it enters 
 the systemic vessel; thus illustrating how the heart's force may be 
 propagated through a complex network of minute capillaries, to 
 both arteries and veins, as well as to the system of capillaries which 
 intervenes between them. 
 
 4. In debilitated animals, it is evident, from the jerking move- 
 ment of the blood in the capillaries, corresponding with the action 
 of the heart, that the impulse of that organ is extended to these 
 vessels, unbroken by the elastic reaction of the muscular contraction 
 of the arteries. This may be well seen in watching the circulation 
 in the frog's web, or in the tale of the tadpole. 
 
 Thus, there can be no doubt that the heart's force is not only fully 
 adequate to, but is the principal agent inj the maintenance of the 
 capillary circulation. When this force fails, the circulation in the 
 vcapillaries suffer as much as, if not more than, that in any other 
 portion of the vascular system ; and the sluggish transmission of the 
 blood through the capillaries, such as we often find when the heart 
 is simply weakened, occasions congestions, particularly of dependent 
 parts, and then, by the filtration of the serous portion of the blood 
 through the parietes of the vessels, oedema and anasarca. 
 
 But however readily we may concede that the heart's action is 
 the principal force, it must be confessed there are certain phenome- 
 na which do not admit of satisfactory explanation, on the supposition 
 that it is the only one employed in the maintenance of the capillary 
 circulation ; and it seems more reasonable to assume the influence 
 and exercise of some other force superadded to this, in order to 
 explain various phenomena which take place in, or which are de- 
 pejident on, the circulation through the capillaries. 
 
 The more remarkable of these phenomena are blushing, or, in 
 more general terms, the influence of mental emotion upon, the capil- 
 lary circulation; the influence of local irritation, whether accidental 
 or morbid ; and the effects of asphyxia. 
 
 It seems highly probable that in the ordinary molecular changes 
 which take place in the nutrition of the tissues, a force is generated, 
 which, in its normal state, must promote, by an attractive influence, 
 the flow of blood through the capillaries. The cessation of such a 
 force would operate unfavourably to the flow of blood through the 
 capillary system, whilst its existence in greater power at one point 
 than at another, would cause a greater afflux of blood ii; thei former 
 than in the latter direction. 
 
 The best illustration of the exercise of this force, which, for the 
 sake of brevity, may be designated the capillary force,* is found in 
 
 * The name Capillary force, -wliicli was given by Dr. Carpenter, must be taken as 
 
696 THE CIRCULATION OP THE BLOOl). 
 
 the circulation of the sap in plants. It is exercised in two situations 
 — at the roots and in the leaves — constituting in the one a vis a tergo, 
 and in the other a vis a fronte. At the roots, a rapid imbibition of 
 fluid takes place with such energy, that it pushes before it the fluid 
 above ; thus, if the stem of a vine, in which the sap is rising, be cut 
 across, a bladder tied over it, will, after a short time, be burst by 
 the fluid accumulated beneath it; or if a bent tube, containing a 
 column of mercury, be affixed to it, the mercury will be raised to the 
 height of forty inches or more. And that a force of attraction is 
 exercised at the leaves, may be shown by placing the lower end of 
 the upper division of the cut vine in water, when an active absorp- 
 tion and circulation of water will take place as long as the vital 
 changes in the leaves go on; but if the vine be taken into a dark 
 room, so as to check these vital changes, the absorption and circula- 
 tion will likewise cease. So also the elaborated sap or latex, which, 
 from its containing the elements for the nutrition and for the various 
 secretions of the plant may be likened to the arterial blood of ani- 
 mals, circulates through a complex system of anastomosing vessels 
 (like the capillaries of animals), in the under surface of the leaves 
 and in the bark, and will ascend towards the stem, even against 
 gravity, in a dependent branch. The circulation of these fluids takes- 
 place with the greatest activity in growing parts, in which nutrient 
 and chemical changes are going on most actively. ' 
 
 Professor Draper, of New York,* has given a definite expression 
 to the nature of the forces which operate in the production of the 
 circulation of the sap in plants, and in that of the blood in animals. 
 The laws of endosmose and exosmose resolve themselves into the 
 following dogma : " That if two liquids communicate with one an- 
 other in a capillary tube, or in a porous or parenchymatous structure, 
 and have for that tube or structure difi^erent chemical affinities, move- 
 ment will ensue; that liquid, which has the most energetic affinity, 
 will move with the greatest velocity, and may even drive the other 
 liquid entirely before it." 
 
 In plants, the rise of the ascending sap from the ground, results 
 from the attractive force of the spongioles. These appropriate cer- 
 tain elements contained in the fluid, and exercise a more energetic 
 attraction on a new supply, which pushes the former before it. Thus 
 the sap ascends to the leaves, pushed on by successive new portions 
 attracted to the spongioles. At the leaves, a new foi:ce of a similar 
 kind, but due to the action'of light, draws it on, and causes it to 
 push before it the newly formed latex or elaborated sap, the flow of 
 which is promoted by its affinity for the vegetable tissues which it 
 permeates. 
 
 In the systemic circulation of animals, the arterial blood has a 
 great affinity for the tissues to which it is brought by the capillary 
 system. This force of attraction draws on the blood from the arte- 
 
 merely denoting that the force is exerted at the capillaries, whether it be exercised by 
 their walls or by a mutual action between the blood within and the tissues outside 
 them. 
 
 * On the Forces which produce the Organization of Plants. ISiS. 
 
THE CAPILLARY CIRCULATION. 697 
 
 rial side of that system, -with a power which helps to propel on the 
 deoxygenized blood into the venous radicles. In the pulmonary cir- 
 culation, venous blood is conveyed to the air-cells by the pulmonary 
 arteries. This kind of blood has a great affinity for the oxygen 
 which is being continually brought to those cells by the movements 
 of respiration. It is therefore forcibly attracted to the air-cells, and, 
 being charged with oxygen, is pushed on by the succeeding portions 
 of venous blood, which the same force is constantly attracting. 
 
 It is by the influence of an attractive force, such as Professor 
 Draper describes, that we can best explain the continuance of a 
 complex circulation in many of the lower animals in which no central 
 organ of impulsion exists, as in some of the Polypifera, and of the 
 Articulata. In the sponge, the remarkable currents of water which 
 flow through the various channels that penetrate its substance, are 
 maintained without any special propelling organ whatever. And the 
 beautiful cyclosis in Chara and Valisneria afibrds a striking instance 
 of a circulation without a vis d tergo. 
 
 In the vascular area of the egg, a circulation exists before a pro- 
 pelling organ. And in the acardiac foetus a similar circulation 
 exists, although in general it has such a connection with a second 
 perfect foetus that the heart of the latter may influence the circula- 
 tion of the former. But that a foetus may grow to a considerable 
 size, and have its various tissues well developed without any con- 
 nection with the twin foetus, by means exclusively of a circulation of 
 its own, of which a heart forms no portion, or upon which it can ex- 
 ercise but a very remote influence, is shown by the case put on record 
 by the late Dr. Houston.* No doubt the same law which influences 
 the movement of fluids in vegetable tissues would be in operation in 
 such cases. 
 
 Now, with reference to the phenomena in the circulation of the blood 
 in man above referred to, it may be asked : Is the assumption of the 
 exercise of a capillary force necessary for explaining them ? Can 
 blushing, and other local determinations of blood, be accounted for, 
 if we admit a vig a tergo as the sole force of the circulation ? In 
 order to explain the accumulation of blood, in the cheeks, for in- 
 stance, under the influence of mental emotion, the advocates of the 
 latter doctrine suppose the capillaries muscular, and affirm that a 
 relaxed state of the walls of the capillary arteries, and perhaps also 
 of the capillaries themselves, is produced by the nervous change 
 which mental emotion excites. Such an explanation is perfectly 
 admissible in this particular case, and it seems highly probable that 
 in the relaxed state of the capillary vessels of the face, their walls 
 yield under the pressure of the heart more than those of neighbouring, 
 vessels, which do not come so completely within the range of the 
 centre of emotion. And in many persons, emotion causes the blood 
 to desert the cheeks, which in consequence become pale. In such 
 cases, the change in the nervous centre must excite an opposite, that 
 is, a contracted state of the capillaries of the cheeks. 
 
 * Dublin Medical Journal, Tol. viii. 
 45 
 
698 THE CIRCULATION OP THE BLOOD. 
 
 But the accumulations of blood ■which are caused by local irrita- 
 tions, do not admit of satisfactory explanation by mere changes in 
 the capillaries of the affected part. 
 
 For example, a particle of dust is thrown into the eye, and as 
 long as it is in contact with the conjunctiva, its capillary yessels are 
 turgid with blood. Is this due to a relaxed state of the capillaries 
 caused by the presence of an irritating agent ? The analogy of the 
 influence of mechanical stimulation upon other vessels would lead us 
 to infer that the irritation of a particle of dust in contact with the 
 conjunctiva would cause the capillary vessels to contract, and a con- 
 tracted state of these vessels would oppose rather than favour the 
 accumulation of blood in them. It seems much more reasonable to 
 suppose that the irritation caused by the foreign particle, increases 
 the attractive force which the tissue naturally exercises on the blood ; 
 and this would give us a clue to explain the two kinds of congestion 
 long recognized by practical men, the passive and the active form. 
 The former is owing simply to a relaxed flaccid state of the parietes 
 of the bloodvessels, which permits them to receive a greater quantity 
 of blood from the heart, and to a minus state of the capillary force, the 
 other to a plus condition of that force, — in virtue of which the tissue 
 attracts a greater quantity of blood. To this latter form of conges- 
 tion pathologists give the name of inflammation. Its phenomena, as 
 observed under the microscope, are such as a vis d tergo alone cctald 
 not develop. For not only are there dilatations of the vessels of 
 the inflamed part, and a great afllux of blood towards a certain point 
 or points in it, but the blood-corpuscles seem to rush thither, as if 
 forcibly attracted towards each other, and also to some common 
 focus. And the rapid and copious process of exudation, and the 
 ■formation of pus-cells, which are so apt to follow an attack of inflam- 
 mation, afford farther strong indication of augmented vital force in 
 the inflamed part.* 
 
 So also in growing tissues, and in organs which enlarge at particu- 
 lar times, or under certain circumstances, the increased flow of blood 
 to the part is a phenomenon in close analogy with the increased flow 
 of sap to a bud ; and is due, not to a vis d tergo, or to a relaxed state 
 of bloodvessels, but to a demand from the tissue for more blood, an 
 attractive force, by which the direction is regulated, and the quan- 
 tity also. The annual renewal of the antlers of the stag, the enlarge- 
 ment of the testes of birds at particular seasons, that of the breasts 
 of women during pregnancy and after parturition, all these cases 
 afford instances in which a demand for blood is created at some point 
 of the periphery, and a greater flow is established to the organs 
 •there placed than previously took place to them. 
 
 We can afford no satisfactory explanation of the localization of 
 certain changes in the capillary circulation, unless on the hypothesis 
 that the constituent elements of the afiected parts are primarily dis- 
 eased, and that their demand for blood is, in consequence, increased 
 
 * The theory of inflammation is extremely well discussed in Mr. J. Simon's Lec- 
 tures on Pathology, Lect. IV. See also Mr. Paget'a Lectures on Inflammation. 
 
THE CAPILLARY CIRCULATION. 699 
 
 or diminislied, and the flow of blood regulated accordingly. Thua 
 the development of gout in a joint takes place often with such 
 rapidity that it appears to the patient to be sudden ; the train of 
 phenomena being in such cases, first, a change in the tissues, so 
 gradual as to be unperceived, then, an increased flow of blood, to such 
 an extent as to cause the heat, the throbbing, and pain which cha- 
 racterize such affections. Again, certain poisons, which seem as it 
 were to spend' their force, in great part at least, on the skin, do not 
 cause a change in the whole capillary circulation so much as in points 
 of it, here and there, determining an increased flow of blood to this ■ 
 point and that, and leaving the intervening parts unaffected. The 
 well-ascertained fact, ubi stimulus, ibi fluxus, cannot be so well ex- 
 plained on the hypothesis that the stimulus creates a relaxation of 
 the tunics of the capillaries of the part, because that is opposed to 
 analogy, as on the supposition that under the operation of the stimulus 
 the demand for blood in the tissues is augmented, and the capillary 
 force becomes exalted in the part, in virtue of which a greater flow 
 of blood is determined to it. 
 
 The phenomena of asphyxia show that a stoppage of the circula- 
 tion may take place at the capillaries, notwithstanding the con- 
 tinuance of the heart's action. When the access of air to the lungs 
 is excluded, the circulation ceases at the pulmonary capillaries, and 
 on examination after death the left auricle and ventricle are found 
 quite empty, and the right cavities of the heart gorged with blood. 
 The repletion of the latter cavities, and the emptiness of the former, 
 indicate the position at which the obstruction to the circulation 
 took place. Instantly the air is readmitted to the lungs, the blood 
 assumes a bright red colour and the circulation goes on, indicating 
 that" the changes which take place between the air and the blood, 
 must generate a force which exercises an important influence on the 
 capillary circulation, and. without which the heart's force is insufficient 
 to propel the blood through the pulmonary vessels. Dr. John Reid* 
 argues, as we think with justice, from the instantaneousness of the 
 restoration of the circulation on the readmission of air, that its stop- 
 page must be due to the cessation of the respiratory changes, and 
 not to a contracted state of the capillary arteries as suggested by Mr. 
 Erichsen, because the relaxation of those arteries, like their contrac- 
 tion, is a slow process, requiring two or three minutes to accomplish 
 it.t 
 
 • John Reid, on the Cessation of the Vital Changes in Asphyxia. Phys. Researches, 
 Edinb, 1848. 
 
 + Our friend and colleague, Dr. Geo. Johnson, has discovered a very interesting 
 point, connected -with the miaute vessels of the kidney in cases of chronic nephritis 
 with shrinking of the organ, which furnishes an additional instance of retardation or 
 stoppage of the circulation at the capillaries, despite the continuance of the heart's 
 action. Dr. Johnson shows that, under the influence of defective secretion, the renal 
 circulation is greatly retarded in the intertubular capillaries, and that the 'Malpighian 
 capillaries are consequently subjected to a greatly increased pressure and distension, 
 giving rise to an escape of serum, or of blood, when a rupture of one or more of the 
 minute vessels has occurre* When such a state of vessels has been of long duration, 
 as in chronic inflammation of the kidneys. Dr. Johnson finds the capillary arteries much 
 thickened, by reason of hypertrophy of liieif circular and longitudinal fibres, .and a thick- 
 
700 THE CIRCULATION OF THE BLOOD. 
 
 On the whole, we are disposed to the following conclusion respect- 
 ing the capillary circulation, namely, that it is maintained by the 
 vis a tergo of the heart; but it is regulated and modified partly by 
 the elasticity of the walls of the capillary bloodvessels, partly also by 
 their contractility, which is greatly influenced by changes in the 
 nervous system, but chiefly by the operation of a force, developed by 
 those chemical and physical changes, which take place between the 
 blood and the tissues, and in which the phenomena of nutrition es- 
 sentially consist. For the due exercise of this force, a normal consti- 
 tution of both the blood and the tissues is the most important condi- 
 tion. 
 
 Of the Oireulation in the Veins. — The blood moves in the veins in 
 a continuous stream, a fact sufiBciently apparent to all who have 
 watched its escape from a vein after venesection, and as is likewise 
 apparent in examining the circulation in minute veins under the 
 microscope. The velocity &f the venous current is considerably less 
 than that of the arterial, but greater than that of the capillaries, and, 
 as Volkmann has shown, it increases in the veins which are nearest 
 to the heart. 
 
 That the vis a tergo of the heart is- sufficient to maintain the circula- 
 tion in the veins, is abundantly provedbyall those facts which have been 
 already recited with reference to its influence on the capillary cirljula- 
 tion. Of these, the most important are the experiments of Magendie 
 already referred to (p. 695), and the fact that in states of debility a 
 distinct venous pulse is formed synchronous with the heart, and 
 evidently resulting from the extension of the heart's impulse through 
 the capillaries. Such a pulse (which may be called the systolic venous 
 pulse) is in rare instances observable in the human subject in states 
 of great prostration of strength, but has been most frequently noticed 
 in observations on the circulation of cold-blooded animals. 
 
 Pulsations synchronous with the heart's beats may be not uncom- 
 monly noticed in the human subject, which it is important that the 
 observer should not confound with those resulting from the extension 
 of the heart's impulse, as above referred to. These may be called 
 the regurgitant, and the communicated venous pulse. The former 
 is caused by the regurgitation which takes place from the right auricle 
 into the large venous trunks connected with it at every systole of 
 that cavity. In a state of health, the regurgitation is so small that 
 its influence extends only to the larger veins — but when the right 
 
 ened and opaque state of the walls of the Malpighian capillaries ; while the intertubu- 
 lar capillaries and veins remain unaltered, save in a diminution of their number, some 
 having become wasted and obliterated in consequence of the aiTested action dt the secret- 
 ing cells. These observations show an obvious connection between the aeti'vity of the 
 organic changes connected with the act of secretion and that of the capillary circula- 
 tion, and, indeed, an interdependence between the movement of the blood and the 
 secretory function of the gland ; but the hypertrophy of the muscular fibres of the 
 capillary arteries seems rather to indicate that, in these extreme capillary arteries, 
 some propulsive power («i« d tergo) may be exercised by their muscular fibres in pro- 
 moting the flow through the capillary system. — See Dr. Johnson's Paper on Albumi- 
 nous Urine and Dropsy, in the 88d vol. ot Med.-Chir. Tram. 
 
THE VENOUS CIRCULATION. 701 
 
 cavities of the heart are dilated, a much larger quantity of hlood is 
 regurgitated and a distinct venous pulse is visible in the superficial 
 jugular veins, and sometimes in all the superficial veins which are 
 distributed over the neck and upper part of the chest. The com- 
 municated venous pulse results simply from the proximity of some 
 large artery, which in its pulsations communicates to the vein a move- 
 ment of a similar nature. 
 
 Hales and Poiseuille estimated the force of the current of blood in . 
 the veins; the former by the introduction of tubes into the large 
 veins, as in his experiments upon arteries ; the latter by the hsema- 
 dynamometer; and their observations have lately been repeated by 
 Valentin and Mogk. Hales found that the blood rose to four feet 
 two inches above the level of the heart, in a tube inserted towards 
 the head into the jugular vein of a mare, the blood rising several 
 inches when the animal strained, but subsiding again when he became 
 quiet ; hence it is pjain that the force of the heart, competent as it is 
 to maintain a column of such a height, must be amply sufficient to 
 return the blood to the heart. Valentin and Mogk's observations 
 show that the force of the blood in the veins of dogs is equal to one- 
 eleventh or one-twelfth of that in the corresponding arteries. 
 
 The venous circulation is influenced a good deal by the respiratory 
 movements, which tend partly to promote, partly to retard it. 
 These effects are produced most plainly by the forced movements of 
 respiration. Thus a deep inspiration, by enlarging the capacity of 
 the chest, generates a tendency to a vacuum, which, under the pressure 
 of the surrounding atmosphere, is filled chiefly by the rush of air 
 into the trachea, and through it to the lungs, but partly by the 
 afflux of the blood, which must be principally venous, since the semi- 
 lunar valves would oppose any reflux in both the great arteries. Sir 
 David Barry illustrated the influence of inspiration in favouring the 
 centripetal flow of blood. He introduced one end of a bent glass 
 tube into the jugular vein of a horse, the vein being tied above the 
 point at which the tube was inserted ; the other end of the tube was 
 immersed in a coloured fluid. At each ins,piration the fluid rose in 
 the tube, being drawn towards the chest, whilst during expiration it 
 sank or remained stationary. 
 
 Forced expiratory efforts, on the other hand, retard the venous 
 circulation, as may be well illustrated by holding the breath for a 
 few seconds, or straining strongly, when the veins, especially those 
 of the neck and chest, will swell up and become distended ; but as 
 soon as the breathing is restored, they return immediately to their 
 former size. Hence it is that persons subject to frequent disturb- 
 ances of the respiratory actions, as in asthma or dyspnoea of any 
 kind, exhibit, after a time, more or less enlargement of the venous 
 system. 
 
 Disturbances in the respiratory actions seem to affect the circula- 
 tion and especially that in the veins, morfe extensively in another 
 way, namely, through the pulmonary capillaries. The imperfect 
 respiratory changes, consequent upon the disturbed breathing, retard 
 the flow of blood through the capillary plexus, which undergoes, by 
 
702 THE CIRCULATION OF THE BLOOD. 
 
 the dilatation and rupture of the air-cells, considerable stretching 
 and widening of its meshes, and even becomes obliterated in parts. 
 These changes also create additional obstacles to the pulmonary cir- 
 culation, which impede the flow from the right ventricle, and increase 
 the backward pressure of the blood on the walls of that cavity, causing 
 it to become dilated and hypertrophied. It is in this way that are 
 produced the hypertrophy and dilatation of the right cavities of the 
 heart, which, to a greater or less extent, are invariable consequents 
 of frequent attacks of asthma or bronchitis. 
 
 The influence of the respiratory movements upon the venous circu- 
 lation is shown in the clearest manner by the use of the haemadynamo- 
 meter, as in the experiments of Poiseuille, Magendie, Ludwig, Va- 
 lentin, and Mogk, the column of mercury rising in expiration, and 
 falling in inspiration ; and these experiments likewise prove that this 
 influence is only felt in the large veins near the chest, and not in the 
 more distant ones. The influence of expiration in retarding is much 
 more powerful than that of inspiration in promoting the venous cir- 
 culation ; for the same physical condition of the chest which exists at 
 the commencement of inspiration, and which favours the rush of 
 blood to it, tends rather .to delay the escape of blood through the 
 arteries, and the heart's action is thereby much weakened and often 
 depressed. 
 
 Muscular movements likewise favour the venous circulation, aa is 
 well shown in the operation of venesection, when the patient is made 
 to move his fingers freely, the flow of blood from the vein being 
 thereby immediately increased. It is the action of the valves which 
 determines the centripetal flow of the blood in the veins under mus- 
 cular pressure ; for, as the contracting muscles simply compress the 
 veins, the blood would be driven either or both ways ; but the valves 
 afi'ording a direct impediment to the centrifugal flow, it is forced to 
 take the opposite course. This is obviously one. of the ways in which 
 exercise favours the circulation and promotes the general health. 
 
 It has been supposed that the contraction of the auricles by par- 
 tially emptying those cavities, calls into play an elastic force in their 
 walls, which favours the rush of blood into them, and that thus a 
 certain suction power of the auricle may be enumerated among the 
 forces which aid the venous circulation. The idea is illustrated by 
 exhausting an India-rubber bag, to which a glass tube is attached, 
 and then immersing the open extremity of the latter in a vessel of 
 water, when the water will pass freely into it under the influence of 
 the atmospheric pressure on the water. The principal fact in favour 
 of this view is the experiment of Wedemeyer, which is thus detailed 
 by Miiller : " Wedemeyer and Guenther having tied the jugular 
 vein of a horse, made an opening into it between the ligature and 
 the heart, and introduced a catheter, to which a bent glass tube had 
 been cemented. The longer descending branch of the tube (two feet 
 in length) was placed in a glass filled with water. At first, the 
 inspirations and the contractions of the heart were nearly simul- 
 taneous, and of the same frequency — namely, thirty in a minute — 
 and the coloured water rose suddenly two or more inches in the tube 
 
SUCTION POWER OF THE AURICLE. 703 
 
 at the moment of each inspiration and pulsation of the heart, and 
 sank again each time to its former level. The inspirations gradually 
 became twice as frequent as the pulsations of the heart, and Wede- 
 meyer and Guenther now observed, for' a long period, that the rise 
 of fluid did not take place at each inspiration, but at every beat of 
 tbe heart, and, consequently, simultaneously with each dilatation of 
 the auricle. This experiipent," adds Mliller, " seems to prove be- 
 yond doubt that the heart exerts a power of suction." It is most 
 probable, however,, that this power is extremely small, and that it 
 does no more than counteract the obstructive influence which would 
 otherwise arise from the regurgitation which takes place into the 
 large venous trunks from the auricles at each systole. 
 
 The veins possess a certain tonic influence similar to that of arte- 
 ries, by which they can adapt themselves to the varying quantity of 
 their contained blood. This is, doubtless, due to the presence of 
 muscular fibres in the tunics of veins already described ; the power 
 of these fibres to alter the caliber of the vein is clearly demonstrable 
 by the influence of galvanism,* which causes an appreciable diminu- 
 tion in the size of the vessel at the point of transit of the current.f 
 
 The flow of blood in the veins, then, it may be concluded, is main- 
 tained chiefly by that same force through which it is driven through 
 the arteries and capillaries, aided by the sort of suction in the cen- 
 tripetal direction which is caused by inspiration and by the diastole 
 of the auricles, and promoted likewise by the contraction of the 
 various muscles, among or through which the veins pass, and by the 
 position and mechanism of the valves. 
 
 It is proper to observe that the venous circulation being moved 
 by Ifess force than the arterial (the heart's power having already 
 very much expended itself on the arteries and capillaries), is more 
 infljuenced by gravity — either favourably or otherwise — than the 
 arterial. Hence, in dependent positions, as in the lower extremities, 
 when the blood has to ascend against gravity, the veins are apt to 
 swell, and to acquire a permanent dilatation and thickening of their 
 coats from the retardation of the current in them. It is important 
 
 • See Kolliker's experiments — Sielbold and Kolliker's Journal. 
 
 t While these pages were passing through the press (Feb. 1852), Mr. Wharton 
 Jones announced, in a paper read to the Royal Society, the discovery that the veins 
 of the bat's wings contract and dilate rhythmically, and that they are provided with 
 valves, some of which completely, others only partially, oppose regurgitation of blood. 
 The rhythmical contractions and dilatations are constantly going on, and that at the 
 rate of ten contractions in the minute. During contraction, the flow of blood in the 
 vein is accelerated, and on the cessation of the contraction the flow is checked, with 
 a tendency to regurgitation. But this check is usually only momentary ; already, 
 even while the vein is in the act of again becoming dilated, the onward flow recom- 
 mences and goes on, though with comparative slowness, until the vein contracts 
 again. It is the heart's action which maintains the onward flow of blood during the 
 dilatation of the vein, whilst it is the contraction of the vein coming in aid of the 
 heart's action, which causes the acceleration. Mr. Jones states that he has not been 
 able to observe unequivocal evidence of tonic contractility in veins, as Kotliker's 
 experiments indicate ; he likewise afflrms, in opposition to a statement of Mr. Paget, 
 quoted at p. 662, that nowhere do the arteries and veins of the bat's wing communi- 
 cate, the only communication being the usual one through the medium of capillaries. — 
 Proceedings of the Royal Society, Feb. 1852. 
 
704 THE CIRCULATION OF THE BLOOD. 
 
 that this fact should be kept in view by the practitioner in the treat- 
 ment of varicose veins, and of anasarcous states of the limbs. 
 
 We have seen thatthe blood moves in the arteries with considerable 
 velocity, and likewise with great, although much diminished, rapidity 
 in the capillaries ; its rate of motion increasing again in the veins, 
 especially in those nearest the heart. It may be inferred from these 
 facts, that any given particle may complete the round of the circula- 
 tion in an exceedingly brief period. It is an important problem — 
 especially with reference to the time in which poisonous substances 
 introduced into the blood may produce their effect — to determine in 
 what space of time a substance introduced into one part of the circu- 
 lation may reach the most distant part ; or how soon, for instance, a 
 substance inserted into the right jugular vein may, after traversing 
 the right heart, the pulmonary circulation, the left heart, the systemic 
 arteries, return to the systemic veins, and be found in the left jugular 
 vein. 
 
 In the present state of our knowledge no exact solution of this 
 problem can be given. But a very close approximation to the truth 
 may be obtained — first by calculation, secondly by experiment. By 
 calculation, we can determine in what space of time the whole blood 
 of the body may circulate through the heart. The data for this 
 problem are, the weight of the whole quantity of blood in the body, 
 the quantity of blood expelled at each systole from the left ventricle, 
 and the number of systolic actions in a minute, or, more exactly, the 
 duration of a pulse. It is plain that, if the left ventricle contract 
 seventy times in a minute, and at each contraction expel five ounces 
 of blood, according to Valentin, or six ounces {xl-^th. part of the 
 weight of the body), according to Volkmann, a quantity of blood 
 equal to th^t of the whole body will in that space of time pass through 
 the heart. It may, then, be assumed from calculation, that the 
 circulation may be completed in a period of time, which, in round 
 numbers, may be expressed as one minute.* 
 
 Bering was the first to experiment on this subject, his object being 
 to ascertain how soon a substance easily recognized (as ferrocyanide 
 of potassium), when introduced into one part of the circulation as 
 the right jugular vein, could be detected in a distant part of the circu- 
 lation as the left jugular. Hering found that this substance would 
 
 * Volkmanu's formula is / = z ^ -where t is the required mean time of the com- 
 
 y 
 
 pletion of the circulation, x is the ivholc quantity of the blood, y the quantity expelled 
 at each systole, and « the mean duration of a pulse. Whence, taking the mean quan- 
 tity of X at 30 lbs., and of y at 6.2 ounces, the duration of a pulse being 0.85 of a 
 
 second, we get i = 0.85 = 67.5 seconds. And as, according to Valentin, the 
 
 188 
 •whole quantity of blood is equal to about l-5th the weight of the body, and as from 
 Volkmann's researches the quantity expelled at each systole of the Tenti'lole is jjjth 
 
 of the weight of the body, calling this weight p, then x = —p and y = — p, and 
 
 6 400 
 
 SO n 
 
 i = z L. , therefore i ^ 80 z; whence it appears that the time of the circulation 
 
 P 
 is directly as the duration of a pulse, and inversely as its frequency. 
 
RAPID EFFECTS OF. POISONS. 705 
 
 pass from the right to the left jugular veins in from twenty to thirty 
 seconds ; and from the jugular vein to the great saphena in twenty 
 seconds ; from the jugular vein to the masseteric artery in from 
 fifteen to thirty seconds. Results quite confirmatory have heen 
 obtained from like experiments by Poiseuille, and also by Blake. 
 The former found that ferrocyanide of potassium, with acetate of 
 ammonia, or nitrate of potash, passed from one jugular vein to the 
 other in from eighteen to twenty-four seconds ; but that the addition 
 of alcohol retarded the rate of transit to from forty to forty-five 
 seconds. Blake found that nitrate of baryta passed from the jugular 
 vein of a horse to the opposite carotid artery in from fifteen to twenty 
 seconds. He found also that the poisonous influence of strychnia on 
 the nervous system, showed itself in twelve seconds after injection 
 into the jugular vein ; in a fowl, in six seconds and a half; and in a 
 rabbit in four seconds and a half.* 
 
 The results obtained from calculation, as regards the rate of the 
 circulation, are less conclusive than those by experiments ; for the 
 obvious reason that we have only the approximative value of the two 
 principal quantities which enter into the calculation, namely, that of 
 the mass of blood . in the body, and that expelled at each systole. 
 But the results of the two modes of inquiry are sufficiently near to 
 each other to denote that the round of the circulation is completed 
 by any given -portion of blood in a marvellously brief period, which, 
 in man, probably, rather falls below than exceeds a minute. We 
 need not, therefore, have recourse to any other hypothesis to explain 
 the rapid effects of certain poisons, than that they enter the blood', 
 and with it are whirled with immense velocity through the substance 
 of the most vital organs. 
 
 * Hering in Tiedemann and Trevii-anus Zeitschrift fur Physiol, b. iii. Poiseuille's 
 Ann. des So. Nat. 1843. Blake, Edin. Med. and Siirg. Journal, 1841. See also on 
 this subject Volkmann's 10th chapter. 
 
 On the subjects discussed in the preceding chapter, the reader is referred to the 
 various systematic works on Physiology, to the supplement lately published by Valen- 
 tin, and to Dr. Allen Thompson's very comprehensive article, Circulation, in the Cyclo- 
 paedia of Anatomy and Physiology. On the anatomy and physiology of the heart, 
 Kurschner's article in Wagner's Handworterbuch, and Dr. Jno. Eeid's article in the 
 Cyclop, of Anat. may be consulted ; and as regards its motions and sounds, we refer 
 to the reports of the Committee of the British Association, collected in the Appendix 
 of Dr. C. J. Williams's work on Diseases of the Lungs, to Dr. Blakiston's admirable work 
 on Diseases of the Chest, to Dr. Walshe on Diseases of the Heart and Lungs, and Dr. 
 Herbert Davies on the same subject; and on the physios of the circulation, to Hales's 
 Statical Essays, vol. ii.; to Dr. Young's Croonian Lecture on the Functions of the 
 Heart and Arteries, Phil. Trans, 1809, and Medical Literature, p. 605 ; Poiseuille snr 
 ]a Force du Coeur Aortique, in Magendie's Journal, vol. viii., and his essay, Rccherohes 
 sur I'Eooulement des liquides consid^rd dans les Capillaires Vivans,' in the Journ. des 
 Sc. Nat. 1843; to the Essays of Ludwig, Spengler, and Mogk, in Miiller's Archiv; 
 Magendie, Le9ons sur les Ph^nomfenes Physiques de la vie, and especially to the very 
 able work of Volkmainn, Die Hsemodynamik nach Versuchen, Leipzig, 1850, which 
 we only received when these pages were in type. The following works may also be 
 mentioned as containing interesting matter relating to the circulation in general: 
 Dr. Graves's Clinical Lectures, lect. i. on the Circulation ; Dr. Todd's three Clinical 
 Lectures on the Pulse, Lond. Med. Gaz. 1851 ; Draper, on the Forces which produce 
 the Organization of Plants, New York, 1845 ; Prof. Jno. Keid's essay on Asphyxia, in 
 his Physiological aid Pathological Researches, ed. 1848. 
 
706 RESPIRATION. 
 
 CHAPTER XXIX. 
 
 ON RESPIRATION. — COMPARATIVE ANATOMY OF THE RESPIRATORY OR- 
 GANS. — ANATOMY OP THE HUMAN LUNGS. — TRACHEA. — BRONCHI. — 
 BRONCHIA. — ULTIMATE PULMONARY TISSUE. — MOVEMENTS OP RE- 
 SPIRATION. — FREQUENCY OF RESPIRATIONS, AND RATIO TO THE PULSE. 
 — AERIAL CAPACITY OP THE LUNGS, AND AMOUNT OP AIR BREATHED. 
 — CHANGES IN THE RESPIRED AIR, CARBONIC ACID EXHALED — 
 OXYGEN INHALED. — CHANGES IN THE BLOOD. — NATURE OP THE RE- 
 SPIRATORY PROCESS. 
 
 Respiration is that function by which an interchange of gases 
 takes place between the interior of an organized being and the ex- 
 ternal medium ; and in the animal kingdom oxygen is the gas re- 
 ceived, and carbonic acid the gas given out. Every part of the sur- 
 face to which the outer medium (whether air or water) has access 
 may be considered to share in respiration ; but in all, except some of 
 the lowest animals, special organs are provided in which the inter- 
 change can be more readily effected. These organs in all cases 
 consist of a membranous surface, adapted for contact with the sur- 
 rounding medium, and capable of exposing the fluids of the body in 
 an especial manner to the action of the air. The interchange of the 
 gases through this respiratory membrane is essentially a purely 
 physico-chemical phenomenon, and must be studied as such. The 
 very great variety of structures with which different animals are 
 furnished for this function, merely present us with modifications of 
 the elementary conditions whereby its activity and extent are 
 governed in the several instances. The contact of air with the blood 
 may be influenced (1) by atmospheric concentration or dilution. In 
 water-breathing animals, the air breathed is that held in solution in 
 the water, and is of course in very small quantity. The density or 
 rarity of the air, according to temperature and barometric pressure, 
 may perhaps affect the activity of respiration in air-breathers. (2) 
 The extent of the respiratory surface ; (3) the thickness of the tissue 
 between the air and the blood, and (4) the more or less complete 
 manner in which the general mass of the blood is brought from the 
 tissues to the respiratory surface — all these exert much influence on 
 the activity of respiration. 
 
 Comparative Anatomy. — In Entozoa, polyps, and medusse, no special respiratory 
 organ exists. In star-fishes and sea-urchins, among the echinodermata, the sea-water 
 gains access to cavities among the viscera, and is renewed continually by special 
 organs, principally cilia. The holothuria has an internal system of arborescent tubes 
 opening from the cloaca, receiving water, and, according to Tiedemann, serving for 
 respiration; its branches end in vesicles. In annelida, there are sometimes tufted 
 branchise, or gills, as in the arenioola, or sand-worm ; sometimes sacs opening sepa- 
 rately, as in lumbrici and leeches. The Crustacea have branchise attached either to 
 the feet or abdominal surface. Of the arachnida, some, as the scorpion, have pulmo- 
 
ORGANS OF RESPIRATION IN MAN. 707 
 
 nary saos, or lungs, ■with parallel lamellsa, situated on the abdomen in from one to 
 four pairs, and each opening by a separate stigma ; others have a system of ramified 
 iijternal air-tubes, termed trachese, or spiral vessels (from a spiral thread in their wall) ; 
 and some both trachese and pulmonary sacs. The myriapoda and all the insecta have 
 trachese. These penetrate the internal organs to their remotest parts, anastomosing 
 freely, and open at several points on the surface. Insects ■which breathe in ■water, as 
 ■well as many aquatic larvse, have branchise ■which first separate air from the -water, 
 and then transmit it along the trachese. The respiration by trachese is probably a 
 very perfect one, the blood and tissues being aerated throughout the body, at every 
 spot in -which they are being deteriorated. 
 
 Among Mollusca, some have branchise, or gills, as the cephalopods, the conchifera, 
 and some gasteropods. Other gasteropods have a pulmonary sac, or Ivnff, e. g. the 
 common snail. This sac opens and shuts so as to change the air, and on its surface 
 the venous blood is distributed ere it reaches the heart. 
 
 Fishes present the greatest development of gills. There are four branchial arches, 
 bearing vascular plates -with lateral offsets. Matteucci estimates the surface of the 
 gills of the common lay to measure 2,250 square inches. All the blood is driven by 
 the heart, through the giUs, to the aorta, and thus comes into close proximity to the 
 ■water in contact vfith the branchial surface. The capillary net^work has close and 
 regular meshes. 
 
 Reptiles have a rudimentary form of lung, combined in many instances with gills, 
 during a part or the whole of life, e. g. in the frog, the gills exist only in the tadpole 
 state; in the proteus, they remain through life. The pulmonary sacs of reptiles are 
 more or less cellulated on their inner surface, and receive a portion only of the venous 
 blood in each circuit. 
 
 In Birds and Mammalia respiration is much more active, being performed by means 
 of large and highly-divided lungs, placed within a bony framework, capable of re- 
 ceiving and rapidly renewing the air in large quantities, and giving passage to the 
 whole blood of the body on its way from the veins to the arteries. In Birds, there is 
 a series of openings from the pulmonary air-tubes, by which the air gains access to 
 passages and spaces amon^ the other organs and tissues, rendering the body specifi- 
 cally lighter, and, perhaps, in some degree, aiding respiration. Farther varieties in 
 the structure of the lungs, modifying their respiratory power, will be alluded to when 
 the human lungs have been described. 
 
 Organs of Respiration in Man. — The lungs, placed in the thoracic 
 cavity, receive air by the nasal passages and trachea, and venous 
 blood from the right side of the heart to transmit it to the left. They 
 form a double organ, ■with a single common air-tube, the trachea, 
 and a single common pulmonary artery, supplying the venous blood. 
 These vessels branch first into a right and left, and then into many 
 subordinate ramifications up to the ultimate air-cells and capillaries. 
 Four veins carry off the aerated blood to the left side of the heart. 
 Being penetrated by the air, the lungs are the lightest organs in the 
 body. In the foetus, before breathing, they are small, and transmit 
 only so much blood as is requisite for their o'wn gro'wth ; but ■when 
 the air enters their volume augments, their absolute ■weight increases 
 in consequence of the greater afflux of blood, ■while their specific 
 gravity diminishes. Krause estimates the average afesolute ■weight 
 of the lungs in men to be three pounds and a half, in -women t-wo 
 pounds and three-quarters, and the left to be smaller than the right 
 by one-tenth. The weight, as compared with that of the whole body, 
 is as one to forty or fifty. 
 
 In shape, the lungs are adapted to that of the cavity in which they 
 are lodged; their apices rise into the neck, their bases rest on the 
 diaphragm, between them lies the heart with the great vessels. They 
 are invested by a serous covering, the pleura, which, after lining the 
 thoracic walls, is reflected over them at their root, and dips into 
 
708 RESPIRATION. 
 
 those fissures, which serve to subdivide them- imperfectly, the right 
 into two, the left into three, lobes. 
 
 The trachea descends in the middle line from the larynx (which is 
 a complicated development "of it for the protection of the orifice of 
 the respiratory organ, and for the production of sound, and which 
 will be afterwards described), as far as opposite the second or third 
 dorsal vertebra, being straight, sub-cylindrical, flat behind, and about 
 three-quarters of an inch wide. It is held permanently open by from 
 sixteen to twenty cartilaginous rings, flattened in the direction of 
 the wall in which they are imbedded, and deficient behind to an 
 extent of one-third. Of these, the highest is the thickest, and the 
 lowest is adapted by its shape to the bifurcation of the trachea into 
 the two bronchi. The free ends of these cartilages are sometimes 
 forked, and contiguous ones are now and then joined. They are 
 immediately invested with perichondrium, a dense, white, fibrous, 
 inelastic membrane, and are connected by a continuation of it ex- 
 tending between their borders and ends. This inelastic membrane, 
 by its toughness, resists undue extension in the longitudinal direction. 
 
 Looking on the trachea behind, we observe the space between the 
 ends of the cartilages covered with irregularly interwoven fibres, in 
 the course of which we have discovered unstriped muscular fibres to 
 occur, especially about the bifurcation. In this fibrous layer are 
 recesses for the tracheal glands, and on dissecting it ofF these glande are 
 exposed, together with a thin sheet of transverse unstriped fibres, 
 completing, as it were, the circle of the cartilaginous rings, and 
 known as the trachealis muscle. The fibres of this are attached a 
 little way from the extremities of the cartilages on their inner surface, 
 and in contraction must serve to approximate them, and thus to 
 narrow the canal. In the horse, they are inserted three-fourths of 
 an inch from the extremities, which almost or quite overlap. In 
 birds, they are composed of striped fibres. 
 
 The cartilages, their interspaces, and the trachealis muscle are 
 lined by a thin layer of longitudinal, el^s1;ic, anastomosing fibres, uni- 
 formly spread out except over the trachealis muscle, where they are 
 gathered up into longitudinal bands, sometimes one-twelfth of an inch 
 thick, very visible through the mucous membrane. These take a 
 serpentine course down the bronchi, and preserve their anastomosing 
 character. The trachea owes its elasticity in the longitudinal direc- 
 tion to the fibres now described. 
 
 The mucous lining of the trachea, the essential part of the duct, 
 to which the above are accessory, is continuous through the glottis 
 with that of the pharynx, and physiologically with the respiratory 
 compartment of that cavity, and with the nasal passages (see ante 
 p. 522). It is covered with ciliated epithelium, and the direction of 
 the movement is probably upwards towards the glottis. The tracheal 
 glands are productions of this membrane, and appear as a layer of 
 reddish, distinct granules, behind the trachealis muscle, each one 
 being furnished with a separate duct, traversing first the muscle and 
 then the layer of longitudinal elastic fibres, to open on the inner 
 surface of the tube. These glands appear to be tubular, not follicu- 
 
THE HUMAN LUNGS. 709 
 
 lar, and are thus relate'd rather to the sudoriferous than to the sali- 
 vary system. They probably furnish much of tl^e halitus of the 
 breath and may determine its odour. 
 
 Of the bronchi or primary subdivisions of the trachea, the right 
 is the shorter, wider, and more horizontal ; the left longer to pass 
 under the aortic arch. Their walls resemble those of the trachea 
 with slight modifications. At the root of the lung, each breaks up 
 into branches corresponding to the lobes (lobal bronchia), and these 
 again into secondary, tertiary, and terminal bronchia, the last named 
 being from one-fortieth to one-sixtieth of an inch in diameter. The 
 terminal bronchia pass to portions of the pulmonary substance more 
 or less distinctly mapped out by areolar tissue, and termed lobules. 
 
 Coats of the Bronchia. — All these become gradually thinner as 
 they approach the air-cells. The cartilaginous pieces, which are 
 irregular in shape and position in the lobal bronchia, become reduced 
 to mere flakes, and finally cease in those of one-sixth or one-tenth 
 of an inch in diameter (Fig. 204). The last are seen mostly where 
 branchings occur. The muscular fibres of the 
 trachea are continued down even to the terminal 
 bronchia, but instead of filling up only the gap in 
 the cartilaginous framework, they form a uniform 
 layer encircling the canal, but excessively thin. 
 The fibres are here arranged in anastomosing 
 bundles (Fig. 203). Within the muscular layer is 
 that of the longitudinal elastic fibres, here disposed 
 as an even layer, and representing the submucous 
 areolar tissue. The ciliated epithelium and the 
 basement-membrane of the mucous tissue both 
 descend into the terminal bronchia. _ On the ex- lailTplnX^taV'^ 
 terior of the bronchia is some areolar tissue separat- ''•ansverse piexifo™ 
 
 _ - . , , . n • n arrangement of the 
 
 ing them from the neighbourmg masses or air-cells, muscular layer, ana its 
 
 1 • L 1 'l1 j_i J. • ■ 1 1 j' disposition at the orifice 
 
 and associated with the arteries, veins, lymphatics, of a branch. From a 
 and nerves belonging to the bronchial wall. SaTdim"'''"*^"^" 
 
 The bronchial arteries are usually two, coming 
 from the aorta, but irregular. They supply the coats of the bronchia, 
 and have corresponding veins. Their capillaries anastomose with 
 those of the pulmonary artery where the terminal bronchia become 
 lobular passages. The distribution and action^ of the pulmonary 
 nerves have been already discussed (pp. 498-506). 
 
 Ultimate Pulmonary Tissue — Lobules. — In some parts of the 
 exterior of the lungs, particularly near the borders, and in some 
 animals throughout, may be noticed a sort of mapping out of the 
 pulmonary substance into small polyhedral masses separated by 
 areolar tissue, and having a very irregular shape. These are the 
 lobules of the lungs. They can only be made out in certain situ- 
 ations, even by dissection, for it does not appear that the whole 
 human lung is thus subdivided by areolar septa. Nevertheless, it 
 seems certain that each terminal twig of the bronchus is in relation 
 with only its own proper set of air-cells, and that such sets of cells 
 do not communicate except through the medium of the bronchia. In 
 
710 
 
 RESPIRATION. 
 
 Fig. 204. 
 
 ^'• 
 
 I A 
 
 this sense lobules exist everywhere, even when" not isolated by areolar 
 tissue, and in this sense we shall use the term, as conveniently de- 
 signating that series of air-cells, associated by 
 dependence on a single terminal air-tube. We 
 shall afterwards show how much difference exists 
 in the isolation of the lobules of the liver even in 
 allied animals, and how unimportant this variety 
 appears to be. 
 
 The superficial lobules derive a covering on 
 one aspect from the pleura, but are separated 
 from it by rather dense areolar tissue, which 
 may be dissected off without rupturing the air- 
 cells. If the interstices between contiguous 
 superficial lobules be explored by the knife, the 
 terminal bronchia are found at the bottom of the 
 fissures, each going to a single lobule, and besides 
 these are seen brariches of the pulmonary artery 
 and vein, not running in company, nor limiting 
 themselves to a single lobule, but common to 
 contiguous lobules ; so that the air-spaces of one 
 lobule do not communicate with those of another 
 across the interstices, but the bloodvessels do. 
 On the exterior of a lobule we observe bubbles of 
 air of various sizes in its tissue, and if the bron- 
 chial tubes be injected, the lobule is distended, 
 and its exterior presents a number of bulgings 
 known as the air-cells, about which much con- 
 troversy has existed. Their shape seems irregu- 
 larly polyhedral, like the lobules themselves. 
 The angles where three or more of "these cells 
 meet, are the points at which the terminal twigs 
 of the pulmonary artery and vein penetrate 
 among the cells, after meandering more or less 
 over the surface of the lobule. In their course 
 in the interior of the lobule, these twigs generally 
 run separately in the lines of junction of three or 
 more cell- walls, branching as they run, 'and break- 
 ing up into their capillaries on either hand. 
 
 As the superficial lobules are truncated where 
 they form the surface of the lung, so the cells are 
 truncated where they form the surface of the lobule. This is most 
 decidedly the case where the lobules are well defined, and admit of 
 separation; but where contiguous lobules are not isolated by areolar 
 tissue (as in most parts of the interior of the lungs, and in the lungs 
 of the smaller mammalia), their superficial cells have their inequal- 
 ities mutually adapted to each other, and even their walls fused 
 together, so that the lobules would not remain distinct, were it not 
 that their air-cells do not communicate across the interval. 
 
 To convey a correct, and at the same time a simple, idea of the 
 cons-titution of the pulmonary lobules, we must regard each as an 
 
 Small bronchial tube 
 laid open, showing the ar- 
 rangement of the last car- 
 tilaginous flakes. The tube 
 haa been cut across above, 
 at the point where it pene- 
 trates the substance of the 
 lung, and below where it 
 has a diameter of about 1- 
 12th of an inch. The 
 elastic and muscular fibres 
 are not represented, but 
 both were so delicate as to 
 allow the adjacent air-cells 
 to be seen through the 
 bronchial wall. Ciliary 
 epithelium was traced in 
 the finest tube that could 
 be opened by scissors, viz. 
 of l-40th inch diameter. 
 From a healthy man uet. 
 twenty-five. Natural size. 
 
THE HUMAN LUNGS. 711 
 
 elementary lung, perfect in itself as an arrangement of a respiratory 
 membrane adapted to the aeration of the blood. First, the terminal 
 bronchial tube pertaining to each lobule, loses its epithelium and 
 muscular tunic at about one-eighth of an inch distant from the last 
 air-cell to which it leads, and is thus reduced to basement tissue and 
 yellow elastic fibres, which become blended into a single coat, the 
 only membrane composing the tubes beyond, and the air-cells. The 
 terminal bronchial tube, thus simplified, ramifies within the lobule, 
 and its branches may be conveniently distinguished from the bronchial 
 tubes under the name of lobular passages.* The lobular passages 
 are wider than the terminal bronchia, and are remarkable (being 
 honeycombed on their interior) for presenting a series of sacculi or 
 cells on their wall. These are the pulmonary air-cells. They form 
 a number of bulgings of the wall, and are separated from one another 
 by septa projecting inwards from the wall toward the axis of the pas- 
 sage (Fig. 206). They each open separately into the lobular pfissages, 
 and do not communicate with each other except through the passages. 
 The terminations of the several lobular passages are air-cells coming 
 up to the surface of the lobule, but some of the air-cells placed 
 laterally on the passages also contribute to form the surface of the 
 lobule. The air-cells thus surround and terminate each lobular pas- 
 sage — and the lobule consists of a number of lobular passages, as- 
 sociated by their dependence on a single terminal bronchial tube, and 
 each clothed as it were, on its sides and at its end, with a honey- 
 comb of air-cells, with orifices open towards the cavity'of the passages. 
 Contiguous cells of the same passage are separated by a simple septum 
 or process of the wall, while the contiguous cells of neighbouring 
 passages are separated by a septum, likewise simple, formed by the 
 union of the walls of each. Where the septa spring from the wall 
 of the passage, or in the angles where neighbouring cells unite, the 
 wall is strengthened by a greater thickness of elastic tissue, which 
 often has the form of arching bands of considerable strength in these 
 situations, as well as around the orifices of the cells. Thus the 
 lobular passages and the air-cells are formed of one tissue, and 
 perform the same function. They are a series of branched cellulated 
 air-passages, not lined with epithelium, or coated with muscular 
 tissue, but highly extensible and elastic, of much larger aggregate 
 capacity than the terminal bronchia which lead to them, and resem- 
 bling closely, in general conformation, the reptilian lung. Indeed, 
 an admirable notion of the essential arrangement of the lobules of the 
 mammalian lung may be derived from an examination of the terminal 
 parts of the sacculated bronchia of the lung of the turtle. The 
 lobular passages are wider than the terminal bronchia of which they 
 are the continuations, and than the cells which pullulate on their 
 walls. They also branch again and again in order to spread from 
 the terminal bronchial tube on every hand throughout the whole area 
 of the lobule ; and as their ramifications observe no certain order or 
 course, it happens that sections carried through the lobules are 
 
 * Dr. W. Addison, Phil. Trans. 1840. 
 
712 
 
 RESPIRATION. 
 
 rarely found to follow any single passage far, so as to display, in a 
 happy manner its mode of distribution. Sometimes, however, this 
 is better seen than at others. 
 
 [M. Kossignol has recently given an elaborate description of the 
 pulmonary structure. He insists particularly on the ultimate bron- 
 chial ramifications being in shape like an inverted funnel, and he 
 terms them the infundihula. The cells, forming a honeycomb on 
 their interior, he calls the alveoli (Figs. 205 and 206). Emphysema, 
 
 Fig. 205. 
 
 Thin Blice from the pleural surface of a cot's lung, considerably magnified. At the thin edge, 6 c (f , 
 alvedU. are Feen. In the centre (as a), "where the slice is thicker, alveoli are seen on the walls of infundi 
 huia. — From Kossignol. 
 
 according to this author, seems to consist in a distension of the pas- 
 sages and cells, and a breaking down and obliteration of the septa, 
 first between the cells of the same passage and then between neigh- 
 boring passages, and even between contiguous lobules. 
 
 The diameter of the lobular passages is from r^ to rk of an 
 inch 
 
 Fig. 206. 
 
 and that of the cells from ^ J^ to 
 
 of an inch according to our measurements. 
 In a preparation of the lung of the calf, 
 given us by our friend Professor Retzius, 
 they measure g^,,; and Dr. W. Addison 
 
 makes them from nrm to -rl-^ of an inch. — 
 
 „ ^ 3CT5 
 
 Ed.] 
 
 The skeleton of the lobule is thus an 
 elastic membrane elaborately arranged, so 
 that the air may be brought into contact 
 with it for the most part on both its surfaces. 
 Over this membrane the whole venous blood 
 of the body is made to course in a continual 
 stream, so as to" be submitted to the action of the air. 
 
 Vascular Element. — The pulmonary artery, conveying the venous 
 blood to the lungs, is about as large as the aorta, and is furnished 
 with a triple valve at its origin from the right ventricle of the heart. 
 It soon divides into a right and left branch, which enter the lungs at 
 their root, and ramify as far as the lobules, in company with the 
 
 Bronchial termination in the 
 lung of the dog. a. Tube (lobular 
 passage) branching towards the 
 infundibula. b. One of the infun- 
 dihula. c. Septa projecting in- 
 wards on the infundibular wall 
 and forming the alveoli, or cells. 
 — From Kossignol. 
 
THE HUMAN LUNGS. 713 
 
 bronchia. Arrived at the lobules, the small branches of the pulmonary 
 artery do not enter in company with the lobular passages, but dis- 
 tribute themselves over the lobules in the interlobular iissures, pene- 
 trating at various points between the air-cells, and occupying tubular 
 channels in the angles where three or more cells meet. These chan- 
 nels are formed of the same yellow elastic tissue which constitutes 
 the lobular passages and air-cells, and' their wall blends with the 
 proper coat of the terminal twigs of the pulmonary artery which 
 occupy them. The capillaries of the lobule are given off both from 
 the twigs which meander over the lobule and from those which pene- 
 trate it, and they form a network which covers the walls of all the 
 cells of the lobule, as well as of the lobular passages, anastomosing 
 with Some twigs of the bronchial arteries where the passages are 
 continuous with the terminal bronchia. This network empties its 
 blood into venules which lie first in intercellular channels similar but 
 intermediate to those which lodge the arterial terminations ; and 
 these venules collecting the now aerated blood from the interior and 
 also from the surface of the lobules, converge to larger veins which 
 lie in the interlobular spaces and tend towards the root of the lungs, 
 but for the most part by a route distinct from that of the arteries 
 and bronchia. Thus the general mass of the lung may be regarded 
 as containing two series of ramified canals, one transmitting the 
 bronchia (with their vessels and nerves) and the pulmonary arteries, 
 the other the pulmonary veins. This interesting fact was well 
 described by Dr. Addison, of Guy's Hospital, in a paper in the 
 Medico-Ohirurgical Transactions in 1840. At the root of the lungs 
 four pulmonary veins result, which forthwith discharge their torrent 
 of arterialized blood into the left auricle of the heart. 
 
 The cause of the separate course of the pulmonary arteries and 
 veins is to be found in the opposite position of their radicles, in re- 
 gard to the capillary network of the lobules, it being a convenient 
 arrangement for the terminal arterial and venous twigs to hold alter- 
 nate positions among the capillary network, so that each arterial 
 twig disperses its blood in all directions, and each venous radicle 
 collects it from all sides. An obvious analogy exists in respect of 
 the course of the vessels and ducts between the liver and lungs, the 
 bile-ducts answering to the air-passages, the hepatic artery to the 
 bronchial arteries, the vena porta to the pulmonary artery, the 
 hepatic vein to the pulmonary vein. The nerves and lymphatics 
 pass in both cases with the ducts. 
 
 The capillary network of the lungs lies on and in the walls of the 
 air-cells and lobular passages. These walls are for the most part 
 much too thin to inclose the capillaries between two. layers of their 
 substance, and therefore the capillaries project fairly into the air- 
 cells, by a great part of their circumference, being adherent to the 
 wall by a narrow line only. The capillary wall is thus exposed and 
 bare, in contact with the air of the cell, and nothing besides the 
 delicate membrane of the capillary intervenes between the air and 
 the \)\6oA. A capillary frequently passes through an aperture in the 
 46 
 
714 
 
 RESPIRATION. 
 
 cell-wall, So as to project first into one cell, and further on into a 
 contiguous one, but never becomes altogether free from the wall. In 
 .passing, its wall is blended with that of the cell. The nuclei seen 
 in the) capillary walls elsewhere are very conspicuous in those of the 
 lungs. 
 
 The best way of proving the arrangement of the capillaries is by 
 injecting a lung with size by the pulmonary artery till the blood- 
 vessel's and the air-cells are both filled, the latter by transudation, 
 and theft slicing it when cold. The capillary wall is then seen to, 
 be uncovered by any tissue, just as is usual in the Malpighian tufts 
 of the kidney. The diameter of the capillaries is about xg'jTj of an 
 inch, which is large, and the blood therefore passes freely. The 
 meshes of the network are not much wider than the vessels them- 
 selves. 
 
 Mr. Rainey says that, on the surface of the lung, the capillary 
 
 Fig. 207. 
 
 "View of a thin section of the lung of a cat, -which, had heen injected by the pulmonary artery with 
 gelatine, so as to fill hloodveaeels and air-cells, and hdd been sliced when cold, a a a. Air-c^lls andlobu- 
 lar*passage in section, fr 6. Their wall in section, c. Their wall in face. tZ. Extremely faint nucleus in 
 the same, e e. Capillaries, h. Nucleus in wall of capillary, n. Small pulmonary artery or vein with 
 simple wall. Magnified 250 diameters. 
 
 network extends over a space corresponding to not more than ten or 
 twelve cells, i. e. over from one-thirtieth to one-twentieth of an inch, 
 and if the rate of the blood be taken at an inch and three-quarters 
 per minute, according to the estimate of Valentin, drawn from ob- 
 servation of the frog's foot, the blood would be somewhere about one 
 second and a half in contact with the air at each circuit. But pro- 
 bably in the higher animals its transit is more rapid. 
 
 "We may here refer to some very interesting observa-tions on the 
 
ANATOMY OF THE LUNG, 
 
 715 
 
 arrangement of the capillaries and terminal air-passages, lately made 
 by Mr. Raihey. This careful and accurate anatomist wq-s the first 
 to insist on the fact that, in mammalia and birds at least, the capil- 
 laries are, as we have above noticed, bare ; exposed on their exterior 
 to the air, liot covered by any membrane, either mucous or serous, 
 or by any epithelium ; and that by this arrangement the most perfect 
 aeration of the blood which traverses them is provided for. The air 
 and the blood may be said to be in contact through the delicate 
 capillary wall, a film less than j^j^ of an inch in thickness. In 
 some of the mammalia, as the kangaroo, the rat, and the mouse, the 
 terminal air-spaces are too minute to contain even a single particle 
 of epithelium, and cannot therefore be lined by a pavement of such 
 particles. The elastic tissue described as forming the cell-wall in 
 the human lung is in such instances very imperfect, being deficient 
 in the areolae of the vascular network, so as to render the cell-walls 
 cribriform, or rather to reduce the terminal air-receptacles into a 
 congeries of inosculating and most minute and irregular passages. 
 
 Iji the bird's lung, the elastic tissue, according to the same anato- 
 mist, is even more scanty. The mucous membrane lining the 
 bronchia ceases at the commencement of the lobular passages, and 
 these passages seem hollowed out in the substance of a solid capil- 
 lary plexus, or one in which the capillaries extend and anastomose 
 indifferently in all directions. This vascular plexus forms the only 
 wall of these passages, and the 
 air has access from the passages 
 into the interstices of the plexus, 
 so as everywhere to surround and 
 touch the whole surface of every 
 capillary. Instead, therefore, of 
 the terminal air-spaces being cells 
 with a plane network of capilla- 
 ries on their walls, they are the 
 mere interstices of a solid vascu- 
 lar plexus. Thus, a more abund- 
 ant intermixture of the blood and 
 air is secured, and the ultimate 
 tissue of the lung is reduced to the 
 simple capillary wall, arranged 
 so that air has access to its exte- 
 rior. The adhesion of the lungs 
 to the costal surface, and the 
 support afforded by the cartila- 
 ginous and other tissues of the 
 bronchial tubes, as well as by the 
 areolar tissue bounding the elon- 
 gated lobules, are .suflScient to 
 maintain the integrity of so frail 
 the vascular plexus are usually even smaller in diameter than the 
 capillaries th"emselves, and, according to Mr. Eainey, average ^g^^ 
 
 Slightly oblique section through a bronchial 
 tube, showing at a the cavity of the tube. 6. Its 
 lining membrane, containing bloodvessels ■with 
 large areolae, c, c. Perforations in this membrane, 
 ■where it ceases at the orifices of the lobular pas- 
 sages, d, d. e, e. Spaces between contiguous lo- 
 bules, containing the terminal pulmonary arterieg 
 and veins supplying the capillary plexus, /,/, tp 
 the meshes of which the air gains access by the 
 lobular passages. '' 
 
 a web. The aerial interstices of 
 
716 RESPIRATION. 
 
 of an inch. The above Fig. (208) is from Mr. Rainey's paper, and 
 is drawn from the lung of the fowl, highly magnified. 
 
 The gradations of perfection in the respiratory surface, considered as to its minute 
 organization in Reptiles, Mammalia, and Birds, may be thus recapitulated: — 
 
 In Reptiles the cells are large and few. The air has access to the respiratory ca- 
 pillaries only on one surface, viz., that towards the cavity of the cell which they line,-> 
 and where two cells are contiguous, but separated by a septum, the septiim has a 
 capillary web on each of its surfaces. 
 
 In Mammalia, for the most part, the cells are much multiplied, and where two lie 
 side by side, the septum between them has but one layer of capillaries, which is, in a 
 great measure, common to them both, and aerated on both its surfaces. And here 
 we may remark the reason of the non-isolation of the lobules by areolar tissue in the 
 mammalian lung, except at the borders and thinner parts, where ^uch isolation is 
 necessary for the movements of the lung in respiration. When the lobules are thus 
 isolated, the capillaries on the cell-walls which bound the lobule can have air only on 
 that surface which is towards the cavity of the cells; whereas, when the contiguous 
 lobules are blended by the fusion of the cell-walls which form their exterior, these 
 cell-walls, like the rest, contain but a single respiratory plexus, which is aerated on 
 both its surfaces. • 
 
 In Birds the respiratory capillary plexus is rendered the most perfect possible, both 
 T)y the omission -of the elastic supporting tissue, and also by the vascular plexus being 
 no longer lamellar, but solid, or extended alike in all directions. It is manifest that 
 by this arrangement a given pulmonary space is made to contain the greatest possible 
 quantity of capillary wall, and that this wall is exposed most completely to the action 
 of the air admitted around it. 
 
 Movements of Respiration. — The thorax is a movable franjework 
 composed of a nearly fixed column, the dorsal spine, on which are 
 movably articulated twenty-four ribs, curved and inclined so as to 
 embrace a large conical space, and ending in cartilages, which, with 
 three exceptions on each side (the floating ribs), are joined in front 
 through the medium of a flat piece, the sternum, the inclination of 
 which is downwards and forwards. The upper orifice, embraced by 
 the vertebral column, first ribs and sternum, is closed by a fascia of 
 dense areolar tissue, rendered extremely irregular by the apices of 
 the lungs rising slightly into the neck, and by the various struc- 
 tures — the oesophagus, trachea, great bloodvessels, muscular and 
 other parts — that pass through it. The lower orifice, which is very 
 much larger, is closed by the .diaphragm, an arched and sloping 
 musculo-tendinous septum between the thorax and abdomen, through 
 which pass the inferior vena cava, the aorta, and great absorbent 
 trunk, as well as the oesophagus and the pneumogastric and sympa- 
 thetic nerves. Between the ribs are placed the two layers of inter- 
 costal muscles with oblique fibres oppositely crossing, and chiefly on 
 the exterior of the bony framework are added other muscles, which 
 may enlarge or diminish the area of the cavity, and thus act in 
 respiration, but which are, for the most part, subservient to the 
 general muscular movements of the body. 
 
 The thorax is capable of enlargement in all its dimensions; in 
 height, depth, width. Its vertical extent is increased by the eleva- 
 tion of the ribs and the widening of the intercostal spaces, but chiefly 
 by the descent of the diaphragm. Its antero-posterior and trans- 
 verse diameters are increased by the elevation of the ribs, which 
 
MOVEMENTS OF RESPIRATIi 
 
 (l)N. 
 
 717 
 
 carry forwards as well as raise the sternum (and the lower end of 
 that bone usually a little more than the upper, in consequence of the 
 greater length apd obliquity of the lower sternal ribs), and which 
 also seem to undergo a slight rotation on a line joining their two 
 extremities, by which their middle part is raised and slightly re- 
 moved from the median plane of the thorax. These are the princi- 
 pal modes provided in the mechanism of the thoracic walls for its 
 dilatation in breathing. It should be added that during the advance 
 of the sternum the arch of the ribs is widened, chiefly by a torsion 
 of their cartilages, and that the elastic rebound of those parts is a 
 powerful agent in expiration. 
 
 Observed Movements. — All the foregoing modes of enlargement 
 of the thorax act in deep inspiration, but in ordinary breathing there 
 are considerable differences 
 according to sex and age. 
 In men, an ordinary inspira- 
 tion is attended with very 
 slight elevation of the ribs, 
 not more than one-twentieth 
 of an inch, according to Dr. 
 Hutchinson's observations; 
 whereas, in women, this 
 movement is very obvious, 
 particularly in the upper ribs. 
 It is not improbable that the 
 cause of this may lie in the 
 narrower waist of the female, 
 obliging an undue enlarge- 
 ment of the upper part of 
 the thorax to compensate for 
 the smaller size and less dila- 
 tability of the ample base. 
 The separation of the ribs 
 and widening of the intercos- 
 tal spaces when the chest is 
 enlarged, are proved by mea- 
 surement both in the living 
 and dead. Dr. Hutchinson 
 has made casts of the interior 
 under both states. Dr. Sib- 
 son divides the ribs into three 
 sets: a superior set of five, 
 separately joining the ster- 
 num; an intermediate set of 
 three with conjoint carti- 
 lages ; and an inferior or diaphragmatic set of four with floating car- 
 tilages. He considers that all, except the upper four in their front 
 part, diverge from one another in inspiration, the inferior set the 
 most, but the lowest of all remaining stationary. Messrs. Beau and 
 
 Diagrams showing the extent of antero-posterior 
 moTement in ordinary and forced respiration in maid 
 and female. " The back is supposed to be fixed in order 
 to throw forward the movement as much as possible." 
 The black line indicates, by its two margins, the limits 
 of ordinary inspiration and expiration. In ftn-ced inspir 
 ratmbf the body comes up to the dotted line, while in 
 forced expiraMan, it recedes to the smallest space indi- 
 cated. Erom Dr. Hutchinson. 
 
718 RESPIRATION. 
 
 Maissiat* describe three varieties of ordinary respiration: 1. Ab- 
 dominal, or that chiefly effected by the diaphragm and apparent in 
 the motion of the abdominal walls. This occurs in infants up to 
 the end of the third year, and in males generally. 2. Costo-inferior, 
 or that in which the lower ribs (those of Mr. Sibson's intermediate 
 and inferior sets) are observed to act. This is observed in boys after 
 three, and in men. 3. Costo-superior, or that effected in a con- 
 siderable degree by the upper ribs. This is observed in females, 
 especially in adults. 
 
 Action of Muscles. — The diaphragm has an arched form, is highest 
 in front, lowest behind. The fibres pass to a central tendon on which 
 is seated the heart in the pericardium, the lungs resting chiefly on 
 the muscular parts. Its contraction would tighten and then depress 
 both the central tendon and the muscle generally, and would also 
 tend to straighten the curve formed by the fibres as they pass from 
 the spine and ribs to the central tendon. Thus the heart would be 
 lowered a little, but, perhaps, the lungs more, and the area of the 
 pulmonary compartments of the thorax would be much enlarged, for 
 the diaphragm acts at their wide and ample base, where a slight 
 range of vertical movement produces a great effect. In its descent, 
 the diaphragm presses down the abdominal viscera, and bulges the 
 abdominal walls. In expiration, it recedes upwards, being pushed 
 upon by the abdominal walls through the medium of the viscera-. 
 
 The action of the intercostal muscles is less obvious, and had been 
 the subject of much difference of opinion, even before the days of 
 Haller. It may be studied on mechanical principles, and by obser- 
 vation. Hambergerf has given the most elaborate and complete 
 exposition of the mechanical view of the subject, and has illustrated 
 it with diagrams and models. ' He shows that if two parallel bars 
 (ribs) slope downward from a fixed vertical column (spine) to which 
 they are separately articulated (heads of the ribs) and are kept 
 separate at their opposite ends (as by the sternum), then a contrac- 
 tile force (muscle) acting between them, will, raise or depress both 
 bars, according to the direction of its obliquity. If the contractile 
 cord slope downward from the column representing the spine (exter- 
 nal intercostal fibres), the bars will both be elevated by its contrac- 
 tion, and will carry upwards the sternal element. As they rise, the 
 cord is seen to shorten. 
 
 If on the other hand the contractile cord slope downwards towards 
 the vertical column (internal intercostal fibres), then the bars will be 
 Tboth depressed by its contraction. It is obvious that the space be- 
 tween the bars will be widened as they rise towards the horizontal 
 line, and narrowed as they fall. Hence it seems clear, without 
 entering upon the mechanical theorems by which the above results 
 may be proved, that the action of the external and internal inter- 
 costals must be antagonistic. That the former must elevate and 
 
 * ArcMv. Qin. de MM. t. xv. p. S99. 
 
 f Physiologia Medioa, Jente, 1751, 4to. p. 140, et seg. 
 
ACTION OF THE INTERCOSTALS. 719 
 
 open out the ribs, the latter depress and approximate them — that, as 
 the fibres of the one are shortened, those of the other must of neces- 
 sity be lengthened. 
 
 It is true that the ribs are curved, and variously flexible, instead 
 of straight and stiff ; that their articulations differ from one another, 
 and are nowhere purely ginglymoid, and that other forces besides 
 the intercostal muscles influence their movements. 
 
 These considerations, however, do not seem to affect the substan- 
 tial accuracy of Hamberger's views, so far as relates to the greater 
 number of the ribs, and indeed to all in the posterior region. And 
 Dr. Hutchinson has done well to call attention to them and to illus- 
 trate them by new researches. But Dr. Sibson has shown by ob- 
 servations both in man and animals, and in the latter especially, by 
 a series of careful experiments upon the actual movements of the 
 thoracic walls and their muscles, exposed during life, that the exter- 
 nal intercostals are not everywhere inspiratory, nor the internal ones 
 expiratory. For, in the upper two or three spaces in front, the in- 
 ternal, as well as the external intercostal fibres, contract and ap- 
 proximate the ribs. Those fibres, also of the internal intercostals, 
 which pass between the cartilages of the ribs, contract during inspira- 
 tion, and correspond with the internal intercostals of the sternal ribs 
 of birds, which are powerfully inspiratory, and slope downwards and 
 backwards from the sternum. These may have their action explained 
 by Hamberger's views, if the sternum be regarded as giving the 
 fulcrum instead of the vertebral column. Again, the lowest external 
 intercostal lengthens in inspiration, and is an expiratory muscle, the 
 eleventh rib in inspiration rising from the twelfth, which is sta- 
 tionary.* 
 
 On the whole we may conclude, that in inspiration, the upper ribs 
 rise by the action of the scaleni — that the rest of the ribs iij their 
 hinder part rise and open out by the action chiefly of the external 
 intercostals ; while in front the intercostal spaces are narrowed above 
 by the rise of the second, third, and fourth ribs towards the first, and 
 at the same time widened midway and below, the flexibility of .the 
 costal cartilages having much to do with this latter movement. It 
 may, also, be regarded as certain that the internal intei;costals, 
 except in front, are muscles of expiration, and approximate the 
 ribs. 
 
 * On February 26, 1851, Dr. Sibson exposed the intercostal muscles in a dog under 
 chloroform, when we noted the following as facts: 1. The lower fibres of the serratus 
 magnus contract dming inspiration; the upper fibres lengthen. 2. The first five 
 intercostal spaces diminish decreasingly during inspiration. 3. The seventh, eighth, 
 and ninth ribs diverge increasingly from the seventh to the ninth, and the tenth, 
 eleventh, and twelfth in a less degree. 4. The twelfth rib is stationary. 5. The 
 
 jSrst external intercostal muscle shortens, the lowest lengthens, during inspiration. 
 6. The first and second internal intercostal muscles, in front, shorten during inspira- 
 tion ; the third, also, in a very slight degree. 7. The sixth internal intercostal elon- 
 gates during inspiration, and the ninth also, but in a greater degree. 8. The eleventh 
 anterior external intercostal of the diaphragmatic ribs shortens during inspiration. 9. 
 
 ■ Behind, the tenth external intercostal shortens, the tenth internal lengthens, during 
 inspiration. 
 
720 RESPIRATION. 
 
 Dr. Sibson has well pointed out that the forces which expand the 
 thorax act, in a great degree, in a separate and independent manner on 
 its several parts; that the lower region, and the lower lobes of the 
 lungs which fill it, are enlarged by the diaphragm arid lower extej-nal 
 intercostals, while the upper region expands under the influence of 
 the scaleni, its external intercostals, and (in front) its internal inter- 
 costals. A variety of morbid conditions of the lungs, where the ex- 
 pansibility of one or more lobes is modified, illustrates this observa- 
 tion, for one side of the chest may be observed to expand without 
 the other, or a portion of one side without the rest. How important 
 this amount of independence of the parts of the chest is to the pre- 
 servation of life, under accident or disease, needs hardly be ex- 
 plained. 
 
 In addition to the muscles now mentioned, the levatores costarum, 
 cervicalis ascendens, and serratus posticus superior are probably 
 muscles of ordinary inspiration ; and those of the abdominal wall, 
 with the levator ani, of expiration ; the latter action being aided by 
 the elasticity of the ribs and their cartilages, and by the resilience 
 of the elastic tissue entering so largely into the composition of the 
 lungs themselves. This resilience (which Dr. Carson showed to be 
 sufficient in sheep and dogs to balance a column of water from one 
 to one foot and a half in height) occasions the collapse of the lungs 
 when the pleural cavity is accidentally opened, as sometimes by 
 wound of the parietes. In such cases the air passes in and out of 
 the thorax through .the wound in respiration, and the air previously 
 in the lung is expelled through the glottis by the elastic force of the 
 pleura and walls of the air-passages and cells. If the lung also 
 be wounded, the air may pass into the pleural sac from the air- 
 passages under the same resilient force, and be thence pumped by 
 the expiratory forces through the wound in the parietes into the 
 areolar tissue of the body, as so often happens in the case of frac- 
 tures of the ribs. 
 
 Extraordinary Muscles of Respiration. — In voluntary deep breath- 
 ing, or when (as in asthma) the head, neck, and upper extremities 
 become fixed points for the muscles passing between them and the 
 thorax, the lower part of the serratus magnus, the pectorales, the 
 subclavii, with the sterno-mastoidei, trapezii, and some others, aid in 
 dilating the chest. Some difference exists among the most recent 
 authors as to the share particular muscles take in the movements of 
 respiration ; and this is not surprising when we consider the com- 
 plexity of the problem, the difficulty of determining the fixed points, 
 or of observing the muscles in separate action. In forced expiration, 
 the triangulares sterni, the serrati postici inferiores, sacro-lumbales, 
 latissimi dorsi, with their accessories as high as the highest costal 
 insertion, probably help to depress and approximate the ribs. 
 
 Power of the Respiratory Muscles. — Dr. Hutchinson has lately 
 made numerous experiments on this subject, and his results and those 
 of Valentin and Mendelssohn agree. He finds as the average of 
 1,500 trials that the expiratory power exceeds the inspiratory by 
 
KXCITATION OF RESPIRATORY MOVEMENTS. 721 
 
 one-third ; that men of 5 feet 7 or 8 inches have the greatest inspi- 
 ratory power, and should on an average raise a column of mercury 
 three inches ; while, above this, the strength gradually decreases as 
 the stature increases, so that a man of 6 feet raises a column of only two 
 inches and a half: also, that occupation or mode of life serves much 
 to modify the relation which the inspiratory and expiratory powers 
 bear to each other. Thus, wrestlers, boxers, and others, accustomed 
 to employ the extraordinary muscles of respiration, in rendering the 
 thorax a fixed point from which other muscles might act, were found 
 to have an unusual power of expiration. In one wrestler he found 
 the expiratory power exceed nearly four times that of the natural 
 inspiratory power. Valentin, in six experiments on young adult 
 males, found the force exerted in ordinary, tranquil inspiration and 
 expiration to be from about one-seventh to three-sevenths of an inch 
 of mercury. Dr. Hutchinson calculates that a man who raises three 
 inches of mercury by an effort of inspiration exerts a force equal 
 to 1,000 lbs. In one man he found the mercury raised to such a 
 height (seven inches) as to indicate a force of 2,200 lbs., or nearly 
 a ton. 
 
 When the capacity of the thorax is augmented, the air in the lungs 
 expands so as to keep them in contact with the walls, and the ex- 
 ternal air enters by the trachea to restore the equilibrium. When 
 the dilating force ceases, the walls of the chest contract upon the 
 lungs, and expel a portion of the air, the lungs themselves conspir- 
 ing- 
 
 Use of the Trachealis Muscle. — That the trachealis in contracting 
 must diminish the area of the trachea and bronchia is obvious from 
 its arrangement no less than from experiment. Dr. Williams found 
 that the lungs taken from an animal just killed manifestly contracted 
 under the stimulus of galvanism. The fibres are allied to those of 
 the ducts of glands, and of the bloodvessels, and are consequently 
 probably incapable of coinciding in action with the. muscles of respi- 
 ration. It further seems impossible to assign an object to any 
 peristaltic action which might be attributed to them. We are dis- 
 posed to consider that the trachealis muscle contracts and dilates the 
 air-tubes slowly, in relation to the activity of the respiratory func- 
 tion at different times of the day, or under other modifying circum- 
 stances. Its contraction would tend to limit the quantity of air 
 transmitted in a given time, or would quicken its passage. It is in 
 all probability contracted spasmodically in spasmodic asthma, and in 
 the early stages of bronchitis. If it contracts during the sensation 
 that precedes and accompanies coughing, this would facilitate the 
 expulsion of mucus by quickening the expelled current of air. 
 
 JExcitation of the Respiratory Movements. — We have alread;^ re- 
 ferred to the share taken by the nerves in respiration. The respi- 
 ratory acts are essentially involuntary, and unconsciously performed, 
 although we have a limited power of checking or accelerating them, 
 of varying their rhythm or force, and can become aware of them by 
 an effort of attention. After holding the breath for fifteen or twenty 
 
722 RESPIRATION. 
 
 seconds during ordinary respiration, or forty seconds after a deep 
 inspiration, there arises an insupportable sensation over the whole 
 chest, concentrated under the sternum, and no effort can maintain 
 the interruption of the respiratory acts. This urgent sensation of 
 want of breath, when carried to its full extent by any mechanical 
 impediment to the aeration of the blood, is one of the most painful 
 and oppressive kind, and is referable to the pulmonary plexuses dis- 
 tributed on the bronchia, and perhaps on the walls of the lobular 
 passages and cells. The impression made on these peripheral nerves 
 by the absence of oxygen, and the undue presence of carbonic acid 
 in the air in contact with them, is propagated to the spinal cord and 
 medulla oblongata by the sympathetic and vagus, and there excites 
 those combined actions of the muscles of inspiration which lead to 
 the renewal of the air; and it may be fairly concluded that the 
 ordinary motions of respiration depend on the same circle of nervous 
 actions, which thus, voluntarily arrested, become apparent by their 
 accumulated force. The muscular actions of expiration, which seem 
 to follow so evenly on those of inspiration, are probably due, in 
 part at least, to the stimulus of elongation of their fibres. When 
 the ribs diverge, the fibres of the internal intercostals, except in 
 front, are extended. 
 
 Frequency of Respirations and Ratio to the Pulse. — The number 
 of respirations per minute in healthy adults is from eighteeo to 
 twenty; but, according to Dr. Hutchinson's observations on more 
 than 1 ,700 persons (when sitting), the range in health may be from 
 six to forty, though most persons breathe from sixteen to twenty- 
 four times per minute. The proportion which the respirations bear 
 to the beats of the heart is liable to much variation, but is in general 
 not far from that of one to four. Dr. Guy has shown that the 
 respirations are rather more frequent in the evening than in the 
 morning, whereas the pulse is rather slower. He has also discovered 
 that the proportion between the respirations and pulsations is much 
 deranged by changes of posture, probably by these modifying the 
 expansion of the lungs at each inspiration, without inducing any 
 corresponding change in the transmission of the blood. 
 
 Aerial Capacity of the Lungs, and Amount of Air Breathed. — 
 When the lungs have been emptied as much as possible of air, by a 
 forced expiration, they still contain a residual quantity, which may 
 be estimated at about forty cubic inches. The mechanical condi- 
 tions under which the orgtins are placed do not allow of their expel- 
 ling this remnant. If, now, the deepest possible inspiration be taken, 
 it is found that they are capable of inhaling a further quantity, vary- 
 ing much in different persons, but on an average about 240 cubic 
 incj^es, which, with the former residual quantity, make a sum of 280 
 cubic inches as the full capacity of the lungs of a person of good 
 height (5 feet 8 inches). But in ordinary breathing, the lungs are 
 neither very empty nor very full — they maintain a middle condition, 
 and their range of movement in natural or ordinary respiration is 
 only BuflScient to pump in and out a quantity of air equal to about 
 
CHANGES IN RESPIRKD AIR. 723 
 
 30 cubic inches. From the best observations, it may be concluded 
 that a person whose full capacity is 280 cubic inches, contains in his 
 lungs, after an ordinary expiration, about 110 cubic inches; and 
 after an ordinary inspiration, about 140 cubic inches, a quantity 
 ■which he is enabled to double by a full ■ inspiration. Thus rather 
 more than one-fifth of the ordinary contents of the lungs are expelled 
 at each expiration, and again renewed by inspiration. 
 
 Dr. Hutchinson, by means of a gasometer, which he terms a spiro- 
 meter, has examined a large number of persons with reference to 
 their power of taking air into the lungs. The person first inspires 
 to the full extent, and then breathes into the instrument as much air 
 as he can, and it results that the height of the individuals has mjich 
 to do with their respiratory range. Thus, while on an average a 
 person of 5 feet breathes 174 cubic inches, one of 5 feet 1 inch will 
 breathe 182 cubic inches, and for every inch of height up to 6 feet, 
 will breathe about 8 cubic inches additional. Weight has much less 
 influence than height, but tends to diminish the respiratory power 
 when beyond a certain limit. In males of the same height, the 
 respiratory range {vital capacity of Hutchinson) increases from 15 
 to 35 years of age; but from 35 to 65 it decreases nearly IJ cubic 
 inches per year. Bourgery agrees nearly with this : he states that 
 more air can be inspired at thirty than at any other age, and that in 
 old persons the range is very limited. Bourgery calculates that a 
 child of ten years of age, with a weight three times less than that 
 of a man of eighty, has a respiratory power eight times greater. 
 This is due to the great difference there is in the range of the respi- 
 ratory movements. The old man being able to increase the amount 
 breathed by less than a half, while the child may increase it nearly 
 fourteenfold. Herbst has shown that the capacity of the lungs is 
 much smaller in the female than in the male. 
 
 Having now considered the anatomy of the respiratory organs, 
 and the movements which regulate the supply of air, we may proceed 
 to consider the changes which occur in the air during its sojourn in 
 contact with the respiratory surface, and also the corresponding 
 changes in the blood circulated there. 
 
 Changes in the Respired Air. — The air consists of a mixture of 
 oxygen and nitrogen, in the respective proportions of about 20.81 
 and 79.19 in 100 parts by volume, with the addition of a very minute 
 portion of carbonic acid gas, not exceeding one part by volume in 
 2,000. It contains watery vapour in variable quantity, according to 
 temperature and other circumstances ; and also non-estimable quan- 
 tities of other gaseous and volatile substances, of no account in re- 
 lation to the respiratory function. In air that has been breathed, 
 the temperature is found to have assumed nearly or quite that of the 
 blood, the quantity of moisture has nearly reached the point of satu- 
 ration, the proportion of oxygen has diminished, and that of cai'bonic 
 acid has increased, while that of nitrogen has slightly increased, or 
 has undergone little change. A small quantity of animal matter 
 has also been received from the air-passages, as is proved by the 
 
724 RESPIRATION. 
 
 brown colour assumed by sulphuric acid, through which the respired 
 air is made to pass. 
 
 Aqueous Vapour Exhaled. — It results from the most careful expe- 
 riments, amongst which may be mentioned those of Valentin and 
 Brunner, and of Moleschott, that the air expired is usually nearly 
 saturated with moisture, and that the quantity of water thus escaping 
 from the system in twenty-four hours, may be estimated in temperate 
 climates at from twelve to twenty ounces. It is, of course, impossi- 
 ble to ascertain, nor is it important, how much of this quantity is 
 derived from th& respiratory surface, strictly so called, and how 
 much from the moist and vascular surfaces of the nasal, pharyngeal, 
 and bronchial passages. 
 
 Exhalation of Carbonic Acid by the Lungs. — It is easy to show 
 that carbonic acid gas is exhaled from the lungs, by breathing into 
 lime-water, which thus becomes turbid by the formation of insoluble 
 carbonate of lime ; or' into a phial, where a taper is then at once 
 extinguished. 
 
 In 100 parts by volume of expired air (as an average of many 
 experiments). 
 
 
 
 Caibonio Acid. 
 
 Coathupe . 
 
 found . 
 
 . 4.02. 
 
 Valentin and ' 
 Brunner . j' 
 
 it 
 
 . 4.38. 
 
 Vierordt 
 
 tt 
 
 . 4.33: 
 
 Thomson 
 
 (C 
 
 . 4.16. 
 
 The general average of the results of Valentin and Brunner, and 
 Vierordt, all of which were performed on adult males, may be ac- 
 cepted for that age and sex, viz. : 4.35 parts of carbonic acid in 100 
 parts of expired air ; or deducting the small quantity of carbonic 
 acid contained in the air when inspired, we may conclude that 4.30 
 parts per cent, by volume of that gas are derived from the lungs at 
 each ordinary expiration. Taking, as before, 30 cubic inches as the 
 volume of each expiration, the actual quantity of carbonic acid in 
 each will be 1.29 cubic inche8== about 23 cubic inches per minute= 
 about 1,393 cubic inches per hour= about 27,864 cubic inches, or 
 16.1 cubic feet per day. In" this last quantity of carbonic acid, 
 there are about seven and a half ounces by weight of carbon. 
 
 A great variety of circumstances no doubt modify the activity 
 with which carbonic acid is formed in the system, and eliminated 
 from it ; some of these are very worthy of notice. Digestion has 
 been observed to be attended with an increased exhalation of it in 
 many of the lower animals ; and Scharling, Valentin, and Vierordt 
 have recently noted the same fact with great accuracy in Man. Thus, 
 one hour after a midday meal, Vierordt found that his pulse was 
 quickened by 15, his respiration by 1, the volume of the expired air 
 was slightly increased, nearly 50 per cent, more of air, and 2^ cubic 
 inches more of carbonic acid were expired in one minute, and the 
 percentage of carbonic acid in the expired air was also augmented 
 in a very trifling degree. If the meal were omitted, these results 
 
BXHALATIOK OP CARBONIC ACID. 725 
 
 did not occur. On the other ha,nd, fasting, especially if prolonged, 
 diminishes the exhalation. 
 
 Particular substances taken into the blood exert a very remarkable 
 influence upon the development of carbonic acid in the system. Dr. 
 Prout long since observed a considerable diminution under alcohol, 
 particularly if taken on an empty stomach ; and his conclusions have 
 been fully confirmed by Vierordt and Bocker. The former found 
 that, having taken more than half a bottle of wine, the carbonic acid 
 fell in a quarter of an hour from 4.54 to 4.01 per cent, of the ex- 
 pired air ; i. e., by about one-ninth of its whole quantity ; and this 
 lasted for two hours. In addition to this, the latter author found 
 that, under the same influence, the whole constituents of the urine 
 are diminished in amount. Dr. Prout states that a dose of strong tea 
 likewise lessens the exhalation of carbonic acid. 
 
 Since the introduction of ether and chloroform as anaesthetics in 
 the practice of surgery, their mode of action has been much inves- 
 tigated, and by no one more extensively or more accurately than by 
 Dr. Snow, who has, among other matters, turned his attention to the 
 amount of carbonic acid gas passing from the lungs under their use. 
 A small animal being placed in a jar, in which the air could be cir- 
 culated in connection with a receptacle containing solution of potash, 
 for absorbing the carbonic acid, the quantity of this gas expired 
 during periods of half an hour was estimated, when the animal 
 breathed firstly air, and afterwards air mixed with certain quantities 
 of the vapour of chloroform. The results were such as the follow- 
 ing : A dog, eight pounds in weight, exhaled in air 10.1 grains of 
 carbonic acid gas ; in air mingled with 36 grains of chloroform va- 
 pour, only 4.8 grains. A half-grown cat expired in air 5.7 grains 
 of carbonic acid gas ; in air mingled with 20 grains of chloroform 
 vapour, only 2.0 grains. And this diminution was observed, on this 
 and other occasions, to be in spite of increased muscular efforts on 
 the first introduction of the chloroform, such as are known to have 
 a tendency to augment the excretion of carbonic acid. 
 
 Exercise increases the exhalation of carbonic acid, and doubtless 
 also the formation of it in the tissues. Mr. Newport observed that 
 the generation of carbonic acid from bees, when at rest, did not 
 exceed that from cold-blooded animals ; but when in active movement, 
 it was more energetic than in any other animals ; and other experi- 
 menters have produced analogous results. With more precision, and 
 in the case of the human adult, Vierordt shows that, during mode- 
 rate exercise, there is an average increase per minute of 19 cubic 
 inches in the expired air, and of 1 cubic inch in the expired carbonic 
 acid. 
 
 The temperature of the surrounding medium was shown by Seguin 
 and Lavoisier to have an important influence on the exhalation of 
 carbonic acid, and their results were corroborated by those of Craw- 
 ford. Vierordt has recently examined this point also. In numerous 
 experiments upon himself, at temperatures of which the average was 
 47° Fahrenheit, he expired 18.25 cubic inches of carbonic acid per 
 47 
 
726 RESPIRATION. 
 
 minute ; wMle at temperatures of which the average was 67° Fah- 
 renheit, he expired only 15.72 cubic inches in the same period. At 
 the lower temperature, the number of respirations was increased, 
 and more air was expired in the proportion of 406 to 366, or about 
 10 to 9. Cqld, therefore, contrary to what might have been expected 
 from its depressing effects on the system, is attended with an aug- 
 mented exhalation of carbonic acid, and, as will be afterwards seen, 
 with an increased development of animal heat. Of course there 
 must be limits to this result. 
 
 MM. Andral and Gavarret have arrived at some remarkable re- 
 sults regarding the influence of sex and age on the exhalation of 
 carbonic acid. They found that, after the age of eight years, the 
 male exhales much more than the female, the average quantity be- 
 tween the ages of 16 and 40 being double in the male. With re- 
 spect to each sex at different ages, the male child between 8 and 15 
 exhales per hour, in the form of carbonic acid gas, 77 grains of car- 
 bon ; the female about 15 grains less. In the male^ the quantity 
 increases rather suddenly at puberty to 157 grains, and continues 
 increasing up to 25, when it averages 191 grains per hour (or 9| 
 ounces per day). It remains about stationary up to 40 years of age; 
 between 40 and 60, it averages only 155 grains ; and between 60 
 and 80, 141 grains per hour. In one man of 102, remarkably hale, 
 it was only 91 grains ; in another of 26, remarkably fine and* mus- 
 cular, it reached 217 grains. In the female, no great or correspond- 
 ing increase takes place at puberty ; and as long as menstruation is 
 regular, the average exhalation of carbon is only 98 grains per hour. 
 During pregnancy, however, and also at the period of the cessation 
 of the menses, it is singular to observe thd.t this quantity is quickly 
 raised to 129 grains. Between 50 and 60, the average is 112 grains ; 
 between 60 and 80, 104 grains. In a woman of 82 it was only 92 
 grains per hour. Scharling has, to some extent, corroborated these 
 results. 
 
 This increase in the male during the period of the greatest activity 
 and muscular vigour, and also the general higher standard in the 
 male, and the decline of both sexes with age, is accordant with what 
 we know of the rate and activity of the changes of nutrition under 
 these several conditions. The varieties in the female are less easily 
 explained, though obviously of great importance. It may be here 
 remarked, that Hutchinson and Bourgery have ascertained that the 
 quantity of air breathed increases up to 30 or 35 years of age, then 
 decreases slowly to 65, and very much in old age ; and also t^at it 
 is less in females. 
 
 Such are some natural circumstances modifying the quantity of 
 carbonic acid exhaled. The following conclus'ions of Vierordt on 
 the influence of the respiratory movements on the amount expired 
 are interesting in themselves, and throw light on the theory of 
 the respiratory function. He finds that, when the respirations are 
 increased in frequency, more carbonic acid is exhaled, although, 
 from the much larger quantity of air breathed, the percentage of 
 
INHALATION OF OXYGEN. 727 
 
 Carbonic acid in the expired air is less. Thus the percentage of 
 this gas bears a certain propbrtion to the frequency of the respira- 
 tions, supposing their biilk to remain the same. 
 
 If the respiratory movements are suspended for a short time, the 
 percentage of carbonic acid in the expired air becomes increased. 
 The total quantity expired is, on the other hand, somewhat dimi- 
 nished ; showing that this increased percentage, in a given quantity 
 of air, does not compensate for the smaller proportion of air entering 
 the lungs under these circumstances. 
 
 Allen and Pepys found, that when the same air was breathed 
 more than once, the proportion of carbonic acid underwent a con- 
 siderable increase. Air breathed nine or ten times, contained 9.5 
 per cent, of carbonic acid ; biit if the air was breathed over again 
 as often as possible, the percentage of this gas could not be in- 
 creased above 10. Mr. Coathupe obtained as niiich as 12.75 per 
 cent, of carbonic acid from air in which animals had been placed 
 until they were suffocated. 
 
 The percentage of carbonic acid varies also at different periods of 
 tiine during the same respiration. By taking the average of twenty- 
 one experiments, Vierordt found, that while the proportion of car- 
 bonic acid in the entire expiration amounted to 4.48 per cent., the 
 first half contained 3.T2, and the last half 5.44 per ceht. It has 
 been estimated, that the air from the air-cells contains as much as 
 5.83 per cent, of carbonic acid, or about 1.3 per cent, more than 
 the air of an ordinary expiration. 
 
 Amount of OHygeh Inhaled.- — The quaiitity of oxygen introduced 
 into the systetn in respiration, is always greater than is required to 
 form the amount of carbonic acid eliminated during this process. 
 This surplus quantity no doubt is employed in oxidizing other sub- 
 stances in the organism besides the carbon ; such, for instance, as 
 sulphur and phosphorus, which are eliminated in the urine in the 
 form of sulphuric and phosphoric acids. Valentin and Brunner 
 found that the proportions of these gases approximated very closely 
 to their diffusive volumes ; for the quantities obtained by direct ex- 
 periment, and by calculation, differed very slightly. Oxygen being 
 the lighter gas, a larger quantity is required to replace the carbonic 
 acid ; 81 parts of the latter will require 95 of the former to replace 
 it according to Graham's law, that the diffusion volume of different 
 gases varies inversely as the square root of the density, or about one 
 volume of absorbed oxygen corresponds to .85 of exhaled carbonic 
 acid. The experiments of Dulong and Despretz, as well as those of 
 Regnault and Reiset, have, however, shown that this relation is by 
 no means constant. 
 
 From the above considerations, it is evident that this respiratory 
 changes cannot be efficiently carried on, unless a certain proportion 
 of air be assigned to each individual living in a confined space. For 
 if the cubic capacity of the apartment be below a certain standard, 
 the air becomes so contaminated by the increased quantity of car- 
 bonic acid expired, as to produce a highly deleterious effect upon the 
 health. 
 
728 RESPIRATION. 
 
 Probably between four and five hundred cubic feet of air pass 
 through the lungs daily, and in the same period, about twenty-three 
 cubic feet of oxygen gas are absorbed. The size of an apartment, 
 therefore, in which persons are confined should be such, and its venti- 
 lation should be so arranged, that each individual may be supplied 
 with the above quantity of pure air as a minimum. The cubic 
 capacity of such rooms should not be less than 800 cubic feet for 
 each person inhabiting them. Leblanc found, that in the Chamber 
 of Deputies in Paris, each individual was supplied with only from 353 
 to 706 cubic feet of air per hour ; and in the air issuing from the 
 apartment, he found from 2 to 4 of carbonic acid in 1000 parts by 
 weight. This proportion of fresh air was probably too small, since 
 it has been found that 1 per cent, of carbonic acid produces a dele- 
 terious effect upon the system when breathed for a long time con- 
 tinuously. In the Model Prison, Pentonville, from 1800 to 2700 
 cubic feet of fresh air pass into each cell per hour. In hospitals, the 
 number of patients in each ward should be so arranged, that not less 
 than from 800 to 1000 cubic feet should be assigned to each. In 
 the new King's College Hospital, each patient has from 1850 to 
 2500 cubic feet of air. 
 
 Dr. Snow has shown that the bad effects of air deteriorated by 
 respiration, are due not only to the increased quantity of carbonic 
 acid which it contains, but also to the diminution of its axygen. 
 From his experiments upon animals he has been led to conclude, 
 "that 5 or 6 per cent, by volume of carbonic acid cannot exist in 
 the air without danger to life, and that less than half this amount 
 will soon be fatal, when it is formed at the expense of the oxygen 
 of the air." 
 
 Exhalation of Nitrogen. — MM. Regnault and Reiset have shown 
 that an extremely small quantity of nitrogen is constantly exhaled, 
 its proportion varying according to the nature of the food. After 
 prolonged fasting, this gas, however, appears to be absorbed, instead 
 of being exhaled. Barral found that the quantity of nitrogen ex- 
 haled from the lungs of man, was about yj^th of the amount of car- 
 bonic acid removed in the same time. It must also be observed, that 
 a very small proportion of nitrogen is constantly being expired in 
 the form of ammonia. 
 
 Changes in the Blood resulting from Respiration, — Dark venous 
 blood in its passage through the capillary vessels of the lungs assumes 
 the bright red colour characteristic of arterial blood. This change, 
 as is well known, depends upon the removal of carbonic acid gas and 
 the absorption of oxygen. Magnus showed that venous blood con- 
 tained 25 per cent, of its volume of carbonic acid, and 5 per cent, of 
 oxygen; and that arterial blood, on the other hand, contained as 
 much as 10 per cent, of its volume of oxygen, and only 23 per cent, 
 of carbonic acid. The seat of this change is clearly in the red blood 
 corpuscles ; but its precise nature has not yet been satisfactorily de- 
 termined. It has been ascribed to a chemical change taking place 
 in the coloured constituent of the blood globule (page 640), but later 
 researches render it probable that it is, at least in some measure, due 
 
CHANGES IN THE BLOOD. 729 
 
 to a physical alteration. Henle was the first observer who referred 
 the change of colour in the blood corpuscle to a^change in its form. 
 
 Scherer states that the blood corpuscles of venous blood are nearly 
 spherical, and their walls thin and transparent, a condition which 
 causes them to transmit light freely. On the other hand, the cor- 
 puscles of arterial blood are bi-concave, their walls thicker, and they 
 reflect light more readily, which is considered to account for the 
 brighter colour of arterial blood. Harless has even been able to 
 measure the difference in size between the blood corpuscles of arterial 
 and venous blood of the frog. 
 
 Magnus proved that serum. would dissolve twice as much carbonic 
 acid as an equal quantity of pure water, a power which Liebig attri- 
 buted to the amount of phosphate of soda contained in blood serum. 
 
 Of the gases existing in the blood, a very small proportion only 
 is in chemical combination with any of the constituents of that fluid, 
 but the greater quantity is held in solution in a free and uncombined 
 state. This is readily proved by passing a current of hydrogen gas 
 through some defibrinated blood placed in a bottle to which tubes are 
 adapted. The hydrogen takes the place of the gas previously held 
 in solution and the latter escape ; and by causing them to pass 
 through lime-water, evidence of the presence of much carbonic acid 
 is at once obtained by the formation of a precipitate of carbonate of 
 lime. If the carbonic acid had existed in a state of chemical com- 
 bination, we should not have been able to obtain evidence of its pre- 
 sence by this process. Besides much carbonic acid, oxygen, and a 
 little nitrogen, are held in solution in blood. 
 
 With reference to the oxygen, it cannot be doubted that part is in 
 chemical combination with the constituents of the blood corpuscle, 
 and part in a state of simple solution. 
 
 The chief agents in effecting the absorption of gases in the blood 
 are undoubtedly the blood corpuscles, for it has been clearly proved 
 by Davy and others, that defibrinated blood possesses the power of 
 absorbing gases in a greater degree than blood serum. Magnus found 
 that blood was capable of absorbing IJ times its volume of carbonic 
 acid gas. 
 
 From the researches of Professor Lehmann upon the crystallizable 
 contents of the blood corpuscle, originally discovered by Otto Funke, 
 we are led to conclude that the colouring matter of the blood is 
 chemically affected by oxygen and carbonic acid gases. 
 
 Lehmann has shown, that if oxygen is allowed to pass through de- 
 fibrinated blood slowly for fifteen minutes, and is followed by the 
 transmission of a current of carbonic acid for five minutes under the 
 influence of light, these crystals are formed in larger quantity, and 
 more rapidly, than if the carbonic acid is passed through the blood 
 first. These crystals are composed of a definite chemical compound; 
 and there can be little doubt that the influences which the gases ex- 
 ert upon its crystallizing properties are of a chemical nature.* 
 
 * For much interesting matter upon the subject of blood-crystallization, the reader 
 is referred to Lehmann's Physiological Chemislry, 1853, translated by Dr. Day, 
 Cavendish Society, vol. iii. 
 
730 RESPIRATION. 
 
 It was formerly supposed that the oxygen of the air combined 
 with the carbon of the venous blood in the pulmonary capillaries, 
 and that the carbonic acid eliminated from the system was formed 
 at the pulmonary surface ; but later researches have shown that this 
 gas exists preformed in the blood, and is therefore only exhaled from 
 the fluid contained in the vessels of the lungs, a view which was first 
 advocated by Lagrange and Hassenfratz in 1791. It has been found 
 that animals will give up carbonic acid wben placed in atmospheres 
 which do not contain any oxygen, a fact which could not ]be a,ccounted 
 for upon the supposition that this gas was formed by the combinati,o.n 
 taking place in the pulmonary organ. Again, the presence of both 
 ^ree oxygen and carbonic acid can be proved in the a,rterial and 
 venous blood. Moreover, blood may be caused to absorb, or to give 
 up, these gases after it has been removed from the body. 
 
 All the tissue? of the body contg^ip a small quantity of dissolved 
 gases ; and carbonic acid can b^ dettected in all the animal fluids, 
 even in the urine. 
 
 Frogs' nfuscles, carefully deprived of nerves and vessels, will give 
 out carbonic acid if placed in an atmosphere of oxygen gas, and it 
 has been shown by G. Liebigj that the muscles continue to absorb 
 oxygen, and to exhale carbonic acid, as long as their power of con- 
 tractility lasts, and that they retain their contractile power for a 
 much longer period in an atmosphere of oxygen gas than in one of 
 hydrogen, nitrogen, etc. The careful observations of Lehmann upon 
 the respiration of insects (in which class the air is directly darried 
 to the elements of the tissues by the tracheae), tend still further to 
 prove the truth of this view. We may therefore conclude, that the 
 oxygen of the air ia carried by the blood to the ultimate elenients of 
 the tissues, and that here chemical combination takes place ajid car- 
 bonic acid is produced ; the carbonic aci,d being then transmitted to 
 the lungs in solution in the venous blood, and there exhaled. 
 
 Quantity of Carbon removed from the ^pdy. — The estimation of 
 the amount of carbon eliminated from the organism in a given time 
 is a matter of great difiicijlty, and the result^ of the experiments of 
 observers present wide diflTerences. Allen and Pepys calculated the 
 daily quantity at rather more than 11 oz. trpy, while Mr. Coathi^pe 
 estimated it at only 4.97 ounces, and Scharling at 7.382 ounces. 
 
 The method employed by Liebig consisted in snbtra,cting the total 
 quantity of carbon in the feces and urine from that present in the 
 food ; the remainder represented the quantity excreted in the breath 
 in the form of carbonic acid- From these data, Ljebig calculates 
 that an adult male, taking moderate exercise, loses 13.9 ounces of 
 carbon daily from the lungs and skin. In order to convert this large 
 quantity of carbon into carbonic acid, 37 ounces of oxygen must be 
 absorbed during the same period by the lungs and skin ; but this 
 estimate is doubtless tQO high. Andral and Gavarret estimated the 
 carbon at nine ounces. 
 
 According to the recent accurate investigations of Scharling, a 
 powerful adult man exhales in the course of twenty-four hours about 
 
THEOKY OF RESPIRATION. T31 
 
 30.6 oz. of carbonic acid, ■which corresponds to 8.34 oz. of carhon, 
 and this we may look upon as a correct estimate. 
 
 Some very accurate experiments upon this subject have been made 
 by M. Barral upon himself during summer and winter. The great , 
 difiference noticed in the quantity of carbon exhaled «it different 
 periods of the year may, to some extent, explain the discrepancies 
 in the results of various observers — 
 
 Carbon excreted. 
 
 Weight of body. Carbon in food. In feces. In urine. "Exhaled, 
 
 lbs. grs. grs. grs. grs. 
 
 In Summer 104.6 6654.1 236.2 2S4.6 5183.3 
 
 In Winter " 4090.0 137..4 211.5 3741.1 
 
 About 10.8 oz. troy of carbon, therefore, passed off daily in the form 
 of carbonic acid in winter, and 7.8 oz. in summer. The amount of 
 carbon eliminated by respiration will also be infuenced by the 
 quantity and nature of the food, and by oth^r cirijumstances, which 
 have been previously adverted to. • 
 
 Theory of Mespiration.'^lBj the interchange of gases in the lungs, 
 the venous blood becomes of the bright scarlet colour characteristic 
 of arterial blood. The oxyg«n and carbonic acid both permeate the 
 delicate, moist, limitary membrane of the air-cells at the same time, 
 but in opposite directions. 
 
 The oxygen, having passed through the capillary walls, is held in 
 solution in the blood ; a small part entering into chemical combina- 
 tion with the contents of the blood corpuscle, and to a less degree 
 with some of the constituents of the serum. 
 
 A portion of the oxygen not improbably acts directly upon certain 
 substances contained in the circulating blood, and contributes to the 
 formation of carbonic acid. In this way some of the elements of the 
 food lately introduced into the blood may become decomposed, and 
 their carbon removed in the form of carbonic aeid. The greater 
 portion of the oxygen is no doubt carried to the capillaries, and 
 much of it then leaving the blood, and passing through the capillary 
 walls, becomes dissolved by the intercellular fluid, in obedience to 
 the same physical laws by which it was absorbed. At the same 
 time, the carbonic acid formed in the interstices of the tissues, and 
 dissolved by the fluid which moistens their ultimate elements, leaves 
 this latter to enter the blood, from which the oxygen has just been 
 removed, and causes it to assume the colour of venous blood. 
 
 Here, then, are two sources of carbonic acid — one resulting from 
 the action of the oxygen upon certain elements recently introduced 
 in the food, giving rise to the production of a certain amount of 
 animal heat, and the other depending upon the union of the oxygen 
 with the carbon of those substances which are produced in the disin- 
 tegration of tissues during the performance of their functions ; in 
 this combination also, heat is developed. 
 
 In purely carnivorous animals, the greater portion of the carbonic 
 acid results from the disintegration of the muscular and nervous tis- 
 sues ; while, in the herbivora, much of the food, rich in carbon and 
 poor in nitrogen, is at once converted into carbonic acid. 
 
732 BBSPIRATION. 
 
 Although the action of the oxygen upon the carbon of the com- 
 pounds, from which the carbonic acid is formed, is a strictly chemical 
 process, the application of this oxygen to the substance to be de- 
 composed, and the removal of the resulting carbonic acid, are 
 dependent solely upon the physical relations which these gases bear 
 to each other, to the membrane through which they pass, and to the 
 fluids in which they are dissolved. 
 
 The blood, loaded with carbonic acid, at length returns to the 
 respiratory surface, where it parts with this gas and absorbs oxygen 
 in obedience to the physical laws above referred to. 
 
 More oxygen is usually absorbed than is necessary to convert the 
 carbon into carbonic acid. This is required for the oxidation of 
 other elements, as sulphur and phosphorus, by which compounds are 
 produced which are eliminated by other emunctories. 
 
 The amount of oxygen inhaled will depend in great measure upon 
 the quantity and nature of the food, and upon the activity of the 
 vital functionSj^and is intimately associated with the production of 
 animal heat, as will appear in the next chapter. 
 
 It has been shown that the activity of the respiratory function is 
 materially influenced by various external and internal conditions. 
 Temperature, a dry or moist state of the atmosphere, the period of 
 the day, the digestive process, rest, exercise, etc., all exert an influ- 
 ence on the amount of oxygen inhaled and of carbonic acid exh«led. 
 These are points which must be borne in mind by the careful prac- 
 titioner in the treatment of such diseases as phthisis, pneumonia, 
 emphysema, and the like. 
 
 Respiration is, therefore, partly a physical and partly a chemical 
 process ; chemical as far as regards the results ; physical, with 
 reference to the means by which these results are produced. The 
 introduction of the restorative oxygen, and the removal of the 
 deleterious carbonic acid, are efiected solely by a physical process ; 
 while the formation of the carbonic acid is essentially a chemical 
 process, and in its production many complicated chemical decompo-s 
 sitions take place. 
 
 The great objects of respiration are, first, the introduction of 
 oxygen, by which the products resulting from the disintegration of 
 tissues are converted into compounds, which are easily eliminated 
 from the body by the difierent organs of secretion; and, secondly, the 
 removal of the most important and most destructive of these, car- 
 bonic acid, at the pulmonary surface. 
 
 tJpon the subjects discnssed in the present chapter, reference may be made to the 
 following -works : Article " Respiration," by Br. John Eeid, Cyolopsedia of Anatomy 
 and Physiology; "Thorax," by Dr. Hutchinson; Physiological, Anatomical, and 
 Pathological Researches, by Dr. John Reid; Reoherches eur la Structure intime du 
 Poumon. Rossignol, Bruxelles, 1846. The following systematic works: Miiller's 
 Physiology ; Rostock's System of Physiology | Principles of Human Physiology, by 
 Dr. Carpenter. 
 
 On the Mechanism of Respiration.— Dt. Sibson, Phil. Trans., 1846; Med.-Chir. 
 Trans,, toI. xxxi. ; Dr. Hutchinson, Med.-Chir. Trans., Tol. xxix. 
 
 On the Chemistry of Respiration. — M. Barral, Ann. de Chim. et Phys., torn. xxv. ; 
 Messrs. Regnault and Reiset, Aunales de Chimie et de Physique, 1849; Comptes 
 Rendus, 1846 ; Lehmann's Physiological Chemistry, translated by Dr. Day, Cavendish 
 Society, 1851-4. 
 
ANIMAL HEAT. 733 
 
 CHAPTER XXX. 
 
 I 
 
 ON ANIMAL HEAT. — DEVELOPMENT OF HEAT IN PLANTS. — DEVELOP- 
 MENT OP HEAT IN ANIMALS. — TEMPERATURE OF THE HUMAN BODY. 
 INFLUENCE OF EXERCISE, SLEEP, AGE, CLIMATE AND SEASONS, FOOD 
 AND DISEASE UPON THE DEVELOPMENT OF HEAT. — HIBERNATION. — 
 THEORY OF ANIMAL HEAT. — INFLUENCE OF THE NERVOUS SYSTEM. 
 BERNARD'S RESEARCHES. 
 
 The chemical changes which are continually taking place in ani- 
 mals, and, at least under some circumstances, in plants, are accom- 
 panied with the development of a certain amount of heat. The 
 elevation of temperature may be so slight as to elude the ordinary 
 means of observation ; and although the sensible temperature of the 
 organized body is very slightly higher than that of the medium in 
 which it is placed, the quantity of heat set free in a given time may 
 be considerable. This development of heat seems to result from the 
 action of the oxygen upon the combustible elements of the food, and 
 in a less degree upon those of the tissues. The chemical combination 
 in which the largest amount of heat is disengaged in the higher 
 animals, and upon which their high temperature seems to depend, 
 is that of carbon and oxygen, resulting in the production of carbonic 
 acid. 
 
 Whenever oxygen combines with carbon, hydrogen, phosphorus, 
 sulphur, etc., or with a metal, hea,t is developed in an amount ex- 
 actly proportioned to the quantity of substance consumed. The 
 sensible temperature produced varies, however, with the intensity 
 and rapidity of the chemical action. When the action is intense, 
 the temperature rises very rapidly, and may reach a very high degree 
 for a short time. If, on the other hand, the action is slow, the 
 temperature may be scarcely elevated above that of the surrounding 
 medium ; but this slight elevation may continue for a considerable 
 time. The quantity of heat developed in the two cases, however, is 
 precisely the same. 
 
 Development of Heat in Plants. — Heat is developed by the seeds 
 of plants during germination ; and at the same time oxygen is 
 removed from the air, and carbonic acid evolved. Buds, flowers^ and 
 ripening fruits also evolve a certain quantity of heat. 
 
 M. Hubert, in the Isle of France, encircled a thermometer with 
 twelve spikes of the arum eordifolium, and found it rise to 121° F., 
 the temperature of the external air being 66°. During the process 
 of flowering, the spathe of the arum maeulatum consumed in 24 
 hours five times its volume of oxygen derived from the surrounding 
 atmosphere, the termination of the spadix, 80 times, and the sexual 
 apparatus 132 times its volume, in the same period. In these ex- 
 periments it was found, that if the plant was protected from the 
 influence of the surrounding air, the development of beat ceased. 
 
734 ANIMAL HEAT. 
 
 In the germination of seeds, the starch is converted into gum or 
 dextrine, and ultimately into sugar. The sugar then disappears 
 while oxygen is absorbed from the air, and carbonic acid evolved. 
 The temperature at the same time rises. 
 
 In these examples, the disappearance of the starch and saccharine 
 matters from the plant, the absorption of oxygen, the formation of 
 carbonic acid, and the development of heat are all manifestly con- 
 nected. A corresponding series of phenomena attends the develop- 
 ment of heat in animalsr. 
 
