A TEXT-BOOK OF HUMAN PHYSIOLOGY, IN'CLUDING HISTOLOGY AND MICROSCOPICAL ANATOMY WITH SPECIAL REFERENCE TO THE REQUIREMENTS OF PRACTICAL MEDICINE. DR. L. LANDOIS. SECOND AMERICAN, TRANSLATED FROM THE FIFTH GERMAN EDITION. WITH ADDITIONS BY WILLIAM STIRLING, M.D., Sc.D, ANU HISTOLOGY IN OWES S COLLEGE AND VICH>KIA UX HONOfKS SCHOOL OF SCIENCE, UNIVERSITY OF OXFOKD FIVE HUNDRED AND EIGHTY-THREE ILLUSTRATIONS. PHILADELPHIA: P. BLAKISTON, SON & CO. No. 10 1 2 Walnut Street. 1887. SIR JOSEPH LISTER, Baronet, M.D., D.C.L., LL.D., F.R.SS. (LOND. AND EDIN.), CLINICAL SURGERY IN KlNO's COLLEGE, LONDON; SURGEON EXTRAORDINARY TO Tl lERLY REGIUS PROFESSOR OF CLINICAL SURGERY IN THE UNIVERSITY OF EDINEURGF IN ADMIRATION OF 'CfiTic ^lUnii oP Science, WHOSE BRILLIANT DISCOVERIES HAVE REVOLUTIONIZED MEDICAL PRACTICE, AND CONTRIBUTED INCALCULABLY TO THE WELL-BEING OF MANKIND; AND IN GRATITUDE TO 'Csfte 'Tlccicfier, WHOSE NOBLE EARNESTNESS IN INCULCATING THE SACREDNESS OF HUMAN LIFE STIRRED THE HEARTS OF ALL WHO HEARD HIM: BY HIS FORMER PUPIL, THE TRANSLATOR. PREFATORY NOTE TO SECOND ENGLISH EDITION. That a Second Edition of this " Text-Book of Physiology " has been called for within little more than six months after the publication of the complete work, indicates that the work has met a felt want. In this Edition, the distinctive character of the work has been adhered to and extended, matter being added bringing forward more clearly the relation of Physi- ology to Practical Medicine AND Surgery; the additions have chiefly been derived from the Fifth German Edition, but there has been incorporated a large amount of new matter. The number of Woodcuts has been increased from 494 to 5S3, to most of the Chapters I have added a paragraph on the Action of Drugs, and the Chapters on the Nervous System have been largely recast, partly with the aid of the Lec- tures on the Diseases of the Brain, by Dr. Gowers. I would wish to tender my thanks to Dr. Lauder Brunton for the use of some illustrations, and for information derived from his Text-Book of Pluirmacology, Therapeutics, and Materia Medica. For some suggestions relating to the Nervous System I am indebted to my friend Professor Schafer, also to Dr. Sidney Martin, who was kind enough to write the paragraph on " Vegetable Proteid Bodies," arid to Dr. Berry Hart for suggestions on the Chapters on Reproduction. Some of the new illustrations are taken from Schenk's Grundriss der normalen Histologic. For some of the new illustrations I am indebted to Professors Victor Horsley, Rutherford and Charteris, Drs. Hart and Johnson, and Mr. Martindale. The others are acknowledged elsewhere. Altogether, the work has been carefully revised, and I trust this Edition will prove as useful to Practitioners and Students as the last one. WILLIAM STIRLING. The Owens College, Manchester, ywwf, 18S6. Digitized by the Internet Archive in 2010 with funding from Columbia University Libraries http://www.archive.org/details/textbookofhumanpOOIand PREFACE TO FIRST ENGLISH EDITION. The fact that Professor Landois' "Lehrluch der F/iysiologie dcs Mensc/n-n" has already passed through four large editions since its first appearance in iSSo, shows that in some special way it has met the wants of Students and Practitioners in Germany. The characteristic which has thus commended the work will be found mainly to lie in its eminent practicality ; and it is this consideration which has induced me to undertake the task of putting it into an English dress for English readers. Landois' work, in fact, forms a Bridge between Physiology and the Practice of Medicine. It never loses sight of the fact that the Student of to-day is the prac- ticing Physician of to-morrow. Thus, to every Section is appended — after a full description of the normal processes — a short resume of the pathological variations, the object of this being to direct the attention of the Student, from the outset, to the field of his future practice, and to show him to what extent pathological pro- cesses are a disturbance of the normal activities. In the same way, the work offers to the busy physician in practice a ready means of refreshing his memory on the theoretical aspects of Medicine. He can pass backioard from the examination of pathological phenomena to the normal pro- cesses, and, in the study of these, find new indications and new lights for the appreciation and treatment of the cases under consideration. With this object in view, all the methods of investigation which may wich advantage be used by the Practitioner, are carefully and fully described ; and Histology, also, occupies a larger place than is usually assigned to it in Text-books of Physiology. A word as to my own share in the present version ; — (i.) In the task of translating, I have endeavored throughout to convey the author's meaning accurately, without a too rigid adherence to the original. Those who from experience know something of the difficulties of such an undertaking will be most ready to pardon any shortcomings they may detect. (2.) Very considerable additions have been made to the Histological and also (where it has seemed necessary) to the Physiological sections. All such additions are enclosed within square brackets []. I have to acknowledge my indebtedness to many valuable Papers in the various Medical Journals — British and Foreign — and also to the Histological Treatises of Cadiat, Ranvier and Klein; Quain's Anatiimy, vol. 11, ninth edition; Htxm.dinn'' s JIandbuch der Fhysiologie ; and the Text-books on Physiology, by Rutherford, Foster and Kirkes ; Gamgee's Physio- logical Chemistry ; Ewald's Digestion ; and Robert's Digestive Ferments. (3.) The Illustrations have been increased to 494 in the English version. These X PREFACE TO FIRST EDITION. additional diagrams, with the sources whence derived, are distinguished in the List of Woodcuts by an asterisk. There only remains for me now to express my thanks to all who have kindly helped in the progress of the work, either by furnishing Illustrations or otherwise especially to Drs. Byrom Bram well. Dudgeon, Lauder Brunton, and Knott; Mr. Hawksley; Professors Hamilton and M'Kendrick; to my esteemed teacher and friend, Professor Ludwig, of Leipzic ; and, finally, to my friend, Mr. A. W. Robertson, M. A., formerly Assistant Librarian in the University, and now Libra- rian of the Aberdeen Public Library, for much valuable assistance while the work was passing through the press. The Second Part will, it is hoped, be issued early in 1885. In conclusion — and forgetting for the moment my own connection with it— I heartily commend the work fcr sd to the attention of Medical Men, and can wish for it no better fate than that it may speedily become as popular in this country as it is in its Fatherland. WILLL\M STIRLING. Aberdeen University, NoT^mber^ 1SS4. GENERAL CONTENTS. INTRODUCTION. The Scope of Physiology, and its Relation to the other Branches of Natural Science . . . xxx Matter xxxi Forces xxxii Law of the Conservation of Energy xxxvi Animals and Plants xxxvi Vital Energy and Life xxxix I. PHYSIOLOGY OF THE BLOOD. 1. Physical Properties of the Blood 17 2. Microscopic Examination of the Blood iS 3. Histology of the Human Red Blood Corpuscles 21 4. Effects of Reagents on the Blood Corpuscles 21 5. Preparation of the Stroma — Making Blood " Lake-Colored " 23 6. Form and Size of the Blood Corpuscles of Different Animals 24 7. Origin of the Red Blood Corpuscles 25 8. Decay of the Red Blood Corpuscles 2S 9. The Colorless Corpuscles — Leucocytes — Blood Plates — Granules 29 10. Abnormal Changes of the Blood Corpuscles 34 11. Chemical Constituents of the Red Blood Corpuscles 35 12. Preparation of Haemoglobin Crystals 36 13. Quantitative Estimation of Haemoglobin 36 14. Use of Spectroscope 38 15. Compounds of Ha:moglobin — Methsemoglobin 39 16. Carbonic Oxide- H.iemoglobin — Poisoning with Carbonic Oxide 40 17. Other Compounds — Haemoglobin 42 iS. Decomposition of Haemoglobin 42 19. Ha-min and Blood Tests 43 20. Haematoidin 44 21. The Colorless Proteid of Hoemoglobin ^^ 22. Proteids of the Stroma 44 23. The other Constituents of Red Blood Corpuscles 45 24. Chemical Composition of the Colorless Corpuscles 45 25. Blood Plasma, and its Relation to Serum 46 26. Preparation of Plasma 46 27. Fibrin — Coagulation of the Blood 47 28. General Phenomena of Coagulation 48 29. Cause of Coagulation of the Blood 49 30. Source of the Fibrin Factors 53 31. Relation of the Red Blood Corpuscles to the Formation of Fibrin 54 32. Chemical Composition of the Plasma and Serum 54 33. The Gases of the Blood 56 34. Extraction of the Blood Gases 57 35. Quantitative Estimation of the Blood (iases 59 36. The Blood Gases 59 37. Is Ozone (O3) present in Blood? 60 38. Carbon dioxide and Nitrogen in Blood 6t 39. .■\rterial and Venous Blood 62 40. Quantity of Blood 63 41. Variations from the Norma! Conditions of the Blood 63 II. PHYSIOLOGY OF THE CIRCULATION. 42. General View of the Circulation 67 43. The Heart 67 44. Arrangement of the Cardiac Muscular Fibres 68 45. .\rrangenient of the Ventricular Fibres 70 SECTION PAGE 46. Pericardium, Endocardium, Valves 7' 47. Automatic Regulation of tlie Heart 73 48. The Movements of the Heart 75 49. Pathological Disturbances of Cardiac Action 77 50. The Apex Beat — The Cardiogram 7^ 51. The Time occupied by the Cardiac Movemenis 83 52. Pathological Disturbance of the Cardiac Impulse 85 53. The Heart Sounds 88 54. Variations of the Heart Sounds 92 55. The Duration of the Movements of the Heart 92 56. Physical Examination of the Heart 9^ 57. Innervation of Heart — Cardiac Nerves 92 58. The Automatic Motor Centres of the Heart 95 59. The Cardio-Pneumatic Movements 104 60. Influence of the Respiratory Pressure of the Heart 105 THE CIRCULATION. 61. The Flow of Fluids through Tubes 108 62. Propelling Force, Velocity of Current, Lateral Pressure 108 63. Currents through Capillary Tubes 110 64. Movements of Fluids and Wave Motion in Elastic Tubes no 65. Structure and Properties of the Blood Vessels in 66. The Pulse— Historical "6 67. Instruments for Investigating the Pulse n? 68. The Pulse Curve or Sphygmogram 122 69. Dicrotic Pulse 126 70. Characters of the Pulse 127 71. Variations in the Strength, Tension and Volume of the Pulse 128 72. The Pulse Curves of various Arteries 129 73. Anacrotism '3° 74. Influence of the Respiratory Movements on the Pulse Curve 131 75. Influence of Pressure upon the Form of the Pulse Curve 133 76. Rapidity of Transmission of Pulse Waves 134 77. Propagation of the Pulse Wave in Elastic Tubes 134 78. Velocity of the Pulse Wave in Man 136 79. Further Pulsatile Phenomena I37 80. Vibrations Communicated to the Body by the Action of the Heart 137 81. The Blood Current 139 82. Schemata of the Circulation 140 83. Capacity of the Ventricles 140 84. Estimation of the Blood Pressure I4' 85. Blood Pressure in the Arteries '45 86. Blood Pressure in the Capillaries >S' 87. Blood Pressure in the Veins '52 88. Blood Pressure in the Pulmonary Artery IS3 89. Measurement of the Velocity of the Blood Stream I55 90. Velocity of the Blood in Arteries, Capillaries, and Veins '57 91. Estimation of the Capacity of the Ventricles '59 92. The Duration of the Circulation '59 93. Work of the Heart '59 94. Blood Current in the Smaller Vessels 160 95. Passage of the Blood Corpuscles out of the Vessels— [Diapedesis] 162 96. Movement of the Blood in the Veins 163 97. Sounds or Bruits within Arteries I04 98. Venous Murmurs '^4 99. The Venous Pulse — Phlebogram 165 100. Distribution of the Blood 167 101. Plethysmography '67 102. Transfusion of Blood lo" THE BLOOD GLANDS. 103. The Spleen — Thymus— Thyroid — Suprarenal Capsules— Hypophysis Cerebri—Coc- cygeal and Carotid Glands 172 104. Comparative '°' 105. Historical Retrospect '82 CONTENTS. XIU III. PHYSIOLOGY OF RESPIRATION. CTION 106. Structure of the Air Passages and Lungs 183 107. Mechanism of Respiration 19° 108. Quantity of Gases Respired 191 109. Number of Respirations • '9- iio. Time occupied by the Respiratory Movements 192 111. Pathological Variations of the Respiratory Movements 195 112. General View of the Respiratory Muscles 196 113. Action of the Individual Respiratory Muscles 197 114. Relative Size of the Chest 201 115. Pathological Variations of the Percussion Sounds 203 116. The Normal Respiratory Sounds 204 117. Pathological Respiratory Sounds 204 ilS. Pressure in the Air Passages during Respiration 205 119. Appendix to Respiration 207 120. Peculiarly Modified Respiratory Sounds 207 CHEMISTRY OF RESPIRATION. 121. Quantitative Estimation of CO2, O, and Watery Vapor 209 122. Methods of Investigation 209 123. Composition and Properties of Atmospheric Air 212 124. Composition of Expired Air 212 125. Daily Quantity of Gases Exchanged 213 126. Review of the Daily Gaseous Income and Expenditure 213 127. Conditions Influencing the Gaseous Exchanges 213 1 2$. Diffusion of Gases within the Lungs 216 129. Exchange of Gases between the Blood and Air 216 130. Dissociation of Gases 21S 131. Cutaneous Respiration 219 132. Internal Respiration 219 133. Respiration in a Closed Space 221 134. Dyspncea and Asphyxia 222 135. Respiration of Foreign Gases 225 136. Accidental Impurities of the Air 225 137. Ventilation of Rooms 226 138. Formation of Mucus 227 139. Action of the Atmospheric Pressure 229 140. Comparative and Historical 230 IV. PHYSIOLOGY OF DIGESTION. 141. The Mouth and its Glands 232 142. The Salivary Glands 233 1 1,. Histc'l igical Changes in the .Salivary Glands 235 144. The Nerves of the Salivary Glands 237 145. Action of Nerves on the Salivary Secretion 237 146. The Saliva of the Individual Glands 242 147. The Mixed .Saliva in the Mouth 243 148. Physiological Action of Saliva 244 149. Tests for Sugar 246 150. (Quantitative Estimation of Sugar 247 151. Mechanism of the Digestive Apparatus 248 152. Introduction of the Food 248 153. The Movements of Mastication 248 154. Structure and Development of the Teeth 249 155. Movements of the Tongue 253 156. Deglutition 254 157. Movements of the Stcunach 256 158. Vomiting 257 159. Movements of the Intestine 259 160. Excretion of Foecal Matter 260 161. Influence of Nerves on the Intestine 262 162. Structure of the Stomach 266 163. The Gastric Juice 269 164. Secretion of Gastric Juice 269 SECTICN PACE 165. Methods of obtaining Gastric Juice 273 166. Process of Gastric Digestion 274 167. Gases in the Stomach . 27S 168. Structure of the Pancreas 27S 169. The Pancreatic Juice 279 170. Digestive Action of the Pancreatic Juice . 280 171. The Secretion of the Pancreatic Juice 2S3 172. Preparation of Peptonized Food 284 173. Structure of the Liver 284 174. Chemical Composition of the Liver Cells 288 175. Diabetes Mellitus, or Glycosuria 290 176. The Functions of the Liver 292 177. Constituents of the Bile 293 178. Secretion of Bile 296 179. Excretion of Bile • 298 180. Reabsorption of Bile 299 181. Functions of the Bile 3°' 182. Fate of the Bile in the Intestine 302 183. The Intestinal Juice 3°3 184. Fermentation Processes in the Intestine 307 185. Processes in the Large Intestine 3" 186. Pathological Variations 3^4 187. Comparative Physiology 3'*' iSS. Historical Retrospect 3' 7 V. PHYSIOLOGY OF ABSORPTION. 189. The Organs of Absorption 319 190. Structure of the Small and Large Intestines 319 191. Absorption of the Digested Food 325 192. Absorptive Activity of the Wall of the Intestine 327 193. Influence of the Nervous System 33' 194. Feeding with "Nutrient Enemata" 33' 195. Chyle Vessels and Lymphatics 33^ 196. Origin of the Lymphatics 33^ 197. The Lymph Glands 335 198. Properties of Chyle and Lymph 337 199. Quantity of Lymph and Chyle 339 200. Origin of Lymph 34° 201. Movement of Chyle and Lymph 34' 202. Absorption of Parenchymatous Effusions 344 203. Congestion of Lymph, Serous Effusions and Qidema 344 204. Comparative Physiology 34^ 205. Historical Retrospect 34^ VI. PHYSIOLOGY OF ANIMAL HEAT. 206. Sources of Heat 347 207. Homoiothermal and Poikilothermal Animals 35° 208. Methods of Estimating Temperature — Thermometry 351 209. Temjierature — Topography 353 210. Conditions Influencing the Temperature of Organs 354 211. Estimation of the Amount of Heat — Calorimetry 35^ 212. Thermal Conductivity of Animal Tissues 357 213. Variations of the Mean Temperature 35^ 214. Regulation of the Temperature 3^' 215. Income and Expenditure of Heat 3^3 2 1 6. Variations in Heat Production 3^5 217. Relation of Heat Production to Bodily Work 3^5 218. Accommodation for different Temperatures 3^6 219. Storage of Heat in the Body 3''7 220. Fever 3^7 221. Artificial Increase of the Temperature 3^9 222. Employment of Heat 3°9 223. Increase of Temperature post-mortem 3^^^ 224. Action of Cold on the Body 37° CONTENTS. FAGB SBCTION 225. Artificial Lowering of Tempeialure 37° 226. Employment of Cold 37i 227. Heat of Inflamed Parts 372 228. Historical and Comparative • 37^ VII. PHYSIOLOGY OF THE METABOLIC PHENOMENA OF THE BODY. 229. General View of Food Stuffs 373 230. Structure and Secretion of the Mammary Glands 375 231. Mdk and its Preparations 377 232. Eggs 381 233. Flesh and its Preparations 3°' 234. Vegetable Foods 3^3 235. Condiments — Coffee, Tea, and Alcohol 3^5 PHENOMENA AND LAWS OF METABOLISM. 236. Eiiuilibrium of the Metabolism 3^8 237. Metabolism during Hunger and Starvation 394 238. Metabolism during a purely Flesh Diet 39^ 239. A Diet of Fat or of Carbohydrates 397 240. Mixture of Flesh and Fat 397 241. Origin of Fat in the Body 39^ 242. Corpulence 399 243. The Metabolism of the Tissues . . 4°° 244. Regeneration of Organs and Tissues 4^2 245. Transplantation of the Tissues 4°$ 246. Increase in Size and Weight during Growth 40S GENERAL VIEW OF THE CHEMICAL CONSTITUENTS OF THE ORGANISM. 247. Inorganic Con'stituents 407 248. Organic Compounds — Proteids 4°^ 249. The Animal and Vegetable Proteids and their Properties 409 250. The Albuminoids 4' I 251. The Fats 4>2 252. The Carbohydrates 415 253. Historical Retrospect 4' 7 VIII. THE SECRETION OF URINE. 254. Structure of the Kidney 4'9 255. The Urine 426 256. Urea 43° 257. Qualitative and Quantitative Estimation of Urea 432 258. Uric Acid 434 259. Qualitative and Quantitative Estimation of Uric Acid 435 260. Krealinin and other Substances 43^ 261. Coloring Matters of the Urine 439 262. Indigo, Phenol, Kresol, Pyrokatechin 44° 263. Spontaneous Changes in Urine, Fermentations 443 264. Albumin in Urine 445 265. Blood in Urine 447 266. Bile in Urine 45° 267. Sugar in Urine 45' 268. Cystin 454 269. I.eucin, Tyrosin 454 270. Deposits in Urine 455 271. General Scheme for Detecting Urinary Deposits 457 272. Urinary Calculi 45^ 273. The Secretion of Urine 459 274. The Preparation of Urine 4^3 275. Passage of Various Substances into the Urine 465 276. Influence of Ntrves on the Renal Secretion 4^5 277. Urjemia, .Vmmonii^niia 4''9 XVI CONTENTS. SECTION PAr.E 27S. Structure and Functions of the Ureter 470 279. Urinary Bladder and Urethra 471 280. Accumulation and Retention of Urine 472 281. Retention and Incontinence of Urine 475 282. Comparative and Historical 475 IX. FUNCTIONS OF THE SKIN. 2S3. Structure of the Skin 477 284. Nails and Hair 479 285. The Glands of the Skm 482 286. The Skin as a Protective Covering 483 2S7. Cutaneous Respiration and Secretion — Sweat 4S4 28S. Conditions Influencing the Secretion of Sweat 486 289. Pathological Variations 488 290. Cutaneous Absorption— Galvanic Conduction 489 291. Comparative — Historical 49° X. PHYSIOLOGY OF THE MOTOR APPARATUS. 292. Ciliary Motion, Pigment Cells 49' 292A. Structure and Arrangement of the Muscles 493 293. Physical and Chemical Properties of Mu^cle 5°° 294. Metabolism in Muscle 5°^ 295. Rigor mortis 5°4 296. Muscular Excitability 5°^ 297. Changes in a Muscle during Contraction 5^' 298. Muscular Contraction 5 '3 299. Rapidity of IVansmission of a Muscular Contraction 5^3 300. Muscular Work 524 301. The Elasticity of Muscle 526 302. Formation of Heat in an Active Muscle 5^9 303. The Muscle Sound 53° 304. J'atigue of Muscle S3' 305. The Mechanism of the Joints 533 306. Arrangement and Uses of the ^luscles of the Body 53S 307. Gymnastics — Pathological Motor Variations 53^ 30S. Standing 539 309. Sitting 54° 310. Walking and Running 54' 311. Comparative 543 VOICE AND SPEECH, 312. Voice and Speech 545 313. Arrangement of the Larynx 545 314. Organs of Voice — Laryngoscopy 55' 315. Conditions Modifying the Laryngeal Sounds 553 316. Range of the Voice 554 317. Speech — The Vowels 555 318. The Consonants 557 319. Pathological Variations of Voice and Speech 55^ 320. Comparative — Historical 559 XI. GENERAL PHYSIOLOGY OF THE NERVES AND ELECTRO- PHYSIOLOGY. 321. Structure and Arrangement of the Nerve Elements 5^' 322 Chemistry of the Nerve Substance 5^^ 323. Metabolism of Nerves 5^8 324. Excitability of Nerves — Stimuli 5''^ 325. Diminution of the Excitability — Degene.ation and Regeneration of Nerves .... 572 326. The Galvanic Current 577 327. Action of the Galvanic Current — Galvanometer 578 328. Electrolysis 579 329. Induction — Extra Current — Magneto- Induction 584 CONTENTS. XVU SECTION PAGB 330. bu EoisReymond's Inductorium 5^^ 331. Electrical Currents in Passive Muscle and Nerve 5^8 332. Currents of Stimulated Muscle and Nerve 59' 333. Currents in Nerve and Muscle during Electrotonus 594 334. Theories of Muscle and Nerve Currents 595 335. Electrotonic Alteration of the Excitability 597 336. Electrotonus — Law of Contraction 600 337. Rapidity of Transmission of Nervous Impulses 602 338. Double Conduction in Nerves 605 339. Therapeutical Uses of Electricity — Reaction of Degeneration 606 340. Electrical Charging of the Body 611 341. Comparative — Historical 611 XII. PHYSIOLOGY OF THE PERIPHERAL NERVES. 342. Classification of Nerve Fibres 613 343. Nervus Olfactorius 615 344. Nervus Opticus 616 345. Nervus Oculomotorius 618 346. Nervus Trochlearis 621 347. Nervus Trigeminus 621 348. Nervus Abducens 630 349. Nervus Facialis 631 350. Nervus Acusticus ^34 351. Nervus Glosso-pharyngeus 637 352. Nervus Vagus 638 353. Nervus Accessorius 644 354. Nervus Hypoglossus 645 355. The Spinal Nerves 645 356. The Sympathetic Ner\-e 649 357. Comparative — Historical 652 XIII. PHYSIOLOGY OF THE NERVE CENTRES. 358. General 653 359. Structure of the Spinal Cord ■ ''54 360. Spinal Reflexes 661 361. Inhibition of the Reflexes 664 362. Centres in the Spinal Cord 668 363. Excitability of the Spinal Cord 67° 364. The Conducting Paths in the Spinal Cord 671 365. General .Schema of the Brain ' 675 366. The Medulla Oblongata 681 367. Reflex Centres of the Medulla Oblongata 685 36S. The Respiratory Centre 686 369. The Cardio- Inhibitory Centre 691 370. The Accelerans Cordis Centre 693 371. Vasomotor Centre and Vasomotor Nerves 695 372. Vaso-dilator Centre and Vaso-dilator Nerves 7°' 373. The .Spasm Centre — The Sweat Centre 7°2 374. Psychical Functions of the Cerebrum 703 375. Structure of the Cerebrum — Motor Cortical Centres 709 376. The Sensory Cortical Centres 7^1 377. The Thermal Cortical Centres 7^4 378. Topography of the Cortex Cerebri 7^5 379. The Basal Ganglia— The Midbrain 733 380. The Structure and Functions of the Cerebellum 739 381. The Protective Apparatus of the Brain 742 382. Comparative — -Historical 746 XIV. PHYSIOLOGY OF THE SENSE ORGANS. I. SIGHT. 383. Introductory Observations 748 384. Histology of the Eye 75° 385. Dioptric Observations 759 CONTENTS. rACB 386. Fonnation of a Retinal Image 764 387. Accommodation of the Eye 766 388. Normal and Abnormal Refraction 770 389. The Power of Accommodation ^^2 390. Spectacles 773 391. Chromatic Aberration and Astigmatism 774 392. The Iris 775 393. Entoptical Phenomena 779 394. Illumination of the Eye — The Ophthalmoscope 781 395. Activity of the Retina in Vision 785 396. Perception of Colors 79° 397. Color Blindness 794 398. Stimulation of the Retina 796 399. Movements of the Eyeballs 799 4CK). Binocular Vision 803 401. Single Vision — Identical Points 803 402. Stereoscopic Vision 805 403. Estimation of Size and Distance 808 404. Protective Organs of the Eye 810 405. Comparative — Historical 812 2. HEARING. 406. Structure of the Organ of Hearing 814 407. Physical Introduction 815 408. Ear Muscles 816 409. Tympanic Membrane 816 410. The Auditory Ossicles and their Muscles 819 411. Eustachian Tube — Tympanum 822 412. Conduction of Sound in the Labyrinth 824 413. Structure of the Labyrinth 825 414. Auditory Perceptions of Pitch 828 415. Perception of Quality — Vowels 830 416. Action of the Labyrinth 833 417. Harmony — Discords — Beats 835 418. Perception of Sound 836 419. Comparative — Historical 837 3. SMELL. 420. Structure of the Organ of Smell 839 421. Olfactory Sensations" 840 4. TASTE. 422. Position and Structure of the Organs of Taste 841 423. Gustatory Sensations 842 5. TOUCH. 424. Terminations of Sensory Nerves 844 425. Sensory and Tactile Sensations 846 426. The Sense of Locality 847 427. The Pressure Sense 850 428. The Temperature Sense 852 429. Common Sensation — Pain 853 430. The Muscular Sense 854 XV. PHYSIOLOGY OF REPRODUCTION AND DEVELOPMENT. 431. Forms of Reproduction 857 432. Testis — Seminal Fluid 857 433. The Ovary— Ovum— Uterus 862 434. Puberty 866 435. Menstruation 867 436. Penis — Erection 869 SECTION PAGE 437. Ejaculation — Reception of the Semen 872 438. Fertilization of the Ovum 872 439. Impregnation and Cleavage of the Ovum 873 440. Structures formed from the Epiblast . . . 877 441. Structures formed from the Mesoblast and Hypoblast 877 442. Formation of the Heart and Embrjo 878 443. Further Formation of the Body 880 444. Formation of the Amnion and Allantois 881 445. Human Fcetal Membranes — Placenta 882 446. Chronology of Human Development 886 447. Formation of the Osseous System 888 448. Development of the Vascular System 892 449. Formation of the Intestinal Canal 895 450. Development of the Genito-urinary Organs 897 451. Formation of the Central Nervous System 900 452. Development of the Sense Organs 901 453. Birth 902 454. Comparative — Historical 903 LIST OF ILLUSTRATIONS. PAGE FIGURE 1. Human colored blood corpuscles >9 2. Apparatus of Abbe and Zeiss for estimating the blood corpuscles 20 3. Mixer ^° *4. Gower's hEemacytometer [HawAsley) 20 5. Red blood corpuscles showing various changes of shape 21 6. Vasoformative cells 26 7. White blood corpuscles 29 *8. White blood corpuscles (A'lein) 3° g. Amreboid movements 3^ 10. Blood plates and their derivatives 33 11. Hsemoglobin crystals 3S *I2. Gower's hcemoglobinometer (//atiZ/fjAy) 37 13. Scheme of a spectroscope 3° 14. Various spectra of hfemoglobin 39 15. Hjeniin crystals 43 16. Ha;min crystals prepared from traces of blood 43 17. Hsematoidin crystals 44 *l8. Hewson's experiment 5° 19. Scheme of Pfliiger's gas pump 5^ 20. Micrococcus, bacterium, vibrio 0° *2I. Bacillus anthracis °° *22. Scheme of the circulation 67 23. Muscular fibres from the heart 68 24. Muscular fibres in the left auricle 69 25. Muscular fibres in the ventricles 7° *26. Lymphatic from the pericardium (Crt//«^) 271 *I76. Section of the tubes of the pancreas {//o«C£.*i?r aK(/5/i>/;>jf) 522 ♦304. Muscle caT\es (K'ronecker and Stirling) 522 *305. Tone inductorium (Kroneeker and Stirling) 522 *3o6. Muscle curves (Marey) 5^4 ♦307. Height of the lift by a muscle 525 *3o8. Dynamometer 5^^ *309. Curves of elasticity (after Marey) 527 *3lo. Curve of elasticity of a muscle (after Marey) 527 311. Curve of elasticity (Marey) 527 *3I2. Fatigue curve (Waller) 533 *3I3. Orders of levers 53^ *3I4. Scheme of the action of muscles on bones 537 315. Phases of walking 54' 316. Instantaneous photograph of a person walking 542 317. Instantaneous photograph of a runner 543 XXVI ILLUSTRATIONS. FIGURE PAGE 31S. Instantaneous photograph of a person jumping 543 319. Larynx from the front 546 320. Larynx from behind 546 321. Larynx from behind 547 322. Nerves of the larynx 547 323. Action of the posterior crico-arytenoid muscles 548 324. Action of the arytenoid muscles 548 325. Action of the lateral crico-arytenoid muscles 549 326. Vertical section of the head and neck 550 327. Examination of the larynx 551 328. Laryngoscopic view of the larynx 552 329. View of the larynx during a high note 553 330. View of the larynx during a deep inspiration 553 331. Rhinoscopy 553 332. View of the posterior nares 553 333. Parts concerned in phonation 556 334. Tumors on the vocal cords . . > 558 335. Histology of nervous tissues 562 *336. Sympathetic nerve fibre (Ranvier) 563 *337. Transverse sections of nerve fibres 563 338. Medullated ner\e fibre 563 *339. Ranvier's crosses {Kaiivier) 563 340. Transverse section of a nerve 5^5 *34I. Cell from the Gasserian ganglion (Schwalbc-) 566 342. Degeneration and regeneration of nerve fibres 573 *343. Waller's experiments (after Valton) 574 344. Rheocord of Du Bois Keymond 578 345. Scheme of a galvanometer 580 *346. Large Grove's battery [Gsiheidlen) 580 *347. Grennet's battery (Gscheidlen) 581 *348. Leclanche's element [Gscheidlen) 581 *349. Non-polarizable electrodes (Elliott Brothers) 582 *350. Thomson's galvanometer (i^/Z/o// ^roMcA-i) 583 *35I. Lamp and scale (Elliott Brothers) 583 *352. Galvanometer shunt (Elliott Brothers) 583 *353* Scheme of the induced currents (Hermann) 585 *354. Helmholtz's modification (Hermann) 585 355. Scheme of an induction machine 586 *356. Inductorium (Elliott Brothers) 587 357. StShrer's apparatus 587 *358. YnzlSonV^'j (Elliott Brothers) 587 *359- P'ug key (Elliott Brothers) 588 *36o. Capillary contact (Kronceker and Stirling) 588 361. Scheme of the muscle current 589 362. Capillary electrometer 589 *363. Secondary contraction 592 *364. Nen-e-niuscie preparation 592 365. Bernstein's differential rheotome 593 366. Nerve current in electrotonus 595 367. Scheme of electrotonic excitability 598 368. Method of testing electrotonic excitability 599 369. Distribution of an electrical current 599 370. Velocity of nerve energy 603 *37i. Scheme for testing velocity of a nerve impulse 604 *372. Curves of a nerve impulse (Marey) 604 *373- Sponge rheophores ( Weiss) 607 *374. Disk rheophore ( Weiss) 607 *375. Metallic brush ( Weiss) 607 376. Motor points of the arm 608 377. Motor points of the arm 608 378. Motor points of the leg 609 379. Motor points of the leg 610 *38o. Scheme of a reflex act (Stirling) 615 381. Optic chiasma 617 *382. Decussation of the optic tracts ( C4«/-fo/) 618 *383. Scheme of images in squinting (Bristowe) 619 ILLUSTRATIONS. FIGURE 384. Medulla oblongata 620 *385. Under surface of the brain 622 386. Connections of the cranial nerves 625 387. Sensory nerves of the face 629 388. Motor points of the face and neck ' . . . . 633 *389. Disposition of the semicircular canals ( W. Stirling) 636 *390. Cardiac nerves of the rabbit ( IV. Stirling) 640 *39i. Spinal ganglion (Cadiat) 646 392. Cutaneous nerves of the arm 647 393. Cutaneous nerves of the leg [Henh] 647 394. Transverse section of the spinal cord 654 *395. Transverse section of the white matter (Cndiai) 655 *396. Multipolar nerve cells of the cord ( Car//rt/) 655 *397. Relation of while and gray matter of the cord (Sc/ui/er) 655 *398. Transverse sections of the spinal cord 656 *399. Transverse section of the cord (Cadiat) 657 *400. Longitudinal section of i\i& cori {Cadiat) 658 *40i. Multipolar nerve cell 658 *402. Injected blood vessels of the cord [Kolliker) 658 403. Conducting paths in the cord 658 *404. Degeneration paths in the cord (j5?-aOT7//(;//) 660 *405. Scheme of a reflex act ( W. S/irling) 661 *406. Section of a spinal segment ( IV. Stirling) 661 *407. Propagation of reflex movements (i9fa««M) 662 *4o8. Effect of section on half of the cord (Erb) 674 *409. Brain, ventricles and basal ganglia 675 410. Scheme of the brain 676 *4II. Connections of the cerebellum 677 *4I2. Diagram of a spinal segment (5;rtOTTWf//) 680 *4I3. Section across the pyramids (Schwalhe) 681 *4I4. Section of the medulla oblongata (5(-A7wa//'f) 683 *4I5. Section of the olivary body (Sc/iwall'e) 683 *4i6. Scheme of the respiratory centres [Rutherford) 687 *4I7. Scheme of the accelerans fibres ( M< 5/«V/«i> ) 693 *4i8. Cardiac plexus of a cat (5y7iw) 694 *4I9. Frog without its cerebrum (Stirling, after Goltz) 705 *420. Frog without its cerebrum [Stirling, after Goltz) 705 *42I. Pigeon with its cerebrum removed (a/?^r Z)a//o») 705 *422. Cerebral convolution 709 *423. Cerebral convolution injected 7'° *424. Left side of the human brain (jE'c/^^r) 71 1 *425. Inner aspect of right hemisphere (^£<-/v;^) 712 *426. Left frontal lobe and island of Kei\ [Turner) 713 *427. Brain from above [Ecker) 7'4 428. Cerebrum of dog, carp, frog, pigeon, and rabbit 716 429. Relation of the cerebral convolutions to the skull 717 *430. Molor cenlKs [after Si/iafer and Horsley) 718 *43I. Motor areas (after Cowers) 7'9 432. Psycho-optic fibres [Alunk] 722 *433. Section of a cerebral hemisphere [Horsley) ■ 726 *434. Secondary degeneration in a crus ( Chareot) 728 *435. Transverse section of the crus cerebri ( C/;(r;ro^) 728 *436. Scheme of aphasia (/^;V//M«>h) 73° *437. Scheme of aphasia (iiVA/Zic/OT) • . 73° *438. Relation of the convolutions to the skull [R. W. Reid) 732 *439. Basal ganglia and the ventricles 734 *440. Transverse section of the right hemisphere [Gegenbaur] 736 *44I. Fibres in pons [Erb) 73^ *442. Section of the cerebellum [Saniey) 740 *443. Cortex cerebri and its membranes [Seh-valbe) 740 *444. Pigeon with its cerebellum removed [Dalton) 742 *445. Circle of Willis ( C/;a?ro/) • 744 *446. Ganglionic arteries ( Charcot) 745 *447. Corneal corpuscles [Ranvier) 750 *448. Corneal spaces (Ranvier) 75° 449. Junction of the cornea and sclerotic 751 XXVIll ILLUSTRATIONS. FIGURE PAGE *45o. Vertical section of cornea [Ranvier] • 752 *45I. Horizontal section of cornea (j?<7«i'/V>-) 75^ 452. Blood vessels of the eyeball 753 *453. Vertical section human retina (Cadial) 755 454. Layers of the retina 755 *455- Vertical section of the fovea centralis [Cadial) 756 *456. Fibres of the lens (A'o//ikt-r) 757 457. Section of the optic nerve 758 458. Action of lenses on light "jito 459. Refraction of light 7^ 460. Construction of the refracted ray 760 461. Optical cardinal points 762 462. Construction of the refracted ray "jbz 463. Construction of the image 763 464. Refracted ray in several media 763 465. Visual angle and retinal image 764 466. Scheme of the ophthalmometer 7^5 467. Horizontal section of the eyeball 767 468. Scheme of accommodation 767 469. Sanson-Purkinje's images 768 *470. Phakoscope (AI' Kendrici) 7^8 471. Scheiner's experiment 77° 472. Refraction of the eye 771 473. Myopic eye 77' 474. Hypermetrophic eye 77^ 475. Power of accommodation 772 *476. Diagram of astigmatism (Tv-w/) 775 477. Cylindrical glasses 775 *478. Scheme of the nerves of the iris {-Brb) 777 *479. Pupilonieter ( Gotham') 778 *4So. Pupilometer [Gorham) 778 481. Entoptical shadows 779 482. Scheme of the original ophthalmoscope 781 483. Scheme of the indirect method 782 484. Action of a divergent lens 782 485. Action of a divergent lens 782 486. View of the fundus oculi 783 *487. Morton's ophthalmoscope (/"/V^a/'rf OKt/ t«r/7) 783 *488. Frost's artificial eye (Frost) 784 489. Action of the orthoscope 784 *490. Mariotte's experiment 785 491. Horizontal section of the right eye 786 *492. M' Hardy's perimeter ( /'?V/'(7r^ <7«(/ O/rry) - 787 *493. Priestley Smith's perimeter [Pickard and Curry) 788 494. Perimetric chart 789 495. Geometrical color cone 792 496. Action of light rays on the retina 793 *497. Cones of the retina (Stirling, after Engelmann) 797 *498. Irradiation 797 499. Scheme of the action of the ocular muscles 802 500. Identical points of the retina 804 501. The horopter 804 502. Two stereoscopic drawings 805 503. Brewster's stereoscope 806 504. Wheatstone's stereoscope 806 505. Telestereoscope 807 506. Wheatstone's pseudoscope 807 507. Rollett's apparatus 809 *5o8. ZoUner's Imes 809 509. Section of an eyelid 8tl 510. Scheme of the organ of hearing 814 511. External auditory meatus 816 512. Left tympanic membrane and ossicles 817 513. Membrana tympani and ossicles 817 514. Tympanic membrane from within 817 ILLUSTRATIONS. XXIX PFGURE PAGE *5I5. "E&r %p&c\i[3. {Krohiie and Sesemann) 8l8 *5i6. Toynbee's artificial membrana tj'mpani (A'r«^«^ aW Sfie-maww) 8l8 517. Right auditory ossicles 818 518. Tympanum and auditory ossicles 819 519. Tensor tympani and Eustachian tube 821 520. Right stapedius muscle 822 *52I. Eustachian catheter 823 *522. Politzer's ear bag (JCro/me and Sesemann) 823 523. Right labyrinth 824 524. Scheme of the cochlea 825 *525. Interior of the right labyrinth 826 *526. Semicircular canals 820 527. Scheme of the canalis cochlearis 827 *S28. Gallon's whistle [Krohite and Sesemann) 829 529. Curve of a musical note and its overtones 831 *530. Kcenig's manometric capsule {Kanig) 832 *53i. Flame pictures of vowels (A'(r«/i^) 833 *532. Kcenig's analyzing apparatus [Ka:>iig) 835 533. Olfactory cells 839 534. Nasal and pharyngo-nasal cavities 839 535. Circumvallate papilla and taste bulbs 841 *S36. Wagner's touch corpuscle (Jianvifi) 844 537. Vertical section of skin 844 538. Pacini's corpuscle 845 *S39- Bouchon epidermique (Hanvier) 846 540. ^^sthesiometer 847 541. ^sthesiometer of Sieveking 848 *542. Aristotle's experiment 849 543. Landois' pressure mercurial balance 850 *S44. Karyokinesis ( Cegenbatir) 856 *545. Section of testis (Scheni) 858 *546. Tubule of testis {Scheiik) 859 *547. Section of epididymis (.Si/ifB.^) 859 548. Spermatic crystals 860 549. Spermatozoa 861 550. Spermatogenesis 861 *55I. h csl'i ovary [Hart and Barbour, aftir Schron) 862 *552. Section of an ovary (Turner) 863 553. Ovary and polar globules 864 *554. ^{\xcausmtmhr2MS o{ ihsuiems {ffart and Barbour, after Turner) 865 *555. Fallopian tube and its annexes (Nenie) 866 *556. Section of Fallopian tube [Scheni) 867 *S57- Uterus before menstruation (J. Williams) 868 *558. Uterus after menstruation {J. IVilliams) 868 *559. Erectile tissue (Cadiat) 869 560. The urethra and adjoining muscles 871 561. Cleavage of the yelk 874 562. The blastoderm 875 563. Schemata of development 876 *564. Embryo of the mole ( IV. K. Parker) 881 *565. Uterine mucous membrane (Cw/^) 883 *566. Placental villi {Cadiat) 884 567. Hare lip 889 *S68. Meckel's cartilage ( W. K. Parker) 889 569. Centres of ossification in the innominate bone 890 570. Development of the heart 893 571. The aortic arches 893 572. Veins of the embryo 894 573. Development of the veins and portal system 895 574. Development of the intestine 896 575. Development of the lungs 896 576. Formation of the omentum 896 577. Development of the internal generative organs 897 XXX ILLUSTRATIONS. PIGtTRE PAGE 578. Development of the external genitals 899 *s79- 1 r 900 *cS I Changes in the external organs of generation in the female (after Schrccder) . -j ^ *S82. J [ 900 583. Development of the eye 901 [The illustrations indicated by the word Hermann are from Hermann's Handhuch dcr Physi- ologie; by Cadiat, from Cadiat's Traiti d'Anatomie Gencrale; by Ranvier, from Ranvier's Traite Technique d' Histologie : by Brunton, from The Practitioner ; Brunton's Text-Book of Pharma- cology, Therapeutics, and Materia Afedica ; by Schenk, from Schenk's Grundriss der normalen Histologic ; by Ecker, from Ecker's Anatomie des Frosches.'\ INTRODUCTION. THE SCOPE OF PHYSIOLOGY AND ITS RELATIONS TO OTHER BRANCHES OF NATURAL SCIENCE. Physiology is the science of the vital phenomena of organisms, or, broadly, it is the Doctrine of Life. Correspondingly to the divisions of organisms, we distinguish — (i) Animal Physiology ; (2) Vegetable Physiology ; and {t,) the Physi- ology of the Lowest Living Organisms, which stand on the border line of animals and plants, /. e., the so-called Protista oi Haeckel, micro-organisms, and those elementary organisms or cells which exist on the same level. The object of Physiology is to establish these phenomena, to determine their regularity and causes, and to refer them to the general fundamental laws of Natural Science, viz., the Laws of Physics and of Chemistry. The following Scheme shows the relation of Physiology to the allied branches of Natural Science : — BIOLOGY. The science of organized beings or organisms (animals, plants, protistae, and elementary organisms). L MORPHOLOGY. The doctrine of the form of organ- isms. IL PHYSIOLOGY. General Morphology. The doctrine of the formed elementary constituents of or- ganisms. (Histology) — (a) Histology of Plants. [b) Histology of Ani- mals. Special Morphology. The doctrine of the parts and orgnns of organisms. ( Organology Anatomy) — (a) Phytotomy. {/>) Zootomy. The doctrine of the vital phenom- ena of organisms. General Physiology. The doctrine of vital phenomena in gen- eral — (n) Of Plants. (l>) Of Animals. Special Physiology, The doctrine of the activities of the in- dividual organs — [a) Of Plants. \b) Of Animals. in. EMBRYOLOGY. The doctrine of the generation and development of organisms. fi. History of the development of single beings, of the indi- vidual (e.g., of man) from the ovum onward (Ontogeny) — (a) In Plants. (/>) In Animals. Morphological part of the doc- trine of development, /. f., the doctrine of form in its stages of development — [a) General. [b) Special. 2. History of the development of a whole stock of organisms from the lowest forms of the series upward (Phylogeny) — (a) In Plants. [b) In Animals. xxxi Physiological part of the doc- trine of development, /'. e., the doctrine of the activity during development — [a) General, {b) Special. XXXll INTRODUCTION. Morphology and Physiology are of equal rank in biological science, and a previous acquaintance with Morphology is assumed as a basis for the comprehen- sion of Physiology, since the work of an organ can only be properly understood when its external form and its internal arrangements are known. Development occupies a middle place between Morphology and Physiology ; it is a morpho- logical discipline in so far as it is concerned with the description of the parts of the developing organism ; it is a physiological doctrine in so far as it studies the activities and vital phenomena during the course of development. MATTER. The entire visible world, including all organisms, consists of matter, /. e., of substance which occupies space. We distinguish ponderable matter which has weight, and imponderable matter which cannot be weighed in a balance. The latter is generally termed ether. In ponderable materials, again, we distinguish their form, i. e., the nature of their limiting surfaces; further, their volume, i. e., the amount of space which they occupy ; and lastly, their aggregate condition, i. e., whether they are solid, fluid, or gaseous bodies. Ether. — The ether fills the space of the universe, certainly as far as the most distant visible stars. This ether, notwithstanding its imponderability, possesses distinct mechanical properties; it is infinitely more attenuated than any known kind of gas, and behaves more like a solid body than a gas, resembling a gelatin- ous mass rather than the air. It participates in the luminous phenomena due to the vibrations of the atoms of the fixed stars, and hence it is the transmitter of light, which is conducted by means of its vibrations, with inconceivable rapidity (42,220 geographical miles per second) to our visual organs {Tyndall). Imponderable matter (ether) and ponderable matter are not separated sharply from each other ; rather does the ether penetrate into all the spaces existing between the smallest particles of ponderable matter. Particles. — Supposing that ponderable matter were to be subdivided continu- ously into smaller and smaller portions, until we reached the last stage of division in which it is possible to recognize the aggregate condition of the matter operated upon, we should call the finely-divided portions of matter in this state particles. Particles of iron would still be recognized as solid, particles of water as fluid, particles of oxygen as gaseous. Molecules. — Supposing, however, the process of division of the particles to be carried further still, we should at last reach a limit beyond which, neither by mechanical nor by physical means, could any further division be effected. We should have arrived at the molecules. A molecule, therefore, is the smallest amount of matter which can still exist in a free condition, and which as a unit no longer exhibits the aggregate condition. Atoms. — But even molecules are not the final units of matter, since every molecule consists of a group of smaller units, called atoms. An atom cannot exist by itself in a free condition, but the atoms unite with other similar or dis- similar atoms to form groups, which are called molecules. Atoms are incapable of furtlier subdivision, hence their name. We assume that the atoms are invari- ably of the same size, and that they are solid. From a chemical point of view, the atom of an elementary body (element) is the smallest amount of the element which can enter into a chemical combination. Just as ponderable matter consists in its ultimate parts of ponderable atoms, so does the ether consist of analogous small ether atoms. Ponderable and Imponderable Atoms. — The ponderable atoms within ponderable matter are arranged in a definite relation to the ether atoms. The ponderable atoms mutually attract each other, and similarly they attract the im- ponderable ether atoms ; but the ether atoms repel each other. Hence, in pon- INTRODUCTION, XXXIII derable masses, ether atoms surround every ponderable atom. These masses, in virtue of the attraction of the ponderable atoms, tend to come together, but only to the extent permitted by the surrounding ether atoms. Thus the ponderable atoms can never come so close as not to leave interspaces. All niatter must, therefore, be regarded as more or less loose and open in texture, a condition due to the interpenetrating ether atoms, which resist the direct contact of the ponder- able atoms. Aggregate Condition of Atoms. — The relative arrangement of the mole- cules, /. e., the smallest particles of matter which can be isolated in a free condi- tion, determines the aggregate condition of the body. Within a solid body, characterized by the permanence of its volume as well as by the independence of its form, the molecules are so arranged that they cannot readily be displaced from their relative position. Fluid bodies, although their volume is permanent, readily change their shape, and their molecules are in a condition of continual movement. When this movement of the molecules takes so wide a range that the individual molecules fly apart, the body becomes gaseous, and as such is characterized by the instability of its form as well as by the changeableness of its volume. Physics is the study of these molecules and their motions. FORCES. I. Gravitation — ^Al^o^k done. — All phenomena appertain to matter. These phenomena are the appreciable expression of the forces inherent in matter. The forces themselves are not appreciable, they are the causes of the phenomena. Gravitation. — The law of gravitation postulates that every particle of pon- derable matter in the universe attracts every other particle with a certain force. This force is inversely as the square of the distance. Further, the attractive force is directly proportional to the amount of the attracting matter, without any refer- ence to the quality of the body. We may estimate the intensity of gravitation by the extent of the movement which it communicates to a body allowed to fall, for one second, through a given distance, in a space free from air. Such a body will fall in vacuo 9.809 metres per second. This fact has been arrived at experi- mentally. Let us represent i; = 9.809 metres, the final velocity of the freely falling body at the end of one second. The velocity, V, of the freely falling body is proportional to the time, /, so that V=.?/ (I); i.e., at the end of the 1st sec, V =^, i =^'- =: 9.S09 M — the distance traversed — s =S^ r- (2); 2 i.e., the distances are as the square of the times. Hence, from (i) and (2) it follows (by eliminat- ing /) that — V = y'2is (3). The velocities are as the square roots of the distances traversed — Therefore, ^ .r (4). ~S The freely falling body, and in fact every freely moving body, possesses kinetic energy, and is in a certain sense a magazine of energy. The kinetic energy of any moving body is always equal to the product of its weight (estimated by the balance), and the height to which it would rise from the earth, if it were thrown from the earth with its own velocity. Let \V represent the kinetic energy of the moving body, and P its weight, then W = V.s, so that from (4) it follows that — W=P''' (5). %' Hence, the kinetic energy of a body is proportional to the square of its velocity. XXXIV INTRODUCTION. Work. — If a force (pressure, strain, tension) be so applied to a body as to move it, a certain amount of work is performed. The amount of work is equal to the product of the amount of the pressure or strain which moves the body, and of the distance through which it is moved. Let K represent the force acting on the body, and S the distance, then the worl< W =: KS. The attraction between the earth and any body raised above it is a source of worlc. It is usual to express the value of K in kilogrammes, and .S in metres, so that the "unit of work" is the kilogramme-metre, i.e., the force which is re- quired to raise i kilo, to the height of i metre. 2. Potential Energy. — The iransfiirmation of Potenfial into Kiintic energy anil conversely: Besides kinetic energy, there is also "potential energy," or energy of position. By this term are meant various forms of energy, which are suspended in their action, and which, although they may cause motion, are not in themselves motion. A coiled watch-spring kept in this position, a stone resting upon a tower, are instances of bodies possessing potential energy, or the energy of position. It requires merely a push to develop kinetic from the potential energy, or to transform potential into kinetic energy. Work, w, was performed in raising the stone to rest upon the tower. w --: /, s, where/ = the weight and s = the height. p = m .g, is ^ the product of the mass (m), and the force of gravity ( g'), so that to = m g s. This is at the same time the expression for the potential energy of the stone. This potential energy may readily be transformed into kinetic energy by merely pushing the stone so that it falls from the tower. The kinetic energy of the stone is equal to the final velocity with which it impinges upon the earth. V = -\/ig s (see above (3) ). V2 = 2gS. mV- = 2m s s. m g s was the expression tor the potential energy of the stone while it was still rest- ing on the height ; — Vj is the kinetic energy corresponding to this potential energy (^Briickc'). Potential energy may be transformed into mechanical energy under the most varied conditions ; it may also be transferred from one body to another. The movement of a pendulum is a striking example of the former. When the pendulum is at the highest point of its excursion, it must be regarded as absolutely at rest for an instant, and as en- dowed with potential energy, thus corresponding with the raised stone in the previous instance. During the swing of the pendulum this potential energy is changed into kinetic energy, which is greatest when the pendulum is moving most rapidly toward the vertical. As it rises again from the vertical po.sition, it moves more slowly, and the kinetic energy is changed mto potential energy, which once more reaches its maximum when the pendulum comes to rest at the utmost limit of its excursion. Were it not for the resistances continually opposed to its movements, such as the resist- ance of the air and friction, the movement of the pendulum, due to the alternating change of kinetic into potential energy and viie versa., would continue uninterruptedly, as with a mathematical pendu- lum. Suppose the swinging ball of the pendulum, when exactly in a vertical position, impinged upon a resting but moving sphere, the potential energy of the ball of the pendulum would be trans- ferred directly to the sphere, provided that the elasticity of the ball of the pendulum and the sphere were complete ; the pendulum would come to rest, while the sphere would move onward with an equal amount of kinetic energy, provided there were no resistance to its movement. This is an ex- ample of the transference of kinetic energy from one body to another. Lastly, suppose that a stretched watch-spring on uncoiling causes another spring to become coiled ; and we have another example of the transference of kinetic energy from one body to another. The following general statement is deducible from the foregoing examples : If, in a system, the individual moving masses approach the final position of equili- brium, then in this system the sum of the kinetic energies increases ; if, on the INTRODUCTION. XXXV other hand, the particles move away from the final jjosition of equilibrium, then the sum of the potential energies is increased at the expense of the kinetic ener- gies, i.e., the kinetic energies diminish {^BriUke'). The pendulum, which, after swinging from the highest point of its excursion, approaches the ver- tical position, i.e., the position of equilibrium of a passive pendulum, has in this position the largest amount of potential energy ; as it again ascends to the highest point of its excursion on the other side, it again gradually receives the maximum of potential energy at the expense of the gradually diminishing movement, and, therefore, of the kinetic energy. 3. Heat. — Its Relation to Potential and Kinetic Energy. — If a lead weight be thrown from a high tower to the earth, and if it strike an unyielding substance, the movement of the mass of lead is not only arrested, but the kinetic energy (which to the eye appears to be lost) is transformed into a lively vibratory moveinent of the atoms. When the lead meets the earth, heat is produced. The amount of heat produced is proportional to the kinetic energy, which is transformed through the concussion. At the moment when the lead weight reaches the earth, the atoms are thrown into vibrations ; they impinge upon each other ; then rebound again from each other in consei]uence of their elasticity, which opposes their direct juxtapo- sition ; they fly asunder to the maximum extent permitted by the attractive force of the ponderable atoms, and thus oscillate to and fro. All the atoms vibrate like a pendulum, until their movement is commimicated to the ethereal atoms surround- ing them on every side, i.e., until the heat of the heated mass is " radiated. '^ Heat is thus a vibratory movement of the atoms. As the amount of heat produced is ]iroportional to the kinetic energy, which is transformed through the concussion, we must find an adequate measure for both forces. Heat Unit. — As a standard of measure of iieat, we have the " heat unit " or calorie. The '• heat unit " or calorie is the amount of energy required to raise the temijerature of i gramme of water 1° C. The " heat unit" corresponds to 425.5 gramme-metres, i.e., the same energy required to heat i gramme of water 1° C. would raise a weight of 425.5 grammes to the height of i metre ; or, a weight of 425.5 grammes, if allowed to fall from the height of i metre, would by its con- cussion produce as much heat as would raise the temperature of i gramme of water 1° C. The "mechanical equivalent" of the heat unit is, therefore, 425.5 gramme-metres. It is evident that from the collision of moving masses an immeasurable amount of heat can be produced. Let us ajjply what has already been said to the earth. Suppose the earth to be dis- turbed in its orbit, and suppose further that, owing to the attraction of the sun, it were to impinge on the latter (whereby, according to J. R. Mayer, its final velocity would be 85 geographical miles per second), the amount of heat produced by the collision would be equal to that produced by the combustion of a mass of pure charcoal more than 5000 times as heavy {Julius Robert Mayer, Helm- holtz). Thus, the heat of the sun itself can be produced by the collision of masses of cold mitter. If the cold matter of the universe were thrown into space, and there left to the attraction of its particles, the collision of these particles would ultimately produce the light of the stars. At the present time, numerous cosmic bodies collide in space, while innumerable small meteors (94,000 to 188,000 bil- lions of kilos, per minute) fall hito the sun. The force of gravity is, perhaps, in fact, the only source of all heat (_/. R. Mayer, Yyndatl ). We have a homely examjile of the transformation of kinetic energy into heat in the fact that a blacksmith may make a piece of iron red hot by hammering it. Of the conversion of heat into ki- netic energy, we have an example in the hot watery vapor (steam) of the steam engine raising the piston. An example of the conversion of potential energy into lieat occurs in a metallic spring, when it uncoils and is so placed as to rub against a rough surface, producing heat by friction. 4. Chemical Affinity : Relation to Heat. — While gravity acts upon the particles of matter without reference to the composition of the body, there is an- other atomic force which acts between atoms of a chemically different nature ; this is chemical affinity. This is the force in virtue of which the atoms of chemi- cally different bodies unite to form a chemical compound. The force itself varies greatly between the atoms of different chemical bodies ; thus we speak of XXXVl INTRODUCTION. strong chemical affinities and weak affinities. Just as we were able to estimate the potential energy of a body in motion from the amount of heat which was produced when it collided with an unyielding body, so we can measure the amount of the chemical affinity by the amount of heat which is formed when the atoms of chem- ically different bodies unite to form a chemical compound. .\s a rule, heat is formed when separate chemically different atoms form a compound body. When, in virtue of chemical affinity, the atoms of i kilo, of hydrogen and S kilos, of oxygen unite to form the chemical compound wah-r, an amount of heat is there- by evolved which is equal to that produced by a weight of 47,000 kilos, falling and colliding with the earth from a height of 1000 feet above the surface of the earth. If i gram, of H be burned along with the requisite amount of O to form water, it yields 34,460 heat units or calories ; and i gram, carbon burned to carbonic acid (carbon dioxide) yields 8080 heat units. Wherever, in chemical processes, strong chemical affinities are satisfied, heat is set free, i.e., chemical affnity is changed into heat. Chemical affinity is a form of potential energy obtaining between the most different atoms, which during chemical pro- cesses is changed into heat. Conversely, in those chemical processes where strong affinities are dissolved, and chemically-united atoms thereby pulled asunder, there must be a diminution of temperature, or, as it is said, heat becomes latent — that is, the energy of the heat which has become latent is changed into chemical energy, and this, after decomposition of the compound chemical body, is again represented by the chemical affinity between its isolated different atoms. LAW OF THE CONSERVATION OF ENERGY. Julius Robert Mayer and Helraholtz have established the important law that, in a system which does not receive any influence and impression from without, the sum of all the forces acting within it is always the same. The various forms of energy can be transformed one into the other, so that kinetic energy may be trans- formed into potential energy, and vice versa, but there is never any part of the energy lost. The transformation takes place in such measure that, from a certain definite amount of one form of energy, a definite amount of another can be obtained. The various forms of energy acting in organisms occur in the following modifications : — 1. Molar motion (ordinary movements), as in the movements of the whole body, of the limbs, or of the intestines, and even those observable microscopically in connection with cells. 2. Movements of Atoms as Heat. — We know, in connection with the vibration of atoms, that the number of vibrations in the unit of time determines whether the oscillations appear as heat, light, or chemically-active vibrations. Heat vibrations have the smallest number, while chemically-active vibrations have the largest number, light vibrations standing between the two. In the human body we only observe heat vibrations, but some of the lower animals are capable of exhibiting the phenomena of light. In the human organism, the molar movements in the individual organs are constantly being transformed into heat, e. g., the kinetic energy in the organs of the circulation is transformed by friction into heat. The measure of this is the "unit of work " = I gramme-metre, and the "unit of heat " = 425.5 gramme-metres. 3. Potential Energy. — The organism contains many chemical compounds which are characterized by the great complexity of their constitution, by the imperfect saturation of their affinities, and hence by their great tendency to split up into simpler bodies. The body can transform the potential energy into heat as well as into kinetic energy, the latter always in conjunction with the former, but the former always by itself alone. The simplest measure of the potential energy is the amount of heat. INTRODUCTION. XXXVU which can be obtained b\- complete combustion of the chemical compounds representing the potential energy. The number of work units can then be calcu- lated from the amount of heat produced. 4. The phenomena of electricity, magnetism and diamagnetism may be recognized in two directions, as movements of the smallest particles, which are recognized in the glowing of a thin wire when it is traversed by strong electrical currents (against considerable resistance), and also as molar movement, as in the attraction or repulsion of the magnetic needle. Electrical phenomena are mani- fested in our bodies by muscle, nerve, and glands, but these phenomena are rela- tively small in amount when compared with the other forms of energy. It is not improbable that the electrical phenomena of our bodies become almost completely transformed into heat. As yet experiment has not determined with accuracy a "unit of electricity" directly comparable with the "heat unit " and the "work unit." It is quite certain that within the organism one form of energy can be trans- formed into another form, and that a certain amount of one form will yield a definite amount of another form; further, that new energy never arises sponta- neously, nor is energy already present ever destroyed, so that in the organism the law of the conservation of energy is continually in action. .\NIMALS AND PLANTS. The animal body contains a quantity of chemically-potential energy stored up in its constituents. The total amount of the energy present in the human body might be measured by burning completely an entire human body in a calorimeter, and thereby determining how many heat units are produced when it is reduced to ashes (see Animal Heat). The chemical compounds containing the potential energy are characterized by the complicated relative position of their atoms, by a comparatively imperfect saturation of the affinities of their atoms, by the relatively small amount of oxy- gen which they contain, by their great tendency to decomposition, and the facility with which they undergo decomposition. If a man were not supplied with food he would lose 50 grammes of his body weight every hour ; the material part of his body, which contains the potential energy, is used up, oxygen is absorbed, and a continual process of combustion takes place ; by the process of combustion simpler substances are formed from the more complex compounds, whereby potential is converted into kinetic energy. It is immaterial whether the combustion is rapid or slow ; the same amount of the same chemical substances always produces the same amount of kinetic energy, /. e., of heat. A person, when fasting, experiences after a certain time the disagreeable feeling of exhaustion of his reserve of potential energy, hunger sets in, and he takes food. All food for the animal kingdom is obtained, either directly or indirectly, from the vegetable kingdom. Even carnivora, which eat the flesh of other animals, only eat organized matter which has been formed from vegetable food. The existence of the animal kingdom presupposes the existence of the vegetable king- dom. All substances, therefore, necessary for the food of animals occur in vegetables. Besides water and the inorganic constituents, plants contain, among other organic compounds, the following three chief representatives of food stuffs — fats, carbohydrates and proteids. .\ll these contain stores of potential energy, in virtue of their complex chemical constitution. The fats contain — -^ C./H,„_,0(OH) = fatty acids \ .^ . 1 lie tats contain . ^ 4-C,H,(_OH),= glycerine J '■^ 2oiJ. XXXVIU INTRODUCTION. The carbohydrates contain : — Ci-.HkiO, . . (*? 252). I t:- 51-5-54-5 1 I H. 6.9- 7.3 I '1 he proteids contain i)er cent. : — ' N. 15. 2-17.0 ; (§§ 24S and 249). I O. 20.9-23.5 I I S. 0.3- 2.0 I A man who takes a certain amount of this food adds thereto oxygen from the air in the process of respiration. Combustion or o.xidation then takes place, whereby chemically potential energy is transformed into heat. It is evident that the products of this combustion must be bodies of simpler constitution — bodies with less complex arrangement of their atoms, with the greatest possible saturation of the affinities of their atoms, of greater stability, partly rich in O, and possessing either no potential energy, or only very little. These bodies are carbon dioxide, C().^; w/ater, H.^O ; and as the chief repre- sentative of the nitrogenous excreta, urea (CO(NH,).), which has still a small amount of potential energy, but which outside the body readily splits into COj and ammonia (NH3). The human body is an organism in which, by the phenomena of oxidation, the complex nutritive materials of the vegetable kingdom, which are highly charged with potential energy, are transformed into simple chemical bodies, whereby the potential energy is transformed mto the equivalent amount of kinetic energy (heat, work, electrical phenomena). But how do plants form these complex ' food stuffs so rich in potential energy ? It is plain that the potential energy of plants must be obtained from some other form of energy. This potential energy is supplied to plants by the rays of the sun, whose chemical light rays are absorbed by plants. Without the rays of the sun there could be no plants. Plants absorb from the air and the soil CO2, H.^O, NH3, and N, of which carbon dioxide, water, and ammonia (from urea) are also ]5roduced by the excreta of animals. Plants absorb the kinetic energy of light from the sun's rays and transform it into potential energy, which is accumulated during the growth of the plant in its tissues, and in the food stuffs produced in them during their growth. This formation of complex chemical compounds is accom- panied by the simultaneous excretion of O. Occasionally, kinetic energy, such as we universally meet with in animals, is liberated in plants. Many plants develop considerable quantities of heat in their flowers, e. g., the arum tribe. We must also remember that during the formation of the solid parts of plants, when fluid juices are changed into solid masses, heat is set free. In plants, under certain circumstances, O is absorbed, and COj is excreted, but these processes are so trivial as compared with the typical condition in the vegetable kingdom, that they may be regarded as of small moment. Plants, therefore, are organisms which, by a reduction process, transform simple stable combinations into complex compounds, whereby potential solar energy is transformed into the chemically-potential energy of vegetable tissues. Animals are living beings, which by oxidation decompose or break up the com- plex grouping of atoms manufactured by plants, whereby potential is transformed into kinetic energy. Thus there is a constant circulation of matter and a con- stant exchange of energy between plants and animals. All the energy of animals is derived from plants. All the energy of plants arises from the sun. Thus the sun is the cause, the original source of all energy in the organism, ;. e., of the whole of life. As the formation of solar heat and solar light is explicable by the gravitation of masses, gravity is, perhaps, the original form of energy of all life. We may thus represent the formation of kinetic energy in the animal body from the potential energy of plants. Let us suppose the atoms of the substances formed in organisms, as simple small Ijodies, balls, or blocks. .\s long as these INTRODUCTION. XXXIX lie in a single layer, or in a few layers, upon the surface, there is a stable arrange- ment, and they continue to remain at rest. If, however, an artificial tower be built of these blocks, so that an unstable erection is produced, and the same tower be afterwards knocked down, then for this purpose we require — (i) the motor power of the workman who lifts and carries the blocks; (2) a blow or other impulse from without applied to the unstable structure — when the atoms will fall together, and as they fall collide with each other and produce heat. Thus the energy employed by the workman is again transformed into the last-named form of energy. In plants, the complex unstable building of the groups of atoms is carried on, the constructor being the sun. In animals, which eat plants, the complex groups of the atoms are tumbled down, with the liberation of kinetic energy. VITAL ENERGY AND LIFE. The forces which act in organisms, in plants, and animals are exactly the same as are recognizable as acting in dead matter. A so-called '" vital force," as a special force of a peculiar kind, causing and governing the vital phenomena of living beings, does not exist. The forces of all matter, of organized as well as unorganized, exist in connection with their smallest particles or atoms. As, how- ever, the smallest particles of organized matter are, for the most part, arranged in a very complicated way, compared with the much simpler composition of inor- ganic bodies, so the forces of the organism connected with the smallest particles yield more complicated phenomena and combinations, whereby it is excessively difficult to ascribe the vital phenomena in organisms to the simple fundamental laws of physics and chemistry. The Exchange of Material, or Metabolism ( " Stoffiveihsel " ) as a Sign of Life. — Nevertheless, there apjjears to be a special exchange of matter and energy peculiar to living beings. This consists in the capacity of organisms to as- similate the matter of their surroundings, and to work it up into their own consti- tution, so that it forms for a time an integral part of the living being, to be given off again. The whole series of phenomena is called Metabolism or Stoffwech- sel, which consists in the introduction, assimilation, integration, and excretion of matter. We have already shown that the metabolism of plants and that of animals are quite different. The processes, as already described, actually occur in the typical higher plants and animals. But there is a large group of organisms which, throughout their entire organiza- tion, exhibit so low a degree of development, that by some observers they are considered as undifferentiated " ground forms." They are regarded as neither plants nor animals, and are the most simple forms of animated matter. Hsckel has called these organisms Protistae, as being the original and primitive forms. We must assume that, corresponding with their simpler vital conditions, their metabolism is also simpler, but on this point we still require further observations. ERRATA Page 42, sixth line from bottom, " Fig. 11.5" should be "Fig. 14.5." Page 45, sixteenth line from top, read hiemoglobin. Page 79, Fig. 32, the letters D E are omitted. Page 84, twentieth line from top, " Fig. 31, E " should be " Fig. 32, E." Page loi, Fig. 55, the, section marked b is reversed. Page 133, Section 75, the references to Fig. 90 are incorrect, because a portion of the cut has been omitted. Page 138, second line from bottom, " Fig. 96 " should be " Fig. 95." Page 734, fourth line from top, "cordate" should be "caudate." Page 757, eleventh line from bottom, "meredional" should be "meridional." PHYSIOLOGY OF THE BLOOD. [The blood is aptly described by Claude Bernard as an internal medium which acts as a " go-between " or medium of exchange for the outer world and the tissues. Into it are poured those substances which have been subjected to the action of the digestive fluids, and in the lungs or other respiratory organs it receives oxygen. It thus contains new substances, but in its passage through the tissues it gives up some of these new substances, and receives in exchange certain effete or waste products and more or less useless substances which have to be got rid of. Its composition is thus highly complex, containing, as it does, things both new and old. Besides carrying the new nutrient fluids to the tissues, it is also the great oxygen carrier, as well as the medium by which part of the waste pre ducts, e.g., CO„ urea, are removed //'w« the tissues and brought to the organs, e. g., the lungs, kidneys, skin, which eliminate them from the body. It is at once a great pabulum-supplying medium and a channel for getting rid of useless mate- rials. As the composition of the organs through which the blood flows varies, it is evident that its com])osition must vary in different parts of the circulatory system ; and it also varies in the same individual under different conditions. Still, with slight variations, there are certain general physical, histological and chemical properties which characterize blood as a w/wie.'\ I. PHYSICAL PROPERTIES OF THE BLOOD.— (i) Color.— The color of blood varies from a bright scarlet red in the arteries to a deep, dark, bluish-red in the veins. Oxygen (and, therefore, the air) makes the blood bright red; want of oxygen makes it dark. Blood free from oxygen (and also venous blood) is dicliroic — /. c, by reflected light it appears dark red, while by transmitted light it is green [Briieke). [Arterial blood is monochroic] In thin layers blood is opaque, as is easily shown by shaking blood so as to form bubbles, or by allowing blood to fall upon a plate with a pattern on it, and pouring it off again. Blood behaves, therefore, like an "opaque color" (Rolleit), as its coloring matter is suspended in the form of fine particles — the blood cor- puscles. Hence, it is possible to separate the coloring matter from the fluid part of the blood by filtration. This is accomplished by mixing the blood with fluids which render the blood corpuscles sticky or rough. If mammalian blood be treated with one-seventh of its volume of solution of sodic sulphate [Figitier), or if frogs' blood be mixed with a 2 per cent, solution of sugar [Joh. A/iiller] and filtered, the shriveled corpuscles, now robbed of part of their water, remain upon the filter. (2) Reaction. — The reaction is alkaline, owing to the presence of disodic phosphate, Naj.H.PO, (A/a/v) [and bicarbonate of soda]. After blood is shed, its alkalinity rapidly diminishes, and this occurs more rapidly the greater the alkalinity of the blood. This is due to the formation of an acid, in which, perhaps, the colored corpuscles take part, owing to the decomposition of their coloring matter. A high temperature and the addition of an alkali favor the formation of the acid (TV; Zuntz). The alkaline reaction of blood is diminished : [a) by great muscular exertion, owing to the formation of a large amount of acid in the muscles; (b) during coagulation ; [c) in old blood, or blood dissolved by water from old blood stains, such blood being usually acid ; fresh cruor has a stronger alkaline reaction than serum; (d\ after the prolonged use of soda the alkalinity is in- creased [Duliilir), after the use of acids it is decreased. 2 17 18 MICROSCOPIC EXAMINATION OF THE BLOOD. Pathological. — The alkalinity is less in persons suffering from ana;mia, cachectic conditions, and chronic rheumatism [Lepine), and also in cholera. [Immediately before death by cholera it may be acid (Can/ani)/] Methods. — Owing to the color of the blood we cannot employ ordinary litmus paper to test its reaction. One or other of the following methods may be used : ( I ) Moisten a strip of glazed red litmus paper with solution of common salt, and dip it quickly into the bit od, or allow a drop of blood to fall on tlie paper, and rapidly wipe it oft* before its coloring matter has time to penetrate and tinge the paper (Ziintz). (2) Kiihne made a small cup of parchment paper, which was placed in water in a watch glass. The colorless diftusate was afterward tested with litmus paper. (3) Liebreich used thin plates of plaster-of- Paris of a perfectly neutral reaction. These are dried, and afterward moistened with a neutral solution of litmus. When a drop of blood is placed upon the porous plate, the fluid part of the blood passes into it, while the corpuscles remain at the surface. The corpuscles are washed off" with water, and the altered color of the litmus-stained slab is ap- parent. [(4) Schafer uses dry, faintly-reddened, glazed litmus paper, and on it is placed a drop of blood, which is wiped off after a few seconds. The place where the blood rested is indicated by a well-defined blue patch upon a red or violet ground.] (3) Odor. — Blood emits a peculiar odor {Halitus sanguinis), which differs in animals and man. It depends upon the presence of volatile fatty acids [Mat/eucci). If concentrated sulphuric acid be added to blood, whereby the volatile fatty acids are set free from their combinations with alka- lies, the characteristic odor becomes much more perceptible (Barruel). [The odor is somewhat similar to that of butyric acid.] (4) Taste. — Blood has a saline taste, depending upon the salts dissolved in the fluid of the blood. (5) Specific Gravity. — The specific gravity is 1055 (extreme limits 1045- 1075) ; in women and young persons it is somewhat less. The specific gravity of the blood corpuscles is 1105, that of the plasma 1027. Hence, the corpuscles tend to sink. The specific gravity of the red blood corpuscles is estimated by allowing the corpuscles to subside to the bottom (which occurs most readily in the blood of the horse) ; but it is more correctly esti- mated by placing the i)lood in a tall cylindrical vessel, and setting the latter in the radius of the revolving disk of a centrifugal apparatus, the base of the cylinder being directed outward. The drinking of water and hunger diminish the specific gravity temporarily, while thirst and the digestion of dry food raise it. If blood be passed through an organ artificially, its specific gravity rises in consequence of the absorption of dissolved matters and the giving off of water. It falls after hem- orrhage, and is less in badly-nourished individuals. (6) [Temperature. — Blood is viscid, and its temperature varies from 36.5° C. (97.7° F.) to 37.8° C. (100° F.). The warmest blood in the body is that of the hepatic vein, while that of the right ventricle is warmer than that of the left side of the heart, § 210.] 2. MICROSCOPIC EXAMINATION OF THE BLOOD.— [Blood, when examined by the microscope, is seen to consist of an enormous number of corpuscles — colored and colorless — floating in a transparent fluid, the plasma, or liquor sanguinis.'\ The RED blood corpuscles were discovered in frogs' blood by Swammerdam in 1658, ai'd in human blood by Leeuwenhoek in 1673. Characters of Human Blood — ((7) Form. — The human red blood cor- puscles are circular, coin-shaped, homogeneous disks, with saucer-like depressions on both surfaces, and with rounded margins ; in other words, they are bi-concave, circular, non-nucleated disks. {b) Size. — According to Welcker the diameter {a />) is 7.7 //,* the greatest thickness {c d) 1.9 11 (Fig. i, C) [/. e., it is ^35^ to ^^nr ^^ ^" '"•^'^ '"^ diameter, and about one-fourth of that in thickness]. The corpuscles are slightly diminished in size by septic fever, inanition, after the .subcutaneous injection of morphia, increased bodily temperature, and CO,,; while they are increased h-j O, wa- tery condition of the blood, cold, consumption of alcohol, <|uinine, hydrocyanic acid and acute anaemia [Manassein). Compare ? 113. :-thousandth of a millimetre (,'/- = o.cxji mm.', and is the sign of a micro-mitli- MICROSCOPIC EXAMINATION OF THE BLOOD. 19 If the total amount of blood in a man be taken at 4400 cubic centimetres, the corpuscles therein contamed have a surface of 2816 square metres, which is equal to a square surface with a side of So paces; 176 cubic centimetres of blood pass through the lungs in a second, and the blood corpuscles in this amount of blood have a superficies of 81 square metres, equal to a square surface with a side of 13 paces ( Welder). (c) Weight. — The weight of a blood corpuscle, according to Welcker, is 0.00008 milligramtnes. {(i) Number. — According to Vierordt, the number exceeds 5,000,000 per cubic millimetre in the male, and 4,500,000 in the female; so that in 10 tbs. of blood there are 25 billions of corpuscles. As a general rule, the number is in inverse ratio to the amount of plasma ; hence, the number must vary with the state of contraction of the blood vessels, the pressure-diffusion currents and other conditions. The number of red corpuscles is increased ; in venous blood (especially in the small cutaneous veins), after the use of solid food. After much sweating, and the excretion of water by the bowel and kidney; during inanition, because the blood plasma undergoes decomposition sooner than the blood corpuscles themselves (Biinlzen); in the blood of the newly-born child (Paniim and So- reiisen), especially when the umbilical cord is long in being tied (^ 40) ; [from the fourth day onward the number is diminished (Hayem)'\, in persons of robust constitution, and in those who live in the Fig. I. A, Human colored blood corpuscles — i, seen on the flat ; 2, on edge ; 3, rouleau of colored corpuscles slightly sepa- rated. B, colored amphibian blood corpuscles— i, seen on the flat, and 2, on edge. C, ideal transverse section of a human colored blood corpuscle magnified 5000 times linear — a d, diameter ; c d, thickness. country. The number is diminished, during pregnancy, after copious draughts of water. In the earlier perioil of fcetal life the number is only J-I million in i c. c. (Cohnheim, Zuntz). (The pathological conditions which affect the number of corpuscles are given at \ 10.) Methods of Estimating the Number of Blood Corpuscles. — The pointed end of a glass pipette (Fig. 3), the mixer, is dipped into the blood, and by sucking the elastic tube/", blood is drawn into the tube until it reaches the mark \, on the stem of the pipette, or until the mark I is reached. The caremlly-cleaned point of the pipette is dipped into the artificial serum, and this is sucked inio the pipette until it reaches the mark, loi. The artificial serum consists of i vol. of solution of gum arable (sp. gr. 1020) and 3 vols, of a solution of equal parts of sodic sulphate and sodic chloride (sp. gr. 1020). The process of mi.xing the two fluids is aided by the presence of a little gla,ss ball [a) in the bulb of the pipette. If blood is sucked up to the mark \, the strength of the mixture is I : 200; if to the mark i, it is I : 100. A small drop of the mixture is allowed to run into the counling chamber of Abb6 and Zeiss (Fig. 2) (the first portions are not used, in order to obtain a uniform sample from the bulb of the pipette). This chamber consists of a gla^s receptacle 0.1 mm. deep, with its base divided into squares, and cemented to a microscopic slide, the whole being covered with a microscopic covering glass. The space over each square = j^^^jj cubic milli- metre. Count, with the aid of a microscope, the number of blood corpuscles in each square, and the number found, multiplied by 4000, will give the number of blood corpuscles in i c.mm. This number, again, must be multiplied by 100 or 200, according as the blood was diluted 100 or 200 times. To ensure greater accuracy, it is well to count the number in several squares, and to take the mean of these. [The method of Malassez was described in the last edition of this work.] 20 MICROSCOPIC EXAMINATION OF THE BLOOD. Apparatus of Abbe and Zeiss for counting the number of corpuscles. A, in section; C, surface view wiihout cover glass ; B, microscopic appearance with the blood corpuscles. Fin. 4. 1 he Melangettr, pipette Gowers" apparatus, made by Hawksley. London. A, pipette for measuring the diluting solution ; B, capillary tube for measuring the blood; C, cell with divisions on the floor, mounted on a slide, to which springs are fixed to secure the cover glass ; D, vessel in which the solution is made; E, spud for mixing the blood and solution; F, guarded spear-pointed needle. EFFECTS OF REAGENTS ON BLOOD CORPUSCLES. 21 [The following is a description of Cowers' instrument (Fig. 4): "The Hsemacytometer consists of — (l) a small pipette, which, when filled to the mark on its stem, holds e.\actly 995 cubic millimetres. It is furnished with an India-rubber tube and mouthpiece to facilitate filling and emptying. (2) A capillary tube marked to contain exactly 5 cubic millimetres, with India- rubber tube for filling, etc. (3) A small glass jar in which the dilution is mau?-m). Similar iorms are obtained by mixing blood with an equal volume of gelatine at 36° C, allowing it to cool, and then making seciiuns of the coagulated mass [Rollett). The corpuscles may be broken up by pressing firmly on the cover glass, in all these experiments no trace of an envelope is observed. Conservation of the Red Blood Corpuscles. — The blood corpuscles retain their characters in the following fluids : — Haycms Fluid. Hydrarg. bichlor., 0.5 Sodic sulphate, 5.0 Sodic chloride, i.o Distilled water, 200.0 Hydrarg. bichlor., 2 Sodic chloride, 4 Glycerine, 26 Distilled Water 226 To be diluted with 2 parts of distilled water before being used. [An excellent reagent for '' fixing " the blood corpuscles is either a dilute solution or the vapor of osmic acid.] In investigating blood with the microscope for forensic purposes, it is necessary to have a solvent for the blood when it occurs as stains on a garment or instrument. Dried stains are dis- solved by a concentrated ( Virchow), or a 30 per cent. (Malinin) solution of caustic potash, or with one of the preserving fluids, care being taken to avoid friction. If the slain be softened with con- centrated tartaric acid, the colorless corpuscles are specially distinct (Stiuice). Nevertheless, cor- puscles are often not found in such stains. If the corpuscles have become very pale, their color may be improved by adding a solution of iodine in iodide of potassium, a s..turated solution of picric acid, 20 per cent, pyrugallic acid, or 3 per cent, solution of silver nitrate [AJe/tzer and Welch), 5. PREPARATION OF THE STROMA— MAKING BLOOD " LAKE-COLORED." — There are many reagents which separate the haemo- globin from the stroma. The haemoglobin dissolves in the serum ; the blood then becomes transparent, as it contains its coloring matter in solution, and hence is called "Lake-colored" by Rollett. Lake-colored blood is dark red. The aggregate condition of the haemoglobin is not altered when the corpuscles are dissolved ; it only changes its place, leaving the stroma and passing into the serum. Hence, the temperature of the blood is not lowered thereby \Landois). Methods. — To obtain a large quantity of the stroma for chemical purposes, add 10 vols, of a solution of common salt (I vol. concentrated solution, and 15 to 20 vols, of water) to 1 vol. of defibrinated blood, when the stromata are thruwn down as a whitish precipitate. 24 FORM AND SIZE OF BLOOD CORPUSCLES. For microscopUal purposes, mix blood with an equal volume of a concentrated solution of sodic sulphate, and cautiously add a I per cent, solution of tartaric acid ( Landois). The following reagents cause a separation of the stroma from the hemoglobin : — (a) Physical Agents.— i. Heating the blood to 60° C. \Schult:e)\ the temperature, however, varies for the blood of diiTerent animals. 2. Repeated freezing and thawing of the blood (RoUell). 3. Sparks from an electrical machine (l-ui not after the addition of salts to the blood) \Kollell)\ the constant and induced currents [iWiiniann). {b\ Chemically active Substances produced within the Body. — 4. Bile (//iine/i'/i/), orWe salts [Planner, v. Dusch], 5. Serum of other species of animals (Landois); thus dog's serum and frog's serum dissolve the blood corpuscles of the rabbit in a few minutes. 6. The addition of lake-colored blood of many species of animals (Landois). (<■) Other Chemical Reagents. — 7. Water. 8. Conduction of vapor of chloroform (5o.Yi-AtT) ; ether {v. IViUic/i) ; amyis, small quanlitiei of alcohol (Rollctt) ; thymol [Marcliand) ; nitrolieiizol, ethylic ether, aceton, petroleum ether, etc. (L. Lewin). 9. Antimoniuretted hydrogen, arseniu- retted hydrogen; carbon uisulphide {Hiinefeld, Hermann] ; boracic acid (2 per cent.), added to amphibian blood, causes the red ma-s (which also encloses the nucleus when such is present), the so-called zooid, to separate from the acoiii. The zooid may shrink from ihe periphery of the corpuscle, or it may even pass out of the corpuscle altogether [Briie^e]; Briicke regards the stroma in a certain sense as a house, in which the remainder of the substance of the corpuscle, the chief part endowed with vital phenomena, lives. 11. Strong solutions of aeids dissolve the Corpuscles; more dilute solutions cause precipitates in the haemoglobin. Thi> is easily seen with carbolic acid {J/ii/s and Lanaois ; Stirling and A'nnnie). 12. Alkalies oi moderate strength cause sudden solution. A 10 per cent, solution of potash, placed at the margin of a cover glass, shows the process of solution going on under the microscope. At first the corpuscles become globular, and so appear smaller, but afterward they burst like soap bubbles. [NH^Cl injected into the blood causts vacuolation of the red cor(jUscles [BobrilziY)-^ [Tannic Acid. — A freshly-prepared solution of tannic acid has a remarkable effect on the colored blood corpuscles of man and animals — causing a separation of the haemoglobin and the stroma. The usual eftect is to produce one or more granular buds of haemoglobin on the side of the cor- puscles; more rarely the haemoglobin collects around the nucleus, if such be present (IV. A'oberls).'] [Ammonium or Potassium Sulphocyanide removes the hsemoglobin, and reveals a reticular structure — inlra nuclear plexus of fibrils (Stirling and Rannie)."] The quantity of gases contained in the blood corpuscles exercises an important influence on their solubility. The corpuscles of venous blood, which contains much CO,, are more easily dissolved than those of arterial blood; while between both stands blood containing CO (Landois, Lilterski, Lipine). When the gases are completely removed from the blood, it becomes lake-colored. Salts increase the resistance of the corpuscles to physical means of solution, while they facilitate the action of chemical solvents (Bernstein and Becker). Resistance to Solvents. — The red blood corpuscles offer a certain degree of resistance to the action of solvents. Method. — Mix a small drop of blood with an equal volume of a 3 per cent, solution of sodic chloride, and then add distilled water until all the colored corpuscles are dissolved. Fill the mixer (Fig. 3) up to the mark I with blood obtained by pricking the finger, and blow this blood into an equal volume of a 3 per cent, solution of NaCl previously placed in a hollow in a micro.scopic glass slide. Mix the tluids, and the corpuscles will remain undissolved. By means of the pipette add distilled water, and go on doing so until all the corpuscles are dissjlved; which is ascertained with the microscope. In normal blood, solution of the corpuscles occurs after 30 volumes of dis- tilled water have been added to the blood (Landois). There are some individuals whose blood is more soluble than that of others ; their corpuscles are soft, and readily undergo changes. Many conditions again, such as choUemia, poisoning with sub- stances which dissjlve the corpuscles, and a markedly venous condition of the blood, affect the corpuscles. Interesting observations are to be made on the blood in infectious diseases, h.iemoglo- binuria, and in cases of burning. In anaemia and fever, the capacity for resistance seems to be diminished (Peiper). [Sodic salicylate, benzoate and colchicin dissolve the red corpuscles (A'. Paton).'\ 6. FORM AND SIZE OF THE BLOOD CORPUSCLES OF DIFFERENT ANIMALS.— .\11 mammals (with the e.xception of the camel, llama, alpaca, and their allies), and the cyclostoniata among fishes, e.g., Petromy- zon, possess circular, bi-concave, non- nucleated, disk-shaped corpuscles. Elliptical corpuscles without a nucleus are found in the above-named mammals, while all birds, reptiles, amphibians (Fig. r, B, i, 2), and fishes (excejit cyclosto- mata) have nucleated, elliptical, bi-convex corpuscles. ORIGIN OF THE RED BLOOD CORPUSCLES. 25 Size {fx = o.ooi Millimetre). Of the Disk-shaped Corpuscles. Of the Elliptical Corpuscles. Short Diameter. 1 Long Diameter. Elephant, .... 94.'-' Man, ..... 7.7 " Dog 7-3 " Rabbit 6.9 " Cat, 6.5 " Sheep 5.0 " Goat 4' " Musk deer, ... 2.5 " Llama 4.0 /x Dove, 6.5 " f-'og. '5-7 " Irilon, ig-S " Proteus 35 " The corpuscles of Amphiu than those of Proteus (Riddel). 8.0 1). 14.7 •' 22.3 " 293 •' 58.0 " Tia are nearly one third larger Among vertebrates, amphioxus has colorless blood. The large blood corpuscles of many amphibia, t-.i,'., amphiuma, are visible to the naked eye. The blood corpuscles of the frog contain, in addition to a nucleus, a nucleolus (Aiierbach, Ranvim), [and the same is true of the colored cor- puscles of the newt [Stirling^. The nucleolus is revealed by acting on the corpuscles with dilute alcohol (I, alcohol; 2, water; Ranvier's '• alcool au //«i").] It is evident that the larger the blood corpuscles are, the smaller must be the number and total superficies of corpuscles in a given volume of blood, in birds, however, the number is relatively larger than in other classes of verte- brates, notwithstanding the larger size of their corpuscles; this, doubtless, has a relation to the very energetic metabolism that lakes place in birds (Mulassez). Among mammals, carnivora have more bliod corpuscles than herbivora. Welcker has ascertained that goat's blood contains 9,720,000 corpuscles per cubic millimetre; the llama's 13,000,000; the bullfinch's, 3,600,000; the lizard'.s, 1,420,000; the frog's, 404,000; the proteus', 36,000. In hybernating animals, Vierordt found that the number of corpuscles diminished from 7,000,000 to 2,000,000 per cubic millimetre during hybernation. The invertebrata generally have colorless blood, with colorless corpuscles; but the earthworm, and the larva of the large gnats, etc., have red blood whose plasma contains haemoglobin, while the blood corpuscles themselves are colorless. Many invertebrates possess red, violet, brown, or green opalescent blood with colorless corpuscles (amreboid cells). In cephalopods, and some crabs, the blood IS blue, owing to the presence of a coloring matter (Haemocyanin) which contains copper, and combines with O [Bert, Rabuteau and Papillon, Fi-edirin], and Krukenberg). [Elaborate measurements of the blood corpusc'es have been made in this country by Gulliver, but the relative size may be best appreciated by comparing the corpuscles from various vertebrates. There is no relation between the size of the animal and the size of its blood corpuscles.] 7. ORIGIN OF THE RED BLOOD CORPUSCLES.— (A) Origin of the Nucleated Red Corpuscles during Embryonic Life. — Blood cor- puscles are developed in the fowl during the first days of embryonic life. [They appear in groups within the large branched cells of the mesoblast, in the vascular area of the blastoderm outside the developing body of the chick or embryo, wliere they form the '■'blood islands'' of Pander. The mother cells form an irregular network by the union of the processes of adjoining cells, and meantime the central masses split up, and the nuclei multiply. The small nucleated masses of pro- toplasm, which represent the blood corpuscles, acquire a reddish hue, while the surrounding protoplasm, and also that of the processes, becomes vacuolated or hollowed out, constituting a branching system of canals ; the outer part of the cells remaining with their nuclei to form the walls of the future blood vessels. A fluid appears within this system of branched canals in which the corpuscles lie, and gradually a communication is established with the blood vessels developed in connection with the heart.] [According to Klein, the nuclei of the protoplasmic wall may also proliferate, and give rise to new corpuscles, which are washed away to form blood corpuscles.] At first the corpuscles are devoid of pigment, nucleated, globular, larger, and more irregular than the permanent corpuscles, and they also e.xhibit amoeboid movements. They become colored, retain their nucleus, and are capable of under- going multiplication by division ; and, in fact, Remak observed all the stages of the process oi division. The process of division is best seen from the 3d-5th day 26 ORIGIN OK THE RED BLOOD CORPUSCLES. of incubation. Increase by division also takes place in the larvae of the salaman- der, triton and toad (Flemming, Percrneschko), and also during the intra-uterine life of a mammal, in the spleen, bone marrow, the liver and the circulating blood {Biszozero, E berth). After the liver is developed, blood corpuscles seem to be formed in it {E. H. Weber, Kolliker). Neumann found in the liver of the embryo protoplasmic cells containing red blood corpuscles. Cells, some with, others without, Hb, but with large nuclei, have been found. These cells increase by division, their nucleus shrivels, and they then ultimately form blood corpuscles I^Lihait). The spleen is also regarded as a centre of their formation, but this seems to be the case only during embryonic life (Net/mann). Here the red corpuscles are said to arise from yellow, round, nucleated cells, which represent transition forms. Foa and Sal- violi found red corpuscles forming endogenously within large protoplasmic cells in lymphatic glands. In the later ])eriod of embryonic life, the characteristic non-nucleated corpuscles seem to be developed from the nucleated corpuscles. The nucleus becomes smaller and smaller, breaks up, and gradually disappears. In the human embryo at the fourth week only nucleated corpuscles are found ; at the third month their number is still \-\ of the total corpuscles, while at the end of foetal life nucleated blood corpuscles are very rarely found. Of course, in .iiiijii of red blood corpuscles withi] , r, the formed corpuscles ; K, K, n :ntum of a r.ibbit seven d.iys rocesses which ultimately unit animals with nucleated blood corpuscles, the nucleus of the embryonic blood cor- puscles remains. (B) Development of Blood Vessels, Formation of Blood Vessels and Blood Corpuscles during Post-embryonic Life. — Kolliker assumed that, in the tail of the tadpole, capillaries are formed by the anastomoses of the processes of branched and radiating connective-tissue corpuscles. These cor- puscles lose their nuclei and protoplasm, become hollowed out, join with neigh- boring capillaries, and thus form new blood channels. J. Arnold and von Golu- bew, on the other hand, oppose this view. They assert that the blood capillaries in the tail of the tadpole give off solid buds at different places, which grow more and more into the surrounding tissues, and anastomose with each other; their pro- toplasm and contents disappearing, they become hollow and a branched system of capillaries is formed in the tissues. Ranvier, be it remarked, noticed the same mode of growth in the omentum of newly-born kittens. The latter observer has recently studied the development of blood vessels and blood corpuscles in the omentum of young rabbits. These animals, when a week old, have, in their omentum, little white or milk spots {" taches /aiteuses," Ran- vier), in which lie " vaso-formative cells," /. e., highly refractive cells of vari- able shape, with long cylindrical protoplasmic processes (Fig. 6). In its refractive ORIGIN OF THE RED BLOOD CORPUSCLES. 27 power the protoplasm of these cells resembles that of lymph corpuscles. Long, rod-like nuclei lie within these cells (K, K), and also red blood corpuscles {r, r), and both are surrounded with protoplasm. These vaso-formative cells give off protoplasmic points and processes {a, a), some of which end free, while others form a network. Here and there elongated connective tissue corpuscles lie on the branches, and ultimately form the adventitia of the blood vessel. The vaso-formative cells have many forms : they may be elongated cylinders ending in points, or more round and oval, resembling lymph cells, or they may be modified connective-tissue corpuscles, as observed by Schafer in the sub- cutaneous tissue of young rats. These cells are ahvavs the seat of origin of non- nucleated red blood corpuscles, which arise in the protoplasm of vaso-formative cells, as chlorophyll grains or starch granules arise within the cells of plants. The corpuscles escape and are washed into the circulation, when the cells form connections with the circulatory system by means of their processes. It is probable that the vessels so formed in the omentum are only temporary. May it not be that there are many other situations in the body where blood is regenerated ? [The observations of Schafer also prove the intra- cellular origin of red blood corpuscles, and although this mode usually cea.ses before birth, still it is found in the rat at birth. The protoplasm of the subcutaneous connective-tissue corpuscles, which are derived from the mesoblast, has in it small colored globules about the size of a colored corpuscle. The mother cells elongate, become pointed at their ends, and unite with processes from adjoining cells. The cells become vacuolated ; fluid or plasma, in which the liberated corpuscles float, appears in their interior, and ultimately a communication is established with the general circulation.] Similar observations have been made by Neumann in the embryonic liver; by Wissotzky in the rabbit's amnion; by Klein in the embryo chicle ; and by Leboucq and Hayem in various animals; all of which go to show that at a certain early period of development blooi corpuscles are formed within other large cells of the mesoblast, and that part of the protoplasm of these blood-forming cells remains to form the wall of the future b^ood vessel. [According to Bayerl red blood corpuscles are formed within cartilage capsules at the line of ossification in the ribs and bones of the extremities of mammalian and human embryos.] (C ) Later Formation of Red Blood Corpuscles. — There is much diversity of opinion as to how colored blood corijuscles are formed in mammals at a later period. [They have been described as derived from colorless corpuscles, one set of observers (including KoUiker) maintaining that the nucleus of these corpuscles disappears, while the perinuclear portion remains, becomes flattened and colored, and assumes the characters of the mammalian blood corpuscles. On the other hand, other observers (including Wharton Jones, Gulliver, Busk, Huxley and Balfour) are of opinion that the nucleus becomes pigmented, and forms the future blood corpuscle. It is still doubtful, however, whether colored corpuscles are developed in either of these ways.] Neumann and Bizzozero described peculiar corpuscles occurring in the red marrow of bone, which they maintain become developed into colored blood corpuscles, undergoing a series of changes, and forming a series of intermediate forms, which may be detected in the red marrow. Bizzozero holds that it is the nucleus of the marrow cell which is colored, while Neumann thinks that it is the perinuclear part which becomes colored, and forms the blood corpuscle. Schafer's observations on the red marrow of the guinea pig rather tend to confirm Neumann's view. These transition cells are said by Erb to be more numerous after severe hemorrhage, the number of them occurring in the blood corresponding with the energy of the formative process. In dogs and guinea pigs, which he had rendered anjemic, Bizzozero found in the marrow and spleen nucleated red blood corpuscles, which increased by division. According to Neumann, the bone marrow of adults contains all transition forms, from nucleated colored corpuscles to true red blood 28 DECAY OF THE RED BLOOD CORPUSCLES. corpuscles. After copious hemorrhage, these transition forms appear in numbers in the blood stream. Red or blood-forming marrow occurs in the bones of the skull, and in ^lo^t of the bones of the trunk, while the bones of the extremities either contain yellow marrow (which is essentially fatly in its nature), or, at most, it is only the heads of the long bones that contain red marrow. When the blood regeneration process is very active, however, the jellow marrow may be changed into red, even throughout all the bones of the extremities (A'eumann). Rindfleisch also regards the connective substance of the red marrow and the spleen as the mother- tissue of the red blood corpuscles, the connective substance or the hreniatogenous connective tissue either temporarily or permanently forming red blood corpuscles. Once the red corpuscles are formed, they easily enter the blood stream, as the capillaries or veins of the red marrow have either no walls [Hoyer, KoHmann), or exceedingly thin, perforated walls. Similar conditions obtain in the spleen. Bizzozero and Torre found that, after severe hemorrhage in birds, the marrow of the bones contained globular, granular, nucleated cells, whose protoplasm was colored with h3;moglobin, while between these and the oval, biconvex, nucleated corpuscles of the bird, there were numerous transition stages. The spleen of the Ijird seems to be of much less importance in the formation of blood corpuscles {A'orn). AH these observations prove that the red marrow of the bones is a great manufactory lor colored blood corpuscles. V. Recklinghausen observed the direct Jransformation of these intermediate forms into blood corpuscles in Irogs' blood which was kept for several days in a moist chamber. A. Schmidt and- Semmer found in the blood large lymph Ctlls, filled with granules of hiemogoblin, and they legard these as intermediate forms between colorless and colored corpuscles. [Malassez, from an investigation of the red marrow of young kids, finds that the cells of the red marrow and certain cells in the spleen form rounded colored projections or buds on their surface, 'ihese gel detached and form young blood corpuscles, which soon become disk-shaped; while the mother cell itself continues to produce other colored corpuscles. Thus gemmation of the splenic and medullary cells constitutes one great process in the manufacture of blood corpuscles. Hence it is apparent why diseases of the bone in children lead to ana;mia, and soon bring about a cachectic condition.] [In mammals, birds, reptiles, and tailless amphibians, colored blood corpuscles divide in bone marrow. In the tailed amphibians ( Triton crista'us) the bone marrow consists of fat, and shows none of the characters of a blood-forming organ. In tailed amphibians, again, Bizzozero and Torre find the first example of animals in which, in atlults, red blood corpuscles are formed in the spleen, where the process of indirect division is very marked, especially if the corpuscles be stained by methyl-violet in i^ per cent. NaCl solution, and afterwaid with ^',' per cent, acetic acid.] 8. DECAY OF THE RED BLOOD CORPUSCLES.— The blood corpuscles must positively undergo decay within a limited time, and the liver is regarded as one of the chief places in which their disintegration occurs, because bile pigments are formed from haemoglobin, and the blood of the hepatic vein contains fewer red corpuscles than the blood of the portal vein. The splenic pulp contains cells which seem to indicate that colored corpuscles are broken up within it. These are the so-called " blood-corpuscle-containiiig cells." Quincke's observations go to show that the red corpuscles — which may live from three to four weeks — when about to disintegrate, are taken up by white blood corpuscles, and by the cells of the spleen and the bone marrow, and are stored up chiefly in the capillaries of the liver, in the spleen, and in the marrow of bone. They are transfortned, partly into colored, and partly into colorless proteids which contain iron, and are either deposited in a granular form, or are dissolved. Part of the products of decomposition is used for the formation of new blood corpuscles in the marrow and in the spleen, and also perhaps in the liver, while a portion of the iron is excreted by the liver in the bile. That the normal red blood corpuscles and other particles suspended in the blood stream are not taken up in this way, may be due to their being smooth and polished. As the corpuscles grow - older and become more rigid, they, as it were, are caught by the amceboid cells. As cells con- taining blood corpuscles are very rarely found in the general circulation, one may assume that the occurrence of these cells within the spleen, liver and marrow of bone is favored by the slowness of the circulation in these organs (Quincke). Pathological. — In certain pathological conditions, ferruginous substances derived from the red blood corpuscles are found in the spleen, in the marrow of bone, and in the capillaries of the liver: (I) When the disintegration of blood corpuscles is increased, as in 3.nxni\a (Sta/iel). (2) When the formation of red blood corpuscles from the old material is diminished. If the excretion THE COLORLESS BLOOD CORPUSCLES. 29 from the liver cells be prevented, iron accumulates within them; it is also more abundant in the blood serum, and it may even accumulate in the secretory cells of the cortex of the kidney and pancreas, in gland cells, and in the tissue elements of other organs [Qtiimke). When the amount of blood is greatly increased (in dogs), after four weeks an enormous number of granules containing iron occur in the leucocytes of the liver capillaries, the cells of the spleen, bone marrow, lymph glands, the liver cells, and the epithelium of the cortex of the kidney ( Quincke). The'iron reaction in the two last situations occurs after the introduction of hasmoglobin, or of salts of iron into the blood (Glae-jcck and v. Stark). When we reflect how rapidly (relatively) large quantities of blood are replaced after heniorrhage and after menstruation, it is evident that there must be a brisk manufactory somewhere. As to the number of corpuscles which daily decay, we have in some measure an index in the amount of bile pigment and urine pigment resulting from the transformation of the liberated haemoglobin (§ 20). 9. THE COLORLESS CORPUSCLES (LEUCOCYTES). BLOOD PLATES AND ELEMENTARY GRANULES.— I. White Blood Corpuscles. — Blood, like many other tissues, contains a number of cells Fig. 7. White blood corpuscles. A, human., without the addit visible ; C, after the action of acetic acid ; D, frogs' ment; E, fibrils of fibrin from co,igulated blood ; F, ^ f ion of any reagent : B, after the addition of water, i :orpuscles showing changes of shape due to amoeboid r :lementaty granules. or corpuscles which reach it from without ; the corpuscles vary somewhat in form, and are called colorless or white blood corpuscles, or "leucocytes" {Hewson, 1770). Similar corpuscles are found in lymph, adenoid tissue, marrow of bone, as wandering cells or leucocytes, in connective tissue, and also between glandular and epithelial cells. They all consist of more or less spherical masses of protoplasm, which is sticky, highly refractile, soft, capable of movement, and devoid of an envelope (Fig. 7). When they are quite fresh (A) it is difficult to detect the nucleus, but after they have been shed for some time, or after the addition of water (B), or acetic acid, the nucleus (which is usually a compound one) appears ; acetic acid clears up the perinuclear protoplasm, and reveals the presence of the nuclei, of which the number varies from one to four, although generally three are found. The subsequent addition of magenta solution stains the nuclei deeply. Water makes the contents more turbid, and causes the corpuscles to swell up. One or more nucleoli may be present in the nucleus. The corpuscles contain proteids, but they also contain fats, lecithin, and salts 80 THE COLORLESS BLOOD CORPUSCLES. (§ 24). The size of the corpuscles varies from four to thirteen ,«, and as a rule they are abotit ^3'13-jj of an inch in diameter, and in the smallest the layer of the protoplasm is extremely thin. They all have the property of exhibiting amceboid movements, which are very apparent in' the larger corpuscles. These movements were discovered by Wharton Jones in the skate, and by Davine in the corpuscles of man. Max Schultze describes three different forms in human blood : — (i) The smallest, round forms, less than the red corpuscles, with one or two nuclei, and a very small amount of protoplasm ; (2) Round forms, the same size as the colored blood corpuscles; (3) The large amoeboid corpuscles, with much protoplasm and distinctly evi- dent movements. [When a drop of human blood is examined under the microscope, more especially after the colored blood corpuscles have run into rouleaux, the colorless corpuscles may readily be detected, there being usually three or four of them visible in the field at once. They adhere to the glass slide, for if the cover glass be moved, the col red corpuscles readily glide over each other, while the colorless can be seen still adhering to the slide.] [White Corpuscles of Newt's Blood. — The characters of the colorless corpuscles are best studied in a drop of newt's blood. Cut otf the tip of the tail and express a drop of blood on to a slide, cover it with a thin glass, and examine. Neglecting the colored corpuscles, search for the colorless, of which there are three varieties: — ( 1) The Large, Finely Granular Corpuscle, which is about jj^ of an inch in diameter, irregu- lar in outline, with fine processes or pseudopodia projecting from its surface. It rapidly changes its shape at the ordinary temperature, and in its interior a bi- or tripartite nucleus may be seen, sur- rounded with fine granular protoplasm, whose outline is continually changing Sometimes vacuoles are seen in the protoplasm. (2) The Coarsely Granular Variety is less common than the first mentioned, but when de- tected its characters are distinct. The protoplasm contains, besides a nucleus, a large number of highly refractive granules, and the corpuscle usually exhibits active amoeboid movements; suddenly the granules may be seen to rush from one .side of the corpuscle to the other. The processes are usually more blunt than those emitted by (i). The relation between these two kinds of corpuscles has not been ascertained. {3) The Small, Colorless Corpuscles are more like the ordinary human colorless corpuscle, and they, too, exhibit amceboid movements. Two kinds of colorless corpuscles like (i) and (2) exist in frogs' blood. In the coarsely granular corpuscles the glancing granules may be of a fatty nature, since they dissolve in alcohol and ether, but other granules exist which are in.soluble in these fluids, and the nature of which is unknown. Very large colorless corpuscles exi»t in the axolotl's blood (/ianvier).'] [Action of Reagents. — {a) Water, when added slowly, causes the colorless corpuscles to become globular, and the granules within them to exhibit Brownian movements (Richardso/i, S/nWcrr). (b) Pigments, such as magenta or carmine, stain the nuclei very deeply, and the protoplasm to a less extent, (r) Dilute Acetic Acid clears up the surrounding protoplasm and brings clearly into view the composite nucleus, which may be stained thereafter with magenta. (^/) Iodine gives a faint port-wine color (horse's blood indicating the presence of glycogen best). ((') Dilute Alcohol causes the formation of clear Fir.. 8. blebs on the surface of the corpuscles, and brings the nuclei clearly into view {Ranvicr, Stirling).'] [.\ delicate plexus of fibrils — intra-nuclear plexus — exists within the nucleus, just as in other cells. It is very probable that the ])rotoplasm itself is pervaded by a similar plexus of fibrils, and that it is continuous with the intra- nuclear plexus (Fig. 8).] The colorless corpuscles divide, and in this way repro- duce themselves (Klein). The Number of Colorless Blood Corpuscles is very much less than that of the red corpuscles, and is sub- 1 1 ject to considerable variations. It is certain that the color- piexus of a colorless cor- |ess corpusclcs are Very much fewer in shed blood than in (A7«>r).*" '"" "'"^^' blood still within the circulation. Immediately after blood AMCEBOID MOVEMENTS OF THE COLORLESS CORPUSCLES. 31 is shed, an enormous number of white corpuscles disappear (see Formation of Fibrin, § 31). [The extent to which this occurs is questioned by different observers.] Al. Schmidt estimates the number that remain at ^'j, of the whole originally present in the circu- lating blood. The proportion is greater in children than in adults {Botichut and Diitfrisay). The following table gives the number in shed blood : — Number ok White Corpuscles in Proportion to Red Corpuscles— In Normal Conditions. In Different Places. In Different Conditions. X : m {Wdcker). I : 357 [Molescholt]. Splenic Vein, l : 60 Splenic Artery, i : 2260 Hepatic Vein, i : 170 Portal Vein, i : 740 Generally more numerous in Veins than Aijeries. Increased by Digestion, Loss of Blood, Pro- longed Suppuration, Parturi- tion, Leuka;mia, Quinine, Bit- ters. Diminished by Hunger, Bad Nourishment. The number also varies with the A^re and Sex :- Age. Sex. White. Red. General Conditions. White. Red. Girls, Boys, Adults Old Age, I : 405 I : 226 ' : 334 I : 38. j While fasting, . . After a meal, . , During pregnancy. I : 716 I : 347 I : 281 The old method of Wchker for estimating the number of colorless corpuscles is unsatisfactory. The blood was defibrlnated, placed in a tall vessel, and allowed to subside, when a layer of color- less corpuscles was obtained immediately under a layer of serum. [It is better to use the hasma- cytometer (p. 21 ) as improved by Cowers.] The AmcEboid Movements of the white corpuscles (so called because they resemble the movements of amceba) consist in an alternate contraction and relaxation of the protoplasm surrounding the nucleus. Processes are given off from the surface, and are retracted again (like the pseudopodia of amoeba). There is an internal current in the protoplasm, and the nucleus has also been observed to change its form [and exhibit contractions without the corpuscle divid- ing. The karyokinetic figures or aster, and convolution of the intranuclear plexus have been seen] {Lawiiowsky). Two series of phenomena result from these movements: (i) The '■ loandering" or locomotion of the corpuscles due to the extension and retraction of their processes ; (2) the absorption of smait particles into their interior (fat, pigment, foreign bodies). The particles adhere to the sticky external surface, are carried into the interior by the internal currents (Freyer), and may eventually be excreted, just as particles are taken up by amoeba and the effete particles excreted. [Max Schultze observed that colored particles were readily taken up by these corpuscles.] [Conditions for Movement. — In order that the amoeboid movements of the leucocytes may take place, it is necessary that there be — (i) a certain temperature and normal atmospheric pressure; (2) the surrounding medium, within certain limits, must be "indifferent," and contain a sufficient amount of water and oxygen ; (3) there must be a basis or support to move on.] Metschnikofl" emphasizes the activity of the leucocytes in retrogressive processes, whereby the parts to be removed are taken up by them in line granules, and, as it were, are " eaten." Hence, he calls such cells " phagocytes." They nny be found in the atrophied tails of batrachians, the Cells containing in their interior whole pieces of nerve fibre and primitive muscular bundles. Schizo- 32 AiMtEBOID MOVEMENTS OF THE COLORLESS CORPUSCLES. mycetes which have found their way into the blood (^ 183) have been found to be partly taken up by the colorless corpuscles. Effects of Reagents. — On a hot stage (35-40° C.) the colorless corpuscles of warm-blooded animals retain their movements for a long time ; at 40° C. for two to three hours; at 50° C. the proteids are coagulated and cause ^^ heat rigor" and death [when their movements no longer recur on lowering the tem- perature]. In cold-blooded animals (frogs), colorless corpuscles may be seen to crawl out of small coagula, in a moist chamber, and move about in the serum. [Draw a drop of newt's blood into a capillary tube, seal up the ends of the latter and allow the blood to coagulate. After a time, examine the tube in clove oil, when some of the colorless corpuscles will be found to have made their way out of the clot.] Induction shocks cause them to withdraw their processes and become Fig. 9. spherical, and, if the shocks be not too severe, their movements recommence. -Strong and continued shocks kill them, causing them to swell up, and completely disintegrating them. Oxygen is necessary for their movements. Diapedesis. — These amosboid movements are of special interest on account of the " wandering out " (diapedesis) of colorless blood corpuscles through the walls ot the blood vessels (§ 95). [Effect of Drugs. — Acids and nllialics, if very dilute, at first increase, but afterward arrest their mcjvcments. Sodic chloride in a I per cent, solution at fiist accelerates their movements, but after- ward produces a tetanic contraction, and, it may be, expulsion of any food particles they contain. The Cinchona alialoids — quinine, quinidine, cinchonidine (I : 1500) — quickly arrest the locomo- tive movements, as well as the protrusion of pscudopodia, although the leucocjtes of different animals vary somewhat in their resistance to the action of drugs. Quinine not only arrests the THE BLOOD PLATES. 33 movements of the leucocytes when applied to them directly, but when injected into the circulation of a frog to the amount of jsJirtr psf of the animal's weight, the leucocytes no longer pass through the walls of the capillaries '(Btn:).'\ The chyle contains leucocytes, which are more resistant than those of the blood, but less so than those of the coagulable transudations (Heyl). The leucocytes of the lymphatic glands may also be dissolved (Rauschenbach). Relation to Aniline Pigments. — Ehrlich has observed a remarkable relation of the white corpuscles to acid (eosin, picric acid, aurantia), baiic (dahlia, acetate of rosanilin), or neulral (picrate of rosanilin) reactions. The smallest jirotoplasmic granules of the cells have diffeient chemical affinities for these pigments. Thus Ehrlich distinguishes " eosinophile," *' basophile," and " neutrophile " granules within the cells. Eosinophile granules occur in the leucocytes which come from bone m-Axxow (^myelogenic leucocytes). The small leucocytes, j'.t"., those about the size of a colored blood corpuscle or slightly larger, are formed in the lymphatic glands {lymphogenic L.). The large amosboid multi-nucleated cells which are found outside Ijie vessels in inflam- mations exhibit a neutrophile reaction. Their origin is unknown, and so is that of the large uni-nucleated cells and the large cells with constricted nuclei {Ehrlich and Einhorn). The eosinophile corpuscles are considerably increased in leukaemia. The basophile granules occur also in connective-tissue corpuscles, especially in the neighborhood of epithelium ; they are always greatly increased where chronic inflammation occurs. As such conditions are always accompanied by an increased supply of the nutritive materials necessary for cells, Ehrhch has called these cells " Mastzellen " ; they do not occur normally in human blood. Fig. io. ' Blood plates" and their deriv.-itives, partly after Bizzozero and Laker, i. red blood corpuscles on the flat; 2, from changed hlood plates; 4, a lymph corpuscle, surrounded with blood plates; 5, blood plates variously altered ; 6, a lymph corpuscle with two heaps of fused blood plates and threads of fibrin ; 7. group of blood plates fused or run together; 8, a similar small heap of partially dissolved blood plates with fibrils of fibrin. 11. Blood Plates. — Special attention has recently been directed to another element of the blood, the " blood plates " or " Blutpliittchen " of Bizzozero ; pale, colorless, oval, round, or lenticular discs of variable size (mean, 3 11). According to Hayem (who called these structures haematoblasts, supposing that they were an early stage in the development of the red blood corpuscles), they are forty times as numerous as the leucocytes. These blood plates may be recognized in circulating blood, as in the mesentery of a chloralized guinea pig and the wing of a bat. They are precipitated in enormous numbers upon threads suspended in fresh shed blood {Bizzozero). They may be obtained from blood flowing directly from a blood vessel, on mixing it with i per cent, solution of osmic acid or Hayem's fluid (p. 23), (Laker). They undergo a rapid change in shed blood (Fig. 10, 5), disintegrating, forming small particles, and ultimately dissolving. When several occur together they rapidly unite, form small groups (7), and collect into finely granular masses or " Kornchenhaufen." These masses may be associated in coagulated blood with fibrils of fibrin (Fig. 10). [These blood plates are seen in shed blood, best in the guinea pig, especially if it be mixed with a solution of sodic sulphate {sp. gr. 1022) or i{ per cent. NaCl tinged with methyl-violet (Bi:zoscro).'] 3 34 CHANGES OF THE RED AND WHITE BLOOD CORPUSCLES. Bizzozero believes that they are the agents which immediately induce coagulation and take part in the formation of fibrin during coagtilalion of the blood ; Eberth and Schimmelbusch ascribe the formation of ihrombi to them. It is not yet determined whether they are derived from partially dismtegrated leucocytes, as a consequence of alteration of the blood [Lniuit), or whether they are independent formations. Along with the leucocytes they are concerned in the formation of fibrin [//lava). These structures were known to early observers (Mux Schultze, Kicss, and others); but their significance has been variously interpreted. Halla found that they are increased in pregnancy, and Afanassiew in conditions of regeneration of the blood. [Gibson's view is that these blood plate-;, which he calls colorh'ss mi(rocyles, are derived from the nucleus of young red blood corpuscles, or, occasionally from the nucleus of white corpuscles.] [As to the ht^iuatoblasts, or, as they have also been called, the "globules of Donn6 " by Pouchet, there seems to be some confusion, for both colored and colorless granules are described under these names. As Gibson suggests, the former are, perhaps, parts of disintegrated colored corpuscles, whilst theJatter are the blood plates.] [The "invisible blood corpuscles" described by Norris seem to be simply decolorized red corpuscles {//art, Giison).'\ III. Elementary Granules. — Blood, especially after a microscopic prepara- tion has been made for a short time, is seen to contain elementary granules (Fig. 7, F), [i.e., the elementary particles of Zimmermann and Beale. They are irregular bodies, much smaller than the ordinary corpuscles, and appear to consist of masses of protoplasm detached from the surface of leucocytes, or derived from the disintegration of these corpuscles, or of the blood plates. Others, again, are completely spherical granules, either consisting of some proteid substance or fatty in their nature. The protoplasmic and the proteid granules disappear on the addition of acetic acid, while the fatty granules (which are most numerous after a diet rich in fats) dissolve in ether]. [Gibson is of opinion that some of the granules are fragments of broken-down red corpuscles. He calls ihem colored muroov/trs, and considers them as representing one stage of Hayem's hsemato- blasts.] [It seems, then, that in addition to the red and white corpuscles, there are two distinct elements in shed blood, one the colored microcyie of Gibson, derived from broken-down red corpuscles, and the other the blood plates ox colorless 7)uirocyte.'\ [When the blood-forming process is particularly active, " nucleated colored corpuscles," or the "corpuscles of Neumann," are sometimes found in the blood. They are identical with the nucleated colored blood corpuscles of the fcetus, being somewhat larger than the non-nucleated colored corpuscle (§ 7).] IV. In coagulated blood, delicate fibrils or threads of fibrin (Fig. 7, E, and 10, 6, 7, 8) are seen, more especially after the corpuscles have run into rouleaux. At the nodes of these fibres are found granules which closely resemble those described under II. [These granules and fibres are stained by magenta and iodine, but not by carmine or picrocarmine {^Ranvier).'\ 10. ABNORMAL CHANGES OF THE RED AND WHITE BLOOD COR- PUSCLES. — ^I) All hemorrhages diminish the number of red corpuscles (at most one-half), and so does incnstniation. The loss is partly covered by the absorption of fluid from the tissues. Menstruation shows us that a moderate loss of red corpuscles is replaced within twenty-eight days. When a large amount of blood is lost, so that all the vital processes are lowered, the time may be extended to five weeks. In acute fevers, as the temperature increases, the number of rc^?" corpuscles diminishes, while the white corpuscles increase in number (Riegel and Boehmann, /-/alia). By greatly cooling peripheral parts of the body, as by keeping the hands in iced water, in some individuals possessing red blood corpuscles of low resisting power, these corpuscles are dissolved, the blood plasma is reddened, and even hemoglobinuria (^ 265) may occur [Lichlheim, Boas). Diminished production of new red corpuscles causes a decrease, since blood corpuscles are continually being used up. In chlorotic girls there seems to be a congenital weakness in the blood- forming and blood-propelling apparatus, the cause of which is to be sought for in some faulty con- dition of the mesoblast. In them the heart and the blood vessels are small, and the absolute number of corpuscles may be diminished one half, although the relative number may be retained, while in the corpuscles themselves the ha:moglobin is aiminished almost one-third (Duncan, Quincke) ; but it rises again after the administration of iron (Hayem). The administration of iron increase^ the amount of hitmoglobin in the blood (Scherpf). 1 he amount of iron in the blood may be diminished one-half. [The action of iron in anaemic persons has been known since the lime of Sydenham. CHEMICAL CONSTITUENTS OF THE RED BLOOD CORPUSCLES. 35 Hayem also finds that in certain forms of anxmia there is considerable variation in the size of the red corpuscles, and that in chronic anaemia the mean diameter of the corpuscles is always less than normal (7 /i to 6 /i). There is, moreover, a persistent alteration in the volume, coloring pmoer, and consistence of the corpuscles, consequently a want of accord between the number of' the corpuscles and their coloring power, ;'. e., the amount of ha-moglobin which they contain, as was pointed out by Johann Duncan.] In so-called /ith/V/ohj- ancemia, in which the continued decrease in the red corpuscles may ultimately produce death, there is undoubtedly a severe affection of the blood-form- ing apparatus. The corpuscles assume many abnormal HinA bizarre forms (microcytes), often beinj^ oval or tailed, irregularly shaped, and sometimes very pale ; while numerous cells containing blood corpuscles are found in the marrow of bone (Riess). Curiously enough, in this disease, although the red blood corpuscles are diminished in number, some may he larger and contain more haemo- globin than do normal corpuscles (Zani-Z/c). The number of colored corpuscles is also diminished in chronic poisoning by lead or miasmata, and also by the poison of syphilis. (2) Abnormal forms of the red corpuscles have been observed after severe bums (Lesser) ; the corpuscles are much smaller, and under the influence of the heat particles seem to be detached from them, just as can be seen happening under the microscope as the effect of heat (IVertAeim). Disinlegralion of the corpuscles into fine droplets has been observed in various diseases, as in severe malarial fevers. The dark granules of a pigment closely related to hoematin are derived from the granules arising from the disintegration of the blood corpuscles, and these particles float in the blood (Melanaemiaj. They are partly absorbed by the colorless corpuscles, but they are also deposited in the spleen, liver, brain and bone marrow (Arnstein). Sometimes the rei corpuscles are ab- normally soft, and readily yield to pressure. The white corpuscles are enormously increased in number in Leukaemia (/. H. Bennet and I'lrchow) ; sometimes even to the extent of the red corpuscles. In some cases the blood looks as if it were mixed with milk. The colorless corpuscles seem to be formed chiefly in bone marrow {£. A^eiimann), but also in the spleen and lymphatic glands (myelogenic, splenic and lymphatic leuka-mia). II. CHEMICAL CONSTITUENTS OF THE RED BLOOD CORPUSCLES.— ij The coloring matter or haemoglobin (Hlj; f Haimatogiobulin, Hasmatocrystaliin 1, is the cause of the red color of blood; it also occurs in muscle, and in traces in the fluid part of blood, but in this last case only as the result of the solution of some red corpuscles. Ix.?, percentage composi- tion is : C 53.85, H 7.32, N 16.17, Fe 0.42, S 0.39, O 21.84 (dog). Its rational formula is unknown, but Preyer gives the empirical formula C^qq, H^jj, Njj^, Fe, S3, Ojjg. Although it is a colloid substance it crystallizes \Hiincfeld, 1840, Heichert) m all classes of vertebrates, according to the rhombic system, and chiefly in rhombic plates or prisms ; in the guinea pig in rhombic tetrahedra (v. Lang) ; in the squirrel, however, it yields hexagonal plates. The varying forms, perhaps, correspond to slight differences in the chemical composition in different cases. Crystals separate from the blood of all classes of vertebrata during the slow evaporation of lake- colored blood, but with varying facility (Fig. 11). The coloring matter crystallizes very readily firom the blood of man, dog, mouse, guinea pig, rat, cat, hedgehog, horse, rabbit, birds, fishes; with difficulty from that of the sheep, ox and pig. Colored crystals are not obtained from the blood of the frog. More rarely a crystal is formed from a single corpuscle enclosing the stroma. Crystals have been found near the nucleus of the large corpuscles of fishes, and in this class of vertebrates colorless crystals have been observed. Hnemoglobin crystals are doubly refractive and pleo-chromatic ; they are bluish red with trans- mitted light, scarlet-red by reflected light. They contain from 3 to 9 per cent, water of crystalliza- tion, and are soluble in water, but more so in dilute alkalies. They are insoluble in alcohol, ether, chloroform, and fats. The solutions are Hemoglobin cr>-suis a, *, from human d, . , - n , 1* 1 , ■ blood; c, irom the cat; tf , from the ichroic ; red m reflected light, and green in guinea pig ;<, hamster ;/,squjrrei. Fig. 36 QUANTITATIVE ESTIMATION OF H.-EMOGLOBIN. transmitted light. [The solutions are readily decomposed by boiling, while they are precipitated by mineral acids, alcohol, and acetic acid.] In the act of crystallization the haemoglobin seems to undergo some internal change. Before it crystallizes it does not diffuse like a true colloid, and it also rapidly decomposes hydric peroxide. If it be redissolved after crystallization, it diffuses, although only to a small extent, but it no longer decomposes hydric peroxide, and is decolorized by it. A body like an acid is deposited from haemoglobin at the positive pole of a battery. [The presence of O favors crystallization.] [Haemoglobin exists in two states, either as reduced haemoglobin, i. e., free from oxygen, or as oxyhjemoglobin. The former is non-crystalline. They differ in their color and spectra ; § 15.] 12. PREPARATION OF HiEMGGLOBIN CRYSTALS.- Method of Rollett.— Place defibrinated blood in a platinum capsule, allow the capsule and the blood to freeze by placing them in a freezing mixture, and then gradually to thaw ; pour the lake-colored blood into a plate, until it forms a stratum not more than i}< mm. in thickness, and allow it to evaporate slowly in a cool place, when crystals will separate. Method of Hoppe-Seyler. — Mix defibrinated blood with 10 volumes of a 20 per cent, salt solution, and allow it to stand for two days. Remove the clear upper fluid with a pipette, wash the thick deposit of blood corpuscles with water, and afterward shake it for a long time with an equal volume of ether, which dissolves the blood corpuscles. Remove the ether, filter the lake-colored blood, add to it |^ of its volume of cold (0°) alcohol, and allow the mixture to stand in the cold for several days. The numerous crystals can be collected on a filter and pressed between folds of blotting paper. Method of Gscheidlen. — Crystals several centimetres in length were obtained by taking de- fibrinated blood which had been exposed for twenty-four hours to the air, and keeping it in a closed tube of narrow calibre for several days at 37° C. When the blood is spread on glass, the crystals form rapidly. [Vaccine tubes answer very well.] [Method of Sterling and Brito — It is in many cases sufficient to mix a drop of blood with a few drops of water on a microscopic slide, and to seal up the preparation. After a few days beautiful crystals are developed. The addition of water to the blood of some animals, such as the rat and the guinea pig, is rapidly followed by the formation of crystals of ha-moglobin. Very large crystals m.iy be obtained from the stomach of the leech several days after it has sucked blood.] 13. QUANTITATIVE ESTIMATION OF HAEMOGLOBIN. — (, b, (, etc. (Fig. 14). 15. COMPOUNDS OF H-^EMOGLOBIN WITH O ; . OXYH/E MOGLOBIN AND METHiEMOGLOBIN. — i. Oxyheemoglobin (C^Hb) behaves as a weak acid, and occurs to the extent of 86.78 to 94.30 per cent, in dry human red corpuscles {/Udell). It is formed very readily whenever Hb comes into contact with O or atmospheric air. i gramme Hb unites with 1.202 cubic centimetres of O at o° and i metre Hg pressure {Hufuer). Oxyhiemo- FiG. 14. Red. Orange. Yelli tTTmTnjrrnT bo 70 80 qo D E F us spectra of haemoglobin and its compounds. globin is a very loose chemical compound, and is slightly less soluble than Hb; its spectrum shows in Vne yello^o and the green two dark absorption fiands {Hoppe- Seyler) whose length and breadth in an 0.18 percent, solution are given in Fig. 14 (2Y [If the solution be very weiik, only the narrow band near D is obtained.] [The two absorption bands lie between the lines D and E, the band nearer D being more sharply defined and narrower than the second band, which is wider and less clearly marked off, and lies nearer E.] It occurs in the blood corpuscles circulating in arteries and capillaries, as was 40 METIL-EMOGLOBIN. shown by the spectroscopic examination of the ear of a rabbit, of the prepuce, and the web of the fingers {Vieivrdt). Reduction of Oxyhaemoglobin. — It gives up its O very readily, however, even when means which set free absorbed gases are used. It is reduced by the removal of the gases by the air pump, by the (onduction through its solution of other gases (CO and NO), and by heating to the boiling point. In the circulating blood its O is very rapidly given up to the tissues, so that in suffocated animals only reduced hcemoglohiii is found in the arteries. Some constituents of the serum and sugar use up O. By adding to a solution of-oxyhaemoglobin reducing sub- stances — e. g., ammonium sulphide, ammoniated tartarate of zinc oxide solution, iron filings, or Stokes's fluid [tartaric acid, iron protosulphate and excess of ammonia] — the two absorption bands of the spectrum disappear, and reduced hemoglobin (gas free) (Fig. 14, 4), with one absorption band, is formed (Stokes, 1864). [The single band which is obtained from reduced hemoglobin lies between D and E, and its most deeply shaded portion is opposite the interval between the two bands of oxyhemoglobin. Its edges are less sharply defined. The color of the blood changes from a bright red to a brownish tint. Hoppe-Seyler applies the term Ha-moglobin to the reduced substance, to distinguish it from oxyhaemo- globin.] The two bands are reproduced by shaking the reduced hemoglobin with air, whereby O.^Hb is again formed. Solutions of oxyhaemoglobin are readily distinguished, by their scarlet color, from the purplish tint of reduced hemoglobin. If a string be tied round the base of two fingers so as to interrupt the circulation, the spectro- scopic examination shows that the o.Nyhremoglobin rapidly passes into reduced Hb {Vicrordt). Cold delays this reduction {FilcJnie), it is accelerated in youth, during muscular activity, or by suppressed respiration, and usually also during fever (Denning). The spectroscopic examination of small blood stains is often of the utmost forensic importance. A minimal drop is sufficient. Dissolve the stain in a few drops of distilled water, and place in a thin glass tube in front of the slit of the spectroscope. [Hemoglobin has certain remarkable characters : — (i) Although it is a crystalloid body it diffuses with difficulty through an animal membrane, owing to the large size of its molecule. (2) It readily combines with O to form an unstable and loose chemical com- pound, oxyhemoglobin. (3) This O it gives up readily to the tissues or other deoxidizing reagents. (4) Its composition is very complex, for in addition to the ordinary elements present in proteids, it contains a remarkable amount of iron (0.4 per cent).] 2. Methaemoglobin (^Hoppe Seyler') is a more stable, crystalline compound. It contains the same amount of O as OjHb, but in a different chemical union, while the O is also more firmly united with it (Kiilz, Hiifner,/. G. Ott). It shows _/tf«r absorption bands like hematin in acid solution (Fig. 14, 5), of which those between C and D are distinct ; the second is very indistinct, while the third and fourth readily fuse, so that these last are only well seen with good apparatus. Methaemoglobin is only formed from solutions of Hb, and not within the blood corpuscles [v Mering). It is produced spontaneously in old brown blood stains, in the crusts of bloody wounds, in blood cysts, and in bloody urine. It is also formed by the addition of minu/e traces of acid to blood, or by heating blood with a trace of alkali. Chemically, it can be prepared in a solu- tion of Hb, by the action of potassic ferricyanide [Jih/erhe/m) or potassic chlorate (Marcliand), [or by adding to a solution of Hb a freshly-prepared solution of potassic permanganate]. If a trace of ammonia be added to a solution of methaemoglobin, it gives an alkaline solution of methcemoglobin, which shows two bands like oxyhjemoglobin, of which the first one is the broailer, and extends more into the red. If ammonium sulphide be added to the metha;moglobin solution, reduced Hb is formed. 16. CARBONIC OXIDE H-^MOGLOBIN AND POISONING \A^ITH CO. — 3. CO-Haemoglobin is a more stable chemical compound than the foregoing, and is produced at once when carbonic oxide is brought into con- POISONING BY CARBONIC OXIDE. 41 tact with pure Hb or OjHb {CI. Bernard, i8j/). It has an intensely florid or c'/wrrj-reJ color, and gives two absorption bands, very like those of 02Hb, but they are slightly closer together and lie more toward the violet (Fig. 14, 3). Reducing substances (which act upon HbOj) do not affect these bands, /. e., they cannot convert the CO compound into reduced Hb. .Another good test to distinguish it from HbO, is the soJa Usf. If a 10 per cent, solution of caustic soda be added to a solution of CO-Hb. and heated, it gives a cinnabar-red color ; while, with an HbOj solution, it gives a dark brown, greenish, greasy mass (^Hoppc-Seyler). Oxidizing substances [solutions of potassic permanganate (0.025 per cent.), potassic chlorate (5 per cent.), and dilute chlorine solution] make solutions of CO-Hb cherry-red in color, while they turn solutions of OjHb pale yellow. After this treatment both solutions show the absorption bands of methremoglobin, but those of the CO-Hb appear considerably later. If ammo- nium sulphide be added, O.^Hb and CO-Hb are reformed (77/. Weyl and v. Anrcp). On account of its stability, CO-Hb resists external influences and even putrefaction for a long time [IIoppc' Styh-r), and the two bands of the spectrum may be visible after many months. Lan- dois ol)tained the soda test and spectroscopic bands in the blood of a woman poisoned eighteen months previously by CO, and after great putrefaction of the body had taken place. [Stirling has kept CO-Hb in a stoppered bottle for four years without its undergoing putrefaction.] If CO is breathed by man, or if air containing it be inspired, it gradually dis- places the O, volume for volume, out of the Hb (Z. Meyer), and death soon occurs; 1000 c.cm. inspired at once will kill a man. .\ very small quantity in the air (ttu "TTnnr) suffices, in a relatively short time, to form a large quantity of CO-Hb ( Grehant). As continued contact with other gases (such as the passing of O through it for a very long time), gradually separates the CO from the Hb (with the formation of OjHb {Donders)), it happens that, in very partial poison- ing with CO, the blood gradually gets rid of the latter, so that only a very small part of the CO is e.\creted by the respiratory organs ; the largest amount is more highly oxidized in the body into CO2 and thus excreted (A'ries). [CO-Hagmo- globin, being a comparatively stable compound when once formed, circulates in the blood vessels ; but it neither gives up oxygen to the tissues, nor takes up oxygen in the lungs, hence its very poisonous properties. The real cause of death in animals poisoned with it is that the internal respiration is arrested.] [Gamgee and Zuntz also find that although the CO-Hb compound is very stable, yet it may be reduced by passing air or neutral gases through it for a lengthened period; it is also reduced when blood is boiled in the mercurial pump.] Poisoning with Carbonic Oxide. — Carbonic oxide is formed during incomplete combustion of coal or coke, and passes into the air of the room, provided there is not a free outlet for the products of combustion. It occurs to the extent of 12-2S per cent, in ordinary gas, which largely owes its poisonous properties to the presence of CO. If the O be gradually displaced from the blood by the respiration of air containing CO, life can only be maintained as long as sufficient O can be obtained fiom the blood to support the oxidations necessary for life. Death occurs before all the O is displaced from the blood. CO has no effect when directly applied to muscle and nerve. When it is inhaled, there is first stimulation and afterward paralysis of the nervous system, as shown by the symptoms induced, (•. i,^, violent headache, great restlessne>s, excitement, increased activity of the heart and respiration, salivation, tremors and spisms. Later, unconsciousness, weakness and paralysis occur, labored respiration, diminished heart beat, and, Lastly, complete loss of sensibilitv, cessation of the respiration and heart beat, and death. .'Vt first the temperature rises several tenths of a degree, but it soon falls 1° or more. The pulse is also increased at first, but afterward it becomes very small and frequent. In poisoning with />!irf CO there is no dyspnoea, but sometimes muscular spasms occur, the coma not being verj' marked. There is also temporary but pronounced paralysis of the limbs, followed by violent spasms. After death, the heart and brain are congested witii intensely florid blood. In poisoning with the vapor of charcoal, where CO and COj both occur, there is a varj'ing degree of coma ; pronounced dyspnoea, muscular spasms which may last several minutes, gradual paralysis and asphyxia, moniliform contractions and subsequent dilatation of the blood vessels, with conges- tion of various organs, occur, accompanied by a fall of the blood pressure {A7eis), indicating initial stimulation and subsequent paralysis of the vaso-motor centre. This also explains the variations in the temperature and the occasional occurrence of sugar in the urine after poisoning with CO. After 42 DECOMPOSITION OF H.EMOGLOBIN. death, the blood vessels are found (o be filled with fluid blood of an exquisitely bright cherry-red color, while all the muscles and viscera and exposed parts of the body (such as the lips) have the same color. The brain is soft and friable, there are catarrh of the respiratory organs and degenera- tion of the muscles, and great congestion and degeneration of the liver, kidneys and spleen. The .spots of Wv'tdhy, fasf-mor^em, ate bright red. After recovery from poisoning with CO there may be paraplegia and (although more rarely) disturbances of the cerebral activity. The poisonous action of the vapois of combusiion was known to .\ristotle. 17. OTHER COMPOUNDS OF HiEMOGLOBIN. — 4. Nitric Oxide Haemoglobin (NO-Hb) is formed when NO is brought into contact with Hb (Z. Hcnnaim). As NO has a great affinity for O, red fumes of nitrogen peroxide (NO,) being formed whenever the two gases meet, it is clear that, in order to prepare NO-HB, the O must first be removed. This may be done by passing H through it [or ammonia may be added to the blood, and a stream of NO passed through it; the ammonia combines with all the acid formed by the union of the NO with the O of the blood]. NO Hb is a more stable chemical compound \\a.n CO-Hb, which, as we have seen, is, again, more stable than O^Hb. It has a bluish-violet tint, and also gives two absorption bands in the spectrum similar to those of the other two compounds, but not so intense. These bands are not abolished by the action of reducing agents. The three compounds of Hb, with O, CO and NO, are crystalline, like Hb; they are isomorphous, and their solutions are not dichroic. All three gases unite in equal volumes with Hb {Preyer, L. Hermann). If O be conducted through a concentrated solution of Hb devoid of gases, a crystalline mass of O.Hb is thereby readily formed. [Nitrites, e.g., amyl, added to fresh blood, give it a chocolate color, and its spectrum is that of meth.-emoglobin. The compound so formed, however, is less stable than tliat with CO, for the decomposition products formed in the blood during asphyxia can reduce the former but not the latter compound.] 5. Cyanogen, CNH {Hoppe-Seyler), and acetylene, CjH^ [Bistrow and Liehreich), form easily decomposable compounds with Hb. The former occurs in poisoning with hydrocyanic acid, and has a spectium identical with that of O^Hb, and, like 0,Hb, it is reduced by special agents. [The existence of these compounds is, however, highly doubtful {Gamgee).'\ 18. DECOMPOSITION OF H.^MOGLOBIN.— In solution and in the dry state, Hb gradually becomes decomposed, whereby the iron-containing pigment hajmatin, along with certain by-products, formic, lactic and butyric acids, are formed. Hsemoglobin, however, tnay be decomposed at once into (i) a body contain- ing iron, hiematin, and (2) a colorless proteid closely related to globulin; by {a) the addition of all acids, even by CO. in the presence of plenty of water: {h) strong alkalies; (<:) all reagents which coagulate albumin, and by heat at 7o°-8o^ C. ; {d^ by ozone. (A) Haematin (Ceg, Hjo, Ns, Fe.j, 0,„) is a bluish-black, amorphous body, which forms about 4 per cent, of hemoglobin (dog). It is insoluble in water, alcohol and ether; soluble in dilute alkalies and acids and in acidulated ether and alcohol. Haetnochromogen. — When Hb containing O is decomposed, haematin is formed at once ; while Hb free from O, on being decomposed, forms, first, a purplish-red body, Hcemochromogen (Cj^.H^, N4,Fe05), which contains less O, and is a precursor of hcematin. In the presence of O it becomes oxidized and passes into ha;matin. In solution, it gives the spectrum shown in Fig. 14, 7 {Hoppe- Seyler). Hsemato- Porphyrin. — Dilute acids in an alkaline solution deprive haemochromogen of its iron, and hie/iiato-porphvrin, a substance which remains stable in contact with air, is produced. It may also be produced from hasmatin by the action of acids, so that haimatin is an oxidation stage of haemochromogen. The following derivatives are know n : — (a) Haematin in Acid Solution — Lecanu extracted it from dry blood corpuscles by using alcohol containing sulphuric and tartaric acids. If acetic acid be added to a solution of Hb, a m ihogany-brown fluid is obtained, containing haematin in acid solution, which gives a spectrum with /our absorption bands in the yellow and green (Fig. II, 5). (ii Haematin in Alkaline Solution. — If this solution he treated with excess of ammonia, hcematin in alkaline solution is formed, which gives one absorption band on the boundary line between red and yellow (Fig. 14, 6). {c) Reduced Haematin. — Reducing agents cause this band to disappear, and produce in the yellow two broad \i3.n&s, which are due to the presence of " reduced lucmatin" (Fig. 14, 7). H.-EMIN AND BLOOD TESTS. 43 Action of CO 2. — If CO, be passed through a solution of oxyha;moglobin for a considerable time, reduced Hb is first formed ; but if the process be prolonged the Hb is decomposed, a precipi- tate of globulin is thrown down, and an absorption band, similar to that obtained when Hb is decomposed with acids, is observed (see p. 42). According to Zinoffsky's analysis there are exactly two atoms of S to each atom of Fe in Hb. When hiemoglubin is extravasated into the subcutaneous tissue, it becomes so altered that ulti- mately hydrated oxide of iron appears in its place. 19. H^MIN AND BLOOD TESTS.— In 1853 Teichmann prepared crystals from blood, which Hoppe-Seyler showed to be chloride of hiematin or hydrochlorate of hcematin. The presence of these crystals is used as a test for blood stains or blood in solution. These crystals of heemin (Fig. 15) are prepared by adding a small crystal of common salt to dry blood on a glass slide, and then an excess of glacial acetic acid ; the whole is gently heated until bubbles of gas are given off. On allowing the preparation to cool, the characteristic hsmin crystals are obtained (Ha;matin -(- 2HCI). Characters. — When well formed, the crystals are small, microscopic, rhombic plates, or rhombic rods; sometimes they are single — at other times they are aggre- gated in groups, often crossing each other. Some kinds of blood (ox and pig) yield very irregular, scarcely crystalline, masses. The crystalline forms of h^emin are identical in all the different kinds of blood that have been examined (Jahnke, Hogyes). They are ilotibly refractive and pleo-chromatic ; by transmitted light they Fig. 15. '/*♦ Va Fig. 16. ^ // / ■ 'X ^-'^i, . Haemin crystals of \ are mahogany brown, and by reflected light bluish black, glancing like steel. They give a brown streak on |)orcelain. (i) Preparation from Dry Blood Stains. — Place a few particles of the blood stain on a glass slide, add two to three drops of glacial acetic acid and a small crystal of common salt ; cover with a cover glass, and heat gently over the flame of a spirit lamp until bubbles of gas are given off. On cooling, the crystals appear in the ]ireparation (Fig. 16). (2) From Stains on Porous Bodies.— The stained object (cloth, wood, blotting paper, earth) is extracted with a small quantity of dilute caustic potash, and afterward with water in a watch glass. Both solutions are carefully filtered, and tannic acid and glacial acetic acid are added until an acid reaction is obtained. The dark precipitate which is formed is collected on a filter and washed. A small l^art of it is placed on a microscope slide, a granule of common salt is added, and the whole dried ; the dry stain is treated as in (i) {Striiwe.) (3) From Fluid Blood. — Dry the blood slowly at a low temperature, and proceed as in ( i). (4) From very Dilute Solutions of Haemoglobin. — (a) Strmve's Method. — Add to the fluid, ammonia, tannic acid, and afterward glacial acetic acid, until it is acid ; soon a black precipitate of tannate of ha;matin is thrown 44 H.EMATOIDIN. down. This is isolated, washed, dried, and treated as in (i), but instead of NaCl a granule of ammonium chloride is added. (d) Gulling and van Geuns recommend the addition of zinc acetate, wliich gives a reddish pre- cipitate; this precipitate is to be treated as in (l). Hjemin crystals may sometimes be prepared from putrefyinfj or lake-colored blood, but they are very small, and here the test often fails. When mixed with iron rust, as on iron weapons, the blood crystals are generally not formed. In such cases, scrape off the stains and boil them with dilute caustic potash. If blood be present, the dissolved hfematin forms a fluid, which in a thin layer is green ; in a thick layer, red {H. Rose). Htemin crystals have been prepared from all classes of vertebrates and from the blood of the earthworm. Chemical Characters. — They are insoluble in water, alcohol, ether, chloroform ; but concen- trated HoSOj dissolves them, expelling the HCl, and giving a violet red color. Ammonia also dis- solves them, and if the resulting solution be evaporated, heated to 130° C, and treated with boiling water (which extracts the ammonium chloride), /;.504 '-635 I Phosphoric Acid 2.067 o 703 y Soda o 2.093 (B""g6). [An approximate estimate of the composition of human blood is given in the following table : — Composition of Human Blood as a Whole. Water 7S0 Solids — of these — Corpuscles 1 34 "| Serum Albumin 1 Serum Globulin ) ' I Fibrin of Clot (? Fibrinogen) 2.2 !■ 220 Inorganic Salts (of serum) 6.0 E.xtractives 6.4 F.atty matters 1.4 Gases, O, COo, N.] 24. CHEMICAL COMPOSITION OF THE COLORLESS COR- PUSCLES. — Investigations have been made on ptis cells, which closely resemble colorless blood corpuscles. They contain several proteids ; alkali albuminate, a proteid which coagulates at 48° C, and another resembling myosin, para- globulin, peptone, and a coagulating ferment ; nuclein in the nuclei {Miescher) {%. 250, 2); perhaps also glycogen (§ 252) {Salomon), lecithin, cerebrin, cholesterin, and fat. 100 parts, by weight, of dry pus contain — Earthy Phosphates, 0.416 I Potash, O.201 Sodic Phosphate, 0.606 | Sodic Chloride, 0.143 46 PREPARATION OF PLASMA. 25. BLOOD- PLASMA AND ITS RELATION TO SERUM.— The unaltered fluid in which the blood corpuscles float is called plasma, or liquor sanguinis. This fluid, however, after blood is withdrawn from the vessels rapidly undergoes a change, owing to the formation of a solid fibrous substance — fibrin. After this occurs, the new fluid which remains no longer coagulates spontaneously (it is plasma, minus the fibrin factors), and is called serum. Apart from the presence of the fibrin factors, the chemical composition of plasma and serum are the same. [When blood coagulates, the following table, I, shows what takes place, while the second table, 11, shows what occurs when it is beaten : — Coagulation. Blood. Corpuscles. Fibrin -factors. I II. When beaten. Blood. I Corpuscles. Defibrinated Blood. The serum, however, still contains a portion of the fibrin ferment, and also some of the fibrinoplastin or fibrinoplastic substance. Plasma is a clear, transparent, slightly thickish fluid, which, in most animals (rabbit, o.x, cat, dog), is almost colorless ; in man it is yellow, and in the horse citron-yellow.] 26. PREPARATION OF PLASMA.— (A) Without Admixture.— Taking advantage of the fact that plasma, when cooled to o^ outside the body, does not coagulate for a considerable time, Briicke prepares the plasma thus : Selecting the blood of the horse (because it coagulates slowly, and its corpuscles sink rapidly to the bottom), he receives it, as it flows from an artery, in a tall, narrow glass, placed in a freezing mixture, and cooled to 0°. The blood remains fluid, and the colored corpuscles subsiding in a few hours, the plasma remains above as a clear layer, which can be removed with a cooled pipette. If this plasma be then passed through a cooled filter, it is robbed of all its colorless corpuscles. [Burdon-Sanderson uses a vessel consisting of three compartments — the outer and inner contain ice, while the blood of the horse is caught in the central compart- ment, which does not exceed half an inch in diameter.] The quantity of plasma may be roughly (but only roughly) estimated by using a tall, graduated measuring glass. If the plasma be warmed, it soon coagulates (owing to the formation of the fibrin), and passes into a trembling jelly. If, how- ever, it be beaten with a glass rod, the fibrin is obtained as a white, stringy ma.ss, adhering to the rod. The quantity of fibrin in a given volume of plasma, is about 0.7-1 per cent., although it varies much in different cases. (B) With Admixture. — Blood flowing from an artery is caught in a tall, graduated measure containing ^ of its volume of a concentrated solution ofsodic sulphate {Hnuson) — or in a 25 per cent, solution of magnesic sulphate (i vol. to 4 vols, blood — Scminer) — or 1 vol. blood with 2 vols, of a 4 per cent, solution of monophosphate of potash {Masia). When the blood is mixed with these fluids and put in a cool place, the corpuscles subside, and the clear stratum of plasma mixed with the salts may be removed with a pipette. If the .salts be removed by dialysis, coagulation occurs ; or it may be caused by the addition of water i/oh. Mailer"). Blood which is mixed with a 4 per cent, solution of common salt does not coagulate, so that it also may be used for the preparation of plasma. [For frogs' blood Johannes Miiller used a ^^ per cent, solution of cane sugar, which FIBRIN COAGULATION OF THE BLOOD. 47 permits the corpuscles to be separated from the plasma by filtration. The plasma mixed with the sugar coagulates in a short time.] 27. FIBRIN — COAGULATION OF THE BLOOD. — General Characters. — Fibrin is that substance which, becoming solid in shed blood, in plasma and in lymph causes coagulation. In these fluids, when left to themselves, fibrin is formed, consisting of innumerable, excessively delicate, closely packed, microscopic, doubly refractive {Hermann) fibrils (Fig. 7, E|. These fibrils en- tangle the blood corpuscles as in a spider's web, and form with them a jelly-like, solid mass, called the blood clot or placenta sanguinis. At first the clot is very soft, and after the first 2 to 15 minutes a few fibres may be found on its surface ; these may be removed with a needle, while the interior of the clot is still fluid. The fibres ultimately extend throughout the entire mass, which, in this stage, has been called criior. After from 12 to 15 hours the fibrin contracts, or, at least, shrinks more and more closely round the corpuscles, and a fairly solid, trembling, jelly-like clot, which can be cut with a knife, is formed. During this time the clot has expressed from its substance a fluid — the blood serum. The clot takes the shape of the vessel in which the blood coagulates. Fibrin may be obtained by washing away the corpuscles from the clot with a stream of water. Crusta Phlogistica. — If the corpuscles subside very rapidly, and if the blood coagulates slowly, the upper stratum of the clot is not red, but only yellowish, on account of the absence of colored corpuscles. This is regularly the case in horse's blood, and in human blood it is observed especially in inflammations; hence this layer has been called crusta phlogistica. Such blood contains more fibrin, and so coagulates more slowly. The crusta is formed under other circumstances, but the cause of its formation is not always clear, e.g., with increased sp. gr. of the corpuscles, or diminished sp. gr. of the plasma (as in hydrcemia and chlorosis), whereby the corpuscles sink more rapidly, and also during pregnancy. The taller and narrower the glass, the thicker is the crusta (compare ^41). The upper end of the clot, where there are few corpuscles, shrinks more, and is, therefore, smaller than the rest of the clot. Ihis upper, lighter-colured layer is called the " huffy" coat ; this, however, gradually passes, both as to size and color, into the normal dark-colored clot. [Sometiines the upper surface of the clot is concave or " cupped." The older physicians used to attribute great importance to this condition, and also to the ojcurrence of the crusta phlogistica, or buffy coat.] Defibrinated Blood.- — -If freshly-shed blood be beaten or whipped with a glass rod or with a bundle of twigs, fibrin is deposited on the rod of twigs in the form of a solid, fibrous, yellowish-white, elastic mass, and the blood which remains is called '■^ dffibrinated blood''' (p. 46). [The twigs and fibrin must be washed in a stream of water, to remove adhering corpuscles.] Coagulation of Plasma. — Plasma shows phenomena exactly analogous, save that there is no well-defined clot, owing to the absence of the resisting corpuscles; there is, however, always a soft, trembling jelly formed when plasma coagulates. [In Hewson's experiment on the blood of a horse tied in a vein, he found that the plasma coagulated — fibrin being formed, so that he showed coagulation to be due to changes in the plasma itself (§ 29).] Properties of Fibrin. — .\lthough the fibrin appears voluminous, it only occurs to the extent of 0.2 per cent, (o.i to 0.3 per cent.) in the blood. The amount varies considerably in two samples of the same blood {Sig- Mayer). It is insol- uble in water and ether ; alcohol shrivels it by extracting water ; dilute hydro- chloric acid (0.1 per cent.) causes it to swell up and become clear, and changes it into syntonin or acid albumin (§ 249, III). When fresh, it has a grayish- yellow, fibrous appearance and is elastic ; when dried, it is horny, transparent, brittle and friable. When fresh, it dissolves in 6 to 8 per cent, solutions of sodium nitrate or sulphate, in dilute alka- lies and in ammonia, thus forming alkali albuminate. Heat does not coagulate these solutions. Hydric peroxide is rapidly decomposed by fibrin into water and O ( Thenard). Fibrin which has been exposed to the air for a long time is no longer soluble in solution of potassic nitrate, but in 48 GENERAL PHENOMENA OF COAGULATION. neurin [Maul/iner). During putrefaction, it passes into solution, albumen being formed {J. v. Ln-ii^). Fibrin contains iron, calcic and magnesic phosphates, whose origin is unknown. Time for Coagulation. — According to H. Nasse, the first appearance of a coigulum occurs in man's blood after 3 minuter 45 seconds, in women's blood after 2 minutes 20 seconds. Age has no effect; withdrawal of food accelerates coagulation (A. VierorJt). 28. GENERAL PHENOMENA OF COAGULATION.— I. Blood which is in direct contact with the living and unaltered blood vessels does not coagulate (Thackrah, 1819). — [Hewson (^1772) found that when he tied the jugular vein of a horse in two places, and excised it (Fig. 18), the blood did not coagulate for a long time.] This important fact was confirmed by Briicke (1857), who filled the heart of a tortoise with blood which had stood fifteen minutes exposed to the air at 0°, and kept it in a moist chamber. The blood was still fluid at the end of 5 V2 hours, while the heart itself still continued to beat. He observed that at 0° the blood was uncoagulated in the contracting heart of a tortoise after eight days. Blood inside a contracting frog's heart preserved under mercury does not coagulate. If the wall of the vessel be altered by pathological processes {c-g-, if the intima becomes rough and uneven, or undergoes inflammatory change), coagulation is apt to occur at these places. Blood rapidly coagulates in a deaii heart, or in blood vessels (but not in capilla- ries) or other canals (^.^., the ureter) ( F/>i-/i(?K'). If blood stagnates in a living vessel, coagulation begins in the central axis, because here there is no contact with the wall of the living blood vessel. II. Conditions which Hinder or Delay Coagulation. — (a) The addition of small quantities of alkalies and ammonia, or of concentrated solutions of neutral salts of the alkalies and earths (alkaline chlorides, sulphates, phosphates, nitrates, carbonates). Magnesic sulphate acts inost favorably in delaying coagulation (i vol. solution of 28 per cent, to 3)4 vols, blood of the horse). {b) The precipitation of the fibrinoplastin by adding weak acids, or by CO2. By the addition oi acetic acid ^n\\\ the reaction is acid, the coagulation is completely arrested. A large amount of CO 2 delays it, and hence venous blood coagulates more slowly than arterial. Hence, also, the blood of suffocated persons remains fluid. (<:) The addition of egg albumin, syrup, glycerine and much water. If un- coagulated blood be brought into contact with a layer of already-formed fibrin, coagulation occurs later. {li) By cold at 0° coagulation may be delayed for one hour (J. Daiy). If blood is frozen at once, after thawing, it is still fluid, and then coagulates (^Hew- son). When shed blood is under high pressure it coagulates slowly (Landois). {e) Blood of embryo fowls does not coagulate before the twelfth or fourteenth day of incubation {Boll) ; that of the hepatic vein very slightly; menstrual blood shows little tendency to coagulate when alkaline mucus from the vagina is mixed with it. If it be rapidly discharged it coagulates in masses. (/) Blood rich in fibrin from inflamed parts coagulates slowly, but the clot so formed is firm. Haeinophilia. — A very slight scratch in some persons may cause very free bleeding. These persons are called colloquially " bleeders," and are said to have haemophilia or the hemorrhagic diathesis. In *' bleeders " coagulation seems not to talvc place, owing to a want of the substances producing fibrin ; hence, in these cases, wounds of vessels are not plugged with fiijrin. [.V ten- dency to hemorrhage occurs m scurvy, purpura, in some infectious diseases, such as typhus, plague, yellow fever, and in poisoning with phosphorus.] Injection of Peptones. — Albertoni observed that if tryptic pancreas ferment (dissolved in gly- cerine) be injected into the blood of an animal, the blood does not coagulate. Schmidt-Mulheim found that after the injection oi pure peftonemio the blood (0.3 to 0.6 grammes per kilo.) of a dog, the blood lost its power of coagulating. [This occurs in tlie dog, but not in the rabbit, moreover, although gastric peptone prevents coagulation, try-plon or pancreas ferment does not do so (^Fano). Peptonized blood, etc., coagulates when it is treated with CO, or water.] A substance is formed in the plasma, which prevents coagulation, but which is precipitated by C02. Lymph behaves similarly (fano). After peptones are injected, there is a great solution of leucocytes in the blood (v. Samson- Himmelstjerna). The secretion of the mouth of the medicinal leech [although its GENERAL PHENOMENA OF COAGULATION. 49 action is not due to a ferment [Haycrn/t)'], z.nA snake poison also prevent coagulation (Wa/l). [Diastatic ferment also prevents coagulation (Saivioli).'] [tJluod coagulates more slowly in a smooth than a rough vessel, and also in a shallow vessel than in a deep one.] III. Coagulation is accelerated — {a) By contact with Foreign Sub- stances of all kinds ; hence, threads or needles introduced into arteries are rapidly covered with fibrin. Even the introduction of air bubbles into the circu- lation accelerates it, and the pathologically altered wall of a vessel acts like a foreign body. Blood shed from an artery rapidly coagulates on the walls of vessels, on the surfaces exposed freely to air, and on the rods or twigs by which it is beat. The passage through it of indifferent gases, such as N and H, and the addition of HjO have the same effect. {b) Heating from 39° to 55° C. rapidly facilitates coagulation {Hewson). {/) Agitation of the blood, as shown by Hewson and Hunter. \{ji) The addition of a small quantity of water. (e) A watery condition of the blood, but in this case the clot is small and soft. (/) Contact with oxygen.] IV. Rapidity of Coagulation. — Among vertebrates, the blood of birds (especially of the pigeon), coagulates almost momentarily; in cold-blooded animals coagulation occurs much more slowly, while mammals stand midway between the two. [The blood of a fowl begins to coagulate in jj to I )^ minute ; that of a pig, sheep, rabbit, in ^ to i^ minute; of a dog, i to 3 minutes; of a horse and ox, 5 to 13 minutes; of man, 3 to 4 minutes ; solidification is completed in 9 to 11 minutes, but rather sooner in the case of women f^Nasse).'\ The blood of invertebrates, which is usually colorless when it is oxidized (J 32), forms a sjft, whitish clot of fibrin. Even in lympk and chyle, a small soft clot is formed. V. When coagulation occurs, the aggregate condition of the fibrin factors is altered, so that heat must be set free ( Valentin, 1884, Schiffer, Lepine). The rise in the temperature may be ascertained with a very delicate thermometer. VI. In blood shed from an artery, the degree of alkalinity diminishes from the time of its being shed until coagulation is completed {Pfliigcr and Zuntz). This is probably due to a decomposition in the blood, whereby an acid is developed, which diminishes the alkalinity (p. 17). VIL Whether or not electricity is developed is not positively proved. Hermann supposes that the parts already coagulated are negative, while non coagulated parts are positive ; but this has not been clearly shown. VIII. During coagulation there is a diminution of the O in the blood, although a similar decrease also occurs in non-coagulated blood. Traces of ammonia are also given off, which Richardson erroneously supposed to be the cause of the coagulation of the blood. [This is refuted — (t) by the fact that blood, when collected under mercury (whereby no escape of ammonia is possible), also coagulates; and (2) by the following experiment of Lister: He placed two ligatures on a ve.n containing blood, moistening one half of the outer surface of the vein with ammonia, leaving the other half intact. The blood coagulated in the first half, and not in the other, owing to the properties of the wall of the vein of the former being altered. Lister also proved that blood will remain fluid for hours in a vein after it has been fiecly exposed to the air, and even after it has been poured in a thin stream from one vein to another.] Neither the decrease of O nor the evolution of ammonia seims to have any causal connection with the formation of fibrin. Pathological. — When the blood coagulates within the vessels during life, the process is called thrombosis, and the coagulum or plug so formed is tenned a thrombus. When a clot of blood or other body is carried by the blood stream to another part of the vascular system where it blocks up a vessel, the plug is called an embolus, and the result embolism. 29. CAUSE OF THE COAGULATION OF THE BLOOD.— Perhaps this subject is best treated historically. [Hewson's Experiments (1772). — Hewson tied the jugular vein of a horse between two liga- tures, removed it, and then suspended it by one end (Fig. 18). He found that the blood remained 4 50 CAUSE OF THE COAGULATION OF THE BLOOD. fluid for a long time (48 hours), while the red corpuscles sank (R.C.) and left a clear layer of plasma on the surface (P). When he drew off some of this clear plasma it coagu- FiG. 18. lated, thus proving coagulation to be due to changes in the plasma. Lister repeated this experiment, and found that even if the upper end of the tube he opened and the blood freely exposed to the air, coagulation is but slightly hastened. Moreover, he proved that the blood might be poured from one vein into another, just as one would pour fluid from one test-tube into another. In this case there were two test-tubes, i.e., the veins — and although the blood, on being poured from the one to the other, came into contact with the air, it did not coagulate. Hewson, however, found that blood poured from the vein into a glass vessel coagulated, so that, in his opinion, the blood vessels exerted a restraining influence on the coagulation. By cooling the blood and preventing it from coagulating, he proved that coagulation was not due to the loss of heat. Nor could it be a vital act, as sodic sulphate or other neutral salt prevented coagulation indefinitely, but coagulation took place when the blood was diluted with water.] [Buchanan's Researches. — The serous sacs of the body contain a fluid which in some respects closely resembles lymph. The pericardium contains pericardial fluid, which in some animals coagulates spontaneously vein 01 a iior.^e tied be- (t'.j,'., in the rabbit, ox, horse, and sheep), if the fluid be removed imnieJi- pTasma'"°W?r""^whit^' "'''-'' "fi^'' '^''"''''- ^f '^is be not done till several hours after death, the and RC, red corpuscles', fluid does not Coagulate spontaneously. The fluid of the tunica vaginalis of the testis, again, sometimes accumulates to a great extent, and constitutes hydrocele, but this fluid shows no tendency to coagulate spontaneously. Andrew Buchanan found, however, that if to the fluid of ascites, to pleuritic fluid, or to hydrocele fluid, there be added clear blood serum, then coagulation takes place, i.e., two fluids — neither of which shows any tendency by itself to coagulate — form a clot when they are mixed (1831). He also found that if " washed blood clot " (which consists of a mixture of fibrin and colorless corpuscles) be added to hydrocele fluid, coagulation occurred. He compared the action of washed blood clot to the action of rennet in coagulating milk, and he imagined the agents which determined the coagulation to be the colorless corpuscles. Thus, the buffy coat of horses' blood is a powerful agent, and it contains very numerous colorless corpuscles. He finally concluded that some constituent in the plasma, to which he gave the name of a " soluble fibrin," is acted upon by the colorless corpuscles and converted into fibrin. The soluble fibrin of Buchanan is comparable to the fibrinogen in Hammarslen's theory. But Buchanan did not separate the substance.] [Denis's Plasmine. — Denis mixed uncoagulated blood with a saturated solution of sodic sul- phate, allowed the corpuscles to subside, and decanted the clear fluid, which was mixed with sodic chloride, until a large amount of precipitate had been obtained. The precipitate, when washed with a saturated solution of sodic chloride, he called plasmine (1859). If plasmine be mixed with water, it coagulates spontaneously, resulting m the formation of fibrin, while another proteid remains in solution. According to the view of Denis, fibrin is produced by the splitting up of plasmine into two bodies — fibrin and an insoluble proteid.] [Researches of A. Schmidt (1861 ). — This observer rediscovered the chief facts already known to Buchanan, viz., that some fluids which do not coagulate spontaneously, clot when mixed with other fluids, which also show no tendency to coagulate spontaneously, e.g., hydrocele fluid and blood serum. He proceeded to isolate from these fluids the bodies which are described as fibrinogen and fibrinoplastin. The bodies so obtained were not pure, but Schmidt supposed that the formation of fibrin was due to the interaction of these two proteids. The reason why hydrocele fluid did not coagulate, he said, was that it contained fibrinogen and no fibrinoplastin, while blood serum con- tained the latter, but not the former. Schmidt afterward discovered that these two substances maybe present in a fluid, and yet that coagulation may not occur (e.g., occasionally in hydrocele fluid). He supposed, therefore, that blood or blood serum contained some other constituent necessary for coagu- lation. This he afterward isolated in an impure condition and caWeA fibrin ferment [Gamgee).'\ Alexander Schmidt's theory is that fibrin is formed by the coming together of .two proteid substances yi\\'\c\\ occmx dissolved in the plasma or liquor sanguinis, viz. : (i) Fibrinogen, i.e., the substance which yields the chief mass of the fibrin, and (2) Fibrinoplastic substance or fibrinoplastin, [ = serum globulin (^Th. Weyl and Hoppe-Seyler) or paraglobulin (^Kiihne) § 32]. In order to determine the coagulation a ferment seems to be necessary, and this is supplied by (3) the .Fibrin ferment. I. Properties of these Substances. — Fibrinogen and fibrinoplastin are not distinguished from each other by well-marked chemical characters. Still they differ, as follows : — (a) Fibrinoplastin is more easily precipitated from its solutions than fibrinogen. CAUSE OF THE COAGULATION OF THE BLOOD. 51 (^b) It is more readily redissolved when once it is precipitated. (c) It forms when precipitated a very light granular powder. {d) Fibrinogen adheres as a sticky deposit to the side of the vessel. It coagu- lates at 56° C. Both substances closely resemble globulin in their chemical composition (Kuhne called fibrinoplastin paraglobulin), and in their reactions they are not unlike myosin. Like all globulins, they require a trace of common salt for their solution (§ 249). On account of their great similarity, both substances are not usually prepared from blood plasma. Fibrinogen is prepared from scnnis transudations (pericardial, abdominal, or pleuritic fluid, or the fluid of hydrocele), which contain no fibrino- plastin. Fibrinoplastin is most readily prepared from serum, in which there is still plenty of fibrinoplastin, but no fibrinogen. 2. Preparation of Fibrinoplastin, Serum Globulin, or Paraglobu- lin. — ((7) Dilute blood serum with twelve times its volume of ice-cold water, and almost neutralize it with acetic acid [add 4 drops of a 25 per cent, solution of acetic acid to every 120 c.c. of diluted serum] ; or (/') pass a stream of carbon dio.xide through the diluted serum, which soon becomes turbid ; and after a time a fine white powder, copious and granular, is precipitated {Schtnidt, 1862). [(<■) The serum may be dialysed for a day ; at the end of this time the contents of the dialyser have become turbid, and when a current of COj is passed through them, a precipitate of tibrino- plastin is obtained.] \_{d) Method of Hammarsten. — All the fibrinoplastin in serum is not pre- cipitated either by adding acetic acid or by COj. Hammarsten found, however, that if crystals of magnesium sulphate be added to complete saturation, it precipi- tates the whole of the serum globulin, but does not precipitate serum albumin {Gamgee) ; it seems that in the ox and horse serum globulin is more abundant than serum albumin, while in the dog and rabbit the reverse obtains ; (com- pare § 32).] Schmidt found that 100 c.c. of the serum of the ox blood yielded 0.7 to 0.8 grms. ; horse's serum, 0.3 to 0.56 grms. of dry fibrinoplastin. Fibrinoplastin occurs not only in serum, but also in red blood corpuscles, in the fluids of connective tissue, and in the juices of the cornea. 3. Preparation of Fibrinogen.— This is best prepared from hydrocele fluid, although it may also be obtained from the fluids of serous cavities, e.g., the pleura, pericardium, or peritoneum. It does not exist in blood serum, although it does exist in blood plasma, lymph, and chyle, from which it may be obtained by a stream of COj, after the paraglobulin is precipitated, {a) Dilute hydrocele fluid with ten to fifteen times its volume of water, and pass a stream of COj through it; or {b) carefully neutralize it by adding acetic acid, (c) .'Vdd powdered common salt to saturation to a serous transudation, when a sticky, glutinous (not very abundant) precipitate of fibrinogen is obtained. [Hammarsten and Eichwald find that, although paraglobulin and fibrinogen are soluble in solutions of common salt (containing 5 to 8 per cent, of the salt), a saline solution of 12 to 16 per cent, is required to precipitate the fibrinogen, leaving still in solution paraglobulin, which is not precipitated until the amount of salt exceeds 20 per cent. {Ganigee).'\ Hammarsten found that it may be prepared from blood (of the horse) by first precipitating all the serum globulin or fibrinoplastin with crystals of magnesium sulphate, and subsequent filtration, which removes the corpuscles; a clear, salted plasma is thus obtained. If to the filtrate a saturated solution of common salt be added, a turbid, flaky, impure precipitate of fibrinogen is obtained. This may be dissolved in dilute common salt, and again precipitated bv a saturated solution of NaCl. Properties of the Fibrin Factors. — They are insoluble in pure water, but dissolve in water containing O in solution. Both are soluble in very dilute alka- 52 THE FIBRIN FACTORS. lies, e.g., caustic soda, and are precipitated from this solution by CO,. They are soluble in dilute common salt — like all globulins — but if a certain amount of common salt be added in excess they are precipitated. Very dilute hydrochloric acid dissolves them, but after several hours they become changed into a body resembling syntonin or acid albumin (§ 249, III). Fibrinogen dissolved in a weak solution of common salt (i to 5 per cent.) is reprecipitated on adding water, so that it resembles fibrin. Its solution in com- mon salt coagulates at 52° to 55° C. (Hammarsten, Frediricq). [Frediricq finds that fibrinogen e.xists as such in the plasma ; it coagulates at 56" C, and the plasma thereafter is uncoagulable (^Gamgee).'\ 4. Preparation of the Fibrin Ferment. — Mix blood serum (ox) with twenty times its volume of strong alcohol, and filter off the deposit thereby pro- duced after one month. The deposit on the filter consists of albumin and the ferment ; dry it carefully over sulphuric acid, and reduce to a powder. Triturate one grainme of the powder with 65 c.c. of water for ten minutes, and filter. The ferment is dissolved by the water, and passes through the filter, while the coagu- lated albumin remains behind (Schmidt). In the preparation of fibrinoplastin, the ferment is carried down with it mechanically. The ferment seems to be formed first in fluids outside the body, very probably by the solution of the colorless corpuscles. More ferment is formed in the blood the longer the interval between its being shed and its coagulation. It is destroyed at 70° C. Blood flowing directly from an artery into alcohol contains no ferment. It is also formed in other protoplasmic parts (Rauschenbach), eg., in dead muscle, brain, suprarenal capsule, spermatozoa, testicle [Foa and Pellacani), and in vegetable micro-organisms {e.g., yeast and protozoa] (Gro/imann) [so that it would seem to be a general product of protoplasm]. [As the ferment does not preexist in colorless blood corpuscles, it seems to be formed from some mother substance in them, the blood plasma itself decomposing this sub- stance ( A\7iist/ien/>ai/i).~\ [Gamgee's Method. — Buchanan's " washed blood clot" (p. 50) is digested in an 8 per cent, solution of common salt. The solution so obtained possesses in an intense degree the properties of Schmidt's fibrin ferment.] Coagulation Experiments. — According to A. Schmidt, if the pure solutions of ( I ) fibrinogen, (2) fibrinoplastin, and (3) fibrin ferment be mixed, fibrin is formed. The process goes on best at the temperature of the body ; it is delayed at 0° ; and the ferment is destroyed at the boiling point. The presence of O seems necessary for coagulation. The amount of ferment appears to be immaterial ; large quantities produce more rapid coagulation, but the amount of fibrin formed is not greater. The amount of salts present has a remarkable relation to coagulation. Solutions of the fibrin factors deprived of salts, and redissolved in very dilute caustic soda, when mixed, do not coagulate until sufficient NaCl be added to make a i per cent, solution of this salt (Schmid/). When blood or blood plasma coagulates, all the fibrinogen is used up, so that the serum contains only fibrinoplastin and fibrin ferment ; hence, the addition of hydrocele fluid (which contains fibrinogen) to serum causes coagulation. According to Hammarsten, fibrin is formed when the ferment is added to a solution of fibrinogen. [Foa and Pellacani find that a filtered watery extract of fresh brain, cap.-u!e of the kidneys, testes, and some other tissues, when injected into the blood vessels of a rabbit, causes coagulation of the blood in the pulmonary circulation and the heart, death being caused by the action of a substance identical with the fibrin ferment.] [Hammarsten's Theory of Coagulation. — Ilammersten's researches led him to believe that fibrinoplastin is quite unnecessary for coagulation. According to him, fibrin is formed from one body, \\z., fibrinogen, which is present in plasma when it is acted upon by the fibrin ferment ; the latter, however, has not been obtained in a pure state. Neither he nor Schmidt asserts that this body is of the nature of a ferment, although they use the term for convenience. It is quite certain that fibrin may be formed when no fibrinoplastin is present, coagulation being caused i^y the addi- tion of calcic chloride or casein prepared in a special way. But, whether OHt' or /wo proteids be required, in all cases it is clear that a certain quantity of salts, especially of NaCl, is necessary.] SOURCE OF THE FIBRIN FACTORS. 53 [The main drift of the foregoing evidence points to the presence of one proteid —fibrinogen — in the plasma, which, under certain circumstances, yields fibrin. In shed blood this act seems to be determined by a ferment, perhaps .derived from the disintegration of colorless corpuscles.] [Theory of ^A^ooldridge. — Wooldridge attributes great importance to lecithin. In shed blood the coagulation is brought about by the interaction of the plasma and the colorless corpuscles. If lecithin (which is present in considerable amount in the colorless corpuscles) diffuses into the blood, coagulation takes place. When peptone is injected into the blood of the dog, the blood does not clot; this is due, according to Wooldridge, to the peptone "preventing the interaction of leucocytes and plasma." If, however, the corpuscular elements are removed by the centrifugal machine, the peptone plasma can be made to clot. He also believes that fibrin ferment does not preexist in normal plasma, but that " it may make its appearance in that plasma in the absence of all cellular elements, and must, therefore, come from some constituent or constituents of the plasma itself."] 30. SOURCE OF THE FIBRIN FACTORS.— Al. Schmidt maintains that all the three substances out of which fibrin is said to be formed arise from the breaking up of colorless blood corpuscles. In the blood of man and mam- mals fibrinogen exists dissolved in the circulating blood as a dissolution product of the retrogressive changes of the white corpuscles. Plasma contains dissolved fibrinogen and serum albumin. The circulating blood is very rich in colorless blood corpuscles — much richer, indeed, than was formerly supposed {Schmidt, Landois). As soon as blood is shed from an artery, enormous numbers of the colorless corpuscles are dissolved (Mantcgazza) — according to Ale.x. Schmidt, 71.7 per cent, (horse). First the body of the cell disappears, and then the nucleus {Hlava). The products of their dissolution are dissolved in the plasma, and one of these products is fibrinoplastin. At the same time the fibrin ferment is also produced, so that it would seem not to exist in the intact blood corpuscles. Fibrinoplastin and fibrin ferment are also produced by the " transition forms'" of blood corpuscles, i.e., those forms which are intermediate between the red and the white corpuscles. They seem to break up immediately after blood is shed. The blood plates (p. 33) are also, probably, sources of these substances. In amphibians and birds the red nucleated corpuscles rapidly break up after blood is shed, and yield the substance or substances which form fibrin. Al. Schmidt convinced himself that in these animals fibrinogen is originally, also, a constituent of the blood corpuscles. It is clear, therefore, according to Schmidt's view, that as soon as the blood corpuscles, white or red, are dissolved, the fibrin factors pass into solution, and the formation of fibrin by the interaction of the three substances will ensue. If a large number of leucocytes be introduced into the circulation of an animal, the leucocytes are dissolved in great numbers in the blood, so that death takes place by diffuse coagulation. Should the animal survive the immediate danger of death, the blood, owing to the want of leucocytes, is completely incapable of coagulating {Grotli). [It is worthy of remark to recall the conclusion arrived at by And. Buchanan, viz., that the potential element of his " washed blood clot " resided in the colorless corpuscles, " primary cells or vesicles." He, like Schmidt, found that the buffy coat of horses' blood, which is very rich in white corpuscles, produced coagulation rapidly. Buchanan compared the action of his washed clot to that of rennet in coagulating milk.] Pathological — A I. Schmidt and his pupils, Jakowicki and Birk, have shown that some ferment, probably derived from the dissolution of colorless corpuscles, is found in circulating blood, and that it is more abundant in venous than in arterial blood, while it is most abundant in shed blood. It is specially remarkable that in se/'/ic fever the amount of ferment in blood may increase to such an extent as to permit the occurrence of spontaneous coagulation (thrombosis), which may even pro duce death [Am. A'ohler). In febrile cases generally, the amount of ferment is somewhat more abundant {EJelberg anJ Birk). Af.er the injection of ichor into the blood, an enormous number of colorless corpuscles are dissolved (F. Hoffman). The injection of peptone (Hb) and, to a less degree, of distilled water, is followed by solution of numerous leucocytes. There are changes in the blood, constituting true bload diseases, in which the physiological meta- bolism of the colorless corpuscles is enormously increased, so that the metabolic products accumu- late in the blood \Alex. Sc/imidt). The result of this is spontaneous coagulation within the circu- latory system, and death even may occur; at the least, there is an increase of temperature. After such a condition, the coagulability of such blood is diminished. 54 CHEMICAL COMPOSITION OF THE PLASMA AND SERUM. 31. RELATION OF THE RED BLOOD CORPUSCLES TO THE FORMA- TION OF FIBRIN. — After the investigations of several observers had shown that the red blood corpuscles [bird [Hoppe-Siyler)^, horse (Beynsiiis), frog (A. Schtmdt and Semnu-r] participate in the production of fibrin, Landois observed, in 1874, under the microscope, that the stromala of the red blood corpuscles of the mammals passed into fibrin. If a drop of dcfibrinated rabbit's blood be placed in serum of frog's blood, without mixing them, the red corpuscles can be seen collecting together; their surfaces are sticky, and they can only be sep.irated by a certain pressure on the cover glass, whereby some of the new spherical corpuscles are drawn out into threads. The cor- puscles soon become spherical, and those at the margin allow the hcemoglobin to escape, when the decolorization progresses, from the margin inward, until at last there remains a mass of stroma adhering together. The stroma substance is very sticky, but soon the cell contours disappear, and the stromata adhere and form fine fibres. Thus (according to Landois) the formation of fibrin from reii blood corpuscles can be traced step by step. The red blood corpuscles of man and animals, when dissolved in the serum of other animals, show much the same phenomena. Stroma Fibrin and Plasma Fibrin. — Landois calls fibrin formed direct from strcma, stroma fibrin. Fibrin which is formed in the usual way by the fibrin factors he ca\\% p!as?iia fibrin. The stroma fibrin is closely related chemically to stroma itself; and as yet the two kinds of fibrin have not been sharply distinguished chemically. Substances which rapidly dissolve red corpuscles cause extensive coagulation, e g., injection of bile or bile salts, or lake-colored blood, into arteries (A'autiyn and Francken). After the injection of foreign blood the newly-injected blood often breaks up in the blood vessels of the recipient, while the finer vessels are frequently found plugged with small thrombi (see Transfusion, \ 102). Coagulable Fluids. — With regard to coagulability, fluids containing proteids may be classified thus: — (1) Those that coagulate spontaneously, i. e., blood, lymph, chyle. (2) Those capable of coagulating, e.g., fluids secreted pathologically in serous cavities; for example, hydrocele fluid, which, as usually containing fibrinogen only, does not coagulate sponta- neously, cogaulates on the addition of fibrinoplastin and ferment (or of blood serum in which both occur). (3) Those which do not coagulate, e. g., inWk or seminal fluid, which do not seem to contain fibrinogen. 32. CHEMICAL COMPOSITION OF THE PLASMA AND SERUM. — I. Proteids occur to the amount of 8 to 10 percent, in the plasma. Only 0.2 per cent, of these go to form fibrin. When coagulation has taken place, and after the separation of the fibrin, the plasma becomes converted into serum. The sp. gr. of human serum is 102710 1029. It contains several proteids. [According to Hammarsten, human serum contains 9.2075 per cent, of solids — of these, 3.103 =^ serum globulin, and 4.516 = serum albumin, /. e., in the ratio of i : 1.5 11. The total amount of proteids in blood seems to be much more constant than are the relative proportions of serum albumin and serum globulin (Salvioli').'] [a) Serum Globulin (77/. Weyl^ or Paraglobulin, 2 to 4 per cent., was formerly believed to occur in much smaller amount than it actually does. Ham- marsten found that if serum be diluted with two volumes of water, and crystals of magnesium sulphate be added to saturation, serum globulin is precipitated, but not serum albumin. In the serum of the horse and ox, serum globulin is more abundant than serum albumin, while in the serum of the rabbit and dog the reverse is the case. It is soluble in 10 per cent, solution of common salt, and coagulates at 75° C. [Serum globulin was carefully described by Panum under the name of " serum casein ;" by Al. Schmidt, as " fibrinoplastic substance ;" and by Kiihne, as " paraglobulin."] As already mentioned, it may also be precipitated, in part, by diluting serum with lo to 15 vols, of water, and passing a stream of COj through it (p. 51). If a trace oi acetic acid be added to serum afer the separation of the serum globulin, Kiihne finds that a fine precipitate of what he calls soda albuminate occurs. [It is, however, highly doubtful if an alkali albuminate does occur in the blood. Hammarsten found that CO2 does not precipitate all the serum globulin, so that it is impos- sible that Kiihne's soda albuminate exists as a distinct substance in serum.] According to A. E. P.urckhard, magnesium sulphate not only precipitates serum globulin, but also another proteid substance more closely resembling albumin. During hunger the globulin increases and the albumin diminishes. PROTEIDS OF THE SERUM. 55 (&) Serum Albumin. — Its solutions begin to be turbid at 60° C, and coagu- lation occurs at 73° C, the fluid becoming slightly more alkaline at the same time. The amount is about 3 to 4 per cent. (^Fredericq). If sodium chloride be cautiously added to serum, the coagulating temperature may be lowered to 50° C. It has a rotatory ]}ower of — 56°. It is changed into syntonin or acid albumin by the action of dilute HCl, and by dilute alkalies into alkali albuminate. [Serum Albumin v. Egg Albumin. — Although serum albumin is closely related to egg albu- min, they differ — («) a.s regards their action upon polarized light; (b) the precipitate produced by adding HCl or HNO3 is readily soluble in 4 c.c. of the reagent in the case of serum albumin, while the precipitate in egg albumin is dissolved with very great difficulty ; (c) egg albumin, injected into the veins, is excreted in the urine as a foreign body, while serum albumin is not [Slockvis) ; (d) serum albumin is not coagulated by ether, while egg albumin is, if the solution is not alkaline (? 249)-] [Serum albumin has never been obtained from free salts, even when it is dialysed for a very long time, as was maintained by Aronstein, whose results have not been confirmed by Heynsius, Haas, Huizinga, Salkowski and others] After all the paraglobulin (serum globulin) in serum is precipitated by magnesium sulphate, serum albumin still remains in soluiion. If this solution be heated to 40 or 50° C. a copious precipitate of non-coagulated serum albumin is obtained, which is soluble in water. If the serum albumin be filtered from the fluid, and if the clear fluid be heated to over 60° C, P'redericq found that it becomes turbid from the precipitation of other proteids ; the amount of these other bodies, however, is small. [Proteids of the Serum. — Halliburton has shown, by the method of "frac- tional heat coagulation " (i. c, ascertaining the temperature at which a proteid is coagulated, filtering the fluid and again heating the filtrate to a higher tempera- ture), that from the same fluid perhaps two or more proteids, all with different temperatures of coagulation, may be obtained. Care must be taken to keep the reaction constant. He finds that serum globulin coagulates at 75° C, while serum albumin in reality consists of three proteids, which coagulate at different tempera- tures ; ((?) at 73°, (/') at 77°, and (/) at 84° C] [Precipitation by Salts. — Sulphate of magnesia not only precipitates serum globulin but also fibrinogen (Hallilnirton). The fluid must be shaken for several hours, to get complete saturation. Sodic sulphate, when added to serum deprived of its globulin by MgSOi, precipitates serum albumin, but it produces no precipi- tate with pure serum. In this way serum albumin may be obtained in a pure, un- coagulated and still soluble condition. But Halliburton finds that serum globulin is thrown down by sodic nitrate, acetate, or carbonate ; while all the proteids of the serum are precipitated by potassic acetate or phosphate, and the same result is brought about by adding two salts, e. g., MgSO, and Na^SOj (in this case sodio- magnesic sulphate is formed) ; MgSO, and NaNOs ; MgSO, and KI ; NaCl and Na^SO,. After serum globulin is thrown down by MgSO,, the addition of MgSO, and NajSO, or the double salt, precipitates the serum albumin, which is still soluble in water.] [The plasma of invertebrata fdecapol crustaceans, some gasteropods, cephalopods, etc.) clots like vertebrate blood, and contains fibrinogen, but it is noteworthy that, in addition, there is found in it a substance corresponding to haemoglobin, and called by Fredericq, Haemocyanin. It exists like Hb in two conditions, one reduced and the other oxyhsemocyanin, the former being colorless, the latter blue. In its general characters it resembles Hb, although it contains copper instead of iron, and gives no absorption bands {Halliburton). In the blood of some decapod crustaceans there is a reddish pigment, Tetronerythrin, which is identical with that in the exoskelcton and hypoderm. It belongs to the group of lipochromes, like some of the pigments of the retina. The hcemocyanin is respiratory in function, and it is remarkable that it is contained in the plasma, and not in the formed elements, like the Hb of vertebrates. So that, stated broadly, in these Invertebrates the plasma is both nutritive and respiratory in its functions, while in Vertebrates the red corpuscles chiefly are respiratory and the plasma nutritive (Fredericq).'] II. Fats (o. I to 0.2 per cent.). — Neutral fats (tristearin, tripalmitin, triolein) occur in the blood in the form of small microscopic granules which, after a meal rich in fat (or milk), render the serum quite milky. [The amount of fat in the serum of fasting animals is about 0.2 per cent. ; during digestion 0.4 to 0.6 per cent. ; and in dogs fed on a diet rich in fat it may 56 GASES OF THE BLOOD. be 1.25 per cent. There are also minute traces of fatty acids (succinic). Rohrig showed that soluble soaps, t. e., alkaline salts of the fatty acids, cannot exist in the blood. Cholesterin may be considered along with the fats. It occurs in considerable amount in nerve tissues, and, like fats, is extracted by ether from the dry residue of blood serum. Hoppe-Seyler found 0.019 to °-3i4 per cent, in the serum of the blood of fattened geese. There is no fat in the red blood corpuscles (^Hoppe-Seyler'). Lecithin (its decomposition products, glycerin-phosphoric acid and protagon) occur in serum and also in the blood corpuscles.] III. Traces of Grape Sugar [o. i to o. 15 per cent. {Seegen) more in the hepatic vein (0.23 per cent.)], derived from the liver and muscles, is increased after hemorrhage (§ 175) (Bernard, v. Mering) ; some glycogen (Faiy'), and another reducing fermentative substance also increased by hemorrhage (_/. G. Off). The amount of grape sugar in the blood increases with the absorjition of sugar from the intestine, and this increase is most obvious in the blood of the portal and hepatic veins ; there is also a slight increase in the arterial blood, but there it is rapidly changed. The presence of sugar is ascertained by co.igulating blood by boiling it with sodium sulphate, pressing out the fluid and testing it for sugar with Fehling's solution (CI. Bernard). Pavy coagulates the blood with alcohol. IV. Extractives. — Kreatin, urea (0.016 per cent., increased after food), succinic acid, and uric acid (more abundant in gouty conditions), guanin (?), car- baminic acid ; all occur in very small amounts. V. Sarcolactic Acid and Indican, also in small amount. VI. Salts (.085 to .09 per cent.). — The most abundant salt is sodium chloride (0.5 per cent.), and next to it sodium carbonate. [It is most important to note that the soda salts are far more abundant in the serum than the potassium salts. The ratio may be as high as to : i.] Animal diet increases the amount of salts, vegetable food diminishes it temporarily. Salts in human blood serum (Hoppt-Scykr). Sodic Chloride, 4.92 per 1000 | Sodic Phosph.ate, . . 015 per 1000 " Sulphate, 0.44 " Calcic Phosphate, ■ lo7j " " Carbonate, 0.21 " j Magnesic, / VII. Water about 90 per cent. VIII. A yellow Pigment. Thudichum regards the pigment of the serum as lutein; Maly, as hydrobilirubin ; and MacMunn as choletelin. 33. THE GASES OF THE BLOOD. -Absorption of Gases by Solid Bodies and by Fluids. — Absorption by Solid Bodies. — A considerable attraction exists between the particles of solid porous bodies and gaseous substances, so that gases are attracted and condensed within the pores of solid bodies, i. e., the gases are absorbed. Thus I volume of boxwood charcoal (at 12° C. and ordinary barometric pressure) absorbs 35 volumes CO^, 9.4 vol. O, 7.5 vol. N, 1.75 vol. H. Heat is always formed when gases are absorbed, and the amount of heat evolved bears a relation to the energy with which the absorption takes place. Non-porous bodies are similarly invested by a layer of condensed gases ou their surfaee. By Fluids. — Fluids can also absorb gases. .4 known quantity of Jliiid at different pressures always absorbs the same %'o!unie of gas. Whether the pressure be great or small, the volume of the gas absorbed is equally great (IF. //enry). But according to Boyle and Mariotte's law (1679), when the pressure within the same volume of gas is increased, the volume varies inversely as the pressure. Hence it follows that, with varying pressure, the volume of gas absorbed remains the same, but the quantity of gas [weight, density) is directly proportional to the pressure. If the pressure =0, the weight of the gas absorbed must also = o. As a necessary result of this, we see that (i) fluids can be freed of their absorbed gases in a vacuum under an air pump. Coefficient of Absorption means the T'lj/aOTf of a gas (0° C. ) which is absorbed by a unit of volume of a liquid (at 700 mm. Hg) at a given temperature. The volume of a gas absorbed, and therefo e the coefficient of absorption, is quite independent of the pressure, while the -weight of the gas is proportional to it. Temperature has an important influence on the coefficient of absorption. With a low temperature it is greatest; it diminishes as the temperature increases; and at the boiling point A^^o. Hence, it follows that (2) absorbed gases may be expelled from fluids simply by causitig the fluids to boil. The coefficient of absorption diminishes for different fluids and gases, with increasing temperature, in a special, and by no means uniform, manner, which must be deter- EXTRACTION OF THE BLOOD GASES. 57 mined empirically for each liquid and gas. Thus the coefficient of absorption for CO^ in water diminishes with an increasing temperature, while that for H in water remains unchanged between 0° and 20° C. Diffusion and Absorption of Gases. — Diffusion of Gases. — Gases which do not enter into chemical combinations with each other mix with each other in quite a regular proportion. If, e. g., the necks of two flasks be placed in communicaiion by means of a glass or other tube, and if the lower flask contain CO^, and the upper one H, the gases mix quite independently of their different specific gravities^ both gases forming in each flask a perfectly uniform mixture. The phenomenon is called the diffusion of gases. If a porous 7nembrane be previously inserted between the gases, the exchange of gases still goes on through the membrane. But (as with endosmosis in fluids) the gases pass with unequal rapidity through the pores, so that at the beginning of the experiment a larger amount of gas is found on one side of the membrane than on the other. According to Gra- ham, the rapidity of the diffusion of the gases through the pores is inversely proportional to the square root of their specific gravities. (According to Bunsen, however, this is not quite correct.) Different Gases Forming a Gaseous Mixture do not Exert Pressure upon One Another. — Gases, therefore, pass into a space filled with another gas, as they would pass into a vacuum. If the surface of a fluid containing absorbed gases be placed in contact with a very large quantity of another gas, the absorbed gases difiuse into the latter. Hence, absorbed gases can be removed by (3) passing a stream of another gas through the fluid, or by merely shaking up the fluid with another gas. Partial Pressure. — \f two or more gases are mixed m a closed space over a fluid, as the difierent gases existing in a gaseous mixture exert no pressure upon each other, the several gases are absorbed. The weight of each absorbed is proportional to the pressure under which each gas would be were it the only gas in the space. This pressure is called the partial pressure of a gas { Bunsen). The absorption of gases from their mixlures. therefore, is proportional to the par- tial pressure. The partial pressure of a gas in a space is at the same time the expression for the tension of the gas absorbed by a fluid. The air contains 0.2096 volume of O, and 0.7904 volume N. If i volume of the air be placed under a pressure, P, over water, the partial pressure under which O is absorbed = 0.2096 P ; that for N =0.7904 P. At 0° C, and 760 mm. pressure, i volume of water absorbs 0.02477 volume of air, consisting of 0.00S62 volume O, and 0.01615 volume N. It contains, therefore, 34 per cent. O and 66 per cent. N. Therefore, water absorbs from the air a mi.xture of gases containing a larger percentage of O than the air itself. 34. EXTRACTION OF THE BLOOD GASES.— [The blood to be analyzed must be collected over mercury, so as to avoid its contact with air. This is easily done by means of a special apparatus, consisting of a graduated tube filled witli mercury and communicating with a glass globe also filled with mercury, which can be lowered as the blood flows into the graduated tube.] The extraction of the gases from the blood, and their collection for chemical analysis, are carried out by means of the mercurial pump (C. Ludwig). Fig. 19 shows in a diagrammatic form the arrangement of Plluger's gas pump. It consists of a receptacle for the blood or " blood bulb " (A), a glass globe capable of containing 250 to 300 c.c, connected above and below with tubes, each of which is provided with a stop-cock, a and b ; b is an ordinary stop-cock, while a has through its long axis a perforation which opens at x, and is so arranged that, according to the position of the handle, it leads up into the blood bulb (position .r, n), or downward through the lower tube (position .x' , a'). This blood bulb is first completely emptied of air (by means of a mercurial air pump), and then carefully weighed. One end [x') of it is tied into an artery or a vein of an animal, and when the lower stop cock is placed in the position (.v, a) blood flows into the receptacle. When the necessar)' amount of blood is collected the lower stop-cock is put into the position x', a', and the blood bulb, after being cleaned most carefully, is weighed, to ascertain the weight of the amount of blood col- lected. The second pirt of the apparatus consists of the froth chamber, B, leading upward and downward into tubes, each of which is provided with an ordinary stop-cock, c and d. The froth chamber, as its name denotes, is to catch the froth which is formed during the energetic evolution of the gases from the blood. The lower aperture of the froth chamber is connected by means of a well-ground tube with the blood bulb, while above it communicates with the third part of the apparatus, the drying chamber, G. This consists of a |J-shaped tube, provided below with a small glass bulb, which is half filled with sulphuric acid, while in its limbs are placed pieces of pumice stone also moistened with sulphuric acid- As the blood gases pass through this apparatus (which may be shut off by the stopcocks, e and/"), they are freed from their watery vapor by the sulphuric acid, so that they pass quite dry through the stop-cock, f. The short, well-ground tube, D, is fixed toy, and to the former is attached t\\e smaW barometric tube or manometer, y, wh\ch indicates the extent of the vacuum. From D we pass to the pump proper. This consists of two lar^e glass bulbs, which are continued above and below into open tubes ; the lower tubes, Z and -c, being united by a caoutchouc tube, G. Both the bulbs and caoutchouc tube contain mercun- — the bulbs being about half full, and F being larger than E. The bulb E is fixed ; but F can be raised or lowered by means of a pulley with a rack and pinion motion. If F be raised, E is filled ; if F be lowered, E is emptied. The upper end of E divides into two tubes, ^^ and /i, of which g is 58 EXTRACTION OF THE BLOOD GASES. united to D. The ascending tube, h (gas-delivery tube), is very narrow, and is bent so that its free end dips into a vessel containing mercury, v (a pneumatic trough), and the opening is placed exactly under the tube for collecting the gases, the eudiometer, J, which is also tilled with mercury. Where^and H unite, there is a two-way stopcock, which in one position, H, places E in commu- nication with A, B, G, D, the chambers to be exhausted, and in the position K, shuts off A, B, G, D, and places the bulb, E, in communication with the gas-delivery tube, //, and the eudiometer, J. B, G, D are completely emptied of air, thus ; The stop-cock is placed in the position, K; raise F until drops of mercury issue from the fine tube, / (not yet placed under J) ; place the stop-cock Fig. 19. Scheme of Pfliiser's Gas Pump. A, blood bulb; a, stop-cock, with a longitudinal perforation opening upward ; a', the same opening downward ; b and c, stop-cocks: B, froth chamber; d,e,/, stop-cocks; G, drying cham- bers, containing sulphuric acid and pumice stone : D, tube, v " " in the position H, lower F; stop-cock in position, K and so on until the barometer, y, indicates a complete vacuum. J is now placed over i. Open the cocks f and i, so that the blood bulb. A, communicates with the rest of the apparatus, and the blood gases froth up in B, and after being dried in G pass toward E. Lower F, and they pass into E; stop-cock in position K, raise F, and the gases are collected in J, under mercury. The repeated lowering and raising of F with the corresponding position of the stop-cocks ultimately drives all the gases into J. The removal of the gases is greatly facilitated by placing the blood bulb, A, in a vessel containing water at 60° C. THE BLOOD GASES. 59 It is well to remove the gases from the blood immediately after it is collected from a bloodvessel, because the O undergoes a diminution if the blood be kept. Of course, in making several analyses it is difficult to do this, and the best plan to pursue in that case is to keep the receptacles containing the blood on ice. Mayow (1670) observed that gases were given off from blood in vacuo. MSgnus (1837) investigated the percentage composition of the blood gases. The more important recent inves- tigations have been made by Loihar Meyer (1857), and by the pupils of C. Ludwig and E. Pfliiger. 35. QUANTITATIVE ESTIMATION OF THE BLOOD GASES. — The gases obtained from blood consist of O, COj, and N. Pfliiger obtained (at 0° C. and i metre Hg pressure), 47.3 volumes per cent, consisting of— O 16.9 per cent. ; COj 29 per cent. ; N 1.4 per cent. As is shown in Fig. 19, the gases are obtained in an eudiometer, i. e., in a nar- row tube, J, closed at one end, and with a very exact scale marked on it, and having two fine platinum wires melted into its upper end, with their free ends projecting into the tube (/ and «). (i) Estimation of the CO2. — A small ball of fused caustic po/as/i. fi.\ed on a platinum wire, is introduced into the mixture of gases through the lower end of the eudiometer, under cover of the mercury. The surface of the potash ball is moistened before it is introduced. The CO, unites with the potash to form potassium carbonate. After it has been in for a considerable time (24 hours), it is withdrawn in a similar manner. The diminution in volume indicates the amount of COj absorbed. (2) Estimation of the O. — [a] Just as in estimating the CO2, a ball of phosphorus on a platinum wire is introduced into the eudiometer (Bertholef); it absorbs the O and forms phosphoric acid. Another plan is to employ a small papier-mache ball saturated with pyroi^allic acid in caustic potash, which rapidly absorbs O {Liebig). After the ball is removed, the diminution in volume indicates the quantity of O. (b) The O is most easily and accurately estimated by explodini; it in the eudiometer ( Volta and Bunsen). Introduce a sufficient quantitv of H into the eudiometer, and accurately ascertain its volume; an electrical spark is now passed between the wires, / and «, through the mixture of gases; the O and H unite to form water, which causes a diminution in the volume of the gases in the eudiometer, of which J-^ is due to the O used to form water (HjO). (<■) Estimation of the N.— When the CO, and O are estimated by the above method, the remainder is pure N. 36. THE BLOOD GASES.— [In hitman blood the average is estimated to be, at 0° C and i metre pressure, C CO2 N Arterial blood 16 30 i to 2 per cent. Venous blood, 6 to 10 35 1 to 2 " or, calculated at 0° C. and 760 mrn. pressure. Arterial blood 20 39 1.4 per cent. Venous blood, 8 to 12 46 1.4 " ] I. Oxygen exists in arterial blood (dog), on an average, to the extent of 1 7 volumes per cent, (at 0° C. and i metre Hg pressure) {Pfliiger). According to Pfliiger, arterial blood (dog) is saturated to Jg- with O, while, according to Hiifner, it is saturated to the extent of \^. In venous blood the quantity varies very greatly ; in the blood of a passive muscle 6 volumes per cent, have been found ; while in the blood after asphyxia it is absent, or occurs only in traces. It is certainly more abundant in the comparatively red blood of active glands (salivary glands, kidney), than in ordinary dark venous blood. [Modifying Conditions. — The amount of O obtainable from the blood depends upon the organ from which the blood comes, or whether the organ be active or at rest. Thus the O present in the Carotid artery is 21 per cent. | Renal vein (kidney active), 17 per cent. Renal artery, 19 " | Renal vein (kidney at rest), 6 " Bert finds that increase of the atmospheric pressure from I to to atmospheres increases the amount of O in arterial blood from 20 to over 24 per cent., and that of N from i.S to over 9 per cent., while the CO, is but slightly affected.] The O in Blood occurs — {a') simply absorbed xn the plasma. This is only a minimal amount, and does not exceed what distilled water at the temperature of 60 THE BLOOD GASES AND OZONE. the body would take up at the partial pressure of the O in the air of the lungs {Lot/iar Meyer). According to Fernet, serum takes up slightly more O than cor- responds to the pressure, and this is perhaps due to the trace of hremoglobin con- tained in the plasma or the serum, and which is derived from the solution of red corpuscles. (h) Almost the total O of the blood is chemically united, and therefore not subject to the law of absorption. It is loosely united to the hasmoglobin of the red corpuscles, with which it forms oxyhcemoglobin (§ 15). The absorption of this quantity of O is completely independent of pressure ; hence, animals con- fined in a closed space until they are nearly asphyxiated, can use up almost all the O from (he surrounding atmosphere. The fact of the union being independent of pressure is proved by the following : The blood only gives off copiously its chemically united O, when the atmospheric pres- sure is lowered to 20 millimetres, Hg. ( Worm Miiller) ; and, conversely, blood only takes up a little more O when the pressure is increased to 6 atmospheres (Bert). Physical Methods of obtaining O from Blood.^Notwithstanding this chemical union between the Hb and O, however, the total O of the blood can be expelled from its state of combination by those means which set free absorbed gases — {a) by introducing blood into a Torricellian vacuum ; (/') by boiling ; {c) by the conduction of other gases [H, N, CO, or NO] through the blood, because the chemical union of the oxyhemoglobin is so loose that it is decomposed even by these physical means. Chemical Reagents. — Among chemical reagents the following reducing substances — ammonium sulphide, sulphuretted hydrogen, alkaline solutions of sub-salts, iron filings, etc., rob blood of its O (p. 40). With regard to the taking up of O, the total quantity of blood behaves exactly like a solution of haemoglobin free from O {Preyer). The absorption of O is more rapid in blood than in a solution of Hb. Relation to Fe. — The amount of iron in the blood (0.55 in 1000 parts) stands in direct relation to the amount of Hb; this to the quantity of blood corpuscles; and this, in turn, to the specific gravity of the blood. The amount of O in the blood, therefore, is nearly proportional to the specific gravity of the blood, and it is also in proportion to the amount of iron in the blood. Picard affirms that 2.36 grammes of iron in the blood can fix chemically i grm. O ; while, according to Hoppe- Seyler, the proportion is i atom iron to 2 atoms O. During morphia narcosis the amount of O in the blood is diminished (E-vald) ; after hemorrhage the arterial blood is saturated with O (/. G. Ott). Disappearance of O. — Even immediately after blood is shed, there is a slight disapp 'arance of O, as a physiological index of respiration of the tissues within the living blood itself (\ 132). When blood is kept long outside of tile blood vessels, the quantity of O gradually diminislies, and if it be kept for a length of tim? at a high temperature it may disappear altogether. This depends upon decomposition occurring within the blood. By this decomposition in the blood (cadaveric phenomenon), reducing substances are formed which consume the O. All kinds of blood, however, do not act with equal energy in consuming O, e. g., venous blood from active muscles acts most energetically, while that from the hepatic vein has very little effect. CO2 appears in the blood in place of the O, and the color darkens. The amount of COj produced is sometimes greater than that of the O consumed. If blood (or a solution of oxyhsemoglobin) be acte 1 upon by acids (e. g., tartaric acid) until it is strongly acid. O may be pumped out in considerably less amount, while the formation of CO2 is not increased. We must, therefore, assume that, during the decomposition of the Hb caused by the acids (5 18), a decomposition product becomes more highly oxidized by the intense chemical union of the O at the moment of its origin [Lothar Meyer ^ Zuntz, Strasshurg). The same phenomenon occurs when oxyhemoglobin is decomposed by boiling. 37. IS OZONE (O3) PRESENT IN BLOOD?— On accoimt of the numerous and energetic oxidations which occur in connection with the blood, the question has often been raised as to whether the O of the blood exists in the form of active O (O,), or ozone. Ozone, however, is contained neither in the blood itself {Sclwiibein) nor in the blood gases obtained from it. Nevertheless, the red corpuscles (and Hb) have a distinct relation to ozone. (i) Tests for Ozone. — Hremoglobin acts as a conveyer of ozone, i.e., it is able to remove the active O of other bodies and to convey or transfer it at once to other easily oxidizable substances. CARBON DIOXIDE AND NITROGEN IN BLOOD. 61 (a) Turpentine which has been exposed to the air for a long time always contains ozone. The tests for the latter are starch and potassium iodide, the ozone decomposing the iodide, when the iodine strikes a lAae with the starch. {6) Freshly-prepared tincture of guaiacum is also rendered blue by ozone. If some tincture of guaiacum be added to turpentine there is no reaction, but on adding a drop of blood a deep blue color is immediately produced, /. f., blood takes the ozone ffom the tur- pentine and conveys it at once to the dissolved guaiacum, which becomes blue [Schonhein, His). It is immaterial whether the Hb contains O or not. (2) It has been asserted also that haemoglobin acts as an ozone producer, i.e., that it can convert the ordinary O of the air into ozone. Hence the reason why red blood corpuscles alone render guaiacum blue. This reaction succeeds best when the guaiacum solution is allowed to dry on blotting paper, and a few drops of blood (diluted 5 to 10 times) are poured on it. That the Hb forms ozone from the surrounding O, is shown by the experiment in which even red blood cor- puscles containing carbonic oxide were found to cause the blue color {^Kilhne and Schoh). According to Pfluger, however, these reactions only occur from decomposition of the Hb, and as a result of this view the blood corpuscles cannot be regarded as producers of ozone. Sulphuretted hydrogen is decomposed by blood (as by ozone itself) into sulphur and water. Hydiic peroxide is decomposed by blood into O and water [but this reaction is prevented by the addition of a small amount of hydrocyanic acid (Schonbein)]. Crystallized Hb does not do this, and HjOj may be cautiously injected into the bloodvessels of animals. This would show that tindiange'd Hb does not produce ozone. Various Forms of Oxygen. — There are three forms of oxygen: (i) The ordinary oxygen (O.2) in tlie air. (2) Active or nascent oxygen (O), which never can occur in the free state, but the moment it is formed acts as a powerful oxidizing agent and produces chemical compounds. It converts w.iter into hydric peroxide — the N of the air into nitrous and nitric acids, and even CO into CO2, which ozone does not. It certainly plays an important part in the organism. (3) Ozone (O3 ), which is formed by the decomposition of several molecules of ordinary oxygen (O2 ) into two atoms of O, and the appropriation of each of these atoms by a molecule of undecomposed oxygen. It is oxygen condensed to | of its volume. 38. CARBON DIOXIDE AND NITROGEN IN BLOOD.— H. Carbon Dioxide. — In arterial blood there are about 30 volumes per cent, of COj (at 0° C. and i metre pressure — Setschenow); but in venous blood the amount is very variable, e.g., in the venous blood of passive muscles there are 35 volumes per cent. {Sezei/ctnu), while in the blood of asphyxia there may be 52.6 volumes per cent. The amount of COj in the lymph of asphyxia is less than that in the blood (Buchner, Gaiile). The CO2 in the entire mass of the blood may be extracted froin it or completely pumped out, but during the process of evacuation, or removal of the gas, a new projierty of the red blood corpuscles is produced, whereby they assume the func- tion of an acid, and thus aid in the c/ifw/Va/ expulsion of the COj. This acid- like property of the red corpuscles occurs especially in the presence of O and heat. (A) The COo in the Plasma.— 77;(; largest portion of the CO^ belongs to the plasma (or serum) and it appears all to be in a state of chemical combination. Serum takes up CO, quite independently of pressure, hence it cannot be merely absorbed. A certain part of the CO.j can be removed from the serum (plasma) by the Torricellian vacuum, while another part is obtained only after the addition of an acid. [The latter is called the " fixed" CO.^, while the former is known as the " loose " CO.j.] The union of CO.^ in the serum may take place in the following ways : — (i) CO2 is united to the soda of the plasma in the form of " sodic carbonate." This portion of the COi can only be displaced from its combination by the addi- tion of an acid. (In depriving blood of its gases the red corpuscles play the role of an acid.) (2) A portion of the CO2 is loosely united to sodic carbonate in the form of sodic bicarbonate ; the carbonate takes up i equivalent of CO2 ; NajCOj -f- COj -f- 62 ARTERIAL AND VENOUS BLOOD. HjO = 2NaHC03. This CO, may be pumped out, as in the process the bi- carbonate splits up again into the neutral carbonate and COj. Preyer has objected to this view on the ground that blood is alkaline in reaction, while all solutions that contain COj in a state of absorption, or loose chemical combination, are always acid. PflUger and Zuntz showed that blood, after being completely saturated with CO^ still remains alkaline. As the bicarbonate only gives up its COj very slowly in vacuo, while blood gives off its CO^ very energetically, perhaps the soda, united with an albuminous body, combines with the CO2 and forms a complex compound, from which the COo is rapidly given otf in vaiuo. (3) A minimal portion of the COj may be chemically united in the plasma with neutral sodic phosphate {Fernet). One equivalent of this salt can fi.K one equiva- lent of CO.,, so acid sodium phosphate and acid sodium carbonate are formed, Na^HPO, + CO, + H2O = NaH.PO, + NaH.CO, {Hermann). When the gases are removed the COj escapes, and neutral sodic phosphate remains. It is probable, however, that almost all the sadic phosphate found in the blood-ash arises from the burning uf lecithin ; we have, therefore, to consider only the very small amount of this salt which occurs in the plasma (Hoppe-Seyler and Sertoli). (B) The COo in the Blood Corpuscles. — The red corpuscles contain COj in a loose chemical combination; lor (i) a volume of blooa can fix nearly as much CO^ as an equal volume of serum lyLudwig, Al. Schmidt); and (2) with increasing pressure, the absorption of COj by blood takes place in a different ratio from what occurs with serum (PflUger, Zuntz). The red corpuscles may fix more COj than their own volume, and the union of the CO, seems to depend upon the Hb; for Setschenow found that when Hb was acted on by CO..,, its power of fixing the latter was increased, which is, perhaps, due to the formation of some substance (paraglobuiin) more suited for fixing CO..,. The colorless corpuscles also fix CO.j after the manner of the serum constituents, and to the extent of \ to jV of the absorbing power of serum (Setschenow). III. Nitrogen exists in the blood to the extent of 1.4 to 1.6 vol. per cent., and it appears to be simply absorbed. After the use of I, Hg, sodic oxalate and nitrate, there is a diminution of CO2 in arterial blood (Feitctberg), and also in fever [Geppert, A/iniowski). [In the last case it is, perhaps, due to the diminished alkalinity, and this is, in part, owing to the acid products formed by the decomposition of the tissues.] It is still doubtful whether a small part of the N exists chemically united in the red corpuscles. Outside the body, when blood is heated, and when there is a free supply of O and warmth, it gives off very minute quantities of ammonia, which are, perhaps, derived from the decomposition of some salt of ammonia as yet unknown (A'ii/ine and ^tratich). 39. ARTERIAL AND VENOUS BLOOD.— Arterial blood contains in solution all those substances which are necessary lor the nutrition of the tissues, those which are employed in secretion, and it also contains a rich supply of O. Venous blood must contain less of all these, but, in addition, it holds the used-up or effete substances derived from the tissues, and the products of their retrogressive metabolism are more numerous ; there is in venous blood a larger amount of CO,, It is evident, also, that the blood of certain veins must have special characters. e.g., that of the portal and hepatic veins. [.According to C. .Schmidt, the blood of the portal vein contains more water, plasma, salts and fats, but less extractives and corpuscles, than the blood of the hepatic vein; while ^when an animal is not digesting) sugar is absent, or, at least, only in traces in the portal vein, and in considerable amount in the hepatic vein (^ 175).] The following are the most important points of difference between arterial blood and venous blood : — Arterial Blood contains — more O, less COj, more water, more fibrin. more extractives, more salts, more sugar, fewer blood corpuscles, less urea. It is bright red, and not dichroic. -As a rule, it is 1° C. warmer. ABNORMAL CONDITIONS OF THE BLOOD. 63 The bright-red color of arterial blood depends on the presence of oxyhaemo- globin, while the dark color of venous blood is due to its smaller proportion of oxyhemoglobin and the quantity of reduced hjemoglobin which it contains. The dark change of color is not to be attributed to the larger quantity of CCX in venous blood {^M a re hand ) ; for if equal qualities of O be added to two portions of blood, and if CO, be added to one of them, the color is not changed (^FJluger). 40. QUANTITY OF BLOOD. — In the adult, the quantity of blood is equal to j^j of the body weight (Bischoff) ; in newly -born children -^ ( IVelcker). According to Schiicking, the amount of blood in a newly-born child depends, to some extent, upon the time at which the umbihcal cord is ligatured. The amount = y'j of the body weight when the cord is tied at once, while if it is tied somewhat later, it may be \. Immediate ligature of the cord may, therefore, deprive a newly. born child of a hundred grammes of blood. Further, the number of corpuscles is less in a child after immediate ligature of the umbilical cord than when it is tied somewhat later (He/o/). Various methods are adopted to ascertain the amount of blood, but perhaps that of Welcker is the best. The methods of Valentin (1838) and Ed. Weber (1850) are not now used, as the results obtained are not sufficiently accurate. Method of Welcker (1854). — Begin by taking the weight of the animal to be experimented on; place a cannula in the carotid, and allow the blood to run into a flask previously weighed, and in which small pebbles (or Hg) have been placed, in order to defibrlnate the blood by shaking. Take a part of this defiiirinated blood, and make it cherry-red in color by passing through it a stream of CO (because ordinary blood varies in color according to the amount of O contained in it — Gscheidlen, Heidenhain). Tie a H" -shaped canula in the two cut ends of the carotid, and allow a 0.6 per cent, solution of common salt to flow into the vessel from a pressure bottle; collect the colored fluid issuing from the jugular veins and inferior vena cava until the fluid is quite clear. The entire body is then chopped up (with the exception of the contents of the stomach and intes- tines, which are weighed, and their weight deducted from the body w-eight), and extracted with water, and after twenty-four hours the fluid is exp.essed. This water, as well as the washings with salt solution, are collected and weighed, and part of the mixture is saturated with CO. A sample of this dilute blood is placed in a vessel with parallel sides (i cm. apart), opposite the light (the so-called hix'matinometer), and in a second vessel of the same dimensions a sample of the undi- luted CO blood is diluted with water from a burette until both fluids give the same intensity of color. From the quantity of water required to dilute the blood to the lint of the washings of the blood vessels, the quantity of blood in the washings is calculated. (On chopping up the muscles alone, we obtain the amount of Hb present in them, which is not taken into calculation —A7;/;«,?.) Quantity of Blood in Various Animals. — The quantity of blood in the mouse = yV to -^^ ; guinea pig y^^ (J- to jL) ; rabbit = ^iy (-j^ to ^V) ; dog = tV (tV to tV ; '^at == jf 5 ; birds = ^V to yV i frog = tV to ^V i ^shes = J^ to ^ of the body weight (^without the contents of the stomach and intestines). Tne specific gravity of the blood ought always to be taken when estimating the amount of blood. The amount of blood is diminished during inanition ; fat persons have relatively less blood ; after hemorrhage the loss is at first replaced by a watery fluid, while the blood corpuscles are gradually regenerated. Blood in Organs. — The estimation of the quantity of blood in different organs is done by suddenly ligaturing their blood vessels intra vttam. A watery extract of the chopped-up organ is prepared, and the quantity of blood estimated as described above. [Roughly it may be said that the lungs, heart, large arteries, and veins contain j^ ; the muscles of the skeleton, y^ ; the liver, }( ; and other organs, }( {/ian/<:e).~\ 41. VARIATIONS FROM THE NORMAL CONDITION OF THE BLOOD.— (A) Pojyaemia. — (I) An increase m the entire mass of the h\ood, itiiiform/v in all organs, caw- stitutes/o/i'tt-w^ij (or //t'Mor«), and in over-nourished individuals it may approach a pathological condition. A bluish-red color of the skin, swollen veins, large arteries, hard, full pulse, injection of the capillaries and smaller vessels of the visible mucous membranes are signs of this state, and when accompanied by congestion of the brain, give rise to vertigo and congestion of the lungs, as shown by breathlessness. After major amputations with little loss of blood a relative increase of blood has been found (?) {plethora apocoptica). [In this case, the plethora is transient.] Transfusion. — Polya;mia may be produced artificially by the injection of blood of the same species. If the normal quantity of blood be increased 83 per cent, no abnormal condition occurs. 64 ABNORMAL CONDITIONS OF THE BLOOD. because the blood pressure is not permanently raised. The excess of blood is accommodated in the greatly distended capillaries, which may be stretched beyond their normal elasticity ( IVorm Mailer). If it be increased to 150 per cent, there are variations in the blood pressure, life is endangered, and there may be sudden rupture of blood vessels ( Worm Miitler). Fate of Transfused Blood. — After the transfusion of blood the formation of lymph is greatly increased ; but in one or two days the serum is used up, the water is excreted chiefly by the urine, and the albumin is partly changed into urea (Zhwi/ok). Hence, the blood at this time appears to be relatively richer in blood corpuscles [Pamim, Lesser, ll'orm Afii/Zer). The red corpuscles break up much more slowly, and the products thereof are partly excreted as urea and partly (but not constantly) as bile pigments. Even after a month an increase of colored blood corpuscles has been observed ( Tschirjew). That the blood corpuscles are broken up slmoly in the economy is proved by the fact that the amount of urea is much larger when the same quantity of blood is swallowed by the animal than when an equal amount is transfused (Tsehirjeiu, LanJois). In the latter case there is a moderate increase of the urea, lasting for days, a proof of the slow decomposi- tion of the red corpuscles. Pronounced over-filling of the vessels causes loss of appetite and a ten- dency to hemorrhage of the mucous membranes. (2) Polyaemia serosa is that condition in which the amount of serum, i. e., the amount of water in the blood, is increased. This may be produced artilicially by the transfusion of blood serum from the same species. The water is soon given off in the urine, and the albumin is decom- po.sed into urea, without, however, passing into the urine. An animal forms more urea in a short time from a quantity of transfused serum than from the same quantity of blood, a proof that the blood corpuscles remain longer undecomposed than the serum [/^orster, Landois), If serum from another species of animal be used {e. g., dog's serum transfused into a rabbit), the blood corpuscles of the recipient are dissolved; hajmoglobinuna is produced {Fonjick); and if there be general disso- lution of the corpuscles, death may occur [Landois). Polyaemia aquosa is a simple increase of the water of the blood, and occurs temporarily after copious drinking, but increased diuresis soon restores the normal condition. Diseases of the kid- neys which destroy their secreting parenchyma produce this condition, and often general dropsy, owing to the passage of water into the tissues. Ligature of the ureter produces a watery condition of the blood. (3) Plethora polycythaemica, Hyperglobulie. — An increase of the red corpuscles has been assumed to occur when customary regular hemorrnagesare interrupted, e. g., menstruation, bleeding from the nose, etc. ; but the increase of corpuscles has not been dehnitely proved. There is a proved case of temporary polycythemia, viz., when similar blood is transfused, a part of the fluid being used up, while the corpuscles remain unchanged for a considerable time. There is a remarkable increase in the number ol blood corpuscles (to 8 82 millions per cubic millimeter, p. 18) in certain severe cardiac affections where there is great congestion, and much water transudes through the vessels. In cases of hemiplegia, for the same reason, the number of corpuscles is greater on the paralyzed congested .side (/"fH;!;/;//). After diarrhcea, which diminishes the water of the blood, there is also an increase {Brouardel). There is a temporary increase in the h.'ematoblasts as a reparative process after severe hemorrhage (J 7), or alter acute diseases. In cachectic conditions this increase con- tinues, owing to tne diminisned non-conversion of these corpuscles into red corpuscles. In the last stages ol cachexia the number diminishes more and more until the formation of hnematoblasts ceases (Nciyeiu). (4) Plethora hyperalbuminosa is a term applied to the increase of albumins in the plasma, such as occurs after taking a large amount of food. A similar condition is produced by transfusing the serum of the same species, whereby, at the same time, the urea is increased. Injection of egg albumin produces albuminuria (Stoiz'is Le/tmann). [The subcutaneous injection of human blood has been practiced with good results in anemia (t^. Ziemssen). When defibrinated human blood is injected sub- cutaneously, while its passage into the circulation is aided by massage, it causes neither pam nor inflammation, but the blood of anima/s, and a solution of hsemo- globin, always induce abscess {Bciiczur). Blood is also rapidly absorbed when injected in small amount into the respiratory passages.] Mellitaemia — The sugar in the blood is panly given off by the urine, and in " diabetes mellitus " 1 kilo. (2.2 It)) may be given off daily, when the ciuanlity of urine may rise to 25 kilos. To replace this loss a large amount of food and drink is required, whereby the urea may be increased threefold. The increased production of sugar causes an increased decomposition of albuminous tissues; hence, the urea is always increased, even though the supply of albumin be insufficient. The patient loses flesh ; all the glands, and even the testicles, atrophy or degenerate (pulmonary phthisis is common) ; the skin and bones become thinner ; the nervous system holds out longest. The teeth become carious on account of the acid saliva, the crystalline lens becomes turbid from the amount of sugar in the fluid of the eye which extracts water from the lens (A'unde, JLeitliel), and wounds heal badly because of the abnormal condition of the blood. Absence of all carbohydrates in the food causes a diminution of the sugar in the blood, but does not cause it to ABNORMAL CONDITION'S OF THE BLOOD. 65 disappear entirely. [The sugar in the blood is also increased after the inhalation of chloroform or amyl nitrite, and after tlie use of curara, nitrobenzole and chloral (^ 175)-] An excessive amount of inosite has been found in the blood and urine (^ 267), constituting melli- turia inosita ( I'o/il). . Lipsemia, or an increase of the Fat in the Blood, occurs after every meal rich in fat, so that the serum may become turbid like milk. Pathologically, this occurs in a high degree in drunk- ards and in corpulent individuals. When there is great decomposition of albumin in the body (and, therefore, in very severe diseases), the fat in the blood increases, and this also takes place after a liberal supply of easily decomposable carbohydrates and much fat. The Salts remain very persistently in the blood. The withdrawal of common salt produces albuminuria, and, if all salts be withheld, paralytic phenomena occur (Forster). Over feeding with salted food, such as salt meat, has caused death through fatty degeneration of the tissues, especially of the glands. Withdrawal of lime and phosphoric acid produces atrophy and softening of the bones. In infectious diseases and dropsies the salts of the blood are often increased, and dimin- ished in inHammatiun and cholera. [NaCl is absent from the urine in certain stages of pneumonia, and it is a good sign when the chlorides begin to return to the urine.] [In Scurvy the corpus, cular elements are diminished in amount, but we have not precise information as to the salts, although this disease is prevented, in persons forced to live upon preserved and salted food, by a liberal use of the salts — especially potash salts — of the organic acids, as contained in lime juice. In Gout, the blood, during an acute attack, and also in chronic gout, contains an e.\cess of uric acid [Garrod ).] The amount of fibrin is increased [hyperinosis] in inflammations of the lung and pleura [croupous pneumonia, erysipelas], hence, such blood forms a criista phlogistica (§ 27). In other diseases where decomposition of the blood corpuscles occurs, the fibrin is increased, perhaps because the dissolved red corpuscles yield material for the formation of fibrin. .After repeated hemorrhages, Sigm. Mayer found an increase of fibrin. Blood rich in fibrin is said to coagulate more s/o-u/v than when less fibrin is present — still there are many exceptions. For the abnormal changes of the red and white blood corpuscles, see ^ 10 ; for Haemophilia, i 28. (H) Diminution of the Quantity of Blood, or its Individual Constituents. — (i) Oligse- mia vera. Anaemia, or diminution of the quantity of blood, occurs whenever there is hemor- rhage. Life is endangered in newly-born children when they lose a few ounces of blood; in children a year old, on losing half a pound ; and in adults, when one-half of the total blood is lost. Women bear loss of blood much better than men. The periodical formation of blood after each menstruation seems to enable blood to be renewed more rapidly in their case. Stout persons, old people, and children do not bear the loss of blood well. The more rapidly blood is lost, the more dangerous it is. [A moderate loss of blood is soon made up, but the fluid part is more quickly restored than are the corpuscles.] Symptoms of Loss of Blood. — Great loss of blood is accompanied by general paleness and coldness of the cutaneous surface, increased oppression, twitching of the eyeballs, noises in the ears and vertigo, loss of voice, great breathlessness, stoppage of secretions, coma ; dilatation of ihe pupils, involuntary evacuations of urine and fceces, and lastly, general convulsions, are sure signs of i/ea^/i by hemorrhage. In the gravest cases restitution is only possible by means of transfusion. Animals can bear the loss of one-fourth of their entire blood without the blood pressure in the arteries permanently failing, because the blood vessels contract and accommodate themselves to the smaller quantity of blood (in consequence of the stimulation of the vasomotor centre in the medulla). The I0.SS of one-third of the total blood diminishes the blood pressure considerably (one-fourth in the carotid of the dog). If the hemorrhage is not such as to cause death, the fluid part of the blood and the dissolved salts are restored by absorption from the tissues, the blood pressure gradu- ally rises, and then the albumin is restored, though a longer time is required for the formation of red corpuscles. At first, therefore, the blood is abnormally rich in water (Jtydrtrmia) and at last abnormally poor in corpuscles lyoligocythizmip, hypoglolnilie'). With the increased lymph stream which pours into the blood, the colorless corpuscles are considerably increased above normal, and during the period of restitution fewer red corpuscles seem to be used up (e.g., for bile). After moderate bleeding from an artery in animals, Buntzen observed that the volume of the blood was restored in several hours; after more severe hemorrhage in 24 to 48 hours. The red blood corpuscles, after a lo^s of blood equal to i.i to 4.4 per cent, of the body weight, are restored only after 7 to 34 days. The regeneration begins after 24 hours. During the period of regenera- tion the number of the smallest blood corpuscles (heematoblasts) is increased. Even in man the duration of the period of regeneration depends upon the amount of blood lost [Lyon) The amount of hiiemoglobin is diminished nearly in propoition to the amount of the hemorrhage [Bizzo- zero and Sa/vio/i). Metabolism in Anaemia. — The condition of the metabolism within the bodies of ana:mic per- sons is important. The decomposition of proteids is increased (the same is the case in hunger), hence the excretion of urea is increased [Bauer, Jiirgensen). The decomposition of fats, on the contrary, is diminished, which stands in relation with the diminution of COj given oft". Ana;mic 5 66 ORGANISMS IN THE BLOOD. and chlorotic persons put on fat easily. The fattening of cattle is aided by occasional bleedings and by intercurrent periods of hunger (Aristotle). (2) An excessive thickening of the blood through loss of water is called Oligsemia sicca. This occurs in man after copious watery evacuations, as in cholera, so that the thick, tarry blood stagnates in the vessels. Perhaps a similar condition — though to a less degree — may exist after very copious perspiration. (3) If the proteids in blood be abnormally diminished, the condition is called Oligaemia hyp- albnminosa ; they may be diminished about one-half. They are usually replaced by an excess of water in the blood [so that the blood is watery, constituting Hydraemia]. Loss of albumin from the blood is caused directly by albuminuria (25 grammes of albumin may be given off by the urine daily), persistent suppuration, great loss of milk, extensive cutaneous ulceration, albuminous diarrhoia (dysentery). Frequent and copious hemorrhages, however, by increasing the absorption of water into the vessels, at first produce oligemia hypalbuminosa. [Organisms in the Blood. — The presence of animal and vegetable parasites in the blood gives rise to certain diseases. Some of these, and especially the vegetable organisms, have the power of Fig. 20. Fig. 21. -y fr^^ /// y\\- A, diagram of rium; C, ■ sple B, bade- Bacillus antl brios: D, bacilli; E, blood (ox (Coliii). multiplying in the blood. The vegetable forms belonging to the Schizomycetes are frequently spoken of collecting under the title bacteria. They are classified by Cohn into L Spha'robacteria IL Microbacteria IlL Desmobacteria exhibit movements. IV. Spirobacteria These forms are shown in Fig. 20. The micrococci (.\) are examples of I; while bacterium termo (B) is an example of II. In III the members are short cylindrical rods, straight (Bacillus, D) or wavy (Vibrio, C). Splenic fever of cattle is due to the presence of Bacillus anthracis ( Fig. 21). These rod-shaped bodies under proper conditions divide transversely and elongate, but they also form spores in their interior, which in turn, under appropriate conditions, may germinate (Fig. 21). Class IV is represented by two genera, Spirochffita and Spirillum (Fig. 20), the former with close, and the latter with open spirals. The Spirochaeta Obermeieri (often spoken of as "Spirillum") is present in the blood during the paroxysms in persons suffering from relapsing fever. Among animal parasites are Filaria sanguinis; Bilharzia haematobia, which occurs in the portal vein and in the veins of the urinary apparatus.] PHYSIOLOGY OF THE CIRCULATION. 42. GENERAL VIEW OF THE CIRCULATION.— The blood within the vessels is in a state of continual motion, ^^^ being carried from the ventricles by the large arteries (aorta and pulmonary) and their branches to the system of capillary vessels, //-c)w which again it passes into the veins that end in the atria of the auricles ( W. Harvey). The Cause of the Circulation is the difference of pressure which exists between the blood in the aorta and pulmonary artery on the one hand, and the two vense cavte and the four pulmonary veins on the other. The blood, of course, moves continually, in its closed tubular system, in the direction of least resistance. The greater the difference of pressure, the more rapid the movement will be. The cessation of the difference of pressure (as after death) naturally brings the move- ment to a standstill (§ 81). The circulation is usually divided into — (i) The greater, or systemic circulation, which includes the course of the blood from the left auricle and left ventricle, through the aorta and all its branches, the capillaries of the body and the veins, until the two vens cavte terminate in the right auricle. (2) The lesser, or pulmonic circulation, which includes the course from the right auricle and right ventricle, the pulmonary artery, the pulmonary capillaries, and the four pulmonary veins springing . from them, until these open into the left auricle. (3J The portal circulation, which is sometimes spoken of as a special circulatory system, although it represents only a second set of capillaries (within the sch. liver) introduced into the course of a venous trunk. It consists of the vena portarum — formed by the union of the intestinal or mesenteric and splenic veins, and it passes into the liver, where it divides into capillaries, from which the hepatic veins arise. These last veins join the inferior vena cava. Strictly speaking, however, there is no special portal circulation. .Similar arrangements occur in other animals in different places; ''" €.g,y snakes have such a system in their suprarenal capsules, and the frog in its kidneys. When an artery splits up into fine branches during its course, and these branches do not form capillaries, but reunite into an arterial trunk, a rete mirabile is formed, such as occurs in apes and edemata. Microscopic retia mirabilia exist in the human mesentery [Sc/wbl). Similar arrange- ments may exist on veins, giving rise to venous retia mirabilia. 43. THE HEART.— Muscular Fibres of the Heart.— The musculature of tue mammalian heart consists of short (50 to 70 /;, man), very fine, transversely striated muscular fibres (C Krause, i8jj), which are actual unicellular elements {Eberth, 1866), devoid of a sarcolemma ( 15 to 25 ,« broad), and usually divided 67 of the circulation — . ride; A, right ventricle; b, left auricle ; B, left ventricle ; i, pulmonary artery ; 2, aorta with semilunar valves ; /, area of pulmonary circulation : K, area of systemic circulation in region supplying the superior vena cava.o; G, area supplying the inferior vena cava, u: d, d, in- testine, ; ;«, mesenteric artery ; g, portal vein; L, liver; h, he- 68 ARRANGEMENT OF THE CARDIAC MUSCULAR FIBRES. at their blunt ends, by which means they anastomose and form a network (Fig. 23, A, B). The individual muscle cells contain in their centre an oval nucleus, and are held together by a cement which is blackened by silver nitrate, and dis- solved by a T,^ per cent, solution of caustic potash. This cement is also dissolved by a 40 per cent, solution of nitric acid. The transverse stria; are not very distinct, and not unfrequently there is an appearance of longitudinal striation, produced by a number of very small granules arranged in rows within the fibres. The fibres are gathered lengthwise in bundles, or fasciculi, surrounded and sepa- rated from each other by delicate processes of the perimysium. When the connective tissue is dissolved by prolonged boiling, these bundles can be isolated, and constitute the so-called " fibres" of the heart. The transverse sections of the bundles in the auricles are polygonal or rounded, while in the ventricles they are somewhat flattened. [The muscular mass of the heart is called the myocardium, and is invested by fibrous tissue. It is important to notice that the connective tissue of the visceral pericardium (epicardium) is continuous with that of the endocarduim by means of the perimysium surrounding the bundles of muscular fibres.] The fine spaces which exist between these bundles form narrow lacuna;, lined with epithelium, and constituting part of the lymphatic system of the heart. Fig. 23. A, branched muscular fibres from the heart of a mammal; B, transverse section of the nective-tissue corpuscles: c, capillaries; C, muscular fibres from the heart of a frog, [The cardiac muscular fibres occupy an intermediate position between striped and plain muscular fibres. Although they are striped they are involuntary, not being directly under the influence of the- will, while they contract more slowly than a voluntary muscle of the skeleton.] [In the frog's heart the muscular fibres are, in shape, elongated spindles, or fusiform, in this respect reseral>ling the plain muscle cells, but they are transversely striped (Fig. 23, C). They are easily isolated by means of a 33 per cent, solution of potash or dilute alcohol ( IVeissmann, Kanvicr).'] 44. ARRANGEMENT OF THE CARDIAC MUSCULAR FIBRES, AND THEIR PHYSIOLOGICAL IMPORTANCE.— The study of the emliryonic heart is the key to a proper understanding of the complicated arrangement of the fibres in the adult heart. Tlie simple tubular heart of the embryo has an outer circular and an inner longitudinal layer of fibres. The septum is formed later ; hence, it is clear that a part, at least, of the fibres must be common to the two auricles, and a part also to the two ventricles, since there is originally, but one chamber in the heart. The muscular fibres of the auricles, are, however, complctclv separated from those of the ventricles by the fibro-cartilaginous rings (Lieutaud, 1782). In the auricles the fundamental arrangement of the embryonic fibres partly remains, while in the ventricles it becomes obscured as the cavities undergo a sac-like dilatation, and also become twisted in a spiral manner. (i) The Muscular Fibres in the Auricles are completely separated from the| fibres of the ventricles by the_/f;5r«/j- rings which surround the auriculo-ventri- ARRANGEMENT OF THE CARDIAC MUSCULAR FIBRES. 69 cular orifices, and which serve as an attachment for the auriculo-ventricular valves (Fig. 24, I). The auricles are much thinner than the ventricles, and their fibres are generally arranged in two layers ; the outer transverse layer is continuous over both auricles, while the inner one is directed loiigittddinally. The outer transverse fibres may be traced from the openings of the venous trunks anteriorly and pos- teriorly over the auricular walls. The longitudinal fibres are specially well marked where they are inserted into the fibro-cartilaginous rings, while in some parts of the anterior auricular wall they are not continuous. In the auricular septian, some fibres, circularly disposed around the/(^W(7 crw/Zj (formerly the embryonic opening of the foramen ovale) are well marked. Circular bands of striped muscle exist around the veins where they open into the heart ; these are least marked on the inferior vena cava, and are stronger and reach higher (2.5 cm.) on the superior vena cava (Fig. 24, II). Similar fibres exist around the pulmonary veins, where they join the left auricle, and these fibres (which are arranged as an inner circular and an outer longitudinal layer) can be traced to the hilus of the lung in man and some mammals; in the ape and rat they extend on the pulmonary veins right into the lung. In the mouse and bat, again, the striped muscular fibres pass so far into the lungs that the walls of the smaller veins are largely composed of striped muscle {Stieda). FiG. 24. scular fibres on the left auricle. Observe the outer transverse and inner longitudinal fibres, the 1 the pulmonary veins (z/. /. i ^ V, the left ventricle (John Reld). II. Arrangement ol the striped muscular fibres on the superior vena cava {Elischer) — a, opening of vena azygos ; v, auricle. Circular muscular fibres are found where the vena magna cordis enters the heart, and in the Valvula Thebesii which guards it. From a physiological point of view, the following facts are to be noted as a result of the anatomical arrangement : — (i) The auricles contj-act independently of the ventricles. This is seen when the heart is about to die ; then there may be several auricular contractions for one ventricular, and at last only the auricles pulsate. The auricular portion of the right auricle beats longest; hence, it is called the " ultimum moriens." Inde- pendent rhythmical contractions of the vena; cavse and pulmonary veins are often noticed after the heart has ceased to beat {Haller, Nysten). [This beating can also be observed in those veins of a rabbit after the heart is cut out of the body.] (2) The double arrangement of the fibres (transverse and longitudinal) pro- duces a simultaneous and uniform diminution of the auricular cavity (such as occurs in most of the hollow viscera). (3) The contraction of the circular muscular fibres around the venous orifices, and the subsequent contraction of the auricle, cause these veins to empty them- selves into the auricle ; and by their presence and action they prevent any large quantity of blood from passing backward into the veins when the auricle c/jn- 70 ARRANGEMENT OF THE VENTRICULAR FIBRES. tracts. [No valves are present in the superior and inferior vena cava in the adult heart, or in the pulmonary veins, hence the contraction of these circular muscular fibres plays an important part in preventing any reflux of blood during the con- traction of the auricles.] 45. ARRANGEMENT OF THE VENTRICULAR FIBRES.— (2) The Muscular Fibres of the Ventricles. — The fibres in the thick wall of the ventricles are arranged in several layers (Fig. 25, A) under the pericardium. First, there is an outer lontyitiitlinal layer (.\), which is in the form of single bun- dles on the right ventricle, but forms a complete layer on the left ventricle, where it measures about one-eighth of the thickness of the ventricular wall. A second loitgitudinal layer of fibres lies on the inner surface of the ventricles, distinctly visible at the orifices, and within the vertically-placed papillary muscles, while elsewhere it is replaced by the irregularly-arranged trabecula; carnea;. Between these two layers there lies the thickest layer, consisting of more or less transversely Fig. 25. ^entricul; of the (C. Ludivig). view of the apex with the vortex {Henfe) : D, fibres passing into a p.ipillary muscle arranged bundles, which may be broken up into single layers more or less circularly disposed. The deep lymphatic vessels run between the layers, while the blood vessels lie within the substance of the layers and are surrounded by the primitive bundles of muscular fibres {ffenle). All three layers are not completely independent of each other ; on the contrary, the fibres which run obliquely form a gradual transition between the transverse layers and the inner and outer longi- tudinal layers. It is not, however, quite correct to assume that the outer lon- gitudinal layer gradually passes into the transverse, and this again into the inner longitudinal layer (as is shown schematically in C) ; because, as Henle pointed out, the transverse fibres are relatively far greater in amount. In general, the outer longitudinal fibres are so arranged as to cross the inner longitudinal layer at an acute angle. The transverse layers lying between these two form gradual transitions between these directions. At the apex of the left ventricle, the outer longitudinal fibres bend or curve so as to meet at the so-called vortex ("Wirbel") PERICARDIUM, ENDOCARDIUM, VALVES. 71 B, where they enter the muscular substance, and, taking an upward and inward direction, reach the papillary muscles, D {Lower) ; although it is a mistake to say that all the bundles which ascend to the papillary muscles arise from the vertical fibres of the^outer surface; many seem to arise independently within the ven- tricular wall. According to Henle, all the external longitudinal fibres do not arise from the fibrous rings or the roots of the arteries. • [The assumption that the muscles of the ventricle are arranged so as to form a figure of 8, or in loops, seems lo be incorrect ; thus, fibres are said to arise at the base of the ventricle, to pass over it, and to reach the vortex, where they pass into the interior of the muscular substance, to end either in the papillary muscles or high up on the inner surface of the heart at its base. Figs C and D give a schematic representation of this view.] A special layer of circular muscular fibres, which acts like a true sphincter, surrounds the arterial opening of the left ventricle, and seems to have a certain independence of action {Henle'). Only the general arrangement of the ventricular muscular fibre=; has been indicated here {Lower, Casp. IVoljf, lySo-gs). C. Ludwig (1849), ^"d more recently Pettigrew (1864), have made the subject a special study, and followed out its complications. .According to the last observer, there are seven layers in the ventricles, viz., three external, a fourth or central layer, and three internal. These internal layers are continuous with the corresponding external layers at the apex, thus —one and seven, two and six. 46. PERICARDIUM, ENDOCARDIUM, VALVES.— The pericardium encloses within its two layers [visceral and parietal] a lym])h space — the pericardial space— which contains a small quantity of lymph — the pericardial fluid. It has the structure of a serous membrane, /. e., it con- sists of connective tissue mixeul with fine elastic fibres arranged in the form of a thin, delicate mem- brane, and covered on its free surfaces with a single layer of epithelium or endothelium, composed of irregular, polygonal, flat cells. A rich lymphatic network lies under the pericardium (Fig- 26) and endocardium ; and also in the deeper layers of the vis- ceral pericardium next the heart, but sto- mata have not been found leading from the pericardial cavity into these lymphat- ics, nor do these openings exist on the parietal layer. [Salvioli has shown that lymphatic spaces also lie between the mus- cular bundles.] Around the coronary arter- ies of the heart exist lymph vessels and deposits of fat ( IVedl), which lie in the furrows and grooves in the subserosa of the epicardium (visceral layer). The endocardium (according to Luschka) does not represent the intima alone, but the wall of a blood vessel. Next the cavity of the heart, it consists of a sins^le layer of polygctnal, fiat, nucleated endothelial cells. [Under this there is a nearly homogeneous hyaline layer (Fig. 27, «), slightly thicker on the left side, which gives tlie endocardium its polished appearance.] Then follows, as the basis of the membrane, a layer of fine elastic fibres — stronger in the auricles, and in some places thereof assuming the char- acters of a fenestrated membrane. Between these fibres a small quantity of connective tissue exists, which is in larger amount and more areolar in its characters next the myocardium. Bundles of non-striped mus- cular fibres (few in the auricles) are scattered and arranged for the most part longitudinally between the elastic fibres. These seem evidently meant to resist the Section of the endocardi distention which is apt to occur when the rf"myoc»"dium"' heart contracts and great pressure is put into the endocard FlG. 26. Fig. 27. im. a, hyaline layer; (^.network ot , network of stronger elastic fibres ; ,th blood vessels, which do not pass 72 STRUCTURE OF THE VALVES. upon the endocardium. In all cases where high pressure is put upon walls composed of soft parts, we always find muscular fibres present, and never elastic fibres alone. No blood vessels occur iu the endocardium [Lander,) The valves also belong to the endocardium — both the semilunar valves of the aorta and pulmonary artery, which prevent the blood from passing feack into the ventricles, and the tricuspid (r/^/;^' auriculo-ventricular) and mitral (/-7S .3033 (bath). 106-110 2675 (exertion only). r 76-80 \ 76-80 .3300 (exertion and normal). 111-115 2475 (mixed cases). .3032 (bath). 1 16-120 2350 (mixed cases). f 81-S5 t 81-S5 .32^0 (exertion and normal). 130 2100 (exertion). .3030 (bath). Fig. 40. These results were obtained by measurements of tracings of cardiograms taken after a Turkish bath, or after exertion.] Endocardial Pressure. — In large mammal.s, such as the horse, Chauveau and Marey determined the duration of the events that occur within the heart, and also the endocardial pressure, by means of a cardiac sound. Small elastic bags attached to tubes were introduced through the jugular vein into the right auricle and ventricle. Each of these tubes was connected with a register- ing tambour (Fig. 40), and simultaneous tracings of the variations of pressure within the cavities of the heart were obtained by causing the writing points of the levers of the tambours to write upon a revolving cylinder. Fig. 41, A, gives the result obtained when the elastic bag was placed in the right auricle, introduced through the jugular vein and superior vena cava ; B, when it was pushed through the tricuspid valve into the right ventricle ; D, in the root of the aorta, pushed in through the carotid ; C, pushed past the semilunar valves into the left ventricle ; while at E a similar bag has been placed externally between the heart's apex and the inner wall of the chest. In all cases 71 = auricular contraction ; V, that of the ventricle ; s, closure of semilunar valves, sooner in C than B; P ^ pause. Method. — The cardiac sound consists of a tube containing two separate air passages, and in con- nection with each of these there is a small elastic bag or ampulla. One of the bags is fixed to the free end of the sound, and communicates with one of the air passages. The other bag is placed in connection with the second air passage in the sound, and at such a distance that, when the former bag lies within the ventricle, the latter is in the auricle. Each bag and air tube communicating with it is connected with a Marey's tambour (Fig. 40), provided with a lever which inscribes its move- ments upon a revolving cylinder. Any variation of pressure within the auricle or ventricle will atfect the elastic ampulla;, and thus raise or depress the lever. Care must be taken that the writing points of the levers are placed exactly above each other. A tracing of the cardiac impulse is taken siinultaneously by means of a cardiograph attached to a separate tambour. .rey's registering tambour, capsule, T, with thin ind it, and bearing an alun upon the writing lever, H walled caoutchouc tube, with any system containing of pressure. ngof a metallic er stretched over disk, which acts By means of a thick- t may be connected 5 to record 86 PATHOLOGICAL DLSTURBANCES OF THE CARDIAC IMPULSE. It has still to be determined whether the auricles and ventricles act alternately, so that at the moment of the beginning of the ventricular contraction the auricles relax, or whether the ventricles are contracted while the auricles still remain slightly contracted, so that the whole heart is contracted for a short time at least. The latter view was supported by Harvey, Bonders, Schiff, and others, while Haller and many of the more recent observers support the view that the action of the auricles and ventricles alternates. In the case of Frau Serafin, whose heart was exposed, v. Ziemssen and Ter Gregorianz obtained curves from the auricles, which showed that the contraction of the auricles continued even after the com- mencement of the ventricular systole. In Marey's curve (Fig. 41) the contrac- tion of the ventricle is represented as following that of the auricle. Fig. 41. -- Right Auricle. — Left Ventricle. btained from the hcirt by the cardiac sound i^Ckaia'eau and Murcy). 52. PATHOLOGICAL DISTURBANCES OF THE CARDIAC IMPULSE.— Change in the Position of the Apex Beat. — The position of the cardi.ic impulse is changed — (l)liylhe accumuUtion of fluids (serum, pus, l)Iood) or g.TS in one pleural cavity. A copious effusion into the left pleural cavity compresses the lung, and may displace the heart toward the right side, while effusion on the right side may push the heart more to the left. As the right heart must make a greater eflbrt to propel the blood through the compressed lung, the cardiac impulse is usually increased. Advanced emphysema of the lung, causing the diaphragm to be pressed downward, displaces the heart downward and inward, while conversely the pushing or pulling up of the diaphragm (by contraction of the lung, or through pressure from below) causes the apex beat to be displaced upward (even to the third intercostal space), and also slightly to the left. Thickening of the muscular walls and dilatation of the cavities of the left ventricle (hyper- trophy with dilatation) make that ventricle longer and broader, while the increased cardiac impulse VARIATIONS OF THE CARDIAC IMPULSE. 87 may be felt to the left of the mammary line, and in the axillary line in the sixth, seven'h, or even eighth intercostal space. Hypertrophy, with dilatation of the right side, increases the breadth of the heart, while the cardiac impulse is felt more to the right, even to the right of the sternum, and at the same time it may be slightly beyond the left mammary line. In the rare cases where the heart is transposed, the apex beat is felt on the right side. When the cardiac impulse goes to the left of the left mammary line, or to the right of the parasternal line, the heart is increased in breadth, and there is hypertrophy of the heart. A greatly increased cardiac impulse may extend to several intercostal spaces. The cardiac impulse is abnormally weakened during atrophy and degeneration of the cardiac muscle, or by weakening of the innervation of the cardiac ganglia. It is also weakened when the heart is separated from the chest wall owing to the collection of the fluids or air in the pericardium, or by a greatly distended left lung; and, indeed, when the left side of the chest is filled with fluid, the cardiac impulse may be extinguished. The same occurs when the left ventricle is very imper- nous forms of curves obtained from the cardiac impulse, a, b, contraction of auricles ; ^, c, venincular systole ; d, closure of aortic, and e of pulmonary valves ; €,/, diastole of ventricle ; P, Q, hypertrophy and dilatation of the left ventricle; E, stenosis of the aortic orifice ; F, mitral insutBciency; G, mitral stenosis ; L, nervous palpi- tation in Basedow's disease ; M, case of so-called hemisystole. fectly filled during its contraction (in consequence of marked narrowing of the mitral orifice), or when it can only empty itself very slowly and gradually, as during marked narrowing of the aortic orifice. An increase of the cardiac impulse occurs during hypertrophy of the walls, as well as under the influence of various stimuli (psychical, inflammatory, fel rile, toxic) which aflect the cardiac ganglia. Great hypertrophy of the left ventricle causes the heart to heave, so that a part of the left chest wall may be raised and also vibrate during systole. A pulling in of the anterior wall of the chest during cardiac systole occurs in the third and fourth interspaces, not unfrequently under normal circumstances, sometimes during increa-sed cardiac action, and in eccentric hypertrophy of the ventricles. As the heart's apex is slightly displaced, and the ventricle becomes slightly smaller during its systole, the empty space is filled by the yielding soft parts of the intercostal space. When the heart is united with the pericardium and the sur- rounding connective tissue, winch renders systolic locomotion of the heart impossible, retraction 88 THE HEART SOUNDS. of the chest wall during systole takes the place of the cardiac impulse {Skoda). During the diastole a diastolic cardiac impulse of the corresponding part of the chest wall may be said to occur. Changes in the cardiac impulse are best ascertained by taking graphic representations of the cardiac impulse, and studying the curves so obtained. This method has been largely followed by many clinicians. In all the following curves, a, *, means auricular contraction; /5, ^, ventricular contraction; d, closure of the aortic valves, and e of the pulmonary; e,f, the time the ventricle is relaxed (Fig- 42). ■ In curve P (much reduced), taken from a case of marked hypertrophy with dilatation, the ventricular contraction, b, c, is usually very great, while the time occupied by the contraction is not much increased. P and Q were obtainpd from a man suffering from marked eccentric hypertrophy of the left ventricle, in consequence of insufficiency of the aortic valves. Curve Q was taken intentionally over the auriculo-ventricular groove, where retraction of the chest wall occurred during systole ; nevertheless, the individual events occurring in the heart are indicated. Fig. E is from a case of aortic stenosis. The auricular contr.iction (17, />) lasts only a short time ; the ventricular systole is obviously lengthened, and after a short elevation (i, c) shows a series of fine indentations (c, e) caused by tlie blood being pressed through the narrowed and roughened aorta. Fig F, from a case of insufficiency of the mitral valve, shows {a, />) well marked on account of the increased activity of the left auricle, while the shock (d) from the closure of the aortic valves is small, on account of the diminished tension in the arterial s\stcm. On the other hand, the shock from the accentuated pulmonary sound (f) is ^ery great, and is in the apex of the curve. On account of the great tension in the pulmonary artery, the second pulmonary tone may be so strong, and succeed the second aortic sound (-. att right auricle, traced in fin ; dotting on the sternum ; v. i, th nary valves do not close simultaneously. Usually, however, the difference in time is so small that Iwih valves make one sound, but the second sound may be double or divided when, through increase of the difference of pressure in the aorta and pulmonary artery, the interval becomes longer. Even in health this VARIATIONS OF THE HEART SOUNDS. 91 may be the case, as occurs at the end of inspiration or the beginning of expiration (v. DuscJi). [The second sound has all the characters of a valvular sound. That the aortic valves are concerned in its production is proved by introducing a curved wire through the left carotid artery and hooking up one or more segments of the valve, when the sound is modified, and it may disappear or be replaced by an abnormal sound or "murmur" {Hope). Again, when these valves are diseased, the sound is altered, and it may be accompanied, or even displaced, by murmurs.] Where the Sounds are Heard Loudest. — The sound produced by the tricuspid valve is heard loudest at the junction of the lower right costal cartilages with the sternum ; as the mitralvalve lies more to the left and deeper in the chest, and is covered in front by the arterial orifice, the mitral sound is best heard at the apex beat, or immediately above it, where a strip of the left ventricle lies next the chest wall. [The sound is conducted to the part nearest the ear of the listener by the muscular substance of the heart.] The aortic and pulmonary orifices lie so close together that it is convenient to listen for the second {aortic^ sound in the direction of the aorta, where it comes nearest to the surface, i.e., over the second right costal cartilage, or aortic cartilage, close to its junction with the sternum. The sound, although produced at the semilunar valves, is carried upward by the column of blood and by the walls of the aorta. The sound pro- duced by the pulmonary artery is heard most distinctly over the third left costal cartilage, somewhat to the left and external to the margin of the sternum (Fig. 44). 54. VARIATIONS OF THE HEART SOUNDS.— .\n increase of the first sound of both ventricles indicates a more energetic contraction of the ventricular muscle and a simultaneously gre.iter and more sudden tension of the auriculo-ventricular valves. An increase of the secund sound is a sign of increased tension in the interior of the corresponding large arteries. Hence, increase of the second (pulmonarj) sound indicates overfilling and excessive tension in the pulmonarj' circuit. Feeble, weak action of the heart, as well as abnormal want of blood in the heart, causes weak heart sounds, which is the case in degenerations of the heart muscle. Irregularities in structure of the individual valves may cause the heart sounds to become " impure.'" If a pathological cavity, filled with air, be so placed, and of such a form as to act as a resonator to the heart sounds, they may assume a "metallic" character. The first and second sounds may be "reduplicated" or [although "duplication" is a more accurate term (£arr)'\ doubled. The reduplication of the first sound is e.\plained by the tension of the tricuspid and that of the mitral valves not occurring simultaneously. Sometimes a sound is produced by a hypertrophied auricle producing an audible presystolic sound, i.e., a sound or "murmur," preceding the first sound. As the aortic and pulmonary valves do not close quite simultaneously, a reduplicated second sound is only an increase of a physiological condition [Landois). All conditions which cause the aortic valves to close rapidly (diminished amount of blood in the left ventricle) and the pulmonary valves to close later (congestion of the right ventricle — both conditions together in mitral stenosis), favor the production of a reduplicated second sound. Cardiac Murmurs. — If iriegularities occur in the valves, either in cases of stenosis or in in- sufficiency, so that the blood is subjected to vibratory oscillations and friction, then, instead of the heart sounds, other sounds — murnnirs or bruits — arise or accompany these. A combination of these sounds is always accompanied by disturbances of the circulation. [These murmurs may be produced within the heart when they are termed endocardial, or outside it when they are called exocardial murmurs. But other murmurs are due to changes in the quality or amount of the blood, when they are spoken of as haemic murmurs. In the study of all murmurs, note their rhythm or exact relation to the normal sounds, their point of ma.ximum intensity and the direction in which the murmur is propagated.'\ It is rare that tumors or other deposits projecting into the ventricles cause murmur<, unless there be present at the same time lesions of the valves and disturbances of the circulation. The cardiac murmurs or bruits are always related to the systole or diastole, and usually the systolic are more accentuated and louder. Sometimes they are so loud that the thora.x trembles under their irregular oscillations (fremitus, fr^missement cataire). In cases where diastolic murmurs are heard there are alvvavs anatomical changes in the cardiac mechanism. These are insufficiency of the arterial valves, or stenosis of the auriculo-ventricular orifices (usually the left). Systolic murmurs do not always necessitate a disturbance in the cardiac mechanism. They may occur on the left side, owing to insufficiency of the mitral valve, stenosis of the aorta, and in calcification and dilatation of the ascending part of the aoita. These murmurs occur very much less frequently on the right side, and are due to insufficiency of the tricuspid and stenosis of the pulmonary orifice. 92 PHYSICAL EXAMINATION OF THE HEART. Functional Murmurs. — Systolic murmurs of'en occur without any valvular lesion, although they are always less loud, and are caused by abnormal vibrations of the valves or arterial walls. They occur most frequently at the orifice of the pulmonary artery [and are generally heard at the base], less frequently at the mitral, and still le-^s frequently at the aortic or the tricuspid orifice. Amemia. general malnutrition, acute febrile affections, are the causes of these murmurs. [Some of these are due to an altered condition of the blood, and are called iiamic, and others to defective cardiac muscular nutrition and are called dynamic ( ]Vtihhe)'\. Sounds may also occur during a certain stage of inflammation of the pericardium (pericarditis) from the roughened surfaces of this membrane rubbing upon each other. Audible friction sounds are thus produced, and the vibration may even be perceptible to touch. [These are " friction sounds," and quite distinct from sounds produced within the heart itself.] 55. DURATION OF THE MOVEMENTS OF THE HEART.— That the heart continues to beat for some time after it is cut out of the body, was known to Cleanthes, a contemporary of Herophilus, 300 B.C. The movement lasts longer in cold-blooded animals (frog, turtle, fish) — extending even to days — than in mammals. .\ rabbit's heart beats from 3 minutes up to 36 minutes after it is cut out of the body. The average of many experiments is about 11 minutes. Panum found the last trace of contraction to occur in the right auricle (rabbit) 15 hours after death; in a mouse's heart, 46 hours; in a dog's, 96 hours. An excised frog's heart beats, at the longest, 234 days ( Valentin). In a human embryo (third month) the heart was found beating after 4 hours. In this con- dition stimulation causes an increase and acceleration of the action. .Afterward, the ventricular contraction first becomes weaker, and soon each auricular con- traction is not followed by a ventricular contraction, two or more of the former being succeeded by only one of the latter. .\t the same time the ventricles contract more slowly (Fig. 39), and soon stop altogether, while the auricles still continue to beat. If the ventricles be stimulated directly, as by pricking them with a pin, they may execute a contraction. The left auricle soon ceases to beat, while the right auricle still continues to contract. The right auricular appendix continues to beat longest, as was observed by Galen and Cardanus (1550). The term "ultimum moriens " is applied to it. Similar observations have been made upon the hearts of persons who have been executed. If the heart has ceased to beat, it may be excited to contract for a short tirne by direct stimulation {Hai-oey), more especially by heat ; even under these cir- cumstances the auricles and their appendices are the last parts to cease contracting. As a general rule, direct stimulation, although it may cause the heart to act more vigorously for a short time, brings it to rest sooner. In such cases, therefore, the regular sequence of events ceases, and there is usually a twitching movement of the muscular fibres of the heart. C. Ludwig found that, even after the excitability is extinguished in the mammalian heart, it may be restored by injecting arterial blood into the coronary arteries : lesion of these vessels is followed by enfeebled action of the heart (§ 47). Hammer found that in a man whose left coronary artery was plugged, the pulse fell from So to 8 beats per minute. Action of Gases on the Heart. — During its activity the heart uses O, and produces CO, so that it beats longest in pure O (I2 hours) (Castell), and not so long in N, — H (l hour)— COj (lO minutes), =C0 (42 minutes)— CI (2 minutes), or in a vacuum (20 to 30 minutes) (Boyle, ibyo: Fontana. Tiedemann. 1847), even when there is watery vapor present to prevent evaporation. If the heart be reintroduced into O it begins to beat again. [A frog's heart ceases to beat in compressed O (10-12 atmo'-pheres) in about one -third of the time it would do were it simply excised and left to itself (A'. B. Lehntann). An excised heirt suspended in ordinary air beats three to four times as long as a heart which is placed upon a glass plate.] A heart which has ceased to contract sponta- neously may contract when an electrical stimulus is applied to it, but it does not do so for a longer time than other muscles (Budge). [56. PHYSICAL EXAMINATION OF THE HEART.]— [The physical methods of diagnosis enable us to obtain precise knowledge regarding the actual state of the heart. The methods available are : — THE CARDIAC NERVES. 93 1. Inspection. I 3. Percussion. 2. Palpation. | 4. Auscultation. To arrive at a correct diagnosis all the methods must be employed.] [Inspection. — The person is supposed to have his chest e.\posed and to be in the recumbent posi- lion. It is important to remember the limits of the heart. The base corresponds to a line joining the upper margins of the third costal cartilages, the apex to the fifth interspace, while transversely it extends from a little to the right of the sternum to within a little of the left nipple ; this area occu- pied by the heart being called the deep cardiac region. Hy the eye we can dttect any alteration in the configuration of the prjecordia, bulging or retraction of the region as a whole or of the inter- costal spaces, and we may detect variations in the position, character, extent of the cardiac impulse, or the presence of other visible pulsations.] [Palpation. — By placing the whole hand flat upon the pra;cordia, we can ascertain the presence or absence, the situation and e.xlent, and any alterations in the characters of the apex beat ; or we may detect the existence of abnormal pulsations, vibrations, thrills, or friction in this region. In feeling for the apex beat, if it be at all feeble, it is well to make the patient lean forward. Of course, it must be remembered that the whole heart may be displaced by tumors or accumulations of fluids pressing upon it, i. e., conditions external to itself, or the apex beat may be displaced from causes within the heart itself, as in hypertrophy of the left ventricle.] [Percussion. — As the heart is a solid organ, and is surrounded hy the lungs, which contain air, it is evident that the sound emitted by striking the chest over the region of the former must be dif- ferent from that produced over the latter. Not only is there a difference in the sound or note emitted, but the " sensation of resistance " which one leels on percussing the two organs is different. We may ascertain — 1. The superficial or absolute cardiac dullne.ss. 2. The deep or relative dullness.] [Superficial Cardiac Dullness. — This, theoretically, is the part of the heart in direct contact with the chest wall and uncovered by lung, but obviously as the lungs vary in size duiing respiration, it must be smaller during inspiration and larger during expiration. It forms a roughly triangular space, whose base cannot be accurately determined, as the heart dullness merges into that of the liver, situate below it, but it corresponds to a horizontal line 2j4 inches long, extending from the apex beat to the middle of the sternum. The internal side corresponding to the left edge of the sternum is 2 inches long, and reaches from the junction of the fourth costal cartilage with the ster- num — apex of the triangle — to the sternal end of the base line. 'I he superior, outer, or oblique line, 3 inches in length, is somewhat curbed, and passes downward and outward from the apex of the triangle to the apex of the heart.] [Deep Cardiac Dullness. — By this method theoretically we seek to define the exact limits of the heart as a whole, and thui to ascertain its absolute size, and ol course, percussion has to be done through a certain thickness of lung tissue, and hence one must strike the pleximeter forcibly. It extends vertically from the third rib and ends at the sixth, but owing to the cardiac merging in the hepatic dullness, this lower limit cannot be accurately ascertained ; while transversely at the fourth rib it extends from just within the nipple line to slightly beyond the right of the sternum.] [By these means we may detect increase in the size of the heart or alterations in the relation of the lungs to the heart, fluid in pericardium, etc.] [Auscultation. — This is one of the most valuable methods, for by it we can detect variations and modifications in the healthy sounds of the heart, the rhythm and frequency of the heart heat, the existence of abnormal sounds, and their exact relation to the normal sounds, also their characteis and relation to the cardiac cycle, and the direction in which these sounds are propagated [\ 54).] 57. INNERVATION OF THE HEART, CARDIAC NERVES. — [Intra- and Extra-Cardiac Nervous Mechanism. — When the heart is removed from the body, or when all the nerves which pass to it are divided, it still beats for some time, so that its movements must depend upon some mechan- ism situated within itself. The ordinary rhythmical movements of the heart are undoubtedly associated loiih the presence of nerve ganglia, which exist in the substance of the heart — the intra-cardiac ganglia. But the movements of the heart are influenced by nervous impulses which reach it from without, so that there falls to be studied an intra-cardiac and an extra-cardiac nervous mechanism.] The cardiac plexus is composed of the following nerves : (i) The cardiac branches of the vagus, the branch of the same name from the external branch of the superior laryngeal, a branch from the inferior laryngeal, and sometimes branches from the pulmonary plexus of the vagus (more numerous on the right side) ; (2) the superior, middle, inferior, and lowest cardiac branches of the three cervical ganglia and the first thoracic ganglia of the sympathetic ; (3) the incon- 94 THE FROG S HEART. stant twig of the descending branch of the hypoglossal nerve, which, according to Luschka, arises from the upper cervical ganglia. From the plexus there proceed — the deep and the supei-ficial nerves (the latter usually at the division of the pul- monary artery under the arch of the aorta, and containing a ganglion) (§ 370). The following nerves may be separately traced from the plexus : — ((z) The plexus coronarius dexter and sinister {Searpa), which contains the vasomotor iieni- tricular groove be divided, the ventricle pulsates again, '<"<■ A, ^"'■''=''=- .^' ventr., SV sinus because Bidder's ganglion has been stimulated by the act of whlch'parts mnt!n^"t^ b'e°aT: in J^he dividing it; while, at the same time, the ventricle is with- ventricle beats at a different rate, drawn from the inhibitory influence of the vagus produced by the first division at the sinus venosus. If the line of separation is so made that Bidder's gan- glion remains attached to the auricles, these pulsate, and the ventricle rests; if it be divided into halves, the auricles and ventricles pulsate, each half being excited by the portion of the ganglion in relation with it. {b) According to another view, both Remak's (a) and Bidder's ganglia [b] are motor centres, but in the auricles there is m addition an inhibitory ganglionic system (c) (Bezold, Traube). Under normal circumstances <; + (5 is stronger than c, while c is stronger than a ox b separately. If the sinus venosus be separated it beats in virtue of a ; on the other hand, the heart rests because c is stronger than b. If the section be made at the level of the auriculo ventricular groove, the auricles stand still, owing to c, while the ventricle beats, owing to b. (2) If the ventricle of a frog's heart be separated from the rest of the heart by means of a ligature, or by an incision carried through it at the level of the auriculo-ventricular groove, the sinus and atria pulsate undisturbed as before lyDescartes, 1644), but the ventricle stands still in diastole. Local stimulation of the ventricle causes a single contraction. If the incision be so made that the lower margin of the auricular septum reinains attached to the ventricle, the latter pulsates {Roseiiberger, i8jO). Even the ventricles of a rabbit's heart, when separated with a part of the auricles in connection with them, pulsate (^Tigerstedt). [Gaskell's Clamp. — Gaskell uses a clamp, regulated by a millimetre screw, to compress the heart, and thus to obstruct the passage of impulses from one part of the heart to the other, or to " block " the way, the pulsations of the auricles and ventricles being separately registered, as described at p. loi. By compressing the heart at the auriculo-ventricular groove, the ratio of auricular and ven- tricular beats alters, and instead of being I : I, there may be 2, 3, or more auricular beats for each beat of the ventricle, expressed thus : — -. -. — , — • I {3) Section of the Heart. — Engelmann's recent experiments show that if the ventricle of a frog's heart be cut up into two or more strips in a zig-zag way, so that the individual parts still remain connected with each other by muscular tissue, the strips still beat in a regularly progressive, rhythmical manner, provided one strip is caused to contract. The rapidity of the transmission is about 10 to 30 mm. per sec. {Enge/manii). Hence, it appears that the conducting paths for 7 98 ACTION OF FLUIDS ON THE HEART. the impulse causing the contraction are not nervous, but must be the contractile mass itself. It has not been proved that nerve fibres proceed from the ganglia to all the muscles. [According to Marchand's experiments, it takes a very long time for the excitement to pass from the auricles to the ventricle — a much longer time, in fact, than it would require to conduct the excitement through muscle — so that it is probable that the propagation of the impulse from the auricles to the ventricle is conducted by nervous channels to the auriculo-ventricular nervous appa- ratus. In fact, in the mammalian heart the muscular fibres of the auricles are quite distinct from those of the ventricle.] (4) It is usually stated that when the apex of a frog's heart is severed from the rest of the heart, it no longer pulsates {Ha'denhaui, Goltz), but such an ape.x, if stimulated mechanically, responds with a single contraction. Action of Fluids on the Heart. — Haller was of opinion that the venous blood was the natural stimulus which caused the heart to contract. That this is not so, is proved at once by the fact that the heart beats rhythmically when it contains no blood. Fig. 51. Fir,. 52. Scheme of a frog manometer, a, h, Mari- otte's flasks for the nutrient fluids ; s, stop-cock : c, cannula : m, manometer ; h, heart ; d, glass cup for h : e, e', elec- trodes; cyl, revolving cylinder. Double-way or perfusion cannula (nat. size) for a frog's heart, c, for fixing an elec- trode ; li, the heart is tied over the flanges , preventing it from slipping out ; e, section oft/. Blood and other fluids which are supplied to an excised heart are not the cause of its rhythmical movements, but only the conditions on which these movements depend. Thus, a heart which is too feeble to contract may be made to do so by supplying it with a fluid containing proteids, when a latent intra-cardiac mechan- ism is brought into action, the albuminous or other fluid merely supplying the pabulum for the excitable elements. [Methods. — The study of the action of fluids upon the excised frog's heart has been rendered possible by the invention of Ludwig's " frog manometer." The apparatus has been improved by Ludwig's pupils, and already numerous important results have been obtained. The apparatus (Fig. 51) consists of ( i) a double-way cannula, <-, which is tied into the heart, k ; (2) a manometer, m, connected with c, and registering the movements of its mercury on a revolving cylinder, <■_>■/,■ (3) two Mariotte's flasks, a and i, which are connected with the other limb of the cannula. Either a oT h can be placed in communication with the interior of the heart by means of the stop-cock, s. The fluid in one graduated tube may be poisoned, and the other not ; <^ is a glass vessel for fluid, in which the heart pulsates, e' and e are electrodes, e is inserted into the fluid in d, e' is attached to the German silver cannula which is shown in Fig. 52.] [In the tonometer of Roy (Fig. 53) the ventricle, h, or the whole heart, is placed in an air-tight ACTION OF FLUIDS ON THE HEART. 99 chamber, o, filled with oil, or with oil and normal saline folution. As before, a " perfusion " cannula is tied into the heart. A piston. y>, works up and down in a cylinder, and is adjusted by means of a thin flexible animal membrane, such as is used by perfumers. Attached to the piston by means of a thread is a writing lever, /, which records the variations of pressure within the chamber, o. When the ventricle contracts, it becomes smaller, diminishes the pressure within o^ and hence the piston and lever rise; conversely, when the heart dilates, the lever and piston descend. Variations in the volume of the ventricle may be registered, without in any way interfering with the flow of fluids through it.] [Two preparations of the frog's heart have been used — (i) The "heart," in which case the cannula is introduced into the heart through the sinus venosus, and a ligature is tied over it aroitnd the auricle., or it may be the sinus venosus. Thus the auriculo-ventricular ganglia and other nervous structures remain in the preparation. This was the heart preparation employed by Luciani and Rossbach. (2) In the " heart apex," or apex preparation, the cannula is introduced as before, but the ligature is lied on it over the ventricle, several millimetres below the auriculo-ventricular groove, so that this preparation contains none of the auriculo-ventricular ganglia, and, according to the usual statement, this part of the heart is devoid of nerve ganglia. This is the preparation which was used by Bowditch, Kronecker and Stirling, Merunowicz, and others. The first effect of the application of the ligature in both cases is, that both preparations cease to beat, but the '-heart" usually resumes its ryhthmical contractions within several minutes, while the "heart apex" does not contract spon- taneously until after a much longer time ( 10 to 90 mins. )]. [If the " heart apex " be filled with a 0.6 per cent, solution of common salt, the contractions are at first of greater extent, but they afterward cease, and the preparation passes into a condition of "apparent death;" while if the action of the fluid be prolonged, the heart may not contract at all, even when it is stimulated electrically or mechanically. It may be made, however, to pulsate again, if it be supplied with saline solution containing blood (l to 10 per cent.). The " Stille" or state of quiescence may last 90 mins. {Kronecker and Merunowicz). If the ventricle be nipped with wire forceps at the junction of the upper with its middle third, so as to separate the lower two-thirds of the ventricle physiologically but not anatomically from the rest of the heart, then the apex will cease to contract, although it is still supplied with the frog's own blood (Bernstein, Bowditch). The physiologically isolated apex may be made to beat by clamping the aortic branches so as to prevent blood passing out of the iieait, and thus raising the intra-cardiac pressure. The rate of the beat of the apex is independent of and slower than that of the rest of the heart. This experiment proves that the amount of pressure within the apex cavity is an important factor in the causation of the spontaneous beats of the ap^x ( Gaskell). If blood serum, to which a trace of delphinin is added, be transfused or " perfused ' through the heart, it begins to beat within a minute, continues to beat for several seconds, and then stands still in diastole {Bo7vditeh). Quinine [Schtschepotjew') and a mixture of atropine and muscarin have a similar action (7'. Basch). These experiments show that, prcroided no nervous apparatus e.xists within the heart apex, the cause of the varying contraction is to be sought for in the musculature of the heart {Kronecker), and that the stimulus necessary for the systole of the heart's apex may arise within itself {.luhert). If there is no nervous apparatus of any kind present, then we must assume that the heart muscle may execute rhythmical movements inde- pendently of the presence of any nervous mechanism, although it is usually assumed that the ganglia 100 ACTION OF HEAT ON THE HEART. excite (he heart muscle to pulsate rhythmically. It is by no means definitely proT'cd that the heart apex is devoid of .all nervous structures, which may act as originators of these rhythmical impulses.] [Action of Drugs. — If the heart apex contains no nervous structures, it must form a good oliject for the study of the action of drugs on the cardiac muscle. Some of these have been mentioned already. Ringer finds that a calcium salt makes the contractions higher and longer. Dilute acids added to saline solution, e. g., lactic, cause complete relaxation of the cardiac musculature, while dilute alkalies produce an opposite effect or tonic contraction, even though the apex be not pulsating. The action of a dilute acid may be set aside by a dilute alkali and vice versa. Digitalin, antiarin, barium, and veratria act like alkalies, while saponin, muscarin, and pilocarpin have the eftect of acids (\ 65).] [The " Heart " preparation in many respects behaves like the foregoing, /. e., it is exhausted after a time by the continued application of normal saline solution (0.6 per cent. NaCl), while its activity may be restored by supplying it with albuminous and other fluids (p. 98).] [C5) Luciani found that such a heart, when filled with pure serum, produced groups of pulsations with a long diastolic pause between every two groups (Fig. 54). The successive beats in each group assume a " staircase " character (p. 102). These periodic groups undergo many changes ; they occur when the heart is filled with pure serum free from blood corpuscles, and they disappear and give place to regular pulsations when defibrinated blood or serum containing hemoglobin or normal saline solution (^Rossbach) is used. They also occur when the blood within the heart has become dark colored, /. c, when it has been deprived of certain of its constituents, and if a trace of veratrin be added to bright red blood they occur.] (6) The same apparatus permits of the application of electrical stimuli to either Fig. 54. Four groups of pulsations with intervening pauses, as obtained by Luciani, with their " staircase " character. The points on the abscissa were marked every 10 seconds. of the above-named preparations. An apex preparation, when stimulated with even a weak induction shock, always gives its maximal contraction, and when a tetanizing current is applied tetanus does not occur {Kivneckcr and Stirling). When the opening and closing shocks of a sufficiently strong constant current are applied to the heart apex, it contracts with each closing or opening shock. [When a constant current is applied to the lower two-thirds of the ventricle (heart apex), under certain conditions the apex contracts rhytlimically. This is an important fact in connection with any theory of the cardiac beat.] . (7) If the bulbus aort^e (frog) be ligatured, it still pulsates, provided the internal pressure be moderate. Should it cease to beat, a single stimulus makes it respond by a series of contractions. Increase of temperature to 35° C, and raising the pressure within it, increase the number of pulsations {Engelmann'). (IIj Direct Stimulation of the Heart. — All direct cardiac stimuli act more energetically on the inner than on the outer surface of the heart. If strong stimuli are applied for too long a time, the ventricle is the part first paralyzed. (a) Thermal Stimuli. — [Heat affects the number or frequency and the amplitude of the pulsations, as well as the duration of the systole and di.astole and the excitability of the heart.] Descartes (1614) observed that heat increases the number of pulsations of an eel's heart. A. v. Humboldt found that wlien a frog's heart was placed in lukewarm water, the number of beats increased from 12 to 40 per minute. As the temperature increases, the number of beats is at first considerably increased, but afterward the beats again become fewer, and if the temperature is raised above a certain limit the heart stands still, the myosin of which its fibres consist is coagulated, ACTION OF MECHANICAL AND ELECTRICAL STIMULI. 