Vw Bongrht of no 1 #to i,! R 3 wo. 96 Washington Street, Chicago. 9 . ■ Univ.of m. Library 62 A TEXT-BOOK OF HUMAN PHYSIOLOGY. LAN DO IS. NOTICES OF THE FIRST EDITION OF LANDOIS’ PHYSIOLOGY. “ It speaks well for the popularity of Professor Landois’ Text-book of Physiology that no fewer than four large editions have been already published in Germany, although the book made its first appearance not more than four or five years ago. Indeed, it has evidently supplied a want in that country. In its German form it has also attained considerable popularity in England. Inasmuch, however, as it is essentially a book for students as well as for practi- tioners of Medicine, no doubt the fact that it has not hitherto been translated has, to a considerable extent, interfered with its wider circulation among that class of readers in this country. We must, therefore, tender to Professor Stirling sincere thanks for undertaking the arduous task of rendering the work into English, thereby giving to English students easy access to one, from their point of view, of the most practical books on physiology ever written. The book, as the translator aptly remarks in his preface, forms a kind of bridge between physiology and practical medicine, as one of its special features consists in the arrangement at the end of the various sections of the physi- ology proper, of an excellently clear and succinct account of the ways in which the normal functions treated of in the preceding paragraphs may be modified under diseased conditions. * * * * Its special qualities are its com- pleteness and conciseness. It contains a very large amount of accurate information put in such a way as to be attractive and not tedious to the reader, and the information is brought up to date Professor Stirling’s translation possesses the great merit of reading as though it were not a translation; and the additional information which he has inserted appears to us to be in all cases ample and judicious. The illustrations of the work are good, both those to be found in the original and those which have been added.” — British Medical Journal, January 31st, 1883. “ It is the most complete and satisfactory text-book on Physiology extant. The translator and pub- lisher have each done something to increase the value of the volume. Dr. Stirling has added numerous useful annor tations and a large number of new plates. * * * * We wish that every student and physician could be drilled in these volumes.” — The Medical Record , New York , Sept. 2bth, 1883. “A careful examination of the work before us will, we think, convince any impartial reader that the claim put forth by Dr. Stirling in favor of Prof. Landois is, at least so far as relates to the ‘ eminent practicality’ of his manual, a well-founded one. Obviously, our author not only teaches his pupils how and to what extent pathological processes are derangements of normal activities, but also most effectively aids the busy physician to trace back from morbid phenomena the course of divergence from healthy physical operations, and to gather in this way new lights and novel indications for the comprehension and scientific treatment of the maladies which he is called upon to cope with in his daily warfare against disease. The superiority of the German work is attractively displayed in the abundant illustra- tion allotted to this portion of the volume, renal anatomy being elucidated by no less than seven figures, including four of Prof. Tyson’s improved modifications of Klein’s and of Henle's pictures. “An additional feature of the great practical value is exhibited in the condensed account of the * Comparative Physiology of the Urinary Apparatus,’ and in the brief historical resume devoted to an outline sketch of the chief discoveries relating to the kidneys, from the days of Aristotle to the present time. Such a narrative of the progress of our knowledge in regard to the renal functions not only serves to gratify a legitimate curiosity, which often forms a powerful incentive to the prosecution of diligent study, but also contributes in an agreeable manner to fix indelibly in the mind of a student the essential facts and many minor details of renal physiology and pathology. — American Journal 0/ Medical Sciences, July, 188b. “ Professor Landois’ work on Physiology is particularly distinguished by its practical nature, and by the con- stancy with which the author brings the facts of physiology into relationship with Medicine. It is a book written especially for medical students and medical practitioners, and the success with which the author has adapted it to their wants is shown by the fact that it has already passed through four large editions in four years. ***** The work is thus calcidated to direct the attention of the student toward a rational system of treatment, and to help' the practitioner rightly to understand and treat the cases under his care. * * * * Professor Stirling has translated the work well. * * * * The work is, however, not a mere translation. Dr. Stirling has made large and valuable additions to it. In places where the German edition begins abruptly, and seems to assume an amount of knowledge which the student may not possess, Dr. Stirling has supplied the necessary introduction. * * * * Is one of the best and most practical treatises on physiology we have ever seen.” — Dr. T. Lauder Brunton, in “Brain,' January, 1883. Price of Second Edition, in Cloth, $6.50 ; in Leather, $7.50. A TEXT-BOOK OF HUMAN PHYSIOLOGY, INCLUDING HISTOLOGY AND MICROSCOPICAL ANATOMY; WITH SPECIAL REFERENCE TO THE REQUIREMENTS OF PRACTICAL MEDICINE. BY DR. L. LANDOIS, PKOFESSOR OF PHYSIOLOGY AND DIRECTOR OF THE PHYSIOLOGICAL INSTITUTE, UNIVERSITY OF GREIFSWALD. SECOND AMERICAN, TRANSLATED FROM THE FIFTH GERMAN EDITION. WITH ADDITIONS BY WILLIAM STIRLING, M.D., Sc.D, BRACKENBURY PROFESSOR OF PHYSIOLOGY AND HISTOLOGY IN OWEN’S COLLEGE AND VICTORIA UNIVERSITY, MANCHESTER; EXAMINER IN THE HONOURS SCHOOL OF SCIENCE, UNIVERSITY OF OXFORD. WITH FIVE HUNDRED AND EIGHTY-THREE ILLUSTRATIONS. PHILADELPHIA: P. BLAKISTON, SON & CO., No. 1012 Walnut Street. 1886. Digitized by the Internet Archive in 2016 with funding from University of Illinois Urbana-Champaign Alternates https://archive.org/details/textbookofhumanp00land_0 TO SIR JOSEPH LISTER, Baronet, M.D., D.C.L., LL.D., F.R.SS. (LOND. AND EDIN.), PROFESSOR OF CLINICAL SURGERY IN KING’S COLLEGE, LONDON; SURGEON EXTRAORDINARY TO THE QUEEN; FORMERLY REGIUS PROFESSOR OF CLINICAL SURGERY IN THE UNIVERSITY OF EDINBURGH IN ADMIRATION OF 91Co/pv Sciewce, WHOSE BRILLIANT DISCOVERIES HAVE REVOLUTIONIZED MEDICAL PRACTICE, AND CONTRIBUTED INCALCULABLY TO THE WELL-BEING OF MANKIND; AND IN GRATITUDE TO ‘Waacftez, WHOSE NOBLE EARNESTNESS IN INCULCATING THE SACREDNESS OF HUMAN LIFE STIRRED THE HEARTS OF ALL WHO HEARD HIM: pcctf-ufty 6De£>icate£> 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 583, 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 Pharmacology , 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,” and to Dr. Berry Hart for suggestions on the Chapters on Reproduction. Some of the new illustrations are taken from Schenk’s Grundriss der normalen Histologie. 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. The Owens College, Manchester, fune , 1886. WILLIAM STIRLING. PREFACE TO FIRST ENGLISH EDITION. The fact that Professor Landois’ “ Lehrluch der Physiologie des Menschen ’ ’ has already passed through four large editions since its first appearance in 1880, 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 resund 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 backward 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 with 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 : — (1.) 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 Anatomy, v ol. 11, ninth edition; Hermann’s Handbuch der Physiologie ; 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 ix 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 Bramwell, 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 per se 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. WILLIAM STIRLING. Aberdeen University, November , 1884. GENERAL CONTENTS INTRODUCTION. PAGE The Scope of Physiology, and its Relation to the other Branches of Natural Science . . . xxxi Matter xxxii Forces xxxiii Law of the Conservation of Energy xxxvi Animals and Plants xxxvii Vital Energy and Life xxxix I. PHYSIOLOGY OF THE BLOOD. SECTION 1. Physical Properties of the Blood 2. Microscopic Examination of the Blood 3. Histology of the Human Red Blood Corpuscles 4. Effects of Reagents on the Blood Corpuscles 5. Preparation of the Stroma — Making Blood “ Lake-Colored” 6. Form and Size of the Blood Corpuscles of Different Animals 7. Origin of the Red Blood Corpuscles 8. Decay of the Red Blood Corpuscles 9. The Colorless Corpuscles — Leucocytes — Blood Plates — Granules .... 10. Abnormal Changes of the Blood Corpuscles 11. Chemical Constituents of the Red Blood Corpuscles 12. Preparation of Haemoglobin Crystals 13. Quantitative Estimation of Haemoglobin 14. Use of Spectroscope 15. Compounds of Haemoglobin — Methaemoglobin 16. Carbonic Oxide- Haemoglobin — Poisoning with Carbonic Oxide .... 1 7. Other Compounds — Haemoglobin 18. Decomposition of Haemoglobin 19. Haemin and Blood Tests 20. Haematoidin 21. The Colorless Proteid of Haemoglobin 22. Proteids of the Stroma 23. The other Constituents of Red Blood Corpuscles 24. Chemical Composition of the Colorless Corpuscles 25. Blood Plasma, and its Relation to Serum 26. Preparation of Plasma 27. Fibrin — Coagulation of the Blood 28. General Phenomena of Coagulation 29. Cause of Coagulation of the Blood 30. Source of the Fibrin Factors 31. Relation of the Red Blood Corpuscles to the Formation of Fibrin . . . 32. Chemical Composition of the Plasma and Serum 33. The Gases of the Blood 34. Extraction of the Blood Gases 35. Quantitative Estimation of the Blood Gases 36. The Blood Gases 37. Is Ozone (0 3 ) present in Blood? 38. Carbon dioxide and Nitrogen in Blood 39. Arterial and Venous Blood 40. Quantity of Blood 41. Variations from the Normal Conditions of the Blood II. PHYSIOLOGY OF THE CIRCULATION. 42. General View of the Circulation 43. The Heart 44. Arrangement of the Cardiac Muscular Fibres 45. Arrangement of the Ventricular Fibres 17 18 21 21 23 24 25 28 29 34 35 36 39 40 42 42 43 44 44 44 45 45 46 46 47 48 49 53 54 54 56 57 59 59 60 61 62 63 63 67 67 68 70 xi Xll CONTENTS. SECTION 46. Pericardium, Endocardium, Valves 47. Automatic Regulation of the Heart 48. The Movements of the Heart 49. Pathological Disturbances of Cardiac Action 50. The Apex Beat — The Cardiogram 51. The Time occupied by the Cardiac Movements 52. Pathological Disturbance of the Cardiac Impulse 53. The Heart Sounds 54. Variations of the Heart Sounds 55. The Duration of the Movements of the Heart 56. Physical Examination of the Heart 57. Innervation of Heart — Cardiac Nerves 58. The Automatic Motor Centres of the Heart „ 59. The Cardio-Pneumatic Movements 60. Influence of the Respiratory Pressure of the Heart THE CIRCULATION. 61. The Flow of Fluids through Tubes 62. Propelling Force, Velocity of Current, Lateral Pressure 63. Currents through Capillary Tubes 64. Movements of Fluids and Wave Motion in Elastic Tubes 65. Structure and Properties of the Blood Vessels 66. The Pulse — Historical 67. Instruments for Investigating the Pulse 68. The Pulse Curve or Sphygmogram 69. Dicrotic Pulse 70. Characters of the Pulse 71. Variations in the Strength, Tension and Volume of the Pulse 72. The Pulse Curves of various Arteries 73. Anacrotism 74. Influence of the Respiratory Movements on the Pulse Curve 75. Influence of Pressure upon the Form of the Pulse Curve 76. Rapidity of Transmission of Pulse Waves 77. Propagation of the Pulse Wave in Elastic Tubes 78. Velocity of the Pulse Wave in Man 79. Further Pulsatile Phenomena 80. Vibrations Communicated to the Body by the Action of the Heart 81. The Blood Current 82. Schemata of the Circulation 83. Capacity of the Ventricles 84. Estimation of the Blood Pressure 85. Blood Pressure in the Arteries 86. Blood Pressure in the Capillaries 87. Blood Pressure in the Veins 88. Blood Pressure in the Pulmonary Artery 89. Measurement of the Velocity of the Blood Stream 90. Velocity of the Blood in Arteries, Capillaries, and Veins 91. Estimation of the Capacity of the Ventricles 92. The Duration of the Circulation 93. Work of the Heart 94. Blood Current in the Smaller Vessels 95. Passage of the Blood Corpuscles out of the Vessels — [Diapedesis] 96. Movement of the Blood in the Veins 97. Sounds or Bruits within Arteries 98. Venous Murmurs 99. The Venous Pulse — Phlebogram 100. Distribution of the Blood 1 01. Plethysmography 102. Transfusion of Blood THE BLOOD GLANDS. 103. The Spleen — Thymus — Thyroid — Suprarenal Capsules — Hypophysis Cerebii — Coc- cygeal and Carotid Glands 104. Comparative 105. Historical Retrospect PAGE 71 73 75 77 78 83 86 88 92 92 92 92 95 104 105 108 108 IIO 1 10 1 1 1 116 11 7 122 126 127 128 129 130 131 133 134 134 136 137 137 139 140 140 141 145 151 152 153 155 157 159 159 159 160 162 163 164 164 165 167 167 168 172 181 182 CONTENTS. Xlll III. PHYSIOLOGY OF RESPIRATION. SECTION 106. Structure of the Air Passages and Lungs 107. Mechanism of Respiration 108. Quantity of Gases Respired 109. Number of Respirations • no. Time occupied by the Respiratory Movements in. Pathological Variations of the Respiratory Movements 1 12. General View of the Respiratory Muscles 1 13. Action of the Individual Respiratory Muscles 1 14. Relative Size of the Chest 1 15. Pathological Variations of the Percussion Sounds 1 16. The Normal Respiratory Sounds 1 17. Pathological Respiratory Sounds 1 18. Pressure in the Air Passages during Respiration 1 19. Appendix to Respiration 1 20. Peculiarly Modified Respiratory Sounds PAGE 183 190 191 192 192 195 196 197 201 203 204 204 201; 207 207 CHEMISTRY OF RESPIRATION. 1 21. Quantitative Estimation of C 0 2 , 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 213 128. Diffusion of Gases within the Lungs 216 129. Exchange of Gases between the Blood and Air 216 130. Dissociation of Ga^es 218 1 3 1 . Cutaneous Respiration 219 132. Internal Respiration * 219 133. Respiration in a Closed Space 221 134. Dyspnoea 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 233 143. Histological 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 Stomach 256 158. Vomiting 257 159. Movements of the Intestine 259 160. Excretion of Feecal 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 XIV CONTENTS. SECTION 165. Methods of obtaining Gastric Juice 166. Process of Gastric Digestion 167. Gases in the Stomach 168. Structure of the Pancreas 169. The Pancreatic Juice 170. Digestive Action of the Pancreatic Juice 171. The Secretion of the Pancreatic Juice 172. Preparation of Peptonized Food 173. Structure of the Liver 174. Chemical Composition of the Liver Cells 175. Diabetes Mellitus, or Glycosuria 176. The Functions of the Liver 177. Constituents of the Bile 178. Secretion of Bile 179. Excretion of Bile • 180. Reabsorption of Bile 181. Functions of the Bile • 182. Fate of the Bile in the Intestine 183. The Intestinal Juice 184. Fermentation Processes in the Intestine 185. Processes in the Large Intestine 186. Pathological Variations 187. Comparative Physiology 188. Historical Retrospect V. PHYSIOLOGY OF ABSORPTION. 189. The Organs of Absorption 190. Structure of the Small and Large Intestines 191. Absorption of the Digested Food 192. Absorptive Activity of the Wall of the Intestine 193. Influence of the Nervous System 194. Feeding with “ Nutrient Enemata ” 195. Chyle Vessels and Lymphatics 196. Origin of the Lymphatics 197. The Lymph Glands 198. Properties of Chyle and Lymph 199. Quantity of Lymph and Chyle . 200. Origin of Lymph 201. Movement of Chyle and Lymph 202. Absorption of Parenchymatous Effusions 203. Congestion of Lymph, Serous Effusions and CEdema 204. Comparative Physiology 205. Historical Retrospect VI. PHYSIOLOGY OF ANIMAL HEAT. 206. Sources of Heat 207. Homoiothermal and Poikilothermal Animals . 208. Methods of Estimating Temperature — Thermometry 209. Temperature — Topography 210. Conditions Influencing the Temperature of Organs 21 1. Estimation of the Amount of Heat — Calorimetry 212. Thermal Conductivity of Animal Tissues 213. Variations of the Mean Temperature 214. Regulation of the Temperature 215. Income and Expenditure of Heat 216. Variations in Heat Production 217. Relation of Heat Production to Bodily Work 218. Accommodation for different Temperatures 219. Storage of Heat in the Body 220. Fever 221. Artificial Increase of the Temperature 222. Employment of Heat 223. Increase of Temperature post-mortem 224. Action of Cold on the Body PACE 2 73 274 278 278 279 280 283 284 284 288 290 292 293 296 298 299 301 302 303 307 3” 3H 316 317 319 319 325 327 33 1 33i 33 2 332 335 337 339 340 34i 344 344 346 346 347 350 351 353 354 356 357 358 361 363 365 365 366 367 367 369 369 369 370 CONTENTS. XV SBCTION PAGE 22 ^. Artificial Lowering of Temperature 370 226. Employment of Cold 37 1 227. Heat of Inflamed Parts 37 2 228. Historical and Comparative 37 2 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. Milk and its Preparations 377 2 3 2 - E gg s 3 81 233. Flesh and its Preparations 381 234. Vegetable Foods 383 235. Condiments — Coffee, Tea, and Alcohol 385 PHENOMENA AND LAWS OF METABOLISM. 236. Equilibrium of the Metabolism 237. Metabolism during Hunger and Starvation 238. Metabolism during a purely Flesh Diet 239. A Diet of Fat or of Carbohydrates 240. Mixture of Flesh and Fat 241. Origin of Fat in the Body 242. Corpulence 243. The Metabolism of the Tissues . 244. Regeneration of Organs and Tissues 245. Transplantation of the Tissues 246. Increase in Size and Weight during Growth 388 394 396 397 397 39 8 399 400 402 405 405 GENERAL VIEW OF THE CHEMICAL CONSTITUENTS OF THE ORGANISM. 247. Inorganic Constituents 407 248. Organic Compounds — Proteids 408 249. The Animal and Vegetable Proteids and their Properties 409 250. The Albuminoids 41 1 251. The Fats 412 252. The Carbohydrates 415 253. Historical Retrospect 417 VIII. THE SECRETION OF URINE. 254. Structure of the Kidney 419 255. The Urine 426 256. Urea 430 257. Qualitative and Quantitative Estimation of Urea 432 258. Uric Acid 434 259. Qualitative and Quantitative Estimation of Uric Acid 435 260. Kreatinin and other Substances 436 261. Coloring Matters of the Urine 439 262. Indigo, Phenol, Kresol, Pyrokatechin 440 263. Spontaneous Changes in Urine, Fermentations 443 264. Albumin in Urine 445 265. Blood in Urine 447 266. Bile in Urine 450 267. Sugar in Urine 451 268. Cystin 454 269. Leucin, Tyrosin 454 270. Deposits in Urine 455 271. General Scheme for Detecting Urinary Deposits 457 272. Urinary Calculi 458 273. The Secretion of Urine 459 274. The Preparation of Urine 463 275. Passage of Various Substances into the Urine 465 276. Influence of Nerves on the Renal Secretion 465 277. Uraemia, Ammoniaemia 469 XVI CONTENTS. SECTION PAGE 278. 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. 283. Structure of the Skin 477 284. Nails and Hair 479 285. The Glands of the Skm 482 286. The Skin as a Protective Covering 483 287. Cutaneous Respiration and Secretion — Sweat 484 288. Conditions Influencing the Secretion of Sweat 486 289. Pathological Variations 488 290. Cutaneous Absorption— Galvanic Conduction 489 291. Comparative — Historical 490 X. PHYSIOLOGY OF THE MOTOR APPARATUS. 292. Ciliary Motion, Pigment Cells 292A.Structure and Arrangement of the Muscles 293. Physical and Chemical Properties of Muscle 294. Metabolism in Muscle 295. Rigor mortis 296. Muscular Excitability 297. Changes in a Muscle during Contraction 298. Muscular Contraction 299. Rapidity of Transmission of a Muscular Contraction 300. Muscular Work 301. The Elasticity of Muscle 302. Formation of Heat in an Active Muscle 303. The Muscle Sound 304. Fatigue of Muscle 305. The Mechanism of the Joints 306. Arrangement and Uses of the Muscles of the Body 307. Gymnastics — Pathological Motor Variations 308. Standing 309. Sitting 310. Walking and Running 31 1. Comparative 49 1 493 500 5°2 504 506 5” 5i3 523 524 526 529 530 53 1 533 535 538 539 540 541 543 VOICE AND SPEECH. 312. Voice and Speech 313. Arrangement of the Larynx 314. Organs of Voice — Laryngoscopy 315. Conditions Modifying the Laryngeal Sounds 316. Range of the Voice 317. Speech — The Vowels 318. The Consonants 319. Pathological Variations of Voice and Speech 320. Comparative — Historical 545 545 55 i 553 554 555 557 558 559 XI. GENERAL PHYSIOLOGY OF THE NERVES AND ELECTRO- PHYSIOLOGY. 321. Structure and Arrangement of the Nerve Elements 322. Chemistry of the Nerve Substance 323. Metabolism of Nerves 324. Excitability of Nerves — Stimuli 325. Diminution of the Excitability — Degeneration and Regeneration of Nerves . . . . 326. The Galvanic Current 327. Action of the Galvanic Current — Galvanometer 328. Electrolysis 329. Induction — Extra Current — Magneto- Induction . . 56i 566 568 568 572 577 578 579 584 CONTENTS. XVII SECTION 330. Du Bois-Reymond’s Inductorium 331. Electrical Currents in Passive Muscle and Nerve 332. Currents of Stimulated Muscle and Nerve 333. Currents in Nerve and Muscle during Electrotonus 334. Theories of Muscle and Nerve Currents 335. Electrotonic Alteration of the Excitability 336. Electrotonus — Law of Contraction 337. Rapidity of Transmission of Nervous Impulses 338. Double Conduction in Nerves 339. Therapeutical Uses of Electricity — Reaction of Degeneration 340. Electrical Charging of the Body 341. Comparative — Historical XII. PHYSIOLOGY OF THE PERIPHERAL NERVES. 342. Classification of Nerve Fibres 343. Nervus Olfactorius 344. Nervus Opticus 345. Nervus Oculomotorius 346. Nervus Trochlearis 347. Nervus Trigeminus 348. Nervus Abducens 349. Nervus Facialis 350. Nervus Acusticus 351. Nervus Glosso-pharyngeus 352. Nervus Vagus 353. Nervus Accessorius 354. Nervus Hypoglossus 355. The Spinal Nerves 356. The Sympathetic Nerve 357. Comparative — Historical XIII. PHYSIOLOGY OF THE NERVE CENTRES. 358. General 359. Structure of the Spinal Cord 360. Spinal Reflexes 361. Inhibition of the Reflexes 362. Centres in the Spinal Cord 363. Excitability of the Spinal Cord 364. The Conducting Paths in the Spinal Cord 365. General Schema of the Brain 366. The Medulla Oblongata 367. Reflex Centres of the Medulla Oblongata 368. The Respiratory Centre 369. The Cardio-Inhibitory Centre 370. The Accelerans Cordis Centre 371. Vasomotor Centre and Vasomotor Nerves 372. Vaso-dilator Centre and Vaso-dilator Nerves 373. The Spasm Centre — The Sweat Centre 374. Psychical Functions of the Cerebrum 375. Structure of the Cerebrum — Motor Cortical Centres 376. The Sensory Cortical Centres 377. The Thermal Cortical Centres 378. Topography of the Cortex Cerebri 379. The Basal Ganglia — The Mid-brain 380. The Structure and Functions of the Cerebellum 381. The Protective Apparatus of the Brain 382. Comparative — Historical XIV. PHYSIOLOGY OF THE SENSE ORGANS. 1. SIGHT. 383. Introductory Observations 384. Histology of the Eye 385. Dioptric Observations B PAGE 586 588 591 594 595 597 600 602 605 606 611 611 613 615 616 618 621 621 630 631 634 637 638 644 645 645 649 652 653 654 661 664 668 670 671 675 681 685 686 691 693 695 701 702 703 709 721 724 725 733 739 742 746 748 75 ° 759 XV 111 CONTENTS. SECTION 386. Formation of a Retinal Image 387. Accommodation of the Eye 388. Normal and Abnormal Refraction 389. The Power of Accommodation 390. Spectacles 391. Chromatic Aberration and Astigmatism . . . . 392. The Iris 393. Entoptical Phenomena 394. Illumination of the Eye — The Ophthalmoscope 395. Activity of the Retina in Vision 396. Perception of Colors 397. Color Blindness 398. Stimulation of the Retina 399. Movements of the Eyeballs 400. Binocular Vision 401. Single Vision — Identical Points 402. Stereoscopic Vision 403. Estimation of Size and Distance 404. Protective Organs of the Eye 405. Comparative — Historical PAGE 764 766 770 772 773 774 775 779 781 785 790 794 796 799 803 803 805 808 810 812 2. HEARING. 406. Structure of the Organ of Hearing . . . 407. Physical Introduction 408. Ear Muscles 409. Tympanic Membrane 410. The Auditory Ossicles and their Muscles 41 1. Eustachian Tube — Tympanum . . . . 412. Conduction of Sound in the Labyrinth . 413. Structure of the Labyrinth 414. Auditory Perceptions of Pitch 415. Perception of Quality — Vowels . . . . 416. Action of the Labyrinth 417. Harmony — Discords — Beats 418. Perception of Sound 419. Comparative — Historical 814 815 816 816 819 822 824 825 828 830 833 835 836 837 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 425. Sensory and Tactile Sensations 426. The Sense of Locality 427. The Pressure Sense 428. The Temperature Sense 429. Common Sensation — Pain . . 430. The Muscular Sense 844 846 847 850 852 853 854 XV. PHYSIOLOGY OF REPRODUCTION AND DEVELOPMENT. 431. Forms of Reproduction 432. Testis — Seminal Fluid 433. The Ovary — Ovum — Uterus 434. Puberty 435. Menstruation 436. Penis — Erection 857 857 862 866 867 869 CONTENTS. XIX SECTION 437. Ejaculation — Reception of the Semen 438. Fertilization of the Ovum 439. Impregnation and Cleavage of the Ovum 440. Structures formed from the Epiblast 441. Structures formed from the Mesoblast and Hypoblast 442. Formation of the Heart and Embryo 443. Further Formation of the Body 444. Formation of the Amnion and Allantois 445. Human Foetal Membranes — Placenta 446. Chronology of Human Development 447. Formation of the Osseous System 448. Development of the Vascular System 449. Formation of the Intestinal Canal 450. Development of the Genito- urinary Organs .... 451. Formation of the Central Nervous System .... 452. Development of the Sense Organs 453. Birth 454. Comparative — Historical PAGE 872 872 873 877 877 878 880 881 882 886 888 892 895 897 900 901 902 903 LIST OF ILLUSTRATIONS FIGURE 1 . Human colored blood corpuscles 2. Apparatus of Abbe and Zeiss for estimating the blood corpuscles 3. Mixer *4. Gower’s hsemacytometer ( Ilawksley ) . . . 5. Red blood corpuscles showing various changes of shape . . . . 6. Vaso-formative cells 7. White blood corpuscles *8. White blood corpuscles [Klein) 9. Amoeboid movements 10. Blood plates and their derivatives 1 1 . Haemoglobin crystals *12. Gower’s hsemoglobinometer [Hawksley) 13. Scheme of a spectroscope 14. Various spectra of haemoglobin 15. Haemin crystals 16. Haemin crystals prepared from traces of blood 17. Haematoidin crystals *18. Hewson’s experiment 19. Scheme of Pfluger’s gas pump 20. Micrococcus, bacterium, vibrio *21. Bacillus anthracis *22. Scheme of the circulation 23. Muscular fibres from the heart 24. Muscular fibres in the left auricle 25. Muscular fibres in the ventricles *26. Lymphatic from the pericardium ( Cadiat) *27. Section of the endocardium [Cadiat) *28. Purkinje’s fibres [Ranvier) 29. Cast of the ventricles of the human heart 30. The closed semilunar valves *31. Various cardiographs [Hermann) 32. Curves of the apex beat 33. Changes of the heart during systole, and sections of thorax . , *34. Dog’s heart, posterior surface [Ludwig and Hesse) *35. Left lateral surface [Ludwig and Hesse) *36. Anterior surface [Ludwig and Hesse) *37. Base of heart [Ludwig and Hesse) *38. Base of heart in systole and diastole [Ludwig and Hesse) . . , 39. Curves from a rabbit’s ventricle *40. Marey’s registering tambour [Hermann) 41. Curves obtained with a cardiac sound 42. Curves from the cardiac impulse *43. Scheme of cardiac cycle *44. Position of the heart in the chest [Luschka and Gairdner) . *45. Heart of frog from the front [Ecker) *46. Heart of frog from behind [Ecker) *47. Auricular septum [Ecker) 48. Bipolar nerve cells from a frog’s heart 49. Frog’s heart [Ecker) *490. Scheme of frog’s heart [Brunton) *50. Stannius’s experiment [Brunton) *51. Scheme of a frog manometer [Stirling) *52. Perfusion cannula [Kronecker and Stirling) *53. Roy’s tonometer [Stirling) *54. Luciani’s groups of cardiac pulsations [Hermann) *55. Curves of a frog’s heart at different temperatures [Hermann) . xxi PAGE 19 20 20 20 21 26 29 30 32 33 35 37 38 39 43 43 44 50 58 66 66 6 7 68 69 70 71 71 72 76 77 79 79 80 82 82 83 83 83 84 85 86 87 89 90 94 94 95 95 95 95 97 98 98 99 100 101 XXII ILLUSTRATIONS. FIGURE 56. Cardio-pneumograph of Landois 57. Apparatus for showing the effect of respiration 58. Cylindrical vessel filled with water 59. Cylindrical vessel with manometers 60. Small artery with its various coats 61. Capillaries injected with silver nitrate *62. Longitudinal section of a vein at a valve ( Cadiat ) 63. Poiseuille’s pulse measurer 64. Sphygmometer of Herisson 65. Scheme of Marey’s sphygmograph *66. Marey’s improved sphygmograph ( B . Bramwell ) *67. Scheme of Marey’s sphygmograph in working order ( B . Bramwell ) *68. Scheme of Marey’s sphygmograph ( B . Bramwell') *69. Dudgeon’s sphygmograph ( Dudgeon ) *70. Mode of applying Dudgeon’s sphygmograph {Dudgeon) *71. Sphygmogram ( Dudgeon ) 72. Scheme of Brondgeest’s pan sphygmograph 73. Scheme of Landois’ angiograph 74. Pulse curves of the carotid, radial, and posterior tibial arteries . . 75. Landois’ s gas sphygmoscope 76. Hsemautographic curve *77. Sphygmogram of radial artery ( Dudgeon ) 78. Sphygmograms of various arteries 79. Pulsus dicrotus, P. caprizans, P. monocrotus *80. Aortic regurgitation *81. Pulsus dicrotus *82. Hyperdicrotic pulse 83. Pulsus alternans 84. Curves of the posterior tibial and pedal arteries 85. Anacrotic pulse curves 86. Anacrotic pulse curves 87. Influence of the respiration on the sphygmogram 88. Pulse curves during Muller’s and Valsalva’s experiments .... 89. Pulsus paradoxus 90. Various radial curves altered by pressure 91. Apparatus for measuring the velocity of the pulse wave 92. Tracing obtained from 91 93. Pulse tracings of the radial artery 94. Tracings from the posterior tibial and carotid arteries 95. Apparatus for registering the molar motions of the body 96. Vibration and heart curves • 9 7. Ludwig and Fick’s kymographs *98. Ludwig’s improved revolving cylinder ( Hermann ) *99. Blood- pressure tracing of the carotid of a dog ( Hermann ) .... *100. Fick’s spring manometer, by Hering {Hermann) 101. Fick’s flat-spring kymograph *102. Scheme of height of blood pressure *103. Depressor curve {Stirling) 104. Blood pressure and respiration tracings taken simultaneously . . . *105. Blood pressure tracing during stimulation of the vagus {Stirling) . *107* | Apparatus of v. Kries for capillary pressure {C. Ludwig) .... *108. Scheme of the blood pressure 109. Volkmann’s haemadromometer no. Ludwig and Dogiel’s rheometer hi. Vierordt’s haematachometer 1 12. Dromograph 1 13. Scheme of sectional area (after Yeo) 1 14. Diapedesis 1 15. Various forms of venous pulse 1 16. Mosso’s plethysmograph *117. Trabeculae of the spleen {Cadiat) » . *118. Adenoid tissue of spleen {Cadiat) *119. Malpighian corpuscle of the spleen {Cadiat) *120. Tracing of a splenic curve {Roy) *121. Thymus gland {Cadiat) PAGE 104 106 108 109 in 112 114 1 17 117 118 1 18 1 18 118 119 119 120 120 121 121 122 122 123 123 124 126 126 127 128 130 130 131 131 132 133 134 135 135 136 136 138 138 141 142 143 144 144 145 147 147 149 151 152 156 156 156 157 157 162 166 168 172 172 173 176 178 ILLUSTRATIONS. XX111 FIGURE * 122 . *123. *124. *125. *126. 127. *128. 129. 130. I 3 I - 132. J 33- z 34- J 35- 136. I 37- >38. : 39- 140. 141. 142. H3- J 44- * x 45* 146. 147. 148. *149. *150. *151- *152. *53- 154. 155- 156. 157. 158. 159* 160. 161. 162. Elements of the thymus gland ( Cadiat) .... Thyroid gland ( Cadiat ) Suprarenal capsule ( Cadiat ) Human bronchus (. Hamilton ) Air vesicles injected with silver nitrate ( Hamilton ) Scheme of the air vesicles of lung Interlobular septa of lung ( Hamilton ) Scheme of Hutchinson’s spirometer Marey’s stethograph (M' Kendrick) Brondgeest’s tambour and curve Pneumatogram Section through diaphragm ( Hermann ) .... Action of intercostal muscles Cyrtometer curve Sibson’s thoracometer Topography of the lungs and heart Andral and Gavarret’s respiration apparatus . . Scharling’s apparatus Regnault and Reiset’s apparatus v. Pettenkofer’s apparatus Valentin and Brunner’s apparatus Ciliated epithelium ( Schenk ) Objects found in sputum Squamous epithelium of mouth Mucous follicle ( Schenk ) Rodded epithelium of a salivary duct Histology of the salivary glands Human sub-maxillary gland ( Heidenhain ) . . . | Sections of a serous gland ( Heidenhain ) . . . Diagram of a salivary gland ( L . Brunton) . . . Apparatus for estimation of sugar Polarization apparatus Vertical section of a tooth Dentine Interglobular spaces Dentine and enamel Dentine and crusta petrosa j- Development of a tooth 163. Section of oesophagus ( Schenk ) 164. Perinaeum and its muscles 165. Levator ani externus and internus *166. Auerbach’s plexus {Cadiat) *167. Meissner’s plexus ( Cadiat ) 1 68. Goblet cells 169. Surface section of gastric mucous membrane . . . . 170. Fundus gland of the stomach 1 7 1 . Pyloric gland 172. Scheme of the gastric mucous membrane *173. Pyloric mucous membrane {Hermann) *174. Pyloric glands during digestion ( Hermann ) . . . . *175. Scheme of pyloric fistula ( Stirling ) *176. Section of the tubes of the pancreas (Hermann) . . 177. Changes of the pancreatic cells during activity . . . 178. Scheme of a liver lobule *179. Human liver cells ( Cadiat) *180. Liver cells during fasting ( Hermann ) 1 81. Bile ducts 182. Various appearances of the liver cells 183. Interlobular bile duct *184. Cholesterin (Ait ken) *185. Biliary fistulse (Stirling) 186. Longitudinal section of the small intestine (Schenk) . 187. Transverse section of Lieberkiihn’s follicles (Schenk) 178 179 180 184 186 187 188 191 193 193 194 198 199 201 202 202 210 210 21 1 21 1 213 225 223 232 233 233 234 235 236 24O 247 247 25O 250 250 251 251 252 256 260 261 263 264 266 266 267 267 268 27O 270 271 278 279 285 286 286 287 287 287 296 298 304 305 XXIV ILLUSTRATIONS. FIGURE *188. Schemata of intestinal fistulae ( Stirling ) *189. Moreau’s fistula (after Brunton ) 190. Bacterium aceti and B. butyricus 191. Bacillus subtilis 192. Bacteria of faeces *193. Scheme of intestinal absorption ( Beaunis ) *194. Villi of small intestine injected {Cadiat) 195. Scheme of an intestinal villus 196. Injected villus ( Schenk ) *197. Villi and Lieberkiihn’s follicles ( Cadiat ) *198. Section of a solitary follicle ( Cadiat ) *199. Section of a Peyer’s patch ( Cadiat ) *200. Section of Auerbach’s plexus ( Cadiat) 201. Section of large intestine ( Schenk ) *202. Lieberkuhn’s gland ( Hermann ) 203. Endosmometer 204. Origin of lymphatics in the tendon of diaphragm *205. Lymphatics of diaphragm silvered ( Kanvier ) 206. Perivascular lymphatics 207. Stomata from lymph sack of frog 208. Section of two lymph follicles *209. Scheme of a lymphatic gland ( Sharpey ) 210. Part of a lymphatic gland *211. Section of the central tendon of diaphragm {Brunton) *212. Section of fascia lata of a dog ( Brunton i) *213. Lymph hearts (. Ecker ) 214. Water calorimeter of Favre and Silbermann 215. Walferdin’s metastatic thermometer 216. Scheme of thermo-electric arrangements 217. Kopp’s apparatus for specific heat 218. Daily variations of temperature *219. Acini of the mammary gland of a sheep ( Cadiat ) 220. Milk glands during inaction and secretion *221. Milk and colostrum ( Stirling ) *222. Section of a grain of wheat ( JBlyth ) 223. Yeast cells growing 224. Composition of animal and vegetable foods *225. Starch grains *226. Longitudinal section of the kidney (. Henle ) *227. Malpighian pyramid ( Tyson after Ludwig) 228. Scheme of the uriniferous tubules ( Klein and Noble Smith.) . . 229. Scheme of the structure of the kidney 230. Glomerulus and renal tubules *231. Convoluted renal tubule {Heidenhain) *232. Irregular tubule ( Tyson after Klein) *233. Transverse section of the apex of a Malpighian pyramid ( Cadiat ) *234. Development of a glomerulus ( Cadiat ) 235A.Graduated urinary flask 235B.Urinometer 236. Graduated burette 237. Urea and urea nitrate *238. Oxalate of urea ( after Beale) 239. Urameter ( Charteris ) 240. Squibb’ s method for urea ( Martindale ) 241. Graduated pipette *242. Uric acid *243. Uric acid ( Wedl ) 244. Kreatinin-zinc chloride *245. Oxalate of lime {Wedl) *246. Oxalate of lime 247. Hippuric acid 248. Spermatozoa and calcic phosphate 249. Deposit in urine during the “ acid fermentation ” 250. Deposit in ammoniacal urine 251. Deposit in ammoniacal urine *252. Ammonio-magnesic phosphate and urates 305 306 308 309 313 319 320 320 321 322 323 323 324 324 325 326 333 334 334 334 335 336 337 342 342 343 347 351 352 356 359 375 376 377 384 387 39i 416 419 420 421 422 423 424 424 426 426 427 427 429 430 431 433 433 433 434 434 437 437 437 438 442 444 444 444 444 ILLUSTRATIONS. XXV FIGURE 253. Blood corpuscles in urine 254. Peculiar forms of blood corpuscles 255. Colored and colorless corpuscles in urine 256. Blood corpuscles and triple phosphate 257. Spectroscopic examination of urine *257A.Picro-Saccharimeter (G. Johnson) *258. Inosit [Beale after Funke) 259. Cystin and oxalate of lime 260. Leucin, tyrosin and ammonium urate 261. Epithelium from the genito-urinary apparatus 262. Micrococci and fungi in urine 263. Blood and granular tube casts 264. Hyaline casts *265. Oncometer {Stirling, after Roy) *266. Oncograph ( Stirling , after Roy ) *267. Renal oncograph curve ( Stirling , after Roy ) *268. Transitional epithelieum {Beale) 269. View of the trigone of the bladder *270. Nervous mechanism of micturition {Power) . *271. Section of epidermis and its nerves 272. Scheme of the structure of the skin 273. Vertical section of the skin *274. Papillae of the skin injected *275. Margarin crystals in fat cells 276. Transverse section of a nail 277. Transverse section of a hair follicle 278. Section of a hair follicle 279. Sebaceous gland 280. Ciliated epithelium 281. Histology of muscular tissue *282. Muscular fibre ( Quain ) 283. Tendon attached to a muscle *284. Injected blood vessels of muscle ( Kolliker ) 285. Motorial end plates 286. Termination of a nerve in muscle *287. Nerve ending in smooth muscle ( Cadiat ) *288. Non-striped muscle cell {Stirling) *289. Frog with its sciatic artery ligatured *290. Scheme of the curara experiment {after Rutherford) .... *291. Platinum electrodes {Elliott Brothers) 292. Microscopic appearances in contracting muscle 293. Helmholtz’s myograph *294. Pendulum myograph *295. Scheme of the pendulum myograph {Stirling) *296. Du Bois-Reymond’s spring myograph 297. Muscle curve *298. Muscle curve {Rutherford) *299. Method of studying a muscular contraction {after Rutherford) 300. Muscle curves 301. Muscle curves, opening and closing shocks 302. Muscle curves, tetanus *303. Curves of a red and pale muscle {Kronecker and Stirling) . *304. Muscle curves {Kronecker and Stirling) *305. Tone inductorium {Kronecker and Stirling) *306. Muscle curves {Marey) *307. Height of the lift by a muscle *308. Dynamometer *309. Curves of elasticity {after Marey ) *310. Curve of elasticity of a muscle {after Marey) 31 1. Curve of elasticity {Marey) *312. Fatigue curve ( Waller) *313. Orders of levers *314. Scheme of the action of muscles on bones 315. Phases of walking 316. Instantaneous photograph of a person walking 317. Instantaneous photograph of a runner 448 448 449 449 45° 453 453 454 454 455 45 6 456 457 467 467 468 47i 47i 474 477 478 479 479 479 480 481 481 483 491 494 495 496 496 497 498 499 499 508 509 509 512 513 5H 515 516 516 517 518 519 519 521 522 522 522 524 525 526 527 527 527 533 536 537 541 542 543 XXVI ILLUSTRATIONS. FIGURE 318. Instantaneous photograph of a person jumping . . 319. Larynx from the front 320. Larynx from behind 321. Larynx from behind 322. Nerves of the larynx 323. Action of the posterior crico-arytenoid muscles . . 324. Action of the arytenoid muscles 325. Action of the lateral crico-arytenoid muscles . . . 326. Vertical section of the head and neck 327. Examination of the larynx 328. Laryngoscopic view of the larynx 329. View of the larynx during a high note 330. View of the larynx during a deep inspiration . . . 331. Rhinoscopy 332. View of the posterior nares 333. Parts concerned in phonation 334. Tumors on the vocal cords 335. Histology of nervous tissues *336. Sympathetic nerve fibre ( Ranvier ) *337. Transverse sections of nerve fibres 338. Medullated nerve fibre *339. Ranvier’s crosses ( Ranvier ) 340. Transverse section of a nerve *341. Cell from the Gasserian ganglion ( Schwalbe ) . . . 342. Degeneration and regeneration of nerve fibres . . *343. Waller’s experiments [after Dalton) 344. Rheocord of Du Bois Reymond 345. Scheme of a galvanometer *346. Large Grove’s battery [Gscheidlen) *347. Grennet’s battery ( Gscheidlen) *348. Leclanche’s element [Gscheidlen) *349. Non-polarizable electrodes [Elliott Brothers) . . . *350. Thomson’s galvanometer [Elliott Brothers) . . . *351. Lamp and scale [Elliott Brothers) *352. Galvanometer shunt [Elliott Brothers) *353. Scheme of the induced currents [Hermann) . . . *354. Helmholtz’s modification [Hermann) 355. Scheme of an induction machine *356. Inductorium [Elliott Brothers) 357. Stohrer’s apparatus *358. Friction key [Elliott Brothers) *359. Plug key [Elliott Brothers) *360. Capillary contact [Kronecker and Stirling) . . . 361. Scheme of the muscle current 362. Capillary electrometer *363. Secondary contraction *364. Nerve-muscle preparation 365. Bernstein’s differential rheotome 366. Nerve current in electrotonus 367. Scheme of electrotonic excitability 368. Method of testing electrotonic excitability .... 369. Distribution of an electrical current 370. Velocity of nerve energy *371. Scheme for testing velocity of a nerve impulse . . *372. Curves of a nerve impulse [Marey) *373. Sponge rheophores ( IVeiss) *374. Disk rheophore ( IVeiss) *375. Metallic brush [IVeiss) 376. Motor points of the arm 377. Motor points of the arm 378. Motor points of the leg 379. Motor points of the leg *380. Scheme of a reflex act [Stirling) 381. Optic chiasma *382. Decussation of the optic tracts [Charcot) *383. Scheme of images in squinting [Bristowe) . . . . PAGE 543 546 546 547 547 548 548 549 550 55i 552 553 553 553 553 556 558 562 563 563 563 5 6 3 5 6 5 566 573 574 578 580 580 581 581 582 583 583 583 585 585 586 587 587 587 588 588 589 589 592 592 593 595 598 599 599 603 604 604 607 607 607 608 608 609 610 615 617 618 619 ILLUSTRATIONS. XXV11 FIGURE 384. Medulla oblongata *385. Under surface of the brain 386. Connections of the cranial nerves 387. Sensory nerves of the face 388. Motor points of the face and neck *389. Disposition of the semicircular canals ( IV. Stirling) . . *390. Cardiac nerves of the rabbit ( IV. Stirling ) *391. Spinal ganglion ( Cadiat ) 392. Cutaneous nerves of the arm 393. Cutaneous nerves of the leg ( Henle ) 394. Transverse section of the spinal cord *395. Transverse section of the white matter ( Cadiat ) . . . . *396. Multipolar nerve cells of the cord ( Cadiat ) *397. Relation of white and gray matter of the cord ( Schafer ) *398. Transverse sections of the spinal cord *399. Transverse section of the cord ( Cadiat ) *400. Longitudinal section of the cord ( Cadiat ) *401. Multipolar nerve cell *402. Injected blood vessels of the cord ( Kolliker ) 403. Conducting paths in the cord *404. Degeneration paths in the cord ( Bramwell ) *405. Scheme of a reflex act ( IV. Stirling) *406. Section of a spinal segment ( W. Stirling) *407. Propagation of reflex movements ( Beaunis ) *408. Effect of section on half of the cord ( Erb ) *409. Brain, ventricles and basal ganglia . . . 410. Scheme of the brain *411. Connections of the cerebellum *412. Diagram of a spinal segment ( Bramwell ) *413. Section across the pyramids ( Schwalbe ) *414. Section of the medulla oblongata ( Schwalbe ) *415. Section of the olivary body ( Schwalbe ) *416. Scheme of the respiratory centres (. Rutherford ) . . . . *417. Scheme of the accelerans fibres ( IV. Stirling) . . . . *418. Cardiac plexus of a cat ( Bohrn ) *419. Frog without its cerebrum ( Stirling , after Goltz) . . . *420. Frog without its cerebrum ( Stirling , after Goltz) . . . *421. Pigeon with its cerebrum removed ( after Dalton) . . . *422. Cerebral convolution *423. Cerebral convolution injected *424. Left side of the human brain ( Ecker ) *425. Inner aspect of right hemisphere {Ecker) *426. Left frontal lobe and island of Reil ( Ttirner) .... *427. Brain from above (Ecker) 428. Cerebrum of dog, carp, frog, pigeon, and rabbit . . . . 429. Relation of the cerebral convolutions to the skull . . . *430. Motor centres ( after Schafer and Horsley) *431. Motor areas ( after Gowers) 432. Psycho-optic fibres ( Munk ) *433. Section of a cerebral hemisphere ( Horsley ) • *434. Secondary degeneration in a crus ( Charcot) *435. Transverse section of the crus cerebri ( Charcot ) . . . . *436. Scheme of aphasia ( Lichtheim ) *437. Scheme of aphasia ( Lichtheim ) *438. Relation of the convolutions to the skull (R. W. Reid) . *439. Basal ganglia and the ventricles *440. Transverse section of the right hemisphere ( Gegenbaur ) *441. Fibres in pons (Erb) *442. Section of the cerebellum (Sankey) *443. Cortex cerebri and its membranes ( Schwalbe ) *444. Pigeon with its cerebellum removed (Dalton) *445. Circle of Willis (Charcot) • . . *446. Ganglionic arteries ( Charcot) *447. Corneal corpuscles (Ranvier) *448. Corneal spaces (Ranvier) 449. Junction of the cornea and sclerotic PAGE 620 622 625 629 633 636 640 646 647 647 654 655 655 655 656 657 658 658 658 658 660 661 661 662 674 675 676 677 680 681 683 683 687 693 694 705 705 705 709 710 711 712 713 714 716 717 718 719 722 726 728 728 730 730 732 734 736 736 740 740 742 744 745 750 75 ° 75i XXV111 ILLUSTRATIONS. FIGURE *450. Vertical section of cornea ( Ranvier ) *451. Horizontal section of cornea ( Ranvier ) . . . . 452. Blood vessels of the eyeball *453. Vertical section human retina (Cadiat) . . . . 454. Layers of the retina *455. Vertical section of the fovea centralis ( Cadiat) . *456. F'ibres of the lens ( Kolliker ) 457. Section of the optic nerve 458. Action of lenses on light 459. Refraction of light 460. Construction of the refracted ray 461. Optical cardinal points 462. Construction of the refracted ray 463. Construction of the image 464. Refracted ray in several media 465. Visual angle and retinal image 466. Scheme of the ophthalmometer 467. Horizontal section of the eyeball 468. Scheme of accommodation 469. Sanson-Purkinje’s images *470. Phakoscope (M’ Kendrick) 471. Schemer’s experiment 472. Refraction of the eye 473. Myopic eye 474. Hypermetrophic eye 475. Power of accommodation *476. Diagram of astigmatism (Frost) 477. Cylindrical glasses *478. Scheme of the nerves of the iris (Erb) . . . . *479. Pupilometer ( Gorham) *480. Pupilometer (Gorham) 481. Entoptical shadows 482. Scheme of the original ophthalmoscope . . . . 483. Scheme of the indirect method 484. Action of a divergent lens 485. Action of a divergent lens 486. View of the fundus oculi *487. Morton’s ophthalmoscope (Pickard and Curry) . *488. Frost’s artificial eye (Frost) 489. Action of the orthoscope *490. Mariotte’s experiment 491. Horizontal section of the right eye *492. M’ Hardy’s perimeter (Pickard and Curry) . . *493. Priestley Smith’s perimeter (Pickard and Curry) 494. Perimetric chart 495. Geometrical color cone 496. Action of light rays on the retina *497. Cones of the retina ( Stirling , after Engelmann) *498. Irradiation 499. Scheme of the action of the ocular muscles . . 500. Identical points of the retina 501. The horopter 502. Two stereoscopic drawings 503. Brewster’s stereoscope 504. Wheatstone’s stereoscope 505. Telestereoscope 506. Wheatstone’s pseudoscope 507. Rollett’s apparatus *508. Zollner’s lines 509. Section of an eyelid 510. Scheme of the organ of hearing 51 1. External auditory meatus 512. Left tympanic membrane and ossicles 513. Membrana tympani and ossicles 514. Tympanic membrane from within 752 752 753 755 755 756 757 758 760 760 760 762 762 763 763 764 765 767 767 768 768 770 771 771 772 772 775 775 777 778 778 779 781 782 782 782 783 783 784 784 785 786 787 788 789 792 793 797 797 802 804 804 805 806 806 807 807 809 809 811 814 816 817 817 817 ILLUSTRATIONS. XXIX FIGURE *515. Ear specula ( Krohne and Sesemann ) *516. Toynbee’s artificial membrana tympani ( Krohne and Sesemann ) . . 517. Right auditory ossicles 518. Tympanum and auditory ossicles 519. Tensor tympani and Eustachian tube . . . 520. Right stapedius muscle *521. Eustachian catheter *522. Politzer’s ear bag ( Krohne and Sesemann ) 523. Right labyrinth 524. Scheme of the cochlea *525. Interior of the right labyrinth *526. Semicircular canals 527. Scheme of the canalis cochlearis *528. Gabon’s whistle {Krohne and Sesemann) 529. Curve of a musical note and its overtones *530. Koenig’s manometric capsule ( Koenig ) *531. Flame pictures of vowels (. Kcenig ) *532. Koenig’s analyzing apparatus ( Kcenig ) 533. Olfactory cells 534. Nasal and pharyngo-nasal cavities 535. Circumvallate papilla and taste bulbs *536. Wagner’s touch corpuscle ( Ranvier ) 537. Vertical section of skin 538. Pacini’s corpuscle *539. Bouchon epidermique ( Ranvier ) 540. ^Esthesiometer 541. ^Esthesiometer of Sieveking *542. Aristotle’s experiment 543. Landois’ pressure mercurial balance *544. Karyokinesis ( Gegenbaur) *545. Section of testis ( Schenk ) *546. Tubule of testis ( Schenk ) *547. Section of epididymis ( Schenk ) 548. Spermatic crystals 549. Spermatozoa 550. Spermatogenesis *551. A cat’s ovary {Hart and Barbour, after Schron) *552. Section of an ovary ( Turner) 553. Ovary and polar globules *554. Mucous membrane of the uterus {Hart and Barbour , after Turner ) *555. Fallopian tube and its annexes {Henle) *556. Section of Fallopian tube {Schenk) *557. Uterus before menstruation {J. Williams) *558. Uterus after menstruation {J. Williams) *559. Erectile tissue ( Cadiat) 560. The urethra and adjoining muscles 561. Cleavage of the yelk 562. The blastoderm 563. Schemata of development *564. Embryo of the mole ( W. K Parker) *565. Uterine mucous membrane {Coste) *566. Placental villi ( Cadiat ) 567. Hare lip *568. Meckel’s cartilage {W. K. Parker) 569. Centres of ossification in the innominate bone 570. Development of the heart 571. The aortic arches 572. Veins of the embryo . . 573. Development of the veins and portal system 574. Development of the intestine 575. Development of the lungs 576. Formation of the omentum 577. Development of the internal generative organs 818 818 818 819 821 822 823 823 824 825 826 826 827 829 831 832 833 835 839 839 841 844 844 845 846 847 848 849 850 856 858 859 859 860 861 861 862 863 864 865 866 867 868 868 869 871 874 875 876 881 883 884 889 889 890 893 893 894 895 896 896 896 897 XXX ILLUSTRATIONS. FIGURE PAGE 578. Development of the external genitals 899 *579. I f 900 *581' ( Chan S es * n externa ^ organs of generation in the female (after Schrader) . j *582. J [ 900 583. Development of the eye 901 [The illustrations indicated by the word Hermann are from Hermann’s Handbuch der Physi- ologic; by Cadiat, from Cadiat’s Traite d’ Anatomic Generate ; by Ranvier, from Ranvier’s Traite Technique d' Histologie ; by Brunton, from The Practitioner ; Brunton’s Text-Book of Pharma- cology, Therapeutics , and Materia Medica ; by Schenk, from Schenk’s Grundriss der normalen Histologie ; 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 (3) the Physi- ology of the Lowest Living Organisms , which stand on the border line of animals and plants, i. e., the so-called Protista of 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). I. MORPHOLOGY. The doctrine of the form of organ- isms. General Morphology. The doctrine of the formed elementary constituents of or- ganisms. (Histology) — (a) Histology of Plants. (3) Histology of Ani- mals. Special Morphology. The doctrine of the parts and organs of organisms. (Organology Anatomy) — (&), whereby the fluid part of the blood is reddened, while the stroma is recognizable only as a faint shadow (/). Similar forms are to be found in decomposing blood, as well as after the action of many other reagents. Action of Heat. — When blood is heated, on a warm stage, to 52 0 C. the corpuscles begin to undergo remarkable changes. Some of them become spherical, others biscuit-shaped; some are perforated, while in others small portions become detached and swim about in the surrounding fluid, a proof that heat destroys the histological individuality of the corpuscles ( Max Schultze). If the heat be con- tinued, the corpuscles are ultimately dissolved (§ 10, 3). Heat acts like the addition of a concentrated solution of urea to blood. If strong pressure be exerted upon a microscopic preparation, the blood corpuscles are compressed, and may break in pieces. This latter process of breaking up the corpuscles is called hsemocytotrypsis, in distinc- tion to that of solution of the corpuscles or haemocytolysis. Cytozoon or Wiirmchen — Gaule’s Experiment. — The following remarkable observation made by Gaule deserves mention here : A few drops of freshly-shed frog’s blood are mixed with LAKE-COLORED BLOOD. 23 5 c.c. of 0.6 per cent, solution of common salt, and the mixture defibrinated by shaking it along with a few c.c. of mercury. A drop of the defibrinated blood is examined on a hot stage (30-32° C.) under a microscope, when a protoplasmic mass, the so-called “ wiirmchen ,” escapes, with a lively movement, from many corpuscles, and ultimately dissolves. Similar “cytozoa” were dis- covered by Gaule in the epithelium of the cornea, of the stomach and intestine, in connective tissue, in most of the large glands, and in the retina (frog, triton). In mammals also he found similar but smaller structures. Most probably these structures are parasitic in their nature, as suggested by Ray Lankester, who called the parasite Drepanidium ranarum. If a finger moistened with blood be rapidly drawn across a warm slip of glass, so that the fluid dries rapidly, very remarkable corpuscle shapes, showing their great ductility and softness, are observed under the microscope. (For the effects of chemical reagents see p. 24.) [Staining Reagents. — Such reagents as magenta, picrocarmine, carmine, and many of the aniline dyes, stain the nucleus deep red when such is present, and although they must traverse the haemoglobin to reach the nucleus, the haemoglobin itself is not stained. When no nucleus is present, therefore, the corpuscles are not stained. Magenta (as pointed out by Roberts) causes one or more small spots or maculae to appear on the edge of the corpuscles. What its significance is, is entirely unknown. Normal saline solution (6 per cent. NaCl), tinged with methyl- violet, is a good staining and preservative agent {Bizzozero).^ [Effect of Agitation with Mercury. — Meltzer and Welch find that if ox blood be shaken up with mercury for 7 or 8 hours, the agitation causes the corpuscles completely to disappear, no trace of stroma or particles of the corpuscles being found in the fluid. On the other hand, the addition of pyrogallic acid (20 per cent ), potassic chlorate (6 per cent.), and silver nitrate (3 per cent.), completely prevents this dissolution of the corpuscles, even though the shaking be kept up for fourteen days.] If blood be mixed with concentrated gum, and if concentrated salt solution be added to it under the microscope, the corpuscles assume elongated forms ( Lindwurm ). Similar forms are obtained by mixing blood with an equal volume of gelatine at 36° C., allowing it to cool, and then making sections 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 : — Pacini’ s Mixture. Hydrarg. bichlor., 2 Sodic chloride, 4 Glycerine, 26 Distilled Water, 226 To be diluted with 2 parts of distilled water before being used. Hayem’s Fluid. Hydrarg. bichlor., 0.5 Sodic sulphate, 5.0 Sodic chloride, 1.0 Distilled water, 200.0 [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 stain be softened with con- centrated tartaric acid, the colorless corpuscles are specially distinct ( Struwe ). 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 saturated solution of picric acid, 20 per cent, pyrogallic acid, or 3 per cent, solution of silver nitrate ( Meltzer 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 (1 vol. concentrated solution, and 15 to 20 vols. of water) to 1 vol. of defibrinated blood, wdien the stromata are thrown down as a whitish precipitate. 24 FORM AND SIZE OF BLOOD CORPUSCLES. For microscopical 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 haemoglobin : — ( a ) Physical Agents. — i. Heating the blood to 6o° C. {Schultze) ; the temperature, however, varies for the blood of different animals. 2. Repeated freezing and thawing of the blood {Rollett). 3. Sparks from an electrical machine (but not after the addition of salts to the blood) ( Rollett ) ; the constant and induced currents ( Neumann ). {b) Chemically active Substances produced within the Body. — 4. Bile ( Hunefeld ), or bile salts ( Plattner , 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 ). (r) Other Chemical Reagents. — 7. Water. 8. Conduction of vapor of chloroform ( Bottcher ) ; ether {v. Wdttich ) ; amyls, small quantities of alcohol ( Rollett ) ; thymol ( Marchand ) ; nitrobenzol, ethylic ether, aceton, petroleum ether, etc. ( L . Lewin). 9. Antimoniuretted hydrogen, arseniu- retted hydrogen; carbon disulphide ( Hunefeld , Hertnann ) ; 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 cecoid. The zooid may shrink from the periphery of the corpuscle, or it may even pass out of the corpuscle altogether ( Brilcke ); 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 acids dissolve the corpuscles ; more dilute solutions cause precipitates in the haemoglobin. This is easily seen with carbolic acid ( Hills and Landois; Stirling and Rannie). 12. Alkalies of 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 4 C 1 injected into the blood causes vacuolation of the red corpuscles ( Bobritzky ).] [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 effect 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. Roberts).'] [Ammonium or Potassium Sulphocyanide removes the haemoglobin, and reveals a reticular structure — intra 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 C 0 2 , are more easily dissolved than those of arterial blood; while between both stands blood containing CO ( Landois , Litter ski , Lepine). 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 1 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 microscopic glass slide. Mix the fluids, and the corpuscles will remain undissolved. By means of the pipette add distilled water, and go on doing so until all the corpuscles are dissolved ; 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 cholaemia, poisoning with sub- stances which dissolve 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, hemoglo- binuria, and in cases of burning. In anemia and fever, the capacity for resistance seems to be diminished {Peiper). [Sodic salicylate, benzoate and colchicin dissolve the red corpuscles (oV. Pat on).] 6. FORM AND SIZE OF THE BLOOD CORPUSCLES OF DIFFERENT ANIMALS. — All mammals (with the exception of the camel, llama, alpaca, and their allies), and the cyclostomata 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. 1, B, 1, 2), and fishes (except cyclosto- mata) have nucleated , elliptical, bi-convex corpuscles. ORIGIN OF THE RED BLOOD CORPUSCLES. 25 Size (/z = 0.001 Millimetre). Of the Disk-shaped Corpuscles. Of the Elliptical Corpuscles. Short Diameter. Long Diameter. Elephant, .... 9 4 ! J - Man, 7.7 “ Dog 7-3 “ 1 Rabbit 6.9 “ Cat, 6.5 “ Sheep, . . . . 5.0 “ Goat 4.1 “ Musk deer, . . . 2.5 “ Llama, 4.0 fx Dove, 6.5 “ Frog, 15.7 “ Triton, 19.5 “ Proteus, 35 o “ The corpuscles of Amphiui than those of Proteus {Riddel). 8.0 fJ- I4.7 “ 22.3 “ 293 “ 58.O “ na are nearly one third larger Among vertebrates, amphioxus has colorless blood. The large blood corpuscles of many amphibia, eg., amphiuma, are visible to the naked eye. The blood corpuscles of the frog contain, in addition to a nucleus, a nucleolus ( Auerbach , Ranvier ), [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 tiers”).] 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 takes place in birds ( Malassez ). Among mammals, carnivora have more blood 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 hsemoglobin, while the blood corpuscles themselves are colorless. Many invertebrates possess red, violet, brown, or green opalescent blood with colorless corpuscles (amoeboid 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, Fredericq , 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, where 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 exhibit 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 of division. The process of division is best seen from the 3d~5th day 26 ORIGIN OF THE RED BLOOD CORPUSCLES. of incubation. Increase by division also takes place in the larvae of the salaman- der, triton and toad ( Flemming , Peremeschko ), and also during the intra-uterine life of a mammal, in the spleen, bone marrow, the liver and the circulating blood (. Bizzozero , EbertK). 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 ( Lowit ). The spleen is also regarded as a centre of their formation, but this seems to be the case only during embryonic life ( Neumann ). 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 period 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 1 of the total corpuscles, while at the end of foetal life nucleated blood corpuscles are very rarely found. Of course, in Fig. 6. Formation of red bipod corpuscles within “ vaso-formative cells,” from the omentum of a rabbit seven days old. r, r, the formed corpuscles ; K, K, nuclei of the vaso-formative cells ; a, a, processes which ultimately unite to form capillaries. 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 laiteuses Ran- vier) ), in which lie “ vaso-formative cells,” i. 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 (0, 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 always 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 intr a- cellular origin of red blood corpuscles, and although this mode usually ceases 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 chick ; 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 blood 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 corpuscles are formed in mammals at a later period. [They have been described as derived from colorless corpuscles, one set of observers (including Kolliker) 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 anaemic, 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 mo i t of the bones of the trunk, while the bones of the extremities either contain yellow marrow (which is essentially fatty 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 yellow marrow may be changed into red, even throughout all the bones of the extremities ( Neumann ). 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 hsematogenous 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 , Kollmann ), 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 haemoglobin, while between these and the oval, biconvex, nucleated corpuscles of the bird, there were numerous transition stages. The spleen of the bird seems to be of much less importance in the formation of blood corpuscles [Korn). All these observations prove that the red marrow of the bones is a great manufactory for colored blood corpuscles. v. Recklinghausen observed the direct transformation of these intermediate forms into blood corpuscles in frogs’ blood which was kept for several days in a moist chamber. A. Schmidt and Semmer found in the blood large lymph Cells, filled with granules of haemogoblin, 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. r lhese get detached and form young blood corpuscles, which soon become disk-shaped; while the mother cell itself continues to produce other colored corpu.-cles. 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 anaemia, 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 f 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 adults, 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 y per cent. NaCl solution, and afterward with y z 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-containing 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 transformed, 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 oider and become more rigid, they, as it were, are caught by the amoeboid 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 (Quinc&e). 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 co.rpuscles is increased, as in anaemia (Stahel). (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 ( Quincke ). 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 haemoglobin, or of salts of iron into the blood ( Glaeveck and v. Stark). When we reflect how rapidly (relatively) large quantities of blood are replaced after hemorrhage 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 ceMs Fig. 7. White blood corpuscles. A, human, without the addition of any reagent : B, after the addition of water, nuclei visible ; C, after the action of acetic acid ; D, frogs’ corpuscles showing changes of shape due to amoeboid move- ment; E, fibrils of fibrin from coagulated blood ; F, elementary 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 , 1776). 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 30 THE COLORLESS BLOOD CORPUSCLES. (§ 24). The size of the corpuscles varies from four to thirteen [x, and as a rule they are about grVg- an mc ^ * n diameter, and in the smallest the layer of the protoplasm is extremely thin. They all have the property of exhibiting amoeboid 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 : — (1) 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 colored 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 off 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 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 (1). 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 amoeboid movements. Two kinds of colorless corpuscles like (1) 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 insoluble in these fluids, and the nature of which is unknown. Very large colorless corpuscles exist in the axolotl’s blood ( Ranvier). ^ [Action of Reagents. — ( a ) Water, when added slowly, causes the colorless corpuscles to become globular, and the granules within them to exhibit Brownian movements ( Richardson , Strieker). ( b ) Pigments, such as magenta or carmine, stain the nuclei very deeply, and the protoplasm to a less extent, (e) Dilute Acetic Acid clears up the surrounding protoplasm and brings clearly into view the composite nucleus, which may be stained thereafter with magenta. ( d ) Iodine gives a faint port-wine color (horse’s blood indicating the presence of glycogen best). ( e ) Dilute Alcohol causes the formation of clear blebs on' the surface of the corpuscles, and brings the nuclei clearly into view ( Ranvier , Stirling).^ [A. delicate plexus of fibrils — intra-nuclear plexus — exists within the nucleus, just as in other cells. It is very probable that the protoplasm 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- ject to considerable variations. It is certain that the color- less corpuscles are very much fewer in shed blood than in blood still within the circulation. Immediately after blood Fig. 8. Intracellular and intranuclear plexus of a colorless cor- puscle with two nuclei (Klein). AMOEBOID 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- 1 ^ of the whole originally present in the circu- lating blood. The proportion is greater in children than in adults ( Bouchut and Dubrisay ). The following table gives the number in shed blood : — Number of White Corpuscles in Proportion to Red Corpuscles — In Normal Conditions. In Different Places. In Different Conditions. I : 335 ( Welcker). I : 357 (Mo/eschotl). Splenic Vein, 1 : 60 Splenic Artery, 1 : 2260 Hepatic Vein, 1 : 170 Portal Vein, 1 : 740 Generally more numerous in Veins than Arteries. Increased by Digestion, Loss of Blood, Pro- longed Suppuration, Parturi- tion, Leukaemia, Quinine, Bit- ters. Diminished by Hunger, Bad Nourishment. The number also varies with the Age and Sex :■ — Age. Sex. White. Red. General Conditions. White. Red. Girls, I : 405 While fasting, . . I : 716 Boys, 1 : 226 After a meal, . . i : 347 Adults 1 : 334 During pregnancy, I : 281 Old Age, I : 381 The old method of Welcker for estimating the number of colorless corpuscles is unsatisfactory. The blood was defibrinated, 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 haema- cytometer (p. 21) as improved by Gowers.] The Amoeboid Movements of the white corpuscles (so called because they resemble the movements of amoeba) 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] ( Lawdowsky ). Two series of phenomena result from these movements: (1) The “ wandering ” or locomotion of the corpuscles due to the extension and retraction of their processes ; (2) the absorption of small 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 ( Preyer ), 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 — (1) 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.] Metschnikoff emphasizes the activity of the leucocytes in retrogressive processes, whereby the parts to be removed are taken up by them in fine granules, and, as it were, are “ eaten.” Hence, he calls such cells “phagocytes.” They may 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 AMOEBOID 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. Human leucocytes, showing amoeboid movements. 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 amoeboid 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 alkalies, if very dilute, at first increase, but afterward arrest their movements. Sodic chloride in a 1 per cent, solution at first accelerates their movements, but after- ward produces a tetanic contraction, and, it may be, expulsion of any food particles they contain. The Cinchona alkaloids — quinine, quinidine, cinchonidine (1 : 1500) — quickly arrest the locomo- tive movements, as well as the protrusion of pseudopodia, although the leucocytes 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 2^00^ P art °f an i ma l’ s weight, the leucocytes no longer pass through the walls of the capillaries (Binz).] 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), basic (dahlia, acetate of rosanilin), or neutral (picrate of rosanilin) reactions. The smallest protoplasmic granules of the cells have different 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 marrow ( myelogenic leucocytes). The small leucocytes, i.e., those about the size of a colored blood corpuscle or slightly larger, are formed in the lymphatic glands ( lymphogenic Li). The large amoeboid multi-nucleated cells which are found outside the 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, Ehrlich has called these cells “Mastzellen ” ; they do not occur normally in human blood. Fig. 10. “ Blood plates” and their derivatives, partly after Bizzozero and Laker. 1, red blood corpuscles on the flat; 2, from the side; 3, unchanged blood 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. II. Blood Plates. — Special attention has recently been directed to another element of the blood, the “ blood plates ” or “ Blutplattchen ” of Bizzozero ; pale, colorless, oval, round, or lenticular discs of variable size (mean, 3 //.). According to Hayem (who called these structures hsematoblasts, 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 1 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 ^ per cent. NaCl tinged with methyl-violet ( Bizzozero ).] 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 coagulation of the blood; Eberth and Schimmelbusch ascribe the formation of thrombi to them. It is not yet determined whether they are derived from partially disintegrated leucocytes, as a consequence of alteration of the blood ( L'bwit ), or whether they are independent formations. Along with the leucocytes they are concerned in the formation of fibrin ( IJlava ). These structures were known to early observers (Max Schultze, Riess , 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 plates, which he calls colorless microcytes , are derived from the nucleus of young red blood corpuscles, or, occasionally from the nucleus of white corpuscles.] [As to the hcematoblasts, or, as they have also been called, the “globules of Donne” 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 the latter are the blood plates.] [The “invisible blood corpuscles” described by Norris seem to be simply decolorized red corpuscles (Hart, Gibson). ] 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), [/.) the precipitate produced by adding HC 1 or HN 0 3 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 ( Stockvis ) ; (d) serum albumin is not coagulated by ether, while egg albumin is, if the solution is not alkaline (8 249)-] [Serum albumin has never been obtained from free salts, even when it is dialysed for a vefv 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 solution. 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 6o° C., Fredericq 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. e., 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 0 C., while serum albumin in reality consists of three proteids, which coagulate at different tempera- tures ; (a) at 73 0 , (b) at 77 0 , and (V) at 84° C.] [Precipitation by Salts. — Sulphate of magnesia not only precipitates serum globulin but also fibrinogen ( Halliburton ). The fluid must be shaken for several hours, to get complete saturation. Sodic sulphate, when added to serum deprived of its globulin by MgS 0 4 , 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., MgS 0 4 and Na 2 S 0 4 (in this case sodio- magnesic sulphate is formed) ; MgS 0 4 and NaN 0 3 ; MgS 0 4 and KI ; NaCl and Na 2 S 0 4 . After serum globulin is thrown down by MgS 0 4 , the addition of MgS 0 4 and Na 2 S 0 4 or the double salt, precipitates the serum albumin, which is still soluble in water.] [The plasma of invertebrata (decapod 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 oxyhaemocyanin, 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 exoskeleton and hypoderm. It belongs to the group of lipochromes, like some of the pigments of the retina. The haemocyanin 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) i\ II. Fats (0.1 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 percent. ; 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 , i. 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 0.314 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 [0.1 to 0.15 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 (. Pavy ), and another reducing fermentative substance also increased by hemorrhage (y. G. Oil). The amount of grape sugar in the blood increases with the absorption of sugar from the intestine, and this increase is most obvious in the biood 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 coagulating blood by boiling it with sodium sulphate, pressing out the fluid and testing it for sugar with Fehling’s solution (Cl. 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 : 1.] Animal diet increases the amount of salts, vegetable food diminishes it temporarily. Salts in human blood serum ( Hoppe-Seyler ). Sodic Chloride, 4.92 per 1000 “ Sulphate, 0.44 “ “ Carbonate, 0.21 “ VII. Water about 90 per cent. VIII. A yellow Pigment. Sodic Phosphate, . . 0.15 per 1000 Calcic Phosphate, . ) (( Magnesic, j 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 1 volume of boxwood charcoal (at 12 0 C. and ordinary barometric pressure) absorbs 35 volumes C 0 2 , 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 on their surface. By Fluids. — Fluids can also absorb gases. A known quantity of fluid at different pressures always absorbs the same volume of gas. Whether the pressure be great or small, the volume of the gas absorbed is equally great ( W. Henry). But according to Boyle and Mariotte’s law' (1679), w'hen 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 = o, the weight of the gas absorbed must also = 0. As a necessary result of this, w'e see that (1) fluids can be freed of their absorbed gases in a vacuum under an air pump. Coefficient of Absorption means the volume of a gas (o° C.) which is absorbed by a unit of volume of a liquid (at 760 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 it — o. Hence, it follows that (2) absorbed gases may be expelled from fluids simply by causing 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 C 0 2 in water diminishes with an increasing temperature, while that for H in water remains unchanged between o° 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 communication by means of a glass or other tube, and if the lower flask contain C 0 2 , 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 membrane 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 diffuse 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. — If two or more gases are mixed in a closed space over a fluid, as the different 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 mixtures, 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 1 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 o° C., and 760 mm. pressure, 1 volume of water absorbs 0.02477 volume of air, consisting of 0.00862 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 mixture 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 with 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 (6’. Ludwig ). Fig. 19 shows in a diagrammatic form the arrangement of Pfliiger’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 x, a), 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 (x, a) blood flows into the receptacle. When the necessary 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 part 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 U-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 stop-cocks, e and f), they are freed from their watery vapor by the sulphuric acid, so that they pass quite dry through the stop-cock,/! The short, well-ground tube, D, is fixed to/", and to the former is attached the small barometric tube or manometer, y, which indicates the extent of the vacuum. From D we pass to the pump proper. This consists of two large glass bulbs, which are continued above and below into open tubes ; the lower tubes, Z and w, being united by a caoutchouc tube, G. Both the bulbs and caoutchouc tube contain mercury — 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, g and h, 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 filled with mercury. Where g and H unite, there is a two-way stop-cock, 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, h, 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, i (not yet placed under J) ; place the stop-cock Fig. 19. Scheme of Pfluger’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,/ y stop-cocks; G, drying cham- bers, containing sulphuric acid and pumice stone ; D, tube, with manometer, y. 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 c and b, 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 6o° 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. Magnus (1837) investigated the percentage composition of the blood gases. The more important recent inves- tigations have been made by Lothar 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, C 0 2 , and N. Pfliiger obtained (at o° C. and 1 metre Hg pressure), 47.3 volumes per cent, consisting of — O 16.9 per cent. ; C 0 2 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 n). (1) Estimation of the C0 2 . — A small ball of fused caustic potash , fixed 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 C 0 2 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 C 0 2 absorbed. (2) Estimation of the O. — (a) Just as in estimating the C 0 2 , a ball of phosphorus on a platinum wire is introduced into the eudiometer (Bertholet); it absorbs the O and forms phosphoric acid. Another plan is to employ a small papier-mache ball saturated with pyrogallic 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 exploding it in the eudio 77 ieter ( Volta and Bunsen ). Introduce a sufficient quantity of H into the eudiometer, and accurately ascertain its volume ; an electrical spark is now passed between the wires, p and n , 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 is due to the O used to form water (H 2 0). ( c ) Estimation of the N. — When the C 0 2 and O are estimated by the above method, the re 77 iainder is pure N. 36. THE BLOOD GASES.— [In human blood the average is estimated to be, at o° C and 1 metre pressure, C Arterial blood, 16 Venous blood, 6 to 10 or, calculated at o° C. and 760 mm. pressure, Arterial blood, 20 Venous blood, 8 to 12 C 0 2 N 30 i to 2 per cent. 35 1 to 2 “ 39 1.4 per cent. 46 1.4 “ ] I. Oxygen exists in arterial blood (dog), on an average, to the extent of 17 volumes per cent, (at o° C. and 1 metre Hg pressure) {Pfliiger). According to Pfliiger, arterial blood (dog) is saturated to T 9 ^ with O, while, according to Hiifner, it is saturated to the extent of L|. 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. I Renal vein (kidney active), 17 per cent. Renal artery, 19 “ | Renal vein (kidney at rest), 6 “ Bert finds that increase of the atTnospheric pressure from 1 to 10 atmospheres increases the amount of O in arterial blood from 20 to over 24 per cent., and that of N from 1.8 to over 9 per cent., while the CO 2 is but slightly affected.] The O in Blood occurs — (a) simply absorbed in 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 (. Lothar 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 haemoglobin con- tained in the plasma or the serum, and which is derived from the solution of red corpuscles. ( b ) 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 haemoglobin 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 the 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 Muller ) ; 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 ; ( b ) by boiling ; ( c ) by the conduction of other gases [H, N, CO, or NO] through the blood, because the chemical union of the oxyhaemoglobin 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 1 grm. O ; while, according to Hoppe- Sevler, the proportion is 1 atom iron to 2 atoms O. During morphia narcosis the amount of O in the blood is diminished ( Ewald ) ; after hemorrhage the arterial blood is saturated with O (J. G. Oil). Disappearance of O. — Even immediately after blood is shed, there is a slight disappearance of O, as a physiological index of respiration of the tissues within the living blood itself ($ 132). When blood is kept long outside of the blood vessels, the quantity of O gradually diminishes, and if it be kept for a length of time 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. C 0 2 appears in the blood in place of the O, and the color darkens. The amount of C 0 2 produced is sometimes greater than that of the O consumed. Tf blood (or a solution of oxyhaemoglobin') be acted upon by acids (e. g., tartaric acid) until it is strongly acid, O maybe pumped out in considerably less amount, while the formation of C 0 2 is not increased. We must, therefore, assume that, during the decomposition of the Hb caused by the acids ($ 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 , Strassburg'). The same phenomenon occurs when oxyhaemoglobin is decomposed by boiling. 37. IS OZONE (O3) PRESENT IN BLOOD ? — On account 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 ( 0 3 ), or ozone. Ozone, however, is contained neither in the blood itself ( Schonbein ) nor in the blood gases obtained from it. Nevertheless, the red corpuscles (and Hb) have a distinct relation to ozone. (1) Tests for Ozone. — Haemoglobin 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 ( cat = 2T-5 ; birds = TO t0 T3 i fr °g = T5 t0 TO > fisheS = lV to jJ-g- of the body weight (without the contents of the stomach and intestines). The 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 vitam. 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 yf ; the muscles of the skeleton, ; the liver, ; and other organs, y^ ( Ranke ).] 41. VARIATIONS FROM THE NORMAL CONDITION OF THE BLOOD.— (A) Polyaemia. — (1) An increase in the entire mass of the blood, uniformly in all organs , con- stitutes polycemia {ox plethora), 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. — Polyaemia 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 Muller). 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 Muller). 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 ( Landois ). Hence, the blood at this time appears to be relatively richer in blood corpuscles ( Panum , Lesser , Worm Muller). 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 slowly 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 ( Tschirjew , Landois). 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 artificially by the transfusion of blood serum from the same species. The water is soon given off in the urine, and the albumin is decom- posed 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 ( Lorster , 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; hsemoglobinuria is produced ( Ponjick ) ; 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 hemorrnages are interrupted, e. g., menstruation, bleeding from the nose, etc.; but the increase of corpuscles has not been definitely proved. There is a proved case of temporary polycythaemia, 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 of 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 ( i Penzoldt). After diarrhoea, which diminishes the water of the blood, there is also an increase ( Brouardel ). There is a temporary increase in the hsematoblasts as a reparative process after severe hemorrhage (| 7), or after 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 of cachexia the number diminishes more and more until the formation of haematoblasts ceases ( Hayem ). (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 ( Stokvis Lehmann). [The subcutaneous injection of human blood has been practiced with good results in anemia ( v . Ziemssen). When defibrinated human blood is injected sub- cutaneously, while its passage into the circulation is aided by massage, it causes neither pain nor inflammation, but the blood of animals , and a solution of haemo- globin, always induce abscess ( Benczur ). Blood is also rapidly absorbed when injected in small amount into the respiratory passages.] Mellitaemia — The sugar in the blood is partly given off by the urine, and in “ diabetes mellitus ” 1 kilo. (2.2 lb) may be given off daily, when the quantity 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 ( Kunde , Hetibel), 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 CONDITIONS OF THE BLOOD. 65 disappear entirely. [The sugar in the blood is also increased after the inhalation of chloroform or amyl nitrite, and after the 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 ( Vohl). Lipaemia, 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 produce? 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 inflammation 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 excess 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 crusta 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 slowly 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, §28. (B) Diminution of the Quantity of Blood, or its Individual Constituents. — (1) Oligae- 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 the pupils, involuntary evacuations of urine and faeces, and lastly, general convulsions, are sure signs of death 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 loss 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 ( hydrcemia ) and at last abnormally poor in corpuscles [oligocythcemia , hypoglobulie) . 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 (. , pulmonary vein ; Ad, and As, right and left auricles ; Ap, communication between the right and left auricle {Ecker). [Frog’s Heart. — The frog's heart consists of the sinus venosus , into which open the single inferior and the two superior venae cavae (Fig. 46). There are two auricles; the right one commu- nicates with the sinus venosus, and opens into the single ventricle ; the left auricle also opens into the single ventricle (Fig. 45, v), and in the latter are mixed the venous blood returned by the right auricle and the arterial blood from the left auricle. The aorta with its bulbus arteriosus conducts the blood from the ventricle (Figs. 46, 490), The various orifices are guarded by projections of tissue, which act like valves. The two auricles are completely separated by a septum. This septum ends posteriorly in a free concave margin (Fig. 49), so as to divide the auriculo-ventricular orifice into a right and a left orifice. Each orifice is guarded by two thick, fleshy valves, which close it.] [Nerves. — The two cardiac branches of the vagi — the nervi cardiaci — proceed to the poste- rior surface of the sinus venosus, and where the latter joins the auricle they interlace, and are mixed with a number of ganglion cells (Figs. 47, 49^). This spot is called Remak’s ganglion, is some- times single, at others double, and it can be seen as a white “ crescent ” when the heart is lifted up and looked at from behind (Fig. 46). The cardiac nerves proceed downward on the auricular septum, exchanging fibres in their course to join two ganglia at the auriculo-ventricular groove, and known as Bidder’s Ganglia (Figs. 47, 49 a. It has been stated by one observer that the bulbus arteriosus contains ganglionic cells, but this is denied by others.] According to Openchowsky, every part of the heart (frog, triton, tortoise) contains nerve fibres which are connected with every muscular fibre. In the auricles, at the end of the non-medullated fibre, a tri-radiate nucleus exists which gives off fibrils to the muscular bundles. There is a network of fine nerve fibres distributed immediately under the endocardium ; these fibres act partly in a centripetal direction on the cardiac ganglia, and are partly motor for the endo- cardial muscles. The parietal layer of the pericardium contains (sensory) nerve fibres. The fol- MOTOR CENTRES OF THE HEART. 95 lowing kinds of nerve cells are found — tinipolar cells , the single processes of which afterward divide ; bipolar pyriform cells (Fig. 48), which in the frog possess a straight (n) and usually, also, a spiral process (0). 58. THE AUTOMATIC MOTOR CENTRES OF THE HEART. — (1) We must assume that the nervous centres which excite the cardiac move- Fig. 47. Fig. 48. Auricular septum of a frog’s heart, a, anterior, and p, poste- rior branch of the cardiac vagus ; B, Bidder’s ganglion ( Ecker ). Pyriform ganglionic bi-polar nerve-cell from the heart of a frog m , sheath; «, straight process ; o, spiral pro- cess. ments, and maintain the rhythm of these movements, lie within the heart, and that they are, probably, represented by the ganglia. (2) There are — not one, but several of these centres in the heart, which are connected with each other by conducting paths. As long as the heart is intact, all its parts are made to move in rhythmical sequence from a principal central point, an impulse being conducted from this centre through the conducting paths Fig. 49 Longitudinal section of frog’s heart ; left side shows a , auricle ; v, ventricle ; s, auricular septum ; p, pul- monary vein, with a sound,/', projecting into left auricle ; v, ventricle ; c, c ' , sound projecting from right auricle into ventricle ; n. upper, and n' lower cardiac nerves. Fig. 49 a . Scheme of nerves of frog’s heart. R. Remak’s, andB, Bidder’s ganglia ; S. V., sinus venosus; A, auricles ; V, ventricle ; B. A., bulbus arte- riosus ; vag. vagi (after Brunton). ( Donders ). What the “discharging forces” of these regular progressive move- ments are is unknown. If, however, the heart be subjected to the action of diffuse stimuli ( e.g ., strong electrical currents), all the centres are thrown into action, and a spasm-like action of the heart occurs. The dominating centre lies in the auricles , hence the regular progressive movement usually starts from- them. If the 96 EXPERIMENTS ON THE HEART. excitability is diminished ( e.g ., by touching the septum with opium — Ludwig , Hoffa), other centres seem to undertake this function, in which case the move- ment may extend from the ventricles to the auricles. If a heart be cut into pieces, so that the individual pieces still remain connected with each other, the regular peristaltic or wave-like movements proceeding from the auricles to the ventricle may continue for a long time {Bonders, Engelmann). If the heart, however, be completely divided into two distinct pieces (auricle and ventricle), the movements of both parts continue, but not in the same sequence — they beat at different rates. According to Kronecker and Schmey, in the dog' s heart there is a spot above the lower limit of the upper third of the ventricular septum which, when it is injured, brings the heart to a standstill ; this has been called a coordi- nating centre. (3) All stimuli of moderate strength applied directly to the heart cause at first an increase of the rhythmical heart beats; stronger stimuli cause a diminution, and it may be paralysis, which is often preceded by a convulsive movement. Increased activity exhausts the energy of the heart sooner. (4) The auricular centres seem to be more excitable than those of the ventricle ; hence, in a heart left to itself the auricles pulsate longest. (5) The heart may be excited (reflexly) from its inner surface. Weak stimuli applied to the inner surface of the heart greatly accelerate the heart’s action, the stimulus required being much feebler than that applied to the external surface of the heart. Strong stimuli, which bring the heart to rest, also act more easily when applied to the inner surface than when they are applied to its outer surface {Henry, 1832). The ventricle is always the part first to be paralyzed. (6) In order that the heart may continue to contract, it is necessary that it be supplied with a fluid which, in addition to O {Ludwig, Volkmann, Goltz), must contain the necessary nutritive materials. The most perfect fluid, of course, is blood. Hence, the heart, after a time, ceases to beat in an indifferent fluid (0.6 per cent, sodium chloride), but its activity may be revived by supplying it with a proper nutritive fluid. Cardiac Nutritive Fluids. — These nutritive fluids are such as contain seium albumin, e.g., blood, serum or lymph. Serum retains its nutritive properties even after it has been subjected to diffusion (. Martins and Kronecker). Milk and whey ( v . Ott), normal saline solution (0.6 per cent. NaCl) mixed with blood, albumin or peptone and 0.3 per cent, sodium carbonate \Kronecker, Meruno- wicz and Stienon) a trace of caustic soda ( Gaule ), or a solution of the salts of serum, are suitable. Alkaline solution of soda revives a feebly beating heart by neutralizing the acid formed in the cardiac muscle (A. Ringer). (7) The independent pulsations of parts of the heart which are devoid of ganglia show that the presence of ganglia is not absolutely necessary in order to have rhythmical pulsation. Direct stimulation of the heart may cause these movements. But the ganglia are more excitable than the heart muscle itself, and they conduct the impulses which lead to the regular alternating action of the various parts of the heart, so that under normal circumstances we must assume that the action of the heart is governed by the ganglia. The chief experiments upon which the above statements are based consist of two classes: (1) Where the heart is incised or divided; and (2) where it is STIMULATED DIRECTLY. (I) Experiments by cutting and ligaturing the heart. These experiments have been made chiefly upon the heart of the frog. The Ligature experiments are performed by tightening and then relaxing a ligature placed around the heart, so that the physiological connection is destroyed, while the anatomical or mechanical connections (continuity of the cardiac wall, intact condition of its cavities) still exist. The most important of these experi- ments are — (1) Stannius’s Experiment. — If the sinus venosus of a frog’s heart be separated from the auricles, either by an incision or by a ligature, the auricles and SECTION OF THE HEART. 97 ventricle stand still in diastole, while the veins and the remainder of the sinus continue to beat (Fig. 50, 1). If a second incision be made at the auriculo- ventricular groove, as a rule, the ventricle begins at once to beat again, while the auricles remain in the condition of diastolic rest. [Thus, the sinus venosus and ventricle continue to beat, while the auricle stands still, but the two former no longer beat with the same rhythm ; the ventricle usually beats more slowly, as is shown in Fig. 50, 2, by the large zig-zags.] According to the position of the second ligature or incision, the auricles may also beat along with the ventricles, or the auricles alone may beat, while the ventricles remain at rest (1852). Theoretical. — Various explanations of these experiments have been given : (a) Remak’s gan- glion in the sinus venosus is distinguished by its great excitability, while Bidder’s ganglion in the auriculo-ventricular groove is less excitable ; in the normal condition of the heart the motor impulse is carried from the former to the latter. If the sinus venosus be separated from the heart, Remak’s ganglion has no action on the heart. The heart stops, for two reasons — first, because Bidder’s gan- glion alone has not sufficient energy to excite it to action, and because the inhibitory fibres of the vagus going to the heart have been stimulated by being divided at this point ( Heidenhain ). [That stimulation of the inhibitory fibres of the vagus is not the cause of the standstill, is proved by the fact that the stand- still occurs even after the administration of atropine, which paralyzes the cardiac inhibitory mechanism.] The passive heart, however, may be made to contract by mechanically stimulating Bidder’s ganglion, e. g., by a slight prick with a needle in the auriculo-ventricular groove ( H . Munk), or by the action of a constant current of moderate strength ( Eck - hard), the ventricular pulsation at the same time preceding the auricular ( v . Bezold, Bernstein ). If the auriculo-ven- tricular groove be divided, the ventricle pulsates again, because Bidder’s ganglion has been stimulated by the act of dividing it ; while, at the same time, the ventricle is with- 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 in addition an inhibitory ganglionic system ( c ) ( Bezold , Traube ). Under normal circumstances a -f- b is stronger than c, while c is stronger than a or 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 (. Descartes , 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 remains attached to the ventricle, the latter pulsates ( Rosenberger , 1850). 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. 101 . By compressing the heart at the auriculo-ventricular groove, the ratio of auricular and ven- tricular beats alters, and instead of being 1 : 1, there may be 2, 3, or more auricular beats for each A II III IV ~i beat of the ventricle, expressed thus : — , — • I V I I I J (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. ( Engelmann ). Hence, it appears that the conducting paths for 7 Fig. 50. Stannius’s experiment. Scheme after Brun- ton. A, auricle, V, ventr., SV, sinus venosus. The zig-zag lines indicate which parts continue to beat ; in 2 the ventricle beats at a different rate. 98 ACTION OP' 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 (. Heidenhain , Goltz ), but such an apex, 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. Scheme of a frog manometer, a, b, 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. Fig. 52. Double-way or perfusion cannula (nat. size) for a fiog’s heart, c, for fixing an elec- trode ; d, the heart is tied over the flanges, preventing it from slipping out ; e, section of d. 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 (1) a double- way cannula, c , which is tied into the heart, h ; (2) a manometer, m , connected with c, and registering the movements of its mercury on a revolving cylinder, cyl ; (3) two Mariotte’s flasks, a and b, which are connected with the other limb of the cannula. Either a or b 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 ; d is a glass vessel for fluid, in which the heart pulsates, e f 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 solution. As before, a “perfusion” cannula is tied into the heart. A piston,/, 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 around 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 Fig. 53. Roy’s apparatus or tonometer for the heart. h. heart ; o, air-tight chamber ; p, piston ; /, writing lever ; e, outflow tube. 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 (1 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 heart, 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 apex ( 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 [Bowditch). Quinine [Schtschepotjew) and a mixture of atropine and muscarin have a similar action [v. Basch). These experiments show that, provided no nervous apparatus exists 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 [Aubert). 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 the heart muscle to pulsate rhythmically. It is by no means definitely proved 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 object 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 effect of acids (| 65).] [The “ Heart ” preparation in many respects behaves like the foregoing, i. 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).] [(5) 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 haemoglobin or normal saline solution (. Rossbach ) is used. They also occur when the blood within the heart has become dark colored, i. e., 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 (. Kronecker 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 rhythmically . This is an important fact in connection with any theory of the cardiac beat.] (7) If the bulbus aortae (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 0 C., and raising the pressure within it, increase the number of pulsations ( Engelmann ). (II) 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 diastole 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 when 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 usually cease to beat before the auricles ( Schelske ). The she and extent 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 0 C is only about T ^ of the time occupied by a contraction occurring at 5 0 C. A heart which has been warmed is capable of reacting pretty rapidly to intermittent stimuli, while a heart at a low tempera- ture 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 ( Gaule ). Cold. — When the temperature of the blood is diminished, the heart beats slower ( Kielmeyer , /ygj). A frog’s heart placed between two watch glasses and laid on ice, beats very much slower ( Ludwig , 1861). The pulsations of a frog’s heart stop when the heart is exposed to a temperature of 4 0 C. to o° (£. Cyon). If a frog’s heart be taken out of warm water, 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 rapidly afterward ( Aristow ). Fig. 55. a c Fig. a, contractions ot a frog’s heart at 19 0 C. ; b , at 34 0 C. ; c, at 3 0 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 distance.] [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.] (b) 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 freshly -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 ( Ludwig and Thiry ). If the intra-cardiac pressure be very greatly increased, the heart’s action becomes very irregular and slower ( Heidenhain ). 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 (g 47, 3), that the number of beats was doubled when a constant uninterrupted strqng 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 ( Ludwig and Hoffa ), and, of course, this results in a fall of the blood pressure ( Sigm . Mayer j. 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. While 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, wheal-like ele- vations — such as occur when the intestinal musculature is stimulated — appear between the elec- trodes. They may last several minutes. A 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 ( Bowditch ). 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 “ maximal ” stimulus (. Kronecker and Stirling). Human Heart. — v. Ziemssen found that he could not alter the heart beats of the human heart ( Frau Serafin, $47, 3), even with strong induction currents. The ventricular diastole seemed to be less complete, and there were irregularities in its contraction. By opening 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 80. When 180 shocks per minute were applied, the action of the heart assumed the characters of the pulsus alternans (§ 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, separated 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 and 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 contracted, 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 groups (p. 100). The question, whether a stimulus will cause a contraction, depends upon what particular phase the heart 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, i. 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 strength 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 ( Rohrig ) 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 (1 per cent.) accelerate the heart beat of the frog (Kronecker and M' Gregor- Robertson), while a solution of ij/2 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 Ludwig ) ; if concentrated, they rapidly arrest its action. Chloral-hydrate paralyzes the heart ( P . v. Rokitansky). 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 C 0 2 paralyzes it, and the presence of C 0 2 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 immediate 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 upon 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. Among these ar z neutral 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 potassic 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 1691, 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 by 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 unfrequently 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 suppose that there are various intra- cardiac mechanisms on which these substances may act. Besides the muscular 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 with the autotnatic ganglia by conducting channels. Muscarin stimulates permanently the inhibitory ganglia, so that the heart stands still ( Schmiede - berg and Koppe). 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. Iodine-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-aldehyd, so that if it be stimulated it contracts. [According to Gaskell, antiarin and digitalin 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 simple 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 simple 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 limb. 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, i. 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 C 0 2 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 maximum, auxocardia.] 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 manometric 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 1 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 membrane 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 (D), 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 — HOLDEN’S ANATOMY. Octavo. 