 Development of Heat in Animah.-^lt is to be observed in the first 
 place, that as all animals give out carbonic acid in their respiration, 
 so all develop heat, whether they are called cold-blooded (reptiles 
 and all below them), or warm-blooded (mammalia and birds). The 
 cold-blooded animals are those which develop so little heat, form and 
 give out so little carbonic acid, that they are unable to maintain a 
 temperature much removed from that of the medium in which they 
 live ; and their circulatory and breathing organs are entirely accord- 
 ant with this feeble calorifacient power. Dr. John Davy, who has 
 made a number of valuable and exact observations on this subject, 
 found that when the average temperature around was 79.7° F., that 
 of reptiles was only 82°, and that of fishes nearly the same. In 
 the case of insects, Crustacea, and moUusca, there is even a closer 
 correspondence with the temperature of the circumambient medium. 
 Insects, however, especially when housed in communities, so that 
 their heat is not rapidly dissipated, have shown a rise of 20° P. 
 above the outward air — provided they were in a state of active 
 movement. On this point, the observations of Mr. Newport are 
 very valuable. On the other hand, warm-blooded animals (birds and 
 mammalia) are those in which nutrition with all its attendant acces- 
 sory functions, assimilation, circulation, respiration, the supply of 
 food and of oxygen, the formation and disengagement of carbonic 
 acid are most active and energetic. These have a nearly uniform 
 temperature within the limits of 96° and 111° F., the mammalia 
 having the lower and birds the higher, in strict accordance with the 
 above-mentioned circumstances. A bird, for its weight, consumes 
 much more oxygen, and sets free much more carbonic acid, while it 
 maintains in the same medium a higher temperature than a mammal. 
 Finally, some degree of warmth is evolved by the egg in its devel- 
 opment during incubation. In this process, oxygen is absorbed, 
 and carbomic acid exhaled through the calcareous envelope. 
 
 The amount of heat developed in the animal organism depends 
 very much upon the nature and quantity of the food. The carbon 
 of the food in its slowly effected union with oxygen within the organ- 
 ism, gives out probably as much heat as if the same quantity were 
 burnt in oxygen gas. The development of animal heat will, there- 
 fore, in great measure depend upon the activity of the functions of 
 respiration and circulation. 
 
 The greater part of the oxygen which an adult consumes in the 
 twenty-four hours, instead of remaining in the body, thereby in- 
 creases its weight, unites with carbon aijd hydrogen, and is removed 
 
TEMPERATURE 01 HUMAN BODT. 735 
 
 in the form of carbonic acid and water. The remainder enters into 
 combination with other elements, and compounds are formed which 
 are removed by the excreting glands. In these combinations a large 
 amount of heat is developed, ranging in amount according to the 
 conditions before referred to. 
 
 Temperature of the Muman Body. — The heat of the interior of 
 the body at those parts which are most accessible to our instruments 
 of measurement, as, for instance in the axilla, within the mouth or 
 rectum, is found to be about 97° or 99° F. ; more frequently the 
 latter. The temperature is, however, liable to variation according 
 to circumstances, which modify the amount of heat generated within 
 the body or the rapidity of its loss. Independently of this, however, 
 great differences have been found to exist in the temperature of 
 different parts, according to the rate of their cooling, their vascu- 
 larity, distance from the centre of circulation, etc. A good idea of 
 this will be derived from the following Table of Dr. Edwards. He 
 examined a strong man, at rest, in July, the air being at 71° F., 
 and found 
 
 Mouth and rectum 102° 
 
 Hands 99°.5 
 
 Axillae and groin 99° 
 
 Cheeky 9,6° 
 
 Feet 96° 
 
 Skin of Epigastnum 95° 
 
 The best experiments on the temperature of internal parts, are 
 those of MM. Becquerel and Breschet, who employed a thermo- 
 electric apparatus, . consisting of two wires of different metals, 
 goldered togejhei;, and having their free ends brought into communi- 
 cation with an excellent thermo-electric multiplier, with an index to 
 show lOt^s of a degree. The wire, passed through various parts of 
 the body, indicated the temperature of the tissues in contact with the 
 point of contact of the two metals. Passing this IJ inch into the 
 calf of the leg, the temperature was found to be 98° P., while at a 
 depth of ^ inch it was only 94°, showing the cooling from the sur- 
 face inwards. The superficial fascia over the biceps was nearly 3° 
 lower than the muscle itself ; on compressing the brachial artery, so 
 as to intercept the flow of blood, the temperature immediately fell 
 several lOths of a deguee. So after the ligature of the main artery 
 for aneurism, the temperature is well known to fall, and to require 
 to be economized with increased clothing. Professor Fiik obtained 
 the following, results in twelve experiments upon living dogs. No 
 difference in the temperature was observed between the right and 
 left ventricle of the heart. The higbjest degree of warmth was 
 always met with in the vagina and rectum (101.75 to 105.79). 
 
 As exercise is attended with quickened circulation, more active 
 respiration, a more abundant interchange of oxygen and carbonic 
 acid, so it occasions an augmentation of animal temperature. The 
 secretions are more copious — there is a more energetic nutrition — 
 the quantity of food required is greater, and we all know how much 
 more keen our appetites are, and how much more food we consume 
 
736 ANIMAL HEAT. 
 
 ■when engaged in employments requiring active exercise, than in 
 sedentary occupations. MM. Becquerel and Breschet have observed, 
 that the muscles during their contraction become hotter by 2° or 3°, 
 a fact which one of us can attest from an experiment on the biceps 
 in his own person, made by these gentlemen themselves. 
 
 Sleep, as it is attended with diminished frequency of respiration 
 and pulse, and a smaller evolution of carbonic acid, is also marked 
 by a slight fall of temperature, viz., of from 1° to 3° F. 
 
 Age has been shown by Dr. Edwards to have much influence on 
 temperature. Old persons, and very young ones, are alike unable to 
 preserve their proper warmth without external aid, and have not the 
 same power as adults of generating heat. For example, he found 
 that young carnivorous and rodent animals, when placed in an atmo- 
 sphere of 50° F. apart from the body of the mother, quickly became 
 cold, though when lying near her they continued within 2° or 3° of 
 her temperature. So, young sparrows one week old were at 97° F. 
 in the nest, but when removed from the nest, fell in one hour to 
 66° F., when the external air was at 62° F. ; and he showed that 
 this result was not to be attributed to their unfledged state. 
 
 Young animals, therefore, require the aid of external warmth, or 
 at least of every means of retaining their own warmth. The nests 
 of birds not only serve to retain the warmth of the parent during 
 incubation, but also that of the young brood during their tender 
 age. The human infant stands no less in need of extraneous warmth 
 — and it may be safely affirmed, that much of the immense mortality 
 of our infant population is owing to the want of artificial heat. 
 
 We must refer to what has been already said in the chapter on 
 food (Chapter XXII. ), for observations on the relation of the kind 
 of food to the animal temperature. 
 
 Influence of Olimate and Seasons. — The best account we possess 
 of the effect of climate results from 4000 experiments made on board 
 the Bonite, a French vessel, during her passage between Cape Horn 
 and the tropics. The mean temperature of 10 men at Cape Horn, 
 with the thermometer at 32° F., was hardly two degrees lower than 
 at Calcutta, where the thermometer stood at 104° F. The tempera- 
 ture of the body was found to rise and fall perceptibly, but slightly 
 — to fall slowly in passing from a warm to a cold climate, and to 
 rise more rapidly in re-entering the torrid zone. 
 
 The rate at which an animal loses its heat will depend both on the 
 coldness of the surrounding air, and on the rapidity of evaporation. 
 In temperate climates these causes differ inversely with the season. 
 In winter there is much loss by radiation, little by evaporation ; in 
 summer the reverse. But Dr. Edwards has well shown that these 
 compensations are not the only cause of the uniformity of temperature 
 so wonderfully maintained, but that there is also in animals a differ- 
 ence in the rate at which heat is produced, according to the season, 
 " the calorific faculty is more active in winter than in summer." " In 
 winter there is a more active production with greater loss, in summer 
 a less production with smaller loss." To test this. Dr. Edwards 
 contrived a box surrounded with ice, having the same external tern- 
 
LOSS OF HEAT BY EVAPOKATION. 737 
 
 perature, and the same humidity of atmosphere in winter and sum- 
 mer, so that the loss by radiation and evaporation should be the 
 same in both cases. Into this apparatus, in February, he placed 5 
 sparrows that had been living in a warm room, and found that after 
 an interval of 3 hours they maintained their previous heat within 1° 
 F. Again, in July, he did the same with 4 others, and these after 
 3 hours were found to have lost 10° F. We may here recall the 
 fact, that the quantity of carbonic acid exhaled is greater when the 
 external temperature is low. Mice and guinea-pigs evolve twice as 
 much carbonic acid at 32° as at 60° F., and birds more than double. 
 Also more food, and of the calorifacient kind, is required in winter 
 than in summer, and in cold climates than in warm. 
 
 The nature of the food must vary with the temperature of the 
 climate, for at the same time that the respirations are less in number 
 in hot than in cold climates, the air is less dense, and contains in a 
 given volume less oxygen ; hence a light and succulent diet is better 
 adapted to the requirements of the system, and comparatively little 
 heat is developed ; while, in cold climates, a large quantity of highly 
 carbonaceous food is necessary in order to furnish the requisite sup- 
 ply of heat. 
 
 In animals which are very active, and which are not subjected to 
 the cooling influence of an atmosphere many degrees lower in tem- 
 perature than their own bodies, it is quite possible that a sufficient 
 amount of heat may be generated in the combination of the elements 
 of their tissues without the necessity of fatty or starchy food form- 
 ing a part of their highly nitrogenous diet. In cold climates, how- 
 ever, a large quantity of readily combustible food is necessary in 
 order to furnish the requisite amount of heat. 
 
 Jjoss of Seat hy Evaporation. — The animal body is continually 
 subject to evaporation of its fluid parts, just as any other moist sub- 
 stance, and the amount of evaporation, and the consequent loss of 
 heat, will depend on the same causes as in the case of inorganic 
 substances. The moisture, or dryness, of the surrounding air, and 
 its state of motion or rest, will mainly influence the result. All the 
 effects of excessive temperature on the body are much more apparent 
 with a moist than a dry atmosphere ; because in the case of a dry 
 atmosphere a greater amount of evaporation takes place, and hence a 
 greater quantity of heat is removed from the system. 
 
 In England it would be impossible to sustain a vapour bath at a 
 temperature of 110° or 120° for more than 10 minutes, whereas the 
 body may be without danger exposed for the same time to a dry 
 temperature twice as high or more. In some well-known experiments 
 Sir Charles Blagden remained immersed for 8 minutes in dry air 
 heated to the extraordinary pitch of 240° or 260° F. An oppres- 
 sive day in summer is one where the air is moist at the same time 
 that it is hot and stagnant. 
 
 Again, the refrigeration, arising from simple contact of cold air, 
 is much increased by motion of the air, i. e., by a rapid renewal of 
 fresh cold particles ; and all the more if the moving air be dry. A 
 cold dry wind is one of the most powerful refrigerators, but we could 
 
738 ANIMAL HEAT. 
 
 hardly realize the full extent to which this is true, 'without an ex- 
 ample* Mr. Fisher, the surgeon to the expedition to the Polar Seas, 
 under Sir Edward Parry, has related its extraordinary efiFects. The 
 hardy sailors found that they could hetter hear a cold which would 
 freeze mercury, (viz., 40° below zero, P.) when the air was perfectly 
 calm, than a temperature of 10° F. i. e., 50° higher) when the wind 
 was up. 
 
 The rate of cooling, and the amount of heat parted with in this 
 manner depends upon the difference in temperature between the body 
 and that of the surrounding medium. The loss of heat must of course 
 be much greater in the Polar regions, where the temperature is 100° 
 or more below that of the body, than in hot climates where the tem- 
 perature of the air approximates to that of the body. Yet the tem- 
 perature of the body is the same in each case. The cooling eifects 
 of cold climates are compensated for by the increased quantity of 
 highly carbonaceous food taken, and the increased activity of the re- 
 spiratory functions. A much larger quantity of carbonic acid is 
 evolved, and a much greater amount of heat liberated, than in warm 
 climates, where the food must be smaller in quantity, and should con- 
 tain less carbon and hydrogen. 
 
 Warm clothing, by protecting the body from the influence of cold 
 air, and so peventing the loss of a certain amount of heat, may be 
 Baid, as Liebig has remarked, to be equivalent in cold countries»to a 
 certain amount of food. The appetite is increased in cold weather, 
 and if in winter we clothe lightly we shall eat more than if warmly 
 clad. We may often remark, that lean spare men, whb take a great 
 deal of exercise, consume many times the quantity of food \^hlch sa- 
 tisfies a moderately plump individual. The former has usually a 
 larger respiratory capacity, and is less protected from thb cooling 
 influence of the external air. 
 
 Influence of Food. — If an insuflScient quantity of food be taken, 
 the temperature of the body falls, and the carbon and hydrogen, en- 
 tering into the composition of the tissues themselves, combine with 
 the oxygen, and thus a certain amount of heat is furnished. Defi- 
 ciency of food is borne much more readily in a high temperature 
 than in a low one. Gold very much expedites death fronl starvation. 
 The highly important and interesting experiments of Chossat* upon 
 animals have shown that in starvation the fatty matters, which are 
 most readily convertible into carbonic acid, are first removed, soon 
 afterwards the substance of the muscles is acted upon, in order to 
 furnish an amount of heat, without the development of whidh life 
 would at once cease ; next the nervous system gives way to this oxid- 
 izing power — life ceases, and every portion of the organic material^ 
 with the exception of the mineral matters combined with it, is brought 
 under the destructive influence of the oxygen. M. Ghossat found 
 that, taking 40 per cent, as the mean, fat lost 93.3, blood 75, heart 
 44,8, muscles 42.3, skin 33,3, bones 16.7, and the nervous system 
 only 1,9 per cent, of their weight in fatal starvation. 
 
 * Eeoherohes exp6riaieiitales sur I'lhanition. 
 
HIBERNATION. 739 
 
 The time required to produce death from starvation varies accord- 
 ing to different circumstanees. If the body be very fat, life will be 
 supported for a longer period than if only a small quantity of fatty 
 material be present. A fat pig, which was confined by a slip of 
 earth, lived 160 days without iood, and during this period he lost 
 more than 120 lbs. (Martell, Trans. Linn. Soc, vol. xi. p. 411, quoted 
 in Liebig's letters). While death from starvation would be retarded 
 by warmth, little or no exercise^ and a moderate supply of water, it 
 would be much accelerated by the converse of these circumstances. 
 
 Influence of Disease. — In acute diseases accompanied with fever, 
 such as pneumonia, pleurisy, acute rheumatism, and in scarlatina, 
 typhoid fever, etc., the temperature often rises several degrees above 
 the normal standard, not unfrequently reaching 105° or 106° P. Dr. 
 Edwards observed the temperature as high &a llOf in a case of teta- 
 nus. This high temperature sometimes decreases rapidly, and some- 
 times very gradually, the diminution being frequently accompanied 
 by free perspiration and copious excretion of lirine, rich in urea and 
 lithates. The frequency of the pulse also diminishes at the same 
 lame. This increased development of heat, during the exacerbation 
 of the fever, is' associiated with the increased amount of disintegration 
 of tissues taking place at that time; while the remission is ac- 
 companied by the elimination of the resulting compounds, free per- 
 spiration, diminished frequency of pulse, and corresponding decrease 
 «f temperature.* 
 
 In those diseases, on the other hand, where the activity of the 
 chemical processes going on in the body is impaired^ the temperature 
 falls many degrees below the normal standard. In cholera, where 
 the dark blood and imperfect respiration mark the introduction of an 
 inefficient supply of oxygen, and the suspension of secretion and 
 the absence of symptoms characteristic of the accumulation of ex- 
 cretory products in the organism, show that the chemical changes 
 accompanying the disintegration of the tissues are only taking place 
 in a slight degree, or are altogether suspended, the temperature often 
 falls to 70°, or even much lower. It is curious that, in many of 
 these conditions, the temperature should rise very rapidly imme- 
 diately after death. The most striking examples of this have been 
 placed on record by Dr. B. Dowler, of New Orleans, and occurred 
 in cases of yellow fever, etc. In one instance, just before death, the 
 temperature was 104° ; and fifteen minutes after death, it had risen 
 to 113° in an incision in the thigh. The temperature still remained 
 very high for several hours after death. 
 
 Hibernation. — The phenomena of hibernation are dependent upon 
 the conditions we have just alluded to. Previous to becoming torpid^ 
 the animal accumulates a quantity of fat, which is, as it were, laid 
 up as in a storehouse, to be consumed slowly, while the period of 
 annual sleep lasts. At this time, the activity of the vital functions 
 is much reduced, the animal lies perfectly still, the frequency of the 
 
 * See a review, by Dr. H. Weber, in the Medico-Chir. Review, Jan. 1853, on Crises 
 and Critical Days, by Dr. L. Traube. Berlin, 1852. 
 
740 ANIMAL HEAT. 
 
 heart's action and of the respirations diminishes; its temperature 
 falls many degrees, and it is placed in a condition the most favourable 
 for supporting life for a considerable period of time with a very 
 small supply of combustible material. The moment the animal is 
 roused, the vital processes again become active, and a supply of food 
 soon becomes necessary. In the case of the marmot, in which 
 animal the hibernation is complete, the pulse falls to about 15 beats 
 in a minute, and the respirations to abo\it 14 in an hour, while in 
 the waking state these are respectively 160 and 500. The tempera- 
 ture of the body, during the hibernating period, may fall as low as 
 35°. If, however, the animal be exposed to warmth, the frequency 
 of the pulse and respiration increases, a much larger quantity of 
 oxygen is consumed, and a corresponding proportion of carbonic acid 
 exhaled. The temperature of the body suddenly rises, and the 
 animal soon dies, unless supplied with food. 
 
 Theory of Animal Meat. — It has been shown, that in certain parts 
 of plants, and in cold as well as warm-blooded animals, heat is de- 
 veloped coincidently with the consumption of oxygen, the combustion 
 of carbon, and the formation of carbonic acid. The heat produced, 
 and the chemical product of combustion, have been observed to bear 
 a certain general correspondence one with the other. 
 
 To understand the real nature of the development of heat in 
 organized bodies, it is necessary to remember, that the heat disen- 
 gaged during the oxidation of carbon or of a metal {i, e. during the 
 combustion of these bodies) is directly proportioned to the amount 
 and not to the intensity of the chemical action. In the words of a 
 distinguished chemist, "The rod of iron that is burnt in oxygen gas, 
 produces a heat which no one will deny ; but the iron which rusts 
 slowly in the air, disengages just as much heat, although its tempera- 
 ture never rises sensibly above that of the surrounding atmosphere. 
 Phosphorus alight burns brilliantly, and produces abundance of heat; 
 phophorus in the cold, still burns, but with little lustre, and the heat 
 which it evolves was for a long time denied."* 
 
 It has been already stated (p. 515-16) that a large portion of the 
 food being destitute of nitrogen, is not the best adapted to form part 
 of the tissues of the body into the composition of which that element 
 enters. This calorifacient food (consisting of various quantities of 
 carbon in combination with oxygen and hydrogen, in the proportion 
 in which these last form water, as starch, sugar, cellulose, or gum, 
 or of carbon and hydrogen in combination with a less proportion of 
 oxygen in fatty matters) seems to be devoted in the main to the pro- 
 duction of heat by the combination of its carbon and hydrogen with 
 the oxygen furnished by respiration. It is a question through what 
 changes it passes ere thus consumed ; but of its eventual destination 
 to the production of heat there would appear to be no doubt. 
 
 As was shown in the chapter on Respiration, more oxygen is 
 taken into the blood by the lungs than is required to form the car- 
 bonic acid exhaled. This superfluous oxygen disappears, the greater 
 
 * Dumas, "Balance of Organic Nature," p. 87. 
 
THEOKY OF ANIMAL HEAT. 741 
 
 part appearing to enter into combination with hydrogen, while a 
 small quantity goes to oxidize the sulphur and phosphorus. The air 
 breathed is likewise found to have lost bulk. Now, gaseous carbonic 
 acid contains its own bulk of oxygen — but oxygen uniting with 
 hydrogen to form water is condensed. Such a condensation of the 
 oxygen would accord with the observed diminution of bulk in air by 
 being respired. It has been remarked that herbivorous animals 
 return to the air, as carbonic acid, only nine out of ten of the 
 volumes of oxygen absorbed in respiration, and that carnivorous 
 animals return in the same form, only five or six out of ten volumes. 
 The carnivora, then, absorb nearly twice as much oxygen as they 
 employ for oxidizing carbon, and a very large proportion of the re- 
 mainder, no doubt, combines with hydrogen to form water. 
 
 To explain the prompt oxidation of the carbon and hydrogen 
 within the body, Liebig has pointed out that the oxygen is presented 
 to them not in a gaseous but in a liquid or solid form — that in the 
 innumerable channels of the circulation, these several elements are 
 not merely brought together in a very subdivided state, but every- 
 where in close proximity to membranous surfaces, mechanically 
 adapted to favour the occurrence of chemical union. Moreover, that 
 the carbon and hydrogen are not offered to the oxygen in their pure 
 and simple state, but in combinations already existing and ready to 
 be dissolved. He also insists, with great force, on the analogy of 
 these actions to those promoted by the presence of a body already 
 undergoing oxidation. For example, " when weak brandy is allowed 
 to trickle over shavings in a close vessel, through which a feeble 
 current of air at from 93° to 97° F. circulates, the alcohol in the 
 brandy remains unchanged; in spite of the greatly increased surface, 
 no oxidation, no formation of acetic acid takes place. But if to 
 the brandy there be added one hundred thousandth part of vinegar, 
 beer, or wine, in the state of acetification, that is, of oxidation, the 
 alcohol disappears with great rapidity, and is converted, by the 
 absorption of oxygen, into an equivalent quantity of acetic acid. In 
 the vessel, the surface of the shavings themselves very soon passes 
 into the state of oxidation, and from this period forth, the brandy is 
 acetified without the addition of a ferment ; the wood, being in the 
 state of decay, eremacausis, or slow combustion, plays the part of a 
 ferment. These vinegar-producing vats give an idea, if only a rough 
 one, of the process of oxidation going on in the animal body. As 
 in the body, so also in these vessels, a temperature higher than that 
 of the surrounding media is kept up, without the aid of external 
 heat."* 
 
 These actions of contact or catalysis may well be supposed to play 
 a large and most important part, not merely in the production of 
 animal heat, but also in all the chemical changes which are ever 
 going on in the body, from the first reception of food to the final 
 expulsion of its elements in other forms of combination. Great 
 
 * "Animal Chemistry," p. 34, 3d edition, Part I. 
 
 48 
 
742 ANIMAL HEAT. 
 
 obscurity, however, still hangs over the series of transformations 
 ■which the food undergoes in its passage through the body. 
 
 It has been seen that both arterial and venous blood contain 
 oxygen and carbonic acid gas in a state of solution ; but into what 
 form of combination, the oxygen first enters, or from what immediate 
 source the carbonic acid is derived, is as yet matter of conjecture 
 only. It may be regarded as most probable that the chemical 
 changes which issue in the formation of carbonic acid and water, and 
 the disengagement of heat, are effected in the tissues themselves, or 
 in the systemic capillaries, in the immediate vicinity of the tissues. 
 
 Influence of the Nervous System. — Much difference of opinion has 
 existed as to the share taken by the nervous system in the produc- 
 tion and maintenance of animal temperature, some distinguished men 
 having argued that this system is in some way the source of heat, 
 while others have limited its operation to the exercise of a controlling 
 and regulating influence over this important function. The latter 
 conclusion is that to which a just estimate of the numerous facts 
 advanced on both sides would appear to lead. The experiments of 
 Dulong, repeated and modified by Despretz, seemed, indeed, for some 
 time to indicate that a portion of the heat developed in the body 
 could not be referred to the consumption of the oxygen inhaled, and 
 that, therefore, some other source for it must be sought. They com- 
 pared the heat given to a calorimeter by an animal placed within it, 
 with that produced by the combustion out of the body of as much 
 carbon and hydrogen as the animal gave off in the same time, in the 
 form of carbonic acid and water, and found that more heat was given 
 off by the animal than the chemical products of its respiration would 
 account for, to the extent of from one-fifth to one-tenth. It has 
 since been shown, however, that, on the one hand, allowance was not 
 made for an actual cooling down of the animal below its normal tem- 
 perature by exposure to the refrigerating influence of the calorimeter, 
 so that the heat indicated had not all been produced within the 
 period of the experiment ; and, on the other, that the heat generated 
 by the corresponding chemical actions out of the body had been 
 under-estimated. Dulong himself furnished a more correct estimate 
 of the heat developed by the combustion of hydrogen ; and his results 
 have been confirmed by Fabre and Silberman. Hence, while it 
 would be premature to attach too much value to such experiments, 
 considering our ignorance of the exact series of chemical changes 
 indicated by the resultant carbonic acid and water, they certainly 
 are not, as they once seemed to be, opposed to the chemical theory 
 of animal heat. 
 
 It may be regarded as certain that the nervous system exerts a 
 considerable influence upon the development of heat in the body. 
 The experiments of Sir Benjamin Brodie, and subsequently those of 
 Le Gallois and Chossat, have established the fact that lesions of the 
 nervous centres are accompanied with a diminution of temperature, and 
 of the power of forming heat. Again, the temperature of paralyzed 
 limbs is almost always less than that of sound limbs, and often so to 
 a very marked degree. In some instances, however, twin lesions of 
 
BERNARD'S RESEARCHES. 743 
 
 the nervous system are followed by an opposite effect. Much light 
 has been thrown upon the influence of the nervous system upon the 
 development of heat, by the recent highly interesting and important 
 researches of M. Bernard. 
 
 Bernard has lately established the very interesting fact, that sec- 
 tion of the sympathetic nerve is followed by a considerable elevation 
 of temperature in that side of the head or face corresponding to the 
 divided trunk. This increase of temperature occurs immediately ; 
 and persists after all increased vascularity and turgescence have dis- 
 appeared, and after the wound in the neck has quite healed. The 
 same observer found that sections of nerves of motion and sensation 
 produce respectively, besides paralysis, a diminution of temperature, 
 while, if a mixed nerve containing fibres of the sympathetic, as the 
 facial, is divided, an exaltation of temperature takes place, arising, 
 doubtless, from the division of the sympathetic fibres. The increase 
 of temperature seems to be a special result of the division of the 
 sympathetic. 
 
 Now, if thd upper extremity of the sympathetic, which has been 
 divided in the neck of an animal, be subjected to an interrupted gal- 
 vanic current, the exalted temperature which follows its division is 
 no longer manifested, and the parts supplied by it actually fall below 
 the normal standard, and they rise again when the current is stopped. 
 When an animal, in which the sympathetic had been divided, was 
 placed under the influence of chloroform, the temperature which had 
 risen several degrees in consequence of the division of the nerve, fell, 
 while it again rose when the animal had recovered from the efiiects 
 of the chloroform. 
 
 Bernard has shown that the increased temperature following divi- 
 sion of the sympathetic, or removal of the superior cervical ganglion, 
 cannot be attributed solely to the increased quantity of blood, which 
 is allowed to enter the vessels in consequence of paralysis of their 
 contractile coats ; for it occurs when the blood is allowed to stagnate 
 in the vessels by tying them. At the same time, it is necessary 
 that the vessels should contain blood. The enlargement of the ves- 
 sels and the increased flow of blood to the parts are to be looked 
 upon as the result of the altered nutritive changes which take place 
 in consequence of the division of the sympathetic, rather than as the 
 cause of the rise of temperature. Whatever may be the exact order 
 and nature of the changes which ensue, they may be looked upon as 
 a more active manifestation of the ordinary phenomena of animal 
 heat. 
 
 This increase of temperature, which is found generally to accom- 
 pany the abstraction of nervous influence, has been accounted for 
 by the supposition that the tissues were more readily acted upon 
 by the oxygen of the air when deprived of the protective agency of 
 the nervous system; but although this increased action of the oxygen, 
 or more rapid combustion, may perhaps have considerable weight in 
 the production of these phenomena, it must, by no means, be re- 
 garded as the sole cause, nor can the chemical theory of animal heat, 
 as it at present stands, be considered as giving an explanation of the 
 
744 VOICE. 
 
 whole of the facts observed in connection with this highly interesting 
 but abstruse subject. 
 
 Upon the subject of Animal Heat, the following works may be consulted : Dr. Craw- 
 ford's " Experiments and Observations on Animal Heat," 1788; Dr. J. Davy's Memoirs 
 in the Philosophical Transactions, 1814; "Recherches Exp^rimentales sur I'lnani- 
 tion," M. Chossat, Paris, 1843 ; Liebig's Animal Chemistry, 3d edition ; Sir Benjamin 
 Brodie's Physiological Researches, and also papers in the Phil. Trans., 1811-12 ; the 
 article Animal Heat, by Dr. Edwards, in the Cyclopsedia of Anatomy and Physiology, 
 vol. ii. ; Lehmann's Physiological Chemistry ; Mr. Newport on the Temperature of 
 Insects, in the Phil. Trans., 1837; Mem. "Sur la Chaleur Animale," par MM. Bec- 
 querel and Breschet, in Ann. des Sciences Nat. , Seconde Serie, torn. iii. iv. et ix. M. 
 Bernard, " Recherches Exp^rimentales eur la Grand Sympathique," Paris, 1854. 
 
 CHAPTER XXXI. 
 
 VOICE. — HOW PRODUCED. — ITS EXISTENCE IN THE ANIMAL KINODOM. 
 — THE HUMAN LARYNX. — ITS CARTILAGES. — THEIR ARTICULATIONS 
 AND LIGAMENTS. — CHORDS VOCALES. — MUCOUS MEMBRANE. — MUS- 
 ,CLES, EXTRINSIC AND INTRINSIC. — ACTION OF THE LARYNGEAL 
 MUSCLES. — NERVES. — ACTION OF THE LARYNX. — THEORY OF tOCAL- 
 IZATION. — CHEST VOICE. — FALSETTO VOICE. — SINGING. — INFLU- 
 ENCE OP THE NERVES ON VOICE. — SPEECH. 
 
 The high development of man's intellect, as compared with that 
 of the lower animals, would be of comparatively little advantage 
 without his peculiar endowment of speech. To this power, an essen- 
 tial subsidiary is that of producing vocal sounds or voice ; which, 
 however, he enjoys in common with a large number of the lower 
 classes. 
 
 The phenomena of voice are produced by a very beautiful and 
 simple mechanical contrivance, the larynx, which is placed at the 
 top of the trachea, to take advantage, as an exciting force, of the 
 air emitted from the lungs during expiration. The air thus expelled 
 creates vibrations in certain tense and elastic membranes (chordse 
 vocales), the boundaries of a chink which is the orifice at once of 
 entrance and of exit for the supply of air to the lungs. These vibra- 
 tions generate voice. 
 
 That the larnyx is the organ of voice is proved by the following 
 very obvious facts : first, the least alteration in the condition of the 
 mucous membrane covering thevocal chords is invariably accompanied 
 by a change in the tone of the voice, e. g. hoarseness ; secondly, 
 ulcerative disease eating through one or both of these vocal chords 
 destroys or greatly impairs the voice ; thirdly, opening the trachea 
 below the vocal chords, so as to divert the current of air in expira- 
 tion from the larynx, will destroy voice ; and fourthly, section of the 
 inferior laryngeal nerves, by which the influence of the will is brought 
 to bear on its muscles, and so the tension of the vocal chords is regu- 
 
HUMAN LARYNX. 
 
 745 
 
 lated, destroys the voice ; lastly, by experiment on the dead larynx, 
 sounds may be produced resembling those of the voice. If a current 
 of air be made to play on the vocal chords by a bellows fixed to the 
 tracheal end of the larynx, or by blowing air through it, distinct 
 vocal sounds are excited which can be' varied by altering the tension 
 of the vocal chords. 
 
 There is no instance of true voice among the lower orders of creation except in 
 those animals that hare a larynx connected with the respiratory apparatus, as in man. 
 In other words, all animals that have no larynx are voiceless. The hum of insects 
 is a phenomenon essentially different from voice,' a;nd is caused by the rapid vibration 
 of an apparatus connected with their wings. , . All the other invertebrated classes are 
 incapable of producing sounds. Fishes, likewise, are voiceless. The Batrachiau 
 reptiles possess a larynx and can pro- 
 
 duce vocal sounds. The hissing of 
 serpents is, likewise, laryngeal. But 
 the Chelonian reptiles have no voice. 
 In birds there are two organs placed, 
 the one in front of the other, to 
 which the name of larynx has been 
 given by anatomists ; of these, the 
 lower, or that nearest the lungs, is 
 the true vocal apparatus ; the upper 
 is merely a resonating or reciprocat- 
 ing cavity destined to enhance the 
 intensity of the sounds generated in 
 the lower. Cuvier showed that an 
 opening between the two organs did : 
 not destroy the power of producing 
 sounds, so long as the inferior larynx 
 was uninjured. 
 
 The human larynx is a 
 kind of box, composed of 
 pieces which may be moved 
 on each other, and incloses 
 the membranous bands in 
 which the vocal vibrations are 
 produced. These pieces, when 
 articulated together, consti- 
 tute the skeleton of the larynx. 
 They are composed of carti- 
 lage, and form a very curious 
 mechanism. There are five 
 distinct pieces (two of which 
 are symmetrical) essential to 
 this mechanism, and there 
 are four smaller, accessory 
 cartilages. The first are the 
 cricoid and the thyroid carti- 
 lages, the epiglottis, and the 
 arytenoid cartilages, which 
 are symmetrical. To these 
 may be added the cuneiform 
 cartilages and the cornicula, 
 "which are merely sesamoid 
 
 Fig. 210. 
 
 CartilageB of larynx and epiglottis, and upper ring;; 
 of trachea in situ seen from behind, From a prepara- 
 tion in the Anatomical Museum, King's College, by Mr. 
 Cane. 
 
 a. Arytenoid cartilages, &. Superior cornu. c. In- 
 ferior cornu, d. Posterior surface of cricoid, e. Fora- 
 men for superior laryngeal nerve. /, Perforations of 
 epiglottis, i. Upper margin of thyroid, t. Trachea, 
 A, Bight inferior tubercle. 
 
746 
 
 VOICE. 
 
 bodies destined to keep the folds of mucous membrane in proper posi- 
 tion. 
 
 The cricoid catilage is a ring, whose lower margin is parallel to, 
 and united by fibrous membrane with the first ring of the trachea. 
 Its upper margin slopes from behind forwards, and from above down- 
 wards, so that the posterior surface of the cartilage is considerably 
 deeper than the anterior, and affords two large concave surfaces 
 for the attachment of the posterior crico-arytenoid muscles. Its 
 upper border is connected in front with the lower margin of the alse 
 of the thyroid cartilage by an expansion of yellow fibrous tissue, 
 which is particularly thick in front, called the crico-thyroid ligament, 
 and which fills up the space called by surgical anatomists the crico- 
 thyroid space. This space and ligament, bounded on each side by 
 the crico-thyroid muscle, are penetrated by the trocar in the ope- 
 ration of laryngotomy. The posterior half of the upper border of 
 the cricoid cartilage exhibits on each side an oval convex articular 
 surface on which plays one of the arytenoid cartilages. 
 
 The thyroid cartilage consists of two square plates of cartilage 
 {alee) united at an acute angle in front ; each of these is prolonged at 
 the upper and lower corners behind, into a long superior process 
 {superior cornu) and a very short inferior process {inferior cornu). 
 By the superior process, and along the whole superior border of its 
 alae, the thyroid cartilage is united to the os hyoides by the thyro- 
 hyoid ligament. Each inferior process rests upon the outer surface 
 
 Pig. 211. 
 
 A. Thyroid oartUaga. a. The notch, h. Superior oornu. e. Inferior conra. d. Slight prominence 
 at median linos of inferior margin for the attaclunent of crico-thyroid ligament, a, h. Superior and 
 inferior tuheroles. e. Ala. /. Pomum Adami. ' t. »> ""J-" 
 
 B. Cricoid oarlUage seen from the side. a. Posterior supeiior margin. 6. Articnlatdng pnrface of 
 arytenoid cartilages. /. Superior deacending margin, h. The right surface articulating Trith inferior 
 tfornu of thyroid. 
 
 C. The right arytenoid cartilage, a. Base; position of the crico-arytenoid articulating grooves. 
 e. Lateral prominence at hase, which gives attachment to the crico-arytenoideus lateralis and postl- 
 cns. d, i. Convex triangular surfaces for the attachment of the superior thyro-arytenoid ligaments. 
 /. Oornlculum laryngis ; between/and e, the posterior aspect of the arytenoid cartilage and concave 
 surfaces giving attachment to the oblique and transverse arytenoid muscles, g. Vertical portion of 
 
VOCAL CHORDS. 747 
 
 of the cricoid cartilage, and plays upon a small circular plane articu- 
 lar facet situated thereon. 
 
 By the angular union of the two alse of the thyroid cartilage in 
 front, a projection is formed beneath the integuments which is most 
 , prominent in the male, and is commonly known as the pomum Adami. 
 Into the hollow angle behind, the vocal chords are inserted, and also 
 the stalk and ligament of the epiglottis. The broad outer surfaces 
 of the alse give attachment to muscles along an oblique line, which 
 is sufficiently conspicuous between the middle and lower third of each. 
 The thyro-hyoid and sterno-thyroid muscles are thus attached. To 
 the inner surface of each ala are inserted the thyro-arytenoid and 
 the crico-thyroid muscles. 
 
 By the gliding of the inferior horns of the thyroid upon the articu- 
 lar facet on the outer surface of the cricoid cartilage, a movement 
 of the one cartilage may take place on the other, round an axis 
 passing transversely through the cricoid. By this movement, the 
 crico-thyroid space may be enlarged or diminished according as the 
 cartilages separate from or approximate each other in front. 
 
 The arytenoid cartilages are two pyramidal bodies articulated by 
 their bases with the oval articular surfaces, already described on the 
 upper margin of the cricoid cartilage. Each presents a concave pos- 
 terior surface in which is implanted the arytenoid muscle which 
 passes from one cartilage to the other; an inner smooth surface 
 covered by mucous membrane, and an outer surface which gives 
 attachment to the crico-arytenoid muscles. From the anterior angles 
 of the bases of the arytenoid cartilages proceed the vocal chords to 
 be inserted into the angle of the thyroid. The mobility of the articu- 
 lation of the arytenoids with the cricoid, and their connection with the 
 vocal ligaments give them great importance in the mechanism of the 
 larynx. 
 
 The cornicula and the cuneiform cartilages are placed beneath the 
 mucous membrane — the former at the apex, the latter parallel to the 
 anterior border of the arytenoid cartilages. 
 
 The Epiglottis is a remarkable valve-like cartilage, in shape like 
 the spout of a ewer. It seems to issue from the angle between the 
 alse of the thyroid cartilage, to which it is attached by a stalk-like 
 ligament. It projects above the root of the tongue, and lies between 
 that organ and the aperture of the larynx, like a valve, which is 
 pressed over the glottis when the tongue is retracted. Its upper 
 border is convex, and its posterior surface is concave, transversely 
 convex in its length. It is a smooth and very flexible cartilage, 
 covered by a mucous membrane, but penetrated by holes and depres- 
 sions in which are lodged the numerous mucous glands of the mem- 
 brane that covers it. 
 
 Such is the skeleton of the larynx; it hangs from the hyoid bone, 
 suspended by the thyro-hyoid ligament and muscleSj and, through the 
 hyoid apparatus and some muscles, it is brought into connection with 
 the lower jaw and the base of the cranium. 
 
 Vocal Chords, or Superior Thyro-Arytenoid Ligaments. — The 
 various cartilages of the larynx are connected to each other by liga- 
 
748 
 
 VOICE. 
 
 menta. Of these, the most important and interesting, as being the 
 essential part of the mechanism for producing vocal sounds, are the 
 bands of fibrous tissue which extend from the anterior angle of the 
 base of the arytenoid cartilages to the angle between the wings of 
 the thyroid. These are the thyro-arytenoid ligaments, or, in physio- 
 logical language, the vocal chords. They are bands of elastic liga- 
 ment, extending between the points named {t, v, Fig. 212). They do 
 not, in the quiescent state, lie parallel to each other, but converge 
 from behind forwards; their relative position, as well as their ten- 
 sion, can be varied to a considerable degree by reason of the mobility 
 of the arytenoid cartilages. The length of the vocal chords is greater 
 in the adult male than in the female, being as 3 : 2. 
 
 The elastic chordae vocales are connected by an expansion of elas- 
 tic tissue with the superior thyro-arytenoid ligaments, which are 
 small bands of the same tissue, extending from the apices of the 
 arytenoid cartilages to the hollow angle of the thyroid, and separated 
 from the inferior by a space called the ventricle of the larynx. 
 These superior ligaments are likewise known as the false chordae 
 vocales. 
 
 Much importance is attached by Lauth, Miiller, and others, to 
 the fact that many of the ligaments of the larynx are composed of 
 elastic tissue, and connected together by a fibrous expansion of a 
 similar structure. Lauth describes the elastic tissue of the larynx 
 as starting from the angle of the thyroid cartilage between the inser- 
 tions of the thyro-arytenoid muscles, whence the fibres radiate down- 
 wards, obliquely backwards, and 
 Fig- 212. even somewhat upwards, forming a 
 
 continuous membrane, which passes 
 to the cricoid and arytenoid carti- 
 lages, lines the ventricles of the 
 larynx, and is connected with the 
 crico-thyroid ligaments and the 
 vocal chords, both true and false. 
 The thyro-hyoid ligament is like- 
 wise elastic; and also the fibrous 
 bands which connect the epiglottis 
 to the thyroid cartilage, and hyoid 
 bone, and the. tongue. " If," says 
 Miiller, "we add to these parts the 
 elastic longitudinal fibres in the 
 membranous part of the trachea 
 and bronchi, we shall have an idea 
 of the great extent of the tissues 
 susceptible of consensual vibration 
 and resonance in the parts sur- 
 rounding the organ of voice."* 
 
 The mucous membrane of the 
 larynx is part of the great respira- 
 
 View of the larynx from above, after Willis. 
 B. Ligaments uniting arytenoid and oricoid 
 cartilages, x and z. Direction of axis on 
 which the thyroid cartilage tnrns. E. Thy- 
 roid cartilage, k. Left thyro-arytenoid mus- 
 cle ; right removed, r, u, X, W. Cricoid car- 
 tilage. N, X. Bight crlco-arytenoid muscle. 
 N. Arytenoid carulages. I. Crico-arytenoidic 
 postlci muscles, r. Posterior part of cricoid 
 cartilage. T, V. Vocal ligaments. 
 
 * MUUer's Physiology, by Baly, vol. ii. p. 1005. 
 
ACTION OF MUSCLES. 
 
 749 
 
 tory tract, described at page 523, and possesses the same anatomical 
 characters at many points, being covered by ciliated epithelium. It 
 is involuted to a considerable extent, forming numerous glands, which 
 cover the epiglottis, and are scattered over the interior of the larynx. 
 
 We have seen that the cricoid cartilage may move freely on the 
 thyroid, or vice versa ; and the arytenoids may be moved in various 
 directions on the upper border of the cricoid. Moreover, suspended 
 as it is, loosely in front of the pharynx and oesophagus, the whole 
 apparatus of the larynx may be moved freely up and down in the 
 neck, approximating, or receding from the lower jaw. For these 
 various movements the larynx is provided with two sets of muscles — 
 the extrinsic, by which the whole organ is moved, and the intrinsic, 
 destined to regulate the movements of the various segments. 
 
 The extrinsic muscles are those which connect the larynx to the 
 sternum below and the hyoid bone above ; the stern o-thyroid, the 
 thyro-hyoid, and, indirectly, the sterno-hyoid, omo-hyoid and stylo- 
 hyoid, and stylo-pharyngeal muscles. 
 
 The intrinsic muscles are the crico-thyroidei, the arytenoidei, the 
 crico-arytenoidei-postici and laterales, and the thyro-arytenoidei. We 
 must refer to works on descriptive anatomy for the details of the 
 connections of these muscles ; it 
 
 must suffice, here, to state that 
 their names denote very accu- 
 rately their attachments to the 
 segments of the larynx upon 
 which they can exert their force. 
 Action of Laryngeal Muscles. 
 — The arytenoid cartilages are 
 attached by ligaments to the 
 posterior surface of the cricoid, 
 which permit a considerable ex- 
 tent of rotation upon an articu- 
 lating surface formed on the 
 summit of the latter; by this 
 arrangement the chordae vocales 
 may be stretched or relaxed, 
 and the aperture of the glottis 
 increased or diminished, accord- 
 ing to the direction of the force 
 which acts upon the arytenoid 
 cartilages. The posterior crico- 
 arytenoid muscles render the 
 vocal chords more tense, but at 
 the same time cause them to 
 diverge from each other, and so 
 the width of the aperture of the 
 glottis is enlarged. On the 
 other hand, the thyro-arytenoid 
 muscles, by drawing the aryte- 
 noid cartilages towards the thy- 
 
 Fig. 213. 
 
 Slagnifled view of internal parte of larynx of 
 right side, after Willis, showing actions of laryn- 
 geal muscles. 
 
 O, P. Axis of articulation of arytenoid carti- 
 lage. T. Direction of force of thyro-arytenoid 
 masclo. X. Direction of force of crico-aryte- 
 noideus lateralis. ' W. Of crico-arytenoideus pos- 
 ticus. T. Of arytenoideus transversus. 
 
 B. Crico-arytenoid ligaments. X. Crico-aryte- 
 noideus. lateralis, Q. Crico-arytenoideus posticus. 
 h. YocBil ligament. 
 
750 VOICE. 
 
 roid, relax the vocal ligaments, while the orico-arytenoidei laterale's, 
 by causing the arytenoid cartilages to rotate inwards upon their axes, 
 approximate the vocal chords and diminish the aperture of the glottis. 
 The arytenoid muscle draws the two cartilages towards each other, 
 and so tends to diminish the aperture of the glottis, especially at its 
 posterior part. 
 
 These different movements are further accelerated, or increased 
 in extent, by the action of certain other intrinsic and extrinsic mus- 
 cles of the larynx. 
 
 Thus the arytenoid cartilages being fixed by the contraction of 
 the arytenoid and posterior crico-arytenoid muscles, the vocal chords 
 will be stretched by the descent of the thyroid cartilage over the 
 cricoid, a movement performed by the crico-thyroid and sterno-thy- 
 roid muscles. The thyro-hyoid muscle, by drawing the thyroid car- 
 tilage upwards towards the hyoid bone, will assist the action of the 
 thyro-arytenoids, and relax the vocal chords. 
 
 By the action of these various muscles, the tension of the vocal 
 chords may be increased or diminished, and the size of the opening 
 of the glottis regulated at will. 
 
 Modes of altering the aperture of the Glottis and the tension of the Vocal Chords. 
 
 Crioo-thyroidei stretch the vocal chords ..... . , 
 
 T>>.,^„ .^.,t»r,„M<.; /relax and place the vocal chords in 1 tgoferu pitch 
 
 Thyro-arytenoidei . . . .| the position for vocalization . .}j "^"^"'r 
 Crico-arytenoideipostid . . . / separate the ftont of the 1 open 1 
 
 '' r ^ arytenoid cartilages . J glottis 
 
 Crico-arytenoideilaterales . . / press together the front of V 
 
 •' t the arytenoid cartilages j 1 close 
 
 Arytenoidei ? press together the back of W glottis . 
 
 •' \ the arytenoid cartilages j 
 
 Nerves. — The nerves of the larynx are derived from the superior 
 and inferior laryngeal branches of the vagus. Those from the for- 
 mer are distributed to the mucous membrane, and to the crico-thyroid 
 muscles, by the external laryngeal branch, those from the latter to 
 all the other intrinsic muscles of the larynx. Both these nerves 
 anastomose with each other beneath the mucous membrane, near the 
 arytenoid muscles. 
 
 The inferior laryngeal or recurrent nerve has relations to the 
 innominata artery on the right side, and to the aorta on the left, 
 which often implicate it in aneurismal tumors, especially of the latter 
 artery. These, by compressing, weaken and paralyze the nerve and 
 the muscles which it supplies, and give rise to those alterations of 
 voice which are sometimes among the earliest indications of the 
 formation of an aneurism within the chest. 
 
 Action of the Larynx and Theory of Vocalization. — In the little 
 apparatus of vocal chords attached to movable cartilages and bounded 
 by a free space above the laryngeal ventricles, and by a free space 
 below the tube of the trachea, in which they vibrate, are found the 
 chief conditions necessary for the production of the vocal sounds 
 over an extensive though variable range of pitch. 
 
 Although all physiologists are agreed that this apparatus is the 
 seat of the production of vocal sounds, there has, nevertheless, been 
 
 govern 
 aperture 
 
 of 
 glottis. 
 
THEORY OP VOCALIZATION. 751 
 
 mucli diflfereiice of opinion as to whether the larynx should be 
 regarded as a stringed instrument, in which the sound depends upon 
 the vibrations produced by the movement of the stretched strings, 
 as a wind instrument, in which sounds result from the vibration of 
 the column of air within them, or as a reed instrument which deve- 
 lops sound by the vibration of one or more highly vibratile tongues 
 acted on by a current of air passing over them. 
 
 By the mechanism we have described, the vocal chords are placed 
 in a position favourable for the production of sounds by their vibra- 
 tion, and the pitch of the sounds so produced modified. 
 
 Professor Willis showed, that in an ordinary respiration the aper- 
 ture of the glottis assumed a V for™ 5 and its lips are inclined from 
 each other ; the apex of the Y is situated towards the thyroid car- 
 tilage. When sound is to be produced, the lips of the glottis are 
 made to approximate each other, and their inner edges become paral- 
 lel. If now a current of air be forced through the chink, a sound 
 is produced, the pitch of which depends entirely upon the tension of 
 the vocal chords. De Kempelin says, that in the production of sounds 
 the lips of the glottis are approximated to the one-tenth or one- 
 twelfth of an inch. The chords in vocalization vibrate throughout 
 their whole length ; but no voi(ye-sounds can be produced by the 
 passage of air through the posterior portion of the chink of the 
 glottis between the arytenoid cartilages. Even when the chords 
 are in contact, sound is produced by the forcible transmission of air. 
 
 When the vocal chords are rendered tense, a high note is produced ; 
 when they are relaxed, a note of low pitch results. A greater num- 
 ber of sonorous vibrations takes place in the former case than in the 
 latter. It has been shown, that in the case of stretched strings, the 
 pitch of the note varies in direct proportion to the amount of tension, 
 according to the law that the number of vibrations produced by 
 strings of similar length varies in proportion to the square-roots of 
 the forces which stretch them. A string stretched by a certain force 
 will produce twice the npmber of vibrations, if the force be increased 
 four times ; or, if a stretched string is caused to vibrate, and so to 
 produce a certain note, if four times the force be employed, we obtain 
 a note which is the octave of the first, requiring for its production 
 twice the number of vibrations. These results, however, cannot be 
 obtained upon the larynx, so that, as Miiller has proved, the pro- 
 duction of vocal sounds in this organ cannot be compared with those 
 produced in a stretched string. 
 
 The distinguished physician, M. Savart, was among the most 
 active supporters of the explanation of the formation of voice, on 
 the principle of wind-instruments. He likened the larynx to a bird- 
 call, and referred the exact seat of the development of sound to the 
 air contained in the ventricles of the larynx, which would be aifected 
 by the upward current from the trachea, just as the air in the cavity 
 of the bird-call is by the current from the mouth. But, to pass . 
 over the argument, that it is very doubtful whether the bird-call can 
 be referred exclusively to the class of wind-instruments, M. Savart's 
 views are decidedly negatived by the fact that in the class of rumi- 
 
752 VOICE. 
 
 nants the superior or false vocal ligaments are absent, and, conse- 
 quently, the ventricle of the larynx. 
 
 Ferrein was the first to show, by experiment, that vibration of the 
 vocal chords was the essential cause of voice. His experiments, 
 published in 1741, were performed on the dead larynx. By them 
 he was enabled to show, that the note varied according to the length 
 and tension of the vocal chords, the same laws regulating the pro- 
 duction of sound by these chords as by strings which are thrown 
 into sonorous vibrations by currents of air. 
 
 The most important experiments upon the production of vocal 
 sounds are those of Professor J. Miiller, of Berlin, and of Professor 
 Willis, of Cambridge. Miiller investigated the action of membran- 
 ous bands, or of tongues formed of caoutchouc, in generating sound 
 under the influence of a current of air. The human organ of voice 
 is imitated by a tube, capable of being varied in length ; to one end 
 of this are applied two membranous vibrating tongues, attached to 
 the wall of the tube, but separated from each other by a chink, 
 through which passes the current of air necessary for throwing them 
 into sonorous vibrations. Willis employed a similar instrument. 
 
 The results of these experiments may be thus briefly stated — 
 
 1st. That elastic bands, forming the lateral boundaries of a chink 
 through which a current of air is driven by a pair of bellows, may 
 be thrown into vibrations so as to produce sounds which resemhle 
 those of the human voice. 
 
 2d. That for such vocalization it is necessary that these bands 
 should have, in addition to a certain degree of tension, a particular 
 position likewise. This, which is called by Willis the vocalizing posi- 
 tion, consists in the parallelism of the margins of the bands. In 
 the quiescent state, during breathing, the lips of the glottis are in- 
 clined from each other ; but in the vocalizing position, or that neces- 
 sary for the production of voice, they become parallel. In the 
 former condition, the glottis is a triangular space, with divergent 
 sides and apex in front ; in the latter, it becomes a simple slit, or 
 nearly so, with parallel sides. In the human larynx, the thyro- 
 arytenoid muscles, lying on the outside of each of the vocal chords, 
 exercise a principal influence in determining their relative position, 
 and in adapting them for vocalization. 
 
 3d. If a tube be adapted to the membranous tongues, in such a man- 
 ner that the air may play upon them through it, and may pass through 
 another tube after it has acted upon them, an influence is exercised 
 not only on the timbre of the sounds produced, but also upon the 
 pitch, which varies with the length of either and of both. In the 
 human organ of voice, the larynx and bronchi represent a tube pre- 
 fixed to the membranous tongues and chordae vocales ; and the cavity 
 in front of the inferior ligaments of the larynx, a tube placed below 
 the tongues.* 
 
 * The reader is referred for the detail of MUUer's experiments to p. 988 et seg., of 
 Dr. Baly's Translation, vol. ii., and to Muller's separate -work, Ueber Compensation 
 der phys. Kriifte am menschlich. Organ — Berlin, 1889. 
 
PRODUCTION OF VOCAL SOUNDS. 
 
 753 
 
 Fig. 214. 
 
 The vocal sounds may be produced by blowing air from the trachea 
 through the aperture of the glottis in a larynx removed from the 
 dead body ; and by adopting means to vary the tension and the rela- 
 tive position of the vocal chords, the phenomena of the voice may be 
 very closely imitated. When 
 air is thus blown through the 
 glottis, the vocal chords being 
 approximated, clear and full 
 tones are generated. They are 
 produced most readily and cer- 
 tainly when the posterior part 
 of the glottis, situated between 
 the arytenoid cartilages, is 
 closed. A certain constriction 
 of the glottis appears neces- 
 sary, as, when it is too open, 
 an indistinct noise is merely 
 produced. The pitch of the 
 note is determined by the ten- 
 
 sion of the vocal chords, that 
 
 Diagram to show parts concerned in vocalization, 
 and tlie character and shape of cavities above and 
 below the vocal chords. 
 
 of both being equal ; it is not 
 
 influenced by changes in the 
 
 width of the aperture of the 
 
 glottis. By increasing the 
 
 weight which stretches the 
 
 vocal chords, the height of the 
 
 notes is raised; on the other 
 
 hand, the relaxation of the 
 
 chords lowers the notes : a 
 
 register of about three octaves may be formed in this way. Even 
 
 after all the parts which lie over the vocal chords have been removed, 
 
 these variations of sound may still be produced. 
 
 The action of the vocal organ in man appears to approach more 
 nearly to that of a reed instrument than to a stringed instrument. 
 The former is characterized by being provided with a flexible vibrat- 
 ing tongue, against which the air can be propelled so as to throw the 
 tongue into vibration, and to excite a musical sound. Such is the 
 mechanism in the organ-pipe, hautboy, bassoon, accordeon, and other 
 instruments ; the form and disposition of the tongue, and the mate- 
 rial of which it is made, diff'ering in each instrument. 
 
 Chest Voice. — In the larynx, as before remarked, the note may 
 be changed, by varying the tension of the vocal chords, provided 
 they be parallel and sufficiently close to each other. When a high 
 note is to be produced, the head is raised and the larynx elevated, in 
 order that the vocal chords may be rendered tense ; on the other 
 hand, if we wish to sound a very low note, the chin must be de- 
 pressed upon the chest, so as to facilitate the relaxation of the vocal 
 ligaments. At the same time, the strength of the blast of air exerts 
 a considerable influence upon the pitch of the note. In reed instru- 
 
764 VOICE. 
 
 ments, it has been found that the note can be rendered higher by in- 
 creasing the force of the blast. 
 
 Falsetto Notes, — The sounds to which we have been referring are 
 produced solely by the vibration of the chordae vocales ; modified no 
 doubt by the epiglottis, soft palate, etc., and the laryngeal cavity 
 below. These notes are all termed chest notes ; but in man tones 
 can be generated very different from those which can be imitated by 
 experiments upon the dead larynx. These are the falsetto notes. 
 The precise mode of their production is obscure. From the experi- 
 ments of Miiller and Lehfeldt, it is probable that these falsetto notes 
 are produced by the vibration of the inner portion of the borders of 
 the vocal ligaments solely. Magendie and iVIayo accounted for them 
 upon the view, that only half the length of the chords was thrown 
 into vibration. 
 
 Mr. Bishop has shown, that in the transition from the chest note 
 to the falsetto note the crico-thyroid chink opens, having been closed 
 immediately before, during the production of the highest note of the 
 chest voice ; so that the vocal ligaments become relaxed ; a change 
 which necessarily follows must take place, if they are to produce a 
 similar note, by vibrating only along half their length. 
 
 Singing. — In singing, a certain succession of tones is produced in 
 definite order by altering the character of the glottis, just as by 
 varying the conditions under which the air is thrown into vibratiftis 
 in musical instruments we are enabled to alter the nature of the 
 note. 
 
 The different varieties of the voice are arranged according to the 
 pitch, which depends upon the length and other conditions of the 
 vocal ligaments, and they are comprised in the following classes : 
 Bass, Tenor, Alto or Contralto, Soprano; the two former belonging 
 to the male, and the two latter to the female sex. Besides these, 
 the Barytone is placed between the Bass and Tenor, and the mezzo- 
 Soprano between the Soprano and Contralto. The compass of the 
 voice varies from one to three octaves. Few singers possess a greater 
 range of voice than the latter, but some of the most celebrated 
 have much exceeded this — Catalani's voice included three and a half 
 octaves. The compass of each kind of voice is shown in the follow- 
 ing table : — 
 
 SOPBANO. 
 
 I CONTBAITO. f 
 
 CDEFGABC'D'E'F'G'A'B'C'D''E^F''G^A'B=C^D5ET'GWB3C^ 
 
 Bass. 
 
 Tenob. 
 
 Before puberty, the pitch of the male and female voice is nearly 
 the same ; but at this period the larynx of the male becomes larger 
 and more prominent, and the vocal ligaments elongated, in virtue of 
 which changes the pitch falls an octave in extent. In eunuchs this 
 alteration does not take place, and they retain the puerile character 
 of voice, which is, nevertheless, louder and stronger than in women. 
 
SIN9ING. 755 
 
 In men the vocal chords are one-third longer than In women, and 
 the larynx is altogether much larger. 
 
 Unlike musical instruments, the human voice is capable of pro- 
 ducing a vast number of notes, intermediate between the successive 
 tones ; and Dodart estimates the number of these which can be ap- 
 preciated by the ear at three hundred. 
 
 Influence of the Nerves on Voice. — The inferior laryngeal and the 
 crico-thyroid branch of the superior laryngeal, from the pneumo- 
 gastric, are the sole channels through which the operations of the 
 will affect the mechanism concerned in the production of the voice- 
 sounds, and as occurs in the case of other muscles, the movements 
 of those muscles whose office it is to regulate the tension of the vocal 
 chords, and govern the aperture of the glottis, are much more rapid 
 and perfect, much more under the control of the will, and capable 
 of executing more delicate movements in some persons than in others; 
 and hence the wide difference between individuals as to their capa- 
 city for singing and vocalization. Something in the difference of 
 vocalizing power is due to minute and inappreciable differences in the 
 length of the vocal chords — size of glottis — quantity of the elastic 
 vocal chord tissue — of the mucous membrane (slight affections of 
 which create hoarseness). 
 
 The movements of the laryngeal muscles, as are the movements 
 of respiration, are much influenced by mental emotions. In laugh- 
 ter, crying, sobbing, we have a combined excitement of respiratory 
 and vocal actions. 
 
 In health, the emotions of grief, joy, and surprise, affect both 
 voice and speech — the latter more frequently and intensely than the 
 former. Diseases which involve more or less disturbance of the 
 centre of emotions, affect both voice and speech. Hysteria, and 
 chorea, may be referred to, the former generally affecting the pro- 
 duction of voice, the latter of speech. 
 
 In certain affections of the brain, speech is impaired or altogether 
 destroyed, or at most limited to a monosyllable, Yes or JVo. This 
 occurs under various conditions; sometimes in consequence of a 
 chronic disease, sometimes of a shock : a diseased state of the convo- 
 lutions or hemispheres is the most frequent concomitant of this symp- 
 tom, but no precise part of the brain can be assigned as a special 
 organ of speech. 
 
 In many diseases of a spasmodic or convulsive character, the action 
 of the muscles of the larynx is affected. In the spasmodic croup or 
 crowing inspiration of children, the chink of the glottis is frequently 
 so firmly closed, and for so long a time as to endanger life. The 
 peculiar "hoop" of hooping-cough, and the curious voice-sounds 
 so common and so varied in hysteria, show that either these nerves 
 themselves or the precise part of the centre with which they are 
 connected, are influenced by the morbid action. In chorea the same 
 want of power of co-ordinating the movements is observed in the 
 little muscles of the larynx as in those which preside over the move- 
 ments of the limbs and other organs. 
 
 In some of the conditions to which we have referred, it is difficult 
 
756 VOICE. 
 
 to say whether the motor nerve or its central origin is affected, or 
 ■whether the disturbance is not excited in the centre through the in- 
 fluence of an afferent nerve. Anything irritating the delicate mucous 
 membrane of the larynx creates violent spasmodic action of the 
 muscles of the glottis, in which those of respiration frequently take 
 part, through the medium of the afferent superior laryngeal nerve. 
 
 Pressure upon the inferior laryngeal excites spasmodic cough, which 
 often forms an important symptom of aneurism, or of mediastinal 
 tumor. Section or disease of the inferior or laryngeal nerve com- 
 pletely destroys the power of vocalization. 
 
 Stammering, at least in the greater number of instances, is an 
 affection of the nervous system, not of the articulating organs. It 
 consists in a defective control over the will, and an imperfect power 
 of co-ordinating the muscles of speech. Stammering is much 
 increased by any mental excitement, sudden surprise, etc., and one 
 of the most important points to be kept in view, in the treatment of 
 this condition, is to avoid all cause of excitement to the patient, and 
 to prevent him from thinking about his condition as much as possi- 
 ble, so that he may gradually obtain that command over the move- 
 ments of the muscles which is required for conversation. 
 
 Speech. — In the vocal apparatus, notes of very various pitch can be 
 produced at will. The different sounds of voice have been shown to 
 be due to variations in the size of the aperture of the glottis, and 
 in the tension of the chordae vocales. The vocal organ, however, 
 is not capable of producing those articulate sounds by which we are 
 enabled to communicate to each other our ideas ; but this end is 
 obtained by an alteration taking place in the cavity situated above 
 the glottis, and in the position of the organs which it contains. 
 
 The most important conditions affecting speech are, first, the size 
 of the oral aperture; secondly, the size of the buccal cavity; and 
 thirdly, the position of the tongue. 
 
 The production of vowel sounds, which are continuous, and can 
 be prolonged at will, depends entirely upon the size of the buccal 
 cavity and outlet. In the sound of the a in ah, these are opened to 
 their widest extent, while in sounding a in fate, the buccal cavity 
 requires to be much reduced in size, by the lateral expansion and 
 elevation of the tongue. When we sound the e in me, cavity and 
 outlet are made still less. The o in no, results from a still further 
 diminution of the oral aperture, while the buccal cavity is much 
 increased ; and in the oo in hoot, the former is contracted to a mini- 
 mum, and the latter increased to its largest size. 
 
 The sounds just enumerated are the vowel sounds of continental 
 languages, and they can all be prolonged for a time limited only 
 by the passage of the air through the vocal apparatus. The Eng- 
 lish i may be looked upon as a diphthongal sound, and, like the true 
 diphthongs, cannot be prolonged like a continued vowel sound. The 
 diphthongal sounds appear to be produced by causing one particular 
 vowel sound to pass into another with a considerable degree of 
 rapidity, thus : ou is formed by the transition of the a in far to the 
 00 in cool. 
 
SECRETION. 757 
 
 In the pronunciation of consonants, the soft palate, the tongue and 
 lips more especially, take part ; and in order to produce many of the 
 sounds, it is necessary that the air should be forced through the pas- 
 sages suddenly, and often with a considerable degree of force, while 
 others can be produced as continuous sounds, like the vowels ; hence 
 the divisions into explosive and continuous consonants. 
 
 The former class includes the b, p, d, t, g, k, the latter, the v, f, 
 1, m, n, r, the sibilant consonants s and z, and the Greek 9 [theta) th, 
 which, like sA, is a perfectly simple sound, and might be represented 
 by one letter. The manner in which these sounds are produced, by 
 the alteration of the position of the organs concerned in the produc- 
 tion of speech, can be studied by every one in his own person ; but 
 for a full description of the position of the several parts concerned 
 in producing them, the reader is referred to the works enumerated 
 at the end of the present chapter. 
 
 For information upon the subjects treated of in the present chapter, the student is 
 referred to the following works: Dissertatio de Loquela, 1700; Rev. Mr. Willis in the 
 "Cambridge Philosophical Transactions," vol. iv., 1832; Lauth, " Mem. de I'Aoade- 
 mie Royale de M^decine," 1835; J. Muller, "Elements of Physiology," translated by 
 Dr. Baly; Articles "Larynx" and "Voice," by Mr.^ Bishop, in the Cyolopsedia of 
 Anatomy and Physiology. 
 
 CHAPTER XXXII. 
 
 ON SECRETION. — SECRETIONS AND EXCRETIONS. — SECRETIONS WHICH 
 
 ARE EXCREMENTITIOUS. SECRETIONS WHICH ARE NOT EXCREMEN- 
 
 TITIOUS, WHICH SERVE ULTERIOR PURPOSES. — VICARIOUS SECRE- 
 TION. — INGESTA AND EGESTA. — ANATOMY OF SECRETING ORGANS 
 GENERALLY. — OF THE GLAND-CELL. — OF THE DUCTS OF GLANDS. 
 
 The function of secretion is that by which organized bodies sepa- 
 rate from some portion of their internal or external surfaces a ma- 
 terial which thereby becomes free or loose, and capable of removal, 
 and which is likewise commonly known as the secretion from such 
 surfaces. It is not sufficient that this material should be separated 
 simply from the blood ; for, if this were so, all the tissues would be 
 secretions ; but it must also be separated from a tissue of a special 
 kind, hence known as a secreting tissue. The blood, then, furnishes 
 the materials which are to form the secretions ; but certain tissues 
 are required, without which, these materials could not become secreted 
 products : and the secreting tissues are anatomically arranged so as 
 to have one surface adapted to set free, in, the form of secretions, the 
 materials derived on the opposite surface from the blood. 
 
 A secretion may be solid or fluid, living or dead, near to, or dis- 
 tant from, the constituents of the tissues in chemical constitution, 
 capable of re-entering the blood, and being further serviceable ia 
 49 
 
758 SECRETION. 
 
 the economy, or requiring to be expelled from the system as useless 
 or hurtful. Thus, a great variety of very dissimilar products are 
 conveniently classed together as secretions, in virtue of their being 
 separated from the body by tissues provided for that purpose. 
 
 Excretions. — Some secretions consist mainly of substances result- 
 ing from the waste of the tissues coincident with their nutrition or 
 renewal, and which are thrown off from the blood through the se- 
 creting surfaces almost as soon as the capillaries receive them from 
 the tissues. Such are the urine, and portions of those matters which 
 escape in the form of faeces ; and, allied to these, is the carbonic 
 acid, which is eliminated, without the intervention of a true secre- 
 ting tissue, directly from the capillaries of the lungs. If these 
 matters were retained, they would accumulate in the blood and 
 tissues, and prove, sooner or later, incompatible with life ; and even 
 a simple delay or retardation in the process of their removal, to 
 whatever cause it may be attributable, must be attended with grave 
 consequences to health. It is, therefore, impossible to over-estimate 
 the importance of distinguishing these products from other secre- 
 tions, and of acquiring the habit of considering them under one 
 common head. They are known as the exerementitious secretions, 
 or, simply as excretions. 
 
 The kidneys are organs through which a large portion of the 
 blood is constantly flowing, and in which the general mass of, that 
 fluid becomes so far purified as to be freed from certain waste ma- 
 terials which have just been thrown into it by the muscular and other 
 tissues. The blood which leaves the kidneys, though rendered venous 
 by the nutrition of the glandular tissue itself, is more free than 
 before to receive the refuse of the other parts. Hence the kidneys 
 must be regarded as a depurating organ, subservient to the functions 
 of other parts of the frame. To prove this, it is only necessary to 
 extirpate the kidneys from an animal, or to see their function arrested 
 by disease : in either case, the blood and tissues become more and 
 more loaded by the urinary matters which continue to be formed in 
 the body, and which should have been eliminated as soon as formed 
 by the extirpated or diseased organs. So essential, indeed, to animal 
 life, is this excretion of nitrogenized matters, resulting from the waste 
 of the nitrogenous tissues, that it may be safely said to be universally 
 present, and to have a kidney, or analogous organ, assigned to it, 
 wherever animals exist having an arrangement of different and 
 mutually dependent parts, on such a scale as to render the direct 
 expulsion of the waste materials at the points where they are formed 
 impossible. 
 
 The principal excretions maybe thus enumerated: 1. carbonic 
 acid gas, formed by the action of the oxygen upon carbon, and 
 separated by the lungs ; its accumulation in the blood is very rapidly 
 fatal to life. 2. Urea, uric acid (in herbivorous animals hippurie 
 acid), kreatine, and kreatinine: all nitrogenized principles of definite 
 composition, resulting principally from the waste of the tissues, and 
 eliminated by the kidneys ; their retention in the blood is soon, but 
 less rapidly, fatal. 3. Various saline matters, separated by the kid- 
 
RECEEMENTITIOUS SECRETIONS. 759 
 
 neys and skin. 4. Lactic acid, principally by the slcin. 5. Cer- 
 tain portions of the hile, already considered (see p. 602), by the 
 liver. To these may be added sundry constituents of the faeces, 
 of imperfectly known composition, but supposed by Liebig to be im- 
 perfectly oxidized matter,* escaping by the mucous lining of the 
 intestinal tract, probably by the tubes of Lieberkuhn and by the 
 solitary glands ; and lastly, also, whatever substances are taken in 
 as food and absorbed into the blood, but which fail to be assimilated, 
 either from their being superfluous in quantity, or incapable of serving 
 any purpose in the economy. 
 
 Secretions which are not composed of excrementitious substances, 
 and which serve important offices in the economy. — Other secretions 
 (and this is a large and diversified class) do not consist of waste 
 materials, the results of the disintegration of the tissues, but are 
 thrown off in certain situations where they are to perform a part 
 useful or necessary to the protection or preservation of other organs, 
 or of the whole body, or of the species. Of these, speaking generally, 
 it may be said that they are formed, as well as eliminated, by the 
 several organs which furnish them ; that they retain more or less 
 resemblance, in chemical constitution, to the food and the nutritious 
 parts of the blood ; and that, in many respects, they are allied to 
 the living tissues of the body from which they are separated. 
 
 The highest example which can be given of these qualities is that 
 of the male and female elements, the semen and the ova, which go 
 to form the new being, and which are the production of organs es- 
 sentially secreting. Here the secreted matter retains its organized 
 form and its living properties, which latter are of so elevated a 
 character, as to end in the development of an entire organism like 
 that which has furnished the secretion. 
 
 Other examples, in which these qualities meet less decidedly, are 
 presented, by the milk, and by some of those secretions which have 
 been already considered under the head of the digestive function, such 
 as the saliva, the gastric juice, and the pancreatic fluid. These are 
 poured out to mingle with the food, and variously to facilitate its 
 entry into the blood ; and there can be no doubt, that after having 
 duly efiected this object, they become in a considerable measure 
 themselves reabsorbed with the food, so as to be further serviceable 
 for a time in the ever-moving circle of the functions of vegetative 
 life. There is no waste here ; and we may suppose that they do not 
 become finally expelled until they have been reduced to forms of 
 combination in which they can no longer minister to the life of the 
 tissues! Such secretions are conveniently classed together as recre- 
 mentitious. 
 
 But it would be an error to suppose that all matters separated 
 from the natural surfaces of the body fall exclusively under one of 
 
 * The fseces have lately been subjected to chemical investigation by Dr. W. Mareet, 
 who has discovered an organic crystalline substance of an alkaline reaction, to which he 
 gives the name of Excreline, an acid olive-coloured substance of a fatty nature, Fx- 
 crelolic add, and a fatty acid, having the properties of Margaric acid, but not con- 
 stantly present. — "Proceedings of the Royal Society," vol. vU. No. 6. 
 
760 SECRETION. 
 
 the foregoing heads ; on the contrary, it happens in some cases that 
 a secreted product is of a mixed kind, partly excrementitious and 
 partly recreraentitious — partly rejected as needless or injurious — 
 partly thrown oif that it may subsequently fulfil a useful purpose in 
 the economy of the individual and species. Thus the bile contains 
 certain matters which are expelled with the excrements, while a large 
 proportion of its elements is reabsorbed in the blood, after their 
 commixture with the chyme in the intestines, and thus furnishes 
 material for the production of animal heat in respiration. 
 
 The chief secretions serving an ulterior purpose, and which are 
 thrown out with that object, are the following: The generative 
 elements — the milk, the salivary, the gastric, pancreatic, and allied 
 fluids ; parts of the biliary fluid ; the mucus from some surfaces ; the 
 epidermis and its appendages from the skin ; the sebaceous and 
 odoriferous matters from certain glands ; the tears. 
 
 Water, as it forms a necessary part of the living frame, and is 
 probably in constant course of formation within it, and as it is, 
 besides, continually received in large quantities as food and drink, 
 is a constant ingredient of the secretions, being thrown off especially 
 by the lungs, skin, and kidneys. By the two former its loss is 
 determined, in a great degree, by simple evaporation into the sur- 
 rounding air ; and this is necessarily influenced much by the hygro- 
 metric state and other conditions of that medium. By the letter, 
 whose office is complemental of that of the preceding, a special 
 apparatus is furnished for draining ofi" the water, while this fluid is 
 made useful in extracting the ingredients of the most important of 
 the excretions from the surface over which it is subsequently made 
 to flow. 
 
 Vicarious Secretion. — It has been remarked, that there is a sort 
 of compensating action between the skin and kidneys in the normal 
 condition of the system, dependent upon variations in temperature 
 and other conditions. A similar power exists, in a more limited 
 extent, in other secreting structures, by virtue of which one organ 
 may take upon itself the work of another, whose healthy function 
 has been temporarily suspended or impaired by disease. Advantage 
 is taken of this circumstance in the treatment of kidney diseases, in 
 which the functions of those organs are temporarily or permanently 
 impaired. In such cases, the removal of the urinary constituents ia 
 promoted through the skin, or from the intestinal tube, by giving 
 purgative medicines, and by promoting secretions. The excretion of 
 biliary matter in the urine in cases of jaundice, and the separation 
 of the menstrual fluid from the mucous membrane of tbe liings or 
 stomach, are familiar examples of this vicarious action. Very nume- 
 rous cases of metastasis of the urinary secretion are on record ; and 
 elements of the urine have been met with in vomit, in the stools, in 
 the tears, and secretions of the ears and nose ; in the milk, and upon 
 the cutaneous surface generally, particularly about the navel. 
 
 If the kidneys of an animal be extirpated, the elements of the 
 urine may be detected in many situations in which they are not nor- 
 mally present. In disease, when the functions of the kidneys are 
 
INGESTA AND EaBSTA. 761 
 
 much impaired, it is not uncommon for the elements of the urine to 
 pass off from the stomach by vomiting. 
 
 Ingesta and Egesta. — It is obvious, that if the weight of the body 
 remains the same, the quantity of matter removed by the dififerent 
 excretory channels will exactly correspond to the ingesta, although 
 the arrangement of the elements will be changed. 
 
 The proportion in which the diiferent elements entering into the 
 composition of the food are removed by the various secreting organs 
 is shown in the following table, the result of some excellent experi- 
 ments of M. Barral : 
 
 Ingested 
 
 Carbon 
 Nitrogen 
 Hydrogen . 
 Oxygen 
 
 as Food. 
 
 21,770-4 grs. 
 
 1,649-0 
 
 8,370 6 
 16,446-7 
 
 In Urine. 
 
 1060-7 
 
 756-6 
 
 213-1 
 
 563-6 
 
 Excreted. 
 
 In Fseces. 
 798-3 
 1420 
 122-0 
 467-8 
 
 By Lungs and Skin. 
 
 19,911-4 
 
 750-4 
 
 3,035 5 
 
 15,415-3 
 
 Total . . 43,236-7 2,594-0 1,530-1 39,112-6 
 
 The quantity of water removed from the body was usually one- 
 fifth or one-sixth more than that taken in, showing that water is 
 really produced in the organism. 
 
 General View of the Anatomical Plan of Secreting Organs. — We 
 have said that the secreting tissues are arranged in such a manner 
 in the body as to have an external anatomical position, so as to be 
 able to set free the secreted product when formed. Some organs of 
 a strictly secreting kind, pour their material directly into the blood. 
 It appears most reasonable to regard the whole lymphatic system as 
 an apparatus of this description, calculated not merely to restore to 
 the circulating current the superfluous or altered plasma, thrown by 
 the capillaries into the interstices of the tissues, but destined by its 
 glandular parts especially to act on the passing fluid, and to pour 
 into it additional secreted matters, which pass by the efl"erent vessels 
 to blend with the general mass of blood. The inner surface of the 
 lymphatic vessels is here the external free surface, to which we refer 
 as that from which the secretion is liberated.* 
 
 Again, there are other organs, viz., the synovial and serous 
 membranes, which are usually and correctly classed as secreting 
 organs. They have been already described (p. 126). The fluid they 
 secrete seems furnished for the purpose of lubricating their surface, 
 so as to facilitate motion. It, consequently, does not leave the sur- 
 face on which it becomes free, but remains in contact with it, and 
 only undergoes the same slow renewal and absorption, as all other 
 solids and fluids with which blood in motion is brought into close 
 contiguity. We have no reason to suppose that the effusions on these 
 surfaces suffer much deterioration by their continued contact. They 
 appear to differ but slightly from the serum of the blood, contain 
 the same saline matters in solution, and in nearly the same propor- 
 tions. The epithelium of these surfaces is no doubt concerned in 
 
 * This view results from Professor Goodsir's anatomical researches, and from con- 
 siderations which hare been ably stated by Dr. Carpenter. — See ante, p. 615. 
 
762 SECEETION. 
 
 furnishing these fluids, but .exerts little catalytic power over the 
 liquor sanguinis, which, consequently, is little altered by being 
 secreted. Mr. Rainey has well pointed out that the epithelium in 
 certain situations is developed in a particular manner upon the pro- 
 jecting folds and fringes of synovial membrane, known as glands of 
 Havers ; and has shown it to be probable that the viscid synovia 
 owes its origin chiefly to the surface of these parts. He has found 
 this disposition not only in the joints, but also in the sheaths of ten- 
 dons, and in the bursas mucosae.* 
 
 But, dismissing these structures, we arrive at that great system 
 of parts, which we have before designated the mucous system, in- 
 cluding, under one common title, the skin, mucous membranes, and 
 true glands ; the term true glands, meaning those which, by a duct, 
 or otherwise, pour their secretion on the external surface, and not 
 into the blood. For a summary account of the tissues forming this 
 order of parts, the note at p. 622 of the present volume should be 
 referred to. The skin, and most of the great regions of the mucous 
 membranes, together with some of the glands, have been already 
 minutely described in difierent parts of the preceding pages ; and it 
 now only remains, before passing to a description, in detail, of the 
 great remaining glands, to ofier some observations on the general 
 plan or scheme of structure, discoverable in these special organs of 
 secretion. 
 
 Between skin, mucous membranes, and glands, there exists every 
 gradation of structure, by which one can be conceived to pass into 
 the other. They are modifications of a common type. The two 
 former are secreting organs, in an expanded form, sometimes pre- 
 senting glandular involutions in their thickness. But, in propor- 
 tion as the glands differ from mere membranes, we find them assum- 
 ing a more solid form, gathered up, as it were, into a more compact 
 mass, in which are to be still recognized all the elements of the simple 
 membrane in their true relative positions — the free surface being 
 still the free surface, though now forming, it may be the lining of 
 ducts, and composing the internal tubular, or follicular recesses of 
 the solid organ — and the deep, or vascular surface preserving the 
 same relation as before to bloodvessels, lymphatics, nerves, or areo- 
 lar tissue, under its various modifications. In particular the epithe- 
 lium, or proper glandular tissue, remains capable by its anatomical 
 position in regard to the external surface, to discharge its product 
 on that surface. Thus the epithelium of the parotid gland, the 
 liver, or the kidney, has such a relation to the remote parts of the 
 excretory ducts of those organs, as that the secretion, resulting from 
 the mutual action of that tissue and the blood, is set free into those 
 channels, which are in reality, continuations of the integument, and 
 therefore, in one sense, portions of the external surface of the body. 
 
 It will be readily seen how close and intimate must be, in all cases, 
 the proximity of the glandular epithelium to the ducts. In fact, in 
 many instances, the epithelium of the ducts is beyond doubt the 
 
 * Proceedings of the Royal Society, May 7, 1846. 
 
STRUCTURE OP GLANDS. 
 
 763 
 
 secreting tissue, and the gland is a congeries of finely divided pas- 
 sages, or ducts, whose epithelium (though in a modified form) is 
 directly continuous with that of the outer surface, on which the 
 duct opens. This, for example, is the case in the sweat glands, 
 in the sebaceous glands, already described (pp. 368,, 369,), and in 
 the kidney. But in other instances, whether owing to the form 
 assumed by the terminal extremities of the duct, or to an actual 
 diflference in the arrangement ■ of the glandular epithelium, the 
 greatest difiiculty exists in determining the exact nature of the 
 anatomical relation of the glandular and ductal epithelium, and of 
 ascertaining whether they are continuous at all times or only at cer- 
 tain periods when the secretion is discharged. For example, in the 
 salivary glands, the pancreas, and some others, the terminal parts 
 of the gland are vesicular, while the ducts are tubular. Vesicular 
 terminations of the ducts may be rendered apparent by mercurial 
 injection ; but it is by no means easy to demonstrate the permanent 
 continuity of the epithelium lining or filling these vesicles with that 
 which lines the ducts. 
 
 It is probable that most or all gland follicles were originally closed 
 vesicles. This has been shown by Dr. Allen Thompson to be the 
 case in the early condition of the gastric glands ; and Henle applies 
 this view to other gland-structures. In his beautiful investigations 
 upon the testicle of Squalus Cornubicus, Professor Goodsir has 
 shown that the primary or mother cells are developed by the growth 
 of isolated nucleated cells attached to the side 
 of the duct. These cells grow and become the 
 future acini, being connected with this duct 
 by a hollow pedicle ; in their interior, second- 
 ary cells, in which the spermatozoa are deve- 
 loped, appear. Still the mother cell is a 
 closed cavity, and separated from the duct by 
 its original wall. At length it gives way 
 at this point and discharges its progeny of 
 cells, containing spermatozoa, into the duct. 
 The follicles then appear to become atrophied. 
 There is another class of gland-structures in 
 which, according to this view, the mother cell 
 remains persistent after it has discharged its 
 first progeny of cells, and continues to pro- 
 duce successive generations of cells ; the deve- 
 lopment of these cells commencing at the 
 caBcal extremity of the follicle. The point at 
 which they originate is looked upon by Pro- 
 fessor Goodsir as the persistent nucleus of 
 the original parent cell; and it is termed by ^A \.:- 
 him, the "germinal centre." Although it is ^rf. >^ 
 scarcely possible to demonstrate the existence 
 of this germinal centre in the gland-follicle, 
 there are many instances in which this view 
 certainly appears to be borne out by the 
 
 Fig. 215. 
 
 Cacal biliary tube of Cray-ish. 
 At a, 6, c, d, e, are siiown cells 
 in different stages as they ad- 
 vance from the lower part to- 
 wards the ontlet. After.Leidy. 
 
764 SECRETION. 
 
 structure of the part when subjected to a careful microscopical ex- 
 amination. In the accompanying drawing of one of the caecal tubes 
 of the liver of the cray-fish {astaeus affinii), after Leidy, the gradual 
 transition from the granular matter at the bottom of the follicle to 
 the perfectly formed cells which are being discharged from its sum- 
 mit is well seen. 
 
 In the glandules of Peyer, already described {ante, p. 581), it 
 would seem that vesicles form underneath, but in immediate con- 
 tiguity with, the mucous membrane, and, becoming filled with glandu- 
 lar contents, having the nature of nuclei, exhibit a great proneness 
 to burst, and liberate their contents, perhaps periodically, on the 
 free surface of the membrane. The ova, too, are very generally 
 elaborated in the first instance in a matrix, or stroma, placed beneath, 
 and not upon, the surface from which they are to be discharged. 
 But notwithstanding these differences, which will be further con- 
 sidered, it must be borne in mind that the gland-cells, or secreting 
 elements, in the true glands, are always so placed as to be able to 
 discharge themselves or their products on the outer surface. 
 
 Of the Crland-Oell. — The gland-cells select and separate from the 
 blood the substances which form their secreted product. These ele- 
 ments form, in fact, in a certain sense, a part of the food or pabulum 
 of these secreting cells, which is set free when the cell has arrived 
 at maturity, either by its rupture or by its complete detachment fPom 
 the surface upon which it has grown, or, as occurs in other instances 
 merely by transudation through its walls upon one side, while new 
 matter is supplied to it from the plasma upon the other. Thus the 
 function of secretion bears a certain analogy to nutrition. The 
 cells in both processes select from the blood certain elements adapted 
 for their growth ; but in secretion, these separate products, after 
 having probably undergone some changes in the cell, are destined 
 soon to be cast off, and no longer form an integral part of the organ- 
 ism ; while, in nutrition, these elements serve to keep up the inte- 
 grity of the structure by which they have been appropriated. It 
 may be remarked that the period of existence of the secreting cell, 
 or the length of its life, varies considerably in different organs. 
 Sometimes a very short time is sufficient for its development, growth 
 and decay, while in other instances, it may persist for a long period 
 of time. Some of the most important modifications of secreting 
 cells will be described under the head of the glands, into the com- 
 position of which they enter. 
 
 Of the Ducts of Grlands. — Ducts are tubular, usually branched 
 passages, forming continuations between the secreting tissue of the 
 glands and the surface of skin, or mucous membrane, on which 
 the secretion is eventually poured. They are a contrivance by 
 which a large mass of secreting tissue, packed in a small solid space, 
 can discharge its product at a given point. They often present 
 dilatations, wherein the secretion may be delayed for a time, and 
 where, in many instances, it may undergo changes ; and they very 
 commonly contain a layer of unstriped muscle in their walls, by 
 whoae agency their contents are propelled in the proper direction, 
 
OF THE DUCTS OF GLANDS. 765 
 
 often against gravity. This contractile tissue is sometimes developed 
 at their orifice into a sphincter muscle. It is only the minuter 
 glands which open directly on a surface {e. g., those of Lieberkiihn 
 or Grew, in the intestinal mucous membrane), which are without a 
 duct. 
 
 The walls of ducts present most internally, an epithelium and 
 basement tissue, continuous with those of the skin or mucous mem- 
 brane. Outside, there are (when present) the muscular coa,t and 
 the areolar tissue, which is prolonged upon their exterior in a 
 modified form. Bloodvessels and nerves ramify upon and within the 
 latter coats. We owe the best description of the anatomy of ducts 
 to Henle. 
 
 The epithelium may vary from the scaly to the columnar or gland- 
 ular variety, and it is sometimes ciliated. The most common is the 
 columnar, particularly in large ducts. In immediate connection with 
 the proper mucous tissue, comes the muscular element, arranged in 
 two sets of fibres, one longitudinal, the other circular, of which the 
 latter can usually be seen to be the more internal. The fibrous ele- 
 ments are commonly nucleated, and resemble those of the muscular 
 coats of bloodvessels ; then follows areolar tissue, forming an outer 
 coat, together with bloodvessels and nerves. The areolar coat gives 
 strength, toughness, and elasticity to the duct ; the bloodvessels serve 
 for its nourishment, and the nerves supply its muscular coat, and 
 endow it with a peculiar sensibility, which, under particular circum- 
 stances of pressure or detention (as in the passage of a biliary or 
 urinary calculus), may rise to the height of the most exquisite pain, 
 reacting fearfully on the whole nervous system. 
 
 The smaller ducts very generally are without muscular parietes, 
 and are reduced to a homogeneous basement membrane, lined with 
 epithelium. Indeed, there is reason to believe that, in some cases, 
 the very smallest consist either of simple epithelium or of mere base- 
 ment tissue. The lobular passages of the lungs are an example of 
 this latter constitution. 
 
 It is not diflScult to prove that the larger ducts are muscular. 
 Take, for example, the ureter. Open a small animal, just killed for 
 the purpose, and this canal will be seen to present occasional peris- 
 taltic contractions, passing rapidly from the kidney to the bladder, 
 which may be easily excited by a mechanical or galvanic irritation, 
 if they do not appear spontaneously. Besides this peristalsis, they 
 undoubtedly undergo, like the bloodvessels, a slow and uniform dila- 
 tation and narrowing, according to the bulk of their contents or 
 other conditions. 
 
 In some of those dilatations of the gland-ducts, which are provided 
 for a temporary reception of the secretion, such as the urinary blad- 
 der and the vesiculse seminales, the muscular coat attains such a 
 thickness as to allow of being readily shown. The muscularity of 
 the coats of the urethra was demonstrated, for the first time, some 
 years ago, by Mr. Hancock. In the gall-bladder, muscle is certainly 
 developed to a far less extent; but even here. Dr. G. H. Meyer 
 states that, by means of a powerful galvanic battery, he has caused 
 
766 SECRETING GLANDS, 
 
 this receptacle in the ox to contract, so as to diminish its capacity 
 one-fourth. The Fallopian tubes, uterus, and vagina, are parts 
 rightly falling under the head of gland-ducts, though wonderfully 
 modified in accordance with the functions they have to perform. 
 The uterus in particular, under the condition of pregnancy, offers 
 an example of the highest development of the involuntary or 
 unstriped muscular fibre-cells anywhere met with. 
 
 We shall now proceed with a description of those glands which 
 have not yet been treated of. Of those pertaining to the alimentary 
 canal, the salivary glands and their secretion (p. 639), and the 
 secretion of the pancreas (p. 592) and the liver (p. 600), have 
 been already spoken of, and the structure only of the two latter 
 remains to be considered. The kidneys and their secretion will fol- 
 low; and we shall defer the consideration of the glands relating to 
 the reproductive function to the chapters devoted to that subject. 
 Such are the ovaries, the testes, the prostate, Cowper's glands, the 
 mamrase. 
 
 The following works may be consulted upon the subject of secretion : Articles, 
 " Secretion" and " Mucous Membrane," in the CyclopEsdia of Anatomy and Physio- 
 logy; "Anatomical and Pathological Observations," Professor Goodsir, 1845; "Lec- 
 tures on Nutrition," Professor Paget ; Medical Gazette, 1847; Principles of Human 
 Physiology," Dr. Carpenter. 
 
 CHAPTER XXXIII. 
 
 SECRETING GLANDS. — OF THE PANCREAS. — OP THE LIVER. — THE LIVER 
 IN INVERTEBRATA. — LOBULES OF THE LIVER. — PORTAL CANALS. — 
 PORTAL VEIN. — HEPATIC ARTERY. — HEPATIC DUCT.^GALL BLADDER. 
 — HEPATIC VEIN. — NERVES AND LYMPHATICS. — LIVER CELLS. — OF 
 THE CONNECTION OF THE SMALLEST DUCTS WITH THE LIVER CELLS. 
 — OF THE PASSAGE OF THE BILE INTO THE DUCTS. — OF THE QUAN- 
 TITY AND USES OF THE BILE. 
 
 Of the Pancreas. — This is a large gland, placed across the spine, 
 behind the stomach, in physiological relation with the duodenum or 
 the first portion of the intestine. It is flattened from before back- 
 wards. Its left extremity, or tail, tapers off towards the spleen ; its 
 right extremity, or head, is much larger, lying close within the curve 
 of the duodenum, and presenting a recurved extremity following the 
 lower portion of that intestine, and sometimes termed the lesser pan- 
 creas.' The ordinary weight of the pancreas, according to Cruveil- 
 hier, is from 2 to 2\ ounces, but may rise to 6 ounces. Its colour 
 is gray, inclining to pink. 
 
 The pancreas, like the salivary glands, is imbedded in areolar 
 tissue, and receives its blood from several neighbouring vessels. Its 
 arteries are derived from the splenic and hepatic branches of the 
 
LIVER. 767 
 
 •coeliac axis, and from the superior mesenteric. The blood is re- 
 turned by the corresponding veins into the vena porta. Its nerves 
 come from the solar plexus. 
 
 In structure, the pancreas appears to resemble the salivary glands. 
 It is subdivided into lobules separated by septa of areolar tissue, which 
 dip inwards from that which forms a common envelop to the whole 
 gland. The lobules are subdivided into smaller parts by similar, 
 but less complete and more delicate inflections of the areolar tissue ; 
 and these minute ultimate granulations or acini of the gland, corre- 
 spond to the terminal extremities of the common duct. The excre- 
 tory duct is concealed within the substance of the gland, and takes 
 a course from the left to the right extremity, receiving very nume- 
 rous tributaries on its way, and thus increasing in size, till it joins 
 the common bile duct, close to its entrance into the duodenum. At 
 its termination it is as large as a crow-quill. Its coats are thin and 
 extensible, its internal surface smooth. It frequently happens that 
 the duct belonging to the lower end of the curved portion or lesser pan- 
 creas opens separately into the intestine. In the rabbit the pancreatic 
 duct opens by a separate orifice, sixteen or seventeen inches lower 
 down the intestine than the bile duct (p. 595), 
 
 It is not diflBcult to inject the duct, and through it the ultimate 
 secreting structure of the pancreas, with mercury. This may be 
 best done in some of the smaller mammalia, where the glandular 
 tissue is disseminated in lamellated grains between the layers of the 
 mesentery, and where consequently the ramifications of the duct are 
 naturally spread out towards the ultimate acini. The metal easily 
 penetrates to these parts, and appears in the form of clusters of 
 minute globules, having an average diameter of 5^5 of an inch. 
 These indicate, with probable truth, the terminal vesicles in which 
 the duct ends, and which are lined with the epithelium, or true 
 secreting tissue, continuous with that of the duct. 
 
 The vesicular terminations lie in the meshes of the capillary net- 
 work, as is the case with the follicles of the salivary, and other con- 
 glomerate glands. 
 
 The secreting cells are more or less spheroidal in form, and vary 
 somewhat in character according to their age. The mature cells are 
 about the j-g^-^ of an inch in diameter, and are opaque, in conse- 
 quence of being filled with numerous minute oil globules. The young 
 cells are smaller than these, and are not so opaque. 
 
 The epithelium in the large ducts is of the columnar variety. 
 The wall of the duct appears to be composed of fibrous tissue, in 
 which elongated nuclei make their appearance upon the addition of 
 acetic acid. The secretion of the pancreas has been described in 
 Chapter XXV., p. 593. 
 
 Liver. — The liver is a large solid glandular organ, of firm consist- 
 ence, of a dark reddish-brown colour. It measures about twelve 
 inches from side to side, and six or seven inches from its anterior to 
 its posterior border. According to the observations of Krause, the 
 bulk of the liver corresponds to about eighty-eight cubic inches ; its 
 weight is between three and four pounds, and in the adult usually 
 
768 LIVER. 
 
 amounts to about l-36th of the weight of the whole body ; but in the 
 foetus it is comparatively much larger. The female liver weighs 
 somewhat less than that of the male. The specific gravity of the 
 liver is about I'Oo in health. • 
 
 The following is an analysis by Prof. Beale of a liver, presumed 
 to be healthy. The organ was taken from the body of a man thirty^ 
 one years of age, who was killed by falling from a second-floor 
 window, while in the enjoyment of perfect health. 
 
 Per 100 of 
 Solid Matter. 
 
 Water 68 58 
 
 Solid matter 31-42 
 
 Fatty matter 3-82 12-16 
 
 Albumen 4-67 14-86 
 
 Extraotiye matter 5 40 17 18 
 
 Alkaline aalts 1-17 3-72 
 
 Vessels, etc., insoluble in water . . . 16-03 6101 
 
 Earthy salts -33 1-05 
 
 , 100-00 
 
 In disease, the proportion of these constituents is liable to very 
 great variation. In fatty degeneration, an enormous amount of fatty 
 matter may accumulate in the organ. In one remarkable case, ana- 
 lyzed by Dr. Beale, the liver contained 75.07 per cent, of solid 
 matter, and of this 65.19 consisted of fatty matter.* In scrofulous 
 degeneration of the liver the albuminous materials and the water are 
 increased, while the fatty matter is diminished in quantity. 
 
 The liver is situated in the right hypochondrium, and reaches over 
 to the left, being thick and indented behind where it crosses the pro- 
 jecting bodies of the vertebrae, convex on its upper surface where it 
 lies in the hollow of the diaphragm, and concave below where it rests 
 against the stomach, colon, and right kidney. It is covered to a 
 great extent by the peritoneum, the reflexions of which on to neigh- 
 bouring parts, serve as ligaments to bind it in place, as well as to 
 allow of the entrance and exit of the nerves and vessels, some of the 
 latter being sufficiently large and strong to aid materially in the 
 mechanical support of the organ. 
 
 The liver is an unsymmetrical organ. In the foetus, it is situated 
 more equally on each side of the median line of the trunk ; but in the 
 adult the right side enormously preponderates, by the wasting or want 
 of development of the left. It is still, however, divisible into a right 
 and left lobe by the broad peritoneal ligament above, and by the 
 longitudinal fissure beneath, both of these commencing in front by a 
 notch in the border, across which passes, between the layers of the 
 broad ligament, the cord-like remnant of the umbilical vein, and both 
 tending towards the notch in the posterior border which lodges the 
 vena cava ; these divisions, however, are both of them on the surface 
 only, and are rather vestiges of the imperfect conditions of foetal ex- 
 istence than of value in the study of the physiological anatomy of 
 the gland. 
 
 • Diseases of the Liver. Dr. Budd. Second edition, 1852. 
 
LOBULES OF THE LIVER. 
 
 769 
 
 Fig. 216. 
 
 On the under surface of the liver, is observed a groove passing off 
 from the longitudinal fissure, transversely,, for a certain distance, on. 
 the surface of the right lobe, and lodging the biliary ducts, the sinus 
 of the vena porta, the hepatic artery, with lymphatics and nerves, 
 all enveloped in ateolar tissue, called the capsule of Glisson, and 
 brought to this transverse fissure between the layers of the gastro- 
 hepatic omentum. From this groove, there extends throughout the 
 substance of the organ a series of tubular passages, so numerously 
 ramified and uniformly distributed, that no part whatever of the he- 
 patic substance is at a greater distance from them than about the 
 thirtieth of an inch. These are called the portal canals (fig. 216), 
 so named by Mr. Kiernan, because they lodge the branches of the 
 portal vein, from which the plexus of capillaries surrounding the 
 biliary-cells takes origin. The portal canals also lodge the bile- 
 ducts, which are thus conducted to that aspect of the mass of bile- 
 cells, where the capillary plexus commences. The same canals also 
 convey the hepatic ■ artery with the lymphatics and nerves of the 
 liver. 
 
 On the posterior border of the liver already referred to, is a deep 
 groove placed obliquely, the fissure for the inferior vena cava; from 
 this there penetrate the substance of the 
 organ, another series of ramified tubular 
 passages, which are completely occupied 
 by a nearly corresponding number of 
 branches of the hepatic veins, or venae 
 cavce hepatiece, which open into the vena 
 cava. These canals, called by the same 
 distinguished anatomist, hepatic venous 
 canals, are so distributed throughout the 
 organ that some part of them comes within 
 .g'j of an inch of every portion of its sub- 
 stance, and they are intermediate to the 
 ramifications of the portal vein. The 
 bases of the lobules adhere to these veins, 
 and when they are cut across they do not 
 collapse. The hepatic veins occupying 
 these canals, throughout the organ, re- 
 ceive the blood of the portal vein after it 
 has traversed the plexus of capillaries 
 which envelops the series of biliary-cells. ' 
 
 This plexus of capillaries we therefore term the portal-hepatic plexus. 
 It is a plexus containing venous blood, from which the bile-cells 
 derive the materials which they secrete. The space which the blood 
 passes over in traversing this plexus, in contiguity to the cells, is 
 measured by the distance between the ramified portal surface and 
 the ramified hepatic venous surface of the liver. The series of bile- 
 cells discharge the bile into the biliary ducts on the portal side of 
 the plexus, i.e., where the blood is entering it, and their most remote 
 parts commence on the hepatic venous side of it, i. e., where the 
 
 A transverse section of a small por- 
 tal canal and its vessels, after Kier- 
 nan. 4. Portal vein. 2. Interlobular 
 branches. 5. Branches of the vein, 
 also giving off interlobular branches, 
 termed by Mr. Kiernan, vaginal 
 branches. 7. Hepatic duct. 6. He- 
 patic artery. 
 
770 
 
 LIVER. 
 
 blood is leaving it, so that the blood circulates in the reverse direc- 
 tion to that in which the bile must flow. 
 
 Fig. 217. 
 
 Human liver in -which the portal Tein (cZJ had been injected white, the artery (e) red, and the 
 hepatic vein (c) lake ; from the surface. Magnified 15 diameters. The capillary plexus is only shown 
 in a few places, a. Portion of portal hepatic plexus. 6. Portal hepatic plexus receiving at its portal 
 surface small branches from the artery, c. Branches of the hepatio vein, interdigitating with the 
 portal canals, d. Branches of the portal vein. «. One of the branches of the artery; some of its 
 branches are seen ramifying upon the coats of the portal vein, and a few join the capillary plexus 6. 
 Dr. Beale. 
 
 The Liver in Tnvertebrata. — The liver is one of the moat constant glandular organs, 
 being met with, in some form, in all animals provided with a digestive cavity. In the 
 polyps, the liver is represented by some coloured cells round the stomach. In many 
 of the annelidn, clusters of biliary cells are seen surrounding the csecal prolongations of 
 the digestive cavity. In the Eolis (one of the nudibranchiate gasteropodous moUusks) 
 a somewhat similar arrangement is observed, the follicles of the alimentary tube being 
 prolonged into the papillse, covering the dorsal surface of the animal. In most other 
 molluska, however, the liver exists as a distinct organ, and is composed of branched 
 follicles, arranged round terminal ducts. The follicles contain coloured cells, in which 
 oil globules are often present in considerable number. In many of the Crustacea, the 
 liver is detached from the intestinal walls, and consists of numerous large oseoa (fig. 
 215), which pour their contents into small ducts, although in others it seems to consist 
 simply of cells arranged in follicles, which are connected with the intestine, as in the 
 lowest classes. In insects, the hepatic organ takes the form of simple or branched 
 tubes, from two to six in number, which open into the intestine. According to our 
 observations, the cells do not appear to be arranged round the tube, so as to leave a 
 distinct central channel, as in the urinifcrous tubule, but lie within the basement 
 membrane, without order or regularity, often completely filling the tube, and not un- 
 frequently, from their large size, causing it to bulge. We shall presently see that a 
 
LOBULES OF THE LIVEH. 
 
 771 
 
 Fig. 218. 
 
 very similar arrangement exists in the tubular network of basement membrane, Trhioh 
 contains the liver-cells in vertebrate animals. 
 
 Throughout the whole animal series, the liver consists essentially of cells containing 
 colouring matter, and usually oil globules, which lie within a tube or follicle of base- 
 ment membrane, continuous with the alimentary canal. 
 
 Having premised these general points, we shall now proceed to 
 consider the anatomy of the liver more in detail. 
 
 Lobules of the Liver. — The terminal twigs of the portal veins and 
 the commencing radicles of the hepatic vein, thus distributfed through 
 the liver with a definite thickness of capillary plexus with nucleated 
 bile-cells interposed, are further arranged in 
 such a manner as that the intervening mass 
 is gathered, not into a folded sheet,* but into 
 a great number of small portions, termed 
 lobules. These lobules are apparent to the 
 eye in many animals ; but in the pig they are 
 each of them invested by a separate and 
 distinct membranous envelope or capsule, 
 which is composed of delicate fibrous tissue 
 (fig. 218). In this animal, each lobule may 
 be regarded as an isolated and separate liver, 
 and the whole gland as an agglomeration of 
 smaller ones, connected by the penultimate 
 branches of the portal vein, artery and duct, which run between the 
 
 Fig. 218. 
 
 fe* 
 
 Portion of fibrous capsule of 
 a lobule of the pig's liver, show- 
 ing arrangement of the fibres — 
 215 diameters. 
 
 Lobules of a cat's liver partially injected through the portal vein, and also through the hepatic 
 vein a Twigs of portal vein. 6. Capillaries springing from them, which serve to mark the outline 
 of the lobules, d. Capillaries in the centre of the lobules injected from the hepatic vein. e. Situa- 
 tions at which the injection forced into the two vessels has met. I. Central parts of lobule not 
 njected. 
 
772 
 
 LIVER. 
 
 lobules, and by the areolar tissue which accompanies them ; but not 
 by any inosculation or coalescence of the ultimate secreting elements, 
 the liver-cells, or the capillaries. In other animals, and in the human 
 subject, the lobules are not thus isolated, but are only imperfectly 
 marked out by the several points of their exterior, to which the ul- 
 timate twigs of the portal vein and duct arrive. The twigs of the 
 vein terminate in a plexus of capillaries common to all the conti- 
 guous lobules, and continuous between them, so that the lobules them- 
 selves have no definite limit (fig. 219), but blend with each other, 
 except at certain points of their exterior. It is not likely that these 
 diflFerences in the isolation of the lobules in various animals are of 
 any physiological importance, but they have, probably, given rise to 
 much of the difference of opinion which exists among anatomists on 
 this subject. 
 
 The shape of the lobules, whether completely defined by an invest- 
 ment of fibrous tissue, or merely mapped out by the position of 
 the several twigs of the portal vein, hepatic artery, and duct, may 
 be said to be determined by the mode of distribution of these vessels. 
 The intralobular hepatic vein occupies the central axis of the lobules, 
 and usually consists of a stem, into which three to five, or even more, 
 subordinate twigs empty the blood derived from the capillary plexus. 
 The lobule is elongated on this vein, and presents a process for each 
 of the subordinate twigs. • 
 
 In all cases, the terminal branches 
 of the portal vein and the duct 
 arrive at the surface of the lobule 
 at several points ; and the surface 
 of the lobule, whether complete or 
 incomplete, is continuous with that 
 of the portal canals. From this 
 surface, in all cases, the capillary 
 plexus tends, by the slight elonga- 
 tion of its close meshes, and con- 
 verges towards the intralobular 
 hepatic vein in the axis of the 
 lobule. It probably follows that, 
 in this latter situation, the blood, 
 after having been nearly deprived 
 of those constituents from which 
 the bile is formed, circulates more 
 rapidly than at the more external 
 parts of the lobule, whither it has 
 just been brought by the portal 
 veins, richly charged with these 
 constituents. 
 
 Portal Canals. — It has been 
 already observed that the portal 
 canals contain a branch of the 
 portal vein, with a branch of the 
 hepatic artery and of the biliary 
 
 Fig. 220. 
 
 Longitudinal section of a small portal vein 
 and canal, after Kieroau, a. Portions of the 
 canal from which the vein has hoen removed. 
 6. Side of the portal vein in contact with the 
 canal, c. The side of the vein which is sepa- 
 rated from the canal by the hepatic artery and 
 duct, with areolar tissue (Olissun's capsu*le}. 
 rf. Internal surface of the portal vein, throttffn 
 which is seen the outline of the lohules and the 
 openings of tho interlobular veins. /. Vaginal 
 veins of Klernan. g. Hepatic artery, li. He- 
 patic duct. 
 
POETAL VEIN. 
 
 773 
 
 duct; not uEfrequentJy the vein is accompanied by two branches of 
 the artery and duct. 
 
 The branches of the artery and duct are connected with those of 
 the portal vein by areolar tissue, which is abundant in the transverse 
 fissure of the liver, and in the larger portal canals, but in the smaller 
 exists chiefly on that side of the vein where the artery and duct lie ; 
 while, as the vessels diminish in size, the amount of this areolar tis- 
 sue becomes less until it entirely ceases, where the small branches 
 ■which supply the lobules are given off. This investment of areolar 
 tissue, described under the name of Glisson's capsule, from its dis- 
 
 Fig. 221. 
 
 s^5^' 
 
 A smaU lobule from tlie pig's liver, showing a, the interlobular branches of the portal Tsin, and b, 
 a portion of the lobular capillary network within the capsule injected. Each branch is seen to give 
 off small branches on either side to the adjacent lobules. After Dr. Beale. 
 
 coverer, has been stated, by many subsequent writers, to be prolonged 
 into every part of the gland, separating the lobules from each other, 
 and forming an investment for each — a description which we have 
 failed to verify in every mammalian animal which we have examined 
 except the pig, where this areolar tissue is really prolonged between 
 the lobules. 
 
 Portal Vein. — The large portal vein is formed by the union of the 
 veins of the stomach and intestines, the pancreatic and splenic veins, 
 and the veins of the mesentery, omentum, and gall-bladder. The 
 portal circulation has been described in p. 676, and we have, there- 
 fore, only to describe the distribution of the vein in the liver. The 
 branches of the portal vein may be said, in general terms, to be 
 arranged round the lobules; but the branches upon different sides 
 do not anastomose so as to encircle each lobule with a venous ring, 
 as many authors, following Kiernan's diagram, have described and 
 represented, but communicate with each other only through the inter- 
 vention of capillaries. Even in the pig there is no vascular ring, 
 50 
 
77 i LIVER. 
 
 although to the naked eye it might appear so. In the liver of the 
 human subject, and in livers allied to it, small branches of the portal 
 vein can often be traced from the interlobular fissures into the lobule, 
 breaking up into capillaries as they go. The arrangement of the 
 branches of the portal vein round one of the smallest lobules of the 
 pig's liver, with a few of the lobular capillaries injected, is shown in 
 fig. 221. 
 
 Hepatic Artery. — Many branches of the artery pass to the cap- 
 sule of the liver, in which they ramify abundantly, forming a net- 
 work, having large meshes. These capsular branches and their 
 anastomoses, are readily injected in the liver of the foetus or child. 
 
 The artery gives off numerous branches in the portal canals. The 
 greater number of these are distributed upon the coats of the ducts. 
 The thick walls of the larger ducts are abundantly supplied with 
 arterial blood ; but the smaller branches of the duct, the coats of 
 which are extremfely delicate, pass through the meshes of an arterial 
 network. In the pig, this network may be demonstrated upon the 
 surface of each lobule (fig. 222), but in the human subject, the 
 branches are less numerous, and are seen only in the interlobular 
 fissures ; other branches supply the coats of the portal and hepatic 
 veins. The greater quantity of blood, after passing through these 
 small arteries, is collected by venous radicles, which empty them- 
 selves into the branches of the portal vein. A few very small' arte- 
 rial branches may be traced from the portal aspect of the lobule for 
 a short distance into its interior, where they join the portal hepatic 
 
 Fig. 222. 
 
 a. Part of arterial ring, with branches ramifying upon the capsules of the lobnles of the pig's liver. 
 b. Arterial -network, e. Portion of lobular capillary network injected from the artery, and small 
 branches of the latter entering it. After Dr. Beale. 
 
 plexus of capillaries. The whole of the arterial blood, therefore, 
 which supplies nutriment to the several structures of the liver, passes 
 through the capillaries of the lobule before it is returned to the heart, 
 and no doubt furnishes a small portion of the matters from which 
 
DUCT. 
 
 775 
 
 the bile is formed. The artery was rightly regarded by Kiernan as 
 one of the sources of the blood conveyed to the secreting structure 
 of the liver, by the branches of the portal vein. 
 
 Fig. 223. 
 
 A small lobule, showing the duct branching upon the capsule, from the pig. The sacculi of the 
 ducts are injected in this specimen. The vessel accompanying the duct is a branch of the portal 
 vein. 
 
 The gall-bladder is also supplied largely with arterial blood. The 
 arteries are arranged so as to form a beautiful network. Each 
 branch of the artery is accompanied by two branches of the vein, 
 one on either side, and when the arterial and venous networks are 
 injected with different colours a most beautiful appearance is pro- 
 duced. A similar disposition of arteries and veins occurs in the 
 transverse fissure, and also in the large portal canals. This arrange- 
 ment has probably the effect of insuring free circulation through 
 the veins in those changes of size and position to which the vessels 
 are liable. 
 
 Duet. — At least one branch of the duct accompanies each branch 
 of the portal vein, but frequently there are two or three. From the 
 branch or branches accompanying the vein, several smaller ones 
 pass off to the secreting structure. In the pig, the interlobular 
 ducts, while running between contiguous lobules, are applied, as it 
 were, to the exterior of their capsules, and give off much smaller 
 twigs on either side, which perforate the capsules, and become con- 
 nected with the cells in the manner presently to be described. 
 
 Parietal Saeeuli and Appendages of the Duets. — In ducts of 
 about the ^35 of an inch in diameter, and larger, there are many 
 little saccular dilatations situated in the coats. These are the so- 
 called glands of the ducts, and in the pig, and most other animals 
 which we have examined, are arranged all round the tube. Dr. 
 
776 LIVER. 
 
 Beale, who has examined them with great care, describes them as, 
 for the most part, simple oval pouches connected with the cavity of 
 the duct by a very narrow neck, often not the 55*55 of an inch in 
 diameter. In the larger ducts, they are branched, and often run for 
 some distance in the coats. Occasionally, the branches of one 
 gland anastomose with those of another. The largest are singularly 
 complicated, and project some distance from the duct lying in the 
 areolar tissue which surrounds it. Fig. 224. 
 
 In the human subject, a different arrangement occurs. Instead of 
 being situated entirely round the tube, the openings form two rows 
 or lines situated upon opposite sides of the ducts. The greater 
 number of these openings are, however, the orifices, not of sacculi, 
 but of small irregular tubes, which run obliquely for some distance 
 
 Fig. 224. 
 
 a. Portion of a large duct-of the pig, injected with vermilion, showing the laxge cavities or glands 
 in the coats of the ducts. The largest and most complicated are represented at c, j ust at the point 
 where a smaller branch is coming off from the tmnk of the dact. b. A small branch without glands. 
 Magnified about ten difimeters. Prom a drawing by Dr. Beale. 
 
 in the coats of the duct and anastomose ; some of these branches 
 leave the ducts anastomose with each other just outside the trunk 
 from which they are given off. 
 
 Many of the small ducts about the 5'^ of an inch in diameter, have 
 numerous csecal pouches connected with them, arranged pretty close 
 together, gradually becoming shorter as the duct becomes smaller, 
 and giving off branches composed of basement membrane only. 
 These irregular ducts with csecal pouches are very numerous in the 
 transverse fissure of the liver, where they form an intricate network 
 connected with the larger branches of the duct in this situation. 
 These were described by Theile as branching mucous glands, but were 
 first noticed and named vasa aberrantia by Weber, who also de- 
 scribed the anastomosis between the right and left hepatic ducts 
 in the transverse fissure, by the intervention of these irregular 
 branches. 
 