101 and " heat rigor " occurs. Even before this stage is reached, however, the heart may stand still, the muscular fibres appear- ing to remain contracted. The ventricles u>ually cease to beat before the auricles (Sche/ske). The she and e.xleitt of the con- tractions increase up to about 20° C, but above this point they diminish (Fig. 55). The time occupied by any single con- traction at 20° C is only about j'j of the time occupied by a contraction occurring at 5° C. A heart which has been warmed is capable of reacting pretty rapidly to intermittent stimuli, while a heart at a low tempera- lure reacts only to stimuli occurring at a considerable interval. If a frog be kept in a cold place its heart beats slowly and does little work, but if the heart be supplied with the extract of a frog which has been kept warm, it is rendered more capable of doing work (Gaiile). Cold. — When the temperature of the blood is diminished, the heart beats slower (Kielmeyer^ '793)- A frog's heart placed between two watch glasses and laid on ice, beats very much slower {Lmlwig, iSbi). The pulsations of a frog's heart stop when the heart is exposed to a temperature of 4° C. to 0° {E. Cyan). If a frog's heart be taken out of warm waier, and suddenly placed upon ice, it beats more rapidly, and con- versely, if it be taken from ice and placed over warm water, it beats more slowly at first and more ra|iKlly afterw.ird (Aristi<-i'\. Fig. 55. Fig. ot a frog's heart at ig"^ C. ; ^, at 34° C. : ^, at 3° C. [Methods. — The effect of heat on a heart may be studied by the aid of the frog manometer, the fluid in which the heart is placed being raised to any temperature required. For demonstration purposes, the heart of a pithed frog is excised and placed on a glass slide under a light lever, such as a straw. The slide is warmed by means of a spirit lamp. In this way the frequency and ampli- tude of the contractions are readily made visible at a distince.] [Gaskell fixes the heart by means of a clamp placed round the auriculo-ventricular groove, while levers are placed horizontally above and below the heart. These levers are fixed to part of the auricles and to the apex by means of threads. Each part of the heart attached to a lever, as it contracts, pulls upon its own lever, so that the extent and duration of each contraction may be registered. This method is applicable for studying the effect of the vagus and other nerves upon the heart.] (/') Mechanical Stimuli. — Pressure applied externally to the heart accelerates its action. In the case of Frau Serafin, v. Ziemssen found that slight pressure on the auriculo-ventricular groove caused a second short contraction of both ventricles after the heart beat. Strong pressure causes a very irregular action of the cardiac muscle. This may readily be produced by compressing the Ireshly-excised heart of a dog between the fingers. The intra-cardiac pressure also affects the heart beat (p. 99). If the pressure within the heart be increased, the heart beats are gradually increased; if it be diminished, the number of beats diminishes (Lmhuig and Thiry). If the intra-cardiac pressure be very greatly increased, the heart's action becomes very irregular and slower (Heiden/iain). A heart which has ceased to beat may, under certain circumstances, be caused to execute a single contraction, if it be stimulated mechanically. (c) Electrical Stimuli. — A constant electrical current of moderate strength increases the number of heart beats, v. Ziemssen found, in the case of Frau Serafin (^47, 3), that the number of beats was doubled when a constant uninterrupted strong current was passed through the ventricles. If the constant current be very strong, or if tetanizing induction currents be used, the cardiac muscle assumes a condition resembling, but not identical with, tetanus (Lud-uiig and Hoffa), and, of course, this results in a fall of the blood pressure (Sigm. Mayer). 102 ACTION OF ELECTRICAL STIMULI ON THE HEART. When a single induction shock is applied to the ventricle of a frog's heart during systole, it has no apparent effect; but if it is applied during diastole, the succeeding contraction takes place sooner. The auricles behave in a similar manner. WTiile they are contracted, an induction shock has no effect; if, however, the stimulus is applied during diastole, it causes a contraction, which is followed by systole of the ventricle {^Hildebrand). Even when strong tetanizing induction shocks are applied to the heart, they do not produce tetanus of the entire cardiac musculature, or, as it is said, "the heart knows no tetanus" {Kronecker and Stirling). Small, white, local, wheallike ele- vations — such as occur when the intestinal musculature is stimulated — appear between the elec- trodes. They may last several minutes. .\ frog's heart, which yields weak and irregular contrac- tions, may be made to execute regular rhythmical contractions synchronous with the stimuli, if electrical stimuli are used (Bo-uiditc/i). In this case the weakest stimuli (which are still active) behave like the stronger stimuli — even with the weak stimulus, the heart always gives the strongest contraction possible. Hence, this minimal electrical stimulus is as effective as a " ma.ximal " stimulus ( Kronecker and Stirling). Human Heart. — v. Ziemssen found that he could not alter the heart beats of the human heart (Frail St'rayin, ^47, 3), even with strong induction currents. The ventricular diastole seemed to be less complete, and there were irregularities in its contraction. By 0[:ening and closing, or by reversing a strong constant current applied to the heart, the number of beats was increased, and the increase corresponded with the number of electrical stimuli; thus, when the electrical stimuli were 120, 140, 180, the number of heart beats was the same, the pulse beforehand being So. When 180 shocks per minute were applied, the action of the heart assumed the characters of the pulsus alternaiis (? 70, 4). Minimal .stimuli were also found to act like maximal stimuli. The normal pulse rate of 80 was reduced to 60 and 50, when the number of shocks was reduced in the same ratio. The rhythm became, at the same time, somewhat irregular. In these experiments a strong current is required, and v. Basch found that the same was true for the frog's heart. Even in healthy persons, v. Ziems en ascertained that the energy and rhythm of the heart could be modified by passing an electrical current through the uninjured chest wall. [In Frau .Serafin's case, the elec- trodes were applied to the heart, sejiarated from it merely by the pericardium. Ziemssen found that the faradic current did not modify the heart's action when the thorax was intact, but that the constant current did, if of sufficient strength. Herbert and Dixon Mann obtained negative results with both kinds of electricity in the normal thorax.] [Method — The apparatus (Fig. 52) is also well adapted for studying the effect of electrical currents upon the heart. Bowditch, Kronecker aud Stirling, and other observers, used the '■ heart apex," as it does not contract spontaneously for some time after the ligature is applied. One elec- trode is attached to the cannula, and the other is placed in the fluid in which the heart is bathed.] [Opening induction shocks, if of sufficient strength, cause the heart to contract, while weak stimuli have no effect; on the other hand, moderate stimuli, when they do cause the heart to con- tract, always cause a maximal contraction, so that a minimal stimulus acts at the same time like a maximal stimulus. The heart either contracts or it does not contract, and when it contracts, the result is always a "maximal" contraction. Bowditch found that the excitability of the heart was increased by its own movements, so that after a heart had once contiacted, the strength of the stimulus required to excite the next contraction may be greatly diminished, and yet the stimulus be effectual. Usually, the amplitude of the first beat so produced is not so great as the second beat, and the second is less than the third, so that a " staircase " (" Treppe ") of beats of successively greater extent were produced (Fig. 54). This staircase arrangement occurs even when the strength of the stimulus is kept constant, so that the production of one contraction facilitates the occurrence of the succeeding one. A staircase arrangement of the pulsations is also seen in Luciani's group; (p. 100). The question, whether a stimulus will cause a contraction, depends upon what particular phase the hean is in when the shock is applied. Even comparatively weak stimuli will cause a heart to contract, provided the stimuli are applied at the proper moment and in the proper tempo, ;'. e., to say, they become what are called " infallible." If stimuli are applied to the heart at intervals which are longer than the time the heart takes to execute its contraction, they are effectual or " adequate ; " but if they are applied before the period of pulsation comes to an end. then they are ineffectual (Kronecker). It is quite clear, therefore, that the relation of the strengtii of the stimulus to the extent of the contraction of the cardiac muscle is quite different from what occurs in a muscle of the skeleton, where, within certain limits, the amplitude of the contrac- tion bears a relation to the stimulus, while in the heart the contraction is always maximal^ (d) Chemical Stimuli. — Many chemical substances, when applied in a dilute solution to the inner surface of the heart, increase the heart beats, while if they are concentrated or allowed to act too long, they diminish the heart beats and paralyze it. Bile (Budge), bile salts (Kohrig) diminish the heart beats (also when they are absorbed into the blood, as in jaundice) ; in very dilute solu- tions, both increase the heart beats (Landois). A similar result is produced by acetic, tartaric, citric, (Bobrik) and phosphoric acids (Leyden). Chloroform and ether, applied to the inner surface, rapidly diminish the heart beats, and then paralyze it; but very small quantities of ether (i per cent.) accelerate the heart beat of the frog (Kronecker and M' Grcgor-Roberlson), while a solution of I j^ to 2 per cent, passed through the heart, arrests it temporarily or completely. Dilute solu- tions of opium, strychnia or alcohol applied to the endocardium increase the heart beats (C. NATURE OF A CARDIAC CONTRACTION. 103 Luitvn'g) ; if concentrated, they rapidly arrest its action. Chloral-hydrate paralyzes the heart {P. V. Rokitansk)'). Action of Gases. — When blood containing different gases was passed through a frog's heart, Klug found that blood containing sulphurous acid rapidly and completely killed the heart; chlorine stimulated the heart at first, and ultimately killed it; and laughing gas rapidly killed it also. Blood containing sulphuretted hydrogen paralyzed the heart without stimulating it. Carbonic oxide also paralyzed it, but if fresh blood was transfused the heart recovered. [Blood containing O excites the heart (Castell), while the presence of much CO., paralyzes it, and the presence of CO2 is more injurious than the want of O. H and N have no effect.] Rossbach found on stimulating the ventricle of a frog's heart at a circumscribed area, either mechanically, chemically, or electrically, during systole, that the part so stimulated relaxes in partial diastole. The immedi.ite direct after effect of this stimulation is, that the muscular fibres in the part irritated remain somewhat shriveled. This part ceases to act, and has lost its vital functions. If the stimulus is applied during diastole, the part irritated always relaxes sooner, and its diastole lasts longer than does that of the parts which were not stimulated. If weak stimuli are allowed to act for a long time U|X5n any part of the ventricle of a frog's heart, the part so stimulated always relaxes sooner than the non stimulated parts, and its diastole is also prolonged. Cardiac Poisons are those substances whose action is characterized by special effects upon the movements of the heart, .\mong these s.x& tteutral salts of potash. [Until 1863 it was believed that these salts were just as slightly active on the heart as the soda salts, but Bernard and Grandeau showed that very small doses of these salts produced death, the heart standing still in diastole. An excised frog's heart ceases to beat after one-half to one minute, when it is placed in a 2 per cent, solution of polassic chloride.] Even a very dilute solution of yellow prussiate of potash injected into the heart of a frog causes the'ventricle to stand still in systole. As early as i6gi, Clayton and Moulin .showed the poisonous action of potassium sulphate and alum, as compared with the non-poisonous action of sodium chloride, which was demonstrated l>y Courten, in 1679. Antiar (Java arrow poison) causes the ventricle to stand still in systole and the auricles in diastole. Some heart poisons, in small doses, diminish the heart's action, and in large doses not unfretjuently accelerate it, e. g., digitalis, morphia, nicotin. Others, when given in small doses, accelerate its action, and in large doses slow it — veratria, aconitin, camphor. Special Actions of Cardiac Poisons. — The complicated actions of various poisons upon the heart have led observers to sujipose that there are various intra-cardiac mechanisms on which these substances may act. Besides the rnusiular fibres of the heart and its automatic ganglia, some toxi- cologists assume that there are inhibitory ganglia into which the inhibitory fibres of the vagus pass, and accelerator ganglia, which are connected with the accelerating nerve fibres of the heart. Both the inhibitory and accelerator ganglia are connected Tvith the automatic ganglia by conducting channels. Muscarin stimulates permanently the inhibitory ganglia, so that the heart stands still (Sckmiede- berg and A'oppe). As atropin and daturin paralyze these ganglia, the stand-still of the heart brought about by muscarin may be set aside by atropin. [If a frog's heart be excised and placed in a watch glass, and a few drops of a very dilute solution of muscarin be placed on it with a pipette, it ceases to beat within a few minutes, and will not beat again. If, however, the muscarin be removed, and a solution of atropine applied to the heart, it will resume its contractions after a short time.] Physos- tigmin [Calabar bean] excites the energy of the cardiac muscle to such an extent, that stimulation of the vagus no longer causes the heart to stand still. lodine-aldehyd, chloroform, and chloral- hydrate paralyze the .automatic ganglia. The heart stands still, and it cannot be made to contract again by atropine. The cardiac muscle itself remains excitable after the action of muscarin and iodine-aldchyd, so that if it be stimulated it contracts. [According to Gaskell, antiarin and digilalin solutions produce an alteration in the condition of the muscular tissue of the apex of the heart of the same nature as that produced by the action of a very dilute .alkali solution, while the action of a blood solution containing muscarin closely resembles that of a dilute acid solution (p. 100, | 65).] [Nature of a Cardiac Contraction. — The question as to whether this is a sini[)le contraction or a compound tetanic contraction has been much discussed. This much is certain, that the systolic contraction of the heart is of very much longer duration (8 to 10 times) than the contraction of a skeletal muscle produced by stimulation of its motor nerve. When the sciatic nerve of a nerve muscle preparation (" rheoscopic limb ") is adjusted upon a contracting heart, a j-/m//^ secondary twitch of the limb, and not a tetanic spasm, is produced when the heart (auricle or ventricle) contracts. This of itself is not sufficient proof that the systole is a simple spasm, for tetanus of a muscle does not in all cases give rise to secondary tetanus in the leg of a rheoscopic liinb. Thus, a simple " initial " con- traction occurs when the nerve is applied to a muscle tetanized by the action of strychnia, and the contracted diaphgram gives a similar result. The question whether the heart can be tetanized, has been answered in the negative, and as yet 104 THE CARDIO-PNEUMATIC MOVEMENT. it has not been shown that the heart can be tetanized in the same way that a skel- etal muscle is tetanized.] The peripheral or extra-cardiac nerves will be discussed in connection with the Nervous System (§ 369 and 370). 59. THE CARDIO PNEUMATIC MOVEMENT.— As the heart within the thorax occupies a smaller space during the systole than during the dias- tole, it follows that when the glottis is open, air must be drawn into the chest when the heart contracts ; whenever the heart relaxes, ;'. e., during diastole, air must be expelled through the open glottis. But we must also take into account the degree to which the larger intra-thoracic vessels are filled with blood. These movements of the air within the lungs, although slight, seem to be of importance in hybernat- ing animals. In animals in this condition, the agitation of the gases in the lungs favors the exchange of CO^ and O in the lungs, and this slow current of air is sufficient to aerate the blood passing through the lungs. [Ceradini called the diminution of the volume of the entire heart which occurs during systole meio- cardia, and the subsequent increase of volume when the heart is distended to its maxmium, auxocardia.] Fig. 56. Landois' cardio-pneumograph, and the curves obtained therewith. A and B, from man : i and 2 correspond to the periods of the first and second heart sounds ; C, from dog : D, method of using the apparatus. Method. — The cardio-pneumatic movements, i, e., the movement of the respiratory gases de- pendent on the movements of the heart and great vessels, may be demonstrated in animals and man. A manomelric flame may be used. Insert one limb of a Y-tube into the opened trachea of an animal, while the other limb passes to a small gas jet, and connect the other tube with a gas jet. It is clear that the movements of the heart will affect the column of gas, and thus affect the flame. Large animals previously curarized are best. It may also be done in man by inserting the tube into one nostril, while the other nostril and the mouth are closed. [A simpler and less irritating plan is to fill a wide curved glass tube with tobacco smoke, and insert one end of the tube into one nostril while the other nostril and the mouth are closed. If the glottis be kept open, and respiration be stopped, then the movements of the column of smoke within the tube are obvious.] Cardio-Pneumograph. — Ceradini employed a special instrument, while Landois uses his cardio- pneumograph, which consists of a tube (D), about I inch in diameter and 6 to 8 inches in length; the tube is bent at a right angle, and communicates with a small metal capsule about the size of a saucer (T), over which a membrane composed of collodion and castor oil is loosely stretched. To this memiirane is attached a glass rod (H) used as a writing style, which records its movements on a glass plate (S) moved by clock work. A small valve (K) is placed on the side of the tube (U), which enables the experimenter to breathe when necessary. The tube (D) is held in an air-tight manner between the lips, the nostrils being closed, the glottis open, and respiration stopped. Fig. 56, A, B, C, are curves obtained in this way. In them we observe — INFLUENCE OF THE RESPIRATION ON THE HEART. 105 (rt) At the moment of the first sound (i), the respiratory gases undergo a sharp expiratory move- ment, because at the moment of the first part of the ventricular systole the blood of the ventricle has not left the thorax, while venous blood is streaming into the right auricle through the venx cavre, and because the dilating branches of the pulmonary artery compress the accompanying bronchi. The blood of the right ventricle has not yet left the thora.x, it passes merely into the pulmonary- circuit. The expiratory movement is diminished somewhat by (a) the muscular mass of the ventricle occupying slightly less bulk during the contraction, and (b) owing to the thoracic cavity being slightly increased by the fifth intercostal space being pushed forward by the cardiac impulse. (h) Immediately after (i) there follows a strong inspiratory current of the respiratory gases. As soon as the blood from the root of the aorta reaches that part of the aorta lying outside the thorax, more blood leaves the chest than passes into it simultaneously through the venre cavae. (c) After the second sound (at 2), indicated sometimes by a slight depression in the apex of the curve, the arterial blood accumulates, and hence there is another expiratory movement in the curv'e. (d) The peripheral wave movements of the blood from the thorax cause another inspiratory movement of the gases. (e) More blood flows into the chest through the veins, and the next heart beat occurs. 60. INFLUENCE OF THE RESPIRATORY PRESSURE ON THE DILATATION AND CONTRACTION OF THE HEART. — The variation in pressure to which all the intra-thoracic organs are subjected, owing to the increase and decrease in the size of the chest caused by the respi- ratory movements, exerts an influence on the movements of the heart, as was proved by Carson in 1S20, and by Bonders in 1854. Examine first the relations in different passive conditions of the thorax, when the glottis is open. The diastolic dilatation of the cavities of the heart (excluding the pressure of the venous blood and the elastic stretching of the relaxed muscle wall ) is funda- mentally due to the elastic traction of tlie lungs. This is stronger the more the lungs are distended (inspiration), and is less active the more the lungs are con- tracted (expiration). Hence it follows : — (i) When the greatest possible expiratory effort is made (of course, with the glottis open) only a small amount of blood flows into the cavities of the heart ; the heart in diastole is small and contains a small amount of blood. Hence the systole must also be small, which further gives rise to a small pulse beat. (2) On taking the greatest possible inspiration, and therefore causing the greatest stretching of the elastic tissue of the lungs, the elastic traction of the lungs is, of course, greatest (30 mm. Hg — Donders^. This force may act so energetically as to interfere with the contraction of the thin-walled atria and appendices, in consequence of which these cavities do not completely empty themselves into the ventricles. The heart is in a state of great distention in diastole, and is filled with blood ; nevertheless, in consequence of the limited action of the auricles, only small pulse beats are observed. In several individuals Bonders found the pulse to be smaller and slower ; afterward it became larger and faster. (3) When the chest is in a position of moderate rest, whereby the elastic traction is moderate (7.5 mm. Hg- — Bonders), we have the condition most favorable to the action of the heart — sufficient diastolic dilatation of the cavities of the heart, as well as unhindered emptying of them during systole. A very important factor is the influence exerted upon the action of the heart, by the volmitary increase or diminution of the intra-thoracic pressure. (i) Valsalva's Experiment. — If the thorax is fixed in the position of deepest inspiration, and the glottis be then closed, and if a powerful expiratory effort be made by bringing into action all the expiratory muscles, so as to contract the chest, the cavities of the heart are so compressed that the circulation of the blood is temporarily interrupted. In this expiratory phase the elastic traction is very limited, and the air in the lungs being under a high pressure also acts upon the heart and the intra-thoracic great vessels. No blood can pass into the thorax from without ; hence the visible veins swell up and become congested, the blood in the lungs is rapidly forced into the left ventricle by the compressed air in the lungs, and the blood soon passes out of the chest. Hence the lungs and the 106 INFLUENCE OF THE RESPIRATION ON THE HEART. heart contain little blood. Hence, also, there is a greater supply of blood in the systemic than in the pulmonary circulation and the heart. The heart sounds dis- appear, and the pulse is absent {E. H. Weber, Donders). (2) J. Miiller's Experiment. — Conversely, if after the deepest possible expiration the glottis be closed, and the chest be now dilated with a great inspira- tory effort, the heart is powerfully dilated, the elastric traction of the lungs, and the very attenuated air in these organs act so as to dilate the cavities of the heart in the direction of the lungs. More blood flows into the right heart, and in pro- portion as the right auricle and ventricle can overcome the traction outward, the blood vessels of the lungs become filled with blood, and thus partly occupy the lung space. Much less blood is driven out of the left heart, so that the pulse may disappear. Hence, the heart is distended with blood and the lungs are congested, Fig. 57. App:iratus for demonstrating the action of inspiration, 11, and expiration, I, on the heart and on the blood streair P,/, lungs ; H, //, heart ; L, /, closed glottis ; M. w/, manometers : E, e, ingoing blood stream, vein ; A, a, on going blood stream, artery ; D, diaphragm during expiration ; d, during inspiration. while the aortic system contains a small amount of blood, /. e., the systemic cir- culation is comparatively empty, while the heart and the pulmonary vessels are engorged with blood. In normal respiration the air in the lungs during inspiration is under slight pressure, while during ex[)iration the pressure is higher, so that these conditions favor the circulation ; inspiration favors the supply of blood (and lymph) through the vena; cavaj, and favors the occurrence of diastole. In operations where the axillary or jugular vein is cut, air may be sucked into the circulation during inspira- tion, and cause death. Expiration favors the flow of blood in the aorta and its branches, and aids the systolic emptying of the heart. The arrangement of the valves of the heart causes the blood to move in a definite direction through it. The elastic traction of the lungs aids the lesser circulation through the lungs INFLUENCE OF THE RESPIRATION ON THE HEART. 107 within the chest ; the blood of the pulmonary capillaries is exposed to the pressure of the air in the lungs, while the blood in the pulmonary veins is exposed to a less pressure, as the elastic traction of the lungs, by dilating the left auricle, favors the outflow from the capillaries into the left auricle. The elastic traction of the lungs acts slightly as a disturbing agent on the right ventricle, and, therefore, on the movement of blood through the pulmonary artery, owing to the overpowering force of the blood stream through the pulmonary artery, as against the elastic traction of the lungs (Donders). The above apparatus (Fig. 57) shows the effect of the inspiratory and expiratory movements on the dilatation of the heart, and on the blood stream in the large blood vessels. The large glass vessel represents the thorax; the elastic membrane. D, the diaphragm; P, /, the lungs; L, the trachea supplied with a stop-cock to represent the glottis; H, the heart; E, the vena; cavae; A, the aorta. If the glottis be closed, and the expiratory phase imitated by pushing up D as in I, the air in P. P is compressed, the heart, H. is compressed, the venous valve closes, the arterial is opened, and the fluid is driven out through A. The manometer, M, indicates the intrathoracic pressure. If ihe glottis be closed, and tlie inspiratory phase imitated, as in \\,p,p and h are dilated, the venous valve opens, the arterial valve closes; hence, venous blood flows from e* into the heart. Thus, inspiration always favors the venous stream, and hinders the arterial ; while expiration hinders the venous, and favors the arterial stream. If the glottis L and / be open, the air in P, V,p,p will be changed during the respiratory movements D and d, so that the action on the heart and blood vessels will be diminished, but it will still persist, although to a much less extent. THE CIRCULATION. 6i. THE FLOW OF FLUIDS THROUGH TUBES.— Toricelli's Theorem (16431 Fig, 5S. \u states that the velocity of efflux (v) of a fluid — through an opening at the l)Otlom of a cylindrical vessel — is exactly the same as the velocity which a body falling fieely would act|uire, were it to fall from the surface of the fluid to the base of the orifice of the outflow. If A be the height of the propelling force, the velocity of efflux is given by the formula — V ^ -y/ 2 g h (where g = 9.8 metres). The rapidity of outflow increases (as shown experimentally) with increase in the height of the propelling force, h. The former occurs in the ratio, hj 1,2, 3, when h increases in the ratio, i, 4, 9, /. e., the velocity of efflux is as the square root of the height of the propelling force. Hence, it fol- lows that the velocity of efllux depends upon the height of the liquid above the orifice of outflow, and not upon the nature of the fluid. Resistance. — Toricelli's theorem, however, is only valid when all resistance to the outflow is absent; but, in fact, in every physical experi- ment such resistance exists. Hence, the propelling force, //, has not only Cylindrical vessel filled with to cause the efflux of the fluid, but has also to overcome resistance. w.iter. /j, height of the These two forces maybe expressed by the heights of two columns of hdaht"of columntffluM wter placed over each other, viz., by the height of the column of water required to overcome the Causing the outflow, F, and the height of the column, D, which over- resistance ; and F. height comes the resistance opposed to the outflow of the fluid. So that of column of fluid caus- ^^ r- , r. ing the efflux. A = F + D. 62. PROPELLING FORCE— VELOCITY OF THE CURRENT, AND LAT- ERAL PRESSURE.— In the case of a fluid flowing through a tube, which it fills completely, we have to consider the propelling force, h, causing the fluid to flow through the various sections of the tube. The amount of the propelling force depends upon two factors: — ( 1 ) On the velocity of the cm rent, v : (2) On the pressure (amount of resistance) to which the fluid is subjected at the various parts of the tube, D. (i ) The velocity of the current, v, is estimated — (a1 from the lumen, /, of the tube ; and (B) from the quantity of fluid, q, which flows through the tube in the unit of time. So that i' = i/ : /. Both values, q as well as I, can be accurately measured. (The circumference of a round tube whose diameter =ng l">ib of ""^ manometer. The tube which papei. connects the artery with the manometer must be flexible and yet inelastic, and a lead tube is best. It is usual to connect a pressure bottle, containing a saturated solution of sodium carbon- ate, by means of an elastic tube, with the tube attached to the manometer. This bottle can be raised or lowered. Before beginning the experiment, raise the pressure bottle until there is a posi- tive pressure of several inches of mercury in the manometer, or until the pressure is about equal to the estimated blood pressure, and then clamp the tube of the pressure bottle where it joins the lead tube. By having this positive pressure, the escape of blood from the artery into the solution of sodium carbonate is to a large extent avoided. When all is ready, the ligature on the cardiac side of the cannula is removed, and immediately the float begins to oscillate and inscribe its movements upon the recording surface. The fluid within the artery exerts pressure latterly upon the sodium carbonate solution, and this in turn transmits it to the mercury.] [Precautions. — In taking a blood-pressure tracing, after seeing that the apparatus is perfect, care must be taken that the animal is perfectly quiescent, as every movement causes a rise of the blood pressure. This may be secured by giving curara and keejjing up artiflcial respiration, or by carefully regulated inhalation of ether. When a drug is to be injected to test its action, if it be in- troduced into the jugular vein, it is apt to affect the heart directly. This may be avoided by inject- ing it into a vein of the leg, the peritoneum, or under the skin. The solution of the drug must not contain particles which will block up the capillaries. Care should also be taken that the carbonate of soda does not flow back into the arter)'.] [Continuous Tracing. — When we have occasion to take a tracing for any length of time, it must be written upon a strij) of ]5aper which is moved at a uniform rate in front of the writing style on the float (Fig. 9S). Various arrangements are employed for this purpose, but it is usual to cause SPRING KYMOGRAPH. 143 a cylinder to revolve so as to unfold a roll or riband of paper placed on a movable bobbin. As the cylinder revolves, it gradually winds oft" the strip of paper, which is kept applied to the revolving surface by ivory friction wheels. In Kick's complicated kymograph a long strip of smoked paper is used. The writing style may consist of a sable brush, or a fine glass pen filled with aniline blue dissolved in water, to which a little alcohol and glycerine are added.] [In order to measure the height of the pressure, we must know the position of the abscissa or line of no pressure, and it may be recorded at the same time as the blood pressure or aQerward.] [In Fig. 99, O — x is the zero line or abscissa, and the height of the vertical lines or ordinates may be measured by the millimetre scale on the left of the figure. The height of the blood pres- sure is obtained by drawing ordinates from the curve to the abscissa, measuring their length, and multiplying by two.] (5) Spring Kymograph.— A. Fick (1864) constructed a "hollow spring kymograph," on the principle of Bourdon's manometer (Fig. 97, II). Fig. 99. BlooU pressure ui-v ■of thee jrotid ol a d. line, or abst issa : y-y i^ the blood p large wave du e to the respiration. mercury. obtained with ; Iter. O— .!-_lineol 1 :h one caused by a he ght of the A hollow C-shaped metallic spring, F, is filled with alcohol. One end of the hollow spring is closed, and the other end, covered by a membrane, is brought into connection with a blood vessel by a junction piece filled with a solution of sodium carbonate. .\s soon as the communication with the artery is opened, the pressure rises, and the spring, of course, tends to straighten itself. To the closed end, b, there is fixed a vertical rod attached to a series of levers, //, /, k, e, one of which writes its movements upon a surface moving at a uniform rate. The blood pressure and the periodic variations of the pulse are both recorded, although the latter is not done with absolute accuracy. [Hering improved Fick's instrument (Fig. 100). a, b, c, is the hollow spring filled with alcohol, and communicating at a with the lead tube, a", passing to the cannula in the artery. To c is attached a series of light wooden levers with a writing style s. The lower part of 4 dips into a vessel, c, filled with oil or glycerine, which serves to damp the vibrations of the levers. At_/ is a syringe communicating with the tube, d, filled with solution of sodic carbonate, and used for regulating the amount of fluid in the tube connecting the manometer with the blood vessel. The whole apparatus can be raised or lowered on the toothed rod, fi, by means of the millhead opposite g, to which all the parts of the apparatus are attached.] 144 FICK S FLAT SPRING KYMOGRAPH. (6) Pick's Flat Spring Kymograph. — Fig. loi shows Fick's latest arrangement. The narrow tube, i7, a (i mm. diam.) is placed in connection with a blood vessel by means of the cannula, ^, and over its vertical expanded end, .\, is fixed a caoutchouc membrane, with a projecting point, j, which presses against a horizontal spring, F, joined to a writing lever, H, by an intermediate piece, b. The whole is held in the metallic frame, R K. In order to estimate the absolute pressure, the instrument must be compared previously with a mercurial manometer. Fig. ioo. Fick's spring manometer, :d by Hering. fB) In man the blood pressure may be estimated by means of (i) .\ properly graduated sphygmograph (§ 67). The pressure required to abolish the move- ment of the lever indicates approximately the vascular tension. Schobel investi- gated the radial pulse in a healthy student, and obtained a mean blood pressure equal to 550 grammes. (2) By a manometric method v. Basch estimated the blood pressure. He Fick's flat spring kymograph. placed a capsule containing fluid upon a pulsating artery, while the capsule itself communicated with a mercurial manometer. .\s soon as the pressure within the manometer sliglitly exceeded that within the artery, the artery was compressed so that a sphygmograph placed on a peripheral portion of the vessel ceased to beat. [This instrument v. Basch called a Sphygmomanometer.] Both arrange- ments, however, do not give the exact pressure within the artery ; they only indi- BLOOD PRESSURE IN THE ARTERIES. 145 cate the pressure which is required to compress the artery and the overlying soft parts. The pressure required to compress the arterial walls, however, is very small compared with the blood pressure. It is only 4 mm. Hg. v. Basch estimated the pressure in the radial artery of a healthy man to be 135 to 165 millimetres of mercury. •Variations. — In children the blood pressure increases with age, height, and weight. In the superficial temporal artery, from 2 to 3 years, it is = 97 mm. ; from I2 to 13 years, 113 mm. Hg. {.4. Eckerl, c. ^ 100). The blood pressure is raised immediately after bodily movements ; it is higher when a person is in the horizontal position than when sitting, and in sitting than in standing [Fn€timann\. After a cold as well as after a warm bath (L. Lek»U7nn],Xhe first effect is an increase of blood pressure and of the iiuantily of urine {Greflierg). 85. BLOOD PRESSURE IN THE ARTERIES.— The following results have been obtained by experiment on systemic arteries : — {a) Mean Blood Pressure. — The blood pressure is very considerable, vary- ing within pretty wide limits : in the large arteries of large mammals, and per- haps in man, it is ^140 to 160 millimetres [5.4 to 6.4 inches] of a mercurial column. The following results have been obtained, those marked thus * by Poiseuille, and those -|- by Volkmann : — * Carotid, Horse, 161 mm. -f " " 122 to 214 mm. * " Dog, 151 mm. " " iTja\.Q\<)omxa.{Litdw>g). -f " Goat, 118 to 135 mm. -|- " Rabbit, 90 mm. 4- " Fowl, 88 to 171 mm. -|- Aorta of frog, 22 to 29 mm. -)- Gill artery of Pike, 35 to 84 mm. Brachial artery of man during an ope- ration, 1 10 to 120 mm. [luiivre). Perhaps too low, owing to the in- jury. E. Albert estimated the blood pressure by means of a manometer, placed in connection with the anterior tibial artery of a boy whose leg was to be amputated, to be 100 to 160 mm. Hg. The ele- vation with each pulse beat was 17 to 20 mm. ; coughing raised it to 20 to 30 Fig. 102 mm. ; tight bandaging of the healthy leg, 15 mm.; while passive elevation ^■^■ of the body, whereby the hydrostatic action of the column of blood was brought into play, raised it 40 mm. The pressure in the aorta of mam- m.als varies from 200 to 250 mm. Hg. .\i a general rule, the blood pressure in large animals is higher than in small ° animals, because in the former the blood ^^^ A c V ""LT'a channel is considerably longer, and there is greater resistance to be over- Scheme of ihe height ot the blood pressure, in A, the arteries: C, -.^ , . ,, capillaries, and V, veins; 0-0, is the abscissa or line of no come. In very young and in very old pressure ; L. v., left ventricle, and R. A., right auricle ; B. P., animals the pressure is lower than in the height of the blood pressure, individuals in the prime of life. The arterial pressure in the fcetus is scarcely the half of that of the newly-born, while the venous pressure is higher, the difference of pressure between arterial and venous blood being scarcely half sc^great as in adult animals [Co/instein and Ztin/z). The Arterial blood pressure is highest in the aorta, and falls as we pass toward the smaller vessels, but the fall is very gradual, as shown in Fig. 102. A great fall takes place as we pass from the area of the arterioles into the capil- lary area (C), while it is less in the venous area, and negative near the heart, as indicated in the dotted line passing below the abscissa, so that the pressure is lowest in the cardiac ends of the venre cava; (compare Fig. 108). (/') Branching of the Blood Vessels. — ^Vithin the large arteries the blood pressure diminishes relatively little as we pass toward the periphery, because the difference of the resistance in the difterent sections of large tubes is very small. .\s soon, however, as the arteries begin to divide fretiuently, and undergo a coii- siderable diminution in their lumen, the blood pressure in them rapidl)' diminishes, 146 RESPIRATORY UNDULATIONS IN THE BLOOD-PRESSURE ' CURVE. because the propelling energy of the blood is much weakened, owing to the resist- ance which it has to overcome (§ 99). ((■) Amount of Blood. — The blood pressure is increased \\\\.\\ greatc-r Ji/Hng of the arteries, and vice versa : hence it 1. With increased and accelerated action of the heart ; 2. In plethoric persons; 3. After considerable increase of the quan- tity of Islood by direct transfusion, or after a copious meal. Decrrases 1. During diminished and enfeebled action of the heart ; 2. In anaemic persons; 3. After hemorrhage or considerable ex- cretions from the blond l)y sweating, the urine, severe diarrhoea. The blood pressure does not vary in the same proportion as the variations in the amount of blood. The vascular system, in virtue of its muscular tissue, has the property, within liberally wide limits, of accommodating itself to larger or smaller quantities of blood (C LuJwig ami IVorm Mii/lfr, \ 102, d). [ In fact, a large amount of blood may be transfused without materially raising the blood pressure.] Small and moderate hemorrhages (in the dog to 2.8 per cent, of the body weight) have no obvious effect on the blood pressure. After a slight loss of blood the pressure may even rise (■Worm Midler). If a large amount of blood be withdrawn, it causes a great fall of the blood pressure [Nn/es, Magendif), and when hemorrhage occurs to 4-6 per cent, of the body weight, the blood pressure = o. The transfusion of a moderate amount of blood does not raise the mean arte- rial blood pressure. [There are important practical deductions from these experiments, viz., that the blood pressure cannot be diminished directly by moderate bloodletting, and that the blood pressure is not necessarily high in plethoric persons.] (r/) Capacity of the Vessels. — The arterial pressure rises when the capacity of the arterial system is diminished, and conversely. The plain, circularly- disposed muscular fibres of the arteries are the chief agents concerned in this pro- cess. When they relax, the arterial blood pressure falls, and when they contract, it rises. These actions of muscular fibres are controlled and regulated by the action of the vasomotor nerves (§ 371 ). {e) Collateral Vessels. — The arterial pressure within a given area of the vascular system must rise or fall according as the neighboring areas are diminished, whether by the application of pressure, or a ligattire, or are rendered impervious, or as these areas dilate. The application of cold or warmth to limited areas of the body — increasing or diminishing the atmospheric pressure on a part — the paralysis or stimulation of certain vasomotor areas (§ 371), all produce remark- able variations in the blood pressure. [The effect of dilatation of a large vascu- lar area on the arterial pressure is well shown by what happens when the blood vessels of the abdomen are dilated. If the central end of the superior car- diac nerve of a rabbit be stimulated, after a few seconds the blood vessels of the abdomen dilate, and gradually there is a steady fall of the blood pressure in the systemic arteries. Fig. 103 is a blood-pressure tracing showing the height of the blood pressure before stimulation, a. The stimulation was continued from a to /', and after a certain latent period there is a steady fall of the blo(xl pressure. The nerve which causes this reflex dihitation of the abdominal blood vessels, and con- sequent lowering of the blood pressure, is also called the depressor nerve.] (/) Respiratory Undulations. — The arterial pressure also undergoes regu- lar variations or undulations owing to the respiratory movements. These undula- tions are called respiratory undulations (Figs. 99 and 104). Stated broadly, during every strong inspiration the blood pressure falls, and during expiration it rises (§ 74). This is not quite correct (see below). These undulations may be explained by the fact that, with every expiration, the blood in the aorta is sub- jected to an increase of pressure through the compressed air in the chest ; with every inspiration, on the other hand, it is ditninished, owing to the rarefaction of the air in the lungs acting upon the aorta. Besides, the inspiratory movements of the chest aspirate blood from the venae cavae toward the heart, while expiration retards it, and thus influences the blood pressure. The undulations are most marked in the arteries lying nearest to the heart. The respiratory inidulations are RESPIRATORY UNDULATIONS IN THE BLOOD-PRESSURE CURVE. 147 due in part to a stimulation or condition of excitement of the vasomotor centre, which runs ])arallel with the respiratory movements. This stimulation of the vasomotor centre causes the arteries to contract, and thus the blood pressure is raised. The variations in the pressure which depend upon a varying activity of the vasomotor centre are known as the "curves of Traube and Hering" (p. Fig. I or 148). In Fig. 104 are represented a blood pressure tracing and a curve of the movements of respiration (thick line) taken simultaneously in a dog by C. Ludwig and Embrodt. The blood-pressure tracing was obtained from the carotid artery, while the pressure within the thorax was measured by means of a manometer placed in connection with one pleural cavity. In this curve, when expiration Fir,. 104. Kymogr.'ipliic blood-pressure tracing (upper, thin line), and i e.r, expiration : tn, inspiration ; c, c, heart beats. The respirations [Ludwt'g attd Einbrodt.') e (lower, thick line), taken simultaneously. in the blood-pressure tracing are due to begins (at c.v), and as the expiratory pressure rises, the blood pressure rises, while when inspiration begins (at in) both fall. The blood curve, however, begins to rise (at c) before expiration commences, /. e., during the last part of the act of inspiration. This is due to the contraction of the arteries, caused by impulses sent from the vasomotor centre. It is also aided bv the circumstance that durinir 148 TRAUBE-HERING CURVES. inspiration there is an increased inflow of venous blood to the heart, so that when it contracts more blood is forced into the arteries. [The maxima and minima of the two curves do not coincide exactly, but in addition the number of pulse beats is greater in the ascent than in the descent. This is well marked in a blood- jjressure tracing from a dog's carotid, while in a rabbit this difference of the pulse rate is but slightly marked. The smaller number of pulse beats during the descent, — /. e., during the greater part of expiration — is due to the activity of the cardio- inhibitory centre in the medulla oblongata. This is proved by the fact, that sec- tion of both vagi in the dog causes the difference of pulse rate to disappear, while other conditions remain the same as before, except that the heart beats more rapidly. It would seem that during the ascent, the cardio-inhibitorv centre is comparatively inactive. It is clear, therefore, that the respiratory and cardio- inhibitory centres in the medulla oblongata act, to a certain extent, in unison, so that it is reasonable to suppose that other centres situated in close proximity to these may also act in unison with them, or, as it were, "in sympathy." As already stated, the vaso-motor centre is also in action during a particular part of the time.] [If a dog be curarized and artificial respiration established, the respiratory undulations still occur, although in a modified form. In artificial respiration, the mechanical conditions, as regards the intra-thoracic pressure, are exactly the reverse of those which obtain during ordinary respiration. Air is forced into the chest during artificial respiration, so that the pressure within the chest is increased during inspiration, while in ordinary inspiration the pressure is diminished. Thus, the same mechanical explanation will not suffice for both cases.] If the artificial respiration be suddenly interrupted in a curarized animal, the blood pressure rises steadily and rapidly. This rise is due to the stimulation of the vasomotor centre in the medulla oblongata by the impure blood. This causes contraction of the small arteries throughout the body, which retards the outflow from the large arteries, and thus the pressure within them is raised. [Stated broadly, the arterial pressure depends on the central organ — the heart, and on the condition of the peripheral organs — the small arteries. Both are influenced by the nervous system. If the action of the vasomotor centre be eliminated by dividing the spinal cord in the cervical region, arrest of the respiration causes a very slight rise of the blood pressure ; hence, it is evident that venous blood acts but slightlv on the heart, or on any local peripheral nervous mechanism, or on the muscular fibres of the arteries. This experiment shows that it is the vasomotor centre which is specially acted upon by the venous blood.] [Traube-Hering Curves. — The following experiment proves that the varying activity of the vasomotor centres suffices to produce undulations in the blood- pressure tracing. Take a dog, curarize it, expose both vagi and establish artificial respiration ; then estimate the blood pressure in the carotid, .\fter section of the vagi, the heart will continue to beat more rapidly, but it will be undisturbed by the cardio-inhibitory centre. Thus the central factor in the causation of the blood pressure remains constant. .Suddenly interrupt the respiration, and, as already stated, the blood pressure will rise steadily and uniformly, owing to the stimula- tion of the vasomotor centre by the venous blood. In this case the peripheral factor or state of tension of the small arteries throughout the body is influenced by the condition of the nerve centre which controls their action. After a time, the blood pressure tracing shows a series of bold curves higher than the original tracing. These can only be due to an alteration in the state of the small arteries, brought about by a condition of rhythmical activity of the vasomotor centre. These curves were described and figured by Traube, and are called the Traube or Traube-Hering curves. As in other conditions, stimulation gives place to exhaus- tion, and soon the venous blood paralyzes the vasomotor centre and the small arteries relax, blood flows freely out of the larger arteries, and the blood pressure rapidly sinks. Variations in the blood pressure have been observed after a VARIATIONS OF THE BLOOD PRESSURE. 149 mechanical pump has Ijeen substituted for the heart, i.e., after all respiratory movements have been set aside, so that the only factor which would account for the ])henomena of the Traube-Hering curves is the variation in the peripheral resistance in the small arteries, determined by the condition of the vasomotor centre.] Variations. — The respirator)' undulations of tlie blood pressure become more pronounced the greater the force of the respirations, which jjroduce greater variations of the intra-thoracic pressure. In man, the diminution of the pressure within the trachea is I mm. Hg, during tranquil inspiration, while during forced respiration, when the respiratory passage is closed, it may be 57 mm. Con- versely, during ordinary expiration, the pressure is increased within the trachea 2-3 mm. Hg, while during forced expiration, owing to the compression of the abdominal muscles, it may reach 87 mm. Hg. Other Factors. — The increase of the blood pressure during inspiration, as well as the fall during expiration, must, in part, depend upon the pressure within the abdomen. As the diaphragm descends during inspiration, it presses upon the abdominal contents, including the abdominal vessels, whereby Fig. 105. lilood pressure tr.icing t.-\ken with a the blood pressure must be increased. The rever.se effect occurs during expiration [Sc/iweitiburg). [Section of both phrenic nerves and opening of the abdominal cavity cause the respiratory undula- tions almost entirely to disappear. The respiratory undulations, therefore, depend in great part upon the changes of the abdominal pressure and the effect of these changes on the amount of blood in the abdominal vessels. When making a blood-pressure ex])erimenl, pressure upon the abdomen of the animal with the liand causes the blood pressure to rise rapidly.] ( i,') Variations with each Pulse Beat. — The mean arterial pressure under- goes a variation with each heart beat ox pulse hfat, causing the so-called pulsatory undulations \ l-'ig. 104, c). The mass of blood forced into the arteries with each ventricular systole causes a positive wave and an increase of the jjressiire cor- responding with it, which, of course, corresponds, in its development and in its form, with the pulse curve. In the large arteries, Volkmann found the increase during the heart beat to be = ^'^ (horse) and y',- (dog) of the total pressure. 150 RELATION OF BLOOD PRESSURE TO PULSE RATE. None of tlie apparatus described in ^ 84 gives an exact representation of the pulse curve. They all show simplv a rise and fall — a simple curve. The sphygmograph alone gives a true expression of the undulations in the hlood pressure which are due to the heart beat. (/?) Arrest of the Heart's Action. — If the heart's action be arrested or interrupted by continued Stimulation of the vagus {Bruiiinr. /Sjj), or by a high positive respiratory piressure {Einhrodt). the arterial blood pressure falls enormously, while it rises in the veins as the blood flows into them from the arteries to equilibrate the difference of pressure in the two sets of vessels. This experiment shows that, even when the difference of pressure is almost entirely set aside, the passive blood presses upon the arterial walls, i.e., on account of the overfilling of the blood vessels, a slight pressure is exerted upon the walls, even when there is no circulation ( Bncnncr). [As already stated, the arterial pressure depends on the condition of the central organ — the heart — and on the peripheral organs — the small arteries. If the action of the heart be arrested, then the blood pressure rapidly falls. Fig. 105 shows the effect on the blood pressure, of arrest- ing the action of the heart, by stimulation of the peripheral end of the vagus. There is a sudden tall of the arterial pressure, as shown by the ra[)id fall of the curve from a.'\ [Variations in Animals. — The pressure in the arterial system depends upon the balance between the inflow and the outflow, /. e., upon the heart and the state of the arterioles. But it is to be noted that the central factor, the heart, varies in diflerent animals. In the rabbit the heart normally beats rapidly, so that section of the vagi does not cause any great increase in the number of beats, nor is the lilood pressure much raised thereby. In the dog, on the other hand, the beats are considerably increased by section of the vagi, while the blood pressure rises considerably. Atropin paralyzes the cardiac terminations of the vagus, and thereby trebles the number of heart beats in the dog, while it only raises it 25 per cent, in the rabbit ; in man, again, the number may be doubled. As Burton has shown, this difference of the initial number of heart beats and the action of the vagus have important relations to the action of drugs on the blood pressure. For example, if an intact rabbit be caused to inhale amyl nitrite, the blood pressure falls at once and rapidly, while in the dog the fall may be slight. The pulse of the dog, however, is greatly accelerated, so much so as to be nearly as rapid as that of the rabbit. In both, the vessels are dilated, but in the dog, notwithstanding this dilatation, which per se would cause the pressure to fall, the heart of the dog beats now so rapidly as to compensate for this, and thus keep the blood pressure nearly normal ; while the increased rate of beating in the rabbit is not sufticient for this puqiose. If the vagi in the dog be divided, the subsequent inhalation of amyl nitrite causes a fall of blood pressure like that in the rabbit (Byttnton)^ [Relation of Blood Pressure to Pulse Rate. — When the blood pressure rises in an intact animal, as a rule the pulse rate falls, owing to stimulation of the vagus centre increasing the cardio-inhibitory action, while a fall of blood pressure is accompanied by an increase of the number of pulse beats, for the opposite rea- son, the action of the medullary cardio-inhibitory centre being increased. But the blood pressure may be increased either by the action of the heart or the arte- rioles. If we divide the vagi, the pulse beats more quickly, and in some animals the blood pressure rises ; in this case, the rise in the two curves occurs together, and if the vagi be stimulated there is a sudden fall of the blood pressure, due to arrest of the heart's action, so that again the two curves are parallel. If the arte- rioles contract, the blood pressure rises, but by and by the pulse rate falls, owing to the cardio-inhibitory action of the vagus ; while, on the other hand, if the arte- rioles are dilated, the blood pressure falls, and the heart beats faster. Thus, in both of these cases the jiulse curve and blood-pressure curve run in opposite direc- tions. These results only obtain when the vagi are intact (^Bninton).'\ For the effects of the nervous system upon the blood pressure, see " Vasomotor Centre" (\ 37')- Pathological. — In persons suflfering from granular or contracted kidney and sclerosis of the arteries, in lead poisoning, and after the injection of ergotin, which causes contraction of the small arteries, it is found, on employing the method of v. Basch, that the blood pressure is raised. It is also increased in cases of cardiac hypertrophy with dilatation, and by digitalis in cardiac affections, while it falls after the injection of morphia {Kristcller). The blood pressure falls in fever i^VVclzel), a fact also indicated in the sphygmograni \\ 69). In chlorosis and phthisis the blood pressure is low ( IValdenhiirg). BLOOD PRESSURE IN THE CAPILLARIES. 151 86. BLOOD PRESSURE IN THE CAPILLARIES.— Methods.— Direct estimation of the capillary pressure is not possible, on account of the smallness of the capillary tubes. If a glass plate of known dimensions be placed on a portion of the skin rich in blood vessels, and if it be weighted until the capillaries become pale, we obtain approximately the pressure necessary to over- come the capillary pressure. N. v. Kries placed a small glass plate (Figs. io6, 107) 2.5-5 ^1- mm., on a suitable part of the skin, eg., the skin at the root of the nail on the terminal phalanx, or on the eaf in man, and on the gum in rabbits. Into a scale pan attached to this, weights were placed until the skin became pale. The pressure in the capillaries of the hand, when the hand is raised, Kries found to be 24 mm. Hg. ; when the hand hangs down, 54 mm. Hg. ; in the ear, 20 mm.; and in the gum of a rabbit, 32 mm. [Roy and Graham Brown ascertained the hydrostatic pressure necessary to occlude the vessels in transparent parts placed under the microscope, e.g-., the web of a frog's foot, tongue or mesentery of a frog, the tails of newts and small fishes. The upper surface of the part to be investigated, t.g., the web of a frog's foot, is made just to touch a ihin glass plate. The under surface is in contact with a delicate transparent membrane covering the upper end of a small brass cylinder, whose lower end contains a piece of glass fitted air-tight into it. The interior of the brass cylinder communicates by means of a tube with an arrangement for obtaining any desired pressure, and the amount of the pressure is indicated by a manometer. Air pressure is used, and this is obtained by compressing a caoutchouc bag between two brass plates. The membrane to be investigated lies between two trans- parent media, an upper one of glass and a lower one of transparent membrane, on which the pres- sure acts. .\ny change in the vessels is observable by means of the microscope. These observers Fig. 106. Fig. 107. Apparatus used by v. Kries for estimating the capillary pressure — rt, the small square of glass. In Fig. 106 the scale pan for the weights is below, and in Fig. 107 above. conclude from their experiments that the capillaries are contractile, and that their contractility is, to all appearance, in constant action. The regulation of the peripheral blood stream is due not only to the cerebro-spinal vasomotor centres, but also to independent peripheral vasomotor mechanisms, which may be nervous in their nature, or are due to some direct action on the walls of the vessels (p. .15).] Conditions Influencing Capillary Pressure. — The intra-capillary blood pressure in a given area increases — ( i) When the afferent small arteries dilate. When they are dilated, the blood pressure within the large arteries is propagated more easily into them. (2) By increasing the pressure in the small afferent arte- ries. (3) By narrowing the diameter of the veins leading from the capillary area. Closure of the veins may quadruple the pressure (f. Kries). (4) By increasing the pressure in the veins, e.g., by altering the position of a limb). A diminution of the capillary pressure is caused by the opposite conditions. Changes in the diameter of the capillaries influence the internal pressure. We have to con- sider the movements of the capillary wall itself (protoplasm moveinents, Strieker — p. 115), as well as the pressure, swelling and consistence of the surrounding tissues. The resistance to the blood stream is greatest in the capillary area, and it is evident that the blood in a long capillary must exert more pressure at the commenceinent than at the end of the capillary ; in the middle of the capillary area the blood pressure is just about one-half of the pressure within the large arteries (Danders). 152 BLOOD PRESSURE IN THE VEINS. The capillar}' pressure must also vary in difl'erent parts of the body. Thus, the pressure within the intestinal capillaries, in those constituting the glomeruli of the kidney, and in those of lower limbs when the person is in the erect posture, must be greater than in other regions, depending, in the former cases, partly upon the double resistance caused by two sets of capillaries, and in the latter case partly on purely hydrostatic causes. 87. BLOOD PRESSURE IN THE VEINS.— In the large venous trunks near the heart ( innominate, subclavian, jugular ) a mean negative pressure of about — o. I mm. Hg. prevails {H. Jacohson). Hence, the lymph stream can flow unhindered. As the distance of the veins from the heart increases, there xs, 2. gradual increase of the lateral pressure ; in the external facial vein (sheep) = -|- 3 mm.; brachial, 4.1 mm., and in its branches 9 mm.; crural, 11. 4 mm. { Jac»6son). [The pressure is said to be negative when it is less than that of the atmosphere.] [The gradual fall of the blood pressure from the capillary area (C) to the venous area (V) is shown in Fig. 108, while within the thora.x, where the veins terminate in the right auricle, the pressure is negative.] Conditions Influencing the Venous Pressure. — (i) All conditions which diminish the difference of pressure between the arterial and venous systems increase the venous pressure, and vice versa. (2) General plethora of blood increases it ; anaemia diminishes it. (3) Respiration, or the aspiration of the thorax, affects specially the pressure in the veins near the heart ; during inspiration, owing to the diminished tension, blood flows toward the chest, while during expiration it is retarded. The effects are greater the deeper the respiratory movement, and these may be very great when the respiratory passages are closed (§ 60). [When a vein is exposed at the root of the neck, it collapses during inspiration, and fill" during expiration — a fact which was known to Valsalva. The respiratory movements do not affect the venous stream in peripheral veins. The veins of the neck and face become distended with blood during crying, and on making violent expiratory efibrts, as in blowing upon a wind instrument, while every surgeon is w ell acquainted with the fact that air is particularly apt to be sucked into the veins, especially in operations near the root of the neck. This is due to the negative intra-thoracic pressure occurring during inspiration.] (4) Aspiration of the Heart. — Blood is sucked or aspirated into the auricles when they dilate (p. 77), so that there is a double Fig. ioS. aspiration — one synchronous with inspiration, and the other, which is but slight, synclironous with the heart beat. There is a corresponding retarda- tion of the blood stream in the venae cavte, caused by the contraction of the auricle (see p. 75, a). The respiratory and cardiac undulations are occa- sionally observable in the jugular vein of a healthy ', person (§ 99). [Braune showed that the femoral vein under Poupart's ligament collapsed when the lower limb was rotated out- ward and backward, but filled again when the limb was restored to its former position. All the veins which open ,-'' into the femoral vein have valves, which permit blood to pass into the femoral vein, but prevent its reflux. This mechanism acts, to a slight degree, as a kind of suction and pressure apparatus when a ))erson walks, and thus favors the onward movement of the blood.] ^'''a'ridef ^''velSri, "neriaiV c\ (s) Changes in the position of the limbs or of capillary: and v, venous areas The the bodv, for hydrostatic reasons, greatlv alter circle indicates the parts within the tho- , ' ^ r,^, . r , i i ' rax: B. P., pressure in the aorta. the venous pressure. 1 he veuis oi the lower ex- tremity bear the greatest pressure, while, at the same time, they contain most muscle {K. Bardelehen, §65). Hence, when these muscles, from any cause, become insufficient, dilatations occur in the veins, giving rise to the iiroduction of varicose veins. BLOOD PRESSURE IX THE PULMONARY ARTERY. 153 [(6) Movements of the Voluntary Muscles. — Veins which lie between muscles are compressed when these muscles contract, and as valves exist in the veins, the flow of the blood is accelerated toward the heart ; if the outflow of blood be obstructed in any way, then the venous pressure on the distal side of the obstruc- tion may be greatly increased. When a fillet is tied on the upper arm, and the person moves the muscles of tlie forearm, the superficial veins become turgid, and can be distinctly traced on the surface of the limb.] [(7) G^/v/r/Vrexercises a greater effect upon the blood stream in the extensile veins than upon the stream in the arteries. It acts on the distribution of the blood, and thus indirectly on the motion of the blood stream. It favors the emptying of descending veins, and retards the emptying of ascending veins, so that the pressure becomes less in the former and greater in the latter. If the posi- tion of the limb be changed, the conditions of pressure are also altered {Pas- chutiii). If a person be suspended with the head hanging downward, the face soon becomes turgid, the position of the body favoring the inflow of blood through the arteries, and retarding the outflow through the veins. If the hand hangs down it contains more blood in the veins than if it is held for a short time over the head, when it becomes pale and bloodless. As Lister has shown, the condition of the vessels in the limb are influenced not only by the position of the limb, but also by the fact that a nervous mechanism is called into play.] [Ligature of the Portal Yein. — The pressure and other conditions vary in particular veins. Thus, if the portal vein be ligatured, there is congestion of the capillaries and rootlets of the portal vein, and dilatation of all the blood vessels in the abdomen, and gradually nearly all the blood of the animal accumulates within its belly, so that, paradoxical as it may seem, an animal may be bled into its own belly, .-^s a consequence of sudden and complete ligature of this vein, the arterial blnod pressure gradually and rapidly falls, and the animal dies very quickly. If the ligature be removed before the blood pressure falls too much, the animal may recover. [Schifif and Laulenbach regard the symptoms as due chiefly to the action of a poison, for when the blood of the portal vein in an animal treated in this way is injected into a frog, it causes death within a few hours, while the ordi- nary blood of the portal vein has no such effect.] Ligature of the Veins of a Limb. — The effect of ligaturing or compressing all the veins of a limb is well seen in cases where a bandage has been applied too tightly. It leads to congestion and increase of pressure within the veins and capillaries, increased transudation of fluid through the capil- laries, and consequent adema of the parts beyond the obstruction. Ligature of one vein does not always produce cedema, but if several veins of a limb be ligatured, and the vasomotor nerves be divided at the same time, the rapid production of cedema is ensured. In pathological cases the pressure of a tumor upon a large vein may produce similar results ( ^ 203).] 88. BLOOD PRESSURE IN THE PULMONARY ARTERY. — Methods. — (i) Direct estimation of the blood pressure in the pulmonary artery by opening the chest was made by C. Ludwig and Beutner ( 1850). Artificial respiration was kept up, and the manometer was placed in connection with the left branch of the pulmonary artery. The circulation through the left lung of cats and rabbits was thereby completely cut oft^, and in dogs to a great extent inter- rupted. There was an additional disturbing element, viz., the removal of the elastic force of the lungs owing to the opening of the chest, whereby the venous blood no longer flows normally into the right heart, while the right heart itself is under the full pressure of the atmosphere. The estimated pressure in the dog = 29.6; in the cat ^= 17.6; in the rabbit, 12 mm. Hg., /. e., in the dog 3 times, the rabbit 4 times, and the cat 5 times less than the carotid pressure. (2) Hering (1850) experimented upon a calf with ectopia cordis. He introduced glass tubes directly into the heart, by pushing them through the muscular walls of the ventricles. The blood ro.se to the height of 21 inches in the right tube, and 33.4 inches in the left (3) Chauveau and Faivre (1856) introduced a catheter through the jugular vein into the right ventricle, and placed it in connection with a recording tambour (p. 85). Indirect measurements have been made by comparing the relative thickness of the walls of the right and left ventricles, or the walls of the pulmonary artery and aorta, for there must be a re- lation between the pressure and the thickness of the muscle in the two cases. Ikutner and Marey estimated the relation of the pulmonary artery to the aortic pressure as i to 3 ; Goltz and Gaule as 2 to 5 ; Fick and Badoud found a pres- sure of 60 mm. in the pultnonary artery of the dog, and in the carotid 11 1 mm. Hg. The blood pressure within the pulmonary artery of a child is relatively iiigher than in the adult (Beneke). 154 IJLOOD PRESSURE IN THE rULMONARV ARTERY. Elastic Tension of Lungs. — The lungs within the chest are kept in a state of distention, owing to the fact that a negative pressure exists on their outer pleural surface. When the glottis is open, the inner surface of the lung and the walls of the capillaries in the pulmonary air vesicles are exposed to the full pressure of the air. The heart and the large blood vessels within the chest are not exposed to the full pressure of the atmosphere, but only to the pressure which corresponds to the atmospheric pressure minus the pressure exerted by the elastic traction of the lungs (§ 60'). The trunks of the pulmonary artery and veins are subjected to the same conditions of pressure. The elastic traction of the lungs is greater the more they are distended. The blood of the pulmonary capillaries will, therefore, tend to flow toward the large blood vessels. As the elastic traction of the lungs acts chiefly on the thin-walled pulmonary veins, while the semilunar valves of the pulmonary artery, as well as the systole of the right ventricle, prevent the blood from flowing backward, it follows that the blood in the capillaries of the lesser circulation must flow toward the pulmonary veins. If tubes with thin walls be placed in the walls of an elastic distensible bag, the lumen of these tubes changes according to the manner in which the bag enclosing them is distended. If the bag be directly inflated so as to increase the pressure within it, the lumen of the tubes is diminished (Funke and Latsihenberger). If the bag be placed within a closed space, and the tension within this space be diminished so that the bag thereby becomes distended, the tubes in its wall dilate. In the latter case — viz., by negative aspiration — the lungs are kept distended within the thorax, hence the blood vessels of the lungs containing air are wider than those of collapsed lungs (^Quincke am/ Pfa'ffer, BonhUtcli ami Garland, De Jdger). Hence also, more blood flows through the lungs distended within the thorax than through collapsed lungs. The dilatation which takes place during /«- spiration acts in a similar manner. The negative pressure that obtains within the lungs during inspiration causes a considerable dilatation of the pulmonary veins into which the blood of the lungs flows readily, while the blood under high pres- sure in the thick-walled pulmonary artery scarcely undergoes any alteration. The velocity of the blood stream m the pulmonary vessels is accelerated during inspi- ration ( De Jliger, Lalcsqiie. ) The blood pressure in the pulmonary circuit is raised when the lungs are inflated. Contraction of small arteries, which causes an increase of the blood pressure in the systemic circulation, also raises the pressure in the pulmonary circuit, because more blood flows to the right side of the heart (i\ Opcnclunuski). The vessels of the pulmonary circulation are very distensible and their tonus is slight. [Occlusion of one branch of the pulmonary artery does not raise the pressure within the aorta (.Beiitner). Even when one pulmonary artery is plugged with an embolon of paraffin, the pressure within the aortic system is not raised {Lichthcim). Thus, when a large branch of the pulmonary artery becomes im- pervious, the obstruction is rapidly compensated, and this is not due to the action of the nervous system. The vasomotor system has much less effect upon the pulmonary blood vessels than upon those of the systemic circulation (Badoiid, Hofmokl, Lichihelm). The compensation seems to be due chiefly to the great dis- tensibility and dilatation of the pulmonary vessels {Lichtheii?l).~\ We know little of the effect of physiological conditions upon the pulmonary artery. According to Lichtheim siispensian of the respiration causes an increase of the pressure. [In one experiment he found that pressure within the pulmonary artery was increased, while it was not increased in the carotid, and he regards this experiment as proving the existence of vasomotor nerves in the lung.] Morel found that electrical and mechanical stimulation of the abdominal organs caused a considerable rise of pressure in the pulmonary artery (dog). During the act of great straining, the blood at first flows rapidly out of the pulmonary veins and afterward ceases to flow, because the inflow of blood in the pulmonary vessels is interfered with. As soon as the straining ceases, blood flows rapidly into the pulmonary vessels [Lii/i-sqiie). MEASUREMENT OF THE VELOCITY OF THE BLOOD STREAM. 155 Severini found that the blood stream through the kings is greater and more rapid when the lungs are filled with air rich in CO, than when the air within them is rich in O. He supposes that these gases act upon the vascular ganglia within the lung, and thus affect the diameter of the vessels. Pathological. — Increase of the pressure within the area of the pulmonary artery occurs frequently in man, in certain cases of heart disease. In these cases the second pulmonary sound is always accentuated, while the elevation caused thereby in the cardiogram is always more marked and occurs earlier (? 52). [Action of Drugs. — The action of drugs on the pulmonary circulation may be tested by Holm- gren's apparatus, which permits of distention of the lung and retention of the normal circulation in the frog. Cold contracts the pulmonary capillaries to one-third of their diameter (Bninton), and anesthetics arrest the pulmonary circulation, chloroform being most and ether least active, while ethidene is intermediate in its effect [.^f Kendric/;^ Coats, A^eiiiffian).^ [Influence of the Nervous System. — The pulmonary circulation is much less dependent on the nervous system than the systemic circulation. Very con- siderable variations of the blood pressure within the other parts of the body may occur, while the pressure within the right heart and pulmonary artery is but slightly affected thereby. The pressure is increased by electrical stimulation of the me- dulla oblongata, and it falls when the medulla is destroyed. Section and stimula tion of the central or peripheral ends of the vagi, stimulation of the splanchnics, and of the central end of the sciatic, have but a minimal influence on the pressure of the pulmonary artery (Au/>ert).~\ 8g. MEASUREMENT OF THE VELOCITY OF THE BLOOD STREAM.— Methods: (i) A.V/ Volkmann's Hasmadromometer. — A glass tube of the .shape of a hair- pin, 60-130 cm. long and 2 or 3 mm. broad, with a scale etched on it, or attached to it, is fixed to a metallic basal plate, B, so that each limb passes to a stop-cock with three channels. The basal plate is perforated along its length, and carries at each end short cannula;, c, e, which are tied into the ends of a divided artery. The whole apparatus is first filled with water [or, better, with salt solu- tion]. The stop-cocks are moved simultaneously, as they are attached to a toothed wheel, and have at first the position given in Fig. 109, 1, so that the blood simply flows through the hole in the basal piece. I.e., directly from one end of the artery to the other. If at a given moment the stop-cock is turned in the direction indicated in Fig. 109, II, the blood has to pass through the glass tube, and the time it takes to make the circuit is noted, and as the length of the tube is known, we can easily calculate the velocity of the blood. Volkmann found the velocity to be in the carotid (dog) = 205 to 357 mm. ; carotid (horse) = 306 ; maxillary (horse) = 232 ; metatarsal =; 56 mm. per second. The method has very obvious defects arising from the narrowness of the tulie ; the introduction of such a tube offers new resistance, while there are no respiratory or pulse variations observable in the stream in the glass tube. (2) C. Ludwig and Dogiel (1867) devised a stromuhr or rheometer for measuring the amount of blood which passed through an artery in a given time (Fig. no). It consists of two glass bulbs, A and B, of exactly the same capacity. These bulbs communicate with each other above, their lower ends being fixed, by means of the tubes, t- and d, to the metal disk, f e^. This disk rotates round the axis, X Y, so that, after a complete revolution, the tube <" communicates with /, and ^/ with ^; y and ^'- are provided with horizontally placed cannula;, /i and/', which are tied into the ends of the divided artery. The cannula // is fixed in the central end, and /> in the peripheral end of the artery (^-.^if., carotid) ; the bulb. A, is filled with oil and B w'th defibrinated blood ; at a certain moment the communication through /; is opened, the blood flows in, driving the oil before it, and passes into B, while the defibrinated blood flows through I' into the peripheral part of the artery. As soon as the oil reaches m — a moment which is instantly noted, or, what is better, inscribed upon a revolving cylinder — the bulbs. A, B, are rotated upon the axis, X, Y, so that B comes to occupy the position of A. The same experiment is repeated, and can be continued for a long time. The quantity of blood which passes in the unit of time (i sec.) is calculated from the time necessary to fill the bulb with blood. Important results are obtained by means of this instrument. 156 MEASUREMENT OF THE VELOCITY OF THE BLOOD STREAM. [As peptone injected into the blood prevents it from coagulating (dog), this fact has been turned to account in using the rheometer.] Fig. no. Fig. 109. Volkmann's haemadromometer (B). I, blond flows from artery to artery; H, blood must pass through the glass tube of B ; c, c, cannulte for the divided Ludwig & Dogiel's stromuhr or rheometer- X, Y, axis of rotation; A, B, glass bulbs ; h, k, cannulx inserted in the di- vided artery ; e, e^, rotates on g,/: c. f iriia J iifJ! (3) Vierordt's Haematachometer (1858) consists of a small meta! l)ox ( Fig. in) vvitli parallel glass sides. To the narrow sides of the box are fitted an entrance, e, and an exit cannula, 11. In its interior is suspended, against the entrance opening, a pendulum,/, whose vibrations may be read off on a curved scale. [This instrument, as well as Volkmann's apparatus, have only an historical interest.] (4) Chauveau and Lortet's (Dromograph) (i860) is constructed on the same principle. A tube. A, B (Fig. 112) of sufficient diameter, with a side tube fixed to it, C, which can be placed in connection with a manometer, is introduced into the carotid arteiT of a horse. At « a small piece is cut out and provided with a covering of VELOCITY OF THE BLOOD IN THE BLOOD VESSELS. 157 gutta-percha which has a small hole in it; through this a light pendulum, a, h, with a long index, //, projects into the tube, ;. e., into the blood current, which causes the pendulum to vibrate, and the extent of the vibrations can be read off on a scale, S, S. G is an arrangement to permit the instru- ment to be held. Both this and the former instrument are tested beforehand with a stream of water sent through them with varying velocities. Fig, Dromograph. .-V, B, b, index moving i The curve of the velocity may be written off on a smoked glass, moving paral- lel with the index, b. The dromograph curve, III, shows the primary elevation, P, and the dicrotic elevation, R. 90. VELOCITY OF THE BLOOD IN ARTERIES, CAPIL- LARIES AND VEINS.^(i) Division of Vessels.— In estimating the velocity of the blood, it is imjiortant to remember that the sectional area of all the branches of the aorta becomes greater as we proceed from the aorta toward the capil- laries, so that the capillary area is 700 times greater than the sectional area of the aorta {Vierordt). As the veins join and form larger trunks, the venous area gradually be- comes smaller, but the sectional area of the venous orifices at the heart is greater than that of the corresponding arterial orifices. [This is shown in Fig. 113. We may repre- sent the result as two cones placed base to base, the bases meeting in the capillary area i^Kiiss). The sectional area of the venous orifice (V) is represented larger than that of the arterial (A). The increased sectional area influences the velocity of the blood current, while the resistance affects the pressure.] The common iliacs are an exception ; the sum of their sectional areas is less than that of the aorta; the sections of the four pulmonary veins are together less than that of the pulmonary artery. (2) Sectional Area. — An equal (juantity of blood must pass through every section of the circulatory system, through the pulmonic as well as through the 158 VELOCITY OF THE BLOOD IN THE BLOOD VESSELS. systemic circulation, so that the same amount of blood must pass through the pulmonary artery and aorta, notwithstanding the very unequal blood pressure in these two vessels. (3) Lumen. — The velocity of the current, therefore, in various sections of the vessels must be inversely as their lumen. (4) Capillaries. — Hence, the velocity must diminish very considerably as we pass from the root of the aorta and the pulmonary artery toward the capillaries, so that the velocity in the capillaries of mammals = 0.8 millimetre per sec. ; frog = 0.53 mm. (E. H. Wi-bt-r) ; man = 0.6 to 0.9 (C. //V/wvtV). According to A. W. Volkmann, the blood in mammalian capillaries flows 500 times slower than the blood in the aorta. Hence, on this view, the total sectional area of all the capillaries must be 500 times greater than that of the aorta. Bonders found the velocity of the stream in the small afferent arteries to be 10 times faster than in the capillaries. Veins. — The current becomes accelerated in the veins, but in the larger trunks it is 0.5 to 0.75 times less than in the corresponding arteries. (5) Mean Blood Pressure. — The velocity of the blood does not depend upon the wean blood pressure, so that it may be the same in congested and in anaemic parts {Volkmann, Hering). (6) Difference of Pressure. — On the other hand, the velocity in any sec- tion of a vessel is dependent on the difference of the pressure which exists at the commencement and at the end of that particular section of a blood vessel ; it depends, therefore, on (i) the vis a tcrgo (/. c, the action of the heart), and (2) on the amount of the resistance at the periphery (dilatation or contraction of the small vessels) (C. Ltuhvig and DogUl). Corresponding to the smaller difference in the arterial and venous pressure in the foetus (^ 85), the velocity of blood is less in this case [Cohnstein and Zuntz). (7) Pulsatory Acceleration. — -With t-wrj/wAc/^^fcz/a corresponding accelera- tion of the blood current (as well as of the blood pressure) takes place in the arteries (pp. 149, 156). In large vessels, Vierordt found the increase of the velocity during the systole to be greater by Y^ to Yz than the velocity during the diastole. The variations in the velocity caused by the heart beat are recorded in Fig. 112, obtained by Chauveau's dromograph from the carotid of a horse. The velocity curve corresponds with a sphygmogram — P represents the primary eleva- tion and R the dicrotic wave. This acceleration, as well as the pulse, disappears in the capillaries. A pulsatory acceleration, more rapid during its first phase, is observable in the small arteries, although these are not themselves distended thereby. (8) Respiratory Effect. — Every inspiration 7-etards the velocity in the arter- ies, every expiration aids it somewhat ; but the value of these agencies is very small. If we comp.ire wh.it has already been said regarding the effect of the respiration on the contrac- tion and dilatation of the heart and on the blood stream (| 60), it is clear that respiration favors the blood stream, so does artiticial respiration. When artificial respiration is interrupted, the blood stream becomes slower [Dogit'l). If the suspension of lespiration lasts somewhat longer, the current is again accelerated on account of the dyspnceic stimulation of the vasomotor centre (Heidenhain) (see Vasomotor Centre, \ 371, I). (9) Conditions Affecting Velocity in the Veins. — Many circumstances affect the velocity of the blood in the veins, (i) There are ;-(?s,7^ /a;- variations in the large veins near the heart ( Valsalini) due to the respiration and t)ie movements of the lieart (§ 50 and 60). (2) Ii-regular variations due to pressure, e. g., from contracting muscles (§ &■]), friction on the skin in the direction or against the direction of the venous current ; the position of a limb or of the body. The pump-like action of the veins of the groin on moving the leg has been referred to (§ 87). When the lower limb is e.xtended and rotated outward, the femoral WORK OF THE HEART. 159 vein in the iliac fossa collapses, owing to an internal negative pressure ; when the thigh is flexed and raised it fills, under a positive pressure {Braune). A similar condition obtains in walking. gi. ESTIMATION OF THE CAPACITY OF THE VENTRICLES.— Vierordt cal- culated the capacity of the left ventricle from the velocity of the blood stream, and the amount of b[ood discharged per second by the right carotid, right subclavian, the two coronary arteries, and the aorta below the origin of the innominate artery. He estimated that with every systole of the heart, 172 cubic centimetres (equal to 1S2 grammes or 6 oz- ) of blood was discharged into the aorta; this, therefore, must lie the capacity of the left ventricle (compare J 83). 92. THE DURATION OF THE CIRCULATION.— The question as to how long the blood takes to make a complete circuit through the course of the circulation was first answered by Hering ( 1S29) in the case of the horse. He injected a 2 percent, solution of potassium ferrocyanide into a special vein, and ascertained (by means of ferric chloride) when this substance appeared in the blood taken frotn the corresponding vein on the opposite side of the body. The ferrocyanide may also be injected into the central or cardiac end of the jugular vein, and the time noted at which its presence is detected in the blood of the peripheral end of the same vein. \'ierordt (1S58) improved this method by placing under the corresponding vein of the opposite side a rotating disk, on which was fixed a nutnber of cups at regular intervals. The first appearance of the potas- sium ferrocyanide is detected by adding ferric chloride to the serum, which separ- ates from the satnples of blood after they have stood for a time. The duration of the circulation is as follows : — Horse 31.5 seconds. I Hedgehog, 7,61 . . . seconds. I Duck 10.64 seconds. Dog 16.7 " Cat, 6.69 " Buzzard, . . . 6.73 Rabbit, . . . 7.79 " I Goose, 10.S6 " | Fowl, .... 5.17 " Results. — When these numbers are compared with the frequency of the normal pulse beat in the corresponding animals, the following deductions are obtained : (i) The mean time required for the circulation is accomplished during 27 heart beats, /. e., for man := 32.2 seconds, supposing the heart to beat 72 times per minute. (2) Generally, the mean time for the circulation in two warm-blooded animals is inversely as the frequency of the pulse beats. Conditions Influencing the Time. — The time is influenced by the follow- ing factors : 1. Long vascular channels {e.g., from the metarlarsal vein of one foot to the other foot) re- quire a longer time than short channels (as between the jugulars). The difference may be equal to 10 per cent, of the time required to complete the entire circuit. 2. In young animals (with shorter vascular channels and higher pulse rate) the time is shorter than in old animals. 3. Rapid and Energetic cardiac contractions (as during muscular exercise) diminish the time. Hence rapid and at the same time less energetic contractions (as after section of both vagi), and slow but vigorous systoles (c. g.., after slight stimulation of the vagus) have no eftcct. C. Vierordt estimated the quantity of blood in a man, in the following manner. In all warm- blooded animals, 27 systoles correspond to the lime for completing the circulation. Hence, the total mass of the blood must be equal to 27 times the capacity of the ventricle, /. e., in man, 187.5 grms. y 27 = 5062.5 grms. This is equal to yVy of the body weight in a person weighing 65. 8 kilos, (compare (i 49). It is not to be forgotten that the salt used is to some extent poisonous (p. 103), but Hermann uses the corresponding innocuous soda salt (25 per cent.). Pathological. — The duration of the circulation seems to be increased during septic fever (E. Wolff). 93. WORK OF THE HEART.— Johann .\lfons Borelli (1679) and JuHus Robert Mayer estimated the work done by the heart. The work of a motor is expressed in kilogramme metres, ;. e., the number of kilos, which the motor can raise in the unit of time to the height of i metre. The left ventricle expels 0.188 kilo, of blood {Volkmami) with each systole, and in doing so it overcomes the pressure in the aorta, which is equal to a column of blood 3.21 metres in height (Dojuirrs). [The amount of blood expelled from 160 BLOOD CURRENT IN THE SMALLEST VESSELS. each ventricle during the systole is about i8o grms. (6 oz. ). It is forced out against a pressure of 250 mm. Hg. = 3.21 metres of blood.] The work of the heart at each systole is 0.188 X 3-21 = 0.604 kilogramme metres. If the number of beats = 75 per minute, then the work of the left ventricle in 24 hours = (0.604 X 75 X 60 X 24) = 55>23o kilogramme metres. While the " work " done by the r^V// ventricle is about one-third that of the left, and therefore = 21,740 kilogramme metres. Both ventricles do work equal to 86,970 kilogramme metres. A workman during eight hours produces 300,000 kilogramme metres, /. e, about four times as much as the heart. As the whole of the work of the heart is con- sumed in overcoming the resistance within the circulation, or rather is converted into heat, the body must be partly warmed thereby (425.5 gramme metres are equal to i heat unit, /. e., the force required to raise 425.5 grammes to the height of I metre may be made to raise the temperature of i cubic centimetre of water 1° C.) So that 204,000 "heat units" are obtained from the transformation of the kinetic energy of the heart. One gramme of coal when burned yields 8080 heat units, so that the heart yields as much energy for heating the body as if about 25 grammes of coal were burned within it to produce heat. 94. BLOOD CURRENT IN THE SMALLER VESSELS.— Methods. — The most important observations for this purpose are made by means of the microscope on transparent parts of living animals. Malpighi was the first to observe the circulation in this way in the lung of a frog (1661). The following parts have been employed : The tails of tadpoles and small fishes ; the web, tongue, mesentery, and lungs of curarized (rogs{Co-u'/>e'r, /■/04]; the wing of the bat, the third eye- lid of the pigeon or fowl ; the mesentery- ; the vessels of the liver of frogs and newts ( Gniithiiiscn), of the pia mater of rabbits, of the skin on the belly of the frog, of the mucous membrane of the inner surface of the human lip (Hiilei-'s Cheilangioscope, 1S79) ; of the conjunctiva of the eyeball and eyelids. .Ml these may be examined by rrjlecli'ii Wghl. [Holmgren's Method. — In studying the circulation in the frog's lung, it must be inflated. A cannula with a bulge on its free end is placed in the larynx, while to the other end is fixed a piece of caoutchouc tubing. The lung is inflated and then the caoutchouc tube is closed, after which the lung is placed in a chamber with glass above and below, and examined microscopically.] [Entoptical appearances of the circulation (Purkinje, iS/j). Under certain conditions a person may detect the movement of the blood corpuscles w'ithin the blood vessels of his own eye. The best methori is that of Rood, viz., to look at the sky through a dark -blue glass, or through sev- eral pieces of cobalt glass placed over each other {^HeImholiz).'\ Form and Arrangement of Capillaries. — Regarding the form and arrangement of the capillaries, we find that : — 1. The diameter, which in the finest permits only the passage of single corpuscles in a row — one behind the other — may vary from 5 /i to 2 11., so that two or more corpuscles may move abreast when the capillary is at its widest. 2. The length is about 0.5 mm. They terminate in small veins. 3. The number is very variable, and the capillaries are most numerous in those tissues where the metabolism is most active, as in lungs, liver, muscles— less numerous in the sclerotic and in the nerve trunks. 4. They form numerous anastomoses, and give rise to networks, whose form and arrangement are largely determined by the arrangement of the tissue elements themselves. Tliey form simple loops in the skin, and polygonal networks in the serous membranes, and on the surface of many gland tubes; they occur in the form of elongated networks, with short connecting branches in muscle and nerve, as well as between the straight tubules of the kidney ; they converge radially toward a central point in the lobules of the liver, and form arches in the free margins of the iris, and on the limit of the sclerotic and cornea. [A great contrast as to the vascularity of two adjacent parts is seen in the gray and white matter of the brain, the former being very vascular, the latter but slightly so.] [Direct termination of Arteries in Veins. — .Arteries sometimes terminate directly in veins, without the intervention of capillaries, i'.<,'., in the ear of the rabbit, in the terminal phalanges (jf the fingers and toes in man and some animals, in the cavernous tissue of the penis {^Hoyer). They may be regarded as secondary channels which protect the circulation of adjacent parts, and they m.ay also be related to the heat-regulating mechanisms of peripheral parts (//.yw).] End Arteries. — In connection with the termination of arteries in capillaries, it is important to ascertain if the arterioles are " end or terminal arteries,'' i. e., if they do not form any fur- CAPILLARY CIRCULATION. 161 ther anastomoses with other similar arterioles, but terminate directly in capillaries, and thus only communicate by capillaries with neighboring arterioles — or the arteries may anastomose with other arteries just before they break up into capillaries. This distinction is important in connection with the nutrition of parts supplied by such arteries (Co/inkeim). Capillary Circulation. — On observing the capillary circulation, we notice th^t the red corpuscles move only in the axis of the current (axial current), while the lateral transparent plasma current flowing on each side of this central thread is free from these corpuscles. [The axial current is the more rapid.] This plasma layer or " Poiseuille's space " is seen in the smallest arteries and veins, where I is taken up with the axial current, and the plasma layer occupies ^ on each side of it (Fig. 114). A great many, but not all, of the colorless corpuscles run in this layer. It is much less distinct in the capillaries. Rud. Wagner stated that it is absent in the finest vessels of the lung and gills [although Gunning was unable to confirm this statement.] The colored corpuscles move in the smallest capillaries in single Jilc, one after the other ; in the larger vessels several corpuscles may move abreast, with a _f/;V//«^'- motion, and in their course they may turn over and even be twisted if any obstruction is offered to the blood stream. As a general rule, in these vessels the movement is uniform, but at a sharp bend of the vessel it may partly be retarded and partly accelerated. Where a vessel divides, not unfre- quently a corpuscle remains upon the projecting angle of the division, and is doubled over it so that its ends project into the two branches of the tube. There it may remain for a time, until it is dislodged, when it soon regains its original form, on account of its elasticity. Not unfrequently we see a red corpuscle becom- ing bent where two vessels meet, but on all occasions it rapidly regains its original form. This is a good proof of the elasticity of the colored corpuscles. Colorless Corpuscles. — The motion of the colorless corpuscles is quite dif- ferent in character ; they /-('// directly on the vascular juall, moistened on their peripheral zone by the plasma in Poiseuille's space, their other surface being in contact with the thread of colored corpuscles in the centre of the stream. Schklarewsky has shown by physical experiments, that the particles of least spe- cific gravity in all capillaries {e.g., of glass) are pressed toward the wall, while those of greater specific gravity remain in the middle of the stream. [Graphite and particles of carmine were suspended in water, and caused to circulate through capillary tubes placed under a microscope, when the graphite kept the centre of the stream, and the carmine moved in the layer next the wall of the tube.] When the colorless corpuscles reach the wall of the vessel, they must roll along, partly on account of their surface being sticky, whereby they readily adhere to the vessel, and partly because one surface is directed toward the axis of the vessel where the movement is most rapid, and where they receive impulses directly from the rapidly moving colored blood corpuscles {Doiulers). The rolling motion is not always uniform; not unfrequently it is retrograde in direction, which seems to be due to an irregular adhesion to the vascular wall. Their slower movement (10 to 12 times slower than the red corpuscles) is partly due to their stickiness, and partly to the fact that as they are placed near the wall, a large part of their surface lies in the peripheral threads of the fluid, which, of course, move more slowly (in fact the layer of fluid next the wall is passive — p. 109). [D. J. Hamilton finds that, when a frog's web is examined in a vertical posi- tion, by far the greater proportion of leucocytes float on the upper surface, and only a few on the lower surface, of a small blood vessel. In experiments to deter- mine why the colored corpuscles float or glide exclusively in the axial stream, while a great many, but not all, of the leucocytes roll in the peripheral layers, Hamilton ascertained that the nearer the suspended body approaches to the spe- cific gravity of the liquid in which it is immersed, the more it tends to occupy the centre of the stream. He is of opinion that the phenomenon of the separa- tion of the blood corpuscles in the circulating fluid is due to the colorless cor- puscles being specifically lighter, and the colored either of the same or of 162 DIAPEDESIS. very slightly greater specific gravity than the blood plasma. Hamilton contro- verts the statement of Schklarewsky, and he finds that it is the relative specific gravity of a bod\» which ultimately determines its position in a tube. These experiments point to the immense importance of a due relation subsisting between the specific gravity of the blood plasma and that of the corpuscles.] In the vessels first formed in the incubated egg, as well as in those of young tadpoles, the move- ment of the blood from the heart occurs in jerks (Spa//amani, jy6S). The velocity of the blood stream is influenced by the diameter of the vessels, which undergo periodic changes of calibre. This change occurs not only in vessels provided with muscular fibres, but also in the capillaries, which vary in diameter, owing to the contraction of the cells composing their walls (p. 115). The amount of water in the blood is of importance, as when it is mcreased the circulation is facilitated and accelerated ( C. A. En'ald ] (% 62). The velocity of the blood is greater in the pulmonary than in the systemic capillaries {Hales, 172J) ; hence, we must conclude that the total sectional area of the pulmonary capillaries is less than that of all the systemic capillaries. 95. PASSAGE OF THE BLOOD CORPUSCLES OUT OF THE VESSELS— DIAPEDESIS. — Diapedesis. — If the circulation be studied in the vessels of the mesentery, we may observe colorless corpuscles passing out of the vessels in greater or less numbers (Fig. 114). The mere contact with the air suffices to excite slight inflammation. At first, the colorless cor- puscles in the plasma space move more slowly ; several accumulate near each other, and adhere to the walls — soon they bore into the wall ; ultimately they pass quite through it, and may wander for a distance into the perivascular tissues. It is doubtful whether they pass through the so-called " stomata " which exist between the endothelial cells, or whether they simply pass through the cement substance between the endothelial cells (p. 113). This process is called Diapedesis, and consists of several acts : ( <7) The adhesion of lymph cells or colorless corpuscles to the inner surface of the vessel (after moving more slowly along the wall up to this point). (/>) They send processes into and through the vascular wall. 1 c) The body of the cell is drawn after or follows the processes, whereby the corpuscle appears constricted in the centre (Fig. 114, c). (d) The complete passage of the corpuscle through the wall, and its further motion in virtue of its own amceboid movements. 1 Hering observed that in large vessels with peri- vascular lymph spaces, the corpuscles passed into these latter, hence, cells are found in lymph before it has passed through lymphatic glands. The cause of the diapedesis is partly due to the inde- pendent locomotion of the corpuscles, and it is partly a physical act, viz., a filtration of the colloid mass of the cell under the force of the blood pressure {Hering) — in the latter respect depending upon the intravascular pressure and the velocity of the blood stream. Hering regards this process, and even the passage of the colored corpuscles diapedesis of the colorlesi corpuscles. »., -u.T vas- through the vascular wall, as a normal process, cular walls ; a, a, Poiseuille's space ; r, r, red cor- The red corpuscles pass out of the vessels when puscles; /, /, colorless corpuscles adhering to the the venous outtlow is obstructed, which also causes g . j'jt ^]^g transudation of plasma through the vascular wall. Tlie plasma carries the colored corpuscles along with it, and at the moment of their passage through the wall they assume extraordinary shapes, owing to the tension put upon them, regaining their shape as soon as they pass out (Coiin- heim'). This remarkable phenomenon was described by Waller in 1846. It was recently redescribed by Cohnheim, and according to him the oiit- wandering is a sign of inflammation, and the colorless cor- puscles which accumulate in the tissues are to be regarded as pus corpuscles, which may undergo further increase by division. Stasis. — When a strong stimulus acts on a vascular part, hyjiera^mic redness and swelting occur. Microscopic observation shows that the capillaries and the small vessels are dilated and overfilled with blood corpuscles; in some cases a temporary naiTowing precedes the dilatation; simultaneously the velocity of the stream changes; rarely there is a temporary acceleration, more frequently it he- eotnes slo7i'er. If the action of the stimulus or irritant be continued, the retardation becomes con- FlG. 114. Small vessel of the enterj' of a frog, showing the tided corpuscles. MOVEMENT OF THE BLOOD IN THE VEINS. 163 siderable, the stream moves in jerks, then follows a to and fro movement of the blood column — a sign that stagnation has taken place in other vascular areas. At last, the blood stream comes completely to a standstill — stasis — and the blood vessels are plugged with blood corpuscles. Numerous colorless blood corpuscles are found in the stationary blood. While these various processes are taking place, the colorless coq:iuscles — more rarely the red — pass out of the vessels. Under favorable circumstances the stasis may disappear. The swelling which occurs in the neigh- l*rhood of inllamed parts is chiefly due to the exudation of plasma into the surrounding tissues. [The vapor of chloroform causes hyperajmia of the web {L:s/c-r).] 96. MOVEMENT OF THE BLOOD IN THE VEINS.— As already mentioned, in the smallest veins coming from tlie capillaries the blood stream is more rapid than in the capillaries themselves, but less so than in the correspond- ing arteries. The stream is uniform, and if no other conditions interfered with it, the venous stream toward the heart ought to be uniform, but many circum- stances affect the stream in different parts of its course. Among these are: (i) The relative /axncss, great distensihility and the ready compressibility of the walls, even of the thickest veins. (2) The incompleti' filling oi the veins, which does not amount to any considerable distention of their walls. (3) The numerous and free anastomoses between adjoining veins, not only between veins lying in the same plane, but also between superficial and deep veins. Hence, if the course of the blood be obstructed in one direction, it readily finds another outlet. (4) The presence of numerous valves, which permit the blood stream to move only in a centripetal direction (Fabricius ah Ai/iiapenile>ile). They are absent from the smallest veins, and are most numerous in those of middle size. Law of the Position of Valves. — The venous valves always have two pouches, and are placed at definite intervals, which correspond to the i, 2, 3, or n"" power of a certain " fundamental dis- tance," which is = 7 mm. for the lower extremity and 5.5 mm. for the upper. Many of the origi- nal valves disappear. On the proximal side of every valve a lateral branch opens into the vein, while on the distal side of each branch lies a valve. The same is true for the lymphatics (A". Banlc-Mn-,i). Effect of Pressure. — As soon as pressure is applied to the veins, the ne.\t lowest valves close, and those immediately above the seat of pressure open and allow the blood to move freely toward the heart. The pressure may be exerted from without, as by anything placed against the body ; the thickened contracted muscles, especially the muscles of the limbs, compress the veins. That the blood flows out of a divided vein more rapidly when the muscles contract, is shown during venesection. If the muscles are kept contracted, the venous blood passing out of the muscles collects in the passive parts, e. g., in the cutaneous veins. The pulsatile pressure of the arteries accompanying the veins favors the venous current iOzanam). From a hydrostatic point of view, the valves are of considerable importance, as they serve to divide the column of blood into •segments {e. g., in the crural vein in the erect attitude), so that the fine blood vessels in the foot are not subjected to the whole amount of the hydrostatic pressure in the veins. The velocity of the venous blood has been measured directly (with the hsemadromometer and the stromuhr — ^Sg). Volkmann found it to be 225 ram. per sec. in the jugular vein. Reil ob- served that 2 '.< times more blood flowed from an arterial orifice than from a venous orifice of the same size. The velocity of the venous current obviously depends upon the sectional area of the vessel. liorelli estimated the capacity of the venous system to be 4 times greater than that of the arterial; while, according to Haller, the ratio is 9 to 4. Large Veins. — As we proceed from the small veins toward the venK cavre, the sectional area of the veins, taken as a whole, becomes less, so that the velocity of the current increases in the same ratio. The velocity of the current in the venae cavK may lie about half of that in the aorta {Nailer'). As the pulmonary veins are narrower than the pulmonary artery, the blood moves more rapidly in the former. [Active pulsation occurs in the veins of the wing of the bat {Sc/iiff).~\ 164 VENOUS MURMURS. 97. SOUNDS OF BRUITS WITHIN ARTERIES.— These murmurs, sounds or bruits occur either .t/iiH/aHew«,r/i', or are produced by the a/'p/ica/ion of external pressuye,v/hexthy \hs lumen of the vessel is diminished. In four-tirths of all healthy men, two sounds — corresponding in duration and other characters to the two heart sounds — are heard in the carotid (Conrad, IFei/). Sometimes only the second heart sound is distinguishable, as its place of origin is near to the carotid. They are not true arterial sounds, but are simply "propagated heart sounds." Arterial Sounds or murmurs are readily produced by pressing upon a strong artery, r.g., the crural in the inguinal region, so as to leave only a narrow passage for the blood ("stenosal murmur"). A fine blood stream passes with great rapidity and force through this narrow part into a wider portion of the artery lying behind the point of compression. Thus arises the " pressure stream " (/". JVta/ii'yer), or the " fluid vein " ('• Veine fluide " of Chauveau). The particles of the fluid are thrown into rapid pscillation, and undergo vibratorv movements, and by their movements produce the sound within the peripheral dilated portion of the tube. A sound is produced in the fluid by pressure \Corrigan, Heynsius). The sounds are not caused by vibrations of the vascular wall, as supposed by Bouillaud. A murmur of this sort is the "sub-clavicular murmur " (j?m«), occasionally heard during systole in the subclavian artery ; it occurs when the two layers of the pleura adhere to the apex of the lung (especially in tubercular diseases of the lungs), whereby the subclavian artery undergoes a local constriction due to its being made tense and slightly curved (Friedreich). This result is indi- cated in a diminution or absence of the pulse wave in the radial artery ( Weil). Arterial murmurs are favored by — (i) Sufficient delicacy and elasticity of the arterial walls (Th. Weber). (2) Diminished peripheral resistance, e.g., an easy outflow of the fluid at the end of the stream {KhviscJi). (3) Accelerated current in the vascular system generally. (4) \ considerable difference of the pressure in the narrow and wide portions of the tube i^Marey). (5) Large calibre of the arteries. It is obvious that arterial murmurs will occur in the human body — (a) When, owing to patho- logical conditions, the arterial tube is dilated at one part, into which the blood current is forcibly poured from the normal narrow tube. Dilatations of this sort are called aneurisms, within which murmurs are generally audible. (b\ When pressure is exerted tipon an artery, c'. ^j,""., by the pressure of the greatly enlarged arteries during pregnancy, or by a large tumor pressing upon a large artery. (<■) A murmur corresponding to each pulse beat is heard, especially where two or more large arteries lie together; hence, during pregnancy, we hear the uterine murmur, or placental bruit, or souffle in the greatly dilated utenne arteries. It is much less distinct in the umbilical arteries of the cord (umbilical murmurs). Similar sounds are heard through the thin walls of the head of infants (Fisher, jSjj). -A. murmur due to the systole of the heart is often he;ird in the carotid (Jurasz). In such cases where no source of external pressure is discoverable, and when no aneurism is present, the spontaneously occurring sounds are favored, when at the moment of arterial rest (cardiac systole) the arterial walls are distended to the slightest extent, and when during the movement of the pulse (cardiac diastole) the tension is most rapid ( Traube, U'eil), i. e., when the low systolic minimum^ tension of the arterial wall passes rapidly into the high maximum tension. This is especially the case in insufficiency of the aortic valves, in which case the sounds in the arteries are audible over a wide area. If the minimum tension of the arterial wall is relatively great, even during diastole, the sounds in the arteries are greatly diminished. In insufficiency of the aortic valves, characteristic sounds may be heard in the crural artery. If pressure be exerted upon the artery, a double blowing murmur is heard ; the first one is due to a large mass of blood being propelled into the artery synchronously with the heart heat, the second to the fact that a large quantity of blood flows back into the heart during di.astole (Duroziez, iSb/). If no pressure be exercised two sounds are heard, and these seem to be due to a wave propagated into the arteries by the auricles and ventricles respectively (Landois) — compare § 73, Fig. 86, III. In atheroma a double sound may sometimes be heard (ii 73, 2). 98. VENOUS MURMURS.— I. Bruit de Diable.— This sound is heard above the clavicles, in the furrow between the two heads of the sterno- mastoid, most frequently on the right side, and in 40 per cent, of all persons examined. It is either a continuous or a rhythmical murmur, occurring during the diastole of the heart or during inspiration ; it has a whistling or rushing character, or even a musical quality, and arises within the bulb of the common jugular vein. THE VENOUS PULSE. 165 When this sound is heard without pressure being exerted by the stethoscope, it is a pathological phenomenon. If, however, pressure be exerted, and if, at the same time, the person examined turns his head to the opposite side, a similar sound is heard in nearly all cases (JFt-//). The pathological dn/Zf de dia/>le occuk especially in anajmic persons, in lead poisoning, syphilitic and scrofulous persons, ^metimes in young persons, and less frequently in elderly people. Sometimes a thrill oi the vascular wall may be felt. Causes. — It is due to the vibration of the blood flowing in from the relatively narrow part of the common jugular vein into the wide bulbous portion of the vessel, and seems to occur chiefly when the walls of a thin part of the vein lie close to each other, so that the current must purl through it. It is clear that pres- sure from without, or lateral pressure, as by turning the head to the opposite side, must favor its occurrence. Its intensity will be increased when the velocity of the stream is increased, hence inspiration and the diastolic action of the heart < both of which assist the venous current) increase it. The erect attitude acts in a similar manner. A similar bruit is sometimes, though rarely, heard in the subclavian, axillary, thyroid (scrofula), facial, innominate and crural veins and superior cava. II. Regurgitant Murmurs. — On making a sudden effort, a murmur maybe heard in the crural vem during expiration, which is caused by a centrifugal current of blood, owing to the incompetence or absence of the valves in this region. If the valves at the jugular bulb are not tight, there may be a bruit with expiration [expiratory jugular vein bruit — ffamernjk), or during the cardiac systole (jtrj/fl/;V jugular vein bruit — v. Bamberger). III. Valvular Sounds in Veins. — When the tricuspid valve is incompetent, during the ventri- cular systole a large volume of blood is propelled backward into the venn; cava;. The venous valves are closed suddenly thereby and a sound produced. This occurs at the bulb or dilatation on the jugular vein (:■. Bamberger), and in the crural vein at the groin [jV. Freidreich), i. e., only as long as the valves are competent. Forced expiration may cause a valvular sound in the crural vein. IS'o sound is heard in the veins under perfectly normal circumstances. 99. THE VENOUS PULSE— PHLEBOGRAM. -Methods.— A tracing of the move- ments of a vein, taken with a lightly-weighted sphygmograph, has a characteristic form, and is called a phlebogram (Fig. 1 15 1. In order to interpret the various events of the phlebogiam it is most important to record simultaneously the event that takes place in the heart. The auricular contraction (compare Fig. 41 ) is synchronous with a b ; b e, with the ventricular systole, during which time the first sound occurs, while (7 1^ is a presystolic movement. The carotid pulse coincides nearly with the apex of the cardiogram, /. e., almost simultaneously with the descending limb of the phle- bogram (Hiegel). Occasionally in healthy individuals a ptilsatile movement, synchronous with the action of the heart, may be observed in the common jugular vein. It is either confined to the lower part of the vein, the so-called bulb, or extends further up along the trunk of the vein. In the latter case, the valves above the bulb are insufficient, which is by no means rare, even in health. The wave motion passes from below upward, and is most obvious when the person is in the passive hori- zontal position, and it is more frequent on the right side, because the right vein lies nearer the heart than the left. The venous pulse resembles very closely the tracing of the cardiac impulse {Landois). Compare Fig. 115, i, with Fig. 32. It is obvious that, as the jugular vein is in direct communication with the right auricle, and as the pressure within it is low, the systole of the right auricle must cause a positive wave to be propagated toward the peripheral end of the jugular vein. Fig. 115, 9 and 10, are venous pulse tracings of a healthy person with insufficiency of the valves of the jugular vein. In these curves, the part a, l> corresponds to the contraction of the auricle. Occasionally this part consists of two elevations, corresponding to the contraction of the atrium and auricle respectively. As the blood in the right auricle receives an impulse from the sudden tension of the triscupid valve synclironoits -with the systole of the right ventricle, there is a positive wave in the jugular vein in Fig. 115, 9 and 10, indi- cated by /'. e. Lastly, the sudden closure of the pulmonary valves may even be 166 THE VENOUS PULSE. indicated (c). As the aorta lies in direct relation with the pulmonary artery, the sudden closure of its valves may also be indicated (Fig. 115, 9, at if). During the diastole of the auricle and ventricle, blood flows into the heart, so that the vein partly collapses and the lever of the recording instrument descends {Rifgel, Francois- Franck ) . Sinus and Retinal Pulse. — The blood in the sinuses of the drain also undergoes a pulsatile movement, owing to the fact that during cardiac diastole much blood flows into the veins (Mosso). I'nder favorable circumstances, this movement may be propagated into the veins of the retina, con- stituting the vaiotis retinal pulse of the older observers [Helfreich). Jugular Vein Pulse. — The venous pulse in the jugular vein is far better marked in insufficiency of the tricuspid valve, and the vein may pulsate violently, but if its valves be perfect the pulse is not propagated along the vein, so that <; pulse in the jugular vein is not necessarily a sign of insuffi- ciency of the tricuspid valve, but only of insulificiency of the valve of the jugular vein (Friedreich). Liver Pulse. — The ventricular systole is propagated into the valveless inferior vena cava, and Fig. 115. rious forms of venous pulses, chiefly after Friedreich — i-S from insufficiency of the tricuspid ; 9 and ic, pulse ot the jugular vein of a healthy person. In all the curves, a, b ^ contraction of the right auricle ; b, c, of the right ventricle ; d, closure of the aortic valves ; e, closure of the pulmonary valves : e,_f, diastole of the right ventricle. causes the liver pulse. With each systole blood passes into the hepatic veins, so that the liver undergoes a systolic swelling and injection. Fig. 115, 2-8, are curves of the pulse in the common jugular vein (after Friedreich). Although at first sight the curves appear to be very different, they all agree in this, that the various events occurring in the heart during a cardiac revolution are indicated more or less completely. In all the curves, a, b = auricular contraction. The auricle, when it contracts, excites a positive wave in the veins [Gendrin (/S4J), Marey, Friedreich). The elevation, l\ c, is caused by the large blood wave produced in the veins, owing to the emptying of the ventricle. It is always greater, of course, in insufficiency of the tricuspid valves than under noniial circumstances (Fig. 115, 9 and 10). In the latter case, the closure of the tricuspid valve causes only a slight wave motion in the auricle. The apex, c, of this wave may be higher or lower, according to the tension in the vein and the pressure exerted by the sphygmograph. As a general rule, at least one notcli (4, 5, 6, e) follows the apex, due to the prompt closure of the valves of the pulmonary artery. The closure of the closely adjacent aortic valves may cause a small secondary wave near to e (as in i and 2, d). The curve fails towardy, corresponding to the diastole of the heart. A well-marked venous pulse occurs when the right auricle is greatly congested, as in cases of insufiiciency of the mitral valve or stenosis of the same orifice. In rare cases, in addition to the PLETHYSMOGRAPHY. 167 pulse in the common jugular vein, the external jugular, the facial, thyroid, external thoracic veins, or even the veins of the upper and lower extremities may pulsate. A similar pulsation must occur in the pulmonary veins in mitral insufficiency, but, of course, the result is not visible. On rare occasions, a pulse occurs in the veins on the back of the hand and foot, owing to the arterial pulse being propagated through the capillaries into the veins. This may occur under normal circumstances, when the peripheral ends of the arteries become dilated and relaxed (Quinike), or when the blood pressure within these vessels rises rapidly and falls as suddenly, as in insufficiency of the aortic valves. \n\>xog!ess\ve effusion iiilo t/w pi-ricardiiim, At first the carotid pulse becomes smaller and the venous pulse larger; beyond a certain pressure, the latter ceases (I^iegel). IOC. DISTRIBUTION OF THE BLOOD.— Methods.— The methods adopted do not give exact results. J. Ranke ligatured the parts during life, removed them, and investigated the amount of blood while the tissues were still warm. In the rabbit, one-fourth of the total amount of the blood is found in each of the following : (7, in the passive muscles ; />, in the liver ; c, in the organs of the circulation (heart and great vessels) ; P^"" cent. of blood might be transfused into the vascular system of an animal without pro- ducing any injurious effects. Hence it follows that the vascular system has the power of accommodating large quantities of blood within it. That the vascular system can accommodate itself to a diminished amount of blood has been known for a long time (§ 85, c). [It is very important to observe that the transfusion of a large quantity of blood does not materially or permanently raise the blood pressure.] ■When Employed. — The transfusion of blood is used — (i) in acute anaemia (§41. I), e.g., after copious hemorrhage. New blood from the same species ot animal is introduced directly into the vessels, to supply the place of the blood lost by the hemorrhage. (2) In cases of poisoning, where the blood has been rendered useless by being mixed with a poisonous substance, and hence is unable to support life. In such cases, remove a considerable quantity of the blood, and replace it by fresh blood. Carbonic oxide is a poison of this kind (Kiihne), and its effects on the body have already been described (§ 16). A similar practice is indicated on poisoning with ether, chloral, chloroform, opium, morphia, strychnine, cobra poison and such substances as dissolve the blood corpuscles, e.g., potassic chlorate. (3) Under certain pathological conditions, the blood may become so altered in quality as to be unable to support life. The morphological elements of the blood may be altered, and so may the relative proportion of its other constituents. Among these conditions may be cited the pathological condition of uraemia, due, it may be, to the accumulation of urea or the products of its decomposition within the blood [or to the retention of the potash and other urinary salts (Feliz and Ritter)'\ ; accumulation of the biliary constituents in the blood (Cholsemia), and great increase of the carbonic acid. All these three conditions, when very pro- nounced, may cause death. In these cases, part of the impure blood may be replaced by normal human blood (Landois). Among conditions where the morplwlogical constituents of the blood are altered qualitatively or quantitatively are : hydrsemia (excessive amount of water in the blood, § 41, i) ; oligocythasmia (abnormal diminution of red corpuscles). When these conditions are highly developed, more especially in pernicious anaemia (§ 10, 2), healthy blood may be substituted. Transfusion is not suited for persons suffering from leukaemia (compare p. 33). After Effects. — A quarter or half an hour after normal blood has been injected into the blood vessels of a man, there is a greater or \ti% febrile reaction, according to the amount of blood transfused (Fever, § 220). Operation. — The operative procedure to -be adopted in the process of transfusion varies according as defibrinated or non-de6brinated blood is used. In order to defibrinate blood, some blood is withdrawn from the vein of a healthy man in tlie ordinary way ; it is collected in an open vessel 170 TRANSFUSION OF BLOOD. and whipped or beaten with a glass rod until all the fibrin is completely removed from it. It is then filtered through an atlas filter, Seated to the temperature of the body (by placing it in warm water), and injected, by means of a syringe, into an artery opened for the purpose. .\ vein (t'. ^j,'., basilic or great saphenous) may be selected for the transfusion, in which case the blood is driven in in the direction of the heart; if an artery is selected (radial or posterior tibial), the blood is injected toward the periphery [Hii/er) or toward the heart [Landois, ScAafir). Dangers. — It is most important not to permit the entrance of air into the circulation, for if it be introduced in sufficient quantity, it may cause death. When air enters the circulation it reaches the right side of the heart, where, ow'ing to the movement of the blood, it forms air bubbles and makes a froth. The air bubbles are pumped into the branches of the pulmonary artery, in which they be- come impacted, arrest the pulmonary circulation, and rapidly cause death. If non-defibrinated human blood is used, the blood maybe passed diredly from the arm of the giver to the arm of the receiver by means of a flexible tube. The tube used must be filled with normal saline solution to prevent the entrance of air. [J. Duncan collects the blood shed during an operation in a 5 per cent. soKuion of sodic phosphate (/'(?-^i'),and injects the mixture, especially where much blood has been lost previously.] Peritoneal Transfusion. — Recently, the injection of defibrinated blood into the peritoneal cavity has been recommended. The blood so injected is absorbed (Ponfick). Even after twenty minutes the inmiber of blood corpuscles in the blood of the recipient (rabbit) is increased, and the number is greatest on the first or second day (Bizzozero and Goigi). The operation, however, may cause death, and one fatal case, owing to peritonitis, is recorded (Mosier). It is evident that this method of transfusion is not applicable in cases where blood must be introduced into the circulation as rapidly as possible (e. g., after severe hemorrhage or in certain cases of poisoning). [Blood has been injected into the subcutaneous cellular tissue of the abdomen in ca.ses of great debility]. Heterogeneous Blood. — Tin- Hood of animals ought never to be transfused into the blood ves- sels of man. Some surgeons have transfused blood directly from the carotid of a lamb into the human subject. It is to be remembtred, however, that the blood corpuscles of the sheep are rapidly dissolved by human blood, so that the active constituents of the blood are rendered useless (Lan- dois). As a general rule, the blood serum of some mammals dissolves the blood corpuscles of other mammals (^ 5' 5)- Solution of the Blood Corpuscles. — The serum of dog's blood is a powerful solvent, while that of the l>lood of the horse and rabbit dissolves corpuscles rel.atively slowdy. The blood corpus- cles of mammals vary very greatly with reference to their power to resist the solvent action of the serum of other animals. The red blood corpuscles of rabbit's blood are rapidly dissolved by the blood serum of other aniiuals, whilst those of the cat and dog resist the solvent action much longer. Solution of the corpuscles occurs in defibrinated as w-ell as in ordinary blood. When the blood of a rabbit or lamb is injected into the blood vessels of a dog, they are dissolved in a few minutes. If blood be withdrawn by pricking the skin with a needle, the partially dissolved corpuscles may be detected. Liberation of Haemoglobin and Haemoglobinuria. — As a result of the solution of the col- ored corpuscles, the blood plasma is reddened by the liberated h.T;moglobin. Part of the dissolved material may be used up in the body of the recipient, some of it for the formation of bile, but if the solution of the corpuscles has been extensive, the hii^moglobin is e.xcreted in the urine (haemo- globinuria) in less amount in the intestine, the bronchi, and the serous cavities [Panum). Bloody urine has been observed in man after the injection of 100 grammes of lamb's blood. Even some of the recipient's blood corpuscles are dissolved by the serum of the transfused blood, f. ,^,^, on transfusing dog's blood into man. In the rabbit, whose corpuscles are readily dissolved, the trans- fusion of the blood serum of the dog, man, pig, sheep, or cat produces serious symptoms, and even death. The dog, whose corpuscles are more resistant, bears transfusion of other kinds of blood well. Dangers — When foreign or heterogeneous blood (/. e., blood from a different species) is trans- fused, two phenomena, which may be dangerous to life, occur : — (1) Before the ccrpuscles are dissolved they usually run together and form sticky masses, consist- ing of 10 or 12 corpuscles, which are apt to occlude capillaries. After a time they give up their hfemoglobin, leaving the stroma, which yields a sticky, fibrin-like mass that may occlude fine vessels a 30- . , . (2) The presence of a large quantity of dissolved haemoglobin may cause extensive coagulation within the blood vessels. The injection of dissolved hemoglobin causes extensive coagulations [jVaunyn and Francken). The coagulation occurs usually in the venous system and in the larger vessels, and may cause death either suddenly or after a considerable time. Dissolved hamoglobin seems greatly to increase the activity of the fibrin femient (J 30), perhaps by accelerating the decomposition of the colorless corpuscles. Haemoglobin exposed to the air gradually loses this properly ; and the fibrin ferment, w-hen in contact with haemoglobin, is either destroyed or rendered less active (Saehssendahl). Vascular Symptoms. — .As a result of the above-named causes of occlusion of the vessels, there are often signs of the circulation being impeded in various organs. In man, after transfusion of TRANSFUSION OF BLOOD. 171 lamb's blood, the skin is bluish red, in consequence of the stagnation of blood in the cutaneous vessels. Difficulty of breathing occurs from obstruction in the capillaries of the lung ; while there may be rupture of small bronchial vessels, causing sanguineous expectoration. The dyspnrea may increase, especially when the circulation through the medulla oblongata — the seat of the respiratory centre — is interfered with. In the digestive tract, for the same reason, increased peristalsis, evacua- tion of the contents of the rectum, vomiting, and abdominal pain may occur. These phenomena are explained by the fact that disturbances of the circulation in the intestinal vessels cause increased ptristaltic movements. Degeneration of the parenchyma of the kidney occurs as a result of the occlusion of some of the renal vessels. The uriniferous tubules become plugged with cylinders of coagulated albumin (Ponfick). Owing to the occlusion of numerous small muscular branches the muscles may become stiff, or coagulation of their myosin may occur. Other symptoms, referable to the nervous system, the sense organs and heart, are all due to the interference with the circulation through them. An important symptom is the occurrence of a considerable amount of fci'er half an hour or so after the transfusion of heterogeneous blood. When many vessels are occluded, rupture of some small blood vessels may take place. This explains the occurrence of slight yet persistent hemorrhages, which occur on the free surfaces of the mucous and serous membranes, and in the parenchyma of organs, as well as in wounds. The blood coagulates with difficulty, and imper- fectly. Transfusion of other Fluids. — Other substances have been transfused. Normal Saline So- lution (0.6 per cent. NaCl) aids the circulation in a purely mechanical way (Goltz), and it even excites the circulation (Kronecker, Sander, Olt). In severe a:tmia this fluid cannot maintain life {Euienburg and Landois). The injection of Peptone, even in moderate amount, is dangerous to life, as it causes paralysis of the vessels. The injection of Milk is accompanied with danger; fever occurs after the injection, and the milk globules cause the occlusion of many vessels, producing sub- sequent degenerations. Fat may appear in the urine, and there may be fatty infiltration of the urinary tubules. The urine contains sugar and albumin, the liver cells often contain fatty granules, and the weight of the body diminishes. If too large a quantity of milk be transfused, death occurs. When unboiled milk is injected, numerous bacteria are developed in the blood (Sclia/er). THE BLOOD GLANDS 103. — I. THE SPLEEN. — Structure. — The spleen is covered by the peritoneum, except at the hilus. Under this serous covering there is a tough, thick, elastic, fibrous capsule, which closely invests the organ and gives a covering to the vessels which enter or leave it at the hilus, so that fibrous tissue is carried into the organ along the course of the vessels. [The capsule cannot be separated without tearing the splenic pulp.] Numerous trabeculae pass into the spleen from the deep surface of the capsule. These trabecul;i; branch and ana.stomose so as to produce a net- work of sustentacular tissue, which is continuous with the connective tissue, prolonged inward and surrounding the blood vessels (Fig. 117). Thus, the connective tissue in the spleen, as in other viscera, is continuous throughout the organ. In this way an irregular dense network is formed, comparable to the meshes of a bath sponge. [This network is easily demonstrated by washing out the pulp lying in its meshes by means of a stream of water, when a beautiful, soft, semi-elastic net- work or framework of rounded and flattened threads is obtained.! Fig. 117. Spleen of a cat injected with gelatine, showing the adenoid reticulum. The Capsule is composed of interlacing bundles of connective tissue mixed with numerous fine fibres of elastic tissue and some non-striped muscular fibres. Reticulum. — Within the meshes of the trabecular framework there is disposed a very delicate network or reticulum of adenoid tissue (Billroth), which, with the other colored elements that fill up the meshes, constitute the splenic pulp (Fig. 118). The reticulum is continuous with the fibres of the trabeculii;. [If a fine section of the spleen be " pencilled " in water, so as to remove the cellular elements, the preparation presents much the same characters as a section of a lymph gland similarly treated, viz., a very fine network of adenoid tissue, continuous with, and surrounding the walls of, the blood vessels. The spaces of this tissue are filled with lymph and blood corpuscles (//»).] The Pulp is a dark, reddish-colored semi-fluid material, which may be squeezed or washed out of the meshes in which it lies. It contains a large number of colored blood corpuscles, and becomes brighter when it is exposed to the action of the oxygen of the air. Blood Vessels and Malpighian Corpuscles. — The large splenic artery splits up into several branches before it enters the spleen, and it is accompanied in its course by the vein. Both vessels and their branches are enclosed in a fibrous sheath, which becomes continuous with the trabecul.t. The smaller branches of the artery gradually lose this fibrous investment, and each one ultimately divides into a group or pencil of arterioles (penicilli) which do not anastomose with each other. [Thus each branch is terminal — a condition which is of great importance in connection with the pathology of embolism or infarction of the vessels of the spleen.] At the points of division of the branches of the artery, or scattered along their course, are small oval or globular masses of adenoid tissue, about the size of a small millet seed (j'j to ^^ inch in diameter} — the Malpighian corpuscles. [These bodies are visible to the naked eye as small, round or oval white structures, about the size of a millet seed, in a section of a fresh spleen.] Thev are very numerous — [7000 172 BLOOD VESSELS OF THE SPLEEN. 173 m man (Safpev)'] — and are readily detected in the dark reddish pulp. We must be careful not to mistake sections of the trabecule for them. These corpuscles consist of adenoid tissue, whose meshes are loaded with lymph corpuscles, and they present exactly the same structure as the solitary follicles of the intestine (compare Lymphatic Glands, \ 197). [They are just small lymphatic accumulations around the arteries — peri-arterial masses of adenoid tissue similar to those masses that occur in a slightly different form in other organs, e. g., thf lungs. In a section of the spleen the artery may pass through the centre of the mass or through one side of it, and in some cases the tissue is collected unequally on opposite sides of the vessel, so that it is lob-sided. They are not surrounded by any special envelope. In some animals the lymphatic tissue is continued for some distance along the small arteries, so that to some extent it resembles a perivascular sheath of adenoid tissue (IV. jMiiller, Sch-weiggir-Seidel). In a well- injected spleen, a few fine capillaries are to be found within these corpuscles (Sanders). The capil- laries distributed in the substance of the .Malpighian corpuscle (Fig. 119) form a network, and ultimately pour their blood into the spaces in the pulp. According to Robin and Legros, these vessels are comparable to the vasa.vasorum of other blood vessels. According to Cadiat, the cor- puscles are separated from the splenic pulp by a lymphatic sinus, which is traversed by efferent capillaries passing to the pulp (Fig. 119I.] Connection of Arteries and Veins. — It is very dittlcult to determine what is the exact mode of termination of the arteries within the spleen, more especially as it is extremely difficult to inject the blood vessels of the spleen. According to Stieda, W. Miiller, Peremeschko and Klein, the Fig. 119. Malpighian corpuscle ot the spleen of a cat injected, a, artery of the pulp injected ; c, the artery of the corpuscl space around the corpuscle is the lymphatic sinus. Lciy .iiuuiid which the corpuscle is placed; ^. m ifying in the lymphatic tissue composing it. The fine " capillary arteries " formed by the division of the small arteries do not open directly into the capillary veins, but the connection between the arteries and veins is by means of the " intermediary intercellular spaces" of the reticulum of the spleen; so that, according to this view, there is no continuous channel lined throughout by epithelium connecting these vessels one with another. Thus, the blood of the spleen flows into the spaces of the adenoid reticulum, just as the lymph stream flows through the spaces in a lymph gland. According to Billroth and Kolliker, a closed blood channel actually does exist between the capillary arteries and the veins, consisting of dilated spaces (similar to those of erectile tissue). These intermediary spaces are said to be completely lined by spindle-shaped epithelium, which abuts externally on the reticulum of the pulp. [.Accord- ing to Frey, owing to the walls of the terminal vessels being incomplete — there being clefts or spaces between the cells comj)osing them — the blood passes freely into spaces of the adenoid tissue of the pulp " in the same way as the water of a river finds its way among the pebbles of its bed," these " intermediary passages " being bounded directly by the cells and fibres of the network of the pulp. From these passages the venous radicles arise. A\ first, their walls are imperfect and crib- riform, and they often present peculiar transverse markings, due to the circular disposition of the elastic fibres of the reticulum. The small veins have at first a different course from the arteries. They anastomose freely, but they soon become ensheathed, and accompany the arteries in their course.] Elements of the Pulp. — The morphological elements are very various — (i) Lymph corpuscles of various sizes, sometimes partly swollen, and at other times with granular contents. (2) Red 174 FUNCTIONS OF THE SPLEEN. blood corpuscles. (3) Transition forms between I and 2 [although this is denied by some observers {^7, C)]. (4) Cells containing red blood corpuscles and pigment granules. [These cells exhibit amceboid movements.] (Compare ^8.) [The Lymphatics undoubtedly arise within the spleen. The lymphatics which leave the spleen are not numerous (A'Sl/iker). There are two systems— a superficial, capsular and trabecular system, and a perivascular set. The superficial lymphatics in the capsule are rather more numerous. .Some of them seem to communicate with the lymphatics within the organ ( Tomsa, Kolliker). In the horse's spleen they communicate with the lymphatics in the trabecular and with the perivascular lymphatics. The exact mode of origin of the perivascular system is unknown, but in part, at least, it begins in the spaces of the adenoid tissue of the Malpighian corpuscles and perivascular adenoid tissue, and runs along the arteries toward the hilus. There seem to be no afferent lym- phatics in the spleen, such as e.^ist in a lymphatic gland.] The Nerves of the spleen are composed, for the most part, of non-medullated nerve fibres, and run along with the artery. Their e.xact mode of termination is unknown, but they probably go to the blood vessels and to the muscular tissue in the capsule and trabecula;. [They are well seen in the spleen of the ox, and in their course very small ganglia, placed wide apart, have been found by Remak and W. .Stirling.] Chemical Composition. — Several of the more highly oxidized stages of albuminous bodies exist in the spleen. Besides the ordinary constituents of the blood, there exist leucin, tyrosin, xanthin, hypoxanthin, also lactic, butyric, acetic, formic, succinic and uric acids, and, perhaps, glycero-phosphoric acid (Sa/kowsH) ; cholesterin, a glutin-like body, inosite, a pigment containing iron, and even free iron oxide (A'asse). The ash is rich in phosphoric acid and iron — poor irt chlorine compounds. The splenic juice is alkaline in reaction; the specific gravity of the spleen = 1059-1066. [The watery extract of the spleen contains a proteid combined with iron.] The Functions of the spleen are obscure, but we know some facts on which to form a theory. [The spleen differs from other organs in that no very apparent effect is produced by it, so that we must determine its uses in the economy from a consideration of such facts as the following: (i) The effects of its removal or extirpation. (2) The changes which the blood undergoes as it passes through it. (3) Its chemical composition. (4) The results of experiments upon it. (5) The effects of diseases.] (i ) Extirpation. — The spleen may be removed from an animal — old or young — without the organism suffering any very obvious change (Galen'). The human spleen has been successfully removed by Kol'trlc, Fia/i, Zacaralla (iS^ip), CreJe and others. As a result (compensatory?), the lymphatic glands enlarge, but not constantly, while the blood-forming activity of the red marrow of bone is in- creased. Small brownish-red patches were observed in the intestines of frogs after extirpation of the spleen. These new formations are regarded by some observers as compensatory organs. Tizzoni asserts that new splenic structures are formed in the omentum (horse, dog) after the destruction of the parenchyma and blood vessels of the spleen. The spleen is absent extremely seldom (Meinhard, Koch and IVachsmuth). [The weight of the animal (dog) diminishes after the operation, but afterward increases. The number of red blood corpuscles is lessened, reaching its minimum about the 150th to the 200th day, while that of the colorless corpuscles is greater. The lymphatic glands (especially the internal, and those in the neck, mesentery and groin) enlarge, while, on section, the cortical substance of these structures is redder, owing to the great number of red corpuscles, many nucleated (Gibson), in the lymph spaces. The marrow of all the long bones (those of the foot excepted) becomes very red and soft, with the characters of embryonic bone marrow. .Such animals withstand hemorrhage (to j/j of the total amount of blood) without any specially bad resuhs (TizMiii, Il'mograi/ow), •Schindeler observed that animals, after extirpation of the spleen, became very ravenous.] Schiff stated, that after extirpation of the spleen, the pancreatic juice failed to digest proteids. The evidence in support of this statement is unsatisfactory, and Mosler affirms that this operation has no effect either on gastric or pancre.atic digestion. Heidenhain also found a similar negative result. The operation ought to be performed on young animals, as old animals often succumb to it. [Regeneration. — Aher entire removal of the spleen, nodules of splenic tissue are reproduced I fox), while new adenoid tissue is formed in the lymphatic glands and in Peyer's patches, the paren- chyma of the former coming to resemble splenic tissue ( Tizzoni, Jifcrnod).'] (2) According to Gerlach and Funke, the spleen is a blood-forming gland. As already mentioned, the blood of the splenic vein contains far more colorless corpuscles than the blood of the splenic artery (p. 31). Many of these corpus- CONTRACTION OF THE SPLEEN. 175 cles undergo fatty degeneration, and disappear in the blood stream iVircliow). That colorless blood corpuscles are formed within the spleen seems to be proved by the enormous number of these corpuscles which are found in the blood in cases of hyperplasia of the spleen or leuksmia (^Bennett {/Sj2), J'irchtno). Bizzozero and Salvioli found that several days after severe hemorrhage, the spleen became enlarged, and its parenchyma contained numerous red nucleated hrematoblasts. According to Schiff, extirpation of the spleen has no effect, either u\)o\\ the absolute or relative number of colored or colorless corpuscles. [According to Picard and Malassez. there is a tempor- ary decrease in the number of the red corpuscles and their haemoglobin, and Gibson also finds a primary decrease in the red and an increase in the number of the white corpuscles.] (3) Other observers {KoHiker and Ecker') regard the spleen as an organ in which colored blood corpuscles are destroyed, and they consider the large protoplasmic cells containing pigment granules as a proof ot^ this (p. 28J. Ac- cording to the observations of von Kusnetzow, these structures are merely lymph corpuscles, which, in virtue of their amceboid movements, have entangled colored blood corpuscles. [Such corpuscles exhibit similar properties when placed upon a warm stage.] Similar cells occur in e.xtravasations of blood ( I'irc/nno]. The colored blood corpuscles within the lymph cells gradually become disintegrated, and give rise to the production of granules of hsmatin and other derivatives of hajmoglobin. Hence, the spleen contains more iron than corresponds to the atnount of blood present in it. When we consider that the spleen contains a large number of extractives derived from the decomposition of proteids, it is very probable that colored blood corpuscles are destroyed in the spleen. Further, the juice of the spleen contains salts similar to those that occur in the red blood cor- puscles. The blood from the spleen is said to have undergone other changes, but the following statement must be accepted with caution : The blood of the splenic vein contains more water and fibrin ; its red blood corpuscles are smaller, brighter, less flattened, more resistant, and do not form rouleaux; its haemoglobin crystallizes more easily, and there is a large proportion of O during digestion. [The spleen has very direct relations to the blood ; in it colored blood cor- jiuscles undergo disintegration, it produces colorless corpuscles, and it is said to transform white corpuscles into red i^Credc Gibson).'] (4) Contraction. — In virtue of the plain muscular fibres in its capsule and trabecule, the spleen undergoes variations in its volume (A"ei). As in other glands there are lobes and lobules.] Each sac is surrounded by a plexus of capillaries which do not penetrate the membrana propria. There are also numerous lymphatics. -At an early period the sacs dilate, their cellular lining atrophies, and their contents undergo colloid degeneration. When the gland vesicles are greatly enlarged " goitre " is produced. The Chemical Composition of this gland has not been much investigated. In addition to the ordinary constituents, leucin, xanthin, sarkin, lactic, succinic, and volatile fatty acids have been found. [Excision. — The effects differ, according to the animal operated on. Thisgland has been excised in the human subject in cases of goitre. Reverdin pointed out that a peculiar condition resulted, called Cachexia stumipriva, and practically the human being becomes a cretin. This operation, therefore, is highly questionable when performed on man (A'ochc-r). Rabbits endure the operation well. Of dogs, only a very small number survive, nearly all die. The immediate effects are fibril- lar contractions, which ultimately influence the gait of the animals, convulsions, aniesthesia, great diminution of sensibility, loss of flesh, redness of the ears and intense heat of the skin (which dis- appear after several days), difficulty in seizing and eating food, kerato-conjunctivitis, and frequently disturbance of the rhythm of respiration with dyspncea and spasms of the abdominal muscles [^Scliiff^ THE THYROID. 179 Zesas,J. IViigner). The arterial blood contains about the same amount of O as venous blood. Certain parts of the peripheral nerves undergo a kind of degeneration similar to that found after nerve stretching. There is albuminuria and fall of the blood pressure (Albertotii and Tizzoni). There is a great tendency for the animal to run backward. Death usually occurs between the third and fourth day, the animals being comatose ( Wagner). Schiff found that if one-half of the gland was excised at once, and the other half a month afterward, death did not occur ; but Wagner denies this, for he asserts that the remaining half hypertrophies, and if it be excised d'eaih occurs, with the usual symptoms. In monkeys, five days after the operation, there are symptoms of nervous disturbance. The animals have lost their appetite, there are fibrillar con- tractions of the muscles of the face, hands, and feet, but the tremors disappear on voluntary efibrt. The appetite returns and is increased, but notwithstanding, the animal grows thin and pale; while the tremors increase and affect all the muscles of the body. These tremors are of central origin, because they disappear on dividing the nerve. Thus there is profound alteration of the motor powers. Among the outward symptoms are puffiness of the eyelids, swelling of the abdomen, increased hebetude, and dyspncea, while afterward there is a fall of the temperature and imbecility; the tremors disappear, there is a pallor of the skin, and ultimately, after five to seven weeks, the animals die in a comatose state. Thus there is a slow onset of hebetude, terminating in imbecility. Very remarkable changes occur in the blood. There is a steady fall of the blood pressure, Fig. 123. ■7:^^r-'e^i&/ .'i^W oligemia (diminution of the red blood corpuscles) or rather profound ansmia, leucocythsmia or leucocylosis, the colorless corpuscles being increased to the ratio of four to fourteen, and lastly mucin is present in the blood, although normally it is not so. The salivary glands are hypertrophied, owing to the presence of mucin, which is found even in the parotid, although this is normally a serous gland (J 141 )• The swelling of the abdomen is due to hypertrophy of the great omentum. Mucin is found in the peritoneal fluid, and the spleen is also enlarged. Thus these symptoms present many features in common with those of Myxoedena described by Ord {v. Norsley).'] [Stages. — Horsley distinguishes three stages. The first or neurotic exhibits constant tremors, S per second, and young animals do not appear to survive this stage. In the second or mucinoid stage, mucin is deposited in the tissues and blood; this change, however, is only seen to perfection in monkeys. If these animals be kept at a high artificial temperature, their life is considerably prolonged. In the third atrophic or marasmic period, the animals die of marasmus, while they lose their excess of mucin. Age seems to exert an important influence in thyroidectomy ; young dogs survive but a short time, while old dogs merely exhibit symptoms of indolence and incapacity ; and as a matter of fact, the activity of the gland seems to be most active when tissue metabolism is most active.] [The following table, after Horsley, indicates the symptoms that follow : — 180 THE SUPRARENAL CAPSULES. Loss of the Function of the Thyroid Gland. Stages. Duration. Symptoms. Remarks. L Neurotic. I to 2 weeks in dogs; I t 3 weeks in mon- keys. A to I w e e k i n dogs; 3 to 7 weeks in mon- keys. Tremo rs, rigid ity , dyspnoea. Young dogs and monkeys alike die in this stage. IL Mucinoid. Commencing hebetude and mucinoid degen- eration of the connec- tive tissues. Dogs survive only to the beginning of this stage ; monkeys die at the end, if not treated. in. Atrophic. 5 1 8 w e e k s in monkeys. Complete imbecility and atrophy of all tissues, especially muscles. Monkeys survive accord- ing to the temperature of the air-bath. Fin ,,_i. Functions The functions of the thyroid gland are very obscure. Perhaps it may be an apparatus for regulating the blood supply to the head (?). It becomes enlarged in Basedow's disease, in which there is great palpitation as well as protrusion of the eyeball [Exophthalmos], which seem to depend upon a simultaneous stimulation of the accelerating nerve of the heart, and the sympathetic fibres for the smooth muscles in the orbital cavity and the eyelids, as well as of the inhibitory fibres of the vessels of the thyroid. In many localities it is common to find swelling of the thyroid constituting goitre, which is sometimes, but far from invariably, associated with idiocy and cretinism. [Horsley finds that its removal is the essential cause of myxredena and cretinism. He regards it (i) as a blood-forming gland, so that it has a ha^mapoietic function, but Gibson finds no grounds for supporting this view. During the anremia resulting from its removal, the blood of the thyroid vein contains 7 per cent, more red blood corpuscles than the corresponding artery {Horsley). (2) It seems to regulate the formation of mucin in the body. After its removal the norma] metabolism is no longer maintained, and there is a corresponding increasingly defective condition of nutrition.] Ill the Tunicata, this gland, represented by a groove, seireles a digestive fluid. In vertebrates, it is an organ which has undergone a retrograde change (Gegenhaur). IV. THE SUPRARENAL CAPSULES.— Structure. — These organs are invested by a thin cap- sule which sends processes into the interior of the organ. They consist of an outer (broad) or cortical layer and an inner (narrow) or medullary layer. The former is yellow- ish in color, firm and striated, while the latter is softer and deeper in tint. In the outermost zone of the cortex (Fig. 124, b), the tiabeculx- form polygonal meshes, whicli contain (he cells of the gland substance ; in the broader middle zone the meshes are elongated, and the cells filling them are arranged in columns radiating out- ward. Here the cells are transparent and nucleated, often containing oil globules; in the innermost narrow zone the polygonal arrangement prevails, antl the cells often contain yellowish-brown pigment. In the medulla [c) the stroma forms a reticulum containing groups of cells of very irreg- ular shape. Numerous blood vessels occur in the gland, especially in the cortex. [The nerves are extremely numerous, and are derived from the renal and solar plexuses. Many of the fibres are medullated. After they enter the gland, numerous ganglionic cells occur in the plexuses which they form. Indeed, some observers regard the cells of the medulla as nervous. Undoubtedly, numerous 7nifltipolar }ierve cells exist within the gland.] — • {Eberth, Creiq/itoit. v. Bninn). Chemical Composition. — The suprarenals contain the constituents of connective tissue and nerve tissue ; also leucin, hypoxanthin, benzoic, hippuric, and tauro- lion of a human suprarenal capsule. «, cap- cliolic acids, taurin, inosit, fats, and a body which becomes sule;/., gland cells of the cortex arranged in pigmented bv oxidation. Among inorganic substances columns; c, glandular network of the me- ^ ^ , , ,' , ■ ■ 1 , , dulla : d, blood vessels. potash and phosphoric acid are most abundant. HYPOPHYSIS CEREBRI. 181 The function of the suprarenal body is very obscure. It is noticeable, however, that in Addi- son's disease ("bronzed skin"), which is perhaps primarily a nervous affection, these glands have frequenlly, but not invariably, been found to be diseased. Owing to the injury to adjacent abdominal organs extirpation of these organs is often, although not always, fatal; in dogs pig- mented patches have been found in the skin near the mouth. Brown Sequard thinks they may be concerned in preventing the over-production of pigment in the blood. .[Spectrum. — MacMunn finds that the medulla of the suprarenal bodies (in man, cat, dog, guinea pig, rat, etc.) gives the spectrum of htemochromogen (? iS), while the co'^tex shows that of what he calls histohaematin, the latter being a group of respiratory pigments. He finds that hre- mochromogen is only found in excretory organs (the bile, the liver) ; hence, he regards the medulla as excretory, so that part of the function of the adrenals may be "to metamorphose effete hoemo- globin or ha^matin into hsemachromogen," and when they are diseased, the effete pigment is not removed ; hence, the pigmentation of the skin and mucous membranes. Taurocholic acid has been found in the medulla ( Vulpinn). MacMunn believes that " they have a large share in the down- ward metamorphosis of coloring matter." Krukenberg regards the pigment as a pyrocatechin compound.] V. HYPOPHYSIS CEREBRI— COCCYGEAL AND CAROTID GLANDS.— The hypophysis cerebri, or pituitary body, consists of an anterior lower or larger lobe, partly em- bracing the posterior lower or smaller lobe. These two lobes are distinct in their structure and development. The posterior lobe is a part of the brain, and belongs to the infundibulum. The nervous elements are displaced by the ingrowth of connective tissue ann blood vessels. The anterior portion represents an inflected and much altered portion of ectoderm, from which it is developed. It contains gland-like structures, with connective tissue, lymphatics and blood vessels, the whole being surrounded by a capsule. According to Ecker and Mihalkowicz, it resembles the suprarenal capsule in its structure, while, according to other observers, in some animals it is more like the thyroid. Its functions are entirely unknown. [Excision. — Ilorsley has removed this gland twice successfully in dogs, which lived from five to six months. No nervous or other symptoms were noticed, but when the cortex of the brain was exposed and stimulated, a great increase in the excitability of the motor regions was induced, even slight stimulation being followed liy violent tetanus and prolonged epilepsy.] Coccygeal and Carotid Glands. — The fonner, which lies on the tip of the coccyx, is composed, to a large extent, of plexuses of small, more or less cavernous arteries, supported and enclosed by septa and a capsule of connective tissue (Z«i(7(/f«). Between these lie polyhedral granular cells, arranged in networks. The carotid gland (Fig. 45) has a similar structure (p. 114). Their func- tions are quite unknown. Perhaps both organs may be regarded as the remains of embryonal blood vessels (AriiolJ). 104. COMPARATIVE. — The heart in fishes, as well as in the larva; of amphibians with gills, is a simple venous heart, consisting of an auricle and a ventricle. The ventricle propels the blood to the gills, where it is oxygenated (arterialized) ; thence it passes into the aorta, to be dis- tributed to all parts of the body, and returns, through the capillaries of the body and the veins, to the heart. The amphibians (frogs) have two auricles and one ventricle. From the latter there proceeds one vessel which gives off the pulmonary arteries, and as the aorta supphes the rest of the body with blood, the veins of the systemic circulation carry their blood to the right auricle ; those of the lung into the left auricle. In fishes and amphibians there is a dilatation at the commencement of the aorta, the bulbus arteriosus, which is partly provided with strong muscles. The reptiles possess two separate auricles and two imperfectly-separated ventricles. The aorta and pulmonary artery arise separately from the two latter chambers. The venous blooil of the systemic and pulmo- nary circulations flows separately into tile right and left auricles, and the two streams are mixed in the ventricle. In some reptiles, the opening in the ventricular septum seems capable of being closed. The crocodile has two quite separate ventricles. The lower vertebrates have valves at the orifices of the vena; cavK, which are rudimentary in birds and some mammals. All birds and mammals have two completely separate auricles and two separate ventricles. In the halicore, the apex of the ventricles is deeply cleft. Some animals have accessory hearts, if .^., the eel, in its caudal vein. They are. very probably, lymph hearts (A'oiin). The veins of the wing of the bat pulsate (Se/iiff). The lowest vertebrate, amphioxus, has no heart, but only a rhythmically-contracting vessel. Among blood glands, the thymus and spleen occur throughout the vertebrata, the latter being absent only in amphioxus and a few fishes. Among invertebrata a closed vascular system, with pulsatile movement, occurs here and there, e,g., among cchinodermata (star fishes, sea urchins, holothurians) and the higher worms. The insects have a pulsating "-dorsal vessel" as the central organ of the circulation, which is a con- tractile tube provided with valves and dilated by muscular action, the blood being propelled rhythmi- cally in one direction into the spaces which lie among the tissues and organs, so that these animals do not possess a closed vascular system. The moUusca have a heart, with a lacunar vascular system. The cephalopods (cuttle fish) have three hearts — a simple arterial heart and two venous simple gill hearts, each placed at the base of the gills. The vessels form a completely closed circuit. 182 HISTORICAL RETROSPECT OF THE CIRCULATION. The Imvest animals have either a pulsatile vesicle, which propels the colorless juice into the tissues (infusoria), or the vascular apparatus may be entirely absent. 105. HISTORICAL RETROSPECT.— The ancients held various theories regarding the movement of the blood, but they knew nothing of its circulation. According to Aristotle (384 I!, c), the heart, the acropolis of the boily, prepared in its cavities the blood, which streamed through the arteries as a nutrient fluid to all parts of the body, but never returned to the heart. With Herophilus and Erasistratus (300 B.c),lhe celebrated physicians of the Alexandrian school, originated the erroneous view that the arteries contain air, which was supplied to them by the respi- ration (hence the name artery'). They were led to adopt this view from the empty condition of the arteries after death. By experiments upon animals, Galen disproved this view (131-201 a.d.) — " Whenever I injured an arterj-," he says, •' blood always flowed from the wounded vessel. On tying part of an artery between two ligatures, the part of the artery so included is always filled with blood." Still, the idea of a single centrifugal movement of the blood was retained, and it was assumed that the right and left sides of the heart communicated directly, by means of openings in the septum of the heart, until Vesalius showed that there are no openings in the septum. Michael Servetus (the Spanish monk, burned at Geneva, at Calvin's instigation, in 1553) discovered the pulmonary circulation. Cesalpinus confirmed this observation, and named it " Circulatio." Fabricius ab Aqua- pendente (Padua, 1574) investigated the valves in the veins more carefully (although they were known in the fifth century to Theodoretus, Bishop in .Syria), and he was acquainted with the cen- tripetal movement of the blood in the veins. Up to this time, it was imagined that the veins carried blood from the centre to the peripherv-, although Vesalius was acquainted with the centripetal direc- tion of the blood stream in the large venous trunks. At length, William Harvey, who was a pupil of Fabricius (1604), demonstrated the complete circulation (1616-1619), and published his great discovery in 162S. [For the history of the discovery of the circulation of the blood, see the works of Willis on " W. Harvey," ''Servetus and Calvin," those of Kirchner, and the v.irious Harveian orations ] According to Hippocrates, the heart is the origin of all the vessels; he was acquainted with the large vessels arising from the heart, the valves, the chordce tendinea?, the auricles, and the closure of the semilunar valves. Aristotle was the first to apply the terms aorta and venje cava" ; the school of Erasistratus used the term carotid, and indicated the functions of the venous valves. In Cicero a distinction is drawn between arteries and veins. Celsus mentions that if a vein be struck below the spot where a ligature has been applied to a limb, it bleeds, while Aretaeus (50 A. D. ) knew that arterial blood was bright and venous dark. Pliny (f 79 A. D.) described the pulsating fontanelle in the child. Galen (131-203 A. D.) was acquainted with the existence of a bone in the septum of the heart of large animals (ox, deer, elephant). He also surmised that the veins communicated with the arteries by fine tubes. The demonstration of the capillaries, however, was only possible by the use of the microscope, and employing this instrument, Malpighi (1661) was the first to demonstrate the cajiillary circulation. Leuwenhoek (1674) described the capillary circulation more carefully, as it may be seen in the web of the frog's foot and other transparent membranes. Blan- card (1676) proved the existence of capillary passages by means of injections. William Cooper (1697) proved that the same condition exists in warm-blooded animals, and Ruysch made similar injections. Stenson (born 163S) established the muscular nature of the heart, although the Hippo- cratic and Alexandrian schools had already surmised the fact. Cole proved that the sectional area of the blood stream became wider toward the capillaries (16S1). Joh. Alfons Borelli (160S-1679) was the first to estimate the amount of work done by the heart. Physiology of Respiration. The object of respiration is to supply the oxygen necessary for the oxidation processes that go on in the body, as well as to remove the carbonic acid formed within the body. The most important organs for. this purpose are the lungs. There is an outer and an inner respiration — the former embraces the exchange of gases between the external air and the blood gases of the respiratory organs (lungs and skin) — the latter, the exchange of gases between the blood in the ca- pillaries of the systemic circulation and the tissues of the body. [The pulmonary apparatus consists of (i) an immense number of small sacs — the air vesicles filled with air, and covered externally by a very dense plexus of capillaries; (2) air passages — the nose, pharynx, larynx, trachea, and bronchi communicating with (i) ; (3) the thorax with its muscles, acting like a pair of bellows, and moving the air within the lungs.] 106. STRUCTURE OF THE AIR PASSAGES AND LUNGS.— The lungs are com- pound tubular (racemose ?) glauds, which separate CO2 from the blood. Each lung is provided with an excretory duct (bronchus) which joins the common respiratory passage of both lungs — the trachea. Trachea. — The trachea and extra-pulmonary bronchi are similar in structure. The basis of the trachea consists of a number (16-20) of Q -shaped, incomplete cartilaginous hoops placed over each other. These rings consist of hyaline cartilage, and are united to each other by means of tough, fibrous tissue containing much elastic tissue, the latter being arranged chiefly in a longitudinal direc- tion. The function of the cartilages is to keep the tube open under varying conditions of pres- sure. Pieces of cartilage having a similar function occur in the bronchi and their branches, but they are absent from the bronchioles, which are less than i mm. in diameter. In the smaller bronchi the cartdages are fewer and scattered more irregularly. [In a transverse section of a large intra- pulmonary bronchus, two, three, or more pieces of cartilage, each invested by its perichondrium, may be found.] At the points where the bronchi subdivide, the cartilages assume the form of ir- regular plates embedded in the bronchial wall. An external fibrous layer of connective tissue and elastic fibres covers the trachea and the extra- pulmonary bronchi externally. Toward the oesophagus, the elastic elements are more numerous, and there are also a few bundles of plain muscular fibres arranged longitudinally. Within this layer there are bundles of non-striped miistiilar fibres which pass transversely between the cartilages behind, and also in the intervals between the cartilages. [These pale reddish fibres constitute the trachealis muscle, and are attached to the inner surfaces of the cartilages by means of elastic tendons at a little distance from their free ends [Aliinniks, 1697). The arrangement varies in dif- ferent animals— thus, in the cat, dog, rabbit, and rat the muscular fibres are attached to the external surfaces of the cartilages, while in the pig, sheep, and ox they are attached to their internal sur- faces (Stirling).} .Some muscular fibres are arranged longitudinally external to the transverse fibres {Kramer). The function of these muscular fibres is to prevent too great distention when there is great pressure within the air passages. The mucous membrane consists of a basis of very fine connective tissue, containing mvtch adenoid tissue with numerous lymph corpuscles. It also contains numerous elastic fibres, arranged chiefly in a longitudinal direction under the basement membrane. They are also abundant in the deep layers of the posterior part of the membrane oppo-ite the intervals between the cartilage^. .\ small quantity of loose subtrucous connective tissue containing the large blood vessels, glands and lymphatics unites the mucous membrane to the perichondrium of the cartilages. The epithelium consists of a layer of columnar ciliated cells with several layers of immature cells under them. [The superficial layer of cells is columnar and ciliated (Fig. 125, li), while those lying under them present a variety of forms, and below all is a layer of somewhat flattened squames, ^, resting on the basement membrane, d. These squames constitute a layer quite distinct from the basement mem- brane, and they form the layer described as Debove's membrane. They are active germinating cells, and play a most important part in connection with the regeneration of the epithelium, after the superficial layers have been shed, in such conditions as bronchitis (y. Drasch, Hamilton). Not 183 184 STRUCTURE OF THE TRACHEA. unfrequemly a little viscid mucus {a) lies on the free ends of the cilia. In the intermediate layer, the cells are more or less pyriform or battledore-shaped \Haniilto7i), with their long, tapering pro- cess inserted among the deepest layer of squames. According to Drasch, this long process is attached to one of these cells and is an outgrowth from it, the whole constituting a " foot cell."] Underneath the epithelial is the homogeneous basement membrane, through which fine canals pass, connecting the cement of the epithelium with spaces in the mucosa. [This membrane is well marked in the human trachea, where it plays an important part in many pathological conditions, ('. g., bronchitis. It is stained bright red with picrocarmine.] The cilia act so as to carry any secre- tion toward the larynx. Goblet cells exist between the ciliated columnar cells. Numerous small compound tubular mucous glands occur in the mucous membrane, chiefly betw'een the cartilages. Their ducts open on the surface by means of a slightly funnel-shaped aperture into which the ciliated epithelium is prolonged for a short distance. [The acini of some of these glands lie out- side the trachealis muscle. The acini are lined by cubical or columnar secretory epithelium. In some animals (dog) these cells are clear, and present the usual characters of a mucus-secreting Fig. 125. -^ i^^-V ansverse section of part of a normal human bronchus (X 450). a, precipitated mucus on the surface of the ciliated epithelium, iJ; i, ciliated columnar epithelium ; f:, deep germinal layer of cells (Debove's membrane) : ^ '^^fj"^ TJj^^jf, lies in the chest, and a connection established with Marey's tambour, p. 85 {Rosenthal). [This mpfhnd ilso enables one to measure the ;«//■«■//(<"•«'';''/'■"■''"■«'• J , ,. . . j- Marev4 s"etWraph or Pneumograph.-[There are two fonns of this instrument, one modi- fie^by P Per and&ore modern form (Fig. .30). A tambour (/,) is fixed at right angles to a thi; elastic plate of steel ( /). The aluminium disk on the caoutchouc of the Umbour is attached toLupigMI I) who.se end lies in contact with a horizontal screwy.) Two arms (./,.) are Ittachedo opposite sides of the steel plate, and to them the belt (.) which fastens the nistrument to the chest °s attached When the chest expands these two arms are pulled asunder, the steel plate L bent and the tambour is aftected, and any movement of the tambour is transmitted to a registering ''Tn th^ cL'e':fTnima 'sVlace'il'lheir backs, Snellen introduced a long needle vertically through the abdommal walls into ?he liver. Rosenthal opened the abdomen and apphed a lever to the under surface of the diaphragm, and thus registered its movements (Phrenograph). The curve (Fig. 131, B) was obtained by placing the tambour of a Brondgeest's pansphygmograph upon the xiphoid process, and recording the ipovement upon a plate attached to a vibrating tuning fork. The /;»//;-^/.W (ascending hmb) begins Sh moderate rapidity, is accelerated in the middle and toward the end again becomes slower. The expiration also begins with moderate rapidity, is 'hen accel- erated, and becomes much slower at the latter part, so that the curve falls very ^'^f^^^Jaiion is slightlv shorter tl>an ^.v//r.//.«.-According to Sibson, the ratio for an adult is as 6 to 7 5 >" women, children and old people 6 to 8 or 6 to 9^ Vierordt found the ratio to be 10 to 1 4.1 (to 24.1 ) ; J- R^ t^vvald 1 1 to 12 It is only occasionally that cases occur where inspiration and expiration are equally long, or where expiration is shorter than inspiration. When respiration proceeds quie ly and ret;ukrly, there is usually no pause (complete rest of the chest wal ) ttuJn the in^iratiln and expiration {Riegei). The very flat part of the expira- PATHOLOGICAL VARIATIONS OF RESPIRATORY MOVEMENTS. 195 tory curve has been wrongly regarded as due to a pause. Of course, we may make a voluntary pause between two respirations, or at any part of a respiratory act. Some observers, however, have described a pause as occurring between the end of expiration and the beginning of the next inspiration (expiration pause), and also another pause at the end of inspi- ration (inspiration pause). The latter is always of very short duration, and considerably shorter than the former. During very deep and slow respiration, there is usually an expiration pause, while it is almost invariably absent during rapid breathing. An inspiration pause is always absent under normal cir- cumstances, but it may occur under pathological conditions. In certain parts of the respiratory curve slight irregularities may appear, which are sometimes due to vibrations communicated to the thoracic walls by vigorous heart beats (Fig. 132). The "type" of respiration may be ascertained by taking curves from various parts during the respiratory movements. Hutchinson showed that in the female the thorax is dilated chiefly by raising the sternum and the ribs (Respiratio cos- talis), while in man, it is caused chiefly by a descent of the diaphragm (Respi- ratio diaphragmatica or abdominalis). In the former there is the so-called "costal type," in the latter the "abdominal or diaphragmatic type." Forced Respiration. — This difference in the type of respiration in the sexes occurs only during normal <|uiet respiration. During deep and forced respiration, in both sexes, the dilatation of the chest is caused chiefly by raising the chest and the ribs. In man, the epigastrium may be pulled in sooner than it is protruded. During sleep, the type of respiration in both sexes is thoracic, while, at the same time, the inspiratory dilatation of the chest precedes the elevation of the abdominal wall iyMosso'). It is not determined whether the costal type of respiration in the female depends upon the con- striction of the chest by corsets or other causes [Siison), or whether it is a natural adaptation to the child-bearing function in women ( Hiitiliiiiion). Some observers maintain that the difference of type is quite distinct, even in sleep, when all constrictions are removed, and that similar differences are noticeable in young children. This is denied by others, while a third class of observers hold that the costal type occurs in children of both sexes, and they ascribe as a cause the greater flexibility of the ribs of children and women, which permits the muscles of the chest- to act more eflSciently upon the ribs. [When a child sucks, it breathes exclusively through the nose ; hence, catarrhal conditions of the nasal mucous membrane are fraught with danger to the child.] III. PATHOLOGICAL VARIATIONS OF THE RESPIRATORY MOVE- MENTS. — [Examination of the Lungs. — The same methods that are applicable to the heart — viz., I, Inspection ; II, Palpation ; III, Percussion ; and IV, . 'Auscultation — apply here also.] [By Inspection we may determine the presence of symmetrical or unilateral alterations in the shape of the chest, the presence of bulging or flattening at one part, and variations in the movement of the chest walls, liy Palpation, the presence or absence, character, seat and extent of any move- ments are more carefully examined. But we may also study what is called Vocal fremitus (J I '7)- For Percussion (jJ 114); Auscultation (J "6).] [In investigating the respiratory movements, we should observe (l) the frequency (^ 109); (2) the type ((( 1 10) ; (3) the nature, character and extent of the movements, noting, also, whether they are accompanied by pain or not (J 1 10) ; (4) the rhythm.] I. Changes in the Mode of Movement — In persons suffering from disease of the respiratory organs, the dilatation of the chest may be diminished (to the extent of 5 or 6 cm.) on both sides or only on one side. In affections of the apex of the lung (in phthisis), the subnormal expansion of the upper part of the wall of the chest may be considerable. Retraction of the soft parts of the thoracic wall, the xiphoid process, and the parts where the lower ribs are inserted, occurs in cases where air cannot freely enter the chest during inspiration, e. g., in narrowing of the larynx ; when this retraction is confined to the upper part of the thoracic wall, it indicates that the portion of the lung lying under the part so affected is le^s extensile and diseased. Harrison's Groove. — In persons suffering from chronic difficulty of breathing, and in whom, at the same time, the diaphragm acts energetically, there is a slight groove, which passes horizon- tally outward from the xiphoid cartilage, caused by the pulling in of the soft parts and correspond- ing to the insertion of the diaphragm. The duration of inspiration is lengthened in persons suffering from narrowing of the trachea or larynx; expiration is lengthened In cases of dilatation of the lung, as in emphysema, where all the expir.xtory muscles must be brought into action (Fig. 132, II). II. Variations in the Rhythm. — When the respiratory apparatus is much affected, there is either an increa-.e or a deepening of the respirations, or both. When there is great difficulty of breathing, this is called Dyspnoea. Causes of Dyspnoea. — (l) Limitation of the exchange of the respiratory gases in the blood due to — (a) diminution of the respiratory surface (as in some diseases of the lungs) ; {b) narrow- 196 THE MUSCLES OF FORCED RESPIRATION. ing of the respiratory passages; (c) diminution of the red blood corpuscles; (i/) disturbances of the respirator}' mechanism {e. g.^ due to affections of the respiratory muscles or nerves, or painful affec- tions of tire chest wall) ; (<■) impeded circulation through the lungs due to various forms of heart disease. (2) Heat dyspncea. — The frequency of the respirations is increased \n febfi/e conditions. The warm blood acts as a direct irritant of the respiratory centre in the medulla oblongata, and raises the number of respirations to 30-60 per minute (" Heat dyspncea"). If the carotids be placed in warm tubes, so as to heat the blood going to the medulla oblongata, the same phenomena are produced {A. Fick), See also " Respiyatoiy centre" {\ 368). [Orthopnoea. — Sometimes the difficulty of breathing is so great that the person can only respire in the erect position, /. (-., when he sits or is propped up in bed. This occurs frequently toward the close of some Iieart affections, notably in mitral lesions ; dropsical conditions, especially of the cavities, may be present.] CheyneStokes' Phenomenon. — This remarkable phenomenon occurs in certain diseases, where the normal supply of blood to the brain is altered, or where the quality of the blood itself is altered, e. g., in certain affections of the brain and heart, and in ur;vmic poisoning. Respiratory pauses of one-half to three-quarters of a minute alternate with a short period {^2-% min.) of in- creased respiratory activity, and during this time 20-30 respirations occur. The respirations consti- tuting this " series " are shallow at first; gradually they become deeper and more dyspnceic ; and finally become shallow or superficial again. Then follows the pause, and thus there is an alterna- tion of pauses and series (or groups) of modified respirations. During the pause, the pupils are contracted and inactive; and when the respirations begin, they dilate and become sensible to light ; the eyeball is moved as a whole at the same time {Letibe). Hein observed that consciousness was abolished during the pause, and that it returned when respiration commenced. A few muscular con- tractions may occur toward the end of the pause (rare). With regard to the causes of this phenomenon there is some doubt. According to Rosenbach, the anomalous nutrition of the brain causes, certain intracranial centres, especially the respiratory centre, to be less excitable and to be sooner exhausted, and this condition reaches its maximum during the respiratory pause. During the pause these centres recover, and they again become more active. As soon as they are again exhausted, their activity ceases. Luciani also regards variations in the excitability of the respiratory centre as the cause of the phenomenon, which he compares with the periodic contraction of the heart (J 58). He observed this phenomenon after injury to the metiulla oblongata above the respiratory centre, and after apncea produced in animals deeply narco- tized with opium. It also occurs in the last stages of asphyxia, during respiration in a closed space. Mosso found a similar phenomenon normally in the hybernating dormouse ( Myoxus) [and traces of it even in normal sleep, while it is sometimes observed in poisoning by morphia or chloral]. Periodic Respiration of Frogs. — If frogs be kept under water, or if the aorta be clamped, after several hours, they become passive. If they be taken out of the water, or if the clamp be re- moved from tlie aorta, they gradually recover and always exhibit the Cheyne-Stokes' phenomena. In such frogs the blood current may be arrested temporarily, while the phenomenon itself remains (Sokolow and Liichsinger). If the blood current be arrested by ligature of the aorta, or if the frogs be bled, the respirations occur in groups. This is followed by a few single respirations, and then the respiration ceases completely. During the pause between the periods, mechanical stimu- lation of the skin causes the discharge of a group of respirations [Siebert and Langendorff). Mus- carin and digitalin cause periodic respiration in frogs [which is not due to the action of these drugs on the heart]. 112. GENERAL VIEW OF THE RESPIRATORY MUSCLES. (A) Inspiration. I. During Ordinary Inspir.^tion are Active. 1. The diaphragm (Nerviis phrenic us.') 2. The Mm. levatores costarum longi et breves (Rami posteriores Abt. dor- saiiuiri). 3. The Mm. intercostales externi et intercartilaginei {Nn. interccntalcs). II. During Forced Respiration are Active. ((z) Muscles of the Trunk. I. The three Mm. scaleni {^Rami musculares of the plexus ccrvicalis et brachi- alls). sternocleidomastoideus (Ram. e.xternus N. accessorii). trapezius (R. externus N. accessorii et Ram. musculares plexus cer- 2. M. 3- M. vicahs). 4- M, pectoralis minor (Xn. ihoracici anteriores). 5. M. serratus posticus superior {N. dorsalis scapula). THE ACTION OF THE DIAPHRAGM. 197 6. Mm. rhomboidei (jV. dorsalis scapiihe). 7. Mm. extensores column;t' vertebralis {Ram. posteriores ncrvoriiin dorsaliiiin. ) [8. Mm. serratus anticus major {_N. thoracicus /ongus). ? ?] {b) Muscles of the Larynx. 1. M. sX^mohyoxd^M's, {Rant. Jesceniie/is hgpog/ossi). 2. M. sternothyreoideus (Ram. descendens hypag/oss:). 3. M. crico-arytEenoideus posticus (N. laryngeus inferior vagi). 4. M. thyreo-arytaenoideus ( 7V^. laryn(jeus inferior vagi). {c) Muscles of tJie Face. 1. M. dilatator narium anterior et posterior (7V./(7c/(z/w). 2. M. levator alae nasi {N. facialis). 3. The dilators of the mouth and nares, during forced respiration [''gasping for breath "], {N. facialis). {d) Muscles of the Pharynx. 1. M. levator veli palatina {N. facialis). 2. M. azygos uvula; {N. facialis). 3. According to Garland, the pharynx is always narrowed. (B) Expiration. I. During Ordinary Respiration. The thoracic cavity is diminished by the weight of the chest, the elasticity of the lungs, costal cartilages and abdominal muscles. II. During Forced Expiration. The Abdominal Muscles. 1. The abdominal muscles [including the obliquus externus and internus, and transversalis abdominis] {Nn. abdominis internus anteriores e nervis intercostalibus, 8-12). 2. Mm. intercostales interni, so far as they lie between the osseous ribs, and the Mm. infracostales {Nn. intercostales). 3. M. triangularis sterni {Nn. intercostales). 4. M. serratus posticus inferior {Ram externi ne/T. dorsalium). 5. M. quadratus lumboruni {Ram muscular e plexu luinhali). 113. ACTION OF THE INDIVIDUAL RESPIRATORY MUSCLES.— (A) In- spiration. — (i) The Diaphragm arises from the cartilages and the adjoining osseous parts of the lower six ribs (costal portion), by two thick processes or crura from the upper three or four lumbar vertebra?, and a sternal portion from the back of the ensiform process. It represents an arched double cupola or dome-shaped partition, directed toward the chest ; in the larger concavity on the right side lies the liver, while the smaller arch on the left side is occupied by the spleen and stomach. During the passive condition, these viscera are pressed against the under surface of the diaphragm, by the elasticity of the abdominal walls and by the intra-abdominal pressure, so that the arcli of the diaphragm is pressed upward into the chest. The elastic traction of the lungs also aids in producing this result. The greater part of the upper surface of the central tendon of the diaphragm is united to the pericardium. The part on which the heart rests, and which is perforated by the inferior vena cava (foramen quadrilaterum) is the deepest part of the middle portion of the diaphragm during the ])assive condition. Action of the Diaphragm. — When the diaphragm contracts, both arched portions become flatter, and the chest is thereby elongated from above down- ward. In this act, the lateral muscular parts of the diaphragm pass from an arched condition into a flatter form (Fig. 133), and during a forced inspiration, the lowest lateral portions, which, during rest, are in contact with the chest wall, 198 CHANGES IN THE CHEST. Fig. 133. become separated from it. The middle of the central tendon where the heart rests ( fixed by means of the pericardium and inferior vena cava) takes no share in this movement, espe- cially in ordinary quiet breathing, but during the deepest inspiration it sinks somewhat (JIc7sse). Undoubtedly, the diaphragm is the most powerful agent in increasing the cavity of the chest. Briicke, in fact, believes that in addition to increasing the length of the thoracic cavity from above downward, it also increases the transverse diameter of the lower part of the chest. It presses upon the abdominal viscera from above, and strives to press these outward, thus tending to push out the adjoining thoracic wall. If the contents of the abdomen are removed from a living animal, every time the diaphragm contracts the ribs are drawn inward (Hallei-y This, of course, hinders the chest from becoming wider below, hence the presence of the abdominal viscera seems to be necessary for the normal activity of the diaphragm. Every contraction of the diaphragm, by increasing the intra-abdominal pressure, favors the venous blood current in the abdomen toward the vena cava inferior ,. Phrenic Nerve. — The immense importance of the > on trie ,. 1 , . . '^ , . , , »'hen the diaphragm as the great inspiratory muscle is pro\ed by scular part of the diaphragm con- the fact that, after both phrenic nerves (third and fourth vedge-shaped space, with its apex cervical nenes) are divided, death occurs (Budge, downward, is formed around the circumfer- r- , , ^, V, , . » a > ence of the lower part of the chest, so that Eiilenkamp). The phrenic nerve contains some sen- the chest is enlarged from above downward. • sory fibres for the pleura, pericardium and a portion of the diaphragm [Sc/ireiber, Henh\ Sitncalhe). The contraction of the diaphragm is not to be regarded as a " simple muscular contraction," since it lasts 4 to 8 times longer than a simple contraction ; it is rather a short tetanic contraction, which we may arrest in any stage of its activity, without bringing into action any antagonistic muscles (Kroiiecier aud Marckwald). (2) The Elevators of the Rib. — The ribs at their vertebral ends (which lie much higher than their sternal ends) are united by means of joints, by their heads and tubercles, to the bodies and transverse processes of the vertebrae. .\ horizontal axis can be drawn through both joints, around which the ribs can rotate upward and downward. If the axes of rotation of each pair of ribs be prolonged on both sides until they meet in the middle line, the angles so formed are greatest above (125°), and smaller below (88°) [A. fV. Volkmann). Owing to the ribs being curved, we can imagine a plane which, in the passive (expiratory) condition of the chest, has a slope from behind and inward to the front and outward. If the ribs move on their axis of rotation this plane be- comes more horizontal, and the thoracic cavity is increased in its transverse diameter. As the axis of rotation of the upper ribs runs in a more frontal, and that of the lower ribs in a more sagittal, direction, the elevation of the upper ribs causes a greater increase from before backward, and the lower ribs from within outward (as the movements of ribs which are directed downward are verti- cal to the axis). The costal cartilages undergo a slight tension at the same time, which brings their elasticity into play. Changes in the Chest. — AH " iiis/tira/on' niuscks" 7vhich act directly upon the chest icall, do Sit by raising the ribs : (a) When the ribs are raised, the inter- costal spaces are widened, {h) When the upper ribs are raised, all the lower ribs and the sternum must be elevated at the same time, because all the ribs are con- nected with each other by means of the soft parts of the intercostal spaces, {c) During inspiration, there is an elevation of the ribs and a dilatation of the inter- costal spaces. (The lowest rib is an exception; during forced respiration, at least, it is drawn downward.) {d ) If, on a preparation of the chest, the ribs be raised as in inspiration, we may regard all those muscles as elevators of the ribs whose origin and insertion become approximated. Every one is agreed that the sca/eni Bind leva- tores costarum longi et brei-cs, the serratus posticus superior, are inspiratory muscles. These are the most important inspiratory muscles which act upon the ribs. INTERCOSTAL MUSCLES. 199 Intercostal Muscles. — With regard to the action of the intercostal muscles, there is a great difference of opinion. According to the above experiment, the external intercostals and the intercartilaginous parts of the internal intercostals act as inspiratory muscles, while the remaining portions of the internal intercostals (as far as they are covered by the external) are elongated when the ribs are raised, while they shorten when the chest wall descends. A muscle shortens only during Its activity. The internal intercostals were regarded by Hamberger as depressors of the ribs or expiratory muscles. In Fig. 134, 1, when the rods, a and b (which represent the ribs), are raised, the intercostal space must be widened (ef^c d). On the opposite side of the figure, it is evident that when the rods are raised, the line, g h, is shortened li i<^ g h, direction of the external intercostals), / /« is length- ened {I m<^ It, direction of internal intercostals). Fig. 13^. H, shows, that when the ribs are raised, the intercartilaginei, indicated by j^' /;, and the external intercostals, indicated by / /■, are shortened. When the ribs are raised, the position of the muscular fibres is indicated liy the diagonal of the rhomb becoming shorter. Fig. 134. y i/^ The mode of action of the intercostal muscles is an old story, Galen (131-203 A.D.) regarding the externals as inspiratorj', the internals as expiratory. Hamberger (1727) accepted this proposition, and considered the intercartilaginei also as inspiratory'. Haller looked upon both the external and internal intercostals as inspiratory, while Vesalius (1540) regarded both as expiratory. Landerer, observing that the upper two or three intercostal spaces became narrower during inspiration, regarded both as active during inspiration and exp'ration. They keep one rib attached to the other, so that their action is to transmit any strain put upon them to the wall of the chest. On this view they will be in action, even when the distance between their points of attachment becomes greater. Landois regards the external intercostals and intercartilaginei as active o)i/r during inspiration, the internal intercostals on/v during expiration. [Martin and Hartwell exposed the internal intercostals and observed whether they contracted along with the diaphragm, or whether the contractions of these two muscles alternate. As the result of their experiments, they conclude that " the internal inter- costal muscles are expiratory throughout the whole extent, at lea.st in the dog and cat ; and that in the former animal they are almost ' ordinary ' muscles of respiration, while in the latter they are * extraordinary ' respiratory mucles."] Landois is of the opinion that the d"///*'/" action of these mus- cles is not to raise or depress the ribs, but rather that the external intercostals and the intercartilaginei 2(K) MUSCLES OF FORCED EXPIRATION. offer resistance to the inspiratory dilatation of the intercostal spaces, and to the simultaneously increased elastic tension of the lungs. The internal intercostals act during powerful expiratory efforts (e'.^'-., coughing), and oppose the distention of the lungs and chest caused by this act. Unless muscles were present to resist the uninterrupted tension and pressure, the intercostal substance would become so distended that respiration would be impossible. [According to Rutherford, the inter- nal intercostals are probably muscles of inspiration.] The Pectoralis Minor and (? Serratus Anticus Major) can only act as elevators of the ribs when the shoulders are fixed, partly by the rhomboidei, and partly by fi.xing the slToulder joint and stipporting the arms, as is done instinctively by persons suffering from breathlessness. (3) Muscles acting upon the Sternum, Clavicle and Vertebral Column. — When the head is fixed by the muscles of the neck, the sternocleido- mastoid can raise the manubrium sterni, and the sternal end of the clavicle so that the thorax is raised and thereby dilated. The scaleni also aid in this act. The clavicular portion of the trapezius may act in a similar although less energetic manner. ^Vhen the vertebral column is straig)itened, it causes an elevation of the upper ribs, and a dilatation of the intercostal spaces which aid inspiration. Dur- ing deep respiration, this straightening of the vertebral column takes place invol- untarily. (4) Laryngeal Movements. — During labored respiration, with every inspiration the larynx descends and the glottis is opened. At the same time the palate is raised, so as to permit a free passage to the air entering through the mouth. {5) Facial Movements. — During labored respiration, the facial muscles are involved ; there is an inspiratory dilatation of the nostrils (well marked in the horse and rabbit). When the need for respiration is very great, the mouth is gradually widened, and the person, as it were, gasps for breath. During expiration, the muscles that are active during (4) and (5) relax, so that a position of equilibrium is established without there being any active expiratory movement to counteract the inspiratory movement. Durmg inspiration the pharynx becomes narrower (^Garland). (B) Expiration. — Ordinary expiration occurs without the aid of muscles, owing to the weight of the chest, which tends to fall into its normal position from the position to wliich it was raised during inspiration. This is aided by the elasticity of the various parts of the chest. When the costal cartilages are raised, which is accompanied by a slight rotation of their lower margins from below forward and upward, their elasticity is called into play. As soon, therefore, as the inspiratory forces cease, the costal cartilages return to theirnormal position, — i.e., the position of expiration — and tend to imtwist themselves; at the same time, the elasticity of the distended lungs draws upon the thoracic walls and the diaphragm. Lastly, the tense and elastic abdominal walls, which, in man chiefly, are stretched and pushed forward, tend to return to their non-dis- tended, passive condition when the abdominal viscera are relieved from the pressure of the contracted diaphragm. (When the position of the body is re- versed, the action of the weight of the chest is removed ; but in place of it, there is the weight of the viscera which press upon the diaphragm.) The abdominal muscles [obliquus internus and externus, transversalis abdo- minis and levator ani] are always active during labored respiration. They act by diminishing the abdominal cavity, and they press the abdominal contents upward against the diaphragm. When they act simultaneously, the abdominal cavity is diminished throughout its whole extent. The Triangularis sterni depresses the sternal ends of the united cartilages and bones, from the third to sixth rib downward ; and the Serratus posticus inferior depresses the four lowest ribs, causing the others to follow. It is aided by the Quadratus lumborum, which depresses the last rib. According to Henle, the serratus posticus inferior fixes the lower ribs for the action of the slips of the diaphragm inserted into them, so RELATIVE DIMENSIONS OF THE CHEST. 201 that it acts during inspiration. According to Landerer, the downward movement of the ribs in the lower part of the thorax dilates the chest. In the erect position, when the vertebr.il column is fixed, deep inspiration and expiration naturally alter the position of the centre of gravity, so that during inspiration, owing to the protrusion of the thoracic and abdominal walls, the centre of gravity lies somewhat more to the front. Hence, with each respiration there is an involuntary balancing of the body. During very deep inspiration, ' the accompanying straightening of the vertebral column and the throwing backward of the head compensate for the protrusion of the anterior walls of the trunk. 114. RELATIVE DIMENSIONS OF THE CHEST.— It is important, from a physi- cian's point of view, to know the dimensions of the thorax, and also the variations it undergoes at different parts. The diameter of the chest is ascertained by means of callipers ; the circumference, with a flexible centimetre or other measure. In strong men, the circumference of the upper part of the chest (immediately under the arms) is 88 centimetres (34.3 inches), in females, 82 centimetres (32 inchesj ; on the level of the ensiform 35- rve t-iken with the cyrtometer. Left side of the chesl retracted in a girl twelve years of age {Eichhorsi). process, 82 centimetres (32 inches) and 78 centimetres (30.4 inches), respect- ively. When the arms are placed hori- zontally, during the phase of moderate expiration, the circumference immedi- ately under the nipple and the angles of the scapulae is equal to half the length of the body ; in man, 82, and during deep inspiration 89 centimetres. The cir- cumference at the level of the ensiform cartilage is 6 centimetres less. In old people, the circumference of the upper part of the chest is diminished, so that the lower part becomes the wider of the two. The right half of the chest is usually slightly larger than the left half, owing to the greater development of the muscles on that side. The long diam- eter of the chest — from the clavicle to the margin of the lowest rib — varies very much. The transverse diameter in man, above and below, is 25 to 26 centimetres (9.7 to 10. 1 inches), in females 23 to 24 centimetres (8.9 to 9.2 inches) ; above the nipple it is one centimetre more. The antero-posterior diameter (dis- tance of anterior chest wall from the tip of a spinous process) in the upper part of the chest is ^ 17 (6.6 inches), in the lower 19 centimetres (7.4 inches). Valentin found that in man, during the deepest inspiration, the chest on a level with the groove in the heart was increased about ^V to \, while Sibson estimates the increase at the level of the nipple to be -^^. Thoracometer. — In order to obtain a knowledge of the degree of movement — rising or falling — of the chest wall during respiration, various instruments have been invented. The thoracometer of Sibson (Fig. 136) measures the elevation in different parts of the sternum. It consists of two metallic bars placed at right angles to each other; one of them. A, is placed on the vertebral column. On B there is placed a movable transverse bar, C, which carries on its free end a toothed rod, Z, directed downward. The lower end of this rod is provided with a pad which rests on the sternum, while its toothed edge drives a small wheel which moves an index, whose excursions are indicated on a circle with a scale attached to it. The Cyrtometer of Woillez is ver\' useful. A brass chain, composed of movable links, is applied in a definite direction to part of the chest wall, e. g., transversely on a level with the nipple, or vertically upon the mammillary or axillary lines anteriorly. There are freely movable links at two parts, which permit the chain to be easily removed, so that as a whole it still retains its form. The chain is laid upon a sheet of paper, and a line drawn with a pencil around its inner margin gives the form of the thorax (Fig. 135). [A lead wire answers the same purpose.] 202 LIMITS OF THE LUNGS. Limits of the Lungs. — The extent and boundaries of the kings are ascer- tained in the living subject by means of percussion, which consists in lightly tapping the chest wall by means of a hammer (percussion hammer). A small Sibson's ihoracometer. Fig. 137. ^■^"-^^l Topography ol the lungs and h'-art dunnc in-^ lung during deepest expiratirn m n, low f heart is uncovered by lung, dull percu'^vion left lung re-iches thib line during deep inspir ir.itiiMi .Mill I \i.;i .III' 'M ir' .''■'■■ '/. /. upward limit ot margii linni dnnii^ il.Tpi-^t iiispir.uii >ii : .',.'', t" , triangular area where ound ; (/, tf , d" , mutned percussion sound ; /, /', anterior margir tion, and during deep expiration it recedes as far as e^ e' . ivory or bony plate (pleximeter), held in the left hand, is laid on the chest, and the hammer is made to strike this plate, whereby a sound is emitted, which sound varies with the condition of the subjacent lung tissue. Whenever the lung sub- PATHOLOGICAL VARIATIONS OF THE PERCUSSION SOUNDS. 203 Stance in contact with the chest wall contains air, a clear resonant tone or sound — such as is obtained by striking a vessel containing air, a clear percussion sound — is obtained. Where the lung does not contain air, a dull sound — like striking a limb — is obtained. If the parts containing air be very thin, or are only partially filled with air, the sound is "muffled." Fig. 137 indicates the relations of the lungs to the anterior surface of the chest. The apices of the /u/i^s reach 3 to 7 centimetres (i. i to 2.7 inches) above the clavicles anteriorly, while posteriorly they extend from the spines of the scapulae as high as the seventh spinous process. The loiver margin of the right lung in the passive position (moderate expiration) of the chest, commences at the right margin of the sternum at the insertion of the sixth rib, runs under the right nipple, nearly parallel to the upper border of the sixth rib, and descends a little in the axillary line, to the upper margin of the seventh rib. On the left side (apart from the position of the heart), the lower limit reaches as far down anteriorly as the right. In Fig. 137 the line a, t, b, shows the lowest limit of the passive lungs. Posteri- orly, both lungs reach as far down as the tenth rib. During the deepest inspiration, the lungs descend anteriorly as far as between the sixth and seventh ribs, and posteriorly to the eleventh rib — whereby the diaphragm is separated from the thoracic wall (Fig. 133). During the deepest expiration, the lower margins of the lungs are elevated almost as much as they descend during inspiration. In Fig. 137, /;;, ;/, indicates the margin of the right lung during deep inspiration ; //, /, during deep expiration. It is important to observe the relation of the margin of the left lung to the heart. In Fig. 137 a somewhat triangular space, reaching from the middle of the point of insertion of the fourth rib to the sixth rib on the left side of the sternum, is indicated. In the passive chest, the heart lies in contact with the thoracic wall in this triangular area (§ 56). This area is represented by the triangle /. /', /", and percussion over it gives a dull sound (superficial dullness). In the area of the larger triangle d, d , d' , where the heart is separated from the chest wall by the thin anterior margins of the lung, percussion gives a muffled sound, while further outward a clear lung percussion sound is obtained. During deep inspiration, the inner margin of the left lung reaches over the heart as far as the insertion of the mediastinum, whereby the dull sound is limited to the smallest triangle, /, /, /'. Conversely, during very complete expiration, the margin of the lung recedes so far that the cardiac dullness embraces the space, /, e, e . 115. PATHOLOGICAL VARIATIONS OF THE PERCUSSION SOUNDS.— Abnormal Dullness. — The normal clear resonant percussion sound of the lungs becomes muffled when infiltration takes place into the lungs, so as to diminish the normal amount of air within them, or when the lungs are compressed from without, e. g., by effusion of blood into the pleura. The percussion sound becomes clearer when the chest wall is verj' thin, as in spare individuals, during very deep inspiration, and especially in emphysema, where the air vesicles of certain parts of the lung (apices and margins) become greatly dilated. The pitch of the percussion sound ought also to be noted. It depends upon the greater or less tension of the elastic pulmonary tissue, and on the elasticity of the thoracic wall. The tension of the elastic tissue is increased during inspiration and diminished during expiration, so that even under physiological conditions the pitch of the sound varies. The sound is said to be tympanitic (Skoda) when it has a musical quality resembling in its timbre the sound produced on a drum, and when it has a slight variation in pitch. If a caoutchouc ball be placed near the ear, on tapping it gently, a well-marked tympanitic sound is heard, and the sound is of higher pitch the smaller the diameter of the ball. A tympanitic sound is always pro duced on tapping the trachea in the neck. A tympanitic sound produced over the chest is always indicative of a diseased condition. It occurs in cases of cavities or vomicae within the substance of the lung (the sound becomes-deeper when the mouth, or better, the mouth and nose, are closed), when air is present in one pleural cavity, as well as in conditions where the tension of the pulmon- ary tissues is diminished. The tympanitic sound resembles the metallic tinkling which is heard in large pathological cavities in the lungs, or which occurs when the pleural cavity contains air, and when the conditions which permit a more uniform reflection of the sound waves within the cavity are present. [When a cavity, freely communicating with a large bronchus, exists in the upper and anterior 204 PATHOLOGICAL RESPIRATORY SOUNDS. part of Ihe lung, a peculiar " cracked-pot " sound is heard on percussing over the part. Some notion of this sound may be obtained by clasping the two hands so as to bring the palms nearly together, leaving an air space between, and then striking them on the knee. When percussion is made over a large cavity communicating with a bronchus, some of the air is expelled, and the sound thereby emitted is blended with the fundamental note of the air in the cavity itself, the combination of these two sounds thus producing the " cracked-pot " sound.] Resistance. — When percussing a chest, we may determine whether the substance lying under the portion of the chest under examination presents great or small resistance to the blow, either of the percussion hammer or of the tips of the fingers, as the case may be, [(•. ^■-., in great pleuritic effusion exerting much pressure on, and so distending the thorax walls]. Phonotnetry. — If the stem of a vibrating tuning-fork be placed on the chest wall over a part containing air, its sound is intensified ; but if it be placed over a portion of the lung which contains little or no air its sound is enfeebled [von Baas). Historical. — The actual discoverer of the art of percussion was Auenbrugger (f 1809). Piorry and Skoda developed the art and theory of percussion, while Skoda originated and developed the physical theory (1839). 116. THE NORMAL RESPIRATORY SOUNDS.— Normal Ves- icular Sound. — If the ear directly, or through the medium of a stethoscope, be placed in connection with the chest-wall, we hear over the entire area, where the lung is in contact with the chest, the so-called " vesicular " sound, which is audi- ble during inspiration, and its typical characters may be studied by listening in the infrascapular region in an adult. It is a fine sighing or breezy sound [which gradually increases in intensity until it reaches a maximum, and falls away before expiration begins]. It is said to be caused by the sudden dilatation of the air vesicles (hence "vesicular") during inspiration, and it is also ascribed to the friction of the current of air entering the alveoli. The sound has, at one time, a soft, at another, a sharper character ; the latter occurs constantly in children up to 12 years of age. In their case, the sound is sharper, because the air, in enter- ing vesicles one-third narrower, is subjected to greater friction. [This is followed by an expiratory sound, which may be absent during quiet breathing. It is a feeble, sighing sound, of an indistinct, soft character, caused by the air passing out of the air vesicles, is three or four times shorter than the inspiratory, is loudest at first, and soon disappears, the latter part of the expiratory act giving rise to no audible sound. Its absence is not a sign of disease, but when it is prolonged and loud, suspicion is aroused.] Bronchial Respiration. — Within the larger air passages — larynx, trachea, bronchi — during inspiration and expiration, there are loud, rough, harsh sounds like a sharp h or ch — the '^ broncliial" — the laryngeal, tracheal, or "tubular" sound, or breathing. [In normal bronchial breathing, as heard over the trachea, there is a pause between the inspiratory and expiratory sounds, which are of nearly equal duration and of about the same intensity throughout.] These sounds are also heard between the scapula;, at the level of the fourth dorsal vertebra (bifurcation of trachea), and they occur also during expiration, being slightly louder on the right side, owing to the slightly greater calibre of the right bronchus. At all other parts of the chest, the vesicular sound obscures the tubular or bron- chial sound. If the air vesicles are deprived of their air, the tubular breathing becomes distinct. It is asserted that, when lungs containing air are placed over the trachea, the tubular sound there produced becomes vesicular. In this case, we must suppose that the vesicular sound arises from the tubular breathing becoming weakened, and being acoustically aUered, by being conducted through the lung alveoli [Baas, Pcnzolilt). A sighing sound is often produced at the apertures of the nose and mouth during forced respiration. 117. PATHOLOGICAL RESPIRATORY SOUNDS.— Historical.— Although several abnormal sounds in connection with diseases of the respiratory organs were known to Hippocrates (succussion sound, friction and several catarrhal sounds) still, Laennec was the discoverer of the method of auscultation (1S16), while Skoda greatly extended our knowledge of its facts. [The breath sounds heard in disease may be merely modifications of the normal vesicular or bronchial sounds, or new sounds, such as friction sounds, rales or rhonchi.] [Puerile Breathing is merely an exaggerated vesicular sound, so called because it resembles PRESSURE IN THE AIR PASSAGES DURING RESPIRATION. 205 the louder vesicular sound heard in children. It occurs when some part of the lung is unable to act, and there is, as it were, extra work of the other parts to compensate, and thus the sound is exaggerated.] (1 ) Bronchial or Tubular Breathing occurs over the entire area of the lung, either when the air vesicles are Ji-i'oid of air, which may be caused by the exudation of fluid or solid constituents, or when the lungs are compressed from without. In both cases vesicular sounds disappear, and the condensed or solidified lung tissue conducts the tubular sound of the large bronchi (o the surface ol the chest. [The sound heard over a hepatized lobe of the lung in pneumonia is a typical example.] It also occurs in large cavities, with resistant walls near the surface of the lung, provided these cavities communicate with a large bronchus. [In this case it is termed Cavernous Breathing]. (2) The amphoric sound is compared to that produced by blowing over the mouth of an empty bottle. It occurs either when a cavity — at least the size of the fist — exists in the lung, which is so blown into during respiration that a peculiar amphoric-liUe sound, with a metallic timbre called metallic tinkling, is produced; or when the lung still contains air, and is capable of expansion; as there is still air in the pleural cavity, it acts as a resonator, and causes an amphoric sound, simultaneous with the change of air in the lungs. [The amphoric sound or echo and metallic tink- ling are the only certain signs of the existence of a cavity in the lung.] (3) If obstruction occurs in the course of the air passages of the lungs, various results may accrue, according to the nature of the resistance : (ach), [but the two processes do not stand in the relation of cause and effect]. [The secretion cannot be e.xcited by stimulating the nerves going to the mucous membrane. This merely causes anaemia of the mucous membrane, while the secretion continues.] Effects of Reagents on the Mucous Secretion. — If ice be placed on the belly of an animal so as to cause the aniirial to " ta/:c a to/u," the respiratory mucous membrane first becomes pale, and afterward there is a copious mucous secretion, the membrane becoming deeply congested. The injection of sodium carbonate and ammonium chloride mto the blood limits the secretion. The local application of alum, silver nitrate, or tannic acid, makes the mucous membrane turbid, and the epithelium is shed. The secretion is excited by apomorphin, emetin, pilocarpin, and ipecacuanha when given internally, while it is limited by atropin and morphia [Rosshach). [Expectorants favor the removal of the secretions from the air passages. This they may do eitiier by {a) altering the character and qualities of the secretion itself, or {/>) by affecting the expul- sive mechanism. Some of the drugs already mentioned are examples of the first class. The second class act chiefly by influencing the respiratory centre, such as ipecacuanha, strychnia, ammonia, senega; emetics also act energetically as expectorants, as in some cases of chronic bronchitis; warmth and moisture of the air are also powerful adjuncts.] Normal Sputum. — Under normal circumstances some mucus — mixed with a little saliva — may be coughed up from the back of the throat. In catarrhal con- ditions of the respiratory mucous membrane, the sputum is greatly increased in amount, and is often mixed with other characteristic products. Microscopic- ally, sputum contains — I. Epithelial Cells — chiefly squames from the mouth and pharynx (Fig. 144), more rarely alveolar epithelium and ciliated epithelium (7) from the respiratory passages. The epithelial cells are often altered, having undergone maceration or other changes. Thus some cells may have lost their cilia (6). The epithelium of the alveoli (2) is .squamous epithelium, the cells beingtwo to four times the breadth of a colorless blood corpuscle. These cells occur chiefly in the morning sputum in indi- viduals over 30 years of age. In younger persons their presence indicates a pathological condition of the pulmonary parenchyma {Gtitiman,U. Schmidt, and Bizzosero). They often undergo fatty degeneration, and they may contain pigment granules (3) ; or they may present the appearance of 228 THE SPUTUM. what Buhl has called " myelin degeneraieJ cells" i. e., cells filled with clear refractive drops of vari- ous sizes, some colorless, others colored particles, the latter having been absorbed (4). Mucin in the form of myelin drops (5) is always present in sputum. 2. Lymphoid cells (9) are to be regarded as colorless blood corpuscles which have wandered out of the blood vessels ; they are most numerous in yellow sputum, and less numerous in the clear, mucus-like excretion. The lymph cells often pre- sent alterations in their characters ; they may be shriveled up, fatty, or present a granular ajipearance. 'Y\\t jiutil siihstance oi X\\^ sputum contains much ////^c«j arising from the mucous glands and goblet cells; together with nuclein, and lecithin, and the constituents of saliva according to the amount of the latter mixed with the secretion. Albu- min occurs only during inflammation of the respiratory passages, and its amount increases with the degree of inflammation. Urea has been found in cases of nephritis. Fig. 144. Various objects found in sputum, i, Detritus and particles of dust : 2, alveolar epithelium with pigment; 3, fatty anci partly pigmented alveolar epithelium ; 4, alve-ilar epithelium containing myelin forms ; 5, free myelin forms ; 6, 7, ciliated epithelium, some changed, others without cilia; 8, squamous epitheluim from the mouth; 9, leu- cocytes ; 10, elastic fibres ; 11, fibrin cast of a small bronchus; 12, leptothrix buccalis with cocci, bacteria, and spirochastae ; a, fatty acid crystals and free fatty granules ; ^, haematoidin ; c, Charcot's crystals ; rf, Cholesterin. Pathological. — In cases of ca/tirrA, the sputum is at first usually sticky and clear (sputa cruda), but later it becomes more firm and yellow (sputa cocta). Under pathological conditions there may be found in the sputum — (a) red blood corpuscles, from rupture of a bloodvessel, [b) Elastic fibres (10) from disintegration of the alveoli of the lung; usually the bundles are fine, curved, and the fibres branched. [In certain cases it is well to add a solution of caustic potash, which dissolves most of the other elements, leaving the elastic fibres untouched.] Their presence always indicates destruction of the lung tissue, (c) Colorless plugs of fibrin (11), casts of the smaller or larger bronchi, occur in some cases of fibrinous exudation into the finer air passages. (} and cholesterin crystals ((/) occur much more rarely. Fungi and other lowly organisms are taken in during inspiration {\ 136). The threads of I^eptothrix buccalis (12) detached from the teeth, are frequently found (\ 147). Mycelium and ACTION OF DIMINISHED ATMOSPHERIC PRESSURE. 229 spores are found in thrush (Oiclium albicans), especially in the mouths of sucking infants. In mal- odorous expectoration rod-shaped bacteria are present. In pulmonary' gangrene are found monads, and cercomonad (A'annenbdi-i;) ; in pulmonary phthisis the tubercle bacillus {R. Koch) \ very rarely sarcina, which, however, is often found in gastric catarrh in the stomach, and also in the urine (Fig. in \ 270). Physical Characters. — Sputum, with reference to its physical characters, is described as mucous, miico-ptirnlent, ox purulent. Abnormal coloration of the sputum — red from blood. When the blood remains long in the lung it undergoes a regular series of changes, and tinges the sputum dark red, bluish brown, brown- ish yellow, deep yellow, yellowish green, or grass green. The sputum is sometimes yellow in jaun- dice. The sputum may be tinged by what is inspired [as in the case of the "black spit" of miners]. The odor of the sputum is more or less unpleasant. It becomes very disagreeable v.'hen it has remained long in pathological lung cavities, and it is stinking in gangrene of the lung. 139. ACTION OF THE ATMOSPHERIC PRESSURE.— At the normal pressure of the atmosphere (height of the barometer, 760 millimetres Hg), pressure is e.xerted upon the entire surface of the body ^ 15,000 to 20,000 kilos., according to the extent of the superficial area {^Galileo). This pressure acts equally on all sides upon the body, and occurs also in all internal lavities containing air, both those that are constantly filled with air (the respiratory pa.ssages and the spaces in the superior maxillary, frontal and ethmoid bones), and those that are temporarily in direct communication with the outer air (the digestive tract and tympanum). As \\\t fluids of tlie body (blood, lymph, secretions, parenchymatous juices) are, practically, incompressible, their volume remains practically unchanged under the pressure ; but they will absorb gases from the air corresponding to the prevailing pressure (/. e., the partial pressure of the individual gases), and accord- ing to their temperature (compare §33.) The solids consist of elementary parts (cells and fibres), each of which presents only a microscopic surface to the pressure, so that for each cell the prevailing pressure of the air can only be calculated at a few millimetres — a pressure under which the most delicate histological tissues undergo development. As an example of the action of the pressure of the atmospheric pressure upon large masses, take that brought about by the adhesion of the smooth, sticky, moist, articular surfaces of the shoulder and hip joints. In these cases, the arm and the leg are supported without the action of muscles. The thigh bone remains in its socket after section of all the muscles and its capsule {Brothers Weber'). Even when the cotyloid cavity is perforated, the head of the femur does not fall out of its socket. The ordinary barometric variations affect the respiration — a rise of the barometric pressure excites, while a fall diminishes, the respirations. The absolute amount of CO... remains the same (§ 127, 8). A Great Diminution of the Atmospheric Pressure, such as occurs in ballooning (highest ascent, 8600 metres), or in ascending mountains, causes a series of characteristic phenomena: (I) In consequence of the diminution of the pressure upon the parts directly in contact with the air, they become greatly congested ; hence, there is redness and swelling of the skin and free mucous membranes; there may be hemorrhage from the nose, lungs, gums, turgidity of the cutaneous veins, copious secretion of sweat, great secretion of mucus. (2) A feeling of weight in the limbs, a press- ing outward of the tympanic membrane (until the tension is equilibrated by opening the Eustachian tube), and, as a consequence, noises in the ears and difficulty of hearing. (3) In consequence of the diminished tension of the O in the air (\ 129), there is difficulty of breathing, pain in the chest, whereby the respirations (and pulse) become more rapid, deeper and irregular. When the atmo- spheric pressure is diminished \--\, the amount of O in the blood is diminished (Bert, Friinkel and Geppert), the CO^ is imperfectly removed from the blood, and, in consequence, there is diminished oxidation within the body. When the atmospheric pressure is diminished to one-half, the amount of CO .2 in arterial blood is lessened ; and the amount of N diminishes proportionplly with the de- crease of the atmospheric pressure (Friinkel and Geppert). The diminished tension of the air prevents the vibrations of the vocal cords from occurring so forcibly, and, hence, the voice is feeble. (5) In consequence of the amount of blood in the skin, the internal organs are relatively anojmic ; hence, there is diminished secretion of urine, muscular weakne.ss, disturbances of digestion, dullness of the senses, and. it may be, unconscimisness, and all these phenomena are intensified by the con- ditions mentioned under (3). Some of ihe'^e phenomena are modified by usage. The highest limit at which a man may still retain his senses is placed by Tissandier at an elevation of Scxx) metres 230 HISTORICAL. (2S0 mm. Hg). In dogs, the blood pressure falls, and the pulse becomes small and diminished in frequency when the atmospheric prssure falls to 200 mm. Hg. Those who live upon high mountains sufter from a disease, mal de montagne, which consists, essentially, in tlie above symptoms, although it is sometimes complicated with anaimiaof the internal organs. Al. v. Humboldt found that in those who lived on the Andes the thorax was capacious. At 6000 to Sooo feet above sea level, water contains only one-third of the absorbed gases, so that fishes cannot live in it {Boussiiigaii/l). Animals may be sulijected to a further diminution of the atmospheric pressure by being placed under the receiver of an air pump. Birds die when the pressure is reduced to 120 mm. Hg; mammals, at 40 mm. Hg; frogs endure repeated evacuations of the receiver, whereby they are much distended, owing to the escape of gases and water ; but after the entrance of air, they become greatly compressed. The cause of death in mammals is ascribed by Hoppe-Seyler to the evolution of bubbles of gas in the blood; these bubbles stop up the capilla- ries and the circulation is arrested. Local Jiminiition of the atmospheric pressure causes marked congestion and swelling of the part, as occurs when a cupping glass is used. Great Increase of the Atmospheric Pressure. — The phenomena which are, for the most part, the reverse of the foregoing, have been observed in pneumatic cabinets and in diving bells, where men may work even under 4^ atmospheres pressure. The phenomena are : (i) Paleness and dryness of the external surfaces, collapse of the cutaneous veins, diminution of perspiration and mucous secretions. (2) The tympanic membrane is pressed inward (until the air escapes through the Eustachian lube, after causing a sharp sound), acute sounds are heard, pain in the ears, and difficulty of hearing. (3) A feeling of lightness and freshness during respiration, the respira- tion becomes slower (by 2-4 per minute), inspiration easier and shorter, e.vpiration lengthened, the pause distinct. The capacity of the lungs increases, owing to the freer movement of the diapliragm, in consequence of the diminution of the intestinal gases. Owing to the more rapid oxidations in the body, muscular movement is easier and more active. The O absorbed and the CO^ excreted are increased. The venous blood is reddened. (4) Difficulty of speaking, alteration of the tone of the voice, inability to whistle. (5) Increase of the urinary secretion, more muscular energy, more rapid metabolism, increased appetite, subjective feeling of warmth, pulse beats slower, and pulse curve is lower (compare ^ 74). In animals subjected to excessively high atmospheric pressure, P. Bert found that the arterial blood contained 30 vols, per cent. O (at 760 mm. Hg) ; when the ainount rose to 35 vols, per cent, death occurred, with convulsions. Compressed air has been used for therapeutical purposes, but in doing so a too rapid increase of the pressure is to be avoided. Waldenburg has constructed such an apparatus, which may be used for the respiration of air under a greater or less pressure. Frogs, when placed in comprfssed O (at 14 atmospheres), exhibit the same phenomena as if tliey were in a vacuum, or pure N. There is paralysis of the central nervous system, sometimes preceded by convulsions. The heart ceases to beat (not the lymph hearts), while the excitability of the motor nerves is lost at the same time, and, lastly, the direct muscular excitability disappears (A'. £. Lchniann], An excised frog's heart placed in O, under a very high pressure (13 atmo- spheres), scarcely beats one-fourth of the time during which it pulsates in air. If the heart be exposed to the air again, it begins to beat ; so that compressed O renders the vitality of the heart latent before abolishing it. Phosphorus retains its luminosity under a high jjressure in O {Schonbeiit), but this is not the case with the luminous organisms, e.g., I.ampyris, and luminous bacteria (A'. B. Lehmann). A very high atmospheric pressure is also injurious to plants. 140. COMPARATIVE AND HISTORICAL —Mammals have lungs similar to those of man. The lungs of birds are spongy, and united to the chest wall, while there are openings on their surface communicating with thin walled " air sacs," which are placed among the viscera. The air sacs communicate with cavities in the bones, which give the latter great lightness [.Aristotle). The diaphragm is absent. In reptiles the lungs are divided into greater and smaller compartments ; in snakes one lung is abortive, while the other has the elongated form of the body. The amphibians (frog) possess two simple lungs, each of which represents an enormous infuiidibulum with its alveoli. The frog pumps air into its lungs by the contraction of its throat, the nostrils being closed and the glottis opened. When young — until their metamorphosis — frogs breathe like fishes, by means of gills. The perennibranchiate amphibians (Proteus) retain their gills throughout life. Among fishes, which breathe by gills and use the O absorbed by the water, the Dipnoi have, in addition to gills, a swim bladder, provided with afferent and eft'erent vessels, which is comparable to the lung. The Cobitis respires also with its intestine [Erman, 180S). Insects and centipedes respire by "trachea;," which are branched canals distributed throughout the body; they open on the surface of the body by openings (stigmata), which can be closed. Spiders respire by means of trachcc^ and tracheal sacs; crabs, by gills. The molluscs and cephalopods have gills; some gasteropods have gills and others luni;s. Among the lower invertebrata some breathe by gills, others by means of a special " water vascular .system," and others again by no special organs. Historical. — Aristotle (384 B. c. ) regarded the object of respiration to be the cooling of the body, so as to moderate the internal warmth. He ob.served correctly that the warmest animals breathe most actively, but in interpreting the fact he reversed the cause and effect. Galen ( 131-203 A. D.) thought that the "soot " was removed from the body along with the expired water. The most im- HISTORICAL. 231 portant experiments on the mechanics of respiration date from Galen ; he observed that the lungs passively follow the movements of the chest; that the diaphragm is the most important muscle of inspiration; that the external intercostals are inspiratory, and the internal, expiratory. He divided the intercostal ner\'es and muscles, and observed that loss of voice occurred. On dividing the spinal cord higher and higher, he found that as he did so the muscles of the thorax lying higher up became paralyzed. Oribasius (360 A. D.) observed that in double pneumothorax both lungs collapsed. Ve^alius (1540) first described artificial respiration as a means of restoring the beat of the heart. Malpighi (1661) described the structure of the lungs. J. A. Borelli (f 1679) gave the first funda- mental description of the mechanism of the respiratory movements. The chemical processes of respiration could only be known after the discovery of the individual gases therein concerned. Van Helmont (t 1644) detected COj. [Joseph Black (1757) discovered, by the following experiment, that COj or " fixed air " is given out during expiration : Take two jars of lime water, breathe into one through a bent glass tube, and force ordinary air through the other, when a white precipitate of calcium carbonate will be found to occur in the former.] In 1 774 Priestley discovered O. Lavoisier delected N (1775), and ascertained the composition of atmospheric air, and he regarded the forma- tion of COj and H^O of the breath as a result of a combustion within the lungs themselves. J. Ingen-Houss (1730-1790) discovered the respiration of plants. Vogel and others proved the exist- ence of CO, in venous blood, and Hoffmann and ethers that of O in arterial blood. The more complete conception of the exchange of gases was, however, only possible after Magnus had extracted and analyzed the gases of arterial and venous blood (J 36). Physiology of Digestion. 141. THE MOUTH AND ITS GLANDS.— The mucous membrane of the cavity of the mouth, which becomes continuous with the skin at the red margin of the lips, has a number of sebaceous glands in the region of the red part of the Hp. The buccal mucous membrane consists of bundles of fine fibrous tissue mixed with elastic fibres, which traverse it in every direction. Papillae — simple or compound — occur near the free surfaces. The submucous tissue, which is directly continuous with the fibrous tissue of the mucous membrane itself, is thickest where the mucous membrane is thickest, and densest where it is firmly fixed to the Fig. 145. periosteum of the bone and to the gum ; it is thinnest where the mucous membrane is most movable, and where there are most folds. The cavity of the mouth is lined by stratified squamous epithelium (Fig. 145), which is thickest, as a rule, where the longest papillce occur. All the glands of the mouth, including the salivary glands, may be divided into different classes, according to the nature of their secretions. 1. The serous or albuminous glands [t>-ue salh'aiy'], whose secretion contains a certain amount of albumin, e. g., the human parotid. 2. The mucous glands, whose secretion, in addition to some albumin, contains the characteristic constituent mucin. 3. The mixed [or miu-o-saliran'] glands, some of the acini secreting an albuminous fluid and other mucin, e.g., the human maxillary gland {HciJcnhaifi). The structure tach1:'d"from of these glands is referred to under the salivary glands. fied squamous epitheliun Numerous mucous glands (labial, buccal, palatine, lingual, molar) have the appearance of small macroscopic bodies lying in the sub-mucosa. They are branched tubular glands, and the contents of their secretory cells consist partly of mucin, which is expelled from them during secretion. The excretory ducts of these glands, which are lined by cylindrical epithelium, are constricted where they enter the mouth. Not unfrequently one duct receives the secretion of a neighboring gland. The glands of the tongue form two groups which differ morphologically and physiologically, (i) The mucous glands ( Iledfr's glands), occurring chiefly near the root of the tongue, are branched tubular glands lined with clear, transparent, secretory cells whose nuclei are placed near the attached end of the cells. The acini have a distinct membrana propria. (2) The serous glands (£bners) are acinous glands occurring in the region of the circumvallate papilla- (and in animals near the papiihe foliatae). They are lined with turljid granular epithelium with a central nucleus, and they secrete saliva [HenU). (3) The glands of Blandin and Nuhn are placed near the tip of the tongue, and consist of mucous and serous acini, so that they are mixed glands {Podunsotzky). The blood vessels are moderately abundant, and the larger trunks lie in the sub muco-sa, while the finer twigs penetrate into the papillre, where they form either a capillary network or simple loops. The larger lymphatics lie in the sub-mucosa, while the finer branches form a fine network placed in the mucosa. The lymph follicles also belong to the lymphatic system (§ 197). On the dorsum of the posterior part of tlie tongue they form an almost continuous layer. They are round or oval (1-1.5 mm. in diameter), and placetl in the sub-mucosa. They consist of adenoid tissue loaded with lyniph corpuscles. The outer part of the adenoid reticulum is compressed so as to form a kind of capsule for each follicle. Similar follicles occur in the intestine as solitary follicles; in the small intestine they are collected together into Peyer's patches, and in the spleen they occur as Malpighian corpuscles. On the dorsum of the tongue several of these follicles form a slightly oval elevation, wliich is surrounded by connective tissue. In the centre of this elevation there is a depression, into which a mucous gland opens, which fills the small crater with mucus (Fig. 146). 232 THE SALIVARY GLANDS. 233 The Tonsils have fundamentally the same structure. On their surface are a number of depres- sions into which the ducts of small mucous glands open. These depressions are surrounded by groups (10-20) of lymph follicles, and the whole is environed by a capsule of connective tissue. After E. H. Weber discovered lymphatics in the neighborhood of the tonsils, Briicke referred these structures to the lymphatic system. Large lymph spaces, communicating with lymphatics, occur m the neighborhood of the tonsils, but as yet a direct connection between the spaces in the follicles and the lymph vessels has not been proved to exist. Similar structures occur in the tubal and pharyngeal tonsils. [Slohr asserts that an enormous number of leucocytes wander out of the tonsils, solitary and Peyer's glands, and the adenoid tissue of the bronchial mucous membrane. The cells pass out between the epithelial cells, but do not pass in'o the interior of the latter.] Nerves. — Numerous medullaled nerve fibres occur in the sub-mucosa, pass into the mucosa, and terminate partly in the individual papillae in Krause's end bulbs, which are most abundant in the hps and soft palate, and not so numerous in the cheeks and in the floor of the mouth. The nerves ad- minister not only to common sensation, but they also are the organs of transmission for tactile (heat and pressure) impressions. It is highly probable, however, that some nerve fibres end in fine ter- minal fibrils, between the epithelial cells, such as occur in the cornea and elsewhere. 142. THE SALIVARY GLANDS.— Structure of the Ducts.— The three pairs of salivary glands, sub-maxillary, sublingual, and parotid, are com- pound tubular glands. Fig. 148, A, shows a fine duct, terminating in the more or less flask-shaped alveoli or acini. [Each gland consists of a number of lobes, and Fig. 146. Closed follicles. i- -^- Section of ; follicle from the dorsum of the tongue {Schenk). each lobe in turn of a number of lobules, which again are composed of acini. All these are held together by a framework of connective tissue. The larger branches of the duct lie between the lobules, and constitute the interlobular ducts, giving branches to each lobule which they enter, constituting the intra- lobular ducts. These intralobular ducts branch and finally terminate in connection with the alveoli, by means of an intermediary or intercalary part. The larger interlobar and interlobular ducts consist of a membrana propria, strengthened outside with fibrous and elastic tissue, and in some places also by non-striped muscle, while the ducts are lined by columnar epithelial cells. In the largest branches there is a second row ^>^^V' .'■.:fl'/;"//'^'/>, of stnaller cells, lying between the large cells and the mem- vV ' brana propria. The intralobular ducts are lined by a single £;;' layer of large cylindrical epithelium. As is shown in Fig. 147. ^;.-; the nucleus occurs about the middle of the cell, while the outer \:-. half, /. e., ne.\t the basement membrane of the cell, is finely V striated longitudinally, which is due to fibrillas ; the inner half ""iin\'i\\\ii-^ next the lumen is granular. The intermediary part is narrow, Rodded epiiheiii and is lined by a single layer of flattened cells, each with an glffid""'" "' Fig. 147. 234 THE STRUCTURE OF THE SALIVARY GLANDS. elongated oval nucleus. There is usually a narrow " neck," where the intra- lobular duct becomes continuous with the intermediary part, and here the cells are polyhedral (A'A-Zn). The acini, or alveoli, are the parts where the actual process of secretion takes place. They vary somewhat in shape ; some are tubular, others branched, some are dilated and resemble a Florence flask, and several of them usually open into one intermediary part of a duct. Each alveolus is bounded by a basement mem- brane, with a reticulate structure made up of nucleated, branched, and anastomos- ing cells, so as to resemble a basket (D). There is a homogeneous membrane bounding the alveoli in addition to this basket-shaped structure. Immediately outside this membrane is a lymph space {Giaiunzi), and outside this again the net- work of capillaries is distributed. [The extent to which this lymph space is filled with lymph determines the distance of the capillaries from the membrana propria. The inter-alveolar lymph spaces communicate with large lymph spaces between the lobules, which in turn communicate with perivascular lymphatics around the arteries and veins.] The lymphatics emerge from the gland at the hilum. The secretory cells vary in structure, according as the salivary gland is A, duct and acini of the parotid gland of a dog: B. acini of the sub-maxillary gland of a dog : c, refractive mucous cells ; ti, g'-anular half-moons of Gianuzzi ; C, similar alveoli after prolonged secretion ; D, basket-shaped tissue " : of a non-meduUated nerve fibre into a secretory cell. mucous [sub-maxillary and sublingual of the dog and cat], a serous [parotid of man and mammals, and sub-maxillary of rabbit], or a mixed gland [human sub-maxillary and sublingual]. Mucous Acini. — The secretory cells of mucous glands, and the mucous acini of mixed glands (Fig. 149), are lined by a single layer of " mucin cells " (^Hcidenhain) (Fig. 148, B, <-), which are large cells distended with mucin-, or, at least, with a hypothetical substance, mucigen, which yields mucin. The mucin cells are more or less spheroidal in shape, clear, shining, highly refractive, and nearly fill the acinus. The flattened nucleus is near the wall of the acinus. Each cell has a fine process which overlaps the fixed parts of the cell next to it. Owing to the fact that the body of each cell is infiltrated with mucin, these cells do not stain with carmine, although the nucleus and its immediately investing protoplasm do. Another kind of cell occurs in the sub-maxillary gland of the dog. It ioxxm z. half-moon-shaped structure lying in direct contact with the wall of the acinus {Gianuzzi). Each " half-moon " or " crescent " consists of a number of small, closely packed, angular, strongly albuminous cells with small oval nuclei, which, however, are separated only with difficulty. Hence, Heidenhain HISTOLOGICAL CHANGES IN THE SALIVARY GLANDS. 235 has called them "composite marginal cells" (B, d). They are granular, darker, devoid of mucin, and stain readily with pigments. [In the sub-maxillary gland of the cat there is a complete layer of these " marginal " carmine-staining cells lying between the mucous cells and the membrana propria.] [Serous Acini. — In true serous glands (parotid of man and mammals) and in the serous acini of mixed glands, the acini are lined by a single layer of secre- tory, columnar, finely granular cells, which, in the quiescent condition, completely fill the acinus, so that scarcely any lumen is left. Just before secretion, or when these cells are quiescent, Langley has shown that they are large and filled with numerous granules, which obscure the presence of the nucleus. As secretion takes place, these granules seem to be used up or discharged into the lumen ; at least, the outer part of each cell gradually becomes clear and more transparent, and this condition spreads toward the inner part of the cell.] [In the mixed or muco-salivary glands {Klein) {e.g., human sub-maxillary), some of the alveoli are mucous and others serous in their characters, but the latter are always far more numerous, and the one kind of acinus is directly continuous with the others (Fig. 149)] P"iG. 149. Section of part of the human 143. HISTOLOGICAL CHANGES DURING THE ACTIVITY OF THE SALIVARY GLANDS.— [The condition of physiological activity of the gland cells is accompanied by changes in the histological characters of the secretory cells.] [Serous Glands. — The changes in the secretory cells have been carefully studied in the parotid of the rabbit. The histological appearances vary some- what, according as the glands are examined in the fresh condition or after harden- ing in various reagents, such as absolute alcohol. When the gland is at rest, in a preparation hardened in alcohol, and stained with carmine, the cells consist of a pale, almost uncolored sulistance, with a few fine granules, and a small, irregu- lar, red-stained, shriveled nucleus, devoid of nucleolus. The appearance of the nucleus suggests the idea of its being shriveled by the action of the harden- ing reagent (Fig. 150).] [During activity, if the gland be caused to secrete by stimulating the sym- pathetic, all parts of the cells undergo a change (Fig. 150, 151). (i) The cells diminish somewhat in size; (2) the nuclei are no longer irregular, but round. 236 HISTOLOGICAL CHANGES IN THE SALIVARY GLANDS. with a sharp contour and nucleoli; (3) the substance of the cell itself is turbid, owing to the diminution of the clear substance, and the increase of the granules, especially near the nuclei; C4) at the same time, the whole cell stains more deeply with carmine {Heideii/iain).'\ [On studying the changes which occur in a living serous gland, Langley found that, during rest, the substance of the cells of the parotid is pervaded by fine granules, which are so numerous as to obscure the nucleus, while the outlines of the cells are indistinct. No lumen is visible in the acini during activity, the granules disappear frotn the outer zone of the cells, the cells themselves becoming more distinct and smaller. After prolonged secretion, the granules largely dis- appear from the cell substance except quite near the inner margin. The cells are smaller, their outlines more distinct, their round nuclei apparent, and the lumen of the acini is wide and distinct. Thus, it is evident that, during rest, granules are manufactured, which disappear during the activity of the cells, the disappear- ance taking place from without inward. Similar changes occur in the cells of the pancreas.] [Mucous Glands. — More complex changes occur in the mucous glands, such as the sub-maxillary or orbital glands of the dog {Lavdovsky). The appearances vary according to the intensity and duration of the secretory activity. The Fig 151. 3^ Fig, 151, after stimulatit nmcous cells at rest are large, clear, and rf'fractive, containing a flattened nucleus (Fig. 148, B, c), surrounded with a small amount of protoplasm, and jilaced near the basement membrane. The clear substance does not stain with carmine, and consists of mucigen lying in the wide spaces of an intracellular plexus of fibrils. After prolonged secretion, produced, it may be, by strong and continued stimulation of the chorda, the mucous cells of the sub-maxillary gland of the dog undergo a great change.] The distended, refractive, and "mucous cells," which occur in the quiescent gland, and which do not stain with carmine, do not appear after the gland has been in a state of activity. Their place is taken by small, dark, protoplasmic cells devoid of mucin (Fig. 148, C). These cells readily stain with carmine, while their nucleus is scarcely, if at all, colored by the dye. The researches of R. Heidenhain ( 1S68) have shed much light on the secretory activity of the salivary glands. The change may be produced in two ways. Either it is due to the "mucous cells" during secretion becoming broken up, so that they yield their mucin directly to the saliva ; in saliva rich in mucin, small microscopic pieces of mucin are found, and sometimes mucous cells themselves are pre--ent. Or, we must assume that the mucous cells simply eliminate the mucin from their bodies \Ewald, St'dhr) ; while, after a period of rest, new mucin is formed. According to this view, the dirk granular cells of the glands, after active secretion, are simply mucous celN, which have given out their mucin. If we assume, with Heidenhain, that the mucous cells break up, then these ACTION OF NERVES ON THE SECRETION OF SALIVA. 237 granular non mucous cells must be regarded as new formations produced by the proliferation and growth of the composite marginal cells, ;'. e., the crescents, or half-moons of Gianuzzi. [During rest, the protoplasm seems to manufacture mucigen, which is changed into and discharged as mucin in the secretion, when the gland is actively secreting. Thus, the cells become smaller, but the protoplasm of the cell seems to increase, , new mucigen is manufactured during rest, and the cycle is repeated.] 144. THE NERVES OF THE SALIVARY GLANDS.— The nerves are for the most part medullated, and enter at the hilum of the gland, where they form a rich plexus provided with ganglia between the lobules. [According to Klein, there are no ganglia in the parotid gland.] {^Krause, Reich, Schliiter.) All the salivary glands are supplied by branches from two different nerves — from the sympathetic and from a cranial nerve. 1. The sympathetic nerve gives branches to {a) the sub-maxillary and the sublingual glands, derived from the plexus on the external maxillary artery ; (^) to the parotid gland from the carotid plexus. 2. The facial nerve gives branches to the sub-maxillary and sublingual glands from the chorda tympani which accompanies the lingual branch of the fifth nerve. The branches to the parotid reach it in a roundabout way. They arise from the tympanic branch of the glosso-pharyngeal nerve (dog). The tympanic plexus sends fibres to the small superficial petrosal nerve (Eckhard), and with it these fibres run to the anterior surface of the pyramid in the temporal bone, emerging from the skull through a fissure between the petrous and great wing of the sphenoid, and then joining the otic ganglion. This ganglion sends branches to the auriculo- temporal nerve (itself derived from the third branch of the trigeminus), which, as it passes upward to the temporal region, under cover of the parotid, gives branches to this gland (?'. Wittich). The sub-maxillary ganglion, v/hich gives branches to the sub-maxiUary and sublingual glands, receives fibres from the tympanico-lingual nerv'e (Chorda tym- pani), as well as sympathetic fibres from the plexus on the external maxillary artery. Termination of the Nerve Fibres. — With regard to the ultimate distribu- tion of these nerves we can distinguish (i ) the vasomotor nerves, which give branches to the walls of the blood vessels, and (2) the secretory nerves proper. Pfliiger states, with regard to the latter, that {a) medullated nerve fibres penetrate the acini; the sheath of Schwann (gray sheath) unites with the membrana propria of the acinus ; the medullated fibre — still medullated — passes between the secre- tory cells, where it divides and becomes non-medullated, and its axial cylinder terminates in connection with the nucleus of a secretory cell. [This, however, is not proved] (Fig. 148, F). (J)) According to Pfliiger, some of the nerve fibres end in multipolar ganglion cells, which lie out- side the wall of the acinus, and these cells send branches to the secret'jry cells of the acini. [These cells probably correspond to the branched cells of the basket-shaped structure.] (c) Again, he describes medullated fibres which enter the attached end of the cylindrical epithe- lium lining the excretory ducts of the glands i^E). Pfliiger thmks that those fibres entering the acini directly are cerebral, while those witli ganglia in their course are derived from the sympathetic system. [(«) The direct termination of nerve fibres has been observed in the salivary glands of the cock- roach by Kupffer.] 145. ACTION OF THE NERVOUS SYSTEM ON THE SECRE- TION OF SALIVA.— (A) Submaxillary Gland.— Stimulation of the facial nerve at its origin {Li/divig and Rahn) causes a profuse secretion of a thin watery saliva, which contains a very small amount of specific constituents (Eckhard). Simultaneously with the act of secretion, the blood vessels of the glands become dilated, and the capillaries are so distended that the pulsatile movement in the arteries is propagated into the veins. Nearly four times as much blood flows out of the veins (CV. Bernard), the blood being of a bright red color. 238 ACTION OF NERVES ON THE SECRETION OF SALIVA. and contains one-third more O than the venous blood of the non-stimulated gland. Notwithstanding this relatively high percentage of O, the secreting gland uses more O than the passive gland (§ 131, i). [I. Stimulation of Chorda. — If a cannula be placed in Wharton's duct, e.g., in a dog, and the chorda tympani be divided, no secretion flows from the cannula. On stimulating X\\^ periplicral end of the chorda tympani \\\\.\\ an interrupted cur- rent of electricity, the same results — copious secretion of saliva and vascular dila- tation, with increased flow of blood and lymph, through the gland — occur as when the origin of the seventh nerve itself is stimulated The watery saliva is called chorda saliva.] Two functionally different kinds of nerve fibres occur in the facial nerve — (i) true secretory fibres, (2) vaso-dilator fibres. The increased amount of secre- tion is not due simply to the increased blood supply, as is proved below. II. Stimulation of the sympathetic nerve causes a scanty amount of a very thick, sticky, mucous secretion (Eckhard), in which the specific salivary constituents, mucin, and the salivary corpuscles are very abundant. The specific gravity of the saliva is raised from 1007 to loio. Simultaneously the blood ves- sels become contracted, so that the blood flows more slowly from the veins, and has a dark bluish color. The sympathetic also contains two kinds of nerve fibres — (i) true secretory fibres, and (2) vaso-constrictor fibres. [Electrical Variations during Secretion. — That changes in the electromotive properties of glands occur during secretion was shown in the frog's skin by Roeber, Engelinann, and Hermann. Bayliss and Bradford find that the same is true of the sub-ma.\illary gland I dog). During secretion the excitatory change on stimulaling the chorda is s. positive variation of the current of rest (the hilus of the gland becoming more positive), but it is frequently followed by a second phase of oppo- site sign. The latent period is always very short, about 0.37". Atropin abolishes the chorda variation. On stimulating the sympathetic, the excitatory change is of an opposite sign to that of the chorda, and the hilus becomes less positive, so that there is a negative variation. It requires a more powerful stimulus, is less in amount, and its latent period is longer (2"-4"), while atropin lessens but does not abolish it.] Relation to Stimulus. — On stimulating the cerebral nerves, at first with a weak and gradually with a stronger stimulus, there is a gradual development of the secretion in which the solid constitu- ents — occasionally the organic — are increased (Heidenhain). If a strong stimulus be applied for a long lime, the secretion diminishes, becomes watery, and is poor in specific constituents, especially in the organic elements, which are more affected than the inorganic ( C. LuJwig and Bee her). After prolonged stimulation of the sympathetic, the secretion resembles the chorda saliva. It would seem, therefore, that the chorda and sympathetic saliva are not specifically distinct, but vary only in de- gree. On continuing the stimulation of the nerves up to a certain maximal limit, tlie rapidity of secretion becomes greater, and the percentage oi salts also increases to a certain maximum, and this independently of the former condition of the glands. The percentage of organic constituents also depends on the strength of the nervous stimulation, but not on this alone, as it is essentially contin- gent upon the condition of the gland before the secretion took place, and it also depends upon the duration and intensity of the previous secretory activity. Very strong stimulation of the gland leaves an " alter tffect " wiiich predisposes it to give off organic constituents into the secretion (Heiden- hain). A latent period of 1.2 sec. {//ering) to 24 sec. (Ludwig) may elapse between the nerve stimulation and the beginning of the secretion. [Langley has shown that in the cat the sympathetic saliva of the sub-maxillary gland is less viscid than the chorda saliva. The following table from Langley shows the difference in percentage com- position between the chorda and sympathttic saliva in the cat: — *of f Sympathetic saliva (weak 1 stimulation . . . . ) J Sympathetic saliva after j I 5 mgrm. atropin v [ (strong stimulation), ) \ Chorda saliva (weak I ' stimulation) .... 1 Chorda saliva (st stimulation) stronger 1 Organic Substance, ? of Ash. Tot.ll < ot* builds. 0-3535 0.4419 °-7954 05250 0.4540 0.9790 0.86566 0-33978 1.20544 0.42598 0.27568 0.70161 ACTION OF NERVES ON THE SECRETION OF SALIVA. 239 Relation to Blood Supply. — The secretion of saliva is not simply the result of the amount of blood in the glands; that there is a factor independent of the changes in the state of the vessels is shown by the following facts : — • (I ) The secretory aclivity of the glands when their nen'es are stimulated continues for some time after the blood vessels of the gland have been ligatured [Luduiig, Czermaci, Giaiiuzzi). [If the head of a rabbit be cut off, stimulation of the seventh nerve, above where the chorda leaves it, causes a flow of saliva, which cannot be accounted for on the supposition that the saliva already present in the salivary glands is force 1 out of them. Thus we may have secretion without a blood stream. The saliva is really secreted from the lymph present in the lymph spaces of the gland (LuJ7vig.)'\ (2) Atropin and Daturin extinguish the activity of the secretory fibres in the chorda tympani i^Keuchel ), that do not affect the vaso-dilator fibres {IJeiden- hain). The same results occur after the injection of acids and alkalies into the excretory duct {Gianiizzi). (3) The pressure in the excretory duct of the salivary gland- — measured by means of a manometer tied into it — may be nearly twice as great as the pressure within the arteries of the glands {Ludwig), or even in the carotid itself. The pressure in Wharton's duct may reach 200 mm. Hg. (4) Just as in the case of muscles and nerves, the salivary glands become fatigued or exhausted after prolonged action. The result may also be brought about by injecting acids or alkalies into the duct, which shows that the secretory activity of the gland is independent of the circulation [Gian- tizzi). [Action of Atropin. — The vascular dilatation and the increased flow of saliva due to tlie activity of the secretory cells, produced by stimulation of the chorda tympani, althougii they occur simultaneously, do not stand in the relation of cause and effect. We may cause vascular dilatation without an increased flow of saliva, as already stated (2). If atropin be given to an animal, stimulation of the chorda produces dilatation of the blood vessels, but no secretion of saliva. Atropin paralyzes the secretory fibres, but not the vaso-dilator fibres (Fig. 152). The increased supply of blood, while not causing, yet favors the act of secretion, by placing a larger amount of pabulum at the disposal of the secretory elements, the tells.] [Secretory Pressure. — The experiment described under (3) proves, in a dennite manner, that the passage of the water from the blood vessels, or at least from the lymph into the acini of the gland, cannot be due to the blood pressure ; that, in fact, it is not a mere process of filtration such as occurs in the glomeruli of the kidney. In the case of the salivary gland, where the pressure within the gland may be double that of the arterial pressure, the water actually moves from the lymph spaces against very great resistance. We can only account for this result by ascribing it to the secretory activity of the gland cells themselves. Whether the activities of the gland cells, as suggested by Heidenhain, are governed directly by two distinct kinds of nerve fibres, a set of solid -secreting fibres, and a set of water-secreting fibres, remains to be proved.] All these facts le.ad us to conclude ih.at the nerves e.xercise a direct effect upon the secretory cells, apart from their action on the blood vessels. This physiological consideration goes hand in hand with the anatomical fact of ihe direct continuity of nerve fibres with the secretoiy cells. When the chorda tympani is extirpated on one side in young dogs, the sub-maxillary gland on that side does not develop so much— its weight is 50 per cent less— while the mucous cells and the " crescents " are smaller than on the sound side (Bii/alini). During secretion the temperature of the gland rises 1.5° C. {Ludwig'), and the blood flowing from the veins is often warmer than the arterial blood. [The electro-motive changes are referred to at p. 238.] " Paralytic Secretion" of Saliva. — By this term is meant the continued secretion oi a thin, watery saliva from the sub-maxillary gland, which occurs twenty-four hours after the section of the cerebral nerves (chorda of the seventh), /. e., those branches of them that go to this gland, whether the sympathetic be divided or not {CI. Bernard). It increases until the eighth day, after which it- 240 REFLEX SECRETION OF SALIVA. gradually diminishes, while the gland tissue degenerates. The injection of a small quantity of curara into the artery of the gland also causes it. [Heidenhain showed that section of one chorda i^ followed by a continuous secretion of saliva from l>o//i sub-maxillary glands. The term " paralytic " secretion is applied to that which takes place on the side on which the nerve is cut, and Langley proposes to call the secretion on the oppo- site side the antilytic. The condition of apncea (J 36S) stops almost or entirely both the para- lytic and antilytic secretion, while dyspncea increases the flow in both cases; and as section of the sympathetic fibres to the gland (where the chorda is cut) arrests the paralytic secretion excited by dyspncea, it is evident that both the paralytic secretion and the secretion following dyspncea are caused by stimuli traveling down the sympathetic fibres (Langley). In the later stages of the para- lytic secretion, the cause is in the gland itself, for it goes on even if all the nerves p.assing to the gland be divided, and is probably due to a local ner/e centre. In this stage the secretion is arrested by a large dose of chloroform. The paralytic secretion in the first stage, according to Langley, is owing to a venous condition of the Ijlood acting on a centr.il secretory centre whose excitability is increased; and in the latter stages probably on local nerve centres within the gland. The fibres of the chorda in the cat are only partially degenerated thirteen days after section (Lang- [Histological Changes. — In the gland during paralytic secretion, the gland cells of the alveoli (serous, mucous and demilunes), diminish in size and show the typical "resting" appearance, even to a greater extent than the normal resting gland (Langley).'\ (B) Sublingual Gland. — Very probably the same relations obtain as in the sub- maxillary gland. Fig. 152. VCS^SBLS vrEtSKD (C) Parotid Gland. — In the dog, stimulation of the sympathetic alone causes no secretion ; it occurs when theglosso-pharyngeal branch to' the parotid is simul- taneously excited. This branch may be reached within the tympanum in the tym- panic plexus. A thick secretion containing much organic matter is thereby obtained. Stimulation of the cerebral branch alone yields a clear, thin, watery secretion, containing a very small amount of organic substances, but a consider- able amount of the salts of the saliva {Hcidenhahi). Reflex Secretion of Saliva. — [If a cannula be placed in Wharton's duct, e. g., in a dog, during fiisting, no saliva will flow out. If the mucous membrane of the mouth hi stimulated by a sapid substance placed on the tongue, there is a copious flow of saliva. If the sympathetic nerve be divided, secretion still takes place when the mouth is stimulated, but if the chorda tympani be cut, secretion no longer takes place. Hence, the secretion is due to a reflex act ; in this case, the lingual is the afferent, and the chorda the efferent nerve carrying impulses from a centre situated in the medulla oblongata (Fig. 152).] In the intact body, the secretion of saliva occurs through a reflex stimulation of the nerves concerned, whereby, under normal circumstances, the secretion is always watery (chorda or facial saliva). The centripetal or afferent nerve fibres concerned are — (i) The nerves of taste. (^2) The sensory branches of the trigeminus of the entire THEORY OF SALIVARY SECRETION. 241 cavity of the mouth and the glosso-pharyngeal (which appear to be capable of being stimulated by mechanical stimuli, pressure, tension, displacement). The movements of mastication also cause a secretion of saliva. Pfliiger found that one- third more saliva was secreted on the side where mastication took place ; and CI. Bernard observed that the secretion ceased in horses during the act of drinking. (3) The nerves of smell, excited by certain odors. (4) The gastric branches of ' the vagus {Frcrichs, Ochl). A rush of saliva into the mouth usually precedes the act of vomiting (§ 158). (5) The stimulation of distant sensory nerves, e.g., the central end of the sciatic — certainly through a complicated reflex mechanism — causes a secretion of saliva ( Owsjannikow and Tschier- jeti'). Stimulation of the conjunctiva, e. g., by applying an irritating fluid to the eye of carnivorous animals, causes a reflex secretion of saliva [Aschenbrandt). Perhaps the secretion of saliva which sometimes occurs during pregnancy is caused in a similar reflex manner. The reflex centre for the secretion of saliva lies in the medulla oblongata, at the origin of the seventh and ninth cranial nerves (Eckhard and Loeh). The centre for the sympathetic fibres is also placed here {Griiizner and Ch/apowski). This region is connected by nerve fibres with the cerebrum ; hence, the thought of a savory morsel, sometimes, when one is hungry, causes a rapid secretion of a thin watery fluid — [or, as we say, " makes the mouth water "]. If the centre be stimulated directly by a mechanical stimulus (puncture), salivation occurs, while asphyxia has the same effect. The reflex secretion of saliva may be inhibited by stimulation of certain sensory nerves, e. g., by pulling out a loop of the intestine {Pawloic). Stimulation of the cortex cerebri of a dog, near the sulcus cruciatus, is often followed by secretion of saliva (Eulenberg and Landois, Bochefontaine, Biibnoff and Heidenhain'). Disease of the brain in man sometimes causes a secre- tion of saliva, owing to the effects produced on the intracranial centre. So long as there is no stimulation of the nerves, there is no secretion of saliva, as in sleep {Mitscheriich). Immediately after the section of all nerves, secretion stops, for a time, at least. Pathological Conditions and Poisons. — Certain affections, as inflammation of the mouth, neu- ralgia, ulcers of the mucous membrane, aftections of the gums, due to teething or the prolonged ad- ministration of mercury, often produce a copious secretion of saliva (or ptyalism). Certain poisons cause the same effect by direct stimulation of the nerves, as Calabar bean (Physostigmin), din-italin, and especially pilocarpin. Many poisons, especially the narcotics — above all, atropin — paralyze the secretory nerve*, so that there is a cessation of the secretion, and the mouth becomes dry ; while the administration of muscarin in this condition causes secretion (Prez'ost). Pilocarpin acts on the chorda tympani, causing a profuse secretion, and, if atropin be given, the secretion is again arrested. Conversely, if the secretion be arrested by atropin, it may be restored by the action of pilocarpin or physostigmin. Nicotin, in small doses, excites the secretory nerves, but in large doaes paralyzes them (IJiiJinhain). Daturin, cicutin, and iodide of a;thystrychnine, paralyze the chorda. [Sialogogues are those drugs which increase the secretion of saliva. Some are topical, and take eflect when applied to the mouth. They excite secretion reflexly by acting on the sensory nerves of the moutfi. They include acids, and various pungent bodies, such as mustard, ginger, pyrethrum, tobacco, ether, and chloroform ; but they do not all produce the same eflect ou the amount or quality of the saliva ; others, the general sialogogues, cause salivation when introduced into the blood, physostigmin, nicotin, pilocarpin, muscarin. The drugs named act after all the nerves going to the gland are divided, so that they stimulate the peripheral ends of the nerves in the glands. The two former also excite the central ends of the secretory nerves.] [Excretion by the Saliva. — Some drugs are excreted by the saliva. Iodide of potassium is rapidly eliminated by the liidneys, and also by the salivary glands, and so also is iodide of iron.] [Anti-sialics are those substances which diminish the secretion of saliva, and they may take eflect upon any part of the reflex arc, i. e., on the mouth, the afferent nerves, the nerve centre and afferent nerves, or upon the blood stream through the glands, or on the glands themselves. Opium and morphia afl'ect the centre ; large doses of physostigmin affect the blood supply ; but atropin is the most powerful of all, as it paralyzes the terminations of the secretory ner\-es in the glands, e. '\, the chorda tympani, and even the sympathetic in the cat (but not in the dog) (Brunlo>t).~\ Theory of Salivary Secretion. — Heidenhain has recently formulated the following theory regarding the secretion of saliva : •' During the passive or quiescent condition of the gland, the organic materials of the secretion are formed from and by the activity of the protoplasm of the secretory cells. A quiescent cell, which has been inactive for some time, therefore contains little 16 242 THE PAROTID SALIVA. protoplasm, and a large amount of these secretory substances. In an actively secreting gland, there are two processes occurring together, but independent of each other, and regulated by t« o difierent classes of nerve fibres; secretory fibres cause the act of secretion, while trophic fibres cause chemical processes within the cells, partly resulting in the formation of the soluble constituents of the secretion, and partly in the growth of the protoplasm. According to the number of both kinds of fibres present in a nerve passing to a gland, such nerve being stimulated, the secretion takes place more rapidly (cerebral nerve) or more slowly (sympathetic), while the secretion contains less or more solid con- stituents. The cerebral nerves contam many secretory fibres and few trophic fibres, while the sympathetic contains more trophic, but few secretory fibres. The rapidity and chemical composition of the secretion vary according to the strength of the stimulus. During continued secretion, the supply of secretory materials in the gland cells is used up more rapidly than it is replaced by the activity of the protoplasm; hence, the amount of organic constituents diminishes, and the microscopic characters of the cells are altered. The microscopic cliaracters of the cells are altered also by the increase of the protoplasm, which lakes place in an active gland. The mucous cells disappear, and seem to be dissolved after prolonged secretion, and their place is taken by other cells derived from the proliferation of the marginal cells. The energy w'hich causes the current of fluid depends upon the protoplasm of the gland cells." The saliva is diminished in amount in man in case?, oi paralysis of the fiacial or sympathetic nerves, as is observed in unilateral paralysis of these nerves. 146. THE SALIVA OF THE INDIVIDUAL GLANDS.— (a) The Parotid Saliva is obtained by placing a fine cannula in Steno's duct [^Eckhard) ; it has an alkaline reaction, but during fasting, the first few drops may be neutral or even acid on account of free COj (^Oehl) — its specific gravity is 1003 to 1004. When allowed to stand it becomes turbid, and deposits, in addition to albuminous matter, calcium carbonate, which is present in the fresh saliva in the form of bicarbonate. Salivary calculi are formed in the ducts of the salivary glands owing to the deposition of lime salts, and they contain only traces of the other salivary constituents : in the same way is formed the tartar of the teeth, which contains many threads of leptothrix, and the remains of low organisms which live in decomposing saliva in carious cavities between the teeth. It contains small quantities (more abundant in the horse) of a globulin-like body, and never seems to be without C N K S sulphocyanide of potassmm (or sodium — Trcviranus, 1814), which, however, is absent in the sheep and dog {Brcttel). The sulphocyanide gives a dark red color (ferric sulphocyanide) with ferric chloride. It also reduces iodic acid when added to saliva, causing a yellow color from the liberation of iodine, which may be detected at once by starch [Solera). Among the organic substances the most important are ptyalin, and a small amount oi urea {^Goliltj), and traces of a volatile acid (^CaproicPj. Mucin is absent, hence the parotid saliva is fluid, is not sticky, and can readily be poured from one vessel into another. It contains 1.5 to 1.6 per cent, of solids in man {Mitschetiich, van Setlcn), of which 0.3 to i.o per cent, is inorganic. Of the inorganic constituents — the most abundant are potassium and sodium chlorides ; then potassium; sodium, and calcium carbonates, some phosphates and a trace of an alkaline sulphate. {fi) The Sub-maxillary Saliva is obtained by placing a cannula in Wharton's duct ; it is alkaline, and may be strongly so. When allowed to stand for a long time, fine crystals of calcium carbonate are deposited, together with an amorphous albuminous body. It always contains mucin (which is precipitated by acetic acid) ; hence, it is usually somewhat tenacious. Further, it contains ptyalin, but in less amount than in parotid saliva; and, according to Oehl, only 0.0036 per cent, of potassium sulphocyanide. Chemical Composition. — Sub-maxillary saliva (dog) : — Water 991-45 per looo. Organic iVIatter . . . 2.89 " " Inorganic Matter. . . 5.66 1 45° Nad and CaCI,. =• ■'J 1. 10 CaCO,, Calcium and Magnesium phosphates. THE MIXED SALIVA IN THE MOUTH. 243 Mixed Saliva Parotid Sub-maxillary (Human) (Human) (Dog) {jMiiim'ilscA). (Hjppc-SeyUr). {Herter). [Water 99-5' 99-32 99-44 Solids 0.4S 0.6S 0.59 Soluble organic bodies (Ptyalin) 0.13 1 f 0.066 Epithelium, mucin 0.16 / •''' \0.17 Inorganic salts 0.182 0.34 0.43 Potassic sulphocyanide o 006 0.03 . . . Potassic and sodic chlorides 0.0S4 ... • • ■ ] Gases. — PflUger found that 100 cubic centimetres of the saliva contained 0.6 O to 64.7 CO^ (part could be pumped out, and part required the addition of phosphoric acid) ; 0.8 N; or, in 100 vol. gas, 0.91 (3 ; 97.88 CO2, I.2I N. [It therefore contains much more COj than venous blood.] {/) The Sublingual Saliva is obtained by placing a very fine cannula in the ductus Rivinianus ( Ochi), is strongly alkaline in reaction, very sticky and cohesive, contains much mucin, numerous salivary corpuscles and some potassium sulpho- cyanide {Longei). 147. THE MIXED SALIVA IN THE MOUTH.— The fluid in the mouth is a mixture of the secretions from the salivary glands and the secretions of the raucous and other glands of the mouth. (ij Physical Characters. — The mixed saliva of the mouth is a somewhat opalescent, tasteless, odorless, slightly glairy fluid, with a specific gravity of 1004 to 1009, and an alkaline reaction. The amount secreted in twenty-four hours = 200 to 1500 grammes (7 to 50 oz.) ; according to Bidder and Schmidt, how- ever, 1000 to 2000 grammes. The solid constituents ^ 5.8 per 1000. Composition. — The solids are: Epithelium and mucus, 2.2; ptyalin and albumin, 1.4; salts, 2.2; potassium sulphocyanide, 0.04 per 1000. The ash contains, chiefly, potash, phosphoric acid and chlorine [Hammerhacher). Decomposition products of epithelium, salivaiy corpuscles, or the remains of food, may render \i acid temporarily, a^ after long fasting and after much speaking (//(y/t'-&)'/e'/-). Even outside the body, saliva containing much epithelium becomes acid before it putrefies [Gorup-Besanez). 'l"he reaction is acid in some cases of dyspepsia and in fever, owing to the stagnation and insuffi- cient secretion. (2) Microscopic Constituents. — {a) The salivary corpuscles are slightly larger than the white blood corpuscles (8 to 11 //), and are nucleated protoplasmic globular cells without an envelope. During their living condition, the particles in their interior exhibit molecular or Brownian movements. The dark granules lying in the protoplasm are thrown into a trembling movement, from the motion of the fluid in which they are suspended. This dancing motion stops when the cell dies. [The Brownian movements of these suspended granules are purely physical, and are exhibited by all fine microscopic particles suspended in a limpiil fluid, e. g., gamboge rubbed up in water, panicles of carmine, charcoal, etc.] [b) J'avcment epitltelial cells from the mucous membrane of the mouth and tongue ; they are very abundant in catarrh of the mouth (Fig. 145). (<\) Living organisms, which live and thrive in the cavities of teeth nourished by the remains of food. Among these are Leptolttrix buaalis (Fig. 144, I2j and small bacteria-like organisms. The threads of the leptothrix penetrate into the canals of the dentine and produce dental caries [Liltcr). Cucci, bacteria, vibrios, spirilla and spirocha^tce may also be lound. (^3) Chemical Properties. — (a) Organic Constituents. — Serum albumin is precipitated by heat and by the addition of alcohol. In saliva, mixed with much water and shaken up with CO^, a. globulin- like body is precipitated ; mucin occurs in small amount. Among the extractives, the most important is ptyalin (Berzelius) ; fats and u>ea occur only in traces. In twenty-four hours 130 milli- grammes of potassium or sodium sulphocyanide are secreted. {b) Inorganic Constituents. — ^Sodium and potassium chlorides, potassium sulpnatc, alkaline and earthy phosphates, ferric phosphate. 244 PHYSIOLOGICAL ACTION OF SALIVA. Abnormal Constituents. — In diabetes mellitus, lactic acid, derived from .i further decomposi- tion of grape sugar, is found (Lchmann). It dissolves the lime in the teeth, giving rise to diaL)etic dental caries. Frerichs found /('«(■/«, and Vulpian increase of albumin, in albuminuria. Of foreign substances tal^en into the body, the following appear in the saliva: Mercury, potassium, iodine and bromine. Saliva of New-born Children. — In new-born children, the parotid alone contains ptyalin. The diastatic ferment seems to be developed in the sub-maxillary gland and pancreas at the earliest after two months. Hence, it is not advisable to give starchy food to infants. No ptyalin has been found in the saliva of infants suffering from thrush (Oidiuni albicans — Zwcifel). The diastatic action of saliva is not absolutely necessary for the suckling, feeding, as it does, upon milk. The mouth, during the first two months, is not moist, but at a later period saliva is copi- ously secreted {Konnoin) ; after the first six months, the salivary glands increase considerably. The eruption of the teeth — owing to the irritation of the mucous membrane — produces a copious secretion of saliva. 148. PHYSIOLOGICAL ACTION OF SALIVA. — I. Diastatic Action. — The most important part played by saliva m digestion is its diastatic or amylolytic action (Leiichs, iSjl), i. e., the transformation of starch into dextrin and some form of sugar. This is due to the ptyalin — a hydrolytic ferment or enzym — which acts in very minute quantity, so that starch takes up water and becomes soluble, the ferment itself undergoing no essential change in the process. [Ptyalin belongs to the group of unorganized ferments. Like all other ferments, u acts only within a certain range of temperature, being most active about 40° C. Its energy is permanently destroyed by boiling. It acts best in a slightly alkaline or neutral medium.] Action on Starch. — [Starch grains consist of ^■';-(7«//'/(V^ or starch enclosed by coats of iiilidose. Cellulose does not appear to be affected by saliva, so that saliva acts but slowly on raw, unboiled starch. If the starch be boiled so as to swell up the starch grains and rupture the cellulose envelopes, the amylolytic action takes place rapidly. If starch paste or starch mucilage, made by boiling starch in water, be acted upon by saliva, especially at the temperature of the body, the first physical change observable is the liquefaction of the paste, the mixture becoming more fluid and transparent. The change takes place in a few minutes. When the action is continued, important chemical changes occur.] According to O'Sullivan, Musculus, and v. Mering, the diastatic ferment of saliva (and of the pancreas) by acting upon starch or glycogen forms dextrin and maltose (both soluble in water). Several closely allied varieties of dextrin, distinguishable by their color reactions, seem to be produced (^Bri/eke). Ery- throdextrin is formed first; it gives a red color with iodine; then a reducmg dextrui — achroodextrin, which gives no color reaction with iodine. The sugar formed by the action of ptyalin upon starch is maltose (Ci.^H„0,i -\- H.^O), which is distinguished from grape sugar (Ci^Hj^Opj) by containing one molecule less of water, which, however, it holds as a molecule of water of hydration, as indicated in the formula given above (Ad. Mayer). [Maltose also differs from grape sugar in its greater rotatory power on polarized light, and in its less power of reducing cupric oxide. Thus, it will be seen that between the original starch and the final product, maltose, several intermediate bodies are formed. The starch gives a blue with iodine, but after it has been acted on for a time it gives a red or violet color, indicating the color of erythrodextrin, there being a simulta- neous production of sugar; but ultimately no color is obtained on adding iodine — achroodextrin, which gives no color with iodine, and maltose being formed. The presence of the maltose is easily determined by testing with Fehling's solution.] [Brown and Heron suggest that the final result of the transformation may be represented by the equation — io(Ci,H,oOi„) -f 8H20 = S(C,,H,,0,,) + 2(C,2Hj(,0,o) Soluble starch. Water. Maltose". Achroodextrin.] FUNCTIONS OF THE SALIVA. 245 [The ferment slowly changes maltose into grape sugar or dextrose. This result may be brought about much more rapidly by boiling maltose with dilute sulphuric or hydrochloric acid.] Achroode.xtrin ultimately passes into maltose, and this again into dextrose ; the other form of dextrin does not seem to undergo this change (Seegen's Dystropodextrin). For the further changes that maltose under- , goes in the intestine, see § 183, II, 2. [The formula of starch is usually expressed as CgHj^Oj, but the researches already mentioned, and those of Brown and Heron, make it probable that it is more complex, which we may provision- ally represent by « (Cj^H^gOj;,). According to Musculus and Meyer, erythrodextrin is a mixture of dextrin and soluble starch.] Preparation of Ptyalin.— (i) Like all other hydrolytic ferments, it is carried down with any copious precipitate that is produced in the fluid which contains it. It is easily isolated from the precipitate. The saliva is acidulated with phosphoric acid, and lime-water is added until the reac- tion becomes alkaline, when a precijiitate of basic calcium phosphate occurs, which carries the ptyalin along with it. This precipitate is collected on a filter and washed with water, which dissolves the ptyalin, and from its watery solution it is precipitated by alcohol as white powder. It is redis- solved in water and reprecipitaled, and is obtained pure (Cohn/ieim). (2) Glycerine or v. WilticKs Method. — The salivary glands [rat] are chopped up, placed in absolute alcohol for twenty-four hours, taken out and dried, and afterward placed in glycerine for several days. The glycerine extracts the ptyalin. It is precipitated by alcohol from the glycerine extract. (3) William Roberts recommends the following solutions for extracting ferments from organs which contain them : (l) A 3 to 4 per cent, solution of a mixture of 2 parts of boracic acid and I part borax, (i) Water, with 12 to IJ per cent, of alcohol. (3) I part chloroform to 200 of water. Diastatic Action of Saliva. — (a) The diastatic or sugar-forming action is known by— (i) The disappearance of the starch. When a small quantity of starch is boiled with several hundred times its volume of water, starch mucilage is obtained, which strikes a blue color with iodine. If to a small quantity of this starch a sufficient amount of saliva be added, and the mixture kept for some time at the temperature of the body, the blue color disappears. (2) The presence o/sugar is proved directly by using the tests for sugar (J 149). (d) The action takes place more slowly in the coM than at the temperature of the body — its action is enfeebled at 55° C, and destroyed at 75° C. (Paschutin). The most favorable temperature is 35° to 39° C. [c) The ptyalin itself does not seem to be changed during its action, but ptyalin which has been used for one experiment is less active when used the second time (Paschutin). Ptyalin differs from di.istase in so far that the latter first begins to act at + 66° C. Ptyalin decomposes salicin into saligenin and grape sugar (Frerichs and Stddlei ), but it has no action on cane sugar and amygdalin. [d) Saliva acts best in a slightly alkaline medium, but it also acts in a neutral and even in a slightly acid fluid ; strong acidity prevents its action. The ptyalin is only active in the stomach when the acidity is due to organic acids (lactic or butyric), and not when free hydrochloric acid is present [van de Velde). In both cases, however, dextrin is formed. Ptyalin is destroyed by hydro- chloric acid or digestion by pepsin [Chittenden and Griswold, Langley). Even butyric and lactic acids formed from grape sugar in the stomach may prevent its action ; but if the acidity be neutral- ized, the action is resumed ( CI. Bernard). [e) The addition of common salt, ammonium chloride, or sodium sulphate (4 per cent, solution), increases the activity of the ptyalin, and so do CO21 acetate of quinine, strychnia, morphia, curara, 0.025 P^f cent, sulphuric acid, if) Much alcohol and caustic potash destroy the ptyalin ; long exposure to the air weakens its action, sodium carbonate and magnesium sulphate delay the action [P/eiffer). Salicylic acid and much atropin arrest the formation of sugar. (g) Ptyalin acts very feebly and very gradually upon raw starch, only after 2 to 3 hours (Schiff) ; while upon boiled starch it acts rapidly, [Hence the necessity for boiling thoroughly all starchy foods.] (/i) The various kinds of starch are changed more or less rapidly, according to the amount of cellulose which they contain ; raw potato starch after two to three liours, raw maize starch after 2 to 3 minutes (//ammarsten). Starch cellulose is dissolved at 55° C. (JVdgeli). WTien the starches are powdered and boiled, they are changed with ec|ual rapidity. (i) A mixture o! the saliva from all the glands is more active than the saliva from any single gland {Jakuhountsch\. while mucin is inactive. [Effect of Tea. — W. Roberts finds that tea has an intensely inhibitory effect on salivary diges- tion, which is due to the large quantity of tannin contained in the tea leaf. Coffee and cocoa have only a slight effect on salivary digestion. The only way to mitigate the inhibitory effect of tea on salivary digestion is " not to sip the beverage with the meal, but to eat first and drink afterward."] 246 TESTS FOR SUGAR. II. Saliva dissolves those substances which are soluble in water ; while the alka- line reaction enables it to dissolve some substances which are not soluble in water alone, but require the presence of an alkali. III. .Saliva moistens dry food and aids the formation of the " bolus," while by its mucin it aids the act of swallowing, the mucin being given off unchanged in the fjeces. The ultimate fate of ptyalin is unknown. [IV. Saliva also aids articulation, while according to Liebig, it carries down into the stomach small quantities of O.] [V. It is necessary to the sense of taste, to dissolve sapid substances, and bring them in relation with the end organs of the nerves of taste.] The presence of a peptone-forming ferment has recently been detected in saliva [Hiifmi; Muni, A'ii/nn-). This ferment is likewise said to occur in the saliva of the horse, which can also convert cane sugar into invert sugar, and slightly emulsionize fats [Ellcnberger and v. Hofmeister). Ac- cording to Hofmeister, the saliva of the sheep has a digestive action on cellulose. Saliva has no action on proteids or on fats. [Perfectly healthy human saliva has no poisonous properties. Those observers (/"(/^too-, Vul- plan and Gautier), who obtained poisonous results by injecting human saliva into animals probably used an unhealthy saliva.] 149. TESTS FOR SUGAR.— (i) Trommer's Test depends upon the fact that in alkaline solutions sugar acts as a reducing agent ; in this case a metallic oxide is changed into a suboxide. To the fluid to be investigated, add j4 of its volume of a solution of caustic potash (soda), specific gravity 1.25, and a few drops of a weak solution of cupric sulphate, which causes at first a bluish pre- cipitate consisting of a hydrated cupric oxide, but it is redissolved, giving a clear blue fluid, if sugar be present. Heat the upper stratum of the fluid, and a yellow or red ring of cuprous oxide is obtained, which indicates the presence of sugar ; 2CuO — O = Cu^O. The solution of hydrated cupric oxide is caused by other organic substances ; but the final stai^e, or the production of cuprous oxide, is obtained only with certain sugars — grape, fruit and milk (but not cane) sug.ir. Fluids which are turbid must be previously filtered, and if they are highly colored they must be treated with basic lead acetate ; the lead acetate is afterward removed by the addition of sodium phosphate and subsequent filtration. If very small quantities of sugar are present along with compounds of ammonia, a yellow color instead of a yellow precipitate may be obtained. In doing the test, care must be taken not to add too much cupric sulphate. [(2) Fehling's Solution is an alkaline solution of potassio-tartarate of copper. Boil a small quantity of the deep-blue colored Fehling's solution in a test tube, and add to the boiling test a few drops of the fluid supposed to contain the sugar. If sugar be present the copper solution is reduced, giving a yellow or reddish pre- cipitate. The reason for boiling the test itself is, that the solution is apt to de- compose when kept for some time, when it is precipitated by heat alone. This is one of the best and most reliable tests for the presence of sugar. In Pavy's modification of this test, ammonia is used instead of a caustic alkali (§ 267).] (3) Buttger's Test. — Alkaline bismuth oxide solution is best prepared, according to Nylander, as follows: 2 grms. bismuth subnitrate, 4grms. potassic and sodic tartrate. loo grms. caustic soda of 8 per cent. Add i c.c. to every lo c.c of the fluid to be investigated. When boiled for several minutes, the sugar causes the reduction and deposits a black precipitate of metallic bismuth. [Ac- cording to Salkowski the urine of a person taking rhubarb gives the same reaction with this test.] (4) Moore and Heller's Test. — Caustic potash or soda is added until the mixture is strongly alkaline ; it is afterward boiled. If sugar be present, a yellow, brown, or brownish-black colora- tion is obtained. If nitric acid be added, the odor of burned sugar (caramel) and formic acid is obtained. (5) Mulder and Neubauer's Test. — A solution of indigo-carmine, rendered alkaline with sodic carbonate, is added to the sugar solution until a slight bluish col^r is obtained. When the mixture is heated the color passes into purple, red and yellow. When shaken with atmospheric air, the fluid again becomes blue. Other tests are described in Vol. ii, \ 266. In all cases where albumin is present it must be removed — in urine by acidulating with acetic acid and boiling; in blood, by adding four times its volume of alcohol and afterward filtering, while the alcohol is expelled by heat. SOLEIL-VENTZKE S POLARIZATION APPARATUS. 247 150. QUANTITATIVE ESTIMATION OF SUGAR.— I. By Fermentation.— Into the glass vessel (Fig. 1^3, (7) a measured quantity (20cm.) of the fluid (sugar) is jilaced along with some yeast, while /' con- Fig. i^JJ. tains concentrated sulphuric acid. The whole apparatus is weighed. When exposed to a sufficient temperature ( 10° to 40° C), the sugar splits into two molecules of alcohol and two of carbon dio.xide, C,H, ,Oe = 2{C,U,0} + 2(C02), grape sugar = 2 alcohol -f- 2 carbon dioxide; and in addi- tion there are formed traces of glycerine and succinic acid. The COo escapes from d, and as it passes through the H^SO.j, Coj yields to the latter its water. The apparatus is weighed after two days, when the reaction is ended, and the amount of sugar is calculated from the loss of weight in the 20 cm. of fluid. 100 parts of water-free sugar = 4S.89 parts COj, or 100 parts CO, correspond to 204.54 parts of sugar. Fig. 154. App Soleil-Ventzke's polarization apparatus. II. Titration. — By means of Fehling's solution, which consists of cupric sulphate, tartrate of potash and soda, caustic soda, and water. It is made of such a strength that all the copper in 10 cubic centimetres of the solution is reduced by 0.05 gramme of grape sugar (I 267). III. Circumpolarization. — The saccharimeter of Soleil-Ventzke may be used to determine the amount of sugar present. It may also be used for the quantitative estimation of albumin. Sugar rotates the ray of polarized light to the right and albumin to the left. The amount of rotation, or 248 THE MOVEMENTS OF MASTICATION. "specific rotatory power," is directly proportional to the amount of the rotating substance present in the solution, so that the amount of rotation of the rays indicates the amount of the substance present. In Fig. 154 the light from the lamp falls upon a crystal of calc-spar. Two Nicol's prisms are placed at v and s ; z* is movable round the axis of vision, while s is fixed. In m Soleil's double plate of quartz is placed ; so that one-half of it rotates the ray of polarized light as much to the right as the other rotates it to the left. In n the field of vision is covered by a plate of left rotatory quartz. At (5 c is the co7npensator, composed of two right rotatory prisms of quartz, which can be displaced laterally by the milled head, y, so that the polarized light pissing through the apparatus can be made to pass through a thicker or thinner layer of quartz. When these right rotatory prisms are placed in a certain position, the rotation of the left rotatory quartz at n is exactly neutralized. In this position the scale on the compensator has its nonius exactly at 0, and both halves of the double plate at m appear to have the same color to the observer, who from v looks through the telescope placed at e. Rotate the Nicol's prism at t' until a bright rose colored field is obtained. In this position the telescope must be so adjusted that the vertical line bounding the two halves shall be distinctly visible. The apparatus is now ready for use. Fill a tube, I decimetre in length, with urine containing sugar or albumin, the urine being per- fectly clear. The tube is placed between in and n By rotating the Nicol's prisms, v, the rose- color is again obtained. The compensator at g is then rotated until both halves of the field of vision have exactly the same color. When this is obtained, read ofi" on tlie scale the number of degrees the nonius is displaced to the right (sugar) or to the left (albumin) from zero. The number of degrees indicates directly the number of grammes of the rotating susbtance present in 100 c. c. of the fluid. If the fluid is very dark-colored, it must be decolorized by filtering it through animal charcoal {Sccgen) [or the coloring matter may be precipitated by the addition of lead acetate.] If the sugary urine contains albumin, the latter must be removed by boiling and filtration. A turbidity not removed by filtration may be got rid of by add;ng a drop of acetic acid, or several drops of sodic carbonate or milk of lime, and afterward filtering. 151. MECHANISM OF THE DIGESTIVE APPARATUS.— This embraces the following acts : — 1. The introduction of the food ; the movements of mastication and those of the tongue ; insalivation and the formation of the bolus of food. 2. Deglutition. 3. The movements of the stomach, of the small and large intestine. 4. The excretion of faecal matters. 152. INTRODUCTION OF THE FOOD.— Fluids are taken into the mouth in three ways: (i) By suction, the lips are applied air tight to the vessel containing the fluid, while the tongue is retracted (the lower jaw being often depressed) and acts like the piston in a suction pump, that causes the fluid to enter the mouth. Herz found, that the negative pressure caused by an infant while sucking = 3 to 10 mm. Hg. (2) The fluid is lapped when it is brought into direct con- tact with the lips, and is raised by aspiration and mixed with air so as to produce a characteristic sound in the mouth. (3) Fluid may be /('«rf(/ into the mouth, and, as a general rule, the lips are applied closely to the vessel containing the fluid. The solids when they consist of small particles are licked up with the lips, aided by the movements of the tongue. In the case of large masses, a part is bitten off with the incisor teeth, and is afterward brought under the action of the molar teeth by means of the lips, cheeks, and tongue. 153. THE MOVEMENTS OF MASTICATION.— The articulation of the jaw is pro- vided with an interarticular cartilage ( Vidius, ij6y) — the meniscus — which prevents direct pressure being made upon the articular surface when the jaws are energetically closed, and which also divides the joint into two cavities, one lying over the other. The capsule is so lax that, in addition to the raising and depressing of the lower jaw, it permits of the lower jaw being displaced for- ward upon the articular tubercle, whereby the meniscus moves with it, and covers the articular surface. The process of mastication consists of the following movements : — {a) The elevation of the jaw is accomplished by the combined action of the temporal, masseter, and internal pterygoid muscles. If the lower jaw was pre- STRUCTURE AND DEVELOPMENT OF THE TEETH. 