208 Illustrations. Cloth, $5.00; Leather, $6.00. IN QIL-CLOTH BINDING, $4.50. A Fifth Edition. Revised, Enlarged and with new Illustrations. Fig. 15. Holden’s Anatomy. Muscles of the Pharynx. This is eminently a student’s book. Its great popularity as a dis- sector suggested to the Publishers binding it in Oil-Cloth. The ad- vantages of this binding are that it does not soil easily, does not retain odors ; it may be washed, and while quite as durable, and as handsome in appearance as either cloth or leather, it admits of its be- ing sold at a lower price. This edition has been very carefully printed and bound, and lays open flat at any page. P. BLAKISTON, SON & CO., 1012 Walnut St., Philadelphia. Orbicularis oris Pterygo-maxil- \ lary ligament f Glosso-pharyngeal n. Stylo-pharyngeus. Mylo-hyoideus . Os hyoides . Thyro-hyoid ) ligament j Pomum Adami . Cricoid cartilage Trachea . . . Superior laryngeal n. and a. External laryngeal n. Crico-thyroideus. Inferior laryngeal n. CEsophagus. Holden’s Anatomy. Fifth Edition. 203 Illustrations. In Oil-cloth •Binding, $4.50. A Manual of Dissection of the Human Body. By Luther Holden, m.d., f.r.c.s., Eng. Fifth Edition, re- vised and enlarged, and with new illustrations. Edited by John Langton, m.d., Surgeon to, and Lecturer on Anatomy at, St. Bartholomew’s Hospital, London, etc. ; with 208 illustrations. 8vo. Oil-cloth Binding, $4.50 ; Cloth, $5.00 ; Leather, $ 6.00 . *** This edition of Holden’s Anatomy is eminently a Student's book , without as well as within. As a text-book it has become so well known that it is unnecessary to speak of its contents. The printing and binding of this new edition, however, should be explained. It has been printed 1 on very handsome paper, so that the minutiae of each wood cut is clearly brought out ; and the student will meet with no difficulty in tracing each muscle, nerve, artery, vein or organ in the illustrations. Many of the cuts have the explanations printed on them; a very great advantage, enabling the reference to be made quickly, and fixing the fact more surely. Marginal references have been inserted throughout the text, to catch the eye, at each important paragraph. The binding has been put on so that the book will lay open at ANY page. It being used so largely in the dissection room suggested to the publishers the binding of it in Oil-cloth. The advan- tages of this binding are, that it will not retain the odors of the dissecting table, does not soil easily, it may be washed without damage, and while quite as durable, allows of our making a lower price for the book than in either cloth or leather binding. It is, therefore, particularly well suited for the dissecting room, operating table or students’ use generally. ’ May be ordered through any bookseller, or from the publishers. P. BLAKISTON, SON & CO., Medical Booksellers, J012 WALNUT STREET, PHILADELPHIA. INFLUENCE OF THE RESPIRATION ON THE HEART. 105 (a) 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 venae cavae,* and because the dilating branches of the pulmonary artery compress the accompanying bronchi. The blood of the right ventricle has not yet left the thorax, 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. (b) 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 venae cavae. (e) 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 curve. (, 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 1820, and by Donders 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 the 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 : — (1) 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 Donders 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 — Donders ), 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 voluntary increase or diminution of the intra-thoracic pressure. (1) 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 , Danders). (2) J. Muller’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. 11 I Apparatus for demonstrating the action of inspiration, IT, and expiration, I, on the heart and on the blood stream. P,/, lungs ; H, h, heart ; L, /, closed glottis ; M, m, manometers : E, e, ingoing blood stream, vein ; A, a, out- going blood stream, artery ; D, diaphragm during expiration ; d, during inspiration. while the aortic system contains a small amount of blood, i. 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 expiration the pressure is higher, so that these conditions favor the circulation ; inspiration favors the supply of blood (and lymph) through the venae cavae, 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 (Bonders). 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 venae 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 intra- thoracic pressure. If the glottis be closed, and the inspiratory phase imitated, as in II,/,/ 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, 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 Fig. 58. 61. THE FLOW OF FLUIDS THROUGH TUBES.— Toricelli’s Theorem (1643^ states that the velocity of efflux ( v ) of a fluid — through an opening at the bottom of a cylindrical vessel — is exactly the same as the velocity which a body falling freely would acquire, were it to fall from the surface of the fluid to the base of the orifice of the outflow. \{- h be the height of the propelling force, the velocity of efflux is given by the formula — height of column of fluid required to overcome the resistance ; and F, height of column of fluid caus- ing the efflux. v = 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, 1, 2, 3, when h increases in the ratio, 1, 4, 9, i. 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 efflux 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, h , has not only to cause the efflux of the fluid, but has also to overcome resistance. These two forces may be expressed by the heights of two columns of water placed over each other, viz., by the height of the column of water causing the outflow, F, and the height of the column, D, which over- comes the resistance opposed to the outflow of the fluid. So that h = F 4- 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. (1) The velocity of the current, v, is estimated — (a) 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 v — q\ l. Both values, q as well as /, can be accurately measured. (The circumference of a round tube whose diameter = d is 3.14.^. The sectional area (lumen of the tube) is ,d 2 ). Having in this way determined v, from it we may calculate the height of the column of fluid, F, which will give this velocity, i. e the height from which a body must fall in vacuo, in order to attain the velocity, v. v 2 In this case F = — (where g = the distance traversed by a falling body in 1 sec. =4.9 metres). (2) The pressure, D (amount of resistance), is measured directly by placing manometers at different parts of the tube (Fig. 59). The propelling force at any part of the tube is ^ = F+D; or, h = ^ — (- D. ( Bonders .) This is proved experimentally by taking a tall cylindrical vessel, A, of sufficient size, which is kept filled with water at a constant level, h. The outflow rigid tube, a , b, has in connection with it a number of tubes placed vertically, 1, 2, 3, constituting a piezometer. At the end of the tube, b , there is an opening with a short tube fixed in it, from which the water issues to a constant height, provided the level of h is kept constant. The height to which it rises depends on the height of the column of fluid causing the velocity, F. As the pressure in the manometric tubes, D 1 D 2 , D 3 , can be read off directly, the propelling force of the water at the sections of the tubes, I, II, III, is — h = F + D 1 ; F + D 2 ; F + D 3 . 108 ESTIMATION OF RESISTANCE. 109 At the end of the tube, b, where D 4 = O, h — F O, i. e., h = F. In the cylinder itself it is the constant pressure, h, which causes the movement of the fluid. It is clear that the propelling force of the water gradually diminishes as we pass from the part where the fluid passes out of the cylinder into the tube toward the end of the tube, b. The water in the pressure cylinder, falling from the height, h, only rises as high as F at b. This diminution of the propelling power is due to the presence of resistances, which oppose the current in the tube, i. e ., part of the energy is transformed into heat. As the propelling power at b is represented only by F, while in the vessel it is h, the difference must be due to the sum of the resistances, D = h — F; hence it follows that h== F -f- D. ( Donders ). ESTIMATION OF RESISTANCE. — Estimation of the Resistance. — When a fluid flows through a tube of uniform calibre, the propelling force, h , diminishes from point to point, on account of the uniformly acting resistance, hence the sum of the resistances in the whole tube is directly proportional to its length. In a uniformly wide tube, fluid flows through each sectional area with equal velocity, hence v and also F are equal in all parts of the tube. The diminution which h (propelling force) undergoes can only occur from a diminution of pressure D, as F remains the same throughout (and h — F -J- D). Experiment with the pressure cylinder shows that, as a matter of fact, the pressure toward the outflow end of the tube becomes gradually diminished. In a uniformly wide tube, the height of the pressure in the manometers expresses the resistances opposed to the current of fluid which it has to overcome in its course from the point investigated to the free orifice of efflux. Nature of the Resistance. — The resistance opposed to the flow of a fluid depends upon the cohesion of the particles of the fluid among themselves. During the current, the outer layer of fluid which is next the wall of the tube, and which moistens it, is at rest ( Girard , Poiseuille). Fig. 59. A cylindrical vessel filled with water, a , b , outflow tube, along which are placed at intervals vertical tubes, 1, 2, 3, to estimate the pressure. All the other layers of fluid, which may be represented as so many cylindrical layers, one inside the other, move more rapidly as we proceed toward the axis of the tube, the axial thread or stream being the most rapidly moving part of the liquid. On account of the movement of the cylindrical layers, one within the other, a part of the propelling energy must be used up. The amount of the resistance greatly depends upon the amount of the cohesive force which the particles of the fluid have for each other ; the more firmly the particles cohere with each other, the greater will be the resistance, and vice versd. Hence, the sticky blood current experiences greater resistance than water or ether. Heat diminishes the cohesion of the particles, hence it also diminishes the resistance to the flow of a current. These resistances are first developed by, and result from, the movement of the particles of the fluid, they being, as it were, torn from each other. The more rapid the current, therefore, i. e., the larger the number of particles of fluid which are pulled asunder in the unit of time, the greater will be the sum of the resistance. As already mentioned, the layer of fluid lying next the tube, and moistening it, is at rest, hence the material which composes the tube exerts no influence on the resistance. EFFECT OF TUBES OF UNEQUAL CALIBRE.— Unequal Diameter.— When the velocity of the current is uniform, the resistance depends upon the diameter of the tube — the smaller the diameter, the greater the resistance ; the greater the diameter, the less the resistance. The resistance in narrow tubes, however, increases more rapidly than the diameter of the tube decreases, as has been proved experimentally. In tubes of unequal calibre, at different parts of their course, the velocity of the current varies — it is slower in the wide part of the tube and more rapid in the narrow parts. As a general rule, in 110 MOVEMENT OF FLUIDS IN ELASTIC TUBES. tubes of unequal diameter the velocity of the current is inversely proportional to the diameter of the corresponding section of the tube; i. e., if the tube be cylindrical, it is inversely proportional 10 the square of the diameter of the circular transverse section. In tubes of uniform diameter, the pro- pelling force of the moving fluid diminishes uniformly from point to point, but in tubes of unequal calibre it does not diminish uniformly. As the resistance is greater in narrow tubes, of course the propelling force must diminish more rapidly in them than in wide tubes. Hence, within the wide parts of the tube the pressure is greater than the sum of the resistances still to be overcome, while in the narrow portions it is less than these. Tortuosities and Bending of the Vessels add new resistance, and the fluid presses more strongly on the convex side than on the concave side of the bend, and there the resistance to the flow is greater than on the concave side. Division of a tube into two or more branches is a source of resistance, and diminishes the pro- pelling power. When a tube divides into two smaller tubes, of course some of the particles of the fluid are retarded, while others are accelerated, on account of the unequal velocities of the different layers of the fluid. Many particles which had the greatest velocity in the axial layer come to lie more toward the side of the tube, where they move more slowly ; and, conversely, many of those lying in the outer layers reach the centre, where they move more rapidly. Hence, some of the propelling force is used up in this process, and the pulling asunder of the particles where the tube divides acts in a similar manner. If two tubes join to form one tube, new resistance is thereby caused, which must diminish the propelling force. The sum of the mean velocities in both branches is independent of the angle at which division takes place {Jacobson). If a branch be opened from a tube, the principal current is accelerated to a considerable extent, no matter at what angle the branch may be given off. 63. CURRENTS THROUGH CAPILLARY TUBES.— Poiseuille proved, experiment- ally, that the flow in the capillaries is subject to special conditions : — (1) The quantity of fluid which flows out of the same capillary tube is proportional to the pressure. (2) The time necessary for a given quantity of fluid to flow out (with the like pressure, diameter of tube and temperature), is proportional to the length of the tubes. (3) The product of the outflow (other things being equal) is as the fourth power of the diameter. (4) The velocity of the current is proportional to the pressure and to the square of the diameter, and inversely proportional to the length of the tube. (5) The resistance in the capillaries is proportional to the velocity of the current. 64. MOVEMENT OF FLUIDS AND WAVE MOTION IN ELASTIC TUBES.— ( 1 ) When an uninterrupted uniform current flows through an elastic tube, it follows exactly the same laws as if the tube had rigid walls. If the propelling power increases or diminishes, the elastic tubes become wider or narrower, and they behave, as far as the movement of the fluid is concerned, as wider or narrower rigid tubes. (2) Wave Motion. — If, however, more fluid be forced in jerks into an elastic tube, i.e., inter- ruptedly, the first part of the tube dilates suddenly, corresponding to the quantity of fluid propelled into it. The jerk communicates an oscillatory movement to the particles of the fluid, which is communicated to all the fluid particles from the beginning to the end ot the tube; a positive wave is thus rapidly propagated throughout the whole length of the tube. If we imagine the elastic tube to be closed at its peripheral end, the positive wave will be reflected from the point of occlusion, and it may be propagated to and Iro through the tube until it finally disappears. In such a closed tube a sudden jet of fluid produces only a wave movement, i.e ., only a vibratory movement, or an altera- tion in the shape of the liquid, there being no actual translation of the particles along the tube. (3) If, however, fluid be pumped interruptedly or by jerks into an elastic tube filled with fluid, in which there is already a continuous current, tlie movement of the current is combined with the wave movement. We must carefully distinguish the movement of the current of the fluid, i.e., the translation of a mass of fluid through the tube, from the wave movement , the oscillatory move- ment, or movement of change of form in the column of fluid. In the former, the particles are actually translated, while in the latter they merely vibrate. The current in elastic tubes is slower than the wave movement, which is propagated with great rapidity. This last case obtains in the arterial system, lhe blood in the arteries is already in a state of continual movement, directed from the aorta to the capillaries (movement of the current of blood) ; by means of the systole of the left ventricle, a quantity of fluid is suddenly pumped into the aorta, and causes a positive wave {pulse wave), which is propagated with great rapidity to the terminations of the arteries, while the current of the blood itself moves much more slowly. Rigid and Elastic Tubes. — It is of importance to contrast the movement of fluids in rigid and in elastic tubes. If a certain quantity of fluid be forced into a rigid tube under a certain pressure, the same quantity of fluid will flow out at once at the other end of the tube, provided there be no special resistance. In an elastic tube, immediately after the forcing in of a certain quantity of fluid, at first only a small quantity flows out, and the remainder flows out only after the propelling force has ceased to act. If an equal quantity of fluid be periodically injected into a rigid tube, with each jerk an equal STRUCTURE OF ARTERIES. Ill quantity is forced out at the other end of the tube, and the outflow lasts exactly as long as the jerk or the contraction, and the pause between two periods of outflow is exactly the same as between the two jerks or contractions. In an elastic tube it is different, as the outflow continues for a time after the jerk; hence, it follows that a continuous outflow current will be produced in elastic tubes when the time between two jerks is made shorter than the duration of the outflow after the jerk has been completed. When fluid is pumped periodically into rigid tubes, it causes a sharp, abrupt out- flow synchronous with the inflow, and the outflow becomes continuous only when the inflow is con- tinuous and uninterrupted. In elastic tubes an intermittent current, under the above conditions, causes a continuous outflow, which is increased with the systole or contraction. 65. STRUCTURE AND PROPERTIES OF THE BLOOD VESSELS. — In the body, the large vessels carry the blood to and from the various tissues and organs, while the thin -walled capillaries bring the blood into intimate relation with the tissues. Through the excessively thin walls of the capillaries the fluid part of the blood transudes, to nourish the tissues outside the capillaries. [At the same time, fluids pass from the tissues into the blood. Thus, there is an exchange between the blood and the fluids of the tissues. The fluid, after it passes into the tissues, constitutes the lymph , and acts like a stream irrigat- ing the tissue elements.] I. The Arteries are distinguished from veins by their thicker walls , due to the greater development of smooth, muscular and elastic tissues; the middle coat (tunica media) of the arteries is specially thick, while the outer coat (t. adventitia) is relatively thin. [The absence of valves is by no means a character- istic feature.] The arteries consist of three coats (Fig. 60). (1) The Tunica intima, or inner coat, consists of a layer of ( a ) irregular, long, fusiform, nucle- ated, squamous cells, forming the excessively thin, transparent endothelium (His, 1866), immediately in contact with the blood stream. [Like other endothelial cells, these cells are held together by a cement substance which is blackened by the action of silver nitrate.] Outside this lies a very thin, more or less fibrous, layer — sub- epithelial layer — in which numerous spindle or branched protoplasmic cells lie em- bedded within a corresponding system of plasma canals. Outside this is an elastic lamina ( b ), which, in the smallest arteries , is a structureless or fibrous elastic membrane — in arteries of medium size it is a fenestrated membrane ( Henle ), while in the largest arteries there may be several layers of elastic laminae or fenestrated elastic membrane mixed with connective tissue. [In some arteries the elastic membrane is distinctly fibrous, the fibres being chiefly arranged longitudinally. It may be stripped off, when it forms a brittle elastic mem- brane, which has a great tendency to curl up at its margins. In a transverse section of a middle- sized artery it appears as a bright, wavy line, but the curves are probably produced by the partial collapse of the vessel. It forms an important guide to the pathologist in enabling him to determine which coat of the artery is diseased.] In middle-sized and large arteries a few non-striped muscular fibres are disposed longitudinally between the elastic plates or laminae ( K . Bardeleben ). Along with the circular muscular fibres of the middle coat, they may act so as to narrow the artery, and they may also aid in keeping the lumen of the vessel open and of Fig. 60. Small artery, to show the various layers which compose its walls, a, endothe- lium ; b , internal elastic lamina ; c, cir- lar muscular fibres of the middle coat ; d, the connective-tissue outer coat (t. adventitia). 112 STRUCTURE OF ARTERIES. uniform calibre. It is not probable that when they act by themselves they dilate the vessel. (2) The Tunica media, or middle coat, contains much non-striped muscle (V), which in the smallest arteries consists of transversely disposed non-striped muscu- lar fibres lying between the endothelium and the T. adventitia, while a finely granular tissue with few elastic fibres forms the bond of union between them. As we proceed from the very smallest to the small arteries, the number of muscular fibres become so great as to form a well-marked fibrous ring of non-striped muscle , in which there is comparatively little connective tissue. In the large arteries the amount of connective tissue is considerably increased, and between the layers of fine connective tissue numerous (as many as 50) thick, elastic, fibrous or fenes- trated laminae are concentrically arranged. A few non-striped fibres lie scattered among these, and some of them are arranged transversely, while a few have an oblique or longitudinal direction. The first part of the aorta and pulmonary artery, and the retinal arteries are devoid of muscle. The descending aorta, common iliac, and popliteal have longitudinal fibres between the transverse ones. Longitudinal bundles lying inside the media occur in the renal, splenic and internal sper- Fig. 61. Capillaries. The outlines of the endothelial cells marked off from each other by the cement which is blackened by the action of silver nitrate. The nuclei of the cells are obvious. made arteries. Longitudinal bundles occur both on the outer and inner surfaces of the umbilical arteries, which are very muscular. (3) The Tunica adventitia, or outer coat, in the smallest arteries consists of a structureless membrane with a few connective-tissue corpuscles attached to it ; in somewhat larger arteries there is a layer of fine, fibrous, elastic tissue mixed with bundles of fibrillar connective tissue ( d ). In arteries of middle size , and in the largest arteries the chief mass consists of bundles of fibrillar connective tissue con- taining connective-tissue corpuscles. The bundles cross each other in a variety of directions, and fat cells often lie between them. Next the media there are numerous fibrous or fenestrated elastic lamellae. In medium-sized and small arteries the elastic tissue next the media takes the form of an independent elastic membrane (Henle’s external elastic membrane). Bundles of non-striped muscle, arranged longitudinally, occur in the adventitia of the arteries of the penis, and in the renal, splenic, spermatic, iliac, hypogastric and superior mesenteric arteries. II. The capillaries, while retaining their diameter, divide and reunite so as to form networks, whose shape and arrangement differ considerably in different tis- sues. The diameter of the capillaries varies considerably, but as a general rule it STRUCTURE OF VEINS. 113 is such as to admit freely a single row of blood corpuscles. In the retina and muscle the diameter is 5-6 //., and in bone marrow, liver, and choroid 10-20 \i. The tubes consist of a single layer of transparent, excessively thin, nucleated, endothelial cells joined to each other by their margins ( Hoyer , Auerbach , Eberth , Aeby , 1865). [The nuclei contain a well-marked intra nuclear plexus of fibrils, like other nuclei.] The cells are more fusiform in the smaller capillaries and more polygonal in the larger. The body of the cell presents the characters of very faintly refractive protoplasm, but it is doubtful whether the body of the cell is endowed with the property of contractility. Action of Silver Nitrate.— If a dilute solution per cent.) of silver nitrate be injected into the blood vessels, the cement substance of the endothelium and of the muscular fibres as well,] is revealed by the presence of the black “ silver lines." The blackened cement substance shows little specks and large black slits at different points. It is not certain whether these are actual holes {/. Arnold ) through which colorless corpuscles may pass out of the vessels, or are merely larger accumulations of the cement substance. [Arnold called these small areas in the black silver lines when they are large stomata, and when small stigmata. They are most numerous after venous congestion, and after the disturbances which follow inflammation of a part ( Cohnheim , Winiwarter). They are not always present. The existence of cement substance between the cells may also be inferred from the fact that indigo- sulphate of soda is deposited in it ( Thoma), and particles of cinnabar and China ink are fixed in it, when these substances are injected into the blood ( Foa).~\ Fine anastomosing fibrils derived from non-medullated nerves terminate in small end buds in relation with the capillary wall ; ganglia in connection with capillary nerves occur only in the region of the sympathetic (. Bremer and Wal- deyer). [If a capillary is examined in a perfectly fresh condition (while living) and with- out the addition of any reagent, it is impossible to make out any line of demarca- tion between adjacent cells, owing to the uniform refractive index of the entire wall of the tube.] The small vessels next in size to the capillaries and continuous with them have a completely structureless covering in addition to the endothelium. III. The veins are generally distinguished from the arteries by their lumen being wider than the lumen of the corresponding arteries; their walls are thinner , on account of the smaller amount of non-striped muscle and elastic tissue (the non-striped muscle is not unfrequently arranged longitudinally in veins). They are also more extensile (with the same strain). The adventitia is usually the thickest coat. The occurrence of valves is limited to the veins of certain areas. (1) The T. intima consists of a layer of shorter and broader endothelial cells, under which, in the smallest veins, there is a structureless elastic membrane, sub- epithelial layer , which is fibrous in veins somewhat larger in size, but in all cases is thinner than in the arteries. In large veins it may assume the characters of a fenestrated membrane, which is double in some parts of the crural and iliac veins. Isolated muscular fibres £xist in the intima of the femoral and popliteal veins. (2) The T. media of the larger veins consists of alternate layers of elastic and muscular tissue united to each other by a considerable amount of connective tissue, but this coat is always thinner than in the corresponding arteries. This coat diminishes in the following order in the following vessels : popliteal, veins of the lower extremity, veins of the upper extremity, superior mesenteric, other abdominal veins, hepatic, pulmonary, and coronary veins. The following veins contain no muscle : veins of bone, central nervous system and its membranes, retina, the superior cava, with the large trunks that open into it, the upper part of the inferior cava. Of course, in these cases the media is very thin. In the 8 114 PHYSICAL PROPERTIES OF THE BLOOD VESSELS. Fig. 62. I Longitudinal section of a vein at the level of a valve, a, hyaline layer of the internal coat ; b, elastic lamina ; c, groups of smooth muscular fibres divided transverse- ly ; d , longitudinal muscular fibres in the adventitia. smallest veins the media is formed of fine con- nective tissue, with very few muscular fibres scattered in the inner part. (3) The T. adventitia is thicker than that of the corresponding arteries; it contains much connective tissue , usually arranged longitudin- ally, and not much elastic tissue. Longitudinally arranged muscular fibres occur in some veins (renal, portal, inferior cava near the liver, veins of the lower extremities). The valves consist of fine fibrillar connective tissue with branched cells. An elastic network exists on their convex surface, and both surfaces are covered by endo- thelium. The valves contain many muscular fibres (Fig. 62). [Ranvier has shown that the shape of the epithelial cells covering the two surfaces of the valves differs. On the side over which the blood passes, they are more elongated than on the cardiac side of the valve, where the long axes of the cell are placed transversely.] The sinuses of the dura mater are spaces covered with endothelium. The spaces are either duplicatures of the membrane, or channels in the substance of the tissue itself. Cavernous spaces we may imagine to arise by numerous divisions and anastomoses of tolerably large veins of unequal calibre. The vascular wall appears to be much perforated and like a sponge, the internal space being traversed by threads and strands of tissue, which are covered with endothelium on their surfaces, that are in contact with the blood. The surrounding wall consists of connective tissue, which is often very tough, as in the corpus cavernosum, and it not unfrequently contains non- striped muscle. Cavernous Formations of an analogous nature on arteries are the carotid gland of the frog (Fig. 45), and a similar structure on the pulmonary arteries and aorta of the turtle, and the coccygeal gland of man (. Luschka ). The last structure is richly supplied with sympathetic nerve fibres, and is a convoluted mass of ampullated or fusiform dilatations of the middle sacral artery (Arnold), surrounded and permeated by non-striped muscle (. Eberth ). Vasa Vasorum. — [These are small vessels which nourish the coats of the arteries and veins. They arise from one part of a vessel and enter the walls of the same or another vessel at a lower level. They break up chiefly in the outer coat, and none enter the inner coat.] In structure they resemble other small blood vessels. The blood circulating in the arterial or venous wall is returned by small veins. [Lymphatics. — There are no lymphatics on the inner surface of the muscular coat, or under the intima in large arteries. They are numerous in a gelatinous layer immediately outside the muscular coat, and the same relation obtains in large muscular veins and lymphatic trunks (Hoggan).] Intercellular Blood Channels. — Intercellular blood channels of narrow calibre, and without walls, occur in the granulation tissue of healing wounds. At first blood plasma alone is found between the formative cells, but afterward the blood current forces blood corpuscles through the channels. The first blood vessels in the developing chick are formed in a similar way from the formative cells of the mesoblast. Properties of the Blood Vessels. — The larger blood vessels are cylindrical tubes composed of several layers of various tissues, more especially elastic tissue and plain muscular fibres , and the whole is lined by a smooth layer of endothelium. One of the most important properties is the contractility of the vascular wall, in virtue of which the blood vessel becomes contracted, so that the calibre of the PHYSICAL PROPERTIES OF THE BLOOD VESSELS. 115 vessel, and therefore the supply of blood to a part, are altered. The contractility is due to the plain muscular fibres, which are, for the most part, arranged circu- larly. It is most marked in the small arteries, and of course is absent where no muscular tissue occurs. The amount and intensity of the contraction depend upon the development of the muscular tissue ; in fact, the two go hand-in-hand. [If an artery be exposed in the living body it soon contracts under the stimulus of the atmosphere (f. Hunter ) acting upon the muscular fibres.] [Action of Alkalies and Acids on the Vascular System. — Gaskell finds that very dilute alkalies and acids have a remarkable effect on the blood vessels and also upon the heart. A very dilute solution of lactic acid (I part to 10,000 parts of saline solution), passed through the blood vessels of a frog, always enlarges the calibre of the blood vessels, while an alkaline solution (1 part sodium hydrate to 10,000 or 20,000 parts saline solution) always diminishes their size, usually to absolute closure, and indeed the artificial constriction of the blood vessels may be almost complete. These fluids are antagonistic to each other as far as regards their action on the calibre of the arteries. Microscopic observations which confirmed these results were also made on the blood vessels of the mylo-hyoid muscle of the frog. Dilute alkaline solutions act on the heart in the same way. After a series of beats, the ventricle stops beating, the stand still being in a state of contraction. Very dilute lactic acid causes the ventricle to stand still in the position of complete relaxation. The action of the acid and alkaline solutions are antagonistic in their action on the ventricle. Gaskell attaches considerable importance to the “tonic” and “atonic” conditions of the whole vascular system produced by very dilute solutions of alkalies and acids respectively.] [Other Drugs. — Cash and Brunton find that dilute acids have a tendency to increase the transudation through the vessels and produce oedema of the surrounding tissues. They also ob- served that barium, calcium, strontium, copper, iron, and tin produce contraction of the blood vessels when solutions of their salts are driven through them, whde the same effect is produced by very dilute solutions of potassium. Nicotin, atropin, and chloral differ in their action, according to the dose. In these experiments the effect was ascertained by the amount of fluid which flowed out of the vessels in a given time.] That the capillaries undergo dilatation and contraction, owing to variations in size of the protoplasmic elements of their walls, must be admitted. Strieker has described capillaries as “ protoplasm in tubes,” and observed that they exhibited movements when stimulated in living animals. Golubew described an active state of contraction of the capillary wall, but he regarded the nuclei as the parts which underwent change. Tarchanoff found that mechanical or electrical stimulation caused a change in the shape and size of the nuclei, so that he regards these as the actively contractile parts. [Severini also attaches great importance to the contractility of the capillaries and especially of their nuclei as influencing the blood stream. Oxygen acts on the nuclei of the capillary wall pnembrana nictitans of frog) and causes them to swell, while C0 2 has an opposite effect. The circulation through a lung suddenly filled with O or atmospheric air, is at first very rapid, but soon becomes small, while with CO z the circulation remains constant.] Strieker’s observations were made on the capillaries of tadpoles. These phe- nomena became less marked as the animal became older. Rouget observed the same result in the capillaries of new-born mammals. As the capillaries are excessively thin and delicate, and as they are soft structures, it is obvious that the form of the individual cells must depend to a considerable extent upon the degree to which the vessels are filled with blood. In vessels w'hich are distended with blood the endothelial cells are flattened, but when the capillaries are collapsed, they project more or less into the lumen of the vessel ( Renaut ). It is a well-known fact that the capillaries present great variations in their diameter at different times. As these variations are usually accompanied by a corresponding contraction or dilatation of the arterioles, it is usually assumed that the variations in the diameter of the capillaries are due to differences of the pressure within the capillaries themselves, viz, to the elasticity of their walls. Every one is agreed that the capillaries are very elastic, but the experiments of Roy and Graham Brown show that they are contractile as well as elastic, and these observers conclude that, under normal conditions, it is by the contractility of the capillary wall as a whole that the diameter of tnese vessels is changed, and to all appearance their contractility is constantly in action. “ The individual capillaries (in all probability) contract or expand in accordance with the requirements of the tissues through which they pass. The regulation of the vascular blood flow is thus more com- plete than is usually imagined” ( Roy and Graham Brown). Physical Properties. — Among the physical properties of the blood vessels, elasticity is the most important; their elasticity is small in amount, i. e., they offer little resistance to any force applied to them so as to distend or elongate them, but it is perfect in quality, i. e., the blood vessels rapidly regain their original size and form after the force distending them is removed. 116 THE PULSE. [Uses of Elasticity. — The elasticity of the arteries is of the utmost importance in aiding the conversion of the unequal movement of the blood in the large arteries into a uniform flow in the capillaries. E. H. Weber compared the elastic wall of the arteries with the air in the air chamber of a fire-engine. In both cases an elastic medium is acted upon— the air in the one case and the elastic tissue in the other — which in turn presses upon the fluid, propelling it onward continually, while the action of the pump or the heart, as the case may be, is intermittent. The ordinary spray producer acts on this principle. A uniform spray or jet is obtained by pumping intermittently, but only when the resistance is such as to bring into action the elasticity of the bag between the pump and the spray orifice.] According to E. H. Weber, Volkmann and Wertheim, the elongation of a blood vessel (and most moist tissues) is not proportional to the weight used to extend it, the elongation being rela- tively less with a large weight than with a small one, so that the curve of extension is nearly [or, at least, bears a certain relation to] a hyperbola. According to Wundt, we have not only to consider the extension produced at first by the weight, but also the subsequent “ elastic after-effect,” which occurs gradually. The elongation which takes place during the last few moments occurs so slowly and so gradually that it is well to observe the effect by means of a magnifying lens. Variations from the general law occur to this extent, that if a certain weight is exceeded, less extension, and, it may be, permanent elongation of the artery not unfrequently occur. K. Bardeleben found, especially in veins elongated to 40 or 50 per cent, of their original length, that when the weight employed increased by an equal amount each time, the elongation was proportional to the square root of the weight. This is apart from any elastic after-effect. Veins may be extended to at least 50 per cent, of their length without passing the limit of their elasticity. [Roy has made careful experiments upon the elastic properties of the ai'terial wall. A portion of an artery, so that it could be distended by any desired internal pressure, was enclosed in a small vessel containing olive oil. The small vessel with oil was arranged in the same way as in Fig. 53 for the heart. The variations of the contents were recorded by means of a lever writing on a revolv- ing cylinder. The aorta and other large arteries were found to be most elastic and most disten- sible at pressures corresponding more or less exactly to their normal blood pressure, while in veins the relation between internal pressure and the cubic capacity is very different. In them the maxi- mum of distensibility occurs with pressures immediately above zero. Speaking generally, the cubic capacity of an artery is greatly increased by raising the intra-arterial tension, say from zero to about the normal internal pressure which the artery sustains during life. Thus in the rabbit the capacity of the aorta was quadrupled by raising the intra-arterial pressure from zero to 200 mm. Hg, while that of the carotid was more than six times greater at that pressure than it was in the undistended condition. The pulmonary artery is distinguished by its excessive elastic distensibility. Its capa- city (rabbit) was increased more than twelve times on raising the internal pressure from zero to about 36 mm. Hg. Veins, on the other hand, are distinguished by the relatively small increase in their cubic capacity produced by greatly raising the internal pressure, so that the enormous changes in the capacity of the veins during life are due less to differences in the pressure than to the great differences in the quantity of blood which they contain (Roy).] Pathological. — Interference with the nutrition of an artery alters its elasticity [and that in cases where no structural changes can be found.] Marasmus preceding death causes the arteries to become wider than normal (Roy). Age also influences their elasticity — in some old people they become atheromatous and even calcified. [The ratio of expansion of strips of the aortic wall to the weights employed to strttch them, remains much the same from childhood up to a certain age {Roy).] Cohesion. — Blood vessels are endowed with a very large amount of cohesion, in virtue of which they are able to resist even considerable internal pressure with- out giving way. The carotid of a sheep is ruptured only when fourteen times the usual pressure it is called upon to bear is put upon it ( Volkmann ). A greater pressure is required to rupture a vein than an artery with the same thickness of its wall. The carotid of a dog resists 50 times the blood pressure, the jugular vein about the half of this ( Grehant and Qiiinqnand') . Pathological. — The cohesion of the arteries is diminished, especially in old age. 66. THE PULSE — HISTORICAL. — Although the movement of the pulse in the super- ficially placed arteries was known to the ancients, still the pulse, as it was affected by disease, was more studied by the older physicians than the normal pulse. Hippocrates (460 to 337 B. c.) speaks of the former as while Herophilus (300 B. c.) contrasted the normal pulse (no-A/ios') with the pulse of disease ( ,g, gas ; x,q, caoutchouc tube attaching glass gas burner, t , to b. For the method of smoking the paper and fixing the tracings see p. 120. It is very convenient to write the curve upon a plate of glass fixed to a tuning-fork kept in vibra- tion. Every part of the curve shows little elevations (whose rate of vibration is known beforehand). All that is required is to count the number of vibrations in order to ascertain the duration of any part of the curve. (Fig. 74). Landois’ Gas Sphygmoscope. — A superficially placed artery communicates its movements to the overlying skin, and also to any freely movable body in contact with the skin. In this instrument (Fig. 75) a thin layer of air over the pulsating artery, a , is enclosed by means of a thin piece of metal, which is so adjusted that its concave side forms a tunnel of air over the artery. The narrow space between the metallic wall, b , and the skin, a, is filled with ordinary gas, one end of the metal shield being connected, by means of a tube, g, with the gas supply, while to the other end there is attached, by means of a short piece of caoutchouc, x, q, a bent glass tube, t , with a very small aperture, which acts as a gas burner. The gas is allowed to flow through the apparatus at a low pressure, and is so regulated that the flame, v , is only a few millimetres in height. The flame rises synchronously with every pulse beat, and the dicrotic beat in the normal pulse is quite observable. Czermak photographed a beam of light set in motion by the movements of the pulse. Haemautography. — Expose a large artery of an animal, and divide it so that the stream of blood issuing from it strikes against a piece of paper drawn in front of the blood stream. A curve (Fig. 76) is obtained which corresponds very closely with the pulse tracing obtained from a normal artery. In addition to the primary wave, P, there is a distinct “ recoil elevation,” or dicrotic wave, R. and slight vibrations, e, e, due to the variations in the elasticity of the arterial wall. The interest which attaches to a curve obtained in this way is, that it shows the movements occur in the blood itself, and are communicated as waves to the arterial wall. By estimating the amount of blood in the various parts of the curve we obtain a knowledge of the amount of blood discharged by the divided artery during the systole and diastole (i, e., the narrowing and dilatation) of the artery — the ratio is 7 : 10. Thus in the unit of time , during arterial dilatation, rather more than twice as much blood flows out as happens during arterial contraction. 68. THE PULSE TRACING OR SPHYGMOGRAM— Analysis. — A sphygmogram or pulse tracing consists of a series of curves (Fig. 77) each one of which corresponds with one beat of the heart. Each pulse curve consists of — 1. The line of ascent ( a to b in Fig. 77). 2. The apex (P in Fig. 79, and b in Fig. 77). 3. The line of descent ( b to K). The line of ascent, up stroke, or percussion stroke ( Mahomed ) is nearly verti- cal, and occurrs during the dilatation of the artery produced by the systole of the Fig. 76. Hsemautographic curve of the posterior tibial artery of a large dog. P, pri- mary pulse wave ; R, dicrotic or recoil wave ; e, e , elevations due to elasticity. THE PULSE CURVE. 123 left ventricle, and occurs when the aortic valves are forced open and the ven- tricular contents are projected into the arterial system. [The ascent is nearly vertical, but in some cases, where the ventricle contracts very suddenly, as occa- sionally happens in aortic regurgitation, it is quite vertical (Fig. 80).] The apex or percussion wave ( Mahomed ) in a normal pulse is pointed. The line of descent is gradual, and corresponds to the diminution of diameter or contraction of the artery. It is interrupted by two completely distinct elevations or secondary waves. The more distinct of the two occurs as a well-marked eleva- tion about the middle of the descent (R in Fig. 79 and /in Fig. 77) ; it is called the dicrotic wave, or, with reference to its mode of origin, the “ recoil wave." Fig. 77. 1 . A . v /] /W /] /] |1 (I V V V ' \ V / f\>- Y V ] Sphygmogram of radial artery : pressure 2 oz. Each part of the curve between the base ot one up stroke and the base of the next up stroke corresponds to a beat of the heart, so that this figure shows five heart beats and part of a sixth ; a, b = the ascent, b, the apex of the up stroke, and b to h the descent, with an elevation, a, called the first tidal or predicrotic wave, e, an angle or notch, the aortic notch, f, a second elevation, called the dicrotic wave,jf, a slight curve, sometimes called the second tidal wave. The descent is continued to h , where the ascent of the next heart beat begins. [As the descent corresponds to the time when blood is flowing out of the arte- ries at the periphery into the capillaries, its direction will depend on the rapidity of this outflow. Thus, it will be more rapid in paralysis of the arterioles and very rapid in aortic regurgitation, where, of course, much of the blood flows backward into the left ventricle (Fig. 80). In this case the artery will recoil suddenly from under the finger or pad of the instrument, and this constitutes the “ pulse of empty arteries.”] The dicrotic wave, recoil wave [or aortic systolic wave (. Bramwell) ] (Fig. 77), corresponds to the time following the closure of the aortic valves, and is pre- ceded in the descent by a slight depression, the aortic notch. Fig. 78. Irregular pulse of mitral regurgitation. [The tidal wave, or pre-dicrotic, occurs between the apex and the dicrotic wave (Fig. yjd). It has also been called th z second ventricular systolic wave, as it occurs after the first systolic wave or apex, and during the contraction of the ventricle {Bramwell'). The tidal wave is best marked in a hard pulse, i. e., where the blood pressure is high, so that it is usually well marked in cirrhotic disease of the kidney, accompanied by hypertrophy of the left ventricle.] [In some cases, e. g., mitral regurgitation , the pre-dicrotic wave may be present in some pulse beats and absent in others (Fig. 78), where the tidal wave is present in the largest pulse and absent in the others, while the base line is uneven. In mitral stenosis, the amount of blood discharged into the left ventricle frequently varies, hence the variations in the characters of the arterial pulse.] J 21 ORIGIN AND CHARACTERS OF THE DICROTIC WAVE. There may be other secondary waves in the lower part of the descent. [Respiratory or Base Line. — If a line be drawn so as to touch the bases of all the up strokes, we obtain a straight line, hence called by this name. The base line is altered in disease and during forced respiration (§ 74).] Fig. 79. 1 11 in iv v I, II, III, Sphygmograms of carotid artery; IV, axillary; V to IX, radial; X. dicrotic radial pulse; XI, XII, crural; XIII, posterior tibial ; XIV, XV, pedal. In all the curves P indicates apex; R, dicrotic wave; e, e, elevations due to elasticity; K, elevation caused by closure of the semilunar valves of the aorta. I. Origin and Characters of the Dicrotic Wave. — The dicrotic or recoil wave, which is always present in a normal pulse, is caused thus: During the ventricular systole, a mass of blood is propelled into the already full aorta, whereby a positive wave is rapidly transmitted from the aorta throughout the arterial system, even to the smallest arterioles, in which this primary wave is extinguished. As soon as the semilunar valves are closed, and no more blood flows into the arterial system, the arteries, which were previously distended CHARACTERS OF THE DICROTIC WAVE. 25 by the mass of blood suddenly thrown into them, recoil or contract, so that, in virtue of the elasticity (and contractility) of their walls, they exert a counter- pressure upon the column of blood, and thus the blood is forced onward. There is a free passage for it toward the periphery, but toward the centre (heart) it impinges upon the already closed semilunar valves. This develops a new posi- tive wave, which is propagated peripherally through the arteries, where it disap- pears in their finest branches. In those cases where there is sufficient time for the complete development of the pulse curve (as in the short course of the carotids, and in the arteries of the upper arm, but not in those of the lower extremity, on account of their length), a second reflected wave may be caused in exactly the same way as the first. Just as the pulse occurs later in the more peripherally placed arteries than in those near the heart, so the secondary wave reflected from the closed aortic valves must appear later in the peripheral arteries. Both kinds of waves — the primary pulse wave, the secondary, and, eventually, even the tertiary reflected wave — arise in the same place, and take the same course, and the longer the course they have to travel to any part of the arterial system, the later they arrive at their destination. The following points regarding the dicrotic wave have been ascertained experimentally : — 1. The dicrotic wave occurs later in the descending part of the curve the further the artery experimented upon is distant from the heart ( Landois , 1863). Compare the curves, Figs. 74, 84, 88. The shortest accessible course is that of the carotid, where the dicrotic wave reaches its maximum 0.35 to 0.37 sec. after the beginning of the pulse. In the upper extremity the apex of the dicrotic wave is 0.36 to 0.38 to 0.40 sec. after the beginning of the pulse beat. The longest course is that of the arteries of the lower extremity. The apex of the dicrotic wave occurs 0-45 to 0*52 to 0-59 sec. after the base of the curve. It varies with the height of the individual. 2. The dicrotic elevation in the descent is lower {Naumami) , and is less dis- tinct {Landois ), the further the artery is situated from the heart. This is just what one would expect, viz., the longer the distance which the wave has to travel, the less distinct it must become. 3. It is more pronounced in a pulse where the primary pulse wave is short and energetic ( Marey , Landois). It is greatest relatively when the systole of the heart is short and energetic. 4. It is greater the lower the tension or pressure of the blood within the arte- ries {Marey, Landois ), [and is best developed in a soft pulse]. In Fig. 79, IX and X were obtained when the tension of the arterial wall was low ; V and VI, medium; and VII with high tension. Conditions influencing Arterial Tension. — It is diminished at the beginning of inspira- tion ($ 74), by hemorrhage, stoppage of the heart, heat, an elevated position of parts of the body, amyl nitrite; it is increased at the beginning of expiration by accelerated action of the heart, stimu- lation of vasomotor nerves, diminished outflow of blood at the periphery, and by inflammatory con- gestion ( Knecht)\ further, by certain poisons, as lead; compression of other large arterial trunks, action of cold and electricity on the small cutaneous vessels, and by impeded outflow of venous blood. When a large arterial trunk is exposed the stimulation of the air causes it to contract, resulting in an increased ten- sion within the vessel. In many diseased conditions the arterial tension is greatly increased — [ e . g., in Bright’s disease, where the kidney is contracted (“granular”), and where the left ventricle is hypertrophied]. In all these conditions increased arterial tension is indicated by the dicrotic wave being less high and less distinct, while with diminished arterial tension it is a larger and apparently more independent elevation. Moens has shown that the time between the primary elevation and the dicrotic wave increases with increase in the diameter of the tube, with diminution of its thickness, and when its coefficient of elasticity diminishes. [The dicrotic wave is absent or but slightly marked in cases of atheroma and in aortic regurgitation (Fig. 80). In this figure observe also the vertical character of the up stroke.] 126 DICROTIC PULSE. II. Origin and Characteristics of the Elastic Elevations. — Besides the dicrotic wave, a number of small, less-marked elevations occur in the course of the descent in a sphygmogram (Fig. 79, e, e). These elevations are caused by the elastic tube being thrown into vibrations by the rapid energetic pulse wave, just as an elastic membrane vibrates when it is suddenly stretched. The artery also executes vibratory movements when it passes suddenfy from the distended to the relaxed condition. These small elevations in the pulse curve, caused by the elastic vibrations of the arterial wall, are called “ elastic eleva- tions ” by Landois. ( 1) The elastic vibrations increase in number in one and the same artery with the degree of tension of the elastic arterial wall. A very high tension occurs in the cold stage of intermittent fever, in which case these elevations are well marked. ^2) If the tension of the arterial wall be greatly diminished these elevations may disappear, so that, while diminished tension favors the production of the dicrotic wave, it acts in the opposite way with reference to the “elastic eleva- tions.” (3) In diseases of the arterial walls affecting their elasticity, these eleva- tions are either greatly diminished or entirely abolished. (4) The further the arteries are distant from the heart, the higher are the elastic elevations. (5) When the mean pressure within the arteries is increased by preventing the outflow of blood from them, the elastic vibrations are higher and nearer the apex of the curve. (6) They vary in number and length in tl?e pulse curves obtained from different arteries of the body. Fig. 81. Development of the Pulsus dicrotus. — P. caprizans ; P. monocrotus. When the arm is held in an upright position, after five minutes the blood vessels empty themselves, and collapse, while the elasticity of the arteries is diminished. 69. DICROTIC PULSE. — Sometimes during fever, especially when the temperature is high, a dicrotic pulse maybe felt, each pulse beat, as it were, being composed of two beats (Fig. 79, X), one beat being large and the other small, and more like an after beat. Both beats correspond to one beat of the heart. The two beats are quite distinguishable by the touch. The phenomenon is only an exaggerated condition of what occurs in a normal pulse. The sensible second beat is nothing more than the greatly increased dicrotic elevation , which, under ordinary conditions, is not felt by the finger. Conditions. — The occurrence of a dicrotic pulse is favored (1) by a short primary pulse wave, as in fevers, where the heart beats rapidly. (2) By diminished tension within the arterial system. A short systole and diminished arterial blood pressure are the most favorable conditions for causing a dicrotic pulse. [So that dicrotism is best marked in a soft pulse.] The double beat may be felt only at certain parts of the arterial system, while at other parts only a single beat is felt. A favorite site is the radial artery of one or other side, where conditions favorable to its occurrence appear to exist. 1 his seems to be due to a local diminution of the blood pressure in this area, owing to the paralysis of its vasomotor nerves {Landois). If the tension be increased by compressing other large arterial trunks or the veins of the part, the double beat becomes a simple pulse beat. The dicrotic pulse in fever seems to be due to the increased temperature (39 0 to 40° C), whereby the artery is more distended, and the heart beat is shorter and more prompt ( Riegel ). (3) It is absolutely necessary that the elasticity of the ai'terial wall be normal. The dicrotic pulse does not occur in old persons with atheromatous arteries {Landois). CONDITIONS AFFECTING THE PULSE RATE. 127 Monocrotic Pulse. — In Fig. 8 1 , A, B, C, we observe the gradual passage of the normal radial curve, A, into the dicrotic beat, B and C, where the dicrotic wave, r, appears as an independent elevation. If the frequency of the pulse increases more and more in fever, the next following pulse beat may occur in the ascending part of the dicrotic wave, D, E, F, and it may even occur close to the apex, G (P. caprizans). If the next following beat occurs in the depression, i, between the primary elevation, p, and the dicrotic elevation, r , the latter entirely disappears, and the curve, H, assumes what Landois calls the “ monocrotic” type. [Degrees of Dicrotism. — When the aortic notch reaches the respiratory or base line, the tidal wave having disappeared, the pulse is said to be fully dicrotic. When the aortic notch falls below the base line, i. ear . . 2 years . . 3 “ • • 4 “ . . 5 “ • • 10 “ Beats per Beats per Minute. Minute. I30 to I40 10 to 15 years .... 78 120 to I30 15 to 20 66 70 105 20 to 25 66 70 IOO 25 to 50 66 70 97 60 6k 74 94 to 90 80 66 79 about 90 80 to 90 66 over 80 ( b ) The length of the body has a certain relation to the frequency of the pulse. The follow- ing results have been obtained by Czarnecki from the formulae of Volkmann and Rameaux : — Length of Body- Pulse Length of Body Pulse in 10 cm. Calculated. Observed. in 10 cm. Calculated. Observed. 80 to 90. . . . .... 90 103 I40 to 150. . . . .... 69 74 90 to IOO. . . . 9 1 150 to 160 . . . . .... 67 68 IOO to I IO. . . . . ... 8l 87 160 to 170 . . . . .... 65 65 I IO to 120 . . . ... 78 84 1 70 to 1 80 . . . . .... 63 64 120 to I30. . . . • ... 75 78 above 180 . . . . .... 60 60 130 to 140. . . . . ... 72 76 (c) The pulse rate is increased by muscular activity , by every increase of the arterial blood pressure , by taking of food , increased temperature , painful sensations , by psychical disturbances , and \in extreme debility ]. Increased heat, fever, or pyrexia increases the frequency, and, as a rule, 128 VARIATIONS IN THE PULSE RHYTHM. the increase varies with the height of the temperature. [Dr. Aitken states that an increase of the temperature of i° F. above 98° F. corresponds with an increase of ten pulse beats per minute ; thus : — Temp. F. 98° . 99° • too 0 . IOI 0 . 102 ° . Pulse Rate. . . 60 • - 70 . . 80 . . 80 . . IOO Temp. F. 103° IO4 0 I05 0 106 0 Pulse Rate. . I IO . 120 . 130 . I40 This is merely an approximate estimate.] It is more frequent when a person is standing than when he lies down. Music accelerates the pulse and increases the blood pressure in dogs and men ( Dogie /). Exposure to increased barometric pressure diminishes the frequency. The variation of the pulse rate during the day — 3 to 6 a.m. == 61 beats; 8 to 11^ a.m. = 74. It then falls toward 2 p.m. ; toward 3 (at dinner time) another increase takes place and goes on until 6 to 8 p.m. = 70 ; and it falls until midnight = 54. It then rises again toward 2 a.m., when it soon falls again, and afterward rises, as before, toward 3 to 6 A.M. [Pulse Rate in Animals. Per Min. Per Min. I Per Min. Elephant . . . . . . . 25-28 Lioness . . 68 Rabbit . . I 20-1 50 Camel • - . 28-32 Tiger. . 74 Mouse • . 150 Giraffe ... 66 Sheep . . 70-80 Goose I IO Horse . . . 36-40 Goat . . . 70-80 Pigeon .... . . 136 Ox . . . 45-50 Leopard 60 Hen . . I40 Tapir ... 44 Wolf (female) . . . 96 Snake . . 24 Ass . . . 46-50 Hyaena . 55 Carp . . 20 Pig . . . 70-80 Dog . . . 90-100 Frog 80 Lion Cat. . . . Fig. 83. 1 20- 1 40 Salamander . . . 72 ( Colin ).] Pulsus alternans. 4. Variations in the Pulse Rhythm. — On applying the fingers to the normal pulse, we feel beat after beat occurring at apparently equal intervals. Sometimes in a normal series a beat is omitted == pulsus intermittens, or intermittent pulse. [In feeling an intermittent pulse, we imagine or have the impression that a beat is omitted. This may be due to a reflex arrest of the ventricular contraction, caused by digestive derangement, in which case it has no great significance ; but if it be due to failure of the ventricular action, intermittent pulse is a serious symptom, being frequently present when the muscular walls are degenerated.] At other times the beats become smaller and smaller, and after a certain time begin as large as before wm p. myurus. When an extra beat is intercalated in a normal series = p. intercurrens. The regular alternation of a high and a low beat = p. alternans ( Traube ) (Fig. 83). In the p. bigeminus of Traube the beats occur in pairs, so that there is a longer pause after every two beats. Traube found that he could produce this form of pulse in curarized dogs by stopping the artificial respiration for a long time. The p. trigeminus and quadrigeminus occur in the same way, but the irregularities occur after every third and fourth beat. Knoll found that in animals such irregularities of the pulse were apt to occur, as well as great irregularity in the rhythm generally, when there is great resistance to the circulation, and consequently the heart has great demands upon its energy. The same occurs in man, when an improper relation exists between the force of the cardiac muscle and the work it has to do ( Riegel ). Complete irregularity of the heart’s action is called arhythmia cordis. 71. VARIATIONS IN THE STRENGTH, TENSION AND VOLUME OF THE PULSE.— Compressibility. — The relative strength or compressibility of the pulse (p. fortis and debilis), i. e., whether the pulse is strong or weak, is estimated by the weight which the pulse is THE PULSE CURVES OF VARIOUS ARTERIES. 129 able to raise. A sphygmograph, provided with an index indicating the amount of pressure exerted upon the spring pressing upon the artery, may be used (Fig. 66). In this case, as soon as the pressure exerted upon the artery overcomes the pulse beat, the lever ceases to move. The weight employed indicates the strength of the pulse. [The finger may be, and generally is, used. The finger is pressed upon the artery until the pulse beat in the artery beyond the point of pressure is obliterated. In health it requires a pressure of several ounces to do this. Handheld Jones uses a sphygmometer for this purpose. It is constructed like a cylindrical letter weight, and the pressure is exerted by means of a spiral spring which has been carefully graduated.] The pulse is hard or soft when the artery, according to the mean blood pressure, gives a feeling of greater or less resist- ance to the finger, and this quite independent of the energy of the individual pulse beats (p. durus and mollis). In estimating the tension of the artery and the pulse, i. e., whether it is hard or soft, it is import- ant to observe whether the artery has this quality only during the pulse wave, i. e., if it is hard during diastole, or whether it is hard or soft during the period of rest of the arterial wall. All arteries are harder and less compressible during the pulse beat than during the period of rest, but an artery which is very hard during the pulse beat may be hard also during the pause between the pulse beats, or it may be very soft, as in insufficiency of the aortic valves. In this case, after the sys- tole of the left ventricle, owing to the incompetency of the aortic semilunar valves, a large amount 6f blood flows back into the ventricle, so that the arteries are thereby suddenly rendered partially empty. [The sudden collapse of the artery gives rise to the characteristic “ pulse of unfilled arteries.” Fig. 80.] Under similar conditions, the volume of the pulse is obvious from the size of the sphygmogram, so that we speak of a large and a small pulse (p. magnus and parvus). Sometimes the pulse is so thready and of such diminished volume that it can scarcely be felt. A large pulse occurs in disease when, owing to hypertrophy of the left ventricle, a large amount of blood is forced into the aorta. A small pulse occurs under the opposite condition, when a small amount of blood is forced into the aorta, either from a diminution of the total amount of the blood, or from the aortic orifice being narrowed [aortic stenosis], or from disease of the mitral valve; again, where the ventricle contracts feebly, the pulse becomes small and thready. Compare the two Radials. Sometimes the pulse differs on the two sides, or it may be absent on one side. [The pulse wave in the two radials is often different when an aneurism is present on one side.] Angiometer. — Waldenburg constructed a “ pulse clock” to register the tension, the diameter of the artery, and the volume of the pulse upon a dial. It does not give a graphic tracing, the results being marked by the position of an indicator. 72. THE PULSE CURVES OF VARIOUS ARTERIES.— 1. Carotid (Fig. 79, I, II, III ; Fig. 88, C and Cj). — The ascending part is very steep — the apex of the curve (Fig. 79, P) is sharp and high. Below the apex there is a small notch — the “Aortic Notch” (Fig. 79, K) — which depends on a positive wave formed in the root of the aorta, owing to the closure of the aortic valves, and propagated with almost wholly undiminished energy into the carotid artery. Quite close to this notch, if the curve be obtained with minimal friction, the first elastic vibration occurs (Fig. 79, II, e). Above the middle of the descending part of the curve is the dicrotic elevation, R, produced by the reflection of a positive wave from the already closed semilunar valves. The dicrotic wave is relatively small, on account of the high tension in the carotid artery. After this the curve falls rapidly, but in its lowest third two small elevations may be seen. Of these the former is due to elastic vibration. The latter represents a second dicrotic wave (Fig. 79, III, R) ( Landois , Moens). Here there is a true tricrotism , which is more easily obtained from the carotid on account of the shortness of the arterial channel. 2. Axillary Artery (Fig. 79, IV). — In this curve the ascent is very steep, while in the descent near the apex there is a small (aortic) elevation, K, caused by a positive wave, produced by the closure of the aortic valves. Below the middle there is a tolerably high dicrotic elevation, R, higher than in the carotid curve ; because in the axillary artery the arterial tension is less, and per- mits a greater development of the dicrotic wave. Further on, two or three small elastic vibrations occur, s) upon the sur- face of the mercury in the open limb of the tube. A writing style, f, placed transversely on the free end of the float, inscribed the movements of the float — and, therefore, of the mercury — upon a cylinder, C, caused to revolve at a uniform rate. This apparatus registered the height of the blood pressure, as well as the pulsatile and other oscillations occurring in the mercury. Volkmann called this instrument a kymograph or “ wave writer. ” The difference of the height of the column of mercury, c, d> in both limbs of the tube indicates the pressure within the vessel. If the height of the column of mercury be multiplied by 13.5, this gives the height of the corresponding column of blood. Setschenow placed 142 ludwig’s kymograph. a stop-cock in the lower bend, h , of the tube. If this be closed so as just to per- mit a small aperture of communication to remain, the pulsatile vibrations no longer appear, and the apparatus indicates the mean pressure. By the term mean pressure is meant the limit of pressure, above and below which the oscillations occurring in an ordinary blood pressure tracing range. [Briefly, it is the average elevation of the mercurial column.] In a blood-pressure tracing, such as Fig. 99, each of the smaller waves corresponds to a heart beat, the ascent corresponds to the systole and the descent to the diastole. The large un- dulations are due to the respiratory move- ments. It is clear that the heart beat is ex- pressed as a simple rise and fall (Fig. 99), so that the curve of the heart beat obtained with a mercurial kymograph differs from a sphygmo- graphic curve. A perfect recording instrument ought to indicate the height of the blood pres- sure, and also the size, form, and duration of any wave motion communicated to it. The mercurial manometer does not give the true form of the pulse wave, as the mercury, when once set in motion, executes vibrations of its own, owing to its great inertia, and thus the finer movements of the pulse wave are lost. Hence a mercurial kymograph is used for regis- tering the blood pressure, and not for obtaining the exact form of the pulse wave. Instruments with less inertia, and with no vibrations pecu- liar to themselves, are required for this purpose. [The theory of the mercurial manometer has been carefully worked out by Mach and also by v. Kries.] [Method. — Expose the carotid of a chloral - ized rabbit, and isolate a portion of the vessel between two ligatures, or two spring clamps. , , . . ,, , . . .. , „ . With a pair of scissors make an oblique slit into moved by the clockwork in the box, A, and regulated ar f ei T> and into it insert a Straight glass by a Foucault’s regulator placed on the top of the box. cannula, directing the open end of the cannula The disk D, moved by the clockwork, presses upon the toward the heart. Fill the cannula with a two wheels, n. which can be raised or lowered by the . , j n ,. r ,. , ..i- screw, L, thus altering the position of n on D, so as to saturated solution of sodium carbonate, taking cause the cylinder to rotate at different rates. The care that no air bubbles enter, and connect it cylinder itself can be raised by the handle, v. On the w i t h the lead tube which goes to the descend- left side of the figure is a mercurial manometer. When • , • , r -i . r™ , , , . , the cylinder is used, it is covered with smoked smooth in § l im b of the manometer. The tube which paper. 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 keeping up artificial 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 artery.] [Continuous Tracing. — When we have occasion to take a tracing for any length of time, it must be written upon a strip of paper which is moved at a uniform rate in front of the writing style on the float (Fig. 98). 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 off the strip of paper, which is kept applied to the revolving surface by ivory friction wheels. In Fick’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 afterward.] [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. Blood pressure curve of the carotid of a dog obtained with a mercurial manometer, O — x= line ot no pressure, zero line, or abscissa ; y — -y 1 is the blood pressure tracing with small waves, each one caused by a heart beat, and the large waves due to the respiration. A millimetre scale shows the height of the pressure in millimetres of mercury. 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. As 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 y there is fixed a vertical rod attached to a series of levers, h, i, 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, d, 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, e, filled with oil or glycerine, which serves to damp the vibrations of the levers. At f 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, h y by means of the millhead opposite g, to which all the parts of the apparatus are attached.] 144 fick’s flat spring kymograph. (6) Fick’s Flat Spring Kymograph. — Fig. ioi shows Fick’s latest arrangement. The narrow tube, a, a (i mm. diam.) is placed in connection with a blood vessel by means of the cannula, c, and over its vertical expanded end, A, is fixed a caoutchouc membrane, with a projecting point, s, 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 R. In order to estimate the absolute pressure, the instrument must be compared previously with a mercurial manometer. Fig. ioo. (B) In man the blood pressure may be estimated by means of (i) A 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 Fig. ioi. Fick’s flat spring kymograph. placed a capsule containing fluid upon a pulsating artery, while the capsule itself communicated with a mercurial manometer. As soon as the pressure within the manometer slightly 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 12 to 13 years, 113 mm. Hg. (A. Eckert, 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 {Friedmann). After a cold as well as after a warm bath {L. Lehmann), the first effect is an increase of blood pressure and of the quantity of urine ( Grefberg ). 85. BLOOD PRESSURE IN THE ARTERIES.— The following results have been obtained by experiment on systemic arteries : — (ci) 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. “ 122 to 214 mm. Dog, 15 1 mm. “ 130 to 190 mm. {Ludwig). Goat, 1 18 to 135 mm. Rabbit, 90 mm. Fowl, 88 to 17 1 mm. -j- Aorta of frog, 22 to 29 mm. -j- Gill artery of Pike, 35 to 84 mm. Brachial artery of man during an ope- ration, 1 10 to 120 mm. {Faivre). 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 jr IG> I02i 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- mals varies from 200 to 250 mm. Hg. As a general rule, the blood pressure in large animals is higher than in small animals, because in the former the blood channel is considerably longer, and there is greater resistance to be over- come. In very young and in very old animals the pressure is lower than in individuals in the prime of life. The arterial pressure in the foetus 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 so great as in adult animals {Coknstein and Zuntz). Scheme of the height oi the blood pressure, in A, the arteries; C, capillaries, and V, veins; O-O, is the abscissa or line of no pressure ; L. V., left ventricle, and R. A., right auricle ; B. P., the height of the blood pressure. 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 venae cavae (compare Fig. 108). (b) Branching of the Blood Vessels. — Within the large arteries the blood pressure diminishes relatively little as we pass toward the periphery, because the difference of the resistance in the different sections of large tubes is very small. As soon, however, as the arteries begin to divide frequently, and undergo a con- siderable diminution in their lumen, the blood pressure in them rapidly diminishes, 10 146 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). (e) Amount of Blood. — The blood pressure is increased with greater filling of the arteries , and vice versa ; hence it Increases 1. With increased and accelerated action of the heart ; 2. In plethoric persons; 3. After considerable increase of the quan- tity of blood by direct transfusion, or after a copious meal. Decreases 1 . During diminished and enfeebled action of the heart ; 2. In anaemic persons ; 3. After hemorrhage or considerable ex- cretions from the blood by 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. Ludwig and IVorm Muller , $ 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 Muller). If a large amount of blood be withdrawn, it causes a great fall of the blood pressure (Hales, Magendie), 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.] ( d ) 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). ( on a suitable part of the skin, eg., the skin at the root of the nail on the terminal phalanx, or on the ear 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, e.g., the web of a frog’s foot, is made just to touch a thin 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. Any change in the vessels is observable by means of the microscope. These observers Fig. 107. Apparatus used by v. Kries for estimating the capillary pressure — a, 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- I! 5 )-] Conditions Influencing Capillary Pressure. — The intra-capillary blood pressure in a given area increases — (1) 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 ( v . 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 movements, Strieker — p. 1 1 5), 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 commencement 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 (Bonders). 152 BLOOD PRESSURE IN THE VEINS. The capillary pressure must also vary in different 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. 1 mm. Hg. prevails (H. Jacobson ). Hence, the lymph stream can flow unhindered. As the distance of the veins from the heart increases, there is z. gradual increase of the lateral pressure ; in the external facial vein (sheep) = -j- 3 mm.; brachial, 4.1 mm., and in its branches 9 mm.; crural, 11.4 mm. (Jacobson). [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 thorax, where the veins terminate in the right auricle, the pressure is negative.] Conditions Influencing the Venous Pressure. — (1) 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 oj 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 efforts, as in blowing upon a wind instrument, while every surgeon is well 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.] -Blood is sucked or aspirated into the auricles when they dilate (p. 77), so that there is a double aspiration — one synchronous with inspiration, and the other, which is but slight, synchronous with the heart beat. There is a corresponding retarda- tion of the blood stream in the venae cavae, 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 tilled again when the dimb 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 person walks, and thus favors the onward movement of the blood.] (5) Changes in the position of the limbs or of the body, for hydrostatic reasons, greatly alter the venous pressure. The veins of the lower ex- tremity bear the greatest pressure, while, at the same time, they contain most muscle (K. Bardeleben, § 65). Hence, when these muscles, from any cause, become insufficient, dilatations occur in the veins, giving rise to the production of varicose veins. (4) Aspiration oj the Heart. Fig. 108. Scheme of the blood pressure. H, heart ; a, auricle; v, ventricle; A, arterial; C, capillary; and V, venous areas. The circle indicates the parts within the tho- rax ; B. P., pressure in the aorta. BLOOD PRESSURE IN 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 the forearm, the superficial veins become turgid, and can be distinctly traced on the surface of the limb.] [(7) Gravity exercises 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 - chutin). 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 Vein. — 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. As a consequence of sudden and co?nplete ligature of this vein, the arterial blood 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. [Schiff and Lautenbach 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 oedema of the parts beyond the obstruction. Ligature of one vein does not always produce oedema, but if several veins of a limb be ligatured, and the vasomotor nerves be divided at the same time, the rapid production of oedema 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. — (1) 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 off, 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., i. 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 rose 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. Beutner and Marey estimated the relation of the pulmonary artery to the aortic pressure as 1 to 3 ; Goltz and Gaule as 2 to 5 ; Fick and Badoud found a pres- sure of 60 mm. in the pulmonary artery of the dog, and in the carotid hi mm. Hg. The blood pressure within the pulmonary artery of a child is relatively higher than in the adult ( Beneke ). 154 BLOOD PRESSURE IN THE PULMONARY 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 Latschenberge r). 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 and Pfeiffer , Bowditch and 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 in- 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 in the pulmonary vessels is accelerated during inspi- ration ( De Jdger , Lalesque. ) 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 [v. Openchoivski). 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 ( Beutner ). Even when one pulmonary artery is plugged with an embolon of paraffin, the pressure within the aortic system is not raised (. Lichtheim ). 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 ( Badoud , Hofmokl , Lichtheim). The compensation seems to be due chiefly to the great dis- tensibility and dilatation of the pulmonary vessels (. Lichtheim). ~\ We know little of the effect of physiological conditions upon the pulmonary artery. According to Lichtheim suspension 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 [Lalesque). MEASUREMENT OF TIIE VELOCITY OF THE BLOOD STREAM. 155 Severini found that the blood stream through the lungs is greater and more rapid when the lungs are filled with air rich in C 0 2 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 ( Brunton ), and anaesthetics arrest the pulmonary circulation, chloroform being most and ether least active, while ethidene is intermediate in its effect Kendrick, Coats, Newman).'] [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 (. Aubert).~\ 89. MEASUREMENT OF THE VELOCITY OF THE BLOOD STREAM.— Methods : (1) A. W Volkmann’s Haemadromometer. — 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 cannulae, c, c, 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 tube ; 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, c and d, to the metal disk, e e 1 . This disk rotates round the axis, X Y, so that, after a complete revolution, the tube c communicates with /, and d with /and g are provided with horizontally placed cannulae, h and k, which are tied into the ends of the divided artery. The cannula h is fixed in the central end, and k in the peripheral end of the artery (e. g., carotid); the bulb, A, is filled with oil and B with defibrinated blood ; at a certain moment the communication through h is opened, the *blood flows in, driving the oil before it, and passes into B, while the defibrinated blood flows through k 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 (1 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. iio. Fig. 109. Volkmann's hsemadromometer (B). I, blood flows from artery to artery; II, blood must pass through the glass tube of B ; c , c, cannulae for the divided artery. Y Ludwig & Dogiel’s stromuhr or rheometer. X, Y, axis of rotation; A, B, glass bulbs ; h, k, cannulae inserted in the di- vided artery ; e, £ lt rotates on g,f: c, d, tubes. Fig. hi. VierOrdt’s haematachometer. A, glass ; e, en- trance ; a, exit cannula ; p , pendulum. (3) Vierordt’s Haematachometer (1858) consists of a small metal box (Fig. 1 1 1) with parallel glass sides. To the narrow sides of the box are fitted an entrance, e , and an exit cannula, a. 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 artery of a horse. At a 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 , b , with a long index, b, projects into the tube, i. 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. Dromograph. A, B, tube inserted in artery; C, lateral tube connected with a manometer; b, index moving in a caoutchouc membrane, a ; G handle. Ill, curve obtained by dromograph. 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. — : ( 1 ) Division of Vessels. — In estimating the velocity of the blood, it is important 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 (. 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 quantity of blood must pass through every section of the circulatory system, through the pulmonic as well as through the Fig. 1 1 3. Scheme of the sectional area. A, arterial, and V, venous orifice. 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. (jE. H. Weber) ; man — 0.6 to 0.9 (C. Vierordt). 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. Donders 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 mean 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 (1) the vis a tergo (J. e ., the action of the heart), and (2) on the amount of the resistance at the periphery (dilatation or contraction of the small vessels) (C. Ludwig and Dogiel). 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 every pulse beat 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 to than the velocity during the diastole. The variations in the velocity caused by the heart beat are recorded in Fig. 1 1 2, 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 retards the velocity in the arter- ies, every expiration aids it somewhat ; but the value of these agencies is very small. If we compare what 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 artificial respiration. When artificial respiration is interrupted, the blood stream becomes slower ( Dogiel ). If the suspension of respiration lasts somewhat longer, the current is again accelerated on account of the dyspnoeic 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. (1) There are regular variations in the large veins near the heart ( Valsalva) due to the respiration and the movements of the heart (§ 50 and 60). (2) Irregular variations due to pressure , e. g., from contracting muscles (§ 87), 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 extended 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. 91. 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 blood 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 182 grammes or 6 oz.) of blood was discharged into the aorta; this, therefore, must be the capacity of the left ventricle (compare g 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 (1829) 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 from 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. Vierordt (1858) improved this method by placing under the corresponding vein of the opposite side a rotating disk, on which was fixed a number 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 samples of blood after they have stood for a time. The duration of the circulation is as follows : — Horse, . . . .31.5 seconds. Dog, .... 16.7 “ Rabbit, , . . 7.79 “ Hedgehog, 7.61 . . . seconds. Cat, 6.69 “ Goose, 10.86 “ Duck, .... 10.64 seconds. Buzzard, . . . 6.73 “ 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 : (1) The mean time required for the circulation is accomplished during 27 heart beats, i. 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 metartarsal 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 ( outlines of fully developed squamous epithelium ; b, alveolar wall ; c, young epithelial cell losing its granular appearance ; ^aggregation of young epithelial cells germinating. stomata ” seem to exist in the cement substance, and are most obvious in distended alveoli [Klein). They open into the lymph-canalicular system of the alveolar wall ( Klein), and through them the lymph corpuscles, which are always to be found on the surface of the air vesicles, migrate, and carry with them into the lymphatics particles of carbon derived from the air.] In the alveolar walls is a very dense plexus of fine capillaries (Fig. 127, e), which lie more toward the cavity of the air vesicle ( Rainey ), being covered only by the epithelial lining of the air cells. Between two adjacent alveoli there is only a single layer of capillaries (man), and on the boundary line between two air cells the course of the capillaries is twisted, thus projecting sometimes into the one alveolus, sometimes into the other. [The number of Alveoli is stated to be about 725 millions, a result obtained by measuring the size of the air vesicles and ascertaining the amount of air in the lung after an ordinary inspiration, and determining how much of this air is in the air vesicles and bronchi respectively. The superficial area of the air vesicles is about 90 square metres, or 100 times greater than the surface of the body (.8 to .9 sq. metre) ( Rosenthal ).] The Blood vessels of the lung belong to two different systems : (A) Pulmonary vessels (lesser circulation). The branches of the pulmonary artery accompany the bronchi and are closely applied to them. [As they proceed they branch, but the branches do not anastomose, and ultimately they terminate in small arterioles which supply several adjacent alveoli, each arteriole splitting up THE PLEURA OF THE LUNG. 187 into capillaries for several air cells (Fig. 127, v, c ). An efferent vein usually arises at the opposite side of the air cells and carries away the purified blood from the capillaries. In their course these veins unite to form the pulmonary veins, which are joined in their course by a few small bronchial veins ( Zuckerkandl ). The veins usually anastomose in the earlier part of their course, while the corresponding arteries do not.] Although the capillary plexus is very fine and dense, its sectional area is less than the sectional area of the systemic capillaries, so that the blood stream in the pulmo- nary capillaries must be more rapid than that in the capillaries of the body generally. The pulmo- nary veins, unlike veins generally, are collectively narrower than the pulmonary artery (water is given off in the lung), and they have no valves. [The pulmonary artery contains venous blood, and the pulmonary veins pure or arterial blood.] (B) The bronchial vessels represent the nutrient system of the lungs. They (1-3) arise from the aorta (or intercostal arteries) and accompany the bronchi without anastomosing with the branches of the pulmonary artery. In their course they give branches to the lymphatic glands at the hilum of the lung, to the walls of the large blood vessels (vasa vasorum), the pulmonary pleura, the bronchial walls, and the interlobular septa. The blood which issues from their capillaries is returned Fig. 127. Semi-diagrammatic representation of the air vesicles of the lung, v, v, blood vessels at the margins of an alveolus ; c, c, its blood capillaries ; E, relation of the squamous epithelium of an alveolus to the capillaries in its wall ; f, alveolar epithelium shown alone; e, e, elastic tissue of the lung. — partly by the pulmonary veins — hence, any considerable interference with the pulmonary circula- tion causes congestion of the bronchial mucous membrane, resulting in a catarrhal condition of that membrane. The greater part of the blood is returned by the bronchial veins which open into the vena azygos, intercostal vein, or superior vena cava. The veins of the smaller bronchi (fourth order onward) open into the pulmonary veins, and the anterior bronchial also communicate with the pul- monary veins ( Zuckerkandl ). [The Pleura. — Each pleural cavity is distinct, and is a large serous sac, which really belongs to the lymphatic system of the lung. The pleura consists of two layers, visceral and parietal. The visceral pleura covers the lung ; the parietal portion lines the wall of the chest, and the two layers of the corresponding pleura are continuous with one another at the root of the lung. The visceral pleura is the thicker, and may readily be separated from the inner surface of the chest. Structurally, the pleura resembles a serous membrane, and consists of a thin layer of fibrous tissue covered by a layer of endothelium. Under this layer, or the pleura proper, is a deep or sub-serous layer of looser areolar tissue, containing many elastic fibres. The layer of the pleura pulmonalis of some animals, as the guinea pig, contains a network of non-striped muscular fibres ( Klein ). Over the lung it is 188 THE LYMPHATICS OF THE LUNG. also continuous with the interlobular septa. The interlobular septa (Fig. 128, e) consist of bands of fibrous tissue separating adjoining lobules, and they become continuous with the peri-bronchial connective tissue entering the lung at its hilum. Thus the fibrous framework of the lung is continu- ous throughout the lung, just as in other organs. The connection of the sub-pleural fibrous tissue with the connective tissue within the substance of the lung, has most important pathological bearings. The interlobular septa contain lymphatics and blood vessels. The endothelium covering the parietal layer is of the ordinary squamous type, but on the pleura pulmonalis the cells are less flattened, more polyhedral, and granular. They must necessarily vary in shape with changes in the volume of the lung, so that they are more flattened when the lung is distended, as during inspiration {Klein). The pleura contains many lymphatics, which communicate by means of stomata with the pleural cavity.] [The Lymphatics of the lung are numerous and are arranged in several systems. The various air cells are connected with each other by very delicate connective tissue, and according to J. Ar- nold in some parts this interstitial tissue presents characters like those of adenoid tissue ; so that the lung is traversed by a system of juice canals or “ Saft-canalchen.”] [In the deep layer of the Fig. 128. pleura, there is (a) sub-pleural plexus of lymphatics partly derived from the pleura, but chiefly from the lymph-canalicular system of the pleural alveoli. Some of these branches proceed to the bronchial glands, but others pass into thei nterlobular septa, where they join ( b ) the perivascular lymphatics which arise in the lymph-canalicular system of the alveoli. These trunks, provided with valves, run alongside the pulmonary artery and vein, and in their course they form frequent anastomoses. Special vessels arise within the walls of the bronchi and occur chiefly in the outer coat of the latter, constituting (c) the peri-bronchial lymphatics, which anastomose with b. The branches of these two sets run toward the bronchial glands. Not unfrequently (cat) masses of adenoid tissue are found in the course of these lymphatics {Klein).] The lymph-canalicular system and the lymphatics become injected when fine colored particles are inspired, or are introduced into the air cells artificially. The pigment particles pass through the semi-fluid cement substance into the lymph-canalicular system and thence into the lymphatics ( v . Wittich ) ; or, according to Klein , they pass through actual holes or pores in the cement (p. 186).] [This pigmentation is well seen in coal miner’s lung or anthracosis, where the particles of carbon pass into and are found in the PHYSICAL PROPERTIES OF T 1 IE LUNGS. 189 lymphatics. Sikorski and Kiittner showed that pigment reached the lymphatics this way during life. If pigment, China ink, or indigo carmine be introduced into a frog’s lung, it is found in the lymphatic system of the lung. Ruppert, and also Schotielius, showed that the same result occurred in dogs after the inhalation of charcoal, cinnabar, or precipitated Berlin blue, and von Ins after the inhalation of silica. A. Schestopal used China ink and cinnabar suspended in ^ per cent, salt solution.] Excessively fine lymph canals lie in the wall of the alveoli in the interspaces of the capillaries, and there are slight dilatations at the points of crossing ( Wydwozoff ). According to Pierret and Renaut every air cell of the lung of the ox is surrounded by a large lymph space, such as occurs in the salivary glands. When a large quantity of fluid is injected into the lung it is absorbed with great rapidity ; even blood corpuscles rapidly pass into the lymphatics. [Nothnagel found that, if blood was sucked in the lung of a rabbit, the blood corpuscles were found within the interstitial connective tissue of the lung after 3^ to 5 minutes, from which he concludes that the communications between the cavity of the air cells and the lymphatics must be very numerous.] The superficial lymphatics of the pulmonary pleura communicate with the pleural cavity by means of free openings or stomata (AT ein), and the same is true of the lymphatics of the parietal pleura, but these stomata are confined to limited areas over the diaphragmatic pleura. [The lymph- atics in the costal pleura occur over the intercostal spaces and not over the ribs [Dybkowski).] The large arteries of the lung are provided with lymphatics which lie between the middle and outer coats ( Grancher ). [The movements of the lung during respiration are most important factors in moving the lymph onward in the pulmonary lymphatics. The return of the lymph is prevented by the presence of valves.] [The Nerves of the lung are derived from the anterior and posterior pulmonary plexuses, and consist of branches from the vagus and sympathetic. They enter the lungs and follow the distribu- tion of the bronchi, several sections of nerve trunks being usually found in a transverse section of a large bronchial tube. These nerves lie outside the cartilages, and are in close relation with the branches of the bronchial arteries. Medullated and non-medullated nerve fibres occur in the nerves, which also contain numerous small ganglia ( Reniak , Klein , Stirling). In the lung of the calf these ganglia are so large as to be microscopic. The exact mode of termination of the nerve fibres within the lung has yet to be ascertained in mammals, but some fibres pass to the bronchial muscle, others to the large blood vessels of the lung, and it is highly probable that the mucous glands are also supplied with nerve filaments. In the comparatively simple lungs of the frog, nerves with numerous nerve cells in their course are found [Arnold, Stirling ), and in the very simple lung of the newt, there are also numerous nerve cells disposed along the course of the intra-pulmonary nerves. Some of these fibres terminate in the uniform layer of non -striped muscle which forms part of the pulmonary wall in the frog and newt, and others end in the muscular coat of the pul- monary blood vessels [Stirling). The functions of these ganglia are unknown, but they may be compared to the nerve plexuses existing in the walls of the digestive tract.] The Function of the Non-striped Muscle of the entire bronchial system seems to be to offer a sufficient amount of resistance to increased pressure within the air passages ; as in forced expiration, speaking, singing, blowing, etc. The vagus is the motor nerve for these fibres, and according to Longet (1842), the “lung- tonus” during increased tension depends upon these muscles. It is not proved to what extent bronchial (spasmodic) asthma depends upon contraction of these muscular fibres due to stimulation of the vagus. [Effect of Nerves. — By connecting the interior of a small bronchus with an oncograph ($ 103) in the case of curarized dogs (the thorax being opened), Graham Brown and Roy found that sec- tion of one vagus causes a marked expansion of the bronchi of the corresponding lung, while stimulation of the peripheral end of a divided vagus causes a powerful contraction of the bronchi of both lungs. Stimulation of the central end of one vagus, the other being intact, also causes a contraction (feebler) under the same circumstances. Especially in etherized dogs, expansion and not contraction results. If both vagi be divided, no effect is produced by stimulation of the central end of either vagus. It seems plain that the vagi contain centripetal or afferent fibres, which can cause both expansion and contraction of the bronchi. Asphyxia causes contraction provided the vagi are intact, but none if they are divided, although in etherized dogs expansion frequently occurs, while stimulation of the central end of other sensory nerves has very rarely any, or if any, but a slight effect on the calibre of the bronchi, so that in the dog, the only connection between the cere- bro-spinal centres and y the bronchi is through the vagi]. Chemistry. — In addition to connective, elastic, and muscular tissue, the lungs contain lecithin, inosit, uric acid (taurin and leucin in the ox), guanin, xanthin (?), hypoxanthin (dog) —soda, pot- ash, magnesium, oxide of iron, much phosphoric acid, also chlorine, sulphuric and silicic acids — in diabetes sugar occurs — in purulent infiltration glycogen and sugar — in renal degeneration urea, oxalic acid, and ammonia salts ; and in diseases where decomposition takes place, leucin and tryosin. [Physical Properties of the Lungs. — The lungs, in virtue of the large amount of elastic tissue which they contain, are endowed with great elasticity, 190 MECHANISM OF RESPIRATION. so that when the chest is opened they collapse. If a cannula with a small lateral opening be tied into the trachea of a rabbit’s or sheep’s lungs, the lungs may be inflated with a pair of bellows or elastic pump. After the artificial inflation, the lungs, owing to their elasticity, collapse and expel the greater part of the air. As much air remains within the light spongy tissue of the lungs, even after they are removed from the body, a healthy lung floats in water. If the air cells are filled with pathological fluids or blood, as in certain diseased conditions of the lung (pneumonia), then the lungs, or parts thereof, may sink in water. The lungs of the foetus, before respiration has taken place, sink in water, but after respiration has been thoroughly established in the child, the lungs float. Hence, this hy- drostatic test is largely used, in medico-legal cases, as a test of the child having breathed. If a healthy lung be squeezed between the fingers, it emits a peculiar and characteristic fine, crackling sound, owing to the air within the air cells. A similar sound is heard on cutting the vesicular tissue of the lung. The color of the lungs varies much ; in a young child it is rose-pink, but afterward it becomes darker, especially in persons living in towns or a smoky atmosphere, owing to the deposition of granules of carbon. In coal miners the lungs may become quite black.] [Excision of the Lung. — Dogs recover after the excision of one entire lung, and they even survive the removal of portions of lung infected with tubercle ( Biondi ).] 107. MECHANISM OF RESPIRATION. — The mechanism of respi- ration consists in an alternate dilatation and contraction of the chest. The dila- tation is called inspiration, the contraction, expiration. As the whole external surface of both elastic lungs are applied directly and in an air-tight manner, by their smooth, moist, pleural investment, to the inner wall of the chest, which is covered by the parietal pleura, it is clear that the lungs must be distended with every dilatation of the chest, and diminished by every contraction thereof. These movements of the lungs, therefore, are entirely passive, and are dependent on the thoracic movements ( Galen .) On account of their complete elasticity and their great extensibility, the lungs are able to accommodate themselves to any variation in the size of the thoracic cavity, without the two layers of the pleura becoming separated from each other. As the capacity of the non-distended chest is greater than the volume of the col- lapsed lungs after their removal from the body, it is clear that the lungs, even in their natural position within the chest, are distended, /. c. c. [100- 1 30 cubic inches]. £ (2) Reserve or Supplemental Air is the volume of air which < can be expelled from the chest after a normal quiet expiration. It is < equal to 1240-1800 c. c. [100 cubic inches]. (3) Tidal Air is the volume of air which is taken in and given £ out at each respiration. It is equal to 500 cubic centimetres [20 £ cubic inches]. < (4) Complemental Air is the volume of air that can be forcibly £ inspired over and above what is taken in at a normal respiration. It £ amounts to about 1500 c. c. [100-130 cubic inches]. f* (5) Vital Capacity is the term applied to the volume of air which can be forcibly expelled from the chest after the deepest possible inspiration. It is equal to 3772 c. c. (or 230 cubic inches) for an Englishman ( Hutchinson ;), and 3222 for a German ( Htzser ). Hence, after every quiet inspiration, both lungs con- tain (1 | 2 + 3) = 3000 to 3900 c.cm. [220 cubic inches]; after a quiet expiration (1 +2)= 2500 to inches]. So that about ^ to \ of the air in the lungs is subject to renewal at each respiration. Estimation of Vital Capacity. — The esti- mation of the vital capacity was formerly thought to be of great consequence, but at the present time not much importance is attached to it, nor is it fre- quently measured in cases of disease. It is esti- mated by means of the spirometer of Hutchinson. This instrument (Fig. 1 29), consists of a graduated cylinder filled with water and inverted like a gasometer over water, and balanced by means of a counterpoise. Into this cylinder a tube projects, and this tube is connected with a The person to be experimented the deepest possible inspiration, closes his nostrils, and breathes forcibly into the mouth piece of the tube. After doing so the tube is closed. The cylinder is raised by the air forced into it, and after the water inside and’ outside the cylinder is equalized, the height to which the cylinder is raised indicates the amount of air expired , or the vital or respiratory capacity. In a man of average height, 5 feet 8 inches, it is equal to 230 cubic inches. The volume of this COMPLEMENTAL TIDAL AIR, 20 RESERVE AIR RESIDUAL AIR IOO 3400 c.cm Fig [200 cubic 129. and mouth piece, upon takes Scheme of Hutchinson’s Spirometer. 