 In the portal canals, the vasa aberrantia occur as already men- 
 tioned, but in diminished number. Dr. Beale considers these cavi- 
 
GALL-BLADDER. 777 
 
 ties, or irregular branches, (ionnected with the ducts, as little reser- 
 voirs in which the bile in ducts with thick coats is brought into 
 closer proximity with the numerous vessels surrounding them, by 
 which means it loses some of its water, and probably undergoes 
 other changes. He observe^, that the arrangement of the vessels 
 around these ducts, both in the transverse fissure of the liver and 
 in the portal canals, is similar to that which exists in the coats of 
 the gall-bladder. A small cavity with a narrow neck seems scarcely 
 adapted for pouring out viscid mucus ; moreover, the bile of animals, 
 in which these so-called gliands are very few in number, as in the 
 rabbit, seems to contain as much mucus as that of the pig, in which 
 animal the glands are very numerous and well developed. Accord- 
 ing to this view of their office, these cavities may be regarded in the 
 light of little gall-bladders. 
 
 The coats of the larger ducts appear to be principally composed of 
 condensed fibrous tissue, but there is reason for supposing that, at 
 least in some of them, there are a few muscular fibre cells, although 
 they do not form a distinct layer or muscular coat. 
 
 The epithelium- of the larger ducts is of the columnar variety. 
 The cells are large and well formed, often exhibiting a distinct nu- 
 cleus. They are frequently tinged with yellow colouring matter, 
 and often contain yellow granules. In the smaller ducts, this epi- 
 thelium becomes shorter, until, in the smallest branches, it approaches 
 more nearly to the tesselated variety. 
 
 Gall-Bladder. — The gall-bladder may be looked upon as a diver- 
 ticulum of the hepatic duct. It lies in a fossa underneath the liver. 
 It is of a. pear shape, and its fundus is directed downwards and for- 
 wards ; it terminates in the cystie duct, which is about an inch in 
 length. The hepatic duct, leaving the liver by the transverse fissure, 
 passes downwards, and soon joins the cystic duct at an acute angle, 
 to form the ductus communis choledochus, which is about three inches 
 in length, and lies between the layers of the gastro-hepatic omentum. 
 After coming into close proximity with the pancreatic duct, the com- 
 mon duct enters the coats of the intestine with the latter, and passes 
 obliquely between them for three-quarters of an inch. The ducts 
 open by an orifice common to both at the junction of the, descend- 
 ing and transverse portions of the duodenum. The mucous mem- 
 brane of the gall-bladder is thrown into reticulated folds, which form 
 the boundaries of numerous polygonal depressions, so that upon its 
 internal surface it presents a honeycombed appearance. It is highly 
 vascular, and is covered with columnar epithelium. The folds are 
 prolonged into the cystic duct, where they are arranged in a cres- 
 Centic manner, their general direction being that of a spiral, and they 
 have been compared to a spiral valve. The peculiar arrangement of 
 the vessels of the gall-bladder has been already referred to. The 
 cystic artery is derived from the right division of the hepatic, and 
 the veins empty themselves into the vena portse. The lymphatics 
 are very numerous. The greater part of the thickness of the walls 
 of the gall-bladder is composed of fibrous tissue, but there also exists 
 a thin layer of delicate muscular fibre cells, which take partly a 
 
778 
 
 LIVER. 
 
 longitudinal and partly a transverse direction. The human gall- 
 bladder is capable of containing about an ounce of fluid, but it un- 
 dergoes great alterations in volume, and in it the bile becomes in- 
 spissated, and probably undergoes other changes. 
 
 This viscus is absent in many genera of fishes ; in pigeons, toucans, and some 
 other birds ; in the elephant, stag, horse, and tapir ; but it is present in the ox, sheep, 
 and antelope. It is always found amongst reptiles. The reason of its absence in 
 the animals above alluded to is not yet satisfactorily explained. 
 
 Hepatic Vein. — The branches of the hepatic vein run in channels, 
 ■which are situated between the portal canals (fig. 217), and in con- 
 sequence of the small quantity of areolar tissue surrounding the 
 hepatic vein, the bases of the adjacent lobules are in contact with 
 it, so that when a branch of the hepatic vein is cut across, it does 
 not collapse, but remains open. The small twigs which collect the 
 blood from the lobules surrounding the trunk of the vein open at 
 once into it, except in the case of the largest branches, where the 
 coats are very thick. This arrangement is shown in fig. 225, after 
 
 Mr. Kiernan. In this draw- 
 Fig. 225. ing the openings of the small 
 branches of the hepatic vein 
 (intralobular vein) are seen in 
 the centre of each lobule, while 
 in fig. 220, which represents a 
 portal vein laid open, the orifices 
 of the smallest branches are 
 seen in the spaces between two 
 lobules (interlobular veins). 
 
 The capillaries in the central 
 part of the lobule open into the 
 small twig of the hepatic vein 
 upon all sides. These points 
 are well seen in the pig's liver, 
 where the lobules are distinct, 
 but in the human and other 
 livers, the arrangement varies 
 slightly in consequence of the 
 lobules communicating with each 
 other in the intervals between 
 the interlobular fissures (fig. 
 217). 
 
 Nerves and Lymphatics. — 
 The nerves of the liver are 
 derived chiefly from the sympa- 
 thetic, but a few branches of 
 the vagus are also distributed to 
 the organ. They consist of tubular and gelatinous nerve fibres, and 
 are distributed principally upon the walls of the artery over which 
 they form a network. 
 Branches may be traced into Glisson's capsule, and to the coats of 
 
 Longitudinal eection of an hepatic vein. a. Por- 
 tion of the canal from which the vein has been 
 removed. 6. Orifices of ultimate twigs of the vein 
 (intralobnlar) situated in the centre of the lobules, 
 after Kiernan, Compare the arrangement of the 
 small veins in this figure with the branches of the 
 portal vein in fig. 220. 
 
LIVIiR CELLS. 
 
 779 
 
 the gall-bladder and larger ducts, as well as to the coats of the larger 
 branches of the hepatic vein. 
 
 The lymphatics are found in considerable abundance in the liver ; 
 they are distributed to the gall-bladder, and form a network upon 
 the surface of the organ underneath the peritoneum. An abundant 
 network of lymphatics exists in the largest portal canals, and when 
 the ducts are injected, it not unfrequently happens that a small 
 branch bursts, and the injection escapes into the lymphatics. In this 
 way, some lymphatic glands near the liver are often injected, and 
 the injection sometimes even reaches the thoracic duct, as occurred 
 to Mr. Kiernan, and also to Dr. Beale. 
 
 Of the Liver Cells. — From what has been already stated, with 
 regard to the arrangement of the solid capillary venous plexus of the 
 lobules, it will be inferred that the cells occupy the meshes of this 
 network. It has long been a question whether the cells lie amongst 
 these capillary vessels, or are enclosed in a basement membrane, as 
 we should expect from the analogy of other glandular organs. It has 
 
 Fig. 226. 
 
 Section of horse's liver, at riglit angles to branches of the hepatic vein, showing the cells forming 
 lines radiating from the centre towards the circumference of the lobules. From a preparation of Dr. 
 Beale's. 
 
 been admitted by all who have examined the liver carefully, that in 
 sections made in a particular direction, the cells are seen to form 
 lines which radiate from the centre towards the circumference of the 
 lobule; these lines being connected with oblique or transverse 
 branches. Such an appearance is not presented in every section, but 
 only in those made exactly at right angles with the small twig of the 
 hepatic vein. This is well seen in fig. 226. The cells are described 
 by Kdlliker and others, as being placed end to end, forming solid 
 cylinders, but not invested with basement membrane. Usually there 
 is only room for one row of cells ; but in some situations, two or three 
 
780 LIVER. 
 
 may be seen between two capillary vessels. Dr. Handfield Jones 
 has been led by his researches to adopt the same conclusion with re- 
 gard to the arrangement of the liver cells, and Dr. Carpenter has 
 expressed himself in favour of a similar view. 
 
 On the other hand, Retzius, Leidy, and some other observers, ad- 
 vocate the presence of a tubular basement membrane, in which the 
 cells lie, and which is continuous with the hepatic ducts. 
 
 The minute anatomy of the liver has lately been subjected to a 
 careful investigation by our friend and former pupil. Dr. Beale; and 
 we believe he has established the existence of this basement mem- 
 brane by several diiferent methods of preparation. His observations 
 have been made upon injected as well as uninjected preparations. 
 The membrane is so exceedingly delicate, that it can be demon- 
 strated alone by the granular matter which adheres to it. Dr. Beale 
 has succeeded in injecting the tubular network in which the cells 
 lie ; and the injection has been seen to pass round the cells, sepa- 
 rating them slightly from each other. When the cells are broken 
 down by the action of chemical reagents, the outline of the tube can 
 often be seen distinctly. This delicate basement membrane in most 
 situations appears to be incorporated with the walls of the capillaries, 
 but in some places it is to be demonstrated distinct from them. 
 
 Not unfrequently cells are met with in the fluid surrounding a 
 section of liver with shreds of membrane attached to them ; and dn a 
 few rare instances this membrane may be seen in the form of a tube, 
 in which the cell is evidently contained. Injection, however, afifords 
 the most satisfactory proof of the existence of this basement mem- 
 brane. In well-injected specimens the outline of the tube in which 
 
 Fig. 227. 
 a. 
 
 
 ^■■"\ 
 
 Portion of tubular network of basement membrane in ■which the liver cells lie, o. from an injected 
 apecimen— the shaded portions show the position of the injection. 6, Cells and fi-ee oil globules lying 
 ■within the tube. c. Specimen in which the cells have been disintegrated. From the pig ; 215 dia- 
 meters. After Dr. Beale, 
 
OF THE SMALLEST DUCTS. 781 
 
 the cells are contained can be seen in some parts of the lobule, sepa- 
 rated from that of the capillary vessels. * 
 
 The liver cells may be broken down in some specimens, and the 
 tubular membrane contain only granular matter suspended in fluid, 
 as represented in fig. 227 c. 
 
 The peculiar and characteristic (jells of which the substance of 
 the liver is chiefly composed, are of a more or less spheroidal form, 
 but often somewhat flattened and many-sided from mutual com- 
 pression. 
 
 They vary from the j-^-^-^ to the j^'jj^ of an inch in diameter, and 
 sometimes even smaller. Their surface is smooth, and their outline 
 distinct and well defined. Each contains a distinct nucleus in the 
 interior, and occasionally cells may be observed with two nuclei. In 
 the nucleus a highly refra/cting nucleolus, with several granules, can 
 nsually be distinguished. 
 
 The contents of the cell appear to be of a firm viscid consistence, 
 so that when pressed between glass, the contents do not escape sud- 
 denly, but the whole cell becomes flattened. Usually there are, in 
 the interior, several oil globules, which, as regards size and number, 
 are subject to great variations. In some cells the entire cavity is 
 occupied by globules, in others not one can be observed ; besides oil 
 globules, distinguished by their light centre and dark well-defined 
 outline, the cell contains in its interior numerous amorphous granules, 
 which may vary in size from a scarcely visible dot, to a particle as 
 large as a blood globule, or even larger. Granules of a bright yellow 
 colour, composed of biliary colouring matter, are often met with, but 
 do not occur constantly. In cases of jaundice from obstruction of 
 the duct, the number and size of these coloured particles often in- 
 crease to an enormous extent, so that the cell appears to be entirely 
 occupied with them, and in extreme cases no distinct cells whatever 
 can be detected. 
 
 In highly fed animals, and in that condition termed fatty degene- 
 ration of. the liver, so common in cases of phthisis, the cells seem 
 almost entirely occupied by large oil globules, without any coloured 
 particles. The cells at the portal aspect of the lobule usually con- 
 tain most oil, while those in the centre contain a greater number of 
 coloured granules, but frequently these yellow granules are present 
 in the cells in both situations. 
 
 In dilute caustic sodaj or potash, the cells swell up and become 
 pale, and of a more rounded form ; after a short time they are dis- 
 solved, unless the solution is very weak. Acetic acid produces a 
 somewhat similar change, but the cell membrane does not appear to 
 be dissolved. The nuclei always appear more distinctly defined after 
 the addition of the acid ; cells which, at first, were found to contain 
 no coloured granules, by being soaked for some time in dilute acetic 
 acid exhibited many. 
 
 Of the smallest Branches of the Hepatic Duct and of their Con- 
 nection with the Sepatie Qells. — Of the manner in which the ducts 
 
 * These specimens were prepared by injectiDg the ducts with Prussian blue, and 
 the portal vessels with plain size. 
 
782 LIVBR. 
 
 commence in the liver, there has been much difference of opinion, 
 
 and the most conflicting views have 
 ^'g- 228. been entertained. Mr. Kiernan 
 
 considered that the ducts com- 
 menced in a lobular plexus although 
 he was never able to prove the ex- 
 istence of such an arrangement. 
 Kplliker gives a diagram to illus- 
 trate his view, which supposes that 
 the open ends of the ducts impinge 
 against the columns of the hepatic 
 cells at the margin of the lobule. 
 ^ . , .. , • . , V , J . -.i. Dr. Handfield Jones traces the 
 
 TermiHal portion of interloDular duct, with • i i 
 
 epithelium within it. Pour hepatic cells to duCtS tO the SamO pOlUt, wherC, he 
 show relative size. To illustrate Br. Handfield it .i , . f -^t j 
 
 Jones' view. believes, they terminate without 
 
 having any direct communication 
 with the hepatic cells ; and he considers that the small cells in these 
 ducts are alone concerned in the secretion of the bile (fig. 228). If 
 this view of the anatomy of the liver be correct, this large organ 
 must be nearly related to the vascular glands.* 
 
 Dr. Beale's researches show that Mr. Kiernan's original view is 
 more nearly allied to the truth. 
 
 In the interlobular fissures numerous finer branches leave the small 
 trunk of the duct and pass towards the secreting cells. In the human 
 subject, many of these may be followed for some distance without 
 giving ofiF branches or anastomosing with each other. These small 
 ducts lie around the small branches of the portal vein, and their 
 course is often tortuous. 
 
 In some animals, particularly in the rabbit, the small ducts anasto- 
 mose, forming a network round the vein. This network is continuous 
 with the network of the lobule in which the cells lie. In the human 
 subject, and in most mammalia, the small ducts do not form a network 
 in this manner, but pass off at once to the cell-containing network 
 with which they are continuous. In the pig, the smallest branches 
 of the duct penetrate the capsule of the lobule at various points, and 
 immediately become connected with an intimate network which lies 
 immediately beneath it, and partly within its substance. This net- 
 work may be regarded as the most superficial portion of the cell-con- 
 taining network, and where the liver is fatty it contains cells dis- 
 tended with oil globules. 
 
 In the human liver, and in those of most animals, except the pig, 
 some of the smallest branches of the duct pass for a short distance 
 beneath the surface of the lobule, and become continuous with some 
 of the branches of the cell-containing network in that situation. In 
 a cursory examination these narrow ducts appear to lie amongst the 
 cells without being connected with them. The greater number of 
 
 * Vide KoUiker's Manual of Human Histology, translated by Busk and Huxley ; 
 Sydenham Society, 1853-54. Dr. Carpenter's General and Comparative Physiology, 
 4th edition. 
 
OF THE SMALLEST DUCTS. 
 
 783 
 
 branches, however, join the cell-containing network round the margin 
 of the fissures. , 
 
 Near to the point where the duct joins the cell-containing network 
 it becomes very much narrowed, and is often not more than the 
 3BTST5 °^ siiVc of ^^ inch in diameter, and even less, in the uninjected 
 state. Several of the narrowest ducts in the pig are represented in 
 fig. 229. 
 
 Fig. 229. 
 
 Fig. 230. 
 
 a. Small branch of interlobtQar dnct— pig. 6. Most superficial part of cell-containing network, 
 with cells filled with oil, and free oil globules, c. Narrowest portions of the duct. Magnified 215 
 diameters. The shaded parts show the points to which the injection reached. After Dr. Beale. 
 
 Fig. 230 represents some of the small ducts and a part of the cell- 
 containing network at the surface of a lobule in the human liver. 
 The cells have been nearly destroyed by the action of reagents in 
 preparing the specimen. 
 
 The epithelial cells which line these minute ducts approach to the 
 tesselated variety. They are, for the most part, round or oval 
 granular cells, some of them about the 
 ^^'jj^th of an inch in diameter, while others 
 are less. They present very similar cha- 
 racters in the different animals which we 
 have examined, and the same general 
 arrangement of the minute ducts has been 
 shown to occur in birds, reptiles, and fishes, 
 with certain unimportant modifications. 
 
 The epithelium of the ducts does not pass 
 by gradations into the secreting epithelium, 
 but terminates at the point where the latter 
 commences. The narrowing of the excre- 
 tory portion of the tube is met with in many 
 other glands, but in none is there a more 
 striking contrast between the excretory and 
 secreting portions of the gland, or between 
 the epithelium lining the ducts and that by 
 which the secretion is formed, than in the 
 liver. / 
 
 Narrowest portions of the duct, 
 lined by ductal epithelium, show- 
 ing their connection with the cell- 
 containing network. Close to the 
 narrow ducts, a venous capillary 
 and a small branch of the artery 
 are represented in section. The 
 liver cells have been destroyed by 
 the mode of preparation. From 
 an uninjected specimen of the 
 human liver, magnified 215 diame- 
 ters. After i>v. Beale. 
 
784 LIVER. 
 
 Of the Passage of the Bile into the Ducts.-^li the view of the 
 anatom^ of the liver which we have described be correct, the secret- 
 ing cells at the surface of the lobule are those which take the most 
 active part in the secretion. These are the cells which the portal 
 blood first reaches ; and it is in this situation that the cells first show 
 an increased quantity of oil globules within them in cases of fatty 
 degeneration. The bile is not formed in the central part of the 
 lobule, and transmitted from cell to cell, as has been described by 
 some authorities, but the bile formed by each individual cell escapes 
 through the interstices between the cells until it reaches the duct. 
 If it be urged, as an objection to this view, that no visible interstices 
 exist between the cells, it may be answered that injection can be made 
 to flow by these channels in a direction the reverse of that which the 
 bile naturally takes, and, therefore, under the greatest disadvantage. 
 There can then be no obstacle to the passage of the bile towards the 
 ducts ; moreover, the great changes in bulk, which we know the liver 
 cells so readily undergo, will readily account for the close contact in 
 which they are often observed to lie. 
 
 From a careful consideration of the anatomy of the parts, we 
 should be led to look upon the liver as a large gland, in which a con- 
 siderable quantity of a highly elaborated secretion was slowly formed, 
 and slowly transmitted in a more highly concentrated form towards 
 the intestine. The arrangement of the vasa aberrantia and of the 
 little cavities in the coats of the thick-walled ducts, the abundance 
 of vessels and lymphatics in such close proximity to the ducts, and 
 the great similarity of their disposition with that of the vessels of 
 the gall-bladder, where we know absorption of fluid takes place, 
 favour the idea that important changes occur in the bile after its 
 formation by the cells of the liver. 
 
 The liver is, therefore, a true gland, consisting of a formative por- 
 tion and a system of excretory ducts directly continuous with it. 
 The secreting cells lie within a delicate tubular network of basement 
 membrane, through the thin walls of which they draw from the blood 
 the materials of their secretion. 
 
 Quantity and Uses of the Bile. — We have already considered the 
 composition and uses of the bile in Chapter XXV.; but since that 
 part of our work was published, some important results have been 
 communicated by Bidder and Schmidt, which we shall here briefly 
 allude to.* 
 
 These excellent observers have concluded, from numerous experi- 
 ments upon different animals, that the quantity of bile secreted dur- 
 ing the twenty-four hours is much larger than had been supposed. 
 Cats secreted 14.5 grammes,' dogs nearly 20 grammes, and sheep 25 
 grammes, for each kilogramme (about 2 lbs. 3 oz. avoirdupois) in the 
 weight of the animal. From these data, it is of course, difiicult to 
 draw a correct inference as to the quantity of bile secreted by the 
 human subject ; but, from calculatiilg from these results, it has been 
 
 * Die Verdautmgssaefte und der Stoffweohsel von Dr. F. Bidder und Dr. C. Schmidt. 
 Mitau und Leipzig, 1862. 
 
SECRETING GLANDS. 785 
 
 rendered probable that an adult man secretes about 54 oz. of pure 
 bile in the twenty-four hours, and this conta,ins about 2J oz. of solid 
 matter. This estimate is very much higher than that which we have 
 given at p. 597. 
 
 The activity of the secretion varies greatly at different periods of 
 the day. For one or two hours after a meal, it is very small in 
 amount ; but from this time, it gradually increases until it attains its 
 maximum, about the fifteenth hour after the last meal. The secre- 
 tion then rapidly diminishes in quantity, until it is not more than it 
 was two hours after the meal. The gall-bladder empties itself about 
 two and a half or three hours after taking food. 
 
 It appears that an exclusively amylaceous, or fatty diet, causes a 
 great diminution in the secretion of bile, while a pure flesh diet 
 induces a very abundant secretion. 
 
 The presence of bile very much promotes the absorption of fatty 
 matter, although a certain quantity of fat is absorbed even if no bile 
 enters the intestine. The presence of bile causes the absorption of 
 two and a half times more fatty matter than would be absorbed with- 
 out it. Bile appears to render the mucous membrane more perme- 
 able to fatty matter. 
 
 Bidder and Schmidt consider that the chief object of the bile is 
 " to prolong the series of changes to which animal matter is sub- 
 mitted within the organism, and thus to render it for a longer time 
 efficient in the discharge of vital processes." 
 
 On the Pancreas, consult article " Pancreas" in the Cyclopedia of Anatomy and 
 Physiology, by Dr. Hyde Salter. Upon the anatomy of the Liver, the following works 
 may be referred to: Kiernan, " The Anatomy and Physiology of the Liver," Phil. 
 Trans., 1833 ; Theile, Art. " Leber," im Wagner's Handworterbuoh der Physiologie; 
 Article " Liver," by Mr. Wilson, in the Cyclopedia of Anatomy and Physiology ; 
 Leidy, in the American Jonrnal of the Medical Sciences ; KoUiker's Mikroskopische 
 Anatomic ; Beale, " On the Ultimate Arrangement of the Biliary Ducts, and on some 
 other Points in the Anatomy of the Liver of Vertebrate Animals," Phil. Trans. 1856. 
 
 CHAPTER XXXIV. 
 
 SECRETING GLANDS. — THE KIDNEYS. — PARENCHYMA. — MATRIX. — URI- 
 NIEEROUS TUBES. — MALPIGHIAN BODIES. — CONVOLUTED PORTION 
 OP THE URINIFEBOUS TUBE. — STRAIGHT PORTION. — VESSELS OP THE 
 KIDNEY. — OP THE SECRETION OP URINE. — URINE. — QUANTITY. — 
 REACTION. — CHEMICAL COMPOSITION. — UREA. — URIC ACID. — HIP- 
 PURIO ACID. — CREATINE. — CREATININE. — EXTRACTIVE MATTERS. — 
 AMMONIACAL SALTS. — PIXED SALTS. — CHLORIDES. — SULPHATES. — 
 PHOSPHATES. 
 
 Next in size and importance to the liver, are the kidneys. These 
 glands are symmetrical organs,, one being placed on each side of the 
 spine in. the. lumbar region. In consequence of the position of the 
 
786 KIDNEY. 
 
 liver, the right kidney is placed rather lower down than the left. 
 These organs are surrounded by a varying quantity of fat, and are 
 placed behind the peritoneum. The kidney is of a dark reddish- 
 brown colour, of a firm consistence, and of a close compact texture. 
 Its general form is that of an ordinary French bean, compressed 
 from before backwards, its convex border being external, and its 
 concave edge, or hilum, where the vessels enter, looking towards 
 the median line. The weight of the' healthy kidney is from 4J to 
 5 oz. in the male, and somewhat less in the female. The kidneys 
 are supplied with blood by the renal arteries, two large trunks which 
 come off at right angles from the abdominal aorta. The blood is 
 returned by the large renal or emulgent veins which open into the 
 inferior cava. These vessels, with the nerves for the supply of the 
 organ, enter the kidney at its notch or hilum, whence also proceeds 
 the ureter. 
 
 Of the Kidney in the lower Animals. — The first trace of an organ which can be re- 
 garded in the light of a kidney is met with among the Polypi, but the renal nature of 
 this is at least doubtful. In Porpita, one of the Acalephce, KoUiker has described 
 an organ which contains guanin, and which he therefore looks upon in the light of a 
 kidney. In the Annelida the existence of a renal apparatus is doubtful ; but there 
 is some reason for believing that the so-called respiratory organs are to be regarded 
 in this light. The existence of these glands is not determined in the Crustacea; but 
 among the Arachnida tubes composed of basement-membrane, and containing epithe- 
 lium, exist. Guanin also has been detected in them, so that there can be little doutt 
 of their real nature. Among Insects, renal organs exist as long narrow tubes, and 
 the presence of uric acid has been detected in several species. In the Mollusca, ex- 
 cept in the lowest class, kidneys are distinctly observed, and are either two in number, 
 or combined to form a single organ with an excretory duct. The spongy organs of 
 the Cephalopoda have been proved to be true kidneys, and uric acid has been detected 
 in them with the murexide test by E. Harless. Kidneys exist throughout the verte- 
 brate classes, and are composed of tubular glands, provided with one or more efferent 
 ducts, connected with which are often observed numerous appendages. The urini- 
 ferous tubule consists essentially of a tortuous tube of basement-membrane, lined 
 with secreting epithelium, and dilated at its closed extremity, so as to embrace a tuft 
 of highly tortuous capillary vessels. 
 
 The specific gravity of the healthy kidney is about 1"050, but is 
 liable to vary somewhat, according to the quantity of fluid which 
 exists in the organ at the time of examination. 
 
 The following is an analysis of the cortical portion of a healthy 
 human kidney by Dr. Beale. The organ was taken from the body 
 of a healthy man, thirty-one years of age, who was killed by falling 
 from a second-floor window : — 
 
 100 parts of 
 Solid Matter. 
 
 Water 76450 
 
 Solid matter > . . . 23-550 
 
 Fatty matter, containing much oholesterine . -939 3 -98 
 
 Extractive matter, soluble in water . . 5-840 24-79 
 
 Fixed alkaline salts 1-010 4-28 
 
 Earthy salts -396 1 -68 
 
 Albumen, vessels, etc 15-365 65-24 
 
 Even in health, the proportion of water and solid matter varies 
 greatly, which fully accounts for the varying statements of different 
 observers with respect to the weight of the healthy kidney. In dis- 
 
PARENCHYMA. 787 
 
 ease, the composition of the secreting structure of the kidney under- 
 goes great alteration. The fat is very much increased in quantity 
 in kidneys in a state of fatty degeneration. The relative proportion 
 of the solids generally may be much diminished in quantity, which is 
 remarkably the case in some specimens of enlarged kidney. The 
 increase of size, in these instances, being accounted for by an un- 
 usual quantity of water in the tissue of the organ ; but in many cases, 
 it is, no doubt, dependent upon deposition of new matter. In a very 
 large kidney, weighing half a pound, only 14-39 per cent, of solid 
 matter was present, so that in this instance the increased weight of 
 the organ was undoubtedly due to a larger proportion of water than 
 occurs in health, rather than to the deposition of any adventitious 
 tissue, or to an increase of the normal gland-textures. 
 
 Surface of the Kidney. — The kidney is immediately invested with 
 a firm fibrous coat, called the capsule, which is composed of con- 
 densed areolar tissue, and is continuous with the tissue constituting 
 the matrix of the kidney, in the meshes of which the tubes ramify : 
 some small vessels also connect the capsule of the kidney with the 
 proper gland-structure. At the hilum, the capsule is continuous with 
 the external or fibrous coat of the pelvis of the kidney and the fibrous 
 coat of the ureter. The vessels also receive an investment from it 
 at this point. 
 
 If the surface of the kidney be carefully examined, it is seen to be 
 imperfectly mapped out into a number of small polyhedral spaces or 
 lobules, in general appearance somewhat resembling the markings of 
 the lobules of the liver. These markings are in part due to the 
 arrangement of small branches of the veins which are spoken of by 
 anatomists as the stellate veins. Commencing at the surface of the 
 kidney, they penetrate the cortical part in a vertical direction, at 
 nearly equal distances, and receive, in their course to the hilum, the 
 blood from the venous plexuses surrounding the secreting tubes. In 
 the spaces just described, may be seen the convolutions of some of 
 the uriniferous tubes. No arteries reach the surface. 
 
 Ferrien supposed that the tubes formed little pyramids, each of 
 which radiated from the medullary towards the cortical part of the 
 kidney, the base of each pyramid consisting of one of these spaces or 
 lobules. It appears, however, that although each pyramid contains 
 many tortuous tubes, with their capillaries, the convolutions of a 
 single tube are by no means confined to one pyramidal space. 
 
 Besides the apparent divisions into lobules just referred to, the 
 surface of the kidney bears the vestiges of several fissures, marking 
 it out into lobes which may be seven or eight or more in number ; 
 these lobes indicate the original condition of the kidney in intra- 
 uterine life when they were separated from each other, and formed 
 distinct renules. In the embryos of mammalia generally, the same 
 arrangement is observed ; and it remains permanent in the cetacea. 
 In the kidney of the otter, seal, ox, and some other animals, it is 
 also conspicuous. In the ox, the division into loBes extends only to 
 the pyramids. 
 
 Parenchyma. — The parenchyma of the kidney consists of two dis- 
 
788 KIDNEY. 
 
 tinct portions ; the one cortical, about half an inch in thickness, 
 forming the whole convex surface of the organ, of a dark red colour, 
 and to the unaided eye of a granular appearaince, and exhibiting nu- 
 merous red spots (Malpigbian bodies) abundantly scattered through 
 it. The medullar^/ portion is embraced in this ; it is pale and smooth, 
 arranged so as to form several pyramids, varying in number from 
 eight to fifteen ; their bases are placed towards the cortex, from 
 which may he traced a number of nearly straight lines, which con- 
 verge towards the summit of the pyramid to which they belong. In 
 this part of the kidney there are no Malpigbian tufts, and even to 
 the unaided eye, it appears to be composed of a number of straight 
 converging lines or tubes. 
 
 These pyramids or cones end by free summits which project on the 
 hilum into the pelyis of the kidney, the mucous membrane lining 
 this cavity being continuous at the summit of the cone (or mammilla) 
 with the tubes. The mucous membrane of the pelvis, however, forms 
 a sort of fossa, or saucer-shaped cavity, around each mammilla, or ter- 
 mination of the pyramid. These calyces receive the urine escaping 
 from the open orifices of the tubes oh the summit of the cones, and 
 convey it toward the pelvis ; they become enormously increased in 
 dimensions if there be any obstruction to the passage of the urine 
 from the ureter or bladder. 
 
 Matrix. — With reference to the presence of a fibro-cellular ma^ix 
 in the kidney, which serves as a support for tb,e vessels and tubes, 
 there has been much difierence of opinion. It was originally de- 
 scribed by Goodsir, and has since been noticed by several observers. 
 
 The matrix appears to us to be composed of a firm transparent 
 and granular substance, in which we have seen small granular cells ; 
 but have not been able to ascertain their precise nature. The fibrous 
 appearance seen in thin sections we believe to be due rather to the 
 crumpled state of the walls of the capillaries and uriniferous tubes, 
 than to the existence of ordinary fibrous tissue in the matrix itself. 
 
 The intervals between the contiguous tubes and capillaries are 
 greater in the pyramids than in the cortical portion of the organ, 
 and consequently the matrix is more distinct in this situation ; bat 
 even here it has only a faintly granular appearance, and we have 
 been unable to see any distinct fibres. 
 
 It appears to us that this structure is of little physiological im- 
 portance ; it probably serves as a support for the tubes and capillary 
 vessels. 
 
 As the tortuous tubes in the cortex pass in and out amongst the 
 interspaces of this matrix, portions appear to be circumscribed, as it 
 were, giving the idea upon a section of a number of small cysts,* an 
 appearance which is often very marked in certain cases of disease, 
 when the tubes are enlarged. In the kidneys of many rodents, espe- 
 cially in that of the mouse, this appearance exists in a very markedl 
 degree, in consequence of the highly developed condition of the 
 matrix in these animals ; but, in all the instances alluded to, the true 
 
 * On Diseases of the Kidneys, by. George Johnson, M.D. 
 
MALPIGHIAN BODIES. 
 
 789 
 
 structure of this part, and often the continuity of the tube as it winds 
 in and out, can be demonstrated with ease. A thin section of the 
 cortical part of the kidney, made in any direction, displays these 
 interspaces containing sections of the tubes, between which may 
 often be seen vessels which' have been cut across. 
 
 Uriniferous Tubes. — The uriniferous tubes, formerly termed tubes 
 of Bellini, in which the characteristic elements of the urine are se- 
 creted, consist of two distinct portions, as already alluded to ; the 
 first, or highly convoluted part of the tubes, which is probably the 
 sole seat of true secretion, and the straight portion, which is directly 
 continuous with the former, and conducts the secretion towards the 
 opening upon the mammilla, from which it passes into the pelvis of 
 the kidney. In the other direction, the convoluted portion of the 
 tube terminates in a dilated 
 
 extremity, which completely 
 invests the vessels of the 
 Malpighian tuft.* 
 
 We shall now consider, 
 first, the minute structure 
 of the Malpighian bodies ; 
 secondly, that of the convo- 
 luted portion of the tube ; 
 and, lastly, that of the 
 straight portion. 
 
 Malpighian Bodies. — The 
 Malpighian bodies are met 
 with in all vertebrata. In 
 the mammalian kidney, 
 where there exists a division 
 into cortical and medullary 
 portions, they are only 
 found in the former. In an 
 injected specimen, they ap- 
 pear to the unaided eye, 
 as coloured points abund- 
 antly scattered throughout 
 the cortex of the organ. 
 They vary much in size in 
 different mammalia, and are 
 often larger towards the 
 ba se of the cones. They are, 
 for the most part, of a 
 spherical, oval, or flask-like 
 form. A small artery affe- 
 rent vessel may be seen to 
 enter the tuft, and a minute 
 venous radicle efferent ves- 
 sel to emerge from it in 
 
 Fig. 231. 
 
 Prom the human subject. This specimen exhibits the 
 termination of a considerable arterial branch wholly in 
 Malpighian tufts, a. Arterial branch, with its terminal 
 twigs. At a, the injection has only party filled the tjift. 
 At li, it has entirely filled .it, and lias also passed out 
 along the efi'erent vessel e/, without any extravasation.. 
 At y it has burst into the capsule, and escaped along the 
 tube t, but has also filled the efi'erent vessel ^. At ^ 
 and e it has extravasated, and passed along the tube. 
 At m and m the injection, on escaping into the capsule^ 
 has not spread over the whole tuft. Magnified about 45 
 diameters. 
 
 51 
 
 * Phil. Trans., 1842. 
 
790 
 
 KIDNBT. 
 
 close proximity to the artery (fig. 231). The Malpighian body itself 
 consists of a rounded bunch of capillaries derived from the afferent 
 and terminating in the efferent vessel, the former dividing over the 
 surface, the latter emerging from the interior. This vascular tuft 
 lies within a clear and perfectly transparent capsule, lined at its 
 lower part with epithelium. The epithelium, which is continued 
 upwards from the uriniferous tube into its flask-like dilatation, 
 cannot usually be traced for more than about one-third of the length 
 of the capsule (fig. 3, p. 76) ; but in the proteus (fig. 232), the 
 capsule is seen to be entirely lined with an exceedingly thin layer of 
 delicate epithelium, the cells of which are of an oval, or polyhedral 
 form, with a very large granular nucleus, and about the ^y^^ of an 
 inch in diameter. The capsule itself consists of hyaloid membrane, 
 which is directly continuous with the basement membrane of the con- 
 voluted portion of the tube. In fact, each uriniferous tubule termi- 
 nates by a dilatation which embraces the vessels of the tuft, and is 
 intimately united to them at the point where they enter and emerge. 
 
 The continuity of the tube with the Malpighian capsule has been 
 proved in several ways. In specimens which have been carefully 
 injected from the artery, not unfrequently it will be found that the 
 coloured material escapes and extravasates from the vessels of the tuft 
 into the cavity of the capsule, and thence runs down the tube (fig. 231). 
 
 In disease, it is not at all uncommon to find the capsule of* the 
 
 tuft, and the tube itself, injected 
 
 Fig. 232. 
 
 Malpighian tuft ; kidney of the Proteus an- 
 guineuB, showing vessels lying within the cap- 
 sule, the inner surface of which is entirely 
 covered with a single layer of tessellated epithe- 
 lium, a. Uriniferous tuhe. 6. Capsule, c. Tuft 
 of vessels which were injected in the prepara- 
 tion from which this drawing was taken, of. 
 Terminal twig of the artery, ef. Efferent 
 yes.sel. Magnified ahoutdO diameters. — A small 
 portion of the capsule, with its epithelial lining, 
 is represented in the smaller figure, magulfled 
 21S diameters. 
 
 with blood, in consequence of 
 hemorrhage from the vessels of 
 the tuft. 
 
 The difl5culty of injecting the 
 capsule by forcing injection from 
 the pelvis of the kidney, cannot 
 reasonably be urged as an objection 
 to this view, for all who have had 
 any experience in injecting the 
 minute ducts of glands, will agree 
 that it is in very few instances, 
 indeed, that the injection can be 
 forced to the termination of the 
 tube. The epithelium within it is 
 apt to be forced towards its csecal 
 extremity, and by its accumulation 
 renders such a result impossible ; 
 while, in the majority of cases, 
 the force requisite to overcome the 
 resistance to the passage of fluid, 
 along a highly convoluted tube in 
 the reverse direction to that which 
 its contents naturally take, is more 
 than sufficient to cause its rupture. 
 
 The kidney of the horse is very 
 favourable for demonstrating these 
 
VESSELS UNCOVERED BY EPITHELIUM. 791 
 
 points, and the double injection composed of acetate of lead and 
 bichromate of potash will be found to furnish the most satisfactory 
 results. 
 
 In the kidney of the frog, or of the newt, the continuity of the 
 capsule with the basement membrane of the tube is exceedingly dis- 
 tinct and easy of demonstration. The tuft of vessels is seen lying 
 naked w-ithin the capsule, uncovered either with epithelium or by 
 any reflection of the basement membrane composing the capsule. 
 In the frog, the neck of the' tube close to and some way within 
 the capsule is lined with ciliated epithelium, which continues in very 
 active motion many hours after the death of the animal (vide fig. 3, 
 p. 76.) In the newt, and in some snakes and other reptiles, the 
 tube is completely lined with ciliated epithelium throughout ; and by 
 the activity of the motion, the epithelium can be traced for one- 
 third of the way within the capsule. Ciliated epithelium has not 
 yet been demonstrated in the kidneys of mammalia ; but in one 
 instance Gerlach has seen it in the kidney of the fowl. In various 
 fishes and in many reptiles it is very frequently met with. 
 
 The statement of Gerlach and other observers, that the vessels of 
 the Malpighian tuft are invested with epithelium, may be explained 
 by the fact that small granular or nucleated cells may be frequently 
 observed in connection with the vessels. After repeated and careful 
 observation, we are convinced that these cells are situated either 
 within the vessel itself or enclosed in its wall (fig. 233). In the 
 tuft of batrachian reptiles, the white cor- 
 puscles of the blood often give the idea of 
 being connected with the wall of the vessels, 
 instead of lying in their interior. When 
 the vessels are much shrunken, and their 
 walls a little plaited, or corrugated, the ap- 
 pearance of cells lying upon the little capil- 
 lary loops is produced when these loops are 
 seen in profile. We have been able, in g^.n portion of a loop of capii- 
 manv instances, however, to demonstrate lary vessels of tie tuft of the wa- 
 
 ,% , ', , ^1 -.1 • ii 11 iiey of the large water newt 
 
 small oval or circular cells witnin tne wall (Triton cristatus), showing nuclei 
 of the capillary vessel itself, and are in- S?lL'aloT:"he°'ves''st/irrhe 
 dined to look upon these as the nuclei of SrSfied'afs'dLmetSs. "''°'-' 
 vessels. Here and there a granular cell 
 
 may sometimes be detected on the surface, but they are very few in 
 number and irregular in their arrangement ; and we are satisfied 
 that it cannot be regarded as a fact of any physiological importance, 
 and that the vessels of the tuft are really bare within the capsule. 
 
 Convoluted Portion of the Tube. — From the capsule of the Mal- 
 pighian tuft, we pass to the convoluted portion of the tube, which is 
 directly continuous with it. This is composed of a delicate base- 
 ment membrane, lined by epithelium. Externally, the basement 
 membrane is in close contact and probably incorporated with the 
 matrix of the organ ; and it is in immediate relation with an abund- 
 ant capillary plexus, which carries the blood after it has passed 
 
792 
 
 KIDNEY. 
 
 through the vessels of the Malpighian body. It is from this blood 
 that the elements characteristic of the urinary secretion are selected 
 by the epithelium lining this part of the tube. The diameter of the 
 tube is less immediately after leaving the tuft, than in the rest of its 
 course further down (fig. 234). The epithelium in the convoluted 
 
 Fig. 234. 
 
 
 Entire nriniferotis tuba of tte larg-o black newt (Triton cristatos, female), a. Artery having upon 
 Its walls numerous branched pigment cells. The commencement of the tube, and that part near the 
 tuft, are of less diameter than the central portion, which is the most active part of the secreting tube. 
 Towards its termination in the upper part of the oviduct, (Z, the tube becomes straight and much 
 narrowed, a. Magnified about 30 diameters, from a drawing of Br. Scale's. 
 
 portion of the tube presents an excellent example of the spheroidal 
 or glandular variety. It consists of polyhedral particles rather less 
 than yjj'jj of an inch in diameter, with a distinct nucleus, and con- 
 taining numerous granules, and occupying as much as one-third or 
 more of the total diameter of the tube. 
 
 The extreme diameter of the convoluted tube is about ^Jj of an 
 inch, while the diameter of the central canal is not more than from 
 TTj'cTJ to ^U of an inch. 
 
 Straight Portion of the Tube. — The straight portion of the tubes 
 of which the medullary cones or pyramids are composed form anas- 
 tomoses, or if traced from the papilla towards the base of the pyra- 
 mid^ the large tubes near the apex may be said to divide dichoto- 
 mously, so that the number of the individual tubes, which would 
 
STRAIGHT PORTION OF THE TCBBg. 
 
 793 
 
 Fig. 235. 
 
 Fig. 236. 
 
 be seen in a transverse section, 
 increases as we proceed from the 
 apices of the pyramids towards 
 their bases, while their diameter 
 gradually diminishes. In the 
 latter situation there may be 
 many thousand tubes, while the 
 number of openings upon the 
 extremity of the mammilla are 
 comparatively very few in num- 
 ber. The tubes at their orifices 
 
 vary in diameter, fromthe ^ J ^ to Transverse section of a pyramid of the human 
 
 the sriTj of an inch, while towards Wdney, about a quarter of an inch from the papiUa. 
 
 I i! e i.\. 'Jl J ^' Section of largest tubes, b. Section of smaller 
 
 the base Ot the pyramid they do tubes, at a point previous to their opening into a 
 
 Tinf t^vnt^oA 1 nf an in/»\\ T^Vi larger one. The thin delicate epithelium approach - 
 
 not exceeu ^-q-q OI an men. J.ne Ing to the squamous variety, is seen lining this 
 
 ncro'VPiratfi nanacitv nf tha +iilioa straight portion of the uriniferous tubes, o. Small 
 
 aggregate capacity or ine tUOeS ^g^els wWch ramify between the tubes in the 
 
 at the base of a cone is enor- transparent granular matrix, d. Magnified about 
 
 , , , 1^1 120 diameters. 
 
 mously greater than that of the 
 
 much smaller number of somewhat larger tubes at their orifices. 
 
 The epithelium in this situation differs in 
 character from that in the convoluted por- 
 tion of the tubes ; the cells are smaller, 
 more transparent, and approach more nearly 
 to the scaly or tessellated variety. They 
 seem rather to serve as a protective layer 
 than to share in the secreting function. 
 The cells here are usually very thin, ap- 
 proaching to squamous epithelium in cha- 
 racter ; and although the total diameter of 
 the tube is less than that of the convoluted 
 portion, the diameter of the central canal 
 is greater. 
 
 Vessels of the Kidney. — The renal arte- 
 ries divide into four or five branches, which 
 enter the kidney at the hilum between the 
 vein and the ureter. These vessels are sur- 
 rounded with a quantity of fat. They pass 
 between the papillse to the bases of the 
 cones over which they spread. From 
 these arteries smaller branches are given 
 ofi", which ascend in the cortical substance 
 nearly to the surface, and, in so doing, give oflf, on all sides, a number 
 of small terminal twigs, the afferent vessels of the Malpighian 
 bodies. Arrived within the capsule, the small afferent vessel at once 
 divides into four or five branches, each of which again divides dichoto- 
 mously. The small capillary vessels form loops, which project towards 
 the opening of the uriniferous tube. The blood is received from these 
 vessels, which lie towards the outside of the tuft, by branches of 
 the efferent vessel which converge towards the more central part of 
 
 Malpighian tuft from the horse. 
 The injection has penetrated only 
 to the capillaries, a. The artery. 
 ^f. Qjie of its terminal twigs (or 
 the afferent vessel), d. The dila- 
 tation and mode of breaking up 
 of the terminal twig after enteiing 
 the capsule. The division of the 
 tuft into lobes, I, ?, 2, is well seen. 
 £, i. Intervals between the lobes. 
 Magnified about SO diameters. 
 
794 
 
 KIDNEY. 
 
 the tuft to form one trunk, which leaves the Malpighian body, and 
 
 soon breaks up into a plexus of capillary 
 Fig- 237. vessels, in the meshes of which the tubes 
 
 lie. The terminal arterial twigs with 
 their appended tufts, when injected with 
 vermilion, have been compared not inaptly 
 to a bunch of currants. 
 
 The size and complexity of the Malpi- 
 ghian bodies diEFer much in different ani- 
 mals, according to the activity of the 
 function theyare called upon to discharge. 
 The vessels present fewer convolutions, 
 the tufts are smaller, and their arrange- 
 ment much simpler, in those animals in 
 which the urine is almost of a solid con- 
 sistence. Compare the complicated ar- 
 rangement in the horse and other mam- 
 malia in figs. 236 and 237, with the few 
 and simple convolutions in birds, fig. 
 238. 
 
 By reference to the table on next page, 
 it will be seen that the diameter of the 
 tuft in the parrot and in the boa, is l^s 
 than in any other instance recorded ; and in 
 these animals, as is well known, the urine 
 is almost solid. It is especially worthy 
 of remark, that the uriniferous tubes do 
 not exhibit a corresponding difference ia 
 dimensions. 
 
 Halpighian tuft, from near the 
 1>aBe of one of the mediUlary cones, 
 injected without extravasation, and 
 showing the efferent vein branching 
 like an artery as it runs into the me- 
 dullary cone. a. Arterial branch. 
 ef. The afferent vessel, m, m, Mal- 
 pighian tuft. (f. The efferent ves- 
 sel, b. Its branches entering the 
 medullary cone. Magnified about 
 70 diameters. 
 
 Fig. 238. 
 
 From the parrot ; injected by the artery, a, a, a. Terminal branches of the artery, a/, ctf, of. Ter- 
 minal twigs of the artery, e2. Dilatation of the terminal twig on entering the Malpighian capsule, 
 m. This dilatation more completely filled, showingits convoluted form ; and, ^ ^, the efferent ves- 
 sel, c. The Malpighian capsule filled by extravasation from the contained vessel, and the tube t like- 
 wise filled. Maguifled about 80 diameters. 
 
MALPIGHIAN TUFTS. 
 
 795 
 
 Table of ike Diameter of Malpighian Bodies, and of the Tubes emerging 
 from them, in Fractions of an English Inch. "* 
 
 
 
 
 Diameter of MalpigWan bodies. 
 
 Diameter of Tubes. 
 
 
 Maximum. 
 
 Mean. 
 
 Minimum. 
 
 Man 
 Dog . 
 Rat 
 
 Horse . 
 Parrot . 
 Tortoise 
 Boa . 
 
 
 
 
 Tk 
 
 irk 
 lie 
 
 
 ik 
 
 sk 
 
 ik 
 
 ik 
 
 ffk to Tk 
 
 Tiff 
 
 The small efferent vessel from the Malpighian tuft passes at once 
 into the plexus round the tubes, and, as it lies between the capil- 
 lary plexus of the tuft, on the one band, and that surrounding 
 the tubes upon the other, it bears 
 
 the same relation to these two Fig. 239. 
 
 capillary systems as the portal 
 vein bears to those of the intes- 
 tinal canal and the liver ; hence 
 these efferent vessels may be re- 
 garded as analogous to a portal 
 system of vessels. This view is 
 further strengthened by an exa- 
 mination of the arrangement of 
 the vessels in the kidney of the 
 boa constrictor, figs. 239, 240. 
 In this animal, the blood, after 
 passing through the capillaries of 
 the Malpighian tuft, enters the 
 efferent vessel, which conducts it 
 into the branch of a portal vein 
 ramifying upon the surface of 
 the lobule. From the portal vein, 
 it passes into a system of venous 
 capillaries surrounding the tubes, 
 from which it is at last carried 
 into the emulgent veins, which, 
 with the artery, lie in the central 
 part of the lobule. 
 
 " The comparison between the 
 hepatic and the renal portal circulation may be thus drawn in more 
 general terms. The portal system of the liver has a double source, 
 one extraneous, the other in the organ itself; so the portal system 
 of the kidney, in the lower tribes, has a twofold origin, one ex- 
 traneous, the other in the organ itself. In both cases, the extraneous 
 source is the principal one, and the artery furnishing the internal 
 source is very small. But in the kidney of the higher tribes, the 
 
 Plan of the arrangement of the elements of a 
 lobe of the kidney in the boa constrictor. The 
 references are the same as in Fig. 240. 
 
796 
 
 KIDNBT. 
 
 portal system has only one internal source, and the artery supply- 
 ing it is proportionably large."* 
 
 Of the Secretion of Urine. — Having passed in review the ana- 
 tomical arrangement of the different structures composing the kidney, 
 
 we shall now proceed to 
 Fig. 240. consider briefly the func- 
 
 tions which the several 
 parts perform. First, with 
 regard to the Malpighian 
 tufts; we have already 
 seen that in animals, in 
 which the urinary excre- 
 ment is passed in an 
 almost solid form, the 
 tufts are small and simple 
 compared with those in 
 the kidneys of animals 
 which pass the urinary 
 constituents in solution in 
 a large quantity of water. 
 There can be little doubt 
 that the special function 
 of the vessels of the taft 
 is, to furnish the fluid 
 portion of the urine, while 
 the solid matter, com- 
 posed of various organic 
 constituents and inorganic 
 salts, is separated by the aid of the glandular epithelium which lines 
 
 the convoluted portion of the tubes. 
 "It would, indeed, be difficult to con- 
 ceive a disposition of parts more calcu- 
 lated to favour the escape of water from 
 the blood than that of the Malpighian 
 body. A large artery breaks up in a 
 very direct manner into a number of 
 minute branches, each of which suddenly 
 opens into an assemblage of vessels of 
 far greater aggregate capacity than itself, 
 and from which there is but one narrow 
 exit. Hence must arise a very abrupt 
 retardation in the velocity of the current 
 of blood. The vessels in which this 
 delay occurs are uncovered by any struc- 
 ture. They lie bare in a cell from which 
 there is but one outlet."t The arrange- 
 ment of the convoluted portion of the 
 tubes is very similar to that of other 
 
 e.v 
 
 Part of Fig 239 shaded, showing the arrangement of the 
 vessels and uriniferous tnhes in the kidney of the boa, and 
 in animals furnished with a portal vein from an extraneoas 
 source, a. Artery, af. 'Terminal twig going to Malpighian 
 body. ef. Efferent vessel of the Malpighian body emptying 
 itself into a branch of the portal vein, pv, on the surface of 
 the lobe. &, &. Ultimate branches of the portal vein entering 
 the capillary plexus, p, surrounding the uriniferous tube, t. 
 u. Branch of the ureter on the surface of the lobe. ev. 
 Emulgent vein within the lobe, receiving the blood from the 
 plexus surrounding the uriniferous tubes. Supposed to be 
 magnified about 40 diameters. 
 
 Fig. 241. 
 
 Plan of the renal circulation in man 
 and mammalia, a. Terminal branch 
 of the artery, giving the terminal 
 twig, 1, to the Malpighian tuft, m, 
 from which emerges the efferent or 
 portal vessel, 2, Other efferent ves- 
 sels, 2, are seen entering the plexus 
 of capillaries surrounding the urini- 
 ferous tube, t. . From this plexus the 
 ^mulgent vein (u) springs. 
 
 * Phil Trans., 1842. 
 
 t Phil. Trans., 1842. 
 
URINE. 797 
 
 secreting tubular gland-structures. We have a delicate basement mem- 
 brane in contact with vessels upon one surface and having secreting 
 epithelium upon the other. The capillary network surrounding the 
 uriniferous tubes is the counterpart of that investing the tubes of the 
 testes ; and the epithelium is allied in structure to the best marked 
 examples of glandular epithelium, and there can be no doubt that 
 the function of these cells is such as we have described. There is no 
 reason for supposing that the cells of epithelium undergo rapid decay 
 and renovation ; it appears more probable that they are not being 
 constantly shed, either in an entire or disintegrated state, but that 
 they have the power of selecting certain materials from the blood, 
 and afterwards giving them up without their destruction. In the 
 straight portion of the tubes the epithelium becomes thinner, and ap- 
 proaches more nearly to the pavement variety. It probably serves 
 principally as a protective covering, and takes no part whatever in 
 the secretion of the urine. 
 
 URINE. 
 
 Healthy urine is a clear, limpid fluid, of a pale straw colour, emitting a peculiar and 
 characteristic odour while warm, and exciting a saline and somewhat bitter taste. As 
 the solid constituents of this fluid are entirely exorementitious, and in great part 
 derived from the disintegration of the tissues concerned in the chemical changes con- 
 nected with animal life, we should be led to expect that any alteration in the activity 
 of these functions would lead to a corresponding variation in the characters of the 
 urine. Even in a state of health the qualities of the urine vary much ; and it has 
 been found that active exercise exerts a considerable influence upon the quantity of 
 some of the most important constituents of this fluid. Nitrogenous matter, taken in 
 greater quantity than is required for the wants of the system, will be eliminated by 
 the kidneys in the form of urea, and the composition of the urine will therefore be 
 influenced by the character, as well as by the quantity of the food.* If an unusual 
 quantity of water be taken into the stomach, a great proportion will rapidly be elimi- 
 nated by the kidneys, and the urine will be found to be very dilute, and of low specific 
 gravity. Again, as the action of the kidneys is materially affected by the activity 
 with which the functions of the skin are discharged, the condition of this great se- 
 creting surface has much to do with the quantity and quality of the urinary secretion. 
 Changes of temperature, for the same reason, will cause the urine to vary in quantity. 
 In hot weather, when the functions of the skin are increased, and a large amount of water 
 is in this way removed from the system, in order tp compensate for the eff^ects of the 
 increased external heat, the urinary secretion is much diminished in quantity, and 
 becomes more concentrated, while, in cold weather, when this cooling effect of evapora- 
 tion is not required, we find the amount of urine much increased, and, therefore, 
 diminished in density. A dry, or humid state of the atmosphere, in consequence of 
 affecting the rapidity of cutaneous transpiration, will exert a certain amount of 
 influence on the quantity of water. It does not appear, however, that the quantity 
 of the solid constituents excreted in a given time is much altered by these circum- 
 stances. The state of the nervous system will often be found to have a decided influ- 
 ence in modifying the characters of this secretion ; and various mental emotions, 
 such as sudden joy, or fright, or anxiety, will cause the secretion of urine having a 
 much larger proportion of water than usual. 
 
 All these circumstances, and many others of less importance, have been found to 
 affect the characters of healthy urine ; and, on this account, considerable difSculty has 
 been felt in attempting to define the precise characters of the secretion in health. 
 Again, the composition of the urine differs at different periods of life, but in a much 
 
 * The frequency with which we meet with an excess of urea in the urine of our country- 
 men is probably dependent in some measure upon the highly nitrogenous nature of our 
 food. On the continent of Europe this is so rare, that some foreign observers appear hardly 
 to credit the statements with reference to the frequent presence of excess of urea. 
 
798 
 
 UKINB. 
 
 Fig. 242. 
 
 less degree in difTerent individuals at the same period. The urine of men, in the 
 prime of life, contains more solid matter, and less water, than that of old men, women, 
 or children. 
 
 Quantity of Urine. — The quantity of urine discharged in the course of twenty-four 
 hours, in a state of health, varies very much, but it may be said to amount to about 
 30 or 40 ounces. The density varies from 1-010 to 1020 or 1025 and the quantity 
 of solid matter from 4 or 5 to 8 per cent. The amount of solid matter eliminated 
 
 from the kidneys of a healthy 
 man who lives well may be 
 roughly stated to be about 
 1000 grains in twenty-four 
 hours. 
 
 Reaction. — Healthy urine 
 exhibits an acid reaction; 
 but the intensity of the re- 
 action varies at certain 
 periods of the days. Dr. 
 Bence Jones, who has lately 
 investigated this subject, 
 found that the urine was 
 most acid immediately be- 
 fore meals, and the intensity 
 of the acidity diminishes 
 until five or six hours after 
 the meal, This condition, 
 occurring in the urine se- 
 creted soon after digestion, 
 depends upon the quantity 
 of alkali set free in the blood 
 in consequence of thedeoem- 
 position of certain salts which 
 furnish the acid entering into the composition of the gastric juice. 
 
 The reaction of healthy urine has been attributed to the presence of free lactic 
 acid, and also to acetic acid ; but the investigations of Liebig have rendered it probable 
 that it depends, not upon the existence of free or unoombined acid, but upon the pre- 
 sence of certain salts which exhibit a decidedly acid reaction, although there is no 
 free oruncombined acid. Such salts are presented to us in the phosphates, which have 
 the property of being very readily changed from the alkaline to the acid, or super-salt. 
 
 Fig. 243. 
 
 a. Various forms of lithic acid crystals. 5. Deposit of lithate 
 of soda, amorphous, c. Lithate of soda forming spherules with 
 irregular crystals projecting from them. d. Oxalate of lime. e. 
 Dumb-bell crystals of oxalate or oxaluxate of lime. 
 
 Casts of the urlnlferous tubes, a. Casts with epithelium, at a a ffee cell of epithelium. 6. Very 
 large cast containing epithelium, c. Small granular casts, d. Small waxy cast. e. Casts contain- 
 ing fat cells and free oil, at x cell filled with fat globules. /. Fus globules, at x once acted upon by 
 acetic acid. 
 
COMPOSITION OF HEALTHY UKINE. 
 
 799 
 
 a. Crystals of triple phosphate, o. Stellate 
 variety, b. Granules of phosphate of lime, d^ 
 Crystals of cystine. 
 
 After standing for some hours, healthy urine deposits a slight precipitate, forming a 
 light flocculent cloud, consisting of yesical mucus, and a little epithelial debris. This 
 deposit is much more abundant in the urine of women, in consequence of the admixture 
 of a considerable quantity of yaginal epithelium. Not unfrequently, epithelium from 
 the urethra, or bladder, -will be found in this deposit, and spermatozoa are occasionally 
 met with. In disease, the deposit may consist of pus, or blood-corpuscles, and fibrin- 
 ous moulds of the uriniferous tubes,* entangling cells of renal epithelium, which may 
 contain many oil globules, and crystals of 
 oxalate of lime, pus, or blood globules, are 
 sometimes found. In such cases, the urine 
 will also contain albumen. Among the de- 
 posits most frequently observed, may be 
 mentioned the amorphous deposit of lithate 
 of soda, crystals of lithic acid, of oxalate of 
 lime, of triple or ammoniaco-magnesian 
 phosphate, and occasionally crystals of cys- 
 tine. 
 
 Composition of Healthy Urine. — The urine 
 is a highly complex fluid, and contains sub- 
 stances having very different properties. Its 
 constituents are composed partly of organic, 
 and partly of inorganic compounds which 
 are held in solution in the aqueous portion 
 of the secretion. A small quantity of carbonic acid gas is likewise often found held in 
 solution. The chief organic constituents of healthy urine are the following : urea, uric 
 or lithic acid, and certain extractive matters, with small quantities of creatine, creatinine, 
 hippuric and lactic acids, and ammoniacal salts. The inorganic constituents consist of cer- 
 tain salts which enter into the composition of the food, but which are not required for 
 the wants of the system, and salts which, having performed certain ofSoes by their pas- 
 sage through the tissues, are no longer required, and certain other saline compounds, 
 which, like many of the organic constituents, are formed by oxidation in the processes 
 concerned in nutrition. The inorganic salts are composed of chlorides, sulphates, and 
 phosphates, with traces of silica, and the bases entering into the composition of these salts 
 are, potash, soda, lime, and magnesia. It is exceedingly difficult to ascertain the precise 
 composition of the salts as they were originally held in solution in the urine ; for, in 
 the processes of evaporation, and subsequent incineration, certain decompositions take 
 place, which entirely alter their nature. The quantities in which these substances 
 occur, vary in different specimens of urine, and the published analyses of the secre- 
 tion in a healthy state, will be found to differ considerably from each other. This 
 difference arises chiefly from the variation in the proportion of water ; for, by calcu- 
 lating the relation existing between the quantities of the several solid constituents, it 
 will be found to be nearly the same in all. 
 
 The following is an analysis of healthy human urine, by Dr. Miller. The percent- 
 age composition of the solid matter is shown in a separate column. Specific gravity, 
 1.020. 1 
 
 In 100 of 
 Solid matter. 
 
 Water 95680 
 
 Solid matter 42-98 
 
 Organic matters 
 29-822 
 
 Fixed Salts 
 13-158 
 
 Urea . 
 Uric acid . 
 Alcohol extractive 
 Water extractive . 
 Vesical mucus 
 Muriate of ammonia 
 Chloride of Sodium 
 Phosphoric acid . 
 Sulphuric acid . 
 Lime , 
 Magnesia . 
 Potash 
 Soda . 
 
 14-23 
 
 33-10 
 
 ■37 
 
 •86 
 
 12-53 
 
 29-15 
 
 1-60 
 
 3-72 
 
 •17 
 
 -39 
 
 •91 
 
 2-11 
 
 7-22 
 
 16 79 
 
 212 
 
 4-93 
 
 1-70 
 
 3 95 
 
 •21 
 
 •48 
 
 •12 
 
 -27 
 
 1-98 
 
 4-40 
 
 -05 
 
 •11 
 
 * Diseases of the Kidney, by George Johnson, M. D, 
 
800 TJRINB. 
 
 Urea (C2'B.^1S^0^ constitutes nearly half of the solid matter of healthy urine, and 
 the secretion itself contains from 2 '5 to 3 '2 per cent, of this substance. The quantity, 
 however, is much increased by exercise, or by a purely animal diet. According to 
 Lehmann, when a highly nitrogenous diet is taken, a quantity of urea equal to nearly 
 five-sixths of the nitrogenous matter introduced is eliminated by the kidneys. A con- 
 siderable quantity of urea, however, is formed when no food whatever is taken, or 
 when a non-nitrogenous diet is adhered to for a considerable period, which clearly 
 shows that a large proportion of urea is derived from the disintegration of the tissues, 
 by the process of secondary assimilation. It is often detected in abnormal quantity 
 in the urine of patients suffering from rheumatism, and certain febrile complaints, and, 
 in various diseases, it may sometimes be obtained from this fluid in very large quanti- 
 ties. This condition is very commonly associated with diseases of the kidneys, and 
 leads to the development of coma, which is often fatal. Urea has been detected in the 
 blood of patients suffering from cholera, and once by Dr. Garrod, in that of a gouty 
 patient. In the serous fluids poured out in various parts of the body, ia cases of kid- 
 ney disease, as well as in several of the secretions, such as the saliva, &o., it has been 
 found in large quantity. Dr. Owen Kees has met with it in milk, and the same ob- 
 server, and Wohler, have found it in the liquor amnii, an observation, however, which 
 others have failed to confirm. It has been detected in the aqueous and vitreous hu- 
 mours of the eye. 
 
 There can be little doubt that urea is formed in the blood by the action of oxygen 
 upon lithic acid, creatine, and, possibly, upon some of the matters comprehended 
 under the indefinite term of extractive matter. In a state of health it is so rapidly 
 separated from the circulating fluid, in its passage through the kidneys, that its pre- 
 sence is not easily recognized ; but, in animals in which these organs have been ex- 
 tirpated, it accumulates in snfBcient quantity in the blood to be detected with facility. 
 Urea cannot be extracted from the muscles, although it is probable that the greater 
 quantity excreted is formed from the effete materials produced by muscular action, 
 since the quantity of urea is so much increased by exercise, and is also produced, 
 although only non-nitrogenous food be taken. At the same time, it is almost certain, 
 that if an amount of nitrogenous food greater than is required by the wants of the 
 system, be taken, the excess becomes converted into urea, and is eliminated from the 
 system by the kidneys.* 
 
 Uric or Lithic Acid (fi^^VI^'S^Og) is always present in healthy urine, and exists in 
 the proportion of about one part in a thousand. It may very readily be obtained by 
 the addition of a few drops of hydrochloric acid to a portion of the urine placed in a 
 conical glass vessel. After the lapse of a few hours, the uric acid is found deposited 
 in the form of small crystalline grains, adhering to the sides or collected at the bottom 
 of the glass. Uric acid prepared in this manner is always highly coloured, which 
 arises from the circumstance of its having a great affinity for the colouring matter of the 
 urine. 
 
 Uric acid exists in healthy urine in combination with soda, and perhaps also with 
 ammonia and lime ; as these salts are only present in small quantity they are held in 
 solution, but in the urine of patients suffering from fever, they often form an abundant 
 deposit, which, in this country, is generally known as lithate of ammonia, although 
 Lehmann, Becquerel, and Heintz, all agree that it is composed principally of lithate 
 of soda. 
 
 In the urine of the oamiVora, uric acid is present in stnall quantity, but, as a 
 general rule, it is absent froih the urine of the hei;bivora; and, curiously enough, also, 
 it cannot be detected in the urine of the omnivorous pig. The excrement of birds, 
 and that of serpents and other reptiles, and of many insects, contains a large quantity 
 
 * It has lately been advanced by Dr. Frerichs, that in cases in which the urea is pre- 
 vented from being eliminated from the bipod, either by the extirpation of the kidneys (as in 
 his experiments upon animals), or in cases in which the functions of these organs have been 
 impaired by disease (as in certain forms of Bright's kidney), tiiis substance is resolved, 
 whilst in the circulating blood, into carbonate of ammonia; the presence of which, according 
 to this observer, gives rise to the coma which so frequently carries off patients in an ad- 
 vanced stage of renal disease. We should, however, state, that this view has not yet 
 received confirmation from the experiments of others. That a considerable quantity of urea 
 may be present in the blood without giving rise to any serious symptoms, we can afiirm 
 from actual experiment ; but at the same time, we consider that there is sufficient evidence 
 to prove that the coma, in many cases of kidney disease, is dependent upon the presence of 
 urea. We have tested the breath of a few patients suffering from this form of coma, in 
 King's College Hospital, and have also examined the blood, but have failed to demonstrate 
 the presence of carbonate of ammonia. 
 
EXTRACTIVE MATTERS. 801 
 
 of alkaline urates. Guano, as is well knoTvn, is chiefly composed of lithate of ammo- 
 nia. 
 
 After profuse perspiration, the quantity of uric acid has been found to be diminished 
 in the urine ; but a purely animal diet exerts but little influence upon the quantity of 
 this substance excreted by the kidneys. It is much increased, however, in all febrile 
 conditions of the system, and after imperfect digestion of food. In cases ■where the 
 respiratory function is impaired, the amount of uric acid has been found to be abnor- 
 mally increased ; and insuf&cient exercise will produce a similar effect. 
 
 Uric acid has been detected in the blood of healthy men by Garrod, and in consider- 
 ably increased proportion in the blood of gouty patients. It has also been detected 
 in the perspiration, and the deposits formed about the joints of gouty persons are 
 largely composed of it. 
 
 According to Wohler and Frerichs, the introduction of lithic acid into the blood is 
 followed by an increased secretion of urea and oxalate of lime in the urine, a point of 
 considerable interest when we know that, by the influence of peroxide of lead, a simi- 
 lar decomposition of the lithic acid may be induced artiflcially. 
 
 When all these circumstances are considered, more especially that, in certain 
 instances in which the respiratory changes are not carried on with the acti-vity con- 
 sistent with perfect health, a greatly increased quantity of lithic acid is eliminated by 
 the kidneys, there appears ample evidence to show that lithic acid is one of the purely 
 excrementitious substances derived from the disintegration of the tissues, and formed 
 by the action of oxygen upon effete material. By a process of further oxidation, the 
 lithic acid itself becomes converted into urea as we just now mentioned. 
 
 Sippuric Acid (C,g Hg NO5, HO), according to Liebig, exists in small quantity in 
 healthy human urine, but it is obtained in considerable quantity from the urine of 
 horses, cows, and other herbivorous animals. It is quite inodorous, has a rather bit- 
 ter taste, is slightly soluble in cold, but very soluble in hot water and alcohol, charac- 
 ters in which it differs from uric acid. It Is easily prepared from the urine of cows 
 by precipitation by hydrochloric ■ acid, and subsequent purification. It is, however, 
 absolutely necessary that the urine should be perfectly fresh, otherwise the hippuric 
 acid will be found to have been entirely converted into benzoic acid, a change which 
 may also be induced in the pure acid by the action of heat and mineral acids. It has 
 been stated by Mr. Ure, that if benzoic acid be taken, it is eliminated from the system 
 as hippuric acid. 
 
 Hippuric acid has been found in the urine of many herbivorous animals, and by 
 Lehmann in that of the tortoise (Testudo Orseca) and many herbivorous insects. It 
 is not present in the urine of the caruivora. In cases of diabetes, it is stated 
 by the same observer to be never absent from the urine ; and in health, may usually 
 be detected if the diet be purely of a vegetable character. This acid, like uric acid, 
 must be looked upon as an excrementitious substance, and plays no other part in the 
 system. 
 
 Creatine (Cj HjNj O4) occurs in very small quantity in the urine. It is a colourless 
 crystalline body, with a strong pungent taste, soluble in cold, and very soluble in boil- 
 ing water; it is almost insoluble in alcohol. Boiled with baryta water, it becomes 
 changed into urea and sarcosine ; and it is probable that a somewhat similar decompo- 
 sition ensues within the organism, and that, of the quantity of creatine formed in the 
 muscular fibre, a large proportion is eliminated from the system in the form of urea, 
 and partly, perhaps, as carbonic acid and ammonia. 
 
 Creatine was obtained, in the beautiful investigation of Liebig, from the flesh of 
 various animals; but the proportion in which it exists is so small that it can only be 
 extracted with great care, and by operating upon large quantities. It occurs most 
 abundantly in the flesh of fowls, and in the heart of the ox. 
 
 Creatinine (Cg H, Nj 0^) is also met with in the urine, and its presence in this fluid 
 was discovered by Liebig, to whom we are indebted for all that is known in reference 
 to this body. Creatinine crystallizes in colourless crystals. It possesses a hot, burn- 
 ing taste, compared to caustic ammonia. It is soluble in water, and, unlike creatine, 
 is freely dissolved by spirit. It is found, with the last mentioned body, in the juice 
 of muscular fibre. Creatinine may be formed by the action of hydrochloric acid upon 
 creatine a change which renders it probable that it is also formed from the last named 
 body in the organism. In urine, creatinine exists in larger quantity than creatine ; 
 while in muscular fibre the latter is found to exceed the former in amount. 
 
 Extractive Matters.— ^Vndet this very unsatisfactory term are included certain sub- 
 stances met with in the urine, blood, and other animal fluids which are not easily iso- 
 lated, whose properties are vnth great difficulty determined, which do not crystallize, 
 are not volatile without decomposition, and cannot be obtained in a pure form. Of 
 
802 URINE. 
 
 Ittte years, however, seyeral substances have been separated from the extractive mat- 
 ters which were formerly included under that term. Of these, albuminate of soda, crea- 
 tine, and creatinine may be referred to as examples. These extractive matters no 
 doubt play a most important part in vital chemistry, and probably represent a stage 
 intermediate between the nutritive pabulum and the tissues formed from it, or between 
 the latter in process of disintegration and the compounds we have been considering, 
 such as urea, lithic acid, etc., but in the present state of our knowledge, little beyond 
 mere speculation can be advanced. 
 
 Our friend, Dr. G. 0. Rees, found that, in cases of albuminuria, connected with 
 kidney disease, large quantities of the extractive matters of the blood passed off in 
 the urine as well as albumen. The test which Dr. Bees employed for detecting the 
 presence of the blood extraction was the tincture of galls.* 
 
 Ammoniacal Salts. — Ammonia exists in very small quantity, if, indeed, it be present 
 in healthy urine, but in disease a considerable proportion may occur. It has been 
 found as hydrochlorate, lactate, biphosphate, ammonio-magnesian or triple phosphate, 
 and in the form of phosphate of ammonia and soda. Its presence usually depends 
 upon the decomposition of some of the nitrogenous constituents of the urine, as pre- 
 viously indicated. 
 
 Fixed Salts. — By the careful incineration of urine, we obtain the fixed salts, and we 
 find that, of the saline residue, part is soluble and part insoluble in water, the latter 
 having been previously held in solution in the urine by some material which has 
 been destroyed by a red heat. Although the presence of certain acids and certain 
 bases in the ash is readily demonstrated, the precise manner in which these were ori- 
 ginally united together is not so easily ascertained. 
 
 The most important saline constituents of normal urine are chlorides, sulphates, 
 anS phosphates ; and the following bases are present — potash, soda, lime, magnesia, 
 with traces of silica and peroxide of iron. 
 
 Chlorides. — The chlorine exists in combination with sodium, in the form of common 
 salt, and perhaps also occasionally as hydrochlorate of ammonia. Almost the whole 
 of the chloride of sodium is probably derived from the food ; although, from rjcent 
 investigations, it appears probable that this substance plays an important part in the 
 development of tissues, and also in certain morbid changes. In growing tissues, it is 
 always abundant, and in the fluid on the surface of healing ulcers it exists in large 
 quantity.! 
 
 Sulphates. — The sulphuric acid exists in combination with potash, and perhaps also 
 with soda. The sulphates are highly important saline constituents, and their propor- 
 tion is much influenced by the activity of the vital functions, and also by an animal 
 diet. , After exercise, the amount of the sulphates, as well as that of the urea, under- 
 goes an increase ; and it has been found that in Chorea (a disease characterized by 
 inordinate action of the muscular system) a large quantity of these salts are excreted 
 in the urine. J The sulphuric acid is, doubtless, in great measure produced by the 
 oxidation of the sulphur contained in the proteine compounds. Unlike the chlorides, 
 the sulphates are not present, or are only met with in very small quantities, in the 
 fluids of the body generally, with the exception of the urine, a. circumstance which 
 points to the importance of the former in the organism, while it clearly shows that 
 the latter are not required in the nutritive changes, and are, therefore, only to be 
 found in the excrements. 
 
 Sulphuretted Sydrogm Is from time to time detected in urine. Dr. Beale met with 
 it frequently in the urine of insane patients. Sulphur is no doubt eliminated in 
 considerable quantity in the urine in certain cases. Cystine contains as much as 26 
 per cent, of this substance. 
 
 Phosphates. — Phosphoric acid is found in combination with soda, lime, and magnesia ; 
 the salts thus constituted have been spoken of as alkaline or earthy phosphates, the 
 former term being confined to the combination of phosphoric acid with soda, and the 
 latter to the phosphates of lime and magnesia, which are precipitated from healthy 
 urine by the simple addition of excess of ammonia. 
 
 The large amount of phosphates present in urine is chiefly derived from the food, 
 but part results from the oxidation of the phosphorus which is contained in the tissues ; 
 the particular tissue concerned in the formation of this phosphoric acid being the 
 nervous, which, it is well known, contains a large proportion of phosphorus. Dr. 
 
 * Lettsomian Lectures. London Medical Gazette, vol. xlviii., 1851. 
 t " On the Diminution of the Chlorides in the Urine in Cases of Pneumonia," by Lionel 
 Beale. Med.-Chir. Trans., vol. xxx. 
 \ Dr. Bence Jones. Med.-Chir. Trans. 
 
PELVIS 01 KIDNEY. 803 
 
 Bence Jones foun 1 an increase in the quantity of the alkaline phosphates in the urine 
 of some cases of inflammation of the brain, and a diminution in quantity in cases of 
 delirium tremens when no food was taken ; but in the latter case the diminution is, 
 probably, too slight to be recognized. This circumstance would account for the result 
 of several experiments we have ourselves made upon this point, in which we have 
 found no diminution in the quantity of phosphates. 
 
 To sum up, the kidneys appear to be special organs for the removal of effete ma- 
 terial produced in the vital processes from the system, and they serve as channels for 
 the elimination of water and certain saline matter, as well as excess of nitrogenous 
 material which is not required for the maintenance of the tissues. The chief con- 
 stituents of the urine consist of compounds resulting from the action of oxygen upon 
 the albuminous or allied substances ; and in urea and uric acid we have probably ei- 
 amples of the highest state of oxidation which the chemical elements of the tissues 
 are capable of undergoing, and urea may be looked upon as the last of a series of com- 
 pounds resulting from the successive action of oxygen upon those bodies which stand 
 above it on this scale. The fixed salts which occur in urine also exist in a highly 
 oxidized state. There can be little doubt, that the highly complex substances entering 
 into the formation of the tissues, by chemical action taking place in the organism, 
 become resolved into bodies of a more simple composition, until they are eliminated 
 in the form of urea or some allied compound, the elements of which are so loosely 
 combined, that by external circumstances alone new substances are formed of a still 
 simpler composition, such as carbonic acid and ammonia. In these, however, the 
 elements are united with such force, that it is only by most powerful chemical action, 
 or by the still more powerful influence of the vital properties of plants, that they can 
 be separated from each other, and again applied to the building up of those highly 
 complicated substances of which the tissues of animals consist, and which, by their 
 vital processes, are again reduced in complexity as before. 
 
 The more actively the vital phenomena are performed, or, in other words, the greater 
 the rapidity with which the disintegration and repair of the tissues take place, the 
 larger is the quantity of urea excreted from the system. With this increase of the 
 urea, there is certainly a corresponding increase of the sulphates, and perhaps also 
 of the phosphates. If, however, the activity of these changes be interfered with, as 
 from impairment of the respiratory apparatus, or from other causes, as might be 
 expected, we find an increase of that constituent which stands next above urea in the 
 descending series of compounds resulting from oxidation, namely, lithic acid. This 
 finds its way out of the system in the form of lithate of soda, forming the amorphous 
 sediment generally known as lithate of ammonia, but which really consists almost 
 entirely of lithate of soda. Under similar circumstances, we often meet with a de- 
 posit of oxalate of lime. The urine of the active carnivora contains, like that of man, 
 a large quantity of urea ; on the other hand, the urine of serpents and many other 
 reptiles consists almost entirely of urie acid in combination with ammonia. The urine 
 of birds much resembles in character that of serpents, which appears somewhat to 
 be opposed to the doctrine we have been endeavouring to inculcate, as the vital changes 
 are carried on with greater activity in this than in any othep class of animals ; but, 
 on the other hand, it may be argued, that the demand for oxygen is so ^eat in birds, 
 and their vital functions so actively carried on, that the extensive respiratory appa- 
 ratus necessary for the supply of sufficient oxygen to convert all the uric acid into 
 urea would be incompatible with the lightness of their bodies, which is so necessary 
 for flight ; while the removal of the urinary constituents in a state of solution involves 
 the necessity of a bladder, or receptacle, in which it can collect, and which would 
 still further add to the weight. We find in the minute anatomy of the bird's lung a 
 beautiful arrangement by means of which not the smallest space where blood can be 
 exposed to the action of air is lost. ( Vide p. 715.) 
 
 Pelvis of Kidney and Ureters. — The mucous membrane lining the 
 pelvis of the kidney is continuous with that of the renal tubes at the 
 point where they open upon the papillss, in which situation it is ex- 
 ceedingly thin, and it is difficult to distinguish its epithelium. The 
 epithelium of the pelvis of the kidney generally is polygonal in form, 
 and constitutes a tolerably thick layer. The deeper cells are small 
 and rounded. Many cells approaching to the columnar form may 
 also be observed ; and these increase in number towards the ureter, 
 which tube is lined with this variety of epithelium. ' 
 
804 BLADDER. 
 
 The ureters have muscular coat composed of two layers, an in- 
 ternal layer of circular, and an external one of longitudinal fibres. 
 These are prolonged upwards. into the pelvis of the kidney, and cease 
 at the calyces. The muscular coat is composed entirely of unstriped 
 muscular fibre cells, the nature of which will be particularly de- 
 scribed when we come to speak of the uterus, and it is invested with 
 an external coat composed of fibrous tissue. 
 
 The ureters reach the base of the bladder, run obliquely through 
 its coats for the distance of nearly an inch, and open into this viscus 
 by two narrow slit-like openings about an inch and a half behind 
 the prostate on its inferior surface, and separated from each other 
 by the distance of nearly two inches. The openings readily permit 
 the urine to pass fnto the bladder ; but, by their arrangement, com- 
 pletely prevent its reflux into the ureter ; the reflection of mucous 
 membrane at their mouth serves the ofiice of a valve. 
 
 We have already referred to the contraction of the ureters in p, 
 765 of the present volume. 
 
 Bladder. — The urinary bladder is the large receptacle into which 
 the urine is poured and in which it, accumulates as it escapes from the 
 ureters. Its size varies very greatly : it may be distended to such a 
 degree as to contain nine, or even twelve pints of urine, in which 
 case its walls of course become exceedingly thin, or it may be con- 
 tracted so much as to leave scarcely any visible cavity in its interior. 
 Its contracted muscular walls may be found half an inch or more in 
 thickness, a condition very often met with in cases of cholera. 
 
 The internal surface of the bladder has a reticulated appearance, 
 owing to the arrangement of the muscular fasciculi. The mucous 
 membrane is sometimes forced through the small spaces between the 
 fibres, and thus a number of sacculi are produced, a condition termed 
 sacculated bladder. 
 
 At the lower part of the bladder is a perfectly smooth and pale 
 surface, of the form of an equilateral triangle, the apex of which 
 points towards the prostate. The ureters open one at each of the 
 posterior angles ; and between them there is a prominent line caused 
 by the mucous membrane being somewhat raised in this situation. 
 This triangular portion of the floor of the bladder is called the tri- 
 gone (triangle), and the mucous membrane is attached more firmly 
 than in other parts to the muscular coat beneath, whence its smooth 
 character. The bladder is only partially covered with peritoneum. 
 It is connected in the male with the rectum, and in the female with 
 the uterus and upper part of the vagina by much loose areolar tissue, 
 which permits great freedom of movement of these parts upon one 
 another. 
 
 The bladder is kept in its position by certain reflections of peri- 
 toneum passing over bands of white fibrous tissue, or reflexions of 
 the vesical fascia [true ligaments), and by folds of peritoneum alone 
 {false ligaments). 
 
 The anterior reflections of the vesical fascia constitute the anterior 
 true ligaments of the bladder. These arise from the lower margin 
 of the pubis on each side of the symphysis. They then pass over 
 
EPITHELIUM OP BLADDER. 805 
 
 the upper surface of the bladder. Many of these fibres are attached 
 to the muscular fibres, and this ligament may be said to serve as the 
 tendon of attachment of many of the fibres which constitute the 
 detrusor urinse muscle. 
 
 The fundus of the bladder is connected with the umbilicus by the 
 suspensory ligament of the bladder, a reflection of peritoneum which 
 encloses the obliterated hypogastric arteries and urachus. 
 
 The muscular coat of the bladder is composed entirely of unstriped 
 fibre-cells, which are much interwoven, but may be described as ar- 
 ranged in two layers, an external longitudinal, and an internal trans- 
 verse or circular. 
 
 The latter are exceedingly numerous round the neck of the bladder, 
 whence they have received the name of Sphincter Vesicae. 
 
 The longitudinal fibres are most abundant upon the anterior and 
 posterior surfaces of the bladder, and constitute the detrusor urince 
 muscle. 
 
 The mucous membrane is of a pale colour, and is loosely connected 
 to the muscular tissue by the intervention of much loose areolar 
 tissue, in which the yellow element is abundant, except over the tri- 
 gone, where it adheres very firmly, by which a perfectly smooth 
 surface is produced in this situation. 
 
 About the neck of the bladder are a number of small glands, each 
 consisting of a few secreting follicles, opening into a short wide duct. 
 These are lined with columnar epithelium, and secrete a perfectly 
 clear transparent mucus. 
 
 Upitheliiim. — The epithelium of the bladder varies much in its 
 character in different situations. Near the orifices of the ureters it 
 is almost entirely of a columnar form ; but over the fundus, generally, 
 it consists of large circular and oval cells, with a distinct nucleus. 
 These are of very large size, and present a very characteristic ap- 
 pearance. Kblliker describes many of these large cells as lying 
 upon the surface of columnar epithelium, their deep aspect being 
 hollowed out to receive the summits of the latter cells. Towards 
 the urethra, the columnar epithelium again predominates. Epithe- 
 lium from various parts of the mucous membrane above referred to 
 is often found in the urine ; and the characters are often so distinctive 
 as to enable the observer to infer with accuracy the locality from 
 whence it was derived, a point which is occasionally of some value 
 in diagnosis. 
 
 We shall consider the anatomy of the urethra, and other organs 
 connected with the bladder, in the chapter on the Organs of Genera- 
 tion. 
 
 The student should consult the following works and monographs for more detailed 
 information upon the subjects treated of ^in the present chapter: M. Malpighi, de 
 Eenibus, 1669 ; Sohumlansky, de Structure renum, 1788 ; W. Bowman, in the Philo- 
 sophical Transactions for 1842 ; Goodsir, in the Monthly Journal of Medical Science, 
 1842 ; Dr. Johnson's article, " Ren," in the Cyclopsedia of Anatomy and Physiology, 
 and his work on Diseases of the Kidney ; and the treatises on Physiology and Minute 
 Anatomy before referred to. 
 
 Upon the Urine.— Dr. Golding Bird, on Urinary Deposits ; Dr. Bence Jones's Lec- 
 tures upon Animal Chemistry; Lehmann's Handbuch der Physiologischen Chemie, 
 
 52 
 
806 SPLEEN. 
 
 Leipzig, 1854; translated by tlie Cavendish Society. J. E. Bowman, Medical Che- 
 mistry. Beale, on the Microscope, and its application to Clinical Medicine, Chapter 
 XIV. 
 
 CHAPTER XXXV. 
 
 ON THE DUCTLESS GLANDS. — SPLEEN. — ITS CAPSULE. — TRABECULAR 
 TISSUE. — SPLEEN PULP. — SPLENIC ARTERY. — MALPIGHIAN CORPUS- 
 CLES. — YEINS OF THE SPLEEN. — LYMPHATICS. — NERVES. — CHANGES 
 IN THE BLOOD IN THE SPLEEN. USES OP THE SPLEEN. SUPRA- 
 RENAL CAPSULES. — THYROID BODY. — USES OF THE THYROID. — 
 THYMUS. — USES OF THE THYMUS. 
 
 We have now to consider a remarkable class of organs present in 
 all the mammalia, which resemble the secretory glands already 
 described in external conformation and in the possession of a solid 
 parenchyma, but differ from them in the absence of any excretory 
 apparatus suitable for carrying off the products of secretion. These 
 organs cannot be associated with such structures as the liver, the 
 kidneys, and the other glands ; inasmuch as they not only differ from 
 them in the essential particular just mentioned ; but they exhibit in 
 their internal structure no mechanical arrangement clearly adapted 
 to a secretory function ; nor is any material (save in the case of the 
 thymus) to be obtained from them bearing any resemblance to a 
 secreted product. Many physiologists, however, suppose that these 
 organs do exert an attractive influence on certain matters in the 
 blood, and separate them from it ; but this hypothesis necessarily 
 involves a second and a less plausible one, that the matter thus 
 extracted must re-enter the circulation. 
 
 These bodies agree in the common characteristic, that their paren- 
 chymatous portion consists of cells and cell-nuclei, with bloodvessels 
 in great number variously disposed. They may probably be regarded 
 as appendages to the vascular system, and, from the absence of any 
 excretory duct, they are usually designated vascular ductless glands : 
 under this head are grouped — the spleen, the supra-renal capsules, 
 the thyroid body, and the thymus. 
 
 Spleen. — The spleen is of an oval form and somewhat compressed; 
 its internal surface is concave, and its external surface is in contact 
 with the diaphragm. The spleen lies in the left hypochondrium, and 
 extends upwards as high as the tenth rib, but when enlarged reaches 
 much higher, and increases upon the lower part of the thoracic cavity. 
 The spleen is of a dark red colour, highly vascular, and of a soft 
 pulpy consistence ; it varies much in size, according to the state of 
 general nutrition, and also at different periods of the digestive process. 
 The weight of the spleen compared to that of the body at birth, is as 
 1 : 350, in adult life, 1 : 320, and in old age, as 1 : 700. The following 
 points have to be noticed in considering the structure of the spleen : 
 
TRABECULAR TISSUE OF THE SPLEEN. 807 
 
 the capsule, the trabecular tissue, the spleen pulp, or proper splenic 
 parenchyma, and the arrangement of the arteries, veins, nerves, and 
 lymphatics. 
 
 Capmle of the Spleen. — The spleen is covered by a reflection of 
 peritoneum, which extends to it from the fundus of the stomach, and 
 is called the gastrosplenio omentum. The proper capsule of the 
 spleen is composed of white and yellow fibrous tissue, and permits 
 of considerable distension. It envelops the organ entirely, and is 
 prolonged into the interior upon the vessels, which are inclosed in 
 sheaths composed of a structure closely resembling the capsule of 
 the organ. In man there is an absence of muscular fibre-cells in the 
 capsule, but in the dog and pig, and some other mammalian animals, 
 they are very numerous. 
 
 Trabecular Tissue of the Spleen. — If a section of a spleen be care- 
 fully washed under a stream of water, the dark coloured, soft, pulpy 
 matter is removed, and a perfectly white and complicated fibrous 
 meshwork remains. The interspaces bounded by these trabeculse 
 vary much in size and form ; but they are all intersected by still 
 smaller trabeculse, and these smaller spaces by fibres visible only by 
 the aid of the microscope. The network thus formed, much resem- 
 bles that of the corpora cavernosa penis, and the fibres composing 
 it are intimately connected with the fibrous capsule of the organ, 
 and also with the sheaths of the vessels supplying 
 it. The spaces or interstices communicate freely I'ig- 245. 
 
 with each other, and in them is situated the pulpy 
 tissue of the spleen. 
 
 The larger trabeculse, like the fibrous capsule of 
 the organ, are composed chiefly of white fibrous tis- 
 sue, with some fibres of the yellow element. The 
 smaller trabeculae are composed of elongated spindle- 
 shaped cells, about the 300th of an inch in length, 
 and about the 55^5*^ "f ^■'^ '^'^^^ hvod^A. in the cen- tecSarSeofspiee'a' 
 tre, which is their widest part. They contain a. tf„*'e"" MaS^mef 2w 
 distinct elongated or oval nucleus. The nucleus is diameters. 
 often found bulging upon one side of the fibre cell, 
 and in some instances appears only connected with it by_ a stalk. 
 The cell is often much curved, and sometimes bent upon itself, an 
 appearance arising from its mode of development, which takes place, 
 according to the observations of Mr. H. Gray, by the solution of 
 the cell wall at a point opposite the nucleus, which latter remains, 
 and the cell wall itself forms the fibres which are prolonged from 
 either side of it. 
 
 In several of the mammalia, both in the capsule and also in the 
 trabeculse, a number of muscular fibre cells, with a distinctly oval 
 elongated nucleus, are present. The fibre may be entirely composed 
 of these cells. They are not present in the human spleen, but may 
 be readily demonstrated in that of the sheep. _ The spleen possesses 
 very slight power of contractility, and in experiments upon the spleen 
 of the ox and sheep, Mr. Gray was unable to_ obtain marked con- 
 tractions by the application of a strong galvanic current. 
 
808 SPLEEN PULP. 
 
 Spleen Pulp. — The spleen pulp, or parenchyma, the proper tissue 
 of the spleen, is composed of peculiar colourless cells, containing 
 
 masses of colouring matter, free 
 Fig. 246. coloured particles, granular mat- 
 
 ,,««„,,,, ter and blood corpuscles. 
 
 I •««''lf™*fci'|[ The colourless portion of _ the 
 
 . k spleen pulp is composed princi- 
 
 r I pally of small circular cells, or 
 
 ' ( t •■ "I i nuclei, about the size of a blood 
 
 ^1 I I corpuscle, and having a faintly 
 
 / I I I granular appearance. These small 
 
 I V I ' lj * nuclei vary somewhat in size, and 
 
 jl / j * ' J f are interspersed with a consider- 
 
 able quantity of granular matter, 
 i ( /f ^ i / which is often collected around 
 
 jj £ •,. ■, I- J ^ them. The spleen pulp also con- 
 
 "■'■"''"*'■''*' tains a few nucleated vesicles, 
 
 nearly xxf'sts*^ °f ^^ ^^^^ ™ *^'*" 
 meter. 
 
 These colourless elements con- 
 stitute a considerable proportion 
 of the spleen pulp, and are in con- 
 tact with the capillary walls, and 
 
 Mnscnlarfibre cells from tbe spleen of the sheep, with the Malpighian COrpUSCleS 
 magnified 400 diameters, a, a. Fibres more highl v f ,i _„i..„ n-«n^i ■.r^-^intl^r^ 
 
 malniaed. After Mr. Gray. 01 the Spleen, (jrreat variation 
 
 occurs in the size and general 
 character of the cells and nuclei which compose the colourless ele- 
 ments, and they vary much in quantity in different physiological 
 conditions of the system. Mr. Gray has shown, that in well-fed 
 animals" they are much more abundant than in those supplied with 
 an insufficient quantity of food, and their proportion increases after 
 the completion of the digestive process. 
 
 They are composed of a proteine compound, and in their chemical 
 characters closely resemble the white corpuscles of the blood. 
 
 The red colour of the spleen pulp is due to the presence of a great 
 number of blood globules and coloured corpuscles, free or contained 
 within cells. 
 
 The blood globules are frequently observed to be smaller than in 
 other situations ; their outline is often indistinct ; sometimes their 
 surface appears corrugated or shrunken, and their walls in some 
 places collapsed ; their ..outline is irregular and angular, and in many 
 instances corpuscles are seen evidently breaking up into small irregu- 
 lar masses of red colouring matter. These appearances indicate that 
 the red blood corpuscles are undergoing a process of disintegration, 
 but this change also appears to be effected in another and very pecu- 
 liar manner, which was first described by KoUiker. Several blood 
 corpuscles (from one to nine or ten) collected together, appear to 
 become covered with an investing membrane, adhering to the interior 
 wall of which, a distinct nucleus may be observed. Such appears to 
 be the manner in which these blood corpuscle-holding cells are 
 
COLOUKLESS CONSTITUENTS. 
 
 809 
 
 formed, but whether the nucleus precedes the formation of the cell 
 or succeeds it, is not known. The blood globules within now undergo 
 disintegration in the manner just referred to, and at length the cell 
 contains only coloured granules, varying in size and form. These 
 granules gradually become of a golden yellow colour, and then paler, 
 until at last the contents of the cell become almost decolourized. 
 
 Fig. 247. 
 
 Pulp of the human spleen, a, a. Blood corpuscles. 6, 6. Dotted nuclei, c, c. Ifucleated vesicles. 
 d, d. Coloured corpuscles of hfematine. From Gray on the Spleen. 
 
 Occasionally, red crystals are seen in the blood corpuscles of the 
 splenic parenchyma, as was first observed by Funke ; and not un- 
 frequently numerous free coloured acicular crystals are met with. 
 
 These appear to be the most important changes which take place 
 in the disintegration of the red blood corpuscles in the spleen pulp. 
 In some animals, the disintegration seems to occur entirely within 
 the large cells ; while in others, the blood corpuscle-holding cells are 
 very rarely met with, and the blood globules become broken down 
 into coloured granules without being at any time enclosed in a cell. 
 In other cases, again, both processes occur. In the course of very 
 numerous observations upon the human subject, Mr. Gray only ob- 
 served blood corpuscles enclosed in cells in two instances, and then 
 in very small number. 
 
 We may observe here, that Gerlach interprets these facts in a 
 totally different manner, and considers that the changes taking place 
 in the blood corpuscle-holding cells occur in the reverse order to 
 that which we have described. In fact, he considers that the blood 
 
810 
 
 SPLEEN. 
 
 corpuscles ^reformed in these cells, commencing as Irregular yellow 
 granules, and gradually becoming developed into the perfect red 
 blood globule. In this view Virchow appears to coincide. Dr. 
 Hughes Bennett, of Edinburgh, also considers the spleen as a blood- 
 forming organ. 
 
 The changes above referred to take place in the spleen pulp which 
 lies between the trabeculse, and, of course, external to the capillary 
 vessels. Now, we have to inquire how the blood corpuscles leave 
 the vessels and enter the pulp. 
 
 Mr. Gray has shown that many of the capillary vessels are not 
 directly continuous with the veins, but that the blood, in passing 
 from one set of vessels to the other, traverses intercellular spaces in 
 the spleen pulp. The veins also, in many cases, appear to com- 
 mence in intercellular spaces, so that it is not difficult to conceive 
 how the contents of the vessels extravasate into, and become mixed 
 with, the constituents of the pulp, especially when the organ is dis- 
 tended with blood. These changes appear also to take place to a 
 more limited extent within the veins themselves. Although this may 
 be the correct explanation of the manner in which the cells in the 
 pulp communicate with the blood in the vessels, we cannot look upon 
 it by any means as demonstrative. 
 
 Splenic Artery. — The splenic artery is the largest branch of the 
 cceliac axis, and the size of this vessel in proportion to the organ to 
 
 rig. 248. 
 
 Transverse section of the linman spleen, showing the mode of distribution of the arteries, and the 
 manner in wUch their sheaths are formed. After Mr. H. Gray. 
 
 which it is distributed, is considerably larger than that of other 
 glands, with the exception of the thyroid. The large size of the 
 vessel would lead to the inference that more arterial blood is dis- 
 tributed to the spleen than is required for the mere purposes of nutri- 
 tion. The branches of the artery are invested with sheaths derived 
 from and continuous with the fibrous capsule of the organ, and they 
 
MALPIGHIAN CORPUSCLES. 
 
 811 
 
 have a similar structure to it. Each arterial branch is distributed 
 to a particular part of the organ, and it does not anastomose with 
 contiguous branches. The smaller arteries, about the jj^ of an inch 
 in diameter, are connected with the Malpighian bodies, which are 
 usually placed in the points of bifurcation of the vessel. 
 
 Malpighian Corpuscles. — Upon making a section of a fresh ox's 
 spleen, a number of small round whitish bodies will be seen. They 
 are sometimes collected in groups of four or six together, and appear 
 to be connected with the smaller arteries, which are in close prox- 
 imity to them. These small bodies have been named Malpighian 
 corpuscles from their discoverer ; they are in close contact with the 
 spleen pulp, except at the points where they are in connection with 
 the coats of the artery. 
 
 The Malpighian corpuscles are very distinct in pigs, sheep, oxen, 
 and guinea pigs. In most other mammalia they are to be demon- 
 strated, although with greater difficulty. In the human subject they 
 are constantly present ; but often are not to be distinguished in con- 
 sequence of rapidly undergoing post-mortem change. In birds, these 
 bodies are very numerous, and have been observed, by Miiller, in 
 the chelonia, among reptiles, but they cannot be seen in the naked 
 amphibia. In fishes, they appear to be absent. 
 
 Fig. 249. 
 
 This figure shows the conneotion of a splenie corpuscle -with the neighbouring vessels, according to 
 Mr. H. Gray. The corpuscle is placed at the angle of bifurcation of one of the small arteries, its ex- 
 ternal surface being covered by a close and delicate capillary plexus, irhilst its circnmference is in- 
 vested by a mesh of large veins, which radiate in every direction from its margins. The compara- 
 tive size of the arteries and veins, the capillary plexus of the pulp, and the mode In which these 
 vessels communicate with the veins, are shown in this figure. 
 
812 SPLEEN. 
 
 The splenic corpuscles are placed upon a small branch of the 
 arteries as upon a short peduncle or stalk, which sometimes consists 
 only of fibrous tissue, prolonged from the sheath of the vessels, or 
 they lie in the angle formed by the divergence of two branches from 
 each other. The artery divides into numerous branches upon the 
 surface of the Malpighian corpuscles. The observations of KoUiker 
 and Dr. Sanders, which have lately been confirmed by Prof. Huxley, 
 have shown that the substance of the corpuscle itself is traversed by 
 small capillary bloodvessels. These small vessels probably pour their 
 blood into small veins which surround the corpuscle, and are of 
 considerable size. According to Mr. Gray, these veins receive the 
 secretion of the Malpighian bodies. 
 
 The Malpighian corpuscle does not appear to us to be invested 
 with a distinct and well-defined membranous capsule ; but we are 
 inclined to agree with Remak and Leydig, who represent their con- 
 tents as not being separated by any distinct line of demarcation 
 from the splenic pulp, although the fibrous tissue derived from the 
 external wall of the vessels appears to form a sort of imperfect 
 capsule. The cells of which these bodies are composed readily pass 
 from them into the pulp. Mr. Gray has made the interesting obser- 
 vation, that these bodies are very large, and well defined in well-fed 
 animals, and that, during the latter part of the digestive process, 
 they increase in size, while, in animals insufficiently fed, they are 
 very small, or absent altogether. In the latter, little increase is 
 noticed in their size after digestion. Their increase is considerable 
 under the influence of an albuminous diet ; but when animals are 
 confined to fat or gelatine, these bodies are not to be distinguished. 
 
 Veins of the Spleen. — The splenic vein is the largest branch of 
 the vena porta, and, like the others, is destitute of valves. The 
 branches into which the vein divides, do not communicate with each 
 other in the substance of the organ. Mr. Gray describes three 
 difiFerent modes in which the veins commence : 1. As continuations 
 of the capillaries of the arteries, which is the most common method : 
 2. By intercellular spaces in the substance of the spleen pulp through 
 which the veins communicate with each other. The smallest veins 
 commence in this manner ; or 3. By forming an imperfect capsule 
 to each Malpighian body. This latter mode of commencement has 
 not been described by other observers, and Mr. Gray considers these 
 small veins as the channels by which the secretion of the Malpighian 
 bodies is carried into the circulation. 
 
 The vein ramifies abundantly upon the surface of the spleen, and, 
 as it enters into the organ, receives an investment of fibrous tissue, 
 which is prolonged upon the branches, forming their sheaths, which 
 are connected with the trabeculse. 
 
 Lymphatics. — But little is known of the ultimate arrangement of 
 the lymphatics of the spleen, or of the manner in which they com- 
 mence. They are certainly not connected with the Malpighian cor- 
 puscles, nor can we look upon them as the channels which carry off 
 the secretion of the organ, a view which has been advocated by many 
 observers. 
 
USES OF THE SPLEEN. 813 
 
 Nerves. — The nerves of the spleen are derived from the splenic 
 plexus formed by branches from the left semilunar ganglion, and 
 from the right pneumogastric nerve. The branches are distributed 
 to the coats of the arteries ; they may be traced upon them for a 
 considerable distance, but gradually they become lost. 
 
 Changes in the Blood in the Spleen. — The most important pecu- 
 liarities in splenic blood appear to be the following : The total 
 quantity of solid matter is considerably less in the blood of the 
 splenic vein than in arterial or venous blood, and the blood cor- 
 puscles are reduced to half the quantity. The greatest reduction 
 seems to occur at the period of the greatest turgescence'of the spleen. 
 Mr. Gray has made the very interesting observation, that in starved 
 animals no change is observable. The albumen is increased, par- 
 ticularly when the amount of blood corpuscles is much diminished. 
 The quantity of fibrine in splenic blood, is also found to be increased. 
 The serum is often observed of a pale reddish-brown colour. 
 
 Uses of the Spleen. — We have now to consider the uses of the 
 spleen in the animal economy. From the large quantity of elastic 
 tissue in its capsule and trabeculae, it seems eminently adapted to 
 undergo great changes in volume ; and the direct experiments of 
 Dobson, and many other observers, have proved that it becomes 
 much enlarged during digestion, as well as when blood was injected 
 into the jugular vein. Connected with the large veins of the portal 
 system, it forms a dilatable diverticulum, or reservoir, in which, blood 
 may, for a certain time, be contained, thus preventing dangerous 
 congestion of the veins of the liver, and some other abdominal viscera, 
 and, indeed, of the venous system generally. The spleen does not 
 appear to be contractile. In several careful experiments, Mr. Gray 
 was never able to cause more than a slight corrugation of the surface 
 of the organ by the galvanic current, although active contractions 
 could be produced in the oesophagus, or stomach, under similar 
 circumstances. In no instance out of twenty experiments, was 
 blood expelled from the organ, or its diameter diminished. Not 
 only does the spleen perform this physical office, but, as has been 
 shown, certain important chemical and microscopical changes are 
 found to have occurred in the blood which has passed through this 
 organ. In 1847, Kolliker advanced the theory that blood corpuscles 
 became disintegrated in the spleen, an opinion which was afterwards 
 supported by Bcker and Bdclard. From various facts which we have 
 alluded to, we cannot but look upon this point as decided in the 
 affirmative, although others have been led to adopt the view, that 
 blood corpuscles are actually formed, instead of being disintegrated 
 in this organ. K(511iker thought that the 'colouring matter of the 
 blood was changed in the spleen, and converted into the peculiar 
 colouring matter of the bile; but Mr. Gray has shown, that yellowish- 
 green bile is found in the gall-bladder of the chick, at a period con- 
 siderably antecedent to the development of the splenic vein. The 
 small size of the spleen in the foetus, as compared with its increase 
 after birth, and in adult life, renders it improbable that in intra- 
 
814 SUPRA-KBNAL CAPSULES. 
 
 uterine life it acts the part either of a blood-forming, or blood-de- 
 stroying, organ. 
 
 Its great increase in size, in well-fed animals, and its diminution 
 in insufiSciently-fed animals, and, especially its increase after the 
 completion of digestion, render it extremely probable that it has the 
 power of storing up albuminous material for future consumption, 
 when a larger quantity of nutrient material is taken than is required 
 for the immediate wants of the system. The cells of the Malpighian 
 corpuscles appear, from Mr. Gray's observations, to be the organs 
 especially concerned in this process. 
 
 Supra-renal Capsules. — The supra-renal capsules are two bodies 
 of a somewhat triangular form, situated one on each side of the 
 spine, a little above the corresponding kidney, to the capsule of which 
 each is connected by loose cellular tissue. 
 
 Each supra-renal capsule is about an inch and a half in depth, 
 somewhat less in width, and usually about half an inch in thickness. 
 The weight varies from one to two drachms. The gland is inclosed 
 in a thin fibrous capsule, which dips down into its substance. It is 
 surrounded with loose areolar tissue, containing an abundant quantity 
 of fat. 
 
 Upon making a section through the body, it is found to be com- 
 posed of two distinct portions, a eortioal and a medullary part. The 
 former is of a yellowish colour, shading into a brown border towai;^s 
 the interior. It tears somewhat readily, and then exhibits a fibrous 
 appearance. The medullary substance is of a paler colour, unless 
 the vessels are injected with blood, and of a somewhat softer consist- 
 ence. If the gland be not perfectly fresh, a cavity is usually seen 
 in the interior, which results from the breaking down of the medul- 
 lary tissue. 
 
 The cortex is divided into a series of compartments or tubes by 
 septa of fibrous tissue prolonged inwards from the capsule of the 
 organ. These spaces extend through the entire thickness of this 
 part of the body, and pass from the surface vertically inwards. They 
 contain numerous oval or spherical bodies, varying considerably in 
 length. These have been looked upon by Ecker as gland-follicles, 
 but Kolliker considers them merely as aggregations of cells not in- 
 vested with a distinct membrane, or inclosed in a larger cell. They 
 are separated from each other by meshes of areolar tissue, the fibres 
 of which often appear to be connected with the surface of the mass. 
 In the outer part of the cortex separate cells, filled with pigment 
 granules, are usually to be met with ; but in the inner portion, round 
 or oval vesicles are found, which are filled with oil globules. 
 
 The medullary substance is composed of a network of areolar 
 tissue which is prolonged from the cortex, and contains numerous 
 vessels, in the meshes of which are found many cells, some of which 
 contain fat or granular pigmentary matter. A distinct nucleus and 
 commonly a nucleolus are seen, and often the cells have many angu- 
 lar processes, or are much branched ; indeed, these cells present an 
 appearance much resembling that of the nerve vesicle. 
 
 Besides the fibrous, vascular, and cellular elements just described, 
 
THYROID, 815 
 
 the medullary portion of the supra-renal hodies is very largely sup- 
 plied with nerve fibres derived from the semilunar ganglia and solar 
 plexus, with a few fibres also from the pneumogastric, and from the 
 phrenic. The nerves appear to perforate the cortical substance in 
 several places, pass through this, and enter the medullary, where 
 they form a plexus amongst the fibrous tissue. The mode of their 
 termination has not been made out. 
 
 The function of these peculiar bodies is entirely unknown. From 
 the great dissimilarity of structure observed in the cortical and 
 medullary portions of the organs, it is probable that each performs 
 a distinct and separate oflBce. In the present state of our knowledge 
 we may continue to classify the former with the ductless or vascular 
 glands, but, from the existence of cells much resembling nerve vesi- 
 cles, and an abundant plexus of nerve fibres, it appears more correct 
 to regard the latter as connected in some manner with the nervous 
 system and probably with the sympathetic. Bergman thinks that 
 this part of the supra-renal body may, perhaps, bear a relation to the 
 sympathetic, similar to that whidh the pituitary body does to the 
 brain. It is interesting to note, in connection with this subject, that 
 our friend, Mr. Brown- S^quard, has observed congestion, and hyper- 
 trophy of the supra-renal capsules, after injuries to the chord in the 
 dorsal region. 
 
 Dr. Addison has lately published an account of several very in- 
 teresting cases of disease of the supra-renal capsules, associated with 
 " anaemic general languor and debility, remarkable feebleness of 
 heart's action, irritability of the stomach, and a peculiar change of 
 colour in the skin."* 
 
 Thyroid. — The thyroid body, or gland, as it is sometimes called, 
 is a soft, and very vascular organ, situated upon the lateral aspect 
 of the upper part of the trachea, as far upwards as the sides of the 
 larynx. It consists of two lateral lobes, united by a thin narrow 
 portion, which has a similar structure to that of the gland itself, 
 extending across the front of the third or fourth rings of the trachea, 
 and known as the isthmus. The middle lobe, which varies some- 
 what in position, is a thin process, extending upwards from the 
 isthmus, or one of the lateral lobes, and often reaches as high as 
 the hyoid bone, to which it is attached by loose fibrous tissue ; 
 indeed, this process itself is not unfrequently composed of fibrous 
 tissue only, and sometimes contains a few fibres of the thyro-hyoid 
 muscle. 
 
 The thyroid body itself is made up of a vast number of small 
 lobules, which are aggregated together in larger globular or oval 
 masses, of which the entire substance of the gland is composed. 
 These are all surrounded by, and connected together with areolar 
 tissue, and each subdivision itself consists of a number of small 
 closed vesicles, between which the vessels ramify, also closely in- 
 
 * On the Constitutional and Local EflFecta of Disease of the Supra-renal Capsules, by 
 Thomas Addison, M. D., Senior Physician to Guy's Hospital, 1855. 
 
816 THYMUS. 
 
 vested with areolar tissue, varying considerably in size, and con- 
 taining fluid, or thick gelatinous matter. 
 
 Each vesicle may, therefore, be described as consisting of a fibrous 
 coat, composed of areolar tissue, internal to which there exists a 
 delicate basement membrane, lined by cells of epithelium, which vary 
 somewhat in character, but usually are seen as polygonal, or almost 
 circular cells of a faintly granular appearance, and having a nucleus, 
 which, however, is by no means invariably present. In most in- 
 stances, the vesicle can be seen to be lined with a single layer of this 
 epithelium, and many free cells are usually found floating in the 
 fluid contained in the cavity. 
 
 The fluid in the vesicles is coagulated by heat and nitric acid, and 
 evidently contains a large quantity of albumen. 
 
 The stroma of the gland consists of fibres of both the white and 
 yellow element, and it supports the bloodvessels, which are ex- 
 ceedingly numerous, and form a capillary plexus round each vesicle. 
 
 The lymphatics in the thyroid are numerous, but of their ultimate 
 distribution nothing is known. 
 
 The following are analyses of the thyroid body, by Dr. Beale.* 
 
 Human. Ox. 
 
 Water 70-60 71-34 
 
 Solid matter 29-40 28-66 
 
 Fibrinous and albuminous matter, vessels, and 
 
 fat 26-384 24-628 
 
 Extractive matter . . . . . . 1-70 — 
 
 Extractive matter, with gelatine .... — 2-888 
 
 Alkaline salts -50 -642 
 
 Earthy salts -816 -502 
 
 Uses of the Thyroid. — Of the uses of the thyroid but little is 
 known. The material found in the vesicles is of an albuminous 
 nature. Mr. Simon has advanced the opinion that the thyroid acts 
 as a diverticulum to the cerebral circulation, and that its nutri^on 
 bears a certain relation to that of the nervous matter of the brain. 
 When the latter is quiescent, the thyroid is supposed to be active in 
 removing from the blood, and storing up in its cells, certain con- 
 stituents which are required by the brain only in its active state, and 
 which are diverted to it when it resumes its activity, This view is 
 based upon the important fact, that the arteries of the thyroid body 
 arise in close proximity to those which supply the brain, the superior 
 thyroids coming off from the external carotid, just immediately above 
 the point of bifurcation of the common carotid, and the inferior 
 thyroid arteries, from the subclavian, almost immediately opposite 
 the origin of the vertebrals. 
 
 Thymus. — The thymus body or gland is an organ only distinctly 
 recognizable during early life. It appears to reach its largest size 
 between the first and third years ; but much variation occurs in this 
 point in different individuals. It lies partly in the thorax and partly 
 in the neck, and is composed of two lobes, which vary considerably 
 in size, sometimes the right and sometimes the left being the largest. 
 
 * Dr. Handfleld Jones, article " Thyroid," Cyolopsodia of Anatomy and Physiology. 
 
MR. SIMON'S RESBAKCHES. 
 
 817 
 
 The organ rests upon the front of the aortic arch and large arte- 
 ries rising from it, and also on the left vena innominata. It is 
 covered by the sternum, and at birth reaches down to the fourth 
 costal cartilage. It extends upwards into the neck, as high as the 
 thyroid bo'dy, and lies upon the front and side of the trachea. 
 
 The researches of Sir Astley Cooper, and more recently those of 
 Mr. Simon, show that this organ consists essentially of an elongated 
 tube, from all sides of which extend numerous small follicles or sac- 
 culi, which pour their contents into the central cavity. Sir Astley 
 Cooper unravelled the gland, and, by having previously injected the 
 central cavity and follicles with alcohol, or coloured size, was enabled 
 to make out their relations and arrangement; although, by these 
 processes^ it is probable that he distended the central cavity to a 
 greater extent than natural, and was thus led to look upon it as 
 much more extensive than it was subsequently proved to be by the 
 conclusive observations of our friend Mr. Simon, which are published 
 in his well-known essay. 
 
 The latter excellent observer, carefully watched the development 
 of this gland, and thus was the first to make out accurately its 
 - anatomy. 
 