249 viously so far depressed that its articular surface rested upon the tubercle, it now passes backward upon the articular surface. (/') The depression of the lower jaw is caused, by its own weight, aided by the action of the anterior bellies of the digastrics, the mylo- and genio-hyoid and platysma {Hallcr). The muscles act during forcible opening of the mouth. The necessary fixation of the hyoid bone is obtained through the action of the omo-and sterno-hyoid, and by the sterno-thyroid and thyro-hyoid. When the articular surface of the lower jaw passes forward on to the tubercle, the external pterygoids actively aid in producing this (Berard). (c) Displacement of both or one articular surface forward or back- ^wa^d. — During rest, when the mouth is closed, the incisor teeth of the lower jaw fall within the arch of the upper incisors. When in this position the jaw is protruded by the external pterygoids, whereby the articular surface passes on to the tubercle (and, therefore, downward), while the lateral teeth are thereby separated from each other. The jaw is retracted by the internal pterygoids with- out any aid from the posterior fibres of the temporals. When one articular sur- face is carried forward, the jaw is protruded and retracted by the external and internal pterygoid of the same side. At the same time, there is a transverse movement, whereby the back teeth of the protruded side are separated from each other. During mastication, when the individual movements of the lower jaw are vari- ously combined, the food to be masticated is kept from passing outward by the action of the muscles of the lips (orbicularis oris) and the buccinators, while the tongue continually pushes the particles between the molar teeth. The energy of the muscles of mastication is regulated by the sensibility' of the teeth, and the muscular sensibility of the muscles of mastication, as well as by the general sensi- bility of the mucous membrane of the mouth and lips. At the same time, the mass is mixed with saliva, the divided particles cohere, and are formed into a mass or bolus of a long, oval shape, by the muscles of the tongue, ready to be swallowed. Nerves of Mastication. — The muscles of mastication and the buccinator receive their motor nerves from the third branch of the trigemirus ; the mylo-hyoid and the anterior belly of the digas- tric being supplied from the same source. The genio-, omo-, and sterno-hyoid, sternothyroid, and thyro-hyoid are supplied by the hypoglossal, while the facial supplies the posterior belly of the di- gastric, the stylo-hyoid, the platysma, and the muscles of the lips. The general centre for the muscles of mastication lies in the medulla oblongata (J 367). When the mouth is closed, the jaws are kept in contact by the pressure of the air, as the cavity of the mouth is rendered free from air, and the entrance of air is prevented anteriorly by the lips, and posteriorly by the soft palate. The pressure e.xerted by the air is from 2 to 4 mm. Hg (Metzger and Danders). [The process of mastication is also influenced by guiding contact sensations from the mouth.] [Effect on the Circulation.— Marey found that mastication trebled the velocity of the blood current in the carotid (horse), while Frangois Frank observed that the circulation of the brain (in man) is increased ; hence it is evident that mastication implies an increased supply of blood to the nerve centres.] 154. STRUCTURE AND DEVELOPMENT OF THE TEETH.— A tooth is just a papilla of the mucous membrane of the gum which has undergone a characteristic development. In its simplest form, as in the teeth of the lamprey, the connective-tissue basis of the papilla is covered with many layers of corneous epithelium. In human teeth, part of the papilla is trans- formed into a layer of calcified dentine, while the epithelium of the papilla produces the enamel, the fang of the tooth being covered by a thin accessory layer of bone, the crusta petrosa or cement. The dentine or ivory which surrounds the pulp cavity and the canal of the fang (Fig. 155) is very firm, elastic and brittle. The matrix of bone, dentine, when treated in a certain way, presents a fibrillar structure (ta £/'«£■;■). It is permeated by innumerable long, tortuous, wavy tubes — the dentinal tubules \LceHwenhoek, i6yS) — each of which communicates with the pulp cavity by means of a fine opening, and passes more or less horizontally outward as far as the outer layers of the dentine. The tubules are bounded l)y an extremely resistant, thin, cuticular membrane, which strongly resists the action of chemical reagents. These tubules are filled completely by soft fibres, the "fibres of Tomes" (1840), which are merely greatly elongated and branched processes of the odontoblasts of the pulp ( Waldeyer, l68j). 250 STRUCTURE AND DEVELOPMENT OF THE TEETH. Pulp Cavity. Fig. 155- The dentinal tubules, as well as the fibres of Tomes, anastomose throughout their entire extent by means of fine processes. As the fibres approach the enamel, which they do not penetrate, seme of tliem beml on themselves, and form a loop (Fig. 15S, C), while others pass into the " interglobular spaces " (Fig. 157) which are so abundant in the outer part of the dentine (Czermak, iSjo), The interglobular spaces are small spaces bounded by curved surfaces. Cer- tain curved lines, " Schreger's lines " (iSoo), may be detected with the naked eye in the dentine (c. ,^., of the elephant's tusk) running parallel with the contour of the tooth. These are caused by the fact that at these parts all the chief curves in the dentinal tubules follow a similar course (Hetzius, The enamel, the hardest substance in the body (resembling apatite), covers the crown of the teeth. It consists of hexagonal flattened prisms (Malpighi, iSdf) arranged side by side like a palisade (Fig. 15S, B and C). They are 3 to 5 !>■ (3555 inch) broad, not quite uniform in thickness, curved slightly in dif- ferent directions, and owing to inequalities of thick- ness, they exhibit transverse markings. They are elongated, calcified, cylindrical, epithelial cells de- rived from the dental papilla. Retzius described dark brown lines running par.allel with the outer boundary of the enamel, due to the presence of pigment (Fig. 155). The fully-formed enamel is negatively doubly refractive and uniaxial, while the developing enamel is positively doubly refractive {Hoppe SeyleA. The cuticula or Nastnyth's membrane (1839) covers the free surface of the enamel as a completely structureless membrane, I to 2 /^ thick, but in quite young teeth it exhibits an epithelial structure, and is derived from the outer epithelial layer of the enamel organ. Fig. 157. Fig. 156. Longitudinal section of ; 1 of dentine— The light rings are the walls of the dentinal tubules ; the dark cen- tres with the light points are the fibres of Tomes lying in the Interglobular spaces in dentine {Schenk). The cement {John Hunter^ lyyS) or crusta petrosa, is a thin layer of bone covering the fang (Fig. 159, a). The bone lacunce communicate directly with the dental tubules of the fang. Haversian canals and lamellce are only found where the layer of cement is thick, and the former may communicate with the pulp cavity {^Salter). Very thin layers of cement may be devoid of CHEMISTRY OF A TOOTH. 251 bone corpuscles. Sharpey's fibres occur in the cement of the dog's tooth ( IValdeyer) ; while in the horse's tooth single bone corpuscles are enveloped by a capsule ( Gerber). In the periodontal membrane, which is just the periosteum of the alveolus, coils of blood vessels similar to the renal glomeruli occur. They anastomose with each other, and are surrounded by a delicate capsule of connective tissue (C IVedl). Section of a tooth bet and enamel, a, enamel ; c, dentinal tubules: B, ( magnified ; C, transverse sections of enamel prisms. el prisms highly Fig. 159. Chemistry of a Tooth. —The teeth consist of a gelatin-yielding matrix infiltrated with calciuin phosphate and carbonate (like bone), (i) The dentine contains — organic matter, 27.70; calcium phosphate and carbonate, 72.06 ; magnesium phosphate, 0.75, with traces of iron, fluorine, and sulphuric acid {Acby, Hofpe-Seyler). (2) The enamel contains an organic proteid matrix allied to the substance of epithelium. It contains 3.60 organic matter and 96.00 of calctum phosphate and car- bonate, 1.05 magnesium phosphate, with traces of cal- cium fluoride and an insoluble chlorine compound. (3) The cement is identical with bone. The Pulp in a fully grown tooth represents the re- mainder of the dental papilla around which the dentine was deposited. It consists of a very vascular, indis- tinctly fibrillar connective tissue, laden with cells. The layers of cells, resembling epithelium, which lie in direct contact with the dentine, are called odontoblasts ( IVal- deyer, iS6^), i. e., those cells which build up the dentine. The cells send off" longbranched processes into the den- tinal tubules, while their nucleated bodies he on the sur- face of the pulp, and form connections by processes with other cells of the pulp and with neighboring odonto- blasts. Numerous non-meduUated nerve fibres (.sensory from the trigeminus) whose mode of termination is unknown, occur in the pulp. The periosteum or periodontal membrane of the fang is, at the same time, the alveolar peri- osteum, and consists of delicate connective tissue, with few elastic fi'Dres and many nerves. The gums are devoid of mucous glands, very vascular, and often provided with long vascular papilla?, which are sometimes compound. Development of a Tooth. — It begins at the end of the second month of fcetal life. Along the whole length of the fcetal gum is a thick projecting ridge (Fig. 160, a'), composed of many layers of epithelium. A depression, the denial groove, also filled with epithelium, occurs in the gum, and runs along under the ridge. The dental groove becomes deeper throughout its entire length, and, on transverse section, presents the appearance of a dilated flask (b), while, at the same time, it is filled with elongated epithelial cells, which form the " enamel organ." A conical ])apiUa.> (the " dentine germ " grows up from the mucous tissue, of which the gum consists, toward the enamel organ (Fig. 161, <-), so that the apex of the papilla comes to have the enamel organ resting upon it, like a double cap. Afterward, owing to the development of connective tissue, the parts of the ansverse section of the fang, bone corpuscles ; 6, dentini tubules : c, boundary betwe 252 ERUPTION OF THE TEETH. enamel organ lying between and uniting the individual dentine germs disappear, and gradually the connective tis'^ue forms a tooth sac enclosing the papilla and its enamel organ (~wa/h), while severe inflammation of the intestine has a similar effect. Under favorable circumstances, the intestine may recover from this condition. Arterial blood admitted into the vessels of the exhausted intestine causes peristalsis, which at first is more vigorous than normal. 5. The continued application of strong stimuli causes complete paralysis of the intestine, such as occurs after violent peritonitis, or inflammation of the mus- culature or mucous coat in man. In this condition the intestine is greatly dis- tended, as the paralyzed musculature does not offer sufficient resistance to the intestinal gases which are expanded by the heat. This constitutes the condition of meteorism. Influence of Nerves. — With regard to the nerves of the intestine, stimula- tion of the vagus increases the movements (of the small intestine), either by conducting impressions to the plexus myentericus, or by causing contraction of the stomach, which stimulates the intestine in a purely mechanical manner \Braam- Houckgeest). The splanchnic is (i) the inhibitory nerve of the small intestine {Pfliiger), but only as long as the circulation in the intestinal blood vessels is undisturbed, and the blood in the capillaries does not become venous {Sigm. Mayer and von Basch) ; when the latter condition occurs, stimulation of the splanchnic increases the ijeristalsis. If arterial blood be freely supplied, the in- hibitory action continues for some time {O. Nasse). Stimulation of tlie origin of the splanchnics of the spinal cord in the dorsal region (under the same conditions), and even when general tetanus has been produced by the administration of strychnia, causes an inhibitory effect. O. Nasse concludes, from these experi- ments, that the splanchnic contains — (2) inhibitory fibres, which are easily ex- hausted by a venous condition of the blood, and also motor fibres, which remain excitable for a longer time, because after death stimulation of the splanchnics always causes peristalsis, just like stimulation of the vagus. (3) The splanchnic is also the vasomotor nerve of all the intestinal blood vessels, so that it governs the largest vascular area in the body. When it is stimulated, all the vessels of the intestine which contain muscular fibres in their walls contract ; when it is divided, they dilate. In the latter case, a large amount of blood accumulates within the blood vessels of the abdomen, so that there is anaemia of the other parts of the body, which may be so great as to cause death — owing to the defi- cient supply of blood to the medulla oblongata. (4) The splanchnic is the sensory nerve of the intestine, and as such, under certain circumstances, it may give rise to extremely painful sensations. As stimulation of the splanchnic contracts the blood ve^^sels, von Basch has raised the question whether the intestine does not come to rest, owing to the want of the blood, which acts as a stim- ulus. But when a weak stimulus is applied to the splanchnic, the intestine ceases to move before the blood vessels contract (T.ian Braam-Honckgiest) ; it would, therefore, seem that the stimulation diminishes the excitabihty of the plexus myentericus. According to Engelmann and v. Brakel, the peristaltic movement is chiefly propagated by direct muscular conduction, as in the heart and ureter, without the intervention of any nerve fibres. EFFECT OF DRUGS ON THE INTESTINE. 265 [Effect of Nerves on the Rectum. — The nervi erigentef, when stimulated, cause the longi- tudinal muscular fibres of the rectum to contract, while the circular muscular fibres are supplied by the hypogastric nen-es. Stimulation of the latter nerves also exerts an inhibitor)- effect on the lon- gitudinal muscles. Stimulation of the erigentes inhibits not only the spontaneous movements of the circular fibres of the rectum, but also those movements excited by stimulation of the hypogastric nerves [Fel/ner.)'] [Artificial Circulation in the Intestine. — Ludwig and Sah-ioli, after exciting a loop of intes- tine from an animal, tied a cannula into an artery and another into a vein. The arterial cannula was connected with a vessel containing defibrinated blood, to which different drugs could be added. A lever rested on the intestine, and registered its movements on a recording surface. The intestine was kept in a warm chamber. As long as arterial blood was transfused, the intestine was nearly quiescent, but when it was arrested, so that the blood became venous, a series of con- tractions occurred. Nicotin diminished the flow of blood and quickened the intestinal movements, while at the same time the circular muscular fibres remained contracted or tetanic. . Tincture of opium, in the proportion of .01 to .04 in the blood, causes at first contraction of the vessels and lessens the amount of blood circulating in the intestine ; but it very rapidly increases — even to six times — the amount of blood which transfuses, while at the same time the movements of the intes- tine cease, the walls of the intestine being contracted.] "Effect of Drugs. — Among the reagents which act upon the intestinal movements, are : (l) Such as diminish the excitability of the plexus myentericus, i.e., which lessen or even abolish intes- tinal peristalsis, e.g., belladonna. (2) Such as stimulate the inhibitory fibres of the splanchnic, and in large doses paralyze them — opium, morphia (.AW/;«<7ff/) ; I and 2 produce constipation. (3) Other agents excite the motor apoaratus — nicotin (even causing spasm of the intestine), muscarin, caffein and many laxatives, which act as purgatives. The movements produced by muscarin are abolished by atropin (Schmiedeberg and Koppe"). These substances accelerate the evacuation of the intestine, and, owing to the rapid movement of the intestinal contents, only a small amount of water is absorbed ; so that the evacuations are frequently fluid. (4) Among purga/ives, colocj'nth and croton oil act as direct irritants. With regard to drugs of this sort, they seem to cause a watery transudation into the intestine ( C. Schmidt, Moreati), just as croton oil causes vesicles when applied to the skin. (5) Calomel is said to limit the absorptive activity of the intestinal wall, and to con- trol the decompo.sitions in the intestine. The stools are thin and greenish, from the admixture of biliverdin. (6) Certain saline purgatives — sodium sulphate, magnesium sulphate, causes fluid evacuations by retaining the water in the intestine (Buchheim) ; and it is said that if they be injected into the blood vessels of animals, they cause constipation (Auieri). [Nothnagel finds that when a crj'stal of a potask salt is applied to the peritoneal surface of the intestine of an animal whose abdomen is opened, it causes merely a local constriction of the mus- cular fibres of the gut, while a sodium salt on the other hand excites a contraction which passes upward toward the stomach, and never toward the rectum. Perhaps this is due to the more power- ful stimulant action of the former. In any case it may serve as a useful guide to the surgeon, in determining which is the upper end of a piece of intestine during an operation on the intestines.] [Action of Saline Cathartics. — From an extended investigation recently made by M.atthew Hay on the action of saline cathartics, it would appear certain that a salt exerts a genuine excito- secretory action on the glands of the intestines, while at the same time, in virtue of its low diffusi- bility, it impedes absorption. Thus, between stimulated secretion and impeded absorption there is an accumulation of fluid within the canal, which, partly from ordinary dynamical laws, partly from a gentle stimulation of the peristaltic movements excited by distention, reaches the rectum and results in purgation. Purgation does not ensue when water is withheld from the diet for one or two days previous to the administration of the salt in a concentrated form. This absence of effect is due to a deficiency of water in the blood, so that the blood cannot, through the intestinal glands, yield enough fluid to the salt in order to produce purgation. When a concentrated solution of a salt is administered to an animal whose alimentary canal is known, from a few hours' preliminary fasting, to be empty, but whose blood is in a natural state of dilution, the blood becomes rapidly very concentrated, and reaches the maximum of its concentration in from half an hour to an hour and a half; within four hours the blood has gradually returned to its normal state of concentration without having reabsorbed fluid from the intestine. It apparently recoups itself fi-om the tissue fluids. After a few days' abstention from water, the tissue fluids are so much dimmished as not to be able any longer to recoup the blood, and the blood itself gradually becomes concentrated ; hence, a concentrated saline solution fails to excite any secretion when administered.] [It is also interesting in connection with saline cathartics that the salt — sulphate of magnesia or sulphate of soda — becomes split up in the small intestine, and the acid is more rapidly absorbed than the base. .\ portion of the absorbed acid shortly afterward returns to the intestines, evidently through the intestinal glands. After the maximum of excretion of the acid has been reached, the salt begins very slowly and gradually to disappear by absorption, which is checked only by the occurrence of purgation. The salt does not purge when injected into the blood, and excites no intestinal secretion ; nor does it purge when injected subcutaneously, unless on account of its caus- ing local irritation of the abdominal subcutaneous tissue, which acts reflexly on the intestines, dila- ting their blood vessels, and perhaps stimulating their muscular movements.] 266 FUNDUS GLANDS OF THE STOMACH. 162. STRUCTURE OF THE STOMACH.— [The stomach receives the bolus, and secretes a juice which acts on certain constituents of the food, while by its muscular walls it moves the latter within its own cavity, and after a time expels the partially digested products toward the duodenum.] Structure. — [The walls of the stomach consist of four coats, which are, from without inward — (i) The sc'ro7(s iayer, from the peritoneum. (2) The miisci//avin). ACTION OF GASTRIC JUICE ON THE VARIOUS TISSUES. 277 There is a " lactic acid ferment " {Hamtnarstui) also present, which changes milk sugar into lactic acid. Part of the milk sugar is changed in the stomach and intestine into grape sugar. Action on Carbohydrates. — Gastric juice does not act as a solvent of starch, imilin, or gums. Cane sugar is slowly changed into grape sugar {Boiich- anlat and Sandras (iS^j), Lehmann). According to Uffelmann, the gastric mucus, and according to Leube, the gastric acids, are the chief agents in this process. Albuminoids. — During the digestion of true cartilage, there is formed a chondrin peptone, and a body which gives the sugar reaction with Trommer's test. Perfectlv pure elastin yields an elastin peptone, similar to albumin peptone, and hemi-elastin similar to hemi-albumose (^Horbaczewski) . Fats formerly were stated not to be acted on, but the recent researches of Cash and Ogata show that a small part of the fats is broken up into glycerine and fatty acids. [On neutral olive oil being injected into the stomach of a dog, after several hours — the pylorus being plugged with an elastic bag — it partly slips up and yields oleic acid {^Ogata).'\ fWe still require further observations on the gastric digestion of fats. Richet observed in his case of fistula that fatty matters remained a long time in the stomach, and Ludwig found the same result in the dog. In some dyspeptics, rancid eructations often take place toward the end of gastric digestion. W. Roberts suggests that there may be some slight decomposition of neutral fats and liberation of fatty acids. In this connection, it is important to remember that fatty acids are liber- ated from neutral fats by bacteroid ferments (zymophytes).] III. Action of Gastric Juice on the Various Tissues. — (i) The gelatin-yielding sub- stance (collagen) of all the connective tissues (connective tissue, white fibro-cartilage, and the matrix of bone), as well as glutin, are dissolve! and peptonized by the gastric juice ( Uffelmann). [Gelatin when acted on by gastric juice no longer solidifies in the cold, but a gelatin peplone is formed, which is soluble and diffusible, although it differs from true peptone.] In the dog, con- nective tissues are specially acted on in the stomach, while the other parts of organs used as food are prepared for digestion in the small intestine, where the cellular and nucle.ar elements are digested by the pancreatic juice (Bikfalvi).'] (2) The structureless membranes (membranre propria;) of glands, sarcolemma, Schwann's sheath of nerve fibres, capsule of the lens, the elastic laminie of the cornea, the membranes of fat cells are dissolved, but the true elastic (fenestrated) membranes and fibres are not affected. (3) Striped muscle, after solution of the sarcolemma, breaks up transversely into disks, and, like non-striped muscle, is dissolved and forms a true soluble peptone, hut parts of the muscle always pass into the intestine. (4) The albuminous constituents of the soft cellular elements of glands, stratified epithelium, endothelium, and lymph cells, form peptones, but the nuclein of the nuclei does not seem to be dissolved. (5) The horny parts of the epidermis, nails, hair, as well as chitin, silk, conchiolin, and spongin of the lower animals are indigestible, and so are amyloid substance and wax. (6) The red blood corpuscles are dis- solved, the haemoglobin decomposed into ha^matin and a globulin-like substance ; the latter is pep- tonized, while the former remains unchanged, and is partly absorbed and transformed into bile pig- ment. Fibrin is easily dissolved to form propeptone and fibrin peptone. (7) Mucin, which is also secreted by the goblet cells of the stomach, passes through the intestines unchanged. (81 Vege- table fats are not affected by the gastric juice; these cells yield their protoplasmic contents to form peptones, while the cellulose of the cell wall, in the case of man at least, remains undigested (I 184)- Why the Stomach does not digest itself. — That the stomach can digest living things is shown by the following facts : The limb of a living frog was introduced through a gastric fistula into the stomach of a dog (CI. Bernard) — The ear of a rabbit [Pa-y) was also introduced — and both were partly digested. The margins cf a gastric ulcer and of gastric fistula; in man are attacked by the gastric juice. John Hunter (1772) discussed the question as to why the stomach does not digest itself. Not unfrequently after death the posterior wall of the stomach is found dige.'-led [more especially if the person die after a full meal and the body be kept in a warm place, whereby the Contents of the stomach may escape into the peritoneum. CI. Bernard showed, that if a rabbit be killed and placed in an oven at the temperature of the body, the walls of the stomach are attacked by its own gastric juice. Fishes are also frequently found with their stomach partially digested after death]. It would seem, therefore, that so long as the circulation continues, the tissues are pro- tected from the action of the acid by the alkaline blood; this action cannot take place if the reac- tion be alkaline (Pavy). Ligature of the arteries of the stomach, according to Pavy, causes diges- tive softening of the gastric mucous membrane. The thick layer of mucus may also aid in protect- ing the stomach from the action of its own gastric juice (C/. Bernard). 278 STRUCTURE OF THE PANCREAS. 167. GASES IN THE STOMACH.— The stomach always contams a certain quantity of gases, which are derived partly from the gases swallowed with the saliva, partly from gases which pass backward from the duodenum, and partly from air swallowed directly. If the lan'nx and hyoid bone (^ 15S) are suddenly and forcibly raised upward and forward, there jiasses into the space behind the larynx a considerable amount of air. which on the latter regaining its position, is swallowed, owing to the peristalsis of the oesophagus. We can feel the passage of such a mass of air as it passes along the oesophagus. In this way a considerable volume of air may be swallowed. The air in the stomach is constantly undergoing changes, whereby its O is absorbed by the blood, and for i vol. of O absorbed 2 vols, of CO2 are returned to the stomach from the blood. Hence, the amount of O in the stomach is very small, the CO. very considerable {Flaner). Gases in the Stomach. — Vol. per cent. (Planer). Human Subject after Vegetable Diet. Dog. I. II. I. Alter Animal Diet. II. After Legumes. CO.,, . . . 20.79 H,' . . . 6.71 N, . . . 72.50 0, 33-83 27-58 38-22 0-37 25.2 68.7 6.1 32-9 66.3 0.8 Fig. 176. By the acid of the stomach a part of the CO.j is set free from the saliva, which contains much CO.j (§ 146). The N acts as an indifferent substance. Abnormal development of gases in persons suffering from gastric catarrh, only occurs when the gastric contents are neutral m reaction; during the butyric acid fermentation H and COj are formed, while the acetic acid and lactic acid fermentations do not cause the formation of gases. Marsh gas (CH^) has also been found, but it must come from the intestine, as it can only be formeil when no O is present (§ 184). 168. STRUCTURE OF THE PANCREAS.— The pancreas is built on the t\ pe of compound tubular or acino tubular glands, and in its general arrangement into lobes, lobules and system of ducts and acini', it corresponds exactly to the true salivary glands. The epithelium lining the ducts is not at all, or only faintly, striated. The acini are tubular or flask-shaped, and often convoluted. They consist of a membrana propria, resem- bling that of the .salivary glands, lined by a single layer of somewhat cylindrical cells, with a more or less conical apex directed toward the very narrow luinen of the acini. [As in the salivary glands, there is a narrow intermediary part of the ducts opening into the acini, and lined by flat- tened epithelium.] The cells lining the acini consist of two zones (Fig. 176) : — (I) The smaller parietal layer (outer) is transparent, homogeneous, sometimes faintly striated, and readily stained with carmme and logwood: and (2) the inner layer {Bernard's granular layer) is strongly granular, and stains but slightly with carmine (Fig. 176). It undoubtedly contributes to the secretion by giving off material, the granules being dissolved, and this zone becoming smaller (^Hcidenhain). The spherical nucleus lies between the two zones. [The lumen of the acini is very small, and spindle-shaped or branched cells (centro- acinar cells) lie in it, and send their processes between the secretory cells, thus Section of the pancreas i condition. THE PANCREATIC JUICE. 279 acting as supporting cells for the elements of the wall of the acini {^Langerhans , Fotiwisotzky).'] During secretion there is a continuous change in the appearance of the cell substance ; the granules of the inner zone dissolve in the secretion ; the homogeneous substance of the outer zone is reversed and transformed into granules, which pass toward the inner zone {Heidenhain, Kiihne and Lea). Changes in the Cells during Digestion. — During theyfri/ stage (6 to lo hours) the granular inner zone diminishes in size, the granules disappear, while the striated outer zone increases in size (Fig 177, 2). In the second stage (lo to 20 hours) the inner zone is greatly enlarged and granular, while the outer zone is small {Fig. 177,3)- During hunger the outer zone again enlarges (Fig. 177. l). In a gland where paralylic secretion takes place, the gland is much diminished in size, the cells are shriveled (Fig. 177, 4) and greatly changed (^Heidenhain). According to Ogata, some cells actually disappear during secretion. Duct. — -The axially-placed excretory duct consists of an inner thick and an outer loose wall of connective and elastic tissues, lined bv a single layer of non-striated columnar epithelium. Small mucous glands lie in the largest trunk-;. The connecti-je tissue separates the gland into lobes and lobules. Non-meduUated nerves, vi\lh ganglia in their course, pass to the acini, but their mode of termination is unknown. The blood vessels form a rich capillary plexus round some acini, while round others there are very few. Kiihne and Lea found peculiar small cells in groups between the alveoli, and supplied with convoluted capillaries like glomeruli. Their significance is entirely unknown. [They are probably lymphatic in their nature.] The lymphatics resemble those of the salivary glands. The pancreas contains water, proteids, ferments, fats and salts. When a colored injection is forced into the ducts under a high pressure, fine intercellular passages between the secreting cells are formed (Saviotti's canals'), h\xX they are <2r//^c/«/ products. [In making experiments upon the pancreatic secretion, it is important to remember that the num- ber of pancreatic ducts varies in different animals. In man there is just one duct opening along Fir,. 177. Changes of the pancreatic cells in varinu-S stages of activity. I, During hunger : 2, In the first stage of digestion ; 3 In the second stage ; 4, During paralytic secretion. with the common bile duct at Vater's ampulla, at the junction of the middle and lower third of the duodenum. The rabbit has two ducts, the larger opening separately about 14 inches (30 to 35 cm.) below the entrance of the bile duct. The dog and cat have each two ducts opening separately.] Chemistry — The fresh pancreas contains water, proteids, the ferments, fats and salts. In a gland which has been exposed for some time, leucin, isoleucin [Nencki), butalin, tyrosin, often xanthin and guanin are found : lactic and fatty acids seem to be formed from chemical decomposi- tions taking place. i6g. THE PANCREATIC JUICE.— Method of obtaining the pancreatic juice. Regner de Graaf (1664) tied a cannula in the pancreatic duct of a dog, and collected the juice in a small bag placed in the abdomen. Other experimenters brought the tube through the abdominal wall, and made a temporary fistula, which after some days became inflamed, so that the cannula fell out- To make a permanent fistula, a duodenal fistula (like a gastric fistula) is made, and Wir- sung's duct is catheierized with a fine tube; or the abdomen is opened (dog), and the pancreatic duct is pulled forward and stitched to the abdominal wall, with which, in certain cases, it unites. Heidenhain cuts out the part of the duodenum where the duct opens into it, from its continuity with the intestine, and fixes it on the outside the abdominal wound. Variations in Secretion. — The secretion obtained from a permanent fistula is a copious, slightly active, watery secretion, containing much sodium carbonate; while the thick fluid obtained from the fistula before inflammation sets in acts far more energetically. This thick secretion, which is small in amount, is the normal secretion. The copious watery secretion is perhaps caused by the increased trans- udation from the dilated blood vessels (possibly, in consequence of the paralysis of the vasomotor nerves). It is, therefore, in a certain sense, a " paralytic secre- tion " (§ 145). The quantity varies much, according as the fluid is thick or 280 DIGESTIVE ACTION OF THE FANCREATIC JUICE. thin. During digestion, a large dog secretes i to 1.5 grammes of a thick secre- tion (C/. Bernard). Bidder and Schmidt obtained in twenty-four hours 35 to 117 grammes of a watery secretion per kilo, of a dog. When the gland is not secreting, and is at rest, it is soft and of a pale yellowish- red color, but during secretion it is red and turgid with blood, owing to the dila- tation of the blood vessels. The normal secretion is transparent, colorless, odorless, saltish to the taste, and has a strong alkaline reaction, owing to the presence of sodium carbonate, so that when an acid is added, CO^ is given off. It contains albumin and alkali albuminate; like thin white of egg, it is sticky, somewhat viscid, flows with diffi- culty, and is coagulated by heat into a white mass. In the cold, there separates a jelly-like albuminous coagulum. Nitric, hydrochloric and sulphuric acids cause a precipitate, while the precipitate caused by alcohol is redissolved by water. CI. Bernard found in the pancreatic juice of a dog 8.2 per cent, of organic substances, and 0.8 per cent, of ash. The juice (dog) analyzed by Carl Schmidt contained in 1000 parts : — f Sodic Chloride 7.36 " Phosphate 0.45 [ Organic 81. S4 " .Sulphate o.io Solids. yo.jS in J Inorganic S.54 ] Soda 0.32 1000 parts, I (like those of blood j Lime 2.22 [ serum). Magnesia 0.05 I Potassic Sulphate 0.02 [ Ferric Oxide 0.02 The more rapid and more profuse the secretion, the poorer it is in organic substances ( IVcinmann, Bernstein), while the inorganic remain almost the same; nevertheless, the total quantity of solids is greater than when the quantity secreted is small [Bernsic'in\. Traces of leucin (Radzicje'wski) and soaps are contained in the fresh juice. [It usually contains few or no structural elements. Any structural elements present in the fresh juice, as well as its proteids, are digested by the peptone- forming ferment of the juice, especially if the juice be kept for some time. If the fresh juice is allowed to stand for some time, and then mixed with chlorine water, a red color is obtained.] Concretions are rarely formed in the pancreatic ducts ; they usually consist of calcic carbonate. Dextrose has been found in the juice in diabetes, and urea in jaundice. The statement made by Schift, that the pancreas secretes only after the absorption of dextrin, has not been confirmed. The secretory activity of the pancreas is not dependent on the presence of the spleen. 170. DIGESTIVE ACTION OF THE PANCREATIC JUICE.— The presence of at least /<>///■ hydrolytic ferments or enzymes makes the pancreatic juice one of the most important digestive fluids in the body. I. The Diastatic Action {Valentin, 1844) is caused by a diastatic ferment, amylopsin, a substance which seems to be identical with the saliva ferment ; but it acts much more energetically than the ptyalin of saliva, on raw starch as well as upon boiled starch ; at the temperature of the body the change is effected almost at once, while it takes place more slowly at a low temperature. Glycogen is changed into dextrin and grape sugar, and achroode.\trin {Briieke' s) into sugar. Even cellulose is said to be dissolved {Sehmiilewitsch), and gum changed into sugar by it {v. Voit), but inulin remains unchanged. •According to v. Mering and Musculus, the starch {as in the case of the saliva, ^ 14S) is changed into maltose, a reducing dextrin, and grape sugar; so, also, is glycogen. Amylopsin changes achioodextrin into maltose ; at 40° C. maltose is slowly changed into dextrose (Brown and Heron), but cane sugar is not changed into invertin. The ferment is ]jrecipitated by alcohol, while it is extracted by glycerine without undergoing any essential change. All conditions which destroy the diastatic action of saliva (i, 148) similarly affect its action, but the admixture with acid gastric juice (its acid being neutralized) or bile does not seem to have any injurious influence. This ferment is absent from the pancreas of new-born children (A-orow:n). Preparation. — The ferment is isolated by the same methods as obtain for the saliva ptyalin (§ 148) ; but the tryptic ferment is precipitated at the same time. The addition of neutral salts (4 per cent, solution), e.g.^ potassium nitrate, common salt, ammonium chloride, increases the diastatic action. DIGESTIVE ACTION OF THE PANCREATIC JUICE. 281 II. The Tryptic Action {CI. Berttard, iSjj), or the action on proteids, depends upon the presence of a hydrolytic ferment which Corvisart (1858) called pancreatin, and W. Kiihne (1S76) termed trypsin. Trypsin acts upon proteids at the temperature of the body, when the reaction is alkaline, and changes them first into a globulin-like substance (serum globulin, §249,y. G. Oft), then into propeptone, and, lastly, into a true peptone, sometimes called tryptone. The proteids do not swell up before they are changed into peptone [but they are eroded or eaten away by the action of the juice]. When the proteid has been previously swollen up by the action of an acid, or when the reaction of the medium is acid, the transformation is interfered with. Substances yielding gelatin, nuclein (Bokay) and Hb resist trypsin ; glutin and swollen-up gelatin- yielding substances are changed into gelatin peptone, but the latter undergoes no further change. O-Hb is split up into albumin and h.'emochromnjen. In other respects, trypsin acts on tissues con- taining albumins just like pepsin (?. 167, III) [Hop/e-Sey/tr). Preparation. — Trypsin is never absent from the pancreas of new-born children [Ztoeifeh, and it may be extracted by water, which, however, also dissolves the albumin. Kiihne has carefully sepa- rated the albumin and obtained the ferment in a pure state. It is soluble in water, insoluble in alcohol. Pepsin and hydrochloric acid together act upon tryp.sin and destroy it; hence it is not advisable to administer trypsin by the mouth, as it would be destroyed in the stomach (Ewald, Mays). When dried it may be heated to l6o° without injury (Sa/iowsii). Origin of Trypsin. — It is formed within the pancreas, from a " mother sub- stance'^ or zymogen (Heidenhain), \\h\c\-\ takes up oxygen. The zymogen is found in small amount, six to ten hours after a meal, in the inner zone of the se- cretory cells, but after sixteen hours it is very abundant in the inner zone of the cells. It is soluble in water and glycerine. Trypsin is formed in the watery solu- tion from the zymogen, and the same result occurs when the pancreas is chopped up and treated with strong alcohol ( IV. Kiihne). The addition of sodium chlo- ride, carbonate, and glycocholate, favors the activity of the tryptic ferment {ffei- denhain). [The following facts show that zymogen {"^uij.ri, ferment), or, as it has been called, trypsinogen, is the precursor of trypsin, that it exists in the gland cells, and requires to be acted upon before trypsin is formed. If a glycerine ex- tract be made of a pancreas taken from an animal just killed, and if another extract be made from a pancreas which has been kept for twenty-four hours, it will be found that an alkaline solution of the former has practically no effect on fibrin, while the latter is powerfully proteolytic. If a fresh and still warm pancreas be rubbed up with an equal volume of a i per cent, solution of acetic acid, and then extracted with glycerine, a powerfully proteolytic extract is at once obtained. Trypsin is formed from zymogen by the action of acetic acid {Heidcnhaiii). There is reason to believe that trypsin is formed from zymogen by oxidation, and that the former loses its proteolytic power after removal of its oxygen. The amount of zymogen present in the gland cells seems to depend upon the number and size of the granules present in the inner granular zone of the secretory cells.] Disturbing Conditions. — The addition of NaCl, sodic glycocholate, and carbonate, increases the activity of the ferment (Heidenhniri), while MgSO^ diminishes it (P/eiff'er). [In dogs poisoned with CO, the trypsin no longer has any action on albumin and fibrin. An infu- sion of the CO-pancreas becomes active \\'hen oxygen is driven through it [Herseti). Poisoning with COo, however, does not aifect the tryptic activity.] Further Effects. — When the trypsin is allowed to act upon the peptone formed by its own action, the peptone is partly changed into the amido acid, leu- cin, or amido- eaproic acid {C^Yiu^O.,, and tyrosin (CaHnNO;,), which belongs to the aromatic series {Kiihne, § 252, IV, 3). Hypoxanthin, xanthin {Salomon), and asparaginic or amido-succinic acid (C,H;NOi), are also formed during the diges- tion of fibrin and gluten, and so are glutaminic acid (CjH.jNO,), amido-valerianic and (CjHiiNO.^). Gelatin is first changed into a gelatin peptone, and afterward is decomposed into glycin and ammonia. 282 DIGESTIVE ACTION OF THE PANCREATIC JUICE. Putrefactive Phenomena. — If the action of the pancreatic juice be still fur- ther |iri)longed, especially if the reaction be alkaline, a body with a stron^, stink- ing, disagreeable fscal odor, ///,/<>/ (C,U.N^, volatile fatty acids, s^-uA?/ (C,,UJ/ic'fi(>/ (CgHgO) and a substance which becomes red on the addition of chlo- rine or bromine water {Bernard) are formed, while, at the same time, H, CO.2, HjS, CHj, and N are given off. The formation of indol and the other substances just mentioned depends upon putrefaction (§ 184, III). Their formation is pre- vented by the addition of calomel, salicvlic acid, or thymol, which kills the organ- isms upon which putrefaction depends {Hiifner. Kiihne). [Artificial Digestion. — If some fibrin be placed in pancreatic juice, or in a i percent, solution of sodium carbonate containing the ferment trypsin, peptones are rapidly formed. When we compare gastric with pancreatic digestion, we find that there are marked differences. The fibrin in pancreatic digestion is eroded, or eaten away, and never swells up. The process takes place in an alka- line medium, and never in an acid one. In fact, a i per cent, solution of sodic carbonate seems to play the same part in assisting trypsin that a .2 per cent, solu- tion of HCl does for pepsin in gastric digestion. In gastric digestion acid albu- min or syntonin is formed in addition to the true peptones. In pancreatic diges- tion a body resembling alkali albumin, which passes into a globulin-like body, and ultimately into a tryptic peptone or tryptone is formed. Of the peptones so formed, one is called antipeptonc, and it is not further changed, but part of the proteid is changed in a by-product, hemipeptone. This body, when acted upon, yields leucin and tyrosin. When putrefaction takes place, the bodies above men- tioned are also formed. We might represent the action of trypsin thus : Proteid + trypsin -f i per cent, sodium carbonate, kept at 38° C. = formation of a globulin-like body, and then antipeptone and hemipeptone are formed. undergoes no further change. yields. Hemip yields. Normal Digestive Products. Putrefactive Products. Leucin, Tyrosin, Hypoxanthin, Asparaginic Acid. Indol. Skatol, Phenol, Volatile Fattv Acids, H, CO,, H,S, CH^, N. It seems that trypsin in pure water can act slowly upon fibrin to produce pep- tone. Pepsin cannot do this without the aid of an acid.] When proteids are boiled for a long; tim'; with dilute H^SO^, we obtain peptone, then leucin and tyroiin {Kuhne); gelatin yields ^/i'«'k. Hypoxanthin and xanthin are obtained in the same way by similarly boiling fibrin, and the former may even be obtained by boiling fibrin with water [Chit- tenden), Papain. — It is very remarkable that the juice of the green fruit of the papaya tree (Ca?-ica fapava) possesses digestive properties [Roy, IVittmnci), and the action is due to an albuminous peptonizing ferment, closely related to trypsin, and called caricin or papain. [It forms a true peptone, an inter- mediate body, leucin and tyrosin. It also contains a milk-coagulating ferment \!ilartin).'\ The milky juice of the fig tree has a similar action. According to Gorup-Besanez, sprouting malt, vetch, hop, hemp during sprouting, and the recep- tacle of the artichoke, contain a peptonizing ferment. Leucin, tyrosin, glutaminic and asparaginic acids, and xanthin are formed in the seeds of some plants; hence we may assume that the processes of decomposition in some seeds are closely allied to the fermentative actions that occur in the intestine (Salotiion). III. The action on neutral fats is twofold : (i) It acts upon fats so as to iorxw z. fine permanent enuihicn (yEberlc). (2) It causes neutral fats to take up a molecule of water and split into glycerine and their corresponding fitty acids : — Tristearin (C5:H„<,0, Water. Glycerine. Stearic Acid. 3(H,0) = {C3H,03)+3(C,,H3,0J. SECRETION OF PANCREATIC JUICE. 283 The latter result is due to the action of an easily decomposable fat-splitting fer- ment {CI. Bernard), zX'io called steapsin. Lecithin is decomposed by it into glycero-phosphoric acid, neurin and fatty acids (Bokay). After the decomposi- tion is completed, the fatty acids are partly saponified hy the alkali of the pancre- atic and intestinal juices and partly emulsionized bv the alkaline intestinal juice {J. Miink). Both the soaps and emulsions are capable of being absorbed (§ 191). Emulsification. — The most important change effected on fats in the small intestine is the pro- duction of an emulsion, or their sulidivision into exceedingly minute particles (? 191 ). This is neces- sary in order that the fats may be taken up by the lacteals. If the fat to be emulsified contains a free fatty acid, /. c, if it be slightly rancid, and if the fluid with which it is mixed be alkaline, emulsifica- tion takes place extremely rapidly {Brucki). A drop of cod-liver oil, which in its unpurified condi- tion alwavs contains fatty acids, on being placed in a drop of 0.3 per cent, solution of soda, instantly gives rise to an emulsion ( Gad). The excessively minute oil globules that compose the emulsion are first covered with a laver of soap, which soon dissolves, and in the process small globules are detached from the original oil globules. The fresh surface is again covered by a soap film, and the process is repeated over and over again until an excessively fine emulsion is obtained ( G. Quincke). If the fat contain much fatty acid and the solution of soda be more concentrated, " myelin forms" are obtained similar to those which are formed when fresh nerve fibres are teased in water (Briicke). Animal oils emulsionize more readily than vegetable oils; castor oil does not emulsionize (Gad). [It is extremely difficult to obtain a perfectly neutral oil, as most oils contain a trace of a fatty acid. In fact, if, on adding a weak solution of sodic carbonate to oil or faUy matters, fluid at the temperature of the body, an emulsion is obtained, one may be sure that the oil contained a fatty acid, so that Bernard's view about an " emulsive ferment " being necessary is not endorsed. The fatty acid set free by the fat-splitting ferment enables the alkaline pancreatic juice at once to produce an emulsion.] Fat-Splitting Ferment. — This is a very unstable body, and must be prepared from the perfectly fresh gland by rubbing it up with powdered glass, glycerine, and a i per cent, solution of sodic car- bonate, and allowing it to stand for a day or two [Griitzner). [This ferment is said to cause an emuKion of oil and mucilage tinged blue with litmus at 40° C. to become red (Gamgee). In per- forming this experiment notice that the mucilage is perfectly neutral, as gum arable is frequently acid ] [Pancreatic Extracts. — The action of the pancreas may be tested by making a watery extract of a perfectly fresh gland. Such an extract always acts upon starch and generally upon fats, but this extract and also the glycerine extract vary in their action upon proteids at different times. If the extract — watery or glycerine — be made from the pancreas of a fasting animal, the tryptic action is slight or absent, but is active if it be prepared from a gland 4 to 10 hours after a meal. The pancreatic preparations of Benger, of Manchester, Savory and Moore, or Burroughs and Welcome, all possess active diastatic and proteolytic properties.] [Pancreas Salt. — Prosser-James proposes to employ common salt mixed with pepsin, which he calls peptic salt ; and he advocates the use of another preparation composed of the pancreatic fer- ments and common salt, pancreatic salt.] The pancreas of nevy-born children contains trypsin and the fat-decomposing ferment, but not the diastatic one {Zti-eifel). A slight diastatic action is obtained after two months, but the full effect is not obtained until after the first year (A'orowin). IV. According to Kiihne and W. Roberts, the pancreas contains a milk-curd- ling ferment, which may be extracted by means of a concentrated solution of cornmon salt. 171. THE SECRETION OF THE PANCREATIC JUICE.- Rest and Activity. — .\s in other glands, we distniguish a quiescent state, during which the gland is soft and pale, and a state of secretory activity, during which the organ swells up and appears pale red. The latter condition only occurs after a meal, and is caused probably in a reflex way, owing to stimulation of the nerves of the stomach and duodenum. Kiihne and Lea found that all the lobules of the gland were not active at the same time. The pancreas of the herbivora secretes uninterruptedly [but in the dog secretion is not constant]. Time of Secretion. — .According to Bernstein and Heidenhain the secretion begins to flow when food is introduced into the stomach, and reaches its maximum 2 to 3 hours thereafter. The amount falls toward the 5th or 7th hour, and rises again (owing to the entrance of the chyme into the duodenum) toward the 9th and nth hour, gradually falling toward the i7th-24th hour, until it ceases com- pletely. When more food is taken the same process is repeated. As a general 284 STRUCTURE OF THE LIVER. rule, when the secretion occurs rapidly it contains less sqlids than when it takes place slowlv. Condition of Blood Vessels. — During secretion, the blood vessels behave like the blood vessels of the salivary glands after stimulation of the chorda — they dilate, and the venous blood is bright red — thus, it is probable that a similar nervous mechanism exists [but as yet no such mechanism has been discovered]. The secretion is excreted at a pressure of more than 17 mm. Hg (rabbit). Effect of Nerves upon the secretion. The nerves arise from the hepatic, splenic, and superior mesenteric plexuses, together with branches from the vagus and sympathetic. The secretion is excited by stimulation of the medulla oblongata {Heiilenhain and Landaii), as well as bv direct stimulation of the gland itself by induction shocks {Kiihne and Lea). [It is not arrested by section of the cervical spinal cord.] The secretion is suppressed by atropin [in the dog, but not the rabbit], by producing vomiting (C/. Bernard), by stimulation of the central end of the vagus (C. Liidwig and Bernstein), as well as by stimulation of other sensory nerves, e.g., the crural and sciatic {Afanassiew and Fazvhnu). E.vtirpation of the nerves accompanying the blood vessels prevents the above- named stimuli from acting. Under these circumstances a thin " paralytic secretion " with feeble digestive powers is formed, but its amount is not in- fluenced by the taking of food {Bernstein). [Secretion is excited by the injection of ether into the stomach.] Extirpation of the gland maybe performed [Sctiiff), or the duct ligatured in animals [Freric/is), without causin ; any very great change in their nutrition ; the absorption of fat from the intestme does not ce.ise. After the duct is ligatured it may be again restored. Ligature of the duct may cause the f irmation of cysts in the duct and atrophy of the gland substance (Fawlow). Pigeons soon die after this operation (^LangcnJorff). [172. PREPARATION OF PEPTONIZED FOOD.]— [Peptonized food may be given to patients whose digestion is feeble. Sir Wni. Roberts, of Manchester, uses various forms of this food. Food may be peptonized either by peptic or tryptic digestion, but the former is not so suitable as the latter, because in peptic digestion the grateful odor and taste of the food are destroyed, while bitter by-products are formed. Hence, Dr. Roberts employs pancreatic diges- tion, which yields a more palatable and agreeable product. As tryspin is destroyed by gastric digestion, obviously it is useless to give extract of the pancreas to a patient along with his food.] [Peptonized Milk. — " A pint of milk is diluted with a quarter of a pint of water and heated to 60° C. Two or three teaspoonfuls of Benger's liquor pancreaticus, together with ten or twenty grains of bicarbonate of soda, are then mixed therewith." Keep the nii.xture at 38° C. for about two hours, and then boil it for two or three minutes, which arrests the ferment action.] [Peptonized Gruel, prepared from oatmeal, or any farinaceous food, is more agreeable than peptonized milk, as the bitter flavor does not appear to be developed in the pancreatic digestion of I'^^^Az/^A' proteids.] Peptonized Milk Gruel yielded Roberts the most satisfactory results, as a complete and highly nutritious food for weak digestions. Make a thick gruel from any farinaceous focd, e.g., oatmeal, and while still hot add to it an equal volume of cold milk, when the mixture will li.ave a tempera- ture of 52° C. (125° F. ). To each pint of this mixture add two or three teaspoonfuls of liquor pancreaticus and 20 grains of bicarbonate of soda. It is kept warm for two hours under a " cosey." It is then boiled for a few minutes and strained. The bitterness of the digested milk is almost completely covered by the sugar produced during the process {Roberts).'\ [Peptonized soups and beef tea have also been made and used with success, and have been administered both by the mouth and rectum.] [Peptonizing powders containing the prouer proportions of ferment and sodic bicarbonate are prepared by Benger, and Burroughs and Welcome.] 173. STRUCTURE OF THE LIVER.— The liver, the largest gland in the body, consists of inntmierable small lobules or acini, i to 2 millimetres (•jV to tV inch) in diaineter. These lobules are visible to the naked eye. All the lobules have the same structure. STRUCTURE OF THE UVER. 285 1. The Connective Tissue and Capsule. — The liver is covered by a thin, fibrous, firmly adherent capsule, which has on its free surface a layer of endothelium derived from the peritoneum. The capsule bends fine septa into the orj^an between the lobules, but it is also continued into the interior at the transverse fissure, where it surrounds the portal vein, hepatic artery, and bile duct, and accompanies these structures as the Capsule of Glisson or interlobular connective tissue. The spaces in which these three structures lie are known as portal canals, in some animals (pi^j, camel, polar bear), the lobules are separated from each other by the somewhat Umellated connective tissue of Glisson's capsule, but in man this is but slightly de\ eloped, so that adjoining lobules are more or less fused. Very delicate connective tissue, but small in amount, is also found within the lobules {FUischl, Kiipffer). Leucocytes are sometimes found in the tissue of Glisson's capsule. 2. Blood Vessels. — (a) Branches of the Venous System. — If the vena porta be traced from its entrance into the liver at the portal fissure, it will be found to give off numerous branches lying between the lobules, and ultimately forming small trunks which reach the periphery of the lobules. Fig. 17S. I. Schem< capiU; giving branche! lobule,— V. J, V. ;, interlobular veins (portal) ; V. :en both; V. j, sub-lobular vein; V. j-, vena vascularis; A, A, brar _ >r, r, to Glisson's capsule and the larger vessels, and ultimately forr _ opening into the intralobular capillaries ; ff, branches of the bile ducts : x, x, between the liver cells ; rf, t/, position of the liver cells between the meshes of the blood capillaries. II, Isolated liver cells — c, a blood capillary ; a, fine bile capillary channel. lobular vein (hepatic) ; c, K hes of the hepatic artei ning the vena: vasculares tralobular bile capillar where they form a rich plexus. These are the interlobular veins (Fig. 178, V. ;). From these Veins numerous capillaries (r, c) are given oft" to the entire periphery of the lobule. The capillaries converge toward the centre of the lobule. As they proceed inward, they form elongated meshes, and between the capillaries lie rows or columns of liver cells (^' /, \ /S °1 0. Human liver cells The cell protoplasm contains Appearanceof the hverCLlU after biliary coloring matter and oil globules, b; d w itholding food for lhirt> has two nuclei. six hours. period of digestion. During hunger, the liver cells are finely granular and very cloudy (Fig. 180). About thirteen hours after a full meal, especially of starchy food, they contain coarse glancing masses of glycogen (Fig. 1S2, 2). The protoplasm near the surface of the cell is condensed, and a fine network stretches toward the centre of the cell, and in it is suspended the nucleus {Kupffer, Hci- dcnhain). [Afanassiew finds that if the formation of bile in the liver be increased [e.g., by section of the hepatic nerves, or feeding with proteids), the cells are moderately enlarged in size, and con- tain numerous granules which are proteid in their nature; such cells resist the action of caustic potash. When there is a great formation of glycogen (as after feeding with potatoes and sugar), all the cells are very large and sharply defined, while their bodies are loaded with granules of gly- cogen, the cells being so large as to compress the capillaries. These cells dissolve quickly in caustic potash. The network within the cells is best seen after solution of the glycogen.] 4. The Bile Ducts. — The finest bile capillaries or canaliculi arise from the centre of the lobule, and, indeed, throughout the whole lobule, they form a regular anastomosing network of very fine tubes or channels. Each cell is surrounded by a polygonal — usually hexagonal — mesh (Fig. 17S, X x). The bile capillaries always lie in the middle of the surface between two adjoining cells (II, a), where they form actual intercellular passages (¥\g. 181) (Hering). [According to some observers, they are merely excessively narrow channels (I to 2 /-t wide) in the cement substance between the cells, while according to others, they have a distinct delicate wall [Fritsc/i, Aliura). The bile capillary network is much closer than the blood capillary network. [Thus, there are three networks within each lobule— (i) A network of blood capillaries; (2) " hepatic cells; (3) " bile capillaries; (Fig. i8i.] STRUCTURE OF THE LIVER. 287 Excessively minute intracellular passages are said to pass from the bile capillaries into the interior of the liver cells, where they communicate with certain small cavities or vacuoles (Asp, Kupffer, Pfliiger — Fig. 182, 3). As the blood capillaries run along the edges of the liver cells, and the bile capillaries between the opposed surfaces of adjacent cells, the two systems of canals within the lobule are kept separate. Some bile capillaries run along the edges of the liver cells in the human liver, especially during embryonic \\iit \Zuckerkandl, Toldl). Tow-ard the peripheral Fig. 181. Blood capillaries, finest bile ducts ^ Finest bile duct. {£■. Htrittg). part of the lobule, the bile capillaries are larger, while adjoining channels anastomose and leave the lobule, where they become interlobular ducts (g), which join with other similar ducts to form larger interlobular bile ducts. These accompany the hepatic artery and portal vein, and leave the liver at the transverse fissure. Ihe finer interlobular ducts frequently anastomose in Glisson's cap- sule (Asp), possess a structureless basement membrane, and are lined by a single layer of low, polyhedral, epithelial cells. The larger interlobular duels have a distinct wall consisting of con- Fig. 183. , Liver cell during fasting ; 2. containing 1 of glycogen ; 3, a liver cell surrounded with bile channels, Irom which fine twigs proceed into the cell substance, where they end in vacuole. like enlargements. From a rabbit's liver injected with Berlin blue from the bile duct. Interlobular bile duct (Human) nective and elastic tissue, mixed with circularly disposed, smooth, muscular fibres (Fig. 183). Capillaries are supplied to the wall, which is lined by a single layer of columnar epithehum. A sub.mucosa occurs only in the largest bile ducts, and in the gall bladder. Smooth muscular fibres, arranged in single bundles, occur in the largest ducts, and as longitudinal and circular layers in the gall bladder, wnose mucous membrane is provided with numerous folds and depressions. The epithelium lining the gall bladder is cylindrical, with a distinct, clear disl<, and between these cells 288 CHEMICAL COMPOSITION OF THE LIVER CELLS. are goblet cells. Small branched tubular mucous glands occur in the small bile ducts and in the gall bladder. Vasa Aberrantia are isolated bile ducts which occur on the surface of the liver, but have no relation to any system of liver lobules. They occur at the sharp margin of the liver in the region of the inferior vena cava, of the gall bladder, and of the parts near the portal fissure. It seems that the bver lobules to which they originally belonged have atrophied and disappeared [Zucierkandl and ToUt). (5) The Lymphatics begin as peri-capillary tubes around the capillaries within the lobules [MacGilta-ry). They emerge from the lobule and run within the wall of the branches of the hepatic and portal veins, and afterward surround the venous trunks (J'/eisi/il, A. Budge), thus form- ing the interlobular lymphatics. These unite to form larger trunks, which leave the liver partly at the portal fissure, partly along with the hepatic veins, and partly at different points on the surface of the organ. There is a narrow superficial meshwork of lymphatics under the peritoneum — sub- peritcmeal — which communicate with the thoracic lymphatics through the triangular ligament and suspensorium, while on the under surface they communicate with the lymphatics of the interlobular connective tissue. (6) The Nerves consist partly of medullated and partly of non-medullated fibres from branches of the sympathetic and left vagus to the hepatic plexus. They accompany the branches of the hepatic artery, and ganglia occur on their branches within the liver. Some of the nerve fibres are vasomotor in function, and according to Pliiger, other nerve fibres terminate directly in connection with liver cells, although this observation has still to be confirmed. Pathological. — The connective tissue between the lobules may undergo great increase in amount, especially in alcohol and gin drinkers, and thus the substance of the lobules may be greatly compressed, owing to the cicatricial contraction ot the newly-formed connective tissue (cir- rhosis of the liver). In such interlobular connective tissue, newly-formed bile ducts are found [Cornil, Charcot and others 1. Ligature of the ductus choledochus [causes enlargement of the spleen (rabbit) and a diminu- tion in the number of the blood corpuscles {Mackey)\, and, after a lime, interstitial inflam- mation of the liver. In rabbits and guinea pigs the liver parenchyma disappears, and its place is taken by newly-formed connective tissue and bile ducts (^Charcot and Gombault). In all these cases of interstitial inflammation, there is proliferation of the epithelium of the bile ducts (/brf, Salvioli). According to Beloussow, the dilated bile ducts partly burst, and partly (owing to pressure) undergo necrosis, and thereafter in the neighborhood of these foci inflammatory reaction sets in, v\ith cell infiltration, formation of new connective tissue, and regenerative new formation of bile ducts. [Regeneration of the Liver. — Tizzoni finds that there may be partial regeneration and new formation of liver lobules in the dog, the process being the same as that which occurs in the embry- onic development of the organ, i. e., the growth of solid cylinders of liver cells, formed by the pre- existing hver cells, which penetrate into the connective tissue uniting the edges of the wound.. These cells ultimately differentiate into hepatic cells and bile ducts. Griffini also confirms the fact of the regeneration of the hepatic substance in the dog and rabbit, but he thinks that the new forma- tion is developed by the outgrowth of the epithelial cells of the bile cells.] 174. CHEMICAL COMPOSITION OF THE LIVER CELLS.— (i) Proteids. — The fresh, soft ])arenchyma of the liver is alkaline in reaction ; after death, coagulation occurs, the cell contents appear turbid, the tissue becomes friable, and gradually an acid reaction is developed. This process closely resembles what occurs in muscle, and is due to the coagulation of a myosin-like body, which is soluble during life, but after death undergoes spontaneous coagula- tion lyPlbsz). The liver contains other albuminous bodies; one coagulating at 45^ C, another at 70° C, and one which is slightly soluble in dilute acids and alkalies. The cell nuclei contain nuclein {Flbsz). The connective tissue yields gelatin. (2) Glycogen or Animal Starch — 1.2 to 2.6 per cent. — is most closely related to inulin, is soluble in water, but diffuses with difficulty, is a true carbohy- drate (C/. Bernard and v. Hensen, iSjj), and has the formula 6(C6H,„05) -|- H^O l^Kulz and Borntrdger). It is stored up in the liver cells {Bock and Hoff- man'), in amorphous granules around the nuclei (Fig. 182, 2), but it is not uni- formly distributed in all parts of the liver {v. Witticli). Like inulin, it gives a deep red color with solution of iodine in iodide of potassium. It is changed into dextrin and sugar by diastatic ferments, and when boiled with dilute mineral acids, it yields grape sugar (§ 148, I ; § 170, I ; § 252, IIIj. Preparation of Glycogen. — Let a rabbit have a hearty meal, and kill it three or four hours therealter. The liver is removed immediately after death ; it is cut into fine pieces, plunged into CHEMICAL COMPOSITION OF THE LIVER CELLS. 289 boiling water, and boiled for some time in order to obtain a watery extract of the liver cells. [It is placed in boiling water to de-troy the ferment supposed to be present in the liver, which would trans form the glycogen into grape sugar.] To the cold filtrate are added alternately dilute hydrochloric acid and polassio- mercuric iodide as long as a precipitate occurs. The albuminates or proteids are precipitated by the iodide compound in the presence of free HCI. It is then filtered, when a clear opalescent fluid, containing the glycogen in solution, is obtained. The glycogen is precipitated from the filtrate, as a while amorphous powder, on adding an excess of 70 to 80 per cent, alcohol. The precipitate is washed with 60 per cent, and afterward with 95 per cent, alcohol, then with ether, and lastly, with absolute alcohol ; it is dried over sulphuric acid and weighed {^Briicke). Ferment. — [F. Eves asserts that \\\^ post-mortem conversion of sugar in the liver is not attribut- able to a ferment action, and the rapid appearance of sugar in the liver after death is due to the specific metabolic activity of the dying cells.] Conditions which influence its amount. — If large quantities of starch, milk-, fruit-, or cane-sugar, or glycerine, but not mannite or glycol {Ltichsinger), or inosite {Kiilz), be added to the proteids of the food, the amount of glycogen in the liver is very greatly increased (to 12 per cent, in the fowl), while a purely albuminous or partly fatty diet diminishes it enormously. During hunger it almost disappears {Favy and Tscherinoff). The injection of dissolved carbohydrates into a mesenteric vein of a starving rabbit causes the liver, previously free from glycogen, to contain glycogen (^Naunyn). [Arsenic, phosphorus, and antimony destroy the glycogenic function of the liver, no glycogen being present in the liver of animals poisoned with these drugs, so that puncture of the floor of the fourth ventricle no longer causes glycosuria in them.] During life, under normal conditions, the glycogen in the liver is either not transformed into grape sugar {Pavy, Hitter, Eiilenbcrg), or, what is more prob- able, only a very small amount of it is so changed. The normal amount of sugar in blood is 0.5 to i per 1000, although the blood of the hepatic vein contains somewhat more. A considerable amount is transformed into sugar only when there is a decided derangement of the hepatic circulation, and in these circum- stances the blood of the hepatic vein contains more sugar. The glycogen under- goes this change very rapidly after death, so that a liver which has been dead for some time always contains more sugar and less glycogen. The Diastatic ferment in the liver is small in amount, and can be obtained from the extract of the liver cells by the same means as are applicable for obtain- ing other similar ferments, such as pytalin ; but it does not seem to be formed within the liver cells, but only passes very rapidly from the blood into them. The ferment seems to be rapidly formed when the blood stream undergoes considerable derangement (Hitter, Schiff). A similar ferment is formed when red blood cor- puscles are dissolved { Fiegel), and, as there is a destruction of red blood corpus- cles taking place continually within the liver, this is one source from which the ferment may be formed, whereby minute quantities of sugar would be continually formed in the liver. If glycogen is injected into the blood, achroodextrin appears in the urine, and also hs^moglobin, as glycogen dissolves red blood corpuscles (Bo/im, Hoffmann). Ligature of the bile duct causes decrease of the glycogen in the liver (y. Wittich); it appears as if, after this operation, the liver loses the property of forming glycogen from the materials supplied to it. (3) The following substances have also been found in the liver cells : Fats, in the form of highly refractive granules in the liver cells, as well as in the bile ducts ; sometimes, when the food contains much fat (more abundant in drunkards and the phthisical), olein, palmitin, stearin, volatile fatty acids, and sarcolactic acid are found. [Fatty Degeneration and Infiltration. — Fatty granules are of common occurrence within the cells of the liver, and when they do not occur in too great amount, do not seem to interfere very greatly with the functions of the liver cells. These fatty granules are common in disease, constitut- ing fatty infiltration and degeneration, and in such cases the cells within a lobule of the liver, next the portal vein, are usually most highly charged with the fatty particles. Fatty particles occur if too 19 290 DIABETES MELLITUS. much fatty food be taken, and they are commonly found in the livers of stall fed animals, and the ■vit\\-)Lr\o-V?-««?-a'), in colorless blood corpuscles, in fresh pus cells which still exhibit amoeboid movements, and, in fact, in all developing animal cells, with amceboid movement; it is a never faihng constituent in cartilage, and in the muscles and liver of invertebrata, such as the oyster {Hoppe-Seyler). There is none in the fresh brain of the dog or rabbit, but it is found in the brain in diabetic coma {Abeles).~\ Persons suffering from diabetes require a large amount of food ; they suffer greatly from thirst, and drink much fluid. They exhibit signs of marked emacia- tion, when the loss of the body is greater than the supply. [In advanced diabetes the glycogenic function of the liver is almost abolished, as was proved by remov- ing with a trocar a small part of the liver from man i^Ehrlich), when almost no glycogen was found. The absorbed sugar in the portal vein passes directly into the general circulation without being submitted to the action of the liver (l<. Frerichs)^ In severe cases, toward death, not unfrequently a peculiar comatose condition — diabetic coma — occurs, when the breath often has the odor of acetone, which is also found in the urine (Fetters). But neither acetone nor its precursor, aceto-acetic acid, nor tethyl-diacetic acid, nor the unknown substance in diabetic urine which gives the red color with ferric chloride (v. JakscJi), is the cause of the coma {Frericlis and Brieger). The urinary tubules often show the signs of coagulation necrosis, which is recognized by a clear, swollen-up condition of the dead cells {Ebstein). As yet there is no satisfactory explanation of those rarer cases of " acetonfemia " without diabetes (A"(i'///(V/'/, Cantiiii, v. JakscJi). 176. THE FUNCTIONS OF THE LIVER.— [In order to under- stand the functions of the liver, we must remember its unique relation to the vascular and digestive systems, whereby many of the products of gastric and in- testinal digestion have to traverse it before they reach the blood, and, in fact, as some of them traverse the liver they are altered. We have still much to learn re- garding these offices of the liver, but it has several distinct functions — some obvious, others not. (i) The liver secretes bile, which is formed by the hepatic cells, and leaves the organ by the bile ducts, to be poured by them into the duo- denum. (2) But the liver cells also form glycogen, which does not pass into the ducts, but in some altered and diffusible torm passes into the blood stream, and leaves the liver by the hepatic veins. Hence, the study of the liver materially influences our conception of a secreting organ. In this case, we have the pro- ducts of its secretory activity leaving it by two different channels — the one by the ducts, and the other by the blood stream. The liver, therefore, is a great store- house of carbohydrates, and it serves them out to the economy as they are required. All this points to the liver as being an organ intimately related to the general metabolism of the body. (3) In a certain period of development it IS concerned in the formation of blood corpuscles (§ 7). (4) It has some relation to the breaking up of blood corpuscles and the formation of urea and other metabolic products (§ 20, § 177, 3)- Cs) Brunton attributes some importance to the liver in connection with the arrest of certain substances absorbed from the alimentary canal, whereby they are either destroyed, stored up in the liver, or, it may be, prevented from entering the general circulation in too large amount. It is possible that ptomains may be arrested in this way (§ 166).] THE BILE ACIDS. 293 177. CONSTITUENTS OF THE BILE.— Bile is a yellowish-brown or dark green colored transparent fluid, with a sweetish, strongly bitter taste, feeble musk-like odor and neutral reaction. The specific gravity of human bile from the gall-bladder = 1026 to 1032, while that from a fistula = loio to loii (^Jacobsi-n). It contains — (i) Mucus, which gives bile its sticky character, and not unfrequently makes it alkaline, is the product of the mucous glands and the goblet cells of the mucous membrane of the larger bile ducts. When bile is exposed to the air, the mucus causes it to putrefy rapidly. It is precipitated by acetic acid or alcohol. [Bile from the gall bladder, when poured from one vessel into another, shows the presence of mucin in the form of thin threads connecting the fluids in the two vessels. When such bile is treated with alcohol, it no longer exhibits this property, but flows like a non viscid watery fluid. The bile formed in the ultimate bile duels does not seem to contain mucin or mucus, but bile from the gall bladder always does. It is formed from the mucous glands in the larger bile ducts (? «73)-] (2) The Bile Acids. — Glycocholic and taurocholic acids, so-called conjugate acids, are united with soda (in traces with potash) to form glycocholate and taurocholate of soda, which have a bitter taste. In human bile (as well as in that of birds, many mammals and amphibians), taurocholic acid is most abundant; in other mammals Cpig, ox) glycocholic acid is most abundant. These acids rotate the plane of polarized light to the right. [The bile from a biliarv- fistula is sometimes not bitter.] (ff) Glycocholic acid, C.jeH^NOs (first discovered and described as cholic acid by Gmelin, and called by Lehmann glycocholic acid). When boiled with caustic potash, or baryta water, or with dilute mineral acids, it takes up H..0 (Strecke7-^, and splits into — Glycin ( = Glycocoll -.= Gelatin Sugar = Amido-acetic acid) ^ C2H5NO2. -f- CholaUc acid (also called Cholic acid) ^= C^^^aO^. = Glycocholic acid + Water = C^^H^jNOe — H,0. {b) Taurocholic acid, CssHjsNSG,, when similarly treated, takes up water and splits into — Taurin ( ^ Amido-tethyl-sulphuric acid) ^ CH.NSOj. -I- Cholalic acid = C^^H^pOs. = Taurocholic acid -1- Water .... = CjeH^^NSO, + H^O {Strecker). [Solutions of taurocholic acid are antiseptic, and if sufficiently strong interfere with the develop- ment of bacteria, and prevent the alcoholic and lactic fermentations, as well as the tryptic and dias- tatic action of the pancreas (iTw/t-/;).] Preparation of the Bile Acids — Bile is evaporated to ]^ of its volume, rubbed up into a paste with excess of animal charcoal, and dried at 100° C. The black mass is extracted with abso- lute alcohol, which is filtered until it is clear. After a part of the alcohol has been removed by distillation, the bile sails are precipitated in a resinous form, and on the addition of excess of ether there is formed immediately a crjsialline mass of glancing needles [P/alncr's " crystallized bile''). The alkaline salts of the bile acids are freely soluble in water or alcohol, and insoluble in ether. A'eiitial lead acetate precipitates the glycocholic acid — as lead glycocholate — from the solution of both salts; the precipitate is collected on a filter, dissolved in hot alcohol, and the lead is precipi- tated as lead sulphide by H,S ; after removal of the lead sulphide, the addition of water precipitates the isolated glycocholic acid. If, after precipitating the lead glycocholate, the filtrate be treated with basic lead acetate, a precipitate of lead taurocholate is formed, from which the lead may be obtained in the same way as described above (Sirecier). When human bile is similarly treated, instead of the " cr>'stallized bile," a resinous non-crystal- line precipitate is obtained. Boiling with barj-ta water isolates the cholalic acid from it, which is obtained from its barium salt by adding hydrochloric acid. When dissolved in ether, it occurs in the form of prismatic crystals if petroleum ether is added. The anthropocholic acid iCi jH^jO^ — H. Bayer), so obtained is not soluble in water, but readily so in alcohol, and rotates the ray of polarized light to the left. With regard to the decomposition products of the bile acids, glycin, as such, does not occur in the body, but only in the bile in combination with cholalic 294 THE BILE ACIDS. acid, in urine in combination with benzoic acid, as hippuric acid, and lastly, in gelatin in complex combination. Cholalic acid rotates the ray of polarized light to the right, and its chemical composition is unknown ; perhaps it is to be regarded as benzoic acid, in which a complex ot" atoms similar to oleic acid is introduced (Hoppf-Scykr'). It occurs free only in the intestine, where it is derived from the splitting up of taurocholic acid, and it passes in part into the fasces. It is insoluble in water, soluble in alcohol, but soluble with difficulty in ether, from which it separates in prisms. Its crystalline alkaline salts are readily soluble in water. Cholalic acid is replaced in the bile of many animals by a nearly related acid, e. g., in pig's bile, by hyo-cholalic acid [Strecker, Gundlach); in the bile of the goose, cheno-cholalic acid is present [Marsson, Otto). When cholalic acid is boiled with concentrated HCl, or dried at 200° C, it becomes an anhydride, thus: — Cholalic acid . . ^= Cj^H^pO,, produces Choloidinic acid . = Co4H3g04 + H,0, and this again yields Dyslysin . . . . = CJ^Hj^Oj = HJO. (Choloidinic acid is, however, improbably a mixture of cholalic acid and dyslysin; dyslysin, when fused with caustic potash, is changed into cholalale of potash — Hoppe-Seyler). If anthro- pochohc acid be heated to 185° C, it gives up I molecule of water, and yields anthropocholdysly- sin \Bayer). By oxidation cholalic acid yields a tribasic acid, as yet uninvestigated, and a fair amount of oxalic acid, but no fatty acids [Cleve). Pettenkofer's Test. — The bile acids, cholalic acids, and their anhydrides, when dissolved in water, yield on the addition of Ji concentrated sulphuric acid (added in drops so as not to heat the fluid above 70'^ C), and several drops of a 10 per cent, solution of cane sugar, a redJis/i-piirp/e transparent fluid, which shows two absorption bands at E and F i^Schenk). [A very good method is to mix a few drops of the cane-sugar solution with the bile, and to shake the mix- ture until a copious froth is obtained. Pour the sulphuric acid down the side of the test tube, and then the characteristic color is seen in the froth. Any albumin present must be removed before applying the test.] According to Drechsel, it is better to add phosphoric acid, instead of sulphuric acid, until the fluid is syrupy, then add the cane sugar, and afterward place the whole in boiling water. When investi- gating the amount of bile acids in a liquid, the albumin must be removed beforehand, as it gives a reaction similar to the bile acids, but in that case the red fluid has only one absorption band. If only small quantities of bile acids are present, the fluid must in the first place be concentrated by evaporation. [Hay's Test for the Bile Acids. — This test depends on the fact, recently ascertained by Matthew Hay in the course of an investigation which is not yet completed, that the bile acids or their soluble salts have a remarkable lowering effect on the surface tension of fluids in which they are dissolved. One part of glycoholic or taurocholic acid in 100,000 or 120,000 parts of water, per. ceptibly lowers the surface tension of the water, and the lowering is very evident in a solution of I in 10,000, This lowering of the surface tension can, of course, be measured in the usual way by means of a capillary tube. But Hay proposes, as a much more conven ent method, the throwing of a small quantity of sulphur (sublimed or precipitated) on the surface of the fluid containing bile acids. If the bile acids are present in greater proportion than I in 5000 or 10,000, the ,sulphur will at once begin to sink, and will be wholly precipitated within one to two or three minutes. Precipi- tation can even be observed, though it takes place much more slowly, in a solution of I in 120,000, especially if the fluid is acidulated with a drop of a dilute mineral acid Thrown on water, sulphur does not sink, even after a week. No other substances in the body, except soaps, have the same action as the bile acids — at least in anything like the same degree ; and soaps can be readily excluded from the fluid under examination, either by precipitation with calcic or baric chloride or by decom- position with a mineral acid, the earthy .salts of the fatty acids, as also the liberated acids themselves, being insoluble in water. Even outside the body. Hay has as yet found no substances, besides soaps, which have the same powerful eflect on the surface tension as the bile acids have. Hay has already used the sulphur test with success for the detection of bile acids in urine. He attaches considerable importance to this physical property of the bile acids in their role in digestion. — (Privately commu- nicated).'] THE BILE PIGMENTS. 295 The origin of the bile acids takes place within the liver. After its extirpa- tion there is no accumulation of biliary matters in the blood (^Joh. Miiller, Kunde, Moleschott). How the formation of the nitrogenous bile acids is effected is quite unknown. They must be obtained from the decomposition of albuminous materials, and it is Important to note that the amount of bile acids is increased by albuminous food. Taurin contains part of the sulphur of albumin ; bile salts contain 4 to 4.6 per cent, of sulphur {y. Voit), which may perhaps be derived from the stroma of the dissolved red blood corpuscles. (3) The Bile Pigments. — The freshly secreted bile of man and many ani- mals has a yellowish-brown color, due to the presence of bilirubin {Stddler). When it remains for a considerable time in the gall bladder, or when alkaline bile is exposed to the air, the bilirubin absorbs O and becomes changed into a green pigment, biliverdin. This substance is present naturally, and is the chief pig- ment in the bile of herbivora and cold-blooded animals. {a) Bilirubin (CajHseN^Og), is, according to Stiidler and Maly, perhaps united with an alkali ; it crystallizes in transparent fox-red clino-rhombic prisms. It is insoluble in water, soluble in chloroform, by which substance it may be separated from biliverdin, which is insoluble in chloroform. It unites as a monobasic acid with alkalies, and as such is soluble. It is identical with Virchow's hcematoidin (§ 20). Preparation. — It is most easily prepared from the red (bilirubin chalk) gall stones of man or the ox. The stones are pounded, and their chalk dissolved by hydrochloric acid ; the pigment is then extracted with chloroform. Source. — That bilirubin is derived from hemoglobin is very probable, considering its identity with hrematoidin. Very probably red blood corpuscles are dissolved in the liver, and their haemo- globin changed into bilirubin. (1^) Biliverdin {Heintz), CsoHanNjOg, is simply an oxidized derivative of the former, from which it can be obtained by various oxidation processes. It is readily soluble in alcohol, very slightly so in ether, and not at all soluble in chloroform. It occurs in considerable amount in the placenta of the bitch. As yet it has not been retransformed by reducing agents into bilirubin. Tests for Bile Pigments. — Bilirubin and biliverdin may occur in other fluids, e.g., the urine, and are detected by the Gmelin-Heintz' reaction. When nitric acid containing some nitrous acid is added to the liquid containing these pigments, a play of colors is obtained, beginning with green (biliverdin), blue, violet, red, ending with yellow. [This reaction is best done by placing a drop of the liquid on a white porcelain plate, and adding a drop of the impure nitric acid.] (c) If when the blue color is reached, the oxidation process is arrested, bilicyanin (Heynsius, Cam/'bcll), in acid solution blue (in alkaline violet), is obtained, which shows two ill-defined absorp- tion band< near D {faffc). [d) Bilifuscin occurs in small amount in decomposing bile and in gall stones = bilirubin -f H,0. {e^ Biliprasin {Stddler) also occurs =: Bilirubin -|- HjO -\- O. (/) The yellow pigment, which results from the prolonged action of the oxidizing reagent, is the choletelin (CjjHjgNjOj) of Maly; it is amorphous, and soluble in water, alcohol, acids, and alkalies. [Spectrum of Bile. — The bile of carnivorous animals is generally free from absorption bands, except when acids are added to it, in which case the band of bilirubin is revealed. Bilirubin and biliverdin yield characteristic spectra only when they .are treated with nitric acid. The bile of some animals yields bands, but when this is the case they are due to the presence of a derivative of hsematin, and MacMunn calls this body Cholohaematin, which gives a three- or four-banded spec- trum (ox, sheep).] {g) Hydro-bilirubin. — Bilrubin absorbs H -|- H,;0 (by putrefaction, or by the treatment of alkaline watery solutions with the powerfully reducing sodium amal- gam), and becomes converted into Maly's hydro-bilirubin (CjjHuNiO,), which is slightly soluble in water, and more easily soluble in solutions of salts, or alkalies. 296 THE SECRETION OF BILE. alcohol, ether, chloroform, and shows an absorption band at b, F. This substance, which, according to Hammarsten, occurs in normal bile, is a constant coloring matter of ffeces, and was called stercobilin by Valulair and Masius, but is iden- tical with hydro bilirubin (Maly). It is. however, probably identical with the urinary pigment urobilin of Jafle {Stokvis, § 20). [The bile of invertebrates contains none of the bile pigments present in vertebrates, although hsmochromogen is found in the crayfish and pulmonate molluscs. In some organs, and in bile, a pigment-like vegetable chlorophyll — entero chlorophyll — is found, but whether it is derived from without or formed within the organism, is not certain. (J/(i£-il/K«K).] (4) Cholesterin, C26H„0(H20), is an alcohol which rotates the ray of polar- ized light to the left, and whose constitution is un- known ; it occurs also in blood, yelk, nervous matter and [gall stones]. It forms transparent rhombic plates, which, usually, have a small oblong piece cut out of one corner (Figs. 184, and 144, r/). It is insoluble in water, soluble in hot alcohol, in ether Crystals of^choksterin, regularly and chloroform. It IS kept in solution in the bile by the bile salts. Preparation. — It is most easily prepared from so-called white gall stones, which not unfrequently consist almost entirely of cholesterin, by extracting them with hot alcohol after they are pulverized. Crystals are excreted after evaporation of the alcohol. Tests. — They give a red color with sul- phuric acid (5 vol. to i vol. H.,0 — Moiesckotf), while they give a blue — as cellulose does — with sulphuric acid and iodine. When dissolved in chloroform, one drop of concentrated sulphuric acid causes a deep red color (//. Sc/iiff). (5) Among the other organic constituents of bile are : Lecithin (§ 23), or its decomposition product, nei\rin (cholin), and glycero-phosphoric acid (into which lecithin may be artificially transformed by boiling with baryta) ; Palmitin, Stearin, Olein, as well as their soda soaps ; Diastatic Ferment {Jacobson, V. WitticK); traces of Urea (Picard); (in ox bile, acetic acid and propionic acid, united with glycerine and metals, Dogiel). (6) Inorganic constituents of bile (0.6 to i per cent.) : — ■ They are — sodium chloride, potassium chloride, calcic and magnesic phosphate and much iron, which in fresh bile gives the ordinary reactions for iron, so that iron must occur in one of its oxid- ized compounds in the bile (Ktinkel); manganese and silica. Gases. — P'reshly secreted bile contains in the dog more than 50 vol., and in the rabbit log vol. per cent. COj {Pfliiger, Bogulju- bow, Charles), partly united in alkalies, partly absorbed, tlie latter, however, being almost com- pletely absorbed within the gall bladder. The mean composition of human bile is: — Water 82 to 90 per cent. I Lecithin 0.5 per cent. Bile Salts 6 to II " | Mucin i to 3 " Fats and Soaps .... 2 " Ash 0.61 " Cholesterin 0.4 • " | Further, unchanged fat, probably, always passes into the bile, but is again absorbed tlierefrom ( Virc/iozu). The amount of S in dry dog's bile = 2.8 to 3.1 per cent., the N ^ 7 to 10 per cent. {Spiro) ; the sulphur of the bile is not oxidized into sulphuric acid, but it appears as a sulphur compound in the urine {^Kunkel^ v. VoW). 178. SECRETION OF BILE.— (i) The secretion of bile is not a mere filtration of substances already existing in the blood of the liver, but it is a chemical production of the characteristic biliary constituents, accompanied by oxidation, within the hepatic cells, to which the blood of the gland only supplies the raw material. The liver cells themselves undergo histological changes during the process of digestion (/Tf/Vf/z/za///, Vv'(7iJfr). It is secreted continually; but part is stored up in the gall bladder, and is poured out copiously during digestion. The higher temperature of the blood of the hepatic vein, as well as the large amount of CO-^ in the bile (^Pfliiger), indicate that oxidations occur within the liver. The water of the bile is not merely filtered through the blood capillaries, as the pressure within the bile ducts may exceed that in the portal vein. CONDITIONS INFLUENCING THE SECRETION OF BILE. 297 (2) The quantity of bile was estimated by v. Witticli, from a biliary fistula, at 533 cubic centimetres in twenty-four hours (some bile passed into the intestine) ; by Westphalen, at 453 to 566 grm. [by Murchison, at 40 oz.] ; by Joh. Ranke, on a biliary-pulmonary fistula, at 652 cubic centimetres. The last observation gives 14 grm. (with 0.44 grm. solids) per kilo, of man in twenty hours. , Analogous values for animals are— I kilo, dog, 32 grm. (1.2 so\ids)~A'o//iief; H. Miiller); I kilo, rabbit, 137 gnn. (2-5 solids); I kilo guinea pig, 176 grm. (5.2 solids)— (^ioWt-r and Schmidt). (3) The excretion of bile into the intestines shows two maxima during one period of digestion; the first, from three to five hours, and the second, from thir- teen to fifteen hours after food. The cause is due to simultaneous reflex excite- ment of the hepatic blood vessels, which become greatly dilated. (4) The influence of food is very marked. The largest amount is secreted after a flesh diet, with some fat added ; less after vegetable food ; a very small amount with a pure fat diet;1Fstops during hunger. Draughts of water increase the amount, with a corresponding relative diminution of the solid constituents. [The biliary solids are increased by food, reaching their maximum about one hour after feeding]. (5) The influence of blood supply is variable : — (a) Secretion is greatly favored by a copious and rapid blood supply. The blood pressure is not the prime factor, as ligature of the cava above the diaphragm, whereby the greatest blood pressure occurs in the liver, arrests the secretion [Heiaenhain). {b) Simultaneous ligature of the hepatic artery (diameter, 5;^ mm.) and the portal vein (diameter, 16 mm.) abolishes the secretion {RShrig). These two vessels supply the raw material for the secre- tion of bile. (c) If the hepatic artery be ligatured, the portal vein alone supports the secretion {Simon, Schiff, Schmulewitsch, Asf). According to Kottmeier, Betz, Cohnheim, and Litten, ligature of the artery or one of its branches ultimately causes necrosis of the parts supplied by that branch, and eventu- ally of the entire liver, as this artery is the nutrient vessel of the liver. (sorbed, while the precipitate adhering to the intestinal wall can be further digested [Maly and Emich). Taurocholic acid behaves in the same way toward gelatine peptone.] Bilious Vomit. — When bile passes into the stomach, as in vomiting, the acid of the gastric juice unites with the bases of the bile salts; so that sodium chloride and free bile acids are formed, and the acid reaction is thereby somewhat diminished. The bile acids are not effective for carrying on gastric digestion; the neutralization also causes a precipiiation of the pepsin and mucin. As soon, however, as the walls of the stomach secrete new acid, the pepsin is redissolved. The bile which passes into the stomach deranges gastric digestion, by shriveling the proteids, which can only be peptonized when they are swollen up. 182. FATE OF THE BILE IN THE INTESTINE.— Some of the biliary constituents are completely evacuated with the fa;ces, while others are re- absorbed by the intestinal walls. (i) Mucin passes unchanged into the faeces. (2) The bile pigments are reduced, and are partly excreted with the faeces as hydro- bilirubin (§ 177, 3 g), and partly as the identical end product, urobilin, by the urine. From Meconium hydro-bilirubin is absent, while crystalline bilirubin and biliverdin and an unknown red oxidation product of it are present [bile acids, even taurocholic, and small traces of fatty acids], [Zioeifel). [So that it gives Gmelin's reaction.] Hence, no reduction — but rather oxidation — processes occur in the fcetal intestine (Hoppe-Seyler). (Composition. — Dary gives 72.7 per cent, water, 23.6 mucus and epithelium, i per cent, fat and cholesterin, and 3 per cent, bile pigments. Zweifel gives 79.78 per cent, water, and solids 20.22 per cent. It does not contain lecithin, but so much bilirubin that Hoppe-Seyler uses it as a good source whence to obtain this pigment. It gives a spectrum of a body related to urobilin ( Vaulair, MacMuiin).] (3) Cholesterin is given off with the fasces. (4) The bile salts are, for the most part, reabsorbed by the walls of the jeju- num and ileum, to be reemployed in the animal's economy. Tappeiner found them in the chyle of the thoracic duct; minute quantities pass normally from the blood into the urine. Only a very small amount of glycocholic acid appears THE INTESTINAL JUICE. 303 unchanged in the feces. The taurocholic acid, as far as it is not absorbed, is easily decomposed in the intestine, by the putrefactive processes, into cholalic acid and taurin ; the former of these is found in the faces, but the taurin, at least, seems not to be constantly present. Part of the cholalic acid is absorbed, and may unite in the liver either with glycin or taurin ( Weiss). As putrefactive decomposition does not occur in the fcetal intestine, unchanged taurocholic acid is found in meconium (Zwei/el). The anhydride stage of cholalic acid (the artificially. prepared choloidinic acid?}, dyslysin, is an artificial product, and does not occur in the fs:ces (/Joppe- SeyUr). (5) The faeces contain mere traces of Lecithin {Wegscheiiier, Bokay). Impaired Nutrition. — The greatest part of the most important biliary constituents, the bile acids, re-enter the blood, and thus is explained why animals with a biliary fistula, where all the bile is re- moved (without the animal being allowed to lick the bile), rapidly lose weight. This depends partly upon the digestion of the fats being interfered with, and also upon the direct loss of the bile salts. If such dogs are to maintain their weight, they must eat twice as much food. In such cases, carbohydrates most beneficially replace the fats. If the digestive apparatus is otherwise intact, the animals, on account of their voracity, may even increase in weight, but the flesh and not the lat is increased. Bile partly an Excretion. — The fact that bile is secreted during the foetal period, while none of the other digestive fluids are, proves it is an excretion. The cholalic acid which is reabsorbed by the intestinal walls passes into the body, and seems ultimately tu be burned to form CO2 and H^O. The glycin (with hippuric acid) forms urea, as the urea is increased after the injection of glycin {^Horsford, Schultsen, A'encki). The fate of taurin is unknown. When large quantities are introduced into the human stomach, it reappears in the urine, as tauro-carbamic acid, along with a small quantity of unchanged taurin. When injected subcuta- neously into a rabbit, nearly all of it reappears in the urine. [Practical. — In practice it is important to remember that bile once in the intestine is liable to be absorbed unless it be carried down the intestine ; hence, it is one thing to give a drug which will excite the secretion of bile, i. e., a hepatic stimulant, and another to have the bile so secreted ex- pelled. It is wise, therefore, to give a drug which will do both, or at least to combine a hepatic stimulant with one which will stimulate the musculature of the intestine as well. Active exercise, whereby the diaphragm is vigorously called into action to compress the liver, will aid in the ex- pulsion of the bile from the liver (Brunton).'] 183. THE INTESTINAL JUICE.— Length of Intestine.— The human intestine is ten times longer than the length of tlie body, as measured from the vertex to the anus. It is longer comparatively than that of the omnivora IHenning). Its minimum length is 507, its maximum 1149 centimetres [17 to 35 feet]; its capacity is relatively greater in children {Beneke). [The average length is 30 feet; 25 feet (small), and 5 to 6 feet large intestine.] In childhood the ab- sorptive elements, in adults the secreto-chemical processes, appear to be most active {Baginsky). The succus entericus is the digestive fluid secreted by the numerous glands of the intestinal mucous membrane. The largest amount is produced by Lieber- kiihn's glands, while in the duodenum there is added the scanty secretion of the small compound Brunner's glands. Brunner's glands are small, convoluted, branched, tubular glands, lying in the sub-mucosa of the duodenum. Their fine ducts run inward, pierce the mucous membrane, and open at the bases of the villi. The acini are lined by cylindrical cells, like those lining the pyloric glands. In fact, Brunner's glands are structurally and anatomically identical with the pyloric glands of the stomach. During hunger, the cells are turbid and small, while during digestion they are large and clear. The glands receive nerve fibres from Meissner's plexus [Drasch). I. The Secretion of Brunner's Glands. — The granular contents of the secretory cells of these glands, which occur singly in man, but form a continuous layer in the duodenum of the sheep, besides albuminous substances, consist of mucin and a ferment substance of unknown constitution. The watery extract of the glands causes — (i) Solution of proteids at the temperature of the body {Kroiow). (2) It also has a diastatic (?) action. It does not appear to act upon fats. [Brown and Heron have shown that the secretion of Brunner's glands, more actively than any other glands of the intestines, converts maltose into glucose.] 304 LIEBERKUHN S GLANDS. On account of the smallness of the objects, such experiments are only made with great difficulty, and, therefore, there is a considerable uncertainty with regard to the action of the secretion. Lieberkhiin's glands are simply tubular glands resembling the finger of a glove [or a test-tube], which lie closely packed, vertically near each other, in the mucous membrane (Fig. iS6) ; they are most numerous in the large intestine, owing to the absence of the villi in this region. They consist of a structureless membrana propria lined by a layer of low cylindrical epithelium, between which numerous goblet cells occur, the goblet cells being fewer in the small intestine and much more numerous in the large (Fig. 201). The glands of the small intestine yield a thin secretion, while those of the large intestine yield a large amount of sticky mucus from their goblet cells (A'/ose and Heidenhain']. [In a vertical section of the small intestine they lie at the base of villi (Fig. 186). In transverse section they are shown in Fig. 187.] II. The Secretion of Lieberkuhn's Glands, from the duodenum onward, is the chief source of the intestinal juice. _ Villi with epitbdit Lieberkuhn's glands. Muscularis mucosae :! Longitudinal r Longitudinal section of the small intestine of a dog, through a Peyer's patch. Intestinal Fistula. — The intestinal juice is obtained by making a Thiry's Fistula (1S64). A loop of the intestine of a dog is pulled forward (Fig. 1S8, i), and a piece about 4 inches in length is cut out, so that the continuity of the intestinal tube is broken, but the mesentery and its blood ves- sels are not divided. One end of this tube is closed, and the other end is left open and stitched to the abdominal wall (Fig. 188, 3), After the two ends of the intestine from which this piece was taken have been carefully brought together with sutures, so as to establish the continuity of the intestinal canal, animals still continue to live (Fig. 1S8, 2). The excised piece of intestine yields a secretion which is uncontaminated with any other digestive secretion. [Thiry's method is very unsatisfactory, as judged from the action of the separated loop in relation to medicaments, probably owing to its mucous membrane becoming atrophied from disuse, or injured by inflammation.] ACTIONS OF THE INTESTINAL JUICE. 305 [Meade Smith has lately used a better method, in which he makes a small opening in the intes- tine, through which he introduces two small, hollow and collapsed India-rubljer balls, one above and the other below the opening, which are then distended by inflation until they completely block a certain length of the intestine. The loop thus blocked off having been previously well washed out, is allowed to become filled with succus, which is secreted on the application of various stimuli. By means of Bernard's gastric cannula (§ 165) inserted into the fistula in the loop, the secretion can be re- moved when desired.] [Valla's Fistula. — Open the belly of a dog, and pull out a loop (30 to 50 ctm.) [l to lyi feet] of small intestine and ligature it ; dividing it above and below, re-establish the continuity of the rest of the intestine. Stitch both ends of the loop of intestine into the wound in the linea alba (Fig. 1S8, 4) so that there is a loop of intestine supplied by its blood vessels and nerves, isolated and with an upper and lower aperture.] Fig. 187. Crypt. -Glandular epithelium. Cavity of the gland. Transverse section of Lieberkiihn's follicles. The intestinal juice of such fistula flows spontaneously in very small amount, and is increased during digestion ; it is increased — especially its mucus — by me- chanical, chemical, and electrical stimuli ; at the same time, the mucous mem- brane becomes red, so that 100 centimetres yield 13 to iS grammes of this juice in an hour ( Thiry, Masloff^. Characters.— The juice is light yellow, opalescent, thin, strongly alkaline, specific gravity loii, evolves CO., when an acid is added; it contains albiitnin and ferments ; mucin occurs in the juice of the large intestine. Its composition is — proteids = 0.80 per cent. ; other organic substances ^ 0.73 per cent. ; salts, 0.88 per cent. ; among these — sodium carbonate, 0.32 to 0.34 per cent. ; water, 07. SO per cent. Fig. 188. of Thiry 's fistula Ahd. Abdominal wall {Stirling), stitched together ; [The intestinal juice obtained by Meade Smith's method contained only 0.39 per cent, of organic matter, and in this respect agreed closely with the juice which A. Moreau procured by dividing the mesenteric nerves of a ligatured loop of intestine. The secretion of the large intestine is much more viscid than that of the small intestine.] Actions of Succus Entericus. — The digestive functions of the fluid of the small intestine are — (i) It has less diastatic action than either the saliva or the pancreatic juice {Schiff, Busch, Quincke, Garland), but it does not form maltose ; while the juice of the large intestine is said to possess this property {Eickhorsi). v. Wittich ex- tracted the ferment with a mixture of glycerine and water. 306 ACTIONS OF THE INTESTINAL JUICE. [The diastatic action of the small intestine is incomparably weaker than that of the saliva, or pan- creatic juice, and barely exceeds that of the tissues and fluids of the bodies generally. A similarly weak diastatic action is possessed by the secretion of the colon.] (2) It converts maltose into grape sugar. It seems, therefore, to continue the diastatic action of the saliva (§ 148) and pancreatic juice (§ 170) which usually form only maltose. Thus maltose seems to be transformed into grape sugar by the intestinal juice. According to Bourquelot this action is due to the intestinal schizomycetes and not to the intestinal juice as such, the saliva, the gastric juice, or invertin. The greater part of the maltose appears, however, to be absorbed unchanged. (3) Fibrin is slowly (by the trypsin and pepsin — Kiihne) peptonized ( Thiry, Leube); less easily albumin {Masloff), i'r?.%\\, casein, flesh, raw or cooked, vege- table albumin {Ko/liker, Schiff ) ; probably gelatin is also changed by a special ferment into a solution which does not gelatinize (^Eichhorsf). [The ferment for this purpose is mainly contained in Brunner's glands, and in Peyer's patches [Brown and Heron') ^ (4) Fats are only partly emulsionized {Si/iiff), and afterward decomposed ( Vella). [M. Hay has never observed any emulsifying action. The appaifnt emulsification in certain instances is due to shaking the alkaline juice with a rancid oil, containing free fatty acids, when a certain quantity of a soap is at once formed.] (5) According to CI. Bernard, invertin occurs in intestinal juice (this ferment can also be extracted from yeast), whereby cane sugar (CioH.jOn) takes up water (-f H.,0) and becomes converted into invert sugar, which is a mixture of left rotating sugar (laevulose, CsHioO^) and of grape sugar (dextrose, CeHuOs). Heat seems to be absorbed during the process {Leiibe). (See Carbohydrates, § 252, for the various kinds of sugar.) [Hoppe-Seyler has suggested that this ferment is not a natural product of the body, but is intro- duced from without with the food. Matthew Hay has recently disproved this theory by, among other reasons, finding it to be invariably present in the intestine of the foetus. It is found in every portion of the small inte;^tine, but not in the large intestine, nor in any other part of the body, and IS much less Jiftusible than diastase.] [Effect of Drugs. — -The subcutaneous injection of pilocarpin causes the mucous membrane of a Vella's fistula [dog) to be congested, when a strongly alkaline, opalescent, watery, and slightly albu- minous secretion is obtained. Ihis secretion produces a reducing sugar, converts cane sugar into invert sugar, emulsifies neutral fats, ultimately splitting them up, peptonizes proteids, and coagulates milk, even although alkaline. The juice auacks the sarcous substance of muscle before the con- nective tissues — the reverse of the gastric juice. The mucous membrane in a Vella's fistula does not atrophy. K. B. Lehmann finds that the succus entericus obtained from the intestine of k goat by a Thiry- Vella fistula has no digestive action ( ?>//«).] [Fate of the Ferments. — With regard to the digestive ferments, Langley is of opinion that they are destroyed in the intestinal canal ; the diastatic ferment of saliva is destroyed by the free HCl of the gastric juice; pepsin and rennet are acted upon by the alka- FiG. 189. line salts of the pancreatic and intestinal juices, and by trypsin; while P the diastatic and peptic fennents of the pancreas disappear under the influence of the acid fermentation in the large intestine.] The Action of the Nervous System on the secretion of the in- testinal juice is not well determined. Section or stimulation of the vagi has no apparent eft'ect ; while extirpation of the large sympathetic abdominal ganglia causes the intestinal canal to be filled with a watery fluid, and gives rise to diarrhcea [Budge). This may be explained by the paralvsis of the vasomotor nerves, and also by the section of large lymphatic vess-els during the operation, whereby absorption is inter- fered with and tiansud.nion is favored. Moreau's Experiment. — A similar result is caused by extirpation of the nerves which accompany the blood vessels going to a loop of intestine (.l/ormw), the bloodvessels tliemselves being intact. [Moreau placed four ligatures on a loop of intestine at equal distances from each other (Fig. 189). The liga- tures were tied so that three loops of intestine were shut oft'. The nerves (N) to the middle loop FUNGI AS EXCITERS OF FERMENTATION. 307 were divided, and the intestine was replaced in the abdominal cavity. After a time, a very small amount of secretion, or none at all, was found in two of the ligatured compartments of the gut, /. <•., in those with the nerves and blood vessels intact (1,3), but the compartment (2) whose nerves had been divided contained a watery secretion. Perhaps the secretion which occurs after section of the mesenteric nerves is a paralytic secretion.] The secretion of the intestinal and gastric juices is diminished in man in certain nervous affec- tions (hysteria, hypochondriasis, and various cerebral diseases); while in other conditions these secretions are increased. Excretion of Drugs. — If an isolated intestinal fistula be made, and various drugs administered, experiment shows that the mucous membrane excretes iodine, bromine, lithium, sulphocyanides, but HI)/ potassium ferrocyanide, arsenious or boracic acid (Quincke), or iron salts (Glaevecke). In sihk/iiigs, not unfrequently a large amount of acid is formed when the fungi in the intestine split up milk sugar or grape sugar into lactic acid (Leii/v). .Starch changed into grape sugar may undergo the same abnormal process; hence, infants ought not to be fed with starchy food. 184. FERMENTATION PROCESSES IN THE INTESTINE. — Those processes wiiich are to be regarded as fermentations or putrefactive pro- cesses, are quite different from those caused b)- the action of distinct ferments {Frerichs, Hoppe-Sey/er). The putrefactive changes are connected with the presence of lower organisms, so-called fermentation or putrefaction producers {Nencki ) : and they may develop in suitable media outside the body. The lower organisms which cause the intestinal fermentation are swallowed with the food and the drink, and also with the saliva. When they are introduced, fermentation and putrefaction begin, and gases are evolved. Intestinal Gases. — During the whole of the fcetal period, until birth, this fermentation cannot occur ; hence, gases are never present in the intestine of the newly born {Brcslau). The first air bubbles pass into the intestine with the saliva which is swallowed, even before food has been taken. The germs of organisms are thus introduced into the intestinal tract, and give rise to the formation of gases. The evolution of intestinal gases goes hand-in-hand with the fermentations. At- mospheric air is also swallowed, and an exchange of gases takes place in the intes- tine, so that the composition of the intestinal gases depends upon various condi- tions. Kolbe and Ruge collected the gases from the anus of a man, and found in 100 vols. — Food. CO.. H. CH,. N. HoS. Milk, Flesh, Peas 16.8 12.4 21.0 43-3 2.1 4.0 0.9 27.5 55-9 38.3 57.S 18.9 Quantity not estimated. With regard to the formation of gas and the processes of fermentation, we note — 1. Air bubbles are swallowed when the food is taken. The O thereof is rapidly absorbed by the walls of the intestinal tract, so that in the lower part of the large intestine, even traces of O are absent. In exchange, the blood vessels in the intestinal wall give off COj into the intestine, so that a part of the CO, in the intestine is derived by diffusion from the blood. 2. H and C0j,NH3, and CH, are also formed from the intestinal contents by fermentation, which takes place even in the small intestine {Planer'). Fungi as Exciters of Fermentation. — The chief agents in the production of fermentations, putrefaction, and other similar decompositions are undoubtedly the group of the fungi called Schizomycetes. They are small unicellular organisms of various forms, globular {.Micrococcus), short rods (Bacterium), long rods (Bacillus), or spiral threads ( Vibrio, Sfirillum, Spirocliieta, Fig. 20). The mode of reproduction is by division, and they may either remain single or unite to form colonies. Each organism is usually capable of some degree of motion. They produce profound chemical changes in the fluids or media in which they grow and multiply, and these changes depend 308 FERMENTATION OF THE CARBOHYDRATES. upon the vital activity of their protoplasm. These minute microscopic organisms take certain con- stituents from the " nutrient fluids" in which they live, and use them partly for building up their own tissues and partly for their own metabolism. In these processes, some of the substances so absorbed and assimilated undergo chemical changes, some fernwnli seem thereby to be produced, which in their turn may act upon material present in the nutritive fluid. These fungi consist of a capsule or envelope enclosing protoplasmic contents. Many of them are provided with excessively delicate cilia, by means of which they move about. The new organ- isms produced by the division of pre-existing ones, sometimes fortn large colonies visible to the naked eye, the individual fungi being united by a jelly-like mass, the whole constituting zoogloea In some fungi, reproduction takes place by spores ; more especially when the nutrient fluids are poor in nutritive materials. The bacteria form longer rods or threads which are jointed, and in each joint or segment small (1-2 /j) highly refractive globules or spores zxt developed (Fig. 191, 7). In some cases, as in the butyric acid fermentation, the rods become fusiform before spores are formed. When the envelope of the mother cell is ruptured or destroyed, the spores are liberated, and if they fall upon or into a suitable medium, they germinate and reproduce organisms similar to those from which they sprung. The process of spore production is illustrated in Fig. igo, 7, 8, 9, and in i, 2, 3, 4 is shown the process of germination in the butyric acid fungus. The spores are very tenacious of life; they may be dried, when they resist death for a very long time ; some of them are killed by being boiled. Some fungi exhibit their vital activiiiesonly in the presence of O (Aerobes), while others require the exclusion of O (Anaerobes, Pasteur). According to the products of their action, they are classified as follows: Those that \>rm\\ict fermentations (zymo- FiG. I go. V5 l.Z 8 %a I accii. in the form of^cocci (l) ; dipli icus — (i) isolated spo 8, 9J formation of spores withii rods (3), and jointed tlireads (4, 5). B, Baal- 3n of tlie spores; (5, 6j stiort and long rods ; (7, genie schizomycetes) ; those that produce pigments (chromogenic) ; those that produce disagreeable odors, as during putrefaction (bromogenic) ; and those that, when introduced into the living tissues of other organisms, \>xo&mq.& pathological conditions, and even death (pathogenic). All these differ- ent kinds occur in the human body. When we consider that numerous fungi are introduced into the intestinal canal with the food and drink — that the temperature and other conditions within this tube are specially favorable for their development ; that there also they meet with sufiicient pabulum for their development and repro- duction — we cannot wonder that a rich crop of these organisms is met witli in the intestine, and that they produce there numerous fermentations. I. Fermentation of the Carbohydrates. — (i) Bacterium lacticum (^Cohii), (^Ferment lactique, Pashur) are biscuit-shaped cells, 1.5-3 //. in length, arranged in groups or isolated. They split up sugar into lactic acid ; I grape-sugar = QHi-^Ob = 2(C3H603) = 2 lactic acid. Milk sugar (Ci.jHjjOn) may be split up by the same ferment causing it to take up H^O, and fonning 2 molecules of grape sugar, 2(CoH,.iOc), which are again split up into 4 molecules of lactic acid, 4(C3H|;03). The fungi which occur everywhere in the atmosphere are the cause of the spontaneous acidifica. tion, and subset^uent coagulation of milk {^Milk (^ 230).) FERMENTATION OF THE FATS. 309 (2) Bacillus butyricus (B. amylobacter, Vii/i Tieghcm ; Clostridium buty- ricum, Vibrion biityrique, Pasteur), which ill the presence of starch is often colored blue by iodine, changes lactic acid into butyric acid, together with CO2 and H {Frazmowski). ( C,H„0;j = I butyric acid. 2(C3H603) lactic acid = -| 2(C02) = 2 carbon dioxide. (^ 4 H = 4 hydrogen. This fungus (Fig. 190, B) is a true anaerobe, and grows only in the absence of O. The lactic acid fungus uses O verj' largely, and is, therefore, its natural precursor. The butyric acid fermenta- tion is the last change undergone by many carbohydrates, especially by starch and inulin. It takes place constantly in the fa;ces. (3) A fungus, whose nature is not yet determined, causes alcohol to be formed from carbo-hydrates {Fitz). The presence of yeast may cause the formation of alcohol in the intestine, and in both cases also from milk sugar, which first becomes changed into dextrose. (4) Bacterium aceti (Fig. 190, A) converts alcohol into acetic acid outside the body. Alcohol (CjHgO) + O = C,,H_,0 (Al(lehyd) + H^O. Acetic acid(C2H^O,) is formed from aldehyd by oxidation. According to Nageli, the same fungus causes the formation of a small amount of CO, and H^O. As the acetic fermentation is arrested at 35° C, this fermentation cannot occur in the intestine, and the acetic acid which is constantly found m the feces must be derived from another source. During putrefaction of the proteids with exclusion of air acetic acid is produced i^Nencki). Fig. 191. BaciUus sttbtilis. i, spore ; 2, 3, 4, germination of the spore : 5. 6, short rods : 7, jointed thread, with the formation of spores in each segment or ctU ; 8, short rods, some of them containing spores ; 9, spores in single short rods ; 10, fungus with a cilium. (5) Starch and cellulose are partly dissolved by the schizomycetes of the intestine. If cellulose be mixed with cloacal mucus (Hoppe-Seylcr), or with the contents of the intestine {^Tappeincr), n molecules, [//(CeHjoOj)], take up n mole- cules of water, + «(H,0), and produce three times n molecules CO.., and three times n molecules of marsh gas 3 ^(CHi). During the solution of cellulose, volatile acids (acetic and butyric) are evolved. When the cel- lulose capsule is dissolved, the digestive juices can act upon the enclosed digestible parts of the vegetable ( Tappeiner, v, Knierieiti). (6) Fungi whose nature is unknown can partly transform y/(7/-t7/ (? and cellulose) into sugar ; others excrete invertin e. g., the Leukonostoc mesenteriodes, which develops in the juice of turnips. Invertin changes cane sugar into invert sugar (§ 183, II, 5). II. Fermentation of the Fats (§ 251). — In certain putrefactive conditions, organisms of an unknown nature cause natural fats to take up water and split into glycerine and their corresponding fatty acid (§ 170"). Glycerine — C3H5(HO)3 — is a triatomic alcohol, and is capable of undergoing several fermentations, accord- ing to the fungus which acts upon it (§ 251 ). With a neutral reaction, in addition to succinic acid, a number of fatty acids, H and CO, are formed. 310 REACTION FOR INDUL. Fitz found, under the influence of the hay (ia <-///;« (Bacillus subtilis. Fig. 191) alcohol with caproic, butyric, and acetic acids; in other cases butylic alcohol is the chief product; van de Velde found butyric, lactic, and traces of succinic acid with CO.,, H2O, N. The fatty acids, especially as chalk soaps, form an excellent material for fer- mentation. Calcium formiate mixed with cloacal mucus ferments and yields cal- cium carbonate, CO.2 and H ; calcium acetate, under the same conditions, produces calciimi carbonate, CO2 and CH,. Among the oxy-acids, we are acquainted with the fermentations of lactic, glycerinic, malic, tartaric, and citric acids. According to Fitz, lactic acid (in combination with chalk), produces propionic and acetic acids, CO,, HjO. Other ferments cause the formation of valerianic acid. Glycerinic acid, \xv addition to alcohol and succinic acid, yields chiefly acetic acid ; malic acid forms succinic and acetic acid. The other acids above enumerated yield somewhat similar products. III. Fermentation of the Proteids (§ 249). — There do not seem to be fungi of sufficient activity in the intestine to act upon undigested proteids and their derivatives. Many schizomycetes, however, can produce a peptonizing fer- ment. We have already seen that pancreatic digestion acts upon the proteids (§ 170, II), forming, among other products, amido acids, leucin, tyrosin, and other bodies. Under normal conditions, this is the greatest decomposition pro- duced by the pancreatic juice. The putrefactive fermentation of the large intes- tine causes further and more profound decompositions {Hiiffner, Nencki). Leu- cin (CeHuNO.j), takes up two molecules of water, and yields valerianic acid iCjCi.iO^) ammonia, CO, and 2(H.i) ; glycin, behaves in a siinilar manner. Tyrosin (CgHnNOa) is decomposed into indol (C„H,N), which is constantly present in the intestine {Kiihne) along with CO,, H,0, H, (^Nencki). If O be present, other decompositions take place. These putrefactive products are absent from the intestinal canal of the foatus and the newly born (Senator). During the putrefactive decomposition of proteids, CO^.HS, also H and CH,, are formed ; the same result is obtained by boiling them with alkalies. Gelatin, under the same conditions, yields much leucin and ammonia, CO,, acetic, butyric, and vale- rianic acids, and glycin (JVencki). Mucin and nuclein undergo no change. Arti- ficial pancreatic digestion experiments rapidly tend to undergo putrefaction. The substance which causes the peculiar faecal odor is produced by putrefaction, but its nature is not known. It clings so firmly to indol and skatol that these sub>tances were formerly regarded as the odorous bodies, but when they are prepared pure they are odorless {Bayer).- The above men- tioned putrefactive processes which also occur in pancreas undergoing decomposition, may be inter- rupted by antiseptics (salicylic acid). The putrefactive products of the pancreas give a red color or precipitate with chlorine water. Indol. - — Among the solid substances in the large intestine formed only by putrefaction is indol (CgHjN), a substance which is also formed when proteids are heated with .alkalies, or by overheating them with water to 200° C. It is the stage preceding the indican in the urine. If the products of the digestion of the pro- teids — the peptones — are rapidly absorbed, there is only a slight formation of indol ; but when absorption is slight, and putrefaction of the products of pan- creatic digestion occurs, much indol is formed, and indican appears in the urine. Jafie found much indican in the urine in strangulated hernia, and when the small intestine was obstructed. Landois observed the same after the transfusion of heterogeneous blood (§ 262, i). Reactions for Indol. — Acidulate strongly with HCl, and shake vigorously after adding a few drops of turpentine. If there be an intense red color, the ])igment is removed by ether. The sub- stance which, after the digestion of fibrin by trypsin, and which gives a violet color with bromine water [\ 170, 2), can be removed by chloroform. In addition to the last pigment, there is a second one, which passes over during distillation, and which can be extracted from the distillate by ether. Both substances seem to belong to the indigo group (Kriikenberg). A. Bayer prepared indigo-blue artificially from ortho phenyl-propionic ncid, by boiling it with dilute caustic soda, after the adthtion of a little grape sugar. He obtained indol and skatol from indigo blue. Hoppe-Seyler found that on feeding rabbits with ortho-nitrophenyl-propionic acid, much indican was present in the urine. . PROCESSES IN THE LARGE INTESTINE. 311 Phenol (CcH^O) is formed by putrefaction in the intestine, and it is also formed when fibrin and pancreatic juice putrefy outside the body {Baumann), while Brieger found it constantly in the fajces. It seems to be increased by the same circumstances that increase indol {Sa/kcnas/ci ), as an excess of indican in the urine is accompanied by an increase of phenyl sulphuric acid in that fluid (§ 262). From putrefying flesh and fibrin amiilo-phenyl propionic acid is obtained, as a decomposition product of tyrosin. A part of this is transformed by putrefactive ferments into hydrocinnamic acid (phenyl propionic acid). The latter is completely oxidized in the body into benzoic acid, and appears as hippuric acid in the urine. Thus is explained the formation of hippuric acid from a purely albuminous diet {£. and H. Salkowski). Skatol (CjHgN) = methyl indol — {Brieger'), is a constant human faecal sub- stance, and has been prepared artificially by Nencki and Secretan from egg albumin, by allowing it to putrefy for a long time under water. It also appears in the urine as a sulphuric acid compound. The excretin of human faeces, described by Marcet, is related to cholesterin, but its history and constitution are unknown. According; to the Brothers Salkowski, skatol and indol are both formed from a common substance which exists preformed in albumen, and which, when it is decomposed, at one time yields more indol, at another skatol, according as the hypothetical " ;'«(/«/y««^'-K.;" or " skalol-fungiis" m the more abundant. It is of the utmost importance, in connection with the processes of putrefac- tion, to determine whether they take place when oxygen is excluded or not {Pas- teur). When O is absent, reductions take place ; oxy-acids are reduced to fatty acids, and H,CHj and H,S are formed ; while the H may produce further reductions. If O be present the nascent H separates the molecule of free ordi- nary oxygen ( =^ O,) into two atoms of active oxygen ( = O). Water is formed on the one hand, while the second atom of O is a powerful oxidizing agent {Hoppe- Seyler). [It is not improbable that some substances, as sulphur, are in part rendered soluble and absorbed by the action of the nascent hydrogen evolved by the schizomycetes, forming a soluble hydrogen compound with the substance (Mat/hew Hay).] It is remarkable that the putrefactive processes, after the development of phenol, indol, skatol, cresol, phenyl propionic and phenyl acetic acids are afterward limited, and after a certain concentra- tion is reached tliey cease altogether. The putrefactive process produces antiseptic substances which kill the micro-organisms [IVeniic/i), so we may assume that these substances limit to a cer- tain extent the putrefactive processes in the intestine. The reaction of the intestine immediately below the stomach is acid, but the pancreatic and intestinal juices cause a neutral and afterward an alkaline reaction, which obtains along the whole small intestine. In the large intestine, the re- action is generally acid, on account of the acid fermentation and the decomposi- tion of the ingesta and the faeces. 185. PROCESSES IN THE LARGE INTESTINE.— Within the large intestine, the fermentative and putrefactive processes are certainly more prominent than the digestive processes proper, as only a very small amount of the intestinal juice is found in it {Kilhne). The absorptive function of the large intestine is greater than its secretory function, as at the beginning of the colon its contents are thin and watery, but in the further course of the intestine they become rnore solid. Water and the products of digestion in solution are not the only substances absorbed, but under certain circumstances unchanged fluid egg- albumin {Voit and Bauer, Czerny and Latschenberger), milk and its proteids {Eichlwrst), flesh juice, solution of gelatin, myosin with common salt, may also be absorbed. Experiments with acid albumin, syntonin, or blood serum gave no result. Toxic substances are certainly absorbed more rapidly than from the stomach {Savoiy). [In the dog the secretion of the large intestine has no 312 CHARACTERS OF THE F.-ECES. digestive properties, but fats are absorbed in it. Klug and Koreck regard its Lieberkiihnian glands not as secreting, but as absorbing structures.] The fecal matters sxt formed ox rather j//(?/c(/ in the lower part of the gut. The crecum of' many animals, e. g., rabbit, is of considerable size, and in it fermentation seems to occur with considerable energy, giving rise to an acid reaction. In man, the chief function of the caecum is absorption, as is shown by the great number of lymphatics in its walls. From the lower part of the small intestine and the crecum onward, the ingesta assume the faecal odor. The amount of faeces is about [5 oz.] or 170 grms. f6o to 250 grms.) in twenty-four hours; but if much indigestible food be taken, it may be as much as 500 grms. The amount is less, and the absolute amount of solids is less, after a diet of flesh and albumin, than after a vegetable diet. The fsces are rendered lighter by the evolution of gases, and hence they float in water. The consistence of the fseces depends on the amount of water present — it is usually about 75 per cent. The amount of water depends partly on the food — pure flesh diet causes relatively dry faeces, while substances rich in sugar yield faeces with a relatively large amount of water. The quantity of water taken has no effect upon the amount of water in the faeces. But the energy of the peristal- sis has this effect, that the more energetic it is, the more watery the faeces are, because sufficient time is not allowed for absorption of the fluid from the ingesta. Paralysis of the blood and lymph vessels, or section of the nerves, leads to a watery condition of the faeces (§ 183). The reaction is often acid in consequence of lactic acid being developed from the carbohydrates of the food. Numerous other acids produced by putrefaction are also present (§ 1S4). If much ammonia be formed in the lower part of the intestine, a neutral or even alkaline reaction may obtain. A copious secretion of mucus favors the occurrence of a neutral reaction. The odor, which is stronger after a flesh diet than after a vegetable diet, is caused by some ffecal products of putrefaction, which have not yet been isolated ; also by volatile fatty acids and by sulphuretted hydrogen, when it is present. The color of the faeces depends upon the amount of altered bile pigments mixed with them, whereby a bright yellow to a dark brown color is obtained. The color of the food is also of niiportance. If much blood be present in the food, the f:eces are almost brownish black, from h;i;matin ; green vegetables = brownish green, from chlorophyll ; bones (dog) = white, from the amount of lime; preparations of iron = black, from the formation of sulphide of iron. The faeces contain — (i) The unchanged residue of animal or vegetable tissues used as food; hairs, horny and elastic tissues; most of the cellulose, woody fibres, spiral vessels of vegetable cells, gum. (2) Portions of digestible substances, especially when these have been taken in too large amount, or when they have not been sufficiently broken up by chewing. Portions of muscular fibres, ham, tendon, cartilage, particles of fat, coagulated albumin — vegetable cells from potatoes and vegetables, raw starch, etc. All food yields a certain amount of residue — white bread, 3.7 per cent. ; rice, 4.1 per cent. ; flesh, 4.7 per cent. ; potatoes, 9.4 per cent. ; cabbage, 14.9 per cent. ; black bread, 15 per cent. ; yellow turnip, 20.7 per cent. [Kubner). (3) The decomposition products of the bile pigments, which do not now give the Gmelin-Heintz reaction ; as well as the altered bile acids (§ 177, 2). This reaction, however, may be obtained in pathological stools, especially in those of a green color ; unaltered bilirubin, biliverdin, glycocholic and taurocholic acids occur in meconium {^Zweifel, Hoppe-Seyler, § 182). [MacMunn found no unchanged bile pigments in the fisces. A substance called stercobilin is obtained from the fxces, and it closely resembles what has been called " febrile " urobilin, but it is certainly different from normal urobilin.] COMPOSITION OF THE F^CES. 313 (4) Unchanged mucin and nuclein — the latter occasionally after a diet of bread, together with partially disintegrated cylindrical epithelium from the intestinal canal, and occasionally drops of oil. Cholesterin is very rare. [Ten grains of a substance, stercorin, said to be a modification of cholesterin, occur in the faeces {Flint).~\ The less the mucus is mixed with the faeces, the lower the part of the intestine from which it was derived {Nothnagel). (5) After a milk diet, and also after a fatty diet, crystalline needles of lime combined with fatty acids and chalk soaps constantly occur, even in sucklings ( Wegscheider). Even unchanged masses of casein and fat occur during the milk cure. Compounds of ammonia with the acids mentioned as the result of putre- faction (§ 184, III) belong to the fKcal matters {Brieger). (6) Among inorganic residues, soluble salts rarely occur in the faeces, because they diffuse readily, e. g., common salt, and the other alkaline chlorides, the com- pounds of phosphoric acid, and some of those of sulphuric acid. The insoluble compounds, of which ammoniaco-magnesic or triple phosphate, neutral calcic phosphate, yellow-colored lime salts, calcium carbonate, and magnesium phos- phate are the chief, form 70 per cent, of the ash. Some of these insoluble sub- stances are derived from the food, as lime from bones, and in part they are excreted after the food has been digested, as ashes are eliminated from food which has been burned. Fig. 192. a I, Bacterium coli commune ; 2, bacterium lactis aerogenes ; 3 and 4, the large bacilli of Bie genous spore formation ; 5, the various stages in the development of the bacillus whicl -Si- IDH:- Concretions. — The excretion of inorganic substances is sometimes so great, that they form in- crustations around other fivcal matters. Usually ammoniaco-magnesic phosphate occurs in large crystals by itself, or it may be mixed with magnesium phosphate. (7) Micro-organisms. — A considerable portion of normal faecal matter con- sists of micrococci and micro-bacteria (Bacterium termo — Woodward, Nothnagel^. Bacillus subtilis is not very plentiful, while yeast is seldom absent {Frerichs, Nothnagel). To isolate the individual fungi, Escherich has made pure cultivations from the intestinal con- tents of sucklinijs, and Bienstock from adults. In the intestine of sucklings which have been nourished entirely on their mother's milk, the Bacteriitm laclis aerogenes (Y\^. 192, 2) causes the lactic acid fermentation with the evolution of CO2 and H, in the upper part of the canal where still some milk sugar is unabsorbed. In the evacuations is the characteristic slender Bacterium coli commune (Fig. 192, I). In addition, occasionally there are other bacilli, cocci, spores of yeast, and a mould [Escherich). In the fieces of an adult, Bienstock detected two large forms of Bacilli (Fig. 192, 3, 4I, closely resembling Bacillus subtilis in form and size, but distinguished only from it by the form of its pure cultivation, by the mode of growth of its spores, and by the absence of movements. These two forms can be distinguished microscopically by the mode of their cultivation, which is either in the form of a grape or a flat membrane. These two do not excite a fermentative action. A third micrococcusdike, small, very slowly developing bacillus occurs in three-fourths of all stools. A fourth kind (ab.sent in sucklings) is the specific bacillus (^ 184, III), causing the decomposition of albumin, resulting in the products of putrefaction and a fsecal odor. This is the only bacillus that excites these processes in the intestine; but it does not decompose casein and alkali-albumin. In Fig. 192, 5, a-g, the stages in the development of this bacillus are represented, but the stages from c and g are absent in the faeces, and are found only in artificial cultivations. 314 PATHOLOGICAL VARIATIONS OF DIGESTION. If the feces are simply investigated microscopically and without special precautions, there are other fungi, some of which may be introduced through the anus. In stools that contain much starch, the bacillus amylobacter, which is tinged blue with iodine, occurs (J 1S4), and other small, globular or rod-like fungi, which give a similar reaction [A^othnagel, Uffelmann). The changes of the intestinal contents have been studied on persons with an accidental intestinal fistula, or an artificial anus. 186. PATHOLOGICAL VARIATIONS.— (A) The taking of food may be interfered with by spasm of the muscles of mastication (usually accompanied by general spasms), stricture of the cesoph.agus. by cicatrices after swallowing caustic fluids (e.g., caustic potash, mineral acids), or by the presence of a tumor, such as cancer. Inflammation of all kinds in the mouth or pharynx inter- feres with the taking of food. Impossibility of swallowing occurs as part of the general phenomena in disease of the medulla oblongata, in consequence of paralysis of the motor centre (superior olives) for the facial, vagus, and hypoglossal nerves, and also for the aft'erent or sensory fibres of the glosso- pharyngeal, vagus and trigeminus. Stimulation or abnormal excitation of these parts causes spas- modic swallowing and the disagreeable feeling of a constriction in the neck (globus hystericus). (Bl The secretion of saliva is a'/«;«/.i/iC(/ during inflammation of the salivary glands; occlusion of their ducts by concretions (salivary calculi) ; also by the use of atropin, daturin, and during fever, whereby the secretory (not the vasomotor) fibres of the chorda appear to be paralyzed (§145). Wlien the fever is very high, no saliva is secreted. The saliva secreted during moderate fever is turbid and thick, and, usually, acid. .'\s the fever increases, the diastatic action of the saliva dimin- ishes (Ufft/»ia?iii). The secretion is increased by stimulation of the buccal nerves (inflammation, ulceration, trigeminal neuralgia), so that the saliva is secreted in great quantity. Mercury and jabo- randi cause secretion of .saliva, the former causing stomatitis, which excites the secretion of saliva reflexly. Even diseases of the stomach accompanied by vomiting cause secretion of saliva. A very thick, tenacious, sympathetic saliva occurs when there is violent stimulation of the vascular system during sexual excitement, and also during certain psychical conditions. The reaction of the saliva is acid in catarrh of the mouth, in fever, in consequence of decomposition of the buccal epithelium, and in diabetes mellitus, in consequence of acid fermentation of the saliva, which contains sugar. Hence, diabetic persons often suffer from carious teeth. Unless the mouth of an infant be kept scrupulously clean, the saliva is apt to become acid. (C) Disturbances in the activity of the musculature of the stomach may be due to paralysis of the muscular layers, whereby the stomach becomes distended, and the ingesta remain a long time in it. A special form of paralysis of the stomach is due to non-closure of the pylorus [Ebstein). This may be due to disturbances of innervation of a central or peripheral nature, or there may be actual paralysis of the pyloric sphincter, or an.i;sthesia of the pyloric mucous membrane, which acts reflexly upon the sphincter muscle; and, lastly, it may be due to the reflex impulse not being transferred to the efferent fibre within the nerve centre. Abnormal activity of the gastric muscula- ture hastens the passage of the ingesta into the intestine ; vomiting often occurs. Gastric digestion is delayed by violent bodily or mental exercise, and sometimes it is arrested altogether. Sudden mental excitement may have the same effect. These effects are, very probably, caused through the vasomotor nerves of the stomach, p'eeble and imperfect digestion may be of a purely nervous nature (Dyspepsia nervosa — Leiibe ; Neurasthenia gastrica — Burkart), An exces- sive formation of acid may be due to nervous disturbance, and is called "nervous gastroxynsis," by Rossbach. [Action of Alcohol, Tea, etc., in Digestion. — According to J. W. Fraser, all infused beverages, tea, coffee, cocoa, retard the peptic digestion of proteids, with few exceptions. The retarding action is less with cofi"ee than with lea. The tannic acid and volatile oil seem to be the retarding ingiedi- ents in teas. Distilled Spirits — brandy, whisky, gin — have but a trifling retarding effect on the digestive processes ; and when one considers their action on the secretory glands, it follows that in moderate dietetic doses they promote digestion. Wines are highly inimical to salivary digestion, but this is due to their acidity; and this effect can be removed by the addition of an alkali. Wines retard peptic digestion, the sparkling less than the still wines. Tea has an intensely inhibitory action on salivary digestion — in fact, a small quantity paralyzes the action of salive — while coff'ee has only a slight effect. This action of tea is due to the tannin. Tea, coffee and cocoa all retard peptic digestion when they form 20 per cent, of the digestive mixture ( \V. Roberts, p. 245).] Inflammatory or Catarrhal Affections of the stomach, as well as ulceration and new forma- tions, interfere with digestion, and the same result is caused by eating too much food which is diffi- cult of digestion, or taking too much highly-spiced sauces or alcohol. In the case of a dog suffer- ing from chronic gastric catarrh, Griitzner observed that the secretion took place continuously, and that the gastric juice contained little pepsin, was turbid, sticky, feebly acid, and even alkaline. The introduction of food did not alter the secretion, so that in this condition the stomach really obtains no rest. The chief cells of the gastric glands were turbid. Hence, in gastric catarrh we ought to eat frequently. l)ut take little at a time, while, at the same time, dilute (0.4 per cent.) hydrochloric acid ought to be administered. Small doses of common salt seem to aid digestion. [Absence of HCl. — HCl is always absent in carcinoma of the stomach {van de Veide); amyloid degeneration of the gastric mucous membrane { Edingej'), a.nd sometimes in fever. In all these cases the aciil reaction is due to lactic or butyric acid. The absence of HCl in cancer of the stomach DIGESTION DURING FEVER AND AN.'EMIA. 315 is an important diagnostic and prognostic symptom. It is not alisent in simple dilatation of the stomacli. Test the contents of the stomach for free HCl with tropjeolin (red colon, methyl violet (blue), and with ferric chloride and carbolic acid {i'ffelmann). 4-^ percent, of free HCl causes the amethyst-blue of the last to become steel-gray, while somewhat more discharges the color altogether.] [In testing for the presence of free lactic acid in the gastric contents, use a freshly prepared solution of 10 c. c. of 4 per cent, carbolic acid, 20 c. c. distilled water, and one drop of the officinal liquor of the perchloride of iron. The amethyst-blue color is made yellow by adding ^A to J^ of its volume of dilute lactic acid (i per 1000). The lactic acid is easily e.\tracted. by ether, from the gastric contents, and the reaction can then be performed with the residue obtained after evapo- rating the ether. A solution of I drop of the liquor perchloride in 50 c. c. of water is made yellow by lactic acid {Vffelmann].'\ Feeble Digestion may be caused either by imperfect formation of acid or pepsin, so that both substances may be administered in such a condition. [It may also be due to deficient muscular power in the wall of the stomach]. In other cases, lactic, butyric and acetic acids are formed, owing to the presence of lowdy organisms. In such cases, small doses of salicylic acid, together with some hydrochloric acid, are useful {Hoppe-Seyhr). Pepsin need not be given often, as it is rarely absent, even from the diseased gastric mucous membrane. Albumin has been found in the gastric juice in cases of gastric catarrh and cholera. (Dl Digestion during Fever and Anaemia. — Beaumont found that in the case of Alexis St. Martin, when fever occurred, a small amount of gastric juice was secreted; the mucous membrane was dry, red, and irritable. Dogs suffering from septica^mic fever, or rendered anaemic by great loss of blood. Secrete gastric juice of feeble digestive power and containing little acid 1 Mmiasscin). [In acute diseases accompanied by fever, the inner cells of the fundus glands of the human stomach may disappear (C. Kupffer.W Hoppe-Seyler investigated the gastric juice of a typhus patient, in which van de Velde found no free acid, and he found the same in gastric catarrh, fever, and in can- cer of the stomach. The gastric juice of the typhus patient did not digest artificially, even after the addition of hydrochloric acid. The diminution of acid, under these circumstances, favors the occur- rence of a neutral reaction, so that, on the one hand, digestion cannot proceed, and on the other, fermentative processes (lactic and butyric acid fermentations with the evolution of gases) occur. These results are associated with the presence of micro-organisms and Sarciiia ventriculi { Good- sjr^. He advises the administration of hydrochloric acid and pepsin, and when there are symp'onis of fermentation, small doses of salicylic acid. Ufielmann found that the secretion of a peptone- forming gastric juice ceased in fever, when the fever is severe at the outset, when a feeble condition occurs, or when the temperature is very high. The amount of juice secreted is certainly diminished during fever. The excitability of the mucous membrane is increased, so that vomiting readily occurs. The increased excitability of the vasomotor nerves during fever (Hcidcnhahi) is disadvan- tageous for the secretion of the digestive fluids. Beaumont obser\'ed that fluids are rapidly ab- sorbed from the stomach during fever, but the absorption of peptones is diminished on account of the accompanying catarrhal condition of the stomach, and the altered functional activity of the muscularis mucosa; [Lciibe). Many salts, when given in lars;e amount, disturb gastric digestion, «•..?■., the sulphates. While the alkaloids, morphia, strychnia, digitalin. narcotin, veratria, have a similar action; quinine favors it ( IVolberg). In some ner\'ous individuals a " peristaltic unrest of the stomach," conjoined with a dyspeptic condition, occurs (Kussmatih. [Professor James directs attention to the value of peptic and pancreatic salts, which are preparations of common salt mixed with pepsin and the ferments of the pancreas respectively.] [Artificial Digestion is affected by various salts according to their nature and dilution. The digestion oi fibrin by pepsin goes on best without the addition of salts, being diminished by magnesic sulphate, sodic carbonate and sulphate. The digestion of fibrin by pancreatic extract is accelerated by sodic carbonate (Heidenhain^. and retarded by MgSO^ and Na2SO.j. The diastatic action of the saliva and pancreas on starch is greatly accelerated by NaCl (2 per cent.) while Na2C03, NajSO^, MgSO^ slow it {Pfeiffer).'\ According to .Schiitz, artificial gastric digestion is retarded by a 2 per cent, solution of alcohol, and also by a solution of salicylic acid (.06 to .1 per cent.). Buchner, however, finds that 10 per cent, of alcohol does not afiect artificial gastric digestion, while above 20 per cent, arrests it. Beer hinders digestion. (E) In acute diseases, the secretion of bile is affected ; it becomes less in amount and more watery, i. e., it contains less specific constituents. If the liver undergoes great structural change, the secretion may be arrested. (F) Gallstones When decomposition of the bile occurs, gall stones are formed in the ^vz// b/adder or in the bi/e diiols. .Some are luhile, and consist almost entirely of stratified layers of crys- tals of cholesterin. The brown forms consist of bilirubin, lime and calcium carbonate, often mixed with iron, copj^er, and manganese. The gall stones in the gall bladder become faceted by rubbing against each other. The nucleus of the white stones often consists of chalk and bile color- ing matters, together with nitrogenous residues, derived from shed epithelium, mucin, bile salts and fats. Gall stones may occlude the bile duct and cause cholxmia. When a small stone becomes 316 COMPARATIVE PHYSIOLOGY OF DIGESTION. impacted in a duct, it gives rise to excessive pain, constituting hepatic colic, and may even cause rupture of the bile duct with its sharp edges. (G) Nothing certain has been determined regarding the pancreatic secretion in disease, but in fever it appears to be diminished in amount and digestive activity. The suppression of the pancre- atic secretion [as by a cancerous tumor of the head of the pancreas] is often accompanied by the appearance of fat in the form of globules or groups of crystals in the fa'ces. (H) Constipation is a most important derangement of the digestive tract. It may be caused by — ( I ) Conditions which obstruct the normal channely e.g., constriction of the gut from stricture — in the large gut after dysentery, tumors, rotation on its axis of a loop of intestine (volvulus), or invagina- tion, occlusion of a coil of gut in a hernial sac, or by the pressure of tumors or exudations from without, or congenital absence of the anus. (2) Too great drviiess of the contents, caused by too little water in the articles of diet, diminution of the amount of the digestive secretions, e.g., of bile in icterus; or in consequence of much fluid being given off by other organs, as after copious secre- tion of saliva, milk, or in fever. (3) Variations in the functional activity of the miise/es and motor 7ieitious apparatus of the gut may cause constipation, owing to imperfect peristalsis. This condition occurs in inflammations, degenerations, chronic catarrh, diaphragmatic inflammation. Affections of the spinal cord, and sometimes also of the brain, are usually accompanied by slow evacuation of the intestine. Whether diminished mental activity and hypochondriasis are the cause of, or are caused by constipation is not proved. Spasmodic contraction of a part of the intestine may cause tempo- rary retention of the intestinal contents, and, at the same time, give rise to great pain or colic; the same is true of spasm of the anal sphincter, which may be excited reflexly from the lower part of the gut. The faecal masses in constipation are usually hard and dry, owing to the water being ab- sorbed ; hence they form large masses or scybala within the large intestine, and these again give rise to new resistance. Among the reagents which prevent evacuation of the bowels, some paralyze the motor apparatus temporarily, e.g., opium, morphia ; some diminish the secretion of the intestinal mucous membrane, and cause constriction of the blood vessels, as tannic acid, vegetables containing tannin, alum, chalk, lead acetate, silver nitr,ate, bismuth nitrate. (I) Increased ei'aeuation of the intestinal contents is usually accompanied by a watery condition of the faeces, constituting diarrhcea. The causes are : — 1. A too rapid movement of the contents through the intestine, chiefly through the large intestine, so that there is not time for the normal amount of absorption to take place. The increased peristal- sis depends upon stimulation of the motor nervous apparatus of the intestine usually of a reflex nature. Rapid transit of the contents through the inte.stine, causes the evacuation of certain sub- stances, which cannot be digested in so short a time. 2. The stools become thinner, from the presence of much water, mucus, and the admixture with fat, and by eating fruit and vegetables. In rare cases, w-hen the evacuations contain much mucin, Charcot's crystals occur (Fig. 144, c). In ulceration of the intestine leucocytes (pus) are present {Nothnagel). 3. Diarrhoea may occur as a consequence of disturbance of the diffusion processes through the intestinal walls, as in affections of the epithelium, when it becomes swollen in inflammatory or catarrhal conditions of the intestinal mucous membrane. [Irritation over the abdomen, as from the subcutaneous injection of small quantities of saline solutions, causes diarrhcea [Af. Hay)^ 4. It may also be due to increased secretion into the intestine, as in capillary diffusion, when magnesium sulphate in the intestine attracts water from the blood. The same occurs in cholera, when the stools are copious and of a rice-water character, and are loaded with epithelial cells from the villi. The transudation into the intestine is so great that the blood in the arteries becomes very thick, and may even on this account cease to circulate. Transudation into the intestine also takes place as a consequence of paralysis of the vasomotor nerves of the intestine. This is perhaps the case in diarrhcea following upon a cold. Certain sub- stances seem directly to excite the secretory organs of the intestines or their nerves, such as the drastic purgatives [\ iSo). Pilocarpin injected into the blood causes great secretion (Mas/off). During febrile conditions, the secretion of the intestinal glands seems to be altered quantita- tively and qualitatively, with simultaneous alteration of the functional activity of the musculature and the organs of absorption, while the excitability of the mucous membrane is increased ( i'ffel- niann). It is important to note that in many acute febrile diseases the amount of common salt in the urine diminishes, and increases again as the fever subsides. 187. COMPARATIVE. — Salivary Glands. — Among Mammals the herbivora have larger salivary glands than the carnivora; while midway between both are the omnivora. The whale has no salivary glands. The pinnipedia have a small parotid, w'hich is absent in the echidna. The dog and many carnivora have a special gland lying in the orbit, the orbita/ or zygomatic gland. In Birds the salivary glands open at the angle of the mouth ; in them the parotid is absent. Among Reptiles the parotid of some species is so changed as to form poison glands ; the tortoise has sub- lingual glands; reptiles have labial glands. The Amphibia and Fishes have merely small glands scattered over the mouth. The salivary glands are large in Insects; some of them secrete formic HISTORICAL ACCOUNT OF DIGESTION. 317 acid. The salivary glands are well developed in molluscs, and the saliva of Dolium galea contains more than 3 per cent, of free sulphuric acid (?). The cephalopods have double glands. A Crop is not present in any manmial; the stomach is either simple^ as in man, or, as in many rodents, it is divided into two halves, into a cardiac and a pyloric portion. The intestine is short in flesh-eating animals and long in herbivora. The stomach of ruminants is compound, and consists of four cavities. The first and largest is the paunch or rumen, then the reticulum. In these two cavities, especially the former, the ingesta are softened and undergo fermentation. They are then returned to the mouth by the action of the voluntary muscular fibres, which reach to the stomach. This is the process of rumination. The ingesta are chewed again in the mouth, and are again swallowed, but this time they enter the third cavity or psalterium— (which is absent in the camel) — -and thence into the fourth stomach or abomasum in which the fermentative digestion takes place. The cjecum is a very large and important digestive organ in herbivora, and in most rodents; it is small in man, and absent in carnivora. The cesophagus in grain-eating Birds not unfrequently has a blind diverticulum or crop for softening the food. In the crop of pigeons during the breeding season, there is formed a peculiar secretion — "pigeon's milk," which is used to feed the young (J. Hunter). The stomach consists of a glandular proventriculus and a strong muscu- lar stomach which is covered with horny epithelium and triturates the food. There are usually two fluid diverticula on the small intestine near where it joins the large gut. In Fishes the intestinal canal is usually simple; the stomach is merely a dilatation of the tube; and at the pylorus there may be one, but usually many, blind glandular appendages (the appendices pyloricse). There are usually longitudinal folds in the intestinal mucous membrane, but in some fishes, <■. i,'., the shark, there is a spiral valve. [It is curious to find that the inversive (cane-sugar) ferment is wanting in the herbivora, as the cow, horse and sheep, but is present in the carnivora, as the dog and cat. It is also met with in birds and reptiles, and in many of the invertebrates, as the ordinary earthworm {Matthew //ay).] In Amphibia and Reptiles the stomach is a simple dilatation ; the gut is larger in vegetable feeders than in flesh feeders. The liver is never absent in vertebrates, although the gall bladder frequently is. The pancreas is absent in some fishes. Digestion in Plants. — The observations on the albumin-digesting power of some plants {Candy, t86g ; Ch. Darwin, iSjj) are extremely interesting. The sun dew or drosera has a series of ten- tacles on the surface of its leaves, and the tentacles are provided with glands. As soon as an insect alights upon a leaf it is suddenly seized by the tentacles, the glands pour out an acid juice over the prey, which is gradually digested ; all e.'icept the chitinous structures. The secretion, as well as the subsequent absorption of the products of digestion, are accomplished by the activity of the pro- toplasm of the cells of the leaves. The digestive juice contains a pepsin-like ferment and formic acid. Similar phenomena are manifested by the Venus fly trap (Diona:a), by pinguicula, as well as by the cavity of the altered leaves of nepenthes. About fifteen species of these " insectivorous " or carnivorous plants are known. [The action of papain, and other ferments analogous in their action to trypsin, are referred to in | 170.] 188. HISTORICAL. — Digestion in the Mouth. — -The Hippocratic school was acquainted with the vessels of the teeth ; Aristotle ascribed an uninterrupted growth to these organs, and he further noticed that animals that were pro\ ided with horns and had cloven hoofs, had an imperfect set of teeth — the upper incisors were absent. It is curious to note that in some cases where men have had an excessive formation of hairy appendages, the incisor teeth have been found to be badly developed. The muscles of mastication were known at an early period; Vidius (f 1567) described the temporo-maxillary articulation with its meniscus. The older observers regarded the saliva as a solvent, and in addition, many bad qualities, especially in starving animals, were ascribed to it. This arose from the knowledge of the saliva of mad animals, and the parotid saliva of poisonous snakes. Human saliva, without organisms, is poisonous \.o\>\x&s {Gautier). The salivary glands have been known for a long time. Galen (131--203 A. D.) was acquainted with Wharton's duct, and Aetius (270 a.d.) with the sub-maxillary and sublingual glands. Hapel de la Chenaye (17S0) obtained large quantities of saliva from a horse, in which he was the first to make a salivary fistula. Spallanzani (17S6) asserted that food mixed with saliva was more easily dige-.ted than food moist- ened with water. Hamberger and Sieliold investigated the reaction, consistence and specific gravity of saliva, and found in it mucus, albumin, common salt, calcium and sodium phosphates. Berzelius gave the name ptyalin to the characteristic organic constituent of saliva, but Leuchs (1831 j was the first to detect its diastatic action. Gastric Digestion. — Digestion was formerly compared to boiling, whereby solution was effected. According to Galen, only substances that have been dissolved passed through the pylorus into the intestine. He described the movements of the stomach and the peristalsis of the intestines. Aelian gave names to the four stomachs of the ruminants. Vidius (■)■ 1567) noticed the numerous small apertures of the gastric glands. Van Helmont (f 1644) expressly notices the acidity of the stomach. Reaumur (1752) knew that a juice was secreted by the stomach, which effected solution, and with which he and Spallanzani performed experiments on digestion outside the body. Car- minati (17S5) found that the stomachs of carnivora during digestion secreted a very acid juice. Prout (1S24) discovered the hydrochloric acid of the gastric juice, Sprott and Boyd (1836) the 318 HISTORICAL. glands of the gastric mucous membrane, while Wasmann and Bischoff noted the two kinds of gastric glands. After Beaumont (1834) had made his observations upon Alexis St. Martin, who had a gastric fistula caused by a gunshot wound, Bassow ( 1842) and Blondlot (1843) made the first artificial gastric fistulas upon animals. Eberle (1834) prepared artificial gastric juice. Mialhe called albumin, when altered by gastric digestion, albuminose ; Lehmann, who investigated this substance more carefully, gave it the nxmt peptone. Schwann isolated ^i?/«« (1836), and estab- lished the fact of its activity in the presence of hydrochloric acid. Pancreas, Bile, Intestinal Digestion. — The Pancreas was known to the Hippocratic School ; Maur. Hoffmann (1642) demonstrated its duct ifowl), and Wirsung described it in man. Regner de Graaf (1664) collected the pancreatic juice from a fistula, and Tiedemann and Gmelin found it to be alkaline, while Lauret and Lassaigne found that it resembled saliva. Valentin discovered its diastatic action, Eberle its emulsionizing power, and CI. Bernard (1846) its tryptic and fat .splitting properties. The last mentioned function was referred to by Purkinje and Pappenheim {1836). Aristotle characterized the bile as a useless secretion; according to Erasistratus (304 B. c. ), fine invisible channels conduct the bile from the liver into the gall bladder. Aretaeus ascribed icterus to obstruction of the bile duct. Benedetti (1493) described gall stones. According to Jasolinus (1573), the gall bladder is emptied by its own contractions. Sylvius de la Boe noticed the lymph- atics of the liver (1640) ; Walaeus, the connective tissue of the so-called capsule of Glisson (1641). Haller indicated the uses of bile in the digestion of fats. The liver cells were described by Henle, Purkinje, and Dutrochet (1838). Heynsius discovered the urea, and CI. Bernard (1853) the sugar in the liver, and he and Hensen (1857) found glycogen in the liver. Kiernan gave a more exact description of the hepatic blood vessels (1834). Beale injected the lymphatics, and Gerlach the finest bile ducts. Schwann (1844) made the first biliary fi-tula ; Demarcay particularly referred to the combination of the bile acids with soda (1838); Strecker discovered the soda compounds of both acids, and isolated them. Corn. Celsus mentions nutrient enemata (3-5 A. D.). Fallopius (1561) described the valvulae conniventes and villi of the intestinal mucous membrane, and the nervous plexus of the mesentery. The agminated glands or patches of Peyer were known to Seveiinus (1645). PHYSIOLOGY OF ABSORPTION. leme of intestinal absorption teal; T. D., thoracic duct; v., portal and hepatic vein? LAC, lac- . V. and H. INT., intcs- 189. THE ORGANS OF ABSORPTION.— [As most substances in the state in whicli tht;y are used for food are either insoluble or diffuse but imper- fectly through membranes, the whole drift of the complicated digestive processes is to render these substances soluble and diffusible, and thus fit them for absorp- tion ; while most of the fats are emulsionized.] The mucous membrane of the whole intestinal tract, as far as it is covered by a single layer of columnar epithelium, /. e., from the cardiac orifice of the stomach to the anus — is adapted for absorption. The mouth and cesophagus, lined as they are by stratified squamous epithelium, are much less adapted for this purpose. Still, poisoning is caused by placing potassium cyanide in the mouth. The channels of absorption in the intestinal tract are (Fig. 193) — ( i) the capillaries \_clirect'\, and (2) the lacteals [/>/o provided with ganglionic cells. It supplies the muscular fibres and arteries of the mucosa, including those of the villi. It also supplies branches to Lieberkuhn's glands (Drasck). Compare Figs. 166 and 167. [Structure of the Large Intestine. — It has four coats like those of the small intestine. The serous coat has the same structure as that of the small intestine. The muscular coat has external longitudinal fibres occurring all round the gut, but they form three Hat, ribbon-like, longitudinal bands in the csecum and colon (Fig. 201). Inside this coat are the ciiciilar fibres. The sub-mucosa is practically the same as that of the small intes- tine. Tlie mucosa is characterized by negative characters. It has no villi and no Peyer's patches, but otherwise it resembles structurally the small intestine, consisting of a basis of adenoid tissue with the simple tubular glands of Lieberkiihn (Fig. 202). These glands are very numerous and somewhat longer than those of the small intestine, and they always contain far more goblet cells — about ten times as many. The cells lining them are de void of a clear disk. Solitary glands occur throughout the entire length of the large intestine. At the bases of Lieberkuhn's glands is the muscularis mucosae. The blood vessels and nerves have a similar arrangement to those in the stomach.] [Blood Vessels. — On looking down on an opaque injection of the mucous membrane of the stomach, one sees a dense meshwork of polygonal areas of unequal size, with depressions here and there. The orifices are the orifices of the gastric glands, each surrounded by a capillary. A somewhat similar appearance is seen in an opaque injection of the mucous membrane of the large intestine, but in the latter the meshwork is uniform, all the orifices (of Lieberkuhn's glands) being of the same size.] 191. ABSORPTION OF THE DIGESTED FOOD.— The physical forces concerned are, endosinosis, diffusion and filtration. All the constituents of the food, with the exception of the fats, which in part are changed into a fine emulsion, are brought into a state of solution by the digestive processes. These substances pass through the walls of the intestinal tract, either into the blood vessels of the mucous membrane or into the beginning of the lymphatics. In this passage of the fluids two physical processes come into play — c-mlosmosis and diffusion, as well as filtration. I. Endosinosis and diffusion occur between two fluids which are capable of foniiing an inti- mate mixture with each other, e. g., hydrochloric acid and water, but never between two fluids which do not form a perfect mixture, such as oil and water. If two fluids capable of mixing with each other, but of dift'erent compositions, be separated from each other by means of a septum with physical pores (which occur even in a homogeneous membrane), an exchange of the constituents ntestlne (.dog). large 326 FORCES CONCERNED IN ABSORPTION. in the fluids occurs until both fluids have the same composition. This exchange of fluids is termed endosniosis or diosinosis. If we remember that within the intestinal tract there are relatively concentrated solutions of those substances which have been brought into solution by the digestive juices — peptone, sugar, soaps and solutions of the sails — while separated from these ijy the porous mucous Fig. 203. membrane and the walls of the blood and lymph capillaries is the blood, ^ which contains relatively less of these substances, it is clear that an endos- molic current must set in toward the blood and lymph vessels. Diffusion.— If the two mixible fluids are placed in a vessel, the one fluid over the other, but without being separated by a porous septum, an exchange of the particles of the fluids also occurs, until the whole mi.\ture is of uniform composition. This process is called diffusion. Conditions Influencing Diffusion. — Graham's investigations showed that the rapidity of diffusion is influenced by a variety of conditions: (I) The nature of the fluids themselves is of importance ; acids diffuse most rapidly ; the alkaline salts more slowly ; and most slowly, fluid albumin, gela- tin, gum, dextrin. These last do not crystallize, and do not form true solu- tions. (2) The more concentrated the solutions, the greater the diffusion. (3) Heat accelerates, while coal retards, the process. (4) If a solution of a body which diff'uses with difficulty be mixed with an easily diffusible one, the former diffuses with still greater difficulty. (5) Dilute solutions of several substances diffuse into each other without any difficulty, but if concentrated solutions are employed, the process is retarded. (6) Double salts, one con- stituent of which diff'uses more readily than the other, may be chemically separated by diffusion. Endosmometer. — The exchange of the fluid particles takes place inde- pendently of the Jiydrostatic pressure. Fig. 203 represents an endosmometer. A glass cyhnder is filled with distilled water, and into this is placed a flask, J, without a bottom, instead of which a membrane, vi, is tied on. A glass tube, R, is fixed firmly by means of a cork into the neck of the flask. The flask is filled up to the lower end of the tube with a concentrated salt solu- tion, and is then placed in the cylindrical vessel until both fluids are on the same level, x. The fluid in the tube, R, soon begins to rise, because water passes through the membrane into the concentrated solution in the flask, and ' this independently of the hydrostatic pressure. Particles of the concentrated Endosmome^ter for os- j^|j solution pass into the cylinder and mix with the water, F. These out- going and ingoing currents continue until the fluids without and within J are of uniform composition, whereby the fluid in R always stands higher (^e. g., at_)'), while it is lowered in the cylinder. The circumstance of the level of the fluid within the tube being so high and remaining so, is due to the fact that the pores in the membrane are too fine to allow the hydrostatic pressure to act through them. Endosmotic Equivalent. — Experiment has shown that equal weights of different soluble sub- stances attract different amounts of distilled water through the membrane, /. e., a known weight of a soluble substance (in the flask) can be exchanged by endosmosis for a definite weight of water. The term endosmotic equivalent indicates the weight of distilled water that passes into the flask of the endosmometer, in exchange for a known weight of the soluble substance (Jolly'). For I grm. alcohol 4.2 grins, water were exchanged ; while for I grm. NaCl 4.3 grms. water passed into the endosmometer. The following numbers give the endosmotic equivalent of — Magnesium sulphate =: 11.7 Potassium sulphate = 12.0 Sulphuric acid = 0.39 Potassium hydrate = 215.0 ugh the membrane into the water of the cylinder ( Vierordt). If the water in the cylinder, there- Acid potassium sulphate = 2.3 Common salt =^ 4.3 Sugar = 7-1 Sodium sulphate =11.6 The amount of the substance which passes thn is proportional to the concentration of the solutio fore, be repeatedly renewed, the endosmosis takes place more rapidly and the process of equilibra- tion is accelerated. The larger the pores of the membrane, and the smaller the molecules of the substance in solution, the more rapid is the endosmosis. Hence, the rapidity of the endosmosis of different substances varies — thus, the rapidity of sugar, sodium sulphate, common salt, and urea is in the ratio of I : I.I : 5 : 9.5 {Eckhard, Hoffmann). The endosmotic equivalent is not eonstant /or each substance. It is influenced by — { I ) The tem- perature, which, as it increases, generally increases the endosmotic equivalent. (2) It also varies with the degree of concentration of the osmotic solutions, being greater for dilute solutions of the substances (C Ltidwig and Cloetta). If a substance other than water be placed in the cylinder, an endosmotic current occurs on both sides until complete equality is obtained. In this case, the currents in opposite directions disturb each other. If two substances be dissolved in the water in the flask at the same time, they diffuse ABSORPTIVE ACTIVITY OF THE INTESTINAL WALL. 327 into water without afl'ecting each other. (3) It also varies with membranes of varying porosity. Common salt, which gives an endosmotic equivalent with a pig's bladder = 4.3, gives 6.4 when an ox bladder is used; 2.9 with a swimming bladder; and 20.2 with a collodion membrane (Hmzer). Colloids. — There is a number of fluid substances which, on account of the great size of their molecules, do not pass, or pass only with difficulty, through the pores of a membrane impregnated with gelatinous bodies, which diffuse slowly. These substances are not actually in a true state of solution, but exist in a very dilute condition of imbibition. Such substances are the fluid proteids, starches, dextrin, gum, and gelatin. These diffuse when no septum is present, but difi'use with difficulty or not at all through a porous septum. Graham called these substances colloids, because when concentrated, they present a glue like or gelatinous appearance ; further, they do not crystal- lize, while those substances which diffuse readily are crystalline, and are called crystalloids. Crystallizable substances may be separated from non-crystallizable by this process, which Graham called dialysis. Mineral salts favor the passage of colloids through membranes (Baranetziy). That Endosmosis takes place in the intestinal tract, through the mucous membrane and the delicate membranes of the blood and lymph capillaries, can- not be denied. On the one side of the membrane, within the intestine, are the highly diffusible peptones, sugar, and soaps, and within the blood vessels are the colloids which are scarcely diffusible, e.g., the proteids of blood and lymph. II. Filtration is the passage of fluids through the coarse intermolecular pores of a membrane, owing to pressure. The greater the pressure, and the larger and more numerous the pores, the more rapidly does the fluid pass through the membrane ; increase of temperature also accelerates it. Those substances which are imbibed by the membrane filter most rapidly, so that the same sub- stance filters through different membranes with varying rapidity. The filtration is usually slower, the greater the concentration of the fluid. The filter has the property of retaining some of the sub- stances from the solution passing through it, e. g., colloid substances — or water (in dilute solutions of nitre). In the former case, the filtrate is more dilute, in the latter more concentrated than before filtration. Other substances filter without undergoing any change of concentration. Many mem- branes behave differently, according to which surface is placed next to the fluid; thus the shell- membrane of an egg permits filtration only from without inward ; [and the same is true to a much less extent with filter paper ; the smooth side of the filter paper ought always to be placed next the fluid to be filtered. The intact skin of the grape prevents the entrance of fungi]. There is a similar difference with the gastric and intestinal mucous membrane. [Filtration of Albumin. — Runeberg finds that the amount of albumin in pathological transuda- tions varies with (I) the capillary area, being least in cedema of the subcutaneous tissue. (2) The presence or absence of inftammatory processes in the vascular wall, non inflammatory pleuritic effu- sion containing 2 per cent., and inflammatory 6 per cent., of albumin. (3) The condition and amount of albumin in the blood. The amount of albumin in the transudate never reaches, although it sometimes approaches, that in blood. In ascites in general dropsy the amount is .03 to .04 per cent. (4) l^ie duration oi the transudation. (5) Perhaps the blood pressure and the condition of the circulation.] [By using numerous layers of filter paper, many colloids and crystalloids are retained in the filter, e.g., ha;moglobin, albumin, and many coloring matters, especially anilin colors, the last being arrested by glass-wool (^Krysinski).'\ Filtration of the soluble substance may take place from the canal of the digest- ive tract when — (i) The intestine contraets and thus e.\erts pressure upon its contents. This is possible when the tube is narrowed at two points, and the mus- culature between these two points contracts upon the fluid contents. (2) Filtra- tion, under negative pressure, may be caused by the villi {Briieke). When the villi contract energetically, they empty their contents toward the blood and lymph vessels. The lymph vessels remain empty, as the chyle is prevented from passing backward into the origin of the lacteal within the villi, owing to the presence of numerous valves in the lymphatics. When the villi pass again into the relaxed condition, they again become filled with fluids from the intestinal contents. 192. ABSORPTIVE ACTIVITY OF THE INTESTINAL WALL.^The process of digestion produces from the food partly solutions and partly finely divided emulsions, whose fine particles are said to be surrounded by an albuminous envelope, the haptogen membrane [of Ascherson], whereby these particles become more stable. Unchanged colloid substances may also be present in the intestinal tract. 328 ABSORPTION OF SOLUBLE CARBOHYDRATES AND PEPTONES. I. Absorption of Solutions. — True solutions undoubtedly pass by endos- mosis into the blood vessels and lymphatics of the intestinal walls, but numerous facts indicate that the protoplasm of the cells of the tube take an active part in the process of absorption. The forces concerned have not as yet been referred simply to physical and chemical processes. (i) The Inorganic substances. — Water and the soluble salts necessary for nutrition are easily absorbed, the latter especially by the blood- and lymph vessels. When saline solutions pass by endosmosis into the vessels, water must pass from the intestinal vessels into the intestine. The amount of water, however, is small, owing to the small endosmotic equivalent of the salts to be absorbed. More salts are absorbed from concentrated than from dilute solutions (Fu>ike). If large quantities of salts, with a high endosmotic equivalent, are introduced into the intestine, e.g., magnesium or sodium sulphate, these salts retain the water ne- cessary for their solution, and thus diarrhcea is caused {Foiscuine, Biichhcini). Conversely, when these substances are injected into the blood a large quantity of water passes from the intestine into the blood, so that constipation occurs, owing to dryness of the intestinal contents {^Aiibcrt). [M. Hay concludes from his ex- periments ($) i6i), that salts, when placed in the intestines, do not abstract water from the blood, or are themselves absorbed, in virtue of an endosmotic relation being established between the blood and the saline solution in the intestines. Ab- sorption is probably due to the filtration and diffusion, or processes of inhibition other than endosmosis, as yet little understood. The result obtained by Aubert, which is not constant, is mostly caused by the great diuresis which the injected salts excites.] Numerous inorganic substances, which do not occur in the body, are absorbed by endosmosis from the intestine, f.^., dilute sulphuric acid, potassium iodide, chlorate, and bromide, and many other salts. (2) The soluble carbohydrates, such as the sugars, of which the chief rep- resentatives are dextrose and maltose, with a relatively high endosmotic equiva- lent. Cane sugar is changed by a special ferment into invert sugar (§ 183, 5). Absorption appears to take place somewhat slowly, as only very small quantities of grape sugar are found in the chyle vessels or the portal vein, at any time. .\ccording to v. Merings the suga}- passes from the intestine into the rootlets of the portal vein ; dextrin also occurs in the portal vein. When the blood of the portal vein is boiled with dilute sulphuric acid, the amount of sugar is increased i^Nau- nyii). The amount of sugar absorbed depends upon the concentration of its solu- tion in the intestine ; hence the amount of sugar in the blood is increased after a diet containing much of this substance (C. Schmidt and v. Becker'), so that it may appear in the urine; in which case the blood must contain at least 0.6 per cent, of sugar {Lehinann and Uhle). A small amount of cane sugar has also been found in the blood (C7. Bernard, Hoppc-Seylcr). The sugar is used up in the bodily metabolism ; some of it is, perhaps, oxidized in the muscles {Ziminer). [Compare effects of injecting grape sugar into the blood (§ 176).] (3) The peptones have a small endosmotic equivalent tyFunke), a 2 to 9 per cent solution ^ 7 to ro. Owing to their great diffusibility they are readily absorbed, and they are the chief representatives of the proteids which are absorbed. The amount absorbed depends upon the concentration of the solution in the intestine. They pass into the bloodvessels {Schmidt- Miilheim). When animals are fed on peptones (with the necessary fat or sugar), they serve to maintain the body weight (Maly, Ftbsz and Gybrgyai). Only minute quantities of peptone have as yet been found in the blood {Drosdorjf ) ; hence, it is assumed, either that they are rapidly converted into true albuminous bodies, or that, in part at least, they undergo further decompositions, with which we are as yet unacquainted. As, however, they can compensate for the total metabolism of the proteids within the body, we must assume that they are converted into proteids. Hofmeister supposes that the ABSORPTION OF FATTY PARTICLES. 329 leucocytes absorb the peptones and act as their carriers, much as the red corpus- cles are oxjgen carriers. They carry the peptones into the mucous membrane of the stomach and small intestine, which are very rich in peptone at the fourth hour of digestion. It is asserted by Salivoli that tiie mucous membrane possesses the property of changing peptone into albumin. Only a part of the peptone passes unchanged into the blood, and disappears from it after its passage through the tissues. [Injection of Peptone into Blood — When peptone is injected into the blood of an animal, within twenty minutes thereafter no trace of the peptone is lo be found in the blood, although it has not been excreted by any of the organs. Peptone so injected prevents the blood of the dog (not of the rabbit or pig) from coagulating (p. 48). Faiio asserts that the peptone is taken up by the red blood corpuscles, which thus become of greater specific gravity, and change it into globulin. After three or more hours the corpuscles return the globulin to the blood, so that the corpuscles represent a reserve store of proteid.] (4) Unchanged true proteids filter with great difficulty, and much albumin remains upon the filter. On account of their high endosmotic equivalent they pass with extreme difficulty, and only in traces, through membranes. Neverthe- less, it has been conclusively proved that unchanged proteids can be absorbed {Briicke), e.g., casein, soluble myosin, alkali albuminate, albumin mixed with common salt, gelatin {Fc?//, Bauer, Eiehhorst). They are absorbed even from the large intestine (Czer/ty and La/se/te//ierger), although the human large intestine cannot absorb more than 6 grms. daily. But the amount of unchanged proteids absorbed is always very much less than the amount of peptone. Egg albumin without common salt, syntonin, serum albumin, and fibrin are not absorbed (Eieh- horst). Landois observed in the case of a young man who took the whites of 14 to 20 eggs along with NaCl, that albumin was given off Ijy the urine for 4 to 10 hours thereafter. The amount of albumin given off rose until the third day and ceased on the fifth day. The more albumin that was taken the sooner the albuminuria appeared and the longer it lasted. The unchanged egg albumin reappeared in the urine. If egg albumin be injected into the blood, part of it reappears in the urine (J 41, 2) [Stoivis, I.ehnianii). (5) The soluble fat soaps represent only a fraction of the fats of the food which are absorbed ; the greater part of the neutral fats being absorbed in the form of very fine jjarticles — as an emulsion (§ 192, 11). The absorbed soaps have been found in the chyle, and as the blood of the portal vein contains more soaps during digestion than during hunger, it has been assumed that the soaps pass into the intestinal blood capillaries. The investigations of Lenz, Bidder and Schmidt render it probable that the organism can absorb only a limited amount of fat within a given period ; the amount perhaps bears a relation to the amount of bile and pancreatic juice. The maximum per i kilo, (cat) was 0.6 grm. of fat per hour. It appears as if the soaps reunite with glycerine in the parenchyma of the villi, to form neutral fats, as Perewoznikoff and Will found, after injecting these two ingredients into the intestinal canal. C. A. Ewald found that fat was formed when soaps and glycerine were brought into contact with the fresh intestinal mucous membrane. Perhaps this is the explanation of the observation of Bruch, who found fatty particles within the blood vessels of the villi. Absorption of other Substances. — Of soluble substances which are introduced into the intes- tinal canal, some are absorbed and others are not. The following are absorbed : alcohol, part of which appears in the urine (not in the expired air), viz., that part which is not changed into COj and HjO, within the body; tartaric, citric, malic, and lactic acids; glycerine, inulin (Komanos); gum and vegetable mucin, which give rise to the formation of glycogen in the liver. Among coloring matters, alizarin (from madder), alkannet, indigo-sulphuric acid, and its soda salt are absorbed ; h;ematin is partly absorbed, while chlorophyll is not. Metallic salts seem to be kept in solution by proteids, are perhaps absorbed along with them, and are partly carried by the blood of the portal vein to the liver (ferric sulphate has been found in chyle). Numerous poisons are very rapidly absorbed, e. g., hydrocyanic acid after a few seconds ; potassium cyanide has been found in the chyle. [If salts (IvI, sulphocyanide of ammonium) be injected into a liga- 330 ABSORPTION OF FATTY PARTICLES. tured loop of intestine (dog, cat, rabbit), these substances are absorbed both by the blood and lymph vessels, and in both nearly simultaneously (A'. B. Leii??innn).~\ II. Absorption of the smallest particles. — The largest amount of the fats is absorbfd in the form of a milk like emulsion, formed by the action of the bile and the ])ancreatic juice, and consisting of excessively sinall granules of uni- form size (i^ 170, III ; § 181). The fats themselves are not chemically changed, but remain as undecomposed neutral fats. The particles seem to be surrounded by a delicate albuminous envelope, or haptogen membrane, partly derived from the pancreatic juice [probably froin its alkali albuminate]. The villi of the small intestine are the chief organs concerned in the absorption of the fatty emulsion, but the epithelium of the stomach and that of the large intestine also take a part. The fatty granules are recognized in the villi — (i) Within the delicate canals? (§ 190) in the clear band of the epithelium {Ko/likcr). [It is highly doubtful if the vertical lines seen in the clear disk of the epithebum of the intestine are due to pores.] (2) The protoplasm of the epithelial cells is loaded with fatty granules of various sizes during the time of absorption, while the nuclei of the cells remain free, although, from the amount of fat within the cells, it is often difficult to dis- tinguish them. (3) The granules pass into the spaces of the parenchyma of the villi ; these spaces communicate freely with each other. (4) The origin of the lacteal in the axis of the villus is found to be filled with fatty granules. The amount of fat in the chyle of a dog, after a fatty meal, is 8 to 10 per cent., while the fat disappears from the blood within thirty hours. Forces concerned. — With regard to the forces concerned in the absorp- tion of fats, V. Wistinghausen proved, that when a porous membrane is moist- ened with bile, the passage of fatty particles through it is thereby facilitated, but this fact alone does not explain the copious and rapid absorption of fats. It is possible that the protoplasm of the epithelial cells is actively concerned in the process, and that it takes the particles into its interior. Perhaps a fine proto- plasmic process is thrown out by these cells, just as pseudopodia are thrown out and retracted by lower organisms. It is possible that absorption may take place through the open mouths of the goblet cells. The protoplasm of the epithelial cells is in direct communication with the numerous protoplasmic lymph cells within the reticulum of the villi, so that the particles may pass into these, and from them through the stomata (?) between the endothelial cells into the central lacteal of the villus. According to this view, the absorption of tatty particles, and perhaps also the absorption of true proteids, is due to an active vital process, as indicated by the observations of Briicke and v. Thanhoffer. This view is suported by the ob- servation of Griinhagen, that the absorption of fatty particles in the frog is most active at the temperature at which the motor phenomena of protoplasm are most lively. That it is due to simple filtration alone is not a satisfactory explanation, for the amount of fatty particles in the chyle is independent of the amount of water in it. If absorption was chiefly due to filtration, we would expect that there would most probably be a direct relation between the amount of water and fat {Luihvig and Zawi/sky). [The observations of Watney have led him to suppose that the fatty particles do not pass through the cell protoplasm to reach the lacteal, but that they pass through the cement siibstaiiee between the epithelial cells cover- ing a villus. If this view be correct, the absorbing surface is thereby greatly di- minished.] [Zuwarykin, and also .Schafer, suggest that the leucocytes, which have been observed between the columnar cells of the villi of the small intestine, are carriers of at least part of the fat from the lumen of the gut to the lacteal ; they also, perhaps, alter it for further use in the economy (p. 322). According to Zuwa- rykin, Peyer's patches, in the rabbit, seem to be especially active in the absorp- tion of fat, so that he attaches great importance to the leucocytes of the adenoid tissue in the absorption of fat.] FEEDING WITH "NUTRIENT ENEMATA." 331 The activity of the cells of the intestine with pseudopodial processes may be studied in the intes- tinal canal of Distomum hepaticum. Sommer has figured these pseudopodial processes actively engaged in the absorption of panicles from the intestine. Spina observed that the intestinal epi- thehum of the larva; of flies shortened when they were stimulated with electricity, and absorbed fluid from the intestinal canal. The cells of the villi of the frog also react to electrical stimulation. The increase in the size of the cells occurs simultaneously with the contraction of the intestine. Spina also supports the view that the cells, by virtue of their activity, possess the property of absorb- ing fluid from the intestinal contents, and again giving it up. An exchange of fluids in the opposite direction never takes place. The statements of former observers, that particles of charcoal, pigments, and even mammalian blood corpuscles (in the frog), were absorbed by the epithelial cells of the intestine, and passed into the blood, are erroneous. Even for the absorption of completely fluid substances, endosmosis and filtration seem to be scarcely sufficient. An active participation of the protoplasm of the cells seems here also — in part, at least — to be necessary, else it is difficult to explain how very slight disturbances in the activity of these cells — e.^., from intestinal catarrh — cause sudden variations of absorption, and even the passage of fluids into the mtestine. If absorption was due to diffusion alone, when alcohol is injected into the intestine, water ought to pass into the intestine, but this does not occur. Brieger found that the injection of a 0.5 to I per cent, solution of salts into a ligatured loop of intestine did not cause water to pass into the intes- tine ; but it appeared when a 20 per cent, solution was injected. 193. INFLUENCE OF THE NERVOUS SYSTEM.— With regard to the influence of the nervous system upon intestinal absorption we know very- little. After extirpation of the semilunar ganglion {Budge), as well as after sec- tion of the mesenteric nerves (jl/frfaw), the intestinal contents become more fluid and are increased in amount (§ 183). This may be partly due to diminished absorption. V. Thanhoffer states that he observed the protrusion of threads from the epithelial cells of the small intestine only after the spinal cord, or the dorsal nerves, had been divided for some time. [Matthew Hay injected saline solutions directly into the exposed intestine. He found that a 20 per cent, solution of sulphate of .soda always excites a profuse secretion, but that a 10 per cent, solution only does so — or, rather, that it only increases in bulk, when injected in sufficient quantity — a certain weight of salt failing to increase the bulk of the fluid secretion when dissolved as a 10 per cent, solution, but exciting a profuse secretion when forming a 20 per cent, solution. Secretion, he has reason to believe, is active in both — perhaps, almost equally active; but absorption is greatly impeded in the case of the concentrated salt, by its injurious action on the absorptive mechanism of the mucous membrane. Moreau has recently maintained that, under .such circumstances, there is, actually, no absorption ; but Hay has disproved this, by observing that strychnia injected into a loop of intestine containing the concentrated salt, still causes death, although after an interval three times longer than when the loop contains a 10 per cent, solution of the salt. Hay has also observed that the local effect of a ligature applied to the intestine is to excite secretion from the mucous membrane in its immediate vicinity, and, therefore, add to the bulk of the saline solution; whereas, the reflex effect of a ligature, as exercised through the nervous system, is to diminish the quantity of the secreted fluid in a remote portion of the intestine, probably by stimulating and accelerating absorption. Division of the vagi does not affect the nature or the quantity of the secretion.] 194. FEEDING WITH " NUTRIENT ENEMATA."— In cases where food cannot be taken by the mouth, e. g.^ in stricture of the oesophagus, continued vomiting, etc., food is given per rectum (Cdstis, 3-5 a. I).). As the digestive activity of the large intestine is very slight, fluid food ought to be given m a condition ready to be absorbed, and this is best done by introducing it into the rectum through a tube with a funnel attached, and allowing the food to pass in slowdy by its own weight. The patient must endeavor to retain the enema as long as possible. When the fluid is slowly and gradually mtroduced, it may pass above the ileo-caecal valve. Solutions of grape sugar, and, perhaps, a small amount of soap solution, are useful ; and among nitrogenous substances, the commercial flesh-, bread- or mdk peptones of Sanders-Ezn, Adam- kiewicz, in Germany, and Darby's fluid meat, and Carnrick's beef peptonoids in this country, are to be recommended. The amount of peptone required is I. II grms. per kilo, of body weight [Catillon) \ less useful are buttermilk, egg albumin, with common salt. Leube uses a mixture of 150 grms. flesh, with 50 grms. pancreas and 100 grms. water, which he slowly injects into the rectum, where the proteids are peptonized and absorbed. [Peptonized food prepared after the method of Roberts is very useful (§ 172).] The method of nutrient enemata only permits imperfect nutrition, and, at most, only % of the proteids necessary for maintaining the metabolism of the body is ab- sorbed (y. Voit, Bauer). [Horace Dobell recommends that a % 11) of cooked beef or mutton be grated, and to it added 20 grms. of pancreas powder and the same of pepsin. Mix the whole in a warm mortar, and add a tablespoonful of brandy and warm water, sufficient to make a semi-fluid mass, which is to be injected into the rectum.] 332 ORIGIN OF THE LYMPHATICS. 195. CHYLE VESSELS AND LYMPHATICS.— Lymphatics— Within the tissues of the body, and even in those tissues which do not contain blood vessels, e.g , the cornea, or in those which contain few blood vesseU, there exists a system of vessels or channels which contain the juices of the tissues, and within these vessels the fluid always moves in a centripetal direction. These canals arise within the tissues in a variety of ways, and unite in their course to form delicate, and afterward thicker, tubes, which, ultimately, terminate in two large trunks which open at the junction of the jugular and subclavian veins; that on the left side is the thoracic duct, and that on the right, the right lymphatic trunk. Lymph. — With regard to the lymph and its movements in different organs, it is to be noticed that this occurs in different ways in different places, (i) In many tissues, the lymphatics represent the nutrient channels, by which the fluid which transudes through the neighboring vessels is distributed, as in the cornea and in many connective tissues. (2) In many tissues, as in glands, e.g., the salivary glands {Gianiizzi) and the testis, the lymph spaces are the chief reservoirs for fluid, from which the cells, during the act of secretion, derive the fluid necessary for that process. (3) The lymphatics have the general func- tion of collecting the fluid which saturates the tissues, and carrying it back again to the blood. The capillary blood system may be regarded as an irrigation system, which supplies the tissues with nutrient fluids, while the lymphatic system may be regarded as a drainage apparatus, which. conducts away the fluids that have transuded through the capillary walls. Some of the decomposition products of the tissues — proofs of their retrogressive metabolism — become mixed with the lymph stream, so that the lymphatics are, at the same time, absorbing vessels. Substances introduced into the parenchyma of the tissues in other ways — e.g., by subcutaneous injection — are partly absorbed by the lymphatics. A study of these conditions shows that the lymphatic system represents an appendix of the blood- vascular system, and, further, that there can be no lymph system when the blood stream is completely arrested ; it acts only as a part of the whole, and with the whole. Lacteals. — When we speak of the lymphatics proper as against the chyle ves- sels or lacteals, we do so from anatomical reasons, because the important and con- siderable lymphatic channels coming from the whole of the intestinal tract are, in a certain sense, a fairly independent province of the lymphatic vascular area, and are endowed with a high absorptive activity, which, from ancient times, has attracted the notice of observers. The contents of the chyle vessels or lacteals are mi.xed with a large amount of fatty granules, giving the chyle a white color, which distinguishes them at once from the clear, watery contents of the true lymphatics. From a physiological point of view, however, the lacteals must be classified with the lymphatics, for, as regards their structure and function, they are true lymphatics, and their contents consist of true lymph mixed with a large amount of absorbed substances, chiefly fatty granules. [The contents of the lac- teals are white only during digestion, at other times they are clear, like lymph.] 196. ORIGIN OF THE LYMPHATICS.— The mode of origin of the lymphatics varies within the different tissues. The following modes are known : — I. Origin in Spaces. — Within the connective tissues (connective tissue proper, bone) are numerous stellate, irregular, or branched spaces, which communicate with each other by numerous tubular processes (Fig. 204, s) ; in these communicating spaces lie the cellular elements of these tissues. These spaces, however, are not completely filled by the cells, but an interval exists be- tween the body of the cell and the \\'all of the space, which is greater or less according to the con- dition of movement of the protoplasmic cell. These spaces are the so-called "juice canals " or " saft canalchen," and they represent the origin of the lymphatic vessels {v. Recklinghausen). As they communicate with neighboring spaces, the movement of the lymph is provided for. The cells which lie in the spaces, and which were formerly but erroneously regarded by Virchow as the ori- gins of the lymphatics, exhibit amceboid movements. Some of these cells remain permanently each in its own space, within which, however, it may change its fomr — these are the so-called " fixed " connective-tissue corpuscles, and bone corpuscles — while others merely \a ander or pass into these spaces, and are called "wandering cells," or "leucocytes ;" but the latter .are merely lymph cor- puscles, or colorless blood corpuscles which have passed out of the blood vessels into the origin of ORIGIN OF THE LYMPHATICS. 333 the lymphatics. These cells exhibit amoeboid movements. These spaces communicate %vith the small tubular lymphatics — the so-called lymph capillaries (L). The spaces lie close together where they pass into a lymph capillary (a). The lymph capillary, which is usually of greater diameter than the blood capillary, generally lies in the middle of the space within the capillary arch (B). The finest lymphatics are lined by a layer of delicate, nucleated endothelial cells (c,^), with characteristic sinuous margins, whose characters are easily revealed by the action of silver nitrate (Fig. 205, L). This substance blackens the cement substance which holds the endothelial cells together. Be- tween the endothelial cells are small holes, or stomata, by means of which the lymph capillaries communicate (at j) with the juice canals. It is assumed that the blood vessels communicate with the juice canals (J. Ar- nold, Thoma, Uskoff), and that fluid passes out of the thin-walled capillaries, through their stomata, into these spaces (§ 65). This fluid nourishes the tissues, the tissues take up the substances appropriate to each, while the effete materials pass back into the spaces, and from these reach the lymphatics, which ultimately discharge them into the venous blood. Whether the cells within these spaces are actively concerned in the pouring out of the blood Fig. 204. Origin of lymphatics from the central tendon of the diaphragm of a rahbit (semi-diagrammatic) ; f, the juice canals, communicating at x with the lymphatics : a, origin of the lymphatics by the confluence of several juice canals. The tissue has been stained witli nitrate of silver. plasma, or take part in its movement, is matter for conjecture. We can imagine that by contracting their body, after it has been impregnated with fluid, this fluid may be propelled from space to space toward the lymphatics. The leucocytes wander through these spaces until they pass into the lymphatics. Fine particles which are contained in these spaces — e.g., after tattooing the skin, and even fatty particles after inunction — are absorbed by the leucocytes, and carried by them to other parts of the body. [The pigment particles used to tattoo the finger are usually found within the first lymphatic gland at the elbow.] After what has been said regarding the passage of colorless blood corpuscles through the stomata of the blood capillaries, or through the walls of the smaller blood vessels (§ 95), the passage of cellular elements from the blood vessels into the origin of the lymphatics is to be considered as a normal process {E. Hering). Granular coloring matter passes from the blood into the protoplasmic body of the cells within the lymph spaces ; and only when the granular pigment is in large amount, does it appear as a granular injection in the branches of the juice spaces (^Uskoff). 334 PERIVASCULAR SPACES. (2) The origin of lymphatics within villi — /. e., of the chyle vessel or lacteal — has been de- scribed [\ 190). The central lacteal communicates with the lacunar interstitial spaces in the ade- noid tissue of the villus, and this again with the protoplasmic body of the epithelial cells. It is assumed that the lymph corpuscles, which lie in the meshes of the adenoid tissue, pass into the Fig. 205. Central tendon of the diaphragm of the lymphatic with its sinuous endothel ewed from the pleural side brought into view by the ; central lacteal {His), while new cells are continually passing out of the blood capillaries of the villi into the tissue, where they perhaps undergo increase through division. (3) Origin of lymphatics in perivascular spaces (Fig. 206). — The smallest blood vessels of bone, the central nervous system, retina, and the liver, are completely surrounded by wide lymph- FlG. 207. Perivascular lymphatics. A, aorta of tortoise ; B, artery from the brain. atic tubes, so that the blood vessels are completely bathed by a lymph stream. In the brain these lymphatics are partly composed of delicate connective-tissue fibres, which traverse the lymph space and become attached to the wall of the included blood vessel (Roth). Fig. 206, B, represents a transverse section of a small blood vessel, B, from the brain; / is the divided perivascular space. LYMPH FOLLICLES. 335 This space is called the perivascular space of His, but in addition to it the blood vessels of the brain have a lymph space within the adventitia of the blood vessels ( Virchom- Robin' s space). It is partly lined by a well defined endothelium. Where the blood vessels begin to increase considerably in diameter, they pass through the wall of the lymphatics, and the two vessels afterward take sepa- rate courses. In all cases, where there is a perivascular space, the passage of lymph and blood corpuscles into the lymphatics is greatly facilitated. In the tortoise the large blood vessels are often surrounded with perivascular lymphatics. Fig. 206, A, gives a representation of the aorta sur- rounded by a perivascular space ( Gegenbaur) which is visible to the unaided eye. In mammals the perivascular spaces are microscopic. (4) Origin in the form of interstitial slits within organs. — Within the testis the lymphatics begin simply in the form of numerous slits, which occur between the coils and twists of the seminal tubules. They take the form of elongated spaces bounded by the curved cylindrical surfaces of the tubules. The surfaces, however, are covered with endothelium. The lymphatics of the testis get independent walls after they leave the parenchyma of the organ. In many other glands the gland substance is similarly surrounded by a lymph space. The blood vessels pour the lymph into these spaces, and from them the secreting cells obtain the materials necessary for the formation of their secretion. (5) Origin by means of free stomata on the walls of the larger serous cavities (Fig. 207, a). — The investigations of v. Recklinghausen, Ludwig, Dybkowsky, Schweigger-Seidel, Dogiel, and others have shown that the old view of Mascagni, that the serous cavities freely communicate with the lymphatics, is correct. The investigation of the serous surfaces is most easily accomplished on the septum of the great abdominal lymph sack of the frog. Silver nitrate distinctly reveals the presence of relatively large free openings or stomata lying between the endothelium. Each stoma Two lymph follicles. A, ; small follicle highly magnified, showing the adenoid r magnified, showing injected blood vessels. B, a follicle less highly is bounded bv several germinating cells, which have a granular appearance, and undergo a change of shape, so that the size of the stoma depends upon the degree of contraction of these cells ; thus the stoma maybe open (o), half open, (i>),or completely closed (c). These stomata are the origin of the lymphatics. The serous cavities belong therefore to tlie lymphatic sy»tem,and fluids placed in the serous cavities readily pass into the lymphatics. The cavities of the peritoneum, pleura, peri- cardium, tunica vaginalis testis, arachnoid space, aqueous chambers of the eye (Sc/iwa/be), and the labyrinth of the ear, are true lymph cavities, and the fluid they contain is to be regarded as lymph. (6) Free open pores have been observed on some n27icoiis membranes^which are regarded as the origin of lymphatics, e. g., in the bronchi (Klein) — the nasal mucous membrane [Njalmar-Neiberg), in the trachea and larynx. Structure. — The larger lymphatics resemble in structure the veins of corresponding size. The valves are particularly numerous in the lymphatics, so that a distended lymphatic resembUs a chain of pearls. [Lymphatics have dilatations here and there in their course (Fig. 205).] 197. LYMPH GLANDS.— The so-called lymphatic glands belong to the lymph apparatus. They are incorrectly terined glands, as they are merely much branched lacunar labyrinthine spaces composed of adenoid tissue, and inter- calated in the course of the lymphatic vessels. They are simple and compound lymph glands. (1) The simple lymph glands, or, more correctly, lymph follicles, are small, rounded bodies, about the size of a pin head. They consist of a mass of ailenoid tissue (Fig. 208, A), ;'. c, of a very delicate network of fine recticular fibres with nuclei at their points of intersection, and in the 336 LYMPHATIC GLANDS. spaces of the meshwork lie the lymph and the lymph corpuscles. Near the surface, the tissue is somewhat denser, where it forms a capsule, which is not however a true capsule, as it is permeated with numerous small, sponge-like spaces. Small lymphatics come directly into contact with these lymph follicles, and often cover their surface in the form of a close network. The surface of the lymph follicles is not unfrequently placed in the wall of a lymph vessel, so that it is directly bathed by the lymph stream. Although no direct canal like opening leads from the follicle into the lymphatic stream in relation with it, a communication must exist, and this is obtained by the numer- ous spaces in the follicle itself, so that a lymph follicle is a true lymphatic apparatus whose juices and lymph corpuscles can pass into the nearest lymphatic (Briukc). The follicles are surrounded by a network of blood vessels which send loops of capillaries into their interior (Fig. 208, B). We may assume that lymph corpuscles pass from these capillaries into the follicle. In connection with these follicles, including those of the back of the tongue, the solitary glands of the intestine and the adenoid tissue in the bronchial tract, the tonsils, Peyer's patches, it is import- ant to remember that enormous numbers of leucocytes pass out between the epithelial cells cover- ing these follicles. The extruded leucocytes undergo disintegration subsequently (PJi. Stdhr). (2) The compound lymph glands — the so-called lymphatic glands— represent a collection of lymph follicles, whose form is somewhat altered. Every lympli gland is covered externally with a connective-tissue capsule (Fig. 209, c), which contains numerous non-striped muscular fibres (O. Heyfelder). From its inner surface, numerous septa and trabeculae (tr) pass into the interior of the gland, so that the gland substance is divided into a large number of compartments. These com- FiG. 209. , lymph s , /, efferent lymphatics ; C, cortical substance ; M , capsule, with trabecule, tr. {Sharpey) partments in the cortical portion of the gland have a somewhat rounded form, and constitute the alveoli, while in the medullary portion they have a more elongated and irregular form. [On making a section of a lymph gland we can readily distinguish the cortical from the medullary portion of the gland.] All the compartments are of equal dignity, and they all communicate with each other by means of openings, so that the septa bound a rich network of spaces within the gland, which communicate on all sides with each other. These spaces are traversed by the follicular threads (Fig. 2\o,f,f). These represent the contents of the spaces, but they are smaller than the spaces in which they lie, and do not come into contact anywhere with the walls of the spaces. If we imagine the spaces to be injected with a mass, which ultimately shrinks to one-half of its original volume, we obtain a conception of the relation of these follicular threads to the spaces of the gland. The blood vessels of the gland {l>) lie within these follicular threads. They are surrounded by a tolerably thick crust of adenoid tissue, with very fine meshes (x, x) filled with lymph corpuscles, and with its surface (0, 0) covered by the cells of the adenoid reticulum, in such a way as to leave free communications through the narrow meshes. Between the surface of the follicular threads and the inner wall of all the spaces of the gland, lies the lymph channel or lymph path 1 B, B), which is traversed by a reticulum of adenoid tissue, containing relatively few lymph corpuscles. It is very probable that these lymph paths are lined by endothelium (v. Recklinghausen). The vasa afferentia (Fig. 209, n, /), of which there are usually several, expand upon the surface LYMPHATIC GLANDS. 337 of the gland, perforate the outer capsule, and pour their contents into the lymph paths (C) of the gland. The vasa efferentia, which are less numerous than the afiTerentia, and come out at the hilum, form large, wide, almost cavernous dilatations, and they anastomose near the gland (c,/). Through them the lymph passes out at the opposite surface of the gland. The lymph percolates through the gland, and passes along the lymph paths, which represent a kind of rete mirabile inter- posed between the afferent and efferent lymph vessels. During its passage through this complicated branched system of spaces, the movement of the lymph through the gland is retarded, and, owing to the numerous resistances which occur in its path, it has very little propulsive energy. The lymph corpuscles which lie in the meshes of the adenoid reticulum are washed out of the gland by the lymph stream (Briicke). The lymph cor- puscles lying within the follicular threads pass through the narrow meshes (O) into the lymph paths. The formation of lymph corpuscles occurs either locally, from division of the pre-existing cells, or new leucocytes wander out into the follicular threads. The movement of the lymph Part of a lymphatic gland. A, Vas afferens; B, B. lymph paths within the gla edge : y,y, follicular strand from the medulla; x,x,\is adenoid reticulun meshed part limiting the follicular strands from the lymph path. througl the gland is favored by the muscular action of the capsule. When the capsule contracts energetically, it must compress the glard like a sponge, and the direction in which the fluid moves is regulated by the position and arrangement of the valves. The researches of Teichmann, His, Frey, Ilriicke and v. Recklinghausen have chiefly contributed to the elucidation of the morpho- logical and physiological relations of the lymph glands. Chemistry. — In addition to the constituents of lymph, the following chemical substances have been fjund in lymphatic glands: Leucin (Frericlis and Stddeler) and Xanthin. 193. PROPERTIES OF CHYLE AND LYMPH.— Chyle and Lymph are albuniinous, colorless, clear juices, containing lymph corpuscles, which are identical with the colorless blood corpuscles (S 9). In some places, e.g.- in the Ij'mphatics of the spleen, especially in starving animals (^Nasse), and 338 COMPOSITION OF CHYLE. in the thoracic duct, a few colored blood corpuscles have been found. The lymph corpuscles are supplied to the lymph and chyle from the lymphatic glands and the adenoid tissue. As to their source see § 200, 2. They also pass out of the blood vessels and wander into the lymphatics. As red blood corpuscles have also been seen to pass out of the blood vessels {^Slricker, J. Arnold), this explains the occasional presence of these corpuscles in some lymphatics; but when the pressure within the veins is high near the ireiUra/ orifice of the thoracic duct, red blood corpuscles may pass into the thoracic duct. But we are not entitled to con- clude from their pressure that lymph cells form red blood corpuscles. In addi- tion, the chyle contains numerous fatty granules each surrounded with an albu- minous envelope. [Thus the chyle, m addition to the constituents of the lymph, contains, especially during digestion, a very large amount of fat, in the form of the finely emulsionized fat of the food, which gives it its characteristic w/ii/t' or milky appearance. During hunger, the fluid in the lacteals resembles ordinary lymph. The fine fat granules constitute the so-called "molecular basis" of the chyle.] Composition of Lymph. — The lymph consists of a plasma with lymph corpuscles suspended in it. The corpuscles — for the most part investigated in the form oi pus cells — consist of a swollen-up /ra/c'/f/ and soluble paraglobulin, together with lecithin, cerebri)!, cholesterin a.nd/i7l, while their nuclei }ield nuclein. Nuclein contains P, and is prepared by the artificial digestion of pus, as it alone remains undigested ; it is soluble in alkalies, and is precipitated from this solution by acids. It gives a feeble xanthoproteic reaction. When subjected to the pro- longed action of alkalies and acids, it yields substances allied to albumin and syntonin. Miescher found glycogen in the lymph corpuscles of serous fluids (§ 24). The lymph plasma contains the three so-called fibrin factors (§ 29), derived very probably from the breaking up of lymph corpuscles. When lymph is withdrawn from the body, these substances cause it to coagulate. Coagula- tion occurs slowly, owing to the formation of a soft, jelly-like, small "lymph clot," which contains most of the lymph corpuscles. The exuded fluid or lymph serum contains alkali albuminate (precipitated by acids), serum albumin (coagulated by heat), ^.wd paraglobulin- — the two latter occurring in the same pro- portion as in blood serum ; 37 per cent, of the coagulable proteids is paraglobu- lin iSalvioli). Peptone has been found in chyle (? and perhaps also in lymph) ; also urea ( Il'urtz), leucin and sugar. (2) Chyle, which occurs within the lacteals of the intestinal tract, can only be obtained in very small amount before it is mixed with lymph, and hence the difficulty of investigating it. A few lymph corpuscles occur even in the origin of lacteals within the villi, but their number increases in the vessels beyond the intestine, more especially after the chyle has passed through the mesenteric glands. The amount of solids which undergoes a great increase during digestion, on the contrary, diminishes when chyle mixes with lymph. After a diet rich in fatty matters, the chyle contains innumerable /«//)' ^iJ7-(?««/« (2-4 /JL in size). [This is the so-called "molecular basis" of the chyle.] The amount of fibrin factors increases with the increase of lymph corpuscles, as they are formed from the breaking up of the lymph corpuscles. Grohe found a iliastatic ferment in chyle, which was probably absorbed from the intestine, occasionally sugar, to 2 per cent. i^Colin); after much starchy food, lactates have been found {Lehmann), peptone in the leucocytes (§ 192, I, 3), and traces of urea and leucin {JVurts). The Chyle of a person who was executed contained : — Water 90.5 per cent. Solids 95 " f Fibrin trace. j Albumin 7.1 ■j Fats 0.9 Extractives I.o [ Salts 0.4 QUANTITY OF LYMPH AND CHYLE. 339 Cl. Schmidt found the following inorganic substances in looo parts of chyle (horse) : — Sodic chloride .... 5.84 I Sulphuric acid .... 0.05 I Magnesic phosphate . . 0.05 Soda 1. 1 7 Phosphoric acid . . . .0.05 Iron trace. Potash 0.13 I Calcic pho.sphate . . .0.20 | (3) The lymph obtained from the beginning of the lymphatic .system also contains very few lymph corpuscles ; it is clear, transparent and colorless, and closely resembles the fluids of serous cavities. That the lymph coming from dif- ferent tissues varies somewhat, is highly probable, but this has not been proved. After lymph has passed through lymphatic glands, it contains more corpuscles, and also more solids, especially albumin and fat. Ritter counted 8200 lymph corpuscles in one cubic centimetre of the lymph of a dog. Hensen and Diihnhardt obtained pure lymph in considerable quantity from a lymphatic fistula in the leg of a man. It had an alkaline reaction and a saline taste. It had the following composition, which may be cornpared with the com- position of serous transudations: — Cerebro-spinal Fluid (Hoppe-Seyler). Water 98.63 Solids 1.37 Fibrin o.ii Albumin 0.14 Alkali albuminate .... 0.09 Extractives Urea, Leucin 1.05 Salts 0.88 70V0I.J4 of CO,, 50% of which could be pumped out, and 20 fc by the addition of an acid. 9S.74 '•25 The cerebro-spinal fluid and ab- dominal lymph contain a kind of sugar (without the property of rotat- ing polarized light — 'Hoppe-Seyter). Pericardial Fluid, (z*. Gorup-Besanez) 9551 4.48 0.08 2.46 1.26 100 parts of the Ash of Lymph contained the following substances: — Sodium chloride . . . 74.48 Soda 10.36 Potash 3.26 Lime 0.98 Magnesia 0.27 Phosphoric acid ... 1 .09 Sulphuric acid 1.28 Carbonic acid S.21 Iron oxide 0.06 Just as in blood, potash and phosphoric acid are most abundant in the corpuscles, while soda (chiefly sodium chloride) is most abundant in the lymph serum. The potash and phosphoric acid compounds are most abundant 111 cerebro-spinal fluid, according to C. Schmidt. The amount of icater in the lymph rises and falls with that of the blood. Gases. — Dog's lymph contains much COj — more than 40 vols, per cent., of which 17 per cent, can be pumped out, and 23 per cent, expelled by acids, while there are only traces of O and 1.2 vols, per cent. N {Ludwig, Hammersten). The observation that when lymph is collected from large vessels and exposed to the air, it becomes red [Funke), is, as yet, unexplained ; but it is certainly not due to the formation of colored corpus- cles from colorless ones, owing to contact with the (.1 of the air. 199. QUANTITY OF LYMPH AND CHYLE.— When it is stated that the total amount of the lymph and chyle passing through the large vessels in twenty-four hours is equal to the amount of the blood (^Bidder and C. Schmidt), it must be remembered that this is merely a conjecture. Of this amount one-half may be lymph and the other half chyle. The formation of lymph in the tissues takes place continually, and without interruption. Nearly 6 kilos, of lymph were collected in twenty-four hours from a lymphatic fistula in the arm of a woman, by Gubler and Quevenne ; 70 to 100 grms. were collected in i^4 to 2 hours from the large lymph trunk in the neck of a young horse. The following conditions affect tlie amount of chyle and lymph : — 340 ORIGIN OF LYMPH. (i) The amount of chyle undergoes very considerable increase during diges- tion, more especially after a full meal, so that the lacteals of the mesentery and intestine are distended with white or milky chyle. During hunger, the lymph vessels are collapsed, so that it is difficult to see the large trunks. ( 2) The amount of blood iiicirases with the activity of the organ from which it proceeds. Active or passive muscular movements greatly increase its amount. Lesser obtained in this way 300 cubic centimetres of lymph from a fasting dog, whereby its blood became so inspissated as to cause death. (3) All conditions which increase the pressure upon the juices of the tissues increase the amount of lymph, and vice versa. These conditions are : — (a) An increase of the blood pressure, not only in the whole vascular system, but also in the vessels of the corresponding organ, augments tlie amount of lymph and vice versa {Luiiwig, Tomsa). This, however, is doubtful, as has been shown by Paschutin and Emminghaus. [In order to increase the amount of lymph depending upon pressure within the vessels, what must happen is increased pressure within the capillaries and veins.] (/') Ligature or obstruction of the efferent veins greatly increases the amount of lymph which flows from the corresponding parts (Bidder, Kmminjrhaus). It may be doubled in amount ( ll'eiss). Tight bandages cause a swelling of the pans on the peripheral side of the bandage, owing to a copious effusion of lymph into the tissue (congestive oedema). [c] An increased supply of arterial blood acts in the same way, but to a less degree. Paralysis of the vasomotor nerves (/,«. Wittic/i). Strychnia accelerates their movements (Scherhcj), and so does heating of the spin.al cord, but if the cord be cooled they are retarded (Fubiiii and Spalitta). A lymph heart arrested by being exposed, or after the action of muscarin, can be caused to beat by filling it under pressure, but this is not the case when the arrest is caused by destruction of its nerves (Boll, Lan- gerdorff). Antiarin paralyzes the lymph heart and the blood heart at the same time ( Vintschgau), while curara paralyzes the former alone (Bidder). In other ani|)hibians, there are two lymph hearts; in the ostrich and cassowary and some swimming birds (Panizza),3.nd in the embryo chick [A. Budge) I or 2. They occur in some fishes, e. g., near the caudal vein of the eel. (7) The nervous system has a direct effect upon the lymph stream) on account of its connection with the muscles of the lymphatics and lymph glands, and with the lymph hearts, where these exist. Further, Kiihne observed that the cornea corpuscles contracted when the corneal nerves were stimulated. Goltz also observed that when a dilute solution of common salt was injected under the skin of a frog, it was rapidly absorbed, but if the central nervous system was destroyed it was not absorbed. If inflammation be produced in the posterior extremities of a dog, and if the sciatic nerve be divided on one side, cedema and a simultaneous increase of the lymph stream occur on that .side (Jankozi'ski). [A combination of congestion and inflammation greatly increases the lymph stream, and this is still more the case when the nerves are divided at the same time.] Ligature the leg of a frog, except the nerves, so as to arrest the circulation, and place the leg in water ; it swells up very rapidly, but a dead limb does not swell up. So that absorption is inde- pendent of the continuance of the circulation. Section of the sciatic nerve, or destruction of the spinal cord (but not section of the brain), arrests absorption (Laii/cn/iack). 202. ABSORPTION OF PARENCHYMATOUS EFFUSIONS.— Fluids which pass from the blood vessels into the spaces in the tissues, or those injected subcutaneously, are absorbed chiefly by the blood vessels, but also by the lymphatics. Small particles, as after tattooing with cin- nabar or China ink, may pass from the tissue spaces into the lymplvitics — and so do blood cor- puscles from extravasations of blood, and fat granules from the marrow of a broken bone. If all the lymphatics of a part are ligatured, absorption takes place quite as rapidly as before (Magendie) ; hence, .ibsorbed fluid must pass through the thin membranes of the blood vessels. The correspond- ing experiment of ligaturing all the blood vessels, when no absorption of the parenchymatous juices taiies place (Emmerl, Henle, v. Diisc/i), does not prove that the lymphatics are not concerned in absorption, for, alter ligaturing the blood vessels of a part, of course, the formation of lymph, and also the lymph stream, must cease. When fluids are injected under the skin absorption takes place very rapidly — ^more rapidly than when the substance is given by the mouth. The subcutaneous injection of many drugs is now extensively used, but, of course, the substances used must not corrode, irritate, or coagulate the tissues. Some substances do not act when given by the mouth, as snake poison, poisons from dead bodies, or putrid things, altliough they act rapidly when introduced subcutaneously. If emulsin be given by the mouth, and amygdalin be injected into the veins of an animal, hydro- cyanic acid is not formed, as the emulsin seems to be destroyed in the alimentary canal. If the emulsin, however, be injected into the blood, and the amygdalin be given by the mouth, the animal is rapidly poisoned, owing to the formation of hydrocyanic acid, as the amygdalin is rapidly absorbed from the intestinal canal. The amygdalin, a glucoside (CjdH,-NOi ,), is acted upon by fresh emulsin like a ferment ; it takes up 21 Hot)) ^"iid poured out varies according to the rapidity with which this occurs. In acute inflamma- tion, effusion or exudation takes place rapidly, and the fluid contains the fibrin factors, so that it tends to coagulate spontaneously. There is every gradation between the non-coagulable hydrocele fluid and the coagulable exudation in inflammation. The fluids in different dropsies vary in com- 346 COMPARATIVE AND HISTORICAL. position, and some have more cells in them, depending on local causes, as in some situations absorp- tion is more active than in others (James). The pleural fluid contains most solids, then ascitic, cerebrospinal, and, lastly, that in the subcutaneous tissue.] [(4) Ostroumoff found that stimulation of the lingual nerve not only causes the blood vessels of the tongue to dilate, but the corresponding side of the tongue becomes cedematous. If a solution of dilute hydrochloric acid or quinine (^ 145) be injected into the duct of the submaxillary gland, and the chorda tynipani stimulated, there is no secretion of saliva, but the gland becomes cedema- tous. In an animal poisoned with atropin, stimulation of the chorda causes dilatation of the blood vessels, although there is no secretion of saliva ; nevertheless, the gland does not become cedema- tous (Heidenhain). As Brunton suggests, this experiment points to some action of atropin on the blood vessels which has, hitherto, been entirely overlooked.] 204. COMPARATIVE PHYSIOLOGY.— In the frog large lymph sacs, lined with endo- thelium, exist under the skin, while large lymph sacs lie in relation with the vertebral column — one on each side — separated from the abdominal cavity by a thin membrane, perforated with stomata. This is the cysterna lymphatica magna of Panizzi. Some amphibians, and many reptiles, have large lymph spaces under the skin, which occupy the whole of the dorsal region of the body. All reptiles and the tailed amphibians have large elongated reservoirs for lymph along the course of the aorta. The lymph apparatus of the tortoise (Fig. 206) is very extensive. The osseous fishes have in the lateral parts of their backs an elongated lymph trunk, which reaches from the tail to the anterior fins, and is connected with the dilated lymphatic rootlets in the base of the tail and in the fins. The largest internal lymph sinus is in the region of the (esophagus. Many birds possess a sinus-like dilatation or lymph space in the region of the tail. The lymph spaces communicate with the venous system — with valves properly arranged — usually in connection with the upper vena cava. Lymph hearts have already been referred to (^ 20[, 6). In carnivora the lymph glands of the mesentery are united into one large, compact mass, the so-called " pancreas Asellii." 205. HISTORICAL. — Although the Hippocratic School was acquainted with the lymph glands, from their becoming swollen from time to time, and although Herophilus and Erasistratus had seen the mesenteric glands, yet Aselli (1662) was the first who accurately described the lacteals of the mesentery with their valves. Pecquet (1648) discovered the receptaculum chyli; Rudbeck and Thorn. Bartholinus, the lymphatic vessels (1650-52) ; Eustachius (1563) was acquainted with the thoracic duct, which Gassendus (1654) maintained that he was the first to see; Lister noticed that the chyle became blue when indigo was injected into the intestine (167 1) ; Sommering observed the separation of fibrin when lymph coagulated; Reuss and Emmert discovered the lymph corpus- cles. The chemical investigations date from the first quarter of this century ; they were carried out by Lassaigne, Tiedemann, Gmelin and others. The last two observers noticed that the white color of chyle was due to the presence of small, fatty granules. Physiology of Animal Heat. 206. SOURCES OF HEAT.— Heat.— The heat of the body is an unin- terrupted evolution of kinetic energy, which we must represent to ourselves as due to vibrations of the corporeal atoms. The ultimate sou7-ce of the heat is contained in the potential energy taken into the body with the food, and with the O of the air absorbed during respiration. The (7otot/«/ of heat formed depends upon the amount of energy liberated (see Introduction). The energy of the food stuffs may be called " latent heat," if we assume that when they are used up in the body — chiefly by a process of combustion — kinetic Water calorimeter of Favre and Silberm.inii. energy is liberated only in the form of heat. As a matter of fact, however, mechanical energy and electrical energy are developed from the potential energy. In order to obtain a unit measure for the energy liberated, it is advisable to ex- press all the potential energy as heat units. The Calorimeter.— This instrument enables us to transform the jiotential energy of the food into heat, and, at the same time, to measure the number of heat units produced. 347 348 CHEMICAL SOURCES OF HEAT. Favre and Silbermann used a water calorimeter (Fig. 214). The substance to be burned is placed in a large cylindrical combustion chamber (K), suspended in a large cylindrical vessel (L) filled with water (-n'), so that the combustion chamber is completely surrounded by the water. Three tubes open into the upper part of the chamber; one of them lO) supplies the a r which is necessary for ombustion ; it reaches almost to the bottom of the chamber; the second tube (^71 is lixed in the middle of the lid, and is closed above with a thick glass plate, and on this is placed, at an angle, a small mirror (j), which enables an observer to see into the interior of the chamber, and to observe the process of combustion at c. The third tube ((/) is used only when combustible gases are to be burned in the chamber. It can be closed by means of a stop-cock. A lead tube (»-, e) with many twists on it, passes from the upper part of the ciiamber through the water, and finally opens at ^. The gaseous products of combustion pass out through this tube, and in doing so help to heat the water. The cylindrical vessel with the water is closed with a lid which transmits tlie four tubes. The w.iter cylinder stands on four feet within a large cylinder (M). which is filled with some good non-conductor of heat, and this again is placed in a large vessel filled with water (W). This is to prevent any heat reaching the inner cylinder from without. A weighed quantity of the substance (c) to be investigated, is placed in the combustion chamber. When combustion is ended, during which the inner water must be repeatedly stirred, the temperature of the water is ascertained by means of a delicate thermometer. If the increase of the temperature and the amount of water are known, then it is easy to calculate the number of heat units produced by the combustion of a known weight of the substance (see Introduction). The ice calorimeter may also be used. The inner cylinder is filled with ice and not with water, and ice is also placed in the outer cylinder, to prevent any heat from without from acting upon the inner ice. The heat given off from the combustion chamber causes a certain amount of the ice to melt, and the water thereby produced is collected and measured. It requires 79 heat units to melt I grm. of ice to i grm. of water at 0° C. Just as in a calorimeter, although much more slowly, the food stuffs within our body are burned up, oxygen being supplied, and thus potential energy is trans- formed into kinetic energy, which in the case of a person at res/, i. e., when the muscles are inactive, almost completely appears in the form of heat (see Introduc- tion). Heat Units. — Favre, Silbermann, Frankland, Rechenberg, B. Danilewsky. and others have made calorimetric experiments on the heat produced by food. Thus, I gramme of the following dry substances yields heat units : — Peptone . . . 4914 Glutin . . . 5493 Chondrin . . 4909 Flesh extract (Liebig) . .3216 As albumin is only oxidized to the stage of urea, we must deduct the heat units obtainable from urea from those of albumin, and as i part of albumin yields in round numbers about \ of urea, we pbtain about 5100 calories [^= 2170 kilogram metres] for I grm. of albumin. Isodynamic foods, i. e., those that produce a similar amount of heat ; 100 grms. animal albumin (after deducting the heat units of urea) ^= 52 fat, ^114 starch = 129 dextrose ; 100 grms. of vege- table albumin := 55 fat, = 121 starch ^ 137 dextrose (Dani/e-u'sky\. Rubner calculated that in man, with a mixed diet, the avai/able heat units for I grm. of albumin r^4IOO; I grm. fat = 9300 ; and for I grm. carbohydrate ^4100 calories. When we know the weight of any of the above-named substances consumed by a man in twenty-four hours, a simple calculation enables us to determine how many heat units are formed in the body by oxidation, /. e., provided the substance is completely oxidized. Sources of Heat. — The individual sources of heat are to be found in the following : — (i) In the transformation of the chemical constituents of the food, endowed with a large amount of potential energy, into such substances as have little or no energy. The organic substances used as food consist of C, H, O, N, so that there takes place — {a) Combustion of C into CO.j, of H into H.X), whereby heat is pro- duced ; I grm. C burned to produce COj yields 80S0 heat units, while i grm. H oxidized to H^O yields 34,460 heat units. The O necessary for these purposes is absorbed during respiration, so that, to a certain extent at least, the amount of Casein . . . 578s Alcohol . . 8958 Grape sugar . 3939 Potatoes . . . 3752 Stearin . • 9036 Cane sugar 4173 Milk . . . . 5093 Palmitin . . 8883 Milk sugar . . 4162 Bread . . . • 3984 Olein . . . 8958 Vegetable fibrir 6231 pice . . . . 3813 Glycerin . . 4t79 Glutin . . . 6141 Starch . . . . 4479 Leucin . . 6141 Legumin . . 5573 Velk of egg . 6460 Creatin . . 4118 Blood fibrin . 5709 PHYSICAL SOURCES OF HEAT. 349 heat produced may be estimated from the amount of O consumed. The same consumption of O gives rise to the same amount of heat whether it is used to oxidize H or C (Pfli/ger). There is a relation, amounting to cause and effect, between the amount of heat produced in the body and the O consumed. The cold-blooded animals, which consume little O, have a low temperature ; among warm-blooded animals, i kilo, of a living rabbit takes up within a hour 0.914 grm. O, and its body is heated to a mean of 38° C. i kilo of a living fowl uses i.i85 grms. O, and gives a mean temperature of 43.9° C. (Rcgnaiilt and Reiset). The amount of heat produced is the same whether the combustion occurs slowly or quickly; the rapidity of the metabolism, therefore, affects the rapidity, but not the absolute amount of heat production. The combustion of inorganic substances in the body, such as the sulphur into sulphuric acid, the phosphorus into phosphoric acid, is another, although very small, source of heat. (^) In addition to the processes of combustion or oxidation, all those chemical processes in our body, by which the amount of the available potential energy which is present is diminished, in consequence of a greater satisfaction of atomic affinities, lead to the production of heat. In all cases where atoms assume more stable positions with their affinities satisfied, chemical energy passes into kinetic thermal energy, as in the alcoholic fermentation of grape sugar, and other similar processes. Heat is .-ilso developed during the following chemical processes : — («) During the union of bases with acids {Andrews). The nature of the base determines the amount of heat produced, while the nature of the acid is without effect. Only in those cases where the acid, e.g., COj, is unable to set aside the alkaline reaction, the amount of heat produced is less. The formation of compounds of chlorine {e.g., in the stomach) produces heat. {b) When a neutral salt is changed into a basic one {AnJrcujs). In the blood the sulphuric and phosphoric acids derived from the combustion of S and P are united with the alkalies of the blood to form basic salts. The decomposition of the carbonates of ihe blood by lactic and phosphoric acids forms a double source of heat, on the one hand, by the formation of a new salt, as well as by the liberation of CO,, which is partly absorbed by the blood. (f) The combination of haemogloiJin with O (j 36). In connection with those chemical processes, whereby the heat of the body is produced, heat-absorbing intermediate compounds are not unfrequently formed. Thus, in order that the final stage of more complete saturation of the affinities be reached, intermediary atomic groups are formed, whereby heat is absorbed. Heat is also absorbed when the solid aggregate condition is dissolved during retrogres- sive processes. But these intermediary processes, whereby heat is lost, are very small compared with the amount of heat liberated when the end products are formed. (2) Certain physical processes are a second source of heat : (a) The transformation of the kinetic mechanical energy of internal organs, when the work done is not transferred outside the body, produces heat. Thus the whole of the kinetic energy of the heart is changed into heat, owing to the obstructions which are opposed to the blood stream (S 93). The same is true of the mechanical energy evolved by many muscular viscera. The torsion of the costal cartilages, the friction of the current of air in the respiratory organs and the ingesta in the digestive tract, all yield heat. An CNcessively minute amount of the mechanical energy of the heart is transferred to surrounding bodies by the cardiac impulse and the superficial pulse beats, but this is infinitesimally small. During respiration, when the respiratory gases and other substances are expired, a very small amount of energy disappears externally, which does not become changed into heat. If we assume that the daily work of the circulation exceeds 86,cxx> kilogram metres, the heat evolved is equal to 204.000 calories, in twenty-four hours {\ 93), which is sufficient to raise the temperature of a person of medium size 2° C. (J?) When, owing to muscular activity, the body produces work which is trans- ferred to e.xternal objects, e. g., when a man ascends a tower or mountain, or throws a heavy weight, a portion of the kinetic energy passes into heat, owing to 350 HOMOIOTHERMAL AND POIKILOTIIERMAL ANIMALS. friction of the muscles, tendons, and the articular surfaces, as well as to the shock and pressure of the ends of the bones against each other. ((■) The electrical currents which occur in muscles, nerves, and glands very probably are changed into heat. The chemical processes which produce heat evolve electricity, which is also changed into heat. This source of heat, however, is very small. (li) Other processes are the formation of heat from the ahsorption of C0„ {Henry'), by the con- centration of water as it passes through membranes {^Regnault and Pouillet), in imbibition (A/at- teiicci, i8j4), formation of the solids, e. g., of chalk in the bones. After death, and in some patho- logical processes during life, the coagulation of blood ( Valentin, Schiffer) and the production of rigor mortis are sources of heat. 207. HOMOIOTHERMAL AND POIKILOTHERMAL ANI- MALS. — In place of tlie old classification of animals into " cold blooded " and " warm blooded," another basis of classification seems desirable, viz., the relation of the temperature of the body to the temperature of the surrounding medium. Bergmann introduced the word homoiothermal for the warm-blooded ani- mals (mammals and birds), because these anitnals can maintain a very uniform temperature, even although the surrounding temperature be subject to considerable variations. The so-called cold-blooded animals are called poikilothermal, because the temperature of their bodies rises or falls, within wide limits, with the heat of the surrounding medium. When homoiothermal animals are kept for a long time in a cold medium, their heat production is increased, and when they are kept for a long time in a warm medium it is diminished. Fordyce gave a proof of the nearly uniform temperature in man. .^ man remained ten minutes in an oven containing very dry hot air (\ 21S), and yet the temperature of the palm of his hand, mouth, and urine was increased only a few tenths of a degree. Becquerel and Brechet investigated the temperature of the human biceps (Ijy means of thermo-electric needles), when the arm had been one hour in ice, and yet the temperature of the muscular tissue was cooled only 0.2° C. The same muscle did not undergo any increase in temperature, or at most 0.2° C, when the man's arm was placed for a quarter of an hour in water at 42° C. If heat be rapidly abstracted (§ 225) or rapidly supplied (§ 221) to the body, so as to produce rapid variation of the temperature, life is endangered. Poikilothermal animals behave very differently ; the temperature of their bodies generally follows, although with considerable variations, the temperature of the surroundings. When the temperature of the surroundings is increased, the arnount of heat produced is increased, and when the surrounding temperature falls, the amount of heat evolved within the body also falls. The following table shows very clearly the characters of poikilothermal animals, e. g., frogs (Rana esculenta), which were placed in air and water of varying temperatures. The frogs were fixed to an iron .support, and immersed up to the mouth. The temperature was measured by means of a thermometer introduced through the mouth into the stomach. In Water. In Air. Temperature of the Temperature of Frog's Temperature of the TemperaUire of Frog's Water. Stomach. Stomach. 41.0° C. 38.0° c. 40.4° C. 31.7° c. 35-2 34-3 35.8 24.2 30.0 29.t> 27.4 19.7 23.0 22.6 19.8 15.6 "20.6 20.7 .6.4 14.6 "•S 12.9 14.7 10.2 5-9 8.0 6.2 7.6 2.8 5-3 5-9 8.6 THERMO-ELECTRIC MEASUREMENT OF HEAT. 351 Birds. T=mp. Thalassidroma . . . 40.30 Procellaria 40.S0 Goose 41-70 Sparrow .... | ^9'°^ Pigeon . . . 41.80-42.50 Turkey 42.70 Guinea fowl .... 43.90 ^-^ {^^ Crow 4l->7 [Temperature of Different Animals. Temp. Panther 38.90 Mouse 41 44-03 J7.8 ■Swallow Gull Mammals. Tiger 37.20 Horse . . . 36.80-37.50 Rat 38 80 Hare 37 80 Cat ... . 38.30-3S.90 Guinea pig .... 38.80 3740 Dog \ 39.00 39.60 Fig. 215. Dolphin 35.5 ( 37-30-40-00 Sheep ... J 39.50-40.00 ( 40.00-40.50 Ape 35.50 Guinea pig . . 35.76-38.00 Rabbit . . . 37.50-38.00 Ox 37-50- Ass 36.95 ( Gavarret and Rosenthal)^ Reptiles. — Snakes, lo°-i2°, but higher when incubating. Amphibians and fishes — °-S°~3° above the temperature of the surroundings. Arlhropoda — o.i°-5.8° above the surroundings. Bees in a hive, 30°-32°, and when swarming, 40°. The following animals have a temperature higher than the surrounding temperature : Cephalopods, 0.57°; molluscs, 0.46° ; echinoderms, 0.40° : medusae, 0.27 ; polyps, 0.21° C. 208. ESTIMATION OF TEMPERATURE— THERMOMETRY.— Thermometry. — liy using thermometric apparatus, we are enabled to obtain informa- tion regarding the degree of heat of the body to be investigated. For this purpose the following methods are employed : — (A) The Thermometer {^Galileo, 1603). — Sanctorius made the first thermometric observations on man (1626). Celsius (1701-1744) divided his thermometer into 100 part*, and each part was again divided into 10 parts, so that ^5° C. could be easily read off. All thermometers which have been used for a long time give too high read- ings [Bellani), hence they should be compared, from time to time, with a normal thermometer. When taking the temperature, the bulbs ought to be surrounded for fif- teen minutes, and during the last five minutes the mercury column ought not to vary. A very sensitive therinometer will indicate the temperature after seven seconds if the urine stream be directed upon its bulb (Oertmann). Minimal and Maximal ther- mometers are often of use to the physician. Walferdin's metastatic thermometer (Fig. 215) is specially useful for compara- tive observation. The tube is very narrow in comparison with the bulb, and in order that the stem be not too long, it is constructed so that the amount of mercury can be varied. A quantity of mercury is taken, so that with the temperature expected the thread of mercury will stand about the middle of the Stem. A small bulb at the upper part of the stem receives the excess of Hg. Suppose a temperature between 37°-40° C. is to be measured, the bulb is first heated a little over 40° C, it is then suddenly cooled, and shaken at the same time, so that the thread of mercury is thereby suddenly broken above 40°. The tube is so narrow that 1° C. is equal to about 10 centimetres of the length of the tube, so that -^^° C. is still i millimetre in length. The scale is divided empirically, but the valve of the divisions must be compared with a normal thermometer. Kronecker and Meyer used very small maximal " outflow thermometers " [Duhng and Petit\, and caused them to pass through the intestinal canal, or through large blooil vessels. The mercury flows out of the short open tube, and, of course, more flows out the higher the temperature. After these small tubes have passed through the animal, a comparison is instituted with a normal thermometer, to determine at what tempera- ture the mercury reaches the free margin of the tube. (B) Thermo.electric Method. — This method enables us to determine the metas- tatic temperature accurately and rapidly (Fig. 216, I). The thermo-electric galvano- meter of Meissner and Meyerstein consists of a circular magnet («), suspended by a thread of silk (c), to which a small mirror (S) is attached. A large stationary bar magnet (M) is placed near the magnet (>n), so that the north poles (h and N| or both magnets point in the same direction, and it is so arranged that the suspended magnet is caused to point to the north by a minimal action of M. A thick copper wire (b, b) is coiled several times round m (although in the figure it is represented as a single coil), and the ends of the wire are soldered to two thermo elements, each composed of two different metals, iron and German silver, the two similar free elements being united by a wire (A,), so that the two thermoelements form part of a closed circuit. A horizontal scale (K, K) is placed at a distance of 3 metres from the mirror, so that the the scale are seen in the mirror. The scale itself rests upon a telescope (F) directed mirror. The observer (B) who looks through the telescope can see the divisions of the divisions of toward the scale in the 352 THERMO-ELECTRIC MEASUREMENT OF HEAT. mirror. When the magnet, and with it the mirror, swing out of the magnetic meridian, the observer notices other divisions of the scale in the mirror. When one of the thermo elements is heated, an electrical current is produced, which passes from the iron to the German silver in the heated couple, and causes a deviation of the suspended magnet. Suppose a person were swimming in the direction of the current in the conducting wire, then the north pole of the magnet goes to the. north (Amfive). The tangent of the angle y, through which the freely movable magnet is diverted by a galvanic current, from its position of rest or zero, in the magnetic meridian, is the same as the galvanic stream; G is proportional to the magnetic energy D, /. e.. tang. « ^ - • If G is Scheme of the : arrangements fo: ng the temperature. to remain the same, and the tang. ^ = 37-36 37-23 37-0 37-0 37-5 II 36.89 37-2 37-2 37-3 Mid-day. . 12 36.87 37-.S* 37-3* 37-5* I 36.83 37-21 37-13 373 37-3 37.4 2 37-05 37-5°* 37-4 37-4 37-5 3 37-15* 37-43 37-4* 37-3* 37-5 4 37-17 37-4 37-3 37-5* 5 37-48 37-05* 5^^=37-21 37-43 37-5 37-5 37-5 b 6K = 36.83 37-29 37-5 ^7-b 37-4 7 37-43 lYz = 36-50* 37-31* 37-5* 37-6* 37-3 8 37-4 37-7 ,S7-i* 9 37.02* 37-4 37-5 36-9 10 37-29 37-3 37-4 36.8 II 36.8s 36.72 36.70 36.81 37-2 S7-I 36.8 Night. . . 12 - - 37-1 36.9 36-9 I 36.65 36-44 37-0 36-9 36-9 2 369 36.7 36.8 .3 36.8 36.7 36.7 4 36-31 36-7 36-7 36-7 [* Indicates taking of food.] 3(J0 CONDITIONS AFFECTING THE MEAN TEMPERATURE. The mean height of all the temperatures taken during a day in a patient is called the "daily mean," and according to Jaeger, it is 37- 13° in the rectum in health. A daily mean of more than 37.8° is a "fever temperature," while a mean under 37.0° C. is regarded as a "collapse temperature." According to I.ichtenfels and Frohlich, the morning temperature rises four to six hours after breakfast until its first maximum, then it falls until dinner time ; and it rises again within two hours to a second maximum, falls again toward evening, while supper does not appear to cause any obvious increase. The daily variation of the temperature is given in Fig. 218, according to Lieber- meister and Jiirgensen. According to Bonnal, the minimum occurs between 12 and 3 A.M. (in winter 36.05, in summer 36.45° C. ), the maximum between 2 and 4 p.m. As the variations occur when a person is starved for a day — although those that occur at the periods at which food ought to have been taken are less — it is obvious that the variations are not due entirely to the taking of food. The daily variation in the frequency of the pulse often coincides with variation of the tem- perature. Barensprung found that the mid-day temperature maximum slightly preceded the pulse maximum (? 70, 3, C). If we sleep during the day, and do all our daily duties during the night, the above described typical course of the temperature is inverted {Kiiegcr). With regard to the effect of activity or rest, it appears that the activity of the muscles during the day tends to increase the mean temperature slightly, while at night the mean temperature is less than in the case of a person at rest (^Liehermeister). The peripheral parts of the body exhibit more or less regular variations of their temperature. In the palm of the hand, the progress of events is the following : After a relatively high night temperature there is a rapid fall at 6 a.m., which reaches its minimum at g to 10 a.m. This is fol- lowed by a slow rise, which reaches a high maximum after dinner; it falls between i and 3 p.m., and after two or three hours reaches a minimum. It rises from 6 to 8 p.m., and falls again toward morning. A rapid fall of the temperature in a peripheral part corresponds to a rise of temperature in internal parts [Komer). (5) Many operations upon the body affect the temperature. After hemor- rhage, the temperature falls at first, but it rises again several tenths of a degree, and is usually accompanied by a shiver or slight rigor; several days thereafter it falls to normal, and may even fall somewhat below it. The sudden loss of a large amount of blood causes a fall of the temperature ^4 to 2° C. Very long-continued hemorrhage (dog) causes it to fall to 31° or 29° C. (^Marshall Hall). This is, obviously, due to the diminution of the processes of oxidation in the anaemic body, and to the enfeebled circulation. Similar conditions, causing diminished metabolism, effect the same result. Continued stimulation of the peripheral end of the vagus, so that the heart's action is enor- mously slowed, diminishes the temperature several degrees in rabbits (Landois and Ammon). The transfusion of a considerable quantity of blood raises the temperature about half an hour after the operation. This gradually passes into a febrile attack, which disappears within several hours. When blood is transfused from an artery to a vein of the same animal a similar result occurs {Albert ami Strieker) (§ 102). (6) Many poisons diminish the temperature, e.g., chloroform {Selieinesson), and the anaesthetics, as also alcohol (§ 235), digitalis, quinin, aconitin, muscarin. These appear to act, partly, by rendering the tissues less liable to undergo molecu- lar transformations for the production of heat. In the case of the anaesthetics, this effect, perhaps, occurs, and is due, possibly, to a semi-coagulation of the nervous substance (?). They may also act partly by influencing the giving off of heat (§ 214, II). Other poisons increase the temperature, for opposite reasons. The temperature is increased by strychnin, nicotin, picrotoxin, veratrin (Hoi^yes), laudanin {F. A. Fakk). Curara (muscarin — //i.\^yes), laudanosin [F. .4. Fa/ck), cause an uncertain effect. (7) Various diseases diminish the temperature, which may be due either to lessened produc- tion of heat (diminution of the metabolism), or to increased expenditure of heat. Loewenhardt found that in paralytics and in insane persons, several weeks before their death, the rectal tempera- ture was 30° to 31° C. ; Bechterew found in dementia paralytica, before death, 27.5° C. (rectum); the lowest temperature obser\'ed, and life retained, in a drunken person, was 24° C. (Kfinie, A'iiolaysen). REGULATION OF THE TEMPERATURE. 361 The temperature is increased in fe-jer, and the highest point reached just before death, and re- corded by Wunderlich, was 44.65° C. (compare \ 220). Increase of temperature, constituting fever, is treated of in \ 220. 214. REGULATION OF THE TEMPERATURE.— As the bodily temperature of man and similar animals is nearly constant — notwithstanding great variations in the temperature of their surroundings — it is clear that some mechanism must exist in the body whereby the heat economy is constantly regulated. This may be brought about in two ways: either by controlling the transformation of potential energy into heat, or by affecting the amount of heat given off according to the amount produced, or to the action of external agencies. I. Regulatory Arrangements Governing the Production of Heat. — Liebermeister estimated the amount of heat produced by a healthy man at 1.8 calories per minute. It is highly probable that, within the body, there exist mechanisms which determine the molecular transformations, upon which the evo- lution of heat depends {Hoppe-Seyler, Liebermeister). This is accomplished, chiefly, in a reflex manner. The peripheral ends of cutaneous nerves (by thermal stimulation), or the nerves of the intestine and the digestive glands (by inechanical or chemical stimulation during digestion or inanition) may be irri- tated, whereby impressions are conveyed to the heat centre, which sends out impulses, through efferent fibres, to the depots of potential energy, either to increase or diminish the extent of the transformations occurring in them. The nerve channels herein concerned are entirely unknown. Many considerations, however, go to support such an hypothesis (§ 377). Heat Centre. — So far, the investigations as to the existence of such a centre are not quite con- clusive. Tschetschechin and Naunyn, Ott and Wood, assume that there is a cerebral heat centre, which inhibits the comlsustion processes in the body by means of fibres descending through the pons, medulla oblongata and spinal cord, so that destruction of this centre, or its conducting paths, increases the production of heat. Aronsohn and Sachs observed that puncture of a rabbit's brain, several millimetres to the side of and behind the large fontanelle, was followed by a temporary rise of the temperature. Richet noted a similar result, but he referred it to increased production of heat ; the animals ate more and lost flesh. Repeated puncture of the brain finally caused emaciation, diminution of temperature (26° C.) and death. The following phenomena indicate the existence of mechanisms regulating the production of heat : — (i) The temporary application of moderate cold raises ike bodilv temperature, while heat, similarly applied to the external surface, lowers it (§222 and 224). (2) Cooling of the surroundings increases the amount of COj excreted, by increasing the production of heat {Liebermeister, Gildermeister), while the O consumed is also increased simultaneously ; heating the surrounding medium di- minishes the COj (§ 127, 5). D. Finkler found, from experiments upon guinea pigs, that the production of heat was more than doubled when the surrounding temperature was diminished 24° C. The metabolism of the guinea pig is increaseil in winter 23 per cent., as compared with summer ; so that the same relation obtains as in the case of a diminution of the surrounding temperature of short duration. C. Ludwig and Sanders- Ezn found that in a rabbit there was a rapid increase in the amount of COj given off, when the surroundings were cooled from 38° to 6° or 7° C. ; while the excretion was diminished when the surrounding temperature was raised from 4°-9° to 35°-37°,.so that the thermal stimulation, due to the temperature of the surrounding medium, acted upon the combustion within the body. Pfluger found that a rabbit which was dipped in cold water used more O and excreted more CO 2. If the cooling action was so great as to reduce the bodily temperature to 30°, the exchange of gases diminished, and where the temperature fell to 20°, the exchange of gases was diminished one- half. It is to be remembered, however, that the excretion of CO, does not go hand in hand with the formation of CO,, so that the increased excretion of CO, in a cold bath is, perhaps, due to more complete expiration, and Berthelot has proved that the formation of CO^ is not a certain test of the amount of heat produced. If mammals be placed in a warm bath, which is 2° to 3° higher than their own temperature, the excretion of CO, and the consumption of O are increased, owing to the stimulation of their metabolism (P/lii^er), while the excretion of urea is also increased in animals {Xaiinyn) and in man (Schleieh) (| 133, 5). 362 REGULATION OF THE TEMPERATURE. (3) Cold acting upon the skin causes involuntary muscular movements (shivering, rigors), and also voluntary movements, both of which produce heat. The cold excites the action of the muscles, which is connected with processes of oxidation (Pfliii^fr). After poisoning with cui%ra, which paralyzes voluntary motion, this rejjulation of the heat falls to a minimum (ke/irig and Ziin/:) [while tlie bodily temperature rises and falls with a rise or fall in the temperature of the surrounding medium]. (4) Variations in the temperature of the surroundings affect the appetite for food ; in winter, and in cold regions, the sensation of hunger and the appetite for the fats, or such substances as yield much heat when they are oxidized, are increased ; in summer, and in hot climates, they are diminished. Thus the mean temperature of the surroundings, to a certain extent, determines the amount of the heat-producing substances to be taken in the food. In winter the amount of ozone in the air is greater, and thus the oxidizing power of the inspired air is increased. II. Regulatory Mechanisms Governing the Excretion of Heat. — The mean amount of heat given off by the human skin in twenty-four hours, by a man weighing 82 kilos., is 2092 to 2592 calories, /. e., 1.36 to 1.60 per minute. (i) Increased temperature causes dilatation of the cutaneous vessels; the skin becomes red, congested, and soft; it contains more fluids, so that it becomes a better conductor of heat ; the epithelium is moistened, and sweat appears upon the surface. Thus increased excretion of heat is provided for, while the evaporation of the sweat also abstracts heat. The amount of heat necessary to convert into vapor I grm. of water at 100° C, is equal to that required to heat 10 grms. from 0° to 53.67° C. The sweat as secreted is .it the temperature of the body; if it were completely changed into vapor, it would require the heat necessary to raise it to the boiling point, and also that necessary to convert it into vapor. Cold causes contraction of the cutaneous vessels ; the skin becomes pale, less soft, poorer in juices, and collapsed ; the epithelium becomes dry, and does not permit fluids to pass through it to be evaporated, so that the excretion of heat is diminished. The excretion of heat from the periphery, and the transverse thermal conduction through the skin, are diminished by the contraction of the vessels and muscles of the skin, and by the expulsion of the well-conducting blood from the cutaneous and subcutaneous ve,ssels. The cooling of the body is very much affected, owing to the diminution of the cutaneous blood stream, just as occurs when the current through a coil or worm of a distillation apparatus is greatly diminished ( Winternitz). If the blood vessels dilate, the temperature of the surface of the body rises, the difference of temperature between it and the surrounding cooler medium is increased, and thus the excretion of heat is increased. Tomsa has shown that the fibres of the skin are so arranged anatomically, that the tension of the fibres produced by the erector pili muscles causes a diminution in the thickness of the skin, this result being brought about at the expense of the easily expelled blood. Landois and Hauschild ligatured the arteries alone, or the arteries and veins (dog), e.g., the axillary artery and vein, the crurals, the carotids and the jugular veins, and found that in a short time the temperature rose several tenths of a degree. By the systemiitic application of stimuli, e.g., cold baths, and washing with cold water, the muscles of the skin and its blood vessels may be caused to contract, and become so vigorous and excitable that, when cold is suddenly applied to the body, or to a part of it, the excretion of heat is energetically prevented, so that cold baths and washing with cold water are, to a certain extent, " gymnastics of the cutaneous muscles," which, under the above circumstances, protect the body from cold (^Rosenthal, Jit Bois Reymond). (2) Increased temperature causes increased heart beats, while diminished temperature diminishes the number of contractions of the heart (§ 58, II, a). The relatively warm blood is pumped by the action of the heart from the internal organs of the body to the surface of the skin, where it readily gives off heat. The more frequently the same volume of blood passes CLOTHING. 363 through the skin — twenty-seven heart beats being necessary for the complete circuit of the blood — the greater will be the amount of heat given off and con- versely. Hence, the frequency of the heart beat is in direct relation to the rapidity of cooling (Walther). In very hot air (over ioo° C.) the pulse rose to over 1 60 per minute. The same is true in fever (§ 70, 3, c). Liebermeister gives the following numbers with reference to the temperature in an adult : — Pulse beats, per min. 78.6 — 91.2 — 99.8 — 10S.5 — no— 137.5. Temperalure in C.° 37° — 38° — 39° — 40° — 41° — 42°. (3) Increased Temperature increases the Number of Respirations. — Under ordinary circumstances, a much larger volume of air passes through the lungs when it is warmed almost to the temperature of the body. Further, a cer- tain amount of watery vapor is given off with each expiration, which must be evaporated, whereby heat is abstracted. Energetic respiration aids the circula- tion, so that respiration acts indirectly in the same way as (2). According to other observers, the increased consumption of O favors the combustion in the body (§ 127, 8), whereby the increased respiration must act in producing an amount of heat greater than normal. This excess is more than compensated by the cooling factors above mentioned. Forced respiration produces cooling, even when the air breathed is heated to 54° C, and saturated with watery vapor. (^Lombard). (4) Covering of the Body. — Animals become clothed in winter with a winter fur or covering, while in summer their covering is lighter, so that the excretion of heat in surroundings of different temperatures is thereby rendered more constant. Many animals which live in very cold air or water (whale) are protected from too rapid excretion of heat by a thick layer of fat under the skin. Man provides for a similar result by adopting summer and winter clothing. (5) The position of the body is also important ; pulling the parts of the body together, approximation of the head and limbs, keep in the heat ; spreading out the limbs, erection of the hairs, pluming the feathers, allow more heat to be evolved. If a rabbit be kept exposed to the air with its legs extended for three hours, the rectal temperature will fall from 39° C. to 37° C. Man may influence his temperature by remaining in a warm or cold room — by taking hot or cold drinks, hot or cold baths — remaining in air at rest or air in motion, e. g., by using a fan. Stimulation of the central end of a sensory nerve (sciatic) increases the surface temperature and diminishes the internal temperature ( Ostroumo-v, Mitropo/siv). Clothing — Warm Clothing is the Equivalent of Food. — As clothes are intended to keep in heat of the body, and heat is produced by the combustion and oxidation of the food, we may say the body takes in heat directly in the food, while clothing prevents it from giving off too much heat. Summer clothes weii;h 3 to 4 kilos , and winter ones 6 to 7 kilos. In connection with clothes, the following considerations are of importance : — ( I ) Their capacity for conduction. — Those substances which conduct heat badly keep us warmest. Hare skin, down, beaver skin, raw silk, taffeta, sheep's wool, cotton wool, flax, spun silk, are given in order, from the worst to the best conductors. (2) The capacity for radiation. — Coarse materials radiate more heat than smooth, but color has no effect. (3) Relation to the sun's rays. — Dark materials absorb more heat than light colored ones. (4) Their hygroscopic properties are important, whether they can absorb much moisture from the skin and gradually give it off by evaporation, or the reverse. The same weight of wool takes up twice as much as linen ; hence, the latter gives it off in evaporation more rapidly. Flannel next the skin is not so easily moistened, nor does it so rapidly become cold by evaporation ; hence it protects against the action of cold. (5) The/^>-- vteability for air is of importance, but does not stand in relation with the heat conducting capacity. The following substances are arranged in order from the most to the least permeable — flannel, buclc- skin, linen, silk, leather, wax cloth. 215. INCOME, EXPENDITURE, AND BALANCE OF HEAT. — As the temperature of the body is maintained within narrow limits, the amount of heat taken in must balance the heat given off, /. c, exactly the same amount of potential energy must be transformed in a given time into heat, as heat is given off from the body. 364 INCOME, EXPENDITURE, AND BALANCE OF HEAT. An adult produces as much heat in half an hour as will raise the temperature of his body i° C. If no heat was given off, the body would become very hot in a short time ; it would reach the boiling point in thirty-six hours, supposing the production of heat continued uninterruptedly. The following are the most important calculations on the subject : — (A) According to Helmholtz, who was the first to estimate numerically the amount of heat produced by a man. (1) Heat Income. — (a) A heahhyaduh, weighing 82 kilos., expires in twenty- four hours 878.4 grms. CO; [Scharling). The combustion of the C therein into CO^ produces 1,730,760 cal. [b) But he takes in more O than reappears in the COj ; the excess is used in oxidation processes,*'.^., for the formation of H^O, by union with H, so that 13,615 grms. H will be oxidized by the excess of O, which gives 318.600 cal. 2,049,360 cal. [c) About 25 per cent, of the heat must be referred to sources other than combustion {Du!ong), so that the total = 2,732,000 cal. 2,732,000 calories are actually sufficient to raise the temperature of an adult weighing 80 to 90 kilos., from 10° to 38 or 39° C, /. e., to a normal temperature. (2) Heat expenditure. — (a) Heating the food and drink, which have a mean temperature of 12° C. 70, 157 cal =^ 2.6 per cent. [b) Heating the air respired = 16,400 grms., with an initial temperature of 20° C. 70,032 cal ^2.6 per cent. ( IV/ien the temperature of the air is 0°, 140,064 cal. = 5.2 per rent.) (c) Evaporation of 656 grms. water by the lungs, 397.536 cal. ^ 14.7 per cent. (i/) The remainder given off by radiation and evaporation of water by the s,k\n, (yj .$ per eeiti. to) =80.1 per cent. (B) According to Dulong. — (i) Heat income. — Dulong, and after him Boussingault, Liebig, and Dumas, sought to estimate the amount of heat from the C and H contained in the food. As we know that the combustion of I grm. C = 8040 heat units, and I grm. H ^ 34.460 heat units, it would be easy to determine the amount of heat were the C simply converted into CO^ and the H into HjO. But Dulong omitted the H in the carbohydrates {e. g., grape sugar = C^H, jO,;) as producing heat, because the H is already combined with O, or at least is the proportion in which it exists in water. This assumption is hypothetical, for the atoms of C in a carbohydrate may be so firmly united to the other atoms, that before oxidation can take place their relations must be altered, so that potential energy is used up, i. e., heat must be rendered latent; so that these considerations rendered the following example of Dulong's method given by Vierordt very prolilematical. An adult eats in twenty- four hours, 120 grms. proteids, 90 grms. fat and 340 grms, starch (carbo- hydrates). These contain : — Grms. C. H. Proteids 120 contain 64.18 and 8.60 Fat 90 " 70.20 " 10.26 Starch 330 " 146.82 " . . 281.20 and 18.86 The urine and fs;ces contain still unconsumed ... 29 8 " 6.3 Remainder to be burned 251.4 and 12.56 As I grm. C =8040 heat units and I grm. H = 34,460 heat units, we have the following calcu- lation : — 251.4 X 8.040 = 2,031,312 (from combustion of C). 12.56 X 34.460 = 432.818 ( " " H). 2.464,130 heat units. (2] Heat expenditure : — Per cent, of ^ ' ^ Heat units. the excreta. 1. 1900 grms. are excreted daily by the urine and f;tces, and they are 25° warmer than the food 47,500 1.8 2. 13,000 grms. air are heated (from 12° to 27° C.) (heat capacity of the air = 0.26) 84. 500 3.5 3. 330 grms. water are evaporated by the respiration ( i grm. = 582 heat units) 192,060 7.2 4. 660 grms. water are evaporated from the skin 384,1^0 14.5 Total 708,180 Remainder radiated and conducted from the skin 1,791,810 72 Total amount of heat units given oft' 2,500,000 * 100 RELATION OF HEAT PRODUCTION TO WORK. 365 (C) Heat income. — Frankland burned the food directly in a calorimeter, and found that l grm. of the following substances yielded — Albumin 4998 heat units Grape sugar 3277 " Ox fat 9069 " The albumin, however, is only oxidized to the stage of urea, hence the heat units of urea must be deducted from 4998, which gives 4263 heat units obtainable from I grm. albumin. When we know the number of grammes consumed, a simple multiplication gives the number of heat units. The heat units will vary, of course, with the nature of the food. J. Ranke gives the following : — With animal diet 2,779,524 heat units. " food free from N 2,059,506 " mixed diet 2,200,000 " " during hunger 2,012,816 " 216. VARIATIONS IN HEAT PRODUCTION.— According to Helmholtz, an adult weighing 82 kilos, produces 2,732,000 calories in twenty-four hours. (1) Influence of the Body Weight. — Accepting the above number, Immermann has given the following formula for the heat production in living tissues : — 3 3 w: W = y'p': y P^ (where W = 2,732,000; P ^ 82 kilos. [W: y^/'- = 144,75] > / = body weight of the person to be investigated, and w represents the heat production which is required). 3 — It is highly desirable that W: ^//^ (= ot) was ascertained as a mean from a large number of observations, that the heat production for any body weight/ would be s — TV = m Y/>^. (2) Age and Sex. — The heat production is less in infancy and in old age, and it is less in pro- portion in the female than in the male. (3) Daily Variation. — The heat production shows variations in twenty-four hours correspond- ing with the temperature of the body (J 213, 4). (4) The heat production is greater in the waking condition, during physical and mental exer- tion, and during digestion, than in the opposite conditions. 217. RELATION OF HEAT PRODUCTION TO WORK.— The potential energy supplied to the body may be transformed into heat and kinetic energy (see Introduction). In the passive condition, almost all the potential energy is changed into heat ; the workman, however, transforms potential energy into work — mechanical work — in addition to heat. These two may be com- pared by using an equivalent measurement, thus i heat unit (energy required to raise i gramme of water 1° C.) = 425.5 gramme metres. Relation of Heat to Work. — The following example may serve to illustrate the relation between heat production and the production of work : Suppose a small steam engine to be placed within a capacious calorimeter, and a certain quantity of coal to be burned, then as long as the engine does not perform any mechanical work, heat alone is produced by the burning of the coal. Let this amount of heat be estimated, and a second e.xperiment made by burning the same amount of coal, but allow the engine to do a certain amount of work — say, raise a weight — by a suitable arrange- ment. This work must, of course, be accomplished by the potential energy of the heating material. At the end of this experiment, the temperature of the water will be much less than in the first ex- periment, i. t., fewer heat units have been transferred to the calorimeter when the engine was heated than when it did no work. Comparative experiments of this nature have shown that in the second experiment the useful work is very nearly proportional to the decrease of the heat (Hirn). In good steam engines only j'j, and in the very best 's, of the potential energy is changed into mechanical energy, while \l to ^ passes into heat. Compare this with what happens within the body : A man in a passive con- dition forms from the potential energy of the food between zyi and 2^ million calories. The work done by a workman is reckoned at 300,000 kilogramme metres (§ 300). If the organism were entirely similar to a machine, a smaller amount of heat, corresponding to the work done, would be formed in the body. .A.s a matter of fact, the organism produces less heat from the same amount of potential energy 366 ACCOMMODATION FOR VARYING TEMPERATURES. when mechanical work is done. There is one point of difference between a work- man and a working machine. The workman consumes much more potential energy in the same time than a passive person ; much more transformed in his body, and hence the increased consumption is not only covered, but even over- compensated. Hence, the workman is warmer than the passive person, owing to the increased muscular activity (§ 210, i, b). Take the following example : Him (1858) remained /aj-JW^', and absorbed 30 grm. O per hour in a calorimeter, and produced 155 calories. When in the calorimeter he did work equal to 27,450 kilogramme metres, which was transferred beyond it; he absorbed 132 grm. O, and produced only 251 calories. In estimating the work done, we must include only the heat equivalent of the work transferred beyond the body ; lifting weights, pushing anything, throwing a weight, and lifting the body, are examples. In ordinary walking there is no loss of heat (apart from overcoming the resistance of the air); when descending from a height there may be increased warmth of the body. The organism is superior to a machine in as far as it can, from the same amount of potential energy, produce more work in proportion to heat. While the very best steam engine gives \ of the potential energy in the form of work, and \ as heat, the body produces \ as work and ^ as heat. Chemical energy can never do work alone, in a living or dead motor, without heat being formed at the same time. 218. ACCOMMODATION FOR VARYING TEMPERATURES. — All substances which possess high conductivity for heat, when brought into con- tact with the skin, appear to be very much colder or hotter than bad conductors of heat. The reason of this is that these bodies abstract far more heat, or con- duct more heat than other bodies. Thus the water of a cool bath, being a better conductor of heat, is always thought to be colder than air at the same tempera- ture. In our climate it appears to us that — Air, at iS° C. is moderately warm; " at 25°-28° C, hot ; " above 28°, very hot. Water, at 18° C. is cold; " from i8°-29° C, cool ; " " 29°-35° C, warm ; " " 37.5° and above, hot. Warm Media. — As long as the temperature of the body is higher than that of the surrounding medium, heat is given off, and that the more rapidly the better the conducting power of the surrounding medium. As soon as the tem- perature of the surrounding medium rises higher than the temperature of the body, the latter absorbs heat, and it does so the more rapidly the better the con- ducting power of the medium. Hence, hot water appears to be warmer than air at the same temperature. A person may remain eight minutes in a bath at 45.5° C. (dangerous to life !) ; the hands may be plunged into water at 50.5° C, but not at 51.65° C, while at 60° violent pain is produced. A person may remain for eight minutes in hot air at 127° C, and a tempera- ture of 132° C. has been borne for ten minutes (Tillett, ij6f). The body tem- perature rises only to 38.6° or 38.9° {Fordyce, Blagden, 1774)- This depends upon the air being a bad conductor, and thus it gives less heat to the body than water would do. Further, and what is more important, the skin becomes covered with sweat, which evaporates and abstracts heat, while the lungs also give off more watery vapor. The enormously increased heart beats — over 160 — and the dilated Hood vessels, enable the skin to obtain an ample supply of blood for the formation and evaporation of sweat. In proportion as the secretion of sweat diminishes, the body becomes unable to endure a hot atmosphere ; hence it is that in air con- taining much watery vapor a person cannot endure nearly so high a temperature as in dry air, so that heat must accumulate in the body. In a Turkish vapor bath of 53° to 60° C, the rectal temperature rises to 40.7° or 41.6° C. (Barthels, Jiirgensen Krishaber). A person may work continuously in air at 31° C. which is almost saturated with moisture {Stapff). FEVER AND ITS PHENOMENA. 367 If a person be placed in water at the temperature of the body, the normal temperature rises i° C. in one hour, and in 1J2 hours about 2° C. {Lieben/ieister). A gradual increase of the temperature from 38.6° to 40.2° C. causes the axillary temperature to rise to 39.0° within fifteen minutes. Rabbits placed in a warm box at 36° C. acquire a constant temperature of 42° C, and lose weight ; but if the temperature of the box be raised to 40°, death occurs, the body temperature rising to 45° C. (_/. Rosenthal). 219. STORAGE OF HEAT IN THE BODY.— As the uniform tem- perature of the body, under normal circumstances, is due to the reciprocal rela- tion between the amount of heat produced and the amount given off, it is clear that heat must be stored up in the body when the evolution of heat is diminished. The skin is the chief organ regulating the evolution of heat ; when it and its blood vessels contract the heat evolved is diminished, when they dilate it is in- creased. Heat may be stored up when — (a) The skin is extensively stimulated, whereby the cutaneous vessels are temporarily contracted {Rohrig). (b) Any other circumstances preventing heat from being given off by the skin ( Win- ternitz). (r) When the 7'asonictor centre is excited, causing all the blood vessels of the body — those of the skin mcluded — to contract. This seems to be the cause of the rise of temperature after the transfusion of blood (Laiidois), and the rise of temperature after the sudden removal of water from the body seems to admit of a similar explanation ; as the inspissated blood occupies less space, and the contracted vessels of the skin admit less blood, [d) When the circulation in the cutaneous vessels of a large area is mechanically slowed, or when the smaller vessels are plugged by the injection of some sticky substance, or by the transfusion of foreign blood, the temperature rises {\ 102). Landois found that ligature of both carotids, and the axillary and crural arteries, caused a rise of 1° C. within two hours. It is also obvious than when a normal amount of heat is given off, an increased production of heat must raise the temperature. The rise of the temperature after muscular or mental exertion, and during digestion, seems to be caused in this way. The rise which occurs several hours after a cold bath is probably due to the reflex excitement of the skin causing an increased production ( Jiirgensen). When the temperature of the body, as a whole, is raised 6° C, death takes place, as in sunstroke. It seems as if there was a molecular decomposition of the tissues at this temperature ; while, if a slightly lower temperature be kept up con- tinuously, fatty degeneration of many tissues occurs {Litten). If animals which have been exposed artificially to a temperature of over 42° to 44° C. be transferred to a cooler atmosphere, their temperature becomes subnormal (36° C.) and may remain so for several days. 220. FEVER. — Cause. — Fever consists in a greatly increased tissue metabolism (especially in the muscles — Finkler, Zuntz), with simultaneous increase of the temperature. Of course, the mechanism regulatmg the balance of formation and expenditure of heat is disturbed. During fever the body is greatly mcapacitated for performing mechanical work. It is evident, therefore, that the large amount of potential energy transformed is almost all converted into heat, so that the non- transformation of the energy into mechanical work is another important factor. We may take intermittent fever or ague as a type of fever, in which violent attacks of fever of several hours' duration alternate with periods free from fever. This enables us to analyze the symptoms. The symptoms of fever are: — (I) The increased temperature of the body {38° to 39° C, slight; from 39° to 41° C. and upward, severe). The high temperature occurs not only in cases where the skin is red, and has a hot, burning feeling (calor mordax), but even during the rigor or the shivering stai;e, the tempera- ture IS raised i^Anl. de Haen, 1760). The congested, red skin is a good conductur of heat, while the pale, bloodless skin conducts badly ; hence, the former feels hot to the touch {v. Bdrcnsprung —compare ^212). The following table in °C and °F indicates generally the degree of fever : — 3S°C. = 95° F. . . 36 = 96.8 . . . . Collapse. . . Low. 39° C. = 102.2° F. 39.5 = 103. 1 }■ Moderate fever. l(^-S = 97-7 37 = 98.6 . . . . . Subnormal. . . . Normal. 40 = 104 40.5 = 104.9 }^ High fever. 37-5 = 99-5) 41 = 105. 8 Hyperpyretic. 3S = 100.4 > . ■ . . Sub-febrile. J-'inlafson.} 38.S =101.3 J 1 368 FEVER AND ITS PHENOMENA. (2) The increased production of heat (assumed by Lavoisier and Crawford) is proved by calonmetric observations. This is, in small part, due to the increased activity of the circulation being changed into heat (§ 206, 2, a), but for the most part it is due to increased combustion withm the body. (3) The increased metabolism gives rise to the " consuming" or "wasting" character of fever, which was known to Hippocrates and Galen, and, in 1852, v. Barensprung asserted that "all the so-called febrile symptoms show that the metabolism is increased." The increase of the metabolism is shown in the increased excretion of COj = 70 to 80 per cent. (LeyJen and J-ianie/), while more O is consumed, although the respiratory quotient remains the same [Zuii/z and Lilicnfeld). According to Dr. Kinkier, the COj excreted shows greater variations than the O consumed. The excretion of urea is increased \ to |. In dogs suffering from septic fever, Naunyn observed that the urea began to increase before the temperature rose, " f re-febrile rise." Part of the urea, however, is sometimes retained during the fever, and appears after the fever is over, " epi-critical excretion of urea" (^Naunyn). The uric acid is also increased; the urine pigment (^ 19), derived from the haemoglobin, may be increased twenty times, while the excretion of potash may be sevenfold. It is important to observe that the oxidation or combustion processes within the body of the fever patient are greatly increased when he is placed in a warmer atmosphere. The oxidation processes in fever, however, are also increased under the influence of cooler surroundings (J 214, 1, 2), but the increase of the oxidation in a warm medium is very much greater than in the cold {D. Finkler). The amount of COj in the blood is diminished, but not at once after the onset even of a very severe k^^r (Geppert). (4) The diminished excretion of heat varies in different stages of a fever. We distinguish several stages in a fever — (a) The cold stage, when the loss of heat is greatly diminished, owing to the pale, bloodless skin, but at the same time the heat production is increased i'/^ to 2yi times. The sudden and considerable rise of the temperature during this stage shows that the diminished excretion of heat is not the only cause of the rise of the temperature. (/>) During the hot stage the ileal given off' from the congested, red skin \s greatly increased, but at the same time more heat is produced. Liebermeister assumes that a rise of 1,2, 3, 4° C. corresponds to an increased pro- duction of heat of 6, 12, 18, 24 per cent, (c) In the sweating stage the excretion of heat through the red, moist skin and evaporation are greatest, more than two to three times the normal [Leyden). The heat production is either increased, normal, or subnormal, so that under these conditions the temperature may also be subnormal (36° C). (5) The heat-regulating mechanism is injured. A warm temperature of the surroundings raises the temperature of the fever patient more than it does that of a non-febrile person. The depression of the heat production, which enables normal animals to maintain their normal tempera- ture in a warm medium (^ 214), is much less in fever (D. Fintler). The accessory phenomena of fever are very important : Increase in the intensity and number of the heart beats (§ 214, II, 2) and respirations (in adults 40, and children 60 per min.),both being compensatory phenomena of the increased temperature; further, dnninished digestive activity (J 1 86, D) and intestinal movements; disturbances of the cerebral activities; of secretion; of muscular activity; slower excretion, e.g., of potassium iodide through the urine (Bachrach, Scholze). In severe fever, molecular degenerations of the tissues are very common. For the condition of the blood corpuscles in fever, see ^ 10; the vascular tension, § 69; the saliva, ^ 146. Quinine, the most important febrifuge, causes a decrease of the temperature- by limiting the production of heat (I.ewisky, Binz, Naunyn, Quincke, Arniz) (§ 213, 6). Toxic doses of the metallic salts act in the same way, while there is at the same time diminished formation of CUj {Lucksinger). [Antipyretics or Febrifuges. — All methods which diminish abnormal temperature belong to this group. As the constant temperature of the body depends on (l ) the amount of heat production, and (2) the loss of heat, we may lower the temperature either in the one way or the other. When cold water is applied to the body, it abstracts heat, /. e., it affects the results of fever, so that Lieber- meister calls such methods antithermic. But those remedies which diminish the actual heat production are true antipyretic. In practice, however, both methods are usually employed, and spoken of collectively as antipyretics.] [Among the methods which are used to abstract heat from the body are the application of colder fluids, such as the cold bath, affusion, douche, spray, ice, or cold mixtures, etc. A person suffering from high fever requires to be repeatedly placed in a cold bath, to produce any permanent reduc- tion of the temperature. Some remedies act by favoring the radiation of heat, by dilating the cutaneous vessels (alcohol), while others excite the sweat glands — i, e., are sudorifics — so that the water, by its evaporation, removes some heat. Among the drugs which influence tissue changes and oxidation — and thereby lessen heat production — are quinine, salicylic acid, some of the salicy- lates, digitalis and veratrin. Blood letting was formerly used to diminish abnormal temperature. Among the newer antipyretic remedies are hydrochlorate of kalrin and antipyrin, both of which belong to the aromatic group (derivatives of benzol), which includes, also, many of our best antiseptics.] INCREASE OF TEMPERATURE POST-MORTEM. 369 221. ARTIFICIAL INCREASE OF THE BODILY TEMPERA- TURE. — If mammals are kept constantly in air at 40° C, the excretion of heat from the body ceases, so that the heat produced is stored up. At first, the tem- perature falls somewhat for a very short time (Obcrnicr), but soon a decided increase occurs. The respirations and pulse are increased, while the latter becomes irregular and weaker. The O absorbed and CO, given off are diminished after six to eight hours {IJtfen), and death occurs after great fatigue, feebleness, spasms, secretion of saliva and loss of consciousness, when the bodily temperature ha.s been increased 4°, or, at most, 6° C. Death does not take place, owing to rigidity of the muscles ; for the coagulation of the myosin of mammals' muscles occurs at 49° to 50° C. ; in birds, at 53° C, and in frogs, at 40° C. If mammals are suddenly placed in air at 100° C, death occurs (in 15 to 20 min.) very rapidly, and with the same phenomena, while the bodily temperature rises 4° to 5° C. In rabbits, the body weight diminishes i grm. per min. Birds bear a high tempera- ture somewhat longer ; they die when their blood reaches 48° to 50° C. Even man may remain for some time in air at 100-110-132° C, but in ten to fifteen minutes there is danger to life. The skin is burning to the touch, and red ; a copious secretion of sweat bursts forth, and the cutaneous veins are fuller and redder {Crawford). The pulse and respirations are greatly accelerated. Violent headache, vertigo, feebleness, stupefaction, indicate great danger to life. The rectal temperature is only 1° to 2° C. higher. The high temperature of fever may even be dangerous to human life. If the temperature remains for any length of time at 42.5° C, death is almost certain to occur. Coagulation of the blood m the arteries is said to occur at 42.6° C. ( Weikart). If the artificial heating does not produce death, fatty infiltration and degeneration of the liver, heart, kidneys and muscles begin, after thirty-si.\ to forty-eight hours {Litten). Cold-blooded Animals, if placed in hot air or warm water, soon have their temperature raised 6° to 10° C. The highest temperature compatible with life in a frog must be below 40° C, as the frog's heart and muscles begin to coagulate at this temperature. Death is preceded by a stage resembling death, during which life may be saved. Most of the juicy plants die in half an hour in air at 52° C, or in water at 46° C. (Sachs). Dried seeds of corn may still germinate after long exposure to air at 120° C. Lowly-organized plants, such as algae, may live in water at 60° C. {Hoppe-Seyler). Several bacteria withstand a boiling temperature ( Tyndall, Chambertand). 222. EMPLOYMENT OF HEAT.— Action of Heat.— The short, but not intense, action of heat on the surface causes, in the first place, a transient slight decrease of the bodily temperature, partly because it retards retlexly the production of heat [JCernii^), and partly because, owing to the dilatation of the cutaneous vessels and the stretching of the skin, more heat is given off (Scnalor). A warm bath above the temperature of the blood at once increases the bodily temperature. Therapeutic Uses. — The application of heat to the entire body is used where the bodily tem- perature has fallen— or is likely to fall — -very low, as in the algid stage of cholera, and in infants born prematurely. The gentral application of heat is obtained by the use of warm baths, packing, vapor baths, and the copious use of hot drinks. The local application of heat is obtained by the use of warm wrappings, partial baths, plunging the parts in warm earth or sand, or placing wounded parts in chambers filled with heated air. After removal of the heating agent, care must be taken to prevent the great escape of heat due to the dilatation of the blood vessels. 223. INCREASE OF TEMPERATURE POST-MORTEM.— Phenomena.— Heiden- hain found that in a dead dog, before the body cooled, there was a constant temporary rise of the temperature, which slightly exceeded the normal. The same observation had been occasionally made on human bodies immediately after their death, especially when death was preceded by mus- cu'ar spasms [also in yellow fever.] Thus, Wunderlich measured the temperature fifty-seven min- utes after death in a case of tetanus, and found it to be 45.375° C. Causes. — (i) A temporary increased production of heat after death, due, chiefly, to the change of the semi-solid myosin of the muscles into a solid form (rigor mortis), ."^s the muscle coagulates, heat is produced (yi. Wather, Fick). All conditions which cause rapid and intense coagulation of the muscles — e.g., spasms — favor a. post-mortem rise of temperature (see J 295) ; a rapid coagulation of the blood has a similar result (^ 28, 5). (2) Immediately after death, a series of chemical processes occur within the body, whereby heat is produced. Valentin placed dead rabbits in a chamber, so that no heat could be given off from the body, and he found that the internal temperature of the animal's body was increased. The 24 370 ARTIFICIAL LOWERING OF THE TEMPERATURE, processes which cause a rise of temperature post-mortem are more active during the first than the second hour; and the higher the temperature at the moment of death, the greater is the amount of heat evolved after death (Quincke and Brieger). (3) Another cause is the diminished excretion of heat postmortem. After the circulation is abolished, within a few minutes little heat is given off from the surface of the liody, as rapid excre- tion implies that the cutaneous vessels must be continually filled with warm blood. 224. ACTION OF COLD ON THE BODY.— Phenomena.— A short, temporary, slight cooling of the skin (removing one's clothes in a cool room, a cool bath for a short time, or a cool douche) causes either no change or a slight rise in the bodily temperature {Liehcniieister). The slight rise, when it occurs, is due to the stimulation of the skin causing reflexly a more ra])id molecular trans- formation, and therefore a greater production of heat {Lichenneister), while the amount of heat given off is diminished, owing to contraction of the small cuta- neous vessels and the skin itself {Jiirgcnscn, Senator). The continuous and intense application of cold causes a decrease of the temperature {Citrn'e), chiefly by conduction, notwithstanding that at the same time there is a greater produc- tion of heat. After a cold bath the temperature may be 34°, 32°, and even 30° C. As an after-effect of the great abstraction of heat, the temperature of the body after a time remains lower than it was before (^'primary after-effect" — Liebermeister) ; thus after an hour it was — 0.22° C. in the rectum. There is a "secondary after-effect" which occurs after the first after-effect is over, when the temperature rises (Jiirgensen). This effect begins five to eight hours after a cold bath, and is equal to -1- 0.2° C. in the rectum. Hoppe-Seyler found that some time after the application of heat there was a corresponding lowering of the tem- perature. Taking Cold. — If a rabbit be taken from a surrounding temperature of 35° C, and suddenly cooled, it shivers, and there may be temporary diarrhoea. After two days the temperature rises 1.5° C, and albuminuria occurs. There are microscopic traces of interstitial inflammation in the liidneys, liver, lungs, heart and nerve sheaths, the dilated arteries of the liver and lung contain thrombi, and in the neighborhood of the veins are accumulations of leucocytes. In pregnant animals the fcetus shows the same conditions (Lassar). Perhaps the greatly cooled blood acts as an irritant, causing inflammation (Rosenthal). Action of Frost.— The continued application of a high degree of cold causes at first contrac- tion of the blood vessels of the skin and its muscles, so that it becomes pale. If continued paraly- sis of the cutaneous vessels occurs, the skin becomes red, ow-ing to congestion of its vessels. As the passage of fluids through the capillaries is rendered more difficult by the cold, the blood stagnates, and the skin assumes a lii'id appearance, as the O is almost completely used up. Thus the peri, pheral circulation is slowed. If the action of the cold be still more intense, the peripheral circula- tion stops completely, especially in the thinnest and most exposed organs — ears, nose, toes and fingers. The sensory nerves are paralyzed, so that there is numbness and loss of sensibility, and the parts may even be frozen through and through. As the slowing of the circulation in the superficial vessels gradually affects other areas of the circulation, the pulmonary circulation is enfeebled, and diminished oxidation of the blood occurs, notwithstanding the greater amount of O in the cold air, so that the nerve centres are aff'ected. Hence arise great dislike to making move- ments or any muscular effort, a painful sensation of fatigue, a peculiar and almost irresistible desire to sleep, cerebral inactivity, blunting of the sense organs, and lastly, coma. The blood freezes at — 3.9° C, while the juices of the superficial parts freeze sooner. Too rapid movements of the frost-bitten parts ought to be avoided. Rubbing with snow, and the very gradual application of heat, produce the best results. Partial death of a part is not unfrequently produced by the pro- longed action of cold. 225. ARTIFICIAL LOWERING OF THE TEMPERATURE. — Phenomena. — The artificial cooling of warm-blooded animals, by placing them in cold air or in a freezing mi.xture, gives rise to a series of characteristic phenomena (A. IVa/ther). If the animals (rabbits) are cooled so that the tem- perature (rectum) falls to 18°, they suffer great depression, without, however, the voluntary or reflex movements being abolished. The pulse falls from 100 or 150 to 20 beats per minute, and the blood pressure falls to several millimetres of Hg. The respirations are few and shallow. Suffocation does not cause spasins (Hor- vath), the secretion of urine stops, and the liver is congested. The animal iTiay HYBERNATION AND USE OF COLD. 371 remain for twelve hours in this condition, and when the muscles and nerves show signs of paralysis, coagulation of the blood occurs after numerous blood cor- puscles have been destroyed. The retina becomes pale, and death occurs with spasms and the signs of asphyxia. If the bodily temperature be reduced to 17° and under, the voluntary movements cease before the reflex acts {Richet and Ron- deau). An animal cooled to 18° C, and left to itself, at the same temperature of the surroundings, does not recover of itself, but if artificial respiration be employed, the temperature rises 10° C. If this be combined with the application of external warmth, the animals may recover completely, even when they have been apparently dead for forty minutes. Walther cooled adult animals to 9° C, and recovered them by artificial respiration and external warmth ; while Horvath cooled I'cwwo- animals to 5° C. Mammals which are born blind, and birds which come out of the egg devoid of feathers, cool more rapidly than others. Mor- phia, and more so, alcohol, accelerate the cooling of mammals, at the same time the exchange of gases falls considerably {Rump/) ; hence, drunken men are more liable to die when exposed to cold. Artificial Cold-blooded Condition. — CI. Bernard made the important observation, that the muscles of animals that had been cooled remained irritable for a long time, both to direct stimuli and to stimuli applied to their nerves; and the same is the case when the animals are asphyxiated for want of O. An '^ artificial cold-blooded condition,^' i. e., a condition in which warm-blooded animals have a lower temperature, and retain muscular and nervous excitability (C7. Bernard), may also be caused in warm-blooded animals, by dividing the cer- vical spinal cord and keeping up artificial respiration ; further, by moistening the peritoneum with a cool solution of common salt (IFegner). Hybernation presents a series of similar phenomena. Valentin found that hybernating animals become half awake when their bodily temperature is 28° C. ; at 18° C they are in a somnolent condition, at 6° they are in a gentle sleep, and at 1.6° C. in a deep sleep. The heart beats and the blood pressure fall, the former to 8 to 10 per minute. The respiratory, urinary and intestinal move- ments cease completely, and the cardio-pneumalic movement alone sustains the slight exchange of gases in the lungs (? 