192 TIME OCCUPIED BY THE RESPIRATORY MOVEMENTS. The following circumstances affect the vital capacity : — (1) The Height. — Every inch added to the height of persons between 5 and 6 feet, gives an increase of the vital capacity = 130 c.c. [8 cubic inches.] (2) The Body weight. — When the body weight exceeds the normal by 7 per cent., there is a diminution of 37 c.c. of the vital capacity for every kilo, of increase. (3) Age. — The vital capacity is at its maximum at 35; there is an annual decrease of 23.4 c.c. from this age onward to 65, and backward to 15 years of age. (4) Sex. — It is less in women than men, and even where there is the same circumference of chest, and the same height in a man and a woman, the ratio is 10 : 7. (5) Position. — More air is respired in the erect than in the recumbent position. (6) Disease. — Abdominal and thoracic diseases diminish it. 109. NUMBER OF RESPIRATIONS. — In the adult, the number of respirations varies from 16 to 24 per minute, so that about 4 pulse beats occur during each respiration. The number of respirations is influenced by many conditions : — (1) The Position of the Body. — In the adult, in the horizontal position, Guy counted 13, while sitting 19, while standing 22, respirations per minute. (2) The Age. — Quetelet found the mean number of respirations in 300 individuals to be Year. Respirations. Year. Respirations. O to I, . . .... 44 ) Average 20 to 25, . . . . . . 18.7 ) Average 5 > • - .... 26 V Number per 25 to 30, . . . ... 16 Number per 15 to 20, . . .... 20 J Minute. 30 to 50, . . . . . . I8.I J Minute. (3) The State of Activity. — Gorham counted in children of 2 to 4 years of age, during stand- ing 32, in sleep 24, respirations per minute. During bodily exertion the number of respirations increases before the heart beats. [Very slight muscular exertion suffices to increase the frequency of the respirations.] [(4) The Temperature of the surrounding medium. — The respirations become more numerous the higher the surrounding temperature, but this result only occurs when the actual temperature of the blood is increased, as in fever. (5) Digestion. — There is a slight variation during the course of the day, the increase being most marked after mid-day dinner ( Vierordt). (6) The Will can to a certain extent modify the number and also the depth of the respirations, but after a short time the impulse to respire overcomes the voluntary impulse. (7) The Gases of the Blood have a marked effect, and so has the heat of the blood in fever.] [(8) In Animals — Mammals. Tiger, .... Per Min. .... 6 Lion, .... .... 10 Jaguar, .... . . 11 Panther, . . . .... 18 Cat, .... 24 Dog, .... .... 15 Dromedary, . . . . 11 Giraffe, . . . . . 8-10 Ox, . . . 15-18 Squirrel, . . . .... 70 Rabbit, . . . .... 55 Rat (waking), . .... 210 Rat (asleep), . .... 100 Rhinoceros, . . .... 6-10 Mammals. Per Min. Hippopotamus, .... 1 Horse, 10-12 Ass, 7 Birds. Condor 6 Sparrow 90 Pigeon 30 Siskin 100 Canary 18 Reptiles. Snake 5 Tortoise 12 Fish. Per Min. Raja 50 Torpedo 51 Perch 30 Mullet 60 Eel 50 Hippocampus 33 Invertebrata. Crab 12 Mollusca 14-65 (P. Perl).] [(9) In Disease. — The number may be greatly increased from many causes, e.g., in fever, pleurisy and pneumonia, some heart diseases, or in certain cases of alteration of the blood, as in aneemia ; and diminished where there is pressure on the respiratory centre in the medulla, in coma. It is important to note the ratio of pulse beats to respirations.] no. TIME OCCUPIED BY THE RESPIRATORY MOVE- MENTS. — The time occupied in the various phases of a respiration can only be accurately ascertained by obtaining a curve or pneumatogram of the respiratory movements. Methods. — (1) Vierordt and C. Ludwig transferred the movements of a part of the chest wall to a lever which inscribed its movements upon a revolving cylinder. Riegel (1873) constructed a “ double stethograph ” on the same principle. This instrument is so arranged that one arm of the VARIOUS FORMS OF STETHOGRAPHS. 193 lever may be applied in connection with the healthy side of a person’s chest, and the other on the diseased side. (2) An air tambour, such as is used in Brondgeest’s pansphygmograph (Fig. 131, A) may be used. It consists of a brass vessel, a , shaped like a small saucer. The mouth of the brass vessel is covered Fig. 130. with a double layer oi caoutchouc membrane, b, c, and air is forced in between the two layers until the external membrane bulges outward. This is placed on the chest, and the apparatus is fixed in position by means of the bands, d , d. The cavity of the tambour communicates by means of a caoutchouc tube, s, with a recording tambour, which inscribes its movements upon a revolving cyl- Fig. 131. A, Brondgeest’s tambour for registering the respiratory movements, b, c , inner and outer caoutchouc membranes ; a, the capsule; d , d, cords for fastening the instrument to the chest; S, tube to the recording tambour ; B, nor- mal respiratory curve obtained on a vibrating plate (each vibration = 0.01613 sec.). inder. Every dilatation of the chest compresses the membrane, and thus the air within the tambour is also compressed. [A somewhat similar apparatus is used by Burdon- Sanderson, and called a “ recording stethograph.” By it movements of the corresponding points on opposite sides of the chest can be investigated.] !3 194 TIME OCCUPIED BY THE RESPIRATORY MOVEMENTS. (3) A cannula or oesophageal sound may be introduced into that portion of the oesophagus which lies in the chest, and a connection established with Marey’s tambour, p. 85 {Rosenthal). [This method also enables one to measure the intra-thoracic pressure .] ^Marey’s Stethograph or Pneumograph. — [There are two forms of this instrument, one modi- fied by P. Bert and the more modern form (Fig. 130). A tambour ( h ) is fixed at right angles to a thin elastic plate of steel (f). The aluminium disk on the caoutchouc of the tambour is attached to an upright ( 6 ), whose end lies in contact with a horizontal screw (£-). Two arms \d, c ) are attached to opposite sides of the steel plate, and to them the belt (c d ). On the opposite side of the figure, it is evident that when the rods are raised, the line, g h, is shortened (i k < ( g h , direction of the external intercostals), l m is length- ened (/ m (T-T,) m(T — Tj) This is a subject which has been very slightly investigated. J. Rosenthal, in his researches, used an ice calorimeter ($ 206). II. Calorimetry is more important for determining the amount of he ai produced in a given ti?ne by the body as a whole, or by its individual parts. Lavoisier and Laplace made the first calorimetic observations on animals in 1783, by means of an ice calorimeter; a guinea pig melted 13 oz. of ice in ten hours. Crawford, and afterward Dulong and Despretz (1824), used Rumford’s water calorimeter, which is similar to the one already described, viz., of Favre and Silbermann. Small animals are placed in the inner thin-walled copper chamber (K), which is placed in a water bath surrounded on all sides by some non-conducting material. We require to know the amount of water, and its original temperature. The number of calories is obtained from the increase of the temperature at the end of the experiment, which lasts several hours. The air is supplied to the animal through a special apparatus resembling a gasometer. The amount of C 0 2 in the gases evolved is estimated chemically. According to Despretz, a bitch forms 14,610 heat units per hour — i. e., 393,000 in twenty-four hours. Other things being equal, a man seven times heavier than this would produce in twenty-four hours about 2,750,000 calories. Senator found that a dog weighing 6330 grms. produced 15,370 calories, and excreted at the same time 367 grms. C0 2 . The first calorimetric experiments on man were made by Scharling (1849). Liebermeister estimated the amount of heat given off by a man placed in a cold bath, which was surrounded with a woolen covering. Leyden placed a lower limb in the calorimeter, whereby 6000 grms. water were raised i° C. in an hour. If we assume that the total superficial area of the body is fifteen times greater than that of the leg, the human body would produce 2,376,000 calories in twenty-four hours. 212. THERMAL CONDUCTIVITY OF ANIMAL TISSUES.— The thermal con- ductivity of animal tissues is of special interest in connection with the skin and subcutaneous fatty tissue. The fatty layer under the skin, more especially in the whale, walrus, and seal, forms a pro- tective covering, whereby the conduction of heat from internal organs is rendered almost impossible. Investigations upon this subject, however, are few. Griess (1870) attempted to estimate the thermal conductivity by heating one part of the tissue, and determining when and in what direction pieces of wax placed on the tissue to be investigated began to melt. He investigated the stomach of the sheep, the bladder, skin, hoof, horn, and bones of an ox, deer’s horn, ivory, mother-of-pearl, shell of haliotis. He found that fibrous tissues conducted heat more readily in the direction of their fibres than at right angles to the course of the fibres. Hence, the figures obtained from the melted wax were usually elliptical. Landois has made similar observations, and he finds that tissues con- duct better in the direction of their fibres. After bones, blood clot was the best conductor, then followed spleen, liver, cartilage, tendon, muscle, elastic tissue, nail and hair, bloodless skin, gastric mucous membrane, washed fibrin. It is specially interesting to note how much better skin con- taining blood in its blood vessels conducts, compared with bloodless skin. Hence little heat is given off from a bloodless skin, while congested skin conducts and gives off much more heat. 358 VARIATIONS OF THE MEAN TEMPERATURE. Like all other substances, the human body is enlarged by heat. A man weighing 60 kilos., and whose temperature is raised from 37 0 C. to 40° C., is enlarged about 62 cubic centimetres. Con- nective tissue (tendon) is extended by heat, while elastic tissue and the skin, like caoutchouc, are contracted ( Lombard and Walton). 213. VARIATIONS OF THE MEAN TEMPERATURE.— (1) General Climatic and Somatic Influences. — In the tropics the mean tem- perature of the body is about y^ 0 C. higher than in temperate climates, where again it is several tenths of a degree warmer than in cold climates (y. Davy ) ; but this has recently been denied by Boileau and Pinkerton. This difference is comparatively trivial, when we remember that a man is subjected to a variation of over 40° C. in passing from the equator to the poles. Observations on more than 4000 persons show that when a person goes from a warm to a cold climate his temperature is but slightly diminished, but when he goes from a cold to a warm climate his temperature rises relatively considerably more. In the temperate zone, the temperature of the body during a cold winter is usually o.i° to 0.3 0 C. lower than it is on a warm summer day. The elevation of a place above sea-level has no obvious effect on the temperature of the body. There seems to be no difference in different races, nor in the sexes, other conditions being the same. Persons of powerful physique and constitution are said to have generally a slightly higher temperature than feeble, weak, ansemic persons. (2) Influence of the General Metabolism. — As the formation of heat de- pends upon the transformation of chemical compounds, whose chief final pro- ducts, in addition to H 2 0, are C0 2 and urea, the amount of heat formed must go pari pas su with the amount of these excreta. The more rapid metabolism which sets in after a full meal causes a rise of temperature to several tenths of a degree (“ Digestion fever”). As the metabolism is much diminished during hunger, this explains why the mean temperature in a fasting man is 36.6°, while it is 37-17° on ordinary days ( Lichienfels and Frohlich ) (§ 237). Jiirgensen also found that the temperature fell on the first day of inanition (although there was a temporary rise on the second day). In experiments made upon starving animals, the temperature at first fell rapidly, then remained constant for a considerable time, while during the last days it fell considerably. Schmidt starved a cat: on the 15th day the temperature was 38°.6 ; on the 1 6th, 38°. 3; 17th, 37°.64; 18th, 35°.8; 19th (death) = 33°.o. Chossat found that starving mammals and birds had a temperature 16 0 C. below normal on the day of their death. (3) Influence of Age. — Age has a decided effect upon the temperature of the body. The extent of the general metabolism is in part an index of the heat of the body at different ages, but it is possible that other as yet unknown influences are also active. Age. Mean Temperature at the Ordinary Temperature. Normal Limits. Where Measured. Newly-born, 3745 ° C. 37 - 35 - 37 - 55 ° C. Rectum. 5-9 y ear » 3772 36.87-37.62 Mouth and Rectum. 15-20 “ 37-37 36.12-38.1 Axilla. 21-30 “ 37-22 25-30 “ 36.91 36 . 25 - 37-5 t< 31-40 “ 37 -i a 41-50 “ 36.87 a 51-60 “ 36.83 tt 80 “ 3746 Mouth. Newly-born Animals exhibit peculiarities owing to the sudden change in their conditions of existence. Immediately after birth, the infant is 0.3 0 warmer than the vagina of the mother, viz., 37.86°. A short time after birth, the tem- perature falls 0.9°, while twelve to twenty-four hours afterward it has risen to the normal temperature of an infant, which is 37.45°. Several irregular variations VARIATIONS OF THE MEAN TEMPERATURE. 359 occur during the first weeks of life. During sleep, the temperature of an infant falls 0.34 0 to 0.56°, while continued crying may raise it several tenths of a degree. Old people, on account of their feeble metabolism, produce little heat ; they become cold sooner, and hence ought to wear warm clothing to keep up their temperature. Fig. 218. Zv;.; Z tr , : - O/tJ- rz ■ k ~ — ■ - m .. — ■ . — —J ■— 1 — . ■ ■ - ■ ' ~ ' ■ T • ‘ --Z ZT / , ■/ _ , ZZ ■ rr __ i 1 2 s ' / "• / t2L ■ ■ [> ■ \ fv ' 1 1 / ' y i \ \ t [ > ~ .. 1 21 x ~~ ; ‘ . ,/• > >■ v ; _U- ' w ■■ V ■ . ■ 7| . n ... ;■ •- • N ■ ... - T • ■ . .. . ,L°_ . z - - 1 <3D-|1 T 9 10 .11 4 2 1 ! 2 :..5 ; . 1 ' ♦ 7 8 9 ' W: 11 1 2 1 2 " T~ 4 ZT H 3 Morning. Mid-day. Evening. Night. Morning. Variations of the daily temperature in health during twenty-four hours. L after Liebermeister ; J after J iirgensen. (4) Periodical Daily Variations. — In the course of twenty-four hours there are regular periodic variations in the mean temperature, and these occur at all ages. As a general rule, the temperature continues to rise during the day (maximum at 5 to 8 p.m.), while it continues to fall during the night (minimum 2 to 6 a.m.). The mean temperature occurs at the third hour after breakfast (. Lichtenfels and Frohlich). Time. Barensprung. J. Davy. Hallmann. Gierse. Jiirgensen. Jager. Morning . . 5 36.7 366 36.9 6 36.68 36.7 36.4 37-i 7 36.94* 36.63 36.98 36.7* 36.5* 37-5* 8 37-i6* . . 36.80* 37.08* 36.8 36.7 37-4 9 36.89 36.9 36.8 37-5 10 37.26 ™ i A = 37-36 37-23 37-o 37-o 37-5 ii . . 36.89 37-2 37-2 37-3 Mid-day. . 12 36.87 37-3* 37-3* 37-5* I 36-83 37.21 37.13 37-3 37-3 37-4 2 37-05 37.50* 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 6 6 K = 3683 37-29 37-5 37-6 37-4 7 37-43 i l A = 36.50* 37-31* 37-5* 37-6* 37-3 8 . . 37-4 37-7 37- 1* 9 37.02* 37-4 37-5 36.9 10 37-29 37-3 37-4 36.8 11 36.85 36.72 36.70 36.81 37-2 37-i 36.8 Night. . .12 37-i 36.9 36.9 1 36.65 36.44 37-o 369 36.9 2 369 36.7 36.8 3 . , 36.8 367 36.7 4 36.31 • * 36.7 36.7 36.7 [* Indicates taking of food.] 360 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 0 in the rectum in health. A daily mean of more than 37.8° is a “fever temperature,” while a mean under 37.0 0 C. is regarded as a “ collapse temperature.” According to Eichtenfels 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 Jurgensen. 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 ( Krieger ). 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 (. Liebermeister ). 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 9 to 10 a.m. This is fol- lowed by a slow rise, which reaches a high maximum after dinner ; it falls between 1 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 ( Romer ). (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 y 2 to 2 0 C. Very long-continued hemorrhage (dog) causes it to fall to 31 0 or 29 0 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 and Strieker ) (§ 102). (6) Many poisons diminish the temperature, e. g., chloroform ( Scheinesson ), 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 (Hogyes), laudanin (F. A. Falck). Curara (muscarin — Hogyes ), laudanosin (F. A. Falck ), 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 0 C. (rectum); the lowest temperature observed, and life retained, in a drunken person, was 24° C. ( Reinke , Nicolaysen). REGULATION OF THE TEMPERATURE. 361 The temperature is increased in fever , 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 mechanical 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 combustion 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: — (1) The temporary application of moderate cold raises the bodily temperature , while heat, similarly applied to the external surface, lowers it (§222 and 224). (2) Cooling of the surroundings increases the amount of C 0 2 excreted, by increasing the production of heat (. Liebermeister , Gilder meister), while the O consumed is also increased simultaneously ; heating the surrounding medium di- minishes the C 0 2 (§ 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 increased 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 CO 2 given off, when the surroundings were cooled from 38° to 6° or 7 0 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. Pfliiger found that a rabbit which was dipped in cold water used more O and excreted more C 0 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 C 0 2 does not go hand in hand with the formation of C 0 2 ,so that the increased excretion of C 0 2 in a cold bath is, perhaps, due to more complete expiration, and Berthelot has proved that the formation of C 0 2 is not a certain test of the amount of heat produced. If mammals be placed in a warm bath, which is 2° to 3 0 higher than their own temperature, the excretion of C 0 2 and the consumption of O are increased, owing to the stimulation of their metabolism {Pfluger), while the excretion of urea is also increased in animals (Naunyri) and in man ( Schleich ) (g 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 (P/ttiger). After poisoning with curara, which paralyzes voluntary motion, this regulation of the heat falls to a minimum ( Rohrig and Zuntz ) [while the 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, i. e ., 1.36 to 1.60 per minute. (1) 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 1 grm. of water at ioo° C., is equal to that required to heat 10 grms. from o° to 53.67° C. The sweat as secreted is at 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 vessels. 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 systematic 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 , du 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 160 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 — 108.5 — no—: 137 - 5 - Temperature in C.° 37° — 38 0 — 39 0 — 40 0 — 41 0 — 42 0 . (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 v/hen the air breathed is heated to 54 0 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 0 C. to 37 0 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. t by using a fan. Stimulation of the central end of a sensory nerve (sciatic) increases the surface temperature and diminishes the internal temperature ( Ostroumow , Mitropolsky). 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 weigh 3 to 4 kilos,, and winter ones 6 to 7 kilos. In connection with clothes, the following considerations are of importance : — ( 1 ) 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 per- meability 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, buck- 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, i. e ., 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 produced by a man. (1) Heat Income. — ( a ) A healthy adult, weighing 82 kilos., expires in twenty- four hours 878.4 grms. C 0 2 ( Scharling ). The combustion of the C therein into C 0 2 produces ( b ) But he takes in more O than reappears in the C 0 2 ; the excess is used in oxidation processes, e. g., for the formation of H 2 0 , by union with H, so that 13,615 grms. H will be oxidized by the excess of O, which gives (c) About 25 per cent, of the heat must be referred to sources other than combustion ( Dulong ), so that the total 2,732,000 calories are actually sufficient to raise the temperature of an adult weighing 80 to 90 kilos., from io° to 38 or 39 0 C., i. e., to a normal temperature. (2) Heat expenditure. — (a) Heating the food and drink, which have a mean temperature of 12 0 C. 70,157 cal (1 b ) Heating the air respired = 16,400 grms., with an initial temperature of 20° C. 70,032 cal ( When the temperature of the air is o°, 140,064 cal. = 5.2 per cent.) (r) Evaporation of 656 grms. water by the lungs, 397,536 cal (d) The remainder given off by radiation and evaporation of water by the skin, (77.5 per cent, to) amount of heat 1, 73°, 76o cal. 318,600 cal. 2,049,360 cal. = 2,732,000 cal. =. 2.6 per cent. = 2.6 per cent. == 14.7 per cent. = 80.1 per cent. (B) According to Dulong. — (1) 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 1 grm. C = 8040 heat units, and 1 grm. H = 34,460 heat units, it would be easy to determine the amount of heat were the C simply converted into C 0 2 and the H into H 2 0 . But Dulong omitted the H in the carbohydrates (e. g ., grape sugar = C 6 H 12 0 6 ) 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 problematical. 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 faeces contain still unconsumed . . . 29 8 “ 6.3 Remainder to be burned 251.4 and 12.56 As 1 grm. C =8040 heat units and 1 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 34460 = 432,818 ( 2,464,130 heat units. (2) Heat expenditure : — 1. 1900 grms. are excreted daily by the urine and faeces, and they are 25 0 warmer than the food 2. 13,000 grms. air are heated (from 12 0 to 27 0 C.) (heat capacity of the air = 0.26) 3. 330 grms. water are evaporated by the respiration (1 grm. = 582 heat units) . . . ' 4. 660 grms. water are evaporated from the skin Total Remainder radiated and conducted from the skin H). Per cent, of Heat units. the excreta. 47.500 1.8 84.500 3-5 192,060 7.2 384,1*0 14-5 708,180 I,79I,8lO 72 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 i grm. of the following substances yielded — Albumin 499 s 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 1 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 . . “ food free from N “ mixed diet . . . “ during hunger . 2,779,524 heat units. 2,059,506 2,200,000 “ 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 : — w : W = Vp^\ l/'P“ 2 (where W = 2,732,000; P = 82 kilos. [W : ^// 2 = 144,75] \ P = body weight of the person to be investigated, and w represents the heat production which is required). 3 It is highly desirable that W: j// 2 (= m) was ascertained as a mean from a large number of observations, that the heat production for any body weight p would be 3 — w = m j// 2 . (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 (g 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 1 heat unit (energy required to raise 1 gramme of water i° 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 experiment 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. e., 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 (Him). In good steam engines only 1 $, and in the very best of the potential energy is changed into mechanical energy, while 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 2^ 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. As 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, 1, b). Take the following example : Hirn (1858) remained passive , 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 f 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 1 8° C. is moderately warm; “ at 25°-28° C., hot; “ above 28°, very hot. Water, at 18 0 C. is cold; “ from i 8°-29° C., cool ; “ “ 29°-35° C., warm ; “ “ 37. 5 0 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 0 C. (dangerous to life!); the hands may be plunged into water at 50.5 0 C., but not at 51-65° C., while at 6o° violent pain is produced. A person may remain for eight minutes in hot air at 127° C., and a tempera- ture of 1 32° C. has been borne for ten minutes ( Tillett , 1763). 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 blood 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 6o° C., the rectal temperature rises to 40. 7 0 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 hours about 2° C. ( Liebermeister ). A gradual increase of the temperature from 38.6° to 40. 2 0 C. causes the axillary temperature to rise to 39. o° within fifteen minutes. Rabbits placed in a warm box at 36° C. acquire a constant temperature of 42 0 C., and lose weight ; but if the temperature of the box be raised to 40°, death occurs, the body temperature rising to 45 0 C. [J. 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 [Roh rig). ( b ) Any other circumstances preventing heat from being given off by the skin ( Win - ternitz). (r) When the vasomotor centre is excited , causing all the blood vessels of the body — those of the skin included — to contract. This seems to be the cause of the rise of temperature after the transfusion of blood ( Landois ), 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 (g 102). Landois found that ligature of both carotids, and the axillary and crural arteries, caused a rise of i° 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 [J urgensen ). 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 0 to 44 0 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 regulating the balance of formation and expenditure of heat is disturbed. During fever the body is greatly incapacitated 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 : — (1) The increased temperature of the body (38° to 39 0 C., slight; from 39 0 to 41 0 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 stage, the tempera- ture is raised [Ant. de Haen , 1760). The congested, red skin is a good conductor of heat, while the pale, bloodless skin conducts badly; hence, the former feels hot to the touch ( v . Barenspi'ung — compare \ 212). The following table in °C and °F indicates generally the degree of fever: — 35 ° C. = 95 ° F. . . . . Collapse. 36 = 96.8 . . . . Low. 36.5 = 97-7 . • 37 = 98.6 . . . . Normal. 37-5 = 99-5 ) 3 « = 100.4 y . . . . Sub-febrile. 38.5 = 101.3J 39° C. = 102.2° F. \ . Moderate fever. 39-5 — IO3. 1 J 40 . High fever. 40-5 = 104.9 / 4 i = 105.8 . Hyperpyretic. Finlay son. ] 368 FEVER AND ITS PHENOMENA. (2) The increased production of heat (assumed by Lavoisier and Crawford) is proved by calorimetric 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 within 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 C 0 2 = 70 to 80 per cent. ( Leyden and FranTid ), while more O is consumed, although the respiratory quotient remains the same ( Zuntz ana Lilienfeld ). According to Dr. Finkler, the C 0 2 excreted shows greater variations than the O consumed. The excretion of urea is increased | to f. In dogs suffering from septic fever, Naunyn observed that the urea began to increase before the temperature rose, “ p 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 (g 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 ($ 214, I, 2), but the increase of the oxidation in a warm medium is very much greater than in the cold {D. Finkler). The amount of C 0 2 in the blood is diminished, but not at once after the onset even of a very severe fever ( 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 iy to 2^ 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. (< b ) During the hot stage the heat given off from the congested, red skin is greatly increased , but at the same time more heat is produced. Liebermeister assumes that a rise of 1, 2, 3, 4 0 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. Finkler ). 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, diminished digestive activity {\ 186, 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 ( Lewizky , Binz, Naunyn , Quincke, Arntz) ($ 213, 6). Toxic doses of the metallic salts act in the same way, while there is at the same time diminished formation of C 0 2 {Luchsinger). [Antipyretics or Febrifuges. — All methods which diminish abnormal temperature belong to this group. As the constant temperature of the body depends on (1 ) 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, i. 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 kairin 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 ( Obernier ), but soon a decided increase occurs. The respirations and pulse are increased, while the latter becomes irregular and weaker. The O absorbed and C 0 2 given off are diminished after six to eight hours ( Litten ), and death occurs after great fatigue, feebleness, spasms, secretion of saliva and loss of consciousness, when the bodily temperature has been increased 4 0 , 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 0 to 50° C. ; in birds, at 53 0 C., and in frogs, at 40° C. If mammals are suddenly placed in air at ioo° C., death occurs (in 15 to 20 min.) very rapidly, and with the same phenomena, while the bodily temperature rises 4 0 to 5 0 C. In rabbits, the body weight diminishes 1 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 ioo-no-132 0 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 i° to 2 0 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 0 C., death is almost certain to occur. Coagulation of the blood in 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-six to forty-eight hours {Litten). Cold-blooded Animals, if placed in hot air or warm water, soon have their temperature raised 6° to io° 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 0 C., or in water at 46° C. (Sacks). 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 6o° C. (Hoppe- Seyler). Several bacteria withstand a boiling temperature (Tyndall, Chamberland). 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 reflexly the production of heat ( Kernig ), and partly because, owing to the dilatation of the cutaneous vessels and the stretching of the skin, more heat is given off (Senator). 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 general 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- cular 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. — (1) 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). As the muscle coagulates, heat is produced (v. Wather, Fick). All conditions which cause rapid and intense coagulation of the muscles — e. g., spasms — favor a post-mortem rise of temperature (see g 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 post-tnortem. After the circulation is abolished, within a few minutes little heat is given off from the surface of the body, 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 ( Liebermeister ). The slight rise, when it occurs, is due to the stimulation of the skin causing reflexly a more rapid molecular trans- formation, and therefore a greater production of heat ( Liebermeister ), while the amount of heat given off is diminished, owing to contraction of the small cuta- neous vessels and the skin itself ( Jiirgensen , Senator). The continuous and intense application of cold causes a decrease of the temperature ( Currie ), 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 0 , 32 0 , 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 0 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 -j- 0.2 0 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 0 C., and suddenly cooled, it shivers, and there may be temporary diarrhoea. After two days the temperature rises 1.5 0 C., and albuminuria occurs. There are microscopic traces of interstitial inflammation in the kidneys, 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 foetus 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, owing 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 livid 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 affected. 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 0 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 mixture, gives rise to a series of characteristic phenomena (. A . Walther). If the animals (rabbits) are cooled so that the tem- perature (rectum) falls to 18 0 , 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 spasms ( Hor- vath ), the secretion of urine stops, and the liver is congested. The animal may 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 0 and under, the voluntary movements cease before the reflex acts (. Richet and Ron- deau). An animal cooled to 18 0 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 io° 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 0 C., and recovered them by artificial respiration and external warmth ; while Horvath cooled young animals to 5 0 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 (. Rumpf ) ; hence, drunken men are more liable to die when exposed to cold. Artificial Cold-blooded Condition. — Cl. 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 (C 7 . 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 ( Wegner). Hybernation presents a series of similar phenomena. Valentin found that hybernating animals become half awake when their bodily temperature is 28° C. ; at 18 0 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-pneumatic movement alone sustains the slight exchange of gases in the lungs (g 59). They cannot endure cooling to o° 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- born mammals resemble hybernating animals more closely in this respect than do adults. Cold-blooded Animals may be cooled to o°. 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 ( Kuhne ). 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 — ioo° C. [Frisch). Varnishing the Skin causes a series of similar phenomena. The varnished skin gives off a large amount of heat by radiation (Krieger), and sometimes the cutaneous vessels are greatly dilated [Laschkewitsch). Hence the animals cool rapidly and die, although the consumption of O is not diminished. If cooling be prevented ( Valentin, Schiff, Brunton) by warming them and keeping them in warm wool, the animals live for a longer time. The blood post-mortem 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 [v. Ziemssen). The addition of stimulating substances, e.g., salts, which cause dila- tation of the cutaneous vessels, facilitates the secretion of heat; even saltwater conducts heat better. If alcohol be given internally at the same time, it lowers the temperature. [b) Cold may be applied 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. (c) 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, i. e ., by a healthy reaction. 227. HEAT OF INFLAMED PARTS. — “Calor,” or heat, is reckoned one of the funda- mental phenomena of inflammation, 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, asserted that the arterial blood flowing to an inflamed part was cooler than the part itself; but v. Barensprung denies this, as J. Hunter did, and so does Jacobson, 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-chemical 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 ( van Helmont, Sylvius , Etlmiiller). 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 calorimetric observations were made by Lavoisier and Laplace. Comparative observations are given at § 207, and also under Hybernation (g 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 faeces, 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 put 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 : (1) Rain water, which most closely resembles distilled or chemically pure water, always contains minute quantities of C 0 2 , NH 3 , 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 C 0 2 ; the C() 2 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.” (3) The running- water of rivers usually contains much less mineral matter than spring water. Spring water floating on the surface rapidly gives off its C 0 2 , whereby many substances — e.g., lime — are thrown out of solution and deposited as insoluble precipitates. Gases. — Spring water contains little O, but much C 0 2 , the latter giving to it its fresh taste. Hence, vegetable organisms flourish in spring water, while animals requiring, as they do, much O, are but poorly represented in such water. Water flowing freely gives up C 0 2 , and absorbs O from the air, and thus affords the necessary conditions for the existence of fishes and other marine ani- mals. River water contains g 1 ^ to 2 ^ 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 0.0001 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 , /. ammonia, salicylic acid glycerine, and ethereal oil of mustard prevent the spontaneous coagulation. Fresh milk makes tincture of guaiacum blue, but boiled milk does not do so ( Schacht , C. Arnold). When milk is exposed to the air for a long time, it gives off C 0 2 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- Seyler, Kemmerich). According to Schmidt- Miil- heim, some of the casein becomes converted into peptone, but this occurs only in unboiled milk. Composition. — 100 parts of milk contain — Human. Cow. Goat. Ass. Water .... 86.23 86.85 89.OI Solids .... 12.39 13-77 I 3-52 IO.99 Casein . . . 3 - 9 2 I 1 .90 to 2.21 { 3-23 2-53 \ Albumin . . . / 1.26/ 3-57 Butter . . . . . 2.67 “ 4 - 3 o 4-50 4-34 1.85 Milk sugar . . • 315 “ 6 09 4-93 3-781 5-05 Salts .... 0.28 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. — Pfliiger and Setschenow found in 100 vols. of milk 5.01 to 7.60 C 0 2 ; o 09 to 0.32 O; 0.70 to 1. 41 N, according to volume. Only part of the C 0 2 is expelled by phosphoric acid. Salts. — Th z potash 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, 0.2 1 ; sulphuric acid, 2.64; silica, traces. The amount of salts present is affected by the salts of the food. Conditions Influencing the Composition. — The more frequently the breasts are emptied , the richer the milk 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 ( Reiset , Heynsius, Forster , ae Leon). Some substances are diminished and others increased in amount, according to the time after delivery. 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 10-nth months, fat; during 1st 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 dill, copaiba, conium, aniseed, garlic ; especially those containing aromatic volatile oils, as the umbelliferse and cruciferae ; 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. Atropin is a true anti-galactagogue. The composition of the milk may be affected by using fatty 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 fine curd of human milk, and they are only ^ dissolved by the digestive juices, while human milk is completely dissolved. Cow’s milk when boiled is less digestible than unboiled {£. 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 dark the former processes go on more slowly, while there is a putrid fermentation without the evolution of gas, but with many bacteria and a feeble acid reaction ( Albini and Malberla).] 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 io to 24 vols. per cent. [The cream is generally about T § 7 .] The specific gravity (fresh cow’s milk, 1029 to 1034 ; when creamed, 1032 to 1040) is estimated with an aerometer or lactometer at 15 0 C. The sugar is estimated by titration with Fehling’s solution (§ 150, II), but in this case 1 cubic centimetre of this solution corresponds to 0.0067 grm. of milk sugar; or its amount may be estimated with th polariscopic apparatus (§ 150). The pro- teids are precipitated and the fats extracted with ether. The fats in lresh milk form about 3 per cent., and in skimmed milk 1 y z 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 1 centimetre apart. A measured quantity of milk is taken, and water is added to it from a burette until the outline of a candle flame placed at a distance of 1 metre can be distinctly seen through the diluted milk. This is done in a dark room. For 1 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, i. e ., the oil globules. Bond uses a shallow cylindrical 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 when they are administered to the mother — many odoriferous 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 ( Gusserow ). Potassium iodide diminishes the secretion of milk by affecting the secretory function ( Stumpf ). Among abnormal constituents are — haemoglobin, bile pigments, mucin, blood corpuscles, pus, fibrin. Numerous fungi and other low organisms develop in evacuated milk, and the rare blue milk is due to the development of Bacterium cyanogeneum (Fuchs, Neelsen ). The milk serum is blue, not the fungus. Blue milk is unhealthy, and causes diarrhoea (Mosler). There are fungi which make milk bluish-black ox green. Red and yellow milk are produced by a similar action of chromogenic fungi ($ 184). 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 ( Ehrenberg ). Some of the pigments seem to be related to the aniline, and others to the phenol coloring matters (Huppe). 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 (g 184) first coagulates casein, then peptonizes it, and finally splits it up, with the evo- lution of ammonia (Huppe) . Milk becomes stringy, owing to the action of cocci ( Schmidt , Miilheim), which form a stringy substance [ = dextran , C 12 H 10 O 10 (Scheibler)’], just as beer or wine undergoes a similar or ropy change. [The milk of diseased animals may contain or transmit directly infectious matter.] Preparations of Milk — (1) Condensed milk — 80 grms. cane sugar are added to 1 litre of milk; the whole is evaporated to A ; 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, Kern). (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 becomes 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 expense 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, whole milk , skim milk, and cream cheese, the last being represented by Stilton, Roquefort, Cheshire, etc. FLESH AND ITS PREPARATIONS. 381 The composition is shown in the following table, after Bauer : — Water. Nitrogeneous Matter. Fat. Extractives. Ash. Cream cheese 35-75 7.16 30-43 2-53 4-13 Whole milk 46.82 27.62 20.54 2-97 3-05 Skim milk 48.02 32.65 8.41 6.80 4.12 Cream cheese, especially if it be made from goat milk, acquires a very 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 — nuclein , 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 haemoglobin ; 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 serum 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). A hen’s egg weighs about 1% oz., of which the shell forms about -V. Composition : — JOUl y-jj-. White of Egg. Yelk. Water .... 84.8 51-5 Proteids .... 12.0 15.O Fats, etc .... 2.0 3 °-° Mineral matter .... 1.2 1.4 Pigment extractives . . . 2.1 This shows the large amount of fatty matter in the yelk.] Relatively more of the nitrogenous constituents than the fatty constituents of eggs are absorbed ( Rubner ). 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 ( 'Kilhne ) ; serum albumin occurs in the fluid of the fibres, in the lymph and blood of muscle. The fats 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 haemo- globin present in the sarcous substance ( Kilhne , Gscheidlen ), but in some muscles, e.g., the heart, there is a special pigment, myo-haematin (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 , Peris ) ; kreatinin, the inconstant inosinic acid , then lactic, or rather sarcolactic acid (§ 293). 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 , Limprichf) ; grape sugar (. Meissner ), but it is very probably derived post-mortem from glycogen (0.43 per cent.), which occurs in considerable amount in foetal muscles ( O . Nasse) ; lastly, volatile fatty acids. Among the salts, potash and phosphoric acid compounds (. Braconnot ) are most abundant ; magnesium phosphate exceeds calcium phosphate in amount. [The composition varies somewhat even in different muscles of the same animal.] In 100 parts Flesh there is, according to Schlossberger and v. Bibra — Ox. Calf. Deer. Pig. Man. Fowl. Carp. Frog. Water 77 - 5 ° 78.20 74-63 78.30 74-45 77-30 79.78 80.43 Solids Soluble albumin 22.50 21.80 25-37 21.70 25-55 22.7 i f 20.22 2-35 19-57 1.86 Coloring matter V 2.20 2.60 I.94 2.40 >■93 3 -o | Glutin 1.30 I.60 O.50 O.80 2.07 1.2 I.98 2.48 Alcoholic extract 1.50 I.40 4-75 I.70 3 - 7 i 1.4 3-47 3-46 Fats Insoluble albumin, Blood vessels, 2.30 1. 11 0.10 etc 17 5 o l6.2 l6.8l 16.81 15-54 16.5 11.31 11.67 In 100 parts Ash there is — Horse. Ox. Calf. Pig- Potash . 39-40 35-94 34-40 37-79 Soda 4.86 2-35 4.02 Magnesia 3-88 3-3i 1:45 4.81 Chalk 1.80 i-73 !-99 7-54 Potassium Sodium W{ 5-36 } IO -59 { 0.40 Chlorine 4.86 0.62 Iron oxide I.IO 0.98 0.27 o-35 Phosphoric acid 46.74 34.36 48.13 44-47 Sulphuric 0.30 3-37 Silicic 2.07 0.81 Carbonic 8.02 Ammonia 0.15 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, 11.12; 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 again 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 6o° to 70° C., as this temperature is sufficient, with the aid of the acids of the flesh, to change the connective tissue into gelatin, whereby the fibres are loosened, so that the gastric 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 water, and afterward boiling. Liebig found that 6 parts per ioo 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 “skimming,” 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 remained dissolved in the soup. By boiling for a very long time, part of the albumin may be redissolved ( Mulder ) . The dissolved substances are : ( 1) 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 stimulating qualities, and a small amount of aromatic extractives. (3) Gelatin, more abundantly extracted from the flesh of young animal-;. According to these facts, therefore, flesh, broth 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 (v. Voit) 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 ( Weiske , Konig ). The more fats that are contained in the vegetable food, the less are the carbohydrates digested and absorbed. 1. 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 Wheat. White Wheat. Wheat .... Rye Barley .... Maize Rice Buckwheat . . 16.52 % 1 1.92 17.70 I3-65 7.4O 6.8-IO.5 56.25 % 60.9I 38.31 77-74 86.21 65-05 27.87 15-75 i-93 9.60 1.36 49-36 0.15 Potash Soda Lime Magnesia .... Iron oxide .... Phosphoric Acid . Silica 33.84 3-09 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 yeast (Saccharomycetes cerevisiae). 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 C 0 2 and alcohol, the C 0 2 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 C 0 2 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 acid. Baking powders consist of carbonate of soda and tartaric acid. In Dauglish’s process for aerated bread, the C 0 2 is forced into water, and a dough is made with this water under pressure, and when the dough is heated, the C 0 2 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 glutin-casein) 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 much albumin , especially vegetable casein or legumin : together with starch, lecithin, cholesterin, and 9 to 19 per cent, water. Peas 384 PULSES, POTATOES, FRUITS. contain 18.02 proteids, and 38.81 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 stuffs,” such as corn 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 tissue, 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 of 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 Fig. 222. Microscopic characters of wheat (X 200). a, cells of the bran ; b, cells of thin cuticle ; c, glutin cells ; d, starch cells ; B, wheat starch (X 350) . so-called pectin (C 32 H 48 0 32 ), 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, dextrin, 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 100 parts of solids 75-5 24-5 89.9 II. I 1 “ 100 “ albumin 46.6 53-4 8l.2 l8.8 “100 “ fats or carbohyd . . 90-3 9-7 96.9 3 -i] [The following table, abridged from Parkes, shows the composition of the chief articles of diet, and is also used for calculating diet tables : — Articles. Water. Proteids. Fats. Carbohydrates. Salts. Beefsteak 74-4 2O.5 3-5 1.6 ; Fat pork 39 -o 9-8 48.9 2-3 Smoked ham .... 27.8 24.8 36.5 IO.I White fish 78.0 I8.I 2.9 1.0 Poultry 74.0 21.0 3-8 1.2 White wheaten bread 40.0 8.0 i -5 49.2 i -3 Wheat flour .... 15.0 II.O 2.0 70-3 i -7 Biscuit 8.0 1 5 -6 i -3 73-4 i -7 Rice 10.0 5 -o 0.8 83.2 0.5 Oatmeal 15.0 12.6 5-6 63.0 3 -o Maize 13-5 10.0 6.7 64-5 1.4 Macaroni 13 1 9.0 o -3 76.8 0.8 Arrow root .... 15-4 0.8 83-3 0.27 Peas (dry) 15.0 22.0 2.0 53 -o 2.4 Potatoes 74.0 2.0 0.16 21.0 1.0 Carrots 85.0 1.6 0.25 8.4 1.0 Cabbage 91.0 1.8 5 -o 5.8 0.7 Butter 6.0 0.3 91.0 2.7 ! Egg ( T V for shell) . 73-5 13-5 1 1.6. 1.0 ! Cheese 36.8 33-5 24-3 5-4 ! Milk (sp. gr. 1032) . 86.8 40 3-7 4.2 0.7 i Cream 66.0 2.7 26.7 2.8 1.8 Skimmed milk . . . 88.0 4.0 1.8 5-4 0.8 Sugar 1 30 96-5 o- 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 (C 8 H 10 N 4 O 2 + H 2 0,) and theobromin (C 7 H 8 N 4 0 2 ), which are regarded as alkaloids of the vegetable bases, and which have 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 these vegetable bases act upon the nervous system; some more feebly (as the above), others more powerfully (quinine) ; some stimulate powerfully, or completely 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 yz 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 1 per cent, ethereal oil, and black tea per cent. ; in green tea there is 18 per cent., in 2 5 386 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: (1) About 95 per cent, of it is oxidized chiefly into C 0 2 and H 2 0 , so that it is so far a source of heat. As 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 paralyzes 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 excites 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 (§ 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 i 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 inverse order of their development, the highest centres being affected first and the lowest last.” The judgment is affected first, although the imagination and “emotions maybe more than usually active.” The motor centres and speech are affected, 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. — Alcoholic 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 cerevisiae ; while in the fermentation of the grape (wine), S. ellipsoideus is the species present (Fig. 223). The yeast takes the substances necessary for the maintenance of its organic processes directly from the mixture of the sugar, viz., carbohydrates, proteids and salts, especially calcium and potassium phosphates and magnesium sulphate. These substances undergo decomposition within the cells of the yeast plant, which multiply during the process, and there are produced alcohol and C 0 2 (§ 150), together with glycerine (3.2 to 3.6 per cent.) and succinic acid (0.6 to 0.7 per cent.). Yeast is either added intentionally or it reaches the mixture from the air, which always contains its spores. When yeast is completely excluded, or if it be killed by boiling [or if its action be prevented by the presence of CONDIMENTS. 387 some germicide], the fermentation does not occur. The alcoholic fermentation is due to the vital activity of a low organism ( Schwann , Mitscherlich . , Pasteur ). In the preparation of brandy, the starch of the grain or potatoes is first changed into sugar by the action of diastase or maltin. Yeast is added, and fermentation thereby produced ; the mixture is distilled at 78.3° C. The fusel oil is prevented from mixing with the alcohol by passing the vapor through heated charcoal. The distillate contains 50 to 55 per cent, of alcohol. In the preparation of wine, the saccharine juice of the grape — the must — after being expressed from the grapes, is exposed to the air at io° to 15 0 C., and the yeast cells, which are floating about, drop into it and excite fermentation, which lasts ten to fourteen days, when the yeast sinks to the bottom. The clear wine is drawn off into casks, where it becomes turbid by undergoing an after- fermentation, until the sugar is converted into alcohol and C 0 2 , which is accompanied by the deposi- tion of some yeast and tartar. If all the sugar is not decomposed — which occurs when there is not sufficient nitrogenous matter present to nourish the yeast — a sweet wine is obtained. Wine contains 89 to 90 per cent, water, 7 to 8 per cent, alcohol, together with sethylic, propylic and butylic alcohol. 1 he red color of some wines is due to the coloring matter of the skin of the grapes, but if the skins be removed before fermentation, red grapes yield white wine. When wine is stored, it develops a fine flavor or bouquet. The characteristic vinous odor is due to oenanthic ether. The salts of wine closely resemble the salts of the blood. In the preparation of beer the grain is moistened, and allowed to germinate, when the tempera- ture rises, and the starch (68 per cent, in barley) is changed into sugar. Thus, “ malt” is formed, Fig. 223. 1, Isolated yeast cells; 2, 3, yeast cells budding; 4, 5, so-called endogenous formation of cells; 6 , sprouting and formation of buds. which is dried, and afterward pulverized, and extracted with water at 70° to 75 0 , the watery extract being the “ wort.” Hops are added to the wort, and the whole is evaporated, when the proteids are coagulated. Hops give beer its bitter taste, make it keep, while their tannic acid precipitates any starch that may be present, and clarifies the wort. After being boiled, it is cooled rapidly (12 0 C. ) ; yeast is added, and fermentation goes on rapidly and with considerable effervescence at io° to 14 0 . Beer contains 75 to 95 per cent, water; alcohol, 2 to 5 per cent, (porter and ale, to 8 per cent.) ; C 0 2 , 0.1 to 0.8 per cent. ; sugar, 2 to 8 per cent. ; gum, dextrin, 2 to 10 per cent. ; the hops yield traces of protein, fat, lactic acid, ammonia compounds, the salts of the grain and of the hops. In the ash there is a great preponderance of phosphoric acid and potash, both of which are of great importance for the formation of blood. In 100 parts of ash there are 40.8 potash, 20.0 phosphorus, magnesium phosphate, 20, calcium phosphate, 2.6, silica, 16.6 per cent. The formation of blood, muscle and other tissues from the consumption of beer is due to the phosphoric acid and potash, while if too much be taken, the potash produces fatigue. Condiments are taken with food, partly on account of their taste, and partly because they excite secretion. Common salt, in a certain sense, is a condiment. We may also include many substances of unknown constitution which act upon the gustatory organs, e. g., substances in the crust of bread [dextrin] and in meat which has been roasted. PHENOMENA AND LAWS OF METABOLISM. 236. EQUILIBRIUM OF THE METABOLISM.— By this term is meant that, under normal physiological conditions, just as much material is absorbed and assimilated from the food as is removed from the body, by the excretory organs, in the form of effete or end products, the result of the retrogressive tissue changes. The income must always balance the expenditure ; wherever a tissue is used up, it must be replaced by the formation of new tissue. During the period of growth, the increase of the body corresponds to a certain increase of forma- tion, whereby the metabolism of the growing parts of the body is 2.5 to 6.3 times greater than that of the parts already formed ( Crusius ). Conversely, during senile decay, there is an excess of expenditure from the body. Methods. — The normal equilibrium of the metabolism of the body is investigated — (1) By determining chemically that the sum of all the substances passing into the body is equal to the sum of all the substances given off from it. Thus the C, H, N, O, salts and water of the food, and the O inspired, must be equal to the C, N, H, O, salts and water given off in the excreta (urine, faeces, air expired, water excreted). (2) The physiological equilibrium is determined empirically by observing that the body retains its normal weight with a given diet; so that, by simply weighing a person, a physician is enabled to determine exactly the state of convalescence of his patient. The tedious process of making an elementary analysis of the metabolic substances was first under- taken in the Munich School by v. Bischoff, v. Voit, v. Pettenkofer, and others. Circulation of C. — In the circulation of materials the total amount of C taken in the food, if the metabolism be in a condition of physiological equilibrium, must be equaled by the C in the C 0 2 given off by the lungs and skin (90 per cent.), together with the relatively small amount of C in the organic excreta of the urine and faeces (10 per cent.). Circulation of N. — Nearly all the N taken in with the food is excreted within twenty-four hours in the form of urea. A very small amount of nitrogenous matter is excreted in the faeces, while the other nitrogenous urinary constituents (uric acid, kreatinin, etc.) represent about 2 per cent, of N. A trace of the N is given off by the breath (§ 124), and a minute proportion in combination, in the epidermal scales (50 milligrammes daily in the hair and nails), and in the sweat. Deficit of N. — That nearly all the N taken in the food reappears in the urine and faeces, as was stated by v. Voit to be the case in the carnivora, by Henneberg, Stohman, and Grouven in the herbivora, and v. Ranke in man, is contradicted partly by old and partly by new observations, which go to show that the whole of the N cannot be recovered from these excretions, but on the contrary there is a considerable deficit. According to Leo, only 0.55 per cent, of the albumin transformed within the body (assuming 15 per cent. N. in albumin) gives off its N in the form of gaseous N (according to Seegen and Nowak 12 times more). In every exact analysis of the metabolism of N this gaseous excretion of N must be taken into account. The Excretion of N after food does not take place regularly from hour to hour, but it increases at once and distinctly, reaches its maximum in five to six hours, and then gradually falls. The same is true of the excretion of S and P ; but in these cases the maximum of excretion is reached at the fourth hour. When fat is added to a diet of flesh, the excretion of N and S is uniformly distributed over the individual hours of the day (v. Voit and Feder). The nitrogenous constituents in the body during metabolism become poorer in C, and richer in N and O. Thus in albumin to 1 atom of N there are 4 atoms C; in gelatin, 3)^ C; in glycocoll, 2 C ; in kreatin, C; in uric acid, ik C; in allantoin, 1 C; in urea, only ]/ 2 atom of C. 388 EQUILIBRIUM OF THE METABOLISM. 389 The H leaves the body chiefly in the form of water — a part, however, is in the combination in other excreta ; the O is chiefly excreted as C0 2 and water ; a little is given off in combination in other excreta ; water is given off by evaporation from the lungs and skin, and also in the urine and faeces. As H is oxidized to form H 2 0, more water is excreted than is taken in. With regard to the salts, most of the readily soluble salts are given off by the urine ; the less soluble salts, especially those of potash, and the insoluble salts, in the faeces ; while others e. g., common salt, are given off in the sweat. Of the sulphur of albumin, about one- half is excreted in the sulphur compounds in the urine, and the other half in the faeces (taurin), and in the epidermal tissues. Every organism has a minimum and a maximum limit of metabolism, according to the amount of work done by the body, and its weight. If less food be given than is necessary to maintain the former, the body loses weight ; while, if more be given after the maximum limit is reached, the food so given is not absorbed, but remains as a floating balance, and is given off with the faeces. When food is liberally supplied and the weight increases, of course the minimum limit rises; hence, during the process of “feeding”, or “fattening,” the amount of food necessary is very much greater than in poorly fed animals, for the same increase of the body weight. By continuing the process, a condition is at last reached, in which the digestive organs are just sufficient to maintain the existing condition, but cannot act so as to admit of new additions being made to the body weight (v. Bischoff, v. Voit , v: Pettenkofer). By the term “ luxus consumption” is meant the direct combustion or oxi- dation of the superfluous food stuffs absorbed into the blood. This, however, does not exist ; on the contrary, the material in the juices is always being used for building up the tissues. The albumin found in the fluids which everywhere per- meate the tissues has been called “ circulating albumin,” and according to v. Voit it undergoes decomposition sooner than the organized “ organic albu- min ” which forms an integral part of the tissues. [Liebig taught that the nitrogenous metabolism of the body depended on a corresponding decom- position of the proteids of the organs, so that the proteids in the food supplied the place of the proteids of the organs thus used up. He called the proteids “ plastic foods ” or “ tissue for- mers,” while he regarded the fats and carbohydrates as respiratory foods,” as he supposed that they alone were concerned in the evolution of heat. As a matter of fact, experiment proved that the N metabolism is to a large extent independent of the proteids of the food. The luxus-con- sumption theory was invented to explain this. It simply means, that proteids taken with the food not only replace the amount of proteids which have been decomposed during the activity of organs and tissues, but any excess is immediately consumed without being converted into tissue, and thus this surplus amount giving rise to heat, being oxidized, to a certain extent it replaced the fats and carbohydrates. But Voit showed that nitrogenous metabolism is not influenced by the activity of the organism, and he proved that in ordinary conditions only a small amount of the organic albumin, i. e.. that composing tissues and organs, undergoes decomposition, w r hile, owing to the action of the cellular elements of the tissues, a large amount of the circulating albumin is split up, so that under ordinary conditions the organic albumin is comparatively stable. This he demonstrated from a comparison of the urea excreted, for the urea may be taken as an index of the N metabolism in well-fed, fasting, and starving animals. But in certain pathological conditions the organic albumin may undergo rapid change, having become less stable, as in fevers, and poisoning with phosphorus.] According to v. Voit only i per cent, of the organic albumin present in the body, while 70 per cent, of the circulating albumin, is transferred in twenty-four hours. Quality and Quantity of the Income in a Healthy Adult. — As far as his organization is concerned, man belongs to the omnivorous animals, i. e., those that can live upon a mixed diet. For an adequate diet man requires for his existence and to maintain health a mixture of the following four chief groups of food stuffs, along with the necessary relishes ; none of them must be absent from the food for any length of time. They are : — 390 REQUISITES FOR A PERFECT DIET. 1. Water — for an adult, in his food and drink, 2700 to 2800 grms. [70 to 90 oz.] daily (§ 229 and § 247, 1). [Thirst. — The needs of the economy for water are expressed by the sensation of thirst. The sensation of heat and dryness may be confined to the tongue, mouth, and fauces, and, indeed, may be excited by inhaling dry air. This local thirst may be allayed by swallowing water or by eating substances which excite the secretion of saliva. More frequently, however, the sensation is the expression of a general condition indicating the diminution of water in the tissues ; or it may be due to excess of saline matters in the blood. In some diseases this sensation is very intense, e.g., dia- betes, and there seems to be a thirst centre in the brain ( A r othnagel\ If water be injected into the blood vessels, or stomach, both the general and local thirst are abolished, even although no water enters the mouth. In some diseased conditions the sensation of thirst is not perceived, owing to the diminution of the excitability of the perceptive centre, and in some cases excessive thirst is complained of even although the body does not seem to be unduly deficient in fluids.] 2. Inorganic Substances are the integral part of all tissues, and without them the tissues cannot be formed. They occur in ordinary food. The addition of too much salt increases the consumption of water, and this in turn increases the transformation of N in the body ( Weiske). If an animal be deprived of salts, nutrition is interfered with ; food deprived of its lime affects the formation of the bones ; deprival of common salts causes albuminuria (§ 247, A, III). The alkaline salts serve to neutralize the sulphuric acid formed by the oxidation of the sulphur of the proteids ( E . Scilkowski ). Iron, which is so essential for the formation of blood, exists in animals and plants in combination with complex organic bodies (Bunge). [The uses of mineral salts are referred to in \ 247, A. Salts form an essential ingredient in soups and broth. Some salts exist in combination with the organized tissues, while others are merely dissolved in the fluids. Forster thinks that it is the latter which are chiefly excreted.] Only in times of famine is man driven to eat large quantities of inorganic substances, to extract the organic matter mixed therewith. A. v. Humboldt states, in regard to the inhabitants of the Orinoco, that they eat a kind of earth which contains innumerable infusoria. 3. At least one animal or vegetable albuminous body or proteid (§§ 248, 250). The proteids are required to replace the used-up nitrogenous tissues, e. g., for muscles. They contain 15.4 to 16.5 per cent. N. The proteids are in blood = 20.56 per cent.; muscles, 19.9 per cent. ; liver, 11.74 per cent. ; brain, 8.63 per cent.; blood plasma, 7.5 per cent.; milk, 3.94 per cent.; lymph, 2.46 per cent. According to Pfliiger and Bohland, a youth of full stature, and 62 kilos. [136 tbs.], decomposes 89.9 grms. of albumin daily. Asparagin, in combination with gelatin, can replace albumin in the food ( Weiske ), while aspara- gin alone limits the decomposition of albumin in herbivora but not in carnivora ( J. Munk ). Ammoniacal salts, glycocoll, sarkosin, and benzamid, increase the amount of albumin in the body. 4. At least one fat (§ 251), or a digestible carbohydrate (§ 252). These chiefly serve to replace the transformed fats and non-nitrogenous constituents. Owing to the large amount of C which they contain, when they undergo oxida- tion, they form the chief source of the heat of the body (§ 206). Fats and car- bohydrates may replace each other in the food, and in inverse proportion too, corresponding to the amount of C which each contains. As far as the mere evo- lution of heat is concerned, 100 parts of fat = 256 of grape sugar = 234 of cane sugar =221 of dry starch ( Rubner ). A man consumes 210 grms. fat daily. (v. Voit and v. Pettenkofer). According to v. Voit, in the economy 175 parts of starch by weight are equal to 1 00 parts of fat. [5. Every proper diet ought to have a certain degree of sapidity or flavor. The substances which give this are not useful in the evolution of energy or build- ing up the tissues, but they stimulate the nervous system and excite secretion. They are called “ Genussmittel ” (means of enjoying food) by the Germans, but we have no exact equivalent for this word in English, though the articles them- selves are included under our expression “condiments.” These substances are the aromatic matter in roast meat (osmasome), tea, vinegar, salt, mustard, pepper, etc.] PROPORTION OF FOODS. 391 [Condition of Diet for Health. — In an adequate diet, not only (i) should the total quantity be sufficient and not more than sufficient, but (2) the constitu- ents should exist in proper proportions, (3) be digestible, and (4) the whole should be in good condition, wholesome, and not adulterated with any substance prejudicial to health.] Fig. 224. EXPLANATION OF THE SIGNS. Water. Beef. Pork. Fowl. Fish. Proteids. Albuminoids. N-free org. bodies. 62 55 73 Salts. mm 1 $; ill 1 L U I 76 J Egg- Cow’s milk. 73,5 _ .-.-vf.o-e -j=\ i ^ ! I 86 Human milk ■ L Wheaten bread Peas. Water. n 89 Animal Foods. EXPLANATION OF THE SIGNS. mm Proteids. Digestible. Non-digestible. N-free organic bodies. *1,3 Salts. V ' M 2 -5 Rice. Potatoes. 75 a- White turnip. Cauliflower. 90,5 90 ■■h Beer. 90 Vegetable Foods. 0.5 Relative Proportion. — With regard to the relative proportions of the various kinds of food which ought to be taken, experience has shown that the diet best suited for the body must contain 1 part of nitrogenous foods to 3^ or , at most , 4 y 2 of the non-nitrogenous . Looking at ordinary foods from this point of view, we see how far they correspond to this requirement, and how several substances may be combined to produce a satisfactory diet. 392 DAILY QUANTITY OF FOOD REQUIRED. Nit. Non- Nit. Nit. Non- Nit. Nit. Non- Nit. I. Veal .... . . IO I 7 - Mutton . . . , , 10 27 13- Rye meal . . . IO 57 2. Hare’s flesh . . . 10 2 8. Pork 10 30 14. Barley meal . . IO 57 3- Beef .... . . IO 17 9 - Cow’s milk . . IO 30 i5- White potatoes . IO 86 4 - Lentils . . . . . IO 21 IO. Human milk . . IO 37 16. Blue “ IO 1 15 5- Beans . . . . . IO 22 11. Wheaten flour . IO 46 i7- Rice 10 123 6. Peas .... . . IO 23 12. Oatmeal , . . . , 10 So 18. Buckwheat meal . IO 130 An examination of this table shows that, in addition to human milk, wheat flour has the right proportion of nitrogenous to non-nitrogenous substances. A man who tries to nourish himself on beef alone, commits as great a mistake as one who would feed himself with potatoes alone. Experience has taught people that man may live upon milk and eggs, but that in addition to flesh we must eat bread or potatoes, while pulses require fat or bacon. Effect of Cold. — The diet varies with the climate and with the season of the year. As the organism must produce more heat in cold latitudes, the inhabitants of northern climates must eat more non-nitrogenous foods, such as fats and sugar or starches, which, on account of the large amount of C they contain, are admirably adapted for producing heat ($ 214, I, 4). The graphic representation of the composition of foods (Fig. 224), taken from Fick, shows at once the relative proportions of the most important food stuffs, and how they vary from the standard of 1 nitrogenous to 3^ or 4 y 2 non- nitro- genous. The absolute amount of food stuffs required by an adult in twenty-four hours depends upon a variety of conditions. As the food represents the chemical reservoir of potential energy, from which the kinetic energy (in its various forms) and the heat of the body are obtained, the absolute amount of food must be increased when the body loses more heat, as in winter, and when more muscular activity (work) is accomplished. As a general rule, an adult requires daily 130 grammes proteids, 84 grammes fats, 404 grammes carbohydrates. The following tables express the mean of numerous single observations : — A Healthy Adult Requires in 24 Hours, of Water-free solids — Food in Grammes. At Rest. {Playfair.) Moderate Work. (. Moleschott .) Laborious Work. {Playfair.) {v. Pettenkofer and v. Voit. ) Proteids 70.87 130 155-92 137 Fats 28.35 84 70.87 117 Carbohydrates (Sugar, Starch, etc.) . 340.20 404 567-50 352 Salts I4.OO 30 40.00 40 [When we record these numbers in ounces we get the following results as water-free solids required by any average man ( Parkes ) : — At Rest. Ordinary Work. Laborious Work. Proteids 2-5 4.6 6 to 7 Fats . • 1.0 3 -o 3-5 ^ 4 5 Carbohydrates 12.0 14.4 16 to 18 Salts 0.5 1.0 1.2 to 1.5 Total water-free food ...» 16.0 23.0 26.7 to 31.0 During ordinary work the proportion is about : — Proteids, 1 : fats, 0.6: carbohydrates, 3.0, i. e . , 1 Nitrogenous to 3.6 non-nitrogenous.] [In a diet for ordinary work (23 oz. of dry solids) a man takes about y^-g- part of his own weight daily; ordinary food , however, as it is consumed, contains between DAILY QUANTITY OF FOOD REQUIRED. 393 50 and 60 per cent, of water ; if we add this proportion of water to the actually dry food we get 48 to 60 oz. of ordinary food (exclusive of liquids). But we consume 50 to 80 oz. of water in some liquid form, making the total amount of water 70 to 90 oz. ( Parkes).~\ In an analogous example from Vierordt, the elementary substances in the food are given (g 215, B), and compared with the income and expenditure. An Adult doing a Moderate Amount of Work takes in : — • C. H. 1 N. j 0 . 120 grammes albumin, containing 90 “ fats, “ 330 “ starch, “ 64.18 70.20 146.82 8.60 IO.26 20.33 18.88 ; ; | 28.34 9-54 162.85 281.20 39-19 18.88 1 200.73 Add 744.11 grm. O from the air by respiration. “ 2818 “ H 2 0 . “ 32 “ Inorganic compounds (salts). The whole is equal to 3^ kilos [7 hbs.], i. e ., about ^ of the body weight ; so that about 6 per cent, of the water, about 6 per cent, of the fat, about 1 per cent, albumin, and about 0.4 per cent, of the salts of the body are daily transformed within the organism. An Adult doing Moderate Work gives off, in grammes: — Water. C. H. N. O. By respiration 330 248.8 ? 651-15 Perspiration 660 2.0 7.2 Urine . . . 1700 9-8 3-3 1*5.8 11. 1 Faeces ... 128 20.0 3-0 3 -o 12.0 2818 201.2 6.3 18.8 681.45 Add to this (besides 2818 grammes water, as drink) 296 grammes water formed in the body by the oxidation of H. These 296 grammes of water contain 3289 grammes H, and 263.41 grammes O ; 26 grammes of salts are given off in the urine, and 6 by the faeces. Effect of Age. — The investigations of the Munich School have shown that the following numbers represent the minimum amount of food necessary for dif- ferent ages : — Age. Nitrogenous. Fat. Carbohydrates. Child until 1 y 2 years “ from six to fifteen years Man (moderate work) Woman Old man Old woman 20-36 grms. 70-80 “ Il8 “ 92 “ IOO “ 80 “ 3°-45 grms. 37-50 “ 56 “ 44 68 50 “ 60-90 grms. 250-400 “ 500 “ 400 “ 350 “ 260 “ [Not only do muscular movements and age influence the amount of food taken, but climate and individual peculiarities, such' as size and the activity of certain organs, also affect it.] Small animals have a more lively metabolism than large ones ( Regnault and Reiset ). In small animals the decomposition of albumin per unit weight of body is greater than in large animals (v. Voii). Small animals, as a rule, consume more proteids than larger ones, because they generally have less bodily fat ( Rubner ). 394 METABOLISM DURING HUNGER AND STARVATION. Relation of N to C. — In most of the ordinary articles of diet, nitrogenous and non-nitrogenous substances are present, but in very varying proportion, in the different foods. Man requires that these shall be in the proportion of i : 3^ to 1 : 4 y*. 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 grins. Lentils 491 “ Peas 582 “ Beef 614 grms. Eggs 968 “ Wheat bread . . 1444 “ Rice 2562 grms. Rye bread . . . 2875 “ 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, in 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. Wheat bread . . . 626 “ Lentils 806 “ Peas 819 grms. Eggs 902 “ Rye bread .... 930 “ Cheese 2011 grms. Potatoes .... 2039 “ 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 1 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 different excreta in the case of a starved cat : — Day. Body Weight. Water taken. 1 1 Urine. Urea. Inorganic Substances \ in Urine. Dry Faeces. Expired C. Water in Urine and Faeces. I. 2464 98 7-9 i -3 1.2 13-9 9I.4 2. 2297 1 1 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 1 1.6 41. 1 7 . 1946 40 3-8 o -5 0.7 1 1 37-5 8. 1873 42 3-9 0.6 1.1 10.6 40 9 - 1782 15-2 42 4 o -5 i -7 10.6 41.4 10. 1717 35 3-3 0.4 i -3 10.5 34 11. 1695 4 32 2.9 0.5 1.1 10.2 3°-9 12. 1634 22.5 30 2.7 0.4 1.1 10.3 29.6 13 - 1570 7 -i 40 3-4 o -5 0.4 IO.I 36.6 14. 1518 3 41 3-4 0.5 0.3 9-7 38 IS- 1434 4 i 2.9 0.4 0.3 9.4 38-4 16. 1389 # . 48 3 0.4 0.2 8.8 45-5 i 7 - 1335 28 1.6 0.2 °-3 7.8 26.6 i8.f 1267 13 0.7 0.1 o -3 6.1 12.9 1 I 3 I -5 775 65-9 9-8 15.8 VO O bo 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 g rm s. ( = 17.01 per cent.) loss of albumin; 1 3 2 * 75 g rms - ( = 11.05 P er 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 necessary — (1) to weigh the animal daily ; (2) to estimate daily all the C and N given off from the body in the faeces, 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 ( Moleschott ) — (6 melancholics who took water died after 41 days) ; small mammals and birds, 9 days, and frogs 9 months. Vigorous adults die when they lose t 4 q of their body weight, but young 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 continuous 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 given in the foregoing table, the diminution in the excretion of urea is much greater than that of C 0 2 , 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 C0 2 , 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 C0 2 . 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 C 0 2 diminishes more rapidly than the consumption of O. It would be wrong, however, to conclude, from the diminished excretion of C 0 2 , 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 C 0 2 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 nourish themselves from the transformation products of other tissues. A starving cat, according to v. Voit, lost — Per cent. Per cent, of Per cent. Per cent, of originally the total loss of originally the total loss of present. body weight. present. body weight. I. Fat . . . ... 97 26.2 10. Lungs . . . . 177 o -3 2. Spleen . . . . 66.7 0.6 11. Pancreas . . . 17.0 0.1 3 - Liver . . • • • 53-7 4.8 12. Bones . . . . 13-9 5-4 4 - Testicles . . . 40.0 0.1 ! 3 - Central Nerv- 5 - Muscles . • • • 30-5 42.2 ous System . 3-2 0.1 6. Blood . . . . . 27.0 3-7 14. Heart . . . . 2.6 0.02 7 - Kidneys . . . • 25.9 0.6 15. Total loss of 8. Skin . . . . . 20.6 8.8 the rest of 9 - Intestine . . . 18.0 2 0 the body . . 36.8 5-o There is a very important difference according as the animals before inanition have been fed freely on flesh and fat \i. 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 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 1 : 1.7 (p. 392). A healthy person excretes 280 grammes [8 to 90Z.] of carbon, in the form of C 0 2 , in the expired air, and in the urine and faeces. If a man is to obtain 280 grammes C from a flesh diet, he must consume — digest and assimilate — more than 2 kilos. [4.4 lbs.] of beef in twenty-four hours. But 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 flesh diet free from fat, provided its body is already well supplied with fat, and is muscular. It consumes J5 to ^ 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 to Jq °f its body weight of flesh, 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 food, as their digestive apparatus is adapted solely for the digestion of vegetable food. [The proteid metabolism depends (1) on the amount of proteids ingested, for the great mass of these becomes changed into circulating albumin (z>. 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, e.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 1 of albumin. The carnivora, which can maintain their metabolism in equilibrium 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 (v. Bischoff \ v. Voit, v. Pettenkofer, 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 (Bauer).'] 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 Brticke, that some albumin is absorbed unchanged (§ 192, 4), and that only this is capable of forming organic albumin, while the peptones, after undergoing a reconversion into albumin, undergo decomposition as such. This view is opposed by many observers (. Adamkiewicz , Plosz, 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 C 0 2 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. 1. It is largely influenced by work, i. e., by the activity of the tissues, and, in fact, with muscular work C 0 2 is excreted in greatly increased amount (§ 127, 6). 2. By the temperature of the surroundings, as more C 0 2 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 first 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, as 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 oxygen used, although the amount of C0 2 formed is increased ( Wolf er s'). [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 which are slowly and gradually oxidized ; in fact, fat may lessen the amount of O taken in, as it diminishes waste.] 240. FLESH AND FAT, OR FLESH AND CARBOHYDRATES. — Since an amount of flesh equal to ^ to 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 (z>. Voit and Gruber). For 100 parts of fat added to the flesh diet, 245 parts of dry flesh 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 ( Rubner ). 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. Petten- 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 absorbed 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 (J. Munk , Will). Glycerin does not diminish the decomposition of albumin within the body ( Lezuin , Tschirwinsky, J. Munk). According 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, i. 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 flesh, 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. Munk). 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 n 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 C 0 2 , and H 2 0 is the substance from which the fat is formed — the latter leaves the body oxidized chiefly to the stage of urea. Examples, — That fats are formed frotn proteids is shown by the following: 1. A cow which produces 1 lb. of butter daily does not take nearly this amount of fatty matter in its food, so that the fat would appear to be formed from vegetable proteids. 2. Carnivora giving suck, when fed on plenty of flesh and some fat, yield milk ricii in fat. 3. Dogs fed with plenty of flesh and some fat, add more fat to their bodies than the fat contained in the food. 4. Fatty degeneration, e.g., of nerve and muscle, is due to decomposition of proteids. 5. The transformation of entire bodies, e.g., such as have lain for a long time surrounded with water, into a mass consisting almost entirely of palmitic acid or adipocere ( Fourcroy ), is also a proof of the transformation of part of the proteids into fats. 6. Fungi are also able to form fat from albumin during their growth ( v . Naegeli , and O. Low). Fats not merely absorbed. — Experiments which go to show that the fat of animals, during the fattening process, is not absorbed as such from the food: 1. Fattening occurs with flesh and soaps; it is most improbable that the soaps are re-transformed into neutral fats by taking up glycerin and giving up alkali ( Kiihne and Radziejewski). 2. If a lean dog be fed with flesh and palmitin- and stearin-soda soap, the fat of its body contains, in addition to palmitin and stearin, olein fat, so that the last must be formed by the organism from the proteids of the flesh. Further, Ssubotin found that when a lean dog was fed on lean meat and spermaceti fat, a very small amount of the latter was found in the fat of the animal. Although these experiments show that the fat of the body must be formed from the decomposition of proteids, they do not prove that all the fat arises in this way, and that none of it is absorbed and redeposited. III. According to v. Voit, no fat is formed in the body directly from carbo- hydrates, e.g., by reduction. As fattening occurs on a diet of pure flesh with CORPULENCE. 399 the addition of carbohydrates, we must assume that the carbohydrates are con- sumed or oxidized in the body, and that thereby a non-nitrogenous body derived from the proteids is prevented from being burned up, and that it is changed into fat, and stored up as such. No doubt fat is formed indirectly in the blood in this way (§ 240). From experiments upon fattening animals, however, Lawes and Gilbert, Leh- mann, Heiden, v. Wolff, think they are entitled to conclude that the carbo- hydrates absorbed are directly concerned in the formation of fats, a view which is supported by Henneberg, B. Schulze, Soxhlet. According to Pasteur, glycerine (the basis of neutral fats) may be formed from carbohydrates. Formerly it was believed that bees could prepare wax from honey alone ; this is a mistake — an equivalent of albumin is required in addition — the necessary amount is found in the raw honey itself. 242. CORPULENCE. — The addition of too much fat to the body is a pathological phe- nomenon which is attended with disagreeable consequences. With regard to the causes of obesity, without doubt there is an inherited tendency (in 33 to 56 per cent, of the cases — Bou- chard , Chalmers ) in many families — and in some breeds of cattle, to lay up fat in the body, while other families may be richly supplied with fat, and yet remain lean. The chief cause, however, is taking too much food, i.e., more than the amount required for the normal metabolism ; corpulent people, in order to maintain their bodies, must eat absolutely and relatively more than persons of spare habit, under analogous conditions of nutrition (£ 236). Conditions favoring Corpulence. — The following conditions favor the occurrence of corpu- lence : (1) A diet rich in proteids , with a corresponding addition of fat ox carbohydrates. As flesh or muscle is formed from proteids, and part of the fat of the body is also formed from albumin (p. 398), the assumption that fats and carbohydrates fatten, or when taken alone, act as fattening agents, is completely without foundation. No one ever becomes fat without taking plenty of albumin. (2) Diminished disintegration of materials within the body, eg., ( a ) diminished muscular activity (much sleep and little exercise) ; ( b ) abrogation of the sexual functions (as is shown by the rapid fattening of castrated animals, as well as by the fact that some women, after cessation of the menses, readily become corpulent) ; ( c ) diminished mental activity (the obesity of dementia), phlegmatic temperament. On the contrary, vigorous mental work, excitable temperament, care and sorrow, counteract the deposit of fat ; ( d ) diminished extent of the respiratory activity , as occurs when there is a great deposition of fat in the abdomen, limiting the action of the diaphragm (breathless- ness of corpulent people), whereby the combustion of the fatty matters, which become deposited in the body is limited ; ( e ) a corpulent person requires to use relatively less heat-giving substances in his body, partly because he gives off relatively less heat from his compact body, than is done by a slender, long-bodied individual, and partly because the thick layer of fat retards the conduction of heat (§ 214, 4). Thus, corresponding to the relatively diminished production of heat, more fat may be stored up ; (f) a diminution of the red blood corpuscles , which are the great exciters of oxidation in the body, is generally followed by an increase of fat — fat people, as a rule, are fat because they have relatively less blood (§ 41) — women with fewer red blood corpuscles are usually fatter than men ; (^) the consumption of alcohol favors the conservation of fat in the body; the alcohol is easily oxidized, and thus prevents the fat from being burned up ($ 235). Well nourished individuals are usually at first both muscular and endowed with a fair amount of fatty tissue. When they begin to put on fat, the development of the muscular system lags behind, partly because the increasing corpulence leads to diminished activity of the muscular system, so that this system is involved secondarily. Some lively corpulent people, nevertheless, retain their muscular energy. When those conditions which favor corpulence are especially active, corpulence may ultimately pass into a condition of great obesity. Disadvantages. — Besides the inconvenience of the great size and weight of the body, corpu- lent people suffer from breathlessness — they are easily fatigued, are liable to intertrigo between the folds of the skin, the heart becomes loaded with fat, and they not unfrequently are subject to apoplexy. In order to counteract corpulence we ought to— (1) Reduce uniformly all articles of diet. The diet and body ought to be weighed from week to week, and as long as there is no diminution in the body weight, the amount of food ought to be gradually and uniformly reduced (notwithstand- ing the appetite). This must be done very gradually and not suddenly. A moderate reduction of fat and carbohydrates in a normal diet, at the same time leads to a diminution of the fat of the body itself. Let a person who is capable of muscular exertion take 156 grms. proteid, 43 grms. fat, and 1 14 grms. carbohydrates; but in those where congestions, hydrsemia, breathlessness have taken place, take 170 grms. proteid, 25 grms. fat, and 70 grms. carbohydrates ( Oertel ). It is not advisable to limit the amount of fat and carbohydrates alone, as is done in the Banting cure or Bantingism. Apart altogether from the fact that fat is formed from proteids, if too little non-nitrogenous food be taken, severe disturbance of the bodily metabolism is apt to occur. (2) It is advisable during the 400 METABOLISM OF THE TISSUES. chief meal to limit the consumption of fluids of all sorts (even until three-quarters of an hour there- after), and thus render the absorption and digestive activity of the intestine less active ( Oertel ). (3) The muscular activity ought to be greatly developed by doing plenty of muscular work, or taking plenty of exercise, both physical and mental. (4) Favor the evolution of heat by taking cold baths of considerable duration, and afterward rubbing the skin strongly so as to cause it to become red ; further, dress lightly, and at night use light bed clothing ; tea and coffee are useful, as they excite the circulation. (5) Use gentle laxatives; acid fruits, cider; alkaline carbonates (. Marienbad , Carlsbad , Vichy , Neuenahr , Ems, etc.), act by increasing the intestinal evacuations and diminishing absorption. (6) If from accumulation of fat there is danger of failure of the heart’s action, Oertel recommends hill climbing, whereby the cardiac muscle is exercised and strengthened. At the same time the circulation becomes more lively and the metabolism is increased. [Oertel’s Method goes on the idea of strengthening the cardiac musculature, which is sought to be accomplished by (1) limiting the amount of fluids consumed, and (2) carefully regulated mus- cular exertion. The amount of food is first reduced one half, and the water to a still lower amount, while the nitrogenous elements in food are increased, the non-nitrogenous are decreased. The per- son is then instructed to take exercise under certain medical precautions, first, on level ground, and then on gradually increasing gradients. Oertel has opened several establishments in Germany (Terrain Curorte) for conducting what he calls his Terrain Cur.] Fatty Degeneration. — The process of fattening consists in the deposition of drops of fat within the fat cells of the panniculus and around the viscera, as well as in the marrow of bone (but they are never deposited in the subcutaneous tissue of the eyelids, of the penis, of the red part of the lips, in the ears and nose). This is quite different from the fatty atrophy or fatty degeneration which occurs in the form of fatty globules or granules in albuminous tissues, e.g. , in muscular fibres (heart), gland cells (liver, kidney), cartilage cells, lymph and pus corpuscles, as well as in nerve fibres separated from their nerve centres. The fat in these cases is derived from albumin, much in the same way as fat is formed in the gland cells of the mammary and sebaceous glands. Marked fatty degeneration not unfrequently occurs after severe fevers, and after artificial heating of the tis- sues; when a too small amount of O is supplied to the tissues, as occurs in cases of phosphorus poisoning ( Bauer ) ; in drunkards ; after poisoning with arsenic and other substances ; and after some disturbances of the circulation and innervation. Some organs are especially prone to undergo fatty degeneration during the course of certain diseases. 243. METABOLISM OF THE TISSUES.— The blood stream is the chief medium whereby new material is supplied to the tissues and the effete products removed from ‘them. The lymph which passes through the thin capil- laries comes into actual contact with the tissue elements. Those tissues which are devoid of blood vessels in their own substance, such as the cornea and cartil- age, receive nutrient fluid or lymph from the adjacent capillaries, by means of their cellular elements, which act as juice-conducting media. Hence, when the normal circulation is interfered with, as by atheroma or calcification of the walls of the blood vessels, these tissues are secondarily affected [this, for example, is the case in arcus senilis of the cornea, due to a fatty degeneration of the corneal tissue, owing to some affection of the blood vessels on which the cornea depends for its nutrition]. Total compression or ligature of all the blood vessels results in necrosis of the parts supplied by the ligatured blood vessels. Atrophies caused by diminution of the normal supply of blood gradually, in the course of time, become less and less ( Samuel J. Hence, there must be a double current of the tissue juices; the afferent or supply current, which supplies the new material, and the efferent stream, which removes the effete products. The former brings to the tissues the proteids, fats, carbohydrates, and salts from which the tissues are formed. It is evident that any interruption of the arterial supply to the tissues will diminish this supply. That such a current exists is proved by injecting an indifferent, easily recognizable substance into the blood, e.g., potassium ferrocyanide, when its presence may be detected in the tissues, to which it has been carried by the outgoing current. The efferent stream carries away the decomposition products from the various tissues, more especially urea, C0. 2 , H 2 0, and salts, and these are transferred as quickly as possible to the organs through which they are excreted. That such a current exists is proved by injecting such a substance as potassium ferrocyanide into the tissues, e.g., subcutaneously, when its presence may be detected in the urine within two to five minutes. METABOLISM OF THE TISSUES. 401 If the current from the tissues to the blood is so active that the excretory organs cannot eliminate all the effete products from the blood, then these products are found in the tissues. This occurs when certain poisons are injected subcutaneously, when they pass rapidly into the blood and are carried in great quantity to other tissues, e. g., to the nervous system, on which they act with fatal effect, before they are eliminated to any great extent from the blood by the action of the excretory organs. The effete materials are carried away from the tissues by two channels, viz., by the veins and by the lymphatics, so that if these be inter- fered with, the metabolism of the tissues must also suffer. When a limb is ligatured so as to compress the veins and the lymphatics, the efferent stream stagnates to such an extent that considerable swelling of the tissues or oedema may occur (§ 203). The action of the muscles and fasciae are very important in removing these effete matters ( Hasse ). H. Nasse found that the blood of the jugular vein is 0.225 per 1000 specifically heavier than the blood of the carotid, and contains 0.9 parts per 1000 more solids; 1000 cubic centimetres of blood circulating through the head yield about 5 cubic centimetres of transudation into the tissues. The extent and intensity of the metabolism of the tissues depend upon a variety of factors. I. Upon their activity. The increased activity of an organ is indicated by the increased amount of blood going into it, and by the more active circulation through it (§ 100). When an organ is completely inactive, such as a paralyzed muscle, or the peripheral end of a divided nerve, the amount of blood and the nutritive exchange of fluids diminish within these parts. The parts thus thrown out of activity become pale, relaxed, and ultimately undergo fatty degeneration. The increased metabolism of an organ during its activity has been proved experi- mentally in the case of muscle, and [(§ 263) also in the brain (Speck)d\ Langley and Sewell have recently observed directly the metabolic changes within sufficiently thin lobules of glands during life. The cells of serous glands (§ 143), and those of mucus- and pepsin-forming glands (§ 164), during quiescence, become filled with coarse granules, which are dark in transmitted light and white in reflected light, which granules are consumed or disappear during granular activity. During sleep, when most organs are at rest, the metabolism is limited ; darkness also diminishes it, while light excites it, obviously owing to nervous influences. The variations in the total metabolism of the body are reflected in the excretion of C0 2 (§ 127, 9) and urea (§ 257), which may be expressed graphically in the form of a curve corresponding with the activity of the organism ; this curve corresponds very closely with the daily variations in the respirations, pulse, and temperature (P- 359)- 2. The composition or quality of the blood has a marked effect upon the current on which the metabolism of the tissues depends. Very concentrated blood, which contains a small amount of water, as after profuse sweating, severe diarrhoea — e.g., in cholera — makes the tissues dry, while if much water be absorbed into the blood, the tissues become more succulent and even oedema may occur. When much common salt is present in the blood, and when the red blood cor- puscles contain a diminished amount of O, and especially if the latter condition be accompanied by muscular exertion causing dyspnoea, a large amount of albumin is decomposed, and there is a great formation of urea. Hence, exposure to a rarefied atmosphere is accompanied by increased excretion of urea. Certain abnormal conditions of the blood produce remarkable results; blood charged with carbonic oxide cannot absorb O from the air, and does not remove C0 2 from the tissues (§ 16). The presence of hydrocyanic acid in the blood (§ 16) is said to interrupt at once the chemical oxidation processes in the blood, so that rapid asphyxia, owing to cessation of the internal respiration, occurs. Fermentation is interrupted by the same substance in a similar way. A diminution of the total amount of the blood causes more fluid to pass from the tissues into the blood ; but 26 402 REGENERATION OF ORGANS AND TISSUES. the absorption of substances, such as poisons or pathological effusions, from the tissues or intestines is delayed. If the substances which pass from the tissues into the blood be rapidly eliminated from it, absorption takes place more rapidly. 3. The blood pressure is of importance, in so far, that when it is greatly in- creased, the tissues contain more fluid, while the blood itself becomes more con- centrated, to the extent of 3 to 5 per 1000 (Nasse). We may convince ourselves that blood plasma easily passes through the capillary wall, by pressing upon the efferent vessel coming from the chorium deprived of its epidermis, e. g., by a burn or a blister, when the surface of the wound becomes rapidly suffused with plasma. Diminution of the blood pressure produces the opposite result. The oxidation processes in the body are diminished after the use of P, Cu, ether, chloroform, chloral ( Nencki and Sieber). 4. Increased temperature of the tissues (several hours daily) does not increase the breaking up of albumin and fats (Koch, Stockvis , Simanowsky , and v. Voit). (See also Artificial Elevation of the Temperature, § 221 ; Fever, § 220 ; and Artificial Cooling, § 225.) 5. The influence of the nervous system on the metabolism is twofold. On the one hand, it acts indirectly through its effect upon the blood vessels, by caus- ing them to contract or dilate through the agency of vaso-motor nerves, whereby it influences the amount of blood supplied, and also affects the blood pressure. But in addition to this, and quite independently of the blood vessels, it is probable that certain special nerves — the so-called trophic nerves, influence the metabolism or nutrition of the tissues (§ 342, c). That nerves do influence directly the transformation of matter within the tissues is shown by the secretion of saliva resulting from the stimulation of certain nerves, after cessation of the circulation (§ 145), and by the metabolism during the contraction of bloodless muscles. Increased respiration and apnoea are not followed by increased oxida- tion (. Pfliiger ) (§ 127, 8). [Gaskell has raised the question as to the existence of katabolic and anabolic nerves control- ling respectively the analytic and synthetic metabolism of the tissues (p. 373).] 244. REGENERATION OF ORGANS AND TISSUES.— The extent to which lost parts are replaced varies greatly in different organs. Among the lower animals the parts of organs are replaced to a far greater extent than among warm-blooded animals. When a hydra is divided into two parts, each part forms a new individual — nay, if the body of the animal be divided into several parts in a particular way, then each part gives rise to a new individual ( Spallanzani ). The Planarians also show a great capability of reproducing lost parts (Du^es). Spiders and crabs can reproduce lost feelers, limbs, and claws; snails, part of the head, 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 ( Philippeaux ). In amphibians and reptiles the regeneration of organs and tissues, as a whole, takes place after the type of the embryonic development ( Praisse , Gotte ), 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 ( Billow ) . 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 (§ 283) 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 ( Klebs , 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 lunule , and if it be destroyed the nail is not reproduced (§ 284). The eyelashes are changed in 100 to 150 days {Do?iders), 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 , Koehnhorri). [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 {Sign. 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 ( Heidelberg ). After several days, the sarcolemma contains numerous nuclei which reproduce new muscular nuclei and the contractile sub- stance (. Kraske , Erbkam). 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. N on- 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 (Sigm. Mayer). The regeneration of peripheral ganglionic cells is unknown, v. Voit, however, observed that a pigeon, part of whose brain was removed, had within five months reproduced a nervous mass within the skull, consisting of medullated 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 (§ 338, 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 Philippeaux and Griffini, if part of the spleen be removed it is reproduced (§ 103). Tizzoni and Collucci 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 ( W. Podwisotzky). 7. Among connective tissues, cartilage, provided its perichondrium be not in- jured, reproduces itself by division of its cartilage cells (. Redfern ) ; 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 off heal again, and become united with the original bone ( Jakimowitsch ). 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 ( P . Burns , MacEwen). 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 and 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 begin 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 of phosphorus ( Wagner) or arsenious acid (Maas) 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 devoid of lime salts is given to an animal, the growth of the bones is not arrested (v. Voit), but the bones become thinner, whereby all parts, even the organic basis of the bone, undergo a uniform diminution ( Chossat , A. Milne-Edivards). 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 lactic acid dissolves the bones {Siedavigrotzky and Hofmeister ). 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, $ 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 fatty degeneration, while others take up nutriment and become converted into large uni- nucleated protoplasma cells, from which giant cells are developed ( Ziegler , 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 form 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 spur of a cock 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 with the adjoining parts. Ollier found that, when periosteum was transplanted, it grew and reproduced bone in its new situation. Even blood and lymph 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 rabbit, 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, when 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 third, about 7 centimetres; while from five to sixteen years the annual increase is about 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 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. Age Length (Cmtr.). Weight (Kilo.). Age Length (Cmtr.). Weight (Kilo.). Man. Woman. Man. Woman. Man. Woman. Man. Woman. O 49.6 48.3 3.20 2.9I 15 155-9 147-5 46.41 41.30 I 69.6 69.0 10.00 9-30 16 161.0 150.O 53-39 44.44 2 79.6 78.O 12.00 II.40 17 167.0 154-4 57-40 49.08 3 86.0 85.O 13.21 12.45 18 170.0 156.2 61.26 53 -io 4 93-2 9I.0 15-07 14.18 19 170.6 63-32 5446 5 99.0 97.O 16.70 15 50 20 i 7 i-i 157.0 65.00 6 104.6 IO3.2 18.04 16.74 25 172.2 157-7 68.29 55 -o 8 7 hi. 2 IO9.6 20.16 18.45 30 172.2 157-9 68.90 55-14 8 117.0 H 3-9 22.26 19.82 40 171-3 155-5 68.81 56.65 9 122.7 120.0 24.O9 22.44 50 166.4 153-6 67-45 58.45 IO 128.2 124.8 26.12 24.24 60 163.9 151.6 65 - 5 o 56.73 1 1 132.7 127.5 27.85 26.25 70 162.3 I5I-4 63-03 53-72 12 135-9 132.7 31.00 3°-54 80 161.3 150.6 61.22 5I-52 13 140.3 138.6 35-32 34-65 90 . . 57-83 49-34 14 148.7 144.7 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 ( Thoma ). 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. [ Water 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 (H 2 0 2 ) is also present in the body.] II. Gases. — [Oxygen is absorbed from the air, and enters the blood, where it forms a loose chemical compound, 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 4 ) (g 124), ammonia (NH 3 ), C 0 2 ($ 38), sulphuretted hydrogen (H 2 S) (§ 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 ($ 409). In some cases it exists in a state of combination with albuminous bodies, as in the blood plasma. Common salt is absolutely necessary for one’s existence ; if it be withdrawn entirely, life soon comes to an end. About 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 (Ca g P 2 0 8 ) is the most abundant salt in the body, as it forms more than one-half of our bones, but 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 (PNa 3 0 4 ), acid sodium phosphate (PNa 2 0 4 ), acid potassium phosphate (PK 2 H 0 4 ). 