 It is probable that it first arises from a row of cells arranged in 
 linear series, which coalesce, and thus become converted into a nar- 
 row tube. The wall of this 
 
 tube then bulges at intervals, ^'g- 250. 
 
 and vesicular cavities are gradu- 
 ally formed. These vesicular 
 dilatations are much more abun- 
 dant in some situations than in 
 others ; and the primary offset 
 divides in a dichotomous or 
 quaternary manner, until, from 
 the number and irregular dis- 
 tribution of these vessels, the 
 gland assumes its ultimate shape 
 and character. The closed 
 cavity of the gland contains 
 granular matter, with numer- 
 ous nuclei dispersed through 
 it. In a thin section, the out- 
 line of the cavities can be 
 readily seen ; they vary from 
 the l-50th to the l-18th of an 
 inch in diameter, and contain 
 numerous granular and nearly 
 spherical nuclei, which are, for 
 the most part, about l-4000th of an inch in diameter, but vary con- 
 siderably in size. Dr. Handfield Jones observes that before any 
 appearance of atrophy has taken place, these elements are alone 
 found, and there is an entire absence of oil particles, and granular 
 material. The nuclei seem to fill the ultimate vesicles completely.. 
 
 fefs 
 
 a. 'Primordial cells in 'a row. 6. Isolated cell, 
 unconnected with tke row, and -undergoing develop- 
 ment in its original cell shape, e. Primary tube, 
 formed by the fusion of the cells, d. Second stage of 
 development of the thymus, showing bulgings of tube 
 in different stages, which ultimately become them- 
 selves divided. After Simon. 
 
818 
 
 THYMUS. 
 
 a. Binary and quaternary division 
 of simple follicles. 6. TTnusual ap- 
 pearance, in which the follicles must 
 have increased considerably in length 
 before undergoing division. From the 
 foetal lamb. 
 
 c. Mature structure of thymus, show- 
 ing the arrangement of the vesicles 
 belonging to one cone, d. Tube of 
 gland. After Simon. Keduced. 
 
 Uses of the Thymus. — Mr. Simon regards the secretion of the 
 thymus as allied to proteine, and of a nutritious nature. 
 
 In the human foetus, the thymus cannot be detected before the 
 
 ninth week, and its functional activity 
 is greatest in the early period of life, 
 before the muscular system is in a very 
 active state ; for when the muscles be- 
 come more fully active, the thymus ap- 
 pears not to be required. It seems con- 
 nected with the preparation of matter 
 for the pulmonary organs in the " age 
 of early growth." Arguing from these 
 and many other facts, Mr. Siifton looks 
 upon the thymus as acting " as a sink- 
 ing fund in the service of respiration." 
 From the twentieth to the twenty-fifth 
 year it diminishes rapidly in size, until 
 no trace of it can be detected in the 
 areolar tissue of the mediastinum. In 
 hibernating animals, previous to the 
 commencement of the winter sleep, the 
 thymus becomes gorged with fat, which 
 is slowly consumed during the period of 
 hibernation. It has been remarked, that 
 the use of the thymus at the diflferent periods of active growth and 
 hibernation is distinct. In the latter case, it doubtless supplies 
 hydro-carbonaceous matter for respiration ; but its office, during the 
 former period, appears rather to be that of elaborating fibrine from 
 albumen and other substances by the action of its numerous nuclei. 
 As the absorbent and other glands connected with the vascular sys- 
 tem become developed, there seems no longer any need of a special 
 organ for this purpose, and consequently the thymus soon disappears. 
 Professor Paget and Dr. Handfield Jones express themselves in 
 favour of this latter view. In the present state of our knowledge, 
 perhaps no better hypothesis of the office of this gland can be sug- 
 gested. The whole subject of the physiology of the vascular duct- 
 less glands (if glands they be) is involved in deep obscurity, and it 
 is impossible to form a theory of their respective functions which is 
 perfectly satisfactory. Not less obscure are their morbid conditions, 
 upon which the improved anatomy of the last few years has thrown 
 but little light. 
 
 The student is referred to the following works for a more detailed statement of the 
 various views now held upon the anatomy and physiology of the vascular glands. 
 
 Spleen. — KoUiker's " Mikroscopische Anatomie," and the Article "Spleen," in the 
 Cyclopaedia of Anatomy and Physiology; Ecker's Art. "Milz," in Wagner's Hand- 
 worterbuoh ; Sanders " On the Structure of the Spleen," in the Annals of Anatomy 
 and Physiology; Bennett "On Leucocythemia:" Mr. Gray's Astley Cooper's Prize 
 Essay upon the " Structure and Use of the Spleen," 1854 ; Mr. Simon's Astley Cooper's 
 Prize Essay on the "Thymus Gland," 1845; also his paper upon the " Thyroid," Phil. 
 Trans., 1844; Dr. Handfield Jones' Articles "Thymus" and "Thyroid," in the 
 Cyclopaedia of Anatomy and Physiology. 
 
GENERATION. 
 
 819 
 
 CHAPTER XXXVI. 
 
 ON GBNBEATION. — FISSIPAEOUS MULTIPLICATION. — GBMMIPAROTJS 
 MULTIPLICATION. — TRUE GENERATION. — METAMORPHOSIS. — META- 
 GENESIS, OR ALTERNATION OF GENERATIONS. — SEXUAL ORGANS. 
 — INVERTEBRATA. — INFUSORIA. — POLYPS. — ACALEPH^. — ECHINO- 
 DERMATA. — BNTOZOA. — ANNELIDA. — MOLLUSCA. — CRUSTACEA. — 
 INSECTA. — PISCES, — REPTILIA. — AVBS. — MAMMALIA. 
 
 Amongst the lower classes of organized beings, both in the animal 
 and vegetable kingdom, the multiplication of individuals, or the pro- 
 pagation of the species, is provided for by three dififerent processes, 
 while in the highest forms of animal life the process of generation is 
 restricted to one of these types. 
 
 The simplest manner in which the multiplication of individuals 
 takes place, consists in the division of the being into two, each of 
 these again dividing into two others, and so on ; this is multiplication 
 by fission. 
 
 The second mode of increase consists in the formation of a bud at 
 some part of the body of the parent : this bud is gradually developed, 
 drops off, becomes independent of its parent, and ultimately assumes 
 a perfect form, resembling in all particulars that from which it 
 sprung. 
 
 The third mode differs materially from the two former, in the fact, 
 that the new organism results from a series of changes occurring in 
 an impregnated ovum, which is produced by the mutual action of the 
 contents of two dissimilar cells, the products of distinct parental 
 organs. The new body differs essentially from either of the two cells 
 which produced it. This is true generation, 
 
 Fissiparous Multiplication. — In the lowest plants, such as the 
 lichens and fungi, this mode of multiplication^very commonly occurs. 
 The cell, or cells, of which the plant consists, divide and subdivide ; 
 and, in this manner, new organisms are produced. The same mode 
 of reproduction' is also seen to be very common amongst the in- 
 fusoria, and may be watched in the common vorticella. 
 
 Fis. 252. 
 
 Vorticella Microstoma multiplying by spontaneous longitudinal division, from Ebrenberg. 
 
820 GENERATION. 
 
 The joints of the common tape-worm multiply in this manner, and 
 after a time, ■when perfectly developed, become free and separate 
 from the trunk of the worm. Amongst the worms (Annelida) repro- 
 duction takes place partly in this manner. In the Nais, three or 
 four young worms, resulting from the division of the parent, may 
 often be seen still connected with its body. As these become de- 
 veloped, they are disconnected from the parent, and, in their turn, 
 give rise to others by a similar process. 
 
 Fig. 253. 
 
 NaYs proTjoscidea, multipl^ring by spontaneons transrerse division, showing the body of the p^ent 
 •worm and three yonng ones in different stages of development, a. Point at which new segments are 
 being formed. After Mlilier. 
 
 In the above instances, multiplication by division occurs as a na- 
 tural process ; but there are many instances in which the parts re- 
 sulting from artificial division ultimately become developed into a 
 perfect animal. Thus a planaria, or a polyp, may be divided into 
 many segments ; and each portion has the power of absorbing to 
 itself nutriment, and of becoming developed into a perfect form. 
 The slightest handling, again, causes some animals to break up in 
 pieces, and each separate part becomes a new being. 
 
 Multiplication hy Q-emmation. — A bud consists of a mass of cells, 
 which possess the power of development, under favourable circum- 
 stances, into a form identical with that from which they were pro- 
 duced. In consequence of this property, the bud of a plant has been 
 termed a phyton; and a tree must, therefore, be looked upon as an 
 assemblage of these phytons. We must, however, bear in mind, that' 
 all buds have not this power, as, for instance, flower buds do not 
 give rise to the formation of new buds of any sort, but produce 
 
 Amongst the lower animals, reproduction by buds is very common, 
 and can be readily examined in the vorticellse and polyps. 
 
 In the hydra, the first change which is observed consists in the 
 formation of a little elevation which soon becomes globular ; next a 
 cavity is formed in this globular mass, and becomes continuous with 
 that of the parent. After a time the channel of communication 
 closes, and the bud begins to assume the form of a polyp, which 
 ultimately drops off ; and in this way a ijew creature is formed. The 
 
METAMOKPHOSIS. 
 
 821 
 
 Figures of ttie fresh-water hydra and 
 vorticella, showing . the multiplication 
 of new individuals hy the formation of 
 huds. 
 
 echinococci multiply by the formation of Kg- 254. 
 
 buds upon the internal surface of the 
 hydatid vesicle. At first they are at- 
 tached by a sort of stem ; but ultimately 
 they become free, and move about in 
 the fluid of the parent cyst by aid of 
 their hooks and suckers. 
 
 A bud differs from an ovum in the 
 important particular, that it contains 
 within itself the power of development, 
 ■while the latter is incapable of becom- 
 ing developed into the form of its pa- 
 rent until it has been subjected to the 
 action of the contents of another cell. 
 The only resemblance between a bud 
 and an ovum is, that in both the organization is imperfect. 
 
 True Generation. — The processes of multiplication above referred 
 to must be distinguished from the one which we are now about to 
 consider. Trne generation consists in the union of the contents of two 
 different cells, called respectively the " sperm cell" and "germ cell," 
 and the production of a structure differing from both, from which the 
 new being is ultimately evolved. The simplest form of this process 
 is seen in the lower algae in conjugation. At first, the opposite cells 
 of two filaments are seen to be swollen on the side turned towards 
 each other ; the swelling increases until a sort of process is formed 
 from each : these at length meet ; the walls become fused, the cavi- 
 ties continuous, and the contents of the two cells 
 become mixed. From this admixture a new body, 
 termed a spore or sporangium, results, by the de- 
 velopment of which the new plant is formed. 
 
 In the higher plants and in animals, distinct 
 organs are set apart for the formation of the sperm 
 cells and germ cells. By the action of the con- 
 tents of the sperm cell the ovum becomes impreg- 
 nated ; and under favourable circumstances, often 
 quite independent of the parent, changes result 
 which give rise to the formation of the embryo 
 from which the adult animal is gradually deve- 
 loped. 
 
 Now, either the perfect form of the being may 
 be attained by the gradual and progressive deve- 
 lopment of the embryo, or several distinct phases 
 of existence may be passed through before the 
 creature reaches its perfectly developed form. 
 This latter condition is seen in many of the lower 
 classes of animals, and is familiar to us in the 
 class of insects ; it is, in fact, what we understand 
 by metamorphosis. 
 
 Metamorphosis. — In metamorphosis, it must be 
 carefully borne in mind, that it is the self-same 
 53 
 
 rig. 255. 
 
 Conferva bipunctata in. 
 the act of conjugation, 
 after Meyen. The cells 
 from contiguous fila- 
 ments approach each 
 other, and ultimately 
 their cavities coalesce. 
 The oval spores result- 
 ing from the action of 
 the contents of one cell 
 upon the other are seen- 
 in two of the cells. 
 
822 GENERATION. 
 
 embryo which passes through certain transitional stages or phases, 
 and ultimately becomes the perfectly developed animal ; a condition 
 essentially different from that which we shall next consider under 
 the term Metagenesis, or alternation of generations, in which suc- 
 cessive generations of larval creatures are produced from larvae 
 without the occurrence of any fresh generative act. Here, instead 
 of one individual passing through several transitional forms, an im- 
 perfectly developed creature produces a multitude of forms, resem- 
 bling either itself or the perfect individuals from which the ovum 
 was formed which evolved it. 
 
 Metagenesis. — In some animals, the embryo, instead of being 
 developed into a form resembling that of its parents, only attains a 
 sort of larval condition, the offspring of which, however, return to 
 the perfect type, instead of assuming the character of their larval 
 patient. Now, between the fully-developed animals of one genera- 
 tion and those of the next succeeding there may be several series of 
 these imperfect or larval forms ; each larva producing without ahy 
 generative act, and, indeed, without itself possessing true generative 
 organs, many similar larval forms, until at last these larvae, instead 
 of producing larvae, give rise to perfect forms, which propagate only 
 by the production of ova. 
 
 This curious phenomenon occurs amongst many classes of animals ; 
 and the subject of late years has engaged the attention of m§.ny 
 naturalists. Steenstrup has described the process under the term 
 alternation of generations. Owen terms it metagenesis and parthe- 
 nogenesis. The facts have been explained differently by different 
 observers ; the two most important theories being the following : 
 according to the first, the subsequent broods result by a process 
 resembling budding, taking place within the bodies of their prede- 
 cessors; while the second supposes that a portion of the original 
 germ-mass is actually transmitted from the parent through the 
 whole series of beings existing between two generative acts. The 
 latter view has been most ably advocated by Professor Owen, in his 
 lectures on Parthenogenesis ; and the former is supported by Dr. 
 Carpenter. In the Campanularia dichotoma, one of the tribe of 
 polyps, at certain periods, buds are developed from the stem, which 
 do not become converted into polyps, but, after having reached a 
 certain stage of development, drop off, and in their mature state are 
 seen as transparent disc-like bodies, having the power of swimming 
 about in the water. These creatures have long been known as 
 Medusae, or jelly-fishes. It must be remarked, that no generative 
 organs are to be found in the polyp ; but these organs are found in 
 the Medusae, in which also ova are developed. The ova become 
 polyps, which eventually put forth Medusa-buds as before. 
 
 In another polyp, the Strobila, at certain periods, multiplication 
 by the formation of buds ceases, and the body of the polyp becomes 
 constricted, and at the same time much elongated. The constric- 
 tions, which may be as many as forty in number, gradually become 
 deeper, until at length the body of the polyp becomes divided into a 
 number of flattened discs. The terminal disc drops off, and appears 
 
ALTERNATION OF GENERATIONS. 823 
 
 as a free swimming Medusa, in which generative organs are found 
 and ova produced. The other discs fall off successively, and in like 
 manner become Medusae. These polyps, therefore, would with pro- 
 priety be considered as belonging to the class Acalephae, the Medusa 
 representing the perfect condition of these animals. 
 
 The livers of various animals are infested with an entozoon termed 
 a fluke. The development of the fluke of the common fresh-water 
 snail (Limnseus stagnalis) presents us with a beautiful example of the 
 curious phenomenon we are now considering. In the first stage of 
 its existence it is seen as a creature (Cercaria) swimming about in 
 the water, and is provided with a tail. After a time, these cercarise 
 fix themselves to the skin of the snail by means of a circlet of hooks. 
 The tail is cast off, and the body becomes covered with mucus, which 
 hardens, until a transparent case is formed. This is the pupa state. 
 Next the creature bores its way into the body of the snail, and 
 reaches the liver ; the hooks drop off, and it possesses all the charac- 
 ters, of a fluke or distoma. The fluke develops ova ; the ova become 
 developed into worm-like creatures, which inhabit the snails. The 
 worm-like body contains, as it were, a progeny, each member of which 
 becomes the parent of another generation. The original larvae are 
 developed from a perfectly spherical germ, consisting of granules. 
 So that the early stages of life of the fluke are passed in the body 
 of a worm-like creature ; the next, in the water, free ; next, attached 
 to the body of a snail ; and lastly, in a perfectly developed form in 
 the liver. Thus this creature assumes three distinct forms at differ- 
 ent periods of its existence, which, until these discoveries were made, 
 had been described as three distinct creatures. 
 
 There are numerous other most striking instances among the ento- 
 zoa of this extraordinary change of character in the course of deve- 
 lopment. It has long been known that the cystic entozoa (as Cysti- 
 cercus, etc.) are not provided with generative organs ; but it was 
 reserved for Van Siebold to show that these entozoa were only the 
 imperfectly developed forms of species occupying a higher position ; 
 and he has been able to prove that the cysticercus fasciolaris, which 
 is found in the liver of the rat and mouse, becomes developed in the 
 intestine of the cat into the tcenia crassicollis, the common tape-worm 
 of that animal. Kuchenmeister and Van Beneden have been able 
 to demonstrate the occurrence of similar changes, in many other 
 entozoa. 
 
 Another beautiful example of metagenesis occurs among, the mem- 
 bers of a much higher class of animals — ^insects. The ovum of the 
 perfect winged aphides, or plant lice, becomes developed into an im- 
 perfect wingless, or larval creature, in which no sexual organs have 
 been discovered. These viviparous, but non-sexual larval forms are 
 capable of producing non-sexual descendants exactly resembling 
 them, without the occurrence of any generative act, and this process 
 is repeated for nine or ten generations. The last autumnal brood, 
 however, of these larvae produce, in the same viviparous manner, 
 perfect male and perfect female insects, with fully developed sexual 
 organs. The female deposits her ova in the axils of the leaves and 
 
824 GENERATIOW. 
 
 Other protected parts of the plant, where they remain until the fol- 
 lowing spring, when they are hatched, and the larvae above described 
 issue forth ; the first larva producing eight, and each of these repeat- 
 ing the process, until, in the course of the summer, millions of larval 
 forms are produced. This must conclude our very imperfect sketch 
 of these interesting processes ; and, for more detailed information, 
 we must refer the reader to the works enumerated at the end of the 
 present chapter. 
 
 Professor Owen considers that the larval forms result from the 
 development of a portion of the original germ-substance of the yolk, 
 which was not converted into a portion of the textures of the beings 
 which resulted from the immediate development of the ovum ; and 
 hence he has applied the term parthenogenesis, or virgin generation, 
 to this process of development. Dr. Carpenter, on the other hand, 
 looks upon the process as akin to gemmation, or budding, rather than 
 one of actual generation. Victor Cams shows that in this process 
 of development the embryo is formed from a granular germ, whereas 
 ordinarily it results from the process of cell-multiplication, as will 
 be shown in the chapter on the development of the embryo. The 
 same author contrasts the process of metamorphosis and metagene- 
 sis in the following words: "Larvae, the subjects of metamorphosis, 
 arrive at the state of perfection by throwing oiF provisional structures 
 which belong to their larval condition ; but nurses,* the subjects of 
 metagenesis, are themselves entirely provisional structures." 
 
 In the present state of knowledge, it is diflScult to group these 
 extraordinary phenomena under one general head. Although we 
 may contrast the processes of metamorphosis and metagenesis with 
 each other, and draw definite distinctions between them, we must 
 remember that there are instances in which both these processes 
 occur ; and although metamorphosis afi"ect3 a single individual, and 
 metagenesis a very numerous progeny, we do not feel ourselves in a 
 position to define the exact relation which one bears to the other, and 
 we think it better to avoid any attempt at generalization until a 
 greater number of facts relating to these wonderful processes should 
 be discovered, rather than adopt a view which future research may 
 show to be erroneous. 
 
 Sexual Organs. — The generative organs are of two kinds, the male 
 and the female organs, the one secreting the " sperm cell," and the 
 other the " germ cell." The generative apparatus consists of two 
 parts : a formative organ, in \?hich the elements are produced, and 
 which is essential; and an efferent duct, by which the products of 
 secretion are carried off'. 
 
 The male and female organs may exist in one individual or in 
 separate individuals. The first condition is termed unisexual, and 
 the second bisexual generation. 
 
 In some unisexual or hermaphrodite animals, self-impregnation 
 
 * The torm " nurse" was originally applied by Steenstrup to these larval forma, 
 but we have purposely avoided its use, as it is for many reasons very objectionable, 
 and likely to convey a wrong idea of the nature of the viviparous larvse. 
 
INVBRTBBRATA. 825 
 
 tates place, as is the case In the common tape- worm (Taenia solium) ; 
 ■while in other instances, concourse is necessary in order that the ova 
 should be exposed to the action of the spermatic fluid ; this is the 
 case with many of the mollusca, as the common snail, etc. In these 
 instances, each hermaphrodite animal impregnates its neighbour. 
 
 Besides the secretion of the formative organ, other secretions are 
 frequently poured into the eflFerent duct. The duct undergoes great 
 modifications in different parts of its course in various animals, 
 according to the particular ofiice it has to fulfil. We shall now con- 
 sider some of the most important characters which the sexual organs 
 exhibit in the different classes of animals. 
 
 Invektebrata. 
 
 The Injmoria multiply by fission, and rarely by gemmation. No sexual organs haye 
 yet been discovered in them, and ova are not met with in this lowest class of the 
 animal series. 
 
 Fission may occur in the longitudinal direction, as in the VoriiceUa : or transversely, 
 as in Stentor and some others ; or in both directions, as in Bursaria, Params^cium, and 
 others. The VorticellK are also propagated by the formation of buds. When divi- 
 sion is about to take place, the cell within the body, known as the nucleus, is seen to 
 divide into two ; each half containing, therefore, a newly-formed nucleus. 
 
 The Polyps multiply by gemmation and by the formation of ova, very rarely by 
 fission. In gemmation, the young polyp may be ultimately set free, as in the Eydra; 
 or it may remain attached to the stem or common body, or polypidon, as in thq 
 majority of the members of this class. Some polyps are hermaphrodite, while in 
 many the sexes are distinct. At the time when the' common hydra is about to propa- 
 gate by ova, the male and female organs are both developed as excrescences upon the 
 outer surface of the body. Others, again, are sexless, and give rise to the develop- 
 ment of medusa-buds, or split up into discs, as already described in p. 822. 
 
 Eeproduction in the class Aealqihse takes place almost entirely by the formation of 
 ova. It has, however, been shown by Professor Huxley, that some multiply by gem- 
 mation as well as by the production of ova (Diphyidae). Some of the species are uni- 
 sexual, and others bisexual. The genital organs are only developed at certain periods 
 and the male and female elements are brought into contact through the influence of the 
 water in which they swim. 
 
 In the Echinodermata, fission has only been observed to occur in one class (Holo- 
 thuria) ; and the generative function, which is developed in this class to a great extent, 
 is carried on almost exclusively by the production of ova. The sexes are distinct, but 
 the ova are impregnated without sexual intercourse. In some there is a proper effer- 
 ent duct ; but in others the elements pass into the respiratory cavity, and thus escape 
 from the body. 
 
 Among the Entozoa great variety is met with in the arrangement and character of 
 the generative organs. Almost all the animals of this class possess true generative 
 organs, and multiply by means of ova, but in many of them fission occurs ; as, for 
 instance, in the tape- worm ; but it is worthy of remark, that the entire animal is not 
 produced in this process. The segments, however, which have been separated con- 
 tinue to live. As already mentioned, the Echinococcus multiplies by the formation of 
 buds. 
 
 Some of the Entozoa are unisexual, and have the power of self-impregnation, and 
 some are bisexual. 
 
 The Annelida reproduce by sexual apparatus, and in some instances, as already re- 
 ferred to, by transverse fission. In the latter case, the different organs, including the 
 tentacles and eyes, are developed before the new animal is separated from the old one. 
 This mode of multiplication, however, only continues for a certain time ; at length it 
 ceases ; genital organs, which before could not be distinguished, are developed, and 
 ova are formed. The Hirudines and Lumbrici are hermaphrodite, but copulation i? 
 necessary for impregnation to take place. 
 
 Amongst the lower MoUuaea, the sexes are sometimes united in one individual, and 
 sometimes distinct. There are no copulatory organs, so that the water forms the 
 medium by which the spermatic particles are conveyed to the ova. Amongst the 
 Tunicata, multiplication also takes place by gemmation. 
 
826 QENBRATIOlSr. 
 
 Of the higher Molluica, some are hermaphrodite, and in others the sexes are dis- 
 tinct. Many families are characterized by the possession of what has been termed an 
 hermaphrodite gland, which is almost always imbedded in the substance of the liver. 
 This gland consists of numerous radiating and branched cseca. Each csecnm consists 
 of an external and internal sac folded within the first. Ova are produced by the ex- 
 ternal sac, and spermatic particles by the internal one. Excretory ducts pass off 
 from these organs, and terminate in two tubes ; the one corresponding to the Fal- 
 lopian tube, the other to the vas deferens. Besides this apparatus, there is also 
 another organ connected with the excretory duct ; this is the albumen gland, which 
 furnishes a secretion in which the ova become imbedded as they pass towards the 
 external orifice. This curious arrangement may be well seen in the common snail. 
 
 Into the same cavity or cloaca in which the genital ducts terminate, is found the 
 opening of another very remarkable organ — the dart sac — ^in which a hard and exces- 
 sively sharp-pointed, and sometimes toothed, calcareous body is formed, which is pro- 
 jected during copulation. The dart may be looked upon as an arrangement for pro- 
 ducing sexual excitement, for each snail has been seen to prick the other just before 
 coition. 
 
 Amongst the Cyihalopoda, the highest of the Mollusca, the sexes are always distinct. 
 Connected with the excretory duct of the ovary is an apparatus which furnishes a 
 secretion by which the eggs are bound together, and a firm horny covering formed for 
 their protection. 
 
 The testicle consists of an oblong organ, situated at the bottom of the cavity of the 
 mantle. Connected with the excretory tube, is a sac in which some very complicated 
 organs, containing the sperm, are developed, from which the contents are expelled by 
 a very remarkable projectile apparatus. Coition appears to take place simply by one 
 animal applying itself to the other. A true intromission of the penis seems hardly 
 possible. 
 
 One of the most curious phenomena which has been discovered in connection with 
 the generation of some of the members of this class must be briefly noticed here. On 
 the male Argonaut is developed a curious elongated body, termed Hectoeotylus, which 
 communicates with the testicle of the Argonaut by a duct. Before this body had been 
 proved to belong to the male Argonaut, and had only been seen upon the female, it 
 was looked upon as a parasite, and Cuvier described it as one of the Trematoda. The 
 Hectoeotylus, which is to be regarded as one of the arms of the animal metamorphosed 
 in a peculiar way, at length becomes filled with spermatic fluid, and drops off. It is 
 now independent, and comes into contact with the female Argonaut, which it impreg- 
 nates. In this point it resembles, "as also by its movements, by a kind of circula- 
 tion, and by the long duration of its life after detachment, a true male animal" 
 (H. MiJller). 
 
 Among different families of the Crustacea, the arrangement of the generative organs 
 varies much. In most, the sexes are distinct ; but one class, Cirrhipoda, is herma- 
 phrodite. Some Crustacea, again, are almost exclusively females ; and these for many 
 generations produce females, and at very long intervals only, males. Some females, 
 again, lay two kinds of eggs, one of which becomes developed spontaneously, while 
 the other requires to be fecundated by the spermatic fluid. The female of the 
 Daphnia, towards the close of the year, produces two eggs, which must be looked 
 upon in the light of gemmae, or buds, as they contain no germinal vesicle. These are 
 the so-called hibernating eggs, and are developed without the fecundating influence 
 of the sperm. 
 
 Among the Crustacea, the genital organs are usually double, and symmetrical in 
 both sexes. Connected with the efferent duct of the female organs are some glands, 
 which secrete a viscid substance, by which the eggs are glued together in clusters t» 
 the posterior abdominal feet, as occurs, for the most part, among the Decapoda 
 (lobster, etc.); but in those species in which these organs are deficient, there is 
 formed a marsupium, or sort of pouch, connected with the lower surface of the thorax, 
 into which the eggs are received and retained until the young escape. The greater 
 number of the Cirrhipoda are hermaphrodite ; but it has been shown by Goodsir, that 
 this is not a universal characteristic of this class. 
 
 Among the different families of the large class Insecta, the arrangement of the gene- 
 rative organs presents great variety. The sexes are always distinct, and impregna- 
 tion is invai-iably effected by copulation ; hence, the external aperture of the efferent 
 duct is found to be variously modified, according to the different circumstances in 
 which the animal lives, and the modification of its general form. In some classes, the 
 females are very few in number, and often whole colonies are developed from one 
 female. This is the case amongst the bees, termites, and ants, in which the great 
 
VERTKBRATA. 827 
 
 • majority of the individuals are found to be neuters or irorkera. In the pupa of these 
 last, the generative organs may be distinguished, but they afterwards become atro- 
 phied. Now it appears probable, that the development of the female organs is de- 
 pendent upon nourishment ; for it has been found, that the larvse which are to become 
 fertile females, or queen bees, have been supplied with a much more stimulating kind 
 of food than that upon which the workers have been fed. 
 
 The generative organs are double and symmetrical in insects, and several accessory 
 organs are found connected with the efferent duct. Of these, the most remarkable is 
 a receptacle connected with the vagina of the female, designed to receive the seminal 
 fluid of the male. This vesicle is termed the receptaculum semink, and in it the sperma- 
 tic particles of the male may be keptinaliving condition foraverylongperiod of time. 
 The ova are impregnated as they pass the orifice of the duct of the receptaculum 
 seminis. Besides this last, there is another organ connected with the lower part of 
 the female genital organs, designed to receive the penis of the male. This is known 
 as the bursa copulalrix, which, however, is not universally present. Mucous glands 
 pour their secretion into the vagina near its external orifice. 
 
 The arrangement of the ovaries differs considerably in various classes. The gland 
 usually consists of csecal tubes, which are four or five in number, and open into the 
 summit of the efferent duct ; while in some the tubes open separately in the sides of 
 the duct. The number of secreting tubes is very variable in the different classes. 
 
 The testicles consist of two or more (and often there are very many) simple csecal 
 tubes, the arrangement of which varies much, and which opens into the vas deferens 
 of the corresponding side. The vasa deferentia are often very long and much con- 
 voluted ; in some instances they are dilated below, so as to form a sort of vesicula 
 seminalis. 
 
 The copulatory organs vary much in their disposition ; usually they consist of hard, 
 horny valvular appendages. In some species, suckers are developed upon the legs ; 
 and other arrangements are found for the purpose of retaining the female during the 
 act. 
 
 The imperfect or larval form of many insects when they leave the egg, has already 
 been alluded to under the heads of metamorphosis and metagenesis, or alternation of 
 generations. 
 
 Veetebrata. 
 
 In the vertebrata, with th^ highest and most perfect development of the generative 
 function, we shall find the progressive elevation characterized by greater complexity 
 of structure, more protracted dependence of offspring on parent, and closer relations 
 of the two sexes. 
 
 Fishes. — There are three types of structure in the generative organs of fishes. First, 
 in the Cyclostomatous Group and in the Eel, the ovary consists of membranous folds 
 depending from the spine, between the layers of which the ova are, at the spawning 
 season, developed. When mature, they escape by the rupture of the membrane into 
 the general peritoneal cavity, in which they may be found in large numbers, and from 
 which they escape by a small opening situated near the anus. The male organs are 
 to the unaided eye so like the female, that it is only in the spawning season that they 
 can be distinguished: the spermatozoa escape into the peritoneal cavity in the same 
 manner as the ova. Secondly, in the Osseous Fishes, the ovary, or roe, consists of a 
 large membranous sac, inclosing the ovigerous folds, between the layers of which the 
 ova are developed, just as in those we have described, so that when the ova escape 
 they are discharged, not into the general peritoneal cavity, but into this ovarian sac, 
 and thence find their way out by a tubular prolongation of it, or excretory duct, which 
 opens just behind the anus. The testicle is strictly analogous. In neither of these 
 classes does copulation take place ; the spawn is cast abroad into the water, and left 
 to be fecundated by the sperm discharged over it by the male, to be devoured, or to 
 perish in an unfeoundated state, as chance may direct. One of the most remarkable 
 points in the history of osseous fishes is their immense fecundity : it is calculated 
 that a Cod discharges nine millions of ova in a single spawning season. The reason 
 of this unparalleled fertility appears to be, that there may be the greater chance of 
 some escaping and surviving the many perils to which they are exposed. Thirdly, in 
 the Cartilaginous Fishes, as the Sharks and Bays, we have a much higher type of the 
 generative function. Copulation takes place ; the male is furnished with an intro- 
 mittent organ, and with certain accessory parts, called "claspers," for seizing and 
 embracing the female during the act of impregnation. In the female, the ovaries are 
 racemose, from the increased size and diminished number of the eggs, which, instead 
 
828 GENERATION. 
 
 of escapiog into the peritonea,! cavity, are seized by the patulous orifices of two long 
 oviducts, whereby they are conveyed out of the body, and by which they are furnished 
 with that peculiar horny shell, which serves at once to protect and to attach them to 
 some fixed point. 
 
 ReplUia. — The Amphibia exhibit, in the function of generation, an interesting link 
 between the piscine and the true reptilian structure ; there is no intromittent organ, 
 and yet copulation takes place, and the ova are fecundated neither after extrusion, as 
 in the osseous fish, nor before extrusion, as in true reptiles, but during the very act 
 of discharge, in exitH,. At the commencement of the spawning season, a remarkable 
 papillary structure is developed on the thumbs of the male frogs, highly sensitive, and 
 giving rise, when stimulated, to a forcible reflex action, by which the upper extremi- 
 ties are approximated, and tightly embrace anything placed between them (p. 
 298.) By means of this, the male frog firmly embraces the female, and continues to 
 do so through the whole time of the expulsion of ova, without any expenditure of 
 voluntary action, and impregnates the ova as they pass from the female beneath him. 
 The vas deferens pass,es through the structure of the kidney, and opens at once into 
 the ureter, the two being thence continued as one duct — a sort of prolonged genito- 
 urinary cloaca. In the Triton, we go a step further, and find the ureter and vas 
 deferens distinct to their termination, and impregnation taking place internally, 
 although there is no rudiment of a penis. The Ophidians present a further advance, 
 and show the first trace of a penis ; it consists of two erectile corpora cavernosa, 
 which, however, are quite separate, and constitute rather an organ of prehension than 
 of intromission. In the Sauriana and Chelonians another step is gained, and the two 
 corpora cavernosa are united in the middle line ; there is still, however, no corpus 
 spongiosum, and no prolongation of the urethra, but the seminal secretion passes into 
 the female along the groove formed by the union of the two cavernous bodies. 
 
 Aves, — The generative organs of birds exhibit a close analogy to those of the higher 
 reptiles, the penis is even less developed, except in the struthious birds (ostrich) and 
 the swimmers. The ovary is racemose and single, the right with its oviduct being 
 permanently atrophied: a singular violation of symmetry which is confined to birds. 
 In this class of vertebrata, incubation, that singular substitute for ntero-gestation, 
 attains its highest perfection ; it appears to arise from the concurrence of these three 
 exigencies: the necessary size and early maturity of the young, the necessity of 
 warmth to their development, and the incompatibility of utero-gestation with flight. 
 
 Mammalia. — It is from the possession of a remarkable accessory organ of generation 
 that this important class of the highest organized beings takes its name. After all 
 organic connection has ceased, the young are still dependent on the parent for nourish- 
 ment, and are supported by the secretion from a special gland with which the female 
 is famished for the purpose — the mammary gland. The mammalia are divided into 
 the monotremata, the marsupialia, and the placental mammalia. The monotremata are 
 as yet imperfectly known, but they present a curious connecting link between the ovi- 
 parous and mammalian type ; they derive their name from possessing but one aperture, 
 that of the cloaca, common to the generative, urinary, and digestive canals, and in 
 this respect resemble birds ; they are represented by the omithorynchus and echidna 
 of Australia. In the male, the penis is perforated by a urethral canal, through which 
 the semen, but not the urine, passes ; in the female, the ovaries are racemose, the ova 
 large, and containing all the elements of an egg, and there are two uteri, opening by 
 distinct apertures into the cloaca. The marsupialia (called so from the possession of 
 a marsnpium, or pouch, in which the young is lodged and suckled after its discharge 
 from the uterus) are ovo-viviparous, that is, the young are brought forth alive, but 
 they never have any placental connection with the parent. Not only are there two 
 uteri, but two vaginse, which terminate by two separate orifices in a sort of genito- 
 urinary cloaca.* About thirty-nine days after conception, the young is expelled into 
 the marsupium, where it becomes attached to one of the nipples by its mouth, and 
 continues thus to draw nourishment from the mother for a period of eight months ; this 
 peculiar method of foetal nourishment necessitates a very advanced and disproportion- 
 ate development of the organs of assimilation, which is the most remarkable charac- 
 teristic of the embryo marsupial. The placental mammalia, in the general structure 
 of their generative organs, resemble man. The testicle consists of seminiferous 
 
 * In the male, the testicles are contained in a scrotum placed above, and not below the 
 penis, in a situation analogous to the marsupium in the female, and supported, like it, by 
 two marsupial bones; the vasa deferentia open into the urethra, which, invested by its cor- 
 pus spongiosum, passes through the centre of the penis, and which now, for the first time, 
 we find forming a complete canal, leading from the bladder to the extremity of the intromit- 
 tent organ. 
 
MALE ORGANS OF GENERATION. 829 
 
 tubules arranged in bundles, and inclosed in a fibrous capsule. The penis is composed 
 of two corpora cavernosa arising from the ischia, a corpus spongiosum urethrse, and 
 glans ; and there are certain accessory glandular structures, yesiculse seminales, pros- 
 tate, and Cowper's glands, opening into the urethra in its course. Into the different 
 numbers, modification, and structure of these organs it is not worth while to enter. 
 In the rabbit, the ovary exhibits some trace of the racemose structure, and, by the 
 difi'erent modifications of the uterus, dependent on the proportionate size of its body 
 and cornua, we are conducted from the marsupialia, in which the two uteri are entirely 
 distinct, to the human female, in which the single uterus exists in its greatest degree 
 of concentration. ^ 
 
 In writing the present chapter, the authors have received much assistance from the 
 following works: Muller's "Elements of Physiology," by Baly; Professor Owen's 
 Lectures "On Comparative Anatomy," and his treatise "On Parthenogenesis;" Dr. 
 Carpenter's "Principles of General and Comparative Physiology;" Victor Cams' 
 "System der Thierischen Morphologic;" Art. Ovum, in the "Cyclopsedia of Anatomy 
 and Physiology," by Dr. Allen Thompson ; " On the Alternation of Generations," by 
 Professor Steenstrup, translated by the Kay Society. 
 
 CHAPTER XXXVII. 
 
 MALE ORGANS OF GENERATION. — TESTICLES. — VASA DEPERENTIA. — 
 VESICUL.Si SEMINALES. — PROSTATE GLAND. — COWPBR'S GLANDS. — 
 PENIS. — URETHRA. — GLANDS OP LITTRE. — GLANDULiE TYSONI. — 
 VBSICULA PROSTATICA. — SEMINAL TUBULES. — SPERMATOZOA. — DE- 
 VELOPMENT OE SPERMATOZOA. — MOVEMENTS OF SPERMATOZOA. 
 
 Male Organs of Generation. — The essential organ of generation, 
 or the secreting portion of the sexual apparatus, in the male, is the 
 testicle. The efferent duct is the vas deferens, -which opens into the 
 membranous portion of the urethra, and connected with it are the 
 vesiculse seminales and Cowper's glands. The urethra is continued 
 forwards along the lower part of the penis, or intromittent organ. 
 
 Testicles. — Each testicle is rather less than two inches in length, 
 and is nearly one inch broad. — Its weight is about six drachms. 
 The testicle is covered by a firm, fibrous, inelastic tunic, or proper 
 covering, the tunica alhuginea or tunica propria, consisting almost 
 entirely of white fibrous tissue, in the substance of which vessels 
 ramify. It is with difficulty divided into two layers, the inner of 
 which is the most vascular. Adhering closely to the tunica albu- 
 ginea, is the visceral layer of the serous membrane, or tunica vagi- 
 nalis, the sac of which was originally formed by the descent of the 
 testicle from the abdomen, when it carries before it a process of 
 peritoneum. In early life, the cavities of the tunica vaginalis and 
 peritoneum are continuous with each other ; and, occasionally, the 
 opening remains unclosed in the adult. The parietal layer of the 
 tunica vaginalis is loose, and united by lax areolar tissue to the other 
 structures which form the scrotum. This layer of the serous mem- 
 brane admits of considerable distension ; and, in disease, a very large 
 quantity of serous fluid will sometimes accumulate in the sac, and 
 distend it to a great extent (Jiydrocele). 
 
830 
 
 MALE ORGANS OF QENBRATION. 
 
 Structure of the Q-land. — The secreting portion of the organ con- 
 sists of a vast number of a minute and highly tortuous tubes, which 
 are arranged in conical lobes, or parcels, each consisting of two or 
 more tubes, which are covered with a layer of condensed areolar tis- 
 sue, continuous with the corpus Highmori. These divisions are, 
 however, not complete ; for the tubes of one parcel communicate with 
 those of the adjoining ones. The highly convoluted seminal tubes 
 commence in blind extremities or in loops ; and, after dividing fre- 
 
 Fig. 256. 
 
 a. Origin in blind extremities and branching of seminal tnbules — ^human Bubjecfc. &. One of tlie 
 blind extremities more highly magnified. * 
 
 quently, and forming anastomoses, they become less tortuous as they 
 approach the mediastinum testis, where two or more unite to form 
 a short straight duct, the vas rectum ; these vasa 
 recta again unite, so as to form a sort of net- 
 work, the rete testis, which occupies the medias- 
 tinum testis or corpus Highmori. From the rete 
 testis pass the vasa efferentia, which are usually 
 about twelve or sixteen in number, and are much 
 convoluted ; and, by being packed together, form 
 part of the epididymis. They open into a single 
 and highly tortuous duct, the vas deferens, which 
 is usually about sixteen inches in length, and 
 forms a very hard, round eiferent duct, readily 
 distinguished, by the feel, from the other struc- 
 tures which compose the spermatic cord. The 
 vas deferens is lined with a single layer of tessel- 
 ated epithelium, and there is a layer of very lax 
 areolar tissue beneath the mucous membrane, 
 which would permit of great increase in the 
 diameter of the canal when it was distended with 
 secretion, b, fig. 257. It passes behind the 
 bladder, and terminates in one of the ejaculatory 
 canals, a very short canal, which is formed by 
 the union of the vas deferens with the corre- 
 sponding vesicula semihalis, which is situated a 
 little external to it, upon the posterior surface of 
 the bladder. 
 
 Transverse section of the 
 vas deferens — a segment 
 only is represented in the 
 drawing, a. Lining mem- 
 brane of the tube connected 
 by a ttAeli layer of lax 
 submucous areolar tissue 
 ip) to a thin longitudinal 
 layer of unstriped muscle 
 (c). d. Layer of circular or 
 transverse jflbres. e. Ex- 
 ternal thick layer of longi- 
 tudinal fibres, surrounded 
 by an outer covering of 
 areolar tissue, /. Prom a 
 drawing by Sr. Beale. 
 
PROSTATE GLAND. 
 
 831 
 
 Vesiculce Seminales. — The vesiculae seminales are two sacculated 
 receptacles, about two inches in length and about three-quarters of 
 an inch in breadth, situated upon the posterior aspect of the bladder, 
 lying between it and the rectum. They converge towards the point 
 at which they open, and almost meet. The narrow terminal portion 
 (duct) lies for a short distance, previous to its opening in the urethra, 
 surrounded by the prostate. Each vesicula may be unravelled, so as 
 to form a caecal tube, with several diverticula projecting from it. It 
 is very much convoluted, and the convolutions are connected together 
 with areolar tissue, to which arrangement the sacculated appearance 
 is due. 
 
 The structure of the vesiculse seminales is ^ig- 258. 
 
 very similar to that of the vasa deferentia, 
 but their walls are much thinner. There is 
 an outer coat, composed of areolar tissue, in 
 which numerous muscular fibre-cells are found. 
 They are lined with a thin layer of tesselated 
 epithelium. 
 
 The vesiculse are usually found to contain a 
 viscid, mucus-like substance, which may be 
 regarded as their secretion ; and which, no 
 doubt, is of a nature favourable to maintain 
 the vital activity of the spermatozoa, and 
 serves also to dilute the semen. These organs 
 were formerly looked upon as the receptacles 
 for the semen; but a comparison of their 
 arrangement, and an examination of their 
 contents, in the lower vertebrata, by no means 
 confirms this view, as our friend, Mr. Pittard, 
 has remarked. In the elephant, the vesiculse 
 seminales open into the vasa deferentia, as in 
 man ; but seminal reservoirs are also found in 
 this animal. In man, however, spermatozoa 
 are very generally found in them ; and it is b. vas deferens, c. vesicuia 
 probable that they serve partly as receptacles S."^'' <«• terminal dif- 
 fer the semen, but at the same time, there can 
 be no doubt that they furnish a proper secretion of their own for its 
 dilution, and for the preservation of its integrity. 
 
 Prostate Q-land. — The prostate may be described as consisting 
 essentially of two distinct structures ; first, of a glandular portion, 
 composed of conical or roundish vesicles lined with cylindrical 
 epithelium and containing brown granules ; and, secondly, of several 
 layers of fibrous tissue, with which many fibres of unstriped muscle 
 are everywhere incorporated ; indeed, the proportion of the muscular 
 and fibrous elements to the glandular structure, is so great that 
 Kolliker calculates that the latter does not constitute more than one- 
 third part of the whole mass of the gland. The muscular fibres 
 covering the prostate, were originally described by Mr. Hancock. 
 
 The secreting follicles open into ducts, which are lined with 
 
 VeBicul^ seminalis, after E. 
 H. Weber, a. Ejaculatory dtict. 
 
832 MALE ORGANS OF GENERATION. 
 
 cylindrical epithelium, presenting similar characters to that found in 
 the prostatic portion of the urethra. 
 
 The ducts, which are very numerous, open into the urethra, upon 
 each side of the caput gallinaginis. 
 
 Little is known with reference to the nature of the secretion of 
 the prostate, or of the function which it performs. The secretion 
 is stated to be very similar in character to that of the vesiculse 
 seminales. 
 
 Small concretions, or prostatic calculi, are very frequently met 
 with in the follicles of the gland, or are voided during life. They 
 usually consist of phosphate of lime, with animal matter, and a 
 trace of carbonate of lime ; and are often remarkable for their per- 
 fectly spherical form and smooth glistening surface. They commence 
 by the deposition of caleareotis matter in the walls of large oval 
 cells, which are, probably, altered epithelial cells of the gland itself. 
 Dr. Handfield Jones has carefully investigated the formation of 
 prostatic concretions.* 
 
 Qowper's Grlands. — These small glands are two in number, and 
 are situated anterior to the prostate, between the layers of the 
 triangular ligament. Their somewhat long excretory ducts open 
 into the bulbous portion of the urethra. They are composed of 
 vesicles, lined with tesselated epithelium, which pour their secretion 
 into ducts lined with columnar epithelial cells. As in the case bf 
 the prostate, the secreting portion of these little glands is imbedded 
 in a fibrous stroma, which contains very numerous unstriped muscu- 
 lar fibre-cells. The secretion of these glands appears to be analogous 
 to ordinary mucus. 
 
 Penia.-^lihe penis of man is a highly vascular organ, traversed 
 on its inferior surface by the urethra ; it is composed principally of 
 erectile tissue, which is capable of being distended with blood. 
 This erectile tissue is arranged in three distinct divisions termed 
 the corpora cavernosa and corpus spongiosum. The corpora cavernosa 
 penis are two in number, and are separated from each other, poste- 
 riorly, by a septum, composed of fibrous tissue ; while anteriorly, 
 they are connected together, and might be considered as one organ. 
 In the middle line above, is situated the dorsal vein, and other 
 vessels and nerves ; while the corpus spongiosum urethree is received 
 into a groove beneath. In the posterior part of the organ, the 
 corpora cavernosa are separated from each other by a considerable 
 interval, and each is inserted into the rami of the ischium and pubis ; 
 these two diverging extremities of the corpora spongiosa are termed 
 the crura of the penis. 
 
 The corpora cavernosa are invested with a layer of firm fibrous 
 tissue, which contains numerous fibres of the yellow elastic element. 
 
 The corpus spongiosum urethrae surrounds the urethra, and com- 
 mences behind, in a dilated portion situated between the crura penis ; 
 and it terminates anteriorly in the expanded glans penis, the rounded 
 
 « Medical Gazette, Aug. 20th, 1847. 
 
URETHRA. 833 
 
 margin of which is termed corona glandis, and the constricted part 
 beneath, the cervix or neck. 
 
 These bodies consist of a vast number of small venous sinuses, 
 which communicate with each other upon all sides, and contain venous 
 blood. The walls of the sinuses or trdbeculae are lined with a layer 
 of tesselated epithelium, external to which is found the proper fibrous 
 tissue, or trabecular tissue. This is composed of white and yellow 
 fibrous tissue, and fibres of organic muscle. The arteries and nerves 
 for the supply of the organ are supported and surrounded by this 
 texture. 
 
 The arteries of the penis are branches of the pudic ; and in their 
 arrangement, present certain peculiari- 
 ties, which are well worthy of notice. .I'ig 259. 
 The smaller divisions, after pursuing a 
 tortuous course in the trabecular tissue, 
 at length open into the venous sinuses, 
 without entering into the formation of 
 any capillary plexus. In the posterior 
 part of the penis, J. Miiller discovered 
 several minute arteries, which were much 
 convoluted, and assumed the twisted 
 appearance of tendrils; whence they 
 were termed the helicine arteries. Kdlli- 
 
 ker has shown that these arteries ter- a small artery of the corpora caver- 
 K^KjL uwo^DuvTT^u wuuiv v..\jK>\j ui^uv^xv^kj vw* BOsa, giTiiig off a latsral braHch, froiu 
 
 minate in minute vessels, and not in ■^iich proceed hellcme arteries, ter- 
 -,,, ,, '..,■, minating in very small vessels, whicli 
 
 blind extremities, as was originally sup- are continued m the trabecular tissue, 
 
 posed; the minute terminal vessels ulti- ^)^»^_^waii ot the arteries. Atter 
 mately open into the venous spaces. The 
 
 arrangement of the arteries in the corpus spongiosum urethrise, is 
 similar to that just described. 
 
 Urethra. — The male urethra is the canal which extends from the 
 neck of the bladder to the end of, the penis. It is about eight inches 
 and a half in length, but varies slightly in different cases. The 
 tube itself is lined with mucous membrane, and its diameter is not by 
 any means the same in its whole extent. Its direction is that of a 
 double curve, like the letter /. The walls of the urethra are strong, 
 and composed principally of fibrous tissue, with a layer of unstriped 
 muscular fibre, the arrangement of which has been well described by 
 Mr. Hancock. 
 
 The urethra is divided, by descriptive anatomists, into three por- 
 tions ; the prostatic, being about twelve lines long ; the membranous, 
 about three-quarters of an inch in length in its upper part, but only 
 half an inch in its lower portion ; and the remainder, by far the most 
 extensive portion of the canal, called the spongy portion, which 
 reaches to the orifice. 
 
 The prostatic portion of the urethra is its widest part, and lies 
 imbedded in the upper part of the prostate, above its middle lobe. 
 
 At the neck of the bladder, the mucous membrane forms a fold, 
 called the uvula vesicae. Anterior to this is a narrow ridge, rising 
 from the floor of the tube, about nine lines in length, and about one 
 
834 MALE OKaANS OF GENERATION. 
 
 and a half lines in height in its highest part, called the verumonta- 
 num, caput gallinaginis, or crest of the urethra.* On each side of 
 this, the mucous memhrane forms a depression, the prostatic sinus, 
 into which the ducts of the prostate gland open. 
 
 At the highest part of the verumontanum is a little sinus, the vesi- 
 cula prostatica. It is here that the ejaculatory ducts open. 
 
 The membranous portion is that narrowest part of the urethra 
 which lies beneath the pubis and passes through the layers of the 
 triangular ligament. It is surrounded with muscular fibres, and the 
 compressor urethras muscle is situated upon this part of the tube ; 
 beneath it are Cowper's glands. This part of the urethra commences 
 at the anterior extremity of the prostate, and terminates in the bulb- 
 ous portion. Its upper surface is rather longer than the lower one, 
 and it curves upwards. 
 
 In the evacuation of the bladder, it is most likely that the com- 
 pressor urethrse muscle, which contains striped fibre, and guards the 
 membranous portion of the urethra, becomes relaxed ; then follows 
 the relaxation of the sphincter vesicae, and the contraction of the 
 fibres of the bladder (detrusor urinae), which causes the urine to 
 escape from the urethra with considerable force. 
 
 The spongy portion of the urethra is about six inches in length, and 
 is BO called, because it is surrounded by the corpus spongiosum 
 urethrae. That part of the canal in the bulb is somewhat dilated, but 
 the diameter of the greater part of this portion of the canal is uni- 
 form. Cowper's glands open near the anterior extremity of the bulb- 
 ous portion. When it reaches the glans, however, it undergoes 
 another dilatation, the /ossa navicularis. At its orifice, the urethra 
 is contracted. 
 
 Mucous Membrane. — The short papillae covering the glans become 
 much elongated at the orifice of the urethra, and highly vascular 
 papillae are found in the anterior half of the fossa navicularis (fossa 
 Morgagnii). They then cease abruptly, but recommence in the 
 posterior part of the glans, and are continued as far as the bulbous 
 portion. 
 
 About one-third of an inch from the meatus, on the dorsal aspect 
 of the fossa navicularis, is situated the lacuna magna. In other 
 parts of the mucous membrane of the urethra, except in the prostatic 
 portion, are numerous small lacunae. 
 
 Glands of Littre. — The majority of these are simple involutions 
 of the mucous membrane, or lacunae ; but some may be described as 
 small branched glands or follicles, which are numerous in the cavern- 
 ous portion of the urethra. These become more simple in the pros- 
 tatic portion, and take the form of simple follicles. 
 
 The epithelium lining the urethra and the small glands just re- 
 ferred to, is for the most part of the columnar form. 
 
 Glandules Tysonianoe. — These little glands are situated in. the 
 fold of skin round the glans penis. They ajJe modified sebaceous 
 
 * Vide article "Vesicula Prostatica," in the Cyclopsedia of Anatomy and Physir 
 ology, by Prof. Kud. Leuckart. 
 
SEMINAL TUBULES. 
 
 835 
 
 Fig. 260. 
 
 glands, and the follicles of which they are composed contain epithe- 
 lium and fatty matter, resembling that which is met with in the 
 ordinary sebaceous follicles of the skin. In this locality these glands 
 open upon the soft skin of the prepuce, and are not associated with 
 hair follicles, as is usual in other situations in which they are found. 
 The peculiar secretion known as the smegma preputii, is not due to 
 these glands alone ; but is rather to be regarded as an accumulation 
 of the moist epithelium of the glans, which is, of course, mixed with 
 the odoriferous sebaceous material. In the beaver, the epithelial 
 secretion is so abundant, as to accumulate in large preputial pouches, 
 the true nature of which was demonstrated by B. H. Weber. The 
 secretion constitutes the substance known as castor. 
 
 Vesicula Prostatica. — Between the openings of the ejaculatory 
 ducts in the middle line of the urethra, and in the substance of the 
 caput gallinaginis, is a samll cavity, lined with columnar epithelium, 
 the prostatic vesicle, or uterus maseulinus, as it has been termed by 
 Weber, from its supposed homology with the female organ. It has 
 since been described under the name of Weberian organ, from its 
 discoverer. 
 
 Seminal Tubules, — The highly tortuous seminal tubes, of which 
 the true secreting portion of the testicle is composed, consist of a 
 fibrous coat, internal to which we find a basement membrane sur- 
 mounted by epithelium. Now the characters of this epithelium, and 
 the nature of the con- 
 tents of the tube, will 
 be found to exhibit dif- 
 ferent appearances, ac- 
 cording to the age of 
 the individual ; and in 
 the lower animals, ac- 
 cording to the period 
 of the year. Sperma- 
 tozoa, which are the 
 fertilizing agents, are 
 not found before pu- 
 berty in man, and 
 among animals are 
 only developed at cer- 
 tain periods. These 
 bodies appear to be 
 formed by certain al- 
 terations taking place 
 in the character of the 
 epithelium lining the 
 tubes, for this latter is 
 most, distinct when 
 spermatozoa are not being formed ; but when the function of the 
 gland is very actively performed, the tubes are seen to be entirely 
 occupied by cells, in which the spermatozoa are ultimately developed. 
 
 When semen is about to be formed, the following changes may be 
 observed to take place in the epithelium. 
 
 Portion of seminal tubnles of man, with enclosed cells. Mag- 
 nified 220 diameters, a. Wall of the tube. b. Nuclei of fibrous 
 coat. c. Basement membrane. — The latter figure represents the 
 action of acetic acid. d. Cells removed from the tubule. 
 
836 MALE ORGANS OF GENERATION. 
 
 The cells become detached from the basement membrane, increase 
 in size, and assume a more spherical form, the contents at this time 
 being entirely granular ; at length, however, several clearer points 
 or nuclei are seen in the interior of the cell, which is now passing 
 down the tubule towards the vas deferens, while it is succeeded be- 
 hind by the formation of new cells. The nuclei in the interior 
 enlarge, and are often seen to contain nucleoli. The parent cell, 
 having much increased in size from the development of its nuclei 
 into cells, appears to undergo no further change ; but in each of the 
 contained cells, which vary much in number, one spermatozoon is 
 developed on the inner wall, in the form of a spiral filament, as was 
 first described by KoUiker. The spermatozoon escapes into the in- 
 terior of the mother cell by the rupture of its development cell. 
 Others are in like manner set free ; and they arrange themselves in 
 a parcel, which may ultimately consist of a vast number of separate 
 spermatozoa, with all the heads arranged in one direction and the 
 tails in the opposite one. 
 
 The cause of this arrangement is probably somewhat similar to 
 that which determines the blood discs to run together, and, assume 
 the form of a small pile of coins. There appears to be a sort of 
 attraction existing between the different spermatic filaments for each 
 other. The contained spermatozoa are at last set free by the rup- 
 ture of the parent cell, and then separate. These changes are usually 
 not completed until the cells arrive at the epididymis ; so that in tie 
 seminal tubules cells alone are found, while in the vas deferens we 
 only meet with perfectly developed spermatozoa. 
 
 Spermatozoa. — The spermatic filament or spermatozoon of man is 
 a perfectly clear hyaloid filamentous body, in which a dilated por- 
 tion, termed the body or head, may be observed, from which is pro- 
 longed a long tail ov filament, which gradually tapers to an extremity 
 which is hardly visible from its extreme tenuity. The head or larger 
 extremity is flattened from side to side and of a conical form, the 
 pointed extremity being anterior. The length of the spermatozoon 
 is about gj^th of an inch, and the width of the body in one direction 
 about the s^^ts^^ and not more than the y^Jjjxjth of an inch in the 
 opposite. The tail varies somewhat in length in different specimens. 
 
 The characters of the spermatozoa vary much in difFer- 
 Fig. 261. ent animals ; thus, in the rat and mouse, the head or body 
 
 is unsymmetrical and curved. In the squirrel, the ante- 
 rior extremity of the head is rounded, and wider than any 
 other portion. In birds, the head is usually attenuated. 
 In reptiles and fishes, the characters of the spermatozoa 
 vary much in different examples. Among the inverte- 
 brata, those of the Crustacea are very remarkable in form. 
 For a detailed account of the characters of the sperma- 
 tozoa in different classes of animals, we must refer the 
 reader to the excellent article. Semen, in the Cyclopsedia 
 of Anatomy and Physiology, by Wagner and Leuckart. 
 
 Development of the Spermatozoa. — The de- 
 
 spermatozoa of the river velopment of the spermatozoa has been care- 
 
 fully investigated by Wagner, Siebold, and 
 
 Kblliker. The different stages are traced more readily in many of 
 
MOVEMENTS OF THE SPERMATIC FILAMENTS. 
 
 837 
 
 DeTelopment of tlie sperma- 
 tic filaments of the rabbit, a,. 
 Parent cell, with five nuclei, 
 &. Bacb nucleus of the parent 
 cell containing a spermatic 
 filament. c. Nucleus with 
 spermatic filament, d. A pa- 
 rent cell, with a number of 
 spermatic filaments set free 
 from the nuclei or cells of 
 development. 
 
 the lower animals than in man. In the rabbit, Kolliker has been 
 able to observe the single spermatic filament within the cell attached 
 to the wall and making two or three turns in a spiral form. It may 
 now be looked upon as almost certain, that each spermatozoon is 
 developed not from any change of the cell, but 
 from the contents within the cell itself. These 
 cells are themselves developed in the interior 
 of a larger or mother cell, into the interior of 
 which the spermatozoa escape by the rupture 
 of their developing cells, and are at last set 
 free by the destruction of the wall of the 
 parent cell itself. Professor Kolliker, in his 
 latest investigations, has arrived at the conclu- 
 sion that the spermatozoa are not developed 
 in the nuclei of the cells, but from them. 
 The nucleus becomes of an oval form, and one 
 extremity is elongated to form the filamentary 
 tail, while its principal part constitutes the 
 body of the filament. In this case, they 
 arrange themselves parallel to each other, the 
 heads being in one direction, and the tails in 
 the opposite. 
 
 Movements of the Spermatic Filaments. — 
 When the spermatozoa have escaped, their active movements com- 
 mence ; and by the continual vibrations of the filamentous tail, they 
 are propelled forwards, according to Henle, at the rate of one inch 
 in seven minutes and a half. The tail alone possesses the power of 
 movement, and the force of the motion is sufficient to move objects 
 many times the weight of the spermatozoon. 
 
 The movements are stopped by all those solutions which act chemi- 
 cally upon the spermatic particle. In water, the activity of the 
 movements is at first increased, but it soon stops altogether, proba- 
 bly in consequence of endosmosis. Urine very soon puts a stop to 
 the movements. The electric spark instantly stops the motions ; 
 but, according to Prevost, galvanism exerts no action upon them. 
 
 After spermatozoa have become quite motionless, and appear to 
 be dead, movements may be excited by the addition of concentrated 
 solutions of different substances, such as sugar, albumen, urea, and 
 various salts. Caustic alkalies in various degrees of concentration, 
 from 5*5 to j%, are special excitants of the movements. Moreover, 
 Kolliker states that semen dried in indifferent substances and in 
 saline solutions, in certain cases, may have its motion restored by 
 dilution with the same fluid or with water. The motions cease in a 
 high or low temperature. 
 
 In the interior of the female organs of generation, the movements 
 continue for a longer period than in any other situation. In the 
 receptacula seminis of insects, spermatozoa have been known to retain 
 their power of movement for many months after they had been dis- 
 charged by the male, and in the higher mammalia, the movement 
 64 
 
838 MALE ORGANS OP GENERATION. 
 
 continues in the mucus lining the generative organs of the female 
 for many days after copulation. 
 
 It must be borne in mind that the semen does not consist only of 
 the secretion of the testicle, but that it also contains the secretions 
 of the prostate, vesiculse seminales, and Cowper's glands. What 
 purposes these different secretions serve, it is difiScult to say, but it 
 is probable that they merely effect the dilution of the fluid in which 
 the spermatozoa move, and thus render it a more favourable medium 
 for their diffusion. 
 
 The movements of the spermatozoa have been regarded by some 
 as due simply to the existence of endosmotic currents, while other 
 authorities have attributed them rather to the inherent contractile 
 property of the tissue of which they are composed. 
 
 The action of certain saline solutions upon these movements, does 
 not seem, to us, to place this question in a much clearer point of 
 view: since the mere physical alteration occurring in their contents 
 would alone be suflScient to excite the contraction of the tissue of the 
 spermatozoon. 
 
 That the spermatozoon is really the essential part of the semen, • 
 and is that in which all the mysterious fecundating power resides, 
 may be now looked upon as proved beyond a doubt. The later 
 beautiful observations upon the ova of the frog, of our lamented 
 friend, Mr. Newport, have shown that impregnation does not take 
 place unless the spermatozoon actually passes through the vitelline 
 membrane and comes into immediate contact with the yolk sub- 
 stance. 
 
 The chemical analysis of the semen has not led to any very im- 
 portant results. The investigations of Frerichs are some of the 
 latest that have been undertaken upon this subject. The most im- 
 portant fact which he has established is, that the spermatozoa con- 
 sists of binoxide of protein, the substance of which epithelial cells 
 are chiefly composed. The other constituents of semen are phosphate 
 of lime, fatty matter, a certain quantity of extractive matter with 
 alkaline sulphates and phosphates, and a small quantity of phos- 
 phorus in an unoxidized state. The imperfectly developed semen 
 contains albumen, but this substance cannot be detected in the fully 
 formed secretion. 
 
 From the various phenomena which we have been considering, 
 and from many other facts which might have been brought forward, 
 we are led to conclude that the spermatozoon is to be regarded in 
 the light of an epithelial cell, or, rather, its nucleus, modified in 
 structure and endowed with peculiar properties. Its mode of de- 
 velopment, the continuous and obviously involuntary nature of the 
 movements, and lastly, its chemical characters, all tend to this con- 
 clusion, while they place the originally received notion of the animal 
 nature of the spermatozoon without the bounds of speculation. 
 
 Upon the nature of the force which is communicated by the sper- 
 matozoon to the ovum, we know nothing. Whether it is to be looked 
 upon as a catalytic action, or whether the changes induced are of a 
 chemical nature, are questions to which we can give no answer. 
 
FEMALE ORGANS OF GENERATION. 839 
 
 Certain it is, that the integrity of the spermatozoon is necessary for 
 fecundation. The spermatozoa of hybrids have been found, upon 
 examination, to exhibit structural imperfections, and it has long 
 been known that these animals are incapable of producing offspring. 
 That all the wonderful changes taking place in the ovum, which 
 lead to the formation of the embryo and the development of the new 
 being, result from the agency of the spermatozoon, is certain ; but 
 how these are brought about, seems beyond the pale of human know- 
 ledge. 
 
 Upon the subjects tre'sted of in the present chapter, the student may refer to Sir 
 Astley Cooper's " Observations on the Structure and Diseases of the Testis ;" Lauth's 
 " M^moire sur la Testicule Humaine ;" Professor KoUiker's Microscopic Anatomy, 
 and articles in the "Microscopical Journal;" Hancock, "On the Physiology of the 
 Male Urethra ;" Article " Semen," in the " Cyclopaedia of Anatomy and Physiology." 
 
 CHAPTER XXXVIII. 
 
 FEMALE ORGANS OP GENERATION. — OVARIES. — GRAAFIAN FOLLICLES. 
 — GERMINAL VESICLE. — PAROVARIUM. — FALLOPIAN TUBE. — UTE- 
 RUS. — VAGINA, AND ACCESSORY ORGANS OF GENERATION IN THE 
 FEMALE. — FEMALE URETHRA. 
 
 Female Organs of Creneration. — The formative organ in the female 
 is the ovary, in which the ova are developed and prepared for fecun- 
 dation. From the ovary, the ova pass into the Fallopian tube or 
 efferent duct, which opens into the uterus, the cavity designed for 
 the reception of the ovum after it has been impregnated, in which 
 the formation of the embryo takes place, and its development into 
 the form of the future being occurs. From the uterus passes the 
 vagina or tube which receives the penis of the male in copulation. 
 With the vagina are connected certain glands and accessory organs. 
 
 Ovaries. — The ovaries are two in number, of an oval form, and 
 flattened antero-posteriorly ; they lie in the cavity of the pelvis, and 
 are enclosed in a fold of the broad ligament of the uterus, with which 
 organ they are connected by a narrow cord or round ligament. 
 Each ovary is invested with a firm capsule of condensed fibrous 
 tissue, which is covered with peritoneum, and is usually attached to 
 the corresponding Fallopian tube by one of the fimbriae of the latter. 
 The ovary is composed of a firm, fibrous, and highly vascular stroma ; 
 in which are imbedded, at various intervals, a number of small cavities 
 or vesicles, originally discovered by De Graaf, hence called G-raafian 
 vesicles. These contain a serous fluid, with a considerable number 
 of cells, amongst which the ovum lies. In the adult ovary, there 
 are usually from ten to fifty, or more, of these Graafian vesicles, 
 varying in size from a small pin's head to that of a pea. The largest 
 are situated chiefly towards the peripheral part of the organ. In 
 
840 FEMALE ORGANS OS QBNEKATION. 
 
 the ovary of the advanced foetus and new-born child, Graafian folli- 
 cles are abundant, and, even at this early period, the ovum 'can be 
 seen within them. The fibrous stroma of the ovary is exceedingly 
 firm and hard ; it consists principally of a modification of white 
 fibrous tissue, the fibres of which interlace in all directions ; but it is 
 highly vascular, especia.lly at the period of paberty. 
 
 Graafian Follicles, — The Gfraafian folUeles or ovisacs consist, 
 when fully developed, of a closed cavity and contents. The walls 
 are composed externally of a firm fibrous membrane, which is con- 
 nected with the fibrous structure of the ovary ; internal to which is 
 a softer and more spongy tissue, containing numerous fusiform cells 
 and fibres, more loosely arranged than in the external part of the 
 
 Fig. 263. 
 
 Ovarj of human subject, a. Graafian follicle -with opening; &. Inner lining of Graafian follicle 
 or memhraaa granulosa, c. Outer portion of the same. a. Ovum. e. Vascular wall of follicle. 
 After CoBte. 
 
 follicle. Internal to this, especially in young follicles, a clear hyaloid 
 basement membrane may be observed, upon the surface of which, 
 lining the entire follicle, is a tolerably thick layer of epithelium, the 
 membrana granulosa of authors. The epithelium is much more 
 abundant in that part of the follicle in which the ovum is situated ; 
 indeed, it is entirely imbedded in it. According to the observations 
 of Dr. Barry, the ovum is attached to the walls of the follicle by 
 certain bands, termed by him retinacula. It is, however, not easy 
 to demonstrate satisfactorily this peculiar arrangement of the mem- 
 brana granulosa. The cells of the membrana granulosa of the 
 Graafian follicle have a polygonal form, and immediately around the 
 ovum are collected into a sort of ring, which is attached to the ex- 
 ternal clear membrane, or zona pellueida, of the ovum. This layer 
 is termed by Dr. Barry the tunica granulosa. The so called retina- 
 cula are composed of similar cells, of which many are also found 
 floating in the fluid of the follicle, which is entirely lined by them. 
 
GERMINAL VBSIOLB. 
 
 841 
 
 Fig. 264. 
 
 (@) 
 
 / 
 
 '(>- 1 >;s' 
 
 "("i ^ \ 
 
 
 
 Ovum. — The ovum is invested with a clear, homtJgeneous, peffectly 
 transparent, firm, elastic, and tolerably 
 thick membrane, exhibiting an appear- 
 ance, when examined by the microscope, 
 very similar to that of the elastic laminas 
 of the cornea, the vitelline or yolk mem- 
 brane, or zona pellucida; the latter 
 being the term always employed in 
 speaking of the mammalian ovum. The 
 zona pellucida appears as a perfectly 
 clear ring, limited on either side by a 
 well defined dark outline. Within this 
 membrane is the yolk, which is composed 
 of a fluid Golfitaining ■prober yolk granules 
 and oil particles, with the clear bright 
 germinal vegiele, containing within it 
 the germinal spot, lying close beneath 
 the zona pellucida. 
 
 The ovum is about yj^th and the ger- 
 minal spot about xxj'jyxjt^ to 5^15*^ of an 
 inch in diameter. 
 
 The yolk granules dififer much in size 
 and form in different animals. They 
 are much more numerous in mature ova 
 than in ova at an early stage of develop- 
 ment, as was pointed out by Bischoff, an 
 observation which we can fully confirm. 
 They appear to be composed of a pro- 
 tein compound, with much fatty matter. 
 
 Fig. 265. 
 
 Mammalian ova. The upper figure 
 'shows an ovum at kn early stage of de- 
 velopment. The second figure, a mature 
 ovum. a. Zona pellucida. o. Yolk. e. 
 'Germinal vesicle, d. Germinal spot. 
 The lower figure shows the zona pellu- 
 cida a, ruptured, and the escape of the 
 yolk granules (6) and germinal vesicle 
 througt the opening. From Costs. 
 
 Ova in various stages of development, from tke toad's oVary. In the right figure some very small 
 ones are observed. 
 
 Germinal VesieU.'^-'Uhe germinal vesicle, or vesicle of Purkinje, 
 consists of a perfectly clear cell, filled with transparent contents, 
 but containing one dark spot, the germinal spot. 
 
 From some observations of Kljlliker aind Bagge upon the deve- 
 lopment of the ova of intestinal worms, it appears that the germinal 
 spot is the part of the ovum whict is first formed ; but it may be 
 regarded as a fact, that the germinal vesicle precedes the formation 
 
842 FEMALE ORGANS OP 6ENEEATI0N. 
 
 of the yolk and the zona pellucida. The immediate formative organ 
 of the ovum is the Graafian vesicle. 
 
 As the ovum approaches maturity, it passes from the centre of 
 the Graafian follicle towards its peripheral portion, and becomes im- 
 bedded in the membrana granulosa, which increases in thickness 
 until it entirely surrounds the ovum. At the same time, the zona 
 pellucida increases in thickness, and the germinal vesicle, which was 
 originally situated in the centre of the yolk, makes its way towards 
 the circumference. 
 
 Parovarium. — Diverging from the hilus of the ovary, may be seen 
 a few canals, which appear to be the remains of the WoiflBan body, 
 an organ which reaches its maximum of development in intra-uterine 
 life. These tubes have been termed the parovarium. 
 
 Fallopian Tube. — The Fallopian tube, or oviduct, is a fibro-mus- 
 cular canal, lined with ciliated epithelium, opening by one extremity 
 into the uterus and terminating in the other by a wide fimbriated 
 orifice, morsus diaboli, which opens into the cavity of the perito- 
 neum. Each Fallopian tube is usually, however, connected to the 
 corresponding ovary by one of its fimbriae. 
 
 The Fallopian tube is invested with peritoneum, and at the fim- 
 briated extremity, the serous membrane becomes continuous with its 
 mucous lining. The muscular fibres of the Fallopian tube are dis- 
 posed in two layers ; the external having a longitudinal and |;Jie 
 more internal a circular course. The contractile fibres are mixed 
 with much fibrous tissue. The contraction of the oviduct has a ver- 
 micular character. The mucous membrane is disposed in longitudi- 
 nal folds, upon which lies a single layer of columnar epithelium. 
 These cells are ciliated, and by the vibration of the cilia, a current 
 is produced, the direction of which is from the ovaries towards the 
 uterus ; so that the transmission of the ovum into the uterus would 
 be favoured, while the passage of the spermatozoa along the tube 
 would be retarded. 
 
 Uterus. — The uterus is a firm hard body, of a pear shape, flattened 
 more or less anteriorly and posteriorly. On each side, at the upper 
 part, are situated the two angles into which the Fallopian tubes open. 
 The portion above this point is called the fundus, while the lower 
 constricted part of the organ is spoken of as the cervix or neck, and 
 that part situated between the cervix and fundus is denominated the 
 body. The highest part of the neck is spoken of as the os internum. 
 The cavity of the uterus is of a triangular shape, about an inch and a 
 half in width at its upper part, where the Fallopian tubes open ; but 
 in the unimpregnated state, its walls almost touch each other, so as 
 to leave a very slight interval, which is usually occupied by mucus. 
 The cavity terminates in the os uteri, or os tincae, a transverse open- 
 ing, bounded anteriorly and posteriorly by two thick and rounded 
 lips. 
 
 The uterus undergoes extraordinary alterations in form and size 
 after the impregnation of the ovum, and becomes very vascular and 
 endowed with a highly contractile power. 
 
 The walls of the unimpregnated uterus are about half an inch in 
 
UTERUS. 
 
 843 
 
 -I 
 
 thickness in their thickest part, and consist of pale organic muscular 
 fibres, .with a certain quantity of 
 fibrous and areolar tissue. The ^'S- 266. 
 
 muscular fibres have been said to be 
 arranged in three layers, but the 
 limits of these layers are not very 
 clearly defined. The outermost layer 
 is very thin, and is incorporated with 
 the sub-peritoneal tissue. It con- 
 sists of longitudinal and transverse 
 fibres, many of the latter, after in- 
 vesting the anterior and posterior 
 surfaces of the organ, lose them- 
 selves upon the Fallopian tubes, or 
 enter the broad and round liga- 
 ments. The middle layer makes up 
 the greater part of the thickness of 
 the uterine walls, and consists of 
 strong bundles; which also run, some 
 in a longitudinal and others in a 
 transverse direction. It is in this 
 layer that the greater number of the 
 vessels which supply the organ, and 
 which become so enormously deve- 
 loped in pregnancy, ramify. The 
 innermost layer is thinner, and com- 
 posed chiefly of thin longitudinal 
 fibres. 
 
 Round the external os uteri, the 
 transverse fibres are very abund- 
 ant, and collected together beneath 
 the mucous membrane, so as to form 
 a sphincter muscle. 
 
 In these diiferent layers, in the 
 virgin uterus, the muscular fibre- 
 cells for the most part are seen as 
 short spindle-shaped cells, in many 
 of which, oval elongated nuclei can 
 be demonstrated. At this period, 
 the cells are often seen to be of very 
 irregular form, and are not always 
 very readily made out. The muscu- 
 lar fibre-cells undergo increased de- 
 velopment in the pregnant state, 
 and towards the end of this period, 
 will be found to be very long cells 
 with a distinct oval nucleus. The 
 cell terminates in long thin and 
 pointed extremities (fig. 266). After 
 delivery, these cells again diminish in dimensions, a number of fat 
 
 S a 
 ■3 S 
 
 S " 
 
 o S 
 
 S3 
 
 
844 
 
 FEMALE ORGANS OF &ENBKATION. 
 
 Mnscnlar fibre cells from the 
 uterus, three weeks after partu- 
 rition, showing the fat globules 
 in their interior. The four cells 
 to the left have been treated witb 
 acetic acid. After KQlliker, 
 
 globules appear in their interior, and ultimately they regain their 
 former appearance (fig. 267) ; while, at the same time, the entire 
 organ returns to its former volume. 
 
 The mucous membrane of the uterus forms 
 a pale and not very thick lining membrane. 
 In the fundus and body of the organ, it is of 
 a redder colour than in the cervix, in conse- 
 quence of the greater vascularity of this 
 part. 
 
 }\nVi I The epithelium is of the ciliated variety. 
 
 f.II / I Imbedded in the mucous membrane of the 
 
 ■ " uterus are numerous glandular follicles, much 
 
 resembling the follicles of Lieberkuhn, in 
 the intestine. These follicles are lined with 
 cylindrical epithelium. They appear to f^m 
 a little whitish mucous secretion. In preg- 
 nancy, these glands are enormously deve- 
 loped; and we shall consider the changes 
 taking place in their structure, when de- 
 scribing the alteration which takes place in 
 the mucous membrane of the uterus after 
 conception. The mucous membrane of the 
 cervix uteri is gathered into deep folds, fox- 
 ing rugse, between which are seen secondary 
 rugge, with a few follicles opening between 
 them. These rugse were described by the older anatomists, under 
 the terms pliooe palmatce, arbor vitce uterinus, etc. 
 
 In the mucous membrane of the neck of the uterus, are situated 
 the so called glandulce, or ovula Nabothi, which secrete the thick 
 mucus usually plugging up this part of the canal. These are closed 
 follicles, and it is probable that, at certain periods, they burst, dis- 
 charging their contents, and are succeeded by the development of 
 new follicles. 
 
 Surrounding the os uteri there are several tongue-like processes of 
 mucous membrane, the villi of the os uteri. Each contains a vascu- 
 lar loop, and is covered with squamous epithelium.* 
 
 The nerves of the uterus are derived from the hypogastric plexus. 
 According to Dr. Beck, the nerves spread out upon the surface of 
 the uterus itself are few in number, and consist of branches which 
 do not unite with each other so as to form a plexus. Dr. Lee de- 
 scribes numerous ganglia connected with these nerves ; and his dis- 
 sections would appear to show that the uterus is much more abund- 
 antly supplied with nerves, than is admitted by anatomists gene- 
 rally. We are not, however, prepared to admit that the textures 
 displayed in the elaborate dissections of Dr. Lee, are entirely or 
 even in great part nervous, or that the bodies which he has repre- 
 sented as ganglia, are really of this nature. This anatomist, like 
 
 * These tUU have lately been carefully described by Dr. Tyler Smitb, Med.-Cbir. 
 Trans., vol. zxxv. 
 
VAGINA. 845 
 
 William Hunter, and Tiedemann, considers, that in the gravid uterus 
 the nerves become much increased in size ; an opinion ■which Dr. 
 Beck has failed to confirm in his very careful and elaborate dis- 
 sections.* 
 
 The ligaments of the uterus are described in works on descriptive 
 anatomy. They are the anterior and posterior ligaments, the broad 
 ligaments and the round ligaments. The two first being merely folds 
 of peritoneum, the latter a rounded cord about five inches in length. 
 Mr. Rainey has shown that the round ligament of the uterus con- 
 tains numerous striped muscular fibres. He describes the round 
 ligament as arising by " thin fasciculi of tendinous fibres ; the inner 
 one from the tendon of the internal oblique and transversalis near 
 the symphysis pubis, the middle one from the superior column of the 
 external abdominal ring near to its upper part, and the external fas- 
 ciculus from the inferior column of the ring just above Gimbernat's 
 ligament." 
 
 The fibres pass backwards and outwards, soon become fleshy, unite 
 to form a rounded cord which runs between the layers of peritoneum 
 forming the broad ligament of the uterus, and is inserted into the 
 upper and anterior part of the uterus. The action of these fibres 
 would be to draw the uterus forwards and thus elongate the 
 vagina.f 
 
 Vagina, and Aocegsory Female Organs of G-eneration. — The vagina 
 consists of an external or fibrous layer, and a muscular coat. It is 
 lined by mucous memjjrane. 
 
 The fibrous tissue of the external coat contains many fibres of the 
 yellow elastic element, and a large network of vessels, with plexuses 
 of veins which form an erectile tissue. 
 
 The muscular fibres run partly in a longitudinal direction, and 
 are partly arranged in transverse bundles which encircle the vagina. 
 
 The mucous membrane is of a pale reddish colour, thrown into 
 many small, firm, prominent folds, columnse rugarum, separated by 
 fissures. The epithelium of the vagina is very large, and of the 
 scaly variety. These cells are almost always present in the urine of 
 females. The nucleus is usually seen very distinctly, and is of an 
 oval form. They present examples of the largest epithelial cells in 
 the body. Close to the external orifice, the mucous membrane forms 
 a reduplication, termed the hymen, which extends across the poste- 
 rior part of the opening. 
 
 There are two small glands, the glands of BarthoKni, in the female, 
 which correspond to Cowper's glands in the male. They are small 
 branched glands, the ultimate vesicles of which are lined with tesse- 
 lated epithelium. They appear to secrete a clear .yellowish thick 
 mucus. 
 
 The corpora cavernosa of the clitoris correspond in structure to 
 those of the penis of the male, but are of very small size. Valentin 
 has described helicine arteries, as in the penis. In the mucous mem- 
 brane of the external female genital organs, are numerous glands ; 
 
 * Phil. Trans. 1846, part ii. f P^''- Trans. 1850, part ii. p. 515. 
 
846 PTJBBRTT. 
 
 and in the labia majora are some sebaceous glands, opening into the 
 hair follicles, which are so numerous in this region. 
 
 The papillse in this situation are very numerous and highly deve- 
 loped, and are covered with scaly epithelium. The submucous tissue 
 is abundant, loose, and without fat ; it contains many fibres of the 
 yellow element. At the labia majora, the mucous membrane becomes 
 continuous with the external skin, to which it gradually approaches 
 in structure. 
 
 Urethra. — The female urethra is much shorter and wider than that 
 of the male. It is about an inch and a half in length, and terminates 
 in the meatus urinarius, which opens in the vulva between the 
 nymphee. This canal may be enormously dilated without danger, 
 and a very large calculus has often been extracted from the female 
 bladder through it. The mucous membrane, especially near the 
 bladder, contains ■ many follicles. 
 
 Besides the works already referred to in the Notes, the authors recommend the 
 reader to consult the following : KolUker's " Manual of Human Histology," translated 
 by Busk and Huxley, Cavendish Society; Dr. Barry's Papers in the Phil. Trans., 
 1838-40; Dr. Lee's " Memoirs on the Ganglia and Nerves of the Uterus," 1849 ; Dr. 
 Snow Beck "On the Nerves of the Uterus," Phil. Trans., 1846; Quain and Sharpey's 
 Anatomy. 
 
 CHAPTER XXXIX. 
 
 PUBERTY. — MENSTRUATION. — MATURATION AND DISCHARGE OP OVA, 
 — FORMATION OP CORPORA LUTEA. — STRUCTURE OP CORPUS LUTBUM. 
 — DISTINCTION OP THE TRUE FROM THE FALSE CORPUS LUTEUM. 
 
 The period of puberty commences at different ages, is characterized 
 by different phenomena, and lasts during widely different periods of 
 time, in the two sexes. In the male, puberty seldom occurs before 
 the fourteenth or fifteenth years. It is marked by increased deve- 
 lopment of the genital organs, the formation of spermatozoa, and the 
 occurrence of sexual feelings. Besides these changes, however, there 
 are others scarcely less striking and characteristic, as the growth of 
 hair on the face and pubes, increased development and symmetry of 
 the limbs and general outline of the body, an alteration in the phy- 
 siognomy, a greater capacity of the respiratory organs, and a strik- 
 ing change in the character of the voice, which becomes of a deep 
 tone, very different from that of boyhood and of the female sex. 
 This alteration of the voice does not take place in eunuchs, who re- 
 tain throughout life a shrill tone, of higher pitch, approximating 
 more in character to the female voice than to that of the male. Per- 
 fectly-formed spermatozoa are not found in the genital organs of the 
 male before the period of puberty. The power of procreation lasts 
 much longer in the male than the female, and often continues up to 
 
MENSTRUATION. 847 
 
 the sixtieth or sixty-fifth years; and instances of virility are recorded 
 at the advanced age of one hundred. 
 
 In the human female, puberty is likewise characterized by the 
 occurrence of certain local changes in the generative organs, and also 
 by changes of a more general character occurring in the body. About 
 this time, which usually occurs between the thirteenth and sixteenth 
 years, but somewhat earlier in hot climates, the organs of generation 
 undergo a considerable increase in size; the breasts enlarge, and 
 an increased deposit of fat takes place over the surface of the body 
 generally. The most important indication, however, of puberty, or 
 aptitude for procreation, in the human female, is the appearance of 
 the catamenia. Nevertheless, instances have occurred in which the 
 menstrual secretion was retarded for several years, or even in which 
 it never appeared, although the susceptibility for procreation existed, 
 and impregnation had taken place. Hence, although the presence 
 of the menstrual discharge indicates that the period of puberty has 
 arrived, its absence cannot be looked upon as a proof of the want of 
 procreative power; while in some instances, the catamenia may 
 appear regularly without impregnation ever taking place, in conse- 
 quence of certain abnormal conditions of the organs of generation. 
 The period 'of puberty is more affected by the habits of the individual 
 than by temperature, although the latter probably exerts some slight 
 influence. . In Africa, menstruation is said to be common as early as 
 the eighth or ninth year ; but in colder climates, and in our own 
 country, it seldom occurs before the thirteenth year, and usually not 
 till the fifteenth or sixteenth year. Still cases are on record in 
 which the catamenia appeared in young children in this country; 
 and their appearance was marked by enlargement of the breasts, and 
 other changes indicative of puberty. 
 
 In both sexes, the period of puberty is much influenced by the 
 conditions under which the child is placed. Habits of indolence, 
 luxury, and indulgence, tend to the early development of puberty ; 
 while, on the contrary, it occurs some years later in those who are 
 inured to active employments, and who are placed under conditions 
 favourable for promoting bodily vigour and mental activity. 
 
 The catamenia occur at intervals of a month, and the discharge 
 usually continues from three to six days. It ceases during pregnancy 
 and lactation, and, in most women, does not recur after the forty- 
 fifth to the fiftieth year ; but exceptions to these statements are met 
 with from time to time. 
 
 At each menstrual period, the mucous membrane of the uterus, 
 and of the generative organs generally, becomes turgid, in conse- 
 quence of an increased local determination of blood. The mucous 
 surface of the uterus is covered by a sanguineous discharge, which 
 escapes from the turgid vessels. 
 
 Of the Menstrual Fluid. — The quantity of the menstrual secretion 
 varies considerably, as also do its characters. In this country, from 
 four to eight ounces are lost at each menstrual period, but sometimes 
 the quantity is much greater. . It is of a dark red colour from the 
 numerous blood corpuscles it contains, and is perfectly fluid, as it is 
 
848 MATURATION OF OVA. 
 
 free from fibrine, a character -which distinguishes it from ordinary 
 blood. Besides blood-corpuscles, it contains a number of smallj 
 pale granular cells, and large corpuscles, containing numerous small 
 oil-globules, the so-called granular corpuscles. 
 
 Dr. Letheby has published an analysis of menstrual fluid which 
 had accumulated to the extent of forty ounces, in consequence of an 
 imperforate hymen. It was thick and black, and it contained no 
 fibrine. Under the microscope were detected altered blood cor- 
 puscles, exudation or granular Corpuscles, mucus cells, epithelium, 
 and granules. 
 
 Water 857-4 
 
 Solid matter 1426 
 
 Fat 5-8 
 
 Albumen 69-4 
 
 Globuline 491 
 
 Hsematin 2-9 
 
 Salts 8-0 
 
 Extractive matter 6-7 
 
 Maturation of Ova', and their Discharge from the Q-raafian Fol- 
 licle. — The most important of the phenomena, however, accompany- 
 ing menstruation, is the maturation and discharge of ova from the 
 ovary. At these periods, a Graafian follicle becomes enlarged, pro- 
 jecting considerably from the surface of the ovary, and_ distended 
 with fluid. Its wall becomes thin at one point, where it at length 
 gives way, and the contents of the follicle escape into the Fallopian 
 tube. The ovum has but rarely been detected in the Fallopian tube, 
 which is scarcely to be wondered at when we consider its small size, 
 and the very few cases in which we have an opportunity of search- 
 ing for it with a chance of success. It has, however, been actually 
 seen in one case in the human female examined by Dr. Letheby, and 
 in another by Mr. Hyett. In animals, it may be detected without 
 diflSculty, although it is only of late years that the escape of the 
 contents of a Graafian follicle at each menstrual period has been 
 placed beyond a doubt. We owe to Dr. Robert Lee, observations, 
 made so long ago as the year 1831, which establish the fact of the 
 rupture of a follicle, and the escape of its contents, at each recur- 
 rence of menstruation. Ova have been detected in the ovaries at a 
 very early age. 
 
 Dr. Ritchie states, that, even during childhood, there is a con- 
 tinual rupture of ovisacs and discharge of ova taking place ; but it 
 is not until the period of puberty that the number of ovisacs be- 
 comes very great, or the ova are perfectly developed and capable of 
 being impregnated. At this time, the stroma of the ovary is seen 
 to be everywhere studded with ovisacs in various stages of develop- 
 ment ; the largest and most mature occupying the peripheral parts 
 of the organ, while those containing mature ova, which are about to 
 be discharged, form considerable prominences, projecting from the 
 surface of the ovary.* 
 
 * Dr. Barry calculates that, in the ovary of the cow, about the period of puberty, 
 there are as many as two hundred millions, corresponding to a cubic inch of the 
 stroma. 
 
HEAT AND KUT IN ANIMALS. 849 
 
 The discharge of ova from the ovary in animals, as in the human 
 subject, occurs only at certain definite periods, which vary much in 
 different animals. It is only at these times that the female animal 
 will receive the male, and that the aptitude for conception exists. 
 At such a time the animal is said to be "in heat" or "rut." In 
 the bitch, this period occurs twice in the year, and lasts for about a 
 fortnight each time ; in the sheep and in the cow, and in domestic 
 animals generally, it occurs much oftener than in wild animals, and 
 the periods of recurrence are not definite. 
 
 If the ovary of an animal be examined at the time of "heat," it 
 will be found turgid with blood, and several Graafian vesicles will be 
 seen projecting from its surface, forming prominences, the most 
 superficial portions of which appear quite thin, and almost ready to 
 rupture and permit the escape of the contents of the follicle. At 
 the same time, a more abundant secretion of mucus takes place from 
 the walls of the vagina and contiguous parts. In a few instances, 
 also, a bloody discharge has been detected in the vagina ; but it must 
 be distinctly borne in mind, that this is not a constant phenomenon. 
 It only occurs in small quantity, and it never appears at each suc- 
 cessive period of beat, while it is always accompanied with increased 
 sexual desire. 
 
 It may be considered as established, that in the human female, at 
 or about the period of menstruation, a discharge of ova takes place ; 
 and at these times the ovaries are extremely turgid, and their vascu- 
 larity is much increased. From very numerous observations, it has 
 been distinctly proved, that conception is more likely to take place 
 a few days after menstruation than at any other period, a fact which 
 has led Naegelp to fix the period of delivery at nine months and 
 eight days after the last menstrual discharge ; while, in a few in- 
 stances, the ovum has actually been seen within a very short time 
 after its escape from the Graafian follicle. 
 
 From these facts, most physiologists have been led to look upon 
 the menstrual periods in the human female as identical with those 
 of heat or rut in animals; a view which has been especially advocated 
 by Bischoff. 
 
 The maturation and escape of ova, then, in all animals, is a peri- 
 odical phenomenon, and even in the human subject, if not' accom- 
 panied with, is shortly followed by, increased sexual desire ; while, 
 in animals, sexual intercourse takes place at these times alone. The 
 rupture of the follicle is probably due to the increased local deter- 
 mination of blood at these periods, by which the contents of the 
 Graafian follicle are forced towards the surface of the ovary. Be- 
 sides the escape of a certain quantity of blood into the follicle, an 
 exudation takes place from its lower part, so that the contents of the 
 follicle are gradually forced towards the surface, and at the same 
 time, the structures at this point gradually become thinner, until at 
 last the peritoneal coat, and the thin layer of the stroma, give way, 
 and the contents of the follicle escape through the fissure. The 
 opening soon closes, leaving a small cicatrix. 
 
 After the ovum has arrived at the most superficial portion of the 
 
860 CORPORA LUTEA. 
 
 follicle in the manner just described, and is about to escape, the 
 fimbriae of the Fallopian tube grasp the ovary ; and the ovum, after 
 it has escaped from the ruptured follicle, ordinarily falls into the 
 funnel-shaped cavity at the base of the fimbriae, whence it is trans- 
 mitted into the Fallopian tube, along which it is gradually propelled, 
 chiefly, no doubt, by the vermicular contractions of the walls, but in 
 part, also, by the vibration of the cilia which line its interior, into 
 the uterus. In some distressing cases, happily very rare, the ovum 
 falls into the cavity of the peritoneum, instead of entering the Fal- 
 lopian tube, and the embryo becomes developed in this situation. 
 These cases usually terminate in death. Sometimes, however, the 
 remains of the foetus escape by suppuration through the abdominal 
 walls, or into the intestine. 
 
 Immediately after the escape of the ovum from the ovary, certain 
 peculiar and characteristic changes ensue in the follicle which con- 
 tained it, and these are influenced by the occurrence of impregna- 
 tion. If impregnation has taken place, the lining membrane of the 
 uterus also becomes the seat of peculiar changes, which do not occur 
 under other circumstances. The changes which affect the ovum 
 itself, consequent upon impregnation, will be more conveniently con- 
 sidered when we have referred to the manner in which corpora lutea 
 are produced. The mode of formation of the membrana decidua will 
 be alluded to afterwards. 
 
 Formation of Corpora Lutea. — If the Graafian follicle of a mam- 
 malian animal be examined soon after the escape of the ovum, it is 
 found to be almost completely filled with an exudation, similar to 
 that which, by its gradual increase in quantity, has caused the ovum 
 to be carried to the surface of the follicle. In a short tiine, the 
 outer portion of the follicle is occupied by a firm yellow substance, 
 which is probably formed from plasma, exuded from its walls. After 
 many careful examinations. Dr. Lee has been led to conclude that 
 this yellow matter is deposited external to both the membranes of 
 the follicle.* Montgomery regards it as situated between the layers, 
 while some authorities look upon the internal surface of the inner 
 membrane as the precise seat of its formation. Dr. Zwicky con- 
 siders the large cells, of which the yellow matter is composed, as 
 modifications of the small cells of the immature follicles. Their 
 nuclei are large and well defined, and they contain numerous oil- 
 globules in their interior. Although bodies, which are liable to be 
 taken for corpora lutea, are, from time to time, found in the virgin 
 ovary, a foetus has never been found in the uterus without the for- 
 mation of an unmistakable corpus luteum. Haller's remark, there- 
 fore, " nullus unquam conceptus est absque corpore luteo," although 
 made so many years ago, may still be regarded as strictly true. 
 
 At first, this exudation is of a dark brown or brownish-red colour, 
 resembling effused blood ; but soon the colour becomes paler, while 
 its consistence is firmer and more dense. At length the follicle is 
 seen to be occupied with a firm mass, which appears to be formed 
 
 * Med.-Chir, Trans., vol. zxii. 
 
MATURATION AND DISCHARGE OF OVA. 
 
 851 
 
 from a secretion poured out from its walla, -which, from its yellow 
 colour in man and many animals, has been called oorpui luteum. 
 
 Corpora Intea of the human female at different periods. 1, Eight days after conception. 2. At the 
 end of the second month. 3. At the termination of the fourth month. 4. At tlie seventh month. 5. 
 Two days after delivery. 6. Twelve weeks after delivery. 7. Corpus luteum of menstruation, or 
 fiilae corpus luteum, four weeks old. 8. Corpus luteum of menstruation thirty days old. 
 
 a. Capsule of ovary. &. Substance of corpus luteum. c. Goagulum occupying cavity in its in- 
 terior, d. Stroma of the ovary. — ^Altered from figures by Montgomery, KOlliker, and Balton. 
 
 Hence, for every follicle in the ovary from which an ovum is dis- 
 charged, a corpus luteum will be found. In cases of twins, two 
 corpora lutea are always present; sometimes one in each ovary, 
 sometimes two in one. The characters which the corpus luteum ex- 
 hibits, and the extent to which the changes giving rise to its forma- 
 tion undergo, will be determined by the circumstance of the ovum 
 being impregnated or not. 
 
 Bischoff proved decisively that the ova in mammalia were detached 
 from the ovary at the time of heat, without coition taking place ; and 
 that corpora lutea were formed in the ovaries, just as if coition had 
 occurred, and impregnation had taken place. 
 
 Raciborski, from numerous experiments upon animals, has shown 
 that whether the rupture of the follicles is or is not accompanied by 
 coitus or by fecundation, the appearance of the lesion which results 
 is, in both cases, absolutely identical. 
 
 Nevertheless, the corpus luteum of pregnancy, except in its earliest 
 stages, has been admitted by all observers, to possess characters by 
 which it may be distinguished from the corpus luteum formed in a 
 follicle from which an ovum has been discharged without subsequent 
 impregnation having occurred. Hence, true and false corpora lutea 
 have been described ; the true occurring only when conception has 
 taken place, while the false are met with in the virgin ovary. This 
 distinction must undoubtedly be recognized ; but there is every reason 
 to believe that the development of a true corpus luteum takes place 
 in obedience to similar nutritive changes which determine the forma- 
 tion of this body, proceeding to a much greater extent than in the 
 case of the false or virgin corpus luteum in consequence of their 
 
852 TRUE AND FALSE CORPORA LUTBA. 
 
 being promoted by the increased determination of nutritive pabulum 
 and the greater vascularity of the ovaries when impregnation has 
 occurred. 
 
 In the cow (according to Dr. Dalton), the corpus luteum reaches 
 its maximum of development in about two weeks after the rupture of 
 the vesicle, and in three weeks more all that remains is a small 
 yellowish spot. If, on the other hand, the rupture of the follicle 
 be followed by impregnation, the corpus luteum does not attain its 
 greatest size till about the middle of the seventh month, and at the 
 termination of the eighth month, it is still of large size, and some- 
 times forms a very remarkable prominence on the surface of the 
 ovary. 
 
 The corpus luteum of menstruation is smaller than that following 
 conception ; its yellow colour appears very rapidly, and soon fades. 
 In the course of one or two months after their first appearance, they 
 are no longer to be distinguished. Virgin corpora lutea are not 
 vascular, and cannot be injected. 
 
 If a section of the corpus luteum be made, a small cavity will be 
 found in the interior, froni which several lines appear to radiate 
 towards its external surface. This little cavity gradually contracts, 
 and ultimately disappears. According to Dr. Montgomery, within 
 the first three or four months of pregnancy, the cavity is large 
 enough to contain a grain of wheat, and often much larger, ^e 
 same observer has always found the cavity absent after the sixth 
 month ; usually it seems to disappear between the fourth and fifth 
 months. A few months after delivery, the corpus luteum entirely 
 disappears. Dr. Montgomery never saw one later than the end of 
 the fifth month after delivery. 
 
 In a medico-legal point of view, the characters of the corpus 
 luteum are sometimes of great importance, and it will be well to 
 recapitulate the most important. The true corpus luteum of preg- 
 nancy possesses very well marked characters, by which it may be 
 distinguished from the false corpus luteum. 
 
 Its projection from the surface of the ovary; its large size, often 
 equal to that of a mulberry, and its rounded form ; the triangular 
 depression and cicatrix upon its surface ; the little cavity in its centre 
 during the earlier period of its formation, or the stellate cicatrix 
 during the latter part of pregnancy; its lobulated or puckered 
 appearance ; its firm consistence and yellow colour ; its great vascu- 
 larity, as may be shown by injection, and its persistence for some 
 time after delivery, are all important points in which the true cor- 
 pora lutea contrast remarkably with those which are formed where 
 conception has not taken place. The false corpora lutea are small 
 in size, and do not project from the surface of the ovary ; they are 
 often angular in form, seldom present any external cicatrix, contain 
 no cavity or stellate marking in the centre ; the material of which 
 they are composed is not lobulated, and their consistence is usually 
 very soft ; they often resemble coagulated blood ; the yellow material 
 exists in the form of a very thin layer, or, as is more commonly the 
 case, not a trace of this substance is present. False corpora lutea 
 
GENERATION. 853 
 
 are easily broken down, and often consist either of small cysts, con- 
 taining serum, or of a simple coagulum. 
 
 The following works and monographs may be consulted upon the subjects treated 
 of In Chapter XXXIX : Dr. W. Hunter on the " Gravid Uterus," 1794 ; Sir Everard 
 Home, in the Phil. Trans., 1817; Df. K. Lee's article; "Ovary," in the Cyolopsedia 
 of Practical Medicine, 1834, and his Lectures on the Theory and Practice of Mid- 
 wifery, 1844; "An Exposition of the Signs and Symptoms of Pregnancy," etc., by 
 W. Montgomery, M. D., 1856 ; Dr. Ritchie's Papers in the Medical Gazette, vol. xxxvi.; 
 Bisohoff, " Beweis von der Begattung unabhangiger Periodischen Eeifung und 
 LosloBung derEier," Giessen, 1844; Raciborski; "Comptes Rendus," 1843; "De la 
 Pubert4 et de I'Age critique chez la Femme et de la Ponte Pgriodique," Paris, 1844 ; 
 M. Pouohet, " Thgorie Positive de I'Ovulation Spontau^e, 1847 ; Miiller's Physiology, 
 supplement by Dr. Baly ; Dr. Paterson's Papers in the Edin. Med. and Surg. Journal, 
 Nos. 142 and 145; Mr. Eoberton's "Essays on Menstruation, and on Practical Mid- 
 wifery," 1851; Zwicky, "Die Metamorphose des Thrombus," Zurich, 1845; Prize 
 Essay on the " Corpus Luteum of Menstruation and Pregnancy," by John C. Dalton, 
 Jun., M. D., Philadelphia, 1851. 
 
 CHAPTER XL. 
 
 IMPREGNATION OP THE OVUM. — CHAN&ES IN THE OVUM IMMEDIATELY 
 SUCCBBDINe IMPREGNATION. — ROTATION OF THE YOLE. — CLEAVAGE 
 OF THE YOLK. — KOLLIKBR'S OBSERVATIONS. — FORMATION OP BLASTO- 
 DERMIC VESICLE, OR GERMINAL MEMBRANE. — FORMATION OF 
 DECIDUA. — STRUCTURE OP THE MEMBRANA DBCIDUA. — DECIDUA 
 REFLEXA. 
 
 Impregnation of the Ovum. — It is exceedingly difficult to give a 
 satisfactory description of the nature of the phenomena occurring 
 in impregnation. It was recently held, by Mr. Newport and other 
 observers, that the contact of the spermatozoa with the exterior of 
 the ovum was sufficient to impregnate it. It was supposed, that 
 liquefaction of the spermatozoa occurred, and that the solution thus 
 formed permeated the vitelline membrane, and impregnated the 
 ovum. The latest researches, however, of the same indefatigable 
 investigator upon the ovum of amphibia, and upon the mammalian 
 ovum, have demonstrated satisfactorily that the spermatozoa actually 
 penetrate and pass through the yolk membrane, and are thus brought 
 into contact with the yolk in the interior. This view was advocated 
 by Dr. Barry several years ago (in 1843), and its accuracy has since 
 been confirmed by the observations of Newport and' BischoiF, and 
 also by Meissner. 
 
 What becomes of the spermatozoa when they have reached the 
 interior is unknown. They disappear, and become liquefied; but 
 the precise manner in which this occurs has not been determined, 
 neither is it known if they penetrate far into the substance of the 
 
 yolk. 
 
 Mioropyle. — In many ova the vitelline membrane is very firm 
 65 
 
854 GBNEEATION. 
 
 and hard ; and it may be fairly asked, how can the delicate sperma- 
 tozoa perforate so tough a structure as the investing membrane of 
 the yolk undoubtedly is in these ova ? Much light has very lately 
 been thrown upon this part of the process of impregnation by the 
 researches of our friend, Dr. Ransom, of Nottingham, by those of 
 Professors Miiller and Remak upon the impregnation of the ova in 
 fishes, and by the investigations of Leuckart,Leydig, and Meissner, 
 upon the eggs of insects, mollusks, and some of the radiata. 
 
 These researches establish the fact of the existence of one or more 
 pores or tubes passing through the coriaceous envelope, and opening 
 upon its interior. Leuckart has shown that these pores are charac- 
 teristic of all insect ova.* 
 
 In July, 1854, Dr. Ransom made some very important observa- 
 tions upon the ova of the stickleback, and demonstrated the exist- 
 ence of a funnel-shaped depression, pierced by a canal, which passes 
 through the chorion in the unimpregnated ovum. This is the micro- 
 pyle, through which the spermatozoa pass to the interior of the ovum. 
 "In the act of impregnation, one or more (as many as four have 
 been seen) spermatozoids pass into the microplye. Actively moving 
 spermatozoids may remain in contact with the chorion for eighteen 
 minutes at least without producing any sensible change in the ovum, 
 provided none of them enter the micropyle ; but when one is seen 
 to enter, in about a quarter of a minute a change is observable, "f^. 
 
 Dr. Ransom has found the micropyle in all the fresh-water fishes 
 which he could obtain. 
 
 The existence of the micropyle in the mammalian ovum has not 
 yet been satisfactorily proved. Remak, however, regards certain 
 streaks existing in the zona pellucida as pores or micropyles through 
 which the spermatozoa may pass. 
 
 Changes in the Ovum immediately succeeding Impregnation. — The 
 period of time at which the ovum leaves the ovary, and passes into 
 the Fallopian tube, varies considerably in different animals ; some- 
 times it occurs within a few hours after impregnation, while in other 
 instances, days, or even weeks, may elapse between the time of coitus 
 and the escape of the ovum from the Graafian follicle. In the dog, 
 the ovum may sometimes be found in the Fallopian tube within 
 thirty-six hours after coitus, and at others, not until ten or twelve 
 days afterwards. In the roe-deer, four months are said to elapse 
 between the act of impregnation and the escape of the ovum, accord- 
 ing to the observations of M. Pockels. About the time that the 
 ovjim leaves the ovary, the cells of the membrana granulosa imme- 
 diately surrounding it undergo a curious change of form, becoming 
 club-shaped ; their pointed extremity being attached to the zona 
 pellucida, by which a stellate appearance is produced (fig. 271, b). 
 Each cell contains a nucleus ; and the ovum, with these radiating 
 cells, presents a stellate appearance. The cells afterwards become 
 round, and disappear about the time that the ovum reaches the 
 
 * MuUer's Archiv,, 1855. 
 
 t Proceedings of the Royal Society, vol. vii. No. 7, Not. 23d, 1854. 
 
ROTATION OF THE YOLK. 855 
 
 uterus, except in the case of the rabbit, where Bischoff has observed 
 that they are lost as soon as it enters the Fallopian tube. 
 
 Soon after the escape of the ovum from the follicle, and in some 
 instances, even before this, the germinal vesicle disappears. Accord- 
 ing to the observations of some observers, amongst whom may be 
 mentioned Barry and Wagner, the germinal vesicle is the seat of 
 cell-formation,* The nature of the earliest changes, however, are 
 very obscure. Eventually, two cells result, which are destined to 
 undergo subsequent division and subdivision. 
 
 As the ovum passes along the Fallopian tube, it increases some- 
 what in size ; the yolk becomes of firmer consistence, and shrinks a 
 little, so as to leave a cavity between it and the zona pellucida, which 
 is occupied with a clear fluid. The original vitelline membrane itself, 
 according to Dr. Barry, disappears by liquefaction. The external 
 investing membrane seems to be derived from the mucous membrane 
 of the Fallopian tube, and it is this which at length becomes deve- 
 loped into the chorion. 
 
 Dr. Bansom describes the changes in the yolk immediately resulting from impreg- 
 nation in the stickleback's egg, as follows: "About fifteen or twenty minutes after 
 impregnation, a remarkable and more vivid contraction begins, causing the yolk to 
 pass through a series of regularly recurring forms. The contraction begins on one 
 side, near the equator, and soon forms a circular constriction, which gives the yolk 
 the figure of a dumb-bell, the longer axis of which is the polar axis of the egg. The 
 constriction travels towards the germinal pole, and next produces a flask-shaped figure ; 
 this is at length lost by the constriction passing on, and the round form is regained in 
 about a minute. This wave reappears, and travels forward again, without any dis- 
 tinct period of rest; and I have seen these movements continue for forty-five minutes, 
 though towards the latter part of this period they are less distinct and more limited 
 in extent. The germinal mass itself, during these contractions, which strongly re- 
 semble the peristaltic movements of the intestine, undergoes changes in form, and has 
 increased in bulk and distinctness. , These movements are unaffected by weak galvanic 
 currents. Cleavage begins in about two hours after impregnation : no embryonic cell 
 was observed before it began, nor in any of the cleavage masses." 
 
 Rotation of the Yolk, — At a very early period after impregnation, 
 Bischoff has observed, in the ovum of the rabbit, guinea-pig, and 
 some other animals, the very interesting phenomenon of the rotation 
 of the yolk. The movements were of a regular rotatory character, 
 and were produced by the active vibration of exceedingly delicate 
 cilia, which had become developed upon the surface of the yolk. 
 This interesting movement may be observed in the ova of frogs and 
 other animals. It can always be seen in those of the common water- 
 snail (Limnceus stagnalis), and forms a most interesting object for 
 observation. 
 
 Cleavage of the Tolk. — Soon after the ovum has become impreg- 
 nated, and the germinal vesicle has disappeared, the yolk of the 
 mammalian animal divides into two large cells, and each of these 
 again subdivides into two, so that the yolk mass now consists of four 
 cells, which soon become sixteen in number ; these sixteen, thirty- 
 two ; and so on, until at last the yolk consists of an aggregation of 
 
 * J. Mailer has shown that in Entochoncha mirahilis (one of the mollusca), the ger- 
 minal vesicle does not disappear, but forms the origin of the embryonic cell in the 
 centre of the yolk. 
 
856 
 
 GENERATION. 
 
 spherical cell-like bodies. Each one of these, in the mammalian 
 ovum, is about the l-2000th of an inch in diameter, and consists of 
 a central light portion, and an external dark part. The external 
 part, which is composed entirely of yolk granules, is not covered by 
 an investing membrane, but the yolk granules seem to be simply ag- 
 gregated round the central clear vesicle, which, when set free, looks 
 very like an oil-globule. According to Bischoff, this vesicle cannot 
 be looked upon in the light of a nucleated embryonic cell. It is pro- 
 bably more correctly considered as a nucleus, around which yolk 
 granules have become attracted. 
 
 The process of cleavage of the yolk is very easily observed in the 
 eggs of the batrachia (frogs, newts, etc.), in which animals the change 
 may be watched from day to day. The division of the yolk has 
 been also very carefully investigated in the ova of certain entozoa, 
 in different species of which two distinct modes of division have been 
 demonstrated. 
 
 KoUiker found in the ova of certain species of Aacaris {nigrovmosa, acuminata, and 
 succisa), that after the disappearance of the germinal vesicle, a new nucleated cell 
 appeared in the centre of the yolk, and in a short time two such cells manifested 
 themselves. Round each one of these cells portions of yolk-mass collected, so that 
 soon the entire yolk was divided into two parts, in the centre of each of which a nucle- 
 
 Cleavage of the yolk in Ascaris mgrovenosa and acuminata, eliowing snccessive steps of the pro- 
 cess of yolk-cleavage. The three figures to the^left are after Kolliker, the two others after Bagge. 
 
 ated cell was situated. Each of these cells again subdivides, and corresponding por- 
 tions of the yolk surround the cells resulting from the original subdivision. This 
 process continues to be repeated until at last the individual cells cannot be distinguished 
 and a granular mass results, from which the young worm is gradually evolved. The 
 division of the yolk appears to result from an attraction existing between its particles 
 and the cells, which divide previous to the subdivision of the yolk-mass. 
 
 In the cephalopoda, only a portion of the yolk undergoes subdivision, the remainder 
 serving for the nutrition of the embryo during incubation ; hence the division into 
 germ-yolk and food-yolk. Amongst the vertebrata, this type is followed in the class 
 of fishes and birds, and in many reptiles. 
 
 In the development of the ovum of ascaris dentata, Kolliker has found that a totally 
 different process occurs. In this entozoon, the first embryonic cell is developed in 
 the centre of the yolk after the disappearance of the germinal vesicle, and grows at 
 the expense of the yolk substance, instead of causing the latter to collect around it. 
 Tliis cell divides into two, which appropriate nutriment in the same manner ; and 
 further division and subdivision occurs, until at last the yolk entirely disappears, and 
 its place is occupied by a number of cells, resulting from the division of the primary 
 cell, and the absorption of the yolk-mass by the subsequent cells. 
 
 Among the invertebrata, therefore, we have seen three distinct types upon which 
 the division and subdivision of the yolk occurs ; but in all we notice the disappearance 
 of the germinal vesicle, and the formation of a new " embryonic" cell, by the division 
 of which a large number of cells is at length produced, giving the ovum the appear- 
 ance of being composed of a granular mass, from which the embryo is at length formed. 
 
GERMINAL MEMBBANB. 
 
 857 
 
 In the mammalia, it is the first of these three modes which is followed. The entire 
 yolk divides, its particles collecting themselves round cells resulting from the division 
 of the embryo-cell, until the yolk-membrane appears to be entirely occupied by granu- 
 lar contents ; in this stage it is often termed the " mulberry mass." 
 
 Fig. 270. 
 
 Multiplication of cells xa tlie yolk. The first four figures are ova of Ascarls deutata ; tlie remaia- 
 der, of CucuUanus elegans. After Kblliker. 
 
 Formation of Blastodermic Vesicle, or Grerminal Membrane. — 
 About the time that the ovum reaches the uterus, the segmentation 
 is complete, and in its general appearance it much resembles the 
 ovarian ovum ; but according to Bischoff, upon careful examination, 
 it is found that the apparently granular mass is really aggregated 
 into minute spherical masses, in the centre of each of which is 
 situated a clear vesicle. Soon each of these collections of granules 
 becomes surrounded with an investing membrane, so that cells are 
 
 Ovum from the ovary of the Guinea-pig, surrounded hy the membrana granulosa, through which 
 the zona pelluolda is distinguished. 
 
858 
 
 GENERATION. 
 
 Fig. 271. 
 Earliest clianges in the mammalian ovum, consequent apon impregnation. 
 
 A perfectly mature ovum from the ovary, showing the spindle- The same ovum with the 
 ehape which the cells of the discus proligerus have assumed. cells of the discus proligerus 
 
 removed. The germinal ve- 
 sicle has disappeared. 
 
 An ovum from the upper third of the 
 ovary. The yolk- does not completely 
 fill the cavity of the zonapellucida. Be- 
 tween it and the zona is seen a clear 
 transparent body, distinct from it. no- 
 tation of the yolk was visible In this 
 ovum. 
 
 An ovum from the middle of the ovary. 
 The yolk is divided into two masses. Two 
 clear vesicles are seen between it and the 
 zona. A spermatozoon is observed upon 
 the zona pellucida. 
 