59). They cannot endure cooling to 0° C, and awake before the tempera- ture falls so low. Hybernating animals may be cooled to a greater degree than other mammals ; they give off heat rapidly, and they become warm again rapidly, and even spontaneously. New- bom mammals resemble hybernating animals more closely in this respect than do adults. Cold-blooded Animals may be cooled to 0°. Even when the blood has been frozen and ice formed in the lymph of the peritoneal cavity, frogs may recover. In this condition they appear to be dead, but when placed in a warm medium they soon recover. A frog's muscle so cooled will contract again (A'iihne). The germs and ova of lower animals, e.g., insects' eggs, survive con- tinued frost; and if the cold be moderate, it merely retards development. Bacteria, e.g.. Bacillus anthracis, survive a temperature of — 130° C. (Pictet and Young); yeast, even — 100° C. (Frisch ). Varnishing the Skin causes a series of similar phenomena. The varnished skin gives off a large amount of heat by radiation {A'rieger), and sometimes the cutaneous vessels are greatly dilated (LaschkeT.uilsch). Hence the animals cool rapidly and die, although the consumption of O is not diminished. If cooling be prevented ( Valentin, Schiff, Brttnton) by warming them and keeping them in warm wool, the animals live for a longer time. The blood post-mortetn does not contain any poisonous substances, nor even are any materials retained in the blood which can cause death, for if the blood be injected into other animals, these remain healthy. Varnishing the human skin does not seem to be dangerous (^Senator). 226. EMPLOYMENT OF COLD.— Cold may be applied to the whole or part of the sur- face of the body in the following conditions : — (a) By placing the body for a time in a cold bath, to abstract as much heat as possible, when the bodily temperature in fever rises so high as to be dangerous to life. This result is best accomplished and lasts longest when the bath is gradually cooled from a moderate temperature. If the body be placed at once in cold water, the cutaneous vessels contract, the skin becomes bloodless, and thus obstacles are placed in the way of the excretion of heat. A bath gradually cooled in this way is borne longer (f. Ziemssen). The addition of stimulating substances, e.g., salts, which cause dila- tation of the cutaneous vessels, facilitates the secretion of heat ; even salt water conducts heat better. If alcohol be given internally at the same time, it lowers the temperature. (b) Cold may be ap|)Ued locally by means of ice in a bag, which causes contraction of the cutaneous vessels and contraction of the tissues (as in inflammation), while at the same time heat is abstracted locally. 372 HISTORICAL AND COMPARATIVE. (<-) Heat may be abstracted locally by the rapid evaporation of volatile substances (ether, car- bon disulphide), which causes numbness of the sensory nerves. The introduction of media of low temperature into the body, respiring cool air, taking cold drinks, and the injection of cold fluids into the intestine act locally, and also produce a more general action. In applying cold it is im- portant to notice that the initial contraction of the vessels and the contraction of the tissues are followed by a greater dilatation and turgescence, ;'. *"., by a healthy reaction. 227. HEAT OF INFLAMED PARTS.— "Calor," or heat, is reckoned one of the funda- mental phenomena of intiammaiion, in addition to rubor (redness), tumor (swelling), and dolor (pain). But the apparent increase in the heat of the inflamed parts is not above the temperature of the blood. Simon, in i860, asseited that the arterial blood flowing to an inflamed part was cooler than the part itself; but v. Baren.sprung denies this, as J. Hunter did, and so does facobson, Bern- hardt, and Laudien. The outer parts of the skin in an inflamed part are warmer than usual, owing to the dilatation of the vessels (rubor) and the consequent acceleration of the blood stream in the inflamed part, and owing to the swelling (tumor) from the presence of good heat-conducting fluids; but the heat is not greater than the heat of the blood. It is not proved that an increased amount of heat is produced owing to increased molecular decompositions within an inflamed part. 228. HISTORICAL AND COMPARATIVE.— According to Aristotle, the heart prepares the heat within itself, and sends it along with the blood to all parts of the body. This doctrine prevailed in the time of Hippocrates and Galen, and occurs even in Cartesius and Bartholinus (1667, " flammula cordis" ). The iatro-mechanical school {Boerhaave, van Swieten) ascribed the heat to the friction of the blood on the walls of the vessels. The iatro-chetnical school, on the other hand, sought the .source of heat in the fermentations that arose from the passage of the ab- sorbed substances into the blood i^van Helmont, Svlvius, E/tmiiller). Lavoisier (1777) was the first to ascribe the heat to the combustion of carbon in the lungs. After the construction of the thermometer by Galileo, Sanctorius (1626) made the first ther- mometric observations on sick persons, while the first ca/onmetric observations were made by Lavoisier and Laplace. Comparative observations are given at § 207, and also under Hybernation y\ 225). Physiology- Metabolic Phenomena By the term metabolism are meant all those phenomena, whereby all — even the most lowly — living organisms are capable of incorporating the substances obtained from their food into their tissues, and making them an integral part of their own bodies. This part of the process is known as assimilation. Further, the organism in virtue of its metabolism forms a store of potential energy, which it can transform into kinetic energy, and which, in the higher animals at least, appears most obvious in the form of muscular work and heat. The changes of the constituents of the tissues, by which these transformations of the poten- tial energy are accompanied, result in the formation of excretory products, which is another part of the process of metabolism. The normal metabolism requires the supply of food quantitatively and qualitatively of the proper kind, the laying up of this food within the body, a regular chemical transformation of the tissues, and the preparation of the effete products which have to be given out through the excretory organs. [Synthetic or constructive metabolism is spoken of as Anabolic, and destructive or analytical metabolism as Katabolic metabolism.] 229. THE MOST IMPORTANT SUBSTANCES USED AS FOOD. — Water. — When we remember that 58.5 per cent, of the body con- sists of water, that water is being continually given off by the urine and fsces, as well as through the skin and lungs, that the processes of digestion and absorption require water for the solution of most of the substances used as food, and that numerous substances excreted from the body require water for their solution, e.g., in the urine, the great importance of water and its continual renewal within the organism are at once apparent. As puf by Hoppe-Seyler, all organisms live in water, and even in running water, a saying which ranks with the old saying — " Corpora non agunt nisi fluida." Water^as far as it is not a constituent of all fluid foods — occurs in different forms as drink : (l) Rain water, which most closely resembles distilled or chemically pure water, always contains minute quantities of CO,, NHj, nitrous and nitric acids. (2) Spring water usually contains much mineral substance. It is formed from the deposition of watery vapor or rain from the air, which permeates the soil, containing much CUj, ; the COj is dissolved by the water, and aids in dissolving the alkalies, alkaline earths and metals which appear in solution as bicarbonates, e.g., of lime or iron oxide. The water is removed from the spring by proper mechanical appliances, or it bubbles up on the surface in the form of a "spring." 13) The running water of rivers usually contains much less mineral matter than spring water. Spring water floating on the surface rapidly gives off' its COj, whereby many substances — e.g., lime — are thrown out of solution and deposited as insoluble precipitates. Gases. — Spring water contains little O, but much COj, the latter giving to it its fresh taste. Hence, vegetable organisms flourish in spring water, while animals requiring, as tliey do, much t), are but poorly represented in such water. Water flowing freely gives up CO.j, and absorbs O from the ail, and thus affords the necessary conditions for the existence of fishes and other marine ani- mals. River water contains j'j to ,'5 of its volume of absorbed gases, which may be expelled by boiling or freezing. Drinking water is chiefly obtained from springs. River water, if used for this purpose, must be filtered, to get rid of mechanically suspended impurities. For household purposes a charcoal filter may be used, as the charcoal acts as a disinfectant. Alum has a remarkable action; if o.oooi per cent, be added, it makes turbid water clear. Investigation of Drinking Water. — Drinking water, even in a thick layer, ought to be completely colorless, not turbid, and without odor. Any odor is best 373 374 SALTS AND OTHER SUBSTANCES IN WATER. recognized by heating it to 50° C, and adding a little caustic soda. It ought not to be too hard, i.e., it ought not to contain too much lime (and magnesia) salts. By the term " degree of hardness " of a water is meant the unit amount of lime (and magne- sia) in 100,000 parts of water; a water of 20 degrees of hardness contains 20 parts of hme (cal- cium oxide) combined with COj, sulphuric or hydrochloric acids (the small amount of magnesia may be neglected). A good drinking luater ought not to exceed 20 degi-ees of hardness. The hardness is determined by titrating the water with a standard soap solution, the result being the for- mation of a scum of lime soap on the surface. The hardness of unboiled water is called its total hardness, while that of boiled water is called permanent hardness. Boiling drives off the CO^, and precipitates the calcium carbonate, so that the water at the same time becomes softer. The presence of sulphuric acid, or sulphates, is determined by the water becoming turbid on adding a solution of barium chloride and hydrochloric acid. Chlorine occurs in small amount in pure spring water, but when it occurs there in large amount ^apart from its being derived from saline springs, near the sea or manufactories — we may conclude that the water is contaminated from water closets or dunghills, so that the estimation of chlorine is of importance. For this purpose use a solution (A) of 17 grms. of crystallized silver nitrate in i litre of distilled water; I cubic centimetre of this solution precipitates 3.55 milligrammes of chlor- ine as silver chloiide. Use also (B) a cold saturated solution of neutral potassium chromate. Take 50 cubic centimetres of the water to be investigated, and place it in a beaker, add to it 2 to 3 drops of B, and allow the fluid A to run into it from a burette until the while precipitate first formed remains red, even after the fluid has been stirred. Multiply the number of cubic centimetres of A used by 7.1, and this will give the amount of chlorine in 100,000 parts of the water. Example — 50 c.cmtr. requires 2.9 c.cnur. of the silver solution, so that 100,000 parts of the water contain 2.9 X 7-1 ^ 20.59 parts chlorine (A'ubel, Tiemann). Good water ought not to contain more than 15 milligrammes of chlorine per litre. The presence of lime may be ascertained by acidulating 50 cubic centimetres of the water with HCl and adding ammonia in excess, and afterward adding ammonia oxalate ; the white precipitate is lime oxalate. According to the degree of turbidity we judge whether the water is "soft " (poor in lime), or " hard " (rich in lime). Magnesia is determined by taking the clear fluid of the above operation, after removing the precipitate of lime, and adding to it a solution of sodium phosphate and some ammonia ; the crys- talline precipitate which occurs is magnesia. The more feeble all these reactions are which indicate the presence of sulphuric acid, chlorine, lime and magnesia, the better is the water. In addition, good water ought not to contain more than traces of nitrates, nitrites, or compounds of ammonia, as their presence indicates the decomposition of nitrogenous organic substances. For nitric acid, take 100 cubic centimetres of water acidulated with two to three drops of concen- trated sulphuric acid, add several pieces of zinc, together with a solution of potassium iodide, and starch solution ; a blue color indicates nilric acid. The following test is very delicate : Add to half a drop of water, in a capsule, two drops of a watery solution of Brucinum sulphuricum, and afterward several drops of concentrated sulphuric acid; a rose-red coloration indicates the presence of nitric acid. The presence of nitrous acid is ascertained by the blue coloration which results from the addi- tion of a solution of potassium iodide, and solution of starch, after the water has been acidulated with sulphuric acid. Compounds of ammonia are detected by Nessler's reagent, which gives a yellow or reddish coloration when a trace of ammonia is present in water; while a large amount of these compounds gives a brown precipitate of the iodide of mercury and ammonia. The contamination of water by decomposing animal substance is determined by the amount of N it contains. In most cases it is sufficient to determine the amount of nitric acid present. F'or this purpose we require (A) a solution of 1.S71 grms. potassium nitrate in i litre distilled water; i cubic centimetre contains I milligramme nitric acid; (B) a dilute solution of indigo, which is pre- pared by rubbing together one part of pulverized indigotin with six parts H2SO4, and allowing the deposit to subside, when the blue fluid is poured into forty times its volume of distilled water, and filtered. This fluid is diluted with distilled water until a layer, 12 to 15 mm. in thickness, begins to be transparent. To lest the activity of B, place I cubic centimetre of A in 24 cubic centimetres water ; add some common sail and 50 cubic centimetres concentrated sulphuric acid, and allow B to flow from a burette into this mixture until a faint green mixture is obtained. The number of cubic Cintimetres of B used coi-respond to I milligramme of nitric acid. 25 cubic centimetres of the water to be investigated are mixed with 50 cubic centimetres of con- centrated Hj.SO^, and titrated with B until a green color is obtained. This process must be repeated, and on the second occasion the solution B must be allowed to flow in at once, when, usually, some- what more indigo solution is required to obtain the green solution. The number of cubic centi- metres of B (corresponding to the strength of B, as determined above) indicates the amount of nitric acid present in 25 c. cmtr. of the water investigated. .\s much .is 10 milligrammes nitric acid have been found in spring water i^Marx, Trommsdorff). MAMMARY GLANDS. 375 Sulphuretted Hydrogen is recognized by its odor, also by a piece of blotting paper moistened witli alkaline solution of lead becoming brown when it is held over the boiling water. If it occurs as a compound in the water, sodium nitro-prusside gives a reddish-violet color It is of the greatest importance that drinking water should be free from the presence i:poses the casein into the precipitated cheese, and also into the slightly soluble whey albumin (Unmmersten, Korstcr), so that the coagulation by rennet is a process quite distinct from the coagulation of milk by the gastric and pancreatic juices [and also from the precipitation pro- duced by acids. The presence of calcium phosphate seems to be necessary for the complete action of the rennet (Hammersten).'\ [Experiments. — Warm a little milk to 40° C, and add a few drops of commercial rennet, set- ting aside the mixture in a warm place; a solid coagulum is soon formed, and by and by the whey separates from it If the milk be previously diluted with water, no coagulum is formed ; and if the rennet be boiled before, it, like other ferments, is destroyed. A solution of rennet may be prepared by extracting the fourth stomach of the calf with glycerine.] COMPOSITION OF MILK. 379 [A milk-coagulating ferment is found in certain plants (artichokes, figs, Carica papays), and causes milk to coagulate in neutral or alkaline solution (Baginsky). It is also found in the small intestine of the calf, while a 5 per cent. NaCl solution of the seeds of H^ithania coagulans coagu- lates milk in an alkaline medium (Ailchison and Lea).'\ [When the milk is coagulated we obtain the curd, consisting of casein with some milk globules entangled in it ; the whey contains some soluble albumin and fat, and the great proportion of the salts and milk sugar, together with lactic acid.] BoiUng (by killing all the lower organisms), sodium bicarbonate (jtj'jj), ammonia, salicyUc acid (jjijjj), glycerine, and ethereal oil of mustard prevent the spontaneous coagulation. Fresh milk makes tincture of guaiacura blue, but boiled milk does not do so (Sc/iacAl, C. ArnoU). When milk is exposed to the air for a long time, it gives off COj and absorbs O; the fats are increased (? owing to the development of fungi in the milk), and so are the alcoholic and ethereal extracts, from the decomposition of the casein (^Hoppe-Scyler, Kemmericli). According to Schmidt-Miil- heim, some of the casein becomes converted into peptone, but this occurs only in unboiled milk. Composition. — too parts of milk contain — Human. Cow. Goat. Ass. Water 87.24 to 90.5S 86.23 86.85 S9.01 Solids 9.42 " 12.39 '3-77 "352 '0-99 Casein 2.91 " 3.92 1 . „„ , , ,. f 3.23 2.53 ) ,,. . ^ .. ■' ' > 1. 90 to 2.21 < -■ ,-' 'i> 1=^7 Albumm " . / I 0.50 1.26 j ^^' Butter 2.67 " 4.30 4-50 4-34 I 85 Mdk sugar . . . 3.15" 609 4.93 3.78 1 Sahs 0.14 " 0.2S 0.6 0.65 / -> ^^ Human milk contains less albumin; which is more soluble than the albumin in the milk of animals. Colostrum contains much serum albumin, and very little casein, while all the other substances, and especially the fats, are more abundant. Gases. — Plliiger and Setschenow found in 100 vols, of milk 5.01 to 7.60 CO, ; o 09 to 0.32 O; 0.70 to 1. 41 N, according to volume. Only part of the CO2 is expelled by phosphoric acid. Salts. — 'Wit polash salts (as in blood and muscle) are more abundant than the soda compounds, while there is a considerable amount of calcium phosphate, which is necessary for forming the bones of the infant. Wildenstein found in 100 parts of the ash of human milk — sodium chloride, 10.73; potassium chloride, 26.33 ; potash, 21.44; lime, 18.78; magnesia, 0.87 ; phosphoric acid, 19; ferric phosphate, 0.21 ; sulphuric acid, 2.64; silica, traces. The amount ot salts present is affected by the salts of the food. Conditions Influencing the Composition. — The more frequently the breasts are emptied, the richer the mdk becomes in casein. The last milk obtained at any time is always richer in butter, as it comes from the most distant part of the gland — viz., the acini {Rtiset, Heynsius, Forster, ae Leon) Some substances are diminished and others increased in amount, according to the time after delivt'fv. The following are increased : Until the 2d month after delivery, casein and fat; until the 5th month, the salts (which diminish progressively from this time onward); from 8-ioth month, the sugar. The following are diminished : From io-24th month, casein; from 5-6th and lo-iith months, fat; during ist month, the sugar; from the 5th month, the salts. [Influence of Drugs. — That cow's milk is influenced by the pasture and food is well known. Turnip as food gives a peculiar odor, taste and flavor to milk, and so do the fragrant grasses. The mental state of the nurse influences the quantity and quality of milk, while many substances given as medicines reappear in the milk, such as ddl, copaiba, conium, aniseed, garlic ; especially those containing aromatic volatile oils, as the umbellifene and cruciferje ; also some of the following drugs: potassium iodide, arsenic, mercury, opium, rhubarb, or its active principle, the purgative principle of castor oil, and the cathartic principle of senna. Jaborandi is the nearest approach to a galactagogue, but its action is temporary. Alropin is a true anti-galactagogue. The composition of the milk may be affected by using faity food, by the use of salts, and above all, by the diet ( Dolan).'\ [Milk may be a vehicle for communicating disease — by direct contamination from the water used for adulterating it or cleansing the vessels in which it is kept; by the milk absorbing delete- rious gases; by the secretion being altered in diseased animals.] The greater the amount of milk that is secreted (woman), the more casein and sugar, and the less butter it contains. The milk of a primipara is less watery. Rich feeding, especially proteids (small amount of vegetable food), increase the amount of milk and the casein, sugar, and fat in it ; a large amount of carbohydrates ^not fats) increases the amount of sugar. Substitutes. — If other than human milk has to be used, ass's milk most closely resembles human milk. Cow's milk is best when it contains plenty of fatty matters — it must be diluted with its own volume of water at first, and a little milk sugar added. The casein of cow's milk differs qualita- tively from that of human milk (Biedert) ; its coagulated flocculi or curd are much coarser than the tine curd of human milk, and they are only I4' dissolved by the digestive juices, while human milk is completely dissolved. Cow's milk when boiled is less digestible than unboiled (E. Jessen). Milk ought not to be kept in zinc vessels, owing to the formation of zinc lactate. 380 TESTS FOR MILK. [Milk exposed to light becomes sour more rapidly, and the cream separates quicker; after a time there is a very acid reaction, an evolution of gases, and few bacteria are present, while in milk kept in the d,irk the former processes go on more slow ly, while there is a putrid fermentation without the evolution of gas, but with many bacteria and a feeble acid reaction [Albitii and Ma/I'crla).'] Tests for Milk. — The amount of cream is estimated by placing the milk for twenty-four hours in a tall cylindrical glass graduated into a hundred parts, or creamometer ; the cream collects on the surface, and ought to form from lo to 24 vols, per cent. [The cream is generally about j§j.] The specitic gravity (fresh cow's milk, 1029 to 1034 ; when creamed, 1032 to 1040) is estimated with an acroiiwter or lactometer at 15° C. The sugar is estimated by titration with Fchling's solution (§ 150, II). but m this case r cubic centimetre of this solution corresponds to 0.0067 gfm- of milk sugar; or its amount may be estimated with X\\^ polariscopic apparatus (\ 150). The pro- teids are precipitated and the fats extracted with ether. The fats in Iresh milk form about 3 per cent., and in skimmed milk i 'i per cent. The amount of water in relation to the milk globules is estimated by the lactoscope or the diaphanometer of Donne (modified by Vogel and Hoppe- Seyler), which consists of a glass vessel with plane parallel sides placed i centimetre apart. A measured quantity of milk is taken, and water is added to it from a burette until the outline of a candle tlame placed at a distance of I metre can be distinctly seen through the diluted milk. This is done in a dark room. For i cubic centimetre of good cow's milk, 70 to 85 centimetres water are required. [Other forms of lactoscope are used', all depending on the same principle of an optical test, viz., that the opacity of milk varies with and is proportional to the amount of butter fats present, ;'. e., the oil globules. Bond uses a shallow cyhndrical vessel with the bottom covered by black lines on a white surface. A measured quantity of water is placed in this vessel, and milk is added, drop by drop, until the parallel lines on the pattern at the bottom of the dish cease to be visible. On counting the number of drops, a table accompanying the appliance gives the percentage of fats. This method gives approximate results. In all cases it is well to use fresh milk.] Various substances pass into the milk liihen they are aJministered to the mother — many ouoriferous vegetable bodies, e.g.^ anise, vermuth, garlic, etc. ; opium, indigo, salicylic acid, iodine, iron, zinc, mercury, lead, bismuth, antimony. In osteomalacia the amount of lime in the milk is increased ( Giisserow). Potassium iodide diminishes the secretion of milk by afi'ecting the secretory function (Stump/). Among abnormal constituents are — haemoglobin, bile pigments, mucin, blood corpuscles, pus, fibrin. Numerous fungi and other low organisms develojj in evacuated milk, and -the rare /'/«t' milk is due to the development of Bacterium cyanogeneum (Fuchs, A'ee/sen). The milk serum is blue, not the fungus. Blue milk is unhealthy, and causes diarrhoea (Mosler). There are fungi which make milk hluish-black ox green. Red &\\A yellow milk are produced by a similar action of chromogenic fungi \\ 1 84). The former is produced by Micrococcus prodigiosus, which is colorless. The color seems to be due to fuchsin. The yellow color is produced by Bacterium synxanthum (Ehrenherg). Some of the pigments seem to be related to the aniline, and others to the phenol coloring matters (Hiippe). The rennet- like action of bacteria is a widely diffused property of these organisms; they coagulate and peptonize casein and may ultimately produce further decompositions. The butyric acid bacillus (^ 184) first coagulates casein, then peptonizes it, and finally splits it up, with the evo- lution of ammonia [Hiippe). Milk becomes stringy, owing to the action of cocci [Schmidt, MUlheim), which form a stringy substance [ = de.xtran, CjjHjdO,^ (Scheibler)'],]ns\. as beer or wine undergoes a similar or ropy change. [The milk of diseased animals may coniain or transmit directly infectious matter.] Preparations of Milk — (i) Condensed milk — 80 grms. cane sugar are added to i litre of milk ; the whole is evaporated to i ; and while hot sealed up in tin cans [Lignac). For children one teaspoonful is dissolved in a pint of cold water, and then boiled. (2) Koumiss is prepared by the Tartars from mare's milk. Koumiss and sour milk are added to milk, the whole is violently stirred, and it undergoes the alcoholic fermentation, whereby the milk sugar is first changed into galactose, and then into alcohol; so that koumiss contains 2 to 3 per cent, of alcohol ; while the casein is at first precipitated, but is afterward partly redissolved and changed into acid albumin and peptone [Dochmann). Tartar koumiss seems to be produced by the action of a special bacterium (Diaspora caucasia, A'ern). (3) Cheese is prepared by coagulating milk with rennet, allowing the whey to separate, and adding salt to the curd. When kept for a long time, cheese "ripens," the casein again liecomes soluble in water, probably from the formation of soda albuminate ; in many cases it becomes semi- fluid when it takes the characters of peptones. When further decomposition occurs, leucin and tyrosin are formed. The fats increase at the exjiense of the casein, and they again undergo further change, the volatile fatty acids giving the characteristic odor. The formation of peptone, leucin, tyrosin and the decomposition of fat recalls the digestive processes. [Cheese is coagulated casein entangling more or less fat, so that the richness of the cheese will depend upon the kind of milk from which it is made. There are, in this sense, three kinds of cheese, wlwle milk, skim milk, and cream cheese, the last being represented by Stilton, Roquefort, Cheshire, etc. FLESH AND ITS PREPARATIONS. The composition is shown in the following table, after Bauer : — 381 Water. Nitrogeneous Matter. Fat. Extractives. Ash. Cream cheese Whole milk Skim milk 35-75 46.S2 48.02 7.16 27.62 32-65 30.43 20.54 8.41 2-53 2-97 6.80 4-13 305 4-12 Cream cheese, especially if it be made from goat milk, acquires a verj' high odor and strong flavor when it is kept and " ripens ;" the casein is partly decomposed to yield ammonia and ammo- nium sulphide, while the fats yield butyric, caproic and other acids.] 232. EGGS. — Eggs must be regarded as a complete food, as the organism of the young chick is developed from them. The yelk contains a characteristic proteid body — vitellin (§ 249), and an albuminate in the envelopes of the yellow yelk spheres — niiilein, from the white yelk ; fats in the yellow yelk (palmitin, olein), cholesterin, much lecithin; and as its decomposition product, glycerin- phosphoric acid — grape sugar, pigments (lutein), and a body containing iron and related to hsemoglobin ; lastly, salts qualitatively the same as in blood — quantita- tively as in the blood corpuscles — and gases. The chief constituent of the white of egg is egg albumin (§ 249), together with a small amount of palmitin and olein partly saponified with soda : grape sugar, extractives ; lastly, salts, qualita- tively resembling those of blood, but quantitatively like those of jvr//w and a trace of fluorine. [The shell is composed chiefly of mineral matter (91 per cent, of calcic carbonate, 6 per cent, of calcic phosphate, and 3 per cent, of organic matter). .^ hen's egg weighs about 1^4 oz., of which the shell forms about j'^. Composition :— White of Egg. Yelk. Water 84.8 51.5 Proleids 12.0 15.0 Fats, etc 2.0 30.0 Mineral matter 1.2 1.4 Pigment extractives 2.1 This shows the large amount oi fatty matter in the yelk.] Relatively more of the nitrogenous constituents than the fatty constituents of eggs are absorbed {Rubncr). 233. FLESH AND ITS PREPARATIONS.— Flesh, in the form in which it is eaten, contains, in addition to the muscle substance proper, more or less of the elements of fat, connective and elastic tissue mixed with it (§ 293). The following results refer to flesh freed as much as possible from the constituents. The chief proteid constituent of the contractile muscular substance is myosin {Kuhne') ; serum albumin occurs in the fluid of the fibres, in the lymph and blood of muscle. 'Y\\efais are for the most part derived from the interfibrillar fat cells, while lecithin and cholesterin come from the nerves of the muscles ; the gelatin is derived from the connective tissue of the perimysium, perineurium, and the walls of blood vessels and tendons. The red color of the flesh is due to the hemo- globin present in the sarcous substance {Kiihne, Gscheidlen), but in some muscles, e.g., the heart, there is a special pigment, myo-hsematir. {MacMunn^. Elastin occurs in the sarcolemma, neurilemma, and in the elastic fibres of the perimysium and walls of the vessels ; the small amount of keratin is derived from the endo- thelium of the vessels. The chief muscular substance, the result of the retrogres- sive metabolism of the sarcous substance, is kreatin ( — 0.25 per cent., Chevreul, Perls) ; kreatinin. the inconstant inosinic acid, then lactic, or rather sarcolactic acid (§ 293I. Further, taurin, sarkin, xanthin, uric acid, carnin, inosit (most abundant in the muscles of drunkards), urea (.01 per cent.), dextrin (in horse and 382 FLESH AND ITS PREPARATIONS. rabbit, not constant — Sanson, Limpricht) ; grape sugar i^Meissner'), but it is very probably derived /' acids. Among the salts, potash and phosphoric acid compounds {Braconnof) are most abundant ; magnesium phosphate exceeds calcium phosphate in amount. [The composition varies somewhat even in different muscles of the same animal.] In icxD parts Flesh there is, according to Schlossberger and v. Bibra — Ox. Calf. Deer. Pig. Man. Fowl. Carp. Frog. Water Solids 77-5° 22.50 1 2.20 1.30 1.50 7820 21.80 2.60 1.60 1.40 74.63 2537 1.94 0.50 4-75 78.30 21.70 2.40 0.80 1.70 74.45 25.55 •■93 2.07 3.71 2.30 15.54 77.30 22.7 3-0 { 1.2 1.4 16.5 79.78 20.22 2.35 80.43 »9-57 1.86 Soluble albumin Coloring matter Glutin Alcoholic extract Fats . . . 1.98 3.47 I. II II.31 2.48 3.46 O.IO 11.67 Insoluble albumin, Blood vessels, etc 17.50 162 16.81 i6.8i In 100 parts Ash there is- Horse. Ox. Calf. Pig. Potash 39-40 4.S6 3.88 1.80 35-94 3.31 '•73 536 4.S6' 0.98 34.36 3.37 2.07 8.02 0.15 34.40 2-35 1:45 1.99 37-79 4.02 4.81 7.54 Chalk I.IO 46.74 0.30 } >o.59 { 0.27 48.13 0.40 0.62 0.35 44.47 Chlorine Iron oxiJe Phosphoric acid 0.81 The amount of fat in flesh varies very much, according to the condition of the animal. After removal of the visible fat, human flesh contains 7.15; ox, II. 12; calf, 10.4; sheep, 3.9; wild goose, 8.8 ; fowl, 2.5 per cent. The amount of extractives is most abundant in those animals which exhibit energetic muscular action; hence it is largest in wild animals. The extract is increased after vigorous muscular action, when sarcolactic acid is developed, and the flesh becomes more tender and is more palatable. Some of the extractives excite the nervous system, e. g., kreatin and kreatinin ; and others give to flesh its characteristic agreeable flavor [" osmasome,"] but this is also partly due to the different fats of the flesh, and is best developed when the flesh is cooked. The extractives in 100 parts of flesh are in man and pigeon, 3 ; deer and duck, 4 ; swallow, 7 per cent. Preparation, or Cooking of Flesh. — As a general rule, the flesh of young animals, owing to the sarcolemma, connective tissue, and elastic constituents being less tough, is more tender and more easily digested than the flesh of old animals ; after flesh has been kept for a time it is more friable and tender, as the inosit becomes changed into sarcolactic acid and the glycogen into sugar, and this .-igain into lactic acid, whereby the elements of the flesh undergo a kind of maceration. Finely divided flesh is more digestible than when it is eaten in large pieces. In cooking meat, the heat ought not to be too intense, and ought not to be continued too long, as the muscular fibres thereby become hard and shrink very much. Those parts are most digestible which are obtained from the centre of a roast where they have been heated to 60° to 70° C , as this temperature is sufticient, with the aid of the acids of the flesh, to change the connective tissue into gelatin, whereby the fibres are loosened, so that the ga>itric juice readily attacks them. In roasting beef, apply heat suddenly at first, to coagulate a layer on the surface, which prevents the exit of the juice. VEGETABLE FOODS. 383 Meat Soup is best prepared by cutting the flesh into pieces and placing them for several hours in cold waier, and afterward boiling. Liebig found that 6 parts per too of ox flesh were dissolved by cold water. When this cold extract was boiled, 2.95 parts were precipitated as coagulated albumin, which is chiefly removed by "skimmini;," so that only 3.05 parts remain in solution. From 100 parts of flesh of fowl, 8 parts were extracted, and of these 4.7 coagulated and 3.3 remamed dissolved in the soup. By boiling for a very long time, part of the albumin may be redissolved (Mulder]. The dissolved substances are : ( i ) Inorganic salts of the meat, of which 82. 27 per cent, pass into the soup ; the earthy phosphates chiefly remain in the cooked meat. (2) Kreatin, kreatinin, the inosin- ates and lactates which give to broth or beef tea their stiniulatinc: qualities, and a small amount of aromatic extractives. (3) Gelatin, more abundantly extracted from the flesh of young animaN. According to these facts, therefore, flesh, brolh or beef-tea is a powerful stimulant, supplying muscle with restoratives, but is not a food in the ordinary sense of the term, as kreatin (-■. Voil) in general leaves the body unchanged. The flesh, especially if it be cooked in a large mass, after the extrac- tion of the broth is still available as a food. Liebig's Extract of Meat is an extract of flesh evaporated to a thick syrupy consistence. It contains no fat or gelatin, and is chiefly a solution of the extractives and salts of flesh. [Extract of Fish. — A similar extract is now prepared from fish, and such extract has no fishy flavor, but presents much the same appearance, odor, and properties as extract of flesh.] 234. VEGETABLE FOODS.— The nitrogenous constituents of plants are not so easily absorbed as animal food {Rubner'). Carbohydrates, starch, and sugar are very completely absorbed, and even a not inconsiderable proportion of cellulose may be digested (yU'ciske, Konig). The more fits that are contained in the vegetable food, the less are the carbohydrates digested and absorbed. I. The cereals are most important vegetable foods; they contain proteids, starch, salts, and water to 14 per cent. The nitrogenous glutin is most abundant under the husk (Fig. 222, c). The use of whole meal containing the outer layers of the grain is highly nutritive, but bread containing much bran is somewhat in- digestible (^Rubner). Their composition is the following : — 100 Parts of the Dry Meal contain 100 Parts of Ash contain Of Albumin. Starch. Red 1 Wheat. 1 White Wheat. Wheat .... Rye Barley .... Maize Rice Buckwheat . . 16.52 % 11.92 17.70 13-65 7.40 6.8-io.s 56.25 % 60.91 3831 77-74 86.21 65.05 27.87 IS-7S 1-93 9.60 1.36 49-36 O.IS Potash Soda Lime Magnesia .... Iron oxide .... Phosphoric Acid . Silica 33.84 309 13-54 0.31 59-21 It is curious to observe that soda is absent from white wheat, its place being taken by other alkalies. Rye contains more cellulose and dextrin than wheat, but less sugar; rye bread is usually less porous. In the preparation of bread the meal is kneaded with water until dough is formed, and to it is added salt and yeasl (Saccharomycetes cerevisioe). When placed in a warm oven, the proteids of the meal begin to decompose and act as a ferment npon the swollen-up starch, which becomes in part changed into sugar. The sugar is further decomposed into CO2 and alcohol, the CO, forms bubbles, which make the bread to "rise" and thus become spongy and porous. The alcohol is driven off by the baking (200°), while much soluble dextrin is formed in the crust of the bread. [But COj may be set free within the dough by chemical means without yeast or leaven, thus forming unfermented bread. This is done by mixing with the dough an alkaline carbonate and then adding an aciti. Baking powders consist of carbonate of soda and tartaric acid. In Dauglish's process for aerated bread, the CO, is forced into water, and a dough is made with this water under pressure, and when the dough is heated, the CO2 expands and forms the spongy bread. Bread as an article of food is deficient in N, while it is poor in fats and some salts. Hence the necessity for using some form of fat with it (butter or bacon).] [Oatmeal contains more nitrogenous substances (gliadin and glutincasein) than wheaten flour, but owing to the want of adhesive properties it cannot be made into bread. The amount of fat and salts is large.] 2. The Pulses contain tnuch albumin, especially vegetable casein i^r legumin : together with starch, lecithin, cholesterin, and 9 to 19 per cent, water. Peas 384 PULSES, POTATOES, FRUITS. contain 18.02 proteids, and 38. Si starch ; beans, 28.54, and 37.50 ; lentils, 29.31, and 40, and more cellulose. Owing to the absence of glutin they do not form dough, and bread cannot be prepared from them. On account of the large amount of proteids which they contain, they are admirably adapted as food for the poorer classes. [3. The whole group of farinaceous substances used as "pudding stuiTs," such as com flour, arrowroot, rice, hominy, are really very largely composed of starchy substance.] 4. Potatoes contain 70 to 81 per cent, water. In the fresh, juicy cellular tis.sue, which has an acid reaction, from the presence of phosphoric, malic, and hydrochloric acids, there is 16 to 23 per cent, of starch, 2.5 soluble albumin, globulin {Zoller), and a trace of asparagin. The envelopes of the cells swell up by boiling, and are changed into sugar and gums by dilute acids. The poisonous solanin occurs in the sprouts. In 100 parts o{ potato ash. May found 46.96 potash, 2.41 sodium chloride, 8. 11 potassium chloride, 6.50 sulphuric acid derived from burned proteids, 7.17 silica. 5. In Fruits the chief nutrient ingredients are sugar and salts; the organic acids give them their characteristic taste ; the gelatinizing substance is the soluble Microscopic characters of wheat (,< 200). a, cells of the bran ; 3, cells of tliin cuticle ; c, glutin cells ; d, starch cells; B, wheat starch (X 350). so-called pectin (Cs^H^hO,,"), which can be prepared artificially by boiling the very insoluble pectose of unripe fruits and mulberries. 6. Green Vegetables are especially rich in salts which resemble the salts of the blood ; thus, dry salad contains 23 per cent, of salts which closely resemble the salts of the blood. Of much less importance are the starch, cell substance, de.xtrin, sugar, and the small amount of albumin which they contain. [Vegetables are chiefly useful for the salts they contain, while many of them are antiscorbutic. Their value is attested by the serious defects of nutrition, such as scurvy, which result when they are not supplied in the food. In Arctic expeditions and in the navy, lime juice is served out as an antiscorbutic] [Preserved Vegetables. — The dried and compressed vegetables of Messrs. Chollet & Company are an excellent substitute for fresh vegetables, and are used largely in naval and military expe- ditions.] Utilization of Food. — As regards what percentage of the food swallowed is actually absorbed, we know that, stated broadly, vegetable food is assimilated to a much less extent than animal food in man. Fr. Hofmann gives the following table as showing this ; — CONDIMENTS, COFFEE, TEA, ALCOHOL. 385 Weight of Food, Vegetable. Animal. Digested. Undigested. Digested. Undigested. Of loo parts of solids " loo " albumin " 100 " fats or carbohyd . . 90-3 24.5 S3-4 9-7 89.9 81.2 96.9 II. I 18,8 3-1] [The following table, abridged from Parkes, shows the composition of the chief articles of diet, and is also used for calculating diet tables : — Beefsteak Fat pork Smoked hain . . . , White fish Poultry White wheaten bread Wheat flour . . . . Biscuit Rice Oatmeal Maize Macaroni Arrow root . . . . Peas (dry) Potatoes Carrots Cabbage .... Butter Egg (tV for shell) Cheese Milk (sp. gr. Cream . . . Skimmed milk Sugar .... 032) 744 39-0 27.8 78.0 74.0 40.0 15.0 8.0 100 15.0 >3-5 '31 '5-4 15.0 74.0 85.0 91.0 6.0 73-5 36.8 86.8 66.0 88.0 30 20.5 9.8 24.8 18.1 21.0 8.0 II.O 15.6 50 12.6 1 0.0 9.0 0.8 22.0 2.0 1.6 1.8 0-3 13s 33-5 40 2.7 4.0 Fats. Carbohyd] s-s 48.9 36-5 2.9 3-« ■•5 2.0 > 3 0.8 S.6 b-7 0-3 2.0 0.16 0.25 5.0 91.0 11.6 243 ,v7 20 7 i.S 96. 1.6 2-3 ■•3 '•7 1-7 o-S 30 1-4 0.8 0.27 2.4 i.o i.o 0,7 2.7 1.0 5-4 0.7 1.8 0.8 0.5] 235. CONDIMENTS, COFFEE, TEA, ALCOHOL.— Some substances are used along with food, not so much on account of their nutritive properties as on account of their stimulating effects and agreeable qualities, which are exerted partly upon the organ of taste and partly upon the nervous system. These are called condiments. Coffee, Tea, and Chocolate are prepared as infusions of certain vegetables [the first of the roasted berry, the second of the leaves, and the third of the seeds]. The chief active ingredients are respectively caffein, thein (CgH,(,N402 + H^O,) and theobromin (C,HgN_,02), which are regarded as alkaloids of the vegetable bases, and which liave recently been prepared artificially from xanthin (E. Fischer). [Guarana, or Brazilian cocoa, is made of the seeds ground into a paste in the form of a sausage. Mate or Paraguay tea, the leaves of a species of holly, are used in .South America, and so also is the coca of the Andes (Erythroxylon Coca).] These "alkaloids " occur as such in the plants containing them ; they behave like ammonia; they have an alkaline reaction, and form crystalline salts with acids. All thesa vegetable bases act upon the nervous system; some more feebly (as the above), others more powerfully (quinine) ; some stimulate powerfully, or com|)letely paralyze (morphia, atropin, strychnin, curarin, nicotin, mus- carin). Effects. — All these substances act on the nervous system ; they quicken thought, accelerate movement, and stir one to greater activity. In these respects they re- semble the stimulating extractives — kreatin and kreatinin — of beef tea. Coffee contains about y'l per cent, of caffein, part of which is only liberated by the act of roasting. Tea has 6 per cent, of thein ; while green tea contains i per cent, ethereal oil, and black tea j/ per cent. ; in green tea there is 18 per cent., in 386 PREPARATION OF ALCOHOLIC DRINKS. black, 15 per cent, tannin ; green tea yields about 46 per cent., and the black scarcely 30 per cent, of extract. The inorganic salts present are also of im- portance ; tea contains 3.03 per cent, of salts, and among these are soluble com- pounds of iron, manganese, and soda salts. In coffee, which yields 3.41 per cent. of ash, potash salts are most abundant ; in all three substances the other salts which occur in the blood are also present. Alcoholic Drinks owe their action chiefly to the alcohol which they contain. The alcohol, when taken into the body, undergoes certain changes and produces certain effects: (i) About 95 per cent, of it is oxidized chiefly into CO.j and H2O, so that it is so far a source of heat. .\s it undergoes this change very read- ily, when taken to a certain extent, it may act as a substitute for the consumption of the tissues of the body, especially when the amount of food is insufficient. [Hammond found that when he lived on an insufficient amount of food, alcohol, if given in a certain quantity, supplied the place of the deficiency of food, and he even gained in weight. If, however, sufficient food was taken, alcohol was unnec- essary. As it interferes with oxidation, and where there is a sufficient amount of other food, in health, it is unnecessary, for dietetic reasons.] Small doses dimin- ish the decomposition of the proteids to the extent of 6 to 7 per cent. Only a very small part of the alcohol is excreted in the urine ; the odor of the breath is not due to alcohol, but to other volatile substances mixed with it, e. g., fusel oil, etc. (2) In small doses it excites, while in large doses it paralvzes the ner- vous system. By its stimulating qualities it excites to greater action, which, however, is followed by depression. (3) It diminishes the sensation of hunger. (4) It e.xcites the vascular system, accelerates the circulation, so that the muscles and nerves are more active, owing to the greater supply of blood. It also gives rise to a subjective feeling of warmth. In large doses, however, it paralyzes the ves- sels, so that they dilate, and thus much heat is given off" (S 213, 7, § 227). The action of the heart also becomes affected, the pulse becomes smaller, feebler, and more rapid. In high altitudes the action of alcohol is greatly diminished, owing to the diminished atmospheric pressure whereby it is rapidly given off from the blood. Alcohol in small doses is of great use in conditions of temporary want, and where the food taken is insufficient in quantity. When alcohol is taken regularly, more especially in large doses, it affects the nervous system, and undermines the psychical and corporeal faculties, partly from the action of the impurities which it may contain, such as fusel oil, which has a poisonous effect upon the nervous sys- tem, partly by the direct effects, such as catarrh and inflammation of the digestive organs, which it produces, and lastly, by its effect upon the normal metabolism. [The action of alcohol in lowering the temperature, even in moderate doses, is most important. By dilating the cutaneous vessels, it thus permits of the radiating of much heat from the blood. When the action of alcohol is pushed too far — and especially when this is combined with the action of great cold — its use is to be condemned.] [Brunton has pointed out that, as regards its action on the nervous system, it seems to induce progressive paralysis, affecting the nervous tissues " in the mverse order of their development, the highest centres being affected first and the lowest last." The judgment is aflected first, although the imagination and "emotions maybe more than usually active." 'Y\\^ motor centres znA speeck are aflected, then the cerebellum is influenced, and afterward the cord, while, by and by, the centres essential to life are paralyzed, provided the dose be sufficiently large.] Preparation. — .Mcoholic drinks are prepared by the fermentation of various carbohydrates, such as sugar derived from starch. The alcoholic fermentation, such as occurs in the manufacture of beer, is caused by the development of the yeast plant, Saccharomycetes cerevisise ; while in the fermentation of the grape (wine), S. ellipsoideus is the species present (Fig. 223). The yeast tal4. If food be taken in which this proportion is not observed, in order to obtain the necessary amount of that substance which is contained in too small proportion in his food, he must consume far too much food. Moleschott finds that a person, in order to obtain the 130 grammes of proteids necessary, must use Cheese 338 grms. I Beef. 614 grms. I Rice 2562 grms. Lentils 491 " Epgs 96S " Rye bread . . . 2875 " Peas 5S2 " I Wiieat bread . . 1444 " | Potatoes . . . 10,000 " provided he were to take only one of these substances as food ; so that it is per- fectly obvious that, if a workman were to live on potatoes alone, m order to get the necessary amount of N, he would have to consume an altogether preposterous amount of this kind of food. To obtain the 448 grammes of carbohydrates, or the equivalent amount of fat necessary to support him, a man must eat Rice 572 grms. I Peas 819 grms. I Cheese 201 1 grms. Wheat bread . . . 626 " Eggs 902 " Potatoes .... 2039 " Lentils 806 " ] Rye bread .... 930 " | Beef 2261 " so that if he were to live upon cheese or flesh alone, he would require to eat an enormous amount of these substances. In the case of the herbivora, the proportion of nitrogenous to non-nitrogenous food necessary is I of the former to 8 or 9 parts of the latter. 237. METABOLISM DURING HUNGER AND STARVATION. — If a warm-blooded animal be deprived of all food, it must, in order to maintain the temperature of its body and to produce the necessary amount of me- chanical work, transform and utilize the amount of potential energy of the con- stituents of its own body. The result is that its body weight diminishes from day to day, until death occurs from starvation. The following table, from Bidder and Schmidt, shows the amounts of the diflerent excreta in the case of a starved cat : — Day. Body Weight. Water taken. Urine. Urea. Inorganic Substances in Urine. Dry Faces. Expired Water in Urine and Faeces. I. 2464 98 7-9 1-3 1.2 13-9 91.4 2. 2297 II.5 54 5-3 0.8 1.2 12.9 50.5 3- 2210 45 4.2 0.7 I.I 12 42.9 4. 2172 68.2 45 3-8 0-7 I.I 12.3 43 5- 2129 55 4-7 0.7 1-7 11.9 54.1 6. 2024 44 4-3 0.6 0.6 11.6 41. 1 7- 1946 40 3-8 °S 0.7 II 37-5 8. 1873 42 3-9 0.6 I.I 10.6 40 9- 1782 15.2 42 4 0-5 1-7 10.6 41.4 10. I717 35 . 3-3 0.4 1-3 lo.s 34 II. 169s 4 32 2.9 0.5 I.I 10.2 3°-9 12. 1634 22.5 30 2-7 0.4 I.I 10.3 29.6 '3- 1570 7-1 40 3-4 0.5 0.4 lO.I 36.6 14. 1518 3 41 3-4 0.5 0-3 9-7 3^ '5- "434 41 2.9 0.4 0-3 9-4 38-4 16. 1389 48 3 0.4 0.2 8.8 45-5 '7- '335 28 1.6 0.2 0-3 7.8 26.6 i8.t 1267 -1197 13 0.7 0.1 03 6.1 12.9 «3i-5 775 659 9.8 158 190.8 737-4 LOSS OF WEIGHT OF ORGANS DURING STARVATION. 395 The cat lost 1197 grms. in weight before it died, and this amount is apportioned in the following way: 204.43 grms. ( = 17.01 per cent.) loss of albumin; 132.75 grms. (:= 11.05 Psr cent.) loss of fat; 863.82 grms. loss of water ( = 71.91 per cent, of the total body weight). Methods. — In order to investigate the condition of inanition it is necessarj- — (i) to weigh the a'pinial daily ; (2) to estimate daily all the C and N given oft' from the body in the feces, urine and expired air. The N and C, of course, can only be obtained from the decomposition of tissues con- taining them. Among the general phenomena of inanition, it is found that strong, well-nourished dogs die after 4 weeks, man after 21-24 days {MoUschott) — (6 melancholies who took water died after 41 days); small mammals and birds, 9 days, and frogs 9 months. Vigorous adults die when they lose y't, of their body weight, but ynung individuals die much sooner than adults. The symptoms are obvious: The mouth is dry, the walls of the alimentary canal become thin, and the digestive secretions cease to be formed ; pulse beats and respirations are fewer; urine very acid from the presence of an increased amount of sulphuric and phosphoric acids, while the chlorine compounds rapidly diminish and almost disappear. The blood contains less water and the plasma less albumin, the gall bladder is distended, which indicates a contmuous decomposition of blood corpuscles within the liver. The liver is small and very dark-colored, the muscles are very brittle and dry, so that there is great muscular weakness, and death occurs, with the signs of great depression and coma. The relations of the metabolism are givn in the foregoing table, the diminution in the excretion of urea is much greater than that of CO^, which is due to a larger amount of fats than proteids being decomposed. According to the calculation, there is daily a tolerably constant amount of fat used up, while, as the starvation continues, the proteids are decomposed in much smaller amounts from day to day, although the drinking of water accelerates their decomposition. The excretion of CO.., therefore, falls more slowly than the total body weight, so that the unit weight of the living animal from day to day may even show an increased production of CO^. The amount of O consumed depends, of course, upon the oxidation of proteids (which require less O), and of fats (which require more O). According to D. Finkler, starving animals consume nearly as much O as well-nourished animals, so that the energy of oxidation is scarcely altered during inanition. Corresponding to this, the tem- perature of a starving animal is the same as normal. The respiratory quotient {\ 124) then falls from 0.9 to 0.7, and the excretion of CO, diminishes more rapidly than the consumption of O. It would be wrong, however, to conclude, i'rom the diminished excretion of CO,, that the oxidation also was diminished, as the simultaneous consumption of O is the only guide to the energy of the metabolism. As starving animals use up their own flesh and fat, they form less CO2 than well- nourished animals, which oxidize carbohydrates chiefly. Loss of Weight of Organs. — It is of importance to determine to what extent the individual organs and tissues lose weight ; some undergo simple loss of weight, e.g., the bones, the fat undergoes very considerable and rapid decomposition, while other organs, as the heart, undergo little change, because they seem to be able to nourisii themselves from the transformation products of other tissues. A starving cat, according to v. Voit, lost — Per cent, originally present. 1. fat 97 2. Spleen .... 66.7 3- Liver 53.7 4. Testicles . . . 40.0 5. Muscles .... 30.5 6. Blood 27.0 7. Kidneys .... 25.9 8. Skin 20.6 9. Intestine . . . 18.0 There is a very important difference according as the animals before inanition have been fed freely on flesh and fat [/. e., if they have a surplus store of food within themselves], or as they have merely had a subsistence diet. Well-fed ani- mals lose weight much more rapidly during the first few days than on the later Per cent of Percent. Pe r cent, of ttie total 1 «sof originally the otal loss of body weight. present. body weight. 26.2 10. Lungs . . . . 17.7 0-3 0.6 II. Pancreas . . . 17.0 0.1 4.8 12. Bones . . . . 13-9 5-4 O.I «3- Central Nerv- 42.2 ous System 3-2 0.1 3-7 14. Heart . . . . 2.6 0.02 0.6 IS- Total loss of 8.8 the rest of 2 the body . . 36.8 50 396 METABOLISM OF PEPTONES. days. V. Voit thinks that the albumin derived from the excess of food occurs in a state of loose combination in the body as " circulating " or " storage albumin,'" so that during hunger it must decompose more readily and to a greater extent than the " organic albumin," which forms an integral part of the tissues (§ 236). Further, in fat individuals, the decomposition of fat is much greater than in slender persons. 238. METABOLISM ON A PURELY FLESH DIET— ALBU- MIN OR GELATIN, PROTEID METABOLISM.— A man is not able to maintain his metabolism in equilibrium on a purely flesh diet ; if he were com- pelled to live on such a diet, he would succumb. The reason is obvious. In beef, the proportion of nitrogenous to non-nitrogenous elementary constituents of food is I : 1.7 (p. 392). A healthy person excretes 280 grammes [8 to 90Z.] of carbon, in the form of COj, in the expired air, and in the urine and fasces. If a man is to obtain 2S0 grammes C from a flesh diet, he must consume — digest and assimilate — more than 2 kilos. [4.4 fts.] of beef in twenty-four hours. I3ut our digestive organs are unequal to this task for any length of time. The person is soon obliged to take less beef, which would necessitate the using of his own tissues, at first the fatty parts and afterward the proteid substances. A carnivorous animal (dog), whose digestive apparatus, being specially adapted for the diges- tion of flesh, has a short intestine and powerfully active digestive flu'ds, can only maintain its meta- bolism in a state of equilibrium when fed on a tiesh diet free from fat, provided its body is already well supplied with fat, and is muscular. It consumes ^-^ to ^L part of the weight of its body in flesh, so that the excretion of urea increases enormously. If it eats a larger amount, it may " put on flesh," when, of course, it requires to eat more to maintain itself in this condition, unless the limit of its digestive activity is reached. If a well-nourished dog is fed on less than 4^ to ^^ of its body weight of tlesh. it uses part of its own fat and muscle, gradually diminishes in weight, and ulti- mately succumbs. Poorly-fed non-muscular dogs are unable from the very beginning to maintain their metabolism in equilibrium for any length of time on a purely flesh diet, as they must eat so large a quantity of flesh that their digestive organs cannot digest it. The herbivora cannot live upon flesh f jod, as their digestive apparatus is adapted solely for the digestion of vegetable food. [The proteid metabolism depends (i) on the amount of proteids ingested, for the great mass of these becomes changed into circulating albumin {v. Voit) ; (2) upon the previous condition of nutrition of the organism, for we know that a certain amount of proteid may produce very different results in the same individual when he is in good health, and when he has suffered from some exhausting disease ; (3) it is also influenced by the use of other foods, c. g., fats and carbohydrates. If a certain amount of fat be added to a diet of flesh, much less flesh is required, so that the N metabolism is reduced by fat. This is spoken of as the " albumin- sparing action" of fats.] Exactly the same result occurs with other forms of proteids as with flesh. It has been proved that gelatin may, to a certain extent, replace proteids in the food, in the proportion of 2 of gelatin to i of albumin. The carnivora, which can maintain their metabolism in equilibriutn by eating a large amount of flesh, can do so with less flesh when gelatin is added to their food. A diet of gelatin alone, which produces much urea, is not sufficient for this purpose, and animals soon lose their appetite for this kind of food {i>. Bischoff, v. Voit, v. Pcttetikofer, Oerum). [Voit has shown that gelatin readily undergoes metabolism in the body and forms urea, and if a small quantity be taken it is completely and rapidly metabolized. When administered, it acts, just like fats and carbohydrates, as an "albumin-sparing" substance. It seems that gelatin is not avail- able directly for the growth and repair of tissues (jS(7«.?;-).] Owing to the great solubility of gelatin, the value of gelatin as a food used to be greatly discussed, and now, again, the addition of gelatin in the form of calf's-foot jelly is recommended to invalids. [When a large amount of gelatin is given as food, owing to the large and rapid excretion of urea the latter excites diuresis.] When chondrin is given along with flesh for a time, grape sugar is found in the urine (Bodeker). [The Metabolism of Peptones. — Most of the proteids absorbed into the blood are previously converted into peptones by the digestive juices. It has been FLESH AND CARBOHYDRATES. 397 asserted, more especially by Briicke, that some albumin is absorbed unchanged (§ 192, 4), and that only this is capable of forming organic albumin, while the jieptones, after undergoing a reconversion into albumin, undergo decomposition as such. This view is opposed by many observers {Adamkiewicz, Plbsz, Maly), who maintain that peptones perform all the functions of proteids, so that peptones, with the other necessary constituents of an adequate diet, form an adequate diet.] 239. A DIET OF FAT OR OF CARBOHYDRATES.— If fat alone be given as a food, the animal lives but a short time. The animal so fed secretes even less urea than when it is starving ; so that the consumption of fat limits the decomposition of the animal's own proteids. This depends upon the fact that fat, being an easily oxidized body, yields heat chiefly, and becomes sooner oxi- dized than the nitrogenous proteids which are oxidized with more difficulty. If the amount of fat taken be very large, all the C of the fat does not reappear, e. g., in the CO^ of the expired air; so that the body must acquire fat, while at the same time it decomposes proteids. The animal thus becomes poorer in proteids and richer in fats at the same time. [The Metabolism of Fats is not dependent on the amount of fats taken with the food. I. It is largely influenced by work, i. e., by the activity of the tissues, and, in fact, with muscular work CO.. is excreted in greatly increased amount (§ 127, 6). 2. By the temperature of the surroundings, as more CO^ is produced in the cold (§ 214, 2), and far more fatty foods are required in high latitudes.] [In their action on the organism, proteids and fats so far oppose each other, as the former increases the waste, and therefore oxidation, while the latter diminish it, probably by affecting the metabolic activity of the cells themselves {Bauer). As a matter of fact, fat animals or persons bear starvation better than spare indi- viduals. In the latter, the small store of fat is soon used up, and then the albumin is rapidly decomposed. For the same reason, corpulent persons are very apt to become still more so, even on a very moderate diet.] When carbohydrates alone are given, they must fir.st be converted by the act of digestion into sugar. The result of such feeding coincides pretty nearly with the results of feeding with fat alone. But the sugar is more easily burned or oxidized within the body than the fat, and 1 7 parts of carbohydrate are equal to 10 parts of fat. Thus the diet of carbohydrates limits the excretion of urea more readily than a purely fat diet. The animals lose flesh, and appear even to use up part of their own fat. [The Metabolism of Carbohydrates. — They also serve to diminish the proteid metabolism, a.s they are rapidly burned up and thus "spare" the circu- lating albumin. But Pettenkofer and Voit assert that they are rapidly destroyed in the body, even when given in large amount, so that they differ from fats in this respect. They are more easily oxidized than fats, so that they are always con- sumed first in a diet of carbohydrates and fat. By being consumed, they protect the proteids and fats from consumption.] The direct introduction of grape sugar and cane sugar into the blood does not increase the amount of o.vygen used, although the amount of CO2 formed is increased (IVo/fers). [The doctrine of Liebig, that the oxygen taken in was a measure of the metabolic processes, is refuted by these and other experiments. It would seem that fat is not directly oxidized by O, but that it is split up into other simpler compounds whidi are slowly and gradually oxidized; in fact, fat may lessen the amount of (J taken in, as it diminishes waste.] 240. FLESH AND FAT, OR FLESH AND CARBOHYDRATES. — Since an amount of flesh equal to ^'3- to -i,'^ of the weight of the body is required to nourish a dog which is fed on a purely flesh diet, if the necessary amount of fat or carbohydrates be added to the diet, a smaller quantity of flesh is required [v. Voit and Grubei-). For 100 parts of fat added to the flesh diet, 245 parts of dry fle.sh or 227 of syntonin can be dispensed with. If instead of fats carbohy- drates are added, then 100 parts of fat =^ 230-250 of the latter {Riibner). 398 ORIGIN OF FAT IN THE BODY. When the amount of flesh is insufficient, the addition of fat or carbohydrates to the food always limits the decomposition of the animal's own substance. Lastly, when too much flesh is given along with these substances, the weight of the body increases more with them than without them. Under these circumstances, the animal's body puts on more fat than flesh. The consumption of O in the body is regulated by the mixture of flesh and non-nitrogenous substances, rising and falling with the amount of flesh consumed. It is remarkable that more O is consumed when a given amount of flesh is taken, than when the same amount of flesh is taken with the addition of fat (v. Pctten- kofer and v. Voit). It seems that, instead of fat, the corresponding amount of fatty acids has the same effect on the metabolism. [If a dog be fed with fatty acids and a sufficient amount of proteid, no fatty acids are found in the chyle, while fat is formed synthetically, the glycerin for the latter probably being pro- duced in the body.] They are abs prbed as an emulsion, just like the fats. When so absorbed, they seem to be reconverted into fats in their passage from the intestine to the thoracic duct, probably by the action of the leucocytes (_/. Muni, U'i/l). Glycerin does not diminish the decomposition of albumin within the body (Lewin, Tscliirwinsky, J. Munk). Accordmg to Lebedeff and v. Voit, it diminishes the decomposition of the fats, and is therefore a food. 241. ORIGIN OF FAT IN THE BODY.— I. Part of the fat of the body is derived directly from the fat of the food, /. e., it is absorbed and depos- ited in the tissues. This is shown by the fact that, with a diet containing a small amount of albumin, the addition of more fat causes the deposition of a larger amount of fat in the body (v. Voit, Hofmann). Lebedeff found that dogs, which were starved for a month, so as to get rid of all their own fat, on being fed with linseed oil, or mutton suet and Hesh, had these fats restored to their tissues. These fats, therefore, must have been absorbed and deposited. J. Munk found the same on feeding animals with rape-seed oil. Fatty acids may also contribute to the formation of fats, as glycerin when formed in the body must be stored up during metabolism ( J. Muni). II. A second source of the fats is their formation from albuminous bodies {Liebig and others). In the case of the formation of fat from proteids which may yield 11 per cent, of fat (according to Henneberg 100 parts of dry albumin can form 51.5 parts of fat), these proteids split up into a non-nitrogenous and a nitrogenous atomic compound. The former, during a diet containing much al- bumin, when it is not completely oxidized into C0„ and H-^O is the substance from which the fat is formed — the latter leaves the body oxidized chiefly to the stage of urea. Examples. — That fa/lanzani). The Plananans also show a great capability of reproducing lost parts (Du^i-s). .Spiders and crabs can ^reproduce lost feelers, limbs, and claws; snails, part of the heart, feelers, and eyes, provided the central nervous system is not injured. Many fishes reproduce fins, even the tail fin. Salamanders and lizards can produce an entire tail, including bones, muscles, and even the posterior part of the spinal cord; while the triton reproduces an amputated limb, the lower jaw and the eye. This re- production necessitates that a small stump be left, while total expiration of the parts prevents repro- duction [Philtppiaux). In amphibians and reptiles the regeneration of organs and tissues, as a whole, takes place after the type of the embryonic development (Fraisse, GSlte), and the same is true as regards the histo- logical processes which occur in the regenerated tail and other parts of the body of the earthworm (BiiUnv). The extent to which regeneration can take place in mammals and in man is very slight, and even in these cases it is chiefly confined to young individuals. A true regeneration occurs in — 1. The blood (compare § 7 and § 41), including the plasma, the colorless and colored corpuscles. 2. The epidermal appendages (§ 2S3) and the epithelium of the mucous membranes are reproduced by a proliferation of the cells of the deeper layers of the epithelium, with simultaneous division of their nuclei. Epithelial cells are reproduced as long as the matrix on which they rest and the lowest layer of cells are intact. When these are destroyed cell-regeneration from below ceases, and the cells at the margins are concerned in filling up the deficiency. Regeneration, REGENERATION OF TISSUES. 403 therefore, either takes place from below or from the margins of the wound in the epithelial covering ; leucocytes also wander into the part, while the deepest layer of cells forms large multi-nucleated cells, which reproduce by division polygonal, flat, nucleated cells (Kiel's, Heller'). [In the process of division of the cells, the nucleus plays an important part, and in so doing it shows the usual karyokinetic figures (§ 431 )•] The nails grow from the root forward ; those of the fingers in four to five months, and that of the great toe in about twelve months, although growth is slower in the case of fracture of the bones, The matrix is co-extensive with the liinule, and if it be destroyed the nail is not reproduced (§ 284). The eyelashes are changed in 100 to i5odays(Z'(i;/(zVr^), the other hairs of the body somewhat more slowly. If the papilla of the hair follicle be destroyed, the hair is not reproduced. Cutting the hair favors its growth, but hair which has been cut does not grow longer than uncut hair. After hair has grown to a certain length it falls out. The hair never grows at its apex. The epithelial cells of mucous membranes and secretory glands seem to undergo a regular series of changes and renewal. The presence of secretory cells in the milk (§ 231) and in the sebaceous secretion (§ 285) proves this ; the spermatozoa are replaced by the action of sper- matoblasts. In catarrhal conditions of mucous membranes, there is a great increase in the formation and excretion of new epithelium, while many cells are but indifferently formed and constitute mucous corpuscles. The crystalline lens, which is just modified epithelium, is reorganized just like epithelium ; its matrix is the anterior wall of its capsule, with the single layer of cells covering it. If the lens be removed and this layer of cells retained, these cells proliferate and elongate to form lens fibres, so that the whole cavity of the empty lens capsule is refilled. If much water be withdrawn from the body, the lens fibres become turbid {Kunde, Koehiihorn). [A turbid or opaque condition of the lens may occur in diabetes, or after the transfusion of strong common salt or sugar solution into a frog.] 3. The blood vessels undergo extensive regeneration, and they are regener- ated in the same way as they are formed (§ 7, B). Capillaries are always the first stage, and around them the characteristic coats are added to form an artery or a vein. When an artery is injured and permanently occluded, as a general rule the part of the vessel up to the nearest collateral branch becomes obliterated, whereby the derivatives of the endothelial lining, the connective-tissue corpuscles of the wall, and the leucocytes change into spindle-shaped cells, and form a kind of cicatricial tissue. Blind and solid outshoots are always found on the blood vessels of young and adult animals, and are a sign of the continual degeneration and regeneration of these vessels {Sigm. Mayer). Lymphatics behave in the same way as blood vessels ; after removal of a lym- phatic gland, a new one may be formed (Bayer). 4. The contractile substance of muscle may undergo regeneration after it has become partially degenerated. This takes place after amyloid or wax-like degeneration, such as occurs not unfrequently after typhus and other severe fevers. This is chiefly accomplished by an increase of the muscle corpuscles. After being compressed, the muscular nuclei disappear, and at the same time the contractile contents degenerate (T/rtV/f-Z/^ifr^). After several days, the sarcolemma contains numerous nuclei which reproduce new muscular nuclei and the contractile sub- stance (^Kraske, Erhkam). In fibres injured by a subcutaneous wound, Neumann found that, after five to seven days, there was a bud-like elongation of the cut ends of the fibres, at first without transverse striation ultimately. If a large extent of a muscle be removed, it is replaced by cicatricial connective tissue. Non- Striped muscular fibres are also reproduced ; the nuclei of the injured fibres divide after becoming enlarged, and exhibit a well-marked intranuclear plexus of fibrils. The nuclei divide into two, and from each of these a new fibre is formed, prob- ably by the differentiation of the perinuclear protoplasm. 404 REGENERATION OF BONE. 5. After a nerve is divided, the two ends do not join at once so as to permit the function of the nerve to be established. On the contrary, marked changes occur. If a piece be cut out of a nerve trunk, the peripheral end of the divided nerve degenerates, the axial cylinder and the white substance of Schwann disap- pear. The interval is filled up at first with juicy, cellular tissue. The subsequent changes are fully described in § 325, 4. There seems to be in peripheral nerves a continual disappearance of fibres by fatty degeneration, accompanied by a con- secutive formation of new fibres {S/gm. Afavfr). The regeneration of peripheral ganglionic cells is unknown, v. Voit, however, observed that a pigeon, part of whose bram was removed, had within five months reproduced a nervous mass within the skull, consisting of niedullated nerve fibres and nerve cells. Eichhorst and Naunyn found that in young dogs, whose spinal cord was divided between the dorsal and lumbar regions, there was an anatomical and physiological regeneration, to such an extent that voluntary movements could be executed (§ 33S, 3). Vau- lair, in the case of frogs, and Masius in dogs, found that mobility or motion was first restored, and afterward sensibility. Regeneration of the spinal ganglia did not occur. 6. If a portion of a secretory gland be removed, as a general rule, it is not reproduced. But the bile ducts (§ 173) and the pancreatic duct may be reproduced (§ 171)- According to Phihppeaux and Griffini, if part of the spleen be removed it is reproduced (§ 103I. Tizzoni and CoUucci observed the formation of new liver cells and bile ducts after injury to the liver (§ 173), and Pisenti makes the same statement as regards the kidney. After me- chanical injury to the secretory cells of glands (liver, kidney, salivary. Meibomian) neighboring cells undergo proliferation and aid in the restoration of the cells ( IF. Podwisotzky). 7. Among connective tissues, cartilage, provided its perichondrium be not in- jured, reproduces itself by division of its cartilage cells {ReJfern) ; but usually when a part of a cartilage is removed, it is replaced by connective tissue. 8. When a tendon is divided, proliferation of the tendon cells occurs, and the cut ends are united by connective tissue. 9. The reproduction of bone takes place to a great extent under certain con- ditions. If the articular end be removed by excision, it may be reproduced, although there is a considerable degree of shortening. Pieces of bone which have been broken off or sawed oft" heal again, and become united with the original bone {Jakiiiiowitsch). If a piece of periosteum be transplanted to another region of the body, it eventually gives rise to the formation of new bone in that locality. If part of a bone be removed, provided the periosteum be left, new bone is rapidly reproduced ; hence the surgeon takes great care to preserve the periosteum intact in all operations where he wishes new bone to be reproduced. Even the marrow of bone, when it is transplanted, gives rise to the formation of bone. This is due to the osteoblasts adhering to the osseous tissue {F. Burns, AlaiEweii). In fracture of a long bone the periosteum deposits on the surface of the ends of the broken bones a ring of substance which forms a temporary support, the external callus. At first this callus is jelly-like, soft, and contains many corpuscles, but afterward it becomes more solid and somewhat like cartilage. A similar condition occurs within the bone, where an internal callus is formed. The formation of this temporary callus is due to an inflammatory proliferation of the marrow. According to Rigal and Vignal, the internal callus is always osseous, and is derived from the marrow of the bone. The outer and inner callus become calcified ami ultimately ossified, whereby the broken ends are reunited. Toward the fortieth day, a thin layer of bone is formed (intermediary callus) between the ends of the bone. Where this begins to be definitely ossified, the outer and inner callus begm to be absorbed, and ultimately the intermediary callus has the same structure as the rest of the bone. There are many interesting observations connected with the growth and metabolism of bones. I. The addition of a very small amount Qi phosphorus ( Wagner) or arseniotts acid [A/aas) to the food causes considerable thickening of the bones. This .seems to be due to the non-absorption of those parts of the bones which are usually absorbed, while new growth is continually taking place. INCREASE IN SIZE AND WEIGHT DURING GROWTH. 405 2. When food dezwid of lime salts is given to an animal, the growth of the bones is not arrested [v. Poll), but the bones become thinner, whereby all parts, even the organic basis of tlie bone, undergo a nnifoTm diminution (dossal, A. A/ilne-Eihitii ids). 3. Feeding with madder makes the bones red, as the coloring matter is deposited with the bone salts in the bone, especially in the grow- ing and last-formed parts. In birds the shell of the egg becomes colored. 4. The continued use of lacliir acid dissolves the bones (Siedamgrotzky and J/o/mcister). The ash of bone is thereby dimin- ished. If lime salts be withheld at the same time, the effect is greatly increased, so that the bones come to resemble rachitic bones. (Development of Bone, J 447.) When a lost tissue is not replaced by the same kind of tissue, its place is always taken by cicatricial connective tissue. When this is the case, the part becomes inflamed and swollen, owing to an exudation of plasma. The blood vessels become dilated and congested, and notwithstanding the slower circulation, the amount of blood is greater. The blood vessels are increased, owing to the formation of new ones. Colorless blood corpuscles pass out of the vessels and reproduce themselves, and many of them undergo falty degeneration, while others take up nutriment and become converted into large uni- nucleated protoplasma cells, from which giant cells are developed (ZiegUr, Cohnheim). The newly-formed blood vessels supply all these elements with blood. 245. TRANSPLANTATION OF TISSUES.— The nose, ear, and even a finger, after having been severed from the body by a clean cut, have, under certain circumstances, become united to the part from which they were removed. The skin is frequently transplanted by surgeons, as, for example, to fomi a new nose. The piece of skin is cut from the forehead or arm. to which it is left attached by a bridge of skin. The skin is then stitched to the part which it is desired to cover in, and when it has become attached in its new situation, the bridge of skin is severed. Re- verdin cut a piece of skin into pieces about the size of a pea and fixed them on an ulcerated sur- face, where they, as it were, took root, grew% and sent off from their margins epithelial outgrowths, so that ultimately the whole surface was covered with epithelium. The excised spiir of a cnck was transplanted and fixed in the comb of the same animal, where it grew (John Hunter). P. Bert cut off the tail and legs of rats and transplanted them under the skin of the back of other rats, where they united witli the adjoining parts. Oilier found that, when periosteum was transplanted, it grew and reproduced bone in its new situation. Even blood and Ivmph may be transfused (Transfusion, § 102). [Small portions (1.5 mm.) of epiphyses, costal cartilage, of a rabbit or kitten, when trans- planted quite fresh into the anterior chamber of the eye, testis, submaxillary gland, kidney, and under the skin of a ralibit, attach themselves and grow, and the growth is more rapid the more vas- cular the site on which the tissue is transplanted. The cartilage is not essentially different from hyaline cartilage, but the cells are fewer in the centre, while the matrix tends to become fibrous. Small pieces of epiphyseal cartilage introduced into the jugular vein were found as cartilaginous foci in the lungs (Zahn, Leopold). Tissues transplanted from embryonic structures grow far better than adult tissues [Zahn]. Many of these results seem only to be possible between individuals of the same species, although Helferich has recently found that a piece of dog's muscle, w-hen substituted for human muscle, united to the adjoining muscle, and became functionally active. [J. R. Wolfe has transplanted the conjunctiva of the rabbit to the human eye.] Most tissues, however, do not admit of transplantation, e.g., glands and the sense organs. They may be removed to other parts of the body, or into the peritoneal cavity, without exciting any inflammatory reaction; they, in fact, behave like inert foreign matter. 246. INCREASE IN SIZE AND WEIGHT DURING GROWTH.— The length of the body, which at birth is usually ^^ of the adult body, undergoes the greatest elongation at an early period : in the first year, 20 ; in the second, 10 ; in the tliird, about 7 centimetres; while from five to sixteen years the annual increase is about 5J.< centimetres. In the twentieth year the increase is very slight. From fifty onward the size of the body diminishes, owing to the intervertebral disks becoming thinner, and the loss may be 6-7 centimetres about the eightieth year. The weight of the body (j'j of an adult) sinks during the first five to seven days, owing to the evacuation of the meconium and the small amount of food which is taken at first. Only on the tenth day is the weight the same as at birth. The increase of weight is greater in the same time than the increase in length. Within the first year a child trebles its weight. The greatest weight is usually reached about forty, while toward sixty a decrease begins, which at eighty may amount even to 6 kilos. The results of measurements, chiefly by Quetelet, are given in the following table ; — 406 INCREASE IN SIZE AND WEIGHT DURING GROWTH. Length (Cmtr.). Weight (Kilo.). Length (Cmtr.). Weight (Kilo.). Age Age Man. Woman. Man. Woman. Man. Woman. Man. Woman. O 49.6 48.3 3.20 2.91 15 "55-9 147-5 46.41 41-30 I 69.6 69.0 10.00 930 16 161.0 150.0 53-39 44-44 2 79.6 78.0 12.00 11.40 17 167.0 154-4 57.40 49.08 3 86.0 85. 13.21 12.45 18 170.0 .56.2 61.26 53-'o 4 93-2 91.0 15.07 14.18 19 170.6 63-32 5 99.0 97.0 16.70 1550 20 171. 1 157.0 6i;.oo 54-46 6 104.6 103.2 1 8. 04 16.74 25 172.2 157-7 68.29 55.08 7 III. 2 109.6 20. 1 6 18.45 30 172.2 '57-9 68.90 55-14 8 II7.0 II3-9 22.26 19.82 40 i7>-3 155-5 6S.81 56.65 9 122.7 120.0 24.09 22.44 50 166.4 153-6 67-45 58-45 lO 128.2 124.8 26.12 24.24 60 163-9 151.6 65-50 56.73 II 1327 127-5 27-85 26.25 70 162.3 151.4 6303 53-72 12 «35-9 132-7 31.00 30-54 80 161.3 150.6 61.22 51.52 '3 140.3 138-6 35-32 34-65 90 57-83 49-34 H 14S.7 144.7 40.50 38-10 (Chiefly from Quetelet.) Between the twelfth and fifteenth years the weight and size of the girl are greater than of the boy. Growth is most active in the last months of foetal life, and afterward from the sixth to ninth year until the thirteenth to sixteenth. The full stature is reached about thirty, but not the greatest weight [T/wiiia). CHEMICAL CONSTITUENTS OF THE ORGANISM. 247. (A) INORGANIC CONSTITUENTS.— I. Water forms 58.5 per cent, of the whole body, but it occurs in different quantity in the different tissues. The kidneys contain the most water, 82.7 per cent. ; bones, 22 per cent. ; teeth, 10 per cent. ; while enamel contains the least, 0.2 per cent. [ Waler is of the utmost importance in the economy, and it is no paradox to say that all organisms live in water, for though the entire animal may not live in water, all its tissues are bathed by watery fluids, and the essential vital processes occur in water (^ 229). A constant stream of water may be said to be passing through organisms; a certain quantity of water is taken in with the food and drink, which ultimately reaches the blood, while from the blood a constant loss is taking place by the urine, the sweat, and breath. The greater quantity of the water in our bodies is derived from without, but it is probable that a small amount is formed within our bodies by the action of free oxygen on certain organic substances. According to some observers, peroxide of hydrogen (HjOj) is also present in the body.] II. Gases. — [Oxygen is absorbed from the air, and enters the blood, where it forms a loose chemical comjround, with the coloring matter or haemoglobin, while a small amount exists in a free state, or is simply absorbed.] Hydrogen is found in the alimentary canal. Nitrogen, [like oxygen, is absorbed from the atmosphere by the blood, in which it is dissolved, and from which it passes into other fluids of the body. It is probable that a very small quantity is formed within the body.] The presence of marsh gas (CH^) (? 124), ammonia (NH3), CO2 (? 38), sulphuretted hydrogen (HjS) (5 184), and ozone (? 37) has been referred to already. III. Salts. — Sodium chloride [is one of the most important inorganic substances present in the body. It occurs in all the tissues and fluids of the body, and it plays a most prominent part in connection with the diffusion of fluids through membranes, and its presence is necessary for the solution of the globulins (^ 4091. In some cases it exists in a state of combination with albuminous bodies, as in the blood pl.isma. Common salt is absolutely necessary for one's existence ; if it be withdrawn entirely, life soon comes to an end. .-Vbout 15 grammes are given off in twenty-four hours, the great part being excreted by the urine. Boussingault showed that the addition of a certain amount of common salt to the daily food of cattle greatly improved their condition.] [Calcium phosphate (CajP^O, ) is the most abundant salt in the body, as it forms more than one-half of our bones, liut it also occurs in dentine, enamel, and, to a much less extent, in the other solids and fluids of the body. Among secretions, milk contains relatively the largest amount (2.72 per cent.). In milk, it is necessary for forming the calcareous matter of the bones of the infant. It gives bones their hardness, solidity, and rigidity. It is chiefly derived from the food, and, as only a small quantity is given off in the excretions, it seems not to undergo rapid removal from the body,] [Sodium phosphate (PNajO,), acid sodium phosphate (VUdL^O^, acid potassium phosphate (PKjHOj). The sodium phosphate and the corresponding potash salt give most of the fluids of the body their alkaline reaction. The alkaline reaction of the blood plasma is partly due to alkaline phosphates, which are chiefly derived from the food. The acid sodium phosphate is the chief cause of the acid reaction of the urine. A small quantity of phosphoric acid is formed in the body owing to the oxidation of "lecithin," which contains phosphorus, and also forms an important constituent of nerve tissue.] [Sodium carbonate (Na,C03) and sodium bicarbonate fNaHC03) exist in small quantities in the food, and are chiefly formed in the body from the decomposition of the .salts of the vegetable acids. They occur in the blood plasma, where they play an important part in carrying the CO2 from the tissues to the lungs.] [Sodium and potassium sulphates (Na^SO^ and K^SO.,) exist in very small quantity in the body, and are introduced with the food, but part is formed in the body from the oxidation of organic bodies containing sulphur.] [Potassium chloride (KCl) is pretty widely distributed, and it occurs specially in muscle, colored blood corpuscles, and milk. Calcium fluoride (CaFlj) occurs in small quantity in bones and teeth. Calcium carbonate (CaCO,) is associated with calcium phosphate in bone, tooth, and in some fluids, but it occurs in relatively much smaller amount. It is kept in solution by alka- line chlorides, or by the presence of free carbonic acid.] [Ammonium chloride (NH^Cl). — Minute traces occur in the gastric juice and the urine.] 407 408 THE ALBUMINOUS OR PROTEID SUBSTANCES. [Magnesium phosphate (Mga^O^) occurs in the tissues and fluids of the body, along with calcium ]>hospliate, but in very much smaller quantity.] IV. Free Acids. — flydrochloric acid ( HCl) [occurs yVc? in the gastric juice, but in combination with the alkalies it is widely distributed as chlorides]. Sulphuric acid (HjSO^) [is said to occur free in the saliva of certain gasteropods, as Dolium galea. In the body it forms sulphates, being chiefly in combination with soda and potash]. V. Bases. — Silicon as silicic acid (SiOj) ; manganese, iron, the last forms an integral constituent of the blood pigment; copper (?), (§ 174)' 248. (B) ORGANIC COMPOUNDS.— I. THE ALBUMINOUS OR PROTEID SUBSTANCES.— I. True Proteids and their Allies.— Proteids or Albumins and their allies are composed of C, H, O, N. aiul S, and are derived from plants (see Introduction). [According to Hoppe-Seyler their general percentage composition is — O. H. N, C. S. From 20.9 6.9 15.2 51.5 0.3 To 23.5 to 7.3 to 17.0 to 54.5 to 2.O.] They exist in all animal fluids, and in nearly all the tissues. They occur partly in the fluid form, although Briicke maintains that the molecule of albumin e.\ists in a condition midway between a state of imbibition and a true solution, and partly in a more concentrated condition. Besides forming the chief part of muscle, nerve, and gland, they occur in nearly all the fluids of the body, including the blood, lymph, and serous fluids; but in lictillh mere traces occur in the sweat, while they are absent from the bile and the urine. Unboiled white of egg is the type. In the alimentary canal they are changed into peptones. The chief products derived from their o.xidation within the body are COj, H,0, and especially urea, which contains nearly all the N of the proteids. Constitution. — Their chemical constitution is quite unknown. The N seems to exist in two distinct conditions, partly loosely combined, so as to yield ammonia readily when they are decom- posed, and partly in a more fixed condition. According to Pfliiger, part of the N in living proteid bodies exists in the form of cyanogen. The proteid molecule is very large, and is, very probably, a complex one ; a small part of the molecule is composed of substances from the group of aromatic bodies (which become conspicuous during putrefaction), the larger part of the molecule belongs to the /(j/Zj bodies (during the oxidation of albumin, fatty acids especially are developed). Carbo- hydrates may also appear as decomposition products (A'rukenberg). For the decompositions during digestion, see ? 170, and during putrefaction, J 184. The proteids form a large group of closely- related substances, all of which are, perhaps, modifications of the same body. When we remember that the infant manufactures most of the proteids of its ever-growing body from the casein in milk, this last view seems not improbable. Characters. — Proteids, the anhydrides of peptones (§ 166), are colloids (| 191), and, therefore, do not diffuse easily through animal membranes ; they are amorphous, and do not crystallize, and, hence, are isolated with difficulty; some are soluble, others are insoluble, in water; are insoluble in alcohol ; rotate the ray of polarized light to the left ; in a flame, they give the odor of burned horn. Various metallic salts and alcohol precipitate tliem from their solution ; they are coagulated by heat, mineral acids, and the prolonged action of alcohol. Caustic alkalies dissolve them (yellow), and from this solution they are precipitated by acids. By powerful oxidizing agents they yield carbamic acid, guanidin and volatile fatty acids. Decompositions. — When acted upon in a suitable manner by acids and alkalies, they give rise to the decomposition products — leucin (10-18 per cent.), tyrosin (0.25-2 per cent ), asparaginic acid, glutamic acid, and also volatile fatty acids, benzoic and hydrocyanic acids, and aldehydes of benzoic and fatty acids; also, indo (Hlasiwetz, Habermann). Similar products are formed during pan- creatic digestion (^ 170), and during putrefaction [\ 184). Reactions. — ( i) They are coagulated by nitric acid, and when boiled therewith, give 2. yellow, the xanthoproteic reaction ; the addition of ammonia gives a deep orange color. (2) Millon's reagent (nitrate of mercury with nitrous acid); when heated with this reagent above 60° C, they give a red, probably owing to the formation of tyrosin. [If the proteids are present in large amount, a red precipitate occurs; but if mere traces are present, only the fluid becomes red.] (3) The addition of a few drops of solution of cupric sulphate, and the subsequent addition of caustic potash or soda, give a violet color, which deepens on boiling [the same color is obtained by adding a few drops of Fehling's solution (biuret reaction).] (4) They are precipitated by acetic acid and potassium ferrocyanide. (5) When boiled with concentrated hydrochloric acid, they give a violet-red color. (6) Sulphuric acid containing molybdic acid gives a blue color [Frohde]. (7) Their solution in acetic acid is colored violet with concentrated sulphuric acid, and shows the absorption band of hydrobilirubin (.-Idamiie-uncz). (8) Iodine is a good microscopic reagent, which strikes a brownish-yellow, while sulphuric acid and cane sugar give a purplish- violet [E. Schultze). NATIVE ALBUMINS, GLOBULINS AND ALBUMINATES. 409 [(g) When boiled with acetic acid and an equal volume of a concentrated solution of sodic sul- phate, they are precipitated. This method is used for removing proteids from other liquids, as it does not interfere with the presence of other substances. Saturation with sodio-magne^ic sulphate precipitates the proteids, but not peptones.] 249. THE ANIMAL PROTEIDS AND THEIR CHARACTERS.— They have been divided into classes : — Class I. — Native Albumins. — Native albumins occur in a natural condition in the solids and fluids of the body. They are soluble in water, and are not precipitated by alkaline carbonates, NaCl, or by very dilute acids. Their solutions are coagulated by heat at 65°-73° C. Dried at 40° C, they yield a clear, yellow, amber-colored, friable mass, " soluble albumin," which is soluble in water. (1) Serum albumin, whose chemico-physical characters are given in ? 32, and its physiological properties at ?,4i. Almost all its salts may be removed from it by dialysis, when it is no longer coagulated by heat {Sc/imiii/). It is coagulated by strong alcohol, and is easily dissolved in strong hydrochloric acid. When precipitated, it is readily soluble in strong nitric acid. It is not coagulated when shaken up with ether. The addition of water to the hydrochloric solution precipitates acid albumin. For its presence in urine, ^ 264. (2) Egg albumin. When injected into the bloodvessels or under the skin, or even when introduced in large quantity into the intestine, part of it appears unchanged in the urine (^ 192, 4, and ^ 264). When shaken with ether, it is precipitated. These two reactions serve to distinguish it from (i). The specific rotation is 37.8°. Amount of S, 1.6 per cent. (Metalbumin and Paralbumin have been found by Scherer in ropy solutions in ovarian cysts; they are only partially precipitated by heat. The precipitate thrown down by the action of strong alcohol is soluble in water. They are not precipitated by acetic acid, by acetic acid and potassium ferrocyanide, by mercuric chloride, or by saturation with magnesium suljihate. Concentrated sul- phuric acid and acetic acid give a violet color (Atiamkiewicz). According to Hammarsten, met- albumin is a mixture of paralbumin and other proteid substances. On being boiled with dilute sul- phuric acid, they yield a reduciuij substance (? sugar)). Class II.— Globulins. — They are native proteids, which are insoluble in distilled water, but soluble in dilute saline solutions, sodium chloride of i per cent., and in magnesium sulphate. These solutions are coagulated by heat, and are precipitated by the addition of a large quantity of water. Most of them z.k precipitated ito^a their sodium chloride solution by the addition of crystals of sodium chloride, and also bv satiiratini^ their neutral solution at 30° 7uith crystals of magnesium sulphate. When acted upon by dilute acids, they yield acid albumin, and by dilute alkalies, alkali albumin. (1) Globulin (Crystallin) is obtained by passing a stream of CO2 through a watery extract of the cry.stalline lens. (2) Vitellin is the chief proteid in the yelk of egg. It is also said to occur in the chyle (?) and in the amniotic fluid ( IVeyl). Both the foregoing are not precipitated from their neutral solutions by saturalinn with sodium chloride. (3) Paraglobulin or Serum globulin (| 29), and in urine, | 264. (4) Fibrinogen ( J 291. (5) Myosin is the chief proteid in dead muscle. Its coagulation in muscle post mortem consti- tutes rigor mortis. If muscle be repeatedly washed, and afterward treated wiih a 10 per cent, solution of sodium chloride, it yields a viscid fluid, which, when dropped into a large quantity of distilled water, gives a white flocculent precipitate of myosin. It is also precipitated from its NaCl solution by cry.stals of NaCl. For Kiihne's method of preparation, see ^ 293. (6) Globin (Preyer), the proteid residue of hemoglobin, ^ 18. Class III. — Derived Albumins (Albuminates). — (i) Acid Albumin or Syntonin. — When proteids are dissolved in the stronger acids, e.i^., hydrochloric, they become changed into acid albumins. They are precipitated from solution by the addition of many salts (NaCl, Na^SOj), or by neutralization with an alkali, e.g., sodic carbonate, but they are not precipitated by heat. The concentrated solution gelatinizes in the cold, and is redissolved by heat. Syntonin, which is obtained by the prolonged action of dilute hydrochloric acid (2 per 1000) upon minced muscle, is also an acid alliumin. It is formed also in the stomach during digestion (J 166, 1). According to Soyka, the alkali- and acid albumins differ from each other only in so far as the proteid in the one case is united with the base (metal) and in the other with the acid. (2) Alkali Albumin. — If egg- or serum albumin be acted upon by dilute alkalies, a solution of alkali albumin is obtained. Strong caustic potash acts upon white of egg, and yields a thick jelly {Liebt-rkiVin). The solution is not precipitated by heat, but it is precipitated by the addition of an acid. ' (3) Casein is the chief proteid in milk [\ 231). It is precipitated by acids and by rennet at 40° C. In its characters it is closely related to alkali albuminate, but, according to O. Nasse, it contains more N. It contains a large amount of phosphorus (0.S3 per cent.). It may be precipitated from milk by diluting it with several times its volume of water and adding dilute acetic acid, or by adding magnesium sulphate crystals to milk and shaking vigorously. Owing to the large amount of phos- 410 VEGETABLE PROTEID BODIES. phorus which it contains, it is sometimes referred to the nucleoalbumins. When it indigested with dilute HC! lo. i ]ier cent.) and pepsin at the temperature of the body, it gradually yields nuclein. Class IV. — Fibrin. — For fibrin, see ^ 27, and for the fibrin factors, '^ 29. Class V. — Peptones. — For peptones and propeptone [hemialbumose], see J 166, I, and in urine, ? 264. Class VI. — Lardacein and Other Bodies. — There fall to be mentioned the " yelk plates." which occur in the yelk: Ichthin (cartilaginous fishes, frog); Ichthidin (osseous fishes); Ichthulin (salmon); Emydin (tortoise — Valenciennes and Fremy); also the indigestible amy- loid substance ( Virehoui) or lardacein, which occurs chiefly as a palhological infiltration into various organs, as the liver, spleen, kidneys and blood vessels. It gives a blue with iodine and sulphuric acid (like cellulose), and a mahogany brown with iodine. It is difificult to change it into an albuminate by the action of acids and alkalies. Class VII. — Coagulated Proteids. — When any native albumins or globules are coagulated, e.g,^ at 70° C. they yield bodies with altered characters, insoluble in water and saline solutions, but soluble in boiling strong acids and alkalies, when they are apt to split up. They are dissolved during gastric and pancreatic digestion, to produce peptones. Appendix : Vegetable Proteid Bodies. — Plants, like animals, contain proteid bodies, although in less amount. They occur either in solution in the juices of living plants or in the solid form. In composition and reaction they resemble animal proteids. [The characters of the proteids occurring in plants have not been sufficiently investigated to generalize on the nature of the bodies themselves. As far as our knowledge at present extends, they have a great resemblance to animal proteids. They have frequently been obtained in a crystalline form [RaJlkofer), e.g., from the seeds of the gourd (Grii/>ler) and various oleaginous seeds {Jii/tkausen). Theyoccurin greatest bulk in the seeds of plants, aleurone grains being for the most part composed of them.] [As regards the kinds of proteid, the researches of late years (since 1S77) have shown that in seeds, globulins and " vegetable peptone" form the greater proportion of the proteid constituents. The existence of this " peptone," however, is denied ( Vines], and other bodies similar in some par- ticulars to peptones have been described, viz., albumoses ( Vines, Martin).'] [Globulins. — Three varieties have been described as occurring in the seeds of plants : vegetable myosin (Hof^pe- Sevier), vitellin ( Weyl), and paraglobulin (Martin). They have practically the same properties as those found in the animal kingdom : vegetable vitellin has. however, not been sufficiently studied. Paraglobulin has been found in papaw juice {^Martin). Myosin occurs in the seeds of leguminos-T:, in flour and in the potato.] [Albumin. — The existence of a body corresponding to egg- or serum albumin in the vegetable kingdom is douljtful { Rittliausen). Such a body has been described in papaw juice (Martin).'] [Vegetable Peptone : Albumoses. — A true peptone has not yet been recognized in plants : what has been described as such is hemialbumose ( Vines). The existence of albumoses in the vegetable kingdom is probably widespread ; up to the present date they have been described as occurring in the seeds of leguminosie, in flour, and in papaw juice. In the last, two forms occur, called respectively a- and ^-phytalbumose. The former, a phytalbumose, agrees with the hemialbumose described by Vines, being soluble in cold and boiling water ; giving also a biuret reaction, and a precipitate by saturation with sodium chloride only in an acid solution. The latter, /3-phytalbumose, is soluble in cold, but not in boiling, distilled water; hence it is precipitated by heat. It is also readily thrown down by saturation with sodium chloride, and gives a faint biuret reaction (Martin).] [Vegetable Casein is said to occur in the seeds of leguminosse; and it is slightly soluble in water, hut readily so in weak alkalies and in solutions of basic calcic phosphate. A solution of this body is precipitated by acids and rennet. Two varieties have been described : (a) legumin, in peas, beans, lentils (1805); acid in reaction, soluble in weak alkalies and very dilute IICl or acetic acid (Ernhof, iSoj); (i>) conglutin, a very similar body occurring in hops and almonds {Ritthaiisen). The existence of vegetable casein is denied ( W' O, in which the half of the H is replaced by a CH compound. Thus, C^Hj (ethyl- hydrogen) passes into 2 5 lo (ethylic alcohol). («) Cholesterin, ^^u^^ l O, is a true mon atomic alcohol, and occurs in blood, yelk, brain, bile (§ 177, 4), and generally in vegetable cells. (OH (i) Glycerine, C3H5 \ OH, is a tri-atomic alcohol. It occurs in neutral fats united with fatty (OH acids and oleic acid ; it is formed by the splitting up of neutral fats during pancreatic digestion (g 170, III), and during alcoholic fermentation (J 150). (c) Phenol (^ phenylic acid, carbolic acid, oxybenzol) (? 184, III). (t/ j Pyrokatechin (^ dioxybenzol) [^ 252). ( Correx Papillary z Longitudinal section of a Malpighian pyramid. PF, pyramids of Ferrein ; R.4, branch of renal artery; RV, lumen of a renal vein receiving an interlobular vein ; VR, vasa recta ; PA, apex of a renal papilla ; 6^ b, embrace the bases of the renal lobules. called Bowman's capsule (^Figs. 228, 229), and, after pursuing a complicated course, altering their direction, diameter and structure, and being joined by other tubules, they ultimately form large collecting tubes, which terminate by minute apertures — visible with the aid of a hand lens — on the apices of the papilhu pro- jecting into the calices of the kidney. Each urinary tubule is composed of a homogeneous membrana propria, lined by epithelial cells, so as to leave a lumen for the passage of the urine from the Malpighian corpuscles to the pelvis of the kidney. The diameter and direction of the tubules vary, and the epithe- lium differs in its characters at different parts of the tube, while the lumen also undergoes alterations in its diameter. Course and Structure of the Tubules. — In the labyrinth of the cortex, tubules arise in the spherical enlargement known as Bowman's capsule (Fig. COURSE OF THE TUBULES. 421 228, i), which invests (in the manner presently to be described^ the tuft of capil- lary blood vessels called a glomerulus or Malpighian corpuscle. By means of a short and narrow neck (2) the capsule becomes continuous with a convoluted tubule, X in Fig. 229 {Bowinati). This tubule is of considerable length, forming many windings in the cortex (Fig. 228, 3) ; the first part of it is 4.5 /i wide, con- stituting \}iie. proximal ox first convoluted tubule. It becomes continuous with the spiral tubule of Schachowa (4), which lies in a medullary ray, where it pursues a slightly wavy or spiral course. On the boundary line between the cortical and 13. Straight part of col- lecting tube. 9. Wavy part of ascend- ing limb of Henle's loop. Inner stratum of cortex without Malpighian Corpuscles. nd 8. Ascending limb of Henle's loop tube. Sub-capsular layei out Malpighic puscles. First part of <: ing tube. CORTEX. Irregular tubule Wavy part of as- cending limb. Constriction or neck Spiral tubule. Malpighian tuft sur- rounded by Bow- man's capsule. 8. Spiral part of cending limb Henle's loop. B. BOUNDARY ZONE. 5. Descending limb of Henle's loop tube. 6. Henle's loop. Diagram of the course of two boundary zone, the spiral tubule suddenly becomes smaller {Isaacs) and passes into the descending portion of Henle's loop (5), which is 14 // in breadth, and is continued downward through the boundary zone into the medulla, where it forms the narrow loop of Henle (6), which runs backward in the medullary part to the boundary zone. Here it becomes wider ( 20-26 /i), and as it continues its undu- lating course, it enters a medullary ray, where it constitutes the ascending loop ////v (7), which becomes narrower in the cortex. Leaving the medullary ray 422 COURSE OF THE TUBULES. again, it passes into the labyrinth, where it forms a tube with irregular angular outlines — the irregular tubule (lo), which is continuous with (Fig. 229, n, n) the second ox distal convoluted tubule or intercalated tubule (" Schaltstiick " of Schweig- ger-Seidel) (11), which resembles the proximal tubule of the same name. Its Fig. 229. I, Blood vessels and uriniferous tubules of the kidney (semi-diagrammatic) ; A, capillaries of the cortex, B, of the medulla; t tube with the urine is introduced into the bottle by means of a pair of forceps in such a way that it does not spill. Close the bottle tightly with the caoutchouc stopper, through which passes a glass tube to connect it with the graduated burette. Incline the bottle so as to allow the urine to mix with the hypobromite solution, when the gases are given off, and pa-ss into the collecting tube, which is gradually raised until the surfaces of the liquids outside and in coin- cide. Time should be allowed to permit the whole apparatus to have the same temperature. Read off the amount of gas N evolved, for the CO, is alisorbed by the caustic soda. The collecting tube is usually graduated beforehand, so that each division of the tube is ^ o.i per cent, of urea, or 0.44 gr. per fluid oz. Thus, suppose 50 03. of urine are passed in twenty-four hours, and that 5 c.c. of urine evolve 18 measures of N, then 0.44 X 18 X 5° = 39^ grs. of urea. If, however, the tube be graduated into c.c, then 30.3 c.c. of N =rT o.i grm. of urea at the ordinary temperature and pres.sure.] [Squibb's Method is simple and expeditious. Measure off i^ oz. of liquor sodje chlor. (U. S.), and place it in A (Fig. 240), together with a glass thimble D, containing 4 c c. of urir.e. QUANTITATIVE ESTIMATION OF UREA. 433 B is filled with water, connected by an India-rubber tube with A, and so adjusted that when it is in the position shown, no water escapes into C. Filter A, and mix the urine in D with the chlorin- ated solution, when N is given off, displacing water from Binto C. All the N escapes in about ten minutes. When the pressure in A and B is restored, the contents of C are measured by a pipette (J), so graduated that each measure is = .0027 grm. urea, from which the calculation is easily made (Afar/im/ale).'] III. Volumetric Method {Liehig). By means of a graduated pipette (Fig. 241), 40 cubic cen- timetres of the urine are taken up and placed in a beaker. To this is added 20 cubic centimetres of barium mixture to precipitate the sulphuric and phosphoric acids. T he barium mixture consists Fig. 239. Fig. 241. of I vol. of a cold saturated solution of barium nitrate and 2 vols, of a cold saturated solution of barium hydrate. Filter through a i/r^' filter, and take 15 cubic centimetres of the filtrate, tfi/«V/< correspond to 10 c.c. of urine, and place in a beaker. Allow a titrated standard solution of mercuric nitrate to drop from a burette into the urine until a precipitate no longer occurs. The mercuric nitrate is made of such a strength that I cubic centimetre of it will combine with 10 milligrammes of urea. Test a drop of the mixture from time to time in a watch glass or piece of glass blackened on its under surface, with a solution of sodic carbonate, which is called the indicator. Whenever the slightest excess of mercuric nitrate is added, the mixture strikes a yello-a< color with the soda. The standard solution must be added drop by drop until this result is 28 434 PROPERTIES OF URIC ACID. obtained. Read off the number of cubic centimetres of the standard solution used ; as each centi- metre corresponds to lo milligrammes of urea, just multiply by ten, and the amount of urea in 10 cubic centimetres of urine is obtained. This method does not give quite accurate results even in normal urine. To urine containing much phosphates is added an equal volume of the barium mixture. Very acid urines may require several volumes to be added. Urine containing albumin or blood must be boiled, after the addition of a few drops of acetic acid, to remove the albumin. The sodic chloride in the urine also inter- feres with the accuracy of the process, as on adding mercuric nitrate to urine mercuric chloride and sodic nitrate are formed, so that the urea does not combine until the sodic chloride is decomposed. When the urine contains, as is usually the case, 1 to I jj per cent. NaCl, deduct 2 c.c. from the number of c.c. of the S.S. added to lo c.c. of urine. 258. URIC ACID = CsH^N.Oj.— Quantity.— Uric acid is the nitro- genous substance which, next to urea, carries off most of the N from the body ; in twenty-four hours 0.5 grm. (7 to 10 grains); during hunger, 0.24 grm. (4 grains); after a strongly animal diet, 2. 11 grm. (30 to 35 grains) are e.xcreted. The proportion of urea to uric acid is 45 : i. It is the chief nitrogenous product in the urine of birds, reptiles, and insects, while it is absent from herbivorous urine. Fig. 242. Fig. 243 Fig. 242 — Uric acid, ti, rhombic tables (whetstone form) ; 6, barrel form ; c, sheaves ; rf, rosettes of whetstone crys- tals. Fig. 243. — Uric acid, a, rhomboidal, truncated, hexahedral, and laminated crystals ; ir, rhombic prism, liorizontally truncated angles of the rhombic prism, imperfect rhomljic prisms : c, prism with a hexahedral basic surlace, barrel-shaped figure, prism with a hexahedral basal surface; ti, cylindrical figure, stellate and superim- posed groups of crystals. If a mammal be fed with uric acid, part of it becomes more highly oxidized into urea, while the oxalic acid in the urine is also increased (§ 260 — IViih/er, v. Frerichs) ; in fowls, feeding with leucin, glycin, or asparaginic acid (v. Knien'cm), or ammonia carbonate {Schroeder'), increases the amount of uric acid. When urea is administered to fowls, it is reduced chiefly to uric acid {Cee/i, H. Mayer, Me). Properties. — Uric acid is dibasic, colorless, and crystallizes in various forms (Figs. 242 and 243), belonging to the rhombic system. When the angles are rounded, the whetstone form (a) is produced, and if the long surfaces be flattened six-sided tables occur. Not unfrequently diabetic urine deposits spontaneously large, yellow, transparent rosettes (//). If 20 c.c. of HCl, or acetic acid, be added to i litre of urine, crystals {b) are deposited, like cayenne pepper, on the surface and sides of the glass, after several hours. [The HCl decomposes the urates, and liberates the acid, which does not crystallize at once, owing to the presence of the phosphates in the urine {Erilcke). Crystals of uric acid are ESTIMATION OF URIC ACID. 435 usually yellowish in color from the pigment of the urine, and they are soluble in caustic potash.] Solubility. — It is tasteless and odorless ; reddens litmus ; is soluble in iS.ooo parts of cold, and in 15,000 of boiling water, and insoluble in alcohol and ether. Horbaczewski prepared it synthetic- ally by melting together glycin, or, as it is also called glycocin, and urea. it IS freely solulile in alkaline carbonates, borates, phosphates, lactates, and acetates, these salts at the same time removing a part of the base ; thus there are formed acid urates and acid salts from the neutral salts. It is soluble in concentrated sulphuric acid, from which it may be precipitated by the addition of water. During dry distillation it decomposes into urea, cyanuric acid, hydrocyanic acid, and ammonium carbonate. Supero.side of lead converts it into urea, allantoin, oxalic acid, and CO, ; while ozone forms the same bubstances, with the addition of allo.xan. When it is reduced by H in slain iiascendi, as by sodium amalgam, it forms xanthin and sarkin. It is a less oxidized metabolic product than urea, but it is by no means proved that uric acid is a precursor of urea. Occurrence. — Uric acid occurs dissolved in the urine in the form of acid urates of soda and potash. These salts occur also in urinary calculi, gravel, and in goutv deposits. Ammonium urate occurs in very small quantity in a deposit of " urates," but is formed in considerable amount when urine becomes ammoniacal from decomposition (Fig. 250). Free uric acid occurs in normal urine only in the very smallest amount. It is sometimes deposited after a time (Fig. 249). It frequently forms urinary calculi, being sometimes deposited around a speck of albumin as a nucleus (^El'stein). [It has also been found in the blood, liver, and spleen. It is remarkable that it has been found in the spleen of herbivora, although, as stated above, it is absent from herbivorous urine. In gout, it accumulates in the blood {Garrod).'\ The urine of newly-lwrn children contains much uric acid. Uric acid and its salts are increased after severe muscular exertion, accompanied by perspiration, in catarrhal and rheumatic fevers, and such conditions as are accompanied by disturbance of the respiration ; in leukaemia and tumors of the spleen, cirrhotic liver, and, generally, m cases of catarrh of the stomach and intestinal tract, fol- lowing the excessive use of alcohol. [It is also increased during ague and fevers, and perhaps this has some relation to the congestion of the spleen which accompanies these conditions.] It is diminished after copious draughts of water, after large doses of quinine, caffein, polassic iodide, common salt, sodic and lithic carbonates, sodic sulphate, inhalation of O, slight muscular exertion. In gout, the amount excreted in the urine is small. In chronic tumors of the spleen, ana;mia and chlorosis, when the respiration is not at the same time embarrassed, it is also diminished. Urates. — Uric acid forms salts — chiefly acid urates — with several bases, which dissolve with difficulty in cold w-ater, but are easily soluble in warm water. Neu- tral urates are changed by CO., into acid salts. Hydrochloric and acetic acids break up the compounds, and crystals of uric acid separate. (i) Acid sodic urate usu.ally appears as a brick-red deposit, more rarely gray or white (lateri- tious deposit), tinged with uroerythrin, in urine, in catarrhal conditions of the digestive organs, and in rheumatic and febrile affections. Microscopically, it is completely amorphous, consisting of granules, sometimes disposed in groups (Fig. 249, h"); sometimes the granules have spines on them. The corresponding potash salt occurs not unfrequently under the same conditions, and presents the same characters. (2) Acid ammonium urate (Fig. 250, a) always occurs as a sediment in ammoniacal urine, either with (l), or mixed with free uric acid, accompanied by triple phosphate. Microscopically, it is the same as (I). (I) and {2) are distitii^nished by the sediment dissotvin^ "uhen the urine is heated. If a drop of hydrochloric acid be added to a microscopic preparation of the sediment, crystals of uric acid separate. (3) Acid calcic urate occurs sometimes in calculi, and is a white, amorphous powder, but slightly soluble in water. When heated on platinum, it leaves an ash of calcium carbonate. Magnesia rarely occurs in urimry calculi. 259. ESTIMATION OF URIC ACID.— I. Qualitative.— i. Micro- scopic Characters. — The appearances presented by uric acid and its salts under the microscope. It is deposited from urine after several hours, on adding acetic or hydrochloric acid. 2. Murexide Test. — Gently heat a urate or uric acid in a porcelain vessel, along with nitric acid. Decomposition takes place, and the color changes to yellow. N and CO. are given off; urea and allo.xan (C^H-^NiO,) remain. F>apo- 436 KREATININ AND OTHER SUBSTANCES. rate slowly, and allow the yellowish-red stain to cool ; on adding a drop of dilute ammonia, a purplish-red color of murexide is obtained ; it becomes blue on the addition of caustic potash. If potash or soda be added, instead of ammonia, a violet color is obtained. 3. Schiff' s Test. — If a little uric acid or a urate be dissolved in a solution of an alkaline car- bonate, and this be dropped upon blotting paper saturated with a solution of siiver nitrate., reduction of the silver takes place at once, and a black spot is formed (H. Schiff). 4. On boiling a solution of uric acid or a urate in an alkali, with Fehling's solution (§ 149, 2), at first white urate of the suboxide of copper is deposited, while later, red copper suboxide is formed. II. The Quantitative estimation may be made by adding 5 cubic centimetres of concentrated HCl to 100 c. c. of urine, and allowing it to stand for forty-eight hours in the dark, when the uric acid is precipitated like fine cayenne pepper crystals. Salkowski and Fokker have improved the method. All the uric acid is not precipitated by the HCl, even after standing for a time. [E. A. Cook uses sulphate of zinc to precipitate the uric acid as urate of zinc. Caustic soda is added to precipitate the phosphates, and then to the clear fluid zinc sulphate solution, which precipitates urate of zinc as a white gelatinous deposit.] [Haycraft's method depends on the fact that uric acid forms a compound with silver — urate of silver, which is very insoluble in water. The solutions required are : i. Centinormal ammonic sul- phocyanate, made by dissolving 8 grms. of crystals in i litre of water, and adjust to decinormal silver solution. Dilute with 9 vols, of water, i c. c. = 0.0016S uric acid. 2. Saturated solution of iron alum (the indicator). 3. Pure HNO3 (20 to 30 per cent.). 4. .Strong ammonia. Ammoniacal silver solution made by dissolving 5 grms. AgNOj in 100 c. c. water, and add NH^HO until the solution becomes clear. Process. — Place 25 c. c. of urine in a beaker, and add i grm. sodic bicar- bonate; then add 2 to 3 c. c. of ammonia to precipitate ammonio-magnesic phosphate. Add I to 2 c. c. of ammoniacal silver solution, which precipitates silver urate in a white gelatinous form. The precipitate is then thoroughly washed on an asbestos filter, anil then dissolved from this by nitric acid, after which the silver is estimated (Volhard's method). In doing so, add a few drops of the indicator, and drop in the centinormal solution of ammonic sulphocyanate. A white precipitate, with a transient reddish coloration, will be formed ; as soon as the red color is permanent, the process is at an end. The uric acid j>resent is ascertained by multiplying the number of cubic centi- metres of the sulphocyanate used by 0.0016S.] 260. KREATININ AND OTHER SUBSTANCES.— Quantity.— Kreatinin, CjHaNjO., (LicMg), is derived from the kreatin of muscle, from which it can be otitained by heating in a watery solution, a molecule of water being given off; and, conversely, kreatinin may take up water and form kreatin. The amount excreted daily is 0.6 to 1.3 grammes (8 to 18 grains). It is diminished in progressive muscular atrophy, tetanus, anemia, marasmus, chlorosis, con- sumption, paralysis ; and is increased in typhus, inflammation of the lung ; it is absent from the urine of sucklings. Properties. — Kreatinin is alkaline in reaction, easily soluble in water and hot alcohol. It occurs in the form of colorless, oblique, rhombic columns. It forms compounds with acids and salts, with silver nitrate, mercuric chloride, and especially with zinc chloriJe. Kreatinin-zinc chloride ( Fig. 244) is used to detect its presence. Test. — Add to urine a few drops of a slightly-brownish solu- tion of nitro-prusside of soda, and then weak caustic soda solution, which cause a Burgundy red color, which soon disappears ( 77;. W'cyl). When heated with acetic acid, the color changes to green or blue [Salkowski). Kreatinin has been prepared artificially. When boiled with baryta water, it decomposes into urea and sarkosin. When administered by the mouth, or when injected into the blood, the greater part of it reappears unchanged in the urine. Xanthin (^ C^H^N^Oj) (Marcet) occurs only to the amount of I gramme in 300 kilos, of urine. It is a substance intermediate between sarkin and uric acid. Guanin and hypoxanthin may be changed into xanthin ; in contact with water and ferments it passes into uric acid. When evapo- rated with nitric acid, it gives a yellow stain, which becomes yellowish-red on adding potash, and violet-red on applying more heat. It is an amorphous, yellowish- white powder, fairly soluble in boiling water. It has also been found in traces in muscles, brain, liver, spleen, pancreas, and thymus. The crystalhne body paraxanthin, and the amorphous heteroxanthin, occur in traces in the urine (Salomon). Sarkin (=: Hypoxanthin), C5H4N4O. — As yet this substance has been found only in the urine of leukfemic patients (Jakubasck), and it has been prepared in the form of needles or llattened scales [Scherer) from muscle, spleen, thymus, brain, bone, liver, and kidney. In normal urine a body nearly related to, and possibly identical with, hypoxanthin occurs [E. Salko-cski). Hypo- xanthin closely resembles xanthin, and can be changed into it by oxidation. Nascent hydrogen, on the other hand, reduces uric acid to xanthin and hypoxanthin. When evaporated with nitric acid OXALIC ACID AND OXALURIA. 437 it gives a light yellow stain, which becomes deeper, but not reddish yellow, on adding caustic soda. It is more easily soluble in water than xanthin, and by this means the two substances can be sepa- rated from each other. Guanin is insoluble in water. Oxaluric acid (CjH^N.O^) occurs in very small quantity comhmeA with ammonia in urine. Physiologically, it is interesting on account of its relation to uric acid. It is a white powder, slightly soluble in water. Ammonia oxalurate can be prepared from uric acid. Oxalic Acid (€21^204). — The series of chemical decompositions of oxaluric acid leads to oxalic acid. It occurs, but not constantly, to the amount of 20 Fig. 244. milligrammes daily as oxalate of lime, which is known by the ■"envelope" shape of the crystals (Figs. 245 and 246) ; insoluble in acetic acid, and forming transparent octahedra. More rarely it assumes a biscut or sand-glass form (Fig. 259, c). According to Neiibauer, soluble oxalate of lime occurs in urine, being kept in solution by acid sodic phosphate. This substance is excreted in a crys- talline form, the more the reaction of the urine becomes neutral. The genetic relation of oxalic acid to uric acid is shown by the fact, that dogs Fig. 245. Fig. 246. a, oclahedr.i ; b, basal plane of an octahedn angle ; c, compound forms ; d, dumb belts. 1 forming fed with uric acid e.xcrete much oxalate of lime {v. FrcrUhs, lllihler). Oxalic acid may also be produced by the oxidation of products derived from the fatty acid series (p. 414). Oxaluria. — The eating of substances containing oxalate of lime (rhubarb) increases the excretion. Increased excretion is called oxaluria; it is regarded as a sign of retarded metabolism (Beiiel-e], and it m.iy give rise to the formation of a calculus. In oxaluria the uric acid is also often increased in amount. Perhaps, in the first instance, there is an increased formation of uric acid, from which oxalic acid, urea, and CO^ may be formed. The amount of oxalic acid is increased after the use of wine and sodic bicarbonate. 438 HIPPURIC ACID. Hippuric Acid = CgHjiNO^ (Benzoylamidoacetic acid) occurs in large amount in the urine of herbivora (Liehig), and in them it replaces uric acid, and is one of the chief end products of the metabolism of nitrogenous substances ; in human urine the daily amount is small, 0.3 to 3.8 grms. (5 to 50 grains). It is an odor- less monobasic acid with a bitter taste, and crystallizes m colorless, four-sided prisms (Fig. 247 j. It is readily soluble in alcohol, and only soluble in 600 parts of water. It is a conjugated acid, and is formed in the body from benzoic acid, or some nearly related chemical body, such as the cuticular substance of plants, or from oil of bitter almonds, cinnamic or chinic acid, which easily pass by reduction (chinic acid) or by oxidation (cinnamic acid) into benzoic acid ; glycin uniting with it, and water being given off — CjHeO, + C.HsNOj = C,H,,N03 + H,0 Benzoic acid -\- Glycin = Hippuric acid -|- Water. [Formation. — When benzoic acid is introduced into the alimentary canal of an animal (rabbit or dog), it appears in the urine as hippuric acid ; while nitro- FlG. 247. benzoic acid appears as nitro-hippuric acid. As the benzoic acid passes through the body it becomes conjugated with glycin or glycocin, chiefly in the kidneys. The hippuric acid in the urine of herbivora is chiefly derived from some substance with a benzoic acid residue present in the cuticular coverings of the food. That hippuric acid, in part at least, is formed in the kidneys is shown by the follow- ing considerations : If arterialized blood, containing benzoic acid and glycin, or even benzoic acid alone, be passed through the blood vessels of a fresh living excised kidney, hippuric acid is found in the blood after it is perfused. Even after forty-eight hours, if the kidney be kept cool, the synthesis takes place. If the kidney be kept too long, the conjugation does not take place. If the fresh kidney be chopped up, and kept at the temperature of the body with benzoic acid and glycin, hippuric acid is formed. Oxygen seems to be necessary for the pro- cess, for, if blood or serum containing carbonic oxide be used, there is no forma- tion of hippuric acid.] According to this view, it is derived chiefly from the food of herbivorous animals, and hence it is absent from the urine of sucking calves. But it is also formed in the body from the proleids. In the dog, the formation of hippuric acid occurs in the kidney [Sc/imiedeberg and Bttnge"), and in the COLORING MATFERS OF URINE. 439 frog also outside the kidney. Kiihne and Halhvachs thought it was formed in the liver, and Jaars- veld and Stockvis in the kidney, liver, and intestine. The observation of Salomon that, after excision of the kidneys in rabbits, and injection of benzoic acid into the blood, hippuric acid was found in the muscles, blood, and liver, goes to show that it must be formed in other organs beside the kidneys. The power of changing benzoic acid introduced into the human body into hippuric acid, may even be abolished in disease of the kidney {^Jaarsveld and Stockvis, Fr. Kronecker). Under certain circumstances it seems that hippuric acid, already formed, may be again decomposed in the tissues. It is greatly increased after eating pears, plums, and cranberries; and it is also increased in icterus, some liver affections, and in diabetes. When boiled with strong acid or alkalies, or with putrid substances, it takes up H,0 and splits into benzoic acid and glycin. [Crystals of hippuric acid when heated in a test tube are decomposed, and a sublimate of benzoic acid and ammonic benzoate condenses on the upper cool part of the tube, while there is an odor of new hay, and oily drops remain in the tube.] It is freely soluble in water, with difficulty in alcohol, and insoluble in ether. Preparation. — .\dd milk of lime to \\^t fresh urine of horses or cows to form calcic hippurate. Filler, evaporate the filtrate to a small bulk, and precipitate the hippuric acid with excess of hydro- chloric acid. To purify the hippuric acid, crystallize it several times from a hot watery solution. Cynuric Acid. — C^^Hj ^NjOg -|- HjO occurs in the urine of dogs (y. v. Liebig). AUantoin, CjHgNjOa, which occurs in the amniotic fluid of the cow, is found in minute traces in normal urine after flesh food, and is more abundant during the first weeks of life, and during pregnancy. After large doses of tannic acid, the amount is increased (Sc/wllin), while in dogs feeding with uric acid also increases it (Sa/kowsii). Properties. — It forms shining, prismatic crystals ; from the urine of sucking calves it crystallizes in transparent prisms. It is decomposed by ferments into urea, ammonium oxalate, and carbonate, and another as yet unknown body. Preparation. — (a) The urine is precipitated with basic lead acetate, the lead in the filtrate is re- moved by sulphuretted hydrogen, and the filtrate itself is then evaporated to a syrup, from which the crystals separate, after standing for several days. They are then washed with water, and re- crystallized from that water (Salko-uiski). 261. COLORING MATTERS OF THE URINE.— i. Urobilin (Jafff) is most abundant in the highly colored urine of fevers, but it also occurs in normal urine. It is a derivative of hKmatin, or of the bile pigments (§ 177) de- rived from the latter. It is identical with the hydrobilirubin of Maly (§117, T„g). It gives a red, or reddish yellow color to urine, which becomes yellow on the addi- tion of ammonia. Preparation. — Prepare a chloroform extract of urine containing urobilin —add iodine to the extract, and remove the iodine by shaking the mixture with dilute caustic potash, which forms potassic iodide. This potash solution becomes yellow or brownish yellow, and. exhibits beautifu green fttorcscence [Gerhardt). Urobilin may be extracted from many urines by ether [Suiko'uski). When subjected to the action of reducing agents, ^.^., sodium amalgam, a colorless product is obtained, which on exposure to the air absorbs O, and becomes retransformed into urobilin. This colorless body is identical with the chromogen which Jaffe found in urine. If urine is treated with soda or potash, the characteristic absorption band lying between d and F, passes nearer to l>, becomes darker and more sharply defined. According to Hoppe-Seyler, urobilin is formed in urine after it is voided, from another urobilin-forming body (Jaffe's chromogen) absorb- ing oxygen. If urine containing urobilin be made alkaline with ammonia, and zinc cliloride be added, it exhibits marked fluorescence ; it has a green shimmer by reflected light. When urobilin is isolated, it fluoresces without the addition of zinc chloride. In cases of jaundice {\ 1 80), where Gmelin's test sometimes fails to reveal the presence of bile pigments, urobilin occurs. This " uro- bilin icterus" { Gerhardt) occurs chiefly after the absorption of large extravasations of blood. Ac- cording to Cazeneuve, the urobilin is increased in all diseases where there is increased disintegration of colored blood corpuscles. 2. Urochrome ( Thudichtim) is regarded as the chief coloring matter of urine. It may be iso- lated in the form of yellow scales, soluble in water, and in dilute acids and alkalies. The watery solution oxidizes, and when exposed to air becomes red owing to the formation of uroerythrin ( Thitdichunt) When acted on by acids, new decomposition products are formed, e. g., urome- lanin. Uroerythrin gives the red color to deposits of urates (? 258). 3 .-V brown pigment containing iron is carried down with uric acid, which is precipitated on the addition of hydrochloric acid {\ 258). By repeatedly addmg sodic urate to the urine, and precipi- tating the uric acid by hydrochloric acid, a considerable amount may be obtained (JCiinkel). 440 INDICAN, PHENOL AND PARAKRESOL. In cases nf melanotic tumors, there has been occasionally observed urine, which becomes dark, owing to melanin (^ 250, 4), or to a coloring matter containing iron [A'unki'i). 262. INDIGO— PHENOL— KRESOL—PYROKATECHIN— AND SKATOL-FORMING SUBSTANCES. — i. Indican [CH^NSOJ or indigo-forming substance (Siht/iick), is derived from indol, CjiH.N {Jcjfc), the basis of indigo (Bayer), and is formed in the intestine by the pancreatic diges- tion of proteids (§ 170, II), but it also arist?S as a putrefactive product (§ 184, 61. Indol, when united with the radical of sulphuric acid, HSOj, and combined with jiotassium, forms the so-called iitdigogen or indican of urine (Briegcr, Baumann). This substance (CgHgNSO^K ;= indoxyl-sulphate of potash ) forms white glancing tablets and plates ; readily soluble in water and less so in alcohol. By oxidation at forms indigo-blue — 2 indican + O, ^ C,6H,„N.j02 (indigo-blue) -f 2HKS0j (acid potassic sulphate). It is more abundant in the urine in the tropics, and it is absent from the urine of the newly-born {Senator). Tests.- (l) Add to 40 drops of urine, 3 to 4 c.c. of strong fuming hydrochloric acid, and 2 to 3 drops of nitric acid. Boil, a violet-red color with the deposition of true ciystallme indigo-blue (rhombic) and indigo-red attest its presence. Putrefaction causes a similar decomposition in indican ; hence, we not unfrequently obser\'e a bluish-red pellicle of microscopic crystals of indigo- blue, or even a precipitate of the same {Hill Hassal, /Sjs)' (2) Mix in a beaker equal quantities of urine and hydrochlorous acid, and add two drops of a solution of chloride of lime; the mixture at first becomes clear, then blue [Jaffi:). Add chloroform, and shake the||mixture vigorously for some time; the chloroform dissolves the blue coloring matter, which is obtained as a deposit, when the chloroform evaporates (Senator, Salkowski). (3) Heat to 70° one part of urine with two pans of nitric acid, and shake up with chloroform; the chloroform dissolves the indigo which is formed, assumes a violet color and gives an absorption band between C and D, slightly nearer D (Hoppe- Seyler). Jaffe found in 1500 c.c. of normal human urine, 4.5 to 19.5 milligrammes of indigo ; horse's urine contains 23 times as much. The subcutaneous injection of indol increases the indican in the urine {J'lffe)- E. Ludwig obtained indican by heating hiematin or urobilin with a caustic alkali and zinc dust. It has also been found in the sweat [Bizio), Pathological — The indican in the urine is increased when much indol is formed in the intes- tine (^ 172, II), e.g., in typhus, lead colic, trichinosis, catarrah and hemorrhage of the stomach, cholera, carcinoma of the liver and stomach; obstruction of the bowel or ileus, peritonitis and diseases of the small intestine — in cachexia?, longstanding suppuration, paraplegia — after taking creosote, oil of bitter almonds, turpentine or nux vomica. 2. Phenol, C„HjO, carbolic acid, monohydroxylbenzol, § 252), was discovered by Stadeler in human urine (more abundant in horse's urine). It does not occur as carbolic acid, but in combination with a substance from which it is separated by distillation with dilute mineral acids. The " phenol-forming substance " is, according to Baumann, " phenolsulphuric acid" (CeHjG, SO3H), which in urine is united with potash. Phenol is derived from the decomposition of proteids by pancreatic digestion (J 172, II), and also from putrefaction (^ 184, 6), the mother substance being tyrosin. Hence, the formation of phenolsulphuric acid is analogous to the formation of indican. If in the employment of carbolic acid it be absorbed, the phenolsulphuric acid becomes greatly increased in z^raount [Alirten, .Salko7uski),so that sulphuric acid must be united with it ; hence, alkaline sulphates are decomposed in the body, so that the latter may be absent from the urine {Baumann). Living muscle or liver, when digested in a stream of air for several hours with blood to which phenol and sodic sulphate are added, yields phenolsulphuric acid; while, under the same circumstances, pyrokatechin forms ethersulphuric acid. Carbolic Urine. — When carbolic acid is used externally or internally, and it is absorbed, it causes a deep, dark-colored urine, due to the oxidation of phenol into hydrochinon (orthobioxy- benzol = CgHgOj), which, for the most part, appears in the urine as ethersulphuric acid {Baii- fnann and others). 3. Parakresol, (hydroxyltoluol, CyHgO) with its isomers ortho- and meta- kresol (the latter in traces), is more abundant in urine {Baumann, Preusse). It also occurs in combination with sulphuric acid. Test for phenol (and also kresol) : Distil 150 c.c. urine with dilute sulphuric acid. The distillate gives a brown crystalline deposit of tribromophenol with bromine water, as well as a red color with MiUon's reagent. Hydroxylbenzol (pyrokatechin, hydrochinon) is obtained from urine, when it is heated for a long time with hydrochloric acid. INORGANIC CONSTITUENTS OF THE URINE. 441 Resorcin which is an isomer of hydrochinon, when administered internally, also appears in the urine as ethersulphuric acid. Toluol and naphthalin behave similarly. 4. Pyrokatechin ^ CeHeO.. (metadihydroxylbenzol) is formed along with hydrochinon from jjhenol, and is an isomer of the former. It behaves like indol and phenol, for when united with sulphuric acid, it forms the pyrokatechin-form- ing substance (Bauinann, Herier). Small quantities sometimes occur in human urine; it is more abundant in the urine of children {Ebstcin and Milller) ; it becomes darker when the urine putrefies. Perhaps pyrokatechin is formed in the body from decomposed carbohydrates, from which Hoppe- Seyler obtained it by heating them with water under a high pressure, as well as by acting on them with alkalies. 5. Skatol (§ 252), which is crystalline, and is formed during putrefaction in the intestine, also appears in the urine as a compound of sulphuric acid. On feeding a dog with skatol, Brieger found much potassic skatol-oxysulphate. Test. — Skatol compounds are recognized by adding dilute nitric acid, which causes a violet color, or of fuming nitric acid, which precipitates red flakes [Ncncki). Its quantity is regulated by the same conditions as indican. The aromatic oxyacids, hyjroparacumaric acid and paraoxyphenylacetic acid (the former a putrefactive product of flesh, the latter obtained by E and H — Salkowski, from putrid albumin), occur in the urine [Baumann, \ 252). Shake the urine treated with a mineral acid with ether, evaporate the latter, and dissolve the residue in water. If aromatic oxyacids are present, they give a red color with Millon's reagent. Baumann gives the following series of bodies, which are formed from tyrosin by decomposition and oxidation ; most of the sutistances are formed both during the decomposition of albumin, and also in the intestine, whence they pass into the urine: Tyrosin, C<,Hj jNOj -[- H, = C^HijOj (hydroparacumaric acid) -j- NH,. CgHj^Oj r= C,Hj(|0 (paraethylphenol, not yet proved) -)- COj. CjHjoO + 03 = CgHgO, (paraoxyphenylaceticacid) + H^O. CgHgOj = C^HjO (parakresol) -1- CO,. CjHgO -|- O3 = CjH^Oj (paroxy benzoic acid, not yet proved) -\- HjG. C,H,0 = C5H5O' (phenol) + CO,. Potassium sulphocyanide, derived from the saliva, also occurs in urine. After acidulation with hydrochloric acid, its presence may be detected by the ferric chloride test (\ 146 — Gscheidlen and J. Muni). One litre of human urine contains 0.02 to 0.08 gramme combined with an alkali. Succinic acid, C^H^O^ [A/eissncr and Shepard ), occurs chiefly after a diet of flesh and fat, and almost disappears after a vegetable diet. It is a decomposition product of asparagin, and therefore occurs in considerable amount in the urine after eating asparagus. It is also a product of the alco- holic fermentation (| 150), and as it passes out of the body unchanged, it occurs in the urine of those who imbibe spirituous liquors. It passes unchanged into the urine (Neuliauei'). Lactic acid (C3H5O3) is a constant constituent of urine (Lehmann, Briicke]. Other observers have found fermentative lactic acid in diabetic urine; sarcolactic acid after poisoning with phos- phorus and in trichinosis. Occasionally traces of volatile fatty acids are present. Some atiimal gum occurs in urine (p. 416), and Bechamp's " Nephrozymose " consists for the most part of gum (Landwehr). This substance is precipitated from urine by adding to it three times its volume of 90 per cent, alcohol. It is not a simple body, but at 60° to 70° C. it transforms starch into sugar (v. Vintsc/igau). Ferments. — Traces of diastatic, peptic, tryptic, and rennet ferment have been found, especially in urine of high specific gravity. Traces of sugar (Briicke, Bence Jones) to the amount of 0.05 to o.oi per cent., and less, occur in normal urine. After the ingestion of milk-, cane-, or grape sugar (50 grms.) these varieties of sugar appear in small quantity m the urine ( ll'orm Mi'dler— \ 267, 7). Krytophanic acid (CjHgNOj), according to Thudichum, occurs as a free acid in urine, but Landwehr regards it as an animal gum. Aceton (C^H^O) is formed when normal urine is oxidized with potassic bichromate and sul- phuric acid, and it is formed from a reducing substance present in normal urine (apparently derived from the grape sugar of the blood). Aceton occurs in traces as a normal urinary constituent, which is increased during increased decomposition of the tissues, e.g., carcinoma, inanition. It has also been found in the blood in {^\ex {v. Jacksch). Test. — Acidulate half a litre of urine with ACl and distil ; when treated with tincture of iodine and ammonia there is a turbidity due to iodoform. II. THE INORGANIC CONSTITUENTS OF THE URINE.— The inorganic constituents are either taken into the body as such with the food and pass off unchanged in the urine, or they are formed in the body owing to the sulphur and phosphorus of the food being oxidized and the products uniting with 442 PHOSPHORIC ACID AND EARTHY PHOSPHATES. bases to form salt. The quantity of salts excreted daily in the urine is 9 to 25 grammes [i^' to 3^ oz.]. 1. Sodic chloride — to the amount of 12 (10 to 13) grammes [180 grains] — is excreted daily. It is increased, after a meal, by muscular exercise, drinking of water, and generally, when the quantity of urine is increased, by the free use of large quantities of common salt, but by potash salts also ; while it is dimin- ished under the opposite conditions. In disease it is greatly diminished ; in pneumonia and other inflammations accompanied by effusions, in continued diarrhoea and profuse sweating, constantly in albuminuria and in dropsies. [In cases of pneumonia, sodic chloride may, at a certain stage, almost disappear from the urine, and it is a good sign when the chlorides begin to reappear.] In other chronic diseases, the amount of NaCl excreted runs nearly parallel with the amount of urine passed. In conditions of excitement the amount of sodic chloride is diminished, and potassic chloride increased; in conditions of de- pression the reverse is the case (Zeiilzfr). Test. — Add to the urine nitric acid and then nitrate of silver solution, which gives a white, curdy precipitate of chloride of silver. In albuminous urine the albumin must first be removed. Alicro- Siopically look for the step like forms of the common salt, and also for the crystals of sodic chloride urea (§ 256, 4). 2. Phosphoric acid occurs in urine as acid sodic phosphate and acid Fig. 248. h, crystalline magnesic phosphate. calcic and magnesic phosphates (Fig. 248, h), to the amount of about 2 grammes daily [30 grains], but it is more abundant after a flesh than after a vege- table diet. The amount uicreases after a mid-day meal until evening, and falls during night until next day at noon. It is partly derived from the alkaline and earthy phosphates of the food, and it is partly a decomposition product of lecithin and nuclein. As phosphorus is an important constituent of the nervous system, the relative increase of phosphoric acid is due to increased metabolism of the nervous substance. Pathological. — In fevers, the increased excretion of potassic phosphate is due to a consumption of blood and muscle (| 220, 3). It is also increased in inflammation of the brain, softening of the bones, diabetes, and oxaluria; and after the administration of lactic acid, morphia, chloral, or chloro- form. It is diminished during pregnancy, owing to the formation of the fcetal bones; also after the use of ether and alcohol, and in inflammation of the kidney. Test. — Earthy phosphates are precipitated by heat. This precipitate is distinguished from albumin, which is- also precipitated by heat, by being soluble in nitric acid, which precipitated albumin is not. [The earthy phosphates are not precipitated until near the boiling point.] SULPHURIC ACID AND OTHER BASES. 443 Quantitative. — The amount of phosphoric acid is estimated by tritation with a standnid solulion of tiraniutit actlnte ; ferrocyanidi: of potassitim being the ittJitalor. The indicator gives a brown- ish-red color when there is an excess of free uranium acetate. In addition to phosphoric acid, phosphorus occurs in an incompletely oxidized form in the urine, e. g.. glycerinphosphoric acid (J 251, 2) (Sotnilzsclie~us.] [{b) Boiling and Nitric Acid. — Place 10 c.c. of urine in a test tube and boil. If albumin be present in small quantity, a faint haziness, which may be detected in a proper light, will be produced. -\dd 10 or 12 drops of HNO^. If the turbidity disappears it is due to phosphates, while if any remains it is due to albumin. If albumin be present in large quantity, a copious whitish coagulum is obtained.] \_Precautions. — (a) In all cases, if the urine be turbid, filter it before applying any test. (^) How to Boil. — Boil the upper strata of the liquid, and take care, if any coagulum be formed, that it does not adhere to the side of the tube, else the tube is liable to break, {c) In performing this test with a neutral solution, note when the precipitate falls, for albumin is precipitated about 70° C, phosphates not till about the boiling point, [d] Amount of Acid. — If too little (2 or 3 drops) HNO3 be added, or too much (30 or 40 drops), we may fail to detect albumin, although present.] (i) Ferrocyanide Test. — By the addition of acetic acid and potassium ferrocyanide [If albu- min be present, a white flocculent precipitate separates in the cold. Dr. Pavy has introduced pel- lets, consisting of a mixture of citric acid and sodic ferrocyanide. All that is required is to add a pellet to the suspected urine. Oliver's papers. — Dr. Oliver uses papers, one saturated with citric acid and another with ferrocyanide of potassium. The two papers are added to the clear filtered urine. (Jther precipitants of albumin, such as small pieces of paper impregnated with polassio-mercuric iodide, are used by Oliver.] () When bloody urine is exposed for some time, especially in a warm place, it becomes more acid, and assumes a dark, brownish-black color. The ha;moglobin becomes changed into methsemoglobin (^ 15). It is precipitated by lead acetate, which does not precipi- tate oxyhccmoglobin ; the spectrum of methsemoglobin resembles that of hncmatin in an acid solu- tion (§ 15, Fig. 14). The two spectra may be combined, (c) The microscopic investigation must never be omitted. The shape of the corpuscles may vary considerably, as is shown in Figs. 253 to 255. 266. BILE IN URINE (CHOLURIA).— The physiological condhions which cause the bile constituents to appear in the urine are mentioned in part at ^ iSo. Haematogenic, or Anhepato^jenic Icterus ( yK!«<-/i"i;), occurs when bilirubin {§ 20) is formed from extravasated blood by the action of the connective-tissue corpuscles, so that bile pigments, in addition to coloring the tissues, pass into the urine. SUGAR IN URINE. 451 I. Bile Pigments. — Their presence is ascertained by Gmelin-Heintz's test. Green (Bili- verdin) is the characteristic hue in the play of colors obtained with this test, which is fully described in I in- Modifications of the Test. — i. If icteric urine be filtered through filtering or blotting paper, a drop of nitric acid containing nitrous acid, when applied to the inner surface of the spread-out filter, gives a yellowish colored ring [Rosenbaih). 2. In order that the reaction may not take place too rapidly, add a concentrated solution of sodic nitrate, and then slowly pour in sulphuric acid (FUischl). 3. On shaking 50 c.c. of icteric urine with 10 c.c. of chloroform, the bilirubin is dis- solved by the latter. On adding bromide water, a beautiful ring of colors is obtained (^/aly). If the chloroform extract be treated with ozonized turpentine and dilute caustic potash, a green color, due to biliverdin, occurs in the watery fluid [Gerhardt). In slight degrees of jaundice, urobilin alone may be found (§ 261, i) [Quincke). In persistent high fever, the urine contains especially biliprasin [Huppert). If it contains choletelin alone, add to the urine some hydrochloric acid, and examine it with the spectroscope, which gives a pale absorption band between b and F (J 177, 3,/). Haematoidin. — Sometimes crystals of Au-ma/oidin (| 20, Fig. 14) appear in the urine, especially when blood corpuscles are dissolved within the blood stream ; occasionally in scarlet fever and typhus, and sometimes in cases of periodic linemoglobinuria. The breaking up of old blood clots in the urinary passages, as in pyonephrosis (Ebstein), or during the dissolution of necrotic areas [Hofmann and Ultzmann') produces them, and similar crystals occur in analogous cases in the sputum (5 13S). In jaundice due to congestion {\ 180), the identical crystalline substance, bilirubin, is found. II. Bile acids occur in largest amount in absorption jaundice, but they are never present to any extent. The test is described at ^177, 2, the cane-sugar solution consisting of 0.5 grm. to i litre of water. If the urine be dilute, it is advisable to concentrate it on a water bath. v. Pettenkofer's test may be used with the alcoholic extract of the nearly dry residue, but no albumin must be present. Dragendorft' found o.S grm. in 100 litres of normal urine. Strassburg's Modification. — Dip filter paper into the urine, to which a little cane sugar has been added ; dry the paper, and apply to it a drop of sulphuric acid. A violet-red color is obtained after a short time. [Hay's Reaction. — The effect of bile salts in lessening the surface tension of a liquid, and thus rapidly causing the precipitation of a dry powder like sulphur, when placed in the liquid, is the basis of this test (\ 177)-] 267. SUGAR IN URINE (GLYCOSURIA). — Diabetes Mellitus.— The excessively minute trace of grape sugar, or dextrose, which is constantly present in normal urine, sometimes becomes greatly increased, and constitutes the conditions of diabetes mellitus and glycosuria. The physiological conditions which determine this result are given at J 175. In this condition, the quantity of urine is greatly increased; it may reach 10 or more litres. Many pints may be passed daily. [The usual abnormal amount of sugar is from i to 8 per cent., although 15 per cent, has been found, i. ) Yeast (S. fermenlum) occurs in diabetic urine, as oval cells with a doited, eccentrically placed nucleus (Fig. 262, rf). 3. Phytomycetes (moulds) occur in putrid urine (Fig. 262, e). They are without clinical sig- nificance. F. Tube Casts. — The occurrence of tube casts, !.«•., casts of the uriniferous tubules {//en/e, jSjy) is of great importance in connection with the diagnosis of renal diseases. If these structures Fig. 262. , micrococci in short chains and groups ; i, sarcinse : c, fungi from acid fermentation ; ^, yeast cells from diabetic urine; e, mycelium of a fungus. Fig. 263. yl.._._ . a, blood are relatively thick and straight, they probably come from the collecting tubules, but if they are sinaller and twisted, they probably come from the convoluted tubules. There are various forms of tube casts : I. Epithelial casts, consisting of the actual cells of the uriniferous tubules. They indicate that there is no very great change going on, but only that, as in catarrhal inflammation of any mucous membrane, the epithelium is in process of desquamation. 2. Hyaline casts (Fig. 264) DETECTION OF URINARY DEPOSITS. 457 are quite clear and homogeneous, usually long and small; sometimes they are " finely granular," from the presence of fat or other particles. They are best seen after the addition of a solution of iodine. They are probably formed from albumin, which passes into the uriniferous tubules. They are dissolved in alkaline urine, while acid urine favors their formation. They usually occur in the late stages of renal disease, after the tubular epithelium has been shed. 3. Coarsely granular casts (Fig. 263, b), brownish-yellow opaque, and granular, usually broader than 2. There are vari- ous forms. Not unfrequently there are fatty granules, and, it may be, epithelial cells in them. 4. Amyloid casts occur in amyloid degeneration of the kidneys (Fig. 263, c). They are refractive and completely homogeneous, and give a blue color (amyloid reaction) with sulphuric acid and iodine. 5. Blood casts occur in capillary hemorrhage of the kidney, and consist of coagulated blood entangling blood corpuscles (Fig. 263, a). When tube casts are present, the urine is always allmminous. II. Unorganized Deposits. — Some of these are crystalline and others are amorphous, and they have been referred to in treating of the urinary constituents. 271. SCHEME FOR DETECTING URINARY DEPOSITS.— I. In acid urine there may occur : — I. An amorphous granular deposit : (a) Which is dissolved by heat and reappears in the cold ; the deposit is often reddish in color ^= urates (Fig. 249). [l>) Which is not dissolved by heat, but is dissolved by acetic acid, but without effervescence = probably tribasic calcic phosphate. Fig. 264. Hyal (c) Small, bright, refractive granules, soluble in ether = fat or oil granules (?. 41) (Lipjemia). Fat occurs in the urine, especially when the round worm, Filaria sanguinis honiinis, is present in the blood ; sometimes, along with sugar, in phthisis, poisoning with phos- phorus, yellow fever, pyaemia, after long-continued suppuration, and lastly, after the injection of fat or milk into the blood (J 102). It occurs also in fatty degeneration of the urinary apparatus, admixture with pus from old abscesses, and after severe injuries to bones. In these cases attention ought to be directed to the presence of cholesterin and lecithin. Very rarely is the fat present in such amount in the urine as to form a cream on the surface (chyluria). 2. A. crystalline deposit may be — (a) Uric acid (Figs. 242, 243, 249). (/') Calcium oxalate (Figs. 249, 259) — octahedra insoluble in acetic acid. (<-) Cystin (Fig. 2591. (J) Leucin and tyrosin — very rare (Fig. 260). I. In alkaline urine there may occur — 1. A compUtely amorphous granular deposit, soluble in acids without effervescence ^= tri- basic calcic phosphate. 2. Sediment crystalline, or with a characteristic form. (o) Triple phosphate (Figs. 250, 251, 252, and 256), soluble at once in acids. 458 URINARY CALCULI. {i) Acid ammonium urate — dark -yellowish, small balls often beset with spines, also amor- phous (I'iss. 250 and 260). (1) Calcium carbonate — small whitish balls or biscuit-shaped bodies. Acids dissolve them with eft'ervescence (Fig. 248). (i/) Leucin and tyrosin (I'ig. 260) — very rare. (e) Neutral calcic phosphate and long plates of tribasic magnesic phosphate (Fig. 24S). Organized deposits njay occur both in alkaline and in acid urine; pus cells are more abundant in alkaline urine, and so are the lower vegetable organisms. 272. URINARY CALCULI. — Urinary concretions may occur in granules the size of sand, or in masses as large as the list. According to their size they are spoken of as sand, gravel, stone or calculi. They occur in the pelvis of the kidney, ureters, bladder and sinus prostaticus. We may classify them as follows ( Ullz/nann) : — 1. Calculi, whose nucleus consists of the sedimentary forms that occur in acid urine (primary formation of calculi). They are all formed in the kidney, and pass into the bladder, w-here they enlarge according to the growth of the crystals in the urine. 2. Calculi, which are either sedimentary forms from alkaline urine, or whose nucleus consists of 2. foreign body (secondary formation of calculil. They are formed in the bladder. The primary formation of calculi begins with free uric acid in the form of sheaves (Fig. 242, c) which form a nucleus, with concentric layers of oxalate of lime. The secondary formation occurs in neutral urine by the deposition of calcic carbonate and crystalline calcic phosphate ; in alkaline urine, by the deposition of acid ammonium urate, triple phosphate and amorphous calcic phosphate. Chemical Investigation. — Scrape the calculus, burn the scrapings on platinum foil to ascertain if they are burned or not. I. Combustible concretions can consist only of organic substances. ((7) Apply the murexide test [\ 259, 2), and if it succeeds uric acid is present. Uric acid cal- culi are very common, often of considerable size, smooth, fairly hard, and yellow to reddish-brown in color. (('<) If another portion, on being boiled with caustic potash, gives the odor of ammonia (or when the vapor makes damp turmeric paper brown, or if a glass rod dipped in HCl and held over it gives white fumes of ammonium chloride), the concretion contains ammonium urate. If b gives no result, pure uric acid if present Calculi of ammonium urate are rare, usually small, of an earthy consistence, i.e., soft and pale yellow or whitish in color. (c) If the xanthin reaction succeeds (J 260), this substance is present (rare). Indigo has been found on one occasion in a calculus (Ord). (d) If, after solution in ammonia, hexagonal plates (Fig. 259, A) are found, cystin is present. (e) Concretions of coagulated blood or fibrin, without any crystals, are rare. When burned they give the odor of singed hair. They are insoluble in water, alcohol and ether; but are soluble in caustic potash, and are precipitated therefrom by acids. (f) Urostealith is applied to a caoutchouc like, soft elastic substance, and is" very rare. When dry it is brittle and hard, brown or black. When warm it softens, and if more heat be applied it melts. It is soluble in ether, and the residue after evaporation becomes violet on being heated. It is soluble in warm caustic potash, with the formation of a soap. II. If the concretions are only partly combustible, thus leaving a residue, they contain organic and inorganic constituents. (a) Pulverize a part of the stone, boil it in water, and filter while hot. The urates are dissolved. To test if the uric acid is united with soda, potash, lime or magnesia, the filtrate is evaporated and burned. The ash is investigated with the spectroscope (J 14), when the characteristic bands of sodmm or potash are observed. Magnesic urate and calcic urate are changed into carbonate by burning. To separate them dissolve the ash in dilute hydrochloric acid and filter. The filtrate is neutralized with ammonia, and again redissolved by a few drops of acetic acid. The addition of ammonium oxalate precipitates calcic oxalate. Filter and add to the filtrate sodic phosphate and ammonia, when the magnesia is precipitated as ammonio-magnesic phosphate. {I') Calcic oxalate (especially in children, either as small, smooth pale stones, or in dark, warty, hard " mulberry calculi ") is not affected by acetic acid, is dissolved by mineral acids without effer- vescence, and again precipitated by ammonia. Heated on platinum foil it chars and blackens, then it becomes white, owing to the formation of calcic carbonate, which effervesces on the addition of an acid. (f) Calcic carbonate (chiefly in whitish-gray, earthy, chalk-like calculi, somewhat rare) dis- solves with effervescence in hydrochloric acid. When burned it first becomes black, owing to admixture with mucus, and then white. [d] Ammonio- magnesic phosphate and basic calcic phosphate usually occur together in soft, white, earthy stones, which occasionally are very large. These stones show that the urine has been ammoniacal for a very long time. The first substance when heated gives the odor of ammo- nia, which is more distinct when heated with caustic potash; is soluble in acetic acid without effer vescence. and is again precipitated in a crystalline form from this solution on the addition of am monia. When heated it fuses into a white, enamel-like mass [hence, it is called " fusible calculus "] GLOMERULAR EPITHELIUM. 459 Basic calcic phosphate does not effervesce with acids. The solution in hydrochloric acid is pre- cipitated by ammonia. When ammonium oxalate is added to the acetic acid solution, it yields calcic oxalate. (f) Neutral calcic phosphate is rare in calculi, while it is frequent in the form of gravel. Physically and chemically, these concretions resemble the earthy phosphates, only they do not con- tain magnesia. 273. THE SECRETION OF URINE.— [The functions of the kidney are — • 1. To excrete waste products, chiefly nitrogenous bodies and salts ; 2. To excrete water ; 3. -\nd perhaps also to reabsorb water from the uriniferous tubules, after it has washed out the waste products from the renal epithelium. The chief parts of the organs concerned in i, are the epithelial cells of the convoluted tubules ; the glomeruli permit water and some solids to pass through them, while the constrictions of the tubules may prevent the too rapid outflow of water, and thus enable part of it to be reabsorbed (Bnuifon)^ Theories. — The two chief older theories regarding the secretion of urine are the following : i. .According to Bowman's view ( 1842), through the glomeruli are filtered only the water and some of the highly diffusible and soluble salts present in the blood, while the specific urinary constituents are secreted by the activity of the epithelium of the urinary tubules, and are extracted or removed from the epithelium by the water flowing along the tubules. This has been called the "vital" theory. 2. C. Ludwig (1844) assumes that very dilute uri/ie is secreted or filtered through the glomerulus. As it passes along the urinary tubules it becomes more concentrated, owing to endosmosis. It gives back some of its water to the blood and lymph of the kidney, thus becoming more concen- trated, and assuming its normal character. [This is commonly known as the " mechanical" theory.] The secretion of urine in the kidneys does not depend upon definite physical forces on/v. A great number of facts force us to conclude that the vital activity of certain secretory cells plays a foremost part in the process of secretion (J?. Heidenhaiii). The secretion of urine embraces — (i) The water, and (2) the urinary con- stituents therein dissolved; both together form the urinary secretion. The amount of urine depends chiefly upon the amount of water which is filtered through or secreted by the glomeruli ; the amount of solids dissolved in the urine determines its concentration. (A) The amount of urine, which is secreted chiefly within the Malpighian capsules, depends primarily upon the blood pressure in the area of the renal artery, and follows, therefore, the laws of filtration [§ 191, II] (Ludicig and Goll). [In this respect the secretion of urine differs markedly from that of saliva, gastric juice, or bile. We may state it more accurately thus, that the amount of urine depends very closely upon the difference of pressure between the blood in the glomeruli and the pressure within the renal tubules. If the ureter be ligatured, the secretion of urine is ultimately arrested, even although the blood pressure be high. The secretion may also be arrested by ligature of the renal vein ; ar.d in some cases of cardiac or pulmonary disease the venous congestion thereby pro- duced may bring about the same result.] Glomerular Epithelium. — The amount of urine secreted does not depend upon the hydrostatic pressure alone, but it seems that the epithelial cells covering the glomerulus also participate aetively in the process of secretion. Besides the water, a certain amount of the salts present in the urine is excreted through the glomeruli. The serum albumin of the blood, however, is prevented from passing through. With regard to the secretory activity of these cells, the quantity of water must also depend upon the amount and rate at which the material to be secreted is carried to the glomeruli by the blood stream, and also upon the amount of the urinary constituents and water present in the blood ( Ji. Heidenhain). 460 RELATION TO THE BLOOD PRESSURE, Only when the vitality of the secretory cells is intact is there independent activity of these secretory cells {Ileidenhain), When the renal artery is closed temporarily, their activity is para- lyzed, so that the kidneys cease to secrete, and even after the compression is removed and the circu- lation re-established, secretion does not take place for some time (Oz'erlieik). That the secretion depends in part upon the blood pressure is proved by the following considerations : — 1 . Increase of the total contents of the vascular system, so as to increase the blood pressure, increases the amount of water which filters through the glomeruli. The injection of water into the blood vessels, or drinking copious draughts of water, acts partly in this way. If the blood pressure rises above a certain height, albu- min may pass into the urine. The active participation of the cells of the glom- eruli is rendered probable by the fact that, after very copious drinking, the blood pressure is not always raised {Pawlow) ; further, after profuse transfusion, the quantity of urine is not increased. Conversely, the excretion of water, owing to profuse sweating or diarrhoea, copious hemorrhage, or prolonged thirst, dimin- ishes the secretion of urine. 2. Diminution of t/ie capacity of the vascular system, jjrovided the jjressure within the renal area be thereby increased, acts in a similar manner. This may be pro- duced by contraction of the cutaneous vessels, owing to the action of cold, stim- ulation of the vasomotor centre, or large vasomotor nerves, ligature, or com- pression of large arteries (§ 85, e), or enveloping the extremities in tight bandages. All these conditions cause an increase in the amount of urine, and, of course, the opposite conditions bring about a diminution of urine, e.g., the action of heat on the skin causing redness and dilatation of the cutaneous vessels, weakening of the vasomotor centre, or paralysis of a large number of vasomotor nerves. 3. Increased action of the heart, whereby the tension and rapidity of the blood in the arteries are increased (§ 85, c), augments the amount of urine ; conversely, feeble action of the heart (paralysis of motor cardiac nerves, disease of the cardiac musculature, certain valvular lesions), diminishes the amount. Artificial stimula- tion of the vagi in animals, so as to slow the action of the heart, and thus dimin- ish the mean blood pressure from 130 to 100 mm. Hg, causes a diininution in the amount of urine to the extent of one-fifth {Goll, CI. Bernard) ; when the pres- sure in the aorta falls to 40 mm. the secretion of urine ceases. [If the medulla oblongata be divided (dog) there is an immediate fall of the general blood pressure, and although, as a general rule, the secretion of urine is arrested when the pressure falls to 40 to 50 mm. Hg, yet secretion has been observed to take place with a lower pressure than this.] 4. The amount of urine secreted rises or falls according to the degree of fulness of the renal artery (Ludwig, Max Herrmann) ; even when this artery is moderately constricted in animals, there is a decided diminution in the amount of urine. Pathological. — In fever the renal vessels are less full, and there is consecutive diminution of urine {Mendetsotin). It is most important, in connection with certain renal diseases, to note that ligature of the renal artery, even when it is obliterated for only two hours, causes necrosis of the epithelium of the uriniferous tubules. When the arterial anjemia is kept up for a long time, the whole renal tissue dies [Litten). After long-continued ligation of the renal artery, the epithelium of the glomeruli becomes greatly changed (Ribbert). 5. Most diuretics act in one or other of the above-mentioned ways. [.Some diuretics act by increasing the general blood pressure (digitalis and the action of cold on the skin), others mny increase the blood pressure loaiUy within the kidney, and this they may do in several ways. The nitrites are said to paralyze the muscular fibres in the vasa afferentia, and thus raise the blood pressure within the glomeruli. But some also act on the secretory epithelittm, such as urea and caft'ein. Brunton recommends the combination of diuretics in appropriate cases, and the diuretics must be chosen according to the end in view — as we wish to remove excess of fluids from the tissues and serous cavities, or as we wish to remove injurious waste products, or merely to dilute the urine.] [6. The amount of urine also depends upon the composition of the blood. Drink- SECRETORY ACTIVITY OF THE RENAL EPITHELIUM. 461 ing a large quantity of water — whereby the blood becomes more watery — increases the amount of urine, but this is true only within certain limits. It is not merely the increase of volume of the blood acting mechanically which causes this increase, as we know that large quantities of blood may be transfused without the general blood pressure being materially raised thereby.] [Heidenhain argues that it is not so much the pressure of the blood in the glomeruli as its velocity, which determines the process of the secretion of water in the kidney. He contends that, while increase of the pressure in the renal artery causes an increased flow of urine, ligature of the renal vein, whereby the pressure in the glomeruli is also increased, arrests the secretion altogether. In both cases the pressure is increased within the glomeruli, and the two cases differ essentially in the velocity of the blood current through the glomeruli.] Pressure in the Vas Afferens. — The pressure in each vas afferens must be relatively great, because (i) the double set of capillaries in the kidney offers con- siderable resistance, and because (2) the lumen of the vas efferens is narrower than that of the vas afferens. Hence, owing to the high blood pressure in the capilla- ries of the renal glomeruli, filtration must take place from the blood into the Malpighian capsules. When the vasa afferentia are dilated, e. g., through the action of the nervous system on their smooth muscular fibres, the filtration pressure is increased, while, when they are contracted, the secretion is lessened. When the pressure becomes so diminished as to retard greatly the blood stream in the renal vein, the secretion of urine begins to be arrested. Occlusion of the renal vein completely suppresses the secretion (/f. Meyer, v. Frerichs). Ludwig con- cluded, from this observation, that the filtration or excretion of fluid could not take place through the renal capillaries />rc;/«-, as, owing to occlusion of the renal vein, the blood pressure in these capillaries must rise, which ought to lead to increased filtration. Such an experiment points to the conclusion that the filtra- tion must take place through the capillaries of the glomeruli. The venous stasis dis- tends the vas efferens, which springs from the centre of the glomerulus, and compresses the capillary loops against the wall of the Malpighian capsule, so that filtration cannot take place through them. It. is not decided whether any fluid is given off through the convoluted urinary tubules. Pressure in Ureter. — As the blood pressure in the renal arlery is about 120 to 140 mm. Hg, and the urine in the ureter is moved along by a very shj^ht propelling force, so that a counter-pressure of from 10 (LSI/ell) to 40 mm. of Hg is sufficient to arrest its flow, it is clear that the blood pressure can also act as a vis a lergo to propel the urine stream through the ureter. The pressure in the ureter is measured by dividing the ureter transversely and placing a manometer in it. (B) Secretory Activity of the Renal Epithelium.— The degree of concentration of the urine depends upon the quantity of the dissolved constit- uents which has passed from the blood into the water of the urine. The secretory cells of the convoluted tubules, by their own proper vital activity, seem to be able to take up, or secrete, some, at least, of these substances from the blood {Bowi/ian, Heidenhain). The watery part of the urine, containing only easily diffusible salts, as it flows along the tubules from the glomeruli, extracts or washes out these substances from the secretory epithelium of the convoluted tubules. Experiments. — i. Sulphindigotate of soda and sodium urate, when injected into the blood, pass into the urine, and are found within the protoplasm of the cells o{t\it convoluted tubules [only in those parts lined by "rodded" epithelium], but not in the Malpighian capsules (^Heidenhain). A little later, these substances are found in the lumen of the urinary tubules, from which they are washed out by the watery part of the urine coming from the glomeruli. If, however, two days before the injection of these substances into the blood, the cortical part of the kidney containing the Malpighian capsules be cauterized \_e. g. , by nitrate of silver] (Heidenhain), or simply be removed with a knife (Hoegyes), the blue pigment remains within the convoluted tubules. It cannot be carried onward, as the water 462 nussbaum's experiments. which should carry it along has ceased to be secreted, owing to the destruction of the glomeruli. This experiment also goes to show that, through the gAu/ifru// the 7vatery part of the urine is chiefly excreted, while through the convcli(ted tubules the specific urinary constituents are excreted. Uric acid salts, injected into the blood, were observed by Heidenhain to be excreted by the convoluted tubules. Von Wittich had previously observed that in birds, crystals of uric acid were excreted by the epithelium of the convoluted tubules. [The presence of crystals of uric acid in the renal epithelium was observed by Bowman, and used as an argument to support his theory.] Nussbaum, in 1878, stated that urea is secreted by the urinary tubules, and not by the glomeruli. The same is true for the bile pigments {Mobius, fSyy), for the iron salts of the vegetable acids when injected subcutaneously {Glaevecke'), and for hLiemoglobin {Landois). After the injection of 7nilk into the blood vessels, numerous fatty granules occur within the epithelium of the urinary tubules {\ 102). [Nussbaum's Experiments. — In the frog and newt, the kidney is supplied with blood in a different manner frotii that obtaining in mammals. The glomeruli are supplied by branches of the renal artery. The tubules are supplied by the renal-portal vein. The vein coming from the posterior extremities divides at the upper end of the thigh into two branches, one of which enters the kidney, and breaks up to form a capillary plexus which surrounds the uriniferous tubules, but this plexus is also joined by the efferent vessels of the glomeruli. These two systems are partly independent of each other. By ligaturing the renal artery, Nussbaum asserted that the circulation in the glomeruli was cut off, while ligature of the renal-portal vein excluded the functional activity of the tubules. By injecting a substance into the blood after ligaturing either the artery or renal-portal vein, and observing whether it occurs in the urine, he infers that it is given off either by the glomeruli or the tubules. Sugar, peptones, and 1?^^ albumin rapidly pass through an intact kidney, but if the renal artery be tied they are not excreted. Urea when injected into the circulation is excreted after the artery is tied, so that it is excreted through the tubules, but at the same time it takes with it a considerable quantity of water. Thus water is excreted in tioo ways from the kidney, by the glomeruli and also from the venous plexus around the tubules along with the urea. Indigo carmine merely passes into the tubular epithelium of the convoluted tubules, but it does not cause a secretion of urine. Albumin passes through the glomeruli, but only after their membranes have been altered in some way, as by clamping the renal artery for a time.] [Adami's Experiments on the kidney of the frog clearly show that Nuss- baum's conclusions are not justified, for Adami found that if the renal arteries in the frog be ligatured, within a few hours a collateral circulation is established, and a certain amount of blood flows through the kidney. He proved this by injecting into the blood carmine or painter's vermilion, in a state of fine suspension, and after ligature of the renal arteries he found it in many of the glomeruli, while laky blood similarly injected revealed its presence as menisci of Hb in the Malpighian capsules. Even secretion of some urine may go on after ligature of the renal arteries. It is evident, then, that Nussbaum's method is not a reliable one for locating the parts of the kidney through which certain substances are excreted.] [Adami's experiments also give some support to Heidenhain's view that tne glomerular epithelium " possesses powers of a selective secretory nature ;" for he finds that in frogs, after ligature of the renal arteries, where, of course, the pres- sure in the glomeruli is just nearly that in the veins, and in the dog after section of the spinal cord, so that the blood pressure has fallen below 40 mm. Hg, whereby the secretion of urine is arrested ; the injection of laky blood causes Hb to appear in the capsules, although there is no simultaneous excretion of water.] Excretion of Pigments. — Only during very copious excretion does the capsule participate. After the introduction of a large amount of sodic sulphinciigotate, and when the experiment has FORMATION OF THE URINARY CONSTITUENTS. 463 lasfed for a long time, the epithelium of the capsule becomes blue (Arnold and Pautynski). In albuminuria the abnormal excretion of urine takes place first in the urinary tubules, and after- ward in \.\\t ca^isMXes [Senator); Hb is partly found in the capsules {Griitzner, Bridges Adams'). According to Xussbaum, egg albumin passes out through the capsule. 2. Even when the secretion of the watery part of the urine is completely arrested, either by ligature of the ureter, or after a very great fall of the blood pressure in the renal artery [as after section of the cervical spinal cord], the before- mentioned substances, when injected into the blood, are found in the cells of the convoluted tubules. The injection of urea under these circumstances causes re- newed secretion. These facts show that, independently of the filtration pressure, the secretory activity of these cells is still maintained {Heidenhain, Neisser, Ustimo- witsch, Griitzner'). The independent vital activity of the secretory cells of the urinary tubules, which as yet we are unable to explain on purely physical grounds, renders it probable that the tubules are not to be compared to an apparatus provided with physical membranes. This is proved by the following ex- periment : Abeles caused arterial blood to circulate through freshly excised living kidneys. A pale, urine-like fluid dropped from the ureter. On adding some urea or sugar to the blood, the secretion became more concentrated. Thus the excised living kidney also excretes substances in a more con- centrated form than when supplied to it in the diluted blood streaming through it. Salts and Gases. — The vital activity explains why the serum albumin of the blood does not pass into the urine, while egg albumin and dissolved haemoglobin readily do so. Among the salts which occur in the blood and blood corpuscles, of course only those in solution can pass into the urine. Those which are united with proteid bodies, or are fixed in the cellular elements, cannot pass out, or at least only after they have been split up. Thus we may explain the difference between the salts of the urine and those of the blood. Similarly, the urine can only contain the absorbed and not the chemically united gases. Ligature of the Ureter. — [f the secretion be arrested by compression or by ligature of the ureter, the lymph spaces of the kidney become filled with fluid, which may pass into the blood, so that the organ becomes cedematous, owing to the passage of fluid into its lymph spaces. The secre- tion undergoes a change, as first water passes back into the blood, then the sodic chloride, sulphuric, and phosphoric acids diminish, and lastly the urea (C Ludvjig, Max Herrmann). Kreatinin is still present in considerable amount. There is no longer secretion of proper urine (Lobell). Non-Symmetrical Renal Activity. — It is remarkable that both kidneys do not secrete sym- metrically — there is an alternate condition of hypersemia and secretory activity on opposite sides {\ too). One kidney secretes a more watery urine, which at the same time contains more XaCl and urea [I.udwig, M. Herrmann). \'on Wittich observed that the excretion of uric acid was not uniform in all the urinary tubules of the same bird. Extirpation of one kidney, or disease of one kidney in man, does not seem to diminish the secretion (Rosenstein). The remaining kidney becomes more active and larger. Reabsorption in the Kidney. — In discussing the secretion of the kidney, we must attach con- siderable importance to the variations in the calibre of the renal tubules in their course. Perhaps in the narrowing of the descending part of the looped tubule of Henle there may be either a reab- sorption of water, so that the urine becomes more concentrated, or there may be absorption even of albumin, which may, perphaps. pass through the glomeruli in small amount. [That reabsorption of fluid takes place within the kidney was part of Ludwig's theory, which is practically a process of filtration and reabsorption. Hiifner pointed out that the structure of the kidneys of various classes of vertebrates corresponded closely with the requirements for reabsorption of water. The experi- ments of Ribbert show that the urine actually secreted in the cortex of the kidney is more watery than that secreted normally by the entire organ. He extirpated the medullary portion in rabbits, leaving the cortical part intact, and in this way collected the dilute urine from the Malpighian cor- puscles before it passed through Henle's loops.] 274. FORMATION OF THE URINARY CONSTITUENTS.— The question has often been discussed, whether all the urinary constituents are merely excreted through the kidneys, /. e., that they exist pre-formed in the blood; or whether some of them do not exist pre-formed in the blood, but are formed within the kidneys, as a result of the activity of the renal epithelium. Seat of Urea Formation. Urea formed outside the Kidney. — In considering the formation of urea, we have to ascertain if it is formed within the kidney or outside of it. Urea exists pre-formed in the blood, from which it is separated by the activity of the kidney. This is proved by the following con- siderations : — 464 FORMATION OF URIC ACID. 1. The blood contains one part of urea in 3000 to 5000 parts (Fr. Simon, 1S41), but the renal vein contains less urea than the blood of the corresponding artery [Picara, i8j6 ; Grehant). This fact is in favor of the excretion of urea from the blood. 2. After extirpation of the kidneys, or nephrotomy {Prevost and Dumas), or after ligature of the renal vessels, the amount of urea accumulates in the blood {Meissner, v. I'oit), and increases with the duration of the experiment to jj^ to ;f^j (Gre/iant). At the same time there is vomiting and diarrhcea, and the fluids so voided contain urea [CI. Bernard, Bareswill). Animals die in from one to three days after the operation. 3. After ligature of the ureters, the secretion of urine is soon arrested. Urea accumulates in the blood, but not to a greater extent than after nephrotomy. It is possible, however, that the kidneys, like other organs, may form a small amount of urea, due to the metabolism of their own tissues. [Urea exists in the blood ; whence does the blood derive it ? It can only obtain it from one or more of several organs — (l) muscle; (2) nervous system; and (3) glands, of which the Hver is the most prominent. This is best stated by the method of exclusion.! [l. That urea is not formed in muscle is shown, among other considerations, by the fact that only a trace of urea occurs in muscle (^ 293). and that amount is not increased by exercise. Blood which has been transfused through a muscle, or the blood after circulating in a muscle during violent exercise, does not contain an increase of urea, nor does the addition of ammonia carbonate to blood circulating through muscle show any increase of urea [Grehant, Quinquand, Salomon). Again, muscular exertion does not (as a rule) increase the amount of urea in the urine, as shown by the experiments of Fick and VVislicenus (\ 294), Parkes, and others. The excretion chiefly increased by muscular exertion is pulmonary CO, (| 127).] [2. From what we know of the nervous system, it is not formed there. We are therefore forced to consider the evidence as to the liver as the organ, or, at least, the chief organ in which it is formed. This evidence is in some respects contradictory, but it is partly experimental and partly clinical. Although Hoppe-Seyler denies the existence of urea in the liver, its existence there is proved by Gscheidlen; and Cyon, on passing blood through an excised liver by the "perfusion" or " Durchstromung " method of Ludwig, found that blood, after being passed several times through the organ, contained an increased amount of urea. The objection to these experiments is, that Cyon's method of estimating the urea was unreliable. But von Schrceder, using a similar method, finds that if blood be perfused though the liver of a dog in full digestion, there is a great increase in the amount of urea, while there is none in the liver of a fasting dog. If ammonia carbonate be added to the blood, there is a very much greater amount of urea in the blood of the hepatic vein. This last fact is confirmed by Salomon. The experiments of Minkowski on the liver of the goose (\ 386) show that when the liver is excluded from the circulation, lactic acid takes the place of uric acid in this bird. Brouardel further states, that if the region of the liver be so beaten as to cause congestion of that organ, there is an increase of the urea in the urine.] [The clinical evidence points strongly to the formation of urea in the liver. Parkes pointed out that in hepatic abscess, during the early congestive stage, the urea in the urine is increased, while it is diminisiied in the suppurative stage, when the hepatic parenchyma is destroyed. The urea is also diminished in cancer of the liver, phthisis, and some forms of hepatic cirrhosis, while it is increased during hepatic congestion, and specially so in some cases of diabetes mellitus. The most striking fact of all is that, in acute yellow atrophy of the liver, the urea is enormously diminished in the urine, and may even disappear from it, while its place is taken by the intermediate products, leucin and tyrosin {v. Frerichs). In poisoning by phosphorus, coincident with the atrophy of the liver, there is a fall in the urea excretion. Noel-Paton finds that some drugs which increase the quantity of bile in dogs in a state of N equilibrium (§ lySl.sodic salicylate and benzoate,colchicum, mercuric chloride and euonymin also increase the urea in the urine; he therefore concludes "that the forma- tion of urea in the liver bears a very direct relationship to the secretion of bile by that organ."] As to the antecedents of urea there is the greatest doubt (§ 256). Seat of Uric Acid Formation. Uric acid formed outside the kidneys. I. Birds' blood normally contains uric acid (Meissner). Ligature of their ureters or blood vessels (Pawlinoff), or the gradual destruction of their secretory parenchyma by the subcutaneous injection of neutral potassium chromate (Fbstein), is followed by the deposition of uric acid in the joints and tissues, and it may even form a white incrustation on the serous membranes. The brain remains free ( Gahani, ijby ; ZaJesky, Opplcr). Acid urates of ammonia, soda, and magnesia are also similarly deposited ( Colasanli). Extirpation of a snake's kidneys gives the same result, but to a less degree. [2. Minkowski found that, after excluding the liver from the circulation, lactic acid took the place of uric acid in the urine (p. 298).] [The latter experiments point to the formation of uric acid in the liver in birds, and this is supposed to be strengthened by the appearance of the deposition of urates in the urine in certain disorders of digestion.] Von Schrceder and Cola- santi, however, as the result of their experiments upon snakes, come to the con- clusion that there is no special organ concerned in the formation of uric acid. PASSAGE OF VARIOUS SUBSTA^XES INTO THE URINE. 465 Hippuric acid is partly formed in the kidney, for the blood of herbivora does not contain a trace of it ( Meissner and Shepard ). In rabbits, perhaps it is formed synthetically, in other tissues as well as in the kidney. If blood containing sodic benzoate and glycin be passed through the blood vessels of a fresh kidney, hippuric acid is formed (\ 260) (Bunge, S-hmiedeberg, Kochs). [The other evidence is given in \ 260.] Kreatinin ha^ intimate relations to kreatin of muscle, but where it is formed is not known. If phenol 3.nA pyrokatechinare digested along with fresh renal substance, a compound of sulphuric (7«'a' similar to that occurring in urine (^ 262) is formed. The latter substance, however, is also formed by similarly digesting liver, pancreas, and muscle. It is concluded from these experiments that these substances are formed in the body within the kidneys, and the other organs mentioned y/Coc/is). Chemistry of the Kidney. — The kidneys contain a very large amount of ij/aCi?r. Besides serum albumin, globulin, albumin soluble in sodium carbonate (Gotlwalt), gelatin-yielding substances, fat in the epithelium, elastic substance derived from the membrana propria of the tubules, the kidneys contain leucm, xanthin, hypoxanthin, kreatin, taurin, inosit, cystin (the last in no other tissue), but only in very small amount. The occurrence of these substances points to a lively metabolism in the kidneys, which is also proved by the liberal supply of blood they receive. Blood Vessels. — The kidneys receive a very large supply of blood, and dur- ing secretion of the blood of the renal vein is bright red {Cl. Bernard']. [In the dog the diameter of the renal artery may be diminished to .5 mm. without the amount of blood flowing through the kidney being thereby greatly interfered with. Hence, within wide limits, the amount of blood is independent of the size of the arterial lumen, and is, therefore, dependent on the blood pressure in the aorta, and the resistance to the blood current within and beyond the kidney {Heiden- hain)r\ The reaction of the kidney is acid^ even in those animals whose urine is alkaline. Perhaps this fact is connected with the retention of the albumin in the vessels {Heynsius). 275. PASSAGE OF VARIOUS SUBSTANCES INTO THE URINE.— I. The fol- lowing substances pass unchanged into the urine : Sulphate, borate, silicate, nitrate, and carbon- ate of the alkalies ; alkaline chlorides, bromides, iodides ; potassium sulphocyanide and ferrocyanide ; bile salts, urea, kreatinin ; cumaric, oxalic, camphoric, pyrogallic, and carbolic acids. Many alka- loids, e.g., morphia, strychnia, curara, quinine, caffein ; pigments, sulphindigotate of soda, carmine, madder, logwood, colormg matter of cranberries, cherries, rhubarb ; santonin ; lastly, salts of gold, silver, mercury, antimony, arsenic, bismuth, iron (but not lead), although the greatest part of these is excreted by the bile and the feces. 2. Inorganic acids reappear in man and carnivora as neutral salts of ammonia [Sckmeideberg and IValter, Hallen'orden) ; in herbivora, as neutral salts of the alkalies (E. Salkowski). 3. Certain substances which, when injected in small amount, seem to be decomposed in the blood, pass in part into the urine, when they occur in such large amount in the blood that they can- not be completely decomposed — sugar, haemoglobin, egg albumin, alkaline salts of the vegetable acids, alcohol, chloroform. 4. Many substances appear in an oxidized form in the urine — moderate quantities of vegetable alkaline salts as alkaline carbonates ( IVohler), uric acid in part as allantoin [Salkowski), sulphides and sulphites of soda, in part as sodium sulphate, potassium sulphide as potassium sulphate, some oxyduls as o.xides, benzol as phenol {Naumyn and Schulzen). 5. Those bodies which are completely decomposed, as glycerin, resins, give rise to no special derivatives in the urine. 6. Many substances combine and appear as conjugated compounds in the urine, e.g., the origin of hippuric acid by conjugation (ji 260), the conjugation of sulphuric acid (^ 262), and the forma- tion of urea by synthesis from carbamic acid and ammonia (Drec/isel) [i, 256). After the use of camphor, chloral, or butylchloral, a conjugated compound with glycuronic acid (an acid nearly related to sugar) appears in the urine. Taurin and sarcosin unite with sulphaminic acid. When bromphenol is given, it unites with mercapturic acid, a body nearly related to cystin (f, 26S). 7. Tannic acid, C]jHj„Og, takes up H,0, and is decomposed into two molecules of gallic acid 8. The iodates of potash and soda are reduced to iodides ; malic acid (C4H5O5) partly to suc- cinic acid (C^HgO^) ; indigo blue (CigH^NjO^) takes up hydrogen and becomes indigo white (C,,H,,N3(),). 9. Some substances do not pass into the urine at all, e.g., oils, insoluble metallic salts and metals. 276. INFLUENCE OF NERVES ON THE RENAL SECRE- TION. — .\t the present time we are acquainted merely with the influence of the vasomotor nerves on the filtration of the urine through the renal vessels. Each 30 466 INFLUENCE OF NERVES ON THE RENAL SECTION. kidney seems to be supplied with vasomotor nerves, which spring from both halves of the spinal cord (^Nicolaidcs). As a general rule, dilatation of the branches of the renal artery, chiefly the vasa afferentia, must raise the pressure within the glom- eruli, and thus increase the amount of water filtered through them. The more the dilatation is confined to the area of the renal artery alone, the greater is the amount of the urine. [As yet we only know that the nervous system influences the secretion of urine only in so far as it modifies the pressure and velocity of the blood current in the kidney. We have no satisfactory evidence of the existence of direct secretory nerves in the kidney.] 1. Renal Plexus and its Centre. — Section of the nerves of the renal plexus — the nerves around the renal artery — generally causes an increase in the secretion of urine [hydruria or polyuria] ; sometimes, on account of the great rise of the pressure within the glomeruli, albumin passes into the urine (and there may be rupture of the vessels of the glomeruli), leading to the passage of blood into the urme. The nerve centre for these renal nerves lies in the floor of the fourth ventricle, in front of the origin of the vagus. Injury to this part of the floor of the fourth ventricle, e. g., by puncture (piqure), may increase the amount of urine (diabetes insipidus ), which is sometimes accompanied by the simulta- neous appearance of albumin and blood in the urine {CI. Beniard~). Section of the parts which lie directly in the course of these fibres, as they pass from the centre in the medulla to the kidney, produces the same effects. Close to this centre in the medulla, there lies the centre for the vasomotor nerves of the liver, whose injury causes diabetes mellitus (§ 175). Eckhard found that stimulation of the vermiform process of the cerebellum produced hydruria. In man, stimula- tion of these parts by tumors or inflammation, etc., produces similar results. 2. Paralysis of Limited Vascular Areas. — If, simultaneously with the paralysis of the nerves of the renal artery, the nerves of a neighboring large vas- cular area be paralyzed, necessarily the blood pressure in the renal artery area will not be so high, as more blood flows into the other paralyzed province. Under these circumstances, there may be only a temporary, or, indeed, no increase of urine, provided the paralyzed area be sufficiently large. There is a moderate increase of urine for several hours after section of the splanchnic nerve. This nerve contains the renal vasomotor nerves (which, in part, at least, leave the spinal cord at the first dorsal nerve and pass into the sympathetic nerve), but it also con- tains the vasomotor nerves for the large area of the intestinal and abdominal viscera. Stimulation of this nerve has the opposite effect (C/. Bernard, Eckhard). [The polyuria thus produced is not so great as after section of the renal nerves, because the splanchnic supplies such a large vascular area, that much blood accu- mulates in that area, and also because all the renal nerves do not run in the splanchnics.] 3. Paralysis of Large Areas. — If, simultaneously with paralysis of the renal nerves, the great majority of the vasomotor nerves of the body be paralyzed [as by section of the medulla oblongata], then, owing to the great dilatation of all these vessels, the blood pressure falls at once throughout the entire arterial system. The result of this may be, provided the pressure is sufficiently low, that there is a great decrease, or, it may be, entire cessation of the secretion of urine. The secretion is arrested when the cervical cord is completely divided, down even as far as the seventh cervical vertebra (EcMard). The polyuria caused by injury to the floor of the fourth ventricle at once disappears when the spinal cord (even down to the twelfth dorsal nerve) is divided. [As already stated, section of the renal nerves is followed by polyuria, owing to the increased pressure in the glomeruli, but this polyuria may be increased by stimu- lating the spinal cord below the medulla oblongata, because the contraction of the blood vessels throughout the body still further raises the blood pressure within the glomeruli. If, however, the spinal cord be divided below the medulla oblongata — the renal nerve being also divided — the polyuria ceases, because of the fall of RENAL ONCOGRAPH AND ONCOMETER. 467 the general blood pressure thereby produced. Merely dividing the spinal cord in the dorsal region also diminishes or arrests the secretion of urine, owing to the fall of the blood pressure, but animals recover from this operation, the general blood pressure rises, and with it the secretion of urine. Stimulation of the cord below the medulla arrests the secretion, as it causes contraction of the renal arteries along with the other arteries of the body.] [Volume of the Kidney — Oncometer. — By means of the plethysmograph (§ loi) we can measure the variations in the size of a limb, while by the oncograph (fs«t'/-), uric acid, and sodic urale (Ranie) is without effect. Schottin and Oppler ascribe the results to an accumulation of normal or abnormal exlractives. It is pos- sible that several substances and their decomposition products (v. Voit, Perls) contribute to produce the result, so that there is a combined action of several factors, but perhaps the retention of the potash stilts plays the most important part. [Alkaloids in Urine (rouchet,iSSo). — Human urine, and especially febrile urine, when injected under the .skin of frogs or rabbits, acts as a poison, and even causes death, by the arrest of the res- piration (CV. Bernard, Boeci, Bouchard). The alkaloids seem to be formed by the action of vege- table organisms in the intestine, whence they are absorbed into the blood and pass into the urine (J 116). LIrine rendered colorless by charcoal loses half its toxic power, and the poisonous sub- stance IS not volatile, and even resists boiling. These alkaloids are increased in the urine in typhoid fever, pneumonia, but not in diabetes [Lepine and Guerin).'^ Ammoniaemia. — When urine undergoes the alkaline fermentation within the bladder, and am- monium carbonate is formed, the ammonia may be absorbed and produce this condition. The 470 STRUCTURE AND FUNCTIONS OF THE URETER. lire.ith and excretions smell strongly of ammonia ; the mouth, pharynx, and skin are very dry j there is vomiting, with diarrhoea or constipation, while ulcers may form in the intestine [Treilz). The patient rapidly loses flesh, and death occurs without any disturbance of the mental faculties. Uric Acid Diathesis. — When too much nitrogenous food, too much alcoholic fluids are persist- ently used, and little muscular exercise taken, especially if the respiratory organs are interfered with, uric acid may not unfrequently accumulate in the blood ( Gan-oJ). It may be deposited in the joints and their ligaments, especially in the foot and hand, giving rise to painful inflammation, and forming gout stones or chalk siones. The heart, liver, and kidneys are rarely affected. The tissues near tliese deposits undergo necrosis. 278. STRUCTURE AND FUNCTIONS OF THE URETER.— Mucous Membrane. — The pelvis of the kidney and the ureter are lined by a mucous membrane^ consisting of connect- ive tissue, and covered with several layers of stratified " transitional "epithelium (Fi". 268). The cells are of various shapes, those of the lowest layer being usually more or less spherical and small, while many of the cells in the upper layers are irregular in shape, often with long processes passing into the deeper layers. Submucosa. — Under the epithelium there is a layer of adenoid tissue [Hamburger, Chiari), which may contain small lymph follicles [embedded in loose connective tissue]. There are a few small mucous glands in the pelvis of the kidney, and also in the ureter [Unruh, £gli). [They are lined by a single layer of columnar epithelium.] The muscular coat consists of an inner somewhat stronger layer of longitudinal, non-striped fibres, and an outer circular layer. In the lowest third of the ureter there are in addition a num- ber of scattered muscular fibres. All these layers are surrounded and supported by connective tissue. The outer layers of the connective tissue form an outer coat or adventitia, which contains the large vessels and nerves [with small ganglia]. The various coats of the ureter can be followed up to the pelvis of the kidney, and to its calices. The papillae are covered only by the mucous membrane, while the muscular layer ceases at the apex of the pyramids, where they are disposed circularly to form a kind of sphincter muscle for each' papilla (Hcnle). The blood vessels supply the various coats, and form a capillary plexus under the epithelium. The nerves .are not very numerous, but they contain medullated (few) and non-medullateil fibres, with numerous ganglia scattered in their course. They are partly motor and supply the muscular layers, and some pass toward the epithelium, and are sensory and excito-reflex in function. It is these nerves which are excited when a calculus, passing along the ureter, gives rise to severe pain. The ureter perforates the wall of the bladder obliquely. The inner opening is a narrow slit in the mucous membrane, directed downward and inward, and provided with a pointed, valve like pro- cess (Fig. 269). Movement of the Urine. — The urine is propelled along the ureter thus : (i ) The secretion, which is continually being formed under a high pressure in the kidney, propels onward the urine in front of it, as the urine is under a low pressure in the ureter. (2) Grcwily aids the passage of the urine when the person is in the erect posture. (3) The muscles of the ureter contract rhythmically and peri- staltically, and so propel it toward the bladder. This movement is reflex, and is due to the presence of the urine in the ureter. Every three-quarters of a min- ute several drops of urine pass into the bladder (Mu/Jer). But the fibres may also be excited directly. The contraction passes along the tube at the rate of 20 to 30 mm per second, always from above downward. The greater the tension of the ureter due to the urine, the more rapid is the peristaltic movement {Sokoleff and Luchsinger). Local Stimulation. — On applying a stimulus to the ureter directly, the contraction passes both upward and downward. Engelmann observed that these movements occur in parts of the ureter where neither nerves nor ganglia were to be found, and he concluded that the movement was propagated by " muscular conduction." If this be so, then an impulse may be propagated from one non-striped muscular cell to another without the intervention of nerves (compare the same result in the heart, \ 58, I, 3). Prevention of Reflux. — The urine is prevented from exerting a backward pressure toward the kidneys, thus: i. The urine which collects in the pelvis of the kidney is under a high pressure, and thus tends uniformly to compress the pyramids, so that the urine cannot pass into the minute orifices of the urinary tubules {E. H. Weber'). 2. When there is a considerable accumulation of urine in a ureter, f. _§. , from the presence of an impacted calculus or other cause, there is also more energetic peristalsis, and, at the same time, the circular mus- cular fibres round the apices of the pyramids compress the pyramids and prevent URINARY BLADDER AND URETHRA. 471 the reflux of urine through the collecting tubules. The urine is prevented from passing back from the bladder into the ureter, by the fact that, when the bladder is greatly distended with urine, the wall of the bladder itself, and the part of the ureter which passes through it, are compressed, so that the edges of the slit-like opening of the ureter are rendered more tense, and are thus approximated toward each other (Fig. 269). 279. URINARY BLADDER AND URETHRA.— Structure.— The mucous mem- brane of the bladder resembles that of the ureter ; the upper layers of the stratified transitional epithelium are flattened. It is obvious that the form of the cells must vary with the state of dis- tention or contraction of the bladder. [The mucous membrane and muscular coats are thicker than in the ureter. There are mucous glands in the mucous membrane, especially near the neck of the bL-idder.] Submucous Coat. — There is a layer of delicate fibrillar connective tissue mixed with elastic fibres between the mucous and muscular layers. [The Serous Coat is continuous with, and has the same structure as, the peritoneum, and it covers only the posterior and upper half nf the organ.] Musculature. — The non-striped muscular fibres are arrange 1 in bundles in several layers, an Fig. 269. insilionnl epithelium from the bhdder. of the large cells lie upon the summit columnar and caudate cells, and depn are seen on their under surface. Lower part of the human bladder laid open, with the lower ends of the ureters. Note the clear part, the trigone, the slit-like openings of the ureters, the divided ureters, and vesiculae seminales : the sinus prostati- cus, and on each side of it the round openings of the ejaculatory ducts, and hi low both the numerous small apertures of the ducts of the pros- external hngitudinal layer, best developed on the anterior and posterior surfaces, and an inner circular \?iyer. [Hetween these two is an ohliqiie layer.] There are other bundles of muscular fibres arranged in different directions. Physiologically, the musculature of the bladder represents a single or common hollow muscle, whose function when it contracts is to diminish uniformly the size of the bladder, and thus to expel it^ contents [\ 306). The blood vessels resemble those of the ureter. The nerves form a plexus, and are placed partly in the mucous membrane and partly in the muscular coat, and, like all the extra renal parts of the urinary apparatus, are provided with ganglia, some of these lying in the mucosa, others in the submucosa, and connected to each other by fibres (Maier). Ganglia occur in the course of the motor nerve fibres in the bladder ( ]V. IVo/ff). Their functions are motor, sensory, excitomotor and vasomotor. [Sympathetic nerve ganglia also exist underneath the serous coat {/". Darzuin).'] A too minute dissection of the several layers and bundles of the musculature of the bladder has given rise to erroneous inferences. Thus, we speak of a special detrusor urinae, which, how- ever, consists chiefly of fibres running on the anterior and posterior surfaces, from the vertex to the fundus. There does not seem to be a special sphincter vesicae internus ; it is merely a thicker circular (6 to 12 mm.) layer of non-striped muscle which surrounds the beginning of the urethra, and which, from its shape, helps to form the funnel-like exit of the bladder. Numerous muscular bundles, connected partly with the longitudinal and partly with the circular fibres of the bladder exist, especially in the trigone, between the orifices of the ureters. 472 ACCUMULATION OF URINE MICTURITION. Sphincter Urethrae. — The projier sphincter urethrte is a Iransversely striped muscle subject to the will, and consists of completely circular fibres which extend downward as far as the middle of the urethra, and partly of longitudinal fibres, which extend only on the posterior surface toward the base of the bladder, where they become lost between the fibres of the circular layer {Henle). In the male urethra, the epithelium of the prostatic part is Ihe same as that in the bladder; in the membranous portion it is stratified, and in the cavernous part the simple cylindrical form. The mucous membrane, under the epithelium itself, is beset 'nXih papillcc, chiefly in the posterior part of the urethra, and contains the mucous glands of Littre. Non-Striped muscle occurs in the prostatic part arranged longitudinally, chiefly at the colUculus seminalis; in the membranous portion the direction of the fibres is chiefly circular, with a few lon- gitudinal fibres intercalated ; the cavernous part has a few circular fibres posteriorly, but anteriorly the muscular fibres are single and placed obliquely and longitudinally. Closure of the Bladder. — As to the means by which the male urethra is kept closed, it must be remembered that the so-called internal vesical sphincter of the anatomists, which consists of non-striped muscle, is in reality an integral part of the muscular coat of the bladder, and surrounds the orifice of the urethra as far down as the prostatic portion, just above the colliculus seminalis. It is, however, not the sphincter muscle. The proper sphincter urethrae (sph. vesica; externusj lies below the latter. It is a completely circular inuscle disposed around the urethra, close above the entrance of the urethra into the septum urogenitale at the apex of the prostate, where it exchanges fibres with the deep transverse muscle of the perinaium which lies under it. Some longitudinal fibres, which run along the upper margin of the prostate from the bladder, belong to this sphincter muscle. Single transverse bundles passing forward from the surface of the neck of the bladder, the transverse bands which lie within the prostate opposite the ape.\ of the colliculus seminalis, and a strong transverse bundle passing in front of the origin of the urethra, into the substance of the prostate — all belong to the sphincter muscle (He)ile'). In the male urethra, the blooii vi^sst'h form a rich capillary plexus under the epithelium, below which is a wide-meshed lyiiiphatit plexus. [Tonus of Sphincter Urethrae. — Open the abdomen of a rabbit, ligature one ureter, tie a cannula in the other, and j)our water into the bladder until it runs out through the urethra, which is usually under a pressure of 1 6 to 20 inches. If the spinal cord be divided between the fifth and seventh lumbar vertebrae, a column of six inches is suflicient to overcome the resistance of the sphincter, while section at the fourth lumbar vertebra has no efl'ect on the height of the pressure. In such an animal the bladder becomes distended, but in one with its cord divided between the fifth and seventh lumbar vertebrre, there is incontinence of urine (Fig. 270). In the former case because the excito-motor impulses are cut ofif from the centre (5 to 7 vert.), and in the latter because the tonus of the sphincter is destroyed (JCupressow). This tonus is denied by Landois and others.] 280. ACCUMULATION OF URINE— MICTURITION.— After emptying the bladder, the urine slowly collects again, the bladder being thereby gradually distended. [A healthy bladder may be said to be full when it contains 20 oz. (^/ai?ics).'\ As long as there is a moderate amount of urine in the bladder, the elasticity of the elastic fibres surrounding the urethra, and that of the sphincter of the urethra (and in the male of the prostate) suffice to retain the urine in the bladder. This is shown by the fact that the urine does not escape from the bladder after death. If the bladder be greatly distended (1.5 to 1.8 litre), so that its apex projects above the pubes, the sensory nerves in its walls are stimulated and cause a feeling of a full bladder, while at the same time the urethral opening is dilated, so that a few drops of urine pass into the beginning of the urethra. Besides the sub- jective feeling of a full bladder, this tension of the walls of the bladder causes a reflex effect, so that the urinary bladder contracts periodically upon its fluid con- tents, and so do the sphincter of the urethra and the muscular fibres of the urethra, and thus the urethra is closed against the passage of these drops of urine. As long as the pressure within the bladder is not very high, the reflex activity of the transversely striped sphincter overcomes the other (as during sleep) ; but, as the jiressure rises and the distention increases, the contraction of the walls of the EFFECT OF NERVES ON MICTURITION. 473 bladder overcomes the closure produced by the sphincter, and the bladder is emptied, as occurs normally in young children. As age advances, the sphincter urethra; comes under the control of the will, so that it can be contracted voluntarily, as occurs in man when he forcibly contracts the bulbo cavernosus muscle to retain urine in the bladder. The sphincter ani usually contracts at the same time. The reflex activity of the sphincter may also be inhibited voluntarily, so that it may be completely relaxed. This is the condi- tion when the bladder is emptied voluntarily. Slight movements, confined to the bladder, occur during psychical or emotional disturbances (e.g., anger, fear), [the bladder may be emptied involuntarily during a fright], after stimulation of sensory nerves {P. Bert, v. Basclt, A/t'ver), auditory impressions, restraining the respiration, and by arrest of the heart's action. There are slight periodic variations coincident with variations in the blood pressure. The contractions of the bladder cease after deep inspiration, and also during apnoea (Mosso and Pe/lacjni). The excised bladder of the frog, and even portions free from ganglia, exhibit rhythmical contractions, which are increased by heat [Pfah). Nerves. — The nerves concerned in the retention and evacuation of the urine are : i. The motor nerves of the sphincter urethra;, which lie in the pudendal nerve (anterior roots of the third and fourth sacral nerves). When these nerves are divided, as soon as the bladder becomes so distended as to dilate the urethral opening, the urine begins to trickle away (incontinence of urine). 2. The sen- sory nerves of the urethra, which excite these reflexes, leave the spinal cord by the posterior roots of the third, fourth, and fifth sacral nerves. Section of these nerves also causes incontinence of urine. The centre in dogs lies opposite the fifth, and in rabbits, opposite the seventh, lumbar vertebra {BiiJge). 3. Fibres pass from the cerebrum — those that convey voluntary impulses through the peduncles, and the anterior columns of the spinal cord (according to Mosso and Pellacani, through the posterior columns and the posterior part of the lateral col- umns), to the motor fibres of the sphincter urethra. 4. The inhibitory fibres concerned in the reflex inhibition of the sphincter urethra, take the same course (perhaps from the optic thalamus?) downward through the cord to where the third, fourth, and fifth sacral nerves leave it. 5. Sensory nerves proceed from the urethra and bladder to the brain, but their course is not known. Some of the motor and sensory fibres lie for a part of their course in the sympathetic. Transverse section of the spinal cord above where the nerves leave it, is always followed in the first instance by retention of urine, so that the bladder becomes distended. This occurs because — (i) the section of the spinal cord increases the reflex activity of the urethral sphincter; and (2) because the inhi- bition of this refiex can no longer take place. As soon, however, as the bladder becomes so distended as in a purely mechanical manner to cause dilatation of the urethral orifice, then the urine trickles away, but the amount of urine which trickles out in drops is small. Thus the bladder becomes more and more dis- tended, as the continuously distended walls of the organ yield to the increased tension, so that the bladder may become distended to an enormous extent. The urine very frequently becomes ammoniacal, and there results catarrh and inflam- mation of the bladder (§ 263). Voluntary Micturition. — Observers are not agreed as to the mechanism concerned in emptying the bladder when it is only partially full. It is stated by some that a voluntary impulse passes from the brain along a cerebral peduncle, the anterior columns of the cord and the anterior roots of the third and fourth sacral nerves, and partly through motor fibres from the second to the fifth lumbar nerves (specially the third), to act directly upon the smooth muscular fibres of the bladder. This is assumed, because electrical stimulation of any part of this nervous channel causes contraction of the bladder. This view, however, does not seem to be the true one. It is to be remembered that Budge showed that the sensory nerves of the wall of the bladder are contained in the first, second, third, and 474 VOLUNTARY MICTURITION. fourth sacral nerves, and also in part in the course of the hypogastric plexus, whence they ultimately pass by the rami communicantes into the spinal cord. According to Landois, the smooth musculature of the bladder cannot be excited directly by a voluntary imp\ilse, but is always caused to contract reflexly. If we wish to micturate when the urinary bladder contains a small quantity of urine, we first excite the sensory nerves of the opening of the urethra, either by causing slight contractions of the sphincter urethrte, or by means of slight abdominal pressure, and thus force a little urine into the urethral orifice. This sensory stimulation causes a reflex contraction of the walls of the urinary bladder. At the same time, this condition is maintained voluntarily, by the action of the intracranial reflex inhibitory centre of the sphincter urethrae. The centre for the reflex stimulation of the movements of the walls of the urinary bladder is placed somewhat higher in the spinal cord than that for the sphincter urethrre. In dogs, it is opposite the fourth lumbar vertebra {Gianuzzi, Budge). Po\\er gives the following account of ihe probable mechanism involved : — " In the first place, looking at the ordinary sensations that are experienced as the bladder fills, we Nervous mechanism of the bladder {PoTver^. a, afferent nerve ot the sphincters ; S and M, sensory and motor centres ; X, sensory fibres to brain ; Z, motor fibres from brain ; Y, inhibitory fibres. may conclude that sensory impressions, rising gradually in intensity, are conveyed (through P) to the sensory ganglia (S), from whence they are reflected (through b) to the motor centre (M), and from thence to the sphincter, causing this to contract more firmly (Fig. 270). " If the bladder becomes greatly distended, the impression is no longer wholly reflected, but passes onward and upward to the brain (through S and along X), and excites conscious uneasiness or pain. If it be desired to retain the water, an impulse is transmitted by motor fibres (through Z) to the motor ganglion, M, and the excito-motor influence (of S) on the sphincter is intensified by the will. " But suppose that, instead of holding the water, it be desired to discharge it ; what happens ? The phenomena that are then presented seem to necessitate the admission of an inhibitory, restraining, or regulating centre, which must be in close proximity with the excito-motor centre, and, therefore, at the lower part of the .spinal cord, for the action of the will in this matter is not, like its own voluntary muscles, rapid and instantaneous, but is exerted only after the lapse of a distinct interval, and the result is a relaxation of the sphincter. " We may conceive this impulse to pass down special fibres, Y, to an inhibitory centre, I, which may either act directly (through L) on the motor centre, M, or possibly may send branches directly to the sphincter muscles." Painful stimulation of sensory nerves causes reflex contraction of the bladder and evacuation of RETENTION AND INCONTINENCE OF URINE. 475 the urine fin children during teething). Reflex contraction of the bladder can be brought about in cats by stimulation of the inferior mesenteric ganglion. After section of all the nerves going to the bladder, hemorrhage and asphyxia cause contraction by a direct effect upon the structures in the wall of the bladder. As yet no one has succeeded in e.xciting artificially the inhibitory centre in the brain for the sphincter muscle (So/;oiLnn and Kowalesky). It seems probable that, as in the case of the anal sphincter {\ l6o), there is not a continuous tonic reflex stimulation of the sphincter urethroe; the reflex is excited each time by the contents. The sphincier vesic.-e of the anatomists, which consists of smooth muscular tissue, does not seem to take part in closing the bladder. Budge and Landois found that, after removal of the transversely-striped sphincter urethr.e, stimulation of the smooth sphincter did not cause occlusion of the bladder, nor could L. Rosenthal or v. \Vitticli convince themselves of the presence of tonus in this muscle. Indeed, its very exi^tence is questioned by Henle. Changes of the Urine in the Bladder. — -When the urine is retained in the bladder for a con- siderable time, according to Kaupp, there is an increase in the sodium chloride and a decrease in the urea and water. Urine which remains for a long time in the bladder is prone to undergo ammoniacal decomposition. Absorption. — The mucous membrane of the bladder is capable of absorbing substances — potas- sium iodide and other soluble salts — very slowly. As the ureters enter near the base of the bladder, the last secreted urine is always lowest. If a person remain perfectly quiet, strata of urine are thus formed, and the urine may be voided so as to prove this (Edlc/sen). The pressure within the bladder, when in the supine position = 13 to 15 centimetres of water. Increase of the intra-abdominal pressure (by inspiration, forced expiration, coughing, bearing down) increases the pressure within the bladder. The erect posture also increases it, owing to the pressure of the viscera from above (.StV/rt/s, /^Kiim). [James obtained 4 to 4.5 inch Hg as the highest expulsive power of the bladder, including the abdominal pressure, voluntary and involuntary. In paraplegia, where there is merely the expulsive power of the bladder, he found 20 to 30 inches of water.] [Hydronephrosis occurs when the ureters and pelvis of the kidney become dilated, owing to partial and gradual obstruction of the outflow of urine from the ureters; if the obstruction become complete, there is cessation of the urinary secretion. James has shown that the bbidder remains contracted for several seconds after it is emptied, and this is specially the case in irritable bladder; so that this condition m.iy also give rise to hydronephrosis, by damming up the urine in the ureters.] During micturition, the amount of urine voided at first is small, but it increases with the time, and toward the end of the act it again diminishes. In men, the last drops of urine are ejected from the urethra by voluntary contractions of the buibo-cavernosus muscle. Adult dogs increase the stream rhythmically by the action of this muscle. 281. RETENTION AND INCONTINENCE OF URINE.— Retention of urine, or ischuria, occurs: i. When there is obstruction of the urethra, from foreign bodies, concretions, stricture, swelling of the prostate. 2. Paralysis or exhaustion of the musculature of the bladder; the litter sometimes occurs after delivery, in consequence of the pressure of the child against the bladder. 3. After section of the spinal cord (p. 473). 4. Where the voluntary impulses are unable to act upon the inhibitory apparatus of the sphincter urethrse reflex, as well as when the sphincter urethras reflex is increased. Incontinence of urine (stillicidium urinae) occurs in consequence of — i. Paralysis of the sphincter urethr.!;. 2. Loss of sensibility of the urethra, which, of course, abolishes the reflex of the sphincter. 3. Trickling of the urine is a secondary consequence of section of the spinal cord, or of its degeneration. Strangury is an excessive reflex contraction of the walls of the bladder and sphincter, due to stimulation of the bladder and urethra; it is observed in inflammation, neuralgia [and after the use of some poisons, e. i;., cantharides]. • Enuresis nocturna, or involuntary emptying of the bladder at night, may be due to an increased reflex excitability of the wall of the bladder, or weakness of the sphincter. 282. COMPARATIVE AND HISTORICAL.— Among vertebrates, the urinary and genital organs are frequently combined, except in the osseous fishes. The Wolffian bodies, which act as organs of excretion during the embryonic period, remain throughout life in fishes and amphi- bians, and continue to act as such (Gcgenl'aur). Fishes. — The myxineids (cyclostomatal have the simplest kidneys; on each side is a long ureter, with a series of short-stalked glomeruli, with capsules arranged along it Both ureters open at the genital pore. In the other fishes, the kidneys lie often as elongated, compact masses along both sides of the vertebral column. The two ureters unite to form a urethra, which always opens behind the anus, either united with the opening of the genital organs or behind this. In the sturgeon and hag fish, the anus and orifice of the urethra together form a cloaca. Bladder-like formations, which, however, are morphologically homologous with the urinary bladder of mammals, occur in fishes, either on each ureter (ray, hag fish), or where both join. In amphibians, the vasa efferentia of the testicles are united with the urinary tubules ; 476 COMPARATIVE AXD HISTORICAL. the duct in the frog unites with the one on the other side, and both conjoined open into the cloaca, while the capacious urinary bladder opens through the anterior wall of the cloaca. From reptiles upward, the kidney is no longer a persistent Wolffian body, but a new organ. In reptiles, it is usually tlattened and elongated; the ureters open singly into the cloaca, ^aurians and tortoises have a urinary bladder. In birds, the isolated ureters open into the urogenital sinus, which opens into the cloaca, internal to the excretory ducts of the genital apparatus. The urinary bladder is always absent. In mammals, the kidneys often consist of many lobules, e. g., dolphin, ox. Among invertebrates, the mollusca have excretory organs in the form of canals, which are provided with an outer and an inner opening. In the mussel, this canal is provided with a spongy- like organ, often with a central cavity, and consisting of ciliated secretory cells, placed at the base of the gills (organ of Bojanus). In gasteropods, with analogous organs, uric acid has been found. Insects, spiders and centipedes have the so-called .Malpighian vessels, which are partly excretory organs for uric acid and partly for bile. These vessels are long tubes, which open into the first part of the large intestine. In crabs, blind tubes, connected with the intestinal tube, perhaps have the same functions. The vermes also have renal organs. Historical. — Aristotle directed attention to the relatively large size of the human bladder; he named the ureters. Massa (1552) found lymphatics in the kidney. Eustachius (f 15S01 ligatured the ureters, and found the bladder empty. Cusanus ( 1565) investigated the color and weight of the urine. Rousset (15S1) described the muscular nature of the walls of the bladder. Vesling de- scribed the trigone (1753). The first important chemical investigations on the urine date from the time of van Helmont (1644). He isolated the solids of the urine, and found among them common salt ; he ascertained the higher specific gravity of fever urine, and ascribed the origin of urinary calculi to the solids of the urine. Scheele (1766) discovered uric acid and calcium phosphate. Arand and Kunckel, phosphorus; Rouelle (1773), urea; and it got its name from Fourcroy and Vauquelin (1799). Berzelius found lactic acid; Seguin, albumin in pathological urine; Liebig, hippuric acid; Heintz and v. Pettenkofer, kreatin and kreatinin ; WoUaston (1810), cystin. Marcet found xanthin ; and Lindbergson, magnesia carbonate. FUNCTIONS OF THE Skin. Fig 283. STRUCTURE OF THE SKIN.— Theskin (3.3 to 2.7 mm. thick; specific gravity, 1057) consists of — [i. The epidermis ; 2. The chorium, or cutis vera, with the papillae (Fig. 272).] The epidermis (o.oS to 0.12 mm. thick) consists of many layers of stratified epithelial cells united to each other by cement substance. The superficial layers — stratum corneum (Figs. 272, />, and 271, c) — consist of several layers of dry, horny, non-nucle- ated squames, which swell up in solution of caustic soda (Fig. 272, E). [It is always thickest where intermittent pressure is applied, as on the sole of the foot and palm of the hand.] The next layer is the stratum lucidum {Oelii) — it is clear and transparent in a section of skm, hence the name. It consists of compact layers of clear cells with ves- tiges of nuclei (Fig. 271, I]- Under this is the rete muco- sum or rete Malpighii (Fig. 272, d), consisting of many layers of nucleated protoplasmic epithelial cells. These cells contain pigment in the dark races, and in the skin of the scrotum, and around the anus. [The superficial cells are more fusiform and contain granules which stain deeply wuh carmine. They constitute, 3, the stratum granulosum (Fig. 271,^). In these cells the formation of keratin is about to begin, and the granules have been called eleidin granules by Ranvier. They are chemically on the way to be transformed into keratin (Fig. 271). All corneous structures contain similar granules in the area where the cells are be- coming corneous. I'hen follow several layers of more or less polyhedral cells, softer and more pLi,stic in their nature, and exhibiting the characters of so called "prickle cells" (Figs. 271, m, and 272, R). The deepest layers of cells are more or less columnar and the cells are placed vertically upon the papillce (Fig. 273,^). Granular leucocytes or wandering cells are sometimes found between these cells (Biesiadecki). This layer, 4, has been called the stratum Malpighii (Fig. 271, /«). The rete Malpighii dips down between adjacent papillre and forms interpapillary processes. According to Klein, a delicate basement membrane sepa- rates the epidermis from the true skin.] The superficial layers of tlie epidermis are continually being thrown oft', while new cells are continually being formed in the deeper layers of the skin by proliferation of the cells of the rete Malpighii. There is a gradual change in the microscopic and chemical characters of the cells as we pass from the deepest to the most superficial layer of the epidermis. (1) Stratum corneum, (2) Stratum lucidum, (3) Stratum granulosum, \ „ . m t i,\ o, ,/„.„ !/■ /*■ L- > Rete Mucosum. (4) ^ytt atum MalpigkiJ, j -^ [In a vertical section of the skin stained writh picrocarmine, the S. granulosum is deeply stained red, and is thus readily distinguished among the other layers of the epidermis.] No pigment is formed within the epidermis itself; when it is present, it is carried by leucocytes from the subcutaneous tissue {Riehl, Ehrmann, Aeby). The chorium (Fig. 272, I, C) is beset throughout its entire surface by numerous (0.5 to o.l mm. high) papillae (Fig. 273, b), the largest being U])on the volar surface of the hand and foot, on the -'^:r- c, Stratum corneutr granulosum : /« nerve fibrils. 1 S. lucidum: Malpighii; [Epidermis (Fig. 271 478 STRUCTURE OF THE SKIN. nipple and glans penis. Most of the papilUi.' contain a looped capillary (j^), while in limited area some of them contain a touch corpuscle (Fig. 273,1'). The p.ipillEe are disposed in groups, whose arrangement varies in ditlerent parts of the body. In the palm of the hand and sole of the foot they occur in rows, which are marked out by the existence of delicate furrows on the surface visible to the naked eye. The chormm consists of a dense network of bundles of white fibrous tissue mixed with a network of elastic fibres, which are more delicate in the papillae. The con- nective tissue contains many connective tissue corpuscles and numerous leucocytes. The deeper Fig. 272. If H I. Vertical section of the skin, with a hair and sebaceous gland, T. Epidermis and chorium shortened— i, outer; 2, inner fibrous layer of tlie hair follicle ; 3, hyaline layer of the hair follicle ; 4, outer root sheath ; 5, Hu,\ley's layer of the inner root sheath : 6, Henle's layer of the same ; /, root of the hair, with its papilla : A, arrector pili muscle ; C, chorium ; a, subcutaneous fatty tissue ; 6, epidermis (horny layer) : ci, rete Malpighii ; g, blood vessels of papillae ; z', lymphatics of the same ; h. horny or corneous substance ; /, medulla or pith ; k, epider- mis or cuticle of hair ; K, coil of sweat gland ; E, epidermal scales (seen from above and en /ace) from the stratum corneum : R, prickle cells from the rete Malpighii; «, superticial, and w, deep cells from the nail; H, hair magnified; r?, cuticle ; c. medulla, with cells ;/,/, fusiform fibrous cells of the substance of the hair ; X, cells of Huxley's layer ; I, those of Henle's layer ; S, transverse section of a sweat gland from the axilla ; a, smooth muscular fibres surrounding it; /, cells from a sebaceous gland, some of them containing granules of oil. connective-tissue layers of the chorium gradually pass into the subcutaneous tissue, where they form a trabecular arrangement of bundles, leaving between them elongated rhomboidal spaces filled for the most part with groups of fat cells (Fig. 272, (?, r?). [In microscopic sections, after the action of alcohol, the fat cells not unfrequently contain crystals of margarin (Fig, 275).] The long axis of the rhomb corresponds to the greater tension of the skin at that part (C Latiger). In some situations the subcutaneous tissue is devoid of fat [penis, eyelids]. In many situations, the NAILS AND HAIR. 479 skin is fixed by solid fibrous bands to subjacent structures, as fasciae, ligaments or bones (tenacula cutis), in other parts, as over bony prominences, burs;e, filled with synovial fluid, occur. Smooth muscular fibres occur in the chorium in certain situations on extensor surfaces (Xeu- mann) ; nipple, areola mamma;, prepuce, perineum, and in special abundance in the tunica dartos of the scrotum. Fig. 273. F^rA^' /i2 Vertical section of the cutis vera and part of the epidermis, g; cells of the rete Vlalpighii : a, c, blood vessels ; J^ nerve fibre entering a Wagner's touch corpuscle, e ; y, section of i apiUary ; 6, papilla : Fig. 275. Fig. 274. PapillfC of the skin, ctjijirims removed, blood vessi jected : some contain a Wagner's touch corpuscle others a capillary loop. ning crystals of margari 284. NAILS AND HAIR. — The nails (specific gravity 1. 19) consist of numerous layers of solid, horny, homogeneous, epidermal or nail cells, which may be isolated with a solution of caustic alkalies, when ihey swell up and exhibit the remains of an elongated nucleus (Fig. 272, «, m). The whole under surface of the nail rests upon the nail bed ; the lateral and posterior edges lie in a deep groove, the nail groove (Fig. 276, e). The chorium under the nail is covered throughout its entire extent by longitudinal rows of papillae (Fig. 276, a"). Above this there lies, as in the 480 DEVELOPMENT OF THE NAILS AND HAIR. skin, many layers of prickle cells like those in the rete Malpighii (Fig. 272, c), and above this again is the substance of the nail (Fig. 276, a). [The stratum granulosum is rudimentary in the nail bed. The substance of the nail represents the stratum lucidum, there being no stratum corneum (A7«'«).] The posterior part of the nail groove and the half moon, brighter part or lunule, form the root of the nail. They are, at the same time, the matrix, from which growth of the nail takes place. The lunule is present in an isolated nail, and is due to diminished transparency of the posterior part of the nail, owing to the special thickness and uniform distribution of the cells of the rete Malpighii ( Toldt). Growth of the NaiL — According to Unna, the matrix extends to the front part of the lunule. The nail grows continually from behind forward, and is formed by layers secreted or formed by the matrix. These'layers run parallel to the surface of the matrix. They run obliquely from above and behind, downward and forward, through the thickness of the substance of the nail. The nail is of the same thickness from the anterior margin of the lunule forward to its free margin. Thus the nail does not grow in thickness in this region. In the course of a year the fingers produce about 2 grms. of nail substance, and relatively more in summer than in winter [A/nlesc/iott, Benecke). Development. — Unna makes the following .statements regarding the development of the nails ; I. From the second to the eighth month of fcetal life the position of the nail is indicated by a partial but marked horny condition of the epidermis on the back of the first phalanx, the " epony- chium." The remainder of this substance is represented during life by the normally-formed epidermal layer, which separates the future nail from the surface of the furrow. 2. The future nail is fonned under the eponychium, with its first nail cells still in front of the nail groove ; then the nail grows and pushes forward toward the groove. At the seventh month, the nail (itself covered by the Fig. 276. b ,. d : section of one-half of a nail. Malpighii of the nail bed ; d, transv the nail ; g^ papillae of the skin on the back of the finger. t, nail substance ; ely divided papil open layer of cells of the nail bed; c, stratum ail groove : y, homy layer of /projecting over eponychium) covers the whole extent of the nail bed. 3. When, at a later period, the eponychium splits oft", the nail is uncovered. After birth the papillae are formed on the bed of the nail, while simultaneously the matrix passes backward to the most posterior part of the groove. Absence of Hairs. — The whole of the skin, with the exception of the palmar surface of the hand, sole of the foot, dorsal surface of the third phalanx of the fingers and toes, outer surface of the eyelids, glans penis, inner surface of the prepuce, and part of the labia, is covered with hairs, which may be strong or fine (lanugo). A Hair (specific gravity 1,26) is fixed by its lower extremity (root) in a depression of the skin or a hair follicle (Fig. 272, \, p) which passes obliquely through the thickness of the skin, some- thnes as far as the subcutaneous tissue. The structure of a hair follicle is the following: I. The outer fibrous layer (Figs. 272, i, 278), composed of interwoven bundles of connective tissue, arranged for the most part longitudinally, and provided with numerous blood vessels and nerves. [It is just the connective tissue of the surrounding chorium.] 2. The inner fibrous layer (Figs. 272, 2, 277) consists of a layer of fusiform cells (? smooth muscular fibres) arranged circularly. [It does not extend throughout the whole length of the follicle] 3. Inside this layer is a trans- parent, hyaline, glass-like basement membrane (Figs. 272, 3, 277), which ends at the neck of the hair follicle; while above it is continued as the basement membrane which exists between the epidermis and chorium. In addition to these coverings, a hair follicle has epithelial coverings which must be regarded in relation to the layers of the epidermis. Immediately within the glass- like membrane is the outer root sheath (Figs. 272, 4, 277, 278), which consists of so many layers of epithelial cells that it forms a conspicuous covering. It is, in fact, a direct continuation of the DEVELOPMENT OF THE NAILS AND HAIR. 481 Stratum Malpighii, and consists of many layers of soft cells, the cells of the outer layer being cylin- drical. Toward the base of the hair follicle it becomes narrower, and is united to, and continuous witli, the cells of the root of the hair itself, at least in fully-developed hairs. The horny layer of the epidermis continues to retain its properties as far down as the orifice of the sebaceous follicle, below this point, however, it is continued as the inner root sheath. This consists of (I ) a single layer of elongated. Hat, homogeneous, non-nucleated cells (Figs. 272, 6, 277, y- — Henle's layer) placed next and within the outer root sheath. Within this lies (2) Huxley's layer (Figs. 272, 5, ^77'g)< consisting of nucleated, elongated, polygonal cells (Fig. 272, x, and 3), while the citticle of the hair follicle is composed of cells analogous to those of the surface of the hair itself. Toward the bulb of the hair these three layers become fused together. Fig. 278. Fig. 277. lion of a hair below the neck of a hair follicle, rt, outer fibrous coat with b, blood vessels ; c, inner circularly disposed layer ; d^ glass-like layer ; e, ovXzT,f^g, inner root sheath ;/, outer layer of the same (Henle's sheath); ^, inner layer of the same (Huxley's sheath) ; h, cuticle ; /, hair. ction of a hair follicle wViile a hair is being shed, a, outer and middle sheaths of hair follicle ; b, hyaline membrane ; c, papilla, with a capillary; d, outer, e, inner root sheath; /, cuticle of the latter ; g, cuticle of the hair ; h, young non-medullated hair; /, tip of new hair ; /, hair knob of the shed hair, with k^ the remainder of the cast-otf outer root sheath. [Coverings of a hair follicle arranged from without inward: — 1. Fibrous layers, \ f^' Longitudinally arranged fibrous tissue. ' \.\p) Circularly arranged spintUe cells. 2. Glass-like (hyaline) membrane. !{a) Outer root sheath. , ,, , , , (b\ Inner root sheath. { [|^^!^ ^ '^y^'- (<-) Cuticle of the hair, '■ 4. The hair itsell. 31 axley's layer. 482 THE GLANDS OF THE SKIN. The arrector pili muscle (Fig. 272, A) is a faiilike arrangement of a layer of smooth muscular 6bres, which is attached below to the side of a hair follicle and extends toward the surface of the chorimii; as it stretches obliquely upward, it subtends the obtuse angle formed by the hair follicle and the surface of the skin, [or, in other words, it forms an acute angle with the hair follicle, and between it and the follicle lies the sebaceous gland]. When these muscles contract, they raise and erect the hair follicles, producing the condition of cutis anserina or goosf siin. As the sebaceous gland lies in the angle between the muscle and the hair follicle, contraction of the muscle compresses the gland and favors evacuation of the sebaceous secretion. It also compresses the blood vessels of the papilla (i'nna). The hair with its enlarged bulbous extremity — hair bulb — sits upon, or rather it embraces, the papilla. It consists of— (l) the marrow or medulla (Fig. 272, i) which is absent in woolly hair and in the hairs formed during the first years of life. It consists of two or three rows of cubical cells (H, c). (2) Outside this lies the thicker cortex (.4|, which consists of elongated, rigid, horny, fibrous cells (H,/,/!, while in and between these cells lie the pigment granules of the hair. (3) The surface of the hair is covered with a cuticle {k), consisting of imbricated layers of non- nucleated squames. Gray Hair. — When the hair becomes gray, as in old age, this is due to a defective formation of pigment in the cortical part. The silvery appearance of white hair is increased when small air cavities are developed, especially in the medulla and to a less extent in the cortex, where they re- flect the light. Landois records a case of the hair becoming stidiienly gray in a man whose hair became gray during a single night, in the course of an attack of delirium tremens. Numerous air spaces were found throughout the entire marrow of the (blond) hairs, while the hair pigment still remained. Development of Hair. — According to KoUiker, from the 12th to 13th week of intra-uterine hfe, solid finger-like processes of the epidermis are pushed down into the chorium. The process becomes flasked shaped, while the central cells of the cylinder become elongated and form a conical body, arising as it were from the depth of the recess. It soon dilTerentiates into an inner darker part, which becomes the hair, and a thinner, clearer, layer covering the former, the inner root sheath. The outer cells, /. e , those lying next the wall of the sac, form the outer root sheath. Outside this, again, the fibrous tissue of the chorium forms a rudimentary hair follicle, while one of the papilla: grows up against it, indents it, and becomes embraced by the bulb of the hair. This is the hair papilla, which contains a loop of blood vessels. The cells of the bulb of the hair prolif- erate rapidly, and thus the hair grows in length. The point of the hair is thereby gradually pushed upward, pierces the inner root sheath, and passes obliquely through the epidermis. The hairs ap- pear upon the forehead at the igth week; at the 23d to 25th week the lanugo hairs appear free, and they have a characteristic arrangement on different parts of the body. Physical Properties. — Hair has very considerable elasticity (stretching to 0,33 of its length), considerable cohesion (carrying 3 to 5 lbs.), resists putrefaction for a long time, and is highly hygro- scopic. The last property is also possessed by epidermal scales, as is proved by the pains that occur in old wounds and scars during damp weather. Growth of a hair occurs by proliferation of the cells on the surface of the hair papilla, these cells representing the matrix of the hair. Layer after layer is formed, and gradually the hair is raised higher within its follicle. Change of the Hair. — The results are by no means uniform. According to one view, when the hair has reached its full length, the process of formation on the surface of the hair papilla is in- terrupted ; the root of the hair is raised from the papilla, becomes horny, remains almost devoid of pigment, and is gradually more and more lifted upward from the surface of the papilla, while its lower bulbous end becomes split up like a brush. The lower empty part of the hair follicle becomes smaller, while on the old papilla a new formation of a hair begins, the old hair at the same time falling out {KoUiker, C. Lunger). According to Stieda, the old papilla disappears, while a new one is formed in the hair follicle, and from it the new hair is developed. According to Gotte, in addition to the hair which grows on the papilla, other hairs developed from the outer root sheath are formed in the same hair follicle. Unna agan describes the growth and change of the hair differently. He believes that each hair grows for a time from the surface of the papilla. It then frees itself, and with its brush-like lower end or bulb is transplanted anew on the outer root sheath, about the middle of the hair follicle. The free papilla can thus produce a new hair, which may even grow alongside the former, until the former falls out. New recesses with new papilla: are formed latterly in the hair follicle, and from them new hairs arise. 285. THE GLANDS OF THE SKIN.— The sebaceous glands (Fig. 272, I. T) are simple acinous glands, which open by a duct into the hair follicles of large hairs near their upper ' pait; in the case of small hairs, they may project from the duct of the gland (Fig. 279). In some situations, the ducts of the glands open free upon the surface, e. g., the glands of labia minora, glans, prepuce (Tyson's glands), and the red margins of the lips. The largest glands occur in the nose and in the labia ; they are absent only from the vola manus and planta pedis. The oblong alveoli of the gland consist of a basement membrane lined with small polyhedral nucleated granular secretory cells (Fig. 272,/). Within this are other polyhedral cells, whose substance contains numer- SKIN AS A PROTECTIVE COVERING. 483 ous oil globules ; the cells become more fatty as we pro- Fig, 279. ceed toward the centre of the alveolus. The cells lining the duct are continuous with those of the outer root sheath. The detritus formed Iiythe fatty metamorphosis of the cells constitutes the sebum or sebaceous secretion. The sweat glands (Fig. 272, I, i), sometimes called sudoriparous glands, consist of a long blind tube, whose lower end is .irranged in the form of a coil placed in the areolar tissue under the skin, while the somewhat smaller upper end or excretory portion winds in a vertical, slightly wave-like manner, through the chorium, and in a cork- screw or spiral manner through the epidermis, where it opens with a free, somewhat trumpet shaped mouth. The glands are both very numerous and large in the palm of the hand, sole of the foot, a.xilla, forehead, and around the nipple; few on the back of the trunk, and are absent on the glans, prepuce, and margin of the lips. The circum- anal glands and the ceruminous glands of the external auditory meatus, and Moll's glands, which open into the hair follicles of the eyelashes, are modifications of the sweat glands. Each gland tube consists of a basement membrane lined by cells; the excretory part or sweat canal of the tube is lined by sfveral layers of cubical cells, whose surface is covered by a delicate cuticular layer, a small central lumen being left. Within the coil the structure is different. The first part of the coil resembles the above, but as the coil is the true secretory part of the gland, its structure differs from the sweat canal. This, the so called dislal portion of the tube, is lined by a single layer of moderately tall, clear nucleated cylindrical epithelium (Fig. 272, S), often con- taining oil globules (Ranvier). Smooth muscular fibres (fColliter) are arranged longitudinally along the tube in Sebaceous gland, with a lanugo hair. ii,granu- the large glands (Fig. 272, S, a). There is a distinct o^s^^ljlir'a"; '*fa[r-%d?s''L^n'd'free''fa"' lumen present in the tube. As the duct passes through rf"^adni: "' hair' follicle^ with a^^snuili the epidermis, it winds its way between the epidermal cells hair,/, without any independent membrane lining it {Heynold). A network of capillaries surrounds the coil. Before the arteries split up into capillaries, they form a true rete mirabile around the coil (Briicke). This is comparable to the glomerulus of the kidney, which may also be regarded as a rete mirabile. Numerous nerves pass to form a plexus, and terminate in the glands ( Tomsa). The total number of sweat glands is estimated by Krause at 2 •< millions, which gives a secretory surface of nearly loSo square metres. These glands secrete sweat. Nevertheless, an oily or fatty substance is often mixed with the sweat. In some animals (glands in the sole of the foot of the dog, and in birds) this oily secretion is very marked. Lymphatics. — Numerous lymphatics occur in the cutis; some arise by a blind end, and others from loops within the papilla, on a plane lower than the vascular capillary. [These open into more or less horizontal networks of tubular lymphatics in the cutis, and these again into the wide lym- phatics of the subcutaneous tissue, which are well provided with valves.] Special lymphatic spaces are disposed in relation with the hair follicles and their glands (Xeumann), [and also with the fat (A'lein). The lymphatics of the skin are readily mjected with Berlin blue by the puncture method.] The blood vessels of the skin are arranged in several systems. There is a superficial system, from which proceed the capillaries for the papilUe. There is a deeper system of vessels which supplies special blood vessels to (a) the fatty tissue; (6) the hair follicles, each of which has a special vascular arrangement of its own, and in connection with this each sebaceous gland receives a special artery ; (e) an artery goes also to each coil of a sweat gland, where it forms a dense plexus of capillaries ( Tomsa). 286. THE SKIN AS A PROTECTIVE COVERING.— The sub- cutaneous fatty tissue fills up the depression between adjoining parts of the body and covers projecting parts, so that a more rounded ajipearance of the body . is thereby obtained. It also acts as a soft, elastic pad and protects delicate parts from external pressure (sole of the foot, palm of the hand), and it often surrounds and protects blood vessels, nerves, etc. It is a bad conductor of heat, and thus acts as one of the factors regulating the radiation of heat (§ 214, II, 4), and, there- fore, the temperature of the body. The epidermis and cutis vera also act in the 484 CUTANEOUS respiration: sebum SWEAT. same manner (§ 212). Klug found that the heat conduction is less through the skin and subcutaneous fatty tissue than through the skin alone ; the epidermis conducts heat less easily than the fat and the chorium. The solid, elastic, easily movable cutis affords a good protection against external, mechanical injuries; while the dry, impermeable, horny epidermis, devoid of nerves and blood vessels, affords a further protection against the absorption of poisons, and at the same time it is capable of resisting, to a certain degree, thermal and even chemical actions. A thin layer of fatty matter protects the free surface of the epidermis from the macerating action of fluids, and from the disintegrating action of the air. The epidermis is important in connection with \\\^ fluids of the body. It exerts a certain pressure upon the cutaneous capillaries, and, to a limited extent, prevents too great diffusion of fluid from the cutaneous vessels. Parts of the skin robbed of their epidermis are red and are always moist. When dry, the epidermis and the epidermal appendages are bad conductors of electricity (§ 326). Lastly, we may say that the existence of uninjured epidermis prevents adjoining parts from growing together. As the epidermis is but slightly extensile, it is stretched over the folds and papilL-e of the cutis vera, which becomes level when the skin is stretched, and the papilUi; may even disappear with strong tension {Leiujtiski). 287. CUTANEOUS RESPIRATION: SEBUM— SWEAT.— The skin, with a surface of more than I'j square metres, ha^ the following secretory functions : — 1. The respiratory excretion ; 2. The secretion of sebaceous matter ; and 3. The secretion of sweat. [Besides this the skin is protective, contains sense organs, is largely con- cerned in regulating the temperature, and may be concerned in absorption.] I. Respiration by the skin has been referred to already (§ 131)- The organs therein con- cerned are the tubes of the sweat glands, moistened as they are with fluids, and surrounded by a rich network of capillaries. It is uncertain whether or not the skin gives olT a small amount of N or ammonia. Rohrig made experiments upon an arm placed in an air-tight metal box. .According to him, the amount of CO, and HjO excreted is subject to certain daily variations ; it is increased l)v digestion, increased temperature of the .surroundings, the application of cutaneous stimuli, and by impeding the pulmonary respiration. The exchange of gases also depends upon the vascularity of certain parts of the skin, while the cutaneous absorption of O also depends upon the number of colored corpuscles in the blood. In frogs and other amphibians, with a thin, always moist epidermis, the cutaneous respiration is more considerable than in warm-blooded animals In winter frogs, the skin alone yields i^ of the total amount of CO, excreted ; in summer frogs, ='3 of the same (Bidder) ; thus, in these animals it is a more important respiratory organ than the lungs themselves. Suppression of the cutaneous activity, e.g., by varnishing or dipping the skin in oil, causes death by asphyxia sooner than ligature of the lungs. Varnishing the Skin. — When the skin of a warm. blooded animal is covered with an impermeable varnish [such as gek^tin] [Fourcault, Becquerel, Brechet), death occurs after a time, probably owing to the loss of too much heat. The formation of crystalline ammonio-magnesic phosphate in the cutaneous tissues of such animals [Edenlmizeti), is not suflicient to account for death, nor are congestion of internal organs and serous effusions satisfactory explanations. The retention of the volatile substances (acids) present in the sweat is not sutlicient. Strong animals live longer than feeble ones; horses die after several days ( Gcrlacli) ; they shiver and lose flesh. The larger the cutaneous surface left unvarnished, the later does death take place. Rabbits die when ^s of 'heir surface is varnished. When the entire surface of the animal is v.arnished, the temperature rapidly falls (to 19°) ; the pulse and respirations vary; usually they fall when the varnishing process is limited; increased frequency of respiration has been observed ( j 225). Pigs, dogs, horses, when one-half of the body is varnished, exhibit only a tem- porary fall of the temperature, and show signs of weakness, but do not die (Elleiiherger and Hof- meisler). [In extensive burns of the skin, not only is there disintegration of the colored blood corpuscles [v. Lesser), but in some cases ulcers occur in the duodenum. The cause of the ulcera- tion, however, has not been ascertained satisfactorily (Curling).'] 2. Sebaceous Secretion. — The fatty matter as it is excreted from the acini of the sebaceous glands is fluid, but even within the excretory duct of the gland CHEMICAL COxMPOSITION. 485 it stagnates and forms a white, fat-like mass, which may sometimes be expressed (at the side of the nose) as a worm-like, white body, the so-called comedo. The sebaceous matter keeps the skin supple, and prevents the hair from becoming loo dry. Microscopically, the secretion is seen to contain innumerable fatty granules, a few gland cells filled with fat, visible after the addition of caustic soda, crystals of cholesterin, and in some men a microscopic, mite-like animal (Demodex foUiculorumj. Chemical Composition. — The consiituent^ are, for the most part, fatty ; chiefly olein (fluid ) and pahnitin (solid) fat, soaps and some cholesterin ; a small amount of albumin and unknown ex- tractives. Among the inorganic constituents, the insoluble earthy phosphates are most abundant ; while the alkaline chlorides and phosphates are less abundant. The vernix caseosa, which covers the skin of a new-born child, is a greasy mixture of sebaceous matter and macerated epidermal cells (containing 47.5 per cent. fat). A similar product is the smegma prseputialus (52.8 per cent, fat), in which an ammonia soap is present. The cerumen, or ear wax, is a mixture of the secretions of the ceruminous glands of the ear (similar in structure to the sweat glands) and the sebaceous glands of the auditory canal. Besides the constituents of sebum, it contains yellow or brownish particles, a bitter yellow extractive sub- stance derived from the ceruminous glands, potash soaps and a special lat (Berztliiis). The secre- tion of the Meibomian glands is sebum. [Lanoline. — Liebreich finds in feathers, hairs, wool, and keratin tissues generally, a cholesterin fat, which, however, is not a true fat, although it saponifies, but an ethereal compound of certain fatty acids with cholesterin. In commerce it is obtained from wool, and is known by the above name; it forms an admirable basis for ointments, and it is ver\' readily absorbed by the skin.] Thus, the fat-like substance for protecting the epidermis is partly formed along with keratin in the epi- dermis itself. 3. The Sweat. — The sweat is secreted in the coil of the sweat glands. .\s long as the secretion is small in amount, the water secreted is evaporated at once from the skin, along with the volatile constituents of the sweat ; as soon, how- ever, as the secretion is increased, or evaporation is prevented, drops of sweat appear on the surface of the skin. The former is called insensible perspira- tion, and the latter sensible perspiration. [Broadly, the quantity is about 2 lbs. in twenty-four hours.] The sensible perspiration varies greatly ; as a rule, the right side of the body perspires more freely than the left. The palms of the hands secrete most, then follow the soles of the feet, check, breast, upper arm and forearm (Peiper). It falls from morning to mid-day, and rises s^ain toward evening ( Tanssen). Method. — .Sweat is obtained from a man by placing him in a metallic vessel in a warm bath ; the sweat is rapidly secreted and collected in the vessel. In this way Favre collected 2560 grammes of sweat in i '•< hours. An arm may be inclosed in a cylindrical vessel, which is fixed air tight round the arm with an elastic bandage (Schottin). Among animals, the horse sweats, so does the ox, but to a less extent; the vola and planta of apes, cats and the hedgehog secrete sweat; the snout of the pig sweats (?), while the goat, rabbit, rat, mouse and dog are said not to sweat [Luchsin<;er). [The skin over the body and the pad on the dog's foot contain numerous sweat glands, which open free on the surface of the pad and into the hair follicles on the general surface of the skin ( IV. Stirling).'^ Microscopically. — The sweat contains only a few epidermal scales accidentally mixed with it, and fine fatty granules from the sebaceous glands. Chemical Composition. — Its reaction is alkaline, although it frequently is acid, owing to the admixture of fatty acids from decomposed sebum. During profuse secretion it becomes neutral, and, lastly, alkaline again {Triimpy and Luchsinger'). The sweat is colorless, slightly turbid, of a saltish taste, and has a characteristic odor, varying in different parts of the body; the odor is due to the presence of volatile fatty acids. The constituents are — water, which is increased by copious draughts of that fluid. The solids amount to 1.180 per cent. (0.70 to 2.66 per cent. — Funke), and of these 0.96 per cent, is organic and 0.33 inor- ganic. Among the organic constituents are neutral fats (palmitin, stearin), also present in the sweat of the palm of the hand, which contains no sebaceous glands (^Krause), cholesterin, volatile fattv acids (chiefly formic, acetic, butyric, propionic, caproic, capric acids), varying qualitatively and quantitatively in different parts 486 INFLUENCE OF NERVES ON THE SECRETION OF SWEAT. of the body. These acids are most abundant in the sweat first (acid) secreted. There are also traces of albumin (similar to casein), and urea, about o i per cent. {Funke, Picard'). In uraemic conditions (anuria in cholera), urea has been found crystallized on the skin {Schottin, Drasche). When the secretion of sweat is greatly increased, the amount of urea in the urine is diminished both in health and in uremia (Lcube). The nature of the reddish-yellow pigment, which is extracted from the residue of sweat by alcohol, and colored green by oxalic acid, is unknown. Among inorganic constituents, those that are easily soluble are more abundant than those that are soluble with difficulty, in the proportion of 17 to I {Scho/tin); sodium chloride, 0.2 ; potassium chloride, 0.2 ; sulphates, 0.0 1 per 1000, together with traces of earthy phosphates and sodium phosphate. Sweat contains COj in a state of absorption and some N. When decomposed with free access of air, it yields ammonia salts {Gorup-Bcsanes). Excretion of Substances.— Some substances when introduced into tlie body reappear in tiie sweat; benzoic, cinnamic, tartaric and succinic acids are readily excreted ; quinine and potassium iodide with more difficulty. Mercuric chloride, arsenious and arsenic acids, sodium and potassium arseniate have also been found. After taking arseniate of iron, arsenious acid has been found in the sweat, and iron in the urine. Mercury iodide reappears as a chloride in the sweat, while the iodine occurs in the sahva. Formation of Pigment. — The leucocytes furnish the material, and the pig- ment is deposited in granules in the deeper layers, and, to a less extent, in the upper layers of the rete Malpighii. This occurs in the folds around the anus, scrotum, nipple [especially during pregnancy], and everywhere in the colored races. There is a diffuse, whitish-yellow pigment in the stratum corneum, which becomes darker in old age. The pigmentation depends on chemical processes, reduction taking place, and these processes are aided by light. Granular pig- ment lies also in the layers of prickle cells. The dark coloration of the skin may be arrested by free O [hydric peroxide], while the corneous change is prevented at the same time {Uniia). Pathological. — To this belongs the formation of liver spots or chloasma, freckles, and the pigmentation of Addison's disease [pigmentation round old ulcers, etc., ] {J 103, IV). [The curious cases of pigmentation, especially in neurotic women, eg., in the eyelids, deserve further study in relation to the part played by the nervous system in this process.] 288. INFLUENCE OF NERVES ON THE SECRETION OF SWEAT. — The secretion of the skin, which averages about Jy of the body weight, i.e., about double the amount of water excreted by the lungs, maybe increased or diminished. The liability to perspire varies much in different indi- viduals. The following conditions influence the secretion : i. Increased tem- perature of the surroundings causes the skin to become red, while there is a pro- fuse secretion of sweat (§ 214, II, i). Cold, as well as a temperature of the skin about 50° C, arrest the secretion. 2. A very watery condition of the blood, e.g., after copious draughts of warm water, increases the secretion. 3. Increased cardiac and vascular activity, whereby the blood pressure within the cuta- neous capillaries is increased, has a similar effect ; increased sweating follows increased muscular activity. 4. Certain drugs favor sweating, e.g., pilo- carpin, Calabar bean, strychnin, picrotoxin, muscann, nicotin, camphor, ammonia compounds, while others, as atropin and morjjhia, in large doses, diminish or paralyze the secretion. [Drugs which excite copious perspiration, so that it stands as beads of sweat on the skin, are called sudorifics, while those that excite the secretion gently are diaphoretics, the difference being one of degree. Those drugs which lessen the secretion are called antihydrotics.] 5. It is important to notice the a/itagonism which exists, probably upon mechanical grounds, between the secretion of sweat, the urinary secretion, and the evacuation of the intestine. Thus, copious secretion of urine (^..i,'. , in diabetes) and watery stools coincide with dryness of the skin. If the secretion of sweat be increased, the percentage INFLUENCE OF NERVES ON THE SECRETION OF SWEAT. 487 of salts, urea {Funke), and albumin is also increased {Leube), while the other organic substances are diminished. The more saturated the air is with watery vapor, the sooner does the secretion appear in drops upon the skin, while in dry air or air in motion, owing to the rapid evaporation, the formation of drops of sweat is prevented, or at least retarded. [The complementary relation between the skin and kidneys is known to every one. In summer, when the skin is active, the kidneys separate less water; in winter, when the skin is less active, it is cold and comparatively bloodless, while the kidneys excrete more water, so that the action of these two organs is in inverse ratio.] The influence of nerves upon the secretion of sweat is very marked. I. Just as in the secretion of saliva (§ 145), vasomotor nerves are usually in action at the same time as the proper secretory nerves ; the vaso-dilator nerves (sweating with a reJ congested skin) are most frequently involved. The fact that secretion of sweat does occasionally take place when the skin is />a/e (fear, death agony) shows that, when the vasomotor nerves are excited, so as to constrict the cutaneous blood vessels, the sweat-secretory nerve fibres may also be active. Under certain circumstances the amount of blood in the skin seems to determine the occurrence of sweating; thus Dupuy found that section of the cervical sympathetic caused secretion on that side of the necli of a horse ; while Nitzelnadel found that percutaneous electrical stimulation of the cervical sympathetic in man limited the sweating.! [We may draw a parallel between the secretion of saliva and that of sweat. Both are formed in glands derived from the outer layer of the embryo. Both are formed from lymph supplied by the blood stream, and if the lymph be in sufficient quantity, secretion may take place when there is no circulation, although in both cases secretion is most lively when the circulation is most active and the secretory nerves of both are excited simultaneously; both have secretory nerves distinct from the nerves of the blood vessels; both may be paralyzed by the action of the nervous system, or in disease (fever), or conversely, both are paralyzed by atropine and excited by other drugs, e.g-., pilocarpin. in the gland cells of both histological, changes accompany the secretory act, and no doubt similar electro-motor phenomena occur in both glands.] II. Secretory nerves, altogether independent of the circulation, control the secretion of sweat. Stimulation of these nerves, even in a limb which has been amputated in a kitten, causes a temporary secretion of sweat, i.e., after complete arrest of the circulation {Goltz, Kendall and Luchsinger, Ostroumoiv). In the intact condition of the body, however, profuse perspiration, at all events, is always associated with simultaneous dilatation of the blood vessels (just as, in stimulation of the facial nerve, an increased secretion of saliva is associated with an increased blood stream — § 145, A, I). The secretory nerves and those for the blood vessels seem to lie in the same nerve trunks. The secretory nerves for the hind limbs (cat) lie in the sciatic nerve. Luch- singer found that stimulation of the peripheral end of this nerve caused renewed secretion of sweat for a period of half an hour, provided the foot was always wiped to remove the sweat already formed. If a kitten, whose sciatic nerve is divided on one side, be placed in a chamber filled with heated air, all the three intact limbs soon begin to sweat, but tlie limb whose nerve is divided does not, nor does it do so when the veins of the limb are ligatured so as to produce congestion of its blood vessels. [The cat sweats only on the hairless soles of the feet.] As to the course of the secretory fibres to the sciatic nerve, some pass directly from the spinal cord {Vulpi an), some pass into the abdominal sympathetic (Z«ir/w«^dv-, Nawrocki, Ostroumow), through the rami communicantes and the anterior spinal roots from the upper lumbar and lower dorsal spinal cord (9th to 13th dorsal ver- tebras — cat) where the sweat centre for the lower limbs is situated. The sweat centre may be excited directly: fi) By a strongly venous con- dition of the blood, as during dyspnoea, e.g., in the secretion of sweat that some- times precedes death; (2) by overheated blood (45° C.) streaming through the centre; (3) by certain poisons (see p. 486). The centre may be also excited reflexly, although the results are variable, e.g., stimulation of the crural and 488 PATHOLOGICAL VARIATIONS OF SWEATING. peroneal nerves, as well as the central end of the opposite sciatic nerve excites it {Liuksinger). [The pungency of mustard in the mouth may excite free perspira- tion on the face.] Anterior Extremity. — The secretory fibres lie in the ulnar and median nerves, for the fore limbs of the cat ; most of them, or indeed all of them {Ncnarocki) pass into the thoracic sympathetic (Ggl. stellatum"), and part (?) runs in the nerve roots direct from the spinal cord {Luchsingcr, Vulpian, Ott). A similar sweat centre for the upper limbs lies in the lower part of the cervical spinal cord. Stim- ulation of the central ends of the brachial plexus causes a reflex secretion of sweat upon the foot of the other side {Adamkiewicz). At the same time the hind feet also perspire. Pathological. — Degeneration of the motor ganglia of the anterior horns of the spinal cord causes loss of the secretion of sweat, in addition to paralysis of the voluntary muscles of the trunk. The perspiration is increa-ied in paralyzed as well as in cedamatous limbs. In nephritis, there are great variations in the amount of water given off by the skin. Head. — The secretory fibres for this part (horse, man, snout of pig) lie in the thoracic sympathetic, pass into the ganglion stellatum, and ascend in the cervical sympathetic. Percutaneous electrical stimulation of the cervical sympathetic in man, causes sweating of that side of the face and of the arm {M. Meyer). In the cephalic portion of the sympathetic, some of the fibres pass into, or become ap[)lied to, the branches of the trigeminus, which explains why stimulation of the infraorbital nerve causes secretion of svveat. Some fibres, however, arise directly from the roots of the trigeminus {Liic/i singer), and the facial ( Vulpian, Adamkiewicz). Undoubtedly the cerebrum has a direct effect either upon the vasomotor nerves (p. 487, I) or upon the sweat-secretory fibres (11), as in the sweating produced by psychical excitement (pain, fear, etc.). • Adamkiewicz and Senator found that, in a man suffering from abscess of the motor region of the cortex cerebri for the arm, there were spasms and perspiration in the arm. Sweat Centre. — According to Adamkiewicz, the medulla oblongata contains the dominating sweat centre (§ t,it,— Marine, JVawrocki). When this centre is stimulated in a cat, all the four feet sweat, even three-quarters of an hour after death (Adamkie^cicz). III. The nerve fibres which terminate in the smooth muscular fibres of the sweat glands act upon the excretion of the secretion. [Changes in the Cells during Secretion. — In the resting glands of the horse, the cylindrical cells are clear with the nucleus near their attached ends, but after free perspiration they become granular, and their nucleus is more central {^Renaut^!\ If the sweat nerves be divided (cat), injection of pilocarpin causes a secretion of sweat, even at the end of three days. After a longer period than six days there may be no secretion at all. This observation coincides with the phenomenon of dryness of the skin in paralyzed limbs. Dieffenbach found that transplanted portions of skin first began to sweat when their sensibility was restored. If a motor nerve (tibial, median, facial) of a man be stimulated, sweat appears on the skin over the muscular area supplied by the nerve, and also upon the corresponding area of the opposite non- stimulated side of the body. This result occurs when the circulation is arrested as well as when it is active. Sensory and thermal stimulation of the skin always cause a bilateral reflex secretion inde- pendently of the circulation. The area of sweating is independent of the part of the skin stimu- lated (Adamkiewicz). 289. PATHOLOGICAL VARIATIONS. — I. Anidrosis or diminution of the secretion of sweat occurs in diabetes and the cancerous cachexia, and along with other disturbances of nutrition of the skin in some nervous diseases, <■.,?■., in dementia paralytica ; in some limited regions of the skin it has occurred in certain trophoneuroses , 1'.^., in unilateral atrophy of the face and in paralyzed parts. In many of these cases it depends upon paralys:s of the corresponding nen'es (Eulsnburg) or their spitial sweat cetitrt's. 2. Hyperidrosis, or increase of the secretion of sweat, occurs in easily excitable persons, in consequence of the irritation of the nerves concerned (? 288), ^. y., the sweating which occurs in debilitated conditions and in the hysterical (sometimes on the head and hands), and the so called CUTANEOUS ABSORPTION. 489 epileptoid sweats {Eulenhurg). Sometimes the increase is confined to one side of the head (H.uni- lateralis). This condition is often accompanied with other nervous phenomena, partly with the symptoms of paralysis of the cervical sympathetic (redness of the face, narrow pupil), partly with symptoms of stimulation of the sympathetic (dilated pupil, exophthalmos). It may occur without these phenomena, and is due, perhaps, to stimulation of the proper secretory fibres alone. [Increased sweating is very marked in certain fevers, both during their course and at the crisis in some ; while the sweat is not only copious, but acid in acute rheumatism. The " night sweats" of phthisis are very marked and disagreeable.] 3. Paridrosis or qualitative changes in the secretion of sweat, e. g., the rare case of '■^ sweat- ing of blood" (Haematohidrosis), is sometimes unilateral. According to Hebra, in some cases this condition represents a vicarious form of menstruation. It is, however, usually one of many phe- nomena of nervous affections. Bloody sweat sometimes occurs in yellow fever. Bile pigments have been found in the sweat in jaundice; blue sweat from indigo {Bizio^, from pyocyanin (the rare blue coloring matter of pus), or from phosphate of the oxide of iron [Osc. Kollniann) i.s ex- tremely rare. Such colored sweats are called chromidrosis. Bacteria are frequently found, both in normal and in abnormal sweat, in yellow, blue, and red sweat. Grape sugar occurs in the sweat in diabetes mellitus; uric acid and cystin very rarely ; and in the sweat of stinking feet, leucin, tyrosin, valerianic acid and ammonia. Stinking sweat (Bromidrosis) is due to the decomposition of the sweat, from the presence of a special micro-organism (Bacterium fcetidum — Thin\. In the sweating stage of ague butyra'e of lime has been found, while in the sticky sweat of acute articular rheumatism there is more albumin {Anseiniino)^ and the same is the case in artificial sweating {Leube); lactic acid is present in the sweat in puerperal fever. The sebaceous secretion is sometimes increased, constituting Seborrhoea, which may be local or general. It may be diminished (Asteatosis cutis). The sebaceous glands degenerate in old people, and hence the glancing of the skin (Remy). If the ducts of the glands are occluded the sebum accumulates. Sometimes the duct is occluded by black particles or ultramarine {C'nna) from the blue used in coloring the Imen. When pressed out, the fatty, worm-shaped secretion is called " comedo." 290. CUTANEOUS ABSORPTION— GALVANIC CONDUCTION.— After long im- mersion in water the superficial layers of the epidermis become moist and swell up. The skin is unable to absorb any substances, either salts or vegetable poisons, from watery solutions of these. This is due to the fat normally present on the epidermis and in the pores of the skin. If the fat be removed from the skin by alcohol, ether, or chloroform, absorption may occur in a few minutes (Parisot). According to Rohrig, all volatile substances, e. g., carbolic acid and others, which act upon and corrode the epidermis, are capable of absorption. While according to Tuhl, such watery solutions as impinge on the skin, in a finely divided spray, are also capable of absorption, which very probably takes place through the interstices of the epidermis. [Inunction. — When ointments are rubbed into the skin so as to press the substance into the pores, absorption occurs, e. g., potassium iodide in an ointment so rubbed in is absorbed, so is mer- curial ointment. v. Voit found globules of mercury between the layers of the epidermis, and even in the chorium of a person who was executed, into whose skin mercurial ointment had been previ- ously rubbed. The mercury globules, in cases of mercurial inunction, pass into the hair follicles and ducts of the glands, wher^ they are aft'ected by the secretion of the glands and transformed into a compound capable of absorption. An abraded or inflamed surface {e.g., after a blister), where the epidermis is removed, absorbs very rapidly, just like the surface of a wound (Endermic method).] [Drugs may be applied locally where the epidermis is intact — Epidermic method — as when drugs which aflect the sensory nerves of a part are painted over a painful area to diminish the pain. Another method, the hypodermic, now largely used, is that of injecting, by means of a hypodermic .syringe, a non-corrosive, non-irritant drug, in solution, into the subcutaneous tissue, where it prac- tically passes into the lymph spaces and conies into direct relation with the lymph and blood stream, absorption takes place with great rapidity, even more so than from the stomach.] Gases. — Under normal conditions, minute traces of O are absorbed from the air ; hydrocyanic acid, sulphuretted hydrogen— CO, CO 2, the vapor of chloroform and ether may be absorbed (Chans- sier, Ger/aeh, Rohrig). In a bath containing sulphuretted hydrogen, this gas is absorbed, while CO, is given off into the water [Rohrig). Absorption of watery solutions takes pkace rapidly through the skin of the hog (Guttmann, W. .Stirling, V. iVittieh). Even after the circulation is excluded and the central nervous system destroyed, much water is absorbed through the skin of the frog, but not to such an extent as when the circulation is intact (.Spina). Galvanic Conduction through the Skin. — If the two electrodes of a constant current be impregnated with a watery solution of certain substances and applied to the skin, and if the direc- tion of the current be changed from time to time, strychnin may be caused to pass through the skin of a rabbit in a few minutes, and that in sufficient amount to kill the animal (H. Munk). In man, quinine and potassium iodide have been introduced into the body in this way, .and their presence detected in the urine. This process is called the cataphoric action of the constant current (I 328). 490 COMPARATIVE HISTORICAL. 2gi. COMPARATIVE — HISTORICAL.— In all vertebrates, the skin consists of chorium and epidermis. In some reptiles, the ej^iderniis becomes horny, and forms large plates or scales. Similar structures occur in the edentata among mammals. The epidermal appendages assume various forms - such as hair, nail, spines, bristles, feathers, claws, hoof, horns, spurs, etc. The scales of some fishes are partly osseous structures. Many glands occur in the skin ; in some am- phibia they secrete mucus, in others the secretion is poisonous. * Snakes and tortoises are devoid of cutaneous glands ; in lizards the *' leg glands " extend from the anus to the bend of the knee. In the crocodile, the glands open under the margins of the cutaneo-osseous scales. In birds, the cutaneous glands are absent; the "coccygeal glands" form an oily secretion for lubricating the feathers. [This is denied by O. Liebreich, as he finds no cholesterin fats in their secretion.] The chvl glands, at the anus of the civet cat, the preputial glands of the musk deer, the glands of the hare, and the pedal glands of ruminants, are really greatly developed sebaceous glands. In some invertebrata, the skin, consisting of epidermis and chorium, is intimately united with the subj.acent muscles, forming a musculo-cutaneous tube for the body of the animal. The cephalopoda have chromatophores in their skin, ;'. e., round or irregular spaces filled with colored granules. Mus- cular fibres are arranged radially around these spaces, so that when these muscles contract the colored surface is increased. The change of color in these animals is due to the play or contraction of these muscles. (Brihkc\) Special glands are concerned in the production of the shells of the snail. The annulosa are covered with a chitinous investment, which is continued for a certain distance along the digestive tract and the trachea. It is thrown off when the animal sheds its cover- ing. It not only protects the animal, but it forms a structure for the attachment of muscles. In echinodermata, the cutaneous covering contains calcareous masses ; in the holothurians, the calca- reous structures assume the form of calcareous spicules. Historical. — Hippocrates (born 460 li. c.) and Theophrastus (born 371 B.C.) distinguished the perspiration from the sweat; and, according to the latter, the secretion of sweat stands in a certain antagonistic relation to the urinary secretion and to the water in the fceces. According to Cassius Felix (97 A. D.), a person placed in a bath absorbs water through the skin; Sanctorius (1614) measured the amount of sweat given off; Albert! (1581) was acquainted with the hair bulb ; Donatus (1588) described hair becoming gray suddenly; Riolan (1626) showed that the color of the skin of the negro was due to the epidermis. Physiology ™e motor Apparatus. 292. CILIARY MOTION — PIGMENT CELLS.— f^?) Muscular Movement. — By far the greatest number of the movements occuring in our bodies IS accomplished through the agency of muscular fibre, which, when it is excited by a stimulus, contracts — /. e., it forcibly shortens — and thus brings its two ends nearer together, while it bulges to a corresponding extent laterally. In muscle, the contraction takes ])lace in a definite direction. (b) Amoeboid Movement. — Motion is also exhibited by colorless blood corpuscles, lymph corpuscles, leucocytes, and some other corpuscles. In these structures we have examples of amoeboid movement (§ 9), which is movement in an indefinite direction. [((•) Ciliary Movement. — There is also a peculiar form of movement, known as ciliary movement. There is a gradual transition between these different forms of movement. The cilia, which are attached to the ciliated epithelium, are the motor agents (Fig. 280,1.] [Ciliated epithelium, and where found. — In the nasal mucous membrane, except the olfactorj' region; the cavities accessory to the nose; the upper half of the pharynx, Eustachian tube, larynx, trachea and bronchi; in the ulerui, except the lower half of the cervix; Fallopian tubes; vasa Ciliated epitlicliii efferentia to the lower end of epididymis ; ventricles of brain (child) ; and the central canal of the spinal cord.] [The cilia are flattened, blade-like or hair-like appendages attached to the free end of the cells. They are about 3t)Vij inch in length, and are, apparently, homogeneous and structureless. They are planted upon a clear, non-contractile disk on the free end of the cell, and some observers state that they pass through (his disk to become continuous with the protoplasm of the cell, or with the plexus of fibrils which pervades the protoplasm ; so that by some observers [Klein ) they are regarded as prolongations of the intraepithelial plexus of fibrils. They are specially modified parts of an epithelial cell, and are contractile and elastic. They are colorless, tolerably strong, not colored by staining reagents, and are possessed of considerable rigidity and flexibility. They are always con- nected with the protoplasm of ce'ls, and are never outgrowths of the solid cell membranes. There may be lo to 20 cilia distributed uniformly on the free surface of a cell (Fig. 280).] [In the large ciliated cells in the intestine of some molluscs (mussel) the cilia perforate the clear retractile disk, which appears to consist of small globules — basal pieces — united by their edge, so that a cilium seems to spring from each of these, while continued downward into the protoplasm of the cell, but not attached to the nucleus, there is a single varicose fibril — rootlet, and the leash of these fibrils passes through the substance of the cell, and may unite toward its lower-tailed extremity [Enge!maiin).'\ [Ciliary motion mav be studied in the gill of a mussel, a small part of the gill being teased in 491 492 FUNCTIONS OF CILIA. sfa water ; or the hard palate of a frog, newly killed, may be scraped, and the scraping examined in 3^ p. c. salt solution. On analyzing the movement, all the cilia will be observed to execute a regular, periodic, toand-fro rhythmical movement in a plane usually vertical to the surface of the cells, the direction of the movement being parallel to the long axis of the organ. The appearance presented by the movements of the cilia is sometimes described as a lashing movement, or like a field of corn moved by the wind. Each vibration of a cilium consists of a rapid forward move- ment or flexion, the tip moving more than the base, and a slower backward movement, the cilium again straiglitening itself. The forward movement is about twice as rapid as the backward move- ment. The ainplitude of the movement varies according to the kind of cell and other conditions, being less when the cells are about to die; but it is the same for all the cilia attached to one cell, and is seldom more than 20° to 50°. There is a certain periodicity in their movement ; in the frog they contract about 12 times per second [Enge/niaun). The result of the rapid forward movement is that the surrounding fluid, and any particles it may contain, are moved in the direction in which the cilia bend. All the cilia of adjoining cells do not move at once, but in regular suc- cession, the movement traveling from one cell to the other; but how this coordination is brought about we do not know. At least, it is quite independent of the nervous system, as ciliary move- ment goes on in isolated cells, and in man it has been observed in the trachea two days after death. Conditions for Movement. — In order that the ciliary movement may go on, it is essential that — (i) the cilia be connected with part of a cell ; (2) moisture ; (3) oxygen be present ; and {4) the temperature is within certain limits.] [A ciliated epithelial cell is a good example of the physiological division of labor. It is derived from a cell which originally held motor, automatic and nutritive functions all combined in one mass of protoplasm ; but in the fully-developed cell the nutritive and regulative functions are confined to the protoplasm, while the cilia alone are contractile. If the cilia be separated from the cell, they no longer move. If, however, a cell be divided so that part of it remains attached to the cilia, the latter still move. The nucleus is not essential for this act. It would seem, therefore, that though the cilia are contractile, the motor impulse probably proceeds from the cell. Each cell can regulate its own nutrition, for during life they resist the entrance of certain colored fluids.] [Effect of Reagents. — Gentle heat accelerates the number and intensity of the movements, cold retards them. A temperature of 45° C. causes coagulation of their proteids, makes them permanently rigid, and kills them, just in the same way as it acts on muscle, causing heat stiffening (p. 5*^5)- Weak alkalies may cause them to contract after their movement is arrested or nearly so ( I'irchinc), and any current of fluid, in fact, may do so. Lister showed that the vapor of ether and chloroform arrests the movements as long as the narcosis lasts, but if the vapor be not applied for too long a time, the cilia may begin to move again. The prolonged action of the vapor kills them. As yet. we do not know any specific poison for cilia, atropin, veratrin and curara acting like other substances with the same endosmotic equivalent [Engelmann).'\ [Functions of Cilia. — The moving cilia propel fluids or particles along the passages which they line. By carrying secretions along the tubes which they line toward where these tubes open on the surface, they aid in excretion. In the respiratory passages, they carry outward along the bronchi and trachea the mucus formed by the mucous glands in these regions. When the mucus reaches the larynx it is either swallowed or coughed up. That the cilia carry particles upward in a spiral direction in the trachea has been proved by actual laryngoscopic inves- tigation, and also by excising a trachea and sprinkling a colored powder on its mucous membrane, when the colored particles (IJerlin blue or charcoal) are slowly carried toward the upper end of the trachea. In bronchitis, the ciliated epi- thelium is shed, and hence the mucus tends to accumulate in the bronchi. They remove mucus from cavities accessory to the nose, and from the tympanum, while the ova are carried, partly by their agency, from the ovary along the Fallopian tube to the uterus. In some of the lower animals they act as organs of locomo- tion, and in others as adjuvants to respiration, by creating currents of water in the region of the organs of respiration.] [The Force of Ciliary Movement. — Wynian and Bowditch found that the amount of work that can be done by cilia is very considerable. The work was estimated by the weight which a measured surface of the mucous membrane of the frog's hard palate was able to carry up an inclined plane of a definite slope in a given time.] [Pigment cells belong to the group of contractile tissues, and are well developed in the frog, and many other animals where their characters have been carefully studied. They are generally regarded as comparable to branched connective-tissue corpuscles, loaded with pigmented granules of melanin. The pigment granules may be diff'used in the cell, or aggregated around STRUCTURE AND ARRANGEMENT OF THE MUSCLES. 493 the nucleus; in the former case, the skin of the frog appears dark in color, in the latter, it is Ijut slightly pigmented. The question has been raised whether they are actual cells or merely spaces, branched, and containing a fluid with granules in suspension. In any case, they undergo marked changes of shape under various influences. If the motor nerve to one leg of a frog be divided, the skin of the leg on that side becomes gradually darker in color than the intact leg. A similar result is seen in the curara experiment, when all parts are ligatured except the nerve. Local applications aft'ect the state of diffusion of the pigment, as v. Wittich found that turpentine or electricity caused the cells of the tree-frog to contract, and the same effect is produced by light. In Rana temporaria local irritation has little effect, but light, on the contrary, has, although the effect of light seems to be brought about through the eye (Lister), probably by a reflex mechanism. A pale colored frog, put in a dark place, assumes, after a time, a diflTerent color, as the pigment is diffused in the dark ; but if it be exposed to a bright light it soon becomes pale again. The same phenomenon may be seen on studying the web of a frog's leg under the microscope. The marked variations of color— within a certain range — in the chameleon is due to the condition of the pig- ment cells in its skin, covered as they are by epidermis, containing a thin stratum of air [Briicie). When it is poisoned with strychnin, its whole body turns pale; if it be ill, its body becomes spotted in a dendritic fashion, and if its cutaneous neri'es be divided, the area supplied by the nerve changes to black. The condition of its skin, therefore, is readily affected by the condition of its nervous system, for psychical excitement also alters its color. If the sympathetic nerve in the neck of a turbot be divided, the skin on the dorsal part of the head becomes black. It is notorious that the color of fishes is adapted to the color of their environment. If the nerve proceeding from the stellate ganglion in the mantle of a cuttle fish be divided, the skin on one.half of the body becomes pale.] 292 a. STRUCTURE AND ARRANGEMENT OF THE MUS- CLrES. — Muscular Tissue is endowed with contractility, so that when it is acted upon by certain forms of energy or stimuli, it contracts. There are two varieties of this tissue — (i) Striped, striated or (voluntary) ; (2) Non-striped, smooth, organic, or (involuntary). Some muscles are completely under the control of the will, and are hence called " voluntary," and others are not directly subject to the control of the will, and are hence called "involuntary;" the former are for the most part striped, and the latter non-striped ; but the heart muscle, although striped, is an involuntary muscle. I. Striped Muscles. — The surface of a muscle is covered with a connective-tissue envelope or perimysium externum, from which septa, carrying blood vessels and nerves, the perimysium internum, pa<^s into the substance of the muscle, so as to divide it into bundles of fiijres or fasci- culi, which are fine in the eye muscles and coarse in the glutei. In each such compartment or mesh there lie a number of miisiulnr Jilires arranged more or less parallel to each other. [The filires are held together by delicate connective tissue or endomesium, which surrounds groups of the fibres; each fibre being, as it were, separated from its neighbor by excessively delicate fibrillar connective tissue.] Each muscular fibre is surrounded with a rich plexus of capillaries [which form an elongated meshwork, lying between adjacent fibres, but never penetrating the fibres, which, however, they cross (Fig. 2S4). In a contracted muscle the capillaries may be slightly sinuous in their course, but when a muscle is on the stretch thde curves disappear. The capillaries lie in the endomysium, and near them are lymphatiis.'\ Each muscular fibre receives a nerve fibre. [Where found. — Striped muscular fibres occur in the skeletal muscles, heart, diaphragm, pharynx, upper part of cesophagus, muscles of the middle ear and pinna, the true sphincter of the urethra, and external anal sphincter.] A muscular fibre (Fig. 2S1, 1) is a more or less cylindrical or polygonal fibre, II to 67 ;i. [y^ to ^j-Lj in.] in diameter, and never longer than 3 to 4 centi- metres [i to ija in.]. Within short muscles, e.g., stapedius, tensor tympani, or the short muscles of a frog, the fibres are as long as the muscle itself; within longer muscles, however, the individual fibres are pointed, and are united obliquely by cement substance with a similar beveled or pointed end of another fibre lying in the same direction. Muscular fibres may be isolated by maceration in nitric acid with excess of potassic chlorate i^Budge), or by a 35 per cent, solution of caustic potash (Mo/eschott). [Each muscular fibre consists of the following parts : — 1. Sarcolemma, an elastic sheath, with transverse partitions, stretching across the fibre at regular intervals — the membranes of Kraiise ; 2. The included sarcous substance; 3. The nuclei or muscle corpuscles.] 494 bTRUCTURE OF STRIPED MUSCLES. Sarcolemma.— Each muscular fibre is completely enclosed by a colorless, structureless, trans- parent elastic sheath (Fig. 281, i. Si, which, chemically, is midway between connective and elastic tissue, and within it is the contractile substance of the muscle. [It has much more cohesion than the sarcous substance which it encloses, so that sometimes, when teasing fresh muscular tissue under the microscope, one may observe the sarcous substance torn across, with the unruptured sarcolemma stretching between the ends of the ruptured sarcous substance. If muscular fibres be teased in distilled water, sometimes fine, clear blebs are seen along the course of the fibre, due to the sarco- lemma being raised by the fluid dilTusing under it. The sarcous substance, but not the sarcolemma, may be torn across by plunging a muscle in water at 55° C, and keeping it there for some time Fig. 28 Histology of muscular tissue, i, Diagram of part of F, fibrillae; K, the muscle nuclei ; N, a nerve fib plate, e, seen in profile; 2, transverse muscular fibrillae ; 4, part of an insect cases ; i, the doubly- refractive substa transversely into disks ; 6, muscular fi human foetus at the third month ; 8, puscles ; 10, smooth "muscular fibres ; fibre ; S, sarcolemma ; Q, transverse stripes ; : ntire entering it witn «, its axis cylinder and Kuhne's motorlal end of part of a muscular fibre, showing Cohnheim's areas, c ; 3, isolated [luscle greatly magnified ; a, Krause-Amici's line limiting the muscular ; f, Hensen's disk ; d, the singly-refractive substance ; 5, fibre cleaving : from the heart of a frog; 7, development of a striped muscle from a muscular fibres of the heart ; c, capillaries ; " transverse section of smooth muscular fibres. Stripes. — The sarcous substance is marked transversely by alternate light and dim layers, bands, stripes or disks (Fig. 2S1, i, Q), so that each fibre is said to be *' transversely striped.** [The stripes do not occur in the sarcolemma, but are confined to the sarcous substance, and they involve its whole thickness.] [The animals most suited for studying the structure of the sarcous substance are some of the insects. The muscles of the water beetle, Dytiscus marginalis. and the Hydrophilus piceus are well suited for this purpose. So is the crab's muscle. In examining a living muscle microscopically, no fluid except the muscle juice should be added to the preparation, and very high powers of the microscope are required to make out the finer details.] STRUCTURE OF A MUSCULAR FIBRILLA. 495 Fig. 2S2. Bowman's Disks. — If a muscular fibre be subjected to the action of hydro- chloric acid (i per 1000), or if it be digested by gastric juice, or if it be frozen, it tends to cleave transversely into disks (Bowman), which are arti- ficial products, and resemble a pile of coins which has been knocked over (Fig. 281, 5). Fibrillse. — Under certain circumstances, a fibre may exhibit longitudinal striation. This is due to the fact that it may be split up longitudinally into an immense number of (i to 1.7 p. in diameter) fine, contractile threads, the primitive fibrillae (Fig. 281, I, F), placed side by side, each of which is also transversely striped, and they are so united to each other by semi-fluid cement substance, that the transverse markings of all the fibrillae lie at the same level. These fibrillae, owing to nmtual pres- sure, are prismatic in form, so that when a trans- verse section of a perfectly fresh muscular fibre is observed after it is frozen, the end of each fibre is mapped out into a number of small polygonal areas called Cohnheim's areas (Fig. 281, 2). Fibrillffi are easily obtained from insects' mus- cles, while those from a mammal's muscle are readily isolated by the action of dilute alcohol, Miiller's portion of a human mu^cuUr fibre fluid [or, best of all, \ per cent, solution of chro- x 300- mic acid] (Fig. 281, 3). [When a living, unaltered muscular fibre is examined microscopically, in its own juice, we observe the alternate dim and light transverse disks. A high power reveals the presence of a line running across the light disk, and dividing it into two (Fig. 2S2). It has been called Dobie's line (Rutherford), and by others it is regarded as due to the existence of a membrane, called Krause's membrane, which runs transversely across the fibre, being attached all round to the sarco- lemma, thus dividing each fibre into a series o{ compartments placed end to end. These muscular compartments contain the sarcous substance, and in each compartment we find (i) a broad, dim disk, which is the contractile part of the sarcous substance. It is doubly refractive (anisotropous), and is composed of Bowman's sarcous elements. (2) On each end of this disk, and between it and Krause's membranes, is a narrower, clear, homogeneous, and but singly refractile (isotropous), soft or fluid substance, which forms the lateral disk of Engel- mann. In some insects it contains a row of refractive granules, constituting the granular layer of Flogel. If a muscular fibre be stretched and stained with logwood, the central part of the dim di'.k appears lighter in color than the two ends of the same disk. This has been described as a separate disk, and is called the median disk of Hensen (Fig. 281, 4, c).] [In an unaltered fibre, the dim, broad stripe appears homogeneous, but after a time it cleaves throughout its entire extent in the long axis of the fibre into a number of prismatic elements or fibrils, the sarcous elements of Bowman (Fig. 281). These at first are prismatic, but as they solidify they shrink and seem to squeeze out of them a fluid, becoming at the same time more constricted in the centre. This separation into fibrils with an interstitial matter gives rise to the appearance seen on transverse section of a frozen muscle, and known as Cohn- heim's areas (Fig. 281, 2, c). In all probability the cleavage also extends through the lateral disks, and thus fibrils are formed by longitudinal cleavage of the fibre.] [According to Haycraft, a muscular fibre is moniliform, being narrowest at the part opposite Krause's memlirane, and thicker in the interval, so that Haycraft attributes the transverse striation to these differences, the surface being undulating.] 