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 2 C 0 3 ) and sodium bicarbonate (NaHC 0 3 ) 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 C 0 2 from the tissues to the lungs.] [Sodium and potassium sulphates (Na 2 S 0 4 and K 2 S 0 4 ) 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 (KC 1 ) is pretty widely distributed, and it occurs specially in muscle, colored blood corpuscles, and milk. Calcium fluoride (CaFi 2 ) occurs in small quantity in bones and teeth. Calcium carbonate (CaC 0 3 ) 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 4 C 1 ). — Minute traces occur in the gastric juice and the urine.] 407 408 THE ALBUMINOUS OR PROTEID SUBSTANCES. [Magnesium phosphate (Mg 3 P 0 4 ) occurs in the tissues and fluids of the body, along with calcium phosphate, but in very much smaller quantity.] IV. Free Acids. — Hydrochloric acid (HC 1 ) [occurs free in the gastric juice, but in combination with the alkalies it is widely distributed as chlorides]. Sulphuric acid (H 2 S 0 4 ) [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 (Si 0 2 ); manganese , iron, the last forms an integral constituent of the blood pigment; copper (?), (§ 174). 248. (B) ORGANIC COMPOUNDS.— I. THE ALBUMINOUS OR PROTEID SUBSTANCES. — 1. True Proteids and their Allies. — Proteids or Albumins and their allies are composed of C, H, O, N, and 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 2.0. ] 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 exists 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 health 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 oxidation within the body are C 0 2 , H 2 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 fatty bodies (during the oxidation of albumin, fatty acids especially are developed). Carbo- hydrates may also appear as decomposition products (. Krukenberg ). For the decompositions during digestion, see § 170, and during putrefaction, \ 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 (g 191), and, therefore, do hot 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 them 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. — (1) They are coagulated by nitric acid, and when boiled therewith, give a 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 6o° 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 molvbdic acid gives a blue color ( Frdhde ). (7) Their solution in acetic acid is colored violet with concentrated sulphuric acid, and shows the absorption band of hydrobilirubin ( Adamkiewicz ). (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 [(9) 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-magnedc 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 g 32, and its physiological properties at $41. Almost all its salts may be removed from it by dialysis, when it is no longer coagulated by heat {Schmidt). It is coagulated by strong alcohol, and is easily dissolved in strong hydrochloric acid. When precipitated, it is readily soluble in strong nitric acid. It is not coagulated when shaken up with ether. The addition of water to the hydrochloric solution precipitates acid albumin. For its presence in urine, \ 264. (2) Egg albumin. When injected into the blood vessels or under the skin, or even when introduced in large quantity into the intestine, part of it appears unchanged in the urine ($ 192, 4, and \ 264). When shaken with ether, it is precipitated. These two reactions serve to distinguish it from (1). 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 sulphate. Concentrated sul- phuric acid and acetic acid give a violet color [Adamkiewicz). 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 reducing substance (? sugar)). Class II.— Globulins. — They are native proteids, which are insoluble in distilled water, but soluble in dilute saline solutions, sodium chloride of 1 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 are precipitated from their sodium chloride solution by the addition of crystals of sodium chloride, and also by saturating their neutral solution at 30° with 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 C0 2 through a watery extract of the crystalline 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 saturation with sodium chloride. (3) Paraglobulin or Serum globulin (g 29), and in urine, $ 264. (4) Fibrinogen (§29). (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 with 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 crystals of NaCl. For Kuhne’s method of preparation, see \ 293. (6) Globin [Preyer), the proteid residue of haemoglobin, $ 18. Class III. — Derived Albumins (Albuminates). — (1) Acid Albumin or Syntonin. — When proteids are dissolved in the stronger acids, e.g., hydrochloric, they become changed into acid albumins. They are precipitated from solution by the addition of many salts (NaCl, Na 2 S0 4 ), 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 albumin. It is formed also in the stomach during digestion ($ 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 [Lieberkuhn). 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 (0.83 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 nucleo-albumins. When it is digested with dilute HC 1 (o.i per 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 g 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 ( Virchow ) or lardacein, which occurs chiefly as a pathological 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 difficult 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, eg., 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 (Radlkofer), eg., from the seeds of the gourd ( G rubier) and various oleaginous seeds ( Ritthausen ). They occur in 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 1877) 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, Marlin ). ] [Globulins. — Three varieties have been described as occurring in the seeds of plants : vegetable myosin (Hoppe- Seyler), 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 leguminosae, in flour and in the potato.] [Albumin. — The existence of a body corresponding to egg- or serum albumin in the vegetable kingdom is doubtful ( Ritthausen ). 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 leguminosae, 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 leguminosge ; and it is slightly soluble in water, but 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 HC 1 or acetic acid (Ernhof, 1805) ; (b) conglutin, a very similar body occurring in hops and almonds (Ritthausen). The existence of vegetable casein is denied ( Weyl, 1877 ; Vines, 1878 to 1880). Vines states that both legumin and conglutin are artificial products, being formed from the globulins present by the dilute alkali used in extraction of the proteids: This is denied by Ritthausen.] [Gluten and Glutin. — Gluten is readily prepared from flour by washing and kneading it in a muslin bag under a stream of water. So prepared it is yellowish-brown in color, very sticky, and capable of being drawn out into long shreds. It is insoluble in water, soluble (but not completely) by prolonged action in dilute acids and alkalies (.2 per cent. KHO and HC 1 ). The prolonged action of alcohol (80 to 85 per cent.) dissolves part of the substance of gluten (Taddei, Liebig), leaving a residue, called by Liebig plant fibrin and by Ritthausen gluten casein. The alcohol con- tains gliadin (glutin), gluten fibrin and mucedin (Ritthausen). Gluten casein is readily soluble in dilute alkalies, almost insoluble in dilute acetic acid, and quite insoluble in cold and boiling water; the products of its decomposition, by heating with H 2 S 0 2 , are leucin, tyrosin, glutamic and asparaginic acids. The three bodies dissolved from glutin by alcohol differ chiefly in their solubility in alcohol and water. Gluten fibrin, the least soluble, is coagulated by the action of absolute alcohol ; it is readily soluble in dilute acids and alkalies, being precipitated by neutralization. Gliadin (gluten, plant gelatin) may be prepared by boiling gluten with water : it deposits on cool- ALBUMINOIDS. 411 ing the solution. Though soluble in water at ioo° C. at first, it becomes insoluble by the prolonged action of water at that temperature. It is, like gluten fibrin, soluble in dilute acids and alkalies. Mucedin differs from gliadin in being less soluble in strong alcohol; it is considered by Ritthausen as a modification of gluten fibrin. The existence of these several constituents of gluten has not been definitely proved : they were first described by Ritthausen (1872). The formation of gluten has been ascribed by Weyl to a ferment action similar to the formation of blood fibrin ; all attempts, however, to isolate a ferment have proved fruitless. The water used in washing the flour in the preparation of gluten contains hemialbumose ( Vines ) and a globulin ( IVeyl). Rye flour, as well as wheaten, yields gluten under similar treatment with water.] [Nitrogenous Crystalline Principles. — Leucin, tyrosin, asparagin, and glutamic acid, have been found in the seeds of plants.] 250. (2) THE ALBUMINOIDS. — These substances closely resemble true proteids in their composition and origin, and are amorphous non-crystalline colloids; some of them do not contain S, but the most of them have not been prepared free from ash. Their reactions and decomposition products closely resemble those of the proteids; some of them produce, in addition to leucin and tyrosin, glycin and alanin (amido-propionic acid). -They occur as organized constituents of the tissues and also in fluid form. It is unknown whether they are formed by oxidation from proteid bodies or by synthesis. 1. Mucin is the characteristic substance present in mucus. It contains no S. That obtained from the submaxillary gland contains — C 52.31, H 7.22, Nil 84, O 28.63. It dissolves in water, mak- ing it sticky or slimy, and can be filtered. It is precipitated by acetic acid and alcohol ; and the alcohol precipitate is again soluble in water. It is not precipitated by acetic acid and ferrocyanide of potassium, but HNO s and other mineral acids precipitate it (Scherer). It occurs in saliva ($ 146), in bile, in mucous glands, secretions of mucous membranes, in mucous tissue, in synovia, and in tendons (A. Rollett ). Pathologically it occurs not unfrequently in cysts; in the animal kingdom, especially in snails and in the skin of holothurians ( Eichwald ). It yields leucin and 7 per cent, of tyrosin when it is decomposed by prolonged boiling with sulphuric acid. [The precipitate called mucin has not always the same characters, and, in fact, it differs according to the animal from which it is obtained (Lcindwehr) ] 2. Nuclein ( Miescher , $ 198) — (C 29, H 49, N 9, P 3, O 22) — contains phosphoric acid, and is slightly soluble in water, easily in ammonia, alkaline carbonates, strong HN 0 3 ; it gives the biuret re- action; no reaction with Millon’s reagent; when decomposed it yields phosphorus. It occurs in the nuclei of pus and blood corpuscles (f 22), in spermatozoids, yelk-spheres, liver, brain, and milk, yeast, fungi, and many seeds. It has resemblances to mucin, and is perhaps an intermediate product between albumin and lecithin (Hoppe- Seyler). It is prepared by the artificial digestion of pus when it remains as an indigestible residue ; acids precipitate it from an alkaline solution. It gives a feeble xanthoproteic re- action; after the prolonged action of alkalies and acid, substances similar to albumin and syntonin are formed. Hypoxanthin and guanin have been obtained as decomposition products from it ( Kossel ). 3. Keratin occurs in all horny and epidermic tissues (epidermic scales, hairs, nails, feathers) — C 50.3-52.5, H 6.4-7, N 15. 2-17, O 20.8-25, S 0.7-5 percent. — is soluble in boiling caustic alka- lies, but swells up in cold concentrated acetic acid. When decomposed by H 2 S 0 4 it yields 10 per cent, leucin and 3.6 per cent, tyrosin. Neuro-keratin, $ 321. 4. Fibroin is soluble in strong alkalies and mineral acids, in ammonia-sulphate of copper ; when boiled with H 2 S 0 4 it yields 5 per cent, tyrosin, leucin, and glycin. It is the chief constituent of the cocoons of insects and threads of spiders. 5. Spongin, allied to fibroin, occurs in the bath sponge, and yields, as decomposition products, leucin and glycin (Stadeler). 6. Elastin, the fundamental substance in elastic tissue, is soluble only when boiled in concen- trated caustic potash — C 55-55.6, H 7. 1-7.7, N 16.1-17.7, O 19.2-21.1 per cent. It yields 36-45 per cent, of leucin and per cent, of tyrosin. 7. Gelatin (Glutin), obtained from connective tissues by prolonged boiling with water; it gela- tinizes in the cold — C 52.2-50.7, H 6. 6-7. 2, N 17.9-18.8, S + O 23.5-25, (S 0.7 per cent.). [The ordinary connective tissues are supposed to contain the hypothetical anhydride collagen, while the organic basis of bone is called ossein.] It rotates the ray of polarized light strongly to the left. By prolonged boiling and digestion it is converted into a peptone-like body (gelatin peptone), which does not gelatinize ($ 161, I). [It swells up, but does not dissolve in cold water ; when dis- solved in warm water, and tinged with Berlin blue or carmine, it forms the usual colored mass which is employed by histologists for making fine transparent injections of blood vessels.] A body resembling gelatin is found in leuksemic blood and in the juice of the spleen ($ 103, I). When decomposed with sulphuric acid it yields glycin, ammonia, leucin, but no tyrosin. It gives insoluble precipitates with mercuric chloride, and tannin. 8. Chondrin (Joh. Muller) occurs in the matrix of hyaline cartilage and between the fibres in fibro-cartilage. It is obtained from hyaline cartilage and the cornea by boiling. It occurs also in the mantle of molluscs — C 49.5-50.9, H 6.6-7. 1, N 14.4-14.9, S -fO 27.2-29 (S 0.4 per cent.). When boiled with sulphuric acid it yields leucin; with hydrochloric acid, and when digested, chondro-glucose (Meissner) ; it belongs to the glucosides, which contain N. When acted upon by oxidizing reagents it is converted into gelatin (Brame). The substance which yields chondrin is 412 ORGANIZED AND UNORGANIZED FERMENTS. called chondrogen, which is perhaps an anhydride of chondrin. The following properties of gelatin and chondrin are to be noted : Gelatin is precipitated by tannic acid, mercuric chloride, chlorine water, platinic chloride, and alcohol, but not by acids, alum, or salts of silver, iron, copper, or lead ; its specific rotation is = — 130°. [Compare these precipitants with those of albumin.] Chondrin is precipitated by acetic acid and dilute sulphuric and hydrochloric acids, by alum, and by salts of silver, iron, and lead ; its specific rotation = — 213°. 9. The hydrolytic ferments have recently been called Enzymes by W. Kuhne, in order to distinguish them from organized ferments, such as yeast. The enzymes, hydrolytic or organic fer- ments, act only in the presence of water. They act upon certain bodies, causing them to take up a molecule of water. They all decompose hydric peroxide into water and O. They are most active between 30 and 35 0 C., and are destroyed by boiling, but when dry they may be subjected to a tem- perature of ioo° without being destroyed. Their solutions, if kept for a long time, gradually lose their properties and undergo more or less decomposition. (a) Sugar forming or diastatic ferment occurs in saliva ($ 148), pancreatic juice (g 170), intestinal juice (£ 183), bile (§ 180), blood (g 22), chyle (§ 189), liver (§ 174), in human milk (§ 231). Invertin in intestinal juice 183). Almost all dead tissues, organic fluids, and even proteids, although only to a slight degree, may act diastatically. Diastatic ferments are very generally distributed in the vegetable kingdom. ( b) Proteolytic, or Ferments 7 uhich act upon Proteids. — Pepsin in gastric juice and in muscle ($ 166), in vetches, myxomycetes ( Krukenberg ), trypsin in the pancreatic juice (£ 170), a similar ferment in the intestinal juice (g 183), and urine (§ 264). f c) Fat-decomposing in pancreatic juice ($ 170), in the stomach ($ 166). (d) Milk-coagulating in the stomach ($ 166), pancreatic juice (§ 170), and perhaps also in the intestinal juice (?) — ( W. Roberts'). [The importance of fermentive processes has already been referred to in detail under ‘‘Digestion.” Ferments are bodies which excite chemical changes in other matter with which they are brought into contact. They are divided into two classes : — (1) Unorganized ; soluble or non-living. (2) Organized, or living.] [Table showing the unorganized ferments present in the body, and their actions. Fluid or Tissues. Ferment. Actions. Saliva, i. Ptyalin, 148) Converts starch chiefly into maltose. 1 iGastric juice, ....-{ 1 r ! 1 1 1. Pepsin, | 2. Milk curdling, 3. Lactic-acid ferment, . . 4. Fat splitting, ^ Converts proteids into peptones in an acid medium, certain by-products being formed ($ 166). Curdles casein of milk. Splits up milk sugar into lactic acid. Splits up fats into glycerine and fatty | acids. j Pancreatic juice, . . . \ r 1 1 . Diastatic or amylopsin, . 2. Trypsin, 3. Emulsive, (?) 4. Fat splitting or steapsin, . | 5. Milk curdling, Converts starch chiefly into maltose. Changes proteids into peptones in an alkaline medium, certain by-pro- ducts being formed (£ 170). Emulsifies fats. . Splits fats into glycerine and fatty acids. Curdles casein of milk. Intestinal juice, . . . - L 1. Diastatic, -j 2. Proteolytic, 3. Invertin, 4. Milk curdling, Does not form maltose, but maltose is changed into glucose (g 183). Fibrin into peptone (?). Changes cane- into grape sugar. (? in small intestine). Blood, Chyle, Liver, (?) Milk, Most tissues, .... - Diastatic ferments. 1 J Muscle, Urine, | Pepsin and other ferments. . . Blood, Fibrin- forming ferment. (Modified from W. Roberts).] FATS. 413 [(i) The Unorganized Ferments are those mentioned in the precedi ng table. They seem to be nitrogenous bodies, although their exact composition is unknown, and it is doubtful if they have ever been obtained perfectly pure. They are produced within the body, in many secretions, by the vital activity of the protoplasm of cells. They are termed soluble because they are soluble in water, glycerine, and some other substances (g 148), while they can be precipitated by alcohol and some other reagents. They do not multiply during their activity, nor is their activity prevented by a certain proportion of salicylic acid. They are not affected by oxygen subjected to the compression of many atmospheres ( P . Bert). They are non-living. Their other properties are referred to above.] [(2) The Organized or living ferments are represented by yeast ($ 235). Other living ferments belonging to the schizomycetes, occurring in the intestinal canal, are referred to in \ 184. Yeast causes fermentation by splitting up sugar into C 0 2 and alcohol ($ 156), but this result only occurs so long as the yeast is living. Hence, its activity is coupled with the vitality of the cells of the yeast. If yeast be boiled, or if it be mixed with carbolic or salicylic acid, or chloroform, all of which destroy its activity, it cannot produce the alcoholic fermentation. As yet no one has suc- ceeded in extracting from yeast a substance which will excite the alcoholic fermentation. All the organized ferments grow and multiply during their activity at the expense of the substances in which they occur. Thus the alcoholic fermentation depends upon the “ life ” of the yeast. They are said to be killed by oxygen subjected to the compression of many atmospheres (B. Bert). But it is important to note that Hoppe- Seyler has extracted from dead yeast (killed by ether) an unor- ganized ferment which can change cane sugar into grape sugar.] 10. Haemoglobin, the coloring matter of blood, which, in addition to C, H, O, N, and S, con- tains iron, may be taken with the albuminoids (§ 11). (3) Glucosides containing Nitrogen. — In addition to chondrin, the following glucosides con- taining nitrogen, when subjected to hydrolytic processes, may combine with water, and form sugar and other substances : — Cerebrin (§ 322) = C 5 v Hj 1 0 N 2 O 25 ( Geoghegan ). Protagon — C 66.29, H 10.69, N 2.39, P 1.068 per cent. — occurs in nerves, and contains phos- phorus (g 322). Chitin, 2(C 15 H 26 N 2 O 10 ), is a glucoside, containing nitrogen, and occurs in the cutaneous cov- erings of arthropoda, and also in their intestine and trachea ; it is soluble in concentrated acids, e.g., hydrochloric or nitric acid, but insoluble in other reagents. According to Sandwick, chitin is an am in- derivative of a carbohydrate with the general formula n(Cj 2 H 20 O 10 ). The hyalin of worms is closely related to chitin. (Solanin, amygdalin ($ 202), and salicin, etc., are glucosides of the vegetable kingdom. ) (4) Coloring Matters containing Nitrogen. — Their constitution is unknown, and they occur only in animals. They are in all probability derivatives of haemoglobin. They are — (1) haematin (g 18, A), myo-haematin ($ 232, \ 292, a), and haematoidin (g 20). (2) Bile pigments (§ 177, 3). (3) Urine pigments (except Indican). (4) Melanin — C 44.2, H 3, N 9.9, O 42.6 — or the black pigment, which occurs partly in epithelium (choroid, retina, iris, and in the deep layers of epidermis in colored races) and partly in connective-tissue corpuscles (Lamina fusca of the choroid). 11. ORGANIC ACIDS FREE FROM NITROGEN.— (1) The fatty acids, with the for- mula C n H 2 n.iO(OH), occur in the body partly free and partly in combination. Free volatile fatty acids occur in decomposing cutaneous secretions (sweat). In combination, acetic acid and caproic acid occur as amido-compounds in glycin ( = amido-acetic acid), and leucin ( = amido-caproic acid). More especially do they occur united with glycerine to form neutral fats, from which the fatty acid is again set free by pancreatic digestion ($ 170, III). (2) The acids of the acrylic acid series, with the formula C n H 2n . 3 0 (H 0 ), are represented in the body by one acid, oleic acid, which in combination with glycerine yields the neutral fat olein. 251. FATS. — (1) Neutral fats occur very abundantly in animals, but they also occur in all plants; in the latter more especially in the seeds (nuts, almonds, cocoanut, poppy), more rarely in the pericarp (olive) or in the root. They are obtained by pressure, melting, or by extracting them with ether or boiling alcohol. They [eg., tristearin, C 57 H 110 O 6 ] contain much less O than the carbohydrates, such as sugar and starch ; they give a greasy spot on paper, and when shaken with colloid substances, such as albumin, they yield an emulsion. When treated with superheated steam, or with certain ferments (p. 412, c), they take up water and yield glycerine and fatty acids, and if the latter be volatile they have a rancid odor. Treated with caustic alkalies they also take up water, and are decomposed into glycerine and fatty acids; the fatty acid unites with the alkali and forms a soap, while glycerine is set free. The soap solution dissolves fats. Glycerine is a tri-atomic alcohol, C 3 H 5 (OH) 3 , and unites with (1) the following monobasic fatty acids (those occurring in the body are printed in italics) : — 414 ACIDS. Acids. 1. Formic . . 2. Acetic . . 3. Propionic . 4. Butyric . . [Isobutyric 5. Valerianic 6. Caproic . . . ch 2 o 2 . c 2 h 4 o 2 . C 3 H 6 0 2 . c 4 h 8 o 2 . c 4 h 8 o 2 ] • C 5 h 10 o 2 . c 6 H 12 o, Acids. 7 - GEnanthylic . . c 7 h 14 o 2 8. Caprylic . . . c 8 h 16 o 2 9 - Pelargonic . • CyHj 8 0 2 10. Capric . . . . c 10 h 20 o : 11. Laurostearic . c 12 h 24 o. 12. Myristic . . .c 14 h 28 o ; i 3 - Palmitic . . • Ci 6 H 32 0 ; Acids. [Margaric, . . C 17 H 34 0 2 is a mixture of 13 and 14.] 14. Stearic . . . . C 18 H 36 0 2 15. Arachinic . . C 20 II 40 O 2 16. Hyartic . . . C 25 H 50 O 2 17. Cerotinic . . . C 27 H 54 0 2 The acids form a homologous series with the formula C n H 2a .iO(OH). With every CH 2 added their boiling point rises 19 0 . Those containing most carbon are solid and non-volatile; those con- taining less C (up to and including 10) are fluid like oil, have a burning acid taste, and a rancid odor. The earlier members of the series may be obtained by oxidation from the latter, by CH 2 being removed, while C 0 2 and H 2 0 are formed; thus, butyric acid is obtained from propionic acid. Nos. 13 and 14 are found in human and animal fat, less abundant and more inconstant are 12, 11, 6, 8, 10, 4. Some occur in sweat ($ 287) and in milk ($ 231). Many of them are developed during the decomposition of albumin and gelatin. Most of the above (except 15 to 17) occur in the contents of the large intestine (£ 185). (2) Glycerine also unites with the monobasic oleic acid, which also forms a series, whose gen- eral formula is C n H 2a . 3 0 ( 0 H) ; and they all contain 2II less than the corresponding members of the fatty acid series. The corresponding fatty acids can be obtained from the oleic acid series, and vice versa. Oleic acid (olein-elainic acid), C 18 H 34 0 2 , is the only one found in the organism; united with glycerine, it forms the fluid fat, olein. The fat of new-born children contains more glycerine of palmitic and stearic acid than that of adults, which contains more glyceride of oleic acid. Oleic acid also occurs united with alkalies (in soaps), and (like some fatty acids) in the lecithins ($ 23). If lecithin be acted on with barium hydrate, we obtain insoluble stearic, or oleic, or palmitic acids and barium oleate, together with dissolved neurin (g 322, b) and baric glycerin phosphate. It ap- pears as if there were several lecithins, of which the most abundant are the one with stearic acid and that with palmitin -j- oleic acid radicle ( Diakonow ). Lecithin occurs in the blood corpuscles (g 23), semen, nerves, while neurin is constantly present in fungi. The neutral fats [palmitin, stearin (both solid), and olein (fluid)], the glycerides of fatty acids, and of oleic acid, are triple ethers of the tri-atomic alcohol glycerine. With the neutral fats may be associated glycerin phosphoric acid, and acid glycerin ether, formed by the union of glycerine and phosphoric acid, with the giving off of a molecule of water (C 3 H 9 P0 6 ) ; it is a decomposition product of lecithin ($ 23). (3) The glycolic acids (acids of the lactic acid series) have the formula C n H 2n . 2 0 ( 0 H) 2 . They are formed by oxidation from the fatty acid series by substituting OH (hydroxyl) for one atom of H of the fatty acids. Conversely, fatty acids may be obtained from the glycolic acids. The fol- lowing acids of this series occur in the body : — (a) Carbonic acid (oxy-formic acid), CO(OH) 2 ; in this form, however, it only makes salts. Free carbonic acid or carbon dioxide is an anhydride of the same = C 0 2 . ( b ) Glycolic acid (oxy-acetic acid), C 2 H 2 0 ( 0 H) 2 , does not occur free in the body. One of its compounds, glycin (glycocoll, amido-acetic acid, or gelatin sugar) occurs as a conjugate acid, viz., as glycocholic acid in the bile ($ 177, 2), and as hippuric acid in the urine ($ 260). Glycin exists in complex combination in gelatin. (c) Lactic Acid (oxy-propionic acid), C 3 H 4 0 ( 0 H) 2 , occurs in the body in two isomeric forms : I. The ethylidene- lactic acid, which occurs in two modifications — as the right rotary sarcolactic acid (paralactic), a metabolic product of muscle; and as the ordinary optically inactive product of lactic fermentation,” which occurs in gastric juice, in sour milk (sauerkraut, acid cucumber), and can be obtained by fermentation from sugar (£ 184). 2. The isomer, ethylene-lactic acid, occurs in the watery extract of muscles ($ 293). ( d ) Leucic Acid (oxy-caproic acid), C 6 H 12 0 3 , does not occur as such, but only in the form of one of its derivatives, leucin (amido caproic acid), as a product of the metabolism in many tissues, and is formed during pancreatic digestion (§ 170, II). Leucic acid may be prepared from leucin, and glycolic acid from glycin, by the action of nitrous acid. (4) Acids of the Oxalic Acid or Succinic Acid Series, having the formula C n H 2n . 4 0 2 (OH) 2 , are bi-basic acids, which are formed as completely oxidized products by the oxidation of fatty acids and glycolic acid, water being removed; and it is important to note their origin from substances rich in carbon, e.g., fats, carbohydrates, and proteids. (#) Oxalic Acid, C 2 0 2 ( 0 H) 2 , arises from the oxidation of glycol, glycin, cellulose, sugar, starch, glycerine, and many vegetable acids — it occurs in the urine as calcium oxalate (§ 260). [b) Succinic Acid, C 4 H 4 0 2 ( 0 H) 2 , has been found in small amount in animal solids and fluids ; spleen, liver, thymus, thyroid ; in the fluids of echinococcus, of hydrocephalus, and of hydro- cele, and more abundantly in dog’s urine after fatty and flesh food ; in rabbit’s urine after feeding with yellow turnips. It is also formed in small amount during alcoholic fermentation (£ 150). THE CARBOHYDRATES. 415 (5) Cholalic Acids in the bile (§ 177) and in the intestine (g 182). (6) Aromatic Acids contain the radicle of benzol. Benzoic acid (= phenylformic acid) occurs in urine united with glycin, as hippuric acid (§ 260). III. ALCOHOLS. — Alcohols are those bodies which originate from carbohydrates, in which the radicle hydroxyl (HO) is substituted for one or more atoms of H. They may be regarded as water, j-O, in which the half of the H is replaced by a CH compound. Thus, C 2 H 6 (ethyl- C H 1 hydrogen) passes into 2 j^ 5 >• O (ethylic alcohol). C H ^ ( 3. boundary layer, j Fat of renal sinus. 4. Transversely coursing medullary rays. Artery. 5. Artery. Longitudinal section through the kidney (Tyson, after Henle). 1 " Labyrinth, i' Medullary rays. MEDULLA. CORTEX. Renal calyx. Ureter. Branch of renal artery. kidney, consisting of an outer cortical and an inner medullary, or pyramidal portion, the latter composed of about twelve conical papillae, or Pyramids of Malpighi, with their apices directed toward the pelvis of the organ, and embraced by the calices of the pelvis of the kidney (Fig. 226). The medullary portion is further subdivided into the boundary layer of Ludwig and the papillary portion. According to Klein, the relative proportions of these three parts are — cortex, 3.5 ; boundary layer, 2.5 ; and papillary portion, 4. The cortex has a light-brown color, and when torn, it presents a slightly granular aspect, with radiating lines or stride running at regular distances. The granules are due to the presence of the Malpighian corpuscles, and the striae to the medullary rays. The 419 420 COURSE AND STRUCTURE OF THE TUBULES. boundary zone is darker, and often purplish in color. It is striated with clear and red lines alternating with opaque ones, the former being blood vessels and the latter uriniferous tubules. The papillary zone is nearly white and uniformly striated, the striae converging to the apex of the pyramid. The me- dulla is much denser and less friable than the cortex, owing to the presence of a large amount of connective tissue between the tubules. The bundles of straight tubes of the medulla may be traced at regular intervals, running outward into the cortex, constituting medullary rays, which become smaller as they pass outward in the Cortical zone, so that they are conical, and form the pyramids of Ferrein (Fig. 227, PF). The portion of the cortex lying between the medullary rays is known as the labyrinth, from the complicated arrangement of its tubules.] [Size, Weight. — The adult kidney is about 11 centimetres (4.4 inches) in length, 5 centimetres (2 inches) wide, and .75 centimetres (.3 inches) in thickness, It weighs, in the male, 1 13.5 to 170 grms. (4 to 6 oz.), in the female, 113. 5 to 156 grms. (4 to 5 y 2 oz.). The width of the cortex is usually 5 to 6 millimetres to \ inch — Tyson ). ] I. The uriniferous tubules all arise within the labyrinth of the cortex by means of a globular enlargement, 200 to 300 fi [yi-g- to yi- inch] in diameter, Fig. 227. PA Longitudinal section of a Malpighian pyramid. PF, pyramids of Ferrein ; RA, branch of renal artery; RV, lumen of a renal vein receiving an interlobular vein ; VR, vasa recta ; PA, apex of a renal papilla; b, 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 papillae 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, 1), 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 ( Bowman ). This tubule is of considerable length, forming many windings in the cortex (Fig. 228, 3) ; the first part of it is 4.5 /x wide, con- stituting the proximal or 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 Fig. 228. boundary zone, the spiral tubule suddenly becomes smaller ( Isaacs ) and passes into the descending portion of Henle' s loop (5), which is 14 /x 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 //.), and as it continues its undu- lating course, it enters a medullary ray, where it constitutes the ascending loop tube (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 (io), which is continuous with (Fig. 229, n , n) the second or distal convoluted tubule or intercalated tubule (“ Schaltstiick ’ ’ of Schweig- ger-Seidel ) (n), 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; a, interlobular artery; i, vas afferens; 2, vas efferens ; r, e , vasa recta; c, venae rectse; v, v, inter- lobular vein ; S, origin of a vena stellata; i, i, Bowman’s capsule and glomerulus ; X, X, convoluted tubules; t, t , Henle’s loop ; n, n, junctional piece ; o, o, collecting tubes ; O, excretory tube. diameter is 40 [i. A short, narrow, wavy junctional or curved collecting tubule (12) connects the latter with one of the straight collecting tubes (13) of a medul- lary ray. As the collecting tubule proceeds through the boundary zone, it receives numerous junctional tubes, and when it reaches the boundary zone, it forms one STRUCTURE OF THE TUBULES. 423 of the collecting tubes (Fig. 229, O), which unite with one another at acute angles to form the larger straight excretory tubes or ducts of Bellini (15), which open on the summit of the Malpighian pyramids into a calyx of the pelvis of the kidney. In the cortex the collecting tubules are 45 [i in diameter, but where they have formed an excretory tube (O), their diameter is 200 to 300 ft ; 24 to 80 of these tubes open on the apex of each of the 12 to 15 Malpighian pyramids. In the lowest and broadest part, the membrana propria is strengthened by the presence of a thick supporting framework of connective tissue. Structure of the Tubules. — [Below the neck, the tubules are lined every- where by a single layer of nucleated epithelium.] Bowman’s capsule, which is about inch in diameter (Fig. 230, II), consists of a homogeneous basement membrane lined internally by a single continuous layer of flattened cells (b). According to Roth, the basement membrane itself is composed of endothelial cells. [In the foetus the lining cells are more polyhedral.] Within the capsule lies the glomerulus or tuft of blood vessels. The cells lining the cap- sule are reflected over and between the lobules of which the glomerulus consists. The glomerulus may not completely fill the capsule, so that, according to the II, Bowman’s capsule and glomerulus, a, vas afferens ; e , vas efferens ; c, capillary network of the cortex ; k, endo- thelium of the capsule ; h , origin of a convoluted tubule. — III, “ rodded" cells from a convoluted tubule — 2, seen from the side, with^-, inner granular zone ; 1, from the surface. — IV, cell lining Henle’s looped tubule. — V, cells of a collecting tube. — VI, section of an excretory tube. activity of the kidney, there may be a larger or smaller space between the glomerulus and the capsule into which the filtered urine passes. The neck is lined by cubical cells. These cells, in some animals, e.g., the rabbit, sheep ( Hassal ), mouse ( Klein ), and frog are ciliated. The proximal convoluted tubule is lined by characteristic epithelium. The cells, which are short or polyhedral, form a single layer, with a turbid or cloudy protoplasm (Fig. 230, III, 1 and 2), which not unfrequently contains oil globules. The cells consist of two parts ; the inner, containing the spherical nucleus, is next the lumen, and granular (III, 2, g ), while the outer part, next the membrana propria, appears fibrillated, or “rodded” (. Heidenhain ), from the presence of rods (Stabchen) or fibrils placed vertically to the basement membrane (Fig. 231). These appear like the hairs of a brush pressed upon a plate of glass (III, 2). The cells are not easily separated from each other, as neighboring cells interlock by means of the branched ridges on their surfaces (III, 1) — ( Hei- denhain , Schachowa). The lumen is well defined, but its size seems to depend upon the state of imbibition of the cells bounding it. 424 BLOOD VESSELS OF THE CORTEX. The spiral tubule has similar epithelium and a correspond- ing lumen, although the epithelium becomes lower and somewhat altered in its characters at the lower part of the tube. The descending limb of Henle’s loop, and the loop itself with a relatively wide lumen, are bounded by clear, flattened epithelial cells, with a bulging nucleus (IV, S) ; the cells lying on one side of the tube being so placed that the bulging part of the bodies of the cells is opposite the thin part of the cells on the opposite side of the tube. [These tubes might be mistaken for blood capillaries, but in addition to their squamous lining, they have a basement membrane, which capillaries have not.] In the ascending limb, the lumen is relatively wide, while its epithelium agrees generally with that in the convoluted tubule, excepting that the “rods” are shorter. Sometimes the cells are arranged in an “ imbricate ” manner. In the irregular tubule, which has a very small lumen, the polyhedral cells lining it contain oval nuclei, and are shorter than those of the convoluted tubules. The cells, again, are very irregular in size, while their “rodded” character is much coarser and more defined (Fig. 232). The distal convoluted tubule closely resembles in its structure the proximal convoluted tubule, and is lined by similar cells. The curved collecting or junctional tubule, although narrow, has a relatively wide lumen, as it is lined Fig. 232. by clear, somewhat flattened cells. The collecting tubes have a distinct lumen, and are lined by clear , somewhat irregular, cubi- cal cells (Fig. 230, V), which, in the larger ex- cretory tubes, are distinctly columnar (VI). The basement membrane is said to be absent in the larger tubes. Epithelium of an irregular tubule of the kidney of a dog ( Klein ). [Klein describes a thin, delicate, nucleated centro-tubular membrane lining the surface of the epithelium next the lumen.] II. The Blood Vessels. — The renal artery (Fig. 226) divides into four or five branches, which pass into the kidney at the hilum. These branches, sur- rounded by connective tissue continuous with that of the capsule, continue to divide, and pass between the papillae, to reach the bases of the pyramids on the limits between the cortical and boundary zones, where they form incomplete arches. From these horizontal trunks the interlobular arteries (Fig. 229, a) run vertically and singly into the cortex, between each two medullary rays, and in their course they give off on all sides the short, undivided vasa afferentia (1), each of which enters a Malpighian capsule at the opposite pole from which the urinary tubule is given off. Within the capsule, each afferent artery breaks up into capillaries arranged in lobules and supported by connective tissue, the whole forming a tuft of capillary blood vessels, or a glomerulus. Each glom- erulus is covered on its surface, directed toward the wall of the capsule by a layer of flat, nucleated epithelial cells (Fig. 230, II), which also dip down between the capillaries (. Heidenhain , Runeberg). A vein, the vas efferens (2), which is always smaller than the afferent arteriole, proceeds from the centre of the glom- erulus, and leaves the capsule close to the point at which the afferent vessel enters it (Fig. 230, II). In their structure and distribution all the efferent vessels re- semble arteries, as they divide into branches to form a dense, narrow-meshed capillary network (Fig. 229, A, and Fig. 230, II, c), which surrounds and ramifies over the convoluted tubules. The meshes are elongated around the tubules of the medullary rays, and more polygonal around the convoluted tubules (Fig. Fig. 231. Convoluted tubule (after ammonium chro- mate) showing “rodded" epithe- lium. LYMPHATICS, NERVES, CONNECTIVE TISSUE. 425 229). Some of the lowest efferent vessels split up into vasa recta, which run toward the medulla. The interlobular arteries become smaller as they pass toward the surface of the kidney, and some of their terminal capillaries communicate with the capillaries of the external capsule itself.] Venous trunks proceed from the capillary network, to terminate in the interlobular veins (V). These veins begin close under the external capsule by venous radicles arranged in a stellate manner (constituting the stellulae Verheynii, or venae stellatae), and accompany the corresponding artery to the limit between the cortex and boundary zone, where they communicate with the large venous trunks in that situation. The blood vessels of the medulla arise from the vasa recta (Fig. 229, r). The latter begin on the limit of the cortex and medulla, either as single, direct, muscular branches (r) of the large arterial trunks, or from those efferent vessels (^) which lie next to the medulla. The latter are said to be devoid of muscle ; while, according to Huschke, a few vasa recta are formed by the union of the capillaries of the medullary rays. All the vasa recta enter the boundary layer, where they split up into a leash or pencil of small arterioles, which pass between the straight tubules toward the pelvis, and form in their course a capillary network with elongated meshes. From these capillaries there arise venous radicles, which, as they proceed toward the limit between the cortex and medulla, form the venae recta (rr), and open into the concave side of the venous trunks in this region. At the apex of the papillae, the capillaries of the medulla form connections with the rosette-like capillaries surrounding the excretory ducts (at I). [The circula- tion through the vasa recta is most important. The cortical system of blood vessels communicates with the medullary, but as most of the vasa recta are derived from the same vessel as the interlobular arteries, it is evident that they may form a side stream through which much of the blood may pass without traversing the vessels of the cortex. Very probably the “short cut ” is useful in congestions of the kidney. The amount of distention of these vessels, also, will influence the size of the tubules lying between them. There are two other channels by which blood can pass through the renal arteries without traversing the glomeruli — (1) The anastomoses between the terminal twigs of the renal artery and the sub- capsular venous plexus ; (2) small branches given off, either by the interlobular arteries, or by the afferent vessels before entering the glomeruli ( K Brunton).~\ The blood vessels of the external capsule are derived partly from the terminal twigs of the interlobular arteries, partly from branches of the supra-renal, phrenic and lumbar arteries, which anastomose with each other. The capillary network has simple meshes. The origins of the veins pass partly into the venae stellatae and partly into the veins of the same name as the arteries. The connection of the area of the renal artery with the other arteries of the capsule explains why, after ligature of the renal artery within the kidney, the blood still circulates in the external capsule [C. Ludwig , M. Herrmann) ; in fact, these blood vessels still supply the kidney with a small amount of blood, which may suffice to permit a slight secretion of urine to take place ( Litten , Pautynski ). III. The lymphatics form a wide-meshed plexus in the capsule of the kidney, while under it they form large spaces ( Heidenhain ). In the parenchyma of the kidney, the lymphatics are said to be represented by large slits, devoid of a wall, in the tissues, and are more numerous around the convoluted than the straight tubules. The slits pass to the surface of the kidney, and expand under the capsule. When the lymphatics are greatly distended, they tend to compress the uriniferous tubules and the blood vessels (C. Ludwig and Zawarykin ). According to Ryndowsky, the uriniferous tubules are surrounded by true lymphatics with an endothelial lining, and they even penetrate into the capsule of Bowman, along with the vas afferens. [The large blood vessels are also surrounded by lymphatics.] Large lymphatics, provided wiih valves, pass out of the kidney at the hilum, while others emerge through the capsule ; both sets are connected with the lymph spaces of the capsule of the kidney ( A . Budge). IV. The nerves form small trunks provided with ganglia [Beale), and accompany the blood vessels. [They are derived from the renal plexus and the lesser splanchnic nerve.] They contain medullated and non-medullated fibres, and the latter have been traced by W. Krause as far as the apices of the papillae. Their mode of termination is unknown. Physiologically , we are certain that they contain both vaso-motor and sensory fibres; perhaps there may be also vaso-dilator and secretory fibres. V. The connective tissue, or interlobular stroma, forms in the papillae, especially at their pices, fibrous, concentric layers of considerable thickness between the excretory tubules (Fig. 233). 426 PHYSICAL CHARACTERS OF URINE. Further outward, the fibrillar character becomes less distinct, while at the same time branched connective-tissue corpuscles occur in greater numbers ( Beer ). In the cortex, the interstitial stroma consists almost entirely of branched corpuscles, which anastomose with each other ( Goodsir). [There is also a small quantity of delicate fibrous tissue around Bowman’s capsule, and along the course of the arteries. The connective tissue often plays an important role in pathological conditions of the kidney, as in interstitial nephritis.] The outer layers of the capsule of the kidney are composed of dense bundles of fibrous tissue, while the deeper layers are more loose, and send processes into the cortical layers. The deeper layers also contain non-striped muscular fibres ( Eberth , W. Krause). The capsule is easily stripped off. None of the secretory substance is removed with it. Under the capsule in the human kidney, there is a thin plexus of non-striped muscular fibres. At the hilum it becomes continuous with the outer fibrous coat of the dilated upper end of the ureter. The fat surrounding the kidney is united to the kidney partly by blood vessels and partly by bands of connective tissue. [The sub-capsular layer of the cortex, and a thin layer next the boundary zone (Fig. 228, a, a), are devoid of Malpighian corpuscles.] [Development of a Malpighian Capsule. — The upper end of the urinary tubule is dilated and closed, and into it there grows a tuft of blood vessels (a), pushing one layer of the tube before it (d ) ; hence the capillaries become invested by it, just as an organ is surrounded by a serous sac, so that one layer — the reflected one (6 ) — of the tubule is closely applied to the blood vessels, while the other (c) lies loosely over it with a space between the two (Fig. 234).] Fig. 233. 255. THE URINE. — Physical Characters. — A knowledge of the com- position of this secretion is of the greatest value to the physician and surgeon. 1. The quantity of urine passed by an adult man in twenty-four hours is between 1000 and 1500 cubic centimetres, or about 50 ozs., and in the female 900 to 1200 c.c. The minimum is secreted between 2-4 a.m., and the maximum between 2-4 p.m. ( Weigelin ). The amount is diminished by profuse sweating, diarrhoea, thirst, non-nitrogenous food, diminu- tion of the general blood pressure, after severe hemorrhage, and in some diseases of the kidneys. The minimum, which may be normal, is 400 to 500 c.c. It is increased by increase of the general blood pressure, or of the pressure within the area of the renal artery, by copious drinking, contrac- tion of the cutaneous vessels through the action of cold, the passage of a large amount of soluble substances (urea, salts, and sugar) into the urine, a large amount of nitrogenous food, as well as by various drugs, such as digitalis, alcohol, squills. After taking fluids charged with C 0 2 , the amount of urine is increased during the following hours [Quincke). The secretion is influenced directly by the nervous system, as in the sudden polyuria following nervous excitement, such as hysteria [when the person usually passes a large amount of very pale- colored urine]; after an epileptic attack, and also after pleasurable excitement ( Beneke ). Lastly, ESTIMATION OF SOLIDS. 427 we have the polyuria unaccompanied by the presence of sugar in the urine, which follows injury to a certain part of the floor of the fourth ventricle ( Cl. Bernard). The urine is measured in tall, graduated, cylindrical vessels (Fig. 235, A). [In estimating the quantity of urine passed, the patient must, of course, be directed always to empty his bladder at a particular hour, and collect the urine passed during the next twenty-four hours.] 2. The specific gravity varies, as a mean, between 1015 and 1025 ; the minimum, after copious draughts of water, may be 1002 ; while the maximum, after profuse perspiration and great thirst, may be 1040. The mean specific gravity is about 1020. In newly-born children, the specific gravity falls very considerably during the first three days, which is due to the ingestion of a large amount of food (. Martin and Ruge ). [The specific gravity of the urine in infants is about 1003 to 1006-.] A healthy adult excretes about 50 grms. [r^ oz.] daily of solids by the urine, or about 1 grm. of solids per 1 kilo, of body weight. The specific gravity is estimated by means of a urinometer (Fig. 235, B), the urine being at the temperature of 16 0 C. [The urinometer, when placed in distilled water, ought to float at the mark o° or zero, which is conventionally spoken of as 1000. The urine itself ought to be tested in an tall cylindrical glass, of such width that the urinometer, when placed in it, may float freely and not touch the sides. Take care that no air bubbles adhere to the instrument. When reading off the mark on the stem, raise the vessel to the eye and bring the eye on a level with the surface of the water, noting the number which corresponds to this. This rule is adopted, because the water rises on the stem in virtue of capillarity. It is essential that a sample of the mixed urine of the twenty- four hours be used for ascertaining the mean specific gravity.] Christison’s Formula. — To estimate the amount of solids in the urine. This may be done approximately Fig. 2 35- by means of the formula of Trapp or Haeser, or, as it A B is called in this country, “ Christison’s formula,” viz., “ Multiply the two last figures of a specific gravity ex- pressed in four figures by 2.33” ( Christison and Haeser ), or by 2 ( Trapp ), or 2.2 ( Loebisch ). This gives the amount of solids in every 1000 parts. [Suppose a person passes 1200 c. c. urine in twenty -four hours, and specific gravity is 1022, then 22 X 2.33 = 51.26 grms. in 1000 c. c. To ascertain the amount in 1200 c. c. 51.26 X 1200 1000 : 1200 : : 51.26 : X 61.51 grms.] 1000 Direct estimation to determine the exact amount of solids. Place 15 c. c. of urine in a capsule of known weight, and evaporate it over a water bath, afterward completely dry the residue in an air bath at ioo° C., and then cool it over concentrated sulphuric acid. During the process, a small amount of urea is decom- posed, so that the value obtained is slightly too small. Of course, the specific gravity varies with the amount of water in the urine. The most concentrated (highest spe- cific gravity) urine is the morning urine (Urina noctis), especially after being retained in the bladder, e.g., in prolonged sleep a certain amount of water is absorbed, so that the urine becomes more concentrated. The most dilute urine is secreted after copious drinking (Urina potus). Under pathological conditions, as in diabetes mellitus ($ 175), the urine is, at the same time, very copious (as much as 10,000 c. c.), and very concentrated, while the specific gravity varies from 1030 to 1060. [The high specific gravity in this case is due to the presence of a large amount of grape sugar.] In fever the urine is concentrated, and small in amount. In polyuria, due to certain nervous conditions, the urine is very dilute and copious, while the specific gravity may be as low as 1001. 3. The color of the urine depends on the coloring matters present in it, and varies greatly, but the differences in color are due loco to 19 ma 1030 .3048 Graduated cylinder and flask for measuring the amount of urine. Urinometer. 428 AMOUNTS OF URINARY CONSTITUENTS. chiefly to the variations in the amount of water. Normally, it has a pale straw color, but if it contains more water than usual it has a very pale tint, and in certain cases (as in the sudden polyuria occurring after an attack of hysteria), it may be as clear as water. Concentrated urine, as after meals, or the first urine passed in the morning, has a darker color ; it is a dark-yellow or brownish-red ; while it is usually dark colored in fever. Foetal urine, and also the urine first passed after birth, are as clear and colorless as water. The admixture of various substances with the urine alters its color. When mixed with blood, according to the degree of decomposition of the haemoglobin, the urine is red or dark brownish-red [more frequently it is swokjy], especially if the blood comes from the kidneys and the urine is acid. When mixed with bile pigments, it is of a deep yellowish-brown, with an intense yellow froth ; senna taken internally makes it intensely red, rhubarb brownish-yellow, and carbolic acid black. Urine undergoing the ammoniacal fermentation may present a dirty, bluish appearance owing to the formation of indigo. The color of urine is estimated by Neubauer and Vogel by means of an empirical “ color scale.” [Amounts of the Several Urinary Constituents ( Loebisch ). Constituents. Man, 28 years of age, weight 72 kilos., observations over 8 days ( Kerne r). Means of analyses in different In 24 hours. individuals. {Vogel.) Min. Max. Mean. In 24 hours. C. C. C. C. C C. C. C. Quantity, IO99 2150 I49I 1500 Specific gravity, IOI5 1027 1021 1020 Water, I44O Solids, . . . ' 38. 'i 60 Urea, 32.00 43-4 35 Uric acid, O.69 i-37 O.94 0-75 Sodium chloride, I5.OO 19.20 l6.8 16.5 Phosphoric acid, 3.00 4.07 342 3-5 Sulphuric acid, 2.26 2.84 2.48 2.0 Phosphorus, Calcium, O.25 0.51 O.38 Magnesium phosphate, .... 0.6 7 1.29 O.97 • • Total quantity of earthy phos- phates 0.92 1.80 i-35 1.2 Ammonia, 0.74 1. 01 0.83 0.65 3 ] Free acid, 1.74 2.20 i-95 [Amounts of the Several Urinary Constituents Passed in 24 Hours {Parkes). By an average man of Per 1 kilo, of body Constituents. 66 kilos. weight. grms. grms. Water, 1 500.000 23.000 Total solids, 72.000 1. 100 Urea, 33-!8o 0.500 Uric acid, o-555 0.0084 Hippuric acid, ....... 0.400 0.0060 Kreatinin, 0.910 0.0140 Pigment and other substances, . 10.300 0.1510 Sulphuric acid, 2.012 0.0305 Phosphoric acid, 3.164 0.048b Chlorine, 7.000 (8.12) 0.1260 Ammonia, 0.770 Potassium, 2.500 Sodium, 1 1 .090 Calcium, 0.260 . . . Magnesium, 0.207 - - - ] REACTION OF URINE. 429 Fluorescence. — Urine, but especially ammoniacal urine, exhibits fluorescence, which disappears on the addition of an acid, and reappears after the addition of an alkali ( Schonbein , Schleiss , v. Lowenfeld). Mucous Cloud. — Normal urine, after standing for several hours, deposits a fine cloud of vesical mucus [like delicate cotton wool]. The froth of normal urine is white, and disappears pretty rap- idly, while that on an albuminous urine persists much longer. The urine not unfrequently contains some epithelial cells from the bladder and urethra. 4. Consistence. — Normal urine, like water, is a freely mobile fluid. Large quantities of sugar, albumin, or mucus make it less mobile; while the so-called chylous urine of warm climates may be like a white jelly. 5. The taste is a saline bitter, the odor is characteristic and aromatic. Ammoniacal urine has the odor of ammonia. Turpentine taken internally gives rise to the odor of violets, copaiba and cubebs a strongly aromatic, and asparagus an unpleasant odor. Valerian, assafoetida, and castoreum [but not camphor] also produce a characteristic odor. [The odor of diabetic urine is described as “ sweet.” ] 6. The reaction of normal urine is acid, owing to the presence of acid salts, chiefly acid sodic phosphate, which seems to be derived from basic sodic phos- phate, owing to the uric acid, hippuric acid, sulphuric acid, and C0 2 taking to themselves part of the soda, so that the phosphoric acid forms an acid salt. After a diet of flesh, acid potassic phosphate is the cause of the acidity. That the urine contains no free acid is proved by the fact that it gives no precipitate with sodic hyposulphite ( v . Voit, Huppert'). The acid reaction is increased after the use of acids, e.g., hydrochloric and phosphoric, also by ammoniacal salts, which are changed within the body into nitric acid ; lastly, after prolonged mus- cular exertion ( Klupfel , Fustier ). The morning urine is strongly acid. The urine becomes less acid or alkaline — fi) By the use of caustic alkalies, alkaline car- bonates, or alkaline salts of the vegetable acids, the last being oxidized within the body into car- bonates. (2) By the presence of calcic, or mag- nesic carbonate. (3) By admixture with alkaline blood, or pus. (4) By removing the gastric juice through a gastric fistula (p. 272 — Maly ) ; further, from one to three hours after a meal [The reac- tion of urine passed during digestion may be neutral, or even alkaline. This is due either to the formation of acid in the stomach ( Bence Jones), or to a fixed alkali derived from the basic alkaline phosphates taken with the food ( W. Rob- erts ).] (5) The urine is rarely alkaline in anaemia, owing to a deficiency of phosphoric and sulphuric acids. [(6) The nature of the food — vegetable food makes it alkaline. (7) By profuse sweating {Jos. Hofmann). (8) By absorption of alkaline transudations (blood serum), Quincke.'] Method. — [The reaction of urine is tested by means of litmus paper. Normal urine turns blue litmus paper red, and does not affect red litmus. An alkaline urine makes red litmus paper blue, while a neutral urine does not alter either blue or red litmus paper.] Sometimes violet litmus paper is used, which becomes red in acid, and blue in alkaline urine. Estimation of the Acidity. — This is done by determining the amount of caustic soda necessary to produce a neutral reaction in 100 c.c. of urine. A soda solution containing 0.0031 grm. of soda in each c.c. is used ; 1 c.c. of this solution exactly neutralizes 0.0063 g rm - oxalic acid. To the 100 c.c. of urine in a beaker, soda solution is added, drop by drop, from a graduated burette ( Fig. 236), until violet litmus paper becomes neither red nor Fig. 236. 430 QUANTITY OF UREA. blue. The number of c.c. of soda solution is now read off on the burette, and as each c.c. corres- ponds to 0.0063 grin. oxalic acid, we can easily calculate the amount of oxalic acid which is equiv- alent to the degree of acidity in 100 c.c. of urine. So that the degree of acidity of the urine is expressed by the equivalent amount of oxalic acid, which is completely neutralized by the same amount of caustic soda. Urine of Mammals. — The urine of carnivora is pale, passing into a golden yellow ; its specific gravity is high, and its reaction strongly acid. The urine of herbivora is alkaline ; it shows a pre- cipitate of earthy carbonates (hence, it effervesces on the addition of an acid), and of basic earthy phosphates. During hunger, the urine presents the character of that of carnivora, as the animal in this case practically lives upon its own flesh and tissues. 256.— I. THE ORGANIC CONSTITUENTS OF URINE.— Urea = CO(NH 2 ) 2 .— Urea, the diamide of C 0 2 , or carbamide, is the chief end product of the oxidation of the nitrogenous constituents of the body. Its com- position is comparatively simple : 1 carbonic acid -j- 2 ammonia — 1 water. It crystallizes in silky, four-sided prisms with oblique ends (rhombic system), with- out water of crystallization (Fig. 237, a), but when it crystallizes rapidly it forms delicate white needles. It has no action on litmus, is odorless, and has a weak, bitter, cooling taste, like saltpetre ; is readily soluble in water and alcohol, but insoluble in ether. It is an isomer of ammonic cyanate, from which it may be Fig. 237. a, Urea; b, hexagonal plates ; and c, smaller scales, or rhombic plates of urea nitrate. prepared by evaporation ( Wohler , 1828 ), whereby the atoms rearrange themselves. It can be prepared artificially in many other ways. Decomposition. — When heated above 120°, it gives off ammonia vapor, while a glassy mass of biuret and cyanic acid is left. When urine undergoes the alkaline fermentation ($ 263), or when urea is treated with strong mineral acids, or boiled with the hydrates of the alkalies, or superheated with water (240° C.), it takes up two molecules of water and produces ammonium carbonate, thus — CO(NH 2 ) 2 + 2 H 2 0 = C 0 (NH 4 0 ) 2 . When brought into relation with nitrous acid, it splits up into water, C 0 2 , and N. The two last decompositions are made the basis of methods for the quantitative estimation of urea (§ 257). Quantity. — In normal urine, urea occurs to the extent of 2.5 to 3.2 per cent. An adult man excretes daily from 30 to 40 grms. [500 grains, or a little over 1 oz.] ; women excrete less, while children excrete relatively more ; owing to the relatively greater metabolism in children, the unit weight of body produces more urea than the unit weight of an adult, in the proportion of 1.7 : 1. If the meta- bolism of the body is in a condition of equilibrium (§ 236), the urea excreted con- tains almost as much N as is taken in with the nitrogenous constituents of the food. QUANTITY OF UREA. 431 Variations in the Quantity. — The amount of urea increases when the amount of proteids in the food is increased ; and also when there is a more rapid breaking up of the nitrogenous tissues of the body itself. As this breaking up is increased by diminution of O ( Frankel , Penzoldt , and Fleischer), and by loss of blood ( Bauer ) ; so these conditions also increase the urea (§ 41). It is also in- creased by drinking large draughts of water, by various salts, by frequent urina- tion, and by exposure to compressed air. In diabetic persons, who eat very large quantities of food, it may exceed 100 grms. [over 3 oz.] per day ; during hunger it sinks to 6.1 grms. [90 grains] per day ( Seegen ). During inanition, the maximum amount is excreted toward mid-day, and the minimum in the morning. The daily amount of urea varies with the quantity of urine ; three to five hours after a meal, the formation of urea is at a maximum, when it sinks and reaches its mini- mum during the night. Muscular exercise, as a rule, does not increase it ( v . Voit , Fick , and Wislicenus — § 295), but only when deficiency of O, causing dyspnoea, occurs at the same time i^Oppenheini). Pathological. — In acute febrile inflammations, and in fevers generally ($ 22,3), the urea in- creases until the crisis is reached, and afterward it diminishes ( Vogel'). After the fever has passed off, the amount excreted is often under the normal. In some cases of high fever, although the amount of urea formed is increased, it may not be excreted ; there is a retention of the urea, while, later on, this may lead to an increased excretion ( Naunyn ). In chronic diseases, the amount depends largely upon the state of the nutrition, the metabolism, and also upon the degree of fever present. Degenerative changes in the liver, e.,g., due to poisoning with phosphorus, may be ac- companied by diminished excretion of urea and increased excretion of ammonia ( Stadelmann ). It is increased in man by morphia, narcotin, marcein, papaverin, codein, thebain ( Fubini ), arsenic ( Gdthgens ), compounds of antimony, and small doses of phosphorus ( Bauer ), which favor the de- composition of proteids. Quinine which “spares” the proteids diminishes it. Occurrence. — Urea occurs in the blood (1 : 10,000), lymph, chyle (2 • iooo), liver, lymph glands, spleen, lungs, brain, eye, bile, saliva, amniotic fluid, and pathologically in sweat, e. g., in cholera, in the vomit and sweat of uraemic patients, and in dropsical fluids. Formation. — It is certain that it is the chief end product of the metabolism of the proteids. Less oxidized products are uric acid, guanin, xanthin, hypo- xanthin, alloxan, allantoin. Uric acid administered internally appears in the urine as urea ; alloxan and hypoxanthin can be changed directly into urea. The urea excretion is increased by the administration of leucin, glycin, aspartic acid, or ammonia salts. ( Schulzen , Nencki.) As yet, it has not been definitely determined where urea is formed, but the liver and, perhaps, the lymph glands are organs where it is produced (§ 178). In birds, the liver forms uric acid from ammonia. The liver can be readily excluded from the circulation in birds, and Minkowski found that after this operation the uric acid was diminished and the ammoniacal salts increased (§ 178). Antecedents. — During digestion, the proteids are converted into leucin, tyrosin, glycin, and as- paraginic acid. If the amido acids, glycin, leucin, or asparaginic acid, or ammoniacal salts, be given to an animal, the amount of urea excreted is increased. As the molecule of the amido acids contains only one atom of N, and the molecule of urea contains two of N, it is probable that urea may be formed synthetically from these acids. It is possible that the amido acids meet with nitro- genous residues in the juices of the body, e.g., carbamic acid or cyanic acid. The union of these may produce urea. According to Salkowski, feeding with these substances causes the breaking up of the proper proteids of the body so as to provide the necessary components. Schmiedeberg is of opinion that urea is formed in the body from ammonia carbonate by the removal of water ; and v. Schroder found that, when he passed blood containing ammonia carbonate through a fresh liver, the urea in the blood was greatly in- creased. Drechsel succeeded in producing urea at ordinary temperatures by the rapid alternating oxidation and reduc- tion of a watery solution of ammonia carbonate. [We know that the greater part of the urea exists in the blood, and that the renal epithelium removes it from the blood. Although it is surmised that some of the proteid bodies named above, more especially leucin, and perhaps, also, Perfect crystals of oxalate of urea. 432 QUALITATIVE AND QUANTITATIVE ESTIMATION OF UREA. kreatin, are the precursors of urea, yet we cannot say definitely how or where the transformation takes place. Perhaps this is effected in the liver, and, it may be, also in the spleen ($ 103).] Preparation. — Urea is readily prepared from dog’s urine (especially after a diet of flesh) by evaporating it to a syrupy consistence, extracting it with alcohol, and again evaporating the filtrate to a syrupy consistence. The crystals which separate are washed with water to remove any extractives that may be mixed with them, and dissolved in absolute alcohol It is then filtered and allowed to crystallize slowly. Or, human urine may be evaporated to one-sixth of its volume and cooled to o°, and excess of strong nitric acid added, which precipitates urea nitrate mixed with coloring matter. This prec pitate is pressed in blotting paper, then dissolved in boiling water containing animal charcoal, and filtered while hot. When it cools, colorless crystals of urea nitrate separate (Fig. 237, c). These crystals are redissolved in warm water, and barium carbonate added until effervescence ceases ; urea and barium carbonate are formed. Evaporate to dryness, extract with absolute alcohol, filter, and allow evaporation to take p ace, when urea separates. Compounds of Urea. — Urea combines with acids, bases and salts. The following are the most important combinations : — 1. Urea nitrate (CH 4 N 2 0 , HN 0 3 ) is easily soluble in water, and not so soluble in water con- taining nitric acid. It forms characteristic rhombic crystals (Fig. 237, b and c). Sometimes the formation of these crystals is used to determine microscopically the presence of urea in a fluid. If a fluid is suspected to contain minute traces of urea, it is concentrated and a drop of the fluid is put on a microscopic slide. A thread is placed in the fluid, and the whole is covered with a cover glass. A drop of concentrated nitric acid is allowed to flow under the cover glass, and after a time crystals of urea nitrate adhering to the thread may be detected with the microscope. 2. Urea oxalate (CH 4 N 2 0 ) 2 , C 2 H 2 0 4 -f- H 2 0 , is made by mixing a concentrated solution of urea with oxalic acid. The crystals form groups of rhombic tables, often of irregular shape. It is only slightly soluble in cold water, and still less so in alcohol (Fig. 238). 3. Urea phosphate (CH 4 N 2 0 , H 3 P 0 4 ) forms large, glancing rhombic crystals, very easily soluble in water. It is obtained by evaporating the urine of pigs fed on dough. 4. Sodic chloride -f- urea (CH 4 N 2 0 , NaCl -f- H 2 0 ) forms rhombic, shining prisms, which are sometimes deposited in evaporated human urine. 5. Urea -j- mercuric nitrate is obtained as a white, cheesy precipitate, when mercuric nitrate is added to a solution of urea. Liebig’s titration method for urea depends on this reaction ($ 257, II). 257. QUALITATIVE AND QUANTITATIVE ESTIMATION OF UREA.— I. The Qualitative Estimation of Urea. — (1) It may be isolated as such. If albumin be present, add to the fluid three to four times its volume of alcohol, and, after several hours, filter. Evapo- rate the filtrate over a water bath, and dissolve the residue in a few drops of water. (2) The crystals of urea nitrate may be detected microscopically (Fig. 237). II. Quantitative Estimation. — (1) Sodic hypobromite decomposes urea into CO 2 , H z O and N. On this reaction depends the Knop-Hiifner method of quantitative estimation. The N rises in the form of small bubbles in the mixed fluid, while the C 0 2 is absorbed by the caustic soda. [The reaction is the following : — N 2 H 4 CO + 3NaBrO = 3 NaBr -f C 0 2 + 2H 2 0 + N. The nitrogen is collected and estimated in a graduated tube, and the amount of urea calculated from the volume of nitrogen. The uric acid is also decomposed, but that can be estimated sepa- rately and a correction made. We may use the apparatus of Russell and West, or Dupre, or that of Charteris (Fig. 239).] [Ureameter. — Make a solution of hypobromite of soda by mixing 100 grammes NaHO in 250 c.c. of water, and adding 25 c.c. of bromine. It is better to be made fre>h, as it decomposes by keeping. The graduated tube is placed in a cylindrical vessel, filled with water, and depressed until the zero on the tube coincides with the level of the water. Introduce 15 c.c. of the hypo- bromite solution into the pyramidal-shaped bottle, while into a short test tube are placed 5 c.c. of urine. The test 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 pass 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 C 0 2 is absorbed by the caustic soda. The collecting tube is usually graduated beforehand, so that each division of the tube is = o. 1 per cent, of urea, or 0.44 gr. per fluid oz. Thus, suppose 50 oz. of urine are passed in twenty-four hours, and that 5 c.c. of urine evolve 18 measures of N, then 0.44 X ^ X 5 ° — 3 96 grs. of urea. If, however, the tube be graduated into c.c., then 30.3 c.c. of N — 0.1 grm. of urea at the ordinary temperature and pressure.] [Squibb’s Method is simple and expeditious. Measure off 1 ]/ z oz. of liquor sodae chlor. (U. S'.), and place it in A (Fig. 240), together with a glass thimble D, containing 4 c.c. of urine. 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 B into 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 ( Martindale ).] III. Volumetric Method [Liebig). 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. The barium mixture consists Fig. 239. Squibb’s Method. 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 dry filter, and take 15 cubic centimetres of the filtrate, which 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 1 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 yellow 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 io milligrammes of urea, just multiply by ten, and the amount of urea in io 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, l to per cent. NaCl, deduct 2 c.c. from the number of c.c. of the S.S. added to 10 c.c. of urine. 258. URIC ACID = C 5 H 4 N 4 0 3 . — 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 excreted. The proportion of urea to uric acid is 45 : 1. It is the chief nitrogenous product in the urine of birds, reptiles, and insects, while it is absent from herbivorous urine. surface, barrel-shaped figure, prism with a hexahedral basal surface; d, 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 tlje oxalic acid in the urine is also increased (§ 260 — Wohler , v. Frerichs ) ; in fowls, feeding with leucin, glycin, or asparaginic acid (v. Knieriem ), or ammonia carbonate ( Schroeder ), increases the amount of uric acid. When urea is administered to fowls, it is reduced chiefly to uric acid ( Cech , H. Mayer , MO- 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 ( d ). If 20 c.c. of HC 1 , or acetic acid, be added to 1 litre of urine, crystals ( b ) are deposited, like cayenne pepper, on the surface and sides of the glass, after several hours. [The HC 1 decomposes the urates, and liberates the acid, which does not crystallize at once, owing to the presence of the phosphates in the urine (. Brilcke ). 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 18,000 parts of cold, and in 15,000 of boiling water, and insoluble in alcohol and ether. Horbaczewski prepared it synthetic- ally by melting together glycitf, ©r, as it is also called glycocin, and urea. It is freely soluble 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. Superoxide of lead converts it into urea, allantoin, oxalic acid, and C 0 2 ; while ozone forms the same substances, with the addition of alloxan. When it is reduced by H in statu nascendi, 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 gouty 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 ( Ebstein ). [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-born 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, in 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, potassic 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, anaemia 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 water, but are easily soluble in warm water. Neu- tral urates are changed by C0 2 into acid salts. Hydrochloric and acetic acids break up the compounds, and crystals of uric acid separate. ( 1 ) Acid sodic urate usually 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, b); 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 (1), or mixed with free uric acid, accompanied by triple phosphate. Microscopically, it is the same as (1). (I) and (2) are distinguished by the sediment dissolving when 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 urinary calculi. 259. ESTIMATION OF URIC ACID. — I. Qualitative. — 1. 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 C0 2 are given off ; urea and alloxan (C 4 H 2 N 2 0 4 ) remain. Evapo- 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 silver 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 HC 1 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 HC 1 , 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 : 1. Centinormal ammonic sul- phocyanate, made by dissolving 8 grms. of crystals in 1 litre of water, and adjust to decinormal silver solution. Dilute with 9 vols. of water, 1 c. c. = 0.00168 uric acid. 2. Saturated solution of iron alum (the indicator). 3. Pure HN 0 3 (20 to 30 per cent.). 4. Strong ammonia. Ammoniacal sdver solution made by dissolving 5 grms. AgNO s in 100 c. c. water, and add NH 4 HO until the solution becomes clear. Process. — Place 25 c. c. of urine in a beaker, and add 1 grm. sodic bicar- bonate; then add 2 to 3 c. c. of ammonia to precipitate ammonio-magnesic phosphate. Add 1 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, and 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 present is ascertained by multiplying the number of cubic centi- metres of the sulphocyanate used by 0.00168.] 260. KREATININ AND OTHER SUBSTANCES. — Quantity.— Kreatinin, C 4 H 9 N 3 0 2 (. Liebig ), is derived from the kreatin of muscle, from which it can be obtained 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, anaemia, 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 chloride. 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 ( Th. Weyl). 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 5 H 4 .N 4 0 2 ) ( Marcet ) occurs only to the amount of 1 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 crystalline body paraxanthin, and the amorphous heteroxanthin, occur in traces in the urine {Salomon). Sarkin (= Hypoxanthin), C 5 H 4 N 4 0 . — As yet this substance has been found only in the urine of leukaemic patients ( Jakubasch ), and it has been prepared in the form of needles or flattened 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 . Salkowski). 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 (C 3 H 4 N 2 0 4 ) occurs in very small quantity combined 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 (C 2 H 2 0 4 ). — The series of chemical decompositions of oxaluric acid leads to oxalic acid. It occurs, but not constantly, to the amount of 20 Fig. 244. Kreatinin-zinc chloride, a, balls with radiating marks; b, crystallized from water; c, rarer forms from an alcoholic extract. 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 Neubauer, 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. Oxalate of lime, a, octahedra ; b, basal plane of an octahedron forming a rectangle ; c, compound forms ; d , dumb bells. Fig. 246. Perfect dumb-bell crystals of oxalate of lime. fed with uric acid excrete much oxalate of lime ( v . Frerichs , Wohler). 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 (. Beneke ), and it may 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 C0 2 may be formed. The amount of oxalic acid is increased after the use of wine and sodic bicarbonate. 438 HIPPURIC ACID. Hippuric Acid = C 9 H 9 N 0 3 (Benzoylamidoacetic acid) occurs in large amount in the urine of herbivora (. Liebig ), 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 in colorless, four-sided prisms (Fig. 247). 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 — c 7 h 6 o 2 + C 2 H 5 N 0 2 = C 9 H 9 N 0 3 + h 2 o 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- Fig. 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 Iflood 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 proteids. In the dog, the formation of hippuric acid occurs in the kidney ( Schmiedeberg and Bunge), and in the COLORING MATTERS OF URINE. 439 frog also outside the kidney. Kiihne and Hallwachs 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 2 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. — Add milk of lime to the fresh urine of horses or cows to form calcic hippurate. Filter, 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 20 H 14 N 2 O 6 -j- H 2 0 occurs in the urine of dogs (J. v. Liebig). Allantoin, C 4 H 6 N 4 0 3 , 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 ( Schottin ), while in dogs feeding with uric acid also increases it ( Salkowski ). 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 ( Salkowski ). 261. COLORING MATTERS OF THE URINE.— 1. Urobilin (J a ffe) is most abundant in the highly colored urine of fevers, but it also occurs in normal urine. It is a derivative of hsematin, or of the bile pigments (§ 177) de- rived from the latter. It is identical with the hydrobilirubin of Maly (§ 117, 3,^). 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 fluorescence ( Gerhardt ). Urobilin may be extracted from many urines by ether ( Salkowski ). When subjected to the action of reducing agents, e.g., 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 b and F, passes nearer to b, 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 chloride 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 (§ 180), 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 ( Thudichum) 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 ( Thudichum) 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. A brown pigment containing iron is carried down with uric acid, which is precipitated on the addition of hydrochloric acid ($ 258). By repeatedly adding sodic urate to the urine, and precipi- tating the uric acid by hydrochloric acid, a considerable amount may be obtained ( Kunkel ). 440 INDICAN, PHENOL AND PARAKRESOL. In cases of melanotic tumors, there has been occasionally observed urine, which becomes dark, owing to melanin (§ 250, 4), or to a coloring matter containing iron ( Kunkel). 262. INDIGO— PHENOL— KRESOL— PYROKATECHIN— AND SKATOL-FORMING SUBSTANCES. — 1. Indican [C 8 H 7 NSOJ or indigo-forming substance ( Schunck ), is derived from indol, C 8 H 7 N {Jaffe), the basis of indigo {Bayer), and is formed in the intestine by the pancreatic diges- tion of proteids (§ 170, II), but it also arises as a putrefactive product (§ 184, 6). Indol, when united with the radical of sulphuric acid, HS 0 3 , and combined with potassium, forms the so-called indigogen or indican of urine ( Brieger , Baumann). This substance (C 8 H 6 NS 0 4 K = indoxyl-sulphate of potash) forms white glancing tablets and plates ; readily soluble in water and less so in alcohol. By oxidation it forms indigo-blue — 2 indican -f- 0 2 = C 16 H 10 N 2 O 2 (indigo-blue) -f- 2HKSO4 (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.— (1) 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 crystalline indigo-bltie (rhombic) and indigo-red attest its presence. Putrefaction causes a similar decomposition in indican ; hence, we not unfrequently observe a bluish-red pellicle of microscopic crystals of indigo- blue, or even a precipitate of the same {Hill Hassal, 1853). ( 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 ( Jaffe ). 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 parts 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 {Jaffe). E. Ludwig obtained indican by heating haematin 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 (g 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 cachexise, long-standing suppuration, paraplegia — after taking creosote, oil of bitter almonds, turpentine or nux vomica. 2. Phenol, C 6 H 6 0 , 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” (C 6 H 5 0 , S 0 3 H), which in urine is united with potash. Phenol is derived from the decomposition of proteids by pancreatic digestion (g 172, II), and also from putrefaction (g 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 amount ( Almen , Salkowski ), 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 == C 6 II 6 0 2 ), which, for the most part, appears in the urine as ethersulphuric acid {Bau- mann and others). 3. Parakresol, (hydroxyltoluol, C 7 H 8 0 ) 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 Millon’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 = C 6 H 6 0 2 (metadihydroxylbenzol) is formed along with hydrochinon from phenol, 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 ( Baumann , Herter). Small quantities sometimes occur in human urine ; it is more abundant in the urine of children ( Ebstein and Muller ) ; 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 ( Nencki ). Its quantity is regulated by the same conditions as indican. The aromatic oxyacids, hydroparacumaric 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 substances are formed both during the decomposition of albumin, and also in the intestine, whence they pass into the urine : Tyrosin, CgHjjNOg -J- H 2 — C 9 H 10 O 3 (hydroparacumaric acid) -J- NH 3 . C 9 H 10 O 3 — C 8 H 10 O (paraethylphenol, not yet proved) -\- C 0 2 . C 8 H 10 O + 0 3 = C 8 H 8 0 3 (paraoxyphenylacetic acid) H 2 0 . C 8 H 8 0 3 == C 7 II 8 0 (parakresol) -+- C 0 2 . C 7 H 8 0 -f- 0 3 = C 7 1 I 6 0 3 (paroxybenzoic acid, not yet proved) -(- H 2 0 . C 7 H 8 0 = C 6 H 6 0 (phenol) -f C 0 2 . 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. Munk). One litre of human urine contains 0.02 to 0.08 gramme combined with an alkali. Succinic acid, C 4 H 6 0 4 ( Meissner 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 (g 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 ( Neubauer ). Lactic acid (C 3 H 6 0 3 ) is a constant constituent of urine ( Lehmann , Brucke ). 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 animal 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 6o° to 70° C. it transforms starch into sugar (v. Vintschgau). Ferments. — Traces of diastatic, peptic, tryptic, and rennet ferment have been found, especially in urine of high specific gravity. Traces of sugar ( Brucke , Bence Jones) to the amount of 0.05 to 0.01 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 in the urine ( Worm Muller — | 267, 7). Krytophanic acid (C 3 H 9 N 0 5 ), according to Thudichum, occurs as a free acid in urine, but Landwehr regards it as an animal gum. Aceton (C 3 H s 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 fever (v. Jacksch). Test. — Acidulate half a litre of urine with AC 1 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 to ^ 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 ( Zeulzer ). 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. Micro- scopically look for the step- like forms of the common salt, and also for the crystals of sodic chloride urea (g 256, 4). 2. Phosphoric acid occurs in urine as acid sodic phosphate and acid Fig. 248. a, Spermatozoa; c, amorphous calcic carbonate ; b, crystalline magnesic phosphate. calcic and magnesic phosphates (Fig. 248, b), 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 increases 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 foetal 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 standard solution of uranium acetate ; ferrocyanide of potassium being the indicator . 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 (§ 251, 2) ( Sotnitzsckewsky ), which occurs to the amount of 15 milli- grammes in a litre of urine, is increased in nervous diseases ( Lepine ), and after chloroform narcosis (Ziilzer). 3. Sulphuric acid occurs in the urine, the greater part in combination with the alkalies , and the remainder united with indol, skatol, and pyrokatechin, in the form of aromatic ethersulphuric compounds (. Baumann ), the ratio being 1 : o 1045. All conditions which favor the formation of indol, skatol, or pyrokatechin, in- crease the amount of combined sulphuric acid. The total daily amount of sul- phuric acid is 2.5 to 3.5 grammes [37 to 52 grains]. It is increased by the administration of sulphur ( Krause ). The sulphuric acid is chiefly derived from the decomposition of proteids, and hence its amount runs parallel with the amount of urea excreted. The amount of alkaline sulphates in the food is, as a rule, very small. An increased excretion of sulphuric acid in fevers indicates an increased metabolism of the tissues of the body. In renal inflammation it has been observed to be diminished, and in eczema it is greatly increased. Feeding with taurin (which contains sulphur), in the case of rabbits (but not in carnivora nor man), increases the sulphuric acid in the urine ( Salkowski ). According to Ziilzer, a copious secretion of bile lessens the relative amount of sulphuric acid in the urine. Test. — Barium chloride gives a copious, white, heavy precipitate of barium sulphate, insoluble in nitric acid. In addition to sulphuric acid, sulphur (i) occurs in an incompletely oxidized form in the urine (potassium sulphocyanide, sulphurous acid, cystin, and sulphur-bearing compounds derived from the bile — Kunkel, v. Voit — $ 177, 6). Hypo sulphurous acid , as an alkaline salt, is an abnormal con- stituent in typhus ; and so is sulphuretted hydrogen, which is recognized by the blackening of a piece of paper moistened with lead acetate and ammonia held over the urine. 4. Excessively minute traces of silicic acid and nitric acid derived from drinking water have been found in urine. Organic acids , e. g., citric and tartaric, when taken internally, increase the amount of carbonates in the urine. The urine may effervesce on the addition of an acid. The sodium in the urine is chiefly combined with chlorine, but a small part of it is united with phosphoric and uric acids ; potassium (which is about of the sodium) is chiefly combined with chlorine. In fevers more potash is excreted than soda, and during convalescence, the reverse is the case ; calcium and magne- sium exist in normal acid urine as chlorides or acid phosphates. If the urine is neutral, neutral calcium phosphate and magnesium phosphate are precipitated. Ebstein found the latter in alkaline urine as large, clear, four-sided prisms in diseases of the stomach. If the urine is alkaline, calcium carbonate (Fig. 248, c) or tribasic calcic phosphate are deposited as such, while the magnesium is precipitated in the form of ammonio-magnesium phosphate, or triple phosphate. The calcium is derived from the food, and depends upon the amount of lime salts absorbed from the intestine. Free ammonia is said to occur (0.72 gramme, or 7 grains daily) in perfectly fresh urine (. Neubauer and Briicke ), and the amount is greater with an animal than with a vegetable diet ( Coranda ). The amount of fixed am- monia is increased by the administration of mineral acids ( Walter , Schmiedeberg, Gathgens'). Iron (1 to 11 milligrammes per litre) is never absent. There is a trace of hydric-peroxide ( Schonbein ), which is detected by its decolorizing indigo solution on the addition of iron sulphate. Gases. — 24.4 c.c. of gas was obtained from one litre of urine — 100 volumes of the gases pumped out consisted of 65.40 vol. C 0 2 , 2.74 O, 13.86 N. After severe muscular action, the amount of CO 2 may be doubled; digestion also increases it. 263. SPONTANEOUS CHANGES IN URINE— FERMENTA- TIONS. — Acid Fermentation. — When perfectly fresh urine is set aside in a cool place, it gradually becomes more acid from day to day. This is called the “ acid fermentation.” It seems to be due to the development of special fungi (Fig. 249, a), and the process is accompanied by the deposition of uric acid (*:), 444 ACID FERMENTATION OF URINE. acid sodium urate , in amorphous grains (l), and calcium oxalate ( d ). According to Scherer, the fungus and the mucus from the bladder decompose part of the urinary pigment into lactic and acetic acids. The latter sets free uric acid from neutral sodium urate, so that free uric acid and sodium urate must be formed. Butyric and forr?iic acids have been found as abnormal decomposition products of other urinary constituents. When the acid fermentation begins, the urine absorbs Fig. 249. Fig. 250. Fig. 251. Fig. 252. Or The more usual forms of triple phosphate X 300 - oxygen (. Pasteur ). According to Briicke, it is the lactic acid formed from the minute traces of sugar present in urine, which causes the acidity. According to Rohmann, who recognizes the acid fermentation as an exceptional phenomenon, the acids are formed from the decomposition of sugar, and from alcohol which may be present accidentally. While the urine is still acid, it becomes turbid and contains nitrous acid, whose source is entirely unknown. According to v. Voit ALBUMIN IN URINE. 445 and Hofmann, phosphoric acid and a basic salt are formed from acid sodium phosphate, whereby part of the uric acid is displaced from sodium urate, thus causing the formation of an acid urate. Alkaline Fermentation. — When urine is exposed for a still longer time, more especially in a warm place, it becomes neutral and ultimately ammoniacal, i. e ., it undergoes the alkaline fermentation (Fig. 250). This condition is accompanied by the formation of the micrococcus ureae (. Pasteur , Cohn ) and Bacterium ureae (Fig. 251), which cause the urea to take up water, and decompose into C 0 2 and ammonia. Urea [C0(HN 2 ) 2 ]2(H 2 0) — ammonium carbonate [(NH 4 ) 2 C 0 3 ]. The property of decomposing urea belongs to many different kinds of bacteria, including even the sarcina of the lungs — whose germs seem to be universally diffused in the air. These organisms pro- duce a soluble ferment (Musculus), which, however, only passes from the body of the cells into the fluid after the cell or organism has .been killed by alcohol ( Sheridan Lea). The presence of ammonia causes the urine to become turbid, and those sub- stances which are insoluble in an alkaline urine are precipitated — earthy phos- phates, consisting of the amorphous calcic phosphate, acid ammonium urate (Fig. 250, a) in the form of small, dark granules covered with spines ; and, lastly, the large, clear, knife-rest or “coffin-lid” form of ammonio-magnesic phosphate, or triple phosphate (Fig. 252). [The last substance does not exist as such in normal urine, but it is formed when ammonia is set free by the decomposition of urea, the ammonia uniting with the magnesium phosphate. Its presence, therefore, always indicates ammoniacal fermentation of the urine.] In cases of catarrh or inflammation of the bladder, this decomposition may take place within the bladder, when the urine always contains pus cells (Fig. 251, b) and detached epithelium ( a ). When much pus is present, the urine contains albumin. Ammoniacal urine forms white fumes of ammonium chloride, when a glass rod dipped in hydrochloric acid is brought near it. [Significance of Triple Phosphate. — If urine be alkaline when it is passed, and the alkalinity be due to a volatile alkali , i.e., to NH 3 , then decomposition of the urine has taken place, and this kind of urine is a sure sign that there is disease of the genito-urinary mucous membrane.] [When ammonia is added to normal urine, triple phosphate is precipitated in a feathery form.] 264. ALBUMIN IN URINE (ALBUMINURIA).— Serum albumin is the most important abnormal constituent in urine which engages the attention of the physician. It is the albumin which occurs in blood (§ 32), and whose characters are described in § 249. Causes of Albuminuria. — 1. Serum albumin may appear in urine without any apparent ana- tomical pr structural change of the renal tissues. This condition has been called by v. Bamberger “ Hcematogenous albuminuria .” It occurs but rarely, however, and sometimes in healthy individu- uals when there is an excess of albumin in the blood plasma ( e.g ., after suppression of the secre- tion of milk), and after too free use of albuminous food. 2. As a result of increased blood pressure in the renal vessels, e.g., after copious drinking. It may be temporary, or it may be persistent, as in cases of congestion following heart disease , emphysema, chronic pleural effusions, infiltrations of the lungs, and after compression of the chest, causing congestion in the pulmonary circuit, which extends even into the renal veins ( Schreiber ), etc. 3. After section or paralysis of the vasomotor nerves of the kidneys, which causes great congestion of these organs. The albuminuria, which accompanies intense and long-continued abdominal pain, is brought about owing to a reflex paralysis of the renal vessels ( Fischel ). 4. After violent muscular exercise. [Senator found that forced marches in young recruits were very frequently followed by the appearance of albumin in the urine, which persisted for several days.] Convulsive disorders, e.g., epilepsy, the spasms of dyspnoea after strychnin poi- soning ( Huppert ); in shock of the brain, apoplexy, spinal paralysis, and violent emotions; the excessive use of morphia, which, perhaps, acts on the vasomotor centres. 5. It may accompany many acute febrile diseases, e.g. , the exanthemata (scarlet fever), typhus, pneumonia and pyaemia. In these cases it may be due to the increase of temperature paralyzing the vessels, but more prob- ably the secretory apparatus of the kidney is so changed (e.g., cloudy swelling of the renal epithe- lium) that the albumin can pass through the renal membranes. 6. Certain degenerations and inflammations of the kidneys at several of their stages. 7. Inflammation or suppuration in the ureter 446 TESTS FOR ALBUMIN IN URINE. or urinary passages. 8. Certain chemical substances which irritate the renal parenchyma, e. g., cantharides, carbolic acid. 9. The complete withdrawal of common salt from the food. The albu- min disappears when the common salt is given again ( Wundt, E. Rosenthal). 10. The epithelium may be in such a condition that it cannot retain the albumin within the vessels , due to imperfect nourishment and functional weakness of the secretory elements. This includes the albuminuria of ischaemia, and that after hemorrhage ( Quincke ), in anaemia, scorbutus, icterus, diabetes. [Besides being derived from the secreting parenchyma of the kidney, albumin may be derived by admixture with the secretions from any part of the urinary tract, including the vagina and uterus in the female. In some cases the transudation of albumin is favored by changes in the capillary walls, the albumin being forced through by the intravascular pressure. Sometimes albu- minuria occurs during the course of severe typhoid fever, and in acute fevers generally where the temperature is persistently above 40° C. (104° F.). The high temperature alters the filtering mem- brane and permits the filtration of albumin.] [Physiological Albuminuria. — This term has been applied to that condition of the urine where traces of albumin are found in individuals apparently in perfect health. Johnson and Pavy cite such cases, while Posner asserts that all urine — even healthy urine — contains traces of proteids, whose presence is ascertained after concentrating the urine. • It is safe to assume that normal urine should give no reaction for albumin.] The tests for albumin in urine depend upon the fact that it is precipitated by various reagents. [(«) Heller’s Test. — Place 10 c.c. of the urine in a test glass, and pour in pure colorless HN 0 3 so as to run down the side of the glass, forming a layer beneath the urine. A white zone of coagulated albumin indicates the presence of albumin. In this test it is important to wait a certain time for the development of the reaction. In urines of high specific gravity, a haziness due to acid urates may be formed above, where the two fluids meet, but its upper edge is not circumscribed. The acid decomposes the neutral urates and forms a more insoluble acid salt. This cloud of acid urates is readily dissolved by heat, while the albumin is not ; the latter is always a sharply-defined zone between the two fluids. In very concentrated urine (rare), nitric acid may gradually precipitate crystalline urea nitrate. In patients taking copaiba, nitric acid, by acting on the resin, causes a slight milkiness.] [( 3 ) 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. Add 10 or 12 drops of HNO a . 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. ( b ) 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) HN 0 3 be added, or too much (30 or 40 drops), we may fail to detect albumin, although present.] (1 c ) 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. Other precipitants of albumin, such as small pieces of paper impregnated with potassio-mercuric iodide, are used by Oliver.] ( d ) By boiling Acid Urine. — If the urine be alkaline, although albumin may be present, it is not precipitated by heat alone. We require to add acetic acid until a slightly acid reaction is obtained. . Boiling may give a precipitate of earthy phosphates in an alkaline urine, owing to the C 0 2 being driven off. This precipitate might be mistaken for albumin, but on adding acetic or nitric acid, the earthy precipitate is dissolved, while the precipitate of albumin is not dissolved. In test- ing for albumin, always use clear urine. If it is turbid, filter it. [(^) Metaphosphoric acid is dissolved in water just before it is to be used and added to clear urine ( Hindenlang ). Graham pointed out that metaphosphoric acid precipitated albumin. A 20 per cent, solution of the ordinary glacial phosphoric acid is a good test for albumin, but it also pre- cipitates peptones. It, however, changes into ordinary phosphoric acid by keeping, and then it no longer precipitates albumin.] \_{f) Acidulate 10 c.c. of urine with acetic acid, and add of its volume of a concentrated solution of sulphate of soda or magnesia. On heating, if albumin be present, a distinct cloudiness is obtained.] [(£•) In picric acid, according to Dr. Johnson, we have a more delicate test for minute traces of albumin than either heat or nitric acid, or than both these tests combined. It is used either in the form of crystals or powder, or as a saturated aqueous solution. Take a four-inch column of HEMATURIA AND HEMOGLOBINURIA. 447 urine in a test tube, hold the tube in a slanting direction, and pour an inch of the picric acid solu- tion on the surface of the urine, where, in consequence of its low specific gravity (1005), it mixes only with the upper layer of the urine. It coagulates any albumin present. The precipitate occurs at once, and is increased by heat, while the urate of soda, which is sometimes precipitated, is soluble on heating.] [Dr. Roberts regards any test for albumin which requires strong acidulation with an organic acid, citric, acetic or lactic, as unsatisfactory, since it precipitates mucin. For this reason he rejects the tungstate, mercuric iodide, and potassic ferrocyanide tests. Dr. Roberts regards the heat test, with the addition of a small definite quantity of acetic acid, as the best test for the detection of small quantities of albumin.] 1. Quantitative Estimation of albumin. — 100 c.c. of urine are boiled in a capsule, some acetic acid being ultimately added, whereby the albumin is precipitated in flakes. The precipitate is collected on a weighed, dried (1 io°), and ash free filter, and repeatedly washed with hot water, then with alcohol, and completely dried in an air bath at 1 io°. Lastly, the dried filter with the albumin is burned in a weighed platinum capsule, and the weight of the ash also deducted from it. [This method is not available for the busy practitioner on account of the time it takes. Practically, it is sufficient to compare from day to day the proportion that the precipitated albumin bears to the bulk of the urine tested. A graduated tube may be used, so that after the precipitate has subsided the physician may see whether it occupies one-fourth or one-tenth of the fluid, as the case may be.] 2. Globulin occurs only in albuminous urine ( Senator , Edlefsen ), and is frequently present. Its presence is ascertained by adding powdered magnesium sulphate in excess to the urine; when it is present it is precipitated (§ 32). The more globulin there is in the presence of albumin, the more difficult it is to precipitate it. [Sometimes, when an albuminous urine is dropped into a large cylinder of water, each drop as it sinks is followed by a milky train, and when a sufficient number of drops has been added, the water becomes opalescent, the opalescence disappearing on adding an acid. The globulin is kept in solution by common salt and other neutral salts, but when these are largely diluted, the globulin is precipitated ( Roberts ).] 3. Peptone (v. Frerichs , 1851) occurs in some specimens of albuminous urine, but also in non- albuminous urine ( Gerhardt ). Maixner found it constantly in the urine in all cases where suppu- ration is present, e.g., in exudations, abscesses, resolution of pneumonia, and in articular rheumatism, when the attack is passing off (v. Jakscfi). Peptone occurs in pus, and the peptonuria in these cases is a sign of the breaking up of the pus cells ( Hofmeister ). Also when many leucocytes are broken up in the blood, or when large quantities of peptone are absorbed fiom the intestinal canal. It is frequently found after childbirth. Test. — Separate the albumin by boiling and the addition of acetic acid. Treat the filtrate with three volumes of alcohol; this precipitates the peptone, which, when dissolved in water, gives the characteristic reactions for peptone (| 166, I). 4. Propeptone occurs very rarely in osteomalacia and intestinal tuberculosis [Macynter and Bence Jones). The urine is treated to saturation with NaCl and a large quantity of acetic acid added, and filtered while hot, to separate the albumin and globulin. In the cold filtrate propeptone forms a turbidity, which is redissolved by heat. The precipitate thrown down by HC 1 and HN 0 3 is soluble by heat ( Kiihne ). The precipitate is isolated by filtration, and dissolved in a little warm water, when it gives with HN 0 3 a yellow reaction; like peptone, the solution gives the biuret reaction. 5. Egg albumin appears in the urine when much egg albumin is taken in the food, and also when it is injected into the blood vessels ($ 192, 4). According to Semmola, the albumin present in the urine in Bright’s disease has undergone a molecular change (similar to egg albumin), and hence it is excreted. 6. Mucus is present in large amount, especially in catarrh of the bladder. It contains numerous mucus corpuscles, which are scarcely distinguishable from pus corpuscles. They contain albumin, so that urine containing much mucus is albuminous ; mucin is not precipitated by heat, but acetic acid gives a flocculent precipitate in clear urine. [Minute traces of mucin occur normally in urine. If clear, normal urine be set aside for a short time, a flocculent haziness, like a cloud of cotton wool, is seen floating in the urine. This is mucus entangling a few epithelial cells from the genito urinary tract. Mucin Reaction. — According to W. Roberts, the addition of a concentrated solution of citric acid to urine, as in Heller’s test ($ 264, a ), where the two fluids meet, causes an opalescent zone gradually to be formed above the layer of acid.] 265. BLOOD IN URINE (HEMATURIA)— HEMOGLOBINURIA.— I. Source of the Blood. — (1) In haematuria, the blood may come from any part of the urinary apparatus. 1. In hemorrhage from the kidney, the amount of blood is usually small and well mixed with the urine. The presence of “blood cylinders,” long, microscopic blood coagula, casts of the uriniferous tubules, washed out of them by the urine, are characteristic when they are found in the urine (Fig. 263). The urine usually has a smoky appearance. [The urine slowly dissolves out the coloring matter, the stroma of the corpuscles after a time being deposited as a brownish sediment. The smoky hue occurs only in acid urine ; if the urine becomes alkaline, the hue becomes brighter red.] The blood corpuscles show peculiar changes of form [they become crenated] (Fig. 253), and exhibit evidence of division, due to the action of urea on them ($ 5). Large coagula are never found in 448 HEMATURIA AND HEMOGLOBINURIA. urine mixed with blood derived from the kidney. 