 The yolk divided into four portions. 
 This ovum was taken from the lower 
 thii'd of the ovary. 
 
 An ovum from the upper part of the 
 uterus, four days old. The segmenta- 
 tion of the yolk has proceeded still 
 further. 
 
FORMATION OF DBCIDUA. 
 Fig. 271. 
 
 859 
 
 An ovum also from the upper part of 
 tlie uterus, showing the further subdi- 
 Tisiou of the yolk ; hut the separate 
 portions are beginning to become incor- 
 porated. 
 
 An ovum from the upper part of the 
 uterus, on the sixth day. The yolk- 
 masses have become incorporated into 
 a single mass, which does not entirely 
 occupy the cavity of the zona pelluclda. 
 
 All the ova delineated in Fig. 271 have been copied from Bischoff's beautiful Memoir on the De- 
 velopment of the Guinea-pig. Glessen, 1852. 
 
 formed, the nuclei of which are represented by the clear central 
 vesicle. The more peripheral cells are first formed, and these from 
 mutual pressure assume a pentagonal or hexagonal form ; they be- 
 come flattened, and united together at their margins, like pavement 
 epithelium. The same process takes place in the interior of the 
 yolk-mass, and as the cells are formed they pass towards the surface, 
 and thus the thickness of the layer first produced becomes increased. 
 A clear fluid only occupies the central part of the yolk. Thus, after 
 the termination of the cleavage process, a membrane composed of 
 cells is formed within the zona pellucida, which BischofF has termed 
 the " blastodermic vegicle." Soon after the formation of this mem- 
 brane, but not until it has increased in thickness by the addition of 
 new cells upon its inner surface, formed from the contained yolk- 
 mass, an opaque roundish spot, consisting of cells and nuclei, makes 
 its appearance at one spot. It is in this space, or " area germinativa," 
 that the first traces of the embryo appear ; and it is developed upon 
 the surface of the " germinal membrane," or " blastodermic vesicle," 
 being covered only by the zona pellucida. As occurs in the bird's 
 egg, the germinal membrane soon becomes divided into two layers : 
 an external or " serous layer" or animal layer, in which the brain 
 and nervous system and different organs of animal life are developed ; 
 and an internal " mucous" or vegetative layer, from which the ali- 
 mentary canal and organs of vegetative life take their rise. 
 
 At the same time that these changes are taking place in the in- 
 terior, the albuminous layer on the external surface of the ovum 
 coalesces with the zona pellucida, forming a single membrane, from 
 which the chorion is formed, or, as maintained by Dr. Barry, the 
 zona pellucida is first removed, and a completely new investing mem- 
 brane produced. 
 
 Formation of Decidua. — Besides the changes which occur in the 
 ovum immediately after conception, which result in the formation of 
 the embryo, and the development of a new covering termed the 
 chorion upon its external surface, alterations of another order arc 
 
860 
 
 GENERATION. 
 
 taking place in the uterus, by which its internal surface becomes 
 adapted for providing nourishment for the embryo in its very early 
 stages, before it has reached that period of development when it is 
 enabled to derive its nutriment by direct absorption from the blood 
 of the mother. The change in question consists in the formation of 
 a soft pulpy tissue, containing cellular elements in great abundance, 
 over the whole internal surface of the uterus. In this soft spongy 
 substance the ovum becomes imbedded, and with it the chorion be- 
 comes intimately connected. This membrane, in consequence of its 
 being thrown off at each parturition, has been termed the "mem- 
 brana deeidua." 
 
 The deeidua was formerly looked upon as an exudation from the 
 mucous membrane of the uterus ; but from the observations of Pro- 
 fessor E. H. Weber and Dr. Sharpey, it has been shown to consist 
 of the much thickened and altered mucous membrane itself. It 
 appears to be composed of glands lined with epithelium, between 
 which ramify vessels surrounded by much soft pulpy tissue, com- 
 posed principally of nucleated cells. At the time of its formation, 
 the ordinary ciliated epithelial lining of the unimpregnated uterus 
 entirely disappears, and its cavity soon becomes filled with a fluid 
 secreted by the soft and swollen deeidua. The os uteri is plugged 
 
 Fig. 272. 
 
 Section of hnman utems at commencing pregnancy, showing the glands in the mncons membrane, 
 and their openings. Twice the natural size. After Weber. 
 
 up by a soft, viscid, mucus-like mass, composed of a secretion from 
 the decidual membrane ; but the cells which are found in it differ 
 materially in character from those immediately surrounding the 
 ovum, in being of an elongated form, while the latter are spherical, 
 and, according to Professor Goodsir, perform the very important 
 office of elaborating the nutrient material for the ovum. 
 
 Structure of the Memhrana Deeidua. — In the unimpregnated 
 uterus of the bitch and other animals, and probably also in that of 
 the human subject, but more minute, are situated numerous small 
 glands, which increase enormously in size immediately after concep- 
 tion. In the human uterus, soon after impregnation, they are seen 
 as elongated wavy tubes, having a tolerably straight course in their 
 more superficial part, but much contorted towards their deep aspect, 
 where they terminate in two or three csecal extremities. The space 
 between these tubes contains capillary vessels and numerous cells, to 
 the increased development and multiplication of which, according to 
 
DECIDITA BEFLEXA. 
 
 861 
 
 Pig. 273. 
 
 Professor Goodsir, the greatly increased thickness of the membrane 
 is due. In the mucous membrane of the uterus of the bitch, Dr. 
 Sharpey has described two distinct kinds of glands, one .simple and 
 the other compound. The openings of both these forms of glands 
 may be readily seen upon the surface of the mucous membrane ; and 
 they soon increase in dimensions, in order to receive the foetal pro- 
 ceases of the chorion, which are covered with epithelium, similar to 
 that lining the follicle. Immediately before the large compound 
 -glands open upon the surface, Dr. Sharpy describes their tube as 
 forming a dilatation or cell, into which a foetal process of the chorion 
 is received. At the bottom of this cell 
 the duct may be seen ; and as it passes 
 towards the deep surface, it is observed 
 to form the branched compound gland. 
 At parturition, the vessels of course 
 come away with the decidual mem- 
 brane, as well as the cells just referred 
 to, but the ducts and branching termi- 
 nations of the glands remain behind. 
 From this arrangement it follows that, 
 in the bitch, the secretion elaborated 
 from the system of the mother by the 
 agency of these glands is brought into 
 close contact with the vessels of the 
 foetus, and afterwards absorbed by them. 
 
 In the human decidua, the openings of the glands may be distinctly 
 seen, and their epithelial lining readily traced. The tubes can be 
 followed through the membrane; in fact, from 
 numerous observations, there can be no doubt 
 that, like the decidual membrane in the bitch, the 
 human decidua consists really of the altered mu- 
 cous membrane of the uterus. 
 
 Leydig has seen ciliary motion in the uterine 
 glands of the sow. 
 
 Next we have to consider how it is, that the 
 ovum becomes covered with the decidual mem- 
 brane. Dr. W. Hunter looked upon the decidua 
 as a closed sac, separating the uterine cavity from 
 the openings of the Fallopian tubes. When the 
 ovum descended, be supposed that it pushed the 
 decidua, as it were, before it, and thus became 
 covered in the same manner that the viscera are 
 invested with peritoneum ; and hence. Dr. Hunter 
 termed that portion of decidua covering the ovum, 
 decidua reflexa, while that lining the uterus was 
 called decidma vera. As the ovum increased in 
 size, that part of it towards the Fallopian tube, 
 which of course remained uncovered by the reflexa, at length received 
 a covering, which was termed decidua serotina. 
 
 Decidua Reflexa. — Since the time of Dr. W. Hunter, much differ- 
 
 TJterine glands of the bitch. Twelve 
 diameters. 1, Simple glands. 2. Com- 
 pound glands. After Br. Sharpey. 
 
 Fig. 274. 
 
 B 
 
 
 Thin section of human 
 decidna soon after im- 
 pregnation had taken 
 -place, sh-owing glands 
 ditvided transversely. 
 Magiiifled twelve dia- 
 imeteis. 1. Tuhe with 
 epithelial lining. 2. 
 Tube from which the 
 epithelium has escaped. 
 After Dr. Bharpey. 
 
862 GENERATION. 
 
 ence of opinion has arisen among anatomists as to the manner in 
 which the ovum became covered with decidual membrane. That his 
 view was incorrect, follows from the fact which has been ascertained 
 by subsequent researches — namely, that the decidua itself consists 
 of the altered mucous membrane of the uterus, and therefore, like it, 
 is continuous with the mucous lining of the Fallopian tubes, and not 
 stretched across the opening, so as to be pushed forwards by the 
 ovum in its descent. The structure of the decidua reflexa, as was 
 pointed out by Goodsir, differs from that of the vera in not contain- 
 ing many ducts. It does, however, contain a few, which are derived 
 from that part of the decidua vera which is continuous with it. 
 
 Dr. Sharpey considers the central part of the decidua reflexa as 
 formed by a layer of exuded lymph, with which the ovum is covered 
 upon its entrance into the uterus, and that the decidua vera extends 
 upwards around it to a point where these two structures become con- 
 tinuous. He also offers the more simple suggestion, that the ovum 
 may first become completely imbedded, and then may carry forward 
 with it a covering of the membrane as it increases in development. 
 A view which agrees in the main with Dr. Sharpey's, and which is 
 probably nearest the truth, is that of M. Coste, who supposes that 
 the ovum becomes partially imbedded in the decidual membrane and 
 soft pulpy matter poured out by its glands. As the ovum increases 
 in size, the decidua grows up around it, so as ultimately to cover it 
 completely. 
 
 The two layers of decidua above referred to, gradually come in 
 contact as the ovum increases in size, until, towards the end of the 
 third month, they are incorporated together and form one mem- 
 brane, which becomes thinner as pregnancy advances, and is ex- 
 pelled with the foetus at the termination of the period of gestation. 
 
 The decidua is a structure admirably adapted for the ovum to be 
 imbedded in in the early stages of its existence, and the numerous 
 glands in its substance seem evidently destined to elaborate a pabu- 
 lum fitted for its nutrition, before its own especial organs are suffi- 
 ciently advanced in development to select and absorb the materials 
 for its subsistence. 
 
 The tufts or villi of the chorion, each of which consists of a col- 
 lection of nucleated cells within a delicate membrane, are the organs 
 by which this nutriment is at first absorbed, just as the collections 
 of cells at the terminations of the minute divisions of the root of the 
 plant absorb and appropriate nutriment from the soil. Soon, how- 
 ever, vessels are prolonged from the foetus into these tufts, and thence- 
 forward it continues to be nourished from the vascular system of the 
 mother; but the nutrient matter is still transmitted through the 
 layer of cells covering the vascular maternal surface, as well as that 
 covering the foetal tuft. The precise nature of this arrangement we 
 shall have to consider when discussing the mode of formation of the 
 placenta. 
 
 Upon the subjects discussed in Chapter XL., the reader is referred to the following 
 works and monographs, besides those mentioned in the notes : Mr. Newport, " On the 
 Impregnation of the Ovum in Amphibia," Phil. Trans. 1851-8; Dr. Barry's "Re- 
 searches in Embryology," Series I. II. Ill,, in Phil. Trans., 1838-40; Dr. Sharpey, 
 
DEVELOPMENT. 863 
 
 " On the Structure and Functions of the Membrana Decidua and the Uterine Glands," 
 in MuUer's Embryology, translated by Dr. Baley; "De Evolut. Strongyli Auric, et 
 Asoarid. aoum. Vivip.," Diss. Inaug. Erlangse, 1841 ; Bischoff, "Entwickel. des Hun- 
 deeies;" Vogt, " Uutersuchungen iiber die Entwickelung der Qeburtshelfer-krote 
 Solothurn," 1841 ; Goodsir's "Anatomical and Pathological Observations ;" M. Coste, 
 " Comptes Kendus," 1847 ; Dr. Ransom, " On the Impregnation of the Ovum in the 
 Stickleback," in the Proceedings of the Royal Society, vol. vii. No. 7, 1854 ; Leuckart, 
 "On the Micropyle and Minute Structure of the Egg-shell in Insects," MiiUer's 
 Archives, 1855. 
 
 CHAPTER XLI. 
 
 ON THE DEVELOPMENT OB THE EMBRYO — EARLY CHANGES IN THE 
 bird's ovum — AREA PBLLUCIDA, AREA GBRMINATIVA, AREA VAS- 
 CULOSA — SEROUS AND MUCOUS LAMINA — INVESTING MEMBRANE 
 AND MEMBRANA INTERMEDIA OF RBICHERT — CHANGES IN THE 
 MAMMALIAN OVUM — PRIMITIVE STREAK — FORMATION OF DORSAL 
 AND VENTRAL LAMIN.® — FORMATION OF THE AMNION — 
 BRANCHIAL FISSURES AND ARCHES — HEART AND LARGE ARTE- 
 RIES — ALLANTOIS — DEVELOPMENT OF THE HUMAN EMBRYO. 
 
 In the last chapter we described the earliest changes resulting 
 from impregnation, and traced them up to the formation of the ger- 
 minal membrane, and the first appearance of the embryo. We have 
 now to consider the manner in which the development of the embryo 
 takes place, and the mode in which the different organs are evolved. 
 It will be most convenient to describe, as briefly as possible, the 
 earliest changes occurring in the bird's egg, in the first instance, and 
 then to consider the development of the mammalian ovum, and that 
 •of the human subject. 
 
 Early Changes in the Bird's Ovum, — In considering the nature 
 of the earliest changes in the egg, resulting from impregnation, but 
 which are dependent for their commencement and continuance upon 
 a temperature varying from 95° to 104° F., we must premise that 
 the yolk of the bird's egg consists of two distinct portions, one 
 which undergoes segmentation, and alone takes part in the formation 
 of the embryo — the germ-yolk ; the other, and by far the larger por- 
 tion, does not undergo segmentation, aTnd takes no part in the forma- 
 tion of the germ, but provides the pabulum for its development and 
 nutrition, whence it is termed t}\ii food-yolk. 
 
 Area Pellucida, Area Crerminativa, and Area Vasculosa. — A few 
 hours after the egg has been exposed to a hatching heat, it will be 
 found that the germ has become less adherent to the vitelline mem- 
 brane. It has assumed a more membranous appearance ; and about 
 the sixth or seventh hour, a clear space may be discerned in its centre. 
 This increases gradually, until it is about a line in diameter. It is 
 called the area pellucida. The darker and more granular part, ex- 
 ternal to the area pellucida, is the area germinativa, in which may 
 
864 DEVELOPMENT. 
 
 be observed a darker portion, which is the future area vasaulosa, so 
 called, because vessels are first observed in this situation. The germi- 
 nal membrane is composed entirely of cells, which result from the 
 original process of cleavage (page 859). These cells increase at its 
 margin ; and in this way the germinal membrane gradually extends 
 itself so as to invest the entire yolk. 
 
 Serous and Mucous Laminse. — At an early period, the germinal 
 membrane manifests a tendency to split into two layers. These are 
 termed laminoe. The upper one, which, in its extent, corresponds to 
 the area pellucida, is the serous laminse. The lower one, which is 
 more extensive, and which extends beyond the vascular area, is called 
 the mucous laminse 
 
 Reichert, however, in his beautiful investigations upon the deve- 
 lopment of the chick, has described the formation of the layers from 
 which the different organs are evolved in a somewhat different 
 manner. 
 
 The "Investing Memhrane" and " Memhrana Intermedia," of 
 Reichert, — The most superficial layer of cells of which the germinal 
 membrane is composed, which is usually known as the " serous layer," 
 has been termed by Reichert the investing membrane. It extends, at 
 its circumference, between the yolk and the vitellary membrane by the 
 apposition of new cells of the yolk to its periphery, and is formed 
 independently of the vascular system. The rudiments of the nervous 
 system are first seen in the form of a line (primitive streak) imme- 
 diately beneath the investing membrane, and are developed from a 
 stratum of cells which has separated itself from the surface of the 
 yolk. Immediately beneath this is another layer of cells which has 
 been termed the mucous layer of the germinal membrane, also the 
 vascular layer ; but Reichert has well described it under the term 
 membrana intermedia. It is beneath the central organs of the nerv- 
 ous system, and in contact with the chorda dorsalis. Lying between 
 the nervous centres on the one hand, and the mucous membrane on 
 the other, and extending beyond the limits of the area pellucida, the 
 membrana intermedia gives origin to the vertebral, cutaneous, and 
 vascular systems, and to the digestive system with the exception of 
 its mucous membrane. In the development of the higher vertebrate 
 animals, according to Dr. Reichert, the membrana intermedia per- 
 forms a most important part. 
 
 About the sixteenth hour, between the external and internal layers 
 of the germinal membrane a new deposition of cells takes place, 
 from which the first traces of vessels are produced. This is the 
 middle layer of the germinal membrane, commonly known as the 
 vascular layer. The vessels are not formed, in the first place, close to 
 the embryo, but at some distance from it, outside the area pellucida, 
 so that now the area pellucida is surrounded by the area vascu- 
 losa ; and this again by the area vitellina. As the vessels increase in 
 number and size, they spread outwards over the area vitellina, and 
 inwards over the area pellucida, until they join the large trunks con- 
 nected with the heart. A little earlier than this, about the four- 
 teenth hour, in the central part of the long axis of the clear oval 
 
FIRST TRACE OF EMBRYO. 
 
 865 
 
 area pellucida, which lies in the transverse axis of the egg, appears 
 a line, thicker at one extremity than the other. This is the first 
 trace of the embryo, and is called the primitive streak or the nota 
 primitiva. 
 
 About the third day of incubation, on each side of the primitive 
 streak, appear two ridges or. 
 
 " ■ " Fig. 275. 
 
 Portion of germinal membrane abont the 
 sixteenth honr of incubation, a. Germinal, 
 membrane, &.' Area Taseulosa. c. Area pellu- 
 cida. d. Nota primitiva or embryo. 
 
 crests, which are termed 
 dorsales. These gradually arch 
 over, and at length inclose the 
 brain and cord. The chorda dor- 
 salis occupies a position under- 
 neath the spinal cord, and appears 
 as a thin gelatinous thread, which 
 corresponds to the axis of the 
 bodies of the vertebrae, which 
 latter, however, are not formed 
 from the chorda dorsalis, but are 
 developed from a double row of 
 four-sided white spots, or verte- 
 bral plates^ arranged symmetri- 
 cally on. each side of the central 
 chorda dorsalis. Passing down- 
 wards from the dorsal laminae, on 
 each side are the ventral laminse, which tend to inclose a space 
 below the chorda dorsalis, like that inclosed by the dorsal laminse 
 above it. The former contains the large vessel. of the trunk (fig. 
 277); the latter the central organs of the nervous system. In 
 this way are produced the hsemal arch and the neural arch of the 
 vertebrae. 
 
 Soon the embryo, and that portion of the germinal membrane 
 immediately connected with it, become somewhat raised ; the embryo - 
 itself taking the form of a boat with its concave surface downwards. 
 This is the first appearance of a visceral cavity, bounded by the 
 ventral laminae, in which the ribs and the transverse processes of 
 the vertebrae are formed. 
 
 That part of the most superficial layerof the germinal membrane, 
 or serous lamina, immedisftely surrounding the embryo, forms a pro- 
 minent fold which soon rises above the surface. According to 
 Reichert, however, the fold is formed from the most superficial layer 
 of the membrana intermedia, and is only covered by the investing 
 membrane. Each fold approaches that on the opposite side, until, 
 by their approximation and communication, a shut sac is formed, into 
 which fluid is poured. In this fluid, the embryo floats. Its open 
 ventral surface gradually becomes closed, until at last it is connected 
 with the yolk only by means of a very narrow pedicle or cord 
 {umbilical cord), which consists of a narrow tube passing from the 
 intestine to the yolk, with certain vascular trunks, through which the 
 nutritive matter absorbed by the vessels ramifying upon the surface 
 of the yolk is carried to the embryo. Of this attenuated cord con- 
 
DEVELOPMENT. 
 
 necting the embryo with the yolk sac or umhilical vesicle we shall 
 speak at some length hereafter. Thus is formed the amnion, to 
 which we shall have to allude more particularly in Chapter XLIII. 
 
 Such are some of the most important changes occurring during 
 the earliest period of incubation in the chick. We shall now con- 
 sider the nature of those which take place in the mammalian ovum. 
 
 Changes in the Mammalian Ovum. 
 
 The essential changes which manifest themselves in the early 
 period of the development of the mammalian embryo are very 
 similar to those which we have briefly described as occurring in the 
 bird's egg ; but in consequence of the small amount of yolk in the 
 former compared with the latter, and therefore the greater depend- 
 ence of the embryo for its nutrition upon external sources, certain 
 differences are observed in the development of the mammalian ovum. 
 
 It has been already stated (p. 857) that by the time the mamma- 
 lian ovum has reached the uterus, the process of segmentation is 
 complete. It is also paler and more transparent. The germinal 
 vesicle had disappeared previous to segmentation ; but whether its 
 contents become mixed up with the substance of the yolk, or new 
 cell-formations primarily result from it, has not yet been conclusively 
 determined. , 
 
 By the aggregation of cells upon the surface of the yolk, a sort of 
 membrane, composed of pentagonal cells with nuclei is formed within 
 the zona pellueida, or yolk-membrane. This is called the hlasto- 
 dermie vesicle, and in its mode of formation nearly corresponds to 
 the germinal membrane of the bird's egg. 
 
 The chorion, or outermost membrane investing the ovum, is formed 
 by the gradual coalescence of the zona pellueida, and the layer of 
 albuminous material with which it is covered. The chorion is at 
 first smooth, but villi are subsequently developed all over its surface. 
 Beneath the chorion is the blastodermic vesicle, which gradually in- 
 creases in thickness by the growth of new cells upon its internal 
 surface. 
 
 In consequence of the great difficulty experienced in procuring 
 human ova at a very early period in a perfectly normal state, and 
 in sufficient number, physiologists have been compelled to make 
 direct observations upon the lower animals, and to assume that a 
 series of changes precisely similar takes place in the human ovum, 
 an inference which has been of late years fully justified by direct 
 observation. In discussing this part of our subject, we shall, there- 
 fore, infer that the early embryonic changes occur in a similar order, 
 and are of the same essential character in all mammalia, except, of 
 course, with reference to the precise period at which they take place, 
 which necessarily differs in various animals, according to the dura- 
 tion of pregnancy. For much that we know of the development of 
 the mammalian ovum, we are indebted to the beautiful researches of 
 Bischoff upon the ova of the dog, rabbit, guinea-pig, and deer. 
 
 Primitive Streak. — At a period varying from the twelfth to the 
 
VBNTKAL LAMINA. 
 
 867 
 
 sixteenth day, the dog's ovum assumes a more oval form. It is 
 ahout three lines in length, and about a line and a half in its short 
 diameter. Its external surface is as yet perfectly smooth, for none 
 of the tufts or villositiea of the chorion are developed. , The central 
 clear space (area pellucida or germinativa) is seen to be surrounded 
 by a darker circle, which eventually becomes the vascular area. 
 
 In the centre of the clear space a line is soon observed. This is 
 the first trace of the embryo, the primitive streak, which appears in 
 the form bf a straight white line, or very shallow groove. It lies 
 across the short axis of the ovum, and therefore occupies a position 
 precisely similar to the embryo chick. 
 
 The primitive streak is formed in the serous or animal layer of 
 the germinal membrane, beneath the investing membrane of Rei- 
 chert. Bischoflf has shown, that in the mammalian ovum the germi- 
 nal membrane becomes divided into two laminae, as in the chick. 
 
 Fig. 276. 
 
 Portion of the germinal membrane of tie bitch's oTum, showing the area pellncida and first traces 
 of the embryo, after Bischoff. A. Germinal membrane. B. Area vascnlosa. C. Area pellncida. D. 
 Laminsc dorsales. E, Primitive trace. Magnified ten diameters 
 
 ■ The external lamina is the serous or animal layer, and the internal 
 one is the mucous or vegetative layer. The middle layer, or mem- 
 hrana intermedia, described by Reichert,_has already been alluded 
 to in page 864, but, according to Bischoff, is not to be detected in the 
 mammalian ovum. 
 
 Formation of Dorsal and Ventral Laminae. — In a short time the 
 cephalic extremity becomes enlarged, and the entire embryo of a 
 guitar-shape in its general outline. As soon as the primitive groove 
 is formed, two oval folds are seen to rise up on each side of it from 
 the serous laminse (d, fig. 276). These are the laminae dorsales, 
 which gradually approximate ; and the groove between them becomes 
 
868 
 
 DEVBLOPMBNT. 
 
 converted into a canal which contains the central organs of the 
 nervous system. 
 
 Beichert supposes that the laminae dorsales actually take part in 
 the formation of the central parts of the nervous system ; but Bis- 
 chofF considers that they represent the dorsal portion of the embryo, 
 and that the nervous system is developed from their lower and inner 
 part only. About this time a few small square-shaped plates make 
 their appearance in the central portion of each dorsal lamina. These 
 
 Plan Bhowing the mode of development of the dorsal and ventral laminie. a. Serons or animal 
 layer ; e. Mucous or vegetative layer ; &, Chorda dorsalis ; c. Ventral laminse, arching downwards 
 to inclose the intestines, the rudiment of which is shown at <2 ; /. Dorsal laminse arching over to 
 convert the groove into a canal for the spinal cord ; g. aorta. 
 
 plates are the first rudiments of the vertebrae. The soft chorda dor- 
 salis, a structure which exists permanently in the lower cartilaginous 
 
 fishes, appears subge- 
 Fig- 278. quently between the rows 
 
 of plates, but this is by 
 no means so distinctly 
 marked in the mamma- 
 lian ovum as it is in the 
 embryo frog or fish, while 
 in the lowest cartilagi- 
 nous fishes, as the myx- 
 ine, the lamprey, and 
 others,, it is persistent. 
 The two plates of oppo- 
 site sides gradually ap- 
 proximate, and ultimately 
 coalesce, including be- 
 tween them a portion of 
 the chorda dorsalis, a tem- 
 porary structure, which 
 disappears entirely with- 
 without being trans- 
 formed into any more 
 
 Germinal memhrane with rudiments of emhryo of the dog. permanent tCXturO. 
 After Bischoff. A. Primitive groove, not closed. B. The rpu 7 • • 7 
 
 three dilatations corresponding to the three vesicles of the ^ ne lammse VlSCeraleS, 
 
 cerebrum. C. Space at lowe* part of groove or »i»j« rtom- nr itenfv/iJ J/ivni'nm aya 
 
 baldaUa. Thestreakatthebottomof the groove is the chorda ", uenirui oamma, are 
 
 do"*"*- also developed in the 
 
 serous layer, and con- 
 tinuous with the laminse dorsales. They project downwards, and 
 ultimately inclose the anterior portion of the embryo. 
 
FORMATION OP THE AMNION. 
 
 In the anterior dilated extremity of the embryo are developed three 
 vesicles, from which the different parts of the brain are ultimately 
 evolved. 
 
 Formation of the Amnion. — The upper layer of the serous lamina 
 becomes raised in the form of a convex ridge, which extends entirely 
 round the circumference of the embryo. This ridge, consisting, of 
 course, of two layers of serous lamina, rises up gradually, and the 
 two portions from opposite sides approximate above the dorsal sur- 
 face of the embryo. The parts of the fold corresponding to the 
 anterior and posterior extremities of the' embryo grow faster than 
 other portions, and soon two considerable reduplications are formed. 
 These are called the cephalic and caudal involucra. The embryo is 
 gradually inclosed by these two layers, which meet over its dorsal 
 surface, and at last coalesce. Thus is formed the amnion ; and the 
 interval between the inner layer and the embryo is the amniotic 
 cavity, which contains a fluid, the liquor amnii. The two layers, 
 after some time, become united into one, except at the points where 
 they are separated by the allantois and umbilical vesicle, forming the 
 single amniotic membrane, which lies within the chorion. The outer 
 layer, however, is separated from the inner surface of the chorion 
 by a quantity of viscid albuminous matter, which is subsequently 
 absorbed. 
 
 The mode of formation of the amnion in mammalian ova is, there- 
 fore, precisely similar to that of the chick, according to Von Baer. 
 Reichert, however, considers that it is formed in a somewhat differ- 
 ent manner to that above described.* 
 
 Fig. 279. 
 
 Fig. 280. 
 
 Plans Bhowlng manner of formation of amnion, allantois, and nmbilical vesicle, a. Chorion with 
 villi most abundant in that part beneath -which the allantois is seen, in flguie 230 ; this portion ulti- 
 mately becomes the placenta. S. Space between the two layers of the amnion, o. Amniotic cavity. 
 d. Situation of intestine, showing its connection with the umbilical vesicle, e. Umbilical vesicle. /. 
 Situation of heart and vessels, g. Allantois. 
 
 In mammalia, the formation of the amnion occurs at a very early 
 period, usually within twenty-four hours after the first appearance of 
 the primitive trace. 
 
 About the twentieth day the ovum is about ten, and the embryo 
 
 56 
 
 * MuUer's Physiology, translated by Dr. Baly, p. 15.52'. 
 
870 DEVELOPMENT 
 
 is between three and four lines in length. The villi of the chorion 
 are beginning to make their appearance, and gradually extend them- 
 selves round the ovum. That portion, however, which is immediately 
 beneath the embryo is the last part of the surface upon which villi 
 appear, while the two ends of the ovum always remain smooth and 
 uncovered with villi. 
 
 By this time, with the exception of their posterior portion, the 
 laminae dorsales have coalesced, and the vertebral plates have in- 
 creased in number. The position of the eye and ear can be deter- 
 mined, and the anterior surface of the body is being gradually closed 
 in by the convergence of the ventral lamince which spring from the 
 under part of the dorsal laminae. At length the body of the embryo 
 appears entirely pinched off as it were, and is only connected with 
 the yolk-sac or umbilical vesicle by a narrow constricted portion, the 
 omphalo-enteric duct. 
 
 Branchial Fissures and Arches. — At this period, three branchial 
 fissures and three visceral arches may be detected. 
 
 The term branchial arch is a bad one, since it conveys the idea 
 that, at a certain period, branchiae are developed in 
 the higher vertebrata, which is not the case. The 
 only structures representing the branchial vessels 
 of fishes are branches which unite to form the de- 
 scending aorta. In fishes, the arches become per- 
 manent, and are surmounted by branchial laminse. 
 They are five in number; at a very early period 
 there are six, but one is not further developed. In 
 the amphibia a similar process takes place, but here 
 the branchiae waste away when the animal assumes 
 its adult form. Usually only two, very rarely four, 
 arches remain in reptiles ; and in birds, mammalia, 
 
 _ and man, only one is persistent. 
 
 Tiscerai or branchial Heart and large Arleries. — About this time also, 
 tterVslhoE^ay tea°n'; the heart and large vessels are formed. The heart 
 » eyes; o, d. right and appears first in the form of a narrow elongated 
 
 -left auricles; e, / right ft- , . , . ,. ,, , . , , , n ,P i 
 
 and left ventrictes; g. tubc, which IS a little twisted, and gradually be- 
 arches.'"i,"2r3, °i"or- comes Completely bent upon itself. The develop- 
 iSrchSircher"' " ment of the heart may be watched in the chick 
 from the beginning of the second day of incubation. 
 It appears between the mucous and serous laminae in the form of a 
 sac, terminating in two or three branches, the future venous trunks. 
 At this early period even rhythmical motions may be observed, but 
 the fluid in its interior is at this time nearly colourless. The large 
 vascular trunk immediately after its origin from the ventricle divides 
 into four vascular arches, which unite again to form the aorta. This 
 vessel, as it passes down close to the spine, again divides, and gives 
 off transverse branches; some of which, the arteriae omphalo mesen- 
 tericse, lying upon the duct of the same name, are conducted to the 
 yolk-membrane, upon the surface of which they are spread out. 
 These vessels absorb the nutrient constituents of the yolk, and carry 
 them to the system of the foetus. With their corresponding veins 
 
OF THE HUMAN EMBRYO. 871 
 
 they form a network over the umhilical vesicle. Their arrangement 
 ■will be more fully described in Chapter XLIIL, on the development 
 of the membranes of the foetus. 
 
 Allantois. — The allantois is first observed as a little solid eminence 
 composed of cells upon the anterior surface of the caudal extremity 
 of the embryo (figs. 279, 280, g). A cavity is soon formed, which 
 is continuous at one period with the lower part of the intestine. 
 
 The allantois grows very rapidly, and in ruminants soon surrounds 
 the entire foetus, its outer surface being in close contact with the 
 chorion ; but in rodent animals, and in man, its chief oflSce is pro- 
 bably that of conducting the vessels of the foetus to the chorion. 
 
 Development op the Human Embeyo. 
 
 It was formerly supposed that man, in his development, passed 
 through various successive stages, each of which was said to have its 
 permanent representative among the lower animals ; but a doctrine 
 80 obviously untrue has long since ceased to have any supporters. 
 Von Baer showed the fallacy of such a statement ; but at the same 
 time proved that up to a certain period of development, the changes 
 occurring in the human embryo were precisely similar to those which 
 take place in the development of all other vertebrate animals ; that, 
 for instance, up to a certain period of its existence, we should be 
 unable to distinguish the embryo of man, or one of the higher verte- 
 brata, from that of a reptile or a fish. All seem to be developed 
 upon one general plan. The organs are evolved in the same order, 
 and the organic functions in the manner of their performance 
 are precisely analogous. After this point has been reached, how- 
 ever, the distinctive characters are well marked, and then it is very 
 easy to say whether the embryo is to assume permanently the con- 
 dition of a fish, reptile, bird, or mammal. 
 
 One of the youngest human ova which has been examined, is de- 
 scribed by Mr. Wharton Jones, and was aborted in the third or fourth 
 week after impregnation. It was about the size of a pea, and was 
 probably detached at a somewhat earlier period. Villi were seen on 
 one side only of the chorion. At one end of the ovum, lying in the 
 midst of a gelatinous material, was the germinal vesicle, but the em- 
 bryo was not yet visible upon it. 
 
 Dr. Allen Thomson has examined two human ova at a somewhat 
 later period. One was a quarter of an inch, and the other half an 
 inch, in diameter. The embryo was about one line in length (fig. 
 282). It lay nearly flat upon the yolk-sac, no constriction being as 
 yet formed. The dorsal laminae were distinct, and had not yet united 
 together. There vas neither allantois nor amniop. This ovum was 
 examined about fifteen days after conception. 
 
 MM. Pockels and Coste have had an opportunity of examining an 
 ovum about this period, in which the umbilical vesicle and allantois 
 were seen very distinctly. The embryo lay in the amniotic fluid ; 
 but the allantois had not yet become connected with the inner sur- 
 
872 DEVELOPMENT 
 
 face of the chorion. In another embryo described by Dr. Allen 
 Thomson, about five or six weeks after conception, the allantois was 
 
 attached to the chorion, and there 
 Fig. 282. existed an umbilical cord, which 
 
 was not yet inclosed in its sheath 
 formed by the amnion. It was the 
 eighth of an.inch in length. The 
 heart projected in the form of a 
 looped vessel from the anterior 
 aspect of the body. The intestine 
 was straight and opened into the 
 yolk-sac, and the opening of the 
 anus was not yet formed. The 
 , ., , ,, J V ,^ umbilical vesicle was becoming 
 
 A human ovum described and figured by Dr. , , rn 
 
 Allen Thomson, about fifteen days after con- narrOWCr near the CmDryO. J. WO 
 
 ception, magnified ten diameters, a. The open , l- i £ „ „ «„«« + 
 
 Tortebral cSnal, bounded by the laminie dor- branchial tSSUrCS WCre present. 
 
 ^itn of'th^etelrt. '"cT. Yoik^s^at ^"Tpi^ce^o" Wagner and Muller have examined 
 
 membrane perhaps connected with the forma- Qya a little further advanCcd. The 
 tion of the chorion. , • i t ,i i j.i_ t_ 
 
 embryo examined by the latter ob- 
 server was two and a half lines in length, and the amnion was 
 seen closely applied to it. There were three pairs of branchial fis- 
 sures and arches. The age of this embryo may be stated with tole- 
 rable certainty to be about twenty-five days. 
 
 Several human ova have been subjected to careful examination by 
 different observers, between three and four weeks old, which may be 
 considered to be in a normal state, and not modified by the occur- 
 rence of any morbid change. At this time, the ovum is about seven 
 lines in length, and the embryo not more than two. It is surrounded 
 by an amnion which adheres to it pretty closely. The chorion is 
 already covered with small villi. Between the chorion and amnion 
 is a considerable quantity of a viscid albuminous material. The 
 embryo is curved. The anterior cerebral vesicles are well marked, 
 and immediately behind them are the very large corpora quadrige- 
 mina. The positions of the ophthalmic and auditory vesicles are 
 indicated. Three or four visceral arches are seen with the branchial 
 fissures between them. The heart is not yet fully formed, and pro- 
 jects from the anterior surface of the body as a bent tube. The 
 anterior and posterior extremities exist in the form of curved flattish 
 appendages. The abdomen is completely open, and the amnion is 
 reflected over the anterior and posterior extremity of the embryo, 
 to form the cephalic and caudal invplucra. 
 
 The heart is large, and consists of a simple auricle and ventricle. 
 Behind the heart is seen the liver, beneath which is situated the 
 intestine, attached by its mesentery. The umbilical vesicle is as 
 large as the embryo, and it is connected with the intestine by a long 
 pedicle, the ductus omphalo-entericus. The vesicle itself is found 
 lying between the chorion and amnion (figs. 280, 294). The duct, 
 with the vessels which accompany it, and the allantois, constitute 
 the umbilical cord, enveloped by the amnion, which membrane forms 
 a tube inclosing these structures. 
 
OF THE HUMAN BMBKYO. 
 Fig. 283. 
 
 873 
 
 Human foetus between the twenty-fifth and twenty-eighth days, to show the relative position of 
 the several organs, a. Chorion with tufts developed over the greater part of its surface. 6. Am- 
 nion ; between the situation of the two b'a the amnion forms a sheath which invests the structures 
 which compose the umbilical cord. c. Position of AUantois with the vessels upon it which ramify in 
 that part of the chorion where the placenta is developed, d. Umbilical vesicle with its narrow 
 pedicle and trunks of omphalo-mesenteric vessels spread out upon its surface, e. The point at which 
 it opens into the intestine. /. Corpora "Wolffiana. g. Liver, h. Heart, i. Eudimeiits^f anterior; 
 and ft rudimentary posterior extremities. I, Branchial fissures and visceral arches, in. Cavities o^f 
 nose and mouth not yet separated. ». Budimeutary eye. o. Rudiments of ear. After Cos te. 
 
874 DEVELOPMENT 
 
 The allantois is seen as a large and well-defined vesicle, which 
 extends to the inner surface of the chorion, to which it is attached. 
 On each side of the mesentery, close to the spine, are situated the 
 large Wolffian bodies. 
 
 About the fourth week, there are three branchial fissures and 
 arches behind the lower jaw. The divisions of the vertebrae are very 
 distinctly marked, and, in consequence of the curvature of the em- 
 bryo, the coccyx and forehead are brought very close together. 
 
 Up to this period, the development of the human embryo is very 
 similar to that of other vertebrate animals. 
 
 The umbilical vesicle, about four or five lines in diameter, dimi- 
 nishes considerably in size during the third month. 
 
 The viscid albuminous material between the chorion and amnion gra- 
 dually becomes absorbed, in consequence of which these two mem- 
 branes approach each other, and almost come into contact, but they still 
 remain separated by a thin membrane, the tunica media of Bischofi'. 
 
 The villi of the chorion increase very much in that portion of its 
 surface situated over the allantois, where the placenta is to be formed. 
 They are not absorbed from other parts, but the interspaces between 
 them gradually become much greater ; and as the ovum increases in 
 size, the tufts appear to be almost limited to the position of the pla- 
 centa, although, with care, they may be seen in other parts of the 
 surface. 
 
 The cord gradually increases in length, and the quantity of liquor 
 amnii in which the ovum floats becomes greater. 
 
 Ossification commences towards the end of the second month, 
 when the foetus is about an inch in length. The septum of the heart 
 begins to be formed, and the aortic arches diminish in number to two, 
 which unite behind to form the descending aorta. One of these 
 arches becomes the pulmonary artery. The development of the kid- 
 neys, ovaries, testes, and external generative organs commences. 
 The bladder is formed somewhat later by the pinching off of a por- 
 tion of the urachus, a narrow tube, which is all that remains of the 
 allantois. The cavities of the mouth and nose are not yet separate ; 
 but the divisions between the fingers and toes are commencing to be 
 marked. 
 
 During the third month, the embryo increases from one inch to 
 about two and a half or three inches in length. In the fourth, it 
 increases another inch ; but during the fifth month, it grows so 
 rapidly as to attain the length of twelve inches. Fat is formed 
 about this time, and the nails are developed. The first movements 
 of the foetus felt by the mother, and termed quickening, usually take 
 place between the fourth and fifth month. The whole surface is 
 covered with lanugo or soft down. The very slow growth of the 
 foetus during the time when the organs are being evolved and it is 
 assuming its distinctive characters, contrasts very remarkably with 
 its rapid increase in size as soon as the various organs have attained 
 a definite form. The process of evolution is a complicated one, and 
 obviously requires much time for the occurrence of the necessary 
 transitional changes. The process of growth is a simple one, and 
 
OP THE SPINAL COLUMN. . 875 
 
 consists merely of the appropriation of new material by structures 
 already formed. The further development of the different textures 
 gradually takes place, and the various organs assume their perma- 
 nent character, until, about the seventh month, the foetus has attained 
 a length of sixteen inches or more, and, under favourable circum- 
 stances, its life may be preserved if it be born at this early period. 
 The testicles descend about the eighth month. 
 
 By the end of the ninth month the foetus has attained the length 
 of eighteen or twenty inches. The head is covered with hair, and 
 the skin becomes invested with a soft pultaceous substance, the vernix 
 caseosa, which consists of cells of epidermis, with a considerable 
 quantity of oily material. The membrana pupiUaris is absorbed. 
 During the latter months of pregnancy, the child lies in utero, with 
 its head downwards, the position in which birth takes place. 
 
 The student is referred, for further information upon the subjects treated of in the 
 present chapter, to the works enumerated at the end of Chapter XL., and to the fol- 
 lowing : Reichert's Observations on the Development of the Chick, in MUller's I'hy- 
 siology, translated by Dr. Baly ; Bischofif's Monographs on the Development of the 
 Dog and Guinea-pig ; De Graaf, Opera Omnia ; Von Baer's Entwickelungs-geschichte ; 
 Dr. Thomson, in the Edinburgh Med. and Surg. Journal, No. 140; Wagner, Icones 
 Physiol. ; Article "Ovum," in the Cyclopsedia of Anatomy and Physiology, by Dr. Allen 
 Thomson. 
 
 CHAPTER XLIL 
 
 ON THE DEVELOPMENT OF THE DIFFERENT ORGANS. — DEVELOPMENT 
 OF THE SPINAL COLUMN. — OP THE FACE AND VISCERAL ARCHES. — 
 DEVELOPMENT OP THE NERVOUS SYSTEM. — OF ORGANS OF VISION 
 AND HEARING. — DEVELOPMENT OF THE HEART AND AORTIC ARCHES. 
 — OP THE ANTERIOR VENOUS TRUNKS. — OP THE LUNGS. — OF THE 
 THYROID. — DEVELOPMENT OF THE ALIMENTARY CANAL. — OF THE 
 LIVER AND PANCREAS. — OP THE SPLEEN. — DEVELOPMENT OF THE 
 WOLFFIAN BODIES AND KIDNEYS. — OF THE SUPRARENAL CAPSULES. 
 — OP THE ORGANS OF GENERATION. 
 
 In the present chapter we have to consider the mode of develop- 
 ment of the most important organs of the body ; but we do not pro- 
 pose to enter further into the process of development of the separate 
 tissues, as this part of the subject has been already treated of in the 
 preceding chapters upon the anatomy of the different organs. 
 
 Development of the Spinal Column.— In man and the higher ver- 
 tebrata, the spinal column is composed of a number of distinct and 
 separate segments, which are connected together by the intervention 
 of a fibrous material. This gives to the whole column a considera- 
 ble amount of mobility. In the lower fishes, however, no such 
 division exists ; and in the place of numerous vertebrae we have a 
 continuous mass of a soft consistence running through the whole 
 
876 . DBVELOPMBNT 
 
 length of the aniraal, and known as the Chorda Dorsalis. The 
 material of which this is composed is the simplest form of cartilage, 
 consisting entirely of a number of large cells, without the interposi- 
 tion of any matrix or intercellular material between them. In the 
 embryonic condition of all vertebrate animals, we meet with a chorda 
 dorsalis entirely composed of cells, and possessing similar characters 
 to the permanent chorda dorsalis of the cartilaginous fishes. It is 
 seen as a faint streak at the bottom of the primitive groove. Above 
 it, the central organs of the nervous system are formed; and imme- 
 diately beneath it, is the great artery of the body, with the viscera. 
 At the anterior and posterior extremities of the embryo, the chorda 
 dorsalis tapers to a point. In its earliest condition, it is composed 
 of a perfectly clear gelatinous material, in the anterior extremity of 
 which cells soon make their appearance, and increase in number un- 
 til the whole becomes cellular. It is surrounded by a delicately 
 fibrous sheath ; external to which the blastema, which gives rise to 
 the development of ossifying cartilage, is deposited. In this situa- 
 tion, after a time, cartilaginous rings make their appearance, and 
 merge by insensible gradations into the fibrous sheath. The fibrous 
 structure gradually disappears, and in its place cartilage is formed, 
 while at the same time the substance of the chorda is removed, to 
 give place to the developing cartilage. The cells of the cord, how- 
 ever, are not transformed into cartilage cells. Eventually only a 
 portion of the cellular substance remains between the bodies of the 
 vertebrae. At a much later period, cartilaginous arches are formed 
 in the inner part of the dorsal laminae, which become converted into 
 the vertebral arches. The outer portion of the laminae dorsales be- 
 comes converted into muscular tissues and integuments. 
 
 The cranium is originally formed from an extension forwards of 
 the chorda dorsalis, and its development occurs at a much earlier 
 period than the bones of the face. In the lamprey and the sturgeon, 
 the connection between the chorda and the cerebral cartilage is per- 
 manent. In mammalia, those portions analogous to the bodies of 
 vertebrae appear in the basis cranii ; and prolonged from these, 
 above, are portions corresponding to the neural arch of the topical 
 vertebra ; and below, parts belonging to the haemal arch. 
 
 The body of the epencephalie or occipital vertebra is represented 
 by a distinct point of ossification, for the basilar process of the 
 occipital bone ; its neural arch by the expanded portion of the bone 
 itself; its hsemal arch by the scapulae, bones of arm, forearm, and 
 hand, and the coracoid processes of the scapula {coracoid bones of 
 oviparous vertebrata). 
 
 The body of the mesencephalic or parietal vertebra is seen in the 
 hasi-sphenoid, or body of the sphenoid bone ; its neural arch is 
 formed by the mastoid portions of the temporal bones, the great wings 
 of the sphenoid and the parietal bones ; its haemal arch by the styloid 
 process of the temporal, and by the body and greater and lesser cornua 
 of the hyoid bones. 
 
 The prosencephalio ov frontal vertebra has its body represented by 
 the anterior or spheno-orbital portion of the sphenoid ; its neural 
 
OF THE FACE AND VISCERAL ARCHES. 877 
 
 arch by the external angular processes of the frontal, the small 
 wings of the sphenoid, and i)iQ frontal hone ; its hsemal arch by the 
 tympanic portion of the temporal bone, and by the articular and 
 dental portion of the inferior maxilla. 
 
 The body of the rhinenoephalic or nasal vertebra is represented 
 by the vomer ; its neural arch by the ossa plana of the ethmoid, and 
 by the nasal bones ; its haemal arch, by the palatine, pterygoid, and 
 malar bones, by the squamous and zygomatic portions of the temporal 
 bones, and by the superior maxillary and intermaxillary bones. 
 
 In thus briefly describing the manner in which the cranial verte- 
 brae are constructed, we feel great regret that our limited space will 
 not permit us to enter more at length into the beautiful and well- 
 known discoveries of Professor Owen in this department. We cannot 
 too strongly recommend the reader to consult upon this important 
 subject, Professor Owen's "Archetype Skeleton," and his "Homo- 
 logies of the Vertebrate Skeleton." 
 
 Development of the Face and Visceral Arches. — The visceral 
 cavity in the upper part of the embryo, at a very early stage of deve- 
 lopment, is bounded above by the cerebral capsule ; and below, and at 
 the sides, by the anterior visceral arch, Reichert has shown that 
 this arch becomes bent upon itself, and from it are formed above 
 the angle, the superior, and below the angle the inferior, maxillary 
 apparatus. 
 
 The superior maxilla grows upwards, and unites with a prominence 
 which is seen in the centre of the forehead, the frontal process of 
 Von Baer — a space being left between the two superior maxillse, 
 which becomes the nasal cavity. Beneath this, the two bones are 
 connected together by the partition which forms the palate, and which 
 does not appear for some time. . 
 
 In animals, besides the maxillary bones, there are a pair of narrow 
 bones between them, extending from the interval between the lower 
 portion of the nasal, and the ascending process of the superior maxilla. 
 These are the intermaxillary bones, which exist in the human foetus 
 in a rudimentary condition. They appear to be formed partly from 
 the nasal process of the forehead, and partly from a portion of 
 blastema which is detached from the lower jaw, to which Reichert 
 gives the name of intermaxillary rudiment. In man this bone is 
 not developed ; but in fishes and amphibia it contains teeth. The 
 intermaxillary bones differ, therefore, in their origin, from the max- 
 illse, and are probably developed from centres independently of the 
 latter. In the monstrosity familiar to us as hare-lip, the superior 
 maxillae and palate bones of opposite sides do not meet, while the 
 intermaxillary bones are united in the centre, and form a prominent 
 tongue of bone, on either side of which is a deep fissure between the 
 intermaxillary and corresponding maxillary bones of each side — 
 thus is produced the deformity of double hare-lip. The cleft of the 
 palate in these cases usually remains open, and in this way the mal- 
 formation is increased. The fissure of the lip seems to arise from 
 the alteration of the deeper parts ; for as such a fissure exists at no 
 
878 DEVELOPMENT 
 
 period of embryonic life in the soft parts, it cannot, like the bony 
 fissure above described, be dependent upon an arrest of development. 
 
 The first visceral arch gives rise to the superior maxillary appa- 
 ratus, consisting of the intermaxillary hones, the vomer, the maxillary 
 and palate hones, and the pterygoid plates of the sphenoid, the lower 
 jaw, and the malleus and incus. 
 
 The second visceral arch gives origin to the hyoid hone, the styloid 
 process, and its ligaments, and the stapes of the ear. In animals a 
 great part of this hyoid apparatus becomes ossified. 
 
 From the third visceral arch arise the posterior cornu and hody of 
 the hyoid hone. 
 
 In the embryo of mammalian animals, the fourth arch is very in- 
 distinct. 
 
 Development of the Nervous System-. — Reichert has shown that, in 
 their earliest condition, the central organs of the nervous system are 
 composed of two laminae united in the middle line, so as to form a 
 central groove. This groove soon becomes converted into a canal, 
 except in the position corresponding to the medulla oblongata. In 
 front of this, certain vesicles appear, from which the several parts of 
 the brain are subsequently developed. 
 
 These vesicles have been named Prosencephalon, Deutencephalon, 
 Mesencephalon, and Epencephalon, by Professor Owen. Of these 
 vesicles, the latter, which corresponds to the cerebellum, is at this 
 early period, the largest of the four. The mesencephalon, or vesicle 
 of the corpora quadrigemina, corresponds to the large optic lobes in 
 fishes, reptiles, and birds, which in these classes are only two in 
 number (corpora higemina), and in the adult human brain is repre- 
 sented by the small corpora quadrigemina (anteriorly nates, poste- 
 riorly testes). In front of this vesiclp is a small one, which is formed 
 before any of the others, and for some time is the most anterior of 
 all. This is the vesicle of the third ventricle, and contains the optic 
 thalami. These points are all well seen in the fish's brain. 
 
 The prosencephalon, from which the cerehral vesicles are formed, 
 lies in front of this, and at first is extremely small ; it bears a pro- 
 portion to the rest of the encephalon not greater than that which the 
 small, unimportant cerebral lobes of the adult fish bear to its entire 
 cerebrum. The prosencephalon soon, however, increases in size, and 
 becomes much larger than all the others. 
 
 Our friend. Professor Retzius, has shown that the three lobes of 
 the hemispheres of the human brain"are developed at difierent 
 periods; the anterior being formed during the second and third 
 months, the middle lobes between the end of the third and beginning 
 of the fifth month, and lastly, the posterior lobes are produced. 
 The cerebellum was seen by Von Baer, in the chick, during the 
 fourth day of incubation. It is formed by the meeting of the laminae 
 of the spinal cord anteriorly to the fourth ventricle ; a short canal 
 is, however, left, which passes towards the corpora quadrigemina or 
 optic lobes, the future iter a tertio ad quartum ventriculum. 
 
 BischofF has demonstrated that, at a very early period, nervous 
 matter is formed along the inner surface of the lips of the primitive 
 
OF THE ORGANS OF VISION AND HEARING. 879 
 
 groove. These two masses of nervous matter gradually approximate, 
 and thus a tube is produced, the walls consisting of nervous matter — 
 while the central cavity, after contracting, becomes the canal of the 
 spinal cord. The upper portion forms the thin dilatations before de- 
 scribed ; while at the opposite end is seen a lancet-shaped depression, 
 the future cauda equina, or sinus rhomboidalis in birds. 
 
 Development of the Organs of Vision and Hearing. — According to 
 Mr. Gray, the eye of the chick is first seen about the thirty-third 
 hour of incubation, in the form of a protrusion from the anterior 
 vesicle, which corresponds to the cerebral lobes, and may be called 
 the optic vesicle. This view agrees with that of Baer; but it does 
 not accord with the observations of Wagner or Huschke. The latter 
 observer states that the eye is developed from a protrusion of the 
 vesicle of the third ventricle — from the deutencephalio enlargement. 
 The retina is a vesicular body which communicates with the cavity of 
 the brain through the hollow, tubular optic nerve. These points 
 may be observed in the chick during the second day of incubation. 
 Bischoff and Mr. Gray have been unable to confirm the statements 
 of Huschke, with reference to the doubling-in of the retina to form 
 two layers. The latter observes that the fibrous lamina and Jacob's 
 membrane are not developed until after the cellular layer of the 
 retina is formed.* 
 
 About the third day of incubation a fissure, which commences at 
 the border of the lens, is seen in the eye of the chick, which Huschke 
 regards as the consequence of inversion of the retina. In fishes, 
 the cleft running from the centre, towards the anterior border of the 
 retina, exists throughout life. In the turtle there is a fissure in the 
 nerve but not in the retina. 
 
 Jacob's membrane is not developed before the thirteenth or four- 
 teenth day of incubation. Mr. Gray describes it as forming at this 
 period an exceedingly fine pale granular stratum upon the choroidal 
 surface of the retina. 
 
 The circle of the iris is seen in the anterior part of the choroid 
 at a very early period ; but the pupil is occupied by a highly vascular 
 membrane, the memhrana pupillaris. This is not attached to the 
 margin of the iris, but to its anterior surface, from which it derives 
 its vessels ; and it is probable that it is reflected over the whole 
 anterior surface of the iris, and possibly lines the anterior chamber 
 of the eye. From the margin of the iris, there extends back- 
 wards another vascular membrane, the membrana capsulo-pupillaris, 
 which is united to the border of the capsule of the lens. This 
 membrane forms a closed sac, the anterior part of which is united 
 to the membrana pupillaris ; while the posterior portion lines the 
 anterior concave surface of the vitreous body. This is supplied 
 with vessels by the capsular branch of the arteria centralis retinae ; 
 and at the margin of the iris, the vessels of the membrana pupillaris, 
 and those of the membrana capsulo-pupillaris, communicate with 
 those of the iris. 
 
 * Phil. Trans., 1850. 
 
880 DEVELOPMENT 
 
 The eyelids are first developed in the form of a ring, which ex- 
 tends over the surface of the eye ; and afterwards the two portions 
 which are to be developed into the lids become adherent to each 
 other. They separate again, either before birth, as in the human 
 subject — or after birth, as in the carnivora and some other classes. 
 
 Organ of Hearing. — The ear appears, at a very early period, upon 
 the vesicular protrusion which ultimately becomes the auditory nerve. 
 It communicates with the cavity of the fourth ventricle, and is 
 situated above the second branchial cleft. The first rudiments of the 
 auditory vesicle were seen by Mr. Gray about the fiftieth hour of 
 incubation in the chick. Throughout the life of the cyclostomous 
 fishes, the ear retains the condition which it presents at an early 
 period of development in the mammalia. Valentin describes the 
 labyrinth as appearing in the form of a separate body of a some- 
 what elongated form. The inner extremity forms a turn and at this 
 point a second vesicle makes its appearance, which becomes the 
 cochlea. 
 
 The semicircular canals are developed by a contraction and folding- 
 in of the walls of the vestibule. From Mr. Gray's careful observa- 
 tions, it appears that the labyrinth, about the twelfth or thirteenth 
 day of development in the chick, has an appearance closely resembling 
 the retina at the same time — a point of great interest. Huechke 
 has shown that the Eustachian tube, the cavity of the tympanum, 
 and the external meatus, are the remains of the first branchial cleft, 
 which eventually becomes divided by the membrana tympani. 
 
 The ossicles of the ear are formed as follows : The malleus and 
 incus, according to Reichert, are produced from the first visceral 
 arch, which also gives origin to the superior and inferior maxillse. 
 The stapes appears to be produced from the second visceral arch, 
 which also gives rise to the hyoid bone and its suspensory apparatus. 
 The ossification of these little ossicles commences in the fourth 
 month of intra-uterine life. 
 
 The development of the mouth and nose have already been alluded 
 to at page 877. 
 
 Development of the Seart and Aortic Arches. — The development 
 of the heart is best studied in the chick. It appears towards the 
 €nd of the second day of incubation, as a small hollow tube between 
 the mucous and serous laminae of the germinal membrane. About 
 the thirty-sixth hour it has become a simple tube, much curved and 
 twisted upon itself. Posteriorly, it terminates in two or three large 
 venous trunks, which are insensibly lost on the germinal membrane ; 
 and anteriorly, it divides into two branches, which unite beneath the 
 vertebral column to form the aorta. The trunk of the vessel again 
 divides into two branches, which are lost on the vascular area. 
 Early on the third day, the heart consists of three cavities — the sinus 
 venosus, the ventricle, and the hulbus aortce ; the first soon becomes 
 divided into the two auricles, and by the' fourth day the ventricle 
 assumes its usual form, and the formation of the septum, which 
 divides its cavity into two portions, commences. 
 
 About the beginning of the third day, the aortic bulb divides into 
 
OF HEART AND AORTIC ARCHES. 881 
 
 four pair of vascular arches. On the fourth day, the first pair dis- 
 appears and is at length obliterated, and the second pair becomes 
 smaller ; but now is formed a fifth pair, which becomes larger on 
 the fifth day, while the second entirely disappears ; so that there 
 are at this time only three pairs, and these of nearly equal size. 
 
 About the sixth day, a considerable alteration takes place in the. 
 circulation. By this time, the allantois forms a vesicle of considera- 
 ble size, upon the surface of which numerous vessels are spread out. 
 These are derived from two branches resulting from the division of 
 the aorta after it has given off the mesenteric artery. The allantois 
 rapidly increases in size ; and as the albumen diminishes in quantity 
 it becomes applied to the membrane of the egg-shell. Through the 
 latter, and through the pores of the shell itself, the air passes to 
 aerate the blood circulating in the vessels of the allantois, which 
 may therefore be looked upon as the great respiratory surface of the 
 chick previous to the formation of lungs. 
 
 About the sixth or seventh day, the heart acquires its character- 
 istic form ; its cavities have approximated more closely, and become 
 conjoined ; the division between the auricles and ventricles can be 
 seen distinctly. The bulb of the aorta appears to rise from both 
 ventricles, immediately over the septum ; and its division into two 
 canals is complete on the seventh day. The pericardium is formed. 
 Only two vascular arches arise on the left side of the aorta, but on 
 
 Fig. 284. 
 
 'h '^ n 
 
 1, 2, 3. Heart of cMck at the ^'ith, 65th, and 85tli honrs of incuhation. After Dr. Allen Thomson. 
 4. Heart of a human embryo about the fifth week. After Von Baer. 1. Venous trunks. 2. Auricle. 
 3. Ventricle. 4. Bulbus arteriosus, e, e. Two aortic arches, which unite posteriorly to form the aorta. 
 g. Auriculo-ventricular opening. A. Septum arising from the lowest part of the caTity of the ven- 
 tricle, i. Inferior vena cara. 
 
 the right there are three. The latter, and the two anterior arches, 
 are the chief divisions of the aorta, and receive the blood transmit- 
 ted from the left ventricle. On the seventh day, the two posterior 
 arches receive blood only from the right ventricle, and become the 
 pulmonary arteries. At present, however, all the arches terminate 
 in the descending aorta. 
 
 At this period, the course of the blood is as follows : From the 
 system of the embryo it is carried by the arterice vitellince, or omphalo- 
 mesentericce, to the network of vessels of the vascular area, whence 
 it passes to the sinus terminalis, which bounds the latter, and which, 
 even on the fourth day, is found to be full of blood. The blood is 
 returned to the heart by two anterior and two posterior venous trunks, 
 arranged in pairs on each side of the median line of the body. The 
 anterior pair are the jugular veins, and the posterior pair are the 
 cardinal veins, which carry back the blood from the Wolffian bodies 
 
882 DEVELOPMENT 
 
 and hinder parts of the embryo. Besides these trunks, however, 
 there is a single one below, which receives the blood from the om- 
 phalo-mesenteric veins, and into this trunk the umbilical veins open 
 subsequently. It becomes eventually converted into the inferior 
 vena cava. 
 
 The pulsations of the heart "commence before any cavity can be 
 observed in the mass of embryonic cells of which it at first consists. 
 Prevost and Lebert have observed the contractions before the deve- 
 lopment of any tissue distinctly muscular — a statement which we 
 can confirm from observations upon the heart of the young field-snake 
 (coluber natrix). Bischofif and Vogt also testify to the very early 
 occurrence of pulsations. 
 
 In the human subject, about the fourth week, the septum between 
 the ventricles commences to be formed. This is completed by the 
 termination of the eighth week. The auricular septum, however, 
 remains incomplete throughout foetal life. The circulation in the 
 foetus, and the peculiarities of the foetal heart, have been already 
 described in page 677 of the present volume. 
 
 Aortic Arches. — In fishes, the vessel continuous with the bulbus 
 arteriosus gives oflF'on either side large branches, which are distri- 
 buted to the gills ; from these organs the blood is collected by small 
 vessels, which ultimately reunite to form a large trunk correspond- 
 ing to the aorta, which lies immediately in front of the spine. Ij 
 the early embryos of all vertebrate animals, similar branches, called 
 aortic arches, may be seen ; and these unite at the back of the vis- 
 ceral cavity, to form the descending aorta. They are visible in the 
 chick about the fortieth hour, according to Dr. Allen Thomson. 
 
 In birds there are at first six aortic arches ; but, as development 
 proceeds, the number becomes less. In mammalia the arches soon 
 diminish to three. One becomes the arch of the aorta, and the other 
 two are the ductus arteriosi of the pulmonary artery, of which the 
 right soon disappears, so that at length only two arches remain — 
 one from the right, and the other from the left ventricle. The an- 
 terior part of the arch from the former becomes the trunk of the 
 pulmonary artery ; while the cavity of the posterior portion {ductus 
 arteriosus), which leads into the aorta, gradually becomes obliterated, 
 and soon after birth nothing remains of it but a fibrous cord, between 
 the aorta and pulmonary artery, which marks its original position 
 throughout life. 
 
 Anterior Venous Trunks. — At an early period of development of 
 the human embryo, the veins entering the heart from the upper part 
 of the body are symmetrical ; and in many of the lower animals they 
 preserve this arrangement throughout life. As the development of 
 the human embryo advances the large venous trunk on the left side 
 diminishes, and subsequently disappears entirely, leaving the right 
 trunk only as a persistent vessel. In a valuable paper published in 
 the Philosophical Transactions, Mr. J. Marshall shows that the 
 dilated portion of the coronary vein, the coronary sinus, is the per- 
 sistent lower portion of the left anterior vein. It is interesting, that 
 in animals which have a left superior cava, the great cardiac coronary 
 
OF ALIMENTARY CANAL. 883 
 
 vein opens into it. Even in the adult human heart there are certain 
 structures which are obviously the remains of the upper portion of the 
 left primitive venous trunk. These observations are very interesting, 
 as they serve to explain certain unusual arrangements in the great 
 anterior veins. Cases are recorded in which the two symmetrical 
 trunks, usually only found at a very early period of development, 
 remain persistent in the adult — an abnormal condition which receives 
 explanation from the investigation of the nature of the early em- 
 bryonic changes. 
 
 Development of the Lungs. — The lungs are first seen in the form 
 of two small masses of cells, at the lower part of the oesophagus. 
 These masses gradually increase in 
 size, and a cavity is formed within. Fig. 285. 
 
 They coalesce at the upper part, a b c 
 
 •which ultimately becomes the trachea. 
 At this period of their development, 
 the respiratory organs appear in the 
 form of vesicles, appended to the 
 lower part of the trachea. 
 
 Reichert has shown that in the 
 chick the lungs appear about the 
 same time as the liver, and states, 
 
 that although they seem to take their . BeTelopment of respiratory organs, show- 
 ti J ^ ing origin of lungs from upper part of ali- 
 
 rise from the memorana intermedia mentary canai, affer Kathke. a. ceso- 
 
 , I . , . .1 J • . phagus of a chick on the fourth day of in- 
 
 (lying between the rudimentary ner- cubation. The rudiments ofthe trachea and 
 vous centres and the mucous mem- '^lSv^:,^lit,Lf$^?- ^n.^l 
 brane, p. 864), the upper portion of re™KrefoV'i;Tofgue!nJ''r:sra- 
 
 the visceral tube, according to his tory organs of the embryo of a horse 1. 
 , ,. • j.T_ 1 t r aT- •„ Tongue; 2. Larynx : 3. Trachea ; 4. Lungs 
 
 observations, is the real seat oi their seen from behind. 
 origin. 
 
 Thyroid Glands. — The first traces of the thyroid are observed in 
 the chick between the sixth and seventh days as a small spherical 
 mass of blastema on each side of the root of the neck. In structure 
 the thyroid resembles that of the spleen. Professor Goodsir de- 
 scribes the thymus, thyroid, and supra-renal capsules as arising from 
 the membrana intermedia ; but Mr. Gray, on the other hand, has 
 pointed out that they are formed from separate and independent 
 masses of blastema. 
 
 The development of the thymus gland, and its subservience to 
 respiration, have been already considered in p. 817. 
 
 Development of the Alimentary Canal. — The alimentary canal is 
 first seen in the form of an elongated straight tube, in which oil glo- 
 bules may be distinguished. According to Reichert's observations 
 on the embryo of the frog, the walls of the intestine appear to be 
 formed originally from the most superficial cells of the yolk. The 
 mucous membrane is developed from a thin layer of smaller cells of 
 the yolk in the interior. Between the outer layer, which becomes 
 converted into the muscular coat, and the inner layer, which con- 
 sUtutes the mucous membrane, a glandular layer is formed. From 
 this tube the different parts are gradually evolved. The omphalo- 
 
884 
 
 DEVELOPMENT 
 
 mesenteric duct is connected with the lower part of the small intes- 
 tine, just previous to its junction with the large intestine. The 
 
 Fig. 286. 
 
 Embryo dog, showing the junction of the umhilical vesicle, with the intestinal canal, a. Nostrils. 
 h. Eyes. c. First visceral arch, d. Second visceral arch, fi, /. Eight and left auricular appendage. 
 g^ h. Eight and left ventricle of the heart, i. Aorta, ft. Liver, between the two lobes of which is re- 
 presented the divided omphalo-mcsenteric vein. I. Stomach. 9n. Intestine, communicating with the 
 umbilical vesicle by the omphalo-mesenteric duct. n. Umbilical vesicle, o. Wolffian bodies, p. 
 Allantois. g. The npper extremities, r. The lower extremities. After Bischoff. 
 
 original connection with the umhilical vesicle is sometimes marked 
 by an elongated pouch, or diverticulum, persistent in the adult. 
 The original jolk-cells, contained in the cavity of the intestine, 
 slowly disappear. The length of the small intestine gradually in- 
 creases, until it assumes its mature form. 
 
 The stomach, at an early period, is not wider than the rest of the 
 canal, and its limits are not to be distinguished. 
 
 Originally, the tube of the intestine is completely closed, both at 
 the mouth and anus. The membrane is gradually removed, and an 
 opening formed. In cases of imperforate anus there is no opening, 
 in which condition an operation is necessary as soon as possible after 
 birth. 
 
 Development of the Liver and Pancreas. — The precise mode of 
 origin of the liver in the embryo has not yet been ascertained with 
 certainty. Some observers hold that this large gland is originally 
 formed upon a diverticulum of the intestine, while others have con- 
 cluded that it is developed from a distinct and separate mass of 
 blastema. In the chick, the first rudiment of this organ may be dis- 
 
OF SPLEEN. 885 
 
 cerned between the fiftieth and sixtieth hour, and is described by 
 Remak as consisting of two sets of cells — an external one, continu- 
 ous with the external surface of the intestine, and an internal layer, 
 composed of epithelium, and lining the sae, which ultimately becomes 
 divided, so as to form ducts. From the epithelial lamina the columns 
 of liver cells are formed ; these extend into the outer lamina, branch 
 and anastomose, and include in the meshes thus produced the cells 
 of the outer surface, from which the vessels, nerves, and areolar tis- 
 sue of the gland are developed. 
 
 MUller describes the liver as formed, on the fourth day of incuba- 
 tion, by a conical protrusion of the intestinal tube. The walls of 
 the protrusion become very thick, and in their substance the ducts 
 ramify. 
 
 According to Reichert, the liver and pancreas in the embryo frog 
 are developed from a portion of yolk, which becomes separated from 
 the general mass at a very early period, and is penetrated by a pro- 
 longation, posteriorly, of the vessel continuous with the cavity of 
 the heart. At first there is no appearance of a division in this mass 
 of yolk substance, which becomes separated from the remainder 
 before any trace of the alimentary canal has manifested itself. Sub- 
 sequently the two organs become more distinctly marked out. In 
 the chick, according to the same observer, these organs are formed 
 from a cellular growth upon the surface of the membrana intermedia, 
 which is separated from the rest of this membrane. At first, the 
 two lobes of the liver are of equal size, but, after a time, the right 
 lobe preponderates, as it does in the adult. 
 
 Mr. Gray has figured the liver and pancreas of the chick. They 
 seem to be developed from two separate protrusions of the intestinal 
 tube, about the ninetieth hour of incubation. No vestige of the 
 spleen is to be detected at this early period. 
 
 The following is Dr. Handfield Jones' account of the development 
 of the liver in the chick. The parenchymatous portion is found to 
 appear first ; soon afterwards, an eminence, for which Dr. H. Jones 
 proposes the name of coUioulus, makes its appearance on the wall of 
 that portion of the intestine which becomes the duodenum. From 
 the latter tube pass two oflsets to the liver ; these, however, waste, 
 but the coUiculus remains. Subsequently, the cystic and hepatic 
 ducts are developed close to the liver ; they extend downwards, and 
 open at the colliculus. In fishes and reptiles, the process of develop- 
 ment is similar. Dr. H. Jones observes that, at one period, the gallr 
 duet in tadpoles is lined by ciliated epithelium. 
 
 Reichert describes the formation of the columns of liver cells, and 
 their increase in number ; but he considers that the cells are not 
 invested with basement membrane. This question has, however, 
 been discussed in Chapter XXXIII. 
 
 Spleen. — Mr. Gray has demonstrated that the spleen arises in a 
 fold of the intestinal laminae about the 114th hour of incubation in 
 the chick ; and it is probable that in the human subject its forma- 
 tion takes place during the third or fourth week. It is quite distinct 
 from the pancreas from the earliest period of development. 
 67 
 
886 DEVELOPMENT 
 
 The first traces of the splenic vein are seen about the thirteenth 
 day of incubation ; and the first blood discs appear in the organ about 
 the eighth day. The Malpighian vesicles are not developed till about 
 the twentieth or twenty-first day, when the period of incubation is 
 near its completion. It is probable that during foetal life this organ 
 plays no very important part, either in the development or destruc- 
 tion of blood corpuscles ; and, as the gall-bladder is found to contain 
 yellowish-green bile, before the formation of the spleen, it is clear 
 that this organ, at least in intra-uterine life, is not concerned in pro- 
 ducing the colouring matter of that fluid — an office assigned to the 
 spleen by Kolliker. 
 
 Wolffian Bodies. — The Wolffian Bodies are two small glands de- 
 veloped at a very early period, and situated upon each side of the 
 spine, extending upwards for some distance. They lie in front of the 
 kidneys and supra-renal capsules, figs. 283, 286. 
 
 Each Wolffian body is provided with an excretory duct, which 
 opens into the cloaca or sinus urino-genitalis, whence its contents 
 pass into the allantois. 
 
 These bodies are to be regarded in the light of temporary kidneys, 
 and bear a similar relation to the permanent organs, that the tempo- 
 rary branchiae of the tadpole bear to the lungs of the fully developed 
 frog. 
 
 In osseous fishes, the corpora Wolffiana are permanent, and con- 
 stitute the kidneys of this class of animals. 
 
 They are much elongated, and are composed of a number of 
 transverse caecal tubes arranged parallel to each other. At first 
 they completely conceal the kidneys, but soon diminish in size, and 
 are at length placed below those organs, which at the same time are 
 gradually assuming importance. 
 
 The Wolffian bodies are not eventually transformed into the epi- 
 didymis, as some have held, or, indeed, into any other organ ; but 
 they disappear completely. The ducts of these glands, however, 
 take part in the formation of the Fallopian tube in the female, and 
 of the vas deferens in the male ; and the last traces' of the tem- 
 porary corpora Wolffiana are found to have some relation to the 
 generative organs. Their remains constitute the parovarium in the 
 female (p. 842). 
 
 From the lower part of the excretory tube, in those animals 
 whose uterus is bifid, its cornua are developed. In the human sub- 
 ject, although at a very early period there are two cornua, these 
 soon coalesce with the central part of the organ which is being 
 developed at the same time, and at last all traces of them are lost. 
 
 The corpora Wolffiana disappear at a much earlier period of de- 
 velopment in the human foetus, than in the lower mammalia ; but 
 Miiller has figured traces of them in an embryo about 3J inches in 
 length. Each body was composed of numerous transverse c^ca, 
 passing from the Fallopian tube towards the corresponding ovary. 
 
 The kidneys are developed independently of the Wolffian bodies, 
 and are situated on the inner side of the ducts of these temporary 
 
OF ORGANS OE GENERATION. 887 
 
 organs. As the latter gradually diminish in size, the development 
 of the former advances. 
 
 Supra-renal Capsules. — The investigatlona of Mr. Gray upon the 
 development of the supra-renal capsules in the chick, have proved 
 that these bodies are not to be recognized before the end of the 7th 
 day, when an ill-defined granular mass, of a reddish colour, makes its 
 appearance between the aorta and upper and inner sides of the Wolf- 
 fian bodies. It seems to have no connection with the thyroid or 
 thymus, as Professor Goodsir described. Its minute structure re- 
 sembled that of the spleen about the fifth day of incubation. By 
 the 8th day, vesicles could be distinguished, and by the 14th day 
 were found to contain oil globules, but no nuclei could be detected 
 in their interior. The capsules were of large size, and of a yellow 
 colour by the 18th day, and now the division into cortical and medul- 
 lary portions was quite distinct. The supra-renal capsules are de- 
 veloped from two separate masses of blastema, situated between the 
 aorta and upper and inner extremities of the Wolffian bodies. They 
 have no connection with the latter, or with each other, and although 
 in their minute structure they resemble the spleen, they arrive at 
 their maximum of development before that organ. 
 
 Organs of Gfeneration, — The sexual organs are developed at a 
 later period than other glands. They are formed from masses of 
 blastema situated upon the inner side of the upper and free part of 
 the ducts of the Wolffian bodies. The ovaries and testicles are 
 developed independently of the Wolffian bodies. At an early period 
 of development the glands in both sexes have very similar characters, 
 and it is not possible to say whether the organ is ultimately to 
 become converted into a testicle, or whether it is to retain its primi- 
 tive characters, which agree with those of the ovary. According to 
 the observations of Valentin, the ovary of mammalian animals is 
 developed in the form of tubes, in which the Graafian follicles are 
 produced. 
 
 The excretory ducts in the lowest vertebrata are two in number, 
 and open into the cloaca, an arrangement which is persistent in 
 many fishes, but in the higher classes they are united, and form a 
 single canal, the arrangement of which has been carefully investi- 
 gated by Miiller. From this canal, in the male, is formed the We- 
 berian organ, or uterus mascuUnus, while in the female it gives 
 origin to the uterus and vagina. 
 
 The upper part of the excretory duct of the Wolffian bodies in 
 the male, becomes much modified in character, and is ultimately con- 
 verted into the epididymis, whilst the lower portion becomes the vas 
 deferens. 
 
 The lower part of the urino-genital canal, which becomes con- 
 verted into the external organs of generation, for some time presents 
 a cleft or fissure on its inferior surface, which in male reptiles and 
 birds remains open throughout life, but in mammalia becomes con- 
 verted into a canal, which extends to the tip of the penis in the male, 
 or along the under surface of the clitoris in the feinale. Sometimes, 
 however, a portion remains open, and the wall of the urethra is de- 
 
888 
 
 DEVELOPMENT. 
 
 ficient in its anterior part below, when the congenital deformity 
 known as hypospadias results. The folds of skin which bound the 
 furrow, ultimately become converted into the scrotlim of the male, or 
 labia of the female. The testicles descend into the cavity of the 
 scrotum about the eighth month, but not unfrequently are retained 
 within the abdominal cavity. 
 
 The authors would refer particularly to the following works with reference to the 
 subjects discussed in the present chapter: MuUer's Physiology; Rathke, Beitrage 
 zur Gesohichte der Thierwelt; Valentin, Entwickelungs-Geschichte ; Dr. Handfield 
 Jones on the Structure and Development of the Liver, Phil. Trans., 1849 ; Victor 
 Gurus' System der Thierischen Morphologie ; Reiohert, das Entwickelungsleben ira 
 Wirbelthier-Keich ; Mr. Marshall's paper On the Development of the great Anterior 
 Veins in Man and Mammalia, Phil. Trans., 1850 ; Mr. Gray's papers On the Develop- 
 ment of the ductless Glands in the Chick, Phil. Trans., 1852; and his paper on the 
 development of the retina and optic nerve, and of the membranous labyrinth and 
 auditory nerve, Phil. Trans., 1850. 
 
 CHAPTER XLIII. 
 
 OF THE MEMBRANES OF THE FCETUS. — OF THE STRUCTURE OF THE 
 CHORION. — OP THE AMNION. — LIQUOR AMNII. — OP THE tTMBI- 
 LICAL VESICLE. — OP THE ALLANTOIS. — ALLANTOIC FLUID. — UMBI- 
 LICAL CORD. — BIRTH. 
 
 Formation of the Placenta. — The early development of the chorion 
 has been described in a former page. At first, the villi are composed 
 entirely of cells, invested on their external surface with a very deli- 
 cate structureless membrane ; but after the vessels, conducted by the 
 allantois, have reached its inner surface, vascular loops are prolonged 
 into them. Bischofif considers that in the human ovum, and in that 
 of the bitch, which are destitute of an albuminous covering, the tufts 
 are formed directly from the zona pellucida alone. 
 
 In two orders of mammalia, the maraupialia and the monotremata, there is no con- 
 nection between the vascular system of the mother and that of the foetus, which is 
 nourished from a very early period with milk. 
 
 The relation between the blood of the foetus and that of the mother is nearly the 
 same in all placental mammalia. The wall of the maternal vessels — a layer composed 
 of cells from the modified mucous membrane of the uterus — and another cellular layer 
 belonging to the foetal tuft, always separate them ; but in the greater number of mam- 
 malia, the foetal tufts come into relation with the capillary vessels of the mother ; while 
 in man they are in contact with the walls of a large cavity containing blood. 
 
 The mode of arrangement of the tufts, or, in other words, the form which the pla- 
 centa assumes, is very different in the various mammalia. Sometimes the whole 
 chorion is covered with villi, as in the pachydermaia (hog, elephant, etc.); sometimes 
 these form little collections or cotyledons, as in the greater number of ruminants 
 (sheep, ox, goat, etc. ) ; sometimes they form a band encircling the central portion of 
 the chorion, as in the carnivora; and in some instances they are confined to one single 
 part, forming a single placenta, as in the rodentia, and also in the human subject (vide 
 figs. 280, 292). 
 
 The beautiful branched and highly complicated conical foetal villi of the ruminant 
 dip into deep recesses in the maternal cotyledons, upon the walls of which the maternal 
 
CHOKION. 
 
 Fig. 287. 
 
 capillary vessels are spread out; while the vascular loops of the human foetus, as was 
 shown by Professor Weber, dip into the dilated vessels of the mother, which become large 
 venous sinuses, and are thus completely bathed on all sides by the mother's blood. 
 
 The villi increase very much in numher and complexity in that 
 part of the chorion which is to become the placenta ; while on other 
 parts of the surface they retain the same characters as at a very 
 early stage. Each villus contains a vascular loop, which is directly 
 continuous with the umbilical vessels of the fcetus ; and the whole of 
 the blood of the foetus is made to pass through the vessels in the 
 tufts by the forces of the foetal circulation. The cells of which the 
 villi were entirely composed, at a very early period diminish in 
 number ; but still several remain towards the apex. 
 
 During this time, the soft membrana decidua has been increasing 
 in thickness and vascularity. Its capillary vessels become enor- 
 mously increased in diameter, and ultimately form small pouches or 
 sinuses containing blood. The foetal tufts come into close relation 
 with the walls of these sinuses, but are still separated by a thin layer 
 of the cellular decidua, and project into their interior, being of course 
 invested with the wall of the sinus, just as the viscera are covered 
 with peritoneum. Such is the relation of the bloodvessels of the 
 foetal placenta to those of the mother, accord- 
 ing to the observations of Dr. J. Reid, Weber, 
 and Goodsir. The structures, therefore, which 
 intervene between the blood of the foetus and 
 that of the mother, are the following : the walls 
 of the foetal capillaries ; the cells at the extre- 
 mity of the foetal tufts ; the delicate investing 
 membrane covering these ; a thin stratum of 
 fluid separating the maternal and foetal portions 
 of the placenta, and containing not only the 
 materials for absorption, but any substances to 
 be removed from the foetal blood ; the cells of 
 the membrana decidua ; and, lastly, the wall of 
 the venous sinus, into which the foetal tuft pro- 
 jects. 
 
 The cells upon the surface of the villus form 
 little groups, and appear to radiate, as it were, 
 from the centre of each collection. This cen- 
 tral point, Professor Goodsir regards in the 
 light of a germinal spot or nutritive centre, which supplies successive 
 generations of cells as the old ones are gradually removed. 
 
 The wall of the venous sinus of the mother, reflected from tuft 
 to tuft, forms numerous tubular processes, passing in various di- 
 rections amongst them ; thus connecting the several tufts with each 
 other, and forming a sort of supporting framework for the entire 
 organ. The tubular prolongations, of course, contain cells of the 
 decidua in their interior, and by their outer surface are continuous 
 with the lining membrane of the venous sinuses of the mother. Dr. 
 J. Reid has shown that the foetal tufts often dip quite into the uterine 
 sinuses. 
 
 Extremity of a viUus, 
 showing capillary vessels. 
 After Weber. 
 
890 
 
 DEVELOPMENT. 
 
 Weber has made some beautiful Injections of the fcetal tufts, which 
 demonstrate very satisfactorily the highly tortuous nature of the 
 capillaries, and show that the convoluted capil- 
 lary vessel may make many turns from one foetal 
 loop into another, before it opens into one of the 
 branches of the umbilical vein. Dr. Reid de- 
 scribes the blood brought by the curling arteries 
 of the uterus as being poured " into a large sae 
 formed by the inner coat of the vascular system 
 of the mother," from which the blood is carried 
 back by the veins. The researches of Dr. J. 
 Reid agree with those of Weber ; but Eschricht 
 holds, that in man the arrangement is essentially 
 the same as in animals ; and that the capillaries 
 of the placenta of the human foetus are brought 
 into relation with the capillaries only of the 
 mother. In many animals, the maternal and foetal portions of the 
 placenta can be very readily separated from each other ; but in man 
 this cannot be done without tearing the vessels. 
 
 Fig. 289. 
 
 Relation betTreen the 
 foetal and maternal ves- 
 sels ; after Dr. Reid. Foetal 
 tuft dipping into dilated 
 venous sinus, a. Curling 
 artery of uterus, b. Ute- 
 rine vein. c. Sinns. d. 
 Vessels of foetal tuft, com- 
 posed of a small braucli of 
 artery and vein. 
 
 Uterine sinuses and fcetal tufts ; after Dr. Reid. c. Curling artery of the uterus, 
 into which a tuft is prolonged, e. Fcetal tuft. b. Foetal vessels branching. 
 
 a. Uterine sinns, 
 
 The formation of the placenta commences in the human subject 
 towards the end of the second month ; and by the third it assumes 
 its ordinary character. As the uterine vessels become enlarged, the 
 rush of blood through them is accompanied with a well-known mur- 
 mur, termed the placental bruit, which is usually detected about the 
 third month; It is one of the most important signs of pregnancy, 
 and is not liable to be mistaken for the sounds of the foetal heart, 
 because it is exactly synchronous with the mother's pulse, and its 
 situation does not vary. 
 
 Towards the termination of the period of pregnancy, the placenta 
 becomes^ hard, and a curious change takes place in its capillary ves- 
 sels, which has only been carefully investigated within the last few 
 years. The alteration consists in the appearance of a number of' 
 oil-globules in the coats of the vessels — in fact, in the occurrence of 
 fatty degeneration of the foetal tufts. In a former page, we described 
 a similar change taking place in muscular fibre-cells of the uterus, 
 when the period of their activity was passed, and the organ was 
 gradually returning to its former volume. The change alluded to 
 
PLACENTA, 
 
 891 
 
 has been looked upon by many pathologists as of a morbid nature, 
 and has been brought forward as one of the causes of abortion ; but 
 
 yilli of the foetal portion of a placenta, ; after E. H. Weber, 
 diameters. 
 
 1. Vein. 2. Artery. Magnified 100 
 
 the observations of our friend, Dr. Druitt,* and others, show that 
 fatty degeneration of the vessels occurs in the great majority of pla- 
 centae which are subjected to examination, although in some it is 
 much more advanced than it is in others. It occurs first in those 
 tufts situated at the circumference of the placenta, in which part the 
 functions of the organ cease first. In numerous instances, also, 
 small masses of earthy phosphates are found in the foetal tufts. 
 Although fatty degeneration is doubtless to be regarded, in many 
 instances, as a morbid alteration, we must at the same time bear in 
 mind, that it does occur as a normal process, and is one of the 
 changes which ensues in tissues prior to their absorption, after the 
 period of their functional activity is brought to a close. It seems 
 to be one of the first of a series of changes which ends in the removal 
 of the tissue, or in the complete disappearance of its ordinary cha- 
 racters. 
 
 From what we have already said with reference to the structure of 
 the human decidua and placenta, it follows, that both are separated 
 at birth, and must be renewed at each successive pregng,ncy. Both 
 the uterine and foetal portions of the placenta are removed, and of 
 course a considerable lesion takes place at the time. The great 
 uterine veins are torn across, and the violent contraction of the 
 uterus alone prevents the death of the mother from hemorrhage at 
 each period of parturition. Should the uterus, from any cause, fail 
 to contract, the death of the mother from hemorrhage is inevitable, 
 as the experience of almost every practitioner but too clearly proves. 
 
 * Medico-Chir. Trans., toI. xxxvi. 
 
892 DEVELOPMENT. 
 
 Such a result, however, would not happen in the ruminants, and in 
 some other animals, where the foetal tufts are readily withdrawn from 
 the maternal sheaths, which merely contract after parturition, and 
 hecome much smaller, hut suffer no lesion whatever. 
 
 Amnion. — The early stages of the development of the amnion 
 have been already fully described (p. 866). It is formed upon the 
 same plan in all classes of animals, as it is in the human subject, as 
 the later researches of Bischoff have conclusively shown. The human 
 ovum, at an early period of development, is seen to be closely in- 
 vested with the amnion ; which membrane, originally consisting of 
 two layers, is separated from the chorion by a considerable space, 
 which is entirely occupied by an albuminous material of a jelly-like 
 consistence, the " corps reticule" of Velpeau. This substance is 
 separated from the chorion by a thin membrane, the endochorion ; 
 so that it appears to be contained within a special sac. 
 
 The amnion consists of a closed sac, and it is prolonged over the 
 structures of the cord, in the form of a tubular sheath, which becomes 
 continuous with the integument of the foetus at the navel. The 
 amnion is tolerably transparent, and not very thick ; but often so 
 firm, that it cannot be ruptured very readily. No vessels, nerves, or 
 lymphatics have yet been demonstrated in the healthy membrane ; 
 but in some cases of disease it has been found to be highly vascular. 
 M. Coste speaks of the amnion as the " epidermis of the blastoderma." 
 
 The sac of the amnion contains a considerable quantity of \a 
 albuminous fluid, the liquor amnii, which, according to Vogt, con- 
 sists of common salt, lactate of soda, albumen, and sulphate and 
 phosphate of lime. Dr. G. 0. Rees has found urea in the liquor 
 amnii, and the presence of this substance has been confirmed by 
 other observers. The liquor amnii, at three and a half months, had 
 a specific gravity of 1-0182, and contained 10-77 of albumen in 1000 
 parts ; and at six months its specific gravity was 1*0092, and it con- 
 tained only 6-67 parts of albumen per 1000. 
 
 Liquor Amnii. — The liquor amnii enters the mouth of the fcetus, 
 and no doubt passes into the trachea as well as the stomach ; but the 
 amount of nutrition which the foetus receives from this source, must 
 indeed be small. At the same time, it is interesting to observe that 
 the composition of the liquor amnii varies at different periods of 
 pregnancy, as has been shown by Vogt; and during the earlier 
 periods of gestation, the quantity of chloride of sodium is much 
 greater than during the latter part of the time. The proportion of 
 this substance appears to be greater at that period of the development 
 of the embryo, when cell-multiplication and growth is most active. 
 
 Dr. Beale has made, for Dr. A. Farre, an examination of liquor 
 amnii at the eighth month, taken from the body of a woman who 
 died at this period of gestation. The fluid was of a very pale straw 
 colour, slightly turbid, and contained flocculi suspended in it. It was 
 quite limpid, and readily dropped from a tube. It was very feebly 
 acid, and remained so for several days after it had been removed. 
 The deposit was subjected to microscopical examination, and found 
 to contain many epithelial cells and oil-globules from the vernix 
 
UMBILICAL VESICLE. 
 
 893 
 
 caneosa, the soft oily coating with which the skin of the foetus becomes 
 covered in the later months of pregnancy. Besides these, there were 
 several clear, transparent, elongated cylindrical bodies, evidently 
 casts of the uriniferous tubes of the kidney of the foetus. This 
 observation proves, very satisfactorily, that the urinary secretion 
 becomes mixed with the liquor amnii in the human subject. 
 
 The specific gravity of this specimen was 1009'2 and it contained 
 in 1000 parts — 
 
 Water 
 
 Solid matter 
 
 . 982-00 
 18-00 
 
 In 100 parts solid 
 matter. 
 
 Organic matter soluble in -water 
 
 Fixed alkaline salts .... 
 
 Albumen, earthy salts, and fatty matter 
 
 6-11 
 8-09 
 3-80 
 
 33-94 
 44-94 
 21-11 
 
 Dr. Prout found sugar of milk in the liquor amnii of a cow, at an 
 early period of pregnancy. 
 
 Umbilical Vesicle. — We have alluded to the mode of formation of 
 the umbilical vesicle in page 866. Our friend, Mr. Grainger, has 
 made some very important observations on its minute structure and 
 functions in the chick. At a very early period, the lining membrane 
 of the umbilical vesicle presents the appearance of a highly organized 
 mucous membrane, the surface of which is perfectly smooth. After 
 a time, a number of folds, which were termed "valves" by Haller, 
 make their appearance. By the ninth day, these are considerably 
 developed, and project into the yolk. The folds become more com- 
 plicated and numerous ; and by the nineteenth day, are as much as 
 -/^ths of an inch in depth in the deepest part. Upon the folds, and 
 in the intervals between them, grayish-white corpuscles are very 
 numerous. Mr. Dalrymple has shown that these cells may be washed 
 away from the vessels beneath, of which he has made very beautiful 
 injections. The yellow appearance of the 
 vessels, whence they have been called vasa 
 lutea by Haller, is due to their being entirely 
 covered with these yellowish corpuscles. The 
 surfaces of the folds of the membrane are 
 highly vascular, and the majority of the capil- 
 laries spread out upon them are probably 
 venous. Thus the surface of the umbilical 
 vesicle is enormously increased in extent, in 
 a manner precisely similar to that in which 
 the mucous membrane of the intestines is ex- 
 tended by the arrangement of the valvulse 
 conniventes. Such is the character of the 
 vascular surface by which all the nutritive 
 constituents of the yolk are absorbed, which 
 are afterwards carried to the system of the 
 chick for its nutrition, throughout the whole 
 period of development within the shell. That 
 portion of the yolk nearest to the vessels becomes quite fluid, and is 
 
 Fig. 291. 
 
 ?» 
 
 Folds of tlie Titellary mem- 
 brane and vasa lutea (after 
 Mr. Dalrymple), showing ar- 
 rangement of tlie vessels. 
 From the chick. 
 
894 DEVELOPMENT. 
 
 therefore in a state most favourable for absorption ; it also becomes 
 mixed with the albumen, by which it was originally surrounded, and 
 which enters by endosmosis through the yolk membrane ; and it 
 undergoes certain chemical changes, as the experiments of Dr. Prout 
 have shown. 
 
 We have already shown (page 866) that the yolk is in direct con- 
 tinuity with the cavity of the intestine, through the intervention of 
 the vitelline duct ; and it is therefore possible for the nutrient mate- 
 rial to reach the system of the chick, by this shorter and more sim- 
 ple course, at a very early period of development. Although there 
 can be no doubt of the existence of this tubular communication at 
 one time, it is nevertheless quite certain that, throughout the greater 
 part of the period of incubation, the duct is impervious, and the 
 nutrient material of the yolk is absorbed by the vessels ramifying 
 upon the surface of the umbilical vesicle, and is carried, by the om- 
 phalo-mesenteric vessels, to the vascular system of the embryo in the 
 manner above described. 
 
 The yolk-sac of the mammalian ovum has a structure very similar 
 to that of the bird. The communication with the intestine is at first 
 very wide, but soon becomes reduced to a narrow tube, the omphalo- 
 mesenteric or vitelline duct. The umbilical vesicle generally disap- 
 pears at a very early period ; and in the embryo calf, not more than 
 six lines in length, according to Bischoff, it is only connected wi^h 
 the embryo by a thread-like pedicle, and is of very small size. In 
 the frog it disappears very early, while in carnivorous animals, and 
 also in the rodents, it remains throughout a considerable period of 
 intra-uterine life, and is very highly vascular. 
 
 The vessels of the umbilical vesicle are well shown in an embryo 
 of Dr. Sharpey's. The foetus was l^'^ of an inch in length. The 
 vesicle was ^^^ of an inch in diameter, and the pedicle ^^ of an inch 
 long. A beautiful engraving of this embryo will be found in Mullers 
 Physiology, translated by Dr. Baly. 
 
 In the human embryo of from two to three lines in length, Miiller 
 found the duct of the umbilical vesicle very short and wide, and was 
 able to trace its walls in direct continuity with those of the intestine. 
 Dr. Allen Thomson also testifies to the same fact, and Weber has 
 delineated its bloodvessels. It is very distinct in the human embryo 
 about the twentieth day. It lies between the chorion and amnion, 
 and is filled with a yellowish-white yolk. By the third month, it is 
 about four or five lines in diameter ; and from this time it becomes 
 smaller, and gradually disappears. Mayer has, however, detected 
 both the vesicle and its thread-like pedicle at the full period of 
 gestation. 
 
 Development of the Allantois. — At a very early period of develop- 
 ment of the mammalian embryo, a collection of cells makes its 
 appearance upon the anterior surface of its caudal extremity. This 
 gradually increases in size, becomes flask-shaped, and a cavity in the 
 interior of the mass becomes visible. The vesicle thus formed rapidly 
 enlarges. It contains fluid, and upon its surface, vessels, which ulti- 
 mately become the umbilical vessels, are seen ramifying. As it 
 
ALLANTOIS. 
 
 895 
 
 Fig. 292. 
 
 grows, these vessels are carried with it towards the inner surface of 
 the chorion. The vessels of the 
 umhilical vesicle waste with this 
 structure, while those conducted to 
 the pjacenta hy the allantois, ulti- 
 mately become the two umbilical 
 arteries and the umbilical vein. In 
 the human embryo, the chief office 
 of the allantois seems to be that of 
 conducting the vessels towards that 
 portion of the chorion which is to 
 become the future placenta; and 
 as soon as the connection between 
 the foetus and the placenta is esta- 
 blished, which in the human embryo 
 takes place between the third and 
 fourth weeks, the allantois is no 
 longer distinguishable. Besides this 
 office, however, the allantois receives 
 the secretion from the temporary 
 kidneys, or corpora Wolffiana, pre- 
 vious to the formation of the per- 
 manent structures. 
 
 In. many of the lower animals, however, 
 the allantois is developed to a much greater 
 extent than it is in man. In birds, and in 
 several mammalian orders^ it forms a very 
 large sac, which completely surrounds the 
 embryo ; and in the ruminants, it contains 
 many quarts of fluid, towards the termina- 
 tion of intra-uterine life. 
 
 The allantois in the chick is readily dis- 
 tinguished before the close of the third day, 
 and appears to be connected with the termi- 
 nal portion of the intestine. Reichert has 
 carefully investigated its development, and 
 has shown that it is not developed from the 
 intestine or from the membrana intermedia, 
 but arises from two masses of cells, situated 
 at the posterior extremity of the Wolffian 
 bodies, which afterwards coalesce, forming 
 a pear-shaped mass, in which a cavity soon 
 manifests itself. Passing from the Wolffian 
 bodies to the two small masses above referred 
 to, are two lines or threads, which ultimately 
 become the excretory ducts of the former 
 organs. 
 
 At an early period, the allantois communi- 
 cates with a common cavity, or cloaca, into 
 which the ureters, the excretory ducts of the 
 Wolffian bodies, and those of the organs of 
 generation open. This is called the sinua 
 urino-gemtalis. The allantois grows very 
 rapidly, and ultimately entirely envelops the 
 embryo with its amnion and yolk, and 
 becomes applied to the inner surface of the 
 
 Diagrams to show the arrangement of the 
 allantois, and the formation of the placenta in 
 different classes of animals ; — 
 
 a. A portion of the wall of the uterus. &. 
 Chorion, c. Allantois. d. Umhilical vesicle. 
 e. Amnion. 
 
 A. In ruminants. The cotyledons, spread 
 out over the internal surface of the uterus, fit 
 into cup-shaped cavities formed hy the altered 
 chorion. The allantois is of a very large size, 
 and entirely surrounds the emhryo. 
 
 B. In the ferse (cat, etc.), the placenta forms 
 a zone which surrounds the emhryo like a ring. 
 There are no cotyledons. 
 
 c. In rodentia and in the human subject. 
 The placenta is limited to one particular part 
 of the chorion. The allantois is very small, 
 and only distinguished at a very early stage. 
 
896 
 
 DEVELOPMENT. 
 
 membrane of the egg-shell. It is highly vaBoular, and is, in fact, the respiratory 
 organ of the chick as long as it remains within the shell. 
 
 The arrangement of the capillaries has been inTestigated by our friend, the late 
 Mr. Dalrymple, who has made some yery successful injections of the allantois of the 
 chick. On the outer surface (that which is in immediate contact with the membrane 
 of the shell), the capillaries are exceedingly abundant and very minute. Mr. Dal- 
 rymple compares their arrangement to that of the vessels in the air-cells of the lung 
 of reptiles — a resemblance of great interest, when we consider that in the bird this 
 membrane performs a most important part in aerating the blood ; indeed, it is through 
 the intervention of the allantois that all the respiratory changes taking place in the 
 chick are carried on. The air passes through thcporea in the shell and membrane 
 beneath, and thus is brought into contact with the blood ramifying in the vessels of 
 the allantois. 
 
 The allantois, as was shown by Reichert and others, is connected with the efferent 
 ducts of the Wolffian bodies, and receives the secretion from these glands. 
 
 In .the human subject, soon after its formation, a dilatation is 
 obsei^«d in that part of the allantois nearest the foetus. This is 
 the rudiment of the urinary bladder. Just at the junction between 
 the vesicular portion and the straight tube which passes from this 
 point to the chorion, a folding or constriction occurs. This indicates 
 
 the first formation of the 
 
 Fig. 293. 
 
 Biiigram of nterns, with a fully formed, but very young 
 ovum. a. Plug of mucus occupying cervix uteri. 6. Opening 
 of Fallopian tube. e. Decidua vera. d. Cavity of uterus, 
 nearly filled with ovum, e. Decidua reflexa. ft. Chorion. 
 /. Decidua serotina. a. AUantoiB in situation of placenta, i. 
 Amnion, h. Umbilical vesicle. 11. Umbilical cord. 12. Space 
 between chorion and amnion, filled with albuminous matter. 
 
 uraehus, which has been 
 erroneously considered to 
 be situated in that part 
 between the vesicle and 
 the foetus. This latter 
 portion, however, soon 
 becomes divided into two 
 tubes, one being con- 
 nected with each Wolffian 
 body. These tubes are 
 ultimately converted into 
 the ureters. The ure- 
 ters and urinary bladder 
 are gradually drawn into' 
 the cavity of the pelvis, 
 through the umbilical 
 opening. This process, 
 according to Langenbeck, 
 is completed between the 
 twelfth and twentieth 
 week. The uraehus, be- 
 tween the bladder and 
 umbilicus, remains tubu- 
 lar long after this, and 
 even at birth in some few 
 instances; in which cases 
 urine has been known to 
 escape from the umbili- 
 cus. 
 
 Mlantoic Fluid is 
 clear, of a brownish yel- 
 low colour. Its specific 
 
UMBILICAL CORD. 897 
 
 gravity varies from 1005 to 1030. It contains alkaline lactates, 
 extractive matters, and ammoniacal salts, with alkaline and earthy 
 phosphates, and chloride of sodium. ' Besides these, however, there 
 is a definite crystallizable substance peculiar to this fluid, termed 
 allantoin, which is closely related to uric acid ; indeed, it may be 
 prepared artificially from this substance, virhile urea is produced at 
 the same time. The composition of allantoic fluid seems nearly 
 identical with that of the urine of calves while suckling, at which 
 time it contains no hippurre acid. This latter substance, however, 
 makes its appearance in the urine as soon as the animal takes vege- 
 table food. Uric acid has been found in the allantoic fluid of birds 
 by Jacobson. 
 
 Velpeau held that the allantois completely surrounded the human 
 embryo, as it does in many animals ; but this statement has been 
 completely refuted by the researches of Miiller, Bischoff, Langen- 
 beck, and others. 
 
 Umbilical Cord. — The umbilical cord is the long, narrow pedicle, 
 contained in a tube of the amnion, which connects the foetus with 
 the placenta. In the advanced embryo, it consists principally of 
 the large vessels, through the intervention of which all the nutrient 
 material absorbed from the blood of the mother is conducted to the 
 system of the foetus. 
 
 At an earlier period of development, the cord is really composed 
 of— 
 
 1. The remains of the omphalo-enteric duct, or pedicle of the 
 umbilical vesicle. 
 
 2. The vasa omphalo-meseraica, or branches of the mesenteric 
 vessels of the foetus. 
 
 3. The urachus, and all that remains of the allantois. 
 
 4. The umbilical vessels ; consisting of one umbilical vein, which 
 brings the blood back from the placenta, and two umbilical arteries, 
 by which the blood is carried to the placenta. 
 
 In animals generally, however, there are two veins, as well as two 
 arteries, which are the chief branches of the hypogastric arteries of 
 the foetus. The circulation of the foetus has been fully described in 
 page 677. 
 
 Birth.'— In the human subject, the period of pregnancy lasts about 
 nine solar, or ten lunar months, or 280 days. It varies, however, 
 within certain limits. 
 
 The phenomena of parturition are specially treated of in works 
 on Midwifery ; so that a very brief reference to this part of the sub- 
 ject will only be required. 
 
 Of the immediate cause of the contraction of the uterus, little is 
 known. Valentin attributes it to the excitement of the organs which 
 always exists at the menstrual periods ; and he considers that par- 
 turition takes place at the tenth menstrual period. Dr. Tyler Smith 
 has advocated a similar view, and believes that the contractions of 
 the uterus are due to the increased action of the ovaries operating 
 upon the cord through the ovarian nerves, which act as excitors; 
 while the uterus is thrown into contraction through the medium of 
 
898 LACTATION. 
 
 the uterine nerves, which are therefore to be regarded as the motor 
 nerves concerned in this reflex action. The action of the uterus is 
 no doubt in part due to the stimulus produced by the increasing bulk 
 of its contents. 
 
 The foetus lies in utero with its head downwards during the later 
 months of pregnancy. The contraction of the thick muscular walls 
 of the uterus tends to force the head upon the os uteri, in conse- 
 quence of which the circular fibres of the latter gradually relax, and 
 the opening dilates. The membranes ar# pressed towards the vagina, 
 and protrude through the os, until at length they burst, and the 
 liquor amnii escapes. 
 
 At each successive pain, the child's head is forced lower and lower 
 into the vagina. The pains increase in force and frequency, and 
 the uterine contractions are assisted by the voluntary contractions of 
 the abdominal muscles ; until at last, in a violent paroxysm of pain, 
 the head is born, and the remainder of the child very quickly follows. 
 
 A little hemorrhage usually occurs immediately after the birth of 
 the child, in consequence of the partial detachment of the placenta. 
 This is followed, however, by contractions ; and the placenta itself 
 is forced into the vagina shortly after the birth of the child. With 
 the placenta are also expelled portions of the membrana decidua, the 
 remains of the chorion, and the amnion. 
 
 After labour, a considerable quantity of fetid discharge takes place 
 from the uterus. At first, this is composed principally of bloocf ; 
 but afterwards it becomes paler, and consists chiefly of mucus, with 
 pus corpuscles, and a certain quantity of fluid exudation. The 
 uterus gradually returns to its former volume. 
 
 For information upon ttie questions discussed in the present chapter, the student 
 is referred to the works previously enumerated. 
 
 CHAPTEE XLIV. 
 
 OF LACTATION. — THE LACTEAL GLANDS. — NIPPLE. — MINUTE STRUC- 
 TURE OF THE GLAND. — BLOODVESSELS. — ABSORBBNTg. — MILK. 
 
 The Lacteal Grlands are two large, symmetrical organs, which are 
 only fully developed in the female. In the male, however, they 
 exist in a very rudimentary state. During the later half of preg- 
 nancy, the lacteal glands increase very much in size ; and about the 
 period of parturition, they begin to secrete milk. They are racemose 
 glands, and are ultimately composed of numerous roundish follicles, 
 arranged round the terminal extremities of the ducts. 
 
 The structure^ of the lacteal glands formed the subject of a very 
 important investigation by Sir Astley Cooper. 
 
LACTEAL GLANDS. 
 
 The lacteal tubes are about twenty in number, and terminate at 
 the extremity of the nipple, by as many orifices. The ducts are 
 
 Fig. 294. 
 
 4w' 
 
 Preparation with six milk-tubes injected from the nipple, by Sir Astley Cooper. — o. The straight 
 or mammillary tubes, proceeding from the apex of the nipple. &. Keserroirs or dilatations of the 
 ducts, c. Branches of the mammary ducts, d. Glandules. 
 
 dilated as they approach the nipple, and the dilatations are called 
 regervoirs. In the human subject, these are very small ; but in the 
 cow, they are large enough to hold a quart. 
 
 The nipple is surrounded by a dark coloured circle, termed the 
 areola, smooth in the child, but slightly tuberculated at the period 
 of puberty. In the child it is about half an inch in diameter ; but 
 in the adult, about an inch ; while during lactation, it increases to 
 two inches. After impregnation, it changes from its reddish colour 
 to a dark brown. 
 
 A secretion is poured out from the mucous follicles, which lubri- 
 cates the skin about the nipple. 
 
 The terminal follicles of the gland were injected by Mascagni ; 
 but for almost all that we know of the minute anatomy of the breast, 
 we are indebted to the beautiful researches of Sir Astley Cooper, 
 published in 1840. 
 
 The surface of the breasts, in the unimpregnated state, is smooth 
 and compact ; but as pregnancy advances, they become uneven, in 
 consequence of the distension of the follicles with secretion. 
 
 The nipple, before puberty, forms an almost smooth conical 
 eminence; but in lactation it becomes flattened, so that its extremity 
 becomes the broader part, and thus it is more readily held by the 
 child's mouth. Its characters have been minutely described by Sir 
 Astley Cooper : " At sixteen years it is slightly wrinkled ; at seven- 
 teen, it has small papillae upon its surface ; from twenty to forty 
 years, the papillae are large ; from forty to fifty, the nipple becomes 
 

 900 LACTATION. 
 
 •wrinkled ; from fifty to sixty, the nipple is elongated ; and in old 
 age, it usually has a warty appearance." 
 
 The cutis of the nipple contains a great number of , papillae. It 
 is sensitive and highly vascular. "The direction of these papillae 
 is from the base towards the apex of the nipple ; so that they are 
 pushed back as the mammilla enters the mouth of the child, and thus 
 greater excitement is produced." Connected with the cutis of the 
 nipple are numerous non-striated muscular fibres, to the presence of 
 which the erection of the nipple is due. 
 
 In their minute structure, the lacteal glands are closely allied to 
 the pancreas and salivary fluids. 
 
 The gland structure is arranged so as to form lobules, which are 
 connected together with a considerable quantity of firm areolar tissue 
 
 The terminal follicles are about the j^^th of an inch in diameter. 
 They are lined with a layer of delicate epithelial cells, which become 
 much altered at the time of lactation. At this time the cells 
 
 become larger arid much more 
 
 Fig. 295. numerous. They contain a 
 
 , '"'^, great number of small oil-glo- 
 
 (*.•*•* •», ,^^ bules, which constitute, when 
 
 ' ' ''Sr* ^^^ f*"^®* *^^ oil-globules of the 
 
 ,'„^ ' ' ',".'"^ milk. In colostrum there aye 
 
 ,,*, , numerous cells of this kind, 
 
 /^■-c» /» V '' M' '• '■ «« k filled with oil-globules. These 
 
 /,': ^ "" ■» ,* ft'i^.Sj* :i^J*^^ have been termed colostrum 
 
 S't \ '11 jftg.^— -..- •"'rf'^ corpuscles, and were first de- 
 
 W;.''''^if»< S'tS' "^ t . . ' \ scribed by Donn^. The ducts 
 
 ''-^ flPk***"*''*- * ' " '^ -b ^""^ liiied with columnar epi- 
 
 ■t^ft ^''^:i^>J•' i^*,^' / thelium. 
 
 ''7^ \^-\ » _%«?>'''' The walls of ducts of mo- 
 
 ' t '"'■i'. derate size are composed of 
 
 \ 4 f -^ fibrous tissue, in which a great 
 
 .' 1, Ja'-' "ti"* number of elongated, wavy, 
 
 '1??* ' ' '(^ and nearly parallel fibres of 
 
 •*'„ - ' "i"*' yellow elastic tissue are seen. 
 
 %a«is^^-" ''" Henle describes muscular 
 
 One of the smallest lobules of a lacteal gland, witli fibrCS in thcSe duCtS ; but Kol- 
 
 met?rs.''°Ster L"an|or' "^""""^ ' ""'^"""'^ ^ ^'*' IJkcr and most Other anatomists 
 
 have failed to detect them. 
 We have searched for them carefully, but with no better success. 
 
 The bloodvessels are very numerous, and their finer branches 
 ramify around the terminal follicles of the gland. 
 
 The ahsorhents have been injected by Sir Astley Cooper, who 
 describes a superficial set beneath the skin, and a deeper set of 
 trunks which penetrate into the substance of the gland, and form a 
 plexus of great beauty in the interior. 
 
 In the male, the lacteal glands exist only in a very rudimentary 
 condition ; but their structure is precisely similar to those of the 
 female, as Sir Astley Cooper demonstrated. In a few very rare 
 
FOLLICLES OF MAMMARY GLANDS. 
 
 901 
 
 instances, they have been unusually developed ; and instances are 
 even on record, -where milk has been secreted by the lacteal gland 
 
 Fig. 296. 
 
 r. I 
 
 Terminal follicles of the lacteal gland, with ducts, from a woman who was not pregnant. The 
 fihres of yellow elastic tissue are numerous upon the wall of the duct. The terminal follicles are 
 separated from each other by a considerable quantity of areolar tissue. Magnified about 150 diameters. 
 
 of the male; indeed it has been related by Humboldt, that the infant 
 has been nourished by the male parent after the death of the female. 
 
 The lacteal- glands are developed 
 like other glands connected with the ^ig- 297. 
 
 skin. In the fourth or fifth month, /"^^ 
 
 according to the observations of Langer ' 
 
 and Kblliker, a papillary projection of ' 
 
 the mucous layer of the epidermis 
 occurs. This increases in size ; and, 
 by the sixth or seventh month, throws 
 off a number of offsets, from which 
 the lobes of the gland are gradually 
 formed. 
 
 Milk is white and opaque, from 
 the presence of numerous oil-globules. 
 Besides these, which are held in sus- 
 pension, and are insoluble, milk con- 
 tains numerous nutritious substances 
 which exist dissolved in the fluid. 
 After it has been allowed to stand for 
 some time, the oil-globules rise to the surface, by reason of their 
 lightness, forming the cream. 
 68 
 
 
 Lacteal gland of a newly-born child. 
 Th,6 rudimentary follicles are well sb.own. 
 After Langer. 
 
902 
 
 LACTATION. 
 
 Fig. 298. 
 
 cles. 
 
 Milk usually does not obtain its normal characters until three or 
 four days after delivery. The first proportion, which is secreted 
 before parturition, is thinner, and contains but a 
 quantity of saccharine and oily materials. In it 
 albumen is often detected. This is called the 
 colostrum. The specific gravity varies from 1020 
 to 1045. 
 
 The oil existing in milk, occurs in a state of 
 minute division, in the form of oil-globules, which 
 are equally dififused throughout the fluid. These 
 oil-globules are each invested with a delicate 
 membranous envelope, composed of caseine, which 
 prevents their running together. If milk and 
 ether be shaken and well mixed, the oily con- 
 stituents are not dissolved, in consequence of the 
 envelope of caseine with which they are in- 
 vested ; but if, previous to the addition of the ether, a little acetic 
 acid or alkali, or alkaline salt, which has the power of dissolving the 
 covering, be added, the globules are immediately dissolved, and the 
 milk becomes perfectly clear. By churning, the envelopes are 
 ruptured, and the oil-globules are made to run together, forming 
 butter. 
 
 If the slightly turbid solution from which the cream has been 
 removed be allowed to stand for some time, or if an acid be added to 
 it, a flocculent precipitate occurs. This is caseine, which is coagu- 
 lated by all acids. It is, however, not coagulated by heat ; but 
 during evaporation, a scum forms upon the surface of solutions con- 
 taining caseine. 
 
 The following analyses show the chemical composition of human 
 milk. Specific gravity, 1030—1034. 
 
 Colostrum corpus- 
 b. Milk globules. 
 In the lower part of the 
 figure, two are seen run- 
 niDg together, in conse- 
 queoce of the investing 
 membrane having been 
 dissolved. Magnified 
 
 about 21d diameters. 
 
 Colostram. * days after 
 parturition. 
 