496 MUSCLE RODS. [Muscle Rods. — Scliafcr describes the appearance differently: " Double rows of granules are seen lying in or at the boundaries of the light streaks (disks), and very tine, longitudinal lines may be detected running through the dark streak (dim disk) and uniting the minute granules. These fine lines, with their enlarged extremities, are muscle rods." They are most conspicuous in in- sects. During the contraction of a living muscular fibre, Schafer describes the " reversal of the stripes" (^ 297) as follows: "When the fibres contract the light stripes are seen, as the fibre shortens and thickens, to become dark, an apparent reversal being thereby produced in the stri^. This reversal is due to the enlargement of the rows of dark dots and the formation by their juxta- position and blending of dark disks, while the muscular substance between these disks has by con- trast a bright appearance."] [With polarized light in a living muscular fibre, all the sarcous substance, except the muscle rod, is doubly refractive or anisotropous, so that it appears bright on a dark field when the Nicol's prisms are crossed, while under the same conditions contracted muscle and dead muscle show alternate dark and light bands (Sc/idfer).'\ The nuclei or muscle corpuscles are found immediately under the sarcolemma in all mammals, and their long axis lies in the long axis of the fibre (8 to 13 /' long, 3 to 4 /* broad). [In the mus- cles of the frog and some other animals, e.g., the red muscles of the rabbit and hare, they lie in the Injected blood vessels of a human muscle, a, small artery : vein : c, capillaries. X 250 {^KoUiker). substance of the fibre surrounded by a small amount of protoplasm.] When they occur immediately under the sarcolemma they are more or less flattened, and lie embedded in a small amount of pro- toplasm (Fig. 281, I and 2, K). They contain one or two nucleoli, and it is said that the proto- plasm sends out fine processes which unite with similar processes from adjoining corpuscles, so that, according to this view, a branched protoplasmic network exists under the sarcolemma. [Each nucleus has a reticulated appearance due to the presence of a plexus of fibrils. The nuclei are not seen in a perfectly fresh muscle, because, until they have undergone some change, their refractive index is the same as that of the sarcous substance.] They become specially evident after the addi- tion of acetic acid. Histogenetically, they are the remainder of the cells from which the muscular fibres were developed (Fig. 2S1, 7). According to M. Schultze, the sarcous substance is an inter- cellular substance differentiated and formed by their activity. Perhaps they are the centres of nutri- tion for the muscular fibres. In amphibians, birds, fishes, and reptiles, they lie in the axis of the fibres between the fibrils. It is said that tlie protoplasm of the muscle corpuscles forms a fine network throughout the whole muscular fibre, the transverse branches taking the course of the lines of Krause or Dobie, and the longitudinal branches running in the interstices between Cohnheim's areas [A'e/ztus, Bremer). NERVES OF A MUSCLE. 497 Relation to Tendons. — According to Toldt, the delicate connective-tissue elements, which cover the several muscular fibres, pass from the ends of the latter directly into the connective-tissue elements of the tendon. The end of the muscular fibre is perhaps united to the smooth surface or hollow end of the tendon by means of a special cement ( PVasmaim — Fig. 283, Si. In arlhropoda, the sarcolemma passes directly into and becomes continuous with the tendon {Leydio^ Reichert). The tendon itself consists of longitudinally arranged bundles of white fibrous tissue with cells — tendon cells — embracing them. There is a loose capsule or sheath of connective tissue— the peri- tendineum of KoUman — surrounding the whole and carrying the blood vessels, lymphatics, and nerves. The tendons move in the tendon sheaths, which are moistened by a mucous fluid. In most situations, muscular fibres are attached by means of tendons to some fixed point, but in other situations (face) the ends terminate between the connective-tissue elements of the skin. [Blood Vessels. — Muscles, being very active organs, are richly supplied with blood. The blood supply of a muscle differs from some organs in not constituting an actual vascular unit, sup- plied only by one artery and one vein, thus being unlike the kidney, spleen, etc. Each muscle usually receives several branches from different arteries, and branches enter it at certain distances along its whole length. The artery and vein usually lie together in the connective tissue of the perimysium, while the capillaries lie in the endomysium. The capillaries lie between the muscular fibres, but outside the sarcolemma, where they form an elongated, rich plexus with numerous transverse branches (Fig. 284). The lymph to nourish the sarcous substance must traverse the sarcolemma to reach the former. In the red muscles of the rabbit |c.^., semitendinosus), the capillaries are more wavy, while on the transverse branches of some of the capillaries, and on the veins (Manvier), there are small, oval, saccular dilatations, which act as reservoirs for blood.] [Lymphatics. — We know very little of the lymphatics of muscle, although the lymphatics of Fig. 285. — Muscle nucleus. d plate tendon and fascia have been carefully studied by Ludwig and Schweigger Seidel. There are lym- phatics in the endomysium of the heart, which are continuous with those under the pericardium. This subject still requires further investigation. Compare the lymphatics of the fascia lata of the dog (Fig. 212, i, 201).] Entrance of the Nerve. — The trunk of the motor nerve, as a rule, enters the muscle at its geometrical centre (Se/izvalbe); hence the point of entrance in muscles with long, parallel, or spindle- shaped fibres lies near its middle. If the muscle with parallel fibres is more than 2 to 3 centimetres [i inch] in length, several branches enter its middle. In triangular muscles, the point of entrance of the nerve is displaced more toward the strong tendinous point of convergence of the muscular fibres. . A nerve fibre usually enters a muscle at the point where there is the least displacement of the muscular substance during contraction. Motor Nerve. — Every muscular fibre receives a motor nerve fibre (Fig. 281, I, N). K:ich nerve does not contain originally as many motor nerve fibres as there are muscular fibres in the muscle it enters ; in the human eye muscles, there are only 3 nerve fibres to 7 muscular fibres ; in other muscles (dog), i nerve fibre to 40 or 80 {Tergast ). Hence, when a nerve enters a muscle it must divide, which occurs dichotomously [at Ranvier's nodes], the structure undergoing no change until there are exactly as many nerve fibres as muscular fibres. In warm-blooded animals each muscular fibre has only one, while cold-blooded animals have seve- ral points of insertion of the nerve fibre {SanJmann). A nerve fibre enters each 32 498 RED AND PALE MUSCLES. muscular fibre, and where it enters it forms an eminence {Doycre, 1846), the " motorial end plate " (Fig. 281, 1, c). The neurilemma unites directly with the sarcolemma, the white substarxe of Schwann ceases, while the axis cylinder passes in and divides within the sarcolemma. There is an elevation of a proto- plasmic nature containing nuclei immediately under the sarcolemma at the entrance of the nerve (Kiihne's end plate, Fig. 285). The branches of the axis cylinder traverse this mass, where they subdivide into fine fibrils recognizable only after the action of gold chloride (Fig. 286). These fibrils penetrate between the fibril- l:e along the whole extent of the fibre, and, perhaps, they terminate in the aniso- tropous substance ( Gcrlacli). Sensory fibres also occur in muscles, and they are the channels for muscular sensibility. They seem to be distributed on the outer surface of the sarcolemma, where they form a branched plexus and wind round the muscular fibres {Artiiit, Sachs) ; but, according to Tschirjew, the sensory nerves traverse the substance of the muscle, and after dividing dichotomously, end on/y in the aponeurosis, either suddenly or by means of a small swelling — a view confirmed by Rauber. The existence of sensory nerves in muscles is also proved by the fact that, stimulation of the central end of a motor nerve, e. g., the phrenic, causes increase of the blood pressure and dilatation of the pupil {Asp, Kowak^osky, Nmarofki), as well as by the fact that when they are inflamed they are painful. They, of course, do not degenerate after section of the anterior root of tlie spinal nerves. Red and Pale Muscles. — In many fishes (skate, pKiice, herring, mackerel) {IV. Stirlini;),h\xi\s, le stained with gold chloride and mammals (rabbits), there are two kinds of striped muscle {Kyaase,), differing in color, hislo- loeical structure (Kanvu-r) and physiological properties [Jironecker and Slirhng). borne are "red " e " the soleus and semitendinosus of the rabbit, and others "pale, e.^., the adductor macnus. In the falc muscles the transverse striation is less regular, and their nuclei fewer than in the red muscles (Kanvier) ; they comain less glycogen and mytjsin. [W. .Stirling finds that the red muscles in many fishes, e. g., the mackerel, contain granules of oil, and present all the appearances of muscle in a stale of fatty degeneration, while the pale muscles, lying side by side, contain no fatty ^'Tspectrum —The red color of the ordinary skeletal muscle is due to haemoglobin in the sarcous substance iKiihne). This is proved by the fact that the color is retained when all the blood is washed out of the vessels, when a thin muscle still shows the absorption bands of hemoglobin when examined with the spectroscope.] . ■ 1 . rMyo-h^matin.— MacMunn points out that, although most voluntary muscles owe their color to haemoglobin, it is accompanied by myoh.emalhi in most cases, and sometimes entirely replaced by it. Myo-ha-matin is found in the hea,-t of vertebrates, and in some muscles of vertebrates and inver- "^ Muscular Fibres of the Heart.— The mammalian cardiac muscle has certain peculiarities already mentioned (3 43): (I ) It is striped, but it is involuntary ; (2) it has no sarcolemma; (3) its fibres branch and anastomose; (4) the transverse striation is not so distinct, and it is sometimes striated longitudinally; (5) the nucleus is placed in the centre of each cell (see I 43)- [The cardiac muscle viewed from a physiologiial point of view, stands midway between striped and unstnped muscle. Its contraction occurs slowly and lasts for a long time (p. 104), while, although it is trans- versely striped, it is involuntary.] rPurkinie's Fibres.— These fibres, which form a plexus of grayi.sh fibres under the endocardium of the heart of ruminants, have been described already (Fig. 2S) ; the cells have, as it were, advanced only to a certain stage of development {\ 46).] NON-STRIPED MUSCLE. 499 Development. — Each muscular fibre is developed from a uninucleated cell of ihe niesoblast, which elongates into the form of a spindle. As the cell elongates, the nuclei multiply. The super- ficial or parietal part of the cell substance shows transverse markings (Fig. 281, 7), while the nuclei with a small amount of protoplasm are continuous along the axis ot the fibre, where they remain in some animals. Young muscles have fewer fibres than those of adults, and the former are also smaller {Biitige). In developing muscles, the number of fibres is increased by the proliferation of the muscle corpuscles, which form new fibres. Striped muscle, besides occurring in the corresponding organs of veitebrata, occurs in the iiis and choroid of birds. The arlhropoda have only striped muscle, the molluscs, worms, and echinoderms chiefly smooth muscles; in the latter, there are muscles with double oblique striation \Sc/iwa!he). 2. Non-Striped Muscle. — [Distribution. — It occurs very widely distributed in the body, in the muscular coat of the lower half of the human cesophagus, stomach, small and large intestine, muscularis mucosae of the intestinal tract, in the arteries, veins and lymphatics, posterior part of the trachea, bronchi, infundibula of the lung, muscular coat of the ureter, bladder, urethra, vas deferens, ves'culas seminalis, and prostate ; corpora cavernosa and spongiosa penis, ovary, P^allopian tube, uterus, skin, ciliary muscle, iris, upper eyelid, spleen and capsule of lymphatic glands, tunica dartos of the scrotum, gall bladder, in ducts of glands, and in some other situations.] Structure Smooth muscular fibres consist of fusiform or spindle shaped elongated cells, with their ends either tapering to fine points or divided (Fig. 281, 10). These contractile fibre cells may Fir.. 287. Fig. 288. Smooth muscular fibre from the mcsen- Termi tery of a newt (ammonium chro- mate). N, nucleus: F, fibrils; S, markings in the sheath. be isolated by steeping a piece of the tissue in a 30 per cent, solution of caustic potash, or a strong solution of nitric acid. They are 45 to 230 fi [ji^ to ji^ in.] in length, and 4 to 10 fi [jjj'jj to uVl '"•] '" breadth. Each cell contains a solid, oval, elongated nucleus, which may contain one or more nucleoli. It is brought into view by the action of dilute acetic acid, or by staining reagents. The mass of the cell appears more or less homogeneous [and is surrounded by a thin elastic envel- ope]. In some places it shows longitudinal fibrillation. [Method. — This fibrillation is revealed mote distinctly thus: Place the mesentery of a newt (A'/ehi) or the bladder of the salamandra musculata (/■lemming) in a 5 per cent, solution of ammonium chromate, and afterward stain it with picrocarmine. Each cell consists of a thin elastic sheath (sarcolemma of Krause) enclosing a bundle of fibrils (F), which run in a longitudinal direction within the fibre (Fig. 287). They are continuous at the poles of the nucleus with the plexus of fibrils which lies within the nucleus, and, according to Klein, they are the contractile part, and when they contract, the sheath becomes shriveled transversely and exhibits what looks like thickenings (S). These fibrils have been observed by Flemming in the cells while ik'ing. Sometimes the cells are branched, while in the frog's bladder they are triradiate.] [Arrangement. — Sometimes the fibres occur singly, but usually they are arranged in groups, forming lamella:, sheets, or bundles, or in a plexiform manner, the bundles being surrounded by connective tissue.] A very delicate elastic cement substance unites the individual cells to each other. [This cement may be demonstrated by the action of nitrate of silver. In transverse section 500 PHYSICAL AND CHEMICAL PROPERTIES OF MUSCLE. ( Fig. 281 , 1 1 ) they appear oval or polygonal, with the delicate homogeneous cement between them ; but, as the fibres are cut at various levels, the areas are unequal in size, and all of them, of course, are not divided at the position of the nucleus.] They vary in length from yj^ to ,^5 of an inch ; those in the blood vessels are short, while they are long in the intestinal tract, and especially in the pregnant uterus. According to Engelmann, the separation of the smooth muscular substance into its individual spindle-like elements is a post- mortem change of the tissue. Sometimes transverse thiclienings are seen, which are not due to transverse striation {/i'rause), but to a partial contraction {Meissiier). Blood Vessels. — Occasionally they have a tendinous insertion. Non-striped muscle is richly supplied with tlood vessels, and the capillaries form elongated meshes between the fibres [although it is not so vascular as striped muscles]. Lymphatics also occur between the fibres. Motor Nerves. — According to J- Arnold, they consist of medullated and non-meduUated fibres [derived from the sympathetic system] which form a ple.xus — ground plexus — partly provided with ganglionic cells, and lying in the connective tissue of the perimysium. [The fibres are sur- rounded with an endothelial sheath.] Small branches [composed of bundles of fibrils] are given off from this plexus, forming the intermediary plexus with angular nuclei at the nodal points. It lies either immediately upon the musculature or in the connective tissue between the individual bundles. From the intermediary plexus, the finest fibriliae (0.3 to 0.5 /') pass off either singly or in groups, and reunite to form the intermuscular plexus (Fig. 28S, d), which lies in the cement suljstance between the muscle cells, to end, according to Franltenhauser, in the nucleoli of the nucleus, or in the neighborhood of the nucleus (Lustig). According to J. Arnold, the fibrils traverse the fibre and the nucleus, so that the fibres appear to be strung upon a fibril passing through their nuclei. According to Lowil, the fibrils reach only the interstitial substance, while Gscheidlen also observed that the finest terminal fibrils, one of which goes to each muscular fibre, ran along the margins of the latter (Fig. 2S8). The course of these fibrils can only be traced after the action of gold chloride. [Ranvier has traced their terminations in the stomach of the leech.] Nerves of Tendon. — Within the tendons of the frog there is a plexus of medullated nerve fibres, from which brush-like divided fibres proceed, which ultimately end with a point in nucleated plates, the nerve flakes of Rollett. According to Sachs, bodies like end bulbs occur in tendons, while Rauber found Vater's corpuscles in their sheaths; Golgi found, in a.Ai\{\on, sjiinJie-s/iaped terminal corptiscles, which he regards as a specific apparatus for estimating tension. 293. PHYSICAL AND CHEMICAL PROPERTIES OF MUS- CLE. — I. The consistence of the sarcous siib.stance is the same as that of living protoplasm, e. g., of lymph cells; it is semi-solid, /. e., it is not fluid to such a degree as to flow like a fluid, nor is it so solid that, when its parts are separated, these parts are unable to cotne together to form a continuous whole. The consis- tence may be compared to a jelly at the moment when it is dissolved (^. g., by heat). The power of imbibition is increased in a contracted muscle {Ranke). Proofs. — The following facts corroborate the view expressed above : {a) The analogy between the function of the sarcous substance and the contractile protoplasm of cells (| 9). (/;) The so- called Porret's phenomenon ( IV. Kiihne) which consists in this, that when a galvanic current is conducted through the living, fresh, sarcous substance, the contents of the muscular fibre exhibit a streaming movement from the positive to the negative pole (as in all other fluids), so that the fibre swells at the negative pole, (f) By the fact that wave movements have been observed to pass along the muscular fibre. (rig/it in the dark field of the micro- scope when the Nicols are crossed (J 297). During contraction of the muscular fibre, the contrac- tile part of the fibre becomes narrow-er, and at the same time broader, whilst the optical constants do not thereby undergo any change. Hence, Briicke concludes that the contractile disks are not simple bodies like crystals, but must consist of a whole series of small, doubly-refractive elements arranged in groups, which change their position during contraction and relaxation. These small elements Briicke called disdiaclasts. According to Schipiloft', Danielewsky, and O. Nasse, the contractile anisotropous substance consists of myosin, which occurs in a crystalline condition, and represents the disdiaclasts. According to Engelmann, however, all contractile elements are doubly refractive, and the direction of contraction always coincides with the optical axis. The investigations of v. Ebner have shown that during the process of growth of the tissue, ten- sion is produced — the tension of bodies subjected to imbiliition — which results in double refraction, and so gives rise to the condition called anisotropous. CHEMICAL COMPOSITION OF MUSCLE SERUM. 501 The chemical composition of muscle undergoes a great change after death, owing to the spontaneous coagulation of a proteid within the muscular fibres. As frog's muscles may be frozen and thawed, and still remain contractile, they cannot, therefore, be greatly changed by the process of freezing. W. Kiihne bled frogs, cooled their muscles to io° or 7° C, pounded them in an iced mortar, and ex- pressed their juice through linen. The juice so expressed, when filtered in the cold, forms a neutral, or alkaline, slightly yellowish, opalescent fluid, the so-called "muscle plasma." Like blood plasma, it coagulates spontaneously; at first it is like a uniform soft jelly, but soon becomes opaque ; doubly-refractive fibres and specks, similar to the fibrin of blood, appear in the jelly, and as these begin to contract, they squeeze out of the jelly an acid "muscle serum." Cold prevents or delays the coagulation of the muscle plasma ; above 0°, coagulation occurs very slowly, and the rapidity of coagulation increases rapidly as the tem- perature rises, while coagulation takes place very rapidly at 40° C. in cold-blooded animals, or at 48° to 50° C. in warm-blooded muscles. The addition of distilled water or an acid to muscle plasma causes coagulation at once. The coagulated proteid, most abundant in muscle, and which arises from the doubly-refractive substance, is called "myosin " (JF. Kuhne). Myosin. — It is a globulin (^ 245), and is soluble in strong fio per cent.) solutions of common salt, and is again precipitated from such a solution by dilution with water, or by the addition of very small quantities of acids (o. i to 0.2 percent, lactic or hydrochloric acid). It is soluble in dilute alkalies or slightly stronger acids (0.5 percent, lactic or hydrochloric acid), and also in 13 per cent, ammonium chloride solution. Like fibrin, myosin rapidly decomposes hydric peroxide. When treated with dilute hydrochloric acid and heat, it is changed into syntonin {\ 245). Myosin may be extracted fioni muscle by a 10 to 15 per cent, solution of NH^Cl, and if it be hca'ed to 65° it is precipitated again yDatiit'Uiuskv). Danielevvsky succeeded in partly changing syntonin into myosin by the action of milk of lime and ammonium chloride. Myosin occurs in other animal structures (cornea), nay, even in some vegetables (O. Nasse). Muscle serum still contains three proteids (2.3 to 3 per cent.), viz.: i. Alkali albuminate, which is precipitated on adding an acid, even at 20° to 24° C. 2. Ordinary serum albumin, 1.4 to 1.7 per cent. (§ 32, a), which coagu- lates at 73° C. 3. An albuminate which coagulates at 47° C. The other chemical constituents of muscle have been referred to in treating of fiesh (§ 233). I. Briicke found traces of pepsin and peptone in muscle juice; Piotrowsky, a trace of a diastatic ferment. 2. In addition to volatile fatty acids (formic, acetic, butyric), there are two isomeric forms q>{ lactic acid (CsHsOa) pre- sent in muscle with an acid reaction : (a) Ethylidene-lactic acid, in the inodifica- tion known as right rotatory sarcolaciic or paralactic acid, which occurs only in muscles, and some other animal structures, {b) Ethylene-lactic acid in small amount (§ 251, 3 c). It was formerly assumed that lactic acid is formed by fer- mentation from the carbohydrates of the muscle (glycogen, dextrin, sugar), and Maly has observed that paralactic acid is occasionally formed when these bodies undergo fermentation. According to Bohm, however, the glycogen of muscle does not pass into lactic acid, as during rigor mortis, if putrefaction be prevented, the amount of glycogen does not diminish. If muscle be suddenly boiled or treated with strong alcohol, the ferment is destroyed, and hence the acidification of the muscular tissue is prevented {Du Bois-jRtymond). Acid potassium phospkate also contributes to the acid reaction. 3. Caniin (CjHgNjOa), which is changed by bromine or nitric acid into sarkin, occurs to the extent of i per cent, in Liebig's extract of meat {IVeidcl). 4. Only o.oi per cent, of urea {Haycrafi). 5. Gly- cogen occurs to the amount of over \ per cent, after copious flesh feeding, and to 0.5 per cent, during fasting. It is stored up in the muscles, as well as in the liver, during digestion, but it disappears during hunger. It is perhaps formed in the muscles from proteids (§ 174, 2). 6. Lccitliin, derived in part from the motor nerve endings (§ 23 and § 251 ). 7. The gases are CO., (15 to 18 vol. per cent.), partly absorbed, partly chemically uniteil ; some absorbed N, but no O, although 502 METABOLISM IN MUSCLE. muscle continually absorbs O from the blood passing through it (Z. Hermann). The muscles contain a substance whose decomposition yields CO,. When muscles are exercised, this substance is used up, so that severely fatigued muscles yield less CO., {Stinzing). [It is to be remembered that all muscles have not the same chemical composition.] 294. METABOLISM IN MUSCLE.— I. A passive muscle continu- ally absorbs a certain amount of U from the blood flowing through its capillaries, and returns a certain amount of CO, to the blood stream. The amount of CO2 given off is less than corresponds to the amount of O absorbed. Excised muscles freed from blood exhibit an analogous but diminished gaseous exchange {Du Bois-Reymond, G. Liebig). As an excised muscle remains longer excitable in O or in air than in an atmosphere free from O, or in indifferent gases {Al. v. Hum- boldf), we must conclude that the above-named gaseous exchange is connected with the normal metabolism, and is a condition on which the life and activity of the muscle depends. If a living muscle be exciserl, and if blood be perfused through its blood vessels, the amount of O used up is, within pretty wide limit*, almost independent of temperature ; if the variations of temperature be great, it rises and falls with the temperature. The CO2 given off by muscular tissue falls when the muscle is cooled (less than the O used up), but it is not increased when the muscle is subsequently warmed {Rubner). This exchange of gases must be distinguished from the putrefactive phenomena due to the devel- opment of living organisms in the muscle. These putrefactive phenomena are also connected with the consumption of O and the excretion of CO,, and occurs soon after death (Z. Hermann). II. In an active muscle the blood vessels are always dilated {Litdwig and Sczelkoio, Gaskell) — a condition pointing to a more lively material exchange in the organ. Hence, the active muscle is distinguished from the passive one by a series of chemical transformations. 1. Reaction. — The neutral or feebly alkaline reaction of a passive muscle (also of the non-striped variety) passes into an acid reaction during the activity of the muscle, owing to the formation of paralactic acid {^Dii Bois-Rcymond, iS^g) ; the degree of acidity increases up to a certain extent, according to the amount of work performed by the muscle {R. Heidenhain). The acidification is due, according to Weyl and Zeitler, to the phosphoric acid produced by the decomposition of lecithin and (? nuclein). It is doubtful if the acidity is due to lactic-acid, as Warren and Astaschewsky find that there is less lactic acid in the active than in the passive muscle. 2. Production of CO,. — An active muscle excretes considerably more COj than a passive one : (a) active muscular exertion on the part of a man or of ani- mals increases the amount of CO, given off by the lungs (§127); {b) venous blood flowing from a tetanized muscle of a limb contains more CO..,, more CO2 being formed than corresponds to the O, which has simultaneously been absorbed (Ludwig and Sczelko7(.i). The same result is obtained when blood is passed through an excised muscle artificially ; {c) an excised muscle caused to contract excretes more CO, {Mattcucci, Valentin). 3. Consumption of Oxygen. — An active muscle uses up more O — {a) when we do muscular work, the bod) absorbs much more O (p. 366) — even 4 to 5 times as much (^Regnauli and Reisef ) : (b) venous blood flowing from an active muscle of a limb contains less O (Liidwig. Sczclkmo and Al. Sclimidt). Nevertheless, the increase of O used up by the active muscle is not so great as the amount of CO, given off {y. Pettenkofer and v. Voit). The increase of O used up may be ascer- tained even during the period of rest directly following the period of activity, and the same is the case with the CO, excreted (?■. Frey). As yet, it is not possilile to prove, by gasometric methods, that O is used up in an excised muscle free from blood. Indeed, the presence of O does not METABOLISM IN MUSCLE. 503 seem to be absolutely necessary for the activity of muscle during short periods, as an excised muscle may continue to contract in a vacuum, or in a mixture of gases free from O, and no O can be obtained from muscular tissue (Z. Hermann). A frog's muscles rob easily reducible substances of their O ; they discharge the color of a solution of indigo ; muscles which have rested for a time, acting less ener- getically than those which have been kept in a state of continued activity ( Griitz- 7ier, Gscheidlen). 4. Glycogen. — The amount of glycogen (0.43 per cent, in the muscles of a frog or rabbit ) and grape sugar is diminished in an active muscle ( O. Nassc, JVass), but muscles devoid of glycogen do not lose their excitability and contractility. Hence, glycogen is certainly not the direct source of the energy in an active muscle. Perhaps it is to be sought for in an as yet unknown decomposition product of glycogen (^Luchsinger). [There is more glycogen in the red than in the pale muscles of a rabbit.] 5. Extractives. — An active muscle contains less extractive substances soluble in water, but more extractives soluble in alcohol {v. Hebnholtz, 1843") > •' ^'so contains less of the substances which form CO.j {Hanke) ; less fatty acids (Sczelkow) ; less kreatin and kreatinin (v. Voif). 6. During contraction, the amount of water in the muscular tissue increases, while that of the blood is correspondingly diminished (J. Ranke). The solid substances of the blood are increased, while they (albumin) are diminished in the lymph ( Fano). 7. Urea. — The amount of urea excreted from the body is not materially increased during muscular exertion (v. Voif, Fick and IVis/iceniis). According to Parkes, however, although the excretion of urea is not increased immediately, yet after i to i}i days there is a slight increase. The amount of work done cannot be determined from the amount of albumin which is changed mto urea. [Relation of Muscular Work to Urea — Ed. Smith, Parkes and others have made numerous investigations on this subject. Fick and Wislicenus (1S66) ascended the Faulhorn, and for seven- teen hours before the ascent and for si.\ hours after the ascent no proteid food was taken — tlie diet, consisting of cakes made of fat, sugar and .starch. The urine was collected in three periods, as follows : — Fick. Wislicenus. 1. Urea of 11 hours before the ascent . . 2. " 8 " during " . . 3. " 6 " after " . . 238 55 grs. 221.05 gr^- 79.S9 " j ^^^ A hearty meal was taken after this period, and the urine of the next eleven hours after the period of rest coiitamed 159.15 grains of urea f/iV/'), and 176 71 ( IVisiitenus). All the e.xperimciits go to show that the amount of urea excreted in the urine is far more dependent upon the nitrogen ingested, i.e., the nature of the food, than upon the decomposition of the muscular substance. A vegetable diet diminishes, while an animal diet greatly increases, the amount of urea in the urine. North's researches confirm those of Parkes, Ijut he finds that the disturbance produced by severe muscular labor is considerable. The elimination of phosphates is not affected, while the sulphates in the urine are increased.] During the activity of a muscle, a!/ the groups of the chemical substances present in muscle undergo more rapid transformations (_/. Ranke). It is still a matter of doubt, therefore, whether we may assume that the kinetic energy of a muscle is chiefly due to the transformation of the chemical energy of the carbo- hydrates which are decomposed or used up in the process of contraction. As yet we do not know whether the glycogen is supplied by the blood stream to the muscles, perhaps from the liver, or whether it is formed within the muscles them- selves from some unknown derivative of the proteids. The normal circulation is certainly one of the conditions for the formation of glycogen in muscle, as gly- cogen diminishes after ligature of the blood vessels (JOhandehm). A muscle in 504 STAGES OF CADAVERIC RIGIDITY. which the blood circulates freely is capable of doing more work than one devoid of blood {Hanke), and even in the intact body more blood is always supplied to the contracted muscles. 295. RIGOR MORTIS. — Cause. — Excised striped, or smooth muscles, and also the muscles of an intact body, at a certain time after death, pass into a con- dition of rigidit) — cadaveric rigidity or rigor mortis. When all the muscles of a corpse are thus affected, the whole cadaver becomes completely stiff or rigid. The cause of this phenomenon depends upon the spontaneous coagulation of a proteid, viz., the myosin of the muscular fibre {Kiihiie), in consequence of the formation of a small amount of an acid. Under certain circumstances, the coagulation of the other proteids of the muscle may increase the rigidity. During the process of coagulation, heat is set free {v. Walthcr, Fick — § 223), owing to the passage of the fluid myosin into the solid condition, and also to the simultaneous and subsequently increased density of the tissue. Properties of a Muscle in Rigor Mortis. — It is shorter, thicker and some- what denser (Schiiiiileioitsili, U\illt-r) ; stiff, compact and solid; turbid and opaque (owing to the coagulation of the myosin) ; incompletely elastic, less extensible, and more easily torn or ruptured ; it is completely inexcitable to stimuli ; the muscular electrical current is abolished (or there is a slight current in the opposite direction) ; its reaction is acid, owing to the formation of both forms of lactic acid (§ 293) glycero-i)hosphoric acid (Diakanow) ; while it also develops free COj. When an incision is made into a rigid muscle, fluid (^muscle serum, p. 501) appears spontaneously in the wound. The first formed lactic acid converts the salts of the muscle into acid salts ; thus potassium lactate and acid potassium phosphate are fonned from potassium phosphate. The lactic acid, which is formed thereafter, remains fiee and ununited in the muscle. Amount of Glycogen. — The newest observations of Bohm are against the view that, during rigor mortis, a partial or complete transformation of the glycogen into sugar and then into lactic acid takes place. During digestion, a temporary storage of glycogen occurs in the muscles as well as in the liver, so that about as much is found iu the muscles as in the liver. There is no diminu- tion of the glycogen when rigidity takes place, provided putrefaction be prevented ; so thai the lactic acid of rigid muscles cannot be formed from glycogen, but more probably it is formed from the decomposition of the albuminates [Demant^ Bohm). The amount of acid does not vary, whether the rigidity occurs rapidly or .slowly (J. Xanie) ; when acidification begins, the rigidity becomes more marked, owing to the coagulation of the alkali albuminate of the muscle. Less CO, is formed from a rigid muscle, the more CO2 it has given off previously, during muscular exertion. A rigid muscle gives off N and absorbs O. In a cadaveric rigid muscle, fibrin ferment is present (.41. SchmiJt anJ others). It seems to be a product of pro- toplasm, and is never absent where this occurs [Rauschenbach'). [Rigor Mortis and Coagulation of Blood. — Thus there is a marked analogy between the coagulation of the blood and that of muscle. In both cases, a fluid body yields a solid body, fibrin from blood, and myosin from muscle, and there are many other points of analogy (p. 506).] Stages of Rigidity. ^ — Two stages are recognizable in cadaveric muscles: In the first stage, the muscle is rigid, but still excitable; in this stage the myosin seems to be in a jelly-like condition. Restitution is still possible during this stage. In the second stage, the rigidity is well pronounced, with all the phe- nomena above mentioned. The onset of the rigidity varies in man from ten minutes to seven hours [and it is complete, as a rule, within four to six hours after death. The muscles of the jaws are first affected, then those of the neck and trunk, afterward (as a rule) the lower limbs, and finally the upper limbs]. Its duration is equally variable — one to six days. After the cadaveric rigidity has disappeared, the muscles, owing to further decotnpositions and an alkaline reaction, become soft and the rigidity dis- appears (Nysten, Sommer). The onset of the rigidity is always preceded by a loss of nervous activity. Hence, the muscles of the head and neck are first affected, and the other muscles in a descending series (§ 325). Disappearance of the rigid- EFFECTS OF HEAT AND WATER ON MUSCLE. 505 ity occurs first in the muscles first affected (A^ysteit). Great muscular activity be- fore death (e.g., spasms of tetanus, cholera, strychnin, or opium poisoning) causes rapid and intense rigidity ; hence the heart becomes rigid relatively rapidly and strongly. Hunted animals may become affected within a few minutes after death. [This is often seen in the fox.] Usually the rigidity lasts longer the later it occurs. Rigidity does not occur in a foetus before the seventh month. A frog's muscle cooled to o° C. does not begin to exhibit cadaveric rigidity for four to seven days. Stenson's Experiment. — The amount of blood in a muscle has a marked effect upon the onset of the rigidity. Ligature of the muscular arteries causes at first in all mammals an increase of the muscular excitability and then a rapid fall of the excitability {Schmiiletvitsch ) ; thereafter stiffness occurs, the one stage following closely upon the other (Swammerdam, Nic. Sfenson, i66j). [If the ligature be removed in the first stage, the muscle recovers, but in the later stages the rigidity is permanent.] If the artery going to a muscle be ligatured, Stannius observed that the excitability of the motor nerves disappeared after an hour, that of the mus- cular substance after four to five hours, and then cadaveric rigidity set in. Pathological. — When the blood vessels of a muscle are occluded, by coagulation taking place within them \ Lmidois), rigidity of the muscles is produced (^ 102). True cadaveric rigidity may be produced by too tight bandaging ; the muscles are paralyzed, rigid, and break up into flakes, while the contents of the fibre are afterward absorbed (R. Volkmann). Occlusion of the blood vessels of muscles by infarcts, especially in persons with atheromatous arteries, roay even cause necrosis of the muscles implicated (Finc/t, Girandcaii). If the circulation be reestablished during the first stage of the rigidity, the muscle soon recovers its excitability {Stannius). When the second stage has set in, restitution is impossible (Kiihne). In cold-blooded animals, cadaveric rigidity does not occur for several days after ligaturing the blood vessels. Brown-Sequard, by injecting fresh oxygenated blood into the blood vessels, succeeded in restoring the excitability of the muscles of a human cadaver four hours after death, /. e., during the first stage of cadaveric rigidity. Ludwig and Al. Schmidt found that the onset of cadaveric rigidity was greatly retarded in excised muscles, when arte- rial blood was passed through their blood vessels. Blood deprived of its O did not produce this effect. Cadaveric rigidity occurs relatively early after severe hemorrhage. If a weak alkaline fluid be conducted through the dead muscles of a frog, cadaveric rigidity is prevented [Schipi/off). Section of Nerves. — Preliminary section of the motor nerves causes a later onset of the rigidity in the corresponding muscles {Brown-Scqiiard, Heineke). Perhaps this is caused by the greater accumulation of blood in the paralyzed parts (due to section of the vasomotor nerves). In fishes, whose medulla oblongata is suddenly destroyed, cadaveric rigidity occurs much more slowly than in those ani- mals that die slowly {Blane). Rigidity may be produced artificially by various reagents : — 1. Heat [" Heat stiffening " (Fickfonf)'] causes the myosin to coagulate at 40° C. in cold-blooded animals, in birds about 53^ C, and in mammals at 48° to 50° C. The protoplasm of plants and animals, e. g., of the amoeba, is coagulated by heat, giving rise to heat rigor. Schmulewitsch found that the longer a muscle had been excised from the bo(ly, the greater was the heat required to produce stiffening. Heat stiffening differs from cadaveric rigidity thus: a 13 per cent, solution of ammonium chloride dissolves out the myosin from a cadaveric rigid muscle, but not from one rendered rigid by heat (S<-/i!/>iloff). If the rigid cadaveric muscles of a frog be heated, another proteid coagulates at 45°, and Lastly at 75° the serum albumin itself. Hence, both processes together make the muscle more rigid (J 295). 2. When a muscle is saturated with distilled water, it produces " water stiffening " — an acid reaction being developed at the same time. Muscles rendered stiff by water still exhibit electro-motive phenomena, while muscles rendered rigid by ether means do not (BicJermann). If the upper limb of a frog be ligatured, deprived of 506 MUSCULAR EXCITABILITY. its skin, and dipped in warm water, it becomes rigid. If the ligature he removed and the circulation reestablished, the rigidity may be partially set aside. If there be well-marked rigidity, it can only be set aside by placing the limb in a lo per cent, solution of common salt, wliich dissolves the coag- ulum of myosin (Pieyer). 3. Acids, even CO.,, rapidly produce "acid stiffening," which is probably different from ordinary stiffening, as such muscles do not evolve any free COj (Z. Hennanii). The injection of o.i to 0.2 per cent, solutions of lactic or hydro- chloric acid into the muscles of a frog produces stiffening at once, which may be set aside by injecting 0.5 per cent, solution of an acid, or by a solution of soda, or by 15 per cent, solution of ammonium chloride. The acids form a compound with the myosin {Sihipi/off). 4. Freezing and thawing a part alternately, rapidly produces stiffening ; and it is aided by mechanical injuries. Poisons. — Rigor mortis is favored by quinine, caffein, digitalin, [a concentrated solution of caffein or digitalin, applied to the muscle of a frog, produces rigor mortis,] veratrin, hydrocyanic acid, ether, chloroform, the oils of mustard, fennel, and aniseed ; direct contact of muscular tissue with potassium sulphocyanide (Bernard, Setulu'now),zxmaom?i, alcohol, and metallic salts. Position of the Body. — The attitude of the body during cadaveric rigidity is generally that occupied at death ; the position of the limbs is the result of the varying tensions of the different muscles. During the occurrence of rigor mortis, a limb, or more frequently the arm and fingers, may move {Sojiimer). Thus, if stiffening occurs rapidly and firmly in certain groups of muscles, this may produce movements, as is sometimes seen in cholera. If cadaveric rigidity occurs very rapidly, the body may occupy the same position which it did at the moment of death, as sometimes happens on the battle-field. In these cases it does not seem that a contracted condition of the muscle passes at once into rigor mortis; but between these two conditions, according to Briicke, there is always a very short relaxation. Muscles which have been plunged into boiling water do not undergo rigor mortis, neither do they become acid (Dii Bnis- KayiiiniiJ), nor evolve free CO, {L. Hermann). Analogy between Contraction and Rigidity. — L. Hermann has drawn attention to the analogy which exists between a muscle in a state of contraction and one in a state of cadaveric rigidity — both evolve CO2 and the other acids from the same source. The form of the contracted and the stiffened muscle is shorter and thicker; both are denser, less elastic, and evolve heat ; in both cases, the muscular contents behave negatively as regards their electro-motive force, in refer- ence to the unaltered, living, resting sulxstance. Hence he is inclined to regard a muscular contrac- tion as a temporary, physiological, rapidly disappearing rigor, whilst other observers regard stiffen- ing as in a certain sense the last flickering act of a living muscle. Work done during Rigidity. — .\ muscle in the act of becoming stiff will lift a weight, but the height to which it is lifted is greater with small weights, but less with heavier weights, than when a living muscle is stimulated with a maximal stimulus. Disappearance of Rigidity. — When rigor mortis passes off, there is a con- siderable amount of acid formed in the muscle, which dissolves the coagulated myosin. After a time putrefaction sets in, accompanied by the presence of micro-organisms and the evolution of ammonia and putrefactive gases (H„S, N, C0,-§ 184). According to Onimus, the loss of excitability which precedes the onset of rigor mortis occurs in the following order in man: Left ventricle, stomach, intestine (55 minutes) ; urinary bladder, right ventricle (60 minutes) ; iris (105 minutes); muscles of face and tongue (iSo minutes) ; the extensors of the extremities (about one hour before the flexors) ; the muscles of the trunk (five to six hours). The oesophagus reinains excitable for a long time (^ 325). 296. MUSCULAR EXCITABILITY.— By the term excitability or irritability of a muscle, is meant that property in virtue of which a muscle shortens when it is stimulated. The condition of excitement is the active condi- tion of a muscle produced by the application of stimuli, and is usually indicated by the act of contraction. Stimuli are simply various forms of energy, and they throw the muscle into a state of excitement, while at the moment of activity the chemical energy of the muscle is transformed into work and heat, so that stimuli act as liberating or " discharging forces." The normal temperature of the body is most favorable for maintaining the normal muscular excitability ; the ex- citability varies as the temperature rises or falls. ACTION OF CURARA. 507 As long as the blood stream within a muscle is uninterrupted, the first effect of stimulation of a muscle is to increase its energizing power, partly because the circulation is more lively and the blood vessels are dilated, but after a time the energizing power is diminished. Even in excised muscles, especially when the large nerve trunks have already lost their excitability, the excitability is increased after a stimulus, so that the application of a series of stimuli of the same strength causes a series of contractions which are greater than at first {J Fund/). Hence, we account for the fact that, although the first feeble stimulus may be unable to discharge a contraction, the second may, because the first one has increased the muscular excitability (Fick). Effect of Cold. — If the muscles of a frog or tortoise be kept in a cool place, they may remain excitable for ten days, while the muscles of warm-blooded animals cease to be excitable after one and a half to two and a half hours. (For the heart, see ^ 55.) .\ muscle, when stimulated direclly, always remains excitable for a longer time when its motor nerve is already dead. [Independent Muscular Excitability. — .Since the time of .Albrecht v. Haller and R. Whytt, physiologists have ascribed to muscle a condition of excitability which is entirely independent of the existence of motor nerves, and which depends on certain constituents of the sarcous substance. Excitability, or the property of responding to a stimulus, is a widely distributed function of proto- plasm or its modifications. A colorless blood corpuscle or an amieba is excitable, and so are secre- tory and nerve cells. In the first cases, the application of a stimulus results in motion in an indefi- nite direction, in the second in a formation of the secretion, and in the third in the discharge of nerve energy. In the case of muscle, a stimulus causes movement in a definite direction, called a contraction, and depending on the contractility of the sarcous sulistance. There are many considera- tions which show that excitability is independent of the nervous system, although in the higher animals nerves are the usual medium through which the excitability is brought into action. Thus plants are excitable, and they contain no nerves.] Numerous experiments attest the " independent excitability " of muscle : I. There are chemical stimuli, which do not cause movement when applied to motor nerves, but do so when they are applied directly to muscle ; ammonia, lime water, carbolic acid. 2. The ends of the sartorius of the frog, in which no nerve terminations are observable by means of the microscope, contract when they are stimulated directly (Kiiline). 3. Curara paralyzes the extremities of the motor nerves, wliile the muscles themselves remain excitable (C/. Bernard, Kolliker). The action of cold, or arrest of the blood supply in an animal, abolishes the excita- bility of the nerves, but not of the muscles at the same time. 4. After section of its nerve, a muscle still remains excitable, even after the nerves have undergone fatty degeneration { B rown- Si'quard , Bidder). 5. Sometimes electrical stimuli act only upon the nerves and not upon the muscle \\.%t\{ (BrUcke). [6. The fcetal heart contracts rhythmically before any nervous structures are discoverable in it.] [The Action of Curara. — Curara, woorali, urari, or Indian arrow poison of South America, is the inspissated juice of the Strychnos crevauxi. A watery extract of the drug, when injected under the skin or into the blood of an animal, acts chiefly upon the motor nerve endings, and does not aft'ect the muscular contractility. An active substance, ciirarin, has been isolated from it fp. 510). I'oison a frog by injecting a few milligrammes into the dorsal lymph sac. In a few minutes after the poison is absorbed, the animal ceases to support itself on its fore limbs; it lies flat on the table, its limbs are paralyzed, and so are the respiratory movements in the throat. When completely under the action of the poison, the frog lies in any position, limp and motionless, neither exhibiting vol- untary nor reflex movements. If the brain be destroyed and the skin removed, on faradizing the sciatic ner\'e no contraction of the muscles of the hind limb occurs; but if the electrical stimulus be applied directly to the muscles, they contract, thus proving that curara poisons the motor connections and not the muscles. If the dose be not too large, the heart still continues to beat, and the vasomotor nerves remain active.] [Methods. — fi) This may be shown also by applying the drug locally. Bernard took two nerve-muscle preparations, put some solution of curara into two watch glasses, and dipped the nerve into one glass and the muscle into the other. The curara penetrated into both preparations, and he found, on stimu- lating the nerve which had been steeped in curara, that its muscle still contracted, so that the curara had not acted on the motor fibres ; while stimulation of the 508 ACTION OF CURARA. 02 with sciatic artery liga- tured. S P, spinal cord ; P, poisoned, N P, non- poisoned leg; M, gastroc- nemius muscles, afferent, efferent, nerve (after .■^utlter/ord and Brun- ton). Fig. 289. nerve of the other preparation produced no contraction, s.R _ although the corresponding muscle contracted. In this case, the curara had penetrated into the muscle and affected the intra-muscular nerve endings.] [(2) But it is the terminal or intra-muscular portions of the nerves, not the nerve trunk, which are paralyzed. Ligature the sciatic artery, or, better still, tie all the parts of the hind limb of a frog at the upper part of a thigh, except the sciatic nerve (Fig. 2S9). Inject curara into the dorsal lymph sac. The poisoned blood will, of course, cir- culate in every part of the body except the ligatured limb. [The shaded parts are traversed by the poison.] The animal can still, at a certain stage of the poisoning, pull up the non-poisoned limb, while it cannot move the poisoned one. At this time, although poisoned blood has circulated in the sacral and intra-abdominal parts of the nerves, yet they are not paralyzed, so that the poison does not act on this part of the trunk of the nerve. But we can show that it does not act on any part of the extra-muscular trunk of the nerve. This is done by ligaturing the arteries going to the gastrocnemius muscle, and then poisoning the animal. On stimulating the nerve on the ligatured side, the gas- trocnemius of that side contracts, although the whole length of the nerve trunk has been supplied by poisoned blood. Therefore, it is ihe infra-muscular terminations oi the nerves which are acted on.] [By means of the following arrangement, we may prove that the actual termina- tions or end plates are paralyzed. Ligature the sciatic artery of one leg of a frog, and then inject curara into a lymph sac. After the animal is fuUv poisoned, dissect out the whole length of the sciatic nerve in both legs, leaving all the muscles below the knee joint, then clean and divide the femur at its middle. Pin a straw flag to each limb, and fix both femora in a clamp, or muscle forceps, with the gastroc- nemii uppermost, as in Fig. 290. Place the two nerves, N, on Du Bois-Reymond's electrodes (Fig. 291), attached to two wires coming from a commutator, C (Fig. 290). From two other binding screws of the commutator, two wires pass and are made to pierce the gastrocnemii. The other two binding screws of the commu- tator are connected with the secondary coil of a Du Bois-Reymond's induction machine (§ 330). The bridge of the commutator can be turned so as to pass the current either through both muscles or both nerves — the latter is the case in the diagram (^H). When both nerves are stimulated, only the non-poisoned leg (N P) contracts. Reverse the commutator, and pass the current through both muscles, when both contract.'] [Rosenthal's Modification. — Pull the secondary coil far away from the primary, and pass the current through both muscles. Gradually approximate the secondary to the primary coil, and in doing so it will be found that the non-poisoned leg contracts first, and on continuing to push up the secondary coil botii limbs contract. Thus the poisoned limb does not respond to so feeble a faradic stimulus as the non poisoned one, a result which is not due to the action of the curara on the excitability of the muscle. The non-poisoned limb responds to a feebler stimulus because its motor nerve terminations are not paralyzed, while the poisoned leg does not do so, because the motor ter- minations are paralyzed. A feebler induced shock suffices to cause a muscle to contract when it is applied to the nerve than when it is applied to the muscle itself directly. In large doses, curara also affects the spinal cord.] The whole question of " specific muscular excitability " has entered upon a new phase, owing to the researches of Gerlach on the terminations of motor nerves in muscle. Since it has been shown that a nerve fibre, after penetrating the sarcolemma, breaks up into inter- fibrillar threads, which come into direct relation with the sarcous substance, we can scarcely speak of an isolated stimulation of a muscle, for all stimuli which are applied to a muscle must at the same time act on the iTerve, for the muscle is the proper end organ of a motor nerve. MUSCULAR AND CHEMICAL STIMULI OF MUSCLE. 509 Neuro- Muscular Cells. — Even in the lower animals, e.^.. Hydra [Alemenlieig), and Medusa (Eimer) there are uni-cellular structures caWeA" nc!iro-mi(sciiiar cel/s" in which the nervous and muscular substances are represented in the same cell. [The outer part of these cells is adapted for the action of stimuli, and corresponds to the nervous receptive organ, while the inner deeper part is contractile, and is the representative of the muscular part.] Muscular Stimuli. — Various stimuli cause a muscle to contract, either by act- ing upon its motor nerve (indirect), or upon the muscular substance itself (direct) (j; 324). 1. Under ordinary circumstances, the normal stimulus causing a muscle to contract is the nerve impulse which passes along a curve, but its exact nature is unknown, e.g., in vokmtary movements, automatic motor movements, and reflex acts. 2. Chemical Stimuli. — \\\ chemical substances, which alter the chemical composition of a muscle with sufficient rapidity, act as muscular stimuli. Accord- ing to Kiihne, mineral acids (HCl o.i) per cent., acetic and oxalic acids, the Fig. 290. Scheme of the curara experiment. B,batler>' : I, primary; II. secondary spiral; N, nerves; F, clamp; N P, ncn-poisoned leg; P. poisoned leg ; C, commutator; K, key (after Rutlu-r/ord). Du Bois-Reymond's platinum electrode over the two pieces of platinum, P, B, universal joint; V, support. salts of iron, zinc, copper, silver and lead, bile (Budge), all act in weak solutions as muscular stimuli ; while they act upon the motor nerve only when they are more concentrated. Lactic acid and glycerin, when concentrated, excite only (?) the nerve ; when dilute, only the muscle. Neutral alkaline salts act equally upon nerve and muscle ; alcohol and ether act on both very feebly. When water is injected into the blood vessels, it causes fibrillar muscular contractions {v. Wittich'), while a 0.6 per cent, solution of NaCl may be passed through a muscle for da}s without causing contraction i^Kolliker, O. Nasse). .4cids, alkalies and extract of flesh diminish the muscular excitability, while the muscular stimuli, in small doses, increase it (Ranke^. Gases and vapors stimulate muscle ; they cause either a simple contraction (e.g., HCl), or at once permanent contraction or con- tracture (e.g., CI). Long exposure to the gas causes rigidity. The vapor of bisulphide of carbon stimulates only the nei-oes, while most vapors (e.g., HCl) kill without exciting them {Kiihne ami Jani). 510 THERMAL, MECHANICAL AND ELECTRICAL STIMULI OF MUSCLE. Method. — In making experiments upon the chemical stimulation of muscle, it is inadvisable to dip the transverse section of the muscle into the solution of the chemical reagent {/iering). The chemical stimulus ought to be applied in solution to a limited portion of the uninjured surface of the muscle ; after a few seconds, we obtain a contraction or fibrillar twitchings of the superficial muscular layers \hering). [Rhythmical Contraction. — While rhythmical contractions are very marked in smooth muscle (especially if it is stretched or subjected to considerable internal pressure, as in the hollow viscera), eg., the intestine, uterus, ureter, blood vessels, and also in the striped but involuntary cardiac mus- culature (j, 58), they are not, as a rule, very common in striped voluntary muscle. Chemical stimuli are particularly effective in producing them,] If the sartoriusof a curarized frog be dipped into a solution composed of 5 grms. NaCl, 2 grms. alkaline sodium phosphate, and 0.5 grm. sodium carbonate in i litre of water, at io° C, the muscle contracts rhythmically, and may do so for several days [especially with a low temperature] (Bieihrmann). This recalls the rhythmical con- traction of the heart. [KUhne found a similar result. The rhythm is arrested by lactic acid and restored by an alkalme solution of NaCl.] Rhythmical movements may also be induced in the sartorius (frog), by the combined action of a dilute solution of sodic carbonate and an ascending constant electrical current. Compare also the action of a constant current on the heart (J 58). 3. Thermal Stimuli. — If an excised frog's muscle be rapidly heated toward 28"' C, a gradually increasing contraction occurs, which, at 30° C, is more pro- nounced, reaching its rnaximum at 45° C. (^EckharJ, Schiimlcwitsch). If the temperature be raised, "heat stiffening" rapidly ensues. The smooth muscles of warm-blooded animals also contract when they are warmed, but those of cold- blooded animals are elongated by heat (Griinhagen, Samkowy). If a frog's muscle be cooled to 0°, it is very excitable to mechanical stimuli (^Griinhagen) ; it is even excited by a temperature under 0° {Eckhard). CI. Bernard observed that the muscles of animals, artificially cooled (| 225), remained excitable many hours after death. Heat causes the excitability to disappear rapidly, but increases it tempo- rarily. 4. Mechanical Stimuli. — Every kind of sudden mechanical stimulus, pro- vided it be applied with sufficient rapidity to a muscle (and also to a nerve), causes a contraction. If stimuli of sufficient intensity be repeated with sufficient rapidity, tetanus is produced. Strong local stimulation causes a weal-like, long- continued contraction at the part stimulated (§ 297, 3, a). Moderate tension of a muscle increases its excitability. 5. Electrical Stimuli will be referred to when treating of the stimulation of nerve (§ 324). Other Actions of Curara. — When injected into the blood or subcutaneously, it causes at first paralysis of the intra-muscular enJs of tlie motor nerves (p. 507), while the muscles themselves re- main excitable ; the sensory nerves, the central nervous system, viscera, heart, intestine, and the blood vessels are not affected at first [CI. Bernard, A'Slliier). [If the skin be stimulated, the frog will still pull up the ligatured leg reflexly, although the other leg will remain quiescent; this shows that the sensory nerve and nerve centres are still intact ; but when the action of the drug is fully developed, no amount of stimulation of the skin or the posterior roots of the nerves will give rise to a reflex act. although the motor nerve of the ligatured limb is known to be excitable, hence it is probable that the nerve centres in the cord themselves are uliimatcly affected. If the dose be very large, the he.art and blood vessels may be affected.] In warm-blooded animals, death takes place by asphyxia, owing to paralysis of the diaphragm, but of course there are no spasms. In frogs, where the skin is the most important respiratory organ, if a suitable dose be injected under the skin, the animal may remain motionless for days and yet recover, the poison being eliminated by the urine [JCii/ine, Bidder'). If the dose be larger, the inhibitory fibres of the vagus may be para- lyzed. In electrical fishes, the sensory nerves concerned with the electrical discharge are paralyzed {^Alarey). In frogs, the lymph hearts are paralyzed. A dose sufficient to kill a frog, when injected under its skin, will do so if administered by the mouth, because the poison seems to be eliminated as rapidly by the kidneys as it is absorbed from the gastric mucous membrane. For the same reason the flesh of an animal killed by curara is not poisonous when eaten. If, however, the ureters be tied, the poison collects in the blood, and poisoning takes place ( L. Hermann). [In this case the mammal may exhibit convulsions. Why ? The action of curara is to paralyze, and it para- lyzes the respiratory nerves, so that asphyxia is produced from the venosity of the blood. It affects the respiratory nerve endings before those in the muscles generally, so that w^hen the venous blood stimulates the nerve centres the partially affected muscles respond by convulsions. In this way, other narcotics may excite convulsions indirectly by inducing a venous condition of the blood, while the motor centres, nerves, and muscles are still unaffected.] Large doses, however, poison unin- TOTAL AND PARTIAL MUSCULAR CONTRACTION. 511 jured animals even when given by the mouth. The nerves [Funke) and muscles ( I'a/eittin) of poisoned animals exhibit considerable electro motive force. [For the effect of curaia on lymph formation (| igg, 6).] Atropin appears to be a specific poison for smooth muscular tissue, but different muscles are differently atlecttd [Szpi/niann, Luchsin^er). [This is oouUful. A small quantity of atropin seems to aft'ect the motor nerves of smooth muscle in the same way that curara does those of striped muscle; we must remember, however, that there are no end plates proper in the former, so that the link between the nerve tibrils and the contractile substance is probably difterent in the two ca^es. It is well known that the amount of striped and smooth muscle varies in the resophagus in different animals. Szpilmann and Luchs.nger find that after the action of atropin, stimulation of the periph- eral end of the vagus will stdl cause contraction of the striped muscular fibres in the oes.,phagus, but not of the smooth fibres, although 1 oth forms of muscular tissue respond to direct stimulation.] Excitability after Section of the Motor Nerves. — After section of the motor nerve of a muscle, the cxcitabihtv undergoes remarkable changes ; after three to four days the excitability of the paralyzed muscle is diminished, both for direct and indirect (/. e., through the nerve) stimuli ; this condition is followed by a stage, during which a constant current is more active than normal, while induction currents are scarcely or not at all effective (| 339, I). The excitability for mechan- ical stimuli is also increased. The increased excitability occurs until about the seventh week; it gradually diminishes until it is abolished toward the sixth to the seventh month. Fatty degenera- tion begins in the second week after section of the motor nerve, and goes on until there is complete muscular atrophy. Immediately after section of the sciatic nerve, bchmulewitsch found that the excitability of the muscles supplied by it was increased. 297. CHANGES IN A MUSCLE DURING CONTRACTION.— I. Macroscopic Phenomena. — i. When a muscle contracts, it becoiiies shorter and at the same time thicker. The degree of contraction, which in very excitable frogs may be 65 lo 85 per cent. (72 per cent, mean) of the total length of the muscle, depends upon various conditions: (a) Up to a cer- tain point, increasing the strength of the stimulus causes a greater degree of contraction ; (b) as the muscular fatigue increases, i. c. , after continued vigorous exertion, ihe stimulus remaining the same, the extent ol contraction is diminished ; (c; the temperature of the surroundings has a certain effect. The extent of the contraction is increased in a irog's muscle — the strength of stim- ulus and degree of fatigue remaining the same — when it is heated to 33° C. If the temperature be increased al)ove this point, the degree of contraction is diminished [Sc/imiilc-witsch). 2. The volume of a contracted inuscle is slightly diminished (Swammeniam, f 1680). Hence, the specific gravity of a contracted muscle is slightly in- creased, the ratio to the non-contracted muscle being 1062 : 1061 {^Valentiii) ; the diminution in volume is, however, only y^y^. Methods. — («) Ernian placed portions of the body of a live eel in a glass vessel filled with an indifferent fluid. A narrow lube communicated with the glass ves.sel, and the fluid rose in the tube to a certain level. As soon as the muscles of the eel were caused to contr,act, the fluid in the index tube sank, [b) Laudois demonstrates the decrease in volume by means of a manometric flame. The cylindrical vessel containing the muscle is provided with two electrodes fi.xed into it in an air- tight manner. The interior of the vessel communicates with the gas supply, while there is a small narrow exit tube for the gas, which is lighted. Every time the muscle contracts the flame dimin- ishes. The same experiment may be performed with a contracting heart. 3. Total and Partial Contraction. — Xormally, all stimuli applied to a muscle or Its motor nerve cause contraction in all its muscular fibres. Thus, the muscle conducts the state of e.xcitement to all its parts. Under certain circumstances, however, this is not the case, viz.: (a) when the muscle is greatly fatigued, or when it is about to die, a violent mechanical stimulus, as a vigorous tap with the finger or a percussion hammer (and also chemical or electrical stimuli !, cause a localized contraction of the muscular fibres. This is Schiff's " idio-muscular contraction." The same phenomenon is e.xhibited by the muscles of a healthy man, when the blunt edge of an instrument is drawn transversely over the direc- tion of the muscular fibres (J//V/;//;(7//jv/-, Auerbach). {I/') Under certain as yet but imperfectly unknown conditions, a muscle exhibits so-called fibrillar contrac- tions, i.e., short contractions occur alternately in different bundles of muscular fibres. This is the case in the muscles of the tongue, after section of the hypo- glossal nerve {Schiff) ; and in the muscles of the face, after section of the facial nerve. 512 MICROSCOPIC PHENOMENA OF MUSCULAR CONTRACTION. [In some phthisical patients there is marked muscular excitabilty, so that if the pectoral muscle be percussed, a local contraction — idio-niuscular — occurs, either confined to the spot, or two waves may proceed outward and return to the spot struck.] Cause of Fibrillar Contraction. — According to Bleuler and Lehmann, section of the hypo- glossal nerve in rabbits is followed by fibrillar contractions after sixty to eighty hours ; these con- tractions may continue for six m jnths, even when the divided nerve has healed and is stimulated above the cicatrix so as to produce movements in the corresponding half of the tongue. Stimulation of the lingual ner\'e increases the fibrillar contractions or arrests them. This nerve contains vaso- dilator fibres derived from the chorda tympani. .Schiff is of opinion that the increased blood stream through the organ is the cause of the contractions. Sig. Mayer found that, by compressing the carotids and subclavian, and again removing the pressure, so as to permit free circulation, the muscles of the face contracted. Section of the motor nerves of the face did not abolish the phe- nomenon, but compression of the arteries did. The cause of the phenomenon, therefore, seems to lie within the muscles themselves. This phenomenon may be compared to the paralytic secretion of saliva, and pancreatic juice which follows section of the nerves going to these glands (pp. 239, 284). Similar fibrillar contractions occur in man under pathological conditions, but they may also occur without any signs of pathological disturbance. [Fibrillar contractions, due to a central cause, occur in monkeys after excision of the thyroid gland ( K jYcri/cv, ? 103, III).] [Some drugs cause fibrillar muscular contractions, e. g., aconitin, guanidin, nicotin, pilocarpin, but physostigmin produces them in warm-blooded animals (not in frogs). According to Brunton, these drugs prob- ably act by irritating the motor nerve endings, as the contractions are gradually abolished by curara.] Fig. 292. licroscopic appearances during a muscular contraction in the individual elements of the librillae. Engelmann) ; 4, 5 (after Mcrkel). II. Microscopic Phenomena. — i. Single muscular yf/w/fe exhibit the same phenomena as an entire muscle, in that they contract and become thicker. 2. There is great difficulty in observing the changes that occur in the individual parts of a muscular fibre during the act of contraction. This much is certain, that the muscular elements become shorter and broader during contraction. Thus, it is evident that the transverse stride must appear to approach nearer to each other {Bowman, 1840). 3. There is great difference of opinion as to the behavior of the doubly-refractive (anisotropous) and the singly-refractive media. Fig. 292, I, on the left, represents, according to Engelmann, a passive muscular element — from £■ to (?is the doubly-refractive contractile substance, with the median disk, y a light lever connected with the muscle. If the muscle lever be " over%veighteii!' or overloaded, i.e., if the lever be loaded, so that when the lights, the course of the curve is varied according to the weight to be lifted. It is necessary, however, to support the lever in the intervals when the muscle is at rest. As the weights are increased, the occurrence of the contraction is delayed. This is due to the fact that the muscle, at the moment of stimulation, must accumulate as much energy as is necessary to lift the weight. The greater the weight the longer is the time before it is raised. Lastly, the muscle may be so " loaded," or " overloaded," that it cannot contract at all : this is the limit of the muscular or mechanical energy of the muscle (7'. Helmholtz). Fatigue. — If a muscle be caused to contract so frequently that it becomes "fati^i^ued," the latent period is longer, the curve is not so high, because the mus- cular contraction is less, and the abscissa is longer, /. e., the contraction is s/otver and lasts longer (Figs. 300, I, 312). Cooling a muscle has the same effect {v. Hehnholtz and others). Soltmann finds that the fresh muscles oi jinv-born animals behave in a similar manner. The myogram has a flat apex and considerable elon- gation in the descending limb of the curve. Constant Current. — If the motor nerve of a muscle be stimulated by a closing or opening shock of a constant earrent, the resulting muscular contraction cor- responds exactly to that already described. If, however, the current be closed or opened, with the muscle itself directly in the circuit, during the closing shock, there is a certain degree of contraction which lasts for a time, so that the curve assumes the form of Fig. 301, where S represents the moment of closing or making the current, and O the moment of opening or breaking it {Witndt — com- pare §336, D). The investigations of Cash and Kronecker show that individual muscles have a special form of muscle curve; the omohyoid of the tortoise contracts more rapidly than the pectoralis. Similar differences occur in the muscles of frogs and mammals. Tlie flexors of the frog contract more rapidly than the extensors ( Grii/zner). .Sometimes within one and the same muscle there are " red " (rich in glycogen) and "pale " fibres (^ 292). The red fibres contract more slowly, are less excitable and less easily fatigued (Grlilzner). The muscles of flying insects contract very rapidly, even more han 100 times per second. EFFECT OF VERATRIN AND OTHER POISONS ON MUSCLE. 519 Poisons. — Ver)' small doses of curara or quinine [ScktsL'ht'potiew) increase the height of the contraction (excited by stimulation of the motor nerve), while larger doses diminish it, and finally abolish it altogether. Guanidin has a similar action in large doses, but the maximum of contrac- tion lasts for a longer time. Suitable doses of veratrin also increase the contractions, but the stage of relaxation is greatly lengthened [Kosslnich anj Closterincytr). Veratrin, antiarin and digitalin, in large doses, act upon the sarcous substance in such a way that the contractions become very pro- longed, not unlike a condition of prolonged tetanus (I/ar/ess, /S6s). The latent period of muscles poisoned with veratrin and strychnin is shortened at first, and afterward lengthened. The gastroc- nemius of a frog supplied by blood containing soda contracts more rapidly [Griitziier). Kunkel is of opinion that muscular poisons act by controlling the imbibition of water by the sarcous substance. As muscular contr.action depends on imbibition (j 297, II), the fonn of the contraction of the poi- soned^muscle will depend upon the altered condition of imbibition produced by the drug. Fig. ^oo. I, Contraction of ayatignei/ irog's muscle writing its vibration = o.oiert second ; a /> = latent period ; & c The most rapid writing movements of the right hand bling tetanic movements of the right forearm inscribe ion on a vibrating plate attached to a tuning fork. Each ge of increasing energy : c d,ai decreasing energy. II, :ribed on a vibrating plate. Ill, The most rapid trem- I the same plate. dl[Veratrin. — If a frog be poisoned with veratrin, and then be made to spring, it does so rapidly, but when it alights again the hind legs are extended, and they are only drawn up after a time. Thus, rapid and powerful contraction, with slow and prolonged relaxation, are the char.icter of the movements. In a muscle poisoned with veratrin the ascent is quick enough, but it remains con- tracted for a long time, so that this condition has been called " contracture." A single stimulation may cause a contraction lasting five to fifteen seconds, according to circumstances. Brunton and Cash find that cold has a marked effect on the action of veratrin ; in fact, its effect may be perma- nently destroyed by exposure to extremes of heat or cold. The muscle curve of a brainless frog Fig. ^01. and u,.. S, clnsing ; O, opening shock {Wundt). cooled artificially, and then poisoned by veratrin, occasionally gives no indications of the action of the poison until its temperature is raised, and this is not due to non-absoqition of the poison. Cold, therefore, abolishes or lessens the contracture peculiar to the veratrin curve. Similar results are obtained with salts of barium, and to a less degree by those of strontium and calcium (Bruiilon ,uulC'chnin { IVtt/ler), the side tupper curve) and not on the other (lower or fatigue curve). with the minimum of material, they afford the greatest resistance as a supporting structure or framework {H. v. Meyer, Culmann, Jul. Wolff). I. The joints permit the freest movements of one bone upon another [such as exist between the extremities of the bones of the limbs. In other cases, sutures are formed, which, while permitting no movement, allow the contents of the cavity which they surround to enlarge, as in the case of the cranium.] The articular end of a fresh bone is covered with a thin layer or plate of hyaline car- tilage, which in virtue of its elasticity moderates any shocks or impulses coinmunicated to the bones. The surface of the articular cartilage is perfectly smooth, and facilitates an easy gliding movement of the one surface upon the other. At the outer boundary line of the cartilage, there is fixed the cap- sule of the joint, which encloses the articular ends of the bones like a sac. The inner surface of the capsule is lined by a synovial membrane, which secretes the sticky, seini-fluid, synovia, moisten- ing the joint. The outer surface of the capsule is provided at various pans with bands of fibrous tissue, some of which strengthen it, while others restrain or limit the movements of the joint. Some osseous processes limit the movements of particular joints, e. g., the coronoid process of the ulna, which permits the forearm to be flexed on the upper arm only to a certain extent ; the olecranon, which prevents over-extension at the elbow joint. The joint surfaces are kept in apposition— ( i ) by the adhesion of the synovia-covered smooth articular surfaces; (2) by the capsule and its fibrous bands; and (3) by the elastic tension and contraction of the muscles. [Structure of Articular Cartilage.— The thin layer of hyaline encrusting cartilage is fixed by an irregular surface upon the corres^ionding surface of the head of the bone. In a vertical section through the articular cartilage of a bone, which has been softened in chromic or other suitable acid, we observe that the cartilage cells are flattened near the free surface of the cartilage, and their long axes are parallel to the surface of the joint ; lower down, the cells are arranged in irregular groups, 534 HINGE AND SCREW-HINGE JOINTS. and further down still, nearer the bone, in columns or rows, whose long axis is in the long axis of the bone. These rows are produced by transverse cleavage of pre existing cells. In the upper two-thirds or thereby the matrix of the cartilage is hyaline, but in the lower third, near the bone, the matrix is granular and sometimes tibrillaled. This is the calcified zone, which is impregnated with lime salts, and shaqjly defined by a nearly straight line from the hyaline zone al)0ve it, and by a bold wavy line from the osseous head of the bone.] Synovial Membrane. — Synovi.^l membrane consists of bundles of delicate connective tissue mixed with elastic tissue, while on its inner surface it is provided with folds, some cf which contain fat, and others blood vessels (synovial villi). The inner surface is lined with endoth< hum. The intra-capsular ligaments and cartilages are not covered by the synovial membrane, nor are they covered by endothelium. The synovia is a colorless, stringy, alkaline fluid, with a chemical com- position closely allied to that of transud.itions, with this difference, that it contains much mucin, together with albumin and traces of fat. Excessive movement diminishes its amount, makes it more inspissated, and increases the mucin, but diminishes the salts. Joints may be divided in'to several classes, according to the kind of movement which they permit : — 1. Joints with movement around one axis : (a) The Ginglymus, or Hinge Joint. — The one articular surface represents a portion of a cylinder or sphere, to which the other surface is adapted by a corresponding depression, so that, when flexion or extension of the joint takes place, it moves only on one axis of the cylinder or sphere. The joints of the fingers and toes are hinge joints of this description. Lateral ligaments, which prevent a lateral displacement of the articular surfaces, are always present. The Screw-hinge Joint is a modification of the simple hinge form (Longer, Henke), e.g., the humcro-uinar articulation. Strictly speaking, simple flexion and extension do nut take place at the elbow joint, but the ulna moves on the capitellum of the humerus like a nut on a bolt ; in the right humerus the screw is a right spiral, in the left, a left spiral. The ankle joint is another ex- ample ; the nut or female screw is the tibial surface, the right joint is like a left-handed screw, the left the reverse, (b) The pivot joint (rotatoria), with a cylindrical surface, e.g., the joint between the atlas and the axis, the axrs of rotation being around the odontoid process of the axis. In the acts of pronation and supination of the forearm at the elbow joint, the axis of rotation is from the middle of the cotyloid cavity of the head of the radius' to the styloid process of the ulna. The other joints which assist in these movements are above the joint between the circumferential part of the head of the radius and the sigmoid cavity of the ulna, and below the joint between the sigmoid cavity of the radius which moves over the rounded lower end of the ulna. 2. Joints with movements arotinJ two axes. — (a) Such joints have two unequally curved surfaces which intersect each other, but which lie in the same direction, e. g., the atlanto occipital joint, or the wrist joint, at which lateral movements, as well as flexion and extension, take place, (b) Joints with curved surfaces, which intersect each other, but which do not lie in the same direction. To this group belong the saddle-shaped articulations, whose surface is concave in one direction, but convex in the other, e. g., the joint between the metacarpal bone of the thumb and the trapezium. The chief movements are — (l) flexion and extension, (2) abduction and adduction. Further, to a limited degree, movement is po.ssible in all other directions; and, lastly, a pyramidal movement can be described by the thumb. 3. Joints with movement on a spiral articular surface [spiral joints), e. g., the knee joint [Good- sir). The condyl of the femur, curved from before backward, in the antero-posterior section of its articular surface, represents a spiral (Ed. Weber'), whose centre lies nearer the posterior part of the condyle, and whose radius vector increases from behind, downward and forward. Flexion and extension are the chief movements. The strong lateral ligaments arise from the condyles of the femur corresponding to the centre of the spiral, and are inserted into the head of the fibula and in- ternal condyle of the tibia. When the knee joint is strongly flexed, the lateral ligaments are relaxed — they become tense as the extension increases; and when the knee joint is fully extended, they act quite like tense bands which secure the lateral fixation of the joint. Corresponding to the sj^iral form of the articular surface, fiexion and extension do not take place around one axis, but the axis moves continually with the p')int of contact; the axis moves also in a spiral direction. The greatest flexion and extension covers an angle of about 145°. The anterior crucial ligament is more tense during extension, and acts as a check ligament for too great extension, while the posterior is more tense during flexion and is a check ligament for too great flexion. The movements of extension and flexion at the knee are further complicated by the fact that the joint has a screw-like move- ment, in that during the greater extension the leg moves outward. Hence, the thigh, when the leg is fixed, must be rotated outward during fiexion. Pronation and supination take place during the greatest flexion to the extent of 41° (Albert) at the knee joint, while with the greatest extension it IS nil. It occurs because the external condyle of tjie tibia rotates on the internal. In all positions during flexion the crucial ligaments are fairly and uniformly tense, whereby the articular surfaces are pressed against each other. Owing to their arrangement, during increasing tension of the anterior ligament (extension), the condyles of the femur must roll more on to the anterior part of the articular ARRANGEMENT AND USES OF THE MUSCLES. 535 surface of the tibia, while by increasing tension of the posterior ligament (flexion) they must pass more backward. 4. Joints with the axis of rotation round one fixed point. — These are the freely movable arthrodial joints. The movements can take place around innumerable axes, which all intersect each other in the centre of rotation. One articular surface is nearly spherical, the other is cup- shaped. The shoulder and hip joints are typical "ball and socket joints." We may represent the movements as taking place around three axes, intersecting each other at right angles. The movements which can be performed at these joints may be grouped as: (l) pendulum like move- ments in any plane; (2) rotation round the long axis of the limb; and (3) circumscribing movements [circumduction], such as are made round the circumference of a sphere; the Centre is in the point of rotation of the joint, while the circumference is described by the limb itself. Limited arthrodial joints are ball joints with limited movements, and where rotation on the long axis is wanting, e.g., the metacarpo-phalangeal joints. 5. Rigid joints or amphiarthroses are characterized by the fact that movement may occur in all directions, but only to a very limited extent, in consequence of the very tough and unyielding external ligaments. Both articular surfaces are usually about the same size, and are nearly plane surfaces, e.g., the articulations of the cirpal and the tarsal bones. II. Symphyses, synchondroses, and syndesmoses unite bones without the formation of a proper articular cavity, are mov.able in all directions, but only to the very slightest extent. Physio- logically, they are closely related to amphiarthrodial joints. III. Sutures unite bones without permitting any movement. The physiological importance of the suture is that the bones can still grow at their edges, which thus renders possible the distention of the cavity enclosed by the bones (Herm. v. Jileyer). 306. ARRANGEMENT AND USES OF THE MUSCLES.— The muscles form 45 per cent, of the total mass of the body, those of the right side being heavier than those on the left (Ed. U'c/'er). Muscles may be arranged in the following groups, as far as their mechanical actions are concerned : — A. Muscles without a definite origin and insertion : — 1. The hollow muscles surrounding globular, oval, or irregular cavities, such as the urinary bladder, gall bladder, uterus, and heart ; or the walls of more or less cylindrical canals (intestinal tract, muscular gland ducts, ureters, Fallopian tubes, vasa deferentia, blood vessels, and lymphatics). In all these cases the muscular fibres are arranged in several layers, e.g., in a longitudinal and a circular layer, and sometimes also in an oblique layer. All these layers act together, and thus diminish the cavity. It is inadmissible to ascribe different mechanical effects to the different layers, e.g., that the circular fibres of the intestine narrow it, while the longitudinal dilate it. Both sets of fibres rather seem to act simultaneously, and diminish the cavity by making it narrower and shorter at the same time. The only case where muscular fibres may act in partially dilating the cavity is when, owing to pressure from without or from partial contraction of some fibres, a fold, projecting into the lumen, has been formed. When the fibres, necessarily stretching across the depression thereby produced, contract, they must tend to undo it, /. c\, enlarge the cavity. The various layers are all innervated from the same motor source, which supports the view of their conjoint action. 2. The sphincters surround an opening or a short canal, and by their action they either constrict or close it, e.g., sphincter papilla;, palpebrarum, oris, pylori, ani, cunni, urethrae. B. Muscles with a definite origin and insertion : — 1. The origin is completely fixed when the muscle is in action. The course of the muscular fibres, as they pass to where they are inserted, permits of the insertion being appro.\imated in a straight line toward their origin during contraction, e.g., the attolens, attrahens, and retrahentes of the outer ear, and the rhomboidei. Some of these muscles are inserted into soft parts which neces- sarily must follow the line of traction, e.g., the azygos uvulae, levator palati mollis, and most of the muscles which arise from bone and are inserted into the skin, such as the muscles of the face, styloglossus, stylopharyngeus, etc. 2. Both Origin and Insertion Movable. — In this case the movements of both points are inversely as the resistance to be overcome. The resistance is often voluntary, which may be increased either at the origin or insertion of the muscle. 536 VARIOUS KINDS OF LEVERS ACTED ON BY MUSCLES. Thus, the sternocleidomastoid may act either as a depressor of the head or as an elevator of the cliest ; the pectoralis minor may act as an adductor and depressor of the shoulder, or as an elevator of the 3d to 5th ribs (when the shoulder girdle is fixed). 3. Angular Course. — Many muscles having a fixed origin are diverted from their straight course ; either their fibres or their tendons may be hcnt out of the straight course. Sometimes the curving is slight, as in the occipito-frontalis and levator palpebrae superioris, or the tendon may form an angle round some bony process, whereby the muscular traction acts in quite a different direction, /. e., as if the muscle acted directly from this process upon its point of insertion, e.g., the obliquus oculi superior, tensor tympani, tensor veli palatini, obturator internus. 4. Many of the muscles of the extremities act upon the long bones as upon levers: ( A VARIOUS KINDS OF LEVER ACTION OF MUSCLES. 537 brachialis. Its moment in this position is = A, // E. When the radius is raised to E R,,then it is ^ A, a E. We must notice, however, that B Rj < B R. Hence, the absolute muscular force must be less in the flexed position, because every muscle, as it becomes shorter, lifts less weight. What is lost in power is gained by the elongation of the lever arm. 5. Many muscles have a double action ; when contracted in the ordinary way they execute a combined movement, e.g., the biceps is a flexor and supinator of the forearm. If one of these movements be prevented by the action of other muscles, the muscle takes no part in the execution of the other movement. If the forearm be strongly pronated and flexed in this position, the biceps takes no part therein ; or, when the elbow joint is rigidly supinated, only the supinator brevis acts, not the biceps. Tl e muscles of mastication are another example. The masseter elevates the lower jaw, and at the same time pulls it forward. If the depressed jaw, however, be strongly pulled backward when the jaw is raised, the masseter is not concerned. The temporal muscle raises the jaw, and at the same time pulls it backward. If the depressed jaw be raised after being pushed forward, then the ttm- poral is not concerned in its elevation. 6. Muscles acting on two or more joints are those which in their course from their origin to their insertion pass over two or more joints. Either the Scheme of the action of tendons may deviate from a straight course, if.^--. , the extensors and flexors of the fingers and toes, as when the latter are flexed ; or the direction is always straight, e.g., the gastrocnemius. The muscles of this group present the following points of interest: (a) The phenomenon of so-called " active insufficiency" (Hueter, Henke). If the position of the joints over which those muscles pass be so altered that their origin and insertion come too near each other, the muscle may require to contract so much before it can act on the bones attached to it, that it cannot contract actively any further than to the extent of the shortening from which it begins to be active, e.g., when the knee joint is bent the gastrocnemius can no longer produce plantar flexion of the foot, but the traction on the tendo Achilles is produced by the soleus. (/') " Passive insufficiency" is shown by many- jointed muscles under the following circumstances : In certain positions of the joint, a muscle may be so stretched that it may act like a rigid strap, and thus limit or prevent the action of other muscles, e.g., the gastrocnemius is too short to permit complete dorsal flexion of the foot when the knee is extended. The long flexors of the leg, arising. from the tuber ischii, are too short to permit com- plete extension of the knee joint when the hip joint is flexed at an acute angle. 538 GYMNASTICS, MASSAGE AND CHANGES IN MUSCLE. The extensor tendons of the fingers are too short to permit of complete flexion of the joints of the fingers when the hand is completely flexed. 7. Synergetic muscles are those which together subserve a certain kind of movement, c. .t,'-., the flexors of the leg, the muscles of the calf, and others. The abdominal muscles act along with the diaphragm in diminishing the abdomen during straining, while the muscles of inspiration or expiration, even the different origins of one muscle, or the two bellies of a biventral muscle, may be regarded from the same point of view. Antagonistic muscles ( Galen) are those which, during their action, have ex- actly the opposite effect of other muscles, e.g., flexors and extensors — pronators and supinators — adductors and abductors — elevators and depressors — sphincters and dilators — inspiratory and expiratory. When it is necessary to bring the full power of our muscles into action, we quite involuntarily bring them beforehand into a condition of the greatest tension, as a muscle in this condition is in the most favorable position for doing work (§300, I, 3 — Schwanti). Conversely, when we execute delicate movements requir- ing little energy, we select a position in which the corresponding muscle is already shortened. All the fascia; of the body are connected with muscles, which, when they contract, alter the ten- sion of the former, so that they are, in a certain sen.se, aponeuroses or tendons of the latter (A' Bariieleben). [For the importance of muscular movements and those of the fascist in connection with the movements of the lymph, see § 201.] 307. GYMNASTICS ; MOTOR PATHOLOGICAL VARIATIONS.— Gymnastic exercise is most important for the proper development of the muscles and motor power, and it ought to be commenced in both sexes at an early age. .Systematic muscular activity increases the volume of the muscles, and enables them to do more work. The amount of blood is increased with increase in the muscular development, while at the same time the bones and ligaments become more resistant. As the circulation is more lively in an active muscle, gymnastics favor the circula- tion, and ought to be practice!, especially by persons of sedentary habits, who are apt to suffer from congestion of the blood in the abdominal organs (f i'., hiemorrhoids), as it favors the move- ment of the tissue juices [^ 201]. An active muscle also uses more O and produces more CO,, so th.at respiration is also excited. The total increase of the metabolism gives rise to the feeling of well-being and vigor, diminishes abnormal irritability, and dispels the tendency to fatigue. The whole body becomes firmer and specifically heavier [jaifer). By Ling's, or the Swedish system, a systematic attempt is made to strengthen certain weak muscles, or groups of muscles, whose weakness might lead to the production of deformities These muscles are exercised systematically by opposing to them resistances, which must either be over- come, or against which the patient must strive by muscular action. Massage, which consists in kneading, pressing, or rubbing the muscles, favors the blood stream; hence, this system may be advantageously used for such muscles as are so weakened by disease that an independent treatment by means of gymnastics cannot be adopted. [The importance of massage as a restorative practice in getting rid of the waste products of muscular activity has been already referred to (J 304). It is much practiced on the Continent.] Disturbances of the normal movements may partly afi'ect the passive motor organs (e.g., the bones, joints, ligaments, and aponeuroses), or the active organs (muscles with their tendons, and motor nerves). Passive Organs — Fractures, caries and necrosis, and inflammation of the bones, which make movements painful, influence or even make movement impossible. Similarly, dislocations, relaxa- tion of the ligaments, arthritis, or anchylosis interfere with movement. Also cunature of bones, hyperostosis or exostosis; lateral curvature of the vertebral column (Scoliosis), backward angular curvature (Kyphosis), or forward curvature (Lordosis). The latter interfere with respiration. In the lower extremities, which have to carry the weight of the body, genu valgum may occur in flabby, tall, rapidly-growing individuals, especially in some trades, e.g., bakers. The opposite form, genu varum, is generally a result of rickets. Flat foot depends upon a depression of the arch of the foot, which then no longer rests upon its three points of support. Its causes seem to be similar to those of genu valgum. The ligaments of the small tarsal joints are stretched, and the long a.xis of the foot is usually directed outward; the inner margin of the foot is more turned to the ground, while pain in the fool and malleoli make walking and standing impossible. Club foot (Talipes varus) m which the inner margin of the foot is raised, and the point of the toes is directed inward and downward, depends upon imperfect development during fretal life. All children are born with a certain very slight degree of bending of the foot in this direction. Talipes equinus, in which the toes, and T. calcaneus, in which the heel touches the ground, usually depend upon STANDING. 539 contracture of the muscles causing these positions of the foot, or upon paralysis of the antago- nistic muscles. Rickets and Osteomalacia. — If the earthy salts be withheld from the food, the bones gradually undergo a change ; they become thin, translucent, and may even bend under pressure. In certain persistent defecfs of nutrition, the lime sails of the food are not absorbed, giving rise to rachitis, or rickets, in children. If fully-formed bones lose their lime salts to the extent of yi to ',^ (halis- terisis), they become brittle and soft (osteomalacia). This occurs to a limited extent in old age. Muscles. — The normal nutrition of muscle is intimately dependent on a proper supply of sodium chloride and potash salts in the food, as these foim integral parts of the muscular tissue {Kenimerich, Forster]. Besides the atrophic changes which occur in the muscles when these substances are withheld, there are disturbances of the central nervous system and digestive apparatus, and the animals ultimately die. The condition of the muscles during inanition is given in § 237. If mus- cles and bones be kept inactive they tend to atrophy (^ 244). In atrophic muscles, and in cases of anchylosis, there is an enormous increase, or " atrophic proliferation," of the muscle corpuscles, which takes place at the e,xpense of the contractile contents {Cohnheim). .\ certain degree of mus- cular atrophy takes place in old age. The uterus, after delivery, undergoes a great decrease in size and weight — from 1000 to 350 grammes — due chiefly to the diminished blood supply to the organ. In chronic lead poisoning, the extensors and interossei chiefly undergo atrophy. Atrophy and degeneration of the muscles are followed by shortening and thinning of the bones to which the muscles are attached. Section and paralysis of the motor nerves cause palsy of the muscle, thus rendering them inactive, and they ultimately degenerate. .Atrophy also occurs after inflammation or softening of the multipolar nerve cells in the anterior horn of the gray matter of the spinal cord, or the motor nuclei (facial, spinal accessory, and hypoglossal of Stilling in the medulla oblongata), in the muscles connected with these parts. Rapid atrophy takes place in certain forms of spinal paralysis and in acute bulbar paralysis (paralysis of the medulla oblongata), and in a chronic form in progressive muscular atrophy and progressive bulbar par,alysis. The muscles and their nerves become small and soft. The muscles show many nuclei, the sarcous substance becomes fatty and ultimately dis- appears. According to Charcot, these areas are at the same time the trophic centres for the nerves proceeding from them as well as for the muscles belonging to them. According to Friedreich, the primary lesion in progressive muscular atrophy is in the muscles, and is due to a primary interstitial inflammation of the muscle, resulting in atrophy and degenerative changes, while the nerve centres are afl'ected secondarily, just as after amputation of a limb the corresponding part of the spinal cord degenerates. In pseudo-hypertrophic muscular atrophy the muscular fibres atrophy completely, with copious development of fat and connective tissue between the fibres, without the nerves or spinal cord undergoing degeneration. The muscular substance may also undergo amyloid or wax like degeneration, whereby the amyloid substance infiltrates the tissue {\ 249, VI). Sometimes atrophic muscles have a deep-brown color, dca^ to a change of the ha;moglobin of the muscle. When muscles are much used, they hypertrophy, as the heart in certain cases of valvular lesion or obstruction (I 49), the bladder and intestine. [In true hypertrophy there is an increased number or increase in the size of its tissue elements, throughout the entire tissue or organ, without any deposit of a foreign body. Perhaps, in hypertrophy of the bladder, the thickened muscular coat not only serves to overcome resistance, but it oflfers greater resistance to bursting under the increased intra-vesical pressure. Mere enlargement is not hypertrophy, for this may be brought about by foreign ele- ments. In atrophy there is a diminution in size or bulk, even when the blood stream is kept up, the decrease being due to pressure. An atrophied organ may be even enlarged, as seen in pseudo- hypertrophic paralysis, where the muscles are larger, owing to the interstitial growth of fatty and connective tissue, while the true muscular tissue is diminished and truly atrophied.] 308. STANDING. — The act of standing is accomplished by muscular action, and is the vertical position of ecjuilibrium of the body, in which a line drawn from the centre of gravity of the body falls within the area of both feet placed upon the ground. In the military attitude the muscles act in two directions — (ij to fix the jointed body, as it were, into one unbending column ; and (2) in case of a variation of the equilibrium, to compensate, by muscular action, for the dis- turbance of the equilibrium. The following individual motor acts occur in standing : — I. The fixation of the head upon the vertebral column. The occiput maybe moved in various directions upon the atlas, as in the acts of nodding. As the long arm of the lever lies in front of the atlas, necessarily when the muscles of the back of the neck relax, as in sleep or death, the chin falls upon the breast. The strong neck muscles, which pull from the vertebral column upon the occiput, fix the head in a firm position on the vertebral column. The chief rotatory movement of the head on a vertical axis occurs round the odontoid process of the axis. The articular surfaces on the pedicles, ar.d part of the bodies of the 1st and 2d vertebne, are conve.x toward each other in the 540 SITTING. middle, becoming somewhat lower in front and behind, so that the head is highest in the erect posture. Hence, when the head is greatly rotated, compression of the medulla oblongata is pre- vented {I/enki). In standing, these muscles do not require to be fixed by muscular action, as no rotation can take place when the neck muscles are at rest. 2. Fix Vertebral Column The vertebral column itself must be fixed, especially where it is most mobile, /. t'., in the cervical and lumbar regions. This is brought about by the strong muscles situate in these regions, e. g., the cervical spinal muscles, Extensor dorsi communis and Quat/ratus Itimboruni. Mobility of the Vertebrae. — The least movable vertebrae are the 3d to the 6th dorsal ; the sacrum is quite immovable. For a certain length of the column, the mobility depends on [a) the number and height of the interarticular fibro-cartilages. They are most numerous in the neck, thickest in the lumbar region, and relatively also in the lower cervical region. They permit move, ment to take place in every direction. Collectively, the interarticular disks form one-fourth of the height of the whole vertebral column. They are compressed somewhat by the pressure of the body ; hence the body is longest in the morning and after lying in the horizontal position. The smaller periphery of the bodies of the cervical vertebras favors the mobility of these vertebr.'E compared with the larger lower ones. (/') The position of the processes also influences greatly the mobility. The strongly-depressed spines of the dorsal region hinder hyperextension. The articular processes on the cervical vertebra; are so placed that their surfaces look obliquely from before and upward, back- ward and downward ; this permits relatively free movement, rotation, lateral and nodding move- ments. In the dorsal region the articular surfaces are directed vertically and directly to the front, the lower directly back\^'ard ; in the lumbar region the jiosiiion of the articular processes is almost completely vertical and antero-posterior. In bending backward as far as possible, the most mobile parts of the colimin are the lower cervical vertebra, the iilh dorsal to the 2d lumbar and the lower two lumbar vertebme (E. H. Weber). 3. The centre of gravity of the head, trunk and arms, when fixed as above, lies in front of the loth dorsal vertebra. It lies further- forward, in a horizontal plane, passing through the xiphoid process ( ll'eber), the greater the distention of the abdomen by food, fat or pregnancy. A line drawn vertically downward from the centre of gravity passes behind the line uniting both hip joints. Hence, the trunk would fall backward on the hip joint, were it not prevented partly by ligaments and partly by muscles. The former are represented by the ileo-femoral band and the anterior tense layer of the fascia lata. As ligaments alone, however, never resist permanent traction, they are aided, especially by the ileo-psoas muscle inserted into the small trochanter, and in part, al.so, by the rectus femoris. Lateral movement at the hip joint, whereby the one limb must be abducted and the other adducted, is prevented especially by the large mass of the glutei. When the leg is extended, the ileo-femoral ligament, aided by the fascia lata, prevents adduction. 4. The rigid part of the body, head and trunk, with the arms and the legs, whose centre of gravity lies lower and only a little in front, so that the vertical line drawn downward inter.sects a line connecting the posterior surfaces of the knee joints, must now be fixed at the knee joint. Falling backward is prevented by a slight action of the quadriceps femoris. aided by the tension of the fascia lata. Indirectly it is aided also by the ileo-femoral ligament. Lateral moven ent of the knee is prevented by the disposition of the strong lateral ligaments. Rotation cannot take place at the knee joint in the extended position [\ 305, I, 3). 5. A line drawn downward from the centre of gravity of the whole body, which lies in the pro- monotory, falls slightly in front of a line between the two ankle joints. Hence, the body would {&\\ forward on the latter joint. This is prevented especially by the muscles of the calf, aided by the muscles of the deep layer of the leg (tibialis posticus, flexors of the toes, peroneus longus et brevis). Other Factors. — (a) As the long axis of the foot forms with the leg an angle of 50°, falling forward can only occur after the feet are in a positii>n more nearly parallel with their long axis. (/') The form of the articular surfaces helps, as the anterior broad part of the astragalus must be pressed between the two malleoli. The latter mechanism cannot be of much importance. 6. The metatarsus and phalanges are united by tense ligaments to form the arch of the foot, which touches the ground at three points— tuber calcanei (heel), the head of the first metatarsal bone (ball of the great toe), and of the fifth toe. Between the latter two points the heads of the metatarsal bones also form points of supports. The weight of the body is transmitted to the highest part of the arch of the foot, the caput tali. The arching of the foot is fixed only by ligaments. The toes play no part in standing, although, when moved by their muscles, they greatly aid the balancing of the body. The maintenance of the erect attitude fatigues one more rapidly than walking. 309. SITTING. — Sitting is that position of equilibrium whereby the body is supported on the tubera ischii, on which a too-and-fro movement may take place (//. v. Meyer), The head and trunk together are made rigid to form an immovable column, as in standing. We may distinguish — ( I ) the forward posture, in which the line of gravity passes in front of the tubera ischii ; the body being supported either against a fixed object, e, g.^ by means of the arm on a table, or against the upper surface of the thigh. (2) The backward posture, in which the line of gravity falls behind the tubera. A person is prevented from falling backward either by leaning on a support, or WALKING, RUNNING AND SPRINGING. 541 by the counter weight of the legs kept extended by muscular action, whereby the sacrum forms an additional point of support, while the trunk is fixed on the thigh by the ileopsoas and rectus femoris, the leg being kept extended by the extensor quadriceps. Usually the centre of gravity is so placed that the heel also acts as a point of support. The latter sitting posture is, of course, not suited for resting the muscles of the low-er limbs. (3) When " sitting erect " the line of gravity falls between the tubera themselves. The muscles of the legs are relaxed, the rigid trunk only requires to be balanced by slight muscular action. Usually the balancing of the head is sufficient to main- tain the equilibrium. 310. WALKING, RUNNING, AND SPRINGING.— By the term walking is understood progression in a forward horizontal direction with the least possible muscular exertion, due to the alternate activity of the two legs. Methods.— The Brothers Weber were the first to analyze the various positions of the body in walking, running, and springing, and they represented them in a continuous series, which represents the successive phases of locomotion. These phases may be examined with the zoetrope (J 398, 3). Marey estimated the lime relations of the individual acts, by transferring the movements by means ol his air tambours to a recording surface. Recently, by means of a revolving camera, he has suc- ceeiled in photographing, in instantaneous pictures (x^'ijj second), the whole series of acts. Of course this series, when placed in the zoetrope, represents the natural movements. Figs. 316, 317, 318 represent these acts. In walking, the legs are active alternately; while one — the "supporting" or "active" leg — carries the trunk, the other is "inactive" or "passive." Each Ptiases of walking. The thick lines represent the active, the thin the passive leg ; h, the hip joint ; k, a, knee ; /,l\ ankle : c, it, heel ; /h, e, ball ot the tarso-metatarsal joints ; js, g, point of great toe. leg is alternately in an active and a passive j)hase. Walking may be divided into the following movements : — I. Act (Fig. 315, 2). — The active \tg is vertical, slightly flexed at the knee, and it alone supports the centre of gravity of the body. The passive leg is completely extended, and touches the ground only with the tip of the great toe (s). This position of the leg corresponds to a right-angled tri- angle, in which the active leg and the ground form two sides, while the passive leg is the hypo- tenuse. II. Act. — For the forward movement of the trunk, the active leg is inclined slightly from its vertical position (cathetus) to an oblique and more forward (hypotenuse) position (3). In order that the trunk may remain at the same height, it is necessary that the active leg be lengthened. This is accomplished by completely extending the knee (3, 4, 5), as well as by lifting the heel from the ground (4, 5), so that the foot rests on the balls or the heads of the metatarsal bones, and lastly, by elevating it on the point of the great toe (2, thin line). During (he extension and forward move- ment of the active leg, the tips of the toes of the passive leg have left the ground (3). It is slightly flexed at the knee joint (owing to the shortening), it performs a " pendulum-like movement " (4,5), whereby its foot is moved as far in front of the active leg as it was formerly behind it. The foot is then placed flat upon the ground (I, 2, thick lines) ; the centre of gravity is now transferred to this active leg, which, at the same lime, is slightly flexed at the knee, and placed vertically. The first act is then repeated. Simultaneous Movements of the Trunk. — During walking the trunk performs certain char- acteristic movements, ^i) It leans every time toward the active leg, owing to the traction of the 542 WALKING, RUNNING AND SPRINGING. glutei and the tensor fascice lata;, so that the centre of gravity is moved, which, in short, heavy per- sons with a broad pelvis, leads to their " waddling " gait. (2) The trunk, especially during ra|reoidea; 1/ ar ir Muse, arytae- ; transversus ; .!//«, rtr. f^/., MusculiarytECnoidei obliqui M cr aryt post ^ Mubculuscnco ajytae; ; posticus; /*«r.v car/. , Pars cartilaEinea: /"rtrj we??//*.. Pars membran the laryn.\. O. h., Oshyoideum ; C. th , Cart, thyreoidea : C. c , Cart cric( M. thyreo-arytaenoideiis : M. cr.-ar. p , M. crico-arytaenoideus posticus M alls: Al.cr.-ih., M. crico-thyreoideus : N. lar. sitfi. v.,'ii. laryngeus sup Ramus ext. : N. Inr. rec. v., N. laryngeus recurrens ; R. I. N L R Rat ext. nervi laryngei recurrcntis vagi. of achese Fig ^2 idei TV Trachea 1/ th -ar., :r ar I M cnco arytaen. later- R I , Ramus internus ; R. E., lus int R E N L R , Ramus muscles. When they contract, they pull both processus musculares of the aryte- noid cartilages backward, downward, and toward the middle line (Fig. 323), so that the processus vocales (I, I) must go apart and upward (II, II). Thus, between tiie vocal cords (glottis vocalis ), as well as between the inner margins of the arytenoid cartilages, a large triangular space is formed (glottis respiratoria), and these spaces are so arranged that their bases come together, so that the aperture between the cords and the arytenoid cartilages has a rhomboidal form. Fig. 323 shows the action of the muscles. The vocal cords, represented by lines converging in front, arise from the anterior angle of the arytenoid cartilages (I, I). When 548 ACTION OF THE LARYNGEAL MUSCLES. these cartilages are rotated into the position (II, II), the cords take the position indicated by the dotted lines. The widening of the respiratory portion of the glottis between the arytenoid cartilages is also indicated in the diagram. PathologicaL — When these muscles are paralyzed, the widening of the glottis does not take place, and there may be severe dyspncea during inspiration, although the voice is unaffected (Jiiegel, L. Weber). 2. The entrance to the glottis is constricted by the arytenoid muscle (transverse), which extends transversely between both outer surfaces of the aryte- noids along their whole length (Fig. 324). On the posterior surface of this muscle is placed the cross bundles (Fig. 321) of the thyro-aryepiglotticus (or arytaenoidei obliqui) ; they act like the foregoing. The action of these muscles is indicated in Fig. 324; the arrows point to the line of traction. Pathological. — Paralysis of this muscle enfeeliles the voice and makes it hoarse, as much air escapes between the arytenoid cartilages during phonation. 3. In order that the vocal cords be approximated to each other, which Fig. 323. Fig. 324. Fig. 323, — Schematic horizontal section of the larynx. I. Position of the horizont.illy divided arytenoid cartilages during respiration ; from their anterior processes run the converging vocal cords. The arrows show the line of traction o( the fiosti'rior crico-arytenoid m\i%c\e% ; II, II, the position of the arytenoid muscles as a result of this action. Fig. 324. — Schematic horizontal section of the larynx, to illustrate theaction of the arytenoid muscle. I, I, position of the arytenoid cartilages during quiet respiration. The arrows indicate the direction of the con- traction of the muscle ; II, II, the position of the arytenoid cartilages after the arytenoideus contracts. occurs during phonation, the processus vocales of the arytenoid cartilages must be closely apposed, whereby they must be rotated inward and downward. This result is brought about by the processus musculares being inoved in a forward and upward direction by the thyro-arytenoid muscles. These muscles are applied to, and, in fact, are imbedded in, the substance of the elastic vocal cords, and their fibres reach to the external surface of the arytenoid cartilages. When they contract, they rotate these cartilages, so that the processus vocales must rotate inward. The glottis vocalis is thereby narrowed to a mere slit (Fig. 326), whilst the glottis respiratoria remains as a broad triangular opening. The action of these muscles is indicated in Fig. 325. The lateral crico-arytenoid muscle is inserted into the anterior margin of the articular surface of the arytenoid cartilage ; hence, it can only pull the car- tilage forward ; but some have supposed it can also rotate the arytenoid cartilage in a manner similar to the thyro-arytenoid (?), with this difference, that the pro- cessus vocales do not come so close to each other. POSITION DURING PRONATION. 549 Scheme of the closure of the glottis by the ihyro-arytenoid muscles, II, II, position of the aiytenoid cartilages during quiet respiration. The arrows indicate the direction of the muscular traction. — I, I, position of the arytenoid carti- lages after the muscles contract. Pathological — Paralysis of both thyro- Fig. 325. arytenoid muscles causes loss of voice. 4. The vocal cords are ren- dered tense by their points of attachment being removed from each other by the action of muscles. The chief agents in this action are the crico-thyroid muscles, which pull the thyroid cartilage forward and downward. At the same time, however, the posterior crico-aryte- noids must pull the arytenoid carti- lages slightly backward, and at the same time keep them fixed. The genio-hyoid and thyro-hyoid, when they contract, pull the thyro'd upward and forward toward the chin, and also tend to increase the tension of the vocal cords (C. Mayer, Griitzner). Pathological. — Paralysis of the crico- thyroid causes the voice to become harsh and deep, owing to the vocal cords not being sufficiently tense. Position during Phonation. — The tension of the vocal cords brought about in this way is not of itself sufficient for phonation. The triangular aperture of the glottis respiratoria between the arytenoid cartilages, produced by the unaided action of the internal thyro-arytenoid muscles (see 3) must be closed by the action of the transverse and oblique arytenoid muscles. The vocal cords themselves must have a concave margin, which is obtained through the action of the crico- thyroids and posterior crico-arytenoids, so that the glottis vocalis presents the appearance of a myrtle leaf {Henle), while the rima glottidis has the form of a linear slit (Fig. 329). The contraction of the internal thyro-arytenoid converts the concave margin of the vocal cords into a straight margin. This muscle adjusts the delicate variations of tension of the vocal cords themselves, causing, more especially, such variations as are necessary for the production of tones of slightly different pitch. -\s these muscles come close to the margin of the cords, and are securely woven, as it were, among the elastic fibres of which the cords consist, they are specially adapted for the above-mentioned purpose. When the muscles contract, they give the necessary resistance to the cords, thus favoring their vibra- tion. As some of the muscular fibres end in the elastic fibres of the cords, these fibres, when they contract, can render certain parts of the cords more tense than others, and thus favor the modifications in the formation of the tones. The coarser variations in the tension of the vocal cords are produced by the separa- tion of the thyroid from the arytenoid cartilages, while the finer variations of tension are produced by the thyro-arytenoid muscles. The value of the elastic tissue of the cords does not depend so much upon its extensibility as upon its property of shortening without forming folds and creases. Pathological. — In paralysis of these muscles, the voice can only be produced by forcible expira- tion, as much air escapes through the glottis ; the tones are at the same time deep and impure. Paralysis of the muscle of one side causes flapping of the vocal cord on that side [Gerkuriit). 5. The relaxation of the vocal cords occurs spontaneously when the stretching forces cease to act ; the elasticity of the displaced thyroid and arytenoid cartilages comes into play, and restores thein to their original position. The vocal cords are also relaxed by the action of the thyro-arytenoid and lateral crico- arytenoid muscles. It is evident from the above statements that tension of the vocal cords and 550 RELAXATION OF THE VOCAL CORDS. narrowing of the glottis are necessary for phonation. The tension is pro- duced by the crico-thyroids and posterior crico-arytenoids ; the narrowing of the glottis respiratoria by the arytenoids, transverse and oblique, the glottis vocalis being narrowed by the thyro-arytenoids and (? lateral crico-arytenoids), the former muscles causing the cords themselves to become tense. Nerves (§ 352, 5). — The crico-thyroid is supplied by the superior laryngeal branch of the vagus, which at the same time is the sensory nerve of the mucous membrane of the larynx. All the other intrinsic muscles of the larynx are sup- plied by the inferior laryngeal. Fig. 326. A vertical section through the head and neck, to the first dorsal vertebra, a. the position of the laryngoscope on observing the posterior part of the glottis, arytenoid cartilages, the upper surface of the posterior wall of the larynx ; ^, its position on observing the anterior angle of the glottis. Large, a, and 6, small laryngoscopic The mucous membrane of the larynx is richly supplied with el.istic fibres, .ind so is the sub- mucosa. The sub-mucosa is more lax near the entrance to the glottis and in the ventricles of Mor- gagni, which explains the enormous swelling that sometimes occurs in these parts in cedema glottidis. A thin, clear limiting membrane lies under the epithelium. The epithelium is stratified, cylindrical, and ciliated with intervening goblet cells. On the true vocal cords and the anterior surface of the epiglottis, however, this is replaced by stratified squamous epithelium, which covers the small papilhe of the mucous membrane. Numerous branched miicoiis glands occur over the cartilages of Wrisberg, the cushion of the epiglottis, and in the ventricles of Morgagni ; in other situations, as on the posterior surface of the larynx, the glands are more scattered. The blood vessels form a dense capillaiy plexus under the membrana propria of the mucous membrane; THE LARYNGOSCOPE. 551 under this, however, there are other two strata of blood vessels. The lymphatics form a superficial narrow mesh-work under the blood capillaries, with a deeper, coarser plexus. The medullated nerves have ganglia in their branches, but their mode of termination is unknown. [W. Stirling has described a rich sub- epithelial ple.xus of medullated nerve fibres on the anterior surface of the epiglottis, while he finds that there are ganglionic cells in the course of the superior laryngeal nerve.] Cartilages. — The thyroid, cricoid, and nearly the whole of the arytenoid cartilages consist of hyaline cartilage. The two former are prone to ossify. The apex and processus vocalis of the arytenoid cartilages consist of yellow Jibro cartilage, and so do all the other cartilages of the larynx. The larynx grows until about the sixth year, when it rests for a time, but it becomes again much larger at puberty (J 434). 314. LARYNGOSCOPY. — Historical.— After Bozzini (1807) gave the first impulse toward the investigation of the internal cavities of the body, by illuminating them with the aid of mirrors, Babington (1S29) actually observed the glottis in this way. The famous singer Manuel Garcia (1854) made investigations both on himself and other singers, regarding the movements of the vocal cords, during respiration and phonation. The examination of the larynx by means of the laryngo- scope was rendered practicable chiefly by Tiirck (1857) and Czermak, the latter observer being the first to use the light of a lamp for the illumination of the larynx. Rhinoscopy was actually first practised by Baumis (1838), but Czermak was the first person who investigated this subject system- atically. Fic. 327. The Laryngoscope consists of a small mirror fixed to a long handle, at an angle of 125° to 130° ( Fig. 326, ., sinus p formes. CONDITIONS AFFECTING THE LARYNGEAL SOUNDS. 553 arrangements were adopted for putting the vocal cords on the stretch and for opening or closing the glottis. 315. CONDITIONS INFLUENCING THE LARYNGEAL SOUNDS.— The pitch of the note emitted by the larynx depends upon : — Fig. 329. Fig. 330. Position of the vocal cords on uttering a high note. ' of the rings and bifurcation of trachea. 1. The Tension of the Vocal Cords, i.e., upon the degree of contraction of the crito-thyroid and posterior crico-arytenoid muscles, and also of the internal thyro-arytenoids (§ 313, II, 4). 2. The Length of the Vocal Cord. — {a) Children and females with short I of the lar>-ngoscopic view. S.n., Septum ra- C.S., lower, middle and upper turbinated bones ; 7'., Eustachian tube ; //'. , tubuiar eminence; A'., groove of Rosen- mUUer: F.m., soft palite; O.R., roof of pharynx; £/., uvula. vocal cords produce high notes. (/^) If the arytenoid cartilages are pressed together by the action of the arytenoid muscles (transverse and oblique), so that the vocal cords alone can vibrate, while their intercartilaginous portions lying between the processus vocales do not, the tone thereby produced is higher 554 RANGE OF THE VOICE. {Garcia). In the production of low notes, the vocal cords, as well as margins of the arytenoid cartilages, vibrate. At the same time the space above the entrance to the glottis is enlarged and the larynx becomes more prominent. (c) Every individual has a certain medium pitch of his voice, which corresponds to the smallest possible tension of the intrinsic muscles of the larynx. 3. The Strength of the Blast. — That the strength of the blast from below raises the pitch of the tones of the human larynx is shown by the fact that tones of the highest pitch can only be uttered by powerful expiratory efforts. With tones of medium pitch, the pressure of the air in the trachea is 160 mm., with iiig/i pitch 200 mm., and with veiy high notes 945 mm., and in whispering 30 mm., of water ( Cagniard-Laiour, Griitzner). These results were obtained from a tra- cheal fistula. Accessory Phenomena. — The following as yet but partially explained phenomena are observed in connection with the production of high notes: («) As the pitch of the note rises, the larynx is elevated, partly because the muscles raising it are active, partly because the increased intra-tracheal pressure so lengthens the trachea that the larynx is thereby raised; the uvula is raised more and more (Lalins). (b) The upper vocal cords approximate to each other more and more, without, however, coming into contact, or participating in the vibrations, [c) The epiglottis inclines more and more backward over the glottis. 4. The falsetto voice with its soft timbre and the absence of resonance in the air tubes (pectoral fremitus) is particularly interesting. Oertel observed that during the falsetto voice the vocal cords vibrated so as to form nodes across them, but sometimes there was only one node, so that the free margin of the cord and the basal margin vibrated, being separated from each other by a nodal line (parallel to the margins of the vocal cord). During a high falsetto note, there may be three such nodal lines parallel to each other. The nodal lines are pro- duced probably by a partial contraction of the fibres of the thyro-arytenoid muscle (p. 54S), while at the same titne the vocal cords must be reduced to as thin plates as possible by the action of the crico-thyroid, posterior arytenoid, thyro- and genio-hyoid muscles (Oertet). The fortn of the glottis is elliptical, while with the chestvoice the vocal cords are limited by straight surfaces (yif/f/y^)', Oertel); the air also passes more freely through the larynx. Oertel also found that during the falsetto voice the epiglottis is erect. The apices of the aryte- noid cartil.iges are slightly inclined backward, the whole larynx is larger from before backward, and narrower from side to side, the aryepiglottidean folds are tense, with sharp margins, and the entrance to the ventricles of Morgagni is narrowed. The vocal cords are narrower, the processus vocales touch each other. The rotation of the arytenoid cartilages necessary for this is brought about by the action of the crico-arytenoid alone, while the thyroarytenoid is to be regarded only as an acces- sory aid. The pitch of the note is increased solely by increased tension of the vocal cords. In addition, there are a number of transverse and longitudinal partial vihralions. During the chest voice, a smaller part of the margin vibrates than in the faUetto voice, so that in the production of the latter we are conscious of less muscular exertion in the larynx. The uvula is raised to the hori- zontal position [Labus). Production of Voice. — In order that voice be produced, the following con- ditions are necessary : (i) The necessary amount of air is collected in the chest ; (2) the larynx and its parts are fixed in the proper position; (3) air is then forced by an expiratory effort either through the linear chink of the closed glottis, so that the latter is forced open, or at first some air is allowed to pass through the glottis without producing a sound, but as the blast of air is strengthened, the vocal cords are thrown into vibration. 316. RANGE OF THE VOICE.— The range of the human voice for chest notes is given in the following schema : — SPEECH AND THE FORMATION OF VOWELS. 555 128 Tenor. 512 The accompanying figures indicate the number of vibrations per second in the corresponding tone. It is evident from c' to/' is common to all voices ; nevertheless, they have a different timbre. The lowest note or tone, which, however, is only occasionally sung by bass singers, is the contra-F, with 42 vibrations : ihe highest note of the soprano voice is a'", with 1708 vibrations. Timbre. — The voice of every individual has a peculiar quality, clang or timbre, which depends u]jon the shape of all the cavities connected with the larynx. In the production of nasal tones, the air in the nose is caused to vibrate strongly, so that the entrance to the nares must necessarily be open. 317. SPEECH— THE VOWELS.— The motor processes connected with the production of speech occur in the resonating cavities, the pharynx, mouth and nose, and are directed toward the production of musical tones and noises. Whispering and Audible Speech. — When sounds or noises are produced in the resonating chambers, the larynx being passive, the vox clandestina, or whispering, is produced ; when the vocal cords, however, vibrate at the same time, "audible speech" is produced. [Whispering, therefore, is speech without voice.] Whispering may be fairly loud, but it requires great exertion, /'. e., a great expiratory blast, for its production ; hence it is very fatiguing. It may be performed both with inspiration and expiration, while audible speech is but temporary and indistinct if it is produced during inspiration. Whispering is caused by the sound produced by the air passing through the moderately-contracted rima glottidis, and passing over the obtuse margin of the cord. During the pro- duction of audible sounds, however, the sharp margins of the vocal cords are directed toward the air by the position of the processus vocales. During speech, the soft palate is in action ; at each word it is raised, while, at the same time, Passavant's transverse band is formed in the pharynx (J 156). The soft palate is raised highest when u and i are sounded, then with and c, and least with a. When sounding m and n it does not move; it is high (like n) during the utterance of the explosives. With 1, s, and especially with the gutteral r, it exhibits a trembling movement (Gentzen, Falksoit). Speech is composed of vowels and consonants. A. Vowels (analysis and artificial formation, 55415). — A. During whisper- ing, a vowel is the musical tone produced, either during expiration or inspiration, by the inflated characteristic form of the mouth {^Danders'), which not only has a definite pitch, but also a particular and characteristic timbre. The characteristic form of the mouth may be called " t'owel cavity." I. The pitch of the vowels may be estimated musically. It is remarkable that the fundamental tone of the "vowel cavity " is nearly constant at different ages and in the sexes. The different capacities of the mouth can be compensated by dift'erent sizes of the oral aperture. The pitch of the vowel cavity may be estimated by placing a number of vibrating tuning forks of different pitch in front of the moutli, and testing them until we find the one which corresponds with the funda- mental tone of the vowel cavity. This is known by the fact that the tone of the tuning fork is intensified by the resonance of the air in the mouth {v. I/elnt/toltz), or the vibrations may be trans- 556 THE FORMATION OF VOWELS. ferred to a vibrating membrane and recorded on a smoked surface, as in the phonautograph of Bonders. According to Konig, the fundamental tones of the vowel cavity are for U = b, O = b', A = b", E = b'", I = b"". If the vowels be whispered in this series, we find at once that their pitch rises. The fundamental tone in the production of a vowel may vary within certain limits. This may be shown by giving the mouth the characteristic position and then percussing the cheeks {^Auerbach) ; the sound emitted is that of the vowel, whose pitch will vary according to the position of the mouth. When sounding A, the mouth has the form of a funnel widening in front (Fig. 333, A). The tongue lies in the floor of the mouth, and the lips are wide open. The soft palate is moderately raised (Czermai). It is more elevated successively with O, E, U, I. The hyoid lione appears as if at rest, but the larynx is slightly raised. It is higher than with U but lower than with I. If we sound A to I, the larynx and the hyoid bone retam their relative position, but both are raised. In passing from A. to U, the larynx is depressed as far as possible. The hyoid bone passes slightly forward [Briiiie). When sounding A, the space between the larynx, posterior wall of the pharynx, soft palate, and the root of the tongue, is only moderately wide ; it becomes wider with E, and especially with I yPurkirtje), but it is smallest with U. When sounding U (Fig. 333), the form of the cavity of the mouth is like that of a capacious Fig. 333. '-V^ n Section of the parts thyroid I, Z. tongue : /, soft palate ; e, epiglottis ; g, glottis ; h, hyoid bone ; ,, 2, 3, cricoid, 4, arytenoid cartilage. flask with a short, narrow neck. The whole resonance apparatus is then longest. The lips are protruded as far as posssible, are arranged in folds and closed, leaving only a small opening. The larynx is depressed as far as possible, while the root of the tongue is approximated to the posterior margin of the palating arch. When sounding O, the mouth, as in U, is like a wide-bellied flask with a short neck, but the latter is shorter and wider as the lips are nearer to the teeth. The larynx is slightly higher than with U, while the resonance chambers also are shorter (Fig. 333). When sounding I, the cavity of the mouth, at the posterior part, is in the form of a small-beUied flask with a long, narrow neck, of which the belly has the fundamental tone, f, the neck that of d"''. The resonating chambers are shortest, as the larynx is raised as much as possible, while the mouth, owing to the retraction of the lips, is bounded in front by the teeth. The cavity between the hard palate and the back of the tongue is exceedingly narrow, there being only a median nar- row slit. Hence, the air can only enter with a clear, piping noise, which sets even the vertex of the skull in vibration, and when tlie ears are stopped the sounds seem very shrill. When the lar- ynx is depressed and the lips protruded, as for sounding U, I cannot be sounded. When sounding E, which stands next to I, the cavity has also the form of a flask with a small belly (fundamental tone, f) and with a long, narrow neck (fundamental tone, h"') [v. HelmhoUz). The neck is wider, so that it does not give rising to a piping noise. The larynx is slightly lower than for I, but not so high as for A. Fundamentally there are only three primary vowels — I, A, U, the others and the so-called diph- thongs standing between them [Briicke). CLASSIFICATION OF CONSONANTS. 557 Diphthongs occur when, during vocalization, we pass from the position of one vowel into that of another. Distinct diphthongs are sounded only on passing from one vowel with the mouth wide open to one with the mouth narrow ; dur- ing the converse process the vowels appear to our ear to be separate {Briicke). II. Timbre or Clang Tint. — Besides its pitch, every vowel has a special timbre, quality, or clang tint. The vocal timbre of U (whispering) has, in addition to its fundamental tone, b, a deep, piping timbre. The timbre depends upon the number and pilch of \.\ie parliah or overtones of the vowel sound I J 415). Nasal Timbre. — The timbre is modified in a special manner when the vowels are spoken with a " nasal " twang, which is largely the case in the French language. The nasal timbre is produced by the soft palate not cutting off the nasal cavity completely, which happens every time when a pure vowel is sounded, so that the air in the nasal cavity is thrown into sympathetic vibration. When a vowel is spoken with a nasal timbre, air passes out of the nose and mouth simultaneously, while with a pure vowel sound it passes out only through the mouth. WTien sounding a pure vowel (non-nasal), the shutting off of the nasal cavity from the mouth is so complete, that it requires an artificial pressure of 30 to 100 mm. of mercury to overcome it (Hartmaitn). The vowels, a, a (se), 6 (oe), o, e, are used with a nasal timbre — a nasal i does not occur in any language. Certainly it is very difficult to sound it thus, because, when sounding i, the mouth is so narrow that, when the passage to the nose is open, the air passes almost completely through the lat- ter, while the small amount passing through the mouth scarcely suffices to produce a sound. In sounding vowels, we must obser\'e if they are sounded through a previously closed glottis, as is done in the German language in all words beginning with a vowel (spiritus lenis). The glottis, however, may be previously opened with a preliminary breath, followed by the vowel sound ; we ob- tain the aspirate vowel (spiritus asper of the Greeks). B. If the vowels are sounded in an audible tone, /. e., along with the sound from the larynx, the fundamental tone of the vocal cavity strengthens in a char- acteristic manner the corresponding partial tones present in the laryngeal sound {IV/ieatsione, v. Helmholtz). 318. CONSONANTS. — The consonants are noises which are produced at certain parts of the resonance chambers. [As their name denotes, they can only be sounded in conjunction with a vowel.] Classification. — The most obvious classification is according to — (I.) Their acoustic properties, so that they are divided into — ( I ) liquid consonants, i. e., such as are appreciable without a vowel (m, n, 1, r, s) ; (2) mutes, including all the others, which cannot be distinctly heard without an accompanying vowel. (II.) According to their mechanism of formation, as well as the type of the organ of speech, by which they are produced. They are divided into — 1. Explosives — Their enunciation is accompanied by a kind of bursting open of an obstacle, or an explosion, occasioned by the confined and compressed air which causes a stronger or weaker noise ; or, conversely, the current of air is suddenly interrupted, while, at the same time, the nasal cavities are cut off by the soft palate. 2. Aspirates, in which one part of the canal is constricted or stopped, so that the air rushes out through the constriction, causing a faint whistling noise. (The nasal cavity is cut off.) In uttering L, which is closely related to the aspirates, but differs from them in that the narrow passage for the rush of air is not in the middle but at both sides of the middle of the closed part. (The nasal cavity is shut off.) 3. Vibratives, which are produced by air being forced through a narrow portion of the canal, so that the margins of the narrow tube are set in vibration. (The nasal cavity is shut off.) 4. Resonants (also called nasals or semi-vowels;. The nasal cavity is completely free, while the vocal canal is completely closed in the front part of the oral channel. According to the posi- tion of the obstruction in the oral cavity, the air in a larger or smaller portion of the mouth is thrown into sympathetic vibration. We may also classify them according to the position in which they are produced — the "articulation positions" of Briicke. These are : — A. Between both lips ; B, between the tongue and the hard palate ; C, between the tongue and the soft palate ; D, between the true vocal cords. A. Consonants of the First Articulation Position. — I. Explosive Labials. — b, the voice is sounded before the slight explosion occurs ; p, the voice is sounded after the much stronger explo- sion has taken place [A'empelen). [The former is spoken of as " voiced " and the latter as " breathed."] 558 PATHOLOGICAL VARIATIONS OF VOICE AND SPEECH. 2. Aspirate Labials. — f, between the upper incisor teeth and the lower lip (labiodental). It is absent in all true Slavic words (Piiriine) ; v, between both lips (labial) ; w is formed when the mouth is in the position for f, but instead of merely forcing in the air, the voice is sounded at the same time. Really there are two different w — one corresponding to the labial f, as in wiirde, and the labiodental, e. g., quelle {Briicke). 3. Vibrative Labials. — The burring sound, emitted by grooms, but which is not used in civilized language. 4. Resonant Labials. — m is formed essentially by sounding the voice whereby the air, in the mouth and nose, is thrown into sympathetic vibration [" voiced "]. B. Consonants of the Second Articulation Position. — I, The explosives, when enunciated sharply and without the voice, are T hard (also dt and th) ; when they are feeble and produced along with simultaneous laryngeal sounds (voice), we have D soft. 2. The aspirates embrace S, including s sharp, written s s or s z, which is produced without any audible laryngeal vibration ; or soft, which requires the voice. Then, also, there are modifica- tions according to the position where the noises are produced. The sharp aspirates include Sch, and the hard English Th ; to the soft belong the French J soft, and the English Th soft. L, which occurs in many modifications, belongs here, e. g., the L soft of the French. L may be sounded soft with the voice, or sharp without it. 3. The vibratives, or R, which is generally voiced, but it can be formed without the larynx. The resonants are N sounds, which also occurs in several modifications. C. Consonants of the Third Articulation Positiott. — I. The explosives are the K sounds, which are hard and breathed and not voiced ; G sounds, which are voiced. 2. The aspirates, when hard and breathed but not voiced, the Ch, and when sounded softly and not voiced, J is formed. 3. The vibrative is the palatal R, which is produced by vibration of the uvula (Briicke). 4. The resonant is the palatal N. D. Consonants of the Fourth Articulation Position. — I. An explosive sound does not occur when the glottis is forced open, if a vowel is loudly sounded with the glottis previously closed. If this occurs during whispering, a feeble, short noise, due to the sudden opening of the glottis, may be heard. 2. The aspirates of the glottis are the H sounds, which are produced when the glottis is moder- ately wide. 3. A glottis-vibrative occurs in the so-called laryngeal R of lower Saxon (Briicke). 4. A laryngeal resonant cannot exist. The combination of different consonants is accomplished by the successive movements necessary for each being rapidly executed. Compound consonants, however, or such as are formed when the oral parts are adjusted simultaneously for two different consonants, so that a mixed sound is formed from the two. Examples: Sch — tsch, tz, ts — Ps (^'0 — Ks (X£'). 319. PATHOLOGICAL VARIATIONS OF VOICE AND SPEECH.— Aphonia.— Paralysis of the motor nerves (vagus) of the larynx by injury, or the pressure of tumors, causes aphonia or loss of voice ( Galen). In aneurism of the aortic arch, the left recurrent nerve may be paralyzed from pressure. The laryngeal nerves may be temporarily paralyzed by rheumatism, over-exertion, and hysteria, or by serous eftusions into the laryngeal muscles. If the tensors are paralyzed, monotonia is the chief result ; the disturbances of respiration in paralysis of the larynx are important. As long as the respiration is tranquil, there may be no di.^turbance, but as soon as increased respiration occurs, great dyspncea sets in, owing to the inability of the glottis to dilate. If only one vocal cord is paralyzed, the voice becomes impure and falsetto-like, while we may feel from without that there is less vibration on the paralyzed s\At [Gerhardt). Sometimes the vocal cords are only so far paralyzed that they do not move during phonation, but do so during forced respiration and during coughing (phonetic paralysis). Diphthongia. — Incomplete unilateral paralysis of the recurrent nerve is sometimes followed by a double tone, owing to the unequal tension of the two vocal cords. According to Tiirck and Schnitzler, however, the double tone occurs when the two Fig. 334. vocal cords touch at some part of their course {e.g.^ from the presence of a tumor. Fig. 334), so that the glottis is divided into two unequal portions, each of which produces its own sound. Hoarseness is caused by mucus upon the vocal cords, by roughness, swelling or looseness of the cords. If, while speak- ing, the cords are approximated, and suddenly touch each other, the ** speech is broken," owing to the formation of nodal points (^ 352). Disease of the pharynx, nasopharyngeal cavity, and uvula may produce a change in the voice reflexly. Paralysis of the soft palate (as well as congenital per. foration or cleft palate) causes a nasal timbre of all vowels ; 1 the larynx. " the former renders difficult the normal formation of consonants COMPARATIVE AND HISTORICAL. 559 of the third articulation position; resonance is imperfect, while the explosives are weak, owing to the escape of the air through the nose. Paralysis of the tongue weakens I ; E and A (JE) are less easily pronounced, while the for- mation of consonants of the second and third articulation position is affected. The term aph- thongia is applied to a condition in which every attempt to speak is followed by spasmodic movements of the tongue (Floury). In paralysis of the lips (facial nerve), and in hare-lip, regard must be had to the formation of consonants of the first articulation position. When the nose is closed, the speech has a character- istic sound. The normal formation of resonants is, of course, at an end. After excision of the larynx, a metal reed enclosed in a tube, and acting like an artificial larynx, is introduced between the trachea and the cavity of the mauth [(^erny). Stammering is a disturbance of the formation of sounds. [Stammering is due to long-con- tinued spasmodic contraction of the diaphragm, just as hiccough is (? 120), and, therefore, it is essentially a spasmodic inspiration. As speech depends upon the expiratory blast, the spasm pre- vents expiration. It may be brought about by mental excitement or emotional conditions. Hence, the treatment of stammering is to regulate the respirations. In stuttering, which is defective speech due to inability to form the proper sounds, the breathing is normal.] 320. COMPARATIVE— HISTORICAL.— Speech may be classified with the " expres- sion of the emotions" (Darioin). Psychical excitement causes in man characteristic movements, in which certain groups of muscles are always concerned, t'.f^., laughing, weeping, the facial expres- sion in anger, pain, shame, etc. These movements afford a means whereby one creature can com- municate with another. Primarily in their origin, the movements of expression are rejiex motor phenomena; when they are produced for purposes of explanation, they are voluntary imitations of this reflex. Besides the emotional movements, impressions upon the sense organs produce char- acteristic reflex movements, which may be used for purposes of expression (Geiger), e.g., stroking or painful stimulation of the skin, movements after smelling pleasant or unpleasant or disagreeable odors, the action of sound and light, and the perception of all kinrls of objects. The expression of the emotions occurs in its simplest form in what is known as expression by means of signs or pantomime or mimicry. Another means is the imitation of sounds by the organ of speech, constituting onamatofocsy, e.g., the hissing of a stream, the roll of thunder, the tumult of a storm, whistling, etc. The expression of speech is, of course, dependent upon the process of ideation and perception. The occurrence of different sounds in different languages is very interesting. Some languages (e.g., of the Hurons) have no labials; in some South Sea Islands, no laryngeal sounds are spoken; f is absent in Sanskrit and Finnish ; the .short e, 0, and the soft sibilants in Sanskrit ; d, in Chinese and Mexican, s, in many Polynesian languages; r, in Chinese, etc. Voice in Animals. — .\nimals, more especially the higher forms, can express their emotions by facial and other gestures. The vocal organs of mammals are essentially the same as those of man. Special resonance organs occur in the orang-outang, mandril, macacus and mycetes monkeys in the form of large cheek pouches, which can be inflated with air, and open between the larynx and the hyoid bone. Birds have an upper (larynx) and a lower larynx (syrinx) the latter being placed at the bifur- cation of the trachea, and is the true vocal organ. Two folds of mucous membrane (three in singing birds) project into each bronchus, and are rendered tense by muscles, and are thus adapted to serve for the production of voice. Among reptiles the tortoises produce merely a sniffling sound, which in the Emys has a peculiar piping character. The blind snakes are voiceless, the chameleon and the lizards have a very feeble voice ; the cayman and crocodile emit a feeble roaring sound, which is lost in some adults owing to changes in the larynx. The snakes have no special vocal organs, but by forcing out air from their capacious lung they make a peculiar hissing sound, which in some species is loud, .-^mong amphibians the frog has a larynx provided with muscles. The sound emitted without any muscu- lar action is a deep intermittent tone, while more forcible expiration, with contraction of the laryn- geal constrictors, causes a clearer continuous sound. The male, in Rana esculenta, has at each side of the angle of the mouth a sound bag, which can be inflated with air and acts as a resonance chamber. The " croaking " of the male frog is quite characteristic. In Pipa, the larynx is pro- vided with two cartilaginous rods, which are thrown into vibration by the blast of air, and act like vibrating rods or the limbs of a tuning fork. Some fishes emit sounds, either by rubbing together the upper and lower pharyngeal bones, or by the expulsion of air from the swimming bladder, mouth or anus. Some insects cause sounds partly by forcing the expired air through their stigmata provided with muscular reeds, which are thus thrown into vibration (bees and many diptera). The wings, owing to the rapid contraction of their muscles, may also cause sounds (flies, cockroach, bees). The Sphinx atropos (death-heap moth) forces air from its sucking stomach. In others, sounds are pro- duced by rubbing their legs on the wing cases (.'^cridiuml, or the wing cases on each other (Gryl- lus, locust), or on the thorax (Cerambyx), on the leg (C.eotrupesl, on the abdomen or the margin of the wing (Nekrophorus). In Cicadacia;, membranes are pulled upon by muscles, and are thus 660 HISTORICAL. caused to vibrate. Friction sounds are produced between the cephalothorax and the abdomen in some spiders (Theridium), and in some crabs (Palinurus). Some mollusca (Pecten) emit a sound on separating their shells. Historical. — The Hippocratic School was aware of the fact that division of the trachea abolished the voice, and that the epiglottis prevented the entrance of food into the larynx. Aristotle made numerous observations on the voice of animals. The true cause of the voice escaped him as well as Galen. Galen observed complete loss of voice after double pneumothorax, after section of the intercostal muscles or their nerves, as well as after destruction of part of the spinal cord, even although the diaphragm still contracted. He gave the cartilages of the larynx the names that still distinguish them ; he knew some of the laryngeal muscles, and asserted that voice was produced only when the glottis was narrowed. He compared the larynx to a flute. The weakening of the voice, in feeble conditions, especially after loss of blood, was known to the ancients. Dodart (1700) was the first to explain voice as due to the vibration of the vocal cords by the air passing between them. The production of vocal sounds attracted much attention among the ancient Asiatics and Ara- bians — less among the Greeks. Pietro Ponce (f 1584) was the first to advocate instruction in the art of speaking incases of dumbness. Bacon (1638) studied the shape of the mouth for the pro- nunciation of the various sounds. Kratzenstein (1781) made an artificial apparatus for the pro- duction of vowel sounds, by placing resonators of various forms over vibrating reeds. Von Kem- pelen (1769 to 1791) constructed the first speaking machine. Rob. Willis (1828) found that an elastic vibrating spring gives the vowels in the series — U, O, A, E, I — according to the depth or height of its tone; further, that by lengthening or shortening an artificial resonator on an artificial vocal apparatus the vowels may be obtained in the same series. The newest and most important inves- tigations on speech are by Wheatstone, v. Helmholtz, Donders, Briicke, etc., and are mentioned in the context. Hensen succeeded in showing exactly the pitch of vocal tone, thus : The tone is sung against a Konig's capsule with a gas flame. Opposite the flame is placed a tuning fork vibrating horizontally, and in front of one of its limbs is a mirror, in which the image of the flame is reflected. When the vocal tone is of the same number of vibrations as the tuning fork, the flame in the mirror shows one elevation, if double, i. e., the octave, two, and with the double octave, four elevations. General Physiology of the Nerves and electro-physiology. 321. STRUCTURE OF THE NERVE ELEMENTS.— The ner- vous elements present two distinct forms: — I. Nerve f Non-medullated. 2. Nerve | Various forms and Fibres. \ Medullated. Cells. \ functions. An aggregation of nerve cells constitutes a nerve ganglion. The fibres rep- resent a cotiihicting apparatus, and serve to place the central nervous organs in connection with peripheral end organs. The nei-ce cells, however, besides trans- mitting impulses, act as physiological centres for automatic or reflex movements, and also for the sensory, perceptive, trophic, and secretory functions. I. Nerve Fibres occur in several forms : — 1. Primitive Fibrils. — The simplest form of ner\e fibril, which is visible with a magnifying power of 500 to Soo diameters linear, consists of primitive nerve fibrils. They are very delicate fibres (Fig. 335, i), often with small varicose swellings here and there in their course, which, however, are due to changes /(?.?/- w^jr/tvw. They are stained of a brown or purplish color by the gold chloride method, and they occur when a nerve fibre is near its termination, being formed by the splitting up of the axis cylinder of the nerve fibre, e.g., in the terminations of the corneal nerves, the optic nerve layer in the retina, the terminations of the olfactory fibres, and in a plexi- form arrangement in non-striped muscle ip. 500). .Similar fine fibrils occur in the gray matter of the brain and spinal cord, and the finely-divided processes of nerve cells. 2. Naked or simple axial cylinders (Fig. 335, 2), which represent bundles of primitive fibrils held together by a slightly granular cement, so that they exhibit very delicate longitudinal striation with fine granules scattered in their course. The best example is the axial cylinder process of nerve cells (Fig. 335, I, ;). [The thickness of the axis cylinder depends upon the number of fibrils entering into its composition.] 3. Axis cylinders surrounded writh Schwann's sheath or Remak's fibres (3.8 to 6.8 ;>. broad), the latter name being given to them from their discoverer (Fig. 335, 3). [These fibres are also called /<;/(■ or non-meduUated, and from their abundance in the sympathetic nervous system, sympathetic] They consist of a sheaih, corresponding to Schwann's sheath [neurilemma, or primitive sheath, which incloses an axial cylinder, while lying here and there under the sheath, and between it and the axial cylinder, are nerve corpuscles. These fibres are always fibrillated longitudi- nally]. The sheath is delicate, structureless, and elastic. Dilute acids clear up the fibres without causing them to swell up, while gold chloride makes them brownish-red. They are widely distributed in the sympathetic nerves \e.g., splenic] and in the branches of the olfactory nerves. All nerves in the embryo, as well as the nerves of many invertebrata, are of this kind. [According to Ran- vier, these fibres do not possess a sheath, but the nuclei are merely applied to the surface, or slightly embedded in the superficial parts of the fibre, so that they belong to the fibre itself These fibres also branch and form an anastomosing network (Fig. 336). This the medullated fibres never do. These fibres, when acted on by silver nitrate, never show any crosses. The branched form occurs in the ordinary nerves of distribution, and they are numerous in the vagus, but the olfactory nerves have a distinct sheath which is nucleated.] 4. Axis cylinders, or nerve fibrils, covered only by a medullary sheath, or white substance of Schwann, are met with in the white and gray matter of the central ner\'ous system, in the optic and auditory nerves. These medtillatt\i ner-je fibres, witliout any neurilemma, often show after death varicose swellings in their course [due to the accumulation of fluid between the medulla or myelin and the axis cylinder]. Hence, they are called varicose fibres. [The varicose appearance is easily produced by squeezing a small piece of the white matter of the spinal cord between a slide and a cover glass. Nitrate of silver does not reveal any crosses, and there are no nodes of Ranvier, while osmic acid reveals no incisures. When acted upon by coagulating reagents, e.^., chromic 36 561 562 STRUCTURE OF NERVE FIBRES. acid, the metiullary sheath appears laminated, so that on transverse section, when the axis cylinder is stained, it is surrounded by concentric circles (Fig. 337)-] 5. MeduUated Nerve Fibres, with Schwann's Sheath (Fig. 335, 5, 6). — These are the most complex nerve fibres, and are 10 to 22.6 'i [jjbjj to .j^'^^ inch] broad. They are most numerous in, and, in fact, they make up the great mass of, the cerebrospinal nerves, although they Fig. 335. Primitive fibrilte ; 2, axis Schwann's she ith ; c. ne neurium ; a, axis cylinder; silver nitrate. I. multipolai ) the right of it a bipol; cell with, ■linder: 3, Remak's fibres: 4, medullated varicose fibre: 5, lemijia: t, t, Ranvier's nodes : b, white substance of Schwa .r, myelin drops ; 7, transverse section of nerve fibres ; 8, nerve fibre lerve cell from the spinal cord ; 2, axial cylinder process ; y, protopla: ell. II, peripheral ganglionic cell, with a connective-tissue capsule piral, and, «, straight process ; m, sheath. are also present in the sympathetic nerves. [When examined in the fresh and living condition in situ, they appear refractive and homogeneous [Ranvier, Stirling) ; but if acted upon by reagents, they are not only refractive, but exhibit a double contour, the margins being dark and well defined.] Each fibre consists of — [l. Schwann's sheath, neurilemma, or primitive sheath; 2. White substance of Schwann, medullary sheath, or myelin; 3. Axis cylinder composed of fibrils; 4. Nerve corpuscles.]. STRUCTURE OF NERVE FIBRES. 563 A. The axis cylinder, which occupies ^ to ^ of the breadth of the fibre, is the essential part of the nerve, and lies in the centre of the fibre (Fig. 335,6, f .,.:/-'-\ '. section of the nerve fibre? of the spinal cord, the axis cylinder; like dots surrounded by a cleai space (myelin). Fig. 338. Remak's fibre from vagus of dog. 6, fibrils ; «, nucleus ; /, protoplasm surrounding ^IG. 339. (single res) stained Endothelial sheath stained, and some nodes ot Kanvier indicated by < fibres blackened by Fromann's Lines. — Chloroform and collodion render it visible, while it is most easily isolated as a solid rod, by the action of nitric acid with excess of potassium chlorate. When acted on by silver nitrate, Fromann observed transverse markings on it, but their significance is unknown (Fig. 335. 8). B. White substance of Schwann, medullary sheath or myelin, surrounds the axis cylinder, like an insulating medium around an electric wire. In the perfectly fresh condition it is quite homo- geneous, highly glistening, bright and refractive ; its consistence is fluid, so that it oozes out of the 564 STRUCTURE OF NERVE FIBRES. cut ends of the fibres in spherical drops (Fig. 335, Jr), [myelin drops, which are always marked by concentric lines, are highly refractive, and best seen when a fresh nerve is teased in salt solution.] After death, or after the action of reagents, it shrinks slightly from tlie sheatii, so that the fibres have a double contour, while the substance itself breaks up into smaller or larger droplets, due not to coagulation [P^rfik], but, according to Toldt, to a process like emulsification, the drops pressing against each other. Thus the fibre it broken up into masses, so that it has a characteristic appear- ance (Fig. 335, 6). It contains a large amount of cereln-in, which swells up to form myelin-like forms in warm water. It also contains fatty matter, so that these fibres are blackened by osmic acid [while boiling ether extracts cholesterin from them]. Chloroform, ether, and benzin, l>y dissolv- ing the fatty and some other constituents of the fibres, make them very transparent. [Some ob- servers describe a fluid lying between the medulla and the axis cylinder.] C. The Sheath of Schwann, or the neurilemma, lies immediately outside of and invests the white sheath (Fig. 335, 6, r), and is a delicate, structureless membrane, comparable to the sarco- lemma of a muscular fibre. D. Nerve Corpuscles. — At fairly wide intervals under the neurilemma, and lying in depressions between it and the medullary sheath, are the nucleated nerve covpuscleSy which are readily stained by pigments. [They may be compared to the muscle corpuscles, the nuclei being surrounded by a small amount of protoplasm which sometimes contains pigment. They are not so numerous as in muscle.] [Adamkiewicz describes nerve corpuscles, or "demilunes'* under the neurilemma, quite dis- tinct from the ordinary nerve corpuscles. They are stained yellow by safranin, while the ordinary nerve corpuscles are stained by methylanilin]. Ranvier's Nodes or Constrictions. — The neurilemma forms in broad fibres at longer and in narrower ones at shorter intervals, the nodes at constrictions of Ranvier (Fig. 335, (i,t,t\ Fig. 338, f, s). They are constrictions which occur at regular intervals along a nerve fibre ; at them the white substance of Schwann is interrupted, so that the sheath of Schwann lies upon the axis cylinder [or its elastic sheath] at the nodes. The part of the nerve lying between any two nodes [is called an interannidar or internodal segment"], and each such segment contains one or more nuclei, so that some observers look upon the whole segment as equivalent to one cell. The function of the Nodes seems to be to permit the diffusion of plasma through the outer sheath into the axis cylinder, while the decomposition products are similarly given off. [A coloring matter like picrocarmine diffuses into the fibre only at the nodes, and stains the axis cylinder red, although it does not diffuse through the white substance of .Schwann.] [Incisures (of Schmidt and Lantermann). — Each interannular segment in a stretched nerve shows a number of oblique lines running across the white substance, which are called incisures. They indicate that the segment is built up of a series of conical sections, each of which is bevelled at its ends, and the bevels are arranged in an imbricate manner, the one over the other (Fig. 33S), while the slight interval between them appears as an incisure. Each such section of the white matter is called a cylinder cone (ICiihnt).\ Neuro- Keratin Sheath. — ."According to Ewald and Kiihne, the axis cylinder, as well as the white substance of Schwann, is covered with an excessively delicate sheath, consisting of neuro- keratin, and the two sheaths are connected by numerous transverse and oblique fibrils, which per- meate the white substance. [The myelin seems to lie in the interstices of this mesh-work.] [Rod-like Structures in Myelin. — If a nerve be hardened in ammonium chroniate (ox picric acid), M'Carthy has shown that the myelin exhibits rod-like structures, radiating from the axis cyl- inder outward, and which are stained with logwood and carmine. The rods are probably not dis- tinct from each other, but are, perhaps, part of the neuro-keratin network already described.] [Action of Nitrate of Silver. — When a small nerve, e.g., the intercostal nerve of a mouse, is acted on by silver nitrate, it is seen to be covered by an endothelial sheath composed of flattened endothelial cells (Fig. 339'), while the nerve fibres themselves exhibit crosses along their course. These crosses are due to the penetration of the silver solution at the nodes, where it stains the cement substance and also part of the axis cylinder, so that the latter sometimes exhibits transverse mark- ings called Fromann's lines (Fig. 335, 8).] [New Methods. — Much progress has recently been made in tracing the course of meduUated nerve fibres by the action of new staining reagents ; thus, acid fuchsin stains the myelin deeply, leav- ing the other parts unstained, at least it can be so manipulated as to yield this result. Weigert finds that the myelin is al.so stained by logwood after a tissue has been hardened in cupric sulphate (or acetate) and a chromium salt. By these methods medullated fibres have been traced where their existence was previously not surmised.] In the spinal nerves those fibres are thickest which have the longest course before they reach their end organ (Schwalbe), while those ganglion cells are largest which send out the longest nerve fibres (Pierret). [Gaskell finds that the longest nerves are not, necessarily, the thickest, for the visceral nerves in the vagus are small nerves, and yet run a very long course.] Division of Nerves. — Nerve fibres run in the nerve trunks without dividing; but when they approach their termination they often divide dichotomously [at a node], giving rise to two similar fibres, but there m.ay be several branches at a node (Fig. 341, /■). STRUCTURE OF THE NERVE SHEATHS. 565 [The divisions are numerous in motor nerves to striped muscles.] In the electrical nerve? of the malapterurus and gymnotus, there is a great accumulation of Schwann's sheaths round a nerve, so that a nerve fibre is as thick as a sewing needle. Such a fibre, when it divides, breaks up inio a bundle of smaller fibres. Nerve Sheaths. — [An anatomical nerve trunk consists of bundles of nerve fibres. The bundles are held together by a common connective-tissue sheath (Fig. 340, c/), the epineurium (A.xe! Key and Jietzius), which con\.3.\ns the larger blood vessels, lymphatics, and sometimes fat and plasma cells ] Each bundle is surrounded with its own sheath or perineurium (/<•) [which consists of lamellated connective tissue disposed circularly, and between the lamella? are lymph spaces hned by flattened endothelial plates]. These lymph spaces may be injected from and communicate with the lymphatics. [The nerve fibres within any bundle are held together by delicate connective tissue, which pene- trates between the adjoining fibres, constituting the endoneurium {ed). It consists of delicate fibres with branched connective-tissue corpuscles (Fig. 335, 6, d), and in it lie the capillaries, which are not very numerous, and are arranged to form elongated open meshes.] [Henle's Sheath. — When a nerve is traced to its distribution, it branches and becomes smaller, until it may consist only of a few bundles or even a single bundle of nerve fibres. As the bundle branches, it has to give oft' part of its lamellated sheath or perineurium to each branch, sn that, as we pass to the periphery, the smaller buntlles are surrounded by few lamellae. In a bundle con- FiG. 340. : (median), c/, epineurium; pe, perineurium ; ed, endoneuriun taining only a few fibres, this sheath may be much reduced, or consist only of thin, flattened connective- tissue corpuscles with a few fibres. A sheath surrounding a few nerve fibres is called Henle's Shealh [Ranvier).'] [Nervi Nervorum. — Marshall and v. Hor.iley have shown that the nerve sheaths are provided with special nerve fibres, in virtue of which they are endowed with sensibility.] Development. — At first nerve fibres consist only of fibrils, which become covered with connective substance, and ultimately the white substance of Schwann is developed in some of them. The growth in length of the fibres takes place by elongation of the individual "interannular" segments, and also by the new formation of these ( Vignnl). II. Ganglionic or Nerve Cells. — i. Multipolar nerve cells (Fig. 335, I) occur partly as /i;;jv cells (100 ,'/, and are, therefore, visible to the unaided eye). In the anterior horn of the spinal cord, and in a diflerent form in the cerebellum, and partly in a smaller form (20 to 10 ,'ji) in the posterior horns of the spinal cord, many parts of the cerebrum and cerebellum, and in the retina. They may be spherical, ovoid, pyramidal [cerebrum], pear- or flask-shaped [cerebellum], and are provided with numerous branched processes which give the cells a characteristic appear- ance. They are devoid of a cell envelope, are of soft consistence, and exhibit a fibrillated structure, which may extend even into the processes. Fine granules lie scattered throughout the cell sub- stance between the fibrils. Not unfrequently yellow or brown granules of pigment are also found, either collected at certain parts in the cell or scattered throughout it. The relatively large 566 CHEMISTRY OF THE NERVOUS SUBSTANCE. Fig. 341. nuc/eus consists of a clear envelope enclosing a resistant substance. It does not appear to have a membrane in youth (Sc/iwa/l/e). Within the nucleus lies the nucleolus, which in the recent condition is angu- lar, provided with processes and capable of motion, but after death is highly refractive and spherical. One of the processes is always until ancheil, constituting the axial cylinder process (1, z), which remains unbranched; but it soon becomes covered with the white substance of Schwann and the other sheaths of a medullated nerve, so that it becomes the axial cylinder of a nerve fibre. [Thus a nerve fibre is merely an excessively long, unbranched process of a nerve cell pushed outward toward the periphery.] It is not definitely ascer- tained that the cerebral cells have such processes. All the other processes divide very frequently until they form a branched, root-like, complex arrangement of the finest primitive fibrils. These are called protoplasmic processes (I,j). By means of these processes ad- joining cells are brought into communication with each other, so that impulses can be conducted from one cell to another. Further, many of these fibrils approximate to each other and join together to form axis cylinders of other nerve fibres. 2. Bipolar cells are best developed in fishes, e. g., in the spinal ganglia of the skate, and in the Gasserian ganglion of the pike. They appear to be nucleated, fusiform enlargements of the axis cylinder (Fig. 335, on the right of I). The white substance often stops short on each side of the enlargement, but sometimes the white substance and the sheath of .Schwann pass over the enlargement. 3. Nerve cells with connective-tissue capsules occur in the peripheral ganglia of man (Fig. 335, II), e. g., in the spinal gan- glia. The solt body of the cell, which is provided with several processes, is coveied by a tliick, tough capsule composed of sev- eral layers of connective-tissue corpuscles; while the inner surface of the composite capsule is lined by a layer of delicate endothelial cells (Fig. 341). The body of the cells in the spinal ganglia is traversed by a network of fine fibrils (Flenuning). The capsule is continuous with the sheath of the nerve fibre. Rawitz and G. Retzius find that the cells of the spinal gangha are unipolar, the outgoing fibre taking a half-turn within the capsule before it leaves the cell (Fig. 341). Retzius [and Ranvier] observed the process to divide like a T. Perhaps this division corresponds to the two processes of a bipolar cell. The jugular ganglion and plexus gangliiformis vagi in man contain only unipolar cells, so that, in this re- spect, they may be compared to spinal ganglia. The same is the case in the Gasserian ganglion; while the ciliary, sphenopalatine, otic and sub- maxillary ganglia structurally resemble the ganglia of the sympathetic. 4. Ganglionic cells with spiral fibres (Baile, J. AniolJ) occur chiefly in the abdominal .sympathetic of the frog. The body of the cell is u>u.illy pyriform in shape, and from it proceeds a straight unbranched process (Fig. 335, III, «), which ultimately becomes the axis cylinder of a nerve. A spiral fibre springs from the cell (? a network), emerges from it, and curves in a spiral direction round the former {0). The whole cell is surrounded by a nucleated capsule («/). We know nothing of the significance of the different fibres. 322. CHEMISTRY OF THE NERVOUS SUBSTANCE.— Me- chanical Properties of Nerves. — i. Proteids. — .-Mbiimin occurs chiefly in the axis cylinder and in the substance of the ganglionic cells. Some of this pro- teid substance presents characters not unlike those of myosin (§ 293). Dilute solution of comtnon salt extracts a proteid from nervous matter, which is precipi- tated by the addition of much water and also by a concentrated solution of common salt ( Petrozosky). Potash a/bu»iin &nA a glohulin-like substance &xt also present. Albuminoids. — Nuclein occurs especially in the gray matter (§ 250, 2), while neuro-keratin, a body containing much sulphur and closely related to keratin, occurs in the corneous sheath of nerve fibres (p. 564). If gray nervous matter be subjected to artificial digestion with trypsin, both of these substances remain undigested {Kiihnc and EivaM). Pure neuro-keratin is obtained by treat- ing the residue with caustic potash. The sheath of Schzcanii does not yield gelatin, but a substance closely related to elastin (§ 250, 6), from which it differs, REACTION AND CHEMICAL COMPOSITION OF NERVES. 567 however, in being more soluble in alkalies. The connective tissue of nerves yields gelatin. 2. Fats and otlwr allied substances soluble in ether, more especially in the white matter : (a) Cerebrin, free from phosphorus (§ 250, 3). It is a white powder composed of spherical granules soluble in hot alcohol and ether, but insoluble in cold water. It is decomposed at So° C, and its solutions are neutral. When boiled for a long time with acids it .splits up into a left rotatory body like sugar, and another unknown pro- duct. Preparation. — Rub up the brain into a thin fluid with baryta water. Extract the separated cuagulum with boiling alcohol. The extract is frequently treated with cold ether to remove the cholcsterin ( W. Miiller). I'arkus separated from cerebrin its homologue, homocerebrin, which is slightly more soluble in alcohol, and the clyster-like body, encephalin, which is soluble in hot water. {b) Lecithin (§ 251) and its decomposition products — glycero-phosphoric acid and oleo-phosphoric acid. Neurin (or Cholin = C.IIjsNO,) is a strongly alkaline, colorless fluid, forming crystalline salts with acids. It is soluble in water and alcohol, and has been formed synthetically from glycol and trimethylamin. Lecithin is a salt of the base neurin. (^) Protagon, which contains N and P, is similar to cerebrin, and is, accord- ing to its discoverer i^Liebreich), the chief constituent of the brain. According to Hoppe-Seyler [and Diaconow], it is a mixture of lecithin and cerebrin. [The investigations of Gamgee and Blankenhorn have shown, however, that protagon is a definite chemical body. They lind that, instead of being unstable, it is a very stable body.] It is a glyco- side, and crystalline, and can be extracted from the brain by warm alcohol, and when boiled with baryta yields the decomposition products of lecithin. 3. The following substances are extracted by water : Xanthin and hypoxanthin {Scherer) kreatin (Lerch), inosit ( /F. Midler^, ordinary lactic acid (Gscheidkn), and volatile fatty acids; leucin (in disease), urea (in urremia). All these substances are for the most part products of the regressive metabolism of the tissues. Reaction. — Nervous substance, when passive, is neutral or feebly alkaline in reaction, while active (? and dead) it is acid {Punkc). The gray matter of the brain, when quite fresh, is alkaline {Liebreicli), but death rapidly causes it to becoine acid (^Gscheidlen). The reaction of nerve fibres varies during life. After introducing methyl-blue into the body of a living animal, Ehrlich found that the axis cylinder became blue, i.e., in those nerves which have an alkaline reaction (cortex cerebri, cardiac, sensory, motor (non-striped), gustatory and olfactory fibres), while the termination of motor (voluntary) nerves remain uncolored. The latter he regards as acid. The nerves after death have a more solid consistence, so that in all probability some coagulation or change, comparable to the stiffening of muscle (§ 295), occurs in them after death, while at the same time a free acid is liberated. It a fresh brain be rapidly " broiled" at 100^ C, it, like a muscle similarly treated, remains alkaline (^§ 295.) Chemical Composition. Gray Matter. White Matter. The sohds consist of — 81.6 per cent. 1S.4 " 6S.4 per cent. 31.6 •• Albumins and glutin 55-4 " 17.2 " 1S.7 " 24,7 " 99 " 52.1 " Lecithin Cholesteria and fats Cerebrin 0.5 " 6.7 " 9.5 " Substances insoluble in ether Salts 1-5 " 0.5 " 1000 100 568 MECHANICAL STIMULI. In loo parts of Ash, Breed found potash 32, soda II, magnesia 2, lime 0.7, XaCl 5, iron phos- phate 1.2, fixed phosphoric acid 39, sulphuric acid o.i, silicic acid 0.4. [Ptomaines (p. 275) are obtained from putrefied lirain. They have an eflfect on the motor nerves like curara, but in a much less degree, while the phenomena last for a much shorter time [Guaresc/ii and Mosio).^ Mechanical Properties. — One of the most remarkable mechanical proper- ties of nerve fibres is the absence of elastic tension according to the varying posi- tions of the body. Divided nerves do not retract ; such nerves exhibit delicate, microscopic, transverse folds (Fontana's transverse markings) [like watered silk]. The cohesion of a nerve is very considerable. When a limb is forcibly torn from the body, as sometiines happens from its becoming entangled in machinery, the nerve not unfrequently remains unsevered, while the other soft parts are rup- tured. [TiUaux found that a weight of no to 120 lbs. was required to rupture the sciatic nerve at the popliteal space, while to break the median or ulnar nerve of a fresh body, a force equal to 40 to 50 lbs. was required. The toughness and elasticity of nerves are often well shown in cases of injury or gun-shot wounds. The median or ulnar nerve will gain 15 to 20 centimetres (6 to 8 inches) before breaking. Weir Mitchell has shown that a healthy nerve will bear a very con- siderable amount of pressure and handling, and, in fact, the method of nerve stretching depends upon this property of a nerve trunk.] 323. METABOLISM OF NERVES.— Influence of Blood Supply. — We know very little regarding the metabolic processes that occur in nerve tissue. Some extractives are obtained from nerve tissue, and they may, perhaps, be re- garded as decomposition products (p. 567). It has not been proved satisfactorily that during the activity of nerves there is an exchange of O and CO.j. That there is an exchange of materials within the nerves is proved by the fact that after com- pression of the blood vessels of the nerves, the excitability of the nerves falls, and is restored again when the circulation is re-established. Compression of the abdominal aorta causes paralysis and numbness of the lower half of the body, while occlusion of the cerebral vessels causes almost instantaneously cessation of the cerebral functions. The metabolism of the central nervous organs is much more active than that of the nerves themselves. [If the abdominal aorta of a rabbit be compressed for a few minutes the hind limbs are quickly paralyzed, the animal crawls forward on its fore legs, drawing the hind limbs in an extended position after it.] The ganglia form much lymph. 324. EXCITABILITY OF THE NERVES— STIMULI.— Nerves possess the property of being thrown into a state of excitement by stimuli, and are, therefore, said to be excitable or irritable. The stimuli may be applied to, and may act upon, any part of the nerve. [The following are the various kinds of stimuli, /. c, modes of motion, which act upon nerves] : — 1. Mechanical stimuli act upon nerves when they are applied with sufficient rapidity to produce a change in the form of the nerve particles, e:g., a blow, pressure, pinching, tension, puncture, section. In the case of sensory nerves, when they are stimulated, pain is produced, as is felt when a limb "sleeps," or when ])ressure is exerted upon the ulnar nerve at the bend of the elbow. When a motor nerve is stimulated, motion results in the muscle attached to the nerve. If the continuity of the nerve fibres be destroyed, or, what is the same thing, if the continuity of the axial cylinder be interrupted by the mechanical stimulus, the conduction of the impulse across the injured part is interrupted. If the molecular arrangements of the nerves be permanently deranged, e. g., by a violent shock, the excitability of the nerves may be thereby extinguished. A slight blow applied to the radial nerve in the fore arm, or to the axillary nerves in the supra- clavicular groove, is followed by a contraction of the muscles supplied by these nerves. Under pathological conditions the e.scitability of a nerve for mechanical stimuli may be increased enor- mously. THERMAL AND CHEMICAL STLMULI. 5G9 Tigerstedt ascertained that the minimal mechanical stimulus is represented by 900 milligram- millimetres, and the maximum by 7000 to 8000. Strong stimuli cause fatigue, but the fatigue does not extend beyond the part stimulated. A nerve when stimulated mechanically does not become acid. Slight pressure without tension increases the excitability, which diminishes afier a short time. The mechanical work produced by an excited muscle in consequence of a stimulus was 100 times greater than the mechanical energy of the mechanical nerve stimulus. Continued pressure upon a mixed nerve paralyzes the motor sooner than the sensory fibres. If the stimultis be applied very gradually, the nerve may be rendered inexcitable without manifesting any signs of its being stimulated (Fon- iana, iJjS). Paralysis, due to continuous pressure gradually applied, may occur in the region supplied by the brachial nerves ; the left recurrent laryngeal nerve also may be similarly paralyzed from the pressure of an aneurism of the arch of the aorta. By increasing the pressure on a nerve by using a gradually increasing weight, there is at first an increase and then a decrease of the excitability. Pressure on a mixed nerve abohshes reflex con- duction sooner than motor conduction {Kionccker and Zederbauni). Nerve stretching is one of the methods that has recently been employed for therapeutical pur- poses. If a nerve be exposed and stretched, or if a certain tension be exerted upon it, this acts as a stimulus. Slight extension increases the reflex excitability (Schleich), while violent extension pro- duces a temporary diminution or abolition of the excitability (I'alenlin). The centripetal fibres (sensory) of the sciatic nerve are sooner paralyzed thereby than the centrifugal motor (Conrad). During the process of extension mechanical changes are produced, either in the nerve itself or in its end organs, causing an alteration of the excitability, but it may also afiect the central organs. The paralysis which sometimes occurs after forcible stretching usually rapidly disappears. There- fore, when a nerve is in an excessively excitable condition, or when this is due to an inflammatory fixation or constriction of the nerve at some part of its course, then nerve stretching may be useful, partly by diminishing the excitability, partly by breaking up the inflammatory adhesions. In cases where stimulation of an afferent nerve gives rise to epileptic or tetanic spasms, nerve stretching miy be useful by diminishing the excitability at the periphery, in addition to the other efi'ects already described. It has also been employed in some spinal affections, which may not as yet have resulted in marked degenerative changes. Tetanomotor. — For physical purposes, a nerve may be stimulated mechanically by means of Heidenhain's tetanomotor, which is simply an ivory hammer attac'.ted to the prolonged spring of a Neefs hammer of an induction machine. The rapid vibration of the hammer communicates a series of mechanical shocks to the nerve upon which it is caused to beat. Rhythmic extension of a nerve causes contractions and even tetanus. 2. Thermal Stimuli. — If a frog's nerve be heated to 45° C, its excitability is first increased and then diminished. The higher the temperature, the greater is the excitability, and the shorter its duration { Afanasieff). If a nerve be heated to 50' C. for a short time, its excitability and conductivity are abolished. The frog's nerve alone regains its excitability on being cooled {Pickford, J. Rosenthal). If the temperature be raised to 65° C, the excitability is abolished without the occurrence of a contraction, while its medulla is broken up (^Eckhard). Sudden cooling of a nerve to 5° C. acts as a stimulus, causing contraction in a muscle, while sudden heating to 40° to 45° C. produces the same result. If the temper- ature be increased still more, instead of a single contraction a tetanic condition is produced. All such rapid variations of temperature quickly exhaust the nerve and kill it. If a nerve be frozen gradually, it retains its excitability on being thawed. The excitability lasts long in a C(wfo/ nerve ; in fact, it is increased in a motor nerve, but the contractions are not so high and more extended, while the conduction in the nerve takes place more slowly. Among mammalian nerves, the afferent and vaso-dilator nerves at 45° to 50° C. exhibit the results of stimulation, while the others only show a change in their excitability. When cooled to + 5° C., the excitability of all the fibres is diminished (^Griitzner). 3. Chemical Stimuli excite nerves when they act so as to change their co.i- stitution with a certain rapidity (p. 509). Most chemical stimuli act by first in- creasing the nervous excitability, and then diminishing or paralyzing it. Chem- ical stimuli, as a rule, have less effect upon sensory than upon motor fibres (Eck- hard, Setschenow). According to Griitzner, the inactivity of chemical stimuli. 570 PHYSIOLOGICAL AND ELECTRICAL STIMULI. so often observed when they are applied to sensory nerves, depends in great part upon the non-simultaneous stimulation of all the nerve fibres. Among chemical stimuli are — (a) rapid abstraction of 7vatcr by dry air, blotting paper, exposure in a chamber containing sulphuric acid, or by the action of solutions which ab- sorb fluids, e.g., concentrated solutions of neutral alkaline salts (NaCl. excites only motor fibres in mammals — Giiifz/icr), sugar, urea, concentrated glycerin (and ? some metallic salts). The subsequent addition of water may abolish the contrac- tions, while the nerve may still remain excitable. The abstraction of water first increases and afterward diminishes the excitability. The imbibition of rvater diminishes the excitability, {b) Free alkalies, mideral acids (not phosphoric), many organic acids (acetic, oxalic, tartaric, lactic), and most salts of the heavy metals. While the acids act as stimuli, only when they are somewhat concen- trated, the caustic alkalies act in solutions of 0.8 to o.i per cent. {Kiihne). Neutral potash salts in a concentrated form rapidly kill a nerve, but they do not ex- cite it nearly so strongly as the soda compounds. Dilute solutions of the neutral potash salts first increase and afterward diminish it {Ranke). (r) Various sub- stances, e.g., dilute alcohol, ether, chloroform, bile, bile salts, and sugar. These substances usually excite contractions, and afterward rapidly kill the nerve. Am- monia {£ckhai-J), lime water {Kiihne), some metallic salts, carbon bisulphide and ethereal oils kill the nerve without exciting it — at least without producing any contraction in a frog's nerve-muscle preparation. Carbolic acid does the same, although when applied directly to the spinal cord it produces spasms. These substances excite the muscles when they are directly applied to them. Tannic acid does not act as a stimulus either to nerve or muscle. As a general rule, the stimulating solutions must be more concentrated when applied to a nerve than to a muscle, in order that a contraction may be prjduced. [Methods. — If a nerve-muscle preparation of a frog's limb be made, and a straw flag (p. 508) attached to the toes while the femur is fixed in a clamp, and its nerve be then dipped in a saturated solulioii of common salt, the toes soon begin to twitch, and by and by the whole limb becomes tetanic, and thus keeps the straw flag extended. The eflect of fluid on a muscle or nerve is easily tested by fixing the muscle in a clamp, while a drop of the fluid is placed on a greased surface, which gives it a convex form [Kiihne). The end of the muscle or nerve is then brought into con- tact with the cupola of the drop.] 4. The Physiological or normal stimulus excites the nerves in the normal intact body. Its nature is entirely unknown. The " nerve motion " thereby set up travels either in a " centrifugal " or outgoing direction from the central nervous system, giving rise to motion, inhibition of motion, or secretion; or in a " centripetal " or ingoing direction from the specific end organs of the nerves of the special senses or the sensory nerves. In the latter case the impulse reaches the central organs, where it may excite sensation or perception, or it may be transferred to the motor areas and be conducted in a centrifugal direction, con- stituting a "reflex " stimulation (§ 360). A single physiological nerve impulse travels more slowly than that excited by the momentary application of an induc- tion shock {Lovcn, v. Kries). It is not a uniform process, excited by varying intensity and greater or less frequency of stimulation, but it is essentially a pro- cess varying considerably in duration, and it may even last as long as J 3 second (?'. Kries). 5. Electrical Stimuli. — The electrical current acts most powerfully upon the nerves at tlie moment when it is applied, and at the moment when it ceases (§ 336) ; in a similar way, any increase or decrease in the strength of a constant current acts as a stimulus. If an electrical current be applied to a nerve, and its strength be very gradually increased or diminished, then the visible signs of stimulation of the nerve are very slight. As a general rule, the stimulation is more energetic the more rapid the variations of the strength of the current applied to the nerve, /. e., the more suddenly the intensity of the stimulating current is increased or diminished {Du Bois-Rcyniond). EFFECT OF CONSTANT CURRENT. 571 An electrical current must have a certain strength [liminal intensity) before it is effective. By uniformly increasing the strength of the current, the size of the contraction increases rapidly at first, then more slowly {Tigerstedt and Willhard). An electrical current, in order to stimulate a nerve, must act at least during 0.0015 second {Pick, i86j, Kihiig); even with currents of slightly longer dura- tion, the ojiening shock may have no effect. If the duration of the closing shock of a constant current be so arranged that it is just too short to be active, then it merely requires to last 1.3 to 2 times longer to produce the most complete effect ( G> tin/iageii) . The electrical current is most active when it flows in the long axis of the nerve ; it is inactive when applied vertically to the axis of the nerve {Galvani,/. Albrecht, A. Meyer). Similarly, muscles are incomparably less excited by transverse than by longitudinal currents {Giiifre). The grea/er the length of nerve traversed by the current, the less the stimulus that is required (Pfaff, Marciise, Tschirjew). Constant Current. — If the constant current be used as a nervous stimulus, the stimulating effect on the sensory nerves is most marked at the moment of closing and opening [or breaking] the current ; during the time the current passes only slight excitement is perceived, but even under these circumstances very strong currents may cause very considerable, and even unbearable, sensations. If a con- stant current be applied to a motor nerve, the greatest effect is produced when the current is closed [closing contraction] and when it is opened [opening contraction]. But while the current is passmg, the stimulation does not cease completely ( Wundt) ; for, with a certain strength of stimulus, the muscle remains in a state of tetanus (galvanotonus or "closing tetanus") (Pfliigcr). For the same effect on muscles, see p. 51S. With strong currents, this tetanus does not appear, chiefly because the current diminishes the excitability of the nerves, and thus develops resistance, which prevents the stimulus from reaching the muscle. According to Hermann, a descending current applied to the nerve, at a distance from the muscles, causes this tetanus more readily, while an ascending current causes it more readily when the current is closed near the muscle. The constant current is said by Griitzner to have no effect on vaso- motor and secretory fibres. Over-maximal Contraction. — By gradually increasing the strength of the electrical stimulus apphed to a motor nerve, Fick observed that the muscular contractions (height of the lift) at first increased proportionally lo the increase of the stmiulus, until a maximal contraction was obtained. If the strength of the stimulus be increased still further, another increase of the contraction above the first-reached maximum is obtained. This is called an " over-maximal contraction^ Occasion- ally between the first maximum and the second there is a diminution, or, indeed, absence of or gap in the contractions (fick). The cause of this lies in the positive pole, which, with a certain strength of current, is sufficient to prevent the further transmission of the excitement (^ 335)- On continuing to increase the induction current, ultimately a stage is reached where the stimulation at the negative pole again becomes stronger than the inhibition at the positive, and this overcomes the latter. The contractions before the gap are caused by the occurrence of the induction current (their latent period is short) ; the contractions (long latent period, like that after all opening shocks — IValter, p. 518) after the gap are caused by the disappearance of the induction current, /. <•., by polarization ; this is added to the stimulation proceeding from the negative pole, which, after the gap, overcomes the inhibition at the positive pole, and excites the over-maximal contractions (Tigcr- stcJt and Willhard). Tetanus. — \{ single shocks of short duration be rapidly applied after each other to a nerve, tetanus in the corresponding muscle is produced (§ 298, III). A motor nerve has a greater specific excitability for electrical stimuli than the muscle substance. This is proved by the fact that a feebler stimulus suffices to excite a muscle when applied to the nerve than when it is applied to the muscle directly, as occurs when the terminations of the motor nerves are paralyzed by curara {Rosenthal). Soltmann found that the excitability of the motor nerves of new-born ani- 572 DIMINUTION OF THE EXCITABILITY. mals for electrical stimuli is less than in adults. The excitability increases until the 5th to loth month. Unequal Excitability. — Under certain circumstances, the nearer the part of the motor nerve stimulated lies to the central nervous system, the greater is the effect produced (contraction ) ; [or, what is the same thing, the further the point of a nerve which is stimulated is from the muscle, the stimulus being the same, the greater is the contraction]. According to Fleischl, all parts of the nerve are equally excitable for chemical stimuli. P'urther, it is said that the higher-placed parts of a nerve are more excitable only when the stimulating current passes in a descending direction ; the reverse is the case when the current s&csnd?, { Hermann, Fleischl). On stimulating a j-^wci-ij nerve, Rutherford and Hiillsten found that the reflex contraction was greater the nearer the point stimulated was to the cen- tral nervous system. Unequal Excitability in the same Nerve. — Nerve fibres, even when func- tionally the same and included in the same nerve trunk, are not all equally excitable. Thus feeble stimulation of the sciatic nerve of a frog causes contraction of the flexor muscles, while it requires a stronger stimulus to produce contraction of the extensors {Riftei; iSoj, Rolletf). According to Ritter, the nerves for the flexors die first. Direct stimuL-ition of the muscles in ciirarized animals shows that the flexors contract with a feebler stimulus (but also fatigue sooner) than the extensors; the pale muscles of the rabbit are also more excitable than the red. As a rule, poisons affect the flexors sooner than the extensors. In some muscles some pale fibres are present, and they are more excitable than the red (Grulsner) (I 298). Unipolar Stimulation. — If one electrode of an induction apparatus be ap- plied to a nerve it may act as a stimulus. Du Bois-Raymond has called this " unipolar induction action." It is due to the movement of the electric current to and from the free ends of the open induction current at the moment of induc- tion. [Unipolar induction is more apt to occur with the opening than the closing shock, because the former is more intense.] Upon muscle electrical stimuli act quite as they do upon nerves. Elec- trical currents of very short duration have no effect iipon muscles whose nerves are paralyzed by curara (Briiche), and the same is true of greatly fatigued muscles, or muscles about to die or greatly weakened by diseased condition (§ 399). 325. DIMINUTION OF THE EXCITABILITY— DEGENERA- TION AND REGENERATION OF NERVES.— i. Normal Nutri- tion. — The continuance of the normal excitability in the nerves of the body depends upon the maintenance of the normal nutrition of the nerves themselves and a due supply of blood. Insufficient nutrition causes in the first instance in- creased excitability, and if the condition be continued the excitability is dimin- ished (§ 339, I). When the physician meets with the signs of increased excitability of the nerves, under bad or abnormal conditions of nutrition, this is to be regarded as the beginning of the stage of decrease of the nerve energy. Invigorating measures are required. If the terminal nervous apparatus be subjected to a temporary disturbance of its nutrition, the return of the normal nutritive process is heralded by a more or less marked stage of excitement. The more excitable the nervous apparatus the shorter must be the duration of the disturbance of nutrition, e.g., cutting off the arterial blood supply or interfering with the respiration. 2. Fatigue. — Continued excessive stimulation of a nerve, without sufficient intervals ot repose, zsecati fatigue of the nerve, and by exhaustion rapidly diinin- ishes the excitability. A nerve is more slowly fatigued than a muscle {Bernstein), but it recovers inore slowly (§ 304). [Nerves of cold-blooded animals ( Widenskii) and mammals {Bowditch) may be tetanized for hours without becoming fatigued.] SEPARATION FROM NERVE CENTRES. 573 Recovery. — When a nerve recovers, at first it does so slowly then more rap- idly, and afterward again more slowly. If recovery does not occur within half an hour after a frog's nerve has been subjected to very long and intense stimula- tion, it will not take place at all. 3. Continued inaction of a nerve diminishes and may ultimately abolish the excitability. Fiu. 342. ABC D E 'it ^ nd regeneration of nerves. A, subdi' B. further disintegration thereof (osmic acid staining) ; of the axial cylinder, which is surrounded ' ' * " D, accumulation of nuclei, with" the spindle-shaped fibre; E, a new nerve f through an old nen sheath of Schwann, Thus the central ends of divided sensory nerves, after amputation of a limb, lose their excita- hilily, although the nerves are still connected with the central nervous system, because the end organs through which they were normally excited have been removed. 4. Separation from their Nerve Centres, — The nerve fibres remain in a condition of normal nutrition only when they are directly connected with their centre, which governs the nutritive processes within the nerve. If a nerve 574 TRAUMATIC AND FATTV' DEGENERATION. within the body be separated from its centre — either by section of the nerve or compressing it — within a short time it loses its excitability, and the peripheral end undergoes fatty degeneration, which begins in four to six days in warm-blooded animals, and after a long time in cold-blooded ones {Joh. Miillcr). See also the changes of the excitability during this condition, the so-called " Reaction of degeneration" (§ 339). If the sensory nerve fibres of the root of a spinal nerve be divided on the central side of the ganglion, the fibres on the peripheral side do not degenerate, for the ganglion is the trophic or nutritive centre for the sensory nerves, but the fibres still in connection with the cord degenerate ( Waller, Bidder). [Wallerian Law of Degeneration. — If a spinal nerve be divided, the peripheral part of the nerve and its branches, including the sensory and motor fibres, degenerate completely (Fig. 343, A), while the central parts of the nerve remain unaltered. If the anterior root of a spinal nerve alone be divided before it joins the posterior root, all the peripheral nerve fibres connected with the an- terior root degenerate (Fig. 343, B), so that in the nerve of distribution only the motor fibres degenerate. The portion of the nerve root which remains attached to the cord does not regenerate. If \.\\t posterior root aXone be divided, between the spinal cord and the ganglion, the effect is reversed, the part of the nerve root lying between the section and the spinal cord degenerates, while the part of the Fig. 343. Diagram of the roots of a spinal nerve showing the effect of section (the black parts represent the degenerated parts). A, section of the nerve trunk beyond the ganglion ; B, of the anterior root, and C, of the posterior ; D, excision of the ganglion ; a, anterior,/, posterior root ; g, ganglion. nerve connected with the ganglion does not degenerate (Fig. 343, C). The cen- tral fibres degenerate because they are separated from the ganglion. If the gan- glion be excised, or if separated, as in Fig. 343, D, both the central and peri- pheral parts of the posterior root degenerate. These experiments of Waller show that the fibres of the anterior and posterior roots are governed by different cen- tres of nutrition or " trophic centres." As the anterior root degenerates when it is separated from the cord, and the posterior when it is separated from its own ganglion, it is assumed that the trophic centre for the fibres of the anterior root lies in the multipolar nerve cells of the anterior horn of the gray matter of the spinal cord, while that for the fibres of the posterior root lies in the cells of the ganglion placed on it. The nature of this supposed trophic influence is entirely unknown.] Traumatic and Fatty Degeneration. — Both ends of the nerve at the point of section imme- diately begin to undergo "traumatic degeneration." (In the frog on the first and second day. ) After a time, neither the myelin nor axis cylinder are distinguishable [Schijf), According to Engelmann, this condition extends only to the nearest node of Ranvier, and afterward the so-called "fatty degen- eration" begins. The process of "yiz//)'" degeneration begins simultaneously in the whole peripheral portion ; the white substance of Schwann breaks up into masses (Fig. 342, A), just as it does after death, in microscopic preparations; afterward, the myelin forms globules and round masses (B), the axial cylinder is compressed or constricted, and is ultimately broken across (C) in many places (7th day). The nerve fibre seems to break up into two substances — one fatty, the other proteid in TROPHIC CENTRES AND EFFECTS OF POISONS ON NERVES. 575 constilulion f^. Afayer), the fat being absorbed. The nuclei of Schwann's sheath swell up and proliferate (D— until the tenth day). According to Ranvier, the nuclei of the interannular segments and their surrounding protoplasm proliferate, and ultimately interrupt the continuity of the axis cylinder and the myelin. They then undergo considerable development with simuhaneous disap- pearance of the medulla and axis cyhnder, or at least the fatty substances formed bv their degenera- tion, so that the nerve fibres look like fibres of connective tissue, [.\ccording to this view, (he pro- cess is in part an aclive one, due to the growth of the nerve corpuscles breaking up the contents of the neurilemma, which then ultimately undergo chemical degenerative changes.] According to Ranvier, Tizzoni, and others, leucocytes wander into the cut ends of the nerves, and also at Ran- vier's nodes, insinuating themselves into the nerve fibres, where they take myelin into their bodies, and subje:t it to certain changes. [These cells are best revealed by the action of osmic acid, which blackens any myelin particles in th-.-ir interior.] Degeneration also takes place in the motorial end plates, beginning first in the nonmedullateil branches, then in the terminal fibrils, and lastly in the nerve trunks [Gessler). Regeneration of Nerves. — In order that regeneration of a divided nerve may take place {Cruickshank, /ygs), the divided ends of the nerve must be broupht into contact (? 244). In man this is done by means of sutures. AI>out the middle of the fourth week, small clear bands appear within the neurilemma, winding between the nuclei and the remains of the myelin (E). They soon become wider, and receive myelin with incisures, and nodes, and a sheath of Schwann (second to third month — F). The regeneration process takes place in each interannular segment, v\'hile the in- dividual segmerts unUe end to end at the nodes of Ranvier (^ 321, I, 5). On this view, each nerve segment of the fibre corresponds to a "cell unit" {E. Neumann, Eichhorst). The same process occurs in nerves ligatured in their course. Several new fibres may be formed within one old nerve sheath. The divided axis cylinders of the central end of the nerve begin to grow about the fourteenth day, untd they meet the newly formed ones, with which they unite. [Primary and Secondary Nerve Suture. —Numerous experiments on animals and man have established the fact that immediate or primary suture of a nerve, after it is divided, either acci- dentally or intentionally, hastens reunion and regeneration, and accelerates the restoration of function. Secondary suture, i.e., bringing the ends together long after the nerve has been divided, has been practiced with success. Surgeons have recorded cases where the function was restored after division had taken place for 3 to 16 months, and even longer, and in most cases the sensibility was restored first, the average time being 2 to 4 weeks. Motion is recovered much later. The ends of the ner\e should be stitched to each other with catgut, the muscles at the same time being kept from becoming atrophied by electrical stimulation and the systematic use of massage (J 307). After suture of a nerve conductivity is restored in the rabbit in 40 days, on the 31st in dogs, and 25th in fowls, but after simple division without suture not till the 60th day in the rabbit. Transplantation of nerve does not succeed ( Johmon).'] Union of Nerves.— The central end of a divided motor nerve may unite with the peripheral end of another and still conduct impulses {Rava). [There seems to be no doubt that sensory fibres will reunite with sensory fibres, and motor fibres with motor fibres, and the regenerated nerve will, in the former case, conduct sensory impulses, and the latter motor impulses. There is very considerable diversity of opinion, however, as to the regeneration or union of sensory with motor fibres. Paul Bert made the following experiment : He stitched the tail of a rat into the animal's back, and after union had taken place, he cut the tail from the body at the root, so that the tail, as it were, grew out of the animal's back, broad end uppermost. On irritating the end of the tail, which was formerly the root, the animal gave signs of pain. This experiment shows that nerve fibres can conduct impulses in both directions. C)ne of two things must have occurred. Either the motor fibres, which normally carried impulses down the tail, now convey them in the opposite direction, and convey them to sensory fibres with which they have united; or the sensory fibres, which normally conducted impulses from the tip upward, now carry them in the opposite direction. If the former weie actually what happened it would show that nerve fibres of different funciion i\ than the lower parts. Whether this arises from injury during preparation (a branch is given off there), or is due to anatomical conditions, e.g., more connective tissue and more nodes in the lower part of the sciatic, is undetermined {Clara Na/person) . This increased excitability may be due to injury to the nerve in preparing it for experiment. After section or compression of a nerve, all electrical currents employed to stimulate the nerve are far more active when the direction of the current passes away from the point of injury than when it passes in the opposite direction. This is due to the fact that the current produced in the nerve after the lesion is added to the stimulation current (§ 33 r, 5). Even in intact nerves — sciatic of a frog (-■. fleischl), where the nen'e ends at the periphery or at the centre, or where large branches are given off, there are points wdiich behave in the same way as those points wdiere a lesion has taken place ( Griitzner and Mosckner). Death of a Nerve. — In a dead nerve the excitability is entirely abolished, death taking place, according to the Ritter-Valli Law, from the centre toward the periphery. The reaction of a dead nerve has been found by some observers to Ije acid (§ 322). The functions of the brain cease immediately after death takes place, while the vital functions of the spinal cord, especially of the white matter, last for a short time ; the large nerve trunks gradually die, then the nerves of the extensor muscles, those of the flexors after three to four hours; while the sympathetic fibres retain their excitability longest, those of the intestine even for ten hours (Onimus). Compare ? 295. The nerves of a dead frog may remain excitable for several days, provided the animal lie kept in a cool place. ELECTRO-PHYSIOLOGY. 577 ELECTRO-PHYSIOLOGY.— Before beginning the study of electro-phys- iology, the student ought to read and study carefully the following short prelimi- nary remarks on the physics of this question : — 326. PHYSICAL PRELIMINARY STATEMENTS— THE GALVANIC CUR- RENT — RHEOCORD.— I. Electro-motive Force.— If two of the under-mentioned bodies be brought in'o direct contact, in one of them positive electricity and in the other negative electricity can be tletccted. The cause of this phenomenon is the electro-motive force. The electro-motive substances may be arranged in a series of the first class, so that if the first-mentioned substance be brought into cont.act with any of the other bodies, the first substance is negatively the last posi- tively electrified. This series is — carbon, platinum, gold, silver, copper, iron, tin, lead, zinc -)- . The amount of the electro-motive force produced by the contact of two of these bodies is greater the wider the bodies are apart in the series. The contact of the bodies may lake place at one or more points. If several 01 the bodies of this series be arranged in a pile, the electrical tension thereby produced is ju't as great as if the two extreme bodies were brought into contact, the inter- mediate ones being left out. 2. The nature of the two electricities is readily determined by placing one of the bodies of the series in contact with a fluid. If zinc be placed in pure or acidulated water, the zinc is -4- (posi- tive) and the water — (negative). If copper be taken instead of zinc, the copper is -|- but the fluid — . Experiment shows that those metals, in contact with fluid, are negatively electrified most strongly which are most acted on chemically by the fluid in which they are placed. Each such combination affords a constant difterence of tension or potential. The tension [or power of over- coming resistance] of the amount of electricity obtained from both bodies depends upon the size of the surfaces in contact. The fluids, e.g., the solutions of acids, alkalies, or salts are called exciters of electricity of the second class. They do not form among themselves a definite series with different tensions. When placed in these fluids, the metals lying next the -)- end of the above series, especially zinc, are most strongly electrified negatively, and to a less extent those lying nearer the — end of the series. 3. Galvanic Battery. — If two different exciters of the first class be placed in fluid without the bodies coming into contact, e.g., zinc and copper, the projecting end of the (negative) zinc shows free negative electricity, while the free end of the (positive) copper shows free positive electricity. .Such a combination of two electromotors of the first class with an electromotor of the second class is called ^galvanic battery. As long as the two metals in this fluid are kept separate the circuit is said to be open, but as soon as the free projecting ends of the metals are connected outside the fluid, e. g., by a copper wire, the circuit or current is closed, and a galvanic or constant current of elec tricity is obtained. The galvanic current has resistance to encounter in its course, which is called " conduction resistance' (Vi). It is directly proportional — (I) to the length (/) of the circuit ; (2), and with the same length of circuit, inversely as the section () thoroughly amalgamated inside, insulated on vulcanite, and filled with a saturated solution of zinc sulphate {s, s). In each trough is placed a thick pad or cushion of white blotting paper (/', />) saturated with the same fluid [deriving cushions]. [The cushion consists of many layers, almost suflScient to fill the trough, and they are kept together by a thread. To prevent the action of the zinc sulphate upon the tissue, each cushion is covered with a thin layer of modeller's clay (/, /), moistened with c.6 per cent, saline solution, which is a good conductor [clay guard]. The clay guard prevents the action of the solution upon the tissue. Connected with the electrodes are a pair of binding screws, whereby the apparatus is connected with the galvanometer (Fig. 345).] Fig. 349. Non-polariz,ible electrode of Du Bois Reymond. Z, zinc ; H. mov;iblc support ; C, clay point — ihe whole on a universal joint. [Reflecting Galvanometer. — The form of galvanometer now used in this country- for physio- logical purposes is that of Sir William Thomson (Fig. 350I. In Germany, Wiedemann's form is more commonly used. In Thomson's instrument the astatic needles are very light, and connected to each other by a piece of aluminum, and each set of needles is suirounded by a separate coil of wire, the lower coil (/) winding in a direction opposite to that of the upper {»). A small, round, light, slightly concave mirror is fixed to the upper set of needles. The needles are suspended by a delicate silk fibril, and they can be raised or lowered as required by means of a small milled head. When the milled head is raised the .system of needles swings freely. The coils are protected by a glass shade, and the whole stands on a vulcanite base, which is levelled by three screws (s, s). On a brass rod (/<) is a feeble magnet {m), which is used to give an artificial meridian. The magnet [m) can be raised or lowered by means of a milled head.] [Lamp and Scale. — When the instrument is to be used, place it so that the coils face east and west. At 3 feet distant from the front of the galvanometer, facing west, is placed the lamp and scale (Fig. 351). There is a .small vertical slit in front of the lamp, and the image of this slit is projected on the mirror attached to the upper needles, and by it is reflected on to the paper scale fixed just above the slit. The spot of light is focused at zero by means of the magnet m. The needles are most sensitive when the oscillations occur slowly. The sensitiveness of the needles can be regulated by means of the magnet. In every case the instrument must be quite level, and for this puqMse there is a small spirit level in the base of the galvanometer.] [Shunt. — As the galvanometer is very delicate, it is convenient to have a shunt to regulate to a certain extent the amount of electricity transmitted through the galvanometer. The shunt (Fig. 352) consists of a brass box containing coils of German silver wire, and is constructed on the same principle as resistance coils or the rheocord (§ 326). On the upper surface of the box are several POLARIZATION AND SECONDARY RESISTANCE. 583 plates of brass separaled from each other, like those of the rheocord, but which can be united liy brass plugs. The two wires coming from the electrodes are connected with the two binding screws, and from the latter two wires are led to the outer two binding screws of the galvanometer. 15y placing a plug between the brass plates attached to the two binding screws in the figure, the current is short circuited. On removing both plugs the whole of the current must pass through the galva- nometer. If one plug be placed between the central disk of brass and the plate marked \ (the other being left out), then yj of the current goes through the galvanometer and /^ to the electrodes. If the plug be placed as shown in the figure opposite j'j, then yjj, part of the current goes to the galvanometer, while ^'j,',, are short circuited. If the plug be placed opposite -^\^, only t^jj^ part goes through the galvanometer. ]- Internal Polarization of Moist Bodies. — Nerves and muscular fibres, the juicy parts of vegetables and anmials, fibrin and other similar bodies possessing a porous structure filled with fluid, exhibit the phenomena of polarization when subjected to strong currents — a condition termed ii.ternal polarization of moist bodies by Du Bois-Reymond. It is assumed that the solid paits in Fig. ^50. Fig. 351 Brothers). the interior of these bodies, which are better conductors, produce electrolys's of th» adjoining fluid, just like metals in contact with fluid. The ions produced by the decompo'^ition of the internal fluids give rise to differences of potential, and thus cause internal polarization [\ 333). Cataphoric Action. — If the two electrodes from a galvanic battery be placed in the two com- partments of a fluid, separated from each other by a porous septum, we observe that the fluid par- ticles pass in the direction of the galvanic current, from the + to the — pole, so that after some time the fluid in the one-half of the vessel increases, while it diminishes in the other. The phe- nomena of direct transference was called by Du Bois-Reymond the cataplioric action of the con- stant current. The introduction of dissolved substances through the skin by means of a constant current depends upon this action (^ 290), and so does the so-called Porret's phenomenon in living muscle 1 \ 293. I, h\. External Secondary Resistance; — This condition also depends on cataphoric action. If each of the copper electrodes of a constant battery be placed in a vessel filled with a solution of cupric sulphate, and from each of which there projects a cushion saturated with this fluid, then, on placing 584 INDUCED OR FARADIC ELECTRICITY. a piece of muscle, cartilage, vegetable tissue, or even a prismatic strip of coagulated albumin across these cushions, we observe that, very soon after the circuit is closed, there is a considerable varia- tion of the current. If the direction of the current be reversed, it lirst becomes stronger, hut after- ward diminishes. By constantly altering the direction of the current we cause the same changes in the intensity. If a prismatic strip of coagulated albumin is used for the experiment, we oliserve that, simultaneously with the enfeeblement of the current in the neighborhood of the -f- pole, the albumin loses water and becomes more shrivelled, while at the — pole the albumin is swollen up and contains more water. If the direction of the current be altered, the phenomena are also changed. The shrivelling and removal of water in the albumin at the positive pole must he the cause of the resistance in the circuit, which explains the enfeeblement of the galvanic cuirent. This phenomenon is called "external secondary resistance" (Dii Bois-Reymond). 329. INDUCTION-EXTRA CURRENT— UNIPOLAR INDUCTION ACTION —MAGNETIC INDUCTION.— Induction of the Extra Current.— If a galvanic element is closed by means of a short arc of wire, at the moment tlie circuit is again opened or l)roken a sliglil spark is observed. If, however, the circuit is closed by means of a very long wire rolled in a coil, then on breaking the circuit there is a strong spark. If the wires be connected with two elec- trodes, so that a person can hold one in each hand, so that the current at the moment it is opened must pass through the person's body, then there is a violent shock communicated to the hand. This phenomenon is due to a current induced in the long spiral of wire, which Faraday called the extra current. It is caused thus : When the circuit is closed by means of the spiral wire, the galvanic current passing along it excites an electric current in the adjoining coils of the same spiral. At the moment of closing or making the circuit in the spiral, the induced current is in the opposite direc- tion to the galvanic current in the circuit ; hence its strength is lessened, and it causes no shock. At the moment of opening, however, the induced current has the fame direction as the galvanic stream, and hence its action is strengthened. Magnetization of Iron — If a rod of soft iron be placed in the cavity of a spiral of copper wire, then the soft iron remains magnetic as long as a galvanic current circulates in the spiral. If one end of the iron rod be directed toward the observer, the other away from him, and if, further, the positive current traverses the spiral in the same direction as the hands of a clock, then the end of the magnet directed toward the person is the negative pole of the magnet. The power of the magnet depends upon the number of spiral windings and on tlie thickness of the iron bar. .•\s soon as tlie curreiit is opened, the magnetism of the iron rod disappears. Induced or Faradic Current. — If a very long, insulated wire be coiled into the form of a spiral roll, which we may call the secondary spiral, and if a similar spiral, the primary spiral, be placed near the former, and the ends of the wire of the primary spiral be connected with the poles of a constant battery, every time the current in the primary circuit is made (closed), or broken (opened), a current takes place, or, as it is said, is induced in the secondary spiral. If the primary circuit be kept closed, and if the secondary spiral be brought nearer to, or removed further from, the primary spiral, a current is also induced in the secondary spiral (Faraday, 1832). The current in the secondary circuit is called the induced or Faradic current. When the primary circuit is closed, or when the two spirals are brought nearer to each other, the current in the secondary spiral has a direction opposite to that in the primary spiral, while the current produced by opening the primary circuit, or by removing the spirals further apart, has the same direction as the primary. Uurijig the lime the primary circuit is closed, or when both spirals remain at the same distance from each other, there is no current in the secondary spiral. Difference between the Opening and Closing Shocks. — The opening [break! and closing [make] shocks in the secondary spiral are distinguished from each other in the following respects (Fig. 353) ; The amount of electricity is the same during the opening as during the closing shock, but during the opening shock the electricity rapidly reaches its maximum of intensity and lasts but a sliort time, while during the closing shock it gradually increases, but does not reach the same high maximum, and this occurs more slowly. [In Fig. 353, P, and Sq are the abscissas of the primary (inducing) and induced currents respectively. The vertical lines or ordinates represent the intensity of the current, while the length of the abscissa indicates its duration. The curve I indicates the course of the primary current, and 2, that in the secondary spiral (induced) when the current is closed, while at I the primary current is suddenly opened, when it gives rise to the induced current, 4, in the secondary spiral.] The c.iuse of this difference is the following: When the pri- mary circuit is closed there is developed in it the extra current, which is opposite in direction to the primary current. Hence, it opposes considerable resistance to the complete development of the strength of the primar)' current, so that the cuirent induced in the secondary spiral must also develop slowly. But when the primary spiral is opened, the extra current in the latter has the same direction as the primary current, there is no extra resistance. The rapid and intense action of the opening induction shock is of great physiological importance. Opening Shock. — [On applying a single induction shock to a nerve or a muscle, the effect is greater w ith the opening shock. If the secondary spiral be separated from the primary, so that the induced currents are not sufficient to cause contraction of a muscle when applied to its motor nerve, then, on gradually approximating the secondary to the primary spiral, the opening shock will cause a contraction before the closing one does so.] HELMIIOLTZ S MODIKICATION. 585 Helmholtz's Modification. — Under certain circumstances, it is desirable to equalize the opening and closing shocks. This may be done by greatly weakening the extra current, which may be accomplished by making the primary spiral of only a few coils of wire. v. Helmholtz accomplishes the same result by introducing a secondary circuit into the primary current. By this arrangement the current in the primary spiral never completely disappears, but by alternately closing and open ing this secondary circuit where the resistance is much less, it is alternately weakened and strength- ened. [In Fig. 354 a wire is introduced between a and/, while the binding screw, f, is separated from (he platinum contact, c, of Neefs hammer, but at the same time the screw, d, is raised so that it touches Neef's hammer. The current passes from the battery, K, through the pillar, a, to/ in the direction of the arrow, through the primary spiral, P, to the coil of soft wire,.?-, and back to the battery, through h and e. But g is magnetized thereby, and. when it is so it attracts c and makes it touch the screw, d. Thus a secondary circuit, or short circuit, is formed through a, b, c, d, c, which weakens the current passing through the electro-magnet, .f, so that the elastic metallic spring flies up again and the current through the primary spiral is long circuited, and thus the process is repeated. In Fig. 353 the lines i and 7 indicate the course of the current in the primary circuit of closing (a ), and opening [e). It must be remembered that in this arrangement there is always a current passing through the primary spiral, P (Fig. 354). The dotted lines, 6 and 8 aliove and below S„, represent the course of the opening {a) and closing shocks {e) in the secondary spiral. Even with this arrange- ment the opening is still slightly stronger than the closing shock.] The two shocks, however, may Fig. 353. Fig. 354. Fig. 353. — Scheme of the induced ( iiing, and E, end of the inducing c primary current is opened ; ! and 4, height: /. A, the strength of the constant inducing < is 'opened and closed during Helmhohz's modificatioi secondary circuit. Fig. 354. — Helmholtz's modificatio with d, s h remains magnetic : thus c is attracted to d, springs back again, and thus the process goes on. Ane I of the primary, and So "f the secondary ( of the primary current weakened by the e.\lra current ; 3, orresponding currents induced in the secondary spiral : Pj, 5 and 7, the curve of the inducing current when it ; 6 and 8, the corresponding currents induced in the of Neefs hammer, .^s long as c is not in contact nd a secondary circuit, a, h, c, d, e, is formed : c then .■ wire is introduced to connect a withyl K, battery. be completely equalized by placing a resistance coil or rheostat in the short circuit, which increases the resistance, and thus increases the current through the primary spiral when the short circuit is closed. Unipolar induction. — When there is a very rapid current in the primary spiral, not only is there a current induced in the secondary spiral when its free ends are closed, e.g., by being connected with an animal tissue, but there is also a current when one wire is attached to a binding screw con- nected with one end of the wire of the secondary sniral (p. 572). A muscle of a frog's leg, when connected with this wire, contracts, and this is called a unipolar induced contraction. It usually occurs when the primary circuit is opened. The occurrence of these contractions is favored when the other end of the spiral is placed in connection with the ground, and when the frog's muscle preparation is not coTipletely insulated. Magneto Induction. — If a magnet be brought near to, or thrust into the interior of, a coil or wire, it excites a current, and also when a piece of soft iron is suddenly rendered magnetic or sud- denly demagnetized. The direction of the current so induced in the spiral is exactly the same as that with F'aradie electricity, ;'. e., the occurrence of the magnetism on approximating the spiral to a magnet, excites an induced current in a direction opposite to that supposed to circulate in the magnet. Conversely, the demagnetization, or the removal of the spiral from the magnet, causes a cu rent in the same direction. Acoustic Tetanus. — If a magnet be rapidly moved to and fro near a spiral, which can easily be done by ti.xing a vibrating magnetic rod at one end and allowing the other end to swing freely 586 DU BOIS-REYMOND S INDUCTORIUM. near the spiral, then the pitch of the note of the vibrating rod gives us the rapidity of the induction shocks. If a frog's nerve-muscle preparation be stimulated we get what Grossmann called " acoustic tetanus." 330. DU BOIS-REYMOND'S INDUCTORIUM— MAGNETO-INDUCTION AP- PARATUS. — Inductorium of Du Bois-Reymond. — The induction apparatus of Du ISois- Reymond, which is used for physiological purposes, is a modification of the magneto-electro-motor apparatus of Wagner and Neef. A scheme of the apparatus is given in Fig. 355. D represents the constant element, /. f., the galvanic battery. The wire from the positive pole, a, passes to a metallic column, S, which has a horizontal vibrating spring, F. attached to its upper end. To the outer end of the spring a squnre piece of iron, c, is attached. The middle point of the upper sur- face of the spring [covered with a little pif-ce of platinum] is in contact with a movable screw, /> A moderately thick copper wire, r, passes from the screw, d, to the primary spiral or coil, -i", .r, which contains in its interior a number of pieces of soft iron wire, t, /, covered with an insulating varnish. The copper wire w-hich surrounds the primary spiral is covered with silk. The wire, (/, is continued from the primary spiral to a Jiorseshoe piece of soft iron, H, around which it is coiled spirally, and from thence it proceeds, at/j back to the negative pole of the battery,^. When the current in this circuit — called the primary circuit — is closed, the following effects are produced : The horseshoe, H, becomes magnetic, in consequence of which it attracts the movable spring or 1: of Du Bois-Riymonri's sledge-induction m.ichine. D, constant element: a. wire from + pole. (^) — S, brass upright : F, elastic spring ; b, binding screw ; c, wire round primary spiral \xr^x), containing!/, {) -on wire ; K, K, secondary spiral, with board (/./) on which it can be moved ; H, soft iron magnetized by nt {d,/\ passing round it. II, key for secondary circuit, as shown it is short circuited. Ill, electrodes (r, r), a key (K) for breaking the circuit. Xeef s hammer, e, whereby the contact of the spring, F, with the screw, b, is broken. Thus the current is broken, the horseshoe is demagnetized, the spring, e, is liberated, and, being elastic, it springs upward again to its original position in contact with b, and thus the current is re-established. The new contact causes H to be magnetized, so that it must alternately rapidly attract and liberate the spring, <■, whereby the primary current is rapidly mide and broken between F and b. A secondary spiral or coil (K, K) is placed in the same direction as the primary f.v, x), but having no connection with it. It moves in grooves upon a long piece of wood (p, p). The secondary spiral consists of a hollow cylinder of wood covered with numerous coils of thin silk-covered wire. The secondary spiral moving in slots, can be approximated to or even pushed entirely over the primary spiral, or can be removed from it to any distance desired. [Fie. 356 shows the actual arranyeinent of Du Bois-Reymond's inductorium. The primary coil (R') consists of about 150 coils of thick insulated copper wire, the wire being thick, to offer slight resistance to the galvanic current. The secondary coil ( W"\ consists of 6000 turns of thin insulated copper wire arranged on a wooden bobbin ; the whole spiral can be moved along the board (B), to which a millimetre scale (I) is attached, so that the distance of the secondary from the primary spiral may be ascertained. At the left end of the apparatus is Wagner's hammer as adapted by Neef. which is just an automatic arrangement for opening and breaking the primary circuit. When Neef s hammer is used, the wires from the battery are connected as in the figure, MAGNETO INDUCTION. 587 but when single shocks are re:|uired, the wires from the battery are connected with a key, and this again with the two terminals of the primary spiral S" and S'".] According to the law of induction (^329), when the primary circuit is closed, a current is induced in the secondary circuit in a direction the reverse of that in the primary, while, when it is opened. J S" Fig. 356. Induction apparatus of Du Bois-Reymond, R', primary, R". secondary spiral ; B, board 011 which R" moves ; T. scale: H . wires from battery; P'. P". pillars; H, Neef's hammer; B'. electro-magnet: S', binding screw touching the steel spring (H) ; S" and S"', binding screws to which to attach wires when Neef's hammer is nut required {Elliott Brothers). the induced current has the same direction. Further, according to the laws of magneto induction, there is the magnetization of the iron rods (;', /) within the primary spiral (.r, x), that causes a reverse current in the secondary spi'al (K, K), while the demagnetization of the iron rods on opening Fig. 358. Magneto induction apparatus, with Stohrer': Du Boi.'-Reymond's friction key. the primary circuit causes an induced current in the same direction. Thus we explain the much more powerful action of the opening shock as compared witii the closing shock. [The direction of the inducing current remains the same, while the induced currents are constantly reversed.] 588 ELECTRICAL CURRENTS IN MUSCLE AND NERVE. The magneto-induction (R) apparatus of Pixii (1832), improved by Saxton, and still further improved by Siohrer, consists of a very powerful horseshoe steel magnet (Fig. 357). Opposite its two poles (X and S) is a horseshoe shaped piece of iron (H), which rotates on a horizontal axis («, ^). On the ends of the horseshoe are fixed wooden bobbins (<:, ), and the divided metal plates (y, z) which pass to the electrodes, the two currents induced in the bobbins are obtained in the same direction. Keys, or arrangements for opening or breaking a circuit, are of great use. Fig. 355. II, shows a scheme of a friction key of Du Bois-Reymond, introduced into the secondary circuit. It con- sists of two brass bars (: and r) fixed to a plate of ebonite, and as long as the key is down on the metal bridge (y, r, z) it is " short circuiieii," i. t"., the conduction is so good through the thick bra^s bars, that none of the current goes through the wires leading from the left of the key. When the bridge (r) is lifted the current is opened. [The term accessory circuit is also used for short circuit ] [Fig. 358 shows the actual form of the key, v being a screw wherewith to clamp it to the table.] Similarly, the key electrodes (111) may be used, the current being made as soon as the spring con- necting plate (<•) is raised by pressing upon k. This instrument is opened by the hand ; a, /> are the wires from the battery or induction machine ; r, r, those going to the tissue; G, the handle of the instrument. [Plug Key. — Other forms of keys are in use, e.g.. Fig. 359, the plug key, the two brass plates to which the wires are attached being fixed on a plate of ebonite. The brass plug is used to connect Fig. 359. Fig. 359. — Plug key. Fig. 360. — Capillary cont.ict. t, into mercury at a : ^, bent tube filled with mercurj* the two brass plates. All these are dry contacts, but sometimes &fiuid contact is used, as in the mercury key, which merely consists of a block of wood, with a cup of mercury in its centre. The ends of the wires from the battery dip into the mercury; when both wires dip into the mercury, the circuit is made, and when one is out it is broken.] [Capillary Contact Key. — When an ordinary mercury key is used to open and close the primary circuit, the layer of oxide formed on the surface by the opening spark disturbs the conduction after a short time; hence, it is advisable to wash the surface of the mercury with a dilute solution of alcohol and water ( IV. Stirling). A handy form of " capillary contact " is shown in Fig. 360, such as was used by Kronecker and Stirling in their experiments on the heart. " A glass T tube is pro- vided at the crossing point with a small opening (a). The vertical tube (b) is bent in the form of a U, and filled so full with mercury that the convex surface of the latter projects within the lumen of the transverse tube (<). One end of c is connected with a Mariolte's flask containing diluted alcohol, and the supply of the latter can be regulated by means of a stop-cock. The fluid flows over the apex of the mercury and keeps it clean. The vibrating platinum style {e] is attached to the end of a rod, which, in turn, is connected with the positive pole of the battery, while the platinum wire (r/) is connected with the negative pole of the battery."] 331. ELECTRICAL CURRENTS IN PASSIVE MUSCLE AND NERVE- SKIN CURRENTS. — Methods.— In order to investigate the laws of the muscle current, we must use a muscle composed of |jarallel (ibres, and with a simple arrangement of its fibres in the form of a pri'-m or cylinder (Fig. 361, I and II). The sartorius muscle of the frog supplies the^e conditions. In such a muscle we distinguish the surface or the natural longitudinal section, its tendinous ends or the natural transverse section; further, when the latter is divided trans- versely ti the long axis, the artificial transverse section (Fig. 361, I, c, ./) ; lastly, the term equator (a, b~m, v) is applied to a line so drawn as exactly to divide the length of the muscle into ELECTRICAL CURRENTS IN MUSCLE AND NERVE. 589 halves. As the currents are very feeble, it is necessary to use a galvanometer with a periodic damped magnet (Figs. 345, I, and 350), or a tangent mirror boussole similar to that u.^ed for thermo-electric purposes (Fig. 216). The wires leading from the tissue are connected with non-polarizable elec- trodes (F'ig. 345, P, P). The capillary electrometer of Lippmann may be used for detecting the current (Fig. 362). A thread of mercury enclosed in a capillary tube and touching a conducting fluid, e. g., dilute sulphuric acid, is displaced by the constant current in consequence of the polarization taking place at the point of contact altering the constancy of the capillarity of the mercury. The displacement of the mer- cury which the observer (B) detects by the aid of the microscope (M) is in the direction of the positive current. In Fig. 362, R is a capillary glass tube, filled from above with mercury, and from below with dilute sulphuric acid. Its lower narrow end opens into a wide glass tube, provided below with a platinum wire fused into it and filled with Hg (q), and this again is covered with dilute sulphuric acid (s). The wires are connected with non-polarizable electrodes applied to the ^ and — surfaces of the muscle. On closing the circuit, the thread of mercury passes downw ard from c in the direction of the arrow. [A very simple and convenient modification of this instru- ment for studying the muscle current has recently been invented by M'Kendrick.] Compensation. — The strength of the current in animal tissues is best measured by the com- FlG. 361. Fig. 362. Capillary electrometer (after mercury in tube ; c. capillary phuric acid: q, Hg : B, ol pensation method of Poggendorf and l)u Bois Reymond. A current of known strength, or which can be accurately graduated, is passed in an opposite direction through the same galvanometer or boussole, until the current from the animal tissue is just neutralized or compensated. [When this occurs, the needle deflected by the tissue current returns to zero. The principle is exactly the same as that of weighing a body in terms of some standard weights placed in the opposite scale pan of the balance.] 1. Perfectly fresh, uninjured muscles yield no current, and the same is true of dead muscle (Z. Hermann, 1867). 2. Strong electrical currents are observed when the transverse section of a muscle is placed on one of the cushions of the non-polarizable electrodes (Fig. 345, I, M), while the surface is in connection with the other (Nohili, Matteticci, Dii Bois-Rcymomi). The direction of the current is from the (positive) longi- tudinal section to the (negative) transverse section in the conducting wires (/. e., within the muscle itself from the transverse to the longitudinal section (Figs. 345, 590 ELECTRICAL CURRENTS IN MUSCLE AND NERVE. I, and 361,) I). This current is stronger the nearer one electrode is to the equator, and the other to the. centre of the transverse section ; while the strength diminishes the nearer the one electrode is to the end of the surface, and the other to the margin of the transverse section. Smooth muscles also yield similar currents between their transverse and longitudinal surfaces (?334. II). 3. Weak electrical currents are obtained when — (a) two points at unequal dis- tances from the equator are connected ; the current then passes from the point nearer the equator (-f) to the point lying further from it ( — ), but of course this direction is reversed within the muscle itself (Fig. 361, II, /v and /(•). (/') Simi- larly weak currents are obtained by connecting points of the transverse section at unequal distances from the centre, in which case the current outside the muscle passes from the point lying nearer the edge of tlie muscle to that nearer the centre of the transverse section (Fig. 361, II, /, <'). 4. When two points on the surface are equidistant from the equator (Fig. 361, I, X, y, V, z, — II, r, e), or two equidistant trom tlie centre of the transverse sec- tion {II, c) are connected, no current is obtained. 5. If the transverse section of a muscle be oblique (Fig. 361, III), so that the muscle forms a rhomb, the conditions obtaining under III are disturbed. The point lying nearer to the obtuse angle of the transverse section or surface is posi- tive to the one lying near to the acute angle. The equator is oblique {a, c). These currents are called " deviation currents " by Du Bois-Reymond, and their course is indicated by the lines i, 2, and 3. Strength of Electro-motive Force. — The electro. motive force of a strong muscle airrciil (frog) is equal to 0.05 to o.oS of a DanielPs element ; while the strongest deviation current may be O.I Daniell. The muscles of a curarized animal at lirst yield stronger currents ; /ij/^'""" ol ''^^ muscle diminishes the strength of the current (Roeber), while it is completely abolished when the muscle dies. Heating a muscle increases the current ; but above 40° C. it is diminished (Steiner). tooting diminishes the electro-motive force. The warmed living muscular and nervous substance (Hermann, IVorm Miiller, Griilzner) is positive to the cooler portions; while, if the dead ti-sues be heated, they behave practically as indifferent bodies as regards the tissues that are not heated. 6. The passive nerve behaves like muscle, as far as 2, 3, and 4 are concerned. The electro-motive force of the strongest nerve current, according to Du Bois-Reymond, is 0.02 of a Daniell. Heating a nerve to i5°-25° C. increases the nerve current, while high temperatures diminish it (Steiner). 7. If the two transversely divided ends of an excised nerve, or two points on the surface equidistant from the equator be tested, a current — the axial current — flows in the nerve fibre in the opposite direction to the direction of the normal impulse in the nerve ; so that in centrifugal nerves it flows in a centripetal direc- tion, and in centripetal nerves in a centrifugal direction (^Mendelsohn and Cliris- tiani). Rheoscopic Limb. — The existence of a muscle current may be proved with- out the aid of a galvanometer : i. By means of a sensitive nerve-muscle prepara- tion of a frog, or the so-called " physiological rheoscope." Place a moist conductor on the transverse and longitudinal surface of the gastrocnemius of a frog. On placing the sciatic nerve of a nerve-muscle preparation of a frog on this conductor, so as to bridge over or connect these two surfaces, contraction of the muscle con- nected with the nerve occurs at once ; and the same occurs when the nerve is removed. [Use a nerve-muscle preparation, or, as it is called, a physiological limb. Hold the preparation by the femur, and allow its own nerve to fall upon the gastrocnemius, and the muscle will contract, but it is better to allow the nerve to fall suddenly upon the cross section of the muscle. The nerve then completes the circuit Vjetween the longitudinal and transverse section of the muscle, so that it is stimulated by the current from the latter, the nerve is stimulated, and through it the muscle. That it is so, is proved by tying a thread round the nerve near the muscle, when the latter no longer contracts.] ELECTRICAL CURRENTS OF ACTIVE MUSCLE. 591 Contraction without Metals. — Make a transverse section of a gastrocnemius muscle of a frog's nerve-muscle preparation, and allow the sciatic nerve to fall upon this transverse section, when the limb contracts, as the muscle current from the longitudinal to the transverse surface now traverses the nerve (^Galvani, Al. v. Hiimhohh). 2. Self-Stimulation of the Muscle. — We may use the muscle current of an isolated muscle to stimulate the latter directly and cause it to contract. If the transverse and longitudinal surfaces of a curarized frog's nerve-muscle preparation be placed on non-polarizable electrodes, and the circuit be closed by dipping the wires coming from the electrodes in mercury, then the muscle contracts. Simi- larly a nerve may be stimulated with its own current (Z>« Bois-Reymond and others). If the lower end of a muscle with its transverse section be dipped into normal saline solution (0.6 per cent. NaCl), which is quite an indifferent fluid, this fluid forms an accessory circuit between the transverse and adjoining longi- tudinal surface of the muscle, so that the muscle contracts. Other indifferent fluids used in tlie same way produce a similar result. 3. Electrolysis. — If the muscle current be conducted through starch mixed with potassic iiniide, then the iodide is deposited at the -f pole, where it makes the starch blue. Frog Current. — It is asserted that the total current in the body is the sum of the electrical cur- rents of the several muscles and nerves which, in a frog deprived of its skin, passes from the lip of the toes toward the trunli, and in the trunk from tlie anus to the head. This is the " corrente pro- pria ddla rena" of Leopoldo Nobih ( 1827), or the "frog lurrent" of Du Bois-Reymond. In mammals ihe corresponding current passes in the opposite direclion. After death the currents disappear sooner than the excitability ( Valentin) ; they remain longer in the muscle than the nerves, and in the latter they disappear sooner in the central portions. If the nerve current after a time becomes feeble, it may be strengthened by making a new transverse section of the nerve. A motor nerve completely paralyzed by curara gives a current {/•'unit), and so does a nerve beginning to undergo degeneration, even two weeks alter it has lost its excitability. Muscles in a state of rigor mortis give currents in the opposite direction, owing to inequalities m the decomposition which takes place. The nerve current is reversed by the action of boiling water or drying. Currents from Skin and Mucous Membranes. — In the skin of the frog the outer surface is -j- , the inner is — , (Z>« Bois-Reymond, Budge), and the same is true of the mucous membrane of the intestinal tract {Rosenthal), the cornea {Griinhagen), as well as the non-glandular skin of fishes {Hermann) and molluscs {Oehler). Stimulation of the Secretory Nerves of the g/andiilar membranes, besides causing secretion, affects the current of rest (/ioeber). This secretion current passes in the same direction in the skin of the frog and warm blooded animals as the current of rest, although in the frog it is occa- sionally in the opposite direction (i/ermaim). If the current be conducted uniformly from both the hind feet of a cat, on stimulating the sciatic nerve of one side, not only is there a secretion of sweat (§ 2S8), but a secretion current is developed {Luchsinger attd Nermann). If two symmet- rical parts of the skin in the leg or arm of a man be similany tested, and the muscle of one side be contracted, a similar current is developed. Destruction or atrophy of the glands abolishes both the power of secretion and the secretion current. There is no secretion current from skin covered with hairs, but devoid of glands (Btibnoff). [The secretion current from the submaxillary gland is referred to in ^ 145 {Sayliss and Bradfoi J ).'\ 332. CURRENTS OF STIMULATED MUSCLE AND NERVE. — I. Negative Variation of the Muscle Current. — If a muscle, which yields a strong electrical <;urrent, be thrown into a state of tetanic contraction by stimulating its motor nerve, then, when the muscle contracts, there is a diminu- tion of the muscle current, and occasionally the needle of the galvanometer may swing almost to zero. This is the negative variation of the muscle current (L)u Bois-Reymond). It is larger the greater the primary deflection of the galva- nomfcter needle and the more energetic the contraction. After tetanus the muscle current is weaker than it was before. If the muscle was so placed upon the electrodes that the current was •' feeble," e jually during tetanus, there is a diminution of this 592 SECONDARY CONTRACTION. current. In the inactive arrangement, the contraction of the muscle has no effect on the needle. If the muscle be prevented from shortening, as by keeping it tense, the negative variation still takes place. 2. Current during Tetanus. — An exa'sei^ frog's muscle Maniset/ through its Nr/Te shows electro-motor force — the so-called "action current." In a tetan- ized frog's gastrocnemius there is a t/escemfi/zg- current. In completely uninjured human muscles, however, thrown into tetanus by acting on their nerves, there is no such current (Z. Hermanii) ; similarly, in quite uninjured frog's muscles, as well as when these muscles are directly and completely fetanized, there is no cur- rent. 3. Current during the Contraction Wave. — If one end of a muscle be directly excited with a momentary stimulus, so that the contraction wave (§ 299) rapidly passes along the whole length of the muscular fibres, then each part of the muscle, successively and immediately before it contracts, shows the negative variation. Thus the " contraction wave" is preceded by a " negative 7vave " of the muscle current, the latter occurring during the latent period. Both waves have the same velocity, about 3 metres per second. The negative wave, which first increases and then diminishes, lasts at each point only 0.003 second {Bernstein). 4. During a Single Contraction. — A single contraction also shows a muscle FiG. 364. Fig. 363. .Secondary contraction. The s £, electrodes applied to the e current. The best object to use for this purpose is a contracting heart, which is placed upon the non-polarizable electrodes connected with a sensitive galva- nometer. Each beat of the heart causes a deflection of the needle, which occurs before the contraction of the cardiac muscle {Kollikcr and H. Mitller). The electrical disturbance in the muscle causing the negative variation always precedes the actual contraction {v. Hclmholtz, 1834). When the completely uninjured frog's gastrocnemius contracts by stitnulating the nerve, there is at first a descend- ing and then an ascending current {Sig. Meyer, § 344, II). Secondary Contraction. — A nerve-muscle preparation may be used to demonstrate the electrical changes that occur during a single contraction. If the sciatic nerve, .\, of such a preparation be placed upon another muscle, B, as in Fig. 363, then every time the latter, B, contracts, the frog's muscle, A, connected with the nerve also contracts. If the nerve of a frog's nerve-muscle preparation be placed on a contracting mammalian heart, then a contraction of the muscle occurs with every beat of the heart {Matteucci, 1842). The diaphragm, even after section of the phrenic nerve, especially the left, also contracts during the heart beat {Schiff). This is the " secondary contraction " of Galvani. NEGATIVE VARIATION OF THE NERVE CURRENT. 593 Secondary Tetanus. — Similarly, if a nerve of a nerve-muscle preparation be placed on a muscle which is tetanized, then the former also contracts, showing " seconda.Ty tetanus" (Du £t)is-J?e)'moni^). The latter experiment is regarded as a proof that, during the process of negative variation in the muscle, many successive variations of the current must take place, as only rapid variations of this kind can produce tetanus by acting on a nerve — continuous variations being unable to do so. Usually there is no secondary tetanus in a frog's nerve muscle preparation when it is laid upon a muscle which is tetanized voluntarily, or by chemical stimuli, or by poisoning with strychnin (^Her- ing and Friedreich, Kiikiie) ; still, LovSn has observed secondary strychnin tetanus composed of six to nine shocks per second. Observations with a sensitive galvanometer, or Lippmann's capil- lary electrometer (Eig. 362), show that the spasms of strychnin poisoning, as well as a voluntary contraction, are discontinuous processes (Loven, p. 521). [Nerve-muscle Preparation. — This term has been used on several occasions. It is simply the sciatic nerve with the gastrocnemius of the frog attached to it Fig. 365. Scheme of Bernstein's differential rheotome; N«, nerve; J, inductio of needle ; E, battery and primary circuit with C for opening it ; electrodes in galvanometer circuit ; S, motor. chine; G, galvanometer; jr.jj', deflectic f, for closing galvanometer circuit ; z, (Fig. 364). The sciatic nerve is dissected out entire from the vertebral column to the knee ; the muscles of the thigh separated from the femur, and the latter divided about its middle, so that the preparation can be fixed in a clamp by the remaining portion of the femur ; while the tendon of the gastrocnemius is divided near to the foot. If a straw flag is to be attached to the foot, do not divide the tendo Achilles.] 5. Negative Variation in Nerve. — If a nerve be placed with its transverse section on one non-polarizable electrode, and its longitudinal surface on the other, and if it be stimulated electrically, chemically or mechanically, the nerve current is also diminished (Du Bois-Reyinoiid). This negative variation can be prop- agated toward Iwth ends of a nerve, and is composed of very rapid, successive, periodic interru])tions of the original current, just as in a contracted muscle {Bern- stein) ; while Hering succeeded in obtaining from a nerve, as from a muscle, a secondary contraction or secondary tetanus. The amount of the negative varia- tion depends upon the extent of the primary deflection, also upon the degree of 38 594 ELECTRICAL CURRENTS DURLN'G ELECTROTUNUS. nervous excitability, and on the strength of the stimulus employed. The negative variation occurs on stimulating with tetanic as well as with single shocks. The negative variation is not observed in completely uninjured nerves. Hering found that the negative variation of the nerve current caused by tetanic stimulation is followed by a positive variation, which occurs immediately after the former. It increases to a certain degree with the duration of the stimulation, as well as with the strength of the stimulus {Effect of Electrotonus, ? 335, I). Negative Variation of the Spinal Cord. — This is the same as in nerves generally. If a cur- rent be conducted from the transverse and longitudinal surfaces of the upper part of the medulla oblongata, we observe spontaneous intermittent ne^^ative variations^ perhaps due to the intermittent excitement of the nerve centres, more es|)ecially of the respiratory centre. Similar variations are obtained refle.xly by single stimuli applied to the sciatic nerve, while strong stimulation by common salt or induction shocks inhibits them. Velocity. — The process of negative variation is propagated at a measureable velocity along the nerve, most rapidly at 15° to 25° C. [Steiner), and at the same rate as the velocity of the nervous impulse itself, about 27 to 28 metres per second. The duration of a single variation (of which the process of negative variation is composed) is only 0.0005 '° 0.0008 second, while the wave length in the nerve is calculated by Bernstein at 18 mm. Differential Rheotome.^J. Bernstein estimated the velocity of the negative variation in a nerve by means of a difterential rheotome (Fig. 365) thus: A long stretch of a nerve (Nn) is so arranged that at one end of it (N) its transverse and longitudinal surfaces are connected with a galvanometer (Gj, while at the other txvX («) are placed the electrodes of an induction machine (J). A disk (B), rapidly rotating on its vertical a.xis (A), has an arrangement (C) at one point of its circumference, by means of which the current of the primary circuit (E) is rapidly opened and closed during each revolution. This causes, with each rotation of the disk, an opening and a closing shock to be applied to the end of the nerve, ."^t the diametrically opposite part of the cir- cumference is an arrangement (c) by which the galvanometer circuit is closed and opened during each revolution. Thus, the stimulation and the closing of the galvanometer circuit occur at the same moment. On rapidly rotating the disk, the galvanometer indicates a strong nerve current, an excursion of the magnetic needle to y- At the moment of stimulation the negative variation has not yet reached the other end of the nerve. If, however, the arrangement which closes the galvanometer circuit be so displaced (to 0) along the circumference that the galvanometer circuit is closed somewhat later than the nerve is stimulated, then the current is weakened by the negative variation (the needle passing backward to x). When we know the velocity of rotation of the disk, it is easy to calculate the rate at which the impulse causing the negative variation passes along a given distance of nerve from N to «. The negative variation is absent in degenerated nerves as soon as they lose their excitability. Eye Currents. — If a freshly-excised eyeball be placed on the non-polarizable electrodes con- nected with a galvanometer, and if light fall upon the eye, then the normal eye current from the cornea ( -)- ) to the transverse section of the optic nerve ( — ) is at first increased. Yellow light is most powerful, and less so the other colors [Holmgren, M' Kendrick and Dezvar). The iiiuer surface of the passive retina is positive to the posterior. When the retina is illuminated there is a double variation, a negative variation with a preliminary positive increase; while, when the light ceases, there is a simple positive variation. Retin;i; in which the visual purple has disappeared, owing to the action of light, show no variations [Kiikne and Steiner'). 333. ELECTROTONIC CURRENTS IN NERVE AND MUS- CLE. — I. Positive Phase of Electrotonus. — If a nerve be so arranged upon the electrodes (,Fig. 366, I) that its transverse section lies on one, and its longi- tudinal on the other, electrode, then the galvanometer indicates a strong current. If now a constant current be transmitted through the end of the nerve pro- jecting beyond the electrodes (the so-called "■polarizing''^ end of the nerve); and if the direction of this current coincides with that in the nerve, then the magnetic needle gives a greater deflection, indicating an increase of the nerve current — "the positive phase of electrotonus." The increase is greater the longer the stretch of nerve traversed by the current, the stronger the galvanic current, and the less the distance between the part of the nerve traversed by the constant current and that on the electrodes. 2. Negative Phase of Electrotonus. — If in the same length of nerve the constant current passes in the opposite direction to the nerve current (Fig, 366, II), there is a diminution of the electro-motive force of the latter — " negative phase of electrotonus." THEORIES OF MUSCLE AND NERVE CURRENTS. 595 3. Equator. — If two points of the nerve equi- distant trom the equator be placed on the electrodes (III), there is no deflection of the galvanometer needle (p. 590, 4). If a constant current be passed through one free projecting end of the nerve, then the galvanometer indicates an electro- motive effect in the same direction as the constant current. Electrotonus. — These experiments show that a constant current causes a change of the electro- motive force of the part of the nerve directly traversed by the constant current, and also in the part of the nerve outside the electrodes. This condition is called electrotonus {Du Bois-IicvmonJ, 1843)- The electrotonic current is strongest not far from the elec- trodes, and it may be twenty-five times as strong as the nerve current of rest (^ 33^^ 5) i it is greater on the anode than on the cathode side; it undergoes a negative variation like the resting nerve current during tetanus; it occurs at once on closing the constant current, although it diminishes uninter- ruptedly at the cathode (Du Boii-Keymond). These phe- nomena take place only as long as the nerve is excitable. If the nerve be ligatured in the projecting part in the galvanometer circuit, the phenomena cease in the ligatured part. The negative variation [\ 332) occurs more rapidly than the electrotonic increase of the current, so that the former is over before the electro-motive increase occurs. The velocity of the electrotonic change in the current is less than the rapidity of propagation of the excitement in the nerves — being only 8 to 10 metres per second ( Tschiijew, Bernstein). " The secondary contraction from a nerve " depends upon the electrotonic state. If the sciatic nerve of a frog's nerve-muscle preparation be placed on an excised nerve, and if a constant current be passed through the free end of the latter — non-electrical stimuli being inactive — the muscles contract. This occurs because the electrotonizing current in the excised nerve stimulates the nerve lying on it. By rapidly closing and opening the current, we obtain " secondary tetanus from a nerve" (p. 593). Paradoxical Contraction. — Exactly the same occurs when the current is applied to one of the two branches into which the sciatic nerve (cut through above) of the frog divides, i.e., the muscles attached to both branches of the nerve contract. Polarizing After-Currents. — When the constant current is opened, there are after-currents depending upon internal polarization [\ 32S). In //:•/«;• nerves, muscle and electrical organs this internal polarization current, when a strong primary current of very short duration is used, is always positive, i.e., has the same direction as the primary current. Prolonged duration of the primary current ultimately causes negative polarization. Between these two is a stage when there is no polarization. Positive polarization is especially strong in nerves when the primary current has the direction of the impulse in the nerve ; in muscle, when the primary current is directed from the point of entrance of the nerve into the muscle toward the end of the muscle (\ 334, II}. 4. Muscle Current during Electrotonus. — The constant current also pro- duces an electrotonic condition in muscle ; a constant current in the same direction increases the mu.scle current, while one in an opposite direction weakens it, but the action is relatively feeble. 334. THEORIES OF MUSCLE AND NERVE CURRENTS.— I. Molecular Theory. — To explain the currents in muscle and nerve, Du Bois- Reymond proposes the so-called molecular theory. According to this theory, a nerve or muscle fibre is composed of a series of small electro-motive molecules arranged one behind the other, and surrounded by a conducting indifferent fluid. The molecules are supposed to have a positive equatorial zone directed toward the surface, and two negative polar surfaces directed toward the transverse section. Every fresh transverse section exposes new negative surfaces, and every artificial longitudinal section new positive areas. This scheme explains the strong currents — when the -j- longitudinal surface is connected with 596 Hermann's difference theory. the — transverse surface, a current is obtained from the former to the latter — hut it does not explain l\ie feeble currents. To explain their occurrence, we must assume that, on the one hand, the electro- motive force of the molecules is weakened with varying rapidity at unequal distances from the equator; on the other, at unequal distances from the transverse sectii n. Then, of course, differences of electrical tension obtain between the stronger and the feebler molecules. Parelectronomy. — But the Ha/;//!?/ transverse section of a muscle, i.e., the end of the tendon, is not negative, but more or less positive electrically. To explain this condition, Du BoisReymond assumes that on the end of the tendon there is a layer of electro- positive muscle substance. He supposes that each of the peripolar elements of muscle consists of two bipolar elements, and that a layer of this /lalf element lies at the end of the tendon, so that its positive side is turned toward the free surface of the tendon. This layer he calls the " parelectronomic layer." It is never com- pletely absent. Sometimes it is so marked as to make the end of the tendon -|- in relation to the surface. Cauterization destroys it. The negative variation is explained by supposing that, during the action of a muscle and nerve, the electro-motive force of all the molecules is diminished. During partial contraction of a muscle the contracted part assumes more the characters of an indifferent conductor, which now becomes connected with the negative zone of the passive contents of the muscular fibres. The electrotonic currents beyond the electrodes in nerves must be explained. To explain the electrotonic condition it is assumed that the bipolar molecules are capable of rotation. The polar- izing current acts upon the direction of the molecules, so that they turn their negative surfaces toward the anode, and their positive surfaces to the cathode, whereby the molecules of the intra- polar region have the arrangement of a Volta's pile. In the part of the nerve outside the elec- trodes, the further removed it is the less precisely are the molecules arranged. Hence, the swing of the needle is less the further the e.\trapolar portion is from the electrodes. II. Difference Theory. — The difference theory was proposed by L. Her- mann, and, according to hini, the four following considerations are sufficient to explain the occurrence of the galvanic phenomena in living tissues: (i) Proto- plasm, by undergoing partial deafh in its continuity, whether by injury or by (horny or mucous) metamorphosis, becomes negative toward the uninjured part. (2) Protoplasm, by being partially excited m its continuity, becomes negative to the uninjured part. (3) Protoplasm, when partially heated in its continuity, be- comes positive, and by cooling negative, to the unchanged part. (4) Protoplasm is strongly J'o/dnzat'/e on its surface (muscle, nerve), the polarization constants diminishing with excitement and in the process of dying. Streamless Fresh Muscles. — It seems that passive, uninjured, and abso- lutely fresh muscles are completely devoid of a current, e.g., the heart {£?!ge/- mann), also the musculature of fishes while still covered by the skin. As the skin of the frog has currents peculiar to itself, it is possible with certain precautions, after destroying the skin with alkalies, to show the streamless character of frogs' muscles. L. Hermann also finds that the muscle current is always developed after a time, which is very short, when a new transverse section is made. Demarcation Current. — Every injury of a muscle or nerve causes at the point of injury (de- marcation surface) a dying substance wiiich behaves negatively to the positive intact substance. The current thus produced is called by Hermann the ^^ Jeinarcation ctirient.^'' If individual parts of a muscle be moistened with potash salts or muscle juice they become negatively electrical; if these substances be removed, these parts cease to be negative (Biedermann). It appears that all living protoplasmic substance has a special property, whereby injury of a part of it makes it, when dying, negative, while the intact parts remain positively electrical. Thus all transverse sections of living parts of plants are negative to their surface {Bii/f): and the same occurs in animal parts, e.g , glands and bones. Engelniann made the remarkable observation that the heart and smooth muscle again lose the negative condition of their transverse section, when the muscle cells are completely dead, as far as the cement substance of the nearest cells; in nerves, when the divided portion dies, as far as the first node of Ranvier. When all these organs are again completely streamless, then the absolutely dead substance behaves essentially as an indifferent moist conductor. Muscles divided subcutaneously and healed do not exhibit a negative reaction of the surface of their section. All these considerations go to show that the pre-existence of a current in living uninjured tissues is very doubtful, and, perhaps, can no longer be maintained. Theoretical. — Griinhagen and L. Hermann explain the electrotonic currents as being due to internal polarization in the nerve fibres between the conducting nucleus of the nerve and the en- closing sheaths. Matteucci found that when a wire is surrounded with a moist conductor, and the covering placed in connection with the electrodes of a constant current, currents similar to the VARIATIONS OF THE EXCITABILITi' DURING ELECTROTONUS. 597 electrotonic currents in nerves, and due to polarization, are developed. If either the wire or the moist covering be interrupted at any part, then the polarization current does not extend beyond the rupture. The polarization developed on the surface of the wire causes the conducted current to extend beyond the electrodes. Muscles and nerves consist of fibres surrounded by indifferent con- ductors. As soon as a constant current is closed, on their surface, internal polarization is developed, which produces the electrotonic variation ; it disappears again on opening or breaking the current. Polarization is detected by the fact that in a living nerve the galvanic resistance to conduction across a fibre is about five times, and in muscles about seven times greater than in the longitudinal direction. Action Currents — The term " action current " is applied by L. Hermann to the currents obtained during the activity of a muscle. When a single stimulation wave (contraction) passes along muscular fibres, which are connected at two points with a galvanometer, then that point through which the wave is just passing is negative to the other. Occasionally, in excised muscles, local contractions occur, and these points are negative to the < tber ]^a-sive parts of the muscle [Bieder- mnnn). In order, therefore, to explain the currents obtained from a frog's leg during tetanus, we must assume that the end of the fibre which is negative partici ates less in the excitement than the middle of the fibre. But this is the case only in dying or fatigued muscles (p. 591, 2). According to J 336, D, the direct application of a constant current to a muscle causes contraction first at the cathode, when the current is closed, and when it is opened, at the anode. This is ex- plained by assuming that, during the closing contraction, the muscle is negative at the cathode, while with the opening contraction the negative condition is at the anode. If a muscle be thrown into contraction by stimulating its nerve, then the wave of excitement travels from the entrance of the nerve to both ends of the muscle, which also behave negatively to the passive parts of the muscle. According to the point at which the nerve enters the muscle, the ascending or descending wave of excitement will reach the end (origin or insertion) of the muscle sooner than the other. On placing such a muscle in the galvanometer circuit, then at first that end of the muscle will be negative which lies nearest to the point of entrance of the nerve (t".^., the upper end of the gastrocnemius), and afterward the lower end. Thus there appears rap- idly after each other, at first a descending and then an ascending current in the galvanometer circuit (of course, reversed within the muscle itself) {Six'. Meyer) (\ 332,4). The same occurs in the muscles of the human forearm. When these were caused to contract through their nerves, at first the point of entrance of the nerve (10 cm. above the elbow joint) was negative, and then followed the ends of the muscles when the contraction wave, with a velocity of 10 to 13 metres per second, reached them (L, Hermann) (\ 399, l). If a completely uninjured, streamless muscle be made to contract directly and in toto. then neither during a single contraction nor in tetanus is there a current, because the whole of the muscle passes at the same moment into a condition of contraction. Nerve Currents. — Hermann also supposes that the contents of dying or active nerves behave negatively to the passive normal portions. Imbibition Currents — When water flows through capillary spaces, this is accompanied by an electrical movement in the same direction ( Quincke, Zollner). Similarly, the forward movement of water in the capillar)^ interspaces of non-living parts (pores of a porcelain platej is also connected with electrical movements, which have the same direction as the current of water. 1 he same effect occurs in the movement of water, which results in that condition known as imbibition of a body. We must remember that at the demarcation surface of an injured nerve or muscle imbibition takes place; that also at the contracted parts of a muscle imbibition of fluid occurs (^ 227, II); and that during secrttion there is a movement of the fluid particles. In Plants, electrical phenomena have been observed during the passive bending of vegetable parts (leaves or stalks), as well as during the active movements which are associated with the bend- ing of certiin parts, e.g., as in the mimosa and dioncea (p. 317) (Burdon Sanderson). These phe- ncmieiia are perhaps explicable by the moveinent of water which must take place in the interior of the vegetable parts (A. G. Kunkel). The root cap of a sprouting plant is negative to the seed coverings (j%/v«rtH«) ; the cotyledons positive to the other parts of the seedling (MiiUer-Hctt- lingen). In the incubated hen's egg the embryo is -f- , the yelk — {Hermann and -v. Gendre). 335. ELECTRONIC ALTERATION OF THE EXCITABIL- ITY. — Cause of Electrotonus. — If a certain stretch of a living nerve be trav- ersed by a constant electrical ( '■'polarizing'' ) current, ^it pas.ses into a condition of altered excitability {Ritter, 1S02, and others), which Du Bois-Reyniond called the electrotonic condition, or i\m\AY eiectrofoniis. This condition of altered e.vcitability extends not only over the ])art actually traversed by the current, iiilra- polar portion, but it is communicated to tlie entire nerve. Pfliiger (1859) dis- covered the following laws of electrotonus : — At the positive iiole anode (Fig. 367, A) the excitability is diminished — this is the region of anelectrotonus ; at the negative pole {cathode — K) it is increased 598 PROOF OK ELECTROTONUS IN MOTOR NERVES. — this is the region of cathelectrotonus. The changes of excitability are most marked in the region of the poles themselves. Indifferent Point. — In the intrapolar region a point must exist where the anelectrotonic and cathelectrotonic regions meet, where therefore the excitability is unchanged ; this is called the indifferent or neutral point. This point lies nearer the anode (/) with a weak current, but with a strong current nearer the cathode (i\'^) ; hence, in the first case, almost the whole intrapolar portion is more excitable ; in the latter, less excitable. [Expressed otherwise, a weak current in- creases the area over which the negative pole prevails, while the reverse is the case w'ith a strong current.] Very strong currents greatly diminish the conductivity at the anode, and indeed may make the nerve completely incapable of conduction at this part. Extrapolar Region. — The extrapolar area, or that lying outside the electrodes, is greater the stronger the current. Further, with the weakest currents, the extra- polar anelectrotonic area is greater than the extrapolar cathelectrotonic. With strong currents this relation is reversed. Fig. 367 shows the excitability of a nerve (A', n) traversed by a constant current in the direction of the arrow. The curve shows the degree of increased excitabihty in the neighborhood of the cathode [/C] as an elevation above the nerve, diminution at the anode [A) as a depression. • The Fig. 367. Scheme of the electrotonic excitability. curve m, 0, i,,,p, r, shows the degree of excitability with a strong current ; e,f, i^, h, k, with a medium current ; lastly, a, h, i, c, tij with a weak cui rent. The electrotonic effect increases with the length of the nerve traversed by the current. The changes of the excitability in eleclrotonus occur instantly when the circuit is closed, while anelec- trotonus develops and extends more slowly. Cold diminishes electrolonus [Hermann ajid v. Genitre). When the polarizing current is opened, at first there is a reversal of the rela- tions of the excitability, and then there follows a transition to the normal condi- tion of excitability of the passive nerve iyPfliiger). At the very first moment of closing, Wundt observed that the excitability of the whole nerve was increased. I. Proof of Electrolonus in Motor Nerves. — To test the laws of electrolonus, take a frog's nerve-muscle preparation (Fig. 364). A constant current (p. 577) is applied to a limited part of the nerve by means of non-polarizable electrodes A stimulus, electrical, chemical (saturated solu- tion of common salt), or mechanical is applied either in the region of the anode or cathode; and we observe whether the contraction which results is greater when the polarizing current is opened or closed. We will consider the following cases (Fig. 36S): — (a) Descending extrapolar anelectrotonus, i. e., with a descending current we have to test the excitability of the extrapolar region at the anode. If the stimulus (common salt) applied at R (while the circuit was open) causes in this case (A) moderately strong contractions in the limb, then these at once become weaker, ox disappear as soon as the constant current is transmitted through the nerve. After the circuit is opened, the contractions produced by the salt again occur of the original strength. PROOF OF ELECTROTONUS IN INHIBITORY NERVES. 599 (b) Descending extrapolar cathelectrotonus (A). The stimulus (salt) is at R, and the con- tractions thereliy produced are at once increased after closing the polarizing current. On opening it they are again weakened. (c) Ascending extrapolar anelectrotonus (B). The salt lies at r. In this case we must distinguish the strenglh of the polarizing current : (i) When the current is very weak, which can b.' obtained with the aid of the rheocord (Fig. 344), on closing the polarizing current, there is an increase of the contraction produced by the salt. (2) If, however, the current is stronger, the contractions become either smaller or cease. This is due to the fact that with strong currents the conductivity of the anode is diminished or even abolished (p. 597). Although the salt acts on the excitable nerve, there is no contraction of the muscle, as the conduction of an impulse is prevented by the resistance in the nerve. The law of electrotonus may also be demonstrated on a completely isolated nerve. The end of the ner\'e is properly disposed upon electrodes connected with a galvanometer, so as to obtain a strong current. If the nerve, when the constant current is closed, is stimu- lated in the anelectrotonic area, e. f., by an induction shock, then the negative variation is weaker than when the polarizing circuit was open. Conver>ely, it is stronger when it is stimulated in the cathelec- trotonic area (Bernstein). The currents from the extrapolar areas of a nerve in a condition of electrotonus exhibit the negative variation when the nerve is stimulated. Proof in Man. — In performing this experiment it is important to remember the distribution of the current in the body. If both elec- trodes, for example, be placed over the course of the ulnar nerve (Fig. 369), the currents entering the nerve at the anode (-(- a a) must diminish the excitability; only aliove and below the anode (at <- r) the positive current emerges from the nerve and excites cathelectrotonus at these points. Similarly, where the cathode is applied (— c c) there is increased excitability; but in higher and lower parts of the nerve, where (at a a) the positive current (coming from +) enters the nerve, the excitability is diminished (anelectrotonus) {v. Hehnholtz, Erb). If we desire to stimulate in the neighborhood of an elec- trode, then we cannot act upon that part of the nerve whose excitability is influenced by the electrode. Method of testing the e.xcil bility in electrotonus. R, R,, r,, where the comm. salt (stimulus) is applied. Fig. 369. Scheme of the distribution of an electrical In order, therefore, to stimulate directly the same point on which the electrode acts, it is necessary I'l apply the stimulus at the same time by the electrode itself, e. g., either mechanically or by con- ducting the stimulating current through the polarizing circuit ( IVa/ier and de IVattevilte). II. Proof of Electrotonus in Sensory Nerves. — Is ilate the sciatic nerve of a decapitated frog. When this nerve is stimulated in its course with a saturated solution of common salt, reflex movements are excited in the other leg, the spinal cord being still intact. These disappear as soon as a constant current is applied to the ner\e, provided the salt lies in the anelectrotonic 3xt3.(Pfliiger, and Zurhelle, Hdllsten). III. Proof of Electrotonus in Inhibitory Nerves. — To show this, proceed thus : On causing dyspnoea in a rabbit, the number of heart heats is diminished, owing to the action of the dyspnoeic blood on the cardio. inhibitory centre in the medulla oblongata. If, after dividing the vagus on one side, a constant descending current be passed through the other intact vagus, the number of pulse beats is again increased (descending extrapolar anelectrotonus). If, however, the current through 600 THE LAW OF CONTRACTION. the nerve be an ascending one, then with weak currents the number of heart beats increases still more (ascending extrapolar calhelectrotonus). Hence, the action of inhibitory nerves in eleclrotonus is the opposite of that in motor nerves. During the electrotonus of muscle, the excitability of the intrapolar portion is altered. The delay in the conduction is confined to this area alone {v. Bezold) —compare §337, i. 336. ELECTROTONUS— LAW OF CONTRACTION.— Opening and Closing Shocks. — A nerve is stimulated both at the moment of the occur- rence and that of disappearance of electrotonus (/. c, by closing and opening the current — Ritter): (i) When the current is closed, the stimulation occurs only at the cathode, /. e., at the moment when the electrotonus takes place. (2) When the current is opened, stimulation occurs only at the anode, /. e., at the moment when the electrotonus disappears. (3) The stimulation at the occurrence of cathelectrotonus is stronger than at the disappearance of anelectrotonus {Pfliigc-)- Ritter's Opening Tetanus. — That stimulation occurs only at the anode, when the current is opened, was proved by PflUger by means of " Ritter's opening tetanus." Ritter's tetanus consists in this, that when a constant current is passed for a long time through a long stretch of nerve, on opening the current, tetanus lasting for a considerable time results. If the current was a descending one, then this tetanus ceases at once after section of the intrapolar area, a proof that the tetanus resulted from the now separated anode. If the current was an ascending one, section of the nerve has no effect on the tetanus. Pfliiger and v. Bezold also proved that the closing contraction at the cathode precedes that at the anode. Thus, they observed that with a descending current the closing contraction in the muscle at the moment of closing occurred earlier than the opening contraction at the moment of opening; and, conversely, with an ascending current, the closing contraction occurred later, and the opening contraction sooner. The difterence in time corresponds to the time required for the propagation of the impulse in the intrapolar region (| 337). If a large part of the intrapolar region in a frog's nerve be rendered inexcitable by applying ammonia to it, then only the electrode next the mus- cle stimulates, i. e., always on closing a descending current and on opening an ascending one [Biedermann). A. The law of contraction is valid for all kinds of nerves. — I. The contrac- tion occurring at the closing or opening of a constant current varies with {a) the direction (Pfaff), and (/') the strength of the current (Heidenhairi). (i) Very feeble currents, in conformity with the third of the above state- ments, cause only a closing contraction, both with an ascending and a descend- ing current. The disappearance of electrotonus is so feeble a stimulus as not to excite the nerve. (2) Medium currents cause opening or closing contractions both with an ascending and a descending current. (3) Very strong currents cause only a closing contraction with a.dcsceniiing cur- rent ; the opening shock does not occur, because, with very strong currents, al- most the whole of the intrapolar portion of the electrotonic nerve is incapable of conducting an impulse (p. 598). Ascending currents cause only an opening con- traction for the same reason. With a certain strength of current, the muscle re- mains tetanic while the current is closed (" closing tetanus^'). [The law of contraction is formulated : — R = rest ; C = contraction.] Strength of Current. Ascending. Descending. On Closing. On Open ing. On Closing. On Open ng. 1 Weak C C R R c c C C C R C R Medium, . Strong, . THE LAW OF CONTRACTION. 601 II. In a dying nerve, losing its excitability, according to the Ritter-Valli law (§ 325, 7), the law of contraction is modified. In the stage of increased excita- bility weak currents cause only closing contractions with both directions of the current. In the following stage, when the excitability begins to diminish, weak currents cause opening and closing contractions with both currents. Lastly, when the excitability is very greatly diminished, the descending current is followed only by a closing contraction, and the ascending by an opening contraction {Ri/ter, III. As the various changes in excitability occur in a centrifugal direction along the nerve, we may detect the various stages simultaneously at different parts along the course of the nerve. According to Valentin, Fick, CI. Bernard, and Schiff, the living intact nerve shows only a closing contraction with both direc- tions of the current, and opening contractions only with very strong currents. Fleischl's Law of Contraction. — v. FleischI and Strieker have stated a different law in re- spect to the fact that the excitability varies at certain points in the course of a nerve. The sciatic nerve is divided into three areas: (l) Stretches from the muscle to the place where the branches for the thigh muscles are given off ; (2) from here to the intervertebral ganglion; (3) from here into the spinal cord. Each of these three areas consists'of two parts (" upper and lower pole "), which adjoin each other at an equator. In each upper pole the excitability of the nerve is greater for descending currents, and in each lower pole for ascending ones. At each equator the excitabil- ity of the nerve is the same for ascending and descending currents. The difference in the activity, due to the direction of the current, is greater for each stretch of nerve the greater this stretch is dis- tant from the equator. The excitability is less at those points of the nerve where the three areas join each other. Eckhard observed that, on opening an ascending medium current applied to the hypoglossal nerve of a rabbit, one-half of the tongue exhibited a trembling movement instead of a contraction, while on closing a descending current the same result occurred (^ 297, 3). According to Pfliiger, the molecules of the passive nerve are in a certain state of medium mobility. In cathelectrotonus the mobility of the molecules is increased, in anelectrotonus, diminished. B. The law for inhibitory nerves is similar. Moleschott, v. Bezold, and Bonders have found similar results for the vagus, with this difference, that, instead of the contraction of a muscle, there is inhibition of the heart. C. For sensory nerves, also, the result is the same, but we must remember that the perceptive organ lies at the central end of the nerve, while in a motor nerve it (muscle ) is at the periphery. Pfliiger studied the effect of closing and open- ing a current on sensory nerves by observing the reflex movement which resulted. Weak currents cause only closing contractions ; medium currents both opening and closing contractions : descending strong currents only opening con- tractions ; and ascending only closing contractions. fFca/' currents applied to the human skin cause a sensation with both directions of the current only at closing ; strong descetuiing cwxxtwVs, S-itVi-izXiow only at opening; strong ascending cwxxtwXi a sensation only at closing {Marianini, Matteucei). When the current is closed there is prickly feeling, which increases with the strength or the current {Volta'). Analo- gous phenomena have been observed in the sense organs (sensations of light and sound) by Volta and Ritter. D. In muscle, the law of contraction is proved thus — by fixing one end of the muscle, keeping it tense, so that it cannot shorten, and opening and closing the current at this end. The end of the muscle, which is free to move, shows the same law of contraction as if the motor nerve was stimulated {v.Bezo/d). On closing the current, the contraction begins at the cathode ; on opening, at the anode {Engelmann). E. Hering and Biedermann showed more clearly that both the closing and opening contractions are purely polar effects ; when a weak cur- rent applied to a muscle is closed, the first effect is a small contraction limited to the cathodic surface of the muscle. Increase of the current causes increased con- traction which extends to the anode, but which is weaker there than at the cathode ; at the same time, the muscle remains contracted dunng the time the cur- rent is closed. On opening, the contraction begins at the anode; even after open- 602 TRANSMISSION OF NERVOUS IMPULSES. ing, the muscle for a time may remain contracted, which ceases on closing the current in the same direction. By killing the end of a muscle in various ways, the excitability is diminished near this part. Hence, at such a place the polar action is feeble (van Loon and Engelmann, Biedermann). Touching a part with extract of flesh, potash, or alcohol diminishes locally the polar action, while soda salts and veratrin increase it [Biedermann'). Closing Continued Contraction. — The moderate continued contraction, which is sometimes observed in a muscle while the current is closed (Fig. 301, O), depends upon the abnormal pro- longation of the closing contraction at the cathode when a strong stimulus is used, or during the stage of dying, or in cooled winter frogs ; sometimes the opening of the current is accompanied by a similar contraction proceeding from the anode (Biedermann'). This tetanus is also due to the summ.ation of a series of simple contractions (\ 298, III). By acting on a muscle with a two per cent, saline solution containing sodic carbonate, the duration of the contraction is increased consid- erably, and occasionally the muscle shortens rhythmically (| 296) (Biedermann). If the whole muscle is placed in the circuit, the closing contraction is strongest with both directions of the current ; during the time the current is closed a con- tinued contraction is strongest when the current is ascending ( Wuuiit). Inhibitory Action. — The constant current, when applied to a muscle in a condition of continued and sustained contraction, has exactly the opposite effect to that on a relaxed muscle. If a constant current be applied by means of non- polarizable electrodes to a muscle in a state of continued contraction, e.g., after poisoning with veratrin or through the contracted ventricle, when the current is closed there is a relaxation beginning at the anode and extending to the other parts; on opening the current applied to muscle in continued contraction, the relaxation proceeds from the cathode. Pawlow found nerve fibres in the adductor muscle of the mussel, whose stimulation caused relaxation of the muscular con- traction. Ritter's Opening Tetanus.^ — If a nerve or muscle be traversed by a constant current for some time, we often obtain a prolonged tetanus, after opening the current (Ritter's opening tetanus, 1798). It is set aside by closing the original current, while closing a current in the opposite direction increases it ("Vo/ta's alternative''''^. The continued passage of the current increases the excitability for the opening of the current in the same direction, and for the closing of the reverse current ; conversely, it diminishes it for the closing of the current in the same direction, and for the opening of the reverse current {Volta, Rosenthal, Wundt). In a nerve-muscle preparation used to prove the law of contraction, of course a demarcation cur- rent is developed in the nerve (\ 334, II). If an artificial, weak stimulating current be applied to such a nerve, we obtain an interference effect due to these two currents; closing a weak current causes a contraction, which, however, is not properly a closing contraction, but depends upon the opening of a branch of the demarcation current ; conversely, the opening of a weak current may excite a contraction, which is really due tn the closing of a side branch of the nerve current in a secondary circuit through the electrodes (Herintr, Biedertnann, Gri'itzner). According to Griitzner and Tiegerstedt, the cause of the opening contraction is partly due to the occurrence of polarizing after-currents (\ 333). Engelmann and Griinhagen explain the occurrence of opening and closing tetanus, thus, as due to 'atent stimulations, drying, variations of the temperature of the prepared nerve, which of them- selves are too feeble to cause tetanus, but which become effective if an increased excitability obtains at the cathode after closure, and at the anode after opening the current. Biedermann showed that, under certain conditions, two successive opening contractions can be ob- tained in a frog's nerve-muscle preparation, the second and later one corresponding to Ritter's tetanus. The first of these contractions is due to the disappearance of anelectrotonus in PflUger's sense; the second is explained, like Ritter's opening tetanus, in Engelmann's and Griinhagen's sense. 337. TRANSMISSION OF NERVOUS IMPULSES.— i. If a motor nerve be stimulated at its central end ( i ) a condition of excitation is set up, and (2) an impulse is transmitted along the nerve to the muscle with a certain velocitv. The latter depends on the former and represents the function of conductivity. The velocity is about 2iY^ metres [about 90 feet] per second METHOD OF ESTIMATING RAPIDITY OF A NERVE IMPULSE. 603 (7'. Hehnholtz) and for the human motor nerves 33.9 [100 to 120 feet per second] (v. Helmholtz and Baxt). The second depends on the first. The velocity is less in the visceral nerves, e.g., in the pharyngeal branches of the vagus 8.2 metres [26 feet] [C/iauveau) ; in the motor nerves of the lobster 6 metres [18 feet] (Fredericq and van de Velde). Modifying Conditions. — The velocity is influenced by various conditions : Temperature. — It is lessened considerably by cold {v. Helmholtz), but both high and low temperatures of the nerve (above or below 15° to 25° C.) lessen it (Steiner and Trojtzkf) ; also eiirara, the electrotonic condition {v. Bezold) ; or only anelectrotonus, while cathelectrotonus increases it {Rutherford, JFnndt). It varies also with the length of the conducting nerve, but it increases with the strength of the stimulus {v. Helmholtz and Baxt ), although not at first (r'. Vint- schgait). Methods. — (i) V. Helmholtz (1850) estimated the velocity of the nerve impulse in a frog's motor nerve, after the method of Pouillet. The method depends upon the fact that the needle of a galvanometer is deflected by a current of very short duration; the extent of the deflection being Fig. 370. w k V. HelmhoUz'i method of estimating the velocity of a nerve impulse. proportional to the duration and strength of the current. The aoparatus is so arranged that the " time-marking current " is closed at the moment the nerve is stimulated, and opened again when the muscle contracts. If the nerve attached to a muscle be now stimulated at the further point from the muscle, and a second time near its entrance to the muscle, then in the latter case the time between the application of the stimulus and the beginning of the contraction of the muscle, i. <■., the deflection of the galvanometer, will be less than in the former case, as the impulse has to trav- erse the whole length of the nerve to reach the muscle. The diff^erence between the two times is the time required by the impulse to traverse a given distance of nerve. Fig. 370 shows in a diagrammatic manner the arrangement of the experiment. The galvanometer, G, is placed in the lime-marking circuit (open at first), a, b (element), c (piece of platinum on a key, W), introduced into the time-marking circuit, d, e,f, h. The circuit is made by closing the key, S, when d de- presses the platinum plate of the key, W. At once, when the current is closed, the magnetic needle is deflected, and its extent noted. At the same moment in which the current between c and d is closed the primary circuit of the induction machine is opened, the circuit being i, k, I (element), m, O (primary spiral),/. Thereby an opening shock is induced in the secondary spiral, R. which stimulates the nerve of the frog's leg at n. Thus, the closing of the galvanometer circuit exactly coincides with the stimulation of the nerve. The impulse is propagated through the nerve to the muscle, M, and the latter contracts when the impulse reaches it, at the same time opening the time- 604 METHOD OF ESTIMATING RAPIDITY OF A NERVE IMPULSE. measuring circuit at the double contact, e and f, by raising the lever, H, which rotates on x. At the moment of opening, the fuither deflection of the magnetic needle ceases. The contact at / is made by a pointed cupola of mercury. Wlien the lever, H, falls after the contact of the muscle, so that the point, e, comes into contact with the underlying solid plate, y, the contact at f still re- mains open, ;'. e., through the galvanometer circuit. If the nerve be stimulated with the opening shock, first es, § a^^- 2. Union of Motor and Sensory Nerves. — If the hypoglossal and lingual nerves be divided in a dog, and if the peripheral end of the hypoglossal be stitched, so as to unite with the central end of the lingual (Bidder), then, several months after the union and restitution of the nerves, stimulation of the central end of the lingual causes contraction in the corresponding half of the tongue. Hence, it has been assumed that the lingual, which is the sensory nerve of the tongue, must conduct the impulse in a peripheral direction to the end of the hypoglossal. This experiment is not conclusive, as tlie trunk of the lingual receives high up the centrifugal fibres from the seventh, viz., the chorda tympani, which may unite w itn those of the hypoglossal. Further, if the chorda be divided and allosved to degenerate before the above described experiment is made, then no contractions occur on stimulating the lingual above the point of union (§ 349). 3, Bert's Experiment. — Paul Bert removed the skin from the tip of the tail of a rat, and stitched it into the skin of the back of the animal, where it united with the tissues. After the first union had taken place, the tail was then divided at its base, so that the tail, as it were, grew out of the skin on the back of the animal. On stimulating the tail, the animal exhibited signs of sensation, so that the impuLes in the sensory nerves must have traversed the nerves from the base to the tip of the tail (\ 325). 4. Electrical Nerves. — If the free end of the electrical centrifugal nerves of the nialapterurus be stimulated, the branches given off above the point of stimulation are also excited, so that the whole electrical organ may discharge its electricity (^Babuchin, Mantey). 339. ELECTRO-THERAPEUTICS— REACTION OF DEGENERATION.