2. In hemorrhage from the ureter, we occa- sionally find worm-like masses of clotted blood, casts of the canal of the ureter. 3. The relatively largest coagula occur in hemorrhage from the bladder. In all cases where blood is present, we must examine microscopically for the blood corpuscles, and it may be for coagula of fibrin. In acid urine, blood corpuscles, but never in rouleaux, may be found after two to three days in urine. The Fig. 253. Crenated red blood corpuscles in urine X 350. Fig. 254. Peculiar changes of the red blood corpuscles in renal haematuria ( Friedreich ). blood corpuscles settle as a red sediment at the bottom. If the hemorrhage is copious, many retain their original shape ; but if the urine is very concentrated, they may become crenated. When there is a small and slow hemorrhage from ruptured, small capillaries, the red blood cor- puscles are of unequal size, many to x /$ the size of normal, while the pigment has become brownish yellow (Fig. 255). BLOOD IN URINE. 449 If a hemorrhage of this kind is accompanied by catarrhal inflammation of the bladder, there is found between the red, numerous shriveled leucocytes (Fig. 255), which in freshly-passed urine often exhibit lively amoeboid movements. If the urine be alkaline, as it usually is, crystals of triple phosphate also occur. If the remains of the red blood corpuscles become very pale, their presence may be frequently ascertained by adding iodine in a solution of KI (Fig. 254). Blood is constantly present in the urine during menstruation. Fig. 255. Colored and («) colorless blood corpuscles of various forms. Fig. 256. Shriveled blood corpuscles in urine (catarrh of the bladder), with numerous lymph corpuscles, and crystals of triple phosphate, X 350. II. Hsemoglobinuria is quite distinct from hsematuria. It depends upon the excretion of haemoglobin as such through the kidneys, and it is produced when haemoglobin occurs free within the blood vessels, as in cases where the colored blood corpuscles have been dissolved inside the blood vessels (haemocytolysis). It occurs when foreign blood is transfused, e.g., when lamb’s blood is transfused into man. The foreign blood corpuscles are dissolved in the blood of the recipient, and the haemoglobin appears in the urine (g 102). In addition, microscopic “cylinders,” 29 450 BILE IN URINE. consisting of a globulin-like body tinged yellow with hsemoglobin, may likewise be found in the urine. It also occurs in cases of severe burns ($ io, 3) ; after decomposition of the blood in pyaemia, scorbutus, purpura, severe typhus, after respiring arseniuretted hydrogen, and after the passage of azobenzol ( Baumann and Herter ), of naphtol [Kaposi), pyrogallic acid, potassic chlorate, chloral, phosphorus, or carbolic acid into the circulation. [The injection of laky blood, water, ether, glycerine (Adams), or toluylendiamin (. Afanassiew ), also causes it, and in such cases Afanassiew asserts that the Hb passes out through the glomeruli, while brown degeneration products of the red blood corpuscles, which are dissolved by these agents, were found in the convoluted tubules.] These substances dissolve the red blood corpuscles. Sometimes it occurs periodically from causes and conditions, as yet but little understood, e. g., the application of cold to the skin. Tests for Blood in Urine. — 1. The color of bloody urine shows every tint, from a faint red to a dark, blackish brown, according to the amount of blood present. The urine is often turbid. 2. Urine containing blood or blood pigment contains albumin. 3. Heller’s Blood-test. — Add to urine half its volume of solution of caustic potash, and heat gently. The earthy phosphates are precipitated, and they carry the hsematin with them, falling as garnet-red flocculi. [This is not a reliable test.] 4. Haemin Test. — The colored earthy phosphates may be collected on a filter, and from them hsemin may be prepared as directed in $ 19. Fig. 257. Spectroscope for investing the presence of hsemoglobin in urine. 5. Almen’s Test. — Add to urine, freshly-prepared tincture of guaiacum and ozonized ether; a blue color indicates the presence of blood ($ 37). 6. Spectroscope (see § 14). Fig. 257 shows the arrangement of the apparatus. The urine is placed in a glass vessel, D, with parallel sides, 1 centimetre apart (haematinometer). Light from a lamp, E, passes through the fluid. The lamp, F, illuminates the scale, which is seen by the observer through the telescope, A. (a) Fresh urine containing blood gives the spectrum of oxyhsemoglobin (Fig. 14). ( b ) 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 hsemoglobin becomes changed into methaemoglobin (§15). It is precipitated by lead acetate, which does not precipi- tate oxyhsemoglobin; the spectrum of methaemoglobin resembles that of hsematin 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 conditions which cause the bile constituents to appear in the urine are mentioned in part at \ 180. Haematogenic, or Anhepatogenic Icterus (Quincke), 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 § 177. Modifications of the Test. — 1. 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 ( Rosenbach ). 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 (. Fleischl ). 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 [Maly). 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 ($261, 1) [Quincke). In persistent high fever, the urine contains especially biliprasin [Huppert). If it contains choletelin alone, add to the urine some hydrochloric acid, and examine it with the spectroscope, which gives a pale absorption band between b and F ($ 177, 3 ,f). Haematoidin. — Sometimes crystals of hcematoidin ($ 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 hsemoglobinuria. 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 ($ 138). 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 1 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. Dragendorff found 0.8 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 (g 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 \ 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 1 to 8 per cent., although 15 per cent, has been found, i. e., found from 5 to 50 grs. per fluid oz., or 300 to 4000 grs. in twenty-four hours [Tyson).] The specific gravity is also increased (1030 to 1040). [In a case where a large amount of urine is passed of a pale color and a specific gravity above 1030, always suspect sugar.] A diabetic person gives off relatively more water by the kidneys and less by the skin (and lungs?) than a healthy person. The color is very pale yellow, although the amount of pigment is, by no means, diminished ; it is only diluted [the depth of the color being inversely as the quantity passed]. The amount of the nitrogenous urinary excreta is increased. The sugar is increased by a diet of carbohydrates and diminished by an albuminous diet. The uric acid and oxalate of lime are often increased at the commencement of the disease, while yeast cells are constantly present after the urine has been exposed to the air for some time. Sugar has been found occasionally after poisoning with, or after the use of, morphia, CO, chloral, chloroform, curara; after the injection of ether and amyl-nitrite into the blood; and in gout, inter- mittent fever, cholera, cerebro- spinal meningitis, hepatic cirrhosis, and cardiac and pulmonary affections. Tests. — Any of the tests described at \ 149 may be used, but the urine must be free from albumin. The quantitative estimation by fermentation and the titration methods are described in $ 149. [The tests for grape sugar described in § 149 are (1) Trommer’s; (2) Fehling’s; (3) Moore & Heller’s; (4) Bottger’s; (5) Mulder and Neubauer’s; (6) Fermentation test.] 7. Worm Muller recommends the following modification of Fehling’s test: Use a 2.5 per cent, solution of cupric sulphate solution, and another of 10 parts of sodio-potassic tartarate in 100 parts of a 4 per cent, solution of soda. Boil 5 c. cm. of urine in a test tube, while in a second test tube is boiled 1 to 3 c. cm. of the copper solution and 2.5 c. cm. of the potassio-tartrate solution. The boiling of both fluids is stopped simultaneously, and after 20 to 25 seconds, the contents of one test tube are added to those of the other, but without shaking the mixture, the reduction taking place spontaneously. 8. Nylander’s modification of Bottger’s test is also good ($ 149). 452 TESTS FOR SUGAR IN URINE. [9. Picric Acid and Potash Test. — Braun showed that grape sugar, when boiled with picric acid and potash, reduces the yellow picric acid to the deep-red picramic acid, the depth of the color depending on the amount of sugar present. Dr. Johnson uses this test for detecting the presence of sugar in urine, and also for estimating the amount of sugar present, the depth of the red color obtained in boiling being compared with a standard dilution of ferric acetate. In doing the test, use 1 drachm of urine, ]/ 2 a drachm of liquor potassse, and 10 minims of picric acid solution ; make up to 2 drachms with distilled water, and boil the mixture for one minute. This test indicates the presence of 0.6 grain of sugar per fluidounce of normal urine. Dr. Johnson claims for this test that it possesses all the advantages of the other tests, while it is not affected by uric acid or any other normal ingredient of urine; neither does the presence of albumin interfere with the action of the test as it does with all the forms of copper testing.] [10. Indigo-carmine Test. — A blue solution of this substance, when boiled with diabetic urine containing sodic carbonate, changes from a blue to a violet, purple-red, yellow, and, finally, straw- yellow color. After cooling and exposure to the air, the various colors are obtained in the reverse order until the mixture becomes blue again. Dr. Oliver uses this test in the form of test papers. One bibulous paper is impregnated with the indigo carmine and the other with sodic carbonate. Drop one of the test papers and a sodic carbonate paper into a test tube containing 1 y 2 inches of water ; heat gently, when a blue solution is obtained. Add the urine slowly, one drop at a time, and boil the mixture, observing any change of color by holding the tube against a white surface below the level of the eye. Uric acid and urates, which reduce Fehling’s solution, do not affect the carmine test, nor does kreatinin, although it reacts with the picric acid test.] [Quantitative Estimation — ( a ) Fermentation Test (g 150). Take 4 oz. (120 c. c.) of the urine ; add a lump of German yeast about the size of a walnut, lightly cork the bottle, and place it aside for twenty- four hours in a moderately warm place, e.g., on the mantelpiece. Take the spe- cific gravity before and after the fermentation. Thus, if the specific gravity be 1038 before and 1013 afterward, the difference, or “ density lost,” is 25, which gives 25 grs. of sugar per fluid oz. [Roberts). If it be desired to get the percentage, multiply the density lost by 0.23 ; thus, 25 X °- 2 3 = 5.69 in 100 parts.] 1 (b) Volumetric Analysis. — 10 c. c. of Fehling’s solution = .05 gramme of sugar. 1. Ascertain the quantity of urine passed in twenty-four hours. 2. Filter the urine, and remove any albumin present by boiling and filtration. 3. Dilute 10 c. c. of Fehling’s solution with about twenty times its volume of distilled water, and place it in a white porcelain capsule on a wire gauze support, under a burette. (It is diluted because any change of color is more easily observed.) 4. Take 5 c. c. of the urine and 95 c. c. of distilled water, and place the diluted urine in a burette. 5. Gradually boil the diluted Fehling’s solution, and while it is boiling, gradually add the diluted urine from the burette, until all the cuprous oxide is precipitated as a reddish powder, and the super- natent fluid has a straw-yellow color, not a trace of blue remaining. Read off the number of c. c. of dilute urine employed. Say 36 c. c. were used — that, of course, represents 1 .8 c. c. of the original urine. Suppose the patient passes 1550 c.c., and as 1.8 c. c. of urine reduced all the cupric oxide in the 10 c. c. of Fehling’s solution, it must contain .05 gramme sugar; hence, 1.8 : 1550 : : .05 : x 55 0 X 237.5 grammes of sugar passed in 24 hours.] ( c ) According to Worm Muller, the polarization method is almost valueless for diabetic urine. If large quantities of dextrose are taken in the food, a part of it (and more in diabetic persons) appears in the urine. Laevulose, when taken internally, does not increase the amount of sugar in diabetes. The free use of starch does not cause glycosuria in health, but in diabetes it increases the amount of sugar. A large consumption of cane- or milk sugar causes the passage of small quantities of both of these sugars into the urine in health, while in diabetes the amount of dextrose is increased ( Worm Muller). According to Kiilz, in diabetic persons cane sugar is split up into grape-fruit sugar, the latter being used up in the body, the former partly excreted ; and the same is the case with milk sugar'. In severe cases of diabetes mellitus, Kiilz found the left rotatory ^-oxybutyric acid (the next highest analogue of lactic acid) in the urine, from which acetic acid is formed by oxidation ($ 175) which in its turn readily yields C0 2 and aceton. a-crotonic acid is formed in urine by the removal of water from oxybutjric acid in the urine in diabetes ( Stadelmann ). The administration of aceton causes albuminuria, and this may in part explain in some cases the complication of albuminuria in diabetes ( Albertoni and Pisenti). [Preparation of Fehling’s Solution. — 34.64 grammes of pure crystalline cupric sulphate are powdered and dissolved in 200 c.c. of distilled water; in another vessel dissolve 173 grammes of Rochelle salts in 480 c.c. of pure caustic soda, specific gravity 1.14. Mix the two solutions, and dilute the deep colored fluid which results to 1 litre. N. B. — Fehling’s solution ought not to be kept too long; it is apt to decompose, and should therefore be preserved from the light, or protected with opaque paper pasted on the bottle. Some other substances in urine, e.g., urates and uric acid, reduce cupric oxide.] Aceton, or Aceton-yielding substance, probably aceto-acetic acid, is sometimes found in diabetic urine. It has a peculiar venous odor, and it has been detected in the urine during fever. Gerhardt described a peculiar substance in diabetic urine, which gave a deep red color with perchloride of MILK, SUGAR AND OTHER SUBSTANCES IN URINE. 453 iron. This substance is probably diacetic ether, and he considered it to be the source of aceton ; but it is more probably derived from aceto-acetic acid. Tests for Aceton. — (i) Perchloride of iron = Burgundy-red color; but this is not reliable. (2) Lieben suggested an iodoform test. Dis- solve 20 grains of KI in fluidrachm of liq. potassse, and boil the fluid. Pour the suspected urine on the surface, when a ring of phosphates is deposited from the urine by the hot alkaline solution. If aceton be present, after a time the deposit becomes yellow, and yellow granules of iodoform appear and sink to the bottom of the test tube ( Ralfe ). The only other substance which may be met with in the urine giving this reaction is lactic acid.] [Picro-Saccharimeter. — G. Johnson uses a stoppered bottle 12 inches long and ^ inch wide, graduated in T L and (Fig. 257, a). To it is fixed a shorter bottle containing the standard iron solution for comparison, a standard solution, composed of liquor ferri perchloride g j, liq. ammon. acetatis ^iv, glacial acetic acid ^iv, liq. ammonige 3 i, and water to make up f ^iv. All B. P. preparations give a color identical with a solution containing 1 gr. of grape sugar per oz., reduced by picric acid and afterward diluted four times, so that this tint = gr. of sugar per oz. Fig. 257 a. Picro-saccharimeter of G. Johnson. Fig. 258. After reducing the sugar with the picric acid, pour into the tall tube the dark, saccharine liquid pro- duced by boiling to occupy ten divisions of the tube, and add distilled water cautiously until the color approaches that of the standard ; read off the level of the fluid. The amount of sugar present is determined from the amount of water added. In making the test, the picric acid must be added in proportion to the amount of sugar added.] Milk sugar is sometimes found in the urine of women who are nursing; when the secretion of milk is arrested, absorption taking place from the breasts ( Kirsten , Spiegelberg). Laevulose is sometimes found in diabetic urine (§ 252). Dextrin has also been found in diabetic urine. Inosit, or muscle sugar (g 252), is sometimes found in diabetes, in polyuria ( Mosler ), and albuminuria. It is found in traces, even in normal urine. Occasionally, after the piqure in animals (g 175), inosit, instead of grape sugar, appears in the urine (Fig 258). In testing for inosit, remove the grape sugar by fermentation, and the albumin by heat, after the addition of a few drops of acetic acid and sodic sulphate. Some of the filtrate is evaporated nearly to dryness on a capsule. To the residue add two drops of mercuric nitrate 454 CYSTIN, LEUCIN AND TYROSIN. (Liebig’s titration fluid for urea), which gives a yellow precipitate. When this colored residue is spread out and carefully heated, a dark-red color, which disappears on cooling, is obtained ( Gallois , Kiilz). [Inosit gives a green when boiled with Fehling’s solution.] 268. CYSTIN. — This left rotatory body, CgHj 2 N 2 S 2 0 4 ( Kiilz , Baumann ), occurs very seldom in large amount in urine, although it seems to be a constituent of normal urine. It may be in solu- tion or in the form of hexagonal crystals (Fig. 259, A). It is insoluble in water, alcohol, and ether, but easily soluble in ammonia, from which solution it may be crystallized. According to Baumann Fig. 259. c A, Crystals of cystin ; B, oxalate of lime; c, hourglass forms of B. Fig. 260. a a, Leucin balls ; b b, tyrosin sheaves ; c, double balls of ammonium urate. and Preusse, there are intermediate products of the metabolism, from which are furnished the materials necessary for the formation of cystin. During normal metabolism these materials undergo further changes, and the sulphur appears oxidized in the urine as sulphuric acid. In rare cases these oxidations do not take place, and then the sulphur appears in the cystin of the urine (Stadthagen). 269 . LEUCIN=C 6 H 1 3 N 0 2 . TYROSIN=C 9 H 1 jNOg. — Both bodies occur in the urine in acute yellow atrophy of the liver, and in poisoning by phosphorus. (Their formation during DEPOSITS IN URINE. 455 pancreatic digestion has been referred to in g 170, II.) As the urea excreted is usually diminished at the same time, it is assumed that, in these diseases, the further oxidation of the derivatives of the proteids is interfered with. Leucin, which is either precipitated spontaneously or obtained after evaporating an alcoholic extract of the concentrated urine, occurs in the form of yellowish, brown balls (Fig. 260, a a), often with concentric markings, or with fine spines on their surface. When heated, it sublimes without fusing. Tyrosin forms silky, colorless sheaves of needles (Fig. 260, b b). When boiled with mer- curic nitrate and nitric acid it gives a red color, and afterward a brownish-red precipitate. When slightly heated with a few drops of concentrated sulphuric acid, it dissolves with a temporary deep red color. On diluting with water, adding barium carbonate until it is neutralized, boiling, filter- ing, and adding dilute ferric chloride, a violet color is obtained ( Piria , Stadeler ). 270. DEPOSITS IN URINE. — Deposits may occur in normal as well as in pathological urine, and they are either “organized” or “unorganized.” I. ORGANIZED DEPOSITS. — A. Blood: red and white blood corpuscles and sometimes fibrin (Figs. 253-255). B. Pus, in greater or less amount, in catarrh or inflammation of the urinary passages. Pus cells exactly resemble colorless blood corpuscles (Figs. 7, 256). Donne’s Test. — Pour off the super- Fig. 261. / b a, epithelium from the human urethra ; b, vagina ; c , prostate ; d , Cowper’s glands ; e, Littre’s glands ; f t female urethra ; g, bladder. natent fluid and add a piece of caustic potash to the deposit ; if it be pus it becomes gelatinous, ropy, and more viscid (alkali-albuminate). Mucus, when so acted on, becomes more fluid and mixed with flocculi. C. Epithelium of various forms occurs, but it is not always possible to say whence it is derived (Fig. 261). D. Spermatozoa may be present (Fig. 248, a). E. Lower organisms occur in the urinary passages very seldom, but they may be present, e.g., in the bladder, when germs are introduced from without by means of a dirty catheter. [Before introducing a catheter into the bladder one ought always to make sure that the instrument is perfectly aseptic.] Micrococci are found in the urine in certain diseases, e.g ., diphtheria. The following forms are distinguished : — 1. Schizomycetes (§ 184). Normal human urine contains neither schizomycetes nor their spores. In pathological conditions, however, fungi may pass from the blood into the urinary tubules and thus reach the urine ( Leube ). During the alkaline fermentation of urine, micrococci, rod- shaped bacteria or bacilli (Figs. 250, 251, may occur). Sarcinae belong to the above group (8 186). 2. Saccharomycetes (fermentation fungi) : ( a ) The fungus of the acid urine fermentation (S. urinae) consists of small, bladder-like cells arranged either in chains or in groups (Figs. 251,^; 456 TUBE CASTS IN URINE. 262, c). (b) Yeast (S. fermentum) occurs in diabetic urine, as oval cells with a dotted, eccentrically placed nucleus (Fig. 262, d ). 3. Phytomycetes (moulds) occur in putrid urine (Fig. 262, e ). They are without clinical sig- nificance. F. Tube Casts. — The occurrence of tube casts, i.e., casts of the uriniferous tubules (. Henle , 1837) is of great importance in connection with the diagnosis of renal diseases. If these structures Fig. 262. a a, micrococci in short chains and groups ; b, sarcinse ; c, fungi from acid fermentation ; d, yeast cells from diabetic urine ; e, mycelium of a fungus. Fig. 263. a, blood casts ; b, granular cast ; c, amyloid or waxy cast. are relatively thick and straight, they probably come from the collecting tubules, but if they are smaller and twisted, they probably come from the convoluted tubules. There are various forms of tube casts : 1. 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 albuminous. 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 : — 1. 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). (b) Which is not dissolved by heat, but is dissolved by acetic acid, but without effervescence = probably tribasic calcic phosphate. Fig. 264. (c) Small, bright, refractive granules, soluble in ether = fat or oil granules (£ 41) (Lipaemia). Fat occurs in the urine, especially when the round worm, Filaria sanguinis hominis, 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 (§ 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). (b) Calcium oxalate (Figs. 249, 259) — octahedra insoluble in acetic acid. (c) Cystin (Fig. 259). (d) Leucin and tyrosin — very rare (Fig. 260). II. In alkaline urine there may occur — 1. A completely amorphous granular deposit, soluble in acids without effervescence = tri- basic calcic phosphate. 2. Sediment crystalline, or with a characteristic fortn. [a) Triple phosphate (Figs. 250, 251, 252, and 256), soluble at once in acids. URINARY CALCULI. 458 (b) Acid ammonium urate — dark -yellowish, small balls often beset with spines, also amor- phous (Figs. 250 and 260). (c) Calcium carbonate — small whitish balls or biscuit-shaped bodies. Acids dissolve them with effervescence (Fig. 248). (d) Leucin and tyrosin (Fig. 260) — very rare. (e) Neutral calcic phosphate and long plates of tribasic magnesic phosphate (Fig. 248). Organized deposits may 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 fist. 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 ( Ultzmann ) : — 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, where 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 a foreign body (secondary formation of calculi). 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. (a) 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. ( b ) 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 HC1 and held over it gives white fumes of ammonium chloride), the concretion contains ammonium urate. If b gives no result, pure uric acid is 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 ($ 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. (/) 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 (g 14), when the characteristic bands of sodium 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. ( b ) 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. (e) 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. ( e ) 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. And 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 1, 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 ( Brunton ).] Theories. — The two chief older theories regarding the secretion of urine are the following : 1. 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 urme 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 only . 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 ( R . Heidenhaiii). The secretion of urine embraces — (1) 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] (. Ludwig 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 ; and 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 actively 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 ( R . 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 ( Heidenhain ). 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 (Overbeck). 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 syste??i, 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 ( Paw low ) ; 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 the capacity of the vascular system , provided the pressure 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 diminution in the amount of urine to the extent of one-fifth ( Goll , Cl. 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 Herrmanri) ; 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 ( Mendelsohn ). 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 anaemia 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 may increase the blood pressure locally 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 epithelium, such as urea and caffein. 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 (Zf. Meyer , v. Frerichs'). Ludwig con- cluded, from this observation, that the filtration or excretion of fluid could not take place through the renal capillaries proper , 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 ?nust 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 artery is about 120 to 140 mm. Hg, and the urine in the ureter is moved along by a very slight propelling force, so that a counter-pressure of from 10 ( Lobell ) 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 tergo 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 (. Bowman , 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. — 1. Sulphindigotate of soda and sodium urate, when injected into the blood, pass into the urine, and are found within the protoplasm of the cells of the 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 glomeruli the watery part of the urine is chiefly excreted , while through the convoluted 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 [Mo bins, 1877), for the iron salts of the vegetable acids when injected subcutaneously ( Glaevecke ), and for haemoglobin ( Landois ). After the injection of milk 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 from 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 egg 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 two 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 sulphinuigotate, and when the experiment has FORMATION OF THE URINARY CONSTITUENTS. 463 lasted 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 the capsules ( Senator ); Hb is partly found in the capsules (Griitzner, Bridges Adams). According to Nussbaum, 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 satis 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. — If 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. . Ludwig , 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 ($ ioo). One kidney secretes a more watery urine, which at the same time contains more NaCl and urea (Ludwig, M. Herrmann). Von 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, i. 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 , 1841 ), but the renal vein contains less urea than the blood of the corresponding artery [Picardy /8j6 ; Grlhant). 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. Voit ), and increases with the duration of the experiment to -gfo to ( Grehant ). At the same time there is vomiting and diarrhoea, and the fluids so voided contain urea {Cl. 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 — (1) muscle; (2) nervous system; and (3) glands, of which the liver is the most prominent. This is best stated by the method of exclusion.] [1. 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 Wislicenus ($ 294), Parkes, and others. The excretion chiefly increased by muscular exertion is pulmonary C 0 2 ($ 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 diminished 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 ($ 178), 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. 1. 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 {Ebstein), 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 ( Galvani, 1767 ; Zalesky , Oppler). Acid urates of ammonia, soda, and magnesia are also similarly deposited ( Colasanti ). 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 Schroeder 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 SUBSTANCES 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, Schmiedeberg, Kochs). [The other evidence is given in § 260.] Kreatinin has intimate relations to kreatin of muscle, but where it is fjprmed is not known. If phenol and pyrokatechin are digested along with fresh renal substance, a compound of sulphuric acid 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 [Kochs). Chemistry of the Kidney. — The kidneys contain a very large amount of water. Besides serum albumin, globulin, albumin soluble in sodium carbonate [Gottwalt), 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 maybe 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 ). ] 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.— 1. 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, coloring 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 faeces. 2. Inorganic acids reappear in man and carnivora as neutral salts of ammonia [Schmeideberg and Walter, Hallervorden) ; 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 aa alkaline carbonates ( Wohler), 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 oxides, 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 (§ 260), the conjugation of sulphuric acid ($ 262), and the forma- tion of urea by synthesis from carbamic acid and ammonia [Drechsel) [$ 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 ($ 268). 7. Tannic acid, C 14 H 10 O 9 , takes up H 2 0, and is decomposed into two molecules of gallic acid = 2(C V H 6 0 5 ). 8. The iodates of potash and soda are reduced to iodides ; malic acid (C 4 H 6 0 5 ) partly to suc- cinic acid (C 4 H 6 0 4 ) ; indigo blue (C 16 H 10 N 2 O 2 ) takes up hydrogen and becomes indigo white (C 16 H 12 N 2 0 2 ). 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. — At 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 3 ° 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 ( Nicolaides ). 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 urine. 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 {CL Bernard ). 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 ( Cl. 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 {Eckhard). 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 (§ ioi) we can measure the variations in the size of a limb, while by the oncograph (o>xo?, volume) similar variations in the volume of the spleen are measured (§ 103). Roy and Cohnheim have measured the variations in the volume of the kidney by means of an instrument which consists of two parts, one termed the oncometer or renal plethysmometer , in which the organ is enclosed, while the other part is the registering portion or oncograph. The kidney is enclosed in a metallic capsule shaped like the kidney (Fig. 265), and it is composed of two halves which move on a hinge, h , to introduce the organ. The renal vessels pass out at a, v. The kidney is surrounded with a thin membrane, and between this membrane and the inner surface of the capsule is a space filled with warm oil through the tube, I, which is closed by means of a stopcock after the space is filled with oil. The tube, T, can be made to communicate with another tube, T l5 leading into a Fig. 265. Oncometer. K, kidney ; the thick line is the metal- Oncograph. C, chamber filled with oil, communicating by Tj lie capsule ; h , hinge ; I, tube for filling appa- with T ; p, piston ; l, writing lever ( Stirling , after Roy). ratus ; T, tube to connect with ; a, v, u, artery, vein, ureter ( Stirling , after Roy). metallic chamber, C 1 , of the oncograph (Fig. 266), which is provided with a movable piston, /, attached by a thread to the writing lever, /. Any increase in the size of the organ expels oil from the chamber, O, into C 1 , and thus the piston is raised, while a diminution in the size of the kidney diminishes the fluid in C 1 and the lever falls. The actual volume of the living kidney depends upon the state of distention of its structural elements, upon the amount of lymph in its lymph spaces, but chiefly upon the amount of blood in its blood vessels, and this again must depend upon the condition of the non-striped muscles in the renal arteries. When the vessels dilate, the kidney will increase in size, and when they contract it contracts, so that we can register on the same revolving cylinder the variations of the volume at the same time that we record the general arterial blood pressure.] [In the normal circulation through the kidney, the kidney curve, i. e., the curve of the volume of the kidney, runs quite parallel with the blood-pressure curve, and shows exactly the large respiratory undulations, as well as the smaller elevations due to the systole of the heart (Fig. 267). Usually, when the blood pressure falls, the kidney curve sinks, and when the blood pressure rises, the volume of the kidney increases. When the blood-pressure curve is complicated by Traube- Hering waves (§ 85), the opposite effect is produced on the kidney curve ; the 468 CONDITIONS AFFECTING THE VOLUME OF THE KIDNEY. highest blood pressure corresponds to the smallest size of the kidney, and con- versely. This is due to the fact that, when these curves occur, all the small arte- rioles — including those in the kidney — are contracted. A kidney placed in an oncometer secretes urine like a kidney under natural conditions.] [Arrest of the respiration in a curarized animal produces a rapid and great diminution of the volume of the kidney, caused by the venous blood stimulating the vasomotor centres, and thus contracting the small arterioles, including those of the kidney. This result occurs whether one or both splanchnics are divided, proving that all the vasomotor nerves of the kidney do not reach it through the splanchnics. When all the renal nerves at the hilum are divided, arrest of the respiration causes dilatation of the organ, which condition runs parallel with the rise of the blood pressure. Stimulation of a sensory nerve, e. g., the central end of the sciatic nerve, while causing an increase of the blood pressure, makes the kidney shrink.] [In poisoning with strychnin, the kidney shrinks while the blood pressure rises. Stimulation of the central or peripheral end of the splanchnics, divided at the diaphragm, causes contraction of the renal vessels of both sides ; the former is a reflex, the latter a direct effect. Stimulation of the peripheral end of one splanchnic sometimes affects both kidneys. Stimulation of the peripheral end of the renal nerves always causes a diminution in the volume of the kidney, so that Fig. 267. B P, blood-pressure curve ; K, curve of the volume of the kidney ; T, time curve, intervals indicate a quarter of a minute; A, abscissa ( Stirling , after Roy). Cohnheim and Roy were forced to conclude that, although there was evidence ot the existence of vasomotor and sensory nerves to the kidney, they found none of the vaso-dilator nerves. By the same method, Cohnheim and Roy con- firmed absolutely the independent action of the two kidneys. The sudden com- pression of one renal artery had not the slightest effect upon the blood current of the other kidney. If a kidney be exposed in an animal, by making an incision in the lumbar region, on stimulating the medulla oblongata directly with elec- tricity, we may observe the kidney itself becoming paler, the pallor appearing in a great many small spots on the surface of the organ, corresponding to the distri- bution of the interlobular arteries ] [The researches of Cohnheim have shown that the composition of the blood has a remarkable effect on the renal circulation. Some substances (water and urea), when injected into the blood, cause the kidney first to shrink and then to expand, while sodic acetate dilates the kidney, even after all the renal nerves are divided — an operation which is very difficult indeed. Provided all the renal nerves be divided, these effects would indicate the existence of some local intra- renal vasomotor mechanism governing the renal blood vessels. The general blood pressure is not thereby modified ; nor need we wonder at this, as ligature of one renal artery does not increase the pressure in the aorta.] [Mosso also showed that the blood stream through an excised organ was mate- URAEMIA AND AMMONLFMIA. 469 rially influenced by the substances mixed with the blood perfused. This effect may, in part, be due to the action of these chemical ingredients upon the nuclei of Ihe endothelial lining of the blood vessels, especially the capillaries.] [The reciprocal relation between the skin and the kidneys is known to every one. On a cold day, when the skin is pallid, owing to contraction of the cutaneous vessels, the amount of urine secreted is great, and, conversely, in summer less urine is passed than in winter. Washing the skin of a dog for two minutes with ice-cold water causes a great contraction of the kidney.] [Strychnin seems to be able to cause contraction of the renal vessels, independently of its action on the general vasomotor centre. Brunton and Power found that digitalis caused an increase of the blood pressure (dog), but the secretion of urine was either at the same time diminished, or it ceased altogether. The latter result was due to contraction of the renal bloodvessels; but when the aort'c blood pressure began to fall, the amount of urine secreted rose much above normal, i. Vertical section of the cutis vera and part of the epidermis, g, cells ol the rete Vlalpighii ; a, capillary ; b, papilla ; c, blood vessels ; d, nerve fibre entering a Wagner's touch corpuscle, e ; /, section of a nerve fibre. Fig. 275. Papillae of the skin, epidermis removed, blood vessels in- Fat cells containing crystals of margarin. jected ; some contain a Wagner's touch corpuscle, a , the others a capillary loop. 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 they swell up and exhibit the remains of an elongated nucleus (Fig. 272, n, 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, d). 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 (AT 'em).] 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 ( Moleschott , Benecke ). Development. — Unna makes the following statements regarding the development of the nails : 1. From the second to the eighth month of foetal 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 formed 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. Transverse section of one-half of a nail, a , nail substance ; b , more open layer of cells of the nail bed ; ^ stratum Malpighii of the nail bed ; d , transversely divided papillae ; e, nail groove ; /, horny layer of e projecting over the nail ; g, papillae of the skin on the back of the finger. eponychium) covers the whole extent of the nail bed. 3. When, at a later period, the eponychium splits off, the nail is uncovered. After birth the papilla 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, I,/) which passes obliquely through the thickness of the skin, some- times as far as the subcutaneous tissue. The structure of a hair follicle is the following : 1. The outer fibrous layer (Figs. 272, 1, 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 with, 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, flat, homogeneous, non- nucleated cells (Figs. 272, 6, 277 ,f- — Henle's layer ) placed next and within the outer root sheath. Within this lies (2) Huxley's layer (Figs. 272, 5, 277,^-), consisting of nucleated, elongated, polygonal cells (Fig. 272, jtr, and 3), while the cuticle 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. 277. b Transverse section of a hair below the neck of a hair follicle, a, outer fibrous coat with b, blood vessels ; c, inner circularly disposed layer; d, glass-like layer ; e, outer , /, g, inner root sheath ; /, outer layer of the same (Henle’s sheath) ; g, inner layer of the same (Huxley’s sheath) ; h, cuticle ; /, hair. Fig. 278. c Section of a hair follicle while 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; i, tip of new hair ; l, hair knob of the shed hair, with k , the remainder of the cast-off outer root sheath. [Coverings of a hair follicle arranged from without inward: 1. Fibrous layers, f (a) Longitudinally arranged fibrous tissue. [ ( 6 ) Circularly arranged spindle cells. 2. Glass-like (hyaline) membrane. (a) Outer root sheath. 3. Epithelial layers, 4. The hair itself. 3 1 (b) (/) Inner root sheath. Cuticle of the hair. j Henle’s layer. \ Huxley’s layer. 482 THE GLANDS OF THE SKIN. The arrector pili muscle (Fig. 272, A) is a fanlike- arrangement of a layer of smooth muscular fibres, which is attached below to the side of a hair follicle and extends toward the surface of the chorium; 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 goose skin. 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 ( Unna ). The hair with its enlarged bulbous extremity — hair bulb — sits upon, or rather it embraces, the papilla. It consists of — (1) 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, e). (2) Outside this lies the thicker cortex (k), which consists of elongated, rigid, horny, fibrous cells (H,/*, f), 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 suddenly 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 Kolliker, from the 12th to 13th week of intra-uterine life, 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 differentiates into an inner darker part, which becomes the hair, and a thinner, clearer, layer covering the former, the inner root sheath. The outer cells, i. 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 papillae 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 19th 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 longtime, 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 papiila, 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 ( Kolliker , C. Longer). 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 agarn 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 papillae 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 part; 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 by the fatty metamorphosis of the cells constitutes the sebum or sebaceous secretion. The sweat glands (Fig. 272, I, k), sometimes called sudoriparous glands, consist of a long blind tube, whose lower end is arranged 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, axilla, 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 several 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 distal 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 (Kolliker) are arranged longitudinally along the tube in the large glands (Fig. 272, S, a). There is a distinct lumen present in the tube. As the duct passes through the epidermis, it winds its way between the epidermal cells without any independent membrane lining it (Reynold). A network of capillaries surrounds the coil. Before the arteries split up into capillaries, they form a true rete mirabile around the coil ( Brilcke ). 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 1080 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 ( Neumann ), [and also with the fat (Klein). The lymphatics of the skin are readily injected 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 papillae. 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 ; (c) an artery goes also to each coil of a sweat gland, where it forms a dense plexus of capillaries (Tomsa). Sebaceous gland, with a lanugo hair, a, granu- lar epithelium ; b, rete Malpighii continu- ous with a ; c, fatty cells and free fat ; d, acini ; e, hair follicle, with a small hair,_/i 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 appearance 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 , 7 ?iechanical 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 the jiuids 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 papillae of the cutis vera, which becomes level when the skin is stretched, and the papillae may even disappear with strong tension ( Lewinski ). 287. CUTANEOUS RESPIRATION : SEBUM— SWEAT.— The skin, with a surface of more than 1 y 2 square metres, has 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.] 1. Respiration by the skin has been referred to already ($ 1 3 1 ). 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 off 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 C 0 2 and H ,0 excreted is subject to certain daily variations; it is increased by 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 of the total amount of C 0 2 excreted; in summer frogs, ^ 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 gelatin] ( Fourcault , Becquerel , Brechet ), death occurs after a time, probably owdng to the loss of too much heat. The formation of crystalline ammonio-magnesic phosphate in the cutaneous tissues of such animals (Edenhuizen), is not sufficient 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 sufficient. Strong animals live longer than feeble ones; horses die after several days ( Gerlach) ; they shiver and lose flesh. The larger the cutaneous surface left unvarnished, the later does death take place. Rabbits die when of their surface is varnished. When the entire surface of the animal is varnished, the temperature rapidly falls (to 19 0 ) ; the pulse and respirations vary; usually they fall when the varnishing process is limited; increased frequency of respiration has been observed (| 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 ( Ellenberger and Hof- meister). [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 COMPOSITION. 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 too 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 folliculorum). Chemical Composition. — The constituents are, for the most part, fatty ; chiefly olein (fluid) and palmilin (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 praeputialus (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 fat ( Berzelius ). 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 very 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. As 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, cheek, breast, upper arm and forearm ( Peiper ). It falls from morning to mid-day, and rises again 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 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 ( Luchsinger ). [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 ( W. 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 fatty 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 uraemia (. Leube ). 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 1 (Schottin) ; sodium chloride, 0.2; potassium chloride, 0.2; sulphates, 0.01 per 1000, together with traces of earthy phosphates and sodium phosphate. Sweat contains C0 2 in a state of absorption and some N. When decomposed with free access of air, it yields ammonia salts ( Gorup-Besanez ). Excretion of Substances. — Some substances when introduced into the body reappear in the 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 saliva. 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 ( Unna ). Pathological. — To this belongs the formation of liver spots or chloasma, freckles, and the pigmentation of Addison’s disease [pigmentation round old ulcers, etc., ] (g 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 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 : 1. Increased tem- perature of the surroundings causes the skin to become red, while there is a pro- fuse secretion of sweat (§ 214, II, 1). 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, muscarin, nicotin, camphor, ammonia compounds, while others, as atropin and morphia, 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 antagonism 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 (e.g., 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 red congested skin) are most frequently involved. The fact that secretion of sweat does occasionally take place when the skin is pale (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 neck 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, eg., 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 Luchsingen , Ostronmozv). 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 the 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 ( Vulpian ), some pass into the abdominal sympathetic (Luchsinger, 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- tebrae — cat) where the sweat centre for the lower limbs is situated. The sweat centre may be excited directly: (1) 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 0 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 (Luchsinger). [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 (. Nawrocki ) pass into the thoracic sympathetic (Ggl. stellatum), and part (?) runs in the nerve roots direct from the spinal cord ( Luchsinger , 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 increased in paralyzed as well as in oedamatous 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 applied to, the branches of the trigeminus, which explains why stimulation of the infraorbital nerve causes secretion of sweat. Some fibres, however, arise directly from the roots of the trigeminus (. Luchsinger ), 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 (II), 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 (§ 373 — Marme , Nawrocki). When this centre is stimulated in a cat, all the four feet sweat, even three-quarters of an hour after death (. Adamkiewicz ). III. The nerve fibres which terminate in the smooth muscular fibres of the sweat glands ^ct 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. — 1. 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, e.g., in dementia paralytica ; in some limited regions of the skin it has occurred in certain tropho-neuroses , e.g., in unilateral atrophy of the face and in paralyzed parts. In many of these cases it depends upon paralysis of the corresponding nerves ( Eulenburg ) or their spinal sweat centres. 2. Hyperidrosis, or increase of the secretion of sweat, occurs in easily excitable persons, in consequence of the irritation of the nerves concerned (§ 288), e.g., 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 ( Eulenburg ). Sometimes the increase is confined to one side of the head (H. uni- lateral^). 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 . Kollmann ) is 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, leuci'n, 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 foetidum — Thin). In the sweating stage of ague butyrate of lime has been found, while in the sticky sweat of acute articular rheumatism there is more albumin ( Ansebnino ), 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 Seborrhcea, 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 ( Unna ) from the blue used in coloring the linen. 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 Juhl, 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, where they are affected 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 affect 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 comes 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, C0 2 , the vapor of chloroform and ether may be absorbed ( Chaus - sier, Gerlach, Rohrig). In a bath containing sulphuretted hydrogen, this gas is absorbed, while C0 2 is given off into the water (Rohrig). Absorption of watery solutions takes place rapidly through the skin of the frog ( Guttmann, W. Stirling , v. Wittich). 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 ($ 328). 490 COMPARATIVE— HISTORICAL. 291. COMPARATIVE— HISTORICAL. — In all vertebrates, the skin consists of chorium and epidermis. In some reptiles, the epidermis 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 civet 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 subjacent muscles, forming a musculo-cutaneous tube for the body of the animal. The cephalopoda have chromatophores in their skin, i. 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. ( Briicke .) 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 b. 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 faeces. 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 ; Alberti (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 ■%* MOTOR APPARATUS. 292. CILIARY MOTION — PIGMENT CELLS. — (a) 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 — i. 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 place in a definite direction. (^) 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. [(V) 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).] [Ciliated epithelium, and where found. — In the nasal mucous membrane, except the olfactory region; the cavities accessory to the nose; the upper half of the pharynx, Eustachian tube, larynx, trachea and bronchi; in the uterus, except the lower half of the cervix; Fallopian tubes; vasa 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 -3^00 length? an( I 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 this 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 cells, and are never outgrowths of the solid cell membranes. There may be 10 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 refractile 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 [Engelmann).~\ [Ciliary motion may be studied in the gill of a mussel, a small part of the gill being teased in 491 492 FUNCTIONS OF CILIA. sea water ; or the hard palate of a frog, newly killed, may be scraped, and the scraping examined in ^ p. c. salt solution. On analyzing the movement, all the cilia will be observed to execute a regular, periodic, to-and-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 straightening itself. The forward movement is about twice as rapid as the backward move- ment. The amplitude 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 ( Engelmann ). 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 — (1) 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 0 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. 505). Weak alkalies may cause them to contract after their movement is arrested or nearly so ( Virchow ), 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 (Berlin 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. — Wyman 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 diffused 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 but 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 affect 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 different 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 ( Brucke ). 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 nerves 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- CLES. — 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 — (1) Striped, striated or (voluntary) ; (2) N on-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. 1. 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, pass into the substance of the muscle, so as to divide it into bundles of fibres 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 muscular fibres arranged more or less parallel to each other. [The fibres 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. 284). In a contracted muscle the capillaries may be slightly sinuous in their course, but when a muscle is on the stretch these curves disappear. The capillaries lie in the endomysium, and near them are lymphatics.'] Each muscular fibre receives a nerve fibre. [Where found. — Striped muscular fibres occur in the skeletal muscles, heart, diaphragm, pharynx, upper part of oesophagus, muscles of the middle ear and pinna, the true sphincter of the urethra, and external anal sphincter.] A muscular fibre (Fig. 281, 1) is a more or less cylindrical or polygonal fibre, 11 to 67 p. [yfo to in.] diameter, and never longer than 3 to 4 centi- metres [1 to 1 y 2 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 ( Budge ), or by a 35 per cent, solution of caustic potash ( Moleschott ). [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 Krause ; 2. The included sarcous substance; 3. The nuclei or muscle corpuscles.] 494 .STRUCTURE OF STRIPED MUSCLES. Sarcolemma. — Each muscular fibre is completely enclosed by a colorless, structureless, trans- parent elastic sheath (Fig. 281, 1, S), 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 diffusing under it. The sarcous substance, but not the sarcolemma, may be torn across by plunging a muscle in water at 55 0 C., and keeping it there for some time (Ranvie >').'] Fig. 281. Histology of muscular tissue. 1, Diagram of part of a striped muscular fibre ; S, sarcolemma ; Q, transverse stripes ; F, fibrillae; K, the muscle nuclei; N, a nerve fibre entering it with a, its axis cylinder and Kiihne’s motorial end plate, e, seen in profile; 2, transverse section of part of a muscular fibre, showing Cohnheim’s areas, c ; 3, isolated muscular fibrillae ; 4, part of an insect’s muscle greatly magnified ; a, Krause-Amici’s line limiting the muscular cases ; b, the doubly-refractive substance ; c, Hensen’s disk; d, the singly-refractive substance ; 5, fibre cleaving transversely into disks ; 6, muscular fibre from the heart of a frog ; 7, development of a striped muscle from a human foetus at the third month ; 8, 9, muscular fibres of the heart ; c , capillaries ; b, connective-tissue cor- puscles ; 10, smooth muscular fibres ; 11, transverse section of smooth muscular fibres. Stripes. — The sarcous substance is marked transversely by alternate light and dim layers, bands, stripes or disks (Fig. 281, 1, 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 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). Fibrillae.- — 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 (1 to 1.7 in diameter) fine, contractile threads, the primitive fibrillae (Fig. 281, 1, 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 mutual 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). Fibrillae are easily obtained from insects’ mus- cles, while those from a mammal’s muscle are readily isolated by the action of dilute alcohol, Muller’s fluid [or, best of all, per cent, solution of chro- 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. 282). 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 of compartments placed end to end. These muscular compartments contain the sarcous substance, and in each compartment we find (1) 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 disk 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, ^).] [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 membrane, and thicker in the interval, so that Haycraft attributes the transverse striation to these differences, the surface being undulating.] Fig. 282. Portion of a human muscular fibre, X 300- 496 MUSCLE RODS. [Muscle Rods. — Schafer describes the appearance differently: “ Double rows of granules are seen lying in or at the boundaries of the light streaks (disks), and very fine, 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 striae. 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 (Schafer).] 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 M long, 3 to 4 M 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 Fig. 284. Fig. 283. Relation of a tendon, S, to its muscular fibre. Injected blood vessels of a human muscle, a, small artery ; b, vein ; c, capillaries. X 250 ( Kolliker ). 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, 1 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. 281, 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 the 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 ( Retzius , 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 ( Weismann — Fig. 283, S). In arthropod a, the sarcolemma passes directly into and becomes continuous with the tendon (Zeydig, 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 Kollman — 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 ( e.g ., semitendinosus), the capillaries are more wavy, while on the transverse branches of some of the capillaries, and on the veins ( Ranvier ), 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 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, \ 201).] Entrance of the Nerve. — The trunk of the motor nerve, as a rule, enters the muscle at its geometrical centre ( Schwalbe ) ; 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 [1 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, 1, N). Each 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), 1 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 ( Sandmann ). A nerve fibre enters each 3 2 498 RED AND PALE MUSCLES. muscular fibre, and where it enters it forms an eminence {Doyere, 184^ the “ motorial end plate ” (Fig. 281, 1, e). The neurilemma unites directly with the sarcolemma, the white substance 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- lse along the whole extent of the fibre, and, perhaps, they terminate in the aniso- tropous substance ( Gerlach ). 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 ( Arndt \ Sachs) ; but, according to Tschirjew, the sensory nerves traverse the substance of the muscle, and after dividing dichotomously, end only 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, Kowalewsky, Nawrocki), 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 the spinal nerves. Red and Pale Muscles.— In many fishes (skate, plaice, herring, mackerel) ( W. Stirling ), birds, Fig. 286. Intra-fibrillar terminations of a motor nerve in striped muscle stained with gold chloride and mammals (rabbits), there are two kinds of striped muscle ( Krause ,), differing in color, histo- logical structure ( Ranvier ) and physiological properties (. Kronecker and Stirling ). Some are “ red,” e.g. , the soleus and semitendinosus of the rabbit, and others “pale,” e.g., the adductor magnus. In th pale muscles the transverse striation is less regular, and their nuclei fewer than in the red muscles ( Ranvier ) ; they contain less glycogen and myosin. [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 state of fatty degeneration, while the pale muscles, lying side by side, contain no fatty granules.] [Spectrum. — The red color of the ordinary skeletal muscle is due to haemoglobin in the sarcous substance \Kiihne). 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 haemoglobin when examined with the spectroscope.] [Myo-hsematin. — MacMunn points out that, although most voluntary muscles owe their color to haemoglobin, it is accompanied by myo-hiematin in most cases, and sometimes entirely replaced by it. Myo-haematin is found in the heart of vertebrates, and in some muscles of vertebrates and inver- tebrates.] Muscular Fibres of the Heart.— The mammalian cardiac muscle has certain peculiarities already mentioned (§ 43) : (1) 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 § 43). [The cardiac muscle, viewed from a physiological point of view, stands midway between striped and unstriped muscle. Its contraction occurs slowly and lasts for a long time (p. 104), while, although it is trans- versely striped, it is involuntary.] [Purkinje’s Fibres. — These fibres, which form a plexus of grayish fibres under the endocardium of the heart of ruminants, have been described already (Fig. 28); the cells have, as it were, advanced only to a certain stage of development ($ 46).] N ON-STRIPED MUSCLE. 409 Development. — Each muscular fibre is developed from a uninucleated cell of the mesoblast, 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 of the fibre, where they remain in some animals. Young muscles have fewer fibres than those of adults, and the former are also smaller ( Budge ). 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 vertebrata, occurs in the it is and choroid of birds. The arthropoda have only striped muscle, the molluscs, worms, and echinoderms chiefly smooth muscles ; in the latter, there are muscles with double oblique striation {Schwalbe). 2. Non-Striped Muscle.— [Distribution. — It occurs very widely distributed in the body, in the muscular coat of the lower half of the human oesophagus, 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 : culae seminalis, and prostate ; corpora cavernosa and spongiosa penis, ovary, Fallopian 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 Fig. 287. Smooth muscular fibre from the mesen- tery of a newt (ammonium chro- mate). N, nucleus; F, fibrils; S, markings in the sheath. Fig. 288. Termination of nerve in non-striped muscle. 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 p to in.] in length, and 4 to 10 p [goVo - to ^ n, l 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 more distinctly thus: Place the mesentery of a newt {Klein) or the bladder of the salamandra musculata {Flemming) 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 living. 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 lamellae, 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 T ^ to °f an ’ th° se 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 thickenings are seen, which are not due to transverse striation ( Krause ), but to a partial contraction {Meissner). Blood Vessels. — Occasionally they have a tendinous insertion. Non-striped muscle is richly supplied with blood 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-medullated fibres [derived from the sympathetic system] which form a plexus — 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 fibrillse (0.3 to 0.5 /-*) pass off either singly or in groups, and reunite to form the intermuscular plexus (Fig. 288, d), which lies in the cement substance between the muscle cells, to end, according to Frankenhauser, 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 LSwit, 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. 288). 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 addition, spindle-shaped terminal corpuscles, which he regards as a specific apparatus for estimating tension. 293. PHYSICAL AND CHEMICAL PROPERTIES OF MUS- CLE. — 1. The consistence of the sarcous substance is the same as that of living protoplasm, e. g., of lymph cells; it is semi-solid, i. 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 come together to form a continuous whole. The consis- tence may be compared to a jelly at the moment when it is dissolved ( e . 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 ($9). ( b ) The so- called Porret’s phenomenon ( W. Kuhne) which consists in this, that when a galvanic current is conducted through the living, fresh, sarcous substance, the contents of the muscular fibre exhibit a streaming movement from the positive to the negative pole (as in all other fluids), so that the fibre swells at the negative pole, {c) By the fact that wave movements have been observed to pass along the muscular fibre. ( d ) Direct observation has shown that a small parasitic round worm (Myoryctes Weismanni) moved freely in the sarcous substance within the sarcolemma, while the semi-solid mass closed up in the track behind it ( W. Kuhne , Eberth ). 2. Polarized Light. — The contractile substance doubly refracts light, and is said to be aniso- tropous, while the ground substance causes single refraction, and is isotropous. According to Briicke, muscle behaves like a doubly- refractive, positively uniaxial body, whose optical axis lies in the long axis of the fibre. When a muscular fibre is examined under the polarization microscope, the doubly-refractive substance is recognized by its appearing bright in the dark field of the micro- scope when the Nicols are crossed ($ 297). During contraction of the muscular fibre, the contrac- tile part of the fibre becomes narrower, 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 Schipiloff, 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 imbibition — 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. Ktihne bled frogs, cooled their muscles to io° or 7 0 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 o°, 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 ” (JV. Kilhne). 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 (0.1 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 from muscle by a 10 to 15 per cent, solution of NH 4 C 1 , and if it be heated to 65° it is precipitated again ( Danielewsky ). Danielewsky 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.: 1. Alkali albuminate, which is precipitated on adding an acid, even at 20° to 24 0 C. 2. Ordinary serum albumin, 1.4 to 1.7 per cent. (§ 32, a ), which coagu- lates at 73 0 C. 3. An albuminate which coagulates at 47 0 C. The other chemical constituents of muscle have been referred to in treating of flesh (§ 233). 1. 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 of lactic acid (C 3 H 6 0 3 ) pre- sent in muscle with an acid reaction : (a) Ethylidene-lactic acid , in the modifica- tion known as right rotatory sarcolactic or paralactic acid, which occurs only in muscles, and some other animal structures. (h) 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 fDu Bois-Reymond'). Acid potassium phosphate also contributes to the acid reaction. 3. Carnin (C 7 H 8 N 4 0 3 ), which is changed by bromine or nitric acid into sarkin, occurs to the extent of 1 per cent, in Liebig’s extract of meat ( Weidel ). 4. Only 0.01 per cent, of urea ( Haycraft ). 5. Gly- cogen occurs to the amount of over 1 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. Lecithin , derived in part from the motor nerve endings (§ 23 and § 251). 7. The gases are C 0 2 (15 to 18 vol. per cent.), partly absorbed, partly chemically united ; some absorbed N, but no O, although 502 METABOLISM IN MUSCLE. muscle continually absorbs O from the blood passing through it (L. Hermanri). The muscles contain a substance whose decomposition yields C0 2 . When muscles are exercised, this substance is used up, so that severely fatigued muscles yield less C0 2 ( 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 O from the blood flowing through its capillaries, and returns a certain amount of C0 2 to the blood stream. The amount of C0 2 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 (. A l . v. Hum- boldt), 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 excised, and if blood be perfused through its blood vessels, the amount of O used up is, within pretty wide limits, almost independent of temperature ; if the variations of temperature be great, it rises and falls with the temperature. The C0 2 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 ( Rnbner ). 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 C0 2 , and occurs soon after death (Z. Hermann) . II. In an active muscle the blood vessels are always dilated (. Ludwig and Sczelkow , 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 (Du Bois-Reymond, 1859) > d e g ree of acidity increases up to a certain extent, according to the amount of work performed by the muscle (R. Heidenhaifi). 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 C 0 2 . — An active muscle excretes considerably more C0 2 than a passive one : (a) active muscular exertion on the part of a man or of ani- mals increases the amount of C0 2 given off by the lungs (§127); (b) venous blood flowing from a tetanized muscle of a limb contains more C0 2 , more C0 2 being formed than corresponds to the O, which has simultaneously been absorbed (Ludwig and Sczelkow). The same result is obtained when blood is passed through an excised muscle artificially ; (c) an excised muscle caused to contract excretes more C0 2 (Matteucci, Valentin). 3. Consumption of Oxygen. — An active muscle uses up more O — (a) when we do muscular work, the body absorbs much more O (p. 366) — even 4 to 5 times as much (Regnault and Reiset ) ; (b) venous blood flowing from an active muscle of a limb contains less O (Ludwig, Sczelkow and Al. Schmidt). Nevertheless, the increase of O used up by the active muscle is not so great as the amount of C0 2 given off (v. 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 C0 2 excreted (v. Frey). As yet, it is not possible to prove, by gasometric methods, that 0 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 ( Grutz- ner , Gscheidleri). 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 (( 9 . Nasse, Weiss), 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. Helmholtz , 1845) ; it also contains less of the substances which form C 0 2 (. Ranke ) ; less fatty acids ( Sczelkow ) ; less kreatin and kreatinin ( v . Volt). 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 . Voit , Fick and Wislicenus). According to Parkes, however, although the excretion of urea is not increased immediately, yet after 1 to 1]^ days there is a slight increase. The amount of work done cannot be determined from the amount of albumin which is changed into urea. [Relation of Muscular Work to Urea — Ed. Smith, Parkes and others have made numerous investigations on this subject. Fick and Wislicenus (1866) ascended the Faulhorn, and for seven- teen hours before the ascent and for six hours after the ascent no proteid food was taken — the 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 “ . . 2 38 55 S rs - ■gg :}■*»•» 221.05 g rs - io 3-4 6 “ \.o -- 79.89 “ J ^-35 A hearty meal was taken after this period, and the urine of the next eleven hours after the period of rest contained 159.15 grains of urea [Fick), and 176 71 ( Wislicenus). All the experiments 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, but 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, all the groups of the chemical substances present in muscle undergo more rapid transformations (J. 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 ( Chandelon ). A muscle in 504 STAGES OF CADAVERIC RIGIDITY. which the blood circulates freely is capable of doing more work than one devoid of blood (Ranke), 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 rigidity — 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 (Kiihne), 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. IValther , 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 (Schmulewitsch, Walter) ; 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-phosphoric acid (Diakanow) ; while it also develops free C 0 2 . 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 formed from potassium phosphate. The lactic acid, which is formed thereafter, remains free 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 in the muscles as in the liver. There is no diminu- tion of the glycogen when rigidity takes place, provided putrefaction be prevented ; so that the lactic acid of rigid muscles cannot be formed from glycogen, but more probably it is formed from the decomposition of the albuminates (Demant, Bohni). The amount of acid does not vary, whether the rigidity occurs rapidly or slowly (J. Ranke) ; when acidification begins, the rigidity becomes more marked, owing to the coagulation of the alkali albuminate of the muscle. Less C0 2 is formed from a rigid muscle, the more C0 2 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 (Al. Schmidt and 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 decompositions 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 (. Nysten ). 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 ( Schmulewiisch ) ; thereafter stiffness occurs, the one stage following closely upon the other ( Swammerdam , Nic. Stenson , 1667 ). [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 ( Landois ), 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 (A\ Volkmann). Occlusion of the blood vessels of muscles by infarcts, especially in persons with atheromatous arteries, may even cause necrosis of the muscles implicated ( Finch , Girandeau). 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, i. 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 ( Schipiloff ). Section of Nerves. — Preliminary section of the motor nerves causes a later onset of the rigidity in the corresponding muscles ( Brown-Sequard , 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 ” ( Pickford )] causes the myosin to coagulate at 40° C. in cold-blooded animals, in birds about 53 0 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 body, 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 ( Schipiloff ). If the rigid cadaveric muscles of a frog be heated, another proteid coagulates at 45 0 , and lastly at 75 0 the serum albumin itself. Hence, both processes together make the muscle more rigid (§ 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 other means do not ( Biedermann ). 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 be 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 io per cent, solution of common salt, which dissolves the coag- ulum of myosin ( Preyer ). 3. Acids, even C 0 2 , rapidly produce “acid stiffening,” which is probably different from ordinary stiffening, as such muscles do not evolve any free C 0 2 (Z. Hermann). The injection of 0.1 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 ( Schipiloff ). 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 , Setschenow), ammonia, 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 ( Sommer ). 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 {Du Bois- Raymond), nor evolve free C0 2 (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 C0 2 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 substance. 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. — A 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 2 S, N, C 0 2 — § 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 (180 minutes) ; the extensors of the extremities (about one hour before the flexors) ; the muscles of the trunk (five to six hours). The oesophagus remains 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 ( Wundt). 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.) A muscle, when stimulated directly , 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 amoeba 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 substance. 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: 1. 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 ( Kiihne ). 3. Curara paralyzes the extremities of the motor nerves, while the muscles themselves remain excitable (Cl. 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 (Brown- Sequard, Bidder). 5. Sometimes electrical stimuli act only upon the nerves and not upon the muscle itself (Briicke). [6. The foetal 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 affect the muscular contractility. An active substance, curarin, has been isolated from it (p. 510). Poison 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 nerve 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. — (1) 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. nerve of the other preparation produced no contraction, 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. 289). 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 the mtra-muscular terminations of 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 fully 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 both 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 nerve, for the muscle is the proper end organ of a motor nerve. Fig. 289. Frog with sciatic artery liga- tured. S P, spinal cord; P, poisoned, N P, non- poisoned leg; M, gastroc- nemius muscles, afferent, efferent, nerve (after .\utherford and Br un- ion). MUSCULAR AND CHEMICAL STIMULI OF MUSCLE. 509 Neuro- Muscular Cells. — Even in the lower animals, eg ., Hydra ( Kleinenberg ), and Medusa (Elmer) there are uni-cellular structures called “ neuro-?nuscular cells,” 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) (§ 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 voluntary movements, automatic motor movements, and reflex acts. 2. Chemical Stimuli. — All chemical substances, which alter the chemical composition of a muscle with sufficient rapidity, act as muscular stimuli. Accord- ing to Kiihne, mineral acids (HC 1 0.1) per cent., acetic and oxalic acids, the Fig. 290. key (after Rutherford). 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 . Witticfi), while a 0.6 per cent, solution of NaCl may be passed through a muscle for days without causing contraction (. Kolliker , O. Nasse). Acids, 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., HCI), or at once permanent contraction or con- tracture (e.g., Cl). Long exposure to the gas causes rigidity. The vapor of bisulphide of carbon stimulates only the nerves, while most vapors (e.g., HCI) kill without exciting them (Kuhne and Jani'). 510 THERMAL, MECHANICAL AND ELECTRICAL STIMULI OF MUSCLE. Method. — In making experiments upon the chemical stimulation of muscle, it is inadvisable lo dip the transverse section of the muscle into the solution of the chemical reagent ( Bering ). 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 (| 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 1 litre of water, at to 0 C , the muscle contracts rhythmically, and may do so for several days [especially with a low temperature] ( Biedermann ). This recalls the rhythmical con- traction of the heart. [Kiihne found a similar result. The rhythm is arrested by lactic acid and restored by an alkaline 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 ($ 58). 3. Thermal Stimuli. — If an excised frog’s muscle be rapidly heated toward 28 J C., a gradually increasing contraction occurs, which, at 30° C., is more pro- nounced, reaching its maximum at 45 0 C. (. Eckhard , SchumlewitscK). 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 o°, it is very excitable to mechanical stimuli ( Griinhagen ) ; it is even excited by a temperature under o° (. Eckhard ). Cl. 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, #). 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 ends of the 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 ( Cl . Bernard , Kolliker ). [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 ultimately affected. If the dose be very large, the heart 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 i^Kuhne, Bidder ). If the dose be larger, the inhibitory fibres of the vagus may be para- lyzed. In electrical fishes, the sensory nerves concerned Avith the electrical discharge are paralyzed ( Marey ). 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 ( Z. 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 when 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 ( Valentin ) of poisoned animals exhibit considerable electro -motive force. [For the effect of curara on lymph formation ($ 199, 6).] Atropin appears to be a specific poison for smooth muscular tissue, but different muscles are differently affected ( Szpilmann , Luchsinger). [This is doubtful. A small quantity of atropin seems to affect 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 fibrils and the contractile substance is probably different in the two cases. It is well known that the amount of striped and smooth muscle varies in the oesophagus in different animals. Szpilmann and Luchsinger find that after the action of atropin, stimulation of the periph- eral end of the vagus will still cause contraction of the striped muscular fibres in the oesophagus, but not of the smooth fibres, although both 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 excitability undergoes remarkable changes ; after three to four days the excitability of the paralyzed muscle is diminished, both for direct and indirect (2. 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, 1 ). 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 becomes shorter and at the same time thicker. The degree of contraction, which in very excitable frogs may be 65 to 85 per cent. (72 per cent, meanj 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. e., after continued vigorous exertion, the stimulus remaining the same, the extent ot contraction is diminished ; (c) the temperature ot the surroundings has a certain effect. The extent of the contraction is increased in a Log’s muscle — the strength of stim- ulus and degree of fatigue remaining the same — when it is heated to 33 0 C. If the temperature be increased above this point, the degree of contraction is diminished ( Sch?nulewitsch ). 2. The volume of a contracted muscle is slightly diminished (, Swammerdam , f 1680). Hence, the specific gravity of a contracted muscle is slightly in- creased, the ratio to the non-contracted muscle being 1062 : 1061 (Valentin) ; the diminution in volume is, however, only y-^yo- Methods. — ( a ) Erman placed portions of the body of a live eel in a glass vessel filled with ah indifferent fluid. A narrow lube communicated with the glass vessel, and the fluid rose in the tube to a certain level. As soon as the muscles of the eel were caused to contract, the fluid in the index tube sank. ( b ) Landois demonstrates the decrease in volume by means of a manometric flame. The cylindrical vessel containing the muscle is provided with two electrodes fixed 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. — Normally, all stimuli applied to a muscle or its motor nerve cause contraction in all its muscular fibres. Thus, the muscle conducts the state of excitement 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 exhibited 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 ( Muhlhauser , Auerbach). ( b ) 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-muscular — 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 months, 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 nerve 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 ( V Horsley, $ 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. d The microscopic appearances during a muscular contraction in the individual elements of the fibrillae. 1, 2, 3 (after Engelmann ) ; 4, 5 (after Merkel ). II. Microscopic Phenomena. — 1. Single muscular fibrillce. 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 striae must appear to approach nearer to each other {Bowman, 1846). 3. There is great difference of opinion as to the behavior of the doubly-refractive (anisotropous) and the singly-refractive media. Fig. 292, 1, on the left, represents, according to Engelmann, a passive muscular element — from c to d is the doubly-refractive contractile substance, with the median disk, a , b , in it; h and g are the lateral disks. Besides these, in each of the singly-refractive disks there is a clear disk — “ sec- ondary disk ” — -f and e, which is only slightly doubly refractive. This occurs only in the muscles of insects. Fig. I, on the right , shows the same element in polarized light, whereby the middle area of the element, as far as the contractile substance proper extends, is, owing to its double refrac- tion, bright; while the other part of the muscular element, owing to its being singly refractive, is black. Fig. 292, 2, is the transition stage, and 3 the proper stage of contraction of the muscular element. In both cases the figures on the left are viewed in ordinary light, and on the right, in polarized light. Engelmann’s View. — According to Engelmann, during contraction (Fig. 292, 3), the singly- refractive disk becomes, as a whole, more refractive, the doubly refractive less so. Consequently, MUSCULAR CONTRACTION. 513 a fibre at a certain degree of contraction (2), when viewed in ordinary light, may appear homoge- neous and but slightly striped transversely = the homogeneous and transition stage. During a greater degree of contraction (3), very dark transverse stripes reappear, corresponding to the singly-refrac- tive disks. At every stage of the contraction, as well as in the transition stage, the singly- and doubly-refractive disks are sharply defined, and are recognized by the polariscope as regular alter- nating layers (in 1,2 and 3 on the right). These do not change places during the contraction. The height of both dLks is diminished during contraction, but the singly -refractive do so more rapidly than the doubly-refractive disks. The total volume of each element does not undergo any appreciable alteration in volume during the contraction. Hence, the doubly-refractive disks increase in volume at the expense of the singly refractive. From this it is concluded that, during the contraction, fluid passes from the singly-refractive into the doubly-refractive disks; the former shrink, the latter swell. Merkel’s view is partially different. In Fig. 292, 4, are two muscular elements at rest; in (5), two in a state of contraction, after Merkel. The gray punctuated areas are the doubly-refractive substance, c, the median disk. According to Merkel, during contraction the dark substance lying in the middle of the element changes its position — either in part or as a whole ; it leaves the middle of the element (the two surfaces of Hensen’s median disks, 4, c), and places itself at the lateral disks, 5, at e and d, while the clear substance leaves the lateral disks, 4, e and d, and applies itself to both surfaces of the median disk, 5, c. The clear substance of the isotropous disks is fluid, and plays a more passive role ; during contraction, it is in part absorbed by the dark substance which thus swells up. This mutual exchange of place of the substances is accompanied by an interme- diate “ stage of dissolution” in which the whole contents of the element appear equally homoge- neous ( Montgomery ); in which, therefore, the fluid, singly-refractive substance has uniformly pene- trated the doubly-refractive substance. At this moment only the lateral disks are still visible. [If a living portion of an insect’s muscle be examined in its own juice, contraction waves may be seen to pass over the fibres. When a contraction wave passes over part of the fibres, the disks become shorter and broader ; at the same time, in the fully-contracted part, the dim disk appears lighter than the centre of the light disk. There is said to be a “ reversal of the stripes ” from what obtains in a passive muscle. Before this stage is reached there is an intermediate stage, where the two bands are almost uniform in appearance.] Methods. — These phenomena are best observed by “ fixing” the different stages of rest or con- traction, by suddenly plunging the muscular fibrillce of insect's muscles into alcohol or osmic acid, which coagulates the muscle substance. The actual contraction may be observed under the micro- scope in the transparent parts of the larvae of insects. Spectrum. — A thin muscle, eg , the sartorius of the frog, when placed directly behind a narrow slit running at right angles to the course of the fibres, yields a diffraction spectrum. When the muscle contracts, as by mechanical stimulation, the spectrum broadens — a proof that the interspaces of the transverse stripes become narrower ( Ranvier ). 298. MUSCULAR CONTRACTION.— Myography— Simple Con- traction — Tetanus. — Methods. — In order to determine the duration of each phase of a muscular contraction, myo- graphs of various forms are used. V. Helmholtz’s Myograph. — Helmholtz constructed a myograph of the form shown in Fig. 293. A muscle, M — say the gastroc- nemius of a frog attached to the femur — is fixed by the femur in a clamp, K, the lower free end of the muscle being attached to a movable lever carrying a scale pan and weight, W, the weight being varied at pleasure. When the muscle contracts, neces- sarily it must raise the lever. To the free end of the lever is attached a movable style, F, capable of adjustment, and which, when properly adjusted, inscribes its movements on a revolving cylinder caused to rotate at a uniform rate by means of clockwork (Fig. 98). The cylinder is covered with enameled paper smoked in the flame of a turpentine lamp. When the muscle contracts, it inscribes a curve — the “ muscle curve,” or “ myo- gram.” The abscissa indicates the dura- tion of the contraction, but of course the rate at which the cylinder is moving must be known. Scheme of V. Helmholtz’s myograph. M, muscle fixed in a The ordinates represent the height of con- S lai "P> F , writing style ; P, weight or counterpoise . K . ^ ior the lever; W, scale pan for weights; S, S, traction at any particular part of the curve. f or the lever. 33 supports 514 PENDULUM MYOGRAPH. The muscle curve may be inscribed upon a smoked glass plate attached to one limb of a vibrating tuning fork (Fig. 91). Such a curve registers the time units in all its parts. Suppose each vibration of the tuning fork = 0.01613 second, then the duration of any part of such a curve is obtained by counting the number of vibrations and multiplying by 0.01613 second. [Pendulum Myograph. — A. Fick invented this instrument. In its improved form by v. Helm- holtz (Fig. 294), it is shown both from the front and the side. A board fixed to the wall carries a heavy iron pendulum, P, whose axis, A, A, moves on friction rollers. At the lower swinging end are two glass plates, G and G ' , fixed to a bearer, T. The plates can be adjusted by means of the screw, .r, so that several curves can be written one above the other. The plate G / , on the posterior Fig. 294. Fick’s pendulum myograph, as improved by v. Helmholtz (^5 natural size), side and front view. surface, is merely a compensator, so that when G is elevated G / is lowered, and thus the duration of the oscillation is not altered. The spring catches, H, H, which can be turned inward or out- ward, are used to fix the pendulum by the teeth, a, a , when it is drawn to one side. The pendu- lum is drawn to one side and fixed, a , in H, so that when H is pulled down, it is liberated and swings to the other side, where it is caught by H at the opposite side. In the improved form, the catches, H, are made to slide along a rod like the arc of a circle, so that the length of the swing can be varied. As the pendulum swings from the one side to the other, the projecting points, a, a, knock over the contact key, b , and the current is opened and a shock transmitted to the muscle. The writing lever to which the muscle is attached is usually a heavy one, and a style writes upon the CONTRACTION CURVE OF HUMAN MUSCLE. 5 15 smoked surface of the glass. Of course, when the pendulum swings, it moves with unequal velo- cities at different parts of its course.] [When using the pendulum myograph to study a muscular contraction, arrange it as in Fig. 295. The frog’s muscle is attached to a writing lever, which is very like the lever in Fig. 293, while the style inscribes its movements on the blackened plate.] [The pendulum is fixed in the catch, C, as shown in the figure ; the key, K 7 , is closed and placed in the primary circuit, while two wires from the secondary coil of an induction machine are attached to the muscle. When the pendulum swings, the projecting tooth, S, knocks over the contact at K/, and breaks the primary circuit, when a shock is instantly transmitted through the muscle. Before stimulating, allow the pendulum to swing to obtain an abscissa. The time is recorded by a vibrating tuning fork, of known rate of vibration, connected with a Depre’s electric chronograph. Depre’s chronograph is merely a small electro-magnet with a fine writing style attached to the magnet, which vibrates when it is introduced in an electrical circuit, in which is placed a vibrating tuning fork. The signal vibrates just as often as the tuning fork.] [Spring Myograph. — This is used by Du Bois-Reymond chiefly for demonstrations (Fig. 296). It consists of a glass plate fixed in a frame, and moving on two polished steel wires, stretched Fig. 295. between the supports A and B. At b is a spring, which, when it is compressed between the upright, B, and the knot, b, drives the glass plate from B to A. As the plate moves from one side to the other, a small tooth, d, on its under surface, opens the key, h, and thus a shock is transmitted to the muscle. The arrangement otherwise is the same as for the pendulum myograph. The smoked glass plate is liberated by the projecting finger plate attached to the upright, A.] [Simple Myograph of Marey. — The gas- trocnemius is attached to a horizontal lever, which inscribes its movements on a revolving cylinder. This form of myograph, when pro- vided with two levers, is very useful for compar- ing the action of a poison on one limb, the other being unpoisoned.] [Pfluger’s stationary form, which is simply a Helmholtz’s myograph (Fig. 293) arranged to record its movements on a stationary glass plate, so that the muscle merely makes a vertical line or ordinate instead of a curve ; it thus merely indicates the height or extent of the contraction, not its duration.] A rapidly rotating disk was used by Valentin and Rosenthal for registering the muscle curve, while Harless used a plate which was allowed to fall rapidly, the so-called “ Fall myograph.” In all these experiments it is necessary to indicate at the same time the moment of stimulation. Scheme of the arrangement of the pendulum myograph. B, battery ; I, primary, II, secondary spiral of the induction machine ; S, tooth ; K', key ; C, C, catches ; K' in the corner, scheme of K' K, key in primary circuit. Contraction Curve of Human Muscle. — In man, another principle is adopted, viz., to measure the increase in thickness during the contraction, either by means of a lever or a compressible tambour ( Marey ), such as is used in Brond- geest’s pansphygmograph (Fig. 72). [The thickening of the adductor muscles of the thumb may be registered by means of Marey’s pince myographique.] I. Simple Contraction. — If a single shock or stimulus of momentary duration be applied to a muscle, a “ simple muscular contraction ” [or shortly, a con- traction, a twitch (. Burdon Sanderson)~\ is the result, i. e., the muscle rapidly shortens and quickly returns again to its original relaxed condition. Myogram or Muscle Curve. — Suppose a single stimulus be applied to a muscle attached to a light writing lever, which is not “ overweighted ” with any weight attached to it, then, when the muscle contracts, the following events take place : — [(1) A period or stage of latent stimulation (Fig. 298). (2) A period of increasing energy or contraction. (3) A period of decreasing energy or more rapid relaxation. (4) A period of slow relaxation, or the elastic after-vibration.] 516 LATENT PERIOD OF A MUSCLE CURVE. The muscle curve proper is composed of 2, 3, and 4, and its characters are shown in Figs. 297, 298. 1. The latent period (Fig. 297, a, b) consists in this, that the muscle does not begin to contract precisely at the moment the stimulus is applied to it, but the contraction occurs somewhat later , i. e., a short but measurable interval elapses between the application of a momentary stimulus and the contraction ( v . Helm- holtz). If the entire muscle be stimulated by a momentary stimulus, e.g., a single Fig. 296. opening induction shock, the duration of the latent period is about 0.01 second. In smooth muscle, the latent period may last for several seconds. [Although no change be visible in a muscle during the latent period, neverthe- less we have proof that some change does take place within the muscle substance, for we know that the electrical current of the muscle is diminished during this Fig. 297. Muscle curve produced by the application of a single induction shock to a muscle, a-/, abscissa ; a-c, ordinate ; a b, period of latent stimulation ; b d, period of increasing energy ; d e, period of decreasing energy ; e /, elastic after-vibrations. period, or we have what is known as the negative variation of the muscle cur- rent (. Bernstein — § 333).] In man the latent period varies between 0.004 and 0.01 second. If the experiment be so arranged that the muscle can contract as soon as the stimulus is applied to it, i. . Helmholtz and others ). Soltmann finds that the fresh muscles of new-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 current , 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 6 the moment of opening or breaking it ( Wundt — 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. The flexors of the frog contract more rapidly than the extensors ( Griitzner ). 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 ( Griitzner). The muscles of flying insects contract very rapidly, even more than 100 times per second. EFFECT OF VERATRIN AND OTHER POISONS ON MUSCLE. 519 Poisons. — Very small doses of curara or quinine ( Schtsehepotiew ) 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 ( Rossbach and Clostermeyer). 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 ( Harless , 1862). 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 ( Grutzner ). Kunkel is of opinion that muscular poisons act by controlling the imbibition of water by the sarcous substance. As muscular contraction depends on imbibition (| 297, II), the form of the contraction of the poi- soned'muscle will depend upon the altered condition of imbibition produced by the drug. Fig. 300. I, Contraction of a fatigued frog’s muscle writing its contraction on a vibrating plate attached to a tuning fork. Each vibration = 0.01613 second ; a b — latent period ; b c, stage of increasing energy ; cd, of decreasing energy. II, The most rapid writing movements of the right hand inscribed on a vibrating plate. Ill, The most rapid trem- bling tetanic movements of the right forearm inscribed on the same plate. [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 character 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. 301. Effect on a muscle of closing and opening a constant current. S, closing; 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-absorption 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 ( Brunton and Casfi).] Smooth Muscles. — The muscle curve of smooth or non-striped muscles is similar to that of the striped muscles, but the duration of the contraction is visibly much longer, and there are other points of difference. Some muscles stand mid- way between these two — at least, so far as the duration of their contractions are concerned. 520 ACTION OF TWO SUCCESSIVE STIMULI. The “ red ” muscles of rabbits, the muscles of the tortoise, the adductors of the common mussel, and the heart, all react in a similar manner. The muscles of flying insects contract extremely rapidly, more than ioo times per second ( H \ Landois). Contraction Remainder. — A contracted muscle assumes its original length only when it is extended by sufficient traction, e.g., by means of a weight (. Kuhne ). Otherwise, the muscle may remain partially shortened for a long time ( v . Helm- holtz, Schiff). This condition has been called “contracture” ( Tiegel ), or, better, contraction remainder (. Hermann ). This condition is most marked in muscles that have been previously subjected to strong, direct stimulation, and are greatly fatigued ( Tiegel ), which are distinctly acid, and ready to pass into rigor mortis, or in muscles excised from animals poisoned with veratrin (v. Bezold'). Rapidity of Muscular Contraction. — In man, single muscular movements can be executed with great rapidity. The time relations of such movements are most readily ascertained by inscribing the movements upon a smoked glass plate attached to a tuning fork. Fig. 300, II, represents the most rapid voluntary movements that Landois could execute, as, e.g., in writing letters, n , n , and every contraction is equal to about 3.5 vibrations (1 vibration = 0.01613 second) = 0.0564 second. In III, the right arm was tetanized, in which case 2 to 2.5 vibra- tions occur = 0.0323 to 0.0403 second. Pathological. — In secondary degeneration of the spinal cord after apoplexy, atrophic muscular anchylosis of the limbs ( Edinger ), muscular atrophy, progressive ataxia, and paralysis agitans of long standing, the latent period is lengthened ; while it is shortened in the contracture of senile chorea and spastic tabes ( Mendelsohn ). The whole curve is lengthened in jaundice and diabetes ( Edin- ger) . In cerebal hemiplegia, during the stage of contracture, the muscle curve resembles the curve of a muscle poisoned with veratrin, and the same is the case in spastic spinal paralysis and amyo- trophic lateral sclerosis; in pseudo-hypertrophy of the muscles the ascent is short and the descent very elongated. In muscular atrophy, after cerebral hemiplegia, and in tabes, the latent period in- creases, while the height of the curve diminishes. In chorea the curve is short. (For the Reac- tion of Degeneration, see \ 339.) In rare cases in man it has been observed that the execution of spontaneous movements results in a very prolonged contraction (Thomson’s disease). In such cases the muscular fibres are very broad, and the nuclei increased ( Erb ). II. Action of Two Successive Stimuli. — Let two momentary stimuli be applied successively to a muscle : (A) If each stimulus or shock be of itself suffi- cient to cause a maximal contraction, i. e , the greatest possible contraction which the muscle can accomplish, then the effect will vary according to the time which elapses between the application of the two stimuli, (a) If the second stim- ulus is applied to the muscle after the relaxation of the muscle following upon the first stimulus, we obtain merely two maximal contractions. ( b ) If, however, the second stimulus be applied to the muscle during the time that the effect of the first is present, i. e., while the muscle is in the phase of contraction or of relaxation ; in this case the second stimulus causes a new maximal contraction, according to the time of the particular phase of the contraction. ( c ) When, lastly, the second stimulus follows the first so rapidly that both occur during the latent period, we obtain only one maximal contraction ( v . Helmholtz). It is to be specially noted that a single maximal stimulus never excites the same degree of shortening as tetanic stimulation (III), but only about of the height of the contraction in tetanus. ( B ) If the stimuli be not maximal, but only such as cause a medium or sub- maximal contraction, the effects of both stimuli are superposed, or there is a summation of the contractions (Fig. 302). It is of no consequence at what particular phase of the primary contraction the second shock is applied. In all cases, the second stimulus causes a contraction, just as if the phase of contraction caused by the first shock was the natural passive form of the muscle, i. e., the new contraction (b, c) starts from that point as from an abscissa (Fig. 302, I, b). Thus, under favorable conditions the contraction may be twice as great as that caused by the first stimulus. The most favorable time for the application of the second stimulus is second after the application of the first ( Sewall ). The effects of TETANUS OF MUSCLE. 