 9 days. 
 
 12 days. 
 
 Average 
 
 Water . . . 828-0 . . . 879-848 . 
 
 . 885-818 . 
 
 . 905-809 . 
 
 891-0 
 
 Solid matter . 172-0 . ... 120-1&2 . 
 
 . 114-182 
 
 . 94-191 . 
 
 109-0 
 
 Albamen . . 400 caseine 35-333 . 
 
 . 36-9] 2 . 
 
 . 29111 . 
 
 33-7 
 
 Butter . . . 50-0 . . . 42-968 . 
 
 . 85-316 . 
 
 . 33-454 . 
 
 37-1 
 
 Sugar of milk. 70-0. . . 41-135. 
 
 . 42-979 . 
 
 . 31-537 . 
 
 38-5 
 
 Salts ... 3-1 .. . 2095 . 
 
 . 1-691 . 
 
 . 1-939 . 
 
 1-9 
 
 The first two analyses are by Franz Simon, and the last three by 
 Clemm. 
 
 Cow's milk contains more caseine and less sugar than human milk. 
 Ass's milk contains less butter and less caseine, but more sugar ; 
 while in goat's milk the caseine preponderates over the other con- 
 stituents. L'Heretier has shown that temperament exerts an influ- 
 upon the character of the milk. The average quantity of solid matter 
 in 1000 parts of milk from fair women, was 120 grains ; and of 
 brunettes, as much as 134 grains. 
 
 The characters of the milk, also, it need hardly be said, are much 
 influenced by the health and diet of the mother, and by the age of 
 the infant. At first, the caseine is small in quantity, and gradually 
 increases up to its normal standard; while, on the other hand, the 
 
MILK. 903 
 
 proportion of sugar is very large at first, and subsequently diminishes 
 in quantity. The proportion of butter varies considerably. Phos- 
 phate of lime is very soluble in solutions of caseine, and in this way, 
 no doubt, is introduced into the system of the young animal. 
 
 In disease, the milk may contain blood, pus, or mucus, and occa- 
 sionally lactic acid and albumen have been detected in it ; urea and 
 bile-pigment have also been found in milk. 
 
 Upon the subject of lactation, the student may refer to the following : On the 
 Anatomy of the Breast, by Sir Astley Cooper, 1839. C. Langer, Ueber den Bau und 
 die Entwioklung der Milohdriisen, mit 3 Taf., Denksohr. d. Wiener Akad. Bd. iii. 
 Wien. 1851. Article "Mammary Gland," by Mr. Solly, in the Cyclopaedia of Ana- 
 tomy and Physiology. And Simon's Animal Chemistry, translated by the Sydenham 
 Society. 
 
INDEX. 
 
 Abdominal, muscles, influence on vomiting, 
 564, action of, in defecation, 608 ; respi- 
 ration, 718 
 
 Absorbents, minute anatomy of, 613 ; con- 
 tractility of, 615 ; contents of, 619 ; func- 
 tion of, 627 ; viewed as a glandular system, 
 627 ; of lacteal glands, 900 
 
 Absorption, 611; influenced by motion of the 
 fluid, 626 ; by pressure, 625 ; by porous 
 solid, 624 ; by quality of fluids, 623 ; me- 
 chanism of, 622 ; of chyle by villi, 578 ; of 
 gum, sugar, alcohol, etc., 678; of tissues, 
 611 ; by bloodvessels, 619 ; by the stomach, 
 562, 588 ; and secretion in the skin, 372. 
 
 AoalephsB, 823 ; renal organs of, 786 ; re- 
 production of, 825 
 
 Aoervulus, 252 
 
 Acetic acid, action of ; upon wall of Pacinian 
 corpuscles, 347 ; upon epidermis, 362 
 
 Achromatism of eye, 432 
 
 Acids, effect of in digestion, 555 ; nature of, 
 in gastric juice, 567; lactic, in gastric 
 juice, 568 
 
 Action of heart, 672 
 
 Adaptation of eye to vision at different dis- 
 tances, 429 
 
 Addison, Dr. W., on fibrin of blood, 634 ; on 
 lobular passages, 712 ; on supra-renal cap- 
 sules, 815 
 
 Adipose tissue, 88 ; vesicles, 89; bloodvessels 
 of, 90; development of, 93; subcutaneous, 
 354 
 
 Admirault on taste, 386 
 
 Aerial capacity of lungs, 722 
 
 After-tastes, 390 
 
 Age, influence of ; upon animal temperature, 
 736; upon quantity of carbonic acid ex- 
 pelled, 726 
 
 Aggregate glands, 583 
 
 Air, accumulation of in stomach, 563; a- 
 mount breathed, 722 ; changes of, in 
 respiration, 723 ; expired, volume of car- 
 bonic acid in, 724; residual, 722; respired, 
 temperature of, 723 
 
 Air-cells, 709 
 
 Albinus, on the muscular coat of the small 
 intestines, 572 
 
 Albinos, light painful to, 434 
 
 Albumen, 53; acted on by gastric juice, 555; 
 digestion of, 656 
 
 Albuminous aliment, 515 
 
 Aloook, Dr., his experiments on taste, 387; 
 on glosso-pharyngeal, 388 ; on sensation 
 in tongue, 388 
 
 Alcohol, its influence on respiration, 725 ; on 
 
 retarding digestion, 562 ; its action on gas- 
 tric juice, 557 
 
 Alexis St. Martin, 561 
 
 Alimentary canal, development of, 883 ; 
 nmcous membrane of, 522 ; compartment 
 of pharynx, 541 
 
 Allantoic fluid, 896 
 
 AUantoin, 897 
 
 AUantois, 871, 894; development of, 881. 
 
 Allen and Pepys ; on the quantity of carbon 
 removed from the body, 730 ; on the pro- 
 portion of carbonic acid in expired air, 727 
 
 Alto voice, 764 
 
 Alveolus, 626, 532 ; of lung, 712 
 
 Amaurosis, 433 
 
 Ammouiacal salts in urine, 802 
 
 Amnion, formation of, 869, 892 
 
 Amphibia, generative organs of, 828 ; organ 
 of hearing of, 443 
 
 Amphioxus lanceolatns, nervous system of, 
 276 
 
 Ampullee, 450 
 
 Amylaceous substances not digested by sto- 
 mach, 688 
 
 Analysis, of blood, quantitative, 643 ; of 
 blood of dog under the influence of vene- 
 section, 646 ; of milk, 902 ; of ox-gall, 
 598 
 
 Anastomosis, of arteries, 656 ; of Jacobson, 
 447 ; of nerves, 201 ; of third nerve, 474 
 
 Anderson, Dr., experiments on vomiting, 564 
 
 Andersch, on the ganglion petrosum, 485 
 
 Andral, cases of lesion of optic thalamus and 
 corpus striatum, 311 
 
 Andral and Gavarret, on the influence of age 
 upon the exhalation of carbonic acid, 726 
 
 Anencephalic foetus, movements of, 278 
 
 Animal heat, 733 ; influence of, on nervous 
 system, 742 ; theory of, 740 
 
 Annelida, liver of, 770 ; renal organs of, 786 ; 
 reproductive of, 820 ; sexual apparatus of, 
 825 
 
 Annulus ovalis, 666 
 
 Ansemia, value of iron in tte treatment of, 
 645 
 
 Ant-eater, tongue of, 524 ; teeth of, 526 
 
 Anterior, chamber, 420 ; columns of cord, 
 282 ; venous trunks, 882 
 
 Antero -lateral columns of cord, function of, 
 284, 285 
 
 Anthelix, 444 
 
 Antiperistaltic action, 584 
 
 Antiseptic power of bile, 698 
 
 Antitragus, 445 
 
 Aorta, origin of, 666 
 
INDEX. 
 
 Aortic arches, 882 ; development of, 880 
 
 Aphis, metagenesis in, 823 
 
 Aponeurosis, 81 
 
 Appendices epiploicse, 668 ; pyloricas, in 
 fishes, 569 
 
 Appendix cseci vermiformis, 567 
 
 Aqua Morgagni, 418 
 
 Aqueduotus, cochleae, 452 ; Fallopii, 447 j 
 course of portio dura nerve in, 477 j Sylvii, 
 261 
 
 Aqueous, alimentary materials, group of, 
 515 ; vapor, exhalation of, 724 
 
 Arachnida, circulation of, 706 ; renal organs 
 of, 786 
 
 Arachnoid membrane, 230 ; subarachnoid 
 cavity, 231 
 
 Area, germinativa, 859 ; pellucida, 863 ; 
 vitellina, 864 
 
 Areola of nipple, 899 
 
 Areolar, framework of skin, 356; tissue com- 
 posed of white and yellow fibrous tissues, 
 84 ; its corpuscles, 84 ; development,- 85 j 
 its cellular spaces, 85 ; its association with 
 bloodvessels, 86 ; distribution, 86 ; and 
 use, 87 ; modifications of its elements, 87 ; 
 in serous membranes, 129 ; physical pro- 
 perties, 88 ; of muscles, 159 ; beneath 
 mucous membrane, 572; of pharynx, 542; 
 sub-basement, 524 
 
 Argonaut, sexual apparatus of, 826. 
 
 Arnold, Bischoff and Bendz, on the spinal 
 accessory nerve, 496 
 
 Arnold, on the otic ganglion, 501 ; on the 
 branch of nerve from the otic ganglion to 
 Tensor tympani, 453 ; on development of 
 teeth, 532 
 
 Arterial, system, 655 ; blood, 629 ; and ven- 
 ous blood, 645 
 
 Arteries, 649 ; development of, 870 ; branch- 
 ing and anastomosis of, 656 ; external coat 
 of, 650 ; middle coat of, 650 ; epithelial 
 layer, 653 ; nerves of, 655 ; vasa vasorum 
 of, 650; of choroid, 407 ; of penis, 546 ; of 
 stomach, 546 
 
 Artery, hepatic, 774 ; posterior communica- 
 ting, 264 ; pulmonary, 707 ; splenic, 810. 
 
 Articulata, digestive organs of, 514; circu- 
 lation in, 697 
 
 Articulation of lower jaw, 538 
 
 Artificial, digestive fluid, 557 ; division, 
 multiplication by, 820 
 
 Arum maculatum, temperature of, 733 
 
 Arytenoid cartilages, 746 
 
 Ascaris dentata, cleavage of yolk in ovum of, 
 866 ; nigrovenosa, cleavage of yolk in ovum 
 of, 856 
 
 Asoidia, heart of, 663 
 
 Asellias, the discoverer of lacteal vessels, 612 
 
 Asphyxia, circulation in pulmonary capil- 
 laries in, 699, 
 
 Ass' milk, 902 
 
 Assimilation, 34 
 
 Astacns fluviatilis, spermatozoa of, 836 
 
 Asthma, nature of, 493 ; following section of 
 vagi, 492 
 
 Atrophy of glands in advancing life, 611 
 
 Attention, its importance in vision, 436 
 
 Attitude, 183 ; standing, 184 ; walking, 185 
 
 Auditory canal, 445 
 
 Auricle of ear, 444 ; use of, 464 
 
 Auricles of heart, 664 ; muscular fibre of, 
 671 ; suction power of, 702 
 
 Auricular appendage, 665 
 
 Auriculo-ventricular orifice, 664 
 
 Autenrieth, on the use of the semicircular 
 canals, 472 
 
 Aves, generative organs of, 828 
 
 Axial reversed current, 585 
 
 Axilla, sweat glands of, 368 
 
 Axis cylinder, in Pacinian corpuscles, 348 
 
 Azotized substances, absorption of by sto- 
 mach, 588 
 
 Babikqton, Dr., on the cause of buffing and 
 cupping, 632 
 
 Baer, Von, on development of superior max- 
 illa, 877 ; on the formation of the amnion, 
 869 
 
 Bagge, on the development of ova of intes- 
 tinal worms, 841 
 
 Baly, Dr., on taste, 388 
 
 Barral, M., on ingesta and egesta, 761 ; on 
 the quantity of carbon removed by respi- 
 ration, 731 
 
 Barry, Sir David, on the influence of respira- 
 tion on the circulation, 701 
 
 Barry, Dr., on the changes in the germinal 
 vesicle, 855 ; on the impregnation of the 
 ovum, 853 ; on retinaoula, 840 
 
 Bartholini, glands of, 845 
 
 Basement membrane, 61, 129, 523 ; of sto- 
 mach, 647 ; of sweat-glands, 369 ; of villi, 
 577 
 
 Bass voice, 754 
 
 Bat, circulation in wings of, 703 ; sense of 
 touch in the wings of, 373 
 
 Batrachia, intestinal canal of, 669 
 
 Beaver, epithelial secretion of penis, 835 
 
 Beale, Dr., his analysis of dog's blood, 646; 
 of healthy kidney, 786 ; liver, 768 ; thyroid, 
 816 ; on chlorides in the urine, 802 ; mode 
 of injecting the tubular network of the 
 liver, 780 ; on the relation of the hepatic 
 ducts to the liver cells, 782 ; on parietal 
 sacculi, 776 ; examination of liquor amnii, 
 892 
 
 Beau, on ordinary respiration, 718 
 
 Beaumont, Dr., on changes in mucous mem- 
 brane of the stomach, 551 ; on the rate of 
 digestion, 661 
 
 Becoaria, on glutinous portion of the food, 
 615 
 
 Beck, Dr. T. Snow, his dissection of the sym- 
 pathetic, 499; on nerves of the uterus, 
 844 
 
 Becquerel, and Breschet, for the temperature 
 of internal parts of the body, 735 ; and 
 Rodier, their analysis of the blood, 644 
 
 Bell, Sir Charles, on the fourth nerve in 
 apes, 476 ; on the functions of roots of 
 nerves, 274 ; on the spinal accessory nerve, 
 497 
 
 Belladonna, effects of, upon the cord, 282 
 
 Bellini, tubes of, 789 
 
 Bellows murmur, 674 
 
 Bennett, Dr. Hughes, on leucocythemia, 
 648 ; on the spleen, 810 
 
 Benzoic acid formed from hippuric acid, 801 
 
 Bergmann, on the supra-renal capsules, 815 
 
 Bernard, on branches of the portal vein, 677 ; 
 on the digestion of fat, 594 ; experiments 
 on the functions of the liver, 604 ; on the 
 influence of the nervous system upon ani- 
 mal heat, 743 ; on pancreatic juice, 592 ; 
 
INDKX. 
 
 907 
 
 and Barreswil on the action of pancreatic 
 fluid on starch, 589 ; on the acid of the 
 gastric juice, 558 ; on the spinal accessory, 
 496 ; and Blondlot upon the acid fluid of 
 the csecum, 608 
 
 Eerzelius, his analysis of fsecea, 609 ; analy- 
 sis of lens, 420 ; analysis of ox-gall, 698 ; 
 of vitreous humour, 417 
 
 Besoin de respirer, not destroyed by section 
 of vagus, 492 
 
 Bichloride of mercury, its action on digestive 
 fluid, 557 
 
 Bidder, on the quantity of lymph, 622 ; and 
 Schmidt on the quantity of bile, 784 
 
 Bicuspid teeth, 527 
 
 Bile, escape through a fistulous opening, 
 597; colouring matter of, §99; fat- of, 
 598 ; its escape favoured by digestion, 597 ; 
 influence on coagulation of blood, 632 ; 
 not exclusively an excretion, 602.; passage 
 into ducts, 784 ; physical and chemical 
 characters of, 698; quantity of, 597, 784; 
 in human faeces, 602 ; uses of, 600 ; se- 
 creted from portal blood, 696 ; saline con- 
 stituents, 600 ; pigment in milk, 903 
 
 Bilifellinic and ISilicholinio acids, 599 
 
 Bilin, 598 
 
 Biliverdin, 599 
 
 Bill of birds, 524 
 
 Biot, M., on the detection of sugar by the 
 polarisoope, 661; on propagation of sound, 
 463 
 
 Biphosphate of lime in gastric juice, 557 
 
 Birds, aortic arches of, 882 ; blood corpuscles 
 of, 635 ; circulation of, 707 j cochlear 
 nerves in, 457 ; digestive organs of, 513 
 crop of, 513 ; early changes in egg of, 863 
 intestinal canal of, 569; heart of, 663 
 organ of hearing of, 444 ; sympathetic in 
 498 ; uric acid in allantoic fluid of, 715 
 vessels of lung of, 897 ; villi of, 676 ; vocal 
 organs of, 745 
 
 Birth, 897 
 
 BischofF, on the amnion, 892; on formation 
 of corpora lutea, 851 ; on formation of 
 blastodermic vesicle, 857 ; on impregnation 
 of ovum, 853 ; on stellate cells of zona 
 pellucida, 855 ; on the development of the 
 eye, 879 ; tunica media of, 874 ; and Vogt 
 on the pulsations of the heart before the 
 formation of muscular fibres, 882 
 
 Bishop, on the production of falsetto notes, 
 754 
 
 Bladder, 804 ; development of, 896 ; forma- 
 tion of, 874 
 
 Blagden, Sir Charles, experiments on the 
 effects of a high temperature on the body, 
 737 
 
 Blainville, De, on the perilymph, 453 
 
 Blake, on the heart's force, 689 ; on the rate 
 of the circulation, 706 
 
 Blastodermic vesicle, 868 ; formation of, 857 
 
 Blindness, coincident with disease of corpora 
 quadrigemina, 313 
 
 Blondlot, on acidity of gastric juice, 557; on 
 escape of bile, 596 ; on use of bile, 602 
 
 Blood, 628 ; analysis of, 643 ; arterial and 
 venous, 629, 645 ; bu&ng and cupping, 
 632 ; changes in, from respiration, 728 ; 
 coagulation of, 629 ; density, 645 ; of dog 
 after venesection, 646 ; fibrin of, 634 ; 
 quantity of, 630; red corpuscles of, 634; 
 
 serum of, 633 ; specific gravity of, 628 ; in 
 anaemia and after hemorrhage, 633 ; in- 
 crease of fibrin in, 647 ; in intermittent 
 fever, 648 ; in gout, 648 ; in rheumatic 
 fever and pneumonia, 647 ; physical analy- 
 sis of, 629 ; temperature of, 645 ; urea in, 
 800 ; of spleen, changes in, 813 ; of vena 
 portse, 645 
 Blood corpuscles, aggregation of, 635 ; colour- 
 less, 637 ; development and decay of, 642; 
 generation of, in the liver, 606; of birds, 
 
 635 ; of camelid^i 635 ; fishes, 636 ; of 
 invertebrata, 636 ; in animals, 636 ; rep- 
 tiles, 635 ; function of, 640 ; nature of, 
 
 636 ; origin of, 639 ; of spleen pulp, 808 ; 
 structure of, 636 
 
 Bloodvessels, 649 ; of adipose tissue, 90 ; of 
 bone, 110; of brain, 263; of cartilage, 99; 
 of fibrous tissue, 80 ; of lacteal glands, 
 627 ; of meninges, 228 ; of muscle, 159 ; 
 of nerves, 200 ; of pulp cavity, 532 ; of 
 villi, 577 
 
 Blubber, 356 
 
 Blumenbach, cases of congenital deficiency 
 of tongue, 387 
 
 Blushing, 697 
 
 Boa, circulation in kidney of, 796 
 
 Body of lens, 418 ; of tooth, 626 
 
 Boerhaave and Bressa, on the use of the 
 Eustachian tube, 469 
 
 Bone, 102; physical and chemical properties, 
 103, 105 ; rickets and mollities ossium, 105 ; 
 general structure, 107; long, flat, and ir- 
 regular, 107 ; Haversian canals, 110 ; gran- 
 ules of the osseous tissue. 111 ; pores and 
 lacunae, 112 ; lamellae, 114, 116 ; nerves, 
 118; development, 118; growth, 122; re- 
 paration, 125 
 
 Bouchardat and Sandras, experiments on 
 chyle, 588 ; on digestion of starch, 561, 
 589 
 
 Bourgery, on inspired air, 723 
 
 Brachet and Dr. J. Beid, on influence of 
 nerves in hunger, 521 
 
 Brain, or encephalon, 237 ; its four segments, 
 237 ; weight, 237 ; association with mind, 
 239 ; circulation in, 263 ; is it compressi- 
 ble ? 267 ; functions of, 303 ; capillaries 
 of, 660 ; convolutions of, 321 ; effects of 
 alterations of pressure upon, 268 
 
 Branchiaa, 706 
 
 Branchial fissures and arches, 870 
 
 Branching of arteries, 656 
 
 Breschet, on the veins of bone, 110 ; on the 
 temperature of internal parts of the body, 
 735 ; on the utrioulus, 443 
 
 Brewster, Sir David, on achromatism of eye, 
 432 ; on adaptation of eye to vision at dif- 
 ferent distances, 429 ; on fibres of lens, 
 419 ; on the refractive power of the lens, 
 419 
 
 Brinton, Dr., on inversion of the action of 
 the stomach, 563 ; on antiperistaltic action, 
 584 
 
 Brodie, Sir B., on chyle, 621 ; experiments 
 on digestion of fat, 661 ; on the uses of the 
 bile, 603 ; on the influence of the nervous 
 system in animal heat, 742 
 
 Bronchi, 709 
 
 Bronzing of skin by sun, 363 
 
 Brown, Kobert, on molecular motion, 71 
 
 Brunn or Brnnner, on exhalation of aqueous 
 
908 
 
 INDEX. 
 
 vapour, 724; on follicles of intestine, 573; 
 
 glands of, 579 
 Bryozoa, digestive organs of, 514 
 Buchanan, Dr., on milky serum, 633 
 Budd, Dr. W., on spinal cord, 283 ; his case 
 
 of paralysis, 283 
 Budge, experiments on cerebellum, 318 
 Buds, reproduction by, 820 
 Bulb of hair, 366 ; of olfactory process, 397 
 Bulbous portion of the urethra, 834 
 Burdach, on termination of nerves in skin, 
 
 359 
 Bursa, 127; copulatrix, 827 
 Butter in milk, 902 
 Butyric acid, from action of pancreatic fluid 
 
 on fat, 594 
 
 Cjecvw, 567; of birds, 569; digestion in, 
 608 ; acid reaction of fluid of, 608 ; in 
 solipeds, 570 ; in herbivora and carnivora, 
 608 ; largo in herbivora, 571 
 
 Calcification of enamel, 530 
 
 Calorifacient food, 616, 740 
 
 Calyces of the kidneys, 788 
 
 Camelidse, blood corpuscles of, 635 
 
 Camera obscura, 402 
 
 Campanularia dichotoma, development of 
 medusae from, 822 . 
 
 Camper on otoliths, 471 
 
 Canal of Petit, 417 
 
 Canalicnli, 426 ; of cementum, 531 
 
 Canine teeth, 526 
 
 Capacity, cubic of rooms, 728. 
 
 Capillaries, 659 ; absorption by in stomach, 
 562; of brain, 266; and circulation in, 
 rate of, 693, 694 ; of foetal tufts, relation 
 to maternal vessels, 888 ; of lungs, 713 ; 
 of lymphatic glands, 616 ; of olfactory 
 region, 395 ; of optic nerve, 423 ; of Pa- 
 cinian corpuscles, 347 ; of papillae, 359 ; 
 portal hepatic plexus of, 769 ; relation of 
 tissues to, 660 ; of retina, 414 ; of villi, 
 677 
 
 Capillary force, 695 
 
 Capsule, of lens, 418 ; of Pacinian corpus- 
 cles, 348 ; of spleen, 807 
 
 Caput, caecum coli, 567 ; gallinaginis, 832 
 
 Carbon, quantity removed from body, 730 ; 
 result of introduction of too much, 606 
 
 Carbonaceous matters eliminated by liver, 
 606 
 
 Carbonic acid, exhalation of by lungs, 724 ; 
 in intestine, 610 ; sources of, 731 
 
 Cardiac plexus, superficial and deep, 671 
 
 Cardinal veins, 881 
 
 Carlisle, Sir A., on the rete mirabile, 658 
 
 Cameae columnae, 665 
 
 Carnivora, Brunner's glands in, 579 ; cho- 
 rion in, 888 ; intestinal canal of, 569 ; 
 Peyer's patches in, 582 ; sources of car- 
 bonic acid in, 731 ; stomach of, 613 ; urine 
 of, 800 
 
 Carotids, 264 
 
 Carpenter, Dr., on arrangement of liver 
 cells, 780 ; on emotional fibres, 289 ; on 
 seat of emotional influence, 314; on the 
 functions of the white blood corpuscles, 
 641 ; on the nervous system, 290, 314 ; on 
 parthenogenesis, 822 ; and Mr. Newport, 
 on sensori-volitional and excito-motory 
 flbres, 290 
 
 Carson, Dr., on resilience of lungs, 720 
 
 Carswell, Dr., experiments on digestion of the 
 stomach, 554 
 
 Cartilage, 95 ; temporary and permanent, 
 95, 118 ; structure of the varieties, 96 ; ves- 
 sels of, 99 ; of ear, 444; of eyelids, 424; 
 of larynx, 746 ;- of nose, 391 ; of trachea, 
 708 
 
 Caruncle, 425 
 
 Cams, Victor, on metagenesis, 824 
 
 Caseine, 55 
 
 Castor, 835 
 
 Casts of uriniferous tubes, 798 ; of foetus in 
 liquor amnii, 893 
 
 Catalytic action of gastric juice, 559 
 
 Catalysis, 741 
 
 Catamenia, 847 
 
 Cauda equina, 270 
 
 Cavity of reserve, 537 
 
 Cells, development from, 63 ; nucleated, the 
 most elementary organic forms, 32, 61 ; 
 transformation of, 63 ; of the colon, 672 ; 
 of hair, 364 ; of liver, 779 ; of spleen pulp, 
 808 ; of stomach, 547 
 
 Cellular coat of arteries, 650 
 
 Cement of teeth, 531 
 
 Centrum ovale of Vieussens, 253 
 
 Cephalopoda ; cleavage of yolk in, 856 ; di- 
 gestive organs of, 513 ; heart of, 663 ; renal 
 organs of, 786 ; sexual organs of, 826 
 
 Ceroaria, 823 
 
 Cerebellum, its connections, 320 ; descriptive 
 anatomy of, 245 ; functions of, 317 ; influ- 
 ence upon locomotion, 285 
 
 Cerebral hemispheres, 253 ; circulation ^n, 
 263 ; commissures, 267 ; convolutions, 264 
 
 Cerebro-cerebellar commissures, 260 
 
 Cerebro-spinal fluid, 231 
 
 Cerebrum, descriptive anatomy of, 250 
 
 Cetacea, eye of, 403 ; intestinal canal of, 
 571 ; olfactory nerves of, 312 
 
 Cerumen, of ear, 445 
 
 Geruminous glands, 371, 445 
 
 Cervical glands, effects of enlarged, 493 
 
 Cervix of glans penis, 833 ; of uterus, 842 
 
 Chamber of deputies, cubic capacity of, 728 ; 
 anterior and posterior of eye, 420 
 
 Cbara and valisneria, 697 
 
 Cheeks, 624 
 
 Cheiroptera, intestinal canal of, 570 
 
 Chelonia, generative organs of, 828 ; intesti- 
 nal canal of, 569 
 
 Chest voice, 753 
 
 Chevreul on the gastric juice, 559 ; on the 
 imbibition of fluids, 623 
 
 Chiasma of optic nerves, 421 
 
 Chick, development of, 863; bile in gall- 
 bladder of, 813 
 
 Chloride of sodium, as a source of the acid 
 in the gastric juice, 564 ; in liquor amnii, 
 892 ; in urine, 802 
 
 Cholepyrrhin, 699 
 
 Cholera, Peyer's patches in, 682 ; tempera- 
 ture of body in, 739 
 
 Cholesterine, 699 
 
 Cholinic acid, 598 
 
 Chondrine, 68 
 
 Chorda dorsalis, 868, 876 
 
 Chorda tympani, 478 ; function of, 479 
 
 Chordas, tendineae, 664 ; vocales, true and 
 false, 748 
 
 Chorea, 307, 316 ; increase of sulphates in 
 urine, 802 
 
INDEX. 
 
 909 
 
 Chorion, 866 ; on papillary structure of tongue, 
 378 
 
 Choroid, 407 ; of birds, 409 
 
 Choroidal gland, 409 
 
 Ohoasat, on effects of impaired nutrition, 521 ; 
 on death from starvation, 738 
 
 Christison on the influence of venesection on 
 the blood, 646 
 
 Chromatic aberration, 428 
 
 Churning, effect of, on oil globules of milk, 
 902 
 
 Chyle, 586, 687 ; analysis of, 622 ; absorption 
 of by villi, 578 ; corpuscles, 587 ; fibrine 
 in, 619 ; white colour dependent upon oily 
 matter, 621 1 and lymph, quantity of, 622 ; 
 transparent and white, cause of, 689 ; 
 white, independent of the bile, 603 
 
 Chyme, 661 
 
 Cicatrix in ovary after the escape of the ovum 
 from the follicle, 849 
 
 CUiary, ganglion, 500 ; motion, 73 ; inde- 
 pendent of nerves, 74 j distribution in the 
 animal kingdom, 75 ; when found in man, 
 75 ; its uses, 76 ; cause, 77 ; ligament, 
 muscle, 412 ; nerves long, 423 ; result of 
 irritating, 434 ; processes, 410 ; of vitreous 
 body, 416 
 
 Ciliated epithelium, 523 ; in kidney of frog 
 and newt, 791 ; of nose, 393 
 
 Circular fibrous coat of arteries, 651 
 
 Circulation of blood, 649 ; in. embryo, 881 ; 
 in arteries, 679 ; in brain, 263 ; course of, 
 676 J in capillaries, 693 ; continuous, 680 ; 
 forces of, 694; in fcetus, 677; forces of, 
 678 ; in frog's foot, 695 ; in lymphatics, 
 618 ; rate of, 704 ; in vascular area of eggs, 
 697 ; in reins, 700 
 
 Circumvallate papillse, 381 
 
 Cirrhopoda, sexual organs of, 826 
 
 Claspers, in cartilaginous fishes, 827 
 
 Cleavage of yolk after impregnation, 855 
 
 Clemm, his analysis of milk, 902 
 
 Climate and seasons, influence of upon tem- 
 perature, 736^ 
 
 Clothing, influence of, upon temperature of 
 the body, 738 
 
 Coagulation of blood, phenomena of, 630 ; 
 of caseine, etc., by gastric juice, 556 
 
 Coathupe, Mr., on volume of carbonic acid 
 in expired air, 724 
 
 Coats of a vein, 658 
 
 Cochlea, 451 ; action of, 471 ; of birds, 444 
 
 Cochlear ligament, 456 
 
 Cochlearis muscle, 455 
 
 Cold climates, food in, 516 ; effects of on taste, 
 388 
 
 Cold-blooded animals, 734 
 
 Cole, on the velocity of the circulation in 
 arteries, 692 
 
 Collard de Martigny, on the lymphatics 
 during fasting, 621 
 
 Collionlus, 885 
 
 Colostrum, 902 ; corpuscles, 900 
 
 Colon, 567 ; cells of, 573 ; muscular coat of, 
 572 
 
 Colour of hair, destroyed by chlorine, 367 
 
 Colouring matter formed by red blood-cor- 
 puscles, 641 
 
 Colourless corpuscles, office o'f, 641 
 
 Columella or modiolus of ear, 451 
 
 Columns of cord, functions of, 282 
 
 Columnae rugarum, of vagina, 845 
 
 Columnar epithelium, 623 ; of bladder, 805 ; 
 
 of ureter, 804 ; of villi, 576 
 Coma, 323, 327 
 
 Commissural fibres of retinse, 440 
 Commissures, cerefiral, 258 ; functions of, 
 
 329 
 Common gall duct, 696 
 Common sensation, 356 ; sensibility, 352 
 Comparative anatomy, its value to phre- 
 nology, 49 
 Compound mucous membrane, 546, 573 ; 
 
 tissues, 62 
 Compressible pulse, 682, 684 
 Compressor urethrae, 834 
 Concha, 446 
 
 Cones, uriniferous tubes in, 793 
 Congestion, active and passive, 698 
 Conical teeth, 526 
 Conium, effect of, on cord, 282 
 Conjugation, 821 
 Conjunctiva, 404; imitation of, from duct, 
 
 698 
 Consciousness, 45 
 Consonants, how produced in vocalization, 
 
 757 
 Contact, or catalysis, 741 
 Contiguity, continuity, 345 
 Contraction, active, 164, 170, 173 ; passive, 
 
 164 ; duration and extent of, 176 
 Contractility, 68, 163 ; of absorbent vessels, 
 
 615 ; of arteries, 654, 682 ; of skin, 365 ; 
 
 varying character of, evidenced by its 
 
 duration, 177 ; by its aptness to excitation, 
 
 179 
 Convoluted portion of uriniferous tubes, 789, 
 
 791 . 
 Convolutions of brain, 253 ; functions of, 
 
 321 
 Convulsions, from lesion of corpora quadri- 
 
 gemina, 313 
 Cooper, Sir Astley, on circulation in the 
 
 brain, 266 ; on the lacteal glands, 898 ; 
 
 absorbents of, 900 ; on the thymus, 817 
 Co-ordination of movements, 301 
 Copulatory organs of insects, 827 
 Cord, invested with amnion, 892 
 Cords, vocal, position of in vocalization, 762 
 Cornea, 404 
 Cornicula laryngis, 747 
 Corona glandis, 833 
 Coronary arteries, 664 ; vein, 664 
 Corpora cavernosa penis, 832 ; lutea, 850, 
 
 851 ; mamillaria, 259 ; quadrigemina, 312 ; 
 
 fibres from, to chiasma, 422 ; and bige- 
 
 mina, 878 ; striata, connections and func- 
 tions, 308, 310 
 Corps reticule of Velpeau, 892 
 Corpus Arantii, 666, 668 ; callosum, functions 
 
 of, 329 ; fornicis, 259 ; Highmori, 830 ; 
 
 spongiosum urethrae, 832 ; striatum, 250 
 Cortex of hair, formation of, 365 
 Cortical portion of kidney, 789 ; of supra- 
 renal capsules, 814 
 Coste, M., on the decidua, 862 
 Costo-superior respiration, 718 
 Cotyledons of ruminants, 888 
 Course of the circulation, 676 
 Cow, corpus luteum of, 852 ; milk of, 902 
 Cowper, glands of, 832, 845 ; on capillaries, 
 
 662 
 Crampton, Sir P. on the ciliary muscle of 
 
 birds, 413 
 
910 
 
 INDEX, 
 
 Cranium, deyelopment of, 876 ; not a solid 
 case, 267 
 
 Cranio-vertebral nerves, 272 
 
 Crassamentum, 628 j oontraotion of, 63\ 
 
 Crawford, on influence of^ exhalation of car- 
 bonic acid upon animal temperature, 726 
 
 Crayfish, follicles of liver of, 764 
 
 Creatine in urine, 799, 801 
 
 Creatinine in urine, 801 
 
 Crest of urethra, or verumontanum, 834 
 
 Cricoid cartilage, 746 
 
 Crown of tooth, 526 
 
 Crura oerebelli, 250 
 
 Crustacea, circulation in, 706 ; heart of, 662 ,■ 
 organ of hearing, 442 ; sexual organs of, 
 826 ; spermatozoa of, 836 
 
 Crushing teeth, 526 
 
 Crystalline lens, 417 
 
 Crystals in blood of spleen, 809 
 
 Cuneiform cartilages, 747 
 
 Cupola, 452 
 
 Cupped and buffed, 631, 632 
 
 Current, direct and inverse, 337 
 
 Cuticle, 359 ; depressions in, for ridges of 
 cutis, 357 ; under surface of, 358 ; very 
 thick on heels and palms of the hands, 360 
 
 Cutis, 354, 356 ; intimate structure of, 354 
 
 Cutting teeth, 626 
 
 Cuvier, on cerebral convolutions, 322 ; on 
 the shape of the jaw and character of the 
 teeth, 539 
 
 Cyclosis, 697 
 
 Cyclostomous fishes, generative organs of, 
 827 
 
 Cystio duct, 596 
 
 Cystic entozoa, multiplication of, 823 
 
 Cysticercus fasciolaris, 823 
 
 Cysticnle, 443 
 
 Cystine, 799, 802 
 
 Daiton, Dr., on corpus luteum, 852 
 Dalrymple, Mr., on the capillaries of the 
 
 allantois, 896; on vasalutea, 893 
 Daphnia, hibernating, eggs of, 826 
 D'Arcy, on the duration of impressions on 
 
 the retina, 434 
 Dart sac in moUusca, 826 
 Dartos, contractile fibres of. 166 
 Davy, on the solubility of carbonic acid in 
 
 defibrinated blood, 729 
 Death, 27, 36 
 
 Decapoda, sexual organs of, 826 
 Decussation of fibres in chiasma, 422 
 Decidua, formation of, 869 ; reflexa, 861 ; 
 
 serotina, 861 
 Decomposition of gastric juice, 556 
 Defecation, 60S 
 Deglutition, 641; dependence on medulla 
 
 oblongata, 306 
 Demodex follioulomm, 370 
 Dental groove, primitive, 532 
 Denticulate lamina of cochlea, 453 
 Dentition, first and second, 636 
 Derma, 353 
 Descartes, Albinus, Hunter and Young, on 
 
 the muscularity of the lens, 429 
 Desmoulins, on the distribution of the third 
 
 nerve in falcons and eagles, 475 
 Detrusor urinffi, 805 ' 
 Development of blood corpuscles, 642 ; of 
 
 animal, and tissues from cells, 63 ; of 
 
 the embryo, 863 ; of the eyelids, 880 ; of 
 
 the heart and aortic arches, 880 ; of the 
 lungs, 883 ; of spermatozoa, 836 ; of Thy- 
 mus, 816 
 
 Dextrine, 660, 688 
 
 Diabetes, presence of hippnrio acid in urine 
 of, 801 ; food in, 520 
 
 Diaphragm, its condition during vomiting, 
 564, 566 
 
 Diarthrosis, 133 
 
 Diastole, 672 
 
 Diet, nature of, 516 
 
 Dietaries in navy and in union workhouses, 
 519 
 
 Diffusion of gases, 727 
 
 Digestive branch of glosBO-pharyngeal, 486 
 
 Digestion, changes in mucous membrane 
 during, 685 ; effect of carbonic acid upon, 
 724; general view of, 512 ; of fatty matter, 
 594 ; influence of alcohol upon, 562 ; of 
 exercise, 562 ; temperature, 656 ; in large 
 intestine, 608 ; not stopped by section of 
 vagi, 493 ; rate of, 661 ; of stomach, 561 ; 
 state of villi during, 578 ; of vegetable 
 substances, 660 
 
 Digestive principle, 556 
 
 Dilated capillaries of olfactory region, 395 
 
 Direct current in galvanizing nerves, 273 
 
 Discharge of ova, 848 
 
 Disease, influence of, upon animal tempera- 
 ture, 739 ; effects of, on blood, 645 
 
 Distinction between plants and animals, 29, 
 44 
 
 Diving-bell, effects of, upon ear, 469 
 
 Dobson, on the use of the spleen, 813 • 
 
 Dodart, on the number of notes produced by 
 the human voice, 755 
 
 Dormouse, intestinal canal of, 570 
 
 Dorsal, laminae, 867 ; vessels of insects, 662 
 
 Double, chin, 354 ; vision in drunkenness, 
 440 
 
 Doubleness of the organ of vision, 439 
 
 Dowler, Dr., on temperature in yellow fever, 
 739 
 
 Draper, Professor, on circulation of sap, 696 
 
 Druitt, Dr., on fatty degeneration of the 
 placenta, 891 
 
 Dry air, effect of, on the quantity of urine, 
 797 
 
 Duct, hepatic, 775 ; smallest branches of, 
 781 ; of glands, 764 ; of the liver, 596 
 
 Ductus, arteriosus' 678, 882 ; communis 
 oholedochiis, 596, 777 ; venosus, 677 
 
 Ductless glands, 806 
 
 Dugong, intestinal canal of, 571 
 
 Dulong and Despretz, on influence of nervous 
 system on animal heat, 742 ; on relation of 
 carbonic acid in respired air, 727 
 
 Dumas, on the acidity of gastric juice, 557 
 
 Dunglison, on gastric juice, 551 
 
 Duodenum, 568 ; Brunner's glands, 579 ; 
 mucous membrane of, 682 ; valvulse con- 
 niventes, 674 
 
 Dnpuy, on extirpation of superior cervical 
 ganglion of sympathetic, 510 
 
 Dupuytren and Orfila, on injecting fluids into 
 the blood to relieve thirst, 622 
 
 Dura mater and its vessels, 227 
 
 Dysentery, 609 
 
 Eau, oeruminous glands of, 371 ; external, 
 444, 463 : in man and ruminants, 464 ; 
 internal, 449 
 
INDEX. 
 
 911 
 
 Eeker, on splenic blood, 607 j on supra-renal 
 capsules, 814 ; and Beclard, on disintegra- 
 tion of blood-oorpuscles of the spleen, 813 
 
 Eoliidna, 828 
 
 Ecliinodermata, reproduction of, 825 
 
 Edentata, intestinal canal of, 670 
 
 Edwards, Dr., on the temperature of the 
 human body, 735 
 
 Efferent vessel of Malpighian body, 789 
 
 Ehrenritter, on the ganglion jugulare, 485 
 
 Ejaculatory canals, 830 
 
 Elaine, 59, 90 
 
 Elastic laminae, anterior and posterior, 406 
 
 Elasticity of arteries, 654 ; of arterial walls, 
 679 ; of tissues, 66 
 
 Electrical fishes, 223 ; organs, 350 ; current 
 in muscles, 332 
 
 Elements of organic matter, essential and 
 incidental, 29 ; mode of combination, 31 ; 
 of respiration in food, 516 
 
 Emotions, 339 ; centres of, 307, 314 ; effects 
 of, on speech, 755 ; mechanism of, 682 
 
 Embryo, blood-corpuscles in, 638; cell, 866 
 
 Emetics, 564 
 
 Emulsion of fat and pancreatic fluid, 694 
 
 Enamel, 530 ; pulp, 533 
 
 Encephalic nerves, 271 
 
 Bnderlin, on ashes of faeces, 610 
 
 Endochorion, 892 
 
 Endolymph, 453 
 
 Endosmose, into blood-corpuscles, 637 j con- 
 cerned in the action of purgatives, 624 ; 
 and ezosmose, 67 
 
 Enemata, action of, 609 
 
 Entozoa, circulation of, 706 j from follicles of 
 skin, 371 ; reproduction of, 825 
 
 Epencephalic vertebra, 876 
 
 Epidermis, 359 ; action of acetic acid upon, 
 361 ; shedding of, 361 
 
 Epididymis, development of, 887 
 
 Epiglottis, 747 
 
 Epilepsy, 281 
 
 Epiploon, 668 
 
 L'Epione, on the action of the stomach in 
 vomiting, 665 
 
 Epithelium of absorbent vessels, 614 ; of 
 aqueous humour, 407 j of artery, 653 ; of 
 bladder, 805 ; of cavities of the heart, 666 ; 
 choroidal, 409 ; ciliated, of Fallopian tube, 
 842 ; conjunctival, 404 ; of convoluted 
 portion of uriniferous tubes, 792 ; of Cow- 
 per's glands, 832 ; of ducts of glands, 765 ; 
 imbricated, of hair, 366 ; of Lieberkiihn's 
 follicles, 573 ; of lymphatic glands, 616 ; 
 of minute hepatic ducts, 783 j of mucous 
 membrane, 523 ; of nasal cavity, 393 ; of 
 oesophagus, 644 j of pancreas, 767; of 
 papillae of tongue, 379 ; of prostate, 831 ; 
 of scalse of cochlea, 467 ; of seminal tu- 
 bules, 835 ; changes in, during the develop- 
 ment of the spermatozoa, 836 ; of skin, 
 363 ; of stomach cells, 647 ; of sweat- 
 glands, 369 ; of uterus, 844; of villi, 576 ; 
 during fasting, 578 ; during intestinal di- 
 gestion, 686 
 
 Erectile tissue, 678 ; of penis, 832 
 
 Erection of nipple, 356, 900 
 
 Eremaeausis, 741 
 
 Erichsen, Mr., his experiments on absorption, 
 611 
 
 Eructation, 563 
 
 Eruption of permanent teeth, period of, 638 
 
 Eruptive stage of development of teeth, 536 
 
 Bsohricht, on the relation of the foetal capil- 
 laries to the maternal vessels, 890 
 
 Ether, effect of inhalation of upon the quan- 
 tity of carbonic acid expired, 725 
 
 Eustachian, tube, 448 ; use of, 469 ; valve, 
 666, 677 
 
 Eyelids, development of, 880 
 
 Excito-motory actions of cord, 280 
 
 Excretion, 34, 768 
 
 Exoretine, 759 
 
 Exercise, favouring or retarding digestion, 
 662 ; effects of, on respiration, 726 ; on 
 temperature of the body, 735 
 
 Expiration, 720 ; muscles of, concerned in 
 vomiting, 566 
 
 Extensibility of tissues, 66 
 
 External meatus, 444 ; tunic of arteries, 650 
 
 Extractive matter in urine^ 801 
 
 Extremities, 141, 145 
 
 Extraordinary muscles of respiration, 720 
 
 Eye, general description of, 402; of birds, 
 cetacea, and fishes, 403 ; of invertebrata^ 
 402 ; lids, 424 
 
 Fabee and Silbermann, on animal heat, 742 
 
 Face, development of, 877 
 
 Facial nerve, 477 ; disease of, 479 
 
 Faeces, analysis of, 609 ; expulsion of, 608 ; 
 quantity of, 609 
 
 Fallopian tube, 842 
 
 False corpora lutea, 851 
 
 Falsetto notes, 754 
 
 Parre, Dr. Arthur, on bryozoa, 614 ; on organ 
 of hearing in Crustacea, 443 
 
 Fascia, subcutaneous, 354 
 
 Fascination of prey by serpent, 342 
 
 Fasting, effects of, 521 ; on quantity of ex- 
 pired carbonic acid, 726 
 
 Fat, 90 ; constituents of, 90 ; ultimate analy- 
 sis of, 91 ; distribution of, in animals, 91 ; 
 in man, 92, 93 ; morbid accumulation of, 
 92 ; whence derived, 93 ; uses, 94 ; in the 
 liver, 605 ; in the stools, 696 ; subcutane- 
 ous, 366 
 
 Fatty degeneration, of foetal tufts, 890 ; of 
 muscular fibre-cells of uterus, 843 ; de- 
 generation of liver, analysis of, 768 ; cells 
 in, 781 ; matter, absorption of, 691 ; action 
 of pancreatic fluid upon, 695 ; in chyle, 
 621, substances, digestion of, 661 
 
 Fauces, mucous membrane of, supplied by 
 glosso-pharyngeal, 487; highly sensitive, 
 307 
 
 Fecundity of osseous fishes, 827 
 
 Feeling in tongue, 387 
 
 Fellinic acid, 698 
 
 Female organs of generation, 839 
 
 Fenestra ovalis and rotunda, 446 
 
 Fenestrated membrane of arteries, 654 
 
 Fernaby, Mr., on the areas of arteries, 692 
 
 Ferrein, on the production of vocal soundF, 
 752 ; on the pyramids of the kidney, 787 
 
 Festoons of heart, 668 
 
 Fever, faeces in, 610 
 
 Fibres of lens, 418 
 
 Fibrin, 54; in blood, 634; in chyle, 587, 
 588 ; and lymph, 619 ; diminution of, in 
 fevers, 648 ; formed by white blood-cor- 
 puscles, 641 ; increase of, in blood, 647 
 
 Fibro-oartilage, structure, properties, and 
 uses of, 100 
 
912 
 
 INDEX. 
 
 Eibrous tissue, white, 79 j yellow, 82 ; coat 
 of artery, 660 ; longitudinal of veins, 659 | 
 gray layer of retina, 413 ; stroma of ovary, 
 840 ; tissue in papillae of tongue, 384; zone 
 of heart, 667 
 
 Fifth, nerve, lingual branch of, 388; ventri- 
 cle, 260 
 
 Figuier, on separating hsematin from globu- 
 lin, 644 
 
 Filamentous tissues, 62 
 
 First trace, or nota primitiva, 865 
 
 Fishes, blood-corpuscles of, 636 ; choroidal 
 gland of, 409 ; cartilaginous, chorda dorsa- 
 lis of, 868; circulation in, 695, 707; di- 
 gestive organs of, 513; heart of, 663; 
 intestinal canal of, 568 ; organ of hearing 
 of, 443 ; organ of smell of, 400 ; sympa- 
 thetic nerve of, 498 ; spermatozoa of, 836 ; 
 teeth of, 626 
 
 Fisher, Mr., on effects of cold in Arctic 
 voyage, 738 
 
 Fissiparous multiplication, 819 
 
 Fissure of Sylvius, 264 
 
 Flocculus, connection of with portio dura, 
 477 
 
 Flourens, M., experiments on the encepha- 
 lon, 304, 317 ; on the destruction of the 
 corpora qnadrigemina, 312 ; on the removal 
 of cerebellum in birds, 317 ; on removal of 
 cerebral hemispheres, 305 
 
 Fluid in stomach during digestion, 551 
 
 Fluke, 823 
 
 Focus of a lens, 427 
 
 Foetal, circulation, 677 ; tufts or villi, 862 
 
 Fcetus, its position in utero during the latter 
 months of pregnancy, 898 
 
 Fohmann, on lymphatic glands, 616 
 
 Folds in large intestine, 575 
 
 Follicles of Lieberkiihn, 573 ; of lacteal 
 gland, 900 ; of mucous membrane of ute- 
 rus, 843 
 
 Food, changes of in small intestine, 587 ; 
 Dr. Front's classification of, 614; effect of, 
 on the temperature of the body, 736, 738 ; 
 effects of too much or too little, 519 ; 
 quantity necessary for health, 618 ; yolk, 
 856 
 
 Foramen, caecum of tongue, 381 ; commune 
 anterius, 259 ; ovale or Botalli, 665 ; fora- 
 mina Thebesii, 666 
 
 Force, of the heart, 684 ; of the stream in 
 arteries, 685 
 
 Forced expiration, 720 
 
 Forces, of the capillary circulation, 694 ; of 
 the circulation, 678 
 
 Fordyce, on frequency of heart's action, 
 675 
 
 Fornix, 258 ; function of, 329 
 
 Fossa, navicularis, 834 ; ovalis, 666 
 
 Fourth nerve, origin, 476 
 
 Fovea hemispherica, semi-elliptioa, 450 
 
 Foville, on the functions of the corpora stri- 
 ata and optic thalamus, 311 
 
 Frequency of heart's action, 675 
 
 Freriohs, Dr., on carbonate of ammonia in 
 the blood in renal disease, 800 ; on con- 
 stituents of semen, 838 
 
 Frsena of Ileo-csecal valve, 675 
 
 Frog, galvanoscopio, 331 ; kidney of, 768 ; 
 proper current of, 334 
 
 Fiik, Prof, on temperature of internal parts 
 of the body, 735 
 
 Functions, organic and animal, 45 ; of nerves, 
 270 ; of the liver, 605 ; of the kidney, 796 ; 
 of plants and animals, general view of the, 
 42, 46 ; of the red blood corpuscle, 640 
 
 Fundus of uterus, 842 
 
 Fungiform papillae, 382 
 
 Funke, on crystallization of blood, 729 ; on 
 crystals in splenic blood, 809 
 
 Fur on tongue, 379 
 
 Furrows of skin, 354 
 
 Gall, arguments against his theory of the 
 function of the cerebellum, 320 
 
 Gall-bladder, 777; use of, 596; not uni- 
 versally present, 697 ; vessels of, 775 
 
 Galvani, his experiments on the frog, 334 
 
 Ganglia, of nerves, structure of, 207 ; cepha- 
 lic, of sympathetic, 500 ; of sympathetic, 
 498 ; of hearing, smell, taste, touch, and 
 vision, 314 
 
 Ganglion, cardiaoum Wrisbergii, 672; impar, 
 498 ; jugulare petrosum, 485 ; ophthalmic, 
 500 ; otic, 501 ; semilunar, 503 ; spheno- 
 palatine, 500 ; submaxillary, 501 ; superior 
 cervical, connections of, 502 
 
 Ganglionic system of nerves, 192 
 
 Garrod, Dr., on the detection of urea in 
 Wood, 800 
 
 Gases, in intestinal canal, 610 
 
 Gasserian ganglion, 481 
 
 Gastric juice, 564; antiseptic power of, 556 ; 
 action of various acids in, 554 ; artificial, 
 554; importance of acid in, 555; orga^c 
 principle of, 566 ; its action on albumen, 
 555, 660 ; on meat, milk, and vegetables, 
 560 
 
 Gasteropoda, heart of, 663 ; organ of hear- 
 ing of, 442 ; stomach teeth of, 525 
 
 Geiger, on the quantity of lymph, 622 
 
 Gelatine, 57 ; producing colourless chyle, 
 621 ; from cutis, 365 
 
 Gelatinous nerve fibres in sympathetic, 196 
 
 Generation, 819 ; female organs of, 839 ; true, 
 821 
 
 Generative organs ; development of, 887 ; of 
 fishes, 827 ; of vertebrata, 827 
 
 Geniculate bodies, connection of optic tracts 
 with, 421 
 
 Genito-urinary mucous membrane, 623 
 
 Gerber, on the termination of nerves in skin, 
 360 
 
 Gerlach, on blood corpuscle-holding cells, 
 809 ; on ciliated epithelium of the kidney 
 of the fowl, 791; on the Malpighian tufts, 
 791 
 
 Germ, cell, 821 ; yolk, 856 
 
 Germinal, centres of glands, 763; spot, 841; 
 vesicle, 841 ; formation of, 857 ; disappear- 
 ance of after impregnation, 855; of Ento- 
 ohoncha, persistence of, 866 ; spot, or nu- 
 tritive centre, 889 
 
 Giddiness, 326 
 
 Gizzard in birds, 569 
 
 Gland cell, 764 
 
 Glands, aggregate, 683 ; of Brunner, 579 ; 
 of Havers, 762; of intestine, 679; ofLittre, 
 834; of Peyer, 581; sebaceous, 370; sweat, 
 368; solitary, 580; tracheal, 708; true, 
 762 
 
 GlanduliB Nabothi, 844; odoriferse, .370; 
 Tysonianae, 834 
 
 Glandular epithelium, 623 
 
 \ 
 
INDEX. 
 
 913 
 
 G-Ians penis, 832 
 
 Glasserian fissure, 447 
 
 Globe of the eye, 402 
 
 Globnline, 59 
 
 Globus hystericus, 307 
 
 Glottis, alteration of aperture of, 750 ; closure 
 of, 494 ; its condition in vomiting, 564 
 
 Glycerine, 91 
 
 Gmelin and Berzelius, on the character of 
 choroidal pigment, 409 
 
 Goat's milk, 902 
 
 Goodsir, on the cavities of reserve, 536 ; on 
 centres of nutrition, 523 ; on cirrhopoda, 
 826 ; on the development of teeth, 532 j 
 on lymphatic glands, 615 ; on matrix of 
 kidney, 788 ; on membrana decidua, 861 ; 
 on the development of the thymus, thyroid, 
 and supra-renal capsules, 883 
 
 Gorup-Besanez, on the reaction of the bile, 
 598 
 
 Gosse, on the rate of stomach digestion, 562 
 
 Gottsche, on the optic lobes of pleuronecta, 
 312 
 
 Gout, 699 
 
 Graafian vesicles, 839 
 
 Graham, Prof., on analysis of blood-corpus- 
 cles of invertebrata, 640 ; his law of diffu- 
 sion of gases, 727 
 
 Grainger, Mr., on effects of the removal of 
 cerebral hemispheres, 306 ; on medulla 
 oblongata, 306 ; on roots of nerves, 271 ; 
 on the spinal cord, 287 ; on the umbilical 
 vesicle, 893 
 
 Grandchamps, on the functions of the cor- 
 pora striata and optic thalami, 311 
 
 Granular, lids, 426 ; layer of dentine, 414 ; 
 cells, 638 ; corpuscles in menstrual fluid, 
 848 
 
 Gravity, influence of upon venous circula- 
 tion, 703 
 
 Gray, Mr. H., on Malpighian corpuscles of 
 the spleen, 812 ; on the use of the spleen, 
 813 ; on the development of the liver and 
 spleen, 885 ; of the supra-renal capsules, 
 887 ; thyroid, 883 ; organs of vision and 
 hearing, 879 
 
 Gray matter of convolutions, 256 ; of cord, 
 predominance of, in lumbar region, 286 
 
 Grew's glands, or Peyer's glands, 681 
 
 Grinding teeth, 526 
 
 Groove on the heart, 664 
 
 Gnanin in the renal organs of arachnida, 
 786 
 
 Gulliver, Mr., on molecular base, 587 ; of 
 chyle, 619 
 
 Gums, 532 
 
 Guy, Dr., on the pulse, 675 ; on the frequency 
 of the respiration, 722 
 
 Guyat, on taste, 386 
 
 Habit, influence of, in the economy, 37 
 Haemadromometer, 690 
 Hsemadynamometer, 686 
 Heemal arch of vertebrae, 865 
 Hsematine, 59, 644; a secretion of the blood 
 
 corpuscles, 641 
 Hemorrhage from the uterine vessels, 891 
 Hair, follicle, 364 ; colour of, 367 ; growing 
 
 white, 366; method of making sections 
 
 of, 365 
 Hall, Dr. Marshall, on the nervous system, 
 
 280, 288, 290 ; on muscular contractility. 
 
 177, 303 ; on excito-motory actions, 280 ; 
 on the vagus, 494 
 
 Haller, on the great cardiac plexus, 505 ; on 
 the formation of corpora lutea, 850 ; on the 
 musular fibres of the meatus, 445 ; on the 
 quantity of bile, 597 ; on the quantity of 
 blood, 630 ; on the folds of the umbilical 
 vesicle, 893 
 
 Hales, on capillaries, 662 ; on the capillary 
 circulation, 680 ; on the force of the heart, 
 678 ; on the pressure of the blood in arte- 
 ries, 684; on the velocity of the blood in 
 arteries, 684 ; and Poiseuille, on the force ^ 
 of the current in the veins, 701 
 
 Hamberger, on the movements of intercostal 
 muscles, 719 
 
 Hamulus, 452 
 
 Hancock, on muscular fibres, of prostate, 
 831 ; of urethra, 833 
 
 Hand, 145 
 
 Hare-lip, 877 
 
 Harless, on the presence of uric acid in the 
 renal organs of the cephalopoda, 786 ; on 
 the diameter of the blood-corpuscles in 
 arterial and venous blood, 729 
 
 Harvey, on the discovery of the circulation, 
 649 ; on the quantity of blood, 630 
 
 Hassenfratz, on carbonic acid in the blood, 
 730 
 
 Hastings, Sir Charles, on the irritability of 
 arteries, 682 
 
 Havers, glands of, 762 
 
 Haversian canals of bone, 110 
 
 Headache, 325 
 
 Hearing, difference of in different persons, 
 472 ; organ of, general description, 442 ; 
 development of, in animal series, 442 ; 
 phenomena of, 463 ; development of organs 
 of, 880 
 
 Heart, 662 ; arrangement of fibres in, 158 ; 
 contractions of, 182 ; of Crustacea, 663 ; 
 development of, 870, 880 ; of birds, 663 ; of 
 fishes, 663 j force of, 684 ; of moUusca, 663 ; 
 muscular tissue of, 669 ; nerves of, 671 ; 
 nutrition of, 671; of reptiles, 663; influ- 
 enced by spinal cord, 302 ; sounds of, 673 
 
 Heart's action, 672 ; frequency of, 675 ; in- 
 fluence of the period of the day, posture of 
 the body, etc., upon, 675. 
 
 Heat, amount of, developed, in organism, 
 734 ; animal, influenced by exercise, 735 ; 
 development of, in animals, 734 ; in plants, 
 733 ; developed when carbon combines 
 with oxygen, 733 ; loss of, by evaporation,. 
 737 ; period of, in animals, 849 ; and cold, 
 sensations of, 376 
 
 Heberden, on frequency of the heart's action,. 
 676 
 
 Hectocotylus, 826 
 
 Heintz, on urate of soda in urine, 800 
 
 Helicotrema, 4:52 
 
 Helix, 444 ; groove, 445 
 
 Hemiplegia, paralysis of tongue in, 480 ; ac- 
 companying lesion of corpora striata, 309 
 
 Hemispheres, cerebral, 253 
 
 Heule, on epithelium of arteries, 653 ; on 
 change of form in the red blood corpuscles, 
 729 ; on lacteal ducts, 900 ; on movements 
 of spermatozoa, 837; and EoUiker on Paci- 
 nian corpuscles, 349 
 
 Hepatic duct, 596 ; vein, 777 
 
 Herbivora, Brunner'a glands in, 579; Peyer's 
 
914 
 
 INDEX. 
 
 patches in, 582 ; sources of oarbonio aoid 
 
 in, 731 . 
 Herbst, on the oapaoity of the lungs, 723 
 Hermaphrodite, 825 
 Herschel, on achromatism of the eye, 432 j 
 
 on intensity of sound, 463 
 Hewson, on coagulation of the blood, 631 
 Hiatus Fallopii, Vidian nerve in, 477 
 Hibernation, 739 ; absorption of fat during, 
 
 612 ; in animals, thymus during, 818 
 Hippocampus major, 262 
 Hippurio aoid, 801 ; in urine, 799 
 Hirudines, reproduction of, 825 
 Hissing of serpents, 745 
 Holding the breath, effects of, 721 
 Home, Sir B., on membrana tympani, 446 
 Hoofs, 363 
 
 Hoop, production of in hooping-cough, 755 
 Hooping-cough, nature of, 493 
 Hope, Dr., on cause of second sound of heart, 
 
 674 
 Horn, on taste, 390 
 Horse, kidney of, 793 
 Houston, Mr., on the folds of the rectum, 
 
 575 
 Houston, Dr., on the circulation in an anen- 
 
 cephalio foetus, 697 
 Hubert, on the temperature of plants, 733 
 Human, embryo, development of, 871 ,■ heart, 
 
 663 
 Humboldt, Baron Von, his case of suckling 
 
 by the male parent, 901 
 Hunefeld's experiments on the action of the 
 
 bile, 603 
 Hunger, 521 
 Hnnter, John, on the contractility of arteries, 
 
 655, 682 ; on the changes in the jaw bone, 
 
 538 ; on the gastric juices, 553 ,- on the 
 
 tonicity of arteries, 683 ; on vomiting, 
 
 565 
 Hunter, Dr. W., on the deoidua, 861 
 Huschke, on the development of the eye, 
 
 879 
 Hutchinson Dr., on the movements of respi- 
 ration, 717; on the force of the respiratory 
 
 muscles, 721 ; on the spirometer, 723 
 Hnxley, Professor, on reproduction in acale- 
 
 phss, 825 ; on the spleen, 812 
 Hyaline, 61 
 
 Hyaloid membrane of vitreous body, 416 
 Hybrids, spermatozoa of, 839 
 Hydrocele, 829 
 
 Hydrochloric acid in gastric jnice, 554 
 Hydrocyanic aoid, its absorption, 619 
 Hydrophobia, part of nervous centres affected 
 
 in, 307 
 Hymen, 845 
 Hypoglossal nerve, 480 
 Hypophysis of pituitary body, 261 
 Hypospadias, 888 
 
 Hypotheses, to explain action of cord, 665 
 Hyrtl, on the escape of the ovum from the 
 
 Graafian follicle, 848 
 Hysteria, 307 ; associated with excited states 
 
 of emotion, 316 ; and chorea, effects of on 
 
 voice, 755 
 
 IcB, its effects upon the cord, 282 
 Ileo-c8Bcal valve, 675 
 Ileum, mucous membrane of, 583 
 Ilg, on the wall of the cochlea, 452 
 Image, formation of on the retina, 432 
 
 Imbibition, 622 
 
 Impregnation of the ovum, 853 
 
 Impressions, duration of on the retina, 434 
 
 Impulse of the heart, 673 
 
 Incisors, 526 
 
 Inoisurse Santorini, 445 
 
 Incus, 448 
 
 Inferior cava, 665 
 
 Infundibulum, 452, 664; of lungs, 712 
 
 Infusoria, multiplication of, 825 
 
 Ingesta and egesta, 761 
 
 Injecting ducte of liver, 780 ; tubes of kidney, 
 789 
 
 Inorganic bodies, their modes ofcombination, 
 23 
 
 Insalivation, 539 
 
 Insects, circulation of, 707 ; dorsal vessel of, 
 662 ; generative organs of, 826 ; gizzard of, 
 525 ; hum of, 745 ; liver of, 770 ; renal 
 organs of, 786 ; temperature of, 734 
 
 Insectivora, intestinal canal of, 570 
 
 Inspiration, full, 723 
 
 Instinct, 46, 186 
 
 Intellectual action, centre of, 323 
 
 Intercostal muscles, movements of, 718 
 
 Interlobular fissures, 782 
 
 Intermaxillary bones, 877 
 
 Intermittent fever, blood in, 648 
 
 Intervertebral discs, 101 
 
 Intestines, large, mucous membrane of, 570, 
 583 ; villi ol, 576 ; development of walla 
 of, 883 ; digestion in, 608 ; movements of, 
 583; muscular boat of, 572; Peyer's glands, 
 581 ; solitary glands, 580 
 
 Intestinal canal, anatomy of, 567 ; in verte- 
 brata generally, 571 ; of birds, carnivora, 
 and insectivora, 569 ; of.cheiroptera, eden- 
 tata, pachydermata, ruminantia, rodentia, 
 and solipeda, 570 ; of cetacea, marsupialia 
 and quadrumana, 571 ; of fishes, 568 ; 
 changes of mucous membrane of, during 
 digestion, 579 
 
 Intestinnm, crassum, 567 ; tenue, 567 
 
 Intromittent organ, 829 
 
 Intumescentia genuformis, 477 
 
 Inverse current, in galvanizing nerves, 273 
 
 Inversion, in action of the stomach, 563 ; of 
 ' image in vision, 428 
 
 Invertebrata, blood-corpuscles of, 636 ; liver 
 of, 770 ; teeth of, 525 
 
 Inverted image, correct vision with an, 
 437 
 
 Investing membrane of Reichert, 864, 867 
 
 Involucra, cephalic and candal, 845 
 
 Involuntary movements, 276 
 
 Ipecacuanha, production of asthma by, 493 
 
 Iris, 410 ; alteration of during the adaptation 
 of the eye to distances, 430 ; influence of 
 corpora quadrigemina upon, 313; office of, 
 431 ; paralysis of, after section of the third 
 nerve, 475 ; its use in protecting the retina 
 from too much light, 433 
 
 Iron in blood-corpuscles, 640 ; state of, ac- 
 cording to Liebig, 645 
 
 Iter a tertio ad quartum ventrioulum, 261 
 
 Jacob, Dr., on the lines of the iris, 411 
 Jacob's membrane, 415; development of, 
 
 879 
 Jacobson, anastomosis of, 447; nerve of, 
 
 485 ; on allantoio fluid of birds, 897 
 Jaw-bones at different ages, 538 
 
INDEX. 
 
 915 
 
 Jejunum, 568 ; mucous membrane of, 582 ; 
 valvulae conniventes, 574 
 
 Johnson, Dr. G., on matrix of kidney, 788 j on 
 vessels of kidney in chronic nephritis, 699 
 
 Joints, 126, 130 ; influence of atmospheric 
 pressure upon, 131 ; forms and classifica- 
 tion of, 131 
 
 Jones, Dr. Benee, on the increase of alkaline 
 phosphates in the urine, in cases of inflam- 
 mation of the brain, 803 ; on the reaction 
 of urine, 798 ; on the increase of the sul- 
 phates in the urine in chorea, 802 
 
 Jones, Dr. Handfield, on the arrangement of 
 the liver-cells, 780 ; on the development of 
 the liver, 885 ; on the relation of the liver- 
 cells to the ducts, 782 ; on the . intestinal 
 mucous membrane, 582 j on prostatic con- 
 cretions, 832 ; on the thymus, 818 
 
 Jones, Mr. Wharton, on the development of 
 the human ovum, 871 ; on the lymph corpus- 
 cle, 620 ,• on the membrane of the black pig- 
 ment, 409 ; on the rhythmical contractions 
 in the veins of the bat's wing, 703 ; on the 
 red blood-corpuscles, 637 j on buffing and 
 cupping, 632 ; on the white blood-corpus- 
 cle, 637 
 
 Jugular vein, 881 
 
 Jurin. Eamsden, and Home, on the change 
 of the cornea in vision, 429 
 
 Kempelis, Dr., on the action of the glottis, 
 751 
 
 Kerner, on the efiects of the loss of the au- 
 ricle, 465 ; on the use of the semicircular 
 canals, 472 
 
 Kidneys, 785 ; analysis of, 786 ; general 
 remarks on the . function of, 803 ; vessels 
 of, 793 ; development of, 886 
 
 Kiernan, Mr., on the hepatic vein, 778; on 
 portal canals, 769 
 
 King's College Hospital, quantity of air 
 allowed to each patient, 728 
 
 Knox, Dr., on the alteration of the curvature 
 of the lens, 429 ; on the frequency of the 
 heart's action, 675 ; on the yellow spot on 
 'the retina, 415 
 
 Kblliker, on the anastomosis and branching 
 of the fibres of the heart, 670 ; on the 
 blood-corpuscles of the spleen, 808 j on the 
 cells of the liver, 779 ; on the cleavage of 
 the yolk in the ova of the intestinal worms, 
 856 ; on the colouring matter of the bile, 
 607 ; on the epithelium of the bladder, 
 805 ; on the helicine arteries of the penis, 
 833 ; on the Malpighian corpuscles of the 
 spleen, 812 ; on the origin of lymphatics, 
 617 ; on lacteal ducts, 900 ; on the prostate 
 gland, 831 ; on the relation of the hepatic 
 ducts to the liver cells, 782 ; on the red 
 blood-corpuscles, 637 ; on the spermato- 
 zoon, 836 J and Bagge, on the development 
 of intestinal worms, 841 
 
 Krause, on the bulk of the liver, 767 j on 
 the weight of the lungs, 707 
 
 Krieger on otoliths, 459 
 
 Kronenberg, on sensitive filaments in the 
 anterior roots of the nerves, 275 
 
 Kuchenmeister, and Van Beneden, on the 
 development of the cystic entozoa, 823 
 
 Labtbinth, 449 | experiments to show the 
 use of, 470 i of birds, 444 
 
 Lachrymal sac, 426 ; gland, 426 
 
 Lactation, 898 
 
 Lacteal, glands, 898 ; of male, 900 ; tubes, 
 899 
 
 Laeteals, distribution of, in intestine, 612 ; 
 filled with chyle, 686 ; of villi, 677 ; do 
 they absorb fat only ? 591; and lymphatics, 
 612 
 
 Lactic acid in osecnra, 608 ; in gastric juice, 
 668 ; formed from digestion of starch, 660 ; 
 in urine, 799 
 
 Lacuna magna, 834 
 
 Lafargue, on the effects of removing the cor- 
 pora striata, 309 
 
 Lagrange and Hassenfratz, on carbonic acid 
 in the blood, 730 
 
 Lamina spiralis, 462 
 
 Laminae dorsales, 867 
 
 Lamprey, mouth of, 524 ; organ of hearing 
 of, 443 ; and myxine, blood-corpuscles of, 
 636 
 
 Lane, Mr., on valves of absorbents, 614 
 
 Langenbeck, on the development of the uri- 
 nary bladder, 896 
 
 Langer and Kblliker, on the development of 
 the lacteal glands, 901 
 
 Lanugo, 874 
 
 Large intestine, 567 
 
 Laryngismus stridulus, how produced, 493 
 
 Larynx, the organ of voice, 744 ; action of, 
 750 
 
 Lassaigne, on the gastric juice, 569 
 
 Lateral pressure in arteries, 684 
 
 Lauth, on lymphatic glands, 616 ; and Muller, 
 on the ligaments of the larynx, 748 
 
 Lee, Dr. E,., on the nerves of the heart, 672 ; 
 on the nerves of the uterus, 844 ; on the 
 rupture of the Graafian follicle, 848 ; on 
 yellow matter of corpus luteum, 850 
 
 Le Gallois, experiments on the medulla ob- 
 longata, 306 
 
 Lehmann, on the acid of the gastric juice, 
 558 ; on crystallization of blood, 729 ; on 
 increase of urea in urine from a nitrogen- 
 ized diet, 800 ; on hippuric acid in the 
 urine of diabetes, 801 
 
 Leidy, on the arrangement of the liver-cells, 
 780 
 
 Letheby, Dr., his case of ovum, detected in 
 the Fallopian tube, 848 ; on the composi- 
 tion of the menstrual fluid, 848 
 
 Lens, 418 ; analysis of, 420 
 
 Lenticular, process of incus, 448 ; ganglion, 
 423, 500 
 
 Leuchs, his experiments on saliva, 541 
 
 Leucocythemia, 648 
 
 Leuret on the weight of the cerebellum, 320 ; 
 on the cerebral convolutions, 264 
 
 Lassaigne on the gastric juice, 569 
 
 Leeuwenhoek, on capillary vessels, 662 ; on 
 the fibres of the crystalline lens, 419 ; on 
 teeth, 627 
 
 Ley, Dr., on laryngismus stridulus, 493 
 
 Leydig, on ciliary motion in the uterine 
 glands of the sow, 861 
 
 L'Heritier, on the effect of temperament upon 
 the character of the milk, 902 
 
 Lieberkiihn; follicles or glands of, 573, 765 
 
 Liebig, Professor, on absorption by animal 
 membrane, 623 ; on the acid of the gastric 
 juice, 559 ; on elements of nutrition, 616 ; 
 on the uses of the bile, 602 ; on the quan- 
 
916 
 
 INDEX. 
 
 tity of oarbouio acid removod from the 
 body, 730 ; on the state of the iron in the 
 blood, 645 J on the reaction of the urine, 
 798 ; on the red blood-corpusole, 640 
 Life, 27, 35 ; dormant, 28 ; theories of, 36, 41 
 Ligaments, their varieties, 80 ; ciliary, 412 ; 
 of bladder, true and false, 804; thyro- 
 arytenoid, 747 ; thyro-hyoid, 748 ; of the 
 uterus, 845 
 Light, composition of, 427 
 Lime salts, in gastric juice, 568 ; in urine, 
 
 799 
 Limnseus stagnalis, fluke in the liver of, 823 ; 
 Lips, 524 ; cuticle of, 356 j as organs of pre- 
 hension, 523 ; ofruminants and rhinoceros, 
 sense of touch in, 373 
 Liquor, chyli, 587 ; amnii, 892 ; sanguinis, 
 629 J still layer of liquor sanguinis, 693 
 
 Lithate of soda, in urine, 799 
 
 Lithio or uric acid, 800 ; in urine, 799 
 
 Littre, glands of, 834 
 
 Liver, 767 ; analysis of, 768 ; cells, 779, 780 ; 
 development of, 884 ; of chick during in- 
 cubation, 606 ; fat in, 604 ; of frog, change 
 of colour in, 607 j function of the, 596 ; 
 subservient to respiration, 602 ; sugar in, 
 604 ; supply of blood, 596 j as a source of 
 the blood-corpuscles, 607 
 
 Lobe of ear, 445 
 
 Lobular passages in lungs, 711 ; diameter of, 
 712 
 
 Lobules, of liver, 771 ; of lung, 709 j on 
 surface of the kidney, 787 
 
 Locomotion, 78, 301 ; passive and active 
 organs of, 78 
 
 Locus niger, connection with third pair, 474 ; 
 motor influence of, 309 
 
 Locus perforatus, chiasma of optic nerves 
 connected with, 421 
 
 Longet, M., experiments on anterior columns 
 of the cord, 284; on optic thalami, 311; 
 on encephalon, 309, 310 ; on motor nerves, 
 273 
 
 Lower on the fibres of the heart, 670 
 
 Ludwig and Volkmann, on the circulation 
 in arteries, 689 
 
 Luminosity of animals, 224 
 
 Lungs, 707 ; resilience of, 720 ; develop- 
 ment of, 883 
 
 Lunula of nail, 363 
 
 Lymph, 612 ; composition of, 622 ; corpus- 
 cles, 619, 620 ; Mr. Wharton Jones on, 
 620 ; and blood, distinction between, 622 
 
 Lymphatics, function of, 627 ; of gall-bladder, 
 777 ; of liver, 779 ; of lower extremities, 
 613 ; in the tail of larvae of batrachia, 
 617 J origin of, 616 j of spleen, 812 ; and 
 capillaries of skin, 372 
 
 Lymphatic glands, number of, 613 ; struc- 
 ture of, 615 
 
 Lymphatic system, as one origin of blood- 
 corpuscles, 642 
 
 Lymphatic hearts, 618 
 
 Lymphatic network of skin, 367 
 
 Lyra, 259 
 
 Madbbr colours bone, 123 
 
 Magnesia, salts of, in urine, 799 
 
 Magnus, on the quantity of oxygen and 
 
 corbonic acid in blood, 728 ; on solubility 
 
 of carbonic acid in serum, 729 
 Maiasiat, on ordinary respiration, 718 
 
 Majendie on absorption, 626 ; on the cere- 
 bellum, 318 ; on the superior and inferior 
 laryngeal nerves, 490 ; on cerebro-spinal 
 fluid, 268 ; on circulation in the veins, 695 ; 
 on cerebellum, 318 ; on the effects of feed- 
 ing dogs on sugar, 518 ; on taste, 386, 390 ; 
 on vomiting, 665 ; and Mayo on falsetto 
 notes, 754 
 Male, organs of generation of, 829 ; lacteal 
 
 glands of, 900 
 Malleus, 448 
 
 Malpighi, on capillary vessels, 662 
 Malpighian bodies of kidney, 789 j corpus- 
 cles of spleen, 811, 886 '■ 
 Mammalia, air-cells of, 716 ; blood-corpuscles 
 of, 635 ; circulation of, 707 ; intestinal 
 canal of, 569 ; generative organs of, 828 ; 
 organ of hearing of, 444 ; ovum of, changes 
 in, 866 
 Man, an omnivorous animal, 514 
 Mandl, on the vitality of hair, 366 
 Manis, teeth of, 626 
 Manubrium of malleus, 448 
 Marcet, Dr., on the composition of fseoes, 759 
 Margarin, 59, 90 
 Mariauini, Dr., contractions produced in 
 
 frog by galvanism, 337 
 Mariotte, on the absence of visual sensation 
 over the point of entrance of the optic 
 nerve, 435 
 Marmot during hibernation, 740 
 Marshall, Mr. J., on the development of the 
 
 anterior venous trunks, 882 
 Marsupialia, 828 ; intestinal canal of, S70 ; 
 connection between foetus and mother, 888 
 Mascagni, on the follicles of the lacteal 
 
 glands, 899 
 Mastication, 541; motor nerve of, 484; 
 
 movements of, 538 
 Mastoid cells, 448 
 Maternal cotyledons, 888 
 Matrix of enamel, 634; of nail, 363 ; of kid- 
 ney, 788 
 Matteucci, electro-physiological experiments, 
 273, 331; on the gills of the ray, 707 ; and 
 Cima, on absorption through membranes, 
 624 ; researches in animal electricity, 223, 
 327, 331, et seq. 
 Mayo, on falsetto notes, 764; on fifth nerve, 
 
 483 ; and Valentin on third nerve, 476 
 Meat, digestion of, 655, 560 
 Meatus auditorius, 446 ; nrinarius, 846 ; of 
 
 the nose, 391 
 Mechanism, of valves, 669; of the skeleton, 
 
 136 
 Meckel's ganglion, nasal branches of, 399 
 Mediastinum testis, 830 
 Medulla of hair, 365 
 
 Medulla oblongata, descriptive anatomy of, 
 239 ; course of fibres in, 244 ; disease of 
 one-half of, 304; function of, 304; in- 
 fluence of in vomiting, 566 ; irritation of, 
 304 ; of&oe of nerves arising from, 304 
 Medullary portion of kidney, 789 ; of supra- 
 renal capsules, 814 
 Medusa buds, formation of, from polyps, 
 
 822 
 Medusaa, circulation in, 706 ; digestive or- 
 gans of, 514 
 Meibomian glands, 425 
 Meissner on the impregnation of the ovum, 
 853 
 
INDEX. 
 
 917 
 
 Melsens and Dumas, on the acidity of gastric 
 juice, 557 
 
 Membrana decidua, 860 ; granulosa, 840 ; 
 intermedia of Keieliert, 864, 867 j pupil- 
 laris and capsulo-pupillaris, 879 ; tympani, 
 446 J action of, 464; secundaria, 451 
 
 Membrane, simple and compound, 61 ; of 
 the aqueous humour, 420 
 
 Membranous, labyrinth, 449, 458 ; poi'tion 
 of urethra, 834 ; zone of cochlea, 454 
 
 Memory, 325 
 
 Men, analysis of the blood of, 644 
 
 Menstrual fluid, 847 
 
 Mercury, bichloride, its action on albumen, 
 53 ; on gastric juice, 557 
 
 Mesencephalic vertebrae, 876 
 
 Mesentery, 668 
 
 Mesenteric glands, 612 
 
 Mesmerism, 328 
 
 Mesocephale, descriptive anatomy of, 248 ; 
 functions of, 303 ; centre of emotion, 307 
 
 MesocsBCum, 568 
 
 Mesocolon, 668 
 
 Metamorphosis, 821 
 
 Metagenesis, 822 ; in insects, 823 
 
 Meyer on the contraction of the gall-bladder, 
 765 
 
 Micropyle, 853 
 
 Microscope, as an aid to research in anatomy, 
 50 
 
 Middle coat of arteries, 650 
 
 Milk, 901 ; cow's, 902 ; goat's, 902 ; acted 
 on by gastric juice, 560 ; alimentary ma- 
 terials in, 515 
 
 Milk teeth, 537 
 
 Miller, Dr., his analysis of urine, 799 
 
 Mind, 45, 238 ; its influence on the organic 
 processes, 317; associated with the cerebral 
 convolutions, 322 ; its influence in sensa- 
 tion, 351 
 
 Mitral orifice and valve, 664 . > 
 
 Mitscherlich, on the quantity of saliva, 540 
 
 Model prison, quantity of air passing through 
 each cell of, 728 
 
 Modiolus, or columella, 451 
 
 Molar teeth, 527 
 
 Molecular, base in chyle, 587, 619 ; motion, 
 organic, 71 
 
 Moleachott, on exhalation of aqueous vapour, 
 724 
 
 Mollusca, circulating organs of, 707; diges- 
 tive organs of, 614 ; heart of, 663 ; liver 
 of, 770 ; organ of hearing, 442 ; reproduc- 
 tion of, 825 
 
 Monotremata, 828 ; intestinal canal of, 670 ; 
 nutrition of embryo in, 888 
 
 Montgomery, Dr., on corpus luteum, 850 
 
 Morganti and Bernard, on the spinal acces- 
 sory, 496 
 
 Mother cell, containing spermatozoa, 835 
 
 Motion, centres of, 308 
 
 visual perception of, 422 
 
 Motores oculi, 473 
 
 Movements, association of, 182 ; symmetrical 
 and harmonious movements, 183 ; co-ordi- 
 nate movements, 183, 319; mode of excita- 
 tion, as by volition and emotion, 186, 293, 
 307; by reflected stimulus, 186, 307; in- 
 stinctive movements, 186 ; mechanical or 
 habitual movements, 186 ; in the interior 
 of the body, 70 ; of the intestine, 683 ; 
 
 69 
 
 of respiration, 716 ; quantity of carbonic 
 acid exhaled in, 726 ; of stomach, 550 
 
 Mucous membrane, descriptive anatomy of, 
 522 ; of bladder, 805 ; of caecum, 583 ; of 
 duodenum, 582 ; of large intestine, 583 ; 
 of intestinal canal, 573 ; of nasal cavity, 
 392 ; of stomach, 561 ; changes in, 546 ; 
 changes in during intestinal digestion, 685 ; 
 of urethra, 834 ; of uterus, 844 ; at men- 
 strual periods, 847 
 
 Mucous or vegetative layer of germinal mem- 
 brane, 859 
 
 Mucus, of bile, 599; of stomach, 651, 659; 
 of stomach cells, 647 
 
 Mulberry mass, 857 
 
 Mulder, his analysis of heematine, 645 ; on 
 the red blood-corpuscles, 635 
 
 MUUer, on the actions of the oesophagus, 545 ; 
 on the arteries of the penis, 833 ; on hectoco- 
 tylus, 826 ; on the impregnation of the ovum , 
 864 ; on the development of the liver, 885 ; 
 on the ofiice of the labyrinth, 470 ; on the 
 Malpighian corpuscles of the spleen, 811; 
 on the roots of the nerves, 274; on the 
 oscillations of the membrana tympani^ 468 ; 
 on vocal sounds, 761 ; on the suction power 
 of the auricle, 702; on Wolfiian bodies, 
 886 ; and Dickhoff on section of the vagi, 
 493; Gurlt and Kornfeld, on section of 
 the lingual nerve, 387 ; and Lehfeldt on 
 falsetto notes, 764; and Dr. J. Keid on 
 functions of the spinal accessory, 496 ; and 
 Volkmann on correct vision with an in- 
 verted image, 438 
 
 Multiplication, 819 
 
 Muscles, how formed, 157 ; shapes and ar- 
 rangement of fibres, 157-8 ; origin and in- 
 sertion, 158 ; bloodvessels of, 159 ; nerves 
 of, 160 ; antagonist muscles, 162 ; ar- 
 rangement of muscles on the skeleton, 162 ; 
 arytenoid, 750 ; buccinator supplied by 
 fifth nerve, 479 ; eervicalis ascendens, 423 ; 
 ciliary, 412 ; cochlearis, 455 ; compressor 
 naris, 392 ; compressor urethroe, 834 ; cor- 
 rugator supercilii, nerve to, 478 ; crico- 
 arytenoidei postici and laterales, and 
 crico-thyroidei, 749 ; depressor aire nasi,. 
 392 ; detrusor urinae, 806, 834 ; digastric,, 
 539 ; external pterygoid, 539 ; internal of 
 malleus, 449 ; internal pterygoid, 539 ; 
 of internal ear, 468 ; intrinsic and extrin- 
 sic of larynx, 749 ; laxator tympani, 449 ; 
 laryngeal, action of, 749 ; levator ani^ 
 levatores costarum, 720 ; levator palpebrse, 
 obliqui and recti oculi, 424; omo-hyoid, 
 sterno-hyoid, stylo-hyoid, and stylo- 
 pharyngeal, 749; orbicularis palpebra- 
 rum, 425 ; pectoral, 720 ; serratus magnus, 
 serrati postici, sterno-mastoidei, and tra- 
 pezii, 720 ; nerves of, 495 ; sphincter 
 vesicae, 805 ; superior, anterior, and pos- 
 terior auris, 445 ; respiratory, 730 ; power 
 of, 720 ; action of, 718 ; stapedius, 447, 
 449 ; thyro-arytenoidei, 437 ; temporal, 
 masseteric, 539 ; trachealis, 708, 721 ; un- 
 striped of absorbents, 614 
 
 Muscular coat of arteries, 652 ; of small in- 
 testine, 672; of colon, 672 
 
 Muscular fatigue, 364 
 
 Muscular, movement, varieties of, 179 ; ac- 
 
918 
 
 INDEX. 
 
 tion of sphincters, 180 ; peristaltic, 180 ; 
 and rhythmical contractions, 182 
 
 Muscular pile, 332 
 
 Muscular sense, 373 
 
 Muscular sound, 173 
 
 Muscular tissue of two kinds, 146 j Striped 
 FihreSf 146 ; their internal structure, 147 ; 
 sarcous elements, 147 j sarcolemma, 150 ; 
 union of tendon to muscle, 151 ; develop- 
 ment, 152; corpuscles or cell-nuclei, 153; 
 growth, 153. Unstriped Fibres, 153 ; 
 distribution of the two varieties of fibre in 
 the body, 155; and in the animal series, 
 156 ; contractility, 68, 163, 176 j stimuli, 
 165 
 
 Muscular tissue ; minute changes during 
 contraction, 167 ; during passive contrac- 
 tion, 170 ; during active contraction, 170 
 exhibited in fatal tetanus, 173 j develop- 
 ment of heat during contraction, 174 
 duration and extent of contraction, 175 
 zigzags explained, 176 ; force at different 
 degrees of contraction, 176 
 
 Muscular contraction ; influence of nervous 
 system upon, 303; development of elec- 
 tricity in, 337 J electrical current, 332 
 
 Muscular fibres, of arteries, 652, 682 ; of 
 heart, 669 ; of oesophagus, 544 j of stomach, 
 546 ; of uterus, 843 
 
 Muscular zone of spiral lamina of cochlea, 
 456 
 
 Muscularity of ducts of glands, 765 
 
 Musculi, papillares, 665 j pectinati, 665 
 
 Musical sound, 462 
 
 Myopia, 430 
 
 Myriapoda, circulation in, 707 
 
 Myxine, chorda dorsalis of, 868 
 
 Naegele, on the duration of pregnancy, 849 
 
 Nails, 363 
 
 Na'is, reproduction of, 820 
 
 Naked capillaries of lung, 713 ; of Malpig- 
 hian tuft, 791 
 
 Nasal, cavity, development of, 877 ; duct, 
 427 J fossffi, 391 
 
 Nasse, Dr., his case of paralysis, 284; on 
 chyle, 622; on the cause of buffing and 
 cupping, 632 
 
 Nasmyth, on the eementum, 536 
 
 Nausea, nature of, 494 
 
 Neck of tooth, 526 
 
 Negro, cuticle of, 363 ; hair of, 367 
 
 Nerves, definition, 191; tubular fibres, 193; 
 gelatinous fibres, 196. Cerebrospinal 
 ^lerves, 200 ; neurilemma, 200 ; bloodves- 
 sels, 200 ; origin, 200 ; branching, 201 ; 
 anastomosis, 201 ; plexuses, 203 ; termina- 
 tion, 204. Ganglionic nerves, tbeir struc- 
 ture, arrangement, and connections, 205 ; 
 regeneration of nerves, 211 ; endowments 
 of, 212. Spiiial 9ierves, 269 ; their func- 
 tions, 274 ; how to determine the function 
 of a nerve, 272 ; peripheral disposijfion of 
 nerves necessary for reflex actions, 298 ; 
 of arteries, 654 ; compound encephalic, 
 481; encephalic, 271, 473; influence of, 
 on voice, 765 ; of heart, 671 ; of larynx, 
 750; of llvor, 778; spinal, 269; of nose, 
 396 ; of spleen, 813 ; of stomach, 546; of 
 taste, 380 ; termination of, in skin, 359 j 
 of uterus, 844; of villi, 578 
 
 Nerves, auditory, portio mollis, 461 ; portio 
 dura, 462 ; chorda tympani, 447; cochlear, 
 457, 461 ; posterior auricular, stylo-hyoid, 
 submastoid, 478 ; eighth pair, 485 ; excitor 
 and motor, 273 ; facial, function of, 478 ; 
 fourth pair, 476 ; fifth pair, 396 ; motor 
 portion of, 481 ; distribution of, 482 ; 
 function of, 483 ; nasal branch of, 423 ; 
 ciliary, 423 ; function of, how determined, 
 272 ; glosso-pharyngeal, 480, 486 ; experi- 
 ments on, 756; branches to ear, 462; 
 ninth, 396; function of, 480; olfactory, 
 396; ophthalmic, 396; of Jaeobaon, 462; 
 inferior cardiac, 504 ; laryngeal, effects of 
 pressure upon, 756 ; nasal, connection with 
 ophthalmic ganglion, 500 ; optic, 403, 421 ; 
 petrosal, 501 ; of Pacinian corpuscles, 348; 
 palatine, 501 ; pneumogastric to heart, 
 671 ; portio dura, 425 ; sixth pair, 476 ; 
 splanchnic, 503 ; spinal accessory, course 
 of, 495; submaxillary, 396; suboccipital, 
 270 ; superficial petrosal, 477, 485 ; sym- 
 pathetic, to heart, 671 ; third pair, action 
 of, 430 ; function of, 474 ; to thyro-hyoid 
 and genio-hyoid muscles, 480 ; Vagus, 
 488 ; anterior pulmonary branches of, 
 489 ; cervical cardiac branches, 489 ; 
 oesophageal, posterior, pulmonary, pharyn- 
 geal, superior and inferior laryngeal, tra- 
 cheal, and thoracic branches, 489 ; vesti- 
 bular, 459 ; Vidian, 501 
 
 Nervi, molles, 502 ; pathetici, 476 
 
 Nervous actions, examples of, 188, 212 ; their 
 connection with mind, 189, 217, 2^9; 
 physical nervous actions, 190 ; laws of the 
 nervous force, 214-217; course of nervous 
 power in the centres, 262 ; theory of certain 
 nervous actions, 295 ; many need a double 
 stimulus, 297 ; in vomiting, 565 
 
 Nervous centres, definition, 191 ; arrange- 
 ment of tubular and vesicular elements in, 
 199; investing membranes, 207, 228; 
 structure of ganglia, 207 ; in the inverte- 
 brata, 209 ; spinal cord, 208 ; medulla 
 oblongata, 239; cerebellum, 245; meso- 
 cephale, 248; cerebrum, 250; inferences 
 upon function of, 330 
 
 Nervous and electricalforces, 213; compared, 
 218 
 
 Nervous matter, vital properties of, 68, '21 3 ; 
 two forms of, vesicular and fibrous, 191 ; 
 physical and chemical properties of, 192 ; 
 fibrous form of nervous matter, 193 ; tubu- 
 lar fibre, its structure, 193 ; gelatinous 
 fibre, its structure, 196 ; vesicular nervous 
 matter, simple and caudate vesicles, 197 ; 
 development of nervous matter, 209 ; re- 
 generation of, 211 
 
 Nervous power, course of, 262 
 
 Nervous system of animal life, 191 ; of or- 
 ganic life, 192; arrangement invertebrate 
 and invertebrate animals, 225 ; develop- 
 ment of, 878 ; effect of lesions upon animal 
 heat, 742 ; influence of, upon animal heat, 
 742 
 
 Neural arch of vertebra, 865, 876 
 
 Newport Mr., on the generation of carbonic- 
 acid by bees, 725 ; on the impregnation 
 of the ovum, 838, 853 ; on the nervous 
 system of myriapoda, 290 ; on the spinal 
 cord, 290 ; on the temperature of insects, 734 
 
INDEX, 
 
 919 
 
 Nipple, 899 ; erection of, 366, 900 
 Nitrogen, exhalation of, 728 ; importance of, 
 
 in food, 618 
 Nobili, on animal electricity, 334 
 Nodal lines, 464 
 Noise, definition of, 462 
 Nose, 391 
 Nostrils, 392 
 Nucleated nerve filaments of olfaotory region , 
 
 Nuclei of capillary Tessels, 661 
 Nurse in metagenesis, 824 
 Nutrition of heart, 671 
 Nutritive food, 516 
 Nutritive centre, 889 
 
 Obstbdctios, efi'ect of, upon the action of 
 the intestines, 584 
 
 Ocelli, 402 
 
 Ocular spectra, 434 
 
 Odours, appreciation of, 400 ; of fsBces, cause 
 of, 610 J occasioning syncope, 342 
 
 (Esopha'gus, 644 ; motions of, dependent on 
 laryngeal nerves, 491 
 
 O'Ferrall on the tunica vaginalis oculi, 424 
 
 Oil, its absorption, 625 ; globules of milk, 
 901 
 
 Oily alimentary materials, 515 
 
 Oily matter, digestion of, 561 
 
 Olfactory, nerves, 396 ; processes, or lobe, 
 397 ; filaments, 397 ; region, 394 
 
 Olivary columns, connection ■with portio dura, 
 477 
 
 Omentum, gastro-hepatic, 546 
 
 Omphalo -mesenteric duct, 870, 894 
 
 Ophidia, intestinal canal in, 569 
 
 Opium producing a polar state of the cord in 
 cold-blooded animals, 281 
 
 Ophthalmic ganglion, 423 
 
 Optic nerve, effects of irritation of, upon the 
 pupil, 475 I incapacity of vision at its en- 
 trance, 435 
 
 Optic thalami, 250 ; functions of, 310 ; at 
 centres of sensation, 310 ; relation to cor- 
 pora striata, 311 
 
 Optie tracts, 260, 421 ; connections of, 313 
 
 Optic vesicle, 879 ^ 
 
 Ora serrata, 409 
 
 Orbit, 402 
 
 Organic compounds, 29 
 
 chemistry, its importance to physi- 
 ology, 51 
 matter, its chemical constituents, 30 
 
 Organized, bodies, distinctive characters of, 
 32 ; origin of, 32 j and unorganized bodies, 
 27 
 
 lOrnithorynchus, 828 
 
 Os internum, of uterus, 842 
 
 Osseous zone, 452 ; labyrinth, 449 
 
 Ossicles, of ear, 448 ; action of, in propaga- 
 ting sound, 465 ; development of, 880 
 
 Ossification of permanent teeth, 537 
 
 Ostrich, generative organs of, 828 
 
 Otic ganglion, branches of, to ear, 462 
 
 Ototonia, 443, 459 
 
 Otolithes, 443, 459 ; action of, 471 
 
 Ova, maturation of, 848 
 
 Ovary, 839 ; of birds, 828 ; of insects, 826 ; 
 state of during the period of heat or rut, 
 849 
 
 Ovisacs, number of in ovary, 848 
 
 Ovula Nabothi, 844 
 
 Ovum, 841 ; changes in, succeeding impreg- 
 nation, 864 ; mammalian, yolk-sac of, 894 ; 
 human, development of, 871; passage of, 
 down Fallopian tube, 850 
 
 Owen, Professor, on the cerebral convolutions, 
 264; on dentine, 527; on parthenogenesis, 
 822 ; on the vertebrate theory, 877 
 
 Oxalate of lime, in urine, 799 
 
 Oxidation, nature of process in body, 741 
 
 Oxygen inhaled, amount of, 727 
 
 Pacchionian bodies, 233 
 
 Pachydermata, intestinal canal of, 570 ; 
 chorion in, 888 
 
 Pacinian corpuscles, 346 ; nerves of, 349 
 
 Paget, Professor, on the areas of arteries, 
 692 ; on the arteries and veins of the bat's 
 wing, 662 ; on the multiplication of blood- 
 corpuscles, 642 ; on the thymus, 818 
 
 Pain, 340 
 
 Pancreas, 766 ; in fishes, 669 ; effects of dis- 
 ease of, 595 ; its office in digestion, 592 ; 
 development of, 885 
 
 Pancreatic duct, point at which it opens, 592 
 
 Pancreatid fluid, its action on starch, 588 ; its 
 action on fat, 594 ; abnormal, 594 ; method 
 of obtaining it in quantity, 692 ; its cha- 
 racters, 593, 694 ; in birds, dogs, horses and 
 rabbits, 589, 594 
 
 Pancreatine, 693 
 
 Panizza, on absorption by veins, 619 ; on the 
 glosso-pharyngeal, 487 ; section of, 387 ; 
 on lymphatic glands, 616 
 
 Papillse, cireumvallatae, 381 ; compound con- 
 ical, 382 ; epithelium of, 380 ; fungiform, 
 380 ; capillary vessels of, 359 ; essential 
 tissue of, 360 ; of fore foot of male frog, 
 282 ; effects of shaving off, 298 ; of skin, 
 358 ; nerves of, 359 ; of taste compared 
 with villi, 385 ; of teeth, 533 ; of tongue, 
 hairlike, 383 ; their influence in taste, 389 ; 
 function of, 389 
 
 Papillary structure of tongue, 378 
 
 Paralysis, of portio dura, 478 ; of oesophagus 
 after section of vagus, 491 ; of fifth nerve, 
 483 ; sensation in, 377 ; of sphincter ani, 
 299 ; third nerve, effects of, 475 
 
 Paraplegia, 280, 302 
 
 Parenchyma of kidney, 788 
 
 Parietal sacculi, 775 
 
 Parotid glands, 639 
 
 Parovarium, 842, 886 
 
 Parrot, no lingual branch of fifth nerve in, 
 386 
 
 Parthenogenesis, 822 
 
 Par vagum, 488 
 
 Pause in heart's action, 674 
 
 Pecten, 409 
 
 Peduncle of pineal body, 262 
 
 Pelvis, 142 ; of kidney, 803 
 
 Penis, 832 ; arteries of, 833 ; erection of, de- 
 pendent upon cord, 302 
 
 Penniform fibres of circular coat of arteries, 
 651 
 
 Pepsine, 656 
 
 Pereira, Dr., on contractility of paralyzed 
 limbs, 303 
 
 Perfect vision, only in or near the axis of 
 vision, 436 
 
 Pericardium, 666 
 
920 
 
 INDEX. 
 
 Perilymph, 453 
 
 Peritoneum, 668 ; of stomach, 54fi 
 
 Per saltum flow of blood in arteries, 681 
 
 Pes anserinus, 478 
 
 Petit, canal of, 417 
 
 Peyer's patches, 681 ; office of, 582 ,• secre- 
 tion of odoriferous matter from, 610 j in 
 typhus and typhoid fever, 682 
 
 Pharynx, 541 
 
 Phosphate in urine, 802 
 
 Phosphoric acid in digestion, 555 
 
 Phrenology, 324 
 
 Phthisis, Peyer's patches in, 582 
 
 Physiology, 324; modes of investigation in, 
 47, 51 
 
 Physiological anatomy, meaning of the term, 
 47 ; its bearing on practical medicine, 47 
 
 Physical, movements of the cord, 280 ; nerv- 
 ous actions, 280, 327, 340 
 
 Phyton, 820 
 
 Pig, stomach of, for artificial digestive fluid, 
 557 
 
 Pig which remained 160 days without food, 
 739 
 
 Pia mater, 232 
 
 Pigment cells of choroid, 408 
 
 Pigment, in cuticle of negro, 363 ; in hair, 
 365 
 
 Pigmentnm nigrum, its uses, 434 
 
 Pillars of the fauces, 642 j of the fornix, 259 
 
 Pineal body, 252 
 
 Pinel on the functions of the corpora striata, 
 and optic thalami, 311 
 
 Pitch, of sounds, 463 ; of the note, how pro- 
 duced, 763 
 
 Pitot, on measuring the velocity of the stream 
 in rivers, 685 
 
 Pittard, on vesiculfB seminales, 831 
 
 Pituitary body, 261 ; regarded as a ganglion 
 by some, 498 
 
 Placenta, 888 
 
 Placental bruit, 890 
 
 Placental mammalia, 828 
 
 Planaria, multiplication of, 820 
 
 Plastic elements of nutrition, 516 
 
 Pleasure and pain, 45 
 
 Pleuronecta, optic lobes of, 312 
 
 Plexus, cavernous or carotid and tympanic, 
 502 ; inferior mesenteric, and hypogastric, 
 504 ; cardiac and pulmonary, 504 ; gangli- 
 formis, 488 ; solar, phrenic, suprarenal, 
 cseliao, hepatic, gastric and splenic, inferior 
 mesenteric, renal and spermatic, 505 
 
 Plexuses of nerves, 203 
 
 Plica polonioa, 367 
 
 Plicae palmatae of uterus, 844 
 
 Pockels, M., on changes in ovum after im- 
 pregnation, 854 ; and Coste, on the deve- 
 lopment of the human ovum, 871 
 
 Poiseuille, on the elasticity of arteries, 679 j 
 on the haemadynamometer, 686 ; on the 
 rate of the circulation, 705 
 
 Polar state of the cord in the male frog in 
 spring, 281 
 
 Polyps, circulation in, 706 ; multiplication, 
 826 ; renal organs of, 788 
 
 Pomura Adami, 747 
 
 Pons Tarini, 260, 261 i Varolii, function of, 
 329 
 
 Porosity of tissues, 66 
 
 Portal canals, 769, 772 
 
 Portal, circulation in liver and in kidneys, 
 676 ; vein, 773 
 
 Porterfleld, on the adaptation of the eye to 
 distances, 429 
 
 Portio dura, 477 ; communication with vagus, 
 480 ; to orbicularis palpebrarum, 425 
 
 Portio intermedia, 461, 477 
 
 Posterior commissure, 258 ; columns of cord, 
 283 ; functions of, 285 
 
 Potash acetate, its absorption, 611 
 
 Potash salts in urine, 799 
 
 Pourfour du Petit, on the office of the sym- 
 pathetic, 610 
 
 Prehension, 523 
 
 Presbyopia, 431 
 
 Prevost, on the movements of spermatozoa, 
 837 ; and Lebert, on the contraction of the 
 heart before the development of muscular 
 fibre, 882 
 
 Primitive streak, 866, 866 
 
 Processus cerebelli ad testem, 249 ; cochleari- 
 formis, 447 
 
 Prochaska on capillaries, 662 
 
 Promontory, 447 
 
 Proper current of the frog, 334 
 
 Prosenoephalio vertebra;, 876 
 
 Prostate gland, 831 
 
 Prostatic portion of the urethra, 833 
 
 Proteine, 56 
 
 Proteus, kidney of, 790 
 
 Prout, Dr. , on the acid of the gastric juice, 
 667 ; experiments on digestion, 664 ; on 
 the efieots of alcohol in respiration 726 ; 
 on the classification of food, 614 ; on tBe 
 gastric juice, 554 j on the absorption of the 
 yolk, 894 
 
 Proximate principles, 29, 30, 52 
 
 Puberty, 846 
 
 Pulmonary, artery, 707 ; sacs, 707 ; tissue, 
 709; veins, 666 
 
 Pulmonic circulation, 676 
 
 Pulp, cavity of tooth, 526 
 
 Pulse, 674, 681 ; quality of, 682 ; small, hard, 
 wiry, 684; of marmot during hibernation, 
 740 
 
 Puncta lachrymalia, 426 
 
 Pupil, 411 
 
 Purgatives, saline, action of, 624 
 
 Purkinje, and Pappenheim, on artificial di- 
 gestion, 562 ; and Valentin, on ciliated epi- 
 thelium of lateral ventricles, 262 
 
 Putrefaction, 39 
 
 Pyloric, follicles in fishes, 669 ; tubes, 549 ; 
 valve in fishes, 569 
 
 Pylorus, characters of the mucous membrane 
 of, 649 ; efieots of obstruction of, 563 
 
 Pyramids of tympanum, 447 ; of kidney, 
 788 
 
 Pyramidal bodies of medulla, disease of, 
 305 
 
 Qdadrtjmana, intestinal canal of, 571 
 
 Quality of sounds, 463 
 
 Quantity of bile secreted in twenty-four 
 
 hours, 784 ; of blood in the body, 630 ; of 
 
 urine, 798 
 
 Rabbit, development of spermatozoa in, 837 ; 
 pancreatic duct of, 692 
 
 Rainey, Mr., on epithelium of serous mem- 
 branes, 762; on the ligaments of the 
 
INDEX. 
 
 921 
 
 nteras, 845 : on the pulmonary eapillaries, 
 714 
 
 Kansom, Dr., on the mioropyle, 864 
 
 Eapp on the nerves of taste, 386 
 
 Rat, spermatozoa of, 836 
 
 Rate of the circulation, 704 
 
 Reaction of healthy urine, 798 
 
 Reaumur on gastric juice, 652 ; and Spal- 
 lanzani on the movements of the stomach, 
 651 
 
 Receptaculum, chyli, 612; seminis, 827 
 
 Eeorementitious suhstances, 769 
 
 Rectum, 668, 608 ; folds of, 575 
 
 Red blood-corpuscles, 634 ; chemical oompo ■ 
 sition of, 644 
 
 Rees, Dr. Gr. 0., analysis of bone, 104; analy- 
 sis of lymph and chyle, 622 ; on extractive 
 matters in the urine, 802 ; on urea in milk, 
 800 
 
 Reflex actions, imperfectly controlled by the 
 ■will, 206 ; in vomiting, 566 
 
 Reflection, law.« of, 427 ; from retina, 432 
 
 Refracting media of eye, 402 ; power of vit- 
 reous body, 417 ; of lens, 420 
 
 Regnault and Reiset on the relation of 
 oxygen and carbonic acid in respired air, 
 727 
 
 Regurgitant venous pulse, 700 
 
 Regurgitation through valves of heart pre- 
 vented, 669 
 
 Reichert, on the development of the allan- 
 tois, 895 ; of the liver, 885 ; of the lungs, 
 883 ; nervous system, 878 ; on the in- 
 vesting membrane and membrana inter- 
 media, 864 
 
 Reid, Dr. John, on asphyxia, 699 ; on the 
 arrangement of the fibres of the heart, 
 670 ; on the glosso-pharyngeal, 486 ; on 
 contractility, 303 ; experiments on laryn- 
 geal nerves, 491 ; on the influence of the 
 nerves in hunger, 621 ; on loss of nutrition 
 in paralyzed muscles, 303 ; on the sympa- 
 thetic, 510 
 
 Remak on the ganglia and nerves of the 
 heart, 605, 672; on the development of the 
 liver, 885 
 
 Rennet, 556 
 
 Reproduction, 33, 819 
 
 Reptiles, air-cells of, 716 ; blood corpuscles 
 of, 635 ; circulation in, 707 ; digestive 
 organs of, 513 ; heart of, 663 ; intestinal 
 canal in, 569; generative organs of, 828; 
 organ of hearing, 444; spermatozoa of, 
 836 
 
 Resilience of lungs, 720 
 
 Respiration, conditions of, 707 ; partly a 
 physical and partly a chemical process, 
 732 ; influence of, upon the circulation, 
 689 ; movements of, 716 ; objects of, 732 ; 
 theory of, 731 ; connection of function of 
 liver with, 602 ; effects of temperature 
 upon, 725 ; effects of posture upon, 722 ; 
 influence of vagus in, 492 
 
 Respirations, freijuency, and ratio to pulse, 
 722 
 
 Respiratory, compartment of the pharynx, 
 642 ; movements, excitation of, 721 ; by the 
 application of cold to the surface, 726 ; mu- 
 cous membrane, 523 
 
 Restiform bodies, functions of, 306 
 
 Rete Malpighi or mucosum, 362 
 
 59* 
 
 Rete mirabile, 668 
 
 Retina, 413 ; capillaries of, 660 ; connection 
 
 with sensorium, 436 
 Retinae, corresponding points in each, 441 
 Retinacula, 840 
 Retains on the arrangement of the liver 
 
 cells, 780 ; on the hemispheres of the brain, 
 
 878 ; his preparations of the lung of the 
 
 calf, 712 
 Rheumatism, diet in, 620 
 Rhinencephalic vertebra, 877 
 Ribes, ganglion of, 498 
 Ridges of cuticle, 357 
 
 Rigor mortis, 178 ; in arteries, 684 ; in mus- 
 cles, 179 
 Ritchie, Dr., on the rupture of ovisacs in 
 
 children, 848 
 Robinson, Dr., on absorption, 626 
 Rodentia, intestinal canal of, 570 ; chorion 
 
 of, 888 
 Rodier, his analysis of the blood, 644 
 Rods of enamel, 530 ; of Jacob's membrane, 
 
 415 
 Roe of fishes, 827 
 Rolando, his experiments on the cerebellum, 
 
 318 
 Roots of the fifth nerve, 481 ; of the spinal 
 
 nerves, 270 ; of the sympathetic, 499 
 Roots of the tooth, 526 
 Rossignol on pulmonary tissue, 712 
 Rotation of the yolk, 855 
 RugSB of uterus, 844 
 Rumbold and Fowler, experiments on the 
 
 third nerve, 475 
 Rumination, 564 
 Rnminantia, action of (esophagus in, 546 ; 
 
 digestive organs of, 613; intestinal canal 
 
 of, 670 ; chorion of, 888 
 Rumkorff's galvanometer, 331 
 Rut in animals, 849 
 Rhythm of the heart, 674 
 
 SAccnARiNE alimentary materials, 615 
 Sacculus, 443, 468 
 Sacculated bladder, 804 
 Saline constituents of bile, 600 
 Saline solutions, action of, upon the move- 
 ments of the spermatozoa, 837 
 Saliva, uses of, 641 
 
 Salter, Dr. Hyde, on the pancreas, 785 
 Salter, Mr. S. J. A., on the anatomy of veins, 
 
 659 
 Salts, fixed, in nrine, 802 
 Sanders, Dr., on the spleen, 812 
 Sarcolemma of muscular fibre, 160 
 Sarcous elements of muscular tissue, 147, 
 
 160 
 Saucerotte on the functions of the optic tha- 
 
 lami and corpora striata, 311 
 Sauria, intestinal canal of, 569 ; generative 
 
 organs, 828 
 Savart, on the formation of the voice, 751 ; 
 
 on hearing, 463, 468 ; on the time which 
 
 sensations of sound last, 473 
 Savi, on electrical organs, 350 
 Scala, tympani, vestibuli, 452 
 Scaly epithelium, 523 
 Scaphoid fossa, 445 
 Scarpa, on the nerves of the heart, 672 ; on 
 
 the spinal accessory nerve, 496 
 Soharling, on the influence of digestion upon 
 
INDEX. 
 
 the quantity of carbonic acid exhaled, 724 ; 
 on the quantity of carbonic acid removed 
 from the body, 730 
 
 Soberer, upon iron in the blood, 645 ; upon 
 the form of the blood-corpuscle in arterial 
 and venous blood, 729 
 
 Scbneiderian membrane, 392 
 
 Sehulz, on the acid fluid secreted in the ess- 
 cum, 608 
 
 Schwann, Professor, his experiments upon 
 the secretion of bile, 601 ; and Miiller on 
 pepsine, 556 
 
 Sclerotic, of eye, 403 ; in aquatic mammalia, 
 birds, and reptiles, 403 
 
 Sclerous tissue, 62 
 
 Scrotum, 829 
 
 Scurvy, causes of, 517 
 
 Sea-sickness, how produced, 494 
 
 Sebaceous follicles of nose, 392 
 
 Sebaceous glands, 370, 372; of labia, 846. 
 