— Elec- tricity is frequently employed for therapeutical purposes, the rapidly interrupted current of the in- duction machine, or Faradic current, being frequently used (especially since Duchenne, 1847), the magiieto-eleclrical apparatus, and the extra-currtnt apparatus. The constant or galvanic current is also used, especially since Remak's time, 1855 (J 330). I. In paralysis, /'araa'/f currents are applied either to the muscles themselves {^Duchenne), or the points of entrance 01 the motor nerves \v. Ziemssen), by means of suitable electrodes, or rheo- phores covered with spjnge, etc., and moistened. [Rheophores. — Many different forms are used, according to the organ or part to be stimulated, or the effect desired. When electricity is applied to the skin to remove anesthesia, hyperaesthesia, or altered sensibility, and we desire to limit the effect to the skin alone, then the rheophores are applied dry, and are usually made of metal. If, however, deeper-seated structures, as muscles or nerve trunks, are to be affected, the skin must be well moistened and soitened by sponging with warm water, while the rJieophores are fitted with sponges moistened with common salt and water which diminishes the resistance of the skin to the passage of electricity (Figs. 373-375)-] > In faradizing the paralyzed muscle, the object is to cause artificial movements in it, and thus pre- vent the degeneration which it would otherwise undergo, merely from inaction. If, in addition to the motor nerves, its trophic nerves are also paralyzed, then a muscle atrophies, notwithstanding the faradization (J 325, 4). The use of the induced current also improves a paralyzed muscle, as it in- creases the blood stream through it, while it affects the metabolism of the muscle reflexly. In addition, weak currents may restore the excitability of enfeebled ner\-es {v. Bczold, Eiigelinann). THERAPEUTICAL ACTIONS OF THE CONSTANT CURRENT. 607 The Figs. 376, 377, 378, and 379 indicate the positions of the motor points of the extremities, where, bv stimulating at the entrance of the nerve, each muscle may be caused to contract singly. In I 349 the motor points of the face, and in J 347 those oi the neck, are indicated. The constant current may be employed as a stimulus when it is closed and opened in the form of an iitterriipled current, by altering its direction and increasing or diminishing its intensity, but it also causes a polai aclion. On closing the current, the nerve at the cathode is stimulated ; similarly, on opening the current, at the anode (J 336). Thus, when the current is closed, the excitability of the nerve is increased at the cathode (^. 335), which may act favorably upon the nerve. Increased excitability in electrotonus at the anode, although feebler, has been observed during percutaneous galvanization in man. This is especially the case by repeatedly reversing the current, sometimes also by opening and closing, or even with a uniform current. If the increase of the excitability is obtained, then the direction of the current increases the excitability on closing the reverse cuirent, and on opening the one in the same direction. Restorative Effect. — Further, in using the constant current, we have to consider its restorative effects, especially when it is ascending. R. Heidenhain found that feeble and fatigued muscles re- cover after the passage of a constant current through them. Fig. 375. Fig. 373. Fig. 374 T Double sponge rheophi Disk rheopho Lastly, the constant current may be useful from its catalytic or cataphoric action {\ 328). The effect is directly upon the tissue elements. It may also act directly or reflexly upon the blood and lymph vessels. Faradization in Paralysis.— If the primary cause of the paralysis is in the muscles themselves, then the induced current is generally applied directly to the muscles themselves by means of sponge electrodes (Fig. 373) ; while, if the motor nerves are the primary seat, then the electrodes are apjilied over them. The current used must be only of very moderate strength; strong tetanic con- tractions are injurious, and so is too prolonged application (Alb. Eulenbitrg). The galvanic current may also be applied to the muscles or to their motor nerves, or to the cen- tres of the latter, or to both muscle and nerve simultaneously. As a rule, the cathode is placed «i'a/cr the centre, as it increases the excitability. When the electrode is moved along the course of the nerve, or when the strength of the current is varied, the action is favored. If the seat of the lesion is in the central nervous system, then the electrodes are applied along the vertebral column, or on the vertebral column, and the course of the nerves at the same time, or one on the head and the other on a point as near as possible to the supposed seat of the lesion. The current must not be too strong nor applied too long. Induced f. Constant Current : Reaction of Degeneration. — Paralyzed nerves and muscles behave quite differently as regards the induced (rapidly interrupted) and the constant oiiitrA. This is called the " reaction of degeneration." We must remember the physiological fact that a dying 608 REACTION OF DEGENERATION. nerve attached to a muscle (^ 325), and also the muscles of a curarized animal, react much less strongly to rapidly interrupted currents than fresh non-curarized muscles. Baierlach, in 1S59, found that in a case of facial paralysis the facial muscles contracted but feebly to the induced current, but very energetically on the constant current being used. The excitability for the constant current may Fig. 376. N. radlalia. M, brachiiL intera / M. surSaatorlong. liial pxi. long. M, eitt^iiB, digit, communis. M. extens. digit, min. M. trifops faput "Xf.l M. triceps ('■aput long) M. deltnideus \ (post. half). tN. axillaris). M. ttbdnct pollic. long. M. extens. pollic. brev M. estens. poll, long (N M. abdact. digif. mIn. (N. olnarU.) dorsal. I. 11, III, et IV. Motor points of the radial nerve and the muscle upplied by it ; dorsal surface. Fig. 377. M. deltoideufi lant. half) N. axillaris. N. muaculo-cuianeus, M. biceps brachiL H. bracb. anticus. "V __| _^ I [ I N. medianu3 M abductor potHo. lireT. Al opponeuB [xiUicia. I M. flex. M. abductor polllc> brer. Miu liimbriua 63 ^ Mm lumbrl cat^IiletlV. M oppoDeDs dii.lt. I M flexor dUIt mm. M. abiuctor dijit uiia. M. t&lo' ulnarifl. M. flexor carpi nlnariB. N. ulnaris. r points of the median and ulnar nerves, with the muscles supplied by them. be abnormally increased, but may disappear on recovery taking place. According to Neumann, it is the longer duration of the constant current as opposed to the momentary closing and openmg of the induced current which makes the contraction of the muscle possible. If the constant current be REACTION OF DEGENERATION. 609 broken as rapidly as the Faradic current is broken, thfen the constant current does not cause contrac- tion. Conversely, the induced current may be rendered effective by causing it tn last longer. We may also keep the primary circuit of the iiuluclion machine closed, and move the secondary spiral to and fro along the slots. Thus we obtain slow gradations of the induced current which act ener- getically upon curarized muscles (Brih/cf). Hence, in stimulating a muscle or ner\'e, we have to consider not only the strength, but also the duration, of the current, just as the deflection of the magnetic needle depends upon these two factors. [Galvanic excitability is the term applied to the condition of a nerve or muscle, whereby it re- sponds to the opening or closing of a continuous current. The effects differ according as the current is opened or closed, and according to its strength. As a rule, the cathode causes a contraction Fig. 378. I r N. obturator. M. pect: M. adductor magni M adduct. longi U J : points of the peroneal and tibial nerves on the front of the leg ; the peroneal c tibial on the right (after Eichhorst). chiefly at closure, the anode at opening the current, while the cathode is the stronger stimulus.. With a weak current the cathode produces a simple contraction on closing the current, but no con- traction from the anode. With a medium current we get with the cathode a strong closing contrac- tion but no opening contraction, while the anode excites feeble opening and closing contractions. With a strong current we get with the cathode a tetanic contraction at closure, and a perceptible contraction at opening, while with the anode there is contraction both at opening and closing.] [The law of contraction is usually expressed by the following formula (lioss, after Erb) : An = anode, Ca = cathode, C = contraction, c = feeble contraction, C ^= strong contraction, S = closure of current, O ^ opening of current, Te = tetanic contraction ; so that, expressing the above statements briefly, we have — 39 610 REACTION OF DEGENERATION. Weak currents produce Ca S C ; Medium " " Ca S C, An S c. An O c; Strong •' " Ca S Te, An S C, An O C, Ca Or.] [Typical Reaction of Degeneration. — When the reaction of the nerve and muscle to electrical stimulation is altered both qualitatively and quantitatively, we have the reaction of degeneration, which is characterized essentially by the following conditions] : The excitability of the muscles is diminished or abolished for the Faradic current, while it is increased for the galvanic current from the 3d-58th day ; it again diminishes, however, with variations, from the 72d-8oth day ; the anode closing contraction is stronger than the cathode closing contrac- tion. The contractions in the affected muscles occur slowly in a peristaltic manner, Fig. 379. /M. biceps, fern. (cap. long.) \ {grt. sciat.). \M. biceps, fern. (cap. brev.) ischiadit adduct. magnus (n. obt.), tendinosus (grt. sciat.) ibranosus (grt. )■ (cap. e (cap. W. flex. dig. conim. long. M. flexor hallucis longus. ches ; the peroneal a and are local, in contrast with the rapid contraction of a normal muscle. The diminution of the excitability of the nerves is similar for the galvanic and Faradic currents. If the reaction of the nerves be normal, while the muscle during direct stimulation with the constant current exhibits the reaction of degeneration, we speak of "partial reaction of degeneration" {Erb), which is constantly present in progressive muscular atrophy {Erb, Giinthcr). [The " reaction of degeneration " may occur before there is actual paralysis, as in lead poison. ing. When it occurs, we have to deal with some affection of the nerve fibres or of the trophic nerve cells. When it is established, (i) stimulation of the nerve with Faradic and galvanic elec- tricity does not cause contraction of the muscle ; (2) direct Faradic stimulation of the muscles does not cause contraction; (3) the galvanic current usually excites contraction more readily than in a normal muscle, so that the muscle responds to much feebler currents than act on healthy muscles; ELECTRICAL CHARGING OF THE BODY. 611 but the contraction is longer and more of a tonic character, and shows a tendency to become tetanic] [The electrical excitability is generally unaffected in paralysis of cerebral origin, and in some forms of spinal paralysis, as primary lateral sclerosis and transverse myelitis (fiossi ; but the "reaction of degeneration " occurs in traumatic paralysis due to injury of the nerve trunks, neuritis, rheumatic facial paralysis, lead palsy, and in affections of the nerve cells in the anterior cornu of the gray matter of the spinal cord.] In rare cases the contraction of the muscles, caused by applying a Faradic current to the nerve, follows a slow peristaltic-like course — "Faradic reaction of degenera- tion " (A. Remak, A'ast, Erh). II. In Various Forms of Spasm (spasms, contracture, muscular tremor) the constant current is most effective (Remak). By the action of anelectrutunus, a pathological increase of the excita- bility is subdued. Hence, the anode ought to be applied to the part with increased excitability, and if it be a case of reflex spasm, to the points which are the origin or seat of the increased excitability. Weak currents of uniform intensity are most effective. The constant current may also be useful from its cataphoric action, whereby it favors the removal of stimuli from the seat of the irritation. Further, the constant current increases the voluntary control over the affected muscles. In spasms of central origin the constant current may be applied to the central organ itself (Fig. 387). Fara- dization is used in spasmodic affections to increase the vigor of enfeebled antagonistic muscles. Muscles in a condition of contracture are said to become more extensible under the influence of the Faradic current (Remak), as a normal muscle is more excitable during active contraction (i30i)- In cutaneous anaesthesia, the Faradtc current applied to the -skin by means of hair-brush electrodes (Fig. 375) is frequently used. When using the constant current, the cathode must be applied to the parts with diminished sensibility. The con.stant current alone is applied to the central seat of the lesion, and care must be taken to what extent the occurrence of cathelectroionus in the centre affects the occurrence of sensation. III. In Hyperassthesia and Neuralgias, Faradic currents are applied with the object of over- stimulating the hypersensitive parts, and thus to benumb them. Besides these powerful currents, loeak currents act reflexty and accelerate the lilood stream, increase the heart's action, and constrict the blood vessels, while stron.; currents cause the opposite effects (O. Naiimann). Both may be useful. In employing the constant current in neuralgia (Remak), ore object is by exciting anelec- trotonus in the hypersensitive nerves, to cause a diminution of the excitability. According to the nature of the case, the anode is placed either on the nerve trunk or even on the centre itself, and thi cathode on an indifferent part' of the body. The catalytic and cataphoric effects also are most important, for by means of them, especially in recent rheumatic neuralgias, the irritating inflamma- tory products are distributed and conducted away from the part. A descending current is trans- mitted continuously for a time through the nerve trunk, and in recent cases its effects are sometimes very striking. Lastly, of course the constant current may be used as a cutaneous stimulus, while the Faradic current also acts reflexly on the cardiac and vascular activity. Recently, Charcot and Bailet have used the electric spark from an electrical machine in cases of anxbthesia, facial paralysis and paralysis agitans. In some cases of spinal paralysis, muscles can be made to contract with the electric spark, which do not contract to a Faradic current. [Elec- tricity is sometimes used to distinguish real from feigned disease, or to distinguish death from a con- dition of trance.] Galvano Cautery. — The electrical current is used for thermal purposes, as in the galvano cautery. Galvano Puncture. — The electrolytic properties of electrical currents are employed to cause coagulation in aneurisms or varix. [If the electrodes from a constant battery in action be inserted in an aneurismal sac, after a time the fibrin of the blood is deposited in the sac, whereby the caviiy of the aneurism is gradually filled up. A galvanic current passed through defibrinated blood causes the formation of a coagulum of proteid matter at the positive pole and bubbles of gas at the negative.] 340. ELECTRICAL CHARGING OF THE BODY.— Saussure investigated by means of the electroscope the "charge" of a person standing on an insulated stool. The phenomena observed by him, which were always inconstant, were due to the /riction of the clothes upon the skin. Gardini, Hemmer, Ahrens (1S17), and Nasse regarded the body as normally charged with positive electricity, while Sjosten and others regarded it as negatively charged. Most probably all these phenomena are due to friction, and are modified effects of the air in contact with the hetero- geneous clothing (Hankel). A strong charge resulting in an actual spark has frequently been described. Cardanus (1553) obtained sparks from the tips of the hair of the head. According to Horsford (1837), long sparks were obtained from the tips of the fingers of a nervous woman in Oxford, when she stood upon an insulated carpet. Sparks have often been observed on combing the hair or stroking the back of a cat in the dark. Freshly-voided urine is negatively electrical ( Vasalli- Eandi, I'olta) ; so is the freshly-formed web of a spider, while the blood is positive. 341. COMPARATIVE— HISTORICAL.— Electrical Fishes.— Some of the most inter- esting phenomena connected with animal electricity are obtained in electrical fishes, of which there are about fifty species, including the electrical eel, oxGymnotus electricus, of the lagoons of the region 612 COMPARATIVE HISTORICAL. of the Orinoco in Soutli America ; it may measure over 7 feet in length. The Torpedo tnartnorala and some allied species, 30 to 70 centimetres [i to zy'^ feet], in the Adriatic and Mediterranean, the Malapteriiriis ehclriciis of the Nile, and the Marmyrus, also of the same river. By means of special electrical organs (Rt\ii, /6(^6), these animals can in part voluntarily (gymnotus and malap- terurus), and in part retlexly (torpedo) give a very powerful electrical shock. The electrical organ consists of •' compartments " of various lorms, separated from each other by connective tissue, and filled with a jelly-like substance, which the nerves enter on one surface and ramify to produce a plexus. From this plexus there proceed branches of the axial cylinder, which end in a nucleated plate, the " electrical plate " (Billharz, M. Scliiihe). When the " electrical nerves " proceeding to the organ are stimulated, an electrical discharge is the result. In Gymnotus the electrical organ consists of several rows of columns arranged along both sides of the spinal column of the animal, under the skin as far as the tail. It receives on the anterior surface several branches from the intercostal nerves. Besides this large organ there is a smaller one lying on both sides above the anal fins. Here the plates are vertical, and the direction of the elec- trical current in the fish is ascending, so that, of course, it is descending in the surrounding water {^Faratiay, Dti Bois-Rcymond). In Malapterurus the organ surrounds the body like a mantle, and receives only one nerve fibre (p. 521), whose axis cylmder arises near the medulla oblongata from one gigantic ganglionic cell {BiUharz), and is composed of protoplasmic processes (I-n/sc/i). The plates are also vertical, and receive their nerves from the posterior surface. The direction of the current is descending in the tish during the discharge {Vit Bois-Reymotid"). In the Torpedo the organ lies immediately under the skin laterally on each side of the head, reaching as far as the pectoral fins. It receives several nerves which arise from the lobus electricus, between the corpora quadrigemina and the medulla oblongata. The plates, which do not increase in number with the growth of the animal (Del/e Chiaje, Bti/>uchin),\\e horizontally, while the nerve fibres enter them on their dorsal surfaces, the current in the fish being from the abdominal to the dorsal surface ( Oalvani). It is extremely probable that the electric organs are modified muscles, in which the nerve terminations are highly developed, the electrical plates corresponding to the motorial end plates of the muscular fibres, the contractile substance havmg disappeared, so that during physiological activity the chemical energy is changed into electricity alone, while there is no " work " done. This view is supported by the observation of Babuchin, that during development the organs are originally formed like muscles ; further, that the organs when at rest are neutral, but when active or dead, acid ; and lastly, they contain a substance related to myo'sin which coagulates after death (§295 — ll'nyl). The organs manifest fatigue ; they have a " latent period " of 0.016 second, while one shock of the organ (comparable to the current in an active muscle) lasts 0.07 second. About twenty-five of these shocks go to make a discharge, which lasts about 0.23 second. The discharge, like tetanus, is a discontinuous process [Matey). Mechanical, chemical, thermal and electrical stimuli cause a discharge; a single induction sliock is not effective [Sachs). During the electrical discharge the current traverses the muscles of the animal itself; the latter contract in the torpedo, while they do not do so in the gymnotus and malapterurus during the discharge [Stehier). A tor- pedo can give about fifty shocks per minute ; it then becomes fatigued, and requires some time to recover itself. It may only partially discharge its organ (Al. v. Humboldt, Sachs). Cooling makes the organ less active, whUe lieating it to 22° C. makes it more so. The organ becomes tetanic with strychnin [^Beajuercl), while curara paralyzes it (^Sachs). Stimulation of the electrical organ of the torpedo causes a discharge {Maiteucci) ; cold retards it, while section of the electrical nerves paralyzes the organ. The electrical fishes themselves are but slightly affected by very strong induc- tion shocks transmitted through the water in which they are swimming [Dti Bois-Keymond). The substance of the electrical organs is singly refractive; excised portions give a current during rest, which has the same direction as the shock ; tetanus of the or^^an weakens the current [Sachs, Du Bois-Rcymoiid ) . Historical. — Richer (1672) made the first communication about the gymnotus. Walsh (1772) made investigations on the torpedo, on its discharge, and its power of communicating a shock. J. Davy magnetized particles of steel, caused a defieciion of the magnetic needle, and obtained elec trolysis with the electrical discharge. Becquerel, Brechet and Matteucci studied the direction of the discharge. Al. v. Humboldt described the habits and actions of the gymnotus of South America. Hausen (1743) and de Sauvages (1744) supposed that electricity was the active force in nerves. The actual investigations into animal electricity began with G. Aloisio Ualvani (1791), who observed that frogs' legs connected with an electrical machine contracted, and also when they were touched with two difterent metals. He believed that nerves and muscles generated electricity. Alessandro \'olta ascribed the second experiment to the electrical current produced by the contact of dissimilar metals, and therefore outside the tissues of the Irog. The contraction without metals described by Galvani was confirmed by Alex. v. Humboldt (1798). Pfaft'(i793) first observed the effect of the direction of the current upon the contraction of a frog's leg obtained by stimulating its nerve. Bunzen made a galvanic pile of Irogs' legs. The whole subject entered on a new phase with the construction of the galvanometer and since the introduction of the classical methods devised by Du Bois-Reymond, i.e., from 1S43 onwards. Physiology ™e peripheral Nerves. 342. FUNCTIONAL CLASSIFICATION OF NERVE FIBRES. — As nerve fibres, on being stimulated, are capable of conducting impulses in both directions (§ 338), it is obvious that the physiological position of a nerve fibre must depend essentially upon its relations to the peripheral end organ on the one hand, and its central connection on the other. Tf.us, each nerve is dis- tributed to a special area within which, under normal circumstances, in the intact body, it performs its functions. I. Centrifugal or Efferent Nerves. — 'a) Motor. — Those nerve fibres whose peripheral end organ consists of a muscle, the central ends of the fibres being connected with nerve cells : — 1. Motor fibres of striped muscle (^ 292 to 320). 2. Motor nerves of the heart (| 57). 3. Motor nerves of smooth muscle, e. g., the intestine (\ 171). The vasomotor nerves are specially treated of in J 371. (b I Secretory. — Those nerve fibres whose peripheral end organ consists of a secretory cell, the central ends of the fibres being connected with nerve cells. Examples of secretory nerves are the secretory nerves for saliva (^ 145) and those for sweating (^ 289, II). It is to be remembered, however, that these fibres not unfrequently lie in the same sheath with other nerve fibres, so that stimulation of a nerve may give rise to several results, accord- ing to the kind of nerve fibres present in the nerve. Thus, the secretory and vasomotor nerves of glands may be excited simultaneously. (c) Trophic. — The end organs of these nerve fibres lie in the tissues them- selves, and are as yet unknown. These nerves are called trophic, because they are supposed to govern or control the normal metabolism of the tissues. Trophic Influence of Nerves. — The trophic functions of certain nerves are referred to as under : On the influence of the trigeminus on the eye ; the mucous membrane of the mouth and nose ; the face (^ 347); the influence of the vagus on the lungs (^ 352) ; motor nerves on muscle (^ 307) ; certain central organs upon certain viscera (^ 379). Section of certain nerves influences the growth of the bones. H. Nasse found that, after section of their nerves, the bones showed an absolute diminution of all their individual constituents, while there was an increase of fat. Section of the spermatic nerve is followed by degeneration of the testicle (A'i-liiton, Oholensky). After extirpation of their secretory nerves, there is degeneration of the submaxillary glands (p. 237). .Section of the nerves of the cock's comb interferes with the nutrition of that organ [L^gros, Schiff^. Section of the cervical sympathetic ner\'e \xi yoting gron'ing animals is followed by a more rapid growth of the ear upon that side {Bidder, Stirling, Stricter), also of the hair on that side (Schiff, Stirling, Sig. Meyer) ; while it is said that the corresponding half of the brain is smaller, which, perhaps, is due to the pressure from the dilated blood vessels ( Bro-'wn- Scquard) . Blood Vessels. — Lewaschew found that continued uninterrupted stimulation of the sciatic nerve of dogs, by means of chemical stimuli [threads dipped in sulphuric acid], caused hypertrophy of the lower limb and foot, together with the formation of aneurismal dilatations upon the blood vessels. Skin and Cutaneous Appendages. — In man, stimulation or paralysis of nerves, or degenera- tion of the gray matter of the spinal cord {Jarisch), is not unfrequently followed by changes in the pigmentation of the skin, in the nails, in the hair and its mode of growth and color. [Injury to the brain, as by a fall, sometimes results in paralysis of the hair follicles, so that, after such an injury, the hair is lost over nearly the whole of the body.] Sometimes there may be eruptions upon the skin apparently traumatic in their origin [v. Biirensprung, Leloir). Sometimes there is a tendency to decubitus (J 379), and in some rare cases of tabes there is a peculiar degeneration of the joints 613 614 INHIBITORY NERVES. (Charcot's disease). The changes which take place in a nerve separated from its centre are de- scribed in § 325. [Trophoneuroses. — Some of the chief data on which the existence of trophic nerves is assumed are indicated above. There are many pathological conditions referable to diseases or injuries of nerves.] [Muscles. — As is well known, paralysis of a motor nerve leads to simple atrophy of the corres- ponding muscle, provided it be not exercised ; but when the motor ganglionic cells of the anterior horn of the gray matter, or the corresponding cells in the crus, pons, and medulla, are paralyzed, there is an active condition of atrophy with proliferation of the muscular nuclei Progressive muscular atrophy, or wasting palsy, is another trophic change in muscle, whereby either individual muscles or groups of muscles are one after the other paralyzed and become atrophied. In pseudo- hypertrophic paralysis there is cirrhosis or increased development of the connective tissue, with a diminution of the tnie muscular elements, so that although the muscles increase in hulk their power is diminished.] [Cutaneous Trophic Affections. — .\mong these may be mentioned the occurrence of red patches or erythema, urticaria or nettle rash, some forms of lichen, eczema, the bullae or blebs of pemphigus, and some forms of ichthyosis, e.ach of which may occur in limited areas after injury to a nerve or its spinal or cerebral centre. The relation between the eruption and the distribution of a nerve is sometimes very marked in herpes zoster, which frei]uently follows the distribution of the intercostal and supraorbital nerves. Glossy skin (/'(ii.v/, ]\\ir Mitchell) is a condition de- pending upon ittipaired nutrition and circulation, and due to injuries of nerves. The skin is smooth and glossy in the area of distribution of certain nerves, while the wrinkles and folds have disap- peared. In myxcedema, the subcutaneous tissue and other organs are infiltrated with, while the blood contains mucin. The subcutaneous tissue is swollen and the patient (adult woman) looks as if suffering from renal dropsy. There is marked alteration of the cerebral faculties, and a condi- tion resembling a " cretinoid state," occurs after the excision of the thyroid gland. Victor Horsley has shown that a similar condition occurs in monkeys after excision of the thyroid gland (§ lO'?, [Laycock described a condition of nervous oedema which occurs in some cases of hemiplegia, and apparently it is independent of renal or cardiac disease.] [There are alterations in the color of the skin depending on nervous affections, including local- ized leucoderma, where circumscribed p.itches of the skin are devoid of pigment. The pigmenta- tion of the skin in Addison's disease or bronzed skin, which occurs in some cases of disease ol the suprarenal capsules, may be partly nervous in its origin, more especially when we consider the remarkable pigmentation that occurs around the nipple and some other parts of the body during pregnancy, and in some uterine and ovarian affections {Laycock).'\ [In anaesthetic leprosy, the anesthesia is due to the disease of the nervous structure, which results in disturbances of motion and nutrition. Among other remarkable changes in the skin, perhaps due to trophic conditions, are those of symmetrical and local gangrene, and acute decu- bitus or bed sores.] [Bed sores.— Besides the simple chronic form, which results from over- pressure, bad nursing, and inattention to cleanliness, combined with some defect of the nervous conditions, there is another form, acute decubitus, which is due directly to nerve influence (C//<7?yo/). The latter usually appears within a few hours or days of the cerebral or spinal lesion, and the whole cycle of changes — from the appearance of erythematous dusky patch to inflammation, ulceration, and gan- grene of the buttock — are completed in a few days. An acute bed sore may form when every at- tention is paid to the avoidance of pressure and other unfavorable conditions. When it depends on cerebral affections it begins and develops rapidly in the centre of the gluteal region on the paralyzed side, but when it is due to disease of the spinal cord, it forms more in the middle line in the sacral region; while in unilateral spinal lesions it occurs not on the paralyzed, but on the anaesthetic side, a fact which seems to show that the trophic, like the sensory fibres, decussate in the cord {Ross).'\ [There are other forms due to nervous disease, including symmetrical gangrene and local asphyxia of the terminal parts of the body, such as the toes, nose, and external ear, caused, perhaps, by spasm of the small arterbiles (Raynaud's disease) ; and the still more curious condition of perforating ulcer of the foot.] [Hemorrhage of nervous origin sometimes occurs in the skin, including those that occur in loco- motor ataxia after severe attacks of pain, and hematoma aurium, or the insane ear, which is specially common in general paralytics.] (d) Inhibitory nerves are those nerves which modify, inhibit, or suppress a motor or secretory act already in progress. Take as an example the effect of the vagus upon the action of the heart. Stimulation of the peripheral end of the vagus causes the heart to stand still in diastole (§ 85); the efl'ect of the splanchnic upon the intestinal movements (\ 161). The vasodilator nerves, or those whose stimu- lation is followed by dilatation of the blood vessels of the area which they supply, are referred to specially in \ 237. [There is the greatest uncertainty as to the nature and mode of action of inhibitory nerves, THE CRANIAL NERVES. 615 but take the vagus as a type, which depresses the function of the heart, as shown by the slower rhythin, diminution of the contractions, relaxation of the muscular tissue, lowering of the excitability and conduction. These phenomena are not due to exhaustion. Gaskell points out that the action is beneficial in its after effects, so that this nerve, although it causes diminished activity, is followed by repair of function, so that he groups it as an anabolic nerve, the outward symptoms of cessation of function indicating that constructive chemical changes are going on in the tissue.] (e) Thermic and electrical nerves have also been surmised to exist. [Gaskell classifies the efferent nerves differently. Besides motor nerves to striped muscle, he groups them as follows : — 1. Nerves to vascular muscles. (a) Vaso-motitr, i. e.. vasoconstrictor, accelerators and augmentors of the heart. (d) Vaso-inltibitory, i. e., vaso-dilators and inhibitors of the heart. 2. Nerves of the visceral muscles. [a) Viscero motor, ib) Viscero inhibitory. 3. Glandular nerves.] [Other terms are applied to nerves with reference to the chemical changes they excite in a tis- sue in which they terminate. The ordinary metabolism is the resultant of two processes, one con- structive the other destructive, or of assimilation and dissimilation respectively. The former process is anabohsm, the latter katabolism. .\ motor nerve excites chemical destructive changes in a mus- cle, and is so far the katabolic nerve of that tissue ; in the same way the sympathetic to the heart, by causing more rapid contraction, is also a katabolic nerve, while the vagus, as it arrests the heart's action, brings about a constructive metabolism of the cardiac tissue, is an anabolic nerve [Gas/till ).'[ II. Centripetal or Afferent Nerves. — (a.^ Sensory Nerves (sensory in the narrower sense), which by means of special end organs conduct sensory impulses to the central nervous system. (b) Nerves of Special Sense. Fig. 3S0. (c) Reflex or Excito-motor Nerves. — When the periphery of one of these nerves is stim- ulated, an impulse is set up which is conducted by them to a nerve centre, from whence it is trans- ferred to a centrifugal or efferent fibre, and the mechanism (I, a, b, c, d) in connection with the peripheral end of this efferent fibre is set in action ; thus there are — Reflex motor, Reflex secre- tory, and Reflex inhibitory fibres. [Fig. 380 shows the simplest mechanism necessary for a reflex motor act. The impulse starts from the skin, S, travels up the nerve a,f, to the nerve centre or nerve cell, N, situate in the spinal cord, where it is modified and transferred to the outgoing fibre, e,f, and conveyed by it to the muscle, M.] III. Intercentral Nerves. — These fibres serve to connect ganglionic centres with each other, as, for example, in coordinated movements, and in extensive reflex acts. THE CRANIAL NERVES.— 343. I. NERVUS OLFACTORIUS.— Anatomical.— The three-sided, prismatic, tractus olfactorius lying in a groove on the under surface of the frontal lobe, arises by means of an inner, outer, and upper root, from the tuber olfactorium (Fig. 3S5, I). The tractus swells out upon the cribriform plate of the ethmoid bone, and becomes the bulbus olfactorius, which is the analigue of the special portion of the brain, existing in different mammals with a well-developed sense of smell (Gratio/et). From twelve to fifteen olfactory filaments pass through the foramina in the cribriform plate of the ethmoid bone. At first they lie between the peri- osteum and the mucous membrane, but in the lower third of their course they enter the mucous membrane of the regio olfactoria. The bulb consists of white maUer below, and above of gray matter mixed with small spindle-shaped ganglionic cells. Henle describes six, and Meynert eight layers of nervous matter seen on tran'^verse section. [The centre for smell lies in the tip of the uncinate gyrus on the inner surface of the cerebral hemisphere [Furrier). According to Hill, the three roots of the olfactory bulb stream backward, the inner one is small, the middle one is a thick bundle, which grooves the head of the caudate nucleus, curves inward to the anterior commissure. 616 CONNECTIONS OF OPTIC TRACT. and crosses via this commissure where it decussates, and passes to the extremity of the temporo- sphenoida! lobe. The outer roots pass transversely into the pyriform lobe, thence via the fornix, corpora albicantia, the bundle of Vicq d'Azyr into the anterior end of the cptic thalamus. Hill also points out that the elements contained in the olfactory bulb are identical with those contained in the four outer layers of the retina.] Function. — It is the only nerve of smell. Physiologically, it is excited only by gaseous odorous bodies — {Sense of Sme//, § 420). Stimulation of the nerve, by any other form of stimulus, in any part of its course, causes a sensation of smell. [It also conveys those impressions which we call flavors, but in this case the sensation is combined with impressions from the organs of taste. In this case the stimulus reaches the nerve by the posterior nares.] Congenital absence or section of both olfactory nerves abolishes the sense of smell (easily performed on young animals. — Biffi). Pathological. — The term Hyperosmia is applied to cases where the sense of smell is exces- sively and abnormally acute, as in some hysterical persons, and in cases where there is a purely sub- jective sense of smell, as in some insane persons. The latter is, perhaps, due to an abnormal stim- ulation of the cortical centre (^ 378, IV). Hyposmia and Anosmia {;'. <■., diminution and abo- lition of the sense of smell) may be due to mechanical causes, or to over-stimulation. Strychnin sometimes increases, while morphia diminishes, the sense of smell. [Method of Testing, § 421.] 344. II. NERVUS OPTICUS.— Anatomical.— The tractus opticus (Fig. 385, IT) arises by a number of fibres from the inner gray substance of the thalamus opticus, anfl the anterior cor- pora quadrigemina ; other fibres cover these structures in the form of a thin plate of nervous matter. The corpora geniculata (Fig. 385, i, e), form ganglia, intercalated, as it were, in the course of cer- tain of the fibres. Another set of fibres, quite distinct from the foregoing, passes between the bun- dles of the eras cerebri, and reaches the multicellular nucleus within the tegmentum of the crus (corpus subthalamicum). Other fibres are said to pass to the spinal cord, directly through the med- ulla oblongata, without the intervention of any gray matter. They are said by Stilling to reach as far as the decussation of the pyramids. According to this view, the optic nerve has a spinal root, which explains the relation of stimulation of the retina to the dilator of the iris. A broad bundle of fibres passes from the origin of the optic tract to the cortical psycho-optic centre, at the apex of the occipital lobe ( Wernii:ke~\ 379, IV). The Optic Tract bends round the pedunculus cerebri, where it unites with its fellow of the oppo- site side to form the chiasma. [Connections of Optic Tract. — There is very considerable difficulty in ascertaining the exact origin of all tlie fibres of the optic tract. Although as yet the statement of Gratiolet is not proved, that the optic tract is directly connected with every part of the cerebral hemisphere in man, from the frontal to the occipital lobe> still, the researches of D. J. Hamilton have shown that its connec- tions are very extensive. It is certain that some of them are ganglionic, i.e., connected with the ganglia at the base of the brain, while others are cortical, and form connections with the cortex cerebri. The ganglionic fibres arise from the corpora geniculata, pulvinar and anterior corpora quadrigemina, and probably, also, from the substance of the thalamus. The cortical fibres join the ganglionic to form the optic tract. According to D. J. Hamilton, the connection with the cortex in the y>-(!K/a/ region is brought about by '• .VIeynert's commissure." The latter arises directly from the lenticular-nucleus loop, decussates in the lamina cinerea, and passes into the optic nerve of the opposite side. The lenticular-nucleus loop is formed below the lenticular nucleus by the junction of the strife meduUares ; the stria? medullares form part of the fibres of the internal capsule, and the inner capsule is largely composed of fibres descending from the cortex. Hamilton also asserts that other cortical connections join the tract as it winds round the pedunculus cerebri, and they include (rt) a large mass of fibres coming from the motor areas of the opposite cerebral hemisphere, crossing in the corpus callosum, entering the outer capsule, and joining the tract directly ; (/') fibres uniting it to the temporo-sphenoidal lobe of the same side, especially the first and second temporo-sphenoidal convolutions; (c^ fibres to the gyrus hippocampi of the same side; (r/) a large leash of fibres forming the "optic radiation" of Gratiolet, which connect it directly with the tip of the occipital lobe. There are probably also indirect connections with the occipital region through some of the basal ganglia. Although some observers do not admit the connections with the frontal and sphenoidal lobes, all are agreed as to its connection with the occipital by means of the " optic radiation."] [The Optic Radiation of Gratiolet is a wide strand of fibres expanding and terminating in the occipital lobes. It is composed of, or, stated otherwise, gives branches to (a) the optic tract directly, [b) the corpus geniculatum internum and externum, (c) to the pulvinar and substance of the thal- amus, (d") a direct sensitive band (Meynert's " sensitive band ") to the posterior third of the poste- rior limb of the inner capsule, \e) fibres which run between the island of Reil and the tip of the occipital lobe {D. J. Hamilton).'] HEMIOPIA AND HEMIANOPSIA 617 Chiasma. — The extent of the decussation of the optic fibres in the chia?ma is subject to variations. As a rule, rather more than half of the fibres of one tract cross to the Fig. 381. optic nerve of the opposite side (Fig. 381), so that the left optic tract sends fibres to the left half of both eyes, while the right tract supplies the right half of both eyes (§378, IV). [Thus, the corresponding regions of each retina are brought into relation with one hemisphere. The fibres which cross are from the nasal half of each retina.] Hence, in man, the destruction of one optic tract (and its central continuation in the occipital lobe of the cere- brum) produces " equilateral or homonymous hemi- Scheme of the semidecussation of the optic opia." In the dog and cat there is a semi-decussalinn; nerves. L /i., left eye; .«. ^., right eye. hence, in these animals extirpation of one eyel)aU causes atrophy and degeneration of half of the nerve fibres in both optic tracts (Cudiien). Baumgarten and Mohr have observed a similar result in mm. A sagittal section of the chiasma in the cat pro- duces partial blindness of both eyes (A'/ra// 1. According to Gudden. the fibres which decussate are more numerous than those which do not, although J. Stilling maintains that they are only slightly more numerous. According to J. Schilling, the decussating fibres lie in the central axis of the nerve, while those which do not decussate form a layer around the former. Other observers maintain that there is complete d -cussation of all the fibres in the chiasma. Htnce, section of one optic nei-'e causes dilatation of the pupil and blindness on the same side, while section of one optic tract causes dilatation of tlie pupil and blindness of the opposite eye (Knoll, Brown-Scqiiard, Mamlelstamm). In o-seous fishes, both optic nerves are isolated and merely cross over each other, while in the cyclostomata they do not cross at all. [Total decus-ation occurs in those animals where the eyes do not act together.] Injury of the external geniculate body and section of the anterior brachium have the same effect as section of the optic tract of the same side (? 359 — Bechternu). In very rare cases the decussation is absent in man, so that the right tract passes directly into the right eyeball, and the left into the left eyeball ( Vesalius, CalUani, Losel), the sight not being inter- fered with ( Vesalius). It is quite certain that the individual fibres do not divide in the chiasma. Two commissures, the inferior commissure ( Giidden) and Meynert's commissure, unite both optic tracts further back. [A special commissure (C. inferior) extends in a curved form across the posterior angle of the chiasma ( Giidden). It does not degenerate after enucleation of the eyeballs, so that it i> regarded as an intercentral connection. After excision of an eye, there is central degeneration of the fibres of the optic nerve entering the eyeball [Giidden), and in man about the half of the fibres in the corresponding optic tract (Baumgarten, Mohr). After section of both optic nerves, or enucleation of both eyeballs, there is a degeneration, proceeding centrally, of the whole optic tract. The degeneration extends to the origins in the corpora quadrigeniina, corpora geniculata, and pulvinar, but not into the conducting paths leading to the cortical visual centre (v. Monakow) (J 378, IV. I).] Hemiopia and Hemianopsia. — When one optic tract is interfered with or divided, there is interference with or loss of sight in the lateral halves of both retinae, the blind part being separated from the other half of the field of vision by a vertical line. When it is spoken of as paralysis of one half of the retina, the term heviiopia is applied to it ; when with reference to the field of vision, the term hemianopsia is used (see Eye). Suppose the left optic tract to be divided or pressed upon by a tumor at K (Fig. 382), then the outer half of the left and the inner half of the right eye are blind, causing right lateral hemianopsia, i. e., the two halves are affected which correspond in ordi- nary vision, so that the condition is spoken of as homonymous hemianopsia. Suppose the lesion to be at T (Fig. 3S2), then there is paralysis of tlie inner halves of both eyes, causing double tem- poral hemianopsia. WTien there are two lesions at N M, which is very rare, the outer halves of both retinie are paralyzed, so that there is double nasal hemianopsia. In order to explain some of the eye symptoms that occasionally occur in cerebral disease, Charcot has supposed that some of the fibres which pass from the external geniculate body to the visual centres in the occipital lobe cross behind the corpora quadrigemina, and this is represented in the diagram as occurring at T Q, in the corpora quadrigemina. On this view, all the occipital cortical fibres from one eye would ulti- mately pass to the cortex of the occipital lobe of the opposite hemisphere. This view, however, by no means explains all the facts, for in cases of homonymous hemianopsia the point of central vision on both sides, i. e., both maculoe lutes are always unaffected; so that it is assumed that each macula lutea is connected with both hemispheres. The second crossing suggested by Charcot probably does not occur. [Affections of the optic nerve, ;'. e., between tlie eyeball and the chiasma, i. e., in the 618 NERVUS OCULOMOTORIUS. orbit, optic foramen, or within the skull, aflfect one eye only; of the middle of the chiasma, cause temporal hemiopia; of the optic tract, between the chiasma and occipital cortex, hemiopia, which is always symmetrical ( Go7uers).^ Munk supposes that there are three areas in the retina corresponding to three cortical visual spheres, or parts of the visual centre in the occipital lobe (dog) (| 376). Function. — The optic nerve is the nerve of sight; physiologically, it is excited only by the transference of the vibrations of the ether to the rods and cones of the retina (§ 383). Every other form of stimulus, when applied to the nerve in its course or at its centre, causes the sensation of light. Section or degen- eration of the nerve is followed by blind- ness. Stimulation of the ojitic nerve causes a refle.x contraction of the pupils, the efferent nerve being the oculomotorius or third cranial nerve. If the stimulus be very strong, the eyelids are closed and there is a secretion of tears. The influ- ence of light upon the general metabolism is stated at § 127, 9. As the optic nerve has special and independent connections with the so-called psycho-optic centre (§ 378, IV), as well as with the centre for narrowing the pupil (§ 345), it is evident that, under patho- logical circumstances, there may be, on the one hand, blindness with retention of the action of the iris, and on the other loss of the movements of the iris, the sense of vision being retained ( Wernicke). Pathological. — Stimulation of almost the whole of the nervous apparatus may cause excessive sen- sibility of the visual apjiaratus (JiypeiiCstliesia optica), or even visual impressions of the most varied kinds (photopsia, chromatopsia), which in cases of stimulation of the psycho-optic centre may become actual visual hallucinations (§ 37^' IV). Material change in, and inflammation of, the nervous apparatus are often followed by a nervous weakness of vision (amblyopia), or even by blindness (amaurosis). IJoth conditions, however, may be the sign^ of disturbances of other organs, i.e., they are " sympathetic " signs, due, it may be to changes in the movement of the blood stream, depending upon stimulation of the vaso- motor nerves. The discovery of the partial origin of the optic nerve from the spinal cord explains the occurrence of amblyopia (with partial atrophy of the optic nerve) in disease of the spinal cord, especially in tabes. Many poisons, such as lead and alcoliol, disturb vision. Hemeralopia and Nyctalopia. — There are remarkable intermittent forms of amaurosis known as day blindness (hemeralopia), which occurs in some diseases of the liver [and is sometimes associated with incipient cataract. The person can see better in a dim light than during the day or in a bright light. In night bindne«s (nyctalopia), the person cannot see at night or in a dim light, while vision is good during the day or in a bright light. It depends upon disorder of the eye itself, and is usually associated with imperfect conditions of nutrition. 345. III. NERVUS OCULOMOTORIUS.— Anatomical.— It springs from the oculo- motorius nucleus (united with that of the trochlearis), which is a direct continuation of the anterior horn of the spinal cord, and Hes under the aqueduct of .Sylvius (Fig. 385). [The motor nucleus (Fig. 384) gives origin to three sets of fibres, for (i) the most of the muscles of the eyeballs, (2) the sphincter papilla;, (3) ciliary muscle. The nucleus of the 3d and 4th nerves is also connected with that of the 6th under the iter, so that alf the nerves to the ocular muscles are thus corelated at their centres.] The origin is connected with the corpora quadrigemina, to which the intraocular fibres may be traced, and also with the lenticular nucleus through the pedunculus cerebri. Beyond the pons it appears on the inner side of the cerebral peduncle between the superior cerebellar and posterior cerebral arteries (Fig. 3S5, III). Diagram of the decussation of the optic tracts. T semi-decussation in the chiasma; TQ, deciissa tion of fibres behind the ext. geniculate Ijodie: (CQ) : a'b, fibres which do not decussate in th< chiasma ; b' a', fibres proceeding from the righ eye, and coming together in the left hemisphert (LOG): LOG, K, lesion of the left optic trac producing right lateral hemianopsia : .4, lesion ii the left hemisphere producing crossed amblyopi; (right eye) ; T, lesion producing temporal he mianopsia ; NN, lesion producing nasal hemian opsia. FUNCTIONS OF THE THIRD CRANIAL NERVE. 619 Function. — It contains — (i) the voluntary motor fibres for all the external muscles of the eyeballs — except the external rectus and superior oblique — and for the levator palpebrre superioris. The coordination of the movements of both eyeballs, however, is independent of the will. (2) The fibres for the sphincter pupilhe, which are excited reflexly from the retina. (3) The voluntary fibres for the muscle of accommodation, the tensor choroidcEe or ciliary muscle. The intra- bulbar fibres of 2 and 3 proceed from the branch for the inferior oblique muscle, as the short root of the ciliary ganglion (Fig. 386). They reach the eyeball through the short ciliary nerves of the ganglion. V. Trautvetter, Adamiik, Hen- sen and Volckers observed that stimulation of the nerve caused changes in the eye similar to those which accompany near vision. The three centres for the muscle of accommodation, the sphincter pupiUse and the internal rectus muscle, lie directly in relation with each other, in the most posterior part of the floor of the third ventricle {Henscn and Viilckers). The centre for the reflex stimulation of the sphincter fibres by light is said to be in the corpora quadrigemina, but newer researches locate it in the medulla oblongata (§§ 379, 392). The narrowing of the pupil, which accompanies the act of accommodation for a near object, is to be regarded as an associated move- ment (§ 392, 5). . Anastomoses. — In man the nerve anastomoses on the sinus cavernosus with the ophthalmic branch of the trigeminus, whereby it receives sensory fibres for the musites to which it is distributed ( ValcnliK, Atiiimiil;), with the sympathetic through the carotid plexus, and (?) indirectly through the abducens, whcrel>y it receives vasomotor fibres (?J. Varieties. — In some rare cases the papillary fibres for the sphincter run in the abducens (Aititmiik), or even m the trigeminus [Sc/tiff, v. Grd/e). Atropin paral zcs the intrabulbar fibres of the oculomotorius, while Calabar bean stimulates them (or paralyzes the sympathetic, or both — compare § 392J. Stimulation of the nerve which causes contraction of the pupil, is best demonstrated on the decapi- tated and opened head of a bird. The pupil is dilated in paralysis of the oculomotorius, in asphyxia, sudden cerebral ancemia (,■. g., by ligature of the carotids, or beheading), sudden venous conges- tion, and at death. Pathological. — Complete paralysis of the oculomotorius is followed by — (i) drooping of the upper eyelid (Ptosis paralytica); (2) immobility of the eyeball; (3) squinting (strabismus) out- ward and downward, and consequently there is double vision (diplopia); (4) slight protrusion of the eyeball, because the action of the superior oblique muscle in pulling the eyeball forward is no longer compensated by the action of three paralyzed recti muscles. In animals provided with a re- tractor bulbi muscle, the protrusion of the eyeliall is more pronounced ; (1;) moderate dilatation of the pupil (mydriasis paralytica) ; (6) the pupil does not contract to light; (7) inability to ac- commod.ite for a near object. It is to be noted, however, that the paralysis may be confined to indivitlual branches of the nerve, i. e., there may be incomplete paralysis. [Squinting. — In paralysis of the Superior Rectus the eye cannot be moved upward, and especially upward and outward. There is diplopia on looking upward, the false image being above the true, and turned to the right when the left eye is affected (Fig. 383, 3). Inferior Rectus Defect of downward, and especially downward and outward movement, the eye being directed up- ward and outward. Diplopia with crossed im.ages, the false one is below the true image and placed obliquely, being turned to the left when the left eye is affected. Diplopia is most troublesome when the object is below the line of vision (Fig. 383, 5). Internal Rectus. — Defective inward move- ment, divergent squint, and diplopia, the images being on the same plane, the false one to the patient's right wlien the left eye is affected. The head is turned to the healthy side when looking 620 FUNCTIONS OF THE FOURTH CRANIAL NERVE. at an object, while there is secondary devialion of the healthy eye outward (Fig. 383, i). Inferior oblique is rare, the eye is turned slightly downward and inward, and defective movement upward. Diplopia with the false image above the true one, especially on looking upward ; the false image is oblique, and directed to the patient's left when the left eye is affected (Fig. 3S3, 4).] The black cross represents the true image, the thin cross the false image. The left eye is affected in all cases (Brislcnv). Stimulation of the branch supplying the levator palpebroe in man causes lagophthalmus spas- ticus, while stimulation of the other motor fibres causes a corresponding strabismus spasticus. This latter form of squinting may be caused also reflexly— f. g., in teething, or in cases of diarrha-a Fig. 384. Drachiuin conjuncti\-um anticum. TpU3 geoicul&ta Podunculua cerebri. rporfiqimtlri.-i _J_ od roeduUam oljlon- j ««'et«ni pamni. or HilVrigr j . ^f cerpbellar I tjl pedunck-. J Medulla oblongata, with the corpora quadrigemina. The numbers JV. — XII. indicate the superficial origins of the cranial nerves, while those (3-12) indicate their deep origin, i". ^., the position of their central nuclei : t^ funiculus in children ; [the presence of worms or other source of irritation in the intestines of children is a frequent cause of squinting.] Clonic spasms occur in both eyes, and also as involuntary movements of the eyeballs constituting nystagmus, which may be produced by stimulation of the corpora quadrigemina, as well as by other means. Tonic contraction of the sphincter pupilla; is called myosis spastica, and clonic contraction, hippus. Spasm of the muscle of accommodation (ciliary muscle) is sometimes observed ; owing to the imperfect judgment of distance, this condition is not unlrequently associated with macropia. [Conjugate Deviation. — Some movements are produced by non corresponding muscles ; thus, on looking to the right, we use the right external rectus and left internal rectus, and the same is the THE OPHTHALMIC BRANCH OF THE FIFTH. 621 case in turning the head to the right £■.,;.'., the inferior oblique, some muscles of the right side act aljng with the left sternomastoid. In hemiplegia the muscles on one side are paralyzed, so that the head and often the eyes are turned away from the paralyzed side, i. <■,, to the side of the brain on which the lesion occurs. This is called " conjugate deviation " of the eyes, with rotation of the head and neck. If the right external rectus be paralyzed from an affection of the sixth nerve, on telling the patient to look to the right it will be found that the left eye will squint more inward even than the right eye, ;. e., owing to the strong voluntary effort of the muscle, the left internal rectus which usually acts along with the right external rectus, contracts vigorously, and so we get second- ary deviation of the sound eye. Similar results occur in connection with paralysis of other ocular muscles.] 346. IV. NERVUSTROCHLEARIS.— Anatomical.— It arises [from the valve of Vieus- sens, i. e., behind the fourth ventricle], but its tibres pas^ to the oculomotorius from the tmc/i/eaiis nucleus (Fig. 3S4), which is to a certain extent a continuation of the anterior horn of the spinal cord. It passes to the lower margin of the corpora quadrigemina, pierces the root of the aqueduct of Sylvius, then into the velum nieduUare superius, and after decussating with the root of the opposite side behind the iter, it pierces the crus at the superior and external border (Fig. 385, IV). Its fibres cross between its nucleus and its distribution. It has also an origin from the locus cceru- leus. The root of the nerve receives some fibres from the nucleus of the abducens of the opposite side. Physiologically, there is a necessity for a conjunction between the centre and the cortical motor centre for the eye muscles. Function. — It is the voluntary motor nerve of the superior oblique muscle. (In coordinated movements, however, it is involuntary.) Anastomoses. — Its connections with the plexus caroticus sympathici, and with the first branch of the trigeminus, have the same significance as similar branches of the oculomotorius. Pathological. — Paralysis of the trochlearis nerve causes a very slight loss of the mobility of the eyeball outward and downward. There is slight squinting inward and upward, with diplopia or double vision. The images are placed obliquely over each other [the false image being the lower, and directed to the patient's right when the left eye is affected (Fig. 383, 6)] ; they approach each other when the head is turned toward the sound side, and are separated when the head is turned toward the other side. The patient at first directs his head forward, later he rotates it round a vertical axis toward the sound side. In rotating his head (whereby the sound eye may retain the primary posi- tion), the eye rotates with it. Spasm of the trochlearis causes squinting outward and downward. 347. V. NERVUS TRIGEMINUS.— Anatomical.— The trigeminus (Fig. 3S6, 5), arises like a spinal nerve by two roots (Fig. 385, V). The smaller, anterior, motor root proceeds from the " motor trigeminal nucleus " ^5), which is provided with many multipolar nerve cells, and lies in the fioor ol the medulla oblongata, not far from the middle line. Fibres connect this nucleus with the cortical motor centres on the opposite side of the cerebrum. Besides this the "descend ing root " also supplies motor fibres, it extends laterally from the corpora quadrigemina along the aqueduct of Sylvius downward to the exit of the neT\e (Henle, Forel). The large posterior sensory root receives fibres : (ij From the small cells of the " sensory trigeminal nucleus" which lies at the level of the pons, and is the analogue of the posterior horn of the gray matter of the spinal cord. (2) From the gray matter of the posterior horn of the spinal coid downward as far as the cervical vertebra. These fibres run into the posterior column of the cord and then appear as the " ascending root " in the trigeminus. (3) Some fibres come from the cerebellum, through the crura cerebelli. The origins of the sensory root anastomose with the motor nuclei of all the nerves arising from the medulla oblongata, with the exception of the abducens. This explains the vast number of reflex relations of the fifth nerve. The thick trunk appears on each side of the pons (Fig. 385), when its posterior root (perhaps in conjunction with some fibres from the anterior) forms the Gasserian ganglion, upon the tip of the petrous part of the temporal bone (Fig. 386). Fibres from the sympathetic proceed from the plexus cavernosus to the ganglion. The nerve divides into three large branches. I. The ophthalmic division (Fig. 386, d) receives sympathetic fibres {vaso- motor niTves) from the plexus cavernosus ; it passes through the superior orbital fissure [sphenoidal] into the orbit. Its branches are :— 1. Ine small recurrent nerve which gives sensory branches to the tentorium cerebelli. Fibres proceed along with it trom the carotid plexus of the sympathetic, which are the vasomotor nerves for the dura mater. 2. The lachrymal nerve gives off — {a) Sensory branches to the conjunctiva, the upper eyelid, and the neighboring part of the skin over the temple (Fig. 3S6, a); {b) true sensory fibres to the lachrymal gland (^?j. Stimulation of this nerve is said to cause a secretion of tears, while its section prevents the reflex secretion excited through the sensory nerves of the eye. After a time, section of 622 THE OPHTHALMIC BRANCH OF THE FIFTH. the nerve is followed by a paralytic secretion of tears {Hcrzemtein and Wolferz, Demtschenko), although the statement is contested by Reich. The secretion of tears may be excited reflexly by strong stimulation of the retina by light by stimulation of the first and second branches of the trigeminus, and through all the sensory cranial nerves (^Demtschenko) (§ 356, A, 6). 3. The frontal (/) gives off the supratrochlear, which supplies sensory d ja Part of the base of the brain, with the origins of the cranial nervfs : the convolutions of the island of Reil on the right side but removed on the left. I', olfactory tract cut short : II, left oplic nerve ; II', right optic tract ; ■J, A, cut surface of the left optic thalamus; C, central lobe, or island of Reil ; .S, j., fissure of Sylvius ; X, X, the locus perforalus anticus : c, the external, and z, the internal, corpus geniculatum ; /(, hypophysis cerebri ; /, c, tuber cinereum, with the infundibulum ; rf, points to one of the corpora albicantia; P, the cerebral pe- duncle ; y, the fillet: in. left oculo-motor nerve; X, the locus perforatus posticus; P, V, pons Varolii : V, the greater part of the fifth nerve ; +, the lesser root (on the right side this mark is placed on the Gasserian ganglion and points to the lesser root); i, ophthalmic division of the fifth; VII, g- and Kratschmer) — (cducens receives a few motor fibres from the cervical sympathetic. Spasm of the abducens causes external squint. Squint — In addition to paralysis or stimulation of certain nerves producing squint, it is to be remembered that it may also be caused by a primary affection of the muscles themselves, if. ^., con- genital shortness, contracture, or injuries of these muscles. It may also be brought about owing to opacities of the transparent media of the eye ; a person with, say an opacity of the cornea, rotates the affected eye involuntarily, so that the rays of light may enter the eye through the clear part of the media. 349. VII. NERVUS FACIALIS.— Anatomical.— This nerve consists entirely of etferent fibres, and arises from the floor of the fourth ventricle from the " facial nucleus " (Fig. 384, 7), which lies behind the orgin of the abducens, and also by some fibres from the nucleus of the ab- ducens [although Gower's observations do not confirm this (\ 3^6).] Other fibres arise from the cerebrum of the opposite side (| 378, I). It consists of two roots, the smaller — portio intermedia of Wrisberg — forms a connection with the auditory nerve (see \ 350). The original fibres ol the portio intermedia are developed from the glosso-pharyngeal nucleus ySapolini). It would thus appear that the sensory and gustatory fibres w hich are present in the chorda tympani enter it through these fibres (Duval, Schultze, I'ltlpian), so that the portio intermedia is a special part of the nerve of taste, H hich becomes conjoined witli the facial, and runs to the tongue in the chorda. Along with the auditory nerve, it traverses the porus acusticus internus, where it passes into the facial or Fallopian canal. At first it has a transverse direction as far as the hiatus of this canal ; it then bends at an acute angle at the " knee " (a) above the tympanic cavity, to descend in an osseous canal in the posterior wall of this space (Fig. 386). It emerges from the stylo-mastoid foramen, pierces the parotid gland, and is distributed in a fan-shaped manner (pes anserinus major). [The superficial origin is at the lower margin of the pons, in the depression between the olivary body and the restiform body, as indicated in Fig. 385, VII a.] Its branches (Fig. 386) are : i. The motor, large superficial petrosal (/). It arises from the " knee " or geniculate ganghon within the Fallopian canal, in the cavity of the skull, runs upon the anterior surface of the temporal bone, traverses the foramen lacerum medium on the under surface of the base of the skull, and passes through the Vidian canal to reach the spheno-palatine ganglion (p. 626). It is uncertain whether this nerve conveys sensory branches from the second division of the trigeminus to the facial. 2. Connecting branches (,?) pass from the geniculate ganglion to the otic gan- glion. For the course and function of these fibres, see Otic ganglion (p. 628). 3. The motor branch to the stapedius muscle (y). 4. The chorda tympani (/, /), arises from the facial before it emerges at the stylo-mastoid foramen (j-), runs through the tympanic cavity (above the tendon of the tensor tympani, between the handle of the malleus and the long process of the incus), passes out of the skull through the petro-tympanic fissure, and then joins the lingual nerve at an acute angle (p. 627, 4). Before it unites with this nerve, it exchanges fibres with the otic ganglion (m). Thus, sensory fibres can enter the chorda from the third division of the trigeminus (E. Bischoff), which may run centripetally to the facial to be distributed along with it. In the same way, sen- sory fibres may pass from the lingual nerve through the chorda into the facial (Longet). Stimulation of the chorda — which even in man may be done in cases where the tympanic membrane is destroyed — causes a prickling feeling in the an- terior margins and tip of the tongue (Troltsch). O. Wolfe found that the section of the chorda in man abolished the sensibility for tactile and thermal stimuli upon the tip of the tongue ; and the same was true of the sense of taste in this region. It is supposed by Calori that these fibres enter the facial nerve at its per- iphery (especially through the auriculo-temporal into the branches of the facial), that they run in a centripetal direction in the facial, and afterward pursue a cen- trifugal course in the chorda. [It is possible that sensory fibres pass from the spheno-palatine ganglion of the fifth through the Vidian nerve and large superfi- 632 BUANCHES OF THE FACIAL. cial petrosal to enter the facial. These fibres may be those that appear in the seventh as the chorda fibres which administer to taste. .Bigelow asserts that the chorda tympani is not a branch of the facial, but the continuation of the nervus intermedins of Wrisberg.] The chorda also contains secretory and vaso-dilator fibres for the sub-maxillary and sublingual glands (§ 145). Gustatory Fibres. — The chorda also contains fibres administering to the sense of taste, for the margin and tip of the tongue (anterior two-thirds), which are conveyed to the tongue along the course of the lingual. Urbantschitsch made observations upon a man whose chorda was freely exposed, and in whom its stim- ulation in the tympanic cavity caused a sensation of taste (and also of touch) in the margins and tip of the tongue. It would seem, therefore, that the gustatory fibres of the chorda have their origin in the glosso-pharyngeal nerve. They may reach the chorda: i. Through the portio intermedia of Wrisberg, as already mentioned. 2. There is a channel beyond the stylomastoid foramen, viz., through the ramus communicans cum glosso-pharyngeo (Fig. 386, e), which passes from the last-mentioned nerve in that branch of the facial which contains the motor fibres for the stylohyoid and posterior belly of the digastric (Henle'sN. styloideus). This nerve also supplies muscular sensibility to the stylohyoid and pos- terior lielly of the digastric muscles. It is also assumed that, by means of these anastomoses, motor fibres are supplied by the facial to the glosso-pharyngeal nerve. 3. A union of the glosso-pharyngeal and facial nerves occurs in the tympanic cavity. The tympanic branch of the glosso-pharyngeal (A) passes into this cavity, where it unites in the tympanic plexus with the small superficial petrosal nerve (,5), which springs from the knee on the facial. The gustatory fibres may first pass into the otic ganglion, which is always connected with the chorda (Otic ganglion, p. 628, 6). Lastly, a connec- tion is described through a twig (tt) from the petrous ganglion of the glosso-pharyngeal, direct to the facial trunk within the Fallopian canal {Garibaldi). Vaso-dilator Fibres. — According to some observers, the chorda contains vaso-iiilator fibres for the tongue, but no motor fibres {^Heidenhain). Pseudo-motor Action. — From one to three weeks after the section of the hypoglossal nerve, stimulation of the chorda causes movements in the tongue [PJiili/'peau.x and I'li/fiaii, /i. Hciden- hain). These movements are not so energetic, and occur more slowly than those caused by stimu- lation of the hypoglossal. A'icotin first excites, then paralyzes, the motor etiect of the chorda. Even after cessation of the circulation, stimulation of the chorda causes movements. Heidenhain supposes that, owing to the stimulation of the chorda, there is an increased secretion of lymph within the musculature, which acts as the cause of the muscular contraction. He called this action " psetido fnotory [If, after the union of the central end of the lingualis and the peripheral end of" the hypoglossal nerve, the lingualis be stimulated, there is a genuine contraction of the musculature of the tongue on that side. If, .after the union of the central end of the hypoglossal with the peripheral end of the lingual, there is no effect. A pseudo-motor contraction is easily distinguished from a true contrac- tion, for when a telephone be connected with the tongue, on stimulating the hypoglossal the tone of the tetanus thereby produced is heard, but on stimulating the lingual, although the pseudo-motor contractions occur, no sound is heard \Ki^go~oiczY~\ 5. Connection with Vagus. — Before the chorda is given off, the trunk of the facial comes into direct relation with the auricular branch of the vagus ('5), which crosses it in the mastoid canal (see Vagus), and supplies it with sensory nerves. 6. Peripheral Branches. — After the facial issues from its canal, it supplies motor fibres to the stylohyoid and posterior belly of the digastric, the occipitalis, and also to all the muscles of the external ear and the muscles of expression, to the buccinator and platysma. The facial also contains secretory fibres for the face (compare § 288). Although most of the branches of the facial are under the influence of the will, yet most men cannot voluntarily move the muscles of the nose and ear. Anastomoses. — The branches of the seventh nerve on the face anastomose with those of the trigeminus. Thus, sensory fibres are conveyed to the muscles of expression. The sensory branches of the auricular branch of the vagus and the great auricular enter the peripheral ends of the facial and supply sensibility to the UNILATERAL AND DOUBLE PARALYSIS OF THE FACIAL. 633 muscles of the ear, while the sensory fibres of the third cervical nerve sirnilarly supply the platysma with sensibility. Section of the facial at the stylomastoid for- amen is painful, but it is still more so if the peripheral branches on the face are divided [Mageniiie) (compare Recurrent sensibility, § 355). Pathological. — In all cases of paralysis of the facial, the most important point to determine is whether the seat of the aftection is in the periphery, in the region of the stylomastoid foramen, or in the course of the long Fallopian canal, or is central (cerebral) in its origin. This point must be determined by an analysis of the symptoms. Paralysis at the stylomastoid foramen is very fre- quently rheuinatic, and probably depends upon an exudation compressing the nerve ; the exuda- tion probably occupying the lymph space described by Riidinger on the inner side of the Fallopian canal, between the periosteum and the nerve, and which is a continuation of the arachnoid space. Other causes are— inflammation of the parotid gland, direct injury, and pressure from the forceps during delivery. In the course of the canal, the causes are — fracture of the temporal bone, effu- sion of the blood into the canal, syphilitic eflusions, and caries of the temporal bone; the last some- FlG. 388. Uppc r branches of the Facial. Trunk of the Facial. Mm. retrahens et atlolens auricul. Muse, occipitalis. Middle branches of the Facial. M. stylohyoideus, M. digastricus. Lower branches of the Facial — M corrugator superciin. M. orbicular palpebr. M compressor nasi et pyram r M levator lab. sup, alaque n; M levator lab. sup, propr. M zygomatic, minor. \I dilatat.narium, M zygomatic major. M . levator menti. M . quadratus men M. triangularis mt r points of the facial d the facial muscles supplied by it. times occurs in inflammation of the ear. Among intracranial causes are — affections of the mem- branes of the brain, and of the base of the skull in the region of the nerve, disease of the " facial nucleus ;" lastly, affection of the cortical centre of the nerve and its connections with the nucleus. [No nerve is so liable as the seventh to be paralyzed independently.] Symptonns of Unilateral Paralysis of the Facial or [Bell's Paralysis]. — i. Paralysis of the muscles of expression : ihe for-head is smooth, without folds, the eyelids remain open (Lagophthalmus paralyticus), the outer angle being slightly lower. The anterior surface of the eye rapidly becomes dry, the cornea is dull, as, owing to the paralysis of the orbicularis, the tears are not properly distributed over the conjunctiva, and, in fact, in consequence of the dryness of the eyeball, there may be temporary inflammation (Keratitis xeroticai. In order to protect the eye- ball from the light, the patient turns it upward under the upper eyelid [Bell), relaxes the levator palpebral, which allows the lid to fall somevvht {Hasse). The nose is immovable, while the naso- labial fold is obliterated. As the nostrils cannot be dilated, the sense of smell is interfered with. The impairment of the sense of smell depends more, however, upon the imperfect conduction of 634 NERVUS ACUSTICUS. the tears, owing to paralysis of the orbicularis palpebrarum and Horner's muscle, and thus causing dryness of the corresponding side of the nasal cavity. Horses, which distend the nostrils widely during respiration, after section of both facial nerves, are said by CI. Bernard to die from interfer- ence with the respiration, or at least they suffer from severe dyspncea [E/lenberger). The face is drawn toward the sound side, so that the nose, mouth, and chin are oblique. Paralysis of the buc- cinator interferes with the proper formatioti of the bolus of food; the food collects between the cheek and the gum, from which it is usually removed by the patient with his fingers; saliva and fluids escape from the angle of the mouth. During vigorous expiration the cheeks are puffed out- ward like a sail. The speech may be affected, owing to the difficulty of sounding the labial con- sonants (especially in double paralysis), and the vowels, u, ii (ue), ii (oe) ; while the s-peech, in paralysis of the branches to both sides of the palate, becomes nasal (^ 62S). The acts of whistling, sucking, blowing, and spitting are interfered with. In double paralysis many of these symptoms are greatly intensified, while others, such as the oblique position of the features, disappear. The features are completely rela.\ed ; there is no mimetic play of the features, the patients weep ane perceptions, and so give rise to abnormal movements of the head. Vulpian regards the rotation of the head as due to strong auditory perceptions (?) in consequence of aftections of the canals. Bottcher, Tomaszewicz and Baginsky regard the injury to the cerebellum as the cause of the phe- nomena. The pendulum-like movements, 1 owever, are so characteristic that they cannot be con- founded with disturbances of the equilibrium which result from injury to the cerebellum. [Kinetic Theory. — In 1875 Crum Brown pointed out that if a person be rotated passively, his eyes being bandaged, he can, up to a certain point, indicate pretty accurately the amount of move- ment, but after a time this cannot be done, and if the rotation, as on a potter's wheel, be stopped, the sense of rotation con- rlG. 309. tinues. Crum Brown suggested that currents were produced in the endolymph, while the terminal hair cells lagged behind, and were, in fact, dragged through the fluid. He pointed out that the right posterior canal is in line with the left superior, and the left posterior with the right superior, a fact which is readily ob- served by looking from behind at a skull, with the semicircular canals exposed (Fig. 3S9). He assumes th.it the canals are paired organs, and that each pair is connected with rbtalion or movement of the head in a particular direction.] Giddiness. — This feeling of false impressions as . RP to the relations of the surroundings and consequent 1 of the disposition of the semi- movements of the body occurs especially during :ircuiar canals. Rs and Ls, right aL(7uiri;d chs.iM'ts in the normal movements of the and left superior; LP and KV , , , , ■ , right and left posterior; LF. and eycs, whether duc to in voluntary to and fro move- RE, right and left external. ments of the cyeballs (nystagmus) or to paralysis of some eye muscle. Active or passive movements of the head or of the body are normally accom- panied by simultaneous movements of both eyeballs, which are characteristic for every position of the body. The general character of these "compensatory" bilateral movements of the eyes consists in this, that during the various changes in the position of the head and body the eyes strive to maintain their primary passive position. Section of the aqueduct of Sylvius at the level of the corpora quadri- gemina, of the floor of the fourth ventricle, of the auditory nucleus, both acustici, as well as destruction of both membranous labyrinths, causes disappearance of these movements ; while, conversely, stimulation of these parts is followed by bilateral associated movements of the eyeballs. Compensatory movements of the eyeballs, under normal circumstances, may be caused refle.xly from the membranous labyrinth. Nerve channels, capable of ex- citing reflex movements of both eyes, proceed from both labyrinths, and, indeed, both eyes are affected from both labyrinths. These channels pass through the auditory nerve to the centre (^nuclei of the 3d, 4th, 6th and 8th cranial nerves), and from the latter efferent fibres pass to the muscles of the eye {Hogyes). Cyon found that stimulation of the horizontal semicircular canal was followed by horizontal nys- tagmus; of the posterior, by vertical, and of the anterior canal, by diagonal nystagmus. Stimula- tion of one auditory nerve is followed by rotating nystagmus, and rotation of the body of the animal on its axis toward the stimulated side. Poisons. — Chloroform and other poisons enfeeble the compensatory movements of the eyeballs, while nicotin and asphyxia suppress them, owing to their action on their nerve centre. It is probable that the disturbances of equilibrium and the feeling of giddiness which follow the passage of a galvanic current through the head between the mas- THE GLOSSO-PHARYNGEAL NERVE. 637 toid processes, are also due to an action upon the semicircular canals of the laby- rinth (§300). Deviation of the eyeballs is produced by such a galvanic current (Hitzii;). The same result is produced when the two electrodes are placed in the external auditory meatuses. Pathological. — Meniere's Disease. — The feeling of giddiness, not unfrequently accompanied by tinnitus, which occurs in Meniere's disease, must be referred to an affection of the nerves of the arnpull.i; or their central organs, or of the semicircular canals themselves. By injecting fluid vio- lently into the ear of a rabbit, giddiness, with nystagmus and rotation of the head toward ihe side operated on, are produced {BagiKsiv). In cases in man, where the tympanic membrane was defective, Lucx, when employing the so-called ear-air douche at o.i atmosphere, observed abduction of the eyeball with diplopia, giddiness, darkness in front of the eyes, while the respiration was deeper and accelerated. These phenomena must be due to stimulation or exhaustion of the ves- tibular branch of the auditory nerve (Hdgvt-s). In chronic gastric catarrh a tendency to giddiness is an occasional symptom (Trousseau's gastric giddiness). This may, perhaps, be caused by stimu- lation of the gastric nerves exciting the vasomotor nerves of the labyrinth, which must affect the pressure of the endolymph. Analogous giddiness is excited from the larynx {^Charcot) and from the urethra (Eyh-nmeyer). [Vertigo, or giddiness, is a very common symptom in disease, and may be produced by a great many diflerent conditions. It literally means "a turning." As Cowers points out, the most common symptom is that the patient himself has a sense of movement in one or other direction; or objects may appear to move before him ; and more rarely there is actual movement " commonly in the same direction as the subjective sense of movement." It is sometimes due to a want of harmony between the impressions derived from different sense organs or "contradictoriness of sensory impres- sions" (Grainger Sle-wart),s& is sometimes felt on ascending or descending a stair, or by some persons while standing on a high tower, constituting tower or cliff giddiness. One of the most remarkable conditions is that called "Agoraphobia " {Benedikt. H'estphal). The person can walk quite well in a narrow lane or street, but when he attempts to cross a wide square he experiences a feeling closely allied to giddiness. The giddiness of seasickness is proverbial, while some persons get giddy with waltzing or swinging. Besides occurring in Meniere's disease, it sometimes occurs in locomotor alaxis and some cerebral and cerebellar a'ffections. including cerebral anx-mia. Very distressing giddiness and headache are often produced by paralysis of some of the. ocular muscles, c. g., the external rectus. Defective or perverted ocular impressions, as well as similar auditory impressions, may give rise to vertigo; in the latter or labyrinthine form the vertigo may be very severe. Severe vertigo is often accompanied by vomiting. A hard plug of ear wax may press on the membrana tympani, and cause severe giddiness. The forms of dyspeptic giddiness and the toxic forms due to the abuse of alcohol, tobacco, and some other drugs are familiar examples of this condition.] [Tinnitus Aurium, or subjective noises in the ear, is a very common symptom in disease of the ear; the noise may be continuous or discontinuous, be buzzing, singing, or rumbling in character.] 351. IX. NERVUS GLOSSO-PHARYNGEUS.— Anatomical.— This nerve (Fig. 386, g) arises from the nucleus of the same name, which consists partly of large cells (motor) and partly of small cells (belonging to the gustatory fibres). The nucleus lies in the lower half of the fourth ventricle, deep in the medulla oblongata, near the olive (Fig. 384). The nucleus is connected w-ith that of the vagus. A special root ascending from the spinal cord applies itself to the fibres, and perhaps (like the spinal roots of the second and eighth nerves) serves for the production of spinal reflexes (Roller). The fibres collect into two trunlis, which afterward unite and leave the medulla oblongata in front of the vagus. In the fossula petrosa it has on it the petrous ganglion, from which, occasionally, a special part on the posterior twig is separated within the skull as the ganglion of Ehrenrilter. Commutticaling branches are sent from the petrous ganglion to the trigeminus, facial (i and -), v.agus and carotid plexus. From this ganglion also the tympanic nerve (/.) ascends vertically in the tympanic cavity, where it unites with the tympanic plexus This branch {\ 349, 4) gives sensory fibres to the tympanic cavity and the Eustachian tube ; while, in the dog, it also carries secretory fibres for the parotid into the small superficial petrosal nerve (Heidenhain — \ 145). Function. — i. It is the nerve of taste for the posterior third of the tongue, the lateral part of the soft palate, and the glosso-palatine arch (^compare § 422). [This is denied by Gowers (p. 630).] The nerve of taste for the anterior two-thirds of the tongue is referred to under the lingual 1 \ 347, III, 4). and chorda tympani n-rves (? 349, 4). The glossal branches are provided with ganglia, especially where the nerve divides at the base of the circumvallate papilli"e (Remak, Kolliker, Schwalbe, Stirling). The nerve ends in the circumvallate papillce (Fig. 320, U), and the end organs are represented by the taste bulbs (J 422). 2. It is the sensory nerve for the posterior third of the tongue, the anterior 638 THE CONNECTING AND OTHER BRANCHES OF THE VAGUS. surface of the epiglottis, the tonsils, the anterior palatine arch, the soft palate, and a part of the pharynx. From this nerve there may be discharged reflexly, move- ments of deglutition, of the palate and pharynx ( I'olkmanii), which may pass into those of vomiting (§ 158). These fibres, like the gustatory fibres, can excite a reflex secretion of saliva (§ 145). 3. It is motor for the stylo-pharyngeus and middle constrictor of the pharynx (Vo/kmann) ; and, according to other observers, to the (?) glosso-palatinus {Heiii) and the (??) levator veli palatini and azygos uvulse (compare Spheno-palatine gang- lion, § 347, II). It is doubtful whether the glosso-pharyngeal nerve is really a motor nerve at its origin — although Meynert, Huguenin, W. Krause, and Duval have described a motor nucleus — or whether the motor fibres reach the nerve at the petrous ganglion, through the communicating branch from the facial. 4. A twig accompanies the lingual artery ; this nerve, perhaps, is vaso-dilator for the lingual blood vessels. Pathological. — There are no satisfactory observations on man of uncomplicated affections of the glosso-pharyngeal nerve. 352. X. NERVUS VAGUS. — Anatomical. — The nucleus from which the vagus arises along with the ninth and eleventh nerve is in the ala cinerea in the lower half of the calamus scrip- torius (Fig. 384, 10) [and it is very probably the representative of the cells of the vesicular column of Clarke (J 366).] It leaves the medulla oblongata by 10 to 15 threads behind the ninth nerve, between the divisions of the lateral column, and has a ganglion (jugular) upon it in the jugular foramen (Fig. 385, VHI). Its branches contain fibres which subserve dift'erent functions. 1. The sensory meningeal branch from the jugular ganglion accompanies the vasoinotor fibres of the sympathetic on the middle meningeal artery, and sends fibres to the occipital and transverse sinus. When it is irritated, as in congestion of the head and inflammation of the dura mater, it gives rise to vomiting. 2. The auricular branch (from the jugular ganglion) receives a communicat- ing branch from the petrous ganglion of the ninth nerve, traverses the canaliculus mastoideus, crossing the course of the facial, with which it exchanges fibres whose function is unknown. On its course it gives sensory branches to the posterior part of the auditory meatus and the adjoining part of the outer ear. A branch runs along with posterior auricular branch of the facial, and confers muscular sensibility on the muscles. When this nerve is irritated, either through inflammation or by the presence of foreign bodies in the outer ear passage, it may give rise to I'omitittg. Stimulation of tlie deep part of the external auditory meatus in the region supplied by the auricular branch causes coughing reflexly [c. g., from tile presence of a pea in the ear]. Similarly, contraction of the blood vessels of the ear may be caused reflexly {Snellen^ Lovhi']. The nerve is the remainder of a considerable branch of the vagus which exists in fishes and the larvK of frogs, and runs under the skin along the side of the body. 3. The connecting branches of the vagus are: (i) A branch which directly connects the petrous ganglion of the 9th with the jugular ganglion of the loth ; its function is unknown. (2) Directly above the plexus gangliiformis vagi, the vagus is joined by the whole inner half of the spinal accessory. This nerve conveys to the vagus the motor fibres for the larynx {Bischoff, i8j2), and the cervical part of the cesophagiis (which, according to Steiner, lie in the inner part of the nerve trunk), as well as the inhibitory y?/vrj- for \\\t heart {CI. Bernard'). (3) The plexus gangliiformis fibres, whose function is unknown, join the trunk of the vagus from the hypoglossal, superior cervical ganglion of the sympathetic, and the cer- vical plexus. 4. Pharyngeal Plexus. — The vagus sends one or two branches from the upper part of the plexus gangliiformis to \.\\e pharyngeal plexus, where at the level of the iniddle constrictor of the pharynx it is joined by the pharyngeal branches of the 9th nerve and those of the upper cervical sym|)athetic ganglion, near the ascending pharyngeal artery, to form the ^haiyngcal plexus. The vagal fibres in this plexus SUPERIOR AND INFEUIOR LARYN'GEAL NERVES. 639 supply the three constrictors of the pharynx with motor fibres, while the tensor palati {Otic ganglion, § 347, III) and levator of the soft palate (compare Spheno- palatine ganglion, § 347, II) also receive motor (? sensory) fibres. Sensory fibres of the vagus from the pharyngeal ple.xus supply the pharynx from the part beneath the soft palate downward. These fibres excite the pharyngeal constric- tors reflexly during the act of swallowing (§ 156). If stimulated very strongly they may cause vomiting. (The sympathetic fibres of the oesophageal plexus give vasomotor nerves to the oesophageal vessels; for the oesophageal branches of the 9th nerve, see above.) 5. The vagus supplies two branches to the larynx, the superior and inferior laryngeal. ((7) The superior laryngeal receives vasomotor fibres from the superior cervical ganglion of the sympathetic. It divides into two branches, external and internal: (1) The external branch receives vasomotor fibres from the same source (they accompany the superior thyroid artervi, and supplv the cricothyroid muscle with motor fibres and sensory fibres to the lower lateral portion of the laryngeal mucous membrane. (2) The internal branch gives oH sensory branches only to the glosso-epiglottidean fold and the adjoining lateral region of the root of the tongue, the aryepiglottidean fold, and to the whole anterior part of the lar- ynx, except the part supplied by the external branch (Longet). Stimulation of any of these sensory fibres causes coughing reflexly. Coughing is produced by stimulation of the sensory branches of the vagus to the tracheal mucous membrane, especially at the bifurcation, and also from the bronchial mucous membrane. Coughing is also caused by stimulation of the auricular branch of the vagus, espe- cially in the deep part of the external auditory meatus, of the pulmonary tissue, especially when altered pathologically; in pathological conditions (inflammation) of the pleura ( ? certain changes in the stomach [stomach cough]), of the liver and spleen (Nai/nyn). The coughing centre is said to lie on each side of the raphe, in the neighborhood of the ala cinerea {Kohts). Cases of violent coughing may, owing to stimulation of the pharynx, be accompanied by vomiting as an associ- ated movement (§ 120). The cough (dog, cat) caused by stimulation of the trachea and bronchi occurs at once, and lasts as long as the stimulus lasts ; in stimulation of the larnyx the first effect is inhibition of the respira- tion accompanied by nioi-ements of deglutition, while the cough occurs after the cessation of the stimulation [Kandarazky). The superior laryngeal contains afferent fibres which, when stimulated, cause arrest of the res- piration and closure of the rima glottidis (Rosentluil) — (see Respiratory centre, \ 368). Lastly, fibres which are efi'erent and serve to excite the vasomotor centre, and are in fact, "pressorfibres" — (see Vasomotor centre, ^ 371, II). {b) The inferior laryngeal (recurrent) bends on the left side around the arch of the aorta, and on the right around the subclavian, and ascends in the groove between the trachea and oesophagus, giving motor fibres to these organs, and the lower constrictors of the pharynx, and passes to the larynx, to supply motor fibres to all its muscles, except the cricothyroid. It also has an inhibitory action upon the respiratory centre (see § 368). A connecting branch runs from the superior laryngeal to the inferior (the anastomosis of Galen), which occasionally gives off sensory branches to the upper half of the trachea (sometimes to the larynx ?) ; perhaps, also, to the cesophagus (Loni;e/), and sensory fibres (?) for the muscles of the larynx supplied by the recurrent laryngeal. According to Frangois Franck, sensory fibres pass by this anastomosis from the recurrent into the superior laryngeal. .According to Waller and Burck- hard, the motor fibres of both laryngeal nerves are all derived from the accessorius ; while Chau- veau maintains that the cricothyroid is an exception. Stimulation of the superior laryngeal is painful, and causes contraction of the cricothyroid muscle (while the other laryngeal muscles contract reflexly). Section of both nerves, owing to paralysis of the cricothyroids, causes slight slow- ing of the respirations (Sklarek). In dogs the voice becomes deeper and coarser. 640 CARDIAC BRANCHES OF THE VAGUS. owing to diminished tension of the vocal cords {Longef). The larynx becomes insensible, so that saliva and particles of food pass into the trachea and lungs, without causing reflex contraction of the glottis or coughing, This excites " trau- matic pneumonia," which results in death (Friedlander). Stimulation of the recurrent nerves causes spasm of the glottis. Section of these nerves paralyzes the laryngeal muscles supplied by them, the voice be- comes husky and hoarse (in the pig — Galen, Riolan, 1618) in marv, dog, and cat ; while rabbits retain their shrill cry. The glottis is small, with every inspiration of the vocal cords approximate considerably at their anterior parts, while during expiration they are relaxed and are separated from each other. Hence, the inspi- ration, especially in young individuals whose glottis respiratoria is narrow, is dif- ficult and noisy {Legallois) ; while the expiration takes place easily. After a few days, the animal (carnivore) becomes more quiet, it respires with less effort, and the passive vibratory movements of the vocal cords become less. Even after a considerable interval, if the animal be excited, it is attacked with severe dyspncea, which disappears only when the animal has become quiet again. Owing to paralysis of the laryngeal muscles, foreign bodies are apt to enter the trachea, while the paralysis renders difficult the first part of the process of swallowing in the tesoph- ageal region. Broncho-pneumonia may be produced {Arnspergcr). 6. The depressor nerve, which in the rabbit arises by one branch from the superior laryngeal, and usually, also, by a second root from Fig. iqo. ^'^^ trunk of the vagus itself [runs down the neck in close relation with the vagus, sympathetic, and carotid artery, enters the thorax], and joins the cardiac plexus (Fig. 390, s(). It is an afferent nerve, and when its central end is stimu- lated [provided both vagi be divided], it diminishes the energy of the vasomotor centre, and thus causes a fall of the blood pressure (hence the name given to it by Cyon and Ludwig, § 371, 11). At the same time [if the vagus on the opposite side be intact], its stimulation affects the cardio- inhihitory centre, and thus reflexly diminishes the number of heart beats. [Its stimulation also gives rise to pain, so that it is the sensory nerve of the heart. If in a rabbit the vagi be divided in the middle of the neck, and the central end of the depressor nerve, which is the smallest of the three nerves near the carotid, be stimulated, after a short time there is no alteration of tlie heart beats, but there is a steady fall of the blood pressure (Fig. 103), which is due to a reflex inhibition of the vasomotor centre, resulting in a dilatation of the blood vessels of the abdomen. Of course, if the vagi be intact, there is a reflex inhibitory effect on the heart. It is doubtful if the depressor comes into action when the heart is over-distended. If it did, of course the blood pressure would be reduced by the reflex dilatation of the abdominal blood vessels.] The depressor nerve is present in the cat [Bernhardt^, hedgehog Scheme of the cardiac n rv s {Aubert, Rover), rat and mouse; in the horse and in the man, fibres in the rabbit. P, pons: analogous to the depressor re-enter the trunk of the vagus (^^'mAffra'/, M, medulla oblongata: Kreidmanti). Depressor fibres are also found in the rabbit in the trunk HortrL^TnierlVur^n: °f '^e vagUS [DrcshfdJ,, StMng). geal ; s c, superior car- diac or depressor; ic, « 'Y\\e. cardiac branches, as well as the cardiac plexus, inferior cardiac or car- , ' , , -i i ■ [> rr^i • , dio-inhibitory;H, heart, havc been described in s 57. 1 hese nerves contain the inhibitory fibres for the heart (Fig. 390, ic — cardio-in- hibitory — Eihvard Weber, November, 1845; Budge, independently in May, 1846), also sensory fibres for the heart [in the frog {Budge), and partly in PNEUMONIA AFTER SECTION OF THE VAGI. G41 mammals (Goltz)\. Lastly, in some animals the heart receives some of the accelerating fibres through the trunk of the vagus. Feeble stimulation of the vagus occasionally causes acceleration of the beats of the heart {Schiff, Molescholt, Gianuzzi). [This occurs when the vagus contains accelerator fibres.] In an animal poisoned with nicotin or atropin, which paralyzes the inhibitory fibres of the vagus, stimulation of the vagus is followed by acceleration of the heart beats {Schiff, Schmiedeberg) [owing to the unopposed action of any accelerated fibres that may be present in the nerve, e.g., of the frog]. 8. The pulmonary branches of the vagus join the anterior and posterior pulmonary plexuses. The aw/evv'c/- pulmonary plexus gives sensory and motor fibres to the trachea, and runs on the anterior surface of the branches of the bronchi into the lungs. The posterior plexus is formed by three to five large branches from the vagus, near the bifurcation of the trachea, together with branches from the lowest cervical ganglion of the sympathetic and fibres from the cardiac plexus. The plexuses of opposite sides exchange fibres, and branches are given off which accompany the bronchi in the lungs. Ganglia occur in the course of the pulmonary branches in the frog (Arnold, W. Stirling) [newt — ■ W. Stirling; and in mammals {Remak, Egerow, W. Stirling)^, in the larynx l^Cock, IF. Stirling'], in the trachea and bronchi [/?'. Stirling, Kanda?azki'\. Branches proceed from the pulmonary plexus to the pericardium and the superior vena cava (Luschka, Zuckerkandl). The functions of the pulmonary branches of the vagus are — (i) they supply motor branches to the smooth muscles of the whole bronchial system (§ io6 — Roy and Graham Broiun) ; (2) they supply a small part of tiie vasomotor nerves of the pulmonary vessels (Schiff), but by far the largest number of these nerves (? all) is supplied from the connection with the sympathetic (in animals from the first dorsal ganglion) — (^Bro^on-Sequard, A. Fick, Badoud, Lichlheim) ; (3) they supply sensory (cough-exciting) fibres to the whole bronchial system, and to the lungs ; ( 4J they give afferent fibres, which, when stimulated, diminish the activity of the vasomotor centre, and thus cause a fall of the blood pressure during forced expiration ; (5 ) and similar fibres which act upon the inhibitory centre of the heart, and so influence it as to accelerate the pulse beats (§ 369, II). Simultaneous stimulation of 4 and 5 alters the pulse rhythm (Sornmerbrodt) ; (6) they also con- tain afferent fibres from the pulmonary parenchyma to the medulla oblongata, which stimulate the respiratory centre. [These fibres are continually in action], and consequently section of both vagi is followed by diminution of the number of respirations ; the respirations become deeper at the same time, while the same volume of air is changed {Valentin). Stimulation of the central end of the vagus again accelerates the respirations ( Traube, J. Rosenthal). Thus labored and diffi- cult respiration is explained by the fact that the influences conveyed by these fibres which excite the respiratory centre reflexly are cut off; so it is evident that cen- tripetal or afferent impulses proceeding upward in the vagus are intimately con- cerned in maintaining normal reflex respiration ; after these nerves are divided, conditions exciting the respiratory movements must originate directly, especially in the medulla oblongata itself (§ 368). Pneumonia after Section of both Vagi. — The inflammation which follows section of both vagi has attracted the attention of many observers since the time of Valsalva, Morgagni (1740), and Legallois (i8i2). In offering an explanation of this phenomenon, we must bear in mind the following considerations: (a) Section of both vagi is lollowed by loss of motor power in the muscles of the larynx, as well as the sensibiHty of the larynx, trachea, bronchi, and the lungs, pro- vided the section be made above the origin of the superior laryngeal nerves. Hence, the glottis is not closed during swallowing, nor is it closed reflexly when foreign bodies (saliva, particles of food, irrespirable gases) enter the respiratory passages. Even the reflex act of coughing, which, under ordinary circumstances, would get rid of the offending bodies, is abolished. Thus, foreign bodies may readily enter the lungs, and this is favored by the fact that, owing to the simultaneous paralysis of the tesophagus, the food remains in the latter for a time, and may therefore easily enter the larjnx. That this constitutes one important factor was proved by Traube, who found that the pneu- 41 642 CESOPHAGEAL AND GASTRIC PLEXUSES. monia was prevented when he caused the animals to respire by means of a tube inserted into the trachea through an aperture in the neck. If, on the contrary, only the motor recurrent nerves were divided and the tesophagus ligatured, so that in the process of attempting to swallow food must necessarily enter the respiratory passages, " traumatic pneumonia " was the invariable re- sult {Tratihe, O. Frey). (b) A second factor depends on the circumstance that, owing to the labored and dithcult respiration, the lungs become surcharged with blood, because during the long time that the thorax is distended, the pressure of the air within the lungs is abnormally low. This condition of congestion, or abnormal filling of the pulmonary vessels with blood, is followed by serous exudation (pulmonary cedema), and even by exudation of blood and the fonnation of pus in the air vesicles (/>' probably due to the reflex spasms which may be discharged from the sensory nerves of several areas (teeth, intestine, skin). The impulse is conducted along the sensory nerves proceeding from these areas to the medulla oblongata, where it causes the discharge of the reflex mechanism which produces the above-mentioned results. 1 here may be spasm of the dilators of the glottis (Frdnt:el 1 and other laryngeal muscles. Stimulation of the sensory ner\'es of the larynx, as is well known, produces coughing. If the stimulation be very intense, as in whooping-cough, the fibres lying in the laryngeal nerves, which inhibit the respiratory centre, may also be stimulated; the number of respirations is diminished, and uhimately the respiration ceases, the diaphragm being relaxed : while, with the most intense stimulation, there may be spasmodic expiratory arrest of the respiration with closure of the glottis, which may last for filteen seconds. Paralysis of the laryngeal nerves, which causes disturbances of speech, has been referred to in \ 313. In bilateral paralysis of the recurrent nerz'es, in conse- quence of tension upon them due to dilatation of the aorta and the subclavian artery, a consider- able amount of air is breathed out, owing to the futile efforts which the patient makes in trying to speak ; expectoration is more difiicult, while violent coughing is impossible {v. Ziemssen). Attacks of dyspnoea occur just as in animals, if the person make violent efforts. Some observers [Salter, Bergson) have referred the asthma nervosum paroxysms, which last for a quarter of an hour or more, and constitute asthma bronchiole, to stimulation of the pulmonary plexus, causing spasmodic contraction of the bronchial muscle (^ io6|. Physical investigation during the paroxysms reveals nothing but the existence of some rhonchi (| 117). If this condition is really spasmodic in its 644 THE SPINAL ACCESSORY NERVE. nature (? of the vessels), it must be usually of a reflex character ; the afferent nerves may be those of the lung, skin or genitals (in hysreria). Perhaps, however, it is clue to a temporary paralysis of the pulmonary nerves (afferent), which excite the respiratory, centre (excito-respiratory). Stimulation of the cardiac branches of the vagus may cause attacks of temporary suspension of the cardiac contractions, which are accompanied by a feeling of great depression and of impending dissolution, with occasionally pain in the region of the heart. Attacks of this sort may be pro- duced reflcxly, €.g.^ by stimulation or irritation of the abdominal organs (as in the experiment of Goltz of tapping the intestines). Hennoch and Silbermann observed slowing of the action of the heart in children suffering from gastric irritation. Similarly, the respiration may be affected reflexly through the vagus, a condition described by Hennoch as asthma dyspepticum. In cases of intermittent paralysis of the cardiac branches of the vagus we rarely find acccleralion of the pulse above l6o [Riegel), 200 ( Ttuzek, L. Langer^ Weil) ; even 240 pulse beats per minute have been recorded i^Kufpert), and in such cases the beats vary much in rhythm and force, and they are very irregular. These cases require to be more minutely analyzed, as it is not clear how much is due to paralysis of the vagus and how much to the action of the accelerating mechani.sm of the heart. Little is known of affections of the ififra-nln/ominal ^hyts of the vagus. It seems that the sensory branches of the stomach do not come from the vagus. If the trunk of the vagus or its centre be paralyzed, there are labored, deep, slow respirations, such as follow section of both vagi ( Gttttmann). 353. XI. NERVUS ACCESSORIUS WILLISII— Anatomical.— This nerve arises by two completely separate roots; otie from the accessorius nucleus of the medulla oblongata ( Fig. 384, II), which is connected with the vagus nucleus ; while the o/ht'r root arises between the anterior and posterior nerve roots from the spinal cord, usually between the 5th and 6th cervical vertebrae. In the interior of the spinal cord Us fibres c^n be traced to an elongated nucleus lying on the outer side of the anterior cornu, as far downward as the 5th cervical vertebra. Near the jugular foramen both portions come together, but do not exchange fibres (Hoi/); both roots after- ward separate from each other to form two distinct l^ranches, the anterior [inner], which arises from the medulla oblongata, passing en masse into the plexus gangliiformis vagi. This branch sup- plies the vagus with most of its 7notor fibres (compare \ 352, 3), and also its cardio-inhibitory fibres. If the accessorius be pulled out by the root m animals, these heart fibres undergo degenera- tion. If the trunk of the vagus be stimulated in the neck four to five days after the operation, the action of the heart is no longer arrested thereby [owing to the degeneration of the cardio-inhibitory fibres] [Waller, Schiff, Daszkieiuiez, Heidenhain); according to Heidenhain, the heart- beats are accelerated immediately after pulling out the nerve. [The upper cervical metameres or segments give origin not only to the anterior and posterior roots of the corresponding nerve roots, but between these roots arise the roots of the spinal accessory nerve. This nerve contains /iz)ycmedullated nerve fibres andyfKf meduUated fibres such as characterize the visceral branches of the thoracic and sacral regions (\ 356). The nerve passes by the jugular ganglion of the vagus, then divides into the external and internal branch. All the large fibres pass into the external branch, which, along with branches from the cer\'ical plexus, supply the sterno-mastoid and trapezius. The internal branch, composed of small fibres, passes Into the ganglion of the trunk of the vagus. Gaskell therefore regards the Internal branch " as formed by the rami viscerales of the upper cervical and vagus nerves." These fine medullated nerve fibres probably arise from the cells of the posterior vesicular column of Clarke. The motor fibres to the trapezius and sterno-mastoid arise from the cells of the lateral horn of gray matter.] The external branch arises from the spinal roots. This nerve communicates with the sensory branches of the posterior root of the ist, more rarely of the 2d cervical nerve, and these fibres supply sensibility to the muscles; it then turns backward above the transverse process of the atlas, and terminates as a motor nerve in the sterno-mastoid and trapezius [Galen, Valentin, Volkmann). The latter muscle usually receives motor fibres also from the cervical plexus (Fig. 386). The external branch communicates with several cervical nerves. These fibres either participate in the innervation of the above-named muscles or the accessorius returns part of the sensory fibres supplied by the posterior roots of the two upper cervical nerves. Pathological. — Stimulation of the outer branch causes tonic or clonic spasm of the above-named muscles, usually on one side. If the branch to the sterno-mastoid be aftected alone, the head is moved with each clonic spasm. If the affection be bilateral, the spasm usually takes place on oppo- site sides alternately, while It is rare to have it on both sides simultaneously. In spasm of the trapezius the head is drawn backward and to the side. Toiiie contraction of the flexors of the head causes the characteristic position of the head known as caput obstipum (spastlcum) or wry- neck. In />aral}'sis of one of these muscles the head is drawn toward the sound side (torticollis paralyticus). Paralysis of the trapezius is usually only partial. Paralysis of the whole trunk of the spinal accessory (usually caused by central conditions), besides causing paralysis of the sterno-mastoid and trapezius, also paralyzes the motor branches of the vagus already referred to [Erb, Frdnkel, Holz). THE SPINAL NERVES. 645 354. XII. NERVUS HYPOGLOSSUS.— Anatomical.— It arises from two large-celled nuclei witliin the lowest part of the calamus scriptorius, and one adjoining small-celled nucleus (Roller), while addiiional filires come from the brain (^ 37S), and also perhaps from the olive (Fig. 384,12). It springs by 10 to 15 twigs in a line with the anterior roots of the spinal neive (Fig. 385, IX). In its development part of the hypoglossal behaves as a spinal nerve (Froriep). Function. — It is motor to all the muscles of the tongue, including the genio- hyoid and thyro-hyoid. Connections. — The trunk of the hypoglbssal is connected with — ( 1 1 the superior cervical ganglion of the svmpathelic, which supplies it with -Hisomotor fibres for the blood vessels of the tongue. After section of the hypoglossal and lingual nerves, the corresponding half of the tongue becomes red and congested [Scliiff). (2) There is also a branch from the plexus gangliiformis vagi, its small lingual branch to the commencement of the hypoglossal arch. These filires supply the hypoglossal with sensory filires for the muscles of the tongue, for even after section of the lingual the tongue still possesses dull sensibility. It is uncertain whether fibres with a similar function are partly derived from the cervical nerves or from the anastomosis which takes place with the lingual. {3) It is united with the np/'er cervical nerves by means of the loops known as the ansa hypoglossi. These connecting fibres run in the de^cendens noni to the sterno-hyoid, omo-hyoid and sterno-thyroid. Cer- vical fibres do not, as a rule, enter the tongue; stimulation of the root of the hypoglossal acts upon the above-named muscles only very rarely and to a very slight extent [Volkmann). (Compare §297, 3, and ^^336, III.) Bilateral section of the nerve causes complete motor paralysis of the tongue. Dogs can no longer lap ; they bite the flaccid tongue. Frogs, which seize their prey with the tongue, must starve ; when the tongue hangs from the mouth, it must prevent the closure of the mouth, so that these animals must die from asphyxia, as air is pumped into the lungs only when the mouth is closed. Pathological. — Paralysis of the hypoglossal (glossoplegia), which is usually central in its origin, causes disturbance of .i/ct-iV; (§ 319). [In unilateral palsy the tongue lies in the mouth in its normal position, but the base is more prominent on the paralyzed side. When the tongue is protruded it passes to the sound side by the genio hyoglossus (J 155)-] Paralysis of the tongue also interferes with mastication, the formation of the bolus in the mouth, and deglutition in the mouth. Owing to the imperfect movements of the tongue, taste is imperfect, and the singing of high notes and the falsetto voice, which require certain positions of the tongue, appear to be impos- sible {Bennati). Spasm of the tongue, which causes aphthongia (| 318), is usually reflex in its origin, and is extremely rare. Idiopathic cases of spasm of the tongue have been described; the seat of the irri- tation lay either in the cortex cerebri or in the oblongata (Berger, E. JHemai). For Pseudo-motor Action, p. 632. 355. THE SPINAL NERVES. — Anatomical. — The thirty-one pairs of spinal nerves arise by means of a posterior root (consisting of a few large rounded Imndles) from the sulcus between the posterior and lateral columns of the spinal cord, and by means of an anterior root (consisting of numerous fine flat strands), from the furrow between the anterior and lateral columns. The posterior roots, with the exception of the 1st cervical nerve, are the larger. Occasionally the roots on opposite sides are not symmetrical ; one or other mot, or even a whole nerve, may be absent from the dorsal region (Adamiicwicz]. On the posterior root is ihe spindle shaped spinal gan- glion (^ 321, II, 3), which is occasionally double on the lumbar and sacral nerves Beyond the ganglion the two roots unite to form within the spinal canal the mixed trunk of a spinal nerve. The branches of the nerve trunk invariably contain fibres coming from both roots. The number of fibres in the nerve trunk is exactly the same as in the two roots; hence, we must conclude that the nerve cells in the spinal ganglion are intercalated in the course of the fibres {Gaule and Birge). [Structure of a Spinal Ganglion. — The ganglion is invested by a thin, firmly adherent sheath of connective tissue, which sends processes into the swelling, and is continuous with the sheaths of the nerve entering and leaving the ganglion (Fig. 39:, e). A longitudinal section of such a gan- glion exhibits the cells arranged in groups, with strands of nerve fibres coursing longitudinally between them (Fig. T^<)i,a,h). The nerve cells are usually globular in form, with a distinct capsule lined with epithelium, and the cell substance itself contains a well-defined nucleus with a nuclear envelope and a nucleolus. The capsule of the cell is c mtiniious with the sheath of Schwann of a nerve fibre. The exact relation between the nerve fibres and the nerve cells is difficult to establish, but it is probable that each nerve cell is connected with a nerve fibre. In the spinal ganglia of the vertebrates above fishes, and also in the Gas=erian ganglion, cells are f.jund with a single process or fibre attached to them, the nerve-fibre process not unfrequently coiling a few times within the cap- sule. This process, after emerging from the capsule, becomes coa'ed with myrlin, and usually soon divides at a node of Ranvier (Fig. 341, /). Ranvier, who first observed this arrangement, described it as a T'^haped fibre. These nerve cells with "T'^'i^P^'J fibres have been observed in the 646 RECURRENT SENSIBILITY. spinal ganglia of all vertebrates above fishes, in the Gasserian and geniculate ganglia, as well as in the jugular and ceniical ganglia of the vagus. In fishes the nerve cells of the spinal ganglia are bipolar (Fig. 335,4).] Bell's Law.- — Sir Charles Bell discovered (181 1) that the anterior roots of the spinal nerves are motor, the posterior are sensory. Recurrent Sensibility. — Magendie discovered (1S22) the remarkable fact X\\-3X sensory fibres zxt also present \n the anterior roots, so that their stimulation causes pain. This is due to the fact that sensory fibres pass into the anterior root after the two roots have joined, and these fibres run in the anterior root in a centripetal direction {Sehiff, CI. Bernard^. The sensibility of the anterior root is abolished at once by section of the posterior root. This condition is called "recurrent sensibility" of the anterior root. When the sensibility of the anterior root is abolished, so is the sensibility of the surface of the spinal cord in the neighborhood of the root. A long time after section of the anterior, and when the degeneration phenomena have had time to develop (§ 325), a few non- degenerated sensory fibres are always to be found in the central stump (Sehiff, Vulpiiih). Sehiff found that, in cases where the motor fibres had undergone degeneration, there were always non -degenerated fibres to be found in the anterior root, which passed into the membranes of the spinal cord. The sensory fibres pass into the motor root, either at the angle of union of the roots, or in 1 of a spin.il g.ingl lis, c, c.ipsule the plexus, or in the region of the peripheral terminations. Sensory fibres enter many of the branches of the motor cranial nerves at their periphery, and after- ward run in a centripetal direction (p. 632). Even into the trunks of sensory nerves, sensory branches of other sensory nerves may enter. This explains the remarkable observation, that after section of a nerve trunk {e.g., the median), its peripheral terminations still retain their sensibility (Arloing and Tripier). The tissue of the motor and sensory nerves, like most other tissues of the body, is provided with sensory nerves (yVtvz'/ nervorum, p. 565). [It does not follow that section of a peripheral cutaneou'! nerve will cause ana'sthesia in the part to which it is distributed; in fact, one of the principal nerve trunks of the brachial plexus may be divided without giving rise to complete anceslhesia in any part of the area of distribution of the sensory branches of the nerve, and even if there be partial or complete cutaneous an.-esthesia it is much less in extent than corresponds to the anatomical area of distribution. The an;vsthetic area tends to become smaller in extent (Ross). Thus there is not complete independence in the distri- bution of these nerves. These results are explained by the anastomosis between branches of nerves, the exchange of fibres in the terminal networks, while some sensory fibres enter the peripheral parts of a nerve and run centripetally, perhaps being distributed to the skin and conferring recurrent sensibility on the peripheral part of the nerve.] Relative Position of Motor and Sensory Fibres. — In embryos (rabbit) the motor fibres stain more deeply with carmine than the sensory fibres, so that their position in the peripheral nerves of DEDUCTION FROM BELL S LAW. 647 distribution may thereby be made out. In the anterior branch of a spinal nerve, the sensory fibres he in the outer part of the branch, the motor in the inner part ; while this relation is reversed in the posterior root (Z. Lowe). Deduction from Bell's Law. — Careful observation of the effects of section of the roots of the spinal nerves {Magendie, 1822), as well as the discovery of the reflex relation of the stimulation of the sensory roots to the anterior, constituting Fig. 393. Fig. 392. siiibution of ihe cutaneous A, dorsal surface;/ sc, supra-clavit axillary ; 3cps, superior posterior 4 c*nd, median cutaneous; 5cpi, i: terior cutaneous; b cm _ cl, lateral cutaneous ; 8 «, ulnar ; q ra, radial'; JO me, median ; B, volar surface ; / sc, supra- clavicular; 2 ajtr, axillary; ^ cmd, internal cutaneous; 4 cl, lateral cutaneous ; j" cm, cu- taneous medius; 6 we, median; 7 u, ulnar. Vpcismjl hmj cutaneous nerves of the leg A. Anterior surface— I, crural . -, — jrnal lateral cutaneous; 3, ilio- inguinal; 4, iumbo-inguinal ; 5, external sper- matic ; 6, posterior cutaneous ; 7, obturator ; 8, great saphenous ; 9, communicating pero- neal ; 10, superficial peroneal ; ri.deep pero- ;al ; 12, communicating tibial. B. Posteri surface — i, posterior cutaneous; femoral cutaneous; 3, obturator posterior femoral cutaneous ; 5, 1 ing peroneal; 6, great saphenous nicating tibial; 8, plantar cutant dian plantar ; lo, lateral plantar. reflex movements {Marshall Hall, Johafities Muller, i8j2), enable us to deduce the following conclusions from Bell's law : i. At the moment of section of the anterior root, there is a contraction in the muscles supplied by this root. 2. There is at the same time a sensation of pain due to the '* recurrent sensibility," 3. After the section, the corresponding muscles ztq paralyzed. 4. Stimulation of 648 FUNCTIONS OF THE ANTERIOR SPINAL ROOTS. the peripheral trunk of the anterior root (immediately after the operation) causes contraction of the muscles, and eventually pain, owing to the recurrent sensibility. 5. Stimulation of the central end is uiithout effect. 6. The peripheral end of the motor nerves degenerates within a short time (§ 325, 4). 7. The central end degenerates somewhat later (§ 325, 3). 8. The sensibility of the paralyzed parts is retained completely. 9. At the moment of section of the posterior root there is severe /(?/>/. 10. At the same time movements are discharged refiexly. II. After the section all parts supplied by the divided roots are devoid of sensi- bility. 12. Stimulation of the peripheral trunk of the divided nerve is without effect. 13. Stimulation of the central end causes pain and reflex movements. 14. With reference to the degeneration of the peripheral end of the sensory fibres, see § 325, 4. 15. The central end ultimately degenerates. 16. Movement is re- tained completely in the paralyzed parts, e. g., in the extremities. Incoordinated Movements of Insensible Limbs. — After section of the posterior roots, e.g., of the nerves for the posterior extremities, the muscles retain their movements, nevertheless there are characteristic disturb.ances of their motor power. This is expressed in the awkward manner in which the animal executes its movements — it has lost to a large extent its harmony and elegance of motion. This is due to the fact that, owing to the absence of the sensibility of the muscles and skin, the animal is no longer conscious of the resistance which is opposed to its movements. Hence the degree of muscular energy necessary for any particular efibrt cannot be accurately graduated. Animals which have lost the sensibility of their extremities often allow their limbs to lie in abnormal positions, such as a healthy animal would not tolerate. In man also, when the peripheral ends of the cutaneous nerves are degenerated, there are ataxic phenomena (^ 364, 3). Increased Excitability. — Harless (185S), Ludwig, and Cyon (controverted by v. Bezold, Uspensky, Griinhagen, and G. Heidenhain) observed that the anterior root is more excitable as long as the posterior roots remain intact and are sensitive, and that their excitability is diminished as soon as the posterior roots are divided. In order to explain this phenomenon, we must assume that in the intact body a series of gentle impulses (impressions of touch, temperature, position of limbs, etc.) are continuously streaming through the posterior roots to the spinal cord, where they are transferred to the motor roots, so that a less .stimulus is required to excite the anterior roots than when these reflex impulses of the posterior root, which increase the excitability, are absent. Clearly, a less stimulus will be required to excite a nerve already in a gentle state of excitement than in the case of a fibre which is not so excited. In the former case, the discharging stimulus becomes, as it were, superposed on the excitement already present. (Compare § 362.) The anterior roots of the spinal nerves supply efferent fibres to — 1. All the voluntary muscles of the trunk and extremities. Every muscle always receives its motor fibres from 5^7'^;'^/ anterior roots (not from a single nerve root). Hence, n'ery root supplies branches to a particular group of muscles {Preyer, P. Bert, Gad). The experiments of Ferrier and Yeo show that stimulation of each of the anterior roots in apes (brachial and lumbosacral plexuses) caused a complex coordinated movement. Section of one root did not cause complete paralysis of these muscles concerned in the coordinated move- ments, although the force of the movement was impaired. These experiments confirm the results of clinical observation on man. The fibres for groups of muscles of different functions {e.g.. for flexors, extensors) arise from special limited areas of the spinal cord. The cervical and lumbar enlargements of the spinal cord are great centres for highly coordinated muscular movements. 2. The anterior roots also supply motor fibres for a number of organs pro- vided with smooth muscular fibres, e. g., the bladder (§ 280), ureter, uterus. [These are the viscero-motor nerves of Gaskell, and from them come also viscero- inhibitory nerves.] 3. Motor fibres for the smooth muscular fibres of the blood vessels, the vaso- motor, vaso-constrictor, or vaso-hypertonic nerves [also accelerator or aug- mentor nerves of the heart]. They run in the sympathetic for a part of their course (§ 371). 4. Inhibitory fibres for the lilood vessels. These are but imperfectly known. They are also called vaso-dilator or vaso-hypotonic nerves (§ 372). [Also inhibitory nerves for the heart, which leave the spinal axis in the vagus.] 5. Secretory fibres for the sweat glands of the skin (§ 289). For a part of their course they run in the sympathetic. 6. The trophic fibres of the tissues (§ 342, I, c). THE SYMPATHETIC NERVE. 649 The posterior roots contain all the sensory nerves of the whole of the skin and the internal tissues, except the front part of the head, face, and the internal part of the head. They also contain the tactile nerves for the areas of the skin already mentioned. Stimuli which discharge reflex movements are conducted to the spinal cord through the posterior roots. The sensory fibres of a mixed nerve trunk supply the cutaneous area, which is moved by those muscles (or which covers those muscles — Preyef) to which the same branch supplies the motor fibres {Schroder van der Kolk). The special distribution of the motor and sensory nerves of the body belongs to anatomy (Figs. 387, 388, 392, 393). 356. THE SYMPATHETIC NERVE.— [Anatomical.— The sympathetic nervous system contains a large number of non-medullated or Remak's fibres, and consists of a series of ganglia lying on each side of the vertebral column and connected to each other by interganglionic fibres. The typical distribution obtains in the thoracic region, where the lateral or vertebral ganglia lie close on the vertebr;e. In front of this is a second series of ganglia, which do not form a double line, but are connected with the former and with each other. They are the prevertebne or collat- eral ganglia, e.g., semilunar, inferior mesenteric, etc., the nerves connecting them with the former being called rami efiferentes. From these fibres proceed to connect them with ganglia lying in or about tissues or organs — the terminal ganglia [Gtiskell).'\ [Each spinal nerve in this region is connected with its corresponding sympathetic ganglion by the ramus communicans, which is formed by fibres both from the anterior and posterior roots of a spinal nerve. It corresponds to the viscer.Tl nerve of the morphologist, and is composed of two parts — a white and a gray ramus. The white ramus is composed entirely of meduUated fibres, and coming from the anterior and posterior roots of a spinal nerve, passes into the lateral and collatenl ganglia. These white rami occur in the dog only from the 2d thoracic to the 2d lumbar nerve {Gaskell). Above and below this the rami are all gray and composed of non-medullated nerve fibres.] [In man the four upper rami communicantes from the four upper cervical nerves all join the superior cervical ganglion (Fig. 386, G g s), the SIh and 6th join the middle cervical, the 7th and 8th the inferior cervical ganglion. The lowest pair of ganglia are generally united by a loop on the front of the first coccygeal vertebra, and they lie in relation with the coccygeal ganglion.] [Cephalic Portion. — As the sympathetic ascends to the head it forms connections with many of the cranial nerves, and there is a free exchange of fibres between these nerves. (The function and significance of these exchanges are referred to under the physiology of the cranial nerves.)] [Dorsal and Abdominal Portion. — Numerous fibres pass from these parts chiefly to the MoraaV and abdominal i'avities.,vj\\tit they form large gangliated plexuses, from which functionally different fibres proceed to the different organs.] [In the dog the 2d, 3d, 4th, and 5th thoracic pass upward into the cervical sympathetic, those in the dorsal region being directed downward from the lateral ganglia to form the splanchnics. The gray non-medullated nerve fibres of each gray ramus are connected with the cells of its ganglion (lateral); the fibres do not go beyond the ganglion, but really run to the corresponding spinal nerve to ramify in the sheaths of the nerves, the connective tissue on the veitebri-e and the dura mater, and perhaps the other spinal membranes; so that, according to Gaskell, no non-medullated nerves leave the central nervous system by the spinal nerve roots. Thus the white rami communicantes alone constitute the rami visceralis of the morphologist, and all the visceral nerves passing out from the central nervous system into the sympathetic system pass out by them alone. All the nerves in the white ramus are of .small calibre (1.8 /t to 2.7 p.) and medullated, while the true motor fibres are much larger (14.4 ,"■ to 19 ,'i). The small while can be traced upward as medullated fibres into the superior cervical ganglion, and in the thorax over the lateral to form the splanchnics into the collateral ganglia, beyond which they cease to be medullated. By the 2d and 3d sacral nerves some fibres of smallest calibre issue to form the nervi erigentes, which pass over and do not com- municate with the lateral ganglia, but enter the hypogastric plexus, whence they send branches upward to the inferior mesenteric plexus and downward to the bladder, rectum, and generative organs. Caskell proposes to call them the pelvic splanchnic nerves.] [In the cervical region there is no white ramus, and the nerve roots contain no nerve fibres of small calibre. But in this region rises the spinal accessory nerve, between the anterior and posterior roots. It contains small and large nerve fibres ; the former pass into the internal division of this nerve and join the ganglion of the trunk of the vagus, while the large motor fibres form its external branch and supply the sterno-mastoid and trapezius muscles.] [All the vasomotor nerves arise in the central nervous system, and they leave the spinal cord as the finest medullated fibres in the anterior roots of all the spinal nerves between the 2d thoracic and 2d lumbar (dog) "along the corresponding ramus visceralis, enter the lateral or main sympa- thetic chain of ganglia, where they become non-medullated, and are thence distributed either directly or after communication with other ganglia" {Gaskelt).'\ ["The vaso-dilator nerves leave the central nervous system among the fine medullated fibres, 650 FUNCTIONS OF THE CERVICAL SYMPATHETIC. which help to form the cervico- cranial and sacral rami viscerales, and pass without altering their character into the distal ganglia" ( Gaskell\.'\ ["The viscero- motor ner\es upon which the peristaltic contraction of the thoracic portion of the oesophagus, stomach, and intestines depends, leave the central nervous system in the outflow of fine mednllated nerves which occurs in the upper part of the cervical region, and pass by way of the rami viscerales of the accessory aud vagus nerves to the ganglion trunci vagi, where they become non-medullated " {^GaskeU).~\ [" The inhibitory nerves of the circular muscles of the alimentary canal and its appendages leave the central nervovis system in the anterior roots, and pass out among the fine medullated fibres of the rami viscerales into the distal ganglia without communication with the proximal ganglia " (^Gaskell)?^ [Structure of a Ganglion. — The structure of the sympathetic nerve fibres and nerve cells has already been described in \ 32 [. On making a section of a sympathetic ganglion, ('.^., the human superior cervical, we observe groups of cells with bundles of nerve fibres — chiefly non- medullated — running between them, and the whole surrounded by a laminated capsule of connective tissue, which sends septa into the ganglion. The nerve cells have many processes, and are, there- fore, multipolar, and each cell is surrounded by a capsule with nuclei on its inner surface (Fig. 335, II). The processes pierce the capsule, and one of them certainly — and perhaps all the processes — are connected with a nerve fibre. Not unfrequenlly yellowish-brown pigment is found in the cell substance. Similar cells have been found in the ophthalmic, sub- maxillary, otic, and sphenopalatine ganglia] Functions. — The following is merely a ^^«ifr«/ summary : — I. Independent functions of the sympathetic are those of certain nerve plexuses which remain after all the nervous connections with the cerebro-spinal branches have been divided. The activities of these plexuses may be influenced ■ — either in the direction of inhibition or stimulation — -through fibres reaching them from the cerebro-spinal nerves. To these belong : — 1. The automatic ganglia of the heart (§ 58). 2. The mesenteric plexus of the intestine (§ 161). 3. The plexuses of the uterus, Fallopian tubes, ureters (also of the blood and lymph vessels). II. Dependent Functions. — Fibres run in the sympathetic, which (like the peripheral nerves) are active only when their connection with the central nervous system is maintained, e. g., the sensory fibres of the splanchnic. Others again convey impulses from the central nervous system to the ga/ig/ia, while the ganglia, in turn, modify the impulses which inhibit or excite the movements of the corre- sponding organs. The following statement is a rhumi of the functions of the sympathetic, according to the ana- tomical arrangement : — A. Cervical Part of the Sympathetic. — i. Pupil-dilating fibres (com- pare Ciliary gang/ion, § 347, I, and Iris, § 39^:). According to Budge, these fibres arise from the spinal cord and run through the upper two dorsal and lowest two cervical nerves into the cervical sympathetic, which conveys them to the head. Section of the cervical sympathetic or its rami communicantes causes contraction of the pupil. (The central origin of these fibres is referred to in § 362, i, and §367- 8.) 2. Motor fibres for Miiller's smooth muscle of the orbit, and partly for the external rectus muscle (§ 348). 3. Vasomotor branches for the outer ear and the side of the face {CI. Ber- nard), tympanum {Prttssak), conjunctiva, iris, choroid, retina {only in part — see Ciliary ganglion, §347, I), for the vessels of the cesophagus, larynx, thyroid gland — fibres for the vessels of the brain and its membranes (Donders and Callcnfels^ ; but, according to Nothnagel, fibres also arise from the cranial nerves which form connections with the carotid plexus. 4. Secretory (trophic) and vasomotor fibres for the salivary glands (§ 145). 5. Sweat-secretory fibres (see § 288, II). 6. .\ccording to Wolferz and Demtschenko, the lachrymal glands receive sym- pathetic secretory fibres (?). SECTION AND STIMULATION OF THE CERVICAL SYMPATHETIC. 651 B. Thoracic and Abdominal Sympathetic. — First of all there is — 1. The sympathetic portion of the cardiac plexus (§ 57, 2), which receives accelerating or augmentor fibres for the heart from the lower cervical and ist thoracic ganglion {CI. Bernard, v. Bezold, Cyan, Schmiedeberg). The fibres arise partly from the sympathetic and partly from the plexus around the vertebral artery \v. Bezold, Bever). (Compare §370.) 2. The cervical sympathetic and the splanchnic contain fibres which, when their central ends are stimulated, excite the cardio-inhibitory system in the me- dulla oblongata (Berns/ein). 3. The cervical sympathetic contains afferent fibres which, when stimulated, excite the vasomotor centre in the medulla oblongata {Auberf). 4. The functions of the splanchnic are referred to in §§164, 175, 276 and 371- 5. The functions of the coeliac and mesenteric plexuses are referred to m §§ 183 and 192. After extirpation of the cceliac ganglion, Lamansky observed temporary disturbance of digestion, undigested food being passed per anum. 6. For the secretory fibres for sweating, see § 289, II. 7. Lastly, the abdominal portion of the sympathetic contains motor and vaso- motor fibres for the spleen, the large intestine (accompanying its arteries), bladder (§ 280), ureters, uterus (running in the hypogastric plexus), vas deferens and vesic- ulse seminales. Stimulation of all of these nerve channels causes increased move- ment of the organs, but it must be remembered that the diminished supply of blood thereby produced also acts as a stimulus (§ 161). Section of these nerves is followed by dilatation of the blood vessels, with subsequent derangement of the circulation, and ultimately of the nutrition. The relation of the suprarenal bodies to the sympathetic is referred to in § 103, IV. The renal plexus is referred to in § 276, while the cavernous plexus is treated of in §436. Pathological. — Considering the numerous connections of the sympathetic, we would naturally suppose that it ofiers an extensive area for pathological changes. It is to be observed that all afifec- lions involvint; the vasomotor system are referred to in ^ 371. The cervical sympathetic is most frequently paralyzed or stimulated 'by traumatic conditions, wounds by bullets or knives, tumors, enlarged lymph glands, aneurisms, inflammation of the apices of the lungs and the adjacent pleurjs, while exostoses of the vertebrje may stimulate it in part or paralyze it in part. The phenomena so produced have been partly analyzed in treating of the cili- ary ganglion (^ 347, I). Stimulation of the cervical sympathetic in man causes dilatation of the pupil (mydriasis spastica), pallor of the face.'and occasionally hyperidrosis or profuse sweating (I 289, 2, and ^ 2S8) ; disturbance of vision for near objects, as the pupil cannot be contracted (see Acfommoitafion')^ and hence the spherical aberration of the lens (§ 39t) must also interfere with vision ; protrusion of the eyeball with widening of the palpebral fissure. Paralysis or section of the cervical sympathetic causes increased fullness of the blood vessels of the side of the head with occasional anidrosis. Contraction of the pupil (myosis paralytica), which undergoes changes in its diameter during accommodation, but not as the effect of the stimulation of light — atropin dilates it slightly. The slit between the eyelids is narrowed, the eyeball retracted and sunk in the orbit, the cornea somewhat flattened, and the consistence of the eyeball diminished. Stimulation of the sympathetic is followed by an increased secrdion of saliva i,\ 145). The above described symp- toms have been occasionally accompanied by unilateral atrophy of the face. [Section of the Cervical Sympathetic. — This experiment is easily done on a rabbit, preferably an albino one. Divide the nerve in the neck, and immedi- ately thereafter (i) the ear and adjoining parts on that side become greatly con- gested with blood, blood vessels appear that were formerly not visible, as a result of the increased quantity of blood in the ear (hyperaemia), there is (2) a rise of the temperature amounting to even 4° to 6° C. {CI. Bernard"). These are the vasomotor changes. (3) The pupil is contracted, the cornea flattened, and there is retraction of the eyeball and consequent narrowing of the palpebral fissure. These are the oculo-pupillary symptoms. Stimulation (electrical) of the peri- pheral end produces the opposite results, — pallor of the ears, owing to contraction of the blood vessels, with consequent fall of temperature ; dilatation of the pupil, bulging of the cornea, protrusion of the eyeball (exophthalmos), and widening 652 COMPARATIVE HISTORICAL. of the palpebral fissure. At the same time, the blood vessels to the salivary glands are contracted, and there is a secretion of thick saliva. The last results are due to the vaso-constrictor and secretory fibres. The vasomotor and oculo-pupillary fibres, although they lie in the same trunk in the neck, do not issue from the cord by the same nerve roots, the latter come out of the cord with the anterior roots of the ist and 2d dorsal nerves (dog), while section of the cord between the 2d and 4th dorsal vertebrae produces the vasomotor changes only. The nasal mucous mem- brane and lachrymal gland are influenced by the sympathetic] [Division of the cervical sympathetic in young t;rou'ing animals results in hypertrophy of the ear, and increaseil growth of the hair on that side [Biddcry \V. S/irlitig).'] [The vagosympathetic nerve (dog) in the neck contains vaso-dilator fibres (really in the sympathetic I for the skin and mucous membianes of that side of the head. Weak stimulation of the central end of the synipatlietic causes dilatation of the blood vessels of these parts. The vaso- dilator fibres of the superior ma)cillary nerve probably come from the same source. The centre for these nerves is in the dorsal region of the cord between the Ist and 5th dorsal vertebr.i?, when the fibres pass out with the rami communicantes to enter the cervical sympathetic (Diis/re and Moral). The vaso-dilator fibres occur in the posterior segment of the ring of Vieussens, and when they are stimulated after section of the 7tli cranial nei-ve, there is a '■ pseudomotor " elTect on the muscles of the cheek and lip (§ 349I.] Irritation in the area of the splanchnic, as occurs occasionally in lead poisoning, is characterized by violent pain (lead colic), inhibition of the intestinal movements (hence, the persistent constipa- tion), slowing of the heart's action, brought about reflexly, just as in Goltz's " tapping" experiment. Irritation in the area of the sensory nerves of the sympathetic may give rise to that condition which is called by Romberg neuralgia hypogastrica, a painful affection of the lower abdominal and sacral regions, hysteralgia, neuralgia testis, which are localized in the plexuses of the sympathetic. In affections of the abdominal sympathclic there may be severe constipation, with diminished or in- creased secretion of the intestinal glands {\ 186). 357. COMPARATIVE— HISTORICAL.— Comparative.— Some of the cranial nerves maybe al^sent, others, again, may be abortive, or exist as branches of other nerves. The facial nerve, which supplies the muscles of expression in man, and is, at the same time, the nerve for facial respiratory movements, diminishes more and more in the lower classes of the vertebrata, /(;W /««;<, with the diminution of the facial muscles. In birds and reptiles it supplies the muscles of the hyoid bone, or the superficial cervical muscles of the nape of the neck. In amphibians (frog) the facial no longer exists as a separate nerve, the nerve which corresponds to it springing from the tri- geminus. In fishes the 5th and 7th nerves form a joint complex nerve. The part corresponding to the facial (also calle 1 ramus opercularis trigemini ) is the chief motor nerve of the muscles of the gill cover, and is, therefore, the respiratory nerve. In the cyclostomata (lamprey) there is an inde- pendent facial. The vagus is present in all vertebrata; in fishes it gives off" a large nerve, the lat- eral nerve of the body (N. lateralis), which runs along each side of the body close to the lateral canal. It is also present ia the tadpole. Its rudimentary representative in man is the auricular branch. In the frog the 9th, loth, and nth arise together from one trunk, and the 7th and 8th from anDthiir. In fishes and amphibia the hypoglossal is the first cervical nerve. In amphioxus the cere- bral and spinal nerves are not disiinct from each other. The spinal nerves are remarkably similar in all classes of the vertebrata. The sympathetic is absent in the cyclostomata, where it is repre- sented by the vagus. Its course is along the vertebral column, where it receives the rami commu- nicantes of the spinal nerves. In the region of the head its connections wdth the 5th and loth nerves are soecially developed. In frogs, and still more so in birds, the number of connections with the cranial nerves increases. Historical. — The vagus and sympathetic were known to the Hippocratic School. According to Erasistratus, all the nerves proceed from the brain and spinal cord. Herophilus was the first to distinguish the nerves from the tendons, which Aristotle confounded with each other. Marianus (So A.D.) recognized seven pairs of cranial nerves. Galen was in possession ot a wide range of im- portant facts in the physiology of the nervous system (§ 140) ; he observed that loss of voice fol- lowed ligature of the recurrent nerves ; and he was acquainted with the accessorius, and the ganglia on the abdominal nerves. The Cauda equina is referred to in the Talmud ; Goiter (1573) prescribed exactly the anterior and posterior spinal nerve roots. Van Helmont (f 1644) st.ates that the peri- pheral motor nerves also give rise to impressions of pain, and Cesalpinus (1571) remarks that inter- ruption of the blood stream makes the parts insensible. Thomas Willis described the chief ganglia (1664). In Des Cartes there is the first indication of reflex movements; Stephen Hales and Robert Whytt showed that the spinal cord was necessary for such acts. Prochaska described the reflex channels [while Marshall Hall established the doctrine of reflex, or, as he called them, " diastal- tic " actions]. Duverney (1761) discovered the ciliary ganglion. Gall traced more carefully the course of the 3d and 6th nerves, and also the spinal nerves into the gray matter. Hitherto only nine nerves of the brain had been enumerated ; Sommerring separated the facial from the auditory nerve, Andersch the 9th, loth, and nth nerves. Physiology of the Nerve Centres. 358. GENERAL. — [The nerve fibres and nerve cells constitute the elements out of which nerve centres are formed, being held together by connective tissue. In the process of evolution groups of nerve cells with connecting fibres are ar- ranged to constitute nervous masses, whereby there is a corresponding integration of function. Thus with structural integration there is a functional integration. When the structure suffers so also does the function, and those parts which are most evolved, as well as those actions which have to be learned by practice, are the first to suffer during the dissolution of the nervous system.] General Functions. — The central organs of the nervous system are in general characterized by the following properties : — 1. They contain nerve cells, which are either arranged in groups in the in- terior of the central organs of the nervous system, or embedded in the peripheral branches of the nerves. [Nerve cells are centres of activity, originate impulses and conduct impulses as well, while nerve fibres are chiefly conductors.] 2. The nerve centres are capable of discharging reflexes, e. g., reflex motor, reflex secretory, and reflex inhibitory acts. 3. The centres may be the seat of automatic excitement, /. e., they may manifest phenomena, without the application of any apparent external stimulus. The energy so liberated may be transferred to act upon other organs. This auto- matic state of excitement or stimulation may be continuous, i. e., may be continued without interruption, when it is called tonic automatic or tonus ; or it may be intermittent, and occur with a certain rhythm {rhythmical automatic). 4. The central organs are trophic centres for the nerves proceeding from them ; they may also perform similar functions for the tissues innervated by them. 5. The physical activities are dependent upon an intact condition of the ganglionic central organs. These various functions are distributed over different centres. As a single momentary stimulus, e. g., an opening induction shock, or a puncture of a transverse section of the spinal cord, may produce a longer tetanus, whilst the same stimulus, if applied to the motor nerves, causes only a single contraction, it seems as if the central nervous system possessed the property of transforming an instantaneous stimulus into a long-continued state of stimulation {R. Marchand). The organs causing continued movement are the ganglionic cells of the anterior horn of the spinal cord [Bir/,-e). [The term " centre " is merely applied to an aggregation of ner\'e cells so related to each other as to subserve a certain function, but inasmuch as these cells are connected to each other and with other cells in many ways, various combinations of them may result; again, we have also to take in account the greater or less resistance in some paths than others, so that the variety of combinations which these cells may subserve is enormous. The.-e cells give off processes which branch, and anastomose with processes from other cells. Thus innumerable ways are opened up to nervous impulses by these combinations, so that in a certain way we may regard a cell as a junction of these conducting fibres, or a " shunt" whereby an impulse may be shunted on to one or other branch in the direction of least resistance, or in the best beaten path as it were, while there may be a " block " in other directions.] 658 THE SPINAL CORD. 359. STRUCTURE OF THE SPINAL CORD.— [The key to the study of the central nervous system is to remember that it begins as an involution of the epiblast, and is original tubular, with a central canal, dilated in the brain end into ventricles. In tiie spinal cord there are three concentric parts: first, the columnar ciliated epithelium, outside this the central gray tube, and covering in all the outer white conducting fibres (Hi/l).'] Structure.— The spinal cord consists of white matter eNternally and gray matter internally. [It is invested l)y membranes, the pin mater, composed of two layers and consisting of connective tissue with blood vessels, being hrmly adherent to the white matter and sending septa into the the centre is the butterfly form of the gray matter surrounded by whil matter. /, posterior, and rt, anterior, horns of the """■"-»"-■■ ■ ^ '^ r...=t..ri.^r m^tc - AR anr^rlnr rnnts nf of the spinal spinal 1 L, L, thela J ......... . P R, posterior . al : P, P, the posterior colu substance of the cord. Both layers dip into the anterior median fissure, and only the inner one into the posterior median groove. The arachnoid \% a more delicate memtirane and non-vascular, while the dura maler is a tough membrane lining the vertebral canal, and forming a theca or protective coat for the cord (J 381).] The gray matter has the form of two crescents )-( placed back to back [or a capital H]> '" which we can distinguish an anterior (a) and a posterior horn (/), a middle part, and gray commissure connecting the two crescents. In the centre of this gray com- missure is a canal — central canal — which runs from the calamus scriptorius downward ; it is lined throughout by a single layer of ciliated cylindrical epithelium [in the fcetus, the cilia not being visible in the adult], and the canal itself is the representative of the embryonal "medullary tube." [The part of the gray commissure in front of this canal is called the anterior, and the part behind, the posterior gxa.y commissure.] [In front of the gray commissure, and between it and the base of the anterior median fissure, are bundles of white nerve fibres passing in a horizontal or oblique direction from the anterior column of one side to the gray matter of the anterior cornu of the opposite side (Fig. 394). These decussating fibres constitute the white commissure.] The white matter surrounds the gray, and is arranged in several columns [anterior, lateial, ami posterior — by the passage of the nerve roots to the cornua]. Along the anterior surface of the cord 654 STRUCTURE OF THE WHITE MATTER. 655 there runs a well-marked fissure, which dips into the cord itself, but does not reach the gray matter, as a mass of white matter — the white commissure — runs from one side of the cord to the other. Between this fissure, known as the anterior median fissure, and the line of exit of the anterior roots of the spinal nerves, lies the anterior column (A); the white matter lying laterally between the origin of the anterior and posterior roots of the spinal nerves is the lateral column (L|, while the white matter lying between the line of origin of the posterior roots and the so-called posterior median fissure is the posterior column (P). [The posterior median fissure is not a real fissure Fig. 396. ""Iti& — -^-^-^ Fig. 395. — Transverse section of the whit I-IG. 396. — Multipolar nerve cells fro cell ; 6, axis cylinder ; c, gray matter matter 01 the spinal cord with connective-tissue septa between the fibn the gray matter of the anterior horn of the spinal cord (ox), u, ncr P C, anterior, lateral and posterior columns : Gr, gray vier's nodes, but provided with the neuro-keratin sheaths of KUhne and Ewald [\ 321), the fibres themselves being chiefly arranged longilittlinally. The nerve fibres of the nerve roots, as well as those that pass from the gray matter into the columns, have a transverse or oblique course. There are also decussating fibres in the anterior or white commissure. [In a transverse section of the white matter of the spinal cord the nerve fibres are of diff^erent sizes, and appear like small circles with a rounded dot in their centre — the axis cylinder; the latter may be stained with carmine or other dye (Fig. 395). They are smallest in the postero-median or Goll's column, and largest in the 656 ARRANGEMENT OF NERVE CELLS. crossed and direct pyramidal tracts, which are motor. The white substance of Schwann, especially in preparations hardened in salts of chromium, often presents the appearance of concentric lines. Fine septa of connective tissue carrying blood vessels lie between groups of the nerve fibres, while here and there between the nerve fibres may be seen branched neuroglia corpuscles. Immediately beneath the pia mater there is a pretty thick layer of neuroglia, which invests the prolongations of the pia into the cord.] [The gray matter ditfers in shape in the different regions of the cord, and so does the gray commissure (Fig. 39S), The latter is thicker and shorter in the cervical than in the dorsal region, while it is very narrow in the lumbar region. '1 he amount of gray matter undergoes a great increase opposite the origins of the large nerves, the increase being most marked opposite the cervical and lumbar enlargements. Ludwig and Woroschilotf constructed a series of curves from measurements by Stilling of the sectional areas of the gray and white matter of the cord, as well as of the several nerve roots. These curves have been arranged in the following convenient form by Schafer, after Woroschiloff (Fig. 397) : — [In the cervical region the lateral white columns are large, the anterior cornu of the gray matter is wide and large, while the posterior cornu is narrow ; Goll's column is marked off by a depression and a prolongation of the pia mater; the cord itself is broadest from side to side. In the dorsal region the gray matter is small in animals, and both cornua are narrow and of nearly equal breadth, while the cord itself is smaller and cylindrical. In it the intermedio lateral and posterior vesicular groups of cells are distinct. They have, probably, relations to viscera. The commissure lies well forward betwten the crescents. In the lumbar region the gray matter is relatively and absolutely greatest, while the white lateral columns are small, the central canal in tile commissure being nearly in the middle of the cord. In the conus medullans the gray matter makes up the great mass of it, with a few white fibres externally (Kig. 39S).] 1 he anterior cornu of the gray matter is shorter and broader, and does not reach so near to the surface as the posterior; moreover, each anterior nerve root arises from it by several bundles; it Contains several groups of large multipolar ganglionic cells (Fig. 396); the posterior cornu is more pointed, longer and narrower, and reaches nearer to the surface, the posterior root arising by a single bundle at the postero-lateral fissure ; while the cornu itself contains a few fusiform nerve cells, and is covered by the substantia gelatinosa of Rolando, which is merely an accumulation of neuroglia. [The outer margin of the gray matter near its middle is not so sharply defined from the white matter as else- where ; and, in fact, a kind of anastamosis of the gray matter projects into the lateral column, especially in the cervical region, constituting \.\\t processus reticttlaris (Fig 399, /)■] [Arrangement of Nerve Cells. — The nerve cells are arranged in four groups, forming columns more or less continuous. There are those of the anterior and posterior pinal curd in dif- horns, those of the lateral column (intermedio-lateral), igfi t e iiiidi ic o ^jjj ji^g po^terior vesicular column of Clarke. The ante- rior and posterior groups exist as continuous columns along the entire cord. The cells of the anterior horn being very large (67 to 135 (J-), while the fusifomi cells of the posterior horn are iS !>■ in diameter. Those of the lateral column are distinct, except in the lumbar and cervical enlarge- ments, where they blend with the anterior hom. The column of Clarke (cells 40 to 90 p-) is dis- continued, and is limited to (l) the thoracic region, (2) cervicocranial region, (3) sacral region, being most conspicuous in ( i ) ( Gaskell), where it corresponds absolutely to the outflow of visceral nerves. In the sacral region it corresponds to the " sacral nucleus of Stilling," while in the cervical region it begins in the dog at the 2d cervical nerve, forming the cervical nucleus, being continued above into the nuclei of the vagus and glosso-pharyngeal nerves. The cells of this column give rise to small mcdullated nerve fibres or the leucenteric fibres of Gaskell.] The multipolar ganglion cells are largest, and arranged in groups in the anterior horns of the gray matter (Fig. 394 — " motor ganglionic cells") ; while smaller spindled-shaped (" sensory ") cells occur in much smaller numbers m the gray mailer of the posterior horn. ferent regit enlargf medull F, at c al; B A, tfiroiigfi ttie dorsal: C, tlie lurab: ; D, upper part of the cont E, at ttie 5th sacral vertebra c: A, B, C, enlarged twice , /, posterit NEUROGLIA. 657 [In a longitudinal section of the cord (Fig. 400) these cells are seen to be arranged in columns, the large multipolar cells in the anterior horn (»;) ; at the same time the longitudinal direction of the nerve fibres in the anterior {a) and posterior white columns (<"), the horizontal direction of the fibres of the anterior and posterior nerve roots {/> andy).l The gray matter contains an exceedingly delicate fibrous network of the finest nerve fibrils {Gerlach), which is produced by the repeated division of the protoplasmic processes of the multi- polar ganglionic cells. MeduUated nerve fibres traverse and divide in the gray matter and become non-medullated ; some of them merely pass through the gray matter of the non-medullated fibres and terminate in Gerlach's network. Fibres pass from the gray matter of one side to that of the other through the commissures in front of and behind the central canal. Gerlach's Theory. — According to Gerlach. the connection of the fibres and cells is as follows : The fibres of the anterior root proceed directly to the ganglionic cells of the anterior horn, with which they form direct communications by means of the unbranched axial cylinder processes (Fig. 401, 2;). The gray network of protoplasmic processes, produced by the repeated branchings of the fibres of these cells, gives origin to broad f\\>xss. A part of the latter (the medinn bundle) passes section of the spinal cord (I P., anterior and posterior media ; ; J, gray commissure : /, reticular format lateral, and posterior column :11s of the anterior horn ; d, posterioi lOt bundles ; h, posterior root bundle: through the anterior white commissure to the other side, and then ascends in the anterior column of the opposite side. Other fibres (the lateral h\inA\e) pass into the lateral column of the same side, and ascend in it as far as the decussation of the pyramids, where they cross in the medulla to the other side. The fibres of (ht postfrior root enter the posterior horn, and, after dividing, terminate in the nervous protoplasmic network of the gray matter. By means of this network they are con- nected indirectly with the ganglionic cells of the posterior horn, which are said not to have an axial cylinder process. The gray network, which connects the ganglia of the anterior and posterior horns with each other, also sends fibres, which pass to the other side of the cord in front of and behind the central canal. They then take a backward course, to ascend partly in the posterior horns and partly in the lateral columns. Neuroglia. — The connective tissue of the spinal cord arises in part from the pia mater and passes only into the white matter, carrying with it blood vessels, and forming septa, which separate the nerve fibres into bundles. We must distinguish from the ordinary connective tissue that special form in the gray matter to which Virchow gave the name of neuroglia, which is the proper sustentacular 42 658 BLOOD VESSELS OF THE SPINAL COKD. tissue. It is composed of a fine network, which consists of round and large branched cells embedded in a completely homogeneous transparent ground substance. The central canal is surrounded with a denser layer of this tissue, known as the " central ependyma." The neuroglia is also abundant on the sides and apex of the posterior horns, where it is called the gelatinous substance of Ro- Fii;. 400, Fig. 40ir , |IWi^i'[^^f^^€ ;,:ii...,yC— '"d" m Fig. 400. — Longiiudii 1 of the human soinal cord, a, anterior, tr, posterior, (/, lateral white cohimns ; />, ;/, horizontal (pyramidal) fibres passing to ;«, cells of anterior cornu ; «, oblique fibres of posterior root FiG. 401. — Multipolar nerve cell, from the anterior horn of the spinal cord. 2, axis cylinder process ; y, branched processes. lando. Similar neurolgia also occurs in the brain. On the surface of the central nervous system, and in the eelatinous substance, is, in addition, a fine network of neurokeratin (| 321). [Blood Vessels. — The anterior median artery gives off branches, which dip into the fissure of the same name, pass to its base, and, after perforating the anterior commissure, divide into two branches, one for each mass of gray matter, and each branch in turn splits into three, which supply Fig. 402. Fig. 403. Fig. 402. — Injected bl i vessels of the spi tbe 3d dorsal nerve. The black pa crossed, pyramidal tracts : ^, anterio e and/, mixed lateral paths ; h, dire cord. Fig. 403. — Scheme of the ; the gray matter, z/, anterior, t tlumn groimd bundle; cr, GoU's erebellar tracts. mducting paths in the spinal cord at Tc, posterior, root; a, direct, and^, olumn ; d, postero-external column ; part of the interior, median, and posterior gray matter. The posterior root artery enters the gray m.itter along the course of the posterior nerve roots. Some branches also pass from the pia mater into the substance of the cord, and are known as the antero- and median-lateral branches, while others dip in near GoU's column, and another in the postero-external column. The large central flechsig's systems of conducting fibres. 659 artery supplies the gray matter. The general result is that the gray matter is much more vascular than the white, as is shown in Fig. 402. Adamkiewicz has given a most minute description of the blood vessels of the spinal cord. Some small vessels come from the pia and send branches to the white matter, and unbranched arteries to the gray matter, where they form a capillary plexus. The blood vessels are surrounded by perivascular lymph spaces (//«).] [With regard to the blood vessels supplying the cord as a whole, Moxon has pointed out that, owing to the cord not being as long as the vertebral canal, the lower nerves have to run down within the vertebral canal before they emerge from the appropriate inter-vertebral foramina. As reenforcing arteries enter the cord along the course of these nerves, necessarily the branches entering along the course of the lumbar and lower dorsal nerves are long, and this, together with their small size, offers considerable resistance to the blood stream. Hence, perhaps, why the lower part of the cord is so apt to be atfected by various pathological conditions.] [Functions of the Spinal Cord. — ( i) It is a great conducting medium, conducting impulses upward and downward, and within itself from side to side, (2) the great reflex centre, or rather series of so-called centres ; (3) impulses originate within it.] Conducting Systems. — The whole of the longitudinal fibres of the spinal cord may be arranged systematically in special bundles, according to their func- tion. [Methods. — The course of the fibres and their division into so-called systems has been ascer- tained partly by anatomical and embryological, partly by physiological and pathological means, .-\part from exjierimental methods, such as dividing one column of the cord and observing the result<, we have the following methods of investigation : (l) Tiirck found that injury or disease of certain parts of the brain was followed by a degeneration downward, or secondary descending degeneration of certain of the nen'e fibres connected with the seat of injury, ; c, tliey were sepa- rated from their trophic centres and underwent degeneration. (2) P. Schieferdecker found also, after section of the cord, that above and below the level of the section, certain definite tracts of white matter underwent degeneration [thus showing that certain tracts had their trophic centre below ; this constitutes secondary ascending degeneration]. [(3) Gudden's Method. — He showed, as regards (he brain, that excision of a sense organ in a young growing animal was followed by atrophy of the nerve fibres and some other parts connected with it. Thus the optic nerve and anterior corpora quadrigemina atrophy after excision of the eyeball in young rabbits.] (4) Embryological. — Flechsig showed that the fibres of the cord [and the brain also | during development became coz'ei-ed with myelin at different periods, those fibres become medullated latest which had the longest course. In this way he mapped out the following system : — Flechsig's System of Fibres. — i. In the anterior column lie (a) the un- crossed, anterior, or direct pyramidal tract ; and external to it is {b') the anterior ground bundle, or anterior radicular zone (Fig. 403). 2. In the posterior column he distinguishes (r) Goll's column, or the pos- tero-median (postero-internal) column ; and {d ) Burdach's funiculus cuneatus, or the posterior radicular zone, or the postero-external column. 3. In the lateral column are {e) the anterior, and (/) the lateral mixed Y>a.ths, (g) the lateral or crossed pyramidal U&ct, and (h) the direct cerebellar ix'xc^.. All the impulses from the central convolutions [motor areas] of the cerebrum, by means of which voluntary movements are executed, are conducted by the pyra- midal tracts a and ^ (| 365). The fibres in these tracts descend from the cen- tral convolutions [/. c. , the motor areas], pass through the white matter of the cerebrum, converging like the rays of a fan to the internal capsule, where they lie in the knee and anterior two-thirds of its posterior segment (the fibres for the face at the knee, and behind in order those for the arm and leg), they then enter the middle third of the crusta, pass through the pons into the anterior pyramids of the medulla oblongata, where the great mass crosses over to the lateral column of the opposite side of the cord (crossed pyramidal tract), a small part descending in the cord on the same side as the antero-median tract (direct pyramidal tract, a). In the cord these fibres are probably connected with large multipolar nerve cells in the anterior cornu, and from the latter the motor nerves proceed to the muscles]. The direct cerebellar tract, h, connects the cerebellum directly by as- cending fibres, which proceed through the restiform body from Clarke's cohniin of nerve cells in the gray matter. As fibres from the posterior roots also enter 660 SECONDARY DEGENERATION AND TROPHIC CENTRES. the latter, it follows that h connects the posterior nerve roots of the trunks (but not of the extremities) with the cerebellum ; /', ^, /(and ? a small part of d) rep- resents the channels which connect the gray matter of the spinal cord and that of the medulla oblongata; they represent the channels for reflex effects, and they also contain those fibres which are the direct continuation of the anterior spinal nerve roots, which enter the cord at different levels and penetrate into the gray matter. In e and/there are some sensory paths. Lastly, c unites the posterior roots with the gray nuclei of the funiculi graciles of the medulla oblongata ; d connects some of the posterior nerve roots through the restiform body with the vermiform pro- cess of the cerebellum (^Flechsig). The direction of conduction in the posterior columns, which are continuations of some of the fibres of the posterior roots, is upward, as part of them degenerates upward after section of the posterior root. Of the fibres of each posterior root, some pass directly into the posterior horn, another part ascends in the posterior column of the same side, and gradually, as it ascends, it comes nearer the posterior median fissure. Some of these fibres enter the gray matter of the posterior horn at a higher level. The fibres of the posterior Fig. 404. d 2 Transverse section of the spinal cord showing the I, i' (CPTJ, region of the crossed pyramidal ti column ; LC, lateral column {B. Bramivell). 1 tracts. AR, anterior, TR, posterior root : :t pyramidal tract; PEC, pustero-external columns run upward only as far as the decussation of the pyramids, where they seem to end, or at least form connections with the nerve cells of the funiculi gra- ciles [clava], and cuneati [triangular nucleus]. Further, the transverse sectional area of the direct and crossed pyramidal tracts [a and^i-), the lateral cerebellar tract (/;), and Goll's column (r) gradually diminish from above downward; they serve to connect intracranial central parts with the ganglionic centres distributed along the spinal cord. The anterior root bundle {^b), the funiculus cuneatus ((/), and the anterior mixed lateral tracts (£') vary in diameter at different parts of the cord, corresponding to the number of nerve roots. It has been concluded from this that these tracts serve to connect the gray matter at different levels in the cordwitli each other, and ultimately with the medulla oblongata, so that they do not pass directly to the higher parts of the brain (Fig. 397). Nutritive Centres of the Conducting Paths. — Tiirck observed that the destruction of certain parts of the brain caused a secondary degeneration of certain parts of the cord, corresponding to the parts called pyramidal tracts hy Fleschig (Fig. 404). P. Schieferdecker found the same effects heloui where he divided the spinal cord in a dog. Hence it is concluded that the nutritive or trophic centre of the pyramidal tracts lies in the cerebrum. The trophic centre for REFLEX SPASMS. 661 the fibres of the anterior root lies in the multipolar nerve cells of the anterior cornu of the gray matter of the cord. After section of the spinal cord, GoU's column and the direct cerebellar tracts degenerate upward. The nutritive centre of the latter is very probably in the nerve cells of Clarke's column, and that of the former perhaps in the spinal ganglion of the posterior root. Those fibres of the spinal cord which do not degenerate after section of the cord, especially numer- ous in the lateral and anterior columns {Schieferdecker, Singer), are commissural in function, connecting ganglionic cells with each other, and are, therefore, pro- vided with a trophic centre at both ends. Time of Development. — With regard to the time of development of the individual systems, Flechsig finds that the first formed paths are those between the periphery and the central gray matter, especially the nerve roots, i. e., they are the first to be covered with the myelin. Then fibres which connect the gray matter at different levels are formed — the fibres which connect the gray matter of the cord with the cerel)ellum, and also the former with the tegmentum of the cerebral peduncle. At last the fibres which connect the ganglia of the pedunculus cerebri, and perhaps also the gray matter of the cortex cerebri with the gray matter of the cord are formed. In cases of anencephalousfcetuses, /. e., where the cerebrum is absent, neither the pyramidal tracts nor the pyramids are developed. In the brain before birth, medullated nerve fibres are formed in the paracentral, central and occipital convolutions, and in the island of Reil, and last of all in the frontal convolutions ( Tiiczek). 360. SPINAL REFLEXES. — By the term reflex movement is meant a movement caused by the stimulation of an afferent (sensory) nerve. The stimulus, on being applied to an afferent Fig. 405. Fig. 406. Fig. 405. — Scheme of a ref Fig. 406- — Section of a sp surface ; M, muscle ; S, sk S, skin ; M, muscle ; N, nerve cell, with of, afferent, anii e/, efferent fibres, segment, showing a unilateral and crossed reflex act. A, anterior, and P, posterior G, ganglion. nerve, sets up a state of excitement (nervous impulse) in that nerve, which state of excitement is transmitted or conducted in a i-<'«/>-;)»^/a/ direction along the nerve to the centre (spinal cord in this case), where the nerve cells represent the nerve centre ; in the centre, the impulse is transferred to the motor, efferent or centrifugal c\\3.wnt\. Three factors, therefore, are essential for a reflex motor act — a centripetal or afferent fibre, a transferring centre, a centrifugal or efl^erent fibre ; these together constitute a reflex arc (Fig. 405). In a purely reflex act, all voluntary activity is ex- cluded. Reflex movements may be divided into the three following groups : — I. The simple or partial reflexes, which are characterized by the fact that stimulation of a sensory area discharges movement in one muscle only, or, at least, in one limited group of muscles. Examples : A blow upon the knee causes a contraction in the quadriceps extensor cruris ; contact with the conjunctiva causes closure of the eyelids. In the former case the afferent channels arise in the tendon of the quadriceps, and the efferent channels lie in the nerve which supplies the quad- riceps; in the latter case the afferent nerve is the 5th and the efferent the 7th cranial nerve. In the former case the centre is in the lumbar region of the cord ; in the latter, in the gray matter of the medulla oblongata. II. The Extensive Incoordinate Reflexes, or Reflex Spasms. — These movements occur in the form of clonic or tetanic contractions; individual groups of muscles, or all the muscles of the body, may be implicated. Causes : K reflex spasm depends upon a double cause — {a) Either the gray matter or the spinal cord is in a condition oi exalted excitability , so that the nervous impulse, after having reached 662 SUMMATION OF STIMULI AND PFLUGER S LAW. Fig, 407. the centre, is easily transferred to the neigh- boring centres. This excessive excitability is produced by certain poisons, more espe- cially by strychnin, brucia, caffein {Aubert), atropin, nicotin, carbolic acid, etc. The slightest touch applied to an animal poi- soned with strychnin is sufficient to throw the animal at once into spasms. Pathologi- cal conditions may cause a similar result ; thus, there is excessive excitability in hydro- phobia and tetanus. On the other hand, the central organ may be in such a condi- tion that extensive reflexes cannot take place ; thus, in the condition of apnoea, the spasms that occur in poisoning with strychnin do not take place (_/. Roserithal and Leiibe, Uspensky), and the same result is brought about by passive artificial respi- ratory movements {v. Ebner — § 361, 3). The performance of other passive periodic movements in various parts of the body also produces a similar condition (Bitchheini). If the spinal cord be cooled very consider- ably, reflex spasms may not occur {Ktanie). (b) Extensive reflex movements may also take place when the discharging stimulus is very strong. Examples of this condi- tion occur m man; thus, intense neuralgia may be accompanied by extensive spasmodic movements. [Fig. 407 shows the mechanism of simple and comple-K reflex movements. Suppose the skin to be stimulated at P, an impulse is sent to A, and from it to a muscle, I, on the same side, resulting in a unilateral simple reflex movement. The resistance being less m this direction than in the other channels. If the impulse be stronger, or the transverse resistance in the cord diminished, the impulse may pass to B, theijce to 2, resulting in a symmetrical reflex movement on both sides. But if a very strong impulse reaches the cord, or if the excitability of the gray matter be increased, e. g., by strychnin, the resistance to the dift'usion of the impulse is diminished, and it passes upward to C and 1), resulting in more complex movements; thus, there is irradiation — or it may even affect the centres in the medulla oblongata, E, giving rise to general convulsive movements.] Summation of Stimuli. — By this term is meant that a single weak stimulus, which in itself is incapable of discharging a reflex act, may, if repeated sufficiently often, produce this act. The single impulses are conducted to the spinal cord, in which the process of "summation " takes place. According to J. Rosenthal, 3 feeble stimuli per second are capable of producing this effect, although 16 stimuli per second are most effective. On increasing the number of stimuli per second, no further increase of the reflex act is possible. Other observers (^Stir- ling, Ward) have found that stimuli, such as induction shocks, are active within much wider limits, e.g., from 0.05 to 0.4 second interval. W. Stirling has shown that it is extremely probable that all reflex acts are due to the repetition of impulses in the nerve centres. [Strychnin interferes with the summation of stimuli, but the reflex excitability is so greatly exalted that a minimal stimulus is at the same time a maximal one.] Pfliiger's Law of Reflex Actions. — (i) The reflex movement occurs on the same side on which the sensory nerve is stimulated, while only those muscles contract whose nerves arise from the same segment of the spinal cord. (2) If the reflex occurs on the othet- side, only the corresponding muscles contract. (3) If the contractions be unequal upon the two sides, then the most vigorous contractions always occur on the side which is stimulated. (4) If the reflex excitement extends to GOLTZ'S CROAKING EXPERIMENT. 663 other motor nerves, those nerves are always affected which lie in the direction of the medulla oblongata. Lastly, all the muscles of the body may lie thrown into contraction. Crossed Reflexes. — They are cvceptions to these rules. If the region of the eye be irritated in a frog whose cerebrum is removed, there is frequently a reflex contraction in the hind limb of the opposite side [Liic/isinger, Langendorffy In beheaded iritons and tortoises, and in deeply-narcotized dogs and cats, tickling one fore limb is frequently followed by a movement of the hind limb of the opposite side [Luc/isinger). This phenomenon is called a "crossed reflex" (Fig. 406). If the spinal cord be divided along the middle line throughout its entire extent, then, of course, the reflexes are confined to one side only (Schiff). Extensor Tetanus. — General spasms usually manifest themselves as "extensor tetanus," because the extensors overcome the flexor muscles. Nerves which arise from the medulla oblongata may be excited through the stimulation of distant afi'erent nerves, without general spasms being produced. Strychnin is the most powerful reflex-producing poison we possess, and it acts upon the gray matter of the spinal cord. [An animal poisoned with strychnin exhibits tetanic spasms on the appli- cation of the slightest stimulus. \\\ the muscles become rigid, but the extensors overcome the flexors.] If the heart of a frog be ligatured, and the poison alterward applied directly to the spinal cord, reflex spasms are produced, proving that strychnin acts upon the spinal cord. During the spasm the heart is arrested in diastole, owing to the stimulation of the vagus, while the arterial blood pressure is greatly increased, owing to stimulation of the central vasomotor centres of the medulla oblongata and spinal cord. Mammals may die from asphyxia during the attack ; still, after large doses, death may occur, owing to paralysis of the spinal cord, due to the frequently-recurring spasms. Fowls are unaffected by comparatively large doses. [We can prove that strychnin docs not produce spa.-.ms by acting on the brain, muscle or nerve. Destroy the brain of a frog, divide one sciatic nerve high up, and inject a small dose of strychnin into the dorsal lymph sack; in a few minutes all the muscles of the body, except those supplied by the divided nerve, will be in spasms, showing that, although the poisoned blood has circulated in the nerves and muscles of the leg, it does not act on them. Destroy the spinal cord, and the spasms cease at once.] Other Poisons. — Chlorojorm diminishes the reflex excitability by acting upon the centre, and a similar effect is produced by picrotoxin, morphia, narcotin, thebain, aconitin, quinine, hydrocyanic acid. [W. .Stirling finds that chloral, potassic bromide and chloride, ammonium chloride, but not sodium chloride, greatly diminish the reflex excitability. Nicotin increases it in Uog%\fyeusbeig) ] A constant current of electricity passed longitudmally through the cord diminishes the reflexes [A'antf), especially if the direction of the current is from above downward (Legros and Onimus, Uspensky'). III. Extensive coordinated reflexes are due to stimulation of a sensory nerve, causing the discharge of complicated reflex movements in whole groups of different muscles, the movements being "purposive" in character, i. e., as if they were intended for a particular purpose. Methods. — The experiments are made upon cold-blooded animals (decapitated or pithed frogs, tortoises, or eels), or upon mammals. In the latter, artificial respiration is kept up, and the lour arteries going to the head are ligatured, in order to eliminate the action of the brain \Sig. Mayer, Luchsinger). The reflexes of the lower part of the spinal cord may be studied on animals ^or men), in cases where the spinal cord is divided transversely in the upper dorsal region. In such cases some time must elapse m order that the primary effect of the lesion (the so-called shock), which usually causes a diminution of the reflexes, may pass off. Very young mammals exhibit reflexes lor a considerable time after they are beheaded. Examples. — i. The protective movements of pithed or decapitated frogs. [If a drop of a dilute acid be applied to the skin of such a frog, immediately it strives to get rid of the offending body, and it generally succeeds in doing so.] Similarly, it kicks against any fixed body pushed against it. These movements are so purposive in their character, and the actions of groups of muscles are so adjusted to perform a particular act, that Pfliiger regarded them as directed by and due to "consciousness of the spinal cord." If a flame be applied to the side or part of the body of an eel, the body is moved away from the flame. The tail of a decapitated triton, tortoise, newt, eel, or snake is directed toward a gentle stimulus, but if a violent stimulus is used, it is directed away from it {Luchsinger). 2. Goltz's Croaking Experiment. — .\ pithed (male) frog, i.e., one with its cerebral lobes alone removed (^or one with its eyes or ears destroyed — Langendorff ), croaks every time the skin of its back or flanks is gently stroked. [Some male frogs, when held up by the finger and thumb immediately behind the fore legs, croak every time gentle pressure is made on their flank.] 664 REFLEX TIME AND INHIBITION OF REFLEXES. 3. Goltz's " Embrace Experiment."— During the breeding season, in spring, the part of the body of the male frog, between the skull and the fourth vertebra, embraces every rigid object which is brought into contact with, and gently stimulates, the skin over the sternum. 4. In mammals (dogs) the following reflex acts are performed by the posterior part of the spinal cord, even after it is separated from the rest of the cord : Scratching with the hind feet a part of the skin which has been tickled (just as in intact animals) ; the movements necessary for emptying the bladder and for deffecation, as well as those necessary for erection ; the movements necessary for parturition {Goltz, Freusberg and Gergens). Coordinated movements do not, as a rule, occur simultaneously in portions of the spinal cord lying widely apart after removal of the medulla oblongata. According to Ludwig and Owsjannikow, the medulla oblongata, perhaps, contains a reflex organ of a higher order, which forms, as it were, a centre for combining, through the medium of the nerve fibres, the various reflex provinces in the spinal cord. 5. Coordinated reflexes may occur in man during sleep, and during patho- logical comatose conditions. Most of the movements which we perform while we are awake, and which we execute uncon- sciously or even when our psychical activities are concentrated upon some other object — really belong to the category of coordinated reflexes. Many complicated motor acts must first be learned g_ cr,^ dancing, skating, riding, walking — before unconscious harmonious coordinated reflexes can again be discharged. The coordinated reflex movements of coughing, sneezing, and vomiting depend upon the spinal cord, together with the medulla oblongata. The following facts are also important : — 1. Reflexes are more easily and more completely discharged when the specific end organ of the afferent nerve is stimulated than when the trunk of the nerve is stimulated in its course {Marshall Hall, i8j~). 2. A stronger stimulus is required to discharge a reflex movement than for the direct stimulation of motor nerves. 3. A movement produced reflexly is of shorter duration than the corresponding movement executed voluntarily. Further, the occurrence of the movement after the moment of stimulation is distinctly delayed. In the frog, a period nearly twelve times as long elapses before the occurrence of the contraction than is occupied in the transmission of the impulse in the sensory and motor nerves {Helmholtz, 18^4). Thus, the spinal cord offers resistance to the transmission of impulses through it. The term "reflex time " is applied lo the time necessary for transferring the impulse from the afferent fibre to the nerve cells of the cord, and from them to the efferent fibre. In the frog it is equal to o.ooS to 0.015 second. The time, however, is increased by almost one-third if the impulse pass to the other side of the cord, or if it pass along the cord, e. g., from the sensory nerves of the anterior extremity to the motor roots of the posterior limb. Heat diminishes the reflex time and increases the reflex excitability. Lowering the temperature (winter frogs), as well as the reflex ex- citing poisons already mentioned, lengthen the reflex lime, while the reflex excitability is simulta- neously increased. Conversely, the reflex time diminishes as the strength of the stimulus increases, and it may even become of minimal duration (^J. Rosenthal). The reflex time is determined by ascertaining the moment at which the sensory nerve is stimulated, and the subsequent contraction occurs. Deduct from this the time of latent stimulation (| 298, 1), and the time necessary for the conduction of the impulse (§ 298) in the afferent and efferent nerves {v. Helmholtz, J. Rosenthal, E.xner, 1 Fundi). [Influence of Poisons. — The latent period and reflex time are influenced by a large number of conditions. In a research as yet unpubhshed, W. Stirling finds that the latent period may re- main nearly constant in a pithed frog for nearly two days, when tested by Tiirck's method. Sodic chloride does not influence the time, nor does sodic bromide or iodide. Potassic chloride, however, lengthens it enormously, or even abolishes reflex action after a very short time, and so do potassic bromide, ammonium chloride and bromide, chloral and croton-chloral. The lithia salts also lengthen the reflex time, or abohsh the reflex act after a time.] 361. INHIBITION OF THE REFLEXES.— Within the body there are mechanisms which can suppress or iiihihit the discharge of reflexes, and they may therefore be termed mechanisms inhibiting the reflexes. These are : — EXAMPLES AND NATURE OF INHIBITION. 665 1. Voluntary Inhibition. — Reflexes may be inhibited voluntarily, both in the region of the spinal cord and brain. Examples : Keeping the eyelids open when the eyeball is touched ; arrest of movement when the skin is tickled. We must observe, however, that the suppression of reflexes is possible only up to a certain point. If the stimulus be strong, and repeated with sufficient frequency, the reflex impulse ultimately overcomes the voluntary effort. It is impossible to suppress those reflex movements which cannot at any time be performed volun- tarily. Thus, erection, ejaculation, parturition, and the movements of the iris, are neither direct voluntary acts, nor can they, when they are excited refle.xly, be suppressed by the will. 2. Setschenow's inhibitory centre is another cerebral apparatus, which in the frog is placed in the optic lobes. If the optic lobes be separated from the rest of tlie brain and spinal cord by a section made below it, the reflex excitability is increased. If the optic lobes be stimulated with a crystal of common salt or blood, the reflex movements are suppressed. The same results obtain when only one side is operated on. Similar organs are supposed to be present in the corpora quadrigemina and medulla oblongata of the higher vertebrates. [Quinine greatly diminishes the reflex excitability in the frog, but if the medulla oblongata be divided, ihe reflex excitability of the cord is restored. The depression is ascribed by Chaperon to the action of the quinine on Setschenow's centres.] 3. Strong stimulation of a sensory nerve inhibits reflex movements. The reflex does not take place if an afferent nerve be stimulated very powerfully (Goltz, Lni'isson,A. Fick,amt Erknmeyer). Examples: Suppressing a sneeze by friction of the nose [compressing the skin of the nose over the exit of the nasal nerve] ; suppression of the movements produced by tickling, by biting the tongue. Very violent stimulation may even suppress the coordinated reflex movements usually controlled by voluntary impulses. Violent pain of the abdom- inal organs (intestine, uterus, kidneys, bladder, or liver) may prevent a person from walking or even from standing. To the same category belongs the fact that persons fall down when internal organs richly supplied with nerves are injured, there being neither injury of the motor nerves nor loss of blood to account for the phenomenon. It is important to note that in the suppression of reflexes, antagonistic muscles are often thrown into action, whether voluntarily or by the stimulaion of sensory nerves, /.^., reflexly. In some cases, in order to cause suppression of the reflex, it appears to be suflicient to direct our attention to the execution of such a complicated reflex act. 'thus, some persons cannot sneeze when they think intently upon this act itself (ZJrtrrc/w). The voluntary impulse rapidly reaches the reflex centre, and begins to influence it so that the normal course of the reflex stimulation, due to an impulse from the peripher\', is interfered with i^Sihlosser'). [Nature of Inhibition. — The foregoing view assumes the existence of inhibitory centres, but it is important to point out that it has been attempted to explain this phenomenon without postulating the existence of inhibitory centres. During inhibition the function of an organ is restrained — dur- ing paralysis it is abolished, so that there is a sharp distinction between the two conditions. The analogy between inhibitory phenomena and the effects of interference of waves of light or sound has been pointed out by Bernard and Romanes, while Lauder Brunton has shown good reason for placing the question on a physical basis, and indicating that inhibition is not dependent on the ex- istence of special inhibitory centres, but that stimulation and inhibition are different phases of excitement, the two terms being relative conditions depending on the length of the path along which the impulse has to travel and the rate of its transmission. Brunton points out that the known facts are more consistent with an hypothesis of the interference of waves, one with another, than that there are inhibitory centres for every so-called inhibitory act in the body (see p. 614).] [Some drugs affect the reflex excitability directly by acting on the spinal cord, ^.(.'., meihylconine, but other drugs may produce the same result indirectly by affecting the heart and the blood supply to the cord. If the abdominal aorta of a rabbit be compressed for a few minutes to cut off the supply of blood to the cord and lower limbs, temporary paraplegia is produced.] If frogs be asphyxiated in air deprived of all its (J, the brain and spinal cord become completely unexcitable, and can no longer discharge reflex acts. The motor nerves and the muscles, however, suffer very little, and may retain their excitability for many days [Auliert). 666 THE SUPERFICIAL KEFLEXES. Tiirck's method of testing the reflex excitability of a frog is the following : A frog IS pithed, and after it has recovered from the shock its foot is dipped into dilute sulphuric acid [^2 per 1000]. The time which elapses between the leg being dipped in and the moment it is withdrawn is noted. [The time may be estimated by means of a metronome, or the movements may be inscribed upon a recording surface {Baxt). The time which elapses is known as the " period of latent stim- ulation."] This time is greatly prolonged after the optic lobes have been stimulated with a crystal of common salt or blood, or after the stimulation of a sensory nerve. Setschenow distinguished tactile reflexes, which are discharged by stimulation of the nerves of touch; and pathic, which are due to stimulation of ji-Kiorj' (patn-conducting) fibres. He and Paschutin suppose that the tactile reflexes are suppressed by voluntary impulses, and the pathic by the centre in the optic lobes. Theory of Reflex Movements. — The following theory has been propounded to account for the phenomena already described : It is assumed that the afferent fibre witliin the gray matter of the spinal cord joins one or more nerve cells, and thus is placed in communication in all directions with the network of fibres in the gray substance. Any impulse reaching the gray matter of the cord has to overcome considerable resistance. The least resistance lies in the direction of those efferent fibres which emerge in the same plane and upon the same side as the entering fibre. Thus the feeblest stimulus gives rise to a simple reflex, which generally is merely a simple protective move- ment for the part of the skin which is stimulated. Still greater resistance is opposed in the direction of other motor ganglia. If the reflex impulse is to pass to these ganglia, either the discharging stimulus must be considerably increased, or the resistance within the connections of the ganglia of the giay matter must be diminished. The latter condition is produced by the action of the above- named poisons, as well as during general increased nervous excitability (hysteria, nervousness). 1 bus, extensive reflex spasms may be produced either by increasing the stimulus or by diminishing the resistance to conduction in the spinal cord. Those conditions which render the occurrence of reflexes more difficult, or abolish them altogether, must be regarded as increasing the resistance in the reflex arc in the cord. The action of the reflex inhibitory mechanism may be viewed in a similar manner. The fibres of the reflex arc must have a connection with the reflex inhibitory paths ; we must assume that equally by the reflex inhibitory stimulation resistance is introduced into the reflex arc. The explanation of extensive coordinated movements is accompanied with difliculties. It is assumed, that by use and also by heredity, those ganglionic cells which are the first to receive the impulse, are placed in the path of least resistance in connection with those cells which transfer the impulse to the groups of muscles, whose contraction, resulting in a coordinated purposive movement, pre- vents the body or the limb from being affected by any injurious influences. Pathological. — Anomalies of reflex activity afford an important field to the physician in the investigation of nervous diseases. Enfeeblement, or even complete abolition ot the reflexes may occur: (i) Owing to diminished sensibility or complete insensibility of the afferent fibres; (2) in analogous aflfections of the central organ ; (J) or, lastly, of the efferent fibres. Where there is general depression of the nervous activity (as after shocks, compression or inflammation of the central nervous organs; in asphyxia, in deep coma, and in consequence of the action of many poisons), the reflexes may be greatly diminished or even abolished. [Reflexes. — The physician, by studying the condition of the reflexes, can form an idea as to the condition of practically every inch of the spinal cord. There are three groups of reflexes, {li) the superficial, [Jt) the deep or tendon, ((t) the organic reflexes.] [The superficial or skin reflexes are excited by stimulating the skin, e.g., by tickling, pricking, scratching, etc. We can obtain a series of reflexes from below as far up as the lower part of the cervical region. The plantar reflex is obtained by tickling the soles of the feet, when the leg on that side, or, it may be, both legs are drawn up. It is always present in health, and its centre is in the lumbar enlargement of the cord. The cremasteric reflex is well marked in boys, and is easily produced by exciting the skin on the inner side of the thigh, when the testicle on that side is retracted. The gluteal reflex consists in a contraction of the gluteal muscles, when the skin over the buttock is stimulated. The abdo- minal reflex consists in a similar contraction of the abdominal muscles, when the skin over the abdomen in the mammary line is stimulated. Tiie epigastric reflex is obtained by stimulating the skin in front between the fourth and sixth ribs. The interscapular reflex results in a contraction of the muscles attached TENDON REFLEXES. 667 to the scapula, when the skin between the scapulae is stimulated, responds to the lower cervical and upper dorsal region.] Its centre cor- [The following table, aflei segments on which it depends ' Cervical 6 Gowers, shows the relation of each reflex to the spinal segment or 1 5 V Interscapular. I J 5) 6 V Epigastric. 7) 81 9l lo ]• Abdominal. " I I2j 1 umbar I ) r- . • ,. I Cremastenc. 3 J I A'k« /^e/7ex. ][ •* I Gluteal. Sacral ')-5!si 2 1 1 I I Plantar. " sJ'^GI- Vesical. " 4 Rectal. " 5 J Sexual.] Tendon Reflexes. — -Under pathological conditions, special attention is directed to the so-called tendon reflexes, which depend upon the fact that a blow upon a tendon (e.g., the quadriceps femoris, tendo-Achilles, etc.), discharges a contraction of the corresponding muscle {^Westphal, Erb (1875), Eitlenberg and others) ; that the patellar tendon reflex (also called " knee phenomenon ") or simply " knee reflex," or "knee jerk," is invariably absent in cases of ataxic tabes dorsalis, while in spastic spinal paralysis it is abnormally strong and extensive {Erb). [The "knee jerk" is elicited by percussing the ligamentum patella;, and is due to a sing/c spasm of the rectus. The latent period is .03 to .04 second, and it is argued by Waller and others that it is doubtful if this tendon reflex is sub- served by a spinal nervous arc, while admitting the effect of the spinal cord in modifying the response of the muscle.] .Section of the motor nerves abolishes the patellar phenomenon in rabbits {Sehultz), and so does section of the cord opposite the 5th and 6th lumbar vertebra {Tschirje70, Senator). Landois finds that in his own person the contraction occurs 0.048 second after the blow upon the ligamentum patellse. Accordmg to Waller, the patellar reflex and the tendo- Achilles reflex occurs 0.03 to 0.4 second, and according to Eulenberg, 0.032 second after the blow. According to Westphal these phenomena are not simple reflex processes, but complex conditions intimately dependent upon the muscle tonus, so that when the tonus of the quadriceps femoris is diminished the phe- nomenon is abolished. In order that the phenomenon may take place, it is neces- sary that the outer part of the ])osterior column of the spinal cord remain intact (^Westphal). [A "jaw jerk " is obtained by suddenly depressing the lower jaw {Go7vers, Beevor and Be JVattez'i7/e), a.nd the last observer finds that the latent period is .02 second, and if this be the case, it is an argument against these so-called "tendon reflexes" being true reflexes, and that they are direct contractions of the muscles due to sudden stimulation by extension.] .\nother important diagnostic reflex is the " abdominal reflex " (O. Eosen- bach), which consists in this, that when the skin of the abdomen is stroked, e. g., with the handle of a percussion haminer, the abdominal muscles contract. When this reflex is absent on both sides in a cerebral affection, it indicates a diff"use disease of the brain ; its absence on one side indicates a local affection of the op- ]iosite half of the brain. The cremasteric, conjunctival, mammilary, pupillary, and nasal reflexes may also be specially investigated. In hemiplegia complicated with cerebral lesions, the reflexes on the paralyzed side are diminished, whilst not unfrequently the patellar reflex maybe increased. In extensive cerebral aff"ections accompanied by coma the reflexes are absent on both sides, including, of course, those of the anus and bladder (<9. Rosenbach). [Horsley finds that in the deepest narcosis produced by nitrous oxide gas the superficial reflexes (f./., plantar, conjunctival) are abolished, when the deep (knee jerk) remain. Ana?niia of the 668 CENTRES IN THE Sl'INAL CORD. lumbar enlargement (compression of the abdominal aorta) causes disappearances of both reflexes (Prh'ost). Chloroform and asphyxia abolish the deep as well as the superficial reflexes. Horsley regards the so-called deep reflex or knee jerk not as depending on a centre in the cord, but the con- traction of the rectus femoris is due to local irritation of the muscle from sudden elongation.] [Method. — The knee jerk is easily elicited by striking the patellar tendon with the edge of the hand or a percussion hammer when the leg is semi-flexed, as when the legs are hanging over the edge of a table or when one leg is crcssed over the other. It is almost invariably present in health, but it becomes greatly exag- gerated in descending degeneration of the lateral columns and lateral sclerosis.] [Ankle clonus is another tendon reflex, and it is never present in health. If the leg be nearly extended, and pressure made upon the sole of the foot so as sud- denly to flex the foot at the ankle, a series of (5 to 7 per second) rhythmical contractions of the muscles of the calf takes place. Gowers describes a modifi- cation elicited by tapping the muscles of the front of the leg, the "front tap con- traction." Ankle clonus is excessive in sclerosis of the lateral columns and spastic paralysis.] [The organic reflexes include a consideration of the acts of micturition, erec- tion, ejaculation, defajcation, and those connected with the motor and secretory digestive processes, respiration, and circiUation.] [In " ankle clonus " excited by sudden passive flexion of the foot, there is a multiple spasm of the gastrocnemius. Here also the latent period is about 0.3 to 0.4 second and the rhythm 8 to 10 per second. This short latent period has led some observers to doubt the essentially reflex nature of this act.] When we are about to sleep (^ 374) there is first of all a temporary increase of the reflexes; in the first sleep the reflexes are diminished, and the pupils are contracted. In deep sleep the abdom- inal, cremasteric, and patellar reflexes are absent; while tickling the soles of the feet and the nose only acts when the stimulus is of a certain intensity. In narcosis, e. g., chloroform or morphia, the abdominal, then the conjunctival and patellar reflexes disappear; lastly, the pupils contract (O. Rosenb(2ch). Abnormal increase of the reflex activity usually indicates an increase of the excitability of the reflex centre, although an abnormal sensibility of the afferent nerve may be the cause. As the har- monious equilibrium of the voluntary movements is largely dependent upon and regulated by the re- flexes, it is evident that in aftections of the spinal cord there are frequent disturbances of the volun- tary movements, e, g.^ the characteristic disturbance of motion in attempting to walk, and in grasp- ing movements exhibited by persons sufi'ering from ataxic tabes dorsahs [or, as it is more generally called, locomotor ataxia.~\ 362. CENTRES IN THE SPINAL CORD.— At various parts of the spinal cord are placed centres capable of being excited reflexly, and which can bring about the discharge of certain complicated, yet well coordinated, motor acts. These centres .still retain their activity after the spinal cord is separated from the medulla oblongata ; further, those centres lying in the lower part of the spinal cord still retain their activity after being separated from the higher centres, but in the normal intact body they are subjected to the control of higher reflex centres in the medulla oblongata. Hence, we may speak of them as subordinate spinal centres. The cerehnim, also, partly by the production of perceptions, and partly as the organ of volition, can excite or suppress the action of certain of these sub- ordinate spinal centres. [For the significance of term " Centre," see p. 653.] I. The cilio-spinal centre (Budge) connected with the dilatation of the pupil lies in the lower cervical part of the cord, and extends downward to the region of the first to the third dorsal vertebra. It is excited by diminution of light ; both pupils always react simultaneously, when one retina is shaded. Uni- lateral extirpation of this part of the spinal cord causes contraction of the pupil on the same side. The motor fibres pass out by the anterior roots of the two lower cervical and two upper dorsal nerves, into the cervical sympathetic (§ 392). Even the idea of darkness may sometimes, though rarely, cause dilatation of the pupil {.Budge\ In goats and cats this centre, even after being separated from the medulla oblongata, can be ex- cited directly by dyspnceic blood, and also retlexly by the stimulation of sensory nerves, e.g.y the MUSCLE TONUS. 669 median, especially when the reflex excitability of the cord is increased by the action of strychnin or atropin [Luc/isinger). For the dilator centre in the medulla oblongata see § 367, 8. 2. The ano-spinal centre {Budget or centre controlling the act of defaeca- tion. The afferent nerves lie in the hfemorrhoidal and inferior mesenteric plexuses, the centre at the 5th (dog) or 6th to 7th (rabbit) lumbar vertebra; the efferent fibres arise from the pudendal plexus and pass to the sphincter muscles. For the relation of this centre to the cerebrum see § 160. After section of the spinal cord [in dogs], Goltz observed that the sphincter contracted rhythmically upon the finger introduced into the anus; the coordinated activity of the centre therefore would seem to be possible only when the centre remains in connection with the brain. 3. The vesico-spinal centre {Budge) for regulating micturition, or Budge's vesico-spinal centre. The centre for the sphincter muscle lies at the 5th (dog) or the 7th (rabbit) lumbar vertebra, and that for the muscles of the bladder some- what higher. The centre acts only in a properly coSrdinated way in connection with the brain (§ 280). 4. The erection centre (§ 436) also lies in the lumbar region. The afferent nerves are the sensory nerves of the penis ; the efferent nerves for the deep artery of the penis are the vaso-dilator nerves, arising from the ist to 3d sacral nerves, or Eckhard's nervi erigentes — while the motor nerves for the ischio-cavernosus and deep transverse perineal muscles arise from the 3d to 4th sacral nerves (§ 356). The latter may also be excited voluntarily, the former also partly by the brain, by directing the attention to the sexual activity. Eckhard observed erection to take place after stimulation of the higher regions of the spinal cord, as well as of the pons and crura cerebri. 5. The ejaculation centre. The afferent nerve is the dorsal of the penis, the centre (Budge's genito-spinal centre) lies at the 4th lumbar vertebra (rabbit) ; the motor fibres of the vas deferens arise from the 4th and 5th lumbar nerves, which pass into the sympathetic, and from thence to the vas deferens. The motor fibres for the bulbo-cavernosus muscle, which ejects the semen from the bulb of the urethra, lie in the 3d and 4th sacral nerves (perineal). 6. The parturition centre (§ 453) lies at the ist and 2d lumbar vertebra {Korner) ; the afferent fibres come from the uterine plexus, to which also the motor fibres proceed. Goltz and Freusberg observed that a bitch became preg- nant after its spinal cord was divided at the ist lumbar vertebra. 7. Vasomotor Centres. — Both vasomotor and vaso-dilator centres are dis- tributed throughout the whole spinal axis. To them belongs the centre for the spleen, which in the dog is opposite the ist-4th cervical vertebrae {Bulgak). They can be excited reflexly, but they are also controlled by the dominating centre in the medulla oblongata (§ 371). Psychical disturbance (cerebrum) influences them (§ 377). [8. Perhaps there are vaso-dilator centres.] 9. The sweat centre is, perhaps, distributed similarly to the vasomotor centre (§ 288). The reflex movements disch.Trged from these centres are orderly coordinated refle.\es, and may thu< be compared to the orderly reflexes of the trunk and extremities. Muscle Tonus. — P'or.nerly automatic functions were ascribed to the spinal cord, one of these being that it caused a moderate active tension of the muscles — a condition that was termed muscle tone, or tonus. The existence of tonus in a striped muscle was thought to be proved by the fact that, when such a muscle was divided, its ends retracted. This is due merely to the fact that all the muscles are stretched slightly beyond their normal length (| 301). Even paralyzed muscles, which have lost their muscular tone, show the same phenomenon. Formerly, the stronger contrac- tion of certain muscles, after paralysis of their antagonists, and the retraction of the facial muscles to the sound side, after paralysis of the facial nerve, were also regarded as due to tonus. This result is simply due to the fact that, after the activity of the intact muscles, the other ones have not sufficient power to restore the parts to their normal median position. The followmg experiment of Auerbach and Heidenhain is against the assumption of a tonic contraction ; If the muscles of the 670 EXCITABILITY OF THE SPINAL CORD. leg of a decapitated frog be stretched, it is found that they do not elongate after section of the sciatic nerve, or after it is paralyzed by touching it with ammonia or carbolic acid. Reflex Tonus. — If, however, a decapitated frog be suspended in an abnormal position, we observe, after section of the sciatic nerve, or the posterior nerve roots on one side, that the leg on that side hangs limp, while the leg of the sound side is slightly retracted. The sensory nerves of the latter are slightly and continually stimulated by the weight of the limb, so that a slight reflex retraction of the leg takes place, which disappears as soon as the sensory ner\'es of the leg are divided. If we choose to call this slight retraction tonus, then it is a reflex tonus (Brondgiest). (See the experiments of Harless, C. Lmhvig, and Cyan — \ 355.) 363. EXCITABILITY OF THE SPINAL CORD.— Even at the pres- ent time observers are by no means agreed whether the spinal cord, like peripheral nerves, is excitable, or whether it is distinguished by the remarkable peculiarity that most of its conducting paths and ganglia do not react to direct electrical and mechanical stimuli. If stimuli be cautiously applied either to the white or gray matter there is neither movement nor sensation ( \'an Deen [/S41), Brozun-Sc'qttard^ Schiff^ Huizinga, Sigm. Mayer). In doing this ex- periment, we must be careful not to stimulate the roots of the spinal nerves, as these respond at once to stimuli, and thus may give rise to movements or sensations, ."^s the spinal cord conducts to the brain impulses communicated to it from the stimulated posterior roots, but does not itself respond to stimuli which produce sensations, Schifi" has applied to it the term " aesthesodic." Further, as the cord can conduct both voluntary and reflex motor impulses, without, however, itself being affected by motor impulses applied to it directly, he calls it "kinesodic." Schiff's views are as follows : — 1. In the posterior columns the sensory root fibres of the posterior root which traverse these columns give rise to painful impressions, but the proper paths of the posterior columns themselves do not do so. The proof that stimulation of the posterior column produces sensory impressions, he finds in the fact that dila- tation of the pupil occurred with every stimulation (§ 392"). Removal of the pos- terior column produces anaesthesia (loss of tactile sensation). Algesia [or the sensation of pain] remains intact, although at first there may even be hyperalgesia. 2. The anterior columns are non-excitable, both for striped and non-striped muscle, as long as the stimuli are applied only to the proper paths of this column. But movements may follow, either when the anterior nerve roots are stimulated, or when, by the escape of the current, the posterior columns are affected, whereby reflex movements are produced. According to Schiff', therefore, all the phenomena of irritation, which occur when an uninjured cord is stimulated (spasms, contracture), are caused either by simultaneous stimulation of the ante- rior roots, or are reflexes from the posterior columns alone, or simultaneously from the posterior columns and the posterior roots. Diseases affecting only the anterior and lateral columns alone never produce symptoms of irritation, but always of paralysis In complete ancfsthesia and apnoea every form of stimulus is quite inactive. According to Schiff's view, all centres, both spinal and cerebral, are inexcitable by artificial means. Direct Excitability. — Many observers, however, oppose these views, and contend that the spinal cord is excitable to direct stimulation. Fick observed movements to take place when he stimulated the while columns of the cord of a frog, isolated for a long distance so as to avoid the escape of the stimulating currents. Biedermann comes to the following conclusions: the transverse section of a motor nerve is most excitable. Weak stimuli (descending opening shocks) excite the cut surface of the transversely divided spinal cord, but do not act when applied further down. . Luchsinger asserts that, after dipping the anterior part of a beheaded snake into warm water, the reflex movements of the upper part of the cord are abolished, while the direct excitability remains. 3. Excitability of the Vasomotors. — The vaso-constrictor nerves, which proceed from the vasomotor centre and run downward in the [lateral columns of the] cord, are excitable by all stimuli along their whole course ; direct stimulation of any transverse section of the cord constricts all the blood vessels below the point of section {C.Liidwig and Thiry). In the same way, the fibres which ascend in the cord, and increase the action of the vasomotor centre — pressor fibres, 2txs aX'io e\c\\.a.h\e {C.Liidwig and Dittinar — § 364, 10). Stimulation of these fibres, although it affects the vasomotor centre reflexly, does not cause CONDUCTING PATHS IN SPINAL CORD. 671 sensation. Schiff maintains, however, that these are not the direct results of stimulation. 4. Chemical Stimuli, such as the application of common salt, or wetting the cut surface with blood, appear to excite the spinal cord. 5. The motor centres are directly excited by blood heated above 40° C, or by asphyxiated blood, or by sudden and complete anaemia of the cord pro- duced by ligature of the aorta {Sigm. Mayer) ; and also by certain poisons — picrotoxin, nicotin and compounds of barium {Luchsinger). Action of Blood and Poisons. — In experiments of this kind tlie spinal cord ought to be divided at the first lumbar vertebra at least twenty hours before the experiment is begun. It is well to divide the posterior roots beforehand to avoid reflex movements. If, in a cat thus operated on, dyspncea be produced, or its blood 07'erheated, then spnsms^ contraction of the vessels and secre- tion of sweat occur in the hind limbs, together with evacuation of the contents of the bladder and rectum, while there are movements of the uterus and the vas deferens. Some poisons act in a similar manner. In animals with the medulla oblongata divided, rhythmical respiratory movements may be prochiced if the spinal cord has been previously rendered very sensitive by strychnin or overheated blood (P. v. A'okitansir, v. Schroff — \ 368). Hyperaesthesia. — After unilateral section of the cord, or even only of the posterior or lateral columns, there is hypenes/hesia on the same side below the point of section {Fodera {182J), and others), so that rabbits shriek on the slightest touch. The phenomenon may last for three weeks, and then give place to normal or sub-normal excitability. On the sound side the sensibility remains perma- nently diminished. A similar result has been observed in cases of injury in man. An analoLi'Dus phenomenon, or a tendency to contraction in the muscles below the section (Hyperkinesia), has been observed by Brown-Sequard after section of the anterior columns. 364. THE CONDUCTING PATHS IN THE SPINAL CORD.— [Posterior Root. — The fibres of the posterior root enter the cord in three bundles {a) the inner one, or internal radicular fasciculus sweeps through the postero-external column to enter the gray matter. It is supposed to convey the impressions from tendons and those for touch and locality. Hence, when this column is diseased, as in locomotor ataxia, the deep reflexes, especially the patellar tendon reflex, are enfeebled, or it may be abolished, while the implica- tion of the fibres of the internal fasciculus gives rise to severe pain. {/>) The outer radicular fibres enter the gray matter of the posterior horn, and are sup- posed to convey the impressions for cutaneous reflexes and temperature, {c) The central fibres pass directly into the gray matter, and are supposed to conduct painful imijressious into the gray matter.] 1. Localized tactile sensations (temperature, pressure and the muscular sense impressions) are conducted upward through the posterior roots to the ganglia of the posterior cornu, and, lastly, into the posterior column of the same side. In man the conducting path from tiie legs runs in GoU's column, while those for the arms run in the ground bundle (Fig. 403) {Flec/isig\. In rabbits the path of localized tactile impressions lies in the lower dorsal region in the lateral columns (Ludzvigand Woroschiloff, Ott and Meade-Smith). Anaesthesia. — Section of individual parts of the lateral columns abolishes the sensibility for the parts of the skin connected with the part destroyed, while total section produces the same result for the whole of the opposite side of the body below the section. The condition where tactile and muscular sensibility is lost is known as aniisthesia. 2. Localized voluntary movements in man are conducted on the satne side through the anterior and lateral columns (§§ 358 and 365), in the parts known as the pyramidal tracts. The impulses then pass into the cells of the anterior cornu, and thence to the corresponding anterior nerve roots to the muscles. The exact section experiments of Ludwig and Woroschiloff showed that, in the lower dorsal region of the rabbit, these paths were confined to the lateral columns. 672 LOCOMOTOR ATAXIA. Every motor nerve fibre is connected with a nerve cell in the anterior horn of the frog's spinal cord (GauL- and Birge). Section of one lateral column abolishes vpluntary movement in the corresponding individual muscles below the point of section. It is obvious, from the conduction in i and 2, that the lateral columns must increase in thickness and number of fibres from below upward {Stilling, Woroscliiloff") [see Fig. 397]. 3. Tactile (extensive and coordinated) Reflexes. — The fibres enter by the posterior root, and proceed to the posterior cornu. The groups of ganglionic cells, which control the coordinated reflexes, are connected together by fibres which run in the anterior tracts, the anterior ground bundle and (?) the direct cerebellar tracts (p. 659). The fibres for the muscles which are contracted pass from the motor ganglia outward through the anterior roots. In ataxic tabes dorsalis, or locomotor ataxia, there is a degeneration of the posterior columns, characterized by a jieculiar motor disturbance. The voluntary movements can be executed with full and normal vigor, l)ut the finer harmonious adjustments are wanting or impaired, both in intensity and extent. These depend in part upon the normal existence of tactile and muscular impressions, whose channels lie in the posterior columns. After degeneration of the latter, there is not only anaesthesia, but also a disturbance in the discharge of tactile reflexes, for whicli the centripetal arc is interrupted. But a simultaneous lesion of the sensory nerves alone may in a similar matter materi- ally influence the harmony of the movements, owing to the analgesia and the disappearance of the pathic reflexes ( ^ 355). As the fibres of the posterior root traverse the white posterior columns, we can account for the disturbances of sensation which characterize the degenerations of these parts [Charcot and Pierrei). But even the posterior roots themselves may undergo degeneration, and this may also give rise to disturbances of sensation (p. 648). The sensory disturbances usu.ally con- sist in an abnormal increase of the tactile or painful sensations, with lightning pains shooting down the limbs, and this condition may lead on to one where the tactile and painful sensations are abol- ished. At the same time, owing to stimulation of the posterior columns, the tactile sensibility is altered, giving rise to the sensation of formication, or a feehng of constriction ["girdle sensa- tion"]. The conduction of sensory impressions is often slowed (^ 337)- The sensibility of the muscles, joints, and internal parts is altered. The maintenance of the equilibrium is largely guided by the impulses which travel inward to the coordinating centres through the sensory nerves, special and general, deep and superficial. In many cases of locomotor ataxia, if the patient place his feet close together and close his eyes, he sways from side to side and may fall over, because by cutting off the guiding sensations obtained through the optic nerve, the other enfeebled impulses obtained from the skin and the deeper struct- ures are too feeble to excite proper coordination. 4. The inhibition of tactile reflexes occurs through the anterior columns ; the impulses pass from the anterior column at the corresponding level into the gray matter, where they form connections with the reflex conducting apparatus. 5. The conduction of painful impressions occurs through the posterior roots, and thence through the whole of the gray matter. There is a partial decussation of these impulses in the cord, the conducting fibres passing from one side to the other. The further course of these fibres to the brain is given in § 365. The experiments of Weiss on dogs, by dividing the lateral column at the limit of the dorsal and lumbar regions, showed that each lateral column contains sensory fibres for both sides. The chief mass of the motor fibres remains on the same side. Section of both lateral columns abolishes completely sensibility and mobility on both sides. The anterior columns and the gray matter are not sufficient to maintain these. If all the gray matter be divided, except a small connecting por- tion, this is sufficient to conduct painful impressions. In this case, however, the conduction is slower (Sehiff). Only when the gray matter is completely divided is the conduction of painful impressions from below completely interrupted. This gives rise to the condition of analgesia, in which, when the posterior columns are still intact, tactile impressions are still conducted. This condition is some- times observed in man during incomplete narcosis from chloroform and morphia ( Thiersch). Those poisons act sooner on the nerves which administer to painful sensations than on those for tactile im- pressions, so that the person operated on is conscious of the contact of a knife, but not of the pain- ful sensations caused by the knife dividing the parts. Irradiation of Pain. — As painful impressions are conducted by the whole of the gray matter, and as the impressions are more pjwerful the stronger the painful impression, we may thus explain the .so called irradiation of painful impressions. During violent pain, the pain seems to extend to wide areas ; thus, in violent toothache, proceeding from a particular tooth, the pain may be felt in the whole jaw, or it may be over one side of the head. CONDUCTION IN THE SPINAI, CORD. 673 6. The conduction of spasmodic, involuntary, incoordinated movements takes place through the gray matter, and from the latter through the anterior roots. It occurs in epilepsy, in poisoning with strychnin, in ursemic poisoning, and tetanus {§ 360, II). The anaemic and dyspnceic spasms are excited in and conducted from the medulla oblongata, and are communicated through the whole of the gray matter. 7. The conduction of extensive reflex spasms takes place from the posterior roots, perhaps, to the cells of the posterior cornu and then to the cells of the anterior cornu, above and below the plane of the entering impulse (Fig. 407), and, lastly, into the anterior roots, under the conditions already referred to in § 360, II. 8. The inhibition of pathic reflexes occurs through the anterior columns downward, and then into the gray matter to the connecting channels of the reflex organ, into which it mtroduces resistance. 9. The vasomotor fibres run in the lateral columns {Dittmar), and, after they have passed into the ganglia of the gray matter at the corresponding level, they leave the spinal cord by the anterior roots. They reach the muscles of the blood vessels either through the paths of the spinal nerves, or they pass through the rami communicantes into the sympathetic, and thence into the visceral plexuses (§ 356). Section of the spinal cord paralyzes all the vasomotor nerves below the point of section ; while stimulation of the peripheral end of the spinal cord causes contraction of all these vessels. [Ott's experiments on cats show that the vasomotor fibres run in the lateral columns, and that they as well as the sudorific nenes decussate in the cord.] 10. Pressor fibres enter through the posterior roots, run upward to the lateral columns, and undergo an incomplete decussation (C. Ludwig and Miescher). They ultimately terminate in the dominating vasomotor centre in the medulla oblongata, which they excite reflexly. Similarly, depressor fibres must pass upward in the spinal cord, but we know nothing as to their course. 11. From the respiratory centre in the meAviWa. ohlongaXa, respiratory nerves run downward in the lateral columns on the same side, and without forming any connections with the ganglia of the anterior cornu (?), pass through the anterior roots into the motor nerves of the respiratory muscles {Schiff ). Unilateral, or total destruction of the spinal cord, the higher up it is done, accordingly paralyzes more and more of the respiratory nerves, on the same or on both sides. Section of the cord above the origin of the phrenic nerves causes death, owing to the paralysis of these nerves of the diaphragm (?"3)- In pathological cases, in degeneration of, or direct injury to, the spinal cord or its individual parts, we must be careful to observe whether there may not be present simultaneously paralytic and irritative phenomena, whereby the symptoms are obscured. [Complete transverse section of the cord results immediately in com- plete paralysis of motion and sensation in all the parts supplied by nerves below the seat of the injury, although the muscles below the injury retain their normal trophic and electrical conditions. There is a narrow hyjierKsthetic area at the upper limit of the paralyzed area, and when this occurs in" the dorsal region, it gives rise to the feeling of a belt tightly drawn round the waist, or the "girdle sensation." There is, also, vasomotor paralysis below the lesion, but the blood vessels soon regain their tone owing to the subsidiary vasomotor centres in the cord. The remote effects come on much later, and are secondary descending degeneration in the crossed and direct pyramidal tracts and ascending degenera- tion in the postero-internal columns (Fig. 404). According to the seat of the lesion, the functions of the bladder and rectum may be interfered with. Injury to the upper cervical region sometimes causes hyperpyrexia.] 43 674 EFFECTS OF SECTION OF THE CORD. [Unilateral section results in paralysis of voluntary motion in the muscles supplied by nerves given off below the seat of the injury, although the muscles do not atrophy, but when secondary descending degeneration occurs they become rigid, and ex- hibit the ordinary signs of contracture. There is vasomotor paralysis on the same side, although this passes off below the injury, while the ordinary and muscular sensibility are dimin- ished on both sides (Fig. 408). There is bilateral anaesthesia. On the opposite side there is total anssthesia and analgesia below the lesion, but on the same side in the dorsal region there is a narrow circular anaesthetic zone (Fig. 408, b), cor- responding to the sensory nerve fibres destroyed at the level of the section. The sensory nerves decussate shortly after they enter the cord, hence the anesthesia on the opposite side, but they do not cross at once, but run obliquely upward before they enter the gray matter of the opposite side, so that a unilateral section will involve some fibres coming from the same side, and hence the slightly diminished sensibility in a circular area on the same side. There is a narrow hypertes- thetic area on the same side as the lesion, at the upper limit of paralyzed cutaneous area (Fig. 408, c), due, perhaps, to stimulation of the cut ends of the sensory fibres on that side. In man there is hypersesthesia (to touch, tickling, pain, heat tiie if/t half of the and cold) on the parts below the lesion on the same side, but doreai region!" \a) the cause of this is not known. The remote effects are due to the usual descending and ascending degeneration which set in.] [In monkeys, after hemisection of the cord in the dorsal region, there is jiaralysis of voluntary motion and retention of sensibility with vasomotor paralysis of the same side, antl retention of voluntary motion with anaes- thesia and analgesia on the opposite side. The existence of hypera-sthesia on the side of the lesion is not certain in these animals, but there is no doubt of it in man. Ferrier also finds (in opposition to Brown-Sequard) that the muscular sense is paralyzed as well as all other forms of sensibility, on the side opposite to the lesion, but unimpaired on the side of the lesion. The muscular sense, in fact, is entirely separalile from the motor innervation of muscle {Ferrier). The power of emptying the bladder and rectum was not affected.] ralysis; («. ,i) plete ansEstheM: r) hyperaesthes the skin (^■W.). THE BRAIN. 365. GENERAL SCHEMA OF THE BRAIN.— In an organ so complicated in its struc- ture as the brain, it is nccessarv to have a general view of the chief arrangements of its individual parts. Meynert gave a plan of the general arrangement of this organ, and although this plan may not be quite correct, still it is useful in the stuly of brain function [A special layer of gray matter of the cerebium is placed externally and spread as a thin coating over the white matter, or centrum ovale, which lies internally, and consists of nerve fibres or the white matter. That part lying in each hemisphere is the centrum senii-ovale. The gray matter is folded into gyri, or convolutions, separated from each other by fissures, or sulci. Some of the latter are very marked, and serve to separate adjacent lobes, while the lobes themselves Fir.. 409. isection of the brain from above, showing the lateral, 3d, and 4th ventricles, with the basal ganglia and < ine parts, a, knee of the corpus callosum : 6, anterior part of the right corpus striatum : d' , gray matter dissected off 10 show white tibres : c, points to taenia semicircularis ; (/, optic thalamus; if, anterior pillars of fornix, with 5th ventricle in front of them, between the two laminae of the septum lucidum : /", middle or soft commissure : £-, 3d ventricle ; A, /, corpora quadrigemina ; ,t, superior cerebellar peduncle; /.hippocampus majo ride collateralis ; o, 4th ventricle ; /*, medulla oblongata ; j, cerebellu are further subdivided by sulci into convolutions. For a description of the lobes, see ^ 375. Some masses of gray matter are disposed at the base of the brain, forming the corpus striatum (pro- jecting into the lateral ventricles), which, in reality, is composed of two parts — the nucleus caudatus and lenticular nucleus ( Fig. 409, /i); the optic thalamus, which lies behind the former and bounds the 31! ventricle ( Kig. 409, i/) ; the corpora quadrigemina, lying on the upper surface of the crura cerebri (Fig. 409, /;. i) ; and within the tegmentum of the crura cerebri are the red nucleus and locus niger. Lastly, there is the continuation of the gray matter of the cord up through the medulla, pons, and around the iter, forming the central gray tube and terminating anteriorly at the tuber cinereum. These various parts are connected in a variety of ways with each other, some 675 676 PROJECTION SYSTEMS OF MEYNERT. by transverse fibres stretching between the two sides of the brain, while other longitudinal fibres bring the hinder and lower parts in relation with the fore parts ] [Under cover of the occipital lobes, but connected with the cerebrum in front and the spinal cord below, is the cerebellum, which has its gray matter externally and its white core internally. Thus, we have to consiiicr cerebrospinal and cerebello-spinal connections.] Meynert's Projection Systems. — The cortex of the cerebium consists of convolutions and Scheme of ihe brain C. C, cortex cerebri : C, J, corpus striatum : N, /, nucleus lenticularis ; T, o, optic thal- amus : 7', corpora quadrigemina ; P, pedunculus cerebri : H, tegmentum; and/, crusta; i, i, corona radiata ot the corpus striatum ; 2.2, of the lenticular nucleus ; 3, 3, of the optic thalamus ; 4, 4, of the corpora quadrigemina ; 5, direct fibres to the cortex cerebri ^Flechsig) ; 6, 6, fibres from the corpora quadrigemina to the tegmentum ; «/, further course of these fibres ; 8, 8, fibres from the corpus striatum and lenticular nucleus to the crusta of the pedunculus cerebri ; I\I, further course of these ; S, S, course of the sensory fibres ; R, transverse section of tht spinal cord : ?', W, anterior, and k, W, posterior roots ; a, a, association systei fibres. II, Transverse section through the posterior pair of the corpora quadrige: of man, — f>, crusta of the peduncle : j, substantia nigra ■ "', corpora quadrigemina, III, The same of the dog : IV, of an ape ; V, of the guinea pig. [See p. 675.] of fibres : c, c, commissural na and the pedunculi cerebri ot the aqueduct. (itha sulci, the "peripheral gray matter" (Fig. 410, C), which is recognized as a nervous structure from the presence of numerous ganglionic cells in it (?358, i). From it proceed all the motor fibres which are excited by the will and to it proceed all the fibres cominsj from the organs of special sense and sensory organs, which give rise to the psychical perception of external impressions. [In Fig. 410 the decussation of the sensory fibres is represented as occurring near the medulla oblongata. It is more probable that a large number of the sensory fibres decussate shortly after CEREBELLO-SPINAL CONNECTIONS. 677 they enter the conl, as is represented in Fig. 4t2. Sonie observers assert that some of the sensory fibres decussate in the medulla oblongata.] First Projection System. — The channels lead to and from the cortex cerebri, some of them traversing the basal ganglia, or ganglia of the cerebrum, the corpus striatum (C, s), composed of the caudate nucleus and lenticular nucleus (A", /), optic thalamus ( T, o) and corpora quadrigemina ; some fibres form connections with cells within this central gray matter. The fibres which proceed from the cortex through the corona radiata in a radiate direction constitute Meynert' s first projection system. Besides these, the white substance also contains two other systems of fibres : {a) Commis- sural fihres^ such as the corpus caliosum and the anterior commissure (r, r), which are supposed to connect the two hemispheres with each other; and (b) a connecting or association system, whereby two different areas of the same side are connected together [a, a). The ganglionic gray matter of the basal ganglia forms the first stage in the course of a large number of the fibres. When they enter the central gray matter they are interrupted in their course. According to Meynert, the corona radiata contains bundles of fibres from the corpus striatum, lenticular nucleus, optic thalamus and corpora quadrigemina. The second projection system consists of longitudinal bundles of fibres, which proceed down- ward and reach the so-called " central gray tube," which is the ganglionic gray matter reaching from the 3d ventricle through the aqueduct of Sylvius and the medulla oblongata to the lowest part of the gray matter of the spinal cord. It lines the inner surface of the medullary tube. It is the Fig. 411 Floor of the fourth ventrit are cut short ; on the mititile one has been ( of the auditory nerve the calamus scriptorii rigemina. of the cerebellum. On the left side the three cerebellar peduncles I of the superior and inferior peduncles have been preserved, while the It short. I, median groove of the fourth ventricle with the fasciculi teretes ; 2, the striae )n each side emerging from it ; 3, inferior peduncle : 4, posterior pyramid and clava, with i above it ; 5, superior peduncle ; 6, fillet to the side of the crura cerebri ; 8, corpora quad- second stage in the course of the fibres extending from the basal ganglia to the central tubular gray matter. The fibres of this system must, obviously, vary greatly in length. [While there are three concentric tubes in the spinal cord (| 359), in the part which forms the brain an extra layer of gray matter is added— the peripheral gray tube — constituting the cortex of the cerebral hemispheres and cerebellum and the corpora quadrigemina. Thus, the white matter lies between two concentric masses of gray matter ( //;//).] Connections of the Cerebellum. —The cerebellum consists of two somewhat flattened hemi- spheres connected across the middle line by the middle lobe or vermiform process, which is the fundamental portion of the organ, as it is best developed in lower animals, while as yet the lateral lobes are but small or absent, e. g., in birds. The surface is furrowed by sulci so as to cause it to resemble a series of folia, leaflets or laminae ; larger fissures divide it into lobes. Peduncles.— The two itt/«w/- j(ii'a'««i-/f.r connect it with the corpora quadrigemina and the crura cerebri. The fibres come from the lower part of the cerebellum and from its dentate nucleus, and the greater por- tion of these fibres decussate in the upper part of the pons and the tegmentum, some of them be- coming connected with the red nucleus in the tegmentum of the opposite side. Some of the fibres seem to connect the cerebellum with the frontal lobes, constituting a fronto-cerebellar tract, and they are also crossed ( Go^vers). When the cerebellum is congenitally absent these fibres are absent {Flechsig). By the two inferior peduncles or restiform bodies, it is connected with all the columns 678 CEREBRO-SPINAL CONNECTIONS. of the spinal cord, and it is to be noted that some of the fibres forming these peduncles are con- nected with the olivary body of the opposite side, so that they decussate. The miiiJU peduncle is formed by the transverse fibres of the pons (I'ig. 41 1). It is evident that there is a cerebello spinal as well as cerebro-spinal connection to be considered. [The gray matter is external and the while internal, and on section the foliated branched ap- pearance of the cerebellum constitutes the arbor vit(C. Within each lateral lobe is a folded mass of jjray matter like that in the olivary body, called the corpus dentatum, and from its interior white fibres proceed. Stilling describes roof nuclei in the front part of the middle lobe, so called be- cause they lie in the roof of the fourth ventricle. As is sh iwn in Fig. 411, the white fibres of the superior peduncle pass to the gray matter on the inferior surface of tlie ctrebellum, whde the inferior peduncular fibres .pass to the superior surface, chiefly of the median part ; but both are said to form connections with the corpus dentatum ; the middle peduncle is connected with the gray matter of the lateral lobes. The minute structure is described in \ 3S0.] The Third Projection System. — Lastly, from the central tubular gray matter there proceeds the third system, or the peripheral nerves, motor and sensory. They are more numerous than the fibres of the second system. Conduction to and from Cerebrum — Voluntary Motor Fibres. — The course of the fibres which convey impulses for voluntary motion — the pyra- midal tracts — proceed from the motor regions of the cerebrum (§§ 375, 378, I), passing into and through the white matter of the cerebrum, and converge to the internal capsule, which lies between the nucleus caudatus and opticus thalamus internally and the lenticular nucleus externally (Fig. 439). [The motor fibres for the face and tongue occupy the knee of the capsule (F), those for the arm the anterior third of the posterior segment or limb (Aj, and those for the leg the middle third (L). They enter the crus and occupy its middle third, the fibres for the face being next the middle line, and those for the leg most external, the fibres for the arm lying between the two. They pass into the pons, where the fibres for the face (and tongue) cross to the opposite side, to become connected with the nuclei from which the facial and hypoglossal nerves arise. The fibres for the arm and leg (and trunk) continue their course to the medulla oblongata, where they form the anterior pyramids.] By far the greater proportion of the fibres cross at the decussation of the pyramids to form the crossed pyramidal tracts or lateral pyramidal tracts of the lateral column of the opposite side. The small uncrossed portion is continued as the direct pyramidal tract on the same side. The latter fibres, perhaps, supply those muscles of the trunk (f. ^f., respiratory, abdominal, and perineal), which always act together on both sides. According to other observers, however, they cross to the other side of the cord through the anterior white commissure, and descend in the crossed pyramidal tract or pyra- midal tract of the lateral column. The fibres of the pyramidal tracts form con- nections with the inultipolar ganglionic cells of the anterior cornu of the gray matter of the spinal cord at successively lower levels, and from each multipolar cell a single unbranched process is directed peripherally, which ultimately becomes a nerve fibre. The j)yramidal tracts thus end in the multipolar nerve cells of the gray matter of the spinal cord, from which the anterior roots of the spinal nerves arise. [The course of the pyramidal tracts and the decussation of these fibres in the medulla oblongata, explains why a hemorrhage involving the cerebral motor centres, or affecting these fibres in any part of their course above the decussation, results in paralysis of the muscles supplied by the fibres so involved on the opposite side of the body.] In their passage through the brain, the paths for direct motor impulses are not interrupted any- where in their course by ganglion cells, not even in the corpus striatum or pons. They pass in a direct uninterrupted course [so that they have the longest course of any fibres in the central nervous system]. Variation in Decussation. — There are variations as to the number of fibres which cross at the pyramids (F/echsig). In some cases the usual arrangement is reversed, and in some rare instances there is no decussation, so that the pyramidal tracts from the brain remain on the same side. In this way we may explain the very rare cases where paralysis of the voluntarvm ivenients lakes pl.nce on the same side as the lesion of the cerebrum (Morgagni, J'ierrel). This is direct paralysis. [Usually about 90 per cent, of the fibres decuss.ite.] COURSE OF THE SENSORY NERVES. 679 The motor cranial nerves have the centres through which they are excited voluntarily in the cortex cerebri (§ 378). The paths for such voluntary impulses also pass through the internal capsule and the crusta of the cerebral peduncle. [In the internal capsule the fibres for the face (and tongue) lie in the knee, while they occupy the part of the middle of the crusta next the middle line. Their course is then directed across the middle line to their respective nuclei, from which fibres proceed to the muscles supplied by these nuclei.] The exact course of many of the fibres is still unknown. The hypoglossal nerve runs with the pyramidal tracts, and behaves like the anterior root of a spinal nerve (§§ 354, 357). [Sensory Paths. — Our knowledge is by no means precise. Sensory impulses, passing into the cord, enter it by the posterior nerve roots, and may pass to the cerebrum or cerebellum. If to the cerebellum, the course probably is partly to the direct cerebellar tract and posterior column to the restiform body, thence to the cerebellum. If to the cerebrum, they cross the middle line in the cord not far above where they enter and pass to the lateral column, in front of the pyra- midal tract. Some enter the posterior column and others ascend in the gray matter to pass upward. In the medulla it is probable that those fibres which do not de- cussate there do so in the pons, the impulses perhaps traveling upward in the formatio reticularis, thence into the posterior half of the pons, into the tegmentum of the crus under the corpora quadrigemina, to enter the posterior third of the posterior limb of the internal capsule (Fig. 439, S). But, of course, the sensory fibres from the face have to be connected with the sensory centres in the cerebrum, so that the sensory paths from the cord, /. e., from the trunk and limbs are joined by those from the face in the pons, and they also occupy part of the posterior third of the posterior segment of the internal capsule, so that this important part of the internal capsule conducts sensory impulses from the opposite half of the body. Some of the fibres pass into the optic thalamus, and others enter the white matter of the cerebrum, but their exact course is very uncertain. The sensory fibres derived from the organs of special sense, e. g., the ear, go to the superior temporo-sphenoidal convolution, but whether directly or indirectly we do not know ; perhaps some of those for vision traverse the optic thalamus. Some of the afferent fibres perhaps go to the occipital region, and Gowers asserts that some of them go to the parietal and central regions, /. e., to the "motor" regions, for he holds " that disea.se of the motor cortex often causes impairment of the tactile sensibility."] [Charcot has called the posterior third of the posterior segment of the internal capsule, lying between the posterior part of the lenticular nucleus and the optic thalamus, the " Carrefour Sensitiv " or " Sensory Crossway " (Fig. 439, Sj. If it be divided, there is hemianresthesia of the opposite side.] Sensory Decussation in Cord. — As the greater part of the sensory fibres from the skin decussate in the spinal cord, and thus pass to the opposite side of the cord (Fig. 41 2 j, unilateral section of the spinal cord in man (and monkey — Ferrier) abolishes sensibility on the opposite side below the lesion. There is hyperesthesia of the parts below the seat of the section on the side of the injury (§ 363). From experiments on mammals, Brown-S6quard concludes that the de- cussating sensory nerve fibres pass to the opposite side within the cord at different levels, the lowest being the fibres for touch, then those for tickling and pain, and, highest of all, those which administer to sensations of temperature. All the fibres, therefore, which connect the s]iinal cord with the gray matter of the brain, undergo a complete decussation in their course. Hence, in man a de- structive affection of one hemisphere usually causes complete motor paralysis and loss of sensibility on the opposite side of the body. The fibres proceeding from the nuclei of origin of the cranial nerves also cross within the cranium. Not unfrequemly the motor paralysis and anaesthesia occur on the same side of the head, in which case the lesion (due to pressure or inflammationj involves the cranial nerves lying at the base of the brain. 680 CONDUCTING PATHS IN THE SPINAL CORD. The positions of decussation are (l) in the spinal cord, (2) in the medulla oblongata, and, lastly (3), in the pons. The decussation is complete in the peduncle. Fig. 412. Diagram of a spinal segment as a spinal centre and conducting medium. B, right, B', left cerebral hemisphere ; MO, lower end of medulla oblongata : i , motor tract from the right hemisphere, the larger part decussating at MO, and passing down the lateral column of the cord on the opposite side to the muscles M and M' ; 2, motor tract from the left hemisphere ; S, S', sensitive areas on the left side of the body : 3', 3, the main sensory tract from the left side of the body— it decussates shortly .ifter entering the cord : S', S', sensitive areas, and 4', 4, tracts from the right side of the body. The arrows indicate the direction of the impulses {Braiinue/l)). [Here all the sensory fibres are shown as crossing the cord.] THE MEDULLA OBLONGATA. 681 Alternate Paralysis. — Gubler observed that unilateral injury to the pons caused paralysis of the facial nerve on the same side, but paralysis of the opposite half of the body. He concluded that the nerves of the trunk decussate before they reach the pons, while the facial fibres decussate within the pons. To these rare cases the name " a//ernate /lemip/ei^ia" h given. [When hemorrhage takes place into the lo-ver part of the lateral half of the pons, there may be alternate paralysis, but when the upper part of the lateral half is injured, the facial is paralyzed on the saine side as the body, I 379.] The olfactory nerve is said not to decussate (?) while the optic nerve undergoes a partial decus- sation at the chiasma (§ 344). Some observers assert that the fibres of the trochlearis decussate at their origin. 366. THE MEDULLA OBLONGATA.— [Structure.— In the medulla oblongata the fibres from the cord are rearranged, the gray matter is also much changed, while new gray matter is added. Each half of the medulla oblongata consists of the following parts from before back- wards : The anterior pyramid, olivary body, restiform body, and posterior pyramid, or funiculus gracilis (Figs. 413, 414, 415)- By the divergence of the posterior pyramids and the resti- form bodies, the floor of the 4th ventricle is exposed. As the central canal of the cord gradually fv.- ction of the decussation of the pyramids. yZa, anterior median fissure, Md: F, anterior column ; C«, anterior cornu, with its nerve cells, _/>-, formatio reticularis : ce, neck, and ff, head ot the posterior corn nerve ; mc, first indication of the nucleus of the funiculus cunealus ; H^, funiculus gracilis ; H^, funiculus cuneatus ; sip, posterior medi: the base of the posterior cornu. X 6. splaced laterally by the fibres decussating , }> cc, central canal ; S, lateral column ; ; r/CY, posterior root of the 1st cervical ', nucleus (clava) of the funiculus gracilis ; fissure ; x, groups of ganglionic cells in comes nearer to the posterior surface of the medulla it opens into the 4th ventricle. At the lower end of the medulla oblongata, on separating the anterior pyramids, we may see the decussation of the pyramids where the fibres cross over to the lateral columns of the cord. The anterior pyramid receives the direct pyramidal tract of the anterior column of the cord from its own side, and the crossed pyramidal tract from the lateral column of the cord of the opposite side (Fig. 413). The decussating fibres (crossed pyramidal tract) of the lateral column pass across in oundles to form the decussation of the pyramids. Most of the pyramidal fibres pass through the pons directly to the cerebrum, a few fibres pass to the cerebellum, while some join fibres proceeding from the olivary body to form the olivary fa.sciculus or fillet.] [Thus only a part of the anterior column of the cord — direct pyramidal tract — is continued into the anterior pyramid, where it Hes e.\ternal to the fibres which pass to the lateral column of the opposite side. The remainder of the anterior column — the antero-e.\ternaI fibres — are continued upward, but lie deeper under cover of the anterior pyramid, where they serve to form part of the formatio reticularis (p. 682).] [Of the fibres of the lateral column of the cord, some, the direct cerebellar tract, pass backward 682 STRUCTURE OF THE MEDULLA OBLONGATA. to join the restiform body and go to the cerebellum. These fibres lie as a thin layer on the surface of the restiforni body. The iro^sed pyramidal fibres cross obliquely at the lower end of the medulla to the anterior pyramid of the opposite side, and in their course they traverse the gray matter of the anterior cornu (Fig. 413,/^'). These fibres form the larger and mesial portion of the anterior pyramid. The remaining fibres of the lateral columns are continued upward, and pass beneath the olivary body, where they are concealed by this structure and also by the arcuate fibres, but they appear in the fioor of the medulla oblongata and are ^z\\^(^ fasciculus leres^ which goes to the cere- brum. As they pa^s upward they help to form the lateral part of the formatio reticularis.] [The posterior pyramid of the oblongata is merely the upward continuation of the postero- median column, or funiculus gracillis of the cord. As it passes upward at the medulla it broadens out, forming the clava, which tapers away above. The clava contains a mass of gray matter — the clavate nucleus.] [The restiform body consists chiefly of the upward continuation of the postero-external column or funiculus cuneatus of the curd. It contains a mass of gray matter, called the cuneate or tri- angular nucleus. Above the level of the clava the funiculus cuneatus forms part of the lateral boundary of the 4th ventricle. Immediately outside this, i.e., between it and the continuation of the posterior nerve roots, is a longitudinal prominence, which Schwalbe has called the funiculus of Rolando. It is formed by the head of the posterior cornu of gray matter C( niing nearer the surface. It also forms part of the restiform body. Some arcuate fibres issue from the anterior median fissure, turn transversely outward over the anterior pyramids and olivary body, and pass along with the funiculus cuneatus, the funiculus of Rolando, and the direct cerebellar fibres, to enter the correspondmg lateral lobe of the cerebellum, all these structures forming its inferior peduncle. Some observers suggest that the funiculus cuneatus and funiculus of Rolando do not pass into the cerebellum.] [The olivary body forms a well-marked oval or olive-shaped body, which does not extend the whole length of the medulla (Fig. 415, 0). Above, it is separated from the pons by a groove from which the 6ih nerve emerges. In the groove between it and the anterior pyramid arise the strands of the hypoglossal nerve, while in a corresponding groove along its outer surface is the line of exit of the vagus, glosso- pharyngeal, and spinal accessory nerves. It is covered on its surface by longi- tudinal and arcuate fibres, while in its interior it contains the dentate nucleus.] [The functions of the olivary bodies are quite unknown, but it is important to remember that they are connected by fibres with the dentate nuclei of the cerebellum. Fibres pass into the olivary body from the posterior column of the cord of the opposite side, and it is also connected with the dentate body of the opposite side, while, as we know, the dentate body is connected with the teg- mentum, so that through the left dentate body of the opposite side the tegmentum of say the right crus is connected with the right olivary body ( Go7vers).'\ [Decussation of the Pyramids is the term given to those fibres which cross obliquely in several bundles at the lower part of the medulla from the anterior pyramid of the medulla into the lateral column of the cord of the opposite side (Fig. 413, d) to form its lateral pyramid tracts or crossed pyramidal tracts. The number of fibres which decussate varies, and in some cases all the fibres may cross.] [The gray matter of the medulla is largely a continuation of that of the cord, although it is arranged difierently. As the fibres from the lateral column of the cord pass over to form part of the anterior pyramid of the medulla on the opposite side, they traverse the gray matier. and thus cut oft the tip of the anterior cornu, which is also pushed backward by t'he olivary body, and exists as a distinct mass, the nucleus lateralis (Fig. 414, nl). Part of the anterior gray matter aUo appears in the floor of the 4th ventricle as the eminence of ihc fasciculus teres, and from part of it s^irings the hypoglossal nerve (Fig. 415, XII). The neck joining the modified anterior and posterior cornua is much broken up by the passage of longitudinal and transverse fibres through ir, so that it forms a formatio reticularis {Fig. 414, _//■), separating the two cornua. The caput cornu posterioris comes to be covered higher up by the ascending root of the 5th nerve (Fig. 414, u V), and arcuate fibres passing to the restiform body. The posterior cornu is also broken up and is thrown outward, its caput giving rise to part of the elevation seen on the surface and described as the funiculus of Rolando, while part of the base now greatly enlarged forms the gray matter in the funiculus gracilis [clavate nucleus] (Fig. 413, «;') and funiculus cuneatus [cuneate or triangular nucleus] (Fig. 413, nc). Nearer the middle line, the gray matter of the posterior gray cornu appears in the floor of the 4th ventricle, above where the central canal opens into it, as the nuclei of the spinal accessory, vagus and glosso-pharyngeal ner\'es.] [In the floor of the 4th ventricle near the raphe, and quite superficial, is a longitudinal mass of large multipolar nerve cells, derived from the base of the anterior cornu from which the several bundles forming the hypoglossal nerve springs, it is the hypoglossal nucleus (Fig. 415, nXII), the nerve fibres passing obliquely outward to appear between the anterior pyramid and the olivary body. Internal to it and next the median groove is a small mass of cells continuous with those in the raphe, and called the nucleus of the funiculus teres (Fig. 415, nt). Around the central canal at the lower part of the medulla is a group of cells (Fig. 415, nXI), which becomes displaced lat- erally as it comes nearer the surface in the floor of the medulla oblongata, where it lies outside the hypoglossal nucleus, and corresponds to the prominence of the ala cinerea (Fig. 415, «A'), and THE GRAY MATTER OF THE MEDULLA OBLONGATA. 683 from it and its continuation upward arise from below upward part of the spinal accessory (nth), and the vagus (loth, corresponding to the position of the eminentia cinerea— Fig. 415, .V), so that this column of cells forms the vago-accessorius nucleus. External to and in front of this is the nucleus for the glossopharyngeal nerve. Further up in the medulla, on a level with the auditory stria- and outside the previous column, is a tract of cells from which the auditory nerve (8th) in great part arises ; it is the principal auditory nucleus. It lies just under the commencement of the inferior cerebellar peduncle ( Fig. 384, S' 8" 8'"). It consists of an outer and inner nucleus, which extend to the middle line. It forms connections with the cerebellum, and some fibres are said to enter the inferior cerebellar peduncle. This is an important relationship, as we know that the ves- tibular branch of the auditory nerve comes partly from the semicircular canals, so that in this way these organs may be connected with the cerebellum.] [Superadded Gray Matter. — There is a superadded mass of gray matter not represented in the cord, that of the olivary body, enclosing a nucleus, the corpus dentatum, with its wavy strip of gray matter containing many small multipolar nerve cells embedded in neuroglia. The gray matter is covered on the surface by longitudinal and transverse fibres. It is open toward the middle line Fig. 414, si/,. of the medui:; -Section of the medulla ublong.11.1 at the so-caUa*l upper nd po-terior median tissnre ; hXI, nucleus of the accessorius vagi ; «A7/, nucleus of the hypoglo i-called superior or anterior decussation of the pyramids ; py, anterior pyramid ; «, Ar, nucleus arciformis ; O^ t median parolivary body ; O, beginning of the nucleus of the olivary body ; «/, nucleus of the lateral column ; Fr, formatio reticularis : (.'. substantia gelatinosa, with trt V) the ascending root of the trigeminus ; nc, nucleus of the funiculus cuneatus : «t-', external nucleus of the funiculus cuneatus ; ng^ nucleus of the funiculus gracilis (or clava) ; //', funiculus gracilis; //^.funiculus cuneatus; cc. central <:.z.nA\\ /a,/a^ ./a^^ external arciform fibres X 4- Fig. 415. — Section of the medulla oblongata through the olivary body. nXlI, nucleus of the hypo- glossal ; «,V, «-V*, more or less cellular parts of the nucleus of the vagus ; XJI, hypoglossal nerve ; X, vagu.i ; «, fi>«, nucleus ambiguus; ///.nucleus lateralis; //, olivary nucleus; t/rt/, external, and /j/i»i, internal parolivary body ; yj, the round bundle, or funiculus solitarius ; Cr, restiform body;/, anterior pyramid, surrounded by arciform fibres ; /ae, pot, fibres proceeding from the olive to the raphe ^pedunculus olivas) ; r, raphe, X 4. (hilum) and into it run white fibres forming \\.% peduncle (Fig. 415,/, 0, /). These fibres diverge like a fan, some of them ending in connection with the small multipolar cells of the dentate body, while others traverse the lamina of gray matter and pass backward to appear as arcuate fibres which join the restiform body ; others, again, pass directly through to the surface of the olivary body, which they help to cover as the superficial arcuate fibres. The accessory olivary nuclei (Fig. 414, o', 0") are two small masses of gray matter similar to the last, and looking as if they were detached from it, one lying above and external, sometimes called the parolivary body, and the other slightly below and internal to the olivary nucleus, the latter 1 e;ng separ.rled fiom the dentate l)ody by the roots of the hypoglossal nerve. The latter is sometimes called internal parolivary body, or nucleus of the pyramid.] [The formatio reticularis occupies the greater part of the central and lateral parts of the me- dulla, and is produced by the intercrossing of bundles of fibres running longitmlinally and mure or less transversely in the medulla (Fig. 414,/", r]. In the more lateral portions are large multipolar nerve cells, perhaps continued upwar l from part of the anterior cornu, while the i>art next the raphe has no such cells. The longitudinal fibres consist of the upward prolongation of the antero-external 684 FUNCTIONS OF THE MEDULLA OBLONGATA. columns of the cord, while some seem to arise from the clavate nuclei and olives as arcuate fibres passing upward. In the lateral portions, the longitudinal fibres are the direct continuation upward of Flechsig's anterolateral mixed tracts of the lateral columns (p. 659). The horizontal fibres are formed by arcuate fibres, some of which run more or less transversely outward from the raphe. The siif-erficial arcuate fibres (Fig. 415,/! a, e) appear in the anterior median fissure, and, perhaps, come through the raphe from the opposite side of the medulla, curve round the anterior pyramids, fonn a kind of capsule for the olives, and join the restiform body (p. 682), but they are reinforced by some of the deep arcuate fibres which traverse the olivary body (p. 682). The (/eep arctta/e fibres run from the clavate and triangular nuclei horizontally inward to the raphe and cross to the other side, others pass from the raphe to the olivary body and through it to the restiform body. In the raphe, which contains nerve cells, some fibres run transver.sely, others longitudinally, and others from before backward.] [Other Nerve Nuclei — Sixth Nerve. — Under the elevation called eminentia teres (Fig. 384) in front of the auditor)' striae, close to the middle line, is a tract of large multipolar nerve cells. It was once thought to be the common nucleus of 6th and 7th facial nerves, but Cowers has shown that "the facial ascends to this nucleus, forms a loop round it (some fibres, mdeed, go through it), and then passes downward, forward and outward to a column of cells more deeply placed in the medulla than any other nucleus in the lower part." But the 7th has no real origin from this nucleus. Facial Nerve. — The nucleus lies deep in the formatio reticularis of the pons under the floor of the 4th ventricle, but outside the position of ihe nucleus of the 6th ( Fig. 384, 7). It extends down- ward about as far as the auditory stri;ie or a little lower. The fifth nerve arises from its motor nucleus (with large multipolar cells), which lies more superficially above and external tu the 6th (F'ig. 384, 5). The fibres run backward, where they are joined by fibres from the upper sensory nucleus, but another sensory nuc eus extends down nearly to the lower end of the medulla (5"). Doubtless, this extensive origin brings this nerve into intimate relation with the other cranial nerves, and accounts for the numerous reflex acts which can be discharged through the 5th nerve. Some sensory fibres are said to pass up beneath the corpora quadrigemina ( Gowers). The fourth nerve arises from the valve of Vieussens, i. e.^ the lamina of white and gray matter which stretches between the superior cerebellar peduncles. It arises, therefore, behind the 4th ventricle, but some of the fibres spring from some nerve cells at the low er part of the nucleus of the 3d nerve. Some fibres also descend in the pons to form a connection with the nucleus of the 6th nerve. The fibres decus- sate behind the aqueduct, so that in it alone, of all the cranial nerves, decussation occurs between its nucleus and its superficial origin {^Gowers). The third nerve arises from a tract of cells beneath the aqueduct and near the m'ddle line, and the fibres descend through the tegmentum to appear at the inner side of the crus cerebri. Gowers points out that, in reality, there are three distinct func- tional centres, (i) for accommodation (ciliary muscle), (2) for the light reflex of the iris, and (3) most of the external muscles of the eyeball. It is important to notice the connection between the nuclei of the 3<-l, 4th and 6th nerves, in relation to innervation of the ocular muscles.] Functions. — The medulla oblongata, which connects the spinal cord with the brain, has many points of resemblance with the former. [Like the cord, it is concerned in the (i) conduction of impulses.] (2) In it numerous reflex cen- tres are present, e. g., for simple reflexes similar to the nerve centres in the spinal cord, e.g., closure of the eyelids [so that they subserve the transference of alTerent into efferent impulses]. There are other centres present which seem to dominate or (T^/z/nV similar centres placed in the cord, e. g., the great vasomotor centre, the sweat-secreting, pupil-dilating centres, and the centre for combining the reflex movements of the body. Some of the centres are capable of being excited re- flexly (§ 358, 2). (3) It is also said to contain automatic centres (S 358, 3). The normal functions of the centres depend upon the exchanges of blood gases effected by the circulation of the blood through the medulla. If this gaseous exchange be interrupted or interfered with, as by asphyxia, sudden anaemia or venous congestion, these centres are first excited, and exhibit a condition of increased excitability, and, if they are over-stimulated, at last they are paralyzed. An excessive temperature also acts as a stimulus. All the centres, however, are not active at the same titne, and they do not all exhibit the same degree of ex- citability. Normally, the respiratory centre and the vasomotor centre are con- tinually in a state of rhythmical activity. In some animals the inhibitory centre of the heart remains continually non-excited, in others it is stimulated very slightly under normal conditions, simultaneously with the stimulation of the respiratory centre and only during inspiration. The spasm centre is not stimulated under normal conditions, and during intra-uterine life the respiratory centre remains quiescent. The medulla oblongata, therefore, contains a collocation of nerve CENTRES IN THE MEDULLA OBLONGATA. 685 centres which are essential for the maintenance of life, as well as various conduct- ing paths of the utmost importance. We shall treat of the reflex, and afterward of the automatic centres. 367, REFLEX CENTRES OF THE MEDULLA OBLONGATA. — The medulla oblongata contains a number of retle.x centres, which minister to the discharge of a large number of coordinated movements. 1. Centre for Closure of the Eyelids. — The sensory branches of the 5th cranial nerve to the cornea, conjunctiva, and the skin in the region of the eye are the aflferent nerves. They conduct impulses to the medulla oblongata, where they are transferred to, and excite part of, the centre of the facial nerve, and through branches of the facial the efferent impulses are conveyed to the orbicu- laris palpebrarum. The centre lies close to the calamus scriptorius {Exner). The reflex closure of the eyelids always occurs on hnlli sides, but closure may be produced volun- tarily on one side (winking). When the stimulation is strong, the corrugator and other groups of muscles which raise the cheek and nose toward the eye may also contr.nct, and so form a more perfect protection and closure of the eye. Intense stimulation of the retina causes closure of the eyelids [and in this case the shortest reflex known, the latent period, is 0.5 second ( VValler)'\. 2. Sneezing Centre. — The afferent channels are the internal nasal branches of the trigeminus and the olfactory, the latter in the case of intense odors. The efferent or motor paths lie in the nerves for the muscles of expiration (§§ 120, 3, and 347, II). Sneezing cannot be performed voluntarily [but it maybe inhib- ited by compressing the nasal nerve at its exit on the nose]. 3. Coughing Centre. — .\ccording to Kohts, it is placed a little above the inspiratory centre ; the afferent paths are the sensory branches of the vagus (§352, 5, (?). The efferent paths lie in the nerves of expiration and those that close the glottis (§ 120, i). 4. Centre for the Movements of Sucking and Mastication. — The afferent paths lie in the sensory branches of the nerves of the mouth and lips (2d and 3d branches of the trigeminus and glosso-pharyngeal). The efferent nerves for suction (§ 152) are: Facial for the lips, hypoglossal for the tongue, the inferior maxillary division of the trigeminus for the muscles which elevate and depress the jaw. For the movements of mastication the same nerves are in action (S 153), but when food passes within the dental arch the hypoglossal is concerned in the movements of the tongue, and the facial for the buccinator. 5. Centre for the Secretion of Saliva (p. 241), which lies in the floor of the 4th ventricle. Stimulation of the medulla oblongata causes a profuse secre- tion of saliva, when the chorda tympani and glosso-pharyngeal nerves are intact, a much feebler secretion when the nerves are divided, and no secretion at all when the cervical symjiathetic is extirjjated at the same time ( Griitzner). 6. Swallowing Centre in the floor of the 4th ventricle (§ 156). — The afferent paths lie in the sensory branches of the nerves of the mouth, palate, and pharynx (2d and 3d branches of the trigeminus, glosso-pharyngeal, and vagusj ; the efferent channels in the motor branches of the pharyngeal plexus (§ 352. 4)- According to .Steiner, every time we swallow there is a slight stimulation of the respiratory centre, resulting in a slight contraction of the diaphragm. [Kronecker has shown that if a glass of water be sipped slowly, the action of the cardio-inhibitory centre is interfered with reflexly, so that the heart tieats much more rapidly, whereby the circulation is accelerated, hence probably why sipping an alcoholic drink intoxicates more rapidly than when it is ijuickly swallowed.] 7. Vomiting Centre (§ 158). — The relation of certain brancHtes of the vagus to this art are given at § 352, 2, and 12, li. 8. The upper centre for the dilator pupillae muscle, the smooth muscles of the orbit, and the eyelids lies in the mtdulla oblongata. The fibres pass out partly in the trigeminus (§ 347^ I, 3), partly in the lateral columns of the spinal cord as fiir down as the cilio-spinal region, and pass out by the two lowest cervical 686 POSITION OF THE RESPIRATORY CENTRE. ard the two upper dorsal nerves into the cervical sympathetic (§ 356, A, i). The centre is normally excited reflexly by shading the retina, /. e., by diminishing the amount of light admitted into the eye. It is directly excited by the circula- tion of dyspnojic blood in the medulla. (The centre for contracting the pupil is referred to at §§ 345 and 392.) 9. There is a subordinate centre in the medulla oblongata, which seems to be concerned in bring, ing the various reflex centres of the cord into relation with each other. Owsjannikow found that, on dividing the medulla 6 mm. above the calamus scriptorius (rabbit) the fcw^'i?/ reflex movements of the body still occurred, and the anterior and posterior extremities participated in such general movements. If, however, the section was made I mm. nearer the calamus, only local partial reflex actions occurred (\ 360, III, 4) ; [thus, on stimulating the hind leg, the fore legs did not react — the transference of the reflex was interfered with]. The centre reaches upward to slightly above the lowest third of the oblongata. Pathological. — The medulla oblongata is sometimes the seat of a typical disease, known as bulbar paralysis, or glosso-pharyngo-labial paralysis (Diichenne, 1S60), in which there is a pro- gressive invasion of the different ner\'e nuclei (centres), of the cranial nerves which arise within the medulla, these centres being the motor portions of an important reflex apparatus. Usually the disease begins with paralysis of the tongue, accompanied by fibrillar contractions, whereby speech, formation of the food into a bolus, and swallowing are interfered with (^ 354). The secretion of thick viscid saliva points to the impossibility of secreting a thin, watery /i?eia/ saliva (§ 145, A), owing to paralysis of this nerve nucleus. Swallowing may be imposihle, owing to paralysis of the pharynx and palate. This interferes with the formation of consonanls [especially the linguals, /, /, J, )-, by and by the labial explosives b, p,] (^318, C); the speech becomes nasal, while fluids and solid food often pass into the nose. Then follows paralysis of the branches of the facial to the lips, and there is a characteristic expression of the mouth " as if it were frozen." All the muscles of the face may be paralyzed; sometimes the laryngeal mttseles are paralyzed, leading to the loss of voice and the entrance of food into the windpipe. The heart bents are often slo-a>edf pointing to stimulation of the cardio-inhibitory fibres (arising from the acces- sorius). Attacks of dyspnaa, like those following paralysis of the recurrent nerves \\ 313, II. I, and J 352, 5, b), and death may occur. Paralysis of the muscles of mastication, contraction of the pupil, and paraWsis of the abducens are rare. [This disease is always bilateral, and it is important to note that it affects the nuclei of those muscles that guard the orifices of the mouth, including the tongue, the posterior nares including the soft palate, and the rima glottidis with the vocal cords.] 368. THE RESPIRATORY CENTRE AND THE INNERVA- TION OF THE RESPIRATORY APPARATUS.— The respiratory centre lies in the medulla oblongata KLcgaUois), behind the point of origin of the vagi, on both sides of the posterior as])ect of the apex of the calamus scrip- torius, between the nuclei of the vagus and accessorius {Flourens), and was named by Flourens the vital point, or noeud vital. The centre is double, one for each side, and it may be separated by means of a longitudinal incision lyLonget), whereby the respiratory movements continue symmetrically on both sides. Section of Vagi. — If one vagus be divided, respiration on that side is slowed. If I'oth vagi be divided, the respirations become much shiver and deeper, but the respiratory movements are symmetrical on both sides. Stimulation of the centra/ end of one vagus, both being divided, causes an arrest of the respiration only on the same side, the other side continues to breathe. The same result is obtained by stimula- tion of the trigetninus on one side {Langendorff). When the centre is divided transversely on one side, the respiratory movements on the same side cease {Schiff). Most probably the dominating respiratory centre lies in the medulla oblongata, and upon it depends the rhythm and symmetry of the respiratory movements ; but, in addition, other and subordinate centres are placed in the spinal cord, and these are governed by the oblongata centre. If the spinal cord be divided in newly-born animals (dog, cat) below the medulla oblongata, respi- ratory movements of the thorax are sometimes observed {^Bracket {i8jj), Laitten- bach, and Langendorff'). [If the cord be divided below the medulla, or the cranial arteries ligatured (rabbit), there may still be respiratory movements, which become more distinct if strychnin be previously administered, so that Langendorfl" assumes the existence of a spinal respiratory centre, which he finds is also in- fluenced by reflex stimulation of sensory nerves.] CEREBRAL INSPIRATORY CENTRE. re of the contractions, more especially the auricles, although in some animals, e. g., the tortoise, the ventricles are not affected ; (c) the power of conduction, i. e., the capacity for conducting the muscular contractions. According to Gaskell, the vagus acts upon the rhyth- mical power of the muscular fibres of tlie heart.] This centre may be excited directly in the medulla, and also reflexly, by stimulating certain afferent nerves. Many observers assume that this centre is in a state of tonic excitement, i. e., that there is a continuous, uninterrupted, regulating and inhibitory action of this centre upon the heart through the fibres of the vagus. .According to Iiernstein, this tonic excitement is caused reflexly through the abdominal and cervical sympathetic. I. Direct Stimulation of the Centre. — This centre may be stimulated directly by the same stimuli that act upon the respiratory centre, (i) Sudden ananiia of the oblongata, by ligature of both carotids, both subclavians, or decapi- tating a rabbit, the vagi alone being left undivided, causes slowing and even temporary arrest of the action of the heart. (2) Sudden venous hyperemia acts in a similar manner, and it can be produced by ligaturing all the veins returning from the head (^Landois, Hermann and Escher). (3) The increased venositx of the blood, produced either by direct cessation of the respirations (rabbit) or by forcing into the lungs a quantity of air containing much COj {Traube). As the circulation in the placenta (the respiratory organ of the fcetus) is interfered with during severe labor, this sufficiently explains the constant enfeeblement of the action of the heart during protracted labor ; it is due to stimulation of the central end of the vagus by the dyspnceic blood (^B. S. Schultze). (^4) .\t the moment the respiratory centre is excited, and an inspiration occurs, there is a variation in the inhibitory activity of the cardiac centre (^Bonders, Pfliiger, Fre- dericij — ^ 74, a, 4). (5) The centre is excited by increased blood pressure within the cerebral arteries. II. The cardio-inhibitory centre may be excited reflexly — (i) By stimulation of sensory nerves {Loven, Kratschmer). (2) By stimulation of the central end of one vagus, provided the other vagus is intact {v. Bezold, Donders, Aubert and Roever). (3) By stimulation of the sensory nerves of the intestines by tapping upon the belly (Goltz's tapping experiment;, whereby the action of the heart is arrested. Stimulation of the splanchnic directly (^Asp and Ludwig), or of the abdominal or cervical sympathetic (^Bernstein), produces the same result. Very strong stimulation of sensory nerves, however, arrests the above-named reflex effects upon the vagus (§ 361, 3). Tapping Experiment. — Goltz's experiment succeeds at once by tapping the intestines of a frog directly, say with the handle of a scalpel, especially if the intestine has been exposed to the air for a short time, so as to become inflamed 1 Tarchanoff). Stimulation of the stomach of the dog causes slowing of the heart \ie.3.\. [Sii;. Mayer, and Pribram). [M'William finds that the action of the heart of the eel may be arrested rellexly with very great facility. The reflex inhibition is ob'.ained 692 STIMULATION OF THE TRUNK OF THE VAGUS. by slight stimulation of the gills (through the branchial nerves), the skin of the head and tail and parietal peritoneum, by severe injury of almost any part of the animal except the abdominal organs.] [Effect of Swallowing Fluids. — Kronecker has shown that the act of swallowing interferes with or abolishes temporarily the cardio-inhibitory action of the vagus, so that the pulse rate is greatly accelerated. Merely sipping a wineglassful of water may raise the rate 30 per cent. Hence, sipping cold water acts as a powerful cardiac stimulant.] According to Hering, the excitability of the cardio-inhibitory centre is diminished by vigorous artificial ventilation of the lungs with atmospheric air. At the same time there is a considerable fall of the blood pressure (§353,8,4). In man, a vigorous expiration, owing to the increased intra-pulmonary pressure, causes an acceleration of the heart beat, which Sommerbrodt ascribes to a diminution of the activity of the vagi. At the same time the activity of the vasomotor centre is diminished (§ 60, 2). Stimulation of the trunk of the vagus from the centre downward, along its whole course, and also of certain of its cardiac branches [inferior cardiac], causes the heart either to beat more slowly or arrests its action in diastole. The result depends upon the strength of the stimulus employed ; feeble stimuli slow the action of the heart, while strong stimuli arrest it in diastole. The frog's heart may be arrested by stimulating the fibres of the vagus upon the sinus venosus. If strong stimuli be applied either to the centre or to the course of the nerve for a long time, the part stimulated becomes fatigued, and the heart beats more rapidly in spite of the continued stimulation. If a part of the nerve lying nearer the heart be stimulated, inhibition of the heart's action is brought about, as the stimulus acts upon a fresh portion of nerve. The following points have also been ascertained regarding the stimulation of the inhibitory fibres : — 1. The experiments of Lowit on the frog's heart, confirmed by Heidenhain, showed that electrical and chemical stimulation of the vagus produces different results as regards the extent of the ven- tricular systole, as well as the number of heart beats ; the contractions either become smaller or less frequent, or they become smaller and less frequent simultaneously. Strong stimuli cause, in addition, well-marked relaxation of heart muscle during diastole. 2. In order to cause inhibition of the heart, a continuous stimulus is not necessary. 3. Bonders, with Prahl and Niiel, observed that arrest of the heart's action did not take place immediately the stimulus was applied to the vagus, but about J of a second— period of latent stimulation — elapsed before the effect was produced on the heart. A rhythmically-intcri-itpted moderate stimulus suffices (?'. Bezold) ; 18 to 20 stimuli per second are required for mammals, and 2 to 3 per second for cold-blooded animals. If the heart be arrested by stimulation of the vagus, it can stiil contract, if it be excited directly, e. g., by pricking it with a needle, when it executes a single contraction. [This holds good only for some animals, c. _^.,frog, tortoise, birds and mammals. In fishes only the ventiicle responds to stimulation during marked inhibition; in the newt only the bulbus arteriosus. In the newt's heart the sinus, auricles and ven- tricle are all inexcitable to direct stimulation dunng strong inhibition.] 5. According to A. B. Meyer, inhibitory fibres are present only in the right vagus in the turtle. It is usually stated that the r/j-/;/ vagus is more effective than the left in other animals, ;•. g., rabbit, [Masoin, Arloing and Tripier); but this is subject to many exceptions (Landois and Langen- dorff). [In the newt the right vagus acts more readily 011 the ventricle than on the other pans of the heart ; slight stimulation of the right vagus can arrest the ventricle, while the sinus and auricles go on beating.] 6. The vagus has been compressed by the finger in neck of man (Czermak, Concato) ; but this experiment is accompanied by danger, and ought not to be undertaken. The electrotonic condition of the vagus is stated in J 335, III. 7. Schitf found that stimulation of the vagus of the frog caused acceleration of the heart beat when he displaced the blood of the heart with saline solution. If blood serum be supplied to the heart the vagus regains its inhibitory action. 8. Many soda salts in a proper concentration arrest the inhibitory action of the vagus, while pot- ash salts restore the inhibitory function of the vagi suspended by the soda salts. If, however, the soda or pot.ash salts act too long upon the heart, they produce a condition in which, after the inhibi- tory function of the vagi is abolished, it is not again restored. The heart's action in this condition is usually arhythmical {Lowit). 9. If the intracardial pressure be greatly increased, so as to accelerate greatly the cardiac pulsations, the activity of the vagus is correspondingly diminished (y. M. Ludwig and Luchsin- [Differences in Animals. — Perhaps the most remarkable fact in the influence of the vagus on the eel's heart and that of all other fishes examined is that vagus stimulation causes the sinus and THE NERVUS ACCELERANS. 693 auricle to be entirely inexcitable to direct stimulation during strong inliibition. Nerve stimulation has, in this case, the very peculiar effect of rendering the muscular tissue temporarily incapable of responding to even the strongest direct stimuli, e.g., powerful induction shocks. This would appear to be decisive evidence that the vagus acts on muscle directly, and not simply on automatic motor ganglia, as was held according to the old view. Poisons. — Muscarin stimulates the terminations of the vagus in the heart, and causes the heart to stand still in diastole [SchmieJeberg atid Kofpe). If alropin be applied in solution to the heart this action is set aside, and the heart begins to beat again. Digilalin diminishes the number of heart beats by stimulating the cardio -inhibitory centre (vagus) in the medulla. Large doses diminish the excitability of the vagus centre, and increase at the same time the accelerating cardiac ganglia, so that the heart beats are thereby increased. In small doses, digitalin raises the blood pressure by stimulating the vasomotor centre and the elements of the vascular wall [Klug'). Nicotin first excites the vagus, then rapidly paralyzes it. I/vdrocyanic acii/h.-ds the same effect (/"/-y e supplies a few vasomotor fibres to its own area of distribution {Schiff, Lovin, Moreau). The vaso- motor nerves to the upper extremities pass through the anterior roots of the middle dorsal nerves REFLEX STIMULATION OK THE VASOMOTOR CENTRE. 697 into the thoracic sympathetic, and upward to the 1st thoracic ganglion, and from thence through the rami comraunicantes to the brachial plexus (Schiff, Cyon). The skin of the trunk receives its vasomotor nerves through the dorsal and lumbar nerves. The vasomotor nerves to the lower ex- tremities pass through the nerves of the lumbar and sacral plexuses into the sympathetic, and from thence to the lower limbs (Pflliver, Schiff, CI. Bernard). The lungs, in addition to a few fibres through the vagus, are supplied from tlie cervical spinal cord through the ist thoracic gan- glion {Brown- ^iijuard. Pick and BaJoudy Liclilhsim). The splanchnic is the greatest vasomotor nerve in the body, and supplies the abdominal viscera (\ 356, B — Bezold, Liid-n'g and Cyon). The vasomotor nerves of the liver (\ 173, 6), kidney (§ 276), and spleen {\ 103) have been referred to already. According to .Strieker, most of the vasomotor nerves leave the spinal cord between the 5lh cervical and the ist dorsal vertebra. [Gaskell finds that in the dog they begin to leave the cord at the 2d dorsal nerve ({ 366).] As a general rule, the blood vessels of the trunk and extremities are innervated from those nerves which give other fibres (e.g., sensory) to those regions. The difterent vascular areas behave differ- ently with regard to the intensity of the action of the vasomotor nerves. The most powerful vaso- motor nerves are those that act upon the blood vessels of peripheral parts, e.g., the toes, the fingers and ears ; while those that act upon central parts seem to be less active (Lewasehe^u), e.g., on the pulmonic circulation [\ 88). II. Reflex Stimulation of the Centre. — There are fibres contained in the different afferent nerves whose stimulation affects the vasomotor centre. There are nerve fibres whose stimulation excites the vasomotor centre, thus causing a stronger contraction of the arteries, and consequently an increase of the arterial blood pressure. These are called "pressor" fibres. Conversely, there are other fibres whose stimulation refle.^ly diminishes the excitability of the vasomotor centre. These act as refle.\ inhibitory nerves on the centre, and are known as " depressor" nerves. Pressor, or e.xcito-vasomotor nerves, have already been referred to in connec- tion with the superior and inferior laryngeal nerves (§ 352, 12, a) \ in the trigem- inus, which, when stimulated directly (§ 347), causes a pressor action, as well as when stimulating vapors are blown into the nostrils {Herutg and Kratschmcr). [The rise of the blood pressure in this case, however, is accompanied by a change in the character of the heart's beat and in the respirations. Rutherford has shown that in the rabbit the vapor of chloroform, ether, amylic nitrite, acetic acid or ammonia held before the nose of a rabbit greatly retards or even arrests the heart's action, and the same is true if the nostrils be closed by the hand. This arrest does not occur if the trachea be opened, and Rutherford regards the result as due not to the stimulation of the sensory fibres of the trigeminus, but to the state of the blood acting on the cardio-inhibitory nerve apparatus.] Hubert and Roever found pressor fibres in the cervical sympathetic ; S. Mayer and Prib- ram found that mechanical stimulation of the stomach, especially of its serosa, caused pressor effects (§ 352, 12, c). According to Lov^n, \.\\t first effect of stimulating every sensory nerve is a pressor action. [If a dog be poisoned with curara, and the central twA. of one sciatic nerve be stimulated, there is a great and steady rise of the blood pressure, chiefly owing to the contraction of the abdominal blood vessels, and at the same time there is no change in the heart beat. If, however, the animal be poisoned with chloral, there is a fall of the blood pressure resembling a depressor effect.] O. Naumann found that weak electrical stimulation of the skin caused at first contraction of the blood vessels, especially of the mesentery, lungs and the web. with simultaneous excitement of the cardiac activity and acceleration of the circulation (frog). Strong stimuli, however, had an oppo- site effect, i.e., a depressor etfect, with simultaneous decrease of the cardiac activity. The applica- tion of heat and cold to the skin produces refiexly a change in the lumen of the blood vessels and in the cardiac activity (Kohrig, Winternitz). Pinching the skin causes contraction of the vessels of the pia mater of the rabbit [Schiiller), and the same result was produced by a warm bath, while cold dilated the vessels. These results are due partly to pressor and partly to depressor effects, but the chief cause of the dilatation of the blood vessels is the increased blood pressure due to the cold constricting the cutaneous vessels. Heat, of course, has the opposite effect. Depressor fibres, i.e., fibres whose stimulation diminishes the activity of the vasomotor centre, are present in many nerves. They are specially numerous in 698 LOCAL AND SECONDARY RESULTS OF VASOMOTOR ACTION. the superior cardiac branch of the vagus, which is known as the depressor nerve (§ 352, 6). The trunk of the vagus below the latter also contains depressor fibres {v. BezoiJ an./ Dreschfeld), as well as the pulmonary fibres (dog) {Ta/jan- zeff). The latter also act as depressors during strong expiratory efforts (§ 74) ; while Hering found that inflating the lungs (to 50 mm. Hg pressure) caused a fall of the blood pressure (and also accelerated the heart beats — § 369, II). Stimu- lation of the central end of sensory nerves, especially when it is intense and long- continued, causes dilatation of the blood vessels in the area supplied them (Lovcn). According to Latschenberger and Deahna, all sensory nerves contain both pressor and depressor fibres. [If a rabbit be poisoned with curara, and the central end of the great auric- ular nerve be stimulated, there is a double effect — one local and the other general; the blood vessels throughout the body, but especially in the splanchnic area contract, so that there is a general rise of the blood pressure, while the blood vessels of the ear are dilated. If the central end of the tibial nerve be stimu- lated, there is a rise of the general blood pressure, but a local dilatation of the saphena artery in the limb of that side {Zoven'). Again, the temperature of one hand and the condition of its blood vessels influences that of the other. If one hand be dipped in cold water, the temperature of the other hand falls. Thus pressor and depressor effects may be obtained from the same nerve. The vaso- motor centre, therefore, primarily regulates the condition of the blood vessels, but through them it obtains its importance by regulating and controlling the blood supply according to the needs of an organ.] The central artery of a rabbit's ear contracts regularly and rhythmically 3 to S times per minute. Schift observed that stimulation of sensory nerves caused a dilatation of the artery, which was pre- ceded by a slight temporary constriction. Depressor effects are produced in the area of an artery to which direct pressure is applied, as occurs, for example, when the sphygmograph is applied for a long time — the pulse curves become larger, and there are signs of diminished arterial tension {\ 75). Rhythmical Contraction of Arteries. — In the intact body slow alternating contraction and dilatation, without there being a uniform rhythm, have been observed in the arteries of the ear of the rabbit, the membrane of a bat's wing, and the web of a frog's foot. This arrangement, observed by Schiff, supplies more or less blood to the parts according to the action of external conditions. It has been called a "-periodic regulatory muscular movement.'" Direct local applications may influence the lumen of the blood vessels ; cold and moderate elec- trical stimuli cause contraction; while, conversely, heat and strong mechanical or electrical stimuli cause dilatation, although with the latter two there is usually a preliminary constriction. Effect on Temperature. — The vasomotor nerves influence the temperature, not only of individual parts, but of the whole body. I. Local Effects. — Section of a peripheral vasomotor nerve, e. t;., the cer- vical sympathetic, is followed by dilatation of the blooil vessels of the parts supplied by it (^such as the ear of the rabbit), the intra-arterial pressure dilating the paralyzed walls of the vessels. Much arterial blood, therefore, passes into and causes a congestion and redness of the parts, or hyperasmia, while at the same time the temperature is increased. There is also increased transudation through the dilated capillaries within the dilated areas ; the velocity of the blood stream is of course diminished, and the blood pressure increased. The pulse is also felt more easily, because the blood vessels are dilated. Owing to the increase of blood stream, the blood may flow from the veins alinost arterial (bright red) in its char- acters, and the pulse may even be propagated into the veins, so that the blood spouts from them {CI. Bernard). Stimulation of the peripheral end of a vaso- motor nerve causes the opposite results — pallor, owing to contraction of the vessels, diminished transudation, and fall of the temperature on the surface. The smaller arteries may contract so much that their lumen is almost obliterated. Con- tinued stimulation ultimately exhausts the nerve, and causes at the same time the phenomena of paralysis of the vascular wall. Secondary Results. — The immediate results of paralysis of the vasomotor nerves lead to other EFFECT ON THE TEMPERATURE OF THE WHOLE BODY. 699 effects ; the paralysis of the muscles of the blood vessels must lead to congestion of the blood in the part ; the blood moves more slowlv, so that the parts in contact with the air cool more easily, and hence the first stage of increase of the temperature may be followed ^y a fall oi the temperature. The ear of a rabbit with the sympathetic divided, after several weeks becomes cooler than the ear on the sound one. If in man the motor muscular nerves, as well as the vasomotor fibres, are para- lyzed, then the paralyzed limb becomes cooler, because the paralyzed muscles no longer contract to aid in the production of heat {\ 33S), and also because the dilatation of the muscular arteries, which accompanies a muscular contraction, is absent. Should atrophy of the paralyzed muscles set in the blood vessels also become smaller. Hence paralyzed limbs in man generally become cooler as time goes on. The primary efl^ect, however, in a limb, e. ^., after section of the sciatic or lesion of the brachial ple.\us, is an increase of the temperature. If, at the same time, the vasomotor nerves of a large area of the skin be par- alyzed, e. g., the lower half of the body after section of the spiniil cord, then so much heat is given off from the dilated blood vessels that either the warming of the skin lasts for a very short time and to a slight degree, or there may be cooling at once. Some observers ( Tsclietschichin, Naiinyn, Quincke, Heidenhain, Wood ) observed a rise of the temperature after section of the cervical spinal cord, but Riegel did not observe this increase. 2. Effect on the Temperature of the Whole Body. — Stimulation or paralysis of the vasomotor nerves of a sma// urea, has practically no effect on the general temperature of the body. If, however, the vasomotor nerves of a consider- able area of the skin be suddenly paralyzed, then the temperature of the entire body falls, because more heat is given off from the dilated vessels than under normal circumstances. This occurs when the spinal cord is divided high up in the neck. The inhalation of a few drops of amyl nitrite, which dilates the blood vessels of the skin, causes a fall of the temperature {Sassefzki and Manasse'iii). Conversely, stimulation of the vasomotor nerves of a large area increases the tem- perature, because the constricted vessels give off less heat. The temperature in fever may be partly explained in this way (§ 220, 4). The activity of the heart, /. e., the number and energy of the cardiac con- tractions, is influenced by the condition of the vasomotor nerves. When a large vasomotor area is paralyzed, the muscular blood channels are dilated, so that the blood does not flow to the heart at the usual rate and in the usual amount, as the pressure is considerably diminished. Hence the heart executes extremely small and low contractions. Strieker even observed that the heart of a dog ceased to beat on extirpating the spinal cord from the first cervical to the eighth dorsal vertebra. Conversely, we know that stimulation of a large vasomotor area by constricting the blood vessels raises the arterial blood pressure considerably. .\s the arterial pressure affects the pressure within the left ventricle, it may act as a mechanical stimulus to the cardiac wall, and increase the cardiac contractions both in number and strength. Hence, the circulation is accelerated {Heidenhain, S/aTjansky). Splanchnic. — By far the largest vasomotor area in the body is that controlled by the splanchnic nerves, as they supply the blood vessels of the abdomen (| 161) ; hence stimulation of their peri- pheral ends is followeil by a great rise of the blood pressure. When they are divided, there is such a fall of the blood pres-ure, that other parts of the body become more or less ansmic, and the animal may even die from " being bled into its own belly." Animals whose portal vein is ligatured die for the same rea on {C. Lna'^uii; and Thiry), [see \ 87]. The capicity of the vascular system, depending as it does in part upon the condition of the vasomotor nerves, influences the body 7veigJit. Stimulation of certain vascular areas may cause the rapid excretion of water, and we may thus account in part for the diminution of the body weight which has been sometimes observed after an epileptic attack terminating with polyuria. Trophic Disturbances sometimes occur after affections of the vasomotor nerves (§ 342, I, c). Paralysis of the vasomotor ner\'es not only causes dilatation of the blood vessels and local increase of the blood pressure, but it may also cause increased transudation through the capillaries [? 