521 both stimuli are obtained even when the second stimulus is applied during the latent period ( v . Helmholtz). III. Tetanus — Summation of Stimuli. — If stimuli, each capable of causing a contraction following each other with medium rapidity, be applied to a muscle, the muscle has not sufficient time to elongate or relax in the intervals of stimulation. Therefore, according to the rapidity of the successive stimuli, it remains in a con- dition of continued vibratory contraction, or in a state of tetanus. Tetanus is, however, not a continuous uniform condition of contraction, but it is a discontinu- ous condition or form of the muscle, depending upon the summation or accu- mulation of contractions. If the stimuli are applied with moderate rapidity, the individual contractions appear in the curve (Fig. 302, II) ; if they occur rapidly, and thus become superposed and fused, the curve appears continuous and unbroken by elevations and depressions (Fig. 302, III). As a fatigued muscle contracts slowly, it is evident that such a muscle will become tetanic by a smaller number of stimuli per second than will suffice for a fresh muscle (. Marey , Fick , Minot.) All muscular movements of long duration occurring in our bodies are probably tetanic in their nature ( Ed . Weber). [Summation of Stimuli. — If a stimulus, insufficient in itself to cause con- traction of a muscle, be repeatedly applied to a muscle in proper tempo and of Fig. 302. I, two successive sub-maximal contractions ; II, successive contractions produced by stimulating a muscle with 12 induction shocks per second ; III, curve produced with very rapid induction shocks (complete tetanus). sufficient strength, at first a slight and then a stronger or maximal contraction may be produced. This process of summation occurs also in nervous tissue (§ 360).] A continued voluntary contraction in man consists of a series of single con- tractions rapidly following each other. Every such movement, on being carefully analyzed, consists of intermittent vibrations, which reach their maximum when a person shivers (Ed. Weber). [Baxt found that the simplest possible voluntary contraction, e. g., striking with the index finger, occupies on an average nearly twice as long time as a similar movement discharged by a single induction shock.] The requisite degree of shortening is obtained by the summation of single stimuli applied to the slowly contracting muscle until the desired degree of shortening is obtained. In estimating exactly the amount of movement we generally oppose some resistance by contracting antagonistic muscles, as is shown by observations on spare individuals ( Brilcke ). The tetanic contractions, which occur normally in an intact body, are proved to consist of a series of successive contractions, because they can give rise to secondary tetanus (\ 332), which may also be caused by muscles thrown into tetanus by strychnin poisoning ( Loven ). The muscle sound cannot be regarded as a certain proof of the oscillatory movement in tetanus [as Helmholtz has shown that this sound coincides with the resonance sound of the ear ( Hering and Friedrich). If a muscle be connected with a telephone, whose wires are brought into connection with two needles, one placed in the tendon, and the other in the substance of the muscle, we hear a sound when the muscle is thrown into tetanus, which proves that periodic vibratory processes, i. «?., succes- sive contractions, occur in the muscle ( Bernstein and Schonlein ). The sound is most distinct when 522 TETANUS OF MUSCLE, the tetanizing Neef’s hammer of an induction machine vibrates about 50 times per sound ( Wedenski and Kronecker). The number of stimuli requisite to produce tetanus varies in different animals, and in different muscles of the same animal. About 15 stimuli per second are required to produce tetanus in the Fig. 303. Opening and closing induction shocks of 300 units, applied at intervals of % second to the pale (lower) and red (upper) muscles of a rabbit. The lowest line, T, marks y second ( Kronecker and Stirling) . Fig. 305. Tone inductorium of Kronecker and Stirling, d, iron rod, clamped at a ; s', primary, s", secondary spiral, with a key, k ; leather rollers,,/" and^ - , driven by wheels, h. muscles of the frog (hyoglossus only 10, gastrocnemius 27) ; very feeble stimuli (more than 20 per second) cause tetanus ( Kronecker ) ; the muscles of the tortoise become tetanic with two to three shocks per second ; the red muscles of the rabbit by 10, the pale by over 20 ( Kronecker and Stir- ling ); muscles of birds not even with 70 ( Marey ); muscles of insects 330 to 340 per second RAPIDITY OF TRANSMISSION OF A CONTRACTION. 523 ( Marey , Landois). Tetanic stimulation of the muscles of the crayfish (Astacus) and also in hydroph- ilus, may cause rhythmical contractions (Richet), or rhythmically interrupted tetanus ( Schonlein ). [The red and pale muscles of a rabbit, as already shown, differ structurally, and also in re- gard to their blood supply (p. 496). They also differ physiologically. When both muscles are caused to contract, by stimulating the sciatic nerve with a single induction shock, the curves obtained are shown in Fig. 303 ; the lower one from the pale, and the upper from the red muscle. The latent period is longer, while the duration of a simple contraction of a red muscle is three times longer than that of a pale muscle. Four stimuli per second cause an incomplete tetanus, and 10 per second a nearly complete tetanus in the red muscles of a rabbit, while the pale muscles require 20 to 30 stimuli per second to be completely tetanized. Fig. 304 shows the results produced by in- duction shocks applied to both muscles at intervals of ^ second.] The extent of shortening in a tetanically contracted muscle, within certain limits, is dependent upon the strength of the individual stimuli — but not upon their frequency. The contraction re- mainder after tetanus is greater the stronger the stimuli, the longer they are applied, and the feebler the muscle used (Bohr). Sometimes a stimulus applied to a muscle immediately after tetanus pro- duces a greater effect than it did before the tetanus (Rossbach, Bohr). Duration of Tetanus. — A tetanized muscle cannot remain contracted to the same extent for an indefinite period, even if the stimuli are kept constant. It gradually begins to elongate, at first some- what rapidly, and then more slowly, owing to the occurrence of fatigue. If the tetanic stimulation is arrested, the muscle does not regain its original position and shape at once, but a contraction re- mainder exists for a certain time, this being more evident after stimulation with induction shocks. O. Saltmann found that the pale muscles of new-born rabbits were rendered tetanic with 16 stimuli per second, so that tetanus was produced in them with the same number of shocks as in fatigued adult muscles. This may serve partly to explain the facility with which spasms occur in new-born animals. Curarized muscles sometimes pass into tetanus on the application of a momentary stimulus ( Kiihne , Hering). IV. If very rapid (224 to 360 per second) induction shocks be applied to a muscle, the tetanus, after a so-called “ initial contraction ” ( Bernstein ), may cease (. Harless , Heidenhain). This occurs most readily when the nerves are cooled ( v. Juries). Kronecker and Stirling, however, found that stimuli following each other at greater rapidity than 24,000 per second produced tetanus. [Tone inductorium of Kronecker and Sterling. — This apparatus (Fig. 305), consists of a rod of iron, d , fixed in an iron upright at a. The primary, s', and secondary spiral, s " , rest on wooden supports, which can be pushed over both ends of the rod. One end of the rod lies between leather rollers,/ and^, which can be made to rub on the rod by moving the toothed wheels, h. In this way a tone is produced by the longitudinal vibrations of the rod, the number of vibrations being proportional to the length of the rod, so that by means of this instrument we can produce from 1000 to 24,000 alternating induction shocks per second.] 299. RAPIDITY OF TRANSMISSION OF A CONTRACTION. — 1. If a long muscle be stimulated at one end, a contraction occurs at that point, and is rapidly propagated in a wave-like manner through the whole-length of the muscle, until it reaches the other end. The condition of excitement or molecular disturbance is communicated to each successive part of the muscle, in virtue of a special conductive capacity of the muscle. The mean velocity of the contraction wave is 3 to 4 metres per second in the frog (. Bernstein , 3.869 metres) ; rabbit, 4 to 5 metres (. Bernstein and Steiner ) ; lobster, 1 metre ( Fre - dericq and van de Velde') ; in smooth muscle and in the heart, only 10 to 15 millimetres per second (. Engelmann , Marchland — pages 97, 98). These results have reference only to excised muscles, the velocity of transmission being much greater in the voluntary muscles of a living man, viz., 10 to 13 metres (. Her- mann, , § 334, II). Methods. — Aeby placed writing levers upon both ends of a muscle, the levers resting trans- versely to the direction of the muscular fibres. The muscle was stimulated, and both levers regis- tered their movements, the one directly over the other, on a revolving cylinder. On stimulating one end of the muscle, the lever nearest to this point is raised by the contraction wave, and a little later the other lever. When we know the rate at which the cylinder is moving, and the distance between the two elevations, it is easy to calculate the rapidity of transmission of the contraction wave. Duration and Wave Length. — The time, corresponding to the length of the abscissa of the muscle curve inscribed by each writing lever, is equal to the 524 MUSCULAR WORK. duration of the contraction of this part of the muscle (according to Bernstein, 0.053 t0 0-098 second). If this value be multiplied by the rapidity of transmis- sion of the muscular contraction wave, we obtain the wave length of the contraction Wave (= 206 to 380 millimetres). Modifying Influences. — Cold (Fig. 306), fatigue, approaching death, and many poisons [Veratrin, KCy] diminishes the velocity and the height of the con- traction wave, while the strength of the stimulus and the extent to which the muscle is loaded are without any effect upon the velocity of the wave (. Aeby ). In excised muscles, the size of the wave diminishes as it passes along the muscle ( Bernstein ), but this is not the case in the muscles of living men and animals. The contraction wave never passes from one muscular fibre to a neighboring fibre. [Fig. 306 shows the effect of cold on the muscles of a rabbit, in delaying the contraction wave. There is a longer distance between 1 and 2 in the lower than in the upper curves.] 2. If a long muscle be stimulated locally near its middle, a contraction wave is propagated toward both ends of the muscle. If several points be stimulated simultaneously, a wave movement sets out from each, the waves passing over each other in their course (, Schiff ). 3. If a stimulus be applied to the motor nerve of a muscle, an impulse is communicated to every muscular fibre ; a contraction wave begins at the end organ Fig. 306. Upper two curves, 2 and 1, obtained from a rabbit’s muscle by the above arrangement; the lower two curves from the same muscle, when it was cooled by ice. [motorial end plate], and must be propagated in both directions along the mus- cular fibres, whose length is only 3 to 4 centimetres. As the length of the motor fibres from the nerve trunk to where they terminate in the motorial end plates is unequal, contraction of all the muscular fibres cannot take place absolutely at the same moment, as the nerve impulse takes a certain time to travel along a nerve. Nevertheless, the difference is so small that, when a muscle is caused to contract by stimulation of its motor nerve, practically the whole muscle appears to contract simultaneously and at once. 4. A complete , uniform , momentary cofitraction of all the fibres of a muscle can only take place when all the fibres are excited at the same moment. This occurs when the electrodes are placed at both ends of the muscle, and an electrical stimulus of momentary duration passes through the whole length of the muscle. 300. MUSCULAR WORK. — Muscles are most perfect machines, not only because they make the most thorough use of the substances on which their activity depends (§ 217), but they are distinguished from all machines of human manu- facture by the fact that by frequent exercise they become stronger, and are thereby capable of accomplishing more work (. Du Bois-Reymond ). The amount of work (W) which a muscle can perform (see introduction) is equal to the product of the weight lifted (/) and the height to which it is lifted LAWS OF MUSCULAR WORK. 525 (, h ), i.e., W = pli. Hence, it follows that when a muscle is not loaded (where p= o), then w must be = o, i.e., no work is performed. If, again, it be overloaded with too great a load, so that it is unable to contract ( h = o), here also the work is nil. Between these two extremes an active muscle is capable of doing a certain amount of “ work.” I. Work with Maximal Stimulation. — When the strongest possible, or maximal stimulus is applied, i.e., when the strength of the stimulus is such as to cause a muscle to contract to the greatest possible extent of which it is capable, the amount of work done increases more and more as the weight is increased, but only up to a certain maximum. If the weight be gradually increased, so that it is lifted to a less height, the amount of work diminishes more and more, and gradually falls to be = o, when the weight is not lifted at all. Example of the work done by a frog’s muscle (Ed. Weber ) : — Weight Lifted in Grammes. Height in Millimetres. Work done in Gramme-Millimetres. 5 27.6 138 15 25.I 376 25 11.45 286 30 7-3 220 [Suppose a muscle be loaded with a certain number of grammes, and then caused to contract, we get a certain height of contraction. Fig. 307 shows the result of an experiment of this kind. The vertical lines represent the height to which the weights (in grammes) noted under them were raised, so that, as a rule, as the weight increases the height to which it is raised decreases.] Laws of Muscular Work. — 1. A muscle can lift a greater load, the larger its transverse section, FlG - 3°7- i.e., the more fibres it contains arranged parallel to each other (. Eduard Weber, 1846). 2. The longer the muscle, the higher it can lift a weight. 3. When a muscle begins to contract, it can lift the largest load ; as the contraction proceeds it can only lift less and less loads, and when it is at its maximum of shortening only relatively very light loads ( Th . Schwann, 1837). 4. By the term “ absolute muscular force,” is meant, according to Ed. Weber, just the weight Height t0 whlC r ai se[j h of the we,ghts 1S which a muscle undergoing maximal stimulation is no longer able to lift (the muscle being in its normal resting phase), and without the muscle at the moment of stimulation being elongated by the weight. 250 grammes. Comparative. — Comparing the absolute muscular force of different muscles, even in different animals, it is usual to calculate it with reference to that of a square centimetre. The mean transverse section of a muscle is obtained by dividing its volume by its length. The volume is equal to the absolute weight of the muscles divided by its specific gravity = 1058. The absolute muscular force for 1 Q centimetre of a frog’s muscle = 28 to 3 kilos. [6.6 lbs.] (J. Rosenthal') ; for 1 k] centimetre of human muscle 7 to 8 ( Henke and Knorz), or even 9 to 10 kilos. [20 to 23 lbs.] ( Korster , Haughton). Insects can perform an extraordinary amount of work — an insect can drag along sixty-seven times its body weight ; a horse scarcely three times its own weight. 5. During tetanus, when a weight is kept suspended, no work is done as long as the weight is suspended, but of course work is done in the act of lifting the load. To produce tetanus, successive stimuli are required, the muscular meta- bolism is increased, and fatigue rapidly occurs. The potential energy in this case is converted into heat (§ 302). When a muscle is stimulated with a maximal stimulus, it cannot lift so great a weight with one contraction as when it is stimu- lated tetanically ( Hermann ). The energy evolved, even during tetanus, is 526 THE ELASTICITY OF MUSCLE. greater the more frequent the stimulation, at least up to ioo stimuli per second (. Bernstein ). II. Medium Stimuli. — If a muscle be caused to contract by stimuli of moderate strength , i.e ., such as do not cause a maximal contraction, there are two possibilities : Either the feeble stimulus is kept constant while the load is varied, in which case the amount of work done follows the same law as obtains for maxi- mal stimulation ; or, the load may be kept the same, while the strength of the stimulus is varied. In the latter case, Fick observed that the height to which the load was lifted increased in a direct ratio with the strength of the stimulus. The stimulus which causes a muscle to contract must reach a certain strength or intensity before it becomes effective, i. e., the “ liminal intensity ” of the stimulus, but this is independent of the weight applied to the muscle. With minimal stimuli a small weight is raised higher than a large one, but as the stimulus is increased, the contractions also increase in a larger ratio with an increased load [v. Fries). The blood stream within the muscles of an intact body is increased during muscular activity. The blood vessels of the muscle dilate, so that the amount of blood flowing through them is increased (. Ludwig and Sczelkow). At the time that the motor fibres are excited, so also are the vaso-dilator fibres, which lie in the same nervous channels (§ 294, II). [Gaskell found that faradization of the nerve of the mylo-hyoid muscle of the frog not only caused tetanus of the muscle, but also dilatation of its blood vessel.] Testing Individual Muscles. — In estimating the absolute force of the individual muscles or groups of muscles in man, we must always pay particular attention to the physical relations, i. e., to the arrangement of the levers, direction of the traction, degree of shortening, etc. (g 306). Dy- namometer. — The absolute force of certain groups of muscles is very conveniently and practically ascertained by means of a dynamometer (Fig. 308). This instrument is very useful for testing the differ- ence between the power of the two arms in cases of paralysis. The patient grasps the instrument in his hand and an index registers the force exerted. Quetelet has estimated the force of certain muscles — the pressure of both hands of a man to be = 70 kilos. ; while by pulling he can move double this weight. The force of the female hand is one- third less. A man can carry more than double his own weight; a woman about the half. Boys can carry about one-third more than girls. [Very convenient dynamometers are made by Salter, of Birmingham, both for testing the strength of pull and squeeze ; in testing the former, the instrument is held as an archer holds his bow when in the act of drawing it, and the strength of pull is given by an index ; in the latter, another form of the instrument is used. Large numbers of observations were made by means of these instruments by Francis Galton, at the Health Exhibition, 1885.] Amount of Work Daily. — In estimating the work done by a man, we have to consider, not only the amount of work done at any one moment, but how often, time after time, he can succeed in doing work. The mean value of the daily work of a man working eight hours a day is 10 (10.5 to 11 at most) kilogramme metres per second, i. e ., a daily amount of work = 288,000 (300,000) kilogramme metres. Modifying Conditions. — Many substances after being introduced into the body diminish, and ultimately paralyze the production of work — mercury, digitalin, helleborin, potash salts, etc. Others increase the muscular activity — veratrin ( Rossbach ), glycogen [caffein, and allied alkaloids], mus- carin ( Klug and Fr. Hogyes), kreatin and hypoxanthin; extract of meat rapidly restores the muscles after fatigue ( Kobert ). [Those drugs which excite muscular tissue restore it after fatigue. Now kreatin is a waste product of muscle, and beef tea and Liebig’s extract of meat, perhaps, owe their restorative qualities partly to these extractives.] 301. THE ELASTICITY OF MUSCLE. — Physical. — Every elastic body has its “natural shape,” i. e., its shape when no external force (tension or pressure) acts upon it so as to distort it. Thus, the passive muscle has a “natural form.” If, however, a muscle be extended in the course of its fibres, the parts of the muscle are evidently pulled asunder. If the stretching be carried only to a certain degree, the muscle, in virtue of its elasticity, will regain its natural form. Such a body is said to possess “complete elasticity,” i.e., after being stretched it regains exactly its original Fig. 308. ELASTIC AFTER-EFFECT. 52 ? shape. By the term “amount of elasticity” ( modulus ' ) is meant the weight (expressed in kilo- grammes) necessary to extend an elastic body I Q millimetre in diameter, its own length, without the body breaking. Of course, many bodies are ruptured before this occurs. For a passive muscle it is = 0.2734 [Wundt) [that of bone — 2264 ( Wertheim ), tendon = 1.6693, nerve = 1.0905, the arterial walls = 0.0726 ( Wundt)]. Thus the amount of elasticity of a passive muscle is small, as it requires only a slight stretching force to extend it to its own length. It has, therefore, no great amount of elasticity. The term “coefficient of elasticity” is applied to the fraction of the length of an elastic body, to which it is elongated by the unit of weight applied to stretch it. It is large in a passive muscle. If the tension be sufficiently great, the elastic body ruptures at last. The “ carrying capacity” of muscular tissue, until it ruptures, is in the following ratios for youth, middle, and old age, nearly 7:3:2. [Instead of the word “elasticity,” Brunton suggests the use ol extensibility and retractibility, terms suggested by Marey, the one referable to the elongation on the application of a weight, and the other to the shortening after its removal.] Curve of Elasticity. — In inorganic elastic bodies, the line of elongation, or the extension , is directly proportional to the extending weight; in organic bodies, and therefore in muscle, this is not the case, as the weight is continually increased by equal increments — the muscle is less extended than at the beginning, so that the extension is not proportional to the weight . If equal weights be added to a scale pan attached to a piece of India-rubber, with a writing lever connected with it, and writing its movements on a plate of glass that can be moved with the hand, we get such a curve as in Fig. 309, while, if the same be done with the sartorius of a frog, we get a result similar to Fig. 310. A straight line joins the apices Fig. 309. Fig. 310. Fig. 31 1. Fig. 309. — Curve of elasticity Irom an inorganic body (India-rubber). Fig. 310. — Curve of elasticity from the sartorius of a frog, obtained by adding equal increments of weight at A, B, C, etc. Fig. 311. — Curve of elasticity produced by continuous extension and recoil of a frog’s muscle ; o x, abscissa before, x' , after extension. of the former, while the curve of elasticity is a hyperbola, or something near it, in the latter case. Elastic After-effect. — At the same time, after the first elongation, corres- ponding to the extending weight, is reached, the muscle may remain for days, and even weeks, somewhat elongated. This is called the “ elastic after-effect ” (§ 65). [Marey attached a lever to a frog’s muscle, and allowed to latter to record its movements on a slowly revolving cylinder. To the lever was fixed a vessel into which mercury slowly flowed. This extended the muscle, and when it had ceased to elongate, the mercury was allowed slowly to run out again. The curve ob- tained is shown in Fig. 31 1. The abscissae, o x and x r , indicate the position of the writing style before and after the experiment, and we observe that od is lower than o x, so that the recoil is imperfect. There has been an actual elongation of the muscle, so that the limit of its elasticity is exceeded. Although a frog’s gas- trocnemius may be loaded with 1500 grammes without rupturing it, 100 grammes will prevent it regaining its original length.] Method. — In order to test the elasticity of a muscle, fix it to a support provided with a gradu- ated scale, and to the lower end of the muscle attach a scale pan, into which are placed various weights, measuring on each occasion the corresponding elongation of the muscle thereby obtained [Ed. Weber). In order to obtain the curve of elongation or extensibility, take as abscissae the successive units of weight added and the elongation corresponding to each weight as ordinates. Example from the hyoglossus of the frog: — 528 ELASTICITY OF ACTIVE AND INTACT MUSCLES. Weight in Grammes. Length of the Muscle in Millimetres. Extension. In Millimetres. Percentage. o-3 24.9 13 30.0 5-1 20 2-3 32-3 2-3 7 3-3 33-4 1. 1 3 4-3 34-2 0.8 2 5-3 34-6 04 I 1 The elasticity of passive muscle is small , but very co 77 iplete , and is com- parable to that of a caoutchouc fibre. Small weights greatly elongate the muscle. If the weights be uniformly increased there is not a uniform elongation ; with equal increments of weight, the greater the load, the increase in elongation always becomes less ; or, to express it in another way, the amount of elasticity of the passive muscle increases with its increased extension {Eel. Weber). In inorganic bodies the curve of extension is a straight line, but in organic bodies it more closely resembles a hyperbola ( Wertheim ). The elas- ticity of a passive, fatigued muscle does not differ essentially from that of a non- fatigued muscle. Muscles in the living body, and still in connection with their nerves and blood vessels, are more extensible than excised ones. Muscles, when quite fresh, are elongated (within certain small limits as regards the weight) at first with a uniformly increasing weight, to an extent proportional to the latter, just as with an inorganic body. When heavy weights are used, we must be careful to take into consideration the “ elastic after-effect ” ( $ 65). The volume of a stretched muscle is slightly less than an unstretched one, similar to the con- tracted (| 297, 2) and stiffened muscle (§ 295). Dead muscles and muscles in rigor mortis have greater elasticity, i. .5 “ 0.5 “ 100 0 100 0 568 MECHANICAL STIMULI. In ioo parts of Ash, Breed found potash 32, soda 11, magnesia 2, lime 0.7, NaCl 5, iron phos- phate 1.2, fixed phosphoric acid 39, sulphuric acid 0.1, silicic acid 0.4. [Ptomaines (p. 275) are obtained from putrefied brain. They have an effect on the motor nerves like curara, but in a much less degree, while the phenomena last for a much shorter time ( Guareschi and Afosso).~\ 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 sometimes happens from its becoming entangled in machinery, the nerve not unfrequently remains unsevered, while the other soft parts are rup- tured. [Tillaux 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 C0 2 . 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, i. e., 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 pressure 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 excitability of a nerve for mechanical stimuli may be increased enor- mously. THERMAL AND CHEMICAL STIMULI. 569 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 after 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 stimulus be applied very gradually, the nerve may be rendered inexcitable without manifesting any signs of its being stimulated {Fon- tana, 1758). 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 abolishes reflex con- duction sooner than motor conduction ( Kronecker 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 ( Valentin). 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 affect 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 may be useful by diminishing the excitability at the periphery, in addition to the other effects 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 attached to the prolonged spring of a Neef’s 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 0 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 0 C. acts as a stimulus, causing contraction in a muscle, while sudden heating to 40° to 45 0 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 cooled 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 0 to 50° C. exhibit the results of stimulation, while the others only show a change in their excitability. When cooled to -f- 5 0 C., the excitability of all the fibres is diminished ( Griitzner ). 3. Chemical Stimuli excite nerves when they act so as to change their con- 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 water 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 — Grictzner ), 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 water 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 0.1 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 ). (c ) 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 (. Eckhard ), 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 produced. [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 solution 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 effect 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 ( Loven , 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 fz second (v. Kries'). 5. Electrical Stimuli. — The electrical current acts most powerfully upon the nerves at the moment when it is applied , and at the moment when it ceases (§ 336) ) i n 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, i. I b and 1 c each represent a unit of resist- ance ; II, double; V> five times; and X, ten times the resistance. The length of wire, I a , can also be shortened by the movable bridge (L) [composed of a small tube filled with mercury, through which the wires pass], the scale (x,y) indicating the length ot the resistance wires. It is evident that, by means of the bridge and by the method of using the brass plugs, the apparatus can be graduated to yield very variable currents for stimulating nerve or muscle. When the bridge (L) is pushed hard up to 1, 2, the current passes directly from A to B, and not through the thin wires (I a). The rheostat is another instrument used to vary the resistance of a galvanic current ( Wheatstone ). 327. ACTION OF THE GALVANIC CURRENT ON A MAGNETIC NEEDLE THE GALVANOMETER.— In 1820 Oerstedt, of Copenhagen, found that a magnetic needle suspended in the magnetic meridian was deflected by a constant current of electricity passed along a wire parallel to it. [The side to which the north pole is deflected depends upon the direction of the current, and whether it passes above or below the needle.] Ampere’S' Rule.— Ampere has given a simple rule for determining the direction. If an observer be placed parallel to and facing the needle, and if the current be passing from his feet to his head, then the north pole of the needle will always be deflected to the left , and the south pole in the opposite direction. The effect exerted by the constant current acts always in a direction toward the so-called electro-magnetic plane. The latter is the plane passing through the north pole of the needle, and two points in the straight wire running parallel with the needle. The force of the con- stant current, which causes the deflection of the magnetic needle, is proportional to the sine of the angle between the electro magnetic plane and the plane of vibration of the needle. ELECTROLYSIS, POLARIZATION, BATTERIES. 579 Multiplicator [or Multiplier]. — The deflection of the needle caused by the constant current may be increased by coiling the conducting wire many times in the same direction on a rectangular frame, or merely around and in the same direction as the needle [provided that each turn of the wire be properly insulated from the other]. An instrument constructed on this principle is called a multiplier. The greater the number of turns of the wire the greater is the angle of deflection of the needle, although the deflection is not directly proportional, as the several turns or coils are not at the same distance from, or in the same position as, the needle. By means of the multiplier we may detect the presence [and also the amount and direction] of feeble currents [The instrument is now termed a Galvanometer]. Experience has shown that, when great resistance (as in animal tissues) is opposed to the weak galvanic currents, we must use a very large number of turns of thin wire round the needle. If, however, the resistance in the circuit is but small, e.g ., in thermo- electrical arrangements a few turns of a thick wire round the needle are sufficient. The multiplier may be made more sensitive by weakening the magnetic directive force of the needle , which keeps it pointing to the north. Galvanometer and Astatic Needles. — In the multiplier of Schweigger, used for physiological purposes, the tendency of the needle to point to the north is greatly weakened by using the astatic needles of Nobili. [A multiplier or galvanometer with a single magnetic needle always requires comparatively strong currents to deflect the needle. The needle is continually acted upon by the directive magnetic influence of the earth, which tends to keep it in the magnetic meridian, and as soon as it is moved out of the magnetic meridian the directive action of the earth tends to bring it back. Hence, such a simple form of galvanometer is not sufficiently sensitive for detecting feeble currents. In 1827 Nobili devised an astatic combination of needles, whereby the action of the earth’s magnetism was diminished.] Two similar magnetic needles are united by a solid light piece of horn [or tortoise shell], and are so arranged that the north pole of the one is placed over or opposite to the south pole of the other (Fig. 345). [If both needles are equally magnetized, then the earth’s influence on the needle is neutralized, so that the needles no longer adjust them- selves in the magnetic meridian ; hence, such a system is called astatic.] As it is impossible to make both needles of absolutely equal magnetic strength, one needle is always stronger than the other. The difference, however, must not be so great that the stronger needle points to the north, but only that the freely suspended system of needles forms a certain angle with the magnetic meri- dian, into which position the system always swings after it is deflected from this position. This angular deviation of the astatic system toward the magnetic meridian is called the “ free deviation.” The more perfectly an astatic condition is reached, the nearer the angle formed by the direction of the free deviation with the magnetic meridian becomes a right angle. The greater, therefore, the astatic condition, the astatic system will make the fewer vibrations in a given time, after it has been deflected from its position. The duration of each single vibration is also very great. [Hence, when using a galvanometer, and adjusting its needle to zero, if the magnets dance about or move quickly, then the system is not sensitive, but a sensitive condition of the needles is indicated by a slow period of oscillation.] In making a galvanometer, the turns of the wire must have the same direction as the needles. In Nobili’s galvanometer, as improved by Du Bois-Reymond, the upper needle swings above a card divided into degrees (Fig. 345), on which the extent of its deflection may be read off. Even the purest copper wire used for the coils round the needles always contains a trace of iron, which exerts an influence upon the needles. Hence, a small fixed directive or compensatory magnet (r) is placed ne^r one of the poles of the upper needle to compensate for the action of the iron on the needles. 328. ELECTROLYSIS, POLARIZATION, BATTERIES.— Electrolysis.— Every galvanic current which traverses a fluid conductor causes decomposition or electrolysis of the fluid. The decomposition products, called ions, accumulate at the poles (electrodes) in the fluid, the positive pole ( -f- ) being called the anode [avri, up, dduq t a way], the negative pole ( — ) the cathode (xard, down, 6 dd$, a way). The anions accumulate at the anode and the kations at the cathode. Transition Resistance. — When the decomposition products accumulate upon the electrodes, by their presence they either increase or diminish the resistance to the electrical current. This is called transition resistance. If the resistance within the battery is thereby increased, the transition resistance is said to be positive ; if diminished, negative. Galvanic Polarization. — The ions accumulated on the electrodes may also vary the strength of the current, by developing between the anions and kations a new galvanic current, just as occurs between two different bodies connected by a fluid medium. This phenomenon is called galvanic polarization. Thus, when water is decomposed, the electrodes being of platinum, the oxygen (negative) accumulates at the +- pole, and the hydrogen (positive) at the — pole. Usually, the polarization current has a direction opposite to the original current ; hence we speak of negative polarization. When the two currents have the same direction, positive polarization obtains. Of course, transition resistance and polarization may occur together during electrolysis. Test. — Polarization, when present, may be so slight as not to be visible to the eye, but it may be detected thus : After a time, exclude the primary source of the current, especially the element con- 580 CONSTANT BATTERIES, ELEMENTS, OR CELLS. nected with the electrodes, and place the free projecting end of the electrodes in connection with a galvanometer, which will at once indicate, by the deflection of its needle, the presence of even the slightest polarization. Secondary Decompositions. — The ions excreted during electrolysis cause, especially at their moment of formation, secondary decompositions. With platinum electrodes in a solution of common salt, chlorine accumulates at the anode and sodium at the cathode ; but the latter at once decom- poses the water, and uses the oxygen of the water to oxidize itself, while the hydrogen is deposited secondarily upon the cathode. The amount of polarization increases, although only to a slight extent, with the strength of the current , while it is nearly proportional to the increase of the tem- perature. The attempts to get rid of polarization, which, obviously, must very soon alter the strength of the galvanic current, have led to the discovery of two important arrangements, viz., to the con- struction of constant galvanic batteries ( Becquerel ), and the so-called non-polarizable elec- trodes ( Du Bois-Reymond'). Constant Batteries, Elements, or Cells. — A perfectly constant element produces a constant current, i. e., one remaining of equal strength, by the ions produced by the electrodes being got rid of the moment they are formed, so that they cannot give rise to polarization. For this purpose each Fig. 345. Scheme of the galvanometer. N, N, astatic needles sus- pended by the silk fibre, G; P, P, non-polarizable elec- trodes, Containing zinc-sulphate solution, s, and pads of blotting paper, b, covered with clay, t, t, on which the muscle, M, is placed; II, III, arrangements of the mus- cle on the electrode ; IV, non-polarizable electrodes ; Z, zinc wire ; K, cork ; a, zinc-sulphate solution ; t, t, clay points. Fig. 346. Large Grove’s element. of the substances from the tension series used is placed in a special fluid ($ 326), both fluids being separated by a porous septum (porcelain cylinder). Grove’s Element has two metals and two fluids (Fig. 346). The zinc is in the form of a roll placed in dilute sulphuric acid [1 acid to 7 of water, which is contained in a glass, porcelain or ebonite vessel]. The platinum is in contact with strong nitric acid [which is contained in a porous cell placed inside the roll of zinc]. The O, formed by the electrolysis and deposited on the zinc plate, forms zinc oxide, which is at once dissolved by the sulphuric acid. The hydrogen on the platinum unites at once with the nitric acid, which gives up O and forms nitrous acid and water, thus — [H 2 + HN 0 3 = hno 2 + H 2 0 .] [Platinum is the -+- pole, and zinc the — .] [Grove’s battery is very powerful, but the nitrous fumes are very disagreeable and irritating; hence these elements should be kept in a special, well- ventilated recess in the laboratory, in an evap- orating chamber, or under glass. The fumes also attack instruments.] Bunsen’s Element is quite similar to Grove’s, only a piece of compressed carbon is substituted for the platinum in contact with the nitric acid. [The carbon is the -(- pole, the zinc the — .] DANIELL, SMEE, GRENNET AND LECLANCHE S ELEMENTS. 581 [Daniell’s Element (1836). — It consists of an outer vessel or glass of earthenware, and some- times of metallic copper, filled with a saturated solution of cupric sulphate. A roll of copper, per- forated with a few holes, is placed in the copper solution, and in order that the latter be kept satu- rated, and to supply the place of the copper used up by the battery when in action, there is a small shelf on the copper roll, on which are placed crystals of cupric sulphate. A porous earthenware vessel containing zinc in contact with dilute sulphuric acid (1 : 7) is placed within the copper cylinder. When the circuit is completed, the zinc is acted on, zinc sulphate being formed, and hydrogen liberated. The hydrogen in statu nascendi passes through the porous cell, reduces the cupric sulphate to metallic copper, which is precipitated on the copper cylinder, so that the latter is always kept bright and clean. The liberated sulphuric acid replaces that in contact with the zinc. Owing to the absence of polarization, the Daniell is one of the most constant batteries, and is gen- erally taken as the standard of comparison.] [The copper is the -{- pole, zinc the — .] Fig. 348. Leclanche’s element. A, outer vessel ; T, porous cylinder, containing K, carbon; B, binding screw; Z, zinc; C, binding screw of nega- tive pole. [Smee’s Element. — There is only one fluid, viz., dilute sulphuric acid(i : 7), in which the two metals, zinc and platinum, or zinc and platinized silver, are placed. The platinum is the pole, and zinc the — .] [Grennet’s or the Bichromate Element. — It consists of one plate of zinc and two plates of compressed carbon in a fluid, which consists of bichromate of potash, sulphuric acid, and water. The fluid consists of 1 part of potassium bichromate dissolved in 8 parts of water, to which 1 part of sulphuric acid is added. Measure by weight .] [The cell consists of a wide-mouthed glass bottle (Fig. 347) ; the carbons remain in the fluid, while the cine can be raised or depressed. When not in action, the zinc, which is attached to a rod (B), is lifted out of the fluid, and hence this battery is very convenient for purposes of demonstration, although it is not a very constant battery. When in action, the zinc is acted on by the sulphuric acid, hydrogen being liberated, which reduces the bichromate of potash. The carbon is the -f- pole, and the zinc the — .] [Leclanche’s Element (Fig. 348) consists of an outer glass vessel containing zinc in a solution of ammonium chloride, while the porous cell contains compressed carbon in a fluid mixture of black 582 REFLECTING GALVANOMETER AND SHUNT. oxide of manganese and carbon. It is most frequently used for electric bells, as its feeble current lasts for a long time. The carbon is the -(- pole, and the zinc the — .] Non-polarizable Electrodes. — If a constant current be applied to moist animal tissues, e.g., nerve or muscle, by means of ordinary electrodes composed either of copper or platinum, of course electrolysis must occur, and in consequence thereof polarization takes place. In order to avoid this, non-polarizable electrodes (Figs. 345 and 349) are used. The researches of Regnault, Mat- teucci and Du Bois-Reymond have proved that such electrodes can be made by taking two pieces of carefully amalgamated pure zinc wire ( z , z), and dipping these in a saturated solution of zinc sulphate contained in tubes (a, a), their lower ends being closed by means of modeller’s clay moistened with 0.6 per cent, normal saline solution. The contact of the tissues with these elec- trodes does not give rise to polarity. Arrangement for the Muscle or Nerve Current. — In order to investigate the electrical cur- rents of nerve or muscle, the tissue must be placed on non-polarizable electrodes, which may either have the form described above, or the original form used by Du Bois-Reymond (Fig. 345). The last consists of two zinc troughs (/, p) thoroughly amalgamated inside, insulated on vulcanite, and filled with a saturated solution of zinc sulphate (j, j). 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 sufficient 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 {t, t), moistened with 0.6 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-polarizable electrode of Du Bois Reymond. Z, zinc ; H, movable support ; C, clay point — the 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. 350). 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 surrounded by a separate coil of wire, the low r er coil (/) winding in a direction opposite to that of the upper (u). 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 (/»), 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 w-est. 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 purpose 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 separated from each other, like those of the rheocord, but which can be united by 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. By 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 yL of the current goes through the galvanometer and y 9 ^ to the electrodes. If the plug be placed as shown in the figure opposite then yi^ part of the current goes to the galvanometer, while T 9 ^ are short circuited. If the plug be placed opposite ^g, only y^g part goes through the galvanometer.] Internal Polarization of Moist Bodies. — Nerves and muscular fibres, the juicy parts of vegetables and animals, 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 internal polarization of moist bodies by Du Bois-Reymond. It is assumed that the solid parts in Fig. 350. bir William Thomson’s reflecting gal- vanometer. u, upper, /, lower coil ; s, s, levelling screws ; in, magnet on a brass support, b. Fig. 351. Lamp and scale for Sir William Thomson’s galvanometer. Fig. 352. Shunt for galvanometer (. Elliott Brothers'). the interior of these bodies, which are better conductors, produce electrolys : s of the adjoining fluid, just like metals in contact with fluid. The ions produced by the decomposition 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 -f- 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 cataphoric 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 (g 293, I, b\. External Secondary Resistance. — This condition also depends on cataphoric action. If each o f 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 first becomes stronger, but 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 observe 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 be the cause of the resistance in the circuit, which explains the enfeeblement of the galvanic current. This phenomenon is called “ external secondary resistance ” ( Du 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 the circuit is again opened or broken a slight 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 same 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 the thickness of the iron bar. As soon as the current 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. During the time 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 short 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, Pj and S 0 are the abscissae 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 1 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 cause 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 primary current, so that the current 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 with 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.] helmholtz’s modification. 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 f> while the binding scr a w, f is separated from the platinum contact, c, of Neef s 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 f in the direction of the arrow, through the primary spiral, P, to the coil of soft wire, g, 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 0, b . c, d, e , which weakens the current passing through the electro -magnet, g, 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 ( the long axis, the artificial transverse section (Fig. 361,1, c,d); lastly, the term equator (a, b-m , n) 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 used for thermo-electric purposes (Fig. 216). The wires leading from the tissue are connected with non-polarizable elec- trodes (Fig. 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 (j). 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 downu 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- Fig. 361. Scheme of the muscle current. Fig. 362. Capillary electrometer (after Christian i). R, mercury in tube ; c. capillary tube ; s, sul- phuric acid; q, Hg ; B, observer; M, microscope. pensation method of Poggendorf and Du 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 , i86y ). 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 ( Nobili , Matteucci, Du Bois-jReymond). 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 (2 334 , 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 (-J-) to the point lying further from it ( — ), but of course this direction is reversed within the muscle itself (Fig. 361, II, ke and le). (b) 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 the muscle to that nearer the centre of the transverse section (Fig. 361, II, i, c). 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 Irom the 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 1, 2, and 3. Strength of Electro-motive Force. — The electro-motive force of a strong muscle current (frog) is equal to 0.05 to 0.08 of a Daniell’s element ; while the strongest deviation current may be o. 1 Daniell. The muscles of a curarized animal at first yield stronger currents ; fatigue ot the 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 ). Cooling diminishes the electro-motive force. The warmed living muscular and nervous substance [Hermann, Worm Muller , Griitzner) is positive to the cooler portions; while, if the dead tbsues 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 Chris- tiam ). Rheoscopic Limb. — The existence of a muscle current may be proved with- out the aid of a galvanometer : 1. 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 between 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. Humboldt). 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 (. Du 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 the same way produce a similar result. 3. Electrolysis. — If the muscle current be conducted through starch mixed with potassic iodide , 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 tip of the toes toward the trunk, and in the trunk from the anus to the head. This is the “ corrente pro- pria della rena ” of Leopoldo Nobili (1827), or the “ frog current ” of Du Bois-Reymond. In mammals the corresponding current passes in the opposite direction. 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 ( Funke ), and so does a nerve beginning to undergo degeneration, even two weeks after it has lost its excitability. Muscles in a state of rigor mortis give currents in the opposite direction, owing to inequalities in 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 — , ( Du 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 ( O elder). Stimulation of the Secretory Nerves of the glandidar membranes, besides causing secretion, affects the current of rest ( Roeber ). 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 ( hermann ). 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 (§ 288), but a secretion current is developed ( Luchsinger and Hermann). If two symmet- rical parts of the skin in the leg or arm of a man be similarly 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 ( Bubnoff ). [The secretion current from the submaxillary gland is referred to in \ 145 ( Bayliss and Bradford).~\ 332. CURRENTS OF STIMULATED MUSCLE AND NERVE. — 1. Negative Variation of the Muscle Current. — If a muscle, which yields a strong electrical current, 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 ( Du Bois-Reymond). It is larger the greater the primary deflection of the galva- nometer 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,” equally 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 variaiion still takes place. 2. Current during Tetanus. — An excised frog’s muscle tetanized through its nerve shows electro-motor force — the so-called “ action current.” In a tetan- ized frog’s gastrocnemius there is a descending current. In completely uninjured human muscles, however, thrown into tetanus by acting on their nerves, there is no such current (Z. Hermann ) ; similarly, in quite uninjured frog’s muscles, as well as when these muscles are directly and completely tetanized , 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 wave ” of the muscle current, the latter.occurring during the late?it 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 sciatic nerve of A lies on B E, electrodes applied to the sciatic nerve of B. Nerve-muscle preparation of a frog. F, femur ; S, Sciatic nerve ; I, tendo Achilles. 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 (. Kolliker and H. Muller). The electrical disturbance in the muscle causing the negative variation always precedes the actual contraction (v. Helmholtz , 1854). When the completely uninjured frog’s gastrocnemius contracts by stimulating 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, A, 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 “ secondary tetanus ” {Du Bois-Reymond). 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 , Kuhne ) ; still, Loven has observed secondary strychnin tetanus composed of six to nine shocks per second. Observations with a sensitive galvanometer, or Lippmann’s capil- lary electrometer (Fig. 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 Fip. 365. Scheme of Bernstein’s differential rheotome; N n, nerve; J, induction machine; G, galvanometer ; x ,y, deflection of needle ; E, battery and primary circuit with C for opening it at o ; c , for closing galvanometer circuit ; z, z, electrodes in galvanometer circuit ; S, motor. (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-Reymond'). This negative variation can be prop- agated toward both ends of a nerve, and is composed of very rapid, successive, periodic interruptions 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 DURING ELECTROTONUS. 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 negative variations , perhaps due to the intermittent excitement of the nerve centres, more especially of the respiratory centre. Similar variations are obtained reflexly 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 0 to 25 0 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 to 0-00C>8 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 differential 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 (G), while at the other end ( n ) are placed the electrodes of an induction machine (J). A disk (B), rapidly rotating on its vertical axis (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. At 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 6 ) 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 n. 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 Dewar). The inner 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. Retinae in which the visual purple has disappeared, owing to the action of light, show no variations ( Kiihne and Steiner). 333. ELECTROTONIC CURRENTS IN NERVE AND MUS- CLE. — 1. 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. 59 5 3. Equator. — If two points of the nerve equi- Fig. 366. distant from 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-Reymond , 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 ($ 331, 5) ; 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 Bois-Reymond ). 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 ( Tschirjew , 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 w’hen 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 ($ 328). In living 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). Nerve current in electrotonus, vanometer ; b, electrodes ; stant current. gal- con- 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 muscle 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 — but it does not explain the 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 section. Then, of course, differences of electrical tension obtain between the stronger and the feebler molecules. Parelectronomy. — But the natural 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 Bois-Reymond 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 half 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 -j- 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 extrapolar portion is from the electrodes. II. Difference Theory. — The difference theory was proposed by L. Her- mann, and, according to him, the four following considerations are sufficient to explain the occurrence of the galvanic phenomena in living tissues: (i) Proto- plasm, by undergoing partial death in its continuity, whether by injury or by (horny or mucous) metamorphosis, becomes negative toward the uninjured part. (2) Protoplasm, by being partially excited in 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 polarizable 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 ( Engel - matin'), 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 which behaves negatively to the positive intact substance. The current thus produced is called by Hermann the “ demarcation current .” 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 {Buff) ; and the same occurs in animal parts, e.g., glands and bones. Engelmann 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. — Grunhagen 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 EXCITABILITY 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 other passive parts of the muscle ( Bieder - mann). 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 $ 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 ( e.g ., 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) (Sig. Meyer ) (g 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, 1). 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 capillary interspaces of non-living parts (pores of a porcelain plate) is also connected with electrical movements, which have the same direction as the current of water. The same effect occurs in the movement of water, which results in that condition known as itnbibition 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 secretion 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 certain parts, e.g., as in the mimosa and dionsea (p. 317) {Bur don- Sanderson). These phe- nomena are perhaps explicable by the movement 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 ( Htrmann ) ; the cotyledons positive to the other parts of the seedling ( Miiller-Hett - 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 passes into a condition of altered excitability ( Ritter , 1802, and others), which Du Bois-Reymond called the electrotonic condition, or simply electrotonus. This condition of altered excitability extends not only over the part actually traversed by the current, intra- polar portion , but it is communicated to the entire nerve. Pfliiger (1859) dis- covered the following laws of electrotonus : — At the positive pole 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 OF 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 (/„) ; 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 with 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 (TV, n) traversed by a constant current in the direction of the arrow. The curve shows the degree of increased excitability in the neighborhood of the cathode (JC) as an elevation above the nerve, diminution at the anode ( A ) as a depression. The Fig. 367. O curve m, 0, i n ,p, r , shows the degree of excitability with a strong current; e,f \ i /} h , k , with a medium current ; lastly, a, b , i, c, d, with a weak current. The electrotonic effect increases with the length of the nerve traversed by the current. The changes of the excitability in electrotonus occur instantly when the circuit is closed, while anelec- trotonus develops and extends more slowly. Cold diminishes electrotonus ( Hermann and v. Gendre). 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 ( Pfliiger ). At the very first moment of closing, Wundt observed that the excitability of the whole nerve was increased. I. Proof of Electrotonus in Motor Nerves. — To test the laws of electrotonus, 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. 368): — (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 Fig. 368. A B (b) Descending extrapolar cathelectrotonus (A). The stimulus (salt) is at R, and the con- tractions thereby 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 strength of the polarizing current: (1) When the current is very weak, which can be 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 nerve 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. g., by an induction shock, then the negative variation is weaker than when the polarizing circuit was open. Conversely, 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 above and below the anode (at c c) 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 (a lelectrotonus) ( v . Helmholtz, 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 excita- bility in electrotonus. R, r, R u r,, where the common salt (stimulus) is applied. Fig. 369. Tn order, therefore, to stimulate directly the same point on which the electrode acts, it is necessary to 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 ( Waller and de Watteville ). II. Proof of Electrotonus in Sensory Nerves. — Isolate 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 nerve, provided the salt lies in the anelectrotonic area ( Pfliiger , and Zurhelle, Hallsten). III. Proof of Electrotonus in Inhibitory Nerves. — To show this, proceed thus: On causing dyspnoea in a rabbit, the number of heart beats 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 cathelectrotonus). Hence, the action of inhibitory nerves in electrotonus 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, 1. 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 ( 7 . e., by closing and opening the current — Ritter ) : (1) When the current is closed, the stimulation occurs only at the cathode, i. e., at the moment when the electrotonus takes place. (2) When the current is opened, stimulation occurs only at the anode, i. e., at the moment when the electrotonus disappears. (3) The stimulation at the occurrence of cathelectrotonus is stronger than at the disappearance of anelectrotonus ( Pfluger ). 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. Pfluger 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 difference 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 ( b ) the strength of the current {H eidenhairi) . (1) 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 descending 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 Opening. On Closing. On Opening. Weak, c R c R Medium, c C c c Strong, R C c R THE LAW OF CONTRACTION. 601 II. In a dying nerve, losing its excitability, according to the Ritter-Valli law (§ 3 2 5> 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 (. Ritter , 1829). 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, Cl. 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. Fleischl 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 : (1) 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 Donders 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. Weak currents applied to the human skin cause a sensation with both directions of the current only at closing ; strong descending currents a sensation only at opening ; strong ascending currents a sensation only at closing (. Marianini , Matteucci ). 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. Bezold). 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 during 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 summation 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 ( Wundt). 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 (“Volta’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 to the closing of a side branch of the nerve current in a secondary circuit through the electrodes [Hering, Biedermann , Griitzner). According to Grutzner 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 latent 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 Pfliiger’s sense ; the second is explained, like Ritter’s opening tetanus, in Engelmann’s and Griinhagen’s sense. 337. TRANSMISSION OF NERVOUS IMPULSES — 1. If a motor nerve be stimulated at its central end (1) a condition of excitation is set up, and (2) an impulse is transmitted along the nerve to the muscle with a certain velocity. The latter depends on the former and represents the function of conductivity. The velocity is about 27^ metres [about 90 feet] per second METHOD OF ESTIMATING RAPIDITY OF A NERVE IMPULSE. 603 (y. Helmholtz ) and for the human motor nerves 33.9 [100 to 120 feet per second] ( v . Helmholtz and Baxf). 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] ( Chauveau ) ; 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 0 to 25 0 C.) lessen it (, Steiner and Trojtzky ) ; also curara , the electrotonic condition (v. Bezold ) ; or only anelectrotonus, while cathelectrotonus increases it (. Rutherford , Wundt). 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 ( v . Vint- schgau). Methods. — (1) 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. V - — — — \ W k V. Helmholtz’s method of estimating the velocity of a nerve impulse. proportional to the duration and strength of the current. The apparatus 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. e., 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 difference 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 time-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 ^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, l (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 further deflection of the magnetic needle ceases. The contact at f is made by a pointed cupola of mercury. When 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, i. e., through the galvanometer circuit. If the nerve be stimulated with the opening shock, first at n> and then at N, the deflection of the needle is greater in the former than in the latter case. From the difference, we calculate the time for the conduction of the impulse in the stretch of the nerve between n and N. [2. A simpler method is that shown in the scheme, Fig. 371. Use a pendulum Fig. 371. Scheme for measuring the velocity of nerve energy, f, clamp for femur ; m, muscle; N, nerve; a, near, b, removed from, C, commutator ; II, secondary ; I, primary spiral of induction machine; B, battery; i, 2, key ; 3, tooth on the smoked plate P. or spring myograph (Fig. 294), and suspend a frog’s gastrocnemius (w), with a long portion of the sciatic nerve (N) dissected out, by fixing the femur in a clamp (._/), while the tendo Achilles is fixed to a lever, which inscribes its movements on the smoked glass plate (P) of the myograph; place the key of the myograph (2) in the circuit with the battery (B), and the primary circuit of the induction machine (I). To the secondary coil (II) attach two wires, and connect them with a commutator without cross-bars (C). Connect the other binding screws of the commutator with two pairs of wires, arranged so that one pair can stimu- Fig. 372. 1, curve obtained on stimulating a nerve (man) near the muscle ; 2, when the stimulus was applied to the nerve at a distance from the muscle ; D, vibrations of a tuning fork (250 per second). late the nerve near the muscle (#), and the other at a distance from it ( b ). When the glass plate swings from one side to the other, the tooth (3) on its framework opens the key (2) in the primary circuit, and if the commutator be in the position indicated, then the induced current will stimulate the nerve at a , and a curve will be obtained on the glass plate. Rearrange the pendulum as before, but turn the handle of the commutator, and allow the pendulum to swing again. This time the induced current will stimulate the nerve at b, and a second contraction, a DOUBLE CONDUCTION IN NERVES. 605 little later than the first one, will be obtained. Register the velocity of the swing by means of a tuning fork, and the curve obtained will be something like Fig. 372, although this curve was obtained on a cylinder traveling at a uniform rate. The difference between the beginning of the a and b curves indicates the time that the nerve impulse took to travel from b to a. This time is measured by the tuning fork, and if the distance between the points a and b is known, then the calculation is a simple one. Suppose the stretch of nerve between a and b to be 2 inches, and the time required by the impulse to travel from b to a to be second, then we have the simple calculation — 2 inches : 12 inches: : : sV? or 80 feet per second. In Fig. 372 the experiment was made on man ; the curve 1 was obtained by stimulating the nerve near the muscle, and 2 when the nerve was stimulated at a distance of 30 centimetres. The interval between the ver- tical lines corresponds to T -J--g second, i. e . , the time required by the nerve impulse to pass along 30 centimetres of nerve, which is equal to a velocity of 30 metres (90 feet) per second.] In man v. Helmholtz and Baxt estimated the velocity of the impulse in the median nerve by causing the muscles of the ball of the thumb to write off their contractions on a rapidly revolving cylinder. [In this case the pince myographique of Marey ($ 708) may be used. The ends of the pince are applied so as to embrace the ball of the thumb, so that when the muscles contract the increase in thickness of the muscles expands the pince, which acts on a Marey’s tambour, by which the movement is transmitted to another tambour provided with a writing style, and inscribing its movements upon a rapidly moving surface, either rotary or swinging.] The nerve is stimulated at one time in the axilla and again at the wrist. Two curves are obtained, which, of course, do not begin at the same time. The difference in time between the beginning of the two curves is the time taken by the impulse to traverse the above-mentioned length of nerve. [The time is easily ascertained by causing a tuning fork of a known rate of vibration to write its movements under the curves.] 3. In the sensory nerves of man the velocity of the impulse is probably about the same as in motor nerves. The rates given vary between 94-30 metres [280-90 feet] per second (v. Helmholtz , Kohlrausch , v. Wittich , Schelske and others ). Method. — Two points are chosen as far apart as possible, and at unequal distances from the brain, and they are successively excited by a momentary stimulus, e.g ., an opening induction shock applied successively to the tip of the ear and the great toe. The moment the stimulus is applied, it is indicated on the registering surface. The person experimented on is provided with a key attached to an electric arrangement, by which he can mark on the registering surface the moment he feels the sensation in each case. Reaction Time. — The time which elapses between the application of the stimulus and the reaction is called the “ reaction time” It is made up of the time necessary for conduction in the sensory nerve, that for the process of perception in the brain, the conduction in the motor nerves to the muscles, by which the signs on the registering surface were made, and lastly by the latent period (p. 516). The reaction time is usually about 0.125 to 0.2 second. Pathological. — The conduction in the cutaneous nerves is sometimes greatly delayed in altera- tions of the cutaneous sensibility in certain diseases of the spinal cord ($ 364). The sensation itself may be unchanged. Sometimes only the conduction for painful impressions is retarded, so that a painful impression on the skin is first perceived as a tactile sensation, and afterward as pain, or con- versely. When the interval of time between these two sensations is long, then there is a distinctly double sensation ( Naunyn , Remak, Eulenburg'). It is rarely that voluntary movements are exe- cuted much more slowly from causes depending on the motor nerves, but occasionally the time between the voluntary impulse and the coniraction is lengthened, but there may be in addition slower or longer continued contraction of the muscle. In tabes dorsalis or locomotor ataxia, the discharge of reflex movements is delayed ; it is slower with thermal stimuli (6o°) than with cold ones (5 0 C., Ewald). 338. DOUBLE CONDUCTION IN NERVES.— Conductivity is that property of a living nerve in virtue of which, on the application of a stimulus, it transmits an impulse. [The nature of a nerve impulse is entirely unknown ; we may conveniently term the process nerve motion, but there is some reason to believe that nerve energy is transmitted by some sort of molec- ular vibration.] The conductivity is destroyed by all influences or conditions 606 THERAPEUTICAL USES OF ELECTRICITY RHEOPHORES. which injure the nerve in its continuity (section, ligature, compression, destruction by chemical agents) ; or which abolish the excitability at any part of its course (absolute deprival of blood ; certain poisons, e.g., curara for motor nerves; also strong anelectrotonus, § 335). Law of Isolated Conduction. — Conduction always takes place only in the continuity of fibres, the impulse never being transferred to adjoining nerve fibres. Double Conduction. — Although apparently conduction in motor nerves takes place only in a centrifugal direction toward the muscles, and in sensory nerves in a centripetal direction, i. e . , toward the centre ; nevertheless, experiment has proved that a nerve conducts an impulse in both directions. If a pure motor or sensory nerve be stimulated in its course, an impulse is propagated at the same time in a centrifugal and in a centripetal direction. This is the phenomenon of * ‘ double conduction . 7 7 Proofs. — 1. If a nerve be stimulated, its electro-motive properties are affected both above and below the point of stimulation (see Negative Variation in Nerves , § 33 2 )- 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 the trunk of the lingual receives high up the centrifugal fibres from the seventh, viz., the chorda tympani, which may unite with those of the hypoglossal. Further, if the chorda be divided and allowed 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 y 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 impulses in the sensory nerves must have traversed the nerves from the base to the tip of the tail (g 325). 4. Electrical Nerves. — If the free end of the electrical centrifugal nerves of the malapterurus 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 , Manley). 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 magneto-electrical apparatus, and the extra- current apparatus. The constant or galvanic current is also used, especially since Remak’s time, 1855 (g 330). 1. In paralysis, Faradic currents are applied either to the muscles themselves ( Duchenne ), or the points of entrance of the motor nerves [v. Ziemssen), by means of suitable electrodes, or rheo- phores covered with sponge, 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 anaesthesia, hypersesthesia, 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 rheophores 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 (g 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 nerves (v. Bezold , Engelmann). 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, by stimulating at the entrance of the nerve, each muscle may be caused to contract singly. In l 349 the motor points of the face, and in \ 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 interrupted current, by altering its direction and increasing or diminishing its intensity, but it also causes a polar action. On closing the current, the nerve at the cathode is stimulated ; similarly, on opening the current, at the anode (§ 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 current, 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. 373. Double sponge rheophore. Fig. 375. Fig. 374 Disk rheophore. Metallic brush ( li'eiss). 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 applied 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 . Eulenburg ). 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 nearer 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 v. Constant Current : Reaction of Degeneration. — Paralyzed nerves and muscles behave quite differently as regards the induced (rapidly interrupted) and the constant current. 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 1859, 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. radialis. M. brachial intern. / M. supinator long. M. radial, ext. long. M. radial ext. brev M. extene. digit, communis. M. extens. digit, min. M. extens. indicis. M. abduct, pollic. long. M. extens. polite, brev. M. extens. poll. long. v M. abduct, digit, min. (N. ulnaris.) Mm. inteross. dorsal. I, II, III, et IV. (N. ulnaris.) M. triceps (caput ext.) M. triceps (caput long V M.deltoideus (post. half). (N. axillaris). Motor points of the radial nerve and the muscles supplied by it ; dorsal surface. Fig. 377. M. deltoideus /ant. half) N. axillaris. Motor 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 opening 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, then the constant current does not cause contrac- tion. Conversely, the induced current may be rendered effective by causing it to last longer. We may also keep the primary circuit of the induction 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 (Briicke). Hence, in stimulating a muscle or nerve, 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. OT O rt u 3 5 O u> 3 > I tu z L N. obturator. M. pectineus. M. adductor magnus. M adduct, longus. N. peroneus. M. tibial. antic. M. exten. dig com. long. M. peroneus longus. M. peroneus brevis. M. extens. hallucis long. N. crural is. M. tensor fasciae latae (Nn. glut. sup.). M. quadriceps femoris (general centre). M. rectus femoris. M. cruralis. M. vastus externus. M. vastus internus. M. gastrocnem. extern. M. soleus. M. flexor hallucis long. M. abductor digiti. min. Mm. interossei dorsales. M. extens. digit, comm, brevis. Motor points of the peroneal and tibial nerves on the front of the leg ; the peroneal on the left, the tibial on the right (after Eichhorst). z n> ►1 < c CO o ►i c ~! Si w' J 2 n> •i < C CO If 5 *’ Si ST 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 contraciion, 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 [Ross, 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 /2d-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.). o iM. biceps, fem. (cap. brev.) U * (grt. sciat.). N. peroneus. M. gluteus maximus (great sciatic). N. ischiadicus. M. adduct, magnus (n. obt.). M. semitendinosus (grt. sciat.) M. semimembranosus (grt. sciat.). N. tibialis. M. gastrocnem. (cap. extr.). M. gastrocnem. (cap. int ). M. soleus. M. flex. dig. comm. long. M. flexor hallucis longus. N. tibialis. Motor points of the sciatic nerve and its branches ; the peroneal and tibial nerves. 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” (. Erl?), which is constantly present in progressive muscular atrophy ( Erb , Gunther). [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, (1) 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 atonic 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 [Ross) ; 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 ” [E. Remak , Kast , Erb ). II. In Various Forms of Spasm (spasms, contracture, muscular tremor) the constant current is most effective [Remak). By the action of anelectrotonus, 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 (§301). In cutaneous anaesthesia, the Faradic 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 constant current alone is applied to the central seat of the lesion, and care must be taken to what extent the occurrence of cathelectrotonus in the centre affects the occurrence of sensation. III. In Hyperaesthesia and Neuralgias, Faradic currents are applied with the object of over- stimulating the hypersensitive parts, and thus to benumb them. Besides these powerful currents, weak currents act reflexly and accelerate the blood stream, increase the heart’s action, and constrict the blood vessels, while strong currents cause the opposite effects [O. Naumann). Both may be useful. In employing the constant current in neuralgia [Remak), one 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 the 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 ancesthesia, 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 cavity 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 friction of the clothes upon the skin. Gardini, Hemmer, Ahrens (1817), 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, Volta) ; 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, or Gymnotus electricus , of the lagoons of the region 612 COMPARATIVE HISTORICAL. of the Orinoco in South America ; it may measure over 7 feet in length. The Torpedo marmorata and some allied species, 30 to 70 centimetres [1 to 2]/^ feet], in the Adriatic and Mediterranean, the Malapterurus electricus of the Nile, and the Marmyrus , also of the same river. By means of special electrical organs ( Redi , 1666), these animals can in part voluntarily (gymnotus and malap- terurus), and in part reflexly (torpedo) give a very powerful electrical shock. The electrical organ consists of “ compartments ” of various forms, 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. Schulze'). 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 {Faraday, Du Bois-Reymond). In Malapterurus the organ surrounds the body like a mantle, and receives only one nerve fibre (p. 521), whose axis cylinder arises near the medulla oblongata from one gigantic ganglionic cell {Billharz), and is composed of protoplasmic processes {Fritsch). The plates are also vertical, and receive their nerves from the posterior surface. The direction of the current is descending in the fish during the discharge {Du Bois-Reymond). 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 {Delle Chiaje , Babuchin), lie horizontally, while the nerve fibres enter them on their dorsal surfaces, the current in the fish being from the abdominal to the dorsal surface {Galvani). 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 having 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 myosin which coagulates after death ($295 — Weyl). 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 (Alarey). Mechanical, chemical, thermal and electrical stimuli cause a discharge; a single induction shock 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 {Steiner). 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, while heating it to 22 0 C. makes it more so. The organ becomes tetanic with strychnin {Becquerel), while curara paralyzes it {Sachs), btimulation of the electrical organ of the torpedo causes a discharge {Matteucci) ; 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 {Du Bois-Reymond). 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 organ weakens the current {Sachs, Du Bois-Reymond). 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 deflection 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 Galvani (1791), who observed that frogs’ legs connected with an electrical machine contracted, and also when they were touched with two different metals. He believed that nerves and muscles generated electricity. Alessandro Volta 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). Pfaff (1793) 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 frogs’ 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 1843 onwards. physiology the 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. Thus, 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. — fa) 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 ($ 1 7 1). The vasomotor nerves are specially treated of in \ 371. (b) 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 (§ 3°7) > 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 ( Nelaton , Obolensky ). 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 ( Legros , Schiff). Section of the cervical sympathetic nerve in young grozuing animals is followed by a more rapid growth of the ear upon that side ( Bidder , Stirling, Strieker), 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 ( Brown- Sequard). 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 . Barensprung, Leloir~). Sometimes there is a tendency to decubitus (| 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 g 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 true muscular elements, so that although the muscles increase in bulk their power is diminished.] [Cutaneous Trophic Affections. — Among 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, each 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 frequently follows the distribution of the intercostal and supraorbital nerves. Glossy skin ( Paget , Weir Mitchell') is a condition de- pending upon impaired 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 ($ 103, m )-l [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 patches 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 of 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 anaesthesia 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 {Charcot}. 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, decus.-ate in the cord (AW).] [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 arterioles (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 haematoma 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 effect of the splanchnic upon the intestinal movements ($ 161). The vaso-dilator 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 rhythm, 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-motor, i. e., vaso -constrictor, accelerators and augmentors of the heart. (b) Vaso-inhibitory, i. e., vaso-dilators and inhibitors of the heart. 2. Nerves of the visceral muscles. [a) Viscero motor. ( b ) Viscero ink ib itory . 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 anabolism, the latter katabolism. A 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 ( Gaskell ).] Sensory Nerves (sensory in end organs conduct sensory Fig. 380. II. Centripetal or Afferent Nerves. — (a) the narrower sense), which by means of special impulses to the central nervous system. (b) Nerves of Special Sense. (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 , /, 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. Scheme of a reflex motor act. S,skin; a, f. afferent nerve ; N, nerve cell; e,f, efferent fibre. 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. 385, I). The tractus swells out upon the cribriform plate of the ethmoid bone, and becomes the bulbus olfactorius, which'is the analogue of the special portion of the brain, existing in different mammals with a well-developed sense of smell [Grati olet). 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 matter 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 transverse section. [The centre for smell lies in the tip of the uncinate gyrus on the inner surface of the cerebral hemisphere [Perrier). 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- sphenoidal 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 optic 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 Smell , § 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 (i. e., 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, II) arises by a number of fibres from the inner gray substance of the thalamus opticus, and 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 crus 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. Abroad bundle of fibres passes from the origin of the optic tract to the cortical psycho-optic centre, at the apex of the occipital lobe ( Wernicke — $ 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 the 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 frontal region is brought about by “ Meynert’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 striae medullares ; the striae 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 ( а ) 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 ; ( b ) 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; ( d ) 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, (б) 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. f. Hamilton).\ HEMIOPIA AND HEMIANOPSIA 617 Chiasma. — The extent of the decussation c is subject to variations. As a rule, rather more than half of the fibres of one tract cross to the 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- opia.” In the dog and cat there is a semi-decussation; hence, in these animals extirpation of one eyeball causes atrophy and degeneration of half of the nerve fibres in both optic tracts ( Gtidden ). Baumgarten and Mohr have observed a similar result in man. A sagittal section of the chiasma in the cat pro- duces partial blindness of both eyes ( Nicati ). 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 laybr around the former. Other observers maintain that there is complete decussation of all the fibres in the chiasma. Hence, section of one optic nerve causes dilatation of the pupil and blindness on the same side, while section of one optic tract causes dilatation of the pupil and blindness of the opposite eye {Knoll, Brown- Sequard, Mandelstamm). In osseous fishes, both optic nerves are isolated and merely cross over each other, while in the cyclostomata they do not cross at all. [Total decussation 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 — Bechterew'). 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 , Caldani , 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 ( Gudden ) 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 {Gudden). It does not degenerate after enucleation of the eyeballs, so that it is regarded as an intercentral connection. After excision of an eye, there is central degeneration of the fibres of the optic nerve entering the eyeball {Gudden), 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 quadrigemina, corpora geniculata, and pulvinar, but not into the conducting paths leading to the cortical visual centre {v. Monakow) {\ 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 hemiopia 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. 382), then there is paralysis of the inner halves of both eyes, causing double tem- poral hemianopsia. When there are two lesions at N M, which is very rare, the outer halves of both retinae are paralyzed, so that there is double nasal hemianopsia. Tn 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 maculae luteae 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, i. e., between the eyeball and the chiasma, i. e., in the the optic fibres in the chiasma Fig. 381. Scheme of the semi-decussation of the optic nerves. L A ., deft eye; Ji. A., right eye. 618 NERVUS OCULOMOTORI US. orbit, optic foramen, or within the skull, affect 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 (Gowers).] 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). Fig. 382. 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 optic nerve causes a reflex 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 apparatus (hypercesthesia 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 (g 378, 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). Both conditions, however, may be the signs 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 alcohol, 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 bindness (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. Diagram of the decussation of the optic tracts. T, semi-decussation in the chiasma; TQ, decussa- tion of fibres behind the ext. geniculate bodies (CQ) ; a'b , fibres which do not decussate in the chiasma ; b' a', fibres proceeding from the right eye. and coming together in the left hemisphere (LOG) ; LOG, K, lesion of the left optic tract producing right lateral hemianopsia ; A, lesion in the left hemisphere producing crossed amblyopia (right eye) ; T, lesion producing temporal he- mianopsia ; NN, lesion producing nasal hemian- opsia. 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 lies under the aqueduct of Sylvius (Fig. 385). [The motor nucleus (Fig. 384) gives origin to three sets of fibres, for (1) the most of the muscles of the eyeballs, (2) the sphincter papillae, (3) ciliary muscle. The nucleus of the 3d and 4th nerves is also connected with that of the 6th under the iter, so that all 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. 385, III). 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 palpebrse superioris. The coordination of the movements of both eyeballs, however, is independent of the will. (2) The fibres for the sphincter pupillce , which are excited reflexly from the retina. (3) The voluntary fibres for the muscle of accommodation , the tensor choroideae 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 pupillae and the internal rectus muscle, lie directly in relation with each other, in the most posterior part of the floor of the third ventricle ( Hensen and Volckers'). 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 muscles to which it is distributed ( Valentin , Adamiik ), with the sympathetic through the carotid plexus, and (?) indirectly through the abducens, whereby it receives vasomotor fibres (?). Fig. 383. 6 © Internal External Superior Inferior Inferior Superior rectus. rectus. rectus. oblique. rectus. oblique. Varieties. — In some rare cases the papillary fibres for the sphincter run in the abducens (Adamiik), or even m the trigeminus ( Schiff \ v . Grafe). Atropin paral; z;s the intrabulbar fibres of the oculomotorius, while Calabar bean stimulates them (or paralyzes the sympathetic, or both — compare § 392). 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 anaemia (e. g., by ligature of the carotids, or beheading), sudden venous conges- tion, and at death. Pathological. — Complete paralysis of the oculomotorius is followed by — (1) 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 eyeball is more pronounced ; (5) moderate dilatation of the pupil (mydriasis paralytica) ; (6) the pupil does not contfact to light; (7) inability to ac- commodate for a near object. It is to be noted, however, that the paralysis may be confined to individual 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 images, 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 when 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 deviation of the healthy eye outward (Fig. 383, 1). 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. 383, 4).] The black cross represents the true image, the thin cross the false image. The left eye is affected in all cases ( Bristow ). Stimulation of the branch supplying the levator palpebrse 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— e. g., in teething, or in cases of diarrhoea Fig. 384. Medulla oblongata, with the corpora quadrigemina. The numbers IV. — XII. indicate the superficial origins of the cranial nerves, while those (3-12) indicate their deep origin, i. e. t the position of their central nuclei ; t, funiculus teres. 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 pupillse 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 e.g., the inferior oblique, some muscles of the right side act along with the left sterno-mastoid. 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. e., 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, i. 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. NERVUS TROCHLEARIS. — Anatomical. — It arises [from the valve of Vieus- sens, i. e., behind the fourth ventricle], but its fibres pass to the oculomotorius from the trochlearis nucleus (Fig. 384), 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 medullare superius, and after decussating with the root of the opposite side behind the iter, it pierces the crus at the supeaor and external border (Fig. 385, IV). Its fibres cross between its nucleus and its distribution, it has also an origin from the locus coeru- 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 lelt 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. 386, 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 of 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 nerve (//en/e, Foret). The large posterior sensory root receives fibres : (1) 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 cord 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. 3 86, d) receives sympathetic fibres ( vaso - jnotor nerves) from the plexus cavernosus ; it passes through the superior orbital fissure [sphenoidal] into the orbit. Its branches are : — 1. The 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. 386, a ) ; ( b ) true sensory fibres to the lachrymal gland (?). 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 ( Herzenstein and Wolferz , Denits chenko), 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 Fig, 385. Part of the base of the brain, with the origins of the cranial nerves ; the convolutions of the island of Reil on the right side, but removed on the left. I', olfactory tract cut short ; II, lelt optic nerve ; II', right optic tract ; T, h, cut surface of the left optic thalamus; C, central lobe, or island of Reil ; b>,y, fissure of Sylvius ; X, X, the locus perforatus anticus ; e , .the external, and i , .the internal, corpus geniculatum ; h, hypophysis cerebri ; t, c, tuber cinereum, with the infundibulum; a, points to one of the corpora albicantia; P, the cerebral pe- duncle ; the fillet; III, 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, a, facial ; VII, b, auditory ; VIII, vagus; VIII, a, glosso-pharyngeal ; VIII, b, spinal accessory; IX, hypoglossal ; fl, flocculus ; /, h, horizontal fissure of the cerebellum ( Ce) ; a, m, amygdala; p, a, anterior pyramid; o, olivary body; e, resti- form body; d, anterior median fissure; c, l, the lateral column of the spinal cord; C, I, the sub-occipital or first cervical nerve. fibres to the upper eyelids, brow, glabelli, and those which excite the secretion of tears reflexly ; and by its supraorbital branch (<£), analogous branches to the upper eyelid, skin of the forehead, and the adjoining skin over the temple as far as the vertex. 4. The nasociliary nerve (;z, c), by its infratrochlear branch supplies fibres, CILIARY NERVES. 623 similar to those of 3, to the conjunctiva, caruncula and saccus lacrymalis, the upper eyelid, brow and root of the nose. Its ethmoidal branch supplies the tip and alae of the nose, outside and inside, with sensory branches, as well as the upper part of the septum and the turbinated bones with sensory fibres, which can act as afferent nerves in the reflex secretion of tears ; while it is probable that vasomotor fibres are supplied to these parts through the same channel. (These fibres may be derived from the anastomosis with the sympathetic (?).) The naso- ciliary nerve gives off the long root (/) of the ciliary ganglion (c), and 1 to 3 long ciliary nerves. The ciliary ganglion (Fig. 386, ), and frontal (/) ; e, second or superior maxillary division of the trigeminus ; R, infraor- bital ; n, spheno-palatine (Meckel’s) ganglion with its roots ; j, from the facial, and v, from the sympathetic ; N, the nasal branches, and pp lf the palatine branches of the ganglion, g, third or inferior maxillary division of the tri- geminus ; k, lingual ; i i, chorda tympani ; m, otic ganglion, with the roots from the tympanic plexus, the carotid plexus, and from the 3d branch, and with its branches to the auriculo-temporal (A), and to the chorda (2 1 ) ; L, sub-maxillary ganglion with its roots from the tympanico-lingual, and the sympathetic plexus on the external maxillary artery (g). 7. Facial nerve— -j, its great superficial petrosal branch ; gang, geniculatum ; { 3 f branch to the tympanic plexus ; y ? branch to the stapedius ; d , anastomatic twig to the auricular branch of the vagus ; i i, chorda tympani; S, stylo-mastoid foramen. 9. Glossopharyngeal — its tympanic branch; tt and connections with the facial; U, terminations of the gustatory fibres of 9 in the circumvallate papillae; S,^, sym- pathetic with G g, s, the superior cervical ganglion ; /, 11 , III, IV, the four upper cervical nerves; P, parotid, M, sub-maxillary gland. 40 626 MECKEL S GANGLION AND ITS CONNECTIONS. stimulation of the Gasserian ganglion in animals. There are other affections of the eye depending upon disease of the vaso-motor nerves, which are quite different from the foregoing, as they never lead to degenerative changes. Such is ophthalmia intermittens (due to malaria), a unilateral, intermittent, excessive filling of the blood vessels of the eye, accompanied by the secretion of tears, photophobia, often accompanied by iritis and effusion of pus into the chambers of the eye. This condition was regarded as a vaso-neurotic affection of the ocular blood vessels by Eulenburg and Landois. Pathological observations, as well as experiments upon animals ( Mooren and Rumpf ), have shown that there is an intimate physiological connection between the vascular areas of both eyes, so that affections of the vascular area of one eye are apt to induce similar disturbances of the opposite eye. This serves to explain the fact that inflammatory processes in the interior of one eye- ball are apt to produce a similar condition in the other eye. This is the so-called “sympathetic ophthalmia.” Thus, stimulation of the ciliary nerves, or the fifth on one side, causes dilatation of the blood vessels not only on its own side, but also on the other side as well {Jesner and Griin- hagen). The pathological condition of glaucoma simplex, where the intraocular tension is greatly increased, is ascribed by Donders to irritation of the trigeminus. [Increased intraocular tension may be produced by irritation of the secretory fibres contained in the fifth nerve {Donders), by stimulating the nucleus of the trigeminus in the medulla oblongata ( Hippell and Griinhagen), and also reflexly by irritation of the peripheral branches of the fifth, as by nicotin placed in the eye. It is possible, however, that some forms of glaucoma are produced by diminished removal of the aqueous humor from the eye.] II. Superior Maxillary Division (E). — Ic gives off — 1. The delicate recurrent nerve, a sensory branch to the dura mater, which accompanies the vasomotor nerves, derived from the superior cervical ganglion of the sympathetic, and is distributed to the area of the middle meningeal artery. 2. The subcutaneous malar (o) (or orbital) supplies by its temporal and orbital branches sensibility to the lateral angle of the eye and the adjoining area of skin of the temple and the cheek. Certain fibres of the nerve are said to be the true secretory nerves for tears. Compare N. lacrymalis, p. 621 (Herzenstein and Wolferz). 3. The dental, anterior, posterior, and medius, and with them the anterior fibres from the infraorbital nerve, supply sensory fibres to the teeth in the upper jaw, the gum, periosteum, and the cavities of the jaw (p. 624). The vasomotor nerves of all these parts are supplied from the upper cervical ganglion of the sym- pathetic. 4. The infraorbital (R), after its exit from the infraorbital foramen, supplies sensory nerves to the lower eyelid, the bridge and sides of the nose, and the upper lip as far as the angle of the mouth. The accompanying artery receives its vasomotor fibres from the superior cervical ganglion of the sympathetic. With regard to the fibres for the secretion of sweat which occur in it (pig), see § 288. The spheno-palatine ganglion (Meckel’s — h) forms connections with the II division. To it pass two short sensory root fibres from the II division itself, which are called spheno-palatine. Motor fibres enter the ganglion from behind, through the large superficial petrosal branch of the facial (j — Bidder, Nuhri) \ and, lastly, gray vasomotor fibres (v) from the sympathetic plexus on the carotid (the deep, large petrosal nerve). The motor and vasomotor fibres from the Vidian nerve, which reaches the ganglion through the canal of the same name. Branches of the Ganglion. — The branches proceeding from the ganglion are : (1) The sensory fibres (N) which supply the roof, lateral walls, and septum of the nose (posterior and superior nasal) ; the terminal fibres of the naso-pala- tine pass through the canalis incisivus to the hard palate, behind the incisor teeth. The sensory inferior and posterior nasals for the lower and middle turbinated bones, and both lower nasal ducts, are derived from the anterior palatine branch of the ganglion, which descends in the palato-maxillary canal. Lastly, the sensory branches for the hard (p) and soft palate (p x ) and the tonsils arise from th e pos- terior palatine nerve. All the sensory fibres of the nose (see also the Ethmoidal nerve), when stimulated, cause the reflex act of sneezing (§ 120). Preparatory INFERIOR MAXILLARY DIVISION. 