 Secondary organic compounds, 30, 52, 60 
 
 Secreting organs, general view of, 761 
 
 Secretion, 757 ; of Brunner's glands, 580 ; 
 of pancreas, 692 ; of urine, 796 
 
 Section of hair, method of making, 365 
 
 Seguin and Lavoisier, on the influence of 
 temperature on the exhalation of carbonic 
 acid, 725 
 
 Sella Turcica, 264 
 
 Semicircular canals, 450 ; membranous, 458 j 
 action of, 472 ; development of, 880 
 
 Semilunar valves, 664 
 
 Seminal tubules, 830, 835 
 
 Sensation, 45; centres of, 305, 308, 310; 
 common and special, 69, 214, 352 ; me- 
 chanism of, 293, 301, 305 ; subjective, 
 objective, 352, 377 ; sympathetic, 340 ; of 
 temperature, 377 
 
 Sense, muscular, 373 
 
 Sensibility of palms of hands and feet, 374 
 
 Septal cartilage of nose, 392 
 
 Septum lucidum, 259 
 
 Serous membranes, 128 ; structure, 129 ; 
 physical and vital properties, 130 ; inflam- 
 mation, adhesion of, 130 
 
 Serous and mucous laminse of bird's egg, 864 
 
 Serous pericardium, 666 
 
 Serous or animal layer of the germinal mem- 
 brane, 859 
 
 Serres, on corpora quadrigemina, 312 
 
 Serum, 628 ; of blood, 633 
 
 Sexual instinct, is it seated in the cerebel- 
 lum? 317 
 
 Sexual organs, 824 
 
 Shaft of hair, 364 
 
 Shape and size, visual perception of, 438 
 
 Sharks and rays, mucous tubes of, 371 
 
 Sharpey, Dr., on ciliary movement, 76 ; on 
 the force of the heart, 678 ; on the forma- 
 tion of the decidua, 860 ; his investiga- 
 tions upon an early human embryo, 894 
 
 Sheaths of the arteries in the spleen, 810 
 _ Shortsightedness, 430 
 
 Sibson. Dr., on the action of the intercostal 
 muscles, 719 ; on the movement of the 
 riba in inspiration, 717 
 
 Sicbold, Van, on cystic entozoa, 823 
 
 Sighing, yawning, coughing, their depend- 
 ence on the medulla oblongata, 306 
 
 Sigmoid flexure of the colon, 567 
 
 Silica in urine, 799 
 
 Simon, Dr. Franz, on demodex, 371 ; on 
 ptyalin, 540 ; on the blood of the vena 
 porta, 645 ; analysis of milk, 902 
 
 Simon, Mr. J., on fibrine as a product of 
 decay, 647 ; on the use of the thymus, 817 ; 
 on the use of the thyroid, 816 
 
 Singing, 754 
 
 Sinus, rhomboidalis, 879 ; urino-genitalis, 
 895 ; venosus, 665 
 
 Sinuses of the nose, 391 
 
 Sixth nerves, 476 
 
 Skeleton, external and internal, 102 ; me- 
 chanism of, 136 
 
 Skin, absorption through, 611 ; contractility 
 of, 355 i functions of, 371 ; general ana- 
 tomy of, 354 ; tanned, 355 ; termination 
 of nerves in, 359 
 
 Skin of external ear, 445 
 
 Sleep, effects of upon the temperature of the 
 body, 736 
 
 Sleep and somnambulism, 327 
 
 Small intestine, 567 
 
 Smegma preputii, 835 
 
 Smell, 391 ; conditions of, 399 
 
 Smith, Dr. Tyler, on the cause of birth, 897 
 
 Smith and Harris, on the smallest portion of 
 the retina capable of independent sensa- 
 tion, 437 
 
 Snow, Dr., experiments of the deleterious 
 nature of respired air, 728 ; on the quan- 
 tity of carbonic acid expelled after the in- 
 halation of chloroform and ether, 725 
 
 Soda salts in urine, 799 
 
 Soemmering on the yellow spot, 415 » 
 
 Soft, palate, 542 ; commissure, 258 
 
 Solid and fluid constituents of animal bodies, 
 51 
 
 Solipeds, intestinal canal of, 570 
 
 Solitary glands, 580 
 
 Solution of meat, albumen, etc., in gastric 
 juice, 555, 560 
 
 Somnambulism, 328 
 
 Soprano voice, 754 
 
 Sound, nature of laws of transmission of, 
 462 ; length which a sensation lasts, 473 ; 
 velocity of, 462 
 
 Sounds of heart, 673 ; vocal, how modified, 
 439 
 
 Spallanzani, experiments on saliva, 541 ; on 
 digestion, 552 j on the movements of the 
 stomach, 551 
 
 Specific gravity of bile, 598 ; blood, 633 ; 
 milk, 628 ; urine, 798 
 
 Spectrum, solar, 427 
 
 Speech, 756 
 
 Spengler, on the pressure of the blood in 
 different arteries, 688 
 
 Spermatozoa, in seminal tubules, 835 ; move- 
 ments of, 837 ; their motions analogous to 
 the ciliary, 77 
 
 Sperm-cell, 821 
 
 Spheno-palatine foramen, 399 
 
 Spherical aberration, 427 ; prevented by iris, 
 431 ^ 
 
 Sphincter vesicae, 805 
 
 Sphincters, action of, 180, 299 
 
 Spinal accessory nerve, 495 
 
 Spinal column, 137; development of, 875 
 
 Spinal cord, 208 ; antero-Iateral columns of, 
 283 ; descriptive anatomy, 233 ; minute 
 anatomy, 235 ; course of fibres, 237; funo- 
 
INDEX. 
 
 923 
 
 tiong, 275, 282 ; its share in mental and 
 physical nervous actions, 275, 301 ; polar 
 state of, 281 ; mechanism of its actions, 
 287 J effect of injury below the phrenics, 
 304 ; lumbar region of, 286 ; functions of, 
 in vertebral animals, 278 ; hypothesis, to 
 explain the action of, 287 ; of Dr. Marshall 
 Hall, Whytt, Prochaska, 288; effects of 
 mental emotions on actions, 289 
 
 Spinal nerves, their double roots, 270 ; their 
 functions, 274 
 
 Spiral duct of sweat-gland, use of, 370 
 
 Spirometer, 723 
 
 Spleen, 806, 885; the seat of destruction of 
 blood-corpuscles, 643 ; uses of, 813 ; pulp, 
 808 
 
 Spongy portion of urethra, 834 
 
 Spore, or sporangium, 821 
 
 Squalus cornubicus, testicle of, 763 
 
 Squirrel, spermatozoa of, 836 
 
 Stammering, 756 
 
 Starch, digestion of, 560, 589 ; its conversion 
 into dextrine by pancreatic fluid, 589; 
 sugar, cellulose, etc., as calorifacient food, 
 740 
 
 Stannius, on pancreas of fishes, 592 
 
 Stapes, 448 
 
 Stark, Dr., effects of a diet without azotized 
 food, 518 
 
 Stearine, 59, 90 
 
 Steenstrup, on the alternation of generations, 
 822 
 
 Stentor, multiplication of, 826 
 
 Stereoscope, 441 
 
 Stevens on digestion, 552 
 
 Stilling, on the fibres of the optic thalami, 
 310 ; and Wallach, on the roots of the 
 nerves, 271 ; on the spinal cord, 236, 243 
 
 Stimuli, to muscle, 165 ; all act on the mus- 
 cular tissue itself, 166 ; to nerves, 165, 
 215 ; a double stimulus necessary to many 
 nervous actions, 297 
 
 Stomach, 545 ; vermicular contractions of, 
 caused by irritation of the vagi, 492 ; its 
 part in vomiting, 565 ; movements of, 550 
 
 Stone in the bladder, sympathetic sensations 
 produced by, 340 
 
 Straight portion of uriniferous tube, 792 
 
 Streoker on the composition of the bile, 600 
 
 Striped muscular fibre of the heart, 669 
 
 Strobila, multiplication of, 742 
 
 Strychnine, its action on the cord, 281 
 
 Subjective phenomena of hearing, 473 ; of 
 smell, 401 ; of taste, 390 
 
 Submaxillary glands, 539 
 
 Submucous tissue, 572 
 
 Succus gastricus, 554 
 
 Suction-power of auricles, 702 
 
 Sugar, in blood, 633; formed in the liver, 
 605 ; formed from starch, 589 ; effects of 
 feeding dogs on, 518 
 
 Sulphates in urine, 802 
 
 Sulphocyanides in saliva, 540 
 
 Sulphuretted hydrogen in intestines, 610 
 
 Superior cava, 665 
 
 Superior longitudinal commissure, 258 
 
 Supra-renal capsules, 814; development of, 
 887 
 
 Supra-orbitar convolution, 255 
 
 SweaJ-glands, 368 
 
 Sylvius, aqueduct of, 261 
 
 Sympathetic, 498 ; cervical ganglia of, 502; 
 lumbar and sacral portions of, 504 ; cervi- 
 cal portion of, 501 ; endowment of fibres 
 of, 508 ; effect of section of, on animal 
 heat, 743 ; effects of division of trunk of, 
 510 ; function of, 506 ; sensations, 340 
 
 Sympathy, sympathetic sensations and mo- 
 tions, 339 ; between digestive and respi- 
 ratory organs, 493 ; contiguous, 345 
 
 Sympathies, affecting the mind, 341 
 
 Synarthrosis, 132 
 
 Synovia, 128 
 
 Synovial sheath, 127, 129 
 
 Syphilitic poison, its absorption, 619 
 
 Systole, 672 ; and diastole, their influence on 
 the circulation, 689 
 
 Tactile papillse, 356 
 
 Tape-worm, multiplication of, 820 
 
 Tapetum lucidum, 409 ; reflection from, 433 
 
 Tarsal cartilage, 424 
 
 Tartar emetic, 566 
 
 Taste, conditions of, 388; heightened by 
 motion, 388; influence of movements of 
 tongue upon, 389 ; nerves of, 386 ; precise 
 seat of, 385 ; persistence of after section of 
 glosso-pharyngeal, 387 ; in soft palate, 386 ; 
 influence of smell upon, 388 ; varieties of, 
 389 
 
 Taste and touch, do they coexist in any of 
 the papillas? 389 
 
 Tastes, bitter, 388 
 
 Taurin, 598 
 
 Tea, effects of, upon the exhalation of car- 
 bonic acid, 725 
 
 Teeth, 525; development of, 632; number of, 
 536 
 
 Temperature, of blood, 629 ; of human body, 
 736 ; its effects upon respiration, 726 ; ele- 
 vation of, after section of the sympathetic, 
 743 
 
 Temporary teeth, 536 
 
 Tench, striped muscular fibres in intestine 
 of, 510 
 
 Tendo oculi, 424 
 
 Tendons, 81 
 
 Tenor voice, 754 
 
 Termination of nerves, 161, 204 
 
 Testicles, 829 ; of insects, 827 
 
 Tetanus, 280 
 
 Thackrah, his experiments on the coagulation 
 of the blood, 631 
 
 Theile, on vasa aberrantia, 776 
 
 Theory and hypothesis, 26 
 
 Third nerve, function of, 474 
 
 Third ventricle of brain, 252 
 
 Thirst, 522 
 
 Thomson, Dr. K., D., on volume of carbonic 
 acid in expired air, 724 ; on the acid of the 
 gastric juice, 658 ; on calorifacient food, 
 616 ; on milky serum, 633 
 
 Thomson, Dr. Allen, on the development of 
 the human ovum, 871 
 
 Thoracic duct, 612 ; contractility of, 615 
 
 Thorax, 140; enlargement of, in respiration, 
 716 
 
 Thymus, 816 
 
 Thyro-hyoid ligaments, 748 
 
 Thyroid, 815; cartilage, 746: development 
 of, 883 
 
 Tic douloureux, 484 
 
924 
 
 INDEX. 
 
 Tiedemann and &melin, on ohyle, 621 ; on 
 the digestion of starch, 660 ; experiments 
 on the uses of the bile, 603 
 Timbre of sound, 463 
 Tingling, tickling, sensations of, 377 
 Tinnitus aurium, 473 
 
 Tissues, composed of cells, 62 ; their classifi- 
 cation and properties, 61; proparties of, 
 65, 68 
 Taenia semiciroularis, 260 
 Tomes, Mr., his researches on bone. 111, et 
 seq. ; on the granular layer of dentine, 529 
 
 Tone, of arteries, 683 ; of muscular system, 
 influence of cord upon, 302 
 
 Ton^^ue, as an organ of mastication, 388; 
 motor nerve of, 480 ; movements of in 
 deglutition, 543; its use as a prehensile 
 organ, 624; its use in mastication, 625; 
 portion in which taste resides, 387 ; used 
 in suction, 524 
 
 Tonicity of muscle, 164; identical with con- 
 tractility, 166 ; not derived from the cord, 
 302 
 
 Tonsils, 543 ; nerves of, 486 
 'Tooth bone, 531 
 
 Torpedo, Matteucci's experiments upon, 338 
 
 Tortoise, intestinal canal of, 669 ; urine of, 
 801 
 
 Touch, 362 ; diffusion of sense of, in man, 
 374 ; in animals, 373 ; organ of, 373 ; ex- 
 isting in the tongue, 388 
 
 Toynbee, Mr., his researches on cartilage, 99 
 
 Trabeculse of penis, 833 
 
 Trabecular tissue of spleen, 807 
 
 Trachea, 708 ; development of, 883 
 
 Trachea;, 707 
 
 Tracheal glands, 708 
 
 Trachealis muscle, 708 ; use of, 721 
 
 Tragus of ear, 445 
 
 Training, diet in, 520 
 
 Transverse fissure of liver, 769 
 
 Tricuspid valve, 664 
 
 Trigone of bladder, 804 
 
 Triple phosphate in urine, 799 
 
 Triton, generative organs of, 828 
 
 Trunk of elephant, supplied by portio dura, 
 478 
 
 Tuber oinereum, 260 
 
 Tubes, of dentine, 528; of stomach, 548; of 
 cornea, 405 
 
 Tubular nerve fibres in syrup, 507 
 
 Tubuli, dentinal, 530 
 
 Tufts of chorion, 862 
 
 Tunica, albuginea and vaginalis testis, 829 ; 
 granulosa, 840; media of Bischoif, 874; 
 Ruysohiana, 408 ; vaginalis oculi, 424 
 
 Tnnioata, multiplication of, by budding, 
 825 ; heart of, 663 
 
 Tympanitis, 610 
 
 Tympanic, cavity, 446 ; plexus, 485 ; ring, 
 445 
 
 Tympanum, its contents, 465 ; use of, 468 ; 
 internal wall of, 446 
 
 Typhus and typhoid fever, Peyer'a patches 
 in, 682 
 
 Ultimate facts, 25 
 
 Umbilical, arteries, 896 ; cord, 897 ; vesicle, 
 
 893 ; vessels, 897 
 Unisexual generation, 824 
 Unstriped muscle of absorbents, 614 
 
 Urachus, 896 
 
 Urea, 800 ; in blood, 634 ; in milk, 903 
 
 Ureters, 804 ; muscularity of, 765 
 
 Urethra, female, 846 ; male, 833 ; muscularity 
 of the, 766 ; development of, 833 
 
 Uric or lithio acid, 800 ; in allantoic fluid, 
 897 
 
 Urinary bladder, 804 ; development of, 896 
 
 Urine, 797; analysis of healthy, 799; secre- 
 tion of, 796 ; diminution of constituents 
 from taking alcohol, 725 
 
 Uriniferous tubes, 789 ; continuity of, with 
 the capsule of the Malpighian body, 790 
 
 Uterus, 842 ; its action in parturition, 302 ; 
 masculinus, 836 
 
 Uteri in marsupialia, 828 
 
 Uterine sinuses, 890 
 
 Utriculus, 443, 458 
 
 Uvea, 411 
 
 Uvula vesicae, 833 
 
 Vagi, distribution of, 488 ; motor branches 
 of, 490 ; office of gastric branches of, 492 
 
 Vagina, 846 
 
 Vagus, conclusions with respect to function, 
 494 ; section of, by Dr. J. Keid, 491 ; its 
 importance in respiration, 492 
 
 Valentin, on the exhalation of aqueous 
 vapour, 724 ; on the cause of the impulse 
 of the heart, 673 ; on the cause of birth, 
 897 ; on circulation in the capillaries, 694; 
 on the rate of the circulation, 704 ; on the 
 force of the heart, 678 ; on the force of the 
 respiratory muscles, 721 ; experiments* on 
 spinal nerves, and their influence on sym- 
 pathetic, 511 ; on the quantity of blood, 
 630 ; and Brunner on the proportion of 
 oxygen and carbonic acid in respired air, 
 724, 727 ; and Mogk, on the force of the 
 cuiTent in the veins, 701 ; Schubert and 
 Panizza, experiments on nerves, 276 ; and 
 Wagner, on section of the glosso-pha.ryn- 
 geal, 387 ; and Wagner, on taste, 386 
 
 Valves, of absorbents, 614; of the heart, 
 604 ; structure of, 667 ; ileo-csfccal, 575 ; 
 mechanism, 669 ; of Thebesius, 666 ; of 
 the umbilical vesicle, 893 ; of veins, 669 ; 
 of Vieussens, 250 
 
 Valvulaj conniventes, 674 
 
 Van Deen,exporimentsupon animals poisoned 
 by strychnine, 299 
 
 Varicose veins, influence of gravity on, 704 
 
 Vas, deferens, 830 ; development of, 887 ; 
 rectum testis, 830 
 
 Vasa, aberrantia, 776 ; efTerentia, 830 ; lutea, 
 893 ; vasorura of arteries, 650 ; vortieosa, 
 408 
 
 Vascular area, 367 ; glands, 806 
 
 Vauquelin, on ashes of hair, 367 ; on colour 
 of hair, 367 
 
 Vegetable substances, digestion of, 560 
 
 Vein, portal, 773 
 
 Veins, 658 ; of choroid, 407 ; oirculation in, 
 700 ; ooats of, 658 ; valves, 659 ; oircula- 
 tion in, of bat's wing, 703 ; pulmonary, 
 666; of spleen, 812 
 
 Velocity of the circulation in arteries, 690 
 
 Velpeau, on the allantois, 897; on the corps 
 reticule, 892 
 
 Velum interpositum, 262 
 
 Venoe oavoe, 658 ; magnee Qaleni, 266 
 
INDEX. 
 
 925 
 
 Venesection, influence of, upon blood, 646 ; 
 over flbrine, 646 
 
 Venous blood, 629, 645 ; absorption by, 562 
 
 Venous circulation, favoured by muscular 
 movements, 702 ; influence of respiratory 
 movements, 701 ; ' influence of gravity 
 upon, 703 
 
 Venous pulse, 700 
 
 Ventilation, importance of, 728 
 
 Ventral laminee, 867 
 
 Ventricles of heart, 664; force of left, 686 
 
 Ventricle, fifth, 260 
 
 Ventricles of the brain, third, lateral, 248, 
 261 
 
 Venus chione, heart of, 663 
 
 Vermicular action of intestines, 583 
 
 Vermiform appendix, 571 
 
 Vernix caseosa, 875 
 
 Verschuir on irritability of arteries, 682 
 
 Vertebra, typical, 876 
 
 Vertebral, arches, 876 ; arteries, 264, 656 ; 
 plates, 865 
 
 Vertebrata, generation in, 827; pancreas in, 
 592 
 
 Vertigo, 325 ; from lesion of corpora quadri- 
 gemina, 313 
 
 Verumontanum, 834 
 
 Vessels, of the iris, 412 ; of the kidney, 793 ; 
 nose, 392 ; of the lungs, 712 ; of the retina, 
 414 ; umbilical, 897 
 
 VesiculsB seminales, 831 
 
 Vesicular gray layer of retina, 414 
 
 Vestibule, 449 ; the essential part of the 
 organ of hearing, 469 
 
 Vicarious secretion, 760 
 
 Vierordt, on the proportion of carbonic acirf 
 in expired air, 724, 727 
 
 Villi, 576; capillaries, lacteals, and nerves 
 of, 577 ; during intestinal digestion, 585 ; 
 of intestines compared to papilla, 385 
 
 Vinegar, formation of, 741 
 
 Virchow, on the spleen, 810 
 
 Vis nervosa, 217 
 
 Vis, a fronte, 696 ; a tergo, 678, 694 ; in- 
 fluence in venous circulation, 700 
 
 Visceral arches, development of, 877 
 
 Vision, development of organs of, 879 ; cor- 
 pora quadrigemina, the special ganglia of, 
 313; distinct, 428; organ of, 401; phe- 
 nomena of, 427 
 
 Visual, angle, 428 
 
 Vital capacity, 723 ; properties, 36, 68 ; of 
 tissues, 68 ; stimuli, 36 
 
 Vitelline, membrane, 841 ; duct, 894 
 
 Vitreous body, 416 
 
 Vocal cords, 747 
 
 Vogt, on the origination of blood corpuscles, 
 639 ; on the liquor amnii, 892 
 
 Voice, 744 
 
 Volition, 45 
 
 Volkmann, on the circulation in the capil- 
 laries, 694 ; on contraction of lymphatic 
 hearts, 618 ; on the force of the heart, 687 ; 
 on the hsemadromometer, 690 ; on the rate 
 of the circulation, 704 
 
 Voluntary motion, 275 j movements, centres 
 of, 304, 309 
 
 Vomiting, 563 ; caused by section of vagi, 
 493 ; effect of nervous changes upon, 566 ; 
 glottis protected in, 643 ; manner in which 
 produced, 566 ; produced by irritation of | 
 
 vagus, 494 ; ccsophagus in, 545 ; sympa- 
 thetic of diseased kidney, or passage of a 
 calculus along the ureter, 341 
 
 Vorticellaj, multiplication of, 823 ; reproduc- 
 tion of, 820 
 
 Vowel sounds, production of, 756 
 
 Wagner, on development of spermatozoa, 
 836 ; on white corpuscles, 641 ; on the 
 changes in the germinal vesicle, 855 ; and 
 Muller on the development of the human 
 ovum, 872 
 
 "Walknaer, on the division of the cord in in- 
 sects, 300 
 
 Wallace, Dr. Clay, on the action of the 
 ciliary muscle, 430 
 
 Ward, Mr., on the skeleton, 139, 142 
 
 Warm-blooded animals, 734 
 
 Water, as a constituent of animal bodies, 52 ; 
 removal of, from body, 760 
 
 Weber, on castor, 836 ; on the circulation in 
 the capillaries, 694; on appreciating the 
 weight of bodies, 376 ; on formation of 
 decidua, 860 ; on the generation of the 
 blood-corpuscles in the liver, 639 ; on ir- 
 ritation of arteries, 683 ; on the organ of 
 hearing in fishes, 443 ; on the striped 
 muscular fibres in the intestine of the 
 loach, 510 ; on vasa aberrantia, 776 ; on 
 the relation of the foetal vessels to those of 
 the mother, 889 
 
 Weber and Goodsir on the placenta, 889 
 
 Webcrian organ, 835, 887 
 
 Webster, Dr., his case of paralysis of motion, 
 283 
 
 Wedenaeyer and Gruenther, on the suction- 
 power of the auricles, 702 
 
 Weight, power of appreciating, 376 ; of the 
 human heart, 664; of spleen, 806 
 
 Whale, the skin of, 366 ; teeth of, 526 
 
 Wheatstone, Professor, on semicircular ca- 
 nals, 472 ; on the stereoscope, 441 
 
 White blood-corpuscles, 637 
 
 White chyle, influence of pancreatic fluid 
 on the formation of, 593 
 
 White of the eye, 403 
 
 White fibrous tissue, 80 ; in the cutis, 354 ; 
 common description of, incorrect, 80 ; its 
 vessels and nerves, 80 ; chemical composi- 
 tion, 80 ; reparation of, 82 
 
 Whytt, cases of numbness of arm, etc., asso- 
 ciated with suppuration of the liver, 340 ; 
 Prochaska, Blane, and Flourens, on the 
 excitation of involuntary movements, 280 
 
 Will, influence of, upon the spinal cord, 293 
 
 Willis, his arrangement of the encephalic 
 nerves, 271; circle of, 265, 656; on the 
 aperture of the glottis, 751 ; on the pro- 
 duction of vocal sounds, 762 ; on the func- 
 tions of the cerebral convolutions, 323 
 
 Wind, action of cold increased by, 738 
 
 Wbhler and Frerichs on the formation of 
 urea from uric acid, 801 
 
 WoUaan bodies, 886 
 
 WoUaston, Dr., on the effects of tension of 
 the membrana tympani, 469 ; and Mayo, 
 on the course of the nerves in optic tracts, 
 440 
 
 Women, analysis of blood of, 644 
 
 Wright, Dr., on saliva, 540 
 
 Wrisberg, poitio intermedia of, 461 
 
926 
 
 INDEX. 
 
 Teilo-w teveb, temperature in, 739 
 
 Yellow fibrous tissue, structure and proper- 
 ties of, 82 I in the cutis, 354 ,■ at the bor- 
 der of the anterior elastic lamina, 411 
 
 Yolk granules, 841 ; sac of mammalian OTum, 
 894 
 
 Young, Dr., lectures on the functions of the 
 heart and arteries, 688 
 
 ZiMMERMANN, on fibrine as a. product of 
 
 decay of tissues, 647 
 Zinn, zone of, 416 
 Zona pellucida, 841 
 Zonula oiliaris, or, of Zinn, 416 
 Zwioky, Dr., on yellow matter of corpus 
 
 luteum, 850 
 
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 In one very handsome octavo Tolume, leather, pp. 566. %Z 00. 
 
 EI&HTH EDITION. 
 THOKOUGHLY REVISED AND EXTENSIVELY MODIFIED AND ENLARGED. 
 
 WITH FIVE HUNDRED AND THIRTY-TWO ILLUSTRATIONS. 
 
 BY ROBLEY DUNGLISON, M. D., 
 
 Professor of Inetitutes of Medicine in the Jefferson Medical College, Philadelphia. 
 In two large and handsomely printed octavo volumes, leather, of about 1600 pages. (Now Beady, 1856.) $7 00. 
 
 lSJ:^]SrTJ.^L OF P^HYSIOLOaY. 
 
 BY WILLIAM SENHOUSE KIRKES, M. D., 
 
 Demonstrator of Morbid Anatomy in St. Bartholomew's Hospital, London. 
 Third American, from the Third and Revised Ijondon Edition. 
 
 WITH NEARLY TWO HUNDRED ILLUSTRATIONS. 
 
 In one large and handsome royal 12mo. volume, of nearly 600 pages, leather, $2 00. 
 
NOW COMPLETE, 
 
 THE 
 
 PHYSIOLOGICAL ANATOMY AND PHYSIOLOGY OF MAN. 
 
 BY EGBERT BEiSTTLEY TODD, M. D., F. R. S., 
 
 Professor of Physiology in King's College, Loudon, &c. 
 
 WILLIAM BOWMAN, F. R. R, 
 
 Demonstrator of Anatomy in King's Collrge, London. 
 
 13Iil^ tina l^nnbuit aub ninetg-jigl^t kadiful lllnstatioits oa WHoolt). 
 
 Complete in one very handsome octavo volume, of over 900 large pages, leather, price $4 50. 
 
 The very great delay which has occurred in the completion of this work has arisen from tlie 
 desire of the authors to verify by their own examination 1 he various questions and statements pre- 
 sented, thus rendering the work one of peculiar value and authority. By the wideness of its scope 
 and the accuracy of its facts it thus occupies a position of its own, and becomes necessary to all 
 physiological students. 
 
 Grentlemen who have received portions of this work, as published in the 
 " Medical News and Library," can now complete their copies, if immediate 
 application be made. It will be furnished as follows, free by mail, in paper covers, 
 with cloth backs. 
 
 Parts I., II., III. (pp. 25 to 552), $2 50. 
 
 Part IV. (pp. 553 to end, with Title, Preface, Contents, &c.), $2 00. 
 
 Also, 
 Part IV., Sect. II. (pp. 725 to end, with Title, Preface, Contents, &c.), $1 25. 
 
 In the present part (third) some of the most diffi- 
 cult subjects in anatomy and physiology are handled 
 in the most masterly manner. Its authors have 
 slated, that this work was intended " for the use of 
 the student and practitioner in medicine and surge- 
 ry," and "we can recommend it to both, confident 
 tliat it is the most perftct- work of its kind. We 
 cannot conclude without strongly recommending the 
 present work to all classes of our readeiB, recogniz- 
 ing talent and depth of researcli in every piige, and 
 believing, as we do, thnt the diffusion of such know- 
 ledge will certainly tend to elevate the science of 
 jut'uicine and surgery. — Dublin Quarterly Journal 
 of Medical Sciences. 
 
 It is highly creditable to the authors of this work, 
 thnt, to the exclusion of theory and speculation, 
 known anatomical facts, many of which are the 
 fruits of their own careful and laborious investiga- 
 tions in microscopic anatomy, are made to serve as 
 the foundations for most ot their physiological de- 
 ductions. The course pursued throughout the work 
 is strictly in jiccordance with thisview. Afull de- 
 scription of the minute structure, cunsritution, and 
 development of an organ or tissue, precedes, always, 
 and is made the basis of conclusions witli regard to 
 its functions j physiological views of their own, and 
 of others, are fairly and candidly given, but none 
 are recommended as worthy of being received and 
 adopted, excepting such aa are strictly in accord- 
 once with anatomical facts. — Illinois and Indiana 
 Medical and Surgical Journal. 
 
 We must urgently reeommend those among our 
 readers who are not already in possession of this 
 Physiolopical Anatomy, no longer to delay adding it 
 to their library. # * # This treatise is quite m- 
 
 dispensable to all who aspire to keep up their know- 
 ledge with the high standard of the present day. ^• 
 * * We must congratulate Dr. Todd and Mr, 
 Bowman, and especially the latter gem leman, thnt 
 they have been able by their admirable and skilful 
 observations to throw so much new light on the 
 delicate organization of many important parts; a 
 merit this of no ordinary kind, when it is recol- 
 lected that the intimate texture of the organs to 
 which we refer has been made the subject ol labori- 
 ous and repeated investigations by sevenil of the 
 most distinguished miuroscopists of Europe, — Medi- 
 co- Chirurg teal Review. 
 
 It cannot fail to recommend itself to students by 
 the clearness of description and the accuracy of the 
 illustrations met with in every' chapter: and we do 
 not hesitate to express our opinion that U supplieaa 
 void which has hitherto existed between works es- 
 pecially devoted to anatomy ami physiology. The 
 engravings represent not only those parts of anato- 
 my which can be easily traced with the scalpel, and 
 which really need no other illustration than that met 
 with in the dissecting-room, but by the aid of the 
 microscope und of sundry chemical appliances, they 
 carry him into the intimate structure of organs, and 
 lay bare to the eye the most minute subdivisions of 
 vessels and nerves. * * * The chnptersare not 
 encumbered with unnecessary details j and those 
 parts of physios which are required for the under- 
 standing of the physiology of the senses, are con- 
 cisely given in the form of notes. * # # It will 
 form, when completed, a most useful addition to the 
 library of every student ami practitioner who sets a 
 value upon the scientific knowledge of his profes- 
 sion —London MeUical Gazette. 
 
BLANCHARD & LEA'S . 
 MEDICAL AID SURGICAL PUBLICATIOIS. 
 
 TO TH6 MEDICAL PROFESSION. 
 
 The prices on the present catalogue are those at which our books can generally 
 be furnished by booksellers throughout the United States, who can readily procure 
 any which they may not have on hand. To physicians who have not convenient 
 access to bookstores, we will forward them by mail, at these prices, /?-ee of postage 
 (as long as the existing facilities are afforded by the post-office), for any distance 
 under 3,000 miles. As we open accounts only with booksellers, the amount must 
 in every case, without exception, accompany the order, and we assume no risks of 
 the mail, either on the money or on the books; and as we deal only in our own 
 publications, we can supply no others. Gentlemen desirous of purchasing will, 
 thprefore,'find it more advantageous to deal with the nearest booksellers whenever 
 practicable. 
 
 BLANCHARD & LEA. 
 
 Fhilidelphia, July, 1859. 
 
 *** We have now ready a new edition of our Illustrated Catalogue of Medical 
 and Scientific Publications, forming an octavo pamphlet of 80 large pages, containing 
 specimens of illustrations, notices of the medical press, &c. &c. It has been pre- 
 pared without regard to expense, and will be found one of the handsomest specimens 
 of typographical execution as yet presented in this country. Copies will be sent to 
 any address, by mail, free of postage, on receipt of nine cents in stamps. 
 
 Catalogues of our numerous publications in miscellaneous and educational litera- 
 ture forwarded on application. 
 
 ^F The attention of physicians is especially solicited to the following important new works 
 and new editions, just issued or nearly ready : — 
 Bucknill and Tuke on Insanity, 
 Bird on Urinary Deposits, 
 Condie on Diseases of Children, 
 Dickson's Elements of Medicine, . 
 Dalton's Human Physiology, . 
 Eriohsen's System of Surgery, 
 Fownes' Manual of Chemistry, 
 
 Flint on the Heart, 
 
 Gray's Anatomy, JDescriptive and Surgical 
 
 Gross's System of Surgery, 
 
 Hamilton on Fractures and Dislocations, 
 
 Meigs on Diseases of Women, 
 
 Morland on the Urinary Organs, 
 
 Ricord and Hunter on Venereal, 
 
 Stille's Therapeutics and Materia MedicE; 
 
 Taylor on Poisons, .... 
 
 Watson's Practice of Physic, . 
 
 Wilson's Human Anatomy, 
 
 West on Diseases of Women, 
 
 See page 4 
 
 u 
 
 4 
 
 t( 
 
 8 
 
 tl 
 
 10 
 
 (I 
 
 11 
 
 a 
 
 14 
 
 " 
 
 14 
 
 11 
 
 IS 
 
 (C 
 
 16 
 
 (C 
 
 16 
 
 (( 
 
 21 
 
 (( 
 
 21 
 
 {( 
 
 22 
 
 c< 
 
 . 26 
 
 (f 
 
 27 
 
 u 
 
 29 
 
 u 
 
 30 
 
 (C 
 
 31 
 
 (1 
 
 32 
 
 TWO MEDICAL PERIODICALS, FREE OF POSTAGE. 
 
 Containing' over Fifteen Hundred large octavo pages, 
 
 FOR FIVE DOIil.AR§i PER AHflVrJTl. 
 
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 THE AMERICAN JOURNAL OF THE MEDICAL SCIENCES, 
 
 Edited bt ISAAC HAYS, M.D., 
 
 is published Quarterly, on the first of January, April, July, and October. Each number contains- 
 at least two hundred and eiglity large octavo pages, handsomely and appropriately illustrated, 
 wherever necessary. It has now been issued regularly f'or nearly forty years, and it has been. 
 1 
 
BLANCHARD & LEA'S MEDICAL 
 
 under the control of the present editor for more than a quarter oi a century. Throu§fhout this 
 long period, it has maintained its position in the highest rank of medical periodicals both at home 
 and abroad, and has received the cordial support of the entire profession in this country. Its list of 
 Collaborators will be found to contain a large number of the most distinguished names of the pro- 
 fession in every section of the United States, rendering the department devoted to 
 
 ORIGINAL COMMUNICATIONS 
 
 full of varied and important matter, of great interest to all practitioners. 
 
 As the aim of the Journal, however, is to combine the advantages presented by all the different 
 varieties of periodicals, in its 
 
 REVIEW DEPARTMENT 
 
 will be found extended and impartial reviews of all important new works, presenting subjects oi 
 novelty and interest, together with very numerous 
 
 BIBLIOGRAPHICAL NOTICES, 
 
 including nearly all the medical publications of the day, both in this country and Great Britain, with 
 a choice selection of the more important continental works. This is followed by the 
 
 QUAKTEKLY SUMMARY, 
 
 being a very full and complete abstract, methodically arranged, of the 
 
 IMPROTEMENTS AND DISCOVERIES IN THE MEDICAL SCIENCES. 
 
 This department of the Journal, so important to the practising physician, is the object oi especial 
 care on the part of the editor. It is classified and arranged under different heads, thus facilitating 
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 ALL THE AMERICAN MEDICAL AND SCIENTIFIC PERIODICALS, 
 
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 To their old subscribers, many of whom have been on their list for twenty or thirty years, the 
 publishers feel that no promises for the future are necessary; but those who may desire for the 
 first time to subscribe, can rest assured that no exertion will be spared to maintain the Journal in 
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 By reference to the terms it will be seen that, in addition to this large amount of valuable and 
 practical information on every branch of medical science, the subscriber, by paying in advance 
 becomes entitled, without further charge, to ' 
 
 THE MEDICAL NEWS AND LIBRARY, 
 
 a monthly periodical of thirty-two large octavo pages. Its "News Departmemt" presents the 
 current information of the day, while the "Library Department" is devoted to presenting stand- 
 ard works on various branches of medicine. Within a few years, subscribers have thus received 
 without expense, many works of Iho highest character and practical value, such as " Watson's' 
 Practice," "Todd and Bowman's Physiology," "Malgaigne^ Surgery," "West on Children" 
 " West on Females, Part I," &c. ' 
 
 While in the number for January, 1858, was commenced a new and highly important work 
 HABERSHON ON DISEASES OF THE ALIMENTARY CANAL. 
 which will be completed during 1859. 
 
 It will be seen that this treatise covers the whole ground of affections of the Digestive Oreans 
 which furnish so very large a portion of the daily practice of the physician. The author's position 
 in Guy's Hospital, and the fact that the work has only just appeared in London, are suflicient suar- 
 antee that it is up to the hour, and presents the most advanced condition of this department of medi- 
 cal science, while its thorough practical character is manifested by the great number of cases on 
 which it is founded. 
 
 It will thus be seen that for the small sum oi FIVE DOLLARS, paid in advance, the subscriber 
 will obtam a Quarterly and a Monthly periodical, ^ "vnnce, me suDscriber 
 
 EMBRACING NEARLY SIXTEEN HUNDRED LARGE OCTAVO PAGES, 
 mailed to any part of the United States, free of postage. 
 
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 ing the Journal will thus be apparent. ""ou uiuer 
 
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 will always receive It free oi postage. ' > "= ouuowiuno 
 
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 Address BLANQHARD & LEA, Philadklphia. 
 
ALLEN (J. M.), M. D., 
 
 Professor of Anatomy in the FemiBylvaiiia Medical College, &c. 
 
 THE PRACTICAL ANATOMIST; or, The Student's Guide iu the Dissecting- 
 
 ROOM. With 266 illustrationa. In one handsome royal 12mO. volume, of over 600 pages, lea- 
 ther. $U 25. ' 
 
 In the arrangement of this work, the author has endeavored to present a complete and thorough 
 course of dissections in a clearer and more available form for practical use, than has as yet been 
 accomplished. The chapters follow each other in the order in which dissections are usually con- 
 ducted in this country , and as each region is taken up, every detail regarding it is fully described 
 and illustrated, so that the student is not interrupted in his labors, by the necessity of referring from 
 one portion of the volume to another. 
 
 However valuable may be the "Dissector's 
 Guides" which We, of late, have had occiisiDn to 
 notice, we feel confident that the work of Dr. Allen 
 is superior to any of them. We believe with the 
 author, that none is so fully illustrated as this, and 
 the arrangement of the work is such as to facilitate 
 the labors of the student in acquiring a thorough 
 practical knowledge of Anatomy. We most cordi- 
 ally recommend it to their attention. — Western Lem- 
 cet. 
 
 We believe it to be one of the most useful works 
 upon the subject ever written. It is handsomely 
 illustrated, well printed, and will be found of con- 
 venient size for use in the dissecting-room. — Med. 
 Examiner, 
 
 From Prof, J, S, Da/vis, University of Va, 
 
 I am not acquainted with any work that attains so 
 fully the object which it proposes. 
 
 From C, P. Fanner, M. D., J>emonstratory Uni- 
 versity of Michigan, 
 
 I have examined the work briefly, but even this 
 examination has convinced me that it is an excellent 
 guide for the Dissector. Its illustrations are beau- 
 tiful, and more than I have seen in a work of this 
 kind. I shall take great pleasure in recommending 
 it to my classes as the text-book of the dissecting- 
 room. 
 
 ANALYTICAL COMPENDIUM 
 OF MEDICAL SCIENCE, containing Anatomy, Physiology, Surgery, Midwifery, 
 
 Chemistry, Materia Medica, Therapeutics, and Practice of Medicine. By John Neill, M. D., 
 and F. G. Smith, M. D. New and enlarged edition, one thick volume royal 12mo. of over 
 1000 pages, with 374 illustrations. $3 00. ^° See Neill, p. 24. 
 
 ABEL (F. A.), F. C. S. AND C. L. BLOXAM, 
 HANDBOOK OP CHEMISTRY, Theoretical, Practical, and Technical ; with a 
 
 Recommendatory Preface by Dr. Hofmann. In one large octavo volume, extra cloth, of 663 
 pages, with illustrations. $3 25. 
 
 ASHWELL (SAMUEL), M.D,, 
 
 Obstetric Physician and Lecturer to Guy's^Hospital, l^ondon. 
 
 A PRACTICAL TREATISE ON THE DISEASES PECULIAR TO WOMEN. 
 
 Illustrated by Cases derived from Hospital and Private Practice. Third American, from the Third 
 and revised London edition. In one octavo volume, extra cloth, of 528 pages, f 3 00. 
 The most useful practical work on the subject in | The most able, and certainly the most standard 
 the English language. — Boston Med. and fiwrg". and practical, work on female diseasetf that we have- 
 Journal, I yet seen. — Medico-Chirurgical Review, 
 
 ARNOTT CNEILL), M. D. 
 ELEMENTS OP PHYSICS; or Natural Philosophy, General and Medical.. 
 
 Written for universal use, in plain or non-technical language. A new edition, by Isaac Hays, 
 M. D. Complete in one octavo volume, leather, of 484 pages, with about two hundred illustra- 
 tions. $2 50. 
 
 BUDD (GEORGE), M, D., F. R. S., 
 
 Professor of Medicine in King's College, London. 
 
 ON DISEASES OP THE LIVER. Third American, from the third and- 
 
 enlarged London edition. In one very handsome octavo volume, extra cloth, with four beaaiti 
 fully colored plates, and numerous wood-cuts. pp. 500, 
 
 Has fairly established for itself a place among the 
 classical medical literature of England.— SriiijA 
 and Foreign Medico-Chir. Review, July, 1857. 
 
 Dr. Budd's Treatise on Diseases of the Liver is 
 now a standard work in Medical literature, and dur- 
 ing the intervals which have elapsed between the 
 successive editions, the author has incorporated into 
 ' the text the most striking novelties which have cha- 
 racterized the recent progress of hepatic physiology 
 and pathology; so thatalthoughthe siae of the book 
 
 $3 00. 
 is not perceptibly changed, the history of liver dis- 
 eases is made more complete, and is kept upon a level 
 with the progress of modern science. It is the bestj 
 work on Diseases of the Liver in any language. — 
 London Med. Times and Gazette, June 27, 18577 
 
 This work, now the standard book of reference on. 
 the diseases uf which it treats, has been carefully 
 revised, and many new illustrations of the viewa-uf 
 the learned author added in the present edition.. — 
 Dublin Quarterly Journal, Aug. 1857^ 
 
 BY THE SAME AUTHOR. 
 
 ON THE ORGANIC DISEASES AND FUNCTIONAL DISORDERS OF 
 
 THE STOMACH. In one neat octavo volume, extra cloth, f 1 50. 
 
 From the high position occupied by Dr. Budd as style, the subjects are well arranged, and tha fiiaetU 
 a teacher, a writer, and a practitioner, it is almost cal precepts, both of diagnosis and treatment, denote 
 needless to state that the present book may be con- the character of a thoughtful and experienced phy- 
 ■ulted with great advantage. It is written m an easy sician. — London Med. Times and Crazetu, 
 
and 
 
 BUCKNILL (J, C), M. D., 
 
 Medical Superintendent of the Devon County Ijunatic Asylum ; 
 DANIEL H. TUKE, M. D., 
 ViBiting Medical Officer to the York Retreat. 
 
 A MANUAL OF PSYCHOLOGICAL MEDICINE; containing the History, 
 
 Nosology, Description, Slalistics, Diagnosis, Pathology, and Treatment of INSANITY. With 
 a Plate. In one handsome octavo volume, of 536 pages. S3 00. {Just Issued, 1S5S ) 
 The increase of mental disease in its various forms, and the difficult questions to which it is 
 constantly giving rise, render the subject one of daily enhanced interest, requiring on the part of 
 the physician a constantly greater familiarity vifith this, the most perplexing branch of his profes- 
 sion. At the same time there has been for some years no work accessible in this country, present- 
 ing the results of recent investigations in the Diagnosis and Prognosis of Insanity, and the greatly 
 improved methods of treatment which have done so much in alleviating the condition or restoring 
 the health of the insane. To fill this vacancy the publishers present this volume, assured that 
 the distinguished reputation and experience of the authors will entitle it at once to the confidence 
 ot both student and practitioner. Its scope may be gathered from the declaration of the authors 
 ihat "their aim has been to supply a text book which may serve as a guide in the acquisition oi 
 such knowledge, sufficiently elementary to be adapted to the wants of th^ student, and sufficiently 
 modern in its views and explicit in its teaching to suffice for the demands of the practitioner." 
 
 BENNETT (J. HUGHES), M. D., F. R. S. E., 
 
 Professor of Clinical Medicine in the University of Edinburgh, &c. 
 
 THE PATHOLOGY AND TREATMENT OP PULMONARY TUBERCU- 
 LOSIS, and on the Local Medication of Pharyngeal and Laryngeal Diseases frequently mistaken 
 for or associated with, Phthisis. One vol. 8vo.,extra cloth, with wood-cuts. pp. 130. f 1 25. 
 
 BENNETT (HENRY), M. D. 
 A PRACTICAL TREATISE ON INFLAMMATION OF THE UTERUS, 
 
 ITS CERVIX AND APPENDAGES, and on its connection with Uterine Disease. New and 
 much enlarged edition, preparing by the author for publication in 1859. 
 
 BY THE SAME AUTHOR. 
 
 A REVIEW OP THE PRESENT STATE OP UTERINE PATHOLOGY. 
 
 bvc, 75 pages, flexible cloth, 50 cents. 
 
 AND 
 
 A new 
 In one 
 
 BIRD (GOLDING), A. M., M. D., Stc. 
 URINARY DEPOSITS : THEIR DIAGNOSIS, PATHOLOGY, 
 
 THERAPEUTICAL INDICATIONS. Edited by Edmund Lloyd Biekett, M. D. 
 American, from the fifth and enlarged London edition. With eighty illustrations on wood, 
 handsome octavo volume, of about 400 pages, extra cloth. f2 00. (Note Ready, June, 1859.) 
 
 The death of Dr. Bird has rendered it necessary to entrust the revision of the present edition to 
 oiher hands, and in his performance of the duly thus devolving on him. Dr. Birkett has sedulously 
 endeavored to carry out the author's plan by introducing such new matter and modifications of 
 the text as the progress of science has called for. Notwithstanding the utmost care to keep the 
 work within a reasonable compass, these additions have resulted in a considerable enlargement. 
 It is, therefore, hoped ihat it will be found fully up to the present condition of the subject, and that 
 (he reputation of the volume as a clear, complete, and compendious manual, will be fully maintained. 
 
 aary_ secretion, which have contributed so much to 
 
 It can scarcely be necessary for us to say anything 
 of the merits of this well-known Treatise, which so 
 admirably brings into practical application the re- 
 salts of those microscopical and chemical researches 
 cegarding the physiology and pathology of the uri- 
 
 the increase of our diagnostic powers, and to the 
 extension and satisfactory employment of our thera- 
 peutic teaoaTces.— The British and Foreign Medico- 
 ChiruTgical Review. 
 
 BOWMAN (JOHN E.), M.D. 
 PRACTICAL HANDBOOK OF MEDICAL CHEMISTRY. Second Ame- 
 
 rican, from the third and revised English Edition. In one neat volume, royal 12mo., extra cloth, 
 with numerous illustrations, pp. 288. $1 25. 
 
 BY THE SAME AUTHOR. 
 
 INTRODUCTION TO PRACTICAL CHEMISTRY, INCLUDING ANA- 
 LYSIS. Second American, from the second and revised London edition. With numerous illus- 
 .4 trations. In one neat vol., royal 12mo., extra cloth, pp.350. SI 25. 
 
 BEALE ON THE LAWiS OF HEALTH IN RE- 
 LATION TO MIND AND BODY. A Series of 
 L>etters from an old Practitioner to a Patient. In 
 one volume, royal ISmo., extra cloth, pp. 200. 
 80 cents. 
 
 BUSHNAN'S PHYSIOLOGY OF ANIMAL AND 
 VEGETABLE LIFEj a Popular Treatise on the 
 Functions and Phenomena of Organic Life. In 
 one handsome royal ]2mo. volume, extra cloth, 
 with over 100 illaatrationa. pp.234. 80 cents. 
 
 BUCKLER ON THE ETIOLOGY, PATHOLOGY, 
 AND TREATMENT OF FIBRO-BRONCHI- 
 TIS AND RHEUMATIC PNEUMONIA. In 
 one Svo. volume, extra cloth, pp. 150. 81 25. 
 
 BLOOD AND URINE (MANUALS ON). BY 
 JOHN WILLIAM GRIFFITH, G. OWEN 
 REESE, AND ALFRED MARKWIOK. One 
 thick volume, royal 12mo., extra cloth, with 
 plates, pp. 460. SI 2S. 
 
 BRODIE'S CLINICAL LECTURES ON SUR- 
 GERY. 1vol. Svo. cloth. 360 pp. 8185. 
 
AND SCIENTIFIC PUBLICATIONS. 
 
 BARCLAY (A. W.) M. D., 
 
 Aseistant Physician to St. George's Hospital, See. 
 
 A MANUAL OF MEDICAL DIAGNOSIS; being an Analysis of the Signs 
 
 and Symptoms of Disease. In one neat octavo volume, extra cloth, of 424 pag^es. $2 00. {A new 
 work^ just isstced. ) 
 
 Of works exclusively devoted to this important 
 branch, our profession has at command, compara- 
 tively, but few, and, therefore, in the pubUcationnf 
 the present work, Messrs. Blanchard & Lea have 
 conferred a great favor upon us. Dr. Uarclayj from 
 having occupied, for a long period, the position of 
 Medical Registrar at St. George's Hospital, pos- 
 sessed advantages for Correct observation and reli- 
 able conclusions, as to the significance of symptoms, 
 which have fallen to the lot of but few, either in 
 his own or any other country. He has carefully 
 systematized the results of his observation of over 
 twelve thousand patients, and by his diligence and 
 judicious classification, the profession has been 
 presented with the most convenient and reliable 
 work on the subject of Diagnosis that it has been 
 our good fortune ever to examine; we can, there- 
 fore, say of Dr. Barclay's work, that, from his sys- 
 tematic manner of arrangement, his work is one of 
 the best works *' for reference" in the daily emer- 
 gencies of the practitioner, with which we are ac- 
 quainted; but, at the same time, we would recom- 
 mend our readers, especially the younger ones, to 
 read thoroughly and study diligently the whole work, 
 and the "emergencies" will not occur so often. — 
 Southern Med. and Surg. Journ., March, 1858. 
 
 To give this information, to supply this admitted 
 
 deficiency, is the object of Dr. Barclay's Manual. 
 The task of composing such a work is neither an 
 easy nor a light one ; but Dr. Barclay has performed 
 it in a manner which meets our most unqualified 
 approbation. He is no mere theorist; he knows his 
 work thoroughly, and in attempting to perfttrm it, 
 has not exceeded his powers. — British Med. Journal j 
 Dec. 5, 1857. 
 
 We venture to predict that the work, will be de- 
 servedly popular, and soon become, like Watson's 
 Practice, an indispensable necessity to the practi- 
 tioner. — N. A. Med. Journal^ April, 1858. 
 
 An inestimable work of reference for the young 
 practitioner and student. — Nashville Med. Journaly 
 May, 1858. 
 
 We hope the volume will have an extensive cir- 
 culation, not among students of medicine only, but 
 practitioners also. They will never regret a faith- 
 ful study of its pages.— C»»cirtna/iiance(, Mar. '58. 
 
 This Manual of Medical Diagnosis is one of the 
 most scientific, useful, and instructive works of its 
 kind that we have ever read, and Dr. Barclay has 
 done good service to medical science in collecting, 
 arranging, and analyzing the signs and symptoms 
 of so many diseases. — N. J. Med. and Surg. Re- 
 porter^ March, 1858. 
 
 BARLOW (GEORGE H.), M. D. 
 
 Physician to Guy's Hospital, London, &.c. 
 
 A MANUAL OF THE PRACTICE OP MEDICINE. With Additions by D. 
 
 F. CoNDiE, JVl.D., author of ''A Practical Treatise on Diseases of Children," &c. In one hand- 
 some octavo volume, leather, of over 600 pag^es. $2 75. 
 
 We recommendDr. Barlow's Manual in the warm- 
 est manner as a most valuable vade-mecum. We 
 have had frequent occasion to consult it, and have 
 found it clear, concise, practical, and sound. It is 
 eminently a practical work, containing all that is 
 essential, and avoiding useless theoretical discus- 
 sion. The work supplies what has been for some 
 time wanting^ a manual of practice based upon mo- 
 dern discoveries in pathology and rational views of 
 treatment of disease. It is especially intended for 
 the use of students and junior practitioners, but it 
 
 will be found hardly less useful to the experienced 
 physician. The American editor has added to the 
 work three chapters — on Cholera Infantum, Yellow 
 Fever, and Gerebro- spinal Meningitis. These addi- 
 tions, the two first of which are indispensable to a 
 work on practice destined for the profession in this 
 country, are executed with great judgment and fi- 
 delityi, by Dr. Condie, who l>as also succeeded hap- 
 pily in imitating the conciseness and clearness of 
 style which are such agreeable characteristics of 
 the original book. — Boston Med. a/nd Surg. Journal, 
 
 BARTLETT (ELISHA), M. D. 
 THE HISTORY, DIAGNOSIS, AND TREATMENT pp THE FEVERS 
 
 OF THE UNITED STATES. A new and revised edition. By Alonzo Clark, M. D., Prof. 
 
 of Pathology and Practical Medicine in the N. Y. College of Physicians and Surgeons, &c. In 
 
 one octavo volume, of six hundred pages, extra cloth. Price f 3 00. 
 
 It 18 the best work on fevers which has emanated 
 from the American^jpresS; and the present editor has 
 carefully availe'd himself of alt information exist- 
 
 ing upon the subject in the Old and New World, so 
 that the doctrines advanced aie brought down to the 
 latest date in the progress of this department of 
 Medical Science.— X.o»rfo» Med. Times and Gazette, 
 May 2, 1857. 
 
 This excellent monograph on febrile disease, has 
 stood deservedly high since its first publication. It 
 will be seen that it has now reached its fourth edi- 
 tion under the supervision of Prof A. Clark, a gen- 
 tleman who, from the nature of his studies and pur- 
 suits, is well calculated to appreciate and discuss 
 the many intricate and difficult questions in patho- 
 
 logy. His annotations add much to the interest of 
 the work, and have brought it well up to the condi- 
 tion of the scienee as it exists at the present day 
 in regard to this class of diseases. — Southern Med. 
 and Surg. Journal, Mar. 1857. 
 
 It is a work of great practical value and interest, 
 containing much that is new relative tO the several! 
 diseases of which it treats, and, with the additions 
 of the editor, is fully up to the times. The distinct- 
 ive features of the different forms of fever are plainly 
 and forcibly portrayed, and the lines of demarcation 
 carefully and accurately drawn, and to the Ameri- 
 can practitioner is a more valuable and safe guide 
 than any work on fever extant. — Ohio Med. and 
 Surg. Journal, May, 1S57, 
 
 BROWN (ISAAC BAKER), 
 
 Surgeon- Accoucheur to St. Mary's Hospital, &c. 
 
 ON SOME DISEASES OP WOMEN ADMITTING OF SURGICAL TEEAT- 
 
 JVIENT. With handsome illustrations. One vol. 8vo., extra cloth, pp. 276. $160. 
 Mr. Brown has earned for himself a high reputa- 
 tion in the operative treatment of sundry diseases 
 
 and injuries to which females are peculiarly subject 
 We can truly say of his work that it is an important 
 addition to obstetrical literature. The operative 
 suggestions and contrivances which Mr. Brown de- 
 scribes, exhibit much practical sagacity and skill, 
 
 and merit the careful attention of every surgeon- 
 accoucheur. — Association Journal. 
 
 We have no hesitation in recommending this book 
 to tae careful attention of all surgeons who make 
 female compiainls a partof their study and practico. 
 — Dublin (Quarterly Journal. 
 
CARPENTER (WILLIAM B.), M. D., F. R, S., &.C., 
 
 Examiner in PhyBiology and Comparative Anatomy in the University of London, 
 
 PRINCIPLES OF HUMAN PHYSIOLOaY; with their chief applications to 
 
 Psychology, Pathology, Therapeutics, Hygiene, and Forensic Medicine. A new American, from 
 the last and revised London edition. With nearly three hundred illustrations. Edited, with addi- 
 tions, by Francis Gurney Smith, M. D., Professor of the Institutes of Medicine in the Pennsyl- 
 vania Medical College, fcc. In one very large and beautiful octavo volume, of about nine hundred 
 large pages, handsomely printed and strongly bound in leather, with raised bands. $4 25. 
 
 In the preparation of this new edition, the author has spared no labor to render it, as heretofore,, 
 a complete and lucid exposition of the most advanced condition of its important subject. The 
 amount of the additions required to effect this object thoroughly, joined to the former large size of 
 the volume, presenting objections arising from the unwieldy bulk of the work, he has omitted all 
 those portions not bearing directly upon Human Physiology, designing to incorporate them in 
 his forthcoming Treatise on General Physiology. As a full and accurate text-book on the Phy- 
 siology of Man, the work in its present condition therefore presents even greater claims upon 
 the student and physician than those which have heretofore won for it the very wide and distin- 
 guished favor wnich it has so long enjoyed. The additions of Prof. Smith will be found to supply 
 whatever may have been wanting to the American student, while the introduction of many new 
 illustrations, and the most careful mechanical execution, render the volume one o/* the most at- 
 tractive as yet issued. 
 
 For upwards of thirteen years Dr. Carpenter's 
 work has been considered by the profession gene- 
 rally, both in this country and England, as the most 
 valuable compendium on the subject of physiology 
 m ou r language. This distinction it owes to the high 
 attainments and unwearied industry of its accom- 
 
 fiiished author. The present edition (which, like the 
 ast American one, was prepared by the author him- 
 selO, is the result of such extensive revision, that it 
 may almost be considered a new work. We need 
 hardly say, in eoncludinff this brief notice, that while 
 the work is indispensable to every student of medi- 
 cine in this country, it will amply repay the practi- 
 tioner for its perusal by the interest and value of its 
 contents. — Boston Med. and Surg. Journal. 
 
 This is a-Btandard work — the text-book used by all 
 medical students who read the English language. 
 It has passed through several editions in order to 
 keep pace with the rapidly growing science of Phy- 
 siology. Nothing need be said in its praise, for its 
 merits are universally known ; we have nothing to 
 say of its defects, for they only appear where the 
 science of which it treats is incomplete. — Western 
 Lancet. 
 
 The most complete exposition of physiology which 
 any language can at present give. — Brit, and For. 
 Med.-Chirurg. Review. 
 
 The greatest, the most reliable, and the best book 
 on the subject which we know of in the English 
 language. — Stethoscope. 
 
 To eulofi:ize this great work would be superfluous 
 We should observe, however, that in this edition 
 the author has remodelled a large portion of the 
 former, and the editor has added much matter of in- 
 terest, especially in the form of illustrations. We 
 may confidently recommend it as the most complete 
 work on Human Physiology in our language.— 
 Southern Med. and Surg. Journal. 
 
 The most complete work on the science in our 
 language. — Am. Med. Journal. 
 
 The most complete work now extant in our lan- 
 guage, — iV. O. Med. Register, 
 
 The best text-book in the language on this ex- 
 tensive subject. — London Med. Times. 
 
 A complete cyclopaedia of this branch of science. 
 —N. Y. Med. Times. 
 
 The profession of this country, and perhaps also 
 of Europe, have anxiously and for some time awaited 
 the announcement of this new edition of Carpenter's 
 Human Physiology. His former editions have for 
 many years been almost the only text-book on Phy- 
 siology in all our medical schools, and its circula- 
 tion among the profession has been unsurpassed by 
 any work m any department of medical science. 
 
 ft is quite unnecessary for us to speak of this 
 work as its merits would justify. The mere an- 
 nouncement of its appearance will afford the highest 
 pleasure to every student of Physiology, while its 
 perusal will be of infinite service in advancing 
 physiological science. — Ohio Med. and Surg. Joum: 
 
 BY the same author. 
 
 PRINCIPLES OF COMPARATIVE PHYSIOLOGY. New American, from 
 
 the Fourth and Revised London edition. In one large and Iiandsome octavo volume, with over 
 three hundred beautiful illustrations, pp. 752. Extra cloth, $4. 80 ; leatlier, raised bands, $5 25, 
 
 The delay which has existed in the appearance of this work has been caused by the very thorough 
 revision and remodelling which it has undergone at the hands of the author, and the large number 
 of new illustrations which have been prepared for it. It will, therefore, be found almost a new 
 work, and fully up to the day in every department of the subject, rendering it a reliable text-book 
 for all students engaged in this branch of science. Every effort has been made to render its typo- 
 graphical finish and mechanical execution worthy of its exalted reputation, and creditable to the 
 mechanical arts of this country. 
 
 This book should not only be read but thoroughly 
 studied bjr every member of the profession. None 
 are too wise or old, to be benefited thereby. But 
 especially to the younger class would we cordially 
 commend it as best fitted of any work in the English 
 language to qualify them for the reception and com- 
 prehension of those truths which are daily being de- 
 veloped in physiology. — Medical Counsellor, 
 
 Without pretending to it, it is an encyclopedia of 
 the subject, accurate and complete in all respects — 
 a truthful reflection of the advanced state at which 
 the science has now arrived. — Dublin Quarterly 
 Journal of Medical Science. 
 
 A truly mugnificent work — in itself a perfect phy- 
 siological study. — Romking^s Abstract. 
 
 This work stands without its fellow. It laone 
 few men in'Gurope could have undertaken ; it in one 
 
 no man, we believe, could have brought to so suc- 
 cessful an issue as Dr. Carpenter, ft required for 
 its production a physiologist, at once deeply read in 
 the labors of others, capable of taking a general, 
 critical, and unprejudiced view of those labors, ana 
 of combining the varied, heterogeneous materials at 
 his disposal, so as to form an harmonious whole. 
 We feel that this abstract can give the reader a very 
 imperfect idea of the fulness of this work, and no 
 idea of its unity, of the admirable manner in which 
 material has been brought, from the most various 
 sources, to conduce to its completeness, of the lucid- 
 ity of tne reasoning it contains, or of the clearnesB 
 or language in which the whole is clothed. Not the 
 profession only, but the scientific world at large, 
 must feel deeply indebted to Dr. Carpenter for this 
 great work. It must, indeed, add largely even to 
 his high reputation. — Medical Times. 
 
AND SCIENTIFIC PUBLICATIONS. 
 
 CARPENTER (WILLIAM BJ, M. D., F. R. S., 
 Examiner in Physiology and Comparative Anatomy in the University of London. 
 
 THE MICKOSCOPE AND ITS REVELATIONS. With an Appendix con- 
 
 taining the Applications of the Microscope to Clinical Medicine, &c. By F. G. Smith, M. D. 
 Illustrated by four hundred and thirty-four beautiful engravings on wood. In one large and ver}' 
 handsome octavo volume, of 724 pages, extra cloth, $4 00 ; leather, $4 50. 
 
 Ur. Carpenter's position as a microscopist and physiologist, and his great experience as a teacher, 
 eminently qualify him to produce what has long been wanted — a good text-book on the practical 
 use of the microscope. In the present volume his object has been, as stated in hi." Preface, " to 
 combine, within a moderate compass, that information with regard to the use of his ' tools,' which 
 is most essential to the working microscopist, with such an account of the objects best fitted for 
 his study, as might qualify him to comprehend what he observes, and might thus prepare him to 
 benefit science, whilst expanding and refreshing his own mind " That he has succeeded in accom- 
 plishing this, no one acquainted with his previous labors can doubt. 
 
 The great importance of the microscope as a means of diagnosis, and the number of microseo- 
 pists who are also physicians, have induced the American publishers, with the author's approval, to 
 add an Appendix, carefully prepared by Professor Smith, on the applications of the instrument to 
 clinical medicine, together with an account of American Microscopes, their modifications and 
 accessories. This portion of the work is illustrated with nearly one hundred wood-cuts, and, it is 
 hoped, will adapt the volume more particularly to the use of the American student. 
 
 Every care has been taken in the mechanical execution of the work, which is confidently pre- 
 sented as in no respect inferior to the choicest productions of the London press. 
 
 The mode in which the author has executed his intentions may be gathered from the following 
 condensed synopsis of the 
 
 CONTENTS. 
 
 Introdtiction — History of the Microscope. Chap. I. Optical Principles of the Microscope, 
 Chap. II. Construction of the Microscope. Chap. III. Accessory Apparatus. Chap. IV. 
 Management of the Microscope Chap. V. Preparation, Mounting, and Collection of Objects. 
 Chap. VI. Microscopic Forms of Vegetable Life — Protophytes. Chap. VII. Higher Cryptoga- 
 mia. Chap. VIII. Phanerogamic Plants. Chap. IX. Microscopic Forms of Animal Life — Pro- 
 tozoa — Animalcules. Chap. X. Foraminifera, Polycystina, and Sponges. Chap. XI. Zoophytes. 
 Chap. XII. Echinodermata. Chap. XIII. Polyzoa and Compound Tunicata. Chap. XIV. 
 Molluscous Animals Generally. Chap. XV. Annulosa. Chap. XVI. Crustacea. Chap. XVII. 
 Insects and Arachnida. Chap XVIII. Vertebrated Animals. Chap. XIX. Applications of the 
 Microscope to Geology. Chap. XX. Inorganic or Mineral Kingdom-^Polarization. Appendix. 
 Microscope as a means of Diagnosis — Injections — Microscopes of American Manufacture. 
 
 Those who are acquainted with Dr. Carpenter's 
 
 frevious writings on Animal and Vegetable Physio- 
 ogy , will fully understand how vast a store of know- 
 ledge he is able to bring to bear upon so comprehen- 
 sive a subject as the revelations of the microscope ; 
 and even those who have no previous acquaintance 
 with the construction or uses of this instrument, 
 will find abundance of information conveyed in clear 
 and simple language. — Med, Times omd Gazette. 
 Although originally not intended as a strictly 
 
 medical work, the additions by Prof. Smith give it 
 a positive claim upon the profession, for which we 
 doubt not he will receive th'eif sincere thanks. In- 
 deed, we know not where the student of medicine 
 will find such acomplete and satisfactory collection 
 of microscopic facts bearing upon physiology and 
 practical medicine as is contained in Pruf. Smith's 
 appendix ;~ and this of itself, it seems to ua, is fully 
 worth the cost of the volume. — Louisville Medical 
 Review. Nov. 1856. 
 
 BY THE same author. 
 
 ELEMENTS (OR MANUAL) OF PHYSIOLOGY, INCLUDING PHYSIO- 
 LOGICAL ANATOMY. Second American, from a new and revised London edition. With 
 one hundred and ninety illustrations. In one very handsome octavo volume, leather, pp. 566. 
 $3 00. 
 
 To say that it is the best manual of Physiology 
 now before the public, would not do sufficient justice 
 to the author. — Buffalo Medical Journal. 
 
 In his former works it would seem that he had 
 exhausted the subjectof Physiology. In the present, 
 he gives the essence, as it were, ol^ the whole. — N. Y. 
 Journal of Medicine. 
 
 "Those who have occasion for an elementary trea- 
 tise on Physiology, cannot do better than to possess 
 
 themselvesof the manual of Dr. Carpenter Medical 
 
 Examiner. 
 
 The best and most complete expose of modern 
 Physiology, in one volume, extant in the English 
 language. — St. Louis Medical Journal. 
 
 BY THE SAME AUTHOR. (Preparing.) 
 
 PRINCIPLES OP GENERAL PHYSIOLOGY, INCLUDING ORGANIC 
 
 CHEMISTRY AND HISTOLOGY. With a General Sketch of the Vegetable and Animal 
 Kingdom. In one large and very handsome octavo volume, with several hundred illustrations. 
 The subject of general physiology having been omitted in the last editions oi the author's " Com- 
 parative Physiology" and "Human Physiology,'! he has undertaken to prepare a volume which 
 shall present it more thoroughly and fully than has yet been attempted, and which may be regarded 
 as an introduction to his other works. ^ 
 
 BY THE SAME AUTHOR. 
 
 A PRIZE ESSAY ON THE USE OP ALCOHOLIC LIQUORS IN HEALTH 
 
 AND DISEASE. New edition, with a Preface by D. F. Condie, M. D., and explanations of 
 scientific words. In one neat I2mo. volume, extra cloth, pp. 178. 50 cents. 
 
8 
 
 BLANCHARD & LEA'S MEDICAL 
 
 CONDIE (D. F.), M. D., &c. 
 A PKACTICAL TKEATISB ON THE DISEASES OF CHILDREN. Fifth 
 
 edition, revised and augmented. In one large volume, 8vo., leather, of over 750 pages. $3 25. 
 
 {Now Ready, 1859.) 
 
 In presenling a new and revised edition oi ttiis favorite work, the publishers have only to slate 
 that the author has endeavored to render it in every respect "a complete and faithful exposition of 
 the pathology and therapeutics of the maladies incident to the earlier stages of existence— a full 
 and exact account of the diseases of infancy and childhood." To accomplish this he has subjected 
 the whole work to a careful and thorough revision, rewriting a considerable portion, and adding 
 several new chapters. In this manner it is hoped that any deficiencies which may have previously 
 existed have been supplied, that the recent labors of practitioners and observers have been tho- 
 roughly incorporated, and that in every point the work will be found to maintain the high reputation 
 it has enjoyed as a complete and thoroughly practical book of reference in infantile affections. 
 
 A few notices of previous editions are subjoined. 
 
 We pronounced the first edition to be the beBt 
 work on the diseases of children in the English 
 language, and, notwithstanding all that has been 
 
 Dr. Condie's scholarship, acumen^ industry, and 
 practical sense are manifested in this, as in all his 
 numerous contributions to science. — Vr. Holmes^s 
 Re-port to the American Medical Association. 
 
 Taken as a whole, in our judgment. Dr. Condie^s 
 Treatise is the one from the perusal of which the 
 practitioner in this country will rise with the great- 
 est satisfaction. — Western Journal of Medicine and 
 Surgery. 
 
 One of the best works upon the Diseases of Chil- 
 dren in the English language. — Western Lancet. 
 
 We feel assured from actual experience that no 
 physician's library can be complete without a copy 
 of this work. — N. Y. Journal of Medicine. 
 
 A veritable psediatric encyclopedia, and an honor 
 to American medical literature. — Ohio Medical and 
 Surgical Journal. 
 
 We feel persuaded that the American medical pro- 
 fession will soon regard it not only as a very good, 
 but as the vbrt best "Practical Treatise on the 
 Diseases of Children.^' — American Medical Journal 
 
 In the department of infantile therapeutics, the 
 work of Dr. Condie is considered one of the best 
 which has been published in the English language. 
 ■—The Stethoscope, 
 
 laiiaua^v, aiiu, iiul w iLiioi.a.iiuiug aii mo.!, uao umvu. 
 
 published, we stili^egard it in that light. — Medical 
 Exiiminer. 
 
 The value of works by native authors on the dis- 
 eases which the physician is called upon to combat, 
 will be appreciated by all; andtheworkof Dr. Con- 
 die has gained for itself the character of a safe guide 
 for students, and a useful work for consultation by 
 those engaged in practice. — N. Y. Med. Times. 
 
 This is the fourth edition of this deservedly popu- 
 lar treatise. During the interval since the last edi- 
 tion. It has been suBjected to a thorough revision 
 by the author; and all new observations in the 
 pathology and therapeutics of children have been 
 included in the present volume. As we said btfure, 
 we do not know of a better book on diseases of chil- 
 dren, and to a large part of its recommendations we 
 yield an unhesitating concurrence. — Buffalo Med. 
 Journal. 
 
 Perhaps the most full and complete work now be- 
 fore the profession of the United States ; indeed, we 
 may say in the English language. It is vastly supe- 
 rior to most of its predecessors. — Transylvania Msd. 
 Journal » 
 
 CHRISTISON (ROBERT), M. D,, V. P. R. S. E., «tc. 
 A DISPENSATORY; or, Commentary on the Pharmacopoeias of Great Britain 
 and the United States ; comprising the Natural History, Description, Chemistry, Pharmacy, Ac- 
 tions, Uses, and Doses of the Articles of the Materia Medica. Second edition, revised and im- 
 proved, with a Sujmlement contaming the most important New Remedies. With copious Addi- 
 tions, and two hundred and thirteen large wood-engravings. By K-. Eglesfeld Griffith, M. D. 
 In one very large and handsome octavo volume, leather, raised bands, of over 1000 pages. $3 50. 
 
 COOPER (BRANSBY B.), F. R. S. 
 LECTURES ON THE PRINCIPLES AND PRACTICE OF SURGERY. 
 
 In one very large octavo volume, extra cloth, of 750 pages, f 3 00. 
 
 COOPER ON DISLOCATIONS AND FRAC- 
 TURES OF THE JOINTS— Edited by Bhansbt 
 B. CooPEB, F. R. S., &e. With additional Ob- 
 BeTvations l)y Prof. J. G. Warren. A new Ame- 
 rican edition. In one handsome octavo volume, 
 extra cloth, of about 500 pages, with numerous 
 illustrations on wood. 83 25. 
 
 COOPER ON THE ANATOMY AND DISEASES 
 OF THE BREAST, with twenty-five Miscellane- 
 ous and Surgical Papers. One large volume, im- 
 perial 8vo., extra cloth, with 852 figures, on 36 
 plates. $2 50. 
 
 COOPER ON THE STRUCTURE AND DIS- 
 EASES OF THE TESTIS, AND ON THE 
 THYMUS GLAND. One vol. imperial 8vo., ex- 
 tra cloth, with 177 figures on 29 plates. S2 CD. 
 
 COPLAND ON THE CAUSES, NATURE, AND 
 TREATMENT OF PALSY AND APOPLEXY. 
 In one volume, royal 12mo., extra cloth, pp. 326. 
 80 cents. .j^ 
 
 CLYMER ON FEVERS; THEIR DIAGNOSIS, 
 PATHOLOGY, AND TREATMENT In one 
 octavo volume, leather, of 600 pages. $1 SO. 
 
 COLOMBAT DE L'ISERE ON THE DISEASES 
 OF FEMALES, and on the special Hygiene of 
 their Sex. Translated, with many Notes and Ad- 
 ditions, by C. D. Mbigs, M. D. Second edition, 
 revised and improved. In one large volume, oc- 
 tavo, leather, with numerous wood-cuts. pp. 720. 
 
 ^ 83 50. 
 
 CARSON (JOSEPH), M. D., 
 
 Professor of Materia Medica and Pharmacy in the University of Pennsylvania. 
 
 SYNOPSIS OF THE COURSE OF LECTURES ON MATERIA MEDICA 
 AND PHARMACY, delivered in the University of Pennsylvania. Second and revised edi- 
 tion. In one very neat octavo volume, extra cloth, of 208 pages, fl 50. 
 
 CURLING (T. B.), F. R.S., 
 
 Surgeon to the London Hospital, President of the Hunterian Society, &c. 
 
 A PRACTICAL TREATISE ON DISEASES OF THE TESTIS, SPERMA- 
 TIC CORD, AND SCROTUM. Second American, from the second and enlarged English edi- 
 tion, la one handsome octavo volume, extra cloth, with numerous illustrations, pp. 420. $2 00. 
 
AND SCIENTIFIC PUBLICATIONS. 
 
 a 
 
 CHURCHILL (FLEETWOOD), M. D., M. R. I. A. 
 ON THE THEORY AND PRACTICE OF MIDWIFERY. Edited, with 
 
 Notes and Additions, by D. Francis Condie, M. D., author of a '* Practical Treatise on the 
 Diseases of Children," &c. With 139 illustrations. In one very handsome octavo volume, 
 leather, pp.610. %3 00. 
 
 No work holds a higher position, or is more de- 
 serving of being placed in the hands of the tyro, 
 the advanced stadeht, or the practitioner. — Medical 
 Examiner. 
 
 Previous editions, under the editorial supervision 
 of Prof. R. M. Huston, have been received with 
 marked favor, and they deserved itj but this, re- 
 printed from a very late Dublin edition, carefully 
 revised and brought up by the author to the present 
 time, does present an unusually accurate and able 
 exposition of every important particular embraced 
 in the department of midwifery. * * The clearness, 
 directness, and precision of its teachings, together 
 with the great amount of statistical research which 
 its text exhibits, have served to place it already in 
 the foremost rank of works in this department of re- 
 medial science. — iV. O. Med. and'Surg. Journal. 
 
 In our opinion, it forms one of the best if not the 
 very best text-book and epitome of obstetric science 
 which we at present possess in the English laU' 
 g}i9%Q.— Monthly Journal of Medical Science. 
 
 The clearness and precision of style in which it ia 
 written, and the great amount of statistical research 
 which it contains, have served to place it in the first 
 rank of works in this department of medical science. 
 — N. Y. Journal of Medicine. 
 
 Few treatises will be found better adapted as a 
 text-book for the student, or as a manual for the 
 frequent consultation of the young pr act! ti oner. -:- 
 American Medical Journal. 
 
 To bestow praise on a book that has received such 
 marked approbation would be superfluous. We need 
 only say, therefore, that if the first edition was 
 thought worthy of a favorable reception by the 
 medical public, we can confidently affirm that this 
 will be found much more so. The lecturer, the 
 practitioner, and the student, may all have recourse 
 to its pages, and derive from their perusal much in- 
 terest and instruction in everything relating to theo- 
 retical and practical midwifery.— i)«6Hn Quarterly 
 Journal of Medical Science. 
 
 A work of very great merit, and such as we can 
 confidently recommend to the study of every obste- 
 tric practitioner. — London Medical Gazette . 
 
 This is certainly the moSt perfect system extant. 
 It is the best adapted for the purposes of a text- 
 book, and that which he whose necessities confine 
 him to one book, should select in preference to all 
 others. — Southern Medical and Surgical Journal. 
 
 The most popular work on midwifery ever issued 
 from the American press. — Charleston Med, Journal. 
 
 Were we reduced to the necessity of having but 
 one work on midwifery, and permitted to choose^ 
 we would unhesitatingly take Churchill. — Western 
 Med. and Surg. Journal. 
 
 It is impossible to conceive a more useful and 
 elegant manual than Dr. Churchill's Practice of 
 Midwifery. — Provincial Medical Journal. 
 
 Certainly, in our opinion, the very best work on 
 the subject which exists. — N. Y. Annalist. 
 
 BY THE SAME AUTHOR. {Lately Published.) 
 
 ON THE DISEASES OF INFANTS AND CHILDREN. Second American 
 
 Edition, revised and enlarged by the author. Edited, with Notes, by W. V. Keating, M. D. In 
 one large and handsome volume, extra cloth, of over 700 pag;es. $3 00, or in leather, $3 25. 
 In preparing this work a second lime for the American profession, the author has spared no 
 labor in giving it a very thorough revision, introducing' several new chapters, and rewriting others. 
 While every portion of the volume has been subjected to a severe scrutiny. The efforts of the 
 American editor have been directed to supplying such information relative to matters peculiar 
 to this country as might have escaped the attention of the author, and the whole may, there- 
 fore, be safely pronounced one of the most complete works on the subject accessible to the Ame- 
 rican Profession. By an alteration in the size of the page, these very extensive additions have 
 been accommodated without unduly increasing the size of the work. 
 
 contribution for the illustration of its topics. The 
 material thus derived has been used with consummate 
 skill, and the result has been a work creditable alike 
 to the author and his country, — N. A. Medico-Chir. 
 Reviewj May, 1858. 
 
 After this meagre, and we know, very imperfect 
 notice of Dr. Churchill's work, we shall conclude 
 by saying, that it is one that cannot fail from its co- 
 piousness, extensive research, and general accuracy , 
 to exalt still higher the reputation of the author in 
 this country. The American reader will benarticu- 
 larly pleased to find that Dr. Churchill has done full 
 justice throughout his work to the various A mericun 
 authors on this subject. The names of Dewees, 
 Eberle, Condie, and Stewart, occur on nearly every 
 page, and these authors are constantly referred to by 
 the author in terms of the highest praise, and with 
 the most liberal courtesy. — The Medical Examiner. 
 
 We recommend the work of Dr. Churchill most 
 cordially, both to students and practitioners, as a 
 valuable and^reliableguide in the treatment of the dis- 
 eases of children. — Ain.Journ.ofthe Med. Sciences. 
 
 We know of no work on this department of Prac- 
 tical Medicine which presents so candid and unpre- 
 judiced a statement or posting up of our actual 
 knowledge as this. — N. Y. Journal of Medicine. 
 
 Its claims to merit both as a scientific and practi- 
 cal work, are of the highest order. Whilst we 
 would not elevate it above every other treatise on 
 the same subject, we certainly believe that very few 
 are equal to it, and none superior. — Southern Med. 
 and Surgical Journal. 
 
 This work contains a vast amount of interesting 
 matter, which is so well arranged and so curtly 
 worded that the book may be regarded as an ency- 
 clopaedia of information upon the subject of which 
 it treats. It is certamly also a monument of Dr. 
 ChurchilPs untiring industry, inasmuch as there is 
 not a single work upon the diseases of children with 
 which we are acquainted that is not fully referred 
 to and quoted from in its pages, and scarcely a con- 
 tribution of the least importance to any British or 
 Foreign Medical Journal, for some years past, wh ich 
 is not duly noticed. — London Lancet^ Feb. 20, 185S. 
 
 Availing himself of every fresh source of informa- 
 tion, Dr. Churchill endeavored, with his accustomed 
 industry and perseverance, to bring his work up to 
 the present state of medical knowledge in all the 
 subjects of which it treats; and in this endeavor he 
 has, we feel bound to say, been eminently success- 
 ful. Besides the addition of more than one hundred 
 and thirty pages of matter, we observe that some 
 entirely new and important chapters are introduced, 
 viz: on paralysis, syphilis, phthisis, sclerema, &c. 
 &c. As the work now stands, it is, we believe, the 
 most comprehensive in the English language upon 
 the diseases incident to early life. — Dubhn Quarterly 
 Journal^ Feb. 1858. 
 
 It brings before the reader an amount of informa- 
 tion not comprised in any similar production in the 
 language. The amount of labor consumed upon its 
 production can only be conceived by those who have 
 been similarly occupied, every work of note pub- 
 lished within the last twenty-five years in the dif- 
 ferent languages of Europe having been laid under 
 
 BY THE SAME AUTHOR. 
 
 ESSAYS ON THE PUERPERAL FEVER, AND OTHER DISEASES PE- 
 
 CULIAR TO WOMEN. Selected from the writings of British Authors previous to the close of 
 the Eiff hteentfa Century. In one neat octavo volume, extra cloth, of about 450 pages. $2 50, 
 
10 
 
 BLANCHARD & LEA'S MfiJDICAL' 
 
 CHURCHILL (FLEETWOOD), M. D., M. R. I. A., Sec. 
 ON THE DISEASES OF WOMEN; including those of Pregnancy and Child^ 
 bed. A new American edition, revised by the Author. With Notes and Additions, by D Fran- 
 cis CoNDiE, M. D., author ol " A Practical Treatise on the Diseases of Children." With nume- 
 rous illustrations. In one large and handsome octavo volume, leather, of 768 pages. $3 00. 
 This edition of Dr. Churchill's very popular treatise may almost be termed a new work, so 
 thoroughly has he revised it in every portion. It will be found greatly enlarged, and thoroughly 
 brought up to the most recent condition of the subjeot, while the very handsome series of illustra- 
 l\OT\b introduced, representing such pathological conditions as can be accurately portrayed, present 
 a novel feature, and afford valuable assistance to the young practitioner. Such additions as ap- 
 peared desirable for the American student have been made by the editor, Dr. Condie, while a 
 marked improvement in the mechanical execution keeps pace with the advance in all other respects 
 which the volume has undergone, while the price has been kept at the former very moderate rate. 
 
 It comprises, unquestionably, one of the most ex- 
 act and comprehenBive expositions of the present 
 state uf medical knowledge in respect to the diseases 
 of women that has yet been published. — Am.Joum. 
 Med. Sciences, July, 1857. 
 
 We hail with much pleasure the volume before 
 as, thoroughly revised, corrected, and brought up 
 to the latest date, by Dr. Churchill himself, and 
 rendered still more valuable by notes, from the ex- 
 perienced and able pen of Dr. D. F. Condie.— South- 
 em Med. and Surg. Journal, Oct. 1&57. 
 
 This work is the most reliable which we possess 
 on this subject; and is deservedly popular with the 
 profession. — Charleston Med. Journal^ July, 1857. 
 
 Dr. Churchill's treatise on the Diseases of Women 
 is, perhaps, the most popular of his works with the 
 profession in this country. It has been very gene- 
 
 rally received both as a text-book and manual of 
 practice. The present edition has undergone the 
 most elaborate revision, and additions of an import- 
 ant character have been made, to render it a com- 
 plete exponent of the present state of our knowledge 
 of these diseases: — N. Vs Joum. of Med. j Sept. 1857. 
 
 We know of no author who deserves that appro- 
 bation, on "the diseases of females," to the same 
 extent that Dr. Churchill does. His, indeed, is the 
 only thorough treatise we know of on the subject; 
 and it may be commended to practitioners and stu- 
 dents as a masterpiece in its particular department. 
 —Thi Western Journal oj" Medicine and Surgery. 
 
 As a comprehensive manual for students, or a 
 work of reference for practitioners, it surpasses any 
 other that has ever issued on the same sabject from 
 the British press. — Dublin Quart. JourtMl. 
 
 DICKSON (S. H.), M. D., 
 
 Professor of Practice of Medicine in the Jefferson Medical College, Philadelphia. 
 
 ELEMENTS OF MEDICINE; a Compendious VieV of Pathology and Therar 
 
 peuiics, or the History and Treatment of Diseases. Second edition, revised. In one large and 
 handsome octavo volume, of 750 pages, leather. $3 75. {Now Ready, June, 1859.) 
 The steady demand which has so soon exhausted the first edition of this work, sufficientlj^shows 
 that the author was not mistaken in supposing that a volume of this character was needed — an 
 elementary manual of practice, which should present the leading principles of medicine with the 
 praclioal results, in a condensed and perspicuous manner. Disencumbered of unnecessary detail 
 and fruitless speculations, it embodies what is most requisite for the student to learn, and at the 
 tame time what the active practitioner wants when obliged, m the daily calls of his profession, to 
 refresh his memory on special points. The clear and attractive style of the author renders the 
 whole ea-y of comprehension, while his long experie^nce gives to his teachings an authority every- 
 where acknowledged. Few physicians, indeed, have had wider opportunities for observation and 
 experience, and few, perhaps, have used them to better purpose. As the result of a long life de- 
 voted to study and practice, the present edition, revised and brought up to the date of publication, 
 will doubtless maintain the reputation already acquired as a condensed and convenient American 
 text-book on the Practice of Medicine. A few notices of the first edition are appended. 
 
 This book is eminently what it professes to be ; a 
 distmguished merit in these days. Designed for 
 ' Teachers and Students of Medicine," and admira 
 
 bly suited to their wants, we think it will be received, 
 on Its own merite, with a hearty welcome. — Boston 
 Med. and Surg. Journal. 
 
 Indited by one of the most accomplished writers 
 of our country, as well as by one who has long held 
 a hi^h position among teachers and practitioners of 
 medicine, this work is entitled to patronage and 
 careful study. The learned author has endeavored 
 to condense in this volume most of the practical 
 matter contained in his former productions, so as to 
 adapt it to the use of those who have not time to 
 devote to more extensive works. — SouthernMed. and 
 Surg. Journal. 
 
 Prof. Dickson's work supplies, to a great extent, 
 a desideratum long felt in American medicine. — N- 
 0. Med. and Surg. Journal. 
 
 Not professing to be a complete and comprehensive 
 treatise, it will not be found full in detail, nor filled 
 with discussions of theories and opinions, but em- 
 bracine: all that is essential in theory and practice, 
 it is admirably adapted to the wants of the American 
 student. Avoiding all that is uncertain, it presents 
 more clearly to the mind of the reader that which is 
 established and verified by experience. The varied 
 and extensive reading of the author is ennspicuously 
 apparent, and all the recent improvements and dis- 
 coveries in therapeutics and pathology are chroni- 
 cled in its \>a.%Q^,~ Charleston Med. Journal. 
 
 In the first part of the work the subject of gene- 
 ral pathology is presented in outline, giving a beau- 
 tiful picture of its distinguishing features, and 
 throughout the succeeding chapters we finti that he 
 has kept scrupulously within the bounds of sound 
 reasoning and legitimate deduction. Dr. Dickson 
 merits a place in the first rank of American writers. 
 —.Westerr Lancet. 
 
 DRUITT (ROBERT), M. R. C. S., &c. 
 THE PRINCIPLES AND PRACTICE OF MODERN SURGERY. Edited 
 
 by F. W. Sargent, M. D., author oi " Minor Surgery,'* &c. Illustrated with one hundred and 
 ninety-three wood -engravings. In one very handsomely printed octavo volume, leatlier, of 576 
 large pages. S3 00. 
 
 the style, though clear and interestingj is so precise* 
 that the book contains more information condensed 
 into a few words than any other surgical work with 
 which we are acquainted. — London Medical Timsa 
 und Gazette. 
 
 Dr.Druitt's researches into the literature of his 
 subject have been not only extensive, but well di- 
 rected; the most discordant authors are fairly and 
 impartially quoted, and, while due credit is given 
 to each, their respective merits are weighed with 
 an unprejudiced hand. The grain of wheat is pre- 
 served, and the chaff is unmercifully stripped off. 
 The arrangement is simple and philosophical, and 
 
 No work, in our opinion, equals it in presenting 
 80 much valuable surgical matter in so small a 
 oompasB.— iSt. Louis Med. and Surgical Journal. 
 
AND SCIENTIFIC PUBLICATIONS. 
 
 11 
 
 DALTON, JR. {J. C), M. D. 
 
 Professor of Physiology in the College of Physicians, New York. 
 
 A TREATISE ON HUMAN PHYSIOLOGY, designed for the use of Students 
 
 and Practitioners of Medicine. With two hundred and fifty-four illustrations on wood. In one 
 very beautiful octavo volume, of over 600 pages, extra cloth, $4 00; leather, raised bands, $4 25. 
 {Now ready, 1859.) 
 
 The object of the author has been to present a condensed view of the present condition of his 
 subject, divested of mere theoretical views and hypothetical reasoning-s, but comprehending- all 
 important details which may be received as definitely settled. His long experience as an investi- 
 gator and as a teacher has given him peculiar advantages in this, and he has endeavored wherever 
 practicable to show the means by which results have been reached, so as to afford the student the 
 means of pursuing original research, as well as a text-book of the science in its most advanced con- 
 dition. Of the numerous illustrations, all are original with the exception of eleven, so that, the 
 whole possesses a completeness and authority not otherwise attainable, and in the mechanical 
 execution every care has been taken to present one of the handsomest volumes as yet produced 
 by the American press. 
 
 The work before ub, however, in our humble judg- 
 ment, is precisely what it purports to be, and will 
 answer admirably the purpose for which it is in- 
 tended. It ia par excellence,^ text-book; and the 
 best text-book in this department that we nave ever 
 seen. We have carefully read the book, and speak 
 of its merits from a more than cursory perusal. 
 Looking back upon the work we have just finished, 
 we must say a word concerning the excellence of its 
 illustrations. No departmeac is so dependent upon 
 good illustrations, and those which keep pace with 
 our knowledge of the subject, as that of physiology. 
 The wood-cuts in the work befote us are the best 
 we have ever seen, and, being original, serve to 
 illustrate precisely what is desired — Buffalo Med. 
 Journal, March, 1859. 
 
 A book of genuine merit like this deserves hearty 
 praise before subjecting it to any minute criticism. 
 We are not prepared to find any fault with its design 
 until we have had more time to appreciate its merits 
 as a manual for daily consultation, and to weie;h 
 its statements and conclusions more deliberately. 
 Its excellences we are sure of; its defects we have 
 yet to discover. It is a work highly honorable to 
 its author ; to his talents, his industry, his training ; 
 to the institution with which he is connected, and 
 to American science.— .Bos(o« Med. and Surgical 
 Journal, Feb. 24, 1859. 
 
 A NEW book and a first rate one ^ an original book, 
 and one which cannot be too highly appreciated, 
 and which we are proud to see emanating from our 
 country's press. It is by an author who, though 
 young, is considerably famous for physiological re- 
 search, and who in this work has erected for him- 
 Belf an enduring monument, a token at once of his 
 labor and his success. — Nashville Medical Journal, 
 March, 1859. 
 
 Throughout the entire work, the definitions are 
 clear and precise, the arrangement admirable, the 
 argument briefly and well stated, and J:he style 
 nervous, simple, and concise. Section third, treat- 
 ing of Reproduction) is a monograph of unap- 
 proached excellence, upon this subject, in the Eng- 
 lish tongue. For precision, elegance and force of 
 style, exhaustive method and extent of treatment, 
 fuinesil of illustration and weight of personal re- 
 search, we know of no American contribution to 
 medical science which surpasaes it, and the day is 
 far distant when ite claims to the respectful atten- 
 tion of even the best informed scholars will not be 
 cheerfully conceded by all acquainted with its range 
 anfl depth. — Charleston Med. Journal, May, 1859. 
 
 A new elementary work on Human Physiology 
 liftinpT up its voice in the presence of late and sturdy 
 editions of Kirke's, Carpenter's, Todd and Bow- 
 man's, to say nothing of Suz gUson's and Draper's, 
 should have something superior in the matter or the 
 manner' of its utterance in order to win for itself 
 deserved attention and a name. That matter and 
 that manner, alter a candid perusal, we think dis- 
 tinguish this work, and we are proud to welcome it 
 not merely for its nativity's sake, but for its own 
 intrinsic excellence. Its language we find to be 
 plain, direct, unambitious, and falling with a just 
 conciseness on hyjiothetical or unsettled questions, 
 and yet with sufficient fulness on those livmg topics 
 already understood, or the path to whose solution 
 is definitely marked out. It does not speak exhaust- 
 i /ely upon every subject that it notices, but it does 
 speak suggestively, experimentally, and to their 
 main utilicies, Into the subject of Reproduction 
 our author plunges with a kind of lovmg spirit. 
 Throughout this interesting and obscure department 
 he is a clear and admirable teacher, sometimes a 
 brilliant leader. — Am. Med. Mont/ily, May, 1859. 
 
 DUNGLISON, FORBES, TWEEDIE, AND CONOLLY. 
 THE CYCLOPEDIA OF PKAGTICAL MEDICINE: comprising Treatises on 
 
 the Nature and Treatment of Diseases, Materia Medica, and Therapeutics, Diseases of Women 
 
 and Children, Medical Jurisprudence, &c. &c. In four large super-royal octavo volumes, of 
 
 3254 double-columned pages, strongly and handsomely bound, with raised bands. $12 00. 
 
 *jfc* This work contains no less than four hundred and eighteen distinct treatises, contributed by 
 sixty-eight distinguished physicians, rendering it a complete library of reference for the country 
 practitioner. 
 
 The most complete work on Practical Medicine 
 extant; or, at least, in our language.— Bw/aio 
 Medical and Surgical Journal. 
 
 For reference, it ia above all price to every prac- 
 titioner. — Western Lancet. 
 
 One of the most valuable medical publications of 
 
 the day as a work of reference it is invaluable. — 
 
 Western Journal of Medicine and Surgery. 
 
 It has been to us, both as learner and teacher, a 
 workfor ready and frequent reference, one in which 
 modern English medicine is exhibited in the most 
 advantageous light. — Medical Examiner. 
 
 We rejoice that this work is to be placed within 
 the reach of the profession in this country, it being 
 unquestionably one of very great value to the prac- 
 
 titioner. This estimate of it has not been formed 
 from a hasty examination, but after an intimate ac- 
 
 Suaintance deriVed from' frequent consultation of it 
 uring the past nine or ten years. The editors are 
 practitioners of established reputation, and the list 
 of contributors embraces many of the most eminen 
 
 frofessorsand teachers of London, Edinburgh, Dub- 
 in, and Glasgow. It is, indeed, the great merit of 
 this work that the principal articles have been fur- 
 nished by practitioners who have not only devoted 
 especial attention to the diseases about which they 
 have written, but have also enjoyed opportunities 
 for an extensive practical acquaintance with them, 
 and whose reputation carries the assurance of their 
 competency justly to appreciate the opinions of 
 others, while it stamps their own doctrines with 
 high and just authority. — American Medical Journ. 
 
 DEWEES'S COMPREHENSIVE SYSTEM OF 
 MIDWIFERY. Illustrated by occasional eases 
 and many engravings. Twelfth edition, with the 
 author's last improvements and corrections In 
 one octavo volume, extra cloth, of 600 pages. $3 20, 
 
 DEWEES'S TREATISE ON THE PHYSICAL 
 
 AND MEDICAL TREATMENT OF CHILD- 
 REN. The last edition. In one volume, octavo, 
 extra cloth, 546 pages. $2 80 
 DEWEES'S TREATISE O^ THE DISEASES 
 OF FEMALES. Tenth edition. In one volume, 
 octavo extracloth, 532 pages, with plates. $3 00. 
 
12 
 
 BLANCHARB & LEA'S MEDICAL 
 
 Ei 
 
 DUNGLISON (ROBLEY), M, D,, 
 
 ProfeBSor of Institutes of Medicine in the Jeiferson Medical College, Philadelphia. 
 
 NEW AND ENLARGED EDITION. 
 
 MEDICAL LEXICON; a Dictjona^rj of Medical Science, containing a concise 
 
 Explanation of the various Subjects and Terms of Anatomy, Physiology, Pathology, Hygiene, 
 Therapeutics, Pharmacology, Pharmacy, Surgery, Obsletrics, Medical Jurisprudence, Dentistry, 
 &:c. Notices of Climate and of Mineral "Waters; Formulse for Officinal, Empirical, and Uieietic 
 Preparations, ficc. With French and other Synonymes. Fifteenth edition, revised and very 
 greatly enlarged. In one very large and handsome octavo volume, of992 double-columned pages, 
 in small type ; strongly bound in leather, with raised bands. Price $4 00. 
 
 Especial care has been devoted in the preparation of this edition to render it in every respect 
 worthy a continuance of the very remarkable favor which it has hitherto enjoyed. The rapid 
 pale of Fifteen large editions, and the constantly increasing demand, show that it is regar^^d by 
 the profession as the standard authority. Stimulated by this fact, the author has endeavored in the 
 
 resident revision to introduce whatever might be necessary " to make it a satisfactory and desira- 
 -ile — if not indispensable — lexicon, in which the student may search without disappointment for 
 every term that has been legitimated in the nomenclature of the science." To accomplish this, 
 large additions have been found requisite, and the extent of the author's labors may be estimated 
 from the fact that about Six Thousand subjects and terms have been introduced throughout, ren- 
 dering the whole number of definitions about Sixty Thousand, to accommodate which, the num- 
 ber of pages has been increased by nearly a hundred, notwithstanding an enlargement in the size 
 of thepaffc. The medical press, both in this country and in England, has pronounced the work in- 
 dispensable to all medical students and pr'actitioner^s, and the piesent improved edition will not lose 
 that enviable* reputation. 
 
 The publisher.* have endeavored to render the mechanical execution worthy of a volume of such 
 universal use in daily reference. The greatest care hns been exercised to obtain the typographical 
 accuracy so necessary in a work ol the kind. By the small but exceedingly clear type employed, 
 an immense amount ot matter is condensed in its thousand ample pages, while the binding will be 
 found strong and durable. With all these improvements and enlargements, the price has tneen kept 
 at the former very moderate rate, placmg it within the reach of all. 
 
 This work, the appearance of the iifteenth edition 
 of which, it has become uur duty and pleasure to 
 annnunce, is perhaps the most stupendous monument 
 t)f labor and erudition in medical literature. One 
 would hardly suppose after constant use of the pre- 
 ceding editions, where v/e have never failed to find 
 a sufficiently full explanation of everj medical term, 
 that in this edition ^^ about six thousand subjects 
 and terms have been added,'^ with a careful revision 
 and correction of the entire work. It is only neces- 
 sary to announce the advent of this edition to make 
 it occupy the place of the preceding one on the table 
 of every medical man, as it is without doubt the best 
 and most comprehensive work of the kind wh ich has 
 ever appeared.— fujiTa^o Med.Joum.j Jan. 1858. 
 
 The work is a monument of patient research, 
 skilful judgment, and vast physical labor, that will 
 perpetuate the name of the author more effectually 
 than any possible device of stone or metal. Dr. 
 Dunglison deserves the thanks not only of the Ame- 
 rican profession, but of the whole medical world.— 
 North Am. Medico-Chir. Review^ Jan. 1858. 
 
 A Medical Dictionary better adapted for the wants 
 of the profession than any other with which we are 
 acquainted, and of a character which places it far 
 above comparison and competition. — Am. Journ. 
 Mud. Sciences^ Jan, 1858. 
 
 We need only say, that the addition of 6,000 new 
 terms, with their accompanying definitions, may be 
 said to constitute a new work, by itself. We have 
 examined the Dictionary attentively^ and are most 
 happy to pronounce it unrivalled of its kind. The 
 erudition displayed, and the extraordinary industry 
 which must nave been demanded, in its preparation 
 and perfection, redound to the lasting credit of its 
 author, and have furnished us with a volume indis- 
 pensable at the present day. to all who would find 
 themselves au mveau with the highest standards of 
 medical information. — Boston Medical and Surgical 
 Journal^ Dec, 31, 1857. 
 
 Good lexicons and encyclopedic works generally, 
 are the most labor-saving contrivances which lite- 
 rary men enjoy; and the labor which is required to 
 produce them in the perfect manner of this examnle 
 IS something appalling to contemplate. Tho author 
 
 tells us in his preface that he has added about six 
 thousand terms and subjects to this edition, which, 
 before, was considered univerBally as the best wor^ 
 of the k|nd in any language. — S%llivian^s Journal. 
 March, 1858, * 
 
 He has razed his gigantic structure to the founda- 
 tions, and remodelled and reconstructed the entire 
 pile. No less than six thousand additional subjects 
 and terms are illustrated and analyzed in this new 
 edition, sw^elling the grand aggregate to beyond 
 sixty thousand ! Thus is placetf before the profes- 
 sion a complete and thorough exponent of medical 
 terminology, without rival or possibility of rivalry. 
 — Nashville Journ. of Med. and Surg., Jan. 1858. 
 
 It is universally acknowledge^, we believe, that 
 this work is incomparably the best and most com- 
 plete Medical Lexicon in the English language. 
 The amount of labor which the distinffuished author 
 has bestowed upon it is truly wonderful, and the 
 learning and research displayed in its preparation 
 are equally remarkable. Comment and commenda- 
 tion are unnecessary, as no one at the present day 
 thinks of purchasing any other Medical Dictionary 
 than this. — St. Lou^s Med. and Surg. Journ.. Jan. 
 1858. 
 
 It is the foundation stone of a good medical libra- 
 ry, and should always be included in the first list of 
 books purchased by the medical student.— >l9n. Med, 
 Monthly^ Jan. 1856. 
 
 A very perfect work of the kind, undoubtedly the 
 most perfect in the English language. — Med. and 
 Surg. Reporter, Jan. 1858. 
 
 II is now emphati<jally the Medical Dictionary of 
 the English language, and for it there is no substi- 
 tute.— iV. H, Med. Journ,, Jan. 1858. 
 
 It is scarcely nccsssary to remark that any medi- 
 cal library wanting a copy of Dunglisoh's Lexicon 
 must be imperfect. — Cin. Lai^cet, Jan. 1858. 
 
 We have ever considered jt thebesUuthority pub- 
 lished, and the present edition we may safely say has 
 no equal in the world — Peninsular Mtd. Journal^ 
 Jan. 1858. 
 
 The most complete authority on the subject to be 
 found in any language. — Ya. Med. Journal, Feb. '58. 
 
 BY THE SAIUE AUTHOR. 
 
 THE PRACTICE OF MEDICINE. A Treatise on Special Pathology and The- 
 rapeutics. Third Edition. In two large octavo volumes, leather, of 1,500 pages. $6 25. 
 
AND SCIENT'lFlO PUBLICATIONS. 
 
 13 
 
 DUNGLISON (R.OBLEY), M.D., 
 Professor of Institutes of Medicine in the JefTerBon Medical College, Philadelphia. 
 
 HUMAN PHYSIOLOGY. Eighth edition. Thoroughly revised and exten- 
 
 sively modified and -enlarged, with five hundred and thiriy-two illustrations. In two large and 
 handsomely printed octavo volumes, leather, of about 15G0 pages, f 7 00. 
 In revising this work for its eighth appearance, the author has spared no labor to render it worthy 
 a continuance of the very great favor wnich has been extended to it by the profession. The whole 
 contents have been rearranged, and to a great extent remodelled ; the investigations which of late 
 years have been so numerous and so important, have been carefully examined and incorporated, 
 and the work in every respect has been brought up to a level with the present state of the subject. 
 The object of the author has been to render it a concise but comprehensive treatise, containing the 
 whole body of physiological science, to which the student and man of science can at all times refer 
 with the certainty of finding whatever they are in search of, fully presented in all its aspects; and 
 on no former edition has the author bestowed more labor to secure this result. 
 
 The best work of the kind in the English lan- 
 guage. — SilliTnan's Journitl. 
 
 The present edition the author has made a perfect 
 mirror of the science as it is at the present hour. 
 Ab a work upon physiology proper, the science of 
 the functions performed by the body, the student wil 1 
 find it all lie wisties. — Naskville Journ. of Med. 
 Sept. 1856. 
 
 That he has succeeded, most admirably succeeded 
 in his purpose, is apparent from the appearance of 
 an eighth edition. It is now the great encyclopaedia 
 on the subject, and worthy of a place in every phy- 
 sician's library. — Western Lancet, Sept. 1856. 
 
 We believe that it can truly be said,no'more com- 
 plete repertory of facts upon the subject treated, 
 can anywhere be found. Theauthorhas, moreover, 
 that enviable tact at description and that facility 
 and ease of expression which render him peculiarly 
 acceptable to the casual, or the studious reader. 
 This faculty, so requisite in setting forth many 
 frraver and less attractive subjects, lends additional 
 charms to one always fascinating. — Boston Med. 
 and Surg. Journal, Sept. 1856. 
 
 The most complete and satisfactory system of 
 Physiology in the English language. — Amer. Med. 
 Journal . 
 
 BY THE SAME AUTHOR. (A new edition.) 
 
 GENERAL THERAPEUTICS AND MATERIA MEDIC A j adapted for a 
 
 Medical Text-book-. With Indexes of Remedies and of Diseases and tlieir JJemedies. Sixth 
 Edition, revised and improved. With one hundred and ninety-three illustrations. In two large 
 and handsomely printed octavo vols., leather, of about 1100 pages. $6 00. 
 
 From the Author's Preface. 
 
 " Another edition of this work being called for, the author has subjected it to a thorough and careful 
 revision. It has been gratifying to him that it has been found so extensively useful by those for whom 
 it was especially intended, as to require that a. sixth edition should be issued in so short a time afier 
 the publication of a fifth. Grateful for the favorable reception of ihe work by the profession, he has 
 bestowed on the preparation of the present edition all those cares which were demanded by the 
 former editions, and has spared no pains to render it a faithful epitome of General Therapeutics 
 and Materia Medica. The copious Indexes of Remedies and of Diseases and their Remedies can- 
 not fail, the author conceives, to add materially to the value of the work." 
 
 Tliis work is too widely and too favorably known to require more than the assurance that the 
 author has revised it with his customary industry, introducing whatever has been found necessary 
 to bring it on a level with the most advanced condition of the subject. The number ofillustraiions 
 has been somewhat enlarged, and the mechanical execution of the volumes will be found to have 
 undergone a decided improvement. 
 
 In announcing a new edition of Dr. Dunglison's 
 General Therapeutics and Materia Medica, we have 
 no words of commendation to bestow upon a work 
 whose merits have been heretofore go often and so 
 justly extolled. It must not be supposed, however, 
 that the present is a mere reprint of the previous 
 edition ; tJie character of the author for laborious 
 research, judicious analysis, and clearness of ex- 
 pression, is fully sustained by the numerous addi- 
 tions he has made to the work, and the careful re- 
 vision to which he has subjected the whole. — JV. A. 
 MedicO'Chir. Review, Jan. 1858. , 
 
 BY THE SAME AUTHOR. (A Tiew Edition.) 
 
 NEW KEMEDIES, WITH FORMULA FOR THEIR PREPARATION AND 
 
 ADMINISTRATION. Seventh edition, with extensive Additions. In one very large octavo 
 
 volume, leather,, of 770 pages. $3 75. 
 
 Another edition of the " New Remedies" having been called for, the author has endesvored to 
 add everything of moment that has appeared since the publication of the last edition. 
 
 The articles treated of in the former editions will be found to have undergone considerable ex- 
 pansion in this, in order that the author might be enabled to introduce, as far as practicable, ilie 
 results of the subsequent experience of others, as well as of his own observation and reflection ; 
 and to make the work still more deserving of the extended circulation with which the preceding 
 editions have been favored by the profession. By an enlargement of the page, the numerous addi- 
 tions have been incorporated without greatly increasing the bulk of the volume. — Preface 
 
 One of the most useful of the author's works. — 
 
 The work will, we have littledoubt, be bought 
 and read by the majority of medical students j lis 
 size, arrangement, and reliability recommend it to 
 all; no one, we venture to predict, will study it 
 without profit, and there are fevr to wh()m it will 
 not be in some measure useful as a work of refer- 
 ence. The young practitioner, mo're especially, will 
 find the copious indexes appendid to this edition of 
 great assistance in the selt-ction and preparation of 
 suitable formulae. — Charleston Med. Journ, and Re- 
 view, Jan. 1858. 
 
 Southern Medical and Surgical Journal 
 
 This elaborate and useful volume should be 
 found in every medical library, for as a book of re- 
 ference, for physicians, it is unsurpassed by any 
 other work in existence, and the double index for 
 diseases and for remedies, will be found greatly to 
 enhance its value. — New York Med. Ccaaette. 
 
 The great learning of the author, and his remark- 
 able industry in pushing his researches into every 
 source whence information is derivable, have enabled 
 him to throw together an extensive mass of facts 
 and statements, accompanied by full reference to 
 authorities; which last feature renders the work 
 practically valuable to investigators who desire te 
 examine the original papers. — Tke American Journal 
 of ^JiMrtnac^ . 
 
14 
 
 BLANOHARD & LEA'S MEDICAL 
 
 ERICHSEN (JOHN), 
 ProfesBor of Surgery in ITJiiversity College, London, ftc. 
 
 THE SCIENCE AND AKT OF SURGERY; being A Treatise on Surgical 
 
 Injuries, Diseases, and Operations. New and improved American, from tlie second enlarged 
 
 and carefully revised London edition. Illustrated with over four hundred engravings on wood. 
 
 In one large and handsome octavo volume, of one thousand closely printed pages, leather, 
 
 raised bands. I|4 50. {Now Ready, January, 1859.) 
 
 The very distinguished favor with which this work has been received on both sides of the Atlan- 
 tic has stimulated the author to render it even more worthy of the position which it has So rapidly 
 attained as a standard authority. Every portion has been carefully revised, numerous additions 
 have been made, and the most watchful care has been exercised to render it a complete exponent 
 of the most advanced condition of surgical science. In this manner the work has been enlarged by 
 about a hundred pages, while the series of engravings has been increased by more than a hundred, 
 rendering it one of the most thoroughly illustrated volumes before the profession. The additions of 
 the author having rendered unnecessary most of the notes of the former American editor, but little 
 has been added in this country; some few notes and occasional illustrations have, however, been 
 introduced to elucidate American modes of practice. 
 
 It is, in our humble judgment, decidedly the best 
 book of the kind in the English language. Strange 
 thai just such books are noloAener produced by pub- 
 lic teachers of surgery in this country and Great 
 Britain Indeed, it is a matterof great astonishment. 
 but no le.«s true than astonishing, that of the many 
 works on surgery republished in this country within 
 the last iifleen or twenty years as text-books for 
 medical students, this is the only one that even ap- 
 proximates to the fulfilment of the peculiar wants of 
 youngmen just enteringupon the study of this branch 
 of the profession. — Western Jour. of Mtd. and Surgery. 
 
 Its value is greatly enhanced by a very copious 
 well-arranged ii^dex. We regard this as one of the 
 most valuable contributions to modern surgery. To 
 one entering his novitiate of practice, we regard it 
 the most serviceable guide which he can consult. He 
 wiU iind a futnessof detailleadinghim through every 
 
 step of the operation, and not deserting him until the 
 final issue of the case is decided. — Sethcscope. 
 
 Embracing, as will be perceived, the whole surgi- 
 cal domain, and each division of itself almost com- 
 plete and perfect, each chapter full and explicit, each 
 subject faithfully exhibited, we can only express oui 
 estimate of it m the aggregate. We consider it an 
 excellent contribution to surgery, as probably the 
 best single volume no^v extant on the subject, and 
 with great pleasure we add it to our text-books. — 
 NashmUe Journal of Medicine and Surgery. 
 
 Prof. Erichsen's work, for its size, has not been 
 surpassed; his nine hundred and eight pages, pro- 
 fusely illustrated, are rich in physiological, patholo- 
 gical, and operative suggestions, doctrines, details, 
 and processes ; and will prove a reliable resource 
 for information, both to physician and surgeon, in the 
 hour of peril.— J\r. 0. Med. and Surg. Journal, 
 
 ELLIS (BENJAMIN), M.D. 
 THE MEDICAL FORMULARY : being a Collection of Prescriptions, derived 
 
 from the writings and practice of many of the< most eminent physicians of America and Europe. 
 Together with the usual Dietetic Preparations and Antidotes for Poisons. To which is added 
 an Appendix, on the Endermic use of Medicines, and on the use of Ether and Chloroform. The 
 whole accompanied with a few brief Pharmaceutic and Medical Observations. Tenth edition, 
 revised and much extended by Robert P. Thomas, M. D., Professor of Materia Medica in the 
 Philadelphia College of Pharmacy. In one neat octavo volume, extra cloth, of 'i96 pages. $1 75. 
 
 FOWNES (GEORGE), PH. D., Sic. 
 A MANUAL OF ELEMENTARY CHEMISTRY; Theoretical and Practical. 
 
 From the seventh revised and corrected London edition. With one hundred and ninety-seven 
 illustrations. Edited by Robert Bridges, M. D. In one large royal 12mo. volume, of 600 
 pages. In leather, $1 65 ; extra cloth, $1 50. {Now Readt/, 3a]y, 18!j9.) 
 
 The death of the author having placed the editorial care of this work in the practiced hands of 
 Drs. Bence Jones and A. W. Hoffman, everything has been done in its revision which experience 
 could suggest to keep it on a level with the rapid advance of chemical science. The additions 
 requisite to this purpose have neces^ilated an enlargement of the page, notwithstanding which the 
 work has been increased by about fifty pages. At the same time every care has been us?d to 
 maintain its distinctive character as a condensed manual for the student, divested of all unnecessary 
 detail or mere theoretical speculation. The additions have, of course, been mainly in the depart- 
 ment of Organic Chemistry, which has made such rapid progress within the last few years, but 
 yet equal attention has been bestowed on the other branches of the snbjeot-^hemioal Physics and 
 Inorganic Chemistry— to present all investigations and discoveries of importance, and to keep up 
 the reputation of the volume as a complete manual of the whole science, admirably adapted for the 
 learner. By the use of a small but exceedingly clear type the matter of a large octavo is compressed 
 within the convenient and portable limits of a moderate sized duodecimo, and at the very low price 
 affixed, it is olTered as one of the cheapest volumes before the profession. 
 A few notices of former editions are appended. 
 We know of no better text-book, especially in the 
 difficult department of organic chemistry, upon 
 which it is particularly full and satisfactory. We 
 would recommend it to preceptors as a capital 
 •* office book" for their students who are beginners 
 in Chemistry. It is copiously illustrated with ex- 
 cellent wood-cuts, and altogether admirably "got 
 ap."—!f. J, Medical Reporter. 
 
 A standard manual, which has long enjoyed the 
 reputation of embodying much knowledge in aamall 
 space. The author has achieved the dimcult task of 
 condensation with masterly tact. His book is con- 
 cise without being dry, and brief without being too 
 dogmatical or general .— Virginia Med. arid Surgical 
 Journal. 
 
 The work of Dr. Fownes has long been before 
 the public, and its merits have been fully appreci- 
 ated BB the best text-book on chemistry now in 
 existence. We do not, of course, place it in a rank 
 superior to the works of Brande, Graham, Turner, 
 Gregory, or Gmelin, but we say that, as a work 
 for students, it is preferable to any of them Lon- 
 don Journal of Medicine, 
 
 A work well adapted to the wants of the student 
 It la an excellent exposition of the chief doctrines 
 and facts of modern chemiHtry . The size of the work, 
 and still more the condensed yet perspicuous atyU 
 in which it is written, absolve it from the charges 
 very properly urged against most manuals termed 
 popular. — Edinburgh Journal of Medical Science. 
 
 FI8KE FUND PRIZE ESSAYS. — THE EF- 
 FEOTS OF CLIMATE ON TUBERCULOUS 
 DISEASE. By Edwin Leb,M.R.C.S .London, 
 and THE INFLUENCE OF PREGNANCY ON 
 THE DEVELOPMENT OF TUBERCLES. By 
 
 Edward Wabebn, M.D.,of Edenton.N. C. To- 
 gether in one neat 8vo. volume, extra cloth. $1 00. 
 FRICK ON RENAL AFFECTIONS! their Diag- 
 nosis and Pathology. With illustrations. One 
 volume, royal 12mo., extra cloth. 75 cents. 
 
ANU SCIENTIFIC PUBLICATIONS. 
 
 15 
 
 FERGUSSON (WILLIAM), F. R, S., , 
 
 Professor of Surgery in King's College, X^ondon, &c. 
 
 A SYSTEM OF PRACTICAL SUEGBRY. Pourtli American, from the third 
 
 and enlarged London edition. In one large and beautifully printed octavo volume, ol about 700 
 
 pages, with 393 handsome illustrations, leather. $3 00. 
 