203]. When the active contraction of the muscles is abolished, at the same time the blood stream becomes slower ; and in some cases the skin becomes livid owing to the venous congestion. There is a diminution of the normal transpiration, and the epidermis may be dry and peel off in scales. The growth of the hair and nails may be affected by the congestion of blood, and other tissues may also suffer. 700 PATHOLOGICAL VASOMOTOR PHENOMENA. Vasomotor Centres in the Spinal Cord. — Besides the dominating centre in tlie medulla oblongatiT, the blood vessels are acted upon by hca/ or su/it»;iiiiatc vasomotor centres in the spinal cord, as is proved by the following observations : If the spinal cord of an animal be divided, then all the blood vessels supplied by vasomotor nerves below the point of section are paralyzed, as the vasomotor fibres proceed from the medulla oblongata. If the animal lives, the blood vessels re- gain their tone and their former calibre, while the rhythmical movements of their muscular walls are ascribed to the subordinate centres in the lower part of the spinal cord {Lister, Goltz, Vulpian — § 362, 7). These subordinate centres may also be influenced rcflcxly; after destruction of the medulla ob- longata the arteries of the frog's web still contract reflexly when the sensory nerves of the hind leg are stimulated {Putnam, Nussbauin, Vulpian'). If now the lower divided part of the cord be crushed, the blood vessels again dilate, owing to the destruction of the subordinate centres. In animals which survive this operation, the vessels of the paralyzed parts gradually recover their normal diameter and rhythmical movements. This effect is ascribed to ganglia which are supposed to exist along the course of the vessels. These ganglia [or peripheral nervous mechanisms] might be compared to the ganglia of the heart, and seem by themselves capable of sustaining the movements of the vascular wall. Even the blood vessels of an excised kidney exhibit periodic variations of their calibre (C Ltuiwig and Mosso). It is important to observe that the walls of the blood vessels contract as soon as the blood becomes highly venous. Hence the blood vessels offer a greater resistance to the passage of venous than to the arte- rial blood ( C. Li/dwig). Nevertheless, the blood vessels, although they recover part of their tone and inobility, never do so completely. The effects of direct mechanical, chemical, and electrical stimuli on blood vessels may be due to their action on these peripheral nervous mechanisms. The arteries may contract so much as almost to disappear, but sometimes dilatation follows the primary stimulus. Lewasch-w found that limbs in which the vasomotor fibres had undergone degeneration reacted like intact limbs to variations of temperature ; heat relaxed the vessels, and cold constricted them. It is, however, doubtful if the variations of the vascular lumen depend upon the stimulation of the peripheral nervims mechanisms. Amyl nitrite and digitalis are supposed to act on those hypothetical mechanisms. The puhalUi:.; veins in the bat's wing still continue to beat after section of all their neives, which is in favor of the existence of local nervous mechanisms (Liu/isin^^er, Sihiff). Influence of the Cerebrum. — The cerebrum influences the vasomotor centre, as is proved by the sudden pallor that accompanies some psychical conditions, such as fright or terror. There is a centre in the gray matter of the cerebrum where stimulation causes cooling of the opposite side of the body. Although there is one general vasomotor centre in the medulla oblongata which influences all the blood vessels of the body, it is really a complex composite centre, consisting of a number of closely aggregated centres, each of which presides over a particular vascular area. We know something of the hepatic (§ 175) and renal centres (§ 276). Many poisons excite the vasomotor nerves, such as ergotin, tannic acid, copaiba, and cubebs ; others yf/-.i/ excite, and then paralyze, e.i;., chloral hydrate, inorphia, landinosin, veratrin, nicotin. Calabar bean, alcohol; others •i^'^xAX-^ paralyze them, c.^., amyl nitrite, CO (? 17), atropin, mus- carin. The paralytic action of the poison is proved by the fact that, after section of the vagi and accelerantes, neither the pressor nor the depressor nerves, when stimulated, produce any effect. Many pathological conditions affect the vasomotor nerves. The veins are also influenced by va.soniotor nerves ( 6-'(?/;'s). and so are the lymphatics, but we know very little about this condition. Pathological. — The angio-neuroses, or nervous affections of blood vessels, form a most im- portant group of diseases. The parts primarily affected may be either the peripheral nervous mechanisms, the suliordmate centres in the cord, the dominating centre in the medulla, or the gray matter of the cerebrum. The effect may be direct or reflex. The dilatation of the vessrK may also be due to stimulation of vasodilator nerves, and the physician must be careful to distinguish VASO-DILATOR CENTRE AND VASO-DILATOR NERVES. 701 whether the result is due to paralysis of the vaso- constrictor nerves or stimulation of the vaso-dilator fibres. Angio-neuroses of the skin occur in affections of the vasomotor nerves, either as a diffuse redness or pallor ; or there may be circumscribed affections. Sometimes, owing to the stimula- tion of individual vasomotor nerves, there are local cutaneous arierio spasms (Nothnagel). In certain acute febrile attacks — after previous initial violent stimulation of the vasomotor nerves, especially during the cold stage of fever — there may be different forms of paralytic phenomena of the cutaneous vessels. In some cases of epilepsy in man. Trousseau observed irregular, red, angio- paralytic patches (taches cerebrales). Continued strong stimulation may lead to interruption of the circulation, which may result in gangrene of the skin ( Weiss) and deeper-seated parts. Hemicrania, due to unilateral spasm of the branches of the carotid on the head, is accompanied by severe headache (Dti Bois-Reymond). The cervical sympathetic nerve is intensely stimulated; a pale, collapsed and cool side of the face, contraction of the temporal artery like a firm whipcord, dilatation of the pupil, secretion of thick saliva are sure signs of this affection. This form may be followed by the opposite condition of paralysis of the cervical sympathetic, where the effects are reversed. Sometimes the two conditions may alternate. Basedow's disease is a remarkable condition, in which the vasomotor nerves are concerned ; the heart beats very rapidly (90 to 120 to 200 beats per minute), causing palpitation; there is swelling of the thyroid gland (struma) and projection of the eyeballs (exophthalmos), with imperfectly coordinated movements of the upper eyelid, whereby the plane of vision is raised or lowered. Perhaps in this disease we have to deal with a simultaneous stimulation of the accelerans cordis (^ 370), the motor fibres of Miiller's muscles of the orbit and eyelids (§ 347, I), as well as of the vaso-dilators of the thyroid gland. The disease may be due to direct stimulation of the sympathetic channels or their spinal origins, or it may be referred to some reflex cause. It has also been explained, however, thus, that the exophthalmus and struma are the consequence of vasomotor paralysis, which resuUs in enlargement of the blood vessels, while the increased cardiac action is a sign of the diminished or arrested inhibitory action of the vagus. All these phenomena may be caused, according to Filehne, by injury to the upper part of both restiform bodies in rabbits. Visceral Angio-neuroses. — The occurrence of sudden hyperasmia with transudations and ecchymoses in some thoracic or abdominal organs may have a neurotic basis. As already men- tioned, injury to the pons, corpus striatum and optic thalamus may give rise to hyperjemia, and ecchymoses in the lungs, pleura;, intestmes and kidneys. According to Brown-Sequard, compression or section of one-halt of the pons causes ecchymoses, especially in the lung of the opposite side ; he also observed ecchymoses in the renal capsule after injury of the lumbar portion of the spinal cord (? 379). The dependence of diabetes mellitus upon injury to the vasomotor nerves is referred to in ^175; the action of the vasomotor nerves on the secretion of urine in J 276; and fever in ?220. 372. VASO-DILATOR CENTRE AND VASO-DILATOR NERVES. — Although a vaso-dilator centre has not been definitely proved to e.xist in the medulla, still its e.xistence there has been surmised. Its action is opposite to that of the vasomotor centre. The centre is certainly not in a con- tinuous or tonic state of excitement. The vaso-dilator nerves behave in their functions similarly to the cardiac branches of the vagus ; both, when stimulated, cause relaxation and rest {Schiff, CI. Bernard). [They are not paralyzed, how- ever, by a large dose of atropin.] Hence, these nerves have been called vaso- inhibitory, vaso-hypotonic or vaso-dilator nerves. The existence of vaso-dilator nerves is assumed in accordance with such facts as the following : If the chorda tympani be divided, there is no change in the blood vessels of the sub-maxillary gland ; but if its peripheral end be stimulated, in addition to other results (§ 145), there is dilatation of the blood vessels of the sub-maxillary glands, so that its veins discharge bright florid blood, while they spout like an artery. Similarly, if the nervi erigentes be divided, there is no effect on the blood vessels of the penis (§ 362, 4) ; but if their /{■/-///zt-nj'/ ends be stimulated with Faradic electricity, the sinuses of the corpora cavernosa dilate, become filled with blood, and erection takes place (§ 436J). [Other examples in muscle and elsewhere are referred to below.] Dyspneeic blood stimulates this centre as well as the vasomotor centre, so that the cutaneous vessels are dilated, while simultaneously the vessels of the internal organs are contracted and the organs anjemic, owing to the stimulation of their vasomotor centre {^Dastre and Morat). 702 SPASM AND SWEAT CENTRE. Course of the Vaso-dilator Nerves. — To some organs they pass as special nerves; to other parts of the body, however, they proceed along with the vasomotor and other nerves. According to Dastra and Morat, the vaso-dilator nerves for the bucco-labial region (dog) pass out from the cord by the 1st to the 5th dorsal nerves, and go through the rami communicantes into the sympa- thetic, then to the superior cervical ganglion, and, lastly, through the carotid and inter carotid plexus into the trigeminus. [The fibres occur in the posterior segment of the ring of Vieussens, and if they be stimulated there is dilatation of the vessels in the lip and cheek on that side (p. 652).] The maxillary branch of the trigeminus, however, also contains vaso-dilator filires proper to itself [Laffonl]. In the gray matter of the cord there is a special subordinate cenlre for the vasodilator hbies of the bucco-labial region. This centre may be acted on reflexly by stimulation of the vagus, especially its pulmonary branches, and even liy stimulating the sciatic nerve. The ear receives its nerves from the 1st dorsal and lowest cerv.cal gangli ju, the upper limb from the thoracic portion, and the lower limb from the abdominal portion of the sympathetic. The vaso-dilator fibres run to the sub-maxillary and sub-lingual glands in the chorda tympani (§ 349, 4), while those for the posterior part of the tongue run in the glosso-pharyngcal nerve (§ 351, 4 — Viilpian). Perhaps the vagus contains those for the kidneys (§ 276J. Stimulation of the nervi erigentes pro- ceeding from the sacral plexus causes dilatation of the arteries of the penis, together with con- gestion of the corpora cavernosa (^436) {Eckkard, Lovin). Eckhard found that erection of the penis can be produced by stimulation of the spinal cord and of the pons as far as the peduncles, which may explain the phenomenon of priapism in connection w ith pathological irritations in these regions. The muscles receive their vaso-dilator fibres for their vessels through the trunks of the motor nerves. Stimulation of a motor nerve or the spinal cord causes not only contraction of the corre- sponding muscles, but also dilatation of their blood vessels (J 294, II — C. Luthoig and Sczelkoiv, Haftz, Gaiktil, Heideithain) — the dilatation of the vessels taking place even when the muscle is prevented from shortening. [Gaskell observed under the microscope the dilatation produced by stimulation of the nerve to the mylo-hyoid muscle of the frog.] Goltz showed that in the nerves to the limbs, e.g., in the sciatic nerve, the vasomotor and vaso-dilator fibres occur in the same nerve If the peripheral end of this nerve be stimulated, immediately after it is divided, the action of the vaso-constrictor fibres overcomes that of the dilators. If the peripheral end be stimulated several days after the section, when the vaso-constrictors have lost their excitability, the blood vessels dilate under the action of the vasodilator fibres. Stimuli, which are applied at long intervals to the nerve, act especially on the vasodilator fibres; while tetanizing stimuli act on the vasomotors. The sciatic nerve receives both kinds of fibres from the sympathetic. It is assumed that the peripheral nervous mechanisms in connection with the blood vessels are influenced by both kinds of vascular nerves; the vasomotors (constrictors) increase, while the vasodilators diminish, the activity of these mech- anisms or ganglia. Psychical con&x'Cxon'i, act upon the vasodilator nerves; the blush of shame, which is not confined to the face, but may even extend over the whole skin, is probably due to stim- ulation of the vaso dilator centre. Influence on Temperature. — The vasodilator nerves obviously have a considerable influence on the tenipeialure of the body and on the heat of the individual parts of the body. Both vascular centres must act as important regulatory mechanisms for the radiation ol heat through the cutaneous vessels [\ 214, II). Probably they are kept in activity reflexly by sensory nerves. Disturbances in their function may lead to an abnormal accumulation of heat, as in fever (\ 220), or to abnormal cooling {\ 213, 7). Some observers, however, assume the existence of an intra cranial "heat-regu- lating centre "( 7if/;f/ii/«V/««, A'izhkjk, (P«;HC/tc'), whose situation is unknown. According to Wood, separation of the medulla oblongata from the pons causes an increased radiation and a di- minished production of heat, due to the cutting off of the influences from the heat-regulating centre (« 377)- 373. THE SPASM CENTRE— THE SWEAT CENTRE.— Spasm Centre. — In the medulla oblongata, just where it joins the pons, there is a cen- tre whose stimulation causes general spasms. The centre may be excited by sud- denly producing a highly venous condition of the blood ("asphyxia spasms," in cases of drowning in mammals, but not in frogs) by sudden ancemia of the riiedulla oblongata, either in consequence of hemorrhage or ligature of both carotids and subclavians(A'««w7 ■'j ■5 .16 ExHT. Do. Do. Do. Do. Donders. V. Vintschgau and Honigschmied. Do. Do. Do. Do. Reaction Time. — This time is known as " rc-aclion time," and is distinctly longer than the simple reflex time required for a reflex act. It can be measured by causing the person experimented on to indicate by means of an electrical signal the moment when the stimulus is applied. The reaction time consists of the following events: (i) The duration of perctption, i:e., when we become conscious of the impression; (2) the duration of the time required to direct the attention to the impression; and (3) the duration of the voluntary impulse, together with (4) the time required for conducting the impulse in the afl^erent nen-es to the centre, ami (5) the time for the impulse to travel outward in the motor nerves. If the signal be made with the hand, then the reaction time for the impression of sounds 0.136 to 0.167 second; for taste, 0.15 to 0.23; touch, o 133 to 0.201 second (Nonch, V. Vintsiki;au and H'dnigschmied, Auerhacli, Exner, and others) ; for olfactory impres- sions, which, of course, depend upon many conditions (the phase of respiration, current of air). 0.2 to 0.5 second. Intense stimulation, increased attention, practice, expectation, and knowledge of the kind of stimulus to be applied, all diminish the time. Tactile impressions are most rapidly perceived when they are applied to the most sensitive parts (;-. Vintse/igau]. I'he time is increased with very strong stimuli, and when objects ditficult to be distinguished are applied {v. Helmholtz and Baxt). The time required to direct the attention to a number consisting of I to 3 figures, Tigerstedt and Bergquist found to be 0.015 'o oo35 second. Alcohol and the anfesthetics alter the time; according to their degree of action they shorten or lengthen it {Krdplin). In order that two shocks applied after each other be distinguished as two distinct impressions, a certain interval must elapse between the two shocks ; for the ear, 0.002 to 0.0075 second ; for the eye, 0.044 'o 0.47 second : for the finger, 0.277 second. [The Dilemma. — When a person is experimented on, and is not told whether the right or lett side is to be stimulated or what colored disk may be presented to the eye, then the time to respond correctly is longer.] [Drugs and other conditions afl'ect the reaction time. Ether and chlor iform lengthen it, while alcohol does the same, but the person imagines he ready reacts quicker. Noises also lengthen it.] In sleep and waking we observe the periodicity of the active and passive conditions of the brain. During sleep there is diminished excitability of the whole nervous system, which is only partly due to the fatigue of aft'erent nerves, but is largely due to the condition of the central nervous system. During sleep we require to apply strong stimuli to produce reflex acts. In the deepest sleep the psychical or mental processes seem to be completely in abeyance, so that a person asleep might be compared to an animal with its cerebral hemispheres removed. Toward the approach of the period when a person wakens, psychical activity may manifest itself in the form of dreams, which difler, however, from normal mental processes. They consist cither of impressions, where there is no objective cause (hallucinations), or of voluntary impulses which are not executed, or trains of thought where the reasoning and judging powers are disturbed. Often, especially near the time of waking, the actual stimuli may so act as to give rise to impressions which become mixed with the thoughts of a dream. The diminished activity of the heart {\ 70, 3, c), the respiration (J 127, 4), the gastric and intestinal movements ((J 213, 4), the formation of heat (J 216, 4), and the secretions, point to a diminished excitability of the corresponding nerve centres, and the diminished reflex excitability to a corresponding condition of the spinal cord. The pupils are contracted during sleep the deeper the latter is, so that in the deepest sleep they do not become contracted on the application of light. The pupils dilate when seusury or auditory stimuli are applied, and that the more the lighter the 708 HYPNOTISM. sleep; they are widest at the moment of awaking (Plo/ke). [Hughlings- Jackson finds that the retina is more anasmic than in the waking state.] During sleep there s-ems to be a condition of increased action of certain sphincter muscles — those for contracting the pupil and closing the eyelids (Rosfniinc/i). The soundness of the sleep may be determined by the intensity of the sound required to waken a person. Kohlschiitler lound that at first sleep deepens very quickly, then more slowly, and the maximum is reached after one hour (according to Monningholf and Priesbergen after I3^ hours); it then rapidly lightens, until several hours before waking it is very light. External or internal stimuli may suddenly diminish the depth of the sleep, but this may be followed again by deep sleep. The deeper the sleep, the longer it lasts. [Durham asserts that the brain is anaemic; the arteries and veins of the pia mater are contracted during sleep and the brain is smaller, but is this cause or effect ?] The cause of sleep is the using up of the potential energy, especially in the central nervous system, which renders a restitution of energy necessary. Perhaps the accumulation of the decom- position products of the nervous activity may also act (? lactates — Freyer) as producers of sleep. Sleep cannot be kept up for above a certain time, nor can it be inteirupted voluntarily. Many narcotics rapidly produce sltep. [The diastolic phase of cerebral activity, as sleep has been called, is largely dependent on the absence of stimuli. We must suppose that there are two factors, one central, represented by the excitability of the cerebrum, which will vary under different conditions, and the impulses reaching the cerebrum through the different sense organs. We know that a tendency to sleep is favored by removal of external stimuli, by shutting the eyes, retiring to a quiet place, etc. The external sensory impressions, indeed, mfluence the whole met.ibolism. Strumjiell describes the case of a boy whose sensory inlets were all paralyzed except one eye and one ear, and when these inlets were closed the boy fell asleep, showing how intimately the waking condition is bound up with sensory afferent impulses reaching the cerebral centres.] [Hypnotics, such as opium, morphia, KBr, chloral, are drugs which induce sleep.] Hypnotism, or Animal Magnetism. — [Most important observations on this subject were made by Braid of Manchester, and many of the recent re- discoveries of Weinhold, Heidenhain, and others confirm Braid's results.] Heidenhain assumes that the cause of this condition is due to an inhibition of the ganglionic cells of the cerebrum, produced by continuous feeble stimulation of the face (slightly stroking the skin or electrical applications), or of the optic nerve (as by gazing steadily at a small, brilliant object), or of the auditory nerve (by uniform sounds) ; while sudden and strong stimulation of the same nerves, especially blowing upon the face, abolishes the condition. Berger [and so did Carpenter and Braid long ago] attributes great importance to the psychological factor, whereby the attention was directed to a particular part of the body. The facility with which differ- ent persons become hypnotic varies very greatly. When the hypnotic condition has been produced a number of times, its subsequent occurrence is facilitated, e.g.., by merely pressing upon the brow, by placing the body passively in a certain position, or by slrol/<-a/ process, which is often very long, and runs toward the surface of the cerebrum, where it is said to terminate in an ovoid corpuscle, closely resembling those in which the ultimate branches of Purkinje's cells of the cere- bellum end; ((i)the unbranched meUian basilar process, which is an axial cylinder process, and becomes continuous with the axial cylinder of a nerve fibre of the white matter. It uhimately becomes invested by myelin. (<-) The lateral pro- cesses are given off chiefly near the base of the cell, and they soon branch to form part of the ground plexus of fibrils which everywhere per- vades the gray matter. At the lowest part of this layer the cells are larger than eKewhere, present- ing some resemblance to the cells of the anterior cornu of the gray matter of the spinal cord. Bv some it is described as a special layer, and termed the ganglion cell layer. This layer is sjiecially well marked in those convolutions which are de- scribed as containing motor'centres. Among the large cells are a few small angular-looking cells, which become more numerous lower down, and form (4) a narrow layer of numerous small branched, irregular, ganglionic cells — the " granular forma- tion'" of .Meynert. (5) A layer of spindle-shaped fusiform branched cells — the claustral formation of Meynert — lyinj for the most part parallel to the surface of the convolution. No layer is com- posed exclusively of one form of cell. The above represents the motor type. Then follows the -white Vertical section of the 3d cerebral convolution fman) I . superficial layer; 2, layer of small pyramidal cells; 3, layer of large pyramidal corpiLscies ; 4. granule layer; 5, layer of fusiform corpuscles; /«,white matter. 710 BLOOD VESSELS OF THE CEREBRUM. matter ^>«\ consisting of medullated nerve fibres, which run in groups into the gray matter, where they lose their myelin. The fibres are somewhat smaller than in the other parts of the nervous system (diameter ^555 inch), and between them lie a few nuclear elements. Each cell is sur- rounded by a lymph space, as in those of the cord.] [Recent Results. — Exner finds that after prolonged immersion of the cerebrum in i per cent, osmic acid and subsequent staining with ammoniacal carmine, that what has hitherto been described as " ground substance " in the gray matter really consists of well-formed medullated fibres. The first layer contains many medullated nerve fibres differing in thickness and direction. In the newborn child none are medullated. .Similar fibres exist in the second layer, while in the third they are in groups, and very numerous in the fourth. The nerve fibres do not seem to divide in the cortex, and Exner suggests that some of them serve to connect the different layers in the cortex. Fuchs finds that thi re are no medullated fibre* either in the cortex or medulla until the end of the fir.st month of life. The medullated fibres ai pear in the u])permost layer at the fifth month, and in the second at the end of the first year, the radial bundles in the deeper layers at the second month. The medullated fibres increase until the seventh or eighth year, when they have the saine arrangement as in the adult.] [Variations. — Although the above description indicates the typical arrangement in the motor area, Fig. 423. 1 , medullary arteries and 1 i in groupb between the convolutions ; 2, 2, a meshed plexus in fir^t layer i> closer plexus m middle layer ; c, opener pie substance, with its vessels {if). ies ot the cortex cerebri ; a, large in the gray matter next the white .•■till, the gray matter difi'ers in different parts of the brain. In the gray matter of the cornu ; the large pyramidal cells of (3) make up the chief mass; in the claustrum (4) is most abundant. In the central convolutions (ascending frontal and parietal 1, according to Betz, Mierzejewski and Bevan Lewis, very large pyramidal cells are found in the lower part of the third layer. Similar cells have been found in the posterior extremities of the frontal convolutions in some animals, the posterior parietal lobule, and paracentral lobule, all of which have motor functions. In those convolu- tions which are regarded as subserving sensory functions, a somewhat different type prevails, e.g., the occipital gyri or annectant convolutions (B. Lewis). The very large pyramidal cells are absent, while the granule layer exists as a well-marked layer between the layer of large pyramidal cells and the ganglion cell layer.] Blood Vessels. — The gray matter is much more vascular than the white, and when injected a section of a convolution presents the appearance shown in Fig. 423. The nutritive arteries con- sist of— (a) the long medullary arteries (i), which pass from the pia mater through the gray matter into the central white matter or centrum ovale. They are terminal arteries, and do not communicate with each other in their course; they thus supply independent vascular areas, nor do they anastomose with any of the arteries derived from the ganglionic system of blood vessels: 12 to CONVOLUTIONS OF THE CEREBRUM. 711 15 of them are seen in a section of a convolution, (i) The short cortical nutritive arteries (2) are smaller and shorter than the foregoing. Although some of them enter the white matter, they chiefly supply the cortex, where they form an open meshed plexus in the first layer (0), while in the next layer (/>) the plexus of capillaries is dense, the plexus again being wider in the inner layers (c).] [Central or Ganglionic Arteries. — From the trunks constituting the circle of Willis (Fig. in I 381), branches are given off, which pass upward and enter the brain to supply the basal ganglia with blood. They are arranged in several groups, but they are all terminal, each one supplying its own area, nor do they anastomose with the arteries of the cortex.] Cerebral Arteries. — From a practical point of view, the distribution of the blood vessels of the brain is im])ortant. The artery of the Sylvian fissure supplies the ttto/or areas of the brain in animals; in man, the precentral lobule is supplied by a branch of the anterior cerebral artery (Durel). The region of the third left frontal convolution, which is connected with the function of speech, is supplied by a special branch of the Sylvian artery. Those areas of the frontal lobes Fig. 424. it side of the human brain (diagrammatic). F, frontal ; P, parietal ; O. occipital ; T, temporo-sphenoidal lobe ; S, fissure of Sylvius : S', horiztmtal, S", ascending ramus of S : c, sulcus centralis, or fissure of Rolando ; A, ascending frontal, and B, ascending parietal convolution : F,, superior, F,, middle, and F3, inferior frontal convo- lutions; yV, superior, and y^, inferior frontal fissures : /j, sulcus pracenlralis : P, superior parietal lobule; P^, inferior parietal lobule, consisting of Pj, supramarginal gyms, and P^', angular gj'rus ; ;^, sulcus interparietalis ; cm, termination of calloso-marginal fissure; O^, first, U3, second, O,, third occipital convolutions; po, parieto- occipital fissure ; (?, transverse-occipit;il fissure ; o^, inferior longitudmal occipital fissure; Ti, first, Ta, second, Tj, temporo-sphenoidal convolutions ; /,, first, /a, second temporo-sphenoidal fissures. whose injury results in disturbance of the intelligence (Ferrier) are supplied by the anterior cerebral artery. Those regions of the cortex cerebri whose injury, according to Ferrier, causes hemianaes- thesia are supplied by the posterior cerebral artery. [In connection with the localization of the centres in the cortex, it is important to be thoroughly acquainted with the arrangement of the cerebral convolutions. Each half of the outer cerebral surface is divided by certain fissures into five lobes — frontal, parietal, occipital, temporo- sphenoidal and central, or island of Rail (Fig. 424). Die frontal lobe (Fig. 424) consists of three convolutions, with numerous secondary folds running nearly horizontal, named superior (F,), middle (F^) and inferior (F3) frontal convolutions. Behind these is a large convolution, the ascending frontal (A), which ascends almost vertically, immediately behind these, separated from them, how- ever, by the precentral fissure (/j), and mapped oft" behind by the fissure ot Rolando, or the central sulcus (.).] 712 CONVOLUTIONS OF THE CEREBRUM. [The parietal lobe (Fig. 424, P) is limited in front by the fissure of Rolando, below, in part by the Sylvian fissure, and behind by the parieto-occipital fissure. It consists of the ascending parietal (posterior central) convolution (Fig. 424, B), which ascends just behind the fissure of Rolando, and parallel to the ascending frontal, with which it is continuous below; above it becomes continuous with the superior parietal lobule (Pj ), while the latter is separated from the inferior parietal lobule ^pli courhe) by the interparietal sulcus. The inferior parietal lobule consists of («) a part arching over the upper end of the Sylvian fissure, the supramarginal convolution (P^), which is continuous with the superior temporo-sphenoidal convolution. Behind is i^h) the angular gyrus (P,^), which arches round the posterior end of the parallel fissure, and becomes connected with the middle temporo-sphenoidal con\olution.] [The temporo-sphenoidal lobe (Fig. 424, T) consists of three horizontal convolutions — supe- rior, middle and inferior — the two former being separated by the parallel sulcus, while the whole lobe is mapped off from the frontal by the Sylvian fissure (S).] [The occipital lobe (Fig. 424, O) is small, forms the rounded posterior end of the cerebrum, and is separated from the parietal lobe by the parieto-occipital fissure, which fissure is bridged over at the lower part by the four annectant gyri (//« de passage of Gratiolet). It has three convolu- tions — superior (O,), middle (O.,) and inferior (O3) — on its outer surface.] [The central lobe, or island of Reil, consists of five or six short, straight convolutions (gyri Fig. 425. Median aspect of the right hemisphere. CC, corpus callosum divided longitudinally : Gf, gyrus fomicafus : H, gyrus liippocampi : A, sulcus hippocampi ; U, uncinate gyrus : c»/. calloso-marginal fissure ; F, first frontal con- volution ; r, terminal portion of fissure of Rolando ; A, ascending frontal ; B, ascending parietal convolution and paracentral lobule : Pi', precuneus or quadrate lobule ; Oz. cuneus ; Po. parieto-occipital fissure ; cj, , transverse occipital fissure ; oc, calcarine fissure : oc', superior, oc", inferior ramus of the same ; D, gyrus descendens ; T4, gyrus occipito-temporalis lateralis {lobulus fusiformis) ; Tg, gyrus occipito-temporalis medialis (lobulus lingualis). operti — Fig. 426) radiating outward and backward from near the anterior perforated spot, and can only be seen when the inargins of the Sylvian fissure are pulled asunder. The operculum, con- sisting of the extremities of the inferior frontal, ascending parietal and frontal convolutions, lie out- side it, cover it, and conceal it from view.] [On the inner or mesial surface of the cerebrum are — the gyrus fornicatus (Fig. 425, Gf ), or convolution of the corpus callosum, which runs parallel to and bends round the anterior and poste- rior extremities of the corpus callosum, terminating posteriorly in the gyrus uncinatus or gyrus hippocampi (Fig. 421;, Hi, and ending anteriorly in a crooked extremity, the subiculum cornu am- monis (Fig. 425, U). Above it is the calloso marginal fissure (Fig. 425, cm), and running parallel to it is the marginal convolution (Fig. 425), which lies between the latter fissure and the margin of the longitudinal fissure; it is, however, merely the mesial aspect of the frontal and parietal con- volutions. The quadrate lobule or praecuneus lies (Fig. 425, Pi) between the posterior extrem- ity of the calloso-marginal fissure and the parieto-occipital fissure ; it is merely the mesial aspect of the ascending parietal convolution. The parieto-occipital fissure terminates below in the calcarine fissure (Fig. 425, oc\, and the latter runs backward in the occipital lobe, dividing it into two branches, oc', oc" . Between the parieto-occipital and calcarine fissures lies the wedge-shaped lobule termed the cuneus (Fig. 425, 0:). The calcarine fissure indicates on the surface the position of the calcar avis or hippocampus minor, in the posterior cornu of the lateral ventricle. The CONDITIONS AFFECTING THE MOTOR CENTRES. 713 dentate fissure or sulcus hippocampi (Fig. 425, h), marks the position of the elevation of the hippocampus major, or cornu animonis, in the lateral ventricle. The temporo-sphenoidal lobe terminates anteriorly in the uncinate gyrus, while, running along the former and the occipital lobes is the collateral fissure (occipito-temporal sulcus), which marks the position of the emenentia collateralis in the descending cornu of the lateral ventricle, while it also separates the superior from the inferior temporo-occipital convolutions (T^ and T,).] Motor Centres. — Fritsch and Hitzig (1870) discovered a series of circum- scribed regions on the surface of the cerebral convolutions, whose stimulation by means of Fig. 426. electricity causes coordinated ?nove»ien/s in quite distinct groups of muscles of the opposite side of the body (Fig. 428, I, II). Methods — Stimulation. — The surface of the cere- brum is exposed in an animal (dog, monkey) by remov- ing a part of the skull covering the so-called motor con- volutions and dividing the dura mater. When the con- volutions are fully exposed, a pair of blunt, non-polariz- able (J 328) needle electrodes are applied near each other to various parts of the cerebral surface. We may employ the closing or opening shock of a constant current, or the constant current may be rapidly inter- rupted, the current being of such a strength as to be distinctly perceived when it is applied to the tip of the tongue [Frilsch and Hitzig). Or the induced current maybe used (Ferrier, iSjj) of such a strength that it is readily felt when applied to the tip of the tongue. The cerebrum is completely insensible to severe opera- tions t/iaile upon it. The areas of the cerebral cortex, whose stimulation discharges the characteristic move- ments, are regarded as actual centres, because the reaction time after stimulation of the centres and the duration of the muscular con- traction are longer than when the subcortical Orbi fibres which lead toward the deeper parts of the brain are stimulated. Another circum- stance favoring this view is that the excitabil- ity of these areas is influenced by the stimu- lation of afferent nerves {Bubnoff and Hei- denhain). It may be that these centres are acted upon by voluntary impulses in the exe- cution of voluntary movements. Hence, they have been called centres." The motor areas of the cerebrum (dog, cat, sheep) are characterized by the presence of specially large pyramidal cells {Betz, Mersejewsky, Bcvan, Lewis) ; while similar cells were found by Obersteiner m the areas marked 4 and 8 (Fig. 428), and Betz found them in the ascending frontal convolution of man, in the third frontal convolution, and in the island of Reil. O. Saltmann found that stimulation of the motor areas in newly-born animals is without result, while only the deeper fibres of the corona radiata are excitable. Modifying Conditions. — In the condition of deep narcosis produced by chloroform, ether, chloral, morphia, or in apncea, the excitability of the centres is abolished {Schiff), whilst the sub- cortical conducting paths still retain Iheir excitability [Buhnoff and Heidejihain). Small doses of these poisons and also of atropin at first increase the excitability of the cenlres. Moderate loss of blood excites them, while a great loss of blood diminishes and then abolishes the excitability (Muni and Orschansky). Slight inflammation increases, while cooling diminishes, the excilabilily. If the cortex cerebri be removed in animals, the excitability of the fibres of the corona radiala is com- pletely abolished about the fourth day, just as in the ca.se of a peripheral nerve separated from its centre (Alliertoni, JMichieli, Dupuy, Franck, and Pitres). al surface of the left frotital lobe and the land of Reil, the tip of the temporo-sphe- noidal lobe removed to show the latter. 17, convolution of the margin of the longitudinal fissure ; O, olfactory- fissure, with the olfactorj* lobe removed ; T R, triradiate fissure : \" and I '", convolutions on the orbital surface; i, i, 1, I, under surface of the infero-frontal convo- lution ; 4, under surface of the ascending frontal, and 5, of the ascending parietal con- volutions ; C, central lobe or island. ' psychomotor 714 COi\UlTIONS AFFECTING THE MOTOR CENTRES. Stimulation of Subcortical Parts. — As the fibres of the corona radiata converge toward the centre of the hemisphere, it is evident tliat, after removal of the cortex, stimulation of these fibres in the deeper parts of the hemisphere is followed by the same motor resahs {G/iiy /■/-/£■?-, J/«j<.7/i7/p/iare). i. <■., they serve as centres for the tactile and muscular sensations and those of the innervation of the opposite side. He asserts that after injury to these regions the corresponding functions are affected. According to Bechterew, the centres for the perception of tactile impressions, those of innerva- tion, of the muscular sense, and painful impressions are placed in the neighborhood of the motor areas (dog) ; the first immediately behind and external to the motor areas, the others in the region close to the origin of the Sylvian fissure. [So far this agrees with the views of Starr 1 p. 719).] Goltz, who first accurately described the disturbances uf vision following upon injuries to the cortex in dogs, is opposed to the view of sensory locahzation. He believes that each eye is con- nected with both hemispheres. He asserts that the disturbance of vision, after injury to the brain, consists merely in a diminished color and space sense. The recovery of the visual perception of one eye after injury of one side of the cortex cerebri he explains by supposing that this injury merely causes a temporary inhibition of the visual activity in the opposite eye, which disappears at a later period. Instead of psychical blindness and deafness he speaks of a " cerebro-optical " and " cerebio-acoustical weakness." 377. THE THERMAL CORTICAL CENTRES.— A. Eulenberg and Landois dis- covered an area on the cortex cerebri whose stimulation produced an undoubted effect upon the temperature and condition of the blood vessels of the opposite extremities. This region (Fig. 428, I, /), generally embraces the area, in which at the same lime the motor centres for the flexors and rotators of the fore Umb (3), and for the muscles of the hind hmb (4) are placed. The areas for the anterior and posterior limbs are placed apart, that for the anterior limb lies somewhat more ante- riorly, close to the lateral end of the crucial salens. Destruction of this region causes increase of the temperature of the opposite extremities; the temperature may vary considerably (1.5° to 2°, and even to 13 °C.). This result has been confirmed by Hitzig, Bechterew, Wood and others. This rise of the temperature is usually present for a considerable time after the injury, although it may then undergo variations. Sometimes it may last three months, in other cases it gradually reaches the normal in two or three days. In well-marked cases there is a diminution of the resist- ance of the wall of the femoral artery to pressure, and the pulse curve is not so high (Jieinke). TOPOGRAPHY OF THE CORTEX CEREBRI. 725 Local electrical stimulation of the area causes a slight temporary cooling of the opposite extremi- ties, which may be detected by the thermo-electric method. Stimulation by means of common salt acts in the same way, but in this case the phenomena of destruction of the centre soon appear. As yet it has not been proved that there is a similar area for each half of the head. The cerebro-epileptic attacks (? 37s ) increase the bodily temperature, partly owing to the increased production of heat by the muscles (^ 302), partly owing to diminished radiation of heat through the cutaneous vessels, in consequence of stimulation of the thermal cortical nerves. The experiments led to no definite results when perfonned on rabbits. .According to Wood, destruction of these centres occasions an increased production of heat that can be measured by calorimetric methods, while stimulation causes the opposite result. These experiments explain how psychical stimulation of the cerebrum may have an effect upon the diameter of the blood vessels and on the temperature, as evidenced by sudden paleness and con- gestion (? -,7S, III). [Heat Production. — Injury to the fore-brain has no effect on the temperature. If the brain of a rabbit be punctured through the large fontanelle and the stylette be forced through the gray matter on the surface, white matter, and the median portion of the corpus striatum right to the base of the brain, there is a rapid rise of the temperature which may last several days. Injury to the gray cortex does not affect the temperature. After puncture of the corpus striatum the highest tem- perature is reached only after twenty-four to seventy hours, but when the puncture reaches the base of the brain this result occurs in two to four hours. Electrical stimulation of these areas causes the same effect on the temperature. Direct injury to certain parts of the brain is followed by a rise of the temperature — or fever. There is at the same time an increase of the O taken in, the CO, given off and a decided increase of the N given off, indicating an increase in the proteid metabolism, which points to an increased production of heat (Aronsohn and Sachs, Richet, Wood).'\ General and Theoretical. — Goltz's View. — Goltz uses a different method to remove the cortex cerebri — he makes an opening in the skuil of a dog, and by means of a stream of water washes away the desired amount of brain matter. He describes, first of all, inhibitory phenomena, which are temporary and due to a temporary suppression of the activity of the ner\ous apparatus, which, however, is not injured anatomically, but may be explained in the same way as the suppres- sion of reflexes by strong stimulation of sensory nerves (\ 361, 3). In addition, there are the per- manent phenomena, due to the disappearance of the activity of the nervous apparatus, which is removed by the operation. A dog witli a large mass of its cerebral cortex removed may be com pared to an eating complex reflex machine. It behaves like an intensely stupid dog, walks slowly, with its head hanging down ; its cutaneous sensibility is diminished in all its qualities — it is less sen- sitive to pressure on the skin ; it takes less cognizance of variations of temperature, and does not comprehend how to feel ; it can with difficulty accommodate itself to the outer world, especially with regard to seeking out and taking its food. On the other hand, there is no paralysis of its muscles. The dog still sees, but it does not understand what it does see ; it looks like a somnam- bulist, who avoids obstacles without obtaining a clear perception of their nature. It hears, as it can be wakened from sleep by a call, but it hears like a person just wakened from a deep sleep by a voice — such a person does not at once obtain a distinct perception of the sound. The same is the case with the other senses. It howls from hunger, and eats until its stomach is filled ; it manifests no symptoms of sexual excitement. With regard to the localization of the different centres in the cerebrum, Goltz obtained the fol- lowing results : He finds that a dog with both parietal lobes destroyed has its sensibility perma- nently blunted, its intelligence diminished, and is vicious ; while when both occipital lobes are destroyed there is severe and permanent disturbance of vision. He supposes that every part of the brain is concerned in the functions of willing, feeling, perception and thinking. Every section is, independently of the others, connected by conductions with all the voluntary muscles, and on the other hand with all the sensory ner^'es of the body. He regards it as possible that the individual lobes have different functions. Inhibitory Phenomena. — Injury to the brain also causes inhibitor)' phenomena, such as the dis- turbances of motion, the complete hemiplegia which is frequently observed after large unilateral injuries of the cortex cerebri ; these are regarded by Goltz as inhibitory phenomena due to the injury acting on lower infra-cortical centres whose action inhibits movement, but these movements are recovered as soon as the inhibitory action ceases. 378. PHYSIOLOGICAL TOPOGRAPHY OF THE HUMAN CORTEX CEREBRI. — We accept the arrangement of convolutions accord- ing to Ecker, of which a short resume is given in § 375. I. The cortical motor regions for the face and the limbs are grouped around the fissure of Rolando, including the ascending frontal, ascending parietal, and part of the parietal lobule (Fig. 431 ). The centre for the face occupies the low- est third of the ascending frontal convolution and reaches also on the lowest fifth of the ascending parietal. The arm centre occupies the middle third of the ascending frontal and middle three-fifths of the ascending parietal convolutions, 726 HEMIPLEGIA. while the leg centre lies at the upper end of the sulcus and extends backward into the parietal lobule (and perhaps on to the superior frontal convolution") (Fig. 431). This leg centre is continued over on to the paracentral lobule opposite the upper end of the fissure of Rolando in the marginal convolution on the mesial aspect of the hemisphere (Fig. 433) where the centres for the muscles of the trunk also exist (p. 719). The centre for speech is in the posterior part of the third left frontal convolution (Fig. 431). Blood Supply. — These convolutions are supplied with blood from four to five branches of the Syl- vian artery, which may sometimes be plugged with an embolon. When a clot lodges in this artery, the branches to the basal ganglia may remain pervious, while the cortical branches may be plugged [Dure/, Heubney) {\ 381). [Hemiplegia consists of motor paralysis of one-half of the body, although, as a rule, all the muscles are not paralyzed to the same extent ; in some there may be Fio. 433. tion of the cerebral hemisphere. CC.i. corpus callosum ; NC, caudate nucleus; NL, lenticular nu- cleus; IC, internal capsule; CA. internal carotid artery; rtSL. lenticular-striate artery ("Artery of hemor- rhaee ") ; F. A, L, T, position of motor areas governing the movements of the face, arm, leg, and trunk muscles of the opposite side {Horsley), complete paralysis, /'. e., they are entirely removed from voluntary control, while in others there is merely impaired voltmtary control. It may be caused by affec- tions of the cortical centres or by lesion of the motor tracts above the medtilla, and the ]jaralysis is always on the side opposite to the lesion owing to the decussa- tion of the motor paths in the medulla. If the case be a severe one, we have what Ciiarcot terms haniplegie centrale vulgaire, or "complete hemiplegia," due to lesion of the cortical centres for the face, arm, and leg. While the arm and leg are completely paralyzed, tlie lower part of the face is more affected than the upper half, which is usually not much affected. All those movements under vol- untary control, and especially those that have been learned, are abolished, while the associated and bilateral movements, which even animals can execute imme- diately after birth, remain more or less unaffected. Hence the hand is more par- alyzed than the arm ; this, again, than the leg ; the lower facial branches more POSITION OF THE MOTOR CENTRES. 727 than the upper ; the nerves of the trunk scarcely at all {Ferrier). When an ex- traordinary effort is made, it will be found that there is some impairment of the power of the muscles of mastication and respiration, although the muscles on o|)posite sides act together { Cowers). The trunk muscles, as a rule, are but slightly affected, or not at all, as their centre is elsewhere. There may be altera- tions of sensibility and of the reflexes.] Conjugate deviation of the eyes with rotation of the head is frequently present in tlie early period of hemiplegia, although it usually disappears. When a person turns his head to one side, there is an .associated movement of certain of the ocular muscles with those of the neck. The head and eyes are usually turned to the side of the lesion ; this is termed " conjugate deviation," so that the power of voluntarily moving the eyes and head to the paralyzed side is temporarily lost. The unopposed muscles rotate the head and eyes to the sound side. If the lesion be in the pos- terior part of the pons, the deviation is to the paralyzed side (Pih'ost). [Subsequent Effects, — If there be say a hemorrhage into these motor regions, or from the leniiculo-striate artery, so as to compress the pyramidal fibres in the knee and anterior two-thirds of posterior segment of the internal capsule, then there is usually tonic or persistent contraction of the muscles affected. These tonic spasms may accompany the hemorrhage, or come on a few days after it and make up the condition of early rigidity. The contraction — if any — accompanying the hemorrhage is due to direct irritation of the pyramidal fibres, while that which comes on a few days later, and usually lasts a few weeks, is also due to irritation of these fibres, probably produced by inflammatory action in and around the seat of the lesion. The affected limb is stiff and resists passive movement. After a few weeks, late rigidity sets in and is persistent, and it is characterized by structural changes in the pyramidal paths which lead to other results. There is secondary de- scending degeneration in the pyramidal tracts, which cause "contracture" {Charcot) \n {he paial/zed limbs, while at the same time the deep or tendinous and periosteal reflexes (ankle clonus, rectus clonus, and the deep reflexes of the arm tendons, are exaggerated). The spastic rigidity is usually more marked in the arm than leg, and it generally affects the flexors more than the extensors, so tlial the upper arm is drawn close to the trunk, the elbow, arm, and fingers flexed ; in the leg the extensors of the leg overcome the peronei. Hitzig has pointed out that the contracture is less during sleep and after rest. The muscles at first can be stretched by sustained pressure, but after months or years structural changes occur in the muscles, ligaments, and tendons, and the limbs assume a permanent and characteristic attitude.] In hemiplegic pfersons, the power of the unparalyzed side is sometimes diminished (Brown- Sequard, Charcot, Pitrcs], which is not sufficiently explained by the fact that some bundles of the pyramidal tracts remain on the snmf side. Acquired Movements. — Some movements performed by man are learned only after much practice, and are only completely brought under the influence of the will after a time, such as the movements of the hand in learning a trade. Such movements are reacquired only very slowly, or not at all, after injury to the psychomotor centres. Those movements, however, which the body performs without previous training, such as the associated movements of the eyeballs, the face, and some of those of the legs, are rapidly recovered after such an injury, or they suft'er but little, if at all. Thus the facial muscles seem never to be so completely paralyzed after a lesion of the facial cortical centre, as in aff'ections of the trunk of the facial nerve the eye especially can be closed. Sucking movements have been observed in hemicephalous fcetuses. Degeneration of the Pyramidal Tracts. — After destruction of the cortical motor areas, descending degeneration of the cortico- motor paths, or "pyramidal tracts," takes place (§ 365). Degenerative changes have been found to occur within the white matter under the cortex, in the anterior two-thirds of posterior segment of the internal capsule [in the middle third of the crusta (Figs. 434.* 435 1 I']> pons, in the pyramids of the medulla oblongata (Fig. 434), and thence they have been traced into the pyramidal paths (anterior and lateral ) of the spinal cord {Charcot, Singer, M. Rosenthal). It is evident that lesions of these tracts at any part of their course must have the same result, viz., to produce hemiplegia. (For the subsequent eflTects, see p. 660. ) In a case of congenital absence of the left fore arm, Edinger found that the right central convolutions were developed. Ataxic motor conditions similar to those that occur in animals (p. 721) take place in man, and are known as cerebral ataxia. The Position of the Centres is given at p. 718. [But we may have localized lesions affecting one or more of the cortical motor areas ; these are called Monoplegiae. Cases in man are now sufficiently 728 POSITION OF THE MOTOR CENTRES. numerous to permit of accurate diagnosis.] Crural [rare lesions recorded in the convolutions at the upper end of the fissure of Rolando, and the continuation of this area on to the paracentral lobule of the marginal convolution], — brachio- crural, more common, upper and middle thirds of the ascending frontal and ascending parietal convolutions — brachial, brachio-facial — facial, the last in the lowest part of the central convolutions. [Convulsions and spasms may be discharged from motor cortical lesions, and these, whether they affect the general or localized areas, give rise to unilateral convolutions and monospasms respectively.] Paralysis of the muscles of the neck and throat indicates a lesion of the central convolutions, and so does paralysis of the muscles of the eye. Lesions of the cortex always cause simultaneous move- ments of the head and eyeballs Irritation of the Motor Centres. — If the motor centres are irritated by pathological processes, such as hyperaemia, or inflammation, in a syphilitic dia- Fic. 434 Fig. 434- — Secondary descending generation in middle third of right cni-i and in medulla after destruction of the cortical motor centres on the right side. FiG. 4S5- — Horizontal section of the cerebral peduncle in secondary degenemtion of the pyramidal tracts, where the lesion w.a.s limited to the middle third of the posterior segment oi the internal capsule. F, healthy cnista : L, locus niger ; P. internal third of the crusta on the diseased side ; D, secondary degeneration in the middle third ol the crusta ; CQ, corpora quadrigemina with the iter below them. thesis — more rarely by tumors, tubercle, cysts, cicatrices, fragments of bone — there arise spasmodic movements in the corresponding muscle groups. This con- dition of a sudden discharge of the gray matter resulting in local spasms is called " Jacksonian or cerebral epilepsy." Monospasm. — .A.ccording to the seat of the spasm, it is called facial, brachial, crural, mono- spasm, ere. C)f course, these spasms may afi'ect several groups of muscles. Barlholow and Scia- manna have stimulated the exposed human brain successfully with electricity. Cerebral Epilepsy. — Very powerful stimulation of one side may give rise to (^//rt/f-n?/ spasms, with loss of consciousness. In this case impulses are conducted to the other hemisphere by commissural fibres (§ 379). Movements of the Eye. — Nothing definite is known regarding the centre in the cortex for voluntary combined movements of the eyeballs in man. In paralytic affections of the cortex and of the paths proceeding from it, we occasionally find both eyes with a lateral deviation. If the par- alytic affection lies in one cerebral hemisphere, the conjugate deviation of the eyeballs is toward APHASIA. 729 the sound side (p. 620). If it is situated in the conducting paths, after these have decussated, viz., in the pons, the eyes are turned toward the paralyzed side (Prhwst). If the part be irritated so as to produce spasms in the opposite half of the body, of course the eyes are turned in the opposite direction to that in pure paralysis (Landouzy ami Grassel). Instead of the lateral deviation of the eyeballs already described, occasionally in cerebral paralysis there is merely a weakenitvj of the lateral recti muscles, so that during rest the eyes are not yet turned toward the sound side, but they cannot be turned strongly toward the affected side (Leichtenstern, Httnnius). The centre for the levator palpebrfe superioris appears to be placed in the gyrus angu- laris {^Grasset, Londonzy^ Chauffard'). II. The Centre for Speech. — The investigations of Bouilland [1825], Dax [1836], Broca [1861], Kussmaul, and Broadbent and others have shown that the third left frontal convolution of the cerebrum (Figs. 429, F, 3, and 431) is of essential iinportance for speech, while probably, also, the insula, or island of Reil, is concerned. It is seen to be deeply placed on lifting up the overhanging part of the brain called the operculum, lying between the two branches of the Sylvian fissure (S). The motor centres for the organs of speech (lips, tongue) lie in this region, and in this region also the psychical processes in the act of speech are com])leted. In the great majority of mankind the centre for speech is located in the left hemisphere. The fact that most men are righf-hmtded also points to a finer construction of the motor apparatus for the upper extremity, which must also be located in the left hemisphere. Men, therefore, with pronounced i-ight-handed- ;/«.f (droitiers) are evidently /if/Z-Z^ra/^^;/ (gauchers du cerveau — Broca). By far the greater number of mankind are "lift-brained speakers" (Kussmaul) ; still there are exceptions. As a matter of fact, cases of left-handed persons have been observed who lost their power of speech after a lesion of the right hemisphere ( Ogle, Hahershon). Investigations on the brains of remarkable men have shown that in them the third frontal convolution is more extensive and more complex than in men of a lower mental calibre. In deaf mutes it is very simple ; inicro- cejjhales and monkeys possess only a rudimentary third frontal (Rudinger). The motor tracts for speech pass along the upper edge of the island of Reil, then into the sub- stance of the hemispheres internal to the posterior edge of the knee of the internal capsule; from thence through the crusta of the left cerebral peduncle into the left half of the pons, where it crosses, then into the medulla oblongata, which is the place where all the motor nerves (trigeminus, facial, hypoglossal, vagus, and respiratory nerves) concerned in speech arise. Total destruction of these paths, therefore, causes total aphasia; while partial destruction causes a greater or less disturbance of the mechanism of articulation, which has been called " anarthria " by Leyden and Wernicke. Conditions. — Three activities are required for speech — ^(i) the normal move- ment of the vocal apparatus (tongue, lips, mouth, and respiratory apparatus) ; (2) a knowledge of the signs for objects and ideas (oral, written, or imitative or mi- metic signs) ; (3) the correct union of both. Aphasia. — Injury of the speech centre causes either a loss or more or less con- siderable disturbance of the power of speech. The less of the ]:)ower of speech is called "aphasia." [Aphasia, as usually understood, means the partial or com- plete loss of the power of articulate speech from cerebral causes.] The following forms of aphasia may be distinguished : — 1. Ataxic aphasia for the oro-lingua! heniiparesis of Ferrier), i.e., the loss of speech, owing to inability to execute the various movements of the mouth necessary for speech. Whenever such a person attempts to speak, he merely executes incoordinated grimaces and utters inarticulate sounds. [The muscles concerned in articulation, however, are not paralyzed, but there is an absence of co- ordination of these muscles due to disease of the cortical centre.] Hence, the patient cannot repeat what is said to him. Nevertheless, the /jrj/(-/;/<-«/ processes necessary for speech are comiiletely re- tained, and all words are remembered ; and hence ihese persons can still give expression to their thoughts graphically or by wnfing. If, however, the finely adjusted movements necessary for writ- ing are lost, owing to an affection of the centre of the hand, then there arises at the same lime the condition of agraphia, or inability to execute those movements necessary for writing. Such a per- son, when he desires to express his ideas in writing, only succeeds in making a few unintelligible scrawls on the paper. Occasionally such patients suffer from loss of the power of imitation or aminia ( A'lissmaiil). 2. Amnesic Aphasia, or Loss of the Memory of Words. — Should the patient, however, hear the 730 APHASIA. word, its significance recurs to him. The movements necessary for speech remain intact ; hence such a patient can at once repeat or write down what is said to him. Sometimes only certain kinds of words are forgotten, or it may be even only parts of these words are spoken; [Nouns and proper names usually go first.] Cases of amnesic aphasia, or the mixed ataxic-amncsic form of disturbance of speech, point to a lesion of the third frontal convolution and of the island of Reil on the left side. Another form of amnesic aphasia consists in this, that the words remain in one's memory but do not come when they are wanted, j.e.^ the association between the idea and the proper word to give ex- pression to it is inhibited (A'ussmaul). It is common for old people to forget the names of persons or proper names ; indeed, such a phenomenon is common within physiological limits, and it may ultimately pass into the pathological condition of amnesia senilis. Among the disturbances of speech o{ cere/irnl or\g\n, Kussmaul reckons the following: — 3. Paraphasia, or the inability to connect rightly the ideas with the proper words to express these ideas, so that, instead of giving expression to the proper ideas, the sense may be inverted, or the form of words may be unintelligible. It is as if the person were continually making a " slip of the tongue." 4. Agrammatism and ataxaphasia, or the inability to form the words grammatically and to ar- range them synthetically into sentences. Besides these, there is — 5. A pathological slow way of speaking (bradyphasia), or a pathological and stuttering way of reading (tumultus sermonis), both conditions being due to derangement of the cortex {A'liss- mail/). The disturbance of speech depending essentially upon affections of \.ht peripheral r\er\ei, or of the muscles of the organs of the voice and speech, are already referred to in J§ 319, 349, and 354- [In word-blindness the person cannot name a letter or a word, so that he Fig. 436. Fig. 437. Figs. 436, 437.— Schemes of aph.isi.i. A, centre or auditory images: M, or mo Oc. eye : E, reading centre; j to 7 lesions {Licktfte cannot understand symbols, such as printed or written words, or it may be any familiar object, although he can see quite well, while he can speak fluently and write correctly.] [In word-deafness the person hears other sounds and is not deaf, but he does not hear words.] [The study of aphasia in its various forms is simplified by a study of the mode of acquisition of language by a child. The child hears spoken words and obtains auditory memories or impressions of these sounds (called by Lichtheim " auditory word-representations "), and this must form the starling-point of language, and by and by it begins to coordinate its muscles to produce sounds imitative of these. Thus we have two centres, one for " auditory images " (Fig. 436, A), and the other for " motor images " (Fig. 436, M), and these two must be connected, thus establishing a reflex arc. There is a receptive and an emissive department as represented in the scheme. We must assume the existence of a higher centre (B), " where conceps are elaborated," where these sounds become intelligible. Volitional language requires a connection between B and M, as well as between A and M. But we have also reading and writing. Suppose O to represent a centre for visual impressions (printed words or writing), which we can understand through the connection between such visual impressions and auditory impressions, whereby a path is established through OA (Fig. 437). In reading aloud, however, the oro-lingual muscles must be coordinated, so we have the path OAM opened up. In writing or copying written characters, the movements of the hand are special, and perhaps require a special centre, or at least a special arrangement of the chan- nels for impulses in the centre ; the movements are learned under the guidance of ocular impres- THERMAL AND SENSORY CORTICAL CENTRES. 731 sions, so we connect O and E, E being the centre guiding the movements in writing. As to volitional writing the impulses pass through M, but does it pass directly to E, or indirectly through A ? Lichtheim assumes that it goes direct from M to E. It is evident that there are seven chan- nels which may be interrupted, each one giving rise to a dilTcrent form of aphasia (i to 7).] [Looked at from another point of view, either the ingoing («) or outgoing («) channels or cen- tres, or the commissural fibres between both, may be affected. If the motor centre is affected, we have Wernicke's " motor aphasia ; " if the sensory, his " sensorial aphasia."] [In the most common form, or ataxic aphasia (A'ussmniil), which was that described by Broca, or the " motor aphasia" of Wernicke, the lesion is in Fig. 436, in M, i. <■., in the motor, or what Ross calls the emissive department. In such a case it is obvious that there will be loss of (i) volitional speech, {2) repetition of words, (3) reading aloud, (4) volitional writing, and (5) writing to dicta- tion ; while there will exist [a) understanding of spoken words, (1^) also of written words, (c) and the faculty of copying. If the lesion be in A, we have the " sensorial aphasia" of Wernicke, i. e., in the acoustic word centre; we find loss of (i) understanding of spoken language, (2) also of written language. (3) faculty of repeating words, (4) and of writing to dictation, (5) and of reading aloud ; there will exist (a) the faculty of writing, (/') of copying words, and (c) of volitional speech, but the volitional speech is imperfect, the wrong word being often used, so that there is the condition of "paraphasia." If the connection between A and M be destroyed, other results will follow, and such cases of " commissural " aphasia have been described by W'ernicke. If the inter- ruption be between B and M we have a not uncommon variety of motor aphasia (4), where there is loss of (i) volitional speech, and (2) volitional writing, and there exist (a) understanding of spoken language, (b) of written language, (c) the faculty of copying; but it differs from Broca's aphasia in that there also exists [li) the faculty of repeating words, (<■) writing to dictation, (y),and reading aloud. If the lesion is in Mm (5) the symptoms will be those of Broca's aphasia, but there will exist (l) the faculty of volitional writing, and (2) of writing to dictation. Many examples of this occur where patients have lost the faculty of speaking, but can express their thoughts in writ- ing. In lesions of the path AB (6) there will be loss of (i) understanding of spoken language, and (2) of written language, and there will exist (a) volitional speech (but it will be paraphasic), (/>) volitional writing (but it will have the characters of paragraphia, (c) the faculty of repeating words, (d) reading aloud, (c) writing to dictation, and (f ) power of copying words. The person will be quite unable to understand what he repeats, reads aloud, or copies.] III. The thermal centre of Eulenberg and Landois for the extremities is associated with the motor areas. Injury or degeneration of these areas causes inequality of the temperature on both sides {^Bechtereri'Y In long-standing paralysis the initially high temperature of the affected limb may fall lower than that of the sound limb (§ 377). In cases of insanity, with general progressive paralysis, due to inflammation of the cortex cerebri, the temperature of the axilla on the same side is usually higher on the side which is the seat of the paralysis. In cases of conviihions, due to in- flammatory irritation of the cortex cerebri, during the attack the temperature on the same side as the centre is several tenths of a degree higher than on the other side [J\einharJ), IV. The sensory regions are those areas in which conscious perceptions of the sensory impressions are accomplished. Perhaps they are the substratum of sensory perceptions, and of the memory of sensory impressions. I. The psycho-optic or visual centre, according to 'Munk, Meynert, and Huguenin, includes the occipital lobes (Fig. 429, o', o', o'j, while according to E.vner the first and second occipital convolutions are its chief seats. Huguenin observed, in a case of long-standing blindness, consecutive disappearance of the occipital convolutions on both sides of the parieto-occipital fissure, while Giova- nardi, in a case of congenital absence of the eyes, observed atrophy of the occi- pital lobes, which were separated by a deep furrow from the rest of the brain. Stimulation of the centre gives rise to the phenomena of light and color. Injury causes disturbance of vision, especially hemiopia of the same side (§ 344 — U'cstphal, Jastroiiiitz). When oz/f centre is the seat of irritation there is pho- tojjsia of the same halves of both eyes {Charcot, Pfinainf). Stimulation of both centres causes the occurrence of the phenomena of light or color, or visual hal- lucinations in the entire field of vision. Cases of injury to the brain, where the sensations of light and space are quite intact, and where the color sense alone is abolished, seem to indicate that the color sense centre must be specially localized in the visual centre {Same/sohn, Steffaii). After injury of certain parts, especially of the lower parietal lobe, " psvihica/ />/hidn<'ss " may occur. A special form of this condition is known as "-word-blindness " or alexia (Coecitas verbalis), which consists in this, that the jjatient is no longer able to recognize ordinary written or printed characters (p. 730). lOZ THE AUDITORY, GUSTATORY AND OLFACTORY CENTRES. Charcot records an interesting case of psychical blindnes's. After a violent paroxysm of rage, an intelligent man suddenly lost the memory of visual impressions; all objects (persons, streets, houses) which were well known to him appearel to be quite strange, so that he did not even recognize him- self in a mirror. Visual perceptions were entirely absent from his dreams. Clinical observations on hemiopia (| 344) show that the field of vision of each eye is divided into a larger outer and a smaller inner portion, separated from each other by a vertical line passing throuiih the macula lutea. Each right or left half of both visual fields is related to one hemisphere ; both left halves are projected upon the left occipital lobes, and both right upon the right occipital lobes. Thus, in binocular vision every picture (when not too small) must be seen in two halves; the left half by the left, the right half by the right hemisphere ( Wernicke). As a result of pathological stimulation of the visual centre, especially in the insane, visual spectres may be produced. Pick observed a case where the hallucin.itions were confined to the right eye. 2. The psycho-acoustic or auditory centre lies on both sides (crossed) in the temporo-sphenoidal lobes ; when it is completely removed deafness results, while partial (left side) injury causes psychical deafness. Among the phenomena caused by partial injury is suniitas verhalis (word-deafness), which may occur Fig. 438. Relation of the fissures and convolutions to the surface of the scalp + Most prominent part of the parietal emi- nence : rt, convex line bounding parietal lobe below ; i, convex line bounding the temporo-sphenoidal lobe behind {R. W. Reid). alone or in conjunction with coecitas verbalis. Wernicke found in all cases of word-deafness softening of the first left temporo-sphenoidal convolution (p. 730). In left-handed persons the centre lies, perhaps, in the right temporo-sphenoidal lobes ( Westphal). Clinical. — We may refer the coecitas and suriiilns verbalis (Kussmaiil) to the aphataxic group of diseases, in so far as they resemble the amnesic form. A person word-blind or word-deaf resem- bles one who, in early youth, has learned a foreign tongue, which he has completely forgotten at a later period. He hears or reads the words and written characters; he can even repeat or write the words, but he has completely lost the significance of the signs. While an amnesic aphasic person has only lost the key to open his vocal treasure, in a person who is word-blind or word-deaf even this is gone. From a case of recovery it is known that to the patient the word sounds like a con- fused noise. Huguenin found atrophy of the temporo-sphenoidal lobes after long-continued deafness. 3. Gustatory and Olfactory Centre. — In the uncinate gyrus, on the inner side of the temporo-sphenoidal lobe (especially on the inner side of that marked THE BASAL GANGLIA. 733 U in Fig. 425), Ferrier locates the joint centres for smell and taste. These two centres do not seem to be distinct locally from each other. 4. Tactile Areas. — According to Tripier, Exner, Petrina, and others, all the tactile cerebral fields from different parts of the body coincide with the motor cortical centres for these parts. Occasionally, in epileptics, strong stimulation of the sen^^ory centres, as expressed in the excessive subjective sensations, accompanies the spasmodic attacks (compare \ 393, 12). .Such epileptiform hallucinations, however, occur without sp.asms, and are accompanied only by disturbances of con- sciousness of very short duration (Bfrger). Course of the Psycho-sensory Paths. — The nerve fibres which conduct impulses from the sensory organs to the sensory cortical centres, pass through the posterior third of the posterior limb of the intestinal capsule between the optic thalamus and the lenticular nucleus (Fig. 439, S). Hence section of this part of the internal capsule causes hemiansesthesia of the opposite half of the body (Charcot, I'eyssiere, Carville, Duret). In such a case sensory functions are abol- ished — only the viscera retaining their sensibility. There may also be loss of hearing {Veller, Donkin), sinell and taste, and heiniopia {Bechterew). In cases where there is more or less injury or degeneration of these paths, there is a corresponding greater or less pronounced loss of the pressure and temperature sense, of the cutaneous and muscular sensibility, of taste, smell, and hearing. The eye is rarely quite blind, but the sharpness of vision is interfered with, the field of vision is narrowed, while the color sense may be partially or completely lost. The eye on the same side may suffer to a slight extent. V. Numerous cases of injury of the anterior frontal region, without inter- ference with motor or sensory functions, have been collected by Charcot, Pitres, Ferrier, and others. On the other hand, enfeeblement of the intelligence and idiocy are often observed in acquired or congenital defects of the prefrontal region. In highly intellectual men, Riidmger found, in addition, a considerable develop- ment of the temporo-sphenoidal lobe. According to Flechsig, there is no doubt that the frontal lobes and the temporo-occipital zone are related to intellectual processes, more especially the " higher " of these. Topography of the Brain. — The relations of the chief fissures and convolutions of the brain to the surface of the skull are given in Fig. 429, the brain being represented after Ecker. [Turner and others have given minute directions for finding the position of the different convolutions by reference to the sutures and other prominent parts of the skull. The foregoing diagram (Fig. 438), by R. W. Reid, shows the relation of the convolutions to certain fixed lines.] 379. THE BASAL GANGLIA— THE MID-BRAIN.— [The corpus striatum in reality consists of two parts, an intra-ventricular portion projecting into the lateral ventricle and called the caudate nucleus, and an extra-ven- tricular portion the lenticular nucleus. Between the head of the caudate nu- cleus internally and the lenticular nucleus externally lies the anterior division of the internal capsule. The fibres which pass between these ganglia do not seem to form connections with them. The expanded head of the caudate nucleus is in front, and lies mside and around the front of the lenticular nucleus, with which and the anterior perforated space it is continuous ; it sweeps backward into a tailed extremity, which nearly surrounds the lenticular nucleus like a loop. The lenticular nucleus is biconvex in a horizontal section (Fig. 439), but triangular and subdivided into three divisions when seen in a vertical section (Fig. 433)-] [The older observations on the corpora striata in man may be dismissed, as a distinction was not drawn between injury to its two parts on the one hand and the internal capsule on the other.] [The caudate nucleus and lenticular nucleus in their development are coordinate with the development of the cortex cerebri (Fig. 439). Electrical stimulation of these ganglia causes general muscular contractions in the oppo- site half of the body. The same result is obtained as if all the motor cortical centres were stimulated simultaneously.] 734 THE BASAL GANGLIA, Gliky did not observe movements on stimulating the corpus striatum in rabbits ; it would seem that in these animals the motor paths do not traverse these ganglia, but merely pass alongside of them. [Lesions of the lenticular nucleus or of the cordate nucleus do not seem to give rise to any permanent symptoms, provided the internal capsule be not injured.] Fig. 43q. Cornu jQtlcum. S, sensory fib Destruction of the internal capsule, however, causes paralysis of motion or sensibility, or both, on the opposite side of the body, according to the part of it which is injured. The corpus striatum is quite insensible to painful stimulation {Longet). THE INTERNAL CAPSULE. 735 Pathological. — In man, a lesion, not too small, destroying the anterior part of the corpus stri- atum is followed by permanent paralysis of the opposite side provided the internal capsule is in- jured, but the paralysis gradually disappears if the lenticular and caudate nucleus only are affected {compare § 365). Sometimes there is dilatation of the blood vessels in consequence of vasomotor paralysis (| 377) if the posterior part is injured (A'otlina^el) ; redness and a slightly increased tem- perature of the paralyzed extremities, at least for a certain time; swelling or oedema of the ex- tremities ; sweating ; anomalies of the pulse detectable by the sphygmograph ; decubitus acutus on the paralyzed side ; abnormalities of the nails, hair, skin ; acute inflammations of joints, especially of the shoulder. Later, contracture or permanent contraction of the paralyzed muscles takes place (Hu:;uenin, Charcot). In some cases there is cutaneous anssthesia, and occasionally enfeeblement of the sense organs of the paralyzed side, and both when the posterior third or sensory crossway of the posterior section of the internal capsule is affected. Usually, however, hemiplegia and hemi- auasl/iesia occur together. Optic Thalamus. — Ferrier did not observe art)' movements to occur on stimulating the optic thalami with electricity. As the pulvinar or posterior ex- tretnity of the optic thalamus is one of the parts connected with the origin of the optic nerve, and is also connected by fibres with the cortex cerebri, it is probably related to the sense of sight. Injury to the posterior third in man results in dis- turbance of vision {Nolhnagel). Ferrier surmises that the sensory fibres pass through the optic thalami on their way to the cortex, so that when they are de- stroyed insensibility of the opposite half of the body is produced. Removal of the optic thalamus, or destruction of the part in the neighborhood of the inspira- tory centre in the wall of th; third ventricle, influences the coordinated move- ments in the rabbit {Christiani). We know very little definitely as to the functions of these organs. After injury to one thalamus there has been observed enfeeblement or paralysis of the muscles of the opposite side, together with mouvements de manege, and sometimes hemianesthesia of the opposite side, with or without affec- tions of the motor spheres, have been recorded. Extirpation of certain cortical areas (rabbit) is followed by atrophy of certain parts of the thalamus (v. Monakow). [Internal Capsule. — In connection with the functions of the basal ganglia, it is most important to retnember their relation to the internal capsule. The corpus stri- atutn consists of an intra-ventricular part, the caudate nucleus ; and an extra-ventric- ular part, the lenticular nucleus. The lenticular nucleus consists of three parts, best seen in a vertical section (Fig. 440, i, 2, 3), with white matter between them, the stria mejullares. The anterior limb of the internal capsule sweeps between the caudate and lenticular nucleus, while the posterior segment lies between the optic thalamus and the lenticular nucleus (Fig. 440). External to the first divi- sion of the lenticular nucleus is the external capsule (Figs. 439, 440), whose function is unknown. External to this is the claustrum, whose function is also unknown. It is evident that hemorrhage into or about the basal ganglia is apt to involve the fibres of the internal capsule. [When the lenticulo-striate artery, or, as it is called, the " artery of hemorrhage" (Fig. 433, aSL), ruptures, it may destroy not only the lenticular nucleus, but the internal capsule will be compressed, and the same is the case with the lenticulo-optic artery ; the external capsule will tend to force the blood inward. We know that in the posterior segment of the capsule the volitional or pyramidal fibres lie in the following order from before backward, those for the face (and tongue) in the knee, in the anterior third those for the arm and hand, and in the middle third for the leg, and, perhaps, behind these those for the trunk (Fig. 439, F, A, L) ; so that a very small lesion in this region will affect a large number of these fibres, converging as they do, like the rays of a fan, from the motor cortical areas, where the arrangement of these cen- tres is a supero-inferior one (Fig. 433), to become an antero-posterior one in the knee and posterior limb of the internal capsule (Fig. 439). The posterior third of this limb is sensory and is the " sensory crossway." [Horsley points out that hemorrhage from the lenticulo-striate artery affects in order the muscles of the face, arm, leg and trunk, while recovery is in the inverse order.] 736 PEDUNCLE AND PONS. Pedunculi Cerebri. — Injury to one cerebral peduncle causes, in the first place, violent pain and spasm of the opposite side, while the blood vessels on that side contract and the salivary glands secrete. These phenomena of irritation are fol- lowed by paralytic symptoms of the opposite side, viz., anaesthesia (§365) and paresis, or incomplete voluntary control over the muscles, as well as paralysis of Fig. 440. r^ Corpus callosun Pillars f the forni;< Inte nal capsul Op ic thalamu Soft commissur ExK rnal capsul ClaustruiT Frontal section through the right cerebral hemisphc (posterior surface of the section). Fig. 441. P.7\f fIp.T the vasomotor nerves. In affections of the cerebral peduncle in man, we must remember the relation of the oculomotorius to it, as the latter is often paralyzed on the same side (^Nothnagel) [while the extremities, tongue, and half the face are paralyzed on the opposite side from the lesion]. The middle third of the crusta of the cerebral peduncle (Fig. 435) includes the direct pyramidal tracts [\\ 365, 378). The fibres of the inner third connect the frontal lobes, through the superior cerebellar peduncles, with the cerebellum. In the outer third are fibres which connect the pons with the temporal and occipital cerebral lobes (Flechsig). The fibres which pass from the tegmentum into the corona radiata conduct sensory impulses (Flechsig). Pons Varolii. — Stimulation or section of the pons causes pain and spasms ; after the section there may be sensory, motor and vasomotor paralysis, together with forced movements. For diagnostic purposes in man, it is important to observe if alternate hemiplegia be present {Nothnagel.') [In lesions situated in the lower half of one side of the pons there is facial paralysis on the same side as the lesion and paraly- sis (motor and sensory, and more or less complete) on the oppo. site side of the body ; this is called alternate paralysis ; while, if the lesion be in the upper half of one side of the pons, the facial paralysis is on the same side as the paralysis of the body. But the parts supplied by the 5th and 6th nerves may also be Scheme of the fib pyramidal «, upper, STIMULATION OF THE CORPORA QUADRIGEMINA. 737 involved. This is explained by Fig. 441, where the upper facial fibres cross in the pons. Sudden and extensive lesions of the pons are often associated with hyperpyrexia, the temperature often rising rapidly within an hour, perhaps from the gray matter in the floor of the 4th ventricle being affected ; but whether it is due to some effect on a heat-regulating or heat-producing centre is un- certain. Tumors of considerable size may press on the pons without producing very marked symptoms, as tumors tend to push aside tissues, unless they be infiltrating in their character. Lesions of the transverse superficial fibres (middle cerebellar peduncles) often give rise to involuntary forced movements, there being a tendency to move to one side or the other.] The Corpora Quadrigemina. — Destruction of these bodies on one side in mammals, or their homologues, the optic lobes in birds, amphibians and fishes, causes actual blindness, which may be on the same or the opposite side, according to the relation of the fibres crossing at the optic chiasma (§ 344). Total destruction causes blindness of both eyes. At the same time, the reflex contraction of the pupil, due to stimulation of the retina with light, no longer takes place i^Flourens), where the optic is the afferent and the oculomotorius the efferent nerve (§ 345). If the cerebral hemispheres alone be removed the pupil still contracts to light, as well as after mechanical stimulation of the optic nerve (yH. Mayo'). Destruction of the corpora quadrigemina interferes with the com- plete harmony of the motor acts ; disturbance of equilibrium and incoordination of movements occur {Serres'). In frogs, CJoltz observed not only awkward, clumsy movements, but at the same time the animals have to a large extent lost the power of completely balancing the body (p. 705). A similar result was observed in pigeons {Af Kendrick) and rabbits (Ferrier). Extirpation of the eye- ball is followed by atrophy of the opposite anterior corpus quadrigeminum {Giidden). According to Bechterew, the fibres of one optic tract pass through the anterior brachium (Fig. 439) into the anterior pair (nates) of the corpora quadrigemina; while those fibres which cross in the chiasma (Fig. 381) pass into the posterior pair (testes). According to this arrangement we have partial blindness, according as one or other pair of these bodies is destroyed. [In man very little is known regarding the effects of disease of the corpora quadrigemina, inter- ference with the ocular muscles being the most marked symptom, but the incoordination of move- ment which has been observed may be due to pressure upon the superior cerebellar peduncle, while it is by no means certain that the defects of vision are directly due to lesions of these bodies.] Stimulation of the Corpora Quadrigemina. — The corpora quadrigemina react to electrical, chemical and mechanical stimuli. The results of stimulation are very variously staled. Accord- ing to some observers there is dilatation of the pupil on the same side ; according to Ferrier, it may be the pupil on the opposite or on the same side. The stimulation may be conducted Irom the cor- pora quadrigemina to the medulla oblongata, and to the origin of the sympathetic, for after section of the sympathetic nerve in the neck dilatation of the pupil no longer takes place ( Knoll). Accord- ing to Knoll, the contraction of the pupil observed by the older experimenters occurs only when the adjoining optic tract is stimulated. Stimulation of the tight anterior corpus quadrigeminum causes deviation of both eyes to the left (and conversely) ; on continuing the stimulation, the head is turned to this side. On dividing the corpora ([uadrigemina by a vertical median incision, stimu- lation of one side causes the result to take place only on one side (AJamiik). Ferrier observed signs of pain on stimulating these organs in mammals. Carville and Duret conclude from their experiments that these organs are centres for the extensor movements of the trunk. Ferrier found, on stimulating one optic lobe in a pigeon, dilatation of the opposite pupil, turning of the head toward the other side and backward, movement of the opposite wing and leg; strong stimulation caused flapping movements of both wings. Danilewsky, Ferrier and Lauder Brunton observed a ri-e of the blood pressure and slowing of the heart beat, together with deeper inspiration and expiration. According to Valentin and Budge, stimulation also causes movement of the intestines and bladder, perhaps excited secondarily by the action of the vasomotor nerves. Bechterew ascribes all the phenomena, except those of vision itself, which accompany injury or stimulation of these bodies, to affections of deeper-seated parts. He asserts that the corpora quad- rigemina contain neither the centre for the movements of the pupils nor that for the combined movements of the eyeballs; not even the centre for maintaining the equilibrium of the body. Stimulation of these bodies causes the animals 10 perform marked movements. Reflex phenomena, nystagmus, forced movements and unsteadiness of the gait only occur, however, when the deeper parts are injured. Pathological. — Lesions of the anterior pair in man, according to the extent of the lesion, cause disturbance of vision, failure of the pupil to contract to light, and even blindness ; there may be paralysis of the oculomotorii on buih sides. Disease of the posterior pair may be associated with disturbances of coordination (lYolhiia^il). 47 738 FORCED MOVEMENTS STRABISMUS AND NYSTAGMUS. Forced Movements. — It is evident from what has been said regarding the importance of the corpora quadrigemina for the harmonious execution of move- ments, that u iiilcUera/ m]ury of such parts as are connected to them by conduct- ing channels must give rise to peculiar unilateral disturbance of the equilibrium, causing variations from the symmetrical movements of both sides of the body. These movements are caWed forced mcvemen/s. To this class belong the mouve- ment de manege, where the animal, instead of moving in a straight line, runs round in a circle ; index movements, where the anterior part of the body is moved round the posterior part, which remains in its place, just like the move- ments of an index round its axis; and rolling movements, when the animal rolls on its long axis. All these forms of movement may pass into each other, and they are, in fact, merely different varieties of the same kind of movement. The parts of the nervous system whose injury produces these movements are the corpus striatum, optic thalamus, cerebral peduncle, pons, middle cerebellar peduncles, and certain parts of the medulla oblongata. Eulenberg observed index move- ments in the rabbit after injury to the surface of the brain, and Bechterew observed the same in dogs. Forced movements, together with nystagmus and rotation of the eyeballs, are caused by injury to the olives {Bechtereiv). The statements of observers vary as to the direction and kind of movement produced by injuring individual parts. The following observations have been made : Sec- tion of the anterior part of the pons and of the crura cerebelli causes index, or, it may be, rolling movements toward the other side ; section of the posterior part of the same regions causes rolling movements toward the same side, while the same result is caused by a deeper puncture into the tuberculum acusticum, or into the restiform body. Section of one cerebral peduncle causes mouvements de manege, while the body is curved with the convexity toward the same side. The nearer to the pons the section is made the smaller is the circle described ; ultimately index movements occur. Injury to one optic thalamus produces results similar to puncture of the anterior part of the cerebral peduncle, because the latter is injured along with it at the same time. Injury to the anterior part of one optic thalamus causes the opposite kind of forced movement, viz., with the con- cavity of the body toward the injured side. Injury to the spinal portion of the medulla oblongata is followed by bending of the head and vertebral column, with the convexity toward the injured side, along with movements in a circle. When the anterior end of the calamus and the part above it are injured, the movements are toward the sound side. Strabismus and Nystagmus. — Among the forced movements may be reck- oned deviation of the eyeballs, strabismus or squinting, and involuntary oscillation of the eyeballs, constituting nystagmus. The latter condition occurs after superfi- cial lesions of the restiform body, as well as of the floor of the 4th ventricle. A unilateral deep transverse injury, from the apex of the calamus upward as far as the tuberculum acusticum, causes the eye of the same side to squint downward and forward, that of the other side backward and upward. Section of both sides causes this condition to disappear (Sc/twa/ui). Hence, Eckhard assumes that the me- dulla oblongata is the seat of an apparatus controlling the movements of the eyes (^Ec-Manf). In pathological degeneration of the olivary body of the medulla oblongata in man, Meschede ob- served intense rotatory movements toward the scime side. Theory. — In order to explain the occurrence of forced movements, it is suggested that there is unilateral incomplete paralyi-is [Lnfarqiie), so that the animal in its efforts to move onward leaves the paralytic side slightly behind the other, and hence there is a variation from the symmetry of the movements. Brown-Sequard regards the matter in exactly an opposite light, viz., as due to stimu- lation from injury causing an excessive activity of one-half of the body. Henle ascribes the move- ments to I'tv/^''', of a feeling of giddiness caused by the injury. In all operations on the central nervous system, where the equilibrium is deeply affected, there is a considerable incre.ise in the number and depth of the respirations ( I.nndois). Other Effects. — Some observers noticed v.-iriations of the blood pressure and a change in the STRUCTUUE AND FUNCTIONS OF THE CEREBELLUM. 739 number of heart beats after stimulation of the cortex cerebri, e.g., after electrical stimulation of the motor areas for the extremities (Boc/ifftnitnine). Balogh observed acceleration of the pulse on stimulating several points on the cortex cerebri of the dog, and from one point slowing of the pulse. Eckhard stimulated the surface of the brain in rabbits, and as a rule he observed that as long as sin- gle crossed movements occurred in the anterior extremities there was no effect upon the heart, but that the heart became affected as soon as other movements occurred. This consists in slow, strong pulse beats, with occasional weaker beats, while at the same time the blood pressure is slightly in- creased (Boi/ie/onlaine). If the vagi be divided beforehand, the effect upon the pulse disappears, while the increase of the blood pressure remains. That psychical processes affect the action of the heart was known to Homer and Chrysipp. Bochefontaine and Lepine, on stimulating several points, especially in the neighborhood of the sulcus cruciatus in a dog, observed increased secretion of saliva, slowing of the movements of the stomach, peristalsis of the intestine, contraction of the spleen, of the uterus, of the bladder, and increased respirations. Bufalini, on stimulating those parts of the cortex which cause movements of the jaw, observed the secretion of gastric juice with in- crease of the temperature of the stomach. .Schiff, Brown-Sequard, Ebstein, Klosterhalfen, and others, have observed that injury to the pons, corpus striatum, thalamus, cerebral peduncle, and medulla oblongata often causes hyperaemia and hemorrhage into the lung (according to Brown- Sequard, especially after injury to one side of the pons, which affects the opposite lung), under the pleura, in the stomach, intestine, and kidneys. Gastric hemorrhage is common after injury to the pons just where the cerebral peduncles join it. Similar phenomena have been observed in man after apoplexy or cerebral hemorrhage. Specially interesting is the cerebral unilateral decubitus acutus described by Charcot, which always occurs on the paralyzed side of the body, i.e., on the side opposite to the cerebral injury. It begins on the second or third day, rapidly causes enormous destruction and sloughing of the tissues on the back and lower extremities, and death soon takes place. The decubitus which occurs after spinal injuries usually begins in the middle line of the buttocks, and extends symmetrically on both sides. In cases of unilateral injury to the spinal cord the decubitus occurs on the corresponding ^\&^ of the sacral region (p. 614). [Corpus Callosum. — It is usually stated that the corpus callosum connects the convolutions of one side of the brain with those of the other, /.?., it is an inter-hemispherical commissure. D.J. Hamilton, however, states that it is not an inter- hemispheric commissure, but is due to cortical tibres coming from the cortex cerebri to be connected with the basal ganglia of the opposite side. On this view, the " corona radiata," as usually understood, consists only of the fibres which pass from the cerebral peduncle directly up to the cortex on the same side, and are contained in the posterior di- vision and knee of the internal capsule. They correspond to the motor pyramidal tracts. Hamilton maintains that all the other fibres of the internal capsule pass into the crossed callosal tract, and, instead of running directly up to the cortex on the same side, cross in the corpus callosum to the cortex of the opposite side. Beevor, relying on the examination of the brain of monkeys, by Wei- gert's method, denies that any filjres of the corpus callosum pass into the external or internal cap- sules, and he maintains the old view that the corpus callosum is a commissure between the two hemi- spheres.] 380. STRUCTURE AND FUNCTIONS OF THE CEREBELLUM.— [Structure. — On examining a vertical section of a cerebellar leaflet we observe the following microscopic ap. pearances : Externally is the pia mater with its blood ve.ssels (Fig. 442, a) which penetrate into the gray matter, within is the medulla composed of white fibres. The gray inatter consists of b, a broad outer or molecular layer largely composed of branched fibrils, and internal to it is ated. In frogs an important organ concerned with motion lies at the junction of the oblongata with the cerebellum [EckUard). After it is removed the animal can no longer execute coordinated jumping movements, nor. can it crawl [Goitz). [In man the cerebellum is connected with the maintenance of the equilibrium. There may be a lesion of the hemispheres without any marked symptoms, but if the middle lobe be injured or 742 PROTECTIVE APPARATUS OF THE BRAIN. pressed on by a tumor there is usually a reeling or staggering gait like that of a drunken man. Ross points out that if the tumor atfect the upper part of this lobe the tendency is to fall backward, and if in the lower part, to fall forward or to revolve round a horizontal axis. Vomiting is fre- quently persistent and well-marked, while there may be nystagmus and tonic retraction of the head.] After injuries of the cerebellum, involuntary oscillations of the eyeballs or nystagmus, as well as squinting [iMn^^ndis^ H^rUoi^)^ have been observed ; while Ferrier observed movements of the eyeballs after electrical stimulation. According to Curschmann, Eckhard and Schwahn, this occurs only when the medulla ol)longala is involved (^ 379). Effects of Electricity and Vertigo.— If an electrical current be passed through the head, by placing the electrodes in the masioid fossx behind both ears, with the \- pole behind the right and the — pole behind the left ear, then on closing the current there is severe vertigo and the head and body lean to the -\- pole, while the objects around seem to be displaced to the left. If the eyes be closed while the current is passing, the movements appear to be transferred to the person himself, so that he has a feehng of rotation to the left [Ptirkinje). At the moment the head leans toward the anode the eyes turn in that direction, and often e.\hibit nystagmus. The electrical cur- rent probably stimulates the nerves of the ampulh^, as we know that affections of these bodies cause vertigo [\ 350). The cerebellum has no relation to the sexual activities, as was maintained by Gall. The contractions of the uterus observed by Valentin, Budge and Spiegelberg, after stimulation of the cerebellum, are as yet unexplained. Pathological. — Lfsions of one hemisphere may give rise to no symptoms, but if the middle lobe is involved there is incc ordination of movement, especially a tendency to fall, unsteady gait and pro- FlG. 44.1. * -d - SiL of the cortex cerebri and us membranes X 2^ co, cortex cerebri : /, intima piae dipping into the arachnoid, connected with/ by means ot the loose subarachnoid trabecule in the subarachnoid space, blood vessels ; d, dura ; and sd, subdural space. nounced vertigo. Irritative lesions of the middle peduncle cause complete gyrating movements of the body around its axis, together with rotation of the eyes (Nonai) and head (Notkimgel). 381. PROTECTIVE APPARATUS OF THE BRAIN.— The Membranes.— The dura mater cerebralis is intimately united to the periosteum of the cavity of the skull, while the .spinal dura mater forms around the spinal cord a freely suspended long sack, fixed only on its ante- rinr surface. It is a fibrous membrane, consisting of firm bundles of connective tissue intermixed with numerous clastic fibres, and provided with flattened connective- tissue corpuscles and Waldeyer's plasma cells. The smooth inner surface is covered with a layer of endothelium. It is but slightly supplied with blood vessels, although they are more numerous in the outer layers; the lymphatics are numerous, while nerves whose terminations are unknown give to the dura its exquisite sensi- bility to painful operations on it. Pacinian corpuscles have been found in the dura over the tem- poral bone. The lymphatic subdural space i Key and Retzhis) lies between the dura and the arachnoid, and between the jiiaand arachnoid is the subarachnoid space (Fig. 444). These two spaces do not communicate directly. The delicate arachnoid, thin and partially perforated, poor in blood vessels and without nerves, is covered on both surfaces with squamous endothelium. Only on the spinal cord is it separated from the pia, so that between the two lies the lymphatic sub- arachnoid space ; over the brain the two membranes are for the most part united together, except the parts bridging over the sulci between adjacent convolutions. The arachnoid passes from convo- lution to convolution without dipping into the sulci, while the pia dips into each sulcus (Fig. 444, a). The ventricles of the brain communicate freely with the lymphatic subarachnoid space, but not THE MOVEMENTS OF THE BRAIN. 743 with the subdural space ( IFa/Jt-yer ami Fischer). The pia consists of delicate bundles of con- nective tissue without any admixture of elastic filires; it is richly supplied with blood vessels and lymphatics, and carries nerves which accompany the blood vessels into the substance of the brain {Kolliker). The lymphatics open into the subarachnoid space {\ 196). [Subarachnoid Fluid, or cerebro spinal fluid, lies in the subarachnoid space, which is traversed by trabecuUe of connective tissue. Within the brain are a series of cavities called ventricles, which communicate one with another in a definite way. The fourth ventricle is lined by a layer of columnar epithelium, and covered in dorsally by a membrane and continuation of the pia mater, from the middle of which there hangs into the roof of the fourth ventricle two vascular processes composed of capillaries— the choroid ple.\uses of the fourth ventricle, which are comparable to the larger plexuses of the lateral ventricles. In this membrane is the foramen of Magendie and two other smaller foramina, whereby the fluid in the subarachnoid space communicates with that in the fourth ventricle ; but the lymphatics of the nerve sheaths can be injected from the subarachnoid space, so that there is direct continuity of the fluid in the ventricles of the brain with that in sub- arachnoid space, perivascular spaces of the cerebral substance, and the perineural lymphatics of nerves. The average quantity is about 2 ounces, and if it be suddenly withdrawn epilepsy or convulsions may be produced, or if it be rapidly increased in amount coma may be produced. The middle and posterior parts of the brain and the medulla oblongata do not rest directly on bone, but are separated by a di.stinct interval from their osseous case, an interval occupied by the cerebro- spinal fluid and traver-ed by trabeculce, so that, as Hilton expresses it, this fluid forms a perfect water bed for those parts, being sustained by the venous circulation and the elasticity of the dura. It has important mechanical functions protecting delicate parts of the brain from injury; by dis- tributing vibratory impulses it insulates the nerve roots and has important relations to the quantity of blood in the brain and the cerebral circulation (Chemical Composition, \ 198).] [Spina Bifida. — Sometimes the laminie of the vertebrs in the lumbar or other region of the spinal column are imperfectly developed, in which case the membranes project through as a tumor distended by cerebro-spinal fluid and covered by skin. The effects of rapid tapping or compressing the sack are readily studied in such cases.] The Pacchionian bodies, or granulations, are connective-tissue villi, which serve for the out- flow of lymph from the subdural and subarachnoid spaces into the sinuses of the dura mater, espe- cially the longitudinal sinus. The subarachnoid space also communicates with the spaces in the spongy bone of the skull, and with the veins of the skull and surface of the face \Kollmann). The subdural space also communicates with the lymphatic spaces in the dura, while the latter com- municate directly with the veins of the dura. Both the subdural and subarachnoid lymphatic spaces communicate with the lymphatics of the nasal mucous membrane. The space outside the dura of the spinal cord is called the epidural space, and may be regarded as lymphatic in its nature ; the pleural and peritoneal cavities may be filled from it ; but it does not communicate with the cavity of the skull ( Waldeyer and Fischer). The plexuses of blood vessels are surrounded by undeveloped connective tissue. The teloe choroideae in the new-born are still covered with ciliated epithelium. The Movements of the Brain. — The pulsations of the large basal cerebral vessels communicate their pulsatile movements (§ 79, 6) to the brain — the respiratory movements also affect it, so that the brain rises during expiration and sinks during inspiration. Lastly, there are slight alternating vascular eleva- tions and depressions, occurring 2 to 6 times per ininute, due to the periodic dilatation and contraction of the blood vessels {% 371)- Psychical e.xcitement influences these, and they are most regular during sleep {BurckharJt, Mays). The moveinents are best seen, especially where the tnembranes of the brain offer little resistance, e.g., over the fontanelles in children, and where the membranes have been exposed by trephining. The presence of the cerebro-spinal fluid is most important for the occurrence of these movements, as it propagates the pres- sure uniformly, so that every systolic and expiratory dilatation of the blood vessels is concentrated upon those parts of the cerebral membrane which do not offer any resistance {Domfcrs). When the fluid escapes, the movements may alinost dis- appear. Mental excitement increases the pulsations of the brain. At the moment of awaking, the amount of blood in the brain diminishes ; sensory stimuli applied durmg sleep, so that the sleeper does not awake, increase the amount of blood. As the arteries within the rigid skull case change their vol- ume with each pulse beat, the veins (sinuses) exhibit at every beat a pulsatile variation in volume, the opposite of that occurring in the arteries [A/osso). The Cerebral Blood Vessels. — The blood vessels of the pia, of course, are regulated by the vasomotor nerves [if^ 356, A, 3), and their calibre may also be influenced by the stimulation of more distant pans of the body (^ 347). Donders trephined the skull so as to make a round hole, and 744 THE GANGLIONIC CEREBRAL ARTERIES. filled it with a piece of glass, so that with a microscope he could observe changes in the calibre of the blood vessels. Paralysis of the vasomotor nerves and narcotics dilate the blood vessels ; they become greatly contracted at death (J 373, I). The blood vessels are dilated during cerebral activity (^ 100, A) as well as during sleep. Increased pressure within the skull causes great de- rangement of the cerebral activity; labored respiration (^ 368, B), unconsciousness even to coma, and paralytic phenomena — all of which may, in part, be referable to disturbances of the circulation. If all the cranial arteries be ligatured suddenly, there is immediate loss of consciousness, together with strong stimulation of the medulla oblongata and its centres, and death takes place rapidly with convulsions (compare ^ 373). By the free anastomosis which takes place at the base of the brain forming the circle of Willis (Fig. 445 ), the individual parts of the brain are preserved from want of blood, when one or other blood vessel is compressed or ligatured. Within the brain the arteries are distributed as "terminal " arteries, i. e., the terminal branches of any one artery end in their own area, and do not anastomose with those of adjoining areas [Cohnheim). On the other hand, the peripheral Fig. 445. Arteries of the base of the brain, or circle of Willis. CC, internal carotids ; Q \, anterior cerebral : SS, Sylvi; teries : V V, vertebrals ; B, basilar ; C P, posterior cerebrals ; 1, 2, 3, 4, 4, 4, groups of nutri dotted line shows the limit of the ganglionic area. arteries (arteries of the corpus callosum, Sylvian fissure, and deep cerebral) which run externally on the brain form free anastomoses ( Tichomirom). [The nutrient or ganglionic arteries for the central ganglia arise in groups from the circle of Willis, or from the first two centimetres of its trunks. The antero-median group (i) supplies the anterior part of the head of the caudate nucleus. The postero-median (2) enter the posterior perforated space and supply the internal surface of the optic thalami and the walls of the third ventricle. The antero-lateral group.s (3,3) from the middle cerebral enter the anterior perforated space, supply the corpora striata, the anterior part of the optic thalamus, and the internal capsule. These branches are apt to rupture. The postero-lateral (4, 4) supply a large part of the optic thalami {C/iaicol). A line drawn at a distance of two centimetres outside the circle of Willis encloses the ganglionic area. The cerebral convolutions are supplied by the large branches of the circle of Willis. The anterior cerebral curves round the corpus callosum, and supplies the gyrus rectus and the supraorbital, the first and second frontal convolutions, the upper part of the ascending frontal, and the inner surface of the hemisphere as far as the quadrate lobule ( Fig. 370, I). The posterior cerebral goes to the region of the occipital lobe and the inferior aspect of the THE VENOUS CIRCULATION. 745 temporal lobe; the middle cerebral or Sylvian artery divides into four branches, which go to the posterior part of the frontal lobe, ascending frontal, and to all the parietal lobes, i. e., chiefly to the motor areas (III), the angular gyrus, and to the first temporo-sphenoidal lobule. The terminal branches of these ganglionic arteries do not anastomose with the cortical system. Fig. 446 shows the ganglionic arteries piercing the basal ganglia. Obviously, when hemorrhage of the lenticulo- striale artery or " artery of hemorrhage " (4, 4) occurs, it will compress the lenticular nucleus, or tear it up, and may even injure the parts outside, such as the external capsule, claustrum (T), and island of Keil (R), or those inside, <>.?■., the internal capsule.] [Thus the anterior cerebral supplies the prefrontal area and a small part of the motor area, that for the leg centre in the paracentral lobule and upper end of the ascending front (and perhaps for the trunk). The posterior cerebral supplies the centre for vision, and that connected with the course of the posterior part of the optic expansion, and also the sensory part of the internal capsule. The middle cerebral supplies the motor areas of the cortex except part of the leg centre and the basal ganglia, the auditory centre, and that for speech [G(yuiers).'\ [The cerebral circulation has many peculiarities. The curves on the arteries serve to modify the effect of the cardiac shock; the circle of Willis permits within limits a free circulation, but in as far as the skull is largely a rigid box, it was at one time taught that, as the brain substance and its fluids were practically incompressible, it was impossible to alter the amount of blood in the brain. This is a mistake. The amount of blood undergoes an alteration in this way, that when Fig. 446. Transverse section of the cerebrum behind the optic chiasma. Arteries of the corpus striatum. C k, optic chiasma : B, section of optic tract ; L, lenticular nucleus ; I, internal capsule ; C. caudate nucleus ; E, external capsule ; T, claustrum: R, convolutions of the island of Reil : V V, section of the lateral ventricles ; P P, pillars of the fornix ; O.gray substance of the third ventricle. Vascular areas— I, anterior cerebral artery; II, Sylvian artery; III, posterior cerebral artery ; i, internal carotid ; 2, Sylvian, 3, anterior cerebral artery ; 4, 4, lenticulo-striate s : 5, 5, lenticular arteries. more blood passes in, some cerebro-spinal fluid moves out, and -'ice zvrsa, so that there is an inti- mite relation between the) from them to the chorio-capillaris. The Veins. — i. The anterior ciliary veins (c) receive the blood from the anterior part of the uvea and carry it outward. These branches are connected with Schlemm's canal and Leber's venous plexus. They do not receive any blood from the iris. 2. The venous plexus of the ciliary processes {r) receives the blood from the iris (^), and passes backward to the choroidal veins. 3. The large vasa vorticosa Stenonis \h) perforate the scleroiic behind the equator of the bulb. The inner margin of the iris rests upon the anterior surface of the lens ; the posterior chamber is small in adults, and in the new-born child it may be said scarcely to exist, it is so small. When BerHn blue is injected into the anterior chamber of the eye, it generally passes into the anterior ciliary veins [SchwalOe). Even in living animals carmin also behaves in a similar manner (//els- rath), so that these observers conclude that there is a direct communication between the veins and the aqueous chamber, as tliese substances do not diffuse through membranes. Internal to the choroid lies the single layer of hexagonal cells (0.0135 '° °°2 tava. in breadth) filled with crystalline pigment. This layer really belongs to the retina. It consists of a single layer of cells as far as the ora-serrata — it is continued on to tlie ciliary processes and the posterior surface of the iris (Fig. 449, -v), where it forms several layers. In albinos it is devoid of pigment; on the other hand, the uppermost cells, which lie on the ridges of the ciliary processes, are always devoid of pigment. [The processes of these cells vary in length with the nature and kind of light acting on the retina (J 39^).] The retina externally is in contact with the layer of hexagonal pigment cells (Pi), which in its development and functions really belongs to the retina. The cells are not flat, but they send pig- mented processes into the spaces betw-een the ends of the rods. In some animals (rabbit) the cells contain fatty granules and other substances. The cells are larger and darker at the ora-serrata (Kiihne). The retina is composed of the following layers proceeding from without inward : — 6. Inner nuclear layer. 7. Inner molecular (granular) layer. [i. Layer of pigment cells. 2. Rods and cones. 3. Extet nal limiting membrane. 4. Outer nuclear layer. 5. Outer molecular (granular or inter- nuclcar) layer. 8. Layer of nerve cells (ganglionic) layer. 9. Layer of nerve fibres. 10. Internal limiting membrane.'\ I. The hexagonal pigment cells already described. 2. The layer of rods and cones (Si) or nenro-epithelium of Schwalbe \_bacillary layer, or the visual cells, or visual epithelium of Kiihne] (Fig. 454). These lie externally next tlie choroid, but they are absent at the entrance of the optic nerve. Then follows the external limiting membrane (Le), which is perforated by the bases of the rods and cones. 3. The external nuclear layer (iiu.K), which with all the succeeding layers are called " brain layers " by Schwallje. 4. The external granular (augr), or internuclear layer, which is perforated by the fibres which proceed inwaid from the nuclei of 3 (Merkel) to reach 5, THE RETINA. 755 the nuclei of the internal nuclear layer iiiiA'}. The nuclei of this layer, which are connected by fibres with the rods and cones, are marlied by transverse lines in the macula lutea (AVrta^^, Denissenko). 6. The finely granular internal granular layer (in./;r), through which the fibres proceeding from the inner nuclear layer cannot be traced. It would seem as if these fibres break up into the finest fibrils, into which, also, the branched processes of the ganfjlionic cells of 7, the ganglionic layer, extend. According to v. Vintschgau, the processes of the ganglionic cells are connected with the fibres. S. The ne.xt. or fibrous layer, consists of the fibres of the optic nerve (o),and most internally is the internal limiting membrane (Li). According to \V. Krause, there are 400,000 broad, and as many narrow, optic fibres, so that for every fibre there are 7 cones, about 100 rods, and 7 pigment cells. The optic filjres are absent from the macula lutea, where, however, there are numerous ganglionic cells. Between the two homogeneous limiting membranes (Le and Li) lies the connective-tissue substance of the retina. It contains the perforating fibres, or Fi.;. 454. Fig. 453. 9.r;ik^r.\L^ror^O.:^'Qck y7* b, ext. andy, int. limit. ? ex .J d^ t gran layers / blood vessel and nerve cells : i, nerve Ft hexagonal p gment cells St rods and cones ; Z,^, ext. limiting membrar . granular layer : inK, int. nuclear ; in.gr, int. granular ; Ggl, ganglionic 1 nembrane; .ffA, fibres of Muller; .^.nuclei; .^, spaces for ttle ext. and f, int. ;. 454— Layers A-, ext. nuclear slls : o, fibres o! elements. Miiller's fibres, which nin in a radiate manner between the two membranes and hold the various layers of the retina together. They begin by a wing-shaped expansion at the internal limiting membrane (fii), and in their course outward contain nuclei (k). They are absent at the yellow spot. The supporting tissue forms a network in all the layers, holes being left for the nervous portions (Sg). The inner segments of the rods and cones are also surrounded by a sustentacular substance. As the retina passes forward to the ora serrata it becomes thinner and thmner, gradually becoming richer in connective-tissue elements and poorer in ner\'e elements, until, in the ciliar)' part, only the cylindrical cells remain ( Fig. 453). [Macula Lutea and Fovea Centralis. — There are no rods in the fovea, while the cones are longer and narrower than in the other parts of the retina (Fig. 455). The other layers, also, are thinner, especially at the macula lutea, but they become thicker toward the margins of the fovea. 756 VISUAL PURPLE OR RHODOPSIN. where the ganglionic layer consifts of several rows of bipolar cells. The yellow tint is due to pigment lying between the layers composing the yellow spot.] The blood vessels of the retina lie in the inner layers near the inner granular layer. Only near the entrance of the optic nerve are they connected by tine brandies with the choroidal vessels; they are surrounded by perivascular lymph spaces. The greatest number of capillaries runs in the layers external to the inner granular layer [//esse, //is). The fovea centralis is devoid of blood vessels (A^elt/ei/iif, Becker). Except in mammals, the eel (Deiiissenko), and some tortoises [//. A/iiiler), the retina receives no blood vessels. Destruction of the retina is followed by blindness. [Retinal Epithelium. — The single layer of pigmentary cells containing granules of melanin sends processes downward, like the hairs of a brush, betvve n the rods and cones. Kiiline has shown that the nature and amount of light influences the condition of these processes (Fig. 497). The protoplasm of these cells in a frog kept for several hours in the dark is retracted, and the pig- ment granules lie chiefly in the body of the cell and in the processes near the cell. In a frog kept in bright daylight, the processes loaded with pigment penetrate downward between the rods and cones as far as the external limiting membrane.] Each rod and cone consists of an outer and an inner segment. During life the outer segment contains a reddish pigment or the visual purple (Boll). Visual purple [or rhodopsin] may be preserved by keeping the eye in darkness, but it is soon bleached by daylight, while it is again restored when the eye is placed in darkness. It can be extracted from the retina by means of a 2.5 per cent, solution of the bile acids, especially from eyes that have been kept in 10 per cent, solution of common salt (Ayres). The rods are 0.04 to 0.06 mm. high and 0.0016 to o.ooiS mm. broad, and exhibit longitudinal striation, pro- FlG. 455. Section of the fovea tear layer ; (/, fibres duced by the presence of fine grooves; a fine fibril runs in their interior [Ritler). The external segment occasionally cleaves transversely into a number of fine transparent disks. [It is a very resistant structure, and in this respect resembles neuro-keratin.] Krause found an ellipsoidal body, the '* rod ellipsoid," at the junction of the inner and outer segments of the rods. The cones are devoid of visual purple, but their outer segment is striated longitudinally, and it also readily breaks across into thin disks. Only cones are present in the macula lutea. In the neighborhood of the yellow spot each cone is surrounded by a ring of rods. The cones become less numerous toward the periphery of the retina. In nocturnal animals, such as the owl and bat, there are either no cones or imperfect ones. The retimie of birds contain many cones, that of the tortoise only cones. The rods and cones rest on the sieve like perforated external limiting membrane (Le). Both send processes through the membrane, the cones to the larger and higher-placed nuclei, the rods to the nuclei, with transverse markings in the extern.al nuclear layer. [The cones are particularly large in some fishes, f.^'., the cod, while the skate h.is no cones, but only rods. The same is the case in the shark and sturgeon, hedgehog, bat and the mole.] [Distribution and Regeneration of Rhodopsin. — Keep a rabbit in the dark for some time, kill it, remove its eyeball, and examine its retina by the aid of monochromatic (sodium) light. The retina will be purple-red in color, all except the macula lutea and a small part at the ora serrata. The pigment is confined to the ouler segments of the rods. It is absent in pigeons, hens and one bat, although the last has only rods. It is found both in nocturnal and diurnal animals. Its color is quickly bleached by light, and it fades rapidly at a temperature of 50° to 76° C , while trypsin, alum and ammonia do not affect it. It is restored in the retina by the action of the retinal epithe- lium. If the retinal epithelium or choroid be lifted off from an excised eye exposed to light, the THE VITREOUS HUMOR. 75/ Fig. 456. purple is destroyed, but if the eye be placed in darkness and the retinal epithelium replaced, the coliir is restored.] Chemistry of the Retina. — The reaction of the retina, when quite fresh, is acid, and becomes alkaline in darkness. The rods and cones contain albumin, neuro-keratrin, nuclein, and in the cones are the pigmented oil globules, the so-called " chromophanes." The other layers contain the constituents of the gray matter of the brain. [Cones. — There is no coloring matter in the outer segment of the cones, but in fishes, reptiles, and birds the inner segment contains a globular colored body often red and yellow, the pigment being held in solution by a fatty body. Kiihne has separated a green (chlorophane), a yellow (xanthophane), and a red (rhodophane) pigment. They all give a blue with iodine [Sckwalbe], and are bleached by light.] The crystalline lens is enclosed in a transparent capsule, thicker anteriorly than posteriorly, and it is covered on the inner surface of the anterior wall by a layer of low epithelium. Toward the margin of the lens, these cells elongate into nucleated fibres [h'oiiinski), which all bend round the margin of the lens, and on both sides of the lens abut with their ends against each of the triradiate figures. The lens fibres contain globulin enclosed in a kind of membrane. Owing to mutual pressure, they are hex- agonal when seen in transverse section (Fig. 456, 2), while in many animals, especially fishes, their margins are serrated [the teeth dovetail into each other]. For the sake of simplicity, we may regard the lens as a biconvex body with spherical surfaces, the posterior surface being more curved. As a matter of fact, the anterior part is part of an ellipsoid formed by rotation on its short axis. The posterior surface resembles the section of a paraboloid, i. e., we might regard it as formed by the rotation of a parabola on its axis [BrihX'e). 1 he outer layers of the lens have less refractive power than the more internal layers. The central part of the lens or nucleus is, at the same time, firmer, and more convex than the entire lens. The margin of the lens is always separated from the ciliary processes by an intermediate space. [Chemistry. — The lens contains about two-thirds of its weight of water, while its chief solid is a globulin, called by Berzelius crystallin (24.6 per cent.), with a little serum albu- min, salts, cholesterin, and fats.] [Cataract. — Sometimes the lens becomes more or less opaque, the opacity beginning either in the middle or outer parts of the lens. This is generally due to fatty degeneration of the fibres, cholesterin being deposited. An opaque cataractous condition of the lens may be produced in frogs by injecting a solution of some salts or sugar into the lymph sacks ; the result is that these salts absorb the water from the lens, and thus make it opaque. The cataract of diabetf s is probably produced from the presence of grape sugar in the blood.] The zonule of Zinn, at the ora serrata, is applied as a folded niemlirane to the ciliary part of the uvea, so that the ciliary processes are pressed into its folds, and are united to it. It passes to the margins of the lens, where it is inserted by a series of folds into the anterior part of the capsule of the lens. Behind the zonule of Zinn, and reaching as far as the vitreous humor, is the canal of Petit. The zonule is a fibrous, perforated membrane {S<'/ni'{i//'^, Vlacowitsch). According to Merkel, the canal of Petit is enclosed by very fine fibres, so that it is really not a canal but a complex communicating system of spaces (Gerluch]. Nevertheless, the zonule represents a stretched mem- brane, holding the lens in position, and m.ay, therefore, be regarded as the suspensory ligament of the lens. Opacity or cloudiness of the lens (gray cataract) hinders the passage of light into the eye. The absence of the lens (Aphakia), as after operations for cataract, may be remedied by a pair of strong convex spectacles. Of course such an eye does not possess the power of accommodation. The vitreous humor, as far as the ora serrata, is bounded by the internal limiting membrane of the retina [f/enle, hatjnojf). From here forward, lying between both, are the meredional fibres of the zonule, which are united with the surface of the vitreous and the ciliary processes. A part of the fibrous layer bends into the saucer-shaped depression, and bounds it. .A canal, 2 mm. in diam- eter, runs from the optic papilla to the posterior surface of the capsule of the lens; it is called the hyaloid canal, and was formerly traversed by blood vessels. The peripheral part of the vitreous humor is laminated like an onion, the middle is homogeneous ; in the former, especially in the fiLtus, are round fusiform or branched cells of the mucous tissue of the vitreous, while in the centre there are disintegrated remains of these cells (Iwanoff). The vitreous contains a very small per- centage of solids, and 1.5 per cent of mucin [and according to Picard there is 0.5 per cent, of urea, and about .75 of sodic chloride]. [Structure. — The vitreous consists essentially of mucous tissue, in whose meshes lies a very 758 INTRAOCULAR PRESSURE. watery fluid, containing the organic and inorganic bodies in solution. According to Younaii, the vitreous contains two types of cells — (i) amoeboid cells of various shapes and sizes. They lie on the inner surface of the lining hyaloid membrane and the other membranes in the coitex of the vitreous; (2) large branching multipolar cells. The vitreous is permeated by a large number of transparent, clear, homogeneous hyaloid membranes, which are so disposed as to give rise to a concentric lamination. The canal of Stilling represents in the adult the situation of the hyaloid artery of the fretus. It can readily be injected l)y a colored fluid. In preparations of the vitreous, Younan finds fibres not unlike elastic fibres, and other fibres more especially after staining with chloride of gold.] The lymphatics of the eye consist of an anterior and a posterior set {Sc/nualbe). The anterior consist of the anterior and posterior chambers of the eye (aqueous), which communicate with the lymphatics of the iris, ciliary processes, cornea, and conjunctiva. The posterior consist of the perichoroidal space between the sclerotic and the choroid \Schwalbe). This space is connected by means of the perivascular lymphatics around the trunks of the vasa vorticosa, with the large lymph space of Tenon, which lies between the sclerotic and Tenon's capsule (Schwalbe). Posteriorly this is continued into a lymph channel, which invests the surface of the optic nerve; while anteriorly it communicates directly with the sub conjunctival lymph spaces of the eyeball (Gerlach). The optic Fig. 457. Tan --^j ^jf'A P^^'j -^^ y' / /' 'IJjMUj )rizontaI section of the entrance of the opii' n ! ili'j eye. rt, inner, /', outer layers of the retin r, choroid ; tance (/, 0) of the lens. The converse of this condition is evident, viz., rays which diverge from a focus and reach the lens pass through it to the other side, parallel with the principal axis, without again coming together. 760 ACTION OF LENSES ON LIGHT. 2. Rays of light proceeding from a srurce of light (IV, /) in the prolonged principal axis, but beyond the focal point (/), again converge to a point on the other side of the lens. The following cases may occur: {a) When the distance of the light from the lens is equal to twice the focal distance, the focus, or point of convergence, lies at the same distance on the other side of the lens, 1) s Figures illustrating the action of lenses upon rays of light passing through them. /'. ^., twice the focal distance. \b) If the luminous point be moved nearer to the focus, then the focal point is moved further away, (c) If the light is still further from the lens than twice the focal distance, then the focal point comes correspondingly near to the lens. 3. Rays proceeding from a jioint of the chief axis (III, b) within the focal distance pass out at Fig. 459. S IG the other side less divergent, but do not come to a focus again. Conversely, rays which are con- vergent and pass through a collecting lens have their focal point within the focal distance. 4. If the luminous point (V, a) is placed in the secondary ray (a, b\, the same laws obtain, pro- vided the angle formetl by the secondary ray with the principal axis is small. REFRACTIVE INDICES. 761 Formation of Images by Convex Lenses. — -After what has been stated regarding the position of the point of convergence of rays proceeding from a luminous point, the construction of the image of any object by a convex lens is easily accomplished. This is done simply by projecting images of the various parts of the object. Thus, evidently in V,/> is the focal point of the object «, while V is the focal point of the object /. The picture is inverted. Collectinj; lenses form an inverted and real image (z. ^., upon a ^crt&n) only of Sitch objeels as are placed beyond the foeal point of the lens. With regard to the size and distance of the image from the lens, there are the following cases : {a) If the object be placed at t« ice the focal distance from the lens, the image of the same is just the same size and at the same distance from the lens as the object is. (l>) If the object be nearer than the focus, the image recedes, and at the same time becomes larger. (<) If the object be further removed from the lens than twice the focal distance, then the image is nearer to the lens, and at the same time becomes smaller. Position of the Focal Point. — The distance of the focal point from the lens is readily calcu- lated according to the following formula : Where / =: the distance of the luminous point, b = the ' + '^=i,or±=L-i. b f b f I Example. — Let /r= 24 centimetres, /= 6 cm. Then -^= — = — ,so that ^ ^ 8 cm., ^ ^ '■' * 6 24 8 i. e., the image is formed 8 cm. behind the lens. Further, let / =^ 10 cm.,/^ 5 cm. (/. e., I = 2 f\. Then _ = — — — =^ — ; so that b = 10, i. e., the image is placed at twice the focal distance •" ,5 5 10 10 ^ ' of the lens. Lastly, let / = 00. Then -■= ~- — — ; so that i =/, ;. e., the image of parallel rays b f c/^ coming from infinity lies in the focal point of the lens. Refractive Indices. — A ray of light, which passes in a perpendicular direction from one medium into another medium of different density, passes through the bitter without changing its course or being refracted. In Fig. 459, if G D, is j_ A B, then so is D D, J^ A B; for a plane surface A B is the horizontal, and G D the vertical line. If the surface is spherical, then the vertical line is the prolonged radius of this sphere. If, however, the ray of light falls obliquely upon the surface, it is "refracted," i. e., it is bent out of its original course. The incident and the refracted ray, never- theless, lie in otte plane. When the oblique incident ray passes from a less dense medium (e.g., air) into one more dense (e.g., water), the refracted or excident ray is bent toward \.\ie. perpendicular. If, conversely, it pass from a more dense to a less dense medium, it is bent away from the perpen- dicular. The angle (/ G D S) which the incident ray (S D) forms with the perpendicular (0 D) is called the angle of incidence, the angle formed by the refracted ray (D S; ) with the prolonged peqiendicular (D D) is called the angle of refraction, D D S, (>). The refractive power is expressed as the " refractive index." The term refractive index (h) means that number which shows for a ceitain substance how many times the sine of the angle of incidence is greater than the sine of the angle of refraction, when a ray of light passes from the air into that substance. Thus, n = sin. i : sin. r = ab, : cd. On comparing the refractive indices of two media, we always assume that the ray passes from air into the medium. On passing from the air into water, the ray of light is so refracted that the sine of the angle of incidence is to the sine of the angle of refraction as 4:3; the refractive index is = — (or more exactly ^= 1.336). With glass the proportion is = 3 : 2 (= 1.535) — (Snellius, 1620 : Descartes'). The construction of the refracted ray, the refractive index being given, is simple. Example. —Suppose in Fig. 460, L = the air. f; = a dense medium (glass) with a spherical surface, x v, and with its centre at m ; p =: the obli<|ue incident ray, then m Z is the perpendicular, <^) = i the angle of incidence. The refractive index given is — ! the object is to find the direction of the refracted way. From o as centre describe a circle with a radius of any length ; from a draw a per- pendicular, a b to m Z\ then a b \i the sine of the angle of incidence, i. Divide the line a b into three equal parts, and prolong it to the extent of two of these parts, viz., to/. Draw the line/ paiallel to m Z. The line joining to « is the direction of the refracted ray. On making a line, «, .r, perpendicular to m Z, n s ^= b p. Further, n s = sine <|) = r. So that a b : s n (or : b p) = •? : 2 or sin. i : sin. r = — ■ Optical Cardinal Point of a Simple Collecting System. — Two refractive media (Fig. 461, L and G) which are separated from each other by a spherical surface (a, b\ form a simple collect- ing system. It is easy to estimate the construction of an incident ray coming from the first medium (L) and falling obliquely upon the surface (a, b) separating the two media, as well as to ascertain its direction in the second medium, G, and also from the position of a luminous point in the first medium to estimate the position of the corresponding focal point in the second medium. The factors required to be known are the following: L (Fig. 461) is the first, and G the second 762 CONSTRUCTION OF A REFRACTED RAY. medium, a,b ^ the spherical surface whose centre is m. Of course, all the radii drawn from m to <7 h (m X, m n) are perpendiculars, so that all rays falling in the direction of the radii must pass unrefracted through m. All rays of this sort are called rays or lines of direction ; /«, as the point of intersection of all these, is called the nodal point. The line which connects in with the vertex of the spherical surface, .r, and which is prolonged in both directions, is called the optic axis, O Q. A plane (E, F) in x, perpendicular to O Q, is called the principal plane, and in it x is the prin- cipal point. The lollowing facts have been ascertained: (I) All ravs [a to (Z^), which in the first medium are parallel with each other and with the optic axis, and fall upon a b, are so refracted in the second medium that they are all again united in one point (/,) of the second medium. This is called the second principal focus. A plane in this point perpendicular to O Q is called \ht second Fic;. 461. focal plane (C, D). (2) All rays [c to Cjl, which in (he first medium are parallel to each other but not parallel to O Q, reunite in a point of the second f >cal plane (r), where the non-refracted directive ray (<-j, m r) meets this. (In this case the angle formed by the rays c to c^ with C Q must be very small.) The propositions i and 2 of course maybe reversed; the divergent rays pro- ceeding from/ toward a h pass into the first medium parallel to each other, and also with the axis C Q [a to a^^ ; and the rays proceeding from r pass into the first medium parallel to each other, but not parallel to the axisO Q (as c to c,). (3) AH rays, which in the second medium are parallel to each other {/> to 16.) and witn the axis O Q. reunite in a point in the first medium (/), called the lirsl fecal point ; of course, the converse of this is true. A plane in this point perpendicular to FiG 462. O Q is called \)a& first focal plane (A, B). The radius of the refractive surface [m, x) is equal to the difference of the distance of both focal points (/ and /,) from the principal focus {x) ; thus m x ^/"i X — p X. Prom these comparatively simple propositions it is easy to determine the fol- lowing points : — I. The Construction of the Refracted Ray. — Let A (Fig. 462) be the first; B the second medium; c, d, the spherical surface separating the two; «, b, the optical axis; k, the nodal point; / the first and/ J the second prmcipal focus; C, D, the second focal plane. Suppose x, y to repre- sent the direction of the incident ray, what is the construction of the refracted ray in the second medium ? Prolong the unrefracted ray, P, X-, Q p.arallel to -i-, y, then y, Q is the direction of the refracted ray (according to 2). CONSTRUCTION OF A REFRACTED RAY. 763 2. Construction of the Image for a given Object. — In Fig. 463, B, ) in the first medium, what is the position of the image in the second medium ? Prolong the unrefracted ray (0, k, P), and draw the ray (o, x) parallel to the axis (n, b). The parallel rays (a, e, and o, x) reunite vap according to proposition l). Prolong J-,/, until it intersects the ray \o, P), then the image of i? is at P, the rays of light (o, x, and k) proceeding from the luminous point (o) reunite in P. Construction of the Refracted Ray and the Image in several Refractive Media. — If Fig. 463. several refractive media be placed behind each other, we must proceed from medium to medium with the same methods as above described. This would be very tedious, especially when dealing with small objects. Gauss (1840) calculated that in such cases the method of construction is very simple. If the several media are " centred," i.e., if all have the same optic axis, then the refrac- tive indices of such a centred system may be represented by two equal strong refractive surfaces at a certain distance. The rays falling upon the first surface are not refracted by it, but are essentially projected forward parallel with themselves to the second surface. Refraction takes place first at the Fig. 464. P ^-..^ i::;:^;;^^^^^ . 1 \ 1 ,%.. F a -f^ -C^"""\ I1 ; H H, h 11 ic krr--...,.^^ \^ F F. • m h \ n F. F a "^^ li H H, k kr~~~~~~-~._ ^^^^=====^ second surface, just as if only one refractive surface was present. In order to make the calculation, we must know the refractive indices of the media, the radii of the refractive surfaces, and the dis- tance of the refractive surfaces from each other. Construction of the refracted ray is accomplished as follows : Let «, i5 (Fig. 464, I), represent the optical axis ; H, the first focal point determined by calculation ; h, h, the principal plane ; H, the second focal point ;/;,,;*,, the second principal plane : k, the first, and /(•,, the second nodal point ; F, the second focal point ; and Fj, Fj, the second focal plane. Make the ray of direction/, k^. 764 FORMATION OF A RETINAL IMAGE. parallel to »»,, «j. According to proposition 2, /, *,, and m^, », mu<;t meet in a point of the plane Fj.Fi- As/, i, passes through unrefracted, the ray from n, must, therefore, fall at r; «, r is, therefore, the direction of the refracted ray. Construction of the Focal Point. — Let o (Fig. 464, II) be a luminous point, what is the posi- tion of its image in the last medium ? Prolong from the ray of direction o, k, and make 0, x par- allel to a, b. Both rays are prolonged in a parallel direction to the second focal plane. The ray parallel to «, b goes through F; /«, k-^ as the ray of direction passes through unrefracted. O, where «, F, and w, k.^ intersect each other, is the position of the image of o. 386. DIOPTRIC LAWS AND THE EYE— FORMATION OF THE RETINAL IMAGE— OPHTHALMOMETER.— Position of the Cardinal Points. — The eye surrounded with .lir on the anterior surface of the cornea, represents a concentric system of refractive media with spherical sepa- rating surfaces. In order to ascertain the course of the rays through the various media of the eye, we must know the position of both principal points, both nodal points as well as the two principal focal points. Gauss, Listing, and v. Helmholtz have calculated the position of these points. In order to make this calculation, we require to know the refractive indices of the media of the eye, the radii of the refractive surfaces, and the distance of the latter from each other. These will be referred to afterward. The following results were obtained : (i) T\\t first principal point \s 2.1746 mm. ; and (2) the second principal point \s 2.5724 mm. behind the anterior surface of the cornea. (3) The first noilal point, o.^s^o mm.; and (4) Fig. 465. \\\e second nodal point, 0.3602 mm. in front of the posterior surface of the lens. (5) The second principal fiocits, 14.6470 mm. behind the posterior surface of the lens; and (6) iht first principal focus, 12.8326 in front of the anterior surface of the cornea. Listing's Reduced Eye. — The distance between the two principal points, on the two nodal points, is so small (only 0.4 mm.), that practically, without introduc- ing any great error in the construction, we may assume one mean nodal or principal point lying between the two nodal or principal points. By this simple procedure we gain one refractive surface for all the media of the eye, and only one nodal point, through which all the rays of direction from without must pass without be- ing refracted. This schematic simplified eye is called " the /-educed eye " of List- ing. Formation of the Retinal Image. — The construction of the image on the retina thus becomes very simple. In distinct vision the inverted image is formed on the retina. Let A B (Fig. 465) represent an object placed vertically in front of the eye. A pencil of rays passes from A into the eye ; the ray of direction, A (/, passes without refraction through the nodal point, i. Further, as the focal point for the luminous point. A, is upon the retina, all the rays proceeding from A must reunite in (/. The same is true of the rays proceeding from B, and, of course, for rays sent out from an intermediate point of the body. A, B. The retinal image THE OPHTHALMOMETER. 765 is, as it were, an endless mosaic of many foci of the object. As all the rays of direction must pass through tlie combined nodal point, k, this is also called the "point of intersection of the visual rays." The inverted image on the retina is easily seen in an excised eye of an albino rabbit, or in any other eye, by removing a portion of the sclerotic and choroid, and supplying its place with a piece of glass. The size of the retinal image may also be calculated, provided we know the size of the object and its distance from the cornea. As the two triangles. A, B, i, and c, i/, k, are similar. A, B ; c, d ^ f,k : k. g, so that c, d = (A, B, i, g) : /, k. All these values are known, viz., /■, g = 15.16 mm. ; further,/, k ^ a, k Ys " where a,/ is measured directly, and a, k ^ 7.44 mm. The size of A B is measured directly. The angle, A ,4 B, is called the visual angle, and of course it is equal to the angle c k d. It is evident that the nearer objects, xy, and r s, must have the same visual angle. Hence, all the three objects, A B, xy, and r s, give a retinal image of the same size. Such objects, whose ends when united with the nodal point form a visual angle of the same size, and consequently form retinal images of the same size, have the same " apparent size." In order to determine the optical cardinal points by calculation after the method of Gauss, we must know the following factors : — I. The refractive indices, which are — for the cornea, 1.377; aqueous humor, 1.377 ; lens, 1.454 (as the mean value of all the layers) ; vitreous humor, 1.336 ; air being taken as i, and water 1.335. Scheme of the ophthalmometer of Helmholtz 2. TTie radii of the spherical refractive surfaces, which are — of the cornea, 7.7 mm. ; of the anterior surface of the lens, 10.3; of the posterior, 6.1 mm. 3. The distance of the refractive surfaces — from the vertex of the cornea to the anterior surface of the lens, 3.4 mm. ; from the latter to the posterior surface of the lens (axis of the lens), 4 mm. ; diameter of the vitreous humor, 14.6 ram. The total length of the optic axis is 22.0 mm. [Kiihne's Artificial Eye. — The formation of an inverted image and the other points in the dioptrics of the eye can be studied most efTectively on Kiihne's artilicial eye, the course of the rays of light being visible in water tinged with eosine.] The Ophthalmometer. — This is an instrument to enable us to measure the radii of the refrac- tive media of the eye. As the normal curvature cannot be accurately measured on the dead eje (Petit, J72J), owing to the rapid collapse of the ocular tunics, we have recourse to the process of Kohlrausch for calculating the radii of the refractive surfaces from the size of the reflected images in the living eye. 7'he size of a luminous body is to the size of its reflected image as the distance of both to half the radius of the convex mirror. Hence it is necessary to measure the size of the re- flected image. This is done by means of the ophthalmometer of Helmholtz (Fig. 466). The apparatus is constructed on the following principle : If we observe an object through a glass plate placed obliquely, the object appears to be displaced laterally; the displacement becomes greater the more obliquely the plate is moved. .Suppose the observer. A, to look through the telescope, F, which has the plate, G, placed obliquely in front of the upper half of its objective, he sees the cor- neal reflected image, a, b, of the eye, B, and the image appears to be displaced laterally, viz., to a', b' . If a second plate, G, be placed in front of the lozver half of the telescope, but placed in the opposite direction, so that both plates, corresponding to the middle line of the objective, intersect at an angle, then the observer sees the reflected image, a b, displaced laterally to a", b". As both glass plates rotate round their point of intersection, the position of both is so .selected that both re- 766 ACCOMMODATION OF THE EYE. fleeted images just touch each other with their inner margins (so that b' abuts closely upon a"). The size of the reflected image can be determined from the size of the angle formed by both plates, but we must take into calculation the thickness of the glass plates and their refractive indices. The size of the corneal image, and also that in the lens, may be ascertained in the passive eye, and also in the eye accommodated for a near object, and the length of the radms of the curved surface may be calculated therefrom {Hebnhollz, DonJcrs, Mautkner). Fluorescence. — All the media of the eye, even the retina, are slightly fluorescent ; the lens most, the vitreous humor least (i'. Ilelmholtz). Erect Vision. — .\s the retinal image is inverted, we must e.xplain how we see objects erect. By a psychical djz\, the impulses from any point of the retina are again referred to the e.xterior, in the direction through the nodal point ; thus the stimulation of the point, d iY\g. 465), is referred to A, that of c to B. The reference of the image to the external world happens thus, that all points appear to lie in a surface floating in front of the eye, which is called the field of vision. The field of vision is the inverted surface of the retina projected externally ; hence the field of vision appears erect again, as the inverted retinal image is again projected externally but inverted. That the stimulation of any point is again projected in an inverse direction through the nodal point, is proved by (he simple experiment that pressure upon the oii/er aspect of the eyeball is projected or referred to the inner asj^ecl of the field of vision. The entoptical phenomena of the retina are similarly projected externally and inverted; so that, e.g., the entrance of the optic nerve lies external to the yellow spot (see jj 393). All sensations from the retina are projected externally, 387. ACCOMMODATION OF THE EYE.— According to No. 2 (p. 760), the rays of light proceeding from a luminous point, eg., a flame, and acted upon by a collecting (convex) lens, are brought to a focus or focal point, which has always a definite relation to the luminous object. If a projection surface or screen be placed at this distance from the lens, a real and inverted image of the object is obtaine, ciliary part of the retina ; ^, canal of Petit, with Z. zonule of Zinn in front of it ; and />, the posterior layer of the hyaloid membrane ; r, anterior, s, posterior part of the capsule of the lens ; t, choroid ; u, pericho- roidal space ; '1', pigment epithelium of the iris ; x, margin of the lens. Fig. 468. Scheme of accommodation for near and distant objects. The right side of the figure represents the condition of the lens during accommodation for a near object, and the left side when the eye is at rest. The letters indicate the same parts on both sides ; those on the right side are marked with a stroke ; A . left, B, right half of the lens ; C, cornea; .S", sclerotic ; C.5.j, canal of Schiemm ; K/f., anterior chamber ; y, iris : /*, margin of the pupil ; V, anterior surface ; //, posterior surface of the lens ; V?, margin of the lens ; >*, margin of the ciliary processes : a and d, space between the two former; the line Z, A, indicates the thickness oi the lens during accommodation for a near object ; Z^ V, the thickness of the lens when the eye is passive. images are obtained of distant objects. Thus, paralysis of the mechanism of accommodation is always accompanied by inability to focus a near object, never a distant object. A temporary 768 paralysis with the same results occurs when a solution of atropin or duboisin is dropped into the eye, and also in poisoning with these drugs (J 392). When the eye is accommodated for a near object [positive accommoda- tion], the lens is thicker, its anterior surface is more curved (convex), and projects further into the anterior chamber of the tye {daiiicr, v. Hchnholtz). The mechanism producing this result is the following : During rest the lens is kept somewhat flattened against the vitreous humor lying behind it by the tension of the stretched zonule of Zinn (Fig. 467, Z), which is attached round the margin of the lens. When the muscle of accommodation, the ciliary muscle (/, in), contracts, it pulls forward the margin of the choroid, so that the zonule of Zinn in intimate relation with it is relaxed. [When we accommodate for a near object the ciliary muscle contracts, pulls forward the choroid, relaxes the zonule of Zinn, and this in turn diminishes the tension of the anterior part of the capsule of the lens.] The lens assumes a more curved form in virtue of its elasticity, so that it becomes more convex as soon as the tension of the zonule of Zinn, which keeps it flattened, is diminished (?'. Helmlioltz). As the posterior surface of the lens lies in the saucer-shaped, unyielding depression of the vitreous humor, the anterior surface of the lens in becoming more convex must neces- sarily protrude more forward. Nerves. — According to Hensen and Volckers, the origin of the nerves of accom- modation lies in the most anterior root bundles of the oculomotorius. Stimu- lation of the posterior part of the floor of the third ventricle causes accommoda- tion ; if a part lying slightly posterior to this be stimulated, contraction of the pupil occurs. On stimulating the limit between the third ventricle and the aque- duct there results contraction of the internal rectus muscle, while stimulation of the other parts around the iter causes contraction of the superior rectus, levator palpebrfe, rectus inferior and inferior oblique muscles. Proofs. — That the lens undergoes an alteration in its curvature during accommodation is proved by the following facts : — I. Purkinje-Sanson's Images. — If a lighted candle be held at one side of the eye, or if light be allowed to fall on the eye through two triangular holes, placed above each other and cut in a piece of cardboard, the oijserver will see in the latter case three pairs of reflected images [in the lormer, three images]. The brightest and most distinct image (or pair of images) is erect, and is Fig. 469. Fig. 470. Sanson-Purkinje's images, a, h, c, during neg.itive, and rt,, l>j, Cf, positive accommodation. produced by the anterior surface of the cornea (Fig. 469, a). The second iiuage (or pair of images) is also erect. It is ihe largest, but it is not so bright {b), and it is reflected by the anterior surface of the lens. (The size of a reflected image from a convex mirror is greater the longer the radius of curvature of the reflecting surface.) The latter image lies 8 ram. behind \\\t plane of the pupil The third image (or pair of images) is of medium size and medium brightness — it is inverted and lies nearly in the plane of the pupil (c). The posterior capsule of the lens which reflects the last image acts like a concave mirror. If a luminous object be placed at a distance from a con- cave mirror, its inverted, diminished, real image lies close to the focus toward the side of the object. If the images rh.\koscope of Helmholi CHANGES DURING ACCOMMODATION. 769 be studied when the observed eye is passive, ;.f., in the phase of negative accommodation on asking the person experimented upon to accommodate his eye for a near object, at once a change In the relative position and size of some of the images is apparent. The middle pair of images reflected by the anterior surface of the lens diminish in si/e and approach each other (dy), which depends upon tlie fact that the anterior surface of the lens has become more convex. At the same time the image (or pair of images) comes nearer to the image formed by the cornea {{jy and c^) as the anterior surface of the lens lies nearer to the cornea. The other images (or pairs of images) neither change their size nor position, v. Helmholtz, with the aid of the ophthalmometer, has measured the diminution of the radius of curvature of the anterior surface of the lens during accom- modation for a near object. [Phakoscope. — These images may be readily shown by means of the phakoscope of v. Helm- holtz (Kig. 470). It consists of a triangular box blackened inside and with its angles cut oflT. The observer's eye is placed at ti, while on the opposite side of the box are two prisms, /', 6^; the observed eye is placed at the side of the box opposite to C. When a candle is held in front of the prisms, 6 and d^, three pairs of images are seen in the observed eye. Ask the person to accommo- date for a distant object, and note the position of the images. On pushing up the slide, C, with a pin attached to it, and asking him to accommodate for the pin, i.e., for a near object, the position and size of the middle images chiefly will be seen to alter as descrilied above.] 2. In consequence of the increased curvature of the lens during accommodation for a near object, the refractive indices within the eye must undergo a change. According to v. Helmholtz, the following measurements obtain in negative and positive accommodation respectively : — Accommodation. Radius of the cornea Radius of anterior surface of lens Radius of posterior surface of lens Position of the vertex of the outer surface of the lens behind ) the vertex of the cornea j Position of the posterior vertex of the lens Position of the anterior focal point Position of the first principal point Position of the second principal point Position of the posterior focal point behind the anterior vertex I of the cornea j Negative— Mm. Positive — Mm. 8 8 10 6 6 55 3-6 3-2 7-2 7-2 12.9 11.24 1.94 2.03 6.96 6.5> 22.23 20.25 3. Lateral View of the Pupil. — If the passive eye be looked at from the side, we observe only a small black strip of the pupil, which becomes broader as soon as the person experimented on ac- commodates for a near object, as the whole pupil is pushed more forward. 4. Focal Line. — If light be admitted through the cornea into the anterior chamber, the " focal line " formed by the concave surface of the cornea falls upon the iris. If the experiment be made upon a person whose eye is accommodated for a distant object, so that the line lies near the margin of the pupil, it gradually recedes toward the scleral margin of the iris, as soon as the person ac- commodates for a near object, because the iris becomes more oblique as its inner margin is pushed forward. 5. Change in Size of Pupil. — On accommod.ating for a near object, the pupil contracts, while in accommodation for a distant object it dilates (Descartes, /6j7). The contraction takes place slightly after the accommodation [Dont/ers). This phenomenon may be regarded as an associated movement, as both the ciliary muscle and the sphincter pupilla; are supplied by the oculomotorius (J 345, 2, 3). A reference to Fig. 467 shows that the latter also directly supports the ciliary muscle; as the inner margin of the iris pa.sses inward (toward r), its tension tends to be propagated to the ciliary margin of the choroid, which also must pass inward. The ciliary pro- cesses are made tense, chiefly by the ciliary muscle (tensor choroids;). Accommodation can still be performed, even though the iris be absent or cleft. 6. Internal Rotation of the Eye. — On rotating the eyeball inward, accommodation for a near object is performed involuntarily. As rotation of both eyeballs inward takes place when the axes of vision are directed to a near object, it is evident that this must be accompanied involuntarily by an accommodation of the eye for a near object. 7. Time for Accommodation. — A person can accommodate from a near to a distant object (which depends upon relaxation of the ciliary muscle) much more rapidly than conversely, from a distant to a near object ( / 'ieroriit, Aeby). The process of accommodation requires a longer time the nearer the object is brought to the eye ( Vieronll, Vo/eiers, and liensen). The time necessary for the image reflected from the anterior surface of the lens to change its place during accommodation is less than that required for subjective accommodation [Auiert and Angelucci). 49 770 REFRACTIVE POWER OF THE EVE. 8. Line of Accommodation. — When the eye is placed in a certain position during accommo- dation, we may see not one point alone distinctly, but a whole series of points behind each other. Czermak called the line in which these points lie the line of accommodalioti. The more the eye is accommodated for a distant object the longer this line becomes. All objects placed at a greater distance from the eye than 60 to 70 metres appear equally distinct to the eye. The line becomes shorter the more we accommodate for a near object, ;. e., when we accommodate as much as pos- sible for a near object, a second point can only be seen indistinctly at a short distance behind the object looked at. 9. The nerves concerned in the mechanism of accommodation are referred to under Oculomo- torius {I 345, and again in ? 704). Scheiner's Experiment. — The experiment which bears the name of Scheiner (1619) serves to illustrate the refractive action of the lens during accommodation for a near object as well as for a distant Fig. 471. object. Make two small pin holes (S, — ~J K (O of the double images of the far needle disappears. An analogous result is obtained on accommodating for the far needle (R). The near needle (P) gives a double image (P^, P^^), because the rays from it have not yet come to a focus. On closing the right hole (i/,), the right double image (PJ dis- appears (yPorterfield). When the eye of Scheiner's experiment. the obscrver is accommodatcd for the near needle, on closing one aperture the double image of the distant point disappears on that side ; but if the eye is accommo- dated for the distant needle, on closing one hole the crossed image of the near needle disappears. 388. REFRACTIVE POWER OF THE EYE— ANOMALIES OF REFRACTION.— Far Point— Near Point.— The limits of distinct vision vary very greatly in different eyes. We distinguish the far point [p. r., punctum remotum] and the near [p. p., punctum proximum] ; the former indicates the distance to which an object may be removed from the eye, and may still be seen distinctly; the latter the distance to which any object may be brought to the eye, and may still be seen distinctly. The distance between these two points is called the range of accommodation. The types of eyeball are characterized as follows : — I. The normal or emmetropic eye is so arranged when at rest that parallel rays (Fig. 472, r, r) coming from the most distant objects can be focussed on the retina (rj. The far point, therefore, is = co (infinity). When accommodating as much as possible for a near object, whereby the convexity of the lens is MYOPIC AND HYPERMETROPIC EYES. 771 r eye and during increased (Fig. 472, a), rays from Fig. 472. a luminous point placed at a dis- tance of 5 inches are still focussed on the retina, i.e., the near point \% = 5 inches (i inch = 27 mm.). The range of accommodation, or ["///^ range of distinct vision"'^, therefore, is from 5 inches (10-12 cm.) to 00 . 2. The short-sighted (myopic or long) eye (Fig. 473 ) cannot, u>/ien at rest, bring parallel rays from infinity to a focus on the retina. These rays decussate within the vitreous humor (at O), and after crossing form a diffusion circle upon the retina. The object must be re- moved from the passive eye to a distance of 60 to 120 inches (to/), in order that the rays may be focussed on the retina. The passive myopic eye, therefore, can only focus divergent rays upon the retina. The far point, therefore, lies abnormally near. With an intense effort at accommodation, objects at a distance of 4 to 2 inches, or even less, from Fig. 473. -./-„ Myopic eye. the eye may be seen distinctly. The near point, therefore, lies abnormally near; the range of accommodation is diminished. Short-sightedness, or myopia, usually depends upon congenital, and frequently hereditary, elongation of the eyeball. This anomaly of the refractive media is easily corrected by using a diverging lens (concave), which makes parallel rays divergent, so that they can then be brought to a focus on the retina. It is remarkable that most children are myopic when they are born. This myopia, however, depends upon a two-curved condition of the cornea and lens, and on the lens being too near to the cornea. As the eye grows, this short-sightedness disappears. The cause of myopia in children is ascribed to the continued activity of the ciliary muscle in reading, writing, etc., or the continued convergence of the eyeballs, whereby the external pressure upon the eyeball is increased. 3. The long-sighted eye (Fig. 474), hypermetropic, hyperoptic (flat eye), when at rest, can only cause convergent rays to come to a focus on the retina. Distinct images can only be formed when the rays proceeding from objects are rendered convergent by means of a convex lens, as parallel rays would come to a focus behind the retina (at /). All rays proceeding from natural objects are either divergent, or at most nearly parallel, never convergent. Hence it follows that no long-sighted person, when the eye '\% passive, i.e., is negatively z.ccoxwcao- dated, can see distinctly without a convex lens. When the ciliary muscle con- tracts, slightly convergent, parallel, and even slightly divergent rays may be focussed, according to the increasing degree of the accommodation. The/f/r 772 THE POWER OR FORCE OF ACCOMMODATION. Fig. 474. Hypermetropic £ point of the eye is negative, the near point abnormally distant (over 8 to 80 inches), while the }-ajige of accommo- dation is infinitely great. The cause of hypermetropia is almormal shortness of the eye, which is generally due 9.\.r--^^fn to imperfect development in all directions. It is corrected hy using a convex lens. [Defective Accommodation. — In the presbyopic eye, or long- sighted eye of old people, the near point is farther away than normal, but the far point is still unaffected. In such cases the person cannot see a near object distinctly, unless it be held at a considerable distance from the eye. It is due to a defect in the mechanism of accommodation, the lens becoming somewhat flatter, less elastic, and denser with old age, while the ciliary muscle becomes weaker. In hypermetropia, on the contrary, the mechanism of accommodation may be perfect, yet from the shape of the eye the person cannot focus on his retina the rays of light from a near object. In presbyopia the range of distinct vision is diminished. The defect is remedied by weak convex glasses. The defect usually begins about forty-five years of of age.] Estimation of the Far Point — Snellen's Types. — In order to determine ihe far point of an eye, gradually bring nearer to the eye objects which form a visual angle of 5 minutes [e. g., Snel- len's small type letters, or the medium type, 4 to 8, of Jaeger), until they can be seen distinctly. The distance from the eye indicates the far point. In order to determine the far point of a myopic person, place at 20 inches distant from the eye the same objects which give a visual angle of 5 minutes, and ascertain the comave tens which will enable the person to see the objects distinctly. To estimate the near point, bring small objects [e. g., the finest print), nearer and nearer to the eye, until it finally becomes indistinct. The distance at which one can still see distinctly indicates the far point. Optometer. — The optometer may also be used to determine the near and far points. A small object, e. g., a needle, is so arranged as to be movable along a scale, along which the eye to be in- vestigated can look as a person looks along the sight of a rifle. The needle is moved as near as possible, and then removed as far as possible, in each case as long as it is seen distinctly. The dis- tance of the near and far point and the range of accommodation can be read off directly upon the scale [Grafe). 389. THE POWER OR FORCE OF ACCOMMODATION.— Force of Accommoda- tion. — The range of accommodation, which is easily determined experimentally, does not by itself determine the proper /o-iitv- or force of accommodation. The measure of the latter depends upon the tneehanieal -work done by the muscle of accommodation, or the ciliary muscle. Of course, this cannot be directly determined in the eye itself. Hence this force is measured by the optical effect, which results in consequence of the change in the shape of the lens, brought about by the energy of the contracting muscle. In the normal eye, during the passive condition, the rays coming from infinity, and, therefore, parallel (which are dotted in Fig. 475), are focussed upon the retina at /. If rays coming from a distance of 5 inches (p. 773) are to be focussed, the whole available energy of the ciliary muscle must be brought into play to allow the lens to become more convex, so that the rays may be brought to a focus at f. The energy of accommodation, therefore, produces an optical effect in as far as it increases the convexity of the anterior Fig. 471;. surface of the passive lens (A), by the amount indicated by 13. Practically, we may regard the matter as if a new convex lens (B) were added to the ex- isting convex lens (.^j. What, there- fore, must be the focal distance of the lens (B) in order that rays coming from the near point (5 inches) may be focussed upon the retina at /'? Evi- dently the lens B must make the diverg- ing rays coming from p parallel, and then A can focus them at /. Convex SPECTACLES. 773 lenses cause those rays proceeding from their focal points to pass out at the other side as parallel rays (^ 385, I). In our case, therefore, the lens must have a focal distance of 5 inches. The nor- mal eye, therefore, with the far point = co, and the near point = 5 inches, has a power of accom- modation equal to a lens of 5 inches focal distance. When the lens by the energy of accommoda- tion is rendered more powerfully refractive, the increase (B) can readily be eliminated by placing be- fore the eye a concave lens which posses-es exactly the opposite optical effect of the increase of ac- commodation (B). Hence, it follows that it is possible to indicate the power (force) of accommo- dation of the eye by a lens of a definite focal distance, i.e, by the optical effect produced by the latter. Therefore, according to Donders, the measure of the force of accommodation of the eye is the reciprocal value of the focal distance of a concave lens, which, when placed before the accommo- dated eye, so refracts the rays of light coming from the near point (/) as if they came from the far point. Example. — We may calculate the force of the accommodation according to the following for- mula: - =: — -— , i.e., the force of accommodation, expressed as the dioptric value of a lens (of jr inch focal distance), is equal to the difference of the reciprocal values of the distances of the near point (/) and of the far point (r) of the eye. In the emmetropic eye, as already mentioned,/ = 5, r = 00. Its force of accommodation is, therefore, - = , so that jr = 5i '■ e.t it is equal to a X p a lens of 5 inches focal distance. In a myopic eye,/ ^ 4, r =: 12, so that - = , i.e., x = 6. In another myopic eye, with / ^ 4 and r =r 20, then jr = 5, which is a normal force of accom- modation. Hence, it is evident thaftwo different eyes, possessing a very different range of accom- modation, may, nevertheless, have the same/o/-«of accommodation. Example. — The one eye has / = 4, r ^ CO , the other,/ = 2, r = 4. In both cases, - = -, so that the force of accommoda- X 4 tion of both eyes is equal to the dioptric value of a lens of 4 inches focal distance. Conversely, two eyes may have the same range of accommodation, and yet their force of accommodation be very unequal. Example. — The one eye has/ ^ 3, »- = 6 ; the other/ = 6, r = g. Both, therefore, have a range of accommodation of 3 inches. For these, the force of accommodation, - ^ - — ~, X 3 6 jr = 6; and - ^ , x ^ l8. JT 6 9 Relation o/the range to M^' force »/ accommodation. — The general law is, that the ranges of accommodation of two eyes being equally great, then l\it\T forces of accommodation are equal, pro- vided that their near points are the same. If the ranges of accommodation for both eyes are equally great, but their near points unequal, then i\ie forces of accommodation are also unequal — the latter being greater in the eyes with the smallest near point. This is due to the fact that every difference of distance near a lens has a much greater effect upon the image compared with differences in the distance /ar from a lens. The emmetropic eye can see distinctly objects at 60 to 70 metres, and even to infinity, without accommodation. While/ and r may be directly estimated in the emmetropic and myopic eyes, this is impossible with the hypermetropic (long-sighted) eye. The far point in the latter is negative, indeed in every pronounced hypermetropia even the near point may be negative. The far point may be estimated by making the hypermetropic eye practically a normal eye by using suitable convex lenses. The relative near point may then be determined by means of the lens. Even from the I5lh year onward, the power of acccmmodalion is generally diminished for near objects —perhaps this is due to a diminution of the elasticity of the lens (Donders). 390. SPECTACLES. — The focal distance of concave (diverging) as well as convex (converg- ing) spectacles depends upon the refractive index of tlie glass (usually 3: 2), and on the length of the radius of curvature. If the curvature of both sides of the lens is the same (biconcave or bicon- vex), then with the ordinary refractive index of glass the focal distance is the same as the radius of curvature. If one surface of the lens is plane, then the focal distance is twice as great as the radius of the spherical surface. Spectacles are arranged according to their focal distance in inches, but a lens of shorter focal distance than I inch is generally not used. They may also be arranged accord- ing to their refractive po-wer. In this case the refractive power of a lens of I inch focus is taken as the unit. A lens of 2 inches focus refracts light only half as much as the unit measure of i inch focus ; a lens of 3 inches focus refracts '^ as strongly, etc. This is the case both with convex and concave lenses, the latter, of course, having a negative focal distance; thus, "concave — ],^ " indi- cates that a concave lens diverges the rays of light one-eighth as strongly as the concave lens of I inch (negative) focal distance. Choice of Spectacles. — Having determined the near point in a myopic eye, of course we re- quire to render parallel the divergent rays coming from the far point, just as if they came from infin- ity. This is dune by selecting a concave lens of the focal distance of the far point. The greatest distance is the far point of the emmetropic eye. -Suppose a myopic eye with a far point of 6 inches. 774 CHROMATIC AND SPHERICAL ABERRATION. then such a person requires a concavi' lens of 6 inches focus to enable him to see distinctly at the gre itest distance. Thus, in a myopic eye, the di-tance of the far point from the eye is directly equal to the focus of the (weakest) concave lens, which enables one to see distinctly objects at the greatest distance. These lenses generally have the same number as the spectacles required to correct the defect. Example. — A myopic eye with a far point of 8 inches requires a concave lens of 8 inches focus, i.e., the concave spectacle. No. S. For the hypermetropic (long-sighted) eye, the focal dis- tance of the strongest convex lens, which enables the hypennetropic eye to see the most distant objects distinctly, is at the same time the distance of the far point from the eye. Example. — A hypermetropic eye which can see the most distant objects with the aid of a convex lens of I2 inches focus has a far point of I2 ; the proper spectacles is convex, No. I2. [Dioptric. — The focal length of a lens used to be expressed in inches, and as the unit was taken as I inch, necessarily all weaker lenses were expressed in fractions of an inch. In the method advocated by Bonders, the standard is a lens of a focal distance of i metre (33.337 English inches, about 40 inches), and this unit is called a dioptric. Thus, the standard is a weak lens, so that the stronger lenses are multiples of this. Thus, a lens of 2 dioptrics is ^ one of about 20 inches focus; 10 dioptrics = 4 inches focus; and so on. The lenses are numbered from No. 1, /. e., I dioptric, onward. It is convenient to use signs instead of the words convex and concave. For convex the sign plus -\- is used, and for concave the sign minus — . Thus, a -\- 4.0 means a convex lens of 4 dioptrics, and a — 40 = a concave lens of 4 dioptrics.] In all cases of myopia or hypermetropia the person ought to wear the proper spectacles. In a myopic eye, when the far point is still more than 5 mches, the patient ought always to wear spec- tacles; but generally the working distance, e. g., for reading, writing, and for handicrafts, is about 12 inches from the eye. If the person desires to do finer work (etching, drawing), requiring the object to be brought nearer to the eye, so as to obtain a larger image upon the retina, then he should either remove the spectacles altogether or use a weaker pair. The hypermetropic person ought to wear his convex spectacles when looking at a near object, and especially when the illumination is feeble, because then, owing to the dilatation of the pupil, the diffusion circles of the eye tend to become very pronounced. It is advisable to wear at first convex spectacles which are slightly too strong. Cylindrical lenses are referred to under .4stigmatism. .Spectacles provided with dull-colored or blue glasses are used to protect the retina when the light is too intense. Stenopaic spectacles are narrow diaphragms placed in front of the eye, which cause it to move in a definite direction in order to see through the opening of the diaphragm. 391. CHROMATIC AND SPHERICAL ABERRATION, ASTIG- MATISM.— Chromatic Aberration. — All the rays of icihite light, which undergo refraction, are at the same time broken up by dispersion mto a bundle of rays, which, when they are received on a screen, form a spectrum. This is due to the fact that the different colors of the spectrum possess different degrees of refrangibility. The violet rays are refracted most strongly, the red rays least. A white point on a black ground does not form a sharp simple image on the retina, but many colored points appear after each other. If the eye is accommodated so strongly as to focus the violet rays to a sharp image, then all the other colors must form concentric diffusion circles, which become larger toward the red. In the centre of all the circles, where all the colors of the spectrum are superposed, a white point is produced by their mixture, while around it are placed the colored circles. The distance of the focus of the red rays from that of the violet in the eye ^ 0.58 to 0.62 mm. The focal distance for red is, according to v, Helmholtz, for the reduced eye, 20.524 mm. ; for violet, 20.140 mm. Hence the near and far points for violet light are nearer each other than in the case of red light; white objects, therefore, appear reddish when beyond the far point, but when nearer than the near point they are violet. Hence the eye must accommodate more strongly for red rays than for violet, so that we judge red objects to be nearer us than violet objects placed at an equal distance {Briickc). Monochromatic or Spherical Aberration. — Apart from the decomposition or dispersion of white light into its components, the rays of white light, proceeding from a point if transmitted through refractive spherical surfaces, we find that before the rays are again brought to a focus, the marginal rays are more strongly refracted than those pas-.ing through the central parts of the lens. Hence there is not one focus, but many. In the eye this defect is naturally corrected by the iris, which, acting as a diaphragm, cuts off the marginal rays (Fig. 465), especially when the lens is most convex, when the pupd also is most contracted. In addition, the margin of the lens has less refractive power than the central substance; lastly, the margins of the refractive spherical surfaces of the eye are less curved toward their margins than the parts lying nearer to the optical axis. Compare the form of the cornea (p. 750) and the lens (p. 757). Imperfect Centring of the Refractive Surfaces. — The sharp projection of an image is some- what interfered with by the fact that the refractive surfaces are not exactly centred (Briicke). Thus, the vertex of the cornea is not exactly in the termination of the optic axis; the vertices of both surfaces of the lens, and even the different layers of the lens itself, are not exactly in the optic axis. The variations, however, and the disturbances produced thereby, are very small indeed. FUNCTIONS OF THE IRIS. 775 Regular Astigmatism. — When the curvature of the refractive surfaces of the eye is unequally great in its different meridians, of course the rays of light cannot be united or focussed in one point. Generally, in such cases, the cornea is more curved in its vertical meridian and least in the hori- zontal (as is shown by ophthalmometric measurements, p. 765). The rays passing through the vertical meridian come to a focus, firsl^ in a horizontal focal line ; while the rays entering horizon- tally unite afterward in a vertical line. There is thus no common focus for the light rays in the eye ; hence the name astigmatism. The lens, also, is unequally curved in its meridians, but it is the reverse of the cornea; consequently, a part of the inequality of the curvature of the cornea is thereby compensated, and only a part of it affects the rays of light. The emmetropic eye has a very slight degree ol this ineiiuality (normal astigmatism). If two very fine hnes of equal thickness be drawn on white paper, so as to intersect each other at right angles, it will be found that, in order to see the horizontal line quite shaiply, the paper must be brought slightly nearer to the eye than when Fig. 476. of light (Frost). FlO. 477. we focus the vertical line. When the inequality of curvature of the meridians is considerable, of course exact vision is no longer possible. [Fig. 476 shows the effect of an astigmatic surface on the rays of light. Let abed be such a surface, and suppose diverging rays to proceed from/! The rays passing through r e a cornea ^.conjunctiva c sclerotic (/, anterior chamber containing the aqueous humor : f, ins fj' pupil g posterior chamber / Petit s canal : y, ciliary muscle ; ^, corneo-scleral limit; !, canal of Schlemm , ;«, choroid , «, retina, o, vitreous humor , A'o, optic nerve ; ji. nerve sheaths ; /, nerve fibres: Ic, lamina criorosa. The line O A indicates the optic axis ; Sr, the axis of vision; r, the position of the fovea centralis. the fovea centralis, which is the area of most acute vision, there are no nerve fibres. Further, Purkinje's figure proves that, as the arteries of the retina lie behind the optic fibres, the latter cannot be concerned in the perception of the former. III. Rods and Cones. — The outer segments of the rods and cones have rounded outlines, and are packed close together, but natural spaces must exist between them, corresponding to the spaces that must exist between groups of THE FOVEA CENTRALIS. 787 bodies with a circular outline. These parts are insensible to light, so that a retinal image is composed like a mosaic of round stones. The diameter of a cone in the yellow spot is 2 to 2.5 ij. {M. Sihu/tzc). If two images of two small points, placed very near each other, fall upon the retina, they will still be distinguished as distinct images, provided that both images fall upon two different cones. The two images on the retina need only be 3-4-5.4 // apart, in order that each may be seen sepa- rately, for then the images still fall upon tico adjoining cones. If the distance be diminished so very much that both images fall upon one cone, or one upon one cone and the other upon the intermediate [cement] substance, then only one image is perceived. The images must be further apart in the peripheral portion of the retina in order that they may be separately distinguished. As the rounded end surfaces of the cones do not lie exactly under each other, but are so arranged that one series of circles is adapted to the interstices of the following series, this explains why fine Fig. 492. M'Hardy's perimeter, i, porcelain button : M, bit: E, for fixing the head : g, k, quadrant ; o, fix )inter for piercing the record chart held in the frame (t-) which i nt and the automatic arrangement of slides {k and /), which ; D, upright supporting the quad- dark lines lying near each other appear to have alternating twists upon them, as the images of these must fall upon the cones, at one time to the right, at another to the left. IV. The fovea centralis is the region of most acute vision, wliere only .cones are present, and where they are very numerous and closely packed (Fig. 455). The cones are less numerous in the peripheral areas of the retina, and consequently vision is much less acute in these regions. We may, therefore, con- clude that the cones are more important for vision than the rods. When we wish to see an object distinctly, we involuntarily turn our eyes so that the retinal image falls upon the fovea centralis. In doing this, we are said to "Jix" our eyes upon an object. The line drawn from the fovea to the object is called the axis of vision (Fig. 491, Sr). It forms an angle of only 3.5-7° with the " o/>/ha/ a.xi's" 788 PERIMETRY. {O A), which unites the centres of the spherical surfaces of the refractive media of the eye. The point of intersection, of course, lies in the nodal point (Kti) of the lens (p. 786). The term "direct vision" is applied to vision when the direction of the axis of vision is in line with the object [/. e., when the image of the object falls directly on the fovea centralis]. "Indirect vision" occurs when the rays of light from an object fall upon the peripheral parts of the retina. Indirect vision is much less acute than the direct. To test the acuity of direct vision, draw two fine parallel lines close to each other, and gradually remove them more and more from the eye, until both appear almost to unite and form one line. The size of the retinal image may be ascertained by determining the distance of the two lines from each other, and the distance of the lines from the eye; or, from the corresponding visual angle, which is generally between 60 to 90 seconds. Perimetry. — In order to test indirect vision we may use the perimeter of Auhert and Forster. The eye is placed opposite a fixed point, from which a semicircle proceeds, so that the eye lies in the centre of it. As the semicircle rotates round the fi.xed point, on rotating the former we can circumscribe the surface of a hemisphere, in the centre of which the eye is placed. Proceeding from the fixed point, objects are placed upon semicircles, and are gradually pushed more and more toward the periphery of the field of vision, until the object becomes indistinct, and finally disappears. The process of testing is continued by placing the arc successively in the ditferent meridians of the field of vision. [M'Hardy's perimeter is a very convenient form (Fig. 492). It consists of two uprights (C and D), which are fixed to the opposite ends of a flat basal plate (A). C carries an arrangement for supporting the patient's head, while D carries the automatic arrangement for the perimetiic record. Both of these can be raised or depressed by the screws (G and b). The patient's chin rests on the chin-rest (E^, while in the mouth is placed Landolt's biting fixation (L), which is detachable. The position of the head can be altered by sliding F on L, which can be fixed in any position by the screw (O). The porcelain button (I) just below the patient's eye (/) is connected with the adjust- ment of the " fixation point." The automatic recording apparatus consists of a revolving quadrant [h, h), which describes a hemisphere round a horizontal axis passing through the centre of the hol- low male axle, turning in the female end of a, which is supported by D. TJie quadrant can be fixed at any point by g. On the front concave surface of the quadrant is fixed a circular white piece of ivory, which represents the " fixation point," from which a needle projects, and which is the zero of the instrument. A carriage (;'), in which the test objects are placed, can be moved in the concave face of the quadrant by means of the milled head (y), which moves the carriage by means of a tooth and pinion wheel.] [When the milled head (j) is turned, it moves the carriage and two slides [i and /), the two slides moving in the ratio of 2 to i. The rate of the carriage is so adjusted that it travels ten times faster than /, and five times faster than k. The pointer (/) is connected with these slides, so that it moves when they move, and records its move- ments by piercing the record chart, which is fixed in the double-faced frame (-e, white, on mixing the colors of the spectrum, be reflected in a rapidly rotating mirror, then the individual components of the white re- appear [Lanilois). 4. Place in front of each of the small holes in the cardboard used for Scheiner's experiment (Fig. 471), two differently colored pieces of glass; the colored rays of light passing through the holes unite on the retina, and produce a mixed color (Czermai). 792 GEOMETRICAL COLOR TABLE. Complementary Colors. — Investigation shows that the following colors of the spectrum are complementary, i. e., every pair gives rise to white : — Red and greenish-blue, Orange and Cyan blue, Yellow and indigo-blue. Greenish-yellow and violet, while green has the compound complementary color purple (v. Helniholtz). The mixed colors may be determined from the following table. At the top of the vertical and horizontal columns are placed the simple colors; the mixed colors occur where they intersect the corresponding vertical and horizontal columns (Dk. = dark; wh. = whitish) : — Violet. Indigo. Cyan-blue. Bluish-green. Green. Greenish-yellow. Yellow. Retl Orange Yellow Gr.-yellow Green Bluish-green Cyan-blue Purple Dk.-rose Wh.-rose White White-blue Water-blue Indigo Dk.-rose Wh.-rose White Wh.-rose White Wh.-green Wh -tTPPn White Wh. -yellow Wh.-yellow Green Wh.-yellow Yellow Gr.-yellow Gold-yellow Yellow Orange. Water-blue iRl -t.rp,.n Water-blue The following results have been obtained from observations on the mixture of colors : — 1. If two simple, but non-complementary, spectral colors be mi.xed with each other, they give rise to a color sensation, which may be represented by a color lying in the spectrum between both, and mixed with a certain quantity of white. Hence we may produce every impression of mixed colors by a color of the spec- trum -f- vvhite {Grass?>iait). 2. The less white the colors contain the more " saturated " they are said to be ; the more white they contain they appear more unsaturated. The saturation of a color diminishes with the intensity of the illumination. Geometrical Color Table. — Since the time of Newton attempts have been made to construct a so-called " geometrical color table," which will enable any mixed color to be readily found. Fig. 495 shows such a color table; white is placed Fig. 495. '" '''^ middle, and from it to every point in the curve, — which is marked with the names of the colors, — suppose each color to be so placed that, proceeding from white, the colors are ar- ranged, beginning with the brighle^t tone, then always follows the most saturated tone, until the pure saturated spectral color lies in the point of the curve marked with the name of the color. The mixed color purple is placed between violet and red. In order to determine from this table the mixed color of any two spectral colors, unite the points of these colors by a straight line. Suppose weights cone- sponding to the units of intensity of these colors be placed on both points of the curve indicating colors, then the position of the Red centre of gravity of both in the line connect- ing the colors indicates the position of the mixed color on the table. The mixed color of two spectral colors always lies on the color Geometrical color cone or table. table in the Straight line connecting the two color points. Further, the impression of the mixed color corresponds to an intermediate spectral color mixed with white. The complementary color of any spectral color is found at once by making a line from the point of this color through white, until it intersects the opposite margin of the color table ; the point of intersection indicates the complementary color. \i pure white be produced by mixing two complementary colors, the color lying nearest white on the connecting line must be specially strong, as then only would the centre of gravity of the lines uniting both colors he in the point marked white. By means of the color table we may ascertain the mixed color of three or more colors. For example, it is required to find the mixed color resulting from the union of the point, a (pale yellow), ^ (fairly saturated bluish-green), and 6- (fairly saturated blue). On the three points place weights corresponding to their intensities, and ascertain the centre of gravity of the w eight, a, b, c ; it « ill Cyan blue YeUow HEKING S THEORY OF COLOR SENSATION. 793 lie at/. It is obvious, however, that the impression of this mixed color, whitish green-blue, can be produceil by green-blue -f white, so that / may be also the centre of gravity of two weights, which lie in the line connecting white and green-blue. We may describe a triangle, V, Gr, R, about the color table so as to enclose it completely. The three fundamental or primary colors lie in the angles of this triangle, red, green, violet. It is evident that each of the colored impressions, ;. e., any point of the color table, may be determined by placing weights corresponding to the intensity of ihe primary colors at the angles of the triangle, so that the point of the color table, or, what is the same thing, the desired mixed color, is the centre of gravity of the triangle with its angles weighted as above. The intensity of the three primary colors, in order to produce the mixed color, must be represented in the same proportion as the weights. Theories. — Various theories have been proposed to account for color sensation. 1. According to one theory, color sensation is produced by one kind of element present in the retina, being excited in different ways by light of different colors (oscillations of the light ether of ditferent wave lengths, number of vibrations, and refractive indices). 2. Young-Helmholtz Theory.— The theory of Thomas Young fiSoy) and V. Helmhohz (1S52) as.sumes that three different kinds of nerve elements, corresponding to the three primary colors, are present in the retina. Stimulation of the first kind causes the sensation of red, of the second green, and of the third violet. The elements sensitive to red are most strongly excited by light with the longest wave length, the red rays; those for green by medium wave lengths, green rays; tho>e for violet by the rays of shortest wave length, violet rays. Further, it is assumed, in order to explain a number of phe- nomena, that e-jery color of the spectrum excites all the kinds of fibres, some of them feebly, others strongly. Suppose in Fig. 496 the colors of the spectrum are arranged in their natural order from red to violet horizontaly, then the three curves raised upon the abscissa might indicate the strength Fig. 496. Gr B of the stimulation of the three kinds of retinal elements. The continuous curve corresponds to the rays producing the sensation of red, the dotted line that of green, and the broken line that of violet. Pure red light, as indicated by the height of the ordinates in R, strongly excites the elements sensi- tive to red, and feebly the other two kinds of termina'ions, resulting in the sensation of red. Simple yellow excites moderately the elements for red and green, and feebly those for violet = sensation oi yellow. Simple green excites strongly the elements for green, but much more feebly the two other kinds = sensation o^ green. Simple blue excites to a moderate extent the elements for green and violet ; more feebly those for red = sensation of blue. Simple violet excites .strongly the cor- responding elements, feebly the others = sensation of 7'iolet. Stimulation of any two elements ex- cites the impression of a mixed color ; while, if all of them be excited in a nearly equal degree, the sensation of white is produced. As a matter of fact, the Voung-Helmholtz theory gives a clear and simple explanation of the phenomena of the physiological doctrine of color. It has been at- tempted to make the results obtained by examination of the structure of the retina to accord with this view. According to Max Schullze, the cones alone are end organs connected with the percep- tion of color. The presence of longitudinal slrialion in their outer segments is regarded as consti- tuting them multiple terminal end organs. Our power of color sensation, so far as it depends on the retina, would, on this view of the ma'ter, bear a relation to the number of cones. The degree of color sensation is most developed in the macula lutea, which contains only cone^. and diminishes as the distance from the point increases, while it is absent in the peripheral pans of the retina. The rods of the retina are said to be concerned only with the capacity to distinguish between quantitative sensations of light. 3. Hering's Theory. — Ew. Hering, in order to explain the sensation of light, proceeds from the axiom stated under I, p. 792. What we are conscious of, and call a visual sensation, is the psjchical expression for the metabolism in the visual substance (" Sehsiibitanz "), i.e., in those n-Tve masses which are excited in the process of vision. I-ike every other corporeal matter, this su stance during the activity of the metabolic process undergoes decomposition or " disassimila- tion ;" while during rest it must be again renewed, or " assimilate " new material. Hering assumes that for the perception of white (bright) and black (dark), two different qualities of the 794 COLOR BLINDNESS. chemical processes take place in the visual substance, so that the sensation of white or bright cor- responds to the disassimilation (decomposition), and that of black (dark) to the assimilation (restitution) of the visual substance. According to this view, the different degrees of distinctness or intensity with which these two sensations appear, occur in the several transitions between pure white and deep black, or the proportions in which they appear to be mixed (gray), correspond to the intensity of these two psycho-physical processes. Thus the consumption and restitution of matter in the visual substance are the primary processes in the sensation of white and black. In the production of the sensation of white, the consumption of the visual substance is caused by the vibrating ethereal waves acting as the discharging force or stimulus, while the degree of the sensa- tion of whiteness (brightness) is proportional to the quantity of the matter consumed. The process of restitution arts. Both processes influence each other simultaneously and conjointly. This explains physiologically the phenomenon of contrast (p. 799), of which the old view could give only a psychical interpretation. Similarly, color sensation is regarded as a sensation of decom- position (disassimilation) and one of the restitution (assimilation) ; in addition to -white, red and yellow are the expression of decomposition ; while green and blue represent the sensation of resti- tution. Thus the visual substance is subject to three different ways of chemical change or meta- bolism. We may thus explain the colored phenomena of contrast and the complementary after images. The sensation of black-white may occur simultaneously with all colors, so that every color sensation is accompanied by that of dark or bright, so that we cannot have an absolutely pure color. There are three different constituents of the visual substance; that connectetl with the sen- sation of black-white (colorless), that with blue-yellow, and that with redgreen. All the rays of the visible spectrum act in disassimilating the black-white substance, but the different rays act in different degrees. The blue- yellow or red-green substances, on the other hand, are disassimilated only by certain rays, some rays causing assimilation, and others are inactive. Mixed light appears colorless when it causes an equally strong disassimilation and assimilation in the blue-yellow and in the red- green substance, so that the two processes mutually antagonize e.-ich other, and the action on the black- white substance appears pure. Two objective kinds of light, which together yield white, are not to be regarded as complementary, but as antagonistic kinds of light, as they do not supplement each other to produce white, but only allow this to appear pure, because, being antagonistic, they mutually prevent each other's action. The imperfection of the Voung-Helmholtz theory of color sensation is that it recognizes only one kind of excitability, excitement and fatigue (corresponding to Hering's disassimilation), and that it ignores the antagonistic relation of certain light rays to the eye. It does not regard white as con- sisting of complementary light rays, which neutralize each other by their action on the colored visual substance, but as uniting to form white [Hering). In applying this theory to color blindness (§ 397), we must assume that those who are red blind want the red-green visual substance ; there are but two partial spectra in their solar spectrum, the black-white and the yellow-blue. The position of green appears to such an one to be colorless ; the rays of the red part of the spectrum are so far visible, as the sensation of yellow and white produced by these rays is strong enough to excite the retina. Hering divides his spectrum into a yellow and a blue half. A violet-blind person wants the yellow-bine visual substance ; in his spectrum there are only two partial spectra, the black- white and the red-green. In cases of complete color blindness, the yellow- blue and red-green substances are absent. Hence, such a person has only the sensation of bright and dark. The sensibility to light and the length of the spectrum are retained ; the brightest part in this case, as in the normal eye, is in the yellow (^Hering). Von Kries devised the following experiment against Hering's theory : AiTange two gray surfaces, one formed by mixing white and black, the other by yellow and blue, and let both appear equally an intense gray. On staring at a red object on these surfaces until the retina is fatigued, and until the object disappears, a gray after image appears in both cases. The mixture of yellow and blue cannot in this case have acted as to cause restitution of the red-gray substance; this is done rather by the mixed gray composed of white and black. 397. COLOR BLINDNESS AND ITS PRACTICAL IMPORT- ANCE. — Causes. — Hy the term color blindness ( Dyschromatopsy) is meant a pathological condition in which some individuals are unable to distin- guish certain colors. Huddart (1777) was acquainted with the condition, but it was first accurately described by Dalton (1794), who himself was red blind. The term color blindness was given to it by Brewster. COLOR BLINDNESS. 795 The supporters of the Young- Heltnholtz theory assume that, corresponding to the paralysis of the three color-perceiving elements of the retina, there are the following kinds of color blindness ; — 1. Red blindness. 2. Green blindness. 3. Violet blindness. The highest degree being termed complete color blindness. The supporters of E. Hering's theory of color sensation distinguish the following kinds: — 1. Complete Color Blindness (Achromatopsy). — The spectrum appears achromatic; the position of the greenish-yellow is the brightest, while it is darker on both sides of it. A colored picture appears like a photograph or an engraving. Occasionally the different degrees of light intensity are ]5erceived in one shade of color, t\^., yellow, which cannot be compared with any other Ciller. O. Becker and v. Hippel observed cases of «>2!7i^). — The spectrum is dichromatic, and consists only of red and green. The blue violet end of the spectrum is usually greatly shortened. In pure cases only the red and green are correctly distinguished (Mauthner's Erythrochloropy), but not the other colors. Unilateral coses h.ive been observed. 3. Red-green Blindness. — The spectrum is also dichromatic. Yellow and blue are correctly distinguished; violet and Ijlue are both taken for blue. The sensations for red and green are absent altogether. There are several forms of this — (a) Green blindness, or the red-green blindness, with undiminished spectrum (Mauthner's Xanthokyanopy), in which bright green and dark red are confounded. In the spectrum yellow abuts directly on blue, or between the two; at most, there is a strip of gray. The maximum of brightness is in the yellow. It is often unilateral and often hereditary. (!•) Red blindness (or the red-green blindness with undiminished spectrum, also called Daltonism), in which bright red and dark green are confounded. The spectrum consists of yellow and blue, but the yellow lies in the orange. The red end of the spectrum is uncolored, or even dark. The greatest brightness, as well as the limit between yellow and blue, lies more toward the right. 4. -Incomplete color blindness, or a diminished color sense, indicates the condition in which the acuteness of color perception is diminished, so that the colors can be detected only in large objects, or only when they are near, and when they are mixed with white they no longer appear as such. .\ certain degree of this form is frequent, in as far as many persons are unable to distinguish greenish-blue from bluish-green. Acquired color blindness occurs in diseases of the retina and atrophy of the optic nerve (Benedict), in commencing tabes, in some forms of cerebral disease (p. 731), and intoxications. At first green blindness occurs, which is soon followed by red blindness. The peripheral zone of the retina suffers sooner than the central area (Schirmer). In hysterical persons there may be intermittent attacks of color blindness {Charcot, Landolt); and the same occurs in hypnotized persons fp. 708). H. Cohn found that, on heating the eyeball of some color blind persons, the color blindness disappeared temporarily. Occasionally in persons without a lens red vision is present, and is due to unknown cause> Percentage. — Holmgren found that 2 7 per cent, of persons were color blind, most being /ev/ and ;-;v. « blind, and very few violet blind. Limits of Normal Color Blindness. — The investigations on the power of color perception in the normal retina are best carried out by means of Aubert-Forster's perimeter, or that of M' Hardy, \ 395. It is found that our color perception is complete only in the middle of the field of vision. Around this is a middle zone, in which only blue and yellow are perceived, in which, therefore, there is red blindness. Outside this zone there is a peripheral girdle, where there is complete color blindness {\ 395). Hence a red-blind person is distinguished from a person with normal vision, in that the central area of the normal field of vision is absent in the former, this being rather included in the middle zone. The field of vision of a green blind person differs from that of a person with normal vision, in that his peripheral zone corresponds to the intermediate and peripheral zones of the normal eye. The violet-blind person is distinguished by the complete absence of the normal peripheral zone. The incomplete color blindness of these two kinds is characterized by a uniformly diminished central field. [When very intense colors are used, such as those of the solar spectrum, the retina can distinguish them quite up to its margin (Landolt).'] In poisoning with santonin, violet blindness (yellow vision) occurs in consequence of the paralysis of the violet perceptive retinal elements, which not unfrequently is preceded by stimulation of these elements, re-ulting in violet vision, i. e., objects seem to be colored violet (Hiifner). Such is the explanation of this phenomenon given by Holmgren. Max Schultze, however, referred the yellow vision, i.e., seeing objects yellow, to an increase of the yellow pigment in the macula lutea. When colored objects are ver)- small, and illuminated only for a short time, the normal eye first fails to ■perceive red {.-ttibert, Lamansky) ; hence it appears that a stronger stimulus is required to excite the sensation of red. Brucke found that verj' rapidly intermittent white light is perceived as green, because the short duration of the stimulation failed to excite the elements of the retina connected with the sensation of red. [The practical importance of color blindness was pointed out by George Wilson, and again more recently by Holmgren.] No person should be employed in the marine or railway Service until he has been properly certified to be able to distinguish red from green. 796 AFTER IMAGES. Methods of Testing Color Blindness. — Following Seebeck, Holmgren used small skeins of colored wools as the simplest material, in red, orange, yellow, greenish-yellow, green, greenish- blue, blue, violet, purple, rose, brown, gray. There are five finely graduated shades of each of the above colors. When testing a person, select only one skein — ^■,^., a bright red or rose — from the mass of colored wools placed in front of him, and place it aside, asking him to seek out those skeins which he supposes are nearest to it in color. Mace and Nacali have measured the acuteness of vision by illuminating a small object with different parts of the spectrum. They compared the observations on red and green-blind persons with their own result.s, and found that a red-blind person perceives green light much brighter than a normal person. The green blind had an excessive sensibility for red and violet. It appears that what the color blind lose in perceptive power for one olor they gain for another. 398. STIMULATION OF THE RETINA.— Positive and Nega- tive After Images — Irradiation — Contrast. — .\s with every other nervous apparatus, a certain but small amount of time elapses after the rays of light fall upon the eye before the action of the light takes place, whether the light acts so as to produce a conscious impression, or produces merely a reflex effect upon the pupil. The strength of the impression produced depends partly and chiefly upon the excitability of the retina and the other nervous structures. If the light acts for a long time with equal intensity, the excitation, after having reached its culminating point, rapidly diminishes again, at first more rapidly, and afterward more and more slowly. [When the retina is stimulated by light there is (i) an effect on the rho- dopsin (p. 756). (2) The electro-motive force is diminished (§ 332). (3) The processes of the hexagonal pigment cells of the retina dipping between the rods and cones are affected ; thus they are retracted in darkness, and protruded in the light (Fig. 497). (4) Engelmann has shown that the length and shape of the cones vary with the action of light. The cones are retracted in darkness and protruded under the influence of light (Fig. 497). This alteration in the shape of the cones takes place even if the light acts on the skin, and not on the eyeball at alf.] After Images. — If the light acts on the eye for some time so as to excite the retina, and if it be suddenly withheld, the retina still remains for some time in an excited condition, which is more intense and lasts longer the stronger and the longer the light was applied and the more e.\citable the condition of the retina. Thus, after every visual perception, especially if it is very distinct and bright, there remains a so-called " after image.'" We distinguish a " positive after image," which is an image of similar brightness and a similar color. " That the impression of any picture remains for some time upon the eye is a physiological phe- nomenon ; when such an impression can be seen for a long time it becomes pathological. The weaker the eye is the longer the image remains upon it. The retina does not recover itself so quickly, and we may regard the action as a kind of paralysis. This is not to be wondered at in the case of dazzling pictures. After looking at the sun, the image may remain on the retina for several days. A similar result sometimes occurs with pictures which are not dazzling. Busch records that the impression of an engraving, with all its details, remained on his eye for 17 minutes." (Goc-lke.) Experiments and Apparatus for Positive After Images. — i. When a burning stick is rapidly rotated it appears as a fiery circle. 2. The thaumatrope of Paris. 3. The phanakistoscope (Plateau'] or the stroboscopic disks (S/ampfir). Upon a disk or a cylinder a series of objects art- so depicted that successive drawings represent individual factors of one continuous movement. On looking through an opening at such a disk rotated rapidly, we see pictures of the different phases moving so quickly that the one rapidly follows the one in front of it. As the impression of the one picture remains until the following one takes its place, it has the appearance as if the successive phases of the movement are continuous, and are one and the same figure. The apparatus under the name of zoetrope, which is extensively used as a toy, is generally stated to have been invented in 1S32. It was described by Cardanus in 1550. It may be used to represent certain movements, f. g., of the spermatozoa and ciliary motion (Puriinje and Vatentin), the movements of the heart and those of locomotion. [Illusions of Motion. — Silvanus P. Thompson points out that if a series of concentric circles in b'ack and white be made on paper, and the sheet on which the circles are drawn be moved with NEGATIVE AFTER IMAGES IRRADIATION. 797 a motion as if one were rinsing out a pail, but with a very minute radius, then all the circles appear to rotate with the same angular velocity as that imparted. Professor Thompson has contrived other forms of this illusion, in the form of Strobic disks.] 4. The color top contains on the sectors of its disk the colors which are to be mixed. As the color of each sector leaves a condition of excitation for the whole duration of a revolution, all the colors must be perceived simultaneously, ;. t colors appear at once, viz., green, blue, or yellow. The phenomenon is made still more distinct by covering the whole with transparent tracing paper [Herm. Meyer). Under similar cir- cumstances, printed matter on a colored ground appears in its complementary color ( W. v. BezolJ). 2. An air bubble in the strongly tinged field of vision of a thick microscopical preparation appears with an intense contrast color [LanJois). 3. Paste four green sectors upon a rotatory white disk, leave a ring round the centre of the disk uncovered by green, and cover it with a black strip. On rotating such a disk the black part appears red and not gray [Briicke). 4. Look with both eyes toward a grayish-whke surface, and place in front of one eye a tube about the length and breadth of a finger, composed of transparent oiled paper, gummed together to such thickness as will permit light to pass through its walls. The part of the surface seen through the tube appears in its contrast color. The experiment also shows the contrast in the intensity of the illumination [Landois). A white piece of paper, with a round black spot in its centre, when looked at through a blue glass, appears blue with a black spot. If a white spot of the same size on a black ground be placed in front, so that it is reflected in the glass plate and just covers the black spot, it shows the contrast color yellow (Ragona Scina). 5. The colored shadows also belong to the group of simultaneous contrasts. " Two conditions are necessary for the production of colored shadows — firstly, that the light gives some kind of a color to the white surface; second, that the shadow is illuminated, to a certain extent, by another light. During the twilight, place a short lighted candle on a white surface, between it and the fading day- light hold a pencil vertically, so that the shadow thrown by the candle is illuminated, but not abol- ished, by the feeble daylight ; the shadow appears of a beautiful blue. The blue shadow is easily seen, but it requires a little attention to observe that the white paper acts like a reddish-yellow sur- face, whereby the blue color apparent to the eye is improved. One of the most beautiful cases of colored shadows is seen in connection with the full moon. The light of the candle and that of the moon can be completely equalized. Both shadows can be obtained of equal strength and distinct- ness, so that both colors are completely balanced. Place the plate opposite the light of the moon. MOVEMENTS OF THE EYEBALLS. 799 the lighted candle a little to one side at a suitable distance. In front of the plate hold an opaque body, when a doulile shadow appears, the one thrown by the moon and lighted by the candle being bright reddish-yellow ; and, conversely, the one thrown by the candle and lighted by the moon ap- pears of a beautiful blue. Where the two shadows come together and unite is black ( Goethe). 6. " Take a plate of green grass of considerable thickness and hold it so as to get the bars of a window reflected in it, the bars will be seen double.; the image formed by the under surface of the glass being green, while the image coming from the under surface of the glass, and which ought really to be colorless, appears to be purple. The experiment may be performed with a vessel filled with water, with a mirror at its base. With pure water colorless images are obtained, while by col- oring the water colored images are produced " [GoelJie). Explanation of Contrast. — Some ot these phenomena may be explained as due to an error of judgment. During the simultaneous action of several impressions, the judgment errs, so that when an effect occurs at one place, this acts to the slightest extent in the neighboring parts. When, there- fore, brightness acts upon a part of the retina, the judgment ascribes the smallest possible action of the brightness to the adjoining parts of the retina. It is the same with colors. It is far more prob- able that the phenomena are to be referred to actual physiological processes {//e>inf). Partial stim- ulation with light affects not only the part so acted on, but also the surrounding area of the retina; the part directly excited undergoing increased i/isassimilalion, the (indirectly stimulated) adjoining area undergoing increased assimilation ; the increase of the latter is greatest in the immediate neighborhood of the illuminated portion, and rapidly diminishes as the distance from it increases. By the increase of the assimilation in those parts not acted on by the image of the object, this is prevented, so that the diffused light is perceived. The increase of the assimilation in the immediate neighborhood of the illuminated spot is greatest, so that the perception of this relatively stronger different light is largely rendered impossible (Hering). Successive Contrast. — Look for a long time at a dark or bright object, or at a colored {e.g., red) one, and then allow the effect of the contrast to occur on the retina, i.e., with reference to the above, bright and dark, or the contrast color green, then these become very intense. This phe- nomenon has also been called " successive contrast." In this case the negative after image obviously plays a part. [Some drugs cause subjective visual sensations, but these do so by acting on the brain, e.g., alcohol, as in delirium tremens, cannabis indica, sodic salicylate and large doses of digitalis (Brunton).'] 399. MOVEMENTS OF THE EYEBALLS— EYE MUSCLES.— The globular eyeball is capable of extensive and free movement on the corre- spondingly excavated fatty pad of the orbit, just like the head of a long bone in the corresponding socket of a freely movable arthroidal joint. The movements of the eyeball, however, are limited by certain conditions, by the mode in which the eye muscles are attached to it. Thus, when one muscle contracts, its antag- onistic muscle acts like a bridle, and so limits the movement; the movements are also limited by the insertion of the optic nerve. The soft elastic pad of the orbit on which the eyeball rests is itself subject to be moved forward or backward, so that the eyeball also must participate in these movements. Protrusion of the eyeball takes place — i. By congestion of the blood vessels, especially of the veins in the orbit, such as occurs when the outflow of the venous blood from the head is interfered with, as in cases of hanging. 2. By contraction of the smooth muscular fibres in Tenon's cap- sule, in the spheno-maxillary fissure, and in the eyelids (J 404), which are innervated by the cer- vical sympathetic nerve. 3. By voluntary forced opening of the palpebral fissure, whereby the pressure of the eyelids acting on the eyeball is diminished. 4. By the action of the oblique muscles, which act by pulling the eyeball inward and forward. If the superior oblique be con- tracted when the eyelids are forcibly opened, the eyeball may be protruded about I mm. When protrusion of the eyeball occurs p,-ithologically (as in I and 2), the condition is called exoph- thalmos. Retraction of the eyeball is the opposite condition, and is caused — i. By closing the eyelids forcibly. 2. By an empty condition of the retrobulbar blood vessels, diminished succulence, or dis- appearance of the tissue of the orbit. 3. Section of the cervical sympathetic in dogs causes the eyeball to sink somewhat in the orbit. The smooth muscular fibres of Tenon's capsule are perhaps antagonistic in their action to the four recti when acting together, and thus prevent the eyeball from being drawn too far backward. Many animals have a special retractor bulbi muscle, e.g. amphi- bians, reptiles and many mammals ; the ruminants have four. The movements of the eyes are almost always accompanied by similar move- ments of the head, chiefly on looking upward, less so on looking laterally, and least of all when looking downward. 800 POSITIONS OF THE EYEBALL. The difficult inve^ti^rations on the movements of the eyelialls have been carried out, especially by Listing, Meissner, Helmholtz, Donders, A. ?"ick and E. Hering. Axis. — All the movements of the eyeball take place round its point of rotation (Fig. 499, 0), which lies 1.77 mm. behind the centre of the visual axis, or 10.957 mm. from the vertex of the cornea [Domidrs). In order to determine more carefully the movements of the eyeball, it is neces- sary to have certain definite data : i. The visual axis (S, S^), or the antero-posterior axis of the eyeball, unites the point of rotation with the fovea centralis, and is continued straight forward to the vertex of the cornea. 2. The transverse, or horizontal axis (Q, Q^), is the straight line con- necting the points of rotation of both eyes and its extension outward. Of course, it is at right angles to I. 3. The vertical axis passes vertically through the point of rotation at right angles to 1 and 2. These three axes form a coordinate system. We must imagine that in the orbit there is a fixed determinate axial system, whose point of intersection corresponds with the point of rotation of the eyeball. When the eye is at rest (primary position), the three axes of the eyeball completely coincide with the three axes of the coordinate .-ystem in the orbit. When the eyeball, however, is moved, two or more axes are displaced from this, so that they must form angles with the fixed orbital system. Planes. — In order to be more exact, and also partly for further estimations, let us suppose three planes passing through the eyeball, and that their position is secured by any two axes. i. The horizontal plane divides the eyeball into an upper and lower half; it is determined by the visual transverse axes. In its course through the retina it forms the horizontal line of separation of the latter ; the coats of the eyeball itself cut it in their horizontal meridian. 2. The vertical plane divides the eyeball into an inner and outer half; it is determined by the visual and vertical axes. It cuts the retma in the vertical line of separation of the latter and the periphery of the bulb in the vertical meridian of the eyeball. 3. The equatorial plane divides the eyeball into an anterior and posterior half; its position is determined by the vertical and transverse axes, and it cuts the sclerotic in the equator of the eyeball. The horizontal and vertical lines of separation of the retina, which intersect in the fovea centralis, divide the retma into four quadrants. In order to define more precisely the movements of the eyeball, v. Helmholtz has introduced the following terms: He calls the straight line which connects the point of rotation of the eye with the fixed point in the outer world the visual line ("Blicklinie"), while a plane passing through these lines in both eyes he called the visual plane ; the ground line of this plane is the line uniting the two points of rotation, viz., the transverse axis of the eyeball. Suppose a sagittal section to be made through the head, so as to .divide the latter into a right and left half, then this plane would halve the ground line of the visual plane, and ivhen prolonged forward would intersect the visual plane in the median line. The visual point of the eye can be (i) raised or lowered — the field which it traverses being called the visual held (•' Blickfeld ") ; it is part of a spherical surface with the point of rotation of the eye in its centre. Proceeding from the primary position of both eyes, which is characterized by both visual lines being parallel with each other and horizontal, then the elevation of the visual plane can be determined by the angle which this forms with the plane of the primary position. This angle is called the angle of elevation — it is positive when the visual plane is raised (to the forehead), and negative when it is lowered (chinwards). (2) From the primary position, the visual line can be turned laterally in the visual plane. The extent of this lateral deviation is measured by the angle of lateral rotation, i.e., by the angle which the visual line forms with the median line of the visual plane ; it is said to be positive when the posterior part of the visual line is turned to the right, negative when to the left. The following are the positions of the eyeball: — 1. Primary position, in which both the lines of vision are parallel with each other, and the visual planes are horizontal. The three axes of the eyeball coin- cide with the three fixed axes of the coordinate system in the orbit. 2. Secondary positions are due to movements of the eye from the primary position. There are two different varieties : ((7) where the visual lines are par- allel, but are directed uptvani or downward. The transverse axis of both eyes remains the same as in the primary position \ the deviations of the other two axes expressed by the amount of the angle of elevation of the line of vision. (J)) The second variety of the secondary position is produced by the convergence or divergence of the lines of vision. In this variety the vertical axes, round which the lateral rotation takes place, remain as in the primary position ; the other axes form angles; the amount of the deviation is expressed by the "angle of lateral rotation." The eye, when in the primary position, can be rotated from this posi- tion 42° outward, 45° inward, 34° upward and 57° downward (Schuunnann'). 3. Tertiary position is the position brought about by the movements of the eye, in which the lines of vision are convergent, and are at the same time inclined upward or downward. All the three axes of the eye are no longer coincident with the axes in the pri- OCULAR MUSCLES. 801 mary position. The exact direction of the visual lines is determined by the amount of the angle of lateral rotation and the angle of elevation. There is still another important point. The eyeball is always rotated at the same time round the line of vision and round its axis ( Volkmann, Hering, Danders). As the iris rotates round the visual line like a wheel round its axis, this rotation is called " circular rotation " {"Raddfehung") of the eye, which is always connected with the tertiary positions. Even oblique movements may be regarded as composed of — (i) a rotation round the vertical axis, and (2) round the transverse axis ; or it may be referred to rotation round a single constant axis placed between the above-named axes, passing through the point of rotation of the eyeball, and at right angles to the secondary and primary direction of the visual axis (line of vision) — (Listing). The amount of circular rotation is measured by the angle which the horizontal separation line of the retina forms with the horizontal sepa- ration line of the retina of the eye in the primary position. This angle is said to be positive, when the eye itself rotates in the same direction as the hand of a watch observed by the same eye, i.e., when the upper end of the vertical line of separation of the retina is turned to the right. According to Donders, the angle of rotation increases with the angle of elevation and the angle of lateral rotation — it may exceed 10°. With equally great elevation or depression of the visual plane, the rotation is greater the greater the elevation or depression of the line of vision. On looking upward in the tertiary position, the upper ends of the vertical lines of separation of the retina dh'erge ; on looking downward they converge. If the visual plane be raised, the eye, when it deviates laterally to the right, makes a circular rotation to the left. When the visual plane is depressed, on deviating the eye to the right or left, there is a corresponding circular rotation to the right or left. Or we may express the result thus : When the angle of elevation and the angle of deviation have the same sign (-f- or — ), then the rotation of the eyeball is negative; when, however, the signs are unequal, the rotation is positive. In order to make the circular rotation visible in one's own eye, accommodate one eye lor a surface divided by vertical and horizontal lines until a positive after image is produced, and then rapidly rotate the eye into the third position. The lines of the after image then form angles with the lines of the background. As the position of the vertical meridian of the eye is important from a practical point of view, it is necessary to note that, in the primary and secondary positions of the eyes, the vertical meridian retains its vertical position. On looking to the left and upward, or to the right and downward, the vertical meridians of both eyes are turned to the left ; conversely, they are turned to the right on looking to the left and down- ward, or to the right and upward. In the secondary positions of the eye, rotation of the axis of the eye never occurs iListing). Very slight rolling of the eyes occurs, however, when the head is inclined toward the shoulder, and in the direction opposite to that of the head {Jaral j — it is about 1° for every 10° of inclination of the head (Sir^/ii/ziy, iVagel). Ocular Muscles. — The movements of the eyeball are accomplished by means of the four straight and two oblique ocular muscles. In order to understand the action of each of these muscles, we must know the plane of traction of the muscles and the axis of rotation of the eyeball. The plane of traction is found by the plane lying in the middle of the origin and insertion of the muscle and the point of rotation of the eyeball. The axis of rotation is always at right angles to the plane of traction in the point of rotation of the eyeball. The rectus internus (I) and externus (E) rotate the eye almost exactly inward and outward (Fig. 499). 'Ihe plane of traction lies in the plane of the paper ; Q, E, is the direction of the traction of the external rectus, Qi, I, that of the internal. The axis of rotation is in the point of rotation, O, at right angles to the plane of the paper, so that it coincides with the vertical axis of the eyeball. 2. The axis of rotation of the R. superior and inferior (the dotted line, R. sup., R. inf.), lies in the horizontal plane of separation of the eye, but it forms an angle of about 20° with the transverse axis ( (^, Q^) ; the direction of the traction for both muscles is indicated by the line, s, i. By the action of these muscles, the cornea is turned upward and slightly inward, or downward and slightly inward. 3. The axis of rotation of both obliiiue muscles (the dotted 51 802 OCULAR MUSCLES. lines, Obi. sup. and Obi. inf.) also lies in the horizontal plane of separation of the eyeball, and it forms an angle of 60° with the transverse axis. The direction of the traction of the inferior oblique gives the line, a, b ; that of the superior, the line, c, d. The action of these muscles, therefore, is in the one case to rotate the cornea outward and upward, and in the other outward and downward. These actions, of course, only obtain when the eyes are in the primary position — in every other position the axis of rotation of each muscle changes. When the eyes are at rest, the muscles are in equilibrium. Owing to the power of the internal recti, the visual axes converge and would meet, if prolonged 40 centimetres in front of the eye. In the movements of the eyeball, one, two, or ^^.v*^^ '>? three muscles may be concerned. One muscle acts only when the eye is moved directly outward or inward, especially the internal and external rectus. Two muscles act when the eyeball is moved directly upward (superior rectus and inferior oblique), or downward (inferior rectus and superior oblique). Three muscles are in action when the eyeballs take a diagonal direction, especially for inward and upward, by the internal and the superior rectus and inferior oblique ; for inward and downward, the internal and inferior rectus and superior oblique ; for outward and downward, the external and inferior rectus and superior oblique ; for outward and upward, the external and superior rectus and inferior oblique. IDENTICAL POINTS OF THE RETINA. 803 [The following table shows the action of the muscles of the eyeball : — Inward. Rectus internus. Outward Rectus externus. „ J j Rectus superior. ^^ \ Obliquus inferior. Rectus inferior. Obliquus superior ( Rectus internus. Downward I {Rectus internus. Rectus inferior. Obliquus superior. Rectus externus. Outward and upward . X Rectus superior. Obliquus inferior. I Rectus externus. ■{i Inward and Upward . . .j Rectus superior. | Outivard and downward. I Rectus inferior. ( Obliquus inferior. [ (Obliquus superior.] Ruete imitated the movements of the eyeballs by means of a model, which he called the oph- thalmotrope • The size of the eyeball and its length diminish with age. The mobility is less in the vertical than in the lateral direction, and less upward than downward. The normal and myopic eye can be moved more outward, and the long-sighted eye more inward, the external and internal rectus act most when the eye is moved outward, the obliqui when it is rotated inward. An eye can be turned inward to a greater extent when the other eye at the same time is turned outward than when the other is turned inward. During near vision, the right eye can be turned less to the right, and the left to the left, than during distant vision [Ilering). Simultaneous Ocular Movements.— Both eyes are always moved simul- taneously. Even when one eye is quite blind, the ocular muscles move when the whole eyeball is excited. When the head is straight, the movements always take place so that both visual planes (visual axes) lie in the same plane. In front both visual axes can diverge only to a trifling extent, while they can converge consider- ably. If individual ocular muscles are paralyzed, the position of the visual axis in the same place is disturbed, and sig results, so that the patient no longer can direct both visual axis simultaneously to the same point, but he directs the one eye after the other. Even nystagmus (p. 738) occurs in both eyes simulta- neously, and in the same direction. The innate simultaneous movement of both eyes is spoken of as an associated movement {Joh. Aluller). E. Hering showed that in all ocular movements, there is a uniformity of the innervation as well. Even during such movements, in which one eye apparently is at rest, there is a movement, due to the action of two antagonistic forces, the movements result- ing in a slight to and fro motion of the eyeball. The motor nerves of the ocular muscles are the oculomotorius (§ 345), the trochlearis (§ 346), and the abducens (ji 348). The centre lies in the corpora quadrigemina, and below it (| 379), and partly in the medulla oblongata (§ 379). 400. BINOCULAR VISION.— Advantages.— Vision with both eyes affords the following advantages : (i) TVt field of vision of both eyes is consider- ably larger than that of one eye. {2) The perception o( depth is rendered easier, as the retinal images are obtained from two different points. (3) A more exact estimate of the distance and size of an object can be formed, in consequence of the perception of the degree of convergence of both eyes. (4) The correction of certain errors in the one eye is rendered possible by the other. When the position of the head is fi.xed, we can easily form a conception as to the form of t/if entire field of vision if we close one eye and direct the open eye inward. We observe that it is pear-shaped, broad above and smaller below, the silhouette, or profile of the nose, causes the de- pression between the upper and lower part of the field. 401. SINGLE VISION— IDENTICAL POINTS— HOROPTER. — Identical Points. — If we imagine the retin.-e of both eyes to be a pair of hollow saucers placed one within the other, so that the yellow spots of both eyes coincide, and also the similar qtiadrants of the retince, then all those points of both retina: which coincide or cover each other are called "identical" or " correspond- ing points " of the retina. The two meridians which separate the quadrants coinciding with each other are called the "lines of separation." Ptiysiologi- cally, the identical points are characterized by the fact that when they are both simultaneously excited by light, the excitement proceeding from them is, by a 804 THE HOROPTER. psychical act, referred to one and the same point of the field of vision, lying, of course, in a direction through the nodal point of each eye. Stimulation of both identical points causes only one image in the field of vision. Hence all those objects of the external world, whose rays of light pass through the nodal points to fall upon identical points of the retina, are seen singly, because their images from both eyes are referred to the same point of the field of vision, so that they cover each other. All other objects whose images do not fall upon identical points of the retina cause " double vision," or "diplopia." Proofs. — If we look at a linear object with the points 1,2, 3, then the corresponding retinal images are I, 2, 3 and I, 2, 3, which are, obviously, identical points of the retina; (Fig. 500). ]f, while looking at this hne, there be a point, A, nearer the eyes, or B, further from them, then, on focussing for I, 2, 3, neither the rays (.\, a. A, a) coming from A, nor those (B, b, B, b) from B, fall upon identical points ; hence A and B appear double. Make a point {e.g., 2) with ink on paper; of course the image will fall upon both fovea; centrales of the retin.-e (2, 2), which, of course, are identical points. Now press laterally upon one eye, so as to displace it slightly; then two points at once appear, because the image of the point no longer falls upon the fovea centralis of the displaced eye, but on an adjoining non-identical jiart of the retina. When we squint voluntarily all objects appear double. Fig. 500. B Fig. 501. 3 b dentical points of the Horopter for the secondary positic convergence of the visual axe The vertical surfaces of separation of the retina do not exactly coincide with the vertical meri- dians. There is a certain amount of divergence (o.5°-3°), less above, which varies in different individuals, and it may be in the same individual at different times (Heriiig, Donders). The hori- zontal Imes of separation, however, coincide. Images which fall upon the vertical lines of separa- tion appear to be vertical to those on the horizontal lines, although they are not actually so. Hence the vertical lines of separation are the apparent vertical meridians. Some observers regard the identical points of the retina as an acquired arrangement ; others regard it as normally innate. Persons who have had a squint from their birth see singly; in these cases the identical points must be differently disposed. The horopter represents all those points of the outer world from which rays of light passing into both eyes fall upon identical points of the retina, the eyes being in a certain position. It varies with the different positions of the eyes. 1. In the primary position of both eyes with the visual axes parallel, the rays of direction pro- ceeding from two identical points of the two retin.-e are parallel and intersect only at infinity. Hence for the primar)' position the horopter is a plane in infinity. 2. In the secondary position of the eyes with converging visual axes, the horopter for the trans- verse lines of separation is a circle which passes through the nodal points of both eyes (Fig. 501, STEREOSCOPIC VISION. 805 K, K) and through the fixed points I, II, III [Joh. Miiller). The horopter of the vertical lines of separation is in this position vertical to the plane of vision. 3. In the symmetrical tertiary position, in which the horizontal and vertical lines of separation form an angle, the horopter of the vertical lines of separation is a straight line inclined toward the horizon. There is no horopter for the identical points of the horizontal lines of separation, as the lines of direction prolonged from the identical points of these points do not intersect. 4. In the unsymmetrical tertiary position (with rolling) of the eyes, in which the fixed point lies at unequal distances from both npdal points, the horopter is a curve of a complex form. All objects, the rays proceeding from which fall upon non-identical points of the retinae, appear double. We can distinguish ilirecf ox crossed Aov^At images, according as the rays prolonged from the non-identical points of the retina inter- sect in front or behind the fixed point. Experiment. — Hold two fingers — the one behind the other — before both eyes, .\ccommodate for the far one, and then the near one appears double ; and when we accommodate for the near one, the far one appears double. If, when accommodating for the near one, the right eye be closed, the left (crossed) image of the far finger disappears. On accommodating for the far finger and closing the right eye, the right (direct) double image of the near finger disappears. Double images are referred to the proper distance from the eyes, just as single images are. Neglect of Double Images. — Notwithstanding the very large number of double images which inust be formed during vision, they do not disturb vision. As a general rule, they are " neglected," so that the attention must, as a rule, be directed to them before they are perceived. This condition is favored thus : — 1. The attention is always directed to the point of the field of vision which is accommodated for at the time. The image of this part is projected on to both yellow spots, which are identical points of the retina. 2. The form and color of objects on the lateral parts of the retina are not perceived so sharply. 3. The eyes are always accommodated for those points which are looked at. Hence, indistinct images with diffusion circles are always formed by those objects which yield double images, so that they can be more readily neglected. 4. Many double images lie so close together that the greater part of them, when the images are large, covers the other. 5. By practice, images which do not exactly coincide may be united. 402. STEREOSCOPIC VISION.— On looking at an object, both eyes do not yield exactly similar iinages of that object — the images are slightly differ- ent, because the two eyes look at the object from two different points of view. With the right eye we can see more of the side of the body directed toward it, and the same is the case with the left eye. Notwithstanding this inequality, the two images are united. How two different images are combined is best under- stood by analyzing the stereoscopic images. Let, in Fig. 502, L and R represent two such images as are obtained with the left and right eyes. These images, when seen with a stereoscope, look like a truncated pyramid, which projects toward the eye of the observer, as the points indicated by the same signs cover each other. On measur- ing the distance of the points, which coincide or cover each other in both figures, we find that the distances A, a, B, b, C, r, D, d, are equally great, and at the same time are the widest of all the points of both figures ; the distances E, e, F,/, G, g, H, h, are also equal, but are smaller than the former. On looking at the coinciding hnes (A, E, a, <-, and B, F, b,f) we observe that all the points of this line which lie near to A (2 and B b are further apart than those lying nearer E e and Y f. Comparing these results with the stereoscopic image, .j.^^ s„reoscopic drawings, we have the following laws for stereoscopic vi- sion : I. All those points of two stereoscopic images, and, of course, of two retinal images of an object, which in both images are equally distant from each other, ap- pear on the same plane. 2. AUpoints which are nearer to each other, compared with the distance of other points, appear to be nearer to the observer. 3. Conversely, 806 THEORY OF STEREOSCOPIC VISION. all points which lie further apart from each other appear perspectively in the background. The cause of this phenomenon lies in the fact that, " in vision with both eyes we constantly refer the position of the individual images in the direction of the visual axis to where they both intersect." Proofs. — The following stereoscopic experiment (Fig. 503) proves this: Take both images of two pairs of points {a, b, and a, ;i), which are at unequal distances from each other on the sur- face of the paper. By means of small, stereoscopic prisms cause them to coincide, then the com- bined point, A of a, and a appears at a distance on the plane of the paper, while the other point, B, produced by the superposition of /' and ,5, floats in the air before the observer. Fig. 503 shows how this occurs. The following experiment shows the same result : Draw two figures, which are to be superposed similar to the lines B, A, A, E, I), a, and a, e, in Fig. 502. In the lines B, A, and b, a, all the points which are to be superposed lie equally distant from each other, while, on the contrary, all the points in A, E, and «, e", which lie nearer E and e^ are constantly nearer to each o'ther. When looked at with a stereoscope, the superposed verticals, A, e, and B, b, lie in the plane of the paper, while the superposed lines, A, a, and E, e, project obliquely toward the observer from the plane of the paper. From these two fundamental experiments we may analyze all pairs of Fig. 503. Fig. 504. I of Brewster's stereoscope Stereoscopic pictures. Thus, in Fig. 502, if we exchange the two pictures, so that R lies in the place of L, then we must obtain the impression of a truncated hollow pyramid. Two stereoscopic pictures, which are so constructed that the one contains the body from the front and above, and the other, it from the front and below (suppose in Fig. 502 the lines A B and a b were the ground lines), can never be superposed by means of the stereoscope. This process has been explained in another way. Of the two figures, R and L (Fig. 502), only A B C D and abed fall upon identical points of the retina, hence these alone can be superposed ; or, when there is a different convergence of the visual axis, only E F G H and efgh can be superposed for the same reason. Suppose the square ground surfaces of the figures are first superposed, in order to explain the stereoscopic impression, it is further assumed that both eyes, after superposition of the ground squares, are rapidly moved toward the apex of the pyramid. As the axis of the eyes must thereby converge more and more, the apex of the pyramid appears to project ; as iril points which require the conver- gence of the eyes for their vision appear to us to be nearer (see below). Thus, all THE TELESTEREOSCOPE. 807 corresponding parts of both figures would be brought, one after the other, upon identical points of the retina by the movements of the eyes {Bhicke). It has been urged against this view that the duration of an electrical spark suffices for stereoscopic vision {Dove) — a time which is quite insufficient for the movements of the eyes.. Although this may be true for many figures, yet in the correct combination of complex or extraordinary figures, these movements of the visual axes are not excluded, and in many individuals they are distinctly advan- tageous. Not only the actual movements necessary for this act, but the sensations derived from the muscles are also concerned. When two figures are momentarily combined to form a stereoscopic picture, there being no movement of the eyes, clearly many points in the stereoscopic pictures are superposed which, strictly speaking, do not fall upon identical points of the retina. Hence we cannot characterize the identical points of the retina as coinciding mathematically; but, from a physiological point of view, we must regard such points as identical, which, as a rule, by simultaneous stimulation, give rise to a single image. The mind obviously plays a part in this combination of images. There is a certain psychical tendency to fuse the double images on the retinas into one image, in accordance with the fact that we, from experience, Fig. 505. Fig. 506. Telestereoscope of v. Helmhohz Wheatstone's Pseudoscope. recognize the existence of a single object. If the differences between two stereo- scopic pictures be too great, so that parts of the retina too wide apart are excited thereby, or when new lines are present in a picture, and do not admit of a stereo- scopic effect, or disturb the combination, then the stereoscopic effect ceases. The stereoscope is an in-trument by means of which two somewhat similar pictures drawn in perspective may be superposed so that they appear single. Wheatstone (183S) obtained this result by means of two mirrors placed at an angle (Fig. 504J; Brewster (1843) by two prisms (Fig. 503). The construction and mode of action are obvious from the illustrations. Some pairs of two such pictures may be combined, without a stereoscope, by directing the visual axis of each eye to the picture held opposite to it. Two completely identical pictures, ;. c, in which all corresponding points have exactly the same relation to each other, as the same sides of two copies of a book, appear quite fiat under the stereo- scope; as soon, however, as in one of them one or more points alters its relation to the corresponding points, this point either projects or recedes from the plane. Telestereoscope. — When objects, placed at a great distance, are looked at, e. g., the most distant part of a landscape, they appear to us to be flat, as in a picture, and do not stand out, because the slight differences of position of our eyes in the head are not to be compared with the great distance. In order to obtain a stereoscopic view of such objects, v. Helmholtz constructed the telestereoscope (Fig. 505), an apparatus which, by mean%of two parallel mirrors, places, as it were, the point of view of both eyes wider apart. Of the mirrors, L and R each projects its image of the landscape 808 ESTIMATION OF SIZE AND DISTANCE. upon / and r, to which both eyes. O, o, are directed. According to the distance between L and R, the eyes, O, o, as it were, are displai'ed to O^, o,. The distant landscape appears hke a stereo- scopic view. In order to see distant parts more clearly and nearer, a double telescope or opera glass may be placed in front of the eyes (p S09). Take two corresponding stereoscopic pictures, with the surfaces black in one case and light in the other. Draw two truncated pyramids like Fig. 502, make one figure exactly like L, i. e., with a white surface and black lines, and the other with white lines and a black surface, then under the stereoscope such objects glance. The causing of the glancing condition is that the glancing body at a certain distance reflects bright light into one eye and not into the other, because a ray reflected at an angle cannot enter both eyes simultaneously {Dm'e). Wheatstone's Pseudoscope consists of two right-angled prisms (Fig. 506, A and B) enclosed in a tube, through which we can look in a direction parallel with the surfaces of the hypotenuses. If a spherical surface be looked at with this instrument, the image formed in each eye is inverted laterally. The right eye sees the view usually obtained by the left eye, and conversely; the shadow which the body in the light throws upon a light ground is reversed. Hence the ball appears hollow. Struggle of the Fields of Vision The stereoscope is also useful for the following purpose : In vision with both eyes, both eyes are almost never active simultaneously and to the same extent ; both undergo variations, so that first the impression on the one retina and then that on the other is stronger. If two different surfaces be placed in a stereoscope, then, especially when they are luminous, these two alternate in the general field of vision, according as one or other eye is active (Piiitiim). Take two surfaces with lines ruled on them, so that when the surfaces are superposed the lines will cross each other, then either the one or the other system of lines is more prominent (Ptiiiiim). The same is true with colored stereoscopic figures, so that there is a contest or struggle of the colored fields of vision. 403. ESTIMATION OF SIZE AND DISTANCE— FALSE ES- TIMATES OF SIZE AND DIRECTION.— Size.— We estimate the size of an object — apart from all other factors — from the size of the retinal image; thus the moon is estimated to be larger than the stars. If, while looking at a distant landscape, a Hy should suddenly pass across our field of vision, near to our eye, then the image of the fly, owing to the relatively great size of the retinal image, may give one the itnpression of an object as large as a bird. If, owing to defective accommodation, the image gives rise to diffusion circles, the size may appear to be even greater. But objects of very unequal size give equally large retinal images, especially if they are placed at such a distance that they form the same visual angle (Fig. 465 ) ; so that in estimating the actual size of an object, as opposed to the apparent size determined by the visual angle, the estimate of distance is of the greatest importance. As to the distance of an object, we obtain some information from the feeling of accommodation, as a greater effort of the muscle of accomtnodation is re- quired for exact vision of a near object than for seeing a distant one. But, as with two objects at unequal distances giving retinal images of the same size, we know from experience that that object is smaller which is near, then that object is estimated to be the smaller for which, during vision, we must accommodate more strongly. In this way we explain the following: A person beginning to use a microscope always observes with the eyes accommodated for a near object, while one used to the microscope looks through it without accommodating. Hence beginners always estimate microscopic objects as too small, and on making a drawing of them it is too small. If we produce an after image in one eye, it at once appears smaller on accommodating for a near object, and again becomes larger during negative ac- commodation. If we look with one eye at a small body placed as near as possible to the eye, then a body lying behind it, but seen only indirectly, appears smaller. Angle of Convergence of Visual Axes. — In estitiiating the size of an object, and taking into account our estimate of its distance, we also obtain much more important information from the degree of eonvergence of the visual axes. We refer the position of an object, viewed with both eyes, to the point where both visual axes intersect. The angle formed by the two visual axes at this point is called the "angle of convergence of the vistial axes" {" Gesichtswinkel"). The larger, therefore, the visual angle, the size of the retinal image remaining the same — we judge the object to be nearer. The nearer the object is, it may be the smaller ESTIMATION OF DISTANCE. 809 in order to form a "visual angle" of the same size, such as a distant large object would give. Hence, we conclude, that with the same apparent size (equally large visual angle, or retinal images of the same size) we judge that object to be smallest which gives the greatest convergence of the visual axes during binocular vision. As to the muscular exertion necessary for this purpose, we obtain infor- mation from the muscular sense of the ocular muscles. Experiments and Proofs. — The Chessboard Phenomenon of H. Meyer. — i. If we look at a uniform chessboard-like pattern (tapestry), then, when the visual axes are directed directly for- ward, the spaces on the pattern appear of a certain size. If, now, we look at a nearer object, we may cause the visual axes to cross, when the pattern apparently moves toward the plane of the fixed point, so that the crossed double images are superposed, and the pattern at once appears smaller. 2. Rollett looks at an object through two thick plates of glass placed at an angle. The plates are at one time so placed that the apex of the angle is directed toward the observer (Fig. 507, II), at another in the reverse position (I). If both eyes,/and i, are to see the object a, in I, then as the glass plates $0 displace the rays, a, c, and a, g, as to make them parallel with the direction of these rays, viz., f,y. and h, i, then the eyes must converge more than when they are turned directly toward a. Hence the object appears nearer and smaller, as at a. In II, the rays, /'j t, and *, 0, from the nearer object d^, fall upon the glass plates. In order to see />^, the eyes (k and q) must Jivei-ge more, so that b appears more distant and larger. Fig. 507. ® Q 6 1 • n I E RoUett's glass plate apparatus, Fig. 50S. 3. In looking through IVIualstone' s reflecting stereoscope (Fig. 504, II), it is obvious that the more the two images approach the observer, the more must the observer converge his visual axes, because the angles of incidence and reflexion are greater. Hence the compound picture now ap- pears to him to be smaller. If the centre of the image, R, recedes to Rj, then of course the angle, S,,, rp, is equal to S,, 'Rj, and the same on the left side. 4. In using the telestereoscope, ihe two e\es are, as it were, separated from each other, then, of course, in looking at objects at a certain distance, the convergence of the visual axes must be greater than in normal vision. Hence objects in a landscape appear as in a small model. But as we are accustomed to infer that such small objects are at a great distance, hence the objects themselves ap- pear to recede in the distance. Estimation of Distance. — When the retinal images are of the same size, we estimate the distance to be greater the less the effort of accommodation, and conversely. In binocular vision, when the retinal images are of the same size, we infer that that object is most distant for which the optic axes are least converged, and conversely. Thus the estimation of size and distance go hand in hand, in great part at least, and the correct estimation of the distance also gives us a cor- rect estimate of the size of objects {Descartes). A further aid to the estimation of distance is the observation of the apparent displacement of objects, on moving 810 THE LACHRYMAL APPARATUS. our head or body. In the latter, especially, lateral objects appear to change their position toward the background, the nearer they are to us. Hence, when travel- ing in a train, in which case the change of position of the objects occurs very rapidly, the objects themselves are regarded as nearer (Sick), and also smaller {JDove). Lastly, those objects appear to us to be nearest which are most distinct in the field of vision. Example. — A light in a dark landscape, and a dazzling crown of snow on a hill, appear to be near to us; looked at from the top of a high mountain, the silver glancing curved course of a river not unfrequently appears as if it were raised from the plane. False Estimates of Size and Direction. — i. A line divided by intermediate points appears longer than one not so divided. Hence, the heavens do not appear to us as a hollow sphere, but as curved like an ellipse; and for the last reason the disk of the setting sun is estimated to be larger than the sun when it is in the zenith (Ptolemv, 150 A.D.). 2. If we move a circle slowly to and fro behind a slit it appears as a horizontal ellipse, if we move it rapidly it appears as a vertical ellipse. 3. If a very fine line be drawn obliquely across a vertical thick black line, then the direction of the fine line beyond the thick one appears to be different from its original direction. 4. Zollner's Lines. — Draw three parallel horizontal lines i centimetre apart, and through the upper and lower ones draw short oblique parallel lines in the direction from above and the left to below and the right; through the middle line draw similar oblique lines, but in the opposite direction, then the three horizontal lines no longer appear to be parallel. [Fig. 50S shows a modification of this. The lines are actually parallel, although some of them appear to converge and others to diverge.] If we look in a dark mom at a bright vertical line, and then bend the head toward the shoulder, the line appears to be bent in the opposite direction (Auliert). 404. PROTECTIVE ORGANS OF THE EYE.— I. The eyelids are represented in section in Fig. 509. The tarsus is in realitv not a cartilage, but merely a rigid plate of connective tissue, in which the Meibomian glands arc imbedded ; acinous sebaceous glands moisten the edges of the eyelids with fatty matter. At the basal margin of the tarsus, especially of the upper one, close to the reflection of the conjunctiva, there opens the acino-tubular glands of Krause. The conjunctiva covers the anterior surface of the bulb as far as the margin of the cornea, over which the epithelium alone is continued. On the posterior surface of the eyelid the conjunctiva is partly provided with papilla". It is covered by stratified prismatic epitheHum. Coiled glands occur in ruminants just outside the margin of the cornea (hfeissner), while outside this, toward the outer angle of the eye in the pig, there are simple glandular sacks {Ma>n). Waldeyer describes modified sweat glands in the tarsal margins in man. .Small lymphatic s.acks in the conjunctiva are called trachoma glands. Krause found enii Inilhs in the conjunctiva bulbi. The blood vessels in the con- junctiva communicate with the juice canals in the cornea and sclerotic (p. 753). The secretion of the conjunctiva, besides some mucus, consists of tears, which may be as abundant as those formed in the lachrymal gland*. The closure of the eyelids is accomplished by the orbicularis palpebrarum (facial nen'e, § 349), whereby the upper lid falls in virtue of its own weight. This muscle contracts — (i) voluntarily; (2) involuntarily (single contractions) ; (3) reflexly, by stimulation of all the sensory fibres of the trigeminus distributed to the bulb and its immediate neighborhood (§ 347), also by intense stimulation of the retina by light ; (4) continued involuntary closure occurs during sleep. The opening of the eyelids is brought about by the passive descent of the lower one. and the active elevation of the upper eyelid by the levator palpebrae superioris (§ 345). The smooth muscular fibres of the eyelids also aid (p. 623). II. The lachrymal apparatus consists of the lachrymal glands, which in structure closely resemble the parotid, their acini being lined by low, cylindrical, granular epithelium. Four to five larger and eight to ten smaller excretory ducts conduct the tears .above the outer angle of the lid into the forni.x conjunctiva. The tear ducts, beginning at the puncta lachrymalia, are composed of connective and elastic tissue, and are lined by stratified squamous epithelium. Striped muscle accompanies the duct, and by its contraction keeps the duct open ( IVeJl). Toldt found no sphincter surrounding the puncta lachrymalia, while Gerlach found an incomplete circular muscu- lature. The connective-tissue covering of the tear sack and canal is united with the adjoining periosteum. The thin mucous membrane, which contains much adenoid tissue and lymph cells, is lined by a single layer of ciliated cylindrical epithelium, which below passes into the stratified form. The opening of the duct is often provided with a valve-like fold (Hasner's valve). The conduction of the tears occurs between the lids and the bulb by means of capillarity, the closure of the eyelids aiding the process. The Meibomian THE CONDUCTION OF TEARS. 811 secretion prevents the overflow of the tears [just as greasing the edge of a glass vessel prevents the water in it from overflowing]. The tears are conducted from the puncta through the duct, chiefly by a siphon action {Ad. JVebi-r). Horner's muscle (also known to Duvernoy, 1678) likewise aids, as every time the eyelids are closed it pulls upon the posterior wall of the sack, and thus dilates the latter, so that it aspirates tears into it {Henke). Fig. 509. Vertical section through the upper eyelid (after Waldeyct). .^.culib; i, epidermis ; 2, chorium ; 5 and 3, subcuta- neous connective tissue : C and 7, orbicularis muscle and its bundles ; Z), loose sub-muscular connective tissue; E, insertion of H. Miiller's muscle ; F, tarsus ; G, conjunctiva : J, inner edge of the lid ; K, outer edge ; 4, pig- ment cells in the cutis ; 5. sweat glands ; 6, hair follicles with hairs : 8 and 23, sections of nerves ; 9, arteries : 10, veins: 11, cilia: I2, modified sweat glands : 13, circular muscle of Riolan ; 14, opening of a Meibomian gland ; 15, section of an acinus of the same; 16, posterior tarsal glands : 18 and 19, tissue of the tarsus ; 20, pretarsa! or sub-muscular connective tissue ; 2t and 22, conjunctiva, with its epithelium ; 24, fat ; 25, loosely woven posterior end of the tarsus : 26, section of a palpebral artery. E. H. Weber and Hastier ascribe the aspiration of the tears to the diminution of the amount of air in the nasal cavities during inspiration. Arlt asserts that the tear sack is compressed by the con- traction of the orl)icularis muscle, so that the tears must l)e forced toward the nose. Lastly, Stell- Hag supposes that when the eyelids are closed, the tears are simply pressed into the puncta, while Gad denies that there is any kind of pumping mechanism in the nasal canal. I.andois points out that the tear ducts are surrounded by. a plexus of veins, which, according to their state of distention, may influence the size of these tubes. 812 COMPARATIVE HISTORICAL. The secretion of tears takes place only by direct stimulation of the lachrymal nerve (§347, I, 2), subcutaneous malar (§347, II, 2) and cervical sympathetic (§ 356, A, 6), which have been called secretory nerves. Secretion may also be excited reflexly (p. 623) by stimulation of the nasal mucous membrane only on the same side {Hcrzcnsiein). The ordinary secretion in the waking condition is really a reflex secretion produced by the stimulation of the anterior surface of the bulb by the air or by the evaporation of tears. In sleep all these factors are absent, and there is no secretion. Histological Changes. — Reichel found that in the active gland (after injection of pilocarpin), the secretory cells became granular, turbid and smaller, while the outlines of the cells became less distinct and the nuclei spheroidal. In the resting gland the cells are bright and slightly granular, with irregular nuclei. Intense stimulation by /ight acting on the optic nerve causes a reflex secretion of tears. The flow of tears accompanying certain violent emotions, and even hearty laughing, is still unexplained. During cough- ing and vomiting the secretion of tears is increased, partly reflexly and partly by the outflow being prevented by the expiratory pressure. Function. — The tears moisten the bulb, prevent it from drying, and float away small particles, being aided in this by the closure of the eyelids. Atropin diminishes the tears (Mogaanf). Composition. — The tears are alkaline, saline to taste, and represent a "serous " secretion. Water, 98.1 to 99; 1.46 organic substances (o. i albumin and mucin, 0.1 epithelium) ; 0.4 to 0.8 salts (especially NaCl). [Action of Drugs. — Essential volatile oils and eserin increase the secretion of tears, atropin arrests it, while eserin antagonizes the effect of atropin and causes an increa>.ed secretion.] 405. COMPARATIVE— HISTORICAL.— Comparative.— The simplest form of visual apparatus is represented by aggregations of pigment cells in the outer coverings of the body, which are in connection with the termination of afferent nerves. The pigment absorbs the rays of light, and in virtue of the light ether discharges kinetic energy, which excites the terminations of the nervous apparatus. Collections of pigment cells, with nerve fibres attached, and provided with a clear refractive body, occur on the margin of the bell of the higher medusi-e, while the lower forms have only aggregations of pigment on the bases of their tentacles. Also, in many lower worms there are pigment spots near the brain. In others the pigment lies as a covering round the termi- nations of the nerves, which occur as "crystalline rods" or "crystalline spheres." In parasitic worms the visual apparatus is absent. In star fishes the eyes are at the tips of the arms, and consist of a spherical crystal organ surrounded with pigment, with a nerve going to it. In all other eehinodermata there are only accumulations of pigment. Among the annulosa there are several grades of visual apparatus — (i) Without a cornea there may be only one crystal sphere (nervous end organ) near the brain, as m the young of the crab; or there may be several crystal spheres forming a compound eye, as in the lower crabs. (2) With a cornea, consisting of a len- ticular body formed from the chitin of the outer integument, the eye itself may be simple, merely consisting of one crystal rod, or it may be compound. The compound eye consists of only one large lenticular cornea, common to all the crystal rods, as in the spiders; or each crystal rod has a .special lenticular cornea for itself. The numerous rods surrounded by pigment are closely packed together, and are arranged upon a curved surface, so that their free ends also form a part of a sphere. The chitinous investment of the head is faceted, and forms a small corneal lens on the free end of each rod. According to one view, each facette, with the lens and the crystal sphere, is a special eye, and just as man has two eyes, so insects have several hundred. Each eye sees the picture of the outer world in toto. This view is supported by the following experiment of van Leeuwenhock : If the cornea be sliced off, each facette thereof gives a special image of an object. If a cross be made on the mirror of a microscope, while a piece of the faceted cornea is placed as an object upon the stage, then we see an image of the cross in each facette of the cornea. Thus, for each rod (crystal sphere) there would be a special image. Each corneal facette, however, forms only a part of the image of the outer world, so that we must regard the image as composed like a mosaic. .■Vmong mollusca the fixed branchipoda have two pigment spots near the brain, but only in their larval condition ; while the mussel has, under similar conditions, pigment spots with a refractive body. The adult mussel, however, has pigment spots (oceli) only in the margin of the mantel, but some molluscs have stalked and highly-developed eyes. Some of the lower snails have no eyes, some have pigment spots on the head, while the garden snail has stalked eyes provided with a cornea, an optic nerve with retina and pigment, and even a lens and vitreous body. Among cephalopoda the nautilus has no cornea or lens, so that the sea water flows freely into the orbits. Others have a lens and no cornea, while some have an opening in the cornea (Loligo, Sepia, Octopus). All the COMPARATIVE HISTORICAL. 813 other parts of the eye are well developed. Among vertebrata aitiphioxus has no eyes. They exist in a degenerated condition in Proteus and the mammal Spalax. In many fishes, amphibians and reptiles the eye is covered by a piece of transparent skin. Some hag-tishes, the crocodile, and birds have eyelids, and a nictitating membrane at the inner angle of the eye. Connected with it is the Harderian gland. In mammals the nictitating process is represented only by the plica semilunaris. Therj is no lachrymal apparatus in fishes. The tears of snakes remain under the watch-glass-like cutis with which the eye is covered. The sclerotic often contains cartilage which may ossify. A vascular organ, the processus falciformis, passes from the middle of the choroid into the interior of the vitreous body in osseous fishes, its anterior extremity being termed the cam- panula Halleri. Similarly, there is the pecten in birds, but it is provided with muscular fibres. In birds the cornea is surrounded by a bony ring. The whale has an enormously thick sclerotic. In aquatic animals the lens is nearly spherical. The muscles of the iris and choroid are trans- versely striped in birds and reptiles. The retinal rods in all vertebrates are directed from before backward, while the analogous elements (crystal rods and spheres) in invertebrata are directed from behind forward. Historical. — The Hippocratic School were acquainted with the optic nerve and lens. Aristotle (384 B.C.) mentions that section of the optic nerve causes blindness — he was acquainted with after images, short and long sight. Herophilus (307 B. c.) discovered the retina, and the ciliary pro- cesses received their name in his school. Galen (131-203 A. D.) described the six muscles of the eyeball, the puncta lachrymalia, and tear duct. Aeranger (1521) was aware of the fatty matter at the edge of the eyelids. Stephanus (1545) and Casseri (1609) described the Meibomian glands, which were afterward redescribed by Meibom (1666). Fallopius described the vitreous membrane and the ciliary ligament. Plater (1 583) mentions that the posterior surface of the lens is more curved. Aldrovandi observed the remainder of the pupillary membrane (1599). Observations were made at the time of Vesalius (1540) on the refractive action of the lens. Leonardo da Vinci compared the eye to a camera obscura. Maurolykos compared the action of the lens to that of a lens of glass, but it was Kepler ( 161 1 ) who first showed the true refractive index of the lens and the formation of the retinal image, but he thought that during accommodation the retina moved forward and back- ward. The Jesuit, Scheiner (f 1650), mentions, however, that the lens becomes more convex by the ciHary processes, and he assumed the existence of muscular fibres in the uvea. He referred long and short sight to the curvature of the lens, and he first showed the retinal image in an excised eye. With regard to the use of spectacles there is a reference in Pliny. It is said that at the beginning of the 14th century the Florentine, Salvino d'.\rmato degli Armati di Fir (f 1317), and the monk, Alessandro de Spina (f 1313), invented spectacles. Kepler (1611) and Descartes (1637) described their action. Mayo [f 1S52), described the third nerve as the constrictor nerve of the pupil. Zinn contributed considerably to our knowledge of the structure of the eye. Ruysch de- scribed muscular fibres in the iris, and Monro described the sphincter of the pupil (1794). Jacob described the bacillary layer of the retina — Scemmering (1791) the yellow spot. Brewster and Chossat (1819) tested the refractive indices of the optical media. Purkinje (1819) studied subjective vision. HEARING. 406. STRUCTURE OF THE ORGAN OF HEARING— Stimu- lation of the Auditory Nerve. — The normal manner in which the auditory nerve is excited by means of sonorous vibrations, which set in motion the end organs of the acoustic nerve, which lie in the endolymph of the labyrinth of the inner ear, on membranous expansions of the cochlea and semicircular canals. Hence the sonorous vibrations are first transmitted to the fluid in the labyrinth, and this, in turn, is thrown into waves, which set the end organs into vibration. Thus the excitement of the auditory nerves is brought about by the mechankal stimulation of the wave motion of the lymph of the /abyiiiith. The fluid or lymph of the labyrinth is surrounded by the exceedingly hard osse- FiG. 510. Scheme of the organ of hearing. A G, external auditory meatus ; T, tympanic membrane ; K, malleus with its head [k), short process {k/), and handle ('«); a, incus with its short process (.v) and long process — the latter is united to the stapes (5) by means ol the Sylvian ossicle (s) ; P, middle ear; o, fenestra ovalis ; r, fenestra rotunda; x, beginning of the lamina spiralis of the cochlea ; pi, its scala t>^mpani, and vt, its scala vestibuli : V, vestibule ; S, saccule ; XJ, utricle; H, semicircular canals, T E ; Eustachian tube. The long arrow indicates the line of " 1 of the tensor tympani ; the short curved one, that of the stapedius. ous mass of the temporal bone (Fig. 510). Only at one small roundish and slightly triangular point {>■), the fenestra rotunda, the fluid is bounded by a delicate yielding membrane, which is in contact with the air in the middle ear or tympanum (P). Not far from the fenestra rotunda is the fenestra ovalis (o), in which the base of the stapes (j) is fixed by means of a yielding membranous ring. The outer surface of this, also, is in contact with the air in the middle ear. As the perilymph of the inner ear is in contact at these two places with a yielding boundary, it is clear that the lymph itself may exhibit oscillatory movements, as it must follow the movements of the yielding boundaries. 814 PHYSICAL INTRODUCTION. 815 The sonorous vibrations may set the perilymph in vibration in three different ways : — 1. Conduction through" the Bones of the Head. — This occurs especially only when the vibrating solid body is applied directly to some part of the head, e.g., a tuning-fork placed on the head, the sound being propagated most intensely in the direction of the prolongation of the handle of the instrument — also when the sound is conducted to the head by means of fluid, as when the head is ducked under water. Vibrations of the air, however, are practically not transferred directly to the bones of the head, as is shown by the fact that we are deaf when the ears are stopped. The soft parts of the head which he immediately upon bone conduct sound best, and of the pro- jecting part the best conductor is the cartilaginous portion of the external ear. But even under the most favorable circumstance, conduction through the bones of the head is far less effective than the conduction of the sound waves through the external auditory meatus. If a tuning-fork be made to vibrate between the teeth until we no longer hear it, its tones m.iy still be heard on bringing it near the ear (Rinne). The conduction through the bones is favored when the oscillations are not trans- ferred from the bones to the tympanic membrane, and are thus transferred to the air in the outer ear. Hence, we hear the sound of the tuning-fork applied to the head better when the ears are stopped, as this prevents the propagation of the sound waves through the air in the outer ear. If, in a deaf person, the conduction is still normal through the cranial bones, then the cause of the deafness is not in the nervous part of the ear, but in the external sound-conducting part of the apparatus. 2. Normal hearing takes place through the external auditory meatus. The enormous vibrations of the air first set the tympanic membrane in vibration (Fig. 510, T) ; this moves the malleus (/i), whose long process is inserted into it ; the malleus moves the incus {a), and this the stapes (xj, which transfers the move- ments of its plate to the perilymph of the labyrinth. 3. Direct Conduction to the Fenestra. — In man, in consequence of occasional disease of the middle ear, whereby the tympanic membrane and auditory ossicles may be destroyed, the auditory apparatu-i may be excited, although only in a very feeble manner, by the vibrations of the air being directly transferred to the membrane of the fenestra rotunda (r), and the parts closing the fenestra ovalis (0). The membrane of the fenestra rotunda may vibrate alone, even when the oval window is rigidly closed ( Weber- Liel). 407. PHYSICAL INTRODUCTION.— Sound.— Sound is produced by the vibration of elastic bodies capable of vibration. Alternate condensation and rarefaction of the surrounding air are thus produced ; or, in other words, sound waves in which the particles vibrate longitudinally or in the direction of the propagation of the sound are excited. Around the point of origin of the sound these condensations and rarefactions occur in equal concentric circles, which conduct the sound vibrations to our outer ear. The vibrations of the sounding body are so called " stationary vibra- tions" (E. H. and IV. Weber), ie., all the particles of the vibrating body are always in the same phase of movement, in that they pass into movement simultaneously, they reach the maximum of movement simultaneously, e.g., in the particles of a sounding vibrating metal rod. Sound is pro- duced by the stationary vibrations of elastic bodies ; it is propagated by progressive wave motion of elastic media, generally the air. The wave length of a tone, i.e., the distance of one maximum of condensation to the next one in the air, is proportional to the duration of the vibration of the body, whose vibrations produce the sound waves. If / is the wave length of a tone, / in seconds the duration of a vibration of the body producing the wave, then /, = «/, where « =340.88 metres, which is ihe rate per second of propagation of sound waves in the air. The rapidity of the transmission of sound waves in water = 1435 metres per second, i.e., nearly four times as rapid as in air; while in solids capable of vibration it is propagated from seven to eighteen times faster than in the air. Sound waves are conducted best through the same medium ; when they have to pass through several media they are always weakened. Reflection of the sound waves occurs when they impinge upon a solid obstacle, in which case the angle of reHeclion is always equal to the angle of incidence. Wave Movements. — We distinguish — I. Progressive wave movements which occur in two forms — (i) As longilttJinal waves (ChlaUni), in which the individual particles of the vibrating body vibrate around their centre of gravity in the direction of the propagation of the wave ; examples are the waves in water and air. This movement causes an accumulation of the particles at certain places, e.g., on the crests of the waves in water waves, while at other places they are diminished. This kind of wave is called a wave of condensation and rarefaction. (2) If, however, each particle in the progressive wave moves vertically up and down, i.e., transversely to the direction of the pro- pagation of the wave, then we have the simple transverse waves (Chladni), or progressive waves, in 816 TYMPANIC MEMBRANE. Fig. 511 which there is no condensation or rarefaction in the direction of propagation, as each particle is merely displaced laterally. An example of this is the progressive -waves in a rope. II. Stationary Flexion Waves. — When all the particles of an elastic vibrating body so oscil- late that all of them are always in the same phase of movement as the limbs of a vibrating tuning, fork or a plucked string, then this kind of movement is described as stationary flexion waves. As bodies, whose expansion in the direction of oscillation is very slight, vibrate 10 and fro in the station- ary flexion wave, so we see that the small parts of the auditory apparatus (tympanic membrane, os- sicles, lymph of the labyrinth) oscillate in stationary flexion waves. 408. EAR MUSCLES— EXTERNAL AUDITORY MEATUS.— External Ear.— When the external ear is ab-ent, little or no impairment of the hearing is observed ; hence, the physiological functions of these organs are but slight. Boerhaave thought that the elevations and depressions of the outer ear might be connected with the reflection of the sound waves. Numerous sound waves, however, must be again reflected oulward; and those waves v^-hich reach the deep p4rt of the concha are said to be reflected toward the tragus, to be reflected by it into the external auditory meatus. According to Schneider, when the depressions in the ear are filled up with wax, hearing is impaired. Mach points out that the dimensions of the external ear are proportionally too small to act as reflecting organs for the wave lengths of noises. Muscles of the External Ear. — (I) The whole ear is moved by the retrahenter, attrahens, and attollens. (2) The/»;v« of the ear may be altered by the tragicus, antitragicus, helicis major and minor internally ; and by the transversus and obliquus auriculae externally. Persons who can move their ears do not find that the hearing is influenced during the movement. The Mm. helicis major and minor are regarded as ele- vators of the helix, the transversus and obliquus auric- ulse as dilators of the concha ; the tragicus and anti- tragicus as constrictors of the meatus. In animals the external ear and the action of its muscles have a marked efl^ect upon hearing. The muscles point the ear in the direction of the sound, while other muscles contract or dilate the space within the external ear. In many div- ing animals the meatus can be closed by a kind of valve. The external meatus is 3 to 3.25 cm. long [i^ to i^ inch], 8 to 9 mm. high, and 6 to 8 mm. broad at its outer opening (Fig. 511). It is the conductor of the sound waves to the tympanic membrane, so that almost all npanic the sound waves first impinge upon its wall, lurpart'of'theSu?! and are then reflected toward the tympanic membrane. To see well down into the meatus, we must pull the auricle upward and backward. Occlusion of the meatus, espe- cially by a plug of inspissated wax (§ 287), of course interferes with the hearing [and when it presses on the membrana tympani may give rise to severe vertigo]. 409. TYMPANIC MEMBRANE.— The tympanic membrane (Fig. 513), which is tolerably laxly fixed in a special osseous cleft, with a thickened margin, is an elastic, unyielding, and almost non-extensible membrane, of about 0.1 mm. in thickness, and with a superficial area of 50 square millimetres. It is elliptical in form, its greatest diameter being 9.5 to 10 mm., and its lesser 8 mm., and it is fixed in the floor of the external meatus obliquely, at an angle of 40°, being directed from above and outward, downward and inward. Both tympanic membranes converge anteriorly, so that if both were prolonged they would meet to form an angle of 130° to 135". The oblique position enables a larger surface to be presented than would be obtained if it were stretched vertically, so that more sound waves can fall vertically upon it. The membrane is not stretched flat, but a little under its centre (umbilicus) it is drawn slightly inward by the handle of the malleus, which is attached to it ; while the short process of the malleus slightly bulges out the membrane near its upper margin (Figs. 510 and 518). between both : ticular surface for the condyle of the lowei jaw (after Urbantschitsch). FUNCTIONS OF THE OUTER EAR. 817 Structure. — The tympanic membrane consists of three layers: (i) The membrana propria is a fibrous membrane with radial fibres on its outer surface, and circularly arranged fibres on its inner aspect. (2) The surface directed toward the meatus is covered with a thin and semi. trans- parent part of the cutis. (3) The side toward the tympanum is covered with a delicate mucous membrane, with simple squamous epithelium. Numerous nerves and lymph vessels as well as inner and outer blood vessels occur in the membrane. [The middle layer, or substantia propria, is fixed to a ring of bone, which is deficient above. It is filled up by a layer composed of the mucous and cutaneous layers called the membrana flaccida, or Shrapnell's membrane.] [Examination. — When examining the outer ear and membrana tympani pull the auricle upward and backward. The membrana tympani is examined by means of an ear speculum (Fig. 515). The speculum is placed in the ear, and light is reflected into it by means of a concave mirror, per- forated in the centre, and having a focal distance of four or five inches. It is convenient to have the mirror fixed to a band placed round the head, as in the case of the laryngoscopic reflector (Fig. 327). It is important to remember that the membrane is placed obliquely, so that the posterior and upper parts are nearer the surface. The membrane in health is grayish in color and transparent, Fig. 512. Fig. 513. Fig. 514. J. 5:2. — Tympanic membrane with the auditory ossicles (leftl seen from within. O", incus ; 0«, malleus; CA, chorda tympani ; T, pouch-like depression (after Urbantschitsch). Kig 51J. — Tympanic membrane and the auditory ossicles (lelt) seen from within, z. (?,, from the tympanic cavity. M, manubrium or handle of the mal- leus; T, insertion of the tensor tympani : A, head; /F, long process of the malleus : a, incus, with the short (K.) nd the long (/) process ; S, plate of the stapes ; \x, A.r, is the S, the pinion-wheel arrangement between the malleus and born child seen from without, with the handle of the malleus (») and posterior [h) ends. iible i s of rotation of the auditory ossicles ; 14. — Tympanic membrane of a new- A/, tympanic ring with its anterior so that the handle of the malleus is seen running from above downward and backward, while at the anterior and inferior part there is a cone of light, with its ape.x directed inward.] Function. — The tympanic membrane catches up the sound waves which pene- trate into the external meatus, and is set into vibration by them, the vibrations corresponding in number and amplitude to the vibrating movements of the air. Politzer connected the auditory ossicles fixed to the tympanic membrane of a duck with a recording apparatus, and could thus register the vibrations produced by sounding any particular tone. Owing to its small dimensions, the tympanic mem- brane can vibrate in toto to and fro in the direction of the sound waves corre- sponding to the condensations and rarefactions of the vibrating air, and therefore executes transverse vibrations, for which it is specially adapted, owing to the rela- tively slight resistance. Fundamental Note. — Stretched strings and membranes are generally only thrown into actual and considerable sympathetic vibration when they are affected 52 818 FUNCTIONS OF THE OUTER EAR. by tones which correspond with their own fundamental tone, or whose number of vibrations is some multiple of the number of vibrations of tlie same, as the octave. When other tones act on them, they exhibit only inconsiderable sympathetic vibration. If a membrane be stretched over a funnel or cylinder, and if a nodule of sealing wax attached to a silk thread be made just to touch the centre of the membrane, then the sealing wax remains nearly at rest when tones or sounds are made in the neighborhood ; as soon, however, as the fundamental or proper tone of this arrangement is sounded, the nodule is propelled by the strong vibrations of the membrane. If we apply this to the tympanic membrane, then it also should exhibit very great vibrations when its own fundamental note is sounded, but only slight vibra- tions when other tones are produced. This, however, would produce great ine- quality in the audible sounds. There is an arrangement of the membrane whereby this IS prevented, (i) Great resistance is offered to the vibrations of the tympanic membrane, owing to its union with the auditory ossicles. These act as a damping apparatus, which provides, as in damped membranes generally, that the tympanic membrane shall not exhibit excessive sympathetic vibrations for its own funda- mental note. But the damping also makes the sympathetic vibrations less for all Fig. 516. Fig. 517. ;. 515.— Ear specula of various sizes. Fig. 516.— Toynbee's artifici.il membrana tympani. FlG. 517.— The audi- tory ossicles (right). C.w, head; C, neck ; /Yr, short process : /"W, long process ; A/, handle of the malleus; O', body : G, articular surface ; //, short, and v, long process of the incus ; 0,S., so-called lenticular ossicle ; C,s., head ; a, anterior, and/, posterior limb ; P, plate of the stapes. the other tones. In this way, aH vibrations of the tympanic membrane are modi- fied ; especially, however, is the excessive vibration diminished during the sounding of its fundamental tone. The membrane is at the same time rendered more capable of responding to the vibrations of different wave lengths. The damping also prevents after vibrations. (2) Corresponding to the small mass of the tympanic membrane, its sympathetic vibrations must also be small. Nevertheless, these slight elongations are quite sufficient to convey the sonorous movements to the most delicate end organs of the auditory nerve ; in fact, there are arrangements in the tympanum which still further diminish the vibrations of the tympanic membrane. As V. Helmholtz has shown, the strong sympathetic vibrations of the tympanic membrane are not completely set aside by this damping arrangement. The painful sensations produced by some tones are, perhaps, due to the sj-mpathetic vibration of the membrana tympani. According to Kessel, certain parts of the membrane vibrate to certain tones. Pathological.— Thickenings or inequalities of the tympanic membrane interfere with the acute- ness of hearing, owing to the diminished capacity for vibration thereby produced. Holes in and loss of its substance act similarly. In extensive destruction, an artificial tympanum is placed in the external meatus, and its vibrations, to a certain extent, replace those of the lost membrane {^Toyn- hte). [Fig. 516 shows an -.rtificial tympanic membrane.] MECHANISM OF THE AUDITORY OSSICLES. 819 410. THE AUDITORY OSSICLES AND THEIR MUSCLES. — Function. — The auditory ossicles have a double function — [^i) By means of the " chain " which they form, they transfer the vibrations of the tympanic mem- brane to the perilymph of the labyrinth. (2) They also afford points of attach- ment for the muscles of the middle ear, which can alter the tension of the mem- brana tympani and \.\\'i pressure on the lymph of the labyrinth. Mechanism. — T\\^ form and position of the ossicles are given in Figures 517 and 518. They form a jointed chain which connects the tympanic membrane, M, by means of the malleus, h, incus, a, and stapes, S, with the perilymph of the labyrinth. The mode of movement of the ossicles is of special importance. The handle of the malleus (Fig. 518, //) is firmly united to the fibres of the tym- panic membrane. Besides this, the malleus is fixed by ligaments which prescribe the direction of its movements. Two ligaments — the lig. mallei anticum (passing from the processus Folianus), and the posticum (from a small crest on the neck) — Fig. 518. Tympanum and auditory ossicles (left) magnified. A.G, e.\ternal meatus : M.membrana tympani, which is attached to the handle of the malleus, «, and near it the short process,/ ; It, head of the malleus ; a, incus ; k, its short process with its ligament : /, long process ; s. Sylvian ossicle ; S, stapes ; A_r, Ajr, is tlie axis of rotation of the ossicles, it is shown in perspective, and must be imagined to penetrate the plane of the paper ; /, line of traction of the tensor tympani. The other arrows indicate the movement of the ossicles when the tensor contracts. together form a common axial band {v. Helmholtz), which acts in the direction from behind forward, i.e., parallel to the surface of the tympanic membrane. The neck of the malleus lies between the insertions of both ligaments. The united ligament determines the " axis of rotation " of the movement of the malleus. When the handle of the malleus is drawn inward, of course its head moves in the opposite direction, or outward. The i?iius, a, is only partially fi.xed by a ligament, which attaches its short process to the wall of the tympanic cavity, in front of the entrance to the mastoid cells, k. The not very tense articulation joining it to the head of the malleus, //, which lies with its saddle-shaped articular surface in the hollow of the incus, is important. The lower margin of the incus (Fig. 517, S) acts like a tooth of a cog-wheel. Thus, when the handle of the malleus moves inward to the tympanic cavity, the incus, and its long process, b. which is parallel to the handle of the malleus, also pass inward. The incus forms almost a right angle with the stapes, S, through the intervention of the Sylvian 820 MODE OF VIBRATION OF THE OSSICLES. ossicle, s. If, however, as by condensation of the air in the tympanum, the membrana tympani and the handle of the malleus move outward, the long pro- cess of the incus does not make a similar movement, as the malleus moves away from this margin of the incus. Hence the stapes is not liable to be torn from its socket. The malleus and incus form an angular lever, which moves round a common axis (Fig. 513 and Fig. 518, h.x, Ajc). In the inwani movement the malleus follows the incus, as if both formed one piece. The common axis (Fig. 513) is not, however, the axial ligament of the malleus, but it is formed anteriorly by the processus Folianus, IF, directed forward, and posteriorly by the short pro- cess of the incus directed backward. The rotation of both ossicles around this axis occurs in a plane vertical to the plane of the membrana tympani. During the rotation, of course the parts above this axis (head of the malleus and upper part of the body of the incus) take a direction opposite to the parts lying below it (the handle of the malleus and the long process of the incus), as is indicated in Fig. 518 by the direction of the arrows. The movement of the handle of the malleus must follow that of the membrana tympani, and vice versa, while the movement of the stapes is connected with the movement of the long process of the incus. As the long process of the incus is only two-thirds of the length of the handle of the malleus (Figs. 510, 513, 518), of course the excursion of the tip of the former, and with it of the stapes, must be correspondingly less than the movement of the tip of the handle of the malleus ; while, on the other hand, the force of the movement of the tip of the handle of the malleus, corresponding to the diminution of the excursion, will be increased. Mode of Vibration. — Thus, the movement of the membrana tympani inward causes a less extensive but a more poiverful movement of the foot of the stapes against the perilymph of the labyrinth. V. Helmholtz and Politzer calculated the extent of the movement to be 0.07 mm. The mode in which the vibrations of the membrana tympani are conveyed to the Ijmph of the labyrinth, through the chain of ossicles, is quite analogous to the mechanism of these parts already described. Long delicate glass threads have been fixed to these ossicles, and their movements were thus graphically recorded on a smoked surface {Folitzer, Nen- sen). Or strongly refractive particles are fixed to the ossicles, while the beam of light reflected from them can be examined by means of a microscoi)e {Buck, v. Helmholtz, Mach and Kessel). All the experiments showed that ilie transference of the sound waves is accomplished by means of the mechanism of the angular lever, composed of the auditory ossicles already described. As the vibrations of the membrana tympani are conveyed to the handle of the malleus, they are weakened to about one-fourth of their original strength {Politzer, Buck). [The membrana tympani is many times (30) larger than the fenestra ovalis, and the relation in size might be represented by a funnel. The arm of the malleal end of the lever where the power acts is 9^ mm. long, while the short or stapedial arm is 6i4 mm., so that the latter moves less than the former, but what is lost in extent is gained in force.] [Methods. — Politzer attached small, very liglit levers to each of the ossicles, and inscribed their movements on a revolving cylinder. An organ pipe was sounded, and when the levers were of the same length, the malleus made the greatest excursion and the stapes the least. Buck attached starch grains to the ossicles, illuminated them, and observed the movements of the refractive starch granules by means of a microscope provided with a micrometer.] [The ossicles move en masse, and not in the way of propagating molecular vibrations.] As the excursions of the ossicles during sonorous vibrations are, how- ever, only nominal, there is practically no change in the position of the joints with each vibration. The latter will only occur when extensive movements take place by means of the muscles. The muscles of the auditory ossicles alter the position and tension of the membrana tympani, as well as the pressure of the lymjih of the labyrinth. The CONTRACTION OF THE TENSOR. 