627 to the act of sneezing there is always a peculiar feeling of tickling in the nose, which is perhaps due to dilatation of the nasal blood vessels. This dilatation is rapidly caused by cold, more especially when it- is applied directly to the skin. The dilatation of the vessels is followed by an increased secretion of watery fluid from the nasal mucous membrane. Stimulation of the nasal nerves also causes a reflex secretion of tears, and it may also cause stand-still of the respiratory move- ments in the expiratory phase ( Hering and Kratschmer ) — (compare Respiratory centre , § 368). (2) The motor branches descend in the posterior palatine nerve through the small palatine canal, and give off (K) motor branches to the elevator of the soft palate and azygos uvulae ( Nuhn , Fruhwald'). The sensory fibres for these muscles are supplied by the trigeminus. According to Politzer, spasmodic contraction of these muscles occasionally causes crackling noises in the ears. (3) The vasomotor nerves of this entire area arise from the sympathetic root, i. e., from the upper cervical ganglion. (4) The root of the trigeminus supplies the secretory nerves of the mucous glands of the nasal mucous membrane. Stimu- lation excites secretion, while section of the trigeminus diminishes it with simul- taneous atrophic degeneration of the mucous membrane. Thus trophic functions for the mucosa have been ascribed to the trigeminus ( Aschenbrandt ). Stimulation of the Ganglion. — Feeble electrical stimulation of the exposed ganglion causes a copious secretion of mucus and an increase of the temperature in the nose ( Prevost ), with dilation of the vessels ( Aschenbrandt ). [Meckel’s ganglion has been excised in certain cases of neuralgia ( Walshani).} III. Inferior Maxillary (G). — It contains all the motor fibres of the fifth, along with a number of sensory fibres ; it gives off — 1. The recurrent, which springs by itself from the sensory root, enters the skull through the foramen spinosum, and, along with the nerve of the same name from the II division, it supplies sensory fibres to the dura mater. Fibres proceed from it through the petroso-squamosal fissure to the mucous membrane of the cells of the mastoid process. 2. Motor fibres for the muscles of mastication, viz., the masseteric, the two deep temporal nerves, and the internal and external pterygoid nerves. The sen- sory fibres for the muscles are supplied by the sensory fibres. 3. The buccinator is a sensory nerve for the mucous membrane of the cheek, and the angle of the mouth as far as the lips. According to Jolyet and Laffont, it contains, in addition, vasomotor fibres for the mucous mem- brane of the cheek, lower lip, and their mucous glands; but these fibres are probably derived from the sympathetic. Trophic Fibres. — As this region of the mucous membrane of the mouth ulcerates after section of the trigeminus, some have supposed that the buccinator nerve contains trophic fibres. But, as Rollett pointed out, section of the inferior maxillary nerve paralyzes the muscles of mastication on the same side, and hence the teeth do not act vertically upon each other, but press against the cheek. Owing to the loss of the sensibility of the mouth, food passes between the gum and the cheek, where it may remain attached, undergo decomposition, and perhaps chemically irritate the mucous membrane. At a later stage, owing to the wearing away of the teeth in an oblique manner, ulcers begin to form on the sound side. Hence, there is no necessity for assuming the existence of trophic fibres in this nerve. After section of the trigeminus, the nasal mucous membrane on the same side becomes red and congested. This is due to the fact that dust or mucus, not being removed from the nose by the usual reflex acts, remains there, irritates, and ultimately causes inflammation. 4. The lingual ( k ) receives at an acute angle the chorda tympani (/ 1), a branch of the facial coming from the tympanic cavity. The lingual does not contain any motor fibres ; it is the sensory and tactile nerve of the anterior two-thirds of the tongue, of the anterior palatine arch, the tonsil, and the floor of the mouth. These, as well as all the other sensory fibres of the mouth, when stimulated, cause a reflex secretion of saliva (compare § 145). The lingual is accompanied by the nerve of taste (chorda) for the tip and margins of the tongue (i. 8 .) 2. Motor fibres for Muller’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 {Cl. Ber- nard ), tympanum ( Prussak ), conjunctiva, iris, choroid, retina ( only in part — see Ciliary ganglion, §347, I), for the vessels of the oesophagus, larynx, thyroid gland — fibres for the vessels of the brain and its membranes {Bonders and Callenfels ) ; 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. According 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 1st thoracic ganglion (Cl. Bernard , v. Bezold , Cyon, 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 (Bernstein). 3. The cervical sympathetic contains afferent fibres which, when stimulated, excite the vasomotor centre in the medulla oblongata (Aubert). 4. The functions of the splanchnic are referred to in §§164, 175, 276 and 37 1 - 5. The functions of the cceliac and mesenteric plexuses are referred to in §§ 183 and 192. After extirpation of the coeliac 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- ulae seminales. Stimulation of ail 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 offers an extensive area for pathological changes. It is to be observed that all affec- tions involving the vasomotor system are referred to in $ 371. The cervical sympathetic is most frequently paralyzed or stimulated Iby traumatic conditions, wounds by bullets or knives, tumors, enlarged lymph glands, aneurisms, inflammation of the apices of the lungs and the adjacent pleurae, while exostoses of the vertebrae 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 (g 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 ($ 289, 2, and \ 288) ; disturbance of vision for near objects, as the pupil cannot be contracted (see Accommodation), and hence the spherical aberration of the lens ($ 391) 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 secretion of saliva ( $ 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 (1) 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 0 to 6° C. (Cl. 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 growing animals results in hypertrophy of the ear, and increased growth of the hair on that side ( Bidder , W. Stirling ).] [The vago sympathetic nerve (dog) in the neck contains vaso-dilator fibres (really in the sympathetic) for the skin and mucous membranes of that side of the head. Weak stimulation of the central end of the sympathetic causes dilatation of the blood vessels of these parts. The vaso- dilator fibres of the superior maxillary nerve probably come from the same source. The centre for these nerves is in the dorsal region of the cord between the 1st and 5th dorsal vertebrae, when the fibres pass out with the rami communicantes to enter the cervical sympathetic ( Dastre and Morat ). The vaso-dilator fibres occur in the posterior segment of the ring of Vieussens, and when they are stimulated after section of the 7th cranial nerve, there is a “ pseudomotor ” effect on the muscles of the cheek and lip (§ 349).] 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 sympathetic 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 absent, 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 , pari passu, 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 called ramus opercularis trigemini) is the chief motor nerve of the muscles of the gill cover, and is, therefore, the respiratory rierve. 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 in the tadpole. Its rudimentary representative in man is the auricular branch. Tn the frog the 9th, 10th, and nth arise together from one trunk, and the 7th and 8th from another. In fishes and amphibia the hypoglossal is the first cervical nerve. In amphioxus the cere- bral and spinal nerves are not distinct 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 with the 5th and 10th nerves are specially 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 (80 a.d.) recognized seven pairs of cranial nerves. Galen was in possession of 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 ; Coiter (1573) prescribed exactly the anterior and posterior spinal nerve roots. Van Helmont (f 1644) states 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, 10th, 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, i. 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 intennittent , 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 ( Birke ). [The term “ centre ” is merely applied to an aggregation of nerve 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.] 653 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 the 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 {Hill').~\ Structure. — The spinal cord consists of white matter externally and gray matter internally. [It is invested by membranes, the pia mater , composed of two layers and consisting of connective tissue with blood vessels, being firmly adherent to the white matter and sending septa into the Fig. 394. Transverse section of the spinal cord; in the centre is the bntterfly form of the gray matter surrounded by white matter. />, posterior, and a, anterior, horns of the gray matter ; P R, posterior roots ; A R, anterior roots of a spinal nerve ; A, A, the white anterior ; L, L, the lateral ; P, P, the posterior columns. substance of the cord. Both layers dip into the anterior median fissure, and only the inner one into the posterior median groove. The arachnoid is a more delicate membrane and non-vascular, while the dura mater is a tough membrane lining the vertebral canal, and forming a theca or protective coat for the cord (g 381).] The gray matter has the form of two crescents )-( placed back to back [or a capital HJ, in 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 foetus, 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 gray 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, lateral, and 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. Fig. 395. — Transverse section of the white matter ot the spinal cord with connective-tissue septa between the fibres. Fig. 396. — Multipolar nerve cells from the gray matter of the anterior horn of the spinal cord (ox), a, nerve cell; b t axis cylinder; c, gray matter; d, white matter of column ; e, e, branches of cells. but is filled up with the inner layer of the pia mater, which dips down from the under surface of this membrane quite to the gray matter of the posterior commissure.] Each posterior column, in certain regions of the cord, may be subdivided into an inner part lying next the fissure, the postero- median or Goll's column , or the inner root zone ( Charcot , Fig. 403, c) ; and an outer larger part next the posterior root, known as the postero-external or Burdach's column , or the outer root zone ( 1 Charcot , Fig. 403, d). The white matter consists chiefly of medullated fibres without the sheath of Schwann and Ran- Fic. 397- Diagram of the absolute and relative extent of the gray matter, and of the white columns in successive sectional areas of the spinal cord, as well as the sectional areas of the several entering nerve roots. N R, nerve roots ; AC, LC, P C, anterior, lateral and posterior columns; Gr, gray matter. vier’s nodes, but provided with the neuro-keratin sheaths of Ktthne and Ewald (g 321), the fibres themselves being chiefly arranged longitudinally. 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 different 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 differs in shape in the different regions of the cord, and so does the gray commissure (Fig. 398). The latter is thicker and shorter in the cervical than in the dorsal region, while it is very narrow in the lumbar region. The 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 Woroschiloff 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 between 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 the commissure being nearly in the middle of the cord. In the conus medullaris the gray matter makes up the great mass of it, with a few white fibres externally (big. 398 ).] Ihe 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 the processus reticularis (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 horns, those of the lateral column (intermedio-lateral), and the posterior 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 / 1 ), while the fusiform cells of the posterior horn are 18 /-t in diameter. Those of the lateral column are distinct, except in the lumbar and cervical enlarge- ments, where they blend with the anterior horn. The column of Clarke (cells 40 to 90 fJ.) is dis- continued, and is limited to (1) the thoracic region, (2) cervico-cranial region, (3) sacral region, being most conspicuous in (1) ( 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 medullated 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 in the gray matter of the posterior horn. Transverse sections of the spinal cord in dif- ferent regions A, through the middle of the cervical; B, the dorsal ; C, the lumbar enlargement; D, upper part of the conus medullaris ; E, at the 5th sacral vertebra ; F, at coccyx ; A, B, (J, enlarged twice ; D, E, F, thrice ; a, anterior, /, posterior root. 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 (m ) ; at the same time the longitudinal direction of the nerve fibres in the anterior (a) and posterior white columns ( c ), the horizontal direction of the fibres of the anterior and posterior nerve roots ( b and f).~) 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. Medullated 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, z). The gray network of protoplasmic processes, produced by the repeated branchings of the fibres of these cells, gives origin to broad fibres. A part of the latter (the median bundle) passes Fig. 399. Transverse section of the spinal cord (lower dorsal). A, L, P, anterior, lateral, and posterior columns ; A. M. F., P. M. F., anterior and posterior median fissures ; a, b, c, cells of the anterior horn ; d, posterior cornu and sub- stantia gelatinosa ; e, central canal ; f, veins ; g, anterior root bundles ; h, posterior root bundles ; i, white com- missure ; j, gray commissure ; l, reticular formation. through the anterior white commissure to the other side, and then ascends in the anterior column of the opposite side. Other fibres (the lateral bundle) 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 the posterior 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 CORD. 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- Fig. 400. Fig. 401. b Fig. 400. — Longitudinal section of the human spinal cord, a, anterior, c, posterior, d, lateral white columns ; b, anterior, c, posterior nerve roots \f, horizontal (pyramidal) fibres passing to m, cells of anterior cornu ; n, oblique fibres of posterior root Fig. 401. — Multipolar nerve cell, from the anterior horn of the spinal cord, z, 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 gelatinous 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 tw r o branches, one for each mass of gray matter, and each branch in turn splits into three, which supply Fig. 402. F ig. 402. — Injected blood vessels of the spinal cord. Fig. 403. — Scheme of the conducting paths in the spinal cord at the 3d dorsal nerve. The black part is the gray matter, v, anterior, h, w, posterior, root: a, direct, and^-, crossed, pyramidal tracts : b, anterior column ground bundle; c, Goll’s column; d, postero-external column ; e and /, mixed lateral paths ; h, direct cerebellar tracts. part of the interior, median, and posterior gray matter. The posterior root artery enters the gray matter 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 Goll’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 ( His).~\ [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 affected by various pathological conditions.] [Functions of the Spinal Cord. — (1) 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. Apart from experimental methods, such as dividing one column of the cord and observing the results, we have the following methods of investigation : (1) 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 nerve fibres connected with the seat of injury, i. e., they 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 the 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 covered 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. — 1. 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 ( c ) 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 paths, (g) the lateral or crossed pyramidal tract, and {h ) the direct cerebellar tract. 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 g (§ 365). The fibres in these tracts descend from the cen- tral convolutions [i. e., 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 column 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 ; b , e, f (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. AR Transverse section of the spinal cord, showing the secondary degeneration tracts. AR, anterior, TR, posterior root; 1, i' (CPT), region of the crossed pyramidal tract; 2, 2' (DPT), direct pyramidal tract; PEC, postero-external column ; LC, lateral column ( B . Bramwell). 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^), the lateral cerebellar tract (h), and Goll’s column (c) 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 ( 6 ), the funiculus cuneatus ( Interscapular. 5 I 6 [ Epigastric. 7 J 8] I umbar Sacral 9 I 10 [ Abdominal. 11 I 12 J 2 I Cremasteric. 3 J | Knee Reflex. ^ | Gluteal. 2 1 *8 | 1 Plantar. 3 J ^ £3 [ Vesical. 4 j Rectal. 5 -1 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), Eulenberg 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 patellae, and is due to a single 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 (Schultz), and so does section of the cord opposite the 5th and 6th lumbar vertebrae {Tschirjew, Senator). Landois finds that in his own person the contraction occurs 0.048 second after the blow upon the ligamentum patellae. According 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 posterior column of the spinal cord remain intact ( Westphal). [A “jaw jerk ” is obtained by suddenly depressing the lower jaw ( Gowers , Beevor and De Watteville), and 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.] Another important diagnostic reflex is the “ abdominal reflex ” (O. Rosen- bach), which consists in this, that when the skin of the abdomen is stroked, e. g., with the handle of a percussion hammer, the abdominal muscles contract. When this reflex is absent on both sides in a cerebral affection, it indicates a diffuse disease of the brain ; its absence on one side indicates a local affection of the op- posite 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 affections accompanied by coma the reflexes are absent on both sides, including, of course, those of the anus and bladder ( O . Rosenbach). [Horsley finds that in the deepest narcosis produced by nitrous oxide gas the superficial reflexes (e. g., plantar, conjunctival) are abolished, when the deep (knee jerk) remain. Anremia of the 668 CENTRES IN THE SPINAL CORD. lumbar enlargement (compression of the abdominal aorta) causes disappearances of both reflexes (Prevost). 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 crossed 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, defaecation, and those connected with the motor and secretory digestive processes, respiration, and circulation.] [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 . Rosenbach). 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 affections 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 suffering from ataxic tabes dorsalis [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 cerebrum , 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.] 1. 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 dyspnoeic blood, and also reflexly by the stimulation of sensory nerves, e.g ., the MUSCLE TONUS. 669 median, especially when the reflex' excitability of the cord is increased by the action of strychnin or atropin ( Luchsinger ). For the dilator centre in the medulla oblongata see \ 367, 8. 2. The ano-spinal centre (Budge) or centre controlling the act of defaeca- tion. The afferent nerves lie in the hemorrhoidal and inferior mesenteric plexuses, the centre at the 5th (dog) or 6th to 7fh (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 codrdinated 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 coordinated 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 1st 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 1st 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 discharged from these centres are orderly coordinated reflexes, and may thus be compared to the orderly reflexes of the trunk and extremities. Muscle Tonus. — Formerly 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 following 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 nerves of the leg are divided. If we choose to call this slight retraction tonus, then it is a reflex tonus ( Brondgeest ). (See the experiments of Harless, C. Ludwig, and Cyon — \ 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 ?nechanical stimuli. If stimuli be cautiously applied either to the white or gray matter there is neither movement nor sensation ( Van Deen ( 1841 ), Brown- Sequard, 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. As 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, Schiff 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 anaesthesia 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 white 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. Ludwig and Thiry). In the same way, the fibres which ascend in the cord, and increase the action of the vasomotor centre — pressor fibres , are also excitable ( C. Ludwig and Dittmar — § 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 the 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, dyspnoea be produced, or its blood overheated , then spasms, 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 produced if the spinal cord has been previously rendered very sensitive by strychnin or overheated blood (P. v. Rokitansky , v. Schroff — $ 36 8). Hyperaesthesia. — After unilateral section of the cord, or even only of the posterior or lateral columns, there is hypercesthesia on the same side below the point of section ( Fodera ( 1823 ), 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 analogous 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 impressions 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 the legs runs in Goll’s column, while those for the arms run in the ground bundle (Fig. 403) ( Flechsig ). In rabbits the path of localized tactile impressions lies in the lower dorsal region in the lateral columns ( Ludwig and 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 anesthesia. 2. Localized voluntary movements in man are conducted on the same 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 (Gaule and Birge). Section of one lateral column abolishes voluntary 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, Woroschiloff ) [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. 65,9). 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 peculiar motor disturbance. The voluntary movements can be executed with full and normal vigor, but 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 which 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 Pierret). But even the posterior roots themselves may undergo degeneration, and this may also give rise to disturbances of sensation (p. 648). The sensory disturbances usually 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 feeling 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 [Schiff). 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, tactde 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 powerful 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 SPINAL 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 uraemic poisoning, and tetanus (g 360, II). The anaemic and dyspnoeic 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 introduces 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 nerves 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 medulla oblongata, 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 (2 " 31 - 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 hyperaesthetic 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. Fig. 408. [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 anaesthesia 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 anaesthesia 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 hyperaes- 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 hyperaesthesia (to touch, tickling, pain, heat and cold) on the parts below the lesion on the same side, but 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 paralysis of voluntary motion and retention of sensibility with vasomotor paralysis of the same side, and retention of voluntary motion with anes- thesia and analgesia on the opposite side. The existence of hyperaesthesia 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 separable from the motor innervation of muscle ( Ferrier ). The power of emptying the bladder and rectum was not affected.] the left half of the spinal cord in the dorsal region. (a) oblique lines, motor and vasomotor pa- ralysis ; ( b , d) com- plete anaesthesia ; i a , r) hyperaesthesia of the skin (Er6). THE BRAIN 365. GENERAL SCHEMA OF THE BRAIN. — In an organ so complicated in its struc- ture as the brain, it is necessarv 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 study of brain function [A special layer of gray matter of the cerebrum 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 semi-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 Fig. 409. Dissection of the brain from above, showing the lateral, 3d, and 4th ventricles, with the basal ganglia and surround- ing parts, a, knee of the corpus callosum ; b, anterior part of the right corpus striatum ; b' , gray matter dissected off to show white fibres ; c, points to taenia semicircularis ; d, optic thalamus; e, anterior pillars of fornix, with 5th ventricle in front of them, between the two laminae of the septum lucidum ; /, middle or soft commissure; g, 3d ventricle; h, i, corpora quadrigemina ; k, superior cerebellar peduncle ; /.hippocampus major; nt, posterior cornu of lateral ventricle ; n, eminentia collaterals ; o, 4th ventricle ; p> medulla oblongata ; s, cerebellum, with r, arbor vitae. • 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, b) ; the optic thalamus, which lies behind the former and bounds the 3d ventricle (Fig. 409, d ) ; the corpora quadrigemina, lying on the upper surface of the crura cerebri (Fig. 409, h , 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 consider cerebro- spinal and cerebello-spinal connections.] Meynert’s Projection Systems. — The cortex of the cerebrum consists of convolutions and Fig. 410. I, Scheme of the brain C, C, cortex cerebri; G, s, corpus striatum; N, /, nucleus lenticularis ; T, o, optic thal- amus; v, corpora quadrigemina ; P, pedunculus cerebri ; H, tegmentum ; and/, crusta; 1, 1, 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 ; m, further course of these fibres ; 8, 8, fibres from the corpus striatum and lenticular nucleus to the crusta of the pedunculus cerebri ; M, further course of these; S, S, course of the sensory fibres ; R, transverse section of the spinal cord ; v, W, anterior, and h, W, posterior roots ; «, a, association system of fibres ; c, c, commissural fibres. II, Transverse section through the posterior pair of the corpora quadrigemina and the pedunculi cerebri of man, — p, crusta of the peduncle; s, substantia nigra r v, corpora quadrigemina, with a section ot the aqueduct. Ill, The same of the dog ; IV, of an ape ; V, of the guinea pig. [See p. 675.] sulci, the “peripheral gray matter” (Fig. 410, C), which is recognized as a nervous structure from the presence of numerous ganglionic cells in it ($358,1). From it proceed all the motor fibres which are excited by the will, and to it proceed all the fibres coming 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 cord, as is represented in Fig. 412. Some 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 ( N , , /), optic thalamus ( T, 0) 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 fibres , such as the corpus callosum and the anterior commissure (c, c), 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. 41 1. Floor of the fourth ventricle and the connections of the cerebellum. On the left side the three cerebellar peduncles are cut short ; on the right the connections of the superior and inferior peduncles have been preserved, while the middle one has been cut short. 1, median groove of the fourth ventricle with the fasciculi teretes ; 2, the striae of the auditory nerve on each side emerging from it; 3, inferior peduncle ; 4, posterior pyramid and clava, with the calamus scriptorius above it ; 5, superior peduncle ; 6, fillet to the side of the crura cerebri ; 8, corpora quad- rigemina. 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 ( Hill).~\ 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 superior peduncles 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 ( Gowers). 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 middle peduncle is formed by the transverse fibres of the pons (Fig. 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 white internal, and on section the foliated branched ap- pearance of the cerebellum constitutes the arbor vitce . Within each lateral lobe is a folded mass of gray 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 shown in Fig. 41 1, the white fibres of the superior peduncle pass to the gray matter on the inferior surface of the cerebellum, while 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 \ 380.] 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 (A), 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 (e.g., 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 multipolar 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 pyramidal 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 ( Flechsig ). 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 voluntary movements takes place on the same side as the lesion of the cerebrum ( Morgagni , Pier ret). This is direct paralysis. [Usually about 90 per cent, of the fibres decussate.] 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, i. 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, i. e., to the “motor” regions, for he holds “ that disease 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, S). If it be divided, there is hemianaesthesia 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. 412;, unilateral section of the spinal cord in man (and monkey— Ferrier) abolishes sensibility on the opposite side below the lesion. There is hyperaesthesia of the parts below the seat of the section on the side of the injury (§ 363)- From experiments on mammals, Brown-Sequard 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 spinal 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 unfrequently the motor paralysis and anaesthesia occur on the same side of the head, in which case the lesion (due to pressure or inflammation] involves the cranial nerves lying at the base of the brain. 680 CONDUCTING PATHS IN THE SPINAL CORD, The positions of decussation are (i) in the spinal cord, (2) in the medulla oblongata, and, iastly (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 ; 1, 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 after entering the cord ; S 3 , S 3 , sensitive areas, and 4', 4, tracts from the right side of the body. The arrows indicate the direction of the impulses (. Bramwell )). [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 “ alternate hemiplegia ” is given. [When hemorrhage takes place into the loruer 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 same side as the body, \ 379.] The olfactory nerve is said not to decussate (?) while the optic nerve undergoes a partial decus- sation at the chiasma (g 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 Fig. 413. Section of the decussation of the pyramids, fla, anterior median fissure, displaced laterally by the fibres decussating . at d; V, anterior column; La, anterior cornu, with its nerve cells, a, b cc, central canal; S, lateral column; fr, formatio reticularis ; ce, neck, and g, head ot the posterior cornu; rpCI, posterior root of the 1 st cervical nerve ; nc, first indication of the nucleus of the funiculus cuneatus ; ng, nucleus (clava) of the funiculus gracilis ; /A, funiculus gracilis: H* , funiculus cuneatus; sip, posterior median fissure; x, groups of ganglionic cells in the base of the posterior cornu. X 6. 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 bundles 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 fasciculus or fillet.] [Thus only a part of the anterior column of the cord — direct pyramidal tract — is continued into the anterior pyramid, where it lies external to the fibres which pass to the lateral column of the opposite side. The remainder of the anterior column — the antero-external 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 restiform body. The crossed 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, / j). 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 floor of the medulla oblongata and are called fasciculus teres , which goes to the cere- brum. As they pass 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 cord. 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 coming 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 corresponding 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 6th 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 ( Go 7 vers).] [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 differently. 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 matter, and thus cut off the tip of the anterior cornu, which is also pushed backward by the olivary body, and exists as a distinct mass, the nucleus lateralis (Fig. 414, nl). Part of the anterior gray matter also appears in the floor of the 4th ventricle as the eminence of the fasciculus teres, and from part of it springs the hypoglossal nerve (Pig. 415, XII). The neck joining the modified anterior and posterior cornua is much broken up by the passage of longitudinal and transverse fibres through it, so that it forms a formatio reticularis (Fig. 414 ,fr), separating the two cornua. The caput cornu posterioris comes to be covered higher up by the ascending root of the 5th nerve (Fig. 414, a 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] (Pig. 413, ng) 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 nerves.] [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 (F'ig. 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) y 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, nX) t 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, X), so that this column of cells forms the vago-accessorius nucleus. External to and in front of this is the nucleus for the glosso-pharyngeal nerve. Further up in the medulla, on a level with the auditory striae 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, 8 ' 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. 415. Fig. 414. — Section of the medulla oblongata at the so-called upper decussation of the pyramids, fla, anterior sip, and posterior median fissure ; nXI, nucleus of the accessorius vagi ; nXIl , nucleus of the hypoglossal ; da, the so-called superior or anterior decussation of the pyramids ; py, anterior pyramid ; n, Ar, nucleus arciformis ; O 1 , median parolivary body ; O, beginning of the nucleus of the olivary body ; nl, nucleus of the lateral column ; Fr, formatio reticularis ; g, substantia gelatinosa, with iaV) the ascending root of the trigeminus; nc, nucleus of the funiculus cuneatus ; nc 1 , external nucleus of the funiculus cuneatus ; ng , , nucleus of the funiculus gracilis (or clava) ; H 1 , funiculus gracilis; H*, funiculus cuneatus; cc, central canal \ fa, fa 1 , fa" 1 , external arciform fibres X 4- Fig. 415. — Section of the medulla oblongata through the olivary body. nXIl, nucleus of the hypo- glossal; nX, nX 1 , more or less cellular parts of the nucleus of the vagus ; XII, hypoglossal nerve ; X, vagu-, ; n, am, nucleus ambiguus ; nl, nucleus lateralis; o, olivary nucleus; oal, external, and oam, internal parolivary body ; fs, the round bundle, or funiculus solitarius ; Cr, restiform body; p, anterior pyramid, surrounded by arciform fibres ; fae, pol, fibres proceeding from the olive to the raphe (pedunculus olivae) : r, raphe. X 4- (hilum) and into it run white fibres forming its peduncle (Fig. 415,/, o, /). 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 being separated fiom the dentate body 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 longitudinally and more or less transversely in the medulla (Fig. 414 ,f,r). In the more lateral portions are large multipolar nerve cells, perhaps continued upward from part of the anterior cornu, while the part 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 antero-lateral 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 superficial 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, form 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 deep arcuate 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 transversely, others longitudinally, and others from before backward.] [Other Nerve Nuclei — Sixth Nerve. — Under the elevation called eminentia teres (Fig. 384) in front of the auditory 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 Gowers has shown that “the facial ascends to this nucleus, forms a loop round it (some fibres, indeed, 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 the nucleus of the 6th (Fig. 384, 7). It extends down- ward about as far as the auditory striae or a little lower. The fifth nerve arises from its motor nucleus (with large multipolar cells), which lies more superficially above and external to the 6th (Fig. 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 (5V). 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. 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 beats much more rapidly, whereby the circulation is accelerated, hence probably why sipping an alcoholic drink intoxicates more rapidly than when it is quickly swallowed.] 7. Vomiting Centre (§ 158). — The relation of certain branches of the vagus to this act are given at § 352, 2, and 12, d. 8. The upper centre for the dilator pupillse muscle, the smooth muscles of the orbit, and the eyelids lies in the medulla oblongata. The fibres pass out partly in the trigeminus (§ 347, I, 3), partly in the lateral columns of the spinal cord as far 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, 1). The centre is normally excited reflexly by shading the retina, i. e., by diminishing the amount of light admitted into the eye. It is directly excited by the circula- tion of dyspnoeic 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 general reflex movements of the body still occurred, and the anterior and posterior extremities participated in such general movements. If, however, the section was made 1 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 ( Duchenne , i860), in which there is a pro- gressive invasion of the different nerve 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 facial saliva ($ 145, A), owing to paralysis of this nerve nucleus. Swallowing may be impossible, owing to paralysis of the pharynx and palate. This interferes with the formation of consonants [especially the linguals, l, t, s, r, 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 muscles are paralyzed, leading to the loss of voice and the entrance of food, into the windpipe. The heart beats are often slowed, pointing to stimulation of the cardio-inhibitory fibres (arising from the acces- sorius). Attacks of dyspnoea, like those following paralysis of the recurrent nerves {§ 313, II. 1, and $ 352, 5, b), and death may occur. Paralysis of the muscles of mastication, contraction of the pupil, and paralysis 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 ( Legallois '), behind the point of origin of the vagi, on both sides of the posterior aspect 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 nceud vital. The centre is double, one for each side, and it may be separated by means of a longitudinal incision ( Longet ), whereby the respiratory movements continue symmetrically on both sides. Section of Vagi. — If one vagus be divided, respiration on that side is slowed. If both vagi be divided, the respirations become much slower and deeper , but the respiratory movements are symmetrical on both sides. Stimulation of the central 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 trigeminus 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 Lauten- 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 Langendorff assumes the existence of a spinal respiratory centre, which he finds is also in- fluenced by reflex stimulation of sensory nerves.] CEREBRAL INSPIRATORY CENTRE. (387 Anatomical. — According to Giercke, Heidenhain, and Langendorff, those parts of the medulla oblongata whose destruction causes cessation of the respiratory movements are not gray cellular substance, but only single or double strands of nervous matter running downward in the substance of the medulla oblongata. These strands are said to arise partly from the roots of the vagus, trigeminus, spinal accessory, and glosso-pharyngeal ( Meynert ), forming connections by means of fibres with the other side, and descending as far downward as the cervical enlargement of the spinal cord (Go//). According to this view, this strand represents an inter- centra/ band connecting the spinal cord (the place of origin of the motor respiratory nerves) with the nuclei of the above-named cranial nerves. Fig. 416. Cerebral Inspiratory Centre. — According to Christiani, there is a cerebral inspiratory centre in the optic thalamus in the floor of the 3d ventricle, which is stimulated through the optic and auditory nerves, even after extirpation of the cerebrum and corpora striata ; when it is stimulated directly, it deepens and accelerates the inspiratory move- ments, and may even cause a stand-still of the respiration in the inspiratory phase. This inspiratory centre may be extirpated. After this operation, an expiratory centre is active in the substance of the anterior pair of the corpora quadrigemina, not far from the aque- duct of Sylvius. Lastly, Martin and Booker describe a second cerebral inspiratory centre in the posterior pair of the corpora quadri- gemina. These three centres are connected with the centres in the medulla oblongata. Inspiratory and Expiratory Centres. — The respiratory centre consists of two cen- tres, which are in a state of activity alternately — an inspiratory and an expiratory centre (Fig. 416), each one forming the motor cen- tral point for the acts of inspiration and ex- piration (§ 1 1 2). The centre is automatic, for, after section of all the sensory nerves which can act reflexly upon the centre, it still retains its activity. The degree of excita- bility and the stimulation of the centre depend upon the state of the blood, and chiefly upon the amount of the blood gases, the O and C 0 2 (J. Rosenthal ). According to the condition of the centre, there are several well-recognized respiratory conditions: — 1. Apnoea. — Complete cessation of the respiration constituting apncea, i.e., cessation of the respiratory movements, owing to the absence of the proper stimu- lus, due to the blood being saturated with O and poor in C 0 2 . Such blood satu- rated with O fails to stimulate the centre, and hence the respiratory muscles are quiescent. This seems to be the condition in the foetus during intra-uterine life. If air be vigorously and rapidly forced into the lungs of an animal by artificial respiration, the animal will cease to breathe for a time after cessation of the arti- ficial respiration (. Hook , 1667 ), the blood being so arterialized that it no longer stimulates the respiratory centre. If a person takes a series of rapid, deep respi- rations, his blood becomes surcharged with oxygen, and long “ apnceic pauses ” occur. Scheme of the chief respiratory nerves ( Ruther- ford ). ins, inspiratory, and exp, expiratory centre — motor nerves are in smooth lines. Expiratory motor nerves to abdominal mus- cles, ab ; to muscles of back, do. Inspiratory motor nerves, ph, phrenic to diaphragm, d; int, intercostal nerves ; rl, recurrent laryn- geal ; ex, pulmonary fibres of vagus that ex- cite inspiratory centre : ex' , pulmonary fibres that excite expiratory centre ; ex", fibres of sup. laryngeal that excite expiratory centre ; ink, fibres of sup. laryngeal that inhibit the inspiratory centre. Apnceic Blood. — A. Ewald found that the arterial blood of apnoeic animals was completely saturated with O, while the C0 2 was diminished; the venous blood contained less O than normal — this latter condition being due to the apnoeic blood causing a considerable fall of the blood pressure 688 ASPHYXIA. and consequent slowing of the blood stream, so that the O can be more completely taken from the blood in the capillaries (. PJluger ). The amount of O used in apnoea, on the whole, is not increased (g 127). Gad remarks that during forced artificial respiration, the pulmonary alveoli contain a very large amount of atmospheric air; hence they are able to arterialize the blood for a longer time, thus diminishing the necessity for respiration. [Drugs. — If the excitability of the respiratory centre be diminished by chloral, apnoea is readily induced, while, if the centre be excited, as by apomorphine, it is difficult to produce it.] 2. Eupncea. — The normal stimulation of the respiratory centre, eupnoea , is caused by the blood in which the amount of O and C 0 2 does not exceed the normal limits (§§ 35 and 36). 3. Dyspnoea. — All conditions which diminish the O and increase the C 0 2 in the blood circulating through the medulla and respiratory centre cause accelera- tion and deepening of the respirations, which may ultimately pass into vigorous and labored activity of all the respiratory muscles, constituting dyspnoea , when the difficulty of breathing is very great (§ 134). [Changes in the rhythm, § hi.] 4. Asphyxia. — If blood, abnormal as regards the amount and quality of its gases, continues to circulate in the medulla, or if the condition of the blood be- come still more abnormal, the respiratory centre is over- stimulated , and ultimately exhausted. The respirations are diminished both in number and depth, and they become feeble and gasping in character ; ultimately the movements of the respi- ratory muscles cease, and the heart itself soon ceases to beat. This constitutes the condition of asphyxia , and if it be continued death from suffocation takes place. (Langendorff asserts that in asphyxiated frogs the muscles and gray nervous sub- stance have an acid reaction.) If the conditions causing the abnormal condition of the blood be removed, the asphyxia may be prevented under favorable circum- stances, especially by using artificial respiration (§ 134) ; the respiratory mus- cles begin to act and the heart begins to beat, so that the normal eupnoeic stage is reached through the condition of dyspnoea. If the venous condition of the blood be produced slowly and very gradually, asphyxia may take place without there being any symptoms of dyspnoea, as occurs when death takes place quietly and very gradually (§ 324, 5). Causes of Dyspnoea. — (1) Direct limitation of the activity of the respiratory organs; diminution of the respiratory surface by inflammation, acute oedema ($ 47), or collapse of the alveoli, occlusion of the capillaries of the alveoli, compression of the lungs, entrance of air into the pleura, obstruction or compression of the windpipe. (2) Obstruction to the entrance of the normal amount of air by strangulation, or enclosure in an insufficient space. (3) Enfeeblement of the circulation , so that the medulla oblongata does not receive a sufficient amount of blood ; in degeneration of the heart, valvular cardiac disease, and artificially by ligature of the carotid and vertebral arteries (ICussmaul and Tenner), or by preventing the free efflux of venous blood from the skull, or by the injection of a large quantity of air or indifferent particles into the right heart. (4) Direct loss of blood, which acts by arresting the exchange of gases in the medulla (J. Rosen- thal). This is the cause of the “biting or snapping at the air” manifested by the decapitated heads of young animals, e.g., kittens. [The phenomenon is well marked in the head of a tortoise separated from the body ( W. Stirling). ] All these factors act rapidly upon the respiratory activity, and at first the respirations are deeper and more rapid, and afterward the respiratory movements become more violent and general convulsions occur, ending with expiratory spasm, which is fol- lowed by a stage of cessation of the respiration and complete relaxation. Before death takes place there are usually a few “snapping ” or gasping efforts at inspiration ( Hogyes , Sigm. Mayer — « in). Condition of the Blood Gases. — As a general rule, in the production of dyspnoea the want of O and the excess of C 0 2 act simultaneously (PJluger and Doh/nen),b\x\. each of these alone may act as an efficient cause. According to Bernstein, blood containing a small amount of O acts chiefly upon the inspiratory centre, and blood rich in C 0 2 on the expiratory centre. Dyspnoea, from want of O, occurs during respiration in a space of itioderate size (| 133), in spaces where the tension of the air is diminished, and by breathing in indifferent gases or those containing no free O. When the blood is freely ventilated with N or H, the amount of C 0 2 in the blood may even be diminished, and death occurs with all the signs of asphyxia (R/luger). Dyspnoea, from the blood being overcharged with C 0 2 , occurs by breathing air containing much C 0 2 ($ 133). Air contain- ing much CO 2 may cause dyspnoea, even when the amount of O in the blood is greater than that in the atmosphere ( Thiry ). The blood may even contain more O than normal (PJluger). Heat Dyspnoea. — An increased temperature increases the activity of the respiratory centre CONDITIONS ACTING ON THE RESPIRATORY CENTRE. 689 (g 214, IT, 3). This occurs when blood warmer than natural flows through the brain, as Fick and Goldstein observed when they placed the exposed carotids in warm tubes, so as to heat the blood passing through them. In this case the heated blood acts directly upon the brain, the medulla and the cerebral respiratory centres {Gad). Direct cooling diminishes the excitability ( Fredericq ). When the temperature is increased, vigorous artificial respiration does not produce apnoea, although the blood is highly arterialized {Ackermann). Emetics act in a similar manner {Hermann and Grim?n). Electrical stimulation of the medulla oblongata separated from the brain discharges respiratory movements {Kronecker and Marckwald), or increases those already present. Langendorff found that electrical, mechanical or chemical (salts) stimulation usually caused an expiratory effect, while stimulation of the cervical spinal cord (subordinate centre) gave an inspiratory effect. According to Laborde, a superficial lesion in the region of the calamus scriptorius causes stand- still of the respiration for a few minutes. If the peripheral end of the vagus be stimulated so as to arrest the action of the heart, the respirations also cease after a few seconds. Arrest of the heart’s action causes a temporary anaemia of the medulla, in consequence of which its excitability is lowered, so that the respirations cease for a time {Langendorff ). Action on the Centre. — The respiratory centre, besides being capable of being stimulated directly, may be influenced by the will, and also reflexly by stimulation of a number of afferent nerves. 1. By a voluntary impulse we may arrest the respiration for a short time, but only until the blood becomes so venous as to excite the centre to increased action. The number and depth of the respirations may be voluntarily increased for a long time, and we may also voluntarily change the rhythm of respiration. 2. The respiratory centre may be influenced reflexly both by fibres which excite it to increased action and by others which inhibit its action. ( a ) The exciting fibres lie in the pulmonary branches of the vagus, in the optic, audi- tory and sensory cutaneous nerves, and normally their action overcomes the action of the inhibitory fibres. Thus a cold bath deepens the respirations, and causes a moderate acceleration of the pulmonary ventilation {Speck). Section of both vagi causes slower and deeper respiratory movements, owing to the cutting off of those impulses which under normal conditions pass from the lungs to excite the respiratory centre. The amount of air taken in and C0 2 given off, however, is unchanged. The inspiratory efforts are more vigorous and not so purposive ( Gad ). Weak tetanizing currents applied to the central end of the vagus cause acceleration of the respirations (. Budge , Eckhard), while at the same time the efforts of the respiratory muscles may be increased or diminished or remain unchanged ( Gad ). Strong tetanizing currents cause stand- still of the respiration in the inspiratory phase ( Traube ) or expiratory phase (. Budge , Burkart). Single induction shocks have no effect (. Marckwald and Kro- necker). Wedenski and Heidenhain have recently reinvestigated the effect of stimulation of the vagus upon the respiration. They find that a temporary weak electrical stimulus applied to the central end of the vagus, at the beginning of inspiration (rabbit), affects the depth of the succeeding inspirations, while a similar strong stimulus affects also the depth of the following expirations. If the stimulus be applied just at the commencement of expiration, stronger stimuli being required in this case, there is a diminution of the expiration and of the following inspiration. Continued tetanic stimulation of the vagus may cause decrease in the depth of the expirations, or at the same time alteration in the depth of the inspirations, without affecting the respiratory rhythm ; when the stimu- lation is stronger, inspiration and expiration are diminished with or without alteration of the fre- quency, and with the strongest stimuli respirations cease either in the inspiratory or expiratory phase. (b) The inhibitory nerves which affect the respiratory centre lie in the superior laryngeal nerve (. Rosenthal '), and also in the inferior ( Pfluger and Burkart , Her- ing , Breuer) (Fig. 416 , ink) . According to Langendorff, direct electrical, mechanical, or chemical stimulation of the centre may arrest respiration, perhaps in consequence of the stimulus affecting the central ends of these inhibi- tory nerves where they enter the ganglia of the respiratory centre. Stimulation of the superior or inferior laryngeal nerves (b) or their central ends causes slowing, and even arrest of the respiration (in expiration — Rosenthal). 44 690 METHODS OF PERFORMING ARTIFICIAL RESPIRATION. Arrest of the respiration in expiration is also caused by stimulation of the nasal (. Hering and Kratschnier ) and ophthalmic branches of the trigeminus ( Christiani ) ; stimulation of the pulmonary branches of the vagus by breathing irritating gases (. Knoll ), although other gases cause stand-still in inspiration. Chemical stimula- tion of the trunk of the vagus — by dilute solutions of sodic carbonate — causes expiratory inhibition of the respiration ; and mechanical stimulation — rubbing with a glass rod — inspiratory inhibition ( Knoll ). The stimulation of sensory cutaneous nerves, especially of the chest and abdomen, as occurs on taking a cold douche, and stimulation of the splanchnics, cause stand-still in expiration ( Schiff \ Falk), the first cause often giving rise to temporary clonic contractions of the re- spiratory muscles. The respirations are often slowed to a very great extent by pressure upon the brain [whether the pressure be due to a depressed fracture or effusion into the ventricles and subarachnoid space]. The respiration may be greatly oppressed and stertorous. The amount of work done by the respiratory muscles is altered during the reflex slowing of the respiratory muscles, the work being increased during slow respiration, owing to the ineffectual in- spiratory efforts (Gad). The volume of the gases which passes through the lungs during a given time remains unchanged ( Valentin ), and the gaseous exchanges are not altered at first ( Voit and Rauber ). Automatic Regulation of the Respiratory Centre. — Under normal cir- cumstances, it would' seem that the pulmonary branches of the vagus act upon the two respiratory centres, so as to set in action what has been termed the self-adjust- ing mechanism ; thus, the inspiratory dilatatiop of the lungs stimulates mechani- cally the fibres which reflexly excite the expiratory centres, while the diminution of the lungs during expiration excites the nerves which proceed to the inspiratory centre (. Hering and Breuer ). Discharge of the First Respiration. — The foetus is in an apnoeic condition until birth, when the umbilical cord is cut. During intra-uterine life O is freely supplied to it by the activity of the placenta. All conditions which interfere with this due supply of O, as compression of the umbilical vessels and prolonged labor pains, cause a decrease of the O and an increase of the C 0 2 in the blood, so that the condition of the foetal blood is so altered as to stimulate the respiratory centre, and thus the impulse is given for the discharge of the first respiratory movement {Schwartz). A foetus still within the unopened foetal membranes may make re- spiratory movements ( Vesalius , 1542). If the exchange of gases be interrupted to a sufficient extent, dyspnoea and ultimately death of the foetus may occur. If, however, the venous condition of the mother’s blood develops very slowly, as in cases of quiet, slow death of the mother, the medulla oblongata of the foetus may gradually die without any respiratory movement being discharged (§ 324, 5). According to this view, the respiratory movements are due to the direct action of the dyspnoeic blood upon the medulla oblongata. Death of the mother acts like compression of the umbilical cord. In the former case, the maternal venous blood robs the foetal blood of its O, so that death of the foetus occurs more rapidly ( Zuntz ). If the mother be rapidly poisoned with CO ($ 17), the foetus may live longer, as the CO-hsemoglobin of the maternal blood cannot take any O from the foetal blood ($ 16 —Hogyes). In slow poisoning, the CO passes into the foetal blood (Grehant and Quin- quand). In many cases, especially in cases of very prolonged labor, the excitability of the respiratory centre may be so diminished, that after birth the dyspnoeic condition of the blood alone is not sufficient to excite respiration in a normal rhythmical manner. In such cases stimulation of the skin also acts, e. g., partly by the cooling produced by the evaporation of the amniotic fluid from the skin. When air has entered the lungs by the first respiratory movements, the air within the lungs also excites the pulmonary branches of the vagus ( PJluoer ), and thus the respiratory centre is stimulated reflexly to increased activity. According to v. Preuschen’s observations, stimulation of the cutaneous nerves is more effective than that of the pulmonary branches of the vagus. In animals which have been rendered apnoeic by free ventilation of their lungs, respiratory movements may be discharged by strong cutaneous stimuli, e. g., dashing on of cold water. The mechanical stimulation of the skin by friction or sharp blows, or the application of a cold douche, excites the respiratory centre (Arti- ficial Respiration, \ 134). DIRECT STIMULATION OF THE CARDIO-INHIBITORY CENTRE. 691 [Action of Drugs on the Respiratory Centre. — Ammonia, salts of zinc and copper, strychnin, atropin, duboisin, apomorphin, emetin, the digitalis group, and heat increase the rapidity and depth of the respirations, while they become frequent and shallower after the use of alcohol, opium, chloral, chloroform, physostigmin. The excitability of the centre is first increased and then di- minished by caffein, nicotin, quinine, and saponin ( Brunton).~\ 369. THE CENTRE FOR THE INHIBITORY NERVES OF THE HEART— (CARDIO-INHIBITORY).— The fibres of the vagus which when moderately stimulated diminish the action of the heart, when strongly stimulated, however, arrest its action and cause it to stand still in diastole (§352, 7), are supplied to the vagus through the spinal accessory nerve (§ 353), and have their centre in the medulla oblongata. [Gaske'll has shown that stimulation of the vagus not only influences the rhythm of the heart’s action, but it modifies the other functions of the cardiac muscle. Stimulation of the vagus influences — (0) the automatic rhythm , i. e., the rate at which the heart contracts automatically; ( b ) the force 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 the 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 Bernstein, 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. (1) Sudden ancemia 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 hypercemia acts in a similar manner, and it can be produced by ligaturing all the veins returning from the head ( Landois , Hermann and -Esc her). (3) The increased venosity of the blood, produced either by direct cessation of the respirations (rabbit) or by forcing into the lungs a quantity of air containing much C0 2 ( Traube ). As the circulation in the placenta (the respiratory organ of the foetus) 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 dyspnoeic blood (i?. S. Schultze). (4) At the moment the respiratory centre is excited, and an inspiration occurs, there is a variation in the inhibitory activity of the cardiac centre (. Donders , Pftiiger, Fre- dericq — § 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 — (1) 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 ( Tarchanoff). Stimulation of the stomach of the dog causes slowing of the heart beat (Sig. Mayer and Pribram). [M’William finds that the action of the heart of the eel may be arrested reflexly with very great facility. The reflex inhibition is obtained 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. Donders, with Prahl and Ntiel, observed that arrest of the heart’s action did not take place immediately the stimulus was applied to the vagus, but about ^ of a second— period of latent stimulation — elapsed before the effect was produced on the heart. A rhythmically -interrupted moderate stimulus suffices ( v . 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 still 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, e.g.,f rog, tortoise, birds and mammals. In fishes only the ventricle 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 inex citable to direct stimulation during 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 right vagus is more effective than the left in other animals, e. 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 on the ventricle than on the other parts 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 § 335, III. 7. Schiff 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 potash 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 (J. M. Ludwig and L,uchsin- ger). [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 inhibition. 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 ( Schmiedeberg and Koppe ). If atropin be applied in solution to the heart this action is set aside, and the heart begins to beat again. Digitalin 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 ( King ). Nicotin first excites the vagus, then rapidly paralyzes it. Hydrocyanic acid has the same effect ( Preyer ). Atropin (v. Bezold ) and curara (large dose — Cl. Bernard and Kolliker ) paralyze the vagi, and so does a very low temperature or high fever. 370. THE CENTRE FOR THE ACCELERATING CARDIAC NERVES AND THE ACCELERATING FIBRES.— Nervus Ac- celerans. — It is more than probable that a centre exists in the medulla oblongata which sends accelerating fibres to the heart. These fibres pass from the medulla oblongata — but from which part thereof has not been exactly ascertained — through the spinal cord, and leave the cord through the rami communicantes of the lower cervical and upper six dorsal nerves {Strieker), to pass into the sympathetic nerve. Some of these fibres, issuing from the spinal cord, pass through the first thoracic sympathetic ganglion and the ring of Vieussens, to join the cardiac plexus (Figs. 417, 418). [These fibres, issuing from the spinal cord, frequently accompany the nerve running along the vertebral artery], and they constitute the Nervus ac- celerans cordis. [Fig. 418 shows the accelerator fibres passing through the ganglion stellatum of the cat to join the cardiac plexus.] If the vagi of an animal be divided, stimulation of the medulla oblongata, of the lower end of the divided ceivical spinal cord, even the lower cervical ganglion, or of the upper dorsal ganglion of the sympathetic {Gang, stellatum), causes acceleration of the heart beats in the dog and rabbit without the blood pressure undergoing any change {Cl. Bernard, v. Bezold, Cyon). On stimulating the medulla oblongata or the cervical portion of the spinal cord, the vasomotor nerves are, of course, simultane- ously excited. The consequence is that the blood vessels, sup- plied by vasomotor nerves from the spot which is stimulated, con- tract, and the blood pressure is greatly increased. Again, a sim- ple increase of the blood pressure accelerates the action of the heart; this experiment does not prove directly the existence of accelerating fibres lying in the upper part of the spinal cord. If, however, the splanchnic nerves be divided beforehand, and, as they supply the largest vasomotor area in the body, the result of their division is to cause a great fall of the blood pressure, then on stimulating the above-named parts, after this operation, the heart beats are still increased in number, so that its increase can- not be due to the increased blood pressure. Indirectly it may be shown, by dividing or extirpating all the nerves of the cardiac plexus, or at least all the nerves going to the heart, that stimula- tion of the medulla oblongata, or cervical part of the spinal cord, no longer causes an increased frequency of the heart’s action to the same extent as before division of these nerves. The slightly increased frequency in this case is due to the increased blood pressure. The accelerating centre is certainly not continually in a state of ionic excitement, as section of the accelerans nerve does not cause Fig. 417. Scheme of the course of the accele- rans fiores. P, pons ; MO, medulla oblongata ; C, spinal cord ; V, in- hibitory centre for heart ; A, accele- rans centre; Vag., vagus; SL, su- perior, IL, inferior laryngeal ; SC, superior, IC, inferior cardiac; H, heart; C, cerebral impulse ; S, cer- vical sympathetic ; a, a, accelerans fibres. 694 THE CARDIAC PLEXUS. slowing of the action of the heart ; the same is true of destruction of the medulla oblongata or of the cervical spinal cord. In the latter case the splanchnic nerves must be divided beforehand to avoid the slowing effect on the action of the heart produced by the great fall of the blood pressure consequent upon destruction of the cord, otherwise we might be apt to ascribe the result to the action of the ac- celerating centre, when it is in reality due to the diminished blood pressure (. Brothers Cyori). According to the results of the older observers (v. Bezold and others ), some accelerating fibres run in the cervical sympathetic. A few fibres pass through the vagus to reach the heart (§ 352, 7), and when they are stimulated the heart beat is accelerated and the cardiac contractions strengthened (. Heidenhain and Lowit). The inhibitory fibres of the vagus lose their excitability more readily than the Fig. 418. Cardiac plexus, and ganglion stellatum ot the cat. R, right, L, left X 'Vi \ i, vagus ; 2', cervical sympathetic, and in the annulus of Vieussens ; 2, communicating branches from the middle cervical ganglion and the ganglion stel- latum ; 2", thoracic sympathetic; 3, recurrent laryngeal; 4, depressor nerve; 5, middle cervical ganglion; 5', communication between 5 and the vagus ; 6, ganglion stellatum (1st thoracic ganglion) ; 7, communicating branches with the vagus; 8, nervus accelerans ; 8, 8', 8", roots of accelerans ; 9, branch of the ganglion stellatum. accelerating fibres, but the vagus fibres are more excitable than those of the accelerans. Modifying Conditions. — When the peripheral end of the nervus accelerans is stimulated, a considerable time elapses before the effect upon the frequency of the heart takes place, i. e., it has a long latent period. Further the acceleration thus produced disappears gradually. If the vagus and accelerans fibres be stimulated simultaneously, only the inhibitory action of the vagus is manifested. If, while the accelera7is is being stimulated, the vagus be suddenly excited, there is a prompt diminution in the number of the heart beats; and if the stimulation of the vagus is stopped, the accelerating effect of the accelerans is again rapidly manifested ( C. Ludwig with Schmiedebeig, Bowditch , Baxt). According to the experiments of Strieker and Wagner on dogs, with both vagi divided, a diminution of the number of the heart beats occured when both accelerantes were divided. This would indicate a tonic innervation of the latter nerves. POSITION OF THE VASOMOTOR CENTRE. 695 [Accelerans in the Frog. — Gaskell showed that stimulation of the vagus might produce two opposing effects ; the one of the nature of inhibition, the other of augmentation. In the crocodile, the accelerans fibres leave the sympathetic chain at the large ganglion corresponding to the ganglion stellatum of the dog, and run along the vertebral artery up to the superior vena cava, and after an anas- tomosing with branches of the vagus, pass to the heart. “Stimulation of these fibres increases the rate of the cardiac rhythm, and augments the force of auricular contractions ; while stimulation of the vagus slows the rhythm, and diminishes the strength of the auricular contractions.’ ’ The strength of the ventricular con- traction, both in the tortoise and crocodile, does not seem to be influenced by stimulation of the vagus, and probably, also, it is unaffected by the sympathetic. The so-called vagus of the frog in reality consists of pure vagus fibres and sym- pathetic fibres, and is, in fact, a vago-sympathetic. Gaskell finds that stimulation of the sympathetic , before it joins the combined ganglion of the sympathetic and vagus, produces purely augmentor or accelerating effects ; while stimulation of the vagus, before it enters the ganglion, produces purely inhibitory effects. The two sets of fibres are quite distinct, so that in the frog the sympathetic is a purely augmentor (accelerator), and the vagus a purely inhibitory nerve. Acceleration is merely one of the effects produced by stimulation of these nerves, so that Gas- kell suggests that they ought to be called “augmentor,” or simply cardiac sympathetic nerves.] [In his more recent researches Gaskell asserts that vagus stimulation produces first an inhibitory or depressing effect, but that it ultimately improves the condition of the heart as regards force, rate or regularity — one or all of these. He regards it as a true anabolic nerve (g 342, d).] 371. VASOMOTOR CENTRE AND VASOMOTOR NERVES.— Vasomotor Centre. — The chief dominating or general centre which sup- plies all the non-striped muscles of the arterial system with motor nerves (vasomotor, vaso-constrictor, vaso-hypertonic nerves) lies in the medulla oblon- gata, at a point which contains many ganglionic cells (. Ludwig and Thiry ). Those nerves which pass to the blood vessels are known as vasomotor nerves. The centre (which is 3 millimetres long and 1 )4 millimetre broad in the rabbit), reaches from the region of the upper part of the floor of the medulla oblongata to within 4 to 5 mm. of the calamus scriptorius. Each half of the body has its own centre placed 2)4 millimetres from the middle line on its own side, in that part of the medulla oblongata which represents the upward continuation of the lateral columns of the spinal cord ; according to Ludwig and Owsjannikow, and Dittmar, in the lower part of the superior olives. Stimulation of this central area causes contraction of all the arteries, and in consequence there is great in- crease of the arterial blood pressure, resulting in swelling of the veins and heart. Paralysis of this centre causes relaxation and dilatation of all the arteries, and consequently there is an enormous fall of the blood pressure. Under ordinary circumstances the vasomotor centre is in a condition of moderate tonic excitement (§ 366). Just as in the case of the cardiac and respiratory centres the vasomotor centre may be excited directly and reflexly. [Position — How Ascertained. — As stimulation of the central end of a sen- sory nerve, e.g., the sciatic, in an animal under the influence of curara, causes a rise in the blood pressure, even after removal of the cerebrum, it is evident that the centre is not in the cerebrum itself. By making a series of sections from above downward, it is found that this reflex effect is not affected until a short distance above the medulla oblongata is reached. If more and more of the medulla ob- longata be removed from above downward, then the reflex rise of the blood pressure becomes less and less, until, when the section is made 4 to 5 mm. above the calamus scriptorius, the effect ceases altogether. This is taken to be the lower limit of the general vasomotor centre. The bilateral centre corresponds to some large multi- polar nerve cells, described by Clarke as the antero-lateral nucleus.] 696 COURSE OF THE VASOMOTOR FIBRES. I. Direct Stimulation of the Centre. — The amount and quality of the gases contained in the blood flowing through the medulla are of primary import- ance. In the condition of apncea (§ 368, 1) the centre seems to be very slightly excited, as the blood pressure undergoes a considerable decrease. When the mixture of blood gases is such as exists under normal circumstances, the centre is in a state of moderate excitement, and running parallel with the respiratory move- ments are variations in the excitement of the centre (Traube-Hering curves — § 85), these variations being indicated by the rise of the blood pressure. When the blood is highly venous, produced either by asphyxia or by the inspiration of air containing a large amount of C0 2 , the centre is strongly excited, so that all the arteries of the body contract, while the venous system and the heart become dis- tended with blood ( Thiry ). At the same time the velocity of the blood stream is increased ( Heidenhain ). The same result is produced by sudden anaemia of the oblongata by ligature of both the carotid and subclavian arteries ( Nawalichin , Sigm. Mayer), and no doubt, also, by the sudden stagnation of the blood in venous hyperaemia. Action of Poisons. — Strychnin stimulates the centre directly, even in curarized dogs, and so do nicotin and Calabar bean. Emptiness of the Arteries after Death. — The venosity of the blood which occurs after death always produces an energetic stimulation of the vasomotor centre, in consequence of which the arteries are firmly contracted. The blood is thereby forced toward the capillaries and veins, and thus is explained the “emptiness of the arteries after death.” Effect on Hemorrhage. — Blood flows much more freely from large wounds when the vaso- motor centre is intact than if it be destroyed (frog). As psychical excitement undoubtedly influences the vasomotor centre, we may thus explain the influence of psychical excitement (speaking, etc.) upon the cessation of hemorrhage. If the hemorrhage be severe, stimulation of the medulla oblon- gata, due to the anaemia, may ultimately cause constriction of the small arteries, and thus arrest the bleeding. Thus, surgeons are acquainted with the fact that dangerous hemorrhage is often arrested as soon as unconsciousness, due to cerebral anaemia, occurs. If the heart be ligatured in a frog, all the blood is ultimately forced into the veins, and this result is also due to the anaemic stimulation of the oblongata ( Goltz). In mammals , when the heart is ligatured, the equilibration of the blood pressure between the arterial and venous systems takes place more slowly when the medulla oblon- gata is destroyed than when it is intact (v. Bezold , Gscheidlen ). [Effect of Destruction of the Vasomotor Centre. — If two frogs be pithed and their hearts exposed, and both be suspended, then the hearts of both will be found to beat rhythmically and fill with blood. Destroy the medulla oblongata and spinal cord of one of them, then immediately in this case the heart, although continuing to beat with an altered rhythm, ceases to be filled with blood ; it appears collapsed, pale, and bloodless. There is a great accumulation of the blood in the abdominal organs and veins, and it is not returned to the heart, so that the arteries are empty. This experiment of Goltz is held to show the existence of venous tonus depending on a cerebro -spinal centre. If a limb of this frog be amputated, there is little or no hemorrhage, while in the other frog the hemorrhage is severe. The bearing of this experiment on conditions of “shock” is evident.] Direct Electrical Stimulation. — On stimulating the centre directly in animals, it is found that single induction shocks only become effective when they succeed each other at the rate of 2 to 3 shocks per second. Thus there is a “ summation ” of the single shocks. The maximum contrac- tion of the arteries, as expressed by the maximum blood pressure, is reached when 10-12 strong-, or 20-25 moderately strong shocks per second are applied (. Kronecker and Nicolaides ). Course of the Vasomotor Nerves. — From the vasomotor centre some fibres proceed directly through some of the cranial nerves to their area of distribution ; through the trigeminus partly to the interior of the eye (§ 347, I, 2), through the lingual and hypoglossal to the tongue ($ 347, III, 4), through the vagus to a limited extent to the lungs (| 352, 8, 2), and to the intestines (g 352, 11 ). All the other vasomotor nerves descend in the lateral columns of the spinal cord (§ 364, 9) ; hence stimulation of the lower cut end of the spinal cord causes contraction of the blood vessels supplied by the nerves below the point of section ( Pflilger ). In their course through the cord these fibres form connections with the subordinate vasomotor centres in the gray matter of the cord ($ 362, 7), and then leave the cord either directly through the anterior roots of the spinal nerves to their areas of distribution, or they pass through the rami communicantes into the sympathetic, and from them reach the blood vessels to which they are distributed ($ 356). Cephalic Vasomotors. — The following is the arrangement of these nerves in the region of the head : The cervical portion of the sympathetic supplies the great majority of the blood vessels of the head (see Sympathetic , \ 356, A, 3 — Cl. Bernard ). In some animals the great auricular nej've supplies a few vasomotor fibres to its own area of distribution ( Schiff \ Loven, Moreau). The vaso- motor nerves to the upper extremities pass through the anterior roots of the middle dorsal nerves REFLEX STIMULATION OF THE VASOMOTOR CENTRE. 697 into the thoracic sympathetic, and upward to the 1st thoracic ganglion, and from thence through the rami communicantes 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 ( Pflilger , Schiff, Cl. Bernard). The lungs, in addition to a few fibres through the vagus, are supplied from the cervical spinal cord through the 1st thoracic gan- glion (Brown- Aequard, Pick and Badoud, Lichtheim). The splanchnic is the greatest vasomotor nerve in the body, and supplies the abdominal viscera ($ 356, B — Bezold, Ludw’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 5th cervical and the 1st dorsal vertebrae. [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 different 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, eg., the toes, the fingers and ears ; while those that act upon central parts seem to be less active (Lewaschew), eg., 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 reflexly diminishes the excitability of the vasomotor centre. These act as reflex inhibitory nerves on the centre, and are known as “ depressor” nerves. Pressor, or excito-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 ( Hering and Kratschmer). [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 Loven, the first effect of stimulating every sensory nerve is a pressor action. [If a dog be poisoned with curara , and the central end 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 effect, with simultaneous decrease of the cardiac activity. The applica- tion of heat and cold to the skin produces reflexly a change in the lumen of the blood vessels and in the cardiac activity (Rohrig, Winternitz). Pinching the skin causes contraction of the vessels of the pia mater of the rabbit (Schuller), 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 (§ 35 2 ? 6). The trunk of the vagus below the latter also contains depressor fibres ( v . Bezold and Dreschfeld ), as well as the pulmonary fibres (dog) ( Taljan - 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 ( Loven ). 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 (. Loven ). 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 5 times per minute. Schiff 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 (g 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. 1. Local Effects. — Section of a peripheral vasomotor nerve, e. g., the cer- vical sympathetic, is followed by dilatation of the blood 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 hypersemia, 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 almost arterial (bright red) in its char- acters, and the pulse may even be propagated into the veins, so that the blood spouts from them ( Cl ’. 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 slowly, 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 by a fall of 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 ($ 338), 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. Th & primary effect, however, in a limb, e. g., after section of the sciatic or lesion of the brachial plexus, 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 spinal 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 ( Ts chets chichin , Naunyn , 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 small area 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 ( Sassetzki and Manassein). 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, i. 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. As 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 , Slavjansky). 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 followed by a great rise of the blood pressure. When they are divided, there is such a fall of the blood pressure, that other parts of the body become more or less anaemic, 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, . Ludwig and Thiry ), [see \ 87]. The capacity of the vascular system, depending as it does in part upon the condition of the vasomotor nerves, influences the body weight. 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 nerves 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 the medulla oblongata, the blood vessels are acted upon by local or subordinate 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 reflexly', 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, Nussbaum, 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. Ludwig 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. Ludwig). Nevertheless, the blood vessels, although they recover part of their tone and mobility, 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. Lewaschew 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 nervous mechanisms. Amyl nitrite and digitalis are supposed to act on those hypothetical mechanisms. The pulsating veins in the bat’s wing still continue to beat after section of all their nerves, which is in favor of the existence of local nervous mechanisms ( Luchsinger , Schiff ). 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 first excite , and then paralyze, e.g ., chloral hydrate, morphia, landanosin, veratrin, nicotin, Calabar bean, alcohol ; others rapidly paralyze them, e.g., 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 vasomotor nerves (Goltz), 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 subordinate 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 vessels may also be due to stimulation of vaso- dilator nerves, and the physician must be careful to distinguish VASODILATOR 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 arterio 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 cerebrates). 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 ( Du 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 Muller’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 results 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 File’nne, by injury to the upper part of both restiform bodies in rabbits. Visceral Angio-neuroses. — The occurrence of sudden hypersemia 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 hypersemia, and ecchymoses in the lungs, pleurae, intestines 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 §276; and fever in I 220. 372. VASO-DILATOR CENTRE AND VASO-DILATOR NERVES. — Although a vaso-dilator centre has not been definitely proved to exist in the medulla, still its existence 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 \ Cl. 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 peripheral ends be stimulated with Faradic electricity, the sinuses of the corpora cavernosa dilate, become filled with blood, and erection takes place (§ 436). [Other examples in muscle and elsewhere are referred to below.] Dyspnoeic 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 anaemic, owing to the stimulation of their vasomotor centre ( Dastre and Moral). 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 fibres proper to itself ( Laffont ). In the gray matter of the cord there is a special subordinate centre for the vaso-dilator fibres of the bucco-labial region. This centre may be acted on reflexly by stimulation of the vagus, especially its pulmonary branches, and even by stimulating the sciatic nerve. The ear receives its nerves from the 1st dorsal and lowest cervical ganglion, 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-pharyngeal nerve (§ 351, 4 — Vulpian). Perhaps the vagus contains those for the kidneys (§ 276). 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) ( Eckhard , 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 with 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 ($ 294, II — C. Ludzuig and Sczelkow , Hafiz, Gaskell , Heidenhain ) — 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 vaso-dilator fibres. Stimuli, which are applied at long intervals to the nerve, act especially on the vaso-dilator 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 vaso-dilators diminish, the activity of these mech- anisms or ganglia. Psychical conditions act upon the vaso dilator 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 vaso dilator nerves obviously have a considerable influence on the temperature 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 of 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 ” ( Tschetschichin , Naunyn, Quincke ), 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 (3 377 ). 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 anaemia of the medulla oblongata, either in consequence of hemorrhage or ligature of both carotids and subclavians ( Kussmaul and Tenner ), and, lastly, by sudden venous stagnation caused by compressing the veins coming from the head. In all these cases the stimula- tion of the centre is due to the sudden interruption of the normal exchange of the gases. When these factors act quite gradually, death may take place without convulsions. Intense direct stimulation of the medulla, as by its sudden destruc- tion, causes general convulsions. Position. — Nothnagel attempted by direct stimulation to map out its position in rabbits ; it ex- tends from the area above the ala cinerea upward to the corpora quadrigemina. It is limited exter- PSYCHICAL FUNCTIONS OF THE BRAIN. 703 nally by the locus coeruleus and the tuberculmn acusticum. In the frog it lies in the lower half of the 4th ventricle ( Heube /). The centre is affected in extensive reflex spasms (§ 364, 6), eg., in poisoning with strychnin and in hydrophobia. Poisons. — Many inorganic and organic poisons, most cardiac poisons, nicotin, picrotoxin, ammo- nia (£ 277), and the compounds of barium, cause death after producing convulsions, by acting on the spasm centre ( Bober , Heubel , Bbhm). If the arteries going to the brain be ligatured so as to paralyze the oblongata, then on ligaturing the abdominal aorta spasms of the lower limbs occur, owing to the anaemic stimulation of the motor ganglia of the spinal cord (Sigm. Mayer). Pathological — Epilepsy. — Schroder van der Kolk found the blood vessels of the oblongata dilated and increased in cases of epilepsy. Brown-Sequard observed that injury to the central ur peripheral nervous system (spinal cord, oblongata, peduncle, corpora quadrigemina, sciatic nerve) of guinea pigs produced ep lepsy, and this condition even became hereditary. Stimulation of the cheek or of the face, “ epileptic zone,” on the same side as the injury (spinal cord), caused at once an at- tack of epilepsy ; but when the peduncle was injured the opposite side must be stimulated. West- phal made guinea pigs epileptic by repeated light blows on the skull, and this condition also became hereditary. In these cases there was effusion of blood in the medulla oblongata and upper part of the spinal cord ($$ 375 and 378, I). Direct stimulation of the cerebrum also produces epileptic convulsions. Strong electrical stimulation of the motor areas of the cortex cerebri is often followed by an epileptic attack (§ 375). [It is no unfrequent occurrence that, while one is stimulating the motor areas of the cortex cerebri of a dog, to find the animal exhibiting symptoms of local or general epilepsy.] Sweat Centre. — A dominating centre for the secretion of the sweat of the entire surface of the body (§ 289, II) — with subordinate spinal centres (§ 362, 8) — occurs in the medulla oblongata ( Adamkiewicz , Marme, Nawrocki ). It is double, and in rare cases the excitability is unequal on the two sides, as is mani- fested by unilateral perspiration (§ 289, 2). Poisons. — Calabar bean, nicotin, picrotoxin. camphor, ammonium acetate, cause a secretion of sweat, by acting directly on the sweat centre. Muscarin causes local stimulation of the peripheral sweat fibres — it causes sweating of the hind limbs after section of the sciatic nerves. Atropin ar- rests the action of muscarin ( Ott, Wood, Field , Nawrocki). [Regeneration of the Spinal Cord — In some animals true nervous matter is reproduced after part of the spinal cord has been destroyed, at least this is so in tritons and lizards (//. Muller ). As is well known, in these animals when the tail is removed it is reproduced, and Muller found that a part of the spinal cord corresponding to the new part of the tail is reproduced. Morphologically the elements were the same, but the spinal nerves were not reproduced, while physiologically the new nerve substance was not functionally active ; it corresponds, as it were, to a lower stage of develop- ment. According to Masius and Vanlair, an excised portion of the spinal cord of a frog is repro- duced after six months ; while Brown-Sequard maintains that reunion of the divided surfaces of the cord takes place in pigeons after six to fifteen months. A partial reunion is asserted to occur in dogs by Dentan, Naunyn, and Eichhorst, although Schieferdecker obtained only negative results, the divided ends being united only by connective tissue ( Schwalbe ).] 374. PSYCHICAL FUNCTIONS OF THE BRAIN.— The hemi- spheres of the cerebrum are usually said to be the seat of all the psychical activities. Only when they are intact are the processes of thinking, feeling, and willing pos- sible. After they are destroyed, the organism comes to be like a complicated machine, and its whole activity is only the expression of the external and internal stimuli which act upon it. The psychical activities appear to be located in both hemispheres, so that after destruction of a considerable part of one of them the other seems to act in place of the part destroyed. [Objection has been taken to the term the “seat of” the will and intelligence, and undoubtedly it is more consistent with what we know, or rather do not know, to say that the existence of volition and intelligence is dependent on the connection of the cerebral cortex with the rest of the brain.] [That a certain condition of the cerebral hemispheres is necessary for the manifestation of the in- tellectual faculties is admitted on all hands, for compression of the brain, e.g., by a depressed frac- ture of the skull, and sudden cessation of the supply of blood to the brain abolish consciousness. The intellectual faculties are affected by inflammation of the meninges involving the surface of the brain, the action of drugs affects the intellectual and other faculties, but while all this is admitted we can- not say precisely upon what parts of the brain ideation depends. The pre-frontal area, or the con- volutions in front of the ascending frontal supplied by the anterior cerebral artery, are sometimes 704 EXTIRPATION OF THE CEREBRUM. regarded as the anatomical substratum of certain mental acts. At any rate, electrical stimulation of these parts is not followed by muscular motion, and, according to Ferrier, if this region be extirpated in the monkey, there is no motor or sensory disturbance in this animal ; the animal exhibits emo- tional feeling, all its special senses remain, and the power of voluntary motion is retained, but never- theless there is a decided alteration in the animal’s character and behavior, so that it exhibits consid- erable psychological alterations, and, according to Ferrier, “ it has lost to all appearance the faculty of attention and intelligent observation.”] Observations on Man. — Cases in which considerable unilateral lesions or destruction of one hemisphere have taken place, without the psychical activities appearing to suffer, sometimes occur. The following is a^ase communicated by Longet : A boy, 16 years of age, had his parietal bone fractured by a stone falling on it, so that part of the protruding brain matter had to be removed. On reapplying the bandages more brain matter had to be removed. After 18 days he fell out of bed, and more brain matter protruded, which was removed. On the 35th day he got intoxicated, tore off the bandages, and with them a part of the brain matter. After his recovery the boy still retained his intelligence, but he was hemiplegic. Even when both hemispheres are moderately destroyed the intelligence appears to be intact; thus Trousseau describes the case of an officer whose fore-brain was pierced transversely by a bullet. There was scarcely any appearance of his mental or bodily faculties being affected. In other cases, destruction of parts of the brain pecu- liarly alters the character. We must be extremely careful, however, in forming conclusions in all such cases. [In the celebrated “ American crowbar case ” recorded by Bigelow, a young man was hit by a bar of iron 1^ inch in diameter, which traversed the anterior part of the left hemi- sphere, going clear out at the top of his head. This man lived for thirteen years without any per- manent alterations of motor or sensory functions ; but “ the man’s disposition and character were observed to have undergone a serious change.” There were, however, some changes which might be referable to injury to the frontal region. In all cases it is most important to know both the exact site and the extent of the lesion. Ross points out that the characteristic features of lesions in the pre-frontal cortical region are afforded by “psychical disturbances, consisting of dementia, apathy and somnolency.”] Imperfect Development of the Cerebrum. — Microcephalia and hydrocephalus yield every result between diminution of the psychical activities and idiocy. Extensive inflammation, degen- eration, pressure, anaemia of the blood vessels, and the actions of many poisons produce the same effect. Flourens’ Doctrine. — Flourens assumed that the whole of the cerebrum is concerned in every psychical process. From his experiments on pigeons, he concluded that, if a small part of the hemispheres remained intact, it was sufficient for the manifestation of the mental functions ; just in proportion as the gray matter of the hemispheres is removed all the functions of the cerebrum are cnieebled, and when all the gray matter is removed all the functions are abolished. According to this view, neither the different faculties nor the different perceptions are localized in special areas. Goltz holds a somewhat similar view to that of Flourens. He assumes that if an uninjured part of the cerebrum remain, it can to a certain extent perform the functions of the parts that have been removed. This Vulpian has called the law of “ functional substitution ” (loi de suppleance). The phrenological doctrine of Gall (f 1828) and Spurzheim assumes that the different mental faculties are located in different parts of the brain, and it is assumed that a large development of a particular organ may be detected by examining the external configuration of the head (Crani- oscopy). Extirpation of the Cerebrum. — After the removal of both cerebral hemi- spheres in animals, every voluntary movement and every conscious impression and sensory perception entirely ceases. On the other hand, the whole mechanical movements and the maintenance of the equilibrium of the movements are retained. The maintenance of the equilibrium depends upon the mid-brain, and is regulated by important reflex channels (§ 379]. The mid-brain (corpora quadri- gemina) is connected not only with the gray matter of the spinal cord and medulla oblongata, the seat of extensive reflex mechanisms (§ 367), but it also receives fibres coming from the higher organs of sense, which also excite move- ments reflexly. The corpora quadrigemina are also supposed to contain a reflex inhibitory apparatus (§ 361, 2). The joint action of all these parts makes the corpora quadrigemina one of the most important organs for the harmonious exe- cution of movements, and this even in a higher degree than the medulla oblongata itself ( Goliz ). Animals with their corpora quadrigemina intact retain the equi- librium of their bodies under the most varied conditions, but they lose this power as soon as the mid-brain is destroyed ( Goltz ). Christiani locates the coordinating centre for the change of place and the maintenance of the equilibrium in mam- mals in front of the inspiratory centre in the 3d ventricle (§ 368). REMOVAL OF THE CEREBRUM FROM A FROG. 705 That impressions from the skin and sense organs are concerned in the maintenance of the equilibrium is proved by the following facts : A frog without its cerebrum at once loses its power of balancing itself as soon as the skin is removed from its hind limbs. The action of impressions communicated through the eyes is proved by the difficulty or impossibility of maintaining the equi- librium in nystagmus (g 350), and by the vertigo which often accompanies paralysis of the external ocular muscles. In persons whose cutaneous sensibility is diminished, the eyes are the chief organs for the maintenance of the equilibrium ; they fall over when the eyes are closed. [This is well illustrated in cases of locomotor ataxia (p. 672).] Frog. — A frog with its cerebrum removed retains its power of maintaining its equilibrium. It can sit, spring or execute complicated coordinated movements when appropriate stimuli are applied ; when placed on its back, it immediately turns into its normal position on its belly ; if stimulated, it gives one or two springs and then comes to rest ; when thrown into water, it swims to the margin of the vessel, and it may crawl up the side, and sit passive upon the edge of the vessel. When incited to move, it exhibits the most complete harmony and unity in all its movements. It sits on the same place continually as if in sleep, it takes no food, it has no feelings of hunger and thirst, it shows no symptoms of fear, and ultimately, if left alone, it becomes desiccated like a mummy on the spot Fig. 419. Frog without its cerebrum avoiding an object placed in its path. Fig. 420. Frog without its cerebrum moving on au inclined board ( Goltz ). Fig. 421. Pigeon with its cerebral hemispheres removed. where it sits. [If the flanks of such a frog be stroked, it croaks with the utmost regularity according to the number of times it is stroked. Langendorff has shown that a frog croaks under the same circumstances when both optic nerves are divided. It seems to be influenced by light ; for, if an object be placed in front of it so as to throw a strong shadow, then on stimulating the frog it will spring not against the object, a , but in the direction, b (Fig. 419). Steiner finds that if a glass plate be substituted for an opaque object like a book, the frog always jumps against this obstacle. Its balancing movements on a board are quite remarkable and acrobatic in character. If it be placed on a board, and the board gently inclined (Fig. 420), it does not fall off as a frog merely with its spinal cord will do, but as the board is inclined so as to alter the animal’s centre of gravity it slowly crawls up the board until its equilibrium is restored. If the board be sloped as in Fig. 420 it will crawl up until it sits on the edge, and if the board be still further tilted, the frog will move as indicated in the figure. It only does so, however, when the board is inclined, and it rests as soon as its centre of gravity is restored. It responds to every stimulus just like a complex machine, answering each stimulus with an appropriate action.] 45 706 REMOVAL OF THE CEREBRUM. A pigeon without its cerebral hemispheres behaves in a similar manner (Fig. 42 1). When undisturbed it sits continuously, as if in sleep , but when stimulated it shows complete harmony of all its movements ; it can walk, fly, perch, and balance its body. The sensory nerves and those of special sensation conduct impulses to the brain ; they only discharge reflex movements, but they do not excite conscious impressions. Hence the bird starts when a pistol is fired close to its ear; it closes its eyes when it is brought near a flame, and the pupils contract ; it turns away its head when the vapor of ammonia is applied to its nostrils. All these impressions are not perceived as conscious perceptions. The perceptive faculties — the will and memory — are abolished ; the animal never takes food or drinks spontaneously. But if food be placed at the back part of its throat it is swallowed [reflex act], and in this way the animal may be maintained alive for months {Flour ens, Longet , Goltz , and others'). Mammals (rabbit), owing to the great loss of blood consequent on removal of the cerebrum, are not well suited for experiments of this kind. Immediately after the operation they show great signs of muscular weakness. When they recover they present the same general phenomena; only when they are stimulated they run, as it were, blindfold against an obstacle. Vulpian observed a peculiar shriek or cry which such a rabbit makes under the circumstances. Sometimes even in man a peculiar cry is emitted in some cases of pressure or inflammation rendering the cerebral hemispheres inactive. Observations on somnambulists show that in man also complete harmony of all movements may be retained, without the assistance of the will or conscious impressions and perceptions. As a matter of fact, many of our ordinary move- ments are accomplished without our being conscious of them. They take place under the guidance of the basal ganglia. The degree of intelligence in the animal kingdom is, in relation to the size of the cerebral hemispheres, in proportion to the mass of the other parts of the central nervous system. Taking the brain alone into consideration, we observe that those animals have the highest intelligence in which the cerebral hemispheres greatly exceed the mid-brain in weight. The mid-brain is repre- sented by the optic lobes in the lower vertebrates, and by the corpora quadrigemina in the higher vertebrates. In Fig. 428, VI represents the brain of a carp; V, frog; and IV, pigeon. In all these cases 1 indicates the cerebral hemispheres ; 2, the optic lobes ; 3, the cerebellum ; and 4, the medulla oblongata. In the carp the cerebral hemispheres are smaller than the optic lobes, in the frog they exceed the latter in size. In the pigeon the cerebrum begins to project backward over the cerebellum. The degree of intelligence increases in these animals in this proportion. In the dog’s brain (Fig. 428,11) the hemispheres completely cover the corpora quadrigemina, but the cerebellum still lies behind the cerebrum. In man the occipital lobes of the cerebrum completely overlap the cerebellum (Fig. 424). [The projection of the occipital lobes over the cerebellum is due to the development of the frontal lobes pushing backward the convolutions that lie behind them, and not entirely to increased development of the occipital lobes.] Meynert’s Theory. — According to Meynert, we may represent this relation in another way. As is known, fibres proceed downward from the cerebral hemispheres through the crusta or basis of the cerebral peduncle. These fibres are separated from the upper fibres or tegmentum of the peduncle by the locus niger, the tegmentum being connected with the corpora quadrigemina and the optic thalamus. The larger, therefore, the cerebral hemispheres the more numerous will be the fibres proceeding from it. In Fig. 428, II, is a transverse section of the posterior corpora quadrigemina, with the aqueduct of Sylvius and both cerebral peduncles of an adult man ; /, p, is the crusta of each peduncle, and above it lies the locus niger, s. P'ig. 428, IV, shows the same parts in a monkey ; III, in a dog; and V, in a guinea pig. The crusta diminishes in the above series. There is a cor- responding diminution of the cerebral hemispheres, and at the same time in the intelligence of the corresponding animals. Sulci and Gyri. — The degree of intelligence also depends upon the number and depth of the convolutions. In the lowest vertebrates (fish, frog, bird) the furrows or sulci are absent (Fig. 428, IV, V, VI) ; in the rabbit there are two shallow furrows on each side (HI). The dog has a com- plexly furrowed cerebrum (I, II). Most remarkable is the complexity of the sulci and convolu- tions of the cerebrum of the elephant, one of the most intelligent of animals. Nevertheless some very stupid animals, as the ox, have very complex convolutions. The absolute weight of the brain cannot be taken as guide to the intelligence. The elephant has absolutely the heaviest brain, but man has relatively the heaviest brain. The mean weight of the brain in man is about 1358 grammes; of woman, 1220 grammes REACTION TIME. 707 ( Bischojf). [We ought, also, to take into account the complexity of the convolutions and the depth of the gray matter, its vascularity, and the extent of anastomoses between its nerve cells.] Time an Element in all Psychical Processes. — Every psychical process requires a certain time for its occurrence — a certain time always elapses between the application of the stimulus and the conscious reaction. Nature of Stimulus. Reaction Time. Name of Observer. Shock on left hand .12 Exner. Shock on forehead •13 Do. Shock on toe of left foot •17 Do. Sudden noise •13 Do. Visual impression of electric spark •15 Do. Hearing a sound .l6 Donders. Current to tongue causing taste • l6 i v. Vintschgau and Honigschmied. Saline taste •15 Do. Taste of sugar .16 Do. “ acids .l6 Do. “ quinine •23 Do. Reaction Time. — This time is known as “ reaction 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 perception, 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 afferent nerves to the centre, and (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 sound is 0.136 to 0.167 second; for taste, 0.15 to 0.23; touch, 0.133 to 0.201 second [Horsch, v. Vintschgau and Hon igsch m ied, Auerbach, 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 ( v . Vintschgau). l'he time is increased with very strong stimuli, and when objects difficult to be distinguished are applied ( v . Helmholtz and Baxt). The time required to direct the attention to a number consisting of 1 to 3 figures, Tigerstedt and Bergquist found to be 0.015 to °-°35 second. Alcohol and the anaesthetics alter the time; according to their degree of action they shorten or lengthen it ( Kraplin ). 