 No work was ever written which more nearly I The addition of many new pages makes this work 
 comprehended the nece'ssities of the student and | more than ever indispensable to the student and prac- 
 
 practitioner, and was more carefully arranged to titioner Ranking's Aistract, 
 
 that single purpose than this.— IV. Y. Med. Journal. \ 
 
 FLINT (AUSTIN), M. D., 
 
 Professor of the Theory and Practice of Medicine in the University of Louisville, &o. 
 
 PHYSICAL EXPLOKATION AND DIAaNOSIS OF DISEASES AFFECT- 
 ING THE RESPIRATORY ORGANS. In one large and handsome octavo volume, extra 
 cloth, 636 pages. $3 00. 
 
 We can only state our general impreesion of the 
 high value of this work, and cordially recommend 
 it to all. NVe regard it, inpointboth of arrangement 
 and of the marked ability of its treatment of the sub- 
 jects, as destined to take the first rank in works of 
 this class. So far as our information extends, it has 
 at present no equal. To the practitioner, as well as 
 the student, it will be invaluable in clearing; up the 
 diagnosis of doubtful cases, and in shedding light 
 npon difficult phenomena. — Buffalo Med. Journal. 
 
 This is the most elaborate work devoted exclu- 
 sively to the physical exploration of diseases of the 
 
 lungs, with which we are acquainted in the English 
 language.— Boston Med. omd Surg. Journal. 
 
 A. work of original observation of the highest merit. 
 We recommend the treatise to every one who wishes 
 to become a correct auscaltator. Based to a very 
 large extent upon cases niimerically examined, it 
 carries the evidence of careful study and discrimina- 
 tion upon every page. It does credit to the author, 
 and, through him, to the profession in this country. 
 It is, what we cannot call every book upon auscul- 
 tation, a readable book.— J.jn. Jour. Med. Sciences. 
 
 BY THE SAME AUTHOR. (In PresS.) 
 
 A PRACTICAL TREATISE ON THE DIAGNOSIS, PATHOLOGY, AND 
 
 TREATMENT OF DISEASES OF THE HEART. In one neat octavo volume, of nearly 
 
 500 pages. 
 
 This important work is now so far advanced that the publishers can promise it with confidence 
 early in the ensuing autumn. The reputation of the author and the attention he has long devoted 
 to this branch of practical medicine, are sufficient guarantee that the present volume will supply the 
 want which has long been felt, of an authoritative treatise on this subject. 
 
 GRAHAM (THOMAS), F.R.S., 
 THE ELEMENTS OP INORGANIC CHEMISTRY, including the Applica- 
 tions of the Science in the Arts. New and much enlarged edition, by Henry Watts and Robert 
 Bridges, M. D. Complete in one large and handsome octavo volume, of over 800 very large 
 pages, with two hundred and thirty-two wood-cuts, extra cloth. $4 00. 
 
 #*^ Part II., completing the work from p. 431 to end, with Index, Title Matter, &c., may be 
 had separate, cloth backs and paper sides. Price $2 50. 
 
 Gentlemen desirous of completing their copies of the work are requested to apply for Part II. 
 without delay. It will be sent by mail, prepaid, on receipt of the amount, f 2 50. 
 
 From Prof. WoUott Gibbs, N. Y. Free Academy, 
 May 25, 1858. 
 
 It is a very acceptable addition to the library of 
 standard boobs of every chemical student. No reader 
 of English works on this science can afford to be 
 without this edition of Prof. Graham's Elements.— 
 Silliman's Journal, March, 1858. 
 
 From Prof. J. L. Orawconr, New Orleans School 
 of Medicine, May 9, 1858. 
 It is beyond all question the best systematic work 
 on Chemistry in the English language, and I am 
 gratifiied to find that an American edition at a mo- 
 derate price has been issued, so as to place it within 
 the means of students. It will be the only text-book 
 I shall now recommend to my class. 
 
 The work is an admirable one in all respects, and 
 its republication here cannot fail to exert a positive 
 influence upon the progress of science in this country. 
 
 From Prof. E. JV. Horsford. Harvard College, Xmi\ 
 27, 1858. 
 
 It has, in its earlier and less perfect editions, been 
 familiar to me, and the excellence of its plan and 
 the clearness and complet'>ness of its discussions, 
 have long been my admiration. 
 
 GRIFFITH (ROBERT E.), M. D., &c. 
 A UNIVERSAL FORMULARY, containing the methods of Preparing and Ad- 
 minlsterinff Officinal and other Medicines. The whole adapted to Physicians and Pharmaceu 
 lists. Second Edition, thoroughly revised, whh numerous additions, by Robeet P. Thomas, 
 M. D., Professor of Materia Medioa in the Philadelphia College of Pharmacy. In one large and 
 handsome octavo volume, extra cloth, of 650 pages, double columns. $3 00; or in sheep, $3 25. 
 
 It was a work requiring much perseverance, and It is one of the mcsl nseful books a country pracii- 
 whenpublished was looked upon as by far the best 
 work of its kind that had issued from the American 
 press. Prof Thomas has certainly "improved," as 
 well as added lo this Formulary, and has rendered it 
 additionally deserving of the confidence of pharma- 
 ceutists and physicians.— Jl»t. Journal of Pharmacy. 
 
 We are happy to announce a new and improved 
 edition of this, one of the most valuable and useful 
 works that have emanated from an American pen. 
 It would do credit to any country, and will be found 
 ofdaily usefulness to practitioners of medicine; it is 
 better adapted lo their purposes than the dispensato- 
 ries. — Southern Med. and Surg. Journal. 
 
 This is a work of six hundred and fifty- one pages, 
 embracing all on the subject of pieparing and admi- 
 nistering medicines that can be desired by the physi 
 cian and pharmaceutist.— Western Lancet. 
 
 Lionercan possibly have in his possession. — Medical 
 Chronicle. 
 
 The amountpf useful, every-day matter, for a prac 
 licinff physician, is really immense. — Bostvn Med. 
 and Surg. Journal. 
 
 This edition of Dr. Griffith's work has been greatly 
 improved by the revision and ample additions of Dr. 
 Thomas, and is now, we believe, one of tlie most 
 complete works of its kind in any laiiguage. The 
 additions amount to about seventy pages, and no 
 effort has been spared to include in them all the re- 
 cent improvements which have been published in 
 medical journals, and systematic treatises. A. work 
 of this kind appears to us indispensable lo the physi- 
 oian^and there is none we can more cordially recom- 
 mend. — JV. Y. Journal of Medixine. 
 
16 BLANCHARD & LEA'S MEDICAL 
 
 GROSS (SAMUEL D.), M. D., 
 
 Professor of Surgery in the Jefieraon Medical College of Philadelphia, Ac. 
 
 ELEMENTS OF PATHOLOGICAL ANATOMY. Third edition, thoroughly 
 
 revised and jB^reatly improved. Id one large and very handsome octavo volume, with about three 
 hundred and fifty beautiful illustrations, of which a larg'e number are from original drawings. 
 Price in extra cloth, f4 75; leather, raised bands, $5 25. {Lately Published.) 
 The very rapid advances in the Science of Pathological Anatomy during the last few years have 
 rendered essential a thorough modification of this work, with a view of making it a correct expo- 
 nent of the present state of the subject. The very careful manner in which this task has been 
 executed, and the amount of alteration which it has undergone, have enabled the author to say that 
 *' with ihe many changes and improvements now introduced, the work may be regarded almost as 
 a new treatise,*' while the efforts of the author have been seconded as regards the mechanical 
 execution of the volume, rendering it one of the handsomest productions of the American press. 
 
 \ye most sincerely congratulate the author on the 
 successful manner in which he has accomplished his 
 prup(>8ed object. His book is most admirably cal- 
 culated to fill up a blank which has long been felt to 
 exist in this department of medical literature, and 
 as such must become very widely circulated amongst 
 all clusees of the profesaion. — Dublin (Quarterly 
 Journ. of Med. Scitnce^ Nov. 1857. 
 
 We have been favorably impressed with the gene- 
 ral manner in which Dr. Gross has executed his task 
 of affording' a comprehensive digest of the present 
 state of the literature of Pathological Anatomy, and 
 have much pleasure in recommending his work to 
 our readers, as we believe one well deserving ot 
 diligent perusal and careful study. — Montreal Med. 
 Chron., Sept. 1857. 
 
 agree with us, that there is no work in the English 
 language which can make any just pretensions to 
 be its equal. — N. Y. Journal of Medicine. 
 
 A volume replete with truths and principles of the 
 utmost value in the investigation of these diseases. — 
 Americcun Medical Journal . 
 
 BY THE SAMS AUTHOR. 
 
 A PRACTICAL TREATISE ON THE DISEASES, INJURIES, AND 
 
 MALFORMATIONS OF THE UKINARY BLADDER, THE PROSTATE GLAND, AND 
 THE URETHRA. Second Edition, revised and much enlarged, with one hundred and eighty- 
 four illi^strations. In one large and very handsome octavo volume, of over nine hundred pages. 
 In leather, raised bands, $5 25 ; extra cloth, $4 75. 
 Philosophical in its design, methodical in its ar- 
 rangement, ample and sound in its practical details, 
 It may in truth be said to leave scarcely anything to 
 be desired on so important a subject. — Boston Med. 
 and Surg Journal. 
 
 Whoever will peruse the vast amount of valuable 
 practical information it contains, will, we think^ 
 
 BY THB SAME AUTHOR. 
 
 A PRACTICAL TREATISE ON FOREIGN BODIES IN THE AIR-PAS- 
 
 SAGES. In one handsome octavo volume, extra eloth, with illustrations, pp. 468. $2 75. 
 BY THE SAME AUTHOR. (Nearly Ready.) 
 
 A SYSTEM OF SURGERY ; Diagnostic, Pathological, Therapeutic, and Opera- 
 tive. With over seven hundred engravings on wood. In two very large octavo volumes. 
 The delay in the appearance of this work has been caused bv the determination of the author to 
 render it what its title purports it to be — a complete System of Surgery in all its branches, to which 
 both student and practitioner can turn with the confidence of finding the information desired on 
 every pjint connected with the subject. In carrying out this object, it has been found necessary 
 to enlarge the size of the work to two very large volumes, which will be found thoroughly illus- 
 trated with many hundred engravings, a large number of which are original. It is now rapidly 
 passing through the press, and will be ready for publication during the summer. 
 
 GRAY (HENRY), F. R. S., 
 
 Lecturer on Anatomy at St. George's Hospital, London, &c. 
 
 ANATOMY, DESCRIPTIVE AND SURGICAL. The Drawings by H. V. 
 
 Carter, M V)., late Demonstrator on Anatomy at St. George's Hospital; the Dissections jointly 
 by the Author and Dr. Carter. In one magnificent imperial octavo Volume, of nearly 800 
 pages, with 363 large and elaborate engravings on wood. Price in extra cloth, $6 25; leather 
 raised bands, $7 00. (Ready this month) 
 
 The author has endeavored in this work to cover a more extended range of subjects than is 
 cui-toraary in the ordinary text-books, by giving not only the details necessary for Ihe student, but 
 also ihe application of those details in the practice of medicine and surgery, thus rendering it both 
 a guide for the learner, and an admirable work of reference tor the active practitioner. The 
 engravings form a special feature in the work, many of them being the size of nature, nearly all 
 original, and having the names of the various parts printed on the body of the cut, in place of figures 
 of reference with descriptions at the foot. They thus form a complete and splendid series, which 
 will greatly assist the student ia obtaining a clear idea of Anatomy, and will also serve to refresh 
 the memory of those who may find in the exigencies of practice the necessity of recalling the de- 
 tails of the dissecting room. Combining, as it does, a complete Atlas of Anatomy, with a thorough 
 treatise on systematic, descriptive, and applied Anatomy, the work will be found of essential use 
 to all physicians who receive students in their offices, relieving both preceptor and pupil of much 
 labor in laying the groundwork of a thorough medical education. Various improvements have been 
 introduced, rendering it superior in iseveral respects to the English edition. 
 
 For t^in truly admirable work the profeBsion 1b 
 indfbied tn ihe diBtinguiBhed author of "Gray on 
 thoSplecn." Tne vacancy it iilla haB been longfelt 
 ti> f\\»t in thJB country. Sir. Gray writea thruuKh- 
 imt with buih brancbes nfhiB subjeut in view. His 
 description of each particular part ib followed by a 
 notice uf its relations to tlie parts with which it is 
 connected, and this, ton, sufficiently ample for all 
 the purpcaefl of the operative Burgeon. After de- 
 scribing the bones and muBcles, be xive% a concise 
 statement of the fractures to which the bonei of 
 
 the extremities are most liable, together with the 
 amount and direction of the displacement ti> which 
 the fragments are subjected by muscular action. 
 The Bectinn on arteries is remarkably full and ac- 
 curate. Not only is the surgical anatomy given to 
 evdry important vessel, with directions for its liga- 
 tion, but at the end of the description of each arte- 
 rial trunk we have a useful summary of the irregu- 
 larities which may occur in its origin, couree, and 
 termination. — N. A. Med. Chir. Review, Mar. 1869. 
 
AND SCIENTIFIC PUBLICATIONS. 
 
 17 
 
 GIBSON (WILLIAM), M. O., 
 
 Late ProfeEsor of Surgery in the Univeraity of Pennsylvania, &o. 
 
 INSTITUTES AND PRACTICE OF SURGERY; being Outlines of a Course 
 
 of Lectures. Eighth edition, improved and altered. With thirty-four plates. In two handsome 
 octavo volumes, containing about 1000 pages, leather, raised bands. $6 50. 
 
 GLUGE (GOTTLIEB), M. D., 
 
 Professor of Physiology and Pathological Anatomy in the University of Brussels, &.G. 
 
 AN ATLAS OF PATHOLOGICAL HISTOLOGY. Translated, with Notes 
 
 and Additions, by Joseph IiEIDY, M. D., Professor of Anatomy in the University of Pennsylva- 
 nia. In one volume, very large imperial quarto, extra eloth, with 320 figures, plain and,colored, 
 on twelve copperplates. $5 00. 
 
 GARDNER'S MEDICAL CHEMISTRY, for the 
 use of Students and the Profession. In one royal 
 ISmn. vol., ex. cloth, pp. 396, with illustrations. 
 SI 00. 
 
 HUGHES' CLINICAL INTRODUCTION TO 
 
 THE PRACTICE OF AUSCULTATION AND 
 OTHER MODES OP PHYSICAL DIAGNOSIS, 
 IN DISEASES OP THE LUNGS AND HEART. 
 Second American, from the second London edition. 
 1 vol. royal 12mo., ex. cloth, pp. 304. $1 00. 
 
 HOBLYN (RICHARD D.), M . D. 
 A DICTIONARY OF THE TERMS USED IN MEDICINE AND THE 
 
 COLLATERAL SCIENCES. A new American edition. Revised, with numerous Additions, 
 by Isaac Hays, M. D., editor ot the " American Journal of the Medical Sciences." In one large 
 royal 12mo. volume, leather, of over 500 double columned pages. $1 50. 
 
 To both practitioner and student, we recommend 
 this dictionary as being convenient in size, accurate 
 in definition, and sufficiently full and complete for 
 ordinary consultation.— CAar2e52on iVfed. Journ. and 
 Review. 
 
 Hoblyn has always been a favorite dictionary, and 
 in its present enlarged and improved form will give 
 greater satisfaction than ever. The American editor. 
 Dr. Hays, has made many very valuable additions. 
 — JV. J. Med. Reporter. 
 
 We know of no dictionary better arranged and 
 adapted . It is not encumbered with the obsolete terms 
 of a bygone age, but it contains all that are now in 
 use ; embracing every department of medical science 
 down to the very latest date. — Western Lcmcet, 
 
 Hoblyn's Dictionary has long been a favorite with 
 us. It is the best book of definitions we have, and 
 ought always to be upon the student's table. — 
 Southern Med. and Surg. Journal. 
 
 HUNTER (JOHN). 
 (See "Ricord," page 26, for Ricord's edition of Hunter on V^enereal.) 
 
 HOLLAND (SIR HENRY), BART., M.D.,F. R. S., 
 
 Physician in Ordinary to the Queen of England, &c. 
 
 MEDICAL NOTES AND REFLECTIONS. From the third London edition. 
 
 In one handsome octavo volume, extra cloth. $3 00. 
 
 HABERSHON (S. O.), M. D., 
 Assistant Physician to and Lecturer on Materia Medica and Therapeutics at Guy's Hospital, &c. 
 
 PATHOLOGICAL AND PRACTICAL OBSERVATIONS ON DISEASES 
 
 OF THE ALIMENTARY CANAL, CESOPHAGUS, STOMACH, C^CUM, AND INTES- 
 TINES. With illustrations on wood. In one handsome octavo volume. (Publishing in the 
 Medical News and Library for 1858 and 185S*.) 
 
 HORNER (WILLIAM E.), M. D., 
 Professor of Anatomy in the University of Pennsylvania. 
 
 SPECIAL ANATOMY AND HISTOLOGY. Eighth editfon. Extensively 
 
 revised and modified. In two large octavo volumes, extra cloth, of more than one thousand 
 pages, handsomely printed, with over three hundred illustrations. $6 00. 
 
 HAMILTON (FRANK H.), M. 6., 
 Professor of Surgery, in Buffalo Medical College, &c. 
 
 A COMPLETE TREATISE ON FRACTURES AND DISLOCATIONS. In 
 
 one handsome octavo volume, with several hundred illustrations. (Preparing for publication 
 in the Autumn q/ 1859.) 
 
 JONES (T. WHARTON), F. R. S., 
 
 Professor of Ophthalmic Medicine and Surgery in University College, London, &c. 
 
 THE PRINCIPLES AND PRACTICE OF OPHTHALMIC MEDICINE 
 
 AND SURGERY. With one hundred and ten illustrations. Second American from the second 
 and revised London edition, with additions by Edwakd Hartshoene, M. D., Surgeon to Wills' 
 Hospital, &c. In one large, handsome royal 12mo. volume, extra cloth, of 500 piiges. f 1 50. 
 
 We are confident that the reader will find, that 
 the work sustains, in every point, the already high 
 reputation of the author as an ophthalmic surgeon 
 as well as a physiologist and pathologist. The 
 book is evidently the result of much labor and re- 
 search, and has been written with the greatest care 
 and attention: it possesses that best quality which 
 a general work, like a system or manual can show, 
 viz; the quality of having all the materials whenoe- 
 aoever derived, so thoroughly wrought up, and di- 
 
 gested in the author's mind, as to come forth with 
 the freshness and impressiveness of an original pro- 
 duction. We entertain little doubt that this book 
 will become what its author hoped it might become, 
 a manual for daily reference and consultation by the 
 student and the general practitioner. The work is 
 marked by that correctness, clearness, and precision 
 of style which distinguish all the productions of the 
 learned author. — BriHsh and For. Med. Review, 
 
18 
 
 BLANCHAKD & LEA'S MEDICAL 
 
 JONES (C. HANDFIELD), F. R. S.> & EDWARD H. SIEVEKING, M.D., 
 
 AsBistant PhysiciaiiB and Lepturers in St. Mary's Hospital, London. 
 
 A MANUAL OF PATHOLOGICAL ANATOMY. First American Edition, 
 
 Revised. "With three hundred and ninety-seven handsome wood engravings. In one large and 
 beautiful octavo volun:ie of nearly 750 pages, leather. f3 75. 
 
 As a concise text-book, containing, in a condensed 
 form, a complete outline of what is known in the 
 domain of Pathological Anatomy, it is perhaps the 
 
 best work in the English language. Its great merit 
 consists in its completeness and orevity, and in this 
 respect it supplies a great desideratum in our lite- 
 rature. Heretofore the student of pathology was 
 obliged to glean from a great number of monographs, 
 and the field was so extensive that but few cultivated 
 it with any degree Of success. As a simple work 
 of reference, therefore, it is of great value to the 
 student of pathological anatomy, and should be in 
 every physician's library. — Western Lancet, 
 
 Tn offering the above titled work to the public, the 
 authors,have not attempted to intrude new views on 
 their profe88i<mal brethren, Itut simply to lay before 
 them, what has long been wanted, an outline of the 
 
 present condition of pathological anatomy. In this 
 they have been completely successful. The work is 
 one of the best compilations which we have ever 
 perused. — Charleston Medical Journal and Review. 
 
 Weurgeupon our, readers and the profession gene- 
 rally the importance of informing themselves in re- 
 gard to modern views of patholpgy, and recommend 
 to them to procure the work before us as the best 
 means of obtaining this information. — Stethoscope. 
 
 From the casual examination we have given we 
 are inclined to regjard it as a text-book, plain, ra- 
 tional, and intelligible, such a book as the practical 
 man needs for daily reference. For this reason it 
 will be likely to be largely useful, as it suits itself 
 to those busy men who have little time for minute 
 investigation, and prefer a summary to an elaborato 
 treatise. — Buffalo Medical Journal, 
 
 KIRKES (WILLIAM SENHOUSE), M. D., 
 
 Demonstrator of Morbid Anatomy at St. Bartholomew's Hospital, &c, 
 
 A MANUAL OF PHYSIOLOGY. ' A new American, from the third and 
 
 improved London edition. With two hundred illustrations. In one large and handsome royal 
 
 12mo. volume, leather, pp. 586. $2 00. {Lately Puhlished.) 
 
 In again passing this work through his hands, the author has endeavored to render it a correct 
 exposition of the present condition oi the science, making such alterations and additions as have 
 been dictated by further experience, or as the progress of investigation has rendered desirable. In 
 every point of mechanical execution the publishers have sought to make it superior to former edi- 
 tions, and at the very low price at which it is offered, it will be found one of the handsomest and 
 cheapest volumes before the profession. > v 
 
 In making these improvements, care has been exercised not unduly to increase its size, thus 
 maintaining its distinctive characteristic of presenting within a moderate compass a clear and con- 
 nected view of its subjects, sufficient for the wants of the student. * 
 
 This is a new and very much improved edition of 
 Dr. Kirkes' well-known Handbook of Physiology. 
 O riginall y constructed on the basis of the admirable 
 treatise of Mutter, it has in successive editions de- 
 veloped itself into an almost original work, though 
 no change has been made in the plan or arrangement. 
 It combines conciseness with completeness, and is, 
 therefore, admirably adapted for consultation by the 
 busy practitioner. — Ditblin Quarterly Journal. 
 
 Its excellence is in its compactness, its clearness, 
 and its carefully cited authorities. It is the most 
 convenient of text-books. These gentlemen, Messrs. 
 Kirkesand Paget, have really an immense talent for 
 silence, which is not so common or so cheap as prat- 
 ing people fancy. They have the gift of telling us 
 what we w^ant to know, without thinking it neces- 
 sary to tell us all they know. — Boston Med. and 
 Surg. Journal. 
 
 One of the ver^ best handbooks of Physiology we 
 possess— presenting just such an outline of the sci- 
 ence, comprising an account of its leading facts and 
 generally admitted principles, as the student requires 
 uring his attendance upon a course of lectures, or 
 for reference whilst preparing for examination.— 
 Am. Medical Journal, 
 
 We need only say, that, without entering into dis- 
 cussions of unsettled questions, it contains all the 
 recent improvements in this department of medical 
 science. For the student beginning this study, and 
 the practitioner who has but leisure to refresh his 
 memory, this book is invaluable, as it contains all 
 that it is important to know, without special details, 
 whifth are read with interest only by those who 
 would make a specialty, or desire to possess a criti- 
 cal knowledge of the subject. — Charteston Medical 
 Journal , 
 
 KNAPP'S TECHNOLOGY: or, Chemistry applied 
 to the Arts and to Manufactures. Edited, with 
 numerous Notes and Additions, by Dr. Esmunb 
 Ronalds and Dr. Thomas Richarhson. First 
 
 American edition, with Notes and Additions, by 
 Prof. Waltbr R. Johnson. In two handsome 
 octavo volumes, extra cloth, with about 500 wood- 
 engravings. S6 UO. 
 
 LUDLOW (J. L.), M. D. 
 
 A MANUAL OF EXAMINATIONS upon Anatomy, Physiology, Surgery, 
 Practice of Medicine, Obstetrics, Materia Medica, Chemistry, Pharmacy, and Therapeutics. To 
 which is added a Medical Formulary. Designed for Students of Mediqine throughout the United 
 States. Third edition, thoroughly revised and greatly extended and enlarged. With three 
 hundred and seventy illustrations. In one larj^e and handsome royal 12mo. volume, leather, of 
 over 800 closely printed pages, (Lately Puhhshed*) f2 50. 
 
 The great popularity of this volume, and I he n umerous demands for it during the two years m which 
 it has been out of print, have induced the author in its revision to spare no pains to render it a 
 correct and accurate digest of the most recent condition of all the branches of medical science. In 
 many respects it may, therefore, be regarded rather as a new book than a new edition, an entire 
 section on Physiology having been added, as also one on Organic Chemistry, and many portions 
 having been rewritten. A very complete series of illustrations has been introduced, and every 
 care has been taken in the mechanical execution to render it a convenient and satisfactory book fof 
 study or reference. 
 
 The arrangement of the volume in the iorm of question and answer renders it especially suited 
 for the office examination of students and for those preparing for graduation. 
 
 We know of no better companion for the student crammed into his head by the various professors to 
 daring the hours spent in the lecture room, or to re- whom he is compelled to listen. — Western Lancetj 
 fresh, at a glance, his memory of the various topics May, 1857. 
 
AND SCIENTIFIC PUBLICATIONS. 19 
 
 LEHMANN (C. G.) 
 PHYSIOLOGICAL CHEMISTRY. Translated from the second edition by 
 
 G-EOEGE E. Day, M. D., F. K. S., &c., edited by R. E. Rogers, M. D., Professor of Chemistry 
 in the Medical Department of the University of Pennsylvania, with illustrations selected from 
 Funke's Atlas of Physiological Cheinistry, and an Appendix of plates. Complete in two large 
 and handsome octavo volumes, extra cloth, containing 1200 pages, with nearly two hundred illus- 
 trations. $6 00. 
 
 This great work, universally acknowledged as the most complete and authoritative exposition of 
 the principles and details oi Zoochemistry, in its passage through the press, has received from 
 Professor Rogers such care as was necessary to present it in a correct and reliable form. To such 
 a work additions were deemed superfluous, but several years having elapsed between the appear- 
 ance m Germany of the first and last volume, the latter contained a supplement, embodying nume- 
 rous corrections and additions resulting from the advance of the science. These have all been incor- 
 porated in the text in their appropriate places, while the subjects have been still furtfter elucidated by 
 the insertion of illustrations from the Atlas of Dr. OttoFunke. With the view of supplying the student 
 with the means of convenient comparison, a large number of wood-cuts, from works on kindred 
 subjects, have also been added in the form of an Appendix of Plates. The work is, therefore, pre- 
 sented as in every way worthy the attention of all who desire to be familiar ■^ith the modern facts 
 and doctrines of Physiological Science. 
 
 The most important contribution as yet made to 
 Physiological Chemistry Am. Journal Med. Sci- 
 ences, Jan. 1856. 
 
 it treats. — Edinburgh Monthly Journal of Medical 
 Science. 
 
 Already well known and appreciated by the scien- 
 tific world, Professor Lehmann's great work re- 
 quires no laudatory sentences, as, under a new garb, 
 it is now presented to us. The little space at our 
 command would ill suffice to set forth even a small 
 portion of its excellences. — Boston Med. and Surg. 
 Journal, Dec. 1855. 
 
 The present volumes belong to the small class of 
 medical literature which comprises elaborate works 
 of thehighest order of merit. — Montreal Med. Chron- 
 icle, Jan. 1856. 
 
 The work of Lehmann stands unrivalled as the 
 most comprehensive book of reference and informa- 
 tion extant on every branch of the subject on which 
 
 BY THE SAME AUTHOR. (Latety Published.) 
 
 MANUAL OP CHEMICAL PHYSIOLOaY. Translated from the German, 
 
 with Notes and Additions, by J. Cheston Morris, M. D., with an Introductory Essay on Vital 
 Force, by Sabiuel Jackson, M. D., Professor of the Institutes of Medicine in the University of 
 Pennsylvania. With illustrations on wood. In one very handsome octavo volume, extra cloth, 
 of 336 pages. $2 25. 
 
 From Prof. Jac&son^s Introductory Essay, 
 In adopting the handbook of Dr. Lehmann as a manual of Organic Chemistry for the use of the 
 students of the University, and in recommending his original work of Physiological Chemistry 
 for their more mature studies, the high value of his researches, and the great weight of his autho- 
 rity in that important department of medical science are fully recognized. 
 
 LAWRENCE (W.), F. R. S., &o. 
 A TREATISE ON DISEASES OP THE EYE. A new edition, edited, 
 
 with numerous additions, and 243 illustrations, by Isaac Hays, M. D., Surgeon to Will's Hospi- 
 tal, &c. In one very large and handsome octavo volume, of 950 pages, strongly bound in leather 
 with raised bands. $5 00. 
 
 This admirable treatise— the safest guide and most 
 eompreh'ensive work of reference, which is within 
 the reach of the profession. — Stethoscope. 
 
 This standard text-book on the department of 
 "whieh it treats, has not been superseded, by any or 
 all of the numerous publications on the subject 
 heretofore issued. Nor with the multiplied improve- 
 ments of Dr. Hays, the American editor, is it at all 
 
 likely that this great work will eease to merit the 
 confidence and preference of students or practition- 
 ers. Its ample extent — nearly one thousand large 
 octavo pages— has enabled both author and editor to 
 do justice to all the details of this subject, and con- 
 dense in this single volume the present state of our 
 knowledge of the whole science in this department, 
 whereby its practical value cannot be excelled — N. 
 Y. Med. Qax. 
 
 LAYCOCK (THOMAS), M. D., F. R. S. E., 
 
 Professor of Practical and Clinical Medicine in the University of Edinburgh, &c. 
 
 LECTURES ON THE PRINCIPLES AND METHODS OP MEDICAL 
 
 OBSERVATION AND RESEARCH. For the Use of Advanced Students and Junior Prac- 
 titioners. In one very neat royal 12mo. volume, extra cloth. Price $1 00. 
 
 LALLEMAND AND WILSON. 
 A PRACTICAL TREATISE ON THE CAUSES, SYMPTOMS, AND 
 
 TREATMENT OF SPERMATORRHCEA. By M. Lallemand. Translated and edited by 
 
 Hehry J MoDougall. Third American edition. To which is added ON DISEASES 
 
 OF THE VESICUL.^ SEMINALES; and their associated organs. With special refer- 
 ence to the Morbid Secretions of the Prostatic and Urethral Mucous Membrane. By Harris 
 i Wilson, M.D. In one neat octavo volume, of about 400 pp., extra cloth. $2 00. {Just Issued.) 
 Although the views of M. Lallemand on Spermatorrhoea hove unquestionably exercised a very 
 great influence, and the treatment advocated by him has been very generally adopted, still, a num- 
 ber of years having elapsed since his work was given to the world, the publishers have thought that 
 the value of the present edition would be enhanced by the addition of 'he little treatise of Dr. 
 Marris Wilson. In it the causes of the dilTerent varieties of Spermatorrhosa are investigated with 
 the aid of modern pathology, from which, combined with the most recent experience of the pro- 
 fession, the attempt is made to deduce a rational system of curative treatment. Whatever defi- 
 ciencies may have been caused in the work of M. Lallemand by the progress of medical science, will, 
 it is hoped, be in this manner supplied. 
 
20 
 
 BLANCHARD & LEA'S MEDICAL 
 
 LA ROCHE (K.), M, D., &c. 
 YELLOW FEVER, considered in its Historical, Pathological, Etiological, and 
 
 Therapeutical Relations. Including a Sketch of the Disease as it has occurred in Philadelphia 
 from 1699 to 1854, with an examination of the connections between it and the fevers known under 
 the same name in other parts of temperate as well as in tropical regions. In two large and 
 handsome octavo volumes of nearly 1500 pages, extra cloth. $7 GO, 
 From Professor S. H. Dickson^ Charleston^ S. C, 
 September 18, 1855, 
 
 A monument of intelligent and well applied re- 
 search, almost without example. It ie, mdeed, in 
 itself, a large library, and is destined to constitute 
 the special resort as a book of reference, in the 
 subject of which it treats, to all future time. 
 
 We have not time at present, engaged as ^ve are, 
 by day and by night, in the work of combating this 
 very disease, now prevailing in our city, to do more 
 than give this cursory notice of what we consider 
 as undoubtedly the most able and erudite medical 
 publication our country has yet produced. But in 
 view of the startling fact, that this, the most malig- 
 nant and unmanageable disease of modern times, 
 has for several years been prevailing in our country 
 to a greater extent than ever before,* that it is no 
 longer confined to either large or small cities, but 
 
 genetrates country villages, plantations, and farm- 
 ouses ; that it is treateawith scarcely better suc- 
 cess now than thirty or forty years ago | that there 
 is vast mi Echief done by ignorant pretenders to know- 
 ledge in regard to the disease, and in view of the pro- 
 bability that a majority of southern physicians will 
 be called upon to treat the disease, we trust that this 
 able and comprehensive treatise will he very gene- 
 rajly read in the south. — Memphis Med. Recorder. 
 This is decidedly the great American medical work 
 of the day — a fall, complete, and systematic treatise, 
 unequalled by any other upon the all-important sub- 
 ject of Yellow Fever. The laborious, indefatigable, 
 and learned author has devoted to it many years of 
 
 arduous research and careful study, and the result 
 is such as will reflect the highest honor upon the 
 author and our country.— Southern Med, and Surg. 
 Journal. 
 
 The genius and scholarship of this great physician 
 could not have been better employed than In th^ 
 ereetionof this towering monument to his own fame, 
 and to the glory of the medical literature of his own 
 country. It is destined to remain the great autho- 
 rity upon the subject of VoUow Fever, The student 
 and physician will find in these volumes a riswni 
 of the sum totul of the knowledge of the world upon 
 the awful scourge which they so elaborately discuss. 
 The style is so soft and so pure as to refresh and in- 
 vigorate the mind while absorbing the thoughts of 
 the gifted author, while the publishers have suc- 
 ceeded in bringing the externals into a most felicitouB 
 harmony with the inspiration that dwells within. 
 Take it all in all, it is a book we have often dreamed 
 of, but dreamed not that it would ever meet our 
 waking eye as a tangible Tesility. —Nashville Journal 
 of Medicine. 
 
 We deem it fortunate that the splendid work of 
 Dr. La Roche should have been issued from the press 
 at this particular time. The want of a reliable di- 
 gest of all that is known in relation to this frightful 
 malady has long been fel t — a want very satisfactorily 
 met in the worK before us. We deem it but faint 
 praise to say that Dr. La Rcche has succeeded in 
 presenting the profession with an able and complete 
 monograph, one which will find its way into every 
 well ordered library. — Va. Stethoscope. 
 
 BY THE SAME AUTHOR. 
 
 PNEUMONIA ; its Supposed Connection, Pathological and Etiological, with Au- 
 tumnal Fevers, including an Inquiry into the Existence and Morbid Agency of Malaria. In one 
 handsome octavo volume, extra cloth, of 500 pages. $3 00. 
 
 MILLER (HENRY), M. D., 
 
 Professor of Obstetrics and Diseases of Women and Children in the University of Louisville. 
 
 PRINCIPLES AND PRACTICE OF OBSTETRICS, &c. ; including the Treat- 
 ment of Chronic Inflammation of the Cervix and Body of the Uterus considered as a frequent 
 cause of Abortion. With about one hundred illustrations on wood. In one very handsome oc- 
 tavo volume, of over 600 pages. (Lately Published.) $3 75. 
 
 The reputation of Dr. Miller as an obstetrician is loo widely spread to require the attention oi 
 the profession to be specially called to a volume containing the experience of his long and extensive 
 practice. The very favorable reception accorded to his " Treatise on Human Parturition," issued 
 some years since, is an earnest that tlie present work will fulfil the author's intention of providing 
 within a moderate compass a complete and trustworthy text-book for the student, and book of re- 
 ference for the practitioner. 
 
 We congratulate the author that the task is done. 
 We congratulate hinj that he has given to the medi- 
 cal public a work which will secure for him a high 
 and permanent position among the standard autho* 
 rities 6n the principles and practice of obstetrics. 
 Congratulations are not less due to the medical pro- 
 fession of this country, on the acquisition of a trea- 
 tise embodying the results of the studies, reflections, 
 and experience of Prof. Miller. Few men, if any, 
 in this country, are more competent than he to write 
 on thisdepartmentof medicine. Engaged for thirty- 
 five years in an extended practice of obstetrics, for 
 many years a teacher of this branch of instruction 
 in one of the largest of our institutions, a diligent 
 student as well as a careful observer, an originafand 
 independent thinker, wedded to no hobbies, ever 
 ready to consider without prejudice new views, and 
 to adopt innovations if they are really improvements, 
 and withal a clear, agreeable writer, a practical 
 treatise from his pen could not fail to possess great 
 value.— TJtt^aJo Med Journal^ Mar. 1858. 
 
 In fact, this volume must take its place among the 
 standard systematic treatises on obstetrics ; a posi- 
 
 tion to which its merits justly entitle it. The style 
 is such that the descriptions are clear, and each sub- 
 ject is discussed and elucidated with due regard to 
 its practical bearings, which cannot fall to make it 
 acceptable and valuable to both students and prac- 
 titioners. We cannot, however, close this brief 
 notice without congratulating the author and the 
 profession on the production of such an excellent 
 treatiee. The author is a western man of whom we 
 feel proud, and we cannot but think that his book 
 will find many readers and warm admirers wherever 
 obstetrics is taught and studied as a science and an 
 art. — The Cincirmati Lancet and Observer^ Feb. 1858. 
 A most respectable and valuable addition to our 
 home medical literature, and one reflecting credit 
 alike on the author and the institution to which he 
 is attached. The student will find in this work a 
 most useful guide to his studies; the country prac- 
 titioner, rusty in his reading, can obtain from its 
 pages a fair resurafe of the modern literature of the 
 science; and we hope to see thisAmericnn produc- 
 tion generally consulted by the profession. — Va. 
 Med. Journal. Feb. 1858. 
 
 MAYNE'S DISPENSATORY AND THERA- 
 PEUTICAL REMEMBRANCER. Comprising 
 the entire lists of Materia Aledica, with every 
 Practical Formula contained in the three British 
 Pharmacopoeias. Edited, with the addition of the 
 FormulBB of the U. S. Pnarmacopeeia, by R. E. 
 Griffith, M.D. llSmo. vol. ex. cl. ,300pp. 75 c. 
 
 MALGAIGNE'S OPERATIVE SURGERY, baaed 
 on Normal and Pathological Anatomy. Trans- 
 lated from the French by Frederick BrittaHi 
 A.B.,M.D. WithnumerouB illustrations on wood. 
 In one handsome octavo volume, extra cloth, r f 
 nearly six hundred pages. 89 36. 
 
AND SCIENTIFIC PUBLICATIONS. 
 
 '21 
 
 MEIGS (CHARLES D.), IVI. O., 
 Professor of Obstetrics, &c. in the Jefferson Medical College, Philadelphia. 
 
 OBSTETRICS : THE SCIENCE AND THE ART. Third edition, revised 
 
 and improved. With one hundred and twenty-nine illustrations. In one beautifully printed octavo- 
 , volume, leather, of seven hundred and fifty-two large pages. $3 75. 
 
 The rapid demand for another edition of this work is a sufficient expression of the favorable 
 verdict of the profession. In thus preparing it a third time for the press, the author has endeavored 
 to render it in every respect worthy of the favor which it has received. To accomplish this he 
 has thoroughly revised it in every part. Some portions have been rewritten, others added, new 
 illustrations have been in many instances substituted for such as were not deemed satisfactory, 
 while, by an alteration in the typographical arrangement, the size of the work has not been increased, 
 and the price remains unaltered. In its present improved form, it is, therefore, hoped that the work 
 will continue to meet the wants of the American profession as a sound, practical, and extended 
 System of Midwifert. 
 
 Though the work has received only five pages of 
 enlargement, its chapters throughout wear the im- 
 press of careful revision. Expunging and rewriting, 
 Temodelling its sentences, with occasional new ma- 
 terial, all evince a lively desire that it shall deserve 
 to be regarded as improved in vnanner as well as 
 matter. In the matter, every stroke of the pen has 
 increased the value of the book, both in expungings 
 and additions — Western Lancet, Jan. 1857. 
 
 BY THE SAME AUTHOH.. 
 
 The best American work on Midwifery that is 
 accessible to the student and practitioner — N. W. 
 Med. and Surg. Journal, Jan. 1857. 
 
 This is a standard work by a great American Ob- 
 stetrician. It is the third and last edition, and, in 
 the Iai]g:uage of the preface, the author has "brought 
 the subject up to the latest dates of real improve- 
 ment in our art and Science." — Nashville Jowrn. of 
 Med. and Surg., May, 1857. 
 
 (Now Keady, June, 1859.) 
 
 WOMAN: HER DISEASES AND THEIR REMEDIES. A Series of Lee- 
 
 tures to his Glass. Fourth and Improved edition. In one large and beautifully printed octavo 
 
 volume, leather, of over 700 pages. $3 60. 
 
 The gratifying appreciation of his labors, as evinced by the exhaustion of three large impressions 
 of this work has not been lost upon the author, who has endeavored in every way to render it 
 worthy of the favor with which it has been received. The opportunity thus afforded for another 
 revision has been improved, and the work is now presented as in every way superior to its pre- 
 decessors, additions and alterations having been made whenever the advance ol science has ren- 
 dered them desirable. The typographical execution of the work will also be found to have under- 
 gone a similar improvement, and the volume, it is hoped, will be found in all respects worthy to 
 maintain its position as the standard American text-book on the Diseases of Females. 
 
 A few notices of the previous editions are appended. 
 
 In other respects, in our estimation, too much can- 
 not be said in praise of this work. Ic abounds with 
 beautiful passages, and for conciseness, for origin- 
 ality, and for all that is commendable in a work on 
 the diseases of females, it is not excelled, and pro- 
 bibly not equalled in the English language. On the 
 whole, we know of no worK on the diseases of wo- 
 men which we can so cordially commend to the 
 student bnd practitioner as the one before us. — Ohio 
 Med. and Surg. Journal. 
 
 The body of the book is worthy of attentive con- 
 sideration, and is evidently the production of a 
 clever, thoughtful, and sagacious physician. Dr. 
 Meigs's letters on the diseases of the external or- 
 gans, contain many interesting and rare cases, and 
 many instructive observations. We take our leave 
 of Dr. Meigs, with a high opinion of his talents and 
 originality.— r/»8 British and Foreign Medico-Chi- 
 rurgical Review. 
 
 Every chapter is replete with practical instruc- 
 tion, and bears the impress of beirtg the composition 
 of an acute and experienced mind. There is a terse- 
 ness, and at the same time an accuracy in his de- 
 scription of symptoms, and in the rules for diagnosis, 
 which cannot fail to recommend the volume to the 
 attention of the reader. — Ranking^s Abstract. 
 
 Itcontains a vast amount of practical knowledge, 
 by one who has accurately observed and retained 
 the experience of many years, and who tells the re- 
 sult in a free, familiar, and pleasant manner. — Dub' 
 lin Quarterly Journal. 
 
 BY THE SAME AUTHOR. 
 
 ON THE NATURE, SiaNS, AND TREATMENT OF CHILDBED 
 
 FEVER. In a Series of Letters addressed to the Students of his Class. In one hfendsome 
 octavo volume, extra cloth, oi 365 pages. $2 50. 
 
 Full of important matter, conveyed in a ready and 
 agreeable msLnner.— St. Louis Med. and Surg. Jour. 
 
 There is an off-hand fervor, a glow, and a warm- 
 beartedness infecting the elTjrt of Dr. Meigs, which 
 is entirely captivating, and which absolutely hur- 
 ries th« reader through from beginning to end. Be- 
 sides, the book tec;ms with solid instruction, and 
 it shows the very highest evidence of ability, viz., 
 the clearness with which the information is pre- 
 sented. We know of no better test of one's imder- 
 Btanding a subject than the evidence of the power 
 of lucidly explaining it. The most elementary, as 
 well as the obscurest subjects, under the pencil of 
 Prof. Meigs, are isolated and made to stand out in 
 such bold relief, as to produce distinct impressions 
 upon the mfnd and memory of the reader. — The 
 Charleston Med. Journal. 
 
 Professor Meigs has enlarged and amended this 
 great work, for such it unquestionably is, having 
 passed the ordeal of criticism at home and abroad, 
 but been improyed thereby ; for in this new edition 
 the author has introduced real improvements, and 
 increased the value and utility of the book im- 
 measurably. It presents so many novel, bright, 
 and sparkling thoughts; such an exuberance of new 
 ideas on almost every page, that we confess our- 
 selves to have become enamored with the book 
 and its author j and cannot withhold our congratu- 
 lations from our Philadelphia confreres, that such a 
 teacher is in their service. — N. Y. Med. Gazette. 
 
 us. It is a delectable book. * * * This treatise 
 upon chiid-bed fevers will have an extensive sale, 
 being destined, as it deserves, to find a place in the 
 library of every practitioner who scorns to lag in the 
 rear. — Nashville Journal of Medicine and Surgery. 
 
 The instructive and interesting author of this 
 work, whose previous labors in the department of 
 medicine which he so sedulously cultivates, have 
 placed his countrymen under deep and abiding obli- 
 gations, again challenges their admiration in the 
 fresh and vigorous, attractive and racy pages before 
 
 BY THE SAME AUTHOR J WITH COLORED PLATES. 
 
 A TREATISE ON ACUTE AND CHRONIC DISEASES OF THE NECK 
 
 OF THE UTERUS. With numerous plates, drawn and colored from nature in the highest 
 style ot art. In one handsome octavo volume, extra cloth. $4 50. 
 
22 
 
 BliANCHARD & LEA'S MEDICAL 
 
 MACLISE (JOSEPH), SUHGEON. 
 SUECrlCAL ANATOMY. Forming one volume, very large imperial quarto. 
 
 With sixty-eight large and splendid Plates, drawn in the best style and beautifully colored. Con- 
 taining one hundred and ninety Figures, many of them the size of life. Together with copious 
 and explanatory letter-press. Strongly and handsomely bound in extra clotn, being one of the 
 cheapest and best executed Surgical works as yet i&sued in this country. $11 00. 
 *^* The size of this work prevents its transmission through the post-office as a whole, but those 
 
 who desire to have copies forwarded by mail, can receive them in five parts, done up in stout 
 
 wrappers. Price $9 00. 
 
 One of the greatest artistic triumphe of the age 
 in Surgical Anatomy. — British American Medical 
 Journal. 
 
 Too mach cannot be said in its praise; indeed, 
 we have not language to do it juBtice. — Ohio Medi- 
 cal and Surgical Journal, 
 
 The most admirable surgical atlas we have seen, 
 To the practitioner deprived of demonstrative dis- 
 sections upon the human subject, it la an invaluable 
 companion. — N, J. Medical Reporter. 
 
 The most accurately engraved and beautifully 
 colored plates we have ever seen in an American 
 book — one of the best and cheapest surgical works 
 ever published. — Buffalo Medical Journal. 
 
 It is very rare that so elegantly i)rinted, so well 
 illustrated, and so useful a work, is offered at so 
 moderate a price. — Charleston Medical Journal. 
 
 Its plates can boast a superiority which places 
 them almost beyond the reach of competition. — Medi' 
 cal Examiner. 
 
 No such lithographic illustrations of surgical re- 
 gions have hitherto, we think, been given. — Boston 
 Medical and Surgical Journal. 
 
 As a surgical anatomist, Mr. Maclise has proba- 
 bly no superior. — British €md Foreign Medico-Chi- 
 rvrgical Revieto. 
 
 Of great value to the student engaged in dissect- 
 ing, and to the surgeon at a distance from the means 
 of keeping up his anatomical knowledge. — Medical 
 Times. 
 
 A work which has no parallel in point of accu- 
 racy and cheapness in the English language. — N. Y. 
 Journal of Medicine. 
 
 Country practitioners will find these plates of im- 
 mense value. — N, Y. Medical Gazette. 
 
 We are extremely gratified to announce to the 
 profession the completion of this truly magnificent 
 work, which, as a whole,, certainly stands unri- 
 valled, both for accur-acy of drawing, beauty of 
 coloring, and all the requisite explanations of the 
 subject in hand. — The New Orleans Medical and 
 Surgical Journal. 
 
 This is by far the ablest work on Surgical Ana- 
 tomy that has come under our observation. We 
 know of no other work that would justify a stu- 
 dent, in any degree, for neglect of actual dissec- 
 tion. In those sudden emergencies that so often 
 arise, and which require the instantaneous command 
 of minute anatomical knowledge, a work of this kind 
 keeps the details of the dissecting-room perpetually 
 fresn in the memory. — The Western Journal of Medi- 
 cine and Surgery. 
 
 MORLAND (W. W.), M. D, 
 
 Fellow of the Massachusetts Medical Society, &c. * 
 
 DISEASES OF THE UEINABY OEGANS; a Compendium of their Diagnosis, 
 
 Pathology, and Treatment. With illustrations. In one large and handsome octavo volume, ot 
 
 about 600 pages, extra cloth. (Just Issued.) $3 50. 
 
 This volume, it is hoped, will supply the want of a work presenting within convenient compass 
 the whole subject of the diseases to which all the urinary organs are liable, with their treatment, 
 both medical and surgical. The aim of the author has been throughout to condense the results of 
 the most recent investigations in a clear and succinct manner, omitting nothing of practical im- 
 portance, without, at the same time, embarrassing the student with unnecessary speculations. 
 Various elaborate and important worlcs have recently appeared on different departments of the 
 subject, but none, it is believed, which thoroughly covers the whole ground in the manner which 
 Dr. Morland has attempted. 
 
 Taken as a whole, we can recommend Dr. Mor- 
 land's compendium as a very desirable addition to 
 the library of every medical or surgical practi- 
 tioner.— ^ni.owrf For. iHed.-CAir. iZev., April, 1859. 
 
 Every medical practitioner whose attention has 
 been to any extent attracted towards the class of 
 diseases to which this treatise relates, must have 
 often and sorely experienced the want of some full, 
 yet concise rncent compendium to which he could 
 refer. This desideratum has been supplied by Dr. 
 Morland, and it has been ably done. He has placed 
 before us a full, judicious, and reliable digest. 
 Each subject is treated with sufficient minuteness, 
 
 yet in a succinct, narrational style, such as to retder 
 the work one of great interest, and one which will 
 prove in the highest degree useful to the general 
 practitioner. To the members of the profession in the 
 country it will be peculiarly valuable, on account 
 of the characteristics which we have mentioned, 
 and the one broad aim of practical utility which is 
 kept in view, and which shines out upon every page, 
 together with the skill which is evinced in the com- 
 bination of this grand requisite with the utmost 
 brevity which a just treatment of the subjects would 
 admit. — JV. Y". Journ. of Medicine, Nov. 1858. 
 
 MACKENZIE (W.), M. D., 
 
 Surgeon Oculist in Scotland in ordinary to Her Majesty, &.c.&c. 
 
 A PKACTICAL TKBATI8E ON DISEASES AND INJUKIES OP THE 
 
 EYE. To wMoh is prefixed an Anatomical Introduction explanatory ol a Horizontal Section ol 
 the Hnman Eyeball, by Thomas Wharton Jones, W. R. S. From the Fourth Revised and En- 
 larg-ed London Edition. With Notes and Additions by Addinell Hewson, M.D., Surgeon to 
 Wills Hospital, &o. &o. In one very large and handsome octavo volume, leather, raised bands, with 
 plates and numerous wood-cuts. $5 25. 
 
 The treatise of Dr. Mackenzie indieputably holds 
 the firstplaee, and forms, in respect of learning and 
 research, an Encyclopedia unequalled in extent by 
 any other woric of theKlnd, either £!nglish or foreign. 
 Dixon on Diseases of the Eye. 
 
 Few modern boolcs on any department of medicine 
 or surgery hare met with such extended circulation, 
 or have procured for their authors a like amount of 
 European celebrity. The immense research which 
 it displayed, the thorough acquaintance with the 
 ■ubiect. oracticallv as well as theoretically , and the 
 
 able manner in which the author's stores of learning 
 and experience were rendered available for general 
 use, at once procured for the first edition, as well on 
 the continent as in this country, that high position 
 as a standard work which each successive edition 
 has more firmly established. We consider it the 
 duty of every one who has the love of his profession 
 and the welfare of his patient at heart, to make him- 
 self familiar with this the most complete work in 
 the English language upon the diseases of the eye, 
 — Mei, Times and Gazette. 
 
AND SCIENTIFIC P U'BLIC ATIONS. 
 
 23 
 
 MILLER (JAMES), F. R, S. E., 
 ProfesBor of Surgery in the University of Edinburgli, &c. 
 
 PRINCIPLES OP SURGERY. Fourth American, from the third and revised 
 
 Edinburgh edition. In one large and very beautiiul volumej leather, of 700 pages, with two 
 hundred and forty illustrations on wood. $3 75. 
 
 putation, or seeks the interests of hia clients, can 
 acquit himself before his God and the world without 
 making: himself familiar with the sound and philo- 
 sophical views developed in the foresfoing book. — 
 New Orleans Med. and Surg. Journal. 
 
 Without doubt the ablest exposition of the prin- 
 ciples of that branch of the healing art in any lan- 
 guage. This opinion, deliberately formed after a 
 careful study of the first edition, we have had no 
 cause to change on examining the second. This 
 edition has undergone thorough revision by the au- 
 thor ; many expressions have been modified, and a 
 mass of new matter introduced. The book is got up 
 in the finest style, and is an evidence of the progress 
 of typography in pur country. — Charleston Medical 
 Journal and Review. 
 
 The work of Mr. Miller is too well and too favor- 
 ably known among us, as one of oar best text-books, 
 to render any further notice of it necessary than the 
 announcement of a new edition, the fourth in our 
 country, a proof of its extensive circulation among 
 us. As a concise and reliable exposition of the sci- 
 ence of modern surgery, it stands deservedly high— 
 we know not its superior. — Boston Med. and Surg. 
 Journal . 
 
 It presents the most satisfactory exposition of the 
 modern doctrines of the principles of surgery to be 
 found in any volume in any language. — JV. Y. Journal 
 of Medicine. 
 
 The work takes rank with Watson's Practice of 
 Physic; it certainly does not fall behind .that great 
 work in soundness of principle or depth of reason- 
 ing and research. No* physician who values hia re- 
 
 BY THE SAME AUTHOR, {Just Issued.) 
 
 THE PRACTICE OF SURGERY. Fourth American from the last Edin- 
 burgh edition. Revised by the American editor. Illustrated by three hundred and sixty- four 
 engravings on wood. In one large octavo volume, leather, of nearly 700 pages. $3 75. 
 
 No encomium of ours could add to the popularity 
 of Miller's Surgery. Its reputation in this country 
 Is unsurpassed by that of any other work, and, when 
 taken in connection with the author's Principles of 
 Surgery^ constitutes a whole, without reference to 
 to which no conscientious surgeon would be willing 
 practice his art. — Southern Med. and Surg. Journal . 
 
 It is seldom that two volumes have ever made so 
 profound an impression in so short a time as the 
 "Principles" and the "Practice" of Surgery by 
 Mr. Miller — or so richly merited the reputation they 
 have acquired. The author is an eminently sensi- 
 ble, practical, and well-informed man, who knows 
 exactly what he is talking about and exactly how to 
 talk it. — Kentucky Medical Recorder. 
 
 By the almost unanimous voice of the profession, 
 
 hia works, both on the principles and practice of 
 surgery have been assigned thehighest rank. If we 
 were limited to but one work on surgery, that one 
 should be Miller's, as we regard it as superior to all 
 others. — iS;. Lowis Med. and Surg. Journal. 
 
 The author has in this and his " Principles," pre- 
 sented to the profession one of the most complete and 
 reliable systems of Surgery extant. His style of 
 writing is original, impressive, and engaging, ener- 
 getic, concise, and lucid. Few have the faculty of 
 condensing so much in small space, and at the same 
 time so persistently holding the attention. Whether 
 as a text-book for students or a book of reference 
 for practitioners, it cannot be too strongly recom- 
 mended. — Southern Journal of Med. and Physical 
 Sciences. 
 
 MONTGOMERY (W. F.), M . D., M . R. I. A., &c., 
 
 Professor of Midwifery in the King and Queen's College of Physicians in Ireland, &c. 
 
 AN EXPOSITION OP THE SIGNS AND SYMPTOMS OP PREGNANCY. 
 
 With some other Papers on Subjects connected with Midwifery. From the second and enlarged 
 English edition. With two exquisite colored plates, and numerous wood-cuts. In one very 
 handsome octavo volume, extra clolh, of nearly 600 pages. (Lately Published.)* $3 75. 
 The present edition o* this classical volume is fairly entitled to be regarded as a new work, every 
 sentence having been carefully rewritten, and the whole increased to more than double the original 
 size. The title of the work scarcely does justice to the extent and importance of the topics 
 brought under consideration, embracing, with the exception of the operative procedures of mid- 
 wifery, almost everything connected with obstetrics, either directly or incidentally ; and there are 
 few physicians who, will not find in its pages much that will prove of great interest and value in 
 their daily practice. The special Essays on the Period of Human Gestation, the Signs of Delivery, 
 and the Spontaneous Amputation and ol her Lesions of the Foetus in Utero present topics of the 
 highest interest fully treated and beautifully illustrated. 
 
 In every ,point of mechanical execution the work will be found one oi the handsomest yet issued 
 from the American press. 
 
 A book unusually rich in practical suggestions. — 
 Am Journal Med. Sciences^ Jan. 1857. 
 
 These several subjects so interesting in them- 
 selves, and so important, every one of them, to the 
 most delicate and precious of social relations, con- 
 trolling often the honor and domestic peace of a 
 family, the legitimacy of offspring, or the life of its 
 parent, are all treated with an elegance of diction, 
 fulness of illustrations, aeuteness and justice of rea- 
 80ning[, unparalleled in obstetrics, and unsurpassed in 
 medicine. The reader's interest can never flag, bo 
 fresh, and vigorous, and classical is our author's 
 style; and one' forgets, in the renewed charm of 
 every page, that it, and every line, and every word 
 
 has been weighed and reweighed through years of 
 preparation; that this is of all others the book of 
 Obstetric Law, on each of its several topics; on all 
 points connected with pregnancy, to be everywhere 
 received as a manual of special jurisprudence^ at 
 once annotincing fact, affording argument, establish- 
 ing precedent, and governing alike the juryman, ad- 
 vocate, £yid judge. It is not merely in its legal re- 
 lations that we find this work so interesting . Hardly 
 a page but that has its hints or facts important to 
 the general practitioner; and not a chapter without 
 especial matter for the anatomist, physiologist, or 
 pathologist. —iV. A. Med.-Chir. Review^ March, 
 1857. 
 
 MOHR (FRANCIS), PH. D., AND REDWOOD (TH EOPH I LUS). 
 PRACTICAL PHARMACY. Comprising the Arrangements, Apparatus, and 
 
 Manipulations of the Pharmaceutical Shop and Laboratory. Edited, with extensive Additions, 
 by Prof. William Procter, of the Philadelphia College of Pharmacy. In one handsomely 
 printed octavo volume, extra oloth, of 570 pages, with over 500 engravings on wood. $2 75 \} 
 
24 
 
 BLANCHARD & iiJ!.&-s Mli^DICAIj 
 
 NEILL (JOHN), M. D., 
 
 Surgeon to theFeiuiBylvauiaHoBpital,&c.; and 
 
 FRANCIS GURNEY SMITH, M.D., 
 
 Professor of Institutes of Medicine in tlie Pennsylvania Medical College. 
 
 AN ANALYTICAL COMPENDIUM OF THE VAKIOUS BRANCHES 
 
 OF MEDICAL SCIENCE ; for the Use and Examination of Students. A new edition, revised 
 and improved. In one very Large and handsomely printed royal 12m o. volume, of about one 
 thousand pages, with 374 wood-cuts. Strongly bound in leather, with raised bands, f 3 00. 
 The very flattering reception which has been accorded to this work, and the hi^h estimate placed 
 upon it by the profession, as evinced by the constant and increasing demand which has rapidlY ex- 
 hausted two large editions, have stimulated the authors to render the volume in its present revision 
 more worthy of the success which has attended it. It has accordingly been thoroughly examined, 
 and such errors as had on former occasions escaped observation have been corrected, and whatever 
 additions were necessary to maintain it on a level with the advance of science have been introduced. 
 The extended series of illustrations has been still further increased and much improved, while, by 
 a slight enlargement of the page, these various additions have been incorporated without increasing 
 the bulk of the volume. 
 
 The work is, therefore, again presented as eminently worthy of the favor with which it has hitherto 
 been received. As a book for daily reference by the student requiring a guide to his more elaborate 
 text-books, as a manual for preceptors desiring to stimulate their students by frequent and accurate 
 examination, or as a source from which the practitioners of older date may easily and cheaply acquire 
 a knowledge of the changes and improvement in professional science, Its reputation is permanently 
 established. 
 
 The best work of the kind with which we are 
 acquainted. — Med. Examiner, 
 
 Having made free use of this volume in our ex- 
 aminations of pupils, we can speak from experi- 
 ence in recommending it as an admirable compend 
 for students, and as especially useful to preceptors 
 who examine their pupils. It will save the teacher 
 much labor by enabling him readily to recall all of 
 the points upon which his pupils should be ex- 
 amined. A work of this sort should be in the hands 
 of every one who takes pupils into his office with a 
 view of examining them ; and this is unquestionably 
 the best of its class. — Transylvania Med. Journal. 
 
 In the rapid course of lectures, where work for 
 
 the students is heavy, and review necessary for an 
 examination, a compend is not only valuable, but 
 it is almost a sine qua non. The one before us is, 
 in most of the divisions, the most unexceptionable 
 of all books of the kind that we know of. The 
 newest and soundest doctrines and the latest im- 
 provements and discoveries are explicitly, though 
 concisely, laid before the student. There is a class 
 to whom we very sincerely commend this cheap book 
 as worth its weight in silver — that class is the gradu- 
 ates in medicine of more than ten years' standing, 
 who have not studied medicine since. They will 
 perhaps find outfromitthatthe science isnot exactly 
 now what it was when they left it off. — The StethO' 
 scope. ■* 
 
 NEILL (JOHN), M. D., 
 
 Professor of Surgery in the Pennsylvania Medical College, &c. 
 
 OUTLINES OP THE VEINS AND LYMPHATICS. With handsome colored 
 
 plates. 1 vol., cloth. $1 25. 
 
 OUTLINES OF THE NERVES. With handsome plates. 1 vol., cloth. $1 25. 
 
 NELIGAN (J. MO9RE), M. D., M . R. I. A., &c. 
 
 (A splendid work^ Just Issued.) 
 
 ATLAS 01* CUTANEOUS DISEASES. In one beautiful quarto volume, extra 
 
 cloth, with splendid colored plates, presenting nearly one hundred elaborate representations of 
 
 disease. $4 50. 
 
 This beautiful volume is intended as a complete and accurate representation of all the varieties 
 of Diseases of the Skin. While it can be consulted in conjunction with any work on Practice, it has 
 especial reference to the author's " Treatise on Diseases of the Skin," so favorably received by the 
 profession some years since. The publishers feel justified in saying that few more beautifully exe- 
 cuted plates have ever been presented to the profession of this country. 
 
 A compend which will very much aid the practi- 
 tioner in this difficult branch of diagnosis. Taken 
 with the beautiful plates of the Atlae, which are 
 remarkable for their accuracy and beauty of color- 
 ing, it constitutes a very valuable addition to the 
 library of a practical laakH.— Buffalo Med, Journal. 
 Sept. 1856. 
 
 Nothing is often more difficult than the diagnosis 
 of disease of the skin ; and hitherto, the only works 
 containing illustrations have been at rather incon- 
 venient prices — prices, indeed, that prevented gene- 
 ral use. The work before us will supply a want 
 Ion? felt, and minister to n more perfect acquaintance 
 virith the nature and treatment of a very frequent 
 and troublesome form of disease. — Ohio Med. and 
 Surg. Journal, July, 1856. 
 
 long existent desideratum much felt by the largest 
 class of our profession. It presents, in quarto size, 
 16 plates, each containing from 3 to figures, and 
 forming in alt a total of 90 distinct representations 
 of the different species of skin affections, t^rouped 
 together in genera or families. The illuBtrations 
 have been taken from nature, and have been copied 
 with such fidelity that they present a striking picture 
 of life; in which the reduced scale aptly serves to 
 give, at a coup d^ceil, the remarkable peculiarities 
 of each individual variety. And while thus thedis 
 ease is rendered more definable, there is yet no losa 
 of proportion incurred by the necessary concentra- 
 tion. Each figure is highly colored, and so truthful 
 has the artist been that the most fastid'ous observer 
 could not justly take exception to the correctness of 
 the execution of the pictures under his scrutiny. — 
 Montreal Med* Ckromcle. 
 
 Neligan*B Atlas of Cutaneous Diseases supplies a 
 
 BY THE SAME AUTHOR. 
 
 A PRACTICAL TREATISE ON DISEASES OF THE SKIN. Second 
 
 American edition. In one neat royal 12mo. volume, extra cloth, oi 334 pages. $1 00. 
 
 The two volumes will be sent by mail on receipt of Five DoUwrs. 
 
 OWEN ON THE DIFFERENT FORMS OF I 
 THE SKEUCTON, AND OF THE TEETH. | 
 
 One vol. royal 13mo,, extra cloth, with numerous 
 illustratlona. 81 25. 
 
AND SCIENTIFIC PUBLICATIONS. 
 
 25 
 
 PEASLEE {E. R.), M. D., 
 
 Professor of Physiology and General Pathology in the New York Medical College. 
 
 HUMAN HISTOLOGY, in its relations to Anatomy, Physiology, and Pathology; 
 
 for the use of Medical Students. With four hundred and thirty-four illustrations. In one hand- 
 some octavo volume, of over 600 pages. {Lately Published.) $3 75. 
 It embraces a library upon the topics discussed 
 
 within itself, and is just what the teacher and learner 
 
 need. Another advantage, by no means to be over- 
 
 looked, everything of real value in the wide range 
 which it embraces, is with great skill compressed 
 into an octavo volume of but little more than six 
 hundred pages. We have not only the whole sub- 
 ject of Histology, interesting in itself, ably and fully , 
 discussed, but what is of infinitely greater interest 
 to the student, because of greater practical value, 
 are its relations to Anatomy, Physiology, and Pa- 
 thology, which are here fully and satisfactorily set 
 forth. These great supporting branches of practical 
 medicine stre thus linked together, and while estab- 
 lishing and illustrating eacli other, are interwoven 
 into a harmonious whole. We commend the work 
 to students and physicians generally. — Nashville 
 Journ. of Med, and Surgery^ Dec. 1857. 
 
 It far surpasses our expectation. We never con- 
 ceived the possibility ot^ compressing so much valu- 
 able information into so compact a form. We will 
 .not consume space with commendations. We re- 
 
 ceive this contribution to physiological science, 
 '' Not with vain thanks, but with acceptance boun- 
 teous." We have already paid it the practical 
 compliment of making abundant use of it in the 
 preparation of our lectures, and also of recommend- 
 ing its further perusal most cordially to our alumni; 
 a recommendation which we now extend to our 
 readers. — Memphis Med. Recorder^ Jan. 1858. 
 
 We would recommend it to the medical student 
 and practitioner, us containing a summary of all that 
 is known of the important subjects which it treats; 
 of all that is contained in the great works of Simon 
 and Lehmann, and the organic chemists in general. 
 Master this one volume, we would say to the medical 
 student and practitioner — master this book and you 
 know all that Ib known of the great fundamental 
 principles of medicine, and we have so hesitation 
 in saying that it is an honor to the American medi- 
 cal profession that one of its members should have 
 
 produced it St, Louis Med. and Surg. Journal, 
 
 March, 1858. 
 
 PEREIRA (JONATHAN), M. D., F. ft. S., AND L. S. 
 THE ELEMENTS OF MATERIA MEDICA AND THEEAPEUTICS. 
 
 Third American edition, enlarged and improved by the author ; including Notices of most of the 
 Medicinal Substances in use in the civilized world, and forming an Enoyclopsedia of Materia 
 Medica. Edited, with Additions, by Joseph Gaeson, M. D., Professor of Materia Medica and 
 Pharmacy in the University of I'ennsylvania. In two very large octavo volumes of 2100 pages, 
 on sTIiall type, with about 500 illustrations on stone and wood, strongly bound in leather, with 
 raised bands. $9 00. 
 jj:*^ Vol. II. will no longer be sold separate. 
 
 PARRISH (EDWARD), 
 Lecturer on Practical Pharmacy and Materia Medica in the Pennsylvania Academy of Medicine, &c. 
 
 AN INTRODUCTION TO PRACTICAL PHARMACY. Designed as a Text- 
 Book lor the Student, and as a Guide for the Physician and Pharmaceutist. With many For- 
 mulfe and Prescriptions. In one handsome octavo volume, extra cloth, of 550 pages, with 243 
 Illustrations. $2 75. 
 
 A careful examination of this work enables us to 
 speak of it in the highest terms, as being the best 
 treatise on practical pharmacy with Which we are 
 acquainted, and an invaluable vade-mecum^ not only 
 to the apothecary and to those practitioners who are 
 accustomed to prepare their own medicines, but to 
 every medical man and medical student. Through- 
 out the work are interspersed valuable tables, useful 
 formulsBj and practical hints, and the whole is illus- 
 trated by a large number of excellent wood-engrav- 
 ings. — Boston Med. and Surg. Journal. 
 
 This is altogether one of the most useful books wc 
 have seen. It is just what we have long felt to be 
 needed by apothecaries, students^ and practitioners 
 of medicme, most of whom in this country have to 
 put up their own prescriptions. Itbears, upon every 
 page, the impress of practical knowledge, conveyed 
 in a plain common sense manner, and adapted to the 
 comprehension of all who may read it. No detail 
 has been omitted, however trivial it may seem, al- 
 though really important to the dispenser of medicine. 
 — Southern Med. and Surg. Journal. 
 
 To both the country practitioner and the city apo- 
 thecary this work of Mr. Parrish is a godsend. A 
 careful study of its contents will give the young 
 graduate a familiarity with the value and mode of 
 administering his prescriptions, which will be of as 
 much use to his patient as to himself. — Va. Med. 
 Journal. 
 
 Mr. Parrish has rendered a very acceptable service 
 to the practitioner and student, by furnishing this 
 book, which contains the leading facts and principles 
 of the science of Pharmacy, conveniently arranged 
 for study, and with special reference to those features 
 of the subject which possess an especial practical in- 
 terest to the physician. It furnishes the student, at 
 the commencement of his studies, with that infor- 
 mation which is of the greatest importance in ini- 
 tiating him into the domam of Chemistry and Materia 
 Medica; it familiarizes him with the compounding 
 of drugs, and supplies those minutiee which but few 
 practitioners can impart. The junior practitioner 
 will, also, hnd this volume replete with instruction. 
 — Charleston Med. Journal and Review. 
 
 There is no useful information in the details of the 
 apothecary's or country physician*s oiBce conducted 
 according to science that is omitted. The young 
 physician will find it an encyclopedia of indispensa- 
 ble medical knowledge, from the purchase of a spa- 
 tula to the compounding of the most learned pre- 
 scriptions. The work is by theablest pharmaceutist 
 in tne United States, and must meet with an im- 
 mense sale. — Nashville Journal of Medicine. 
 
 We are glad to receive this excellent work. It 
 will supply a want long felt by the profession, and 
 especially by the student of Pharmacy, A large 
 majority of physicians are obliged to compound 
 their own medicines, and to them a work of this 
 kind is indispensable. — N. 0. Medical and Surgical 
 Journal . 
 
 PARKER (LANGSTON), 
 
 Surgeon to the Q,ueen's Hospital, Birmingham. 
 
 THE MODERN TREATMENT OF SYPHILITIC DISEASES, BOTH PRI- 
 
 MARY AND SECONDARY; comprising the Treatment of Constitutional and Confirmed Syphi- 
 lis, by a safe and successful method. With numerous Cases, Formulas, and Clinical Observa- 
 tions. From the Third and entirely rewritten London edition. In one neat octavo volume 
 extra cloth, of 316 pages. 91 75. 
 
26 
 
 BLANCHAKD «B LEA'S MEDICAL 
 
 P I ARIE (WILLIAM), F. R. S. E., 
 
 Profesaor of Surgery in the University of Aberdeen. 
 
 THE PRINCIPLES AND PRACTICE OF SURGERY. Edited by John 
 
 Neill, M. D., Professor of Surgery ia the Penna. Medical College, Surgeon to the Pennsylvania 
 Hosipital, &CC. In one very handsome octavo volume, leather, oi 780 pages, with 316 illustrations. 
 $3 75. 
 
 We know of no other surgical woric of a reason- 
 able size, wherein there ia so much theory and prac- 
 tice, or where subjects are more aoundly or clearly 
 taught. — Ths Stethoscope. 
 
 There is scarcely a disease of the bonee or soft 
 parts, fracture, or dislocation, that is not illustrated 
 by accurate wood-engravinga. Then, again, every 
 instrument employed T)y the Burgeon is thus repre- 
 sented. These engravings are not only correct, but 
 
 really beautiful, showing the astonishing degree of 
 oerfeetion to which the art of wood -engraving has 
 arrived. Prof. Pirrie, in the wor* before us, has 
 elaborately discussed the principles of surgery, and 
 a safe and effectual practice predicated upon them. 
 Perhaps no work upon this subject heretofore issued 
 is so full upon the science of the art of surgery. — 
 NasfwilU Journal of Medicine and Surgery. 
 
 RICORD (P.), M. 0. 
 A TREATISE ON THE VENEREAL DISEASE. By John Hunter, F.R.S. 
 
 With copious Additions, by Ph. Ricord, M. D. Translated and Edited, with Notes, by Freeman 
 J. BuMSTEAD. M.D , Lecturer on Venereal at the College of Physicians and Surgeons, New York. 
 Second edition, revised, containing a resume of Ricord's Recent Lectures on Chancre. In 
 one handsome octavo volume, extra cloth, of 550 pages, with eight plates. $3 25. {Now Beady.) 
 In revising this work, the editor has endeavored to introduce whatever matter of interest the re- 
 cent investigations of syphilographers have added to our knowledge of the subject. The principal 
 source from which this has been derived is the volume of "Lectures on Chancre," publib.hed a few 
 months since by M. Ricord, which affords a large amount of new and instructive material on many 
 controverted points. In the previous edition, M. Ricord's-addilions amounted to nearly one-third 
 of the whole, and with the matter now introduced, the work may be considered to present his views 
 and experience more thoroughly and completely than ^ny other. The value of the original treatise 
 of Mr. Hunter is too well known to require praise. Perhaps no medical work in the English lan- 
 guage has so thoroughly stood the test of time, or has so completely assumed the position of a 
 cla'isio, and a volume like \he present, containing the united labors of the highest authorities on so 
 difficult and important a subject, becomes indi>pensable to all who desire to keep themselves on a 
 level with the progress of medical science. 
 
 Every one will recognize the attractiveness and 
 value which Ihlswork derives from thus presenting 
 the opinions of these two masters side by side. But, 
 It must be admitted, wIiri has made the fortune of 
 the book, is the faci that it contains the " most com- 
 plete embodiment of the veritable doctrines of the 
 HQpital du Midi," which has ever been made public. 
 The doctrinal ideas of M. Ricord, ideas which, if nojt 
 universally adopted, are tnconlestably dominant, have 
 heretofore only been interpreted by more or less skilful 
 
 secretaries, sometimes accredited and sometimes not. 
 in the notes to Hunter, the master substitutes him- 
 self for his Interpreters, and gives hia original iljoughts 
 Ui the world in a lucid and perfectly intelligible man- 
 ner. In conclusion we can say that this is incon- 
 testablythe best treatise on syphilis with which we 
 are acquainted, and, as we do not oAen employ the 
 phrase, we may be excused for expressing the hope 
 that it mny find a place in the library of every phy- 
 sician. — Virginia Med. and Surg. Journal. 
 
 BY THE SAME AUTHOR. 
 
 RICORD'S LETTERS ON SYPHILIS. Translated by W. P. Lattimore, M. D. 
 
 In one neat octavo volume, of 270 pages, extra cloth. $2 00. 
 
 ROKITANSKY 
 
 Curator of the Imperial Pathological Museum 
 
 A MANUAL OF PATHOLOGICAL 
 
 bound in two, extra cloth, of about 1200 pages. 
 KING, C. H. Moore, and G. E. Day. $5 50 
 The profession is too well acquainted with the re- 
 putation of Rokitansky's work to need our assur- 
 ance that this is one of the mostprofound, thorough, 
 and valuable books ever issued from the medical 
 press. It is sui generis^ and has no standard of com- 
 parison. It is only necessary to announce that it is 
 issued in a form as cheap as is compatible with its 
 size and preservation, and its sale follows as a 
 matter of course. No library can be called com- 
 plete without it. — Buffalo Med. Journal. 
 
 An attempt to give our readers any adequate idea 
 of the vast amount of instruction accumulated in 
 these volumes, would be feeble und hopeless. The 
 effort of the distinguished author to concentrate 
 in a small space his great fund of knowledge, has 
 
 (CARL), M. D., 
 
 and Professor at the University of Vienna, &c. 
 
 ANATOMY. Four volumes, octavo, 
 Translated by W. E. Swaine, Edward Sieve- 
 so charged his text with valuable truths, that any 
 attempt of a reviewer to epitomize is at once para- 
 lyzed, and must end in a failure. — Western Lancet, 
 
 As this is the highest source of knowledge upon 
 the important subject; of which it treats, no real 
 student can afford to be without it. The American 
 publishers have entitled themselves to the thanks of 
 the profession of their country, for this limeous and 
 beautiful edition. — Nashville Journal of Medicine, 
 
 As a book of reference, therefore, this work must 
 prove of inestimable value, and we cannot too highly 
 recommend it to the profession,— CAar2esCon Med, 
 Journal oMd Review. 
 
 This book is a necessity to every practitioner.— 
 Am. Med. Monthly. 
 
 RIGBY (EDWARD), M.D,, 
 
 Senior Physician to the General Lying-in Hospital, &c. 
 
 a system of midwifery. With Notes and Additional Illustrations. 
 
 Second American Edition. One volume octavo, extra cloth, 422 pages. $2 50. 
 BY THE SAME ADTHOR. (Lately PnbUsIied.) 
 
 ON THE CONSTITUTIONAL TREATMENT OF FEMALE DISEASES. 
 
 In one neat royal 12mo. volume, extra cloth, of about 250 pages. $1 00. 
 
 BOYLE'S MATERIA MEDIC A AND THERAPEUTICS; including the 
 Preparations of the Pharmaoot)(Eias of London, Edinburgh, Dublin, and of the United States. 
 With many new medicines. Edited by Joseph Cakson, JV[. D. With ninety-eight illustrations. 
 In one large octavo volume, extra cloth, of about 700 pages. $3 00, 
 
AND SCIENTIFIC PUBLICATIONS. 
 
 27 
 
 RAMSBOTHAM (FRANCIS H.), M.D. 
 THE PRINCIPLES AND PRACTICE OP OBSTETRIC MEDICINE AND 
 
 SURGERY, in reference to the Process of Parturition. A new and enlarged edition, thoroughly 
 revised by the Author. With Additions by W. V. Keatins, M. P. In one large and handsome 
 imperial octavo volume, of 650 pages, strongly bound in leather, with raised bands; with sixty- 
 four beautiful Plates, and numerous Wood-cuts in the text, containing in all nearly two hundred 
 large and beautiful figures. $5 00. 
 
 From Prof. Hodge^ of the University of Pa. 
 To the American public, it is most valuable, from its intrinsic undoubted excellence^ and as being 
 
 the best authorized exponent of British Midwifery. Its circulation will, I trust, be extensive throughout 
 
 our country. 
 
 The publishers have shown their appreciation of 
 the merits of this work and secured its success by 
 the truly elegant style in which they have brought 
 it out, excelling themselves in its production, espe- 
 cially in its plates. It is dedicated to Prof. Meigs, 
 and has the emphatic endorsement of Prof. Hodge, 
 as the best exponent of British Midwtfery. we 
 know of no text-book which deserves in all respects 
 to be more highly recommended to students, and we 
 could wish to see it in the hands of every practitioner, 
 for they will find it invaluable for reference. — Med. 
 Gazette. 
 
 But once in a long time some brilliant genius rears 
 his head above the horizon of science, and illumi- 
 nates and purifies every department that he investi- 
 gates ; and his works become types, by which innu- 
 merable imitators model their feeble productions. 
 Such a genius we find in the younger Ramsbotham, 
 arid such a type we find in the work now before us. 
 The binding, paper, type, the engravings and wood- 
 cuts are alfso excellent as to make this book one of 
 the finest specimens of the art of printing that have 
 given such a world-wide reputation to its enter- 
 prising and liberal publishers. We welcome Rams- 
 botham's Principles and Practice of Obstetric Medi- 
 
 cine and Surgery to our library, and confidently 
 recommend it to our readers, with the assurance 
 that it will not disappoint their most sanguine ex- 
 pectations. — Western Lancet. 
 
 It is unnecessary to say anything in regard tp the .^ 
 utility of this work. It is already appreciated in our 
 country for the value of the matter, the clearness of 
 its style, and the fulness of its illustrations. To the 
 physician's library it is indispensable, while to the 
 student as a- text-book, from which to extract the 
 material for laying the foundation of an education on 
 obstetrical science, it has no superior. — Ohio Med, 
 and Surg. Journal. 
 
 We will only add that the student will learn from 
 it all he need to know, and the practitioner will find 
 it, as a book of reference, surpassed by none other. — 
 Stethoscope. 
 
 The character and merits of Dr. Ramsbotham's 
 work are so well known and thoroughly established, 
 that comment is unnecessary and praise superfluous. 
 The illustrations, which are numerous and accurate, 
 are executed in the highest style of art. We cannot 
 too highly recommend the work to our readers. — Si. 
 Louis Med. and Surg. Journal. 
 
 STILLE (ALFRED), M. D. 
 
 THERAPEUTICS AND MATERIA MEDICA; a Systematic Treatise on the 
 History, Description, Action, and Uses of Medicinal Agents. In two large and handsome octavo 
 volumes, of over 1500 pages. {In press.) 
 
 The length of time during which this work has been in preparation has afforded to the author the 
 opportunity of rendering it complete and perfect in all its details. His aim has been to present a 
 complete view ot the general principles of Therapeutics, as well as the practical application of the 
 Materia Medica. Details interesting only to the naturalist or to the dealer have been passed over 
 to make room for that which is of essential importance to the physician — the actions, uses and 
 administrations of medicines. All the articles of the Materia Medica will thus be found treated 
 from the stand-point of Ihe advanced state of science at the present day, physiological, and patholo- 
 gical. The work is now passing rapidly through the press, and the publishers trust to have it 
 in readiness for the fall sessions. . 
 
 , SMITH (HENRY H.), M.D., 
 Professor of Surgery in the University of Pennsylvania, &e. 
 
 MINOR SURGERY; or, Hints on the Every-day Duties of the Surgeon. Illus- 
 trated by two hundred and forty-seven illustrations. Third and enlarged edition. In one hand- 
 some royal 12mo. volume, pp, 456. In leather, $2 25; extra oloth, $2 00. 
 
 BY THE SAME AUTHOR, AND 
 
 HORNER (WILLIAM E.), M. D., 
 Late Professor of Anatomy in the University of Pennsylvania. 
 
 AN ANATOMICAL ATLAS, illustrative of the Structure of the Human Body. 
 In one volume, large imperial octavo, extra cloth, with about six hundred and fifty beautiful 
 figures. $3 00. 
 
 These figures are well selected^ and presc 
 lomnlete and accurate representation of tnat i 
 
 present a 
 complete and accurate representati^on of tnat won- 
 *derfal fabric, the human body. The plan of this 
 Atlas, which renders it so peculiarly convenient 
 for the student, and its superb artistical execution, 
 have been already pointed out. We must congratu- 
 
 late the student upon the completion of thisAtlasj 
 as it is the most convenient work of the kind that 
 has yet appeared ; and we must add, the very beau- 
 tiful manner in which it is "got up" is so creditable 
 to the country as to be flattering to our national 
 pride. — American Medical Journal. 
 
 SMITH (W. TYLER), M. D., 
 
 PhysiciaQ Accoucheur to St. Mary's Hospital, Ice. 
 
 ON PARTURITION, AND THE. PRINCIPLES AND PRACTICE OF 
 
 OBSTETRICS. In one royal 12mo. volume, extra cloth, of 400 pages. $125. 
 
 BY THE SAME AUTHOR. 
 
 A PRACTICAL TREATISE ON THE PATHOLOGY AND TREATMENT 
 
 OF LEUCORUHCEA. With numerous illustrations. In one very handsome octavo volume, 
 extra cloth, of about 250 pages, f I 50. 
 
28 
 
 BLANCHARD & tiEA'S MEDICAL 
 
 SHARPEY (WILLIAM), M. D., JONES QUAIN, M.D., AND 
 
 RICHARD QUAIN, F. R. S., &c. 
 
 HUMAN ANATOMY. Eevised, with Notes and Additions, by Joseph Leidt, 
 
 M. D., ProfesBor of Anatomy in the University of Pennsylvania. Complete in two large octavo 
 volumes, leather, of about thirteen hundred pages. Beautifully illustrated with over five hundred 
 engravings on wood. $6 00. 
 
 SARGENT (F. W.), M. D, 
 ON BANDAGING AND OTHEK OPERATIONS OF MINOR SURGERY. 
 
 Second edition, enlarged. One handsome royal 12mo. vol., of nearly 400 pages, witli 182 wood- 
 cuts. Extra cloth, $1 40 ; leather, $1 50. 
 
 Sargent's Minor Surgery has always been popular, 
 and deservedly so. It furnishes that knowledge of the 
 most frequently requisite performances of surgical 
 art which cannot be entirely understood by attend- 
 ing clinical lectures. The art of bandaging, which 
 is regularly taught in Europe, is very frequently 
 overfooked by teachers in this country ; the student 
 and junior practitioner, therefore, may often require 
 that knowledge which this little volume so tersely 
 and happily supplies. — Charleston Med. Journ. and 
 Reviewj March, 1856. 
 
 A work that has been so long and favorably known 
 to the profession as Dr. Sargent's Minor Surgery, 
 needs no commendation from us. We would remark, 
 however, in this connection, that minor surgery sel- 
 dom gets that attention in onr schools that its im- 
 portance deserves. Our larger works are also very 
 defective in their teaching on these small practical 
 points. This little book will supply the void which 
 all must feel who have not studied its pages. — WesU 
 em Lancetj March, 1656. 
 
 SKEY'S OPERATIVE SURGERY. In one very 
 handsome octavo volume, extra cloth, of over 650 
 pages, with about one hundred wood-cuts. S3 25. 
 
 STANLEY'S TREATISE ON DISEASES OF 
 THE BONES. In one volume, octavo, extra cloth, 
 286 pages. SI SO. 
 
 SOLLY ON THE HUMAN BRAIN; its Structure, 
 Physiology, and Diseases. Fro.-n the Second and 
 
 much enlarged London edition. In one octavo 
 volume, extra cloth, of 500 pages, with 120 wood- 
 cuts. $2 00. 
 
 SIMON'S GENERAL PATHOLOGY, as conduo-" 
 ive to the Establishment of Rational Principles 
 for the prevention and Cure of Disease. In one 
 neat octavo volume, extra cloth, of 212 pages. 
 f 1 25. 
 
 TANNER (T. H.), M. D., 
 
 Physician to the Hbspital for Women, &e. 
 
 A MANUAL OF CLINICAL MEDICINE AND PHYSICAL DIAGNOSIS. 
 
 To which is added The Code of Ethics of the American Medical Association. Second 
 
 American Edition. In one neat volume, small 12mo., extra cloth, 87j cents. 
 
 The work is an honor to its writer, and must ob- .1 tioners, it has only to be seen, to win foW itself a 
 
 tain a wide circulation by its intrinsic merit alone, place upon the shelves of every medical library. 
 
 Suited alike to the wants of students and practi- | — Boston Med andSvrg. Journal. 
 
 TODD (ROBERT BENTLEY), M. D., F. R. S., 
 
 Professor of Physiology in King's College, London ; and 
 
 WILLIAM BOWMAN, F. R. S., 
 
 Demonstrator of Anatomy in King's College, London. 
 
 THE PHYSIOLOGICAL ANATOMY AND PHYSIOLOGY OF MAN. With 
 
 about three hundred large and beautiful illustrations on wood. Complete in one large octavo 
 
 volume, of 950 pages, leather. Price $4 50. 
 
 ^° Gentlemen who have received portions of this work, as published in the « Medical News 
 AND Library," can now complete their copies, if immediate applieatiofi be made. It will be fur- 
 nished as follows, free by mail, in paper covers, with cloth backs. 
 
 Parts I., II., III. (pp. 25 to 552), $2 50. 
 
 Part IV. (pp. 553 to end, with Title, Preface, Contents, &c.), f 2 00. 
 
 Or, Part IV., Section II. (pp. 725 to end, with Title, Preface, Contents, &c.), $1 25. 
 
 A magnificent contribution to British medicine, 
 and the American physician who shall fail to peiuse 
 it, will have failed to read one of the most instruc- 
 tive books of the nineteenth century N. O. Med 
 
 and Surg. Journal^ Sept. 1657. 
 
 ' It is more concise than Carpenter's Principles, and 
 more modern than the accessible edition of Mflller's 
 Elements; its details are brief, but sutlicieEt; its 
 descriptions vivid ; its illustrations exact and copi- 
 ous ; and its language terse and perspicuous 
 
 Charleston Med. Journal^ July, 1657. 
 
 We kAow of nc work on the subject of physiology 
 so well adapted to the wants of the medical student. 
 
 Its completion has been thus long delayed, that the 
 authors might secure accuracy by personal observa- 
 tion. — Si. Louis Med. and Surg. Journal, Sept. '57. 
 
 Our notice, thongh it conveys but a very feeble 
 and imperfect idea of the magnitude and importance 
 of the work now under consideration, already tran- 
 scends our limits ; and, with the indulgmce of our 
 readers, and the hope that they will peruse the book 
 for themselves, as we feel we can with confidence 
 recommend it, we leave it in their hands for them 
 to judge of its merits.— TA« Northwestern Med. and 
 Surg. Journal, Oct. 1857. 
 
 TODD (R. B.), M. D., F. R. S., &c. 
 CLINICAL LECTURES ON CERTAIN DISEASES OF THE URINARY 
 
 ORGANS AND ON DROPSIES. In one octavo volume. {Jiist Issued, 1857.) $1 50 
 
 BY THE SAME AUTHOR. (In PreSS.) 
 
 CLINICAL LECTURES ON CERTAIN ACUTE DISEASES. In one neat 
 
 octavo volume, to match the above. 
 
 WILSON (MARRIS), M. D. 
 ON DISEASES OF THE VESICUL^ SEMINALES. 
 
 page lU. 
 
 See "Lallemand," 
 
 WHITEHEAD ON THE CAUSES AND TREAT- I 
 MENT OP ABORTION AND STERILITY. 
 
 Second American Edition. In one volume, octa- 
 vo, extra cloth, pp. 308. SI 75. 
 
AND SCIENTIFIC PUBLICATIONS. 29 
 
 TAYLOR (ALFRED S.), M. D., F. R. S., 
 
 Lecturer on Medical Jurisprudence and Chemistry in Guy's Hospital. 
 
 MEDICAL JURISPRUDENCE. Fourth American Edition. With Notes and 
 
 References to American Decisions, by Edward Hartshorne, M. D. In one larg:e octavo volume, 
 
 leather, of over seven hundred pages. $3 00. 
 
 This standard work has lately received a very thorough revision at the hands of the author, who 
 has introduced whatever was necessBry to render it complete and satisfactory in carrying out the 
 objects in view. Tue editor has likewise used every exertion to make it equally thorough with 
 regard to all matters relating to the practice of this country. In doing this, he has carefully ex- 
 amined all thai has appeared on the subject since the publication of the last edition, and has incorpo- 
 rated all the new information thus presented. The work has thus been considerably increased in 
 size, notwithstanding which, it has been kept at its former very moderate price, and in every respect 
 it will be found worthy of a continuance of the remarkable favor which has carried it through so 
 many editions on both sidfes of the Atlantic. A few notices of the former editions are appended. 
 
 We know of no work on Medical Jurisprudence we do not hesitate to affirm that after having once 
 which contains in the same space anything like the 
 same amount of valuable matter. — N. Y. Journal of 
 Medicine. 
 
 No work upon the subject can be put into the 
 hands of students either of law or medicine which 
 will engage them, more closely or profitably; and 
 none could be ofiered to the busy practitioner of 
 either calling, for the purpose of casual or hasty 
 reference, that would be more likely to afford the aid 
 desired. We therefore recommend it as the best and 
 safest manual for daily use. — American Journal oj 
 Medical Sciences. 
 
 This work of Dr. Taylor's is generally acknow- 
 ledged to be one of the ablest extant on the subject 
 of medical jurisprudence. It is certainly one of the 
 most attractive books that we have met with ; sup- 
 plying so much both to interest and instruct, that 
 
 commenced its perusal, few could be prevailed upun 
 to delist before completing it. In the last London 
 edition, all the newly observed and accurately re- 
 corded facts have been inserted, including much that 
 is recent of Chemical, Microscopical, and Patholo- 
 gical research, besides papers on numerous subjects 
 never before pabiiBhed.-Ckarleston Medical Journal 
 and Review . 
 
 It is not excess of praise to say that the volume 
 . before us is the very best treatise extant on Medical 
 Jurisprudence. In saying this, we do not wish to 
 be understood as detractingfrom the merits of the 
 excellent works of Beck, Ryan, Traill, Guy, and 
 others; but in interest and value we think it must 
 be conceded that Taylor is superior to anything that 
 has preceded it.— iV. W. Medical and Surg. Journal, 
 
 BY THB SAME AUTHOR. (JVisw Edition, now ready.) 
 
 ON POISONS, IN RELATION TO MEDICAL JURISPEUDENCE AND 
 
 MEDICINE. Second American, from a second and revised London edition. In one large 
 
 octavo volume, oi 755 pages, leather. $3 50. 
 
 The length of time which has elapsed since the first appearance of this work, has vi^rought so 
 great a change in the subject, as to require a very thorough revision to adapt the volume to the 
 present wants of the profession. The rapid advance of Chemistry has introduced into use many 
 new substances which may become fatal through accident, carelessness, or design — while at the 
 same time it has likewise designated new and more exact modes of counteracting or detecting those 
 previously treated of. Mr. Taylor's position as the leading medical jurist of England, has during 
 this period conferred on him extraordinary advantages in acquiring experience in all that relates to 
 this department, nearly all cases of moment being referred to him for examination, as an expert 
 whose testimony is generally accepted as final. The results of his labors, therefore, as gathered 
 together in this volume, carefully weighed and sifted, and presented in the clear and intelligible 
 style for which he is noted, may be received as an acknowledged authority, and as a guide to be 
 followed with implicit confidence. 
 
 In his Preface the author says: — 
 
 " My space has been limited, and I have endeavored to fill it with materials which may be of 
 profit to the practitioners of law and medicine, for whose especial use this volume is intended. 
 Under this view the plan of the former edition has been entirely changed. Many chapters have 
 been struck out, and an equal number of new chapters introduced. The requirements of a period 
 dating no longer ago than len years are different from those of the present day, and it is the duty 
 of an author, so far as it may be in his power and consistent with the scope of his labors, to fulfil 
 these requirements by an entire remodelling of his subject. 
 
 WILLIAMS (C. J. B.), M.D,, F. R. S., 
 
 Professor of Clinical Medicine in University College, London, *c. 
 
 PRINCIPLES OF MEDICINE. An Eletnentaiy View of the Causes, Nature, 
 
 Treatment, Diagnosis, and Prognosis of Disease ; with brief remarks on Hygienics, or the pre- 
 servation of health. A new American, from the third and revised London edition. In one octavo 
 volume, leather, of about 600 pages. $2 50. (J-ust Issued.) 
 
 The very recent and thorough revision which this work has enjoyed at the hands of the author 
 has brought it so completely up to the present state of the subject that in reproducing it no additions 
 have been found necessary. The success which the work has heretofore met shows that its im- 
 portance has been appreciated, and in its present form it will be found eminently worthy a continu- 
 ance of the same favor, possessing as it does the strongest claims to the attention of the medical 
 student and practitioner, from the admirable manner in which the various inquiries in the different 
 branches of pathology are investigated, combined and generalized by an experienced practical phy- 
 sician, and directly applied to the investigation and treatment of disease. 
 
 recommend it for a text-book, guide, and constant 
 companion to every practitioner and every student 
 who wishes to extricate himself from the well-worn 
 ruts of empiricism, and tOLbase hia practice of medi- 
 cine upon principles. — London Lancet. 
 
 A text-book to which no other in our language is 
 comparable. — Charleston Medical Journal. 
 
 No work has ever achieved or maintained a more 
 deserved reputation. — Va. Med. and Surg. Journal. 
 
 We find that the deeply-interesting matter and 
 style of this book have so far fascinated us, that we 
 have unconsciously hung upon its pages, not too 
 l<mg, indeed, for our own profit, but longer than re- 
 viewers can be permitted to indulge. We leave the 
 further analysis to the student and practitioner. Our 
 jadKment of the work has already been sufficiently 
 expressed. It is a judgment of almost unqualified 
 praise The work is not of a controversial, but of 
 a didactic character; and as such we hail it, and 
 
30 
 
 BLANCHARD & LEA'S MEDICAL 
 
 New and much enlarged edition — (Now Ready.) 
 WATSON (THOMAS), M. D., &c. 
 
 Late Physician to the Middlesex Rospital, &c. 
 
 LECTURES ON THE PRINCIPLES AND PRACTICE OF PHYSIC. 
 
 Delivered at King:'s College, Loadon. A new American, from the last revised and enlarged 
 English edition, with Additions, by D. Francis Condie, M. D., author of " A Practical Treatise 
 on the Diseases of Children," &c. With one hundred and eighty.five illustrations on wood. In 
 one very large and handsome volume, imperial octavo, of over 1200 closely printed pages in 
 small type ; the whole strongly bound in leather, with raised bands. Price $4 25. 
 The publishers feel that they are rendering a service to the American profession in presenting at 
 so very moderate a price this vast body of sound practical information. Whether as a guide for 
 the student entering on a course of instruction, or as a book of reference for daily consultation by 
 the practitioner, " watson^s Practice" has long been regarded as second to none; the soundness 
 and fulness of its teachings, the breadth and liberality of its views, and the easy and flowing style 
 m which it is written having won for it the position of a general favorite. That this high reputa- 
 tion might be fully maintained, the author has subjected it to a thorough revision ; every portion 
 has been examined with the aid of the most recent researches in pathology, and the results of 
 modern investigations in both theoretical and practical subjects have been carefully weighed and 
 embodied throughout its pages. The watchful scrutiny of the editor has likewise introduced 
 whatever possesses immediate importance to the American physician in relation to diseases inci- 
 dent to our climate which are Utile known in England, as well as those points in which experience 
 here has led to different modes of practice ; and he has also added largely to the series of illustra- 
 tions, believing that in this manner valuable assistance may be conveyed to the student in elucidat- 
 ing the text. The work will, therefore, be found thoroughly on a level with the most advanced 
 state of medical science on both sides of the Atlantic. 
 
 The additions which the work has received are shown by the fact that notwithstanding an en- 
 largement in the size of the page, more than two hundred additional pages have been necessary 
 to accommodate the two large volumes of the London edition (which sells at ten dollars), within 
 the compass of a single volume, and in its present form it contains the matter of at least three 
 ordinary octavos. Believing it to be a work which should lie on the table of every physician, and 
 be in the hands of every student, the publishers have put it at aprice within the reach of all, making 
 it one of the cheapest books as yet {presented to the American profession, while at the same lime 
 the beauty of its mechanical execution renders it an exceedingly attractive volume. 
 
 It would appear almost superfluous to adduce commendatory notices of a work which has so 
 ong been established in the position of a standard authority as "Watson's Practice." A few ex- 
 
 tracts are, however, subjoined from reviews of the new and improved edition. 
 
 The fourth edition now appears, so carefully re- 
 vised, as to add considerably to the value of a book 
 already acknowledged, wherever the English lan- 
 guage is read, to be beyond all comparison the best 
 s> stematic work on the Principles and Practice of 
 Physic in the whole range of medical literature. 
 Every lecture contains proof of the extreme anxiety 
 of the author to keep pace with the advancing know- 
 ledge of the day, and to bring the results of the 
 labors, not only of phyBicians, but of chemists and 
 bistolugists, before his readers, wherever they can 
 be turned to useful account. And this is done with 
 such a cordial appreciation of the merit due to the 
 industrious observer, such a generous desire to en- 
 courage younger and rising men, and such a candid 
 acknowledgment of his own obligations to them, 
 that one scarcely knows whether to admire most the 
 pure, simple, forcible English — the vast amount of 
 useful practical information condensed into the 
 Lectures — or the manly, kind-hearted, unassuming 
 character of the lecturer shining through his work. 
 —London Med. Times and Gazette, Oct. 3^) 1857. 
 
 Thus these admirable volumes come before the 
 profession in their fourth edition, abounding in those 
 distinguished attributes of moderation, judgment, 
 erudite cultivation, clearness, and eloquence, with 
 which they were from the first invested, but yet 
 richer than before in the results of more prolonged 
 observation, and in the able appreciation of the 
 latest advances m pathology and medicine by one 
 of the most proftiund medical thinkers of the day, — 
 London Lancet y.Tiov. 14, 1857. 
 
 The lecturer's skill, his wisdom, his learning, are 
 equalled by the ease of his graceful diction, 1Kb elo- 
 quence, and the far higher qualities of candor, of 
 courtesy^ of modesty, and of generous appreciation 
 of merit m others. May he long remain to instruct 
 us, and to enjoy, in the glorious sunset of his de- 
 clining years, the honors, the confidence and love 
 gained during his useful life.— iV. A. Med.-Chir. 
 Revievfj July, 1858. 
 
 Watson's unrivalled, perhaps unapproachable 
 work on Practice — the copious addiiions made fo 
 which (the-fourth edition) have given it all the no- 
 velty and much of the interest of a new book. — 
 Charleston Med. Journal, July, lfcJ58. 
 
 Lecturers, practitioners, and students of medicine 
 will equally hail the reappearance of the work of 
 Dr. Watson in theformof anew — a fourth — edition. 
 We merely do justice to our own feelings, and, we 
 are sure, of the whole profession, if we thank him 
 for having, in the trouble and turmoil of a large 
 practice, made leisure to supply the hiatus caused 
 by the exhaustion of the publisher's stock of the 
 third edition, which has been severel}' felt for the 
 last three years. For Dr. Watson has not merely 
 caused the lectures to be reprinted, but scattered 
 through the whole work we find additions or altera- 
 tions which prove that the author has in every way 
 sought to bring up his teaching to the level of the 
 most recent acquisitions in science.— £nf. and For. 
 Medico-Ckir. iJevuw, Jan. 1858. 
 
 WILDE (W. R.), 
 Surgeon to St. Mark's Ophthalmic and Aural Hospital, Dublin. 
 
 AURAL SURGERY, AND THE NATURE AND TREATMENT OF DIS- 
 EASES OF THE EAR. In one handsome octavo volume, extra cloth, of 476 paffes, with 
 illustrations. $2 80. 
 
 WHAT TO OBSERVE 
 AT THE BEDSIDE AND AFTER DEATH, IN MEDICAL CASES. 
 
 Published under the authority of the London Society for Medical Observation. A new American 
 
 from the second and revised Londoi. edition. In one very handsome volume, royal 12mo., extra 
 
 cloth. $1 00, 
 
 To the observer who prefers accaracy to blui'ders I One of the finest aids to a young practitioner w« 
 and precision to carelessneas, thia little book is in- have ever Been.— PeninsMlar Journal of Medieint 
 valuable.— JV. II. Journal ofMedicin$, \ 
 
AND SCIENTIFIC PUBLICATIONS. 
 
 31 
 
 New and much enlarged edition— (No'w Ready.) 
 
 WILSON (ERASMUS), F. R. S., 
 
 A SYSTEM OF HUMAN ANATOMY, General and Special. A new and re- 
 
 vised American, from the last and enlarged Englit-h Edition. Edited by "W. H. Gobrecht, M. D., 
 Professor of Anatomy in the Philadelphia Medical College, &c. Illustrated with three hundred 
 and ninety-seven engravings on wood. In one large and exquisitely^rmted octavo volume, of 
 over 600 large pages; leather. $3 25. 
 
 The publishers trust that the well earned reputation so long enjoyed by this work will be more 
 than maintained by the present edition. Besides a very thorough revision by the author, it has been 
 most carefully examined by the editor, and the efforts of both have been directed to introducing 
 everything which increaced experience in its use has suggested as desirable to render it a complete 
 text-book for those seeking to obtain or to renew an acquaintance with Human Anatomy. The 
 amount of additions which it has thus received may be estimated from the fact that the present 
 edition contains over one-fourth more matter than the last, rendering- a smaller type and an enlarged 
 page requisite to keep the volume within a convenient size. The author has not only thus added 
 largely to the work, but he has also made alterations throughout, wherever there appeared the 
 opportunity of improvmg the arrangement or style, so as to present every fact in its most appro- 
 priate manner, and to render the whole as clear and intelligible as possible. The editor has 
 exercised the utmost caution to obtain entire accuracy in the text, and has largely increased the 
 number of illustrations, of which there are about one hundred and fifty more in this edition than 
 in the last, thus bringing distinctly before the eye of the student everything of interest or importance. 
 
 The publishers have felt that neither care nor expense should be spared to render the external 
 finish of the volume worthy of the universal favor with which it has been received by the American 
 profession, and they have endeavored consequently to produce in its mechanical execution an im- 
 provement corresponding with that which the text has enjoyed, it will therefore be found one of 
 the handsomest specimens of typography as yet produced in this country, and in all respects suited 
 to the office table of the practitioner, notwithstanding the exceedingly low price at which it has 
 been placed. 
 
 A few notices of former editions are subjoined. 
 
 This is probably the prettiest medical book ever 
 published, and we believe that its intrinsic merits 
 are in keeping with its exterior advantages, having 
 examined it sufficiently to satisfy us ttiat it may be 
 recommended to the student as no less distinguished 
 by its accuracy and clearness of description than by 
 its typographical elegance. The wood-cuts are ex- 
 quisite. — British and Foreign Medical Review. 
 
 An elegant edition of one of the moat useful and 
 accurate systems of anatomical science which has 
 been issued from the press. The illustrations are 
 really beautiful. In its style the work is extremely 
 concise and intelligible. No one can possibly take 
 up this volume without being struck with the great 
 bpauty of its mechanical execution, and the clear- 
 ness of the descriptions which it contains is equally 
 
 evident. Let students, by all means examine the 
 claims of this work on their notice, before they pur- 
 chase a text- book of the vitally important science 
 which this volume so fully and easily unfolds. — 
 Lancet. 
 
 In every respect, this work, as an anatomical 
 
 ?utde fot the student who seeks to obtain know- 
 edge which he has not yet acquired, and for the 
 practitioner who wishes to keep up that which he 
 find! gradually fading from his mind, merits our 
 warmest and most decided praise. — Med. Gazette. 
 • We regard it as the best system now extant for 
 students. — Western Lancet. 
 
 It therefore receives our highest commendation. — 
 Southern Med. and Surg. Journa,l. 
 
 BY THE SAME AUTHOR. {JliSt IsSUed.) 
 
 ON DISEASES OF THE SKIN. Fourth and enlarged American, from the last 
 and improved London edition. In one large octavo volume, of 650 pages, extra cloth, $2 75. 
 The writings of Wilson, upon diseases of the skin, 
 
 are by far the most scientific and practical that 
 
 have ever been presented to the medical world on 
 
 this subject. The present edition is a great improve- 
 
 ment on all its predecessors. To dwell upon all the 
 great merits and high claims of the work before ua, 
 seriatim^ would indeed be an agreeable service ; it 
 would be a mental homage which we could freely 
 offer, but we should thus occupy an undue amount 
 of space in this Journal. We will, however, look 
 at some of the more salient points with which it 
 abounds, and which make it incompura oiy superior in 
 excellence to all other treatises on the subject of der- 
 matology. No mere speculative views are allowed 
 
 a place in this volume, which, without a doubt, will, 
 for a very long period, be acknowledged as the chief 
 standard wort on dermatology. The principles of 
 an enlightened and rational therapeia are introduced 
 on every appropriate occasion. The general prac- 
 titioner and surgeon who, peradventure, may have 
 for years regarded cutaneous maladies as scarcely 
 worthy their attention, because, forsooth, they are 
 not fatal in their tendency; or who, if they have 
 attempted their cure, have followed the blind guid- 
 ance of empiricism, will almost assuredly be roused 
 to a new and becoming interest in this department 
 of practice, through the inspiring agency of this 
 hook. — Am. Jour. Med. SciencCy Oct. 18S7. 
 
 ALSO, NOW READY, 
 
 A SERIES OP PLATES ILLUSTEATING WILSON ON DISEASES OF 
 
 THE SKIN; consisting of nineteen beautifully executed plates, of which twelve are exquisitely 
 colored, presenting the Normal Anatomy and Pathology of the Skin, and containing accurate re- 
 presentations of about one hundred varieties of disease, most of them the size of nature. Price 
 in cloth $4 25. 
 
 In beauty of drawing and accuracy and finish of coloring these plates will be found equal to 
 anything of the kind as yet issued in this country. 
 
 One of the best specimens of colored lithographic 
 illustrations that have ever been published in this 
 country. The representations of diseases of the 
 skin, even to the most minute shade of coloring, are 
 remarkably accurate, giving the student or practi- 
 tioner a very correct idea of the disease he is study- 
 ing. We know of no work so well adapted to the 
 wants of the general practitioner as Wilson's, with 
 the accompanying plates. — Med. and Surg. Re- 
 porter, May, 1858. 
 
 We have already expressed our high appreciation 
 of Mr. Wilson's treatise on Diseases of the Skin. 
 The plates are comprised in' a separate volume, 
 which we counsel all those who possess the text to 
 purchase. It is a beautiful epecimen of color print- 
 ing, and the repiesentations of the various forms of 
 skin disease are as faithful as is possible in plates 
 of the size.— Boston Med. and Surg. Journal, April 
 S, 1858. 
 
32 BLANCHARD & LEA'S MEDICAL PUBLICATIONS. 
 
 WILSON (ERASMUS), M. D., F. R. S. 
 
 Lecturer on Anatomy, London. 
 
 THE DISSECTOK'S MANUAL; or, Practical and Surgical Anatomy. Third 
 
 American, from the last revised and enlarged Eng-lish edition. Modified and rearranged, by 
 William Hunt, M. 1)., Demonstrator of Anatomy in the University of Pennsylvania. In one 
 large and handsome royal 12mo. volume, leather, of 582 pages, with 154 illustrations. $2 00. 
 The modifications and additions which this work has received in passing recently through the 
 author's hands, are sufficiently indicated by the fact that it is enlarged by more than one hundred 
 pages, notwithstanding that it is printed in smaller type, and with a greatly enlarged page. 
 
 BY THE SAME AUTHOR. 
 
 ON CONSTITUTIONAL AND HEREDITARY SYPHILIS, AND ON 
 
 SYPHILITIC ERUPTIONS. In one small octavo volume, extra cloth, beautifully pinted, with 
 four exquisite colored plates, presenting more than thirty varieties of syphilitic eruptions. $2 2S. 
 
 BY THE SAME AUTHOB.. ^ 
 
 HEALTHY SKIN; A Popular Treatise on the Skin and Hair, their Preserva- 
 tion and Management. Second American, from the fourth London edition. One neat-volume, 
 royal 12mo., extra cloth, of about 300 pages, with numerous illustrations. $1 00 ; paper cover, 
 75 cents. 
 
 (No'TO- Complete.) 
 WEST (CHARLES), M. D., 
 
 Accoucheur to and Lecturer on Midwifery at St. Bartholomew's Hospital, Physician to the Hospital for 
 
 Sick Children, &c. 
 
 LECTURES ON THE DISEASES OP WOMEN. Now complete in one hand- 
 
 some octavo volume, extra cloth, of about 500 pages ; price $2 50. 
 Also, for sale separate, Part II, being pp. 309 to end, with Index, Title matter, 
 
 &e., 8vo., cloth, price $1. 
 ^^ Copies done up in paper covers, for mailing, will be sent, free of postage, to any address within 
 
 the United States on receipt of One Dollar in current funds or postage stamps. Subscribers to the 
 
 "Medical News and Library" who received the first portion of this work as published in 1856 
 
 and 1857, should lose no time in securing the completion. 
 Part I will no longer be sold separate. 
 
 As the first part of this work formed a complete treatise on the Diseases of the Uterus, so Part 
 II is complete in itself as a text-book on the affections of the Uterine Appendages, the Ovaries, 
 Vagina, Bladder, and External Organs. It will be found fully to maintain the high character ac- 
 quired by the preceding portion immediately on its appearance, and the whole will constitute a 
 reliable text-book on this interesting and difficult branch ot practice. 
 
 A few notices of Part I are added. " 
 
 painstaking, practical phyEician is apparent on every 
 page. — N. Y. Journal of Medicine ^ MarcJi, 1853. 
 
 AVe know of no treatise of the kind so complete 
 an-l yet so compact. — Chicago Med. Journal. Janu- 
 ary, 1858. 
 
 A fairer, more honest, more earnest, and more re- 
 liable inveatigator of the many diseases of women 
 and children is not to be found in any country. — 
 Southern Med. and Surg. Journalj January 1858. 
 
 We gladly recommend his Lectures as in the high- 
 est degree instructive to all who are interested in 
 obstetric practice. — London Lancet. 
 
 We have to say of it, briefly and decidedly, that 
 it is the best work on the subject in any language; 
 and that it stamps Dr. West as the facile princeps 
 of British obstetric authors. — Edinb, Med. Joum. 
 
 BY THE SAME AUTHOR. 
 
 LECTURES ON THE DISEASES OF INFANCY AND CHILDHOOD. 
 
 Second American, from the Second and Enlarged London edition. In one volume, octavo, 
 
 extra cloth, of nearly five hundred pages. $2 00. 
 
 We take leave of Dr. West with great respect for 
 his attainments, a due appreciation of his acute 
 powers of observation, ana a deep sense of obliga- 
 tion for this valuable contribution to our profes- 
 sional literature. His book is undoubtedly in many 
 respects the best we possess on diseases of children. 
 
 As a writer, Dr. West stands, in our opinion, se- 
 cond only to Watson, the" Macaulay of Medicine;" 
 he possesses that happy faculty of clothing instruc- 
 tion in easy garments; combining pleasure 'with 
 profit, he leads his pupils, in spite of the ancient 
 proverb, along a royal roaa to learning. His work 
 IS one which will not satisfy the extreme on either 
 side, but it is one that will please the great ma- 
 jority who are seeking truth, and one that will con- 
 vince the student that he has committed himself to 
 a candid, safe, and valuable guide. We anticipate 
 ^vith pleasure the appearance of the second part of 
 the work, which, it it equals this part, will com- 
 plete one of our very best volumes upon diseases of 
 females. — N. A> Med.-Chirurg. Review, July, 1858. 
 
 "VVe must now conclude this hastily written sketch 
 with the confident assurance to our readers that the 
 work will well repay perusal. The conscientious. 
 
 ligation by this able, thorough, and finished work 
 upon a subject which almost daily taxes to the ut- 
 most the skill of the general practitioner. He has 
 with singular felicity threaded his way through all 
 the tortuous labyrinths of the difficult subject he has 
 undertaken to elucidate, and has in many of the 
 darkest corners left a light, which will never be 
 extinguished. — Nashville Medical Journal. 
 
 Dublin Quarterly Journal of Medical Science, 
 Dr. West has placed the profession under deep ob- 
 
 BY THE same AUTHOR. 
 
 AN ENQUIRY INTO THE PATHOLOGICAL IMPORTANCE OP ULCER. 
 
 ATION OF THE OS UTERI. In one neat octavo volume, extra cloth. $1 00. 
 
 YOUATT (WILLIAM), V. S. 
 
 THE DOG. Edited by E. J. Lewis, M. D. With numerous and beautiful 
 
 iiluBtrations In one very handsome volume, crown Svo., crimson cloth, gill. $1 25. 
 
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