821 tensor tympani, which lies in an osseous groove Fig. 519. above the Eustachian tube, has its tendon deflected round an osseous projection [processus cochleari- formis], which lies external to it, almost at right angles to the groove above it, and is inserted im- mediately above the axes of the malleus (Fig. 519, M). When the muscle contracts in the direction of the arrow, / (Fig. 518), then the handle of the malleus (//) pulls the membrana tympani (M) in- ward and tightens it. This also causes a move- ment of the incus and stapes (S) which must be pressed more deeply into the fenestra ovalis, as al- ready described. When the muscle relaxes, then, owing to the c/aJ-Z/ir//)' of the rotated axial ligament Tensor tympani— the Eustachian tube (left). and the tense membrana tympani itself, the posi- tion of equilibrium is again restored. The motor nerve of this muscle arises from the trigeminus, and passes through the otic ganglion (p. 628). C. Ludwig and Politzer observed that stimulation of the fifth nerve within the cranium [dog] caused the above-mentioned movement. Use of the Tension. — The tension of the membrana tympani caused by the tensor tympani has a double function {/oh. Miiller). — i. The tense membrane offers very great resistance to sympathetic vibrations when the sound waves are very intense, as it is a physical fact {Savart) that stretched membranes are more difficult to throw into sym[)athetic vibration the tenser they are. Thus, the tension so far protects the auditory organ, as it prevents too intense vibrations applied to the membrana tympani from reaching the terminations of the nerves. 2. The tension of the membrana tympani must vary according to the degree of contraction of the tensor. Hereby the membrana for the time being has a different fundamental tone, and is thus capable of vibrating to the correspondingly higher tone, it, as it were, being in a certain sense accommodated. Comparison with Iris. — The membrana tympani has been compared with the iris. Both mem- branes prevent by contraction — narrowing of the pujiil and tension of the membrana tympani — the too intense action of the specific stimulus from causing too great stimulation, and both adapt the sensory app.iratus for the action of moderate or we.ik stimuH. This movement in both membranes is brought aliout reflexly in the ear through the N. acusticus, which causes a reflex stimulation of the motor fibres for the tensor tympani. Effect of Tension. — That increased tension of the membrana tympani renders it less sensitive to sound waves is easily proved, thus: Close the mouth and nose, and make either a forced expiration, so that the air is forced into the Eustachian tube, which bulges out the membrana tympani, or inspire forcibly, whereby the air in the tympanum is diminished, so that the membrai.a bulges inward. In both cases hearing is interfered with as long as the increased tension lasts. If a funnel with a small lateral opening, and whose wide end is covered by a membrane, be placed in the external meatus, hearing becomes less distinct when the membrane is stretched (Joh. Miiller). Normally, the tensor tympani is excited reflexly. The muscle is not directly and by itself subject to the control of the will. According to L. Fick, the following phenomenon is due to an "associ- ated movement " of the tensor : When he pressed his jaws firmly against each other he heard in his ear a piping, singing tone, while a capillary tube, which was fixed air tight into the meatus, had a drop of water which was in it rapidly drawn inward. During this experiment, a person with normal hearing hears all musical tones as if they were louder, while all the highest non-musical tones are enfeebled (Z«c«f). When ji;a//n«n, v. Helmholtz and Politzer found that hearing was enfeebled for certain tones. Contraction of the Tensor. — Hensen showed that the contraction of the tensor tympani during hearing is not a continued contraction, but what might be termed a " twitch." A twitch takes place at the beginning of the act of hearing, which favors the perception of the sound, as the membrana tympani thus set m motion vibrates more readily to higher tones than when it is at rest. On expos- ing the tympanum in cats and dogs, it was found that this contraction or twitch 822 THE EUSTACHIAN TUBE. occurs only at the beginning of the sound, and that it soon ceases, although the sound may continue. Action of the Stapedius. — This muscle arises within the Fig. 520. eminentia pyramidalis, and is inserted into the head of the stapes and Sylvian ossicle (Fig. 520) ; when it draws upon the head of the stapes, as indicated in Fig. 510, by the small curved arrow, it must place the bone obliquely, whereby the posterior end of the plate of the stapes is pressed somewhat deeper in- ward into the fenestra ovalis, while the anterior is, as it were, displaced somewhat cmizvard. The stapes is thereby more fi.xed, as the fibrous mass [annular ligament] which surrounds the fe- nestra ovalis and keeps the stapes in its place becomes more tense. Right stapedius muscle. The activity of this muscle, therefore, prevents too intense shocks, which may be communicated from the incus to the stapes, from being conveyed to the perilymph (§ 808, 5). It is supplied by the facial nerve (§ 349, 3). The stapedius in many persons executes an associated movement when the eyelids are forcibly closed (^ 349). Some persons can cause it to contract refle.xly by scratching the skin in front of the meatus, or by gently stroking the outer margin of the orbit ( Hen/e). Other Views. — According to Lucae, when the stapes is displaced obliquely, its head forces the long process of the incus, and also the membrana tynipani, oulward, so tliat it is regarded as an antagonisl of the tensor tympani. Politzer observed that the pressure within the labyrinth fell when he stimulated the muscle. According to Toynbee, the stapedius acts as a lever and moves the stapes slightly out of the fenestra ovalis, thus making it more free to move, so that it is more capable of vibrating. Henle supposes that the stapedius is more concerned in /f.r/«^'than in moving the stapes, and that it comes into action when there is danger of too great movement being commu- nicated to the stapes from the incus. Landois agrees with this opinion, and compares the stapedius with the orbicularis palpel>rarum, both being protective muscles. Pathological. — Immobility of the auditory ossicles, either by adhesions or anchyloses, causing diminished vibrations, interferes with hearing; while the same result occurs when the stapes is firmly anchylosed into the fenestra ovalis. The tendon of the tensor tympani has been divided in cases of contracture of the muscles. For paralysis of the tensor, see p. 629, and for the stapedius, p. .634- 411. EUSTACHIANTUBE— TYMPANUM.— The Eustachian tube [4 centimetres in length, iS/g in.] is the ventilating tube of the tympanic cavity. It keeps the tension of the air within the tympanum the same as that within the pharynx and outer air (Figs. 510, 519). Only when the tension of the air is the same outside and inside the tympanum is the normal vibration of the membrana tympani possible. The tube is generally closed, as the surfaces of the mucous membrane lining it come into apposition. During swallowing, however, the tube is opened, owing to the traction of the fibres of the tensor veli palatini [spheno-salpingo-staphylinus sive abductor tubae {v. Trd/tsik'', sive dilator tubae {Riidi>iger)] inserted into the membrano-cartilaginous part of the tube (^Toynbee, Politzer, Moos). (Compare § 139, 2.) When the tube is closed the vibrations of the membrana tympani are transferred in a more undiminished condition to the auditory ossicles than when it is open, whereby part of the vibrating air is forced through the tube (^Mach and Kessel). If, however, the tympanic cavity is closed perma7icntly, the air within it becomes so rarefied (§ 139) that the mem- brana tympani, owing to the abnormally low tension, becomes drawn inward, thus causing difficulty of hearing. As the tube is lined by ciliated epithelium (p. 491), it carries outward to the pharynx the secretions of the tympanum. Noise in the Tube. — A sharp hissing noise is heard in the tube during swallowing, when we swallow slowly and at the same time contract the tensor tympani, due to the separation of the adhesive surfaces of its lining membrane. Another person may hear this noise by using a stetho- scope or his ear. In Valsalva's experiment (\ 60), as soon as the pressure of the air reaches 10 to 40 mm. Hg air enters the tube. T he sound is heard first, and then we feel the increased tension of the tympanic membrane, owing to the entrance of air into the tympanum. During forced inspiration, when the nose and mouth are closed, air is sucked out, while the tympanum is ultimately drawn inward. RELATIONS OF THE T\-MPANUM. 823 The M. levator veli palatini, as it passes under the base of the opening of the tube into the pharynx, forms the levator eminence or cushion (Fig. 332, W). Hence, when this muscle contracts and its belly thickens, as at the commencement of the act of deglutilion and during phonation, the lower wall of the pharyngeal opening is raised, and the opening thereby narrowed { Lucae). The contrnction of the tensor, occurring during the latter part of the act of deglutition, dilates the tube. Other Views. — According to Rudinger, the tube is always open, although only by a very narrow passage in the upper part of the canal, while the canal is dilated during swallowing. According to Cleland, the tube is generally open, and is closed during swallowing. [Practical Importance. — The tympanic cavity forms an osseous box, and, therefore, a protective organ for the auditory ossicles and their muscles, while the increased air space, obtained by its communication with the mastoid cells, permits free vibration of the membrana tympani. The six sides of the tympanum have important practical relations. It is about half an inch in height, and one or two lines in breadth, /. e., from without inward. Its roof is separated from the cavity of the brain by a very thin piece of bone, which is sometimes defective, so that encephalitis may follow an abscess of the middle ear. The outer wall is formed by the membrana tympani, while on the inner ^sW. are the fenestra ovalis and rotunda, the ridge of the aqueductus Fallopii, the promontory and the pyramid. Fig. 521. Fig. 522. The floor consists of a thin plate of bone, which roofs in the jugular fossa and separates it from the jugular vein. Fractures of the base of the skull may rupture the carotid artery or internal jugular vein ; hence hemorrhage from the ears is a bad symptom in these cases. Caries of the ear may extend to other organs. The anterior wall is in close relation with the carotid artery, while the posterior com- municates with the mastoid cells, so that fluids from the middle ear sometimes escape through the mastoid cells.] That the air in the tympanum can communicate its vibrations to the membrane of the fenestra rotunda is true (p. 814), but normally \\\\s is so slight, when compared with the conduction through the auditory ossicles, that it scarcely need be taken into account. Structure. — The tube and tympanum are lined by a common mucous membrane, covered by ciliated epithelium, while the membrana is lined by a layer of squamous epithelium. Mucous glands were found by Troltsch and Wendt in the mucous membrane. [The epithelium covering the ossicles and tensor tympani is not ciliated.] Pathological. — The tube is often occluded, owing to chronic catarrh and narrowing from cica- trices, hypertrophy of the mucous membrane, or the presence of tumors. The deafness thereby produced may often be cured by catheterizing the tube from the nose (Fig. 521 ). Effusions into or suppuration within the tympanum, of course, paralyze the sound-conducting mechanism, while in- flammation often causes subseciuent affections of the plexus tympanicus. If the temporal bone be 824 METHOD OF TESTING SOUND CONDUCTION. destroyed by progressive caries within the tympanum, inflammation of the neighboring cerebral structures may occur and cause death. [Methods. — Not unfrequently the aurist is called upon to dilate the Eustachian tube, which, in certain cases, requires the use of a Eustachian catheter introduced into the tube along the floor of the nose (Fig. 521). At other times he requires to fill the tympanic cavity with air, which is easily done by means of a Politzer's bag (Fig. 522). The nozzle is introduced into one nostril, while the other nostril is closed, and the patient is directed to swallow, while at the same moment liie surgeon compresses the bag, and the patient's mouth being closed, air is forced through tlie open Eustachian tube into the middle ear. Sometimes a small, curved, narrow manometer, containing a drop of colored water, is placed in the outer ear [Poli/zer). Normally, when the patient swallows, the fluid ought to move in the tube.] 412. CONDUCTION OF SOUND IN THE LABYRINTH.— The vibrations of the foot of the stapes in the fenestra ovalis give rise to waves in the perilymph within the inner ear or labyrinth. These waves are so-called "flexion waves,'^ i. e., the perilymph moves in mass before the impulse of the base of the stapes. This is only possible from the existence of a yielding membrane — that filling the fenestra rotunda, and sometimes called the membrana secundaria, which during rest bulges inward to the scala tympani, and can be bulged outward toward the tym- panic cavity by the impulse communicated to it by the move- ment of the perilymph (Fig. 510, r). The flexion waves the"'raby*rmtir,"f"n1str°a niust Correspond in number and intensity to the vibrations of ovalis, cochlea to the {he auditory ossicles, and must also excite the free termina- lett, and ( f) the upper, . r ^ ^■ i-in r • ^ ^ ^ 1 (h) horizontal, and (s) tious 01 the auditory nerve, which float tree in the endolymph. canluicft) ^''""^"■'^"'^'' As the endolymph of the saccule and utricle lying in the vestibule receive the first impulse, and as they communicate anteriorly with the cochlea, and posteriorly with the semicircular canals, conse- quently the motion of the perilymph must be propagated through these canals. To reach the cochlea the movement passes from x\\^ saccule (lying in the fovea hemispherica) along the scala vestibuli to the helicotrema, where it passes into the scala tympani, where it reaches the membrane of the fenestra rotunda, and causes it to bulge outward. From the utricle (lying in the fovea hemielliptica), in a similar manner, the movement is propagated through the semicircular canals. Politzer observed that the endolymph in the superior semicircular canal rose when he caused contraction of the tensor tympani by stimulating the trigeminus, just as the base of the stapes must be forced against the perilymph with every vibration of the membrani tympani. [Practical. — It is well to view the organ of hearing as consisting of two mech- anisms : — 1. The sound-conducting apparatus. 2. The sound-perceiving apparatus. The former includes the outer ear, with its auricle and external meatus ; the middle ear and the parts which bound it, or open into it. The latter consists of the in7ter ear with the expansion of the auditory nerve in the labyrinth, the nerve itself, and the sound-perceiving and interpreting centre or centres in the brain (P- 723)-] [Testing the Sound Conduction. — In any case of deafness it is essential to estimate the degree of deafness by the methods stated at p. 815, and it is well to do so both for such sounds as those of a watch and conversation. We have next to determine whether the sound-conducting or the sound-perceiving apparatus is affected. If a person is deaf to sounds transmitted through the air, on applying a sounding tuning-fork to the middle line of the head or teeth, and if it be heard distinctly, then the sound-perceiving apparatus is intact, and we have to look for the cause of deafness in the outer or middle ear. In a healthy person, the sound of the tuning-fork is heard of ecjual intensity in both ears. In this case the sound is conducted directly to the labyrinth by the cranial bones. In cases of disease STRUCTURE OF THE LABYRINTH. 82o of the sound-conducting mechanism, the sound of the tuning-fork is heard loudest in the deafer ear. Ed. Weber pointed out that, if one ear be stopped and a vibrating tuning-fork placed on the head, the sound is referred to the plugged ear, where it is heard loudest. It is assumed that when the ear is plugged, the sound waves transmitted by the cranial bones are prevented from escaping (Mach). If, on the contrary, the sound be heard loudest in the good ear, then in all proba- bility there is some affection of the sound-perceiving apparatus or labyrinth, although there are exceptions to this statement, especially in elderly people. Another plan is to connect two telephones with an induction machine, provided with a vibrating Neef 's hammer. The sounds of the vibrations of the latter are reproduced in the telephones, and if they be placed to the ears, then the healthy ears hear only one sound, which is referred to the middle line, and usually to the back of the head. In diseased conditions this is altered — it is referred to one side or the other.] 413. STRUCTURE pF THE LABYRINTH, AND TERMINATION OF THE AUDITORY NERVE.— Scheme.— The vestibule (Fig. 524, III) contains two separate sacks, one of them the saccule, j (round sack or S. hemispha;ricus), communicates with the ductus Fig. 524. ..^ ^^^ 1 of a tum of the cochlea; II, A, ampulla of a semicircular canal with the crista acustica ; a, p. aiiaitory cells ; f, provided with a fine hair; T, otoliths ; III, scheme of the human labyrinth ; IV, scheme of a bird's labyrinth ; V, scheme of a fish's labyrinth. cochlearis, C c, of the cochlea, the other the utricle, U (elliptical sack, or sacculus hemiellipticus), communicates with the semicircular canals, C s,Q. s. The cochlea consists of 2|^ turns of a tube dispo^e<3 round a central column or modiolus. The tube is divided into two compartments (Fig. 527, Fig. 524, I ) by a horizontal septum, partly osse- ous and partly membranous, the lamina spiralis ossea and membranacea. The lowei compart- ment is the scala tympani, and is separated from the cavity of the tympanum by the membrane of the fenestra rotunda. The upper compartment is the scala vestibuli, which communicates with the vestibule of the labyrinth (Fig. 524, I). These two compartments communicate directly by a small opening at the apex of the cochlea, a sickle-shaped edge [" hamulus "] of the lamina spiralis bounding the heli- cotrema (Fig. 510). The scala vestibuli is divided by Reissner's membrane (Fig. 524, 1), which arises near the outer part of the lamina spiralis ossea, and runs obliquely outward to the wall of the cochlea so as to cut off a small triangular canal, the ductus or canalis cochlearis, or scala media, C c, whose floor is formed for the most part by the lamina spiralis membranacea, and on which the end organ of the auditory nerve — Corti's organ— is placed. The lower end of the can- alls cochlearis Is blind, III, and divided toward the saccule, with which it communicates by means of the small canalis reuniens, C r (/fensen). The utricle (Fig. 524, III, U) communicates with the three semicircular canals, C s, C s — each by means of an ampulla, within which lies the termi- nations of the ampullary nerves, but as the posterior and the superior canals unite there is only one 826 MACUL.^ ACUSTIC^ AND COCHLEA. common ampulla for them. The membranous semicircular canals lie within the osseous canals, perilymph lying between the two. Perilyinph also fills the scala vestibuli and tympani, so that all the spaces within the labyrinth are filled by fluid, while the spaces themselves are lined by short cylindrical epithelium. The system of spaces, filled by endolymph, is the only part containing the nervous end organs for hearing. .All these spaces communicate with each other ; the semicircular canals directly with the utricle, the ductus cochlearis with the saccule through the canalis reuniens; and, lastly, the sac- cule and utricle through the " saccus endolymphaticus," which springs by an isolated limb from each sack ; the limbs then unite, as in the letter Y. and pass through the osseous aqueductus vestibuli to end blindly in the dura mater of the brain (t'ig. Ill, R — Bollcher, Retzhis). The aqueductus cochleae is another narrow passage, which begins in the scala tympani, immediately in front of the fenestra rotunda, and opens close to the fossa jugularis. It forms a direct means of communication between the perilymph of the cochlea and the subarachnoid space. Semicircular Canals and Vestibular Sacks — The membranous semicircular canals do not fill the corresponding osseous canals completely, but are separated from them bv a pretty wide space, which is filled with perilymph (Fig. 525). At the concave margin they are fixed by connective tis. sue to the osseous walls. The ampulla', however, completely fill the corresponding osseous dilata- tions. The canals and ampullae consist externally of an outer, vascular, connective-tissue layer, on which there rests a well-marked hyaline layer, bearing a single layer of flattened epithelium. Crista Acustica. — The vestibular branch of the auditory nerve sends a branch to each ampulla and to the saccule and utricle (Fig. 526). In the ampullae (Fig. 524, II, A), the nerve (<) termi- FlG. 525. Fig. 526. interior of the right labyrinth with its membranous canals and nerves. In Fig. 525. A, the outer wall of the bony labyrinth is removed to show the membranous parts within — i, commencement of the spiral tubeof the cochlea ; 2, posterior semicircular canal, partly opened ; 3, horizontal : 4, superior canal : 5, utricle ; 6, saccule ; 7, lamina spiralis; /.scala tympani; 8, ampulla of the superior membranous canal; 9. of the horizontal; 10, of the posterior canal. FlG 526 shows the membranous labyrinthand nerves detached — i, facial nerve in the internal auditory meatus ; 2, anterior division of the auditory nerve giving branches to 5, 8, and g, the utricle and the ampullse of the superior and horizontal canals ; ^, posterior division of the auditory nerve, giving branches to the saccule, 6, and posterior ampulla, 10, and cochlea, 4 ; 7, united part of the posterior and superior canals; II, posterior extremity of the horizontal canal. nates in connection with the crista acustica. which is a yellow elevation projecting into the equa- tor of the ampulla. The medullated nerve fibres, «, form a plexus in the connective-tissue layer, lose their myelin as they pass to the hyaline basement membrane, and each ends in a cell provided with a rigid hair (o,p) 90 u in length, so that the crista is largely covered with these hair cells (Hatimann), but between them are supporting cells like cylindrical epithelium (i?!, and not unfre- quently containing granules of yellow pigment. The hairs or "auditory hairs " (.)/. Schulfze) are com[X>sed of many fine fibres (Ki-tzius). An excessively fine membrane (membrana tectoria) covers the hairs (PritcharJ, Latisr). Maculae Acusticae. — The nerve terminations in the maculje acustic;E of the saccule .and utricle are exactly the same as in the ampullar, only the free surface of their membrana tectoria is sprinkled with small, white, chalk-hke crystals or otoliths (II, T), composed of calcic carbonate, which are sometimes amorphous and partly in the form of arragonite, lying fixed in the viscid endo- lymph. The non-medullated axis cylinders of the saccular nerves enter directly into the substance of the hair cells. The terminations of the nerves have been investigated, chiefly in fishes, in the rays. Cochlea. — The terminations of the cochlear branch of the auditory nerve lie in connection with Corti's organ, which is placed in the canalis or ductus cochlearis (Fig. 524, I, C c, and III, C c, and Fig. 527), the small triangular chamber or [scala media], cut off from the scala vestibuli by the membrane of Reissner. Corti's organ is placed on the lamina spiralis membranacea. and con- sists of a sufipprlini:^ apparatus composed of the so-called Corti's arches, each of which consi.sts of two Corti's rods (:,}'), which lie upon each other like the beams of a house. But every two INTRA-LABYRINTHINE PRESSURE. 827 rods do not form an arch, as there are always three inner to two outer rods [Clauiiius). There are about 4500 uuter rods ( IVii/i/^yer}. The ductus cochlearis becomes larger toward the apex of the cochlea, and the rods also become longer; the inner ones are 30 // long in the first turn, and 34 /i in the upper, the outer rods 47 11 and 69 « respectively. The span of the arches a'so increases [Heii^en), [The arches leave a Iri.ingular tunnel beneath them.] The proper end organs of the cochlear nerve are the cylindrical " hair cells " {Kolliker] previously observed by Corti. which are from 16,400 to 20,000 in number (Nt-nsfit. IVa/tleyer). There is one row of inner cells (/) which rests on a layer of small granular cells (K) [Bottcher, Waiiieyer); the outer cells (a, a) number 12,000 in man (Ketzius\, and rest upon the basement membrane, being disposed in three or even four rows. Between the outer hair cells there are other cellular structures, which are either regarded as special cells (Deiter's cells), or are regarded merely as processes of the hair cells i^Lavdou'sky), [The cochlear branch of the auditory nerve enters the modiolus, and runs upward in the osseous channels there provided for it, and as it does so gives branches to the lamina spiralis, where they run between the osseous plates which form the lamina.] The fibres (N) come out of the lamina spiralis after traversing the gan- glionic cells in their course (Figs. 524, 527, I, G), and end by fine varicose fibrils in the hair cells (Fig. 527) ( Waldeyer, Got/stein, Lavdowsky, Ketzius). Fig. 527. lerae of the ductus cochlearis and the organ of Corti. N, cochlear nerve: K, inner, and P, outer hair cells; «, nerve fibrils terminating in P ; a, a, supporting cells : d, cells in the sulcus spiralis : z, inner rod of Corti ; ^I b. Corti, membrane of Corti, or the membrana tectoria ; o, the membrana reticularis; H, G. cells filling up the space near the outer wall. Membrana Reticularis. — Corti's rods and the hair cells are covered by a special membrane (<>), the membrana reticularis of Kolliker. The upper ends of the hair cells, however, project through holes in this membrane, which consists of a kind of a cement substance holding these parts together [Lavdoiusky'\. [Springing from the outer end of the lamina spiralis, or crista spiralis, is the membrana tinctoria, sometimes called the membrane of Corti. It is a well-defined struc- ture, often fibrillated in appearance, and extends outward over the organ of Corti.] Waldeyer regards it as a damping apparatus for this organ (Fig. 527, Mb. Corti). [Basilar Membrane. — Its breadth increases from the base to the apex of the cochlea. This fact is important in connection with the theory of the perception of tone. It is supposed that high notes are appreciated by structures in connection with the former, and low notes by the upper parts of the basilar membrane. In one case, recorded by Moss and Steinbrugge, a patient heard low notes only in the right ear, and after death it was found that the auditory nerve in the first turn of tile cochlea was atrophied.] Intra- Labyrinthine Pressure. — The lymph within the labyrinth is under a certain pressure. Every diminution of the pressure of the air in the tym])anum is accompanied by a corresponding diminution of the intra-labyrinthine pressure, while conversely every increase of pressure is accom- panied by an increase of the lymph pressure (/'. Bezotd). 828 THE QUALITY OF A TONE. The perilymph of the inner ear flows away chiefly through the aqueductus cochleffi, in the circumference of the foramen jugulare, into the peripheral lym- phatic system, which also takes up the cerebro-spinal fluid of the subarachnoid space, while a small part drains away to the subdural space through the internal auditory meatus. The endolymph flows through the arachnoid sheath of the N. acusticus into the subarachnoid space (C Hasse). 414. QUALITY OF AUDITORY PERCEPTIONS-PERCEP- TION OF THE PITCH AND STRENGTH OF TONES.— Tones and Noises. — Every normal ear is able to distinguish musical tones and lunscs. Physical experiments prove that tones are produced when a vibrating elastic body executes periodic movements, i.e., when the sounding body executes the same movement in equal intervals of time, as the vibrations of a string which has been plucked. A noise is produced by non-periodic movements, i.e., when the sounding body executes unequal movements in equal intervals of time. [The non-periodic movements clash together on the ear, and produce dissonance, as when we strike the keyboard of a piano at random.] This is readily proved by means of the siren. Suppose that there are forty holes in the rotatory disk of this instrument, placed at exactly the same distance from each other — on rotating the disk and directing a current of air against it, obviously with every rotation the air will be rarefied and condensed exactly forty times. Every two condensations and rarefactions are separated from each other by an equal \x\\.tx\2\ of time. This arrangement yields a characteristic musical tone or note. If a similar disk with holes perforated in it at unequal distances be used, on air being forced against it, a whirring, non-musical nnise is produced, because the movements of the sounding body (the condensations and rarefactions of the air) are non-periodic . [The double siren of v. Helmholtz is an improved instrument for showing the same facts.] The normal ear also distinguishes in every tone three distinct factors : — [(i) Intensity or force ; (2) Pitch ; (3) Quality, timbre or " klang."'\ 1. The intensity of a tone depends upon the greater or lesser amplitude of the vibrations of the sounding body. Every one knows that a vibrating string emits a feebler sound when its excursions are smaller. (The intensity of a sound corresponds to the degree of illumination or brightness in the case of the eye.) 2. The pitch depends upon the number of vibrations which occur in a given time {Mersenne, i6j6) [or the length of time occupied by a single vibration]. This is proved by means of the siren. If the rotating disk have a series of forty holes at equal intervals, and another series of eighty equidistant from each other, on blowing a stream of air against the rotating disk we hear two sounds of unequal pitch, one being the octave of the other. (The perception of pitch corresponds to the sensation of color in the case of the eye.) 3. The quality or timbre {"Klangfar-be"^ is peculiar to different sonorous bodies. [It is the peculiarity of a musical tone by which we are enabled to distin- guish it as coming from a particular instrument, or from the human voice. Thus, the same note struck on a piano and sounded on a violin differs in quality or timbre.~\ It depends upon the peculiar form of the vibration, or the form of the wave of the sonorous body. (There is no analogous sensation in the case of light.) I. Perception of Pitch. — By means of the organ of hearing we can determine that dift'erent tones have a different pilch. In the so called musical scale, or gamut, this difference is very marked to a normal ear. But in the scale there are again four tones, which, when they are sounded together, cause in a normal ear the sensation of an agreeable sound, which once heard can readily be repro- duced. This is the tone of the so-called Accord, Triad, or Common Chord, consisting of the ist, 3d, and 5th tones of the scale, to which the 8th tone or octave is added. We have next to determine the pitch of the tones of the chord, and then that of the other tones of the scale. The siren is used for the fundamental experiment, from which the others can easily be calculated. Four concentric circles are drawn upon the rotatory disk of the siren ; the inner circle contains 40 holes, the second PERCEPTION OF PITCH. 829 50, the third 60, and the outer So — all the holes being at equal distances from each other. If the disk be rotated, and air forced against each series of holes in /urn, we distinguish successively the four tones of the accord (major chord with its octave) ; when all the four series are blown upon simullaneously, we hear in complete purity the major chord itself. The relative number of the holes in the four series indicates in the simplest manner the relative pitch of the tones of the major chord. While one revolution of the disk is necessary to produce the fundamental ground tone (key-note or tonic) with 40 condensations and rarefactions of the air — in order to produce the octave, we must have double the number of condensations and rarefactions during one revolution in the same time. Thus, the relation of the number of vibrations of the Ground tone or Tonic to the Octave ne.\t above it, is I : 2. In the second series we have 50 holes, which cause the pitch o( the Third ; hence, the relation of the Ground tone to the Third in this case is 40 : 50, or i : i ^ = |, i. e., for every vibration of the Ground tone there are J vibrations in the Third. In the third series are 60 holes, which, when blown upon, yield the Fifth ; hence, the ratio of the Ground tone to the Fifth in our disk is 40 : 60, or i : i^ = |. In the same way we can estimate the pitch of the Fourth tone, and we tind that the number of vibrations of the First, Third, Fifth, and Octave are to each other as I : 1 : 3 : 2. The Minor chord is quite as characteristic to a normal ear as the Major. It is distinguished essentially from the latter by its Third being half a tone lower. We can easily imitate it by the siren, as the Minor Third consists of a number of vibrations which stand to the Ground tone as 6 : 5, i. e., if 5 vibrations occur in a given time in the Ground tone, then 6 occur in the Minor Third; its vibration number, therefore, is f . From these relations of the Major and Minor common chords we may calculate the relative tones in the scale, and we must remember that the Octave of a tone always yields the fullest and most complete harmony. It is evident that as the Major Third, the Minor Third, and the Fifth harmonize with the fundamental Ground tone or key-note, they must also harmonize with the Octave of the key-note. We obtain from the Major Third with the number of vibrations J, the Minor Sixth with |, from the Minor Third with |, the Major Sixth = (^^ =) |; from the Fifth with |, the Fourth = |. These relations are known as the ■' Inversions ot the intervals." These relations of the tones are, collectively, the consonant intervals of the scale. The dissonant stages, or discords, of the scale can be obtained as follows: Suppose that we have the Ground tone or key-note C, with the number of vibrations = I, the Third E ^ J, the Fifth G = |, and the Octave ^= 2, we then derive from the Fifth or Dommant G a Major chord — this is G, B, L)i. The relative number of vibrations of these 3 tones is the same as in the Major chord of C,, C, E, G. Hence, the number of vibraSons of G : B is as C : E. When we substitute the values we obtain | : B := i : J — i. e., B = '/ . But D' : B = G : E ; so that D : '/' — 3 • t> '■ '^■> '-'' = ¥' °'' ^" octave lower, we have D = |. Deduce from F (subdominant) a Major chord, F, A, CI. The relation of A : Cl= E : G, or A : 2 ^ | : ?, !. e-., A = f . Lastly, F : A = C : E, or F : f = I : ^, !. ir., F = |. So that all the tones of the scale have the following number of vibrations: I, C = i ; II, D = | ; HI, E = f; IV, F = f ; V, G = | ; VI, A = 5 ; VII, B = V ; VIII, C = 2. Conventional Estimate of Pitch. — Conventionally, the pitch or concert pitch of the note, a, is taken at 440 vibrations in the second [Scheiblcr, 18^4), although in France it is taken at 435 vibrations per second. From this we can estimate the absolute number of vibrations for the tjncs of the scale: C = 33, D = 37.125, E = 41.25, F = 44, G = 49.5, A = 55, B = 61.875 vibrations. The number of vibrations of the next highest octave is found at once by multiplying these numbers by 2. Musical Notes. — The lowest notes used in mu»ic are the double bass, E, with 41.25 vibrations, piano-forte C with 33, grand piano A' with 27.5, and organ C with 16.5. The highest notes in music are the piano-forte C with 4224, and d'' on the piccolo flute, with 4752 vibrations per .second. Limits of Auditory Perception. — According to Preyer, the limit of the perception of the lowest audible tone lies between sixteen and twenty-three vibra- tions per second, and e"" with 40,960 vibrations as the highest audible tone; so that this embraces about 11 1^ octaves. ^^^' [Audibility of Shrill Notes. — This varies very greatly in different persons (ll'ollaston). There is a remarkable falling off' of the power as age advances [Galton). For testing this, Gallon uses a small whistle (Fig. 528) made of a brass tube, with a diameter of le-s than j'^th of an inch. A plug is fitted at the lower end to lengthen or shorten the lube, whereby the pitch of the note is ahered. Among animals Galton finds none superior to cats in the power of hear- ing shrill sounds, and he attributes this "to differentiation by natural selection among these animals until they have the power of hearing all the high notes made by mice and other little creatures they have to catch."] Variations in Auditory Perception. — It is rare to find that tones produced by more than 35,000 vibrations per second are heard. When the tensor tympani is contracted, the perception may be increased for tones 3000 to 5000 vibrations higher, but rarely more. Pathologically, the perception for high notes may be Galton': 830 PERCEPTION OF QUALI'n\ abnormally acute — (i) When the tension of the sound-conducting apparatus generally is increased. (2) By elimination of the sound-conducting apparatus of the middle ear, which offers greater or less resistance to the propagation of very high notes, as perforation of the membrana tympani, or loss of the incus and malleus. In these cases the stapes is directly set in vibration by the sound waves, when tones up to So.ooo vibrations have been perceived. Diminished tension of the sound- conducting apparatus causes diminution of the perception foi high tones (Bluie). A smaller number of vibrations than 16 per second (as in the organ) are no longer heard as a tone, but as single, dull impulses. The tones thai are produced b.yond the highest audible note, as by stroking small tuning-forUs with a violin bow, are also no longer heard as tones, but they cause a painful cutting kind of impression in the ear. In the musical scale the range is, approxi- mately, from C of the first octave with 16.5 vibrations to e, the eighth octave. Comparison of Ear and Eye. — In comparing the perception of the eye with that of the ear, we see at once that the \ange of accommodation of the ear is much greater. Red has 456 billions of vibrations per second, while the visible violet has but 667, so that the eye only takes cognizance of vibrations which do not form even one octave. Lowest Audible Tone. — As to the smallest number of successive vibrations which the ear can perceive as a sensation of tone, Savart and Pfaundler considered that two would suffice. If, however, we exclude in our experiments the possibility of the occurrence of over- tones (4 to 8) {Afach), or even 16 to 20 vibrations {F. Aiterbach, Kohlrausch) are necessary to produce a characteristic tone. When tones succeed each other rapidly, they are still perceived as distinct, when at least o.i second intervenes between two successive tones {11. Helmholtz) ; if they follow each other more rapidly they fuse with each other, although a short- time interval is sufficient for many musical tones. By the term, "fineness of the ear," or, as we say, a " good ear," is meant the capacity of distinguishing from each other, as different, two tones of nearly the same number of vibrations. This power can be greatly increased by practice, so that musicians can distinguish tones that differ in pitch by only -5-^, or even j-jVif of their vibrations. With regard to the time sense, it is found that beats are more precisely per- ceived by the ear than by the other sense organs {Horing, Mach, Vierordt). Pathological. — According to Lucae, there are some ears that are better adapted for hearing low notes ami others for high notes. Both conditions are disadvantageous for hearing speech. Those who hear low notes best hear the highest consona'its imperlectiy. The low notes are heard abnor- mally loud in rheumatic facial paral)sis, while the high tones are heard abnormally loud in cases of loss of the membrana tympani, incus, and malleus. The stapedius is in full action, whereby the highest tones are heard louder at the expense of the lower notes. Many persons with normal liear- ing hear a tone higher with one ear than with the otner. This condition is called diplacusis bin- auralis. In rare cases sudden loss of the perception of certain tones has been observed, e. g., the base-deafness of Moos. In a case described by Magnus, the tones dl,bl,were not heard (S316). II. Perception of the Intensity of Tone. — The intensity of a tone depends upon the ampli- tttdc of the vihrations ol the sounding body. The intensity of the tone is proportional to the square of the amplitude of vibration of the sounding body, /. e., with 2, 3, or 4 times the amplitude the intensity of the tone is 4, 9, 16 times as strong. As sonorous vibrations are communicated to our ears by the wave movements of the air, it is evident that the tones must become less and less intense the further we are from the source of the sound. The intensity of the sound is inversely propor- tional to the square of the distance of the source of the sound from the ear. Tests. — I. Place a watch horizontally near the ear, and test how close it may be brought to the ear, and also how far it may be removed, and still its sounds be heard. Measure the distance. 2. Itard uses a small hammer suspended like a pendulum, and allowed to fall upon a hard surface. 3. Balls of different weights are allowed to fall from varying heights upon a plate. In this case the intensity of the sound is proportional to the product of the weight of the ball into the height it falls. As to the limits of the perception of the intensity of a tone, it is found that a spherule weighing I milligram, and falling from a height of i mm, upon a glass plate, is heard at a distance of 5 cen- timetres (Sc/iaf/uiiilt). 415. PERCEPTION OF QUALITY— ANALYSIS OF VOWELS.- By the term quality (" Klangfarbe "J, musical color or timbre, is understood a peculiar character of the tone, by \\'hich it can be distinguished apart from its pitch and intensity. Thus, a flute, horn, violin, and the human voice may all sound the same note with equal intensity, and yet all the four are distin- guished at once by tlieir specific quality. Wherein lies the essence (" Wesen "') of tone color? The ANALYSIS OF VOWELS. 831 investigations of v. Helmholtz have proved that, among mechanisms which produce tones, only those that produce pendulum-like vibrations, /. i., the to-andfro viljrations of a metallic rod with one end fixed, and tuning-forks, execute simple pendulum like vibrations. This can be shown by making a tuning-fork write off' its vibrations on a recording surface, when a completely uniform wave line, with equal elevations and depressions, is noted. The term " tone " is restricted to those sounds, hardly ever occurring in nature, which are due to simple pentlulum like vibrations. Other investigations have shown that the tones of musical instruments and of the human voice, all of which have a characteristic quality of their own, are composed of many single simple tones. Among these one is characterized by its intensity, and at the same time it determines the pitch of the whole compound musical "tone-picture." This is called the fundamental tone or key-note. The other weaker tones which, as it were, spring from and are mingled with this, vary in dilTerent instruments both in intensity and number. They are " upper tones," and their vibrations are always some multiple — 2, 3, 4, 5 ... . times — of the fundamental tone or key-note. In general, we say that all those outbursts of sound which embrace numerous strong upper tones, especially of high pitch, in addition lo the fundamental tone, are characterized by a sharp, piercing, and rough quality, such as emanates from a trumpet or clarionet, and that conversely the quality is characterized by mildness and softness when the over-tones are few, leeble, and low, e. g., such as are produced by the flute. It requires a well-trained musical ear to distinguish, in an instrumental burst, the over-tones apart from the fundamental tone. But this is very easily done with the aid of resonators (Fig. 532). These consist of spherical or funnel-shaped hollow bodies, made of brass or some other substance, which, by means of a short tube, can be placed in the outer ear. If a resonator be placed in the ear, we can hear the feeblest over-tone of the same number of vibrations as the fundamental tone. Thus, musical instruments are distinguished by the number, intensity, and pitch of the over-tones which they produce. A vibrating metallic rod and a tunmg fork have no over. tones ; they only give the fundamental tone. As already mentioned, the term simple tone is appUed to sounds due to simple pendulum-like vibrations, while a sound composed of a fundamental tone and over-tones is called a " klang " or compound musical tone. Vibration Curve of a Musical Tone. — When we remember that a musical tone or clang con- sists of a fundamental tone and a number of over- tones of a certain intensity, which determine its quality, then we ought to be able to construct geometrically the vibration curve of the musical tone. Let A represent the vibration curve of the fundamental tone, and B that of the first moder- ately weak over-tone (Fig. 529). The combina- tion of these two curves is obtained simply by computing the height of the ordinates, whereby the ordinates of the over-tone curve, lying above the abscissa or horizontal line, are added to the fundamental tone curve, while those of the ordi- nates below the line are subtracted from it. Thus we obtain the curve C, which is not a simple pen- dulum-like curve, but one which corresponds to an unsteady movement. A new curve of the second over tone may be added to C, and so on. The result of all these combinations is that the vibration curves correspondm^ to the compound musical tones are unsteady periodic curves. All these curves must, of course, vary with the number and pitch of the compounded over -tone curves. Displacement of the Phases. — The form of ^^ the vibration of one and the same musical tone may vary greatly, if, in compounding the curves A and B, the curve B is only slightly displaced laterally. If B is displaced so that the hollow of the wave r falls under A, the addition ol both curves yields the curve r, r, r, with small elevations and broad valleys. If B be displaced still further, until the elevation of the wave, //, coincides with A, we obtain still another form, so that by displacement of i\ie phases of the wave motions of the compounded pendulum-like vibrations, we obtain numerous different forms of the same musical tone. The displacement of the phases, however, hartments by a piece of thin sheet India-rubber. Ordinary gas passes into the chamber on one side of the membrane, through the stop-cock, and it is lighted at a small burner. To the other compartment is attached a wider tube, with a mouth piece. The whole is fixed on a stand (Fig. 530), and near it is placed a four-sided rotating mirror, M, as suggested by Wheatstone. On speaking or singing a vowel into the mouth piece, and rotating the mirror, a toothed or zigzag flame picture is obtained in the mirror. The lorm of the flame picture is characteristic for each vowel, and varies, of course, with the pitch.] [Fig. 531 shows the form of the flame picture obtained in the rotating mirror when the vowels ou, o. A, a.e sung at the pilch of «/,, sol^ and ut^. This series shows how they difter in quality.] [Koenig has also invented the apparatus (Fig. 532) for analyzing any compound tone whose fundamental tone is UTj. It consists of a series of resonators, from UT, to UT-, fixed in an iron frame. Each resonator is connected with its special flame, which is pictured in a long, narrow, square, rotating mirror. If a tuning-fork UT, be sounded, only the flame ur, is aflfected, and so on with each tuning-fork of the harmonic series. Suppose a compound note containing the funda- mental tone UT,, and its harmonics be sounded, then the flame of UTj, and those of the other har- monics in the note are also affected, so that the tone can be analyzed optically. The same may be done with the vowels.] 416. ACTION OF THE LABYRINTH DURING HEARING.— If we ask what role the ear plays in the perception of the qiitiliiv of sounds, then we must assume that, just as with the help of resonators a musical note can be S3 834 ACTION OF THE LABYRINTH DURING HEARING. resolved into its fundamental tone and over-tones, so the ear is capable of per- fornaing such an analysis. The ear resolves the complicated wave forms of mu- sical tones into their components. These components it perceives as tones harmo- nious with each other ; with marked attention each is perceived singly, so that the ear distinguishes as different tone colors only different combinations of these simple tone sensations. The resolution of complex vibrations, due to quality, into simple pendulum-like vibrations is a characteristic function of the ear. What apparatus in the ear is capable of doing this? If we sing vigorously — e.g., the musical vowel A on a definite note, say b b — against the strings of an open piano- forte while the damper is raised, then we cause all those strings, and only those, to vibrate sympathetically, which are contained in the vowel so sung. We must, Fig. 532. Koenig's apparatus for aiialy therefore, assume that an analogous sympathetic apparatus occurs in the ear, which is tuned, as it were, for different pitches, and which will vibrate sympathetically like the strings of a piano-forte. " If we could so connect every string of a piano with a nerve fibre that the nerve fibre would be excited and perceived as often as the string vibrated, then, as is actually the case in the ear, every musical tone which affected the instrument would excite a series of sensations exactly corre- sponding to the pendulum-like vibrations into which the original movements of the air can be resolved ; and thus the existence of each individual over-tone would be exactly perceived, as is actually the case with the ear. The perception of tones of different pitch would, under these circumstances, depend upon dif- ferent nerve fibres, and hence would occur quite independently of each other. SIMULTANEOUS ACTION OF TWO TONES. 835 Microscopic investigation shows that there are somewhat similar structures in the ear. The free ends of all the nerve fibres are connected with small elastic par- ticles, which we must assume are set into sympathetic vibration by the sound waves" (<■. Helmholtz). Resolution by the Cochlea.— Formerly, v. Helmholtz considered the rods of Corti to be the apparatus that vibrated and stmiulated the terminations of the nerves. But, as birds and amphibians, which certainly can distinguish musical tones, have no rods {Hasse), the stretched radial fibres of the membrana basilaris, on which the organ of Corti is placed, and which are shortest in the first turn of the cochlea, becoming longer toward the apex of the cochlea, are now regarded as the vibrating threads {Hensen). Thus, a string-like fibre of the mem- brana basilaris, which is capable of vibrating, corresponds to every possible simple tone. According to Hensen, the hairs of the labyrinth, which are of unequal length, may serve this purpose. Destruction of the apex of the cochlea causes deafness to deeper tones (^JSaginsky). [Hensen' s Experiments. — That the hairs in connection with the hair cells vibrate to a particular note is also rendered probable by the experiments of Hensen on the crustacean Mysi's. He found that certain of the minute hairs (auditory hairs) in the auditory organ of this animal, situate at the base of the antennce, vibrated when certain tones were sounded on a keyed horn. The movements of the hairs were observed by a low-power microscope. In mammals, however, there is a difficulty, as the hairs attached to the cells appear to be all about the same length. We must not forget that the perception of sound is a mental act.] This assumption also explains the perception of muses. Of noises in the strictly physical sense, it is assumed that they, like single impulses, are perceived by the aid of the saccules and the ampullae. It is assumed that the saccules and the ampullae are concerned in the general perception of hearing, ;>., of shocks communicated to the auditory nerve (by impulses and noises) ; while by the cochlea we estimate the pitch and depth of the vibrations, and musical character of the vibrations produced by tones. The relation of the semicircular canals to the equilibrium of the body is referred to in § 350. 417. SIMULTANEOUS ACTION OF TWO TONES— HAR- MONY — BEATS- DISCORDS — DIFFERENTIAL TONES. — When l7o<> tones of different pitch fall upon the ear simultaneously, they cause different sensations, according to the difference in pitch. 1. Consonance.— -If the number of vibrations of the two tones is in the ratio of simple multiples, as i : 2 : 3 : 4, so that when the low note makes one vibra- tion the higher one makes 2 : 3 or 4 ... . then we experience a sensation of com- plete harmony or concord. 2. Interference. — If, however, the two tones do not stand to each other in the relation of simple multiples, then when both tones are sounded simultaneously interference takes place. The hollows of the one sound wave can no longer coin- cide with the hollows of the other, and the crests with the crests, but, corre- sponding to the difference of number of vibrations of both curves, sometimes a wave crest must coincide with a wave hollow. Hence, when wave crest meets wave crest, there must be an increase in the strength of the tone, and when a hollow coincides with a crest, the sound must be weakened. Thus we obtain the impression of those variations in tone intensity which have been called " beats." The number of vibrations is, of course, always equal to the difference of the number of vibrations of both tones. The beats are perceived most distinctly when two organ tones of low pitch are sounded together in unison, but slightly out of tune. Suppo.se we take two organ pipes with ^t, vibrations per second, and so alter one pipe that it gives 34 vibrations per second, then one distinct beat will be heard every second. The beats are heard more frequently the greater the difl'erence between the number of vibrations of the two tones. 836 PERCEPTION OF THE DIRECTION OF SOUNDS. Successive Beats.— The beats, however, produce very different impressions upon the ear, according to the rapidity with which they succeed each other. 1. Isolated Beats. — When they occur at long intervals, we may perceive them as completely isolated, but single intensifications of the sound with subsequent enfeeblement, so that they give rise to the impression of isolated heats. 2. Dissonance. — When the beats occur more rapidly they cause a continuous disagreeable whirring impression, which is spoken of as dissonance, or an unhar- monious sensation. The greatest degree of unpleasant painful dissonance occurs when there are 33 beats per second. 3. Harmony. — If the beats take place more rapidly than 33 times per second, the sensation of dissonance gradually diminishes, and it does so the more rapidly the beats occur. The sensation passes gradually from moderately inharmonious relations (which in music have to be resolved by certain laws) toward consonance or harmony. The tone relations are successively the Second, Seventh, Minor Third, Minor Sixth, Major Third, Major Sixth, Fourth, and Fifth. 4. Action of the Musical Tones ("A7(ir;/^f "). — Two musical "klangs," or compound tones, falling on the ear simultaneously, produce a result similar to that of two simple tones; but in this case we have to deal not only with the two fundamental tones, but also with the over-tones. Hence the degree of dissonance of two musical tones is the more pronounced the more the fundamental tones and the over-tones (and the " differential " tones) produce beats which number about 33 per second. 5. Differential Tones. — Lastly, two "klangs," or two simple musical tones sounding simultaneously, may give rise to new tones when they are uniformly and simultaneously sounding in corresponding intensity. VVe can hear, if we listen attentively, a third new tone, whose number of vibrations corresponds to the dif- ference between the two primary tones, and hence it is called a '■^differential tone. ' ' Summational Tones. — It was formerly supposed that new tones cculd arise from the summation or addilion of their number of vibralions, but it has been shown that tliese tones are, in reality, differential tones of a high order [A/'pimn, Preyer). 418. PERCEPTION OF SOUND— FATIGUE OF THE EAR- OBJECTIVE AND SUBJECTIVE AUDITION— AFTER SEN- SATION. — Objective Auditory Perceptions. — When the stimulation of the terminations of the nerves of the labyrinth is referred to the _ outer world, then we have objective auditory perceptions. Such stimulations are only referred to the outer world as are conveyed to the membrana tympani by vibrations of the air, as is shown by the fact that if the head be immersed in water, and the audi- tory meatuses be filled thereby, we hear all the vibrations as if they occurred within our head itself {Ed. JFelier), and the same is the case with our own voice, as well as with the sound waves conducted through the bones of the head, when both ears are firmly plugged. Perception of Direction. — As to the perception of the direction whence sound comes, we obtain some information from the relation of both meatuses to the source of the sound, especially if we turn the head in the supposed direction of the sound. We distinguish more easily the direction from which noises mixed with musical tones come than that of tones {Raylcigh). When both ears are stimulated equally, we refer the source of the sound to the middle line anteriorly, but when one ear is stimulated more strongly than the other, we refer the source of the sound more to one side (Kessel). The position of the ear muscles, which, perhaps, act like an ear funnel, is important. According to Ed. Weber, it is more difficult to determine the direction of sound when the ears are firmly fixed to the side of the head. Further, if we place the hollow of both hands in front of the ear, as to form an open cavity behuid them, we are apt to suppose that a sounding body placed in front is behind us. COMPARATIVE HISTORICAL. 837 The distance of a sound is judged of partly by the intensity or loudness of the sound, such as we have learned to estimate from sound at a known distance. But still we are subject to many misconceptions in this respect. Among subjective auditory sensations are the a/Ur vibrations, especially of intense and continued musical tones ; the tinnitus aurium (p 637), which often accompanies abnormal move- ments of the blood in the ear, may be due to a mechanical stimulation of the auditory fibres, perhaps by the blood stream [Brenner). [Drugs. — Cannabis indica seems to act on the hearing centre, giving rise to subjective sounds; the hearing is rendered more acute by strychnin; while quinine and sodic salicylate in large doses cause ringing in the ears (BrtiMton).'\ Entotical perceptions, which are due to causes within the ear itself, are such as hearing the f'ulse beats in the surrounding arteries, and the rushing sound of the blood, which is especially strong when there is increased resonance of the ear (as when the meatus or tympanum is closed, or when fluid accumulates in the latter), during increased cardiac action, or in hypersesthesia of the auditory nerve (Brenner). Sometimes there is a cracking noise in the maxillary articulation, the noise pro- duced by traction of the muscles on the Eustachian tube (J 411), and when air is forced into the latter, or when the membrana tympani is forced outward or inward (§ 350). Fatigue. — The ear after a time becomes fatigued, either for one tone or for a series of tones which have acted on it, while the perceptive activity is not affected for other tones. Complete re- covery, however, takes place in a few seconds ( G'rbantscJiilseii). Auditory After Sensations. — (l) Tho^e that correspond to positive after sensations, where the after sensation is so closely connected with the original tone that both appear to be continuous. (2) There are some after sensations, where a pause intervenes between the end of the objective and the beginning of the subjective tone ( Urbantschitsch). (3) There seems to be a form corresponding to negative after images. In some persons the perception of a tone is accompanied by the subjective colors, or the sensation of light, e.g., the sound of a trumpet, accompanied by the sensation of yellow. More seldom are visual sensations of this kind observed when the nerves of taste, smell, or touch are excited [Xiiss- baiimer, Lehmann and Bleuler). It is more common to find that an intense sharp sound is accom- panied by an associated sensation of the sensory nerves. Thus many people experience a cold shud- der when a slate pencil is drawn in a peculiar manner across a slate. [Color Associations. — Color is in some persons instantaneously associated with sound, and Gal- ton remarks that it is rather common in children, although in an ill-developed degree, and the ten- dency seems to be very hereditary. Sometimes a particular color is associated with a particular letter, vowel sounds particularly evoking colors. Galton has given colored representations of these color associations, and he points out their relation to what he calls number forms, or the associa- tion of certain forms with certain numbers.] An auditory impulse communicated to one ear at the same time often causes an increase in the auditory function of the other ear, in consequence of the stimulation of the auditory centres of both sides [C'rbantschitseh, Eitelberg). Other Stimuli. — The auditory apparatus, besides being excited by sound waves, is also affected by heterologous stimuli. It is stimulated meehanical/yhy a sudden blow on the ear. The effects of eleetrieity and pathological conditions are referred to in § 350. 419. COMPARATIVE— HISTORICAL.— The lowest fishes, the cyclostoniata (Petromy- zon), have a saccule provided with auditory hairs containing otoliths, and communicating with two semicircular canals, while the myxinoids have only one semicircular canal. Most of the other fishes, however, have a utricle communicating with three semicircular canals. In the carp, prolongations of the labyrinth communicate with the swimming bladder. In amphibia, the structure of the laby- rinth is somewhat like that in fishes, but the cochlea is not typically developed. Most amphibia, except the frog, are devoid of a membrani tympani. Only the fenestra ovalis (not the rotunda) ex- ists, and it is connected in the frog by three ossicles with the freely exposed membrana tympani. Among reptiles the appendix to the saccule, corresponding to the cochlea, begins to be prominent. In the tortoise it is saccular, but in the crocodiles it is longer, and somewhat curved and dilated at the end. In all reptiles the fenestra rotunda is developed, whereby the cochlea is connected with the labyrinth. In crocodiles and birds the cochlea is divided into a scala vestibuli and S. tympani. Snakes are devoid of a tympanic cavity. In birds both saccules (Fig. 524, IV, U S') are united {//asse), the canal of the cochlea (U C), which is connected by means of a fine tube (C). with the saccule, is larger, and .shows indications of a spiral arrangement, and has a flask-like blind end, the lagena (L). The auditory ossicles in reptiles and birds are reduced to one column-like rod, corre- sponding to the stapes, and called the columella. The lowest mammals (Echidna) have struc- tures very like those of birds, while the higher mammals have the same type as in man (Fig. 524, HI). The Eustachian tube is always open in the whale. Among invertebrata the auditory organ is very simple in medusa; and mollusca. It is merely a bladder filled with fluid, with the auditory nerves provided with ganglia in its walls. Hair cells occur in the interior, provided with one or more otoliths. Hensen observed that in some of the 838 COMPARATIVE HISTORICAL. annulosa, when sound was conducted into the water, some of the auditory bristles vibrated, being adapted for special tones. In cephalopoda we distinguish the first ditTerentiation into a membran- ous and cartilaginous labyrinth. Historical.— Empedocles (473 B.c) referred auditory impressions to the cochlea. The Hippo cratic School was acquainted with the tympanum, and Aristotle (384 B.c) with the Eustachian tube. Vesalius (1561) described the tensor tympani; Cardanus (1560) the conduction through the boms of the head; while Fallopius (1561) described the vestibule, the semicircular canals, chorda tym- pani, the two fenestrse, the cochlea, and the aqueduct. Eustachius (f 1570) described the modio- lus, the lamina spiralis of the cochlea, the Eustachian lube, as well as the muscles of tlie ear; Plater the ampulla; (1583); Casseri (1600) the lamina spiralis membranacea. Sylvius (1667) discovered the ossicle called by his name ; Vesling (1641) the s'apedius. Mersenne (1618) was acquainted with over-tones ; Gassendus (1658) experimented on the conduction of sound. Acoustics was greatly advanced by the work of Chladni (1802). The most recent and largest work on the ear in verte- brates is by G. Retzius (1881-84). THE ORGAN OF SMELL. 420. STRUCTURE OF THE ORGAN OF SMELL.— Regio Olfactoria.— The area of the distribution of the olfactory nerve is the regio olfactoria, which embraces the upper part of the septum, the upper (Fig. 534, Cs), and part of the middle (Cm) turbinated bone. All the re- mainder of the nasal cavity is called the regio respiratoria. These two regions are distinguished as follows: (i) The regio olfactoria has a thicker mucous membrane. (2) It is covered by a sin- gle layer of cylindrical epithelium (Fig. 533, E), the cells being often branched at their lower ends, and contain a yellow or brownish-red pigment. (3) It is colored by this pigment, and is thereby distinguished from the uncolored regio respiratoria, which is covered by cilated epithelium. (4) It contains peculiar tubular glands (Bowman's glands), while the rest of the mucous membrane contains numerous acinous serous glands ( Heidenhain). (5) Lastly, the regio olfactoria embraces the end organs of the olfactory nerve (/I/. Schul/ze). The long, narrow olfactory cells (N) are distributed between the ordinary cylindrical epithelium (E) covering the regia olfactoria. The body of the cell is spindle shaped, with a large nucleus containing nucleoli, and it sends upward between the cylindrical cells a narrow (0.9 to 1.8 /i), smooth rod, quite up to the free surface of the mucous membrane. In the frog («), the free end carries delicate projecting hairs or bristles. In the deeper F'G- 533- Fig. 534. 333. — N, olfactory celh (human) ; «, from the frog ; pnaryngo-nasal cavities. L, levator elevation ; \ nated bones {UriuntS'Jiitsch). ;, epitheln i/»., plica 1 of the regio olfactoria. Fig. 534 — Nasal and lalpingo-palatina ; Ls, Cut, Ci, the three liirbi- part of the mucous membrane the olfactory cells pass into, and become continuous with, varicose tine nerve fibres, which pass into the olfactory nerve (^ 321, I, I). According lo C. K. Hoffmann and Exner, after section of the olfactory nerve the specific olfactory end organs become changed into cylindrical epithelium (frog), and in warm blooded animals they undergo fatty degeneration, even on the 15th day. V. Brunn found a homogeneous limiting membrane, which had holes in it for transmitting the processes of the olfactory cells only. [The respiratory part of the nasal mucous membrane is lined by ciliated epithelium stratified like that in the trachea and resting on a basement membrane. Below this there are many lymph corpuscles and aggregations of adenoid tissue.] [The organ of Jacobson is present in all mammals, and consists of two narrow tubes protected by cartilage, and placed in the lower and anterior part of the nasal septum. Each tube terminates blindly behind, but anteriorly it opens into the nasal furrow or into the nasopalatine canal (dog). The wall next the middle line is covered by olfactory epithelium, and receives olfactory nerves (rabbit, guinea pig), and it contains glands similar to those of the olfactory region; the outer wall IS covered by columnar epithelium ciliated in some animals (A7«'«).] 839 840 OLFACTORY SENSATIONS. 421. OLFACTORY SENSATIONS.— Olfactory sensations are produced by the action of gaseous odorous substances being brought into direct contact with the olfactory cells, during the act of inspiration. The current of air is divided by the anterior projection of the lowest turbinated bone, so that a part above the latter is conducted to the regio olfactoria. Odorous bodies taken into the mouth and then expired through the posterior nares are said not to be smelled {BiMer). During inspiration the air streams along close to the septum, while little of it passes through the nasal passages, especially the superior [Paulsen and Exner). T\\t first moment of contact between the odorous body and the olfactory mucous membrane appears to be the time when the sensation takes place, as, when we wish to obtain a more exact perception, we j///^ several times, /. e,, a series of rapid inspirations are taken, the mouth being kept closed. During sniffing, the air within the nasal cavities is rarefied, and as air rushes in to equilibrate the pressure, the air laden with odorous particles, streams over the olfactory region. Odorous fluids are said not to give rise to the sensation of smell when they are brought into direct contact with the olfactory mucous membrane, as by pouring eau de Cologne into the nostrils [Tourtiial, 182/ ; E. H. Weher, 1841). This is, perhaps, due to the action of the fluid on the olfactory cells paralyzing them, per- haps, owing to imbibition, shriveling, or chemical action. Even water alone temporarily affects the cells. We know practically nothing about the nature of the action of odorous bodies, but many odorous vapors have a considerable power of absorbing heat {Tyndall ). The intensity of the sensation depends on — i. The size of the olfactory surface, as animals with a very keen sense of smell are found to have complex turbinated bones covered by the olfactory mucous membrane. 2. The concen- tration of the odorous mixture of the air. Still, some substances may be attenu- ated enormously {e.g., musk to the two-millionth of a milligram), and still be smelled. 3. The frequency of the conduction of the vapor to the olfactory cells (sniffing). [The acuteness of the sense of smelt is greatly improved by practice. A boy named James Mitchell, who was deaf, dumb, and blind, used his sense of smell, like a dog, to distinguish persons and things.] Elfctrical, chemical, or thermal stimuli do not give rise to olfactory sensations. [Althaus found that electrical stimulation of the olfactory mucous membrane gave rise to the sensation of the smell of phosphorus.] The variations are referred to in § 343. If the two nostrils are filled with different odorous substances there is no mixture of the odors, but we smell sometimes the one and sometimes the other ( Valentin'). The sense of smell, however, is very soon blunted, or even paralyzed. Mor- phia, when mixed with a little sugar and taken as .snuff, paralyzes the olfactory apparatus, while strychnin makes it more sensitive [Lichtenfels and frohlich). The sensory nerves of the na^al mucous membrane (\ 347, II) [/. i-., those supplied from the fifth cranial nerve] are stimulated by irritating vapors, and may even cause pain, e.g., ammonia and acetic acid. In a very diluted condition, they may c en act on the olfactory nerves. The nose is useful as a sentinel for guarding against the introduction of di.sagreeable odors and foods. The sense of smell is aided by the sense of taste, and conversely. [Flavor depends on the sense of smell, and, to test it, use substances, solid or fluid, with an aroma or boiupict, such as wine or roast beef. J [Method of Testing. — In doing so, avoid the use of pungent substances like ammonia, whicli excite the fifth nerve. Use some of the essential volatile oils, such as cloves, berganiot, and the fetid gum resins, or musk and camphor. Electrical stimuli are not available. Action of Drugs, J 343] Comparative. — In the lowest vertebrata, pits, or depressions provided with an olfactory nerve, represent the simplest olfactory organ, .^mphioxus and the cyclistomata have only one olfactory pit; all other vertebrates have two. In some animals (frog), the nose communicates with the mouth by ducts. The olfactory nerve is absent in the whale. Historical. — Rufus Ephesius (97 a.d. ) described the passage of the olfactory nerve through the ethmoid bone. Rudius (1600) dissected the body of a man with congenital anosmia, in whom the olfactory nerves were absent. Magendie orii;inally supposed that the nasal branch of the fifth was the nerve of smell, a view successfully combated by Eschricht. THE ORGAN OF TASTE. 422. STRUCTURE OF THE GUSTATORY ORGANS.— Gusta- tory Region. — There is considerable difference of opinion as to what regions of the mouth are endowed with taste : (i) The root of the tongue in the neighbor- hood of the circumvallate papillae, the area of distribution of the glosso-pharyngeal nerve, is undoubtedly endowed with taste (§ 351). (2) The tip and margins of the tongue are gustatory, but there are very considerable variations ( Urhantschitsck). (3) The lateral part of the soft palate and the glosso-palatine arch are endowed with taste from the glosso-pharyngeal nerve. (4) It is uncertain whether the hard ])alate and the entrance to the larynx are endowed with taste {Drielsma). The middle of the tongue is not gustatory. Taste Bulbs. — The end organs of the gustatory nerves are the taste bulbs discovered by Schwalbe and Loven (1867). They occur on the literal surfaces of the circumvallate papilla; (Fig. 535, I), also upon the opposite side, K, of the fossa or capillary slit, R R, which surrounds the I, Transverse section of allate pap W, the papilla ; t/j, t-j, the wall in sectic bulbs in position ; N. N, the nerves. 11, isolated taste bulbs lis ; K, under end ; E, free end, open, with the projecting apices of the taste c 11 (d) with a UTSte cell (<■). R, R.the circular slit D, supporting or pro- Is. Ill, Isolated pro- central eminence or papilla; they occur more rarely on the surface. They also occur on the fungi- form papillse, in the papilla of the soft palate and uvula {A. Hoffman\, on the under surface of the epiglottis, the upper part o( the posterior surface of the epiglottis, and the inner side of the arytenoid cartilages ( Versott, Davis), and on the vocal cords (Siniancrwsky). Many buds or bulbs disappear in old age. Structure. — The taste bulbs are Si fi high and 33 // thick, are barrel shaped and embedded in the thick stratified squamous epithelium of the tongue. Each bulb consists of a seritsof lancet- shaped, bent, nucleated, outtr, supporting or protective cells, arranged like the staves of a barrel (Fig. 535, II, D. isolated in III. n). They are so arranged as to leave a small opening, or the " gustatory pore " at the free eml of the liulb. Surrounded by tliee cells and lying in the axis of the bud are i to 10 gustatory cells 1 II, E), some of which are provided with a delicate process (III, e) at their free ends, while their lower fixed ends send out basal processes, which become continuous with the terminations of the nerves of taste, which have become non mf^dullated. .After section of the glosso pharyngeal, the taste buds degenerate, while the protective cells become changed into ordinary epithelial cells within four months (v. V'intschgau and Honigschmied). Very similar 841 842 GUSTATORY SENSATIONS. structures were found by Leydig in the skin of fresh-water fishes. The glands of tlie tongue and their secretory fibres from the 9th cranial nerve are referred to in § 141 (Drasch). 423. GUSTATORY SENSATIONS.— Varieties.— There are >;//- dif- ferent gustatory iiualities, the sensations of 1. Sweet. 3. Acid. 2. Bitter. 4. Saline. Acid and saline substances at the same time also stimulate the sensory nerves of the tongue, but when greatly diluted they only excite the end organs of the specific nerves of taste. Perhaps there are special nerve fibres for each different gustatory quality (i>. Vintschgau). Conditions. — Sapid substances, in order that they may be tasted, require the following conditions : They must be dissolved in the fluid of the mouth, espe- cially substances that are solid or gaseous. The intensity of the gustatory sen- sation depends on : i. The size of the surface acted on. Sensation is favored by rubbing in the substance between the papillce, in fact, this is illustrated in the rubbing movements of the tongue during mastication (§ 354). 2. The concen- tration of the sapid substance is of great importance. Valentin found that the following series of substances ceased to be tasted in the order here stated, as they were gradually diluted — syrup, sugar, common salt, aloes, quinine, sulphuric acid. Quinine can be diluted 20 times more than common salt and still be tasted ( C Merkel's tactile cells ( ll^aUeyer). The genital corpuscles of Krause, which occur in the skin and mucous membrane of the glans penis, clitoris, and vagina, appear to be end bulbs more or less fused together. The articulation nerve corpuscles occur in the synovial mucous membrane of the joints of the Pacini's corpuscle, a, stalk e fibre entering it: c,ii,cai :-tissue envelope ; e axis cylii ith its end divided aty". 846 SENSORY AND TACTILE SENSATIONS. fingers. They are larger than the end bulbs, and have numerous oval nuclei externally, while one to four nerve tibres enter them. 4. Tactile or touch corpuscles of Merkel, sometimes also called the corpuscles of Grandry, occur in the beak and tongue of the duck and goose, in the epidermis of man and mammals, and in the outer root sheath of tactile hairs or feelers. They are small bodies, composed of a capsule enclosing two, three or more large, granular, somewhat flattened nucleated and nucleolated cells, piled one on the other in a vertical row, like a row of cheeses. Each corpuscle receives at one side a medullated nerve fibre, which loses its myelin, and branches, to terminate, according to some observers {A/erkel)^'\n the cells themselves, and according to others {A'tifiz'ier, Izqtiierdo, Hesse)^ in the protoplasmic transparent substance or disk lying between the cells. [This intercellular disk is the " disk tactil " of Kanvier, or the " Tastphitte" of Hesse.] When there is a great aggregation of these cells, large structures are formed, which appear to form a kind of transition between these and touch corpuscles. [According to Klein, the terminal fibrils end neither in the touch cells nor tactile disk, but in minute swellings in the interstitial substance between the touch cells, in a manner very similar to that occurring in the end bulbs.] [According to Merkel, tactile cells, either isolated or in groups, but in the latter case never form- ing an independent end organ, occur in the deeper layers of the epidermis of man and mammals, and also in the papilla;. They consist of round or flask-shaped cells, with the lower pointed neck of the flask continuous with the axis cylinder of a nerve fibre. They are regarded by Merkel as the simplest form of a tactile end organ, but their existence is doubted by some observers.] Among animals there are many other forms of sensory end organs. [Herbst's corpuscles occur in the mucous membrane of the tongue of the duck, and resemble small Vater's corpuscles, but their lamellce are thinner and nearer each other, while the axis cylinder within the central core Fig. 539. Bouchon epidermique from the groin of a guinea pig, after the action of gold chloride, n, nerve fibre ; rt, tactile cells ; ;«, tactile disks ; c, epithelial cells. is bordered on each sid-; by a- row of nuclei.] In the nose of the mole there is a peculiar end organ (Eimer), while there are "end capsules" in the penis of the hedgehog and the tongue of the elephant, and " neKZ'e rings" in the ears of the mouse. 5. [Other Modes of Ending of Sensory Nerves. — Some sensory ner\'es terminate not by means of special end organs, but their axis cylinder splits up into fibrils to form a nervous network, from which fine fibrils are given off to terminate in the tissue in which the nerve ends. The^e fibrils, as in the cornea (§ 384), terminate by means of free ends between the epithelium on the anterior surface of the cornea, and some observers state that the free ends are provided with small enlarge- ments ("boutons terminals ") (Fig. 539, a). These enlargements or " tactile cells " occur in the groin of the guinea pig and mole. .\ similar mode of termination occurs between the cells of the epidermis in man and mammals (Fig. 271).] 6. Tendons, especially at their junction with muscles, have special end organs {Sachs, RolUtt, Golgi), which assume various forms; it may be a network of primitive nerve fibrils, or flattened end flakes or plates in the sterno-radial muscle of the frog, or elongated oval end bulbs, not unlike the end bulbs of the conjunctiva, or small simple, Pacinian corpuscles.] 425. SENSORY AND TACTILE SENSATIONS.— In the sensory nerve trunks there are two functionally different kinds of nerve fibres: (i) Those which administer to /a//y9// impressions, which are sensory nerves in the narrower sense of the word ; and (2) which administer to tactile impressions, and may, therefore, be called tactile nerves. The sensations of temperature and pressure are also reckoned as belonging to the tactile group. It is extremely probable that the THE SENSE OF LOCALITY. 847 sensory and tactile nerves have different end organs and fibres, and that they have also special perceptive nerve centres in the brain, although this is not definitely proved. This view, however, is supported by the following facts: — I. That sensory and tactile impressions cannot be discharged at the same time from all the parts which are endowed with sensibility. Tactile sensations, in- cluding pressure and temperature, are only discharged from the coverings of the skin, the mouth, the entrance to and floor of the nose, the pharynx, the lower end of the rectum and genito-urinary orifices ; feeble, indistinct sensations of tem- perature are felt in the oesophagus. Tactile sensations are absent from all internal viscera, as has been proved in man in cases of gastric, intestinal and urinary fistulas. Pain alone can be discharged from these organs. 2. The conduction channels of the tactile and sensory nerves lie in different parts of the spinal cord (§364, I and 5). This renders probable the assumption that their central and peripheral ends also are different. 3. Very probably the reflex acts discharged by both kinds of nerve fibres — the tactile and pathic — are controlled, or even inhibited, by special central nerve organs (§ 361 — ?). 4. Under pathological conditions, and under the action of narcotics, the one sensation may be suppressed while the other is retained (§ 364, 5). Sensory Stimuli. — In order to discharge a painful impression from sensory nerves, relatively strong stimuli are required. The stimuli may be mechanical, chemical, electrical, thermal, and somatic, the last being due to inflammation or anomalies of nutrition and the like. Peripheral Reference of the Sensations. — These nerves are excitable along their entire course, and so is their central termination, so that pain may be produced by stimulating them in any part of their course ; but this pain, according to the "law of peripheral perception," is always referred to the periphery. The tactile nerves can only discharge a tactile impression or sensation of con- tact when moderately strong mechanical pressure is exerted, while thermal stimuli are required to produce a temperature sensation ; and in both cases the results are obtained only when the appropriate stimuli are applied to the end organs. If pressure or cold be applied to the course of a nerve trunk, e. g., to the ulna at the inner surface of the elbow joint, we are conscious of painful sensations, but never of those of temperature, referable to the peripheral terminations of the nerves in the inner fingers. All strong stimuli disturb normal tactile sensations by over- stimulation, and hence cause pain. 426. THE SENSE OF LOCALITY.— We are not only able to distin- guish differences of pressure or temperature by our sensory nerves, but we are able to distinguish the part which has been Fig. 540. touched. This capacity is spoken of as the sense of space or locality. Methods of Testing. — Place the two blunted points of a pair of com- passes (tig. 540) upon the part of the skin to be investigated, and determine the smallest fiistance at which the two points are felt only as one impression. Sieveking's eesthesiometer (Fig. 541) may be used instead; one of the points is movable along a graduated rod, while the other is fixed. 2. The distance between the points of the instrument being kept the same, touch several parts of the skin, and ask if the person feels the impression of the points coming nearer to or going wider apart. 3. Touch a part of the skin with a blunt instrument, and observe if the spot touched is correctly indicated by the patient. The investigations have led to the following results : The sense of locality of a part of the skin is more acute under the following conditions : I. The greater the ««»/^fr^/a^///^«^/-Z'« in the correspond- ' .;EsthesioniM<:r. ing part of the skin. 848 MODIFYING CONDITIONS. 2. The greater the mobility of the part, so that it increases in the extremities toward the fingers and toes. The sense of locality is always very acute in parts of the body that are very rapidly moved (^Vierordt). 3. The sensibility of the limbs is finer in the transverse axis than in the long axis of the limb, to the extent of Yz on the flexor surface of the upper limb, and Y, o" t'^^ extensor surface. 4. The moiie of application of the points of the ssthesiometer : {a) According as they are applied one after the other, instead of simultaneously, or as they are considerably warmer or colder than the skin {King), a person may distinguish a less distance between the points, {b) If we begin with the points wide apart and approximate them, then we can distinguish a less distance than when we proceed from imperceptible distances to larger ones, {c) If the one point is warm and the other cold, on exceeding the next distance we feel two impressions, but we cannot rightly judge of their relative positions {Czennak). 5. Exercise greatly improves the sense of locality ; hence the extraordinary acuteness of this sense in the blind, and the improvement always occurs on both sides of the body ( Volkmanii). [Fr. Gallon finds that the reputed increased acuteness of the other senses in the case of the bUnd is not so great as is generally alleged. He tested a large number of boys at an educational blind asylum, with the result that the performances of the blind boys were by no means superior to those Fii;. 541. of other boys. He points out, however, that " the guidance of the blind depends mainly on the multitude of collateral indications, to which they give much heed, and not in their superiority to any one of them."] 6. Moistening \\\^ skin with indifferent fluids increases the acuteness. If, how- ever, the skin between two points, which are still felt as two distinct objects, be slightly tickled, or be traversed by an imperceptible electrical current, the im- pressions become fused {Suslowa). The sense of locality is rendered more acute at the cathode when a constant current is used (S//slo7va), and when the skin is congested by stimulation (Klinkenberg), and also by slight stretching of the skin {Schmey) ; further, by baths of carbonic acid {v. Basch and v. Dietl), or warm common salt, and temporarily by the use of caffein {Rumff). 7. A?ice>nia, produced by elevating the limbs, or venous hypenemia (by com- pressing the veins), blunts the sense, and so does too frequent testing of the sense of locality, by producing fatigue. The sense is also blunted by cold applied to the skin, the influence of the anode, strong stretching of the skin, as over the ab- domen during pregnancy, previous exertion of the muscles under the part of the skin tested, and some poisons, ?. ^., atropin, daturin, morphin, strychnin, alcohol, potassium bromide, cannabin, and chloral hydrate. Smallest Appreciable Distance. — The following statement gives the smallest distance, in millimetres, at which two points of a pair of compasses can ^STHESIOMETRY. 849 Millimetres. Eyelid 11.3 [9] Centre of hard palate 13.5 [113] Lower third of the forearm, volar surface 15. In front of the zygoma 15.8 [11.3] Plantar surface of the great toe . .15.8 [9.] Inner surface of the lip 20.3 [13.5] Behind the zygoma 22.6 [15.8] Forehead 22.6 [18.] Occiput 27.1 [22.0] Back of the hand 31.6 [22.6] Under the chin 33.8 [22.6] Vertex 33.8 [22.6] Knee 36.1 [31.6] Sacrum, gluteal region 44.6 [33.8] Forearm and leg 45.1 [33. 8J Neck 54.1 [36.1] Back at the fifth dorsal vertebra, lower dorsal and lumbar region . 54.1 Middle of the neck 67.7 Upper arm, thigh and centre of the back 67.7 [31.6-40.6] Still be distinguished as double by an adult. The corresponding numbers for a boy twelve years of age are given within brackets : — Millimetres. Tip of tongue i.i [!•'] Third phalanx of finger, volar surface 2.-2.3 [''7] Red part of the Up 4.5 [3.9] Second phalanx of finger, volar surface. 4-4-5 [3-9] First phalanx of finger, volar surface 5--5-5 Third phalanx of finger, dorsal surface 6.8 [4.5] Tip of nose 6.8 [4.5] Head of metacarpal bone, volar . 5-.6.8 [4.5] Ball of thumb ." 6.5-7. Ball of little finger 5-5-6- Centre of palm 8.-g. Dorsum and side of tongue, white of the lips, metacarpal part of the thumb. 9. [6.8] Third phalanx of the great toe, plantar surface 1 1.3 [6.8] Second phalanx of the fingers, dorsal surface 1 1.3 [9.] Back 1 1.3 [9.] Illusions of the sense of locality occur very frequently ; the most marked are: (i) A uni- form movement over a cutaneous surface appears to be quicker in those places which have the finest sense of locality. (2) If we merely touch the skin with the two points of an a;sthesiometer, then they feel as if they were wider apart than when the two points are moved along Vne skin (Fechner). (3) A sphere, when touched with short rods, feels larger than when long rods are used ( Toitrtual). (4) When the fingers of one hand are crossed, a small pebble or sphere placed between them feels double (Aristotle's experiment). [When a pebble is rolled between the crossed index and middle finger (Fig. 542, B), it feels as if two balls were present, but with the fingers uncrossed single, (5) When pieces of skin are transplanted, e.g., from the forehead, to form a nose, the person operated on feels, often for a long time, the new nasal part as if it were his fore- head.] Theoretical. — Numerous experiments were made by E. H. Weber, Lotze, Meissner, Czermak and others, to explain the phenomen.i of the sense of space. Weber's theory goes Fig. 542. upon the assumption, that one and the same nerve fibre proceeding from the brain to the skin can only take up one kind of impres- sion, and admimsterihereto. He calleti the part of the skin to which each single nerve fibre is distributed a " circle of sensa- tion." When two stimuli act simultaneously upon the tactile end organ, then a double sensation is felt, when one or more circles of sensation lie between the two points stimu- lated. This explanation, based upon ana- tomical considerations, does not explain how it is that, with practice, the circles of sensa- tion become smaller, and also how it is that only one sensation occurs, when both points of the instrument are so applied, that both points, although further apart than the di- ^• ameter of a circle of sensation, at one time Aris he upon two adjoining circles, at another between two others with another circle intercalated between them. AWundt's Theory. — In accordance with the conclusions of Lotze, Wundt proceeds from a psycho-physiological basis, that every part of the skin with tactile sensibility always conveys to the brain the locilily of the sensation. Every cutaneous area, therefore, gives to the tactile sensation a " lottil color" or quality, which is spoken of as the " local sign." He assumes that this local color diminishes from point to point of the skin. This gradation is very sudden in those parts of the skin where the sense of space is very acute, but occurs very gradually where the sense of space is 54 B. xpenmcnt. 850 THE PRESSURE SENSE. more obtuse. Separate impressions unite into a common one, as soon as the gradation of the U)cal color becomes imperceptible. By practice and attention differences of sensation are experienced, which ordinarily are not observed, so that he e.xpUins the diminution of the circles of sensation by practice. The circle of sensation is an area of the skin, within which the local color of the sensa- tion changes so little that two separate impressions fuse into one. 427. THE PRESSURE SENSE.— By the sense of pressure we obtain a knowledge of the amount of weight or pressure which is being exercised at the time on the different parts of the skin. Methods. — i. Place, on the part of the skin to be investigated, different weights, one after the other, and ascertain what perceptions they give rise to, and the sense of the difterence of pressure to which they give rise. We must be careful to exclude differences of temperature and prevent the displacement of the weights — the weights must always be placed on the same spot, and the skin should be covered beforehand with a plate, while the muscular sense must be eliminated (§ 430). Fig. 543. 1 balance for testing the pressun [This is done by supporting the hand or part of the skin which is being tested, so that the action of all the muscles is excluded.] 2. A process is attached to a balance and made to touch the skin, while by placing weights in the scale pan or removing them, we test what differences in weight the person experimented on is able to distinguish (Dohrn). 3. In order to avoid the necessity of changing the weights, A. Eulenberg invented his bar£esthesiometer, which is constructed on the same principle as a spiral spring paper clip or balance. There is a small button which rests on the skin and is depressed by the spring. An index shows at once the pressure in grammes, and the instrument is so arranged that the pressure can be very easily varied. 4. Goltz uses a pulsating elastic tube, in which he can produce waves of different height. He tested how high the latter must be before they are experienced as pulse waves, when the tube is placed upon the skin. 5. Landois uses a mercurial balance (Fig. 543). The beam of a balance (W) moves upon two knife edges (O, O), and is carried on the horizontal arm |ii) of a heavy support (T). One arm of the beam is provided with a screw (/n) on which an equilibrating weight (S) can be moved. The RESULTS OF THE PRESSURE SENSE. 851 other arm (d) passes into a vertical calibrated tube (R). Below this is the pressure pad (Pi, which can be loaded as desired by a weight (G). and which can be placed upon the part of the skin to be tested (H). From an adjoining burette (B) held in a clamp (A), mercury can pass through a tube in the direction of the arrows, to one part of the balance and into the tube (R). On the stop-cock (/;) being closed, whenever pressure is exerted on the tube | D, I)),the mercury rises through d into R, and increases the pressure on P. We measure the weight of the mercury corresponding to each division of the tube (R). This instrument enables rapid variations of the weight to be made with- out giving rise to any shock. In estimating both the pressure sense and temperature sense, it is best to proceed on the principle of " the least perceptible difference," i.e., the different pressures or tem- peratures are graduated, either beginning with great differences, or proceeding from the smallest difference, and determining the limit at which the person can distinguish a difference in the sensa- tion. Results. — I. The smallest perceptible pressure, when applied to different parts of the skin, varies very greatly according to the locality. The greatest acuteness of sensibility is on the forehead, temples, and the back of the hand and forearm, which perceive a pressure of 0.002 grm. ; the fingers first feel with a weight of 0.005 'o 0.015 grm. ; the chin, abdomen, and nose with 0.04 to 0.05 grm. ; the finger nail i grm. {^Kammler and Aubert). The greater the sensibility of the skin, the more rapidly can single stimuli succeed each other, and still be perceived as single impressions; 52 stimuli per second may be applied to the volar side of the upper arm, 61 on the back of the hand, 70 to the tips of the fingers, and still be felt singly i^Bloch). 2. Intermittent variations of pressure, as in Goltz's tube, are felt more acutely by the tips of the fingers than with the forehead. 3. Differences between two weights are perceived by the tips of the fingers when the ratio is 29 : 30 (in the fore arm as 18.2 : 20), provided the weights are not too light or too heavy, In passing from the use of very light to heavy weights, the acuteness or fineness of the perception of difference increases at once, but with heavier weights, the power of distinguishing differences rapidly diminishes again ( E. Heriiig, Ltvwit, and Biedei-mann). This observation is at variance with the psycho-physical law of Fechner (§ 383). 4. A. Eulenberg found the following gradations in the fineness of the pressure sense : The forehead, lips, dorsum of the cheeks, and temples appreciate differ- ences of ^jj to -^^ (200 : 205 to 300 : 310 grm.). The dorsal surface of the last phalanx of the fingers, the fore arm, hand, ist and 2d phalanx, the volar surface of the hand, fore arm, and upper arm, distinguishes differences of j'lj to -^jj (200 : 220 to 220 : 210 grm.). The anterior surface of the leg and thigh are smiilar to the fore arm. Then follow the dorsum of the foot and toes, the sole of the foot, and the posterior surface of tlie leg and thigh. Dohrn determined the smallest additional weight, which, when added to i grm. already resting on the skin, was appreciated as a difference, and he found that for the 3d phalanx of the finger it was .499 grm. ; back of the foot, 0.5 grm. ; 2d phalanx, 0.771 grm. ; ist pha- lanx, 0.02 grm. ; leg, i grm. ; back of the hand, 1.156 grm. ; palm, 1.018 grm. ; patella, 1.5 grm.; fore arm, 1.99 grm.; umbilicus, 3.5 grms. ; and the back, 3.8grms. 5. Too long time must not elapse between the application of two successive weights, but 100 seconds may elapse when the difference between the weights is 4: ^ {£. ff. Weber). 6. The sensation of an after pressure is very marked, especially if the weight is considerable and has been applied for a length of time. But even light weights, when applied, must be separated by an interval of at least ^^ to -^\-^ second, in order to be perceived. When they are applied at shorter intervals, the sensations become fused. When Valentin pressed the tips of his fingers against a wheel provided with blunt teeth he felt the impression of a smooth margin, when the teeth were applied to the skin at the intervals above mentioned ; when the wheel was rotated more slowly, each tooth gave rise to a distinct impression. \'ibrations 852 RESULTS OF THE TEMPERATURE SENSE. of strings are distinguished as such when the number of vibrations is 1506 to 1552 per second (r. JVi'/tiih and Griinhageti). 7. It is remarkable that pressure produced by the uniform compression of a part of the body, e.g., by dipping a finger or arm in mercury, is not felt as such ; the sensation is felt only at the limit of the fluid, on the volar surface of the finger, at the limit of the surface of the mercury. 428. THE TEMPERATURE SENSE.— The temperature sense makes us acquainted with the variations of the lieat of the skin. The circumstance de- termining the sensation of temperature is, according to E. Hering, the tempera- ture of the thermal end organs themselves. As often as any part of the skin has a temperature above its zero, /. e., its neutral proper temperature, we feel warm ; in the opposite condition we feel cold. The one or the other sensation becomes stronger the more the temperature of the thermal end organ differs from its zero temperature. The zero temperature, however, may vary pretty rapidly from ex- ternal causes within certain limits. Methods. — To the surface of the skin objects of the same size and with the same thermal con- ductivity are apphed successively at different temperatures: i. Nothnagel uses small wooden cups with a metallic base, and filled with warm and cold water, the temperature being regislered by a thermometer placed in the cups. [2. Clinically, two test tubes filled with cold and warm water, or two spoons, the one hot and the other cold, may be used.] Results. — I. As a general rule, the feeling of cold is produced when a body applied to the skin robs it of heat ; and, conversely, we have a sensation of warmth when heat is communicated to the skin. 2. The greater the thermal conductivity of the substance touching the skin, the more intense is the feeling of heat or cold (§ 218). 3. At a temperature of i5S°-35° C., we distinguish distinctly differences of temperature of o.2°-o.i6° R. with the tips of the fingers {E. H. Weber). Tem- peratures just below that of the blood (33°-27° C. — Nothnagel) are distinguished most distmctly by the most sensitive parts, even to differences of 0.05° C. {Lin- dermann). Differences of temperature are less easily made out when dealing with temperatures of 33°-39° C, as well as between i4°-2 7° C. A temperature of 55° C, and also one a few degrees above zero, cause distinct pain in addition to the sensation of temperature. 4. The different parts of the skin also vary in the acuteness of their thermal sense, and in the following order ; Tip of the tongue, eyelids, cheeks, lips, neck, and body. The perceptible minimum Nothnagel found to be 0.4° on the breast; 0.9° on the back ; 0.3°, back of the hand ; 0.4°, palm ; 0.2°, arm ; 0.4° back of the foot; 0.5°, thigh; 0.6° leg; o.4°-o. 2°, cheek; o.4°-o.3° C, temple. The thermal sense is less acute in the middle line, e.g., the nose, than on each side of it {£. H. Weber). 5. Differences of temperature are most easily perceived when the same part of the skin is affected successively by objects of different temperature. If, however, two different temperatures act simultaneously and side by side, the impressions are apt to become fused, especially when the two areas are very near each other. [Goldschneider finds that when two cold or two warm cylinders are applied to the skin, the sensation of heal and cold can be appreciated as double at exceedingly small distances apart, e.g., cold to the forehead, cheek, or chin at 0.8 mm. apart, palm of the little finger o. i mm,] 6. Practice improves the temperature sense; congestion of venous blood in the skin diminishes it ; diminution of the amount of blood in the skin improves it (J/. Alsberg). When large areas of the skin are touched, the perception of differences is more acute than with small areas. Rapid variations of temperature produce more intense sensations than gradual changes of temperature. [Goldschneider asserts that there are special cutaneous nerves, some of which administer only to the sensation of cold, and others for that of heat, others for pressure, and, lastly, those for touch. In the " cold points " of the skin, when gently touched with a cold conical metal cylinder, only the COMMON SENSATION PAIN. 853 sensation of cold is felt, and in tlie " heat points " only heat, while such points are insensible to a gentle touch. The sensation of cold occurs at once, that of heat gradually increases, and is more diffuse. Pain cannot be discharged from these "temperature points." Illusions are very common : i. The sensations of heat and cold sometimes alternate in a para- doxical manner. ^Vhen the skin is dipped first into water at io° C. we feel cold, and if it be then dipped at once into water at l6° C. we have at first a feeling of warmth, but soon again of cold. 2. The same temperature applied to a large surface of the skin is estimated to be greater than when it is applied to a small area, (■ g., the whole hand when placed in water at 29.5° C. feels warmer than when a finger is dipped into water at 32° C. 3. Cold weights are judged to be heavier than warm ones. Pathological. — Tactile sensibility is only seldom increased (hjrperpselaphesia), but great sen- sibility to differences of temperature is manifested by areas of the skin whose epidermis is partly removed or altered by vesicants or herpes zoster, and the same occurs in some cases of locomotor ataxia ; while the sense of locality is rendered more acute in the two former cases and in erysipelas. An abnnrmal condition of the sense of locality was described by BrownSequard, where three points were felt when only two were apjjlied, and two when one was applied to the skin. Landois finds that in himself pricking the skin of the sternum over the angle of Ludovicus is always accompanied by a sensation in the knee. [.Some persons, when cold water is applied to the scalp, have a sensa- tion referable to the skin of the loins (^StirUng).'\ A remarkable variation of the sense of locality occurs in moderate poisoning with morphia, where the person feels himself abnormally large or greatly diminished. In degeneration of the posterior columns of the cord, Obersteiner observed that the patient was unable to say whether his right or left side was touched ('* AUochiria"). Ferrier observed a case where a stimulus applied to the right side was referred to the left, and vice versa. Diminution and paralysis of the tactile sense (Hypopselaphesia and Apselaphesia) occur either in conjunction with simultaneous injury to the sensory nerves, or alone. It is rare to find that one of the qualities of the tactile sense is lost, e. g., either the tactile sense or the sense of temperature — a condition which has been called '^partial taclile paralysis." Limbs which are ^^ sleeping'^ feel heat and not cold \//erzen). 429. COMMON SENSATION— PAIN.— Definition.— By the term common sensation we understand pleasant or unpleasant sensations in those parts of our bodies which are endowed with sensibility, and which are not refer- able to external objects, and whose characters are difficult to describe, and cannot be compared with other sensations. Each sensation is, as it were, a peculiar one. To this belong pain, hunger, thirst, malaise, fatigue, horror, vertigo, tickling, well-being, illness, the respiratory feeling of free or impeded respiration. Pain inay occur wherever sensory nerves are distributed, and it is invariably caused by a stronger stimulus than normal being applied to sensory nerves. Every kind of stimulation, mechanical, thermal, chemical, electrical, as well as somatic (inflammation or disturbances of nutrition) may excite pain. The last appear to be especially active, as many tissues become extremely painful during inflamma- tion (1".^'., muscles and bones), while they are comparatively insensible to cutting. Pain may be produced by stimulating a sensory nerve in any part of its course, from its centre to the periphery, but the sensation is invariably referred to the peripheral end of the nerve. This is the law of the peripheral reference of sensations. Hence, stimulation of a nerve, as in the scar of an amputated limb, may give rise to a sensation of pain which is referred to the parts already removed. Too violent stimulation of a sensory nerve in its course may render it incapable of conducting impressions, so that peripheral impressions are no longer perceived. If a sufficient stimulus to produce pain be then applied to the cen- tral part of the nerve, such an impression is still leferred to the ])eripheral end of the nerve. Thus we explain the paradoxical anaesthesia dolorosa. In con- nection with painful impressions, the patient is often unable to localize them ex- actly. This is most easily done when a small injury ( prick of a needle) is made on a peripheral part. When, however, the stimulation occurs in the course of the nerve, or in the centre, or in nerves whose peripheral ends are not accessible, as in the intestines, pain (as belly-ache), which cannot easily be localized, is the result. Irradiation. — During violent pain there is not unfrequently irradiation of the pain (§ 364, 5), whereby localization is impossible. It is rare for pain to remain continuous and uniform ; more generally there are exacerbations and diminutions of the intensity, and sometimes periodic intensification, as in some neuralgias. 854 METHODS OF TESTING PAIN THE MUSCULAR SENSE. The intensity of the pain depends especially upon the excitability of the sen- sory nerves. There are considerable individual variations in this respect, some nerves, e.g., the trigeminus and splanchnic, being very sensitive. The larger the number of fibres affected the more severe the pain. The duration is also of im- portance, in as far as the same stimulation, when long continued, may become unbearable. We speak of piercing, cutting, boring, burning, throbbing, press- ing, gnawing, dull, and other kinds of pain, but we are quite unacquainted with the conditions on which such different sensations depend. Painful impressions are abolished by anaesthetics and narcotics, such as ether, chloroform, morphia, etc. (§ 364, 5). Methods of Testing. — To test the cutaneous sensibility, we usually employ the constant or in- duced electrical current. Determine first the minimum sensibility, i.e., the strength of the current which excites the first trace of sensation, and also the minimum of pain, i.e., the feeblest strength of the current which first causes distinct impressions of pain. The electrodes consist of thin metallic needles, and are placed i to 2 cm. apart (I'ig. 375). Pathological. — When the excitability of the nerves which administer to painful sensations is in- creased, a slight touch of the skin, nay, even a breath of cold air, may excite the most violent pain, constituting cutaneous hyperalgia, especially in inflammatory or exanthematic conditions of the skin. The term cutaneous paralgia is applied to certain anomalous, disagieeable, or painful sen- sations which are frequently referred to the skin — itching, creeping, formication, cold, and burning. In cerebro-spinal meningitis, sometimes a prick in the sole of the foot produces a double sensation of pain and a double reflex contraction. Perhaps this condition may be explained by supposing that in a part of the nerve the condition is delayed (| 337, 21. In neuralgia there is severe pain, oc- curring in paroxysms, with violent exacerbations and pain shooting into other pans (p. 629). Very frequently excessive pain is produced by pressure on the nerve where it makes its exit from a fora- men or traverses a fascia. Valleix's Points Douloureux (l84i).^The skin itself to which the sensory nerve runs, espe- cially at first, may be very sensitive; and when the neuralgia is of long duration the sensibility may be diminished even to the condition of analgesia ( /"arc/J) ; in the latter case there may be pro- nounced ani"esthesia dolorosa (p. S53). Diminution or paralysis of the sense of pain (hypalgia and analgia) may be due to afTections of the ends of the nerves, or of their course, or central terminations. Metalloscopy. — In hysterical patients suffering from hemiana'Sthesia, it is found that the feeling of the paralyzed side is r-stored, when small metallic plates or larger pieces of different metals are applied to the affected parts (Buret/, Charcot). At the same time that the affected part recovers its sensibility the opposite limb or side becomes anaesthetic. This condition has been spoken of as transference of sensibility. The phenomenon is not due to galvanic currents developed by the metals. The phenomenon is, perhaps, explained by the fact that, under physiological conditions, and in a healthy person, every increase of the sensiljility on one side of the body, produced by the application of warm metallic plates or bandages, is followed by a diminution of the sensibility of the opposite side. Conversely, it is found that when one side of the body is rendered less sensitive by the application of cold plates, the homologous part of the other side becomes more sensitive (Rumpf and M. Rosenthal). 430. THE MUSCULAR SENSE.— Muscular Sensibility.— The sen- sory nerves of the muscles (§ 292) always convey to us impressions as to the activ- ity or non-activity of these organs, and in the former case these impressions enable us to judge of the degree of contraction. It also informs us of the amount of the contraction to be employed to overcome resistance. Obviously, the muscular sense must be largely supported and aided by the sense of pressure, and conversely. E. H. Weber showed, however, that the muscle sense is finer than the pressure sense, as by it we can distinguish weights in the ratio of 39 : 40, while the pressure sense only enables us to distinguish those in the ratio of 29 : 30. In some cases there has been observed total cutaneous insensibility, while the muscular sense was retained completely. A frog deprived of its skin can spring without any apparent disturbance. The muscular sense is also greatly aided by the sensibility of the joints, bones arid fasciae. Many muscles, e.g., those of respiration, have only slight muscular sensibility, while it seems to be absent normally in the heart and non-striped muscle. [The muscular sense stands midway between special and common sensations, and by it we obtain a knowledge of the condition of our muscles, and to what METHODS OF TESTING THE MUSCULAR SENSE. 855 extent they are contracted ; also the position of the various parts of our bodies and the resistance offered by external objects. Thus, sensations accompanying muscular movement are twofold — (n) the movements in the unopposed muscles, as the movements of the limbs in space; and (l>) those of resistance where there is opposition to the movement, as in lifting a weight. In the latter case the sen- sations due to innervation are important, and, of course, in such cases we have also to take into account the sensations obtained from mere pressure upon the skin. Our sensations derived from muscular movements depend on the direction and duration of the movements. On the sensations thus conveyed to the senso- rium we form judgments as to the direction of a point in space, as well as of the distance between two points in space. This is very marked in the case of the ocular muscles. It is also evident that the muscular sense is ultimately related to, and often combined with, the exercise of the sensations of touch and sight iSully\-\ Methods of Testing. — Weights are wrapped in a towtl and suspended to the part to be tested. The patient estimates the weight by raising and lowering it. The electro-muscular sensibility also may be proved thus : cause the muscles to contract by means of induction shocks, and observe the sensation thereby produced. [Direct the patient to place his feet together while standing, and then close his eyes. A healthy person can stand quite steady, but in one with the muscular sense im- paired, as in locomotor ataxia, the patient may move to and fro, or even fall. Again, a person with his muscular sense impaired may not be able to touch accurately and at once some part of his body when his eyes are closed.] Section of a sensory nerve causes disturbance of the fine gradation of movement (p. 646). Meynert supposes that the cerebral centre for muscular sensibility lies in the motor cortical centres, the muscles being connected by motor and sensory paths with the ganglionic cells in these centres. Too severe muscular exercise causes the sensation of fatigue, oppression and weight, in the limbs (§ 304). Pathological. — Abnormal increase of the muscular sense is rare [^muscular hyperlagia and hyperiTsthesia), as in anxietas tibianim, a painful condition of unrest which leads to a continual change in the position of the limbs. In cramp there is intense pain, due to stimulation of the sensory nerves of the muscle, and the same is the case in inflammation. Diminution of the mus- cular sensibility occurs in some choreic and ataxic persons {\ 364, 5). In locomotor ataxia the muscular sense of the upper extremities may be normal or weakened, while it is usually consider- ably diminished in the legs. [The muscular sense is said to be increased in the hypnotic condition and in somnambulists.] REPRODUCTION AND DEVELOPMENT. 431. FORMS OF REPRODUCTION.— I. Abiogenesis (Generatio fcquivoca, sive spon- tanea, spontaneous generation). — It was formerly assumed that, under certain circumstances, non-living matter derived from the decomposition of organic materials became changed sponta- neously into living beings. While Aristotle ascribed this mode of origin to insects, the recent observers who advocate this form of generation restrict its action solely to the lowest organism. Experimental evidence is distinctly against spontaneous generation. If organized matter be heated to a very high temperature in sealed tubes, and be thus deprived of all living organisms or their spores, there is no generation of any organism. Hence the dictum " Ornne vh'itm ex ovo " {^Harvey^ or ex viva). Some highly-organized invertebrate animals (Gordius, Anguillula, Tardigrada, and Rotatoria) may be dried, and even heated to 140° C, and yet regain their vital activities on being moistened (Anabiosis). II. Division or fission occurs in many protozoa (amoeba, infusoria). The organism, just as is the case with cells, divides, the nucleus, when present, taking an active part in the process, so that two nuclei and two masses of protoplasm, forming two organisms, are produced. Tlie Ophidiasters, among the echinoderms, divide spontaneously, and they are said to throw off an arm which may develop into a complete animal. According to Trembley (1744), the hydra may be divided into pieces, and each piece gives rise to a new individual [.althbugh under normal circumstances the hydra gives oft" buds, and is provided with generative organs]. [Division of Cells. — Although a cell is defined as a " nucleated mass of living protoplasm," recent researches have shown that, from a histological point of view, a cell is really a very complex structure. The apparently homogeneous cell substance Fig. 544. is traversed by a tine plexus of fibrils, with a homoge- neous substance in its meshes, while a similar network of fibrils exists within the nucleus itself (Fig. 544). A cell may divide directly, as it were, by simple cleavage, and in the process the nucleus usually divides before the cell protoplasm. The nucleus becomes constricted in the centre, has an hourglass shape, and soon divides into two. But recent observations, confirmed by a great number of investigators, conclusively prove that the pro- cess of division in cells is a very complicated one, the Changes in a cell nucleus during karyokinesis. changes in the nucleus being very remarkable. The term karyokinesis, or indirect division, has been applied to this process. Fig. 544 shows the changes that take place in the nucleus. The intranuclear network {a) passes into a convolution of thinner fibrils, while the nuclear envelope becomes less distinct, the fibrils at the same time becoming thicker and forming loops, which gradually arrange themselves around a centre {c and d) in the form of a wreath or rosette. The fibres curve round both at the periphery and the centre; but when their peripheral connections are severed or dis- solved, we obtain a star-shaped form, or aster, composted of single loops radiating from the centre (c). After further subdivision, the whole is composed of fine radiating fibrils (/), which gradually arrange themselves around two poles, or new centres, to form a diaster, or double star ([,'), the two groups being separated by a substance called the equatorial plate. Each of the groups of fibrils becomes more elongated, and forms a nuclear spindle, which indicates the position of a new nucleus. The separate groups of fibrils again become convoluted ; each group gets a nuclear membrane, while the cell protoplasm divides, and two daughter nuclei are obtained from the original cell.] III. Budding or gemmation occurs in a well-marked form among the polyps and in some in- fusorians (Vorticella). A bud is given oflT by the parent, and gradually comes more and more to resemble the latter. The bud either remains permanently attached to the parent, so that a complex organism is produced, in which the digestive organs communicate with each other directly, or in some cases there may be a " colony " with a common nervous system, such as the polyzoa. In .some composite animals (siphonophora) the difl'erent polyps perform different functions. Some have a digestive, others a motor, and a third a generative function, so that there is a physiological division of labor. Buds which are given off from the parent are formed internally in the rhizopoda. In some animals (polyps, infusoria), which can reproduce themselves by buds or divisions, there is also 85« TESTIS. 857 the formation of male and female elements of generation, so that they have a sexual and non sexual mode of reproduction. IV. Conjugation is a form of reproduction which leads up to the sexual form. It occurs in the unicellular Gregarinae. The anterior end of one such organism unites with the posterior end of another ; both become encysted, and form one passive spherical body. The conjoined structures form an amorphous mass, from which numerous globular bodies are formed, and in each of which numerous oblong structures — the pseudo-navicelli — are developed. These bodies become, or give rise to, an amoeboid structure, which forms a nucleus and an envelope, and becomes transformed into a gregarina. Sexual reproduction requires the formation of the embryo from the conjunction of the male and female reproductive elements, the sperm cell and the germ cell. These products may be formed either in one individual (hermaphroditism, as in the flat worms and gasteropods), or in Iwo separate organisms (male or female). Sexual reproduction embraces the following varieties: — V. Metamorphosis is that form of sexual reproduction in which the embryo from an early period undergoes a series of marked changes of external form, e. i^., the chrysalis stage, and the pupa stage, and in none of these stages is reproduction possible. Lastly, the final sexually developed form (the imago stage in butterflies) is produced, which forms the sexual products whose union gives rise to organisms which repeat the same cycle of changes. Metamorphosis occurs extensively among the insects; some of them have several stages (holo-metabolic), and others have few stages (hemimetabolic). It also occurs in some arthropoda, and woims, c.^., trichina; the sexual form of the animal occurs in the intestine, the numerous larzue wander into the muscles, where they become encysted, and form undeveloped sexual organs, constituting the pupa stage of the muscular trichina. When the encysted form is eaten by another animal, the sexual organs come into activity, a new brood is formed, and the cycle is repeated. Metamorphosis also occurs in the frog and in petromyzon. [This is really a condition in which the embryo undergoes marked changes of form before it becomes sexually mature.] VI. Alternation of Generations (Steensfrup). — In this variety some of the members of the cycle can produce new beings nonsexually, while in the final stage reproduction is always sexual. From a medical point of view the life-history of the tapeworm or Taenia is most important. The segments of the tapeworm are called proglottides, and each segment is hermaphrodite, with testes, vas deferens, penis, ovary, etc., and numerous ova. The segments are evacuated with the fieces. The eggs are fertilized after they are shed, and from them is developed an elliptical embryo, pro- vided with six booklets, which is swallowed by another animal, the host. These embryos bore their way into the tissues of the host, where they undergo development, forming the encysted stage (Cysficercus, Coenurus, or Echinococcus). The encysted capsule may contain one (cysticercus) or many (coenurus) sessile heads of the t:enia. In order to undergo further development, the cysti- cercus must be eaten alive by another animal, when the head or scolex fixes itself by its booklets and suckers to the intestine of its new host, where it begins to bud and produce a series of new segments between the head and the last-formed segment, and thus the cycle is repeated. The most important flat worms are : Taenia solium, in man ; the Cysticercus cellulose in the pig, where it constitutes the measle in pork; Ttenia mediocanellala, the encysted stage, in the ox; Tcenia toenurus, in the dog's intestine ; the encysted stage, or Coenurus cerebralis, in the brain of the sheep, where it gives rise to the condition of "staggers;" Tccnia echinococcus, in the dog's intestine; the embryos or scolices occur in the liver of man as " hydatids." The medusii! also exhibit alternation of generations, and so do some insects, especially the plant lice or aphides. VII. Parthenogenesis (Owen v. Siebolcf). — In this variety, in addition to sexual reproduction, new individuals may be produced without sexual union. The non-sexually produced brood is always of one sex, as in the bees. A bee-hive contains a queen, the workers, and the drones or males. During the mutual flight the queen is impregnated by the males, and the seminal fluid is stored up in the receptaculum seminis of the queen, and it appears that the queen may voluntarily pennit the contact of this fluid with the ova or withhold it. All fertilized eggs give rise to female, and all un- fertilized ones to male bees. VIII. Sexual reproduction without any intermediate stages occurs in, besides man, mammals, birds, reptiles, and most fishes, 432. TESTIS— SEMINAL FLUID.— [Testis.— In the testis or male reproductive organ, the seminal fluid which contains the male element or spermatozoa is formed. The framework of the gland consists of a thick, strong, white fibrous covering, the tunica albuginea, composed chiefly of white interlacing fibrous tissue. Externally this layer is covered by the visceral layer of the serous membrane, or the tunica vaginalis, which invests the testis and epididymis. The tunica albuginea is prolonged for some distance as a vertical septum into the posterior part of the testis, to form the mediastinum testis or corpus Highmori. Septa or trabeculte — more or less complete — stretch from the under surface of the T. albuginea toward the mediastinum, so that the organ is subdivided thereby into a number of compartments or lobules, with their bases directed outward and their apices toward the media-stihum. From these, finer sustentacular fibres pass into the com- partments to support the structures lying in these compartments. ] 858 STRUCTURE OF A SEMINAL TUBULE. [Arrangement of Tubules. — Each compartmenl contains several seminal tubules, long con- voluted tubules (y^5 in. in diam.) which rarely branch except at their outer end ; they are about two feet in length and exceed 800 in number. These tubules run toward the mediastinum, those in one compartment uniting at an acute angle with each other, to form a smaller number of narrower, straight tubules— tubuli recti (Fig. 546). These straight tubules open into a network of tubules in the mediastinum to form the rete testis, a dense network of tubules of irregular diameter (Fig. 546). From this network there proceed 12 to 15 wider ducts — the vasa efferentia — which after emerging from the testis are at first straight, but soon become convoluted — and form a series of conical eminences — the coni vasculosi — which together form the head of the epididymis. These tubes gradually unite with each other and form the body and globus minor of the epididymis, Seminal tubules c ^ Transverse section of the testis (low-power view). which, when unraveled, is a tube about 20 feet long terminating in the vas deferens (2 feet long), which is the excretory duct of the testis]. [Structure of a Tubule. — The seminal tubules consist of a thick, well-marked basement membrane, composed of flattened, nucleated cells arranged like membranes (Fig. 550, I). These tubes are lined by several layers of more or less cubical cells ; there is an outer row of such cells next the basement membrane, and often showing a dividing large nucleus. Internal to these are several layers of inner large clear cells with nuclei often dividing, so that they form many daughter cells which lie internal to them and next the lumen. From these daughter cells are formed the spermatozoa, and they constitute the spermatoblasts. These several layers of cells leave a CHEMICAL COMPOSITION OF THE SEMINAL FLUID. 859 distinct lumen. The tubuli recti are narrow in diameter, and lined by a single layer of squamous or flattened epithelium (Fig. 546). The rete testis consists merely of channels in the fibrous stroma without a distinct membrana propria, but lined bytlallened epithelium. The vasa efferentia and cotii vasculosi have circular smooth muscular fibres in their walls, and are lined by a layer of columnar ciliated epithelium with striated protoplasm. At the bases of these cells in some parts ' is a layer of smaller granular cells. These tubules form the epididymis, whose tubules have the same structure (Fig. 547). In the sheep pigment cells are often found m the basement mem- brane. The vas deferens is lined by several layers of columnar epithelium re>ting on a dense layer of fibrous tissue — the mucosa. Outside this is the muscular coat, a thick layer of non- striped muscle composed of a thick inner circular, and ihick outer loni^iliidinal layer, a ihin sub- mucous coat connecting the muscular and mucous coats together; outside all is the fibrous adventitia.] [The interstitial tissue (Fig. 545), supporting the seminal tubules, is laminated, and covered by endothelial plates, with slits or spaces between the I imells, which form the origin of the lym- phatics. These lymph spaces are easily injected by the puncture method. In fact, if Berlin blue be forced into the testis the lymphatics of the testis and spermatic cord are readily filled with the injection. In some animals (boar), and a less extent in man, dog, there are also fairly large poly- hedral interstitial cells, often with a large nucleus and sometimes pigmented. They represent the residue of the epithelial cells of the Wolffian bodies (Klein), or, according to Waldeyer, they Fig. 546. Fig. 547. Transverse section nf a lube of epididymis. are plasma cells. The blood vessels are numerous, and form a dense plexus outside the base- ment membrane of the seminal tubules.] Chemical Composition. — The seminal fluid, as discharged from the urethra, is mixed with the secretion of the glands of the vas deferens, Cowper's glands, and those of the prostate, and with the fluid of the vesiculse seminales. Its reaction is neutral or alkaline, and it contains 82 per cent, of water, serum- albumin, alkali-albuminate, nuclein, lecithin, cholesterin, fats (protamin?), phos- phorized fat, salts (2 per cent.), especially phosphates of the alkalies and earths, together with sulphates, carbonates, and chlorides. The odorous body, whose nature is unknown, was called "■ sper matin" by Vanquelin. Seminal Fluid. — The sticky, whitish-yellow seminal fluid, largely composed of a mixture of the secretions of the above-named glands, when exposed to the air, becomes more fluid, and on adding water it becomes gelatinous, and from it separates whitish, transparent flakes. When long exposed, it forms rhomboidal crystals, which, according to Schreiner, consist of phosphatic sails with an organic base (CjHjN). ' These crystals ^Fig. 548) are said to be derived from the pros- 860 DEVELOPMENT OF SPERMATOZOA. permatK tatic fluid, and are identical with the so-called Charcot's crystals (Fig. 144, c, and ^ 138). The prostatic tluid is thin, milky, amphoteric, or of slightly acid reaction, and is possessed of the seminal odor. The phosphoric acid necessary for the formation of tlie crystals is obtained from the seminal fluid. A somewhat similar odor occurs in the albumin of eggs not quite fresh. The secretion of the vesiculae seminales of the guinea pig contains much fibrinogen (Hcnsen and Landwehr). The spermatozoa are 50 /z long, and consist of a flattened, pear-shaped head (Fig. 549, I and 2, k), which is followed by a rod-shaped middle piece, m (Schweigger-Seiiiel), and a long tail-like Fig. 548. prolongation or cilium, /. The whole spermatozoon is propelled forward by the to-and-fro movements of the tail at the rate of 0.05 to 0.5 mm. per second ; the movement is most rapid immediately after the fluid is shed, but it gradually becomes feebler. Finer Structure. — The observations of Jensen have shown that the middle piece and head are still more complex, although this is not the case in human spermatozoa and thoseof tlie bull [G. I\et- zius). These consist of a flattened, long, narrow, transparent, protoplasmic mass, with a fibre com- posed of many delicate threads in both margins. M the tip of the tail both fibres unite into one. The fibre of the one margin is gentrally straight ; the other is thrown into wave-like folds, or winds in a spiral manner round the other ( ]V. A'raiise, Gi/i/'es). G. Retzius describes a special terminal filament (Fig. 549, <■). An axial thread, sur- rounded by an envelope of protoplasm, traverses the middle piece and the tail (Eimcr, v. Braun). [Leydig showed that in the salamander there is a delicate membrane attaclied to the tail, and Gibbes lias described a spiral thread attached to the head (nevvtl and connected with the middle piece by a hyaline memlirane.] Motion of the Spermatozoa. — [.^fter the discharge of the .seminal fluid, the spermatozoa ex- hibit spontaneous movements for many hours or days.] The movements are due to the lashing movements of the tail, which moves in a circle or rotates on its long axis, the impulse to movement proceeding from the protoplasm of the middle piece and the tail, which seem to be capable of mov- ing when they are detached {Eiiiwr). These movements are comparable to those that occur in cilia (J 292), and there are transition forms between ciliary and amceboid movements, as in the Monera. Reagents. — Within the testis they do not exhibit movement, as the fluid is not sufficiently dilute to permit them to move. Their movements are specially lively in the normal secretion of the female sexual organs [Bischoff), and they move pretty freely, and for a long time, in all normal animal secretions except saliva. Their movements are paralyzed by water, alcohol, ether, chloro- form, creosote, gum. dextrin, vegetable mucin, syrup of grape sugar, or very alkaline or acid uterine orvaginal mucus (Donne), acids and metallic salts, and a too high or too low temperature. The narcotics, as long as they are chemically indifferent, behave as indifferent fluids, and so do medium solutions of urea, sugar, albumin, common salt, glycerin, amygdalin, etc. ; but if these be too dilute or too concentrated, they alter the amount of water in the spermatozoa and paralyze them. The quiescence produced by water may be set aside by dilute alkalies ( Virc/ioni), as with cilia (p. 491 ). Engelmann finds that minute traces of acids, alcohol, and ether excite movements. The sperma- tozoa of the frog may be frozen four times in succession without killing them. They bear a heat of 43.75° C, and they will live for 70 days when placed in the abdominal cavity of another frog (Aluntegazza). Resistance. — Owing to the large amount of earthy salts which they contain, when dried upon a microscopical slide they still retain their form ( I'li/entin). Their form is not destroyed by nitric, sulphuric, hydrochloric, or boiling acetic acid, or by caustic alkalies; solutions of NaCl and salt- petre (10 to 15 per cent.) change them into amorphous masses. Their organic basis resembles the semi-solid albumin of epithelium. .Seminal fluid, besides spermatozoa, also contains seminal cells, a few epithelial cells from the seminal passages, numerous lecithin granules, stratified amyloid bodies (inconstant), granular yellow pigment, especially in old age, leucocytes, and sperma crystals (Fiirhiitgcr). Development of Spermatozoa. — The walls of the seminal tubules, n, which are made up of spindle-shaped cells, are lined by a nucleated, protoplasmic layer DEVELOPMENT OF SPERMATOZA. 861 (Fig. 550, I, b, and IV, h), from which there project into the lumen of the tube, long (0.053 mni.) column-like prolongations, (I, c, and II, III, IV), which break Fig. 549. , human (X 600), the head seen Irom the side ; 2, on edge : k, head ; ;«, middle piece ; /, tail : e, ter- minal filament ; 3, from the mouse ; 4, bothriocephalus latus ; 5, deer : 6, mole ; 7, green woodpecker ; 8, black swan ; 9, from a cross between a goldfinch (M) and a canary (Fj ; 10, from cobitis. up at their free end into several round or oval lobules (II) — the spermatoblasts {v. Ehner^ ; these consist of soft, finely granular protoplasm, and usually have an oval nucleus in their lower part. During development, each lobule of the sper- FiG. 550. Semi-diagrammatic spermatogenesis: I, transverse section of a seminal tubule — «, membrane ; <^, protopla lining ; c, spermatoblast ; s, seminal cells. II, Unripe spermatoblast—:/", rounded cleavate lobules ; ft, semn.al cells. IV, spermatoblast, with ripe spermatozoa {k) not yet detached ; tail, r ; «, wall of the seminal tubule ; k, its protoplasmic layer. Ill, spermatoblast with a spermatozoon free, t. niatoblast elongates into a tail (IV, r), while the deeper part forms the head and middle piece of the future spermatozoon (IV, k). At this stage the spermatoblast 862 STRUCTURE OF THE OVARY. is like a greatly enlarged, irregular, cylindrical, epithelial cell. When develop- ment is complete, the head and middle piece are detached (III, i), and ultimately the remaining part of the spermatoblast undergoes fatty degeneration. Not un- frequently in spermatozoa we may observe a small mass of protoplasm adhering to the tail and the middle piece (III, /). Between the spermatoblasts are numerous round amoeboid cells devoid of an envelope, and connected to each other by pro- cesses. They seem to secrete the Jl/a'd part of the semen, and they may, therefore, be called seminal cells (I, s, II, III, IV, /). A spermatozoon, therefore, is a detached, independently mobile cilium of an enlarged epithelial cell. Some observers adhere to the view that the spermatozoa are, in part, at least, formed within round cells, by a process of endogenous development. Shape. — The spermatozoa of most animals are like cilia with larger or smaller heads. The head is eUiptical (mammals), or pear-shaped (mammals), or cylindrical (birds, amphibians, fish), or cork- screw (singing birds, paludina), or merely like hairs (insects — Fig. 549). Immobile seminal cells, quite ditTerent from the ordinary forms, occur in mynapoda and the oyster. 433. THE OVARY— OVUM— UTERUS.— [Structure of the Ovary (Fig. 551).— The ovary consists of a connective-tissue framework, with blood vessels, nerves, lymphatics, and numer- ous non-striped muscular fibres. The ova are embedded in this matrix. The surface of the ovary is covered with a layer of columnar epithelium (Fig. 552, e), the remains of the germ epithelium. Fig. 551. it's ovary. The pi I corpus luteum. The most superficial layer is called the albuginea ; it does not contain any ova. Below it is the cortical layer of Schron, which contains the smallest Graafian follicles (^^5 inch — Fig. 551), while deeper down are the larger follicles (^'^ to i-Jj inch). There are 40,000 to 70,000 follicles in the ovary of a female infant. Each ovum lies within its follicle or Graafian vesicle.] Structure of an Ovum. — The human ovum {C. E. v. Baer, iS^-j) is 0.18 to 0.2 mm. [yjj in.] in diameter, and is a spherical, cellular body with a thick, solid, elastic envelope, the zona pellu- cida, with radiating strise. The zona pellucida encloses the cell contents, represented by the pro- toplasmic, granular, contractile vitellus or yelk, which in turn contains the eccentrically-placed spherical nucleus or germinal vesicle (40-50 /i — Purkinje, iS^s : Coste, 1SJ4). The germinal vesicle contains the nucleolus or germinal spot (5-7 /i — H. Wagner, /Sjj). The chemical com- position is given in | 232. [Ovum. Cell. Zona pellucida corresponds to the Cell wall. Vitellus '• " Cell contents. Germinal vesicle " " Nucleus. Germinal spot " " Nucleolus.] [This arrangement shows the corresponding parts in a cell and the ovum, snd in fact the ovum represents a typical cell] The zona pellucida (Fig. 553, V, Z), to which cells of the Graafian follicle are often adherent, is a cuticular membrane formed secondarily by the follicle IPJUiger). .According to van Beneden, it is lined by a tliin membrane next the vitellus, and he regards the thin membrane as the original cell membrane of the ovum. The fine radiating .stri;e in the zona are said to be due to the exist- DEVELOPMENT OF THE OVA. 863 ence of numerous canals {Kolliker, v. Sehleti). It is still undecided whether there is a special niicropyle or hole for the entrance of the spermatozoa. A micropyle has been observed in some ova (holothurians, many fishes, mussels). The ova of some animals (many insects, e.g.^ the flea) have porous canals in some part of their zona, and these serve both for the entrance of the spermatozoa and for the respiratory exchanges in the ovum. The development of the ova takes place in the following manner : The surface of the ovary is covered with a layer of cylindrical epithelium — the so- called " germ epithehum " — and between these cells lie, somewhat spherical, "primordial ova" (Fig. 553, I, a, a). The epithelium covering the surface dips into the ovary at various places to form " ovarian tubes" { IVa/deyer). These tubes, from and in which the ova are developed ( Wahieyer), become deeper and deeper, and they contain, in their interior, large, single spherical cells with a nucleus and a nucleolus, and other smaller and more numerous cells lining the tube. The large cells are the cells (primordial ova) that are to develop into ova, while the smaller cells are the epithelium of the tube, and are direct con- tinuations of the cyhndrical epithelium on the surface of the ovary. The upper extremities of the tubes become closed, while the tube itself is divided into a Section of an ovarj-, e, genu t.\ luicjuuti . i, l.irgc ^i7cd f ■llii.lcb . 2, 2, middle-sized, and 3, 3, smaller-sized follicles ; (7, ovum withm a Graahan fulliclc , v, v, blood vesseU of the stroma , ff, cells of the membrana granulosa. number of rounded compartments — snared off, as it were, by the ingrowth of the ovarian stroma (I, c'). Each compartment so snared off usually contains one, or, at most, two, ova (IV, o, o), and becomes developed into a Graafian follicle. The embryonic follicle enlarges, and fluid appears within it ; while its lateral small cells become changed into the epithelium lining the Graafian follicle itself, or those of the membrana granulosa. The cells of the membrana granulosa form an elevation at one part — the discus proligerus — by which the ovum is attached to the membrana granulosa. The follicles are at first only 0.03 mm. in diameter, but they become larger, especially at puberty. [The smaller ova are near the surface of the ovary, the larger ones deeper in its substance (Fig. 551). When a Graafian follicle with its ovum is about to ripen (IV), it sinks or passes down- ward into the substance of the ovary, and enlarges at the same time by the accu- mulation of fluid — the liquor foUiculi — between the tunica and membrana granulosa. It is covered by a vascular outer membrane — the theca foUiculi — which is lined by the epithelium constituting the membrana granulosa (IV, g). When a GraaRan follicle is about to burst, it again rises to the surface of 864 DEVELOPMENT OF THE OVA. the ovary, and attains a diameter of i.o to 1.5 mm., and is now ready to burst and discharge its ovum. [The tissue between the enlarged Graafian follicle and the surface of the ovary gradually becomes thinner and thinner and less vascular, and at last gives way, when the ovum is discharged and caught by the fimbriated extremity of the Fallopian tube embracing the ovary, so that the ovum is shed into the Fallopian tube itself.] Only a small number of the Graafian follicles undergo development normally, by far the greatest number atrophy and never ripen. (The study of the development of the ova and ovary was advanced par- ticularly by Martin Barry, Pfliiger, Billroth, Schron, His, Waldeyer, Kolliker, Koster, Lindgren, Schulin, Foulis, Balfour and others.) .According to Waldeyer, the mammalian ovum is not a simple cell, but a compound structure. The original primitive ovum is, according to him, formed only of the germinal vesicle and ger- FiG. 553. 1 tube in process of development (new-born girl), a, a, young surface of the ovary ; (i, the ovarian tube with ova and epithelial cells ; c an ovum. II, Open ovarian tube from a bitch. Ill, Isolated primordial < two ova {o, 0) and the tunica granulosa (.^) of a bitch. V, Part of the zona pellucida ; d^ vitellus , e, adherent cells of the membrana granulosa. Formation of the second polar globule {Fol). the epithelial cells on the a small follicle cut off and enclosing ■um (human). IV, Older follicle with irface ol a ripe ovum of a rabbit — z, VI, First polar globule formed. VII, minal spot, with the surrounding membranous clear part of the vitellus (Fig. 553, III). The remainder of the vitellus is developed by the transformation of granulosa cells, which also form the zona pellucida. Holoblastic and Meroblastic Ova. — The ova of frogs and cyclostomata are built on the same type as mammalian ova; they are called holoblastic ova, because all their contents go to form cells which take part in the formation of the embryo. In contrast with these, the birds, the mono- tremes alone among the mammals (CuUwell), the reptiles, and the other fishes have meroblastic ova [Jieichert). The latter, in addition to the white or formative yelk, which corresponds to the yelk of the holoblastic eggs, and gives rise to the embryonic cells, contains the food yelk (yellow in birds), and which during development is a reserve store of food for the developing embryo. Hen's Egg. — The small, white, round, finely granular speck, the cicatricula, blastoderm, or tread, which is 2.5-3.5 "i™- broad and 0.2S-0.37 thick, lying upon the surface of the yellow yelk, corresponds to the contents of the mammalian ovum, and is, therefore, the formative yelk. [The STRUCTURE OF A HEN S EGG. 865 cicatricula in an unincubated egg is always uppermost whatever the position of the egg, provided the contents can rotate freely, and this is due to the lighter specific gravity of that part of the yell< in connection with the cicatricula. In a fecundated egg the cicatricula has a white margin (the area opaca), surrounding a clear, transparent area, the beginning of the area pellucida, containing an opaque spot in its centre. If an egg be boiled very hard and a section mad:: of the yelk, it will be found to consist of alternating layers of white and yellow yelk. The outermost layer is a thin layer of white yelk, which is slightly thicker at the margin of the cicatricula. Within the centre of the yelk is a flask-shaped mass of white yelk, the neck of the flask being connected with the white yelk outside. This flask-shaped mass does not become so hard on being boiled, and its upper, expanded end is known as the " nucleus of Pander " The great mass of the yelk is made up, however, of yellow yelk] Microscopically, the yellow yelk consists of soft, yellow spheres, of from 23-100 ft in diameter, and they are often polyhedral from mutual pressure. [They are very delicate and non-nucleated, but filled with fine granules, which are, perhaps, proteid in their nature, as they are insoluble in ether or alcohol. Thev are developed by the proliferation of the granulosa cells of the Graafian follicle, which also seem ultimately to form the granulo-fibrous double envelope or the vitelline membrane (Eimer). The whole yelk of the hen's egg is regarded by some ob- FlG. 554. Vertical section of the ular glands ; membrane of the human uterus, e, columnar epithelium, the cilia absent; ffg, utric- i-glandular connective tissue ; v, v, blood vessels ; mm, mu^cularis mucosz. servers as equivalent to the mammalian ovum plus the corpus luteum. Microscopically, the white yelk consists of small vehicles (5-75 f^) containing a refractive substance, and larger spheres con- taining several smaller spherules. The whole yelk is enveloped by the vitelline membrane, which is transparent, but possesses a fine fibrous structure, and it seems to be allied to elastic tissue.] When the yelk is fully developed within the Graafian follicle of the hen's ovarium, the follicle bursts and discharges the yelk, which passes into the oviduct, where in its passage it rotates, owing to the direction of the folds of the mucous membrane of the oviduct. The numerous glands of the oviduct secrete the albumin, or white of the egg, which is deposited in layers around the yelk in its passage along the duct, and forms at the anterior and posterior poles the chalazae. [The chalazae are two twisted cords composed of twisted layers of the outer, denser part of the albumin. They extend from the poles of the yelk not quite to the outer part of the albumin.] [The albumin is invested by the membrana testacea, or shell membrane, which is composed of two layers — an outer thicker and an inner thinner one. Over the greater part of the albumin these two layers are united, but at the broad end of the hen's egg they tend to separate, and air passing through the porous shell separates them more and more as the fluid of the egg evaporates. This air space is not found in fresh-laid eggs.] The layers consist of spontaneously coagulated keratin-like fibres arranged in a 55 866 PUBERTV'. spiral manner around the albumin (Lindvall and Haviarsicti). [External to this is the test, or shell, which consists of an organic matrix impregnated with lime salts.] The shell consists of albumin impregnated with lime salts, which form a very jxirous mortar. [The shell is porous, and its inner layer is perforated by vertical canals, through which the respiratory exchange of the gases can lake place.] In the eggs of some birds there is an outer structureless, porous, slimy, or fatty cuticula. The shell is secreted in the lower part of the oviduct. The shell is partly used up for the development of the bones of the chick ( Front, Gruwe, although this is denied by Poll and Preyer). The pigment which often occurs in many layers on the surface of the eggs of some birds appears to be a derivative of hssnioglobin and biliverdin. Chemical Composition.— The yellow yelk is alkaline and colored yellow, owing to the presence of lutein, which contains iron. It contains several proteids [including a globulin body called vitellin (p. 409)], a body resembling nuclein, lecithin, vitellin, glycerin-phosphoric acid, cholesterin, olein, palmitin, dextrose, potassic chloride, iron, earthy phosphates, fluoric and silicic acids. The presence of cerebrin, glycogen, and starch is uncertain. [Dareste states that starch is present.] [The albumin of egg contains— water, 86 per cent.; proteids, 12; fat and extractives, 1. 5; saline matter, including sodic and potassic chlorides, phosphates, and sulphates, .5 per cent.] [The uterus, a thick, hollow, muscular organ, is covered externally by a serous coat, and lined internally by a mucous membrane, while between the two is the thick muscular coat composed of smooth muscular fibres arranged in a great number of layers and in different directions. The Fig. 555. Left broad ligament, Fallopian tube, ovary and parovarium, a, uterus ; A, isthmus of Fallopian tube ; g, timbriaied end of the tube, with the parovarium to its right ; e, ovary ; /, ovarian ligament npulla ; mucous membrane of the body of the uterus in the unimpregnated condition has no folds, while the muscularis mucosae is very well developed and forms a great part of uterine muscular wall. The mucous membrane is lined by a single layer ol columnar ciliated epithelium. A vertical section shows the mucous membrane to contain numerous tubular glands (Fig. 554) — the uterine glands — which branch toward their lower ends. They have a membrana propria, and are lined by a single layer of ciliated epithelium, a small lumen being left in the centre. The utricular glands are not formed during intra uterine life {Turner), nor are there any glands in the human uterus at birth [G. J. Engelmann). There are numerous slit-like lymphatic spaces in the mucous membrane {Leopold), which communicate with well-marked lymphatic vessels existing in this and the other layers of the organ. In the cervix the mucous membrane is folded, presenting in the virgin the appearance known as the arbor vita;. The external surface of the vaginal part of the neck is covered by stratified squamous epithelium, like the vagina.] [The Fallopian tubes are really the ducts of the ovaries (Fig. 555). They consist of a serous, muscular (an external, longitudinal and an internal circular layer of non-striped muscle), and a mucous layer thrown into many folds and lined by a single layer of ciliated columnar epithelium, but no glands (Fig. 556).] 434. PUBERTY. — The term puberty is applied to the period at which a human being becomes capable of procreating, which occurs from the 13th to isth SIGNS OF MENSTRUATION. 867 years in the female and the 14th to i6th in the male. In warm climates, puberty may occur in girls even at 8 years of age. Toward the 40th to 50th year the procreative faculty ceases in the female with the cessation of the menses ; this constitutes the menopause or grand climacteric, while in man procreation has been observed up to any age. From the age of puberty onward, the se.vual appetite occurs, and the ripe ova are discharged from the ovary. [It seems, how- ever, that ova are discharged even before puberty or menstruation has occurred.] At puberty the internal and external generative organs and their annexes become more vascular and undergo development ; the pelvis of the female assumes the characteristic female shape. For the changes in the mammae, see § 230. At the same time hair is developed on the pubes and axilla, and in the male on the face, while the sebaceous glands become larger and more active. Other changes occur, especially in the larynx. In the boy the larynx elongates in its antero- posterior diameter, the thyroid, or .\dam's apple, becomes more prominent, while the vocal cords lengthen, so that the voice is hoarse, or husky, or " breaks," the voice being lowered at least an octave. In the female the larynx becomes longer, while the compass of the voice is increased. The vital capacity (§ 108), corresponding to the increase in the size of the chest, undergoes a con- FlG. 556. J Connective tissue. ■ Ciliated epithelium. Circular muscular tibri section of the Fallopian tube. siderable increase ; the whole form and expression assume the characteristic sexual appearance, while the psychical energies also receive an impulse. 435. MENSTRUATION.— External Signs.— .\t regular intervals- of time, of 27I3-2S days, in a mature female, there is a rupture of one or more ripe Graafian follicles, while at the same time there is a discharge of blood from the external genitals. This is known as the process oi menstruation (or menses, cata- menia or periods). Most women menstruate durihg the first quarter of the moon, and only a few at new and full moon {Stro/iD. In mammals, the analogous con- dition is spoken of as the period of heat [or the " rut " in deer]. There is a slightly bloody discharge from the external genitals in carnivora, the mare and cow (Aristotle), while apes in their wild condition have a well-marked menstrual discharge {Neubert). [Observations on cases where abdominal section has been performed have shown that the Graafian follicles mature and burst at any time i^Larvson Tait, Leopold).^ The onset of menstruation is usually heralded by constitutional and local phenomena— there is an increased feeling of congestion in the internal generative organs, pain in the back and loins, ten- sion in the region of the uterus and ovaries, which are sensitive to pressure, fatigue in the limbs, 8G8 OVULATION. Fig. 558. alternate feeling of heat and cold, and even a slight increase of the temperature of the skin {/CerscA). There may be retardation of the process of digestion and variations in the evacuation of the fcECes and urine, and in the secretion of sweat. The discharge is s/imy at first, and then becomes bloody, lasting three to four days ; the blood is venous, and shows Hltle tendency to coagu- late, provided it is mixed with much alkaline mucus from the genital passages; but if the hemor- rhage be free, the blood may be clotted. The quantity of blood is 100 to 200 grms. [The blood contains many white blood corpuscles and epithelial cells.] After cessation of the discharge of blood there is a moderate amount of mucus given oft. The characteristic internal phenomena which accompany menstruation are : (i) The changes in the uterine mucous membrane; and (2) the rupture of the Graafian follicle. I. Changes in the Uterine Mucous Membrane. — The uterine mucous membrane is the chief source of the blood. The ciliated epithelium of the con- gested, swollen, and folded, soft, thick (3 to 6 mm.) mucous membrane is shed. The orifices of the numerous mucous glands of the mucous membrane are distinct, the glands enlarge, and the cells undergo fatty degeneration, and so do the tissue and the blood vessels lying between the glands. The tissue contains more leucocytes than normal. This fatty degeneration and the excretion of the degenerated tissue occur, however, only in the superficial layers of the mucosa, whose blood vessels, when torn across, yield the blood. The deeper layers remain in- tact, arid from them, after menstruation is over, the new mucous membrane is devel- oped {Kundrat and G. J. Engehnann'). [Leopold denies the existence of this fatty degeneration. According to Williams, the entire mucous membrane is removed at each menstrual period, and it is regenerated from the muscular coat (Fig. 558). The mucous membrane of the cervix remains free from these changes.] 2. Ovulation. — The second important _"meIbrant.''''°Fir"5°8"--TCur when '"'^'■"^1 P'i<^"oni«^"on is oviilation, in which menstruationhasjustceased, showing the cavity process the OVary bcCOmeS more Vascular — - of the body deprived of mucous membrane ( /. -u r ii* 1 . ■ j ti a ■ j j ■ Williams). the ripe follicle is turgid with tluid, and in part projects above the surface of the ovary. The follicle ultimately bursts, its membranes and the epithelium covering of the ovary being torn or give way under the pressure, the bursting being accompanied by the discharge of a small amount of blood. At the same time, the congested, turgid, and erected fimbriated extremity of the Fallopian tube (Fig. 555) is applied to the ovary, so that the discharged ovum, with its adherent granulosa cells, and the liquor folliculi, are caught by the funnel-shaped extremity of the tube. The ovum, when discharged, is carried toward the uterus by the ciliated epithelium (§ 433) of the tube, and perhaps, also, partly by the contraction of its muscular coat. Ducalliez and Kiiss found that, by fully injecting the blood vessels, they could imitate the erection of the Fallopian tube. Rouget points out that the non-striped muscle of the broad ligaments may cause constriction of the vessels, and thus secure the necessary injection of the blood vessels of the Fallopian tube. Pfiiiger's Theory. — There are two theories as to the connection between ovulation or the dis- charge of an ovum and the escape of blood from the uterine mucous membrane. Pfluger regards the bloody discharge from the superficial layers of the uterine mucous membrane as a puysiological preparation or " freshening " of the tissue (in the surgical sensej, by which it will be prepared to ERECTION OF THE PENIS. 869 receive the ovum when the latter reaches the uterus, so that union can take place between the ovum and the freshly-exposed surface of the mucous membrane, and thus the ovum will receive nourish- ment from a new surface. Reichert's Theory. — This view is opposed to that of Reiehert, Engelmann, Williams, and others, .-\ccording to Reichert's theory, before an ovum is discharged at all there is a sympathetic change in the uterine mucous membrane, whereby it becomes more vascular, more spongy, and swollen up. Tire mucous membrane so altered is spoken of as the tmmhrana decidua meitstntaiis, and from its nature it is in a proper condition to receive, retain, and nourish a fertilized ovum which may come into contact with it. If the ovum, however, be not fertilized, and escapes from the gen- ital passages, then the uterine mucous membrane degenerates and blood is shed as above described. According to this view, the hemorrhage from the uterine mucous membrane is a sign of the non- occurrence of pregnancy; the mucous membrane degenerates because it is not required for this occasion ; the menstrual blood is an external sign that the ovum has not been impregnated. So that pregnancy, ;'. c, the development of the embryo in utero, is to be calculated, not from the last men- struation, but from some time between the last menstruation and the period which does not occur. In some cases the ovulation and the formation of the decidua nienstrualis occur separately, so that there may lie menstruation without ovulation, and ovulation without menstruation. Corpus Luteum. — When a Graafian follicle bursts, it discharges its contents and collapses ; in the interior are the remains of the membrana granulosa and a small effusion of blood, which soon coagulates. The small rupture soon heals, after the serum is absorbed. The vascular wall of the Fig. SS9. 'V uo. trabeculje of connective t 'ith elastic fibres and smooth muscles (C) ; d, \ follicle swells up. Villous prolongations or granulations of young connective tissue, rich in cipil- laries and cells, grow int ) the interior of the follicle. Colorless blood corpuscles also wander into the interior. At the same time the cells of the granulosa proliferate, and form several layers of cells, which ultimately, after the disappearance of a number of blood vessels, undergo fatty degen- eration, lutein and fatty matter being formed, and it is this mass which gives the corpus luteuni its yellow color. The capsule becomes more and more fused with the ovarian stroma. If pregnancy does not take place after the menstruation, then the fatty matter is rapidly absorbed, and the efiused blood is changed into hojmatoidin (^ 20) and other derivatives of ha'mogloliin, while there is a gradual slirivelling of the whole mass, which is complete in about four weeks, only a very small remainder being left. Such a corpus luteum, /'. t"., one not accompanied by pregnancy, is called a false corpus luteum. If, however, pregnancy occurs, then the corpus luteum, instead of shrivel- ling, grows and becomes a large body, especially at the third and fourth month, the walls .ire thicker, the color deeper, so that the corpus luteum at the period of delivery may be 6 to id mm. in diam- eter, and its remains may be found in the ovary (or a verj' long time thereafter (Fig 551). This form is sometimes spoken of as a true corpus luteum [Bischoff). [We cannot draw too sharp a distinction between these two forms.] Only a very small number of the ova in the ovary undergo development and are discharged; by far the greater number degenerates [Slnvjansky). 436. PENIS ERECTION. — Penis. — [The penis is composed of two long cylindrical corpora cavernosa, the corpus spongiosum, which lies between and below them, and surrounds the 870 MECHANISM OF ERECTION. urethra; these are held together by fibrous and muscular sheaths, and are composed of erectile tissue.] Our knowledge of the distribution of the blood within the penis is chiefly due to C. Langer's researches. The albuginea of the corpus spongiosum consists of tendinous connective tissue, containing thickly-woven elastic ti>sue and smooth muscular fibres, which together form a solid fibrous envelope, from which numerous interlacing trabecukis pass into the interior, so that the corpus spongiosum comes to resemble a sponge. The anastomosing spaces bounded by these tra- becul?e fonn a series of inter-communicating venous spaces, or sinuses, filled with blood and lined by a layer of endothelium constituting erectile tissue (Fig. 559). The largest sinuses lie in the lower and external part of the corpus caverno.sum, while they are less numerous and smaller in the upper part. The small arteries arise from the A. profunda penis, which runs along the septum, and pass to the trabecule after following a very sinuous course. At the outer part of the corpus spongiosum some of the small arteries become directly continuous with the larger venous sinu«es; some of them, however, terminate in capillaries both in the outer part and within the corpus spongi- osum, the capillaries ultimately terminating in the venous sinuses. The helicine arteries of the penis described by |oh. Miiller are merely much twisted arteries. The deep veins of the penis arise by fine veinlets within the body of the organ, while the veins proceeding from the cavernous spaces pass to the dorsum of the penis to form the vena dorsalis penis. As these vessels have to traverse the meshes of the vascular network in the cortex of the corpora cavernosa penis, it is evident that, when the network is congested by being filled with blood, it must compress the outgoing venous trunks. The corpus cavernosum urethri-e consists, for the most part, of an external layer of closely- packed anastomosing veins, which surround the longitudinally-directed blood vessels of the urethra. In the dog all the arteries of the penis run at first toward the surface, where they divide into penicilli. The veins arise from the capillary loops in the papilla, and they empty their blood into the cavernous spaces. Only a small part of the blood passes to the cavernous spaces through the internal capillaries and veins, but arterial blood never flows directly into these spaces (J/, v. Frey). Mechanism of Erection. — Erection is due to the overfilling of the blood vessels of the penis with blood, whereby the volume of the organ is increased four or five times, while at the same titne there are also a higher temperature, increased blood pressure (to | of that in the carotid — Eck/uird), with at first a pulsatile movement, increased consistence, and erection of the organ. Regner de Graaf obtained complete erection of the penis by forcibly injecting its blood vessels {1668). The preliminary phenomena consist in a considerable increase of the arte- rial blood supply, the arteries being dilated and pulsating strongly. The arteries are controlled by the nervi erigentes. The nervi erigentes [called by Gaskell the pelvic splanchnics (p. 649)] arise chiefly from the second (more rarely the third) sacral nerves (dog), and have ganglionic cells in their course (Loven, Nikolskv). These nerves contain vaso-dilator fibres, which can be e.xcited in part refiexly from the sensory nerves of the penis, the transference centre being in the centre for erection in the spinal cord (§ 362, 4). Sensory impressions pro- duced by voluntary movements of the genital apparatus (by the ischio- and bulbo- cavernosi and cremaster muscles) can also discharge this reflex ; while the thought of sexual imptilses, referable to the penis, tends to induce erection. The nervi erigentes also supply the longitudinal fibres of the rectum {Fellner). The centre for erection in the spinal cord (§362, 2) is, however, controlled by the dominating vaso-dilator centre in the medulla oblongata (§372), and the two centres are connected by fibres within the cord ; hence stimulation of the upper part of the cord, as by asphyxiated blood (§ 362, 5) or muscarin, may also be followed by erection {Nikolsky). [The seminal fluid is frequently found dis- charged in persons who have been hanged.] The psychical activity of the cerehrtim has a decided influence on the genital vaso-dilator nerves. Just as the psychical disturbance which accompanies anger or shame is followed by dilatation of the blood vessels of the head, owing to stimulation of the vaso-dilator fibres; so when the attention is directed to the sexual centres, there is an action upon the nervi erigentes. This action of the brain is more comprehensible, since we know that the diameter of the blood vessels is afi'ected by the cortex cerebri (§ 377). The fibres probably pass from the cerebrum through the peduncles of the cerebrum and the pons ; as a matter of fact, if these parts be stimulated, erection may take place (§362, 4) {Eckhani). MECHANISM OF ERECTION. 871 When the impulse to erection is obtained by the increased supply of arterial blood, \\\t full completion of the act is brought about by the activity of the follow- ing transversely striped muscles: (i) The ischio-cavernosus (Fig. 164) arises from the coccyx, and by its tendinous union surrounds the root of the penis. When it contracts it compresses the root of the penis from above and laterally, so that the outflow of blood from the penis is hindered. It has no action on the dorsal vein of the penis, as this vessel lies in a groove on the dorsum of the penis, and is, therefore, protected from compression by the tendon. (2) The deep transversus perinei is perforated by the vense profundse penis, which come from the corpora cavernosa, so that when it contracts it must compress these veins be- tween the tense horizontal fibres (Fig. 560, 6). The deep veins of the penis join the common pudendal vein and the plexus Santorini. (3) Lastly, the bulbocav- crnosus is concerned in the hardening of the urethral corpus spongiosum, as it com- Anterior wall of the pelvis with the urogenital septum seen from the front. The corpus cavernosum (4) with the ure- thra (3) is cut across below its exit from the pelvis, i, symphysis pubis; 2, dorsal vein of the penis; 5, part of the bulbo-cavemosus : /, deep transversus perinei with its fascia (_/) ; 6, vena profunda penis ; 7, artery and vein of the bulbo-cavemosus. presses the bulb of the urethra (Figs. 560, 5, 164). k\\ these muscles are partly under the control of the will, whereby the erection mav be increased. Normally, however, their contraction is excited reflexly by stimulation of the sensory nerves of the penis (§ 362, 4). The congestion of blood is not complete, else, in pathological cases, continuous erection, as in satyriasis, would give rise to gangrene. The accumulation of the blood in the penis is favored by the fact that the origins of the veins of the penis lie in the corpus cavernosum, which, when it en- larges, must compress them. There are also trabecular, smooth, muscular fibres, which compress the large venous plexus of Santorini. That erection is a complex motor act depending on the nervous system, is proved by an experi- ment of Hausmann, who found that section of the nerves of the penis prevented erection in a stal- lion. The imperfect erection which occurs in the female is confined to the corpora cavernosa clito- ridis and the bulhi vestibuli. During erection, the passage from the urethra to the l>ladder is closed, partly by the swelling of the caput gallinaginis, and partly by the action of the sphincter urethrje, which is connected with the deep transversus perinei. 872 FERTILIZATION OF THE OVUM. 437. EJACULATION— RECEPTION OF THE SEMEN.— In con- nection with the ejaculation of the seminal fluid, we must distinguish two differ- ent factors — (i) its passage from the testicles to the vesiculae seminales ; (2) the act of ejaculation itself. The former is caused by the newly-secreted fluid forcing on that in front of it, by the action of the ciliated epithelium (which lines the epididymis to the beginning of the vas deferens), and also by the peristaltic inovements of the smooth muscular fibres of the vas deferens. Ejaculation, how- ever, requires strong peristaltic contractions of the vasa deferentia and the vesiculae seminales, which are brought about by the reflex stimulation of the ejaculation centre in the spinal cord (§ 362, 5). As soon as the seminal fluid reaches the ure- thra, there is a rhythmical contraction of the bulbo-cavernosus muscle (produced by the mechanical dilatation of the urethra), whereby the fluid is forcibly ejected from the urethra. Both vasa deferentia and vesiculcc do not always eject their contents into the urethra simultaneously. With moderate excitement the contents of only one may be discharged. The ischio-cavernosus and deep transversus per- inei contract at the same time as the bulbo-cavernosus, although the former have no effect on the act of ejaculation. In the female also, undernormal circum- stances, at the height of the sexual excitement there is a reflex movement corre- sponding to ejaculation. It consists of a movement analogous to that in man. At first there is a reflex peristaltic movement of the Fallopian tube and uterus, pro- ceeding from the end of the tube toward the vagina, and produced reflexly by the stimulation of the genital nerves. Derabo observed that stimulation of the ante- rior upper wall of the vagina in animals caused a gradual contraction of the uterus. By this movement, corresponding to that of the vasa deferentia in man, a certain amount of the mucus normally lining the uterus is forced into the vagina. This is followed by the rhythmical contraction of the sphincter cunni (analo- gous to the bulbo-cavernosus), also of the ischio-cavernosus, and deep transversus perinei. The uterus is erected by the powerful contraction of its muscular fibres and round ligaments, while at the same time it descends toward the vagina, its cavity is more and more diminished, and its mucous contents are forced out. When the uterus relaxes after the stage of excitement, it aspirates into its cavity the sem- inal fluid injected into the vestibule {Aristotle, Bischoff). But the suction of the greatly excited uteras is not necessary for the reception of the semen (Aris- totle). The spermatozoa may wriggle by their own movements from the vagina into the orifice of the uterus (Kristeller'). The cases of pregnancy where, from some pathological causes (partial closure of the vagina or vulva), the penis has not passed into the vagina during coition, prove that the spermatozoa can traverse the whole length of the vagina, and pass into the uterus. 438. FERTILIZATION OF THE OVUM.— The ovum is fertilized by a spermatozoon passing into it. Swammerdam (f 16S5) proved that contact of tlie semen with the ovum was necessary for fer- tilization. Spallanzani ( 1 76S) proved that the fertilizing agent was the spermatozoa, and not the clear, filtered fluid part of the semen, and that the spermatozoa, even after being enormously diluted, were still capable of action. Martin Barry (1S50) was the first to observe the entrance of a sperma- tozoon into the ovum of the rabbit. This occurs pretty rapidly, by a boring movement through the vitelline membrane (Leuck/iart). The entrance is effected either through the porous canals or the micropyle [Keber, p. 863). Theories. — As to the manner in which the spermatozoon affects the ovum, there are great differ- ences of opinion. Aristotle compared it to an action like that of rennet on milk ; Bischoff, to that of yeast on a fermentable mass, i. e., to a catalytic action. These theories, however, are quite un- satisfactory, as we know that the unfertilized ova of the hen, rabbit (Hensen), pig {Bischoff), salpa {Kuppfer), (but not the frog — Pfiiiger) can undergo the initial stages of development as far as the stage of cleavage, and the star fishes even as far as the larval form (Gieef). Place of Fertilization. — The place where fertilization occurs is either the ovary, as indicated by the occurrence of abdominal pregnancy, or the Fallopian tube, and the numerous recesses in the latter afford a good temporary nidus for the spermatozoa. This view is supported by the occurrence of tubal pregnancy. Thus the spermatozoa must be able to pass through the Fallopian tube to the ovary, MATURATION OF THE OVUM. 873 which is probably'brought about chiefly by the movements proper to the sperma- tozoa themselves. It is uncertain whether the peristaltic movements of the uterus and Fallopian tube are concerned in this process; certainly ciliary movement is not concerned, as the cilia of the Fallopian tube act from above downward. When once the ovum has passed unfertilized into the uterus, it is not fertilized in the uterus. It is assumed that the ovum reaches the uterus within two to three weeks fin the bitch, 8 to 14 days). Twins occur in i in 87 pregnancies, but oftener in warm climates: triplets, I : 7600 ; four at a birth, i : 330,000. More than six at a birth have not been observed. The average number of pregnancies in a woman is 414. Superfecundation.^By this term is understood the fertilization of two ova at the same men- struafioH, by two different acts of coition. Thus, a mare may throw a foal and a mule, after being covered first by a stallion and then by an ass. A white and a black child have been born as twins by a woman. Superfoetation is when a second impregnation takes place at a later period of pregnancy, as in the second or third month. This, however, is only possible in a double uterus, or when menstrua, tion persists until the time of the second impregnation. It is said to occur frequently in the hare. Hybrids are produced when there is a cross between different species (horse, ass, zebra — dog, jackal, wolf — goat, ibe.x — goat, sheep — species of llama — camel, dromedary — tiger, lion — species of pheasant — goose, swan — carp, crucian — species of butterflies). Most hybrids are sterile, espe- cially as regards the formation of properly formed spermatozoa ; while the hybrid females are for the most part fertile with the male of both parents, e. g., the mule; but the characters of the off- spring tend to return to those of the species of the parents. Very few hybrids are fertile when crossed by hybrids. In many species of frogs the absence of hybrids is accounted for by the me- chanical obstacles to fertilization of the ova. Tubal Migration of the Ovum. — Under exceptional circumstances, the ovum discharged from a ruptured Graafian follicle passes into the Fallopian tube of the other side, as is proved by the occurrence of tubal pregnancy and preg- nancy of an abnormal rudimentary horn of the uterus, in which case the true corpus luteum is found on the other side of the ovary. This is spoken of as " ex- ternal migration " (Kussmaul, Leopold). This observation coincides with experiment, a-s granular fluids, e. g., China ink, when injected into the peritoneal cavity, pass into both Fallopian tubes, and are carried by the ciliated epithelium to the uterus {Pinner^. In animals, with a double uterus with two orifices, the ova may migrate through the os of the one into the other uterus, a condition which is spoken of as " internal migration." 439. IMPREGNATION OF THE OVUM— CLEAVAGE— LAY- ERS AND POSITION OF THE EMBRYO.— Maturation of the Ovum. — In birds and mammals important changes occur in the ovum before im- pregnation. The genninal vesicle comes to the surface and disappears from view, while the germinal spot also disappears (^Reiii). In place of the germinal vesicle, a spindle-shaped body appears. The granular elements of the protoplasmic vitellus arrange themselves around each of the two poles of the spindle, in the form of a star, the double star, or diaster of Fol — nuclear spindle. When this takes place \\\& peripheral pole of the nucletis or altered germinal vesicle, along with some of the cellular substance of the ovum, protrudes upon the surface of the vitellus, where they are nipped off from the ovum in the form of small corpuscles just like an excretory product (Fig. 553). These bodies, which are not made use of in the further development and growth of the ovum, are called polar or directing globules (Fol, Biitsehli, O. Hertwig), although the elimination of small bodies from the yelk was known to Dumortier [1837], Bischoff, P. J. vanBeneden, Fritz Miiller [1848], Rathke, and others. The remaining part of the germinal vesicle stays within tlie vitellus and travels back toward the centre of the ovum, to form the female pronucleus {O. Hertwig, Fol, Selenka, E. van Beiieden). [Before, however, the altered germinal vesicle travels downward again into the substance of the ovum, it divides again as before, and from it is given off the second polar globule, and then the remainder of the germinal vesicle forms the female pro- 874 BLASTODERM. nucleus. At the same time the vitellus shrinks somewhat \v4thin the vitelline membrane.] Impregnation. — As a rule, only one spermatozoon penetrates the ovum, and as it does so it moves toward the female pronucleus, while its head becomes sur- rounded with a star; it then loses its head and cilium or tail, the latter only serving as a motor organ, while the remaining middle piece swells up to form a second new nucleus, the male pronucleus ( Fol, Selenkd). According to Flem- niing, it is the anterior part of the head, and according to Rein and Eberth, it is the head which is so changed. Thereafter, the male and female ])ronucleus unite, undergoing amoeboid movements at the same time, to form the new nu- cleus of \.\\t fertilized ovum. The female pronucleus receives the male pronucleus in a little depression on its surface. Thereafter the yelk assumes a radiate appear- ance {Rein). [The union of the representatives of the male and female elements forms the first embryonic segmentation sphere or blastosphere.] In Echinoderms, O. Hertwig and Fol observed that several embryos were formed when, under abnormal conditions, several spermatozoa penetrated an ovum. The male pronuclei, formed from the several spermatozoa, then fused each with a fragment of the female pronucleus. Under similar circumstances, Born observed in amphibians abnormal cleavage, but no further develop- ment. Cleavage of the Yelk. Fig. 561. -In an ovum so fertilized the yelk contracts some- what around the newly-formed nucleus, so that it becomes slightly separated from the vitelline membrane, and for the first time the nucleus and the yelk divides into two nucleated spheres. This process is spoken of as complete cleavage or fission. Each of these two cells again divides into two, and the process is repeated, so that 4, 8, 16, 32, and so on, spheres are formed (Fig. 561). This constitutes the cleavage of the yelk, and the process goes on until the whole yelk is subdivided into numer- ous small, nucleated spheres, the "mulberry mass" or "segmentation spheres " or " morula," or the protoplasmic primordial spheres (20 to 25 /i) which are devoid of an envelope. Variation of Lines of Cleavage. — According to the observations of Pfliiger, the ova of the frog can be made to undergo cleavage in very different directions, according to the angle between the axis of the egg and the line of gravitation. This, of course, we can alter as we please, by placing the eggs at any angle to the line of gravitation. By the axis of the ovum is meant a line connecting the centre of the black surface and the middle of the white part, which, in the fertilized ovum, is always vertical. In such cases of abnormal cleavage the deposition of the organs takes place from other constituents of the egg than those from wliich tliey are formed under normal con- ditions. Under normal circumstances, according to Roux, the first line of cleavage in the frog is in the same direction as the central nervous system. The second intersects the first at a right angle, so as to divide the mass of the ovum into two unequal parts, the larger of which forms the anteri'.r part of the embryo. Blastoderm. — During this time the ovum is enlarging by absorption of fluid into its interior. All the cells, from mutual pressure against each other, become polyhedral, and are so arranged as to form a cellular envelope or bladder, the blastoderm, which lies on the internal surface of the vitelline membrane {De Graaf, v. Baer, Bischoff, Coste). A small part of the cells not used in the for- mation of the blastoderm is found on some part of the latter. [In the ovum of the bird, where there is only partial segmentation, the blastoderm is a small round body resting on the surface of the yelk, under the vitelline membrane, so that it does not completely surround the yelk, or a hollow cavity, as in mammals.] The hollow sphere, composed of cells, is called the blastodermic vesicle by Reichert, and in the human embryo it is formed at the loth to 12th day, in the STRUCTURE OF THE BLASTODERM. 875 rabbit at the 4th, the guinea pig at the 3'^, the cat 7th, dog nth, fox i4lh, ruminantia at the loth to 12th day, and the deer at the 60th day. When the blastoderm grows to 2 mm. (rabbit), whereby the vitelline membrane is distended to a very thin, delicate membrane, then at one part of it there appears the germinal area, the area germinativa, or the embryonal shield {Coste, Kblliker), as a round white spot, in which the blastoderm, owing to proliferation of its cells, becomes double. The upper laj'cr is called the ectoderm or epi- blast, and in some animals it consists of several layers of cells, while tlie lower layer is the endoderm or hypoblast. The hypoblast continues to grow at its edges, so that it ultimately forms a completely closed sack, on which the epiblast is applied concentrically. The embryonal area soon becomes more pear-shaped, and afterward biscuit-shaped. At the same time the surface of the zona pellu- cida develops numerous small, hollow, structureless villi, and is called the primi- tive chorion. At the posterior part of the embryonic shield, the primitive streak (Fig. 562, I, Pr) appears at first as an elongated circular thickening (^Hensen), and later as a longer streak or groove, the primitive groove. This thickening, however, is confined to the epiblast, while the hypoblast is completely unchanged in the region of the streak, and the former consists of three layers of cells. At the same time a new layer of cells is developed between the epiblast and hypo- blast, the mesoderm or mesoblast (Fig. 563, I), which soon extends over the embryonal area, and into the blastoderm. Blood vessels are formed within the mesoblast, and are distributed over the blastoderm to form the area vasculosa. Medullary Groove. — .\ longitudinal groove, the medullary groove, is formed at the anterior part of the embryonal shield, but it gradually extends posteriorly, embrac- Fig. 562. ing the anterior part of the primitive streak with its divided posterior end, while the primitive streak itself gradually becomes relatively and absolutely smaller and less dis- tinct, until it disappears altogether (Fig. 562, I and II, Pr—Kolliker). The position of the embryo is indicated by the central part becoming more trans- parent, — the area pellucida, — which is surrounded by a more opaque part — the area opaca. [The area opaca rests directlv upon ., U-. n • .1 r 1 J •» .. r Pr, primilive streak : ;?. medullary groove ; U, the white yelk in the fowl, and it takes no first protovenebra. share in the formation of the embryo, but gives rise to structures which are temporary, and are connected with the nutrition of the embryo. The embryo is formed in the area pellucida alone.] From the epiblast \jieuro-epidermal layer] are developed the central nervous system and epidermal tissues, including the epithelium of the sense organs. From the mesoblast are formed most of the organs of the body [including the vascular, muscular, and skeletal systems, and, according to some, the connect- ive tissue. It also gives rise to the generative glands and excretory organs]. From the hypoblast, epithelio-glandular layer [which is the secretory layer], arise the intestinal epithelium, and that of the glands which open into the intestine. [The mouth and anus being formed by an inpushing of the epiblast, are lined by epiblast, and are sometimes called the stomodceum and protodceum respect- ively.] [Structure of the Blastoderm.— Originally it is composed of only two layers, and in a vertical section of it the epiblast consists of a single row of nucleated granular cells arranged side by side, with their long axes placed verti- cally. The hypoblast consists of larger cells than the foregoing, although they vary in size. They are spherical and very granular, so that no nucleus is visible «76 STRUCTURES FORMED FROM THE EPIBLAST. Fig. 563. I, The three layers of the blastoderm of the mammalian ovum — Z, zona pellucida ; E, ectoderm, or epiblast ; m, mesoblast ; f, endoderm, or hypoblast. II, Section of an embryo, with six proto vertebrae at the ist day — M, medullary groove; A, somatopleure ; U, protovertebra ; c, chorda dorsalis ; S, the lateral plates divided into two ; e, hypoblast. Ill, Section of an embryo chick at the zd day in the region behind the heart — M, medullary groove ; /t, outer part of somatopleure ; u, protovertebra ; c, chorda : ■zu. Wolffian duct ; K, calom ; x, inner part of somatopleure ; y. inner part of splanchnopleure ; A, amniotic fold : a, aorta; e, hypoblist. IV, Scheme of a longitudinal section of an early embryo. V, Scheme of the formation of the head- and tail-folds — r, head- fnld ; T>, anterior extremity of the future intestinal tract ; S. tail-fold, first rudiment of the cavity of the reclum. VI, Scheme of a longitudinal section through an embryo after the formation of the heid-and tail-folds — A o, om- phalo-mesenteric arteries ; V (j, omphalo-mesenteric veins ; rf, position of the allantois ; A, amniotic fold. VII, Scheme of a longitudinal section through a human ovum — Z, zona pellucida ; S, serous cavity ; r, union of the amniotic folds ; A, cavity of the amnion ; a, allantois ; N, umbilical vesicle ; t/i, mesoblast ; A, heart ; U, primitive intestine. VIII. Schematic transverse section of the pregnant uterus during the formation of the placenta ; U, muscular wall of the uterus ; /, uterine mucous membrane, or decidua vera ; ^, maternal part of the placenta, or decidua serontina ; r, decidua reflexa; c/t, chorion ; A, amnion ; «, umbilical cord; n, allantois, with the urachus; N, umbilical vesicle, with D, the omphalo-mesenteric duel : / i, openings of the Fallopian tubes ; G, canal of the cervix uteri. IX, Scheme of a human embryo, with the visceral arches still persistent — A, amnion: V, fore- brain; M, mid-brain; H, hind-brain ; N, after-brain ; U, primitive veriebra ; a, eye ;/, nasal pits ; S, frontal process; j*. internal nasal process; m, external nasal process; /•, superior maxillary process of the 1st visceral arch ; 1,2.3 ^'^'^ 4> ^^^ f*^"*" visceral arches, with the visceral clefts between them ; e>, auditory vesicle; /i. heart, with f, primitive aorta, which divides into five aortic arches ; X. descending aorta ; om, omphalo-mesenteric ar- tery; ^, the omphalo-me'senteric arteries on the umbilical vesicle; c, omphalo-mesenteric vein; L, Liver, with venae advehentes and revehentes ; D, intestine ; /, inferior cava ; T, coccyx ; «//, allantois, with s, one umbilical artery, and x, an umbilical vein. STRUCTURES FORMED FROM THE MESOBLAST. 877 in them. The cells form a kind of network, and occur in more than one layer, especially at the periphery. It rests on white yelk, and under it are large spher- ical refractive cells, spoken of as formative cells.] The cells of the epiblast, and especially those of the hypoblast, nourish themselves by the direct absorption and incorporation of the constituents of the yelk into themselves. The amoeboid move- ments of these cells jjlay a part in the process of absorption. The absorbed particles are changed, or, as it were, digested within the cells, and the product used in the processes of growth and de- velopment (Kollmann). 440. STRUCTURES FORMED FROM THE EPIBLAST.— Laminae Dorsales. — The medullary groove upon the epiblast (also called outer, serous, sensorial, corneal, or animal layer j becomes deejjer (Fig. 563, II). The two longitudinal elevations or laiiiime dorsales consist of a thickening of the epiblast, and grow up over the tneduUary groove, to meet each other and coalesce by their free edges in the middle line posteriorly. Thus the open groove is changed into a closed tube — the medullary or neural tube (III). The cells next the lumen of the tube ultimately become the ciliated epithelium lining the central canal of the spinal cord, while the other cells of the nipped-ofif portion of the epiblast form the ganglionic part of the central nervous system and its pro- cesses. Primary Cerebral Vesicles. — [The laminae dorsales unite first in the region of the neck of the embryo, and soon this is followed by the union of those over the future head.] The medullary tube is not of uniform diameter, for at the anterior end it becomes dilated and mapped out by constrictions into the primary vesicles of the brain, which at first are arranged, one behind the other, in the following order: Each one being smaller than the one in front of it ; the fore- brain (representing the structures from which the cerebral hemispheres are devel- oped) ; the mid-brain (corpora quadrigemina) ; the hind-brain (cerebellum); and the after-brain (medulla oblongata), which is gradually continued into the spinal cord (IV and V). The posterior part of the medullary tube has a dilatation at the lumbar enlargement. In birds, the medullary groove remains open in this situation to form a lozenge-shaped dilatation, the sinus rhomboidalis. Cranial Flexures. — The anterior part of the medullary tube curves on itself, especially at the junction of the spinal cord and oblongata, between the mid-brain and hind-brain, and again almost at right angles between the fore-brain and mid- brain. [Thus is produced a displacement of the primary vesicles, and the head of the future embryo is mapped off.] At first all the cerebral vesicles are devoid of convolutions and sulci. On each side of the fore-brain there grows out a stalked, hollow vesicle (VI), the primary optic vesicle. The remainder of the ejjiblast forms the epidermal covering of the body. At an early period we can distinguish the stratum corneum and the Malpighian layer of the skin (ij 283) ; from the former are developed the hairs, nails, feathers, etc. Partial Cleavage. — Only a partial cleavage takes place in the eggs of birds and in mesoblastic ova, i. e., only the white yctk in the neighborhood of the cicatricula divides into numerous segmen- tation spheres (Coste, JS4S). The cells arrange themselves in two layers, lying one over the other. The upper layer or epiblast is the larger, and contains small, pale cells ; the lower layer, or hype- blast, which at iirst is not a continuous layer, ultimately forms a contmuous layer, but its periphery is smaller than the upper layer, while its cells are larger and more granular. Between the epiblast and hypolilast, from the primitive streak outward, is formed the mesoblast, which is said by Kolliker to be due to the division of the cells of the epiblast. It gradually extends in a peripheral direction between the two other layers. All the three layers grow at their periphery. In the mesobla.st blood vessels are developed. .All the three layers, as they grow, come ultimately to enclose the yelk, so that their margins come together at the opposite pole of the )'elk. 441. STRUCTURES FORMED FROM THE MESOBLAST AND HYPOBLAST.— The mesoblast (^vascular layer or middle laycrj forms, immediately under the medullary groove, a cylindrical, cellular cord, the chorda dorsalis, or notochord, which is thicker at the tail than at the cephalic 878 FORMATION OF EMBRYO, ETC. end (Fig. 563, II, III, c). It is present in all vertebrata, and also in the larval form of the ascidians, but in the latter it disappears in the adult form (Kowa- lewsky). In man it is relatively small. It forms the basis of the bodies of the vertebrje, and around it, as a central core, the substance of the bodies of the vertebra is deposited, so that they are strung on it, as it were, like beads on a string. After it is formed it becomes surrounded by a double sheath-like covering ( Gegenbaiir, KoUiker). The recent observations of L. Gerlach and Strahl ascribe the origin of the chorda to the hypoblast. It does not contain chondrin or glutin, but albumin {Kdzius). Protovertebrae. — The cells of the mesoblast, on each side of the chorda, arrange themselves into cubical masses, always disposed in pairs behind each other, the protovertebrse (U and //). The first pair correspond to the atlas. At a later period each protovertebra shows a marginal, cellular area and a nuclear area. Only part of it goes to form a future vertebra. The part of the mesoblast lying external to the protovertebra, the lateral plates (II, s), splits into two layers (^Wolff, J768), an upper one and a lower one, which, however, are united by a median plate at the protovertebrae. The space between the two layers of the mesoblast is called the pleuro-peritoneal cavity, or the coelom (III, K) of Haeckel. The upper layer of the lateral jjlate becomes united to the epiblast, and forms the cutaneo-muscular plate of German authors, or the somatopleure (III, .v), while the inner one unites with tjie hyiJoblast to form the intestinal plate of German authors, or the splanchnopleure (III, 1). On the surfaces of these plates, which are directed toward each other, the endothelium lining the pleuro- peritoneal cavity is developed. On the surface of the median plate, directed toward the coelom, some cylindrical cells, the " germ epithelium " of Waldeyer, remain, which form the ovarian tubes and the ova (Ji 433). .According to Remak, the skin, the muscles of the trunk, and the hlood vessels, and according to His, only the musculature of the trunk, are derived from the somatopleure. Both observers agree that the splanchnopleure furnishes the musculature of the initstinal tract. Parablastic and Archiblastic Cells. — According to His the blood vessels, blood, and connective tissue are not developed from true mesoblastic cells, but he asserts that for this purpose certain cells wander in from the margins of the blasto- derm between the epiblast and hypoblast, these cells being derived from outside the position of tiie embryo, from the elements of the white yelk. His calls these structures parablastic, in opposition to the arc/i/b/as/ic, which belong to the three layers of the embryo. Waldeyer also adheres to the parablastic structure of blood and connective tissue, but he assumes that the material from which the latter is formed is continuous protoplasm, and of equal value with the elements of the blastoderm. The hypoblast does not undergo any change at this time ; it applies itself to the inner layer of the mesoblast, as a single layer of cells to form the splanchno- pleure. 442. FORMATION OF EMBRYO, HEART, PRIMITIVE CIR- CULATION.— Head- and Tail-Folds. — Up to this time the embryo lies with its three layers in the plane of the layers themselves. The cephalic end of the future embryo is first raised above the level of this plane (Fig. 563, V). In front of, and under the head, there is an inflection or tucking in of the layers, which is spoken of as the head-fold {Y , r). [It gradually travels backward, so that the embryo is raised above the level of its surroundings.] The raised cephalic end is hollow, and it communicates with the space in the interior of the umbilical vesicle. The cavity in the head is spoken of as the head-gut or fore-gut (V, D). The formation of the fore-gut, by the elevation of the head from the plane of the three layers, occurs on the second day in the chick, and in the dog on the 22d day. The tail-fold is formed in precisely the same way in the chick on the 3d day, and in the dog on the 22d day. The caudal elevation, S, also is hollow, FORMATION OF THE HEART. 879 and the space within it is the hind-gut, d. Thus the body of tlie embryo is sup- ported or rests on a hollow stalk, which at first is wide, and communicates with the cavity of the umbilical vesicle. This duct or communication is called the om- phalo-mesenteric duct, or the vitello-intestinal or vitelline duct. The saccular vesicle attached to it in mammals is called the umbilical vesicle (VII, N), while the analogous much larger sack in birds, which contains the yellow nutri- tive yelk, is called the yelk-sack. The omphalo-mesenteric or vitelline duct in course of time becomes narrower, and is ultmiately obliterated in the chick on the 5th day. The point where it is continuous with the abdominal wall is the abdom- inal umbilicus, and where it is inserted into the primitive intestine, the intestinal umbilicus. [Sometimes part of the vitelline duct remains attached to the intestine, and may prove dangerous by becoming so displaced as to constrict a loop of intestine, and thus cause strangulation of the gut.] Heart. — Before this process of constriction is complete, some cells are mapped off from that part of the splanchnopleure which lies immediately under the head- gut ; this indicates \\\& position of the heart, which appears in the chick at the end of the first day, as a small, bright red, rhythmically contracting point, the piinetuni saliens, or the ariynri xi-jouiiivri of Aristotle. In mammals it appears much later. The heart, VI, begins first as a mass of cells, some of which in the centre dis- appear to form a central cavity, so that the whole looks like a pale hollow bud (originally a pair) of the splachnopleure. The central cavity soon dilates ; it grows, and becomes suspended in the coelom by a duplicature like a mesentery (meso-cardium), while the space which it occupies is spoken of as lh.e fovea car- dica. The heart now assumes an elongated tubular form with its aortic portion directed forward and its venous end backward ; it then undergoes a slighty-shaped curve (Fig. 570, i). From the middle of the 2d day the heart begins to beat in the chick at the rate of about 40 beats per minute. [It is very important to note that at first, although the heart beats rhythmically, it does not contain any nerve cells.] From the anterior end of the heart there proceeds from the bulbus aortas the aorta, which passes forward and divides into two arches the primitive aortae, which then curve and pass backward under the cerebral vesicles, and run in front of the protovertebra:. Opposite the omphalo-mesenteric duct each primitive aorta in the chick sends off one, in mammals several (dog 4 to 5), omphalo-mesenteric arteries (VI, A, 0), which spread out to form a vascular network within the meso- blast of the umbilical vesicle. From this network there arise the omphalo-mesen- teric veins, which run backward on the vitelline duct, and end by two trunks in the venous end of the tubular heart. In the chick these veins arise from the sinus terminalis of the subsequent vena terminalis of the area vasculosa. Thus the first or primitive circulation is a closed system, and functionally it is concerned in carrying nutriment and oxygen to the embryo. In the bird the latter is supplied through the porous shell, and the former is supplied up to the end of incubation by the yelk. In mammals both are supplied by the blood vessels of the uterine mucous membrane to the ovum. In birds, owing to the absorption of the con- tents of the yelk-sack, the vascular area steadily diminishes, until ultimately, to- ward the end of the incubation time, the shriveled yelk-sack slips into the abdom- inal cavity. In mammals, the , circulation on the umbilical vesicle, i.e., through the omphalo-mesenteric vessels, soon diminishes, while the umbilical vesicle itself shrivels to a small appendix, and the second circulation is formed to replace the omphalo-mesenteric system. The first blood vessels are formed in the chick, in the area vasculosa, outside the position of the embryo, at the last quarter of the first day, before any part of the heart is visible. The blood vessels begin in vaso-formative cells [constituting the " blood islands " of Pander]. At first they are solid, but they soon become hollow (§ 7, A). A narrow-meshed plexus of lynifhatics is formed in the area vasculosa of the chick (His), and it commun cates with the amniotic cavity (A. Bud^e). 880 VERTEBRAL COLUMN. 443. FURTHER FORMATION OF THE BODY.— Body Wall. — (i) The coelom, or pleuro-peritoneal cavity, becomes larger and larger, while, at the same time, the difference between the body wall and the wall of the intes- tine becomes more pronounced. The latter becomes more separated from the pro to vertebra, as the middle plate begins to be elongated to form a mesentery. The body wall, or somatopleure, composed of the epiblast and the outer layer of the cleft mesoblast, becomes thickened by the ingrowth into it of the muscular layer from the muscle plate, and the position of the bones and the spinal nerves from the protovertebrae. These grow between the epiblast and the outer layer of the mesoblast {Jiemak). [The somatopleure, or parietal lamina, from each side grows forward and toward the middle line, where they meet to form the body wall, while at the same time the splanchnopleure, or visceral lamina, on each side also grow and meet in the middle line, and when they do so they enclose the intestine. Thus, there is one tube within the other, and the space between is the pleuro-peritoneal cavity.] 1 2 ) Vertebral Column. — A dorsally-placed structure, called the muscle plate \^Iit»mk'. is differentiated from each of the protovertebrse ; the remainder of the protovertebra, the protovertebra proper (Kolliker), coalesces with that on the other side, so that both completely surround the chorda, to form the mem- brana reuniens inferior {Rdchert ), in the chick on the 3d, and in the rabbit on the loth day, while at the same time they close over the medullary tube dor- sally in the chick at the 4th day, to form the membrana reuniens superior. Thus, there is a union of the masses of the protovertebrs in front of the medul- lary tube, which encloses the chorda, and represents the basis of the bodies of all the vertebrae, whilst the membrana reuniens superior, pushed between the muscle plates and the epiblast on the one hand and the medullary tube on the other, represents the position of the entire vertebral lamintr as well as the intervertebral ligaments between them. In some rare cases the membrana reuniens superior is not developed, so that the medullary tube is covered only by the epiblast (epidermis), either throughout its entire extent or at certain parts. This constitutes the condi- tion of spina bifida, or, when it occurs in the head, hemicephalia. The vertebral column at this membranous stage is in the same condition as the vertebral column of the cyclostomata (Petromyzon). The membranes of the spinal cord, the spinal ganglia, and spinal ner\-es are formed from the membrana reuniens superior. Lastly, parts of the somatopleures also grow toward the middle line of the back, and insinuate themselves between the muscle plate and the epiblast ; thus, the dorsal skin is formed {^Jiemak). In the membranous vertical column there are formed the several cartilaginous vertebrae, the one behind the other, in man at the 6th to 7th week, although at first they do not form closed vertebral arches; the latter are closed in man about the 4th month. Each cartilaginous vertebra, however, is not formed from a pair of protovertebrae, /. e., the 6th cervical vertebra from the 6th pair of protover- tebrte, but there is a new subdivision of the vertebral column {Rcmak), so that the lower half of the preceding protovertebra and the upper half of the succeeding protovertebra unite to form the final vertebra. While the bodies are becoming cartilaginous the chorda becomes smaller, but it still remains larger in the inter- vertebral disks. The body of the first vertebra or atlas unites with that of the axis to form its odontoid process (Rathke), and, in addition, it forms the arcus anterior atlantis and the transverse ligament {Hasse). The chorda can be followed upward through the ligamentum suspensorium dentis as far as the posterior part of the sphenoid bone. The histogenetic formation of cartilage from the indifferent formative cells takes place by division and growth of the cells, until they ultimately form clear nucleated sacks. The cement sub- stance is probably formed by the outer parts of the cells (parietal substance) uniting and secreting the intercellular substance. It is supposed by some that the latter contains fine canals, which connect tlie protoplasm of the adjoining cells. FORMATION OF THE AMNION AND ALLANTOIS. 881 Visceral Clefts and Arches. — Each side of the cervical region contains four slit-like openings — the visceral clefts or branchial openings i Rathke) ; in the chick the y\q. 564. upper three are formed at the 3d, and the fourth on the 4th day. Above the slits are thickenings of the lateral wall, which constitute the visceral or branchial arches. The clefts are formed by a perforation from the fore- gut, but which, perhaps, does not always occur in the chick, mammal and man (His), and they are lined by the cells of the hypoblast. On each side in each viscera! arch, i.e., above and below each cleft, there runs an aortic arch, five on each side (Fig. 563, IX). These aortic arches persist in fishes. In man all the slits close except the uppermost one, from which the auditory meatus, the tympanic cavity, and the Eustachian tube are developed i^Huschke, Rathke, . Reichert). The four visceral arches are, for the most part, made use of later for other forma- Embrjo of the mole ( x ?)■ tions I p. 8S9 ). Primitive Mouth and Anus. — Immediately under the fore-brain, in the middle line, is a thin spot, where there is at first a small depression, and ulti- mately a rupture, forming the primitive oral aperture, which represents both the mouth and the nose. Similarly, there is a depression at the caudal end, and the depression ultimately deepens, thus communicating with the hind-gut to form the anus. When the latter part of the process is incomplete there is atresia ani, or imperforate anus. Several processes are given off from the primitive intestine, including the hypoblast and its muscular layers, to form the lungs, the liver, the pancreas, the caecum (in birds), and the allantois. The extremities appear at the sides of the body as short, unjointed stumps or projections at the 3d or 4th week in the human embryo (Fig. 564). 444. FORMATION OF THE AMNION AND ALLANTOIS.— Amnion. — During the elevation of the embryo from its surroundings, imme- diately in front of the head (at the end of the 2d day in the chick), there rises up a fold consisting of the epiblast and the outer layer of the mesoblast, which gradually extends to form a sort of hood over the cephalic end of the embryo (VI, A). In the same way, but somewhat later, a fold rises at the caudal end, and between both along the lateral borders similar elevations occur, the lateral folds (Fig. 563, III, A). All these folds grow over the back of the embryo to meet over the middle line posteriorly, where they unite at the 3d day in the chick to form the amniotic sack. Thus, a cavity which becomes filled with fluid — the amniotic fluid-s— is developed around the embryo [so that the embryo really floats in the fluid of the amniotic sack]. In mammals, also, the amnion is devel- oped very early, just as in birds (Fig. 563, VII, A). From the middle of preg- nancy onward the amnion is applied directly to the chorion, and united to it by a gelatinous layer of tissue, the tunica medica of Bischoff. Amniotic Fluid. — The amnion, and the allantois as well, are formed only in mammals, birds and reptiles, which have hence been called amniota, while the lower vertebrates, which are devoid of an amnion, are called anamnia. Composition. — The amniotic fiuid\% a clear, serous, alkaline fluid, specific gravity 1007 to ion, containing, besides epithelium, lanugo hairs, )/^ to 2 per cent, of fixed solids. Among the latter are albumin (yjto \i per cent.), mucin, globulin, a vitelline like l)ody, some grape sugar, urea, ammonium carbonate, ver)- probably derived from the decomposi- tion of urea, sometimes lactic acid and kreatinin, calcic sulphate and phosjihate, and common salt. -About the middle of pregnancy it amounts to about 1-1-5 k'lo- [2.2-3.3 ft>s.], and at the end about 0.5 kilo. The amniotic fluid is of fcetal origin, as is shown bv its occurrence in birds, S6 882 ALLANTOIS. and is, perhaps, a transudation through the fatal membranes. In mammals, the urine of the foetus forms part of it during the second half of pregnancy (Gtisserow). In the pathological condition of Hydramnion, the blood vessels of the uterine mucous membrane secrete a watery fluid. The fluid preserves the fa;tus, and also the vessels of the foetal membranes, from mechanical injuries; it permits the limbs to move freely, and protects them from growing together; and, lastly, it is import- ant for dilating the os uteri during labor. The amnion is capable of contraction at the 7th day in the chick ; and this is due to the smooth muscular fibres which are developed in the cutaneous plate in its mesoblastic portion [/iema/t), but nerves have not been found. Allantois. — From the anterior surface of the caudal end of the embryo there grows out a small double projection, which becomes hollowed out to form a sack projecting into the cavity of the coelom or pleuro-peritoneal cavity (VI, a); it constitutes the allantois, and is formed in the chick before the 5th day, and in man during the 2d week. Being a true projection from the hind-gut, the allan- tois has two layers, one from the hypoblast and the other from the muscular layer, so that it is an offshoot from the si)lanchnopleure. From both sides there pass on to the allantois the umbilical arteries from the hypogastric arteries, and they ramify on the surface of the sack. The allantois grows, like a urinary bladder gradually being distended, in front of the hind-gut in the pleuro-peritoneal cavity toward the umbilicus ; and, lastly, it grows out of the umbilicus, and projects beyond \X alongside the omphalo-mesenteric or vitelline duct, its vessels growing with it (VII, a) ; but after this stage it behaves differently in birds and mammals. In birds, after the allantois passes out of the umbilicus, it undergoes great development, so that within a short time it lines the whole of the interior of the shell as a highly vascular and saccular membrane. Its arteries are at first branches of the primitive aoitse, but with the development of the posterior extremities they appear as branches of the hypogastric arteries. Two allantoidal, or um- bilical veins, proceed from the numerous capillaries of the allantois. They pass backward through the umbilicus, and at first unite with the omphalo-mesenteric veins to joni the venous end of the heart. In birds this circulation on the allantois, or second circulation, is respiratory in function, as its vessels serve for the exchange of gases through the porous shell. This circulation gradually assumes the respiratory functions of the umbilical vesicle, as the latter gradually becomes smaller and smaller, and ceases to be a sufficient respiratory organ. Toward the end of the period of in- cubation, the chick may breathe and cry within the shell (Aristotle) — a proof that the respiratory function of the allantois is partly taken over by the lungs. The allantois is also the excretory organ of the urinary constituents. Into its cavity in mammals the ducts of the priiiiitiie kidneys, or the Wolffian duets, open, but in birds and reptiles, which possess a cloaca, these open into the posterior wall of the cloaca. The primitive kidneys, or Wolftian bodies, consist of many glomeruli, and empty their secretion through the Wolffian ducts into the allantois (in birds into the cloaca), and the secretion passes through the allantois, per the umbilicus, into the peripheral part of the urinary sack. Remak found ammonium and sodium urate, allantoin, grape sugar, and salts in the contents of the allantois. From the eighth day onward, the allantois of the chick is contractile ( Vulpian), owing to the presence of smooth fibres derived from the splanchnopleure. Lymphatics accompany the branches of the arteries (A. BiiJi^'e). Allantois in Mammals. — In mammals and man the relation of the allantois is somewhat different. The first part or its origin forms the urinary bladder, and from the vertex of the latter there proceeds through the umbilicus a tube, the urachus, which is open at first (^VIII, a). The blind part of the sack of the al- lantois outside the abdomen is in some animals filled with a fluid like urine. In man, however, this sack disappears during the second month, so ttiat there remains only the vessels which lie in the muscular part of the allantois. In some animals, however, the allantois grows larger, does not shrivel, but obtains through the urachus froin the bladder an alkaline turbid fluid, which contains some albumin, sugar, urea, and allantoin. The relations of the umbilical vessels will be described in connection with the foetal membranes. 445. FCETAL MEMBRANES, PLACENTA, FCETAL CIRCU- LATION. — Decidua. — WHien a fecundated ovum reaches the uterus, it then becomes surrounded by a special covering, which William Hunter ( 17 75) described as tiie membrana decidua, because it was shed at birth. We distinguish the decidua vera 1 Fig. 563, \'11I,/), which is merely the thickened, very vascular, softened, more spongy, and somewhat altered mucous membrane of the uterus. STRUCTURE OF THE DECIDUA VERA. 883 [Sometimes in a diseased condition, as in dysmenorrhcea, the superficial layer of the uterine mucous membrane is thrown off nearly en masse in a triangular form (Fig. 565 ). This serves to show the shape of the decidua, which is that of the uterus.] When the ovum reaches the uterus it is caught in a cryi)t or fold of the decidua, and from the latter there grow up elevations around the ovum ; but these elevations are thin, and soon meet over the back of the ovum to form the de- cidua reflexa (VIII, /-). At the second to third month there is still a space in the uterus outside the reflexa ; in the fourth month the whole cavity is filled by the ovum. At one part the ovum lies directly upon the d. vera [and that part is spoken of as the decidua serotina], but by far the greatest part of the surface of the ovum is in contact with the reflexa. In the region of the d. serotina the placenta is ultimately formed. Structure of the Decidua Vera. — The d. vera at the third month is 4 to 7 mm. thick, and at the fourth only i to 3 mm., and it no longer has any epithelium ; but it is very vascular, and is possessed of lymphatics around the glands and blood vessels (Leopold), and in its loose substance are large round cells (decidua cells — A'd/liker), which in the deeper parts become changed into fibre cells — there are also lymphoid cells. The uterine glaiids, which become greatly developed at Fig. 565. A dysmenorrhceal membrane laid open. the commencement of pregnancy, at the third to the fourth month form non-cellular, wide, bulging lubes, which become indistinct in the later months, and in which the epithelium disappears more and more. The reflexa, much thinner than the vera from the middle of pregnancy, is devoid of eoithelium, and is without vessels and glands. Toward the end of pregnancy both deciduxe unite. The ovum, covered at first with small hollow villi, is surrounded by the decidua. From the formation of the amnion it follows that, after it is closed, a completely closed sack passes away from the embryo to lie next the primitive chorion. This membrane is the "serous covering" of v. Baer (Fig. 563, VII, .f), or the false amnion. It becomes closely applied to the inner surface of the chorion, and extends even into its villi. The allantois proceeding from the umbilicus comes to lie directly in contact with the ftetal memb'rane ; its sack disappears about the second month in man, but its vascular layer grows rapidly and lines the whole of the inner surface of the chorion, where it is found on the eighteenth day ( Coste). From the fourth week the blood vessels, along with a covering of connective tissue, branch and penetrate into the hollow cavities of the villi, and completely fill them. At this time the primitive chorion disappears. Thus we have a stage 884 PLACENTA. of general vascularization of the chorion. In the place of the derivative of the zona pellucida we have the vascular villi of the allantois, which are covered by the epiblastic cells derived from the false amnion. This stage lasts only until the third month ; when the chorionic villi disappear all over the surface of the ovum in contact with the decidua reflexa. On the other hand, the villi of the chorion, where they lie in direct contact with the decidua serotina, become larger and more branched. Thus there is distinguished the chorion laeve and c. frondosum. The chorion laeve, which consists of a connective-tissue matrix covered externally by several layers of cells, has a few isolated villi at wide intervals. Between the chorion and the amnion is a gelatinous substance (membrana intermedia) or undeveloped connective tissue. Placenta. — The large villi of the chorion frondosum penetrate into the tissue of the decidua serotina of the uterine mucous membrane. [It was formerly sup- posed that the chorionic villi entered the mouths of the uterine glands, but the researches of Ercolani and Turner have shown that, although the uterine glands enlarge during the early months of utero-gestation, the villi do not enter the Fig. 566. Hum.in pl.-icent.ll villi. Blood glands. The villi enter the crypts of the uterine mucous membrane. The glands of the inner layer of the decidua serotina soon disappear.] As the villi grow into the decidua serotina they push against the walls of the large blood vessels, which are similar to capillaries in structure, so that the villi come to be bathed by the blood of the mother in the uterine sinuses, or they float in the colossal decidual capillaries (VIII, b). The villi do not float naked in the maternal blood, but thpy are covered by a layer of cells derived from the decidua. Some villi, with bulbous ends, unite firmly with the tissue of the uterine part of the placenta to form a firm bond of connection. [The placenta is formed by the mutual inter- growth of the chorionic villi and the decidua serotina.] Thus, it consists of a foetal part, including all the villi, and a maternal or uterine part, which is the very vascular decidua serotina. At the time of birth, both parts are so firmly united that they cannot be separated. Around the margin of the placenta is a large venous vessel, the marginal sinus of the placenta. [Friedlander found the uterine sinuses below the placental site blocked by giant cells after the 8th month STRUCTURE OF THE UMBILICAL CORD. 885 of pregnancy. Leopold confirms this, and found the same in the serotinal veins.] Functions. — The placenta is the nutritive, excretory, and respiratory organ of the fLetus (§ 368) ; the latter receives its necessary pabulum by endosmosis from the maternal sinuses through the coverings and vascular wall of the villi in which the fcetal blood circulates. [The placenta also contains ^/irc^if//.] [Structure. — If a piece of a fresh placenta be leased in normal saline solution, one sees the structure at once. The villi are provided with lateral otTshoots, and consist of a connective-tissue framework, containing a capillary network with arteries and veins (Fig. 566), while the villi them- selves are covered by a layer of somewhat cubical epithelium.] Uterine Milk. — Between the villi of the placenta there is a clear fluid which contains numerous small albuminous globules, and this fluid, which is abundant in the cow, is spoken of as the uterine milk. It seems to be formed by tiie break- ing up of the decidual cells. It has been supposed to be nutritive in function. [The maternal placenta, therefore, seems to be a secreting structure, while the fcetal part has an absorbing function. The uterine milk has been analyzed by Gamgee, who found that it contained fatty, albuminous, and saline constituents, while sugar and casein were absent.] The investigations of Walter show that after poisoning pregnant animals with strychnin, morphia, veratrin, curara, and ergotin, these substances are not found in the foetus, although many other chemical substances pass into it. [Savory fouiid that strychnin injected into a foetus in utero caused tetanic convulsions in the mother (bitch), while syphilis may be communicated from the father to the mother through the medium of the fcetus (Hutchinson). A. Harvey's record of observations on the crossing of breeds of animals— chiefly of horses and allied species — show that materials can pass from the foetus to the mother.] On looking at a placenta, it is seen that its villi are distributed on large areas separated from each other by depressions. This complex arrangement might be compared with the cotyledons of some animals. The position of the placenta is, as a rule, on the anterior or posterior wall of the uterus, more rarely on the fundus uteri, or laterally from the opening of the Fallopian tube, or over the internal orifice of the cervix, the last constituting the condition of placenta praevia, which is a very dan- gerous form of placental inserti m, as the placenta has to be ruptured before birth can take place, so that the mother often dies from hemorrhage. The umbilical cord may be inserted in the centre of the placenta (insertio centralis), or more towarrt'-on;/), and those behind it ( post-oral ),ha.\t a relation to certain nerves. The lachrymal slit between the frontal and nasal processes is supplied by the first division of the tri- geminus. The nasal slit between the superior maxillary process and the nasal process is supplied by the bifurcation of the thin/ ner-je. The oral cleft, between the superior maxillary processes and the mandibular arch, is supplied by the second and third divisions of the trigeminus. The first post- oral or tympanic- Eustachian cleft, between the mandibular arch (ist) and the hyoid arch, is sa^- plied by the /()r//o r/K/-r7. The next cleft is supplied by the ^/oiw-/.inry«^t'rt/, and the succeeding clefts by branches of the vagus.^ The thymus and thyroid glands are formed as paired diverticula from the epithelium covering the branchial arches. The epithelium of the last two clefts does not disappear (pig), but proliferates and pushes inward cylindrical processes, which develop into two epithelial vesicles, the paired com- mencement of the thyroid glands. These vesicles have at first a central slit, which communicates with the pharynx ( IVol/ler). According to His, the thyroid gland appears as an epithelial vesicle 890 DEVELOPMENT OF THE BONES OF THE LIMBS. in the region of the 2d pair of visceral arches in front of the tongue — in man at the 4th week. Solid buds, which ultimately become hollow, are given off from the cavity in the centre of the embryonic thyroid gland. The two glands ultimately unite together. The only epithelial part of the thymus which remains is the so-called concentric corpuscles (p. 178). According to Born, this gland is a diverticulum from the 3d cleft, while His ascribes its origin to the 4th and 5th aortic arches in man at the 4th week. The carotid gland is of epithelial origin, being a variety of the thyroid {^Stiida). The Extremities. — The origin and course of the nerves of the brachial plexus show that the t4ppcr exiretnily was originally placed much nearer to the cranium, while the position of \ht poste- rior pair corresponds to the last lumbar and the 3d or 4th sacral vertebrre {His). The clavicle, according to Bruch, is not a membrane bone, but is formed in cartilage like the furculum of birds ( Ce^evlHiui). At the 2d month it is four times as large as the upper limb ; it is the first bone to ossify at the 7th week. At puberty a sternal epiphysis is formed. Episternal bones must be referred to the clavicles ( Gotte). Ruge regards pieces of cartilages existing between the clavicle and the sternum, as the analogues of the episternum of animals. The clavicle is absent in many mammals (carnivora) ; it is very large in flying animals, and in the rabbit is half membranous. The furculum of birds represents the united clavicles. The scapula at first is united with the clavicle {Rathke, Gotte), and at the end of the 2d month Fig. 569. it has a median centre of ossification, which rapidly extends. Morphologically, the accessory centre in the coracoid process is interesting ; the latter also forms the upper part of the articular surface. In birds the corresponding structure forms the coracoid bone, and is united with the sternum; while in man only a membranous band stretches from the tip of the coracoid process to the sternum. The long, basal, osseous strip corresponds to the sitfrasiapiilar bone of many animals. The other centres of ossification are —one in the lower angle, two or three in the acromion, one in the articular surface, and an inconstant one in the spine. Complete consolidation occurs at puberty. The humerus ossifies at the 8th to the 9th week in its shaft. The other centres are —one in the upper epiphysis, and one in the capitellum (ist year) ; one in the great tuberosity and one in the small tuberosity (2d year) ; two in the condyles (5th to loth year) ; one in the trochlea (12th year). The epiphyses unite with the shaft at the i5th to 20th year. The radius ossifies in the shaft at the 3d month. The other centres are — -one in the lower epi- physis (5th year), one in the upper (6th year), and an inconstant one in the tuberosity, and one in the styloid jarocess. They unite at puberty. The ulna also ossifies in the shaft at the 3d month. There is a centre in the lower end (6th year), two in the olecranon (nth to 14th year), and an inconstant one in the coronoid process, and one in the styloid. process. They consolidate at puberty. CHEMICAL COMPOSITION OF BONE. 891 The carpus is arranged in mammals in two rows. The first row contains three bones — the radial, intermediate and ulnar bones. In man these are represented by the scaphoid, semilunar and cuneiform bones; the pisii'orm is only a sesamoid bone in the tendon of the flexor carpi ulnaris. The second row really consists of as many bones as there are digits {eg., salamander). In man the common position of the 4th and 5th fingers is represented by the unciform bone. Morphologic- ally, it is interesting to observe that an os centrale, corresponding to the os carpale centrale of reptiles, amphibians, and some mammals, is formed at first, but disappears at the end of the 3d month, or unites with the scaphoid. Only m very rare cases is it persistent. All the carpal bones are cartilaginous at birth. They ossify as follows : Os magnum, unciform ( 1st year), cuneiform (3d year), trapezium, semilunar (5lh year), scaphoid (6th year), trapezoid (7th year), and pisiform (12th year). The metacarpal bones have a centre in their diaphyses at the end of the 3d month, and so have the phalanges. All the phalanges and the first bone of the thumb have their cartilaginous epiphyses at the central end, and the other metacarpal bones at the peripheral end, so that the first bone of the thumb is to be regarded as a phalanx. The epiphyses of the metacarpal bones ossify at the 2d, and those of the phalanges at the 3d year. They consolidate at puberty. The innominate bone, when cartilaginous, consists of two parts — the pubis and the ischium {Hosenberg). Ossification begins with three centres — one in the dium (3d to 4th month), one in the descending ramus of the ischium (4th to 5th month), one in the horizontal ramus of the pubis (5th to 7th month). Between the 6th to the 14th year three centres are formed where the bodies of the three bones meet in the acetabulum, another in the superficies ouricularis, and one in the symphysis. Other accessory centres are : One in the anterior inferior spine, the crest of the ilium, the tuberosity and the spine of the ischium, the tuberculum pubis, eminentia ileopectinea, and floor of the ace- tabulum. At first the descending ramus of the pubis and the a.'cending ramus of the ischium unite at the 7th to 8th year; the Y-shaped suture in the acetabulum remains until puberty (Fig. 569). The femur has its middle centre at the end of the 2d month. At birth there is a centre in the lower epiphysis ; slightly later in the head. In addition, there is one in the great trochanter (3d to I ith year), one in the lesser trochanter (13th to 14th year), two in the condyles (4th to 8th yearl ; all unite about the time of puberty. The pattlla is a sesamoid bone in the tendon of the quadriceps femoris. It is cartilaginous at the 2d month, and ossifies from the 1st to the 3d year. The tarsus generally resembles the carpus. The os calcis ossifies at the beginning of the 7th month, the astragalus at the beginning of the 8th month, the cuboid at the end of the loth, the scaphoid (ist to 5th year), the I and II cuneiform (3d year), and the III cuneiform (4th year). An accessory centre is formed in the heel of the calcaneum at the 5lh to loth year, which consoli- dates at puberty. The metatarsal bones are formed like the metacarpals, only later. [Histogenesis of Bone. — The great majority of our bones are laid down in cartilage, or are preceded by a cartilaginous stage, including the bones of the limbs, backbone, base of the skull, sternum and ribs. These consist of solid masses of hyaline cartilage covered by a memb/ane, which is identical with and ultimately becomes the periosteum. The formation of bone, when preceded by cartilage, is called endochondral bone. Some bones, such as the tabular bones of the vault of the cranium, the facial bones, and part of the lower jaw, are not preceded by cartilage. In the latter there is merely a membrane present, while from and in it the future bone is formed. It becomes the future periosteum as well. This is called the intra-membranous or periosteal mode of formation.] [Endochondral Formation. — (i) The cartilage has the shape of the future bone, only in minia- ture, and it is covered with periosteum. In the cartilage an opaque spot or centre of ossification appears, due to the deposition of lime salts in its matrix. The cartilage cells proliferate in this area, but the first bone is formed under the periosteum in the shaft, so that an o.sseous case, like a mufT, surrounds the cartilage. This bone is formed by the subperiosteal osteoblasts. (2) Blood vessels, accompanied by osteoblasts and connective tissue, grow into the cartilage from the osteogenic layer of the periosteum [periosteal processes of Virchow), so that the cartilage becomes channelled and vascular. As these channels extend they open into the already enlarged cartilage lacuna-, absorption of the matrix taking place, while other parts of the cartilaginous matrix become calcified. Thus, a series of cavities, bounded by calcified cartilage — the primary medullary cavities — are formed. They contain the primary or cartilage marrow, consisting of blood vessels, osteoblasts, and osteoclasts, carried in from the osteogenic layer of the periosteum, and, of course, the cartilage cells that have been liberated from their lacunae. (3) The osteoblasts are now in the interior of the cartilage, where they dispose themselves on the calcified cartilage, and secrete or form around them an osseous matrix, thus enclosing the calcified cartilage, while the osteoblasts themselves become embedded in the products of their own activity and remain as bone corpuscles. Bone, therefore, is at first spongy bone, and as the primary medullary spaces gradually become filled up by new osseous matter it becomes denser, while the calcified cartilage is gradually absorbed. It is to be remembered that, pari passu with the deposition of the new bone, bone and cartilage are being absorbed by the osteoclasts.] Chemical Composition of Bone. — Dried bone contains \ of organic matter or ossein, from which gelatin can be extracted by prolonged boiling; and about 5 mineral matter, which consists of neutral calcic phosphate, 57 per cent. ; calcic carbonate, 7 per cent. ; magnesic phosphate, I to 2 892 DEVELOPMENT OF THE HEART. per cent. ; calcic fluoride, I per cent., with traces of chlorine ; and water, about 23 per cent. The marrow contains fluid, fat, albumin, hypoxanthin, cholesterin and extractives. Tlie red marrow contains more iron, corresponding to its larger proportion of haemoglobin (Nasse). [The medullary cavity of a long bone is occupied hy yel/o~v marrow, which contains about 96 per cent, of fat. The red marrow occurs in the ends of long bones, in the flat bones of the skull, and in some short bones. It contains very little fat, and is really lymphoid in its characters, being, in fact, a blood-forming tissue (p. 28).] Growth of Bones. — Long bones grow in thickness by the deposition of new bone from the periosteum, the osteoblasts becoming embedded in the osseous matrix to form the bone corpuscles. Some of the fibres of the connective tissue, which are caught up, as it were, in the process, remain as Sharpey's fibres, which are calcified fibres of while fibrous tissue, bolting together the peripheric lamelloe. [Miiller and Schafer have shown that there are also fibres in the peripheric lamellre com- parable to yellow elastic fibres ; they branch, stain deeply with magenta, and are best developed in the bones of birds.] [At the same time that bone is being deposited on the surface it is being absorbed in the marrow cavity by the action of the osteoclasts, so that a metallic ring placed round a hone in a young animal ultimately comes lo lie in the medullary cavity [Diihaviel). The growth in length takes place by the continual growth and ossification of the epiphysial cartilage. Tlie cartilage is gradu- ally absorbed from below, but it proliferates at the same time, so that what is lost in one direction is more than made up in the other (y. Hunter).'] When the growth of bone is at an end, the epiphysis becomes united to the diaphysis, the epi- physiai cartilage itself becoming ossified. It is not definitely proved whether there is an interstitial expansion or growth of the true osseous substance itself, as maintained by WoW (§ 244, 9). [Howship's Lacunae. — The osteoclasts or myeloplaxes are large muUinucIear giant cells, which erode bone. They can be seen in great numbers lying in small depressions, corresponding to them — Howship's lacunne — on the fang of a temporary tooth, when it is being alisorhed. They are readily seen in a microscopical section of spongy bone with the soft parts preserved.] The form of a bone is influenced by external conditions. The bones are stronger the greater the activity of the muscles acting on them. If pressure acting normally upon a bone be removed, the bone develops in the direction of least resistance, and becomes thicker in that direction. Bone develops more slowly on the side of the greatest external pressure, and it is curved by unilateral pressure [Lesshaft). 448. DEVELOPMENT OF THE VASCULAR SYSTEM.— Heart. — [The heart appears as a solid mass of cells in the splanchnopleure, at the front end of the embryo, immediately under the "fore-gut." Very soon a cavity appears in this mass of cells; some of the latter float free in the fluid, while the cellular wall begins to pulsate rhythmicallv. This hollow cellular structure elongates into a tube, which very soon assumes a shape somewhat like an S (Fig. 570, I), and there are indications of its being subdivided into (a) an upper aortic part with the bulbus arteriosus ; [b) a middle or ventricular part; and (v\ a lower venous or auricular part. The heart then curves on itself in the form of a horseshoe (2), so that the venous end f.A) comes to lie above and slightly behind the arterial end. On the right and left side, respectively, of the venous part is a blind hollow outgrowth, which forms the large auricle on each side (3, 0, Oj). The flexure of the body of the heart corresponding to the great curvature (2, V) is divided into two large compart- ments (3), the division being indicated by a slight depression on the surface. The large truncus venosus (4, V), which joins with the middle of the posterior wall of the auricular part, is composed of the superior and inferior venae cava>. This common trunk is absorbed at a later period into the enlarging auricle, and thus arise the separate terminations of the superior and inferior venii; cavEe. In man, the heart soon comes to lie in a special cavity, which in part is bounded by a portion of the diaphragm {//is). At the 4th-5th week the heart begins to be divided into a right and a left half. Corresponding to the position of the vertical ventricular furrow, a septum grows upward vertically in the interior of the heart, and divides the ventricular part into a right and lefi ventricle (5, R, L). There is a constriction in the heart between the auricular and ventricular portions, forming the canalis auricularis. It contains a communication between the auricle and both ventricles, lying between an anterior and posterior projecting lip of endothelium, from which the auriculo-ventricular valves are formed (F. Schmidt). The ventricular septum grows upward toward the canalis auricularis, and is complete at the 8th week. Thus, the large undivided auricle commu- nicates by a right and left auriculo-ventricular opening with the corresponding ventricle (5). At the same time two septa (4, /(?) appear in the interior of the truncus arteriosus (4, ;>|, which ultimately meet, and thus divide this tube into two tubes (5, a f>), the latter forming the aorta and pulmonary artery, and are disposed toward each other like the tubes in a double-barrelled gun. The septum grows downward until it meets the ventricular septum (5), so that the right ventricle comes to be connected with the pulmonary artery, and the left with the aorta. The division of the truncus arteriosus, however, takes place only in the first part of its course. The division does not take place above, so that the pulmonary artery and aorta unite in one common trunk above. This communication between the pulmonary artery and the aorta is the ductus arteriosus Botalli (7, B). DEVELOPMENT OF THE HEART. 893 In the auricle a septum grows from the front and behind, ending internally with a concave margin. The vena cava superior f6, Cs) terminates to the right of this fold, so that its blood will tend to go toward the right ventricle, in the direction of the arrow in 6, x. The cava inferior, on the other hand (6, C7), opens directly opposite the fold. On the left of its orifice, the valve of the Fig. 570. Development of the heart, i. Early appearance of the heart; — a, aortic part, with the bulbus, d; v, venous end. 2, Horseshoe-shaped curving of the neart — a, aortic end, with the bulbus, 1^; K, ventricle : W, auricular part. 3, Formation of the auricular appendages, 0, o^ , and the external furrow in the ventricle. 4, Commencing division of the aorta,/, into two tubes, a. 5. View from the behind of the opened auricle, v, v, into the L and R ven- tricles, and between the two latter the projecting ventricular septum, while the aorta {a) and pulmonarj' artery (p) open into their respective ventricles. 6. Relation of the orifices of the superior {Cs) and inferior vena cava (O") to the auricle (scnematic view from above) — x, direction of the blood of the superior vena cava into the right auricle ; y, that of the inferior cava to the left auncle ; tL, tubercle of Lower. 7. Heart of the ripe fcetus — ^, right, /.,,left ventricle; a, aorta, with the innominate, c.c, carotid, c, and left subclavian artery, s; B, ductus arteriosus ; p, pulmonary artery, with the small branches / and ^, to the lungs. Fig. 571. The aortic arches, i. The first position of the i, 2 and 3 arches ; 2, 5, aortic arches ; ta, common aortic trunk ; ad. descending aorta. Disappearance of the upper two arches on each side — 5, subclavian artery ; v, vertebral artery; rtjr, axillary artery. 4. Transition to the final stage — ^, pulmonary artery ; W, aorta; rf5, ductus arte- riosus {Botalli) ; S, right subclarian, united with the right common carotid, which divides into the internal (Cr) and external carotid (CV) ; ajc, axillary ; f, vertebral artery. foramen ovale is formed by a fold growing toward the auricular fold, so that the blood current from the inferior vena cava goes only to the left^ in the direction of the arrow, _>/ : on the right of the orifice of the cava, and opposite the fold, is the Eustachian valve, which, in conjunction with the tubercle of Lower (/Zj, directs the stream from the inferior vena cava to the left into the left 894 DEVELOPMENT OF THE VEINS. auricle, through the previous foramen ovale. Compare the fcetal circulation (]). 885). After birth, tlie valve of the foramen ovale closes that aperture, while the ductus arteriosus also becomes impervious, so that the blood of the pulmonary artery is forced to go through the pulmonary branches proceefimg to the expanding lungs. Sometimes the foramen ovale remains pervious, giving rise to serious symptoms after a time, and constituting morbus ceruleus. Arteries. — Witli the formation of the branchial arches and clefts, the number of aortic arches on each side becomes increased to 5 (Fig. 571), which nm above and below each branchial cleft, in a branchial arch, and then all reunite behind in a common descending trunk (2, ad) [Knthke). These blood vessels remain only in animals that breathe by gills. In man, the upper two arcltes disappear completely (3). When the truncus arteriosus divides into tlie pulmonary artery and the aorta (4, P, A), the lowest arch on the left side, with its origin, forms the pulmonary artery (4), and it springs from the right side of the heart. Of these the lefl lowest arch forms the ductus arteriosus ((/^l, and from the commencement of the latter proceed the pulmonary branches of the pulmonary artery. Of the remaining arches which are united with the aorta, the left middle one {i.e., the fourth left) forms the permanent aortic arch into which the ductus arteriosus opens, while the right one (fourth) forms the subclavian artery: the third arch forms on each side the origin of the carotids (O', Ce). The arteries of the first and second circulations have been referred to already (p. 879). When the umbilical vesicle, with its primary circulation, diminishes, only I, First appearance of the veins of the embryo. II, Their transformations to form the final arrangement. one omphalo-inesenteric artery is present, which gives a branch to the intestine. At a later period the omphalo-mesenteric arteries atrophy, while the artery to the intestine — the superior mesenteric — becomes the largest of all, it being originally derived from one of the omphalo-mesenteric arteries. Veins of the Body. — The veins first formed in the body of the embryo it'elf are the two cardinal veins ; on each side an anterior (Fig. 572, I, c s), and a posterior (, e, bronchi; /, projecting vesicles. glands, while the mesoblastic part of the splanchnopleure forms the membranes of the glands, giv- ing them their form. The diverticula are as follows : — 1 . The salivary glands, which grow out from the oral cavity at first as simple solid buds, but afterward become hollow and branched. [The salivary glands are developed from the epiblast lin- ing the mouth (stomodceum),] 2. The lungs, which arise as two separate hollow buds (Fig. 575, A, 1), and ultimately have only one common duct, are protrusions from the oesophagus. The upper part of the united tracheal of the omentum. I and \\.~kg, gastro-hepatic ligament; ///, great, «, lesser curvature of the stomach ; J, posterior, and i anterior fold or plate of the omentum ; tnc, mesocolon ; c, colon. III.— L, Liver; t, small in- testine ; 3, mesentery ; /*, pancreas; ^, duodenum ; r, rectum; N, great omentum. tube forms the larynx. The epiglottis and the thyroid cartilage originate from the part which forms the tongue ( Gan^ho/ner). The two hollow spheres grow and ramify like branched tubular glands with hollow processes (B,/). In the first period of development there is no essential difference between the epithelium of the bronchi and that of the primitive air vesicles {Slieda). The spleen DEVELOPMENT OF THE URINARY APPARATUS. 897 and suprarenal capsules, however, are not developed in this way. The former arises in a fold of the mesogastrium (/^is) at the second month ; the latter are originally larger than the kidneys. 3. The pancreas arises in the same way as the salivary glands, but is not visible at the fourth week (His). 4. The liver begins very early, and appears as a diverticulum, with two \\o\\ovi primilive hepatic duels, which branch and form bile ducts. At their periphery they penetrate between the solid massis of cells — the liver cells — which are derived from the hypoblast. At the second month the liver is a large organ, and secretes at the third month (j* 1S2). 5. In birds two small blind sacks are formed from the hind-gut. 6. The fetal respiratory organ, the allantois, is treated of specially {\ 444). Peritoneum and Mesentery. — The inner surface of the coeloin, or body cavity, the surface of the intestine, and its mesentery are covered by a serous coat — \.\ie peri/oneum. At first the simple nitestine is contained in a fold, or duplicature of the per toneum ; on the stomach, which is merely at first a spindle-shaped dilatation of the tube placed vertically, it is called mesogastrium. After- ward, the stomach turns on its side, so that the left surface is directed forward and the right back- ward. Thus, the insertion of the mesogastrium, which originally was directed backward (to the vertebral column), is directed to the left ; the line of insertion forming the region of the great cur- vature, which becomes still more curved. From the great curvature the mesogastrium becomes elongated like a pouch (Fig. 576, I and II, s, i), constituting the omental sack, which extends so far Development of the internal generative organs. I, UndifTerential condition — D, reproductive gland, lying tubules ol the Wolffian body : VV, Wolffian duct ; M, Mullerian duct : S, urogenital sinus. ll.Tra ' in the female — F, ftmbria, with the hydatid, A'; T, Fallopian tube; U, uterus ; S, uro-genital sinus P, parovarium. Ill, Transformations in the male — H, testis; E, epididymis, with the hydatid, A; rans : V, vas deferens; S, uro-genital sinus; », male uterus; 4, ^, hind-gut ; a, allantois ; u, l w, perineum ; ^, position of the bladder ; S, uro-genital sinus. downward as to pass over the transverse colon and the loops of the small intestine (III, N). As the mesogastrium originally consists of two plates, of course the omentum must consist of four plates. .-\t the fourth month the posterior surface of the omental sack unites with the surface of the transverse colon (yc/i. Miillcr). 450. DEVELOPMENT OF THE URINARY AND GENERATIVE ORGANS. — Urinary Apparatus. — The first indication of this apjiaratus occurs in the chick at the second day, and in the rabbit at the ninth, as the ducts of the primitive kidneys or Wolffian ducts (Fig. 577. I. W), which are formed from some cells mapped off from the lateral plate above and to the side of the protovertebra;, and extending from the fifth to the last vertebra. Tlie ducts are solid at first, but soon become hollow, and from their cavities there extend laterally a series of small tubes, which in the chick communicate freely with the peritoneal cavity [A'o/IHer). Into one end of each of these tubes grows a tuft of blood vessels forming a structure resembling the glomeruli of the kidney. The tubes elongate, form convolutions, and increase in number. The upper end of the Wolffian duct is closed at first, its lower end, which lies in a projecting fold — the plica urogenitalis of Waldeyer — in the peritoneal cavity, opens into the urogenital sinus. Close above the orifice of the Wolffian duct appears the ureter as the duct of the kidney. The duct elongates, and branches at its upper end. Each canal at its end is like a stalked c.routchouc sack ( ToLil), and into it there grows the already formed glomerules. The duct of the kidney opens independently into the uro- genital sinus, and forms the ureter. The part where the 1 .ranching of the duct stops forms the 57 898 DEVELOPMENT OF THE OVARY AND TESTICLE. pelvis of the kidney, and the branches themselves the renal tubules. Toldt found Malpighian cor- puscles in the human kidney at the second month, and Henle's loops at the fourth. The first ap- pearance of the urinary bladder is at the fourth week (//is), and is more distinct at the second month, as the dilated first part of the allanlois (Fig. 577, 4, a). The upper part of the allantois remains as the obliterated urachus, in the middle vesical ligament. Internal Reproductive Organs. — In front of and internal to the Wolffian bodies, there arises in the mesoblast the elongated reproductive gland or mass of germ epithelium (Fig. 577, I, D), which in both sexes is originally alike. In addition, there is formed a canal or duct parallel to the Wolffian duct (W), which also opens into the urogenital sinus; this is Midler's duct (M). The elevation of the future reproductive gland is covered originally by germ epithelium [Wa/devt-r) The upper end of the Miillerian duct opens free into the abdominal cavity, while the lower ends of both ducts unite for a distance. Some of the germinal cells covering the surface of the future ovary enlarge to form ova, and sink into the stroma to form ova embedded in their Graafian follicles (^ 43^). In the female, the Miillerian ducts form the Fallopian tube (II, T),and the lower united ends the uterus. In the male the germ epithelum is not so tall. According to Waldeyer, there are two kinds of tubes in the Wolffian bodies and some of these penetrate the position of the reproductive gland. These tubes, which are connected with the Wolftian ducts, become the seminiferous tubules (v. VVilluh), and the Wolffian duct itself becomes the vas deferens, with the vesicula; seminales. According to some other observers, however, lubes which become the seminiferous tubules, are de- veloped within the reproductive gland itself, and these tubes Uned with their germ epithelium ulti- mately form a connection with the Wolffian ducts. The Miillerian ducts, which are really the ducts of the reproductive glands, disappear in man, all except the lowest part, which becomes the male uterus or vtsicula prostatica (III, u) — the homo- logue of the uterus. The upper tubules of the Wolffian body unite at the 3d month with the reproductive gland (which has now become the body of the testis), and become the coni vasculosi of the epididymis, which are lined by ciliated epithelium (E); the remainder of the Wolffian body disappears. Some detached tubules form the vasa aberrantia (a) of the testicle (A'oliel/). The hydatid of Morgagni [h), at the head of the epididymis, according to Luschka and others, is a part of the epididymis — Fleischl regards it as the rudiment of the male ovary. The organ of Girald^s is part of the Wolffian body. The Wolffian duct itself becomes the vas deferens (V) from which the vesicula; seminales are developed. The two Wolffian and two Miillerian ducts, as they enter the pelvis, unite to form a common cord — the genital cord. In the female the tubes of the Wolffian bodies disappear, all except a few tubules, lined with ciliated epithelium, constituting the parovarium, or organ of Rosemiiller (Fig. 555) and a part analogous to the organ of Giraldes in the broad ligament of the uterus (iraMtycr) (Fig. 577, P). The same is the case with the Wolffian ducts. In some animals (ruminants, pig, cat, and fox) they remain permanently as the ducts of Gaertner. The Miillerian duct is frayed out at its upper end to form the fimbrise of the Fallopian tube, and it is often provided with a hydatid (/;'). That part of the uro-genital sinus into which the four ducts open grows above into a hollow sphere, which forms the vagina (Rathie). According to Thiersch and Leuckart, however, the two Miillerian ducts unite at their lower ends to form the united uterus (U) and vagina, while their free upper ends form the Fallopian tubes (T). The Miillerian ducts at first open into the posterior part of the urinary bladder below the ureters (uro- genital sinus, S), while uUimately this part of the bladder becomes so elongated posteriorly that the vagina (the united Miillerian ducts) and the urethra are united below and deeply within the vesti- bule of the vagina. At the 3d to the 4th month, the uterus and vagina are not separate from each other, but at ihe 5th to 6th month the uterus is defined from the vagina. The testicles lie originally in the lumbar region of the abdominal cavity (Fig. 578, V /), and are carried by a fold of the peritoneum — the mesorchium (w). From the hilum of the testicle a cord, the gubernaculum testis, runs through the inguinal canal into the base of the scrotum. At the same time a septum-like process is developed independently from the peritoneum to the base of the scrotum (/. t'). The testicle passes through the inguinal canal into the scrotum, but the mechanism and cause of the descent are not accurately ascertained. — [^Descent of testis, \ 446.] The ovaries also descend somewhat. The round ligament of the uterus corresponds to the gubernaculum testis. A process of the peritoneum passes in the female into the inguinal canal as Nuck's canal. It is rare to find the ovaries descending into the labia majora. [The origin of the urinary and generative organs is undoubtedly associated with the development of the Wolffian bodies. The researches of Semper and Balfour on elasmobranch fishes show that the process is a very complex one. There is a mass of cells on each side of the vertebral column, which is divided into three parts, the first called the pronephros, or head kidney of Balfuur and Sedgwick, the middle one, the mesonephros or Wolffian body, and the posterior one or meta- nephros, which is formed after the other two, gives origin to the permanent kidney in the amniota. The Miillerian duct is connected with the pronephros, the Wolffian duct with the mesonephros, and the ureter to the metanephros.] [The following table, modified from Quain, shows the destiny of these structures: — DEVELOPMENT OF THE EXTERNAL GENITALS. 899 Femah. Fallopian tubes. Hydatid. Uterus and vairina. MuLLERiAN Ducts (Ducts of the Pronephros). Male. Hydatid of Morgagni. Male uterus. Wolffian Bodies (Mesonephros). Vasa efferentia, Coni vasculosi. Organ of Giraldes, Vasa aberrantia. Gubernaculum testis. Wolffian Ducts. Convoluted tube of epididymis. Vas deferens and vesiculje seminales. Metanephros. Ureter.] The external genitals are at first not distinguishable in the two sexes (Fig. 578, I). At the 4th week there is merely a hole at the posterior extremity of the trunk, representing both the anus and the opening of the urachus, and forming a cloaca (Fig. 577, 4, K). In front of this an elevation — the genital eminence — appears about the 6th week, and on each side of the orifice a large cutane- ous elevation (II, w). At the end of the 2d month there is a groove on the under surface of the genital eminence, leading back to the cloaca, and with distinct walls bounding it (II, r). At the Parovarium. Paroophoron. Round ligament of the uterus. Chief tube of parovarium. Ducts of Gaertner. Kidney. Development of the ternal genitals, /and//, — Genital Penis : R^ raphe penis : S, V and F/— Descent of the testicle ; /, M, abdominal wall; 5, scrotum. : r, genital groo' r, clitoris ; /, labi a : / r, processus vagi , coccyx : tv, cutaneous ele- alis of the perito- middle of the 3d month the cloacal opening is divided by the growth of the perineum, between the urachus (now become the urinary bladder) (Fig. 578, 5, b) and the rectum (M). In the male the genital eminence enlarges, its groove deepens from the opening of the bladder onward to the apex of the elevation at the loth week. The two edges unite to enclose the groove which becomes the urethra. When this does not take place, hypospadias occurs. At the 4th month the glaus, and at the 6th the prepuce, are formed. The large cutaneous folds meet in the middle line or raphe to form the scrotum. In the female the undifferentiated condition remains to a certain extent permanent. The small genital eminence remains as the clitoris, the margins of its furrow become the nymphcr, the cutane- ous elevations remain separate to form the labia majora. The uro genital sinus remains short as the vestibule of the vagina, while in man, by the closing of the genital groove, it has a long additional tube, the urethra. [The following illustrations, after Schroeder, show the changes of the external organs of generation in the female. In the early p;riod (6th week) the hind-gut (Fig. 579, R,) al- lantois {All), and the Miillerian ducts (M) communicate, but not with the exterior. .J^bout the loih week a depression or inflection of the skin takes place, genital cleft, until it meets the hindgut and allantois, whereby the cloaca (Fig. 580, CI) is formed. The cloaca is then divided into an anterior part, the urogenital sinus, into which the Miillerian ducts open, and a posterior part the anus. There is a downward growth of the tissue between the hind-gut and the allantois to form the peri- neum (Fig. 581). The uro. genital sinus then contracts at its upper part to form the short urethra, its lower part remaining as the vestibule (Fig. 582, Sv), while the vagina has been formed by the union of the lower parts of the two Miillerian ducts. The bladder (B) is the expanded lower end of the stalk of the allantois.] The causes of the difference of sex are by no means well known. From a statistical analysis of 80,000 cases, the influence of the age of the parents has been shown by Hofacker and Sadler. If the husband is younger than the wife, there are as many boys as girls; if Ixith are of the same 900 FORMATION OF THE CENTRAL NERVOUS SYSTEM. age, there are 1029 boys to 1000 girls; if the husband is older, 1057 boys to 1000 girls. In insects, food has a most important influence. Pfliiger's investigations on frogs show that all external condi- tions during development are without effect on the determination of the se.\, so that the latter would seem to be determined before impregnation. 451. FORMATION OF THE CENTRAL NERVOUS SYSTEM.— Fore brain.— At each side of the fore brain, or anterior cerebral vesicle, which is covered externally by epiblast and internally by the ependyma, there grows out a large stalked hollow vesicle, the rudiment of the cere- bral hemispheres. The relatively wide opening in the stalk, or communication, ultimately be- comes very small, and is the foramen of Monro. The middle part between the two cerebral vesi- cles remains small, and is the 'tween or inter brain with the 3d ventricle in its interior. It elon- gates at the second month toward the base of the brain as a funnel shaped projection, to form the tuber cinereum with the infundibulum. The thalami optici, projecting and enlarging from the sides of the 3d ventricle, narrow the foramen of Monro to a semilunar slit. At the base of the brain are formed, in the 2d month, the corpora albicantia, at the 3d thechiasma; while within the 3d ventri- cle, the commissures are formed. The hypophysis, belonging to the mid-brain, is a diverticulum of the nasal mucous membrane, extending through the base of the skull toward the hollow infundibulum, which grows to meet it. The choroid plexus, which grows into the ventricles of the hemispheres through the foramen of Monro, is a vascular development of the tependyma. At the 4th month, the conarium (pineal gland) is formed, and at this time the corpora quadrigemina cover the hemi- spheres. The corpora striata begin to be developed in the cerebral (lateral) ventricle at the 2d month, while the cornu ammonis is formed at the 4th month. At the 3d month the Sylvian fissure is formed, and the basis of the island of Reil. The permanent cerebral convolutions are formed from the 7th month onward. Fig. 579. Fig. 5 So. Fig. 581 Fig. 582. ^/^vV/ with the rectum and a genital sinus (Su) and to form the vagina (V) nuous with the allantois (.■!//— bladder) ; M, duct of MUlIer (v e. growing inward to lorm the vulva. Fig. 580. — I'he depre) llantois, to form the cloaca (C L). '- - — - by the downward gri Fig. 582.— Perineum cot •th of the I ipletely forn al septum. The du : A, depressio as become co ling divided , of M tiller ar The mid brain, or middle cerebral vesicle, is gradually covered over by the backward growth of the hemispheres; its cavity forms the aqueduct of Syh'itis. Depressions appear on the surface of the vesicle to divide it into four, the corpora quadrigemina, the longitudinal depression being formed at the 3d, and the transverse one at the 7th month. The cerebral peduncle is formed by a thickening in the base of this vesicle. In the hind-brain are formed the cerebellar hemispheres, which grow backward to meet in the middle line. The vermes is formed at the 7th month. The cerebellum covers in the part of the medullary tube lying below it, and which is not closed, as far as the calamus. The pons arises in the floor of the hind-brain at the 3d month. The spindle-shaped narrow after brain forms the medulla oblongata, with the opening of the medullary tube in its upper part. [The following table, from Quain, shows the destiny of each cerebral vesicle: — C Cerebral hemispheres, corpora striata, ■( corpus callosum, fornix lateral ven- \ tricles, olfactory bulb. 12. Thalamencephalon . . f Thalami optici, pineal gland, pitttitary (inter or 'tween brain.) \ ^"fX' """"^ «'''='^"' ^q^^duct of >- ^ ' y Sylvius I. Anterior Primary Vesicle . . . I. Prosencephalen . (fore-brain. ] , optic nerve. II. Middle Primary Vesicle . . . III. Posterior Primary Vesicle . . . f 3. Mesencephalon ( ^°''^°'f quadrigemina. crura , \ (mid-brain.) \ ^q^educt of Sylvms, optic l ^ ' \ (secondarily). cerebri, nerve ("4. Epencephalon f Cerebellum, pons, anterior part of the J (hind-brain.) \ fourth ventricle. j 5. Aletencep/ialon | Medulla oblongata, fourth ventricle, [ (after-brain.) \ auditory nerve. [Spinal Cord. — The spinal cord is developed from the medullary tube behind the medulla oblongata, first the gray matter around the canal, while the white matter is added afterward outside this. The ganglionic cells increase by division in amphibians [Lominsky). At first the spinal cord reaches the coccyx. The first muscles are formed in the back at the 2d month ; at the 4th month DEVELOPMENT OF THE SENSE ORGANS. 901 they are red. The spinal ganglia are formed from a special strip of cells, and they are seen at the 4th week, and so are the anterior spinal roots and some of the trunks of the spinal nerves, while the posterior roots are still absent. The peripheral nerves grow out from the ganglia of the spinal cord (first the motor and afterward the sensory nerves), and penetrate into the other parts of the body [His]. At first tliey are devoid of myelin. 452. DEVELOPMENT OF THE SENSE ORGANS.— Eye.— The primary optic vesicle grows out from the fore-brain toward the outer covering of the head or epiblast, and soon becomes folded in on itself (4th week), so that the stalked optic vesicle is shaped like an eggcup (Fig. 583, 1). The cavity in the anterior of this cup is called the secondary optic vesicle. The inflected part becomes the retina (IV, r), while the posterior part becomes the choroidal epithelium (IV, yt). The stalk becomes the optic nerve. At the under surface of the depression there is a slit — the choroidal fissure — which permits some of the mesoblast to gain access to the interior of the eye. This slit forms the coloboma (II) ; it is prolonged backward on the stalk, and contains the central artery of the retina. The margins of the colobonia afterward unite completely with each other, but in some rare conditions this does not take place, in which case we have to deal with a coloboma of the choroid or retina, as the case may be. In the bird, the embryonic colo- boma slit does not close up, but a vascular process of the mesoblast dips into it, and passes into the eye to form the pecten (p. 813) (Lieberku/in). The same is the case in fishes where there is a large vascular process of the meso- and epiblasl forming \he processus falciformis (p. 813). Development of the eye. I. — inflexion of the sack of the lens (L) into the primary opti ///, mesoblast. II. — The inflexion seen from below — », optic nerve; tf, the ouce inflected vesicle ; L, lens. HI. — Longitudinal section of II. IV — Further developl f, cornea ; m, membrana capsulo-pupiltaris : L, lens ; mia, 292 Acetylene, 42 Achromatopsy, 795 Achroodextrin, 244 Acid albumin, 409 Acids, free, 413 Acoustic nerve, 634 tetanus, 585 Acquired movements, 727 Acrylic acid series, 413 Action currents, 597 Active insufficiency, 537 Addison's disease, 486, 614 Adelomorphous cells, 267 Adenoid tissue, 335 Adipocere, 398 Adventitia, 112 -Kgophony, 205 Aerobes, 308 .•Esthesiometer, S47 .-Esthesodic substance, 670 Afferent nerves, 615 After birth, 902 After images, 797 After sensation, 749 Ageusia, 843 Agoraphobia, 637 Agrammatism, 730 Agraphia, 729 Ague, 367 Air, changes in respiration, 212. collection of, 209 composition of, 212 diffusion of, 216 expired, 213 impurities in, 225 quantity exchanged, 213 Air cells, 184 Alanin, 41 1 Albuminoids, 411 Albumins, 408 Albuminuria, 445 Albumoses, vegetable, 410 Alcohol, 3S5 Alcohols, 415 Alcoholic drinks, 386 Aleurone grains, 410 Alexia, 731 Alkali albumin, 409 Alkaline fermentation, 445 Alkaloids, 3S5 Alkophyr, 275 Allantoin, 417, 439 Allantois, 882 Allochiria, 853 Alloxan, 435 Alm^n's test, 450 Alternate hemiplegia, 68: paralysis, 681 Alternation of generations, 857 Amaurosis, 618 Amblyopia, 618 American crow-bar case, 704 Amido acids, 733 Amido-caproic acid, 281 Amines, 417 Aminia, 729 Ammoniafmia, 469 Amnesia, 730 Amnion, 881 Amniota, 881 Amniotic ffuid, 881 905 Amneboid movement, 31 Ampere's rule, 578 Amphiarthroses, 535 Amphoric breathing, 205 Amygdalin, 344 Amyloid substance, 410 Amylopsin, 280 Amylum, 416 Anabiosis, 856 Anacrotism, 130 Anaemia, 34, 65 metabolism in, 65 pernicious, 35 Anaerobes, 30S Ansesthesia dolorosa, 853 Anaesthetic leprosy, 614 Ancesthetics, 854 Anabolic, 373 Anakusis, 635 Analgesia, 672 Analgia, 854 Anamnia, 88 1 Anarthria, 729 Anasarca, 345 Anelectrotonus, 597 Aneurism, 137 Angiometer, 129 Angioneuroses, 700 Angiograph, 121 Anidrosis, 488 Animals, characters of, xxxvii Animal foods, 390 magnetism, 708 Anions, 579 Anisotropous substance, 495 Ankle clonus, 668 Anode, 579 Anosmia, 616 Antagonistic muscles, 538 Anthracometcr, 209 Anthracosis, 188, 226 Anthropocholic acid, 293 Anti-albumin, 274 Antiar, 344 Antihydrotics, 486 Antipeptone, 282 Antiperislalsis, 259 Anti-sialics, 241 Aortic valves, 72 Aperistalsis, 262 Apex beat, 78, 86 Aphakia, 757 Aphasia, 729, 730 Aphonia, 558 Apncea, 687 Appunn's apparatus, S33 906 INDEX. Apselaphesia. 853 Aqueous humor, 75S Arachnoid mater, 743 Archiblastic cells, 878 Area opaca, S65 pellucida, 865 vasculosa, S79 Argyll Robertson pupil, 777 Arhythmia cordis, 12S Aristotle's experiment, S49 Aromatic acids, 415 oxyacids, 417 Arrector pili muscle, 482 Arteries, 11 1 development of, 894 emptiness of, 696 rhythmical contraction of, 698 sounds in, 164 structure of, in tension in, 145 termination in veins, 160 Arteriogram, 121 Arterial tension, 125 Arthrodial joints, 535 Articular cartilage, 533 Articulation nerve corpuscles, S45 Artificial cold-blooded condition, 371 Artificial digestion, 275 gastric juice, 273 pancreatic juice, 283 Artificial respiration, 224 Marshall Hall's me- thod, 224 Sylvester's method, 224 Artificial selection, 903 Asparaginic acid, 417 Asphyxia, 222, 688 artificial respiration in, 224 recovery from, 224 Aspirates, 55S Aspiration of heart, 152 Assimilation, 373 Associated movement, 803 .■\static needles, 579 Asteatosis, 4S9 Asthma nervosum, 643 dyspepticum, 644 Astigmatism, 774 correction of, 775 test for, 775 Atavism, 903 Ataxaphasia, 729 Ataxia, 648, 721, 729, 731 Ataxic tabes, 672 Atelectasis, 225 Atmospheric pressure, 229 diminution of, 229 increase of, 230 Atresia ani, 881 Atrophy, 539 of the face, 630 Atropin, 511 in eye, 619, 777 Attention, time for, 707 Audible tone, lowest, 830 Auditory after sensations, 837 area, 723 auras, 723 centre, 723 delusions, 635 meatus, S16 nerve, S14 ossicles, 819 paths, 724 perception, 829 Auerbach's plexus, 262, 325 Auricles of heart, 68, 75, 83 Auscultation of heart, 93 of lungs, 195 Automatic excitement, 653 Autonomy, 70S Auxocardia, 104 Axis of vision, 787 Bacillus. 66, 307 amylobacter, 309 anthracis, 66 butyricus, 309 subtilis, 310 tubercle and others, 226 Bacterium, 66, 307, 313, 3S0 aceti, 309 cyanogeneum, 380 fcetidum, 489 lacticum, 308, 378 synxanthum, 380 termo, 313 Ball and socket joints, 535 Bantingism, 399 Barsesthesiometer, 850 Bas.-il ganglia, 733 Basetorical — Absorption, 346 Circulation, 182 Digestion, 317 Hearing, 837 Heat, 372 Kidney and urine, 475 Nerves and electro- physi- ology, 611 Nerve centres, 746 Peripheral nerves, 652 Reproduction and develop- ment, 903 Respiration, 230 Sight, 812 Skin, 490 Voice and speech, 559 Hoarseness, 558 Holoblastic ova, 864 Homoiothermal animals, 350 Homologous stimuli, 748 Horopter, 804 Howship's lacunce, 892 Humor, aqueous, 758 Hunger and starvation, 394 Hyaloid canal, 757 Hybernation, 371 Hybrids, S73 Hydatids, 857 Hydra-mia, 66 Ilydramnion, 882 Hydrobilirubin, 295 Hydrocephalus, 745 Hydrochinon, 440 Hydrochloric acid, 269 Hydrocyanic acid, 42 INDEX. 913 Mydrogen given off, 418 in body, 407 Ilydrolytic ferments, 412 Hydronephrosis, 475 Hydrostatic lest, 190 Hydroxylbenzol, 440 HypaUusis, 635 Uypalgia, 854 Hyperivsthesia, 671 I lyperakusis, 634, 635 Hyperalgia, 854 Hyperdicrotism, 127 Hypergeusia, 843 Hyperglobulie, 64 Hyperidrosis, 4S8 Hyperinosis, 65 Hyperkinesia, 671 Hypernietrojjia, 771, 774 Hyperoptic, 771 Hyperosmia, 616 Hyperpselaphesia, S53 Hypertrophy of heart, 77 muscle, 539 Hypnotism, 708 Hypoblast', 875 Hypogeusia, 843 Hypoglossal nerve, 645 Hypophysis cerebri, 181, 900 Hypopselaphesia, 853 Hyposmia, 616 Hypospadias, 899 Hypoxanthin, 41 1 Ichthidin, 410 Icterus, 299 Identical points, S03 Ileo-colic valve, 259 Ileus, 259 Illumination of eye, 781 Illusion, 749 Images, formation of, 761 Imbibition currents, 597 Impregnation, 874 Impulse, cardiac, 78 Impulses in brain, course of, 671,678 Inanition, 395 Income, 389 Indican, 440 Indifferent point, 590 Indigo blue, 440 Indigogen, 440 Indirect vision, 7S4 Indol, 310 Induction, 584 Inductorium, 586 Inferior maxillary nerve, 627 Inhibition, nature of, 665 Inhibition of reflexes, 664 Inhd^itory action of brain, 725 nerves, 614 for heart, 691 for intestine, 264 for respiration, 686 Inosinic acid, 417 Inosit, 416 Insectivorous plants, 317 5S Inspiration, 196 muscles of, 196 ' ordinary, 196 Intelligence, degree of, 706 Intercellular blood channels, 1 14 Intercentral nerves, 615 Intercostal muscles, 199 Interference, 835 Interglobular spaces, 250 Interlobular vein, 285 Internal capsule, 734 reproductive organs, S98 respiration, 219 Intestinal fistula, 304 gases, 307 juice, 303 actions of, 305 paresis, 264 Intestine, 259 artificial circulation, 265 development of, 895 effect of drugs on, 265 fermentation processes in, 307 large, 311, 320 movements of, 259 small, 319 Intralobular vein, 285 Intraocular pressure, 624, 758 Intussusception, 259 Inulin, 416 Inunction, 489 Invertin, 306 Invert sugar, 306 Ions, 579 Iris, 775 Iris, action of poisons on, 777 blood vessels of, 776 functions of, 775 movements of, 778 muscles of, 776 nerves of, 776 Irradiation, 797 of pain, 672, 853 Ischuria, 475 Island of Reil, 711 Isidynamic foods, 348 Isolated beats, 836 Isotropous, 500 Jacksonian epilepsy, 717, 728 lacobson's organ, 839 Jaeger's types, 771 Jaundice, 299 Jaw.jerk, 667 Joints — Arthrodial, 535 Hall and socket, 535 Cinglymus, 534 Mechanism of, 533 Kigid, 535 Screw-hinge, ^34 Juice canals, 332 Karyokinesis, 856 Kattibolic, 373, 615 Katalepsy, 708 Kations, 579 Keratin, 411 Keratitis, 633 Key-note, 829 Keys — Capillary contact, 58S Friction, 588 Plug, 588 Kidney, 419 blood of, 424 chemistry of, 465 conditions affecting, 466 reabsnrption in, 463 structure of, 419 volume of, 467 Kinaesodic substance, 670 Kinetic energy, 347 theory, 636 Klang, 828, 836 Knee phenomenon, 667 reflex, 667 Koenig's manometric flames, S33 Koumiss, 380 Krause's end bulbs, 845 Kreatin, 417 Kreatinin, 417, 436 properties, 436 quantity, 436 test, 436 Kresol, 417 Kryplophanic acid, 441 Kymograph, 141 Pick's, 143 I.udwig's, 141 Kyphosis, 53S Labials, 557 Labor, power of, 902 Labyrinth, 824 Lachrymal apparatus, 810 Lacteals, 319 Lactic acid, 414, 441 ferment, 277 Lactoprotein, 378 Lactose, 376 Litvulose, 415 Lagoplithalmus, 620 Lambert's method, 791 Lamina spiralis, 825 Laminoa dorsales, 877 Language, 729 Lanoline, 485 Lanugo, 480 Lapping, 248 Lardacein, 410 Large intestine, 311, 319 absorption in, 311 Laryngoscope, 551 Larynx — Cartilages of, 545 During respiration, 200 Experiments on, 552 Illumination of, 551 Mucous membrane of, 550 Muscles of, 547 View of, 552 Vocal cords, 546 914 INDEX. Latent heat, 347 period, 664 Lateral plates, S78 Laughing, 208 Law of conservation of energy, xxxvi contraction, 601 isolated conduction, 606 peripheral perception, 847 specific energy, 748 Leaping, 542 Lecithin, 45, 414, 567 Legumin, 383, 410 Ler.s, chemistry of, 757 crystalline, 757 development of, goi Lenticular nucleus, 733 Leptothrix buccalis, 22S Leucic acid, 414 Leucin, 310, 414, 454 Leucocytes, 29 Leucoderma, 614 Leukcemia, 35 Levers, 536 Lichenin, 416 Lieberkiihn's glands, 304 Liebig's extract, 383 Life, xxxix Liminal intensity, 748 Line of accommodation, 770 Ling's system, 538 Lingual nerve, 627 Lipaemia, 65 Liquor sanguinis, 46 Listing's reduced eye, 764 Liver, 2S4 chemical composition, 288 cirrhosis of, 2S8 development of, 897 fat in, 289 functions of, 292 glycogen in, 291 influence on metabolism, 298 pathology of, 28S pulse in, 166 regeneration of, 2S8 structure of, 284 Locality, sense of, 847 illusions of, 849 Lochia, 903 Locomotor ataxia, 672 Lordosis, 538 Loss of weight, 395 Loss by skin, 219 Lowe's ring, 781 Lungs, 183 chemical composition of, 189 development of, 896 elastic tension of, 154 examination of, 194 excision of, 190 limits of, 202 physical properties, 1 89 structure of, 1 88 Lungs, tonus, 189 Lunule, 480 Lutein, 869 Luxus consumption, 3S9 Lymph, 332 movement of, 341 gases of, 220 Lymph corpuscles, 337 origin and decay of, 340 Lymphatics, 332 of eye, 75S origin of, 332 Lymph follicles, 335 glands, j^^ hearts, 343 Macropia, 620 Macula lutea, 755 Macula; acusticie, S26 Madder, feeding with, 405 Magnetization, 584 Magneto-induction, 5S5 Major cord, 829 MalapterUrus, 616 Malt, 387 Maltose, 244, 415 Mammary glands, 375 changes in, 375 development of, 376 structure of, 375 Manometer, 106 Manometric flames, S33 Marey's tambour, 80 Margarin, 478 Mariotte's experiment, 785 Mastication, 248 muscles of, 248 nerves of, 249 Massage, 538 Mate, 385 Matter, xxxii Maturation of ovum, 873 Meat soup, 383 Meckel's cartilage, 889 ganglion, 626 Meconium, 302 Medulla oblongata — Functions of, 682 Gray matter of, 6S2 Reflex centres in, 685 Structure of, 681 Medullary groove, 875 tube, 877 Meiocardia, 104 Meissner's plexus, 262 Melanivmia, 35 Melanin, 413 Melitose, 416 Mellitxmia, 64 Membrana decidua menstrualis, 882 flaccida, 817 reticularis, S27 reuniens, 8S0 secundaria, S24 tectoria, S27 Membranes of brain, 742 Meniere's disease, 637 Menopause, S67 Menstruation, 867 Merkel's cells, S46 Merobiastic ova, S64 Mesentery, development of, S97 Mesoblast, 875 Mesonephros, 898 Metabolic equilibrium, 3SS phenomena, 373 Metabolism, xxxix, 373, 3S8 Metakresol, 440 Metalbumin, 409 Metallic tinkling, 205 Metalloscopy, 854 Metamorphosis, 857 Metanephros, 89S Meteorism, 264 Meth^moglobin, 39 Methylamine, 417 Meynert's projection systems, 676 theory, 706 Micrococci, 66 Micrococcus ureoe, 445 Microcytes, 34 Micropyle, 863 Micturition, 473 centre for, 669 Migration of ovum, S73 Milk, 377 action of drugs on, 379 coagulation of, 378 colostrum, 379 composition of, 379 curdling ferment, 276, 283, 379 digestion of, 276 fever, 377, 903 globules of, 377 plasma, 378 preparations of, 380 substitutes for, 379 sugar. 378. 415 tests for, 380 Millon's reagent, 275 Mimetic spasm, 634 Mimicry, 559 Minor chord, 829 Mixed colors, 791 Molecular basis of chyle, 33S Molecules, xxxii Monoplegia, 727 Monospasm, 728 Moore's test, 246 Moreau's experiment, 306 Morphology, xxxii Morula, 874 Motor centres, dog, 715 excision of, 721 nerves, 613 Motor points on the surface, 606 Mouth, 232 glands of, 232 Mouvement de Manege, 738 Movements of the eye, 799 forced, 738 INDEX. 915 Movements, incoordinated, 648 Mucedin, 411 Mucigen, 321 Mucin, 411 Mucous membrane currents, 591 tissue, 758 Mucus, effect of drugs on, 227 formation of, 227 Mulberry mass, S74 Mulder's test, 246 Miiller's ducts, 89S experiment, 106, 133 fibres, 755 valve, 209 Multiplicator, 579 Murexide test, 435 Murmurs, cardiac, 91 venous, 164 Musca: volitantes, 779 Muscarin, 259 Muscle, 493 action of two stimuli on, 520 action of veratrin, 519 active changes in, 511 arrangement of, 535 atrophic proliferation of, 539 blood vessels of, 500 cardiac, 498 changes during contrac- tion, 511 chemical composition, 500 curve of, 515 degenerations of, 539 development of, 499 effect of acids on, 506 effect of cold on, 507 effect of distilled water on, 505 effect of exercise on, 502 effect of fatigue on, 51S effect of heat on, 505 elasticity of, 526 electricity of, 588 excitability of, 506 extractives of, 503 fatigue of, 531 formation of heat in, 529 glycogen in, 503 of heart, 67 involuntary, 493 lymphatics of, 497 metabolism of, 502 myosin of, 501 nerves of, 497 nutrition of, 538 perimysium of, 493 physical characters, 500 plasma of, 501 polarized light on, 496 red and pale, 49S, 523 relation to tendons, 497 rhythmical contraction, 510 Muscle, rigor mortis of, 504 rods, 496 sensibility, 529, 854 serum of, 501 smooth, 499 sound of, 530 spectrum of, 498 stimuli of, 506 structure of striped, 493 tetanus, 521 tonus, 529, 669 uses of, 535 voluntary, 493 work of, 524 Muscle current, 591 theories, 595 Muscle plate, 878 Muscular contraction (see Myo- gram), rate of, 523 Muscular sense, 854 work, 524 laws of, 525 Mutes, 558 Mydriasis, 619 Mydriatics, 777 Myelin forms, 2S3, 564 Myocardium, 68 Myogram, effect of weights on, 518 effect of fatigue on, 518 effect of constant cur- rent on, 518 method of studying, 513 stages of, 515 Myograph, Helmholtz's, 514 pendulum, 515 Pfliiger's, 515 simple, 515 spring, 515 Myohxmatin, 413 Myopia, 771, 773 Myoryctes Weismanni, 500 Myosin, 381, 409, 501 Myosis, 620 Myotics, 777 Myxoedema, 179, 614 Nails, 479 Narcotics, 854 Nasal breathing, 207 timbre, 557 Nasmyth's membrane, 250 Native albumins, 409 Natural selection, 903 Near point, 770 Neef 's hammer, 585 Negative accommodation, 766 pressure, 327 variation, 591, 593 Nephrozymose, 441 Nerve cells, bipolar, 566 multipolar, 565, 659 of cerebrum, 709 Purkinje's, 739 with a spiral fibre, 566 Nerve centres, general functions, 653 Nerve current, s8S Ner^'e fibres, 561 action of nitrate of silver on, 564 chemical properties of, 566 classification of, 613 death of, 576 degeneration of, 572 development of, 365 division of, 564 effect of a constant cur- rent on, 571 electrical current of, 591, 594 excitability of, 568 fatigue of, 572 incisures of, 564 mechanical properties of, 568 medullated, 562 metabolism of, 568 nutrition of, 572 Ranvier's nodes, 564 reaction of, 567 regeneration of, 575 sheaths of, 562 stimuli of, 568 structure of, 561 suture of, 575 terminations of, 844 to glands, 237 traumatic degeneration of. 574 trophic centres of, 574 unequal excitability of, 572 Nerve impulse, rate of. 602 method of measuring, 603 modifying conditions, 603 variations of, 605 Nerve motion, 606 Nerve-muscle preparation, 593 Nerves, anabolic, 615 cranial, 615 electrical, 606 imercentral, 615 katabolic, 373, 615 motor, 613 secretory, 613 sensory, 615 special sense, 615 spinal, 645 trophic, 613 union of, 575 visceral, 61 5 Nerve stretching, 569 Nervi nervorum, 565 Ner\'ous system, 561 development of, 900 Nervus abducens, 630 accessorius, 644 acusticus, 634 depressor, 132, 640 916 INDEX. Nervus erigens, 669, 701, 870 facialis, 631 glossopharyngeiis, 637 hypoglossus, 645 oculomotorius, 618 olfactorius. 615 opticus, 616 sympathicus, 649 trigeminus, 621 trochlearis, 621 vagus, 63S Neubauer's test, 346 Neuralgia, S54 Neuraftube, 827 Neurasthenia gastrica, 315 Neurin, 414 Neuro-epitheliuni, 756 Neuroglia, 657 Neurokeratin,4ll, 564 Neuro-niuscular cells, 509 New-born child, digestion of, 2S3 • pulse, 127 size, 405 temperature, 35S urine of, 428 weight, 405 Nictitating membrane, 813 Nitrites, 42 Nitrogen in air, 212 in blood, 62 in body, 407 given oft', 393 Nceud vital, 686 Noises, 828 Nose, development of, 901 structure, 839 Notochord, 877 Nuclear spindle, 873 Nuclein, 45, 411 Nucleus of Pander, S65 Nussbaum's experiments, 462 Nutrient arteries, 744 enemata, 331 Nyctalopia, 61S Nystagmus, 620, 73S Oatmeal, 3S3 ( )culomotorius, 61S Odontoblasts, 249 Gldema, 344 cachectic, 345 pulmonary, 207 Oesophagus, 256 Ohm's law, 577 Oidium albicans, 229 Oleic acid, 414 Oligsmia, 66 Olfactory centre, 724 nerve, 941 sensations, 819 Omphalo-mesenteric duct, 879 vessels, 879 Onamatopoesy, 559 Oncograph, 467 Oncometer, 467 Ontogeny, 904 Opening shock, 5S4 Ophthalmia neuro-paralytica, 624 intermittens, 626 sympathetic, 626 Ophthalmic nerve, 621 Ophthalmometer, 765 Ophthalmoscope, 7S3 Optic nerve, 616 radiation, 616 thalamus, 735 tract, 616 vesicle, 877 Optical cardinal points, 764 Optogram, 790 Optometer, 772 Organ albumin, 388 Organic albumin, 389 compounds, 408 reflexes, 668 Orthopncea, 196 Orthoscope, 784 Osmasome, 382 Ossein, 41 1 Osseous system, formation of, 888 Osteoblasts, 89 1 Osteoclasts, 892 Osteomalacia, 539 Otic ganglion, 62S Ovarian tubes, 863 Ovary, 862, 898 Overcrowding, 226 Ovulation, 868 theories of, 868 Ovum, 862 development of, 863 discharge of, 863 fertilization of, 872 impregnation of, 873 maturation of, S73 migration of, 873 structure of, S62 Oxalic acid, 414, 437 series, 414 Oxaluria, 437 Oxaluric acid, 437 Oxy-acids, 417 Oxygen, absorption of, 217 in blood, 59 estimation of, 209 fonns of, 61 in body, 407 Oxyhemoglobin, 39 Oxyakoia, 634 Ozone in blood, 60 Pacchionian bodies, 743 Pacini's corpuscles, 844 Pain, 853 irradiation of, 853 Painful impressions, conduction of, 672 Palmitic acid, 414 Palpitation, 78 Pancreas, 27S changes in, 279 Pancreas, development of, 897 fistula of, 279 juice of, 279 paralvtic secretion, 2Si Pancreatic secretion, 2S3 actions of, 2S3 artificial juice, 2S2 action of nerves on, 284 action of poisons on, 2S4 composition, 280 extracts, 283 Panophthalmia, 624 Pansphygmograph, 120 Papain, 282 Papilla foliata, 844 Parablastic cells, 878 Paradoxical contraction, 595 reaction, 244 Paraglobulin, 409 Parakresol, 440 Paralbumin, 409 Paralgia, 854 Paralytic secretion of saliva, pancreatic juice, 283 Paramylum, 416 Paraphasia, 731 Paraxanthin, 417, 436 Parelectronomy, 596 Paridrosis, 4S9 ParoSphoron, 899 Parotid gland, 233 Parovarium, 898 Parthenogenesis, 857 Partial pressure, 57 reflexes, 661 Particles, xxxii Parturition, centre for, 669 Passavant's elevation, 254 Passive insufficiency, 537 Patellar reflex, 667 Pathic reflex, 666 Pavy's test, 246 Pecten, 813, 901 Pectoral fremitus, 205 PeduncuU cerebri, 736 Penis, erection of, 869 Pepsin, 269 Pepsinogen, 271 Peptic glands, 266 changes in, 270 Peptone, 274 forming ferment, 270, 280 metabolism of, 396 tests for, 275 Peptonized foods, 284 Peptonuria, 447 Percussion of heart, 93 lungs. 195, 203 Perforating ulcer of the foot, 614 Pericardium, 71 Perilymph, S26 INDEX. 917 Perimeter, Aiibert and Forster, 78S McHardy's, 7SS Priestley Smith's, 789 Perimetric chart, 789 Perimetry, 78S Perimysium, 493 Perineurium, 565 Periodontal membrane, 251 Peristaltic movement, 259 action of blood on, 262 action of nerves on, 264 Peritoneum, development of, 897 Perivascular spaces, 334 Pettenkofer's test, 294 Peyer's glands, 318 Pfliiger's law, 601 law of reflexes, 662 Phagocytes, 31 Phakoscope, 769 Phanakistoscope, 796 Phases, displacement of, S31 Phenol, 311, 415, 440 Phenolsulphuric acid, 440 Phlebogram, 165 Phonation, 547 Phonograph, 833 Phonometry, 204 Phosphoric acid, 442 Phosijhenes, 7S0 Photophobia, 634 Photopsia, 61 8 Phrenograph, 194 Phrenology, 704 Phylogeny, 904 Phytalbumose, 410 Phytomycetes, 456 Pia mater, 742 Picric acid test, 452 Picrosaccharinieter, 453 Pigment cells, 492 Pitch, S28 Placenta, 884 Placental bruit, 164 Plantar reflex, 666 Plants, characters of, xxxviii electrical currents in, 597 Plasma cells, 742 of blood, 46, 54 of lymph, 338 of milk, 378 of muscle, 501 Plasmine, 50 Plethora, 64 Plethysmography, 167 Pleura, 187 Pleuro-peritoneal cavity, 878 Pleximeter, 202 Pneumatogram, 194 Pneumatometer, 206 Pneumograph, 194 Pneumonia after section of vagi, 641 Pneumothorax, 190 Poikilothermal animals, 350 Poiseuille's space, 161 Poisons, heart, 103 on vasomotor nerves, 696 spinal cord, 664 Polar globules, 873 Polarization, galvanic, 579 internal, 583 Polarizing after currents, 595 Politzer's ear bag, 824 Polyitmia, 63 apocoptica, 63 aquosa, 64 hyperalbuminosa, 64 polycythixmica, 64 serosa, 64 transfusoria, 63 Polyopia monocularis, 775 Pons Varolii, 736 Porret's phenomenon, 500, 583 Portal canals, 2S5 circulation, 67 system, development of, 89s vein in liver, 285 vein, ligature of, 153 Positive accommodation, 768 after images, 796 Potash salts, 407 Potassium sulphocyanide, 441 Potatoes, 384 Presbyopia, 772 Pressor fibres, 673, 697 Pressure, arterial, 145 atmospheric, 229 intra-labyrinthine, 827 of blood, 141 respiratory, 205 sense of, 850 Presystolic sound, 91 Prickle cells, 477 Primitive anus, 881 chorion, 875, 883 circulation, S79 groove, 875 kidneys, 897 mouth, 881 streak, 875 Primordial cranium, 888 ova, 803 Principal focus, 759 point, 761 Progressive muscular atrophy, 539 Pronephros, 898 Pronucleus, male, 874 female, 873 Propepsin, 271 Propeptone, 274 Protagon, 413, 567 Proteids, 408 coagulated, 410 gastric digestion of, 274 fermentation of, 310 Proteids, pancreatic digestion of, 280 reactions of, 40S vegetable, 410 Protista;, xxxi Protodoeum, 875 Protovertebrse, 878 Pseudo-hypertrophic paralysis , 539 Pseudo-motor action, 632 Pseudoscope, 80S Pseudo-stomata, 1 86 Psychical activities, 703 blindness, 722 deafness, 723 Psycho-acoustic centre, 732 geusic centre, 732 motor centre, 71S optic centre, 731 physical law, 74S sensorial centres, 721 sensory paths, 731 Ptomaines, 275 Ptosis, 619 Ptyalin, 244 Ptyalism, 241 Puberty, 866 Pulmonary artery, pressure in, 1 5 3 Pulmonary cedema, 207 Pulp of tooth, 251 spleen, 173 Pulse, 117 capillary, 140 catacrotic, 121 characters of, 127 conditions afl'ecting, 127 curve, 129 dicrotic, 126 entoptical, 137, 780 historical, 116 hyperdicrotic, 127 in animals, 1 28 in jugular vein, 166 influence of pressure on, influence of respiration on, 131 instruments for investi- gating, 1 17 in liver, 166 monocrotic, 127 of various arteries, 129 paradoxical, 133 pathological, 137 recurrent, 130 trigeminal, 128 variatians in, 128 venous, 165 wave, 132, 136 Pulses, 383 Pulsus alternans, 128 bigeminus, 12S caprizans, 127 dicrotus, 126 intercurrens, 12S myurus, 12S Pumping mechanisms, 342 918 INDEX. Pupil, 776 action of poisons on, 777 Argyll Robertson, 777 functions of, 775 movements of, 776 photometer, 77S size of, 378 Purgatives, 265 Purkinje, cells of, 739 fibres of, 72, 49S figure, 779 Sanson's images, 76S Putrefactive processes, 307 Pyloric glands, 267 changes in, 270 Pyramidal tracts, 67S degeneration of, 727 Pyrokatechin, 415, 440 Quality of a note, S2S Quantity of blood, 63, 159 food, 389 Rales, dry, 205 moist, 205 Rami communicantes, 649 Range of accommodation, 770 Ranvier's nodes, 564 Raynaud's disease. 614 Reaction impulse, 81 Reaction of degeneration, 607, 610 Reaction time, 605 Recovery, 533 Rectum, 265 Recurrent pulse, 130 sensibility, 646 Red blindness, 794 Reduced eye of Listing, 764 Reductions in intestine, 308 Reflex acts, examples of, 662 inhibition of, 664 movements, 666 movements, theory of, 666 nerves, 615 spasms, 661 tactile, 672 time, 664 tonus, 670 Refracted ray, 761 Refractive indices, 761 Regeneration of tissues, 402 nerve, 575 Regio olfactoria, 839 respiratoria, 839 Reissner's membrane, 825 Relative proportions of diet, 389 Remak's ganglion, 94 Renal plexus, 461 Rennet, 276, 37S Reproduction, forms of, 856 Requisites in a proper diet, 389 Reserve air, 191 Residual air, 191 Resistance, 109 Resonance organs, 545 Reson.ants, 557 Resonators, 11,31 Respiration, 1S3 amphoric, 205 artificial, 224 bronchial, 204 centre for, 686 chemistry of, 209 cog-wheel, 205 cutaneous, 219 forced, 195 in a closed space, 221 in animals. 192 internal, 219 intestinal, 230 mechanism of, 190 muscles of, 196 nasal, 207 number of, 192 periodic, 196 pressure during, 205 sounds of, 204 time of, 192 type, 195 variations of, 192 vesicular, 204 Respiratory apparatus, 183 Andral and Gavar- ret, 209 centre, 686 mechanism of, 190 v. Pettenkofer, 211 quotient, 212 Regnault and Rei- set, 21 1 Scharling, 210 Rete mirabile, 67 Retina, 754 activity in vision, 785 blood vessels of, 753 chemistry of, 757 capillaries, movements in, 779 epithelium of, 756 rods and cones of, 756 stimulation of, 796 structure of, 757 visual purple of, 756 Retinal image, formation of, 764 size of, 765 Retinoscopy, 7S4 Rigor mortis, 504 Rheocord, 578 Rheometer, 155 Rheophores, 606 Rheoscopic limb, 590 Rheostat, 578 Rheotom, 593 Rhinoscopy, 552 Rhodophane, 757 Rhodopsin. 756 Rickets, 539 Ritter's opening tetanus, 600, 602 Ritter's tetanus, 600 Ritter-VaUi law, 576 Rods and cones, 756 Rotatory disk for colors, 791 Running, 543 Saccharomycetes, 386 Saccharose, 415 Saccule, 825 Saftcanalchen, 332 Saline cathartics, 265 Saliva, action of nerves on, 237 action of poisons on, 241 action on starch, 244 chorda, 238 composition of, 243 Saliva facial, 237 functions of, 244 mixed, 243 new-born child, 244 parotid, 240 pathological, 314 ptyalin, 245 reflex secretion of, 2 38 sublingual, 243 submaxillary, 242 sympathetic, 238 theory of secretion, 239 Salivary corpuscles, 243 glands, 233 changes in, 235 development of, 896 nerves of, 237 Salts, 407 Sanson-Purkinje's images, 779 Saponification, 283 Sarcini ventriculi, 315 Sarcolactic acid, 501 Sarcolemma, 494 Sarkin,4i7, 436 Sarkosin, 417 Saviotti's canals, 279 Scheiner's experiment, 770 Schift's test, 436 Schizomycetes, 66 Schmidt's researches, 50 Schreger's lines, 250 Schwann's sheath, 562 Sclerotic, 753 Scoliosis, 538 Scotoma, 7S9 Screw-hinge joint, 534 Scrotum, formation of, S99 Scurvy, 65 Scyllit, 417 Sebaceous glands, 482 secretion, 483 Seborrhoea, 489 Secondary circulation, 879 contraction, 592 degeneration, 660 tetanus, 592 Secretion currents, 596 Secretory nerves, 613 Sectional area, 157 Segmentation sphere, 874 Self-stimulation of muscle, 59 1 INDEX. 919 Semen, composition of, 860 ejaculation of, 872 reception of, 872 Semicircular canals, 826 Sensation, 748 Sense organs, 748 development of, 901 Sensory areas, 724 crossway, 679 paths, 679 Serin, 417 Serum of blood, 46, 54 Serum albumin, 55, 409 globulin, 54, 409 Setschenovv's centres, 665 Sex, difference of, 900 Shadows, lens, 779 colored, 79S Sharpey's fibres, 892 Short-sightedness, 771 Shunt, 582 Sialogogues. 241 Sighing, 208 Simple colors, 791 Simultaneous contrast, 7S4 Single vision, 803 Sitting, 540 Sire, 405 estimation of, 808 false estimate of, 808 Skatol, 311, 441 Skin, absorption by, 4S9 chorium of, 477 epidermis, 477 functions of, 484 galvanic conduction of, 4S9 glands of, 482 historical, 490 protective covering, 483 respiratory organ, 484 structure of, 477 varnishing the, 371, 484 Skin currents, 591 Sleep, 707 Small intestine, 319 absorption by, 327 structure of, 319 Smegma, 485 Smell, sense of, 839 Sneezing, 207 Snellen's types, 772 Sniffing, 840 Snoring, 208 Sodic chloride, 407, 442 salts, 408 Solitary follicles, 324 Somatopleure, 878 Sorbin, 417 Sound, 815 conduction to ear. Si 5 direction of, 836 distance of, 837 perception of, S37 retlection of, 815 Sounds, cardiac, 85 cracked-pot, 204 tymianilic, 203 Sounds, vesicular, 204 Spasm centre, 702 Spasmus nictitans, 634 Specific energy, 790 Spectacles,'773, 813 Spectra, absorption, 38 flame, 38 optical, 781 Spectroscope, 38 Spectrum mucro-Iacrimale, 779 of bile, 295 of blood, 39 of muscle, 496 Speech, 555 centre for, 729 pathological variations, 558 Spermatin, 860 Spermatozoa, S60 Spermatoblasts, 85S Spina bifida, 743, 880 Spinal accessory nerve, 644 Spinal cord, 654 action of blood and poi- sons on, 671 anterior roots of, 647 blood vessels of, 658 centres, 668 conducting paths in, 671 conducting system of, 659 development of, 901 degeneration of, 659 excitability of, 670 Flechsig's systems, 659 ganglion, 645 Gerlach's theory, 657 nerves, 645 neuroglia of, 657 nutritive centres in, 660 posterior roots of, 648 reflexes, 661 regeneration of, 703 secondary degeneration of, 659 segment of, 680 structure of, 654 time of development, 661 transverse section of, 673 unilateral section of, 674 vasomotor centres in, 696 Woroschiloff's observa- tions, 656 Sphenopalatine ganglion, 626 ' Spherical aberration, 774 Sphincters, 535 Sphincter ani, 260 pupilla^ 754 urethra", 472 Sphymograph, 1 1 8 r)udgeon's, 120 Marey's, 118 Sphygmometer, 129 Sphygmogram, 122 Sphygmomanometer, 144 Sphygmoscope, 122 Spiral joints. 534 Spirillum, 66 Spiroclu'eta, 66 Spirometer, 191 Splanchnic nerve, 65 1 Splanchnopleure, 878 .Spleen, 172 action of drugs on, 175 chemical composition, 174 contraction of, 175 extirpation of, 1 74 functions of, 174 influence of nerves on, 176 oncograph, 175 regeneration of, 174 structure, 172 tumors of, 177 Spongin, 41 1 .Spontaneous generation, S56 Spores, 308 Spring kymograph, 143 Spring myograph, 515 Springing, 542 Sputum abnormal, 229 normal, 227 Squint, 619 Stammering, 559 Standing, 539 .Stannius's experiment, 96 Stapedius, 822 Starch, 416 Stasis, 162 Statical theory of Goltz, 637 Stationary vibrations, 816 Steapsin, 283 Stenopaic spectacles, 774 Stenosis, 88 Stenson's experiment, 505 Stercobilin, 296, 312 Stercorin, 313 Stereoscope, 807 Stereoscopic vision, 805 Sternutatories, 207 Stethograph, 193 Stigmata, 113 .Stilling, canal of, 758 Stimuli, 506 adequate, 748 heterologous, 74S homologous, 748 muscular, 509 Stoffwechsel, xxxix Stomach, 266 catarrh of, 319 changes in glands, 270 diseases of, 314 gases in, 278 glands of, 266 movements of, 256 structure of, 266 Stomata, 113, 335 Stomodceum, 875 .Storage albumin, 388 Strabismus, 738 Strangury, 475 Strasburg's test, 451 Strobic disks, 797 920 INDEX. Stroma filniii and plasma fibrin, 54 Struggle for existence, 903 Strychnin, action of, 663 Stuttering, 559 Subarachnoid space, 742 fluid, 743 Subdural space, 742 Subjective sensations, 749 Sublingual gland, 240 Submaxillary ganglion, 628 atropin on, 239 gland, 237 saliva, 239 Successive beats, 836 contrast, 799 Succinic acid, 414 Succus entericus, 303 action of drugs on, 306 Suction, 24S Sudorifics, 486 Sugars, 415 estimation of. 247 tests for, 246 Sulphindigotate of soda, 461 Summation of stimuli, 521, 622 Summational tones, 836 Superfecundation, 873 Superficial reflexes, 666 Superfcetation, S73 Superior maxillary nerve, 626 Suprarenal capsules, i8o Surditas verbalis, 732 Sutures, 535 Sweat, 4S4 chemical composition, 48s conditions influencing se- cretion, 486 excretion of substances by, 4S6 glands, 483 insensible, 485 nerves, 487 pathological variations of, 488 centre, 488 spinal, 670 Swimming, 544 Sympathetic ganglion, 649 nerve, 649 section, 651 stimulation of, 651 Sympheses, 535 Synchondroses, 535 Syncope, 78 Synergetic muscles, 538 Synovia, 534 Syntonin, 274 Systole, cardiac, 75 Tabes, 672 Taches cerebrales, 701 Tactile, areas, 724 corpuscles, 846 sensations, conduction of, 846 T.-enia, 857 Tail.fdld, 878 Talipes calcaneus, 538 equinus, 538 varus, 538 ■ Tambour, Marey's, 120 Tapetum, 784 Tapping experiment, 691 Taste bulbs, 841 organ of, 841 testing, 842 Taurin, 417 Taurocholic acid, 293 Tea, 385 Tears, 8 10 Tegmentum, 676 Telestereoscope, 807 Temperature of animals, 351 accommodation for, 366 artificial increase of, 369 estimation of, 35 1 how influenced, 354 lowering of, 370 postmortem, 369 regulation of, 361 topography of, 353 variations of, 358 Temperature sense, 852 illusions of, 853 Tendon, 500 nerves of, 500, 846 reflexes, 667 Tensor, choroideEe, 753 tympani, 821 Testicle, descent of, 887 Testis, 857 Tetanomotor, 569 Tetanus, 521, 571, 663 secondary, 592 Thaumatrope, 796 Theobromin, 385 Thermal cortical centre, 160 Thermo-electric methods, 351 needles, 353 Thermometer, 351 metastatic, 35 1 maximal and mini- mal, 351 outflow, 351 Thermometry, 351 Thirst, 390 Thiry's fistula, 304 Thomson's disease, 520 Thoracometer, 201 Thymus, 177 development of, 889 Thyroid, 178 development of, 889 Tibial air, 191 wave, 123 Timbre, 557, 828 Time in psychical processes, 707 Time sense, 830 Tinnitus, 637 Tissue formers, 390 regeneration of, 402 Tissue metabolism, 400 Tobin's tubes, 227 Tomes, fibres of, 249 Tone inductorium, 523 Tones, 828 Tongue, glands of, 232 movements of, 253 nerves of, 253 taste bulbs, 841 Tonometer, 98 Tonus, 670 Tonsils, 233 Tooth, 249 action of drugs on, 253 chemistry of, 251 development of, 251 eruption of, 252 permanent, 252 pulp of, 251 structure of, 249 temporary, 252 Toricelli's theorem, 108 Torpedo, 612 Torticollis, 644 Touch corpuscles, 844 Touch, sense of, 844 Trachea, 183 Transfusion, 63, 168 of blood, 16S of other fluids, 171 Transitional epithelium, 471 Transudations, 345 Transplantation of tissues, 405 Trapezius, spasm of, 644 Traube-Hering curves, 147 Traumatic degeneration of nerves, 574 Trichina, 857 Trigeminus, 624 ganglia of, 623, 626, 628 inferior maxillary branch, 627 neuralgia of, 629 ophthalmic branch, 621 paralysis of, 629 pathological, 629 section of, 628, 630 superior maxillary branch, 626 trophic functions of, 624 Triple phosphate, 445 Trismus, 629 Trochlearis, 621 Trommer's test, 246 Troiihic centres, 575 fibres, 624 nerves, 613, 624 Trophoneuroses, 614 Trotting, 544 Trypsin, 281 Trypsinogen. 28 1 Tryptone, 281 Tube casts, 456 Tubes, capillary, 115 division of, 115 INDEX. 921 Tubes, elastic, 115 movements of fluids in, 116 rigid, 134 Tumultus sermonis, 730 Tunicin, 416 Tiirck's method, 666 Twins, S73 Twitch, 515 Tympanic membrane, S16 artificial, 81 S Tyrosin, 310, 41 1, 454 Ulcer of foot, perforating, 614 Unipolar induction, 585 stimulation, 572 Umbilical arteries, 882 cord, S85 veins, 8S2, 886 vesicle, S79 Upper tones, 831 Urachus, 882 Ur,T:mia, 469 Urates, 435 Urea, 417, 430 compounds of, 432 decomposition, 430 eflfect of exercise on, 431 ferment, 443 formation of, 431, 463 nitrate of, 432 occurrence of, 431 oxalate of, 432 pathological, 431 phosphate of, 432 preparation of, 432 properties of, 430 qualitative estimation of, 432 quantitative estimation of, 432 quantity of, 430 relation of, to muscular work, 431, 503 Ureameter, 432 Ureter, ligature of, 463 structure and functions of, 470 Uric acid, 417 diathesis, 470 formation of, 434, 464 occurrence, 435 properties of, 434 qualitative estimation, 435 quantitative estimation, 436 quantity, 434 solubility, 435 tests for, 435 Urinary bladder, 471 calculi, 458 closure of, 472 deposits, 455 development of, 882 organs, 419 pressure in, 475 Urine, 426 accumulation of, 472 Urine, acid fermentation, 443 acidity, 430 albumin in, 445 alkaline fermentation, 445 alkaloids in, 469 amount of solids, 427 bile in, 450 blood in, 447 calculi, 458 changes of in bladder, 475 color, 427 coloring matters of, 428 consistence, 429 cyslin in, 454 deposits in, 455 dextrin in, 453 effect of blood pressure on, 465 egg albumin in, 447 electrical condition of, 611 excretion of pigments by, 462 fermentations of, 443 fluorescence, 429 fungi in, 455 gases in, 443 globulin in, 447 incontinence of, 475 influence of nerves on, 465 inorganic constituents, 441 inosit in, 454 leucin in, 454 milk sugar in, 453 movement of, 470 mucin in, 447 mucus in, 447 organisms in, 455 passage of substances into, 465 peptone in, 447 phosphoric acid in, 442 physical characters of, 426 pigments of, 427 preparation of, 463 propeptone in, 447 quantity, 426 reaction, 429 retention of, 475 secretion of, 459 silicic acid in, 443 sodic chloride in, 442 specific gravity, 427 spontaneous changes in, 443 sugar in, 451 sulphuric acid in, 443 taste of, 429 test for albumin in, 446 tube casts in, 456 tyrosin in, 454 volume of, 467 Urinometer, 427 Urobilin, 439 Urochrome, 439 Uroerythrin, 439 Uro-genital sinus, 899 Uroglaucin, 439 Uromelanin, 439 Urostealith, 458 Uterine milk, 885 Uterus, 866 development of, 898 involution of, 903 nerves of, 902 Utricle, 825 Uvea, 753 Vagus, 638 cardiac branches, 640 depressor nerve of, 146, 640 effect of section, 641 pathological, 643 pneumonia after sec- tion, 641 reflex effects of, 643 stimulation of, 1 50 unequal excitability of, 643 Valleix's points douloureux, 854 Valsalva's experiment, 105, 132, 822 Valve, ileo-colic, 259 pyloric, 257 Valves of heart, 71 disease of, 88 injury to, 78 of veins, 113 sounds of, 165 Valvulie conniventes, 319 Varicose fibres, 561 Varix, 152 Varnishing the skin, 484 Vas deferens, 859 Vasa vasorum, 1 14 Vascular system, development of, 892 Vaso-dilator centre, 701 nerves, 701 Vaso-formative cells, 26 Vasomotor centre, 695 spinal, 700 Vasomotor nerves, course of, 696 Vater's corpuscles, 845 Vegetable albumin, 410 casein, 410 foods, 383 proteids, 410 Veins, 1 1 3 cardinal, 894 development of, 894 movement of blood in, 163 murmurs in, 164 pressure in, 152 pulse in, 152 structure of, 112 tonus of, 700 922 INDEX. Veins, valves in, 113 valvular sounds in, 165 varicose, 152 velocity of blood in, 157 Velocity of blood stream, 155 Ventilation, 226 Ventricles, 70, 75 aspiration of, 75 capacity of, 140, 159 duration of, 1 59 impulse of, Si negative pressure in, 77 systole of, 82 Veratrin, 519 Vernix caseosa, 485 Vertebra;, mobility of, 540 Vertebral column, 880 Vertigo, 637 Vibrations of body, 137 Vibratives, 557 Vibrio, 66 Villus intestinal, 320 absorption by, 32S chorionic, 875 contractility of, 322 placental, 885 Violet blindness, 794 Visceral arches, 881 clefts, 881 Vision binocular, 803 single, 803 stereoscopic, 805 Visual angle, 765 apparatus, 750 centre, 722 purple, 756, 790 Vital capacity, 191 Vitellin, 409, 866 Vitelline duct, 879 Vitreous humor, 757 Vocal cords, 546 conditions influencing the, 553 varying conditions of, 549 Voice, falsetto, 554 in animals, 559 pathological variations of, 558 physics of, 545 pitch of, 545 production of, 554 range of, 554 Vomiting, 257 centre for, 25S Vowels, S30 analysis of, 555 artificial, 832 formation of, 555 Koenig's apparatus for, 833 Waking, 707 Walking, 541 Wallerian law of degeneration, 574 \\ arm-blooded animals, 350 Washed-blood clot, 50 Water, 373, 390, 407 absorbed by skin, 4S9 absorption of, 328 amount of, 407 exhaled by skin, 219, 484 exhaled from lungs, 212 hardness of, 374 impurities, 374 in urine, 428 vapor of, in air, 212 Wave pulse, 122 propagation of, 136 Wave movements, 815 Waves, in elastic lubes, 134 Weber's paradox, 528 law, 749 Weight, 405 Wharton's jelly, 885 Whispering, 555 White of egg, 409 Wine, 587 Wolffian bodies, 897 ducts, 899 Word blindness, 730, 731 deafness, 723 Work, 524 unit of, xxxiv Xanthin, 417, 436 Xanthokyanopy, 795 Xanthophane, 757 Xanthoproteic, reaction, 40S Xerosis, 624 Yawning, 20S Yeast, 386 Yelk, 865 sack, 879 Yellow spot, 7S0 Young- Hehnholtz theory, 793 Zimmermann, particles of, 34 Zinn, zonule of, 757 Zoetrope, 796 Zollner's lines, 810 Zona pellucida, 862 Zoogloea, 308 Zymogen, 281 Zyraophytes, 277 ,,^^ COLUMBIA UNIVERSITY LIBRARY 1 l^^^^^l This book is due on the date indicated below, or at the | "^^^^^1 expiration of a definite period after the date of borrowing, '^H as provided by the rules of the Library or by special ar- ^H rangement with the Librarian in charge. ;^^^^^| DATE BORROWED DATE DUE DATE BORROWED DATE DUE ^^^1 ^^M 'iHH J J^H ^^B fl J ^mh ^^H j^^H ^^H ^^H ^^H ^^H ^^H ^^1 c.a...,„,oo 18fi7