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 to 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 left 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 affect the reaction time. Ether and chloroform 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 afferent 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 differ, however, from normal mental processes. They consist either 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 (g 70, 3, c), the respiration ($ 127, 4), the gastric and intestinal movements ($ 213, 4), the formation of heat (§ 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 sensory or auditory stimuli are applied, and that the more the lighter the 708 HYPNOTISM. sleep; they are widest at the moment of awaking ( Plotke ). [Hughlings- Jackson finds that the retina is more anaemic than in the waking state.] During sleep there seems to be a condition of increased action of certain sphincter muscles — those for contracting the pupil and closing the eyelids (. Rosenbach ). The soundness of the sleep may be determined by the intensity of the sound required to waken a person. Kohlschiitter found that at first sleep deepens very quickly, then more slowly, and the maximum is reached after one hour (according to Monninghoff and Priesbergen after 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 — Preyer ) as producers of sleep. Sleep cannot be kept up for above a certain time, nor can it be inteirupted voluntarily. Many narcotics rapidly produce sleep. [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, influence the whole metabolism. Strumpell 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 stroking the skin. In some people the mere idea of the condition suffices. A hypnotized person is no longer able to open his eyelids when they are pressed together. This is followed by spasm of the apparatus for accommodation in the eye, the range of accommodation is diminished, and there may be deviation of the position of the eyeballs; then follow phenomena of stimulation of the sympathetic in the oblongata; dilatation of the fissure of the eyelids and the pupil, exophthalmos, and increase of the respiration and pulse. At a certain stage there may be a great increase, in the sensitiveness of the functions of the sense organs, and also of the muscular sensibility. Afterward there may be analgesia of the part stroked, and loss of taste ; the sense of temperature is lost less readily, and still later that of sight, smell, and hearing. Owing to the abolition or suspension of consciousness, stimuli applied to the sense organs do not produce conscious impressions or perceptions. But stimuli applied to the sense organs of a hypnotized person cause movements, which, however, are unconscious, although they stimulate voluntary acts. In persons with greatly increased reflex excitability, voluntary movements may ex- cite reflex spasms ; the person may be unable to cobrdinate his organs for speech. Types. — According to Griitzner, there are several forms of hypnotism : (i) Passive sleep , where words are still understood, which occurs especially in girls; (2) owing to the increased reflex ex- citability of the striped muscles certain groups of muscles maybe contracted — a condition which may last for days, especially in strong people ; at the same time ataxia may occur, and the muscles may fail to perform their functions (artificial catalepsy). During the stage of lethargy in hyster- ical persons the tendon reflexes are often absent ( Charcot and Richer ) ; (3) autonomy at call , i. e., the hypnotized person — in most cases the consciousness is still retained — obeys a command, in his condition of light sleep. When the hand is grasped or the head stroked he executes involuntary movements — runs about, dances, rides on a stool, and the like ; (4) hallucinations occur only in some individuals when they waken from a deep sleep, the hallucinations (usually consisting of the sensation of sparks of fire or odors) being very strong and well pronounced; (5) imitation is rare, ordinary movements, such as walking, are easily imitated, the finer movements occur rarely. The “echo speech” is produced by pressure upon the neck, speaking into the throat, or against the abdomen. Pressure over the right eyebrow often ushers in the speech. Color sensation is sus- pended by placing the warm hand on the eye, or by stroking the opposite side of the head ( Cohn ). Stroking the limbs in the reverse direction gradually removes the rigidity of the limbs and causes the person to waken. Blowing on a part does so at once. Insane persons can be STRUCTURE OF THE CEREBRUM. 709 hypnotized. Disagreeable results follow only when the condition is induced too often and too con- tinuously. Hypnotism in Animals. — A hen remains in a fixed position when an object is suddenly placed before its eyes, or when a straw is placed over its beak, or when the head of the animal is pressed on the ground and a chalk line made before its beak (Kircher’s experimentum mirabile, 1644). [Langley has hypnotized a crocodile.] Birds, rabbits, and frogs remain passive for a time after they have been gently stroked on the back for a time. Crayfish stand on their head and claws ( Czermak ). 375. STRUCTURE OF THE CERE- BRUM— MOTOR CORTICAL CEN- TRES. — [Cerebral Convolution. — A vertical section of a cerebral convolution consists of a thin layer of gray matter externally inclosing a white core (Fig. 423). The cortex consists of cells embedded m a matrix, and to these proceed nerve fibres from the white matter. The cells of the cortex vary in size, form, and distribution in the different layers and also in different convolutions. Taking such a convolution as the ascending frontal we get the appearances shown in Fig. 422. It is cov- ered on its surface by the pia mater. (1) The most superficial layer is narrow, and consists of much neuroglia, a network of branched nerve fibrils, and a few scattered small multipolar nerve cells; (2) a layer of close-set small pyramidal nerve cells ; (3) the thickest layer or formation of the cornu ammonis, consisting of several layers of large pyramidal cells , which are larger in the deeper than in the more superficial layers. Each cell is more or less pyramidal in shape, giving off several processes — (a) an apical 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 ; ( b ) the unbranched median basilar process, which is an axial cylinder process, and becomes continuous with the axial cylinder of a nerve fibre of the white matter. It ultimately becomes invested by myelin. ( Fibres of the lens ; 2, transverse sec- lens. This is generally due to fatty degeneration of the fibres, tions ol the lens 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 diabetes 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 membrane 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 ( ScJnvalbe , 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 ( Gerlach ). Nevertheless, the zonule represents a stretched mem- brane, holding the lens in position, and may, 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 ( Henle , Iwanoff). P'rom 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 foetus, 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 Fig. 456. 758 INTRAOCULAR PRESSURE, watery fluid, containing the organic and inorganic bodies in solution. According to Younan, 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 cortex 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 foetus. It can readily be injected by 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 [Schwalbe). 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. Horizontal section of the entrance of the optic nerve and the coats of the eye. a, inner, b, outer layers of the retina ; c, choroid ; d, sclerotic ; e, physiological cup ; /, central artery of retina in axial canal ; g, its point of bifurcation ; h, lamina crihrosa ; /, outer (dural) sheath ; in, outer (subdural) space; n , inner (subarachnoid) space ; r, middle (arachnoid) sheath ; p, inner (pial) sheath ; i, bundles of nerve fibres ; k, longitudinal septa of connective tissue. nerve has three sheaths — (1) the dural; (2) the arachnoid; and (3) the pial sheath, derived from the corresponding membranes of the brain. Two lymph spaces lie between these three sheaths — the subdural space between 1 and 2, and the subarachnoid space between 2 and 3 (Fig. 547). Both spaces are lined by endothelium; and the fine trabeculae passing from one wall to the other are similarly covered. According to Axel Key and Retzius, these lymph spaces communicate an- teriorly with the perichoroidal space. The aqueous humor closely resembles the cere bro -spinal fluid, and contains albumin and sugar ; the former is increased, and the la‘ter disappears after death. The same occurs in the vitreous. The albumen increases when the difference between the blood pressure and the intraocular pressure rises. Such variations of pressure, and also intense stimuli applied to the eye, cause the production of fibrin in the anterior chamber (Jesner and Griinhagen). Intraocular Pressure. — The cavity of the bulb is practically filled with watery fluids, which, during life, are constantly subjected to a certain pressure, the “ intraocular pressure.” Ultimately, this depends upon the blood pressure within the arteries of the retina and uvea, and must rise and fall with it. The pressure is determined by pressing upon the eyeball, and ascertaining whether it is tense, or soft and compressible. Just as in the case of the arterial pressure, the intraocular pres- > DIOPTRIC OBSERVATIONS. 759 sure is influenced by many circumstances ; it is increased at every pulse beat and at every expiration, while it is decreased during inspiration. The elastic tension of the sclerotic and cornea regulates the increase of the arterial pressure by acting like the air chamber in a fire engine ; thus, when more arterial blood is pumped into the eyeball, more venous blood is also expelled. The constancy of the intraocular pressure is also influenced by the fact that, just as the aqueous humor is removed, it is secreted, or rather formed, as rapidly as it is absorbed [\ 392). The secretion of the aqueous humor occurs pretty rapidly, as may be surmised from the fact that haemoglobin is found in the aqueous humor half an hour after dissolved blood (lamb’s) is in- jected into the blood vessels ol a dog. It is rapidly reformed, after evacuation, through a wound in the cornea. According to Knies, the watery fluid within the eyeball is secreted, especially from the chorio-capillaris, and reaches the suprachoroidal space, in the lymph sheaths of the optic nerve, and partly through the network of the sclerotic. It saturates the retina, vitreous, lens, and for the most part passes through the zonula ciliaris into the posterior chamber, and through the pupil into the anterior chamber. The movements of the fluid within the eyeball have been recently studied by Ehrlich, who used fluorescin, an indifferent substance, which on being introduced into the body passes into the fluids of the eyeball, and in a very dilute solution may be recognized by its green fluor- escence in reflected light. From observations on the entrance of this substance into the eye Scholer, and Uhthoff regard the posterior surface of the iris and the ciliary body as the secretory organs for the aqueous humor. It passes through the pupil into the anterior chamber ; some passes into the lens, and along the canal of Petit into the vitreous humor ( PJiuger ). Section of the cervical sym- pathetic, and still more of the trigeminus, accelerates the secretion of the aqueous, but its amount is diminished. If the substance is dropped into the conjunctival sack it percolates toward the centre of the cornea, and through the latter into the anterior chamber [PJiuger). The outflow of the aqueous humor, according to Leber and Heisrath, takes place chiefly between the meshes of the ligamentum pectinatum iridis (Fig. 449, m, m), through which it passes into the channels of the circulus venosus, and the canal of Schlemm (z, k). A very small part of the aqueous passes through the cornea into the sub-conjunctival connective tissue, and even into the conjunctival sack. After burning the limbus corneae with a hot needle this outflow is arrested, the eyeball becomes very hard, so that the intrabulbar vessels are subjected to high pressure [Scholer). Perhaps there is a direct communication between the anterior ciliary veins and the anterior chamber (p. 754). None of the water is conducted from the eyeball by any special efferent lymphatics [Leber). Under normal circumstances the pressure is nearly the same in the vitreous and aqueous chambers, but atropin seems to diminish the pressure in the former and to increase it in the latter, whilst Calabar bean has an opposite action [Ad. Weber). Arrest of the outflow of the venous blood often increases the pressure in the vitreous, and diminishes that in the aqueous chamber. Compression of the bulb from without causes more fluid to pass out of the eye temporarily than enters it. The diminution of the intraocular pressure is well marked after section of the trigeminus, while it rises when this nerve is stimulated. The statements vary regarding the effect of the sym- pathetic nerve upon the pressure. Interruption to the venous outflow increases the pressure, while an imperfect supply of blood, the outflow being normal, diminishes the pressure. The innervation of the blood vessels of the eye is referred to at $ 347. 385. DIOPTRIC OBSERVATIONS. — The eye as an optical instrument is comparable to a camera obscura ; in both an inverted diminished image of the objects of the external world is formed upon a background, the field of projection. [In the case of the eye this is represented by the retina ] Instead of the single lens of the camera, the eye has several refractive media placed behind each other — cornea, aqueous humor, lens (whose individual parts — capsule, cortical layers, and nucleus, all possess different refractive indices), and vitreous humor. Every two of these adjacent media are bounded by a “ refractive surface,” which maybe regarded as spherical. The field of projection of the eye is the retina, which is colored with the visual purple [Boll, Kiihne). As this substance is bleached chemically by the direct action of light, so that the pictures may be tem- porarily fixed upon the retina, the comparison of the eye with the camera of the photographer be- comes more striking. In order that the passage of the rays of light through the media of the eye may be rightly understood, we must know the following factors: (1 ) the refractive indices of aU the media ; (2) the form of the refractive surfaces; (3) the distance of the various media from each other, and from the field of projection or retina. Action of a Converging Lens. — We must know how a convex lens acts upon light. In a convex lens we distinguish the centre of curvature (Fig. 458, I, m, m x ), i. e., the centre of both spherical surfaces. The line connecting both is called the chief axis ; the centre of this line is the optical centre of the lens ( the object is to find the direction of the refracted way. From 0 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 is 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 p. Draw the line p parallel to m Z. The line joining 0 to n is the direction of the refracted ray. On making a line, n , s, perpendicular to m Z, n s = b p. Further, ns — sine <) = r. So that a b : s n (or : b p) . . . 3 = 3 : 2 or sm. i : sin. r = 0 2 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 a b ( 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 ; m , as the point of intersection of all these, is called the nodal point. The line which connects m with the vertex of the spherical surface, x, 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 rays (a to a b ), 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 (p x ) of the second medium. This is called the second principal focus. A plane in this point perpendicular to O Q is called the second Fig. 461. k E focal plane (C, D). (2) All rays (c to c 2 ), which in the 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 (c x , 7 n r) meets this. (In this case the angle formed by the rays c to c 2 with C Q must be very small.) The propositions 1 and 2 of course maybe reversed; the divergent rays pro- ceeding from p toward a b pass into the first medium parallel to each other, and also with the axis C Q (a to ; and the rays proceeding from r pass into the first medium parallel to each other, but not parallel to the axis O Q (as c to c 2 ). (3) All rays, which in the second medium are parallel to each other (b to b 5 ) and with the axis O Q, reunite in a point in the first medium (/), called the first focal point ; of course, the converse of this is true. A plane in this point perpendicular to Fig. 462. O Q is called the 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 p x ) from the principal focus ( x ) ; thus m x = p x x — p x. From these comparatively simple propositions it is easy to determine the fol- lowing points : — 1. 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; a , b, the optical axis; k, the nodal point; p the first and p x the second principal 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, k, Q parallel to x, 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, c , d, a,b, k, p, and p lt C, D are as before. Suppose a luminous point ( 0 ) 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 ( 0 , x) parallel to the axis (a, b). The parallel rays (a, e, and 0, x) reunite in p according to proposition 1). Prolong x,p y until it intersects the ray (0, P), then the image of 0 is at P, the rays of light ( 0 , x, and 0 6) proceeding from the luminous point ( 0 ) 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. 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 a , b (Fig. 464, I), represent the optical axis ; H, the first focal point determined by calculation ; h, k, the principal plane ; H, the second focal point ; h x , h x > the second principal plane ; k, the first, and k lf the second nodal point ; F, the second focal point ; and F 2 , Fj, the second focal plane. Make the ray of direction/, k lf 764 FORMATION OF A RETINAL IMAGE. parallel to m lt n 1 . According to proposition 2, p, k x , and m lt n x must meet in a point of the plane Fj.Fj. As /, k x passes through unrefracted, the ray from n x must, therefore, fall at r\ n x r is, therefore, the dii*ection of the refracted ray. Construction of the Focal Point. — Let 0 (Fig. 464, II) be a luminous point, what is the posi- tion of its image in the last medium ? Prolong from 0 the ray of direction 0, 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 a , b goes through F ; m, k x as the ray of direction passes through unrefracted. O, where n, F, and m, k x 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 air 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 : (1) The first principal point is 2.1746 mm. ; and (2) the second principal point is 2.5724 mm. behind the anterior surface of the cornea. (3) The first nodal point , 0.7580 mm. ; and (4) Fig. 465. the second nodal point, 0.3602 mm. in front of the posterior surface of the lens. (5) The second principal focus, 14.6470 mm. behind the posterior surface of the lens; and (6) the 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 reduced 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 d, passes without refraction through the nodal point, k. Further, as the focal point for the luminous point, A, is upon the retina, all the rays proceeding from A must reunite in d. 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 the combined nodal point, k , this is also called the ‘ ‘ point of intersection of the visual rays. 1 ’ 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, k, and c, d , k , are similar, A, B : c, d = f, k : k, g, so that c, d = (A, B, k, g ) : f k. All these values are known, viz., k> g = 15.16 mm. ; further,/, k — a, k X a >/> where a,f is measured directly, and a, k = 7.44 mm. The size of A B is measured directly. The angle, A k 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 : — 1. 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 1, and water 1.335. Fig. 466. Scheme of the ophthalmometer of Helmholtz. 2. The 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 mm. 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 effectively on Kuhne’s artificial 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, 1723), 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. The 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 lower 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 TIIE 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 radius of the curved surface may be calculated therefrom ( Helmholtz , Donders, Mauthner). Fluorescence. — All the media of the eye, even the retina, are slightly fluorescent ; the lens most, the vitreous humor least ( v . Helmholtz). Erect Vision. — As the retinal image is inverted , we must explain how we see objects erect. By a psychical act, the impulses from any point of the retina are again referred to the exterior, in the direction through the nodal point ; thus the stimulation of the point, d (Fig. 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 the simple experiment that pressure upon the outer aspect of the eyeball is projected or referred to the inner aspect 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 | 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, e.g., 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 obtained upon the screen. If the screen be placed nearer to the lens (Fig. 760, IV, a, b), or further away from it (e, d), no distinct image of the object is formed, but diffusion circles are obtained, because in the former case the rays have not united, and in the latter because the rays, after uniting, have crossed each other and become divergent. If the luminous point be brought nearer to, or removed further from, the lens, in order to obtain a distinct image, in every case the screen must be brought nearer, or removed from the lens, to keep the same distance between the lens and the screen. If, however, the screen be fixed permanently, while the distance between the luminous point and the lens varies, a distinct image can only be obtained upon the screen, provided the lens, as the luminous point approaches it, becomes more convex, i.e., refracts the rays of light more strongly — conversely, when the distance between the luminous point and the lens becomes greater, the lens must become less curved, i.e., refract less strongly. In the eye, the projection surface or screen is represented by the retina, which is permanently fixed at a certain distance ; but the eye has the power of forming distinct images of near and distant objects upon the retina, so that the refractive power, i. e., the form of the crystalline lens in the eye, must undergo a change in curvature corresponding in every case to the distance of the object. [It is imporiant to remember that we cannot see a near object and a distant one with equal distinctness at the same time , and hence arises the necessity for accommodation.] Accommodation. — By the term accommodation of the eye is understood the property of the eye, whereby it forms distinct images of distant as well as near objects upon the retina. This power depends upon the fact that the crystalline lens alters its curvature, becoming more convex (thicker), or less curved (flatter), according to the distance of the object. When the lens is absent from the eyeball, accommodation is impossible ( Th . Young , Donders — p. 758). During rest [or negative accommodation], or when the eye is passive, it is accommodated for the greatest distance, i. e., images of objects placed at an infinite distance (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 (Dove). 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 ( Ptolemy , 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 1 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. 508 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 room at a bright vertical line, and then bend the head toward the shoulder, the line appears to be bent in the opposite direction (. Aubert ). 404. PROTECTIVE ORGANS OF THE EYE.— I. The eyelids are represented in section in Fig. 509. The tarsus is in reality 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 papillae. It is covered by stratified prismatic epithelium. Coiled glands occur in ruminants just outside the margin of the cornea (Meissner), while outside this, toward the outer angle of the eye in the pig, there are simple glandular sacks ( Manz ). Waldeyer describes modified sweat glands in the tarsal margins in man. Small lymphatic sacks in the conjunctiva are called trachoma glands. Krause found end bulbs 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 glands. The closure of the eyelids is accomplished by the orbicularis palpebrarum ( facial nerve, § 349), whereby the upper lid falls in virtue of its own weight. This muscle contracts — (1) 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 fornix 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 ( Wedl ). 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. Weber). 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 Waldeyex). A, cutis ; i, epidermis; 2, chorium ; B and 3, subcuta- neous connective tissue ; C and 7, orbicularis muscle and its bundles ; D, loose sub-muscular connective tissue ; E, insertion of H. Muller’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; 12, 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, pretarsal or sub-muscular connective tissue ; 21 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 Hasner 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 orbicularis muscle, so that the tears must be forced toward the nose. Lastly, Stell- wag 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. Landois 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 (. Herzenstein ). 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 light 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 ( Mogaard ). Composition. — The tears are alkaline, saline to taste, and represent a “serous ” secretion. Water, 98.1 to 99 ; 1.46 organic substances (0.1 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 increased 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 medusas, 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 echinodermata there are only accumulations of pigment. Among the annulosa there are several grades of visual apparatus — (1) Without a cornea there may be only one crystal sphere (nervous end organ) near the brain, as in 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 Leeuwenhoek : 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. Among 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 amphioxus 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-fishes, 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. There 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 (15 21 ) 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 (1583) 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 ( 1 6 1 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, Schemer (f 1650), mentions, however, that the lens becomes more convex by the ciliary 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’Armato degli Armati di Fir (f 1317), and the monk, Alessandro de Spina (f 1313), invented spectacles. Kepler ( 1 61 1 ) and Descartes (1637) described their action. Mayo (f 1852), 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 — Soemmering ( 1 79 1 ) 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 mechanical stimulation of the wave motion of the lymph of the labyrinth . 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 (h), short process (k f)> and handle ( m ) ; a, incus with its short process (x) and long process — the latter is united to the stapes ( s ) by means ot the Sylvian ossicle (2) ; P, middle ear ; o, fenestra ovalis ; r , fenestra rotunda ; x, beginning of the lamina spiralis of the cochlea ; pt, its scala tympani, and vt, its scala vestibuli ; V, vestibule ; S, saccule ; U, utricle ; H, semicircular canals, T E ; Eustachian tube. The long arrow indicates the line of traction 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 ( r ), 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 lie 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 may 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 (^), whose long process is inserted into it; the malleus moves the incus (a), and this the stapes (. s ), which transfers the move- ments of its plate to the perilymph of the labyrinth. 3. Direct Conduction to the Fenestra. — In man, inconsequence of occasional disease of the middle ear, whereby the tympanic membrane and auditory ossicles may be destroyed, the auditory apparatus 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 W. Weber), i e., 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 A is the wave length of a tone, t in seconds the duration of a vibration of the body producing the wave, then A = n t, where n — 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 reflection is always equal to the angle of incidence. Wave Movements. — We distinguish — I. Progressive wave movements which occur in two forms — (1) As longitudinal waves ( Chladni ), 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. 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 to 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. Fig 408. EAR MUSCLES— EXTERNAL AUDITORY MEATUS.— External Ear.— When the external ear is absent, 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 outward ; and those waves which reach the deep part 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. — (1) The whole ear is moved by the retrahenter, attrahens, and attollens. (2) The form 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- ulae 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 effect 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 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 the sound waves first impinge upon its wall, 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]. The external auditory meatus and the tympanic cavity. M, osseous spaces in the temporal bone ; Pc', cartilaginous part of the meatus ; L, membranous union between both : F, ar- ticular surface for the condyle of the lower jaw (after Urbantschitsch). 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 o. 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 0 . 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). 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 coveied 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. 514. Fig. 513. Fig. 512. — Tympanic membrane with the auditory ossicles (left) seen from within. Ci, incus; Cm, malleus ; Ch, chorda tympani ; T, pouch-like depression (after Urbantschitsch). Fig. 513. — Tympanic membrane and the auditory ossicles (left) seen from within, i.e., from the tympanic cavity. M, manubrium or handle of the mal- leus; T, insertion of the tensor tympani ; h, head; l¥, long process of the malleus ; a, incus, with the short (K) and the long (/) process ; S, plate of the stapes ; Ax, Ax, is the common axis of rotation of the auditory ossicles ; S, the pinion-wheel arrangement between the malleus and incus. Fig. 514. — Tympanic membrane of a new- born child seen from without, with the handle of the malleus visible on it. At, tympanic ring with its anterior ( v ) and posterior ( h ) ends. 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 apex 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 5 2 818 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 the 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. 515. Fig. 515. — Ear specula of various sizes. Fig. 516. — Toynbee's artificial membrana tympani. Fig. 517. — The audi- tory ossicles (right). C.m, head; C, neck; Pbr, short process; Prl, long process; M, handle of the malleus; Ct, body ; G, articular surface ; h, short, and v, long process of the incus ; O.S., so-called lenticular ossicle ; C.s., head ; a, anterior, and p, posterior limb ; P, plate of the stapes. the other tones. In this way, all 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 sympathetic 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- bee). [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 — (1) 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 the pressure on the lymph of the labyrinth. Mechanism. — The 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, n ) 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, external meatus ; M, membrana tympani, which is attached to the handle of the malleus, n , and near it the short process, / ; h, head of the malleus ; a, incus ; k , its short process with its ligament ; l, long process ; s, Sylvian ossicle ; S, stapes ; Ax, Ax, is the axis of rotation of the ossicles, it is shown in perspective, and must be imagined to penetrate the plane of the paper ; t, 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 incus , a , is only partially fixed 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, h , 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, Ax, Ax). In the inward 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 powerful 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 lymph 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 ( Politzer , Hen- 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 microscope (Buck, v. Helmholtz , Mach and Kessel). All the experiments showed that the 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 6)4 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 light 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 lymph of the labyrinth. The CONTRACTION OF THE TENSOR. 821 tensor tympani, which lies in an osseous groove 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, t (Fig. 518), then the handle of the malleus ( n ) 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 elasticity of the rotated axial ligament 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 ( Joh . Muller). — 1. 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 sympathetic 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 pupil and tension of the membrana tympani — the too intense action of the specific stimulus from causing too great stimulation, and both adapt the sensory apparatus for the action of moderate or weak stimuli. This movement in both membranes is brought about 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 membrana 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. Muller ). Normally, the tensor tympani is excited rejlexly. 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 inw'ard. 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 ( Lucae ). When yawning, 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 in 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 Fig. 519. Tensor tympani — the Eustachian tube (left). 822 THE EUSTACHIAN TUBE. Fig. 520. 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 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 oulward. The stapes is thereby more fixed, 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 rejlexly by scratching the skin in front of the meatus, or by gently stroking the outer margin of the orbit ( Henle ). Other Views. — According to Lucae, when the stapes is displaced obliquely, its head forces the long process of the incus, and also the membrana tympani, outward , so that it is regarded as an antagonist 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 fixing 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 palpebrarum, 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. EUSTACHIAN TUBE— TYMPANUM.—' The Eustachian tube [4 centimetres in length, 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 . Troltsch ), sive dilator tubae ( Riidinger)~\ 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 permanently , 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. The 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 TYMPANUM. 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 deglutition and during phonation, the lower wall of the pharyngeal opening is raised, and the opening thereby narrowed ( Lucae ). The contraction of the tensor, occurring during the latter part of the act of deglutition, dilates the tube. Other Views. — According to Riidinger, 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, i. 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 wall are the fenestra ovalis and rotunda, the ridge of the aqueductus Fallopii, the promontory and the pyramid. Fig. 521. Eustachian catheter. Fig. 522. Politzer’s ear bag. 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 this 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 c atheterizing 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 subsequent 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 unfrequcntly 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 the surgeon compresses the bag, and the patient’s mouth being closed, air is forced through the 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 ( Politzer ). 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 must correspond in number and intensity to the vibrations of the auditory ossicles, and must also excite the free termina- tions of the auditory nerve, which float free in the endolymph. 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 the 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 inner 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 equal intensity in both ears. In this case the sound is conducted directly to the labyrinth by the cranial bones. In cases of disease Fig. 523. External appearance of the labyrinth, fenestra ovalis, cochlea to the left, and ( f) the upper, (h) horizontal, and (s) posterior semicircular canal (left). STRUCTURE OF THE LABYRINTH. 825 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 OF THE LABYRINTH, AND TERMINATION OF THE AUDITORY NERVE. — Scheme. — The vestibule (Fig. 524, III) contains two separate sacks, one of them the saccule, s (round sack or S. hemisphsericus), communicates with the ductus Fig. 524. 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, C s. The cochlea consists of 2]/ 2 turns of a tube disposed 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 lowet 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- alis cochlearis is blind, III, and divided toward the saccule, with which it communicates by means of the small canalis reuniens, C r ( Hensen ). 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 I»iACUL<« ACUSTIC.E AND COCHLEA. common ampulla for them. The membranous semicircular canals lie within the osseous canals, perilymph lying between the two. Perilymph 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 > an d passthrough the osseous aqueductus vestibuli to end blindly in the dura mater of the brain (Fig. Ill, R — Bottcher , Retzius). 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 ampullae, 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 (c) termi- Fig. 525. Fig. 526. The 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 — 1, commencement of the spiral tube of the cochlea ; 2, posterior semicircular canal, partly opened ; 3, horizontal ; 4, superior canal ; 5, utricle ; 6, saccule ; 7, lamina spiralis; 7', scala tympani; 8, ampulla of the superior membranous canal; 9, of the horizontal; 10, of the posterior canal. Fig. 526 shows the membranous labyrinth and nerves detached — 1, facial nerve in the internal auditory meatus ; 2, anterior division of the auditory nerve giving branches to 5, 8, and 9, the utricle and the ampullae of the superior and horizontal canals ; 3, 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 ; 11, 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, n, 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 // in length, so that the crista is largely covered with these hair cells ( Hartmann ), but between them are supporting cells like cylindrical epithelium ( a ), and not unfre- quently containing granules of yellow pigment. The hairs or “ auditory hairs ” ( M Schultze ) are composed of many fine fibres [Retzius). An excessively fine membrane (membrana tectoria) covers the hairs ( Pritchard , Lang). Maculae Acusticae. — The nerve terminations in the maculae acusticae of the saccule and utricle are exactly the same as in the ampullae, only the free surface of their membrana tectoria is sprinkled with small, white, chalk-like 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 supporting apparatus composed of the so-called Corti’s arches, each of which consists of two Corti’s rods (z,y), 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 {Claudius). There are about 4500 outer rods ( Waldeyer). 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 fi in the upper, the outer rods 47 u and 69 fj. respectively. The span of the arches also increases ( Hensen ). [The arches leave a triangular 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 {Hensen, Waldeyer). There is one row of inner cells (i) which rests on a layer of small granular cells (K) ( Bottcher , Waldeyer ); the outer cells {a, a) number 12,000 in man ( Relzius ), 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 {Lavdowsky). [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 , Gott stein, Lavdowsky , Retzius). Fig. 527. Scheme of the ductus cochlearis and the organ of Corti. N, cochlear nerve; K, inner, and P, outer hair cells; n, nerve fibrils terminating in P ; a, a , supporting cells; d, cells in the sulcus spiralis ; 0, inner rod of Corti; Mb. 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 (o), 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 {Lavdowsky). [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 the 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 tympanum 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 {F. Bezold). 828 THE QUALITY OF A TONE. The perilymph of the inner ear flows away chiefly through the aqueductus cochleae, 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 noises. 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 bv 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 interval 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 noise 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 : — [(1) Intensity or force; (2) Pitch; (3) Quality, ti?nbre 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 , 1636) [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 (“ Klangfarbe ”) 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 different tones have a different pitch. 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 1st, 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 80 — all the holes being at equal distances from each other. If the disk be rotated, and air forced against each series of holes in turn , we distinguish successively the four tones of the accord (major chord with its octave) ; when all the four series are blown upon simultaneously, 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 next above it, is 1 : 2. In the second series we have 50 holes, which cause the pitch of the Third; hence, the relation of the Ground tone to the Third in this case is 40: 50, or 1 : i£ = |, i. e., for every vibration of the Ground tone there are | 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 : = §. In the same way we can estimate the pitch of the Fourth tone, and we find that the number of vibrations of the First, Third, Fifth, and Octave are to each other as 1 : | | : 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 |, the Minor Sixth with f, from the Minor Third with f , the Major Sixth = (*=)*; from the Fifth with f, the Fourth = J. These relations are known as the Inversions of 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 = 1, the Third E — the Fifth G = f, and the Octave = 2, we then derive from the Fifth or Dominant G a Major chord — this is G, B, Di. 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 vibrations of G : B is as C : E. When we substitute the values we obtain § : B = 1 : | — i. e., B = L 5 . But D 1 : B = G : E; so that D : J g 5 § : f, i. e., D 1 = *y 8 , or an octave lower, we have D = |. Deduce from F (subdominant) a Major chord, F, A, Cl. The relation of A : Cl= E : G, or A : 2 = | : |, i. e., A = |. Lastly, F : A = C : E, or F : f = 1 : f, i. e., F = f . So that all the tones of the scale have the following number of vibrations : I, C = 1 ; Ii, D = | ; III, E = |; IV, F = | ; V, G = § ; VI, A = g ; VII, B = V 5 ; 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 ( Scheibler , 1834), although in France it is taken at 435 vibrations per second. From this we can estimate the absolute number of vibrations for the tones 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 music are the double bass, E, with 41.25 vibrations, piano- forte C with 33, grand piano A 1 with 27.5, and organ C with 16.5. The highest notes in music are the piano-forte c v with 4224, and d v 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 viii with 40,960 vibrations as the audible tone; so that this embraces about 11 % octaves. [Audibility of Shrill Notes. — This varies very greatly in different persons ( Wollaston). There is a remarkable falling off of the power as age advances ( Galton ). For testing this, Galton 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 tube, whereby the pitch of the note is altered. 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’s Whistle. highest Fig. 528. 830 PERCEPTION OF QUALITY. 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 80,000 vibrations have been perceived. Diminished tension of the sound- conducting apparatus causes diminution of the perception foi high tones ( Blake ). 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 that are produced beyond the highest audible note, as by stroking small tuning-forks 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 range 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) ( Mach ), or even 16 to 20 vibrations Auerbach , Kohlrausch ) are necessary to produce a characteristic tone. When tones succeed each other rapidly, they are still perceived as distinct, when at least 0.1 second intervenes between two successive tones ( v . 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 -^-q, or even 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 and others for high notes. Both conditions are disadvantageous for hearing speech. Those who hear low notes best hear the highest consonants imperfectly. The low notes are heard abnor- mally loud in rheumatic facial paralysis, 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 hear- 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 (I 316 ). II. Perception of the Intensity of Tone. — The intensity of a tone depends upon the ampli- tude of the vibrations of the sounding body. The intensity of the tone is proportional to the square of the amplitude of vibration of the sounding body, i. 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. — 1. 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 1 milligram, and falling from a height of 1 mm. upon a glass plate, is heard at a distance of 5 cen- timetres ( Schafhault ). 415. PERCEPTION OF QUALITY— ANALYSIS OF VOWELS.- By the term quality (“ Klangfarbe ”), musical color or timbre , is understood a peculiar character of the tone, by which 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 their specific quality. Wherein lies the essence (“ Wesen ”) of tone color? The ANALYSIS OF VOWELS. 831 Fig. 529. investigations of v. Helmholtz have proved that, among mechanisms which produce tones, only those that produce pendulum-like vibrations, i. . Helmholtz). Resolution by the Cochlea. — Formerly, v. Helmholtz considered the rods of Corti to be the apparatus that vibrated and stimulated 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 (. Baginsky ). [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 Mysis. He found that certain of the minute hairs (auditory hairs) in the auditory organ of this animal, situate at the base of the antennae, 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 noises. 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, i. e . , 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 two 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 1 : 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. Suppose we take two organ pipes with 33 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 difference 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 beats. 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 Klange ”). — 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 M 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. We 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 toner Summational Tones. — It was formerly supposed that new tones could arise from the summation or addition of their number of vibrations, but it has been shown that these tones are, in reality, differential tones of a high order ( Appunn , 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 . Weber), 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 {Rayleigh). 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 behind 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 after 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 ( Brunton ). ] Entotical perceptions, which are due to causes within the ear itself, are such as hearing the pulse 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 hyperaesthesia 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 ($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 ( Urbantschitsch). Auditory After Sensations. — (1) Those 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 (Nuss- baumer , 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 ( Urbantschitsch , Eitelberg). Other Stimuli. — The auditory apparatus, besides being excited by spund waves, is also affected by heterologous stimuli. It is stimulated mechanically by a sudden blow on the ear. The effects of electricity and pathological conditions are referred to in $ 350. 419. COMPARATIVE — HISTORICAL. — The lowest fishes, the cyclostomata (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 (Hasse), 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, III). The Eustachian tube is always open in the whale. Among invertebrata the auditory organ is very simple in medusae 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 differentiation 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 bones of the head; while Fallopius (1561) described the vestibule, the semicircular canals, chorda tym- pani, the two fenestrae, the cochlea, and the aqueduct. Eustachius (f 1570) described the modio- lus, the lamina spiralis of the cochlea, the Eustachian tube, as well as the muscles of the ear ; Plater the ampullae (1583) ; Casseri (1600) the lamina spiralis membranacea. Sylvius (1667) discovered the ossicle called by his name ; Vesling (1641) the stapedius. 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: (1) 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 (M. Schultze). 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 fi), smooth rod, quite up to the free surface of the mucous membrane. In the frog ( n ), the free end carries delicate projecting hairs or bristles. In the deeper Fig. 534. N Fig. 533. — N, olfactory cells (human) ; n, from the frog ; E, epithelium of the regio olfactoria. Fig. 534 — Nasal and pharyngo-nasal cavities. L, levator elevation; P, j p., plica salpingo-palatina ; Cs, Cm, Ci, the three turbi- nated bones ( Urbj.ntsr kitsch). part of the mucous membrane the olfactory cells pass into, and become continuous with, varicose fine nerve fibres, which pass into the olfactory nerve (g 321, I, 1). According to 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 naso-palatine 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 (Klein).'] 839 Fig. 533. 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 (. Bidder ). 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). The 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 sniff several times, i. Merkel’s tactile cells ( Waldeyer). 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 F-g. 538. 846 SENSORY AND TACTILE SENSATIONS. fingers. They are larger than the end bulbs, and have numerous oval nuclei externally, while one to four nerve fibres 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 (Merkel), in the cells themselves, and according to others (Ranvier, Izquierdo, Hesse), in the protoplasmic transparent substance or disk lying between the cells. [This intercellular disk is the “disk tactil” of Ranvier, or the “ Tastplatte' 1 '' 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 papillae. 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 lamellae 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 ; a, tactile cells ; in, tactile disks ; c, epithelial cells. is bordered on each side 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 “ nerve rings'''' in the ears of the mouse. 5. [Other Modes of Ending of Sensory Nerves. — Some sensory nerves 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. These fibrils, as in the cornea (g 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. A 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, Rollett, 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: (1) Those which administer to painful 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 fistulae. 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, 1 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 (Fig. 540) upon the part of the skin to be investigated, and determine the smallest distance at which the two points are felt only as one impression. Sieveking’s sesthesiometer (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 number of tactile nerves in the correspond- 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 }£ on the flexor surface of the upper limb, and on the extensor surface. 4. The mode of application of the points of the aesthesiometer : ( 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. (V) 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 ( Czermak ). 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 ( Volkma?i?i ). [Fr. Galton finds that the reputed increased acuteness of the other senses in the case of the blind 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 Fig. 541. iEsthesiometer of Sieveking. 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 the 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 (Suslowa), 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 ( Rumpf ). 7. Ancemia, produced by elevating the limbs, or venous hypercemia (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 skm tested, and some poisons, e. g., 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 i'ESTHESIOMETRY. 849 still be distinguished as double by an adult. The corresponding numbers for a boy twelve years of age are given within brackets : — Millimetres. [II] Tip of tongue Third phalanx of finger, volar surface. 2.-2. 3 [1.7] Red part of the lip 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 f 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 Centre of palm s:- 9 . 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] [9-] Second phalanx of the fingers, dorsal surface ”•3 Back 113 [9-] volar Millimetres. i-3 [9] Eyelid Centre of hard palate . . . Lower third of the forearm surface In front of the zygoma .... Plantar surface of the great toe Inner surface of the lip . . . Behind the zygoma Forehead Occiput Back of the hand Under the chin Vertex Knee Sacrum, gluteal region .... Forearm and leg Neck Back at the fifth dorsal vertebra lower dorsal and lumbar region Middle of the neck 67.7 Upper arm, thigh and centre of the back 67.7 [31.6-40.6] - 13-5 [ 1 1 -3] r - 15- . 15.8 [11.3] . 15.8 [9 D . 20.3 .13.5] . 22.6 [ 1 5-8] . 22.6 [18.] . 27.1 22.6 . 3i- 6 22.6' .33-8 "22. 6 = • 33-8 = 22.6 = ; 3 i.6; [33-8] . 45-i [33-8] . 54- 1 [36.1] 54-1 Illusions of the sense of locality occur very frequently ; the most marked are: (1) 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 sesthesiometer, then they feel as if they were wider apart than when the two points are moved along the skin ( Fechner ). (3) A sphere, when touched with short rods, feels larger than when long rods are used ( Tourtual). (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 phenomena of the sense of space. Weber’s theory goes 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 administer thereto. He called 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 lie upon two adjoining circles, at another between two others with another circle intercalated between them. Wundt’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 locality of the sensation. Every cutaneous area, therefore, gives to the tactile sensation a “ focal 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 Fig. 542. A. B. Aristotle’s experiment. 850 THE PRESSURE SENSE. more obtuse. Separate impressions unite into a common one, as soon as the gradation of the local color becomes imperceptible. By practice and attention differences of sensation are experienced, which ordinarily are not observed, so that he explains 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. — 1. 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 difference 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 (g 430). Fig. 543. [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 baraesthesiometer, 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 ( b ) of a heavy support (T). One arm of the beam is provided with a screw (m) 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 (P), 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 (, h ) being closed, whenever pressure is exerted on the tube (D, D),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 fore arm, which perceive a pressure of 0.002 grm. ; the fingers first feel with a weight of 0.005 to °- OI 5 g rm * > the chin, abdomen, and nose with 0.04 to 0.05 grm. ; the finger nail 1 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 (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 2-9 : 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. Hering , Loewit , and Biedermann). 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 to -g 1 ^- (200 : 205 to 300 : 310 grm.). The dorsal surface of the last phalanx of the fingers, the fore arm, hand, 1st and 2d phalanx, the volar surface of the hand, fore arm, and upper arm, distinguishes differences of to (200 : 220 to 220 : 210 grm.). The anterior surface of the leg and thigh are similar to the fore arm. Then follow the dorsum of the foot and toes, the sole of the foot, and the posterior surface of the leg and thigh. Dohrn determined the smallest additional weight, which, when added to 1 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. ; 1st pha- lanx, 0.02 grm. ; leg, 1 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, 3.8 grms. 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 : 5 (E. H ; 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 ¥ -|~o 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. Vibrations 852 RESULTS OF THE TEMPERATURE SENSE. of strings are distinguished as such when the number of vibrations is 1506 to 1552 per second (v. Wittich and Grilnhagen). 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 heat 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, i. 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 applied successively at different temperatures: 1. Nothnagel uses small wooden cups with a metallic base, and filled with warm and cold water, the temperature being registered 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. — 1. 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 i5.5°-35° C., we distinguish distinctly differences of temperature of o .2°- o . i 6° R. with the tips of the fingers (. E . H. Weber). Tem- peratures just below that of the blood ( 33 0 — 27 0 C. — Nothnagel) are distinguished most distinctly 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 S3°~39° C., as well as between i4°-2 7° C. A temperature of 55 0 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 0 on the breast; 0.9 0 on the back ; 0.3 0 , back of the hand ; 0.4 0 , palm ; 0.2 0 , arm ; 0.4 0 back of the foot; 0.5 0 , thigh; o.6° leg; o.4°-o. 2 0 , 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 (E. 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 heat 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 0.1 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/i 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 the “ 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. When the skin is dipped first into water at io° C. we feel cold, and if it be then dipped at once into water at i6° 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, e.g ., the whole hand when placed in water at 29. 5 0 C. feels warmer than when a finger is dipped into water at 32 0 C. 3. Cold weights are judged to be heavier than warm ones. Pathological. — Tactile sensibility is only seldom increased (hyperpselaphesia), 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 abnormal condition of the sense of locality was described by Brown-Sequard, where three points were felt when only two were applied, 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 (Stirling) i\ 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 (“ Allochiria ”). 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 tactile paralysis .” Limbs which are “ sleeping ” feel heat and not cold (Herzen). 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 may 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 (e.g.) 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 peripheral 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 1 to 2 cm. apart (Fig. 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, 2). In neuralgia there is severe pain, oc- curring in paroxysms, with violent exacerbations and pain shooting into other parts (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 (1841). — 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 ( Tilrck) ; in the latter case there may be pro- nounced anaesthesia dolorosa (p. 853). Diminution or paralysis of the sense of pain (hypalgia and analgia) may be due to affections of the ends of the nerves, or of their course, or central terminations. Metalloscopy. — In hysterical patients suffering from hemianaesthesia, it is found that the feeling of the paralyzed side is restored, when small metallic plates or larger pieces of different metals are applied to the affected parts ( Burcq , Charcot). At the same time that the affected part recovers its sensibility the opposite limb or side becomes anesthetic. 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 sensibility 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 di>turbance. The muscular sense is also greatly aided by the sensibility of the joints, bones and 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 — (a) the movements in the unopposed muscles, as the movements of the limbs in space ; and (h) 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 (Sully).-] Methods of Testing. — Weights are wrapped in a towel 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 h\percesthesia ), as in anxietas tibiarum , 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 aequivoca, 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 “ Oinne vivum ex ovo” ( Harvey , or ex vivo). 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. The 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 [although under normal circumstances the hydra gives off 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 is traversed by a fine 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 hour-glass 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 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, composed of single loops radiating from the centre ( e ). 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 off 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 different 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 85ft Fig. 544. l r 1 % mu,\ Changes in a cell nucleus during karyokinesis. 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 two 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. g., 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 (hemi-metabolic). It also occurs in some arthropoda, and woims, e. g., trichina; the sexual form of the animal occurs in the intestine, the numerous larvce 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 ( Steenstrup ). — In this variety some of the members of the cycle can produce new beings non-sexually, 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 faeces. The eggs are fertilized after they are shed, and from them is developed an elliptical embryo, pro- vided with six hooklets, 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 (Cysticercus, Coenurus, or Echinococcus). The encysted capsule may contain one (cysticercus) or many (coenurus) sessile heads of the taenia. 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 hooklets 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 cellulosae in the pig, where it constitutes the measle in pork ; Teenia medio canellata, the encysted stage, in the ox ; Tcenia coenurus , 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;” Tcenia echinococcus , in the dog’s intestine ; the embryos or scolices occur in the liver of man as “ hydatids.” The medusae also exhibit alternation of generations, and so do some insects, especially the plant lice or aphides. VII. Parthenogenesis ( Owen v. Siebo/d). — 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 permit 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 trabeculae — 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 mediastinum. 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 compartment contains several seminal tubules, long con- voluted tubules 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, Fig. 545. T. albuginea. 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 by flattened epithelium. The vasa efferentia and coni 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 in 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 thick outer longitudinal layer, a thin 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 limellse, 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 (Jflein), or, according to Waldeyer, they Fig. 546. End of convo- luted tube. Narrow part. Rete testis. Fig. 547. Blood vessel. ilVu Transverse •iflj II 1 section of a tube il;l I of epididymis. Ciliated cylindrical epithelium. Blood vessel. Interstitial Transverse section of the tubules of the epididymis. Convoluted seminal tubule opening into a narrow straight tubule. 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 vesiculae 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 ' 1 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 sahs with an organic base (C 2 H 5 N). These crystals (Fig. 548) are said to be derived from the pros- 860 DEVELOPMENT OF SPERMATOZOA. tatic fluid, and are identical with the so-called Charcot’s crystals (Fig. 144, c , and \ 138). The prostatic fluid is thin, milky, amphoteric, or of slightly acid reaction, and is possessed of the seminal odor. The phosphoric acid necessary for the formation of the crystals is obtained from the seminal fluid. A somewhat similar odor occurs in the albumin of eggs not quite fresh. The secretion of the vesiculse seminales of the guinea pig contains much fibrinogen ( Hensen and Landwehr). The spermatozoa are 50 ft long, and consist of a flattened, pear-shaped head (Fig. 549, 1 and 2, k), which is followed bv a rod-shaped middle piece, m (Schweigger- Seidel ) , and a long tail-like prolongation or cilium, f 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 those of the bull ( G . Ret- zius). These consist of a flattened, long, narrow, transparent, protoplasmic mass, with a fibre com- posed of many delicate threads in both margins. At the tip of the tail both fibres unite into one. The fibre of the one margin is generally straight ; the other is thrown into wave-like folds, or winds in a spiral manner round the other ( W. Krause , Gibbes ). G. Retzius describes a special terminal filament (Fig. 549, e ). An axial thread, sur- rounded by an envelope of protoplasm, traverses the middle piece and the tail ( Eimer , v. Braun). [Leydig showed that in the salamander there is a delicate membrane attached to the tail, and Gibbes has described a spiral thread attached to the head (newt) and connected with the middle piece by a hyaline membrane.] Motion of the Spermatozoa. — [After 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 [Eimer). These movements are comparable to those that occur in cilia (§ 292), and there are transition forms between ciliary and amoeboid 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 ( Virchow), 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 (Mantegazza). Resistance. — Owing to the large amount of earthy salts which they contain, when dried upon a microscopical slide they still retain their form ( Valentin). 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 ( Fiirbinger ). 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 Fig. 548. DEVELOPMENT OF SPERMATOZA. 861 (Fig. 550, I, by and IV, h ), from which there project into the lumen of the tube, long (0.053 mm.) column-like prolongations, (I, c , and II, III, IV), which break Fig. 549. Spermatozoa 1, 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 . Ebner) ; 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 — a, membrane; b, protoplasmic inner lining; c, spermatoblast ; s, seminal cells. II, Unripe spermatoblast— -f, rounded cleavate lobules; /.seminal cells. IV, spermatoblast, with ripe spermatozoa (k) not yet detached ; tail, r ; «, wall of the seminal tubule ; A, its protoplasmic layer. Ill, spermatoblast with a spermatozoon free, t. matoblast 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, t ), 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 fluid part of the semen, and they may, therefore, be called seminal cells (I, s, II, III, IV, p). 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 elliptical (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 different from the ordinary forms, occur in myriapoda 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. Section of a cat’s ovary. The place ot attachment or hilum is below. On the left is a 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 (ji^inch — Fig. 551), while deeper down are the larger follicles {-fa to 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 , 1827) is 0.18 to 0.2 mm. [ T ^ in.] in diameter, and is a spherical, cellular body with a thick, solid, elastic envelope, the zona pellu- cida, with radiating striae. 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 fi — Purkinje , 1825; Coste , 1834). The germinal vesicle contains the nucleolus or germinal spot (5-7 — R. Wagner , 1833). 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, and 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 (Pfliiger). According to van Beneden, it is lined by a thin membrane next the vitellus, and he regards the thin membrane as the original cell membrane of the ovum. The fine radiating striae in the zona are said to be due to the exist- DEVELOPMENT OF THE OVA. 863 ence of numerous canals ( Kolliker , v. Sehlen). It is still undecided whether there is a special micropyle 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 epithelium ” — 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” ( Waldeyer ). These tubes, from and in which the ova are developed ( Waldeyer ), 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 cylindrical epithelium on the surface of the ovary. The upper extremities of the tubes become closed, while the tube itself is divided into a Fig. 552. Section of an ovary, e, germ epithelium ; 1, large-sized follicles ; 2, 2, middle-sized, and 3, 3, smaller-sized follicles; o, ovum within a Graafian follicle ; v, v, blood vessels of the stroma ; g, 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, 0, d), 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 folliculi — between the tunica and membrana granulosa. It is covered by a vascular outer membrane — the theca folliculi — which is lined by the epithelium constituting the membrana granulosa (IV, g). When a Graafian 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, Waldever, 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- I, an ovarian tube in process of development (new-born girl), a, a , young ova between the epithelial cells on the surface of the ovary ; b , the ovarian tube with ova and epithelial cells ; c, a small follicle cut off and enclosing an ovum. II, Open ovarian tube from a bitch. Ill, Isolated primordial ovum (human). IV, Older follicle with two ova (0, 0) and the tunica granulosa (g) of a bitch. V, Part of the surface ol a ripe ovum of a rabbit — z, zona pellucida ; d, vitellus , e, adherent cells of the membrana granulosa. VI, First polar globule formed. VII, Formation of the second polar globule (Fob). 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 ( Caldwell ), the reptiles, and the other fishes have meroblastic ova [Reichert). 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 mm. broad and 0.28-0.37 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 yelk 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 made 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 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. They 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 ( Elmer ). The whole yelk of the hen’s egg is regarded by some ob- Fig. 554. Vertical section of the mucous membrane of the human uterus, e , columnar epithelium, the cilia absent; gg, utric- ular glands ; c t, intra-glandular connective tissue ; v, v, blood vessels ; in in, muscularis mucosae. servers as equivalent to the mammalian ovum plus the corpus luteum. Microscopically, the white yelk consists of small vesicles (5-75 //) 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 PUBERTY. spiral manner around the albumin ( Lindvall and Hamarsien). [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 porous mortar. [The shell is porous, and its inner layer is perforated by vertical canals, through which the respiratory exchange of the gases can take 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 ( Prout , Gruwe, although this is denied by Polt 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 haemoglobin 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 ; b, isthmus of Fallopian tube; c, ampulla; g , fimbriated end of the tube, with the parovarium to its right ; e, ovary ; f, ovarian ligament. mucous membrane of the body of the uterus in the unimpregnated condition has no folds, while the muscularis mucosse is very well developed and forms a great part of uterine muscular wall. The mucous membrane is lined by a single layer of 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 vitse. 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 15th SIGNS OF MENSTRUATION. 867 years in the female and the 14th to 16th 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 sexual 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 Adam’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- Fig. 556. Connective tissue. Ciliated epithelium. Circular muscular fibres. Muscular fibres cut across. Transverse 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. — At regular intervals of time, of 27^-28 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 of menstruation (or menses, cata- menia or periods). Most women menstruate during the first quarter of the moon, and only a few at new and full moon ( StrohD . 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 (. Lawson 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, 868 OVULATION. alternate feeling of heat and cold, and even a slight increase of the temperature of the skin (. Kersch ). There may be retardation of the process of digestion and variations in the evacuation of the fseces and urine, and in the secretion of sweat. The discharge is slimy at first, and then becomes bloody , lasting three to four days ; the blood is venous, and shows little 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 ioo 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 off. The characteristic internal phenomena which accompany menstruation are : (1) The changes in the uterine mucous membrane; and (2) the rupture of the Graafian follicle. 1. 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, and from them, after menstruation is over, the new mucous membrane is devel- oped ( Kundrat and G. J. Engelmann). [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.] Fig. 557. — Diagram of the uterus just before men- 2 . Ovillatioil. The Second important internal Phenomenon is ovulation, in which menstruation has just ceased, showing the cavity process the ovary becomes more vascular — HWiamff deprived of mucous membra ” e U ■ the ripe follicle is turgid with fluid, 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. Pfliiger’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. Pfliiger regards the bloody discharge from the superficial layers of the uterine mucous membrane as a physiological 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- ex posed 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 Reichert, Engelmann, Williams, and others. According 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. The mucous membrane so altered is spoken of as the viembrcina decidua menstrualis, 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, i. e., 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 menstrualis occur separately, so that there may be 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. 559. Erectile tissue, a, trabeculae of connective tissue with elastic fibres and smooth muscles (C); b, venous spaces. follicle swells up. Villous prolongations or granulations of young connective tissue, rich in capil- laries and cells, grow into 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 luteum 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 effused blood is changed into haematoidin ($ 20) and other derivatives of haemoglobin, while there is a gradual shrivelling of the whole mass, which is complete in about four weeks, only a very small remainder being left. Such a corpus luteum, i. ), and through the ductus arteriosus of Botalli (B) into the aorta. There are, therefore, two streams of blood in the right auricle which cross each other, the descending one from the head through the superior vena cava, passing in front of the transverse one from the inferior vena cava to the foramen ovale.] Only a small amount of the blood passes through the as yet small branches of the pulmonary artery to the lungs (Fig. 570, 7, 7, 2). The course of the blood makes it evident that the head and upper limbs of the foetus are nourished by purer blood than the remainder of the trunk, which is supplied with blood mixed with the blood of the superior vena cava. After birth the umbilical arteries are obliterated, and become the lateral liga- ments of the bladder, while their lower parts remain as the superior vesical arte- ries. The umbilical vein is obliterated, and remains as the ligamentum teres, or round ligament of the liver, and so is the ductus venosus Arantii. Lastly, the foramen ovale is closed, and the ductus arteriosus is obliterated, the latter form- ing the lig. arteriosus. The condition of the membranes where there are more foetuses than one: (1) With twins there are two completely separated ova, with two placentae and two deciduae reflexse. (2) Two completely separate ova may have only one reflexa, whereby the placentae grow together, while their blood vessels remain distinct. The chorion is actually double, but cannot be separated into two lamellae at the point of union. (3) One reflexa, one chorion, one placenta, two umbilical cords and two amnia. The vessels anastomose in the placenta. In this case there is one ovum with a double yelk, or with two germinal vesicles in one yelk. (4) As in (3), but only one amnion, caused by the formation of two embryos in the same blastoderm of the same germinal vesicle. Formation of the fcetal membranes in animals. — The oldest mammals have no placenta or umbilical vessels; these are the Mammalia implacentalia ( Owen), including the monotremata and marsupials. The second group includes the Mammalia placentalia. Among these (a) the non-deciduata possess only chorionic villi supplied by the umbilical vessels, which project into the depressions of the uterine mucous membrane, and from which they are pulled out at birth (PI. dif- fusa, e.g., pachydermata, cetacea, solidungula, camelidae). In the ruminants the villi are arranged in groups or cotyledons, which grow into the uterine mucous membrane, from which they are pulled out at birth, (b) In the deciduata there is such a firm union between the chorionic villi with the uterine mucous membrane, that the uterine part of the placenta comes away with the foetal part at birth. In this case the placenta is either zonary (carnivora, pinnipedia, elephant), or dis- coid (apes, insectivora, edentata, rodentia). 446. CHRONOLOGY OF HUMAN DEVELOPMENT.— Development during the 1st Month. — At the I2th-I3th day the ovum is saccular (5.5 mm. and 3 mm. in diameter) ; there is simply the blastodermic vesicle, with the blastoderm at one part, consisting of two layers; the zona pellucida beset with small villi {Reichert). At the I5th-i6th day the ovum (5-6 mm.) is covered with simple cylindrical villi. The zona pellucida consists of embryonic connective tissue covered with a layer of flattened epithelium. The primitive groove and the laminae dorsales appear. Then follows the stage when the allantois is first formed. At the I5th-i8th day Coste investigated an ovum. It was 13.2 mm. long, with small branched villi; the embryo itself was 2.2 mm. long, of a curved form, and with a moderately enlarged cephalic end. The amnion, umbilical vesicle with a wide vitelline duct, and the allantois were developed, the last already united to the false amnion. The S-shaped heart lies in the cardiac cavity, shows a cavity and a bulbus aortas, but neither auricles nor ventricles. The visceral arches and clefts are indicated, but they are not perforated. The omphalo-mesenteric vessels forming the first circulation on the umbilical vesicle are developed, the duct (vitelline) is still quite open, and two primitive aortae run in front of the protovertebrae. The allantois attached to the foetal membranes is provided with blood vessels. The two omphalo- CHRONOLOGY OF HUMAN DEVELOPMENT. 887 mesenteric veins unite with the two umbilical veins, and pass to the venous end of the heart. The mouth is in process of formation. The limbs and sense organs absent ; the Wolffian bodies pro- bably present. At the 20th day all the visceral arches are formed, and the clefts are perforated. The mid-brain forms the highest part of the brain, while the two auricles appear in the heart. The connection with the umbilical vesicle is still moderately wide. The embryo is 2. 6-3. 3-4 mm. long, while the head is turned to one side {His). At a slightly later period the temporal and cervical flexures take place, and the hemispheres appear more prominently ; the vitelline duct is narrowed, the position of the liver is indicated, while the limbs are still absent {His). At the 2 1st day the ovum is 13 mm. long and the embryo 4-4.5 mm. ; the umbilical vesicle 2.2 mm., and the intestine almost closed. Three branchial clefts, Wolffian bodies laid down, and the first appearance of the limbs , three cerebral vesicles, auditory capsules present [R. Wagner). Coste also observed, in addition, the nasal pits, eye, the opening for the mouth, with the frontal and supe- rior maxillary processes, the heart with two ventricles and two auricles. End of the 1st Month. — The embryos of 25-28 days are characterized by the distinctly stalked condition of the umbilical vesicle and the distinct presence of limbs. Size of the ovum, 17.6 mm.; embryo, 13 mm. ; umbilical vesicle, 4.5 mm., with blood vessels. 2d Month. — The embryos of 28-35 ^ a y s are more elongated, and all the branchial clefts are closed except the first. Th^ allantois has now only three vessels, as the right umbilical vein is ob- literated. At the 5th week the nasal pits are united by furrows with the angle of the mouth, which close to form canals at the 6th week {Toldt). At 35-42 days the nasal and oral orifices are sepa- rated, the face is flat, the limbs show three divisions, the toes are not so sharply defined as the fingers. The outer ear appears as a low projection at the 7th week. The Wolffian bodies are much reduced in size. End of the 2d Month. — Ovum, 6^ cm.; villi, 1.3 mm. long; the circulation on the umbilical vesicle has disappeared; embryo, 26 mm. long, and weighs 4 grammes. Eyelids and nose present, umbilical cord 8 mm. long, abJominal cavity closed, ossification beginning in the lower jaw, clavicle, ribs, bodies of the vertebrae ; sex indistinct, kidneys laid down. 3d Month. — Ovum as large as a goose’s egg, beginning of the placenta, embryo 7-9 cm., weigh- ing 20 grammes, and is now spoken of as a foetus. External ear well formed, umbilical cord 7 cm. long. Beginning of the difference between the sexes in the external genitals, umbilicus in the lower fourth of the linea alba. 4th Month. — Foetus, 17 cm. long, weighing 120 grammes, sex distinct, hair and nails beginning to be formed, placenta weighs 80 grammes, umbilical cord 19 cm. long, umbilicus above the lowest fourth of the linea alba, contractions or movements of the limbs, meconium in the intestine, skin with blood vessels shining through it, eyelids closed. 5th Month. — Foetus, 18 to 27 cm., weighing 284 grammes; hair on the head and lanugo dis- tinct; skin still somewhat red and thin, and covered with vernix caseosa (§ 287, 2), is less trans- parent; weight of placenta, 178 grammes ; umbilical cord, 31 cm. long. 6th Month. — Foetus, 28 to 34 cm., weighing 634 grammes; lanugo more abundant; vernix more abundant; testicles in the abdomen; pupillary membrane and eyelashes present ; meconium in the large intestine. 7th Month. — Foetus, 28.34 cm. long, weighing 1218 grammes, the descent of the testicles begins — one testicle in the inguinal canal, the eyes open, the pupillary membrane often absorbed at its centre in the 28th week. In the brain other fissures are formed besides the primary ones. The foetus is capable of living independently. At the beginning of this month there is a centre of ossi- fication in the os calcis. 8th Month. — Foetus, 42 cm., weighing 1.5 to 2 kilos. (3.3 to 4.4 lbs.), hair of the head abun- dant, 1.3 cm. long, nails with a small margin, umbilicus below the middle of the linea alba, one testicle in the scrotum. gth Month. — Foetus, 47 cm., weighing 2]/ z kilos. (5.5 lbs.), and is not distinguishable from the child at the full period. Foetus at the Full Period. —Length of body, 51 cm. [20 inches], weight 3^ kilos. [7 lbs.], lanugo present only on the shoulders, skin white. The nails of the fingers project beyond the tips of the fingers, umbilicus slightly below the middle of the linea alba. The centre of ossification in the lower epiphysis of the femur is 4 to 8 mm. broad. Period of Gestation or Incubation. Coluber . , Days. . ... 12 Rabbit . . . , Days. Dog . . . Weeks. . . . ) Hen . . . . . . I 21 Hare . . . . - Fox. . . Duck. . . Weeks. Foumart . : : . i Goose . . . ... 29 Rat . 5 Badger . . : : : } ,c Stork . . . ... 42 Guinea pig . 7 Wolf . . Cassowary . ... 65 Cat ’ ’l . 8 Lion . . . .... 14 Mouse . . . ... 24 Marten . . . • 1 Pig . . . .... 17 : 1 30 36-40 Woman 40 Horse, Camel, 13 months ; Rhinoceros, 18 months; and the Elephant, 24 months [Schenk). Limitation of the supply of O to eggs, during incubation, leads to the formation of dwarf chicks. Sheep . . Goat . , . Roe . . . Bear . . . Small apes Deer . Weeks. . . 21 . . 22 • • 24 888 FORMATION OF THE OSSEOUS SYSTEM. 447. FORMATION OF THE OSSEOUS SYSTEM.— Vertebral Column.— The ossi- fication of the vertebra begins at the 8th to the 9th week, and first of all there is a centre in each vertebral arch, then a centre is formed in the body behind the chorda [Robin), which, however, is composed of two closely apposed centres. At the 5th month the osseous matter has reached the surface, the chorda within the body of the vertebra is compressed ; the three parts unite in the 1st year. The atlas has one centre in the anterior arch and two in the posterior ; they unite at the 3d year. The epistropheus has a centre at the 1st year. The three points of the sacral vertebrae unite or anchylose between the 2d and the 6th year, and all the vertebrae (sacral) become united to form one body between the 18th and 25th years. Each of the four coccygeal vertebrae has a centre from the 1st to 10th year. The vertebrae in later years produce 1 to 2 centres in each process; 1 to 2 centres in each transverse process ; 1 in the mammillary process of the lumbar vertebrae ; and one in each articular process (8 to 15 years). Of the upper and under surfaces of the body of a vertebra each forms an epiphysial, thin osseous plate, which may still be visible at the 20th year. Groups of the cells of the chorda are still to be found within the intervertebral disks. As long as the coccy- geal vertebrae, the odontoid process, and the base of the skull are cartilaginous, they still contain the remains of the chorda [H. Muller). The coccygeal vertebrae form the tail, and they originally project in man like a tail (Fig. 563, IX, T), which is ultimately covered over by the growth of the soft parts [His). The ribs bud out from the protovertebrae, and are represented on each vertebra. The thoracic ribs become cartilaginous in the 2d month and grow forward into the wall of the chest, whereby the seven upper ones are united by a median portion ( Rathke ), which represents the position of one- half of the sternum, and when the two halves meet in the middle line the sternum is formed. When this does not occur we have the condition of cleft sternum. At the 6th month there is a centre of ossification in the manubrium, then 4 to 13 in pairs in the body, and 1 in the ensiform process. Each rib has a centre of ossification in its body at the 2d month, and at the 8th to 14th one in the tubercle and another in the head. These anchylose at the 14th to 25th year. Sometimes cervical ribs are present in man, and they are largely developed in birds. The skull. — The chorda extends forward into the axial part of the base to the sphenoid bone. The skull at first is membranous, or the primordial cranium ; at the second month the basal portion becomes cartilaginous, including the occipital bone, except the upper half, the anterior and posterior part and wings of the sphenoid bone, the petrous part and mastoid process of the tem- poral bone, the ethnoid with the nasal septum, and the cartilaginous part of the nose. The other parts of the skull remain membranous, so that there is a cartilaginous and a membranous primor- dial cranium. I. The occipital bone has a centre of ossification in the basilar part of the 3d month, and one in the condyloid part and another in the fossa cerebelli, while there are two centres in the mem- branous cerebral fossae. The four centres of the body unite during intra-uterine life. All the other parts unite at the 1st to 2d year. II. The post-sphenoid. — From the 3d month it has two centres in the sella turcica, two in the sulcus caroticus, two in both great wings, which also form the lamina externa of the pterygoid pro- cess, while the non- cartilaginous and previously formed inner lamina arises from the superior max- illary process of the first branchial arch. During the first half of foetal life these centres unite as far as the great wings; the dorsum sellse and the clinoid process, as far as the synchondrosis spheno- occipitalis, are still cartilaginous, but they ossify at the 13th year. III. The pre-sphenoid at the 8th month has two centres in the small wings and two in the body. At the 6th month they unite, but cartilage is still found within them even at the 13th year. IV. The ethrrioid has a centre in the labyrinth at the 5th month, then in the 1st year a centre in the central lamina. They unite about the 5th or 6th year. V. Among the membranous bones are the inner lamina of the pterygoid process (one centre), the upper half of the tabular plate of the occipital (two points), the parietal bone (one centre in the parietal eminence), the frontal bone (one double centre in the frontal eminence), three small centres in the nasal spine, spina trochlearis and zygomatic process, nasal (one centre), the edges of the parietal bones (one centre), the tympanic ring (one centre), the lachrymal, vomer, and inter- maxillary bone. The facial bones are intimately related to the transformations of the branchial arches and branchial clefts. The median end of the first branchial arch projects inward from each side toward the large oral aperture. It has two processes, the superior maxillary process, which grows more laterally toward the side of the mouth, and the inferior maxillary process, which surrounds the lower margin of the mouth (Fig. 563, IX). From above downward there grows as an elongation of the basis cranii the frontal process (.y), a broad process with a point (y) at its lower and outer angle, the inner nasal process. The frontal and the superior maxillary processes [r) unite with each other in such a way that the former projects between the two latter. At the same time there is anchylosed with the superior maxillary process the small external nasal process [n), a prolongation of the lateral part of the skull, and lying above the superior maxillary process. Between the latter and the outer nasal process is a slit leading to the eye [a). Thus the mouth is cut off from the nasal apertures which lie above it. But the separation is continued also within the mouth ; the superior maxillary process produces the upper jaw, the nasal process, and the intermax- BRACHIAL CLEFTS AND THEIR RELATION TO NERVES. 889 illary process ( Goethe ) — the latter is present in man, but is united to the upper jaw. The inter- maxillary bone, which in many animals remains as a separate bone (os incisivum), carries the incisor teeth. At the 9th week the hard palate is closed, and on it rests the septum of the nose, descending vertically from the frontal process. The lower jaw is formed from the inferior maxil- lary process. At the circumference of the oral aperture the lips and the alveolar walls are formed. The tongue is formed behind the point of the union of the second and third branchial arches {His ) ; while, according to Born, it is formed by an intermediate part between the inferior maxillary pro- cesses. These transformations may be interrupted. If the frontal process remains separate from the superior maxillary processes, then the mouth is not separated from the nose. This separation may occur only in the soft parts, constituting hair-lip (Fig. 567) ; or it may involve the hard palate, con- stituting cleft palate. Both conditions may occur on one or both sides. From the posterior part of the first branchial arch are formed the malleus (ossified at the 4th month), and Meckel’s carti- lage (Fig. 568), which proceeds from the latter behind the tympanic ring as a long cartilaginous process, extending along the inner side of the lower jaw, almost to its middle. It disappears after the 6th month ; still its posterior part forms the internal lateral ligament of the maxillary articula- tion. Near where it leaves the malleus is the processus Folii ( Baumuller ). A part of its median end ossifies, and unites with the lower jaw. The lower jaw is laid down in membrane from the first branchial arch, while the angle and condyle are formed from a cartilaginous process. The union of both bones to form the chin occurs at the 1st year. From the superior maxillary process are formed the inner lamella of the pterygoid process, the palatine process of the upper jaw, and the palatine bone at the end of the 2d month, and, lastly, the malar bone. The second arch \hyoid ] , arising from the temporal bone, and running parallel with the first arch, gives rise to the stapes (although, according to Salensky, this is derived from the first arch), the eminentia pyramidalis, with the stapedius muscle, the incus, the styloid process of the temporal Fig. 567. Fig. 568. Fig. 567. — Hare-lip on the left side. Fig. 568. — Inner view of the lower jaw of an embryo pig 3 inches long (X 3 %). ink, Meckel’s ca r tilage ; d, dentary bone ; cr, coronoid process ; ar, articular process (condyle) ; ag, angular process; ml, malleus ; mb, manubrium. bone, the (formerly cartilaginous) stylo- hyoid ligament, the smaller cornu of the hyoid bone, and, lastly, the glosso- palatine arch {His). The third arch \thyro-hyoicT\ forms the greater cornu and body of the hyoid bone and the pharyngo-palatine arch {His). The fourth arch gives rise to the thyroid cartilage {His). Branchial Clefts. — The first branchial or visceral is represented by the external auditory meatus, the tympanic cavity, and the Eustachian tube ; all the other clefts close. Should one or other of the clefts remain open, a condition that is sometimes hereditary in some families, a cervical fistula results, and it may be formed either from without or within. Sometimes only a blind diverticulum remains. Branchiogenic tumors and cysts depend upon the branchial arches {R. Volkmann). [Relation of Branchial Clefts to Nerves. — It is important to note that the clefts in front of the mouth {pre-oral ), and those behind it {post-oral), have 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 third nerve. 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 sup- plied by the portio dura. The next cleft is supplied by the glosso-pharyngeal , 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 ( Wolfier). 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 ( Stieda ). The Extremities. — The origin and course of the nerves of the brachial plexus show that the upper extremity was originally placed much nearer to the cranium, while the position of the poste- rior pair corresponds to the last lumbar and the 3d or 4th sacral vertebrae [His). The clavicle, according to Bruch, is not a membrane bone, but is formed in cartilage like the furculum of birds ( Gegenhaur). 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. Centres of ossification of the innominate bone. 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 suprascapular 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 (1st year) ; one in the great tuberosity and one in the small tuberosity (2d year) ; two in the condyles (5th to 10th year) ; one in the trochlea (12th year). The epiphyses unite with the shaft at the 16th 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 process. 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 pisiform 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 in 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 (5th 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 {Rosenberg). Ossification begins with three centres — one in the ilium (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 auricularis, 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 ascending 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 1 ith year), one in the lesser trochanter (13th to 14th year), two in the condyles (4th to 8th year) ; all unite about the time of puberty. Th z patella 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 ealcis ossifies at the beginning of the 7th month, the astragalus at the beginning of the 8th month, the cuboid at the end of the 10th, the scaphoid (1st 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 5th to 10th 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 membrane, 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. — (1) 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 osseous case, like a muff, surrounds the cartilage. This bone is formed by the sub-periosteal 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 lacunae, 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 f mineral matter, which consists of neutral calcic phosphate, 57 per cent. ; calcic carbonate, 7 per cent. ; magnesic phosphate, 1 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. The red marrow contains more iron, corresponding to its larger 'proportion of haemoglobin (Nasse). [The medullary cavity of a long bone is occupied by yellow 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 white fibrous tissue, bolting together the peripheric lamellae. [Muller and Schafer have shown that there are also fibres in the peripheric lamellae 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 bone in a young animal ultimately comes to lie in the medullary cavity ( Duhamel ). The growth in length takes place by the continual growth and ossification of the epiphysial cartilage. The 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 (J. Hunter ).] When the growth of bone is at an end, the epiphysis becomes united to the diaphysis, the epi- physial 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 Wolff (g 244, 9). * [Howship’s Lacunae. — The osteoclasts or myeloplaxes are large multinuclear giant cells, which erode bone. They can be seen in great numbers lying in small depressions, corresponding to them — Howship’s lacunee — on the fang of a temporary tooth, when it is being absorbed. 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 rhythmically. This hollow cellular structure elongates into a tube, which very soon assumes a shape somewhat like an S (Fig. 570, 1), 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 (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, of). 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 cavse. This common trunk is absorbed at a later period into the enlarging auricle, and thus arise the separate terminations of the superior and inferior venae cavae. In man, the heart soon comes to lie in a special cavity, which in part is bounded by a portion of the diaphragm ( His ). 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 lefc 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 ,p a) appear in the interior of the truncus arteriosus (4 , p), which ultimately meet, and thus divide this tube into two tubes (5, a p), 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 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 (6, 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, Ci ), opens directly opposite the fold. On the left of its orifice, the valve of the Fig. 570. Development of the heart. 1, Early appearance of the heart; — a, aortic part, with thebulbus, b; v, venous end. 2, Horseshoe-shaped curving of the heart — a, aortic end, with the bulbus, b\ V, ventricle; A, auricular part. 3, Formation of the auricular appendages, o , o 1 , 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 pulmonary artery open into their respective ventricles. 6. Relation of the orifices of the superior (Cr) and inferior vena cava (Ci) to the auricle (schematic 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 auricle ; tL , tubercle of Lower. 7. Heart of the ripe foetus — K, right, L, left ventricle ; a, aorta, with the innominate, c, c, carotid, c, and left subclavian artery, $ ; B, ductus arteriosus ; p, pulmonary artery, with the small branches 1 and 2, to the lungs. Fig. 571. The aortic arches. 1, The first position of the 1, 2 and 3 arches ; 2, 5, aortic arches ; ta, common aortic trunk ; ad, descending aorta. Disappearance of the upper two arches on each side — S, subclavian artery ; v, vertebral artery; ax, axillary artery. 4. Transition to the final stage — P, pulmonary artery ; A , , aorta ; dB, ductus arte- riosus (Botalli) ; S, right subclavian, united with the right common carotid, which divides into the internal (Ci) and external carotid (Ce) ; ax, axillary ; v , 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 {tL), 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 foetal circulation (p. 885). After birth, the 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 proceeding to the expanding lungs. Sometimes the foramen ovale remains pervious, giving rise to serious symptoms after a time, and constituting morbus ceruleus. Arteries. — With the formation of the branchial arches and clefts, the number of aortic arches on each side becomes increased to 5 (Fig. 571), which run above and below each branchial cleft, in a branchial arch, and then all reunite behind in a common descending trunk (2, ad) ( Rathke ). These blood vessels remain only in animals that breathe by gills. In man, the upper two arches disappear completely (3). When the truncus arteriosus divides into the 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 left lowest arch forms the ductus arteriosus (dB), 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 ( Ci, 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 Fig. 572. I, First appearance of the veins of the embryo. II, Their transformations to form the final arrangement. one omphalo-mesenteric 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 itself are the two cardinal veins ; on each side an anterior (Fig. 572, I, c s), and a posterior {ci — Rathke ), which proceed toward the heart and unite on each side to form a large trunk, the duct of Cuvier (DC 1 , which passes into the venous part of the heart. The anterior cardinal veins give off the subclavian veins (bb) and the common jugular veins, which divide into the external (I •• V 'V *' ^ < V.: : - ■ -• • • ^ .